Section 2 Ferroptosis

### **Chapter 3**

## Ferroptosis in Leukemia: Lessons and Challenges

*Baoquan Song and Leisheng Zhang*

### **Abstract**

Ferroptosis is a newly defined programmed cell death (PCD) process with the hallmark of the accumulation of iron-dependent lipid peroxidation, which is more immunogenic over apoptosis. Ferroptosis shows great potential as a therapeutic target against acute kidney injury (AKI), cancers, cardiovascular diseases, neurodegenerative diseases, and hepatic diseases. Accumulating evidence has highlighted that ferroptosis plays an unneglectable role in regulating the development and progression of multiple pathologies of leukemia including acute myeloid leukemia (AML), chronic myeloid leukemia (CML), acute lymphoblastic leukemia (ALL), and chronic lymphocytic leukemia (CLL). Herein, we focus on the state-of-the-art renewal in the relationship of ferroptosis with leukemia. Meanwhile, this chapter further highlights the iron, lipid and amino acid metabolism, as well as ferroptosis-based molecular mechanisms. Collectively, we summarize the contribution of ferroptosis to the pathogenesis of leukemia and discuss ferroptosis as a novel therapeutic target for different types of leukemia.

**Keywords:** ferroptosis, programmed cell death, leukemia, metabolism, novel therapeutic targets, lipid peroxides

### **1. Introduction**

Ferroptosis is a new type of iron-dependent programmed cell death (PCD) that was first reported by Dixon et al*.* in 2012, which is initiated by lipid peroxidation and terminates in toxic lipid peroxidation and mitochondrial dysfunction [1, 2]. As a new form of PCD, ferroptosis can be distinguished from other types of cell death such as necrosis, pyrolysis, apoptosis, and autophagy in regard to morphology and biochemistry [3, 4]. As to the morphological characteristics, the major manifestation of ferroptosis is increase in mitochondrial membrane density, unspoilt cytomembranes, cell volume shrinkage, decline or even deficiency in mitochondrial cristae, outer membrane rupture and mitochondrial membrane crumpling, and normal cellular nucleus size with unconsolidated chromatin [5, 6]. As to the biochemical characteristics, ferroptosis results from the accumulation of iron-catalyzed lipid-based reactive oxygen species (ROS), which is commonly initiated by either the loss of the activity of the lipid repair enzyme named glutathione peroxidase 4 (Gpx4) or the inactivation of the antioxidant defenses depending on the cellular glutathione (GSH) [7]. As to the genetic characteristics, a considerable number of genes have been indicated to

modulate ferroptosis by acting as inhibitors or inducers, which can be divided into the system Xc-, Gpx4, GSH, lipid peroxidation-associated genes, and iron metabolism regulation-associated genes on the basis of the variations in targets, whereas the specific regulatory mechanisms of ferroptosis still need to be further explored [8].

Taken together, ferroptosis has been regarded with initiation by the failure of the aforementioned GSH-dependent antioxidant defenses, which thus results in the uncontrolled process during lipid peroxidation and the concomitant cell death [9, 10]. Similarly, the out-of-balance phenomenon between GSH-dependent Gpx4 inactivity and the iron-catalyzed lipid ROS production eventually triggers the occurrence of ferroptosis. Accordingly, the lipophilic antioxidants and iron chelators can effectively suppress the process of ferroptotic cell death [11]. The former inhibits the initiation and accumulation of the lipid peroxidation by capturing or eliminating targeting lipoxygenase and free radicals, including ferrostatin-1 (Fer-1), *N*-acetylcysteine (NAC), vitamin E, and liproxstatin-1 (Lip-1) [12]. The latter can efficaciously prevent the aforementioned iron-catalyzed-associated lipid peroxidation by acerating the depletion of free iron, including deferiprone (DFP) and deferoxamine (DFO) [13]. In spite of the rapid development of the multifaceted assumptions and considerable validations, the systematic and detailed molecular mechanisms of ferroptosis are still far from being fully clarified. The regulatory mechanisms of ferroptosis are complicated and involve a variety of metabolic networks and signaling pathways, including abnormal iron metabolism, lipid metabolism, amino acid metabolism, and signaling pathways associated with ferroptosis. For instance, a number of studies have reported the involvement of several signaling pathways with ferroptosis such as ferritinophagy, iron and amino acid metabolism, cell adhesion, and Keap1/Nrf2, mTOR, and p53 signaling pathways [14–16].

Nowadays, ferroptosis has been considered to perform a critical role in various diseases and pathologies, such as cancer, stroke, cardiomyopathy, kidney and liver injury, and neurodegeneration [17, 18]. Meanwhile, both the indicated inhibitors and activators have been continuously identified and introduced to explore the molecular mechanisms of ferroptosis, which collectively benefit the development of novel therapeutic strategies for the administration of ferroptosis-related diseases and pathologies [19]. In the meantime, accumulating evidence has indicated the changes in iron metabolism during leukemia, which thus has been considered as a crucial feature as well. To date, high oxidative stress and high iron requirements are identified with association to the alteration of iron metabolism during leukemia, which thus suggests that leukemia cells are more vulnerable to variations in ROS and iron levels when compared with the normal cells [20]. Therefore, targeting iron metabolism may provide new insights into approaches to the treatment of leukemia.

### **2. Ferroptosis and leukemia**

Leukemia is a group of heterogeneous hematopoietic stem cell (HSC) malignancies. It is characterized by aberrant accumulation of undifferentiated blasts capable of unrestrained proliferation in the bone marrow, which interferes with the production of normal blood cells. Leukemic cells uniquely possess the innate ability for migration and invasion. Differentiated, malignant leukocytes retain the benign leukocytes' capacity for cell motility and survival in the circulation, while acquiring the potential for rapid and uncontrolled cell division. Currently, a variety of cancer cells of hematological malignancies (e.g., multiple myeloma, leukemia, and lymphoma) have been

*Ferroptosis in Leukemia: Lessons and Challenges DOI: http://dx.doi.org/10.5772/intechopen.108576*

identified to be sensitive to ferroptosis because large amounts of iron are acquired by leukemia cells for the maintenance of rapid growth and proliferation. As a consequence, targeting iron metabolism holds the potential to supply new insights into developing novel approaches for the administration of leukemia.

As a cancer of the bone marrow and blood cells, leukemia threatens human health seriously. Recent insights into iron metabolism along with the recent discovery of ferroptosis have opened new avenues in the field of antitumor therapies. Emerging evidence has revealed that ferroptosis is essentially a nexus among metabolism, redox biology, and diseases including cancers. The discovery of ferroptosis is a major breakthrough in the development of cancer treatments. Therefore, targeting ferroptosis may provide new insights into approaches to the treatment of leukemia. Leukemia is classified into four main subgroups, including acute myeloid leukemia (AML), acute lymphoblastic leukemia (ALL), chronic myeloid leukemia (CML), and chronic lymphoblastic leukemia (CLL). Therefore, we focus on these entities in this chapter.

### **2.1 Ferroptosis in acute myeloid leukemia**

AML is the most common type of leukemia in adults, which is characterized by the rapid growth of abnormal lineage-specific hematopoietic precursor cells that do not differentiate into functional granulocytes or monocytes during hematopoiesis in the bone marrow microenvironment [21–24]. As a classical paradigm of myeloid disease with multiple life-threatening complications, AML is characterized by a significant reduction of physiological differentiation of hematopoietic stem and progenitor cells (HSPCs) toward myeloid and lymphoid lineages in parallel with aberrant activation of pathological hematopoiesis that is dominated by the continuous accumulation of the dysfunctional leukemic blast populations [25, 26]. Despite the dramatic progresses in exploring the pathogenesis and exploring advanced targeted therapies, the majority of the AML patients are still bearing immune dysregulation and the concomitant outcomes [25]. Long-term survival remains limitation with the standardof-care chemotherapies combining anthracyclines with cytarabine. Development of resistance to chemotherapeutic agents is a major hurdle in the effective treatment of patients with AML [27]. New therapies are needed to improve chemotherapy efficacy in AML [25, 28]. Meanwhile, many endeavors have been made to ascertain *de novo* biomarkers and improve risk stratification and prognostic assessment in different AML subgroups [21]. However, more and more studies have proved that ferroptosis is closely related to the pathophysiology of AML and thus shed light on studying the pathogenesis of AML and search for new therapeutic targets.

A variety of molecular and pathological changes in ferroptosis have been observed in experimental AML models and samples from AML patients (**Table 1**). Among ferroptosis-related genes (FRGs), GPX-1, GPX-3, GPX-4, and GPX-7 were highly expressed in *n* AML patient samples and associated with poorer prognosis of overall survival (OS) [30]. AKR1C2 and SOCS1 are promising biomarkers for predicting prognosis in patients with AML [31]. Huang et al. [32] established a prognostic model of 12-FRGs in AML. The model successfully divided patients into high- and low-risk (LR) patient groups with mean OS as the basis. Wei et al*.* [15] showed that ferroptosis-related genes (FRGs), DPP4 and TFRC, act as biomarkers for predicting and diagnosing AML, and their expression levels also have significant correlations with drug resistance in AML. Other markers of ferroptosis, among the 12 ferroptosisrelated genes (PHKG2, HSD17B11, STEAP3, HRAS, ARNTL, CXCL2, SLC38A1, PGD, ENPP2, ACSL3, DDIT4, and PSAT1), were screened to generate a prognostic model,


 *Bioinformatics studies predicting prognosis of leukemia patients based on the expression of ferroptosis-related genes*

**Table 1.**

### *Cell Death and Disease*

### *Ferroptosis in Leukemia: Lessons and Challenges DOI: http://dx.doi.org/10.5772/intechopen.108576*

which stratified patients into a low- (LR) or high-risk (HR) group [33]. Another study showed that 18 signature genes, including DLL3, EFNB3, ZSCAN4, ASTN1, FAM155B, CCL23, ZFPM2, FOXL1, HMX2, LGALS1, LHX6, PCDHB12, MXRA5, HRASLS, TMEM56, PRINS, TWIST1, and ZNF560, were unified for the development of establishing the prognostic risk-scoring model. With the aid of the model, AML patients can be grouped into high-risk and low-risk groups, and those inpatients with low risk consistently revealed preferable survival over the high-risk inpatients [34]. In another study, investigators have identified and verified seven ferroptosis-related lncRNA signatures (AP001266.2, AC133961.1, AF064858.3, AC007383.2, AC008906.1, AC026771.1, and KIF26B-AS1) with independent prognostic value in patients with AML (**Table 1**) [35]. In summary, we conducted and validated a novel ferroptosisrelated prognostic model for outcome prediction and risk stratification in AML, with great potential to guide individualized treatment strategies in the future [31, 36–38].

Currently, ferroptosis has been characterized by the well-established irondependent accumulation of the lipid hydroperoxides, which eventually leads to the severe impairments of the mitochondrial outer membrane as well as the decrease of mitochondria crista. Interestingly, cancer cell death has been proved to be involved in ferroptosis as well. Therewith, new treatment remedies by developing effective activators and inhibitors targeting ferroptosis will benefit the development of novel treatment paradigms for AML patients. As early as 2015, researchers found that the ferroptosis inducer Erastin enhances sensitivity of acute myeloid leukemia cells to chemotherapeutic agents [39]. Later, researchers demonstrated that DHA would induce autophagy and ferroptosis in AML cell lines and revealed the role of iron metabolism in DHA-induced cell death [40]. High mobility group box 1 (HMGB1) is a novel regulator of ferroptosis *via* the RAS-JNK/p38 pathway and a potential drug target for therapeutic interventions in leukemia. It plays an important role in leukemia pathogenesis and chemotherapy resistance [29]. Typhaneoside (TYP) is a major flavonoid in the extract of pollen typhae, showing significant biological and pharmacological effects. Zhu et al. [24] found that TYP significantly triggered autophagy in AML cells by promoting the activation of AMP-activated protein kinase (AMPK) signaling, contributing to ferritin degradation, ROS accumulation, and ferroptotic cell death ultimately. APR-246, also known as PRIMA-1MET, is a promising new therapeutic agent that targets TP53-mutated cancers. The association of APR-246 with induction of ferroptosis (either by pharmacological compounds or by genetic inactivation of SLC7A11 or GPX4) had a synergistic effect on the promotion of cell death, both *in vivo* and *ex vivo* [41]. circKDM4C is negatively associated with AML, and the downregulated circKDM4C leads to AML progression, which otherwise induces ferroptosis by regulating has-let-7b-5p and P53. This may be explored further to develop a potential AML therapy [42]. Aldehyde dehydrogenase 3a2 protects AML cells from oxidative death and the synthetic lethality of ferroptosis inducers. Combination of Aldh3a2 inhibition with ferroptosis inducers or with standard AML induction chemotherapy deserves further consideration as a cancer therapy [43]. Subsequent studies verified that HMOX1 was a critical target in honokiol-induced ferroptosis [44]. These results reveal that honokiol is an effective antileukemia agent in AML cell lines and may be a potential ferroptosis activator in AML.

### **2.2 Ferroptosis in acute lymphoblastic leukemia**

Acute lymphoblastic leukemia (ALL) is a malignant clonal disorder of lymphoblastic hematopoiesis with high heterogeneity [45, 46]. Survival rates of ALL have improved remarkably by intensive induction chemotherapy, with complete remission (CR) rates of up to 80%. However, relapse occurred in patients ranging from 25% to 35% [47]. Interestingly, ferroptosis is suggested to be a promising strategy for cancer treatment and therefore should also be evaluated in ALL [48, 49].

After the exploration of the potential role of ferroptosis in Ph-neg B-ALL with the clinical data and the RNA-seq results of 80 Ph-neg B-ALL, a Cox regression model based on 8 FRGs (ALOX15, ATP5G3, CARS, CDKN1A, LPCAT3, SAT1, SLC1A5, and TFRC) was established to help evaluate the prognosis of Ph-neg B-ALL patients [50]. Lukas et al. reported that the glutathione (GSH) peroxidase 4 (GPX4) inhibitor RSL3 triggers lipid peroxidation, production of reactive oxygen species (ROS) and cell death in ALL cells. Importantly, LOX inhibitors, including the selective 12/15-LOX inhibitor Baicalein and the pan-LOX inhibitor nordihydroguaiaretic acid (NDGA), protect ALL cells from RSL3-induced ferroptosis [51]. Artesunate (ART), a widely used antimalarial compound, exerted potent anti-ATLL effects through inducing reactive oxygen species production, resulting in cell death mediated by apoptosis, ferroptosis, and necroptosis [52]. Greco et al. [53] reported that sulforaphane (50 μM) induced U-937 cell ferroptosis through depletion of glutathione (GSH), decreased GSH peroxidase 4 protein expression, and lipid peroxidation. PAQR3 (also known as RKTG) has been proved to take part in many human cancers by acting as a tumor suppressor. Jin and Tong [48] showed PAQR3 inhibited proliferation and aggravated ferroptosis in ALL through modulation of Nrf2 stability. This study suggested that PAQR3 may serve as an effective biological marker for ALL treatment. Meanwhile, Hydnocarpin D (HD) is a bioactive flavonolignan compound that possesses promising antitumor activity, although accumulation of lipid ROS and decrease of GSH and GPX4, while inhibition of autophagy, impeded ferroptotic cell death [54]. Poricoic acid A (PAA) is the main chemical constituent on the surface layer of the mushroom Poria Cocos and exerts protective effects against various diseases. PAA treatments also provoked ferroptosis in T-ALL cells with reduced glutathione (GSH) levels and elevated malonaldehyde (MDA) content through inducing autophagic cell death and ferroptosis [55]. Yang et al. provided the first direct evidence that circ\_0000745 promoted glycolytic metabolism and cell cycle progression but suppressed the occurrence of ferroptosis and apoptosis of acute lymphoblastic leukemia (ALL) cells *via* orchestrating the miR-494-3p/NET1 axis. That is, the Circ\_0000745/miR-494-3p/NET1 axis might serve as a novel potential target for the treatment and diagnosis of ALL as well [56]. Another study found that FBXW7 was adequate to participate in degrading VDAC3 via modulating ubiquitination of cells to promote Erastin-induced ferroptosis during ALL, which could explain the potentially regulatory link between ferroptosis and autophagy. Moreover, Zhu et al. [49] also demonstrated the value and impact of the combination of Erastin and Rapa for ALL management both *in vivo* and *in vitro*.

### **2.3 Ferroptosis in chronic leukemia**

Chronic leukemias are composed of a broad spectrum of subtypes such as including chronic monocytic leukemia, chronic mylocytic leukemia (juvenile, adult, and familial), chronic myelomonocytic leukemia, and chronic lymphocytic leukemia (CLL), which collectively account for lower than 5% of the childhood hematologic malignancies [57–59]. Recently, some studies have revealed the prognostic value of ferroptosis-related genes in chronic leukemia. For instance, Gong et al. indicated that ferroptosis-related genes can be used to stratify CLL patients based on overall

*Ferroptosis in Leukemia: Lessons and Challenges DOI: http://dx.doi.org/10.5772/intechopen.108576*

survival (OS) (**Table 1**). Meanwhile, they developed a risk signature containing eight ferroptosis-related genes for predicting the OS of CLL patients [60].

Several reports have shown the potential of triggering ferroptosis for chronic leukemia therapy, particularly for eradicating aggressive malignancies that are resistant to traditional therapies [60–63]. For decades, cysteine metabolism has been identified to have a critical role in cancer cell proliferation and survival, and cysteine depletion has been indicated to inhibit cancer growth and induce tumor cell ferroptosis. Furthermore, Liu et al*.* [64] have recently showed that cysteine depletion can induce ferroptosis in CML cells and TXNRD1 may be a key regulator gene. This illustrates that cysteine metabolism-induced ferroptosis may be a new idea for the treatment of CML except chemotherapy. Meanwhile, Song et al. [65] found that ferroptosis was involved in imatinib mesylate (IMA)-induced cardiotoxicity during the treatment of CML. In detail, they verified that IMA could downregulate Nrf2 expression but upregulate the P53 and TfR expression and thus increase the cellular ROS and iron, which collectively provided evidence for ferroptosis participation in IMA-induced cardiotoxicity and highlighted ferroptosis as a novel target in IMAexposed patients.

### **3. Conclusions and perspectives**

Ferroptosis is a newly discovered form of regulated cell death. Iron-dependent lipid peroxidation is a major driver of ferroptosis, and ferroptosis may also occur in leukemia. Ferroptosis is critically involved in the pathogenesis of various leukemia, including acute myeloid leukemia, acute lymphoblastic leukemia, chronic myeloid leukemia and chronic lymphocytic leukemia. With ongoing research, prognostic value of ferroptosis-related genes and potential therapeutic strategy for overcoming chemotherapy resistance are likely to become effective therapeutic strategies for leukemia.

### **Acknowledgements**

The authors would like to thank the members of The First Affiliated Hospital of Soochow University, Gansu Provincial Hospital, Chinese Academy of Sciences (CAS), Hefei Institute of Physical Science, and Institute of Health-Biotech, Health-Biotech (Tianjin) Stem Cell Research Institute Co., Ltd., for their technical support. This study was supported by grants from the National Natural Science Foundation of China (82260031, 81700119, and 81900175), Natural Science Foundation of Jiangsu Province (BE2018652, BK20201168, and BK20190181), the project Youth Fund funded by Shandong Provincial Natural Science Foundation (ZR2020QC097), science and technology projects of Guizhou Province (QKH-J-ZK[2021]-107), the project Youth Fund funded by Jiangxi Provincial Natural Science Foundation (S2021QNJJL0277), Jiangxi Provincial Key New Product Incubation Program from Technical Innovation Guidance Program of Shangrao city (2020G002 and 2020K003), Jiangxi Provincial Novel Research & Development Institutions of Shangrao City (2022AB003, 2020AB002, and 2021F013), Natural Science Foundation of Jiangxi Province (20212BAB216073), the 2021 Central-Guided Local Science and Technology Development Fund (ZYYDDFFZZJ-1), and the Non-profit Central Research Institute Fund of Chinese Academy of Medical Sciences (2019PT320005).

### **Conflict of interest**

The authors declare no conflict of interest.

### **Notes/thanks/other declarations**

Not applicable.

### **Abbreviations**


*Ferroptosis in Leukemia: Lessons and Challenges DOI: http://dx.doi.org/10.5772/intechopen.108576*

### **Author details**

Baoquan Song1,2,3 and Leisheng Zhang4,5,6,7,8\*

1 National Clinical Research Center for Hematologic Diseases, Jiangsu Institute of Hematology, The First Affiliated Hospital of Soochow University, Suzhou, China

2 Institute of Blood and Marrow Transplantation, Soochow University, Suzhou, China

3 Key Laboratory of Thrombosis and Hemostasis of Ministry of Health, Soochow University, Suzhou, China

4 Key Laboratory of Molecular Diagnostics and Precision Medicine for Surgical Oncology in Gansu Province and NHC Key Laboratory of Diagnosis and Therapy of Gastrointestinal Tumor, Gansu Provincial Hospital, Lanzhou, China

5 Jiangxi Research Center of Stem Cell Engineering, Jiangxi Health-Biotech Stem Cell Technology Co., Ltd., Shangrao, China

6 Center for Cellular Therapies, The First Affiliated Hospital and Shandong Provincial Qianfoshan Hospital, Shandong First Medical University, China

7 Key Laboratory of Radiation Technology and Biophysics, Hefei Institute of Physical Science, Chinese Academy of Sciences, Hefei, China

8 Institute of Health-Biotech Group, Tianjin, China

\*Address all correspondence to: leisheng\_zhang@163.com

© 2022 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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### **Chapter 4**

## The "Irony" of Ferroptosis: A Review on Neurological Challenges

*Chayan Munshi and Shelley Bhattacharya*

### **Abstract**

Ferroptosis in recent days has gained high impact due to its implication in inducing several neurological challenges. Impairment of iron homeostasis (mainly surplus iron deposition) is the key reason for the induction of the ferroptotic cell death. This type of programmed cell death in the neurons can trigger neuropathological abnormalities. Ferroptosis has been given clinical importance, where biomedical researchers are working on the pathological detection of ferroptosis and finding clinical ways to arrest it. In this review, we have elucidated the impact of ferroptotic cell death on the pathophysiology of several neurological challenges.

**Keywords:** Ferroptosis, cell death, neurological challenges, oxidative stress, iron

### **1. Introduction**

Ferroptosis is recently discovered non-apoptotic, iron-dependent programmed cell death instigated by the upsurge of intracellular lipid reactive oxygen species. Despite of the importance of iron in the body, the proper cellular homeostasis is important. The cellular mechanistic pathways which are related to ferroptosis are majorly iron metabolism and lipid peroxidation. Ferroptosis has been reported to have direct execution for several neurological disorders. As we know that ferroptosis is rather a very new area of research, intricate research is needed to work on the molecular crosstalk between ferroptosis, apoptosis, autophagy, and necrosis. A comparative molecular mechanism of ferroptotic pathophysiology in several neurological diseases needs to be revealed. Furthermore, research on the establishment of ferroptosis as a therapeutic approach for several neurological diseases is also important [1].

The ideal purpose of iron homeostasis in body must be established in the system, which not only transfers iron in the brain but also reduces its concentration, if exceed the optimum level. Irregularities in iron homeostasis, especially for surplus iron, relates to several critical cellular dysfunction and signifies a serious stage for neurodegenerative physiology. Ferroptosis is characterised by iron-dependent oxidative damage in the lipid bilayer. It is mainly instigated by the disparity in the oxidation and anti-oxidation proportion in the cell. Disturbances in iron and

lipid metabolism cause excessive accumulation of lipid peroxides within the lipid bilayer, causing oxidative destruction of the cell membrane. Disorder in the cellular antioxidant procedures results in the incapability to remove the lipid peroxides which is generated from the induction of oxidative stress. Eventually which is the reason for the massive annihilation of the lipid bilayer membrane and eventually causes programmed cell death. As accumulation of iron and lipid peroxides play the major roles in the triggering of ferroptosis, thus it can be decreased by the administration of iron chelators or by lipophilic antioxidants in the system. Recent findings have specified its major role in the brain maturation and adverse effects on the nervous system and its pathophysiology eventually initiating neural dysfunctions.

Lipid hydroperoxides are formed in the process of lipid peroxidation [2]. Glutathione peroxidase (GPX4) is a glutathione (GSH) dependent enzyme that acts to reduce lipid hydroperoxides (L-OOH) to from lipid alcohols (L-OH). This can inhibit the iron induced formation of toxic lipid reactive oxygen species (L-ROS). GSH is a cofactor of GPX4 and effectively sustains the GPX4 level through cystine/glutamate antiporter system known as the Xc- system. The inhibition of Xc- system or GSH synthesis, or GPX4 activity will eventually initiate the accumulation of lipid peroxides and initiation of ferroptotic cell death. The dysfunction of iron metabolism system, iron uptake (transferrin receptor), iron export (ferroportin), iron accumulation (ferritin) induces surplus of iron load and which results in the catalysis of hazardous L-ROS production [3]. The antiporter is a 12-pass transmembrane subunit (SLC7A11) where anionic cystine enters inside the cell via facilitated diffusion and in exchange, anionic glutamate moves out of the cell by facilitated diffusion. This antiporter also has 1-pass transmembrane subunit (SLC3A2), connected to the transporter by a disulfide bond. The capability of glutamate analogues to provoke ferroptosis in neurons is straightway correlated with their capability to inhibit cystine uptake in the cell. Cysteine in the extracellular domain is quickly oxidised to cystine where two molecules of cysteines are linked covalently by a disulfide bond. After transportation inside the cell, cystine is reduced to cysteine by glutathione reductase. Inhibition of cystine uptake results in the exhaustion of cysteine and eventually related exhaustion of GSH [4].

In this chapter, we have reviewed the impact of ferroptotic cell death on the pathophysiology of several neurological challenges.

### **2. Mechanistic overview of the pathophysiological manifestation during ferroptosis-induced neurological challenges**

The propagation of ageing in nervous system, induces clinical conditions like Alzheimer's disease (AD), Parkinson's disease (PD), Huntington's disease (HD), anxiety, depression, stroke, and traumatic brain injury which appears to be predominant in a population. The molecular mechanism of neurological disorders is multifarious, and there is lack of applicable therapeutic protocols. Molecules, manifesting ferroptosis-induced neurological disorders, such as reactive oxygen species (ROS), nuclear factor erythroid 2-related factor 2/antioxidant response element (Nrf2/ARE), iron ion (Fe2+), nicotinamide adenine dinucleotide phosphate (NADPH), NADPH oxidase (NOX), play crucial role in the pathophysiology. In the cells, due to the activity of acyl-CoA synthetase long chain family member 4 (ACSL4), cytochrome p450 oxidoreductase (POR), lipoxygenases (ALOX), polyunsaturated fatty acids (PUFA) produce phospholipid hydroperoxides (PLOOH) over a sequence of biochemical reactions, eventually from which, PLOO is generated. This results in lipid peroxidation. GPX4 activity can reduce PLOOH to PLOH to constrain lipid peroxidation occurrence. Mitochondria generates reactive ROS through, which causes oxidative stress. Fe2+ is oxidised to ferric ion (Fe3+) after absorption in the duodenum. Fe3+ enters the cell by combining with transferrin (Tf) and transferrin receptor (Tfr) to procedure a complex. Iron decomposition from endosome can induce ferroportin (FPN) protein activation on the cell membrane, where iron ions enter iron pool. Tf-Tfr complex triggers for the next cell cycle. During neurological disorders, excessive iron produces a large volume of ROS, which cause ferroptosis [5].

Neurodegeneration, cardiovascular disease, and diabetes, where ferroptosis might provoke the neuronal, cardiomyocyte, and β-cell loss. Regarding ferroptosis research, the transcription factor Nrf2 and its transcriptional target genes play in the inhibition process or in certain situations activating of the ferroptotic cascade. This concludes that cautious attention should be given in terms of Nrf2 pathway, which signify practical targets to recruit ferroptosis in tumour cell types, without damaging their normal cell types. Another therapeutic option is using the activation of Nrf2 or other essential anti-ferroptotic moderators in terms of avoiding ferroptosis. In homeostatic circumstances, Nrf2 is ubiquitylated and embattled for proteasomal.

degradation by a KEAP1-CUL3-RBX1 E3 ubiquitin ligase complex. During the pathophysiology of oxidative stress, or mutations occurred in Nrf2 or KEAP1/CUL3, the Nrf2 is not degraded, which in turn allows nuclear translocation and activation of antioxidant response element encompassing genes. Nrf2 is involved in iron metal metabolism, along with the detoxification system of the cell through glutathione synthesis, all of these play a crucial key role in the inhibition of ferroptosis. In the circulation (blood), Fe3+ is transported by Tf. Fe3+-Tf is bound by tfr1 and endocytosed. In the endosome, the acidic pH promotes detachment of Tfr and Fe3+. This is further reduced to Fe2+ by the activity of metalloreductase STEAP3. Fe2+ is further transported to the cytosol by divalent metal transporter 1 (DMT1), donating to the iron pool. FPN1 plays a role in exporting of Fe2+ out of the cell by incorporating it into iron-containing proteins or storing by ferritin as Fe3+. Ferritinophagy is the autophagic mechanism which regulates the degradation of ferritin through nuclear receptor coactivator 4 (NCOA4). The degradation of ferritin, results in the reduction of Fe3+ to Fe2+ by STEAP3 and eventually exported from the lysosome to the cytosol by DMT1 to contribute to the iron pool. Notably, the physiology of iron metabolism, storage, and transport, along with ferritinophagy are transcriptionally controlled by Nrf2 [6].

Both oxidative and nitrosative stress can unfavourably disturbs the mechanistic pathways and effective proteins regulating cellular iron homeostasis, like iron controlling protein/iron response element system, and can eventually be a basis of unusually high levels of iron and a cause of lethal levels of lipid membrane peroxidation. Moreover, neuroinflammation governs the upregulation of bivalent metal transporter-1 on the surface of astrocytes, microglia, and neurones, which make them extremely sensitive to excess iron in the occurrence of elevated levels of nontransferrin bound iron, therefore, initiation of iron mediated neuropathology occurs. Mechanisms regulating the iron homeostasis physiology and the effectiveness of ferritin and mitochondria are important. Negative regulation of ferroptosis by GSH, GPX4, the cystine/glutamate antiporter system, heat shock protein 27 and Nrf2 is crucial. The possible role of deglycase (DJ-1) inactivation in the reduction of ferroptotic cell death is simultaneously critical. Therapeutic approach in terms of coenzyme Q10, iron chelation therapy, deferiprone, deferoxamine (desferrioxamine) and deferasirox, and N-acetylcysteine is of high clinical importance [7].

### **3. Ferroptotic influence on the manifestation of neurological challenges**

Iron overload in cell (dysregulation of iron homeostasis) is contemplated to be a precarious situation for neurodegeneration. The current findings, emphasise β-amyloid, tau proteins, α-synuclein, and demyelination process connected to ferroptosis which induces neurodegeneration. The theory built on the possible role of dysregulation of iron homeostasis and ferroptosis in the pathophysiology of neurodegenerative diseases can be further supported by clinical experiments and epidemiological analyses [8].

Despite of the fact that ferroptosis was first defined in cancer cells, however, developing indications, include this cell death process with cerebral ischemia and brain haemorrhage also. Neonatal brain injury is a significant reason for the developmental damage and everlasting neurological insufficiencies. Different cell death processes, including iron-dependent ferroptotic pathways, have been identified for neonatal brain injury. Iron chelators and erythropoietin have been acknowledged as neuroprotective agents against neonatal brain injury. Generally, ferroptosis is principally defined through activators and inhibitors. Ferroptosis in adults are reported to generate ischemic and intraventricular haemorrhage-induced neuronal cell death. The inhibition of ferroptosis decreases the rate of neuronal death and behavioural abnormalities. Contemplating the recent paradigms in ferroptotic research, investigation on the relation between neonatal brain injury and ferroptosis should be considered seriously [9].

The propagation of ferroptosis incorporates the pathophysiology of autophagy as well as the inclusion of the activities of well-studied proteins such as Nrf2, p53 etc. The manifestation and regulatory molecular pathways of ferroptosis are constantly developing. There are indications that ferroptosis and its correlated genes may be concerned in a sequence of neural maturation, maintenance, and ageing physiology. In turn these genes can play a critical role in the pathophysiology of neurodegenerative diseases, neurological disorders, strokes, epilepsy, brain tumours etc. Investigating the incidence and expansion of ferroptosis in the brain tumours and endeavouring to stimulate tumour cell death with ferroptosis inducers are expected to collaborate with traditional tumour therapeutics and immunotherapy protocols. However, in the perspective of glioma treatment by endorsing ferroptosis, it is possible for the destruction of neuronal cells simultaneously, thus provoking the collective neurodegenerative diseases, stroke, and other neurological disorders, which will result to the similar indications in glioma patients [10].

In ferroptosis, a cloud of pharmacological modulators has been discovered considering the target proteins involved in iron homeostasis, in terms of origination and reduction of lipid peroxides or cystine import and GSH metabolism. Several machineries of the ferroptosis cascade are target genes of the transcription factor Nrf2, representing its analytical role in facilitating the ferroptotic reaction. Ferroptosis, is controlled by various cellular metabolic pathways. Research on the effect of ferroptotic cell death in inducing numerous neurological disorders has gained acceleration nowadays. Genetic regulation behind ferroptosis-induced neurological disorders and the probable functioning of ferroptosis in the development of brain is of serious concern. There are reports on 42 ferroptosis genes, which play crucial roles in the brain development and the gene co-expression system for the human dorsolateral prefrontal cortex development, where cluster of 22 genes actively participate. 12 genes out of these 22 genes are considered for the conservation of elementary cellular functions (non-transitional), which include RNA processing.

### *The "Irony" of Ferroptosis: A Review on Neurological Challenges DOI: http://dx.doi.org/10.5772/intechopen.108737*

The rest 10 genes with postnatal line are effective for the upgradation of patterns in neuron and glial cells. Stress affects the differential gene expression pattern during the process of brain development [11].

Cumulative substantiation designates a probable connection between neuroinflammation and neurological disorders, including AD, PD, HD, and stroke. Ferroptosis can possibly explain this connection. Research have shown that disorders of iron homeostasis, glutamate excitative toxicity, L-ROS, and some other factors related to ferroptosis can be detected in several neurological disorders which is caused by neuroinflammation. Convincing indication regarding the damage-associated molecular pattern molecules, like ROS, generated during the pathophysiological process of ferroptosis, trigger glial cells by stimulating neuroimmune pathways and then generate a sequence of inflammatory factors which initiate neurological disorders. Complicated biochemical reactions occur throughout ferroptosis. Activated microglia, reactive astrocytes, invasive T-cells, and overproduction of inflammatory molecules, establish the neuroinflammatory response. During the early phase, acute inflammatory responses cause trauma in the central nervous system, which can have a defensive role, restraining the strictness of the injury thus augmenting neuronal repair. If the acute inflammatory response does not decrease adequately, it will be directed into chronic inflammation which can be uncontrollable. In this situation, glial cells incline to intensify oxidative stress on neurons. Neuroinflammation is not essential during the early stage of neurological disorders, however, a constant inflammatory response can produce aggravation of the diseases. The detail pathophysiology of ferroptosis and its connection with neuroinflammation, have been understood in a rudimentary level. The practice of inhibitors of ferroptosis in investigational animal models can improve the rigorousness of the neural diseases. However, medications targeting ferroptosis can play a critical role in the medical treatment of chronic neuroinflammatory diseases. This needs rigorous clinical trials [12].

The active equilibrium of cardiomyocytes and neurons is vital to continue the normal physiological functions of heart and brain. If unnecessary cell death occurs in the tissues, severe cardio-cerebrovascular diseases (CCVD) like, hypertension, myocardial infarction, and ischemic stroke happens. The mechanistic regulation of cell death possesses a key role in endorsing these diseases. Worldwide, major mortalities and morbidities occur due to CCVDs. Excess of iron has been established to be a crucial element for pathogenic response in cardiocerebrovascular toxicity and manifest diverse CCVDs, thus ferroptosis, has received serious attention for its pathophysiology for CCVDs. Many studies have shown that ferroptosis occurs in atherosclerosis, heart failure, diabetic cardiomyopathy, hypertensive brain injury, ischemic stroke, and myocardial infarction. Inhibitors of ferroptosis may stop these diseases by inhibiting the ferroptotic pathway both in cardiac tissue and neurons. Cardio-cerebrovascular cell death is a central pathophysiological procedure and in fact, ferroptosis strikes throughout the CCVDs. However, in terms of abridged level of ferroptosis inhibitors (like GSH, GPX4, and Nrf2) and alterations in the gene expression levels, which are known to be expressed during CCVDs, the existing assays are not totally appropriate for predictable and routine clinical diagnosis. Damaged mitochondrial structure is an important feature of ferroptosis. Growing figure of inducers and inhibitors of ferroptosis have been showed. However, the best therapeutic agent among these inducers and inhibitors are still to known properly. Ferroptosis leads to pathophysiological alterations like inflammation and endoplasmic reticulum stress. However, it is a complex issue to explain the whole pathway across which ferroptosis works with the initiation of ischemia and hypoxia, iron discharges

through the upregulation of heme oxygenase 1 (Hmox1), thus stimulating ferroptosis, resulting in myocardial pathologic modification and myocardial cell damage. Heart failure enthused by enhancement of the iron pool resulting in the surplus iron and the incidence of ferroptosis, eventually which leads to myocardial edema, arrhythmia, and cardiomyocyte cell death [13].

Intracerebral haemorrhage (ICH) is another critical medical condition with high morbidity and mortality. Brain injury due to ICH is primarily recognised due to oxidative stress and haemoglobin lysate (which include iron), indicates unalterable harm to neurons. Therefore, ferroptosis has become a recent paradigm in neuronal cell death research after ICH [14].

The blood–brain barrier (BBB) is crucial in regulating the homeostasis within the CNS. Brain microvascular endothelial cells are effectively arrayed to make the vessel walls and have tight junction complexes that restrict the paracellular pathways of BBB. These walls effectively controls the movement of ions, molecules, and cells between the blood and the brain. This is extremely important for the protection of the neural tissues in the brain from hazardous toxins and pathogens. Primary damage due to the ill functioning of BBB can damage the tight junctions, transport proteins and leukocyte adhesion molecules, which can cause brain edema, imbalance in ion homeostasis, changed signalling pathways and immune infiltration, leading eventually to neuronal cell death. Several neurological disorders can happen due to BBB dysfunction. Ferroptosis can play a key role in BBB dysfunction [15].

Severe central nervous system (CNS) injuries, like stroke, traumatic brain injury, and spinal cord injury is a serious cause of concern for clinicians due to high morbidity and mortality. In fact, the therapeutic strategies for these diseases are not sufficient some time. Oxidative stress, neuroinflammation, excitotoxicity, and programmed cell death (including ferroptosis) plays crucial roles in the pathophysiology of acute CNS damages. Reports develop relations between acute CNS injuries and ferroptosis. Pharmaceutical agents, such as iron chelators, ferrostatin-1 (Fer-1), and liproxstatin-1 (Lip-1), can have inhibitory effect on the ferroptosis and may have neuroprotective capabilities even after acute CNS injuries. Till date, edaravone is the single approved medicine with accepted clinical effectiveness and safety for the CNS injury [16].

### **4. Conclusion**

Recent research on programmed cell death complemented by ferroptosis, is indicating to find novel theories on ferroptotic mechanism to design therapeutic protocols for ferroptosis-related neurological diseases. A medical perception is indeed necessary for the treatment strategy to combat the dysregulation of iron homeostasis and/or inhibition of ferroptosis to reduce the rate of neurodegenerative pathophysiology induced by ferroptosis. Our knowledge on ferroptosis is still at the base level. It is extremely important to depict a ferroptotic biomarkers for biomedical identification. Ferroptosis has distinctive process which has produced abundant chemotherapeutic potentials for treating cancers. The concrete pathophysiological implication of ferroptotic pathway, encompassing reasonable translational methods is still evolving. Growing data propose that the inhibition of ferroptosis may efficiently avoid neuronal diseases.

*The "Irony" of Ferroptosis: A Review on Neurological Challenges DOI: http://dx.doi.org/10.5772/intechopen.108737*

### **Author details**

Chayan Munshi1,2\* and Shelley Bhattacharya3

1 International Health Management Programme, Berlin School of Business and Innovation, Berlin, Germany

2 Ethophilia (An Autonomous Research Group), Santiniketan, India

3 Department of Zoology, Visva Bharati University, Santiniketan, India

\*Address all correspondence to: chayanbio@gmail.com

© 2022 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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[2] Forcina GC, Dixon SJ. GPX4 at the crossroads of lipid homeostasis and ferroptosis. Proteomics. 2019;**19**(18):1800311

[3] Yao MY, Liu T, Zhang L, Wang MJ, Yang Y, Gao J. Role of ferroptosis in neurological diseases. Neuroscience Letters. 2021;**747**:135614

[4] Ratan RR. The chemical biology of ferroptosis in the central nervous system. Cell Chemical Biology. 2020;**27**(5):479-498

[5] Li J, Jia B, Cheng Y, Song Y, Li Q, Luo C. Targeting molecular mediators of Ferroptosis and oxidative stress for neurological disorders. Oxidative Medicine and Cellular Longevity. 2022;**2022**:1-14

[6] Anandhan A, Dodson M, Schmidlin CJ, Liu P, Zhang DD. Breakdown of an ironclad defense system: The critical role of NRF2 in mediating ferroptosis. Cell Chemical Biology. 2020;**27**(4):436-447

[7] Morris G, Berk M, Carvalho AF, Maes M, Walker AJ, Puri BK. Why should neuroscientists worry about iron? The emerging role of ferroptosis in the pathophysiology of neuroprogressive diseases. Behavioural Brain Research. 2018;**341**:154-175

[8] Viktorinova A, Durfinova M. Mini-review: Is iron-mediated cell death (ferroptosis) an identical factor contributing to the pathogenesis of some neurodegenerative diseases? Neuroscience Letters. 2021;**745**:135627 [9] Wu Y, Song J, Wang Y, Wang X, Culmsee C, Zhu C. The potential role of ferroptosis in neonatal brain injury. Frontiers in Neuroscience. 2019;**13**:115

[10] Zhou Y, Lin W, Rao T, Zheng J, Zhang T, Zhang M, et al. Ferroptosis and its potential role in the nervous system diseases. Journal of Inflammation Research. 2022;**15**:1555

[11] Kim SW, Kim Y, Kim SE, An JY. Ferroptosis-related genes in neurodevelopment and central nervous system. Biology. 2021;**10**(1):35

[12] Cheng Y, Song Y, Chen H, Li Q, Gao Y, Lu G, et al. Ferroptosis mediated by lipid reactive oxygen species: A possible causal link of Neuroinflammation to neurological disorders. Oxidative Medicine and Cellular Longevity. 2021;**2021**

[13] Luo MY, Su JH, Gong SX, Liang N, Huang WQ , Chen W, et al. Ferroptosis: New dawn for overcoming the cardiocerebrovascular diseases. Frontiers in Cell and Developmental Biology. 2021;**9**:1-18

[14] Bai Q, Liu J, Wang G. Ferroptosis, a regulated neuronal cell death type after intracerebral hemorrhage. Frontiers in Cellular Neuroscience. 2020;**14**:591874

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[16] Shen L, Lin D, Li X, Wu H, Lenahan C, Pan Y, et al. Ferroptosis in acute central nervous system injuries: The future direction? Frontiers in Cell and Developmental Biology. 2020;**8**:594

### **Chapter 5**

## The Roles of Iron and Ferroptosis in Human Chronic Diseases

*Yanbo Shi, Junyong Zhang, Kaitao Luo, Sunfeng Pan, Hanqiang Shi, Lie Xiong and Shuqin Du*

### **Abstract**

Ferroptosis, an iron-dependent novel type of cell death, has been characterized as an excessive accumulation of lipid peroxides and reactive oxygen species. A growing number of studies demonstrate that ferroptosis not only plays an important role in the pathogenesis and progression of chronic diseases, but also functions differently in different diseases. As a double-edged sword, activation of ferroptosis could potently inhibit tumor growth and increase sensitivity to chemotherapy and immunotherapy in various cancer settings. Therefore, the development of more efficacious ferroptosis agonists or inhibitors remains the mainstay of ferroptosis-targeting strategy for cancer therapeutics or cardiovascular and cerebrovascular diseases and neurodegenerative diseases therapeutics.

**Keywords:** iron metabolism disorder, ferroptosis, tumor, neurodegeneration, vascular diseases

### **1. Introduction**

Chronic diseases are non-infectious, of long duration, and are persistent diseases. These diseases mainly include cardiovascular and cerebrovascular diseases, tumors, diabetes, and chronic respiratory diseases, etc. According to the statistics of WHO, approximately 41 million people worldwide die of chronic diseases, accounting for 73.6% of all deaths in 2021 [1]. The occurrence and development of chronic diseases are not only complicated in pathological mechanisms, but also affected by many factors such as genetics, understanding of the molecular mechanisms underlying the pathogenesis of chronic diseases is helpful for diagnosis and treatment. In 2012, a new way of cell death, ferroptosis, was discovered and reported, to some extent, the discovery is a milestone in the study of cell death; it provides a new perspective to study the occurrence, development, and prevention of chronic diseases.

As an essential trace element, iron is present in nearly all forms of life and involved in various of biological processes, including respiration, oxygen transport, intermediary metabolism, gene regulation, and nucleotide synthesis and repair [2, 3]. However, dysregulated iron homeostasis leads to common hematological, metabolic, and neurodegenerative diseases.

### *Cell Death and Disease*

Ferroptosis is an iron-dependent cell death, it is different from apoptosis, pyroptosis, or necrosis in morphology, genetics, metabolism, and molecular biology [4]. The morphology is mainly manifested as mitochondrial swelling, increased membrane density, smaller volume, decreased number of cristae, increased lamellar phenotype, and increased autophagosomes, etc. Molecular biology is mainly manifested as glutathione (glutathione, GSH) depletion or inactivation of glutathione peroxidases (GPX4), increased intracellular free iron content, and increased production of reactive oxygen species (ROS), etc., ultimately manifested as the accumulation of toxic lipid hydroperoxides in cells [4]. Its main characteristics are excessive accumulation of lipid peroxides and reactive oxygen species [5]. Since the production of toxic lipid hydroperoxides mostly depends on ferrous iron, and specific iron chelators can inhibit iron-disturbance-mediated ferroptosis. Therefore, iron metabolism and lipid peroxidation play an important regulating role in ferroptosis pathways [6, 7], the possible molecular mechanism is shown in **Figure 1**.

Ferric ions in the circulation are bound to transferrin and transported into the cells through transferrin receptor 1 (TFR1), which is located on the cell membrane. After being reduced to divalent iron in the cell, ferric iron is transported by divalent metal transport1 (DMT1) and released into the cytoplasmic iron pool, excess iron is stored

**Figure 1.** *Molecular mechanism of ferroptosis.*

### *The Roles of Iron and Ferroptosis in Human Chronic Diseases DOI: http://dx.doi.org/10.5772/intechopen.108790*

in ferritin. Some studies showed that ferritin selective autophagy promotes ferritin getting into autophagosomes through the nuclear receptor co-activator 4 pathway and results in the releasing of free iron [8].

Generally, it is believed that excess iron causes ferroptosis mainly through reactive oxygen species produced by the Fenton reaction, application of iron chelators can effectively inhibit ferroptosis [10]. Lipid peroxides play the role of agents in the process of ferroptosis, phosphatidyl ethanolamine (PE) is the substrate of choice for lipid oxidation. Therefore, hydrogen peroxide-PE (OOH-PE) is considered to be the main signal of ferroptosis [9]. In the process of lipid peroxidation accumulation, NADPH oxidase, lipoxygenase, Acyl-CoA long-chain family member 4(ACSL4), and lysophosphatidyl cholinyltransferase 3 may play important roles in the occurrence and development of ferroptosis [10–12]. The commonly used ferroptosis inhibitors ferrostatin-1(Fer-1), liproxstatin-1(Lip-1), and small-molecule compounds such as vitamin E inhibit ferroptosis mainly by scavenging lipid peroxides [13].

Glutathione peroxidase 4 (GPX4) is a crucial enzyme in the regulation of ferroptosis; it catalyzes the reduction of lipid peroxides, converts OOH-PE into OH-PE, further suppressing the occurrence of ferroptosis [14]. Small-molecule compounds such as RSL3 and ML162 can inhibit GPX4 activity, lead to the accumulation of fatty acid free radicals, eventually lead to ferroptosis. Reduced glutathione is coenzyme factor of GPX4, the rate-limiting step in its synthesis is the absorption of cystine [15]. Cystine/glutamate transporter consists of the membrane transporters solute carrier family 7 members of 11 (SLC7A11) and regulatory proteins across the membrane of solute carrier family 3 member 2 (SLC3A2); it can transport cystine into the cell and excrete the same amount of glutamate at the same time [16], serves as an important regulator of ferroptosis. Small molecules such as erastin can inhibit glutamic acid/cystine reverse transporter, causing ferroptosis. Wang lab first reported that gene Slc7a11 knockout can promote the occurrence of ferroptosis in mice [17]. Additionally, a novel ferroptosis inhibiting factor 1 (FSP1) was discovered independently in two labs recently, in their studies, NADPH was used to reduce ubiquinone (CoQ10) to ubiquinol (CoQ10H2), leading to the reduction of lipid peroxidation of cell membranes, thereby inhibiting ferroptosis [18, 19]; these findings provide an important basis of developing drugs targeting ferroptosis.

Although the specific mechanisms of ferroptosis are not fully clarified, with the deepening of the research, researchers gradually found that ferroptosis plays an important role in the development of major chronic diseases [20]. So far, a growing evidence showed that ferroptosis is involved in the pathophysiological process of neurodegenerative diseases, tumors, ischemia–reperfusion injury, kidney injury, and other diseases; recent studies have found that ferroptosis plays an important role in cardiovascular disease. Here, we summarized the latest research progress of ferroptosis in cancer, neurodegenerative diseases, and cerebrovascular diseases, to provide new ideas and strategies for the prevention and treatment of major chronic diseases.

### **2. Ferroptosis and tumor**

Tumor cells can proliferate by avoiding cell death, and apoptosis, necrosis, autophagy also played important roles in the development of tumor. In **Table 1**, we summarized the latest research progress of molecular mechanism studies on ferroptosis in common tumors, to provide a series of potential new targets for tumor prevention and control.


### **Table 1.**

*Ferroptosis in cancer.*

### **2.1 Ferroptosis and hepatocellular carcinoma (HCC)**

Targeting ferroptosis is a potential mechanism in the treatment of hepatocellular carcinoma (HCC) [21]. Retinoblastoma (Rb)-deficient cancer cells are more sensitive to ferroptosis induced by sorafenib [22], it is likely that it enhances the oxidative stress response by affecting the concentration of reactive oxygen species in mitochondria. Furthermore, Sun et al. found that nuclear factor E2–related factor 2 (NRF2) protects hepatocellular cancer cells from ferroptosis induced with sorafenib, indicating that targeting p62-Keapl-NRF2 pathway may overcome sorafenib resistance in

hepatocellular carcinoma cells [23–26]. Additionally, NRF2 also induces expression of metallothionein1G (MT-1G), an important negative regulator of ferroptosis, through the cythionase pathway, leading to sorafenib resistance in cancer cells [27]. CDGSH [Fe-S]-containing domain 1 can protect the mitochondria from ferroptosis in hepatocellular cancer cells and can be upregulated by erastin in an iron-dependent manner [28]. Moreover, p53S47 mutation carried by hepatocellular carcinomas causes ferroptosis tolerance by inhibiting ASCL4 [28].

In hepatocellular carcinoma, the expression of ferroptosis-related genes is related to the prognosis of patients, the mRNA expression levels of *SLC7A11* in HCC tissues and adjacent normal tissues were compared between 130 cases of hepatocellular carcinoma (HCC) tissues and adjacent normal tissues by Kinoshita et al. [29], it showed that the expression of *SLC7A11* in HCC tissues was significantly higher than that in normal tissues, the survival time and disease-free survival time of liver cancer patients were significantly shorter than those of *SLC7A11* low expression of hepatocellular carcinoma patients. In addition, in the process of sorafenib treatment of hepatocellular carcinoma patients, the high expression of Rb and MT1 is also associated with the poor prognosis of patients [22, 27].

### **2.2 Ferroptosis and pancreatic cancer**

The main mechanism of pancreatic cancer is that mutated KRAS gene reprograms pancreatic ductal adenocarcinoma (PDAC) cells to a state that is highly resistant to apoptosis. Artesunate can induce tumor cell apoptosis by generating reactive oxygen species [30]. Eling et al. found that artesunate can induce ferroptosis in PDAC cells with KRAS mutations and the process can be effectively inhibited by Fer-1 [31]. Yamaguchi et al. found that the natural product piperamide can induce ferroptosis in tumor cells by promoting the generation of reactive oxygen species, and its antitumor effect can be inhibited by antioxidants, ferroptosis inhibitors, and iron chelators [32]. The combined use of piperamide, Cotylenin A (a plant growth regulator), and sulfasalazine has a good synergistic effect on pancreatic cancer. These results suggest that ferroptosis inducers are expected to be used in the treatment of pancreatic cancer.

### **2.3 Ferroptosis and renal cell carcinoma**

Renal cell carcinoma originates from the renal parenchyma urothelial system and is a highly malignant tumor in the urinary system. Yang et al. [33] found that GPX4 is a key regulator of the ferroptosis signaling pathway in clear cell renal cell carcinoma. When compared with the other tumor cell from other tissues (lung cancer, colon cancer, central nervous system, melanoma, ovarian cancer, breast cancer, and leukemia), renal cells were more sensitive to ferroptosis induced with inhibition of GPX4. Renal cancer cells are induced by the hepatocyte factor -1β-1-acylglycerol-3 phosphate oxyacyltransferase 3 (AGPAT3) axis and the HIF-2α-HILPDA pathway, which can induce polyunsaturated fatty acyl lipid–enriched cells state, thereby increasing its susceptibility to ferroptosis [34]. Recently, Yang et al. [35] found that the sensitivity of renal cancer cells to ferroptosis is regulated by cell density and transcriptional regulator 1 (TAZ)-TAZ regulation of epidermal membrane protein 1 (EMP1)/NOX4 pathway [34, 35], suggesting that TAZ is a potential therapeutic target for ferroptosis.

### **2.4 Ferroptosis and breast cancer**

Breast cancer is derived from breast epithelial tissue. Ma et al. [36] found that the lysosomal interfering agent siramesine and the tyrosine kinase inhibitor lapatinib can disrupt the iron homeostasis in breast cancer cells to generate reactive oxygen species and induce cell ferroptosis, and overexpression of trasnferrin receptor 1 (TfR1) or iron chelators can reduce siramesine and lapatinib-induced reactive oxygen species.

Some studies have shown that the formation of a complex between mucin 1C subunit and SLC7A11 can upregulate the expression of reduced glutathione and inhibit ferroptosis in triple-negative breast cancer cells [37]. Timmerman et al. [38] found a subpopulation of glutamine auxotrophic triple-negative breast cancer cells that were highly dependent on SLC7A11 acquires cystine for glutamine metabolism. The SLC7A11 inhibitor sulfasalazine can inhibit tumor growth by promoting ferroptosis. In addition, the activities of SLC7A11 and glutamate/cystine antiporter can be regulated by the Keap1/NRF2 redox pathway. Lanzardo et al. [39] believed that SLC7A11 is closely related to drug resistance and metastasis of triple-negative breast cancer cells. The increased expression of TFR1 in breast cancer cells is negatively correlated with the expression of estrogen receptor, and the high expression of TFR1 in breast cancer tissue is associated with poor prognosis of patients [40, 41].

### **2.5 Ferroptosis and bladder tumors**

Intracellular iron concentration is closely related to the progression of bladder tumors. Martin-Sanchez et al. [42] analyzed the relationship between intracellular iron concentration and bladder tumor proliferation and found that when transferrin combined with iron, the free iron decreased in tumor cells, which was conducive to the proliferation of bladder cancer cells. When the application of gallium (Ga) to transferrin interferes with the binding of iron to transferrin, the intracellular free iron increases and thus inhibits the proliferation of bladder tumor cells. Mazdak et al. [43] found that the serum iron level of patients with bladder tumors was significantly lower than that of the normal control group, suggesting that the decreased serum iron level may be an important reason for the occurrence of bladder tumors. Tang et al. [44] proposed the phenomenon of ferritin phagocytosis, which releases intracellular free iron through ferritin and increases the content of intracellular free iron, which may play a role in inhibiting bladder tumors. The results suggest that activating ferroptosis can achieve ideal therapeutic effect on bladder tumors. These studies suggest that increasing intracellular iron concentration may help to inhibit bladder tumor progression.

### **2.6 Tumor-associated ferroptosis regulatory protein**

### *2.6.1 SLC7A11 regulates ferroptosis*

SLC7A11(also known as xCT) is the substrate-specific subunit of System Xc<sup>−</sup> responsible for the transport of cystine from the extracellular to the intracellular. The nuclear factor erythroid-like 2 (Nrf2) and transcription factor 4 (activating factor 4, ATF4) can induce SLC7A11 expression when cells are in a state of oxidative stress and L-cysteine deficiency [45]. Studies have found that SLC7A11 is highly expressed in tumor tissues, and that high expression of SLC7A11 can inhibit ROS-induced ferroptosis. p53 leads to cystine deficiency by inhibiting the expression of SLC7A11, which in turn increases the sensitivity to ferroptosis. Importantly, the survival and

proliferation of SLC7A11-overexpressing cancer cells are dependent on glucose, such tumors may be sensitive to glucose-blocking drugs, also suggesting a role for SLC7A11 in modulating nutrient dependence and demonstrating another therapeutic strategy for tumors with high SLC7A11 expression [46].

### *2.6.2 p53 regulates ferroptosis*

p53 is a widely recognized tumor suppressor that can induce senescence and programmed cell death in human cancer. It can affect ferroptosis of tumor cells through transcriptional or posttranslational mechanisms. Also, it can inhibit tumors by regulating cell cycle arrest, apoptosis, or premature aging.

Increasing the stability of wild-type p53 can promote the expression of its transcriptional target gene CDKN1A (encoding p21 protein), which can increase the intracellular glutathione level, inhibit the accumulation of ROS, and negatively regulate ferroptosis of cancer cells. Acetylation-deficient p53 increased the sensitivity of tumor cells to ferroptosis by inhibiting *SLC7A11* expression and System Xc− function.

Jiang et al. [47] found that three lysines in the DNA-binding domain of p53 were mutated to arginine (K117/161/162R, namely p533KR), p533KR can further restrict cystine uptake by inhibiting SLC7A11 gene transcription, make tumor cells more sensitive to oxidative stress-induced ferroptosis. Wang et al. [48] found that the site K98 in the DNA-binding domain of p53 is particularly important for the regulation of SLC7A11. Additionally, the mutant S47 of p53 fails to inhibit the transcription of SLC7A11 and induces ferroptosis resistance in hepatocellular carcinoma cells, increasing the risk of cancer in mice [49]. Moreover, p53 can make colon cancer cells insensitive to ferroptosis by inhibiting dipeptidyl peptidase 4 activity [50].

### *2.6.3 NRF2 regulates ferroptosis*

NRF2 is an important transcriptional regulator in oxidative reactions [51], and its overexpression can inhibit apoptosis and lead to drug resistance in some tumors [52]. NRF2 plays an important role in protecting hepatocellular carcinoma cells from ferroptosis [22]. After treatment of hepatocellular carcinoma cells with Erastin and Sorafenib, p62 inhibits the degradation of NRF2 and induces NRF2 accumulation in the nucleus through the inactivation of Keap1, thereby regulating downstream gene transcription. Inhibition of NRF2 by the alkaloid trigonelline can induce ferroptosis in hepatocellular carcinoma cells, and combined use with chemotherapeutic drugs has the application prospect of overcoming tumor drug resistance [22]. Thus, activation of the p62-Keap1-NRF2 pathway can activate ferroptosis to reverse tumor chemotherapeutic drug resistance.

### *2.6.4 ACSL4 regulates ferroptosis*

ACSL4 is expressed on the mitochondrial outer membrane and endoplasmic reticulum and can convert long-chain fatty acids into fatty acyl-CoA, which plays an important role in lipid biosynthesis and fatty acid degradation. ACSL4 increases the sensitivity of cells to ferroptosis by accumulating long-chain polyunsaturated ω-6 fatty acids in the cell membrane [10]. Studies have shown that in basal-like breast cancer cell lines, liver cancer cells, leukemia cells, and prostate cancer cells, the expression level of ACSL4 can be used to predict the sensitivity of tumor cells to ferroptosis [10, 28, 52]. The results suggest that ACSL4 is expected to be a potential target and biological marker for targeting ferroptosis in tumor therapy.

### *2.6.5 GPX4*

Glutathione peroxidase 4 (GPX4) is the only glutathione peroxidase that can use glutathione as the electron donor to reduce the toxic lipid hydroperoxides in biofilms to corresponding alcohols. Tumor cells with high GPX4 show impaired proliferation, decreased proliferation, and inhibition of angiogenesis. Overexpression of GPX4 in hepatocellular carcinoma cells can inhibit the formation and development of hepatocellular carcinoma by decreasing ROS level, increasing glutathione and decreasing the formation of the cytokine-cytokine IL-8, inhibiting cell cycle progression and cell migration [53]. Based on the clinicopathological study and in vitro cell death analysis, it was found that overexposure to GPX4 in diffuse large B-cell lymphoma (DLBCL) inhibited ROS-induced ferroptosis [54]. GPX4 is a major target molecule for ferroptosis inducers such as erastin and RSL3. Erastin inhibits GPX4 activity by depleting glutathione, whereas RSL3 can directly inhibit GPX4 activity. In addition, previous studies have demonstrated that GPX4 can induce ferroptosis in mouse tumor xenograft models [33].

### *2.6.6 FSP1 inhibits ferroptosis*

FSP1 inhibits ferroptosis FSP1 was originally named mitochondrial apoptosisinducing factor 2 (AIFM2), as the newly discovered GPX4-independent ferroptosis inhibitor, and its expression is closely related to the sensitivity of tumor cells to ferroptosis. Recently, Doll's group and Bersuker's group simultaneously screened independently and found that FSP1 levels are different in different cell lines, and the resistance level of various tumor cell lines to ferroptosis was positively correlated with the FSP1 level, which results in differences in the sensitivity of different tumor cell lines to ferroptosis [18, 19]. Additionally, it was also reported that FSP1 was a novel KEAP1/NRF2 target gene regulating ferroptosis and radioresistance in lung cancers [55]. These achievements provide important evidences for the development of drug-targeted ferroptosis in tumors.

### **3. Ferroptosis and neurodegenerative diseases**

Iron homeostasis is critical for brain and neural development and cognitive function, especially in the fetal or early neonatal period, iron deficiency can severely affect neurodevelopment, leading to impaired memory and learning [56]. Iron accumulates gradually in the brain with age, and accumulation studies have shown that iron accumulation is related to neurodegenerative diseases such as Alzheimer's disease, Parkinson's disease, and amyotrophic lateral sclerosis [57]. In recent years, studies have found that there are main characteristics of ferroptosis such as increased lipid peroxidation, decreased glutathione, and GPX4 inhibition in neurodegenerative diseases and cognitive impairment. The use of ferroptosis inhibitors can effectively protect neurons and improve cognitive function. Related research progress is shown in **Table 2**.

### **3.1 Ferroptosis and Alzheimer's disease**

Patients with Alzheimer's disease possess destabilization of metal metabolism, inflammatory response, oxidative stress, abnormal mitochondrial function, and impaired glial function [57, 58]. Studies have shown that iron accumulation in the


### **Table 2.**

*Ferroptosis in neurodegenerative diseases.*

brain is associated with the formation of senile plaques and neurofibrillary tangles, elevated iron levels in the brain increase the risk of Alzheimer's disease, and ferritin levels in cerebrospinal fluid predict the progression from mild cognitive impairment to Alzheimer's disease [59–61]. The chronic inflammation, neuronal degeneration, and lack of downstream apoptosis indicators associated with Alzheimer's disease suggest the existence of other cell death manners such as ferroptosis in Alzheimer's disease [62–64].

An investigation on the Gpx4-specific knockout mice in cerebral cortex and hippocampal neurons exhibited cognitive decline and degeneration of hippocampal neurons in the water maze test, after feeding with a vitamin-E-rich diet or Lip-1, the neuronal degeneration of the mice was significantly alleviated, suggesting that ferroptosis plays an important role in neuronal degeneration [62]. Another study found that overexpression or hyperphosphorylation of tau protein can induce ferroptosis in neurons, while α-lipoic acid can rescue neurons by downregulating TfR1, reducing p38 phosphorylation level, and upregulating the expression of Slc7a11 and Gpx4 [63]. In addition, feeding with a deuterated polyunsaturated fatty acid in a mouse model of Alzheimer's disease can alleviate the lipid peroxidation of tissues and reduces β-amyloid deposition [64, 65].

### **3.2 Ferroptosis and Parkinson's disease**

An important feature of Parkinson's disease is iron accumulation in neurons and substantia nigra glia, and the concentration of iron accumulation is positively correlated with disease severity [66, 67]. Significant changes in iron regulatory protein 1(IRP1), divalent metal transporter 1(DMT1), and other key proteins involved in iron homeostasis have been observed in Parkinson's disease patients and mouse models [68–72]. The τ knockout mice developed parkinsonism with iron accumulation in the nigra, which can be inhibited by iron chelators [73–75]. In addition to elevated iron

levels in the substantia nigra pars compactus, parkinsonism is also characterized by ferroptosis, such as reduced glutathione depletion and lipid peroxidation [76], iron chelators and N-acetylcystine can alleviate and improve some of the symptoms in patients and mouse model of Parkinson's disease [77, 78], suggesting that ferroptosis may be involved in the occurrence and development of Parkinson's disease.

Do Van et al. [79] found that dopaminergic neurons' ferroptosis occurred in LUHMES cell lines, brain tissue slices cultured *in vitro*, and 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced Parkinson's disease models. However, the use of Fer-1, Lip-1, and iron chelators can alleviate or reverse the symptoms of Parkinson's disease. Gouel et al. [80] found that human platelet lysate can make LUHMES cells resistant to Earstin-induced neuronal ferroptosis. In addition, astrocytes have a strong iron storage capacity, which prevent iron overload in neurons [81]. Astrocytes provide neurons with glutathione S-transferase Mu2 (GSTM2) and other antioxidant factors to protect neurons from oxidative damage. In conclusion, the dysregulation of the interaction between astrocytes and neurons may lead to ferroptosis in dopaminergic neurons [82, 83].

### **3.3 Ferroptosis and amyotrophic lateral sclerosis**

Iron accumulation occurred in the brain of amyotrophic lateral sclerosis model mice [84–86], and the therapeutic effect of iron chelators confirms the role of iron in the pathogenesis of amyotrophic lateral sclerosis. Patients with amyotrophic lateral sclerosis have increased lipid peroxidation in cerebrospinal fluid and plasma and decreased levels of reduced glutathione in the motor cortex, suggesting the possibility of ferroptosis occurrence [87, 88]. Knockout of Gpx4 in mouse neurons can cause symptoms of amyotrophic lateral sclerosis, mainly characterized by rapid paralysis, severe muscle atrophy, and death, which is related to ferroptosis of spinal motor neurons [62]. However, no significant neurodegeneration was observed in the cortex of neuronal Gpx4-inducible knockout and other Gpx4-selective cortical neuron knockout mouse models. It is suggested that Gpx4 plays an important role in the process of ferroptosis of spinal motor neurons [62].

### **4. Ferroptosis and cardiovascular disease**

Cardiomyocyte and neuron death in cardiovascular and cerebrovascular diseases are related to a variety of cell death manners, and ferroptosis is also involved. The relevant research progress is shown in **Table 3**.

### **4.1 Ferroptosis and cardiovascular disease**

In some pathological conditions, the heart exhibits excessive accumulation of iron, production of reactive oxygen species, and pathological transformation of membrane lipids, which are all important factors that constitute ferroptosis. So far, there are few studies directly linking ferroptosis with cardiovascular disease. The latest research results of the Wang group in 2019 revealed the important role of ferroptosis in cardiomyopathy and ischemia–reperfusion-induced cardiac injury for the first time [89]. This landmark discovery provides a new strategy for the prevention and treatment of cardiomyopathy and other heart diseases.


### **Table 3.**

*Ferroptosis in cardiovascular and cerebrovascular diseases.*

### *4.1.1 Ferroptosis is involved in tissue and organ induced by ischemia: reperfusion damage*

During cardiac ischemia–reperfusion, excess reactive oxygen species, lipid peroxidation, and iron accumulation caused by the release of iron in heme will be produced [90–92]. Gao et al. [93] established an isolated mouse cardiac ischemia–reperfusion model and found that inhibiting glutamine metabolism could inhibit ferroptosis, thereby reducing cardiac injury. Fang et al. [89] established an in vivo myocardial ischemia–reperfusion model and found that Fer-1 and iron chelators can significantly reduce the acute and chronic cardiac injury of ischemia–reperfusion, confirming the role of ferroptosis in cardiac ischemia–reperfusion injury. In addition, ferroptosis is also involved in ischemia–reperfusion injury in the kidney [94] and liver [95].

### *4.1.2 Ferroptosis is involved in antitumor drug-induced myocardial injury*

As a broad-spectrum antitumor drug, adriamycin was limited in clinical use due to its cardiotoxicity. Autophagy, apoptosis, necrosis, and other cell death type are involved in the myocardial injury caused by adriamycin [96–98]. Fang et al. [89] found that ferroptosis occurred in cardiomyopathy induced by doxorubicin in mice deficient in apoptosis and proposed that heme oxygenase 1 (HO-1) may be a key

regulator in this procedure. They also found that iron accumulation and lipid peroxidation in cardiomyocytes occur in mitochondria and the mitochondria-targeting antioxidant MitoTEMPO can effectively inhibit ferroptosis and protect the heart.

### *4.1.3 Ferroptosis is involved in myocardial injury after heart transplantation*

In Li's studies [99], it was found that the recruitment of neutrophils after heart transplantation is regulated by ferroptosis. The donor heart can induce ferroptosis in cardiomyocytes due to ischemia, hypoxia, and other reasons after transplantation, and the cellular contents are released and recruit neutrophils to produce necrotic inflachannelled by TLR4 / Trif/type I interflammatory via TLR/Trif/type I interferon pathway. Fer-1 can reduce arachidyl phosphatidylethanolamine after heart transplantation and decreased cardiomyocyte death and neutrophil recruitment.

### *4.1.4 Ferroptosis and diabetic cardiomyopathy*

In diabetes, persistent high blood glucose and insulin resistance can cause a vicious circle by altering cellular metabolism, promoting the accumulation of peroxidation and the death of cells. So far, diabetes has been verified to be associated with abnormal iron metabolism. For example, systemic iron overload can contribute to abnormal glucose metabolism and the onset of type 2 diabetes (T2DM) [100] and aggravate insulin resistance [101]. Recently, Cai group [102] identified the role of ferroptosis in DCM and reported that Nrf2 activation by sulforaphane inhibited ferroptosis and prevented DCM, suggesting that it is feasible to treat DCM by inhibiting ferroptosis. Due to the limited regenerative capacity of the myocardium in mammalian adult hearts, inhibition of cardiomyocyte death might be one of the important ways to alleviate DCM [103]. In our studies, we induced DCM models in diabetic C57BL6 mice and treated with canagliflozin and found that canagliflozin mitigates ferroptosis and improves myocardial oxidative stress in mice with diabetic cardiomyopathy [104]. Taken together, taking ferroptosis as the starting point may provide a new strategy for the prevention and control of DCM.

### **4.2 Ferroptosis and cerebrovascular disease**

Both ischemic stroke and hemorrhagic stroke can lead to neuronal ferroptosis [105, 106].

### *4.2.1 Ferroptosis and ischemic stroke*

Before the discovery of ferroptosis, iron accumulation in clinical and animal models of ischemic stroke has been shown to aggravate neuronal damage during reperfusion [107–110]. Iron chelators can reduce the risk of post-ischemic stroke in experimental animals [111–114]. Speer et al. [115] proposed that ferroptosis leads to neuronal death after cerebral ischemia, and hypoxia-inducible factor prolyl hydroxylase may be the target for the beneficial effects of iron chelators. Inhibition of ferroptosis in a mouse model can protect neurons from ischemia–reperfusion injury [105].

### *4.2.2 Ferroptosis and hemorrhagic stroke*

Chang et al. [116] found that epicatechin could alleviate early brain injury in hemorrhagic stroke by reducing cerebral iron accumulation and ferroptosis-related

### *The Roles of Iron and Ferroptosis in Human Chronic Diseases DOI: http://dx.doi.org/10.5772/intechopen.108790*

protein expression. Later, they found that Fer-1 could alleviate hemoglobin-induced brain injury. Cell death in slices and alleviation of neuronal death in a mouse model of collagenase-induced hemorrhagic stroke [117]. At the same time, Zille et al. [118] found that ferroptosis inhibitors such as Fer-1 and deferoxamine can inhibit the production of ferroptosis in mice. The expression level of Gpx4 in rats with acute hemorrhagic stroke decreased sharply, and increasing the level of Gpx4 could avoid secondary ferroptosis injury in neurons and improve the prognosis of hemorrhagic stroke [119]. Therefore, the ferroptosis pathway may be involved in the process of neuronal death in stroke, and it is speculated that targeted inhibition of ferroptosis may be an effective treatment for alleviating stroke.

### **5. Conclusion**

Besides tumors, neurodegenerative diseases, cardiovascular and cerebrovascular diseases, ferroptosis has also been reported in liver diseases such as non-alcoholic fatty liver disease and non-alcoholic steatohepatitis [120–124].

ROS-induced ferroptosis can inhibit tumor growth and increase the sensitivity of tumor cells to chemotherapy and radiotherapy. Contrary to tumor treatment strategies, ferroptosis can promote the occurrence and development of neurodegenerative diseases and cardiovascular and cerebrovascular diseases. Therefore, relevant translational medicine research mainly focuses on the discovery of small molecules that can effectively inhibit ferroptosis. These small-molecule activators targeting ferroptosis can be used directly as chemotherapeutics, or as chemosensitizers in combination with chemotherapeutics. However, ferroptosis is complex in different types of tumors and different gene mutations (such as p53 or RAS mutations), and its feasibility in preclinical and clinical research needs to be further studied. Notably, the discovery of GPX4 pathway-independent FSP1 and the discovery of new mechanisms and targets such as CD8+ T cells inducing ferroptosis in tumor cells through the release of interferon-gamma [18, 19, 125], it provides a new perspectives and strategy for tumor treatment and drug discovery.

Iron accumulation and ferroptosis in the brain and nerve tissue have been proved to be closely related to Alzheimer's disease and Parkinson's disease. There is a direct relationship between the pathogenesis of various neurodegenerative diseases such as Parkinson's disease and amyotrophic lateral sclerosis. At present, various clinical trials using iron chelators to treat neurodegenerative diseases are emerging, but there is still no effective treatment for stroke. Given the important role of ferroptosis in neuronal death after stroke, effective inhibition of ferroptosis is expected to provide a new strategy for preventing neuronal death caused by stroke.

Similar to the pathogenesis of neurodegenerative diseases, many cardiac diseases share common ferroptosis features, such as iron overload, oxidative stress, endoplasmic reticulum stress, and mitochondrial dysfunction. Previous studies by the author's team suggest that ferroptosis inhibitors can effectively prevent and treat cardiomyopathy and heart failure induced by myocardial cell iron overload, doxorubicin-induced cardiotoxicity, and cardiac ischemia–reperfusion [89]. Five different approaches, including ferroptosis inhibitors, iron chelators, mitochondria-specific antioxidants, heme oxygenase 1 inhibitors, and low-iron diets, can effectively prevent ferroptosis in cardiomyocytes, thereby protecting the heart. And these ferroptosis inhibitors are relatively safe and feasible in mice. It provides an optimistic prospect for clinical translational research on targeting ferroptosis to prevent and treat heart disease [121, 126, 127].

With a view to clinical translation, here are some issues need to be considered, e.g., which disease or tumor needs to be considered for ferroptosis-targeted therapies? In clinical or preclinical experiments, drugs targeting ferroptosis need high tissue-organ specificity and fewer adverse reactions, and nano-targeted drug delivery systems have shown some advantages [128, 129]. Although there is a growing awareness of ferroptosis, some key scientific questions related to ferroptosis still need to be resolved, such as what are the key executive molecules in ferroptosis? To what extent is lipid peroxidation related to ferroptosis? Does ferroptosis exist in physiological processes? Is ferroptosis conservative in the evolutionary process? We are well aware of the long road ahead. With the deepening and expansion of ferroptosis-related research, we believe that it will provide a basis for the clinical translation of targeting ferroptosis to prevent and treat major chronic diseases.

### **Acknowledgements**

This work was supported by grants from Medicine and Health Science and Technology Plan Projects of Zhejiang Province (YS, 2020PY029), Science and Technology Innovation Special Project of Jiaxing Science and Technology Bureau (YS, 2020AY30003), Zhejiang Provincial Health Science and Technology Program of Traditional Chinese Medicine (YS, 2021ZB283), Zhejiang Basic Public Welfare Research Program (YS, LGF18H200004), and Jiaxing Key Laboratory of Diabetic Angiopathy.

### **Conflict of interest**

The authors declare no conflict of interest.

### **Author details**

Yanbo Shi1 \*, Junyong Zhang2 , Kaitao Luo3 , Sunfeng Pan4 , Hanqiang Shi5 , Lie Xiong<sup>5</sup> and Shuqin Du6

1 Central Laboratory of Molecular Medicine Center, Zhejiang Chinese Medical University Affiliated Jiaxing Traditional Chinese Medicine Hospital, Jiaxing Key Laboratory of Diabetic Angiopathy Research, Zhejiang, China

2 College of Biological, Chemical Sciences and Engineering, Jiaxing University, Zhejiang, China

3 Jiaxing Key Laboratory of Integrative Rehabilitation of Cerebrovascular Disease, Zhejiang Chinese Medical University Affiliated Jiaxing Traditional Chinese Medicine Hospital, Zhejiang, China

4 Department of Burns and Plastic Surgery, Zhejiang Chinese Medical University Affiliated Jiaxing Traditional Chinese Medicine Hospital, Jiaxing Key Laboratory of Diabetic Angiopathy Research, Jiaxing Burn and Wound Repair Therapy Center, Zhejiang, China

5 Central Laboratory of Molecular Medicine Center, Jiaxing Traditional Chinese Medicine Hospital, Jiaxing Key Laboratory of Diabetic Angiopathy Research, Jiaxing, Zhejiang, China

6 School of Pharmacy, Zhejiang University of Technology, Hangzhou, China

\*Address all correspondence to: shiyanbocas@163.com

© 2022 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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