**2.4 Cardiomyopathy**

*Advances in Precision Medicine Oncology*

lead to the glomerulosclerosis [23].

tion based on the genetic makeup of the individual.

in the brain cells and further led to cause cell damage.

**2.3 Neurotoxicity**

epithelial degeneration occurs at renal glomerulus where the filtration occurs may

DOX interferes with the glandular podocytes of the kidney and cause nephropathy the most accepted mechanism behind the nephropathy is an accumulation of proteinuria in the kidney by the local passage of leaked proteins [23]. Increase in the structural changes in nephrons causes hypertension, steroid resistance, high incidents of renal failure and glomerular vacuolization, inflammation, tubular dilation, intestinal fibrosis, permeability differences in the glomerulus, and certain conditions like hypoalbuminemia, dyslipidemia, hypercoagulation, size differences in kidney most likely observed [24]. A study conducted on the DOX effect on the mitochondria by the Lebrecht suggested that DOX interfere the mitochondrial mtDNA in the kidney with ROS produced from it and accelerating the damaging of the nephron. Another study reports suggesting that DOX forming an iron-mediated anthracycline complex, which produces the ROS led to an increase in the oxidative lesions in the cells causing damage to the critical cellular components [25, 26].

The decreasing the levels of the GSH (Glutathione), vitamin E levels and other natural oxidant levels production from the liver cells enhances the nephropathic conditions which may initially affect the Bowman's capsule thickness and the glomerular tuft of the nephron. The study conducted by Rook et al. [26] Reported as Angiotensin-converting enzyme is said to be one of the responsible factors for tissue damage triggered by the DOX therapy. The ACE is causing the pro-inflammatory, pro-fibrotic effects which make interference in the kidney and nephrons to maintain the glomerular pressure and filtration rate of blood [27, 28]. The cases of nephropathy and proteinuria are rare in humans susceptibility towards such condi-

The brain is the largest and most complex organ in the human body contains about 100 billion neurons with 1 trillion established connections throughout the body. DOX is not able to transfer through the blood–brain barrier (BBB), therefore DOX effects against the brain via indirect way [29, 30]. These effects include: depression, anxiety, decrease in motor functions, haemoglobin levels, perception skills affected, and menopausal status, visuospatial skills are affected through cancer chemotherapy. The recovery of the cognitive functions may take up to a year [31]. The DOX mediate increase TNF-α level (inflammatory cytokines produced by the macrophages/monocytes during the acute inflammation involved in many signalling pathways) in the brain at cortex and hippocampus of mice [32–34]. The mitochondrial activity, glutathione-S-transferase, GSH levels, and MnSOD levels in the brain are decreased and increase in levels of 4-hydroxynoneal (HNA), thiobarbituric acid reactive substances (TBARS), malondialdehyde (MDA) and increase in levels of protein carbonyl groups [35–38], which causes increase the oxidative stress

The MnSOD levels in the brain generally detoxify the oxygen free radicals, inactivated by the Nitric oxide (NO). The DOX indirectly increased the concentration of NO by overexpressing the Nitric oxide synthase enzyme [37]. A study conducted on the NOS dependent brain injury with DOC reinforcing the nitric oxide tissue damage [38]. The mitochondrial activity is very important in the brain because it is a powerhouse of cells (energy production) brain uses 20% of body glucose for energy production to conduct and maintain the regular activities [39]. The DOX induces generation of MDA, TBARS, and HNA which cause the decrease the mitochondrial activities. A study conducted on the DOX-induced toxicity on rats with 10 mg/kg dose, the rats died between 10 and 50 days with observed

**172**

This side effect found to be a dose-dependent on DOX. The DOX-induced cardiotoxicity occurs acutely and chronically. The acute effects occur within one week period the patient may experience arrhythmia, hypotension, and super ventricular tachycardia. These abnormalities are generally reversible in a noticeable period [41]. The chronic effects are shown in only 1.7% of patients with a 50% mortality rate [42, 43]. The chronic effect of DOX such as congestive heart failure reported in a study, when the patients are treated with dose 500–550 mg/m<sup>2</sup> in more than 4% of patients when treated with the dose is 551–600 mg/m<sup>2</sup> 18% of patients cause the CHF, and almost 35% of patients observed with CHF when treated with >601 mg/m<sup>2</sup> [44, 45].

A study conducted by the Zordosky and EI-kadi on DOX-induced toxicity reported as the induction of Brain natriuretic peptides, atrial natriuretic peptides genes, monooxygenases, cytochrome P genes and hypertrophy markers responsible for the xenobiotics and certain endogenous substances [46]. The inductions of these genes are cause cardiac hypertrophy leading to heart failure and altered the arachidonic acid mechanisms. A study reported the DOX effects based on the concentrations, at low concentrations DOX dose (o.5–1 μM) causes the alterations in structural proteins (includes sarcomeric myosin, nuclear lamina), plasma membrane blebbing (causes change in cell shape), and mitochondrial depolarization and fragmentation. At high concentration causes (5–50 μM) causes the cytoplasm vacuolization, swelling of mitochondrial cells, promote the cellular alterations (**Figure 2**) at the cellular and nuclear membranes [47]. The DOX reportedly binds

**Figure 2.** *DOX-mediated effects on the Heart.*

to the cardiolipin (a mitochondrial inner membrane component), which raises the accumulation of the DOX inside the mycoplasma when compared to the other body cells. The high concentration existence of the NADPH dehydrogenase inside the mitochondria initiates the redox reaction in the complex and promotes the production of the Reactive oxygen species. Myocytes are generally having low levels of anti-oxidants when compared to the other tissue cells, considerably DOX shows enhanced effects on the heart and cause toxicity [48–50].

The antioxidant level differences were observed in rats under DOX treatment based on the age differences, younger Fischer rats contain more levels of antioxidants when compared to old Fischer rats. A recent study stated the involvement of the Toll-like receptor TLR-4 (a specific receptor in the immune system generally recognise the multiple bacterial antigens and plays a major role in the maturation of the phagosomes) [51]. The increase in TLR-4 expression in the DOX-induced Cardiomyocytes, when studied the cardiomyopathic cells in humans and animals. The deficiency of TLR shows decreased in lipid peroxidation and nitrotyrosine levels in cardiomyopathic cells. The other study on the glutathione peroxidase 1 (GPx) enzyme is present in both cytosol and mitochondria play a major role in the detoxification. The study conducted with the insertion of DOX on non-GPx and wild type mice, the results showed based on the study on myocytes of the non-GPx mice having the high concentration of the DOX deposits in cells, when compared to wild type mice [52–54].

The oxidative stress is a major cause for the exhibiting the cardiotoxicity, involved the generation of higher amounts of ROS cause the cellar alterations and damage are referred to as oxidative stress. The ROS is countered by the anti-oxidant system in the body, in cancer patients under the DOX chemotherapy observed the decreased the levels of GSH, TRAP levels in the body. The ROS is generation is catalysed by NADPH oxidase enzyme [55, 56].

$$\begin{aligned} \text{O}\_2 \star \text{e}^\cdot &\rightarrow \stackrel{\cdots}{\text{O}\_2} \\ 2\text{O}\_2 \star \text{NADPH} &\rightarrow 2\text{O}\_2^{\cdot -} \star \text{NADP}^\cdot \star \text{H}^\cdot \end{aligned} \tag{1}$$

In mitochondrial cells, the same reaction is mediated by NADH –ubiquinone oxidoreductase enzyme.

$$\text{H}\,\text{2O}\_2 + \text{NADH} + \text{H}^\* \rightarrow \text{O}\_2{}^- + \text{NAD}^\* + \text{2H}^\* \tag{2}$$

The generated oxygen radical undergo dimutation with hydrohen molecules and forms hydrogen peroxide reaction is mediated by the SOD enzyme [55].

$$\text{2O}\_2^{\cdot-} + \text{2H} \xrightarrow{\text{SOD}} \text{H2O}2 + \text{O}\_2 \tag{3}$$

The generated less active hydrogen peroxide is removed by the enzymes like catalase, glutathione peroxidase.

$$\begin{array}{c} \text{H2O2} \xrightarrow{\text{Catalase}} \text{2H2O+O2} \\ \text{2GSH} + \text{H2O2} \xrightarrow{\text{GPx}} \text{GSSG} + \text{2H2O} \end{array} \tag{4}$$

The generated oxygen radicals combine with the H2O2 and form the highly active hydroxyl radicals. The H2O2 also reacted with the ferrous ions resulting in the formation of ferric ions and reactive hydroxyl radicals [55].

$$\begin{aligned} \text{O}\_{2}^{\cdot -} + \text{H}2\text{O}2 &\rightarrow \text{OH}^{\cdot -} + \text{OH}^{\cdot} + \text{O}\_{2} \\ \text{Fe}^{2+} + \text{H}2\text{O}2 &\rightarrow \text{Fe}^{3+} + \text{OH}^{\cdot} + \text{OH}^{\cdot} \\ \text{Fe}^{3+} + \text{O}\_{2}^{\cdot -} &\rightarrow \text{Fe}^{2+} + \text{O}\_{2} \end{aligned} \tag{5}$$

**175**

*Overview on the Side Effects of Doxorubicin DOI: http://dx.doi.org/10.5772/intechopen.94896*

myocytes lead the death of cells.

*2.5.1 Cellular hypertrophy*

*2.5.2 ECM remodelling*

*2.5.3 Impaired cardiac contraction*

Under stress conditions, oxygen radical facilitates the ferrous iron from the ferric ion. The iron, under normal conditions sequestered within the ferritin (a globular protein and forms the nanocage with the metal-protein complexes) but with regards to DOX when converted to its semi-quinone form complexes with iron-free radical and converted to DOX forms while generating the oxygen free radical. The generated complexes block the iron-free regulating proteins (IRP), and then these IRPs bound to the iron-responsive elements in mRNA ferritin. The tremendous amounts of free iron releases and gain complexes with the DOX. This

The ROS acts as secondary signalling molecules shows direct effects on the lipids, proteins, DNA, and RNA in various pathways involved in cell proliferation, cell death and maintain the homeostasis. It is domineering to maintain the levels of ROS in the body, in case of the heart the effect is maximum by ROS due to lack of efficient levels of anti-oxidants in myocytes. The conditions such as cellular hypertrophy, alterations in the gene expressions, ventricular remodelling, the extracellular matrix of the mitochondria transformation, calcium transient perturbation and cell death activation such kinds of pathological changes may be observed in

A particular disorder marked by an increase in cell size and volume. The abnormality shows an improvement in the degree of protein synthesis, increased in the organisation of sarcomere (contractile muscle fibre unit). At molecular level induction of hypertrophy associated genes are triggered by the DOX treatment which are alpha myosin heavy chain, ventricular myosin light chain-2, and atrial natriuretic peptide genes [60]. The main signalling cascades of the hypertrophy are tyrosine kinases, PI3K/Akt [61], and NF-B [62, 63], protein kinase C (PKC), mitogenactivated protein kinases (AMPK [64]; ERK1/2 [65], p38 [66], and JNK) which are

specific condition magnifies the production of ROS in cells [57–59].

**2.5 Mechanisms involved at different levels of cardio toxicity**

increased in DOX therapy induce cellular hypertrophic conditions [67].

and all other agents together promote remodelling and apoptosis [70].

The heart cells (cardiomyocytes) composed of myofibrils with typical contraction and relaxation. Pump and propel the blood to systemic circulation. Myofibrils contain multiple contractile units called sarcomere, which have actin and myosin filaments. In a calm state, actin is coated in tropomyosin and protects

Extra cellular matrix is a molecular network consisting of glycol conjugates, proteins, glycosaminoglycans and adhesive receptors that associate with each other and forms frame network, where cells reside on them [68]. The ECM frame work is present in all tissues it continuously shifts in quantitative and qualitative terms on a daily basis. In case of myocytes ECM is essential for attachment, alignment and orientation facilities the cellular contractions in myocytes. Changes in the ECM of the heart found in DOX treatments, the symptoms of DOX are related to the activation of the Membrane Metalloproteinase enzymes MMP-2 & 9 in 4 weeks of treatment [69]. Changes in MMP-2 activate the Akt channels; suppress the superoxide dismutase enzyme, which raises the amount of superoxide levels, and induce caspase-3

#### *Overview on the Side Effects of Doxorubicin DOI: http://dx.doi.org/10.5772/intechopen.94896*

*Advances in Precision Medicine Oncology*

to the cardiolipin (a mitochondrial inner membrane component), which raises the accumulation of the DOX inside the mycoplasma when compared to the other body cells. The high concentration existence of the NADPH dehydrogenase inside the mitochondria initiates the redox reaction in the complex and promotes the production of the Reactive oxygen species. Myocytes are generally having low levels of anti-oxidants when compared to the other tissue cells, considerably DOX shows

The antioxidant level differences were observed in rats under DOX treatment based on the age differences, younger Fischer rats contain more levels of antioxidants when compared to old Fischer rats. A recent study stated the involvement of the Toll-like receptor TLR-4 (a specific receptor in the immune system generally recognise the multiple bacterial antigens and plays a major role in the maturation of the phagosomes) [51]. The increase in TLR-4 expression in the DOX-induced Cardiomyocytes, when studied the cardiomyopathic cells in humans and animals. The deficiency of TLR shows decreased in lipid peroxidation and nitrotyrosine levels in cardiomyopathic cells. The other study on the glutathione peroxidase 1 (GPx) enzyme is present in both cytosol and mitochondria play a major role in the detoxification. The study conducted with the insertion of DOX on non-GPx and wild type mice, the results showed based on the study on myocytes of the non-GPx mice having the high concentration of the DOX deposits in cells, when compared to wild type mice [52–54]. The oxidative stress is a major cause for the exhibiting the cardiotoxicity, involved the generation of higher amounts of ROS cause the cellar alterations and damage are referred to as oxidative stress. The ROS is countered by the anti-oxidant system in the body, in cancer patients under the DOX chemotherapy observed the decreased the levels of GSH, TRAP levels in the body. The ROS is generation is

> - 2 2

− →

−

O +e O 2O +NADPH 2O +NADP +H

→

In mitochondrial cells, the same reaction is mediated by NADH –ubiquinone

2O NADH H O NAD 2H 2 2

SOD 2O 2H H2O2 O 2 2

The generated less active hydrogen peroxide is removed by the enzymes like

Catalase

→ +

GPx H2O2 2H2O O2

2GSH H2O2 GSSG 2H2O

2 2 2 3·

+ → ++ + →+ + +→ +

O 2 2 OH OH O Fe H2O2 Fe OH OH Fe O Fe O

+ + − + ⋅− +

2 2

The generated oxygen radicals combine with the H2O2 and form the highly active hydroxyl radicals. The H2O2 also reacted with the ferrous ions resulting in

3 2

⋅− −

**H O**

the formation of ferric ions and reactive hydroxyl radicals [55].

+→+

The generated oxygen radical undergo dimutation with hydrohen molecules and

2 2

forms hydrogen peroxide reaction is mediated by the SOD enzyme [55].

+ +

⋅− +→ + (3)

+ ⋅− + + + +→ + + (2)

·

(1)

(4)

(5)

enhanced effects on the heart and cause toxicity [48–50].

catalysed by NADPH oxidase enzyme [55, 56].

oxidoreductase enzyme.

catalase, glutathione peroxidase.

**174**

Under stress conditions, oxygen radical facilitates the ferrous iron from the ferric ion. The iron, under normal conditions sequestered within the ferritin (a globular protein and forms the nanocage with the metal-protein complexes) but with regards to DOX when converted to its semi-quinone form complexes with iron-free radical and converted to DOX forms while generating the oxygen free radical. The generated complexes block the iron-free regulating proteins (IRP), and then these IRPs bound to the iron-responsive elements in mRNA ferritin. The tremendous amounts of free iron releases and gain complexes with the DOX. This specific condition magnifies the production of ROS in cells [57–59].

The ROS acts as secondary signalling molecules shows direct effects on the lipids, proteins, DNA, and RNA in various pathways involved in cell proliferation, cell death and maintain the homeostasis. It is domineering to maintain the levels of ROS in the body, in case of the heart the effect is maximum by ROS due to lack of efficient levels of anti-oxidants in myocytes. The conditions such as cellular hypertrophy, alterations in the gene expressions, ventricular remodelling, the extracellular matrix of the mitochondria transformation, calcium transient perturbation and cell death activation such kinds of pathological changes may be observed in myocytes lead the death of cells.
