**4. Bacterial and viral infections causing variations in erythrocytes**

Erythrocytes were assumed to only function as innate oxygen carriers. However, recent studies have shown them to be important in modulating the innate immune response [105–107]. Mammalian erythrocytes, unlike the erythrocytes of birds, amphibians and fishes, are enucleate and lack major cell organelles. The organelles of the latter modulate the immune response through production of cytokine like factors, upregulating viral response genes and pathogen sequestering through phagocytosis. Mammalian erythrocytes on the other hand modulate the innate immune response through generation of reactive oxygen species (ROS) to promote inflammatory and autoimmune response against invading microorganisms [108].

Minasyan, 2014 highlighted the role of erythrocytes in conferring bacterial immunity, which is comparable to phagocytic leukocytes as: (i) they are more numerous in number; (ii) fend off microorganisms repeatedly without injury; and (iii) resistant to infection. Erythrocytes have a longer lifespan when compared with leukocytes as well as being produced at a faster rate. The cytosol of erythrocytes is unfavorable to parasitic organisms such as chlamidiae, mycoplasmas, rickettsiae, viruses, etc. Erythrocytes elevate to the primary line of defense against bacterial infections when: (i) there is a presence of massive microbial load; (ii) ineffective recruitment of phagocytes; (iii) faster proliferation and spread of the microorganisms than the phagocytes' capacity; and (iv) ineffectiveness of the phagocytes against the invading microorganisms [109].

#### **4.1 Bacterial infections**

Sepsis is one of the most recognized life-threatening dysfunctions that is caused due to infections and is the leading cause for mortality in non-cardiac ICUs (intensive care units) around the world. Sepsis may be caused by gram-positive,

*Erythrocyte - A Peripheral Biomarker for Infection and Inflammation*

OS offers protection against invading microorganisms, and on the other hand

Erythrocytes being heme rich, provides the invading bacteria a rich source of iron for its metabolism. Bacteria have evolved mechanisms to scavenge the iron through hemolytic toxins and heme scavenging systems [85–87]. Erythrocytes counteract the bacteria through the production of ROS. The α and β sub units of hemoglobin possess high affinity binding sites for lipopolysaccharides (LPS), and leads to macrophage cytokine production and enhances the macrophage binding to LPS. Hemoglobin in μM concentrations have shown to inhibit yeast and bacterial

The protection conferred by hemoglobin against invading organisms have a detrimental effect in case of pathological states. Elevations in free hemoglobin is associated with increased mortality. Globin is associated with the protective properties, whereas heme triggers the proinflammatory response. During endotoxemia, the protective effects of hemoglobin is attributed to globin scavenging free heme, which has the property of activating a host of proinflammatory proteins and ROS generation. It has also been shown to increase the transcription of proinflammatory

The ROS cascade in erythrocytes begins with the autooxidation of hemoglobin (Hb) into methemoglobin (MetHb). Oxidation of MetHb results in the formation of sulfhemoglobin (SulfHb) along with superoxide anion (O2). Erythrocytes have an innate antioxidant system that detoxifies the cells. The superoxide generated is detoxified by superoxide dismutase into H2O and H2O2, which is further detoxified by catalase and glutathione peroxidase (with the help of glutathione) into H2O and O2. Erythrocytes also contain non-enzymatic antioxidants such as glutathione, ascorbic acid (Vit C), and α-tocopherol (Vit E). This antioxidant mechanism helps the erythrocyte's survival in an oxygen-rich environment. Glutathione redox system: reduced glutathione (GSH), glutathione disulfide (GSSG), glutathione reductase (GR), glutathione peroxidase plays an important role in inactivating the

The lifespan of erythrocytes *in vivo* is around 120 days. About 1% of the erythrocytes are cleared or phagocytized from circulation every day in humans. The membrane of erythrocytes comprises of proteins (50%), lipids (40%), and carbohydrates (10%). Hb comprises about 95% of the total cytoplasmic proteins. The membrane-associated proteins include band 3 (anion exchanger), band 4.1, spectrin, ankyrin, and glycophorin C which are responsible for maintaining the

As the reticulocyte ages and transforms into erythrocyte, various changes occur in its membrane, composition, appearance and catalytic functions [96]. Aging of erythrocytes is associated with the changes in physical, biochemical and physiological properties. Thus, aged cells are more prone to be trapped and ultimately

**2. OS has dual role in diseases**

can cause damage to cells/tissues.

genes by 100-fold [91–93].

**3.1 ROS cascade**

ROS [94, 95].

**3.2 Erythrocyte aging**

structure of the cell [94].

growth through the production of ROS [88–90].

**3. Modulations in erythrocytes due to OS**

**38**

gram-negative and poly microbial infection. It results in elevated OS caused due to inflammatory response, which alters erythrocytes leading to phagocytosis by macrophages and polymorphonuclear leukocytes (PMN). This activation of the macrophages and PMN results in a positive feedback mechanism, as the modified erythrocytes trigger its continuous activation with the generation of ROS. This mechanism may further lead to septic shock, even if the blood-derived bacteria have been cleared off the system [110].

Sepsis develops when bacteria in the bloodstream survive oxidation on the surface of erythrocytes [109]. The changes in erythrocytes can be caused due to several reasons, one of them being OS, and these interactions seem to be interconnected. The levels of antioxidants and oxidants are inversely proportional in septic patients. Decrements in Vitamin E, ascorbate, β-carotene and retinol, while increments in lipid peroxidation were observed. Antioxidant supplementation improved the outcome of patients. Thus, erythrocytes can be model cells for the management of sepsis/septic shock to improve the outcome of patients [111]. Larsen *et al*., 2010, have reported that one of the major causes for sepsis is the increasing levels of free heme released due to hemolysis. It can be sequestered and cleared off using hemopexin, as its administration reduced tissue damage and lethality [112].

## **4.2 Viral infections**

Studies have shown that viruses cause cell death by generating OS within infected cells [113–115]. The influenza virus and parmovirus activates monocytes to generate ROS *in vitro* [113]. The influenza virus also possesses hemagglutinin glycoprotein on its surface, which helps the virus in binding to cells rich in sialic acids like erythrocytes. Influenza carries hemagglutinin in its inactive form (HOA), which is activated by proteases by cleaving HOA into hemagglutinin 1 and hemagglutinin 2 (HA1 and HA2). HOA can be activated by ROS resulting in a non-infectious virus getting converted into an infectious one [116, 117]. Thus, an increase in ROS levels is beneficial for the invading influenza virus.

COVID-19, caused by severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) was believed to interact with Hb, facilitating the removal of heme, which was proposed by Liu and Li as likely pathway for the loss of function of hemoglobin (Hb) and the accumulation of free heme resulting in elevated OS. De Martino *et al*., 2020, reported that COVID-19 did not exhibit any hemolytic anemia. The levels of Hb, bilirubin, lactate dehydrogenase, iron, ferritin and haptoglobin in COVID-19 patients were similar to those with acute respiratory distress syndrome (ARDS) not infected with COVID-19, suggesting that the oxygen delivery impairment was not due to red cell hemolysis and removal of iron from heme. [118].

#### **4.3 Bacterial v/s viral infections**

Trefler et al., 2014 compared the patterns of OS in bacterial origin community acquired pneumonia [BCAP] and 2009 A/H1N1 virus community acquired pneumonia [VCAP], revealing the distinct responses between bacterial and viral infections. Erythrocyte GR activity was significantly higher in patients with VCAP in respect of BCAP patients. Lower TBARS levels were observed in VCAP patients in comparison to BCAP, suggesting an increase of antioxidant activity related to the redox glutathione system. GR, GSSG, GSSG/GSH and GPx levels were more elevated in patients with viral pneumonia. A higher antioxidant activity in patients with 2009 A/H1N1 viral pneumonia was observed (**Figure 1**) [119].

**41**

**5. Conclusion**

*acid reactive substances.*

**Figure 1.**

infections.

**Acknowledgements**

**Conflict of interest**

University) for their support.

*Modulations in Oxidative Stress of Erythrocytes during Bacterial and Viral Infections*

ROS levels increase rapidly leading to lipid peroxidation and protein oxidation in erythrocytes during infections. Generally, there is a decline in the antioxidant capacity of erythrocytes. Nevertheless, some microbes evade their destruction by altering the antioxidant enzymes of erythrocytes. Thus, OS biomarkers can be used to gain insights into the effects of bacterial and viral infections on the erythrocyte microenvironment. Therefore, erythrocytes act as good indicators and can be promising candidates as peripheral biomarkers during bacterial and viral

*Oxidative modifications in Erythrocytes during Bacterial and Viral infections [109, 112, 118–120]. SOD – Superoxide dismutase; CAT – Catalase; ROS – Reactive oxygen species; GSH – Glutathione; Vit C – Vitamin C; Vit E – Vitamin E; MDA – Malondialdehyde; GR – Glutathione reductase; GPx – Glutathione peroxidase; TBARS – Thiobarbituric* 

The authors acknowledge Dr. Leela Iyengar, and JAIN (Deemed-to-be

The authors have no conflict of interest to disclose.

*DOI: http://dx.doi.org/10.5772/intechopen.98236*

*Modulations in Oxidative Stress of Erythrocytes during Bacterial and Viral Infections DOI: http://dx.doi.org/10.5772/intechopen.98236*

#### **Figure 1.**

*Erythrocyte - A Peripheral Biomarker for Infection and Inflammation*

have been cleared off the system [110].

is beneficial for the invading influenza virus.

lethality [112].

**4.2 Viral infections**

from heme. [118].

**4.3 Bacterial v/s viral infections**

gram-negative and poly microbial infection. It results in elevated OS caused due to inflammatory response, which alters erythrocytes leading to phagocytosis by macrophages and polymorphonuclear leukocytes (PMN). This activation of the macrophages and PMN results in a positive feedback mechanism, as the modified erythrocytes trigger its continuous activation with the generation of ROS. This mechanism may further lead to septic shock, even if the blood-derived bacteria

Sepsis develops when bacteria in the bloodstream survive oxidation on the surface of erythrocytes [109]. The changes in erythrocytes can be caused due to several reasons, one of them being OS, and these interactions seem to be interconnected. The levels of antioxidants and oxidants are inversely proportional in septic patients. Decrements in Vitamin E, ascorbate, β-carotene and retinol, while increments in lipid peroxidation were observed. Antioxidant supplementation improved the outcome of patients. Thus, erythrocytes can be model cells for the management of sepsis/septic shock to improve the outcome of patients [111]. Larsen *et al*., 2010, have reported that one of the major causes for sepsis is the increasing levels of free heme released due to hemolysis. It can be sequestered and cleared off using hemopexin, as its administration reduced tissue damage and

Studies have shown that viruses cause cell death by generating OS within infected cells [113–115]. The influenza virus and parmovirus activates monocytes to generate ROS *in vitro* [113]. The influenza virus also possesses hemagglutinin glycoprotein on its surface, which helps the virus in binding to cells rich in sialic acids like erythrocytes. Influenza carries hemagglutinin in its inactive form (HOA), which is activated by proteases by cleaving HOA into hemagglutinin 1 and hemagglutinin 2 (HA1 and HA2). HOA can be activated by ROS resulting in a non-infectious virus getting converted into an infectious one [116, 117]. Thus, an increase in ROS levels

COVID-19, caused by severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) was believed to interact with Hb, facilitating the removal of heme, which was proposed by Liu and Li as likely pathway for the loss of function of hemoglobin (Hb) and the accumulation of free heme resulting in elevated OS. De Martino *et al*., 2020, reported that COVID-19 did not exhibit any hemolytic anemia. The levels of Hb, bilirubin, lactate dehydrogenase, iron, ferritin and haptoglobin in COVID-19 patients were similar to those with acute respiratory distress syndrome (ARDS) not infected with COVID-19, suggesting that the oxygen delivery impairment was not due to red cell hemolysis and removal of iron

Trefler et al., 2014 compared the patterns of OS in bacterial origin community acquired pneumonia [BCAP] and 2009 A/H1N1 virus community acquired pneumonia [VCAP], revealing the distinct responses between bacterial and viral infections. Erythrocyte GR activity was significantly higher in patients with VCAP in respect of BCAP patients. Lower TBARS levels were observed in VCAP patients in comparison to BCAP, suggesting an increase of antioxidant activity related to the redox glutathione system. GR, GSSG, GSSG/GSH and GPx levels were more elevated in patients with viral pneumonia. A higher antioxidant activity in patients

with 2009 A/H1N1 viral pneumonia was observed (**Figure 1**) [119].

**40**

*Oxidative modifications in Erythrocytes during Bacterial and Viral infections [109, 112, 118–120]. SOD – Superoxide dismutase; CAT – Catalase; ROS – Reactive oxygen species; GSH – Glutathione; Vit C – Vitamin C; Vit E – Vitamin E; MDA – Malondialdehyde; GR – Glutathione reductase; GPx – Glutathione peroxidase; TBARS – Thiobarbituric acid reactive substances.*

### **5. Conclusion**

ROS levels increase rapidly leading to lipid peroxidation and protein oxidation in erythrocytes during infections. Generally, there is a decline in the antioxidant capacity of erythrocytes. Nevertheless, some microbes evade their destruction by altering the antioxidant enzymes of erythrocytes. Thus, OS biomarkers can be used to gain insights into the effects of bacterial and viral infections on the erythrocyte microenvironment. Therefore, erythrocytes act as good indicators and can be promising candidates as peripheral biomarkers during bacterial and viral infections.

### **Acknowledgements**

The authors acknowledge Dr. Leela Iyengar, and JAIN (Deemed-to-be University) for their support.

### **Conflict of interest**

The authors have no conflict of interest to disclose.

*Erythrocyte - A Peripheral Biomarker for Infection and Inflammation*
