**3. The pharmacological influences on the blood cell metabolism – Antioxidant drugs in cardiovascular risk status and roll of red blood cell antioxidant defense capacity**

There are growing evidences on the role of adaptive mechanisms of erythrocyte in pathological processes: atherosclerosis, ischemic attack, bacterial infections, etc. All of this processes involve as main mechanism oxidative stress. Erythrocytes have an intracellular enzyme and non-enzyme defense system. In order to remove reactive species of oxygen, superoxide dismutase (SOD), glutathione peroxidase (GPx) and catalase act together. Glutathione (GSH) participates as a co-substrate for GPx in order to detoxify H2O2 generated by SOD enzyme. GSH is a critical tripeptide that oxidizes to glutathione disulphide (GS-SG) inactive form after reacting with oxygen radicals. GSH proves to be essential for reactive species detoxification as a consequence it is permanently restore in its reduced active form by glutathione reductase based on nicotinamide adenine dinucleotide phosphate-oxidase (NADPH) from Glucose-6-phosphate dehydrogenase (G6P-DH) catalysed reaction in pentose phosphate pathway. When reactive species of oxygen are quickly and intensely generated under external or internal stimulus the activity of SOD, GPx and GSH concentration are severely changed.

When erythrocytes are undergo shear stress in constricted vessels, they release ATP which causes the vessel walls to relax and dilate so as to promote normal blood flow [78].

52 Blood Cell – An Overview of Studies in Hematology

thrombotic process.

[76].

metabolism in [77].

**antioxidant defense capacity** 

concentration are severely changed.

within these domains, resulting in impaired function in [74]. The result is the promotion of

Hcy acts on both endothelial cells and smooth muscle where it generates contrasting effect. On endothelium it promotes injury and impairs DNA repair, in smooth muscle Hcy stimulates proliferation in [69]. Md S. Jamaluddin considers that Hcys promotes vascular injury through hypomethylation. When Hcys accumulates it uses adenosine, a normal constituent of all cells, to form S-adenosyl-homocysteine (SAH) a potent inhibitor of cellular methylation. By impairing methylation Hcy arrests cell growth, increases cellular SAH concentration in endothelial cells (EC) and decreased DNA synthesis thus decreasing cellular repair. This chain of events was not found in vascular smooth muscle cells in [75].

Erythrocytes are also affected by homocysteine-induced hypometilation. High intracellular SAH impairs the posttranslational methylation of membrane proteins. Reduction in membrane protein methylation was particularly observed for erythrocyte cytoskeletal component ankyrin, which is known to be involved in membrane stability and integrity. Because of hypomethylation, structural damages accumulate in erythrocyte membrane proteins, and are not adequately repaired thus affecting membrane physical properties. Erythrocyte deformability is a crucial properties for circulatory function in

As a conclusion the effect of elevated homocysteine appears multifactorial affecting both the vascular wall structure and the blood coagulation system as well as erythrocytes

**Antioxidant drugs in cardiovascular risk status and roll of red blood cell** 

There are growing evidences on the role of adaptive mechanisms of erythrocyte in pathological processes: atherosclerosis, ischemic attack, bacterial infections, etc. All of this processes involve as main mechanism oxidative stress. Erythrocytes have an intracellular enzyme and non-enzyme defense system. In order to remove reactive species of oxygen, superoxide dismutase (SOD), glutathione peroxidase (GPx) and catalase act together. Glutathione (GSH) participates as a co-substrate for GPx in order to detoxify H2O2 generated by SOD enzyme. GSH is a critical tripeptide that oxidizes to glutathione disulphide (GS-SG) inactive form after reacting with oxygen radicals. GSH proves to be essential for reactive species detoxification as a consequence it is permanently restore in its reduced active form by glutathione reductase based on nicotinamide adenine dinucleotide phosphate-oxidase (NADPH) from Glucose-6-phosphate dehydrogenase (G6P-DH) catalysed reaction in pentose phosphate pathway. When reactive species of oxygen are quickly and intensely generated under external or internal stimulus the activity of SOD, GPx and GSH

**3. The pharmacological influences on the blood cell metabolism –**

Also, when their hemoglobin molecules are deoxygenated, erythrocytes release **S**nitrosothiols which acts to dilate vessels, thus directing more blood to areas of the body depleted of oxygen in [35].

Using L-arginine as substrate, erythrocytes can also synthesize nitric oxide enzymatically, just like endothelial cells. The nitric oxide synthase is activated when the erythrocytes are exposure to physiological levels of shear stress, thus, nitric oxide is synthesized, exported and it may contribute to the regulation of vascular tonus [79].

Another mechanism that involves the erythrocytes in relaxing vessel walls is the production of hydrogen sulfide. It works as a signaling gas. It is believed that the cardioprotective effects of garlic are due to erythrocytes converting its sulfur compounds into hydrogen sulfide. [80]

The free radicals released by erythrocytes when they are lysed by pathogens break down the pathogen's cell wall and cell membrane, and so, they are killing them. This represents the involving of erythrocytes in the body's immune response in [81].

On the other hand, as response of injury after several stressors, including oxidative stress, energy depletion, as well as a wide variety of endogenous mediators and xenobiotics, the erythrocytes can initiate the self suicidal death (eryptosis). Eryptosis is characterized by cell shrinkage, membrane blebbing, activation of proteases, and phosphatidylserine exposure at the outer membrane leaflet. This can make the macrophages to recognized and engulf erythrocyte to be degraded. Eryptosis can be considered a mechanism of defective erythrocytes to escape hemolysis. Conversely, excessive eryptosis favors the development of anemia. Conditions with excessive eryptosis include iron deficiency, lead or mercury intoxication, sickle cell anemia, thalassemia, glucose 6- phosphate dehydrogenase deficiency, malaria, and infection with hemolysis-forming pathogens. Inhibitors of eryptosis include erythropoietin, nitric oxide, catecholamine and high concentrations of urea in [82, 83]

The red blood cell SOD activity has been found to be useful in evaluating the biochemical index of copper, zinc and manganese nutrition. The largest amount of SOD enzyme is found in liver and erythrocytes. There are two forms of SOD in human tissue. One form is present in cytosol and it is a protein containing two atoms each of copper and zinc. The other form is a much larger molecule containing four atoms of manganese and it is found in mitochondria and cytosol. Significant changes in cellular concentration of copper, manganese and zinc have the potential of altering the antioxidant activity of SOD. On the other hands, the correlation between of copper and zinc plasma level, the oxidase activity of ceruloplasmin in serum, and Cu,Zn-SOD activity in erythrocytes can be a way to investigate involvement of oxidative stress in pathological conditions, as atherosclerosis obliterans [84]

Another element involved in the function of necessary enzyme for cellular protection is selenium. Selenium functions primarily as an activator of enzymes necessary for cellular protection from oxidative damage and maintenance of normal redox potentials. A primary role of selenium in erythrocytes appears to be the activation of the enzyme glutathione peroxidase whereby glutathione (the critical tripeptide antioxidant/antitoxin for all cells) reacts with oxygen radicals. Importantly, selenium catalyzes glutathione reductase, an enzyme that maintains the glutathione in its reduced or active form [85].

Homocysteine in Red Blood Cells Metabolism – Pharmacological Approaches 55

In recent studies was shown that probucol protect against diabetes-associated and adriamycin-induced cardiomyopathy by enhancing the endogenous antioxidant system

Specific for hypercholesterolemia status is the high production of free oxygen radicals. These can impair the endothelial function because destroying of nitric oxide (NO) and secondary affecting its beneficial and protective effects on the vessel wall. Most of the other cholesterol-lowering therapies present, also, antioxidant effects. There are two way improving antioxidant defence system in hypercolesterolemiant patients: either increasing the activities of CuZn-SOD and GSH-Px or preventing the production of the superoxide

Malone dialdehyde (MDA), more than cholesterol plasma level, is considered a marker of patients with increased risk of coronary heart disease, because MDA is a marker of lipid peroxidation. In individuals who smoke or who have diabetes are particularly prone to oxidative stress that can lead to the formation of oxidized LDL (oxLDL). Oxidatively modified LDL is considered to be highly atherogenic and can be considered a biochemical risk marker for coronary heart disease. Oxidative modification of LDL increases their ability to bind to the extracellular matrix, increasing its retention within the intima and accumulation of oxLDL in macrophages, so, it contributes to the formation of an

The oxLDL accumulation within macrophages promotes the chemotaxis of monocytes into the vessel wall and initiates the various pro-inflammatory effects by different scavenger receptor pathways: CD36 class B scavenger receptors from human macrophages (activates nuclear factor kB that regulates the expression of many pro-inflammatory genes), class A scavenger receptors (modify macrophage activation), lectin-like oxidized LDL receptor - LOX-1 (the expression of endothelial cell adhesion molecule). On the other hands, the accumulation of inflammatory cells can further increase the levels of oxidative stress. Oxidative stress inactivates nitric oxide (NO) and inhibits its synthesis by endothelial nitric oxide synthase (eNOS). On this way, the vasoprotectant effect of NO (anti-inflammatory,

Statins inhibit 3-hydroxy-3-methylglutaryl-CoA (HMG-CoA) reductase the rate-limiting enzyme in the mevalonate pathway through which cells synthesizes cholesterol. On this way, the "statins" increase the resistance of LDL to oxidation. Statins may also exert effects beyond cholesterol lowering. These "pleiotropic" vascular effects of statins are involved in restoring or improving endothelial function: by increasing the bioavailability of nitric oxide, promoting reendothelialization, reducing oxidative stress, and inhibiting inflammatory

Other effects of statins that explain their involving in preserving normal vascular function and blood flow are: inhibition of the uptake and generation of Ox-LDL*,* decreasing the

including glutathione peroxidase, catalase and superoxide dismutase [90].

*3.1.2. The HMG Co-A reductase inhibitors, or "statins"* 

anti-platelets, antioxidant and vasodilator) is affected [92].

radicals*.*

atherosclerotic lesion.

responses.

Specify participation of erythrocyte enzymatic system as adaptive mechanism to different pathological processes and specify how nutritional deficiencies and oxidative drugs can interfere these systems introduces the chapter on pharmacology of erythrocyte antioxidant system.
