Reactive Oxygen Species and Their Involvement in Red Blood Cell Damage in Chronic Kidney Disease

Reactive oxygen species (ROS) released in cells are signaling molecules but can also modify signaling proteins. Red blood cells perform a major role in maintaining the balance of the redox in the blood. The main cytosolic protein of RBC is hemoglobin (Hb), which accounts for 95-97%. Most other proteins are involved in protecting the blood cell from oxidative stress. Hemoglobin is a major factor in initiating oxidative stress within the erythrocyte. RBCs can also be damaged by exogenous oxidants. Hb autoxidation leads to the generation of a superoxide radical, of which the catalyzed or spontaneous dismutation produces hydrogen peroxide. Both oxidants induce hemichrome formation, heme degradation, and release of free iron which is a catalyst for free radical reactions. To maintain the redox balance, appropriate antioxidants are present in the cytosol, such as superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), and peroxiredoxin 2 (PRDX2), as well as low molecular weight antioxidants: glutathione, ascorbic acid, lipoic acid, α-tocopherol, β-carotene, and others. Redox imbalance leads to oxidative stress and may be associated with overproduction of ROS and/or insufficient capacity of the antioxidant system. Oxidative stress performs a key role in CKD as evidenced by the high level of markers associated with oxidative damage to proteins, lipids, and DNA in vivo. In addition to the overproduction of ROS, a reduced antioxidant capacity is observed, associated with a decrease in the activity of SOD, GPx, PRDX2, and low molecular weight antioxidants. In addition, hemodialysis is accompanied by oxidative stress in which low-biocompatibility dialysis membranes activate phagocytic cells, especially neutrophils and monocytes, leading to a respiratory burst. This review shows the production of ROS under normal conditions and CKD and its impact on disease progression. Oxidative damage to red blood cells (RBCs) in CKD and their contribution to cardiovascular disease are also discussed

Indoxyl Sulfate Induces Oxidative Changes in Plasma and Hemolysate

The deteriorating function of the kidneys in chronic kidney disease (CKD) is associated, among other things, with the retention of many unnecessary metabolic products in the body. Indoxyl sulfate (IS) belongs to the group of uremic toxins with a high protein binding affinity. Moreover, this compound can generate oxidative stress. We hypothesized that a high concentration of IS might induce oxidative changes in erythrocytes and plasma components, and could therefore contribute to CKD progression. In this study, we evaluated the influence of IS on the oxidative stress parameters in plasma and hemolysate. Moreover, as a result of the action of IS, we observed a decrease in the total antioxidant capacity and a change in the activity of catalase and superoxide dismutase in hemolysate and plasma. The obtained results indicate that IS induces oxidative damage to hemolysate and plasma components. Greater changes in the parameters of oxidative stress were observed in hemolysate than in plasma treated with indoxyl sulfate. The obtained results suggest that the increased concentration of IS in patients with chronic kidney disease may lead to a decrease in the lifespan of erythrocytes in their bloodstream

Alterations in conformational state of albumin in plasma in chronic hemodialyzed patients.

In chronic hemodialyzed (CH) patients the balance between production of reactive oxygen species and antioxidant defense system is disturbed and shifted towards oxidative conditions. The properties of albumin in CH patients were studied before hemodialysis (HD) and post-HD.Two oxidants were applied, organic t-butyl hydroperoxide (t-BOOH) and inorganic hydroperoxide (H2O2), for oxidation of albumin molecules. By comparison, albumin from healthy donors was also modified by both oxidants. The thiol content in albumin was determined by the Ellman method. Albumin properties were evaluated with the spin labelling technique using two covalently bound spin labels, maleimide (MSL) and iodoacetamide (ISL), and fatty acid spin probe, 16-doxylstearic acid (16-DS).A decrease in thiols level in HD albumin was greater than in control albumin. The t-BOOH modified the microenvironment at the binding site of MSL and ISL in control albumin molecules to a greater extent than hydrogen peroxide. Control albumin treated with t-BOOH and H2O2 showed an increase in the mobility of 16-DS. However, no changes were observed in albumin from CH patients treated with either of the oxidizing agents.Both oxidants induced strong conformational changes in albumin from healthy volunteers, but were less effective or ineffective in modification of albumin derived from CH patients. These results show that albumin from CH patients is highly modified in vivo and is not vulnerable to oxidation in the same way as normal albumin

Modulation of the Human Erythrocyte Antioxidant System by the 5- and 6-Membered Heterocycle-Based Nitroxides

Nitroxides are stable radicals consisting of a nitroxyl group, >N-O•, which carries an unpaired electron. This group is responsible for the paramagnetic and antioxidant properties of these compounds. A recent study evaluated the effects of pyrrolidine and pyrroline derivatives of nitroxides on the antioxidant system of human red blood cells (RBCs). It showed that nitroxides caused an increase in the activity of superoxide dismutase (SOD) and the level of methemoglobin (MetHb) in cells (in pyrroline derivatives) but had no effect on the activity of catalase and lactate dehydrogenase. Nitroxides also reduced the concentration of ascorbic acid (AA) in cells but did not cause any oxidation of proteins or lipids. Interestingly, nitroxides initiated an increase in thiols in the plasma membranes and hemolysate. However, the study also revealed that nitroxides may have pro-oxidant properties. The drop in the AA concentration and the increase in the MetHb level and in SOD activity may indicate the pro-oxidant properties of nitroxides in red blood cells

Alterations in the Plasma and Red Blood Cell Properties in Patients with Varicose Vein: A Pilot Study

The varicose vein results from the inefficient functioning of the valves in the lower limb veins, making the blood flow slow down and leading to blood stasis and hypoxia. This type of vein dysfunction might be a result of the development of oxidative stress. We compared oxidative stress markers in the plasma and erythrocytes obtained from peripheral veins and varicose veins in the same patients (glutathione, nonenzymatic antioxidant capacity (NEAC), catalase (CAT) and acetylcholinesterase (AChE) activity, thiols, thiobarbituric acid-reactive substance (TBARS), and protein carbonyls). We found a decrease in NEAC in the plasma obtained from the varicose veins compared to the peripheral veins. We detected a decrease in thiols in the plasma, hemolysate, and plasma membranes and increase in protein carbonyl compounds and TBARS levels in the varicose veins. These changes were accompanied by a decrease in CAT and AChE activity. For the first time, our results show changes in the plasma, erythrocyte membrane, and hemolysate protein properties in varicose vein blood in contrast to the plasma and erythrocytes in peripheral vein blood from the same patients. The increased oxidative stress accompanying varicose vein disease might result from the local inefficiency of the antioxidant defense system

Alterations in conformational state of albumin in plasma in chronic hemodialyzed patients

<div><p>Objective</p><p>In chronic hemodialyzed (CH) patients the balance between production of reactive oxygen species and antioxidant defense system is disturbed and shifted towards oxidative conditions. The properties of albumin in CH patients were studied before hemodialysis (HD) and post-HD.</p><p>Methods</p><p>Two oxidants were applied, organic t-butyl hydroperoxide (t-BOOH) and inorganic hydroperoxide (H₂O₂), for oxidation of albumin molecules. By comparison, albumin from healthy donors was also modified by both oxidants. The thiol content in albumin was determined by the Ellman method. Albumin properties were evaluated with the spin labelling technique using two covalently bound spin labels, maleimide (MSL) and iodoacetamide (ISL), and fatty acid spin probe, 16-doxylstearic acid (16-DS).</p><p>Results</p><p>A decrease in thiols level in HD albumin was greater than in control albumin. The t-BOOH modified the microenvironment at the binding site of MSL and ISL in control albumin molecules to a greater extent than hydrogen peroxide. Control albumin treated with t-BOOH and H₂O₂ showed an increase in the mobility of 16-DS. However, no changes were observed in albumin from CH patients treated with either of the oxidizing agents.</p><p>Conclusion</p><p>Both oxidants induced strong conformational changes in albumin from healthy volunteers, but were less effective or ineffective in modification of albumin derived from CH patients. These results show that albumin from CH patients is highly modified <i>in vivo</i> and is not vulnerable to oxidation in the same way as normal albumin.</p></div

Changes in h_w/h_s ratio of maleimide spin label attached to albumin isolated from CH patients and healthy volunteers treated with t-butyl hydroperoxide or hydrogen peroxide.

<p>Data expressed as mean ± SD.</p

Basic and biochemical data for CH patients and healthy volunteers.

<p>Basic and biochemical data for CH patients and healthy volunteers.</p

Changes in thiol group levels of albumin isolated from CH patients and healthy volunteers, treated with t-butyl hydroperoxide and hydrogen peroxide.

<p>Data expressed as mean ± SD.</p