Edyta Gołembiewska

Oxidative Stress and Antioxidative Enzyme Activities in Chronic Kidney Disease and Different Types of Renal Replacement Therapy

The incidence and diagnosis of chronic kidney disease (CKD) is on the rise all over the world. CKD is related to ageing of the society and high morbidity due to lifestyle diseases like diabetes, atherosclerosis, and hypertension. CKD is associated with increased oxidative stress generated by uremic toxicity, chronic inflammatory state, lack of vitamins and microelements, parenteral iron administration, and dialysis procedure itself. In terms of cellular physiology, erythrocytes and blood platelets in particular have effective enzymatic and non-enzymatic antioxidative system. The most efficient enzymatic antioxidants include superoxide dismutase, catalase, glutathione peroxidase, glutathione reductase, and glucose-6-phosphate dehydrogenase. Glutathione is the leading non-enzymatic free radical scavenger. In CKD, antioxidative defense is impaired and the abnormal activity of the enzymes and glutathione concentration is described in literature. The imbalance between the formation of reactive oxygen species and antioxidative system efficiency takes part in the pathogenesis of cardiovascular complications. It contributes to increased morbidity and mortality in patients with CKD. The severity of these processes depends on the type of renal replacement therapy; haemodialysis (HD) is more predisposing to such disorders than peritoneal dialysis (PD), or even conservative treatment. This can influence the outcome and the possibility of kidney transplantation. Moreover, the early function of kidney allograft seems to be dependent on perioperative antioxidative ability of platelets, which can play a potential protective role in kidney transplantation.

End-Stage Renal Disease, Inflammation and Cardiovascular Outcomes

Despite marked improvements in renal replacement therapy during the last 30 years, the age-adjusted mortality rate in end-stage renal disease (ESRD) patients is still unacceptably high and comparable to that of many malignancies. Cardiovascular disease (CVD) remains the major cause of morbidity and mortality in ESRD patients. However, traditional risk factors can only partially explain the high premature cardiovascular burden in this population. Nontraditional risk factors, including persistent low-grade inflammation, are critical in the pathogenesis of atherosclerosis, vascular calcification, and other causes of CVD and may also contribute to protein-energy wasting and other complications in chronic kidney disease (CKD) patients. Inflammatory biomarkers, such as high sensitivity C-reactive protein and interleukin-6, independently predict mortality in these patients. The causes of inflammation in CKD are multifactorial and include imbalance between increased production (due to multiple sources of inflammatory stimuli such as oxidative stress, acidosis, volume overload, co-morbidities, especially infections, genetic and epigenetic influences, and the dialysis procedure) and inadequate removal (due to decreased glomerular filtration rate or in ESRD patients, inadequate dialytic clearance) of pro-inflammatory cytokines. Though there are currently no established guidelines for the treatment of low-grade inflammation in ESRD patients, several strategies have been proposed, such as lifestyle modifications, pharmacological treatment, and optimization of dialysis. Further studies on pathways involved in pathogenic processes of inflammation in ESRD, and long-term effects of anti-inflammatory interventions targeting production or removal of cytokines or both on premature CVD and clinical outcomes in this patient group are warranted.

Influence of angiotensin I‐converting enzyme polymorphism on development of post‐transplant erythrocytosis in renal graft recipients

Abstract:  Background:  Post‐transplant erythrocytosis (PTE) is estimated at 5–20%. Angiotensin II generated by angiotensin I‐converting enzyme (ACE) stimulates erythropoiesis. The highest activity of ACE is observed in DD genotype. The question arises if ACE gene polymorphism influences PTE.

Oxidative stress modulates the organization of erythrocyte membrane cytoskeleton.

BACKGROUND Apart from their main role in transporting oxygen and carbon dioxide, erythrocytes play also an important role in organism antioxidative defence. Direct exposure to reactive oxygen species (ROS) results in shortening of their half-life, even by 50%. The presence of glucose, being the substrate in pentose phosphate pathway (PPP) cycle, is one of the factors that can have influence on the level of oxidative stress. The activity of PPP increases during oxidative stress. Glucose guarantees normal PPP functioning with the production of reductive equivalents in the amounts necessary to reproduction of glutathione--nonenzymatic free radical scavenger. In available literature there are no reports regarding the changes in protein contents of erythrocyte cytoskeleton exposed to t-butyl hydroperoxide in relation to glucose presence in incubation medium. MATERIAL/METHODS Erythrocytes taken from 10 healthy subjects were used to assess the influence of generated free radicals on erythrocyte proteins and chosen parameters of oxidative stress. Erythrocytes were incubated in the solutions containing deferent concentrations of t-butyl hydroperoxide and glucose. Electrophoresis was performed on polyacrylamide gel in denaturating conditions. The contents of tryptophan in membranes was evaluated spectrofluorometrically. RESULTS/CONCLUSIONS In vitro conditions oxidative stress leads to protein damage in erythrocyte cytoskeleton, both in proteins inside the cell as well as having contact with extracellular environment. In consequence, the amount of low-molecular proteins--mainly globin, which bind to cytoskeleton, increases. This process takes place independently of glucose presence in incubation medium. One of the element of protein cytoskeleton, tryptophan, also undergoes degradation. The decrease of its contents is higher during erythrocyte exposure to t-BOOH in environment containing glucose, what can suggest prooxidative influence of glucose in conditions in vitro.

Oxidative Stress Indices in Rats Under Immunosuppression

Immunosuppressants lead to generation of reactive oxygen species (ROS). Oxidative stress (OxS) can initiate chronic allograft nephropathy (CAN). The most active antioxidant enzymes, superoxide dysmutase (SOD) and catalase (CAT), are present in erythrocytes. Glutathione peroxidase (GPx) is produced in the proximal tubules of nephrons. Malonyldialdehyde (MDA) concentrations are a marker of OxS intensity in plasma. In vitro and animal model studies have shown increased or decreased OxS during treatment with tacrolimus (Tac) or cyclosporine (CyA). Results obtained in humans after solid organ transplantation have been contradictory, because of confounding factors such as ischemia-reperfusion injury, donor and recipient ages, endothelial injury, and comorbidity. The aim of this study was to assess the intensity of OxS among rats under chronic immunosuppression (IS) without a transplantation. We examined 49 male Wistar rats. IS started at 12 weeks of age was continued for 6 months: group I were controls (n=7); group II, Tac+sirolimus (Rapamycin [Rapa])+corticosteroids (CS; n=6); group III, CyA+Rapa+CS (n=4 of which 2 died); group IV, Rapa+mycophenolate mofetil (MMF)+CS (n=6); group V, CyA+MMF+CS (n=6); group VI, CsA+MMF+CS for 3 months followed by conversion to Rapa (n=6); group VII, Tac+MMF+CS (n=6 rats); and group VIII, Tac+MMF+CS for 3 months followed by conversion to Rapa (n=6). The drug doses were as follows: Tac 4 mg/kg/d; MMF 20 mg/kg/d; CyA 5mg/kg/d; Rapa 0.5 mg/kg/d; and CS 4 mg/kg/d. Multiple regression analysis revealed that all IS drugs decreased GPx activity (P<.001) except CS, which increased it (P<.0001). Multiple regression analysis showed that CsA and Tac decreased plasma MDA concentrations (P<.01), whereas CS increased them (P<.05). In conclusion, all IS drugs except CS damage proximal tubules of nephrons.

Prooxidative-Antioxidative Balance of Cells in Different Types of Renal Replacement Therapy

Background: Patients suffering from chronic kidney disease (CKD) are exposed to increased oxidative stress and disturbances manifesting in the enzymatic and non-enzymatic antioxidative defence system. The object of the research was to assess the differences between conservative treatment, peritoneal dialysis and haemodialysis in moderating cellular antioxidative agents. Methods: The group examined comprised 145 patients. The activities of superoxide dismutase, catalase, glutathione peroxidase, glutathione reductase and glucose-6-phosphate dehydrogenase were obtained using kinetic methods. The spectrophotometric method established the concentrations of reduced glutathione, albumin, uric acid, glucose, total protein and lipids. Results: The type of treatment determined significant changes in antioxidative enzyme activities and concentrations of non-enzymatic antioxidative compounds. Conclusions: Peritoneal dialysis provides better antioxidant protection than other types of therapy in CKD and should be considered as first-choice treatment despite more metabolic disorders.

Copper modifies the activity of sodium-transporting systems in erythrocyte membrane in patients with essential hypertension.

The aim of the study was to verify the hypothesis if copper could influence the activity of sodium-transporting systems in erythrocyte membrane that could be related to essential hypertension. The examined group of patients consisted of 15 men with hypertension. The control group was 11 healthy male volunteers. The Na+/H+ exchanger (NHE) activity in erythrocytes was determined according to Orlov et al. The activity of transporting systems (ATP-Na+/K+; co-Na+/K+/Cl−; ex-Na+/Li+; free Na+ and K+ outflow [Na+, K+-outflow]) was determined according to Garays method. The concentration of copper in plasma was assessed using atomic absorption spectrometry. The activity of ATP-Na+/K+ (μmol/L red blood cells [RBCs]/h) in hypertensive patients was 2231.5±657.6 vs 1750.5±291 in the control (p<0.05), the activity of co-Na+/K+/Cl− (μmol/L RBCs/h) in hypertensives was 171.3±77.9 vs 150.7±53.9 in the control (NS). Na+-outflow (μmol/L RBCs/h) in hypertensives was 118.3±51.6 vs 113.3±24.4 in the control (NS). The K+-outflow (μmol/L RBCs/h) in hypertensives was 1361.7±545.4 vs 1035.6±188.3 in the control (NS). The activity of ex-Na+/Li+ (μmol/L RBCs/h) in hypertensive patients was 266.1±76.1 vs 204.1±71.6 in the control (p<0.05). NHE activity (mmol/L RBCs/h) in hypertensives was 9.7±2.96 vs 7.7±1.33 in the control (p<0.05). In hypertensive patients, negative correlation was found between the activity of Na+/K+/Cl− co-transport and plasma copper concentration (Rs=−0.579, p <0.05) and between the activity of ex-Na+/Li+ and plasma copper concentration (Rs=−0.508, p<0.05). Plasma copper concentration significantly influences the activity of sodium transporting systems in erythrocyte membrane. Copper supplementation could be expected to provide therapeutic benefits for hypertensive patients.

The Activity of Erythrocyte Sodium-Proton Exchanger in Women with Pregnancy- Induced Hypertension

Background: Hypertension that develops after 20 gestational weeks and is defined as pregnancy-induced hypertension (PIH). The main cause of PIH is vasoconstriction and the thickening of vascular media, which decreases vascular capacity and increases peripheral resistance. One of the theories postulated to explain this phenomenon is that a transmembrane sodium transport disorder causes an increase in intracellular sodium concentration. In the latest literature, special attention is paid to the role of the increased intracellular sodium concentration in the pathogenesis of essential hypertension (EH). One of the best documented phenotypes for EH is the increased activity of the sodium-proton exchanger (NHE). The aim of this study was to assess if increased NHE activity could be the mechanism responsible for the development of PIH. Subjects and methods: The study included 30 women: 10 pregnant women with PIH after gestational week 30, 10 women with physiological pregnancy after 30 gestational weeks, and 10 healthy non-pregnant women. NHE activity was determined according to Orlov’s method as amiloride-sensitive H+ efflux from acid-loaded cells. Results: The NHE activity in the group of women with PIH was significantly higher than that in women with physiological pregnancy: 10.09 ± 1.65 vs. 6.81 ± 2.3 mmol/L RBC/h (p < 0.049) and in the group of non-pregnant women: 10.09 ± 1.65 vs. 7.56 ± 1.66 mmol/L RBC/h (p < 0.029). Erythrocyte NHE activity did not differ in the group of women with physiological pregnancy and in the group of non-pregnant women. Conclusion: These results seem to suggest that erythrocyte NHE activity is elevated in PIH pregnancies.

Successful pregnancy in the patient with Fanconi‐Bickel syndrome undergoing daily hemodialysis

Successful Pregnancy in the Patient With Fanconi-Bickel Syndrome Undergoing Daily Hemodialysis Karolina Kędzierska, Sebastian Kwiatkowski, Andrzej Torb e,* Mal-gorzata Marchelek-Myśliwiec, Oliwia Marcinkiewicz, Katarzyna Bobrek-Lesiakowska, Edyta Gol-embiewska, Ewa Kwiatkowska, RafalRzepka, Kazimierz Ciechanowski, Ryszard Czajka, and Ren e Santer Department of Nephrology, Transplantology and Internal Medicine, Pomeranian Medical University, Szczecin, Poland Department of Obstetrics and Gynecology, Pomeranian Medical University, Szczecin, Poland Department of Children Diseases, University Hospital of Hamburg, Hamburg, Germany

Creatinine Clearance after Cimetidine Administration—Is It Useful in the Monitoring of the Function of Transplanted Kidney?

Background. Determination of clearance of endogenous creatinine using its plasma and urinary concentration (standard clearance), Cockroft and Gault formula, or MDRD formula (estimated clearance) is commonly performed for assessment of glomerular filtration rate. Although the evaluation of renal function in this way is useful, it is biased with an error resulting from secretion of creatinine in tubules. This error can be reduced by determining the clearance after administration of cimetidine, which competitively blocks creatinine tubular transport. Methods. The study was performed in the group of 87 patients after renal transplantation. In this group, estimated clearance and creatinine clearance after cimetidine administration (1000 mg in 75 patients and then 1600 mg in 12 patients with plasma creatinine above 3 mg/dL) were determined. Results. Analysis of mean percentage differences between clearance values after cimetidine administration and estimated clearance shows increasing contribution of creatinine tubular secretion along with plasma creatinine increase in renal transplant recipients. A higher dose of cimetidine resulted in lower clearance values in renal transplant recipients with plasma creatinine above 3 mg/dL. Conclusions. Creatinine clearance after administration of 1000 mg cimetidine seems to be a useful measure of glomerular filtration rate in renal graft recipients with plasma creatinine concentration below 2.5 mg/L. Higher dose of cimetidine would be needed to effectively block tubular excretion at higher concentrations of creatinine. Establishing an efficient but safe dose of cimetidine for such patients needs further investigations. As we have noticed that creatinine clearance calculated according to MDRD formula was similar to the clearance after administration of cimetidine, we propose a strategy of one GFR measurement at baseline using 24h urine collection after cimetidine administration and follow-up with creatinine clearance calculated from MDRD formula during standard check-up visits.