The erythrocyte glutathione S-transferase (e-GST) is a member of a superfamily of inducible enzymes involved in cell detoxification that shows an increased expression in chronic kidney disease (CKD) patients. We propose a new automated analysis procedure for e-GST activity that has been validated in 72 CKD patients and 62 maintenance hemodialysis patients (MHD). Regression analysis was carried out to assess association between e-GST activity data, main clinical variables, and plasma homocysteine (Hcy), a modified sulfur amino acid known as potential risk factor for cardiovascular disease that is increased above normal levels in more than 90% of the uremic patients. An increased e-GST activity was confirmed in MHD patients (N=62; 10.2±0.4 U/gHb) compared with healthy subjects (N=80; 5.8±0.4 U/gHb), and as an original finding, a significant increase of e-GST activity was observed in pre-dialysis CKD patients with a positive correlation with disease severity weighted according to the four stages of "Kidney Disease Outcomes Quality Initiative" classification (7.4±0.5, 8±1, 9.5±0.6, 12±1 U/gHb, respectively). No correlation was found between e-GST activity and hemoglobin, transferrin, blood iron and the markers of systemic inflammation and renal function such as alpha-1 acid glycoprotein and high-sensitive C-Reactive Protein, beta-2 microglobulin and the index of malnutrition-inflammation PINI, while a significant correlation was observed for the first time between plasma Hcy and e-GST activity (r2=0.64, P<0.0001) in MHD patients. Hcy, however, was not identified as an inhibitor of e-GST enzyme. The results in this study suggest the potential for automated e-GST analysis as a valuable tool to further explore phase II-related uremic toxicity in CKD and MHD patients.

a b s t r a c tProject: Oxidative stress (OS) is enhanced in hemodialysis (HD) patients. Lipid peroxidation and oxidative damage to glycids, proteins and nucleic acids are the main consequences of OS and are associated with increased cardiovascular risk. Vitamin E and glutathione peroxidase (GSH-Px) represent the main antioxidant systems in human cells. Selenium (Se), bound to the active sites of GSH-Pxs, plays a critical role in this antioxidant defence system. Statins are widely used and extensively investigated in the prevention of cardiovascular disease, notably in high-risk subjects. Several studies show antioxidant effects of statins not related to their lipid-lowering action. Our study aimed to compare serum Se concentration in ESRD patients on maintenance HD and in homogeneous healthy subjects and to investigate whether chronic treatment with statins may interfere with serum Se concentration in HD patients. Procedure: A total of 103 HD patients and 69 healthy subjects were enrolled; HD patients were divided into patients who were not treated with statins (group A) and patients who assumed statins since 6 months at least (group B). Serum Se was determined by atomic absorption spectrometry. Results: Serum Se was significantly lower in HD patients of group A compared with healthy subjects (81.65719.66 Vs. 96.47715.62 mcg/L, po0.0040). However, in HD patients who assumed statins serum, Se was significantly higher than in HD patients who did not (111.83718.82 vs. 81.65719.66 mcg/L, po0.0001). Conclusions: Our results suggest that in HD patients chronic treatment with statins is related to higherserum Se concentration.

Reactive oxygen species formation and release of pro-inflammatory/pro-atherogenic cytokines, that is, interleukin 1-beta and tumor necrosis factor-alpha, need the activation of the arachidonic acid cascade via the enzyme 5-lipoxygenase (5-Lox). 5-Lox activity and expression are significantly increased in peripheral blood mononuclear cells (PBMCs) of end-stage renal disease (ESRD) patients on maintenance hemodialysis (HD). Diets enriched with n-3 polyunsaturated fatty acids (PUFAs) (omega-3) have been associated to a lower incidence of coronary heart disease (CHD) and a reduction in atherosclerotic lesions. Omega-3 may interfere with the arachidonic acid cascade by inhibiting 5-Lox. Lipid peroxidation, leukotriene B(4) (LTB(4)) production, 5-Lox activity and expression were investigated in PBMC isolated from ESRD patients under maintenance HD before and after a 3-month oral supplementation with omega-3 at a daily dose of 2700 mg of n-3 PUFAs at the average eicosapentaenoic acid/docosaesaenoic acid ratio of 1.2 and finally after a further 3-month washout with no omega-3 supplementation. PBMCs from non-uremic volunteers were also investigated for comparison to normal parameters. Administration of omega-3 reduced significantly lipid peroxidation (P < 0.0001), LTB(4) synthesis (P < 0.0001) and 5-Lox activity (P < 0.0001), with no effect on 5-Lox protein expression. After the 3-month washout, all parameters were comparable to those observed before treatment. Our results resemble those obtained after oral administration of vitamin E and are consistent with a reversible, dose-dependent inhibition of 5-Lox by omega-3. Upregulation of 5-Lox may also be related to the increased mitochondrial damage and apoptosis of PBMCs observed in ESRD patients compared to non-uremic controls. Omega-3 may thus protect PBMCs of ESRD patients against oxidative stress.

No abstract