Ana Savic-Radojevic

Glutathione S -transferases in kidney and urinary bladder tumors

Exposure to potential carcinogens is an etiologic factor for renal cell carcinoma (RCC) and transitional cell carcinoma (TCC) of the urinary bladder. Cytosolic glutathione S-transferases (GSTs) are a superfamily of enzymes that protect normal cells by catalyzing conjugation reactions of electrophilic compounds, including carcinogens, to glutathione. Some GST enzymes possess antioxidant activity against hydroperoxides. The most well characterized classes have been named alpha (GSTA), mu (GSTM), pi (GSTP) and theta (GSTT); each of these classes contains several different isoenzymes. Several types of allelic variation have been identified within classes, with GSTM1-null, GSTT1-null and GSTP1-Ile105/Ile105 conferring impaired catalytic activity. The effects of GSTM1 and GSTT1 polymorphism on susceptibility to RCC depend on exposure to specific chemicals. Individuals with the GSTM1-null genotype carry a higher risk for TCC. The roles of GSTT1 polymorphism in TCC and GSTP1 polymorphisms in both cancers are still controversial. During kidney cancerization, expression of GSTA isoenzymes tends to decrease, which promotes the pro-oxidant environment necessary for RCC growth. In the malignant phenotype of TCC of the bladder, upregulation of various GST classes occurs. Upregulation of GSTT1 and GSTP1 might have important consequences for TCC growth by providing a reduced cellular environment and inhibition of apoptotic pathways.

Glutathione S-transferase A1, M1, P1 and T1 null or low-activity genotypes are associated with enhanced oxidative damage among haemodialysis patients

BACKGROUND Increased oxidative stress is a hallmark of end-stage renal disease (ESRD). Glutathione S-transferases (GST) are involved in the detoxification of xenobiotics and protection of oxidative damage. We hypothesized that genetic polymorphism in antioxidant enzymes GSTA1, GSTM1, GSTP1 and GSTT1 is more frequent in ESRD and modulates the degree of oxidative stress in these patients. METHODS GSTA1, GSTM1, GSTP1 and GSTT1 genotypes were determined in 199 ESRD patients and 199 age- and gender-matched controls. Markers of protein and lipid oxidative damage [thiol groups, carbonyl groups, advanced oxidative protein products, nitrotyrosine, malondialdehyde (MDA) and MDA adducts], together with total oxidant status and pro-oxidant-antioxidant balance were determined. RESULTS Individual GST polymorphisms influence vulnerability to both protein and lipid oxidation, with GSTM1-null gene variant having the most pronounced effect. Furthermore, a strong combined effect of null/low-activity GSTM1, GSTT1, GSTA1 and GSTP1 genotypes in terms of susceptibility towards oxidative and carbonyl stress was found in ESRD patients. When patients were stratified according to GSTM1 and GSTT1, the highest oxidant damage was noted in those with the GSTM1-null/GSTT1-null genotype. The observed effect was even stronger in patients with the third low-activity GSTP1 or GSTA1 genotype. Finally, the level of oxidative and carbonyl stress was most pronounced in the subgroup of patients with all four null or low-activity GSTM1, GSTT1, GSTP1 and GSTA1 genotypes. CONCLUSIONS According to the GST genotype, ESRD patients may be stratified in terms of the level of oxidative and carbonyl stress that might influence cardiovascular prognosis, but could also improve efforts towards individualization of antioxidant treatment.

Dyslipidemia and oxidative stress in PCOS.

Polycystic ovary syndrome (PCOS) is a common metabolic and reproductive disorder in women. An increased cardiovascular risk has to be anticipated in PCOS as it is a metabolically unstable condition. Among cardiovascular risk factors, dyslipidemia is certainly the most persistent and highly prevalent. Predominant observation is an elevation of LDL cholesterol in all PCOS patients. Decreased concentrations of HDL cholesterol are found in obese PCOS from the third decade of life onwards while triglycerides start to rise from the second decade of life. PCOS is associated with oxidative stress, namely increased production of free radicals followed by decreased serum antioxidant levels and antioxidant enzyme activity. Broad range of endocrine and metabolic disturbances like obesity, hyperinsulinemia as well as dyslipidemia might be responsible for PCOS-associated oxidative stress. Therapeutic interventions in PCOS women based on lifestyle modification as well as use of insulin sensitizers did not show significant effect on dyslipidemia. Statins are considered to be a group of promising agents that are safe and effective in improving total cholesterol, LDL cholesterol and triglycerides, and possess antioxidant activity. Supplementation with omega-3 fatty acids, α-lipoic acid and N-acetylcysteine is considered to have an anti-inflammatory and antioxidant effect and to improve dyslipidemia and insulin sensitivity in PCOS women.

Evaluation of Oxidative Stress after Repeated Intravenous Iron Supplementation

Parenteral iron has been recommended for the treatment of iron deficiency in the majority of maintenance hemodialyzed (HD) patients. However, iron supplementation and consequent over saturation of transferrin and high iron levels, may aggravate oxidative stress already present in these patients. This study aimed to further clarify the role of repeated intravenous iron therapy as a supplementary cause of oxidative stress in HD patients. Markers of free radical activities (carbonyl reactive derivatives, CRD, thiol groups, SH, malondialdehyde, MDA) and antioxidant enzyme activities (superoxide dismutase, SOD and glutathione peroxidase, GPX) were determined in plasma and red blood cells (RBC) of 19 hemodialysis patients given a total iron dose of 625 mg (ferrogluconat, Ferrlecit, 62.5 mg). Blood samples were taken before the first and after the last dose of iron. Twenty apparently normal subjects served as healthy controls. Before iron treatment, HD patients exhibited increased concentrations of MDA and CRD in plasma and red blood cells, accompanied with impaired antioxidant capacity. All patients responded to iron therapy with a significant increase in their serum ferritin, serum iron, hemoglobin, and red blood cells levels. However, iron treatment resulted in enhanced oxidative stress in plasma of HD patients, since significant increase in plasma MDA and CRD concentrations, together with a decrease in nonprotein SH groups levels were detected. Supplementation with iron did not significantly influence plasma SOD and GPX activities, nor did any of the red blood cell parameters tested. Our data show that, despite improvement in hematological parameters, an increase in iron stores due to supplementation could also contribute to increased free radical production in HD patients.

GSTA1, GSTM1, GSTP1, and GSTT1 polymorphisms and susceptibility to smoking-related bladder cancer: A case-control study

OBJECTIVES Glutathione S-transferases (GSTs) are a family of enzymes involved in detoxification. Genes encoding for GSTA1, GSTM1, GSTP1, and GSTT1 proteins are polymorphic, which can result in complete or partial loss of enzyme activity. Previous studies have associated polymorphisms of GSTA1, GSTM1, and GSTP1 genes with a higher risk of bladder cancer, but this is still controversial. Potential role of GSTA1 polymorphism in susceptibility to bladder cancer in Whites is lacking. We examined association between GSTA1, GSTM1, GSTP1, and GSTT1 gene variants and bladder cancer risk and evaluated whether they were modified by smoking. MATERIALS AND METHODS A hospital-based case-control study recruited 201 incidence cases and 122 age-matched controls. Deletion polymorphism of GSTM1 and GSTT1 was identified by polymerase chain reaction method. Single nucleotide polymorphism of GSTA1 and GSTP1 was identified by restriction fragment length polymorphism method. Uniconditional multivariate logistic regression was applied to model association between genetic polymorphisms and bladder cancer risk, as well as effect modification by smoking. RESULTS No significant difference was observed in the distributions of GSTM1, GSTT1, GSTA1, and GSTP1 gene variants between patients and controls. None of the examined polymorphisms was significantly associated with bladder cancer risk independently. The results of gene-smoking interaction analyses indicated a significant combined effect of smoking and all common GST polymorphisms tested (P for trend = 0.001). However, the most significant effect on bladder cancer risk was observed in smokers carrying lower activity GSTA1-AB/BB and GSTM-null genotype (OR = 3.5, P < 0.05) compared with GSTA1-AA and GSTM1-active non-smokers. Overall, the risk observed did not significantly differ with respect to quantity of cigarettes smoked. However, heavy smokers with GSTM1-null genotype had 2 times higher risk of bladder cancer than GSTM1-null light smokers (OR = 4.8 vs. OR = 2.0) when GSTM1-active non-smokers served as reference group. Smokers carrying both GSTM1-null and GSTA1-AB + BB genotypes exhibited the highest risk of bladder cancer (OR = 2.00, P = 0.123). CONCLUSIONS Null or low-activity genotypes of the GSTA1, GSTM1, GSTT1, and GSTP1 did not contribute independently towards the risk of bladder cancer in our patients. However, in association with smoking, both low activity GSTA1 and GSTM1-null genotype increase individual susceptibility to bladder cancer.

Altered antioxidant capacity in human renal cell carcinoma: role of glutathione associated enzymes.

PURPOSE We aimed to discern the role of glutathione (GSH) associated enzymes in maintaining high GSH levels in renal cell carcinoma (RCC) of the clear cell type and analyze RCC enzyme antioxidant capacity. Since changes in cellular redox balance in RCC might also be related to alterations of glutathione S-transferase (GST) phenotype, GST class alpha and pi expression was also explored. METHODS AND MATERIALS Human kidney specimens of tumor and distant nontumor regions were obtained from 15 patients with RCC at the time of surgery. The activities of GSH-replenishing enzymes, gamma-glutamylcysteine synthetase (gamma-GCS), gamma-glutamyl transferase (gamma-GT), and glutathione reductase (GR), as well as the activities of antioxidant enzymes glutathione peroxidase (GPX) and catalase (CAT) were determined spectrophotometrically. GST alpha and pi class expression was determined by immunoblot. RESULTS In the course of renal cancerization, significant changes appear in the activities of GSH-replenishing and antioxidant enzymes. The activity of the key enzyme of GSH synthesis, gamma-GCS, is up-regulated (P < 0.001), while the activities of gamma-GT and GR are down-regulated in renal tumors compared to nontumor tissue (P < 0.001 and P < 0.05, respectively). Activities of GPX and CAT were also down-regulated (P < 0.001 and P < 0.05, respectively) in RCC. Changes in enzyme antioxidant capacity in RCC were associated with decreased GST class alpha (P < 0.001) and unchanged GST pi expression at the protein level. CONCLUSIONS Changes in redox status in RCC as a consequence of decreased enzyme antioxidant capacity, together with altered GST alpha expression, may be important factors in development and tumor growth. The up-regulation of gamma-GCS and high levels of GSH in RCC may be an attempt to limit injury caused by oxidative stress.

Enhanced GSTP1 expression in transitional cell carcinoma of urinary bladder is associated with altered apoptotic pathways

OBJECTIVES Glutathione S-transferase P1 (GSTP1) provides an important link between activity of regulatory stress kinases and apoptotic pathways. It can be hypothesized that up-regulated GSTP1, in TCC, might enhance apoptosis inhibition. We aimed to establish whether relationship between GSTP1 expression and executive (pro-caspase 3, cleaved caspase 3) and regulatory (Bcl-2) apoptotic pathways in TCC exists. MATERIALS AND METHODS Samples were obtained from 84 TCC patients (41 consecutive patient with muscle noninvasive and 43 consecutive patients with muscle invasive TCC tumors), who underwent surgery at the Institute of Urology and Nephrology, Clinical Centre of Serbia, during 2006 and 2007. Expression of GSTP1, pro-caspase 3 (CPP32), and Bcl-2, as well as cleaved caspase-3 labeling index (LI) were determined by immunocytochemistry. Levels of expression were correlated with tumor stage, grade, and invasiveness. RESULTS GSTP1 protein expression was demonstrated in all tumor samples examined. According to GSTP1 status, all tumors were divided into groups with low, moderate, or high GSTP1 status. Expression of CPP32 and cleaved caspase 3 was positive in 80% of TCC patients. Their levels differed significantly between groups with various GSTP1 expression (P < 0.05), with the lowest CPP32 expression and cleaved caspase 3 LI in tumors with high GSTP1 status. Moreover, significant negative correlation was found between GSTP1 level and cleaved caspase 3 LI (r = -0.459, P = 0.041). The positive rate of Bcl-2 protein expression was 48%. Most of the Bcl-2 positive patients exhibited at the same time high GSTP1 positivity (P = 0.078). Significant association with tumor grade and stage was found for all examined parameters except for CPP32 regarding tumor grade. CONCLUSIONS Based on results obtained, we conclude that enhanced GSTP1 expression in TCC of urinary bladder is associated with altered apoptotic pathways. Molecular interplay between GSTP1 and members of apoptotic cascade might, at least partially, play a role in development of invasive characteristics of TCC.

Serum gamma glutamyl-transferase is a sensitive but unspecific marker of metastatic renal cell carcinoma

Objective:  To address the role of serum γ‐glutamyl transferase (GGT) as a marker of metastases in patients with renal cell carcinoma.

Down-regulation of experimental allergic encephalomyelitis in DA rats by tiazofurin

The immunomodulatory potential of tiazofurin (TR) on experimental autoimmune encephalomyelitis (EAE) was investigated. Given continuously, TR dose-dependently suppressed the development of EAE in Dark Agouti (DA) rats immunized with either rat spinal cord homogenate (SCH) or myelin oligodendrocyte glycoprotein (MOG). Amelioration of clinical signs was also obtained when the drug was administered during the inductive phase only (day 0 to 8), or during the effector phase (day 10 to 20) of the disease. Efficacy of TR was further evaluated by adoptive transfer of the disease with myelin basic protein (MBP)-sensitized draining lymph node cells (DLNC). Cells from TR-protected rats failed to transfer the disease into naive syngeneic recipients; in addition, TR treatment of recipient rats that had received MBP-sensitized lymphoid cells diminished the adoptively transferred EAE. A reduction of clinical EAE in TR-treated rats was accompanied with the absence of mononuclear infiltration in the spinal cord and defective adhesive cell-cell interactions. The anti-MOG autoAb production was also decreased. Importantly, no evidence for a generalized impairment of the T cell activity, nor decreased in vitro proliferative antigen specific response of LNC from TR-treated animals was found. These results suggest that TR exerts its EAE protective and suppressive effects by limiting adhesive interactions involved in the autoimmune pathogenic process, and due to the lack of general immunosuppressive activity, it should be considered as a candidate drug for the treatment of neuroinflammatory diseases like multiple sclerosis (MS).

Markers of oxidative damage in chronic heart failure: role in disease progression

Abstract Background: We aimed to study the relationship between markers of oxidative lipid or protein damage and ventricular remodeling and the validity of 8-epi-prostaglandin F2α (8-epi-PGF2α) as an indicator of disease severity in patients with ischemic chronic heart failure (CHF). Patients and methods: We enrolled four groups of 12 patients with varying CHF according to the New York Heart Association (NYHA) classification and 25 controls. Urinary 8-epi-PGF2α and plasma malondialdehyde and protein thiol (P-SH) groups were correlated with echocardiographic indices of remodeling. The reliability of isoprostanes was analyzed by a receiver operating characteristics (ROC) curve. Results: NYHA class III and IV patients exhibited elevated 8-epi-PGF2α levels, increased malondialdehyde concentrations and decreased P-SH groups when compared to controls and NYHA I and II patients. 8-Epi-PGF2α and P-SH groups correlated significantly with indices of remodeling. The ROC curve drawn for 8-epi-PGF2α allowed us to differentiate NYHA class III and IV patients from NYHA class I and II patients with a sensitivity of 95.8% and specificity of 95.8% (cut off 0.84 ng/mg creatinine; area under curve 0.99; P < 0.001). Conclusions: Markers of oxidative damage are unlikely to play a significant role in early stages of CHF. However, they might become important in the course of CHF when their concentrations reach critical levels. Urinary 8-epi-PGF2α is a reliable indicator of symptomatic CHF.