Ashok Kumar Tripathi

Advanced glycation end products enhance reactive oxygen and nitrogen species generation in neutrophils in vitro

Increased oxidative stress (OS) in diabetes mellitus is one of the major factors leading to diabetic pathology. However, the mediators and mechanism that provoke OS in diabetes is not fully understood, and it is possible that accumulation of advanced glycation end products (AGEs) formed secondary to hyperglycemic conditions may incite circulating polymorphonuclear neutrophils (PMN) to generate reactive oxygen species (ROS). In this report, we aim to investigate the effect of AGE on reactive oxygen and nitrogen species generation and subsequent OS in PMN. AGE-HSA exert dose- and time-dependent enhancement of ROS and reactive nitrogen intermediates (RNI) generation by PMN. Increased ROS and RNI generation were found to be mediated through the upregulation of NADPH oxidase and inducible nitric oxide synthase (iNOS), respectively, as evident from the fact that AGE-treated neutrophils failed to generate ROS and RNI in presence of diphenyleneiodonium, a flavoprotein inhibitor for both enzymes. Further increased generation of ROS and RNI ceased when the cells were incubated with anti-RAGE antibody suggesting the involvement of AGE–RAGE interaction. Also increased malondialdehyde (MDA) and protein carbonyl formation in AGE-exposed PMN suggest induction of OS by AGE. This study provides evidence that AGEs may play a key role in the induction of oxidative stress through the augmentation of PMN-mediated ROS and RNI generation and this may be in part responsible for development of AGE-induced diabetic pathology.

Association of glutathione S-transferase M1 and T1 gene polymorphism with oxidative stress in diabetic and nondiabetic chronic kidney disease

Background and Objective: Glutathione S-transferases (GSTs) belong to a family of ubiquitous and multifunctional enzymes that work as one of the endogenous antioxidants in our body. This study was designed to look into the association of GST polymorphism with oxidative stress in both diabetic and nondiabetic chronic kidney disease (CKD). Design and Methods: Three groups of patients (50 in each): diabetics without CKD (DM), diabetic CKD (DM-CKD), and nondiabetic CKD (NDM-CKD) and 50 age- and sex-matched healthy controls were recruited. Genotyping was done for GSTM1 and GSTT1 genes using a multiplex polymerase chain reaction. Serum GST and malondialdehyde (MDA) as a marker of oxidative stress were measured spectrophotometrically. Results: Based on genotyping, subjects were categorized as GSTM1+/GSTT1+, GSTM1−/GSTT1+, GSTM1+/GSTT1−, and GSTM1−/GSTT1−. Serum GST levels were lower among subjects with deletion in one/both GST genes, whereas MDA levels were found to be correspondingly raised. A negative correlation for MDA versus GST levels was observed among genotypes with one/both gene deletions. Presence of GSTM1+/GSTT1− and GSTM1−/GSTT1− was significantly higher among patients with CKD in both diabetics and nondiabetics. Interpretations and Conclusions: GSTM1 and GSTT1 deletions singly or together were associated with lower GST levels and higher oxidative stress in both diabetic and nondiabetic CKD. Interestingly, GSTT1 deletion appears to be associated with both diabetic and nondiabetic CKD irrespective of the GSTM1 status.

Protective effects of dietary ginger (Zingiber officinales Rosc.) on lindane-induced oxidative stress in rats.

The protective effect of dietary feeding of Zingiber officinales Rosc. (ginger) against lindane‐induced oxidative stress was investigated in male albino rats. Oxidative stress was monitored by estimating the extent of lipid peroxidation, activities of the oxygen free radical (OFR) scavenging enzymes superoxide dismutase (SOD) and catalase (CAT) and the status of the glutathione redox cycle antioxidants. Lindane administration (30 mg/kg bw orally for 4 weeks) was associated with enhanced lipid peroxidation and compromised antioxidant defenses in rats fed a normal diet. Concomitant dietary feeding of ginger (1%w/w) significantly attenuated lindane‐induced lipid peroxidation, accompanied by modulation of OFR scavenging enzymes as well as reduced glutathione (GSH) and the GSH dependent enzymes glutathione peroxidase (Gpx), glutathione reductase (GR) and glutathione‐S‐transferase (GST) in these rats. These findings suggest that a diet containing naturally occurring compounds is effective in exerting protective effects by modulating oxidative stress. Copyright

Endosulfan-induced apoptosis and glutathione depletion in human peripheral blood mononuclear cells: Attenuation by N-acetylcysteine.

Present study investigated whether endosulfan, an organochlorine pesticide is able to deplete glutathione (GSH) and induce apoptosis in human peripheral blood mononuclear cells (PBMC) in vitro. The role of oxidative stress in the induction of apoptosis was also evaluated by the measurement of the GSH level in cell lysate. The protective role of N‐acetylcysteine (NAC) on endosulfan‐induced apoptosis was also studied. Isolated human PBMC were exposed to increasing concentrations (0–100 µM) of endosulfan (α/β at 70:30 mixture) alone and in combination with NAC (20 µM) up to 24 h. Apoptotic cell death was determined by Annexin‐V Cy3.18 binding and DNA fragmentation assays. Cellular GSH level was measured using dithionitrobenzene. Endosulfan at low concentrations, i.e., 5 and 10 µM, did not cause significant death during 6 h/12 h incubation, whereas a concentration‐dependent cell death was observed at 24 h. DNA fragmentation analysis revealed no appreciable difference between control cells and 5 µM/10 µM endosulfan treated cells, where only high molecular weight DNA band was observed. Significant ladder formation was observed at higher concentration, which is indicative of apoptotic cell death. Intracellular GSH levels decreased significantly in endosulfan‐treated cells in a dose‐dependent manner, showing a close correlation between oxidative stress and degree of apoptosis of PBMC. Cotreatment with NAC attenuated GSH depletion as well as apoptosis. Our results provide experimental evidence of involvement of oxidative stress in endosulfan‐mediated apoptosis in human PBMC in vitro.

Study on organochlorine pesticide levels in chronic kidney disease patients: association with estimated glomerular filtration rate and oxidative stress.

Nephrotoxicity of organochlorine pesticides (OCPs) has been established in experimental animal models. This study was designed to evaluate the relationship of the blood OCPs level with the estimated glomerular filtration rate (eGFR) and oxidative stress (OS) in chronic kidney disease (CKD) patients. Patients in different stages of CKD (n = 150) and age, sex matched healthy controls (n = 96) were recruited. The blood OCPs level were analyzed by gas chromatography, and plasma levels of several OS parameters such as malondialdehyde (MDA), protein carbonyl, advanced oxidation protein products (AOPP), and total thiols were quantified by standard spectrophotometric methods. We observed significantly higher levels of hexachlorocyclohexane (α, γ), endosulfan, aldrin, p,p′‐dichlorodiphenyldichloroethylene (DDE), and total pesticides in CKD patients. Negative correlation was also observed for aldrin, p,p′‐DDE and total pesticides (p < 0.05) with eGFR. Plasma levels of MDA and AOPP showed significant positive association with the total pesticides level, indicating augmentation of OS with increased accumulation of OCPs in CKD patients.

A study on serum advanced glycation end products and its association with oxidative stress and paraoxonase activity in type 2 diabetic patients with vascular complications.

OBJECTIVES Enhanced formation of advanced glycation end products (AGEs) formed secondary to hyperglycemic conditions has been linked to diabetes mellitus (DM) associated complications. We investigated the clinical relevance of estimating AGEs and their relationship with oxidative stress (OS) and paraoxonase (PON1) activity in type 2 DM (T2DM) in relation to development of vascular complications. DESIGN AND METHODS Serum AGEs along with PON1 activity, protein carbonyl (PCO), advanced oxidation protein products (AOPP), lipid peroxidation (MDA), and total thiol (T-SH) were determined in 157 T2DM patients (DM without complications n=57, DM micro-vascular complications n=53, DM macro-vascular complications n=47) and 40 healthy controls. RESULTS Serum AGE level increased significantly in various study groups in following manner: healthy control<DM without complications<DM-macro<DM-micro. Logistic regression analysis using diabetic complications as dependent variable showed significant association with AGE level and PON1 activity even after adjustment for confounding factors. Receiver-operating-characteristics curve analysis showed that 2-fold increased in glycation and 50% decrease in PON1 activity may lead to development of vascular complications in diabetic subjects. PCO, AOPP and MDA were higher and PON1 activity was lower in T2DM with complications than those without complications. Among diabetic patients AGEs showed significant positive correlation with HbA(1C), MDA, AOPP, and negative correlation with PON1 activity and T-SH. CONCLUSION High serum AGE concentration and low PON1 activity may be considered as additional risk factor for development of vascular complications in T2DM. AGE formation plays significant role in induction of OS in diabetes.

Role of advanced glycation end product (AGE)-induced receptor (RAGE) expression in diabetic vascular complications.

AIMS Vascular complications are the major causes of morbidity and mortality in diabetic subjects. Interaction of advanced glycation end products (AGEs) with their receptor (RAGE) induces signal transduction that culminates in vascular complications. Therefore, in the present study we investigated the dependence of RAGE expression on circulating AGEs and evaluated the outcome of AGE-RAGE interaction by the oxidative stress and nature of vascular complications in type 2 diabetes mellitus (T2DM) patients. METHODS RAGE expression was determined by quantitative real-time PCR and western blotting, serum AGEs were estimated by ELISA and spectrofluorometry and oxidative stress markers namely protein carbonyl (PCO), advanced oxidation protein products (AOPP) and lipid peroxidation (MDA) were assayed spectrophotometerically in 75 T2DM patients (DM without vascular complication n=25; DM with microvascular complications n=25; DM with macrovascular complications n=25) and 25 healthy controls. RESULTS Serum AGE level was significantly higher in diabetic patients having vascular complications as compared to T2DM without complications (p<0.01). RAGE m-RNA expression level in PBMCs assayed by quantitative real time PCR was four times higher in diabetic subjects without vascular complications while DM patients having microvascular and macrovascular complications showed 12 fold and 8 fold higher RAGE m-RNA expression respectively compared to healthy controls. Circulating AGE level showed significant positive correlation with RAGE m-RNA expression and oxidative stress markers. CONCLUSION AGE-mediated exacerbation of RAGE expression may contribute to oxidative stress generation that plays a key role in pathogenesis of vascular complications in diabetes.

Role of HSP27 and reduced glutathione in modulating malathion-induced apoptosis of human peripheral blood mononuclear cells: ameliorating effect of N-acetylcysteine and curcumin.

Malathion exerts cholinergic effects at high doses. However, a consequence of low dose (non-cholinergic) exposure causes immunotoxicity and oxidative stress. Hence, this study was designed to find out (i) the cytotoxic and apoptotic effects of cholinergic and non-cholinergic doses of malathion using cultured peripheral blood mononuclear cells (PBMCs) and (ii) the role of GSH and HSP27 and (iii) protective effects of N-acetylcysteine (GSH inducer) and curcumin (HSP27 inducer). In low doses, malathion caused mild depletion of GSH, threefold increase in HSP27 level and a range bound cytotoxicity and apoptosis of PBMC. In contrast, cholinergic dose exposures caused severe GSH depletion and exhibited dose dependent cytotoxicity and necrosis without any significant effect on HSP27 levels. Curcumin increased the levels of HSP27 in PBMC only in presence of low doses and not at high doses of malathion. Both NAC and curcumin were able to prevent malathion-mediated apoptosis of PBMC effectively at non-cholinergic doses and at this concentration of malathion, HSP27 induction keeps apoptosis and GSH depletion under control. Also NAC and curcumin may act as potential therapeutic agents to prevent malathion-induced immunotoxicity.

Low intensity microwave radiation induced oxidative stress, inflammatory response and DNA damage in rat brain.

Over the past decade people have been constantly exposed to microwave radiation mainly from wireless communication devices used in day to day life. Therefore, the concerns over potential adverse effects of microwave radiation on human health are increasing. Until now no study has been proposed to investigate the underlying causes of genotoxic effects induced by low intensity microwave exposure. Thus, the present study was undertaken to determine the influence of low intensity microwave radiation on oxidative stress, inflammatory response and DNA damage in rat brain. The study was carried out on 24 male Fischer 344 rats, randomly divided into four groups (n=6 in each group): group I consisted of sham exposed (control) rats, group II-IV consisted of rats exposed to microwave radiation at frequencies 900, 1800 and 2450 MHz, specific absorption rates (SARs) 0.59, 0.58 and 0.66 mW/kg, respectively in gigahertz transverse electromagnetic (GTEM) cell for 60 days (2h/day, 5 days/week). Rats were sacrificed and decapitated to isolate hippocampus at the end of the exposure duration. Low intensity microwave exposure resulted in a frequency dependent significant increase in oxidative stress markers viz. malondialdehyde (MDA), protein carbonyl (PCO) and catalase (CAT) in microwave exposed groups in comparison to sham exposed group (p<0.05). Whereas, levels of reduced glutathione (GSH) and superoxide dismutase (SOD) were found significantly decreased in microwave exposed groups (p<0.05). A significant increase in levels of pro-inflammatory cytokines (IL-2, IL-6, TNF-α, and IFN-γ) was observed in microwave exposed animal (p<0.05). Furthermore, significant DNA damage was also observed in microwave exposed groups as compared to their corresponding values in sham exposed group (p<0.05). In conclusion, the present study suggests that low intensity microwave radiation induces oxidative stress, inflammatory response and DNA damage in brain by exerting a frequency dependent effect. The study also indicates that increased oxidative stress and inflammatory response might be the factors involved in DNA damage following low intensity microwave exposure.

Detection of Low Level Microwave Radiation Induced Deoxyribonucleic Acid Damage Vis-à-vis Genotoxicity in Brain of Fischer Rats.

Background: Non-ionizing radiofrequency radiation has been increasingly used in industry, commerce, medicine and especially in mobile phone technology and has become a matter of serious concern in present time. Objective: The present study was designed to investigate the possible deoxyribonucleic acid (DNA) damaging effects of low-level microwave radiation in brain of Fischer rats. Materials and Methods: Experiments were performed on male Fischer rats exposed to microwave radiation for 30 days at three different frequencies: 900, 1800 and 2450 MHz. Animals were divided into 4 groups: Group I (Sham exposed): Animals not exposed to microwave radiation but kept under same conditions as that of other groups, Group II: Animals exposed to microwave radiation at frequency 900 MHz at specific absorption rate (SAR) 5.953 × 10–4 W/kg, Group III: Animals exposed to 1800 MHz at SAR 5.835 × 10–4 W/kg and Group IV: Animals exposed to 2450 MHz at SAR 6.672 × 10–4 W/kg. At the end of the exposure period animals were sacrificed immediately and DNA damage in brain tissue was assessed using alkaline comet assay. Results: In the present study, we demonstrated DNA damaging effects of low level microwave radiation in brain. Conclusion: We concluded that low SAR microwave radiation exposure at these frequencies may induce DNA strand breaks in brain tissue.