Comparative study on glutathione transferases of rat brain and testis under the stress of phenobarbitol and beta-methylcholanthrene

Sensitivity of glutathione S-transferases to high doses of acrylamide in albino wistar rats: Affinity purification, biochemical characterization and expression analysis

The main objectives of this study were to purify the glutathione S-transfereses (GSTs) and assess the effect of high doses of acrylamide (ACR) on male albino Wistar rat liver, kidney, testis and bran GST activities, and expression analysis of GST. ACR (50 mg/300 ml) was ingested for 40 days (20 doses) in drinking water on alternative days, on 40 day post ingestion the control and treated tissues were collected for GST purification by affinity column and biochemical characterization of GSTs by substrate specificities, and GST expression by immuno dot blots. In the analysis of the purified GSTs, we observed that liver GSTs were resolved in to three bands known as Yc, Yb and Ya; kidney GSTs were resolved in to two bands known as Yc and Ya; testis and brain GSTs were resolved as four bands known as Yc, Yb, Yβ and Yδ on 12.5% sodium dodecyl sulfate polyacrylamide gel (SDS PAGE). In the analysis of biochemical characterization, we observed a significant decrease (p < 0.05) in the specific activities of liver GST isoforms with the substrates 1-chloro 2,4-dinitrobenzene (CDNB), bromosulfophthalein (BSP), p-nitrophenyl acetate (pNPA), p-nitrobenzyl chloride (pNBC) and cumene hydroperoxide (CHP), but showed no activity with ethacrynic acid (ECA) and significant decrease (p < 0.05) in the specific activities of kidney GST isoforms with the substrates CDNB, pNPA, pNBC and CHP, but showed no activity with BSP and ECA, and a significant decrease (p < 0.05) in the specific activities of testis and brain GST isoforms with the substrates CDNB, BSP, pNPA, pNBC, ECA and CHP. In the analysis of immuno dot blots, we observed a decreased expression of liver, kidney, testis and brain GSTs. Through the affinity purification and biochemical characterization, we observed a tissue specific distribution of GSTs that is liver GSTs possess Yc, Yb and Ya sub units known as alpha (α) and mu (μ) class GSTs; kidney GSTs possess Yc and Ya sub units known as (α) alpha class GST; testis and brain GSTs possess Yc, Yb, Yβ and Yδ sub units known as alpha (α), mu (μ) and pi (π) class GSTs. Purification studies, biochemical characterization and immuno dot blot analysis were revealed the GSTs were sensitive to high doses of ACR and the high level exposure to ACR cause the damage of detoxification function of GST due to decreased expression and hence lead to cellular dysfunction of vital organs.

Role of Glutathione-S-transferases in neurological problems

INTRODUCTION

Role of Glutathione-S-transferases (GSTs) has been well explored in the cellular detoxification process, regulation of redox homeostasis and S-glutothionylation of target proteins like JNK, ASK1 etc. However, altered levels or functions of this enzyme or their subtypes have emerged in the development of several pathologies diseases such as Alzheimer's disease, Parkinson's disease, cancer and related conditions. Oxidative stress is one of the possible pathological events that contributes significantly to activation of degenerating cascades inside neuronal cells. The central nervous system is highly sensitive to oxidative stress because of low levels or capacities of antioxidant enzymes. The brain is highly metabolic in nature making it susceptible to oxidative stress. Areas covered: The present review provides a comprehensive overview of the multiple connections of GSTs within diverse neurological diseases including cancer. Furthermore, the authors have made significant efforts to discuss the regulation of different GST isoforms that have been associated with various pathological processes such as glioblastoma, Alzheimer's disease, Parkinson's disease, stroke and epilepsy. Expert opinion: Though GSTs have been one of the key areas of scientific research over the last few decades, much remains to be elucidated about their physiological functions as well as pathological involvement of GSTs and their polymorphic variants.

Oral administration of Azadirachta indica (L.) seed kernel active principle protects rat liver hepatocytes and testis seminiferous tubules from phenobarbitol-induced damage

The male albino rat testis and liver showed tissue modification upon exposure to phenobarbitol (PB), 24 mg/100 g of body weight, for about 3 weeks and upon staining of their sections with hematoxylin and eosin. In this procedure, the control liver showed normal hepatocytes with centrally placed nuclei, and the PB-treated hepatocyte showed degeneration of cytoplasm and nucleus, necrosis and fragmentation of nucleus, and pushing of nucleus to periphery. The control rat testis showed epithelial layer having broad seminiferous tubules, spermatids, mature spermatozoa, and lumen of seminiferous tubules, and the PB-treated rat testis showed degenerative and necrotic changes in seminiferous tubules and clumping of seminiferous tubules. These changes almost returned to normal conditions in rat liver and testis upon the oral administration of an antioxidant that is present in Azadirachta seed-kernel extract (ASKE, 100 mg/kg body weight). In the case of enzymes, glutathione transferase and glutathione peroxidase were induced upon PB or ASKE treatment and the combination of both the treatments. The lipid peroxides were reduced in all the three cases in both liver and testis. The histological studies and enzymatic analysis revealed that the potential role of ASKE in the protection of the testis and liver tissues from PB-induced damage.

Expressions of glutathione S-transferase alpha, mu, and pi in brains of medically intractable epileptic patients

BACKGROUND

Glutathione S-transferases (GSTs) play an important role in metabolizing anti-epileptic drugs (AEDs) in liver. Expressions of GSTs in brain, which may result in poor efficacy of AEDs, have not been well studied. Using clinical cortex specimen from 32 intractable epileptic subjects and 8 non-epileptic controls, the present study investigated the correlation between GSTs and intractable epilepsy.

RESULTS

Three different GST isoforms (alpha, mu, and pi) were detected with immunohistochemistry. GST-alpha expression was not seen in any cortex specimens. Sixty three percent (63%) of control and 53% of intractible epileptic specimens showed GST-mu immunoreactivity. No significant difference in intensity of GST-mu staining was observed between these two groups. GST-pi expression was found in endothelial cells and glial cells/astrocytes. Fifty percent (50%) of the control patients and 66% of the epileptic patients were GST-pi positive. The grading of epileptic patients was significantly higher than that of control patients (p < 0.01).

CONCLUSION

High levels of GST-pi in endothelial cells and glial cells/astrocyte correlate to medical intractable epilepsy, suggesting that GST-pi contributes to resistance to AED treatment.

Gene variations in GSTM3 are a risk factor for Alzheimer's disease

Oxidative stress is a relevant pathomechanism in Alzheimer's disease (AD) and gene variations in the glutathione S-transferase M3 gene (GSTM3), involved in the detoxification of oxygen radicals, might influence the risk of AD. We investigated the effect of three polymorphisms in GSTM3: rs1332018 (C/A); rs1799735 (del/AGG); rs7483 (G/A), on the risk of AD in 363 AD patients and 358 healthy controls. Single marker association analyses revealed that the AGG/AGG genotype of the GSTM3 rs1799735 (del/AGG) polymorphism was associated with an increased risk of AD (p=0.05), especially in the group of APOE4-allele non-carriers (p=0.004; OR=2.07). Examination of the haplotypes identified a two-marker haplotype (C/AGG) consisting of rs1332018 (C/A) and rs1799735 (del/AGG) to increase the risk of AD (p=0.029), this effect was also most prevalent in APOE4-allele non-carriers (p=0.009; OR=1.95). The population attributable risk of this haplotype in APOE4-allele non-carriers was 32.2%. Our results suggest that there is a group of AD patients in which variations in metabolism of oxidative stress play an important role.

Inhibition of cytosolic glutathione S-transferase activity from rat liver by copper

H(2)O(2) inactivation of particular GST isoforms has been reported, with no information regarding the overall effect of other ROS on cytosolic GST activity. The present work describes the inactivation of total cytosolic GST activity from liver rats by the oxygen radical-generating system Cu(2+)/ascorbate. We have previously shown that this system may change some enzymatic activities of thiol proteins through two mechanisms: ROS-induced oxidation and non-specific Cu(2+) binding to protein thiol groups. In the present study, we show that nanomolar Cu(2+) in the absence of ascorbate did not modify total cytosolic GST activity; the same concentrations of Cu(2+) in the presence of ascorbate, however, inhibited this activity. Micromolar Cu(2+) in either the absence or presence of ascorbate inhibited cytosolic GST activity. Kinetic studies show that GSH but no 1-chloro-2,4-dinitrobenzene prevent the inhibition on cytosolic GST induced by micromolar Cu(2+) either in the absence or presence of ascorbate. On the other hand, NEM and mersalyl acid, both thiol-alkylating agents, inhibited GST activity with differential reactivity in a dose-dependent manner. Taken together, these results suggest that an inhibitory Cu(2+)-binding effect is likely to be negligible on the overall inhibition of cytosolic GST activity observed by the Cu(2+)/ascorbate system. We discuss how modification of GST-thiol groups is related to the inhibition of cytosolic GST activity.