Deepa Agrawal

Oxidative damage and changes in the glutathione redox system in erythrocytes from rats treated with hexachlorocyclohexane

The concentration of reduced glutathione in the erythrocytes of rats was significantly decreased 24-72 hr after the rats were treated with 300 mg commercial hexachlorocyclohexane/kg body weight (one-third of the LD50), given ip. The activities of glutathione reductase, glutathione-S-transferase and glucose-6-phosphate dehydrogenase were also significantly decreased 24 hr after treatment but there was no change in glutathione peroxidase activity. The results suggest that hexachlorocyclohexane produces significant changes in the glutathione redox system of rat erythrocytes leading to oxidative membrane damage.

Glutathione S-transferase M1 and T1 polymorphism and response to neoadjuvant chemotherapy (CAF) in breast cancer patients.

PurposeResponse to neoadjuvant chemotherapy (NACT) for breast cancer patients cannot be predicted; however, polymorphism of the glutathione S-transferase genes GSTM1 and GSTT1 can modify the response to chemotherapy. The aim of this study was to establish whether there is an association between the polymorphism of GSTM1 and GSTT1 and response to NACT.MethodsThe subjects of this study were 45 patients with locally advanced breast cancer (LABC), who received the cyclophosphamide, adriamycin, and 5-fluorouracil (CAF) regimen as NACT. We analyzed the relationship between the genotypes and responses to chemotherapy.ResultsThe response rates to chemotherapy were better, although not significantly so, in patients with the GSTM1 and GSTT1 null genotypes (odds ratio [OR] 2.06 and 1.45). Similar findings were noted in patients with either or both of the null genotypes (OR 2.67 and 1.16). Among the responders, patients with the GSTM1 and GSTT1 null genotypes had higher rates of complete response following chemotherapy than those with one or more active allele (OR 1.8 and 1.3), although the difference was not significant.ConclusionsThere was an association between the polymorphism of glutathione S-transferases and responses to chemotherapy, but the differences were not significant. However, larger studies are needed to investigate the role and efficiency of GST polymorphism in predicting response to chemotherapy.

Role of GSTM1 and GSTT1 Polymorphism: Susceptibility to Oral Submucous Fibrosis in the North Indian Population

Molecular epidemiological studies have provided evidence that individual susceptibility to cancer is mediated by both genetic and environmental factors. Several allelic variants of polymorphic glutathione s-transferases (GSTs) show impaired enzyme activity and are suspected to increase the host’s susceptibility to various cancers. To determine the association of GST variants with the risk of oral submucous fibrosis (OSF), the distribution of polymorphisms in GSTM1 and GSTT1 was studied in 90 OSF patients and 130 healthy controls. Genotypic analysis was performed by multiplex PCR. The relationship between the null genotypes and the risk of OSF was assessed by means of odds ratios (OR) with 95% confidence intervals (CI) calculated by logistic regression. The frequency of both the GSTM1 and GSTT1 null genotypes was higher in the OSF cases than in the controls. The prevalence of the GSTM1 null genotype in the OSF cases was 46.6% as compared to 29.2% in the controls (OR 2.12, 95% CI 1.2–3.9) and GSTT1 null was 24.4% in the OSF cases versus 10.7% in the controls (OR 2.68, 95% CI 1.22–5.96). There was evidence of an increased risk with the absence of both genotypes (7.5-fold; OR 7.5, 95% CI 2.3–24). Our findings suggest that the GSTM1 and GSTT1 null genotypes, separately or in combination, increase the risk of developing OSF in the North Indian population.

Alterations in rat erythrocyte membrane due to hexachlorocyclohexane (technical) exposure

1 Hexachlorocyclohexane (HCH), an organochlorine pesticide having hydrophobic molecule is known to act on membranes. HCH mediated alterations in erythrocyte membrane occur through disorganization of the lipid bilayer. Therefore the changes in erythrocyte membrane fluidity, osmotic fragility and certain membrane bound enzymes were studied. Administration of HCH (technical) to rats at 5 mg/kg, orally, 5 days a week for 1, 2 and 3 months caused marked increase in erythrocyte membrane fluidity, osmotic fragility anddecreaseinlevelsofNa+, K+-ATPase, acetylcholinesterase in erythrocytes and glutathione in blood. 2 These changes indicate that HCH adversely affects membrane structure and function.

Biochemical and structural alterations in rat erythrocytes due to hexachlorocyclohexane exposure

The changes in biochemical constituents of rat erythrocyte membranes were observed after a single ip exposure to 300 mg commercial HCH/kg body weight (one-third of the LD50). The phospholipid:cholesterol ratio was altered, and there were changes in the activities of the membrane-bound enzymes ATPase and acetylcholinesterase. The phospholipid content was increased while cholesterol and ATPase and acetylcholinesterase activities were significantly decreased. The erythrocytes also showed morphological changes (cell deformity and echinocyte formation).

Effect of methyl isocyanate (MIC) on rat erythrocytes

Changes in surface morphology of rat erythrocytes were studied by scanning electron microscopy after a single and repeated exposure of methyl isocyanate under static conditions. Marked morphological changes (echinocytes and spherocytes) were observed, followed by an increase in osmotic fragility of the erythrocyte membrane. The activity of the membrane bound enzyme adenosine triphosphatase (Na+, K+, Mg++) was inhibited.

Influence of hexachlorocyclohexane on phosphoinositides in rat erythrocyte membranes and brain

Single exposure of rats to hexachlorocyclohexane (100 mg/kg) did not cause any significant change in phosphoinositide levels in rat erythrocyte membrane and cerebrum (fore brain) 2 or 24 h after exposure. However, the phosphoinositide turnover and generation of second messengers from phosphoinositides were increased in the treated erythrocyte membranes as judged from a marked increase in the incorporation of [2-3H]inositol into phosphoinositides 24 h after the treatment. A significant decrease in phosphatidylinositol (PI), phosphatidylinositol 4-phosphate (PIP) and phosphatidylinositol 4,5-bisphosphate (PIP2) was observed in the erythrocyte membrane and cerebrum of rats repeatedly exposed to the pesticide for 3 or 6 months. This drastic reduction in phosphoinositide levels suggests adverse effects on vital membrane and cell functions modulated by phosphoinositides.

Association of CYP1A1, GSTM1, and GSTT1 gene polymorphism with risk of oral submucous fibrosis in a section of North Indian population

Genetic alterations in the genes expressing drug metabolizing enzymes can make an individual susceptible to various cancers. This study detects the polymorphisms at CYP1A1, GSTM1, and GSTT1 genes in a section of North Indian population and determines the susceptibility to oral submucous fibrosis (OSF). In this case–control study one hundred and two OSF patients were genotyped to detect the GSTM1, GSTT1, CYP1A1 polymorphism. Two hundred healthy controls were also included. Genotypes were determined using polymerase chain reaction-restriction fragment length polymorphism (PCR–RFLP) approach. The frequency of GSTM1 and GSTT1 genotype was higher in OSF patients, as compared to controls. A trend risk analysis showed 7.6 fold increase in risk, when both the genes were absent. The frequency of CYP1A1 (m1) and CYP1A1 (m2) genotypes was higher in controls. No polymorphic alleles were detected in the m4 site. CYP1A1 (m1) wild genotype in the absence of GSTM1 null genotype, falls under the highest risk group (OR 3.74). Our findings suggest that CYP1A1 (m1) genotype and (m2) genotype singly acts as a protective factor but in the absence of GSTM1 and/or GSTT1 gene significantly alters risk towards OSF.

Effects of the level of dietary protein on the toxicity of hexachlorocyclohexane in rats

Male albino rats were fed for 28 days from weaning on diets containing 5% (group 1), 10% (group 2) and 21% (group 3, normal protein) protein as casein. At the end of dietary period, HCH was administered daily for 30 days to investigate the interaction between protein deficiency and pesticide toxicity. The results indicated that rats fed a lower protein diet and HCH had a higher mortality, lower rate of growth, increased liver weight and deposition of the pesticide in blood and tissues in larger amounts. Blood pressure (systolic and diastolic) was significantly increased and the heart rate showed tachycardia in low protein exposed animals. A significant increase of total lipids, cholesterol, triglycirides, free fatty acids in serum and tissues of animals exposed to low protein was observed. A close correlation existed between lipid accumulation and storage of HCH in tissues and dietary protein seemed to play an important role in detoxification.

Bioreactivity of glutathionyl hydroquinone with implications to benzene toxicity.

Glutathionyl hydroquinone (GHQ), a highly reactive metabolite of benzene, has been implicated as a causative intermediate of benzene toxicity. To substantiate, the bioreactivity of GHQ was investigated under in vitro and in vivo conditions using end points, characteristic of benzene toxicity. Under in vitro conditions, the presence of GHQ: (a) linearly increased the release of aldehydic products from L-glutamate or deoxyuridine at GHQ concentrations of 5-25 microM and from rat liver homogenates at GHQ concentrations of 50-250 microM; (b) cleaved plasmid pUC 18 supercoiled DNA through a single strand nick to yield open circular relaxed DNA, and through a double strand cut to give out linear DNA at GHQ concentrations of 25-200 microM, with evidence of protection by catalase and superoxide dismutase; and (c) induced cross-linking and polymerization of lymphocyte nuclear DNA through in situ generation of GHQ, which was protected by pretreatment of lymphocytes with N-ethylmaleimide. In vivo exposure of Swiss albino mice to GHQ (100 mg/kg, intraperitoneally once daily for 30 days) resulted in significant increase of liver weight and inhibition of mitotic index in the bone marrow. The other test parameters, namely spleen weight, hematological indices, hepatic sulphahydryl content and nonenzymatic lipid peroxidation, and chromosomal aberrations in the bone marrow were, however, unaffected by GHQ treatment. The observations indicate pro-oxidant and cytotoxic potential of GHQ, mediated by the reactive oxygen species generated during the course of its auto-oxidation. Bioreactivity of GHQ with cellular macromolecules in vitro and inhibition of mitotic index of bone marrow on in vivo exposure have relevance to benzene toxicity, although in situ generation of GHQ at the site of action appears critical in bringing about hematological and chromosomal effects that were probably spared due to rapid metabolic disposition and, consequently, poor bioavailability of intraperitoneally administered GHQ.