Protection of sodium arsenite-induced ovarian toxicity by coadministration of L-ascorbate (vitamin C) in mature wistar strain rat

Effect of L-ascorbic acid supplementation on testicular oxidative stress and endocrine disorders in mature male rats exposed to intensive swimming exercise

In order to investigate the ameliorative potential of L-ascorbic acid on intensive swimming exercise induced testicular oxidative stress, 18 Wistar male rats (age: 3 months, weight: 127.5 ± 5.3 g) were randomly divided into the following groups: (i) control group (CG, n = 6); (ii) experimental group (EG, n = 6); and (iii) supplemented group (SG, n = 6). An exercise protocol of 3 h swimming per day, five days per week was followed for 6 weeks in EG and SG with no exercise in CG. In SG, L-ascorbic acid was supplied orally at a dose of 25-mg/kg of bodyweight each day for 6 weeks. A significant decrease (P < 0.05) was noted in paired testicular weights, epididymal sperm count, testicular Δ⁵, 3β-hydroxyseroid dehydrogenase, 17β-hydroxyseroid dehydrogenase, plasma levels of testosterone luteinizing hormone, follicle stimulating hormone, prolactin, the numbers of preleptotine spermatocytes, midpachytene spermatocytes and stage 7 spermatids of stage VII seminiferous epithelium cycle in EG when compared with CG. A significant elevation (P < 0.05) in plasma corticosterone and testicular content of malondialdehyde along with a significant reduction (P < 0.05) in glutathione, ascorbic acid, α-tocopherol, superoxide dismutase, catalase and glutathione-peroxidase, and glutathione-S-transferase were noted in testes of EG compared with CG. No significant change was noted in final bodyweight or numbers of spermatogonia-A among the groups. Furthermore, L-ascorbic acid supplementation restored the above parameters to the control level. Conclusion:  It can be concluded that intensive swimming exercise induced oxidative stress causes dysfunctions in the male reproductive system, which can be protected by L-ascorbic acid. (Reprod Med Biol 2006; 5: 145-153).

Effect of L-ascorbic acid supplementation on testicular oxidative stress and endocrine disorders in mature male rats exposed to intensive swimming exercise

In order to investigate the ameliorative potential of L-ascorbic acid on intensive swimming exercise induced testicular oxidative stress, 18 Wistar male rats (age: 3 months, weight: 127.5 ± 5.3 g) were randomly divided into the following groups: (i) control group (CG, n = 6); (ii) experimental group (EG, n = 6); and (iii) supplemented group (SG, n = 6). An exercise protocol of 3 h swimming per day, five days per week was followed for 6 weeks in EG and SG with no exercise in CG. In SG, L-ascorbic acid was supplied orally at a dose of 25-mg/kg of bodyweight each day for 6 weeks. A significant decrease (P < 0.05) was noted in paired testicular weights, epididymal sperm count, testicular Δ⁵, 3β-hydroxyseroid dehydrogenase, 17β-hydroxyseroid dehydrogenase, plasma levels of testosterone luteinizing hormone, follicle stimulating hormone, prolactin, the numbers of preleptotine spermatocytes, midpachytene spermatocytes and stage 7 spermatids of stage VII seminiferous epithelium cycle in EG when compared with CG. A significant elevation (P < 0.05) in plasma corticosterone and testicular content of malondialdehyde along with a significant reduction (P < 0.05) in glutathione, ascorbic acid, α-tocopherol, superoxide dismutase, catalase and glutathione-peroxidase, and glutathione-S-transferase were noted in testes of EG compared with CG. No significant change was noted in final bodyweight or numbers of spermatogonia-A among the groups. Furthermore, L-ascorbic acid supplementation restored the above parameters to the control level. Conclusion:  It can be concluded that intensive swimming exercise induced oxidative stress causes dysfunctions in the male reproductive system, which can be protected by L-ascorbic acid. (Reprod Med Biol 2006; 5: 145-153).

Arsenite induces aberrations in meiosis that can be prevented by coadministration of N-acetylcysteine in mice

OBJECTIVE

To evaluate in vitro effects of arsenite and of arsenite plus N-acetylcysteine on mouse oocyte meiosis.

DESIGN

Morphological study using mouse oocytes submitted to in vitro maturation (IVM).

SETTING

Laboratory of reproductive biology.

ANIMAL(S)

Six-week-old CD-1 mice superovulated with pregnant mare serum gonadotropin.

INTERVENTION(S)

During IVM, mouse oocytes were exposed to arsenite alone or to arsenite plus N-acetylcysteine.

MAIN OUTCOME MEASURE(S)

Meiotic anomalies were assessed using immunofluorescence microscopy and PolScope (Cambridge Research and Instrumentation, Boston, MA) imaging.

RESULT(S)

In vitro arsenite administration produced dose-dependent and time-dependent meiotic anomalies, characterized by spindle disruption or chromosome misalignment. After 12-14 hours of IVM, exposure to 2 microg/mL of arsenite for 12-14 hours or to 8 microg/mL of arsenite for 2 hours arrested oocyte maturation at the germinal vesicle or germinal-vesicle breakdown stage. Exposure to 4 microg/mL of arsenite for 2 hours arrested oocyte maturation at metaphase I stage in 95% of exposed oocytes (80% exhibiting abnormalities) after 12-14 hours in IVM. After 12-14 hours in IVM, of the oocytes exposed to 2 microg/mL of arsenite for 2 hours, only 15% reached the meiosis II stage (5% exhibiting abnormalities). After 15-17 hours in IVM, however, of the oocytes exposed to 2 microg/mL of arsenite for 2 hours, 65.2% reached the meiosis II stage (43.5% exhibiting abnormalities). Co-administration of N-acetylcysteine prevented the arsenite-induced meiotic abnormalities and the delayed IVM.

CONCLUSION(S)

In vitro arsenite exposure caused meiotic abnormalities that were prevented by co-administration of N-acetylcysteine, suggesting that arsenite-induced meiotic aberrations are mediated by reactive oxygen species.

Strategies for Safe and Effective Therapeutic Measures for Chronic Arsenic and Lead Poisoning

Exposure to toxic metals remains a widespread occupational and environmental problem in world. There have been a number of reports in the recent past suggesting an incidence of childhood lead poisoning and chronic arsenic poisoning due to contaminated drinking water in many areas of West Bengal in India and Bangladesh has become a national calamity. Low level metal exposure in humans is caused by air, food and water intake. Lead and arsenic generally interferes with a number of body functions such as the central nervous system (CNS), the haematopoietic system, liver and kidneys. Over the past few decades there has been growing awareness and concern that the toxic biochemical and functional effects are occurring at a lower level of metal exposure than those that produce overt clinical and pathological signs and symptoms. Despite many years of research, we are still far from an effective treatment of chronic plumbism and arsenicosis. Medical treatment of acute and chronic lead and arsenic toxicity is furnished by chelating agents. Chelating agents are organic compounds capable of linking together metal ions to form complex ring-like structures called chelates. They have been used clinically as antidotes for acute and chronic poisoning. 2, 3-dimercaprol (BAL) has long been the mainstay of chelation therapy for lead or arsenic poisoning. Meso 2, 3, -dimercaptosuccinic acid (DMSA) has been tried successfully in animals as well as in a few cases of human lead and arsenic poisoning. DMSA could be a safe and effective method for treating lead or arsenic poisoning, but one of the major disadvantages of chelation with DMSA has been its inability to remove lead from the intracellular sites because of its lipophobic nature. Further, it does not provide protection in terms of clinical/ biochemical recovery. A new trend in chelation therapy is to use combined treatment. This includes the use of structurally different chelators or a combination of an adjuvant and a chelator to provide better clinical/biochemical recovery in addition to lead mobilization. The present review article attempts to provide update information about the current strategies being adopted for a safe, effective and specific treatment for two major toxic metals or metalloid.

Vitamin C protects HL60 and U266 cells from arsenic toxicity

Although there is no compelling evidence that vitamin C has antitumor activity in humans, clinical trials are testing the hypothesis that ascorbic acid (AA) will enhance the efficacy of arsenic trioxide (As2O3) in myeloma. In vitro, AA cytotoxicity depends on its interaction with free transition metal ions in culture media leading to the generation of H2O2 and other reactive oxygen species (ROSs). Therefore, to circumvent the extracellular in vitro pro-oxidant effects of AA, we loaded HL60, U266, and RPMI-8226 cells with vitamin C by incubation with dehydroascorbic acid (DHA). Loading cells in this manner resulted in prominent, dose-dependent protection of As2O3-treated cells as measured by viability, colony formation, and apoptosis assays. Glutathione depletion enhanced cell sensitivity to the cytotoxic effects of As2O3 and vitamin C loading provided protection. AA was found to generate cytotoxic concentrations of H2O2 in culture medium without cells and copper/iron chelators inhibited this reaction. However, AA did not generate H2O2 in simple buffer or human plasma. Direct incubation with AA resulted in increased intracellular ROSs, whereas DHA incubation decreased it. These results clarify an apparent paradox and indicate that vitamin C loading in HL60, U266, and RPMI-8226 cells ameliorates As2O3 cytotoxicity.

Biomarkers of lead exposure in petrol station attendants and auto-mechanics in Abeokuta, Nigeria: effect of 2-week ascorbic acid supplementation

In order to study the ameliorative effects of ascorbic acid in chronic lead poisoning, petrol station attendants and auto-mechanics in Abeokuta, Nigeria, who have been shown to be occupationally exposed to lead and university students (serving as control), were supplemented daily with 500mg ascorbic acid for 2 weeks. Blood and urine samples were collected from the subjects before and after ascorbic acid regimen and analysed for lead and biochemical effects associated with lead toxicity. The 2-week ascorbic acid supplementation resulted in a significant (P < 0.05) reduction in blood lead in the occupationally exposed subjects. The reduction in blood lead amounted to 57% in male petrol station attendants, 50% in female petrol station attendants and 44% in the auto-mechanics. Urinary excretion of lead increased remarkably in the occupationally exposed subjects (P < 0.05). The biochemical effects associated with the toxic effects of lead also responded positively to the ascorbic acid regimen. Plasma and urine aminolevulinic acid (ALA) were reduced significantly (P < 0.05) by as much as 55% and 57% respectively. Plasma calcium also increased significantly (P < 0.05) in the subjects. Decreased levels of reduced glutathione (GSH) and hemoglobin observed in the occupationally exposed subjects were reversed by ascorbic acid. Glutathione-S-transferase (GST) and catalase (CAT) activities were not affected. Our findings indicate that ascorbic acid may be useful as an economical and convenient prophylactic agent for lead poisoning.

Chronic arsenic poisoning in the rat: treatment with combined administration of succimers and an antioxidant

The influence of the coadministration of vitamin C or vitamin E on the efficacy of two thiol chelators, meso-2,3-dimercaptosuccinic acid (DMSA) or monoisoamyl DMSA, in counteracting chronic arsenic toxicity was investigated in rats. Vitamin C and vitamin E were only mildly effective when given alone or in combination with the above chelators in mobilizing arsenic from the target tissues. However, combined administration of vitamin C plus DMSA and vitamin E plus MiADMSA led to a more pronounced depletion of brain arsenic. The supplementation of vitamins was significantly effective in restoring inhibition of blood delta-aminolevulinic acid dehydratase (ALAD) oxidative stress in liver, kidneys, and brain as reflected by reduced levels of thiobarbituric acid reactive substance and oxidized and reduced glutathione levels. The results thus lead us to suggest that coadministration of vitamin E or vitamin C may be useful in the restoration of altered biochemical variables (particularly the effects on heme biosynthesis and oxidative injury) although it has only a limited role in depleting arsenic burden.

Oxidative stress contributes to arsenic-induced telomere attrition, chromosome instability, and apoptosis

The environmental contaminant arsenic causes cancer, developmental retardation, and other degenerative diseases and, thus, is a serious health concern worldwide. Paradoxically, arsenic also may serve as an anti-tumor therapy, although the mechanisms of its antineoplastic effects remain unclear. Arsenic exerts its toxicity in part by generating reactive oxygen species. We show that arsenic-induced oxidative stress promotes telomere attrition, chromosome end-to-end fusions, and apoptotic cell death. An antioxidant, N-acetylcysteine, effectively prevents arsenic-induced oxidative stress, telomere erosion, chromosome instability, and apoptosis, suggesting that increasing the intracellular antioxidant level may have preventive or therapeutic effects in arsenic-induced chromosome instability and genotoxicity. Embryos with shortened telomeres from late generation telomerase-deficient mice exhibit increased sensitivity to arsenic-induced oxidative damage, suggesting that telomere attrition mediates arsenic-induced apoptosis. Unexpectedly, arsenite did not cause chromosome end-to-end fusions in telomerase RNA knockout mouse embryos despite progressively damaged telomeres and disrupting embryo viability. Together, these findings may explain why arsenic can initiate oxidative stress and telomere erosion, leading to apoptosis and anti-tumor therapy on the one hand and chromosome instability and carcinogenesis on the other.

Arsenic induced changes in growth development and apoptosis in neonatal and adult brain cells in vivo and in tissue culture

Arsenic at a nonlethal level in drinking water consumed over a period of time has been reported to produce chronic toxicity and various types of health problems ranging from skin cancer to disturbance in memory. Neurotoxic effects have been reported in clinical cases with chronic exposure to arsenic. Physiological detoxication of arsenic occurs partially through methylation. Arsenic and its methylated derivatives are distributed in different organs and systems. The present study examined the possible interference in the neuronal development and differentiation due to the exposure to arsenic during gestation. The experiments were carried out to examine short and long term effects of arsenic on brain explants and cells grown and maintained in tissue culture system. The effects of arsenic exposure showed changes in brain cell membrane function indicated by generation and release of reactive oxygen-nitrogen intermediates. On the morphological aspect the explants' growth was reduced, ground matrix was lost and neural networking was inhibited. Cells showed signs of apoptotic changes. Arsenic toxicity may induce damage to brain cells prior to more visible clinical conditions. The deleterious effects also pass from the maternal to fetal tissue across the transplacental barrier.