Efficacy of DL-alpha-lipoic acid on methanol induced free radical changes, protein oxidative damages and hsp70 expression in folate deficient rat nervous tissue.

DL-alpha-Lipoic acid (LPA) was reported to be effective in reducing free radicals generated by oxidative stress. The protective of effect of LPA on methanol (MeOH) induced free radical changes and oxidative damages in discrete regions of rat brain have been reported in this study. Folate deficient rat (FDD) model was used. The five animal groups (saline control, FDD control, FDD+MeOH, FDD+LPA+MeOH, LPA control) were used. The FDD+MeOH and FDD+LPA+MeOH animals were injected intraperitoneally with methanol (3gm/kg). After 24h, the level of free radical scavengers such as, superoxide dismutase, catalase, glutathione peroxidase, reduced glutathione was estimated in six discrete regions of brain, retina and optic nerve. Level of protein thiol, protein carbonyl and lipid peroxidation was also estimated. Expression of heat shock protein 70 mRNA (hsp70) was studied in the cerebellum and hippocampus by reverse transcriptase PCR. All the samples showed elevation in the level of free radical scavenging enzymes and reduced level of glutathione in the FDD+MeOH group in relation to the other groups. hsp70 expression was more in FDD+MeOH group when compared to FDD+LPA+MeOH group. In conclusion, MeOH exposure leads to increased free radical generation and protein oxidative damages in the rat nervous tissue. Treatment with LPA prevents oxidative damage induced by MeOH exposure.

Oxidative stress induced by methotrexate alone and in the presence of methanol in discrete regions of the rodent brain, retina and optic nerve.

The vulnerability of the nervous system due to methanol (MeOH) intoxication is a well known fact and reports on the production of free radicals due to MeOH exposure and their involvement in excitotoxicity and neuronal apoptosis are being increasingly reported. We report on MeOH induced free radical changes and oxidative damages to proteins in the discrete regions of rat brain, retina and optic nerve. The present study used rats administered with methotrexate (MTX) to induce folate deficiency. Three groups of animals, namely saline control, MTX control, MTX-MeOH group were tested. The rats were injected intraperitoneally with MeOH (3 g/kg). After 24 h of MeOH administration, the levels of free radical scavengers, superoxide dismutase, catalase, glutathione peroxidase and reduced glutathione levels were estimated in the six discrete regions of brain (cerebral cortex, cerebellum, midbrain, pons medulla, hippocampus and hypothalamus), retina and optic nerve specimens. The levels of protein thiol, protein carbonyl and lipid peroxidation were also estimated and the expression of HSP70 in the hippocampus was analyzed by Western blot. Marked reduction in the levels of glutathione in the MTX-MeOH group in relation to MTX control was observed and found to be increased in MTX control in relation to saline control. Increased protein carbonyls and decreased protein thiols were documented in all the specimens tested. In addition, marked expression of HSP70 was observed in the hippocampus. The present investigation suggest that MeOH exposure results in increased generation of free radicals and significant protein oxidative damage and attempts to study the underlying mechanisms involved might reveal more insights to our existing knowledge on MeOH intoxication and related areas.

Detoxification of formate by formate dehydrogenase-loaded erythrocytes and carbicarb in folate-deficient methanol-intoxicated rats.

BACKGROUND: Formic acid is a toxic metabolite responsible for the metabolic acidosis in methanol poisoning. Formate dehydrogenase (EC 1.2.1.2) converts formate into CO2 in the presence of NAD. We examined the in vitro and in vivo efficiency of formate dehydrogenase-loaded carrier erythrocytes along with carbicarb in eliminating the formate in methanol-intoxicated folate-deficient rats. METHOD: Formate dehydrogenase-loaded erythrocytes were prepared by hypotonic dialysis method. Carbicarb (carb) (equimolar solution of sodium carbonate and sodium bicarbonate) was used to treat metabolic acidosis. Folate depletion was induced by methotrexate (MTX) treatment. Experimental design consisted of 8 groups: saline control, methanol control, MTX control, ELE control, MTX-methanol control, MTX-methanol-carb, MTX-methanol-carb-ELE, and MTX-MeOH-ELE group. Male Wistar rats treated with MTX (0.3 mg/kg) for a week were injected (i.p.) with methanol (4 g/kg). Twelve hours later, the carbicarb solution was infused, and then a formate dehydrogenase-loaded erythrocytes suspension (40% hematocrit) was infused (i.v.) in bolus. Blood samples were collected every hour for 4 h from the cannulated left jugular vein. Blood methanol and formate were estimated respectively with HPLC and fluorimetric assay. Blood pH, blood pO2, pCO2 and bicarbonate were also measured. RESULTS: There was marked elimination of formate in selected groups. CONCLUSION: Formate dehydrogenase-loaded erythrocytes, along with carbicarb, facilitates removal of formate, in methanol poisoning.

Therapeutic response to single intravenous bolus administration of formate dehydrogenase in methanol-intoxicated rats.

Methanol remains to be a major public and environmental health hazard. Formic acid is the toxic metabolite responsible for the metabolic acidosis observed in methanol poisoning in humans, in non-human primates and in folate-depleted rodents. Cytochrome oxidase inhibition by formate leads to lactic acid accumulation, which contributes significantly to metabolic acidosis. Toxic effects in human beings are characterized by formic acidemia, metabolic acidosis, ocular toxicity, nervous system depression, blindness, coma and death. Elimination of formate is one of the principles of management in methanol poisoning. Hemodialysis facility is not readily available in all the places, in developing countries like India. Formate dehydrogenase (EC 1.2.1.2) acts directly over formate and converts formate into CO(2) in the presence of NAD. Effect of single intravenous bolus infusion of formate dehydrogenase, obtained from Candida boidinii; in methanol-intoxicated folate deficient rat model was evaluated. Folate depletion induced by methotrexate (MTX) treatment. Carbicarb (Carb) (equimolar solution of sodium carbonate and sodium bicarbonate) was used to treat metabolic acidosis. Experimental design consists of seven groups, namely Saline control, methanol control, MTX control, Enzyme control, MTX-methanol control, MTX-methanol-Carb and MTX-methanol-Carb-Enz group. Male wistar rats treated with MTX (0.3mg/kg) for a week, were injected (i.p.) with methanol (4 gm/kg), 12h latter, Carbicarb solution was infused, following this enzyme was infused (i.v.) in bolus. Blood samples were collected every 15 min for an hour from the cannulated left jugular vein and blood methanol, formate were estimated, respectively, with HPLC and fluorimetric assay. Blood pH, blood gases pO(2), pCO(2) and bicarbonate were monitored with blood gas analyzer in order to evaluate acid base status of the animal. Results obtained show that there is significant elimination of formate within 15 min. It may be concluded that single bolus infusion of formate dehydrogenase facilitates fast removal of formate, a highly toxic metabolite in methanol poisoning.