Glutathione depletion modulates methanol, formaldehyde and formate toxicity in cultured rat conceptuses

Abstract

The proposed use of methanol (H3COH) as an alternative to fossil fuels has prompted concern about potential health risks resulting from widespread environmental exposure. Methanol is teratogenic in rodents and, although the exact toxic species is not known, teratogenesis may result from the enzymatic biotransformation of H3COH to formaldehyde (CH2O) and formic acid causing increased biological reactivity and toxicity. A protective role for the antioxidant glutathione (GSH) has been described for H3COH, CH2O and formic acid toxicity in various biological systems but has yet to be evaluated in the developing conceptus. Whole embryo culture studies were conducted using GD 10-11 rat conceptuses to elucidate the relationship between H3COH and its metabolites and GSH status. Methanol exposure produced a decrease in normal growth parameters and a dose-dependent loss of viability. CH2O had deleterious effects on embryo growth and viability. Sodium formate (HCOONa) exposure resulted in a high mortality rate but viable embryos did not manifest any abnormalities. Methanol, CH2O, and HCOONa all produced a significant depletion of GSH in both embryo and VYS. Inhibition of GSH synthesis by L-buthionine-S,R-sulfoximine (BSO) treatment exacerbated H3COH, CH2O and HCOONa embryotoxicity. Interestingly, only H3COH/BSO and CH2O/BSO co-treatments caused increased malformation, while embryos treated with HCOONa/BSO did not produce any developmental deformities. These results implicate CH2O as the most embryotoxic H3COH metabolite, on a molar basis, in terms of causing dysmorphogenesis, alterations of normal growth parameters and embryolethality. HCOONa was selectively embryolethal and did not produce dysmorphogenesis. CH2O toxicity is potentiated by GSH depletion, indicating that GSH may be more directly involved in its detoxication in the embryo.

Influence of ethanol on methanol‐induced oxidative stress and neurobehavioral deficits

“…However, in animals coexposed to methanol and ethanol, the levels were comparable to those in the controls. The decrease in glutathione levels is in accordance with previous studies showing increased free radical generation during methanol toxicity is associated with decreased cellular GSH levels [28,29]. The restoration of GSH levels toward the normal in the methanol and ethanol cotreated animals might be due to the preference of ethanol metabolism over methanol resulting in slower rate of formaldehyde formation.…”

Inhibition of proteolysis in histiotrophic nutrition pathways alters DNA methylation and one-carbon metabolism in the organogenesis-stage rat conceptus

“…Animals were kept on a 12 h-12 h light/dark cycle, and were given food and water ad libitum . On the day of each experiment dams were anesthetized, exsanguinated, and sacrificed as previously described [19]. Conceptuses were explanted on GD10, prepared for culture, and placed into 60 ml culture bottles containing 10 ml of control media.…”

“…To optimize growth, bottles were gassed on GD10 after explantation with 20% O 2 /5% CO 2 and on the morning of GD11 with 95% O 2 /5% CO 2 . Culture bottles were incubated at 37°C in a roller apparatus throughout the culture period as described previously [10, 19, 20]. …”

Reproductive and developmental toxicity of formaldehyde: A systematic review

“…Harris et al . exposed mouse whole-embryos (gestation day 10–12) to formaldehyde in culture medium and found that formaldehyde had deleterious effects on embryo growth and viability and produced a depletion of glutathione (GSH) in the visceral yolk sac and embryo [90]. Neuropore closure, crown-rump length and somite number were reduced by formaldehyde.…”