Overexpression of cerebral cytochrome P450s in prenatally exposed offspring modify the toxicity of lindane in rechallenged offspring

Prenatal exposure to low doses of lindane, an organochlorine insecticide used in public health and agriculture, induced a persistent increase in the expression of cerebral cytochrome P450s (CYPs) in rat offspring and modify the adult response to a later exposure of xenobiotics. To understand the mechanism involved in the modification of adult response, rat offspring exposed prenatally to lindane (p.o.; 0.25 mg/kg b.wt. from gestation day 5-21) were rechallenged with lindane (p.o.; 5 mg/kg X 5 days) postnatally at 9- or 18- or 27 weeks. The greater magnitude of increase in the expression of cerebral CYPs in rechallenged offspring and decline in the magnitude of increase in CYPs with increasing age correlated with the amount of lindane accumulating in the brain. Significant alterations in the circulatory levels of hormones in the rechallenged offspring suggest that these alterations may partly account for the persistence in the increase in the cerebral CYPs during development. Epigenetic data further revealed alterations in histone H3 acetylation and DNA methylation in promoter regions of cerebral CYPs isolated from rechallenged offspring at 9- or 18- or 27 weeks. Bisulphite sequencing revealing critical CpG methylation changes in the promoter regions in rechallenged offspring at 9 weeks demonstrated imprinting of the cerebral CYPs. Further, a greater magnitude of increase in apoptosis in the brain of re challenged offspring has suggested that enhanced responsiveness of cerebral CYPs, which may result due to alterations in circulatory hormones, increased accumulation of lindane in the brain and epigenetic regulation of CYPs, is of toxicological relevance.