Transient exposure of methylparaben to zebrafish (Danio rerio) embryos altered cortisol level, acetylcholinesterase activity and induced anxiety-like behaviour.

Abstract

Parabens are widely used as antimicrobial preservatives. Recent studies have reported the endocrine disrupting effects of these chemicals, especially methylparaben. Previously, we have reported the alteration in Vtg gene expression upon exposure to environmentally relevant doses of methylparaben in zebrafish (Danio rerio) embryos. However, studies reporting neurobehavioural outcomes on exposure to methylparaben are limited. Therefore, this study was aimed at investigating the methylparaben-induced effects on developmental and neurobehavioural endpoints. Zebrafish embryos were exposed to sub-lethal concentrations of methylparaben: 0.1\u202fppb, 1\u202fppb, 10\u202fppb and 100\u202fppb. Alterations in developmental landmarks such as heart rate and hatching percentage were observed in embryos exposed to 10\u202fppb and 100\u202fppb of methylparaben. Results obtained from the novel tank diving test established that anxiety-like behaviour is induced in larvae exposed to 0.1\u202fppb and 1\u202fppb of methylparaben. A significant inhibition in the acetylcholinesterase (AChE) activity was also recorded in methylparaben-exposed groups. An increase in cortisol levels was observed in the exposed groups, which further supports the observations made in the novel tank diving test, establishing methylparaben as an anxiogenic agent even at sub-lethal concentrations. The underlying molecular mechanism needs further elucidation to investigate whether the behavioural effects are proximally or distally induced by early developmental exposure to methylparaben.