Temporal and sexual heterogeneity in single paraben-induced interference of hypothalamic-pituitary axes in juvenile...

As typical preservatives, methylparaben (MeP) and propylparaben (PrP) are detected increasingly in environment and humans. Our previous studies showed that MeP and PrP are estrogenic, yet the underlying mechanisms for their effects on neurobehavior and sexual development throughout life remain unclear. This study employed a chronic exposure design covering the key developmental period from 4 h post-fertilization (hpf) to 72 days post-fertilization (dpf), to investigate the effects of single paraben (1.5-150 μg/L, MeP and 0.6-60 μg/L, PrP) on behaviors consistent with an anxiety-like phenotype, and sexual development in juvenile zebrafish. We demonstrated that MeP and PrP act as a plausible molecular initiating event (MIE) by activating the glucocorticoid receptor (GR), which ultimately dysregulated the HPI axis and triggered anxiety-like behavioral response in early development. Notably, this disruption exhibited distinct temporal and sexual heterogeneity, with heightened sensitivity during early sex differentiation (36 dpf) and in females after sex differentiation (72 dpf). Concurrently, MeP and PrP disrupted the sexual development by antagonizing androgen receptor (AR) and perturbed the hypothalamic-pituitary-gonadal (HPG) axis, with a more pronounced effect in male fish. In vitro experiments and molecular simulations provided strong supports for the hypothesis that both parabens perturbed GR and AR transcriptional activities. In conclusion, MeP and PrP disrupt the crosstalk between HPI and HPG axes via cortisol-mediated endocrine mechanisms, with the effects being time- and sex-dependent. These findings provide crucial insights into the molecular mechanisms underlying the neuro-behavioral and sexual developmental toxicity of representative parabens.