Exercise prevents the increased anxiety-like behavior in lactational di-(2-ethylhexyl) phthalate-exposed female rats in late adolescence by improving the regulation of hypothalamus-pituitary-adrenal axis

Abstract

Both the detrimental effects of early life adversity and the beneficial effects of exercise on the hypothalamic-pituitary-adrenal (HPA) axis have been reported. Early life exposure to di-(2-ethylhexyl)-phthalate (DEHP) may impair the development of endocrine system. In this study, we investigated the effects of lactational DEHP exposure on stress responses in late adolescent female rats and examined the protective role of treadmill running. Sprague-Dawley dams were fed with DEHP (10mg/kg per day) or vehicle during lactation. After weaning, the female offspring rats were trained to exercise on a treadmill for 5 weeks and then stressed by exploring on an elevated plus maze. The activities of HPA axis were evaluated by measuring the plasma levels of ACTH and corticosterone, the expressions of adrenal enzymes cholesterol side-chain cleavage enzyme (CYP11A1) and cytochrome P-450 11β-hydroxylase (CYP11B1), and the expression of hypothalamic glucocorticoid receptors (GR). The results demonstrate that DEHP-exposed rats exhibited enhanced anxiety-like behaviors. Increased hypothalamic GR and plasma ACTH levels, but decreased adrenal CYP11A1 and corticosterone levels, were observed in DEHP-exposed animals under stressed condition. Importantly, in DEHP-exposed animals, exercise during childhood-adolescence reduced anxiety-like behaviors by normalizing stress-induced alterations in ACTH level and adrenal CYP11A1 expression. The findings of this study suggest that treadmill running may provide beneficial effects on ameliorating the dysregulation of HPA axis in lactational DEHP-exposed adolescent female rats.

Keywords: Anxiety-like behavior; Di-(2-ethylhexyl)-phthalate; Hypothalamic-pituitary-adrenal axis; Treadmill.