IGF1/MAPK/ERK signaling pathway-mediated programming alterations of adrenal cortex cell proliferation by prenatal caffeine exposure in male offspring rats

Abstract

Our previous study proposed a glucocorticoid-insulin-like growth factor 1 (GC-IGF1) axis programming mechanism for prenatal caffeine exposure (PCE)-induced adrenal developmental dysfunction. Here, we focused on PCE-induced cell proliferation changes of the adrenal cortex in male offspring rats before and after birth and clarified the intrauterine programming mechanism. On gestational day (GD) 20, the PCE group had an elevated serum corticosterone level reduced fetal bodyweight, maximum adrenal sectional area, and elevated adrenal corticosterone and aldosterone contents. However, in postnatal week (PW) 6, the serum corticosterone level was decreased, and the bodyweight, with catch-up growth, adrenal cortex maximum cross-sectional area and aldosterone content were relatively increased, while the adrenal corticosterone content was lower. On GD20, the expression of adrenal IGF1, IGF1R and proliferating cell nuclear antigen (PCNA) were decreased, while the expression of these factors at PW6 were increased in the PCE group. Fetal adrenal gene chip analysis suggested that the mitogen-activated protein kinase/extracellular regulated protein kinase (MAPK/ERK) signal pathway was suppressed in the PCE group. Moreover, in the rat primary adrenal cells, corticosterone (rather than caffeine) was shown to significantly inhibit cell proliferation, IGF1 and PCNA expression, and ERK phosphorylation, which could be reversed by exogenous IGF1. Meanwhile, the effects of exogenous IGF1 were reversed by the ERK pathway inhibitor (PD184161). In conclusion, PCE could induce programming alterations in adrenal cortical cell proliferation before and after birth in male offspring rats. The underlying mechanism is associated with the inhibition of fetal adrenal IGF1-related MAPK/ERK signaling pathway caused by high glucocorticoid levels.