Thromboxane A2 Modulates de novo Synthesis of Adrenal Corticosterone in Mice via p38/14-3-3γ/StAR Signaling

Abstract

Prostanoids are endogenous lipid bioactive mediators that play essential roles in physiological processes such as glucocorticoid secretion. Here, it is found that the thromboxane (Tx)A₂ receptor (TP) is highly expressed in the adrenal cortex of mice. Both global and adrenocortical-specific deletion of the TP receptor lead to increased adiposity in mice by elevating corticosterone synthesis. Mechanistically, the TP receptor deletion increases the phosphorylation of steroidogenic acute regulatory protein (StAR) and corticosterone synthesis in adrenal cortical cells by suppressing p-p38-mediated phosphorylation of 14-3-3γ adapter protein at S71. The activation of the p38 in the adrenal cortical cells by forced expression of the MKK6EE gene attenuates hypercortisolism in TP-deficient mice. These observations suggest that the TxA₂/TP signaling regulates adrenal corticosterone homeostasis independent of the hypothalamic-pituitary-adrenal axis and the TP receptor may serve as a promising therapeutic target for hypercortisolism.

Keywords: 14‐3‐3γ; adrenal corticosterone; p38; steroidogenic acute regulatory protein; thromboxane receptor.