Testosterone Suppresses IL-17 Expression by Targeting RORγt Functions.

Th17 cells play a crucial role in autoimmune disease pathogenesis. However, the mechanisms behind the sex differences in immune responses, particularly women's higher susceptibility to autoimmune diseases, remain unclear. This study investigated the role of testosterone in modulating the IL-17 response. IL-17 levels and IL-17-expressing cells were compared between males and females, and testosterone's effect on Th17 differentiation was evaluated. In an imiquimod-induced psoriasis mouse model, testosterone supplementation reduced psoriasis severity in female mice, whereas castration of male mice exacerbated psoriasis. Testosterone inhibited both in vitro Th17 differentiation and in vivo IL-17 expression, correlating with reduced psoriasis severity. Molecular studies indicated that testosterone is an inverse agonist of related orphan receptor gamma (RORγt), a key transcription factor for IL-17 expression. These findings offer mechanistic insights into how testosterone limits tissue inflammation in psoriasis and suggest a basis for developing novel testosterone derivatives to target RORγt and suppress Th17-mediated inflammation.