17β-estradiol Inhibits Lipopolysaccharide-induced Inflammation and Pyroptosis of Leydig Cells of the Domestic Yak (Bos Grunniens) Via the SIRT1/Nox4/ROS Pathway

Estradiol (E2) secreted by Leydig cells (LCs) can accumulate in the testes due to constriction of the reproductive lumen. Estrogen is not only important for reproduction, but also protects against inflammation. In this study, the role of pyroptosis in testicular inflammation and the effects of E2 against inflammation and pyroptosis of yak interstitial cells were investigated. Inflamed testes exhibited structural damage and pyroptosis with decreased E2, testosterone, and estrogen receptor β (ERβ) levels in testicular fluid. E2 alone inhibited testosterone secretion and increased ERβ expression in mature LCs. In LCs, lipopolysaccharide (LPS) causes inflammation by activation of TNF-α and IL-6, and pyroptosis via activation of the classical and non-classical pyroptosis pathways. LPS inhibits sex hormone secretion and ERβ expression in LCs. E2 inhibited the LPS-induced decrease of ER expression in LCs and also inhibited LPS-induced interstitial cell inflammation and pyroptosis, which was partially blocked by Selisistat (EX-527, SIRT1 inhibitor) or Fulvestrant (ICI 182,780, E2 non-genomic receptor inhibitors). In conclusion, E2 relieved LPS-induced inflammation and pyroptosis of yak LCs via the SIRT1/Nox4/ROS pathway. This finding provides new insights into the role of estrogen in male reproductive health and offers a potential therapeutic strategy to improve testicular immune and reproductive function by modulating hormonal homeostasis.