BACKGROUNDTumor necrosis factor alpha (TNF-α) is important in promoting relative adrenal insufficiency (RAI) due to systemic inflammatory response syndrome (SIRS). We identified the TNF-α receptor involved in the inhibition of adrenal corticotrophin (ACTH)-stimulated hydrocortisone release by studying the expression of TNF-α receptors in adrenal cortex Y1 cells and the effect of downregulating TNF receptors on ACTH-stimulated hydrocortisone release.

METHODSWe used real-time PCR and immunocytochemistry to evaluate the expression of TNF receptors on Y1 cells. TNF-receptor 1 (TNF-R1) DNA fragments corresponding to the short hairpin RNA (shRNA)-sequences were synthesized and cloned into pcDNA(TM) 6.2-GW/EmGFP expression vector. Knockdown efficiency of TNF-R1 expression was evaluated in miRNA transfected and mock-miRNA transfected Y1 cells by quantitative real-time PCR (Q-PCR). Hydro-cortisone expression levels were determined in TNF-R1-knockdown and control Y1 cells treated with TNF-α and ACTH.

RESULTSMouse adrenal cortex Y1 cells were positive for type I TNF-R1, but not type II TNF-receptor (TNF-R2). Blocking TNF-R1 expression resulted in loss of TNF-α-mediated inhibition of ACTH-stimulated hydrocortisone expression, suggesting a role for the TNF-R1 related signaling pathway in ACTH-stimulated hydrocortisone synthesis.

CONCLUSIONThe inhibitory effect of TNF-α on ACTH-stimulated hydrocortisone synthesis was mediated via TNF-R1 in adrenal cortex.