Leptin interferes ACTH-cAMP signaling on steroid biosynthesis in human NCI-H295 adrenocortical tumor cell line
Date Issued
2005
Date
2005
Author(s)
Hsu, Hao-Ting
DOI
en-US
Abstract
Leptin, mainly secreted from adipose tissues surrounding adrenal glands, is proposed to locally control the biosynthesis of adrenal steroid hormones. The human adrenocortical NCI-H295 cells were treated with or without leptin, adrenocorticotropic reagent, or both. Two major adrenal steroid products, progesterone and cortisol secreted in their cultured media were measured by ELISA. Cholera toxin, an activator of cAMP-protein kinase A pathway, mimicked ACTH effect to stimulate the secretion of progesterone and cortisol in time- and dose-dependent fashions. Leptin did not affect basal secretion of both steroid hormones; however, it effectively inhibited ACTH- or cholera toxin-induced secretion of progesterone and cortisol. Furthermore, the induction of cholera toxin on the protein amounts of P450scc, the first and rate-limiting steroidogenic enzyme, 3b-HSD, the essential enzyme for synthesis of bioactive steroids, and P450c21, the critical enzyme in secreting corticoids, were reduced by leptin. Similar inhibition of leptin was observed at the mRNA levels of P450scc and 3b-HSD. The involvement of leptin in regulating CYP11A1 promoter activity was evaluated by 5’-serial deletion. The deletion clones containing CYP11A1 promoter over 1.7 kb were responsive, whereas the shorter clone with 1.5-kb CYP11A1 promoter was silent to cAMP stimulation. The cAMP-inducible promoter activity was decreased by leptin. The inhibition of leptin on cAMP-regulated steroidogenesis and CYP11A1 promoter activity was prevented by the JAK1/2 specific inhibitor AG490 and PI3 kinase specific inhibitor Wortmannin as well as a general PDE inhibitor IBMX and a PDE3 selective inhibitor SKF94836; moreover, leptin failed to interfere the induction of N6-MB-cAMP, a PDE3B resistant cAMP analogue. Collectively, this study demonstrated leptin reduced adrenocorticotropic reagent-induced steroidogenesis possibly through a hypothesized JAK1/2-PI3 kinase-PDE3B-cAMP pathway.
Subjects
瘦體素
leptin
SDGs
Type
thesis
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