Leptin Interferes with Adrenocorticotropin/3′,5′-Cyclic Adenosine Monophosphate (cAMP) Signaling, Possibly through a Janus Kinase 2-Phosphatidylinositol 3-Kinase/Akt-Phosphodiesterase 3-cAMP Pathway, to Down-Regulate Cholesterol Side-Chain Cleavage Cytochrome P450 Enzyme in Human Adrenocortical NCI-H295 Cell Line

• Published in: The journal of clinical endocrinology and metabolism 2006-07, Vol.91 (7), p.2761-2769
• Main Authors: Hsu, Hao-Ting, Chang, Yuan-Ching, Chiu, Yi-Ning, Liu, Chien-Liang, Chang, King-Jen, Guo, Ing-Cherng
• Format: Article
• Language: English
• Subjects: Adrenal Cortex - drug effects; Adrenal Cortex - metabolism; Adrenal Cortex Neoplasms - enzymology; Adrenocorticotropic Hormone - metabolism; Adrenocorticotropic Hormone - pharmacology; Biological and medical sciences; Cell Line, Tumor; Cholera Toxin - pharmacology; Cholesterol Side-Chain Cleavage Enzyme - genetics; Cyclic AMP - metabolism; Endocrinopathies; Fundamental and applied biological sciences. Psychology; Gene Expression - drug effects; Humans; Janus Kinase 2; Leptin - pharmacology; Medical sciences; Phosphatidylinositol 3-Kinases - metabolism; Phosphoric Diester Hydrolases - metabolism; Phosphorylation; Promoter Regions, Genetic - genetics; Protein-Tyrosine Kinases - metabolism; Proto-Oncogene Proteins - metabolism; Proto-Oncogene Proteins c-akt - metabolism; RNA, Messenger - analysis; Signal Transduction - drug effects; Steroids - biosynthesis; Vertebrates: endocrinology
• ISSN: 0021-972X; 1945-7197
• DOI: 10.1210/jc.2005-2383

Context: Obesity has adverse effects on adrenocortical functions. Adipocyte-derived leptin, a biomarker molecule of obesity, may directly control adrenal steroidogenesis via an unclear mechanism. Objective: We studied the mechanism underlying leptin action on adrenal steroidogenesis in human adrenocortical NCI-H295 tumor cell line. Methods: Levels of progesterone, cortisol, and cAMP were determined by ELISA. Western blotting was used to detect protein amounts of P450 side-chain cleavage (P450scc), Janus kinase 2 (JAK2), Akt, and their phosphorylated forms. The mRNA expressions of P450scc and leptin receptors were measured by RT-PCR and real-time PCR. P450scc promoter activity was analyzed with a luciferase reporter system. Results: Cholera toxin mimicked ACTH action by increasing adrenal cAMP levels and steroid secretion. Leptin did not affect basal release but significantly inhibited ACTH/cholera toxin-induced steroid secretion. The concomitant inhibitions by leptin on cholera toxin-induced protein and ACTH/cholera toxin-induced mRNA expression of P450scc were confirmed. Leptin inhibited ACTH/cholera toxin-induced CYP11A1 promoter activity via a known cAMP-responsive region located between −1.7 and −1.5 kb. Leptin activated phosphorylations of JAK2 and Akt. Inhibitory effects of leptin on ACTH/cholera toxin-induced cAMP levels, CYP11A1 promoter activity, and steroid secretion were blunted by either inhibitor of JAK2 (AG490) or phosphatidylinositol 3-kinase/Akt (wortmannin) as well as inhibitors of cAMP-degrading phosphodiesterases (PDEs), including nonspecific 3-isobutyl-1-methylxanthine and PDE3-specific SKF94836. Leptin failed to affect the inductions of CYP11A1 promoter activity and steroid secretion by PDE-nonhydrolyzable N6-monobutyryl-cAMP. Conclusions: Leptin interferes with ACTH/cAMP signaling, possibly through a cAMP-degrading mechanism involving activation of JAK2, phosphatidylinositol 3-kinase, and PDE3, to down-regulate P450scc expression and consequent adrenal steroidogenesis.