Novel action of activin and bone morphogenetic protein in regulating aldosterone production by human adrenocortical cells.
We have uncovered a functional bone morphogenetic protein (BMP) and activin system complete with ligands (BMP-6 and activin betaA/betaB), receptors (activin receptor-like kinase receptors 2, 3, and 4; activin type-II receptor; and BMP type-II receptor), and the binding protein follistatin in the human adrenocortical cell line H295R. Administration of activin and BMP-6 to cultures of H295R cells caused concentration-responsive increases in aldosterone production. The mRNA levels of steroidogenic acute regulatory protein or P450 steroid side-chain cleavage enzyme, the rate-limiting steps of adrenocortical steroidogenesis, were enhanced by activin and BMP-6. Activin and BMP-6 also activated the transcription of steroidogenic acute regulatory protein as well as the late-step steriodogenic enzyme CYP11B2. Activin enhanced ACTH-, forskolin-, or dibutyryl-cAMP- but not angiotensin II (Ang II)-induced aldosterone production, whereas BMP-6 specifically augmented Ang II-induced aldosterone production. Activin and ACTH but not BMP-6 increased cAMP production. Follistatin, which inhibits activin actions by binding, suppressed basal and ACTH-induced aldosterone secretion but failed to affect the Ang II-induced aldosterone level. Furthermore, MAPK signaling appeared to be involved in aldosterone production induced by Ang II and BMP-6 because an inhibitor of MAPK activation, U0126, reduced the level of aldosterone synthesis stimulated by Ang II and BMP-6 but not activin. In addition, Ang II reduced the expression levels of BMP-6 but increased that of activin betaB, whereas ACTH had no effect on these levels. Collectively, the present data suggest that activin acts to regulate adrenal aldosterone synthesis predominantly by modulating the ACTH-cAMP-protein kinase A signaling cascade, whereas BMP-6 works primarily by modulating the Ang II-MAPK cascade in human adrenal cortex in an autocrine/paracrine fashion.
Suzuki
Jiro
J
Department of Medicine and Clinical Science, Okayama University Graduate School of Medicine and Dentistry, 2-5-1 Shikata-cho, Okayama City 700-8558, Japan.
Otsuka
Fumio
F
Inagaki
Kenichi
K
Takeda
Masaya
M
Ogura
Toshio
T
Makino
Hirofumi
H
D028341:Activins / Q000235:genetics / Q000494:pharmacology*; D000302:Adrenal Cortex / Q000187:drug effects* / Q000378:metabolism*; D000306:Adrenal Cortex Neoplasms; D000324:Adrenocorticotropic Hormone / Q000494:pharmacology; D000450:Aldosterone / Q000096:biosynthesis*; D000804:Angiotensin II / Q000494:pharmacology; D055418:Bone Morphogenetic Protein 6; D019485:Bone Morphogenetic Proteins / Q000235:genetics / Q000494:pharmacology*; D002455:Cell Division / Q000187:drug effects; D002460:Cell Line; D002786:Cholesterol Side-Chain Cleavage Enzyme / Q000235:genetics; D017077:Culture Media, Conditioned; D000242:Cyclic AMP / Q000096:biosynthesis; D054746:Cyclic AMP-Dependent Protein Kinase Type II; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D019405:Cytochrome P-450 CYP11B2 / Q000235:genetics; D004357:Drug Synergism; D038681:Follistatin / Q000494:pharmacology; D015870:Gene Expression / Q000187:drug effects; D006801:Humans; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D010750:Phosphoproteins / Q000235:genetics; D011401:Promoter Regions, Genetic / Q000235:genetics; D012333:RNA, Messenger / Q000032:analysis; D015398:Signal Transduction; D013252:Steroid 11-beta-Hydroxylase / Q000235:genetics; D014162:Transfection; D014407:Tumor Cells, Cultured; D000098682:Steroidogenic Acute Regulatory Protein
C525816:BMP6 protein, human; D055418:Bone Morphogenetic Protein 6; D019485:Bone Morphogenetic Proteins; D017077:Culture Media, Conditioned; D038681:Follistatin; D010750:Phosphoproteins; D012333:RNA, Messenger; D000098682:Steroidogenic Acute Regulatory Protein; D028341:Activins; D000804:Angiotensin II; D000450:Aldosterone; D000324:Adrenocorticotropic Hormone; D000242:Cyclic AMP; D019405:Cytochrome P-450 CYP11B2; D013252:Steroid 11-beta-Hydroxylase; D002786:Cholesterol Side-Chain Cleavage Enzyme; D054746:Cyclic AMP-Dependent Protein Kinase Type II; D017868:Cyclic AMP-Dependent Protein Kinases; D020928:Mitogen-Activated Protein Kinases