Transforming growth factor-beta1 inhibits the growth of primary adult rat hepatocyte cultures by increasing cAMP levels.
We investigated the mechanisms of transforming growth factor-beta1 (TGF-beta1) inhibition on transforming growth factor-alpha (TGF-alpha)-induced DNA synthesis and proliferation in primary cultures of adult rat hepatocytes. TGF-alpha (1.0 ng/ml) produced a 4.2-fold elevation of DNA synthesis during 3 h of culture and a 1. 2-fold increase in nucleus number (proliferation) during 4 h of culture. TGF-beta1 dose dependently inhibited the TGF-alpha-induced hepatocyte DNA synthesis and proliferation: half-maximal inhibition occurred at a TGF-beta1 concentration of 0.08 ng/ml. The inhibitory effects of 1.0 ng/ml TGF-beta1 were almost completely reversed by adenylate cyclase inhibitors, 2,4-dideoxyadenosine (10(-6) M), and somatostatin (3 x 10(-7) M), or by a specific inhibitor of protein kinase A, H-89 (N-[2-(p-bromocinnamylamino)ethyl]-5-isoquinolinesulfonamide dihydrochloride; 10(-7) M). In addition, while TGF-alpha did not affect the basal cellular adenosine 3',5'-monophosphate (cAMP) levels, TGF-beta1 was found to produce dose-dependent increases in cellular cAMP levels. The cAMP-elevating effects of TGF-beta1 were also reversed by 2,4-dideoxyadenosine (10(-6) M), and somatostatin (3 x 10(-7) M), but not by H-89 (10(-7) M). The present results suggest that the specific mechanisms involved in the growth inhibitory effect of TGF-beta1 on TGF-alpha-induced hepatocyte DNA synthesis and proliferation are via stimulation of adenylate cyclase, which increases intracellular cAMP and subsequently activates protein kinase A.
Kimura
M
M
Department of Pharmacology and Therapeutics, Faculty of Pharmaceutical Sciences, Josai University, 1-1, Keyakidai, Sakado City, Japan.
Ogihara
M
M
D000322:Adrenergic Agonists / Q000494:pharmacology; D018674:Adrenergic Antagonists / Q000494:pharmacology; D058666:Adrenergic beta-2 Receptor Agonists; D058672:Adrenergic beta-2 Receptor Antagonists; D000818:Animals; D000963:Antimetabolites / Q000494:pharmacology; D002455:Cell Division / Q000187:drug effects; D002478:Cells, Cultured; D000242:Cyclic AMP / Q000378:metabolism*; D004247:DNA / Q000096:biosynthesis / Q000187:drug effects; D016048:Dideoxyadenosine / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004347:Drug Interactions; D004791:Enzyme Inhibitors / Q000494:pharmacology; D007546:Isoquinolines / Q000494:pharmacology; D008099:Liver / Q000166:cytology / Q000187:drug effects*; D008297:Male; D051381:Rats; D017208:Rats, Wistar; D013004:Somatostatin / Q000494:pharmacology; D013449:Sulfonamides; D016211:Transforming Growth Factor alpha / Q000502:physiology; D016212:Transforming Growth Factor beta / Q000494:pharmacology*
D000322:Adrenergic Agonists; D018674:Adrenergic Antagonists; D058666:Adrenergic beta-2 Receptor Agonists; D058672:Adrenergic beta-2 Receptor Antagonists; D000963:Antimetabolites; D004791:Enzyme Inhibitors; D007546:Isoquinolines; D013449:Sulfonamides; D016211:Transforming Growth Factor alpha; D016212:Transforming Growth Factor beta; D016048:Dideoxyadenosine; D013004:Somatostatin; D004247:DNA; D000242:Cyclic AMP; C063509:N-(2-(4-bromocinnamylamino)ethyl)-5-isoquinolinesulfonamide