title: Regulation of angiotensinogen gene expression and protein in neonatal rat cardiac fibroblasts by glucocorticoid and beta-adrenergic stimulation.
abstract: We previously demonstrated the presence of components for a renin-angiotensin system in fibroblasts cultured from neonatal rat ventricles, the regulation of expression of which has not been studied. Since glucocorticoids and beta-adrenergic stimuli have been implicated in cardiac hypertrophy, and function as regulators of the circulating renin-angiotensin system, we examined the effects of dexamethasone and isoproterenol on angiotensinogen mRNA levels and protein secretion in cultured neonatal rat cardiac fibroblasts. Treatment of cardiac fibroblasts for 8 h with 10 micromol/l isoproterenol or 100 nmol/l dexamethasone increased angiotensinogen mRNA levels by 246 +/- 7% and 1406 +/- 207%, respectively. Over 24 h, dexamethasone and isoproterenol increased angiotensinogen secretion by 148 +/- 32% and 123 +/- 26%, respectively. Angiotensin II, which has been reported to be a positive regulator of angiotensinogen synthesis and secretion in liver, markedly attenuated the effects of dexamethasone and isoproterenol on angiotensinogen mRNA expression and secretion. In the presence of 1 micromol/l angiotensin II, the stimulation in angiotensinogen secretion observed with dexamethasone and isoproterenol was decreased by 62% and 76%, respectively. The negative feedback of angiotensin II on angiotensinogen expression was primarily mediated through the type one angiotensin II (AT1) receptor (IC50 = 0.30 +/- 0.02 nmol/l). In summary, results from this study demonstrate that angiotensinogen mRNA levels and protein secretion in cardiac fibroblasts are positively regulated by glucocorticoid and beta-adrenergic stimulation. In addition, angiotensinogen production by cardiac fibroblasts is under negative feedback control of angiotensin II.
authors.affiliation: The Cardiovascular Research Institute, Division of Molecular Cardiology, The Texas A&M University System HSC, Temple 76504, USA. Ddostal@medicine.tamu.edu
authors.forename: D E
authors.initials: DE
authors.lastname: Dostal
authors.forename: G W
authors.initials: GW
authors.lastname: Booz
authors.forename: K M
authors.initials: KM
authors.lastname: Baker
mesh_terms: D000318:Adrenergic beta-Agonists / Q000494:pharmacology*; D000804:Angiotensin II / Q000037:antagonists & inhibitors; D000808:Angiotensinogen / Q000235:genetics*; D000818:Animals; D000831:Animals, Newborn / Q000502:physiology; D046508:Culture Techniques; D003907:Dexamethasone / Q000494:pharmacology*; D005347:Fibroblasts / Q000502:physiology*; D015870:Gene Expression / Q000187:drug effects*; D005938:Glucocorticoids / Q000494:pharmacology*; D007545:Isoproterenol / Q000494:pharmacology*; D009206:Myocardium / Q000166:cytology*; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley
chemical_list: D000318:Adrenergic beta-Agonists; D005938:Glucocorticoids; D012333:RNA, Messenger; D000808:Angiotensinogen; D000804:Angiotensin II; D003907:Dexamethasone; D007545:Isoproterenol