Abstract
To shed light on mechanisms of angiotensin-converting enzyme (ACE) upregulation, we used a rabbit endothelial cell model to characterize intracellular pathways of beta-adrenergic stimulation. In these cells, ACE activity is increased by isoproterenol (ISO). The stably transfected 1273-bp ACE promoter is stimulated by ISO in the presence of isobutyl methylxanthine. This effect is abolished by propranolol. Promoter stimulation is mimicked by cholera toxin, forskolin, and 8BrcAMP, but not by 8BrcGMP. Promoter stimulation by ISO and isobutyl methylxanthine is blocked by protein kinase A inhibitors, indicating that beta-adrenergic stimulation of the ACE gene depends on phosphorylation of protein kinase A targets. Activation by cAMP, resistance to phorbol ester, and lack of synergism between cAMP and phorbol ester suggest that promoter regulation is due to cAMP responsive element rather than to activating protein-2 sequences. Okadaic acid potentiation of 8BrcAMP induction indicated that promoter activation by cAMP is regulated by phosphatases controlling activation of typical cAMP responsive element regulated genes. In summary, beta-adrenergic activation of rat ACE promoter is specific; uses G(s) proteins, adenylyl cyclase, protein kinase A; and probably includes cAMP responsive element-like sequences.
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