Calcineurin-GATA4 Pathway Is Involved in β-Adrenergic Agonist-responsive Endothelin-1 Transcription in Cardiac Myocytes

Abstract

Increases in the expression of endothelin-1 (ET-1) in cardiac myocytes play a critical role in the development of heart failure in vivo. Whereas norepinephrine (NE) is a potent inducer of ET-1 expression in cardiac myocytes, the signaling pathways that link NE to inducible cardiac ET-1 expression are unknown. Adrenergic stimulation results in an increase in intracellular calcium levels, which in turn activates calcineurin. Here, we have shown that stimulation with NE markedly increased the expression of the ET-1 gene in primary cardiac myocytes from neonatal rats. This increase was severely attenuated by a ␤-adrenergic antagonist, metoprolol, but not by an ␣-adrenergic antagonist, prazosin. Consistent with these data, the ␤-adrenergic agonist isoproterenol (ISO) activated the rat ET-1 promoter activity to an extent that was similar to NE. The ISO-stimulated increase in promoter activity was significantly inhibited by a Ca 2؉ -antagonist, nifedipine, and an immunosuppressant, cyclosporin A, which blocks calcineurin. Mutation analysis indicated that the GATA4 binding site is required for ISO-responsive ET-1 transcription. Stimulation with ISO enhanced the interaction between NFATc and GATA4 in cardiac myocytes. Consistent with this interaction, overexpression of GATA4 and NFATc synergistically activated the ET-1 promoter. These findings demonstrate that NE-stimulated ET-1 expression in cardiac myocytes is mediated predominantly via a ␤-adrenergic pathway, and that calcium-activated calcineurin-GATA4 plays a role in this process. Endothelin-1 (ET-1)1 was initially identified as a 21 amino acid vasoconstrictive peptide in porcine vascular endothelial cells (1). Later work showed that ET-1 acts not only as a vasoconstrictor but also as a potent growth-promoting peptide. For example, ET-1 can induce myocyte hypertrophy (2, 3) through coupling of ET receptors with the G q protein. Whereas ET-1 is mainly produced by endothelial cells in the basal state, a number of cell types can synthesize ET-1 in response to various stimuli (4 -7). ET-1 expression in cardiac myocytes is induced by myocardial stretch, angiotensin II, and norepinephrine (5-7). Left ventricular levels of ET-1 increase markedly in close association with the deterioration of systolic function following myocardial infarction and pressure overload (8 -10). Immunohistochemical studies have demonstrated that ET-1 in the failing heart is localized in cardiac myocytes. ET receptor antagonists bosentan or BQ123 prevent the remodeling of the heart and have been shown to improve survival following myocardial infarction and pressure overload (9, 10). These findings demonstrate that upregulated expression of ET-1 in cardiac myocytes plays a critical role in the development of heart failure in vivo. However, the precise mechanisms leading to this upregulation in the failing heart are unclear at present.Because a number of neurohormonal factors are activated in congestive heart failure (11, 12), they may possibly play positive and negative roles in regulating ET-1 expr...

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