Alterations in adrenergic receptor signaling in heart failure.

In the failing heart, several changes occur in cardiac adrenergic receptor-signal transduction pathways. The most striking of these changes occur in beta-ARs, and of the changes in beta-adrenergic receptors, beta1-receptor down-regulation is the most prominent. Other changes include uncoupling of beta2-adrenergic receptors and increased activity of the inhibitory G-protein, Gi. Most of these changes appear to be related to increased activity of the adrenergic nervous system, i.e. increased exposure to norepinephrine. Antagonists of the adrenergic nervous system improve left ventricular function and outcome in patients with heart failure. This fact supports the notion that activation of these neurohormonal systems exerts a net long-term detrimental effect on the natural history of chronic heart failure and that myocardial adrenergic desensitization phenomena are at least partially adaptive in the setting of left ventricular dysfunction.