α-adrenergic Blockade Attenuates Septic Cardiomyopathy by Increasing Cardiac Norepinephrine Concentration and Inhibiting Cardiac Endothelial Activation

Cardiomyopathy is a common complication associated with increased mortality in sepsis, but lacks specific therapy. Here, using genetic and pharmacological approaches, we explored the therapeutic effect of α-adrenergic receptor (AR) blockade on septic cardiomyopathy. CLP-induced septic rats were treated with BRL44408 (α-AR antagonist), prazosin (α-AR antagonist) and/or reserpine. CLP-induced cardiomyopathy, indicated by reduced dP/dt and increased cardiac troponin I phosphorylation, was attenuated by BRL44408, this was associated with reduced cardiac TNF-α and endothelial VCAM-1 expression, cardiomyocyte apoptosis and related signal molecule phosphorylation. BRL44408 increased cardiac norepinephrine (NE) concentration in CLP rats. Pretreatment with reserpine that exhausts cardiac NE without affecting the circulating NE concentration or with prazosin partially abolished the cardioprotection of BRL44408 and reversed its inhibitory effects on myocardial TNF-α, apoptosis and related signal molecule phosphorylation, but not on VCAM-1 expression in septic rats. These effects of BRL44408 were confirmed by α-AR gene deletion in septic mice. Furthermore, α-AR agonist not only enhanced LPS-induced TNF-α and VCAM-1 expression in cardiac endothelial cells that express α-AR, but also enhanced LPS-induced cardiac dysfunction in isolated rat hearts. Our data indicate that α-AR blockade attenuates septic cardiomyopathy by promoting cardiac NE release that activates myocardial α-AR and suppressing cardiac endothelial activation.