Role of Alpha1-adrenoreceptors in Cocaine-induced NADPH Oxidase Expression and Cardiac Dysfunction

Objective: We assessed whether alpha1-adrenoreceptor (alpha1-AR) stimulation contributes to activation of myocardial NADPH oxidase in a rat model of cocaine-induced cardiac dysfunction.

Methods And Results: After 7 days of cocaine injection (2 x 7.5 mg/kg/day, i.p., Coc), NADPH activity assessed by chemiluminescence increases as well as phosphorylation of p47phox, one of the cytosolic components of NADPH oxidase. The alpha1-AR antagonist prazosin (Prz), administered 1 h before each cocaine injection (2 x 1 mg/kg/day, i.p., Coc+Prz), prevents these effects. Moreover, Prz pretreatment reduces left ventricular/body weight (LV/BW) ratio and partially prevents the cocaine-induced alterations in fractional shortening and cardiac index assessed by echocardiography. In order to confirm the involvement of alpha1-AR stimulation in NADPH oxidase up-regulation in vivo, we used phenylephrine (Phe) administration with the same protocol of injections as that used with cocaine (2 x 5 microg/kg/day, i.p.). After Phe administration, as expected, NADPH oxidase activity increases as well as phosphorylation of p47phox. These effects occur in the absence of sustained hemodynamic changes.

Conclusion: This study demonstrates the involvement of the alpha1-AR in NADPH oxidase activation and in cocaine-induced LV dysfunction. We suggest that alpha1-AR stimulation, at least in part via NADPH oxidase induction, plays a critical role in the events leading to the cardiomyopathy observed after cocaine abuse.