Negative Inotropic Effects of Cytokines on the Heart Mediated by Nitric Oxide

The direct effects of pro-inflammatory cytokines on the contractility of mammalian heart were studied. Tumor necrosis factor α, interleukin-6, and interleukin-2 inhibited contractility of isolated hamster papillary muscles in a concentration-dependent, reversible manner. The nitric oxide synthase inhibitor N$^G$-monomethyl-L-arginine (L-NMMA) blocked these negative inotropic effects. L-Arginine reversed the inhibition by L-NMMA. Removal of the endocardial endothelium did not alter these responses. These findings demonstrate that the direct negative inotropic effect of cytokines is mediated through a myocardial nitric oxide synthase. The regulation of pro-inflammatory cytokines and myocardial nitric oxide synthase may provide new therapeutic strategies for the treatment of cardiac disease.