Activation of cardiac endothelium as a compensatory component in endotoxin-induced cardiomyopathy - Role of endothelin, prostaglandins, and nitric oxide

Background-In view of growing evidence of an important endothelial paracrine regulation of cardiac function, the present study investigated the role of cardiac endothelium-derived endothelin-1 (ET-1), prostaglandins, and nitric oxide (NO) during endotoxin-induced cardiomyopathy in rabbits. Methods and Results-Immunohistochemical studies showed a marked transient coinduction of the inducible isoforms of NO synthase (NOS-2) and cyclooxygenase (COX-2) in endocardial endothelium and coronary arteriolar endothelium of hearts 12 hours after intravenous administration of lipopolysaccharide (LPS + 12h); staining for both isoforms was much weaker 24 hours later (LPS + 36h). Nitrotyrosine localization was similar to that of NOS-2, suggesting a NOS-2-related endothelial formation of peroxynitrite in septic hearts. Contractile performance of papillary muscles was depressed in both LPS-treated groups. In the LPS + 12h group, however, isometric twitches were significantly prolonged (482 +/- 14 versus 420 +/- 14 ms in the saline-treated group, P <0.005). This twitch prolongation was completely reversed by simultaneous administration of BQ-123 and indomethacin to block endogenous ET-1 and prostaglandins, respectively. In addition, in the LPS+12h group, myocardial inotropic responsiveness to exogenous ET-1 was enhanced (P <0.01). Conclusions-Cardiac endothelial activation and myocardial sensitization to endothelium-derived mediators may be part of an adaptive response in the early (12 hours) stages of septic cardiomyopathy.