Infusion of adrenomedullin improves acute myocarditis via attenuation of myocardial inflammation and edema

Objective: Our aim was to assess whether adrenomedullin (AM), a potent vasodilator peptide with a variety of cardioprotective effects, has a therapeutic potential for the treatment of acute myocarditis in a rat model. Methods: One week after myosin injection, rats received a continuous infusion of AM or vehicle for 2 weeks, and pathological and physiological investigations were performed. Results: AM treatment significantly reduced the infiltration of inflammatory cells in myocarditic hearts, and decreased the expressions of macrophage chemoattractant protein-1, matrix metalloproteinase-2 and transforming growth factor-β. Myocardial edema indicated by increased heart weight to body weight ratio and wall thickness was attenuated by AM infusion (5.7±0.5 vs. 6.5±0.4 g/kg, and 1.9±0.3 vs. 2.8±0.5 mm, respectively). Infusion of AM significantly improved left ventricular maximum dP/dt and fractional shortening of myocarditic hearts (4203±640 vs. 3450±607 mm Hg/s, and 21.3±4.1 vs. 14.7±5.1%, respectively). Conclusion: Infusion of AM improved cardiac function and pathological findings in a rat model of acute myocarditis. Thus, infusion of AM may be a potent therapeutic strategy for acute myocarditis.