Background: Monocyte chemoattractant protein-1 (MCP-1) is a key mediator of left ventricular (LV) remodeling during the early phase of myocardial infarction (MI). The hypothesis tested was that myocardial MCP-1 expression would increase during the chronic phase of MI and an angiotensin-II type 1 receptor blocker (ARB) would attenuate macrophage infiltration through decreased myocardial MCP-1 expression.
Methods and results: MI was produced by ligation of the left coronary artery in Wistar rats, which were then randomized to treatment with vehicle (MI/C), candesartan (10 mg.kg(-1).day(-1)) for 6 weeks (MI/ARB0-6W), or candesartan for 2 weeks, starting 4 weeks after MI (MI/ARB4-6W). LV systolic and end-diastolic pressures 6 weeks after MI were decreased in MI/ARB0-6W compared with MI/C or MI/ARB4-6W, however, there were no differences in other hemodynamic or echocardiographic parameters among infarcted rat groups. Both long- and short-term treatments with ARB similarly reduced mRNA expressions of MCP-1, transforming growth factor-beta1, and procollagen type I and III, macrophage infiltration, and myocardial fibrosis in the border zone.
Conclusions: In post-MI heart failure, ARB attenuated MCP-1 expression and macrophage infiltration in the border zone, resulting in less myocardial fibrosis. ARB may exert its beneficial effect, at least in part, by inhibiting myocardial macrophage-related inflammation.