Abstract 592: Erythropoietin Attenuates the Development of Experimental Autoimmune Myocarditis

Background: Myocarditis is a major cause of dilated cardiomyopathy (DCM) and end-stage heart failure; however, no effective treatment has been established. Recent evidence indicates that autoimmunity plays an important role in the development of myocarditis and DCM. Since erythropoietin (EPO) has been shown to not only have cardioprotective effects but also attenuate autoimmune diseases, we investigated whether EPO attenuates the development of a rat experimental autoimmune myocarditis (EAM) model. Methods and Results: Male Lewis rats were immunized on day 0 with porcine cardiac myosin to establish EAM. Rats were received human recombinant EPO (EPO group: 6000 IU/kg, 3 days/week, day 0 to 20, n = 14) or saline (control group, n = 15) subcutaneously, and evaluated on day 21. In EPO group, the myocarditis-affected area and heart/body weight ratio was significantly attenuated compared with those in control group (area: 7.7 ± 2.5 vs. 27.4 ± 4.3%, p<0.001; ratio: 3.79 ± 0.8 vs. 4.81 ± 1.4, p<0.05). Echocardiogram and blood pressure (BP) study demonstrated significant improvement of left ventricular contraction and systolic BP in EPO group (%FS: 45.1 ± 1.8 vs. 38.5 ± 2.8%, p< 0.05; BP: 113.4 ± 4.7 vs. 97.8 ± 2.4 mmHg, p<0.001). Immunohistochemistry showed that EPO treatment decreased the infiltration of macrophages (ED1: 30.2 ± 10.7 vs. 122.9 ± 3.3/HPF, p<0.01) and T cells (OX-38: 10.6 ± 2.7 vs. 41.6 ± 2.9/HPF, p<0.01), and %degranulation of mast cells (27.5 ± 7.5 vs. 62.5 ± 7.5%, p<0.05). Real-time RT-PCR analysis revealed that EPO treatment decreased the expression of inflammatory cytokines, such as IFN-γ (p<0.01), MCP-1 (p<0.01), and osteopontin (p<0.01), but not TNF-α and IL-10, in the myocardium. We further tested the effect of EPO on cardiac myosin-induced lymphocyte proliferation and cytokine expression in the splenocytes isolated from EAM rats in vitro. Treatment with cardiac myosin significantly stimulated proliferation and the expression of IFN-γ and TNF-α; however, EPO failed to inhibit them. Conclusions: These findings suggest that EPO attenuated inflammatory cell infiltration and cytokine expression, and improved cardiac function in EAM; thus, EPO has a therapeutic potential for the treatment of myocarditis.