Abstract 1410: Clarithromycin Inhibited MMP-9 Activation and Attenuated Acute and Chronic Rejection in Murine Cardiac Allografts
Background: Matrix metalloproteinases (MMPs) are critical in the development of inflammation and tissue remodeling. MMP-9 is a key member of MMPs and the level is associated with the rejection of heart transplantation. Clarithromysin (CAM), a major macrolide antibiotic, has been many biological functions including MMP regulation. However, little is known about the effect of CAM in heart transplantation via MMP-9.
Methods and Results: To clarify the role of MMPs regulated by CAM in the progression of rejection, we orally administered CAM (100mg/kg) into murine cardiac allograft recipients. CAM improved acute rejection judged by graft survival (control: 7.3+/−0.2 days n=8; CAM: 9.7+/−0.2 days n=8; P<0.05) and by myocardial cell infiltrating area (control: 35.7+/−1.9% n=9; CAM: 19.7+/−3.0% n=9, P<0.05) in a total allomismatch combination. 8 weeks after transplantation, CAM significantly suppressed the development of graft arterial disease (5.1+/−3.0%, n=6) compared to that of non-treatment (25.1+/−6.3%, n=6; P<0.05) in the class II mismatch combination. Immunohistochemically, non-treated allografts showed enhanced expression of T-cells, macrophages, MMP-9 and NF-kappaB while CAM decreased these positive cell numbers. RPA also revealed that CAM-treated allografts significantly attenuated the expression of proinflammatory cytokines such as IFN-gamma, IL-6, IL-10 and IL-15 compared with non-treated grafts. In situ zymography indicated that enhanced MMPs activities were observed in non-treated hearts, while CAM suppressed the levels. In vitro study showed that CAM inhibited the expression of MMP-9 using Western blot and RT-PCR in cytokine stimulated macrophages and SMCs. The effects of inhibited MMP-9 by CAM suppressed SMCs migration (native: 23.5+/−4.5 cells, control: 97.0+/− 5.0, CAM: 53.4+/−4.5, P<0.05) and proliferation (native: 0.44+/−0.01OD, control: 0.56+/−0.03, CAM: 0.44+/−0.004, P<0.05) compared with control.
Conclusion: CAM is useful to suppress allograft remodeling because it is critically involved in the prevention of cardiac rejection through the suppression of MMP-9.