ABSTRACT
<p><b>OBJECTIVE</b>To investigate the effect of the sera of rabbits fed with Tongxinluo on the expression and secretion of matrix metalloproteinase-9 (MMP-9) and tissue inhibitor of metalloproteinase-1 (TIMP-1) in U937 monocyte-derived macrophages.</p><p><b>METHODS</b>Atherosclerosis was induced in rabbits by high-cholesterol feeding, and the serum was obtained from the rabbits after administration of the aqueous solution of Tongxinluo or simvastatin by gavage. U937 monocyte-derived macrophages were incubated with the sera at different concentrations for 24 hours, and the changes in MMP-9 and TIMP-1 gene expression and secretion were detected by RT-PCR and enzyme-linked immunosorbent assay, respectively.</p><p><b>RESULTS</b>The serum of rabbits fed with Tongxinluo concentration-dependently inhibited the expression and secretion of MMP-9 in U937 macrophages, but did not affect TIMP-1 expression or secretion.</p><p><b>CONCLUSION</b>Tongxinluo may stabilize the atherosclerotic plaques by inhibiting the expression and secretion of MMP-9.</p>