Abstract 559: Dominant-negative Mutation of Monocyte Chemoattractant Protein-1 Prevents Vulnerable Plaques from Rupture
Active inflammation is an important feature of vulnerable plaques and monocyte chemoattractant protein-1 (MCP-1) is a key chemokine that promotes monocyte-endothelium binding and initiates inflammation. The purpose of this study was to test the hypothesis that dominant-negative mutation of MCP-1 may block the MCP-1 signaling pathway and prevent vulnerable plaques from rupture. The mutant MCP-1 was produced by deletion of the N-terminal amino acids 2 through 8 (7ND) and a eukaryotic expressing vector pIRES-EGFP-7ND was constructed and transfected into HK293 cells. The transwell chamber was used to assay chemotaxis of monocytes in vitro. Twenty New Zealand white rabbits underwent balloon-induced abdominal aortic endothelial injury and were fed a diet of 1% cholesterol for 8 weeks. The rabbits were then randomly divided into group A (n=10) and group B (n=10), and pIRES-EGFP-7ND and pIRES-EGFP were transfected into skeletal muscles in group A and B, respectively. Four weeks later, pharmacological triggering was performed with the injection of Chinese Russell’s viper venom and histamine in both groups. Serum lipids and inflammatory markers were measured and intravascular ultrasound (IVUS) imaging was performed to measure the external elastic membrane area (EEMA), plaque area (PA) and percentage of lumen area stenosis (LAS%) of the abdominal aorta. Plaque contents were evaluated by immunohistochemistry and the vulnerability index (VI) was calculated as:VI = (macrophage +lipid) / (SMC+collagen) contents. The results showed that in vitro transfection of pIRES-EGFP-7ND resulted in a more significant inhibition of recruitment and chemotaxis of monocytes (P<0.05), and in vivo transfection of pIRES-EGFP-7ND significantly increased VI and the thickness of plaques caps, and decreased EEMA, PA, LAS% and the occurrence of plaque rupture (0% vs. 64%) in group A compared with group B (P<0.05). There was no significant difference in serum lipid levels between the two groups but the concentration of serum inflammatory markers was significantly reduced in group A in comparison with group B (P<0.05). In conclusion, PIRES-EGFP-7ND transfection effectively blockades MCP-1/CCR-2 pathway, inhibits plaque inflammation and prevents vulnerable plaques from rupture.