Dominant-negative mutation of monocyte chemoattractant protein-1 prevents vulnerable plaques from rupture in rabbits independent of serum lipid levels

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Abstract

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. We aimed to determine whether dominant-negative mutation of MCP-1 could reverse atherosclerotic lesion progression and prevent vulnerable plaques from rupture regardless of serum lipid levels. The mutant MCP-1 was produced by deletion of the N-terminal amino acids 2 to 8 (7ND), and a eukaryotic expression vector plRES-EGFP-7ND was constructed. The transwell chamber was used to assay chemotaxis of monocytes in vitro. Thirty New Zealand white rabbits underwent balloon-induced abdominal aortic endothelial injury and were randomly divided into control group without gene intervention (group A, n = 10), plRES-EGFP-7ND treatment group (group B, n = 10) and empty vector treatment group (group C, n = 10). All rabbits were fed a diet of 1% cholesterol for 8 weeks, and then group A rabbits were killed, whereas groups B and C rabbits received an intramuscular injection of plRES-EGFP-7ND and an empty lipofectamine, respectively, and remained on a high cholesterol diet for 4 weeks. At the end of week 12, groups B and C rabbits underwent pharmacological triggering by injection with Chinese Russellis viper venom and histamine. Serum lipids and inflammatory markers were measured, and high-frequency ultra-sonography and intravascular ultrasound imaging were performed. Immunohistochemistry and RT-PCR were used to examine expression of inflammatory markers in the plaques. In vitro transfection of plRES-EGFP-7ND resulted in a significant inhibition of monocyte chemotaxis (P < 0.05) and in vivo transfection of plRES-EGFP-7ND significantly increased the thickness of the fibrous caps and decreased plaque vulnerability index. The incidence of plaque rupture in group B was 0% as compared with 56% in the empty vector treatment group (P< 0.05). The serum levels and expression of inflammatory markers were significantly reduced in group B. In conclusion, PIRES-EGFP-7ND transfection effectively inhibits plaque inflammation, reverses plaque progression and prevents vulnerable plaques from rupture. These therapeutic effects are independent of serum lipid levels and demonstrate that inhibition of plaque inflammation alone without lipid lowering can stabilize vulnerable plaques.

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