Telomere-independent Rap1, modulates NF-kB-dependent inflammation in macrophages

Abstract

AIM: The activity of nuclear factor (NF-κB) is modulated by cytoplasmic repressor activator protein 1 (Rap1) in cancel cells. Experiments were designed to test whether or not Rap1 is present in atheromatous lesions and affects NF-κB dependent inflammation in macrophages, the predominant cell type involved in the progression of atherosclerotic lesions. METHODS: The expression of Rap1 and macrophages in human atheromatous lesions was detected by immunohistochemistry. The expression of lipopolysaccharide- (LPS, 50 ng/mL, 4 h) and tumor necrosis factor alpha (TNF-α, 100 ng/mL, 4 h) induced NF-κB dependent genes and proteins in wild type and Rap1 knockdown THP-1 cells were measured using real-time PCR and enzyme-linked immune sorbent assays. Western blotting was applied to determine the expression of p65 and its phosphorylation in wild type and Rap1 knockdown THP-1 cells. RESULTS: Rap1 co-localized with macrophages and its staining positively correlated with graded human atherosclerosis. In THP-1 cells, Rap1 knockdown suppressed the phosphorylation of p65 and reduced the expression of LPS- or TNFα-induced NF-κB dependent pro-inflammatory cytokines at mRNA and protein levels. CONCLUSION: Telomere-independent Rap1 is present in human athermanous lesions. Cytoplasmic Rap1 within macrophages may impact on inflammation during atherosclerosis.