OxLDL upregulates caveolin‐1 expression in macrophages: Role for caveolin‐1 in the adhesion of oxLDL‐treated macrophages to endothelium

Abstract

Caveolin-1, a principle component of caveolae, is present in several cell types known to play an important role in the development of atherosclerosis. In this study, its distribution and expression were studied in the arterial walls of hypercholesterolemic rabbits and apo-E-deficient mice and in oxidized low-density lipoprotein (oxLDL)-treated RAW264.7 macrophages. Immunohistochemical studies showed that staining for caveolin-1 expression was stronger in atherosclerotic lesions in hypercholesterolemic rabbits and apo-E-deficient mice compared to normal rabbits and mice and was closely associated with macrophages. OxLDL treatment increased caveolin-1 protein expression in RAW264.7 macrophages in a time- and dose-dependent manner. The increase in caveolin-1 expression was dependent on phosphorylation of the mitogen-activated protein kinases (MAPKs) extracellular signal-regulated kinase1/2 (ERK1/2), p38, and Jun N-terminal kinase (JNK) and the transcriptional activation and translocation of nuclear factor-?B (NF-kappaB). OxLDL also induced caveolin-1 mRNA expression and this effect was not seen in the presence of inhibitors for transcription or de novo protein synthesis. OxLDL increased the adhesion of RAW264.7 macrophages to endothelial cells via an increase in caveolin-1 expression, and the adhesion was reduced by the use of anti-caveolin-1 antibody or caveolin-1-specific shRNA. These results show that oxLDL increases caveolin-1 expression in macrophages through the MAPKs/NF-kappaB pathway. The caveolin-1 levels are closely associated with the adherence of monocytes/macrophages to endothelial cells and their accumulation within the arterial intima after hypercholesterolemia insult, resulting in the progression of atherosclerosis.