Urokinase receptor surface expression regulates monocyte migration and is associated with accelerated atherosclerosis.

Background: The urokinase receptor (uPAR) is a key regulator of pericellular proteolysis, cell adhesion and migration, all of which are fundamental processes in atherogenesis. We hypothesized that increased monocytic uPAR expression in circulation is associated with the formation and development of atherosclerosis.

Methods: A total of 42 male apoE-/- mice were ramdonly divided into high-fat (HF) diet and normal diet (n=21 per group). The percentage of uPAR expressing monocytes (PUEM) and the expression of uPAR within different types of atherosclerotic plaques were measured at an interval of 3 weeks from week 10 to week 16. In vitro, uPAR expression upon ox-LDL stimulation and the migration of monocytes were examined.

Results: PUEM in circulation was significantly higher in animals with HF diet compared with those having normal diet (p<0.03). The augmented levels of PUEM were associated with body weight, visceral fat weight and numbers of uPAR+macrophages within atherosclerotic lesions. Accumulation of uPAR+macrophages increased with the progression of atherosclerosis. Monocytes upon ox-LDL stimulation exhibited an increased uPAR expression and uPAR antibody markedly suppressed monocyte migration induced by monocyte chemotactic protein-1. uPAR modulated monocyte migration was accelerated by uPA and was suppressed by amino terminal fragment of uPA dependent.

Conclusions: Over-expression of uPAR both in circulating monocytes and in atherosclerotic lesions is associated with the development of atherosclerotic plaques. uPAR and its interaction with uPA may contribute to enhanced monocyte migration. Thus, uPAR may be a novel target for prevention of uncontrolled monocyte recruitment in inflammatory atherogenic process.