Received for publication July 29, 2008.
Revised November 19, 2008.
Accepted for publication November 19, 2008.

Everolimus inhibits monocyte/macrophage migration in vitro and their accumulation in carotid lesions of cholesterol-fed rabbits

Abstract

Monocytes/macrophages recruited into the arterial wall during atherogenesis are crucial in the initiation and progression of atherosclerosis and play a fundamental role in the destabilization process that is the main causal event of acute coronary syndromes. In the present study, we investigated the effect of the mammalian target of rapamycin inhibitor everolimus on macrophage accumulation within carotid lesions elicited by perivascular collar placement in cholesterol-fed rabbits. Everolimus (1.5 mg/kg given 1 day before collaring followed by 1 mg/kg/day for 14 days, administered by oral gavage) markedly decreased lesion macrophage content as compared to vehicle control (-65%; p<0.01). This effect was associated with a reduction in intimal thickening and occurred in the absence of changes in plasma cholesterol concentrations. To gain insights on the potential mechanism(s) underlying this effect, we investigated the influence of everolimus on chemoattractant-induced migration of human monocytes in vitro. Pretreatment with therapeutic concentrations of everolimus (10 nM) significantly lowered monocyte chemotaxis in response to various chemotactic factors, (i.e., MCP-1/CCL2, fractalkine/CX3CL1, interleukin-8/CXCL8, the complement component C5a, or fMLP),without inducing monocyte cell death. These results suggest that everolimus may favorably influence the atherosclerotic process by affecting the recruitment of monocytes into early lesions.

Key words: atherosclerosis, chemotaxis, inflammation, intimal thickening, mTOR inhibitors, perivascular carotid collar model