Immunomodulatory effects of statins: mechanisms and potential impact on arteriosclerosis

Clinical trials with statins have demonstrated a marked reduction of cardiovascular mortality. However, it remains controversial whether these clinical benefits stem from powerful cholesterol-lowering effects of statins or whether they are due in part to their cholesterol-independent effects on vascular function, plaque growth, plaque rupture, or thrombosis. The identification of several mechanisms through which statins decrease the recruitment of monocytes and T cells into the arterial wall and inhibit T cell activation and proliferation in vitro have prompted speculations that immunomodulatory effects of statins may be beneficial in recipients of organ transplants. Hypercholesterolemia is frequent in these patients, and delayed-type hypersensitivity reactions in the arterial walls of the graft may be compounded by chronic inflammation associated with conventional atherogenesis. To assess the potential clinical relevance of immunomodulatory effects of statins, the role of the immune system in atherogenesis and the effects of statins in vitro in experimental models and in clinical trials will be reviewed. It is concluded that despite solid in vitro evidence, clinical evidence for an independent immunosuppressive effect of statins in organ transplant patients is presently insufficient; however, further investigation of their in vivo occurrence and clinical relevance is warranted.