DEXAMETHASONE-INDUCED SUPPRESSION OF AORTIC ATHEROSCLEROSIS IN CHOLESTEROL-FED RABBITS - POSSIBLE MECHANISMS

We investigated the mechanisms by which corticosteroids affect atheros clerosis. Male New Zealand White rabbits were injected with 0.125 mg d examethasone (n = 10) or vehicle (control group, n = 10). Both groups were fed a 1% cholesterol diet for 8 weeks. Although the dexamethasone -treated animals exhibited a greater degree of hyperlipidemia, they ex hibited significantly less atherosclerotic plaque of the aortic surfac e than control animals (7.8% versus 47.2%). Immunofluorescence study o f the aortic plaque specimens showed that dexamethasone administration reduced both macrophages and T lymphocytes. In vitro, dexamethasone s uppressed the proliferation and differentiation of U937 cells and inhi bited uptake and degradation of beta-very low density lipoproteins by mouse peritoneal macrophages. These findings suggest that dexamethason e suppresses the development of atherosclerosis in the aorta of rabbit s by inhibiting recruitment and proliferation of macrophages and the f ormation of foam cells in plaques.