Masaki Kitahara (1), Kyomi Toyada (1), Toshie Yamashita (1), Mitsuaki Sakashita (1), Sakuya Tanaka (1) and Yasushi Saito (2)
(1) Shiraoka Research Station of Biological Science, Nissan Chemical Industries, Ltd., 1470 Shiraoka Minamisaitama, Saitama 349-02, Japan
(2) The Department of Laboratory Medicine, Yamagata University School of Medicine, 2-2-2 Iida-Nishi, Yamagata 990-230, Japan
Abstract: The effects of efonidipine hydrochloride (efonidipine), a dihydropyridine calcium antagonist, on the cholesterol ester metabolism induced by beta-migrating very low density lipoprotein (beta-VLDL) in J774 macrophages were studied. The cholesteryl ester content in the macrophages was increased by incubation with beta-VLDL, and the increase was inhibited by efonidipine. Oleic acid incorporation into cellular cholesteryl ester was increased by beta-VLDL in J774 macrophages. The incorporation at an early phase of beta-VLDL induction (0-3 hr) was inhibited by efonidipine. This inhibitory effect of efonidipine was greater at an early phase of beta-VLDL induction (0-3 hr) than at a late phase of the induction (8-11 hr). Pretreatment of the cells with efonidipine enhanced the inhibitory effect. Efonidipine also inhibited beta-VLDL degradation but not the binding and association in macrophages without pretreatment. beta-VLDL binding and association to macrophages were decreased by pretreatment of the cells with efonidipine. beta-VLDL metabolism was also decreased by dibutyryl cyclic AMP pretreatment. The decrease of beta-VLDL metabolism by efonidipine was prevented by co-treatment with efonidipine and HA1004, a protein kinase A inhibitor. Furthermore, efonidipine increased the intracellular cyclic AMP content in J774 macrophages. These findings suggest that efonidipine suppresses cholesterol ester deposition in atherosclerotic foam cells by inhibiting the modified lipoprotein metabolism and cholesterol esterification mainly through elevation of the cellular cyclic AMP level.
Keywords: Efonidipine, Macrophage, Cholesteryl ester, beta-Very low density lipoprotein, Cyclic AMP