Chymase inhibition suppresses high-cholesterol diet-induced lipid accumulation in the hamster aorta

Objective: The role of chymase (a mast cell-derived angiotensin II-forming serine proteinase) in aortic lipid deposition was investigated using an orally active, non-peptide chymase inhibitor, SUN-C8257. Methods: Male golden Syrian hamsters, 8 weeks old, were fed with a standard rodent meal supplemented with or without 0.5% cholesterol and 10% coconut oil for 12 weeks. The hamsters fed high cholesterol diet were further separated into two groups treated with or without SUN-C8257 for 12 weeks. The aortic lipid deposition was visualized by Oil red 0 staining and planimetrically measured. Immunohistochemical staining for angiotensin 11 (Ana 11) of the aortic root region was performed. Aortic Ana II-forming activity was measured using Ana I as a substrate. Plasma total-, low-density lipoprotein (LDL)-, high-density lipoprotein (HDL)-cholesterol and triglyceride were quantified by enzymatic methods. Plasma Ana I and Ana 11 were measured by radioimmunoassay. Results: After 12 weeks of high cholesterol diet, aortic chymase activity in the untreated group increased significantly and showed a positive correlation with plasma total- and LDL-cholesterol. This group of hamsters developed marked lipid deposits in the aortic intima. However, treatment with SUN-C8257 significantly suppressed aortic lipid deposition without changing body weight, blood pressure, plasma LDL-cholesterol and Ang II levels. The level of the adventitial Ang II-immunoreactivity was markedly inhibited in the group treated with SUN-C8257. Conclusion: Our results suggest that arterial chymase may participate in the acceleration of lipid deposition in arterial walls exposed to high plasma cholesterol and that inhibition of arterial chymase may retard the progression of atherosclerosis. (C) 2002 Elsevier Science B.V. All rights reserved.