Abstract
1. We investigated the profound involvement of mast cell chymase, an alternative angiotensin II-generating enzyme, in angiogenesis using a specific chymase inhibitor. We also studied the functional profiles of this novel inhibitor in basic fibroblast growth factor (bFGF)-induced angiogenesis. 2. In this study, angiogenesis was induced by daily injections of bFGF (0.3 micro g site(-1) day(-1)), angiotensin I (2 nmol site(-1) day(-1)) or angiotensin II (2 nmol site(-1) day(-1)) into sponges implanted to male hamsters subcutaneously for 7 days. Angiogenesis in the granulation tissue surrounding sponges was evaluated by measuring the haemoglobin (Hb) content and local blood flow as the parameters for angiogenesis. 3. A chymase inhibitor, BCEAB (4-[1-[[bis-(4-methyl-phenyl)-methyl]-carbamoyl]-3-(2-ethoxy-benzyl)-4-oxo-azetidine-2-yloxy]-benzoic acid), was simultaneously administered into the implanted sponges (2 or 5 nmol site(-1) day(-1), for 7 days) treated with bFGF and strongly suppressed the haemoglobin contents in sponge granulomas. In the studies using a laser doppler perfusion imager, BCEAB (5 nmol site(-1) day(-1)) also attenuated the bFGF-induced increase of local blood flow around the implanted sponge granuloma. 4. In bFGF-induced angiogenesis, chymase activity in sponge granulomas was substantially increased. It was also confirmed that the chymase activity increased by bFGF was significantly and dose-dependently inhibited by BCEAB (2, 5 nmol site(-1) day(-1)). 5. BCEAB inhibited the Hb contents and the expression of vascular endothelial growth factor (VEGF) mRNA induced by angiotensin I but not by angiotensin II. 6. These results suggest that the significance of chymase in bFGF-induced angiogenesis was confirmed, and a novel inhibitor, BCEAB, strongly suppresses the bFGF-induced angiogenesis through the chymase-angiotensin II-VEGF dependent pathway.