Abstract 919: Suppression of Abdominal Aortic Aneurysms in the Angiotensin II-infused ApoE Deficient Mice by Treatment with Chymase Inhibitor
Chymase promotes not only angiotensin II production but also matrix metalloproteinase (MMP)-9 activation, which have a critical role on development of abdominal aortic aneurysms (AAAs). The purpose of this study is to examine the effects of chymase inhibitor, NK3201, on the MMP-9 activity and development of AAA in the angiotensin II-induced apolipoprotein E (apoE)-deficient mice. Method: Angiotensin II (1000ng/kg/min) (vehicle group) or saline (control group) were infused into 16-week-old male apoE-deficient mice for 4 weeks. To examine the effect of chymase inhibition for AAA, we administered NK3201 (30mg/kg/day) to angiotensin II-infused group (NK3201-treated group) for the same period. At the end of angiotensin II infusion, we measured the diameters of suprarenal and infrarenal aorta. AAA severities were scored using the suprarenal aortic diameter/infrarenal aortic diameter ratio and presence of thrombus formation, i.e. under 2.0 was 0, from 2.0 to 2.5 was 1, from 2.5 to 3.0 was 2, over 3.0 was 3, and presence of thrombus was 4. We also determined the chymase and MMP-9 activities using total aorta. Results: The scores that reflected the progression and severity of AAA were increased in vehicle group compared with control group ( 2.35±0.30 vs. 0.27±0.12, p<0.01). This progression was inhibited in NK3201-treated group compared with vehicle group (1.13±0.35, p<0.05 vs. vehicle group). Chymase activity was significantly increased in vehicle group compared with control group. MMP-9 activity was also increased in vehicle group, however it was decreased significantly in NK3201-treated group.Discussion: We demonstrated that chymase inhibition could reduce AAA progression through inhibition of MMP-9 in angiotensin II-induced apoE-deficient mice. Chymase inhibitor might be a novel strategy for preventing AAAs.