Hypertension Does Not Account for the Accelerated Atherosclerosis and Development of Aneurysms in Male Apolipoprotein E/Endothelial Nitric Oxide Synthase Double Knockout Mice

Abstract

Background Apolipoprotein E (apoE)/endothelial nitric oxide synthase (eNOS) double knockout (DKO) mice demonstrate accelerated atherosclerosis and develop abdominal aortic aneurysms and aortic dissection, suggesting a role for eNOS in suppressing atherogenesis. To test whether accelerated atherosclerosis and aortic aneurysms were due to hypertension, we administered hydralazine to male apoE/eNOS DKO mice to reduce blood pressure. Methods and Results Male apoE/eNOS DKO mice were treated with hydralazine in their drinking water (250 mg/L) using a dose that lowers the blood pressure to levels seen in apoE KO mice. The mice were fed a Western-type diet for 16 weeks, and lesion formation was assessed by inspection of the vessel and staining with Sudan IV. Hydralazine-treated, normotensive male apoE/eNOS DKO mice developed increased aortic lesion areas (30.0±2.8%, n=11) compared with male apoE KO mice (14.6±0.8%, n=7). The extent of lesion formation was not significantly different from male apoE/eNOS DKO mice that were not given hydralazine (28.3±3.1%, n=9). Four of 11 hydralazine-treated male apoE/eNOS DKO mice developed abdominal aortic aneurysms. Conclusions Hypertension is not required for the accelerated atherosclerosis seen in apoE/eNOS DKO animals, and control of hypertension during a 16-week period does not prevent aortic aneurysm formation.