Accelerated Atherosclerosis, Aortic Aneurysm Formation, and Ischemic Heart Disease in Apolipoprotein E/Endothelial Nitric Oxide Synthase Double-Knockout Mice

Abstract

Background-To test whether deficiency in endothelial nitric oxide synthase (eNOS) affects atherosclerosis development, we compared lesion formation in apolipoprotein E (apoE)/eNOS-double knockout (DKO) and apoE-knockout (KO) control animals. Methods and Results-After 16 weeks of "Western-type" diet, apoE/eNOS-DKO males and females showed significant increases in lesion area of 93.6% and 59.2% compared with apoE-KO mice. All apoE/eNOS-DKO animals studied developed peripheral coronary arteriosclerosis, associated with perivascular and myocardial fibrosis, whereas none of the apoE-KO mice did. Transthoracic echocardiography showed a significantly increased left ventricular wall thickness and decreased fractional shortening in DKO animals. Mean arterial pressure was increased in DKO mice and was comparable in degree to eNOS-KO animals. Male DKO animals developed atherosclerotic abdominal aneurysms and aortic dissection. Conclusions-eNOS deficiency increases atherosclerosis in Western-type diet-fed apoE-KO animals and introduces coronary disease and an array of cardiovascular complications, including spontaneous aortic aneurysm and dissection. This phenotype constitutes the first murine model to demonstrate distal coronary arteriosclerosis associated with evidence of myocardial ischemia, infarction, and heart failure. Hypertrophy and reduced left ventricular function cannot be explained by increased blood pressure alone, because eNOS-KO animals do not develop these complications.

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

“…Mice eNOS KO mice, 3 apoE KO mice 1 (Jackson Laboratories, Bar Harbor, Maine), and apoE/eNOS DKO mice 5 were all on a C57BL/6 genetic background. Mice were fed a Western-type diet (42% of total calories from fat; 0.15% cholesterol; Harlan-Teklad) for 16 weeks.…”

“…In untreated apoE/eNOS DKO mice after 16 weeks of a Western-type diet, 5 of 12 male mice developed aortic aneurysms; 2 additional mice had aortic dissection. 5 …”

“…5 These complications have not been observed in apoE KO mice. 1,2 Because eNOS deficiency is associated with hypertension, both by itself 3 and in the presence 5 of apoE deficiency, it is possible that hypertension contributes to the increased extent of atherosclerotic lesions and the development of aortic aneurysms. To test this hypothesis, we treated male apoE/ eNOS DKO mice with hydralazine at a dose that lowers the blood pressure down to the levels seen in apoE KO mice.…”

“…5,6 We previously found that apoE/eNOS double knockout (DKO) mice develop increased aortic lesions after 16 weeks of a Westerntype diet; these lesions are also associated with distal coronary artery disease and left ventricular dysfunction. Furthermore, male apoE/eNOS DKO mice developed abdominal aortic aneurysm and aortic dissection.…”

Ambulatory blood pressure, left ventricular mass and vascular phenotypes in relation to the endothelial nitric oxide synthase gene Glu298Asp and intron 4 polymorphisms in a population-based family study

“…1 Mice lacking eNOS gene have higher blood pressure, insulin resistance, hyperlipidaemia 2 and advanced atherosclerosis. 3 The significant role of NO in the regulation of basal and inducible vasorelaxation suggests that abnormal eNOS activity caused by eNOS mutation may be associated with a number of pathologies such as arterial hypertension or atherosclerosis. 4 Furthermore, it has been shown that NO release and synthesis are decreased in patients with atherosclerosis.…”