Abstract 1682: Genetic Deletion of Angiotensin-converting Enzyme 2 Develops More Atherosclerosis in Apolipoprotein E-deficient Mice through Local Accumulation of Angiotensin II and Inflammatory Responses by Activating the JNK Pathway
Angiotensin-converting enzyme 2 (ACE2) cleaves angiotensin II (Ang-II) and functions as a negative regulator of the renin-angiotensin system, although its role and mechanism of action on atherogenesis remain undetermined. Male apolipoprotein E-deficient (ApoE−/−) mice simultaneously lacking ACE2 (ApoE−/−-ACE2−/y mice) were fed a Western-type diet for 3 months. ApoE−/−-ACE2−/y mice developed more atherosclerosis in thoracic aorta than do ApoE−/− mice. Percent plaque area in the luminal surface were 11.2 ± 2.2% in ApoE−/− mice and 19.4 ± 4.8% in ApoE−/−-ACE2−/y mice (p < 0.05). Histologically, accumulation of macrophages in aortic root’s plaque was augmented more significantly in ApoE−/−-ACE2−/y mice. Western blotting revealed that ACE2 protein is mildly but evidently expressed in vascular cells of aortic wall in ApoE−/− mice, although not observed in ApoE−/−-ACE2−/y mice. This might account for the finding that the concentration of Ang-II in aortic tissue was higher in ApoE−/−-ACE2−/y mice than in ApoE−/− mice (p < 0.05). In addition, in aortic tissue, mRNA expression of several inflammatory molecules such as MCP-1, TNFα, MMP9, and VCAM-1 was increased in ApoE−/−-ACE2−/y mice than in ApoE−/− mice. Similarly, in cultured THP-1 (human monocytic) cells stimulated with TNFα, mRNA expression of MCP-1, IL-6, and MMP9 was all increased, whereas recombinant human ACE2 peptides attenuated the enhanced expression of these molecules. Next, we analyzed phosphorylation status of mitogen-activated protein kinases in aortic tissue. In ApoE−/− mice, ERK1/2 and JNK signaling pathways were both activated in aorta, compared with wild-type mice. Notably, ACE2 deletion induced the additional increase of JNK phosphorylation, not ERK1/2, in aorta of ApoE−/− mice. Intriguingly, an ARB olmesartan (1 mg/kg/day) attenuated the development of atherosclerosis and the increase of JNK phosphorylation in aorta in ApoE−/−-ACE2−/y mice without alteration of blood pressure level. ACE2 deletion induces local accumulation of Ang-II and the Ang-II-related inflammatory responses in aorta by activating the JNK pathway, resulting in severe development of atherosclerosis in ApoE−/− mice. Thus, ACE2 may confer atheroprotection.