Genetic Ace2 deficiency accentuates vascular inflammation and atherosclerosis in the ApoE knockout mouse

Merlin C Thomas, Raelene J Pickering, Despina Tsorotes, Audrey Koitka, Karen Sheehy, Stella Bernardi, Barbara Toffoli, Thu-Phuc Nguyen-Huu, Geoffrey A Head, Yi Fu, Jaye Chin-Dusting, Mark E Cooper, Chris Tikellis
Circulation Research 2010 October 1, 107 (7): 888-97

RATIONALE: Angiotensin-converting enzyme (ACE)2 opposes the actions of angiotensin (Ang) II by degrading it to Ang 1-7.

OBJECTIVE: Given the important role of Ang II/Ang 1-7 in atherogenesis, we investigated the impact of ACE2 deficiency on the development of atherosclerosis.

METHODS AND RESULTS: C57Bl6, Ace2 knockout (KO), apolipoprotein E (ApoE) KO and ApoE/Ace2 double KO mice were followed until 30 weeks of age. Plaque accumulation was increased in ApoE/Ace2 double KO mice when compared to ApoE KO mice. This was associated with increased expression of adhesion molecules and inflammatory cytokines, including interleukin-6, monocyte chemoattractant protein-1, and vascular cell adhesion molecule-1, and an early increase in white cell adhesion across the whole aortae on dynamic flow assay. In the absence of a proatherosclerotic (ApoE KO) genotype, ACE2 deficiency was also associated with increased expression of these markers, suggesting that these differences were not an epiphenomenon. ACE inhibition prevented increases of these markers and atherogenesis in ApoE/ACE2 double KO mice. Bone marrow macrophages isolated from Ace2 KO mice showed increased proinflammatory responsiveness to lipopolysaccharide and Ang II when compared to macrophages isolated from C57Bl6 mice. Endothelial cells isolated from Ace2 KO mice also showed increased basal activation and elevated inflammatory responsiveness to TNF-α. Similarly, selective inhibition of ACE2 with MLN-4760 also resulted in a proinflammatory phenotype with a physiological response similar to that observed with exogenous Ang II (10(-7) mol/L).

CONCLUSIONS: Genetic Ace2 deficiency is associated with upregulation of putative mediators of atherogenesis and enhances responsiveness to proinflammatory stimuli. In atherosclerosis-prone ApoE KO mice, these changes potentially contribute to increased plaque accumulation. These findings emphasize the potential utility of ACE2 repletion as a strategy to reduce atherosclerosis.

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