Apelin signaling antagonizes Ang II effects in mouse models of atherosclerosis
Hyung J. Chun, Ziad A. Ali, Yoko Kojima, Ramendra K. Kundu, Ahmad Y. Sheikh, Rani Agrawal, Lixin Zheng, Nicholas J. Leeper, Nathan E. Pearl, Andrew J. Patterson, Joshua P. Anderson, Philip S. Tsao, Michael J. Lenardo, Euan A. Ashley, Thomas Quertermous
Hyung J. Chun, Ziad A. Ali, Yoko Kojima, Ramendra K. Kundu, Ahmad Y. Sheikh, Rani Agrawal, Lixin Zheng, Nicholas J. Leeper, Nathan E. Pearl, Andrew J. Patterson, Joshua P. Anderson, Philip S. Tsao, Michael J. Lenardo, Euan A. Ashley, Thomas Quertermous
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Research Article Cardiology

Apelin signaling antagonizes Ang II effects in mouse models of atherosclerosis

Abstract

Apelin and its cognate G protein–coupled receptor APJ constitute a signaling pathway with a positive inotropic effect on cardiac function and a vasodepressor function in the systemic circulation. The apelin-APJ pathway appears to have opposing physiological roles to the renin-angiotensin system. Here we investigated whether the apelin-APJ pathway can directly antagonize vascular disease-related Ang II actions. In ApoE-KO mice, exogenous Ang II induced atherosclerosis and abdominal aortic aneurysm formation; we found that coinfusion of apelin abrogated these effects. Similarly, apelin treatment rescued Ang II–mediated increases in neointimal formation and vascular remodeling in a vein graft model. NO has previously been implicated in the vasodepressor function of apelin; we found that apelin treatment increased NO bioavailability in ApoE-KO mice. Furthermore, infusion of an NO synthase inhibitor blocked the apelin-mediated decrease in atherosclerosis and aneurysm formation. In rat primary aortic smooth muscle cells, apelin inhibited Ang II–mediated transcriptional regulation of multiple targets as measured by reporter assays. In addition, we demonstrated by coimmunoprecipitation and fluorescence resonance energy transfer analysis that the Ang II and apelin receptors interacted physically. Taken together, these findings indicate that apelin signaling can block Ang II actions in vascular disease by increasing NO production and inhibiting Ang II cellular signaling.

Authors

Hyung J. Chun, Ziad A. Ali, Yoko Kojima, Ramendra K. Kundu, Ahmad Y. Sheikh, Rani Agrawal, Lixin Zheng, Nicholas J. Leeper, Nathan E. Pearl, Andrew J. Patterson, Joshua P. Anderson, Philip S. Tsao, Michael J. Lenardo, Euan A. Ashley, Thomas Quertermous

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Figure 6

AT1R and APJ receptors form heterodimer complexes.

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AT1R and APJ receptors form heterodimer complexes. (A) Immunoprecipitati...
(A) Immunoprecipitation using α-GFP antibody, followed by Western blot with α-HA antibody to detect APJ demonstrated a physical association between the 2 receptors. In the bottom panel control blot, the filled circle identifies AT1R-GFP and the triangle represents GFP. The band present in both lanes is the immunoprecipitating antibody detected by the secondary antibody. Numbers on the right reflect weights of protein standards in kDa. The lanes are from the same gel that were noncontiguous. (B) FRET analysis was performed with HEK293 cells cotransfected with APJ and AT1R expression constructs, with coding regions fused to either CFP or YFP. Specific interaction between APJ and AT1R is shown by increased FRET signal (blue curve) but not between either of these receptors and the Fas receptor (red curve). (C) Immunoprecipitation of AT1R-GFP and blotting of APJ-HA was employed to show increased association in the presence of Ang II at 1 hour and even greater association at 6 hours. Coadministration of apelin resulted in a modest increase in association compared with Ang II alone at 6 hours. A13, apelin-13. (D) FRET analysis showed an increase in AT1R and APJ association when cells were stimulated with Ang II. Addition of apelin led to a modest increase in FRET signal in cells treated with apelin alone compared with unstimulated cells and Ang II plus apelin–treated cells compared with cells treated with Ang II alone.