AICAR promotes endothelium-independent vasorelaxation by activating AMP-activated protein kinase via increased ZMP and decreased ATP/ADP ratio in aortic smooth muscle

Rajkumar Pyla; Thomas J. Hartney; Lakshman Segar

doi:10.1515/jbcpp-2021-0308

Article

AICAR promotes endothelium-independent vasorelaxation by activating AMP-activated protein kinase via increased ZMP and decreased ATP/ADP ratio in aortic smooth muscle

Rajkumar Pyla , Thomas J. Hartney and Lakshman Segar

Published/Copyright: May 4, 2022

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From the journal Journal of Basic and Clinical Physiology and Pharmacology Volume 33 Issue 6

Abstract

Objectives

AICAR, an adenosine analog, has been shown to exhibit vascular protective effects through activation of AMP-activated protein kinase (AMPK). However, it remains unclear as to whether adenosine kinase-mediated ZMP formation or adenosine receptor activation contributes to AICAR-mediated AMPK activation and/or vasorelaxant response in vascular smooth muscle.

Methods and Results

In the present study using endothelium-denuded rat aortic ring preparations, isometric tension measurements revealed that exposure to 1 mM AICAR for 30 min resulted in inhibition of phenylephrine (1 μM)-induced smooth muscle contractility by ∼35%. Importantly, this vasorelaxant response by AICAR was prevented after pretreatment of aortic rings with an AMPK inhibitor (compound C, 40 µM) and adenosine kinase inhibitor (5-iodotubercidin, 1 µM), but not with an adenosine receptor blocker (8-sulfophenyltheophylline, 100 µM). Immunoblot analysis of respective aortic tissues showed that AMPK activation seen during vasorelaxant response by AICAR was abolished by compound C and 5-iodotubercidin, but not by 8-sulfophenyltheophylline, suggesting ZMP involvement in AMPK activation. Furthermore, LC–MS/MS MRM analysis revealed that exposure of aortic smooth muscle cells to 1 mM AICAR for 30 min enhanced ZMP level to 2014.9 ± 179.4 picomoles/mg protein (vs. control value of 8.5 ± 0.6; p<0.01), which was accompanied by a significant decrease in ATP/ADP ratio (1.08 ± 0.02 vs. 2.08 ± 0.06; p<0.01).

Conclusions

Together, the present findings demonstrate that AICAR-mediated ZMP elevation and the resultant AMPK activation in vascular smooth muscle contribute to vasorelaxation.

Keywords: AICAR; AMPK; vascular smooth muscle; vasorelaxation; ZMP

Corresponding author: Lakshman Segar, PhD, Charlie Norwood VA Medical Center, Department of Pharmacology and Toxicology, Augusta University, Augusta, Georgia, USA 30912-2691; Center for Pharmacy and Experimental Therapeutics, University of Georgia College of Pharmacy, Augusta, Georgia, USA; Vascular Biology Center, Department of Pharmacology and Toxicology, Augusta University, Augusta, Georgia, USA; Department of Medicine, Pennsylvania State University College of Medicine, Hershey, Pennsylvania, USA, Phone: +1 706 733 0188 ext. 2498, Fax: +1 706-823-2268, E-mail: lsegar@augusta.edu

Funding source: National Heart, Lung, and Blood Institute

Award Identifier / Grant number: R01-HL-097090

Funding source: National Institutes of Health

Award Identifier / Grant number: Unassigned

Funding source: U.S. Department of Veterans Affairs

Award Identifier / Grant number: Unassigned

Acknowledgments

This work was supported by the National Heart, Lung, and Blood Institute/National Institutes of Health Grant (R01-HL-097090). This material is the result of work supported with resources and the use of facilities at the Charlie Norwood Veterans Affairs Medical Center, Augusta, Georgia, USA. The contents of this article do not represent the views of the U.S. Department of Veterans Affairs or the United States Government.

Research funding: This work was supported by the National Heart, Lung, and Blood Institute/National Institutes of Health Grant (R01-HL-097090).
Author contribution: All authors have accepted responsibility for the entire content of this manuscript and approved its submission.
Competing interests: Authors state no conflict of interest.
Informed consent: Not applicable.
Ethical approval: All animal experiments were performed in accordance with the Charlie Norwood Veterans Affairs Medical Center Institutional Animal Care and Use Committee guidelines and were approved by the committee.

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Received: 2021-10-14

Accepted: 2022-04-05

Published Online: 2022-05-04

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Articles in the same Issue

https://doi.org/10.1515/jbcpp-2021-0308

Keywords for this article

AICAR; AMPK; vascular smooth muscle; vasorelaxation; ZMP