Activation of AMPK/proteasome/MLCK degradation signaling axis by telmisartan inhibits VSMC contractility and vessel contraction

https://doi.org/10.1016/j.bbrc.2020.02.007Get rights and content

Highlights

  • Telmisartan, but not losartan or fimasartan, increases p-AMPK-Thr172 in a PPARγ-independent manner.

  • Increased AMPK activity stimulates proteasomal MLCK degradation.

  • Reduced MLCK levels decrease p-MLC-Ser19, consequently inhibiting VSMC contractility.

  • Activation of AMPK/proteasome/MLCK degradation signaling axis by telmisartan leads to reduced vessel contraction.

Abstract

Telmisartan, an angiotensin II type 1 receptor blocker (ARB), is widely used to treat hypertension. Dysfunction of vascular smooth muscle cells (VSMCs) is well-established to contribute to the pathogenesis of various vascular diseases. A growing body of evidence indicates that increased VSMC contractility plays a primary role in the development of pathological artery spasms. Nevertheless, effect of telmisartan on VSMC contractility, and its mechanism of action remain unknown. Here, we investigated the mechanism by which telmisartan inhibits VSMC contractility and vessel contraction in rat VSMCs and endothelium-deprived aortas. Telmisartan inhibited phenylephrine-induced vessel contraction in endothelium-deprived aortas, and decreased myosin light chain kinase (MLCK) levels (without altering corresponding mRNA levels) and myosin light chain (MLC) phosphorylation at Ser19 (p-MLC-Ser19) in VSMCs. MG-132 but not doxycycline significantly restored telmisartan-inhibited MLCK expression and p-MLC-Ser19. Telmisartan induced AMP-activated protein kinase (AMPK) phosphorylation at Thr172 (p-AMPK-Thr172), and compound C or ectopic expression of the dominant negative (dn)-AMPKα1 gene significantly reversed telmisartan-inhibited MLCK expression and p-MLC-Ser19. Of the ARBs tested (including losartan and fimasartan), only telmisartan increased p-AMPK-Thr172, and inhibited MLCK expression and p-MLC-Ser19. GW9662 had no effects on telmisartan-induced changes. Similar to the in vitro results, telmisartan enhanced p-AMPK-Thr172, and inhibited MLCK expression and p-MLC-Ser19 in endothelium-deprived aortas. Furthermore, the telmisartan-inhibited vessel contraction in the aortas was significantly reversed by MG-132 or compound C. In conclusion, we demonstrated that telmisartan inhibits VSMC contractility and vessel contraction by activating AMPK/proteasome/MLCK degradation signaling axis. These results suggest that telmisartan can be used to treat pathological vasospasms.

Introduction

Telmisartan, an angiotensin II type 1 receptor blocker (ARB), known to dampen the body’s renin-angiotensin-aldosterone system, is widely used to treat hypertension. Apart from its blood pressure-lowering effect, telmisartan exhibits various organoprotective effects [1,2]. In addition, telmisartan is reported to act as a partial agonist for peroxisome proliferator-activated receptor γ (PPARγ), and shows its ancillary effects, including vascular protection through either PPARγ-dependent or -independent signaling pathways [3,4].

Vascular smooth muscle cells (VSMCs) comprise a large portion of blood vessels and play an essential role in the maintenance of normal vascular homeostasis [5,6]. Increased VSMC contractility and dysregulation of vasoconstrictor signaling pathway in VSMCs have been associated with the development of various vascular diseases such as hypertension, atherosclerosis, and vasospasms [7,8]. Furthermore, the central mechanism for pathological vasospasms has been recently revealed as VSMC hypercontraction, and not endothelial dysfunction, which leads to fatal vascular diseases and/or complications including coronary artery spasm and subarachnoid hemorrhage (SAH)-induced cerebral vasospasm [9,10].

Previously, acute treatment with telmisartan (at 30 μM for 30 min in the organ bath) is reported to attenuate vasoconstriction in response to phenylephrine (PE) [11], and endothelium-dependent nitric oxide (NO) and prostanoid productions are responsible for the acute inhibitory effect of telmisartan [11]. However, direct and long-term effect of telmisartan on VSMC contractility, and its mechanism of action remain unknown. In the present study, we investigated the mechanism by which telmisartan inhibits VSMC contractility and vessel contraction in rat VSMCs and endothelium-deprived aortas.

Section snippets

Materials

Telmisartan and losartan were purchased from Cayman Chemicals (Ann Arbor, MI, USA). Fimasartan was a kind gift from Boryung Pharmaceuticals (Seoul, Korea). D-glucose, GW9662, MG-132, doxycycline, PE, and dimethyl sulfoxide (DMSO) were obtained from Sigma-Aldrich (St. Louis, MO, USA). Compound C was purchased from Calbiochem (Darmstadt, Germany). Antibodies against myosin light chain kinase (MLCK) and β-actin were purchased from Sigma-Aldrich. MLC, p-MLC-Ser19, AMP-activated protein kinase

Telmisartan attenuates PE-induced vessel contraction by decreasing MLCK expression and p-MLC-Ser19 levels through proteasomal MLCK degradation in VSMCs

Although endothelium-dependent NO and prostanoid productions have been previously reported to mediate acute inhibitory effect of telmisartan (at 30 μM for 30 min in the organ bath) on vasoconstriction [11], direct and long-term effect of telmisartan on VSMC contractility and consequent vessel contraction remain unknown. To this end, we incubated the endothelium-deprived rat aortic rings in the absence or presence of 40 μM telmisartan for 24 h ex vivo, and then performed PE-induced aortic ring

Discussion

Abnormal or hyperactive VSMC contractility is associated with the development of various vascular diseases such as hypertension, atherosclerosis, and pathological vasospasms. In this regard, coronary artery spasm is well known to play important roles in the pathogenesis of a wide range of ischemic heart diseases, including angina pectoris, myocardial infarction, and sudden cardiac death [21]. Additionally, cerebral vasospasm after aneurysmal SAH is recognized as a serious complication with a

Declaration of competing interest

The authors declare that there are no conflicts of interest.

Acknowledgements

This work was supported by National Research Foundation (NRF) grants (2018R1D1A1B07050732) and the Medical Research Center Program (2015R1A5A2009124), funded by the Korean government.

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