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Antagonism of Nav channels and α1-adrenergic receptors contributes to vascular smooth muscle effects of ranolazine.

ABSTRACT: Ranolazine is a recently developed drug used for the treatment of patients with chronic stable angina. It is a selective inhibitor of the persistent cardiac Na(+) current (INa), and is known to reduce the Na(+)-dependent Ca(2+) overload that occurs in cardiomyocytes during ischemia. Vascular effects of ranolazine, such as vasorelaxation,have been reported and may involve multiple pathways. As voltage-gated Na(+) channels (Nav) present in arteries play a role in contraction, we hypothesized that ranolazine could target these channels. We studied the effects of ranolazine in vitro on cultured aortic smooth muscle cells (SMC) and ex vivo on rat aortas in conditions known to specifically activate or promote INa. We observed that in the presence of the Nav channel agonist veratridine, ranolazine inhibited INa and intracellular Ca(2+) calcium increase in SMC, and arterial vasoconstriction. In arterial SMC, ranolazine inhibited the activity of tetrodotoxin-sensitive voltage-gated Nav channels and thus antagonized contraction promoted by low KCl depolarization. Furthermore, the vasorelaxant effects of ranolazine, also observed in human arteries and independent of the endothelium, involved antagonization of the α1-adrenergic receptor. Combined α1-adrenergic antagonization and inhibition of SMCs Nav channels could be involved in the vascular effects of ranolazine.

SUBMITTER: Virsolvy A

PROVIDER: S-EPMC4674695 | biostudies-other | 2015 Dec

REPOSITORIES: biostudies-other

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Project description:Recently, we provided evidence that α1-adrenergic receptors (ARs) in vascular smooth muscle are regulated by chemokine (C-X-C motif) receptor (CXCR) 4 and atypical chemokine receptor 3 (ACKR3). While we showed that CXCR4 controls α1-ARs through formation of heteromeric receptor complexes in human vascular smooth muscle cells (hVSMCs), the molecular basis underlying cross-talk between ACKR3 and α1-ARs is unknown. We show that ACKR3 agonists inhibit inositol trisphosphate production in hVSMCs on stimulation with phenylephrine. In proximity ligation assays and co-immunoprecipitation experiments, we observed that recombinant and endogenous ACKR3 form heteromeric complexes with α1A/B/D-AR. While small interfering RNA knockdown of ACKR3 in hVSMCs reduced α1B/D-AR:ACKR3, CXCR4:ACKR3, and α1B/D-AR:CXCR4 complexes, small interfering RNA knockdown of CXCR4 reduced α1B/D-AR:ACKR3 heteromers. Phenylephrine-induced inositol trisphosphate production from hVSMCs was abolished after ACKR3 and CXCR4 small interfering RNA knockdown. Peptide analogs of transmembrane domains 2/4/7 of ACKR3 showed differential effects on heteromerization between ACKR3, α1A/B/D-AR, and CXCR4. While the transmembrane domain 2 peptide interfered with α1B/D-AR:ACKR3 and CXCR4:ACKR3 heteromerization, it increased heteromerization between CXCR4 and α1A/B-AR. The transmembrane domain 2 peptide inhibited ACKR3 but did not affect α1b-AR in β-arrestin recruitment assays. Furthermore, the transmembrane domain 2 peptide inhibited phenylephrine-induced inositol trisphosphate production in hVSMCs and attenuated phenylephrine-induced constriction of mesenteric arteries. α1-ARs form hetero-oligomeric complexes with the ACKR3:CXCR4 heteromer, which is required for α1B/D-AR function, and activation of ACKR3 negatively regulates α1-ARs. G protein-coupled receptor hetero-oligomerization is a dynamic process, which depends on the relative abundance of available receptor partners. Endogenous α1-ARs function within a network of hetero-oligomeric receptor complexes.

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Antagonism of Nav channels and α1-adrenergic receptors contributes to vascular smooth muscle effects of ranolazine.

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