Nonpeptidic antagonists of ETA and ETB receptors reverse the ET-1-induced sustained increase of cytosolic and nuclear calcium in human aortic vascular smooth muscle cells

Ghassan Bkaily, Sanaa Choufani, Levon Avedanian, Lena Ahmarani, Moni Nader, Danielle Jacques, Pedro D'Orléans-Juste, Johny Al Khoury

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17 Scopus citations

Abstract

Our previous work showed that ET-1 induced a concentration-dependent increase of cytosolic Ca2+ ([Ca]c) and nuclear Ca 2+ ([Ca]n) in human aortic vascular smooth muscle cells (hVSMCs). In the present study, using hVSMCs and 3-dimensional confocal microscopy coupled to the Ca2+ fluorescent probe Fluo-3, we showed that peptidic antagonists of ETA and ETB receptors (BQ-123 (10-6 mol/L) and BQ-788 (10-7 mol/L), respectively) prevented, but did not reverse, ET-1-induced sustained increase of [Ca] c and [Ca]n. In contrast, nonpeptidic antagonists of ETA and ETB (respectively, BMS-182874 (10 -8-10-6 mol/L) and A-192621 (10-7 mol/L)) both prevented and reversed ET-1-induced sustained increase of [Ca]c and [Ca]n. Furthermore, activation of the ETB receptor alone using the specific agonist IRL-1620 (10-9 mol/L) induced sustained increases of [Ca]c and [Ca]n, and subsequent administration of ET-1 (10-7 mol/L) further increased nuclear Ca 2+. ET-1-induced increase of [Ca]c and [Ca]n was completely blocked by extracellular application of the Ca2+ chelator EGTA. Pretreatment with the G protein inhibitors pertussis toxin (PTX) and cholera toxin (CTX) also prevented the ET-1 response; however, strong membrane depolarization with KCl (30 mmol/L) subsequently induced sustained increase of [Ca]c and [Ca]n. Pretreatment of hVSMCs with either the PKC activator phorbol-12,13-dibutyrate or the PKC inhibitor bisindolylmaleimide did not affect ET-1-induced sustained increase of intracellular Ca2+. These results suggest that both ETA- and ETB-receptor activation contribute to ET-1-induced sustained increase of [Ca]c and [Ca]n in hVSMCs. Moreover, in contrast to the peptidic antagonists of ET-1 receptors, the nonpeptidic ET A-receptor antagonist BMS-182874 and the nonpeptidic ET B-receptor antagonist A-192621 were able to reverse the effect of ET-1. Nonpeptidic ETA- and ETB-receptor antagonists may therefore be better pharmacological tools for blocking ET-1-induced sustained increase of intracellular Ca2+ in hVSMCs. Our results also suggest that the ET-1-induced sustained increase of [Ca]c and [Ca] n is not mediated via activation of PKC, but via a PTX- and CTX-sensitive G protein calcium influx through the R-type Ca2+ channel.

Original languageBritish English
Pages (from-to)546-556
Number of pages11
JournalCanadian Journal of Physiology and Pharmacology
Volume86
Issue number8
DOIs
StatePublished - Aug 2008

Keywords

  • A-192621
  • BMS-182874
  • BQ-123
  • BQ-788
  • ET-1, ET receptor
  • ET receptor
  • Human vascular smooth muscle
  • Nuclear calcium
  • R-type calcium channel

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