Arachidonate-regulated Ca2+ influx in human airway smooth muscle

Michael A. Thompson, Y. S. Prakash, Christina M. Pabelick

Research output: Contribution to journalArticle

11 Scopus citations

Abstract

Plasma membrane Ca2+ influx, especially store-operated Ca 2+ entry triggered by sarcoplasmic reticulum (SR) Ca2+ release, is a key component of intracellular calcium concentration ([Ca 2+]i) regulation in airway smooth muscle (ASM). Agonist-induced Ca2+ oscillations in ASM that involve both influx and SR mechanisms have been previously demonstrated. In nonexcitable cells, [Ca2+]i oscillations involve Ca2+ influx via arachidonic acid (AA) -stimulated channels, which show similarities to store-operated Ca2+ entry, although their molecular identity remains undetermined. Little is known about AA-regulated Ca2+ channels or their regulation in ASM. In enzymatically dissociated human ASM cells loaded with the Ca2+ indicator, fura-2, AA (1-10 μM) triggered [Ca 2+]i oscillations that were inhibited by removal of extracellular Ca2+. Other fatty acids, such as the diacylglycerol analog, 1-oleoyl-2-acetyl-SN-glycerol, oleic acid, and palmitic acid (10 μM each), failed to elicit similar [Ca2+]i responses. Preincubation with LaCl3 (1 μM or 1 mM) inhibited AA-induced oscillations. Inhibition of receptor-operated channels (SKF96,365 [10 μM]), lipoxygenase (zileuton [10 μM]), or cyclooxygenase (indomethacin [10 μM]) did not affect oscillation parameters. Inhibition of SR Ca2+ release (ryanodine [10 μM] or inositol 1,4,5-trisphosphate receptor inhibitor, xestospongin C [1 μM]) decreased [Ca2+]i oscillation frequency and amplitude. Small interfering RNA against caveolin-1, stromal interaction molecule 1, or Orai3 (20 nM each) reduced the frequency and amplitude of AA-induced [Ca2+]i oscillations. In ASM cells derived from individuals with asthma, AA increased oscillation amplitude, but not frequency. These results are highly suggestive of a novel AA-mediated Ca2+-regulatory mechanism in human ASM, reminiscent of agonist-induced oscillations. Given the role of AA in ASM intracellular signaling, especially with inflammation, AA-regulated Ca2+ channels could potentially contribute to increased [Ca2+]i in diseases such asthma.

Original languageEnglish (US)
Pages (from-to)68-76
Number of pages9
JournalAmerican journal of respiratory cell and molecular biology
Volume51
Issue number1
DOIs
StatePublished - Jul 2014

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Keywords

  • Arachidonic acid
  • Bronchial smooth muscle
  • Calcium
  • Influx
  • Sarcoplasmic reticulum

ASJC Scopus subject areas

  • Molecular Biology
  • Pulmonary and Respiratory Medicine
  • Clinical Biochemistry
  • Cell Biology

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