Pharmacological profile of phosphatidylinositol 3-kinases and related phosphatidylinositols mediating endothelin(A) receptor-operated native TRPC channels in rabbit coronary artery myocytes

Br J Pharmacol. 2012 Aug;166(7):2161-75. doi: 10.1111/j.1476-5381.2012.01937.x.

Abstract

Background and purpose: Endothelin(A) (ET(A) ) receptor-operated canonical transient receptor potential (TRPC) channels mediate Ca²⁺ influx pathways, which are important in coronary artery function. Biochemical pathways linking ET(A) receptor stimulation to TRPC channel opening are unknown. We investigated the involvement of phosphatidylinositol 3-kinases (PI3K) in ET(A) receptor activation of native heteromeric TRPC1/C5/C6 and TRPC3/C7 channels in rabbit coronary artery vascular smooth muscle cells (VSMCs).

Experimental approach: A pharmacological profile of PI3K was created by studying the effect of pan-PI3K, pan-Class I PI3K and Class I PI3K isoform-selective inhibitors on ET(A) receptor-evoked single TRPC1/C5/C6 and TRPC3/C7 channel activities in cell-attached patches from rabbit freshly isolated coronary artery VSMCs. The action of phosphatidylinositol 3-phosphate- [PI(3)P], 4-phosphate- [PI(4)P] and 5-phosphate- [PI(5)P] containing molecules involved in PI3K-mediated reactions were studied in inside-out patches. Expression of PI3K family members in coronary artery tissue lysates were analysed using quantitative PCR.

Key results: ET(A) receptor-operated TRPC1/C5/C6 and TRPC3/C7 channel activities were inhibited by wortmannin. However, ZSTK474 and AS252424 reduced ET(A) receptor-evoked TRPC1/C5/C6 channel activity but potentiated TRPC3/C7 channel activity. All the PI(3)P-, PI(4)P- and PI(5)P-containing molecules tested induced TRPC1/C5/C6 channel activation, whereas only PI(3)P stimulated TRPC3/C7 channels.

Conclusions and implications: ET(A) receptor-operated native TRPC1/C5/C6 and TRPC3/C7 channel activities are likely to be mediated by Class I PI3Kγ and Class II/III PI3K isoforms, respectively. ET(A) receptor-evoked and constitutively active PI3Kγ-mediated pathways inhibit TRPC3/C7 channel activation. PI3K-mediated pathways are novel regulators of native TRPC channels in VSMCs, and these signalling cascades are potential pharmacological targets for coronary artery disease.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Coronary Vessels / physiology*
  • Enzyme Inhibitors / pharmacology
  • In Vitro Techniques
  • Myocytes, Cardiac / physiology
  • Phosphatidylinositol 3-Kinases / physiology*
  • Phosphatidylinositols / pharmacology
  • Phosphoinositide-3 Kinase Inhibitors
  • Rabbits
  • Receptor, Endothelin A / physiology*
  • Thiazolidinediones / pharmacology
  • Transient Receptor Potential Channels / physiology*
  • Triazines / pharmacology
  • Xanthenes / pharmacology

Substances

  • 5-(5-(4-fluoro-2-hydroxyphenyl)furan-2-ylmethylene)thiazolidine-2,4-dione
  • Enzyme Inhibitors
  • Phosphatidylinositols
  • Phosphoinositide-3 Kinase Inhibitors
  • Receptor, Endothelin A
  • Thiazolidinediones
  • Transient Receptor Potential Channels
  • Triazines
  • Xanthenes
  • ZSTK474
  • gallein