PKA-dependent activation of the vascular smooth muscle isoform of KATP channels by vasoactive intestinal polypeptide and its effect on relaxation of the mesenteric resistance artery

Biochim Biophys Acta. 2008 Jan;1778(1):88-96. doi: 10.1016/j.bbamem.2007.08.030. Epub 2007 Sep 12.

Abstract

Vasoactive intestinal polypeptide (VIP) is a potent vasodilator and has been successfully used to alleviate hypertension. Consistently, disruption of VIP gene in mice leads to hypertension. However, its downstream targets in the vascular regulation are still not well demonstrated. To test the hypothesis that the vascular smooth muscle isoform of KATP channels is a downstream target of the VIP signaling, we performed the studies on the Kir6.1/SUR2B channel expressed in HEK293 cells. We found that the channel was strongly activated by VIP. Through endogenous VIP receptors, the channel activation was reversible and dependent on VIP concentrations with the midpoint-activation concentration approximately 10 nM. The channel activation was voltage-independent and could be blocked by KATP channel blocker glibenclamide. In cell-attached patches, VIP augmented the channel open-state probability with modest suppression of the single channel conductance. The VIP-induced Kir6.1/SUR2B channel activation was blocked by PKA inhibitor RP-cAMP. Forskolin, an adenylyl cyclase activator, activated the channel similarly as VIP. The effect of VIP was further evident in the native tissues. In acutely dissociated mesenteric vascular smooth myocytes, VIP activated the KATP currents in a similar manner as in HEK293 cells. In endothelium-free mesenteric artery rings, VIP produced concentration-dependent vasorelaxation that was attenuated by glibenclamide. These results therefore indicate that the vascular isoform (Kir6.1/SUR2B) of KATP channels is a target of VIP. The channel activation relies on the PKA pathway and produces mesenteric arterial relaxation.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • ATP-Binding Cassette Transporters / metabolism
  • Animals
  • Cell Line
  • Cyclic AMP-Dependent Protein Kinases / metabolism*
  • Humans
  • In Vitro Techniques
  • Ion Channel Gating / drug effects*
  • Isoenzymes / metabolism
  • KATP Channels / metabolism*
  • Male
  • Mesenteric Arteries / cytology
  • Mesenteric Arteries / drug effects
  • Mesenteric Arteries / enzymology*
  • Muscle, Smooth, Vascular / cytology
  • Muscle, Smooth, Vascular / drug effects
  • Muscle, Smooth, Vascular / enzymology*
  • Myocytes, Smooth Muscle / cytology
  • Myocytes, Smooth Muscle / drug effects
  • Myocytes, Smooth Muscle / enzymology
  • Potassium Channels / metabolism
  • Potassium Channels, Inwardly Rectifying / metabolism
  • Rats
  • Rats, Sprague-Dawley
  • Receptors, Drug / metabolism
  • Sulfonylurea Receptors
  • Vasoactive Intestinal Peptide / pharmacology*
  • Vasodilation / drug effects*

Substances

  • ATP-Binding Cassette Transporters
  • Abcc9 protein, mouse
  • Isoenzymes
  • KATP Channels
  • Potassium Channels
  • Potassium Channels, Inwardly Rectifying
  • Receptors, Drug
  • Sulfonylurea Receptors
  • uK-ATP-1 potassium channel
  • Vasoactive Intestinal Peptide
  • Cyclic AMP-Dependent Protein Kinases