Activation of KCa3.1 by SKA-31 induces arteriolar dilatation and lowers blood pressure in normo- and hypertensive connexin40-deficient mice

Br J Pharmacol. 2013 Sep;170(2):293-303. doi: 10.1111/bph.12267.

Abstract

Background and purpose: The calcium-activated potassium channel KCa3.1 is expressed in the vascular endothelium where its activation causes endothelial hyperpolarization and initiates endothelium-derived hyperpolarization (EDH)-dependent dilatation. Here, we investigated whether pharmacological activation of KCa3.1 dilates skeletal muscle arterioles and whether myoendothelial gap junctions formed by connexin40 (Cx40) are required for EDH-type dilatations and pressure depressor responses in vivo.

Experimental approach: We performed intravital microscopy in the cremaster muscle microcirculation and blood pressure telemetry in Cx40-deficient mice.

Key results: In wild-type mice, the KCa3.1-activator SKA-31 induced pronounced concentration-dependent arteriolar EDH-type dilatations, amounting to ∼40% of maximal dilatation, and enhanced the effects of ACh. These responses were absent in mice devoid of KCa3.1 channels. In contrast, SKA-31-induced dilatations were not attenuated in mice with endothelial cells deficient in Cx40 (Cx40(fl/fl):Tie2-Cre). In isolated endothelial cell clusters, SKA-31 induced hyperpolarizations of similar magnitudes (by ∼38 mV) in Cx40(fl/fl):Tie2-Cre, ubiquitous Cx40-deficient mice (Cx40(-/-)) and controls (Cx40(fl/fl)), which were reversed by the specific KCa3.1-blocker TRAM-34. In normotensive wild-type and Cx40(fl/fl):Tie2-Cre as well as in hypertensive Cx40(-/-) animals, i.p. injections of SKA-31 (30 and 100 mg·kg(-1)) decreased arterial pressure by ∼32 mmHg in all genotypes. The depressor response to 100 mg·kg(-1) SKA-31 was associated with a decrease in heart rate.

Conclusions and implications: We conclude that endothelial hyperpolarization evoked by pharmacological activation of KCa3.1 channels induces EDH-type arteriolar dilatations that are independent of endothelial Cx40 and Cx40-containing myoendothelial gap junctions. As SKA-31 reduced blood pressure in hypertensive Cx40-deficient mice, KCa3.1 activators may be useful drugs for severe treatment-resistant hypertension.

Keywords: 2-d]thiazol-2-ylamine); Ca2+-activated K+ channel; SKA-31 (naphtho[1; endothelium-derived hyperpolarizing factor; gap junction; hypertension; microcirculation; myoendothelial coupling.

Publication types

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

MeSH terms

  • Animals
  • Benzothiazoles / administration & dosage
  • Benzothiazoles / pharmacology*
  • Blood Pressure / drug effects
  • Connexins / genetics*
  • Dose-Response Relationship, Drug
  • Endothelial Cells / drug effects
  • Endothelium, Vascular / drug effects
  • Gap Junctions / drug effects
  • Gap Junctions / metabolism
  • Genotype
  • Heart Rate / drug effects
  • Hypertension / drug therapy*
  • Hypertension / physiopathology
  • Intermediate-Conductance Calcium-Activated Potassium Channels / drug effects*
  • Intermediate-Conductance Calcium-Activated Potassium Channels / metabolism
  • Mice
  • Mice, Knockout
  • Microcirculation / drug effects
  • Pyrazoles / pharmacology
  • Telemetry
  • Vasodilation / drug effects

Substances

  • Benzothiazoles
  • Connexins
  • Intermediate-Conductance Calcium-Activated Potassium Channels
  • Kcnn4 protein, mouse
  • Pyrazoles
  • TRAM 34
  • connexin 40
  • naphtho(1,2-d)thiazol-2-ylamine