title: Activation of KCa3.1 by SKA-31 induces arteriolar dilatation and lowers blood pressure in normo- and hypertensive connexin40-deficient mice.
abstract: OBJECTIVE
  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.
  
  
  METHODS
  We performed intravital microscopy in the cremaster muscle microcirculation and blood pressure telemetry in Cx40-deficient mice.
  
  
  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
  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.
authors.affiliation: Institut für Physiologie, Universität zu Lübeck, Lübeck, Germany; DZHK (German Centre for Cardiovascular Research), partner site Hamburg/Kiel/Lübeck, Lübeck, Germany.
authors.forename: Josephine
authors.initials: J
authors.lastname: Radtke
authors.forename: Kjestine
authors.initials: K
authors.lastname: Schmidt
authors.forename: Heike
authors.initials: H
authors.lastname: Wulff
authors.forename: Ralf
authors.initials: R
authors.lastname: Köhler
authors.forename: Cor
authors.initials: C
authors.lastname: de Wit
mesh_terms: D000818:Animals; D052160:Benzothiazoles / Q000008:administration & dosage / Q000494:pharmacology*; D001794:Blood Pressure / Q000187:drug effects; D017630:Connexins / Q000235:genetics*; D004305:Dose-Response Relationship, Drug; D042783:Endothelial Cells / Q000187:drug effects; D004730:Endothelium, Vascular / Q000187:drug effects; D017629:Gap Junctions / Q000187:drug effects / Q000378:metabolism; D005838:Genotype; D006339:Heart Rate / Q000187:drug effects; D006973:Hypertension / Q000188:drug therapy* / Q000503:physiopathology; D051660:Intermediate-Conductance Calcium-Activated Potassium Channels / Q000187:drug effects* / Q000378:metabolism; D051379:Mice; D018345:Mice, Knockout; D008833:Microcirculation / Q000187:drug effects; D011720:Pyrazoles / Q000494:pharmacology; D013686:Telemetry; D014664:Vasodilation / Q000187:drug effects; D000097003:Gap Junction alpha-5 Protein
chemical_list: D052160:Benzothiazoles; D017630:Connexins; D051660:Intermediate-Conductance Calcium-Activated Potassium Channels; D011720:Pyrazoles; D000097003:Gap Junction alpha-5 Protein; C496925:Kcnn4 protein, mouse; C411671:TRAM 34; C535212:naphtho(1,2-d)thiazol-2-ylamine
keywords: 2-d]thiazol-2-ylamine); Ca2+-activated K+ channel; SKA-31 (naphtho[1; endothelium-derived hyperpolarizing factor; gap junction; hypertension; microcirculation; myoendothelial coupling