title: Involvement of transglutaminase 2 and voltage-gated potassium channels in cystamine vasodilatation in rat mesenteric small arteries.
abstract: OBJECTIVE
  Vasodilatation may contribute to the neuroprotective and vascular anti-remodelling effect of the tissue transglutaminase 2 (TG2) inhibitor cystamine. Here, we hypothesized that inhibition of TG2 followed by blockade of smooth muscle calcium entry and/or inhibition of Rho kinase underlies cystamine vasodilatation.
  
  
  METHODS
  We used rat mesenteric small arteries and RT-PCR, immunoblotting, and measurements of isometric wall tension, intracellular Ca(2+) ([Ca(2+)]i ), K(+) currents (patch clamp), and phosphorylation of myosin phosphatase targeting subunit 1 (MYPT1) and myosin regulatory light chain, in our experiments.
  
  
  RESULTS
  RT-PCR and immunoblotting revealed expression of TG2 in mesenteric small arteries. Cystamine concentration-dependently inhibited responses to phenylephrine, 5-HT and U46619 and for extracellular potassium. Selective inhibitors of TG2, LDN 27129 and T101, also inhibited phenylephrine contraction. An inhibitor of PLC suppressed cystamine relaxation. Cystamine relaxed and reduced [Ca(2+)]i in phenylephrine-contracted arteries. In potassium-contracted arteries, cystamine induced less relaxation without changing [Ca(2+)]i , and these relaxations were blocked by mitochondrial complex inhibitors. Blockers of Kv 7 channels, XE991 and linopirdine, inhibited cystamine relaxation and increases in voltage-dependent smooth muscle currents. Cystamine and the Rho kinase inhibitor Y27632 reduced basal MYPT1-Thr(855) phosphorylation, but only Y27632 reduced phenylephrine-induced increases in MYPT1-Thr(855) and myosin regulatory light chain phosphorylation.
  
  
  CONCLUSIONS
  Cystamine induced vasodilatation by inhibition of receptor-coupled TG2, leading to opening of Kv channels and reduction of intracellular calcium, and by activation of a pathway sensitive to inhibitors of the mitochondrial complexes I and III. Both pathways may contribute to the antihypertensive and neuroprotective effect of cystamine.
authors.affiliation: Department of Biomedicine, Pulmonary and Cardiovascular Pharmacology, Aarhus University, Denmark.
authors.forename: Morten
authors.initials: M
authors.lastname: Engholm
authors.affiliation: Department of Biomedicine, Pulmonary and Cardiovascular Pharmacology, Aarhus University, Denmark.
authors.forename: Estéfano
authors.initials: E
authors.lastname: Pinilla
authors.affiliation: Department of Biomedicine, Pulmonary and Cardiovascular Pharmacology, Aarhus University, Denmark.
authors.forename: Susie
authors.initials: S
authors.lastname: Mogensen
authors.affiliation: Department of Biomedicine, Pulmonary and Cardiovascular Pharmacology, Aarhus University, Denmark.
authors.forename: Vladimir
authors.initials: V
authors.lastname: Matchkov
authors.affiliation: Department of Biomedicine, Pulmonary and Cardiovascular Pharmacology, Aarhus University, Denmark.
authors.forename: Elise Røge
authors.initials: ER
authors.lastname: Hedegaard
authors.affiliation: Department of Biomedicine, Pulmonary and Cardiovascular Pharmacology, Aarhus University, Denmark.
authors.forename: Hua
authors.initials: H
authors.lastname: Chen
authors.affiliation: Department of Biomedicine, Pulmonary and Cardiovascular Pharmacology, Aarhus University, Denmark.
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Mulvany
authors.affiliation: Department of Biomedicine, Pulmonary and Cardiovascular Pharmacology, Aarhus University, Denmark.
authors.forename: Ulf
authors.initials: U
authors.lastname: Simonsen
mesh_terms: D000818:Animals; D000968:Antimycin A / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism; D003538:Cystamine / Q000494:pharmacology*; D042967:Electron Transport Complex I / Q000037:antagonists & inhibitors; D014450:Electron Transport Complex III / Q000037:antagonists & inhibitors; D066298:In Vitro Techniques; D008297:Male; D008638:Mesenteric Arteries / Q000378:metabolism / Q000502:physiology*; D010656:Phenylephrine / Q000494:pharmacology; D024642:Potassium Channels, Voltage-Gated / Q000502:physiology*; D000091345:Protein Glutamine gamma Glutamyltransferase 2; D054645:Protein Phosphatase 1 / Q000502:physiology; D017208:Rats, Wistar; D012402:Rotenone / Q000494:pharmacology; D011503:Transglutaminases / Q000235:genetics / Q000378:metabolism*; D014661:Vasoconstriction / Q000187:drug effects; D014664:Vasodilation / Q000187:drug effects / Q000502:physiology*
chemical_list: D024642:Potassium Channels, Voltage-Gated; C000717609:Tgm2 protein, rat; D012402:Rotenone; D010656:Phenylephrine; D000968:Antimycin A; D000091345:Protein Glutamine gamma Glutamyltransferase 2; D011503:Transglutaminases; C499850:Ppp1r12a protein, rat; D054645:Protein Phosphatase 1; D042967:Electron Transport Complex I; D014450:Electron Transport Complex III; D003538:Cystamine; D002118:Calcium