title: Cardiac overexpression of constitutively active Galpha q causes angiotensin II type1 receptor activation, leading to progressive heart failure and ventricular arrhythmias in transgenic mice.
abstract: BACKGROUND
  Transgenic mice with transient cardiac expression of constitutively active Galpha q (Gαq-TG) exhibt progressive heart failure and ventricular arrhythmias after the initiating stimulus of transfected constitutively active Gαq becomes undetectable. However, the mechanisms are still unknown. We examined the effects of chronic administration of olmesartan on heart failure and ventricular arrhythmia in Gαq-TG mice.
  
  
  RESULTS
  Olmesartan (1 mg/kg/day) or vehicle was chronically administered to Gαq-TG from 6 to 32 weeks of age, and all experiments were performed in mice at the age of 32 weeks. Chronic olmesartan administration prevented the severe reduction of left ventricular fractional shortening, and inhibited ventricular interstitial fibrosis and ventricular myocyte hypertrophy in Gαq-TG. Electrocardiogram demonstrated that premature ventricular contraction (PVC) was frequently (more than 20 beats/min) observed in 9 of 10 vehicle-treated Gαq-TG but in none of 10 olmesartan-treated Gαq-TG. The collected QT interval and monophasic action potential duration in the left ventricle were significantly shorter in olmesartan-treated Gαq-TG than in vehicle-treated Gαq-TG. CTGF, collagen type 1, ANP, BNP, and β-MHC gene expression was increased and olmesartan significantly decreased the expression of these genes in Gαq-TG mouse ventricles. The expression of canonical transient receptor potential (TRPC) 3 and 6 channel and angiotensin converting enzyme (ACE) proteins but not angiotensin II type 1 (AT1) receptor was increased in Gαq-TG ventricles compared with NTG mouse ventricles. Olmesartan significantly decreased TRPC6 and tended to decrease ACE expressions in Gαq-TG. Moreover, it increased AT1 receptor in Gαq-TG.
  
  
  CONCLUSIONS
  These findings suggest that angiotensin II type 1 receptor activation plays an important role in the development of heart failure and ventricular arrhythmia in Gαq-TG mouse model of heart failure.
authors.affiliation: Department of Molecular and Cellular Pharmacology, Iwate Medical University School of Pharmaceutical Sciences, Shiwa, Iwate, Japan; Department of Pharmacology, Iwate Medical University School of Medicine, Shiwa, Iwate, Japan.
authors.forename: Naoko
authors.initials: N
authors.lastname: Matsushita
authors.affiliation: Department of Molecular Pharmacology, Shinshu University School of Medicine, Matsumoto, Nagano, Japan.
authors.forename: Toshihide
authors.initials: T
authors.lastname: Kashihara
authors.affiliation: Department of Pathology, Shinshu University School of Medicine, Matsumoto, Nagano, Japan.
authors.forename: Hisashi
authors.initials: H
authors.lastname: Shimojo
authors.affiliation: Department of Cardiology and Hematology, Fukushima Medical University, Fukushima, Fukushima, Japan.
authors.forename: Satoshi
authors.initials: S
authors.lastname: Suzuki
authors.affiliation: Department of Molecular Pharmacology, Shinshu University School of Medicine, Matsumoto, Nagano, Japan.
authors.forename: Tsutomu
authors.initials: T
authors.lastname: Nakada
authors.affiliation: Department of Cardiology and Hematology, Fukushima Medical University, Fukushima, Fukushima, Japan.
authors.forename: Yasuchika
authors.initials: Y
authors.lastname: Takeishi
authors.affiliation: Cardiovascular Research Center, Division of Cardiology, Rhode Island Hospital & The Alpert Medical School of Brown University, Providence, Rhode Island, United States of America.
authors.forename: Ulrike
authors.initials: U
authors.lastname: Mende
authors.affiliation: Department of Pharmacology, Iwate Medical University School of Medicine, Shiwa, Iwate, Japan.
authors.forename: Eiichi
authors.initials: E
authors.lastname: Taira
authors.affiliation: Department of Molecular Pharmacology, Shinshu University School of Medicine, Matsumoto, Nagano, Japan.
authors.forename: Mitsuhiko
authors.initials: M
authors.lastname: Yamada
authors.affiliation: Department of Pharmacotherapeutics, Iwate Medical University School of Pharmaceutical Sciences, Shiwa, Iwate, Japan.
authors.forename: Atsushi
authors.initials: A
authors.lastname: Sanbe
authors.affiliation: Department of Molecular and Cellular Pharmacology, Iwate Medical University School of Pharmaceutical Sciences, Shiwa, Iwate, Japan.
authors.forename: Masamichi
authors.initials: M
authors.lastname: Hirose
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000235:genetics* / Q000378:metabolism; D000818:Animals; D009320:Atrial Natriuretic Factor / Q000378:metabolism; D024042:Collagen Type I / Q000378:metabolism; D004195:Disease Models, Animal; D043802:GTP-Binding Protein alpha Subunits, Gq-G11 / Q000235:genetics*; D005786:Gene Expression Regulation / Q000187:drug effects; D006333:Heart Failure / Q000235:genetics / Q000503:physiopathology* / Q000517:prevention & control; D007093:Imidazoles / Q000008:administration & dosage*; D051379:Mice; D008822:Mice, Transgenic; D018995:Myosin Heavy Chains / Q000378:metabolism; D013777:Tetrazoles / Q000008:administration & dosage*; D018879:Ventricular Premature Complexes / Q000235:genetics / Q000503:physiopathology* / Q000517:prevention & control
chemical_list: D048868:Adaptor Proteins, Signal Transducing; C119712:Agtrap protein, mouse; D024042:Collagen Type I; D007093:Imidazoles; C551613:Myh7 protein, mouse; D013777:Tetrazoles; D009320:Atrial Natriuretic Factor; C437965:olmesartan; D018995:Myosin Heavy Chains; D043802:GTP-Binding Protein alpha Subunits, Gq-G11