title: A non-neuronal cardiac cholinergic system plays a protective role in myocardium salvage during ischemic insults.
abstract: BACKGROUND
  In our previous study, we established the novel concept of a non-neuronal cardiac cholinergic system--cardiomyocytes produce ACh in an autocrine and/or paracrine manner. Subsequently, we determined the biological significance of this system--it played a critical role in modulating mitochondrial oxygen consumption. However, its detailed mechanisms and clinical implications have not been fully investigated.
  
  
  OBJECTIVE
  We investigated if this non-neuronal cardiac cholinergic system was upregulated by a modality other than drugs and if the activation of the system contributes to favorable outcomes.
  
  
  RESULTS
  Choline acetyltransferase knockout (ChAT KO) cells with the lowest cellular ACh levels consumed more oxygen and had increased MTT activity and lower cellular ATP levels compared with the control cells. Cardiac ChAT KO cells with diminished connexin 43 expression formed poor cell-cell communication, evidenced by the blunted dye transfer. Similarly, the ChAT inhibitor hemicholinium-3 decreased ATP levels and increased MTT activity in cardiomyocytes. In the presence of a hypoxia mimetic, ChAT KO viability was reduced. Norepinephrine dose-dependently caused cardiac ChAT KO cell death associated with increased ROS production. In in vivo studies, protein expression of ChAT and the choline transporter CHT1 in the hindlimb were enhanced after ischemia-reperfusion compared with the contralateral non-treated limb. This local effect also remotely influenced the heart to upregulate ChAT and CHT1 expression as well as ACh and ATP levels in the heart compared with the baseline levels, and more intact cardiomyocytes were spared by this remote effect as evidenced by reduced infarction size. In contrast, the upregulated parameters were abrogated by hemicholinium-3.
  
  
  CONCLUSIONS
  The non-neuronal cholinergic system plays a protective role in both myocardial cells and the entire heart by conserving ATP levels and inhibiting oxygen consumption. Activation of this non-neuronal cardiac cholinergic system by a physiotherapeutic modality may underlie cardioprotection through the remote effect of hindlimb ischemia-reperfusion.
authors.affiliation: Department of Cardiovascular Control, Kochi Medical School, Nankoku, Kochi, Japan. kakinuma@kochi-u.ac.jp
authors.forename: Yoshihiko
authors.initials: Y
authors.lastname: Kakinuma
authors.forename: Tsuyoshi
authors.initials: T
authors.lastname: Akiyama
authors.forename: Kayo
authors.initials: K
authors.lastname: Okazaki
authors.forename: Mikihiko
authors.initials: M
authors.lastname: Arikawa
authors.forename: Tatsuya
authors.initials: T
authors.lastname: Noguchi
authors.forename: Takayuki
authors.initials: T
authors.lastname: Sato
mesh_terms: D000109:Acetylcholine / Q000378:metabolism*; D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D015153:Blotting, Western; D002450:Cell Communication / Q000235:genetics / Q000502:physiology; D002460:Cell Line; D002795:Choline O-Acetyltransferase / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D007150:Immunohistochemistry; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D017202:Myocardial Ischemia / Q000378:metabolism*; D009206:Myocardium / Q000378:metabolism*; D017382:Reactive Oxygen Species / Q000378:metabolism
chemical_list: D017382:Reactive Oxygen Species; D000255:Adenosine Triphosphate; D002795:Choline O-Acetyltransferase; D000109:Acetylcholine