title: Acetylcholine inhibits the hypoxia-induced reduction of connexin43 protein in rat cardiomyocytes.
abstract: In a recent study, we demonstrated that vagal stimulation increases the survival of rats with myocardial infarction by inhibiting lethal arrhythmia through regulation of connexin43 (Cx43). However, the precise mechanisms for this effect remain to be elucidated. To investigate these mechanisms and the signal transduction for gap junction regulation, we investigated the effect of acetylcholine (ACh), a parasympathetic nerve system neurotransmitter, on the gap junction component Cx43 using H9c2 cells. When cells were subjected to hypoxia, the total Cx43 protein level was decreased. In contrast, pretreatment with ACh inhibited this effect. To investigate the signal transduction, cells were pretreated with L-NAME, a nitric oxide synthase inhibitor, followed by ACh and hypoxia. L-NAME was found to suppress the ACh effect. However, a NO donor, SNAP, partially inhibited the hypoxia-induced reduction in Cx43. To delineate the mechanisms of the decrease in Cx43 under hypoxia, cells were pretreated with MG132, a proteasome inhibitor. Proteasome inhibition produced a striking recovery of the decrease in the total Cx43 protein level under hypoxia. However, cotreatment with MG132 and ACh did not produce any further increase in the total Cx43 protein level. Functional studies using ACh or okadaic acid, a phosphatase inhibitor, revealed that both reagents inhibited the decrease in the dye transfer induced by hypoxia. These results suggest that ACh is responsible for restoring the decrease in the Cx43 protein level, resulting in functional activation of gap junctions.
authors.affiliation: Department of Clinical Laboratory, Kochi Medical School, Japan.
authors.forename: Yanan
authors.initials: Y
authors.lastname: Zhang
authors.forename: Yoshihiko
authors.initials: Y
authors.lastname: Kakinuma
authors.forename: Motonori
authors.initials: M
authors.lastname: Ando
authors.forename: Rajesh G
authors.initials: RG
authors.lastname: Katare
authors.forename: Fumiyasu
authors.initials: F
authors.lastname: Yamasaki
authors.forename: Tetsuro
authors.initials: T
authors.lastname: Sugiura
authors.forename: Takayuki
authors.initials: T
authors.lastname: Sato
mesh_terms: D000109:Acetylcholine / Q000494:pharmacology*; D000818:Animals; D002450:Cell Communication; D015687:Cell Hypoxia; D002460:Cell Line; D018031:Connexin 43 / Q000378:metabolism*; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology; D017629:Gap Junctions / Q000187:drug effects / Q000201:enzymology; D007976:Leupeptins / Q000494:pharmacology; D032383:Myocytes, Cardiac / Q000187:drug effects* / Q000201:enzymology; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D009569:Nitric Oxide / Q000378:metabolism; D020030:Nitric Oxide Donors / Q000494:pharmacology; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors / Q000378:metabolism; D019319:Okadaic Acid / Q000494:pharmacology; D010749:Phosphoprotein Phosphatases / Q000037:antagonists & inhibitors / Q000378:metabolism; D010766:Phosphorylation; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism; D061988:Proteasome Inhibitors; D051381:Rats; D026423:S-Nitroso-N-Acetylpenicillamine / Q000494:pharmacology; D013997:Time Factors
chemical_list: D018031:Connexin 43; D015853:Cysteine Proteinase Inhibitors; D007976:Leupeptins; D020030:Nitric Oxide Donors; D061988:Proteasome Inhibitors; D019319:Okadaic Acid; D009569:Nitric Oxide; D026423:S-Nitroso-N-Acetylpenicillamine; D019001:Nitric Oxide Synthase; D010749:Phosphoprotein Phosphatases; D046988:Proteasome Endopeptidase Complex; D000109:Acetylcholine; C072553:benzyloxycarbonylleucyl-leucyl-leucine aldehyde; D019331:NG-Nitroarginine Methyl Ester