title: Aldehyde dehydrogenase 2 knockout accentuates ethanol-induced cardiac depression: role of protein phosphatases.
abstract: Alcohol consumption leads to myocardial contractile dysfunction possibly due to the toxicity of ethanol and its major metabolite acetaldehyde. This study was designed to examine the influence of mitochondrial aldehyde dehydrogenase-2 (ALDH2) knockout (KO) on acute ethanol exposure-induced cardiomyocyte dysfunction. Wild-type (WT) and ALDH2 KO mice were subjected to acute ethanol (3g/kg, i.p.) challenge and cardiomyocyte contractile function was assessed 24h later using an IonOptix edge detection system. Western blot analysis was performed to evaluate ALDH2, protein phosphatase 2A (PP2A), phosphorylation of Akt, and glycogen synthase kinase-3beta (GSK-3beta). ALDH2 KO accentuated ethanol-induced elevation in cardiac acetaldehyde levels. Ethanol exposure depressed cardiomyocyte contractile function including decreased cell shortening amplitude and maximal velocity of shortening/relengthening as well as prolonged relengthening duration and a greater decline in peak shortening in response to increasing stimulus frequency, the effect of which was significantly exaggerated by ALDH2 KO. ALDH2 KO also unmasked an ethanol-induced prolongation of shortening duration. In addition, short-term in vitro incubation of ethanol-induced cardiomyocyte mechanical defects was exacerbated by the ALDH inhibitor cyanamide. Ethanol treatment dampened phosphorylation of Akt and GSK-3beta associated with upregulated PP2A, which was accentuated by ALDH2 KO. ALDH2 KO aggravated ethanol-induced decrease in mitochondrial membrane potential. These results suggested that ALDH2 deficiency led to worsened ethanol-induced cardiomyocyte function, possibly due to upregulated expression of protein phosphatase, depressed Akt activation, and subsequently impaired mitochondrial function. These findings depict a critical role of ALDH2 in the pathogenesis of alcoholic cardiomyopathy.
authors.affiliation: Department of Physiology, Xijing Hospital, Fourth Military Medical University, Xi'an, 710032 China.
authors.forename: Heng
authors.initials: H
authors.lastname: Ma
authors.forename: Lu
authors.initials: L
authors.lastname: Yu
authors.forename: Emily A
authors.initials: EA
authors.lastname: Byra
authors.forename: Nan
authors.initials: N
authors.lastname: Hu
authors.forename: Kyoko
authors.initials: K
authors.lastname: Kitagawa
authors.forename: Keiichi I
authors.initials: KI
authors.lastname: Nakayama
authors.forename: Toshihiro
authors.initials: T
authors.lastname: Kawamoto
authors.forename: Jun
authors.initials: J
authors.lastname: Ren
mesh_terms: D000444:Aldehyde Dehydrogenase / Q000037:antagonists & inhibitors / Q000172:deficiency* / Q000378:metabolism; D000071396:Aldehyde Dehydrogenase, Mitochondrial; D000818:Animals; D001696:Biomechanical Phenomena / Q000187:drug effects; D004781:Environmental Exposure; D000431:Ethanol / Q000008:administration & dosage / Q000633:toxicity*; D038362:Glycogen Synthase Kinase 3 / Q000378:metabolism; D000071679:Glycogen Synthase Kinase 3 beta; D053078:Membrane Potential, Mitochondrial / Q000187:drug effects; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D008928:Mitochondria / Q000187:drug effects / Q000473:pathology; D009206:Myocardium / Q000201:enzymology* / Q000473:pathology*; D032383:Myocytes, Cardiac / Q000187:drug effects / Q000201:enzymology / Q000473:pathology; D010766:Phosphorylation / Q000187:drug effects; D054648:Protein Phosphatase 2 / Q000378:metabolism*; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects
chemical_list: D000431:Ethanol; C515029:ALDH2 protein, mouse; D000444:Aldehyde Dehydrogenase; D000071396:Aldehyde Dehydrogenase, Mitochondrial; D000071679:Glycogen Synthase Kinase 3 beta; C000605507:Gsk3b protein, mouse; D051057:Proto-Oncogene Proteins c-akt; D038362:Glycogen Synthase Kinase 3; D054648:Protein Phosphatase 2