title: ALDH2 modulates autophagy flux to regulate acetaldehyde-mediated toxicity thresholds.
abstract: A polymorphic mutation in the acetaldehyde dehydrogenase 2 (ALDH2) gene has been epidemiologically linked to the high susceptibility to esophageal carcinogenesis for individuals with alcohol use disorders. Mice subjected to alcohol drinking show increased oxidative stress and DNA adduct formation in esophageal epithelia where Aldh2 loss augments alcohol-induced genotoxic effects; however, it remains elusive as to how esophageal epithelial cells with dysfunctional Aldh2 cope with oxidative stress related to alcohol metabolism. Here, we investigated the role of autophagy in murine esophageal epithelial cells (keratinocytes) exposed to ethanol and acetaldehyde. We find that ethanol and acetaldehyde trigger oxidative stress via mitochondrial superoxide in esophageal keratinocytes. Aldh2-deficient cells appeared to be highly susceptible to ethanol- or acetaldehyde-mediated toxicity. Alcohol dehydrogenase-mediated acetaldehyde production was implicated in ethanol-induced cell injury in Aldh2 deficient cells as ethanol-induced oxidative stress and cell death was partially inhibited by 4-methylpyrazole. Acetaldehyde activated autophagy flux in esophageal keratinocytes where Aldh2 deficiency increased dependence on autophagy to cope with ethanol-induced acetaldehyde-mediated oxidative stress. Pharmacological inhibition of autophagy flux by chloroquine stabilized p62/SQSTM1, and increased basal and acetaldehyde-mediate oxidative stress in Aldh2 deficient cells as documented in monolayer culture as well as single-cell derived three-dimensional esophageal organoids, recapitulating a physiological esophageal epithelial proliferation-differentiation gradient. Our innovative approach indicates, for the first time, that autophagy may provide cytoprotection to esophageal epithelial cells responding to oxidative stress that is induced by ethanol and its major metabolite acetaldehyde. Defining autophagymediated cytoprotection against alcohol-induced genotoxicity in the context of Aldh2 deficiency, our study provides mechanistic insights into the tumor suppressor functions of ALDH2 and autophagy in alcohol-related esophageal carcinogenesis.
authors.affiliation: Gastroenterology Division, Department of Medicine, University of Pennsylvania Perelman School of MedicinePhiladelphia, PA, USA; University of Pennsylvania Abramson Cancer CenterPhiladelphia, PA, USA.
authors.forename: Koji
authors.initials: K
authors.lastname: Tanaka
authors.affiliation: Gastroenterology Division, Department of Medicine, University of Pennsylvania Perelman School of MedicinePhiladelphia, PA, USA; University of Pennsylvania Abramson Cancer CenterPhiladelphia, PA, USA.
authors.forename: Kelly A
authors.initials: KA
authors.lastname: Whelan
authors.affiliation: Gastroenterology Division, Department of Medicine, University of Pennsylvania Perelman School of MedicinePhiladelphia, PA, USA; University of Pennsylvania Abramson Cancer CenterPhiladelphia, PA, USA.
authors.forename: Prasanna M
authors.initials: PM
authors.lastname: Chandramouleeswaran
authors.affiliation: Gastroenterology Division, Department of Medicine, University of Pennsylvania Perelman School of MedicinePhiladelphia, PA, USA; University of Pennsylvania Abramson Cancer CenterPhiladelphia, PA, USA.
authors.forename: Shingo
authors.initials: S
authors.lastname: Kagawa
authors.affiliation: Gastroenterology Division, Department of Medicine, University of Pennsylvania Perelman School of MedicinePhiladelphia, PA, USA; University of Pennsylvania Abramson Cancer CenterPhiladelphia, PA, USA.
authors.forename: Sabrina L
authors.initials: SL
authors.lastname: Rustgi
authors.affiliation: Department of Biochemistry and Molecular Biology, Drexel University College of Medicine Philadelphia, PA, USA.
authors.forename: Chiaki
authors.initials: C
authors.lastname: Noguchi
authors.affiliation: Department of Animal Biology, Mari Lowe Center for Comparative Oncology, School of Veterinary Medicine, University of Pennsylvania Philadelphia, PA, USA.
authors.forename: Manti
authors.initials: M
authors.lastname: Guha
authors.affiliation: Department of Animal Biology, Mari Lowe Center for Comparative Oncology, School of Veterinary Medicine, University of Pennsylvania Philadelphia, PA, USA.
authors.forename: Satish
authors.initials: S
authors.lastname: Srinivasan
authors.affiliation: Department of Therapeutic Oncology, Graduate School of Medicine, Kyoto University Kyoto, Japan.
authors.forename: Yusuke
authors.initials: Y
authors.lastname: Amanuma
authors.affiliation: Department of Therapeutic Oncology, Graduate School of Medicine, Kyoto University Kyoto, Japan.
authors.forename: Shinya
authors.initials: S
authors.lastname: Ohashi
authors.affiliation: Department of Therapeutic Oncology, Graduate School of Medicine, Kyoto University Kyoto, Japan.
authors.forename: Manabu
authors.initials: M
authors.lastname: Muto
authors.affiliation: Histopathology Facility and Cancer Biology Program, Fox Chase Cancer Center Philadelphia, PA, USA.
authors.forename: Andres J
authors.initials: AJ
authors.lastname: Klein-Szanto
authors.affiliation: Department of Biochemistry and Molecular Biology, Drexel University College of Medicine Philadelphia, PA, USA.
authors.forename: Eishi
authors.initials: E
authors.lastname: Noguchi
authors.affiliation: Department of Animal Biology, Mari Lowe Center for Comparative Oncology, School of Veterinary Medicine, University of Pennsylvania Philadelphia, PA, USA.
authors.forename: Narayan G
authors.initials: NG
authors.lastname: Avadhani
authors.affiliation: Gastroenterology Division, Department of Medicine, University of Pennsylvania Perelman School of MedicinePhiladelphia, PA, USA; University of Pennsylvania Abramson Cancer CenterPhiladelphia, PA, USA.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Nakagawa
keywords: ALDH2; Autophagy; acetaldehyde; alcohol; esophageal squamous cell carcinoma; reactive oxygen species; tobacco