title: Intrinsic resistance triggered under acid loading within normal esophageal epithelial cells: NHE1- and ROS-mediated survival.
abstract: The transition to a pathological phenotype such as Barrett's esophagus occurs via induction of resistance upon repeated contact with gastric refluxate in esophagus. This study examined the molecular changes within normal esophageal epithelial cells (EECs) under short-term acid loading and the role of these changes in defensive resistance against acidic cytotoxicity. After primary cultured EECs were exposed to pH 4-acidified medium (AM4), cell viability was determined by the MTT assay. Reactive oxygen species (ROS) and NAD(P)H oxidase (NOX) activity were measured. Activation of the mitogen-activated protein kinases (MAPKs) MEK/ERK1/2, p38 and JNK; phosphoinositol-3-kinase (PI3K)/Akt, and nuclear factor-kappa B (NF-κB) were detected by Western blot analysis or immunofluorescence staining. AM4 incubation induced intracellular ROS generation accompanied by increase in NOX activity, which was further increased by Na(+) /H(+) exchange-1 (NHE1)-dependent inhibition but was prevented by inhibition of NOX or mitochondria complex I. AM4 also induced phosphorylation of MEK/ERK1/2, p38 MAPK, PI3K/Akt, and nuclear translocation of NF-κB, and all these effects, except for p38 MAPK phosphorylation, were abolished by inhibition of ROS. ROS-dependent PI3K/Akt activation, which mediates NF-κB nuclear translocation, was inhibited by protein tyrosine kinase (PTK) inhibitors and NHE1-specific inhibitor. All inhibitors of NHE, ROS, PTK, PI3K, or NF-κB further decreased AM4-induced cell viability. Acid loading in the presence of NHE1-dependent protection induced ROS generation by activating NOX and mitochondria complex I, which stimulated PTK/PI3K/Akt/NF-κB-dependent survival in EEC. Our data indicate that normal EEC initially respond to acid loading through intrinsic survival activation.
authors.affiliation: Department of Pharmacology, College of Pharmacy, Chung-Ang University, Seoul, South Korea.
authors.forename: Sun Young
authors.initials: SY
authors.lastname: Park
authors.forename: Yeon Joo
authors.initials: YJ
authors.lastname: Lee
authors.forename: Eun Jeong
authors.initials: EJ
authors.lastname: Cho
authors.forename: Chang Yell
authors.initials: CY
authors.lastname: Shin
authors.forename: Uy Dong
authors.initials: UD
authors.lastname: Sohn
mesh_terms: D000818:Animals; D027682:Cation Transport Proteins / Q000235:genetics / Q000378:metabolism*; D002415:Cats; D002470:Cell Survival; D003470:Culture Media / Q000737:chemistry; D004847:Epithelial Cells / Q000187:drug effects / Q000502:physiology*; D004947:Esophagus / Q000166:cytology; D005260:Female; D005786:Gene Expression Regulation / Q000502:physiology; D006146:Guanidines / Q000494:pharmacology; D006863:Hydrogen-Ion Concentration; D008297:Male; D020929:Mitogen-Activated Protein Kinase Kinases / Q000235:genetics / Q000378:metabolism; D016328:NF-kappa B / Q000235:genetics / Q000378:metabolism; D019869:Phosphatidylinositol 3-Kinases / Q000235:genetics / Q000378:metabolism; D011505:Protein-Tyrosine Kinases / Q000235:genetics / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt / Q000235:genetics / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism*; D017923:Sodium-Hydrogen Exchangers / Q000235:genetics / Q000378:metabolism*; D013450:Sulfones / Q000494:pharmacology
chemical_list: D027682:Cation Transport Proteins; D003470:Culture Media; D006146:Guanidines; D016328:NF-kappa B; D017382:Reactive Oxygen Species; D017923:Sodium-Hydrogen Exchangers; D013450:Sulfones; C093373:cariporide; D019869:Phosphatidylinositol 3-Kinases; D011505:Protein-Tyrosine Kinases; D051057:Proto-Oncogene Proteins c-akt; D020929:Mitogen-Activated Protein Kinase Kinases