title: Pepsin in nonacidic refluxate can damage hypopharyngeal epithelial cells.
abstract: OBJECTIVE
  Studies using combined multichannel intraluminal impedance with pH monitoring reveal a role for nonacidic reflux in laryngopharyngeal symptoms and injury. We have discovered that pepsin is taken up by laryngeal epithelial cells by receptor-mediated endocytosis. This finding reveals a novel mechanism by which pepsin could cause cell damage, potentially even in nonacidic refluxate. The objective of this study was to determine whether pepsin, at pH 7.4 and thus in nonacidic refluxate, causes cell damage.
  
  
  METHODS
  Cultured hypopharyngeal epithelial (FaDu) cells were exposed to human pepsin (0.1 mg/mL) at pH 7.4 for either 1 hour or 12 hours at 37 degrees C and analyzed by electron microscopy, cytotoxicity assay, and SuperArray.
  
  
  RESULTS
  We report mitochondrial and Golgi complex damage in cells exposed to pepsin at neutral pH, observed by electron microscopy. We also report cell toxicity of pepsin at pH 7.4, measured by a cytotoxicity assay. Furthermore, using SuperArray, we found that pepsin at pH 7.4 significantly alters the expression levels of multiple genes implicated in stress and toxicity.
  
  
  CONCLUSIONS
  These findings are perhaps the first to explain why many patients have symptoms and injury associated with nonacidic reflux, and could have important implications for the development of new therapies for reflux, such as pepsin receptor antagonists and/or irreversible inhibitors of peptic activity.
authors.affiliation: Department of Otolaryngology and Communication Sciences, Medical College of Wisconsin, Milwaukee, WI 53226, USA.
authors.forename: Nikki
authors.initials: N
authors.lastname: Johnston
authors.forename: Clive W
authors.initials: CW
authors.lastname: Wells
authors.forename: Tina L
authors.initials: TL
authors.lastname: Samuels
authors.forename: Joel H
authors.initials: JH
authors.lastname: Blumin
mesh_terms: D002478:Cells, Cultured; D004847:Epithelial Cells / Q000187:drug effects / Q000473:pathology; D050782:Esophageal pH Monitoring; D005764:Gastroesophageal Reflux / Q000503:physiopathology*; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007013:Hypopharynx / Q000166:cytology*; D008854:Microscopy, Electron; D010434:Pepsin A / Q000032:analysis / Q000502:physiology*
chemical_list: D010434:Pepsin A