title: Calpain activation in plasma membrane bleb formation during tert-butyl hydroperoxide-induced rat hepatocyte injury.
abstract: OBJECTIVE
  The mechanism of plasma membrane blebbing (dissociation of the lipid bilayer from the membrane cytoskeleton) in hepatocyte injury is not known. The aim of this study was to investigate the role of calpain, a calcium-dependent cytosolic protease, in bleb formation induced by oxidative stress.
  
  
  METHODS
  Hepatocytes from Wistar rats were injured with tertbutyl hydroperoxide in the presence or absence of ethylene glycol-bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid (EGTA) or a specific calpain inhibitor, calpeptin (Z-Leu-nLeu-H). Bleb formation was examined by phase-contrast and transmission electron microscopies. Intracellular calcium concentration was measured using Fura-2. Western blot analyses were performed for cytoskeletal proteins (talin, alpha-actinin, and vinculin) and the intermediate (activated) and proactivated forms of calpain mu.
  
  
  RESULTS
  tert-Butyl hydroperoxide induced a sustained increase in intracellular calciu, bleb formation, and, ultimately, hepatocyte death. Talin and alpha-actinin were degraded in a time-dependent manner, although no apparent changes of actin filament were observed. Before the cytoskeletal protein degradation, the intermediate form of calpain mu appeared as its proactivated form decreased. In addition, calpeptin or EGTA inhibited not only calpain mu activation but also cytoskeletal protein degradation and bleb formation.
  
  
  CONCLUSIONS
  In tert-butyl hydroperoxide-treated hepatocytes, the activation of calpain promotes membrane blebbing via degradation of cytoskeletal proteins.
authors.affiliation: Department of Surgery II, Osaka University Medical School, Japan.
authors.forename: H
authors.initials: H
authors.lastname: Miyoshi
authors.forename: K
authors.initials: K
authors.lastname: Umeshita
authors.forename: M
authors.initials: M
authors.lastname: Sakon
authors.forename: S
authors.initials: S
authors.lastname: Imajoh-Ohmi
authors.forename: K
authors.initials: K
authors.lastname: Fujitani
authors.forename: M
authors.initials: M
authors.lastname: Gotoh
authors.forename: E
authors.initials: E
authors.lastname: Oiki
authors.forename: J
authors.initials: J
authors.lastname: Kambayashi
authors.forename: M
authors.initials: M
authors.lastname: Monden
mesh_terms: D000818:Animals; D002118:Calcium / Q000502:physiology; D002154:Calpain / Q000037:antagonists & inhibitors / Q000502:physiology*; D002462:Cell Membrane / Q000378:metabolism; D003598:Cytoskeletal Proteins / Q000378:metabolism; D004151:Dipeptides / Q000494:pharmacology; D008099:Liver / Q000187:drug effects* / Q000473:pathology; D008297:Male; D008854:Microscopy, Electron; D010545:Peroxides / Q000494:pharmacology*; D051381:Rats; D017208:Rats, Wistar; D017382:Reactive Oxygen Species / Q000502:physiology; D020122:tert-Butylhydroperoxide
chemical_list: D003598:Cytoskeletal Proteins; D004151:Dipeptides; D010545:Peroxides; D017382:Reactive Oxygen Species; C071482:calpeptin; D020122:tert-Butylhydroperoxide; D002154:Calpain; D002118:Calcium