title: Hypoosmotic stress activates p38, ERK 1 and 2, and SAPK/JNK in rat hepatocytes.
abstract: BACKGROUND
  Following hepatocyte injury, changes in the perihepatocyte milieu modulate cell volume and influence growth. Hypoosmotic stress activates nuclear factor-kappa B (NF-kappaB), a transcription factor believed to prime cell cycle progression in hepatocytes. In this study, we investigate the role of mitogen-activated protein kinases (MAPKs) in the activation of NF-kappaB.
  
  
  METHODS
  Quiescent primary hepatocytes were exposed to hypoosmotic serum-free William's E (WE) medium (200 mOsm/liter), with or without a 1-h pretreatment with either PD 98059 (15 microM) or SB 202190 (3 microM). Parallel experiments were conducted using hepatocyte growth factor (HGF) at 0.1 mg/ml and normoosmotic WE medium as positive and negative controls, respectively (n = 3). Relative densitometries of Western blots measured phosphorylated cytoplasmic p38, ERK 1 and 2, and SAPK/JNK. Electromobility shift assays examined nuclear NF-kappaB activation.
  
  
  RESULTS
  (i) Hypoosmolar WE medium phosphorylated p38, ERK 1 and 2, and SAPK/JNK by 5 min. (ii) Hypoosmolar WE medium activated NF-kappaB at 60 min. (iii) HGF phosphorylated all three MAPKs and activated NF-kappaB with profiles similar to those of hypoosmotic stress. (iv) Both PD 98059 and SB 202190 abrogated the activation of NF-kappaB in HGF-stimulated cells but not in hypoosmotically stressed cells.
  
  
  CONCLUSIONS
  (i) Both hypoosmotic cell swelling and HGF phosphorylate p38, ERK 1 and 2, and SAPK/JNK, and (ii) HGF, but not hypoosmotic stress, activates NF-kappaB via p38 and ERK 1 and 2 phosphorylation. These data suggest that cell swelling activates NF-kappaB through a pathway separate from that of growth factors.
authors.affiliation: Department of Surgery, University of Massachusetts Medical School, Worcester, MA 01655, USA.
authors.forename: R D
authors.initials: RD
authors.lastname: Kim
authors.forename: C E
authors.initials: CE
authors.lastname: Darling
authors.forename: H
authors.initials: H
authors.lastname: Cerwenka
authors.forename: R S
authors.initials: RS
authors.lastname: Chari
mesh_terms: D000818:Animals; D017228:Hepatocyte Growth Factor / Q000494:pharmacology; D007038:Hypotonic Solutions / Q000494:pharmacology*; D008099:Liver / Q000166:cytology / Q000201:enzymology*; D008297:Male; D019950:Mitogen-Activated Protein Kinase 1 / Q000502:physiology*; D048052:Mitogen-Activated Protein Kinase 3; D048055:Mitogen-Activated Protein Kinase 8; D020928:Mitogen-Activated Protein Kinases / Q000502:physiology*; D016328:NF-kappa B / Q000502:physiology; D010766:Phosphorylation; D051381:Rats; D017207:Rats, Sprague-Dawley; D048051:p38 Mitogen-Activated Protein Kinases
chemical_list: D007038:Hypotonic Solutions; D016328:NF-kappa B; D017228:Hepatocyte Growth Factor; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D048055:Mitogen-Activated Protein Kinase 8; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases