Hypoosmotic Stress Activates p38, ERK 1 and 2, and SAPK/JNK in Rat Hepatocytes

• Published in: The Journal of surgical research 2000-05, Vol.90 (1), p.58-66
• Main Authors: Kim, Robin D., Darling, Chad E., Cerwenka, Herwig, Chari, Ravi S.
• Format: Article
• Language: English
• Subjects: Animals; Hepatocyte Growth Factor - pharmacology; hypoosmotic; Hypotonic Solutions - pharmacology; Liver - cytology; Liver - enzymology; Male; MAPK; Mitogen-Activated Protein Kinase 1 - physiology; Mitogen-Activated Protein Kinase 3; Mitogen-Activated Protein Kinase 8; Mitogen-Activated Protein Kinases - physiology; NF-kappa B - physiology; NF-κB; p38 Mitogen-Activated Protein Kinases; Phosphorylation; Rats; Rats, Sprague-Dawley
• ISSN: 0022-4804; 1095-8673
• DOI: 10.1006/jsre.2000.5866

Background. Following hepatocyte injury, changes in the perihepatocyte milieu modulate cell volume and influence growth. Hypoosmotic stress activates nuclear factor-kappa B (NF-κB), 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-κB. Materials and 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 μM) or SB 202190 (3 μM). 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-κB activation. Results. (i) Hypoosmolar WE medium phosphorylated p38, ERK 1 and 2, and SAPK/JNK by 5 min. (ii) Hypoosmolar WE medium activated NF-κB at 60 min. (iii) HGF phosphorylated all three MAPKs and activated NF-κB with profiles similar to those of hypoosmotic stress. (iv) Both PD 98059 and SB 202190 abrogated the activation of NF-κB in HGF-stimulated cells but not in hypoosmotically stressed cells. Conclusion. (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-κB via p38 and ERK 1 and 2 phosphorylation. These data suggest that cell swelling activates NF-κB through a pathway separate from that of growth factors.