Hypertonicity-induced p38MAPK activation elicits recovery of corneal epithelial cell volume and layer integrity.
In hypertonicity-stressed (i.e., 600 mOsm) SV40-immortalized rabbit and human corneal epithelial cell layers (RCEC and HCEC, respectively), we characterized the relationship between time-dependent changes in translayer resistance, relative cell volume and modulation of MAPK superfamily activities. Sulforhodamine B permeability initially increased by 1.4- and 2-fold in RCEC and HCEC, respectively. Subsequently, recovery to its isotonic level only occurred in RCEC. Light scattering revealed that in RCEC 1) regulatory volume increase (RVI) extent was 20% greater; 2) RVI half-time was 2.5-fold shorter. However, inhibition of Na-K-2Cl cotransporter and Na/K-ATPase activity suppressed the RVI response more in HCEC. MAPK activity changes were as follows: 1) p38 was wave-like and faster as well as larger in RCEC than in HCEC (90- and 18-fold, respectively); 2) increases in SAPK/JNK activity were negligible in comparison to those of p38; 3) Erk1/2 activity declined to 30-40% of their basal values. SB203580, a specific p38 inhibitor, dose dependently suppressed the RVI responses in both cell lines. However, neither U0126, which inhibits MEK, the kinase upstream of Erk, nor SP600125, inhibitor of SAPK/JNK, had any effect on this response. Taken together, sufficient activation of the p38 limb of the MAPK superfamily during a hypertonic challenge is essential for maintaining epithelial cell volume and translayer resistance. On the other hand, Erk1/2 activity restoration seems to be dependent on cell volume recovery.
Bildin
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Department of Biological Sciences, College of Optometry, State University of New York, 33 West 42nd St., New York, NY 10036, USA. vbildin@sunyopt.edu
Wang
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Iserovich
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Reinach
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PS
D000222:Adaptation, Physiological / Q000502:physiology; D000818:Animals; D002460:Cell Line; D048429:Cell Size / Q000187:drug effects / Q000502:physiology; D017097:Electric Impedance; D004789:Enzyme Activation; D019573:Epithelium, Corneal / Q000166:cytology* / Q000187:drug effects / Q000502:physiology*; D006706:Homeostasis / Q000502:physiology*; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D009995:Osmosis / Q000187:drug effects / Q000502:physiology; D009997:Osmotic Pressure; D011817:Rabbits; D020127:Recovery of Function / Q000502:physiology*; D012235:Rhodamines / Q000493:pharmacokinetics; D012462:Saline Solution, Hypertonic / Q000494:pharmacology*; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism*; D013045:Species Specificity; D048051:p38 Mitogen-Activated Protein Kinases
D012235:Rhodamines; D012462:Saline Solution, Hypertonic; C022027:lissamine rhodamine B; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; D000254:Sodium-Potassium-Exchanging ATPase