Bildin V N, Wang Z, Iserovich P, Reinach P S
Department of Biological Sciences, College of Optometry, State University of New York, 33 West 42nd St., New York, NY 10036, USA.
J Membr Biol. 2003 May 1;193(1):1-13. doi: 10.1007/s00232-002-2002-8.
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.
在高渗应激（即600 mOsm）的SV40永生化兔和人角膜上皮细胞层（分别为RCEC和HCEC）中，我们表征了跨层电阻随时间变化、相对细胞体积与MAPK超家族活性调节之间的关系。在RCEC和HCEC中，磺酰罗丹明B的通透性最初分别增加了1.4倍和2倍。随后，只有RCEC恢复到等渗水平。光散射显示，在RCEC中：1）调节性容积增加（RVI）程度高20%；2）RVI半衰期短2.5倍。然而，抑制Na-K-2Cl共转运体和Na/K-ATP酶活性对HCEC中RVI反应的抑制作用更大。MAPK活性变化如下：1）p38呈波浪状，在RCEC中比在HCEC中更快且幅度更大（分别为90倍和18倍）；2）与p38相比，SAPK/JNK活性的增加可忽略不计；3）Erk1/2活性下降至其基础值的30%-40%。特异性p38抑制剂SB203580剂量依赖性地抑制了两种细胞系中的RVI反应。然而，抑制Erk上游激酶MEK的U0126和SAPK/JNK抑制剂SP600125对此反应均无影响。综上所述，在高渗刺激期间，MAPK超家族的p38分支充分激活对于维持上皮细胞体积和跨层电阻至关重要。另一方面，Erk1/2活性的恢复似乎依赖于细胞体积的恢复。
