Stratified corneal limbal epithelial cells are protected from UVB-induced apoptosis by elevated extracellular K+
Stratified corneal limbal epithelial cells are protected from UVB-induced apoptosis by elevated extracellular K+
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DOI：
10.1016/j.exer.2011.09.005
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发表时间：
2011-11-01
影响因子：
3.4
通讯作者：
Ubels, John L.
中科院分区：
文献类型：
--
作者：
Schotanus, Mark R.;Koetje, Leah R.;Ubels, John L.
本研究的目的是确定是否升高[K+]保护分层角膜上皮细胞进入细胞凋亡后暴露于环境水平的UVB辐射。将人角膜缘上皮（HCLE）细胞分层以在培养物中形成多层构建体。将细胞暴露于100-250 mJ/cm（2）的UVB剂量，然后在含有5.5-100 mM K+的培养基中孵育。K+的保护作用通过测量分层HCLE构建体的半胱天冬酶-3和-8活性和TUNEL染色来确定。作为对UVB暴露的响应，细胞凋亡途径的激活在24小时达到峰值。在100-250 mJ/cm（2）的UVB照射下，分层细胞中的Caspase-8被激活，而50或100 mM K+的活性显著降低。Caspase-3在100-250 mJ/cm（2）UVB照射下被激活，在25、50或100 mM K+照射下活性显著降低。TUNEL染色显示，暴露于200 mJ/cm（2）UVB后，DNA断裂增加，与25-100 mM K+孵育后，DNA断裂减少。这些结果表明，在模拟完整角膜上皮的培养系统中，升高的细胞外K+可以减少UVB诱导的细胞凋亡，这被认为是由K+从细胞中丢失引发的。这是UVB暴露引起角膜上皮损伤的基础。基于这些观察结果，建议泪液中相对较高的K+浓度（20-25 mM）可能在保护角膜上皮免受环境UVB辐射方面发挥作用。(C)2011爱思唯尔有限公司保留所有权利。
The goal of this study was to determine whether elevated [K+] protects stratified corneal epithelial cells from entering apoptosis following exposure to ambient levels of UVB radiation. Human corneal limbal epithelial (HCLE) cells were stratified to form multilayered constructs in culture. The cells were exposed to UVB doses of 100-250 mJ/cm(2) followed by incubation in medium with 5.5-100 mM K+. The protective effect of K+ was determined by measuring the caspase-3 and -8 activity and TUNEL staining of the stratified HCLE constructs. In response to UVB exposure, activation of apoptotic pathways peaked at 24 h. Caspase-8 in stratified cells was activated by exposure to UVB at 100-250 mJ/cm(2), and activity was significantly reduced in response to 50 or 100 mM K+. Caspase-3 was activated in the stratified cells in response to 100-250 mJ/cm(2) UVB and showed a significant reduction in activity in response to 25, 50 or 100 mM K+. DNA fragmentation, as indicated by TUNEL staining, was elevated after exposure to 200 mJ/cm(2) UVB, and decreased following incubation with 25-100 mM K+. These results show that in a culture system that models the intact corneal epithelium, elevated extracellular K+ can reduce UVB-induced apoptosis which is believed to be initiated by loss of K+ from cells. This is the basis of damage to the corneal epithelium caused by UVB exposure. Based on these observations it is suggested that the relatively high K+ concentration in tears (20-25 mM) may play a role in protecting the corneal epithelium from ambient UVB radiation. (C) 2011 Elsevier Ltd. All rights reserved.