Elevated extracellular K+ inhibits; apoptosis of corneal epithelial cells exposed to UV-B radiation
Elevated extracellular K+ inhibits; apoptosis of corneal epithelial cells exposed to UV-B radiation
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DOI：
10.1016/j.exer.2009.02.023
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发表时间：
2009-08-01
影响因子：
3.4
通讯作者：
Ubels, John L.
中科院分区：
文献类型：
--
作者：
Singleton, Katherine R.;Will, David S.;Ubels, John L.
本研究的目的是确定泪液中的高[K+]（20-25 mM）是否有助于保护角膜上皮细胞在暴露于环境UV-B辐射后免于凋亡。将培养的人角膜缘上皮（HCLE）细胞暴露于剂量为50-200 mJ/cm（2）的UV-B，然后测量K+通道激活和凋亡途径的活性。膜片钳记录了在80 mJ/cm（2）或150 mJ/cm（2）的UV-B暴露后K通道的激活，以及随着[K+]（o）的增加，UV诱导的K+流出减少，UV激活电流部分被特异性K+通道阻断剂BDS-1阻断。通过TUNEL检测，在暴露于100-200 mJ/cm（2）的UV-B后，诱导了DNA断裂。当细胞暴露于UV-B后在25、50或100 mM K-o（+）中孵育时，DNA断裂显著减少。在50-200 mJ/cm（2）的UV-B照射下，效应物半胱天冬酶（caspase-3）被激活，但当细胞在25、50或100 mM K-o（+）中孵育后暴露于UV-B时，激活显著降低。在暴露于100-200 mJ/cm 2的UV-B后，线粒体电位降低，这可能是半胱天冬酶-3的激活剂。100 mM K可防止线粒体电位的降低;然而，25或50 mM K提供的保护最小。Caspase-9，这是在从线粒体电位的变化，以caspase-3激活的途径，表现出很小的激活UV-B辐射。Caspase-8是一种激活caspase-3的引发剂caspase，暴露于50-200 mJ/cm（2）的UV-B可激活caspase-8，而25-100 mM K-o（+）可显着降低这种紫外线激活作用。数据显示，25 mM的生理相关[K+]（o）可以抑制UV-B诱导的细胞凋亡途径的激活。这表明泪液中相对高的[K+]减少了角膜上皮细胞响应于UV暴露的K+损失，从而有助于保护眼表面免受环境UV辐射。(C)2009爱思唯尔有限公司保留所有权利。
The goal of this study was to determine if the high [K+] in tears, 20-25 mM, serves to protect corneal epithelial cells from going into apoptosis after exposure to ambient UV-B radiation. Human corneal-limbal epithelial (HCLE) cells in culture were exposed to UV-B at doses of 50-200 mJ/cm(2) followed by measurement of K+ channel activation and activity of apoptotic pathways. Patch-clamp recording activation of K channels after UV-B exposure at 80 mJ/cm(2) or 150 mJ/cm(2) and a decrease in UV-induced K+ efflux with increasing [K+](o), The UV-activated current was partially blocked by the specific K+ channel blocker, BDS-1. DNA fragmentation, as measured by the TUNEL assay, was induced after exposure to UV-B at 100-200 mJ/cm(2). DNA fragmentation was significantly decreased when cells were incubated in 25, 50 or 100 mM K-o(+) after exposure to UV-B. The effector caspase, caspase-3, was activated by exposure to UV-B at 50-200 mJ/cm(2), but there was a significant decrease in activation when the cells were incubated in 25, 50 or 100 mM K-o(+) following exposure to UV-B. A decrease in mitochondrial potential, a possible activator of caspase-3, occurred after exposure to UV-B at 100-200 mJ/cm(2). This decrease in mitochondrial potential was prevented by 100 mM K; however, 25 or 50 mM K provided minimal protection. Caspase-9, which is in the pathway from mitochondrial potential change to caspase-3 activation, showed little activation by UV-B radiation. Caspase-8, an initiator caspase that activates caspase-3, was activated by exposure to UV-B at 50-200 mJ/cm(2), and this UV-activation was significantly reduced by 25-100 mM K-o(+). The data show that the physiologically relevant [K+](o), of 25 mM can inhibit UV-B induced activation of apoptotic pathways. This suggests that the relatively high [K+] in tears reduces loss of K+ from corneal epithelial cells in response to UV exposure, thereby contributing to the protection of the ocular surface from ambient UV radiation. (C) 2009 Elsevier Ltd. All rights reserved.