Mechanisms of Environmental Stress Affecting Corneal Epithelial Wound Healing

描述（由申请人提供）：伤口愈合的动态过程对于维持角膜上皮层的正常功能非常重要，角膜上皮层保护角膜、晶状体和其他眼部底层结构免受环境损伤。紫外线（UV）照射和其他生物危害可诱导应激相关的细胞反应，从而破坏伤口愈合的动态过程。我们实验室最新获得的数据表明，紫外线应激诱导的细胞信号反应导致角膜上皮细胞在细胞最终凋亡之前的早期阶段伤口愈合迟缓。初步数据表明：1)紫外线胁迫诱导的细胞反应是由细胞膜上K+通道的过度激活开始的；2)细胞内K+离子的快速流失导致细胞体积收缩；3)细胞收缩诱导JNK信号通路中脚手架酪氨酸激酶（FAK/Src）和MEKK1/4的激活。随后，JNK级联的激活反过来增加p53的磷酸化水平，导致细胞周期停滞。在角膜上皮中，FAK很可能将来自uv诱导的体积收缩输入的信号协调到JNK信号通路。基于初步的研究结果，我们假设紫外线应激诱导的角膜上皮伤口愈合迟缓是由复杂的信号串扰调控的，包括细胞体积改变、支架酪氨酸激酶活性增加、JNK级联激活和细胞周期停止。为了验证这一假设，我们将执行和研究三个特定的目标：1)支架酪氨酸激酶激活和细胞骨架重组，2)JNK信号通路中FAK/Src和MEKK1/4激活之间的串扰，以及3)信号传导成分对紫外线诱导的伤口愈合延迟的影响。我们预测，支架蛋白激酶在紫外线诱导的细胞收缩和JNK级联激活的连锁反应中发挥重要作用，导致细胞周期进程的快速抑制，导致角膜上皮伤口愈合迟缓。然而，UV应激诱导的JNK级联激活和后期发生的ONA断裂是触发角膜上皮细胞凋亡的原因。因此，对紫外线应激诱导的信号事件的研究为理解角膜上皮损伤愈合过程的机制提供了重要的见解。

DESCRIPTION (provided by applicant): The dynamic process of wound healing is important for maintaining the corneal epithelial layer's normal function that protects the cornea, lens and other underlying ocular structures from damage caused by environmental insults. Ultraviolet (UV) irradiation and other biohazards can induce stress-related cellular responses resulting in damage to the dynamic process of wound healing. Newly obtained data from our lab suggest that that UV stress-induced cellular signaling responses resulting in wound healing retardation in corneal epithelial cells during the early stage before the cells eventually commit apoptosis. Preliminary data suggest that: 1) UV stress-induced cellular response is started by hyperactivation of K+ channels in the membrane; 2) the fast loss of intracellular K+ ions causes cell volume shrinkage; and 3) cell shrinkages induce activations of scaffolding tyrosine kinases (FAK/Src) and MEKK1/4 in the JNK signaling pathway. Subsequently, the activation of JNK cascades in turn increases the phosphorylation level of p53 leading to cell cycle arrest. It is very likely in the corneal epithelium that FAK coordinates signals from inputs of UV-induced volume shrinkage to the JNK signaling pathway. Based on the preliminary study results, we hypothesize that UV stress-induced corneal epithelial wound healing retardation is regulated by complex crosstalks in signaling processes involving altered cell volume, increased scaffolding tyrosine kinase activity, activated JNK cascades and cell cycle cessation. Three specific aims will be performed and studied to test this hypothesis: 1) scaffolding tyrosine kinase activation and cytoskeleton reorganization, 2) crosstalk among activations of FAK/Src and MEKK1/4 in the JNK signaling pathway, and 3) effects of signaling components on UV- induced wound healing retardation. We predict that scaffolding protein kinases play important roles in the linkage of UV-induced cell shrinkage and the activation of JNK cascades, resulting in a quick inhibition of cell cycle progression that causes corneal epithelial wound healing retardation. However, UV stress-induced activation of JNK cascades and ONA fragmentation that occurs in a later time are responsible for triggering apoptosis in corneal epithelial cells. Thus, studies of UV stress-induced signaling events provide significant insight for understanding the mechanisms that underlie the corneal epithelial wound healing processes from damages caused by environmental insults.