Airborne particulate matter impairs corneal epithelial cells migration via disturbing FAK/RhoA signaling pathway and cytoskeleton organization.

BACKGROUND: Cornea is the outmost structure of the eye and exposed directly to the air pollution. However, little is known about the effect of PM2.5 on corneal epithelium, which is critical for maintenance of cornea homeostasis and visual function. OBJECTIVE: We investigated the influence of PM2.5 exposure on corneal epithelial migration and the possible mechanisms involved in the process. METHODS: We observed wound healing in mouse model of cornea abrasion, evaluated the migration and mobility of cultured corneal epithelial cells with wound scratch assay and Transwell migration assay, detected the phosphorylation and interaction of FAK/paxillin with immunofluorescence and immunoprecipitation, and determined the RhoA activity and actin reorganization, in response to PM2.5 exposure. RESULTS: Exposure to PM2.5 remarkably inhibited corneal epithelial cell migration both in mouse model of corneal abrasion and in cell culture model. We found the phosphorylation and interaction of FAK/paxillin, RhoA activity as well as actin reorganization were suppressed by PM2.5 exposure. Moreover, formation of ROS might play a role in the action of PM2.5. CONCLUSIONS: PM2.5 exposure could result in delay of corneal epithelium wound healing by inhibiting cell migration, thus more attention should be paid to the potential risk of corneal infection and effort should be made to protect eyes against impairment induced by PM2.5.

Regulation of Apoptosis by miR-122 in Pterygium via Targeting Bcl-w.

PURPOSE: To identify the differently expressed micro (mi) RNAs in pterygium compared with normal conjunctiva and investigate the potential role of miRNAs in the pathogenesis of pterygium. METHODS: With microRNA microarray and quantitative RT-PCR, we identified that microRNA-122 (miR-122) was significantly decreased in pterygium tissue. We detected the expression of Bcl-w, a predicted target of miR-122, in both pterygium and normal conjunctiva, as well as its correlation with the expression of miR-122. Pterygium epithelial cells were isolated and cultured, and transfected with miR-122 mimic or miR-122 inhibitor to change the miR-122 levels. The regulation of Bcl-w expression by miR-122 was examined with luciferase activity assay, quantitative (q) RT-PCR, and Western blot. The effect of the miR-122 on the apoptosis of cultured pterygium epithelial cells was investigated with TUNEL staining and caspase activity assay. RESULTS: We found the expression of Bcl-w, with an inverse correlation with the expression of miR-122, was significantly increased in pterygium, especially in the superficial layer of epithelium. In cultured pterygium epithelial cells, miR-122 could specifically combine with Bcl-w mRNA, and negatively regulated the expression of Bcl-w. Suppression of miR-122 could reduce apoptosis and caspase activity in pterygium epithelial cell treated with TNFα/cycloheximide (CHX), and this effect was abolished by inhibition of the expression of Bcl-w with specific siRNA. CONCLUSIONS: Decreased expression of miR-122 in pterygium might result in abnormal cell apoptosis via its regulation of the expression of Bcl-w, and subsequently contribute to the development of pterygium.

Assessment of DNA Damage and Cell Senescence in Corneal Epithelial Cells Exposed to Airborne Particulate Matter (PM2.5) Collected in Guangzhou, China.

PURPOSE: To assess the genotoxic effect of airborne particulate matter on corneal epithelial cells and investigate the role of reactive oxygen species (ROS) formation in this process. METHODS: Immortalized human corneal epithelial cells (HCECs) and primary bovine corneal epithelial cells were exposed to airborne particulate matter collected from Guangzhou for 24 hours. The cell viability and toxicity were measured by the CCK-8 test and lactate dehydrogenase (LDH) release, respectively. The DNA breaks and DNA repair were examined by alkaline comet assay and by immunofluorescence staining of the phosphorylated histone variant H2AX (γH2AX), respectively. Reactive oxygen species production was assessed by the fluorescent probe, CM-H2DCFDA. Cell senescence was evaluated with senescence-associated ß-Galactosidase staining, and cell ultrastructure was observed with transmission electron microscopy. RESULTS: Exposure to PM2.5 at the concentration of 20 µg/mL to 200 µg/mL decreased cell viability and increased LDH release. Remarkably increased DNA double-stand breaks, increased expression of DNA repair-related protein γH2AX, elevated ROS formation, and altered cell ultrastructure were observed in HCECs after treatment with PM2.5. The genotoxic effect of PM2.5 was attenuated by the ROS inhibitor N-acetyl-l-cysteine (NAC). CONCLUSIONS: Particulate matter 2.5 could induce DNA damage and cell senescence in corneal epithelial cells, probably by promoting ROS formation. Thus, whether long-term exposure of PM2.5 might be related to potential risk of abnormality in corneal epithelium renewal and regeneration should be further investigated.