Transcriptomic profiling of human corneal epithelial cells exposed to airborne fine particulate matter (PM).

Purpose: To explore the molecular mechanisms of PM-induced dysfunction in human corneal epithelial cells (HCECs) and the potential role of the plasminogen activator inhibitor type-2 (PAI-2) in PM-induced autophagy in vitro and in vivo.

Methods: RNA-Seq was performed to identify the differentially expressed genes (DEGs) in PM-exposed HCECs compared to unexposed condition, followed by validation via real-time PCR (qRT-PCR). Corneal fluorescein staining and tear secretion were assessed in the PM-exposed rat model. The expression of PAI-2 and autophagy-related markers were examined via immunoblotting, immunofluorescence staining and/or qRT-PCR in PM-exposed or unexposed HCECs and rat corneas. PAI-2-knockdown HCECs were generated to study PAI-2's role in the PM-induced autophagy in HCECs.

Results: A total of 434 DEGs-240 up-regulated and 194 down-regulated-were identified in PM-exposed HCECs rather than unexposed HCECs. The expression of a few genes related to proliferation, inflammation, and aryl hydrocarbon stimulation were significantly altered by PM exposure. PAI-2 expression was up-regulated in PM-exposed HCECs, sharing a similar fluctuation trend with autophagy-related markers LC3B II and BECN1 according to various exposure periods. Moreover, PAI-2 knockdown significantly suppressed the expression of LC3B and BECN1 in PM-exposed HCECs. The corneal fluorescein staining was enhanced and tear secretion was significantly reduced in PM-exposed rat eyes. PAI-2 expression was also increased in PM-exposed rat corneas, together with the up-regulation of several autophagy-related markers.

Conclusion: The present study identified the altered expression of hundreds of genes in PM-exposed HCECs, which suggests the importance of PM for cornea health. The involvement of PAI-2 was discovered in the PM-induced autophagy in HCECs as well as likely in rat corneas, which implied that PAI-2 may become a potential target of clinical treatment of PM-associated ocular surface diseases.