IL-37 prevents corneal barrier disruption by inhibiting TNF-α/CTSS signaling in primary human corneal epithelial cells under hyperosmotic stress

Abstract

Purpose : To explore novel role and molecular mechanism of a natural anti-inflammatory cytokine interleukin (IL) 37 in preventing corneal epithelial barrier disruption from hyperosmolar stress as occurs in dry eye.

Methods : Primary human corneal epithelial cells (HCECs) were cultured from fresh donor limbal explants. An in vitro dry eye model with hyperosmolar stress was established by switching HCECs from isosmolar (312mOsM) to hyperosmolar medium (350-500 mOsM) alone or with rhIL-37, some cells were treated with TNF-α, for different periods (2-48 hours). The expression of cytokines and cathepsin S, and barrier protein integrity were evaluated by RT-qPCR, ELISA, and immunofluorescent staining with confocal microscopy.

Results : The integrity of epithelial barrier was significantly disrupted in HCECs exposed to hyperosmolar medium, as shown by immunofluorescent images of tight junction (ZO-1, occludin and claudin-1) and adheren junction (E-cadherin) proteins. The opposite responses were observed between TNF-α stimulated and IL-37 suppressed in HCECs exposed to hyperosmolarity. Cathepsin S, encoded by CTSS gene, was found to directly disrupt epithelial barrier. Interestingly, CTSS expression was significantly induced by TNF-α and hyperosmolarity, while exogenous rhIL-37 inhibited TNF-α and CTSS expression at mRNA and protein levels following hyperosmolar stress. rhIL-37 further restored barrier protein integrity, observed in 2D and 3D confocal immunofluorescent images, in HCECs under hyperosmolar stress.

Conclusions : Our findings demonstrate a novel signaling pathway by which the anti-inflammatory cytokine IL-37 suppresses TNF-α and CTSS stimulated corneal epithelial barrier disruption under hyperosmotic stress. This study provides new insight into mechanisms disrupting or preventing corneal barrier in dry eye disease.

This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.