Abstract
Purpose :
IL-36 family cytokines are such a unique system that comprises three agonists and two antagonists, and show novel protective and destructive effects in inflammatory diseases. However, little is known about IL-36 in human eyes and the ocular surface. This study aimed to explore the regulatory role and molecular mechanism of IL-36 cytokines in dry eye disease.
Methods :
Two dry eye models, an in vitro human corneal epithelial cells (HCECs) exposed to hyperosmolarity stress and an in vivo mouse model induced by desiccating stress, were performed. Hyperosmolarity model was established by switching primary HCECs from isosmotic (312mOsM) to hyperosmotic medium (350-500 mOsM) alone or with addition of rhIL-36RA or rhIL-38 for 2-48 hours. Some cultures were treated with IL-36α (1-10 ng/ml) with or without rhIL-36RA or rhIL-38. Dry eye mice were created in C57BL/6 under desiccating stress. Gene expression was detected by RT-qPCR, and protein production and barrier disruption were evaluated by ELISA and/or immunofluorescent staining.
Results :
All IL-36 cytokines were found to be differentially expressed in primary HCECs. Among 3 pro-inflammatory agonists, IL-36α, but not IL-36β and IL-36γ, was distinctly induced at osmolarity-dependent manner while two antagonist IL-36RA and IL-38 were significantly suppressed in HCECs exposed to hyperosmotic stress. IL-36α increased to 4.4-fold in mRNA and 6.9-fold at protein levels by 450 mOsM, but dramatically inhibited by addition of rhIL-36RA or rhIL-38. Exogenous rhIL-36α stimulated expression of TNF-α and IL-1β at mRNA and protein levels and disrupted tight junction proteins ZO-1 and occludin. However, rhIL-36RA or rhIL-38 suppressed TNF-α and IL-1β production and protected corneal barrier from disruption in response to IL-36α or hyperosmolarity. In C57BL/6 mice, desiccating stress stimulated IL-36α expression, inhibited IL-38 levels, and disrupted the integrity of ZO-1 and occludin in cornea and/or conjunctival epithelium.
Conclusions :
Our findings demonstrate that the stimulated pro-inflammatory IL-36α with the suppressed antagonists IL-36RA and IL-38 is a novel mechanism by which hyperosmolarity and desiccating stress induces inflammation in dry eye model in vitro and in vivo, respectively. IL-36RA and IL-38 may have a therapeutic potential in dry eye.
This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.