NLRP12- and NLRC4-mediated corneal epithelial pyroptosis is driven by GSDMD cleavage accompanied by IL-33 processing in dry eye

Dry eye disease (DED) is a common and multifactor-induced autoimmune ocular surface disease. Environmental factors, such as desiccating stress (DS) and hyperosmolarity, affect the corneal epithelium to induce ocular surface inflammation in DED. We aimed to explore the potential mechanisms by which innate immunity and pyroptosis are initiated in the mucosal epithelium in response to environmental stress. Experimental dry eye was established in C57BL/6 J mice and genetic mice on the background of C57BL/6 J mice by subcutaneous injection of scopolamine and exposure to a desiccating environment. SDHCEC cell line was subjected to hyperosmolarity stress (450 mOsM). The phenol red thread tear test and corneal epithelial defects evaluation were used as assessments of severity of DED. RNA-sequencing, quantitative real-time PCR, western blotting and immunofluorescence staining were performed in this study. Loss-of-function studies indicated that genetic deletion of GSDMD alleviates DS-induced corneal epithelium defects, and GSDMD is needed for IL-33 processing. We further found that NLRP12 collaborates with NLRC4 inflammasome to initiate GSDMD-dependent pyroptosis, which requires TLR4-induced caspase-8 (CASP8) activation in the mucosal corneal epithelium in response to DS. These findings provide compelling evidence that GSDMD-dependent pyroptosis plays a pivotal role in DED. A novel mechanism involving NLRP12 and NLRC4 inflammasomes-induced GSDMD-dependent pyroptosis, accompanied by IL-33 processing is responsible for ocular surface epithelial defects in response to environmental stress. GSDMD is required for IL-33 processing and the subsequent amplification of inflammatory cascades. These findings reveal novel therapeutic targets for treating DED.