Upregulation of NLRP3 inflammasome components in Mooren's ulcer

Mooren's ulcer (MU) is a peripheral corneal ulceration of presumed autoimmune etiology. NLRP3 inflammasome has been shown to be involved in a variety of autoimmune and auto-inflammatory diseases. However, the role of NLRP3 inflammasome in MU has not been investigated. Here, we evaluate the expression of NLRP3 inflammasome and its downstream inflammatory factors in human MU. Conjunctival biopsy specimens were obtained from seven patients with MU and six healthy donors. The removed conjunctivas were histopathologically evaluated for NLRP3 inflammasome component expression using antibodies directed against NLRP3, Caspase-1 (CASP1), and Interleukin-1 beta (IL-1 beta). Quantitative real-time PCR was used to measure the mRNA expression of NLRP3 and IL-1 beta, and the protein expressions of NLRP3, pro-CASP1, CASP1, and IL-1 beta were detected by Western blotting. NLRP3 and IL-1 beta mRNA expression showed higher levels in the MU group than in healthy controls. Western-blot and immunofluorescence analysis also showed that basal expression of NLRP3 inflammasome components (NLRP3, CAPS1, and IL-1 beta) was elevated in patients with MU compared with healthy controls. Most importantly, we found that the cleavaged form of CASP1 and IL-1 beta was significantly increased in MU patients compared with healthy donors, which indicates that the upregulation of NLRP3 inflammasome was probably responsible for the enhanced IL-1 beta production in MU patients. This study demonstrated that the expression of the NLRP3-CASP1-IL-1 beta signaling pathway was markedly increased in the conjunctival lesions of patients with MU, suggesting the involvement of NLRP3 inflammasome in the onset and development of the inflammation in MU.