Purchase this article with an account.
Xia Hua, Xiaoyong Yuan, Wei Chi, Jin Li, Zongduan Zhang, Stephen C Pflugfelder, De-Quan Li; Protective Role and Mechanism of NLRP3/Caspase-1 Inflammasome Induced IL-33 Production by Corneal Epithelium in Fungal Keratitis. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):1881.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
To explore the protective role and mechanism of innate immunity by corneal epithelium through NLRP3/caspase-1 inflammasome-induced IL-33 production in response to fungal infection using Candida albicans (C. albicans) infected fungal keratitis (FK) mouse model and in vitro human corneal epithelial cells (HCECs) exposed to heated killed C. albicans (HKCA).
Fungal keratitis was established in C57BL/6 mice by 106 CFU of C. albicans strain SC5314 isolated from patients. Primary HCECs, established from donor limbal explants, were challenged by HKCA (104-106 cells/ml) with or without prior incubation of inhibitors to NLRP3 (glybenclamide), caspase-1 (z-YVAD fmk) or dectin-1 (laminarin and syk inhibitor). The production and/or activity of NLRP3 inflammasome associated molecules and IL-33 were evaluated by reverse transcription and quantitative real time PCR (RT-qPCR), immunofluorescent staining, caspase activity assays, ELISA and Western blot analysis. FK mice were also treated by recombinant mature form of mouse IL-33 (rmIL-33) to evaluate its efficacy.
The mRNA and protein levles of IL-33 was found to be significantly induced, which accompanied by increased production and activity of NLRP3, ASC, caspase-1, in FK mice compared with the mock mice as controls. The dose-dependent production and activity of NLRP3 inflammasome and IL-33 were also observed in HCECs exposed to HKCA compared to normal control. Glybenclamide inhibited NLRP3 activation, and also blocked the activation of caspase-1. Both inhibitors to NLRP3 or caspase-1 suppressed maturation of IL-33. Interestingly, IL-33 maturation and NLRP3 activation were also suppressed in HCECs exposed to HKCA with pretreated dectin-1 inhibitors (laminarin and syk inhibitor) and NF-ĸB inhibitors (BAY11-7082 and quinazoline). Furthermore, the keratitis was attenuated in severity and recovered rapidly by rmIL-33 subconjunctival injection, while it was exacerbated with treatment of inhibitors to NLRP3 or caspase-1in FK mice.
Our findings reveal a novel mechanism and signaling pathway of innate immunity by corneal epithelium, which produces IL-33 through dectin-1 mediated activation of NLRP3/caspase-1 inflammasome to defense against C. albicans invasion in fungal keratitis. The studies provide new insight in the innate immunity that protects cornea from fungal infection.
This PDF is available to Subscribers Only