A Study On Molecular Mechanism Of Dexamethasone Inhibiting Pyroptosis In Corneal Alkali Burn

Background: Corneal alkali burn（CAB）is a serious clinical chemical ocular injury.Considerable studies have shown that the pathological mechanism of corneal injuries mediated by alkali burns are associated with Nucleotide-binding oligomerization domain（NOD）-like receptor（NLR）family pyrin domain containing3 protein（NLRP3）-related corneal sterile inflammation.Both NLRP3 inflammasome mediated pyroptosis-associated signaling factors and the executive protein GSDMD of pyroptosis are present in CAB remain to be investigated.Dexamethasone（Dex）is a commonly used drug for ocular surface diseases that can maintain corneal transparency and anti-inflammatory effects by early topical administration.However,the effect of dexamethasone in the early treatment of CAB is still unclear.Objective: The purpose of this study is to explore the relationship between the pathological mechanism of corneal alkali burn and pyroptosis.We also want to know that the effect of dexamethasone on the expression of caspase-1/GSDMD signaling pathway in the early treatment of corneal alkali burn.This experiment is expected to provide a novel theoretical basis for the pathological mechanism and treatment of corneal alkali burns.Methods: The alkali burn model of C57BL/6 mice was established in our study.Healthy female C57BL/6 adult mice were numbered and randomly divided into four groups: control group（unburned healthy cornea）,placebo group（CAB+PBS）,0.05%Dex group（CAB+0.05%Dex）and 0.1% Dex group（CAB+0.1%Dex）.Corneas of mice in each group were observed and analyzed on day 3 and day 7 after burn.The corneal morphology of each group was observed by HE staining,and the expression levels of related factors（NLRP3,caspase-1,cleaved-caspase-1,GSDMD,GSDMD-N,pro-IL-1β,pro-IL-18,IL-1β and IL-18）in the classical pathway of pyroptosis were detected by immunofluorescence（IF）,real-time quantitative PCR（RT-PCR）and western blot（WB）.Results:（1）After alkali burn（day 3 and day 7）,the corneal opacity score and neovascularization score of mice in the 0.05%Dex group and 0.1%Dex group were lower than those in the placebo group,respectively,with statistically significant differences among the three groups.HE staining sections of each group showed that the degree of corneal epithelial defect and stromal corneal edema in Dex groups of different concentrations were significantly improved compared with placebo group.（2）The results of IF,RT-PCR and WB showed that the expression trends of Inflammation factors were approximately the similarity,and the differences were statistically significant.Compared with the control group,the expression of inflammatory factors（NLRP3,pro-IL-1 β,pro-IL-18,IL-1β and IL-18）in the corneal tissues of mice in the placebo group was significantly up-regulated on day 3 and slightly decreased on day 7,while the expression of inflammatory factors in the corneal tissues of mice in the Dex group were inhibited.（3）Compared with the control group,the expression level of key proteins（caspase-1,C-caspase-1,GSDMD,GSDMD-N）associated with pyroptosis in the corneal tissues of mice in the placebo group increased（day 3 was higher than day 7）,and the expression level of key proteins associated with pyroptosis in the corneal tissues of mice in the Dex group were inhibited.Similarly,the results of IF,RT-PCR and WB showed similar trends,and the differences were statistically significant.Conclusion: Early topical application of dexamethasone can reduce corneal injury and corneal neovascularization after alkali burn.Dexamethasone can inhibit the activation of caspase-1/GSDMD signaling pathway in alkali-burned corneal tissues,thereby reducing corneal inflammation and maintaining corneal transparency.