Effect of proinflammatory cytokines on the human MUC5AC promoter activity in vitro and in vivo

PURPOSE: To investigate the effect of inflammatory cytokines on the activity of the human MUC5AC promoter in vitro and in vivo. METHODS: Conjunctival epithelial cells transfected with MUC5AC-luciferase plasmids challenged with different cytokines (tumor necrosis factor-α [TNF-α], interleukin [IL]-1β, IL-2, IL-6, and IL-8) at various concentration (1, 10, 20, 50, 100, 200, 500, 1000, and 2000 pg/mL) for 24 hours. A Helio Gene Gun system (Bio-Rad Laboratories, Hercules, CA, USA) was used to deliver MUC5AC-luciferase plasmids into rabbit conjunctivas, which were also challenged with these cytokines (1000 pg/mL) at the frequency of every six hours for 48 hours. The activity of MUC5AC-luciferase was then evaluated using the luciferase assay. RESULTS: Results of the studies demonstrated that IL-1β and TNF-α upregulated the activity of MUC5AC-luciferase in cultured conjunctival cells, while IL-2, IL-6, and IL-8 had no effect. In rabbit conjunctival tissues, TNF-α, IL-1β, IL-2, IL-8, and IL-6 significantly upregulated MUC5AC gene expression. CONCLUSIONS: This suggests that MUC5AC mucin gene expression is regulated by proinflammatory cytokines, which could have implications in ocular surface disorders.