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-alpha [TNF-alpha], interleukin [IL]-1beta, 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-1beta and TNF-alpha 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-alpha, IL-1beta, 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.