IL-6 induction in desiccated corneal epithelium in vitro and in vivo

PURPOSE To investigate the effect of desiccation on secretion of inflammatory cytokines in corneal epithelial cells and in the rat desiccation model. METHODS A human corneal epithelial cell line (CEPI) was grown in keratinocyte growth medium 2 (KGM2) to approximately 80% confluence. The medium was aspirated and dishes were left for 0 to 30 min with the cover left open to dry the cells (short-term desiccation). After desiccation, KGM2 was added to the dishes and collected from the dishes 15 min later to measure the concentrations of cytokines in the medium by sandwich enzyme immunoassay (ELISA). Viability of the cells was estimated with alamer blue. To study the effect of long-term desiccation, cultivated cells on transwells were used. After dessiccation for up to 8 h, the viability of the cells and levels of cytokines in the culture medium were examined. The expression of cytokines in the cornea of the dry eye model rat was measured by real-time PCR. RESULTS Short-term dessication of CEPI cells significantly increased the interleukin (IL)-6 level and slightly increased the tumor necrosis factor (TNF)-α level. Anti-IL-6 antibody partially suppressed cell death caused by desiccation. Upon long-term desiccation, IL-6 and IL-8 levels were increased. 
In the dry eye model rats, the IL-6 mRNA level in the cornea significantly increased, whereas TNF-α mRNA level slightly increased. CONCLUSIONS Desiccation induced IL-6 expression in corneal epithelial cells, suggesting that IL-6 participates in desiccation-induced cell death.