Glucocorticoids inhibit the innate immune system of human corneal fibroblast through their suppression of toll-like receptors

PURPOSE To evaluate the effect of glucocorticoids on the expression and function of Toll-like receptors (TLRs) in human corneal fibroblasts (HCFs). METHODS Cultured HCF cells were stimulated with three different concentrations of hydrocortisone. The effect on the expression of TLR2 and TLR4 was determined by real-time PCR. The TLR2, TLR4, and pIkappaB-alpha proteins were compared by western blot. The release of IL-6 and IL-8 was measured using enzyme-linked immunosorbent assay in the presence and absence of TLR2 and TLR4-specific blocking antibodies. RESULTS Incubation of HCFs with hydrocortisone markedly inhibited the expression of TLR2 and TLR4 mRNAs and decreased the release of IL-6 and IL-8 in a dose-dependent manner. Western blot analysis confirmed that expression of TLR2, TLR4, and pIkappaB-alpha was also downregulated in response to hydrocortisone. The result of ELISA also showed the release of IL-6 and IL-8 can also be inhibited by hydrocortisone. However, all these inhibitions were counteracted after pretreatment with anti-TLR2 and anti-TLR4 monoclonal antibodies. CONCLUSIONS Glucocorticoids, such as hydrocortisone, can inhibit the expression of TLR2 and TLR4 on HCFs, and thus may increase susceptibility to cornea infections. Our results suggest that topical glucocorticoids may affect the cornea's innate immunity through TLRs.