Dectin-1 agonist curdlan modulates innate immunity to Aspergillus fumigatus in human corneal epithelial cells

AIM: To explore the immunomodulatory effects of curdlan on innate immune responses against Aspergillus. fumigatus (A. fumigatus) in cultured human corneal epithelial cells (HCECs), and whether C -type lectin receptor Dectin -1 mediates the immunomodulatory effects of curdlan. METHODS: The HCECs were stimulated by curdlan in different concentrations (50, 100, 200, 400 mu g/mL) for various time. Then HCECs pretreated with or without laminarin (Dectin -1 blocker, 0.3 mg/mL) and curdlan were stimulated by A. fumigatus hyphae. The mRNA and protein production of tumor necrosis factor -alpha (TNF-alpha) and interleukin -6 (IL-6) were determined by real-time quantitative polymerase chain reaction and enzyme linked immunosorbent assay, respectively. The protein level of Dectin-1 was measured by Western blot. RESULTS: Curdlan stimulated mRNA expression of TNF-a and IL-6 in a dose and time dependent manner in HCECs. Curdlan pretreatment before A. fumigatus hyphae stimulation significantly enhanced the expression of TNF-alpha and IL-6 at mRNA and protein levels compared with A. fumigatus hyphae stimulation group (P<0.05). Both curdlan and A. fumigatus hyphae up -regulated Dectin -1 protein expression in HCECs, and Dectin -1 expression was elevated to 1.5- to 2 -fold by curdlan pretreatment followed hyphae stimulation. The Dectin -1 blocker laminarin suppressed the mRNA expression and protein production of TNF-alpha and IL -6 induced by curdlan and hyphae (P<0.05). CONCLUSION: These findings demonstrated that curdlan pretreatment enhanced the inflammatory response induced by A. fumigatus hyphae in HCECs. Dectin -1 is essential for the immunomodulatory effects of curdlan. Curdlan may have high clinical application values in fungal keratitis treatment.