Role of Dectin-1 in the innate immune response of rat corneal epithelial cells to Aspergillus fumigatus

Abstract

Background: To observe Dectin-1 expression in fungal keratitis on rat models and to determine the role of Dectin-1 in innate immune response to Aspergillus fumigatus.

Methods: Wistar rats were randomly divided into control, fungal keratitis and pretreatment (pretreated with Laminarin) groups. Samples were used for conducting immunohistochemical staining and real-time PCR to observe expression of cytokines like CCL2, CCL3, CXCL1, CXCL2, IL-1β, TNF-α, IL-6, IL-10.

Results: After fungal stimulations, all 7 inflammatory factors, except IL-10, increased with different levels. After 4 h of fungal stimulations, IL-1β, IL-6, CCL2, CXCL1 and CXCL2 of pretreatment groups were significantly (p < 0.05) lower than fungal groups, while the other 3 cytokines had no significant changes. After 8 h of fungal stimulations, IL-6 and CXCL1 of pretreatment groups were still significantly (p < 0.05) lower than fungal groups.

Discussion: With progress of fungus stimulation, expression of IL-1β,CXCL1 ,CXCL2,MCP-1 gradually increased, whilepretreated with Laminarin to block Dectin-1, these expression decreased, indicating that Dectin-1 maypromote immune reaction through them. IL-10 decreased in fungal group because of itsimmunosuppressive effect at 4h, and it began to increase at 8h to suppress Th1 inflammation response inorder to avoid excessive tissue damage.

Conclusion: Dectin-1 in early period of innate immune responses in rat fungal keratitis might work through IL-1β, IL-6, CCL2, CXCL1, CXCL2 to recruit neutrophils and macrophages to participate anti-fungal immunity.

Fig. 1

Morphology of fungal infections models. a 4 h after fungal infection b 8 h after fungal infection c 16 h after fungal infection d 24 h after fungal infection

Fig. 2

Immunocytochemistry results immunohistochemical staining × 400. a normal rat group b fungal group. The eight inflammatory factors were mainly expressed in cytoplasm in the corneal epithelium and shallow stroma. The fungal groups and pretreatment groups showed clear pictures by comparing with normal rat groups, while there were no obvious difference between fungal groups and pretreatment groups

Fig. 3

Real-time RT-PCR results. After fungal stimulations, all 7 inflammatory factors, except IL-10, increased with different degrees, during which, IL-1β, TNF-α, CCL3 peaked at 16 h and decreased at 24 h, CXCL1 peaked at 4 h, IL-6 peaked at 8 h, CCL2 and CXCL2 continued rising. IL-10 decreased at 4 h, increased from 8 h, peaked at 16 h, and reduced from 24 h

Fig. 4

Real-time RT-PCR results. After 4 h of fungal stimulations, IL-1β, IL-6, CCL2, CXCL1 and CXCL2 of pretreatment groups were lower than fungus groups and was statistically significant (p < 0.05), while the other 3 factors with no statistically significant. After 8 h of fungal stimulations, IL-6 and CXCL1 of pretreatment groups were still lower than fungus groups and was statistically significant (p < 0.05)