Indoleamine 2,3-dioxygenase adjusts neutrophils recruitment and chemotaxis in keratitis.

AIM

To explore the effect of indoleamine 2,3-dioxygenase (IDO) on recruitment and chemotaxis function of neutrophils in keratitis.

METHODS

C57BL/6 mice models of keratitis were established by inoculating hyphae of evenly on the corneas. The clinical scores and inflammatory cytokines expression were measured respectively on the 1, 3, 5 day after infection. The 1-MT (1 mg/mL) was administered by gavage to exert an inhibitory effect on IDO during infection. The mice were divided into control group, 1-MT group, (A.F.) group, and 1-MT+A.F. groups. The corneas were monitored by slit lamp microscopy, and recorded disease scores in 3d after infection. Myeloperoxidase (MPO) assay was done to evaluate the neutrophils infiltration. Immunofluorescence staining was used to detect the recruitment of neutrophils in murine corneas. The mRNA of inflammatory cytokines was measured with reverse transcription-polymerase chain reaction (RT-PCR).

RESULTS

The corneal inflammation and the clinical score reached the peak on the 3 day after the corneal infection. The mRNA of inflammatory cytokines of the A.F. group reached the highest on the 3 day after the infection accordingly. Meanwhile, the results of slit light photography indicated that inhibitors of IDO made inflammation more serious contrasted with the A.F. group on the 3 day. Besides, imunofluorescence staining and MPO indicated that 1-MT enhanced the recruitment, infiltration and chemotaxis of neutrophils obviously in contrast to the A.F. group. RT-PCR indicated that 1-MT increased the expression of CXCL-1, ICAM-1, IL-1β, and IL-8 significantly.

CONCLUSION

IDO participates in the pathogenesis of keratitis and plays an important role in inducing immune protection by inhibiting neutrophils-related inflammatory reaction and suppressing recruitment and chemotaxis of the neutrophils.