Expression of macrophage migration inhibitory factor in keratitis.

Aim: To investigate the expression of macrophage migration inhibitory factor (MIF) and detect its role in the innate immune response of fungal keratitis (FK).

Methods: We collected the paraffin-embedded cornea tissues from 10 FK and 6 ocular trauma patients to explore the MIF expression by immunohistochemistry. Then we cultured telomease-immortalized human corneal epithelial cells (THCEs), stimulated by the hyphae suspension of () to detect the change of MIF with or without the pretreatment of MIF inhibitor [4-Iodo-6-phenylpyrimidine (4-IPP)] by real-time polymerase chain reaction (PCR). The protein level of MIF was also tested by immunohistochemistry, and the level of tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6) mRNA were compared between normal, hyphae stimulated and 4-IPP pretreated groups by real-time PCR to study the influence of MIF on the expression of TNF-α and IL-6. Corneal severity of rats' FK models was documented by clinical scores, and real-time PCR. Western blot and immunohistochemistry were used to test the expression of MIF, TNF-α and IL-6 in rats' corneas.

Results: In the corneas of FK patients, there was much stronger expression of MIF than that in the normal group showed by immunohistochemistry. In cultured THCEs stimulated by , the expression of MIF became stronger in both immunohistochemistry and PCR at 16, 24, 32 and 48h post infection (p.i.; <0.01, <0.01, <0.01, <0.05). After pretreated with 4-IPP, the expression of MIF reduced at 4, 8, 16h p.i. (<0.05, <0.05, <0.05) and the downstream TNF-α and IL-6 decreased obviously (<0.05, <0.01). In rats with keratitis, the relative mRNA and protein level of MIF increased than those in the normal group by PCR (at 1d: <0.01, 3d: <0.01, 5d: <0.01), Western blot and immunohistochemistry. After blocked MIF with 4-IPP, the clinical outcomes of rat keratitis showed markedly reduced inflammatory response (<0.01), with TNF-α and IL-6 decreased in accordance with those in THCEs by PCR (<0.05, <0.01).

Conclusion: The expression of MIF increased significantly in FK patients, THCEs and rats stimulated by . After blocked with 4-IPP, the expression of MIF reduced, and so did its downstream cytokines: TNF-α and IL-6. The inflammation reaction of the rats' corneas lightened after pretreated with 4-IPP. MIF may play a role in the innate immune response of the corneal resistance against .