Abstract
AIM: To investigate the anti-inflammatory and neurorestorative effects of neuroprotectin D1 (NPD1) in Aspergillus fumigatus (A. fumigatus) keratitis in C57BL/6 mice. METHODS: The left corneas of C57BL/6 mice were infected with A. fumigatus. Each mouse was injected intraperitoneally with 2 µg NPD1 at 1, 3, and 5d post infection (p.i.) and injected subconjunctivally with 5 µL NPD1 once a day. The severity of keratitis was observed by slit lamp and classified by clinical score at 1, 3, and 5d p.i. Hematoxylin and eosin (HE) staining was used to evaluate the histological changes and inflammatory cell infiltration of corneas at 3 and 5d p.i. Polymerase chain reaction (PCR), enzyme-linked immunosorbent assay (ELISA), and Western blot were performed to detect the expression of IL-1β, MIP-2, CGRP, p-p38/p38 MAPK, Nrf-2, and HO-1. Immunofluorescence staining was utilized to assess the neutrophil infiltration and neural innervation. Flow cytometry assay was performed to test the number of total, M1 and M2 macrophages. RESULTS: In A. fumigatus infected C57BL/6 mice, NPD1 treatment ameliorated the severity of keratitis. Compared with the phosphate-buffered saline (PBS) control group, NPD1 treatment inhibited the infiltration of neutrophils and macrophages, increased the ratio of CD206(+)/CD86(+) macrophages, reduced the phosphorylation level of p38 MAPK, and enhanced the expression of Nrf-2/HO-1 at 3d p.i. The number of corneal nerves and the mechanical sensitivity threshold of the NPD1 treatment group were significantly higher than the PBS group at 3 and 5d p.i. Meanwhile, the expression of IL-1β and MIP-2 in the NPD1 treatment group was significantly lower at 3 and 5d p.i. CONCLUSION: NPD1 improves the prognosis of A. fumigatus keratitis in mice by inhibiting the recruitment of neutrophils and macrophages, promoting M2 macrophage polarization and corneal nerve regeneration.