α- MSH Plays Anti-inflammatory and Anti-fungal Role in Aspergillus Fumigatus Keratitis

ABSTRACT

Purpose

To investigate the anti-inflammatory and antifungal role of α-melanocyte stimulating hormone (α-MSH) in Aspergillus Fumigatus (A. fumigatus) keratitis.

Method

Corneas of C57BL/6 mice were infected with A. Fumigatus. α-MSH (5 ul, 1×10⁻⁴ mmol/ml) was given by subconjunctival injection from day 1 to day 3 post infection (p.i.). After 3 days p.i., clinical score was recorded and HE staining was tested. Fungal load in mice corneas was observed by plate counting. Proinflammatory mediators and pattern recognition receptors (PRRs) were detected. The number of neutrophils and macrophages was tested by immunofluorescence staining. The role of α-MSH in RAW264.7 cells after A. fumigatus stimulation were evaluated by PCR and Western blot, and MPKA protein levels including total-JNK (T-JNK), phosphorylated-JNK (P-JNK), total-ERK (T-ERK), and phosphorylated-ERK (P-ERK) were tested via Western blot with or without α-MSH treatment.

Results

Compared with PBS control group, α-MSH treatment alleviated disease response and decreased clinical score at 3 days p.i. HE staining showed less infiltration in corneal tissue after α-MSH treatment. Plate counting experiment showed that number of viable fungus in corneas of α-MSH treated group was less than control group. mRNA levels of IL-1β, TNF-α, IL-6, MIP-2, LOX-1, Dectin-1, and iNOS were decreased. Protein levels of IL-1β, TNF-α, IL-6, and Dectin-1 were decreased. α-MSH treatment also decreased the infiltrating neutrophils and macrophages. The levels of proinflammatory cytokines, Dectin-1 and LOX-1 stimulated by A. fumigatus, were also suppressed by pretreatment of α-MSH in RAW264.7 cells. The ratio of P-JNK/T-JNK and P-ERK/T-ERK was downregulated in α-MSH group compared with PBS control group.

Conclusion

α-MSH alleviates the severity and decreases fungal load of A. fumigatus keratitis in mice. Migration of neutrophils and macrophages are restrained. α-MSH downregulates the expression of dectin-1 and the ratio of P-JNK/T-JNK and P-ERK/T-ERK in A. fumigatus infection.

KEYWORDS:

• α-msh
• Aspergillus fumigates
• inflammation
• macrophages
• neutrophils

Author’s contributions

Cui Li, Mengqi Wu, Lingwen Gu, and Min Yin carried out most of the experimental work. Jing Lin, Nan Jiang, and Qian Wang conducted cellular experiments. Hui Li, Yuan Wu, and Qiang Xu conducted the cell culture and immunofluorescent staining. Cui Li and Guiqiu Zhao supervised the project and wrote the manuscript. All authors reviewed the manuscript.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was supported by National Natural Science Foundation of China (81800800); Taishan Scholars Program (tsqn 202103188).