The Therapeutic Role and Mechanism of Glabridin Under Aspergillus fumigatus Infection.

Purpose: To characterize the efficiency of glabridin alone and in combination with clinical antifungals in Aspergillus fumigatus keratitis. Methods: The broth microdilution method was performed to investigate whether glabridin exerted an antifungal role on planktonic cells and immature and mature biofilm. Antifungal mechanism was evaluated by Sorbitol and Ergosterol Assays. The synergistic effect of glabridin and antifungals was assessed through the checkerboard microdilution method and time-killing test. Regarding anti-inflammatory role, inflammatory substances induced by A. fumigatus were assessed by real-time quantitative polymerase chain reaction, western blot, and enzyme-linked immunosorbent assay. Drug toxicity was assessed by Draize test in vivo. Macrophage phenotypes were examined by flow cytometry. Results: Regarding antifungal activity, glabridin destroyed fungal cell wall and membrane on planktonic cells and suppressed immature and mature biofilm formation. After combining with natamycin or amphotericin B, glabridin possessed a potent synergistic effect against A. fumigatus. Regarding anti-inflammatory aspects, Dectin-1, toll‑like receptor (TLR)-2 and TLR-4 expression of human corneal epithelial cells were significantly elevated after A. fumigatus challenge and reduced by glabridin. The elevated expression of interleukin-1β and tumor necrosis factor-alpha induced by A. fumigatus or corresponding agonists were reversed by glabridin, equivalent to the effect of corresponding inhibitors. Glabridin could also contribute to anti-inflammation by downregulating inflammatory mediator expression to suppress macrophage infiltration. Conclusions: Glabridin contributed to fungal clearance by destroying fungal cell wall and membrane, and disrupting biofilm. Combining glabridin with clinical antifungals was superior in reducing A. fumigatus growth. Glabridin exerted an anti-inflammatory effect by downregulating proinflammatory substance expression and inhibiting macrophage infiltration, which provide a potential agent and treatment strategies for fungal keratitis.