Eugenol attenuates the inflammation of Fusarium-induced keratitis through PI3K/AKT signaling pathway

Abstract

AIM: To investigate the protective effect of eugenol against Fusarium solani(F.solani)-induced fungal keratitis(FK)in mice and to preliminarily explore possible underlying mechanisms.METHODS: A modified epifluorescence microscopy method was used to prepare the FK mouse model. An equal amount of DMSO(0.05%)was applied to the conjunctiva of the right eye of rats in the dimethyl sulfoxide(DMSO)group. The eugenol group was prepared by applying eugenol(160 μg/mL)to the conjunctival sac of the right eye of mice. The insulin-like growth factor-1(IGF-1)group was coated with the PI3K/AKT pathway activator IGF-1(10 nmol/mL)in the conjunctival sac of the right eye in addition to the administration of eugenol. The corneal morphology was observed under a slit-lamp microscope on days 1, 3, and 5 of inoculation with F.solani suspension, respectively. Hematoxylin eosin(HE)staining was used to assess corneal histopathological damage. The bacterial load of corneal tissue was determined. Enzyme-linked immunosorbent assay and Western blot were used to analyze the levels of inflammatory mediators interleukin-6(IL-6)and interleukin-1β(IL-1β)and the expression of PI3K/AKT pathway proteins.RESULTS: Eugenol treatment improved the morphological symptoms of keratitis and inflammatory response in FK mice, and reduced corneal pathologic tissue damage and fungal load. At 3 d after F.solani infection, corneal tissue IL-6 levels were significantly higher and IL-1β levels were significantly lower in the eugenol group compared with the DMSO group(both P<0.05); corneal tissue IL-6 levels were significantly higher and IL-1β levels were significantly lower in the eugenol group than in the IGF-1 group(both P<0.05). At 5 d after infection, both IL-6 and IL-1β levels in corneal tissue of the eugenol group were significantly lower than those of the DMSO and IGF-1 groups(P<0.05); compared with the DMSO group, the expression of p-PI3K and p-Akt in the corneal tissues of the eugenol group was significantly reduced(P<0.05); the expression of p-PI3K and p-Akt in corneal tissues was significantly lower in the eugenol group than that of the IGF-1 group(both P<0.05).CONCLUSION: Eugenol may attenuate F.solani-induced corneal inflammation by inhibiting the PI3K/AKT pathway, and it has a protective effect against F.solani keratitis in mice.

Keywords

• eugenol
• fungal keratitis
• pi3k/akt pathway
• inflammatory response
• fungal load