Piperine inhibits fungal growth and protects against pyroptosis in Aspergillus fumigatus keratitis by regulating the mTOR/HIF-1α pathway.

PURPOSE

To confirm the antifungal ability of piperine (PIP) and to assess its therapeutic potential in the treatment of Aspergillus fumigatus (A. fumigatus) keratitis.

METHODS

The toxicity of PIP was measured to determine the optimal therapeutic concentration both in human corneal epithelial cells (HCECs), RAW264.7 cells and mice fungal keratitis models. The antifungal efficacy of PIP was confirmed through the minimum inhibitory concentration (MIC) test, biofilm formation inhibition test, Calcofluor white and PI staining, and anti-adhesion of A. fumigatus conidia test. Hematoxylin-eosin (HE) staining, corneal fungal load assay, RT-qPCR, western blot, and Elisa were used to assess the therapeutic effect and anti-inflammatory ability of PIP in fungal keratitis. The significance of the mTOR/HIF-1α signal pathway after PIP treatment of A. fumigatus keratitis was evaluated.

RESULTS

PIP had no obvious toxicity to HCECs, RAW 264.7 cells, or mouse cornea at the concentration of 30 µg/mL. PIP effectively inhibited A. fumigatus from growing and showed synergistic effects when combined with NATA. PIP not only reduced fungal load and the aggregation of inflammatory cells, but also dramatically reduced the expression levels of NLRP3, caspase-1, cleaved caspase-1, GSDMD, GSDMD-N, IL-18, and IL-1β, which were linked to pyroptosis. Additionally, PIP decreased mTOR phosphorylation and HIF-1α expression. The pretreatment with mTOR agonists reversed the inhibition of NLRP3, caspase-1, cleaved caspase-1, GSDMD, GSDMD-N, IL-18, and IL-1β protein levels caused by PIP.

CONCLUSION

PIP exhibited antifungal and anti-inflammatory properties, and alleviated pyroptosis in A. fumigatus keratitis via inhibiting the mTOR/HIF-1α signaling pathway.