Sennoside A alleviates fungal keratitis by modulating inflammation and immune responses through the caspase-1/GSDMD pathway.

PURPOSE: This study was designed to systematically investigate the therapeutic efficacy and mechanistic underpinnings of the natural plant-derived anthraquinone glycoside, sennoside A (SA), in fungal keratitis.

METHODS

We rigorously assessed the safety and therapeutic efficacy of SA in primary peripheral blood neutrophils, THP-1 macrophages, and mouse corneas. Safety was evaluated using CCK-8 viability assays and corneal fluorescein sodium staining. Therapeutic outcomes and immune responses were determined through clinical scoring, hematoxylin-eosin (H&E) staining, immunofluorescence (IF), myeloperoxidase (MPO) activity assays, and flow cytometry. Anti-inflammatory mechanisms were investigated by quantifying caspase-1 and GSDMD protein expression, together with downstream IL-1β and IL-18 mRNA and protein levels, using quantitative real-time PCR (qRT-PCR), Western blotting, and IF. Meanwhile, we explored the translational potential of combining SA with the antifungal agent natamycin.

RESULTS

SA (100 μg/mL) showed no toxicity to cells, corneas, or organs. It significantly reduced corneal clouding, swelling, and clinical severity scores in infected mice. Treatment also decreased the recruitment of pathogenic immune cells (neutrophils/macrophages) and shifted macrophages toward a repair-promoting phenotype. SA inhibited the caspase-1/GSDMD inflammatory pathway, leading to reduced levels of key inflammatory cytokines (IL-1β, IL-18). When combined with natamycin, SA provided better protection than either treatment alone.

CONCLUSION

SA effectively mitigated fungal keratitis-induced damage by suppressing harmful inflammation and modulating immune responses. Its synergistic action with existing antifungal therapies underscores its promising clinical potential.