Combination of isobavachalcone and amphotericin B has antifungal effect against Cryptococcus neoformans and protects host tissue damage by inhibiting ferroptosis.

Despite recent advancements in antifungal therapy, the antifungal armamentarium remains limited compared to antibiotics available for bacterial infections. Developing novel and effective therapeutic strategies is imperative but challenging. One promising approach involves synergizing existing antifungals with complementary agents to enhance efficacy and reduce the required dosages. This study investigates the synergistic effect of isobavachalcone (IBC) and amphotericin B (AmB) against Cryptococcus neoformans in vitro and in vivo, focusing on ferroptosis modulation. Ferroptosis-related markers, including glutathione (GSH), malondialdehyde (MDA), ferrous ions, and reactive oxygen species (ROS), were analyzed in Caenorhabditis elegans model infected with C. neoformans. IBC (4 μg/mL) significantly lowered AmB's MIC from 1 μg/mL to 0.25 μg/mL, indicating a fourfold enhancement in potency. The IBC-AmB combination caused structural damage to C. neoformans, compromising membrane permeability and cell wall integrity. The combination elevated host GSH levels while reducing ferrous ions, MDA, and ROS in the infected C. elegans model. Mechanistically, the treatment upregulated antioxidant/stress response genes (SKN-1, GST-4, GST-5, GPX-1, DAF-16, CNC-11) and antimicrobial peptides (NLP-29). Conversely, the pro-inflammatory pathway gene PMK-1 was downregulated. The IBC-AmB combination not only reduces the MIC of AmB by fourfold but also enhances antifungal efficacy through a multifaceted mechanism that directly targets the fungal pathogen and modulates the host response. This dual action has the potential to reduce the adverse effects of AmB and improve therapeutic outcomes in the treatment of cryptococcal infections.