Role of antioxidants in regulating anti-fungal drug resistance in the pathogenic fungus Cryptococcus neoformans

Cryptococcus neoformans is an encapsulated yeast causing deadly meningitis in severely immunocompromisedhosts. The antifungal drug fluconazole (FLU) causes cell growth defects in C. neoformans by preventing ergosterol production. Previous studies suggested that FLU leads to a moderate increase in reactive oxygen species (ROS) in adifferent yeast, Candida albicans. Using a variety of assays, we determined that FLU leads to an increase in ROS in C.neoformans.Treatment with antioxidants leads to reduced ROS in the presence of FLU and rescue of FLU -induced inhibition of growth. Further, we found that mutants lacking the metallothionein proteins, Cmt1 and Cmt2, are moresensitive to FLC and do not rescue cell death and ROS induced by FLC. Metallothionein genes regulate copperhomeostasis, scavenge free radicals, and are upregulated during oxidative stress in Candida albicans. Our study indicates that FLC causes a moderate increase in ROS in C. neoformans and identifies the metallothionein proteins to be involved in FLU resistance in C. neoformans