Investigation of the action mechanism and the antifungal effect of urease inhibitors on Cryptococcus spp.

• Grant number: 20/04229-6
• Support type: Scholarships in Brazil - Doctorate
• Effective date (Start): November 01, 2021
• Effective date (End): February 28, 2025
• Field of knowledge: Biological Sciences - Microbiology
• Principal researcher: Kelly Ishida
• Grantee: Thayná Lopes Barreto
• Home Institution: Instituto de Ciências Biomédicas (ICB). Universidade de São Paulo (USP). São Paulo , SP, Brazil

Abstract

Cryptococcosis is a mycosis caused by Cryptococcus spp. with high incidence in HIV/AIDS patients leading to high rates of mortality and morbidity. Current therapy is based on the combination of antifungals amphotericin B, fluconazole and 5-fluorocytosine. Although resistance to antifungals in Cryptococcus is relatively uncommon, the risk of developing tolerance or heteroresistance in patients with relapses has been reported. In addition, other factors such as high toxicity, unfavorable pharmacokinetics, high cost and unavailability further reduce the therapeutic options for cryptococcosis. Thus, new antifungal molecules are being researched in recent years, approaching new targets of action, and the enzyme urease can be an interesting candidate. The urease produced by Cryptococcus spp. catalyzes the hydrolysis of urea into ammonia, which weakens the endothelial wall of the blood-brain barrier, facilitating the access of the pathogen into the central nervous system, an important step in establishing cryptococcal meningitis. Considering that urease is naturally absent in humans, enzyme inhibition can be an interesting strategy in the treatment of cryptococcal meningitis, mainly in association with conventional antifungals. Some urease inhibitors proposed in this project were previously tested in other microorganisms confirming the inhibition of enzymatic activity. In this project we will investigate synthetic molecules of new chemical classes for the control of cryptococcosis, aiming at a different target from conventional antifungals. Thus, we will evaluate the molecular interaction and inhibitory activity of the inhibitors with the purified urease, the antifungal activity of these inhibitors on the planktonic and biofilm cells of Cryptococcus spp., and finally, evaluate the effect of these inhibitors on the parasite-host interaction in mammalian cells and in vivo models of infection. (AU)