Organoseleniums: antifungal activity and mechanisms of inhibition and death in Cryptococcus gattii

• Grant number: 23/13608-9
• Support Opportunities: Scholarships in Brazil - Doctorate
• Start date: March 01, 2024
• End date: November 30, 2027
• Field of knowledge: Biological Sciences - Microbiology
• Principal Investigator: Kelly Ishida
• Grantee: Letícia Serafim da Costa
• Host Institution: Instituto de Ciências Biomédicas (ICB). Universidade de São Paulo (USP). São Paulo , SP, Brazil

Abstract

The "List of Priority Fungal Pathogens to Guide Research, Development, and Public Health Action" was published by the World Health Organization in 2022. Among the species mentioned in the high-priority category are those of the Cryptococcus genus, responsible for causing cryptococcosis. Cryptococcosis is a mycosis caused by Cryptococcus spp., with the host's lungs serving as the entry organ, which can then disseminate to the central nervous system, resulting in cryptococcal meningitis. Cryptococcus gattii is known to cause mycoses in immunocompetent patients due to its ability to evade the host's immune system cells, as well as its higher tolerance to the drug therapies used for cryptococcosis. Given this fact and the increasing antifungal resistance in various fungal species, the search for new drug therapies to treat pulmonary cryptococcosis and cryptococcal meningitis becomes necessary. Among the various drug development research directions, the search for new molecules and drug repositioning stands out, and these are the paths followed by our research group. Recently, our research group demonstrated the antifungal potential of the organoselenium LQA_78, which showed inhibitory activity in vitro and in an in vivo Galleria mellonella model against C. neoformans and C. gattii species. This makes the compound LQA_78 an interesting target for the development of antifungals against cryptococcosis. Meanwhile, the organoselenium Ebselen has already shown potential as an antifungal against invasive mycoses in a murine model of aspergillosis and candidiasis. Therefore, the present work aims to identify and demonstrate the inhibitory potential of the compounds LQA_78 and Ebselen on C. gattii fungal cells using the broth microdilution technique under C. gattii morphotypes and through the action of the compounds on virulence factors, such as melanin production, laccase enzyme activity, and the quantification of cell wall components. Additionally, the mechanisms of cell death caused by the compounds will be investigated by assessing mitochondrial membrane potential using Rhodamine 123, reactive oxygen species using 2'7'-Dichlorofluorescin Diacetate, DNA fragmentation using TUNEL, and chromatin condensation using Hoechst 33342. Subsequently, the gene expression of virulence and tolerance factors in C. gattii will be evaluated following treatment with LQA_78 or Ebselen. Finally, the action of both compounds will be evaluated in a murine model of cryptococcosis, where infected and treated animals will be subsequently evaluated through histopathological analysis and colony-forming unit counting in the lungs and brain. Therefore, we hope that the current project contributes to providing new perspectives on cryptococcosis treatments and expanding knowledge regarding the use of organoselenium compounds on the treatment of fungal infections.