Evaluation of the Anti-Histoplasma capsulatum Activity of Indole and Nitrofuran Derivatives and Their Pharmacological Safety in Three-Dimensional Cell Cultures

Abstract

Histoplasma capsulatum is a fungus that causes histoplasmosis. The increased evolution of microbial resistance and the adverse effects of current antifungals help new drugs to emerge. In this work, fifty-four nitrofurans and indoles were tested against the H. capsulatum EH-315 strain. Compounds with a minimum inhibitory concentration (MIC90) equal to or lower than 7.81 µg/mL were selected to evaluate their MIC90 on ATCC G217-B strain and their minimum fungicide concentration (MFC) on both strains. The quantification of membrane ergosterol, cell wall integrity, the production of reactive oxygen species, and the induction of death by necrosis–apoptosis was performed to investigate the mechanism of action of compounds 7, 11, and 32. These compounds could reduce the extracted sterol and induce necrotic cell death, similarly to itraconazole. Moreover, 7 and 11 damaged the cell wall, causing flaws in the contour (11), or changing the size and shape of the fungal cell wall (7). Furthermore, 7 and 32 induced reactive oxygen species (ROS) formation higher than 11 and control. Finally, the cytotoxicity was measured in two models of cell culture, i.e., monolayers (cells are flat) and a three-dimensional (3D) model, where they present a spheroidal conformation. Cytotoxicity assays in the 3D model showed a lower toxicity in the compounds than those performed on cell monolayers. Overall, these results suggest that derivatives of nitrofurans and indoles are promising compounds for the treatment of histoplasmosis.

Mebendazole Inhibits Histoplasma capsulatum In Vitro Growth and Decreases Mitochondrion and Cytoskeleton Protein Levels

“…A more accessible alternative is drug repurposing, a strategy to identify new uses for existing and marketed drugs for treatments different from those initially described [ 41 ]. Some studies point to promising drug repurposing results for Histoplasma [ 19 , 20 ], Cryptococcus [ 26 , 42 ], and Paracoccidioides infections [ 43 ]. In fact, due to the paucity of currently approved antifungal drugs, more repurposing studies for these life-threatening pathogens are necessary.…”

“…This drug inhibited Histoplasma growth in vitro and in a macrophage infection model with low host cell cytotoxicity [ 19 ]. Another study points to nitrofuran and indole derivatives as promising drugs for histoplasmosis treatment [ 20 ]. Nitrofurans are described as antibiotics with a broad spectrum of action [ 21 ] and chemical compounds containing indole rings have been explored in different applications, such as cancer, microbial and viral infections, as well as inflammation [ 22 , 23 ].…”