Potent In Vitro Antiproliferative Synergism of Combinations of Ergosterol Biosynthesis Inhibitors against Leishmania amazonensis

Abstract

e Leishmaniases comprise a spectrum of diseases caused by protozoan parasites of the Leishmania genus. Treatments available have limited safety and efficacy, high costs, and difficult administration. Thus, there is an urgent need for safer and more-effective therapies. Most trypanosomatids have an essential requirement for ergosterol and other 24-alkyl sterols, which are absent in mammalian cells. In previous studies, we showed that Leishmania amazonensis is highly susceptible to aryl-quinuclidines, such as E5700, which inhibit squalene synthase, and to the azoles itraconazole (ITZ) and posaconazole (POSA), which inhibit C-14␣-demethylase. Herein, we investigated the antiproliferative, ultrastructural, and biochemical effects of combinations of E5700 with ITZ and POSA against L. amazonensis. Potent synergistic antiproliferative effects were observed against promastigotes, with fractional inhibitory concentration (FIC) ratios of 0.0525 and 0.0162 for combinations of E5700 plus ITZ and of E5700 plus POSA, respectively. Against intracellular amastigotes, FIC values were 0.175 and 0.1125 for combinations of E5700 plus ITZ and E5700 plus POSA, respectively. Marked alterations of the ultrastructure of promastigotes treated with the combinations were observed, in particular mitochondrial swelling, which was consistent with a reduction of the mitochondrial transmembrane potential, and an increase in the production of reactive oxygen species. We also observed the presence of vacuoles similar to autophagosomes in close association with mitochondria and an increase in the number of lipid bodies. Both growth arrest and ultrastructural/biochemical alterations were strictly associated with the depletion of the 14-desmethyl endogenous sterol pool. These results suggest the possibility of a novel combination therapy for the treatment of leishmaniasis.

Antileishmanial Efficacy and Pharmacokinetics of DB766-Azole Combinations

“…Interestingly, two combinations containing posaconazole had superior efficacy compared to these drugs when administered alone in a mouse model of T. cruzi infection (28). In vitro synergy has been described between the squalene synthase inhibitor E5700 and both posaconazole and itraconazole against intracellular L. amazonensis (29). We earlier reported in vitro synergy between DB766 and posaconazole in an intracellular assay using ␤-lactamase-expressing L. donovani parasites (7).…”

Antifungal Activity of Latex and Lupenonefrom Jatropha multifida L. (Euphorbiaceae)

“…A estirpe de C. tropicalis testada apresenta resistência a um dos antifúngicos mais utilizados atualmente, o fluconazol. 9 A descoberta de novas substâncias com potencial antifúngico para estirpes já resistentes aos fármacos atuais é de grande importância, ampliando as possibilidades de tratamento e cura dessas infecções.…”

“…17 A lupenona oriunda do extrato hexânico de folhas de J. multifida apresentou potencial antifúngico à mesma estirpe de C. tropicalis resistente a fluconazol. 9 Devido a essa característica, foi avaliada se a substância poderia possuir ação sinérgica com o fármaco na qual a estirpe é resistente. Verificou-se que a lupenona possui efeito aditivo ao fluconazol, de forma que ela foi capaz de reduzir pela metade a quantidade de fármaco necessária para inibir o crescimento fúngico da mesma quantidade de inóculo.…”

“…Candida albicans ATCC 24433, C. albicans Sorologia A ATCC 36801, C. albicans Sorologia B ATCC 36802, Candida grablata ATCC 2001, Candida krusei ATCC 6258, Cryptococcus neoformans ATCC 66031 e Candida tropicalis ATCC 28707, sendo esta última uma estirpe resistente a fluconazol, itraconazol e anfotericina B 9. …”

Antileishmanial Activity of Ezetimibe: Inhibition of Sterol Biosynthesis, In Vitro Synergy with Azoles, and Efficacy in Experimental Cutaneous Leishmaniasis

“…Drug combination in the treatment of infectious diseases is an interesting approach. Drugs acting in the same pathway can be combined to improve their activities (31). Thus, we evaluated the activity of ezetimibe in combination with ketoconazole or miconazole.…”