RESUMO
BACKGROUND: Resistance to fluconazole, a commonly used azole antifungal, is a challenge for the treatment of fungal infections. Resistance can be mediated by overexpression of ABC transporters, which promote drug efflux that requires ATP hydrolysis. The Pdr5p ABC transporter of Saccharomyces cerevisiae is a well-known model used to study this mechanism of antifungal resistance. The present study investigated the effects of 13 synthetic compounds on Pdr5p. RESULTS: Among the tested compounds, four contained a tellurium-butane group and shared structural similarities that were absent in the other tested compounds: a lateral hydrocarbon chain and an amide group. These four compounds were capable of inhibiting Pdr5p ATPase activity by more than 90%, they demonstrated IC50 values less than 2 µM and had an uncompetitive pattern of Pdr5p ATPase activity inhibition. These organotellurides did not demonstrate cytotoxicity against human erythrocytes or S. cerevisiae mutant strains (a strain that overexpress Pdr5p and a null mutant strain) even in concentrations above 100 µM. When tested at 100 µM, they could reverse the fluconazole resistance expressed by both the S. cerevisiae mutant strain that overexpress Pdr5p and a clinical isolate of Candida albicans. CONCLUSIONS: We have identified four organotellurides that are promising candidates for the reversal of drug resistance mediated by drug efflux pumps. These molecules will act as scaffolds for the development of more efficient and effective efflux pump inhibitors that can be used in combination therapy with available antifungals.
Assuntos
Transportadores de Cassetes de Ligação de ATP/metabolismo , Antifúngicos/farmacologia , Farmacorresistência Fúngica/efeitos dos fármacos , Inibidores Enzimáticos/metabolismo , Fluconazol/farmacologia , Proteínas de Saccharomyces cerevisiae/metabolismo , Saccharomyces cerevisiae/efeitos dos fármacos , Telúrio/metabolismo , Transportadores de Cassetes de Ligação de ATP/genética , Butanos/metabolismo , Butanos/toxicidade , Eritrócitos/efeitos dos fármacos , Eritrócitos/fisiologia , Concentração Inibidora 50 , Saccharomyces cerevisiae/genética , Proteínas de Saccharomyces cerevisiae/genética , Telúrio/toxicidadeRESUMO
The poor outcome of treatments for fungal infections is a consequence of the increasing incidence of resistance to antifungal agents, mainly due to the overexpression of efflux pumps. To surpass this mechanism of resistance, a substance able to inhibit these pumps could be administered in association with antifungals. Saccharomyces cerevisiae possesses an efflux pump (Pdr5p) homologue to those found in pathogenic yeast. Digoxin is a natural product that inhibits Na+, K+-ATPase. The aim of this study was to evaluate whether digoxin and its derivatives (i.e., DGB, digoxin benzylidene) can inhibit Pdr5p, reversing the resistance to fluconazole in yeasts. An S. cerevisiae mutant strain that overexpresses Pdr5p was used in the assays. The effects of the compounds on yeast growth, efflux activity, and Pdr5p ATPase activity were measured. All derivatives enhanced the antifungal activity of fluconazole against S. cerevisiae, in comparison to fluconazole alone, with FICI values ranging from 0.031 to 0.500. DGB 1 and DGB 3 presented combined effects with fluconazole against a Candida albicans strain, with fractional inhibitory concentration index (FICI) values of 0.625 and 0.281, respectively The compounds also inhibited the efflux of rhodamine 6G and Pdr5p ATPase activity, with IC50 values ranging from 0.41 µM to 3.72 µM. The results suggest that digoxin derivatives impair Pdr5p activity. Considering the homology between Pdr5p and efflux pumps from pathogenic fungi, these compounds are potential candidates to be used in association with fluconazole to treat resistant fungal infections.
RESUMO
Oroidin was isolated from the marine sponge Agelassventres and inhibited the activity and function of Pdr5p, an enzyme responsible for the multidrug resistance phenotype in Saccharomyces cerevisiae. This compound may help in the development of new drugs that reverse this dangerous phenotype of pathogenic yeast and fungi.
Assuntos
Transportadores de Cassetes de Ligação de ATP/efeitos dos fármacos , Pirróis/farmacologia , Proteínas de Saccharomyces cerevisiae/efeitos dos fármacos , Saccharomyces cerevisiae/enzimologia , Animais , Membrana Celular/química , Membrana Celular/metabolismo , Resistência a Múltiplos Medicamentos/genética , Biologia Marinha , Estrutura Molecular , Poríferos/química , Pirróis/química , Pirróis/isolamento & purificação , Saccharomyces cerevisiae/metabolismoRESUMO
Leishmania (Leishmania) infantum chagasi is one of the agents that cause visceral leishmaniasis. This disease occurs more frequently in third world countries, such as Brazil. The treatment is arduous, and is dependent on just a few drugs like the antimonial derivatives and amphotericin B. Moreover, these drugs are not only expensive, but they can also cause severe side effects and require long-term treatment. Therefore, it is very important to find new compounds that are effective against leishmaniasis. In the present work we evaluated a new group of synthetic amides against the promastigote and amastigote forms of L. infantum chagasi. The results showed that one of these amides in particular, presented very effective activity against the promastigotes and amastigotes of L. infantum chagasi at low concentrations and it also presented low toxicity for mammal cells, which makes this synthetic amide a promising drug for combating leishmaniasis.
Assuntos
Antiprotozoários/farmacologia , Leishmania infantum/efeitos dos fármacos , Fenetilaminas/farmacologia , Animais , Antiprotozoários/síntese química , Antiprotozoários/química , Brasil , Linhagem Celular , Descoberta de Drogas , Leishmania/efeitos dos fármacos , Leishmania/ultraestrutura , Leishmania infantum/crescimento & desenvolvimento , Leishmania infantum/fisiologia , Leishmania infantum/ultraestrutura , Estágios do Ciclo de Vida/efeitos dos fármacos , Macrófagos Peritoneais/efeitos dos fármacos , Camundongos , Fenetilaminas/síntese química , Fenetilaminas/químicaRESUMO
Chemical investigation of a propolis sample collected in Honduras has led to the isolation of the new (E,Z)-cinnamyl cinnamate (2) together with 14 known compounds: 6 cinnamic ester derivatives, 2 flavanones, 1 chalcone, 2 triterpenes, and 3 aromatic acids. Structural determination was accomplished by spectroscopic analysis, particularly two-dimensional (2D) nuclear magnetic resonance (NMR) and electrospray ionization-tandem mass spectrometry (ESI-MS/MS) techniques. Futhermore, we checked the ability of the propolis extract and the most representative compounds of each class (1, 5, 8, and 10) to inhibit the activity of Pdr5p, a protein responsible for a multidrug resistance phenotype in yeast. The present study appears to be the first report on Honduras propolis. Isolated cinnamic ester derivatives indicated the possible relation between Honduras propolis and the genus Liquidambar .
Assuntos
Transportadores de Cassetes de Ligação de ATP/antagonistas & inibidores , Própole/química , Proteínas de Saccharomyces cerevisiae/antagonistas & inibidores , Saccharomyces cerevisiae/metabolismo , Honduras , Espectroscopia de Ressonância Magnética , Espectrometria de Massas por Ionização por ElectrosprayRESUMO
Multidrug resistance of cancer cells and pathogenic microorganisms leading to the treatment failure of some forms of cancer or life-threatening bacterial or fungal infections is often caused by the overexpression of multidrug efflux pumps belonging to the ATP-binding cassette transporters superfamily. The multidrug resistance of fungal cells often involves the overexpression of efflux pumps belonging to the pleiotropic drug resistance (PDR) family of ABC transporters. Possibly the best-studied fungal PDR transporter is the multidrug resistance transporter Pdr5p of Saccharomyces cerevisiae. Some research groups have been searching for new inhibitors of these efflux pumps in order to alleviate resistance. Natural products are a great source for the discovery of new compounds with biological activity. Propolis is a complex resinous material collected by honeybees from exudates and buds of certain plant sources and this material is thought to serve as a defense substance for bee hives. Propolis is widely used in traditional medicine and is reported to have a broad spectrum of pharmacological properties. Literature reported some biological functionalities of propolis, such as antibacterial, antiviral, fungicidal, anti-inflammatory and anti-carcinogenic activities. The chemical composition of propolis is qualitatively and quantitatively variable. Components isolated from methanolic extract of red Brazilian propolis (Alagoas, Northeast of Brazil) are isoflavonoids (including pterocarpans, isoflavans, isoflavones), flavanones and polyprenylated benzophenones. In this work we demonstrated the effects of five different isolated compounds on the ATPase activity of Pdr5p. Out of all five substances tested, only BRP-1 was able to completely abolish the enzymatic activity while others worked as positive modulators of the enzyme activity. BRP-1also inhibited the efflux of Rhodamine 6G from yeast cells overexpressing Pdr5p. Taken together, these results demonstrate that Brazilian propolis could be a source of promising compounds that can alleviate the MDR phenomenon, particularly in some fungi, where it could be used as an adjuvant for the treatment with azoles.