Planejamento e desenvolvimento de novos compostos com atividade frente a Leishmania spp: Síntese, avaliação da atividade e toxicidade de derivados 5-nitro-2-furfurilidênicos e estudos de relações estrutura-atividade / Design of new compounds against Leishmania spp: synthesis, biological evaluation and toxicity of 5-nitro-2-furfurylidene derivates and structure-activity relationship studies

A leishmaniose é uma zoonose de ampla distribuição mundial, causada pelos parasitas tripanossomatídeos do gênero Leishmania. Infelizmente, o arsenal terapêutico disponível é precário, mas vê-se crescente o interesse científico pela busca do potencial de derivados nitroheterocíclicos como alternativas terapêuticas. Nesse contexto, este trabalho analisou o potencial de derivados 5-nitro-2-furfurilidênicos contra diferentes cepas de Leishmania, assim como investigou um possível modo de ação para esta classe de nitrocompostos. Para tal, a quimioteca foi sintetizada de acordo com publicações prévias do grupo. O potencial de inibição de crescimento das culturas de promastigotas de L. (L.) infantum (Linf) e L. (L.) major (Lmaj) foi determinado, utilizando miltefosina (MILT) (Linf - IC50: 8,28±0,33 µM), anfotericina B (AMB) (Linf - IC50: 0,02±0,002 µM) e nifurtimox (NFX) (Lmaj - IC50: 3,5±0,09 µM) como referência. A maioria dos compostos apresentaram maior potencial que as referênias, destacando o composto 40 (Linf - IC50: 0,2±0,019 µM/ Lmaj - IC50: 0,087 ± 0,001 µM) como mais eficaz. Contra as formas amastigotas intracelulares, para Linf os compostos 40, 13 e 15 foram mais eficazes em reduzir a carga parasitária dos macrófagos infectados que fármacos de referência. Para Lmajor, o composto 40 (IC50: 0,006 ± 0,0003 µM) foi mais ativo que o NFX (IC50: 2,15 ± 0,01 µM). Também foi determinada a atividade da quimioteca frente a enzima nitrorredutase (NTR1), utilizando cepas de T. brucei superexpressantes de NTR1, e os compostos analisados foram até 18 vezes mais eficazes que à cepa wild-type. Ademais, a partir da análise exploratória de dados por análise de componentes principais (PCA) e de grupamentos hierárquicos (HCA), foi reconhecida a influência das propriedades relacionadas com o equilíbrio hidrófilo-lipófilo e da natureza estérica/geométrica das moléculas para atividade anti-Leishmania

Leishmaniasis is a worldwide zoonosis caused by trypanosomatid parasites of the genus Leishmania. Unfortunately, the available therapeutic arsenal is precarious, but there is growing scientific interest in searching the potential of nitroheterocyclic derivatives as therapeutic alternatives. In this context, this work analyzed the potential of 5-nitro-2-furfurylidene derivatives against different Leishmania strains, as well as investigated the potential mode of action for this nitro compounds class. To this end, the chemolibrary was synthesized according to our group's previous publications. The growth inhibitory potential potential for promastigote cultures of L. (L.) infantum (Linf) and L. (L.) major (Lmaj) was determined using miltefosine (MILT) (Linf - IC50: 8.28±0.33 µM), amphotericin B (AMB) (Linf - IC50: 0.02±0.002 µM) and nifurtimox (NFX) (Lmaj - IC50: 3.5±0.09 µM) as reference. Most of the compounds were more potent than the references, highlighting compound 40 (Linf - IC50: 0.2±0.019 µM/ Lmaj - IC50: 0.087 ± 0.001 µM) as the most effective. Against intracellular amastigote, for Linf, compounds 40, 13 and 15 were more effective in reducing the parasite load of infected macrophages than reference drugs. For Lmajor, compound 40 (IC50: 0.006 ± 0.0003 µM) was more active than NFX (IC50: 2.15 ± 0.01 µM). The activity against nitroreductase (NTR1) enzyme was determined using overexpressing NTR1 mutant T. brucei strains, and the analyzed compounds were up to 18 times more effective than wild-type. Furthermore, exploratory data analysis using principal component analysis (PCA) and hierarchical clustering (HCA) methods were used. The influence of properties related to the hydrophiliclipophilic balance and the steric/geometric nature of the molecules was associated with the anti-Leishmanial activity

Identification of a type I nitroreductase gene in non-virulent Trypanosoma rangeli

ABSTRACT Trypanosomatid type I nitroreductases (NTRs), i.e., mitochondrial enzymes that metabolise nitroaromatic pro-drugs, are essential for parasite growth, infection, and survival. Here, a type I NTR of non-virulent protozoan Trypanosoma rangeli is described and compared to those of other trypanosomatids. The NTR gene was isolated from KP1(+) and KP1(-) strains, and its corresponding transcript and 5' untranslated region (5'UTR) were determined. Bioinformatics analyses and nitro-drug activation assays were also performed. The results indicated that the type I NTR gene is present in both KP1(-) and KP1(+) strains, with 98% identity. However, the predicted subcellular localisation of the protein differed among the strains (predicted as mitochondrial in the KP1(+) strain). Comparisons of the domains and 3D structures of the NTRs with those of orthologs demonstrated that the nitroreductase domain of T. rangeli NTR is conserved across all the strains, including the residues involved in the interaction with the FMN cofactor and in the tertiary structure characteristics of this oxidoreductase protein family. mRNA processing and expression were also observed. In addition, T. rangeli was shown to be sensitive to benznidazole and nifurtimox in a concentration-dependent manner. In summary, T. rangeli appears to have a newly discovered functional type I NTR.

Frecuencia de mutaciones de la nitrorreductasa RdxA de Helicobacter pylori para la activación del metronidazol en una población del departamento del Cauca, Colombia / Frequency of Helicobacter pylori nitroreductase RdxA mutations for metronidazole activation in a population in the Cauca Department, Colombia

RESUMEN Introducción. La resistencia al metronidazol es un factor clave relacionado con el fracaso del tratamiento contra la infección por Helicobacter pylori asociada, principalmente, con mutaciones en la nitrorreductasa RdxA. A pesar de su importancia, los estudios sobre esta proteína son aún incipientes en Popayán, Colombia. Objetivo. Evaluar la frecuencia de las mutaciones en la nitrorreductasa RdxA en una población de pacientes con enfermedad gastrointestinal por H. pylori. Materiales y métodos. El ADN de 170 biopsias gástricas se amplificó mediante reacción en cadena de la polimerasa (PCR) para detectar las mutaciones en la nitrorreductasa RdxA. Se analizaron las secuencias traducidas a aminoácidos y se compararon con la cepa de referencia 26695. Resultados. La frecuencia de mutaciones de la nitrorreductasa RdxA en la población de estudio fue de 78 %. Su distribución más frecuente se detectó en las posiciones D59N (en 153 muestras), R131K (en 101 muestras), R90K (en 97 muestras), A118T (en 42 muestras), I160F (en 32 muestras), H97T (en 26 muestras) y en los codones de parada Q50*; D59*; E75*; C159* y I160* en cinco, una, tres, diez y seis muestras, respectivamente. El genotipo de virulencia más frecuente fue el vacAs1/m1 negativo para cagA (48,6 %). Conclusiones. La gran frecuencia de mutaciones en la nitrorreductasa RdxA en aislamientos de H. pylori en Popayán sugiere que los tratamientos empíricos con metronidazol no serían una opción válida para su erradicación en pacientes de la población estudiada.

ABSTRACT Introduction: Resistance to metronidazole is a key factor associated with Helicobacter pylori treatment failure. Even though resistance is mostly associated with RdxA nitroreductase mutations, studies of this H. pylori protein in Popayán (Colombia) are still incipient. Objective: To evaluate the frequency of mutations in the RdxA nitroreductase in a population of patients with H. pylori-positive gastrointestinal disease. Materials and methods: We amplified the DNA of 170 gastric biopsies by PCR to detect mutations in the RdxA nitroreductase. An analysis of DNA sequences translated into amino acid sequences was done and then compared to the reference strain 26695. Results: The frequency of RdxA nitroreductase mutations in this study population was 78%. Its most frequent distribution was found in positions D59N (153 samples), R131K (101 samples), R90K (97 samples), A118T (42 samples), I160F (32 samples) and H97T (26 samples), and meaningful stop codons Q50*, D59*; E75*, C159* and I160* in five, one, three, ten and six samples, respectively. The most common virulence genotype was vacAs1/m1 cagA negative (48.6 %). Conclusions: The high frequency of RdxA nitroreductase mutations in H. pylori isolates in Popayán (Colombia) indicates that empirical therapy with metronidazole may not be a valid option for the eradication of H. pylori in patients of the studied population.

Megazol and its bioisostere 4H-1,2,4-triazole: comparing the trypanocidal, cytotoxic and genotoxic activities and their in vitro and in silico interactions with the Trypanosoma brucei nitroreductase enzyme

Megazol (7) is a 5-nitroimidazole that is highly active against Trypanosoma cruzi and Trypanosoma brucei, as well as drug-resistant forms of trypanosomiasis. Compound 7 is not used clinically due to its mutagenic and genotoxic properties, but has been largely used as a lead compound. Here, we compared the activity of 7 with its 4H-1,2,4-triazole bioisostere (8) in bloodstream forms of T. brucei and T. cruzi and evaluated their activation by T. brucei type I nitroreductase (TbNTR) enzyme. We also analysed the cytotoxic and genotoxic effects of these compounds in whole human blood using Comet and fluorescein diacetate/ethidium bromide assays. Although the only difference between 7 and 8 is the substitution of sulphur (in the thiadiazole in 7) for nitrogen (in the triazole in 8), the results indicated that 8 had poorer antiparasitic activity than 7 and was not genotoxic, whereas 7 presented this effect. The determination of Vmax indicated that although 8 was metabolised more rapidly than 7, it bounds to the TbNTR with better affinity, resulting in equivalent kcat/KM values. Docking assays of 7 and 8 performed within the active site of a homology model of the TbNTR indicating that 8 had greater affinity than 7.

APPLICATION OF 6-NITROCOUMARIN AS A SUBSTRATE FOR THE FLUORESCENT DETECTION OF NITROREDUCTASE ACTIVITY IN Sporothrix schenckii / Aplicação de 6-nitrocumarina como substrato fluorescente para detecção de atividade nitroredutásica em Sporothrix schenckii

Introduction Sporothrix schenckii is a thermal dimorphic pathogenic fungus causing a subcutaneous mycosis, sporotrichosis. Nitrocoumarin represents a fluorogenic substrate class where the microbial nitroreductase activity produces several derivatives, already used in several other enzyme assays. The objective of this study was the analysis of 6-nitrocoumarin (6-NC) as a substrate to study the nitroreductase activity in Sporothrix schenckii. Methods Thirty-five samples of S. schenckii were cultivated for seven, 14 and 21 days at 35 °C in a microculture containing 6-nitrocoumarin or 6-aminocoumarin (6-AC) dissolved in dimethyl sulfoxide or dimethyl sulfoxide as a negative control, for posterior examination under an epifluorescence microscope. The organic layer of the seven, 14 and 21-day cultures was analyzed by means of direct illumination with 365 nm UV light and by means of elution on G silica gel plate with hexane:ethyl acetate 1:4 unveiled with UV light. Results All of the strains showed the presence of 6-AC (yellow fluorescence) and 6-hydroxylaminocoumarin (blue fluorescence) in thin layer chromatography, which explains the green fluorescence observed in the fungus structure. Conclusion The nitroreductase activity is widely distributed in the S. schenckii complex and 6-NC is a fluorogenic substrate of easy access and applicability for the nitroreductase activity detection. .

Introdução Sporothrix schenckii é um fungo dimórfico térmico, agente etiológico de micose subcutânea, a esporotricose. Nitrocumarina representa classe de substratos fluorogênicos em que a atividade nitroredutásica microbiana produz vários derivados, já utilizados em vários outros ensaios enzimáticos. O objetivo deste estudo foi analisar 6-nitrocumarina (6-NC) como substrato para estudo da atividade nitroredutásica em Sporothrix schenckii. Métodos Trinta e cinco isolados de S. schenckii foram cultivados por sete, 14 e 21 dias a 35 °C em um microcultivo contendo 6-nitrocumarina ou 6-aminocumarina (6-AC) solubilizada em dimetilsulfóxido ou dimetilsulfóxido como controle negativo, para posterior análise em microscópio de epifluorescência. A fase orgânica da cultura de sete, 14 e 21 dias foi analisada por meio de iluminação direta com luz UV de 365 nm e por eluição em placas de sílica gel G com hexano:acetato de etila 1:4 e revelada com luz UV. Resultados Todos os isolados mostraram a presença de 6-AC (fluorescência amarela) e 6-hidroxilaminocumarina (fluorescência azul) em cromatografia em camada delgada, que explica a fluorescência verde observada na estrutura dos fungos. Conclusão A atividade nitroredutásica é amplamente distribuída no complexo S. schenckii e 6-NC é um substrato fluorogênico de fácil obtenção e aplicabilidade para detecção da atividade nitroredutásica. .

Benznidazole biotransformation in rat heart microsomal fraction without observable ultrastructural alterations: comparison to Nifurtimox-induced cardiac effects

Benznidazole (Bz) and Nifurtimox (Nfx) have been used to treat Chagas disease. As recent studies have de-monstrated cardiotoxic effects of Nfx, we attempted to determine whether Bz behaves similarly. Bz reached the heart tissue of male rats after intragastric administration. No cytosolic Bz nitroreductases were detected, although microsomal NADPH-dependent Bz nitroreductase activity was observed, and appeared to be mediated by P450 reductase. No ultrastructurally observable deleterious effects of Bz were detected, in contrast to the overt cardiac effects previously reported for Nfx. In conclusion, when these drugs are used in chagasic patients, Bz may pose a lesser risk to heart function than Nfx when any cardiopathy is present.

Alteraciones ultraestructurales en la mucosa del colon de ratas tratadas con nifurtimox / Ultrastructural alterations in colonic mucosa of nifurtimox treated rats

El nifurtimox (Nfx) es un fármaco empleado en el tratamiento del Mal de Chagas agudo que ha evidenciado en su uso clínico y en estudios experimentales efectos colasterales tóxicos que comprometen su empleo. Estos efectos fueron correlacionados con la nitrorreducción del Nfx a radical nitroanión y la generación de aniones superóxidos a través de un ciclo redox. El objetivo de este trabajo fue verificar si después de la administración oral de Nfx ( 100g/ kg-1) a rata macho Sprague Dawley se observan alteraciones ultraestructurales en el colon. Los resultados mostraron que 24 horas después de administrar el Nfx se observan alteraciones consistentes en una dilatación moderada del retículo endoplasmático y en una dilatación intensa del Complejo de Golgi en las células epiteliales colónicas. El Nfx está presente en el tejido colónico 1 y 3 horas después de su administración oral, en concentraciones de 9.7 + o - 2.9 y 7.0 + o - nmol/g-1 respectivamente. Los estudios de actividad nitrorreductásica del Nfx, espectrofotómetricos y por HPLC, en fracciones subcelulares, permiten establecer su presencia en la fracción microsomal, con valores de 0.72 + o - 0.29 y 0.26 + o - 0.04 nmol Nfx/min-1/mg-1 proteína , pero no en el citosol. Los resultados una correlación entre la localización del año observado y la fracción celular donde ocurre la nitrorreducción. El daño intenso del complejo de Golgi producido por el Nfx sugiere potenciales alteraciones en las funciones de síntesis y/o almacenamiento de productos de secreción de la mucosa colónica.