Memantine, an antagonist of the NMDA glutamate receptor, affects cell proliferation, differentiation and the intracellular cycle and induces apoptosis in Trypanosoma cruzi

Chagas' disease is caused by the protozoan parasite Trypanosoma cruzi and affects approximately 10 million people in endemic areas of Mexico and Central and South America. Currently available chemotherapies are limited to two compounds: Nifurtimox and Benznidazole. Both drugs reduce the symptoms of the disease and mortality among infected individuals when used during the acute phase, but their efficacy during the chronic phase (during which the majority of cases are diagnosed) remains controversial. Moreover, these drugs have several side effects. The aim of this study was to evaluate the effect of Memantine, an antagonist of the glutamate receptor in the CNS of mammals, on the life cycle of T. cruzi. Memantine exhibited a trypanocidal effect, inhibiting the proliferation of epimastigotes (IC50 172.6 µM). Furthermore, this compound interfered with metacyclogenesis (approximately 30% reduction) and affected the energy metabolism of the parasite. In addition, Memantine triggered mechanisms that led to the apoptosis-like cell death of epimastigotes, with extracellular exposure of phosphatidylserine, increased production of reactive oxygen species, decreased ATP levels, increased intracellular Ca2+ and morphological changes. Moreover, Memantine interfered with the intracellular cycle of the parasite, specifically the amastigote stage (IC50 31 µM). Interestingly, the stages of the parasite life cycle that require more energy (epimastigote and amastigote) were more affected as were the processes of differentiation and cell invasion.Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP grant #11/50631-1 to AMS)Instituto Nacional de Biologia Estrutural e Química Medicinal em Doenças Infecciosas (INBEQMeDI)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq grant #470272/201 to AMS

Characterization and evaluation of the role of histidine degradation in Trypanosoma cruzi bioenergetics.

Trypanosoma cruzi é capaz de incorporar histidina, um aminoácido essencial, através de um sistema de transporte saturável, de alta especificidade e dependente de ATP. Uma vez no citoplasma, a histidina amônio-liase (TcHAL), catalisa a deaminação não oxidativa da His a urocanato, quem é convertido pela urocanato hidratase (TcUH) ao intermediário 4-imidazolona-5-propionato. Posteriormente, duas enzimas (imidazolona propionase e formiminoglutamase) atúam para gerar glutamato. TcHAL e TcUH foram caracterizadas cinetica e bioquímicamente. O α-cetoglutarato, produto da deaminação do Glu gerado na degradação de His, ingressa ao ciclo de Krebs e os electrons gerados são capazes de restabelecer o potencial de membrana mitocondrial, promover a síntese de ATP e consumo de oxigênio na mitocôndria. Além disso, His é capaz de estimular a metaciclogênese: estudos metabolômicos mostraram que His é utilizada como fonte energética principalmente no inicio da diferenciação. Nossos dados mostram a relevância da His na bioenergética de T. cruzi, nos estágios presentes no inseto vetor.Trypanosoma cruzi incorporates histidine, an essential amino acid, through a saturable, highly specific and ATP dependent transport system. Once in the cytoplasm, a histidine ammonia-lyase (TcHAL) catalyzes the non-oxidative deamination of His to urocanate, which is converted by an urocanate hydratase (TcUH) to the intermediate 4-imidazolone-5-propionate. Afterwards, two enzymes (imidazolonepropionase and fomiminoglutamase) complete the glutamate formation. Kinetic and biochemical parameters of TcHAL and TcUH were determined. We observe that His degradation can feed Krebs cycle, and the electrons produced are able to restore the mitochondrial inner membrane potential, promote ATP biosynthesis and oxygen consumption at the mitochondrion. Furthermore, His was able to stimulate metacyclogenesis: a metabolomics approach shows that His is used as an energy source, mainly, in early stages of differentiation. Our data shows the relevance of His in T. cruzi bioenergetics, mainly in insect vector stages

Do dietary patterns determine levels of vitamin B6, folate, and vitamin B12 intake and corresponding biomarkers in European adolescents? The Healthy Lifestyle in Europe by Nutrition in Adolescence (HELENA) study

OBJECTIVES: To determine dietary patterns (DPs) and explain the highest variance of vitamin B6, folate, and B12 intake and related concentrations among European adolescents. METHODS: A total of 2173 adolescents who participated in the Healthy Lifestyle in Europe by Nutrition in Adolescence study met the eligibility criteria for the vitamin B intake analysis (46% boys) and 586 adolescents for the biomarkers analysis (47% boys). Two non-consecutive, 24-h, dietary recalls were used to assess the mean intakes. Concentrations were measured by chromatography and immunoassay testing. A reduced rank regression was applied to elucidate the combined effect of food intake of vitamin B and related concentrations. RESULTS: The identified DPs (one per vitamin B intake and biomarker and by sex) explained a variability between 34.2% and 23.7% of the vitamin B intake and between 17.2% and 7% of the biomarkers. In the reduced rank regression models, fish, eggs, cheese, whole milk and buttermilk intakes were loaded positively for vitamin B intake in both sexes; however, soft drinks and chocolate were loaded negatively. For the biomarkers, a higher variability was observed in the patterns in terms of food loads such as alcoholic drinks, sugars, and soft drinks. Some food items were loaded differently between intakes and biomarkers such as fish products, which was loaded positively for intakes but negatively for plasma folate in girls. CONCLUSIONS: The identified DPs explained up to 34.2% and 17.2% of the variability of the vitamin B intake and plasma concentrations, respectively, in European adolescents. Further studies are needed to elucidate the factors that determine such patterns