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

New Antibody-Free Mass Spectrometry-Based Quantification Reveals That C9ORF72 Long Protein Isoform Is Reduced in the Frontal Cortex of Hexanucleotide-Repeat Expansion Carriers

International audienceFrontotemporal dementia (FTD) is a fatal neurodegenerative disease characterized by behavioral and language disorders. The main genetic cause of FTD is an intronic hexanucleotide repeat expansion (G4C2)n in the C9ORF72 gene. A loss of function of the C9ORF72 protein associated with the allele-specific reduction of C9ORF72 expression is postulated to contribute to the disease pathogenesis. To better understand the contribution of the loss of function to the disease mechanism, we need to determine precisely the level of reduction in C9ORF72 long and short isoforms in brain tissue from patients with C9ORF72 mutations. In this study, we developed a sensitive and robust mass spectrometry (MS) method for quantifying C9ORF72 isoform levels in human brain tissue without requiring antibody or affinity reagent. An optimized workflow based on surfactant-aided protein extraction and pellet digestion was established for optimal recovery of the two isoforms in brain samples. Signature peptides, common or specific to the isoforms, were targeted in brain extracts by multiplex MS through the parallel reaction monitoring mode on a Quadrupole-Orbitrap high resolution mass spectrometer. The assay was successfully validated and subsequently applied to frontal cortex brain samples from a cohort of FTD patients with C9ORF72 mutations and neurologically normal controls without mutations. We showed that the C9ORF72 short isoform in the frontal cortices is below detection threshold in all tested individuals and the C9ORF72 long isoform is significantly decreased in C9ORF72 mutation carriers

Synthesis and biological activity of nitro heterocycles analogous to megazol, a trypanocidal lead.

As part of our efforts to develop new compounds aimed at the therapy of parasitic infections, we synthesized and assayed analogues of a lead compound megazol, 5-(1-methyl-5-nitro-1H-2-imidazolyl)-1,3,4-thiadiazol-2-amine, CAS no. 19622-55-0), in vitro. We first developed a new route for the synthesis of megazol. Subsequently several structural changes were introduced, including substitutions on the two rings of the basic nucleus, replacement of the thiadiazole by an oxadiazole, replacement of the nitroimidazole part by a nitrofurane or a nitrothiophene, and substitutions on the exocyclic nitrogen atom for evaluation of an improved import by the glucose or the purine transporters. Assays of the series of compounds on the protozoan parasites Trypanosoma brucei, Trypanosoma cruzi, and Leishmania donovani, as either extracellular cells or infected macrophages, indicated that megazol was more active than the derivatives. Megazol was then evaluated on primates infected with Trypanosoma brucei gambiense, including late-stage central nervous system infections in combination with suramin. Full recovery was observed in five monkeys in the study with no relapse of parasitemia within a 2 year follow-up. Because there is a lack of efficacious treatments for sleeping sickness in Africa and Chagas disease in South America, megazol is proposed as a potential alternative. The mutagenicity of this compound is at present being reevaluated, and metabolism is also under investigation prior to possible further developments

In vitro evaluation of the activity of aromatic nitrocompounds against Trypanosoma cruzi

Fourteen compounds were evaluated for their activity against Trypanosoma cruzi blood stream forms at the concentration of 500 µg/ml. Six compounds were active and re-tested at lower concentrations