Identification of Aryl Polyamines Derivatives as Anti-Trypanosoma cruzi Agents Targeting Iron Superoxide Dismutase.

Chagas disease (CD) is a tropical and potentially fatal infection caused by Trypanosoma cruzi. Although CD was limited to Latin America as a silent disease, CD has become widespread as a result of globalization. Currently, 6-8 million people are infected worldwide, and no effective treatment is available. Here, we identify new effective agents against T. cruzi. In short, 16 aryl polyamines were screened in vitro against different T. cruzi strains, and lead compounds were evaluated in vivo after oral administration in both the acute and chronic infections. The mode of action was also evaluated at the energetic level, and its high activity profile could be ascribed to a mitochondria-dependent bioenergetic collapse and redox stress by inhibition of the Fe-SOD enzyme. We present compound 15 as a potential compound that provides a step forward for the development of new agents to combat CD.

Three-Finger Toxins from Brazilian Coral Snakes: From Molecular Framework to Insights in Biological Function.

Studies on 3FTxs around the world are showing the amazing diversity in these proteins both in structure and function. In Brazil, we have not realized the broad variety of their amino acid sequences and probable diversified structures and targets. In this context, this work aims to conduct an in silico systematic study on available 3FTxs found in Micrurus species from Brazil. We elaborated a specific guideline for this toxin family. First, we grouped them according to their structural homologue predicted by HHPred server and further curated manually. For each group, we selected one sequence and constructed a representative structural model. By looking at conserved features and comparing with the information available in the literature for this toxin family, we managed to point to potential biological functions. In parallel, the phylogenetic relationship was estimated for our database by maximum likelihood analyses and a phylogenetic tree was constructed including the homologous 3FTx previously characterized. Our results highlighted an astonishing diversity inside this family of toxins, showing some groups with expected functional similarities to known 3FTxs, and pointing out others with potential novel roles and perhaps structures. Moreover, this classification guideline may be useful to aid future studies on these abundant toxins.

Aerolysin nanopores decode digital information stored in tailored macromolecular analytes.

Digital data storage is a growing need for our society and finding alternative solutions than those based on silicon or magnetic tapes is a challenge in the era of "big data." The recent development of polymers that can store information at the molecular level has opened up new opportunities for ultrahigh density data storage, long-term archival, anticounterfeiting systems, and molecular cryptography. However, synthetic informational polymers are so far only deciphered by tandem mass spectrometry. In comparison, nanopore technology can be faster, cheaper, nondestructive and provide detection at the single-molecule level; moreover, it can be massively parallelized and miniaturized in portable devices. Here, we demonstrate the ability of engineered aerolysin nanopores to accurately read, with single-bit resolution, the digital information encoded in tailored informational polymers alone and in mixed samples, without compromising information density. These findings open promising possibilities to develop writing-reading technologies to process digital data using a biological-inspired platform.

In Vivo Biological Evaluation of a Synthetic Royleanone Derivative as a Promising Fast-Acting Trypanocidal Agent by Inducing Mitochondrial-Dependent Necrosis.

The life-long and life-threatening Chagas disease is one of the most neglected tropical diseases caused by the protozoan parasite Trypanosoma cruzi. It is a major public health problem in Latin America, as six to seven million people are infected, being the principal cause of mortality in many endemic regions. Moreover, Chagas disease has become widespread due to migrant populations. Additionally, there are no vaccines nor effective treatments to fight the disease because of its long-term nature and complex pathology. Therefore, these facts emphasize how crucial the international effort for the development of new treatments against Chagas disease is. Here, we present the in vitro and in vivo trypanocidal activity of some oxygenated abietane diterpenoids and related compounds. The 1,4-benzoquinone 15, not yet reported, was identified as a fast-acting trypanocidal drug with efficacy against different strains in vitro and higher activity and lower toxicity than benznidazole in both phases of murine Chagas disease. The mode of action was also evaluated, suggesting that quinone 15 kills T. cruzi by inducing mitochondrion-dependent necrosis through a bioenergetics collapse caused by a mitochondrial membrane depolarization and iron-containing superoxide dismutase inhibition. Therefore, the abietane 1,4-benzoquinone 15 can be considered as a new candidate molecule for the development of an appropriate and commercially accessible anti-Chagas drug.

Repositioning of leishmanicidal [1,2,3]Triazolo[1,5-a]pyridinium salts for Chagas disease treatment: Trypanosoma cruzi cell death involving mitochondrial membrane depolarisation and Fe-SOD inhibition.

Trypanosomatidae is a family of unicellular parasites belonging to the phylum Euglenozoa, which are causative agents in high impact human diseases such as Leishmaniasis, Chagas disease and African sleeping sickness. The impact on human health and local economies, together with a lack of satisfactory chemotherapeutic treatments and effective vaccines, justifies stringent research efforts to search for new disease therapies. Here, we present in vitro trypanocidal activity data and mode of action data, repositioning leishmanicidal [1,2,3]Triazolo[1,5-a]pyridinium salts against Trypanosoma cruzi, the aetiological agent of Chagas disease. This disease is one of the most neglected tropical diseases and is a major public health issue in Central and South America. The disease affects approximately 6-7 million people and is widespread due to increased migratory movements. We screened a suite of leishmanicidal [1,2,3]Triazolo[1,5-a]pyridinium salt compounds, of which compounds 13, 20 and 21 were identified as trypanocidal drugs. These compounds caused cell death in a mitochondrion-dependent manner through a bioenergetic collapse. Moreover, compounds 13 and 20 showed a remarkable inhibition of iron superoxide dismutase activity of T. cruzi, a key enzyme in the protection from the damage produced by oxidative stress.

Single-molecule sensing of peptides and nucleic acids by engineered aerolysin nanopores.

Nanopore sensing is a powerful single-molecule approach for the detection of biomolecules. Recent studies have demonstrated that aerolysin is a promising candidate to improve the accuracy of DNA sequencing and to develop novel single-molecule proteomic strategies. However, the structure-function relationship between the aerolysin nanopore and its molecular sensing properties remains insufficiently explored. Herein, a set of mutated pores were rationally designed and evaluated in silico by molecular simulations and in vitro by single-channel recording and molecular translocation experiments to study the pore structural variation, ion selectivity, ionic conductance and capabilities for sensing several biomolecules. Our results show that the ion selectivity and sensing ability of aerolysin are mostly controlled by electrostatics and the narrow diameter of the double ß-barrel cap. By engineering single-site mutants, a more accurate molecular detection of nucleic acids and peptides has been achieved. These findings open avenues for developing aerolysin nanopores into powerful sensing devices.

Rational modification of Mannich base-type derivatives as novel antichagasic compounds: Synthesis, in vitro and in vivo evaluation.

The current chemotherapy against Chagas disease is inadequate and insufficient. A series of ten Mannich base-type derivatives have been synthesized to evaluate their in vitro antichagasic activity. After a preliminary screening, compounds 7 and 9 were subjected to in vivo assays in a murine model. Both compounds caused a substantial decrease in parasitemia in the chronic phase, which was an even better result than that of the reference drug benznidazole. In addition, compound 9 also showed better antichagasic activity during the acute phase. Moreover, metabolite excretion, effect on mitochondrial membrane potential and the inhibition of superoxide dismutase (SOD) studies were also performed to identify their possible mechanism of action. Finally, docking studies proposed a binding mode of the Fe-SOD enzyme similar to our previous series, which validated our design strategy. Therefore, the results suggest that these compounds should be considered for further preclinical evaluation as antichagasic agents.

A step towards development of promising trypanocidal agents: Synthesis, characterization and in vitro biological evaluation of ferrocenyl Mannich base-type derivatives.

Chagas disease is a neglected chronical parasitosis caused by the parasite Trypanosoma cruzi (T. cruzi). Nine ferrocenyl Mannich base derivatives were synthetized and characterized to explore their in vitro activity on three T. cruzi strains of the parasite and their cytotoxicity on Vero cells to calculate the selectivity index (SI). Compound 2, 1-ferrocenyl-3-(4-(4-(trifluoromethyl)phenyl)piperazin-1-yl)propan-1-one, stood out as the most promising derivative showing a half maximal inhibitory concentration (IC50) value around 5 µM in both amastigote and trypomastigote forms of T. cruzi and SI values higher than 13, being the best value on the trypomastigote forms of the Arequipa strain (SI = 41.7). Moreover, 2 decreased the number of infected cells and was not genotoxic. Furthermore, its possible mechanism of action was studied through the alteration of the metabolites excreted by the parasite during glucose metabolism, the detection of mitochondrial alterations and the inhibition of superoxide dismutase (SOD). Finally, docking studies were executed to analyze the binding mode of the studied compounds to Fe-SOD enzyme.

Mapping the sensing spots of aerolysin for single oligonucleotides analysis.

Nanopore sensing is a powerful single-molecule method for DNA and protein sequencing. Recent studies have demonstrated that aerolysin exhibits a high sensitivity for single-molecule detection. However, the lack of the atomic resolution structure of aerolysin pore has hindered the understanding of its sensing capabilities. Herein, we integrate nanopore experimental results and molecular simulations based on a recent pore structural model to precisely map the sensing spots of this toxin for ssDNA translocation. Rationally probing ssDNA length and composition upon pore translocation provides new important insights for molecular determinants of the aerolysin nanopore. Computational and experimental results reveal two critical sensing spots (R220, K238) generating two constriction points along the pore lumen. Taking advantage of the sensing spots, all four nucleobases, cytosine methylation and oxidation of guanine can be clearly identified in a mixture sample. The results provide evidence for the potential of aerolysin as a nanosensor for DNA sequencing.

Second Generation of Mannich Base-Type Derivatives with in Vivo Activity against Trypanosoma cruzi.

Chagas disease is a potentially life-threatening and neglected tropical disease caused by Trypanosoma cruzi. One of the most important challenges related to Chagas disease is the search for new, safe, effective, and affordable drugs since the current therapeutic arsenal is inadequate and insufficient. Here, we report a simple and cost-effective synthesis and the biological evaluation of the second generation of Mannich base-type derivatives. Compounds 7, 9, and 10 showed improved in vitro efficiency and lower toxicity than benznidazole, in addition to no genotoxicity; thus, they were applied in in vivo assays to assess their activity in both acute and chronic phases of the disease. Compound 10 presented a similar profile to benznidazole from the parasitological perspective but also yielded encouraging data, as no toxicity was observed. Moreover, compound 9 showed lower parasitaemia and higher curative rates than benznidazole, also with lower toxicity in both acute and chronic phases. Therefore, further studies should be considered to optimize compound 9 to promote its further preclinical evaluation.

Structural, physicochemical and dynamic features conserved within the aerolysin pore-forming toxin family.

Aerolysin is the founding member of a major class of ß-pore-forming toxins (ß-PFTs) found throughout all kingdoms of life. PFTs are cytotoxic proteins produced as soluble monomers, which oligomerize at the membrane of target host cells forming pores that may lead to osmotic lysis and cell death. Besides their role in microbial infection, they have become interesting for their potential as biotechnological sensors and delivery systems. Using an approach that integrates bioinformatics with molecular modeling and simulation, we looked for conserved features across this large toxin family. The cell surface-binding domains present high variability within the family to provide membrane receptor specificity. On the contrary, the novel concentric double ß-barrel structure found in aerolysin is highly conserved in terms of sequence, structure and conformational dynamics, which likely contribute to preserve a common transition mechanism from the prepore to the mature pore within the family.Our results point to the key role of several amino acids in the conformational changes needed for oligomerization and further pore formation, such as Y221, W227, P248, Q263 and L277, which we propose are involved in the release of the stem loop and the two adjacent ß-strands to form the transmembrane ß-barrel.

In Vitro and in Vivo Anti-Trypanosoma cruzi Activity of New Arylamine Mannich Base-Type Derivatives.

Chagas disease is a neglected tropical disease with 6-7 million people infected worldwide, and there is no effective treatment. Therefore, there is an urgent need to continue researching in order to discover novel therapeutic alternatives. We present a series of arylaminoketone derivatives as means of identifying new drugs to treat Chagas disease in the acute phase with greater activity, less toxicity, and a larger spectrum of action than that corresponding to the reference drug benznidazole. Indexes of high selectivity found in vitro formed the basis for later in vivo assays in BALB/c mice. Murine model results show that compounds 3, 4, 7, and 10 induced a remarkable decrease in parasitemia levels in acute phase and the parasitemia reactivation following immunosuppression, and curative rates were higher than with benznidazole. These high antiparasitic activities encourage us to propose these compounds as promising molecules for developing an easy to synthesize anti-Chagas agent.

Cryo-EM structure of aerolysin variants reveals a novel protein fold and the pore-formation process.

Owing to their pathogenical role and unique ability to exist both as soluble proteins and transmembrane complexes, pore-forming toxins (PFTs) have been a focus of microbiologists and structural biologists for decades. PFTs are generally secreted as water-soluble monomers and subsequently bind the membrane of target cells. Then, they assemble into circular oligomers, which undergo conformational changes that allow membrane insertion leading to pore formation and potentially cell death. Aerolysin, produced by the human pathogen Aeromonas hydrophila, is the founding member of a major PFT family found throughout all kingdoms of life. We report cryo-electron microscopy structures of three conformational intermediates and of the final aerolysin pore, jointly providing insight into the conformational changes that allow pore formation. Moreover, the structures reveal a protein fold consisting of two concentric ß-barrels, tightly kept together by hydrophobic interactions. This fold suggests a basis for the prion-like ultrastability of aerolysin pore and its stoichiometry.

Novel sulfonylurea derivatives as H3 receptor antagonists. Preliminary SAR studies.

The combination of antagonism at histamine H(3) receptor and the stimulation of insulin secretion have been proposed as an approach to new dual therapeutic agents for the treatment of type 2 diabetes mellitus associated with obesity. We have designed and synthesized a new series of non-imidazole derivatives, based on a basic amine ring connected through an alkyl spacer of variable length to a phenoxysulfonylurea moiety. These compounds were initially evaluated for histamine H(3) receptor binding affinities, suggesting that a propoxy chain linker between the amine and the core ring could be essential for optimal binding affinity. Compound 56, 1-(naphthalen-1-yl)-3-[(p-(3-pyrrolidin-1-ylpropoxy)benzene)]sulfonylurea exhibited the best H(3) antagonism affinity. However, since all these derivatives failed to block K(ATP) channels, the link of these two related moieties should not be considered a good pharmacophore for obtaining new dual H(3) antagonists with insulinotropic activity, suggesting the necessity to propose a new chemical hybrid prototype.

Building a MCHR1 homology model provides insight into the receptor-antagonist contacts that are important for the development of new anti-obesity agents.

Melanin-concentrating hormone (MCH) regulates feeding and energy homeostasis through interaction with its receptor, the melanin-concentrating receptor 1 (MCHR1), making it a target in the treatment of obesity. Molecular modeling and docking studies were performed in order to find a binding model for the docking of two new series of MCHR1 antagonists to the receptor. Results suggested interactions between the ligands and two glutamines (Gln5.42 and Gln6.55) not conserved in many of the GPCRs family members. Histamine 3 receptor (HRH3) presents two apolar residues in the aforementioned positions and the available biological data against this receptor supported the role of the two glutamines in the binding of antagonists to the MCHR1. This knowledge could be useful in the development of new, more active and more selective MCHR1 antagonists.

Melanin-concentrating hormone receptor 1 antagonists: a new perspective for the pharmacologic treatment of obesity.

Obesity is a chronic disease characterized by the accumulation of excess adipose tissue associated with an increased risk of multiple morbidities and mortality. At the present time, only three drugs have been approved by the Food and Drug Administration (FDA) for the treatment of obesity. Agonists and antagonists of some of the substances implicated in the regulation of energy homeostasis represent opportunities for anti-obesity drug development. The most promising targets are alpha-melanocyte stimulating hormone (alpha-MSH) receptors, cannabinoid receptors, the 5-hydroxytryptamine (5-HT) receptors and melanin-concentrating hormone (MCH) receptors. MCH receptors could be major potential targets for the treatment of obesity. Many pharmaceutical companies have described MCH-R1 antagonists that have appeared over the past year. Recently, two compounds went into phase I clinical trials that evaluate MCH receptor antagonists as a new perspective for the pharmacologic treatment of obesity. In this review, structure-activity relationships (SAR) in the development of MCH-R1 antagonists are provided.

New amide derivatives as melanin-concentrating hormone receptor 1 antagonists for the treatment of obesity.

Melanin-concentrating hormone (MCH) is a recently discovered central nervous system (CNS) target for treating obesity. Two novel series of amide derivatives were synthesized and evaluated biologically as MCH-R1 (melanin-concentrating hormone receptor 1) antagonists. The results showed that diphenyl substituents on the amide lead to better activity than biphenyl substituents.

Novel series of substituted biphenylmethyl urea derivatives as MCH-R1 antagonists for the treatment of obesity.

We have designed and synthesized two novel series of MCH-R1 antagonists based on a substituted biphenylmethyl urea core. SAR was explored, suggesting that optimal binding with the receptor was achieved when the biphenylmethyl group and the linker were substituted on the same nitrogen of the urea moiety. Compound 1-(3'-cyano-4-biphenylmethyl)-3-(2-hydroxy-1,1-dimethylethyl)-1-{2-[1-(4-methylbenzyl)-4-piperidinyl]ethyl}urea 2t showed the best antagonist binding activity to the MCH-R1 with a 43 nM K(i).