Trypanosoma cruzi, the protozoan parasite that causes Chagas' disease, exhibits peculiar biological features. Among them, the presence of a unique mitochondrion is remarkable. Even though the mitochondrial DNA constitutes up to 25% of total cellular DNA, the structure and functionality of the mitochondrion are dependent on the expression of the nuclear genome. As in other eukaryotes, specific peptide signals have been proposed to drive the mitochondrial localization of a subset of trypanosomatid proteins. However, there are mitochondrial proteins encoded in the nuclear genome that lack of a peptide signal. In other eukaryotes, alternative protein targeting to subcellular organelles via mRNA localization has also been recognized and specific mRNA localization towards the mitochondria has been described. With the aim of seeking for mitochondrial localization signals in T. cruzi, we developed a strategy to build a comprehensive database of nuclear genes encoding predicted mitochondrial proteins (MiNT) in the TriTryps (T. cruzi, T. brucei and L. major). We found that approximately 15% of their nuclear genome encodes mitochondrial products. In T. cruzi the MiNT database reaches 1438 genes and a conserved peptide signal, M(L/F) R (R/S) SS, named TryM-TaPe is found in 60% of these genes, suggesting that the canonical mRNA guidance mechanism is present. In addition, the search for compositional signals in the transcripts of T. cruzi MiNT genes produce a list, being worth to note a conserved non-translated element represented by the consensus sequence DARRVSG. Taking into account its reported interaction with the T. brucei TRRM3 protein which is enriched in the mitochondrial membrane fraction, we here suggest a putative zip code role for this element. Globally, here we provide an inventory of the mitochondrial proteins in T. cruzi and give evidence for the existence of both peptide and mRNA signals specific to nuclear encoded mitochondrial proteins.

Trypanosoma cruzi is the protozoan parasite causing American trypanosomiasis or Chagas disease, a neglected parasitosis with important human health impact in Latin America. The efficacy of current therapy is limited, and its toxicity is high. Since parasite proliferation is a fundamental target for rational drug design, we sought to progress into its understanding by applying a genome-wide approach. Treating a TcI linage strain with hydroxyurea, we isolated epimastigotes in late G1, S and G2/M cell cycle stages at 70% purity. The sequencing of each phase identified 305 stage-specific transcripts (1.5-fold change, p≤0.01), coding for conserved cell cycle regulated proteins and numerous proteins whose cell cycle dependence has not been recognized before. Comparisons with the parasite T. brucei and the human host reveal important differences. The meta-analysis of T. cruzi transcriptomic and ribonomic data indicates that cell cycle regulated mRNAs are subject to sub-cellular compartmentalization. Compositional and structural biases of these genes- including CAI, GC content, UTR length, and polycistron position- may contribute to their regulation. To discover nucleotide motifs responsible for the co-regulation of cell cycle regulated genes, we looked for overrepresented motifs at their UTRs and found a variant of the cell cycle sequence motif at the 3' UTR of most of the S and G2 stage genes. We additionally identified hairpin structures at the 5' UTRs of a high proportion of the transcripts, suggesting that periodic gene expression might also rely on translation initiation in T. cruzi. In summary, we report a comprehensive list of T. cruzi cell cycle regulated genes, including many previously unstudied proteins, we show evidence favoring a multi-step control of their expression, and we identify mRNA motifs that may mediate their regulation. Our results provide novel information of the T. cruzi proliferative proteins and the integrated levels of their gene expression control.

In the protozoan parasite Trypanosoma cruzi, as in other trypanosomatids, transcription of protein coding genes occurs in a constitutive fashion, producing large polycistronic transcription units. These units are composed of non-functionally related genes which are pervasively processed to yield each mRNA. Therefore, post-transcriptional processes are crucial to regulate gene expression. Considering that nuclear compartmentalization could contribute to gene expression regulation, we comparatively studied the nuclear, cytoplasmic and whole cell transcriptomes of the non-infective epimastigote stage of T. cruzi, using RNA-Seq. We found that the cytoplasmic transcriptome tightly correlates with the whole cell transcriptome and both equally correlate with the proteome. Nonetheless, 1,200 transcripts showed differential abundance between the nuclear and cytoplasmic fractions. For the genes with transcript content augmented in the nucleus, significant structural and compositional differences were found. The analysis of the reported epimastigote translatome and proteome, revealed scarce ribosome footprints and encoded proteins for them. Ontology analyses unveiled that many of these genes are distinctive of other parasite life-cycle stages. Finally, the relocalization of transcript abundance in the metacyclic trypomastigote infective stage was confirmed for specific genes. While gene expression is strongly dependent on transcript steady-state level, we here highlight the importance of the distribution of transcripts abundance between compartments in T. cruzi. Particularly, we show that nuclear compartmentation is playing an active role in the developmental stage determination preventing off-stage expression.

Casiopeínas® are mixed-chelate copper complexes with antitumor tested potential. Their activity, both in vitro and in vivo, as antiproliferative, cytotoxic, and genotoxic drugs has been assessed. Biological results of these copper compounds have deserved some of them entering clinical trials. Significant efforts have been devoted to the in-depth identification of their mechanism of action. Using gel electrophoresis analysis, we have previously shown that the interaction of the Casiopeínas® Cas II-gly, [Cu(4,7-dimethyl-1,10-phenanthroline)(glycinate)]NO 3 with DNA, triggers the cleavage of the biomolecule by a free radical mechanism. In this work, we further study the behavior of different complexes of the same Casiopeínas® series also including glycinate as co-ligand {Cas VI-gly (5,6 dimethyl-1,10-phenanthroline glycinato copper(II) nitrate), Cas VII-gly (1,10-phenanthroline glycinato copper(II) nitrate), and Cas IX-gly (2,2′-bipyridine glycinato copper(II) nitrate)} and of a Casiopeínas® with a different co-ligand (Cas III-Cs; 4,7-dimethyl-1,10-phenanthroline salicylaldehydato-copper(II) nitrate). While all of them produce DNA degradation, the performance in the presence of a radical scavenger suggests the existence of differences in their mechanism of interaction with DNA.

Five new fac-Re-I(CO)(3)-tridentate semicarbazone complexes were synthesized, characterized and evaluated on Trypanosoma cruzi. The atypical bidentate coordination mode observed was supported by DFT calculations.Expanding our previous work on salicylaldehyde semicarbazone metal complexes as prospective anti-trypanosomal agents, five new fac-Re-I(CO)(3)-containing complexes with ligands of this semicarbazone series were synthesized and characterized. An atypical coordination mode of these potentially tridentate ligands through only the carbonylic oxygen and the azomethine nitrogen (the so-called N,O fashion) was demonstrated by IR spectroscopy and supported by theoretical calculations. Three of the compounds showed moderate in vitro anti-Trypanosoma cruzi activity and increased activity with respect to the corresponding free ligands. The brominated ligands, 5-bromo-2- hydroxybenzaldehyde semicarbazone (L2) and 5-bromo-2-hydroxy-3-methoxybenzaldehyde semicarbazone (L5), led to the most active rhenium(I) complexes. These compounds are among the few reported examples of rhenium complexes bearing in vitro activity against T. cruzi.

As a contribution to the identification of the relevant species for biological activity and the understanding of structure–activity relationships of [VIVO(L-2H)(NN)] antitrypanosomal complexes (NN is a bidentate polypyridyl DNA intercalator; L is a tridentate salicylaldehyde semicarbazone derivative), new [VVO2(L-2H)] complexes and [VIVO(L-2H)(NN)] complexes including bipy or dppz (dipyrido[3,2-a: 2′,3′-c]phenazine) co-ligands are prepared and characterized in the solid state and in solution. Their activity is evaluated on Trypanosoma cruzi. The lipophilicity, as structural descriptor related to bioactivity, of the whole [VIVO(L-2H)(NN)] series is determined. Furthermore, the antiproliferative effect of those new compounds showing activity against T. cruzi is evaluated on the genetically related parasite T. brucei with the aim to develop broad spectrum agents. The new [VIVO(L-2H)(dppz)] complexes are about ten to fifteen times more toxic to T. cruzi than the bipy analogues and show quite good in vitro activity on T. brucei brucei. They are shown to interact with DNA, suggesting that this biomolecule may be the parasite target. The stability of the VIVO-complexes in solution is accessed by several techniques. Globally the data suggest that the relevant species for biological activity are the [VIVO(L-2H)(NN)] compounds, their order of activity being dependent on the NN nature, but not much on the substitution on the salicylaldehyde semicarbazone moiety. A parabolic relationship between biological response and lipophilicity (determined as RM=log [(1/Rf)−1] by a TLC method) is obtained. From this correlation an optimum RM value, close to 1.44, was found, which may be used as design guide for future development of antitrypanosomal compounds.

In the search for new agents against Trypanosoma cruzi and cancer the effect of the nature of the metal center and of the presence of a polypiridyl coligand on the antitrypanosomal and antitumoral activities of selected N,N,O ligands [2-(benzothiazol-2-yl-hydrazonomethyl phenol (HL1) and 2-(benzothiazol-2-yl-hydrazonomethyl)-6-methoxyphenol (HL2)] is explored. The new complexes [VVO2(L1)], [VVO2(L2)], [VIVO(L1-H)(phen))] and [GaIII(L2)2](NO3) were synthesized and characterized by using different techniques. The stability of the vanadium complexes in solution was investigated by EPR and 51V NMR spectroscopies and that of the gallium compound by UV–Vis spectroscopy, 1H NMR and conductivity measurements. While the vanadium complexes show high stability in DMSO, the gallium complex shows very good stability in DMSO and moderate stability in aqueous – DMSO medium.The cytotoxicity on human tumor cell lines (ovarian A2780, breast MCF7 and prostate PC3 cell lines) that show different sensitivity to cisplatin was evaluated. All the compounds evidenced antiproliferative activity in the micromolar range. The highest cytotoxic activity, in molar units, is shown by [GaIII(L2)2](NO3) (IC50: 1.7μM) and [VIVO(L1-H)(phen)] (IC50: 2.7μM) against the ovarian cancer cells. With the exception of [VVO2(L1)], the cytotoxic activity of the ligands and complexes is similar to that of cisplatin in A2780 cells and surpass cisplatin in the other tumor cells. Regarding the activity on T. cruzi, [VIVO(L1-H)(phen)] showed a 10-fold decrease of IC50 with respect to HL1 and an IC50 value (10.7μM) in the same order of that of the antitrypanosomal drug Nifurtimox (IC50: 6.0μM). HL2 showed significant growth inhibitory effect on the parasite (IC50: 23.5μM) and its coordination to Ga(III) lead to a 2-fold increase in activity in molar units (IC50: 14.2μM). In order to explain the high inhibitory activity of [VIVO(L1-H)(phen)] against the parasite and the tumor cells, the interaction of this compound with plasmid DNA was preliminarily evaluated by AFM. The corresponding images suggest that DNA may be considered as a potential target.

Searching for new promising metal-based drugs for the treatment of parasitic diseases against Trypanosoma cruzi, three related oxidovanadium(IV) complexes, [(VO)-O-IV(SO4)(H2O)(2)(NN)], with the phenanthroline derivatives (NN) [1,2,5] thiadiazolo[3,4-f][1,10] phenanthroline (tdzp), 1,10-phenanthroline-5,6-dione (phendione), and 5,6-epoxy-5,6-dihydro-1,10-phenanthroline (epoxyphen) are synthesized, characterized, and evaluated in vitro as anti-T. cruzi agents. The compounds are characterized in the solid state and in solution by elemental analysis, electrospray ionization mass spectrometry (ESI-MS), conductimetric measurements, and infrared (FTIR), UV/Vis, and electronic paramagnetic resonance (EPR) spectroscopy. EPR spectroscopy suggests that the ligands act as bidentate, binding through both nitrogen donor atoms in an axial-equatorial mode. DFT calculations corroborate the structural assignments. The stability of the complexes in solution is evaluated by EPR and V-51-NMR spectroscopy and all complexes show reasonable stability. The anti-T. cruzi activity of the complexes was tested by measuring the growth inhibitory effect on the epimastigote life cycle form of the parasite (Dm28c strain). All complexes show IC50 values in the micromolar range against T. cruzi and display activities of the same order of that of Nifurtimox, but lower than that of the previously reported analogue [(VO)-O-IV(SO4)(H2O)(2)(dppz)] (dppz = dipyrido[3,2-a:2',3'-c]phenazine). Furthermore, DNA was evaluated as a potential target by using atomic force microscopy (AFM), showing that the complexes display ability to interact with this biomolecule.

The mixed-chelate copper(II) complexes Casiopeínas® have been tested in several models in vitro and in vivo, showing promising antitumoral results. However, their mechanism of action remains to be defined. Trying to get a deeper insight into their molecular mode of action, further analyses, including gel electrophoresis, atomic force microscopy and circular dichroism were carried out to study their interaction with DNA and some cytoskeleton proteins. Our results revealed that the interaction of Casiopeínas triggers DNA cleavage by a free radical mechanism. The tested complexes showed a differential response to reducing and scavenger agents. Differences on target preference were also evident using double stranded oligonucleotides as sequence competitors. Surprisingly, distamycin A, a minor groove binder, enhanced the Casiopeínas' action on DNA. On the other hand, the tested Casiopeínas produce strong changes in protein structure of tubulin, integrin and fibronectin. All together these results suggest a multiple mode of action for these metal-based drugs. In addition, since it has been proposed that antitumor drugs efficiently interacting with DNA could also show activity against Trypanosoma cruzi, etiologic agent of Chagas disease, we evaluated the activity of these compounds on this protozoan parasite. The tested complexes showed in vitro anti-T. cruzi activity similar to the anti-trypanosomal reference drug Nifurtimox.

In the search for new therapeutic tools against diseases produced by kinetoplastid parasites five vanadyl complexes, [VIVO(L-2H)(phen)], including 1,10-phenanthroline (phen) and tridentate salicylaldehyde semicarbazone derivatives as ligands have been synthesized and characterized in the solid state and in solution by using different techniques. EPR suggested a distorted octahedral geometry with the tridentate semicarbazone occupying three equatorial positions and phen coordinated in an equatorial/axial mode. The compounds were evaluated in vitro on epimastigotes of Trypanosoma cruzi, causative agent of Chagas disease, Leishmania panamensis and Leishmania chagasi and on tumor cells. The complexes showed higher in vitro anti-trypanosomal activities than the reference drug Nifurtimox (IC50 values in the range 1.6–3.8μM) and increased activities in respect to the free semicarbazone ligands. In vitro activity on promastigote and amastigote forms of Leishmania showed interesting results. The compounds [VO(L1-2H)(phen)] and [VO(L3-2H)(phen)], where L1 = 2-hydroxybenzaldehyde semicarbazone and L3 = 2-hydroxy-3-methoxybenzaldehyde semicarbazone, resulted active (IC50 2.74 and 2.75μM, respectively, on promastigotes of L. panamensis; IC50 19.52 and 20.75μM, respectively, on intracellular amastigotes of L. panamensis) and showed low toxicity on THP-1 mammalian cells (IC50 188.55 and 88.13μM, respectively). In addition, the complexes showed cytotoxicity on human promyelocytic leukemia HL-60 cells with IC50 values of the same order of magnitude as cisplatin. The interaction of the complexes with DNA was demonstrated by different techniques, suggesting that this biomolecule could be a potential target either in the parasites or in tumor cells.