6-Methyl-7-Aryl-7-Deazapurine Nucleosides as Anti-Trypanosoma cruzi Agents: Structure-Activity Relationship and in†vivo Efficacy.

Chagas disease is a tropical infectious disease resulting in progressive organ-damage and currently lacks efficient treatment and vaccine options. The causative pathogen, Trypanosoma cruzi, requires uptake and processing of preformed purines from the host because it cannot synthesize these de novo, instigating the evaluation of modified purine nucleosides as potential trypanocides. By modifying the pyrimidine part of a previously identified 7-aryl-7-deazapurine nucleoside, we found that substitution of a 6-methyl for a 6-amino group allows retaining T. cruzi amastigote growth inhibitory activity but confers improved selectivity towards mammalian cells. By keeping the 6-methyl group unaltered, and introducing different 7-aryl groups, we identified several analogues with sub-micromolar antitrypanosomal activity. The 7-(4-chlorophenyl) analogue 14, which was stable in microsomes, was evaluated in an acute mouse model. Oral administration of 25 mg/kg b.i.d. suppressed peak parasitemia and protected mice from infection-related mortality, gave similar reductions as the reference drug of blood parasite loads determined by qPCR, but as benznidazole failed to induce sterile cure in the short time period of drug exposure (5 days).

Discovery of Novel 7-Aryl 7-Deazapurine 3'-Deoxy-ribofuranosyl Nucleosides with Potent Activity against Trypanosoma cruzi.

Chagas disease is the leading cause of cardiac-related mortality in Latin American countries where it is endemic. Trypanosoma cruzi, the disease-causing pathogen, is unable to synthesize purines de novo, necessitating salvage of preformed host purines. Therefore, purine and purine-nucleoside analogues might constitute an attractive source for identifying antitrypanosomal hits. In this study, structural elements of two purine-nucleoside analogues (i.e., cordycepin and a recently discovered 7-substituted 7-deazaadenosine) led to the identification of novel nucleoside analogues with potent in vitro activity. The structure-activity relationships of substituents at C-7 were investigated, ultimately leading to the selection of compound 5, with a C-7 para-chlorophenyl group, for in vivo evaluation. This derivative showed complete suppression of T. cruzi Y-strain blood parasitemia when orally administered twice daily for 5 days at 25 mg/kg and was able to protect infected mice from parasite-induced mortality. However, sterile cure by immunosuppression could not be demonstrated.

Copper(II)-fluoroquinolone complexes with anti-Trypanosoma cruzi activity and DNA binding ability.

Copper(II) complexes of fluoroquinolone antibacterial agents levofloxacin (LEV) and sparfloxacin (SPAR), containing or not a nitrogen donor heterocyclic ligand, 2,2'-bipyridine (bipy) or 1,10-phenathroline (phen), were prepared and characterized. The complexes are of the type [CuCl(2)(H(2)O)(L)], [CuCl(bipy)(L)]Cl and [CuCl(2)(phen)(L)], where L = LEV or SPAR. The data suggest that LEV and SPAR act as zwitterionic bidentade ligands coordinated to Cu(II) through the carboxylate and ketone oxygen atoms. The electron paramagnetic resonance spectra of the [CuCl(bipy)(L)]Cl and [CuCl(2)(phen)(L)] complexes (L = LEV and SPAR) in aqueous and DMSO solutions indicate mixture of mononuclear and binuclear forms. The Cu(II) complexes, together with the corresponding ligands, were evaluated for their trypanocidal activity in vitro against Trypanosoma cruzi, the causative agent of Chagas disease. The assays performed against bloodstream trypomastigotes showed that all complexes were more active than their corresponding ligands. Complexes [CuCl(2)(phen)(LEV)] and [CuCl(2)(phen)(SPAR)] were revealed, among all studied compounds, to be the most active with IC(50) = 1.6 and 4.7 µM, respectively, both presenting a superior effect than benznidazole. The interactions of fluoroquinolones and their Cu(II) complexes with calf-thymus DNA were investigated. These compounds showed binding properties towards DNA, with moderated binding constants values, suggesting that this structure may represent a parasite target.

SB-431542, a transforming growth factor beta inhibitor, impairs Trypanosoma cruzi infection in cardiomyocytes and parasite cycle completion.

The antiinflammatory cytokine transforming growth factor beta (TGF-beta) plays an important role in Chagas disease, a parasitic infection caused by the protozoan Trypanosoma cruzi. In the present study, we show that SB-431542, an inhibitor of the TGF-beta type I receptor (ALK5), inhibits T. cruzi-induced activation of the TGF-beta pathway in epithelial cells and in cardiomyocytes. Further, we demonstrate that addition of SB-431542 greatly reduces cardiomyocyte invasion by T. cruzi. Finally, SB-431542 treatment significantly reduces the number of parasites per infected cell and trypomastigote differentiation and release. Taken together, these data further confirm the major role of the TGF-beta signaling pathway in both T. cruzi infection and T. cruzi cell cycle completion. Our present data demonstrate that small inhibitors of the TGF-beta signaling pathway might be potential pharmacological tools for the treatment of Chagas disease.

Trypanocidal activity of the phenyl-substituted analogue of furamidine DB569 against Trypanosoma cruzi infection in vivo.

OBJECTIVES: Aromatic diamidines have been successfully used to combat a wide range of parasites that cause important human infections. One such compound is furamidine (DB75) and we recently reported that one of its analogues, an N-phenyl analogue (DB569), exhibits higher trypanocidal dose and time-dependent effects against different forms of Trypanosoma cruzi as compared with DB75. Our present aim was to investigate the efficacy of DB569 in a T. cruzi mouse model. METHODS: The trypanocidal activity of the compound was evaluated by clinical, parasitological, histopathological and biochemical investigations. RESULTS: Treatment with DB569 significantly reduced cardiac parasitism, partially increased the survival rates of mice and lowered the levels of alanine aminotransferase and creatinine indicating a protective role against renal and hepatic lesions caused by the parasite infection. CONCLUSIONS: Altogether, the data support the potential effect of this class of compounds against T. cruzi and motivate the screening of new diamidines for efficacy against Chagas' disease.

The expression of mannose receptors in skin fibroblast and their involvement in Leishmania (L.) amazonensis invasion.

Leishmania are protozoa that invade mononuclear phagocytes with the involvement of different ligand-receptor systems, including mannose receptors. Until now, scant data are available concerning the mechanisms that govern the infection of Leishmania in other host cell types such as fibroblasts. Our aim was to analyze the expression of mannose receptors in primary cultures of skin fibroblasts (SF) further characterizing their role during the invasion of promastigotes of Leishmania (L.) amazonensis. Both fluorescent, light, and electron microscopy assays revealed that SF have mannose receptors since they bound and internalized mannosylated ligands in addition to being positively labeled by fuc-BSA-FITC probes. d-mannose competition assays revealed the participation of mannose receptors during the parasite association with SF presenting upregulated receptor expression during the initial steps of the infection. After longer periods of Leishmania:fibroblasts contact, the modulation noted in the host mannose receptors was reverted concomitantly to the infection control, suggesting that the parasites were required for the alteration maintenance and providing evidences that the SF may display microbicidal mechanisms to control the Leishmania infection.