1,3-Thiazole derivatives as privileged structures for anti-Trypanosoma cruzi activity: Rational design, synthesis, in silico and in vitro studies.

Chagas disease is a deadly and centenary neglected disease that is recently surging as a potential global threat. Approximately 30% of infected individuals develop chronic Chagas cardiomyopathy and current treatment with the reference benznidazole (BZN) is ineffective for this stage. We presently report the structural planning, synthesis, characterization, molecular docking prediction, cytotoxicity, in vitro bioactivity and mechanistic studies on the anti-T. cruzi activity of a series of 16 novel 1,3-thiazoles (2-17) derived from thiosemicarbazones (1a, 1b) in a two-step and reproducible Hantzsch-based synthesis approach. The anti-T. cruzi activity was evaluated in vitro against the epimastigote, amastigote and trypomastigote forms of the parasite. In the bioactivity assays, all thiazoles were more potent than BZN against epimastigotes. We found that the compounds presented an overall increased anti-tripomastigote selectivity (Cpd 8 was 24-fold more selective) than BZN, and they mostly presented anti-amastigote activity at very low doses (from 3.65 µM, cpd 15). Mechanistic studies on cell death suggested that the series of 1,3-thiazole compounds herein reported cause parasite cell death through apoptosis, but without compromising the mitochondrial membrane potential. In silico prediction of physicochemical properties and pharmacokinetic parameters showed promising drug-like results, being all the reported compounds in compliance with Lipinski and Veber rules. In summary, our work contributes towards a more rational design of potent and selective antitripanosomal drugs, using affordable methodology to yield industrially viable drug candidates.

NPCdc, a synthetic natriuretic peptide, is a substrate to neprilysin and enhances blood pressure-lowering induced by enalapril in 5/6 nephrectomized rats.

NPCdc is a natriuretic peptide synthesized from the amino acid sequence of the Crotalus durissus cascavella snake venom peptide, NP2Casca. NPCdc presents hypotensive and antioxidants effects. This study aimed to investigate in vivo whether angiotensin I-converting enzyme (ACE) inhibition would influence the impact of NPCdc in arterial pressure of rats submitted to 5/6 nephrectomy (Nx). Adult male Wistar rats following a 5/6 Nx were treated with enalapril (NxE group, 10 mg/kg/day, n = 9) or vehicle (Nx group, n = 8) for two weeks. On the 15th day after Nx, rats were anaesthetized and submitted to mean arterial pressure (MAP) determination before and after receiving two intravenous injections of saline (vehicle, n = 9) or NPCdc (0.3 µg/kg dissolved in saline, n = 18) separated by a 20-min interval. The kidneys were submitted to oxidative stress analysis. The basal MAP of the NxE group was nearly 20% lower (P < 0.05) than non-treated rats. NPCdc administration decreased the MAP in both groups; however, in the NxE group, the effects were observed only in the second injection. The peptide also decreased the NADPH oxidase activity in the renal cortex. Additionally, the hydrolysis of NPCdc by recombinant neprilysin (NEP) was monitored by mass spectrometry. NPCdc was cleaved by NEP at different peptides with an inhibition constant (Ki) of 1.5 µM, determined by a competitive assay using the NEP fluorescence resonance energy transfer (FRET) peptide substrate Abz-(d)Arg-Gly-Leu-EDDnp. Docking experiments confirmed the high affinity of NPCdc toward NEP. These findings provide new insights into the antihypertensive and antioxidant mechanism of action of NPCdc. Altogether, the results presented here suggest that NPCdc must be further studied as a potential therapy for cardiorenal syndromes.