Metronidazole Interaction with Cu2+ and Zn2+: Speciation Study in Aqueous Solution and Biological Activity Evaluation.

Metronidazole (2-methyl-5-nitro-1H-imidazole-1-ethanol, MNZ) is a well-known and widely used drug for its excellent activity against various anaerobic bacteria and protozoa. The purpose of this study is to elucidate the ability of MNZ to form metal complexes with Cu2+ and Zn2+ and to demonstrate that complexation increases its bioactivity profile against different pathogenic microorganisms. The interaction of MNZ with Cu2+ and Zn2+ was investigated in NaCl aqueous solution under different conditions of temperature (15, 25, and 37 °C) and ionic strength (0.15, 0.5, and 1 mol L-1) by potentiometric and spectrophotometric titrations. The obtained speciation models include two species for the Cu2+-containing system, namely, CuL and CuL2, and three species for the Zn2+-containing system, namely, ZnLH, ZnL, and ZnLOH. The formation constants of the species were calculated and their dependence on temperature and ionic strength evaluated. Comparison of the sequestering ability of MNZ under physiological conditions revealed a capacity toward Cu2+ higher than that toward Zn2+. A simulation under the same conditions also showed a significant percentage of the Cu2+-MNZ species. The biological assessments highlighted that the complexation of MNZ with Cu2+ has a relevant impact on the potency of the drug against two Trypanosoma spp. (i.e., T. b. brucei and T. b. rhodesiense) and one gram-(-) bacterial species (i.e., Escherichia coli). It is noteworthy that the increased potency upon complexation with Cu2+ did not result in cytotoxicity against MRC-5 human fetal lung fibroblasts and primary peritoneal mouse macrophages.

Design and Synthesis of 1,3-Diarylpyrazoles and Investigation of Their Cytotoxicity and Antiparasitic Profile.

Herein, we report a series of 1,3-diarylpyrazoles that are analogues of compound 26/HIT 8. We previously identified this molecule as a 'hit' during a high-throughput screening campaign for autophagy inducers. A variety of synthetic strategies were utilized to modify the 1,3-diarylpyrazole core at its 1-, 3-, and 4-position. Compounds were assessed in vitro to identify their cytotoxicity properties. Of note, several compounds in the series displayed relevant cytotoxicity, which warrants scrutiny while interpreting biological activities that have been reported for structurally related molecules. In addition, antiparasitic activities were recorded against a range of human-infective protozoa, including Trypanosoma cruzi, T. brucei rhodesiense, and Leishmania infantum. The most interesting compounds displayed low micromolar whole-cell potencies against individual or several parasitic species, while lacking cytotoxicity against human cells.

Novel quinoline derivatives with broad-spectrum antiprotozoal activities.

Several quinoline derivatives incorporating arylnitro and aminochalcone moieties were synthesized and evaluated in vitro against a broad panel of trypanosomatid protozoan parasites responsible for sleeping sickness (Trypanosoma brucei rhodesiense), nagana (Trypanosoma brucei brucei), Chagas disease (Trypanosoma cruzi), and leishmaniasis (Leishmania infantum). Several of the compounds demonstrated significant antiprotozoal activity. Specifically, compounds 2c, 2d, and 4i displayed submicromolar activity against T. b. rhodesiense with half-maximal effective concentration (EC50) values of 0.68, 0.8, and 0.19 µM, respectively, and with a high selectivity relative to human lung fibroblasts and mouse primary macrophages (∼100-fold). Compounds 2d and 4i also showed considerable activity against T. b. brucei with EC50 values of 1.4 and 0.4 µM, respectively.

DNDI-6174 is a preclinical candidate for visceral leishmaniasis that targets the cytochrome bc1.

New drugs for visceral leishmaniasis that are safe, low cost, and adapted to the field are urgently required. Despite concerted efforts over the last several years, the number of new chemical entities that are suitable for clinical development for the treatment of Leishmania remains low. Here, we describe the discovery and preclinical development of DNDI-6174, an inhibitor of Leishmania cytochrome bc1 complex activity that originated from a phenotypically identified pyrrolopyrimidine series. This compound fulfills all target candidate profile criteria required for progression into preclinical development. In addition to good metabolic stability and pharmacokinetic properties, DNDI-6174 demonstrates potent in vitro activity against a variety of Leishmania species and can reduce parasite burden in animal models of infection, with the potential to approach sterile cure. No major flags were identified in preliminary safety studies, including an exploratory 14-day toxicology study in the rat. DNDI-6174 is a cytochrome bc1 complex inhibitor with acceptable development properties to enter preclinical development for visceral leishmaniasis.

Hit-to-lead optimization of a 2-aminobenzimidazole series as new candidates for chagas disease.

Chagas disease is a neglected tropical disease caused by Trypanosoma cruzi. Because current treatments present several limitations, including long duration, variable efficacy and serious side effects, there is an urgent need to explore new antitrypanosomal drugs. The present study describes the hit-to-lead optimization of a 2-aminobenzimidazole hit 1 identified through in vitro phenotypic screening of a chemical library against intracellular Trypanosoma cruzi amastigotes, which focused on optimizing potency, selectivity, microsomal stability and lipophilicity. Multiparametric Structure-Activity Relationships were investigated using a set of 277 derivatives. Although the physicochemical and biological properties of the initial hits were improved, a combination of low kinetic solubility and in vitro cytotoxicity against mammalian cells prevented progression of the best compounds to an efficacy study using a mouse model of Chagas disease.

Antiplasmodial activity of constituents and their metabolites after in vitro gastrointestinal biotransformation of a Nauclea pobeguinii extract.

Nauclea pobeguinii is traditionally used for treatment of malaria. Previous studies on the plant extract and strictosamide, the putative active constituent, showed a profound in vivo activity of the extract but no in vitro activity of strictosamide. This might indicate that one or more compounds present in the extract, most likely alkaloids, act as prodrugs undergoing biotransformation after oral administration resulting in the active compounds. The phytochemical composition of a N. pobeguinii extract was characterized using UHPLC-UV-HRMS (Ultrahigh-Performance Liquid Chromatography-Ultraviolet-High Resolution Mass Spectrometry) data. An in vitro gastrointestinal model was used to simulate biotransformation of the extract allowing monitoring of the relative abundances of individual constituents over time on one hand, while antiplasmodial activity and cytotoxicity of the biotransformed extract could be evaluated on the other hand. A diversity of compounds was (tentatively) identified in the extract, mainly saponins and alkaloids, including 32 compounds that have not been reported before in N. pobeguinii. The automated data analysis workflow used for unbiased screening for metabolites showed that glycosylated compounds decreased in intensity over time. Alkaloids containing no sugar moieties, including angustine-type alkaloids, showed no gastrointestinal biotransformation. In vitro gastrointestinal biotransformation of strictosamide did not result in a major metabolite. Moreover, multivariate data analysis using Orthogonal Partial Least Square-Discriminant Analysis (OPLS-DA) showed no in vitro activity of strictosamide or its metabolites suggesting that other compounds or metabolites present in the extract are responsible for the antiplasmodial effect of the N. pobeguinii extract. The OPLS-DA proposes alkaloids with a ß-carboline moiety as active principles, suggesting that antiplasmodial activity of N. pobeguinii derives from an additive or synergistic effect of multiple minor alkaloids and their metabolites present in the bark extract of N. pobeguinii.

Overexpression of a constitutively active protein kinase G mutant reduces neointima formation and in-stent restenosis.

BACKGROUND: Neointima formation after arterial injury is associated with reduced vascular cyclic guanosine monophosphate (cGMP) and cGMP-dependent protein kinase (PKG), a major cGMP effector in vascular smooth muscle. We tested the effect of PKG overexpression on the neointimal response to vascular injury. Methods and Results- Infection of cultured rat aortic smooth muscle cells (RASMCs) with an adenoviral vector specifying a cGMP-independent, constitutively active PKG mutant (AdPKGcat) reduced serum-induced migration by 33% and increased serum-deprivation-induced apoptosis 2-fold (P<0.05 for both). Infection with wild-type PKG (AdPKG), in the absence of cGMP, did not affect migration or apoptosis. Two weeks after balloon-injured rat carotid arteries were infected with 1x 10(10) pfu AdPKGcat (n=12), AdPKG (n=8), or a control adenovirus (n=8), intima-to-media ratio was less in AdPKGcat-infected arteries than in AdPKG- or control adenovirus-infected vessels (0.26+/-0.06 versus 0.61+/-0.12 and 0.70+/-0.12, respectively, P<0.05 for both). Two weeks after intramural administration of 1.75x10(10) pfu AdPKGcat (n=8) or a control adenovirus (n=8) into porcine coronary arteries with in-stent restenosis, luminal diameter was greater in AdPKGcat-infected arteries than in control adenovirus-infected vessels (2.32+/-0.16 versus 1.81+/-0.13 mm, P=0.028), associated with reduced neointimal area (3.30+/-0.24 versus 4.15+/-0.13 mm(2), P=0.008), neointima-to-vessel area ratio (0.42+/-0.05 versus 0.58+/-0.04, P<0.05), and percent stenosis (45+/-6% versus 70+/-4%, P<0.05). CONCLUSIONS: Expression of a constitutively active PKG reduces neointima formation after balloon injury in rats and reduces coronary in-stent restenosis in pigs. PKGcat gene transfer may be a promising strategy for vasculoproliferative disorders.

Preexisting antiadenoviral immunity and regional myocardial gene transfer: modulation by nitric oxide.

The utility of adenoviral vectors, currently used in cardiovascular gene transfer protocols, is limited by the brevity of transgene expression and by antiadenoviral immune responses. The effect of preexisting antiadenoviral immunity on intracardiac gene transfer or its modulation by nitric oxide is unknown. Adenoviral vectors, expressing the firefly luciferase gene (AdLuc) or the human nitric oxide synthase 3 (NOS3) gene (AdNOS3), were infused into the great cardiac vein of naive pigs or immunized pigs. Pigs were immunized by intravenous injection of control virus AdRR5 and the resulting neutralizing antibody titers (median, 1:178; p < 0.0001 vs. baseline) were similar to preexisting titers in 54% of randomly selected coronary artery bypass graft patients. In naive animals distribution of transgene expression in the left ventricular free wall was focal. In immunized pigs myocardial luciferase expression 3 days after AdLuc gene transfer was more than 1000-fold lower than in naive pigs, whereas no change in NOS3 transcript levels was detected after AdNOS3 gene transfer. Severe, grade III-IV mononuclear cell infiltration and myocyte apoptosis were observed in four of five AdLuc-infected, immunized animals, compared with low-level inflammation and apoptosis in five of six AdNOS3-infected pigs. Coinfusion of AdLuc and AdNOS3 in immunized pigs resulted in spatially colocalized transgene expression, reduced T cell-mediated inflammation, and myocyte apoptosis and was associated with 200-fold greater median reporter transgene expression levels in the subendocardium (1.0 x 10(3) light units [LU]/mg protein, n = 8, vs. 4.5 x 10(1) LU/mg protein in AdLuc- and AdRR5-coinfected pigs, n = 7, p = 0.02). Preexisting antiadenoviral immunity abrogates myocardial gene expression in pigs and is associated with severe inflammation and myocyte apoptosis. Intracardiac NOS3 gene transfer may reduce these barriers to adenovirus-mediated myocardial gene transfer.