Cure of mice infected with Trypanosoma rhodesiense by cis-diamminedichloroplatinum (II) and disulfiram rescue

The repositioned drugs disulfiram/diethyldithiocarbamate combined to benznidazole: Searching for Chagas disease selective therapy, preventing toxicity and drug resistance

Chagas disease (CD) affects at least 6 million people in 21 South American countries besides several thousand in other nations all over the world. It is estimated that at least 14,000 people die every year of CD. Since vaccines are not available, chemotherapy remains of pivotal relevance. About 30% of the treated patients cannot complete the therapy because of severe adverse reactions. Thus, the search for novel drugs is required. Here we tested the benznidazole (BZ) combination with the repositioned drug disulfiram (DSF) and its derivative diethyldithiocarbamate (DETC) upon Trypanosoma cruzi in vitro and in vivo. DETC-BZ combination was synergistic diminishing epimastigote proliferation and enhancing selective indexes up to over 10-fold. DETC was effective upon amastigotes of the BZ- partially resistant Y and the BZ-resistant Colombiana strains. The combination reduced proliferation even using low concentrations (e.g., 2.5 µM). Scanning electron microscopy revealed membrane discontinuities and cell body volume reduction. Transmission electron microscopy revealed remarkable enlargement of endoplasmic reticulum cisternae besides, dilated mitochondria with decreased electron density and disorganized kinetoplast DNA. At advanced stages, the cytoplasm vacuolation apparently impaired compartmentation. The fluorescent probe H2-DCFDA indicates the increased production of reactive oxygen species associated with enhanced lipid peroxidation in parasites incubated with DETC. The biochemical measurement indicates the downmodulation of thiol expression. DETC inhibited superoxide dismutase activity on parasites was more pronounced than in infected mice. In order to approach the DETC effects on intracellular infection, peritoneal macrophages were infected with Colombiana trypomastigotes. DETC addition diminished parasite numbers and the DETC-BZ combination was effective, despite the low concentrations used. In the murine infection, the combination significantly enhanced animal survival, decreasing parasitemia over BZ. Histopathology revealed that low doses of BZ-treated animals presented myocardial amastigote, not observed in combination-treated animals. The picrosirius collagen staining showed reduced myocardial fibrosis. Aminotransferase de aspartate, Aminotransferase de alanine, Creatine kinase, and urea plasma levels demonstrated that the combination was non-toxic. As DSF and DETC can reduce the toxicity of other drugs and resistance phenotypes, such a combination may be safe and effective.

Design of copper DNA intercalators with leishmanicidal activity

The complexes [Cu(dppz)(NO(3))]NO(3) (1), [Cu(dppz)(2)(NO(3))]NO(3) (2), [Cu(dpq)(NO(3))]NO(3) (3), and [Cu(dpq)(2)(NO(3))]NO(3) (4) were synthesized and characterized by elemental analysis, FAB-mass spectrometry, EPR, UV, and IR spectroscopies, and molar conductivity. DNA interaction studies showed that intercalation is an important way of interacting with DNA for these complexes. The biological activity of these copper complexes was evaluated on Leishmania braziliensis promastigotes, and the results showed leishmanicidal activity. Preliminary ultrastructural studies with the most active complex (2) at 1 h revealed parasite swelling and binucleated cells. This finding suggests that the leishmanicidal activity of the copper complexes could be associated with their interaction with the parasitic DNA.

A Short Pb.Pb Separation in the Polymeric Compound Bis(pyrrolidinecarbodithioato)lead(II) and a Conformational Pathway Interconversion for the "Pb(II)S(4)" Framework

The X-ray structure of bis(pyrrolidinecarbodithioato)lead(II), Pb(II)(pdtc)(2), C(10)H(16)N(2)S(4)Pb, shows the metal to be on a crystallographic 2-fold axis. The primary Pb-S bonds are equal, 2.89 Å; this is a unique feature of this compound compared to other Pb(II) dithiocarbamate structures. The crystal structure consists of polymeric Pb(pdtc)(2) units stacked along the c axis in two antiparallel columns; successive Pb(pdtc)(2) units are staggered. There are weaker Pb-S bonding interactions with the unit above (secondary Pb-S bonds) such that the coordination polyhedron formed by the eight S atoms bound to the Pb atom is a distorted square antiprism. Successive antiprisms share the pyramidal base, and the Pb.Pb distance between neighboring Pb(pdtc)(2) units is 3.886(1) Å. We analyze the structures of other PbS(4) compounds and find that the Pb lone pair is important in defining their geometry. The large variety of Pb configurations results from peripheral changes in the ligand. This is due to a compromise between the efficient use of space in the crystal and the tendency of lead to have different coordination numbers. These configurations can be described by a pathway of conformational interconversion from a 4-sided pyramidal geometry to an octahedral system. The title compound crystallizes in the orthorhombic space group Pccn with z = 4; cell constants are a = 13.839(14) Å, b = 14.058(16) Å, c = 7.763(6) Å.

Cure with cisplatin (II) or murine malaria infection and in vitro inhibition of a chloroquine-resistant Plasmodium falciparum isolate

Antiplasmodium properties of cisplatin [cis-platinum (II) diamine dichloride], a neoplastic drug, have been assessed in in vivo and in vitro model systems of malarial parasite. A well-tolerated dose of 6 mg/kg body weight of the compound cured the mice infected with Plasmodium berghei and the amount of cisplatin required for in vitro inhibition (IC50) of a chloroquine-resistant Plasmodium falciparum isolate was smaller than either chloroquine or quinine. The minimum inhibitory concentration (MIC) needed to prevent the in vitro multiplication of asexual blood parasites was 30 ng/ml. Late ring and trophozoite stages of the erythrocytic cycle were the most susceptible, whereas schizont and early ring stages were the least sensitive to the toxic effect of cisplatin. Multiple smaller doses were more effective in curing malaria in mice than a single large dose. In a few of the mice treated with a single intraperitoneal large dose of 6 mg/kg body weight, there was a delay in appearance of parasitemia but most of them recovered completely but slowly. This compound exerts its toxicity mainly by randomly damaging and cross-linking DNA strands as shown by Southern hybridization with a synthetic oligonucleotide probe, which is a repeat sequence in the falciparum genome. The report clearly demonstrates the antimalarial potentials of this compound and suggests a closer evaluation of this and other related compounds, specially in combination with antimalarial drugs to probe their synergistic properties.

Diethyldithiocarbamate increases distribution of cadmium to brain but prevents cadmium-induced neurotoxicity

Dithiocarbamates exhibit potent metal-binding properties which have been exploited in a variety of applications, one of which is chelation therapy for heavy metal toxicity. Such therapy, however, promotes the accumulation of metals in the brain, a side effect which may result in neurotoxicity. To examine this possibility we used morphological and biochemical indices to assess the effects of diethyldithiocarbamate (DDC) on cadmium-induced neurotoxicity in the newborn rat. Co-administration of DDC prevented the neurotoxic effects of cadmium while causing a persistent increase in the distribution of cadmium to brain.

Trypanosoma brucei gambiense: growth in vitro of bloodstream forms inhibited by dichlorodiammineplatinum (II) compounds and hypolipidemic drugs

Infectious bloodstream forms of Trypanosoma brucei gambiense were grown in microcultures of murine bone marrow cells in 96-well tissue culture plates. Limiting dilution studies showed that fewer than 10 cultured trypanosomes developed into populations of about 5 X 10(4) parasites per well in a week. Bloodstream parasites were reisolated with high efficiency from mice infected with cultured parasites; fewer than 10 bloodstream parasites successfully established a trypanosome population in a microculture. Both the cis and trans isomers of dichlorodiammineplatinum (II) (cisplatin and transplatin) and a hypolipidemic agent, Wy 14643, were found to have activity against T. b. gambiense growing in microcultures. The minimum concentration of drug necessary to completely eliminate parasites from microcultures was 4 microM for cisplatin, 40 microM for transplatin, and 500 microM for Wy 14643. A preformed complex of cisplatin and bovine serum albumin and another hypolipidemic agent, chlofibric acid, were inactive. This culture system should be useful for rapid screening of large numbers of compounds for trypanocidal activity.

Trypanocidal and antitumour activity of platinum-metal and platinum-metal-drug dual-function complexes

A number of antitumour platinum-metal complexes related to cis-platin showed trypanocidal activity against Trypanosoma rhodesiense in vitro but not in vivo. New platinum- and rhodium-metal complexes of diamidine and plenanthridinium trypanocides are described which showed higher therapeutic indices than the parent drugs, due to increased activity in the former drug type and decreased toxicity in the latter. Some evidence of potentiation of antitumour activity was noted in these drug complexes. At the ultrastructural level, complex-treated trypanosomes showed a number of nuclear effects and other lesions specifically attributable to platinum-metal action. Some of the lesions were similar to those induced by cis-platin in tumour cells.

Capacity of a cis-diammineplatinum[II]-polyglutamic acid complex to cure Trypanosoma congolense infections in mice

A cis-diammineplatinum(II)-polyglutamic acid complex proved to have marked trypanocidal activity in vivo. When 5 mg of platinum per kg was administered daily for 5 days or when 20 mg of platinum per kg was administered on days 1, 3, and 6, five of five treated Trypanosoma congolense-infected mice were cured. In contrast, cis-platin was ineffective at all doses tested. We believe that the complex has a much higher therapeutic ratio than does uncomplexed drug because it is less toxic.