Identification of thioredoxin glutathione reductase inhibitors that kill cestode and trematode parasites.

Parasitic flatworms are responsible for serious infectious diseases that affect humans as well as livestock animals in vast regions of the world. Yet, the drug armamentarium available for treatment of these infections is limited: praziquantel is the single drug currently available for 200 million people infected with Schistosoma spp. and there is justified concern about emergence of drug resistance. Thioredoxin glutathione reductase (TGR) is an essential core enzyme for redox homeostasis in flatworm parasites. In this work, we searched for flatworm TGR inhibitors testing compounds belonging to various families known to inhibit thioredoxin reductase or TGR and also additional electrophilic compounds. Several furoxans and one thiadiazole potently inhibited TGRs from both classes of parasitic flatworms: cestoda (tapeworms) and trematoda (flukes), while several benzofuroxans and a quinoxaline moderately inhibited TGRs. Remarkably, five active compounds from diverse families possessed a phenylsulfonyl group, strongly suggesting that this moiety is a new pharmacophore. The most active inhibitors were further characterized and displayed slow and nearly irreversible binding to TGR. These compounds efficiently killed Echinococcus granulosus larval worms and Fasciola hepatica newly excysted juveniles in vitro at a 20 µM concentration. Our results support the concept that the redox metabolism of flatworm parasites is precarious and particularly susceptible to destabilization, show that furoxans can be used to target both flukes and tapeworms, and identified phenylsulfonyl as a new drug-hit moiety for both classes of flatworm parasites.

Hydrogen peroxide induced stress in human keratinocytes and its effect on bithionol toxicity.

Exposure to hydrogen peroxide causes oxidative stress in keratinocytes. Previous work has shown that the antiparasitic drug bithionol has an EC(50) of 0.7 microg/ml (2 microM) with primary human keratinocytes, but that these cells do not respond to photoactivated bithionol. Bithionol is known to be photoactivated by UV-A visible light, therefore this study aims to investigate the effects of inducing oxidative stress in the cells prior to bithionol treatment alone and in the presence of UV-A visible light. Oxidative stress, by hydrogen peroxide treatment, caused the cells to become sensitive to photoactivated bithionol. Bithionol alone reduced the amount of oxidative stress, while following photoactivation, an augmentation in the amount of oxidative stress and cell cytotoxicity was observed. The hydrogen peroxide treatment did not alter the sensitivity of the keratinocytes to 5 J/cm(2) UV-A visible light.

[The technology for manufacturing antiparasitic preparations. 6. The development of a technology for producing the anthelmintic Azinox (praziquantel) and the evaluation of its toxic and anthelmintic properties]. / Tekhnologiia proizvodstva protivoparazitarnykh preparatov. 6. Razrabotka tekhnologii polucheniia antigel'mintika Azinoksa (prazikvantelia) i otsenka ego toksicheskikh i protivogel'mintnykh svoistv.

The paper outlines a procedure for manufacturing the anthelminthic Azinox (biltricide) using the new interfacial transfer catalyst benzyl-di-propyl (beta-hydroxyethyl)ammonium chloride. Azinox has been shown to be identical to biltricide (praziquantel) in its properties. Azinox tests on models of Opisthorchis felineus in golden hamsters and of Hymenolepis nana in albino outbred mice have indicated that the agent is not inferior to biltricide in its antitrematodal and anticestodal activities. Azinox displayed a high activity at the preimaginal stages of O. felineus and H. nana and at the larval stage of H.nana.

Experimental Schistosoma bovis infection in goats: pathological consequences of praziquantel treatment.

Schistosoma bovis-infected goats were treated with praziquantel (60 mg/kg) and killed for examination 1, 7 or 28 days later. Infected non-treated goats and parasite-free, treated or non-treated goats were included for comparison. The gross pathological changes seen in the infected non-treated groups were mild to moderate. The liver appeared discoloured and moderately enlarged. The intestinal lesions were most prominent in the small intestines, which showed catarrhal inflammation with numerous tiny corpuscles beneath the luminal surface. The mesenteric lymph nodes were slightly to moderately enlarged. In contrast, on macroscopical examination, the infected treated groups invariably showed pronounced liver changes and marked enlargement of the lymph nodes, whereas the lesions in the intestines were comparatively slight. Histological lesions related to dead worms were seen in the livers of all treated animals. These lesions included pronounced inflammatory cellular infiltrates, thrombophlebitis, necrosis and periportal fibrosis, still severe 4 weeks after treatment. In the intestines, the deposition of new eggs with little cellular reaction had almost completely ceased 1 week after treatment. Four weeks after treatment, only a very few egg-associated lesions were noted in the intestines. The presence of severe lesions attributable to dead worms in the liver indicates the need for caution when treating animals with high worm loads or concomitant liver disease.

[The results of an experimental study of an anti-Opisthorchis preparation made from plant raw material]. / Rezul'taty éksperimental'nogo izucheniia protivoopistorkhoznogo preparata iz rastitel'nogo syr'ia.

Agents and biologically active fractions derived from medical plants grown in Siberia were tested in vitro and in vivo. The extract from the aspen bark displayed the highest antiopisthorchiatic activity. This agent given at a concentration of 10(-3) caused 100% death of Opisthorchis 72 hours later. In golden hamster experiments, the efficiency of the aspen bark extract was 73.48-83.0%. Butanolic and ethylacetatic extracts were found to have the greatest antiopisthorchiatic activity. The results of chemical and chromatographic studies indicated that active fractions contained salicine and its derivatives. The aspen bark extract produces no substantial toxic effect on laboratory animals and belongs to the class "Low-toxic substances".

[The search for new antiparasitic agents. 16. A study of the anti-Fasciola activity of N-[(chloro-naphthyloxy)phenyl]benzamides]. / Poisk novykh protivoparazitarnykh sredstv. 16. Izuchenie protivofastsioleznoi aktivnosti nekotorykh N-[(khlor-naftiloksi)fenil]benzamidov.

The study was undertaken to examine the fasciolacidal activity of the agents G-1411, G-1423, and G-1439. Tested, G-1439 was chosen for detailed investigations as a non-toxic fasciolacide.

[The technology for manufacturing antiparasitic preparations. 4. The development of a technology for producing the anthelmintic bromoksan in finely dispersed form and the evaluation of its antifascioliasis activity]. / Tekhnologiia proizvodstva protivoparazitarnykh preparatov. 4. Razrabotka tekhnologii polucheniia antigel'mintika bromoksana v melkodispersnoi forme i otsenka ego protivofastsioleznoi aktivnosti.

A manufacturing procedure has been developed to prepare the anthelmintic bromoxane as a finely divided dosage form. The maximum toxic dose of the drug was 1 g per kg mice body weight. Its therapeutic dose in sheep fascioliasis was 20 mg/kg.

[Study of the mechanism of action of fasciolocides using bimolecular phospholipid membranes]. / Issledovanie mekhanizma deistviia fastsiolotsidov s pomoshch'ie bimolekuliarnykh fosfolipidnykh membran

The effects of compounds (see article), where M = -S-, -SO-, -SO2- and of some of their derivatives (18 substances) on electroconductivity of bimolecular lipid membranes (BLM) of different composition in 30 mM tris-HCl (pH 7.5) is studied. The results obtained are compared with literature data concerning fasciolocide and toxic effect of these substances. Certain correlations are found between the action on BLM and biological effects of substances. The analysis of the results allowed a conclusion that the latter are concerned with a discoupling effect of substances on oxidative phosphorylation in mitochondria of helmets and their host. BLM may be applied for evaluating the value of fasciolocide and toxic effects of the substances protonophores.