Differential effects of oltipraz and its oxy-analogue on the viability of Schistosoma mansoni and the activity of glutathione S-transferase

Adult worms of Schistosoma mansoni recovered from mice treated with oltipraz (OPZ) showed a significant diminution in their ability to reduce 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) to formazan, a measure of parasite viability. Incubation of glutathione S-transferase (GST) from S. mansoni with OPZ resulted in a time- and concentration-dependent inhibition of enzyme activity. RP 36,642 (an inactive oxy-derivative of OPZ) had a minimal effect on the viability of the worms and no effect on GST activity. The structural integrity of OPZ, particularly the thione sulphur, appears to be necessary for expression of the antischistosomal effects of the drug. OPZ-induced inhibition of GST was non-competitive with either reduced glutathione (GSH) or 1-chloro-2,4-dinitrobenzene (CDNB), indicating that the drug is not a substrate for GST-catalysed conjugation reactions. In addition, the inhibition of GST could not be reversed by dialysis or repurification of the enzyme via a GSH-agarose affinity column. The effects of OPZ on GST activity could render the parasite vulnerable to damage by host-derived reactive oxygen species and aldehydic products of lipid peroxidation. The effects of OPZ on GST activity may play a role in the antischistosomal action of OPZ.     

Activity of epiisopiloturine against Schistosoma mansoni

Schistosomiasis, caused by blood flukes of the genus Schistosoma, still imposes a considerable public health burden on large parts of the world. The control of this disease depends almost exclusively on the drug praziquantel, and there are no alternative drugs in sight. Natural compounds have recently attracted significant attention due to their relevance to parasitic infection and potential development into new therapeutic agents. Epiisopiloturine is an imidazole alkaloid isolated from the leaves of Pilocarpus microphyllus (Rutaceae), a native plant from Brazil. Here, we report the in vitro effect of this drug on the survival time of Schistosoma mansoni of different ages, such as 3 h old and 1, 3, 5, and 7 days old schistosomula, 49-day-old adults, and on egg output by adult worms. Epiisopiloturine at a concentration of 300 μg/mL caused the death of all schistosomula within 120 h. Extensive tegumental alterations and death were observed when adult schistosomes had been exposed to 150 μg/mL of the epiisopiloturine. At the highest sub-lethal dose of alkaloid (100 μg/mL), a 100% reduction in egg laying of paired adult worms was observed. Additionally, epiisopiloturine showed selective antischistosomal activity and exhibited no cytotoxicity to mammalian cells. This report provides the first evidence that epiisopiloturine is able to kill S. mansoni of different ages and inhibit worm egg laying.     

A benzodiazepine derivative and praziquantel: Effects on musculature of Schistosoma mansoni and Schistosoma japonicum

Summary The benzodiazepine derivative (Ro 11-3128) which has central nervous effects similar to other benzodiazepines, and praziquantel (PZ), are two new antischistosomal drugs. At low concentrations these drugs will produce a marked spastic paralysis of male Schistosoma mansoni musculature. An analysis of the action of these drugs on the parasite's musculature shows that Ro 11-3128 and PZ produced a rapid rise in the tension of the musculature of male schistomomes. Various compounds known to interact with the schistosome's neuroreceptive sites did not block or potentiate the action of these drugs. Removal of Ca²⁺ or addition of Mg²⁺ to the incubation medium blocked the action of these drugs on the schistosome's musculature. Uptake studies of inorganic cations by male schistosome's indicate that Ro 11-3128 and PZ decrease the influx of K⁺ but stimulate the influx of Ca²⁺ and Na⁺ into the male schistosome. It is suggested that this interference with inorganic ion transport mechanisms causes the contraction of the schistosome musculature.     

The effect of 5-thioglucose on the energy metabolism of Schistosoma mansoni in vitro

5-Thioglucose (5-TG) had a marked effect on the energy metabolism of Schistosoma mansoni in vitro: the conversion of external glucose into lactate by intact worms was severely inhibited. This inhibition of glycolysis was instantaneous, independent of the oxygen concentration and competitive with respect to glucose. Degradation of 0.5 mM external (14C-labelled) glucose was inhibited for 80% in the presence of 20 mM 5-TG. On the other hand the degradation of endogeneous glycogen to lactate was uninhibited. This shows that the inhibition of glucose breakdown occurred at the entrance of glucose into the cell and/or at the hexokinase reaction. It was demonstrated that 5-TG inhibited both the uptake of glucose and the activity of hexokinase. However, it was concluded that in the intact worm 5-TG blocked glycolysis by its competitive inhibition of hexokinase. In intact S. mansoni worms hexokinase is probably the rate-limiting enzyme of glycolysis. Krebs-cycle activity and lactate production do not occur at a fixed ratio: at lower rates of pyruvate formation Krebs-cycle activity was favoured.     

Schistosomicidal effects of Pavetta owariensis and Harrisonia abyssinica in mice infected with Schistosoma mansoni

The schistosomicidal properties of ethanol and acetone extracts of Pavetta owariensis and an ethanol extract of Harrisonia abyssinica were assessed in mice infected with Schistosoma mansoni. Spleen weight, number of adult worms and eggs and size of liver granulomas were the main parameters studied. All P. owariensis extracts containing proanthocyanins were shown to cause a reduction in size of periovular granuloma formation in the liver. This effect was most pronounced with ethanol extracts of both "white bark" and "red bark" varieties of the plant. Acetone extracts of P. owariensis "red bark" variety, containing the highest concentration of proanthocyanins, caused a marked reduction of egg numbers in the liver and intestine whereas the ethanol extract of H. abyssinica proved to be inactive.     

Effect of Schistosoma mansoni infection and treatment on drug metabolizing enzymes

The effect of Schistosoma mansoni infection on drug-metabolizing enzymes was investigated before and after treatment of S. mansoni-infected male albino mice with the antibilharzial drug praziquantel (CAS 55268-74-1). The drug was given in a total dose of 1000 mg/kg, and was administered at 500 mg/kg of body weight for two consecutive days each of 500 mg/kg of body weight. The drug was given 49 days after infection with 80 Egyptian strains of S. mansoni cercariae/mouse. The hepatic content of cytochrome P-450, cytochrome b-5 and NADPH cytochrome P-450 reductase were determined at 4, 8, 24, 72 h, one and two weeks after the second dose of treatment. The enzymes were determined in the microsomal fraction after homogenization and ultracentrifugation at 105,000 x g. The results indicate a marked decrease of most enzymes in the infected groups compared to normal controls. Two weeks after treatment there was an improvement of the level of most enzymes towards the normal values. The levels of liver function tests were also improved. Concerning the oogram pattern, there was a rapid change even after 8 h after the second dose of treatment. It was concluded that the antibilharzial drug could be considered as a safe drug with a rapid onset of action.     

蒿甲醚引起小鼠体内日本血吸虫和曼氏血吸虫皮层变化

蒿甲醚引起小鼠体内日本血吸虫和曼氏血吸虫皮层变化１肖树华，沈炳贵，ＪａｃｋＨＯＲＮＥＲ２，ＢｒｉａｎＡＣＡＴＴＯ３（中国预防医学科学院寄生虫病研究所，世界卫生组织疟疾、血吸虫病和丝虫病合作中心，上海２０００２５，中国；２ＤｅｐａｒｔｍｅｎｔｏｆＣｌｉ...