Synthesis and biological evaluation of novel imidazolidine derivatives as candidates to schistosomicidal agents

INTRODUCTION:

Schistosomiasis is an infectious parasitic disease caused by trematodes of the genus Schistosoma, which threatens at least 258 million people worldwide and its control is dependent on a single drug, praziquantel. The aim of this study was to evaluate the anti-Schistosoma mansoni activity in vitro of novel imidazolidine derivatives.

MATERIAL AND METHODS:

We synthesized two novel imidazolidine derivatives: (LPSF/PTS10) (Z)-1-(2-chloro-6-fluorobenzyl)-4-(4-dimethylaminobenzylidene)-5-thioxoimidazolidin-2-one and (LPSF/PTS23) (Z)-1-(2-chloro-6-fluoro-benzyl)-5-thioxo-4-(2,4,6-trimethoxy-benzylidene)-imidazolidin-2-one. The structures of two compounds were determined by spectroscopic methods. During the biological assays, parameters such as motility, oviposition, mortality and analysis by Scanning Electron Microscopy were performed.

RESULTS:

LPSF/PTS10 and LPSF/PTS23 were considered to be active in the separation of coupled pairs, mortality and to decrease the motor activity. In addition, LPSF/PTS23 induced ultrastructural alterations in worms, after 24 h of contact, causing extensive erosion over the entire body of the worms.

CONCLUSION:

The imidazolidine derivatives containing the trimetoxy and benzylidene halogens showed promising in vitro schistosomicidal activity.

[Chronic toxicity test of fangyouling by transdermal administration in rabbits]

OBJECTIVE

To observe the toxicity of fangyouling after one month' s transdermal administration in rabbits and evaluate its security.

METHODS

Forty rabbits were randomly divided into 4 groups including a control group and low, middle and high dose groups of fangyouling. The rabbits in the control group were administered with sunflower oil, and the other rabbits were administrated dermally with fangyouling of 50,300 and 2,000 mg/kg respectively once a day for 4 weeks. The general condition, the skin irritation reaction, body weight, food consumption, hematology, blood biochemistry, organ coefficients and histopathological changes of all the rabbits were observed.

RESULTS

There was no obvious effect on the general condition in all the rabbits. However, the mild skin irritation was observed in 2 rabbits of the middle dose group and 4 rabbits of the high-dose group. The decreases of body weight and food consumption were noted in the high dose group. No changes were detected of hematology, blood biochemistry or viscera pathological at all dose levels.

CONCLUSION

The dose of non-toxic response of fangyouling is 50 mg/kg at this study condition.

Antioxidant, antibacterial and antischistosomal activities of extracts from Grateloupia livida (Harv). Yamada

The present study was designated to evaluate the antioxidant, antibacterial and antischistosomal activities of Grateloupia livida (GL) extracts in vitro. A GL Ethanol extract (EE) was separated into petroleum ether (PE), ethyl acetate (EA), n-butyl alcohol (BuOH) and aqueous (AQ) fractions to fractionate the polar and non-polar compounds in the EE. Extracts antioxidant activities were evaluated in vitro by DPPH radical-scavenging, deoxyribose radical scavenging, and β-carotene bleaching assays, all using butylated hydroxytoluene (BHT) as the reference antioxidant compound. The most effective antioxidant properties were observed in the PE fraction in all three assays. Antimicrobial testing showed that the PE fraction exhibited broad-spectrum antimicrobial activity, with the PE fraction also exhibiting strong activity against the human pathogenic trematode S. japonicum adult worm. In order to investigate the relationships between bioactivity and chemical composition, the chemical composition of the PE fraction was analyzed by gas chromatography-mass spectrometry (GC-MS). In total, 25 components were identified in the PE fraction, most of which have known antioxidant and antimicrobial activities. However, none of the compounds have reported activity against Schistosoma, suggesting that the schistosomicidal activity of the PE fraction may be related to minor constituents present in the extract, or governed by more intricate synergistic or additive relationships. Finally, fractions with the greatest biological activity displayed neither cellular cytotoxicity, at concentrations up to 100 ug/ml, or acute oral toxicity in mice, at doses up to 2000 mg/kg. Based on antioxidant, antimicrobial, antischistosomal activities, and low toxicity, the PE fraction possesses properties useful for food preservation and overall improvement of human health.

[Surveillance and forecast system of schistosomiasis in Jiangsu Province. IV. Establishment of Schistosoma japonicum cercaria-killing method by spraying niclosamide suspension on water surface]

OBJECTIVE

To investigate the effect of suspension concentrate of niclosamide (SCN) on killing cercariae of Schistosoma japonicum on water surface, optimization and impact on fish, so as to establish an emergency-treatment intervention for rapidly killing cercariae and eliminating water infectivity.

METHODS

SCN was formulated into different concentrations of solutions, and then the solutions were sprayed on the surface of water containing S. japonicum cercariae. The water infectivity was determined by using mice at 0, 10, 30 min after spraying SCN. SCN was formulated into a solution of 100 mg/L and then sprayed on the surface of the water by using the spraying values of 0.01, 0.02, 0.03 g/m2 and 0.04 g/m2. At 30 min and 60 min after spraying, the water infectivity was determined by using mice. Zebra fish were transferred into the static water, then 100 mg/L SCN (s), using spraying values of 0.01, 0.02, 0.03 g/m2 and 0.04 g/m2, were sprayed on water surface. At 0, 10, 30, 60 min after spraying, the samples were collected at water depths of 0, 10, 20, 30, 40 cm, and niclosamide was determined by using high-performance liquid chromatography. The death of zebra fish was continually observed within 96 h after spraying SCN.

RESULTS

At 0, 10, 30 min after spraying 1 000, 100, 10, 1, 0.1 mg/L SCN on water surface, the infectivity of water significantly decreased. At 30 min after spraying 1 000 mg/L and 100 mg/L SCN, no schistosome infectivity was detected in the water. At 30 min after spraying 100 mg/L SCN, with spraying values of 0.01, 0.02, 0.03, 0.04 g/m2, the water infectivity significantly reduced, and no infectivity was found 60 min after spraying SCN. After the surface of static water was sprayed with 100 mg/L SCN, the peak concentration was found at 0 min, and the solution diffused to site with a water depth of 10 cm after 10 min, and 30 min later, SCN diffused to the whole water body, and distributed evenly. After spraying 100 mg/L SCN on the surface of water with a volume of (3.14 x 20(2) x 50) cm3, by using the spraying value of 0.02 g/m2, 96 h later, no death of zebra fish was found.

CONCLUSIONS

From 30 to 60 min after spraying 100 mg/L SCN, with the value of 0.02 g/m2, on the surface of S. japonicum-infested water, the water infectivity can be eliminated, and there is no evident toxicity to fish. This cercaria-killing method, as an emergency-treatment intervention for infested water, can be applied in those surveillance and forecast sites.

Pharmacokinetics and therapeutic effects of oltipraz after consecutive or intermittent oral administration in rats with liver cirrhosis induced by dimethylnitrosamine

Pharmacokinetics and therapeutic effects of oltipraz were evaluated after consecutive (once per day at 30 mg/kg/day for 7 and 14 days) or intermittent (once per week at 100 mg/kg/week for 1-3 weeks) oral administration to rats with liver cirrhosis induced by dimethylnitrosamine. The AUC of oltipraz was significantly greater in cirrhotic rats than controls (890 compared with 270 microg . min/mL) due to impaired liver function in cirrhotic rats. However, the AUC values after consecutive 7 (421 compared with 753 microg . min/mL) and 14 (309 compared with 821 microg . min/mL) days oral administration of oltipraz in cirrhotic rats were significantly smaller than those in respective vehicle-treated cirrhotic rats. Moreover, the AUC values after intermittent 2 and 3 weeks in cirrhotic rats were also significantly smaller than that in 1 week vehicle-treated cirrhotic rats (2370 and 1690 compared with 4760 microg . min/mL). This could be due to induction of CYP isozymes and considerably greater numbers of normal liver cells in cirrhotic rats by oral administration of oltipraz. Improved liver function by oltipraz in cirrhotic rats was proved by liver microscopy; livers are free of significant fibrosis, although evidence of bridging necrosis is still present in many rats.

Synthesis and schistosomicidal activity of new substituted thioxo-imidazolidine compounds

Synthesis and physico-chemical properties of 3-benzyl-5-(4-fluoro-benzylidene)-1-methyl-2-thioxo-imidazolidin-4-ones, 5-benzylidene-3-(4-nitro-benzyl)-2-thioxo-imidazolidin-4-ones and 4-acridin-9-ylmethylene-1-benzyl-5-thioxo-imidazolidin-2-ones compounds are described. These thioxo-imidazolidine derivatives were prepared by alkylation and condensation with 4-fluoro-benzaldehyde or nucleophilic Michael addition with cyanoacrylates. The schistosomicidal activity of 3-benzyl-5-(4-fluoro-benzylidene)-1-methyl-2-thioxo-imidazolidin-4-one compounds was evaluated.

Investigation of induced biochemical and histopathological parameters of acetonitril extract of Jatropha carcus in albino rats

Toxicological and histopathological investigations were carried on the acetonitril extract from J. carcus in comparison to praziquantel, the known antischistosomal drug. On a constant weight dose bases (single dose of 50 mg/Kg body weight injected orally to albino rats), the acetonitril extract from J. carcus showed mild toxicological parameters (AST p < 0.001, ALT & creatinine, non-significant), biochemical parameters (total lipids, cholesterol, triglycerides, HDL, LDL, proteins, albumins globulins, ascorbic acid and bilirubin, non-significant) and histo-pathological profile (slight alterations in liver, kidney and spleen), in comparison to control. However, these side-effects were very little as compared to the severe side-effects caused by Praziquantel.

Molluscicidal and in-vitro schistosomicidal activities of the latex and some extracts of some plants belonging to Euphorbiacea

Plant molluscicicdes proved to be good means for controlling fresh water snails of schistosomiasis. The molluscicidal activities of the natural and lyophilized latex extracts of Euphorbia royleana and E. mouritanica and acetonitril and chloroform extracts of Jatropha carcus were investigated against Biomphalaria alexandrina the intermediate hosts for S. mansoni. The lyophilized latex extract of E. royleana showed the highest toxicity against snails with LC90 value of 11 ppm. While the natural latex extract of E. mouritanica showed the lowest toxicity against snails with LC90 value of 60 ppm. While, the acetonitril extract of Jatropha carcus gave high toxicity against snails with LC90 value of 6 ppm and the chloroform extract gave low toxicity against snails with LC90 value of 55 ppm. The in-vitro schistosomicidal activities of the lyophilized latex extract of E. royleana and the acetonitril extract of J. carcus were studied against S. mansoni adults showed that the lyophilized latex extract of E. royleana gave 100% mortality after exposure to 30 ppm for 4 consecutive days and 66.7% mortality after exposure to 10 ppm for 5 consecutive days. The acetonitril extract of J. carcus gave 91.7% mortality after exposure to 100 ppm for 4 consecutive days and 58.3% mortality after exposure to 50 ppm for 5 consecutive days.

Mutagenicity of sulfoscanate: a comparative study

The mutagenic activity of sulfoscanate (SSC) (4-isothiocyanate-4'-nitrodiphenyl sulphide) has been compared with that of the following reported drugs: (a) nitroscanate (NSC) (4-isothiocyanate-4'-nitrodiphenyl ether) which is a veterinary anthelmintic drug and (b) amoscanate (ASC) (4-isothiocyanate-4'-nitrodiphenyl amine) which is effective against schistosomes. SSC has been found to be a very potent mutagen towards TA98 and TA100 inducing 26.0 and 475.5revertants/nmole, respectively. NSC was found to induce mutations at a rate of 11.1 and 21.5revertants/nmole in TA98 and TA100, respectively. ASC was found to be non-mutagenic as such, but the urine of animals given the drug displayed mutagenicity. When SSC was tested in TA98/1,8-DNP(6), deficient in O-acetyltransferase, the activity decreased to 10.0revertants/nmole. However, in case of NSC the mutagenic activity was reduced to 0.24revertants/nmole, indicating the importance of O-acetyltransferase in generating N-acetoxyarylamine. In TA98NR, deficient in nitroreductase, the mutagenicity of SSC and NSC was totally absent. The positional isomers of SSC, 4-isothiocyanate-3'-nitro- and 4-isothiocyanate-2'-nitrodiphenyl sulphide, were found to be non-mutagenic in both TA98 and TA100. Our comparison of the mutagenic activity of SSC, NSC and ASC indicates that the pattern of activity is SSC>NSC>ASC.

Synthesis of a new antischistosomally active and toxicologically tolerant C-12 monothione surrogate of the universal antihelmintic praziquantel

A new C-12 monothione mimic (III) of the universal antihelmintic Praziquantel (I) namely, 2-cyclohexylthiocarbonyl( 1,2.3,6,7,11b)-hexahydro-4H-pyrazino[2-1a] isoquinoline-4-one was chemically synthesized and structurally elucidated (Elemental analysis. El-Mass, 13C-NMR and IR spectroscopy). Antischistosomal potency in the order of -76% comparable to that for our newly reported C-12 and C-4 dithion mimic II (-70%) and Praziquantel. Praziquantel (100%, mice infected with S. mansoni cercariae), was realized. Toxicological evaluation (mice liver and kidney functions) and biochemical parameters (cholesterol, triglycerides, albumin, total serum proteins and amino acid profile of liver protein homogenate) were also assayed. Comparable to the parent drug, general insignificant toxicological diferences could be attributed for III. Interestingly, III exhibited intermediate biological figures between I and II. An order of II<III<I with respect to the antischistosomal potency and II>III>I, for the other tested biochemical parameters was observed. A consideration of obtained results could indicate that, structurally, an intact glycine amide segment of the pyrazine moiety, as it is the case in both I and III, and not in II (glycine thioamide) seemed now more crucial for exhibiting an optimum antihelmintic potency as well as a more tolerant toxicity characteristics. Additionally, the obtained comparable amino acid profile of mice liver protein homogenate after the treatment by III, could suggest similar biochemical, lethal mechanistic and metabolic routes for II, III and I. The new lipophilic candidatee III seems to merit more profound chemical, biological, and pharmaceutical investigations.

Evaluation of nitrification-inhibition measurements

A screening method for nitrification-inhibition determination has been evaluated at two laboratories, one in Sweden and one in Spain. Allyl-thiourea (ATU), methanol, chromium and zinc were used as reference toxicants in combination with different kinds of full-scale sludge and sludge produced in the laboratory. Different results were obtained with different combinations of activated sludge and toxicants. It was found that activated sludge often exposed to small amounts of a variety of toxic substances may build up a general resistance to toxic substances. Specific adaptation to certain substances was also observed. Domestic activated sludge responded in the same way to ATU regardless of whether it originated from Sweden or Spain. Synthetic sludge and domestic sludge exhibited the same inhibition of nitrification when tested with ATU as a toxicant. Synthetic activated sludge from two laboratory-scale plants run in parallel did not exhibit exactly the same sensitivity to certain toxicants. The variation in repeated tests with the synthetic sludges was about the same as for repeated tests with full-scale sludge and for other biological toxicity tests. Limits of detection were calculated to be about 5% for a single sample with three blanks as references at both the laboratories.

Review of subchronic/chronic toxicity of antimony potassium tartrate

Subchronic/chronic toxicity studies on antimony potassium tartrate (APT) have been reviewed. One of the older studies (H. A. Schroeder et al., 1970, J. Nutr. 100 (1), 59-68), on which are based the EPA reference dose value and a number of state, national, and international drinking water criteria for antimony, has severe inadequacies in study conduct making it uninterpretable and inappropriate for characterization of APT toxicity. In particular, the manner in which control data were generated and utilized in this study is considered invalid. More recent drinking water studies conducted by the NTP (1992, "NTP Technical Report on Toxicity Studies of Antimony Potassium Tartrate in F344/N Rats and B6C3F(1) Mice (Drinking Water and Intraperitoneal Injection Studies)," NTP Toxicity Report Series, No. 11) and Poon et al. (1998, Food Chem. Toxicol. 36, 20-35) showed antimony to be of low toxicity. The NOAEL in the 14-day NTP study was 2500 ppm by the oral route in both rats and mice, while Poon et al. (1998) suggested a NOAEL of 0.5 ppm in their 90-day study. However, upon close examination, it was determined that this value was based on subtle histological changes in the thyroid gland that were physiological, not toxicological, in nature. This conclusion is supported further by an absence of these changes in a well-conducted 13-week intraperitoneal exposure study in rats that utilized APT at much higher doses (NTP, 1992). Thus, the NOAEL by Poon et al. (1998) should more appropriately be 50 ppm. When regulatory criteria for antimony are established and/or reviewed, the findings in the NTP study and this critical reevaluation of the Poon et al. (1998) study should be considered when establishing a NOAEL for subchronic exposure to antimony in the future.

O6-methylguanine and O6-methylguanine-DNA [corrected] methyltransferase activity in tissues of BDF-1 mice treated with antiparasitic drugs

Levels of the DNA promutagenic methylation damage, O6-methylguanine (O6-MeG) and the activity of the O6-methylguanine-DNA methyltransferase (MGMT), the enzyme responsible for repairing O6-MeG, were measured at various time intervals in tissues of BDF-I mice administered a single therapeutic dose of the antischistosomal agents hycanthone, oxaminiquine and metrifonate. Hycanthone increased O6-MeG in the liver-DNA after 6 h, then decreased by 3-fold after 48 h. Lower levels of the adduct and a slower rate of formation were found in the intestine and bladder. MGMT activities were significantly lower in the liver (74%) and bladder (25%) compared to control animals after 6 h, then restored by 48 h. Oxaminiquine increased O6-MeG in all tissues, but spleen, after 6 h and persisted only in the bladder after 48 h. Liver and bladder tissues of these animals exhibited a pattern of alteration in the MGMT activity similar to that observed for hycanthone. Metrifonate induced a profile of O6-MeG comparable to that of oxaminiquine but the levels of the adduct were about 2-fold lower. Hepatic MGMT in these animals was significantly lower (approximately 38%) than the control values after 6 h, then restored by 48 h. A significant negative correlation was obtained between O6-MeG and MGMT activity in the liver (r=- 0.85), intestine (r=- 0.62) and bladder (r=- 0.59). These results demonstrate that treatment with antischistosomal agents may lead to the formation of promutagenic alkylation damage in the tissue DNA and alterations in the DNA repair capacity.

Antimony-induced alterations in thiol homeostasis and adenine nucleotide status in cultured cardiac myocytes

Cultured cardiac myocytes were exposed for up to 4 h to 50 and 100 microM potassium antimonyl tartrate (PAT). After 4 h, 50 and 100 microM PAT killed 14 and 33% respectively of the cardiac myocytes. PAT-induced alterations in both protein and nonprotein thiol homeostasis. Transient increases in oxidized glutathione disulfide (GSSG) levels were detected after cells were treated with 100 microM PAT for 2 h. After 4 h, both concentrations of PAT significantly depleted reduced glutathione (GSH) levels. Protein thiols levels were also decreased after a 2-h exposure to 50 and 100 microM PAT. Cells treated with 50 microM and 100 microM PAT had a 15% and 40% reduction respectively in protein thiols after 4 h. PAT also significantly inhibited glutathione peroxidase and pyruvate dehydrogenase activity in cardiac myocytes. Pyruvate dehydrogenase activity levels were inhibited as early as 1 h after cells were treated with both concentrations of PAT. Cardiac myocyte ATP levels were also decreased by PAT, but only after a 4-h exposure to 50 microM and 100 microM PAT. Decreases in cellular ATP levels paralleled PAT toxicity put appeared to be secondary to other cellular changes initiated by PAT exposure.

Effect of schistosomal infection and its treatment on some key enzymes of glucose metabolism in mice livers

Three antischistosomal drugs, praziquantel (CAS 55268-74-1, EMBAY 8440, Prz), oxamniquine (CAS 21738-42-1, Oxa) and oltipraz (CAS 64224-21-1, Olt) were examined for their ability to reverse the disturbances in carbohydrate metabolism induced by Schistosoma mansoni (S. mansoni) infection. The infected mice were screened every 2 weeks for 16 weeks for their body and liver weights in addition to assessment of the activities of liver pyruvate kinase (PK), phosphofructokinase (PFK) (glycolysis), citrate synthase (CS) (Krebs' cycle) glycogen phosphorylase (GP) (glycogenolysis), glucose-6-phosphate dehydrogenase (G6PDH) and 6-phosphogluconate dehydrogenase (6PGDH) (hexose monophosphate shunt). Results of the study showed that infection with S. mansoni caused the following changes in mice livers: 1. significant increase in liver weights from the 6th week of infection, which coincided with schistosomal egg deposition, whereas body weights were reduced, 2. remarkable increase in the activities of PK and PFK from the 4th week of infection, 3. marked reduction in CS, GP, G6PDH and 6PGDH. These results lead to the conclusion that glycolysis is largely stimulated in the livers of infected mice on the expense of other metabolic pathways of glucose utilization. Administration of Prz to infected mice caused normalization of all measured enzyme activities almost from the 2nd week of infection, whereas liver and body weights were improved from the 10th week. Oxa was less effective in these regards while Olt was the least. These data support the selection of Prz as a drug of choice for S. mansoni infection.

Preliminary investigations of some derivatives of oxamniquine

Oxamniquine is a potent schistosomicide used clinically in the treatment of infections due to Schistosoma mansoni. Although relatively well tolerated, some central nervous system (CNS) effects characterised by convulsions have been reported in a small proportion of the population receiving this drug. Oxamniquine, the major metabolite and the secondary alcohol have been screened for convulsant activity by assessing their ability to potentiate catechol induced seizures in urethane anaesthetised mice. Significant (p < 0.05) potentiation was observed with subconvulsive doses (1.5 mg/kg) of strychnine. In contrast, oxamniquine and the secondary alcohol, each at 200 mg/kg ip, both produced significant (p < 0.05) depressions of seizures in this model whereas no effect was seen following 140 mg/kg ip of the acid derivative. These results indicate anticonvulsant rather than convulsant activity in oxamniquine and the alcohol derivative. The failure to observe any effect with the acid derivative may have been due to poorer CNS penetration.

An experimental study on the effect of praziquantel and oltipraz on some lysosomal enzymes

The in-vivo effect of the schistosomicidal drugs praziquantel and oltipraz on the activities of the liver lysosomal enzymes in Schistosoma mansoni-infected and non-infected mice was studied. The effect of S. mansoni infection and the administration of the schistosomicidal drugs on the activities of beta-glucuronidase, acid ribonuclease and alpha-naphthyl acetate esterases may be considered as indices for carcinogenicity. Drugs were given orally in subcurative doses, either in a single dose of 400 mg kg-1 for praziquantel or in five daily doses of 50 mg kg-1 oltipraz. The increase in enzymatic activities in infected animals was attributed to deranged metabolic function as a result of liver cell injury. Treatment of uninfected animals with either praziquantel or oltipraz significantly increased the activities of the three lysosomal enzymes. Praziquantel possesses reversible and less toxic effects on the liver than oltipraz. The role of these antischistosomal drugs cannot be ignored as a possible aetiological factor implicated in the process of carcinogenesis associated with schistosomiasis infection through modulation of the operating potential of the enzymes concerned with detoxification, protein and fat metabolism.

Sex differences in micronucleus induction with hycanthone methanesulfonate in bone marrow cells of mice

The clastogenic effect of the antischistosomal drug hycanthone methanesulfonate was studied with the micronucleus test in mouse bone marrow cells. Male and female (102/El x C3H/El)F1 mice were treated with single i.p. injections. Bone marrow was sampled 18, 24 and 30 h after treatment with 100 mg/kg. The highest micronucleus yield occurred at 24 h. The dose response for micronucleus induction at 24 h after treatment was non-linear for doses between 5 and 300 mg/kg. The lowest effective dose was 5 mg/kg for females and 10 mg/kg for males. The experiments revealed a significantly higher sensitivity of female mice for the induction of micronuclei in polychromatic erythrocytes by hycanthone methanesulfonate. This result supports the recommendation to use both sexes for quantitative assessment of genotoxicity in the micronucleus test.

Mechanisms of inactivation of Schistosoma mansoni and mammalian glutathione S-transferase activity by the antischistosomal drug oltipraz

Glutathione S-transferase (GST) purified from Schistosoma mansoni or human placenta was inhibited by the antischistosomal drug oltipraz (OPZ) in a time- and concentration-dependent manner. Inhibition of placenta GST was complete at a low concentration of drug, whereas that of parasite GST was incomplete and relatively high amounts of OPZ were needed to reach 50% inhibition. Complete reactivation of GST from placenta was achieved with dithiothreitol (DTT) and other sulfhydryl-containing compounds, while the inactivation of parasite GST was irreversible. The oxy-derivative of OPZ (RP 36,642), in which the thione sulfur is replaced with oxygen, did not inhibit GST activity. There were no differences between OPZ and RP 36,642 in their patterns of binding to the hydrophobic non-substrate site of GST. GST from the placenta incorporated much higher levels of [14C]N-ethylmaleimide compared to schistosome GST. The incorporation of [14C]N-ethylmaleimide by GST was inhibited by OPZ but not by RP 36,642. Yeast and S. mansoni hexokinases were similarly inhibited by OPZ but not by RP 36,642. Both hexokinase preparations recovered their activity following incubation with DTT. These data suggest that the inactivation of these enzymes by OPZ is a result of its interaction with their SH groups. Thus, the antischistosomal activity of OPZ may be accounted for by its interaction with the SH groups of macromolecules in general.

International Commission for Protection Against Environmental Mutagens and Carcinogens. ICPEMC publication No. 18. Review of the genotoxicity and carcinogenicity of antischistosomal drugs; is there a case for a study of mutation epidemiology? Report of a task group on mutagenic antischistosomals

One of the interests of ICPEMC is to identify situations in which the possible induction of inherited defects in man by mutagen exposure could actually be studied. The large-scale use of mutagenic drugs in field programmes against schistosomiasis, mainly during the 1970's, was considered a possible case. An ICPEMC task group approached the problem by (1) updating the genetic toxicology data base for antischistosomal drugs, and (2) reviewing possible study areas. Expertise was combined from genetic toxicology, mutation epidemiology and tropical medicine. It was considered that: (a) if any, hycanthone would be the most appropriate candidate drug for study; (b) it would be virtually impossible to meet the basic requirements of an appropriate mutation epidemiology study, in endemic countries; (c) as more defined genetic endpoints would be selected (e.g. sentinel phenotypes) the required large sample sizes would seem prohibitive, since documentation on past programmes is limited and local demography would render the reliable tracking of substantial numbers of offspring of treated persons an almost impossible task; (d) in most endemic countries proper diagnosis and registration of inherited defects is largely lacking; (e) the problems encountered in demonstrating inherited effects in humans after heavy or chronic exposure to established animal mutagens such as ionizing radiation and cancer chemotherapy, in combination with the ambiguous nature of the animal germ cell data with hycanthone, do not particularly warrant large expectations; (f) since non-mutagenic antischistosomal drugs are now in use, the problem is academic and of low priority in the endemic countries whose medical and research resources are often limited. Thus, studying offspring of hycanthone-treated people to demonstrate the mutagenic potential of the drug in man is not a viable enterprise.

Antimuscarinic activities of hycanthone analogs: possible relationship with animal toxicity

The antimuscarinic activity of hycanthone and five antischistosomal analogs was determined in three biological assays of cholinergic systems. A linear relationship was established between the LD50 values of hycanthone analogs in mice and 1) the Ki values obtained from the inhibition of [3H]quinuclidinyl benzilate binding to the muscarinic receptors of N4TG1 neuroblastoma cells; 2) the I50 values obtained from the inhibition of alpha-amylase secretion induced by carbachol in pancreatic acini cells; and 3) the KB values obtained from the inhibition of guinea-pig ileum contraction induced by acetylcholine. The linear relationship established between antimuscarinic potency and toxicity in mice suggests that a possible relationship exists between the toxicity of the hycanthone analogs and their antimuscarinic activities. On the other hand, no correlation was established between antischistosomal efficacy and antimuscarinic potency. The Ki and I50 values ranged from 10(-7) to 10(-5) M for the inhibition of the binding of [3H]quinuclidinyl benzilate to the muscarinic receptors and for the inhibition of alpha-amylase secretion. The KB values determined by the guinea-pig ileum assays were approximately 10(-5) to 10(-6) M. The ranking of antimuscarinic potency of the compounds in the three different assays were in good agreement.

Results of toxicological studies on praziquantel

Praziquantel (2-cyclohexylcarbonyl-1,2,3,6,7, 11b-hexahydro-4H-pyrazino[2,1-a]isoquinolin-4-one, EMBAY 8440, Biltricide) is an anthelminthic drug with activity against all species of schistosomes pathogenic to man and a wide range of cestodes, including the cysticerci of Taenia solium in human tissues and organs, also the CNS. Praziquantel does not reveal any undesired pharmacodynamic effects. After oral administration praziquantel is quantitatively and rapidly absorbed, metabolized and excreted as a variety of metabolites predominantly via the kidneys. The acute toxicity in rats, mice, rabbits and dogs is very low. Rats tolerated by oral administration doses of up to 1000 mg/kg repeated daily for four weeks, and dogs up to 180 mg/kg for 13 weeks without any organ damage. Praziquantel did not disturb reproduction in rats (up to F2-generation), nor did it reveal teratogenic effects in mice, rats and rabbits. In extensive mutagenicity trials performed by different laboratories worldwide, in a variety of test systems, no induction of point mutations, gene conversion, DNA-repair, sister chromatid exchanges (SCEs), or X-linked recessive lethals was detected. Besides, Salmonella tests with urines of praziquantel treated mice, rats, healthy and Schistosoma-infected persons gave no indication of a mutagenic effect. In different in vivo mammalian assays praziquantel not mutagenic either. Low toxicity of praziquantel was not mutagenic either. Low toxicity of praziquantel was demonstrated also in the combined chronic toxicity and carcinogenicity tests which were performed in rats and Syrian hamsters. In none of these species praziquantel exerted a carcinogenic action, and both doses were tolerated.

Effect of phosphonium salts and phosphoranes on the acetylcholinesterase activity and on the viability of Schistosoma mansoni parasites

In this study we investigated the effects of a series of phosphonium salts and phosphoranes on the catalytic activity of acetylcholinesterase and on the viability of the various life stages of Schistosoma mansoni worms. All the tested compounds showed an inhibitory effect towards the S. mansoni acetylcholinesterase (AChE) activity. The most effective compound, p-xylylene bis(triphenylphosphonium) dibromide (No. 16) displayed approximately 100% inhibition at concentration of 10(-5)-10(-6)M. No significant difference was found in the sensitivity of the enzyme obtained from the various stages of the parasite life cycle to the effect of the drugs. Each compound was also tested for its toxicity towards 3 h old schistosomula and 7-9 week adult worms under in vitro culture conditions. In the case of the larvae, after 2 days in culture, only three compounds (Nos. 4, 11 and 12) out of sixteen tested exhibited efficient killing of the schistosomula while the others had a very slight toxic activity or no toxicity at all. On the other hand, all the compounds showed a significant toxicity towards the adult worms and the most effective one, allytriphenylphosphonium bromide (No. 11), retained its toxic effect even at an extremely high dilution (10(-8)M). However, the cumulative results in this paper do not demonstrate a significant correlation between the inhibitory effect of the phosphonium salts and phosphoranes on the AChE activity of the schistosomes and their toxicity towards the worms. The LD50 value (i.v.) of the compound which showed the highest toxic effect in vitro (No. 11) was found to be 30 +/- 1.7 mg/kg in mice.(ABSTRACT TRUNCATED AT 250 WORDS)

Neuropathology of the antischistosomal agent amoscanate administered in high oral doses to rats

Amoscanate is a highly effective antischistosomal agent when administered as a 5% absorbable aqueous suspension. This preparation produces lesions in the brains of young adult rats given extremely high oral doses. Lesions are confined to areas adjacent to the lateral ventricles and are dominated by necrosis of the neuropil of the medial striatum, with relative sparing of bundles of myelinated fibers in the necrotic zone. There is a striking accumulation of calcium-containing microgranules in these areas. The ependyma survives on the ventricular wall overlying the necrotic zone, but pyknosis and increased extracellular space are apparent among ependymal and subependymal cells in the region. Occasionally, fibers of the fornix are focally damaged in immediate proximity to the lateral ventricle; the corpus callosum is rarefied, and microhemorrhages also occur. It is hypothesized that high concentration of the toxic agent in ventricular cerebrospinal fluid plays an important role in pathogenesis. The neuropil of the medial striatum is selectively vulnerable.

Toxicological profile of praziquantel, a new drug against cestode and schistosome infections, as compared to some other schistosomicides

2-Cyclohexylcarbonyl-1,2,3,6,7,11b-hexahydro-4H-pyrazino[2,1-a] isoquinolin-4-one (praziquantel, EMBAY 8440, Biltricide), a new anthelminthic drug with activity against all species of schistosomes pathogenic to man, and against a wide range of cestodes, did not reveal any undesired pharmacodynamic effects. After oral administration praziquantel is quantitatively and rapidly absorbed, metabolized and excreted as a variety of metabolites predominantly via the kidneys by all species tested, including man. Its acute toxicity tested in rats, mice, rabbits and dogs is very low as compared with other schistosomicidal drugs. After repeated oral administration rats tolerated daily doses of up to 1000 mg/kg for four weeks, and dogs up to 180 mg/kg for thirteen weeks without any organ damage. In contrast to some other schistosomicidal drugs praziquantel did not disturb the whole reproductive process (up to F2-generation) in rats, nor did it reveal teratogenic effects in mice, rats and rabbits. In extensive mutagenicity trials performed in different European laboratories in a variety of test systems no induction of point mutations, nor of gene conversion, nor of DNA-repair, nor of sister chromatid exchanges (SCEs), nor of X-linked recessive lethals was detected. Besides, Salmonella tests with urines of praziquantel-treated mice, rats, healthy and Schistosoma-infected persons gave no indication of a mutagenic effect. In different in vivo mammalian assays praziquantel was not mutagenic either. In contrast to these findings other schistosomicidal drugs demonstrated mutagenic potential, in bacterial tests at least. According to the results available so far from carcinogenicity studies with oral doses of 100 and 250 mg praziquantel/kg, given once weekly to Syrian hamsters for 80 weeks and to rats for 104 weeks, there is no hint of a carcinogenic potential of praziquantel in small rodents, while hycanthone had cancerogenic effects in mice and niridazole was carcinogenic in mice, rats and Syrian hamsters.

Mutagenic activation of an antischistosomal drug by enteric Streptococcus sps in vitro and in vivo

Previous studies have shown that a new antischistosomal drug, 4-isothiocyano-4'-nitro diphenylamine (CGP 4540, amoscanate), is not mutagenic in vitro, but the urines of animals treated with this drug have mutagenic activity. Mutagenicity can be eliminated by coadministration of some antibacterial agents and is not demonstrable in germ-free animals. The present study describes attempts to isolate and identify intestinal microorganisms responsible for the mutagenic activation of amoscanate. Streptococcus equinus, isolated from the intestinal tract of mice, as well as some other species of Streptococcus, were found to produce mutagenic activation of amoscanate when introduced into animals pretreated with antibacterial agents. Similarly, incubation of these strains with amoscanate in vitro resulted in the formation of a mutagenic product.

Hycanthone analogs: dissociation of mutagenic effects from antischistosomal effects

N-Oxidation at the diethylamino group of hycanthone, of lucanthone, and of two chlorobenzothiopyranoindazoles resulted in a marked reduction in mutagenic activity, while antischistosomal activity was retained or even enhanced. Introduction of chlorine into the 8-position of benzothiopyranoindazoles reduced acute toxicity but had no effect on chemnotherapeutic potency. These dissociations of biological activities indicate that safer antischistosomal compounds of this class can be developed.