Synthesis and orally macrofilaricidal evaluation of niclosamide lymphotropic prodrugs

The development of new macrofilaricidal drugs is described following a strategy for the promotion of the lymphatic transport of anthelminthic drugs by-passing the liver. The selected compound was niclosamide (CAS 50-65-7) which is very effective in vitro against infective larvae but has no significant antifilarial activity when orally administered at 200 mumol/kg. To estimate the interest of such an approach, the synthesis of 5 prodrugs was achieved in a first stage. The intrinsic antifilarial activity and the delayed effect of these compounds were evaluated in vitro. Then, in vivo tests were performed with Molinema dessetae infective larvae to select the best ligands. The prodrug V 1,3-dihexadecanamido-2-[4-chloro(2- chloro-4-nitroanilinocarbonyl)phenyloxy-carbonylpropanoyl oxy]propane (having a diamide function) was responsible for an in vitro delayed effect and an orally in vivo activity (200 mumol/kg when administered in a single dose). The biological improvement of this easily micellizable prodrug which is stable to intestinal enzymes in respect to Niclosamide confirms such a strategy.

Macrofilaricidal activity of albendazole-ivermectin combination: histopathological evaluation of adult Molinema dessetae

The macrofilaricidal effect of albendazole in association with ivermectin was assessed in the rodent Proechimys oris, infected with Molinema dessetae. The drug combination was given to five rodents 190 days after infection. A similar group was used as control. The doses administered were 10 mg per kg for albendazole and 0.04 mg per kg for ivermectin over five days. The histological examination of intra-peritoneal nodules done six weeks after therapy revealed a clear-cut macrofilaricidal effect. The number of dead worms was significantly higher in the treated group. The histological examination revealed a lesion pattern that was related to the drug exposure. This consisted of nodules, each containing a necrotic worm that had its morphology preserved and was surrounded by a foreign body granuloma. This lesion was only seen in the treated group. A pattern related with the spontaneous death of worms was also observed. The results obtained here show the importance that albendazole-ivermectin combination could have in human filariasis therapy. Further studies in man should be done to confirm the macrofilaricidal effect of this drug combination in human filariasis.

Study of lymphotropic targeting and macrofilaricidal activity of a melphalan prodrug on the Molinema dessetae model

This study deals with the design of a new macrofilaricidal drug derived from melphalan and having a lymphotropism to avoid the hepatic first pass effect and enhance bioavailability after oral administration. Melphalan was linked to a ligand leading to a prodrug called 1,3-dp-melphalan which has structural analogy to triglycerides. The Molinema dessetae/Proechimys oris model was used for antiparasitic evaluation. Melphalan was macrofilaricidal in vitro against Molinema dessetae at 1mM, inactive in vivo after an oral single dose at 164 mumol/kg while the prodrug 1,3-dp-melphalan was active against adult worms after a single dose at 82 mumol/kg. After an oral administration of the prodrug to rats, the maximum concentration and the cumulated quantities of melphalan in lymph were about 45-fold higher than those observed with the free drug under the same conditions. Moreover, the plasma concentration of melphalan was 2-fold higher than those observed after the administration of the free drug. These results are in favor of lymphotropic targeting as a novel approach to develop new orally active macrofilaricides.

[Chemotherapy in Alzheimer's disease. Retrospective study in a specialized hospital center]

In this study, our aim was to analyse the prescriptions of drugs used to improve Alzheimer's disease at CHS Paul Guiraud. This study was carried out a posteriori on 16 hospitalized patients. We have seen that for our patients there is no general rule, nor therapeutic scheme but the choice of treatment is carried out according to the professional experience of the physician. The treatment therefore is composed of symptomatic drugs alone or associated with etiologic drugs. Eleven anxiolytic or hypnotic drugs were prescribed. Alimemazine is the most prescribed in the sixteen cases. The preferential use of this drug can be explained by its presentation in the form of drops. In two cases, behavioural improvements were noted, in two other cases, we noted accentuation of dementia. Meprobamate used in seven cases of the sixteen, was never used alone. We find neuroleptics in fifteen of the sixteen cases studied: In seven cases they were administered from the beginning of the hospitalisation; for the others they were introduced later during a phase of agitation or delirium. On the whole, they were effective on aggressive agitation, in particular thioridazine. Eight of the patients, were treated with halopéridol. In two cases, the behaviour disorders were not stopped; in four cases, there was a worsening of dementia. We noted depression in 6 cases from the beginning of hospitalization, and two cases during hospitalization. The anti-depressive drugs besides their main effect, reduce also anxiety. In two cases, we observed an aggravation of disorientation and confusion following of the prescription of amitryptiline and mianserine.(ABSTRACT TRUNCATED AT 250 WORDS)

Synthesis and nematocidal activity of arylmercaptovinyltetrahydropyrimidines

A set of mercaptovinyl tetrahydropyrimidines was synthesized in good yields by lithiation of 1,2-dimethyltetrahydropyrimidine with n-butyl lithium in tetrahydrofurane, followed by condensation with aromatic thioesters. Against three nematode genera, anthelminthic screening shows little activity; 2b and 2d were the most potent against Molinema dessetae.

Activity of albendazole-ivermectin combination and other filaricidal drugs against infective larvae, preadult, microfilariae and adult worms of Molinema dessetae in the rodent Proechimys oris

The efficacy of albendazole-ivermectin combination was tested an adult and developing stages of Molinema dessetae in the rodent Proechimys oris. Albendazole and ivermectin, both given alone, suramin and diethylcarbamazine were used as reference compounds. The drug combination (albendazole at 10 mg/kg/ day x 5 days and Ivermectin at 0.04 mg/kg/day x 5 days) was effective against infective larvae and preadult worms, and substantially reduced the number of live adult worms. The known filaricidal agents, diethylcarbamazine (400 mg/kg twice daily x 5 days), ivermectin (0.2 mg/kg/day x 5 days), and suramin (40 mg/kg/day x 5 days), as well as albendazole (50 mg/kg/day x 5 days) were active on infective larvae, preadult worms, microfilariae and adult worms. All drugs had the same level of efficacity on infective larvae. Albendazole had the highest efficacy against adult and preadult worms and diethylcarbamazine was the most active on microfilariae. Although the drug combination was not as effective against preadult and adult worms as albendazole alone, the results indicate that albendazole-ivermectin combination at a low dose had prophylactic effect and suggest a possible macrofilaricidal activity.

Inhibitory activity of saccharomyces yeasts on the adhesion of Entamoeba histolytica trophozoites to human erythrocytes in vitro

Adhesion to target cells represents the first step in infection by Entamoeba histolytica. Binding of axenic amoeba (HMI strain) to human red cells in vitro was employed as a model of the adhesion process. The influence of precontact of trophozoites with suspensions of live Saccharomyces boulardii yeasts, their fractions (membranes and yeast-content supernatant before and after filtration to eliminate the membrane) or yeast culture medium before and after fermentation was investigated. N-Acetylgalactosamine (GalNAC) was employed as the reference inhibitory sugar. The percentage of amoebae bearing red cells after pretreatment of amoebae with the various suspensions and derivates was determined. Adhesion was also evaluated by scanning electron microscopy (SEM). Pretreatment of amoebae with the live yeast suspension led to a significant reduction in the percentage of adhesion [32% vs 70% in the phosphate-buffered saline (PBS) control]. Reduced adhesion was also observed with the filtered and unfiltered supernatant of the yeast suspension homogenate [32% and 34%, respectively, vs 69% in the PBS control], yeast culture medium at the end of fermentation [49% vs 76% in the PBS control] and GalNAC [32% vs 72% in the PBS control]. SEM showed a decrease in the number of amoebae bearing red cells and a reduction in the number of red cells adhering to amoebae. We conclude that substances produced by the yeasts compete with red cells for adhesion sites on amoebae.

Levels of ecdysteroid-like material in adults of Nippostrongylus brasiliensis during the intestinal phase

Total ecdysteroid-like immunoreactive material was assayed and quantified in adults of the parasitic nematode N. brasiliensis during the intestinal phase in the rat in order to detect possible physiological fluctuations in titre. Worms of the same sex isolated from one rat were pooled in order to quantify ecdysteroids using enzyme immunoassay (EIA). The concentration of ecdysteroids fluctuated during adult life according to the sex and the age of the parasite. Important differences of levels of ecdysteroid-like compounds between the two sexes of parasites were noted particularly at 128 and 168 h post-infection. The peak at 128 h, present in female, but not in male worms, corresponds to the time of egg-laying. Following HPLC-EIA analysis, the presence of ecdysone, 20-hydroxyecdysone and apolar ecdysteroid-like material was ascertained during this peak. The physiological role and the possible origin of ecdysteroids in this nematode are discussed.

Design, synthesis and biological study of new antiparasitic spiroarsoranes

Thirty-eight new spiroarsoranes were synthesized after structure-activity relationship studies from the first series. These compounds were predicted to cross more easily the membrane of protozoae or the cuticle of Nematodes and to reach their biological target with efficiency. The spiroarsoranes were evaluated for their antiparasitic properties, on helminths and protozoa models in regard of their parent arsonic acids. The following parasite models were used: Entamoeba histolytica and Trichomonas vaginalis in vitro; Molinema dessetae infective larvae in vitro, adults and microfilariae in vivo; Nippostrongylus brasiliensis infective larvae in vitro. The results obtained on these models indicated that the "spiranization" of arsonic acids produced new compounds with a biological activity 10-fold superior to those of arsonic acids. Nevertheless, each parasite had its own sensitivity to spiroarsoranes. Moreover, in vivo results showed that the lipophilicity of the molecules should be optimal to avoid high toxicity in host such as arsenical encephalopathy.

Microtopography of Nippostrongylus brasiliensis (Nematoda: Heligmosomatidae): parasitic larval stages and adults

Specimens of the rat hookworm, Nippostrongylus brasiliensis (Nematoda) were recovered from lungs (third- and fourth-stage larvae) and intestine (fourth-stage larvae and adults). The following features were studied in the different stages by scanning electron microscopy: cephalic structures, especially sense organs, synlophe, cervical region, and caudal part. The main differences between the third and fourth stages concerned the lip-like structures around the oral aperture, the appearance of the cephalic space with the presence of a cephalic cap in fourth-stage larvae, the pattern of longitudinal ridges, and sexual differentiation. Pore-like papillae, not seen in third-stage larvae, developed in later stages. Deirids were observed only in adults, and phasmids were poorly discerned. Some of these morphological features, such as the cephalic sense organ apertures and cuticle pores and micropores, can be observed only by scanning electron microscopy. The possible functions of these different structures and their relationship with the behavior of the worms during their life cycle are discussed.

Microtopography of Nippostrongylus brasiliensis (Nematoda: Heligmosomatidae): free-living larval stages

Microtopographic features of the various growth stages of the three free-living larval stages of the rat hookworm Nippostrongylus brasiliensis (Nematoda) were surveyed by scanning electron microscopy. These worms have a rounded anterior end and an elongated tail. Cuticular annulations were observed along the body, which also bore two ribbon-like lateral alae. Two rings of six lip-like lappets were observed around the triradiate oral opening in all larval stages. The cephalic space contained two lateral amphidial pits. The excretory pore in the third anterior part was observed in a ventral view of the larvae. No deirids were observed. The anus with a crescent-shape opening was located posteriorly. Phasmidial apertures, only observed in the third-stage larvae, opened on the lateral alae in the tail region.

Synthesis of some 4-oxo-delta 2-thiazolin-2-ylhydrazones as potential antiprotozoal agents

Several 4-oxo-delta 2-thiazolin-2-ylhydrazone derivatives 6 (6-1 - 6-19) derived from the cyclization reaction between the thiosemicarbazones 5 and homologous alpha-chloroacids were prepared. Only compound 6-2 was found to be active against Entamoeba histolytica and Trichomonas vaginalis.

Spiroarsoranes of second generation: evaluation of trypanocidal properties against Trypanosoma brucei brucei

The spiroarsoranes are a series of pentavalent arsenicals having interesting trypanocidal properties. They are less toxic than trivalent arsenicals but their activity appear at higher doses and concentrations. The structure-activity relationships study from the first series led to a new generation of spiroarsoranes which has been synthesized and evaluated in vitro and in vivo against Trypanosoma brucei brucei bloodstream forms. Among 40 compounds, 5 were active in vitro at concentrations less than 10 mumol/l and 7 were active in vivo. The most interesting compound of this series (compound I e 2) showed an in vitro activity at 125 mumol/l after 24 hours incubation time and in vivo all the mice were cured after a subcutaneous treatment at 600 mumol/kg in one single dose. The spiranization and the substitution of para-arsanilic acid allowed to obtain a better mean survival time at 300 mumol/kg comparatively to para-arsanilic acid itself used as reference compound. Nevertheless, this second generation of compounds was less active than the selected compound of the first series which was efficient at 150 mumol/kg in subcutaneously one single dose.

Effects of ecdysteroids on reproductive physiology of Nippostrongylus brasiliensis (Nematoda) in vivo

1. The influence of ecdysteroids (ecdysone and ecdysterone) was investigated on the control of reproduction in the parasitic nematode Nippostrongylus brasiliensis in vivo. 2. Infestive larvae (L3) were immersed in solutions of ecdysteroids (2.2 microM) at 37 degrees C for 4 hr before injection into the host. The effect on egg-laying was observed two stages later. 3. The treatment increased egg-laying, but had no influence on the timing of the reproductive period. The greatest effect was observed with ecdysone, ecdysterone only inducing a small and non-significant stimulation under our experimental conditions. 4. The physiological role of ecdysteroids in meiosis and gonadal development in nematodes is discussed.

Comparative effects of anthelmintics on c-MDH from Molinema dessetae (Nematoda: Filarioidea) and from a mammal

Malate dehydrogenase (MDH) (E.C.1.1.1.37) activity was detected in the filaria Molinema dessetae at a level similar to those found in other filariae. In M. dessetae, the cytoplasmic form (c-MDH) predominated and the study was performed on partially purified fractions. The pH optimum for oxaloacetate reduction was 6.1, with maximal activity at 7811 nmol min-1 mg protein-1, but high concentrations of oxaloacetate inhibited MDH activity. The Km value for oxaloacetate was determined as 22 microM for M. dessetae c-MDH and 33 microM for mammalian c-MDH. Anthelmintic drugs were compared as potential inhibitors of filarial and mammalian c-MDH. Among the compounds evaluated, amocarzine showed a specific inhibitory effect on filarial c-MDH through only at high concentrations. Suramin alone showed an inhibitory effect at low concentrations (Ki = 1.15 microM) but without selective action towards filarial c-MDH. The suramin type of inhibition was found to be competitive. Suramin probably acts on both enzymes in the same manner. Nevertheless, M. dessetae c-MDH is proposed as a suitable enzyme assay model to screen MDH inhibitors as potential filaricides.

Purification and properties of phosphoenolpyruvate carboxylase from Molinema dessetae (Nematoda: Filarioidea)

The presence of phosphoenolpyruvate (PEP) carboxylase (EC 4.1.1.31), an enzyme at the branchpoint of glycolysis and the Krebs cycle was detected in the Filaria Molinema dessetae. This enzyme has not previously been identified in Helminths, which have so far been found to only possess a phosphoenolpyruvate carboxykinase (EC 4.1.1.32). This enzyme had a level of activity comparable to that of pyruvate kinase, and was relatively less active than enzymes such as malate dehydrogenase or lactate dehydrogenase. We propose here a method of purification of M. dessetae PEP-carboxylase. When purified to electrophoretic homogeneity, the enzyme had a molecular weight of 64 kDa. Kinetic studies indicated that the carboxylation reaction had an optimal pH of 5.8. The enzyme was inhibited by cations such as Fe2+, Zn2+, Cd2+, Cu2+ but required the presence of Mg2+ or Mn2+. The enzyme was thermostable. The apparent Km value of 2.38 mmol for phosphoenolpyruvate for the carboxylation reaction was higher than previously reported values. The Km value for KHCO3 was found to be 1.6 mmol. PEP-carboxylase did not catalyse the reverse reaction.

Synthesis of the orally macrofilaricidal and stable glycerolipidic prodrug of melphalan, 1,3-dipalmitoyl-2-(4'(bis(2''-chloroethyl)amino)phenylalaninoyl)gl ycerol

A new strategy is presented to develop macrofilaricidal compounds orally administered and able to concentrate in the lymphatic system. A diglyceride derivative of melphalan, 1,3-dipalmitoyl-2-(4'(bis(2''-chloroethyl)amino)phenylalaninoyl)gl y cerol, was synthesized. The esterification of melphalan by 1,3-dipalmitin allowed chemical stabilization of the alkylating agent in aqueous dispersion. No degradation of this prodrug was observed after a 3-month storage of an aqueous dispersion at 4 degrees C. The filaricidal activity of the prodrug was compared with those of melphalan in vitro against adults, infective larvae and microfilariae of Molinema dessetae, and evaluated in vivo on Molinema dessetae infected Proechimy oris. In vitro, melphalan and the glycerolipidic prodrug were inactive against microfilariae but active at 1 mmol/l against infective larvae and adults. In vivo studies were performed with rodents subcutaneously inoculated with infective larvae from Aedes aegypti. The number of macrofilariae was significantly reduced following treatment with a single oral dose of the alkylating agent prodrug (0.082 mmol/kg).

Pharmacomodulations on new organometallic complexes of Ir, Pt, Rh, Pd, Os: in vitro and in vivo trypanocidal study against Trypanosoma brucei brucei

New organometallic complexes have been synthesized by association of an active organic molecule with a metallic element such as Pt, Rh, Ir, Pd, Os. Their trypanocidal activity was studied in vitro and in vivo against T. b. brucei. The more active compounds were pentamidine derivatives. The Ir- COD-pentamidine complex, and Iridium (I) cationic and organometallic complex showed and in vitro activity at 60 micrograms/l. Moreover, all infected mice were cured by this compound subcutaneously administered in a single dose at 0.5 mg/kg (0.317 mumol/kg). In the same conditions, pentamidine cured all the mice at 5 mumol/kg. Ir-COD-pentamidine (or P1995) was 16 fold more efficient than pentamidine. Since the chemotherapeutic index of this molecule was 7.5 fold higher than those of pentamidine, P1995 can be considered as a potential trypanocidal drug of the future.

A new in vitro model of Entamoeba histolytica adhesion, using the human colon carcinoma cell line Caco-2: scanning electron microscopic study

The human colon carcinoma cell line Caco-2, which is widely used to study the adhesion and cytotoxicity of enterobacteria, was used to investigate the adhesion of the trophozoites of Entamoeba histolytica. We observed a high percentage of adhesion of amoebae to Caco-2 cells. Scanning electron microscopy showed that amoebial membrane structures were involved in adhesion and the cytolytic action. These differentiated cells should prove to be a useful model system for investigation of the pathogenic action of amoebae.

Biogenic amine levels in the cockroach Blaberus craniifer Burm. nervous system

1. Apart from octopamine, the same indolamines and catecholamines were detected in the whole nervous system of the cockroach Blaberus craniifer Burm., at the same time. 2. However, levels were found to depend on sex, age, and the anatomic region within the nervous system. 3. Although not established, it is thought that these substances act synchronously from the ganglia. 4. The differences in levels between males and females and between anatomical regions during imaginal life suggest, in this species of cockroach, the physiological importance of the metameric organization in metabolic pathways or functional aspects of biogenic amines.

Indolamines and onset of vitellogenesis in the imaginal molt-decapitated cockroach Blaberus craniifer Burm

1. The effects of 5-hydroxytryptamine, 5-hydroxyindoleacetic acid and N-acetyl-5-hydroxytryptamine on oocytes of Blaberus craniifer, in which vitellogenesis was prevented by imaginal molt decapitation, were investigated. 2. Sites binding anti-egg-protein antibodies were detected in the periphery of basal oocytes of treated females, with individual variability. 3. In this ovoviviparous cockroach, the onset of vitellogenesis may thus not be triggered solely by juvenile hormone, and indolamines may play a role in the uptake of haemolymphatic proteins by oocytes.

Biogenic amines in newly-ecdysed cockroaches

1. Simultaneous quantification (HPLC and electrochemical detection) of biological extracts have shown dopamine, N-acetyl dopamine, tryptophan, 5-hydroxytryptamine, a 5-hydroxyindolacetic acid-like substance in nervous tissue and hemolymph of Blaberus craniifer and Periplaneta americana. 2. 5-Hydroxytryptophan was only detected in head and thoraco-abdominal nerve cord. 3. Octopamine, but not N-acetyl-5-HT was quantified in the hemolymph.