To Target or Not to Target Schistosoma mansoni Cyclic Nucleotide Phosphodiesterase 4A?

Schistosomiasis is a neglected tropical disease with high morbidity. Recently, the Schistosoma mansoni phosphodiesterase SmPDE4A was suggested as a putative new drug target. To support SmPDE4A targeted drug discovery, we cloned, isolated, and biochemically characterized the full-length and catalytic domains of SmPDE4A. The enzymatically active catalytic domain was crystallized in the apo-form (PDB code: 6FG5) and in the cAMP- and AMP-bound states (PDB code: 6EZU). The SmPDE4A catalytic domain resembles human PDE4 more than parasite PDEs because it lacks the parasite PDE-specific P-pocket. Purified SmPDE4A proteins (full-length and catalytic domain) were used to profile an in-house library of PDE inhibitors (PDE4NPD toolbox). This screening identified tetrahydrophthalazinones and benzamides as potential hits. The PDE inhibitor NPD-0001 was the most active tetrahydrophthalazinone, whereas the approved human PDE4 inhibitors roflumilast and piclamilast were the most potent benzamides. As a follow-up, 83 benzamide analogs were prepared, but the inhibitory potency of the initial hits was not improved. Finally, NPD-0001 and roflumilast were evaluated in an in vitro anti-S. mansoni assay. Unfortunately, both SmPDE4A inhibitors were not effective in worm killing and only weakly affected the egg-laying at high micromolar concentrations. Consequently, the results with these SmPDE4A inhibitors strongly suggest that SmPDE4A is not a suitable target for anti-schistosomiasis therapy.

Itraconazole, a cytochrome P450 inhibitor, enhanced the efficacy of praziquantel against Schistosoma mansoni infection and alleviated liver injury in mice

Treatment of schistosomiasis is heavily reliant on the single antischistosomal drug praziquantel (PZQ). The use of synergistic drug-drug interactions is one possible solution, which could be used to mitigate PZQ's poor and variable bioavailability. Itraconazole (ITZ), a triazole antifungal agent, is a potent CYP3A inhibitor that can cause significant drug-drug interactions when used with CYP3A substrates. This study investigates the effect of ITZ as adjuvant therapy with PZQ on worm load, egg deposition and maturation, and the consequent histopathology and biochemical abnormalities in the liver during the immature and mature stages of Schistosoma mansoni (S. mansoni) infection. S. mansoni-infected mice were divided into five groups of eight-ten mice each: (I) infected untreated, (II) infected and treated with PZQ 3 weeks PI, (III) infected and treated with both ITZ and PZQ 3 weeks PI, (IV) infected and treated with PZQ 7 weeks PI, and (V) infected and treated with both ITZ and PZQ 7 weeks PI. All mice were killed by rapid decapitation 9 weeks PI. Data revealed that ITZ in combination with PZQ at both immature and mature stages improved the parasitological criteria of cure, and greatly reduced inflammation, granuloma and fibrotic tissue formation, and apoptosis versus PZQ alone. Furthermore, it showed the greatest impact on improving liver injury and oxidative stress markers. Notably, the effect was considerably stronger at the mature stage of S. mansoni infection. These findings support the notion that ITZ increased PZQ's antischistosomal activity by inhibiting CYP450 expression, potentially reducing PZQ metabolism and increasing systemic exposure.

Schistosomicidal and hepatoprotective activity of gamma-aminobutyric acid (GABA) alone or combined with praziquantel against Schistosoma mansoni infection in murine model

OBJECTIVE

This study aimed to evaluate the efficacy of gamma-aminobutyric acid (GABA) alone or combined with praziquantel (PZQ) against Schistosoma (S) mansoni infection in a murine model.

METHODS

Five groups, 8 mice each, were studied; GI served as normal controls; GII: S. mansoni-infected control group and the other three S. mansoni-infected groups received drug regimens for 5 consecutive days as follows GIII: Infected-PZQ treated group (200 mg/kg/day); GIV: Infected-GABA treated group (300 mg/kg/day) and GV: Infected-PZQ-GABA treated group (100 mg/kg/day for each drug). All animal groups were sacrificed two weeks later and different parasitological, histopathological and biochemical parameters were assessed.

RESULTS

Combined GABA-PZQ treated group recorded the highest significant reduction in all parasitological, histopathological and biochemical parameters followed by PZQ and finally GABA groups. Combined GABA-PZQ treatment led to the complete disappearance of immature eggs and marked reduction of deposited eggs in liver tissues and improved liver pathology. Significant improvement in hepatic oxidative stress levels, serum albumin and total protein in response to GABA treatment alone or combined with PZQ.

CONCLUSION

GABA had schistosomicidal, hepatoprotective and antioxidant activities against S. mansoni infection, GABA disrupted parasite pairing and activity, reduced the total number of worms recovered and the number of ova in the tissues. GABA may be considered an adjuvant therapy to potentiate PZQ antiparasitic activity and eradicate infection-induced liver damage and oxidative stress.

Cloning and functional complementation of ten Schistosoma mansoni phosphodiesterases expressed in the mammalian host stages

Only a single drug against schistosomiasis is currently available and new drug development is urgently required but very few drug targets have been validated and characterised. However, regulatory systems including cyclic nucleotide metabolism are emerging as primary candidates for drug discovery. Here, we report the cloning of ten cyclic nucleotide phosphodiesterase (PDE) genes of S. mansoni, out of a total of 11 identified in its genome. We classify these PDEs by homology to human PDEs. Male worms displayed higher expression levels for all PDEs, in mature and juvenile worms, and schistosomula. Several functional complementation approaches were used to characterise these genes. We constructed a Trypanosoma brucei cell line in which expression of a cAMP-degrading PDE complements the deletion of TbrPDEB1/B2. Inhibitor screens of these cells expressing only either SmPDE4A, TbrPDEB1 or TbrPDEB2, identified highly potent inhibitors of the S. mansoni enzyme that elevated the cellular cAMP concentration. We further expressed most of the cloned SmPDEs in two pde1Δ/pde2Δ strains of Saccharomyces cerevisiae and some also in a specialised strain of Schizosacharomyces pombe. Five PDEs, SmPDE1, SmPDE4A, SmPDE8, SmPDE9A and SmPDE11 successfully complemented the S. cerevisiae strains, and SmPDE7var also complemented to a lesser degree, in liquid culture. SmPDE4A, SmPDE8 and SmPDE11 were further assessed in S. pombe for hydrolysis of cAMP and cGMP; SmPDE11 displayed considerable preferrence for cGMP over cAMP. These results and tools enable the pursuit of a rigorous drug discovery program based on inhibitors of S. mansoni PDEs.

Deciphering the enzymatic target of a new family of antischistosomal agents bearing a quinazoline scaffold using complementary computational tools

A previous phenotypic screening campaign led to the identification of a quinazoline derivative with promising in vitro activity against Schistosoma mansoni. Follow-up studies of the antischistosomal potential of this candidate are presented here. The in vivo studies in a S. mansoni mouse model show a significant reduction of total worms and a complete disappearance of immature eggs when administered concomitantly with praziquantel in comparison with the administration of praziquantel alone. This fact is of utmost importance because eggs are responsible for the pathology and transmission of the disease. Subsequently, the chemical optimisation of the structure in order to improve the metabolic stability of the parent compound was carried out leading to derivatives with improved drug-like properties. Additionally, the putative target of this new class of antischistosomal compounds was envisaged by using computational tools and the binding mode to the target enzyme, aldose reductase, was proposed.

A novel praziquantel solid lipid nanoparticle formulation shows enhanced bioavailability and antischistosomal efficacy against murine S. mansoni infection

Background

Schistosomiasis is responsible for a considerable global disease burden. This work aimed to improve the therapeutic outcome of the only available antischistosomal drug worldwide, praziquantel (PZQ), by incorporating it into a novel carrier, “solid lipid nanoparticles (SLNs)”, to enhance its solubility, bioavailability and efficacy. A simple, cost-effective method was used to prepare SLN-PZQ.

Results

Compared to market PZQ (M-PZQ), SLN-PZQ was more bioavailable, as denoted by higher serum concentrations in both normal and infected mice where elevated K_a, AUC_0–24, C_max, and t_1/2e with a decrease in k_el were demonstrated. The AUC_0–24 for SLN-PZQ in normal and Schistosoma mansoni-infected groups was almost nine- and eight-fold higher, respectively, than that for M-PZQ in corresponding groups. In normal and S. mansoni-infected mice, SLN-PZQ was detectable in serum at 24 h, while M-PZQ completely vanished 8 h post-treatment. Additionally, enhanced absorption with extended residence time was recorded for SLN-PZQ. Compared to M-PZQ, SLN-PZQ revealed superior antischistosomal activity coupled with enhanced bioavailability in all treated groups where higher percentages of worm reduction were recorded with all dosages tested. This effect was especially evident at the lower dose levels. The ED₉₅ of SLN-PZQ was 5.29-fold lower than that of M-PZQ, with a significantly higher reduction in both the hepatic and intestinal tissue egg loads of all treated groups and almost complete disappearance of immature deposited eggs (clearly evident at the low dose levels).

Conclusions

SLN-PZQ demonstrated enhanced PZQ bioavailability and antischistosomal efficacy with a safe profile despite the prolonged residence in the systemic circulation.

Screening of a PDE-focused library identifies imidazoles with in vitro and in vivo antischistosomal activity

We report the evaluation of 265 compounds from a PDE-focused library for their antischistosomal activity, assessed in vitro using Schistosoma mansoni. Of the tested compounds, 171 (64%) displayed selective in vitro activity, with 16 causing worm hypermotility/spastic contractions and 41 inducing various degrees of worm killing at 100 μM, with the surviving worms displaying sluggish movement, worm unpairing and complete absence of eggs. The compounds that did not affect worm viability (n = 72) induced a complete cessation of ovipositing. 82% of the compounds had an impact on male worms whereas female worms were barely affected. In vivo evaluation in S. mansoni-infected mice with the in vitro 'hit' NPD-0274 at 20 mg/kg/day orally for 5 days resulted in worm burden reductions of 29% and intestinal tissue egg load reduction of 35% at 10 days post-treatment. Combination of praziquantel (PZQ) at 10 mg/kg/day for 5 days with NPD-0274 or NPD-0298 resulted in significantly higher worm killing than PZQ alone, as well as a reduction in intestinal tissue egg load, disappearance of immature eggs and an increase in the number of dead eggs.

MCR synthesis of praziquantel derivatives

Schistosomiasis, a high volume neglected tropical disease affecting more than 200 million people worldwide, can only be effectively treated by the tetrahydroisoquinoline drug praziquantel (PZQ). Herein, we describe an efficient approach to access PZQ derivatives by the Ugi 4-component reaction followed by the Pictet-Spengler reaction in a two-step, one-pot procedure. 30 novel PZQ derivatives are described based on the Ugi 4-component reaction and an X-ray structure of a novel derivative revealing different conformation compared with PZQ is discussed. Several analogues comparable in activity to the drug PZQ have been identified based on an in vitro Schistosoma mansoni worm viability assay.

Further assessment of Mirazid as antischistosomal drug in experimental schistosomiasis hematobium

Conflicting reports are found in the literature about the efficacy of Mirazid (MZ), which is a special formulation of myrrh obtained from the stem of Commiphora molmol (Nees), Engl. tree (Burseraceae), as an antischistosomal drug. This initiated the present study to further assess this drug in experimental schistosomiasis hematobium. The drug was administered orally to hamsters infected with Schistosoma hematobium ( Bilharz, 1852 ) using 500 mg/kg body weight for six successive days on an empty stomach. The drug effect was examined after three periods: 4, 8 and 12 weeks post-treatment. Emphasis was given to certain parameters such as change in worm load, number of ova/mg tissue, oogram pattern and number of ova/g stool, and tegumental changes in the worms by electron microscopy after prolonged observation periods. The results showed very slight 3.4% worm reduction by MZ after the longest evaluation period (12 weeks), versus very high reduction (100%) by the reference drug praziquantel (PZQ). In comparison with the untreated control no change was found in the number of ova/mg tissue in MZ-treated hamsters regardless of the date of observation (4-12 weeks), versus significantly high reduction (99.6%) observed in the case of PZQ treatment. However, a significant decrease (22%) in the ratio of immature and increase in dead ova in tissues of MZ-treated hamsters was obvious at 12 weeks post treatment. In MZ-treated animals, a slight reduction (18.3%) in the number of stool eggs versus absence of eggs in PZQ-treated animals 12 weeks after treatment. Scanning electron microscopic examination of S. hematobium worms revealed intact tubercles, spines and sensory bulbs and no effect of the ventral side after MZ treatment. Meanwhile, PZQ treatment revealed extensive disruption of the tegument worm. Therefore, this experimental study gives extra support to previously reported negative evaluation about the effectiveness of this drug in the treatment of schistosomiasis against many other published positive results. This controversy about the efficacy of MZ may be attributed to inconsistency of its material which is obtained from natural origin.

Antischistosomal activity of hexadecyloxypropyl cyclic 9-(S)-[3-hydroxy-2-(phosphonomethoxy)propyl]adenine and other alkoxyalkyl esters of acyclic nucleoside phosphonates assessed by schistosome worm killing in vitro

9-(S)-[3-Hydroxy-2-(phosphonomethoxy)propyl]adenine [(S)-HPMPA] has been reported to have antischistosomal activity. Ether lipid esters of (S)-HPMPA and cidofovir (CDV) have greatly increased activities in antiviral assays and in lethal animal models of poxvirus diseases. To see if ether lipid esters of CDV and (S)-HPMPA enhance antischistosomal activity, we tested their alkoxyalkyl esters using Schistosoma mansoni worm killing in vitro. Hexadecyloxypropyl (HDP)-cyclic-(S)-HPMPA and HDP-cyclic-CDV exhibited significant in vitro antischistosomal activities and may offer promise alone or in combination with praziquantel.

Synthesis and in vitro evaluation of new benzothiazole derivatives as schistosomicidal agents

A series of benzothiazol-2-yl-dithiocarbamates 3a-d along with their copper complexes 4a-c were synthesized via the reaction of suitable alkyl, aralkyl or heteroaryl halides with the sodium salt of benzothiazol-2-yl-dithiocarbamic acid, followed by complexation with copper sulphate. N-(4-Acetyl-5-aryl-4,5-dihydro-1,3,4-thiadiazol-2-yl)-N-benzothiazol-2-yl-acetamides 7a-c were synthesized by cyclization of the appropriate thiosemicarbazones 6a-c in acetic anhydride. Selected compounds were screened for in vitro schistosomicidal activity against Schistosoma mansoni at three different dosage levels (10, 50 and 100 microg/mL). Three of these products, 4a-c, showed schistosomicidal activity similar to praziquantel, with 100% worm mortality at 10 microg/mL. These compounds would constitute a new class of potent schistosomicidal agents.

Dynamics of multiple quantum coherences in dipole-coupling spins in solid

A perturbation method deals with dipolar coupling spins in solids is presented. As example of application the method, the multiple-quantum coherence dynamics in clusters of a linear chain of four nuclear spins and a ring of six spins coupled by dipole-dipole interaction are considered. The calculated 0Q and 2Q intensities in a linear chain of four nuclear spins and 6Q intensity in a ring of six spins vs. the duration of the preparation period agree well with the exact solutions (for linear chain of four nuclear spins) and simulation data (for linear chain of four nuclear spins and a ring of six spin).

Effect of praziquantel on the immature stages of Schistosoma haematobium

Schistosoma mansoni is known to be refractory to praziquantel treatment in the pre-patent period of infection. Since Schistosoma haematobium has a much longer pre-patent period (10-12 weeks vs. 5-6 for the former species), we asked the question whether a correspondingly longer period of insusceptibility exists in urinary schistosomiasis. In hamsters treated at different times after infection, S. haematobium was partially refractory to praziquantel when treatment was given at week 5, but showed practically full sensitivity at 7-8 weeks and later times. Schistosoma haematobium worms obtained at different times after infection and exposed in vitro to praziquantel were refractory to low drug concentrations between 4 and 6 weeks, but were clearly affected at higher concentrations and at later time points. We conclude that S. haematobium does not have a praziquantel-insensitive window longer than in S. manson, in spite of its much longer maturation period. In addition, refractoriness of immature stages can be overcome at higher drug concentrations.

Validation of sensitivity to praziquantel using Schistosoma mansoni worm muscle tension and Ca2+-uptake as possible in vitro correlates to in vivo ED50 determination

Schistosome worm muscle tension and [45Ca2+]-uptake were tested as possible correlates of susceptibility to praziquantel (PZQ) assessed by estimating the drug ED50. Schistosoma mansoni cercariae of PZQ sensitive (S-CD, S-MOC and S-GP) and insensitive S. mansoni isolates (I-EE2, I-BANL and I-Senegal 47) were used to infect batches of CD-1 Swiss albino mice. Seven weeks after infection, animals of each batch were divided into six groups. Five of them received PZQ in doses of 12.5, 25, 50, 100 or 200 mg/kg PZQ, respectively, for five consecutive days, while the sixth was left as untreated controls. Two weeks after treatment mice were sacrificed, perfused and PZQ ED50's were estimated. Male worms recovered from infected untreated controls were examined for their muscle tension increase in response to PZQ using a physiological recorder coupled to a photooptic transducer. [45Ca2+]-uptake of male worms in the presence and absence of PZQ was determined using a liquid scintillation beta counter. Data revealed that PZQ insensitive isolates had significantly higher drug ED50 (>130 mg/kg) than PZQ sensitive isolates with ED50's <100 mg/kg. Moreover, in response to PZQ they were found to possess significant reductions in their worm muscle tension and their [45Ca2+]-uptake were <100%. Both parameters showed a significant negative correlation to PZQ ED50 in vivo and a significant positive correlation to each other.

Lack of evidence for an antischistosomal activity of myrrh in experimental animals

In a multicenter investigation of the potential antischistosomal activity of myrrh, a resin obtained from an African plant, different derivatives of the resin, including the commercial preparation Mirazid, were tested at different doses in mice and hamsters infected with Schistosoma mansoni. In mice infected with the Egyptian (CD) strain of S. mansoni, four of six groups treated with Mirazid did not show significant worm reduction, while the remaining groups showed significant but trivial reductions. In mice infected with the Puerto Rican (Mill Hill) strain of S. mansoni, a Mirazid solution was toxic for mice at high doses and produced modest or no worm reduction at lower doses. In hamsters and mice infected with Puerto Rican (NMRI) and Brazilian (LE) strains of S. mansoni and treated with the crude extract of myrrh in doses ranging from 180 to 10,000 mg/kg, no signs of antibilharzial activity were observed. Total tissue egg load and egg developmental stages were not affected by any of the treatment regimens. These results were in contrast to those obtained in praziquantel-treated animals in which 94% worm reduction and 100% egg reduction was observed. Based on the findings of this work, we cannot recommend the use of Mirazid in human cases of schistosomiasis.

Activity of 9-(S)-[3-hydroxy-2-(phosphonomethoxy)propyl]adenine against Schistosomiasis mansoni in mice

The activity of the acyclic nucleotide analogue 9-(S)-[3-hydroxy-2-(phosphonomethoxy)propyl]adenine [(S)-HPMPA] against Schistosoma mansoni was investigated in mice. The compound was injected intraperitoneally, usually on two or five consecutive days, at 10 to 20 mg/kg of body weight/day. The treatment started before, at the time of, and after the onset of egg laying (oviposition) by S. mansoni. The animals were killed from 7 to 40 days after the cessation of treatment. Significant reductions in the total numbers of female and coupled worms were found. Female fecundity and both hepatic and intestinal egg loads were suppressed. These effects were more pronounced with dosing regimens launched before the time of oviposition. The complete disappearance of immature eggs and a significant reduction to the complete absence of mature eggs, with 99 to 100% of the eggs being dead, were produced. No hepatic egg-induced granulomas were present in mice treated at the time of oviposition, and the granulomas were smaller in mice treated before S. mansoni oviposition. These preliminary findings extend the knowledge of the antiparasitic properties of (S)-HPMPA.

Effect of simultaneous and/or consecutive administration of the broad spectrum anthelmintic flubendazole together with praziquantel in experimental Schistosoma mansoni infection

This study is a trial to demonstrate the effect of the broad spectrum anthelmintic drug flubendazole (methyl 5-(p-fluoro-benzoyl)-2-benzimidazolecarbamate, CAS 31430-15-6), a mebendazole derivative, together with praziquantel (CAS 55268-74-1, EMBAY 8440, Biltricide) in murine schistosomiasis mansoni. Moreover, the relationship between the posttreatment worm burden, oogram pattern, tissue egg load and hepatic granuloma volume was also investigated. Three main groups of Swiss albino mice infected with Schistosoma mansoni cercariae were used in the experiment. Group I included infected untreated control mice. Group II: Subgroup II (a): Animals received 1/3 the dose of praziquantel 25 days post infection. Subgroup II (b): Mice were given 1/3 dose of flubendazole 25 days post infection. Subgroup II (c): Animals received the combination (1/3 dose of flubendazole + 1/3 the dose of praziquantel 25 days post infection. Group III: Subgroup III (a): Mice were given 1/3 the dose of praziquantel 7 weeks post infection. Subgroup III (b): Mice received 1/3 dose of flubendazole 25 days post infection. 24 days later, 1/3 the dose of praziquantel was given. Mice given the consecutive drug regimen (flubendazole 1/3 single oral dose 25 days post infection, then praziquantel 1/3 oral dose for two successive days 24 days later, revealed a significant reduction in the recovery of adult schistosomes after portal perfusion (95.9%), absence of immature stages of ova development, a higher level of dead ova in the oogram and the smallest granuloma mean diameter. These data were less conspicuous in mice given the simultaneous drug regimen.

Ferric sulphate and formocresol pulpotomies in baboon primary molars: histological responses

AIM

To compare pulpal reactions to ferric sulphate and formocresol pulpotomies in primary molar teeth with inflamed pulps.

STUDY DESIGN

An experimental study in 15 juvenile baboons (Papio ursinus).

MATERIALS AND METHODS

Pulpitis was induced with fresh human carious dentine or Streptococcus mutans placed into occlusal cavities in 57 primary molars; after 14 days a pulpotomy was performed on the same primary molars with the two pulp medicaments randomly allocated; the pulp was covered with IRM and the cavity filled with amalgam. After 90 days specimens were harvested and examined under the light microscope with the examiner blind to the treatment.

RESULTS

Reaction frequencies in the ferric sulphate-treated and formocresol-treated teeth were: recognisable pulp 52% and 50%, dentine bridges 16% and 12%, internal root resorption 12% and 4%, external resorption 28% and 31%, bacteria 12% and 23%, peri-apical abscesses 32% and 38%.

STATISTICS

Fisher's exact probability test showed no statistically significant differences between reaction frequencies in the two treatment groups.

CONCLUSION

A pulpotomy in a primary tooth may be clinically successful in the presence of adverse histological reactions.

Stability and reproductive fitness of Schistosoma mansoni isolates with decreased sensitivity to praziquantel

These studies are focused on schistosomes derived from human infections not cured by three successive doses of praziquantel that also produced infections in mice that were significantly more difficult to cure than infections with control worms. Half (three of six) of these isolates retained their decreased response to praziquantel after multiple passages through the life-cycle in the absence of therapeutic pressure. Two of the isolates, including the one initially least sensitive to praziquantel; reverted, to a sensitivity not significantly different from controls. For example, the EE6 isolate initially required 680 mg/kg praziquantel to affect a 50% reduction in worm load in murine infections, but after only six passages through the life cycle over 5 years this was reduced to 113 mg/kg, not different from control infections. The stability of some of the isolates and the reversion of others indicates that the biological or genetic factors conferring decreased praziquantel response varies among the isolates. The three isolates that retained decreased sensitivity to praziquantel all showed compromises in reproductive fitness in the laboratory, expressed most frequently as a decreased cercarial production from snails infected with those isolates compared to controls. For example, the total cercarial production of snails infected with the EE10 isolate was only 57% that of controls. The reversion of some of the isolates to a praziquantel sensitive state and the decreased reproductive fitness of those that did not revert suggest that there is some biological cost associated with the relative praziquantel insensitivity of these worms, which could help limit the impact of such isolates in the field. Infections with the less sensitive isolates also produced significantly less circulating schistosomal antigen in mice, suggesting that a decrease in the host immune response elicited by these worms could be one of the factors contributing to the diminished praziquantel efficacy.

Praziquantel-induced tegumental damage in vitro is diminished in schistosomes derived from praziquantel-resistant infections

The aggressive use of praziquantel to combat schistosomiasis in Egpyt raises concern about the possible emergence of resistance. Eggs from Egyptian patients with praziquantel-resistant infections (not cured by 3 doses of praziquantel) have been used to establish infection-specific schistosome isolates in mice. The response of these worms to the drug was observed in vitro, in order to determine if the isolates obtained from these resistant infections were, in fact, less responsive to praziquantel. One of the hallmark effects of praziquantel on schistosomes in vitro is a disruption of the worm's outer surface, the tegument. Here, praziquantel-induced tegumental damage is observed in 3 distinct isolates, 2 derived from resistant infections and 1 from an infection cured by a single dose. The isolates from the resistant infections were less susceptible to praziquantel-induced tegumental damage in vitro, suggesting that the worms are in some way less responsive to the drug.

Effect of the broad spectrum anthelmintic drug flubendazole upon Schistosoma mansoni experimentally infected mice

The effect of the broad spectrum anthelmintic drug flubendazole (methyl 5-(p-fluorobenzoyl)-2-benzimidazolecarbamate, CAS 31430-15-6), a mebendazole derivative with a molecular weight of 313.29, on Schistosoma mansoni infection in mice was evaluated. Moreover, the relationship between the posttreatment worm burden, hepatic granuloma volume, and serum immunoglobulin profile (immunoglobulin G and immunoglobulin M, IgG and IgM), was also investigated. Two main groups of Swiss albino mice infected with Schistosoma mansoni cercariae were used in the experiment. Group I consisted of infected untreated control mice. The mice of group II were submitted to treatment with flubendazole 100 mg/kg body weight as single oral dose at different time intervals: Group IIa received treatment 24 h before infection. Group IIb received treatment 4 h after infection. Group IIc received treatment 25 days after infection. Mice treated 25 days after infection, compared to those treated in other time intervals, revealed a significant reduction in the recovery of adult schistosomes after portal perfusion (79.5%), a lower immunoglobulin level (IgG and IgM), and the smallest granuloma mean diameter (220.0 +/- 10.3 microns). These data were less salient in mice treated 4 h after, and 24 h before infection.

Resistance to praziquantel: direct evidence from Schistosoma mansoni isolated from Egyptian villagers

Recent evidence suggest that resistance to praziquantel (PZQ) may be developing. This would not be surprising in countries like Egypt where the drug has been used aggressively for more that 10 years. The classic phenotype of drug resistance is a significant increase in the 50% effective dose value of isolates retrieved from patients not responding to the drug. In a previous publication, we reported that such phenotypes have been isolated from humans infected with Schistosoma mansoni. Since the action of PZQ may be dependent upon the drug and host factors, most notably the immune system, we analyzed the quantitative effects of PZQ on single worms that differed in their response to PZQ when maintained in mice. Our hypothesis was that the in vitro action of the drug would correlate with it in vivo action. We confirmed this hypothesis and conclude that the in vitro action of the drug is related to its in vivo action. Knowing this relationship will assist in our ability to detect or survey for the PZQ resistant phenotype in human populations.

Stimulation of tyrosylprotein sulfotransferase activity by ethanol: role of increased enzyme level

Tyrosylprotein sulfotransferase (TPST), an enzyme involved in the posttranslational modification of proteins, plays important role in the biological activity and secretion of proteins. Previously we have shown an increased activity of this enzyme in gastric mucosa of alcoholics. In the present study, effect of ethanol on TPST was examined in rat liver and gastric mucosa utilizing enzyme assays and Western blot analyses for TPST levels. Male Sprague-Dawley rats were pair-fed Leiber-DeCarli liquid diets for 10 days and controls received a liquid diet in which dextrose was isocalorically substituted for ethanol. After ethanol feeding, rats were sacrificed and liver and gastric mucosa were processed for Golgi membrane preparation. The TPST activity was measured using poly(Glu6, Ala3, Tyr1) as the sulfate acceptor and PAPS as sulfate donor. There was a threefold increase in TPST activity of gastric mucosa of animals subjected to chronic alcohol feeding. In the liver, the increase in tyrosine sulfating activity was also around threefold. The kinetic studies performed to understand the mechanism involved in ethanol stimulation of TPST activity showed no change in the Km values of the enzyme by ethanol. In control and ethanol-treated animals, the Km for EAY was 0.41-0.53 and 0.43-0.53 microM, and the Km for PAPS was 10-12.5 and 9-17 microM, respectively. The Vmax in ethanol-fed animals was increased by 1.5- to 2-fold. The increase in TPST activity in experimental rats was further tested by analyzing the Western blots by Imaging Densitometer for TPST levels. Analysis of TPST levels also showed over threefold increase in the stomach and liver of ethanol-fed rats. Our results indicate that stimulation of TPST by ethanol involves increased TPST level rather than change in affinity for its substrates.

Purification of tyrosylprotein sulfotransferase from rat submandibular salivary glands

Tyrosylprotein sulfotransferase (TPST), the enzyme responsible for the sulfation of tyrosine residues, has been identified and characterized in submandibular salivary glands. In the present study, this enzyme was purified from the Golgi membranes of rat submandibular salivary glands using a Cibacron blue F3GA affinity column chromatography. Antibodies raised in rabbit against TPST detected the purified enzyme (50-54 kDa) and proteins consisting of molecular mass 50-54 kDa in the Golgi membranes of liver, submandibular salivary glands, stomach, cerebellum, thalamus, and pituitary. The protein levels in liver and salivary glands were higher compared to those found in the stomach, cerebellum, thalamus, and pituitary. The levels of immunoreactivity in cytosol and endoplasmic reticulum fractions of salivary glands were either undetectable or very low. The antibody was also used to immunoprecipitate the TPST activity and to isolate protein by immunoaffinity column. MnCl2 was required for the purified TPST. The enzyme exhibited optimum activity between pH 6.2 and 6.8 at 20 mM MnCl2. The apparent K(m) values of the purified enzyme for poly-(Glu6, Ala3, Tyr1) (EAY: M(r) 47,000) and 3'-phosphoadenosine 5'-phosphosulfate were 3 and 20 microM, respectively. The results presented here collectively demonstrate the purification of TPST and, for the first time, development of polyclonal antibody that recognizes this enzyme.

Effect of lipids on glycoprotein sulphotransferase activity in rat submandibular salivary glands

Although glycoprotein sulphation has been implicated in the processing of salivary mucin, little is known about the regulation of the enzyme responsible for this event. Using desulphated glycoprotein as sulphate acceptor, the glycoprotein sulphotransferase (GPST) from Golgi membranes of submandibular salivary gland was used to study the effect of various lipids on its activity. The GPST activity in the Golgi membrane was 0.7 pmol/mg protein per min and the activity was extractable by Triton S-100. The Km of the solubilized GPST for glycoprotein and 3'-phosphoadenosine 5'-phosphosulphate (PAPS) were 11 and 0.2 microM, respectively. Among the various lipids tested, phosphatidylinositol and sphingosine stimulated the GPST activity, while other lipids such as sphingomyelin, phosphatidylcholine and phosphatidylserine did not produce a significant effect. At 12 mol% (when expressed as mol% of sphingosine to total phospholipids plus Triton X-100) of sphingosine concentration, the enzyme activity was increased nearly 1.7-fold. The stimulatory effect of sphingosine was accompanied by a significant decrease in Km for glycoprotein from 11 to 2 microM but the increase in Vmax was small. In contrast, the sphingosine effect did not change the Km for PAPS but increased the Vmax nearly two fold. Of the two sphingosine analogues tested, threosphinganine and erythrosphinganine had a lesser stimulatory effect than sphingosine. Stearylamine was partially active, whereas the amino acids (glutamate, aspartate, glutamine, asparagine and serine) were not. These observations and our earlier finding of tyrosylprotein sulphotransferase inhibition by sphingosine demonstrate diverse sphingosine effects on the post-translational sulphation involved in the processing of salivary proteins and suggest an important role for sphingosine in the regulation of salivary protein sulphation.

Effect of prostaglandins on tyrosylprotein sulfotransferase activity in rat submandibular salivary glands

1. Tyrosylprotein sulfotransferase (TPST) is a key enzyme in the processing of several secretory proteins, including those found in saliva. In this report, the effect of prostaglandins (PG) on TPST activity in submandibular salivary gland was investigated. 2. The results revealed that PGE2 exhibited TPST stimulatory activity with a 1.5-fold stimulation at 100 microM concentration and a half maximal stimulation at 50 microM. The PGE2 stimulation was accompanied by an increase in the affinity of TPST towards sulfate acceptor (Km 1.4 microM-->0.12 microM) with little change in Vmax. 3. The TPST activity was also stimulated by two other major prostaglandins of salivary glands, PGF2 alpha and 6-Keto-PGF 1 alpha, however to lesser extent, 22 and 23%, respectively. Arachidonic acid, an intermediate prostaglandin precursor, had no effect on TPST activity. 4. The results suggest that prostaglandins and in particular PGE2 may play a role in the regulation of TPST catalyzed secretory protein tyrosine sulfation in salivary glands.

Biochemical evaluation of the antiulcerogenic effect of Cauvery-100 (an ayurvedic formulation) in rats

Due to the varied pathogenesis of ulcers, a number of pharmacologically different antiulcer drugs are now used in the treatment of the condition. The suitability of certain of these drugs is still to be established. Cauvery-100 is an ayurvedic formulation consisting of plant ingredients, and has been suggested to be useful in the treatment of gastrointestinal disorders. In the present study this drug was tested for its antiulcerogenic effect. The number of lesions on gastric mucosa decreased markedly after 15 days oral treatment with Cauvery-100 in rats with indomethacin-induced ulcers. The volume and total acidity of the gastric juice also decreased in the treated rats. The hexose, hexosamine and sialic acid levels of gastric contents, which were increased in untreated rats returned to near normal levels after 15 days of treatment. Protein in the gastric juice was elevated in untreated rats but returned to near normal levels after 15 days of treatment. Cauvery-100 acts both to decrease the acidity and to increase the mucosal defence in the gastric areas, thereby justifying its use as an antiulcerogenic agent.

Biochemical studies on the antidiarrhoeal effects of Cauvery-100, an ayurvedic formulation, in rats

Diarrhoea is a common gastrointestinal disorder which is a state of fluid and ion loss from the gut. Cauvery-100, an Ayurvedic formulation has been used in this study for the treatment of diarrhoea. Diarrhoea was induced in experimental rats by oral administration of castor oil. The increased gastrointestinal motility in diarrhoea was brought back to near normal levels on the treatment of Cauvery-100. The activities of the enzymes alkaline phosphatase, total ATPase and Na+,K(+)-ATPase were decreased in the diarrhoeal group and was brought back to near normal levels in the treated group. The serum levels of sodium and potassium were decreased in the diarrhoeal group and brought back to normal levels in the treated group. Prior treatment of the drug Cauvery-100 did not induce diarrhoea on administration of castor oil, suggesting the protective influence of the drug on the gastrointestinal tract.

Toxic effect of morphine and the antagonistic role of naloxone on isolated rat hepatocytes

Isolated rat hepatocytes when incubated with various concentrations of morphine exhibited a marked decrease in the level of glutathione and resulted in cell death. The formation of electrophilic intermediates make the cell more susceptible to peroxidative attack, which is reflected by the increase in thiobarbituric acid reactant material as well as lipid fluorescence. Pretreatment of cells with naloxone blocked the morphine induced damage and itself has no cytotoxic effects on the cells.

In vivo absorption of 14C-glucose and 14C-glycine by the rat intestine during ochratoxin A toxicosis

Ochratoxin A was administered orally at a dose level of 6 mg/kg/day for eight weeks to rats. Studies on the intestinal cellular macromolecules, activities of membrane bound enzymes and in vivo absorption of 14C-glucose and 14C-glycine exhibited significant alterations. The observed reduction in the absorption of these nutrients during ochratoxin A toxicosis is corroborated by the changes observed in the levels of cellular macromolecules and the activity of membrane bound enzymes which are involved in the transport system.

Antioxidant effect of vanadate on experimental diabetic rats

The activities of enzymes involved in cellular defence mechanisms such as superoxide dismutase, catalase, glutathione peroxidase and glutathione level have been found to be altered in experimental diabetes. Rats were made diabetic by a single i.v. injection of streptozotocin (55 mg/kg body weight) in citrate buffer. After the onset of diabetes, the diabetic rats were treated with sodium orthovanadate (0.3 mg/ml) for 15 days. Decreased activities of glutathione peroxidase, catalase, superoxide dismutase and glutathione content found in diabetic rats were corrected to near normal. The altered levels of plasma lipid peroxide, glycoproteins and erythrocyte membrane phospholipids in diabetic rats were restored to control levels by vanadate treatment. These observations clearly indicate the antioxidant potential of vanadate on experimental diabetes.

Insulinic actions of vanadate in diabetic rats

Oral administration of sodium orthovanadate (0.3 mg/dl) normalizes blood glucose and reduces glycosylated HbA1 levels in streptozotocin induced diabetic rats without any increase in the serum insulin levels. However, diabetic condition reappears after withdrawal of vanadate. Assays of carbohydrate metabolizing enzymes clearly indicate that vanadate activates the glycolysis, glycogenesis and depresses the glycogenolysis and gluconeogenesis in diabetic rats. These results demonstrate that vanadate substitutes insulin action in chronic experimental diabetics.