Protective effect of berberine chloride on Plasmodium chabaudi-induced hepatic tissue injury in mice

The present study aimed to investigate the protective role of berberine (BER) against Plasmodium chabaudi-induced infection in mice. Animals were divided into three groups. Group I served as a vehicle control. Group II and group III were infected with 1000 P. chabaudi infected erythrocytes. Group III was gavaged with 100 μl of 10 mg/kg berberine chloride for 10 days. All mice were sacrificed at day 10 post-infection. The percentage of parasitemia was significantly reduced more than 30%, after treatment of mice with BER. Infection caused marked hepatic injuries as indicated by histopathological alterations as evidenced by the presence of hepatic lobular inflammatory cellular infiltrations, dilated sinusoids, vacuolated hepatocytes, increased number of Kupffer cells and the malaria pigment, hemozoin. These changes in livers led to the increased histological score. Also, infection induced a significant increase in liver alanine aminotransferase and aspartate aminotransferase and a significant increase in the total leucocytic count. Moreover, mice became anemic as proved by the significant decrease in erythrocyte number and haemoglobin content. BER showed a significant protective potential by improving the above mentioned parameters. Based on these results, it is concluded that berberine could offer protection against hepatic tissue damage.     

Neuronal activation and plasticity in Schistosoma mansoni infected mice

Schistosomiasis leads to structural and functional changes which may result from unbalanced release of some inflammatory mediators. The aim of the study was to investigate the effect of intestinal parasitic infection on nitric oxide release and to evaluate the neural plasticity that leads to motility disturbance. Experiments were performed in Swiss mice 8- and 12-weeks following infection with Schistosoma mansoni compared to untreated controls. Jejunal motility was assessed using a Trendelenburg preparation to study aboral directed peristaltic pressure waves. Histological examination was used to determine the pathological characteristics of inflammation.Parasitic infection produces diffuse inflammatory infiltrate in both 8- and 12-weeks infected animals. Inflammation had significant effect on peristaltic pressure waves amplitude and intervals at 8-weeks compared to control; whereas, in 12-weeks post infection there was a significant decrease in peristaltic pressure waves amplitude and interval compared to 8- weeks and control.Nitric oxide synthase inhibitor (L-NAME 100 μM) induced a significant increase in amplitude and decrease in intervals in control, 8- and 12- weeks infected animals. In conclusion, parasitic infection leads to disturbance in the release of the inflammatory mediators. This study indicated the role of nitric oxide in developing granulomatous inflammation and participating in motility disturbance.     

Schistogram changes after administration of antischistosomal drugs in mice at the early phase of Schistosoma mansoni infection

Mice infected with Schistosoma mansoni were treated with oxamniquine, praziquantel, artesunate at the pre-patent phase, aiming at observing schistogram alterations. Half of the animals were perfused five days post-treatment for counting and classification of immature worms, based on pre-established morphological criteria (schistogram); the remaining animals were evaluated 42 or 100 days after infection and perfusion of the portal-system was performed for collection and counting of adult worms and oogram. It was observed that oxamniquine and artesunate treatment administered at the pre-postural phase causes significant reduction in the number of immature and adult worms. However, there was little reduction with praziquantel when used at the dose of 400 mg/kg for treatments administered 14, 15, 21 or 23 days post-infection. Artesunate was responsible for significant alterations in development of young worms, as well as for a higher number of worms presenting intestinal damages. Immature adult worms were detected in mice treated with artesunate or oxamniquine at the pre-patent phase of infection and recovered by perfusion 100 days after infection. Schistogram proved to be a very useful tool for experimental evaluation of the activity of antischistosomal drugs and a good model to identify the most sensitive stages to drugs.     

T regulatory cell responses to immunization with a soluble egg antigen in Schistosoma mansoni-infected mice

The aim of the study is to characterize the phenotypes of CD4⁺ CD25⁺ T regulatory cells within the liver granulomas and association with both Foxp-3 gene expression and splenic cytokines. Naïve C57BL/6 mice were intravenously injected with multiple doses of the soluble egg antigen (SEA) 7 days before cercarial infection. The immunized and infected control groups were sacrificed 8 and 16 weeks post-infection (PI). Histopathology, parasitological parameters, splenic phenotypes for T regulatory cells, the FOXP-3 expression in hepatic granuloma using real-time PCR, and the associated splenic cytokines were studied. Histopathological examination of the liver revealed remarkable increase in degenerated ova within hepatic granuloma which decreased in diameter at weeks 8 and 16 PI (P<0.01). The percentage of T regulatory cells (CD4⁺ CD25⁺) increased significantly (P<0.01) in the immunized group compared to the infected control at weeks 8 and 16 PI. The FOXP-3 expression in hepatic granulomas increased from 10 at week 8 to 30 fold at week 16 PI in the infected control group. However, its expression in the immunized group showed an increase from 30 at week 8 to 70 fold at week 16 PI. The splenic cytokine levels of pro-inflammatory cytokines, IFN-γ, IL-4, and TNF-α, showed significant decreases (P<0.05) compared to the infected control group. In conclusion, the magnitude and phenotype of the egg-induced effects on T helper responses were found to be controlled by a parallel response within the T regulatory population which provides protection in worm parasite-induced immunopathology.     

Effects of exogenous glucose on survival and infectivity of Schistosoma mansoni cercariae

The effects of exogenous glucose in artificial spring water (ASW) were studied on the survival and infectivity of Schistosoma mansoni cercariae. The mean percent survival of cercariae maintained in 1% glucose in ASW for 36 and 48 hr was significantly greater than that of cercariae maintained identically in ASW. Cercariae maintained in ASW with or without glucose for 24 hr, fixed in neutral buffered formalin, and stained in Oil Red O, showed an accumulation of neutral lipid in the tail. Cercariae maintained as described above and stained in periodic acid-Schiff exhibited depleted glycogen, mainly from the tail. Cercariae maintained in ASW with glucose for 24 hr did not resynthesize glycogen. Cercariae maintained in ASW with glucose for 24 hr were as capable of infecting male FVBN202 mice as were freshly emerged cercariae, and increased the percent of worm recovery. Exogeneous glucose added to ASW prolonged the survival of S. mansoni cercariae and increased infectivity in terms of worm recovery.     

Potential correlation between carboxylic acid metabolites in Biomphalaria alexandrina snails after exposure to Schistosoma mansoni infection

Carboxylic acids play an important role in both aerobic and anaerobic metabolic pathways of both the snail and the parasite. Monitoring the effects of infection by schistosome on Biomphalaria alexandrina carboxylic acids metabolic profiles represents a promising additional source of information about the state of metabolic system. We separated and quantified pyruvic, fumaric, malic, oxalic, and acetic acids using ion-suppression reversed-phase high performance liquid chromatography (HPLC) to detect correlations between these acids in both hemolymph and digestive gland gonad complex (DGG's) samples in a total of 300 B. alexandrina snails (150 infected and 150 controls) at different stages of infection. The results showed that the majority of metabolite pairs did not show significant correlations. However, some high correlations were found between the studied acids within the control group but not in other groups. More striking was the existence of reversed correlations between the same acids at different stages of infection. Some possible explanations of the underlying mechanisms were discussed. Ultimately, however, further data are required for resolving the responsible regulatory events. These findings highlight the potential of metabolomics as a novel approach for fundamental investigations of host-pathogen interactions as well as disease surveillance and control.     

Carboxylic Acids as Biomarkers of Biomphalaria alexandrina Snails Infected with Schistosoma mansoni

Biomphalaria alexandrina snails play an indispensable role in transmission of schistosomiasis. Infection rates in field populations of snails are routinely determined by cercarial shedding neglecting prepatent snail infections, because of lack of a suitable method for diagnosis. The present study aimed at separation and quantification of oxalic, malic, acetic, pyruvic, and fumaric acids using ion-suppression reversed-phase high performance liquid chromatography (HPLC) to test the potentiality of these acids to be used as diagnostic and therapeutic biomarkers. The assay was done in both hemolymph and digestive gland-gonad complex (DGG) samples in a total of 300 B. alexandrina snails. All of the studied acids in both the hemolymph and tissue samples except for the fumaric acid in hemolymph appeared to be good diagnostic biomarkers as they provide not only a good discrimination between the infected snails from the control but also between the studied stages of infection from each other. The most sensitive discriminating acid was malic acid in hemolymph samples as it showed the highest F-ratio. Using the Z-score, malic acid was found to be a good potential therapeutic biomarker in the prepatency stage, oxalic acid and acetic acid in the stage of patency, and malic acid and acetic acid at 2 weeks after patency. Quantification of carboxylic acids, using HPLC strategy, was fast, easy, and accurate in prediction of infected and uninfected snails and possibly to detect the stage of infection. It seems also useful for detection of the most suitable acids to be used as drug targets.     

Effect of somatostatin on gastrointestinal contractility in Schistosoma mansoni infected mice

Schistosoma mansoni infection induces severe gastrointestinal motility disturbances which are characterised by hyperactivity of intestinal muscle, abdominal pain, diarrhoea, vomiting and nausea. During schistosomiasis, the neuropeptide somatostatin is generated within inflammatory granulomas. However, somatostatin is also an important inhibitory modulator of gastrointestinal motility. In the present study, we have investigated the potential of somatostatin to reduce schistosomiasis-induced hyperactivity of gastrointestinal smooth muscle. Organ bath experiments were performed to study the contractility of isolated smooth muscle strips of intestine from control mice and from mice that were infected with S. mansoni for 2, 4, 8 and 16 weeks. Electrical field stimulation (0.5-8 Hz) of enteric nerves induced frequency-dependent neurogenic contractions of cholinergic origin in all regions of the small intestine. Somatostatin (0.1-1 microM) concentration-dependently inhibited the contractions to enteric nerve stimulation in the small intestine from uninfected control mice and from acutely S. mansoni infected mice (2 and 4 weeks of infection). After 8 weeks of infection with S. mansoni, this inhibitory effect of somatostatin was less pronounced and after 16 weeks of infection it was completely abolished. Histology demonstrated that chronic infection of mice with S. mansoni was associated with significant alterations in the musculature of the small intestine. These alterations may be associated with physiological changes in the responsiveness to somatostatin and suggest that the somatostatin neuroregulatory circuit of enteric neurotransmission in the small intestine is disturbed during chronic schistosomiasis mansoni.     

Fasciola gigantica fatty acid binding protein (FABP) as a prophylactic agent against Schistosoma mansoni infection in CD1 mice

Although schistosomicidal drugs and other control measures exist, the advent of an efficacious vaccine remains the most potentially powerful means for controlling this disease. In this study, native fatty acid binding protein (FABP) from Fasciola gigantica was purified from the adult worm's crude extract by saturation with ammonium sulphate followed by separation on DEAE-Sephadex A-50 anion exchange chromatography and gel filtration using Sephacryl HR-100, respectively. CD1 mice were immunized with the purified, native F. gigantica FABP in Freund's adjuvant and challenged subcutaneously with 120 Schistosoma mansoni cercariae. Immunization of CD1 mice with F. gigantica FABP has induced heterologous protection against S. mansoni, evidenced by the significant reduction in mean worm burden (72.3%), liver and intestinal egg counts (81.3% and 80.8%, respectively), and hepatic granuloma counts (42%). Also, it elicited mixed IgG(1)/IgG(2b) immune responses with predominant IgG1 isotype, suggesting that native F. gigantica FABP is mediated by a mixed Th1/Th2 response. However, it failed to induce any significant differences in the oogram pattern or in the mean granuloma diameter. This indicated that native F. gigantica FABP could be a promising vaccine candidate against S. mansoni infection.     

Schistosoma mansoni-Related Hepatosplenic Morbidity in Adult Population on Kome Island,Sengerema District,Tanzania

Schistosomiasis is one of the important neglected tropical diseases (NTDs) in Tanzania, particularly in Lake Victoria zone. This baseline survey was a part of the main study of integrated control of schistosomiasis and soil-transmitted helminths (STHs) aimed at describing morbidity patterns due to intestinal schistosomiasis among adults living on Kome Island, Sengerema District, Tanzania. Total 388 adults from Kome Islands (about 50 people from each village) aged between 12 and 85 years, were examined by abdominal ultrasound according to the Niamey protocol. Liver image patterns (LIPs) A and B were considered normal, and C-F as distinct periportal fibrosis (PPF). The overall prevalence of PPF was 42.2%; much higher in males than in females (47.0% in male vs 34.4% in females, P=0.007). Abnormal increase of segmental branch wall thickness (SBWT) and dilated portal vein diameter (PVD) were also more common in males than in females. Hepatosplenomegaly was frequently encountered; 68.1% had left liver lobe hepatomegaly and 55.2% had splenomegaly. Schistosoma mansoni-related morbidity is quite high among adults in this community justifying the implementation of integrated control strategies through mass drug administration, improved water supply (pumped wells), and health education that had already started in the study area.     

Monoclonal Antibody-Based Dipstick Assay: A Reliable Field Applicable Technique for Diagnosis of Schistosoma mansoni Infection Using Human Serum and Urine Samples

A field applicable diagnostic technique, the dipstick assay, was evaluated for its sensitivity and specificity in diagnosing human Schistosoma mansoni infection. A monoclonal antibody (mAb) against S. mansoni adult worm tegumental antigen (AWTA) was employed in dipstick and sandwich ELISA for detection of circulating schistosome antigen (CSA) in both serum and urine samples. Based on clinical and parasitological examinations, 60 S. mansoni-infected patients, 30 patients infected with parasites other than schistosomiasis, and 30 uninfected healthy individuals were selected. The sensitivity and specificity of dipstick assay in urine samples were 86.7% and 90.0%, respectively, compared to 90.0% sensitivity and 91.7% specificity of sandwich ELISA. In serum samples, the sensitivity and specificity were 88.3% and 91.7% for dipstick assay vs. 91.7% and 95.0% for sandwich ELISA, respectively. The diagnostic efficacy of dipstick assay in urine and serum samples was 88.3% and 90.0%, while it was 90.8% and 93.3% for sandwich ELISA, respectively. The diagnostic indices of dipstick assay and ELISA either in serum or in urine were statistically comparable (P>0.05). In conclusion, the dipstick assay offers an alternative simple, rapid, non-invasive technique in detecting CSA or complement to stool examinations especially in field studies.     

Structural bioinformatics study of PNP from Schistosoma mansoni

The parasite Schistosoma mansoni lacks the de novo pathway for purine biosynthesis and depends on salvage pathways for its purine requirements. Schistosomiasis is endemic in 76 countries and territories and amongst the parasitic diseases ranks second after malaria in terms of social and economic impact and public health importance. The PNP is an attractive target for drug design and it has been submitted to extensive structure-based design. The atomic coordinates of the complex of human PNP with inosine were used as template for starting the modeling of PNP from S. mansoni complexed with inosine. Here we describe the model for the complex SmPNP-inosine and correlate the structure with differences in the affinity for inosine presented by human and S. mansoni PNPs.     

Effect of artemether alone and in combination with grapefruit juice on hepatic drug-metabolising enzymes and biochemical aspects in experimental Schistosoma mansoni

Artemether is an efficacious antimalarial drug that also displays antischistosomal properties. Grapefruit juice increases the oral availability of a variety of the CYP3A4 substrates. This study was designed to evaluate the effect of repeated administration of grapefruit juice with artemether on the hepatic activities of cytochrome P-450 (CYP450) and cytochrome b5 (cyt b5), on the serum levels of some biochemical enzymes and antischistosome efficacy. Results showed that administration of grapefruit juice alone induced more inhibition in the hepatic activities of CYP450 and cyt b5 than that produced by Schistosoma mansoni infection. Moreover, it enhanced degeneration of eggs and accelerated healing of the pathological granulomatous lesions. Treatment of S. mansoni-infected mice with artemether at a total dose of 300 mg/kg resulted in total and female worm burden reductions of 66.7 and 90.1%, respectively, hence protecting the host from damage induced by schistosome eggs. Treatment of S. mansoni-infected mice with artemether at 150 mg/kg reduced the total and female worm numbers by 43.3 and 54.4%, respectively, thus somewhat ameliorating hepatic granulomatous lesions compared with the infected untreated group. This was associated with no change in the hepatic activities of CYP450 and cyt b5 and in the serum levels of total protein, albumin, globulin and alanine aminotransferase compared with the uninfected control group. Coadministration of grapefruit juice with the lower dose (150 mg/kg) of artemether eliminated eggs and granulomatous reactions. In this group, the inhibitory effects of grapefruit juice on CYP450 and cyt b5 were apparent but serum liver enzymes were unchanged compared with the uninfected control group. Coadministration of grapefruit juice with artemether achieved complete protection of the host from damage induced by schistosomal infection.     

Extracellular lipid droplets promote hemozoin crystallization in the gut of the blood fluke Schistosoma mansoni

Hemozoin (Hz) is a heme crystal produced upon hemoglobin digestion as the main mechanism of heme disposal in several hematophagous organisms. Here, we show that, in the helminth Schistosoma mansoni, Hz formation occurs in extracellular lipid droplets (LDs). Transmission electron microscopy of adult worms revealed the presence of numerous electron-lucent round structures similar to LDs in gut lumen, where multicrystalline Hz assemblies were found associated to their surfaces. Female regurgitates promoted Hz formation in vitro in reactions partially inhibited by boiling. Fractionation of regurgitates showed that Hz crystallization activity was essentially concentrated on lower density fractions, which have small amounts of pre-formed Hz crystals, suggesting that hydrophilic-hydrophobic interfaces, and not Hz itself, play a key catalytic role in Hz formation in S. mansoni. Thus, these data demonstrate that LDs present in the gut lumen of S. mansoni support Hz formation possibly by allowing association of heme to the lipid-water interface of these structures.     

Hepatic granulomas induced by Schistosoma mansoni in mice deficient for connexin 43 present lower cell proliferation and higher collagen content

Granuloma formation involves a coordinated interaction between monocytes and macrophages, epithelioid cells, lymphocytes, eosinophils, neutrophils and fibroblasts. It has been established that extracellular communication via cytokines is important for the assembly of granulomas. However, the importance of gap junctions and intercellular communication to granuloma formation and development had never been assessed. Connexins are proteins that form gap junctions, and connexin 43 (Cx43) is present in macrophages, lymphoid cells, myelogenous cells, fibroblasts and others. We analyzed the effect of heterologous deletion of Gja1 (Cx43 gene) on the formation and development of hepatic granulomas induced by Schistosoma mansoni eggs. Heterozygous (Cx43(+/-)) and wild-type (Cx43(+/+)) mice were infected subcutaneously with S. mansoni cercarie and evaluated after 6, 8 and 12 weeks. Granuloma cells express Cx43, as revealed by real-time PCR in isolated granulomas, and by immunohistochemistry. Cx43 expression was reduced in Cx43(+/-) mice, as expected. No differences in the average area of granulomas or number of cells per granuloma were observed between mice of different genotypes. However, granuloma cells from Cx43(+/-) mice displayed a reduced index of the proliferating cell nuclear antigen (PCNA) labeling at 8 and 12 weeks post-infection. Moreover, Cx43(+/-) granulomas unexpectedly presented a higher degree of fibrosis, quantified by morphometric analysis in Sirius Red-stained slides. Our results indicate that the deletion of one allele of the Cx43 gene, and possibly the reduced gap junction intercellular communication capacity (GJIC), may impair the interactions between granuloma cells, reducing their proliferation and increasing their collagen content, thereby modifying the characteristics of S. mansoni granuloma in mice.     

Antischistosomal activity of a calcium channel antagonist on schistosomula and adult Schistosoma mansoni worms

Current schistosomiasis control strategies are largely based on chemotherapeutic agents and a limited number of drugs are available today. Praziquantel (PZQ) is the only drug currently used in schistosomiasis control programs. Unfortunately, this drug shows poor efficacy in patients during the earliest infection phases. The effects of PZQ appear to operate on the voltage-operated Ca2+channels, which are located on the external Schistosoma mansoni membrane. Because some Ca2+channels have dihydropyridine drug class (a class that includes nifedipine) sensitivity, an in vitro analysis using a calcium channel antagonist (clinically used for cardiovascular hypertension) was performed to determine the antischistosomal effects of nifedipine on schistosomula and adult worm cultures. Nifedipine demonstrated antischistosomal activity against schistosomula and significantly reduced viability at all of the concentrations used alone or in combination with PZQ. In contrast, PZQ did not show significant efficacy when used alone. Adult worms were also affected by nifedipine after a 24 h incubation and exhibited impaired motility, several lesions on the tegument and intense contractility. These data support the idea of Ca2+channels subunits as drug targets and favour alternative therapeutic schemes when drug resistance has been reported. In this paper, strong arguments encouraging drug research are presented, with a focus on exploring schistosomal Ca2+channels.