Does the neuropeptide somatostatin have therapeutic potential against schistosomiasis?

In vitro anti-echinococcal activity of octreotide: Additive effect of metformin linked to autophagy

Cystic echinococcosis (CE) is a worldwide zoonosis caused by the Echinococcus granulosus larval stage. The currently available therapy for this disease is based on benzimidazoles, which are rarely curative and cause several adverse effects. Therefore, new treatment options are needed. Octreotide (Oct) is a somatostatin analogue which exhibits anti-proliferative and anti-secretory effects over several cancer cell lines expressing somatostatin receptors. Here, we assessed the in vitro pharmacological effect of Oct against the E. granulosus larval stage. The drug caused a significant dose-dependent decrease in the viability of both protoscoleces and metacestodes. SEM and TEM analysis showed ultrastructural damage in both larval forms under drug treatment. Based on this, we investigated the possible presence of an Oct binding receptor in the parasite. The putative somatostatin/allatostatin-like receptor (Eg-s/ast) conserves the characteristic topology and signature sequences of the prototype somatostatin receptor common to vertebrates and is expressed in both metacestodes and protoscoleces. Moreover, Oct treated-parasites showed the presence of autophagic structures and a significant increase in transcriptional expression of autophagy key genes such as Eg-atg6, Eg-atg8, Eg-atg12 and Eg-atg16. In addition, by in toto immunolocalization assays, an increase in the punctate pattern and Eg-Atg8 protein expression was detected in Oct-treated metacestodes. Subsequently, the combination of Oct and Met had an additive effect on the viability of both larval forms. Our results provide additional evidence for the participation of PI3K/AKT/TOR/autophagy pathway in the Echinococcus survival and suggest the concomitant use of these drugs as potential therapeutic agents in treating of CE.

Eugenol, a potential schistosomicidal agent with anti-inflammatory and antifibrotic effects against Schistosoma mansoni, induced liver pathology

Introduction

Schistosomiasis is one of the most prevalent parasitic infections in developing countries. Although chemotherapy is one of the main strategies in controlling the disease, it is less effective in reversal of schistosome-induced pathology especially in the chronic and advanced stages of schistosomiasis. New strategies and prospective therapeutic agents with antifibrotic effects are needed. Eugenol has a wide anti-inflammatory effect. In the present study, we investigated the possible antischistosomal effect of eugenol on Schistosoma mansoni.

Materials and methods

The murine model of S. mansoni was established in three groups of adult male Balb-c mice; group I (infected non-treated group) and groups II and III (infected groups) treated orally with eugenol and praziquantel (PZQ), respectively. The expression of the sensitive immunohistochemical marker α-smooth muscle actin (α-SMA) in schistosome-infected tissues was determined. In addition, parasitological, biochemical, and histological parameters that reflect disease severity and morbidity were examined.

Results

Eugenol treatment showed significant reduction in total worm burden by 19.2%; however, the oogram pattern showed no marked difference compared to that of the PZQ group. Yet, eugenol significantly reduced the serum levels of hepatic enzymes: aspartate aminotransferase and alanine aminotransferase. Histopathological examination revealed a significant reduction in both numbers and diameters of hepatic granulomata, which was consistent with reduction in collagen fiber deposition. Additionally, the antifibrotic effect of eugenol was validated by its considerable reduction in the expression of the sensitive marker α-SMA in both eugenol- and PZQ-treated groups.

Conclusion

Although eugenol could not totally eradicate adults of S. mansoni, the significant amelioration of liver enzymes and hepatic fibrosis potentiate eugenol’s role as a promising antifibrotic and a complementary antischistosomal agent.

Computational modelling of the antischistosomal activity for neolignan derivatives based on the MIA-SAR approach

Theoretical models for exploring the antischistosomal activity of a dataset of 18 synthetic neolignans are built using the multivariate image analysis applied to structure-activity relationships (MIA-SAR) approach. The obtained models were validated using the accuracy (Acc) in leave-one-out cross-validation, external validation and Y-randomization procedures, yielding correct classification superior to 80%, 70% and 60%, respectively. Additionally, a comparison was made of the models obtained from binary (black and white) and coloured images; the colours (pixel values) were selected to correspond to chemical properties. It was observed that the models obtained from coloured images with pixel values corresponding to electronegativity (known as the aug-MIA-SAR(colour) approach) generally yielded superior statistical parameters compared with those obtained from binary images (MIA-SAR) and randomly coloured images (atoms are coloured according to their type) with atomic sizes corresponding to Van der Waals radius (aug-MIA-SAR), respectively. Mechanistic interpretation of the influence of different substituents on the antischistosomal activity revealed that methoxy substituents in the R1 (or R2) and R5 positions of the neolignan scaffold are indispensable for the antischistosomal activity. The obtained results provide knowledge of the possible structural modifications to yield novel neolignan compounds with antischistosomal activity.

In vitro and in vivo effects of hesperidin treatment on adult worms of Schistosoma mansoni

Hesperidin has been reported to exert a wide range of pharmacological effects, including antifungal, antiviral, antioxidant, anti-inflammatory and anticarcinogenic activities. Herein, the schistosomicidal activity of this compound was evaluated in vitro and in vivo. Using an in vitro assay, a concentration of 200 μg/ml of hesperidin resulted in the mortality of 100% adult worms of Schistosoma (S.) mansoni within 72 h and a partial tegumental alteration in 10% of worms. However, after 144 h incubation, 50 and 100 μg/ml concentrations showed 0% and 10% mortality in adult worms, respectively, without any changes to the tegument. Sublethal doses did not influence egg output nor the development of eggs deposited by pairs of adult worms. In an in vivo study, mice infected with S. mansoni and treated with 600 mg hesperidin/kg body weight showed a respective reduction of 50, 45.2, 50 and 47.5% of males, females, worm pairs and total worm burden. In addition, a respective reduction, based on the number of eggs/g tissue, of 41.5, 63.7 and 58.6% was observed in the liver, intestine and liver/intestinal tissue combined. Furthermore, S. mansoni-specific IgG level significantly increased with hesperidin treatment, whereas IgA and IgE levels were not significantly changed. IgM levels decreased in response to cercarial antigen preparation but were not altered in response to soluble worm or soluble egg antigen. As in hesperidin-treated mice, praziquantel-treated mice showed a similar pattern of specific antibody response to S. mansoni antigens. The present study represents the first report on the effects of the schistosomicidal activity of hesperidin.

Role of resident liver cells in the pathogenesis of schistosomiasis

Pathology in schistosomiasis occurs as a result of eggs deposited in the liver by the schistosome parasite. A granulomatous reaction occurs, resulting in portal hypertension and hepatic fibrosis. Resident non-parenchymal cells within the liver take part in this process, including hepatic stellate cells, which are responsible for collagen production, and Kupffer cells, the liver macrophages involved in both host protection and in pathology. Other cells such as liver sinusoidal endothelial cells or portal fibroblasts may also be involved in this process. This review discusses the possible role of these resident liver cells in the pathology associated with schistosomiasis and provides information which may assist our understanding of the mechanisms associated with chronic liver disease in general.

Imaging schistosomes in vivo

Schistosomes are intravascular, parasitic helminths that cause a chronic, often debilitating disease afflicting over 200 million people in over 70 countries. Here we describe novel imaging methods that, for the first time, permit visualization of live schistosomes within their living hosts. The technology centers on fluorescent agent uptake and activation in the parasite's gut, and subsequent detection and signal quantitation using fluorescence molecular tomography (FMT). There is a strong positive correlation between the signal detected and parasite number. Schistosoma mansoni parasites of both sexes recovered from infected experimental animals exhibit vivid fluorescence throughout their intestines. Likewise, the remaining important human schistosome parasites, S. japonicum and S. hematobium, also exhibit gut fluorescence when recovered from infected animals. Imaging has been used to efficiently document the decline in parasite numbers in infected mice treated with the antischistosome drug praziquantel. This technology will provide a unique opportunity both to help rapidly identify much-needed, novel antischistosome therapies and to gain direct visual insight into the intravascular lives of the major schistosome parasites of humans.

Immunomodulatory effects of curcumin treatment on murine schistosomiasis mansoni

Curcumin is a polyphenol derived from the dietary spice turmeric. It has been shown to regulate numerous transcription factors, cytokines, adhesion molecules, and enzymes that have been linked to inflammation. In addition to inhibiting the growth of a variety of pathogens, curcumin has been shown to have nematocidal activity. The present study was designed to evaluate the schistosomicidal activity of curcumin in vivo as well as immunomodulation of granulomatous inflammation and liver pathology in acute schistosomiasis mansoni. Mice were infected each with 80 Schistosoma (S.) mansoni cercariae and injected intraperitoneally with curcumin at a total dose of 400mg/kg body weight. Curcumin was effective in reducing worm and tissue-egg burdens, hepatic granuloma volume and liver collagen content by 44.4%, 30.9%, 79%, and 38.6%, respectively. Curcumin treatment restored hepatic enzymes activities to the normal levels and enhanced catalase activity in the liver tissue of infected mice. Moreover, hepato-spleenomegaly and eosinophilia induced by S. mansoni infection were largely improved with curcumin treatment. Infected mice treated with curcumin showed low serum level of both interleukin (IL)-12 and tumor necrosis factor alpha (TNF-alpha), but IL-10 level was not significantly altered. Specific IgG and IgG1 responses against both soluble worm antigen (SWAP) and soluble egg antigen (SEA) were augmented with curcumin treatment, but IgM and IgG2a responses were not significantly changed. In conclusion, curcumin treatment modulates cellular and humoral immune responses of infected mice and lead to a significant reduction of parasite burden and liver pathology in acute murine schistosomiasis mansoni.

The therapeutic effect of the neuropeptide hormone somatostatin on Schistosoma mansoni caused liver fibrosis

Background

The neuropeptide somatostatin is one of the major regulatory peptides in the central nervous system and the digestive tract. Our recent work has delineated an association between fibrosis and low levels of endogenous somatostatin plasma levels in Schistosoma mansoni infected subjects. Based on these results this paper explores the therapeutic potential of somatostatin in a mouse model of hepatic fibrosis associated with S. mansoni infections.

Methods

Groups of outbred Swiss mice were infected with 100 S. mansoni cercariae, infection maintained till weeks 10 or 14, and then somatostatin therapy delivered in two regimens – Either a one or a two-day treatment. All animals were sacrificed one week after therapy and controlled for liver, spleen and total body weight. Circulating somatostatin levels in mice plasma were measured at the time of sacrifice by means of a radio-immuno assay. GraphPad Prism^® was used for statistical calculations.

Results

Somatostatin administration showed little toxicity, probably due to its short half-life. Total liver and spleen weights of S. mansoni infected animals increased over time, with no changes observed due to somatostatin therapy. Total body weights were decreased after infection but were not affected by somatostatin therapy. Snap frozen liver sections were stained with haematoxylin-eosin or Masson's trichrome to study parasite count, hepatocyte status, granuloma size and cellularity. After somatostatin treatment mean egg counts per liver section (43.76 ± 3.56) were significantly reduced as compared to the egg counts in untreated mice after 10 weeks of infection (56.01 ± 3.34) (P = 0.03). Similar significant reduction in parasite egg counts were also observed after somatostatin treatment at 14 weeks of infection (56.62 ± 3.02) as compared to untreated animals (69.82 ± 2.77)(P = 0.006). Fibrosis was assessed from the spectrophotometric determination of tissue hydroxyproline. Infection with S. mansoni caused increased hydroxyproline levels (9.37 ± 0.63 μmol at wk10; 9.65 ± 0.96 μmol at wk14) as compared to uninfected animals (1.06 ± 0.10 μmol). This significant increase in collagen content (P = 0.01; 0.007 respectively) marks the fibrosis observed at these time points. Treatment with somatostatin resulted in a significant decrease in hydroxyproline levels both at wk10 (4.76 ± 0.58 μmol) and at wk14 (5.8 ± 1.13 μmol) (P = 0.01; 0.03 respectively). Endogenous somatostatin levels were increased at wk10 (297 ± 37.24 pg/ml) and wk14 (206 ± 13.30 pg/ml) of infection as compared to uninfected mice (119 ± 11.99 pg/ml) (P = 0.01; 0.008 respectively). Circulating somatostatin levels in infected animals were not significantly affected by somatostatin treatment. Hepatocyte status remained unaltered and granulomas were not remarkably changed in size or cellularity.

Conclusion

Our experiments reveal an antifibrotic effect of somatostatin in schistosomiasis. We have previously shown that the somatostatin receptors SSTR2 and SSTR3 are present on the parasite egg and worms. We therefore hypothesize that somatostatin reduces either the number of parasite eggs or the secretion of fibrosis inducing-mediators. Our data suggest somatostatin may have therapeutic potential in S. mansoni mediated liver pathology.

Secretion of inflammatory mediators by isolated rat Kupffer cells: the effect of octreotide

AIMS

We studied the production of inflammatory mediators by rat KC and the possible in vitro effect of the somatostatin analogue octreotide.

METHODS

Primary KC cultures were incubated with LPS added alone or with different concentrations of octreotide. The production of TNFalpha, IL-6, IL-10, IL-12 and IL-13 was assessed in culture supernatants by ELISA and that of nitric oxide (NO) by a modification of the Griess reaction.

RESULTS

Isolated KC produced a basal amount of TNFalpha, IL-6, IL-12, IL-13, and NO but not IL-10. LPS-stimulated KC secreted significantly increased amounts of TNFalpha (P < 0.001), IL-6 (P < 0.01), IL-10 (P < 0.001), IL-12 (P < 0.01), and NO (P < 0.001) whereas IL-13 production remained constant. Octreotide reduced IL-12 (P < 0.05) and increased IL-13 (P < 0.05) production by unstimulated KC. Furthermore, octreotide suppressed TNFalpha production (P < 0.05), without modifying TNFalpha mRNA expression and decreased iNOS expression and NO (P approximately 0.05) production by LPS-activated KC. These effects were reversed with Wortmannin pre-treatment suggesting that octreotide may act via interference with phosphatidylinositol 3-kinase pathways.

CONCLUSIONS

These data demonstrate that KC is a source of multiple inflammatory mediators, indicating a critical role in liver inflammatory disorders. Octreotide modulates inflammatory mediator production by isolated KC, suggesting that it might have immunoregulatory and anti-inflammatory effects in liver diseases.

Can somatostatin control acute bleeding from oesophageal varices in Schistosoma mansoni patients?[ISRCTN63456799]

BACKGROUND

Management of patients with bleeding oesophageal varices comprises of mainly diagnostic endoscopy, sclerotherapy and band ligation. One of the major problems to do any of the above is the active bleeding which makes any intervention difficult. The neuropeptide hormone somatostatin administered exogenously has caused a reduction in portal hypertension and variceal bleeding in patients suffering from liver cirrhosis. We believe that the symptomatic use of somatostatin for variceal bleeding in Schistosoma mansoni infected subjects can reduce bleeding, thereby alleviating the pathology caused by schistosomiasis.

METHODS/DESIGN

We herein present a study protocol for establishing this neuropeptide as a potential therapeutic agent in schistosomiasis. Adolescent subjects, age range varying from 12-17 years will be selected, based on several inclusion criteria, most important being infection with Schistosoma mansoni with bleeding from oesophageal varices in the last 24 hours. One group of schistosomiasis patients will be treated with somatostatin and praziquantel, the other with propanolol and praziquantel. Survival graphs will be set up to correlate somatostatin administration with survival time. A two part questionnaire will be set up to control treatment outcomes. The pre-treatment part of the clinical questionnaire will identify inclusion criteria questions, the post-treatment part of the questionnaire will identify treatment outcomes.

DISCUSSION

We expect that the administration of somatostatin as a bolus followed by a 24 hour long infusion, will stop bleeding immediately, delay rebleeding as compared to the control study group and delay mortality in the somatostatin treated subjects.

Circulating levels of the neuropeptide hormone somatostatin may determine hepatic fibrosis in Schistosoma mansoni infections

The neuropeptide hormone somatostatin reduces fibrosis and Schistosoma-caused clinical morbidity in the rodent model. In our study we aimed to delineate an association between fibrosis and the inability to generate critical levels of endogenous somatostatin in S. mansoni infected subjects. In June 2001, 85 subjects from the district dispensary at Richard Toll in the Medical Region of Saint-Louis, Senegal, were selected. Fifty-seven subjects were infected with S. mansoni of whom 32 were suffering from severe morbidity (SM). Twenty-eight subjects showed an inactive disease status with no evident infection at the actual time of study. All subjects were classified according to age, sex, occupation, height, weight, and parasite eggs per gram. All 85 participated in a water contact and morbidity questionnaire, underwent a clinical examination and donated 5ml of peripheral blood for detecting plasma levels of somatostatin. Ultrasonography detected fibrosis grade in all the subjects. To address whether inherent somatostatin levels determined clinically evident disease severity (epg, hepatomegaly, splenomegaly, hematemesis, ascites), the mean somatostatin values of the inactive disease status group and severe morbidity group were compared. Low somatostatin levels were depicted in subjects with severe morbidity symptoms associated with schistosomiasis as compared to exposed but inactive disease status subjects residing in the same region. Logistic regression analysis indicated that with decreasing somatostatin values the probability of severe morbidity increased with age being a confounding factor. To address whether inherent somatostatin levels determined fibrosis and if this association was significant, plasma somatostatin levels of non-fibrotics (ultrasonographic grading A), and fibrotics (ultrasonographic grading B-E) were compared. In all age groups as well as in adults alone, mean somatostatin levels were higher in the non-fibrotic group as compared to the fibrotics group, the difference being significant. The group B comprised of borderline fibrotic cases, therefore a separate analysis was done between groups A (non-fibrotics) and groups C, D (confirmed fibrotics). Mean somatostatin values were higher in the non-fibrotic group as compared to the fibrotics group, the difference being borderline significant. In schistosomiasis patients, circulating levels of somatostatin by binding to hepatic stellate cells (HSC) may modulate fibrosis. This phenomenon is regulated by age whereas gender and prior treatment have no effect on this association. Host specific somatostatin levels may create a 'preset environment' status that can determine progression to severe fibrosis.

Lower levels of the circulating neuropeptide somatostatin in Schistosoma mansoni infected patients may have pathological significance

In recent years, cases of severe morbidity (fibrosis, haematemesis, hepatosplenomegaly, ascites) caused to Schistosoma mansoni infections are on the rise in Northern Senegal. The neuropeptide somatostatin is reported to decrease portal pressure, control variceal bleeding and fibrosis, and reduce Schistosoma-caused clinical morbidity in the rodent model. The aim of this study was to delineate the role of somatostatin in S. mansoni-caused pathogenesis, by studying host levels of somatostatin in the peripheral blood of uninfected and S. mansoni-infected individuals. Subjects from the district dispensary at Richard Toll, in the Medical Region of Saint-Louis, Senegal, infected with S. mansoni and suffering from severe morbidity were selected. A separate group consisted of individuals resident in the same region but uninfected at the time of the study. Significantly lower somatostatin levels were detected in severe morbidity patients, compared with the exposed but uninfected subjects. In patients with schistosomiasis physiological levels of somatostatin may determine disposition of particular individuals towards severe morbidity, as opposed to others. Host pathology can thus be alleviated by the therapeutic ability of somatostatin to treat bleeding oesophageal varices, reduce portal pressure and prevent progression to severe fibrosis.