An ex vivo model for studying hepatic schistosomiasis and the effect of released protein from dying eggs

NLRP3 inflammasome inhibition decreases Schistosomiasis japonica-induced granulomatous inflammation and fibrosis in BALB/c mice

To research the role of the NLRP3 inflammasome in Schistosoma japonicum-induced granuloma formation and liver fibrosis. In in vivo tests, BALB/c mice were used. shNLRP3 plasmid based on adeno-associated virus serotype 8 (AAV8-shNLRP3) was injected to block NLRP3 inflammasome via tail vein. Serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST) levels were detected to assess liver injury. H&E staining was used for routine histopathological assessment; Masson's trichrome staining was used to detect fibrous tissues and collagen fibers. Hepatic expression of NLRP3, procaspase-1, bioactive caspase-1, collagen-1, tissue inhibitor of metalloproteinases-1 (TIMP-1), and α-smooth muscle actin (α-SMA) were detected by western blot. Serum levels of IL-1β were detected by enzyme-linked immunosorbent assay (ELISA). The inflammatory cell infiltration and hepatic expression of IL-1β around the granuloma were detected by immunohistochemistry staining. Treatment of S. japonicum infected mice with AAV8-shNLRP3 significantly reduced the hepatic levels of bioactive caspase-1 and IL-1β, as well as circulating IL-1β concentrations, while reducing the amounts of myeloperoxidase (MPO) and F4/80 positive cells around the granuloma. Moreover, collagen deposition, TIMP-1, and α-SMA, which are markers of hepatic stellate cell (HSC) activation, were reduced around the liver granuloma. These findings highlight a therapeutic potential of AAV8-shNLRP3 in schistosomiasis cirrhosis.

The heavy subunit of ferritin stimulates NLRP3 inflammasomes in hepatic stellate cells through ICAM-1 to drive hepatic inflammation

Serum ferritin concentrations increase during hepatic inflammation and correlate with the severity of chronic liver disease. Here, we report a molecular mechanism whereby the heavy subunit of ferritin (FTH) contributes to hepatic inflammation. We found that FTH induced activation of the NLRP3 inflammasome and secretion of the proinflammatory cytokine interleukin-1β (IL-1β) in primary rat hepatic stellate cells (HSCs) through intercellular adhesion molecule-1 (ICAM-1). FTH-ICAM-1 stimulated the expression of Il1b, NLRP3 inflammasome activation, and the processing and secretion of IL-1β in a manner that depended on plasma membrane remodeling, clathrin-mediated endocytosis, and lysosomal destabilization. FTH-ICAM-1 signaling at early endosomes stimulated Il1b expression, implying that this endosomal signaling primed inflammasome activation in HSCs. In contrast, lysosomal destabilization was required for FTH-induced IL-1β secretion, suggesting that lysosomal damage activated inflammasomes. FTH induced IL-1β production in liver slices from wild-type mice but not in those from Icam1-/- or Nlrp3-/- mice. Thus, FTH signals through its receptor ICAM-1 on HSCs to activate the NLRP3 inflammasome. We speculate that this pathway contributes to hepatic inflammation, a key process that stimulates hepatic fibrogenesis associated with chronic liver disease.

Impact of acute schistosomiasis mansoni and long-term ethanol intake on mouse liver pathology

While the effect of ethanol and schistosomiasis mansoni on liver injury has been well-documented, the influence of comorbidity on liver pathology remains unclear. To address this gap, schistosomiasis-infected mice were given one daily dose of 18% ethanol for 28 consecutive days, from day 35 post-infection. Mice were assigned to four groups: A. control; B. uninfected/ethanol gavage; C. infected; and D. infected/ethanol gavage. At day 64 post-infection, mice were euthanized by CO₂ asphyxiation, livers were excised, fixed in 10% buffered formalin, paraffin embedded and cut into 5 μm sections. These were stained with hematoxylin and eosin (HE), Lennert's Giemsa and picrosirius red (for polarization microscopy) to assess histopathological and stereological changes. Group B showed alcoholic liver disease (ALD), including microsteatosis, hepatocyte karyopyknosis, karyorrhexis, karyolysis, increased frequency of Kupffer cells, hydropic degeneration of hepatocyte, thickened plasma membrane and binucleated hepatocytes. Infected mice showed typical exudative and exudative-productive hepatic granulomas, and destruction of the adjacent hepatic parenchyma, resulting in necrotic tissue and periovular leukocyte infiltrate. Group D showed hyperemia (parenchymal panlobular lesions), and liquefactive necrosis in hepatic abscess area. There was also reduced liver collagen deposition (-76%; p = 0.0001) and reduced microsteatosis (-80%, p = 0.0079) compared to group C and group B, respectively. In conclusion, comorbidity exacerbated liver damage.

Alternate-day fasting, a high-sucrose/caloric diet and praziquantel treatment influence biochemical and behavioral parameters during Schistosoma mansoni infection in male BALB/c mice

Schistosoma mansoni-induced granulomas result in severe damage to the host's liver, as well as neurological and metabolic disorders. We evaluated the biochemical and behavioral changes during schistosomiasis under three diet protocols: ad libitum (AL), alternate-day fasting (ADF) and a high-sucrose/caloric diet (HSD). Healthy male BALB/c mice were divided into noninfected, matched infected and infected/treated [praziquantel (PZQ)] groups. Caloric intake and energy efficiency coefficients associated with diets were measured. Behavioral (exploratory and locomotor) and biochemical (glucose, triglycerides, total cholesterol, AST, ALT, ALP, and γ-GT) tests and histological analysis were performed. Fifteen weeks postinfection, HSD and PZQ promoted weight gain, with higher caloric consumption than ADF (p < 0.05), reflecting serum glucose levels and lipid profiles. HSD and PZQ prevented liver dysfunction (AST and ALT) and significantly prevented increases in granuloma area (p < 0.05). HSD and PZQ also significantly improved mouse physical performance in exploratory and locomotor behavior (p < 0.05), reversing the impaired motivation caused by infection. These findings showed that ADF worsened the course of S. mansoni infection, while HSD and PZQ, even with synergistic effects, prevented and/or attenuated biochemical and behavioral impairment from infection.

Modulation of the Host Immune Response by Schistosome Egg-Secreted Proteins Is a Critical Avenue of Host-Parasite Communication

During a schistosome infection, the interactions that occur between the mammalian host and the parasite change rapidly once egg laying begins. Both juvenile and adult schistosomes adapt to indefinitely avoid the host immune system. In contrast, the survival of eggs relies on quickly traversing from the host. Following the commencement of egg laying, the host immune response undergoes a shift from a type 1 helper (Th1) inflammatory response to a type 2 helper (Th2) granulomatous response. This change is driven by immunomodulatory proteins within the egg excretory/secretory products (ESPs), which interact with host cells and alter their behaviour to promote egg translocation. However, in parallel, these ESPs also provoke the development of chronic schistosomiasis pathology. Recent studies using high-throughput proteomics have begun to characterise the components of schistosome egg ESPs, particularly those of Schistosoma mansoni, S. japonicum and S. haematobium. Future application of this knowledge may lead to the identification of proteins with novel immunomodulatory activity or pathological importance. However, efforts in this area are limited by a lack of in situ or in vivo functional characterisation of these proteins. This review will highlight the current knowledge of the content and demonstrated functions of schistosome egg ESPs.

Coalescing beneficial host and deleterious antiparasitic actions as an antischistosomal strategy

Conventional approaches for antiparasitic drug discovery center upon discovering selective agents that adversely impact parasites with minimal host side effects. Here, we show that agents with a broad polypharmacology, often considered ‘dirtier’ drugs, can have unique efficacy if they combine deleterious effects on the parasite with beneficial actions in the host. This principle is evidenced through a screen for drugs to treat schistosomiasis, a parasitic flatworm disease that impacts over 230 million people. A target-based screen of a Schistosoma serotoninergic G protein coupled receptor yielded the potent agonist, ergotamine, which disrupted worm movement. In vivo, ergotamine decreased mortality, parasite load and intestinal egg counts but also uniquely reduced organ pathology through engagement of host GPCRs that repressed hepatic stellate cell activation, inflammatory damage and fibrosis. The unique ability of ergotamine to engage both host and parasite GPCRs evidences a future strategy for anthelmintic drug design that coalesces deleterious antiparasitic activity with beneficial host effects.

More than 200 million people worldwide are infected with parasitic worms that cause the disease schistosomiasis. Most cases occur in sub-Saharan Africa. Long-term infections can damage organs, and children who are affected may suffer delayed growth and learning difficulties. Despite its significant health and economic impact, schistosomiasis is still considered a ‘neglected’ tropical disease. This means there has not been adequate investment into developing new treatments or cures.

A drug called praziquantel is currently the only treatment for schistosomiasis. However, the drug has unpleasant side effects, cannot cure all infected individuals, and there is a concern that worms may develop resistance to its effects. This means there is an urgent need to develop new therapies. One possible approach would be to develop drugs that interfere with the worm’s ability to move.

Chan et al. screened thousands of existing chemicals for interactions with a protein that is known to control how the worms move. A drug called ergotamine, which is currently used to treat migraines, strongly interacted with the protein. Treating infected mice with ergotamine eliminated the parasites and reduced the organ damage caused by the infection. Praziquantel also reduced the number of parasites in the mice but it did not prevent organ damage.

The results presented by Chan et al. show that a single drug can interact with targets in both the worm and the animals it infects. Searching for drugs that have this dual effect may help to develop more effective treatments for schistosomiasis and other diseases caused by parasites. Ergotamine itself is unlikely to be used to treat people for schistosomiasis because of the side effects produced when using it repeatedly. However, these findings will help researchers identify and develop safer drugs with similar benefits.

Schistosome-Induced Fibrotic Disease: The Role of Hepatic Stellate Cells

Hepatic fibrosis is a common pathology in various liver diseases. Hepatic stellate cells (HSCs) are the main cell type responsible for collagen deposition and fibrosis formation in the liver. Schistosomiasis is characterised by granulomatous fibrosis around parasite eggs trapped within the liver and other host tissues. This response is facilitated by the recruitment of immune cells and the activation of HSCs. The interactions between HSCs and schistosome eggs are complex and diverse, and a better understanding of these interactions could lead to improved resolution of fibrotic liver disease, including that associated with schistosomiasis. Here, we discuss recent advances in HSC biology and the role of HSCs in hepatic schistosomiasis.

An ex vivo abomasal ovine model to study the immediate immune response in the context of Haemonchus contortus larval-stage

We have set up an ex vivo ovine abomasal model, which can mimic the multicellular process to explore the early steps in haemonchine nematode infection using RNA-seq technology. Ovine abomasal explants were collected for histological and transcriptional analysis and supernatants collected to quantitate lactate dehydrogenase (LDH) enzymes. Atotal of 233 were substantially induced genes between L₄-inoculated and uninoculated-control tissues, respectively. However, a total of 14 were considerably down-regulated genes between the 51 aforementioned tissues. Fifteen pathways were annotated by Kyoto Encyclopedia of Genes, and Genomes pathway analysis accounted for the significant percentage in immediate response to larval-stage of H. contortus. Key genes upregulated in response to the addition of L₄-inoculum of H. contortus were IL-6, IL-8, C1q, Atypical chemokine receptor-3, chemokine ligand-2, manganese superoxide dismutase, integrin alpha-7, -8, -9, integrin subunit beta-1, integrin subunit beta 6, intercellular adhesion molecule-1 and actin alpha-1. This study shows for the first time that galectin-1 is up-regulated in an ex vivo abomasal segment model exposed to L₄-inoculum of H. contortus following 6 h of incubation. The abomasal segment model has been shown to be a suitable tool to study the haemonchine larval-stage effects on the ovine abomasal tissues prior to in vivo assessment.

Taurocholate Induces Biliary Differentiation of Liver Progenitor Cells Causing Hepatic Stellate Cell Chemotaxis in the Ductular Reaction: Role in Pediatric Cystic Fibrosis Liver Disease

Cystic fibrosis liver disease (CFLD) in children causes progressive fibrosis leading to biliary cirrhosis; however, its cause(s) and early pathogenesis are unclear. We hypothesized that a bile acid-induced ductular reaction (DR) drives fibrogenesis. The DR was evaluated by cytokeratin-7 immunohistochemistry in liver biopsies, staged for fibrosis, from 60 children with CFLD, and it demonstrated that the DR was significantly correlated with hepatic fibrosis stage and biliary taurocholate levels. To examine the mechanisms involved in DR induction, liver progenitor cells (LPCs) were treated with taurocholate, and key events in DR evolution were assessed: LPC proliferation, LPC biliary differentiation, and hepatic stellate cell (HSC) chemotaxis. Taurocholate induced a time-dependent increase in LPC proliferation and expression of genes associated with cholangiocyte differentiation (cytokeratin 19, connexin 43, integrin β4, and γ-glutamyltranspeptidase), whereas the hepatocyte specification marker HNF4α was suppressed. Functional cholangiocyte differentiation was demonstrated via increased acetylated α-tubulin and SOX9 proteins, the number of primary cilia⁺ LPCs, and increased active γ-glutamyltranspeptidase enzyme secretion. Taurocholate induced LPCs to release MCP-1, MIP1α, and RANTES into conditioned medium causing HSC chemotaxis, which was inhibited by anti-MIP1α. Immunofluorescence confirmed chemokine expression localized to CK7⁺ DR and LPCs in CFLD liver biopsies. This study suggests that taurocholate is involved in initiating functional LPC biliary differentiation and the development of the DR, with subsequent induction of chemokines that drive HSC recruitment in CFLD.

The Tao survivorship of schistosomes: implications for schistosomiasis control

Schistosomiasis, caused by blood flukes of the genus Schistosoma, is a major public health problem which contributes substantially to the economic and financial burdens of many nations in the developing world. An array of survival strategies, such as the unique structure of the tegument which acts as a major host-parasite interface, immune modulation mechanisms, gene regulation, and apoptosis and self-renewal have been adopted by schistosome parasites over the course of long-term evolution with their mammalian definitive hosts. Recent generation of complete schistosome genomes together with numerous biological, immunological, high-throughput "-omics" and gene function studies have revealed the Tao or strategies that schistosomes employ not only to promote long-term survival, but also to ensure effective life cycle transmission. New scenarios for the future control of this important neglected tropical disease will present themselves as our understanding of these Tao increases.

Characterising granuloma regression and liver recovery in a murine model of schistosomiasis japonica

For hepatic schistosomiasis the egg-induced granulomatous response and the development of extensive fibrosis are the main pathologies. We used a Schistosoma japonicum-infected mouse model to characterise the multi-cellular pathways associated with the recovery from hepatic fibrosis following clearance of the infection with the anti-schistosomal drug, praziquantel. In the recovering liver splenomegaly, granuloma density and liver fibrosis were all reduced. Inflammatory cell infiltration into the liver was evident, and the numbers of neutrophils, eosinophils and macrophages were significantly decreased. Transcriptomic analysis revealed the up-regulation of fatty acid metabolism genes and the identification of Peroxisome proliferator activated receptor alpha as the upstream regulator of liver recovery. The aryl hydrocarbon receptor signalling pathway which regulates xenobiotic metabolism was also differentially up-regulated. These findings provide a better understanding of the mechanisms associated with the regression of hepatic schistosomiasis.