CEBPα/miR-101b-3p promotes meningoencephalitis in mice infected with Angiostrongylus cantonensis by promoting microglial pyroptosis.

BACKGROUND: Angiostrongylus cantonensis (A. cantonensis) infection can induce acute inflammation, which causes meningoencephalitis and tissue mechanical injury to the brain. Parasite infection-induced microRNAs play important roles in anti-parasite immunity in non-permissive hosts. miR-101b-3p is highly expressed after A. cantonensis infection; however, the role of miR-101b-3p and the transcription regulation of miR-101b-3p in A. cantonensis infection remain poorly characterized. RESULTS: In the present study, we found that miR-101b-3p inhibition alleviated inflammation infiltration and pyroptosis in A. cantonensis infection. In addition, we found that CCAAT/enhancer-binding protein alpha (CEBPα) directly bound to the - 6-k to - 3.5-k region upstream of miR-101b, and CEBPα activated miR-101b-3p expression in microglia. These data suggest the existence of a novel CEBPα/miR-101b-3p/pyroptosis pathway in A. cantonensis infection. Further investigation verified that CEBPα promotes pyroptosis by activating miR-101b-3p expression in microglia, and microglial pyroptosis further promoted inflammation. CONCLUSIONS: Our results suggest that a CEBPα/miR-101b-3p/pyroptosis pathway may contribute to A. cantonensis infection-induced inflammation and highlight the pro-inflammatory effect of miR-101b-3p. Video Abstract.

Immunomodulatory effect of different extracts from Angiostrongylus cantonensis on airway inflammation in an allergic asthma model.

This study aimed to evaluate the effects of early-life exposure to different extracts of Angiostrongylus cantonensis (A. cantonensis) on airway inflammation in an allergic asthma model. The total soluble extract (TE) and the soluble extracts of the digestive (AcD), reproductive (AcR), and cuticle (AcC) systems of A. cantonensis were used for immunisation before ovalbumin (OVA)-sensitisation/challenge in an OVA-induced allergic asthma model. The initial hypothesis of the study was that some soluble extract of the systems (AcD, AcR, or AcC) could be more potent to the modulation of inflammation than the TE. Our data, however, shows that immunisation with the TE is more promising because it decreased the high influx of inflammatory cells on airways and promoted an increase of interferon-γ (IFN-ɣ) and interleukin-10 (IL-10) levels. Besides this, the immunisation with the TE also led to a reduction of goblet cells and mucus overproduction in the lung tissue of asthmatic mice. We believe that the extracts have a distinct capacity to modulate the immune system, due to the TE possessing a greater variability of molecules, which together leads to control of airway inflammation. In conclusion, this is the first study to reveal that the TE of A. cantonensis adult worms has a greater potential for developing a novel therapeutic for allergic asthma.

Immunomodulatory action of excretory-secretory products of Angiostrongylus cantonensis in a mouse tumour model.

Excretory-secretory products (ESPs) of parasitic helminths are well known to exert immunostimulation and immunomodulation in hosts. Immune regulation plays a key role in anti-tumour therapy. The present study explored the anti-tumour effect of ESPs released by Angiostrongylus cantonensis. In Hepa1-6 mouse tumour models, ESPs significantly reduced tumour growth. Tumour-bearing mice treated with ESPs had significantly higher CD3+, CD4+, and CD8+ T cell counts than those treated with Freund's adjuvant. In vitro, human hepatocarcinoma HepG2 cells, human lung cancer A549 cells, and normal human liver HL-7702 cells were co-incubated with ESPs for 24 h and 48 h. ESPs significantly accelerated HepG2 apoptosis but had no inhibitory effect on the proliferation of A549 and HL-7702 cells. Apoptotic HepG2 cells displayed condensed nuclei, apoptotic bodies, and swollen endoplasmic reticulum (ER). Expression of the endoplasmic reticulum stress (ERS)-related factors activating transcription factor 6 (ATF6) and C/EBP-homologous protein (CHOP) in HepG2 cells increased with increasing ESP concentration and treatment time. Calreticulin (CRT) is a key effector protein of ESPs, and recombinant calreticulin (rCRT) was produced in BL21 Escherichia coli (E. coli). In contrast to ESPs, rCRT markedly reduced the proliferation of HepG2 cells. The expression levels of ATF6 and CHOP in HepG2 cells treated with 30 µg/mL rCRT significantly increased at 48 h. Notably, these findings synergistically suggest that ESPs and rCRT are promising candidates for anti-tumour immunotherapy.

Proteomic analysis of excretory-secretory products from young adults of Angiostrongylus cantonensis.

BACKGROUND: Angiostrongyliasis is caused by the nematode Angiostrongylus cantonensis and can lead to eosinophilic meningitis and meningoencephalitis in humans. The young adult worms play central pathogenic roles in the central nervous system (CNS); however, the underlying mechanism is unclear. Excretory-secretory products (ESPs) are good investigation targets for studying the relationship between a host and its parasite. OBJECTIVES: We aimed to profile, identify, and characterise the proteins in the ESPs of A. cantonensis young adults. METHODS: The ESPs of young adult worms were collected from culture medium after incubation ranging from 24 to 96 h. Proteomic and bioinformatics analyses were performed to characterise the ESPs. FINDINGS: A total of 51 spots were identified, and the highly expressed proteins included two protein disulphide isomerases, one calreticulin, and three uncharacterised proteins. Subsequently, approximately 254 proteins were identified in the ESPs of A. cantonensis young adults via liquid chromatography-mass spectrometry (LC-MS/MS) analysis, and these were further classified according to their characteristics and biological functions. Finally, we identified the immunoreactive proteins from a reference map of ESPs from A. cantonensis young adults. Approximately eight proteins were identified, including a protein disulphide isomerase, a putative aspartic protease, annexin, and five uncharacterised proteins. The study established and identified protein reference maps for the ESPs of A. cantonensis young adults. MAIN CONCLUSIONS: The identified proteins may be potential targets for the development of diagnostic or therapeutic agents for human angiostrongyliasis.

Unveiling the oxidative metabolism of Achatina fulica (Mollusca: Gastropoda) experimentally infected to Angiostrongylus cantonensis (Nematoda: Metastrongylidae).

For the first time, alterations in the oxidative metabolism of Achatina fulica experimentally infected with different parasite loads of Angiostrongylus cantonensis were determined. For this, the hemolymph activities of lactate dehydrogenase (LDH) and hexokinase and the glucose concentrations in the hemolymph, as well as the polysaccharide reserves in the digestive gland and cephalopedal mass, were assessed. Additionally, the contents of some carboxylic acids in the hemolymph of infected and uninfected snails were determined by high-performance liquid chromatography (HPLC), permitting a better understanding of the alterations related to the host's oxidative metabolism. As the main results, activation of oxidative pathways, such as the glycolytic pathway, was demonstrated in response to the increase in the activity of hexokinase. This tendency was confirmed by the decrease in the contents of glucose in the hemolymph of parasitized snails, indicating that the infection by A. cantonensis alters the host's metabolism, and that these changes are strongly influenced by the parasite load. This metabolic scenario was accompanied by activation of the anaerobic fermentative metabolism, indicated not only by an increase in the activity of (LDH), but also by a reduction of the content of pyruvic acid and accumulation of lactic acid in the hemolymph of parasitized snails. In this circumstance, maintenance of the host's redox balance occurs through activation of the fermentative pathways, and LDH plays a central role in this process. Together, the results indicate that A. cantonensis infection induces activation of the anaerobic metabolism of A. fulica, characterized not only by the accumulation of lactic acid, but also by a reduction in the pyruvic acid and oxalic acid contents in the hemolymph of the infected snails.

Angiostrongylus Cantonensis-Conditioned Culture Medium Induces Myelin Basic Protein Alterations via Erk1/2 and NF-κB Activation in Rat RSC96 Schwann Cells.

Eating of excessive raw or undercooked environmental snails produces angiostrongyliasis demyelination caused by Angiostrongylus cantonensis (A. cantonensis). The aim of this study was to investigate the association between extracellular signal-regulated kinase (Erk)1/2-nuclear factor (NF)-κB pathway and myelin basic protein (MBP) expression in RSC96 Schwann cells treated with A. cantonensis-conditioned culture medium, which was prepared by culturing the third-stage (L3) nematode larvae in DMEM for 72 h. The supernatants were collected and filtered before use. Our results showed that MBP was produced in the RSC96 cells at 16 h to 48 h post-stimulation (PS). Phosphorylated (p)-NF-κB levels were significantly increased from 8 h to 48 h PS, as were the p-Erk1/2 levels at the same time points. Additionally, expression of p-NF-κB and MBP was significantly decreased by treatment with QNZ, an NF-κB inhibitor. Treatment with PD98059, an Erk kinase inhibitor, efficiently reduced p-Erk1/2, p-NF-κB and MBP expression in the Schwann cells. These results suggest that A. cantonensis-conditioned culture medium induced suppression of the Erk1/2-NF-κB signaling pathway leading to reduced MBP production in RSC96 Schwann cells. Thus, inhibiting this signaling intermediate involved in MBP expression may be a potential method for controlling inflammatory development of A. cantonensis-induced MBP changes in preceded demyelination.

Cross-reactivity of the 31 kDa antigen of Angiostrongylus cantonensis - Dealing with the immunodiagnosis of meningoencephalitis.

The primary causative agent of eosinophilic meningoencephalitis (EoM) in endemic regions is the nematode Angiostrongylus cantonensis. The occurrence of EoM was previously restricted to countries in Southeast Asia and the Pacific Islands; however, more recently, it has been reported from other regions, including Brazil. The commonly used diagnosis is detection of specific antibody reactivity to the 31 kDa antigen, which is derived from female worm somatic extracts. Here we report the occurrence of cross-reactivity to this antigen in sera from other parasitic infections, especially those that may cause EoM, such as gnathostomiasis, toxocariasis, hydatidosis and strongyloidiasis. We also demonstrated that the cross-reactivity, in part, is dependent of the concentration of antigen used in Western blot assays. We discuss the importance of these findings on the interpretation of this test.

Soluble antigen derived from IV larva of Angiostrongylus cantonensis promotes chitinase-like protein 3 (Chil3) expression induced by interleukin-13.

Angiostrongyliasis caused by Angiostrongylus cantonensis (A. cantonensis) is an emerging food-borne parasitic disease, which refers basically to eosinophilic meningitis. Chitinase-like protein 3 (Chil3), a member of chitinase-like protein family which has chemotactic activity for eosinophils, is reported to be highly upregulated in brain of mouse infected with A. cantonensis. The mechanisms of high expression of Chil3 and the association between A. cantonensis and Chil3 are rarely reported. In order to understand the mechanism of high expression of Chil3 in A. cantonensis-infected mouse, we measured the level of Chil3 in RAW 264.7 and BV2 cell lines stimulated with soluble antigen of A. cantonensis by qPCR and ELISA. To explore the role of Chil3 in inflammation caused by A. cantonensis, we extracted and cultured brain mononuclear cells (BMNCs) and detected the eosinophil chemotactic activity of Chil3 using transwell assay and flow cytometer. Furthermore, we treated the infected mice by injection with rmChil3 and then counted the number of larvae in brains of infected mice and treated mice to examine the association between the worm and Chil3. Our results showed the soluble antigen from A. cantonensis could promote the Chil3 expression in macrophage and microglial cell lines induced by interleukin-13. In conclusion, we supposed that high expression of Chil3 enhanced by soluble antigens from A. cantonensis might be the reason of serious eosinophil infiltration in mouse brain after A. cantonensis infection.

Comparative studies on the proteomic expression patterns in the third- and fifth-stage larvae of Angiostrongylus cantonensis.

Angiostrongylus cantonensis is an important zoonotic parasite causing eosinophilic meningitis and eosinophilic meningoencephalitis in humans. In this study, the protein expression profiles of the infective third- and pathogenic fifth-stage larvae (L3 and L5) of this parasite were compared by proteomic techniques. Isolated protein samples were separated by two-dimensional gel electrophoresis (2-DE), stained with silver nitrate, and analyzed by matrix-assisted laser desorption/ionization-time-of-flight mass spectrometry (MALDI-TOF MS). Proteins from L5 were mainly at pH 5-7 and with molecular weight (MW) 40-100 kDa, whereas those from L3 were at pH 5-6 and with 5-35 kDa. Of 100 protein spots identified, 33 were from L3 whereas 67 from L5 and 63 had known identities, whereas 37 were hypothetical proteins. There were 15 spots of stress proteins, and HSP60 was the most frequently found heat stress proteins in L5. More binding and protein transport-related proteins were found in L5 including peptidylprolyl isomerase (cyclophilin)-like 2, serum albumin, preproalbumin precursor, and dilute class unconventional myosin. L3 had a higher expression of cytoskeleton and membrane proteins than L5. In addition, four protein spots were identified in the sera of the rat host by Western blot analysis. The present proteomic study revealed different protein expression profiles in L3 and L5 of A. cantonensis. These changes may reflect the development of L3 from the poikilothermic snails to L5 in the homoeothemic rats. This information may be useful for the finding of stage-specific proteins and biomarker for diagnosis of angiostrongyliasis.

MicroRNA expression profile in the third- and fourth-stage larvae of Angiostrongylus cantonensis.

The pathogenesis of angiostrongyliasis, resulting from the third-stage and the fourth-stage Angiostrongylus cantonensis larvae invasion of the human central nervous system, remains elusive. MicroRNAs are important regulators of gene expression and involved in many biological processes. The aim of this study was to determine and characterize miRNAs of third (L3) and fourth (L4) larvae of A. cantonensis by Solex deep sequencing. A total of 629 conserved miRNAs (526 and 376 miRNAs in L3 and L4 larvae of A. cantonensis, respectively) and three novel candidate miRNA from L3 and L4 larva of A. cantonensis were identified with bioinformatic analysis. There were 163 miRNAs upregulated and 54 miRNAs downregulated (fold changes ≥5.0) in the L4 of A. cantonensis compared with that of L3 of A. cantonensis. Interestingly, Gene Ontology "biological process" classifications revealed that 26 miRNAs of significantly differential expression are associated with the immune system, which implies that these miRNAs might participate in the pathogenesis of angiostrongyliasis by regulating genes involved in immune response pathways. Furthermore, the differential expression patterns of 26 conserved miRNAs between L3 and L4 of A. cantonensis were verified. The results of real-time PCR and Northern blot showed that the aca-miR-124 and aca-miR-146a-5p have a low level expression in L3 larvae but high level expression in L4 larvae. Transfection of aca-miR-124 mimics alone significantly downregulated the mRNA expression of IL-6 and IL-1ß and TNF-a in the N9 cells, compared to the combination transfection of aca-miR-124 mimics and inhibitor (P < 0.05), suggesting that miR-124 of A. cantonensis have an important role in the suppression of microglia activation. In conclusion, the study presents a general picture of the expression of small RNAs in L3 and L4 of A. cantonensis and highlights conserved miRNAs differentially expressed between L3 and L4 larvae. Our data revealed that miRNAs of parasite may mediate important roles in A. cantonensis immune evasion and aca-miR-146a-5p can serve as a potential biomarker to diagnose angiostrongyliasis.

Uptake and utilization of arachidonic acid in infective larvae of Angiostrongylus cantonensis.

Infective larvae of Angiostrongylus cantonensis may take up and incorporate exogenous arachidonic acid into their lipid pool. By scintillation counting, uptake and incorporation were determined to be time dependent. Arachidonic acid was mainly incorporated into phospholipid (56.8%) and neutral lipid (22.4%) pools. In the neutral lipids, 64.0% was diglyceride and 36.0% triglyceride. Phosphatidylcholine was the predominant fatty acid in the phospholipid pool. In addition to the release of leukotriene B4, the parasite was found to generate radiolabelled CO2 after incubation with [U-14C]arachidonate. Moreover, enzymatic analysis of crude extracts revealed the presence of acyl-CoA dehydrogenase (short and long chain), thiolase, enoyl-CoA hydratase and 3-hydroxyacyl-CoA dehydrogenase. These findings suggest that infective larvae of A. cantonensis not only take up and incorporate exogenous arachidonic acid into their lipid pool, but may also utilize the fatty acid through a functional ß-oxidation pathway.

3-Hydroxybenzaldehyde and 4-Hydroxybenzaldehyde enhance survival of mouse astrocytes treated with Angiostrongylus cantonensis young adults excretory/secretory products.

BACKGROUND: Human cerebral angiostrongyliasis, induced by Angiostrongylus cantonensis, is an emerging disease in many parts of the world. A. cantonensis is also an important causative agent of eosinophilic meningitis and eosinophilic meningoencephalitis in humans. 3-Hydroxybenzaldehyde (3-HBA) and 4-Hydroxybenzaldehyde (4-HBA) have been shown to increase intracellular antioxidant activity, vasculoprotective potency, wound healing, and cell migration. However, the function of 3-HBA and 4-HBA in mouse astrocytes in response to A. cantonensis young adults excretory-secretory products (ESPs) treatment remains unclear. METHODS: Here, we examined the effect of 3-HBA and 4-HBA by real-time qPCR, western blotting, and cell viability assay in astrocytes after A. cantonensis young adults ESPs treatment. The real-time qPCR, western blotting were employed to detect the expression of apoptosis- and Shh pathway-related molecule. The percentage of cell viability was monitored by CCK-8 assay. RESULTS: We demonstrated that expression of apoptosis-related molecules was increased in response to A. cantonensis young adults ESPs treatment. However, the cell viability of astrocytes was elevated by treatment with 3-HBA and 4-HBA. Further investigation found that 3-HBA and 4-HBA activate the Shh signaling pathway and inhibit apoptosis-related molecule expression. CONCLUSIONS: These findings were confirmed using A. cantonensis young adults ESPs to activate apoptosis-related pathways in astrocytes. Moreover, 3-HBA and 4-HBA induced a protective phenotype through regulation of apoptosis in response to A. cantonensis young adults ESPs treatment. Hence, 3-HBA and 4-HBA represent potential therapeutic drugs for the treatment of human angiostrongyliasis.

Exosome-Depleted Excretory-Secretory Products of the Fourth-Stage Larval Angiostrongylus cantonensis Promotes Alternative Activation of Macrophages Through Metabolic Reprogramming by the PI3K-Akt Pathway.

Angiostrongylus cantonensis (AC), which parasitizes in the brain of the non-permissive host, such as mouse and human, is an etiologic agent of eosinophilic meningitis. Excretory-secretory (ES) products play an important role in the interaction between parasites and hosts' immune responses. Inflammatory macrophages are responsible for eosinophilic meningitis induced by AC, and the soluble antigens of Angiostrongylus cantonensis fourth stage larva (AC L4), a mimic of dead AC L4, aggravate eosinophilic meningitis in AC-infected mice model via promoting alternative activation of macrophages. In this study, we investigated the key molecules in the ES products of AC L4 on macrophages and observed the relationship between metabolic reprogramming and the PI3K-Akt pathway. First, a co-culture system of macrophage and AC L4 was established to define the role of AC L4 ES products on macrophage polarization. Then, AC L4 exosome and exosome-depleted excretory-secretory products (exofree) were separated from AC L4 ES products using differential centrifugation, and their distinct roles on macrophage polarization were confirmed using qPCR and ELISA experiments. Moreover, AC L4 exofree induced alternative activation of macrophages, which is partially associated with metabolic reprogramming by the PI3K-Akt pathway. Next, lectin blot and deglycosylation assay were done, suggesting the key role of N-linked glycoproteins in exofree. Then, glycoproteomic analysis of exofree and RNA-seq analysis of exofree-treated macrophage were performed. Bi-layer PPI network analysis based on these results identified macrophage-related protein Hexa as a key molecule in inducing alternative activation of macrophages. Our results indicate a great value for research of helminth-derived immunoregulatory molecules, which might contribute to drug development for immune-related diseases.

Oxidative stress in mice infected with Angiostrongylus cantonensis coincides with enhanced glutathione-dependent enzymes activity.

This study aimed to estimate reactive oxygen species (ROS) production, antioxidants activity, and biomarkers level of oxidative damage to protein and DNA in the cerebrospinal fluid (CSF) of C57BL/6 mice infected with Angiostrongylus cantonensis. The mean ROS concentration in the CSF of infected mice increased gradually, and the increase in ROS in CSF became statistical significance at days 12-30 post-infection compared to that before infection (P<0.001), and then ROS returned to normal level at day 45 after infection. In parallel with the increase in ROS in the CSF, infected mice showed similar of changes in reduced glutathione (GSH), glutathione reductase (GR), glutathione peroxidase (GPx), and glutathione S-transferase (GST) as that in ROS in the CSF. GSH, GR, GPx, and GST in the CSF of infected mice were all significantly higher than they were before infection during days 12-30 post-infection. However, protein carbonyl content and 8-hydroxy-2'-deoxyguanosine, biomarkers of oxidative damage to protein and DNA, respectively, were also significantly higher in the CSF of infected mice during this period. These results suggest that oxidative stress occur in the cells of central nervous system of mice infected with A. cantonensis during days 12-30 after infection due to ROS overproduction in CSF despite the increase in antioxidants during this period.

Downregulated RPS-30 in Angiostrongylus cantonensis L5 plays a defensive role against damage due to oxidative stress.

BACKGROUND: Eosinophilic meningitis, caused by fifth-stage larvae of the nematode (roundworm) Angiostrongylus cantonensis, is mainly attributed to the contribution of eosinophils to tissue inflammatory responses in helminthic infections. Eosinophils are associated with the killing of helminths via peroxidative oxidation and hydrogen peroxide generated by the dismutation of superoxide produced during respiratory bursts. In contrast, when residing in the host with high level of eosinophils, helminthic worms have evolved to attenuate eosinophil-mediated tissue inflammatory responses for their survival in the hosts. In a previous study we demonstrated that the expression of the A. cantonensis RPS 30 gene (Acan-rps-30) was significantly downregulated in A. cantonensis L5 roundworms residing in cerebrospinal fluid with a high level of eosinophils. Acan-RPS-30 is a protein homologous to the human Fau protein that plays a pro-apoptotic regulatory role and may function in protecting worms from oxidative stress. METHODS: The isolation and structural characterization of Acan-RPS-30 were performed using rapid amplification of cDNA ends (RACE), genome walking and bioinformatics. Quantitative real-time-PCR and microinjection were used to detect the expression patterns of Acan-rps-30. Feeding RNA interference (RNAi) was used to knockdown the apoptosis gene ced-3. Microinjection was performed to construct transgenic worms. An oxidative stress assay was used to determine the functions of Acan-RPS-30. RESULTS: Our results showed that Acan-RPS-30 consisted of 130 amino acids. It was grouped into clade V with C. elegans in the phylogenetic analysis. It was expressed ubiquitously in worms and was downregulated in both L5 larvae and adult A. cantonensis. Worms expressing pCe-rps30::Acan-rps-30::rfp, with the refractile "button-like" apoptotic corpses, were susceptible to oxidative stress. Apoptosis genes ced-3 and ced-4 were both upregulated in the transgenic worms. The phenotype susceptible to oxidative stress could be converted with a ced-3 defective mutation and RNAi. rps-30-/- mutant worms were resistant to oxidative stress, with ced-3 and ced-4 both downregulated. The oxidative stress-resistant phenotype could be rescued and inhibited by through the expression of pCe-rps30::Acan-rps-30::rfp in rps-3-/- mutant worms. CONCLUSION: In C. elegans worms, downregulated RPS-30 plays a defensive role against damage due to oxidative stress, facilitating worm survival by regulating downregulated ced-3. This observation may indicate the mechanism by which A. cantonensis L5 worms, with downregulated Acan-RPS-30, survive in the central nervous system of humans from the immune response of eosinophils.

The excretory/secretory products of fifth-stage larval Angiostrongylus cantonensis induces autophagy via the Sonic hedgehog pathway in mouse brain astrocytes.

Angiostrongyliasis is induced by the nematode Angiostrongylus cantonensis and leads to eosinophilic meningitis and meningoencephalitis in humans. Excretory-secretory products (ESPs) are important investigation targets for studying the relationship between hosts and nematodes. These products assist worms in penetrating the blood-brain barrier and avoiding the host immune response. Autophagy is a catabolic process that is responsible for digesting cytoplasmic organelles, proteins, and lipids and removing them through lysosomes. This process is essential to cell survival and homeostasis during nutritional deficiency, cell injury and stress. In this study, we investigated autophagy induction upon treatment with the ESPs of the fifth-stage larvae (L5) of A. cantonensis and observed the relationship between autophagy and the Shh pathway. First, the results showed that A. cantonensis infection induced blood-brain barrier dysfunction and pathological changes in the brain. Moreover, A. cantonensis L5 ESPs stimulated autophagosome formation and the expression of autophagy molecules, such as LC3B, Beclin, and p62. The data showed that upon ESPs treatment, rapamycin elevated cell viability through the activation of the autophagy mechanism in astrocytes. Finally, we found that ESPs induced the activation of the Sonic hedgehog (Shh) signaling pathway and that the expression of autophagy molecules was increased through the Shh signaling pathway. Collectively, these results suggest that A. cantonensis L5 ESPs stimulate autophagy through the Shh signaling pathway and that autophagy has a protective effect in astrocytes.

Excretory/secretory products of Angiostrongylus cantonensis fifth-stage larvae induce endoplasmic reticulum stress via the Sonic hedgehog pathway in mouse astrocytes.

BACKGROUND: Angiostrongylus cantonensis is an important food-borne zoonotic parasite. Humans are non-permissive hosts, and this parasite develops into fifth-stage larvae (L5) in the brain and subarachnoid cavity and then induces eosinophilic meningitis and eosinophilic meningoencephalitis. Excretory/secretory products (ESPs) are valuable targets for the investigation of host-parasite interactions. These products contain a wide range of molecules for penetrating defensive barriers and avoiding the immune response of the host. Endoplasmic reticulum (ER) stress has been found to be associated with a wide range of parasitic infections and inflammation. ER stress can increase cell survival via the activation of downstream signalling. However, the mechanisms of ER stress in A. cantonensis infection have not yet been clarified. This study was designed to investigate the molecular mechanisms of ER stress in astrocytes after treatment with the ESPs of A. cantonensis L5. RESULTS: The results demonstrated that A. cantonensis infection activated astrocytes in the mouse hippocampus and induced the expression of ER stress-related molecules. Next, the data showed that the expression of ER stress-related molecules and the Ca2+ concentration were significantly increased in activated astrocytes after treatment with the ESPs of L5 of A. cantonensis. Ultimately, we found that ESPs induced GRP78 expression via the Sonic hedgehog (Shh) signalling pathway. CONCLUSIONS: These findings suggest that in astrocytes, the ESPs of A. cantonensis L5 induce ER stress and that the Shh signalling pathway plays an important role in this process.

[Expressed sequence tags (ESTs) analysis of Angiostrongylus cantonensis].

A total of 1,277 ESTs of Angiostrongylus cantonensis were downloaded from GenBank and analyzed with BlastX. SignalP V3.0 analysis was applied to predict potential putative antigen or allergen relative proteins with N-terminal secreted signal peptides or signal anchors. BlastX analysis showed that there were 614 ESTs scored more than 100, of which 14 were identical with A. cantonensis, 60 ESTs did not match any proteins in the databases. The identified 614 ESTs could be grouped into 10 categories, 80 ESTs expressed 22 antigen or allergen relative proteins, in which 12 had N-terminal secreted signal peptides and 3 had signal anchors.

Proteomic Analysis of Differentially Expressed Proteins in Intracranial Angiostrongylus cantonensis Larvae in Permissive and Non-Permissive Hosts.

Angiostrongylus cantonensis infection can lead to severe neuropathological damage caused by the development of these nematodes in the central nervous system after penetrating the blood-brain barrier. They commonly cause eosinophilic meningitis or meningoencephalitis in non-permissive hosts (e.g., mice). It has been shown that differences exist in the brains of permissive and non-permissive hosts during the larval development of A. cantonensis; however, the mechanism underlying the difference is not completely understood. This study analyzed and characterized the differentially expressed proteins in the intracranial A. cantonensis larvae in rat (ILR) and mouse (ILM) brains by using proteomics. We found that 29 proteins were differentially expressed: 12 of these proteins were highly expressed in ILR, whereas the remaining 17 proteins were highly expressed in ILM. Three protein spots were homologous to the actin-2, actin-1, and disorganized muscle protein 1 (dim-1) of Caenorhabditis elegans. In addition, proteomic analyses revealed that act-1 and act-2 were up-regulated in ILM compared to ILR, whereas dim-1 was down-regulated in ILM. Annotation using gene ontology revealed that act-1, act-2, and dim-1 were mainly associated with adenosine triphosphate (ATP) catabolic processes and ATP binding. Quantitative real-time polymerase chain reaction analyses of act-1 and dim-1 using the first internal transcribed spacers of A. cantonensis 18S ribosomal RNA (rRNA) was consistent with 2-dimensional gel electrophoresis (2-DE) and the sizes of these parasites; ILR was longer and wider than ILM. These results indicate that the differentially expressed proteins dim-1 and act-1 could be related to the development and pathogenicity of A. cantonensis in different hosts.

Anti-apoptotic effects of Sonic hedgehog signalling through oxidative stress reduction in astrocytes co-cultured with excretory-secretory products of larval Angiostrongylus cantonensis.

Angiostrongylus cantonensis, the rat lungworm, is an important aetiologic agent of eosinophilic meningitis and meningoencephalitis in humans. Co-culturing astrocytes with soluble antigens of A. cantonensis activated the Sonic hedgehog (Shh) signalling pathway and inhibited the apoptosis of astrocytes via the activation of Bcl-2. This study was conducted to determine the roles of the Shh signalling pathway, apoptosis, and oxidative stress in astrocytes after treatment with excretory-secretory products (ESP) from A. cantonensis fifth-stage larvae. Although astrocyte viability was significantly decreased after ESP treatment, the expression of Shh signalling pathway related proteins (Shh, Ptch-1 and Gli-1) was significantly increased. However, apoptosis in astrocytes was significantly decreased after activation of the Shh signalling pathway. Moreover, superoxide and hydrogen superoxide levels in astrocytes were significantly reduced after the activation of Shh pathway signalling due to increasing levels of the antioxidants catalase and superoxide dismutase. These findings indicate that the anti-apoptotic effects of the Shh signalling pathway in the astrocytes of mice infected with A. cantonensis are due to reduced levels of oxidative stress caused by the activation of antioxidants.