Excretory-Secretory Products Secreted by Paragonimus westermani Delay the Spontaneous Cell Death of Human Eosinophils through Autocrine Production of GM-CSF

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.

A herbal formula comprising Rosae Multiflorae Fructus and Lonicerae Japonicae Flos, attenuates collagen-induced arthritis and inhibits TLR4 signalling in rats

RL, a traditional remedy for Rheumatoid arthritis (RA), comprises two edible herbs, Rosae Multiflorae Fructus and Lonicerae Japonicae Flos. We have reported that RL could inhibit the production of inflammatory mediators in immune cells. Here we investigated the effects and the mechanism of action of RL in collagen-induced arthritis (CIA) rats. RL significantly increased food intake and weight gain of CIA rats without any observable adverse effect; ameliorated joint erythema and swelling; inhibited immune cell infiltration, bone erosion and osteophyte formation in joints; reduced joint protein expression levels of TLR4, phospho-TAK1, phospho-NF-κB p65, phospho-c-Jun and phospho-IRF3; lowered levels of inflammatory factors (TNF-α, IL-6, IL-1β, IL-17A and MCP-1 in sera and TNF-α, IL-6, IL-1β and IL-17A in joints); elevated serum IL-10 level; reinvigorated activities of antioxidant SOD, CAT and GSH-Px in the liver and serum; reduced Th17 cell proportions in splenocytes; inhibited splenocyte proliferation and activation; and lowered serum IgG level. In conclusion, RL at nontoxic doses inhibited TLR4 signaling and potently improved clinical conditions of CIA rats. These findings provide further pharmacological justifications for the traditional use of RL in RA management.

The Dynamics of Treg/Th17 and the Imbalance of Treg/Th17 in Clonorchis sinensis-Infected Mice

Clonorchiasis, caused by the liver fluke Clonorchis sinensis, is a chronic parasitic infection regulated by T cell subsets. An imbalance of CD4⁺CD25⁺ Foxp3⁺regulatory T (Treg) and interleukin (IL)-17-secreting T cells (Th17) may control inflammation and play an important role in the pathogenesis of immune evasion. In the present study, we assessed the dynamics of Treg/Th17 and determined whether the Treg/Th17 ratio is altered in C. sinensis-infected mice. The results showed that the percentages of splenic Treg cells in CD4⁺ T cells were suppressed on day 14 post-infection (PI) but increased on day 56 PI, while Th17 cells were increased on day 56 PI compared with normal control (NC) mice. The Treg/Th17 ratio steadily increased from day 28 to day 56 PI. The hepatic levels of their specific transcription factors (Foxp3 for Treg and RORγt for Th17) were increased in C. sinensis-infected mice from day 14 to 56 PI, and significantly higher than those in NC mice. Meanwhile, serum levels of IL-2 and IL-17 were profoundly increased in C. sinensis-infected mice throughout the experiment; while the concentrations of IL-6 and transforming growth factor β₁ (TGF-β₁) peaked on day 14 PI, but then decreased on day 28 and 56 PI. Our results provide the first evidence of an increased Treg/Th17 ratio in C. sinensis-infected mice, suggesting that a Treg/Th17 imbalance may play a role in disease outcomes of clonorchiasis.

Proteomic analysis of different period excretory secretory products from Clonorchis sinensis adult worms: molecular characterization, immunolocalization, and serological reactivity of two excretory secretory antigens-methionine aminopeptidase 2 and acid phosphatase

The excretory secretory products (ESP) of Clonorchis sinensis are the causative agents of clonorchiasis and biliary diseases. The parasites' ESP play important roles in host-parasite interactions. The protein compositions of ESP at different secretory times are different and have not been systemically investigated so far. In this study, we collected ESP from six different periods (0-3 h, 3-6 h, 6-12 h, 12-24 h, 24-36 h, and 36-48 h) from C. sinensis adults. Using a shotgun LC-MS/MS analysis, we found 187, 80, 103, 58, 248, and 383 proteins, respectively. Among these proteins, we selected methionine aminopeptidase 2 (MAP-2, presented in 24-36 h and 36-48 h ESP) and acid phosphatase (AP, presented in 3-6 h, 12-24 h, 24-36 h, and 36-48 h ESP) for further study. Bioinformatics analysis showed that CsMAP-2 has metallopeptidase family M24, unique lysine residue-rich and acidic residue-rich domain, SGTS motif, and auto-cleavage point; and that CsAP has possible signal sequence cleavage site, acid phosphate domain, and two histidine acid phosphatases active regions. CsMAP-2 and CsAP's cDNA have 1,425 bp and1,410 bp ORF, encoding 475 and 470 amino acid proteins and weighing 55.3840 kDa and 55.2875 kDa, respectively. MAP-2 and AP were identified as antigens present in the ESP and circulating antigens by immunoblot analysis, which were also found expressing in the eggs, metacercaria, and adult stages of C. sinensis. Immunofluorescence analysis showed that they were located in tegument and intestinal cecum of adult. MTT assay showed that they could inhibit hepatic stellate cell line (LX-2) proliferation. These findings presented the compositions of different period excretory secretary products from C. sinensis adults.

Eosinophil-mediated tissue inflammatory responses in helminth infection

Eosinophilic leukocytes function in host protection against parasitic worms. In turn, helminthic parasites harbor specific molecules to evade or paralyze eosinophil-associated host immune responses; these molecules facilitate the migration and survival of parasitic helminths in vivo. This competition between eosinophil and worm leads to stable equilibria between them. An understanding of such dynamic host-eosinophil interactions will help us to uncover mechanisms of cross talk between host and parasite in helminth infection. In this review, we examine recent findings regarding the innate immune responses of eosinophils to helminthic parasites, and discuss the implications of these findings in terms of eosinophil-mediated tissue inflammation in helminth infection.

Excretory-secretory products from Paragonimus westermani increase nitric oxide production in microglia in PKC-dependent and -independent manners

Excretory-secretory products (ESP) from helminthic parasites may play pivotal roles in the immune regulation in hosts. Previously, we reported that ESP produced from Paragonimus westermani induced morphological activation of microglial cells and markedly stimulated nitric oxide (NO) production via activation of mitogen-activated protein kinases (MAPKs). In the present study, we investigated the role of protein kinase C and protein kinase A in MAPKs-dependent NO production by ESP. We found that treatment with protein kinase C inhibitor Go6976 strongly inhibited the phosphorylation of p38 and JNK, but not ERK, of MAPKs and decreased the production of NO in ESP-stimulated microglial cells. Inhibition of ERK, p38 or PKC decreased the ESP-induced activation of NF-kappaB, an important transcription factor for iNOS expression. Furthermore, ESP increased the level of p-CREB in microglial cells. However, adenylyl cyclase activator (forskolin), adenylyl cyclase inhibitor (SQ22536), cAMP analogue (db-cAMP) or protein kinase A inhibitor (H89) was not able to change iNOS expression and NO production in ESP-treated microglial cells. It implies that the cAMP-PKA-CREB pathway is not implicated in the ESP-evoked NO production in microglial cells. Thus, our results indicate that ESP stimulates microglial expression of iNOS via both PKC-dependent and -independent MAPKs phosphorylation and NF-kappaB activation.

A 27 kDa cysteine protease secreted by newly excysted Paragonimus westermani metacercariae induces superoxide anion production and degranulation of human eosinophils

Eosinophil degranulation plays a crucial role in tissue inflammatory reactions associated with helminth parasitic infections and allergic diseases. Paragonimus westermani, a lung fluke causing human paragonimiasis, secretes a large amount of cysteine proteases, which are involved in nutrient uptake, tissue invasion, and modulation of hos's immune responses. There is, however, limited information about the response of eosinophils to direct stimulation by cysteine proteases (CP) secreted by P. westermani. In the present study, we tested whether degranulation and superoxide production from human eosinophils can be induced by stimulation of the 2 CP (27 kDa and 28 kDa) purified from excretory-secretory products (ESP) of P. westermani newly excysted metacercariae (PwNEM). A large quantity of eosinophil-derived neurotoxin (EDN) was detected in the culture supernatant when human eosinophils isolated from the peripheral blood were incubated with the purified 27 kDa CP. Furthermore, the 27 kDa CP induced superoxide anion production by eosinophils in time- and dose-dependent manners. In contrast, the purified 28 kDa CP did not induce superoxide production and degranulation. These findings suggest that the 27 kDa CP secreted by PwNEM induces superoxide production and degranulation of human eosinophils, which may be involved in eosinophil-mediated tissue inflammatory responses during the larval migration in human paragonimiasis.

Macrophageal/microglial cell activation and cerebral injury induced by excretory–secretory products secreted by Paragonimus westermani

Cerebral paragonimiasis causes various neurological disorders including seizures, visual impairment and hemiplegia. The excretory-secretory product (ESP) released by Paragonimus westermani has a cysteine protease activity and plays important roles in its migration in the host tissue and modulation of host immune responses. To gain more insight into the pathogenesis of ESP in the brain, we investigated the inflammatory reaction and cerebral injury following microinjection of ESP into rat striatum. The size of injury was maximally observed 3 days after microinjection of ESP and then declined to control levels as astrocytes have repopulated the injury. ED1-positive monocytes and microglia were confluently found inside the injury. The mRNA expression of inducible nitric oxide synthase (iNOS) occurred as early as 9h after ESP injection and then declined to control levels within 1 day. The iNOS inhibitor aminoguanidine largely decreased the expression of iNOS but did not reduce the size of lesion caused by ESP. Interestingly, however, heat inactivation of ESP caused a decrease of injury formation with no altered expression of iNOS. The data indicate that ESP produces brain tissue injury by recruiting activated monocytes/microglia via heat-labile protease activity.

Identification of immunodominant excretory–secretory cysteine proteases of adultParagonimus westermani by proteome analysis

Paragonimus westermani causes inflammatory lung disease in humans. The parasite excretes a host of biologically active molecules, which are thought to be involved in pathophysiological and immunological events during infection. Analyses of the 2-DE protein profiles of the excretory-secretory products (ESP) of adult P. westermani revealed approximately 147 protein spots, at least 15 of which were identified as cysteine proteases (CPs), at pHs between 4.5 and 8.5, and molecular weights (MWs) between 27 and 35 kDa. An additional three CPs (designated as PwCP-3, -8 and -11) were newly recognized by TOF/TOF MS. Their molecular biological information, which shared a high level sequence homology, was elucidated. The majority of the CPs reacted strongly with sera from paragonimiasis patients. When we observed the chronological changes in the antibody responses of the respective CPs against canine sera collected serially at 1, 3, 5, 7, 11 and 14 wk after experimental infection, these molecules exhibited a multiplicity of distinct immune recognition patterns. Our results clearly showed that P. westermani adult ESP were principally composed of excretory-secretory CPs, and that these CPs may exert effects not only on host tissue degradation and nutrient uptake, but also on the immune-regulating cells via synergistic and independent interactions.

Excretory-Secretory Products Produced by Paragonimus westermani Differentially Regulate the Nitric Oxide Production and Viability of Microglial Cells

BACKGROUND

Tissue-invading helminth parasites secrete a large amount of cysteine proteases that may play critical roles in tissue invasion and immune modulation. However, roles of excretory-secretory products (ESP) secreted by Paragonimus westermani in the activation and death of microglial cells in brain are poorly understood.

OBJECTIVES

In the present study, we investigated whether ESP could regulate microglial nitric oxide (NO) production and viability.

METHODS

The NO production and cell viability were assessed by respectively measuring the formation of nitrite and the release of lactate dehyrogenase.

RESULTS

At a low (0.2 microg/ml) concentration, ESP significantly stimulated NO production with no apparent cell injury or death in cultured microglial cells. However, at high (> or =2 microg/ml) concentrations, ESP induced severe cell death. Inhibition of inducible NO synthase significantly reduced the NO productivity, but not cytotoxicity, of ESP. Similarly, inhibitors of the extracellular signal-regulated kinase, p38 and nuclear factor kappa B also blocked only the NO productivity of ESP. Interestingly, heat inactivation did not hamper the ability of ESP to stimulate microglial NO production. Similarly, pretreatment with thiol-crosslinking reagents dramatically reduced both proteolytic activity and cytotoxicity of ESP, but did not alter NO production in microglial cells. Interestingly, although cysteine protease competitive inhibitors and thiol-alkylating reagents markedly reduced the proteolytic activity of ESP, they did not influence the NO productivity and cytotoxicity of ESP.

CONCLUSION

The present results indicate that the NO production and cytotoxicity by ESP may be differentially regulated via unknown mechanisms, not related with cysteine protease activity.

Trichuris suis excretory secretory products (ESP) elicit interleukin-6 (IL-6) and IL-10 secretion from intestinal epithelial cells (IPEC-1)

Immune responses to gastrointestinal helminth infections have received increasing attention due to similarities to allergen-induced responses. In fact, the whipworm parasite of swine, Trichuris suis, has been used in beginning clinical trials as an antidote to inflammatory bowel disease. This strategy was based on this similarity and the recognition that other worms have been documented to induce anti-inflammatory responses in the host. In an effort to understand the basis for this response, we hypothesized that the proteins and peptides secreted by T. suis stimulate local intestinal epithelial cells to produce anti-inflammatory cytokines. To test this hypothesis in a correlate system of the natural swine host, T. suis excretory secretory products (ESP) were used to treat both differentiated and undifferentiated intestinal pig epithelial cells (IPEC-1) in vitro as a model for the effect on villus tip and crypt epithelial cells in the vicinity of the worms. IPEC-1 were exposed to low-level doses (0.3mg/ml) of T. suis ESP, and IL-4, IL-6 and IL-10 cytokine responses were measured by an enzyme-linked immunosorbant assay (ELISA). IL-6 was the predominant cytokine produced, accompanied by moderate IL-10 secretion from both differentiated and undifferentiated cells. As expected, IL-4 was not produced by IPEC-1. Additionally, IL-6 and IL-10 cytokines were produced within 24h, suggesting that these two cytokines form part of the primary host response to T. suis infections. These data suggest that T. suis ESP could enhance host immune responses and modulation through the induction of enteric IL-6 and IL-10.

Production of eosinophil chemoattractant activity by ovine gastrointestinal nematodes

Eosinophilia is a well documented feature of helminth infections but the precise nature of the interaction between parasite and eosinophil remains an enigma. This paper describes experiments demonstrating that ruminant gastrointestinal trichostrongyles produce potent chemoattractant activity for ovine bone marrow-derived eosinophils in vitro. This activity was initially identified as a constituent of whole worm extracts of third and fourth larval (L3, L4), and adult stages of Teladorsagia circumcincta, and adult Haemonchus contortus. Similar activity was detected in excretory/secretory (E/S) material derived from live T. circumcincta L3. Subsequently, by adapting the assay technique to incorporate live worms directly into the system, it was shown that L3 of both T. circumcincta and H. contortus produced eosinophil chemoattractant activity. In contrast, neither whole worm extracts, or E/S preparations from mixed stages of the free-living nematode Caenorhabditis elegans contained eosinophil chemoattractant activity, and there was no evidence of chemoattractant production by live C. elegans. The results described are challenging to the traditional dogma that eosinophils are host-protective effector cells, and raise the intriguing possibility that ovine nematodes actively encourage recruitment of eosinophils. Local eosinophil-mediated mucosal damage, comparable to that seen in the asthmatic lung, may then provide a permissive local microenvironment for the parasite. Moreover, if they prove important for pathogenicity, nematode chemoattractants could offer future potential as novel therapeutic targets.

Lung-migrating digenean parasites: in vitro influence on nitric oxide production from normal rat pulmonary macrophages

Nitric oxide (NO) is one of the most versatile players in the immune system. Most parasites induce inflammation in the host associated with NO production. Here, we compare the in vitro effect of Schistosoma bovis somatic (SbS) and excretory-secretory (SbES) antigens, and excretory-secretory Paragonimus mexicanus adult worm (PmES) molecules on rat alveolar macrophages NO production measured by the Griess method and by RT-PCR. Additionally, we address the divergence of the NO stimulatory/inhibitory effects of these two parasites. Polymyxin B was used to assess possible LPS contamination. In vitro incubation of rat alveolar macrophages with PmES (10 microg/ml) and SbS (50 microg/ml), but not with SbES extracts, resulted in NO production and an increase in iNOS cell mRNA. This production was specific and inhibited by L-NAME and L-canavanine. Different effects were observed when cells were incubated with P. mexicanus and S. bovis antigens.

Biochemical assessment of intracellular signal transduction pathways in eosinophils: implications for pharmacotherapy

Allergic asthma and allergic rhinitis are inflammatory diseases of the airway. Cytokines and chemokines produced by T helper (Th) type 2 cells (GM-CSF, IL-4, IL-5, IL-6, IL-9, IL-10 and IL-13), eotaxin, transforming growth factor-beta, and IL-11 orchestrate most pathophysiological processes of the late-phase allergic reaction, including the recruitment, activation, and delayed apoptosis of eosinophils, as well as eosinophilic degranulation to release eosinophilic cationic protein, major basic protein, and eosinophil-derived neurotoxin. These processes are regulated through an extensive network of interactive intracellular signal transduction pathways that have been intensively investigated recently. Our present review updates the cytokine and chemokine-mediated signal transduction mechanisms including the RAS-RAF-mitogen-activated protein kinases, Janus kinases (signal transducers and activators of transcription), phosphatidylinositol 3-kinase, nuclear factor-kappa B, activator protein-1, GATA, and cyclic AMP-dependent pathways, and describes the roles of different signaling pathways in the regulation of eosinophil differentiation, recruitment, degranulation, and expression of adhesion molecules. We shall also discuss different biochemical methods for the assessment of various intracellular signal transduction molecules, and various antagonists of receptors, modulators, and inhibitors of intracellular signaling molecules, many of which are potential therapeutic agents for treating allergic diseases.

Caspase-3-mediated apoptosis of human eosinophils by the tissue-invading helminth Paragonimus westermani

BACKGROUND

Eosinophils are important cells in host immunity to infections by parasitic worms. Tissue-invasive helminthic parasites have been known to induce apoptosis of immune cells for their successful establishment in vivo. We have previously found that high doses of excretory-secreted products (ESP) secreted by lung fluke Paragonimus westermani newly excysted metacercariae (PwNEM), which cause pulmonary or extrapulmonary paragonimiasis in human beings, accelerate eosinophil cell death. However, little is known about the mechanism of eosinophil apoptosis induced by the Paragonimus-derived products.

OBJECTIVE

We examined involvement of caspase 3 activation in eosinophil cell death induced by ESP produced by PwNEM.

METHODS

Eosinophils were isolated from the peripheral blood of healthy donors by CD16-negative immunomagnetic selection. We examined the inhibitory effect of pan-caspase inhibitor on ESP-triggered phosphatidylserine (PS) externalization on the outer surface of eosinophils and intracellular activation of caspase 3 in cell lysates treated with the ESP.

RESULTS

When ESP secreted by PwNEM were incubated for up to 3 h with eosinophils, they increased surface exposure of PS on eosinophils in a time- and dose-dependent manner. This proapoptotic effect of the ESP on eosinophils was significantly inhibited by pretreatment of cells with pan-caspase inhibitor z-VAD-fmk, and was completely abolished by heat inactivation of ESP at 56 degrees C. The activated forms of caspase 3 were also clearly detected in eosinophils incubated with ESP. Moreover, ESP potently inhibited prolonged survival of eosinophils induced by cytokines such as IL-5, IL-3, and GM-CSF.

CONCLUSION

These results suggest that ESP secreted by PwNEM contain biological active factors causing caspase-3-mediated apoptosis of human eosinophils, thereby enabling the larvae to evade and to subvert the tackle by eosinophils during the early phase of the infection.