Critical role for signal transducer and activator of transcription factor 6 in mediating intestinal muscle hypercontractility and worm expulsion in Trichinella spiralis-infected mice

The Role of Inflammatory Mediators in the Development of Gastrointestinal Motility Disorders

Feeding intolerance and the development of ileus is a common complication affecting critically ill, surgical, and trauma patients, resulting in prolonged intensive care unit and hospital stays, increased infectious complications, a higher rate of hospital readmission, and higher medical care costs. Medical treatment for ileus is ineffective and many of the available prokinetic drugs have serious side effects that limit their use. Despite the large number of patients affected and the consequences of ileus, little progress has been made in identifying new drug targets for the treatment of ileus. Inflammatory mediators play a critical role in the development of ileus, but surprisingly little is known about the direct effects of inflammatory mediators on cells of the gastrointestinal tract, and many of the studies are conflicting. Understanding the effects of inflammatory cytokines/chemokines on the development of ileus will facilitate the early identification of patients who will develop ileus and the identification of new drug targets to treat ileus. Thus, herein, we review the published literature concerning the effects of inflammatory mediators on gastrointestinal motility.

Trichuris muris Model: Role in Understanding Intestinal Immune Response, Inflammation and Host Defense

Several parasites have evolved to survive in the human intestinal tract and over 1 billion people around the world, specifically in developing countries, are infected with enteric helminths. Trichuris trichiura is one of the world’s most common intestinal parasites that causes human parasitic infections. Trichuris muris, as an immunologically well-defined mouse model of T. trichiura, is extensively used to study different aspects of the innate and adaptive components of the immune system. Studies on T. muris model offer insights into understanding host immunity, since this parasite generates two distinct immune responses in resistant and susceptible strains of mouse. Apart from the immune cells, T. muris infection also influences various components of the intestinal tract, especially the gut microbiota, mucus layer, epithelial cells and smooth muscle cells. Here, we reviewed the different immune responses generated by innate and adaptive immune components during acute and chronic T. muris infections. Furthermore, we discussed the importance of studying T. muris model in understanding host–parasite interaction in the context of alteration in the host’s microbiota, intestinal barrier, inflammation, and host defense, and in parasite infection-mediated modulation of other immune and inflammatory diseases.

Th2 signals are not essential for the anti-arthritic effects of Trichinella spiralis in mice

AIMS

Many parasitic helminths are known to alter host immune responses and consequently affect the progression of autoimmune and allergic diseases. The parasitic nematode Trichinella sp has been reported to suppress several experimental diseases in rodents, including experimental autoimmune encephalomyelitis, type 1 diabetes, colitis, airway inflammation and autoimmune arthritis. We tried to clarify requirement of Th2 cytokines in the anti-arthritic effects of Trichinella spiralis (Ts) against collagen-induced arthritis (CIA).

METHODS AND RESULTS

We infected Ts and then induced CIA in STAT6KO DBA/1 mice, comparing the disease progression with that in wild-type (WT) DBA/1 mice, Ts significantly mitigated arthritis in WT mice, in addition to the impairment of anti-type II collagen (IIC) IgG production in a subclass-independent manner. The genetic absence of STAT6 in the mice did not abrogate the anti-arthritic effects of Ts. Alteration of splenic cytokines was not related to the anti-arthritic effects of the parasite. Moreover, lack of IL-10 did not abrogate the anti-arthritic effects of Ts.

CONCLUSION

Our results suggest that the anti-arthritic effects of Ts do not require host Th2 signals.

TGFβ-activation by dendritic cells drives Th17 induction and intestinal contractility and augments the expulsion of the parasite Trichinella spiralis in mice

Helminths are highly prevalent metazoan parasites that infect over a billion of the world's population. Hosts have evolved numerous mechanisms to drive the expulsion of these parasites via Th2-driven immunity, but these responses must be tightly controlled to prevent equally devastating immunopathology. However, mechanisms that regulate this balance are still unclear. Here we show that the vigorous Th2 immune response driven by the small intestinal helminth Trichinella spiralis, is associated with increased TGFβ signalling responses in CD4+ T-cells. Mechanistically, enhanced TGFβ signalling in CD4+ T-cells is dependent on dendritic cell-mediated TGFβ activation which requires expression of the integrin αvβ8. Importantly, mice lacking integrin αvβ8 on DCs had a delayed ability to expel a T. spiralis infection, indicating an important functional role for integrin αvβ8-mediated TGFβ activation in promoting parasite expulsion. In addition to maintaining regulatory T-cell responses, the CD4+ T-cell signalling of this pleiotropic cytokine induces a Th17 response which is crucial in promoting the intestinal muscle hypercontractility that drives worm expulsion. Collectively, these results provide novel insights into intestinal helminth expulsion beyond that of classical Th2 driven immunity, and highlight the importance of IL-17 in intestinal contraction which may aid therapeutics to numerous diseases of the intestine.

The DH31/CGRP enteroendocrine peptide triggers intestinal contractions favoring the elimination of opportunistic bacteria

The digestive tract is the first organ affected by the ingestion of foodborne bacteria. While commensal bacteria become resident, opportunistic or virulent bacteria are eliminated from the gut by the local innate immune system. Here we characterize a new mechanism of defense, independent of the immune system, in Drosophila melanogaster. We observed strong contractions of longitudinal visceral muscle fibers for the first 2 hours following bacterial ingestion. We showed that these visceral muscle contractions are induced by immune reactive oxygen species (ROS) that accumulate in the lumen and depend on the ROS-sensing TRPA1 receptor. We then demonstrate that both ROS and TRPA1 are required in a subset of anterior enteroendocrine cells for the release of the DH31 neuropeptide which activates its receptor in the neighboring visceral muscles. The resulting contractions of the visceral muscles favors quick expulsion of the bacteria, limiting their presence in the gut. Our results unveil a precocious mechanism of defense against ingested opportunistic bacteria, whether they are Gram-positive like Bacillus thuringiensis or Gram-negative like Erwinia carotovora carotovora. Finally, we found that the human homolog of DH31, CGRP, has a conserved function in Drosophila.

The intestine is the first barrier to fight non-commensal bacteria ingested along with the food. The innate immune system is the main mean mounted by the gut lining in response to ill-causing bacteria to avoid detrimental impact. Intestinal cells produce chlorine bleach and antimicrobial peptides that destroy exogenous bacteria. Here, we identified and characterized a new mechanism of gut defense that occurs rapidly after ingestion of exogenous bacteria. We found that the enteroendocrine cells perceive the presence of chlorine bleach in the lumen thanks to a sensor. This sensor promotes a calcium flux within enteroendocrine cells that allows the release of a hormone. This hormone acts locally on the visceral muscle surrounding the intestine by provoking its strong contractions (or spasms). We show that these strong but brief visceral contractions are helping to the quick expulsion of the ingested bacteria thus limiting their potential detrimental impact on the intestine. Markedly, the bleach-sensor is well known to be involved in pain. Therefore we have deciphered in this study a biological mechanism that has so far been described only empirically by medicine, potentially explaining intestinal pain and visceral spasms upon food poisoning.

Host Resistance Assays

The goal of immunotoxicity testing is to obtain data useful for immunotoxicity safety assessment. Guidance in the performance of immunotoxicity safety evaluations is provided in documents from the US EPA for chemicals and the ICH S8 document for pharmaceuticals. The ICH S8 document outlines a tiered approach that includes (1) standard toxicity studies with associated hematology, immune system organ weights, and histopathology data; (2) functional assays, such as cytotoxic T lymphocyte (CTL) assays, natural killer (NK) cell assays, respiratory burst, phagocytosis, and T-cell-dependent antibody response (TDAR) assays; and (3) host resistance assays. Host resistance assays are considered the gold standard in immunotoxicity testing and provide a critical overview of the extent to which innate, adaptive, and homeostatic regulatory immune functions are integrated to protect the host. Both comprehensive and targeted host resistance assays are available, each with distinct advantages. This chapter serves to provide a general overview of the various assays that may be used, as well as a summary of procedures.

Diverse Effects of Gut-Derived Serotonin in Intestinal Inflammation

The gut is the largest producer of serotonin or 5-hydroxytryptamine (5-HT) in the human body, and 5-HT has been recognized as an important signaling molecule in the gut for decades. There are two distinct sources of enteric 5-HT. Mucosal 5-HT is predominantly produced by enterochromaffin (EC) cells of the gastrointestinal (GI) tract, and neuronal 5-HT in the gut is produced by serotonergic neurons of the enteric nervous system (ENS). The quantity of mucosal 5-HT produced vastly eclipses the amount of neuronal 5-HT in the gut. Though it is difficult to separate the functions of neuronal and mucosal 5-HT, in the normal gut both types of enteric 5-HT work synergistically playing a prominent role in the maintenance of GI functions. In inflammatory conditions of the gut, like inflammatory bowel disease (IBD) recent studies have revealed new diverse functions of enteric 5-HT. Mucosal 5-HT plays an important role in the production of pro-inflammatory mediators from immune cells, and neuronal 5-HT provides neuroprotection in the ENS. Based on searches for terms such as "5-HT", "EC cell", "ENS", and "inflammation" in pubmed.gov as well as by utilizing pertinent reviews, the current review aims to provide an update on the role of enteric 5-HT and its immune mediators in the context of intestinal inflammation.

Immune responses in mice vaccinated with a DNA vaccine expressing serine protease-like protein from the new-born larval stage of Trichinella spiralis

Trichinella spiralis is a parasitic helminth that can infect almost all mammals, including humans. Trichinella spiralis infection elicits a typical type 2 immune responses, while suppresses type 1 immune responses, which is in favour of their parasitism. DNA vaccines have been shown to be capable of eliciting balanced CD4⁺ and CD8⁺ T cell responses as well as humoral immune responses in small-animal models, which will be advantage to induce protective immune response against helminth infection. In this study, serine protease (Ts-NBLsp) was encoded by a cDNA fragment of new-born T. spiralis larvae, and was inserted after CMV promoter to construct a DNA vaccine [pcDNA3·1(+)-Ts-NBLsp]. Ts-NBLsp expression was demonstrated by immunofluorescence. Sera samples were obtained from vaccinated mice, and they showed strong anti-Ts-NBLsp-specific IgG response. Mice immunized with the pcDNA3·1(+)-Ts-NBLsp DNA vaccine showed a 77·93% reduction in muscle larvae (ML) following challenge with T. spiralis ML. Our results demonstrate that the vaccination with pcDNA3·1(+)-Ts-NBLsp plasmid promoted the balance of type 1 and 2 immune responses and produced a significant protection against T. spiralis infection in mice.

M-RNA Gene Expression of INF-Γ and IL-10 during Intestinal Phase of Trichinella spiralis after Myrrh and Albendazole Treatment

BACKGROUND

The protective response developed against Trichinella spiralis infection provokes immune and inflammatory responses mediated by cytokines released from T helper cells. We aimed to evaluate the effect of albendazole or myrrh on the expression of IFN-γ and IL-10 in BALB/c mice infected with T. spiralis.

METHODS

This study was done at the Animal House of Faculty of Medicine, Assiut University (Assiut, Egypt) from April to December 2015. Mice were infected with 300 T. spiralis larvae and treated with albendazole (50 mg/kg per day) or myrrh (500 mg/kg per day) for 3 consecutive days post-infection (pi). The expression of INF-γ and IL-10 was detected in the intestinal tissue by reverse transcription (RT) PCR.

RESULTS

The expression of IFN-γ in mice treated with albendazole and myrrh was detected on days 3 and 15 pi respectively. In the control group, it was found on days 5, 10, 15 and 20 pi with the highest expression on day 15 pi. The expression of IL-10 was detected on days 3, 20 pi in the albendazole and myrrh treated groups, respectively. In the control group, IL-10 expression appeared on days 5 and day 20 pi.

CONCLUSION

The target of albendazole and myrrh on the profile of IFN-γ and IL-10 on these cytokines were encouraging to reinforce their therapeutic use against trichinellosis.

Developmental profile of select immune cells in mice infected with Trichinella spiralis during the intestinal phase

Trichinella spiralis can cause immunosuppression during the intestinal phase of early infection. However, changes in the peripheral blood during T. spiralis early infection remain unclear. Here, select immune cells in mice infected with 500 muscle larvae (ML) of T. spiralis during the intestinal phase of infection were studied. First, the recovery rates of the intestinal worms and female fecundity were determined, and the results showed that the intestinal worms were completely eliminated at 17 days post-infection (dpi) and that large numbers of new-born larvae (NBL) were generated from 5 to 9dpi. Using flow cytometry, it was shown that the number of CD4+ T cells and CD8+ T cells increased over the entire intestinal phase, except on 7dpi when CD4+ T cells decreased significantly compared to the control groups. Although both CD4+ and CD8+ T cells increased, CD8+ T cells increased more than CD4+ T cells, leading to a lower CD4+/CD8+ ratio compared to the control group. Subsequently, a depression of the proliferative response of T cells to concanavalin A (Con A) was noticed at 7 and 11dpi. Although the proliferative response of B cells to LPS was enhanced, the number of B cells from mouse peripheral blood stimulated by T. spiralis antigens showed no differences with the control group prior to 11dpi. The expression of CD14 on monocyte-macrophages decreased during the same period, which meant that the antigen-presenting response was reduced in the immune system of the infected mice. Moreover, the alternatively activated macrophages were induced in T. spiralis early infection. These data provide a better understanding of the development of the intestinal immune response in mice infected with T. spiralis.

Strategies targeting the IL-4/IL-13 axes in disease

IL-4 and IL-13 are pleiotropic Th2 cytokines produced by a wide variety of different cell types and responsible for a broad range of biology and functions. Physiologically, Th2 cytokines are known to mediate host defense against parasites but they can also trigger disease if their activities are dysregulated. In this review we discuss the rationale for targeting the IL-4/IL-13 axes in asthma, atopic dermatitis, allergic rhinitis, COPD, cancer, inflammatory bowel disease, autoimmune disease and fibrotic disease as well as evaluating the associated clinical data derived from blocking IL-4, IL-13 or IL-4 and IL-13 together.

Induction of protection in murine experimental models againstTrichinella spiralis: an up-to-date review

The parasitic nematodeTrichinella spiralis, an aetiological agent of the disease known as trichinellosis, infects wild and domestic animals through contaminated pig meat, which is the major source forTrichinellatransmission. Prevention of this disease by interrupting parasite transmission includes vaccine development for livestock; however, major challenges to this strategy are the complexity of theT. spiralislife cycle, diversity of stage-specific antigens, immune-evasion strategies and the modulatory effect of host responses. Different approaches have been taken to induce protective immune responses byT. spiralisimmunogens. These include the use of whole extracts or excretory–secretory antigens, as well as recombinant proteins or synthesized epitopes, using murine experimental models for trichinellosis. Here these schemes are reviewed and discussed, and new proposals envisioned to block the zoonotic transmission of this parasite.

Increased intestinal epithelial cell turnover and intestinal motility in Gymnophalloides seoi-infected C57BL/6 mice

The changing patterns of goblet cell hyperplasia, intestinal epithelial cell turnover, and intestinal motility were studied in ICR and C57BL/6 mice infected with Gymnophalloides seoi (Digenea: Gymnophallidae). Whereas ICR mice retained G. seoi worms until day 7 post-infection (PI), C57BL/6 mice showed a rapid worm expulsion within day 3 PI. Immunosuppression with Depo-Medrol significantly delayed the worm expulsion in C57BL/6 mice. Goblet cell counts were increased in both strains of mice, peaking at day 1 PI in C57BL/6 mice and slowly increasing until day 7 PI in ICR mice. In C57BL/6 mice infected with G. seoi, newly proliferating intestinal epithelial cells were remarkably increased in the crypt, and the increase was the highest at day 1 PI. However, in ICR mice, newly proliferating intestinal epithelial cells increased slowly from day 1 to day 7 PI. Intestinal motility was increased in G. seoi-infected mice, and its chronological pattern was highly correlated with the worm load in both strains of mice. Meanwhile, immunosuppression of C57BL/6 mice abrogated the goblet cell proliferation, reduced the epithelial cell proliferation, and suppressed the intestinal motility. Goblet cell hyperplasia, increased intestinal epithelial cell turnover, and increased intestinal motility should be important mucosal defense mechanisms in G. seoi-infected C57BL/6 mice.

Involvement of interleukin-17A-induced hypercontractility of intestinal smooth muscle cells in persistent gut motor dysfunction

BACKGROUND AND AIM

The etiology of post-inflammatory gastrointestinal (GI) motility dysfunction, after resolution of acute symptoms of inflammatory bowel diseases (IBD) and intestinal infection, is largely unknown, however, a possible involvement of T cells is suggested.

METHODS

Using the mouse model of T cell activation-induced enteritis, we investigated whether enhancement of smooth muscle cell (SMC) contraction by interleukin (IL)-17A is involved in postinflammatory GI hypermotility.

RESULTS

Activation of CD3 induces temporal enteritis with GI hypomotility in the midst of, and hypermotility after resolution of, intestinal inflammation. Prolonged upregulation of IL-17A was prominent and IL-17A injection directly enhanced GI transit and contractility of intestinal strips. Postinflammatory hypermotility was not observed in IL-17A-deficient mice. Incubation of a muscle strip and SMCs with IL-17A in vitro resulted in enhanced contractility with increased phosphorylation of Ser19 in myosin light chain 2 (p-MLC), a surrogate marker as well as a critical mechanistic factor of SMC contractility. Using primary cultured murine and human intestinal SMCs, IκBζ- and p38 mitogen-activated protein kinase (p38MAPK)-mediated downregulation of the regulator of G protein signaling 4 (RGS4), which suppresses muscarinic signaling of contraction by promoting inactivation/desensitization of Gαq/11 protein, has been suggested to be involved in IL-17A-induced hypercontractility. The opposite effect of L-1β was mediated by IκBζ and c-jun N-terminal kinase (JNK) activation.

CONCLUSIONS

We propose and discuss the possible involvement of IL-17A and its downstream signaling cascade in SMCs in diarrheal hypermotility in various GI disorders.

Signal transducer and activator of transcription factor 6 signaling contributes to control host lung pathology but favors susceptibility against Toxocara canis infection

Using STAT6(-/-) BALB/c mice, we have analyzed the role of STAT6-induced Th2 response in determining the outcome of experimental toxocariasis caused by embryonated eggs of the helminth parasite Toxocara canis. Following T. canis infection wild-type BALB/c mice developed a strong Th2-like response, produced high levels of IgG1, IgE, and IL-4, recruited alternatively activated macrophages, and displayed a moderate pathology in the lungs; however, they harbored heavy parasite loads in different tissues. In contrast, similarly infected STAT6(-/-) BALB/c mice mounted a weak Th2-like response, did not recruit alternatively activated macrophages, displayed a severe pathology in the lungs, but efficiently controlled T. canis infection. These findings demonstrate that Th2-like response induced via STAT6-mediated signaling pathway mediates susceptibility to larval stage of T. canis. Furthermore, they also indicate that unlike most gastrointestinal helminths, immunity against larvae of T. canis is not mediated by a Th2-dominant response.

Trichuris muris: a model of gastrointestinal parasite infection

Infection with soil-transmitted gastrointestinal parasites, such as Trichuris trichiura, affects more than a billion people worldwide, causing significant morbidity and health problems especially in poverty-stricken developing countries. Despite extensive research, the role of the immune system in triggering parasite expulsion is incompletely understood which hinders the development of anti-parasite therapies. Trichuris muris infection in mice serves as a useful model of T. trichiura infection in humans and has proven to be an invaluable tool in increasing our understanding of the role of the immune system in promoting either susceptibility or resistance to infection. The old paradigm of a susceptibility-associated Th1 versus a resistance-associated Th2-type response has been supplemented in recent years with cell populations such as novel innate lymphoid cells, basophils, dendritic cells and regulatory T cells proposed to play an active role in responses to T. muris infection. Moreover, new immune-controlled mechanisms of expulsion, such as increased epithelial cell turnover and mucin secretion, have been described in recent years increasing the number of possible targets for anti-parasite therapies. In this review, we give a comprehensive overview of experimental work conducted on the T. muris infection model, focusing on important findings and the most recent reports on the role of the immune system in parasite expulsion.

Signal Transducers and Activators of Transcription (STAT) family members in helminth infections

Helminth parasites are a diverse group of multicellular organisms. Despite their heterogeneity, helminths share many common characteristics, such as the modulation of the immune system of their hosts towards a permissive state that favors their development. They induce strong Th2-like responses with high levels of IL-4, IL-5 and IL-13 cytokines, and decreased production of proinflammatory cytokines such as IFN-γ. IL-4, IFN-γ and other cytokines bind with their specific cytokine receptors to trigger an immediate signaling pathway in which different tyrosine kinases (e.g. Janus kinases) are involved. Furthermore, a seven-member family of transcription factors named Signal Transducers and Activators of Transcription (STAT) that initiate the transcriptional activation of different genes are also involved and regulate downstream the JAK/STAT signaling pathway. However, how helminths avoid and modulate immune responses remains unclear; moreover, information concerning STAT-mediated immune regulation during helminth infections is scarce. Here, we review the research on mice deficient in STAT molecules, highlighting the importance of the JAK/STAT signaling pathway in regulating susceptibility and/or resistance in these infections.

Cytokine-induced alterations of gastrointestinal motility in gastrointestinal disorders

Inflammation and immune activation in the gut are usually accompanied by alteration of gastrointestinal (GI) motility. In infection, changes in motor function have been linked to host defense by enhancing the expulsion of the infectious agents. In this review, we describe the evidence for inflammation and immune activation in GI infection, inflammatory bowel disease, ileus, achalasia, eosinophilic esophagitis, microscopic colitis, celiac disease, pseudo-obstruction and functional GI disorders. We also describe the possible mechanisms by which inflammation and immune activation in the gut affect GI motility. GI motility disorder is a broad spectrum disturbance of GI physiology. Although several systems including central nerves, enteric nerves, interstitial cells of Cajal and smooth muscles contribute to a coordinated regulation of GI motility, smooth muscle probably plays the most important role. Thus, we focus on the relationship between activation of cytokines induced by adaptive immune response and alteration of GI smooth muscle contractility. Accumulated evidence has shown that Th1 and Th2 cytokines cause hypocontractility and hypercontractility of inflamed intestinal smooth muscle. Th1 cytokines downregulate CPI-17 and L-type Ca²⁺ channels and upregulate regulators of G protein signaling 4, which contributes to hypocontractility of inflamed intestinal smooth muscle. Conversely, Th2 cytokines cause hypercontractilty via signal transducer and activator of transcription 6 or mitogen-activated protein kinase signaling pathways. Th1 and Th2 cytokines have opposing effects on intestinal smooth muscle contraction via 5-hydroxytryptamine signaling. Understanding the immunological basis of altered GI motor function could lead to new therapeutic strategies for GI functional and inflammatory disorders.

Low-grade inflammation plays a pivotal role in gastrointestinal dysfunction in irritable bowel syndrome

The pathogenesis of irritable bowel syndrome (IBS) is considered to be multifactorial and includes psychosocial factors, visceral hypersensitivity, infection, microbiota and immune activation. It is becoming increasingly clear that low-grade inflammation is present in IBS patients and a number of biomarkers have emerged. This review describes the evidence for low-grade inflammation in IBS and explores its mechanism with particular focus on gastrointestinal motor dysfunction. Understanding of the immunological basis of the altered gastrointestinal motor function in IBS may lead to new therapeutic strategies for IBS.

Role of enteric nerves in immune-mediated changes in protease-activated receptor 2 effects on gut function

BACKGROUND

Protease-activated receptors (PARs) are expressed on structural and immune cells. Control of initiation, duration, and magnitude of PAR effects is linked to the level of receptor expression, availability of proteases, and the intracellular signal transduction machinery. We investigated nematode infection-induced changes in PAR(2) expression and the impact on smooth muscle and epithelial responses to PAR(2) agonists.

METHODS

Smooth muscle and epithelial cell function were assessed in wild-type, and IL-4, IL-13 or STAT6 gene-deficient mice following treatment with vehicle, Nippostrongylus brasiliensis or Heligmosomoides polygyrus, or IL-13. The role of enteric nerves was determined using tetrodotoxin to block nerve conduction. Expression of PAR(2) was assessed by real-time PCR, western blot and immunohistochemistry.

KEY RESULTS

Nematode infection induced a STAT6- and IL-13-dependent up-regulation of PAR(2) mRNA expression. The infection-induced hypercontractility to PAR(2) agonists required STAT6/IL-13 and was neurally mediated. In contrast, the infection-induced decrease in epithelial secretion to PAR(2) agonists was partly dependent on STAT6 and independent of enteric nerves. The hyposecretion was correlated with decreased PAR(2) immunofluorescent staining on the apical surface of epithelial cells, but enhanced lamina propria immunostaining for PAR(2).

CONCLUSIONS & INFERENCES

This is the first study to demonstrate an immune regulation of PAR(2) expression that impacts both smooth muscle and epithelial cell responses to PAR(2) agonists. Differences in responses between smooth muscle and epithelial cells are related to the contribution of enteric nerves. These data provide a mechanism by which activation of PAR(2) in immune-based pathologies can induce both transient and long-lasting changes in gut function.

Low-grade inflammation plays a pivotal role in gastrointestinal dysfunction in irritable bowel syndrome

The pathogenesis of irritable bowel syndrome (IBS) is considered to be multifactorial and includes psychosocial factors, visceral hypersensitivity, infection, microbiota and immune activation. It is becoming increasingly clear that low-grade inflammation is present in IBS patients and a number of biomarkers have emerged. This review describes the evidence for low-grade inflammation in IBS and explores its mechanism with particular focus on gastrointestinal motor dysfunction. Understanding of the immunological basis of the altered gastrointestinal motor function in IBS may lead to new therapeutic strategies for IBS.

Persistent gut motor dysfunction in a murine model of T-cell-induced enteropathy

BACKGROUND

Inflammatory bowel disease (IBD) patients in remission often experience irritable bowel syndrome (IBS)-like symptoms. We investigated the mechanism for intestinal muscle hypercontractility seen in T-cell-induced enteropathy in recovery phase.

METHODS

BALB/c mice were treated with an anti-CD3 antibody (100 microg per mouse) and euthanized at varying days post-treatment to investigate the histological changes, longitudinal smooth muscle cell contraction, cytokines (Th1, Th2 cytokines, TNF-alpha) and serotonin (5-HT)-expressing enterochromaffin cell numbers in the small intestine. The role of 5-HT in anti-CD3 antibody-induced intestinal muscle function in recovery phase was assessed by inhibiting 5-HT synthesis using 4-chloro-DL-phenylalanine (PCPA).

KEY RESULTS

Small intestinal tissue damage was observed from 24 h after the anti-CD3 antibody injection, but had resolved by day 5. Carbachol-induced smooth muscle cell contractility was significantly increased from 4 h after injection, and this muscle hypercontractility was evident in recovery phase (at day 7). Th2 cytokines (IL-4, IL-13) were significantly increased from 4 h to day 7. 5-HT-expressing cells in the intestine were increased from day 1 to day 7. The 5-HT synthesis inhibitor PCPA decreased the anti-CD3 antibody-induced muscle hypercontractility in recovery phase.

CONCLUSIONS & INFERENCES

Intestinal muscle hypercontractility in remission is maintained at the smooth muscle cell level. Th2 cytokines and 5-HT in the small intestine contribute to the maintenance of the altered muscle function in recovery phase.

Parasite challenge as host resistance models for immunotoxicity testing

Identification of potentially immunosuppressive compounds typically involves assessing a combination of observational endpoints as surrogates for functional endpoints and functional endpoints as surrogates for resistance to infectious or neoplastic disease. Host resistance assays are considered to be the "gold standard" against which suppression of immune function at the molecular or cellular level can be judged, because resistance to infection, regardless of the actual pathogen, involves multiple pathways of effector function to neutralize or eliminate pathogens. Resistance to infection with the parasitic nematode Trichinella spiralis has been used to assess immune function following exposure to a variety of immunotoxicants at the whole animal level. The various immunological mechanisms that are responsible for resistance to different phases of the life cycle are well documented, as are the effects of immunosuppression on the outcome of infection. This chapter describes methods to assess elimination of adult parasites from the small intestine, body burdens of larvae, as well as antibody responses and lymphocyte responses to parasite antigens.

CD40 and the immune response to parasitic infections

The interaction between CD40 and CD154 regulates many aspects of cellular and humoral immunity. The CD40-CD154 pathway is important for resistance against a variety of parasites. Studies done with these pathogens have provided important insight into the various mechanisms by which this pathway enhances host protection, mechanisms by which pathogens subvert CD40 signaling, conditions in which the CD40-CD154 pathway promotes disease and on modulation of this pathway for immunotherapy.

The roles of eotaxin and the STAT6 signalling pathway in eosinophil recruitment and host resistance to the nematodes Nippostrongylus brasiliensis and Heligmosomoides bakeri

Expulsion of adult Nippostrongylus brasiliensis worms from the small intestine is profoundly impaired in signal transducer and activator of transcription (STAT)6-deficient mice. IL-5 transgenic (Tg) mice with constitutive eosinophilia show profound early resistance in the skin and/or later pre-lung phase of primary infections with N. brasiliensis. This study was designed to assess the importance of the eosinophil chemokine eotaxin and the STAT6/interleukin (IL)-4/IL-13 signalling pathway in early resistance to N. brasiliensis. Eosinophil recruitment into the skin following injection of N. brasiliensis larvae was reduced in STAT6- or eotaxin-deficient/IL-5 Tg double mutant mice. While ablation of eotaxin did not impair resistance in the pre-lung phase of N. brasiliensis infections in IL-5 Tg mice, elimination of STAT6 caused a modest reduction in resistance in both primary and secondary infections on this genetic background. STAT6(-/-)-, IL-13(-/-)- and IL-4Ralpha(-/-)-deficient single mutant and IL-13(-/-)/IL-4Ralpha(-/-) double mutant mice were more susceptible than WT mice during the pre-lung phase of secondary N. brasiliensis infections. In contrast, primary or secondary resistance were unaffected at either the pre-lung or gut stages of infection in eotaxin(-/-) single mutant mice. STAT6(-/-) and eotaxin(-/-) mice with or without the IL-5 transgene, were no more susceptible than WT or IL-5 Tg mice to protracted primary infections with Heligmosomoides bakeri, a parasitic nematode that is restricted to the gut. Our data suggest that parasitic nematodes that transit through the skin and lungs en route to the gut may be susceptible to early (pre-lung) innate and adaptive immune mechanisms that are dependent on the STAT6/IL-4/IL-13 signalling pathway, and this may be important for the development of effective therapies and vaccines.

Physiological changes in the gastrointestinal tract and host protective immunity: learning from the mouse-Trichinella spiralis model

Infection and inflammation in the gastrointestinal (GI) tract induces a number of changes in the GI physiology of the host. Experimental infections with parasites represent valuable models to study the structural and physiological changes in the GI tract. This review addresses research on the interface between the immune system and GI physiology, dealing specifically with 2 major components of intestinal physiology, namely mucin production and muscle function in relation to host defence, primarily based on studies using the mouse-Trichinella spiralis system. These studies demonstrate that the infection-induced T helper 2 type immune response is critical in generating the alterations of infection-induced mucin production and muscle function, and that this immune-mediated alteration in gut physiology is associated with host defence mechanisms. In addition, by manipulating the host immune response, it is possible to modulate the accompanying physiological changes, which may have clinical relevance. In addition to enhancing our understanding of immunological control of GI physiological changes in the context of host defence against enteric infections, the data acquired using the mouse-T. spiralis model provide a basis for understanding the pathophysiology of a wide range of GI disorders associated with altered gut physiology.

Functional group/guild modelling of inter-specific pathogen interactions: a potential tool for predicting the consequences of co-infection

Although co-infection is the norm in most human and animal populations, clinicians currently have no practical tool to assist them in choosing the best treatment strategy for such patients. Given the vast range of potential pathogens which may co-infect the host, obtaining such a practical tool may seem an intractable problem. In ecology the joint concepts of functional groups and guilds have been used to conceptually simplify complex ecosystems, in order to understand how their component parts interact and may be manipulated. Here we propose a mechanism by which to apply these concepts to pathogen co-infection systems. Further, we describe how these groups could be incorporated into a mathematical modelling framework which, after validation, could be used as a clinical tool to predict the outcome of any particular combination of pathogens co-infecting a host.

Innate immune response mechanisms in the intestinal epithelium: potential roles for mast cells and goblet cells in the expulsion of adult Trichinella spiralis

SUMMARYGastrointestinal infection with the nematode Trichinella spiralis is accompanied by a rapid and reversible expansion of the mucosal mast cell and goblet cell populations in the intestinal epithelium, which is associated with the release of their mediators into the gut lumen. Both goblet cell and mast cell hyperplasia are highly dependent on mucosal T-cells and augmented by the cytokines IL-4 and IL-13. However, the contribution of both mast and goblet cells, and the mediators they produce, to the expulsion of the adults of T. spiralis is only beginning to be elucidated through studies predominantly employing T. spiralis-mouse models. In the present article, we review the factors proposed to control T. spiralis-induced mucosal mast cell (MMC) and goblet cell differentiation in the small intestine, and focus on some key MMC and goblet cell effector molecules which may contribute to the expulsion of adult worms and/or inhibition of larval development.

Mast cell-mediated changes in smooth muscle contractility during mouse giardiasis

Giardia intestinalis is a significant cause of diarrheal disease worldwide. Infections in animal models have been shown to cause changes in gastrointestinal transit that depend on adaptive immune responses and are mediated, in part, through neuronal nitric oxide synthase. Nitric oxide is an inhibitory neurotransmitter, and we therefore investigated potential excitatory pathways that might be involved in the response to Giardia infection. Infected mice exhibited increased spontaneous and cholecystokinin (CCK)-induced contractions of longitudinal smooth muscle. In contrast, enhanced contractile responses were not observed in response to acetylcholine, 5-hydroxytryptamine, or the protease-activated receptor-1 agonist peptide TFFLR. Giardia-induced changes in smooth muscle function appear to be mediated primarily by mast cells, as both spontaneous and CCK-induced contractions were blocked by pretreatment with either ketotifen or compound 48/80. Together, these data support a model in which CCK release triggers mast cell degranulation, leading to increases in smooth muscle contractility. These contractions, coupled with nitric oxide-mediated muscle relaxation, promote intestinal transit and parasite elimination.

Cytokine modulation of muscarinic receptors in the murine intestine

The extent to which gut motility and smooth muscle contractility are altered by intestinal inflammation depends on the nature of the underlying immune activation. The muscarinic receptor on smooth muscle plays a critical role in mediating acetylcholine-driven motor function. We examined the ability of cytokines to influence muscarinic receptor characteristics on intestinal longitudinal muscle and related the findings to studies on carbachol-induced contraction. Cells were isolated from longitudinal muscle myenteric plexus (LMMP). Cytokine receptor expression, muscle contractility, and muscarinic agonist receptor characteristics were examined by agonist displacement of [N-methyl-(3)H]scopolamine ([(3)H]NMS) binding. The TGF-beta1 receptor (543 bp) and the IFN-gamma receptor 1 (660 bp) were identified on smooth muscle cells. Scatchard analysis revealed dissociation constant and maximum binding values for [(3)H]NMS of 2.6 nM and 2.4 x 10(4) sites/cell, respectively, in control cells. Nematode infection was accompanied by a reduction in inhibitory constant of the high-affinity sites (K(H)), and this was independent of signal transduction and activator of transcription 6. Preincubation with TGF-beta1 enhanced longitudinal muscle contractility and decreased the K(H) to 2.2 pM (increased muscarinic receptor affinity), whereas preincubation with IFN-gamma increased the K(H) to 0.4 muM (decreased muscarinic receptor affinity) and decreased longitudinal muscle contractility. Preincubation of LMMP with IL-13 decreased the K(H) to 0.2 nM. Cytokines exert differential effects on the muscarinic receptor on intestinal longitudinal smooth muscle. These findings explain the basis for altered muscle contractility observed in Th1 and Th2 models of inflammation, as well as in the post-nematode-infected state.

IL-10 Regulates Movement of Intestinally Derived CD4+T Cells to the Liver

Diseases that affect the intestine may have hepatic manifestations, but the mechanisms involved in establishing hepatic disease secondarily remain poorly understood. We previously reported that IL-10 knockout (KO) mice developed severe necrotizing hepatitis following oral infection with Trichinella spiralis. In this study, we used this model of intestinal inflammation to further examine the role of IL-10 in regulating hepatic injury. Hepatic damage was induced by migrating newborn larvae. By delivering the parasite directly into the portal vein, we demonstrated that an ongoing intestinal immune response was necessary for the development of hepatitis. Intestinally derived CD4+ cells increased in the livers of IL-10 KO mice, and Ab-mediated blockade of MAdCAM-1 inhibited the accumulation of CD4+alpha(4)beta(7)+ cells in the liver. Moreover, adoptive transfer of intestinally primed CD4+ T cells from IL-10 KO mice caused hepatitis in infected immunodeficient animals. Conversely, transfer of wild-type donor cells reduced the severity of hepatic inflammation in IL-10 KO recipients, demonstrating regulatory activity. Our results revealed that IL-10 prevented migration of intestinal T cells to the liver and inhibited the development of hepatitis.

Nematodes as host resistance models for detection of immunotoxicity

Greater susceptibility to infection is a hallmark of compromised immune function in humans and animals, and is often considered the benchmark against which the predictive value of immune function tests are compared. The focus of this paper is resistance to infection with the parasitic nematode Trichinella spiralis as a model of host resistance. Topics include overviews of parasite biology, host immune responses that limit infection and methods used to evaluate the host response to infection. Detailed protocols are provided for adult and larval parasite counts, female parasite fecundity, parasite antigen-driven lymphocyte proliferation and antibody responses to infection.

IL-4 gene transfer to the small bowel serosa leads to intestinal inflammation and smooth muscle hyperresponsiveness

Intestinal mucosal inflammation can lead to altered function of the underlying smooth muscle, which becomes hyperreactive to most contractile stimuli. Through nematode parasite infection models, T helper type 2 (Th2) cytokines have been implicated in intestinal muscle dysfunction; however, the mechanisms involved and the relevance of these findings to other forms of intestinal inflammation are unclear. Through gene transfer, we explored whether the Th2 cytokine IL-4 can mediate changes in longitudinal muscle function in the context of an adenoviral infection. Following abdominal surgery on mice, control beta-galactosidase-encoding recombinant adenoviruses and IL-4-encoding adenoviruses were applied to the serosal surface of the jejunum, leading to infection of cells in the serosa and in the mesentery. Marker transgene expression lasted for 3 wk and was accompanied by the recruitment of macrophages, lymphocytes, and neutrophils into the peritoneal cavity and mild inflammation at the site of infection. IL-4 transgene expression led to a stronger inflammatory response characterized by tissue eosinophilia and increased numbers of peritoneal mast cells and plasma cells. Whereas control virus infection had no effect on intestinal muscle function, infection with the IL-4 virus led to significant jejunal muscle hypercontractility, evident by day 7 postinfection. This modulation of smooth muscle function was shown to be IL-4 specific, since the application of an IL-5-encoding adenovirus induced tissue eosinophilia but did not alter muscle function. These results highlight an important causal role for IL-4 in the pathological regulation of enteric smooth muscle function and identify a novel strategy for gene transfer to the intestine.

Gut motor function: immunological control in enteric infection and inflammation

Alteration in gastrointestinal (GI) motility occurs in a variety of clinical settings which include acute enteritis, inflammatory bowel disease, intestinal pseudo-obstruction and irritable bowel syndrome (IBS). Most disorders affecting the GI tract arise as a result of noxious stimulation from the lumen via either microbes or chemicals. However, it is not clear how injurious processes initiated in the mucosa alter function in the deeper motor apparatus of the gut wall. Activation of immune cells may lead to changes in motor-sensory function in the gut resulting in the development of an efficient defence force which assists in the eviction of the noxious agent from the intestinal lumen. This review addresses the interface between immune and motor system in the context of host resistance based on the studies in murine model of enteric nematode parasite infection. These studies clearly demonstrate that the infection-induced T helper 2 type immune response is critical in producing the alterations of infection-induced intestinal muscle function in this infection and that this immune-mediated alteration in muscle function is associated with host defence mechanisms. In addition, by manipulating the host immune response, it is possible to modulate the accompanying muscle function, and this may have clinical relevance. These observations not only provide valuable information on the immunological control of gut motor function and its role in host defence in enteric infection, but also provide a basis for understanding pathophysiology of gastrointestinal motility disorders such as in IBS.

Mechanisms underlying the maintenance of muscle hypercontractility in a model of postinfective gut dysfunction

BACKGROUND & AIMS

Acute gastroenteritis is a strong risk factor for the development of irritable bowel syndrome (IBS). We have developed an animal model in which transient acute infection leads to persistent muscle hypercontractility. Here, we investigate the mechanisms underlying the maintenance of this hypercontractility in the postinfective (PI) state.

METHODS

Muscle contraction and messenger RNA (mRNA) or protein expression of cytokines were examined from jejunal longitudinal muscle cells of NIH Swiss mice infected with Trichinella spiralis or incubated with or without cytokines.

RESULTS

During acute infection, interleukin (IL)-4 or IL-13, transforming growth factor (TGF)-beta1, and cyclooxygenase (COX)-2 were increased in the muscle layer ( P < .05). In the PI phase of the model, T helper (Th)2 cytokines returned to normal, but TGF-beta1 remained in the muscle ( P < .05). Exposure of muscle cells to IL-4 or IL-13 increased TGF-beta1 ( P < .01), COX-2 protein, and prostaglandin (PG)E 2 . Exposure of muscle cells to TGF-beta1 increased PGE 2 ( P < .05) and COX-2 protein. Incubation of tissue with IL-4, IL-13, TGF-beta1, or PGE 2 enhanced carbachol-induced muscle cell contractility ( P < .05). COX-2 inhibitor attenuated TGF-beta1-induced muscle hypercontractility ( P < .05).

CONCLUSIONS

These results support the hypothesis that Th2 cytokines induce muscle hypercontractility during infection by a direct action on smooth muscle. The maintenance of hypercontractility results from Th2 cytokine-induced expression of TGF-beta1 and the subsequent up-regulation of COX-2 and PGE 2 at the level of the smooth muscle cell. We propose that PI gut dysfunction reflects mediator production in the neuromuscular tissues and that this may occur in PI-IBS.

Immune-mediated alteration in gut physiology and its role in host defence in nematode infection

Activation of the mucosal immune system of the gastrointestinal tract in nematode infection results in altered intestinal physiology, which includes changes in intestinal motility and mucus production. These changes are considered to be under direct immunological control rather than a non-specific consequence of the inflammatory reaction to the infective agent. However, little is known about the immunological basis for the changes in intestinal physiology accompanying nematode infection, or the precise role of these changes in host defence, which remains an important area to explore. In this review we describe the mechanisms by which the immune response to nematode infection influences the changes in two major cells of intestinal physiology, namely smooth muscle and goblet cells, and how these changes in intestinal physiology contribute to the host defence. Data clearly demonstrate that the T helper (Th) 2 type immune response generated by nematode infection plays an important role in the development of infection-induced intestinal muscle hypercontractility and goblet cell hyperplasia and that these immune-mediated changes in intestinal physiology are associated with worm expulsion. These observations strongly suggest that intestinal muscle contractility, goblet cell hyperplasia and worm expulsion share a common immunological basis and may be causally related. These data not only provide insights into host defence in nematode infection in the context of muscle function and goblet cell response, but also have broad implications in elucidating the pathophysiology of a wide range of gastrointestinal disorders associated with altered gut physiology.

Interleukin-4- and -13-induced hypercontractility of human intestinal muscle cells-implication for motility changes in Crohn's disease

Crohn's disease is an idiopathic inflammatory condition. However, little is known about the changes that occur in the muscularis externa, despite the fact that this tissue contributes to motility changes and stricture formation. We characterized immune activity in the muscularis externa from intestinal segments of Crohn's disease patients and evaluated the role of IL-4 and -13 as well as signal transducer and activator of transcription (STAT)6 in the contractility of the cultured human intestinal smooth muscle cells. CD3+ve cells (P < 0.01) and IL-4 protein (P < 0.01) were significantly increased in the muscularis externa of Crohn's disease patients compared with noninflamed controls. Preincubation of human cultured smooth muscle cells with IL-4 (P < 0.001) or IL-13 (P < 0.05) significantly enhanced carbachol-induced contraction, and this was significantly inhibited by the STAT6 inhibitor leflunomide (P < 0.0001). A similar profile was observed in muscle cells isolated from Crohn's disease patients. Both IL-4 and IL-13 increased specific STAT6-DNA binding in control cells, and this was inhibited by anti-STAT6 Ab (P < 0.05) or leflunomide (P < 0.05). IL-4 and IL-13 mediate the hypercontractility of intestinal muscle via a STAT6 pathway at the level of the smooth muscle cell. The STAT6 pathway may contribute to the hypercontractility of intestinal muscle in Crohn's disease.

Quantitative appraisal of murine filariasis confirms host strain differences but reveals that BALB/c females are more susceptible than males to Litomosoides sigmodontis

Litomosoides sigmodontis, a rodent filarial nematode, can infect inbred laboratory mice, with full development to patency in the BALB/c strain. Strains such as C57BL/6 are considered resistant, because although filarial development can occur, circulating microfilariae are never detected. This model system has, for the first time, allowed the power of murine immunology to be applied to fundamental questions regarding susceptibility to filarial nematode infection. As this is a relatively new model, many aspects of the biology remain to be discovered or more clearly defined. We undertook a major analysis of 85 experiments, to quantitatively assess differences in filarial survival and reproduction in male versus female and BALB/c versus C57BL/6 mice over the full course of infection. This large dataset provided hard statistical support for previous qualitative reviews, including observations that the resistant phenotype of C57BL/6 mice is detectable as early as 10 days postinfection (dpi). An unexpected finding, however, was that filarial survival was reduced in male BALB/c mice compared to their female counterparts. Worm recovery as well as the prevalence and density of microfilariae were higher in female compared with male BALB/c mice. Therefore, L. sigmodontis bucks the filarial trend of increased susceptibility in males. This could be partially explained by the different anatomical locations of adult L. sigmodontis versus lymphatic filariae. Interestingly, the effects of BALB/c sex upon microfilaremia were independent of worm number. In summary, this study has significantly refined our understanding of the host-L. sigmodontis relationship and, critically, has challenged the dogma that males are more susceptible to filarial infection.

Helminth parasites--masters of regulation

Immune regulation by parasites is a global concept that includes suppression, diversion, and conversion of the host immune response to the benefit of the pathogen. While many microparasites escape immune attack by antigenic variation or sequestration in specialized niches, helminths appear to thrive in exposed extracellular locations, such as the lymphatics, bloodstream, or gastrointestinal tract. We review here the multiple layers of immunoregulation that have now been discovered in helminth infection and discuss both the cellular and the molecular interactions involved. Key events among the host cell population are dominance of the T-helper 2 cell (Th2) phenotype and the selective loss of effector activity, against a background of regulatory T cells, alternatively activated macrophages, and Th2-inducing dendritic cells. Increasingly, there is evidence of important effects on other innate cell types, particularly mast cells and eosinophils. The sum effect of these changes to host reactivity is to create an anti-inflammatory environment, which is most favorable to parasite survival. We hypothesize therefore that parasites have evolved specific molecular strategies to induce this conducive landscape, and we review the foremost candidate immunomodulators released by helminths, including cytokine homologs, protease inhibitors, and an intriguing set of novel products implicated in immune suppression.

Disruption of CD40-CD40 ligand pathway inhibits the development of intestinal muscle hypercontractility and protective immunity in nematode infection

In our previous studies, we demonstrated that during Trichinella spiralis infection, T helper (Th) 2 cells contribute to the development of intestinal muscle hypercontractility and worm expulsion from the gut via STAT6. In addition, we have linked the altered muscle contractility to the eviction of the parasite and thereby to the host defense. However, the initial events linking infection to the development of muscle hypercontractility are poorly understood. In this study, we examined the contribution of CD40-CD40 ligand (CD40L) interaction in the development of intestinal muscle hypercontractility, in monocyte chemoattractant protein-1 (MCP-1) production, and in the Th2 response in CD40 ligand-deficient (CD40L -/-) mice infected with T. spiralis. Expulsion of intestinal worms was substantially delayed in CD40L -/- mice compared with the wild-type mice after T. spiralis infection. Consistent with delayed worm expulsion, there was a significant attenuation of intestinal muscle contractility in CD40L -/- mice. Infected CD40L -/- mice also exhibited marked impairment in the production of MCP-1, IL-4, IL-13, IgG1, IgE, and mouse mucosal MCP 1 (MMCP-1), and in goblet cell response. These results demonstrate that CD40-CD40 ligand interaction plays an important role in MCP-1 production, Th2 response, intestinal muscle hypercontractility, and worm expulsion in nematode infection. The present data suggest that the early events leading to the generation of Th2 response include CD40-CD40 ligand interaction, which subsequently influences the production of Th2 cytokines, most likely via upregulation of MCP-1.

An asthma-associated genetic variant of STAT6 predicts low burden of ascaris worm infestation

Th-2 immune mechanisms are involved in the pathology of asthma and in the protective immune response to parasitic worms. Common upregulating genetic variants of Th-2 immune signalling are risk factors for asthma, and we tested whether they may confer a counteradvantage in protecting against parasitic worms. We examined the intensity of infection by the parasitic worm, Ascaris lumbricoides, by microsopic counting of ascaris eggs in the stool of 614 schoolchildren from an area of endemic ascaris infection in China. We investigated the relationship between the intensity of ascaris infection and common, asthma-associated genetic variants of Th-2 and Th-1 immune signalling. Ascaris egg counts per gram of stool (epg), mean 1068 epg, ranged from barely detectable (<240 epg) to heavy (approximately 9600 epg) in a skewed distribution. Logistic regression, after exploratory discriminant analysis, showed a major association between a common genetic variant of the 3'-UTR regulatory elements of the signal transducer and transactivating factor (STAT6) (P=0.0002) and egg counts, at the 77 th centile. Linear regression after log transformation of egg counts confirmed a highly significant association with this STAT6 variant (P=0.001). Thus, a common, asthma-associated, genetic variant of the pivotal transduction and transactivating factor for Th-2 immune signalling, STAT6, predicts increased resistance to ascaris worm infection. The evolution of enhanced resistance to parasitic worm infection, through human genetic variation in Th-2 immune signalling, may represent one origin for asthma.

Lactobacillus paracasei normalizes muscle hypercontractility in a murine model of postinfective gut dysfunction

BACKGROUND & AIMS

The effects of probiotics on gut dysfunction in postinfective irritable bowel syndrome are unknown. We tested whether probiotics influence persistent muscle hypercontractility in mice after recovery from infection with Trichinella spiralis and analyzed the underlying mechanisms.

METHODS

Mice were gavaged with Lactobacillus paracasei, Lactobacillus johnsonii, Bifidobacterium longum, or Bifidobacterium lactis in spent culture medium from days 10 to 21 after infection. Additional mice received heat-inactivated Lactobacillus paracasei, Lactobacillus paracasei -free spent culture medium, or heat-inactivated Lactobacillus paracasei -free spent culture medium. Lactobacilli enumeration, immunohistochemistry, and cytokine detection (enzyme-linked immunosorbent assay) were performed. Mice were also treated with Lactobacillus paracasei or Lactobacillus paracasei -free spent culture medium from days 18 to 28 after infection. Contractility was measured on days 21 and 28 after infection.

RESULTS

Lactobacillus paracasei, but not Lactobacillus johnsonii, Bifidobacterium lactis, or Bifidobacterium longum, attenuated muscle hypercontractility. This was associated with a reduction in the Trichinella spiralis -associated T-helper 2 response and a reduction in transforming growth factor-beta1, cyclooxygenase-2, and prostaglandin E 2 levels in muscle. Attenuation of muscle hypercontractility by Lactobacillus paracasei -free spent culture medium was abolished after heat treatment. Improvement of muscle hypercontractility at day 28 after infection was also observed after the administration of Lactobacillus paracasei or Lactobacillus paracasei -free spent culture medium from day 18 after infection.

CONCLUSIONS

Probiotics show strain-dependent attenuation of muscle hypercontractility in an animal model of postinfective irritable bowel syndrome. This likely occurs via both a modulation of the immunologic response to infection and a direct effect of Lactobacillus paracasei or a heat-labile metabolite on postinfective muscle hypercontractility. Lactobacillus paracasei may be useful in the treatment of postinfective irritable bowel syndrome.

Enteric nematodes induce stereotypic STAT6-dependent alterations in intestinal epithelial cell function

Infection with gastrointestinal nematodes exerts profound effects on both the immune and physiological responses of the host. We showed previously that the Th2 cytokines, IL-4 and IL-13, induce STAT6-dependent changes in intestinal epithelial cell permeability, absorption, and secretion that are similar to those observed in a secondary infection with Heligmosomoides polygyrus. In the current study we investigated whether nematode-induced effects on epithelial cell function were 1) generic, 2) dependent upon STAT6, and 3) attributable to direct effects on the epithelial cells themselves or mediated by effects on enteric nerves. Our results demonstrate that infection of BALB/c mice with three different gastrointestinal nematodes (H. polygyrus, Nippostrongylus brasiliensis, and Trichinella spiralis) alters intestinal epithelial cell function by decreasing resistance, glucose absorption, and secretory responses to 5-hydroxytryptamine and acetylcholine, two critical mediators in the submucosal reflex pathway. These modified responses are dependent on STAT6 and are the result of both direct effects and indirect effects mediated through enteric nerves.

Establishment of T-Helper-2 immune response based gerbil model of enteric infection

BACKGROUND

The reciprocal antagonism of T-helper-1 (Th-1) and Th-2 type immune responses suggests that helminth parasitic infection may ameliorate disease where a Th-1 type response dominates. The Mongolian gerbil has been useful in the investigation of the pathogenesis of gastric cancer, since long-term infection of gerbils with Helicobacter pylori induces adenocarcinoma. In this study the kinetics of worm expulsion and associated immune responses in gerbils infected with Trichinella spiralis were investigated in an attempt to establish an animal model of parasitic infection that could be helpful when investigating the effect of a Th-2 type response on Th-1-based intestinal disorders.

METHODS

Gerbils were infected with various doses of infective T. spiralis larvae and were euthanized on different days after infection to investigate the intestinal worm recovery, goblet cell population, eosinophil response and serum IgG1 responses.

RESULTS

The number of worms recovered from the intestine was dependent on the number of larvae used for the infection. Almost all worms were expelled spontaneously by day 26 post-infection, when the gerbils had been infected with 375 or 750 larvae. The number of intestinal goblet cells, eosinophils and the serum IgG1 level significantly increased following infection compared with the control.

CONCLUSION

This is the first comprehensive report on the time-course of T. spiralis infection in gerbils. The data indicate that the T. spiralis-infected gerbil could be used as a model of the Th-2-based response to investigate the effect of a parasite-induced Th-2 response on various Th-1-mediated intestinal disorders such as H. pylori-induced gastritis and gastric carcinoma.

Role of phosphoinositide 3-kinase signaling in mast cells: new insights from knockout mouse studies

Phosphoinositide 3-kinases (PI3Ks) are a family of lipid kinases essential for diverse physiological reactions. In recent years a series of gene-targeted mice lacking different types of PI3Ks and related molecules have been generated which enable us to understand the role of PI3K pathways, particularly class I members, in vivo. Analyses of such gene-targeted mice have led to major discoveries in the physiological roles of PI3K signaling in mast cell biology. In particular the role of PI3Ks has been extensively studied in signaling through the high-affinity IgE receptor (FcepsilonRI), since mast cells are the main effector cells in type I allergic reaction associated with IgE-dependent mechanisms. Furthermore, the knockout mice have provided significant information concerning the role of PI3K signals in mast cell differentiation. This review presents several new insights into mast cell biology, which have been elucidated by the analyses of these knockout mice.