Augmented leptin-induced trefoil factor 3 expression and epidermal growth factor receptor transactivation differentially influences neoplasia progression in the stomach and colorectum of dietary fat-induced obese mice

Obesity is a risk factor for gastrointestinal malignancies and tumors. However, which factors either protect or predispose the gastrointestinal organs to high-fat diet (HFD)-induced neoplasia remains unclear. Here, we demonstrate that HFD impacts the stomach to a greater extent as compared to the colorectum, resulting in leptin receptor (LepR) signaling-mediated neoplasia in the tissues. HFD activated leptin signaling, which in turn, accelerates the pathogenesis in the gastric mucosa more than that in the colorectum along with ectopic TFF3 expression. Moreover, in the stomach, higher levels of phosphorylated epidermal growth factor receptor (EGFR) in addition to the activation of STAT3 and Akt were observed as compared to the colorectum. The mice with LepR deletion in the gastrointestinal epithelium exhibited a suppressed induction of leptin, TFF3, and phosphorylated EGFR in the stomach, whereas the levels in the colorectum were insignificant. In co-transfected COS-7 cells with LepR and EGFR plasmid DNA, leptin transactivated EGFR to accelerate TFF3 induction along with activation of STAT3, ERK1/2, Akt, and PI3K p85/p55. Furthermore, TFF3 could bind to EGFR but did not transactivate LepR. Leptin-induced TFF3 induction was markedly suppressed by inhibitors of PI3K (LY294002) and EGFR (Erlotinib). Together, these results suggest a novel role of LepR-mediated signaling in transactivating EGFR that leads to TFF3 expression via the PI3K-Akt pathway. Therefore, this study sheds light on the identification of potentially new therapeutic targets for the treatment of pre-cancerous symptoms in stomach and colorectum.

Dietary Fat-Accelerating Leptin Signaling Promotes Protumorigenic Gastric Environment in Mice

Excess of fat intake leads to obesity and causes a variety of metabolic diseases and cancer. We previously demonstrated that high-lard diet induces intestinal metaplasia, a precancerous lesion of the stomach mediated by leptin signaling. This study aims to investigate which kinds of dietary fat cause the intestinal metaplasia onset. We fed eight kinds of high-fat diets (HFDs) of animal or plant origin to mice evaluated their effect on gastric pathogenesis. Five types of dietary fat were divided according to their observed effects: Obese with high metaplasia (group I; beef tallow, lard, and hydrogenated coconut oil), non-obese with high metaplasia (group II; linseed oil), obese without metaplasia (group III; corn oil and olive oil), non-obese without metaplasia (group IV, soybean oil) and lean without metaplasia (group V; cocoa butter). The group I and II diets induced leptin, phosphorylated leptin receptor (ObR), signal transducer and activator 3 (STAT3), and increased intracellular β-catenin accumulation in the stomach. Moreover, mice fed these HFDs with 1-methyl-3-nitro-1-nitrosoguanidine (MNNG), a gastric carcinogen, and further accelerated dysplasia in the stomach. Lactobacillus occupancy in the stomach increased in all HFDs except hydrogenated coconut oil. Our findings suggest that HFDs inducing leptin signaling accelerate the enhancement of protumorigenic gastric microenvironment independent of body mass gain or microbiome changes.

Gastric Leptin and Tumorigenesis: Beyond Obesity

Leptin, an adipocyte-derived hormone and its receptor (ObR) expressed in the hypothalamus are well known as an essential regulator of appetite and energy expenditure. Obesity induces abundant leptin production, however, reduced sensitivity to leptin leads to the development of metabolic disorders, so called leptin resistance. The stomach has been identified as an organ that simultaneously expresses leptin and ObR. Accumulating evidence has shown gastric leptin to perform diverse functions, such as those in nutrient absorption and carcinogenesis in the gastrointestinal system, independent of its well-known role in appetite regulation and obesity. Overexpression of leptin and phosphorylated ObR is implicated in gastric cancer in humans and in murine model, and diet-induced obesity causes precancerous lesions in the stomach in mice. While the underlying pathomechanisms remain unclear, leptin signaling can affect gastric mucosal milieu. In this review, we focus on the significant role of the gastric leptin signaling in neoplasia and tumorigenesis in stomach in the context of hereditary and diet-induced obesity.

Antagonizing effect of CLPABP on the function of HuR as a regulator of ARE-containing leptin mRNA stability and the effect of its depletion on obesity in old male mouse

Cardiolipin and phosphatidic acid-binding protein (CLPABP) is a pleckstrin homology domain-containing protein and is localized on the surface of mitochondria of cultured cells as a large protein-RNA complex. To analyze the physiological functions of CLPABP, we established and characterized a CLPABP knockout (KO) mouse. Although expression levels of CLPABP transcripts in the developmental organs were high, CLPABP KO mice were normal at birth and grew normally when young. However, old male mice presented a fatty phenotype, similar to that seen in metabolic syndrome, in parallel with elevated male- and age-dependent CLPABP gene expression. One of the reasons for this obesity in CLPABP KO mice is dependence on increases in leptin concentration in plasma. The leptin transcripts were also upregulated in the adipose tissue of KO mice compared with wild-type (WT) mice. To understand the difference in levels of the transcriptional product, we focused on the effect of CLPABP on the stability of mRNA involving an AU-rich element (ARE) in its 3'UTR dependence on the RNA stabilizer, human antigen R (HuR), which is one of the CLPABP-binding proteins. Increase in stability of ARE-containing mRNAs of leptin by HuR was antagonized by the expression of CLPABP in cultured cells. Depletion of CLPABP disturbed the normal subcellular localization of HuR to stress granules, and overexpression of CLPABP induced instability of leptin mRNA by inhibiting HuR function. Consequently, leptin levels in old male mice might be regulated by CLPABP expression, which might lead to body weight control.

Leptin receptor signaling is required for high-fat diet-induced atrophic gastritis in mice

Background

Obesity increases the risk for malignancies in various tissues including the stomach. Atrophic gastritis with precancerous lesions is an obesity-associated disease; however, the mechanisms that underlie the development of obesity-associated atrophic gastritis are unknown. Leptin is a hormone derived from stomach as well as adipose tissue and gastric leptin is involved in the development of gastric cancer. The aim of the current study is to investigate the involvement of leptin receptor signaling in the development of atrophic gastritis during diet-induced obesity.

Methods

Male C57BL/6, ob/ob and db/db mice were fed a high-fat diet (HFD) or a control diet (CD) from 1 week to 5 months. Pathological changes of the gastric mucosa and the expression of molecules associated with atrophic gastritis were evaluated in these mice.

Results

HFD feeding induced gastric mucosal hyperplasia with increased gastric leptin expression. Mucosal hyperplasia was accompanied by a higher frequency of Ki67-positive proliferating cells and atrophy of the gastric glands in the presence of inflammation, which increased following HFD feeding. Activation of ObR signaling-associated molecules such as ObR, STAT3, Akt, and ERK was detected in the gastric mucosa of mice fed the HFD for 1 week. The morphological alterations associated with gastric mucosal atrophy and the expression of Muc2 and Cdx2 resemble those associated with human intestinal metaplasia. In contrast to wild-type mice, leptin-deficient ob/ob mice and leptin receptor-mutated db/db mice did not show increased Cdx2 expression in response to HFD feeding.

Conclusion

Together, these results suggest that activation of the leptin signaling pathway in the stomach is required to develop obesity-associated atrophic gastritis.

Electronic supplementary material

The online version of this article (doi:10.1186/s12986-016-0066-1) contains supplementary material, which is available to authorized users.

TWEAK/Fn14 pathway promotes a T helper 2-type chronic colitis with fibrosis in mice

Tumor necrosis factor (TNF)-like weak inducer of apoptosis (TWEAK), a TNF superfamily member, induces damage of the epithelial cells (ECs) and production of inflammatory mediaters through its receptor Fn14 in a model of acute colitis. In our current study of chronic colitis induced by repeated rectal injection of a hapten, we found that inflammation, fibrosis, and T helper 2 (Th2)-type immunity were significantly reduced in Fn14 gene knockout (KO) mice when compared with wild-type (WT) control mice. Expression of thymic stromal lymphopoietin (TSLP) was lower in Fn14 KO colon ECs than in WT ECs. TWEAK potentiates the induction of TSLP by interleukin-13 (IL-13) in colon explants from WT but not in Fn14 KO tissue. TSLP receptor KO mice exhibit milder chronic colitis, similar to that in Fn14 KO mice. TWEAK and IL-13 synergistically promote fibroblast proliferation. Thus we propose an IL-13-TWEAK/Fn14-TSLP axis as a key mechanism underlying chronic colitis with fibrosis.

Microbiota-derived lactate accelerates colon epithelial cell turnover in starvation-refed mice

Oral food intake influences the morphology and function of intestinal epithelial cells and maintains gastrointestinal cell turnover. However, how exactly these processes are regulated, particularly in the large intestine, remains unclear. Here we identify microbiota-derived lactate as a major factor inducing enterocyte hyperproliferation in starvation-refed mice. Using bromodeoxyuridine staining, we show that colonic epithelial cell turnover arrests during a 12- to 36-h period of starvation and increases 12-24 h after refeeding. Enhanced epithelial cell proliferation depends on the increase in live Lactobacillus murinus, lactate production and dietary fibre content. In the model of colon tumorigenesis, mice exposed to a carcinogen during refeeding develop more aberrant crypt foci than mice fed ad libitum. Furthermore, starvation after carcinogen exposure greatly reduced the incidence of aberrant crypt foci. Our results indicate that the content of food used for refeeding as well as the timing of carcinogen exposure influence the incidence of colon tumorigenesis in mice.

SOCS, inflammation, and cancer

Signal transduction pathways elicited by cytokines and hormones have been shown to regulate distinct stages of development. Suppressor of cytokine signaling (SOCS) proteins are negative feedback regulators of cytokine signaling mediated by the JAK-STAT signaling pathway. In particular, SOCS1 and SOCS3 are potent inhibitors of JAKs and can play pivotal roles in inflammation, as well as in the development and progression of cancers. Abnormal expression of SOCS1 and SOCS3 in cancer cells has been reported in human carcinoma associated with dysregulation of signals from cytokine receptors, Toll-like receptors (TLRs), and hormone receptors, resulting in malignancies. In this review, we focus on the role of SOCS1 and SOCS3 in cancer development. In addition, the potential of SOCS as a therapeutic target and diagnostic aid will be discussed.

γδ T cells play a protective role during infection with Nippostrongylus brasiliensis by promoting goblet cell function in the small intestine

The intestinal epithelium is rich in γδ T cells and the gut is a site of residence for a wide variety of pathogens, including nematodes. Although CD4+ T-cell receptor (TCR) -αβ+ T helper type 2 T cells are essential for the expulsion of intestinal nematodes, little information is available on the function of γδ T cells in this type of infection. Here, we demonstrate two major functions of γδ T cells as a potently protective T-cell population against Nippostrongylus brasiliensis infection using γδ T-cell-deficient (TCR-δ(-/-) ) mice. First, γδ T cells are required to initiate rapid expulsion of adult worms from the intestine and to limit egg production. Second, γδ T cells prevent the pathological intestinal damage associated with nematode infection, evident by increased clinical disease and more severe microscopic lesions in infected TCR-δ(-/-) mice. γδ T-cell deficiency led to delayed goblet cell hyperplasia in association with reduced expression of phosphorylated STAT6, MUC2, Trefoil factor-3 (TFF3) and T helper type 2 cytokines including interleukin-13 (IL-13). TCR-δ(-/-) mice also produced more interferon-γ than wild-type mice. Within the intraepithelial lymphocyte compartment, γδ T cells produced IL-13. Adoptive transfer of γδ T cells or administration of recombinant IL-13 to TCR-δ(-/-) mice successfully reduced the egg production by N. brasiliensis. Collectively, these data provide strong evidence that γδ T cells play an important role in controlling infection with intestinal nematodes and limiting infection-induced pathology.

Interleukin-13 damages intestinal mucosa via TWEAK and Fn14 in mice-a pathway associated with ulcerative colitis

BACKGROUND & AIMS

TWEAK, a member of the tumor necrosis factor (TNF) superfamily, promotes intestinal epithelial cell injury and signals through the receptor Fn14 following irradiation-induced tissue damage and during development of colitis in mice. Interleukin (IL)-13, an effector of tissue damage in similar models, has been associated with the pathogenesis of ulcerative colitis (UC). We investigated interactions between TWEAK and IL-13 following mucosal damage in mice.

METHODS

We compared patterns of gene expression in intestinal tissues from wild-type and TWEAK knockout mice following γ-irradiation. Intestinal explants from these mice were used to detect cell damage induced by IL-13 and TNF-α. Levels of messenger RNA for IL-13, TWEAK, and Fn14 were measured in mucosal samples from patients with UC.

RESULTS

Based on gene expression analysis, TWEAK mediates γ-irradiation-induced epithelial cell cycle arrest and apoptosis. However, TWEAK alone did not induce damage or apoptosis of primary intestinal epithelial cells. On the other hand, exogenous IL-13 activated caspase-3 in naïve intestinal explants; this process required TWEAK, Fn14, and secretion of endogenous TNF-α which was mediated by ADAM17. Conversely, activation of caspase by exogenous TNF-α required IL-13, TWEAK, and Fn14. In mucosa from patients with UC, messenger RNA levels of IL-13, TWEAK, and Fn14 increased with level of disease severity.

CONCLUSIONS

IL-13-induced damage of intestinal epithelial cells requires TWEAK, its receptor (Fn14), and TNF-α. IL-13, TNF-α, TWEAK, and Fn14 could perpetuate and aggravate intestinal inflammation in patients with UC.

Interleukin-17A is required to suppress invasion of Salmonella enterica serovar Typhimurium to enteric mucosa

Salmonella enterica serovar Typhimurium (S. typhimurium) causes a localized enteric infection and its elimination is dependent on a T helper type 1 immune response. However, the mechanism of the protective immune response against the pathogen in gut-associated lymphoid tissue (GALT) at an early stage of the infection is not yet clarified. Here, we show that interleukin-17A (IL-17A) was constitutively expressed in GALT; it was also detected on crypt and epithelial cells of the small intestine. Neutralization of the IL-17A in the intestinal lumen exacerbated epithelial damage induced by intestinal S. typhimurium infection at an early stage of the infection. The result suggests that IL-17A has a pivotal role in the immediate early stage of protection against bacterial infection at the intestinal mucosa. As IL-17A neutralization also suppressed the constitutive localization of β-defensin 3 (BD3), an IL-17A-induced antimicrobial peptide, at the apical site of the intestinal mucosa, it is estimated that IL-17A constitutively induces the expression of the antimicrobial peptide to kill invading pathogens at the epithelial surface immediately after the infection. In contrast, interferon-γ is induced around 3 days after S. typhimurium infection, and its expression level increases thereafter. Taken together, the findings lead to the hypothesis that IL-17A participates in the immediate early stage of protection against S. typhimurium intestinal infection whereas interferon-γ is important at a later stage of the infection.

An enzymatic photometric assay for 2-deoxyglucose uptake in insulin-responsive tissues and 3T3-L1 adipocytes

An enzymatic assay adapted to photometric analysis with 96-well microplates was evaluated for the measurement of 2-deoxyglucose (2DG) uptake in insulin-responsive tissues and differentiated 3T3-L1 adipocytes. For in vivo measurements, a small amount of nonradiolabeled 2DG was injected into mice without affecting glucose metabolism. For photometric quantification of the small amount of 2-deoxyglucose 6-phosphate (2DG6P) that accumulates in cells, we introduced glucose-6-phosphate dehydrogenase, glutathione reductase, and 5,5'-dithiobis(2-nitrobenzoic acid) to the recycling amplification reaction of NADPH. We optimized the enzyme reaction for complete oxidation of endogenous glucose 6-phosphate (G6P) and glucose in mouse tissues in vivo and serum as well as in 3T3-L1 adipocytes in vitro. All reactions are performed in one 96-well microplate by consecutive addition of reagents, and the assay is able to quantify 2DG and 2DG6P in the range of 5-80 pmol. The results obtained with the assay for 2DG uptake in vitro and in vivo in the absence or presence of insulin stimulation was similar to those obtained with the standard radioisotopic method. Thus, the enzymatic assay should prove to be useful for measurement of 2DG uptake in insulin-responsive tissues in vivo as well as in cultured cells.

Adrenomedullin treatment reduces intestinal inflammation and maintains epithelial barrier function in mice administered dextran sulphate sodium

Hyperactivation and hyperpermeability of the intestinal epithelium is a hallmark of IBD. AM has been shown to reduce the severity of colitis in the acetic acid and TNBS-induced colitis model, however the mechanism of the therapeutic effect of AM against the colitis has not been clarified. Here, we show that the protective capability of AM is associated with suppression of inflammation and maintenance of the intestinal epithelial barrier function. In the DSS-induced colitis model, intra-rectal AM-treated mice showed a reduction in loss of body weight and severity of colitis. AM-treatment suppressed phosphorylation of STAT1 and STAT3 in the colonic epithelium, and altered the cytokine balance in the intestinal T cells, with lower levels of IFN-gamma and TNF-alpha but higher levels of TGF-beta. Expression of the epithelial intercellular junctions such as tight and adherence junctions were sustained in the AM-treated mice. In contrast, the epithelial junctions were down-regulated in the control mice, leading to loss of epithelial barrier integrity and enhanced permeability. Collectively, these data indicate a broad spectrum of AM-induced effects with respect to protection against DSS-induced colitis, and suggest a potential therapeutic value of this treatment for IBD.

Intestinal intraepithelial lymphocytes sustain the epithelial barrier function against Eimeria vermiformis infection

Eimeria spp. are intracellular protozoa that infect intestinal epithelia of most vertebrates, causing coccidiosis. Intestinal intraepithelial lymphocytes (IEL) that reside at the basolateral site of epithelial cells (EC) have immunoregulatory and immunoprotective roles against Eimeria spp. infection. However, it remains unknown how IEL are involved in the regulation of epithelial barrier during Eimeria sp. infection. Here, we demonstrated two distinct roles of IEL against infection with Eimeria vermiformis, a murine pathogen: production of cytokines to induce protective immunity and expression of junctional molecules to preserve epithelial barrier. The number of IEL markedly increased when oocyst production reached a peak. During infection, IEL increased production of gamma interferon (IFN-gamma) and tumor necrosis factor alpha (TNF-alpha) and decreased transforming growth factor beta (TGF-beta) production. Addition of IFN-gamma and TNF-alpha or supernatants obtained from cultured IEL from E. vermiformis-infected mice reduced transepithelial electrical resistance (TER) in a confluent CMT93 cell monolayer, a murine intestine-derived epithelial line, but antibodies against these cytokines suppressed the decline of TER. Moreover, TGF-beta attenuated the damage of epithelial monolayer and changes in TER caused by IFN-gamma and TNF-alpha. The expression of junctional molecules by EC was decreased when IEL produced a high level of IFN-gamma and TNF-alpha and a low level of TGF-beta in E. vermiformis-infected mice. Interestingly, IEL constantly expressed junctional molecules and a coculture of EC with IEL increased TER. These results suggest that IEL play important multifunctional roles not only in protection of the epithelium against E. vermiformis-induced change by cytokine production but also in direct interaction with the epithelial barrier when intra-EC junctions are down-regulated.

Suppressor of cytokine signalling 1 in lymphocytes regulates the development of intestinal inflammation in mice

BACKGROUND AND AIMS

Imbalance between pro- and anti-inflammatory cytokines produced by intestinal T cells induces inflammatory bowel diseases (IBD). However, the importance of regulation of cytokine signalling in IBD has not been fully clarified. We have demonstrated that suppressor of cytokine signalling 1 (SOCS1) is expressed in inflamed tissues in an experimental colitis model. In the present study, we investigated the role of SOCS1 in colitis models to clarify the mechanism of IBD development.

METHODS

Intestinal T cells in transgenic mice expressing high levels of SOCS1 in lymphocytes (SOCS1Tg mice) were characterised by flow cytometric analysis and cytokine production from intestinal T cells was determined by ELISA. 2,4,6-Trinitrobenzene sulphonic acid (TNBS) induced colitis was induced in SOCS1Tg mice and severity was compared with control littermates by measurement of survival rates. Intracellular signalling was assessed by western blotting analysis.

RESULTS

SOCS1Tg mice developed colitis spontaneously with age. Young SOCS1Tg mice less than 15 weeks of age, before the onset of colitis, were susceptible to TNBS induced colitis. Intestinal T cells of SOCS1Tg mice showed increased interferon gamma and tumour necrosis factor alpha production and decreased transforming growth factor beta production. Expression of cytotoxic T lymphocyte associated antigen 4 (CTLA-4), a negative regulator of T cell activation, in SOCS1Tg mice was severely impaired at the protein level although mRNA levels of CTLA-4 in SOCS1Tg mice were comparable with those in control mice.

CONCLUSIONS

Our data suggest that SOCS1 plays an important role in the regulation of colitis by controlling intestinal T cell activation mediated through CTLA-4 expression.

Intraepithelial lymphocytes express junctional molecules in murine small intestine

Intestinal intraepithelial lymphocytes (IEL) that reside at basolateral site regulate the proliferation and differentiation of epithelial cells (EC) for providing a first line of host defense in intestine. However, it remains unknown how IEL interact and communicate with EC. Here, we show that IEL express junctional molecules like EC. We identified mRNA expression of the junctional molecules in IEL such as zonula occludens (ZO)-1, occludin and junctional adhesion molecule (JAM) (tight junction), beta-catenin and E-cadherin (adherens junction), and connexin26 (gap junction). IEL constitutively expressed occludin and E-cadherin at protein level, while other T cells in the thymus, spleen, liver, mesenteric lymph node, and Peyer's patches did not. Gammadelta IEL showed higher level of these expressions than alphabeta IEL. The expression of occludin was augmented by anti-CD3 Ab stimulation. These results suggest the possibility of a novel role of IEL concerning epithelial barrier and communication between IEL and EC.

The Role of p53 and Fas in a Model of Acute Murine Graft-versus-Host Disease

Graft-vs-host disease (GVHD) is a devastating, frequently fatal, pathological condition associated with lesions in specific target organs, including the intestine, liver, lung, and skin, as well as pancytopenia and alopecia. Bone marrow (BM) atrophy is observed in acutely diseased animals, but the underlying mechanisms of hemopoietic stem cell depletion remained to be established. We used an experimental mouse model of acute GVHD in which parental cells were injected into F(1) hosts preconditioned by sublethal irradiation. The resulting graft-vs-host response was kinetically consistent, resulting in lethality within 3 wk. We observed disease pathology in the liver and small intestine, and consistent with previous observations, we found BM atrophy to be a factor in the onset of acute disease. The product of the protooncogene, p53, is known to be a key player in many physiological examples of apoptosis. We investigated the role of p53 in the apoptosis of BM cells (BMC) during the development of acute disease and found that at least one copy of the p53 gene is necessary for depletion of BM and subsequent lethality in host animals. BM depletion was preceded by induction of the death receptor, Fas, on the surface of host stem cells, and induction of Fas was coincidental with the sensitization of BMC to Fas-mediated apoptosis. Our data indicate that BM depletion in acute GVHD is mediated by p53-dependent up-regulation of Fas on BMC, which leads to Fas-dependent depletion and subsequent disease.

Chronic intestinal nematode infection induces Stat6-independent interleukin-5 production and causes eosinophilic inflammatory responses in mice

The role of Stat6 (signal transducers and activators of transcription) in the recruitment and activation of eosinophils has been studied in detail in asthma and other allergic diseases. In this study, we demonstrated that eosinophil responses occur in a Stat6-independent manner in mice infected with the intestinal nematode, Nippostrongylus brasiliensis. Stat6-deficient (Stat6(-/-)) mice cannot expel N. brasiliensis and establish chronic infections. Prominent blood and intestinal eosinophilia were induced after day 14 postinfection (p.i.) and maintained at this level in Stat6(-/-) mice, whereas in wild-type mice eosinophil responses reached a peak on day 10 p.i. and declined thereafter. The introduction of a secondary infection of N. brasiliensis into wild-type mice induced rapid and exaggerated eosinophilia, whereas secondary infection in Stat6(-/-) mice resulted in almost the same eosinophil responses as those of the primary infection, suggesting a lack of memory responses. Blood eosinophilia was also induced in Stat6(-/-) mice implanted with N. brasiliensis in the small intestine, suggesting that intestinal exposure to parasitic antigen is sufficient to induce eosinophil responses. Furthermore, this prominent eosinophil response of Stat6(-/-) mice after day 14 was closely associated with an increase of interleukin (IL)-5 production in serum and intestine. Neither IL-4 nor eotaxin were significantly induced in Stat6(-/-) mice after infection with N. brasiliensis. We also found that mRNA for IL-5, GATA-3 and eosinophil peroxidase (EPO) are induced in the intestine of Stat6(-/-) mice on day 14 p.i. Taken together, these results provide evidence for Stat6-independent IL-5 production and subsequent eosinophil responses after chronic infection with N. brasiliensis.

Mucosal T cells bearing TCRgammadelta play a protective role in intestinal inflammation

Intestinal intraepithelial lymphocytes (IEL) bearing TCRgammadelta represent a major T cell population in the murine intestine. However, the role of gammadelta IEL in inflammatory bowel diseases (IBD) remains controversial. In this study, we show that gammadelta IEL is an important protective T cell population against IBD. gammadelta T cell-deficient (Cdelta(-/-)) mice developed spontaneous colitis with age and showed high susceptibility to Th1-type 2,4,6-trinitrobenzene sulfonic acid (TNBS)-induced colitis at a young age. Transfer of gammadelta IEL to Cdelta(-/-) mice ameliorated TNBS-induced colitis, which correlated with decrease of IFN-gamma and TNF-alpha production and an increase of TGF-beta production by IEL. Furthermore, a high level of IL-15, which inhibits activation-induced cell death to terminate inflammation, was expressed more in intestinal epithelial cells (EC) from TNBS-treated Cdelta(-/-) mice than in those from wild-type mice. EC from wild-type mice significantly suppressed the IFN-gamma production of IEL from TNBS-treated Cdelta(-/-) mice, whereas EC from TNBS-treated Cdelta(-/-) mice did not. These data indicate that gammadelta IEL play important roles in controlling IBD by regulating mucosal T cell activation cooperated with EC function. Our study suggests that enhancement of regulatory gammadelta T cell activity is a possible new cell therapy for colitis.

Negative regulation of cytokine signaling by CIS/SOCS family proteins and their roles in inflammatory diseases

Immune and inflammatory systems are controlled by multiple cytokines, including interleukins (ILs) and interferons. These cytokines exert their biological functions through Janus tyrosine kinases (JAKs) and STAT transcription factors. The CIS (cytokine-inducible SH2 protein) and SOCS (suppressors of cytokine signaling) are a family of intracellular proteins, several of which have emerged as key physiological regulators of cytokine responses, including those that regulate the inflammatory systems. In this review, we focused on the molecular mechanism of the action of CIS/SOCS family proteins and their roles in inflammatory diseases. Furthermore, we illustrate several approaches for treating inflammatory diseases by modulating extracellular and intracellular signaling pathways.

Negative regulation of cytokine signaling and inflammatory diseases

Immune and inflammatory systems are controlled by multiple cytokines, including interleukins and interferons. These cytokines exert their biological functions through Janus tyrosine kinases and signal transducer and activators of transcription (STATs). The cytokine-inducible SH2 proteins (CIS) and suppressors of cytokine signaling (SOCS) are a family of intracellular proteins, several of which have emerged as key physiological regulators of cytokine responses, including those that regulate the inflammatory system. Several recent advances have been made in this field, including treatment of inflammatory diseases by modulating extracellular and intracellular signaling pathways.

SOCS-3 regulates onset and maintenance of T(H)2-mediated allergic responses

Members of the suppressor of cytokine signaling (SOCS) family are involved in the pathogenesis of many inflammatory diseases. SOCS-3 is predominantly expressed in T-helper type 2 (T(H)2) cells, but its role in T(H)2-related allergic diseases remains to be investigated. In this study we provide a strong correlation between SOCS-3 expression and the pathology of asthma and atopic dermatitis, as well as serum IgE levels in allergic human patients. SOCS-3 transgenic mice showed increased T(H)2 responses and multiple pathological features characteristic of asthma in an airway hypersensitivity model system. In contrast, dominant-negative mutant SOCS-3 transgenic mice, as well as mice with a heterozygous deletion of Socs3, had decreased T(H)2 development. These data indicate that SOCS-3 has an important role in regulating the onset and maintenance of T(H)2-mediated allergic immune disease, and suggest that SOCS-3 may be a new therapeutic target for the development of antiallergic drugs.

The N-terminal truncated isoform of SOCS3 translated from an alternative initiation AUG codon under stress conditions is stable due to the lack of a major ubiquitination site, Lys-6

The suppressor of cytokine signaling-3 (SOCS3/CIS-33/SSI-3) is an important negative regulator of cytokine signaling. Here, we show that an N-terminal truncated isoform (DeltaN-SOCS3) translated from the internal AUG codon 12 was profoundly induced by endoplasmic reticulum (ER) stress- or active double-stranded RNA-activated protein kinase PKR, as a result of induction of eukaryotic initiation factor 2alpha phosphorylation. DeltaN-SOCS3 exhibited a stronger cytokine-inhibitory activity and a higher stability than WT-SOCS3 in Ba/F3 hematopoietic cells. A potential ubiquitination residue, Lys-6, at the N terminus is evolutionary conserved among SOCS3 species. The K6Q-SOCS3 mutant showed a much longer half-life than WT-SOCS3 in Ba/F3 cells. Furthermore, inhibition of the 26 S proteasome pathway increased both ubiquitination and protein levels of WT-SOCS3 but had no effect on K6Q-SOCS3. SOCS3 mutant lacking the carboxyl-terminal SOCS-box exhibited the same stability as K6Q-SOCS3. These observations suggest that the short form of SOCS3 is a naturally occurring stabilized inhibitory protein, whereas WT-SOCS3 is a short-lived protein modulated by Lys-6 ubiquitination and proteasome-dependent degradation. Our findings provide strong evidence for the first time that translational control plays an important role in stabilization and function of SOCS3.

Radiation-induced crypt intestinal epithelial cell apoptosis in vivo involves both caspase-3-dependent and -independent pathways

Caspases play a major role in virtually all forms of apoptosis. Radiation is well known to induce apoptosis of crypt intestinal epithelial cells (IEC). Here, we examined the role of caspase-3 in radiation-induced IEC apoptosis. We demonstrate that while caspase-3 is present in IEC and activated upon irradiation, IEC in caspase-3-deficient mice partially underwent radiation-induced apoptosis. Typical morphological changes of IEC undergoing radiation-induced apoptosis (ie, blebbing, shrinkage, and nuclear condensation) can occur independently of caspase-3; however DNA fragmentation, as analyzed by terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling (TUNEL) staining, is mostly, but not entirely, caspase-3-dependent. Overall, these results demonstrate that radiation-induced crypt IEC apoptosis has both caspase-3-independent and -dependent components.

SOCS1/JAB is a negative regulator of LPS-induced macrophage activation

Bacterial lipopolysaccharide (LPS) triggers innate immune responses through Toll-like receptor (TLR) 4. We show here that the suppressor of cytokine-signaling-1 (SOCS1/JAB) is rapidly induced by LPS and negatively regulates LPS signaling. SOCS1(+/-) mice or SOCS1(-/-) mice with interferon-gamma (IFNgamma)-deficient background were more sensitive to LPS-induced lethal effects than were wild-type littermates. LPS-induced NO(2)(-) synthesis and TNFalpha production were augmented in SOCS1(-/-) macrophages. Furthermore, LPS tolerance, a protection mechanism against endotoxin shock, was also strikingly reduced in SOCS1(-/-) cells. LPS-induced I-kappaB and p38 phosphorylation was upregulated in SOCS1(-/-) macrophages, and forced expression of SOCS1 suppressed LPS-induced NF-kappaB activation. Thus, SOCS1 directly suppresses TLR4 signaling and modulates innate immunity.

Critical involvement of CD40 in protection against herpes simplex virus infection in a murine model of genital herpes

We studied the requirement for CD40+ cells in the resolution of vaginal infection with avirulent herpes simplex virus type I (HSV-1) in vivo using CD40-deficient mice, which were susceptible to infection with avirulent HSV-1. Compared with wild-type mice, CD40-deficient mice could not eliminate HSV-1 virus effectively from the vaginal mucosa and produced lower amounts of interleukin-12 and interferon-gamma. These results show that the induction and activation of CD40+ cells are important for HSV prevention, facilitating the activation of T cells to induce an efficient HSV clearance from the vaginal mucosa and to prevent lethal illness due to HSV infection.

Effect of the deletion of US2 and US3 from herpes simplex virus type 2 on immune responses in the murine vagina following intravaginal infection

We investigated the effects of US2 and US3 deficiencies of herpes simplex virus type 2 (HSV-2) on host immunity in a murine model of genital herpes infection. Viral clearance from the vaginal mucosa was more rapid in mice infected with a US3-deficient mutant L1BR1 as compared with a wild-type 186 or YY2 (US2-deficient mutant) infection, although there was no significant difference among them in initial growth in the early stage of infection. Flow cytometric studies revealed that the number of vaginal mononuclear cells in L1BR1-infected mice was significantly greater than that in 186- or YY2-infected mice. Dendritic cells, macrophages and T cells were induced more rapidly and in greater numbers within the vaginas of L1BR1-infected mice. Moreover, the levels of IL-12 and IFN-gamma increased in L1BR1-infected mice over levels in 186-infected mice. These results indicate that a US3 deficiency alters the induction of the host immune response; therefore, the inactivation of US3 may be a promising strategy in the development of novel vaccines for genital herpes.

IL-7 prevents both caspase-dependent and -independent pathways that lead to the spontaneous apoptosis of i-IEL

Intestinal intraepithelial lymphocytes (i-IEL) readily undergo spontaneous apoptosis in vitro through an unclear mechanism. Here we examined the relationship between caspases, which plays a major role in apoptosis, and IL-7 in the spontaneous apoptosis of i-IEL in vitro. We demonstrated that IL-7 and zVAD prevented the spontaneous apoptosis of i-IEL by approximately 50% and 25% respectively with no additive protection seen when both are used. IL-7 preferentially prevented the apoptosis of gammadelta i-IEL, while zVAD equally prevented the apoptosis of gammadelta and alphabeta i-IEL. Lastly, we demonstrated that the spontaneous apoptosis of i-IEL is associated with a marked increase in caspase activity. Caspase activity was completely inhibited by zVAD, but only slightly by IL-7. Overall these results suggest that two pathways lead to the spontaneous apoptosis of i-IEL, one which is caspase dependent and the other which is caspase independent. IL-7 appears to exert its effect on i-IEL undergoing spontaneous by partially inhibiting both apoptotic pathways.

Impaired induction of protective immunity by highly virulent herpes simplex virus type 2 in a murine model of genital herpes

We investigated the immune events in the vagina of mice intravaginally infected with highly virulent herpes simplex virus type 2 (HSV-2) strain 186, and compared them with those induced by HSV type 1 strain KOS, a widely known laboratory strain. Although there was no significant difference between 186 and KOS in the viral replication in the initial stage of infection, inadequate and delayed clearance of virus from the vaginal mucosa was observed in 1 86-challenged mice. The induction of antigen-presenting cells (APC) such as dendritic cells (DC) and macrophages (Mphi) in the vagina was slow in 186-challenged mice, and the number of T cells in the vagina in 186-challenged mice was much lower than that in KOS-challenged mice. Furthermore, the level of IL-12 as well as that of IFN-gamma was significantly lower in 186-challenged mice than in KOS-challenged mice, while the level of IL-4 in 186-challenged mice was higher than that in KOS-challenged mice. On the basis of these observations, we suggest that the weak activation of epithelial cells and the delayed induction of APC by 186-infection may be involved in the inadequate activation of T cells and the ineffective virus clearance from the vaginal mucosa.

p53-dependent radiation-induced crypt intestinal epithelial cells apoptosis is mediated in part through TNF-TNFR1 system

Radiation induces apoptosis of crypt intestinal epithelial cells (IEC) through a pathway that is largely dependent on p53. However, exactly how p53 mediates IEC apoptosis is unclear. Studies in vitro suggest that one mechanism by which p53 mediates apoptosis is through its ability to transactivate members of the TNF receptor family of 'Death Receptors'. Here, we examined the role of one of its member, TNF receptor type 1 (TNFR1), in an in vivo model of p53-dependent radiation-induced IEC apoptosis. We demonstrate that mice genetically engineered to be deficient in TNF receptor type 1 (TNFR1(-/-)) and mice injected with TNFR1-fusion chimeric protein (TNFR1-Fc; a competitive inhibitor of TNFR1) were partially protected (30-40%) from p53-dependent radiation-induced IEC apoptosis. However, we found no evidence to support the possibility p53 transcriptionally regulates the expression of TNFR1 nor increases the susceptibility of IEC to TNF-mediated apoptosis. Interestingly, we found that injection of TNF readily induced IEC apoptosis and that radiation induced a p53-dependent increase in the intestinal level of TNF. Furthermore, injection of a neutralizing anti-TNF mAb reduced p53-dependent radiation-induced IEC apoptosis by approximately 60%. Overall, these results suggest that p53-dependent radiation-induced IEC apoptosis is mediated in part through ability of p53 to regulate TNF, which subsequently induces IEC apoptosis through TNFR1.

Mitochondrial distribution and function in herpes simplex virus-infected cells

In this study, mitochondria migrated to a perinuclear region in the cytoplasm in herpes simplex virus (HSV)-infected cells. HSV infection did not promote the expression of cytochrome c oxidase subunit 2 but did promote that of stress-responsive HSP60, both of which are known to be components of mitochondria. The levels of cellular ATP and lactate and mitochondrial membrane potential were maintained for at least 6 h but decreased at the late stage of infection. It was also found that the UL41 and UL46 gene products, both of which are known to be tegument proteins, accumulated in the perinuclear region. The clustering of mitochondria and the accumulation of tegument proteins were completely blocked by the addition of nocodazole and vinblastine. These results suggest that mitochondria respond to the stimulation of HSV infection, migrating with tegument proteins along microtubules to a site around the nucleus, and maintain function until at least the middle stage of infection.

Nucleolar localization of the UL3 protein of herpes simplex virus type 2

A rabbit polyclonal antiserum was raised against a recombinant 6 x His-UL3 fusion protein expressed in Escherichia coli and used to examine the intracellular localization of the UL3 protein of herpes simplex virus type 2 (HSV-2). The antiserum reacted specifically with 31 and 34 kDa proteins in HSV-2 186-infected Vero cells and with 31 and 35 kDa proteins in UL3-expressing COS-7 cells. The UL3 protein localized both in the cytoplasm and in five to ten bright fluorescent granules in the nucleus close to the nuclear membrane at 4 h post-infection (p.i.). These structures became bigger at 5 h p.i. and showed doughnut-like forms at 6 h p.i. In transfected Vero cells, the UL3 protein localized exclusively in the nucleoplasm and specifically in the nucleolus. Five deletion mutants of the UL3 protein were constructed for transfection assays and the results showed that the region containing amino acids 100-164 was important for nucleolar localization. Moreover, green fluorescent protein (GFP)-targetting experiments showed that the region containing amino acids 100-164 was able to transport non-nucleolar GFP to the nucleolus as a fusion protein.

A thymic hormone protects mice from enteropathy during acute graft-versus-host disease

We have previously reported that a nonapeptide thymic hormone, facteur thymique serique (FTS), is involved in the differentiation and activation of intestinal intraepithelial lymphocytes (i-IEL) in mice. In this study, we examined the effect of FTS treatment on enteropathy in a murine model for acute graft-vs.-host disease (GVHD) induced by injection of parental C57BL/6 splenocytes into unirradiated (C57BL/6 x DBA/2) F1 hybrids. FTS treatment significantly protected mice from developing acute GVHD as assessed by mortality rate, splenomegaly and enteropathy. The infiltration of donor-derived TCR alpha beta i-IEL bearing CD8 alpha beta was significantly inhibited in the small intestine of FTS-treated mice, and the frequencies of apoptosis of crypt cells in the intestinal mucosa were decreased in these mice during acute GVHD. These results suggest that FTS treatment contributes to protection against enteropathy of acute GVHD. Thus, FTS may provide a useful approach to control acute GVHD after blood transfusion or bone marrow transplantation.

Murine model of IgE production with a predominant Th2-response by feeding protein antigen without adjuvants

Stimulation of systemic antigen-specific IgE production plays an important role in the mediation of food allergy; however, the mechanism of IgE production against food antigens is not fully understood. The development of relevant animal models may help to elucidate the pathogenesis of food allergy. We here show that DBA/2 mice receiving a casein diet without any adjuvant produced high levels of IgE specific for casein, accompanied by predominant Th2-like responses in liver lymphocytes, mesenteric lymph node cells and spleen cells. This model of IgE production produced by feeding protein antigen as a constituent of the diet can be applied to investigate the mechanism of IgE production and to develop reagents for controlling food allergy.

Interleukin-15 preferentially promotes the growth of intestinal intraepithelial lymphocytes bearing gamma delta T cell receptor in mice

Several cytokines including stem cell factor (SCF) and interleukin (IL)-7 are known to be required for development of gamma delta T cell receptor (TCR) intestinal intraepithelial lymphocytes (i-IEL) in mice. We show here the effects of IL-15 on the proliferation and maintenance of murine gamma delta i-IEL in vitro. gamma delta i-IEL constitutively expressed a high level of IL-15 receptor alpha mRNA and proliferated in response to IL-15 more vigorously than alpha beta i-IEL. V gamma/delta repertoire analysis revealed that IL-15, like IL-2, induced polyclonal expansion of gamma delta i-IEL, whereas gamma delta i-IEL responding to IL-7 showed a V gamma/delta repertoire skewed towards V gamma 1/V delta 4, V delta 5. IL-15 efficiently prevented gamma delta i-IEL from apoptosis induced by growth factor deprivation. This rescue was accompanied by up-regulation of Bcl-2 expression. These results suggest that IL-15 plays important roles in proliferation and maintenance of gamma delta i-IEL.

Potential for involvement of Fas antigen/Fas ligand interaction in apoptosis of epithelial cells by intraepithelial lymphocytes in murine small intestine

Intestinal epithelial cells (i-EC), which move to the villus tips from the crypts, rapidly die by apoptosis at the villus tips and are perpetually renewed at the crypts. To determine whether the Fas antigen (Fas)/Fas ligand (FasL) system is involved in the mechanism leading to apoptosis of i-EC, we examined the expression of Fas and FasL on the i-EC and intestinal intraepithelial lymphocytes (i-IEL) in normal mice. A high level of Fas was expressed on both the i-EC and i-IEL, whereas FasL was expressed in the i-IEL, especially in high-density fraction upon separation (high-density i-IEL), but not in the i-EC. The high-density i-IEL exhibited cytotoxicity against not only Fas transfectant but also the i-EC, and the cytotoxicity was inhibited by addition of Fas-Fragment c chimeric fusion protein. Thus, a significant fraction of i-IEL, such as high-density i-IEL, may partly contribute to induction of apoptosis in the effete i-EC via Fas/FasL interaction.

Fas-mediated cytotoxicity by intestinal intraepithelial lymphocytes during acute graft-versus-host disease in mice

BACKGROUND & AIMS

Host-derived intestinal intraepithelial lymphocytes (IELs) increase in number during acute graft-versus-host disease (GVHD) in mice. In the present study, we examined Fas-mediated cytotoxicity by host-derived IELs against Fas-expressing target cells to see whether Fas/Fas ligand (Fas-L) interaction is involved in the pathogenesis of enteropathy during acute GVHD.

METHODS

Acute GVHD was induced by injection of parental spleen cells into nonirradiated F1 mice. The expression of Fas antigen on the intestinal epithelial cells (IECs) was examined by flow cytometry, and the expression of messenger RNA (mRNA) for Fas-L, interleukin 2, and interferon gamma in host-derived IELs was assessed by reverse-transcription polymerase chain reaction. Fas-mediated cytotoxicity by host-derived IELs was assessed using Fas-transfected cells, IECs, and Fas immunoglobulin Fc fusion protein (Fas Fc).

RESULTS

Fas antigen was constitutively expressed on the cell surface of IECs before and after GVHD induction. Although Fas-L mRNA was not detected or detected scarcely in either alphabeta or gammadelta IELs before GVHD induction, both IELs expressed high levels of mRNA for Fas-L and interferon gamma after GVHD induction. Host-derived IELs during acute GVHD showed cytotoxicity against Fas-transfected target cells and IECs, which was partly blocked by addition of Fas Fc.

CONCLUSIONS

Fas/Fas-L-mediated cytotoxicity by host-derived IELs may be partly responsible for the enteropathy during acute GVHD.

Apoptosis of intestinal intraepithelial lymphocytes induced by exogenous and endogenous glucocorticoids

To investigate the effect of glucocorticoids on apoptosis in intestinal intraepithelial lymphocytes (i-IEL), we examined the changes of i-IEL followed by in vivo treatment with dexamethasone. The fragmented DNA of i-IEL were significantly increased at 15 hr after dexamethasone treatment and, subsequently, the number of total i-IEL were decreased by day 4 after treatment. Although all subsets of i-IEL including CD8 alpha/alpha(+), CD8 alpha/beta(+), CD4+ and CD4+CD8+ i-IEL were decreased after dexamethasone treatment, CD8 alpha/alpha(+) i-IEL appeared to be relatively resistant to dexamethasone-induced apoptosis. Consistent with the in vivo findings, CD8 alpha/alpha(+) i-IEL exhibited less susceptibility to dexamethasone-induced cell death in vitro than other subsets. To investigate whether this process occurs under physiological conditions, we examined the kinetics of i-IEL after treatment with 15-hr water immersion stress. In mice subjected to water immersion stress, plasma glucocorticoids were remarkably elevated soon after the 15-hr stress. The increase in the fragmented DNA of i-IEL and subsequent decrease in the number of i-IEL were observed in the stressed mice in the same kinetics as seen in the dexamethasone-treated mice. Similar to dexamethasone-induced ell death, CD8 alpha/alpha(+) i-IEL appeared to be relatively resistant to stress-induced apoptosis compared with other i-IEL subsets. The expression level of Bcl-2 was significantly higher in CD8 alpha/alpha(+) i-IEL than in CD8 alpha/beta(+) i-IEL. Our results indicate that i-IEL are subjected to cell death via apoptosis by exogenous and endogenous glucocorticoids and that different sensitivity to steroid-induced apoptosis may exist among i-IEL subsets in relation to their Bcl-2 expression.

Effects of a nonapeptide thymic hormone on intestinal intraepithelial lymphocytes in mice following administration of 5-fluorouracil

A significant fraction of murine small intestinal intraepithelial lymphocytes (i-IELs) mature in local sites outside the thymus. However, there is evidence suggesting that extrathymic differentiation of i-IELs is still influenced by the thymus or thymus-derived factors. Facteur thymique serique (FTS), a nonapeptide thymic hormone, is involved in several aspects of intra- and extrathymic T cell differentiation in vivo. In this study, we investigated the effects of FTS on the kinetics of i-IELs in mice following a single administration of 5-fluorouracil (5-FU). FTS treatment significantly accelerated the recovery in cell number of i-IELs after administration of 5-FU. Flow cytometric analysis revealed that this accelerated recovery was mainly due to a rapid increase in CD8 alpha alpha+ i-IELs. Similar findings were also evident in adult thymectomized (ATX) mice, indicating that FTS treatment caused a rapid recovery of CD8 alpha alpha+ i-IELs following 5-FU administration in the absence of a functional thymus. Furthermore, expression levels of the mRNAs for interleukin-2, interferon-gamma, and transforming growth factor beta 1 in the i-IELs were augmented by FTS treatment. Notably, FTS treatment protected mice from 5-FU-induced lethal toxicity, accompanied with an inhibition of the translocation of Enterobacteriaceae. These results suggest that FTS has an important function in the extrathymic maturation and activation of i-IELs in the small intestine following 5-FU administration, which may contribute at least partly to the protection against 5-FU-induced lethal toxicity.