Apoptosis: one of the mechanisms that maintains unresponsiveness of the intestinal mucosal immune system

Aryl Hydrocarbon Receptor Signalling in the Control of Gut Inflammation

Aryl hydrocarbon receptor (AHR), a transcription factor activated by many natural and synthetic ligands, represents an important mediator of the interplay between the environment and the host's immune responses. In a healthy gut, AHR activation promotes tolerogenic signals, which help maintain mucosal homeostasis. AHR expression is defective in the inflamed gut of patients with inflammatory bowel diseases (IBD), where decreased AHR signaling is supposed to contribute to amplifying the gut tissue's destructive immune-inflammatory responses. We here review the evidence supporting the role of AHR in controlling the "physiological" intestinal inflammation and summarize the data about the therapeutic effects of AHR activators, both in preclinical mouse models of colitis and in patients with IBD.

The Complex Relationship Between Microbiota, Immune Response and Creeping Fat in Crohn's Disease

In the last decade, there has been growing interest in the pathological involvement of hypertrophic mesenteric fat attached to the serosa of the inflamed intestinal segments involved in Crohn's disease [CD], known as creeping fat. In spite of its protective nature, creeping fat harbours an aberrant inflammatory activity which, in an already inflamed intestine, may explain why creeping fat is associated with a greater severity of CD. The transmural inflammation of CD facilitates the interaction of mesenteric fat with translocated intestinal microorganisms, contributing to activation of the immune response. This may be not the only way in which microorganisms alter the homeostasis of this fatty tissue: intestinal dysbiosis may also impair xenobiotic metabolism. All these CD-related alterations have a functional impact on nuclear receptors such as the farnesoid X receptor or the peroxisome proliferator-activated receptor γ, which are implicated in regulation of the immune response, adipogenesis and the maintenance of barrier function, as well as on creeping fat production of inflammatory-associated cells such as adipokines. The dysfunction of creeping fat worsens the inflammatory course of CD and may favour intestinal fibrosis and fistulizing complications. However, our current knowledge of the pathophysiology and pathogenic role of creeping fat is controversial and a better understanding might provide new therapeutic targets for CD. Here we aim to review and update the key cellular and molecular alterations involved in this inflammatory process that link the pathological components of CD with the development of creeping fat.

Apoptosis in peripheral blood lymphocytes in intestinal tuberculosis and Crohn's disease: Implications to diagnostic differentiation

AIM

Intestinal tuberculosis (ITb) and Crohn's disease (CD) mimic each other often leading to misdiagnosis. We evaluated the difference between ITb and CD using the extent of apoptosis in peripheral blood lymphocytes.

METHODS

CD4⁺ cells as a percentage of the lymphocytes and viable, dead, total apoptotic, early apoptotic, and late apoptotic CD4⁺ cells were assessed in the peripheral blood by flow cytometry in healthy controls and patients with confirmed active ITb and CD prior to initiating therapy. Early apoptotic and total apoptotic cells were further expressed as a proportion of the percentage of CD4⁺ cells.

RESULTS

The percentages of CD4⁺ cells (6.5 [3.0, 8.7] vs. 13.40 [10.15, 13.40]; p < 0.001), total apoptotic cells (0.13 [0.0, 0.22] vs. 0.08 [0.0, 0.21]; p = 0.045), early apoptotic (1.24 [0.55, 2.54] vs. 0.71 [0.40, 1.30]; p = 0.037), and the proportion of the latter two parameters (17.18 [5.61, 57.33] vs. 4.84 [2.71, 9.83]; p-value 0.039) and (17.18 [7.4, 67.50] vs. 5.51 [3.10, 11.03]; p-value 0.036) were significantly different between patients with ITb and CD. The best sensitivity, specificity, and positive and negative predictive values for the diagnosis of ITb were seen with the CD4⁺ cell percentage (82.6%, 82.4%, 86.4%, 77.8%, respectively) and the proportion of early apoptotic cells (73.9%, 70.6%, 77.3%, 66.7%, respectively).

CONCLUSION

CD4⁺ cells as a percentage of peripheral blood lymphocytes and the proportion of early apoptotic CD4⁺ cells show promise to diagnostic differentiation between ITb and CD.

Scutellarein suppresses Aβ-induced memory impairment via inhibition of the NF-κB pathway in vivo and in vitro

The flavonoid compound scutellarin (Scu) is a traditional Chinese medicine used to treat a variety of diseases; however, the use of scutellarein (Scue), the hydrolysate of Scu, and its mechanisms of action in Alzheimer's disease (AD) have not been fully elucidated. In the present study, the effects of Scue on amyloid β (Aβ)-induced AD-like pathology were investigated. An in vitro model of inflammation and an aged rat model were used to confirm the effects of Scue. In vitro MTT assays and flow cytometry were used to assess the effects of Scue on cell viability and apoptosis, respectively. A Morris water maze was used to evaluate spatial learning and memory, and the levels of Aβ deposition, superoxide dismutase, malondialdehyde, apoptosis, neuro-inflammatory factors and nuclear factor-κB (NF-κB) activation in hippocampal tissues in vivo were measured to determine the effect of Scue in AD. Scue may be protective, as it decreased the apoptosis of hippocampal cells in vitro, inhibited Aβ-induced cognitive impairment, suppressed hippocampal neuro-inflammation and suppressed activation of NF-κB in vivo. Therefore, Scue may be a useful agent for the treatment of Aβ-associated pathology in the central nervous system through inhibition of the protein kinase B/NF-κB signaling pathway and thus, future studies are required to investigate the efficacy of Scue in patients with AD.

Immunopathogenesis of Crohn's Disease

This review highlights the huge advances made in the understanding of Crohn's disease in the last 15 years. The pathogenic immune response in the gut wall is a highly polarised T helper cell type 1 response, probably directed against antigens of the commensal flora. There is marked over-expression of pro-inflammatory cytokines such as tumor necrosis factor (TNF)-alpha and increased production of matrix degrading enzymes by fibroblasts and macrophages, which are probably responsible for ulceration and fistula formation. Crohn's disease runs in families and the susceptibility genes identified so far are associated with innate recognition of microbial products (Nod2) or epithelial barrier function (OCTN cation transporter genes and DLG5). Endogenous healing pathways mediated by transforming growth factor (TGF)-beta1 are inhibited because mucosal inflammatory cells express Smad7, the endogenous intracellular inhibitor of TGF-beta signalling. This makes it unlikely that enteral feeds containing TFG-beta are therapeutic by means of direct anti-inflammatory effects, however TGF-beta may still be involved because it is a well known epithelial motogen and may promote mucosal healing, in synergy with changes in mucosal bacterial populations as a result of the change in the diet.

Deoxyschizandrin suppresses dss-induced ulcerative colitis in mice

BACKGROUND/AIMS

Deoxyschizandrin as one of the most important component of Schisandra chinensis (Turcz.) Baill plays an immunomodulatory role in a variety of diseases, yet its role in ulcerative colitis remains to be elucidated. We aimed to investigate the role of deoxyschizandrin in DSS-induced ulcerative colitis in mice.

PATIENTS AND METHODS

In the present study, an inflammation model of cells was constructed to confirm the anti-inflammatory effect of deoxyschizandrin. Then a mouse model with Dextran sulfate sodium sulfate (DSS)-induced ulcerative colitis was constructed, and the effects of deoxyschizandrin on mouse colon inflammation, apoptosis, and CD4 T lymphocyte infiltration in ulcerative colitis were examined.

RESULT

Deoxyschizandrin could improve the symptoms of ulcerative colitis, determined by hematoxylin-eosin (HE) staining and histopathological scores. Moreover, deoxyschizandrin reduced the levels of inflammatory cytokines, suppressed CD4 T cell infiltration, and effectively inhibited apoptosis in the colon of DSS-induced ulcerative colitis mice.

CONCLUSION

In summary, deoxyschizandrin can effectively rescue the symptoms of DSS-induced ulcerative colitis in mice by inhibiting inflammation. T cell infiltration and apoptosis in the colon, suggesting that deoxyschizandrin could be a potential drug in treating ulcerative colitis.

Regional Specialisation of T Cell Subsets and Apoptosis in the Human Gut Mucosa: Differences Between Ileum and Colon in Healthy Intestine and Inflammatory Bowel Diseases

BACKGROUND AND AIMS

There is very limited information regarding region-specific immunological response in human intestine. We aimed to determine differences in immune compartmentalisation between ileum and colon in healthy and inflamed mucosa.

METHODS

T cell profile and its apoptosis were measured by flow cytometry, Th1, Th17, Treg [CD4(+)CD25(+)FOXP3(+)], double positive [DP, CD3(+)CD4(+)CD8(+)] and double negative T cells [DN, CD3(+)CD4(-)CD8(-)], immunohistochemistry [FOXP3, caspase-3], and real-time polymerase chain reaction [PCR] [IFN-γ, IL-17-A, and FOXP3] on biopsies from different regions of healthy intestine and of intestine in inflammatory bowel diseases.

RESULTS

Healthy colon showed higher percentages of Treg, Th17, and DN, and lower numbers of DP T cells compared with ileum [p < 0.05]. Some but not all region-specific differences were lost in inflammatory conditions. Disease-specific patterns were found: a Th1/Th17 pattern and a Th17 pattern in Crohn's disease and ulcerative colitis respectively, whereas a reduction in Th1/Th17 was found in microscopic colitis. In colonic Crohn's disease and microscopic colitis, DN T cells had a pattern inverse to that of Th1/Th17 (increase in microscopic colitis [p < 0.05] and decrease in Crohn's disease [p < 0.005]). Higher levels of lymphocyte apoptosis were found in healthy colon compared with the ileal counterparts [p = 0.001]. All forms of colonic inflammation presented a dramatic decrease in apoptosis compared with healthy colon. By contrast ileal Crohn's disease showed higher levels of cleaved-Caspase(+) CD3(+) cells.

CONCLUSIONS

Immunological differences exist in healthy gastrointestinal tract. Inflammatory processes overwhelm some location-specific differences, whereas others are maintained. Care has to be taken when analysing immune response in intestinal inflammation, as location-specific differences may be relevant.

Protective effects of cathelicidin-encoding Lactococcus lactis in murine ulcerative colitis

BACKGROUND AND AIM

Intrarectal administration of mouse cathelin-related antimicrobial peptide (mCRAMP) reduced intestinal inflammation in mice. In the current study, we examined whether mCRAMP-transformed Lactococcus lactis given orally attained similar protective effects.

METHOD

mCRAMP was produced and secreted from the transformed L. lactis. Murine colitis was induced by ingestion of 3% dextran sulfate sodium (DSS) for 7 days. Eight or 10 log colony forming unit (cfu) L. lactis or the transformed strains with or without nisin induction were given orally as a parallel treatment with DSS. The body weight, fecal microbiota populations, clinical symptoms and histological examinations of colonic tissues were determined. Myeloperoxidase (MPO) activity and malondialdehyde (MDA) level were also evaluated to reflect the degree of inflammation. A prototype anti-inflammatory drug sulfasalazine was used as a reference drug to compare the efficacy and mechanisms of action for ulcerative colitis (UC).

RESULT

Compared with the control group with colitis, cathelicidin-transformed L. lactis could improve the clinical symptoms, maintain crypt integrity and preserve mucus content (P < 0.01). The number of apoptotic cells, MPO activity and MDA level were also significantly reduced (P < 0.05). The increases of fecal microbiota in colitis animals were markedly prevented (P < 0.001). Unlike mCRAMP-encoding L. lactis, effective doses of sulfasalazine only alleviated the clinical symptoms (P < 0.01) but not the mucosal damage in the colon.

CONCLUSION

mCRAMP-transformed L. lactis has been shown to produce mCRAMP, effectively preventing murine UC. Oral administration of this biological preparation is better than sulfasalazine for the treatment of UC.

Butyrate suppresses colonic inflammation through HDAC1-dependent Fas upregulation and Fas-mediated apoptosis of T cells

Butyrate, an intestinal microbiota metabolite of dietary fiber, has been shown to exhibit protective effects toward inflammatory diseases such as ulcerative colitis (UC) and inflammation-mediated colorectal cancer. Recent studies have shown that chronic IFN-γ signaling plays an essential role in inflammation-mediated colorectal cancer development in vivo, whereas genome-wide association studies have linked human UC risk loci to IFNG, the gene that encodes IFN-γ. However, the molecular mechanisms underlying the butyrate-IFN-γ-colonic inflammation axis are not well defined. Here we showed that colonic mucosa from patients with UC exhibit increased signal transducer and activator of transcription 1 (STAT1) activation, and this STAT1 hyperactivation is correlated with increased T cell infiltration. Butyrate treatment-induced apoptosis of wild-type T cells but not Fas-deficient (Fas(lpr)) or FasL-deficient (Fas(gld)) T cells, revealing a potential role of Fas-mediated apoptosis of T cells as a mechanism of butyrate function. Histone deacetylase 1 (HDAC1) was found to bind to the Fas promoter in T cells, and butyrate inhibits HDAC1 activity to induce Fas promoter hyperacetylation and Fas upregulation in T cells. Knocking down gpr109a or slc5a8, the genes that encode for receptor and transporter of butyrate, respectively, resulted in altered expression of genes related to multiple inflammatory signaling pathways, including inducible nitric oxide synthase (iNOS), in mouse colonic epithelial cells in vivo. Butyrate effectively inhibited IFN-γ-induced STAT1 activation, resulting in inhibition of iNOS upregulation in human colon epithelial and carcinoma cells in vitro. Our data thus suggest that butyrate delivers a double-hit: induction of T cell apoptosis to eliminate the source of inflammation and suppression of IFN-γ-mediated inflammation in colonic epithelial cells, to suppress colonic inflammation.

Intraperitoneal but not intravenous cryopreserved mesenchymal stromal cells home to the inflamed colon and ameliorate experimental colitis

Background and Aims

Mesenchymal stromal cells (MSCs) were shown to have immunomodulatory activity and have been applied for treating immune-mediated disorders. We compared the homing and therapeutic action of cryopreserved subcutaneous adipose tissue (AT-MSCs) and bone marrow-derived mesenchymal stromal cells (BM-MSCs) in rats with trinitrobenzene sulfonic acid (TNBS)–induced colitis.

Methods

After colonoscopic detection of inflammation AT-MSCs or BM-MSCs were injected intraperitoneally. Colonoscopic and histologic scores were obtained. Density of collagen fibres and apoptotic rates were evaluated. Cytokine levels were measured in supernatants of colon explants. For cell migration studies MSCs and skin fibroblasts were labelled with Tc-99m or CM-DiI and injected intraperitonealy or intravenously.

Results

Intraperitoneal injection of AT-MSCs or BM-MSCs reduced the endoscopic and histopathologic severity of colitis, the collagen deposition, and the epithelial apoptosis. Levels of TNF-α and interleukin-1β decreased, while VEGF and TGF-β did not change following cell-therapy. Scintigraphy showed that MSCs migrated towards the inflamed colon and the uptake increased from 0.5 to 24 h. Tc-99m-MSCs injected intravenously distributed into various organs, but not the colon. Cm-DiI-positive MSCs were detected throughout the colon wall 72 h after inoculation, predominantly in the submucosa and muscular layer of inflamed areas.

Conclusions

Intraperitoneally injected cryopreserved MSCs home to and engraft into the inflamed colon and ameliorate TNBS-colitis.

Cellular and molecular mechanisms in the two major forms of inflammatory bowel disease

The factors involved in the pathogenesis of Crohn's disease and ulcerative colitis, the two major types of inflammatory bowel disease (IBD) are summarized. Intestinal antigens composed of bacterial flora along with antigen presentation and impaired mucosal barrier have an important role in the initiation of IBD. The bacterial community may be modified by the use of antibiotics and probiotics. The dentritic cells recognize the antigens by cell surface Toll like receptor and the cytoplasmic CARD/NOD system. The balance between Th1/Th2/Th17 cell populations being the source of a variety of cytokines regulates the inflammatory mechanisms and the clearance of microbes. The intracellular killing and digestion, including autophagy, are important in the protection against microbes and their toxins. The homing process determines the location and distribution of the immune cells along the gut. All these players are potential targets of pharmacological manipulation of disease status.

Regulation of homeostasis and inflammation in the intestine

The gastrointestinal tract is the largest immune interface with the environment. Exposure to large numbers of dietary and microbial antigens requires complex and highly regulated immune responses by different mucosal cell types, which result in the induction and maintenance of intestinal homeostasis. Defects in this equilibrium can disrupt the homeostatic mechanisms and lead to chronic intestinal inflammation. We review the cell populations and mechanisms involved in the control of intestinal homeostasis and inflammation, focusing on inflammatory bowel diseases. We describe some aspects of gut immunity that could alter the delicate balance between inflammatory and tolerogenic responses and result in chronic gastrointestinal tract inflammation in patients.

Apoptosis and inflammation: role of adipokines in inflammatory bowel disease

OBJECTIVES

Leptin and adiponectin (APN) are adipokines produced by adipocytes that participate in the modulation of immune and inflammatory responses. In Crohn's disease (CD), fat wrapping surrounding the inflamed intestine produces high levels of leptin and APN. In inflammatory bowel disease (IBD), apoptosis resistance of lamina propria T lymphocytes (LPL-T) is one of the mechanisms that maintains chronic inflammation. We addressed the mechanism by which leptin and APN regulate inflammation and apoptosis in IBD.

METHODS

Immune cell infiltration, several factors expressed by adipose tissue (AT), and spontaneous release of cytokines by adipocytes were measured. The presence of APN and leptin in intestinal mucosa was detected and their effect on LPL-T apoptosis, signal transducer and activator of transcription 3 (STAT3), Suppressor of Cytokine Signaling 3 (SOCS3), Bcl-2 and Bcl-xL expression, and cytokine production was studied. In addition, the effects of globular and high-molecular-weight (HMW) APN on LPL-T cytokine production and apoptosis were studied.

RESULTS

Higher levels of several chemokines, cytokines, and growth factors were present in AT near active than near inactive disease. A significantly higher amount of inflammatory infiltrate was present in AT near active CD than near ulcerative colitis, controls, and near the inactive area of CD. There were no changes in the ratios of APN molecular weight in control and IBD adipocyte products. Leptin and APN inhibited anti-CD3-stimulated-LPL-T apoptosis and potentiated STAT3 phosphorylation, Bcl-2, and Bcl-xL expression in IBD and control mucosa. However, SOCS3 expression was suppressed only in IBD. Both globular and HMW APN have similar effects on LPL-T cytokine production and apoptosis. Leptin and APN enhanced interleukin (IL)-10 production by anti-CD3-stimulated LPL-T in IBD only. APN, but not leptin, increased anti-CD3-induced IL-6 levels in LPL-T only in IBD patients. IL-10 exerts its anti-inflammatory activity in the presence of SOCS3 suppression by leptin or APN.

CONCLUSION

Leptin and APN maintain the inhibition of anti-CD3-stimulated LPL-T apoptosis by enhancing Bcl-2 and Bcl-xL overexpression and promoting STAT3 phosphorylation while suppressing SOCS3.

Fat intake interacts with polymorphisms of Caspase9, FasLigand and PPARgamma apoptotic genes in modulating Crohn's disease activity

BACKGROUND & AIMS

Crohn's disease (CD) is a multifactorial disease where resistance to apoptosis is one major defect. Also, dietary fat intake has been shown to modulate disease activity. We aimed to explore the interaction between four single nucleotide polymorphisms (SNPs) in apoptotic genes and dietary fat intake in modulating disease activity in CD patients.

METHODS

Polymerase Chain Reaction (PCR) and Restriction Fragment Length Polymorphism (RFLP) techniques were used to analyze Caspase9+93C/T, FasLigand-843C/T, Peroxisome Proliferator-Activated Receptor gamma+161C/T and Peroxisome Proliferator-Activated Receptor gamma Pro12Ala SNPs in 99 patients with CD and 116 healthy controls. Interactions between SNPs and fat intake in modulating disease activity were analyzed using regression analysis.

RESULTS

None of the polymorphisms analyzed influenced disease susceptibility and/or activity, but a high intake of total, saturated and monounsaturated fats and a higher ratio of n-6/n-3 polyunsaturated fatty acids(PUFA), was associated with a more active phenotype (p < 0.05). We observed that the detrimental effect of a high intake of total and trans fat was more marked in wild type carriers of the Caspase9+93C/T polymorphism [O.R(95%CI) 4.64(1.27-16.89) and O.R(95%CI) 4.84(1.34-17.50)]. In the Peroxisome Proliferator-Activated Receptor gamma Pro12Ala SNP, we also observed that a high intake of saturated and monounsaturated fat was associated to a more active disease in wild type carriers [OR(95%CI) 4.21(1.33-13.26) and 4.37(1.52-12.51)]. Finally, a high intake of n-6 PUFA was associated with a more active disease in wild type carriers for the FasLigand-843C/T polymorphism [O.R(95%CI) 5.15(1.07-24.74)].

CONCLUSIONS

To our knowledge, this is the first study to disclose a synergism between fat intake and SNPs in apoptotic genes in modulating disease activity in CD patients.

Association of Fas/Apo1 gene promoter (-670 A/G) polymorphism in Tunisian patients with IBD

AIM: To detect a possible association between the polymorphism of the (-670 A/G) Fas/Apo1 gene promoter and susceptibility to Crohn’s disease (CD) and ulcerative colitis (UC) in the Tunisian population.

METHODS: The (-670 A/G) Fas polymorphism was analyzed in 105 patients with CD, 59 patients with UC, and 100 controls using the polymerase chain reaction restriction fragment length polymorphism method.

RESULTS: Significantly lower frequencies of the Fas -670 A allele and A/A homozygous individuals were observed in CD and UC patients when compared with controls. Analysis of (-670 A/G) Fas polymorphism with respect to sex in CD and UC showed a significant difference in A/A genotypes between female patients and controls (P corrected = 0.004 in CD patients and P corrected = 0.02 in UC patients, respectively). Analysis also showed a statistically significant association between genotype AA of the (-670 A/G) polymorphism and the ileum localization of the lesions (P corrected = 0.048) and between genotype GG and the colon localization (P corrected = 0.009). The analysis of inflammatory bowel disease patients according to clinical behavior revealed no difference.

CONCLUSION: Fas-670 polymorphism was associated with the development of CD and UC in the Tunisian population.

Peroxisome proliferator-activated receptor-alpha modulates the anti-inflammatory effect of glucocorticoids in a model of inflammatory bowel disease in mice

Glucocorticoids (GCs) are effective anti-inflammatory agents widely used in therapeutic approach to treatment of inflammatory bowel disease (IBD). Previous results suggest that peroxisome proliferator-activated receptor [alpha] (PPAR-[alpha]), an intracellular transcription factor activated by fatty acids, plays a role in control of inflammation. With the aim to characterize the role of PPAR-[alpha] in GC-mediated anti-inflammatory activity, we tested the efficacy of dexamethasone (DEX), a synthetic GC specific for GR, in an experimental model of IBD induced by dinitrobenzene sulfonic acid, comparing mice lacking PPAR-[alpha] (PPAR-[alpha]KO) with wild-type (WT) mice. Results indicate that DEX-mediated anti-inflammatory activity is weakened in PPAR-[alpha]KO mice as compared with WT controls. In particular, DEX was less effective in PPAR-[alpha]KO compared with WT mice, as evaluated by inhibition of proinflammatory cytokines production, cell migration, oxidative stress, apoptosis, and colon injury. These results indicate that PPAR-[alpha] can contribute to the anti-inflammatory activity of GCs in IBD.

Does nicotine influence cytokine profile and subsequent cell cycling/apoptotic responses in inflammatory bowel disease?

BACKGROUND

Smoking differentially influences susceptibility to the inflammatory bowel diseases (IBDs) Crohn's disease (CD) and ulcerative colitis (UC). We investigated the effects of nicotine on cytokine, cell cycle, and apoptotic responses in peripheral blood mononuclear cells (PBMCs) from IBD patients and healthy controls (HCs).

METHODS

PBMCs from IBD patients and HC were stimulated with lipopolysaccharide (LPS; 1 microg/mL) or phytohemagglutinin (PHA, 5 or 0.5 microg/mL), +/- nicotine (1, 10, 100 microg/mL). Cytokines (IL1beta, IL2, IL10, IL12/IL23p40, TGFbeta, TNFalpha) were measured in supernatants at 24 hours. After 72 hours cells were analyzed by flow cytometry for cell cycle and apoptosis. Statistical modeling was used to identify interactions between cytokines and cell cycle / apoptosis and minimize confounding effects.

RESULTS

Stimulation by LPS and PHA (5 microg/mL) increased IL12/IL23p40 production from CD and UC versus HC (P < 0.05); PHA (0.5 microg/mL) increased IL1beta in UC and decreased TGFbeta from CD and UC (P < 0.01). In all groups, nicotine reduced LPS- and PHA (0.5 microg/mL)-stimulated production of IL1beta, IL10, TGFbeta, and TNFalpha (P < 0.001). Cell cycle analysis showed that PHA, but not LPS, induced proliferation and decreased G(0)/G(1) resting cells in CD and UC versus HC (P < 0.001). Nicotine decreased PHA-stimulated S-phase proliferation and increased G(0)/G(1) resting cells (P < 0.01). Modeling showed independent associations between IL12/IL23p40 and apoptosis (P = 0.01), IL1beta and resting cells (P = 0.006), TNFalpha and proliferating cells (P < 0.001). Disease activity and smoking habit had no effect.

CONCLUSIONS

Dysregulated cytokine profiles in UC and CD are associated with specific alterations in cell cycle responses; these effects may be modified by nicotine, and potentially by anticytokine therapies.

Visilizumab induces apoptosis of mucosal T lymphocytes in ulcerative colitis through activation of caspase 3 and 8 dependent pathways

Visilizumab, a humanized low-Fc receptor binding anti-CD3 antibody, induces rapid clinical response in patients with steroid-refractory ulcerative colitis (UC). Several effective treatments in IBD have been linked to the induction of mucosal T cell apoptosis. The aim of the present study was to evaluate the effect of visilizumab on the apoptosis of lamina propria (LP) and peripheral blood (PB) lymphocytes isolated from patients with UC. Visilizumab induced dose- and time-dependent apoptosis of LP T cells isolated from non-IBD individuals, UC or CD patients. Maximal effect was seen at a concentration of 100 ng/ml and it was 33% for normal, 34% for UC and 23% for CD LP T cells following 24 h stimulation. Visilizumab induced apoptosis predominantly of CD4(+) LP T cells, whereas CD8(+) LP T cells were relatively resistant to apoptosis. Visilizumab did not induce apoptosis of PB T cells from UC patients. Visilizumab-induced apoptosis of LP T cells was dependent on caspase 3 and 8, but not caspase 9 activation and did not involve the Fas/FasL pathway. Low-Fc receptor binding Abs such as visilizumab may be highly effective for the treatment of UC through induction of apoptosis of LP T cells and rapid elimination of lesional pathogenic T cells in the gut mucosa.

Melatonin reduces bacterial translocation and apoptosis in trinitrobenzene sulphonic acid-induced colitis of rats

AIM: To investigate the effects of exogenous melatonin on bacterial translocation and apoptosis in a rat ulcerative colitis model.

METHODS: Rats were randomly assigned to three groups: groupI: control, group II: experimental colitis, group III: colitis plus melatonin treatment. On d 11 after colitis, plasma tumor necrosis factor-α, portal blood endotoxin levels, colon tissue myeloperoxidase and caspase-3 activity were measured. Bacterial translocation was quantified by blood, lymph node, liver and spleen culture.

RESULTS: We observed a significantly reduced incidence of bacterial translocation to the liver, spleen, mesenteric lymph nodes, portal and systemic blood in animals treated with melatonin. Treatment with melatonin significantly decreased the caspase-3 activity in colonic tissues compared to that in trinitrobenzene sulphonic acid- treated rats (16.11 ± 2.46 vs 32.97 ± 3.91, P < 0.01).

CONCLUSION: Melatonin has a protective effect on bacterial translocation and apoptosis.

The Immunology of Immediate and Delayed Hypersensitivity Reaction to Gluten

The immunology of gluten hypersensitivity and celiac disease has been pursued with significant interest in the past 20 years. For the prevention of systemic diseases, most pathogens that gain entry into our bodies must be met with an effective immune response, yet in the gastrointestinal tract it is equally important that commensal bacteria and a diverse collection of dietary proteins and peptides be recognized without eliciting an active immune response or constant activation of the inflammatory pathway. This phenomenon of hyporesponsiveness to food antigens is known as oral tolerance. This oral tolerance to dietary antigens is maintained by three different mechanisms: anergy, cell deletion and immune suppression. However, in the presence of mechanical/chemical stressors and infections, this tolerance may break down, and gut associated lymphoid tissues (GALT) will react to different luminal antigens. The reaction of GALT to these antigens may lead to the production of pro-inflammatory cytokines, opening of tight junctions, entry of undigested antigens into the circulation, and the subsequent production of IgA, IgG, IgM and IgE antibodies in blood and secretory components. Like any other food hypersensitivity reaction, gluten sensitivity can be divided into immediate and delayed hypersensitivities. In this review an attempt is made first to differentiate immediate hypersensitivity to gliadin, mediated by IgE, from delayed hypersensitivity, which is mediated by IgA and IgG. Furthermore, we attempt to differentiate between gluten hypersensitivity with enteropathy (celiac disease) and gluten hypersensitivity without enteropathy.

Reduced apoptosis in BALB/c mice infected with Heligmosomoides polygyrus

We evaluated levels of apoptosis and the immune response ex vivo in BALB/c mice infected with Heligmosomoides polygyrus. Cell proliferation, apoptosis and cytokine production were measured in mesenteric lymph nodes (MLN) without exposure to H. polygyrus antigens in culture. The inhibited apoptosis and cytokine production reported might reflect a state of cell hyporesponsiveness in the prepatent phase of infection. These changes were accompanied by changes in the percentage of CD4+ cells in MLN and popliteal lymph nodes (PLN). The prolonged reduction in apoptosis coexisted with induced cell proliferation, elevated TNF-alpha, IL-12p70, IFN-gamma, IL-6, IL-10 and TGF-beta synthesis, but lowered IL-4 and IL-2 levels. In the chronic phase of infection an increasing production of IFN-gamma, monocyte chemotactic protein-1 (MCP-1), IL-10 and TGF-beta with decreasing concentrations of other cytokines resulted in restored apoptosis. The cytokine response in serum showed moderate production of TNF-alpha, temporary involvement of IL-12p70, induction of IFN-gamma and IL-10 synthesis, as well as growing IL-6 and MCP-1 production. It is suggested that a synchronized synthesis of distinct cytokines is accompanied by different levels of inhibited apoptosis during the prepatent and chronic phases of H. polygyrus infection in BALB/c mice. We suggest that immunosuppression provoked by the nematode is not the outcome of parasite-induced apoptosis, but rather results from a hyporesponsiveness experienced by cells during H. polygyrus infection.

Melatonin modulates signal transduction pathways and apoptosis in experimental colitis

Various evidences have documented that the pineal secretory product melatonin exerts an important anti-inflammatory effect in different experimental models including colitis. The aim of the present study was to evaluate whether melatonin regulates the inflammatory response of experimental colitis in rats at the level of signal transduction pathway. Colitis was induced by intracolonic instillation of dinitrobenzene sulfonic acid (DNBS). Four days after DNBS administration, a substantial increase of colon TNF-alpha production was associated with the colon damage. In DNBS-treated rats, the colon injury correlated with a significant rise of apoptosis (evaluated by TUNEL coloration) which was associated with a significant increased expression of proapoptotic Bax and decreased colon content of antiapoptotic Bcl-2. This inflammatory response was also related to activation of nuclear factor-kappaB (NF-kappaB) and phosphorylation of c-Jun as well as FAS ligand expression in the colon. Treatment with melatonin (15 mg/kg daily i.p.) was associated with a remarkable amelioration of colonic disrupted architecture as well as a significant reduction of TNF-alpha. Melatonin also reduced the NF-kappaB activation and phosphorylation of c-Jun as well as the Fas ligand expression in the colon. Furthermore, melatonin reduced the expression of Bax and prevented the loss of Bcl-2 proteins as well as the presence of apoptotic cells caused by DNBS. The results of this study show that melatonin administration exerts beneficial effects in inflammatory bowel disease by modulating signal transduction pathways.

Apoptosis resistance in ulcerative colitis: high expression of decoy receptors by lamina propria T cells

Intestinal mucosa is constantly exposed to normal environmental antigens. A significant number of intestinal mucosal T cells are being deleted through apoptosis. In contrast, T cells from inflamed mucosa of ulcerative colitis patients did not undergo apoptosis. In this study, we determined whether the apoptosis of normal mucosal T cells was induced by antigen receptor stimulation and further determined pathways that mediated the apoptosis. Freshly isolated lamina propria T cells were stimulated with CD3 mAb and apoptosis was determined by Annexin V staining. Normal mucosal T cells underwent apoptosis upon CD3 mAb stimulation whereas the T cells from inflamed mucosa did not. The apoptosis in normal T cells was blocked by TRAIL-R1:Fc and an inhibiting CD95 antibody. Interestingly, decoy receptor (DcR)1, DcR2, and DcR3 that compete with death receptor (DR)4/5 and CD95 were highly expressed by the T cells from inflamed mucosa, but much lower by T cells from normal mucosa. Our data suggest that normal mucosal T cells are constantly deleted in response to environmental antigens mediated through DR4/5 and CD95 pathways and mucosal T cells from ulcerative colitis resist to undergoing apoptosis due to highly expression of DcR1, DcR2, and DcR3.

The development of the mucosal immune system pre- and post-weaning: balancing regulatory and effector function

The mucosal immune system fulfils the primary function of defence against potential pathogens that may enter across vulnerable surface epithelia. However, a secondary function of the intestinal immune system is to discriminate between pathogen-associated and 'harmless' antigens, expressing active responses against the former and tolerance to the latter. Control of immune responses appears to be an active process, involving local generation of IgA and of regulatory and/or regulated T lymphocytes. Two important periods of maximum exposure to novel antigens occur in the young animal, immediately after birth and at weaning. In both cases the antigenic composition of the intestinal contents can shift suddenly, as a result of a novel diet and of colonisation by novel strains and species of bacteria. Changes in lifestyles of man, and husbandry of animals, have resulted in weaning becoming much more abrupt than previously in evolution, increasing the number of antigens that must be simultaneously evaluated by neonates. Thus, birth and weaning are likely to represent hazard and critical control points in the development of appropriate responses to pathogens and harmless dietary and commensal antigens. Neonates are born with relatively undeveloped mucosal immune systems. At birth this factor may prevent both expression of active immune responses and development of tolerance. However, colonisation by intestinal flora expands the mucosal immune system in antigen-specific and non-specific ways. At weaning antibody to fed proteins can be detected, indicating active immune responses to fed proteins. It is proposed that under normal conditions the ability of the mucosal immune system to mount active responses to foreign antigens develops simultaneously with the ability to control and regulate such responses. Problems arise when one or other arm of the immune system develops inappropriately, resulting in inappropriate effector responses to harmless food proteins (allergy) or inadequate responses to pathogens (disease susceptibility).

A functional role of flip in conferring resistance of Crohn's disease lamina propria lymphocytes to FAS-mediated apoptosis

BACKGROUND & AIMS

There is evidence that, in Crohn's disease (CD), lamina propria T lymphocytes (LPLs) are resistant to FAS-mediated apoptosis and that this defect contributes to the mucosal T-cell accumulation. In this study we examined the functional role of Flip, a Flice inhibitor protein, in the resistance of CD LPL to FAS-mediated apoptosis.

METHODS

Biopsy specimens and LPLs were taken from CD and ulcerative colitis (UC) patients and normal controls and analyzed for Flip by Western blotting. We also examined whether inhibition of Flip by antisense oligonucleotide restored the susceptibility of CD LPLs to FAS-induced apoptosis. LPL apoptosis was assessed by flow cytometry.

RESULTS

After FAS stimulation, the rate of apoptosis of CD3+ LPLs was higher in normal controls and patients with UC than in patients with CD. Enhanced expression of both long and short Flip isoforms was seen in biopsy specimens and purified CD3+ and CD45RO+ LPLs of CD patients in comparison with UC patients and normal controls. No increase in Flip was documented in untreated celiac disease mucosa, thus suggesting the possibility that induction of Flip in the gut does not simply rely on the ongoing inflammation. Finally, we showed that inhibition of Flip by antisense oligonucleotide reverted the resistance of CD LPLs to FAS-induced apoptosis.

CONCLUSIONS

Data suggest a role for Flip in the resistance of CD LPLs to FAS-mediated apoptosis.

Perils at mucosal front lines for HIV and SIV and their hosts

HIV-1 and simian immunodeficiency virus (SIV), as well as their hosts, face perils at mucosal front lines in early infection. At these sites, 'resting' CD4+ memory T cells fuel infection (because they are hosts for virus), depleting CD4+ memory T cells throughout the lymphoid tissues, particularly in the gut, and eliciting an immunosuppressive regulatory T-cell response that impairs host defence. But HIV-1 and SIV also risk elimination at the earliest stage of infection, at the mucosal point of entry, if founder populations of infected cells do not expand sufficiently to establish a self-propagating infection. Microbicides and vaccines could increase these viral vulnerabilities at mucosal front lines.

In vivo corticosterone administration at levels occurring with intense exercise does not induce intestinal lymphocyte apoptosis in mice

Intestinal lymphocyte apoptosis can occur following physiological and pathophysiological stress as well as exhaustive exercise. In this study we investigated whether corticosterone (CORT) administration at physiological concentrations observed following strenuous exercise induces intestinal lymphocyte apoptosis and cell loss in mice. CORT injection (14 mg/kg; i.p.) caused a four-fold increase in plasma CORT concentrations, but did not affect intestinal lymphocyte cell loss or alter baseline intestinal lymphocyte apoptosis, as measured by phosphatidylserine externalization, cell viability, mitochondrial membrane depolarization, caspase 3, Bcl-2 and cytosolic cytochrome c protein levels. These findings indicate that CORT at levels observed following strenuous exercise is not involved in intestinal lymphocyte apoptosis and cell loss.

Gliadin as a stimulator of innate responses in celiac disease

In celiac disease (CD) we have the prototype of an immune mediated response dominated by the activation of the adaptive immune system and in particular of CD4+ HLA class II restricted T cells. Various seminal studies have established the precise mechanism of how antigen (prolamine) specific activation of CD4+ mucosal T cells occurs. Thus, CD is a condition in which T cells and their activation is the essential hinge in the pathogenic process. These functional studies have provided the explanation for the genetic association between CD and certain HLA alleles (HLA DQ2 and DQ8). These genetic, molecular and functional studies have permitted the clarification of a powerful Th1 dominated pro-inflammatory response that characterises the small intestine of active CD patients. Despite this unassailable set of information and reports there are some intriguing points that have been raised by a series of studies which have indicated that CD is not only defined by an aberrant prolamine-induced activation of the adaptive immune system. New evidence and re-assessments of old studies, point to a more complex pathogenic cascade, which may help to unravel some of the residual obscure points of CD pathogenesis. Here, we outline the current concepts that indicate a direct involvement of the adaptive immune system and we discuss all the evidence supporting a direct activation of the innate immune system by fragments of prolamines, which are not recognized T cell epitopes and how they could influence CD. The gliadin-induced activation of the 'innate' immune system might also have a significant role in the induction and persistence of many CD complications and most definitively for the most aggressive one, namely mucosal T cell lymphomas. We further suggest a novel way to harness the unwanted immune response to toxic prolamine, and thus indicate new potential therapeutic strategies to treat or at least control CD.

Apoptosis in the intestinal mucosa of patients with inflammatory bowel disease: evidence of altered expression of FasL and perforin cytotoxic pathways

BACKGROUND AND AIMS

Abnormal apoptosis may result in the persistence of activated intestinal T-cells in inflammatory bowel disease (IBD). We investigated apoptosis in distinct mucosal compartments, and the expression of Fas/Fas ligand and perforin in the inflamed and non-inflamed intestinal mucosa of patients with IBD.

METHODS

Colon specimens from 15 patients with ulcerative colitis (UC) and inflamed and non-inflamed mucosa from 15 patients with Crohn's disease (CD) were analysed for densities and distribution of apoptotic cells determined by the terminal deoxynucleotidyltransferase-mediated dUDP-biotin nick-end labelling (TUNEL) method. Fas, FasL, and perforin-expressing cells were assessed by immunoperoxidase, and with anti-CD3, anti-CD20 and anti-CD68, by double immunofluorescence with confocal microscopy. Quantitative analysis was performed using a computer-assisted image analyser.

RESULTS

Colonic lamina propria (LP) and epithelium from patients with UC showed higher rates of apoptosis than controls, but no difference was shown regarding patients with CD. In LP, co-expression of Fas was reduced with T-cells in inflamed CD mucosa, and with macrophages in all patients with IBD. No difference was found in the expression of Fas on B-cells. Rates of FasL-expressing cells in LP were higher in IBD than in controls, with no correlation with the rates of apoptosis. Rates of perforin-expressing cells in LP were greater in UC than in controls, and correlated to the rates of apoptosis. No difference was shown regarding the inflamed and non-inflamed CD mucosa. Rates of FasL and perforin-expressing intra-epithelial lymphocytes showed no difference among groups.

CONCLUSIONS

Increased expression of FasL in IBD colonic LP not parallelled by Fas on T-cells and macrophages may indicate a reduced susceptibility to the Fas/FasL-mediated apoptosis of lymphoid cells. Expression of perforin is correlated to the tissue damage, and may represent the enhancement of a distinct cytotoxic pathway in UC.

Inflammatory bowel disease: dysfunction of GALT and gut bacterial flora (I)

Gut-associated lymphoid tissue (GALT) is the largest lymphoid organ in the body. This is not surprising considering the huge load of antigens (Ags) from food and commensal bacteria with which it interacts on a daily basis. Gut-associated lymphoid tissue has to recognise and allow the transfer of beneficial Ags whilst concurrently dealing with and successfully removing putative and overtly harmful Ags. This distinctive biological feature of GALT is believed to be crucial to good health. Deregulation or dysfunction of GALT is thought to predispose to inflammatory bowel diseases (IBD) such as ulcerative colitis and Crohn's disease. The exact mechanism(s) underlying the pathogenesis of IBD is (are) poorly understood and the immunological defects in GALT are poorly documented. Advances in immunology have highlighted the importance of dendritic cells (DCs), which are the key Ag presenting cells in tissues and lymphoid compartments. Their crucial role in GALT, in health and disease is discussed in this review. Interaction of DCs with T cells in the gut produces a subset of T lymphocytes, which have immunosuppressive function. Inappropriate Ag uptake and presentation to naïve T cells in mesenteric lymph nodes may lead to T cell tolerance in GALT. These various complex factors in the gut are discussed and their possible relevance to IBD evaluated.

Polyethylene glycol but not mifepristone prevents intestinal lymphocyte loss following treadmill exercise in mice

Circulating lymphocyte numbers decrease following intense physical activity, possibly due to exercise-induced apoptosis. Increased reactive oxygen species (ROS) and glucocorticoids (GC) following exercise contribute to lymphocyte apoptosis. Intestinal lymphocyte (IL) numbers also decrease following exercise.

AIM

The purpose of this study was to determine the contribution of GC to exercise-induced IL loss.

METHODS

Female C57BL/6 mice (n = 178) were randomized to five drug conditions: (1) single injection of the glucocorticoid receptor antagonist mifepristone (MIF) solubilized in polyethylene glycol (PEG); (2) three injections of MIF (repeated MIF) PEG; (3) single injection of PEG (PEG); (4) three injections of PEG (repeated PEG); or (5) repeated injections of saline (SAL). Within each drug group mice were further randomized to exercise conditions: (1) control condition (non-exercised); (2) treadmill running with sacrifice immediately following the exercise; or (3) treadmill running with sacrifice 24 h after completion of the exercise.

RESULTS

There was a significant exercise effect, across all T lymphocyte subsets, in SAL (P < 0.01), PEG (P < 0.01) and MIF (P < 0.01) treated mice but not in mice given repeated PEG or repeated MIF exposure. The exercise effect was due to reduced IL numbers 24 h post-exercise compared with non-exercised controls.

CONCLUSION

These results suggest that GC are not directly responsible for IL cell loss following exercise. Repeated exposure to PEG may confer protection in the gastrointestinal tract from exercise-induced lymphocyte depletion. Because PEG inhibits ROS generation in experimental cell injury, the mechanisms for IL loss after exercise may involve oxidative stress.

Association of Fas-670 gene polymorphism with inflammatory bowel disease in Chinese patients

AIM: Recent studies suggest that Fas-mediated apoptosis is involved in the pathogenesis of inflammatory bowel disease (IBD). It has been hypothesized that either increased apoptosis of intestinal epithelium or decreased apoptosis of lamina propria lymphocytes may induce inflammation of gut. The aim of this study was to determine whether the Fas gene promoter polymorphism at position-670 was associated with IBD in Chinese patients.

METHODS: Fifty unrelated Chinese patients with IBD (38 patients with ulcerative colitis and 12 with Crohn’s disease) and 124 healthy controls were genotyped for the Fas-670 polymorphism by PCR-restriction fragment length polymorphism method. The PCR product was digested by Mva I restriction enzyme.

RESULTS: Distribution of the Fas-670 gene polymorphism was 33% for the AA genotype, 52% for the AG genotype and 15% for the GG genotype in 124 healthy subjects. In patients with IBD, 30% was for the AA genotype, 42% for the AG genotype and 28% for the GG genotype respectively. However, there was no significant difference in the genotype (P = 0.1498), allele frequencies (P = 0.3198) and carriage frequencies (P = 0.4133) between healthy controls and IBD patients. Furthermore, we did not find any difference between the left-sided colitis and total colitis (P = 0.8242).

CONCLUSION: Fas-670 polymorphism is not associated with IBD in Chinese patients.

Activator protein-1 signalling pathway and apoptosis are modulated by poly(ADP-ribose) polymerase-1 in experimental colitis

Poly(ADP-ribose) polymerase-1 (PARP-1) is activated in response to DNA injury in the nucleus of eukaryotic cells and has been implicated in intestinal barrier dysfunction during inflammatory bowel diseases. In this study we investigated whether PARP-1 may regulate the inflammatory response of experimental colitis at the level of signal transduction mechanisms. Mice genetically deficient of PARP-1 (PARP-1(-/-)) and wild-type littermates were subjected to rectal instillation of trinitrobenzene sulphonic acid (TNBS). Signs of inflammation were monitored for 14 days. In wild-type mice, TNBS treatment resulted in colonic ulceration and marked apoptosis, which was associated with decreased colon content of the antiapoptotic protein Bcl-2, whereas the proapoptotic Bax was unchanged. Elevated levels of plasma nitrate/nitrite, metabolites of nitric oxide (NO), were also found. These inflammatory events were associated with activation of c-Jun-NH(2) terminal kinase (JNK), phosphorylation of c-Jun and activation of the nuclear transcription factor activator protein-1 (AP-1) in the colon. In contrast, PARP-1(-/-) mice exhibited a significant reduction of colon damage and apoptosis, which was associated with increased colonic expression of Bcl-2 and lower levels of plasma nitrate/nitrite when compared to wild-type mice. Amelioration of colon damage was associated with a significant reduction of the activation of JNK and reduction of the DNA binding of AP-1. The data indicate that PARP-1 exerts a pathological role in colitis possibly by regulating the early stress-related transcriptional response through a positive modulation of the AP-1 and JNK pathways.

Adrenalectomy in mice does not prevent loss of intestinal lymphocytes after exercise

Exhaustive exercise is associated with an increase in circulating glucocorticoids (GCs), lymphocyte apoptosis, and a reduction in intestinal lymphocyte number. The present study examined the role of GCs on the numerical changes seen in intestinal lymphocytes after exercise. Female C57BL/6 mice were bilaterally adrenalectomized (ADX; n = 18) or given sham surgery (Sham; n = 18) and assigned to one of three exercise conditions: treadmill running (28 m/min, 90 min, 2 degrees slope) and killed immediately or after 24 h recovery, or not exercised and killed immediately after 90-min exposure to the treadmill environment. Lymphocytes were isolated from the intestines with CD45(+) cells collected by positive selection using magnetic bead separation columns, and lymphocyte subpopulations were analyzed by flow cytometry for CD45(+), CD3alphabeta(+), CD3gammadelta(+), CD8beta(+), CD8alpha(+), CD4(+), and NK(+) phenotypic markers. ADX mice had significantly more intestinal CD45(+) leukocytes (P < 0.05) and CD3alphabeta(+) (P < 0.05), CD3gammadelta(+) (P < 0.01), CD8alpha(+) (P < 0.001), and NK(+) (P < 0.05) intestinal lymphocytes than Sham mice. There was a significant effect of exercise condition on total intestinal CD45(+) leukocytes (P < 0.01) and CD3alphabeta(+) (P < 0.05), CD8alpha(+) (P < 0.001), and CD4(+) (P < 0.05) intestinal lymphocytes, with fewer cells at 24 h postexercise compared with the other treatment conditions. There were no surgical x exercise interaction effects on the CD3 and CD8 phenotype numbers. Plasma corticosterone was virtually nil in ADX mice regardless of exercise condition but was significantly elevated in Sham mice immediately postexercise (P < 0.001). The data indicate that ADX does not prevent the loss of lymphocytes from the intestinal mucosa 24 h after strenuous exercise and GCs are not directly causal in the leukopenia of exercise.

Cytolytic capabilities of lamina propria and intraepithelial lymphocytes in normal and chronically inflamed human intestine

Cell-mediated lymphocyte cytotoxicity in ileum and colon of patients with ulcerative colitis (UC), Crohn's disease (CD) and controls was investigated. Frequencies of cells expressing perforin and Fas-ligand (FasL) were determined by immunomorphometry. mRNA expression of perforin, granzyme B and FasL in T cells and subsets was assayed by reverse transcriptase-polymerase chain reaction. Cytotoxicity of intraepithelial and lamina propria lymphocytes was analysed without ex vivo activation in three functional assays: (1) anti-CD3-dependent T-cell receptor (TCR)-/CD3-mediated redirected cytotoxicity, (2) Fas-/FasL-mediated TCR-/CD3-independent cytotoxicity and (3) natural killer (NK) cell cytotoxicity. Inflammation in ileum of CD patients caused increased frequency of perforin-expressing cells and enhanced perforin-dependent TCR-/CD3-mediated cytotoxicity. In contrast, lymphocytes in the inflamed colon of UC or Crohn's colitis patients did not display this cytotoxicity nor did lymphocytes of normal colon. Normal colon lymphocytes showed spontaneous Fas-/FasL-mediated cytotoxicity. This activity was retained but not enhanced in inflamed UC colon. In contrast, a significant increase of FasL-expressing cells was seen in situ. Inflammation did not induce NK cell activity in colonic lymphocytes. Intestinal lymphocytes comprise effectors active in two different cytolytic processes. 'Classical' cytotoxic T lymphocytes in small intestine and lymphocytes executing TCR-/CD3-independent FasL-/Fas-mediated killing of unknown biological role present throughout the intestinal mucosa. Ongoing normal cytolytic processes seem to be enhanced by chronic inflammation.

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β-adrenergic receptor blockade during exercise decreases intestinal lymphocyte apoptosis but not cell loss in mice

Catecholamines induce apoptosis in various lymphoid populations. This process can occur with both α- and β-adrenoreceptors. Heavy exercise increases plasma catecholamine concentrations, and is also a cause of lymphocyte apoptosis, a possible explanation for postexercise lymphocytopenia. The purpose of this study was to examine the effects of adrenoreceptor antagonism on exercise-induced decreases and apoptosis of intestinal lymphocytes. Mice received an intraperitoneal injection of phentolamine (a nonselective α-blocker), nadolol (a nonselective β-blocker), or saline (vehicle) prior to an exhaustive bout of exercise. Total intestinal lymphocyte numbers, percent and number of CD3+ lymphocytes, and cell viability were assessed. Neither α- nor β-antagonism prevented exercise-induced cell loss in the intestine; however, pretreatment with nadolol significantly reduced the number of apoptotic and necrotic cells. Phentolamine administration appeared to increase the incidence of cell death among intestinal lymphocytes. Both drugs decreased the percentage of CD3+ intestinal lymphocytes. Our study suggests that catecholamines are not responsible for postexercise lymphocytopenia, but β-adrenoceptor blockade may confer protection against exercise-induced apoptosis of intestinal lymphocytes.Key words: catecholamines, exhaustive exercise, apoptosis, intestinal lymphocytes, rodents.

Mechanisms of acupuncture and moxibustion in regulation of epithelial cell apoptosis in rat ulcerative colitis

AIM: To investigate the effect of acupuncture and moxibustion on epithelial cell apoptosis and expression of Bcl-2, Bax, fas and FasL proteins in rat ulcerative colitis.

METHODS: A rat model of ulcerative colitis was estabelished by immunological methods and local stimulation. All rats were randomly divided into model control group (MC), electro-acupuncture group (EA), herbs-partition moxibustion group (HPM). Normal rats were used as normal control group (NC). Epithelial cell apoptosis and expression of Bcl-2, Bax, fas and FasL proteins were detected by TUNEL and immunohistochemiscal method respectively.

RESULTS: The number of epithelial cell apoptosis in MC was significantly higher than that in NC, and was markedly decreased after the treatment with herbs-partition moxibustion or electro-acupuncture. The expression of Bcl-2, Bax, fas and FasL in colonic epithelial cells in MC was higher than that in NC, and was markedly down- regulated by herbs-partition moxibustion or electro-acupuncture treatment.

CONCLUSION: The pathogenesis of ulcerative colitis in rats involves abnormality of apoptosis. Acupuncture and moxibustion can regulate the expression of Bcl-2, Bax, fas and FasL proteins and inhibit the apoptosis of epithelial cells of ulcerative colitis in rats by Bcl-2/Bax, fas/FasL pathways.

Targeting tumor necrosis factor-alpha in inflammatory bowel disease: why, how, and when?

A large proportion of patients with inflammatory bowel disease require more effective therapy, especially for the prevention of disease relapse. Recent therapeutic advances have focused on biologicals (monoclonal antibodies, therapeutic peptides, antisense oligonucleotides) that aim to neutralize specific proinflammatory proteins. This has proved successful for the anti-TNF-alpha antibody infliximab in patients with Crohn disease, but recent studies failed to demonstrate the efficacy of different anti-TNF-alpha strategies. Therefore, it seems essential to fully comprehend the molecular mechanisms of such compounds. An exciting development has been the association between drug efficacy and the induction of apoptosis in apoptosis-resistant lamina propria T cells in Crohn disease. Furthermore, TNF-alpha can also be targeted by "small molecules" to circumvent certain disadvantages of biologicals such as the nonoral route of administration, the potential immunogenicity, and the high costs of treatment. Several of these developments will certainly be relevant for designing future anti-TNF-alpha based strategies.

CD44v7 interferes with activation-induced cell death by up-regulation of anti-apoptotic gene expression

Blockade of CD44v7 was described to cure trinitrobenzene sulfonic acid-induced colitis, a disease not developed by mice with targeted deletion of the CD44v7 exon. There was evidence for a reduction in activation-induced cell death on lamina propria lymphocytes of control as compared with CD44v7-deficient mice. To elucidate the mechanism underlying the relative apoptosis resistance of CD44v7-competent as compared with CD44v7-deficient lymphocytes, T cell activation and induction of apoptosis were analyzed on mesenteric lymph node cells and Peyer's patch lymphocytes of CD44v7-deficient and CD44v4-v7-transgenic mice, which overexpress rat CD44v4-v7 on T lymphocytes. CD44v7 deficiency was characterized by an increase in the percentage of apoptotic cells after stimulation, increased numbers of CD95L- and CD152-positive cells, low levels of the anti-apoptotic proteins Bcl-2 and Bcl-Xl, and decreased phosphorylation of the pro-apoptotic protein BAD. Also, lymphocytes from CD44v4-v7-transgenic mice displayed reduced levels of CD95L, low numbers of apoptotic cells, and constitutively elevated levels of Bcl-Xl. When stimulating lymphocytes by CD3 cross-linking, CD44v7 was not recruited toward the immunological synapse and preferentially associated with the cytoskeletal-linker protein ezrin. Thus, as opposed to the CD44 standard isoform, CD44v7 does not function as an accessory molecule; instead, it supports survival of activated T cells by interfering with activation-induced cell death.

Infliximab but not etanercept induces apoptosis in lamina propria T-lymphocytes from patients with Crohn's disease

BACKGROUND & AIMS

Steroid-refractory Crohn's disease responds to therapy with the chimeric anti-tumor necrosis factor (TNF)-alpha antibody infliximab. Etanercept, a recombinant TNF receptor/immunoglobulin G fusion protein, is highly effective in rheumatoid arthritis but not in Crohn's disease. Because both infliximab and etanercept are TNF-alpha-neutralizing drugs, we investigated the differences in TNF-alpha-neutralizing capacity and human lymphocyte binding and apoptosis-inducing capacity of both molecules.

METHODS

We used a nuclear factor kappaB reporter assay and a cytotoxicity bioassay to study TNF-alpha neutralization by infliximab and etanercept. Lymphocyte binding and apoptosis-inducing capacity was investigated using fluorescence-activated cell sorter analysis, annexin V staining, and cleaved caspase-3 immunoblotting using mixed lymphocyte reaction-stimulated peripheral blood lymphocytes (PBL) from healthy volunteers and lamina propria T cells from patients with Crohn's disease.

RESULTS

Both infliximab and etanercept neutralized TNF-alpha effectively. Infliximab bound to activated PBL and lamina propria T cells, whereas binding of etanercept was equal to a nonspecific control antibody. Infliximab but not etanercept induced peripheral and lamina propria lymphocyte apoptosis when compared with a control antibody. Infliximab activated caspase 3 in a time-dependent manner, whereas etanercept did not.

CONCLUSIONS

Although both infliximab and etanercept showed powerful TNF-alpha neutralization, only infliximab was able to bind to PBL and lamina propria T cells and subsequently to induce apoptosis of activated lymphocytes. These data may provide a biological basis for the difference in efficacy of the 2 TNF-alpha-neutralizing drugs.

Connections between psoriasis and Crohn's disease

The prevalence of psoriasis in patients with Crohn's disease (CD) is higher than chance would allow if they were mutually exclusive diseases. A close examination reveals genetic and pathologic connections between these diseases. An appreciation for the role of tumor necrosis factor-alpha in both diseases has proven very important. Increased levels of this inflammatory cytokine have been measured in CD lesions, and in 1997 a clinical trial demonstrated the response of this disease to infliximab, a monoclonal antibody specific for tumor necrosis factor-alpha. A subsequent clinical trial evaluated infliximab in a patient with CD and psoriasis, another disease in which increased levels of tumor necrosis factor-alpha are seen in lesions. Scientists noticed the marked skin improvement of this patient and later demonstrated the efficacy of infliximab for psoriasis in a randomized, double-blind, placebo-controlled trial. Thus, an appreciation for connections between psoriasis and CD can suggest novel therapeutic strategies with ensuing benefits to patients. This article reviews epidemiologic, genetic, and pathologic connections between psoriasis and CD and discusses pharmaceuticals targeting inflammatory mediators common to each disease. (J Am Acad Dermatol 2003;48:805-21.)

LEARNING OBJECTIVE

At the completion of this learning activity, participants should understand how psoriasis and Crohn's disease are related at epidemiologic, genetic, and pathological levels and should appreciate how to use this knowledge to treat these diseases.

Celiac disease: a model autoimmune disease with gene therapy applications

Gene therapy (GT) is still at the 'experimental' stage and some recent setbacks have cooled the potential use of this therapeutic tool even in life-threatening conditions. However, this therapeutic approach has a potential, which is not limited to disease for which we have not other option. There are increasing evidence that GT will be soon used in diseases that are not life threatening. One group of diseases that can benefit from GT is the autoimmune one. Several experimental animal models have indicated the efficacy (proof of principle) of GT. In the present review, we have addressed the possibility that even extremely benign autoimmune-like diseases such as Celiac Disease (CD) might one day profit from this type of therapy. We further point that in conditions such as CD, where the trigger is well known and the pathogenic cascade is relatively well defined, a situation not common in autoimmunity, we can even have a better situation where to explore and use GT to control disease initiation and progression. Once the risks that are still intrinsic to GT will have been reduced the therapeutic options we outline in the present review might not appear too far from reality.

Treating Crohn's disease by inducing T lymphocyte apoptosis

Apoptosis is one of the most important regulatory mechanisms in immunological homeostasis. Disturbances in the apoptotic pathways lead to autoimmune disease. Crohn's disease is a chronic inflammatory bowel disease of unknown origin, which seems to be mediated by excessive T cell-mediated immunity. Recently, disturbances in apoptotic pathways of lamina propria T lymphocytes of patients with Crohn's disease have been identified. In the uninflamed, normal intestinal mucosa, lamina propria (LP) T cells are susceptible to activation-induced cell death, but these cells show a resistance to apoptosis based on several disturbances compared to controls. Recently, intriguing data were published using cytokine-targeted therapy (anti-IL12, anti-IL6 receptor, anti-TNF). Actually, these medications restored mucosal immunological imbalance by inducing apoptosis of the LP T cells and seemed to be beneficial in models of Crohn's disease. In this review, mechanisms of immunological homeostasis will be discussed. We will also discuss the fascinating new results of cytokine-targeted therapy in animal models of Crohn's disease and the effects of these drugs in patients with Crohn's disease.

Toll-like receptors and gastrointestinal diseases: from bench to bedside?

The family of Toll-like receptors (TLRs) plays a key role in mediating innate immune responses to numerous luminal commensal- and pathogen-derived pattern molecules by the intestinal mucosa. Recent findings have identified several ligands recognized by TLRs as well as the complex downstream signaling effects resulting from activation of these receptors. Understanding is emerging of the importance of TLRs in mucosal host defense-potentially triggering gastrointestinal diseases.