p53 mediates TNF-induced epithelial cell apoptosis in IBD

Chronic ulcerative colitis (CUC) is characterized by increased intestinal epithelial cell (IEC) apoptosis associated with elevated tumor necrosis factor (TNF), inducible nitric oxide synthase (iNOS), and p53. We previously showed that p53 is increased in crypt IECs in human colitis and is needed for IEC apoptosis in chronic dextran sulfate sodium-colitis. Herein, we examined the roles of TNF and iNOS in regulating p53-induced IEC apoptosis in CUC. The IEC TUNEL staining, caspases 3, 8, and 9, and p53 protein levels, induced by anti-CD3 monoclonal antibody (mAb) activation of T cells, were markedly reduced in TNF receptor 1 and 2 gene knockout mice. Induction of IEC apoptosis correlated with increased p53, which was attenuated in iNOS(-/-) mice. IEC p53 levels and apoptosis were reduced in IL-10(-/-) colitic mice treated with neutralizing TNF mAb and the iNOS inhibitor, aminoguanidine, further suggesting that TNF and iNOS are upstream of p53 during colitis-induced IEC apoptosis. IEC apoptosis and p53 levels were assessed in control versus untreated or anti-TNF-treated CUC patients with equivalent levels of inflammation. Data indicated that IEC apoptosis and p53 levels were clearly higher in untreated CUC but markedly reduced in patients treated with anti-TNF mAb. Therefore, TNF-induced iNOS activates a p53-dependent pathway of IEC apoptosis in CUC. The inhibition of IEC apoptosis may be an important mechanism for mucosal healing in anti-TNF-treated CUC patients.

Radiofrequency ablation for dysplasia in Barrett's esophagus restores β-catenin activation within esophageal progenitor cells

BACKGROUND AND AIMS

Endoscopic therapies for Barrett's esophagus (BE) associated dysplasia, particularly radiofrequency ablation (RFA), are popular alternatives to surgery. The effect of such therapies on dysplastic stem/progenitor cells (SPC) is unknown. Recent studies suggest that AKT phosphorylation of β-Catenin occurs in SPCs and may be a marker of activated SPCs. We evaluate the effect of RFA in restoring AKT-mediated β-Catenin signaling in regenerative epithelium.

METHODS

Biopsies were taken from squamous, non-dysplastic BE, dysplastic BE and esophageal adenocarcinoma (EAC). Also, post-RFA, biopsies of endoscopically normal appearing neosquamous epithelium were taken at 3, 6, and 12 months after successful RFA. Immunohistochemistry and Western blot analysis was performed for Pβ-Catenin(552) (Akt-mediated phosphorylation of β-Catenin), Ki-67 and p53.

RESULTS

There was no difference in Pβ-Catenin552 in squamous, GERD, small bowel and non-dysplastic BE. There was a fivefold increase in Pβ-Catenin(552) in dysplasia and EAC compared to non-dysplastic BE (P < 0.05). Also, there was a persistent threefold increase in Pβ-Catenin(552) in neosquamous epithelium 3 months after RFA compared to native squamous epithelium (P < 0.05) that correlated with increased Ki-67. Six months after RFA, Pβ-Catenin(552) and Ki-67 are similar to native squamous epithelium.

CONCLUSIONS

Enhanced AKT-mediated β-Catenin activation is seen in BE-associated carcinogenesis. Three months after RFA, squamous epithelial growth from SPC populations exhibited increased levels of Pβ-Catenin(552). This epithelial response becomes quiescent at 6 months after RFA. These data suggest that elevated Pβ-Catenin(552) after RFA denotes a repair response in the neosquamous epithelium 3 months post-RFA.

P-selectin glycoprotein ligand-1 is needed for sequential recruitment of T-helper 1 (Th1) and local generation of Th17 T cells in dextran sodium sulfate (DSS) colitis

BACKGROUND

Activated effector T cells contribute to tissue injury observed in inflammatory bowel disease. T cells are recruited to effector sites after activation in peripheral lymph nodes directs expression of tissue-specific homing receptors. One such mechanism for effector T cell recruitment employs activation-induced fucosylation of P-selectin glycoprotein ligand (PSGL)-1 that mediates binding to endothelial P-selectin. Here we examine the differential role of PSGL-1 in recruiting effector T-cell subsets in colitis.

METHODS

C57BL/6 wildtype and PSGL-1 mice received 2.5% dextran sodium sulfate (DSS) for 6 days and were euthanized 7 and 14 days after the initiation of DSS. Disease activity was monitored throughout. Histologic colitis scores, colonic CD4+ accumulation, and cytokine production were assessed at days 7 and 14. Recruitment of T-helper (Th) subsets was assessed by enumerating adoptively transferred Th1 or Th17 CD4+ cells 2 days after transfer to DSS-treated mice.

RESULTS

DSS colitis increases CD4+ T cells in colonic tissue and induces Th1 (interferon gamma [IFN-γ], tumor necrosis factor [TNF]) and Th17 (interleukin [IL]-17, IL-22) cytokines. Loss of PSGL-1 attenuates DSS colitis, decreases colonic CD4+ T cell numbers, and reduces both Th1 and Th17 cytokine production. Colitis increases recruitment of Th1 (19-fold) and Th17 (2.5-fold) cells. PSGL-1 deficiency in transferred T cells abrogates colonic recruitment of Th1 cells in DSS colitis, whereas Th17 recruitment is unaffected.

CONCLUSIONS

PSGL-1 selectively controls Th1 recruitment in colitis. Whereas Th17 recruitment is independent of PSGL-1, generation of colonic Th17 cytokine requires initial Th1 recruitment. Therefore, attenuating PSGL-1 binding may prevent colonic recruitment of disease-causing Th1 cells that promote local Th17 generation.

The potential role of a self-management intervention for ulcerative colitis: a brief report from the ulcerative colitis hypnotherapy trial

Inflammatory bowel diseases (IBD) are chronic inflammatory illnesses marked by unpredictable disease flares, which occur spontaneously and/or in response to external triggers, especially personal health behaviors. Behavioral triggers of flare may be responsive to disease self-management programs. We report on interim findings of a randomized controlled trial of gut-directed hypnotherapy (HYP, n = 19) versus active attention control (CON, n = 17) for quiescent ulcerative colitis (UC). To date, 43 participants have enrolled; after 5 discontinuations (1 in HYP) and 2 exclusions due to excessive missing data, 36 were included in this preliminary analysis. Aim 1 was to determine the feasibility and acceptability of HYP in UC. This was achieved, demonstrated by a reasonable recruitment rate at our outpatient tertiary care clinic (20%), high retention rate (88% total), and our representative IBD sample, which is reflected by an equal distribution of gender, an age range between 21 and 69, recruitment of ethnic minorities (∽20%), and disease duration ranging from 1.5 to 35 years. Aim 2 was to estimate effect sizes on key clinical outcomes for use in future trials. Effect sizes (group × time at 20 weeks) were small to medium for IBD self-efficacy (.34), Inflammatory Bowel Disease Questionnaire (IBDQ) total score (.41), IBDQ bowel (.50), and systemic health (.48). Between-group effects were observed for the IBDQ bowel health subscale (HYP > CON; p = .05) at 20 weeks and the Short Form 12 Health Survey Version 2 (SF-12v2) physical component (HYP > CON; p < .05) at posttreatment and 20 weeks. This study supports future clinical trials testing gut-directed HYP as a relapse prevention tool for IBD.

Behavioral interventions may prolong remission in patients with inflammatory bowel disease

Inflammatory Bowel Diseases (IBDs) are chronic, relapsing and remitting gastrointestinal conditions with no known cure. Previous studies have linked behavioral factors, including stress and medication adherence, to relapse.

PURPOSE

We sought to determine the effect of participation in a behavioral self-management program on incidence of flare within 12 months following behavioral intervention when compared to the natural history of flare incidence prior to program participation.

RESULTS

Results from a 2-level regression model indicated that those participants in the treatment group were 57% less likely to flare in the following 12 months (compared to 18% in the control group). The decline in "flare odds" was about 2 times greater in treatment versus controls (OR=0.52, t(34)=2.07, p<0.05). Office visits, ER visits, and disease severity (all p<0.05) were identified as moderators of flare risk.

CONCLUSIONS

We have demonstrated 1) a statistical model estimating the likelihood of flare rates in the 12 months following a behavioral intervention for IBD (compared to a control condition), and 2) that the introduction of a behavioral intervention can alter the natural course of a chronic, relapsing and remitting gastrointestinal condition such as IBD.

Phosphoinositide 3-kinase signaling mediates beta-catenin activation in intestinal epithelial stem and progenitor cells in colitis

BACKGROUND & AIMS

Mechanisms responsible for crypt architectural distortion in chronic ulcerative colitis (CUC) are not well understood. Data indicate that serine/threonine protein kinase Akt (Akt) signaling cooperates with Wingless (Wnt) to activate beta-catenin in intestinal stem and progenitor cells through phosphorylation at Ser552 (P-beta-catenin(552)). We investigated whether phosphoinositide 3-kinase (PI3K) is required for Akt-mediated activation of beta-catenin during intestinal inflammation.

METHODS

The class IA subunit of PI3K was conditionally deleted from intestinal epithelial cells in mice named I-pik3r1KO. Acute inflammation was induced in mice and intestines were analyzed by biochemical and histologic methods. The effects of chemically blocking PI3K in colitic interleukin-10(-/-) mice were examined. Biopsy samples from patients were examined.

RESULTS

Compared with wild-type, I-pik3r1KO mice had reduced T-cell-mediated Akt and beta-catenin signaling in intestinal stem and progenitor cells and limited crypt epithelial proliferation. Biochemical analyses indicated that PI3K-Akt signaling increased nuclear total beta-catenin and P-beta-catenin(552) levels and reduced N-terminal beta-catenin phosphorylation, which is associated with degradation. PI3K inhibition in interleukin-10(-/-) mice impaired colitis-induced epithelial Akt and beta-catenin activation, reduced progenitor cell expansion, and prevented dysplasia. Human samples had increased numbers of progenitor cells with P-beta-catenin(552) throughout expanded crypts and increased messenger RNA expression of beta-catenin target genes in CUC, colitis-associated cancer, tubular adenomas, and sporadic colorectal cancer, compared with control samples.

CONCLUSIONS

PI3K-Akt signaling cooperates with Wnt to increase beta-catenin signaling during inflammation. PI3K-induced and Akt-mediated beta-catenin signaling are required for progenitor cell activation during the progression from CUC to CAC; these factors might be used as biomarkers of dysplastic transformation in the colon.

Mesalamine inhibits epithelial beta-catenin activation in chronic ulcerative colitis

BACKGROUND & AIMS

Mesalamine is a mainstay therapeutic agent in chronic ulcerative colitis (CUC) in which condition it reverses crypt architectural changes and reduces colitis-associated cancer (CAC). The present study addressed the possibility that mesalamine reduces beta-catenin-associated progenitor cell activation, Akt-phosphorylated beta-catenin(Ser552) (P-beta-catenin), and colitis-induced dysplasia (CID).

METHODS

Effects of mesalamine on P-beta-catenin staining and function were assessed by immunohistochemistry and quantitative reverse-transcription polymerase chain reaction (qRT-PCR) in biopsy specimens of CUC in mild or "refractory" severe mucosal inflammation. Effects of mesalamine on epithelial proliferation and activation of Akt and beta-catenin were assessed in interleukin (IL)-10(-/-) colitis and CID by immunohistochemistry and Western blotting. Dysplasia was assessed by counting the number and lengths of lesions per colon.

RESULTS

Data from IL-10(-/-) and human colitis samples show that mesalamine reduced Akt activation and P-beta-catenin levels in the middle and upper crypt. Reductions in P-beta-catenin in CUC biopsy specimens with severe inflammation suggested that mesalamine reduced P-beta-catenin levels in tissue refractory to mesalamine's anti-inflammatory effects. In IL-10(-/-) mice, mesalamine reduced CID concordant with inhibition of crypt Akt and beta-catenin signaling.

CONCLUSIONS

The results are consistent with the model that mesalamine contributes to chemoprevention in CAC by reducing beta-catenin signaling within intestinal progenitors.

Epithelial NF-kappaB enhances transmucosal fluid movement by altering tight junction protein composition after T cell activation

In inflammatory bowel disease (IBD), aberrant activation of innate and adaptive immune responses enhances mucosal permeability through mechanisms not completely understood. To examine the role of epithelial nuclear factor (NF-kappaB) in IBD-induced enhanced permeability, epithelial-specific IkappaBalpha mutant (NF-kappaB super repressor) transgenic (TG) mice were generated. NF-kB activation was inhibited in TG mice, relative to wild-type mice, following T cell-mediated immune cell activation using an anti-CD3 monoclonal antibody. Furthermore, epithelial NF-kappaB super repressor protein inhibited diarrhea and blocked changes in transepithelial resistance and transmucosal flux of alexa350 (0.35 kDa) and dextran3000 (3 kDa). In vivo perfusion loop studies in TG mice revealed reversed net water secretion and reduced lumenal flux of different molecular probes (bovine serum albumin, alexa350, and dextran3000). Cell-imaging and immunoblotting of low-density, detergent-insoluble membrane fractions confirmed that tight junction proteins (occludin, claudin-1 and zona occludens-1) are internalized through an NF-kappaB-dependent pathway. Taken together, these data suggest that IBD-associated diarrhea results from NF-kappaB-mediated tight junction protein internalization and increased paracellular permeability. Thus, reduction of epithelial NF-kappaB activation in IBD may repair defects in epithelial barrier function, reduce diarrhea, and limit protein (eg, serum albumin) losses. Epithelial NF-kappaB activation induced by mucosal T cells, therefore, actively plays a role in opening paracellular spaces to promote transmucosal fluid effux into the intestinal lumen.

Therapeutic benefit of pentostatin in severe IL-10-/- colitis

BACKGROUND

Pentostatin, an adenosine deaminase (ADA) inhibitor, is a purine antimetabolite used for the treatment of leukemias. ADA inhibition blunts expansion of proliferating lymphocytes and increases adenosine release, a potent anti-inflammatory molecule. Human inflammatory bowel disease (IBD) is driven by expansion of effector T cells (T(eff)) that overwhelm reulatory T cells (T(reg)) and propagate innate immune reponses. Here we study the therapeutic benefits of ADA inhibition to impair T(eff) cell expansion and reduce inflammatory cytokine release in IL-10-deficient (IL-10-/-) mice.

METHODS

Colitis was induced in IL-10-/- mice by administering piroxicam for two weeks. Mice were treated with daily pentostatin or phosphate-buffered saline for 1 week and effects on tissue inflammation, lymphocyte numbers and cytokine production examined.

RESULTS

Pentostatin reduced inflammation by >50% and nearly normalized serum amyloid A levels. Lymphocyte expansions in the colon and mesenteric lymph node (MLN) (3.5-fold and >5-fold respectively) dropped by >50-90%. Pro-inflammatory factors in the colon and MLN (IL-1beta, IFN-gamma, IL-6, CXCL10, TNF) dropped whereas FoxP3 and TGF-beta were unchanged. Reductions in cytokine production from equivalent numbers of T cells from pentostatin-treated mice after in vitro (36h) or in vivo (3h) activation suggested anti-inflammatory effects of pentostatin independent of lymphodepletion contributed to its therapeutic benefit. Analysis of mucosal lymphocyte subsets suggested pentostatin reduced numbers of effector CD4+ CD69+ T cells, while sparing CD4+ CD62L+ T cells.

CONCLUSIONS

Pentostatin dosages that avoid severe lymphocyte depletion effectively treat colitis by impairing T(eff) cell expansion and reducing pro-inflammatory cytokine production while preserving regulatory T(reg) populations and function.

Epithelial apoptosis in mechanistically distinct methods of injury in the murine small intestine

Gut epithelial apoptosis is involved in the pathophysiology of multiple diseases. This study characterized intestinal apoptosis in three mechanistically distinct injuries with different kinetics of cell death. FVB/N mice were subjected to gamma radiation, Pseudomonas aeruginosa pneumonia or injection of monoclonal anti-CD3 antibody and sacrificed 4, 12, or 24 hours post-injury (n=10/time point). Apoptosis was quantified in the jejunum by hematoxylin and eosin (H&E), active caspase-3, terminal deoxynucleotidyl transferase dUTP-mediated nick end labeling (TUNEL), in situ oligoligation reaction (ISOL,) cytokeratin 18, and annexin V staining. Reproducible results were obtained only for H&E, active caspase-3, TUNEL and ISOL, which were quantified and compared against each other for each injury at each time point. Kinetics of injury were different with early apoptosis highest following radiation, late apoptosis highest following anti CD3, and more consistent levels following pneumonia. ISOL was the most consistent stain and was always statistically indistinguishable from at least 2 stains. In contrast, active caspase-3 demonstrated lower levels of apoptosis, while the TUNEL assay had higher levels of apoptosis in the most severely injured intestine regardless of mechanism of injury. H&E was a statistical outlier more commonly than any other stain. This suggests that regardless of mechanism or kinetics of injury, ISOL correlates to other quantification methods of detecting gut epithelial apoptosis more than any other method studied and compares favorably to other commonly accepted techniques of quantifying apoptosis in a large intestinal cross sectional by balancing sensitivity and specificity across a range of times and levels of death.

PTEN-deficient intestinal stem cells initiate intestinal polyposis

Intestinal polyposis, a precancerous neoplasia, results primarily from an abnormal increase in the number of crypts, which contain intestinal stem cells (ISCs). In mice, widespread deletion of the tumor suppressor Phosphatase and tensin homolog (PTEN) generates hamartomatous intestinal polyps with epithelial and stromal involvement. Using this model, we have established the relationship between stem cells and polyp and tumor formation. PTEN helps govern the proliferation rate and number of ISCs and loss of PTEN results in an excess of ISCs. In PTEN-deficient mice, excess ISCs initiate de novo crypt formation and crypt fission, recapitulating crypt production in fetal and neonatal intestine. The PTEN-Akt pathway probably governs stem cell activation by helping control nuclear localization of the Wnt pathway effector beta-catenin. Akt phosphorylates beta-catenin at Ser552, resulting in a nuclear-localized form in ISCs. Our observations show that intestinal polyposis is initiated by PTEN-deficient ISCs that undergo excessive proliferation driven by Akt activation and nuclear localization of beta-catenin.

Proapoptotic Bid is required for pulmonary fibrosis

The molecular mechanisms of pulmonary fibrosis are poorly understood. Previous reports indicate that activation of TGF-beta1 is essential for the development of pulmonary fibrosis. Here, we report that the proapoptotic Bcl-2 family member Bid is required for the development of pulmonary fibrosis after the intratracheal instillation of bleomycin. Mice lacking Bid exhibited significantly less pulmonary fibrosis in response to bleomycin compared with WT mice. The attenuation in pulmonary fibrosis was observed despite similar levels of inflammation, lung injury, and active TGF-beta1 in bronchoalveolar lavage fluid 5 days after the administration of bleomycin in mice lacking Bid and in WT controls. Bleomycin induced similar levels cell death in vitro in alveolar epithelial cells isolated from WT and bid(-/-) mice. By contrast, alveolar epithelial cells from bid(-/-) mice were resistant to TGF-beta1-induced cell death. These results indicate that Bcl-2 family members are critical regulators for the development of pulmonary fibrosis downstream of TGF-beta1 activation.

Oral tolerance therapy in inflammatory bowel disease

Oral tolerance is a long-recognized method of inducing immune tolerance or systemic hyporesponsiveness induced by feeding protein. Oral tolerance has been used to prevent and/or treat a variety of T-cell-mediated autoimmune disorders. Feeding colonic extracts prevented colitis in animal model of inflammatory bowel disease (IBD), but the clinical efficacy of oral tolerance in human IBD was unknown. In this issue, the study by Margalit and colleagues suggested that oral administration of autologous colonic extracts to moderately severe Crohn's disease patients might reduce disease activity; however, the study did not employ conventional clinical endpoints. These data provide an important first step to developing "Ag-specific" treatment strategies for IBD in the future. Larger scale studies using variable dosages, modes, and durations of Ag delivery will be required to optimize oral tolerance therapy in IBD.

Epithelial myosin light chain kinase-dependent barrier dysfunction mediates T cell activation-induced diarrhea in vivo

Disruption of the intestinal epithelial barrier occurs in many intestinal diseases, but neither the mechanisms nor the contribution of barrier dysfunction to disease pathogenesis have been defined. We utilized a murine model of T cell-mediated acute diarrhea to investigate the role of the epithelial barrier in diarrheal disease. We show that epithelial barrier dysfunction is required for the development of diarrhea. This diarrhea is characterized by reversal of net water flux, from absorption to secretion; increased leak of serum protein into the intestinal lumen; and altered tight junction structure. Phosphorylation of epithelial myosin II regulatory light chain (MLC), which has been correlated with tight junction regulation in vitro, increased abruptly after T cell activation and coincided with the development of diarrhea. Genetic knockout of long myosin light chain kinase (MLCK) or treatment of wild-type mice with a highly specific peptide MLCK inhibitor prevented epithelial MLC phosphorylation, tight junction disruption, protein leak, and diarrhea following T cell activation. These data show that epithelial MLCK is essential for intestinal barrier dysfunction and that this barrier dysfunction is critical to pathogenesis of diarrheal disease. The data also indicate that inhibition of epithelial MLCK may be an effective non-immunosuppressive therapy for treatment of immune-mediated intestinal disease.

Epithelial myosin light chain kinase-dependent barrier dysfunction mediates T cell activation-induced diarrhea in vivo

Disruption of the intestinal epithelial barrier occurs in many intestinal diseases, but neither the mechanisms nor the contribution of barrier dysfunction to disease pathogenesis have been defined. We utilized a murine model of T cell-mediated acute diarrhea to investigate the role of the epithelial barrier in diarrheal disease. We show that epithelial barrier dysfunction is required for the development of diarrhea. This diarrhea is characterized by reversal of net water flux, from absorption to secretion; increased leak of serum protein into the intestinal lumen; and altered tight junction structure. Phosphorylation of epithelial myosin II regulatory light chain (MLC), which has been correlated with tight junction regulation in vitro, increased abruptly after T cell activation and coincided with the development of diarrhea. Genetic knockout of long myosin light chain kinase (MLCK) or treatment of wild-type mice with a highly specific peptide MLCK inhibitor prevented epithelial MLC phosphorylation, tight junction disruption, protein leak, and diarrhea following T cell activation. These data show that epithelial MLCK is essential for intestinal barrier dysfunction and that this barrier dysfunction is critical to pathogenesis of diarrheal disease. The data also indicate that inhibition of epithelial MLCK may be an effective non-immunosuppressive therapy for treatment of immune-mediated intestinal disease.

Anti-interferon-inducible chemokine, CXCL10, reduces colitis by impairing T helper-1 induction and recruitment in mice

BACKGROUND

Colitis in interleukin (IL)-10 mice is a CD4 T helper 1 (TH1)-mediated disease characterized by intermittent, transmural inflammation reminiscent of human Crohn's disease. In this study, we investigated the hypothesis that production of the CXC chemokine CXCL10 (interferon [IFN]gamma-inducible protein 10) enhances induction of inflammatory responses in draining lymph nodes (LNs) and promotes colonic TH1 cell recruitment.

METHODS

Colitis was induced in B6 IL-10 mice. Mice were given anti-CXCL10 mAb in 2-week intervals before and after peak colitis. Colitis severity was graded and cytokine/chemokine levels were analyzed by real-time polymerase chain reaction. Cell yields were quantitated and effector cell recruitment was assessed by recovery of transferred D011.10 TH1 cells shortly (72 h) after transfer.

RESULTS

Treatment with anti-CXCL10 during colitis development decreased clinical and histologic disease severity as well as cytokine/chemokine mRNA and accumulation of mononuclear cells in LNs and colon. Treatment of mice with severe colitis reduced colitis scores and cell yields to lesser degrees. Anti-CXCL10 specifically decreased recruitment of transferred TH1 cells into mesenteric LNs (MLNs) and colon of IL-10 mice by 75% (P<0.05).

CONCLUSION

These results suggest that CXCL10 plays a dual role in colitis development by enhancing TH1 cell generation in inductive sites and promoting effector cell recruitment to inflamed tissue. Blockade of CXCL10 may be a useful adjunct to remission-inducing therapies in inflammatory bowel disease (IBD) by impairing disease recurrence through selective inhibition of effector cell generation and trafficking in vivo.

IP-10-induced recruitment of CXCR3 host T cells is required for small bowel allograft rejection

BACKGROUND & AIMS

Chemokines mediate cell trafficking in inflammatory states such as allograft rejection. However, their role in small-bowel allograft rejection has not been defined. The aim of this study was to examine the roles of type 1 helper T-cell chemokines in small-bowel allograft rejection.

METHODS

Mucosal histology, chemokine messenger RNA (real-time polymerase chain reaction), and cell isolates were examined in small-bowel allografts and isografts. Interferon-gamma-inducible protein-10/CXC chemokine receptor (CXCR) 3 interactions were specifically evaluated by using allografts from interferon-gamma-inducible protein-10(-/-) donors and adoptive transfer of CXCR3(-/-) T cells into recombination activating gene (RAG)-1(-/-) recipients of small-bowel allografts.

RESULTS

Type 1 helper T-cell cytokine (interferon-gamma) and chemokine (interferon-gamma-inducible protein-10, monokine induced by interferon-gamma, macrophage-inflammatory protein-1 alpha, and regulated on activation, normal T cells expressed and secreted) messenger RNA up-regulation was detected (real-time polymerase chain reaction) by postoperative day 3 in small-bowel allografts. Interferon-gamma-inducible protein-10(+/+) small-bowel allograft rejection was associated with a dramatic (>7-fold) increase in CXCR3(+) host T cells in the graft lamina propria. With interferon-gamma-inducible protein-10(-/-) small-bowel allografts, CXCR3(+) host T-cell infiltration of the graft lamina propria was markedly decreased and rejection was significantly delayed. Whereas adoptive transfer of wild-type B6 (CXCR3(+/+)) T cells into B6 (RAG-1(-/-)) recipients induced rapid rejection of CB6F1 small-bowel allografts, rejection was significantly delayed (29.2 +/- 8.7 days vs. 16.5 +/- 3.1 days; P < 0.01) in B6 (RAG-1(-/-)) mice reconstituted with T cells from B6 (CXCR3(-/-)) mice.

CONCLUSIONS

Recruitment of CXCR3(+) host T cells by donor derived interferon-gamma-inducible protein-10 may precipitate small-bowel allograft rejection. These data highlight the importance of type 1 helper T cell-related chemokines in promoting cell-mediated rejection responses in small-bowel allografts and suggest that interferon-gamma-inducible protein-10 is an attractive therapeutic target for humanized monoclonal antibody strategies.

c-Myc sensitization to oxygen deprivation-induced cell death is dependent on Bax/Bak, but is independent of p53 and hypoxia-inducible factor-1

Deregulated expression of c-Myc can sensitize cells to a variety of death stimuli, including loss of growth factors and oxygen. In this study, we examined whether rodent fibroblasts that conditionally express c-Myc undergo a similar mechanism of cell death in response to serum or oxygen deprivation. Our results demonstrate that murine embryonic fibroblasts from bax-/-bak-/- mice that conditionally express c-Myc did not die in response to either oxygen or serum deprivation. Fibroblasts from p53-/- mice that conditionally express c-Myc died in response to oxygen (but not serum) deprivation. The inability of p53 to regulate oxygen deprivation-induced cell death was due to the lack of induction of p53 target genes Puma, Noxa, and Pten. In contrast, serum deprivation transcriptionally induced Puma and Pten in cells that conditionally express c-Myc. The failure of p53 to regulate oxygen deprivation-induced cell death led us to hypothesize whether hypoxia-inducible factor (HIF) might be a critical regulator of cell death during oxygen deprivation. Fibroblasts from HIF-1beta-/- cells that conditionally express c-Myc were not able to transcriptionally activate HIF during oxygen deprivation. These cells died in response to oxygen deprivation. Thus, oxygen deprivation-induced cell death in fibroblasts with deregulated expression of c-Myc is independent of p53 or HIF-1 status, but is dependent on the Bcl-2 family member Bax or Bak to initiate mitochondrial dependent cell death.

P-selectin and P-selectin glycoprotein ligand 1 are major determinants for Th1 cell recruitment to nonlymphoid effector sites in the intestinal lamina propria

The recruitment of activated T cell subsets to sites of effector immune responses is mediated by homing receptors induced upon activation in secondary lymphoid tissue. Using an adoptive transfer model, the intestinal recruitment of CD4+ T cells activated with intraperitoneal antigen in complete Freund's adjuvant was examined. The data demonstrate that activated CD4+ T cells recruited to intestinal Peyer's patches (PP) and lamina propria (LP) up-regulate functional P-selectin glycoprotein ligand 1 (PSGL-1). Blockade of IL-12 inhibited functional PSGL-1 expression and reduced PP and LP CD4+ T cell recruitment by >40%. P-selectin blockade reduced LP recruitment of activated cells by 56% without affecting PP recruitment. Studies of mice examined 3 d after adoptive transfer of differentiated T cell subsets revealed that Th1 but not Th2 cells were recruited to small intestine PP and LP. Mucosal addressin cell adhesion molecule blockade reduced Th1 recruitment to PP by 90% and to LP by >72%, whereas P-selectin blockade reduced Th1 recruitment to PP by 18% and Th1 recruitment to LP by 84%. These data suggest that IL-12-induced functional PSGL-1 expression is a major determinant for the recruitment of Th1 effector cells to noninflamed as well as inflamed intestine.

T cell activation causes diarrhea by increasing intestinal permeability and inhibiting epithelial Na+/K+-ATPase

Inflammatory bowel disease (IBD) is associated with mucosal T cell activation and diarrhea. We found that T cell activation with anti-CD3 mAb induces profound diarrhea in mice. Diarrhea was quantified by intestinal weight-to-length (wt/l) ratios, mucosal Na(+)/K(+)-ATPase activity was determined and ion transport changes were measured in Ussing chambers. Anti-CD3 mAb increased jejunal wt/l ratios by more than 50% at 3 hours, returning to base line after 6 hours. Fluid accumulation was significantly reduced in TNF receptor-1 (TNFR-1(-/-)), but not IFN-gamma knockout mice. Anti-CD3 mAb decreased mucosal Na(+)/K(+)-ATPase activity, which was blocked by anti-TNF mAb and occurred to a lesser degree in TNFR-1(-/-) mice. Neither alpha nor beta subunits of Na(+)/K(+)-ATPase decreased in abundance at 3 hours. Intestinal tissue from anti-CD3-treated mice exhibited increased permeability to mannitol at 1 hour and decreases in electroneutral Na(+) absorption, Na(+)-dependent glucose absorption, and cAMP-stimulated anion secretion at 3 hours. Furthermore, enteral fluid accumulation was observed in CFTR(-/-) mice, indicating a minor role of active anion secretion. These data suggest that diarrhea in IBD is due to TNF-mediated malabsorption rather than to secretory processes. T cell activation induces luminal fluid accumulation by increasing mucosal permeability and reducing epithelial Na(+)/K(+)-ATPase activity leading to decreased intestinal Na(+) and water absorption.