MUC13 Cell Surface Mucin Limits Salmonella Typhimurium Infection by Protecting the Mucosal Epithelial Barrier

BACKGROUND & AIMS

MUC13 cell surface mucin is highly expressed on the mucosal surface throughout the intestine, yet its role against bacterial infection is unknown. We investigated how MUC13 impacts Salmonella typhimurium (S Tm) infection and elucidated its mechanisms of action.

METHODS

Muc13-/- and wild-type littermate mice were gavaged with 2 isogenic strains of S Tm after pre-conditioning with streptomycin. We assessed clinical parameters, cecal histology, local and systemic bacterial load, and proinflammatory cytokines after infection. Cecal enteroids and epithelial cell lines were used to evaluate the mechanism of MUC13 activity after infection. The interaction between bacterial SiiE and MUC13 was assessed by using siiE-deficient Salmonella.

RESULTS

S Tm-infected Muc13-/- mice had increased disease activity, histologic damage, and higher local and systemic bacterial loads. Mechanistically, we found that S Tm binds to MUC13 through its giant SiiE adhesin and that MUC13 acts as a pathogen-binding decoy shed from the epithelial cell surface after pathogen engagement, limiting bacterial invasion. In addition, MUC13 reduces epithelial cell death and intestinal barrier breakdown by enhancing nuclear factor kappa B signaling during infection, independent of its decoy function.

CONCLUSIONS

We show for the first time that MUC13 plays a critical role in antimicrobial defense against pathogenic S Tm at the intestinal mucosal surface by both acting as a releasable decoy limiting bacterial invasion and reducing pathogen-induced cell death. This further implicates the cell surface mucin family in mucosal defense from bacterial infection.

An Extremes of Phenotype Approach Confirms Significant Genetic Heterogeneity in Patients with Ulcerative Colitis

BACKGROUND AND AIMS

Ulcerative colitis [UC] is a major form of inflammatory bowel disease globally. Phenotypic heterogeneity is defined by several variables including age of onset and disease extent. The genetics of disease severity remains poorly understood. To further investigate this, we performed a genome wide association [GWA] study using an extremes of phenotype strategy.

METHODS

We conducted GWA analyses in 311 patients with medically refractory UC [MRUC], 287 with non-medically refractory UC [non-MRUC] and 583 controls. Odds ratios [ORs] were calculated for known risk variants comparing MRUC and non-MRUC, and controls.

RESULTS

MRUC-control analysis had the greatest yield of genome-wide significant single nucleotide polymorphisms [SNPs] [2018], including lead SNP = rs111838972 [OR = 1.82, p = 6.28 × 10-9] near MMEL1 and a locus in the human leukocyte antigen [HLA] region [lead SNP = rs144717024, OR = 12.23, p = 1.7 × 10-19]. ORs for the lead SNPs were significantly higher in MRUC compared to non-MRUC [p < 9.0 × 10-6]. No SNPs reached significance in the non-MRUC-control analysis (top SNP, rs7680780 [OR 2.70, p = 5.56 × 10-8). We replicate findings for rs4151651 in the Complement Factor B [CFB] gene and demonstrate significant changes in CFB gene expression in active UC. Detailed HLA analyses support the strong associations with MHC II genes, particularly HLA-DQA1, HLA-DQB1 and HLA-DRB1 in MRUC.

CONCLUSIONS

Our MRUC subgroup replicates multiple known UC risk variants in contrast to non-MRUC and demonstrates significant differences in effect sizes compared to those published. Non-MRUC cases demonstrate lower ORs similar to those published. Additional risk and prognostic loci may be identified by targeted recruitment of individuals with severe disease.

Gut inflammation and adaptive immunity amplify acetaminophen toxicity in bowel and liver

BACKGROUND AND AIM

Prevention of liver failure arising from accidental or deliberate paracetamol (acetaminophen [APAP]) overdose remains a vexed health problem despite well-publicized guidelines for its early detection and treatment. It is recognized that the gut may aggravate liver pathology, via the gut-liver axis. The main aim of this study was to assess the role of the colon in APAP-induced liver toxicity.

METHODS

Liver necrosis and colitis were studied following sublethal doses of APAP administered intraperitoneally to C57Bl/6 wild-type (WT) mice, as well as to C57Bl/6 Winnie mice, which develop a spontaneous colitis caused by a SNP in Muc2, and WT mice with acute DSS-induced colitis. Repeated APAP exposure was studied in WT and Rag1 ko mice that lack mature T and B lymphocytes.

RESULTS

APAP overdose resulted in significant colonic injury in WT mice (P < 0.05), which resolved by 24 h. Underlying colitis was not associated with liver necrosis, but colitis exacerbated APAP-induced liver injury and extended APAP-colonic injury. Prior APAP exposure exacerbated both APAP-liver and APAP-colonic injury more so in WT than Rag1 ko mice. APAP impaired barrier function with increased intestinal permeability and associated bacterial translocation to the liver and spleen in mice with the Winnie phenotype.

CONCLUSIONS

This study identifies novel roles for APAP in causing colitis, the amplification of APAP-liver toxicity where there is underlying colitis, and involvement of immune memory in APAP-toxicity. The latter could be key for decoding the poorly understood but important clinical entity of chronic APAP liver failure.

Secreted NF-κB suppressive microbial metabolites modulate gut inflammation

Emerging evidence suggests that microbiome-host crosstalk regulates intestinal immune activity and predisposition to inflammatory bowel disease (IBD). NF-κB is a master regulator of immune function and a validated target for the treatment of IBD. Here, we identify five Clostridium strains that suppress immune-mediated NF-κB activation in epithelial cell lines, PBMCs, and gut epithelial organoids from healthy human subjects and patients with IBD. Cell-free culture supernatant from Clostridium bolteae AHG0001 strain, but not the reference C. bolteae BAA-613 strain, suppresses inflammatory responses and endoplasmic reticulum stress in gut epithelial organoids derived from Winnie mice. The in vivo responses to Clostridium bolteae AHG0001 and BAA-613 mirror the in vitro activity. Thus, using our in vitro screening of bacteria capable of suppressing NF-κB in the context of IBD and using an ex vivo organoid-based approach, we identify a strain capable of alleviating colitis in a relevant pre-clinical animal model of IBD.

Association of Genetic Variants in NUDT15 With Thiopurine-Induced Myelosuppression in Patients With Inflammatory Bowel Disease

IMPORTANCE

Use of thiopurines may be limited by myelosuppression. TPMT pharmacogenetic testing identifies only 25% of at-risk patients of European ancestry. Among patients of East Asian ancestry, NUDT15 variants are associated with thiopurine-induced myelosuppression (TIM).

OBJECTIVE

To identify genetic variants associated with TIM among patients of European ancestry with inflammatory bowel disease (IBD).

DESIGN, SETTING, AND PARTICIPANTS

Case-control study of 491 patients affected by TIM and 679 thiopurine-tolerant unaffected patients who were recruited from 89 international sites between March 2012 and November 2015. Genome-wide association studies (GWAS) and exome-wide association studies (EWAS) were conducted in patients of European ancestry. The replication cohort comprised 73 patients affected by TIM and 840 thiopurine-tolerant unaffected patients.

EXPOSURES

Genetic variants associated with TIM.

MAIN OUTCOMES AND MEASURES

Thiopurine-induced myelosuppression, defined as a decline in absolute white blood cell count to 2.5 × 109/L or less or a decline in absolute neutrophil cell count to 1.0 × 109/L or less leading to a dose reduction or drug withdrawal.

RESULTS

Among 1077 patients (398 affected and 679 unaffected; median age at IBD diagnosis, 31.0 years [interquartile range, 21.2 to 44.1 years]; 540 [50%] women; 602 [56%] diagnosed as having Crohn disease), 919 (311 affected and 608 unaffected) were included in the GWAS analysis and 961 (328 affected and 633 unaffected) in the EWAS analysis. The GWAS analysis confirmed association of TPMT (chromosome 6, rs11969064) with TIM (30.5% [95/311] affected vs 16.4% [100/608] unaffected patients; odds ratio [OR], 2.3 [95% CI, 1.7 to 3.1], P = 5.2 × 10-9). The EWAS analysis demonstrated an association with an in-frame deletion in NUDT15 (chromosome 13, rs746071566) and TIM (5.8% [19/328] affected vs 0.2% [1/633] unaffected patients; OR, 38.2 [95% CI, 5.1 to 286.1], P = 1.3 × 10-8), which was replicated in a different cohort (2.7% [2/73] affected vs 0.2% [2/840] unaffected patients; OR, 11.8 [95% CI, 1.6 to 85.0], P = .03). Carriage of any of 3 coding NUDT15 variants was associated with an increased risk (OR, 27.3 [95% CI, 9.3 to 116.7], P = 1.1 × 10-7) of TIM, independent of TPMT genotype and thiopurine dose.

CONCLUSIONS AND RELEVANCE

Among patients of European ancestry with IBD, variants in NUDT15 were associated with increased risk of TIM. These findings suggest that NUDT15 genotyping may be considered prior to initiation of thiopurine therapy; however, further study including additional validation in independent cohorts is required.

Anti-TNF Therapeutic Drug Monitoring in Postoperative Crohn's Disease

BACKGROUND

Anti-TNF prevents postoperative Crohn's disease recurrence in most patients but not all. This study aimed to define the relationship between adalimumab pharmacokinetics, maintenance of remission and recurrence.

METHODS

As part of a study of postoperative Crohn's disease management, some patients undergoing resection received prophylactic postoperative adalimumab. In these patients, serum and fecal adalimumab concentration and serum anti-adalimumab antibodies [AAAs] were measured at 6, 12 and 18 months postoperatively. Levels of Crohn's disease activity index [CDAI], C-reactive protein [CRP] and fecal calprotectin [FC] were assessed at 6 and 18 months postoperatively. Body mass index and smoking status were recorded. A colonoscopy was performed at 6 and/or 18 months.

RESULTS

Fifty-two patients [32 on monotherapy and 20 on combination therapy with thiopurine] were studied. Adalimumab concentration did not differ significantly between patients in endoscopic remission vs recurrence [Rutgeerts ≥ i2] [9.98µg/mL vs 8.43 µg/mL, p = 0.387]. Patients on adalimumab monotherapy had a significantly lower adalimumab concentration [7.89 µg/mL] than patients on combination therapy [11.725 µg/mL] [p = 0.001], and were significantly more likely to have measurable AAA [31% vs 17%, p = 0.001]. Adalimumab concentrations were lower in patients with detectable AAA compared with those without [3.59 µg/mL vs 12.0 µg/mL, p < 0.001]. Adalimumab was not detected in fecal samples. Adalimumab serum concentrations were lower in obese patients compared with in non-obese patients [p = 0.046].

CONCLUSION

Adalimumab concentration in patients treated with adalimumab to prevent symptomatic endoscopic recurrence postoperatively is, for most patients, well within the therapeutic window, and is not significantly lower in patients who develop recurrence compared with in those who remain in remission. Mechanisms of anti-TNF failure to prevent postoperative recurrence remain to be determined in these patients.

The role of IL-22 in the resolution of sterile and nonsterile inflammation

In a broad sense, inflammation can be conveniently characterised by two phases: the first phase, which is a pro-inflammatory, has evolved to clear infection and/or injured tissue; and the second phase concerns regeneration of normal tissue and restitution of normal physiology. Innate immune cell-derived pro-inflammatory cytokines and chemokines activate and recruit nonresident immune cells to the site of infection, thereby amplifying the inflammatory responses to clear infection or injury. This phase is followed by a cytokine milieu that promotes tissue regeneration. There is no absolute temporal distinction between these two phases, and cytokines may have dual pleiotropic effects depending on the timing of release, inflammatory microenvironment or concentrations. IL-22 is a cytokine with reported pro- and anti-inflammatory roles; in this review, we contend that this protein has primarily a function in restitution of normal tissue and physiology.

Serologic antibodies in relation to outcome in postoperative Crohn's disease

BACKGROUND AND AIM

Disease recurs frequently after Crohn's disease resection. The role of serological antimicrobial antibodies in predicting recurrence or as a marker of recurrence has not been well defined.

METHODS

A total of 169 patients (523 samples) were prospectively studied, with testing peri-operatively, and 6, 12 and 18 months postoperatively. Colonoscopy was performed at 18 months postoperatively. Serologic antibody presence (perinuclear anti-neutrophil cytoplasmic antibody [pANCA], anti-Saccharomyces cerevisiae antibodies [ASCA] IgA/IgG, anti-OmpC, anti-CBir1, anti-A4-Fla2, anti-Fla-X) and titer were tested. Quartile sum score (range 6-24), logistic regression analysis, and correlation with phenotype, smoking status, and endoscopic outcome were assessed.

RESULTS

Patients with ≥ 2 previous resections were more likely to be anti-OmpC positive (94% vs 55%, ≥ 2 vs < 2, P = 0.001). Recurrence at 18 months was associated with anti-Fla-X positivity at baseline (49% vs 29%; positive vs negative, P = 0.033) and 12 months (52% vs 31%, P = 0.04). Patients positive (n = 28) for all four antibacterial antibodies (anti-CBir1, anti-OmpC, anti-A4-Fla2, and anti-Fla-X) at baseline were more likely to experience recurrence at 18 months than patients negative (n = 32) for all four antibodies (82% vs 18%, P = 0.034; odds ratio 6.4, 95% confidence interval 1.16-34.9). The baseline quartile sum score for all six antimicrobial antibodies was higher in patients with severe recurrence (Rutgeert's i3-i4) at 18 months, adjusted for clinical risk factors (odds ratio 1.16, 95% confidence interval 1.01-1.34, P = 0.039). Smoking affected antibody status.

CONCLUSIONS

Anti-Fla-X and presence of all anti-bacterial antibodies identifies patients at higher risk of early postoperative Crohn's disease recurrence. Serologic screening pre-operatively may help identify patients at increased risk of recurrence.

Abstract 3564: MUC13 protects colorectal cancer cells from death by activating the NF-κb pathway and is a potential therapeutic target

MUC13 is a transmembrane mucin glycoprotein that is overexpressed by many cancers, although its functions are not fully understood. NF-κB is a key transcription factor promoting cancer cell survival, but therapeutically targeting this pathway has proved difficult because NF-κB has pleiotropic functions. Here, we report that MUC13 prevents colorectal cancer cell death by promoting two distinct pathways of NF-kB activation, consequently up-regulating BCL-XL. MUC13 promoted TNF-induced NF-κB activation by interacting with TNFR1 and the E3 ligase, cIAP1, to increase ubiquitination of RIPK1. MUC13 also promoted genotoxin-induced NF-κB activation by increasing phosphorylation of ATM and SUMOylation of NEMO. Moreover, elevated expression of cytoplasmic MUC13 and NF-κB correlated with colorectal cancer progression and metastases. Our demonstration that MUC13 enhances NF-κB signalling in response to both TNF and DNA damaging agents provides a new molecular target for specific inhibition of NF-κB activation. As proof of principle, silencing MUC13 sensitized colorectal cancer cells to death in response to cytotoxic drugs and inflammatory signals and abolished chemotherapy-induced enrichment of CD133+ CD44+ cancer stem cells, slowed xenograft growth in mice, and synergized with 5-fluourouracil to induce tumor regression. Therefore, these data indicate that combining chemotherapy and MUC13 antagonism could improve the treatment of metastatic cancers.

Citation Format: Yong H. Sheng, Yaowu He, sumaira Z. hasnain, Ran Wang, Hui Tong, Daniel T. Clarke, Rohan Lourie, Iulia Oancea, kuanyau wong, John W. Lumley, Timothy H. Florin, Philip Sutton, John. D. Hooper, Nigel A. Mcmillan, Michael A. Mcguckin. MUC13 protects colorectal cancer cells from death by activating the NF-κb pathway and is a potential therapeutic target. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 3564.

MUC13 protects colorectal cancer cells from death by activating the NF-κB pathway and is a potential therapeutic target

MUC13 is a transmembrane mucin glycoprotein that is over produced by many cancers, although its functions are not fully understood. Nuclear factor-κB (NF-κB) is a key transcription factor promoting cancer cell survival, but therapeutically targeting this pathway has proved difficult because NF-κB has pleiotropic functions. Here, we report that MUC13 prevents colorectal cancer cell death by promoting two distinct pathways of NF-kB activation, consequently upregulating BCL-X_L. MUC13 promoted tumor necrosis factor (TNF)-induced NF-κB activation by interacting with TNFR1 and the E3 ligase, cIAP1, to increase ubiquitination of RIPK1. MUC13 also promoted genotoxin-induced NF-κB activation by increasing phosphorylation of ATM and SUMOylation of NF-κB essential modulator. Moreover, elevated expression of cytoplasmic MUC13 and NF-κB correlated with colorectal cancer progression and metastases. Our demonstration that MUC13 enhances NF-κB signaling in response to both TNF and DNA-damaging agents provides a new molecular target for specific inhibition of NF-κB activation. As proof of principle, silencing MUC13 sensitized colorectal cancer cells to killing by cytotoxic drugs and inflammatory signals and abolished chemotherapy-induced enrichment of CD133⁺ CD44⁺ cancer stem cells, slowed xenograft growth in mice, and synergized with 5-fluourouracil to induce tumor regression. Therefore, these data indicate that combining chemotherapy and MUC13 antagonism could improve the treatment of metastatic cancers.

High Fat Diets Induce Colonic Epithelial Cell Stress and Inflammation that is Reversed by IL-22

Prolonged high fat diets (HFD) induce low-grade chronic intestinal inflammation in mice, and diets high in saturated fat are a risk factor for the development of human inflammatory bowel diseases. We hypothesized that HFD-induced endoplasmic reticulum (ER)/oxidative stress occur in intestinal secretory goblet cells, triggering inflammatory signaling and reducing synthesis/secretion of proteins that form the protective mucus barrier. In cultured intestinal cells non-esterified long-chain saturated fatty acids directly increased oxidative/ER stress leading to protein misfolding. A prolonged HFD elevated the intestinal inflammatory cytokine signature, alongside compromised mucosal barrier integrity with a decrease in goblet cell differentiation and Muc2, a loss in the tight junction protein, claudin-1 and increased serum endotoxin levels. In Winnie mice, that develop spontaneous colitis, HFD-feeding increased ER stress, further compromised the mucosal barrier and increased the severity of colitis. In obese mice IL-22 reduced ER/oxidative stress and improved the integrity of the mucosal barrier, and reversed microbial changes associated with obesity with an increase in Akkermansia muciniphila. Consistent with epidemiological studies, our experiments suggest that HFDs are likely to impair intestinal barrier function, particularly in early life, which partially involves direct effects of free-fatty acids on intestinal cells, and this can be reversed by IL-22 therapy.

Efficacy of thiopurines and adalimumab in preventing Crohn's disease recurrence in high-risk patients - a POCER study analysis

BACKGROUND

Crohn's disease recurs in the majority of patients after intestinal resection.

AIM

To compare the relative efficacy of thiopurines and anti-TNF therapy in patients at high risk of disease recurrence.

METHODS

As part of a larger study comparing post-operative management strategies, patients at high risk of recurrence (smoker, perforating disease, ≥2nd operation) were treated after resection of all macroscopic disease with 3 months metronidazole together with either azathioprine 2 mg/kg/day or mercaptopurine 1.5 mg/kg/day. Thiopurine-intolerant patients received adalimumab induction then 40 mg fortnightly. Patients underwent colonoscopy at 6 months with endoscopic recurrence assessed blind to treatment.

RESULTS

A total of 101 patients [50% male; median (IQR) age 36 (25-46) years] were included. There were no differences in disease history between thiopurine- and adalimumab-treated patients. Fifteen patients withdrew prior to 6 months, five due to symptom recurrence (of whom four were colonoscoped). Endoscopic recurrence (Rutgeerts score i2-i4) occurred in 33 of 73 (45%) thiopurine vs. 6 of 28 (21%) adalimumab-treated patients [intention-to-treat (ITT); P = 0.028] or 24 of 62 (39%) vs. 3 of 24 (13%) respectively [per-protocol analysis (PPA); P = 0.020]. Complete mucosal endoscopic normality (Rutgeerts i0) occurred in 17/73 (23%) vs. 15/28 (54%) (ITT; P = 0.003) and in 27% vs. 63% (PPA; P = 0.002). The most advanced disease (Rutgeerts i3 and i4) occurred in 8% vs. 4% (thiopurine vs. adalimumab).

CONCLUSIONS

In Crohn's disease patients at high risk of post-operative recurrence adalimumab is superior to thiopurines in preventing early disease recurrence.

Effect of intestinal resection on quality of life in Crohn's disease

INTRODUCTION

Patients with Crohn's disease have poorer health-related quality of life [HRQoL] than healthy individuals, even when in remission. Although HRQoL improves in patients who achieve drug-induced or surgically induced remission, the effects of surgery overall have not been well characterised.

METHODS

In a randomised trial, patients undergoing intestinal resection of all macroscopically diseased bowel were treated with postoperative drug therapy to prevent disease recurrence. All patients were followed prospectively for 18 months. C-reactive protein [CRP], Crohn's Disease Activity Index [CDAI], and faecal calprotectin [FC] were measured preoperatively and at 6, 12, and 18 months. HRQoL was assessed with a general [SF36] and disease-specific [IBDQ] questionnaires at the same time points.

RESULTS

A total of 174 patients were included. HRQoL was poor preoperatively but improved significantly [p < 0.001] at 6 months postoperatively. This improvement was sustained at 18 months. Females and smokers had a poorer HRQoL when compared with males and non-smokers, respectively. Persistent endoscopic remission, intensification of drug treatment at 6 months, and anti-tumour necrosis factor therapy were not associated with HRQoL outcomes different from those when these factors were not present. There was a significant inverse correlation between CDAI, [but not endoscopic recurrence, CRP, or FC] on HRQoL.

CONCLUSION

Intestinal resection of all macroscopic Crohn's disease in patients treated with postoperative prophylactic drug therapy is associated with significant and sustained improvement in HRQoL irrespective of type of drug treatment or endoscopic recurrence. HRQoL is lower in female patients and smokers. A higher CDAI, but not direct measures of active disease or type of drug therapy, is associated with a lower HRQoL.

Measurement of fecal calprotectin improves monitoring and detection of recurrence of Crohn's disease after surgery

BACKGROUND & AIMS

Crohn's disease (CD) usually recurs after intestinal resection; postoperative endoscopic monitoring and tailored treatment can reduce the chance of recurrence. We investigated whether monitoring levels of fecal calprotectin (FC) can substitute for endoscopic analysis of the mucosa.

METHODS

We analyzed data collected from 135 participants in a prospective, randomized, controlled trial, performed at 17 hospitals in Australia and 1 hospital in New Zealand, that assessed the ability of endoscopic evaluations and step-up treatment to prevent CD recurrence after surgery. Levels of FC, serum levels of C-reactive protein (CRP), and Crohn's disease activity index (CDAI) scores were measured before surgery and then at 6, 12, and 18 months after resection of all macroscopic Crohn's disease. Ileocolonoscopies were performed at 6 months after surgery in 90 patients and at 18 months after surgery in all patients.

RESULTS

Levels of FC were measured in 319 samples from 135 patients. The median FC level decreased from 1347 μg/g before surgery to 166 μg/g at 6 months after surgery, but was higher in patients with disease recurrence (based on endoscopic analysis; Rutgeerts score, ≥i2) than in patients in remission (275 vs 72 μg/g, respectively; P < .001). Combined 6- and 18-month levels of FC correlated with the presence (r = 0.42; P < .001) and severity (r = 0.44; P < .001) of CD recurrence, but the CRP level and CDAI score did not. Levels of FC greater than 100 μg/g indicated endoscopic recurrence with 89% sensitivity and 58% specificity, and a negative predictive value (NPV) of 91%; this means that colonoscopy could have been avoided in 47% of patients. Six months after surgery, FC levels less than 51 μg/g in patients in endoscopic remission predicted maintenance of remission (NPV, 79%). In patients with endoscopic recurrence at 6 months who stepped-up treatment, FC levels decreased from 324 μg/g at 6 months to 180 μg/g at 12 months and 109 μg/g at 18 months.

CONCLUSIONS

In this analysis of data from a prospective clinical trial, FC measurement has sufficient sensitivity and NPV values to monitor for CD recurrence after intestinal resection. Its predictive value might be used to identify patients most likely to relapse. After treatment for recurrence, the FC level can be used to monitor response to treatment. It predicts which patients will have disease recurrence with greater accuracy than CRP level or CDAI score.

Crohn's disease management after intestinal resection: a randomised trial

BACKGROUND

Most patients with Crohn's disease need an intestinal resection, but a majority will subsequently experience disease recurrence and require further surgery. This study aimed to identify the optimal strategy to prevent postoperative disease recurrence.

METHODS

In this randomised trial, consecutive patients from 17 centres in Australia and New Zealand undergoing intestinal resection of all macroscopic Crohn's disease, with an endoscopically accessible anastomosis, received 3 months of metronidazole therapy. Patients at high risk of recurrence also received a thiopurine, or adalimumab if they were intolerant to thiopurines. Patients were randomly assigned to parallel groups: colonoscopy at 6 months (active care) or no colonoscopy (standard care). We used computer-generated block randomisation to allocate patients in each centre to active or standard care in a 2:1 ratio. For endoscopic recurrence (Rutgeerts score ≥i2) at 6 months, patients stepped-up to thiopurine, fortnightly adalimumab with thiopurine, or weekly adalimumab. The primary endpoint was endoscopic recurrence at 18 months. Patients and treating physicians were aware of the patient's study group and treatment, but central reading of the endoscopic findings was undertaken blind to the study group and treatment. Analysis included all patients who received at least one dose of study drug. This trial is registered with ClinicalTrials.gov, number NCT00989560.

FINDINGS

Between Oct 13, 2009, and Sept 28, 2011, 174 (83% high risk across both active and standard care groups) patients were enrolled and received at least one dose of study drug. Of 122 patients in the active care group, 47 (39%) stepped-up treatment. At 18 months, endoscopic recurrence occurred in 60 (49%) patients in the active care group and 35 (67%) patients in the standard care group (p=0.03). Complete mucosal normality was maintained in 27 (22%) of 122 patients in the active care group versus four (8%) in the standard care group (p=0.03). In the active care arm, of those with 6 months recurrence who stepped up treatment, 18 (38%) of 47 patients were in remission 12 months later; conversely, of those in remission at 6 months who did not change therapy recurrence occurred in 31 (41%) of 75 patients 12 months later. Smoking (odds ratio [OR] 2.4, 95% CI 1.2-4.8, p=0.02) and the presence of two or more clinical risk factors including smoking (OR 2.8, 95% CI 1.01-7.7, p=0.05) increased the risk of endoscopic recurrence. The incidence and type of adverse and severe adverse events did not differ significantly between patients in the active care and standard care groups (100 [82%] of 122 vs 45 [87%] of 52; p=0.51) and (33 [27%] of 122 vs 18 [35%] of 52; p=0.36), respectively.

INTERPRETATION

Treatment according to clinical risk of recurrence, with early colonoscopy and treatment step-up for recurrence, is better than conventional drug therapy alone for prevention of postoperative Crohn's disease recurrence. Selective immune suppression, adjusted for early recurrence, rather than routine use, leads to disease control in most patients. Clinical risk factors predict recurrence, but patients at low risk also need monitoring. Early remission does not preclude the need for ongoing monitoring.

FUNDING

AbbVie, Gutsy Group, Gandel Philanthropy, Angior Foundation, Crohn's Colitis Australia, and the National Health and Medical Research Council.

HLA-DQA1-HLA-DRB1 variants confer susceptibility to pancreatitis induced by thiopurine immunosuppressants

Pancreatitis occurs in approximately 4% of patients treated with the thiopurines azathioprine or mercaptopurine. Its development is unpredictable and almost always leads to drug withdrawal. We identified patients with inflammatory bowel disease (IBD) who had developed pancreatitis within 3 months of starting these drugs from 168 sites around the world. After detailed case adjudication, we performed a genome-wide association study on 172 cases and 2,035 controls with IBD. We identified strong evidence of association within the class II HLA region, with the most significant association identified at rs2647087 (odds ratio 2.59, 95% confidence interval 2.07-3.26, P = 2 × 10(-16)). We replicated these findings in an independent set of 78 cases and 472 controls with IBD matched for drug exposure. Fine mapping of the HLA region identified association with the HLA-DQA1*02:01-HLA-DRB1*07:01 haplotype. Patients heterozygous at rs2647087 have a 9% risk of developing pancreatitis after administration of a thiopurine, whereas homozygotes have a 17% risk.

Glucocorticoids alleviate intestinal ER stress by enhancing protein folding and degradation of misfolded proteins

Dexamethasone suppresses ER stress in inflammatory bowel disease by promoting correct protein folding and ER-associated degradation.

Endoplasmic reticulum (ER) stress in intestinal secretory cells has been linked with colitis in mice and inflammatory bowel disease (IBD). Endogenous intestinal glucocorticoids are important for homeostasis and glucocorticoid drugs are efficacious in IBD. In Winnie mice with intestinal ER stress caused by misfolding of the Muc2 mucin, the glucocorticoid dexamethasone (DEX) suppressed ER stress and activation of the unfolded protein response (UPR), substantially restoring goblet cell Muc2 production. In mice lacking inflammation, a glucocorticoid receptor antagonist increased ER stress, and DEX suppressed ER stress induced by the N-glycosylation inhibitor, tunicamycin (Tm). In cultured human intestinal secretory cells, in a glucocorticoid receptor-dependent manner, DEX suppressed ER stress and UPR activation induced by blocking N-glycosylation, reducing ER Ca²⁺ or depleting glucose. DEX up-regulated genes encoding chaperones and elements of ER-associated degradation (ERAD), including EDEM1. Silencing EDEM1 partially inhibited DEX’s suppression of misfolding-induced ER stress, showing that DEX enhances ERAD. DEX inhibited Tm-induced MUC2 precursor accumulation, promoted production of mature mucin, and restored ER exit and secretion of Winnie mutant recombinant Muc2 domains, consistent with enhanced protein folding. In IBD, glucocorticoids are likely to ameliorate ER stress by promoting correct folding of secreted proteins and enhancing removal of misfolded proteins from the ER.

Oral bismuth for chronic intractable diarrheal conditions?

Objective

Bismuth has antidiarrheal, antibacterial, and anti-inflammatory properties. We report our single-center experience with oral colloidal bismuth subcitrate (CBS) treatment for patients with chronic intractable diarrhea.

Method

We interrogated our web-based Inflammatory Bowel Disease Clinical and Research database to ascertain clinical details on all patients in our tertiary hospital gastroenterology service treated with CBS between 2000 and 2010. Treatment responses were based on prospective scoring of daily number of liquid stools. Responses were recorded prior to commencement of CBS and at follow-up visits over 12 months.

Results

Thirty-one patients, mean age 47 years (range 17–79 years) and a mean duration of diarrhea of 22 weeks (range 6–104 weeks), were prescribed CBS at doses ranging from 120 mg to 480 mg/day for ≥1 month. Of these, 23 patients (74%) had an initial clinical response and 12 (39%) who continued with this treatment had a sustained clinical response at 1 year. Twelve patients with pouchitis and four patients with indeterminate colitis had initial responses of 92% and 75%, respectively, and sustained responses of 50% and 75%, respectively. Ulcerative colitis patients (n = 5) responded poorly with respect to both initial and sustained responses. Three patients with microscopic colitis showed encouraging initial response of 100% but did not have any sustained benefit. Three of four patients with diarrhea-predominant irritable bowel syndrome (dIBS) had an initial response and two (50%) had good sustained responses. There were no serious adverse events. One patient stopped therapy because of nausea.

Conclusion

This is the largest report of oral bismuth treatment in chronic intractable diarrhea. CBS is cheap and appears to have the potential to be effective for ameliorating diarrheal symptoms in indeterminate colitis, pouchitis, and dIBS. An appropriately powered, blinded, randomized, controlled study appears warranted to establish the position of oral bismuth in routine practice.

IL-10 promotes production of intestinal mucus by suppressing protein misfolding and endoplasmic reticulum stress in goblet cells

BACKGROUND & AIMS

Protein misfolding and endoplasmic reticulum (ER) stress have been observed in intestinal secretory cells from patients with inflammatory bowel diseases and induce intestinal inflammation in mice. However, it is not clear how immune factors affect ER stress and therefore disease symptoms.

METHODS

We analyzed the effects of interleukin (IL)-10 on ER stress in intestinal tissues in wild-type C57BL/6, Winnie, IL-10(-/-), and Winnie × IL-10(+/-) mice. In Winnie mice, misfolding of the intestinal mucin Muc2 initiates ER stress and inflammation. We also analyzed the effects of different inhibitors of IL-10 signaling and the N-glycosylation inhibitor tunicamycin in cultured human LS174T goblet cells.

RESULTS

Administration of neutralizing antibodies against IL-10 or its receptor (IL-10R1) to Winnie mice rapidly exacerbated ER stress and intestinal inflammation compared with mice given vehicle (controls). Antibodies against IL-10 also increased accumulation of misfolded Muc2 in the ER of goblet cells of Winnie mice and increased T-cell production of inflammatory cytokines. Winnie × IL-10(+/-) mice and IL-10(-/-) mice with a single Winnie allele each developed more severe inflammation than Winnie mice or IL-10(-/-) mice. Administration of tunicamycin to wild-type mice caused intestinal ER stress, which increased when IL-10R1 was blocked. In LS174T cells, induction of ER stress with tunicamycin and misfolding of MUC2 were reduced by administration of IL-10; this reduction required STAT1 and STAT3. In LS174T cells incubated with tunicamycin, IL-10 up-regulated genes involved in MUC2 folding and in ER-associated degradation and maintained correct folding of MUC2, its transport from the ER, and its O-glycosylation and secretion.

CONCLUSIONS

IL-10 prevents protein misfolding and ER stress by maintaining mucin production in goblet cells and helps the intestine preserve the mucus barrier.

Mucin dynamics and enteric pathogens

The extracellular secreted mucus and the cell surface glycocalyx prevent infection by the vast numbers of microorganisms that live in the healthy gut. Mucin glycoproteins are the major component of these barriers. In this Review, we describe the components of the secreted and cell surface mucosal barriers and the evidence that they form an effective barricade against potential pathogens. However, successful enteric pathogens have evolved strategies to circumvent these barriers. We discuss the interactions between enteric pathogens and mucins, and the mechanisms that these pathogens use to disrupt and avoid mucosal barriers. In addition, we describe dynamic alterations in the mucin barrier that are driven by host innate and adaptive immune responses to infection.

ER stress and the unfolded protein response in intestinal inflammation

Endoplasmic reticulum (ER) stress is a phenomenon that occurs when excessive protein misfolding occurs during biosynthesis. ER stress triggers a series of signaling and transcriptional events known as the unfolded protein response (UPR). The UPR attempts to restore homeostasis in the ER but if unsuccessful can trigger apoptosis in the stressed cells and local inflammation. Intestinal secretory cells are susceptible to ER stress because they produce large amounts of complex proteins for secretion, most of which are involved in mucosal defense. This review focuses on ER stress in intestinal secretory cells and describes how increased protein misfolding could occur in these cells, the process of degradation of misfolded proteins, the major molecular elements of the UPR pathway, and links between the UPR and inflammation. Evidence is reviewed from mouse models and human inflammatory bowel diseases that ties ER stress and activation of the UPR with intestinal inflammation, and possible therapeutic approaches to ameliorate ER stress are discussed.

ATG16L1 T300A shows strong associations with disease subgroups in a large Australian IBD population: further support for significant disease heterogeneity

OBJECTIVES

Crohn's disease (CD) and ulcerative colitis (UC) are the two most common forms of inflammatory bowel disease (IBD), representing a significant health-care burden. A variant in the autophagy gene ATG16L1 (T300A) has been newly identified as a CD susceptibility locus by genome-wide association. Our aim was to assess the contribution of T300A in determining disease susceptibility and phenotype in two independent Australian IBD cohorts and explore the relationship between T300A and known CD risk factors (NOD2[nucleotide-binding oligomerization domain containing 2] status and smoking).

METHODS

In total, 669 CD and 543 UC cases, and 1,244 controls (study 1), 154 CD cases and 420 controls (study 2), and 702 unaffected parents from both groups were genotyped. We conducted case-control and family association analyses, and investigated relationships between T300A and disease subgroups and between NOD2 status and cigarette smoking (CD only).

RESULTS

The strong association between CD and T300A was confirmed (P < 0.001), with a two-fold increase in disease risk associated with the GG genotype (odds ratio [OR] 1.96, 95% confidence interval [CI] 1.49-2.58), while ileal CD risk was almost three-fold (OR 2.73, CI 1.87-4.0). ATG16L1 and NOD2 were found to contribute independently to CD risk. A greater than seven-fold increased CD risk was observed for current smokers with a GG genotype (vs nonsmoking AA genotype; P < 0.001, OR 7.65, CI 4.21-13.91). A significant inverse association was found between T300A and UC (P= 0.002). This was strongest for patients with extensive, severe disease.

CONCLUSIONS

We confirm the strong association between T300A and CD, specifically ileal subphenotype, and also report the first strong association of this variant with UC.

MUC1 cell surface mucin is a critical element of the mucosal barrier to infection

Cell surface mucin glycoproteins are highly expressed by all mucosal tissues, yet their physiological role is currently unknown. We hypothesized that cell surface mucins protect mucosal cells from infection. A rapid progressive increase in gastrointestinal expression of mucin 1 (Muc1) cell surface mucin followed infection of mice with the bacterial pathogen Campylobacter jejuni. In the first week following oral infection, C. jejuni was detected in the systemic organs of the vast majority of Muc1(-/-) mice but never in Muc1(+/+) mice. Although C. jejuni entered gastrointestinal epithelial cells of both Muc1(-/-) and Muc1(+/+) mice, small intestinal damage as manifested by increased apoptosis and enucleated and shed villous epithelium was more common in Muc1(-/-) mice. Using radiation chimeras, we determined that prevention of systemic infection in wild-type mice was due exclusively to epithelial Muc1 rather than Muc1 on hematopoietic cells. Expression of MUC1-enhanced resistance to C. jejuni cytolethal distending toxin (CDT) in vitro and CDT null C. jejuni showed lower gastric colonization in Muc1(-/-) mice in vivo. We believe this is the first in vivo experimental study to demonstrate that cell surface mucins are a critical component of mucosal defence and that the study provides the foundation for exploration of their contribution to epithelial infectious and inflammatory diseases.

Angiotensinogen and transforming growth factor beta1: novel genes in the pathogenesis of Crohn's disease

BACKGROUND

Angiotensin peptides may act locally as cytokines in several organ systems with elevated mucosal levels present in Crohn's disease. A variant in the angiotensinogen gene promoter results in increased peptide production, while transforming growth factor beta1 (TGFbeta1) codon 25 variants demonstrate variable peptide production, predisposing to fibrosis in several organs.

AIMS

Conduct an Australian-based analysis of the angiotensinogen-6 variant in two independent inflammatory bowel disease (IBD) cohorts, and examine the role of angiotensinogen-6 and TGFbeta1 codon 25 variants in shaping Crohn's disease phenotype.

METHODS

IBD Patients (Crohn's disease = 347, ulcerative colitis = 147) and CD families (n = 148) from two cohorts, together with 185 healthy controls were genotyped for angiotensinogen-6. Genotype-phenotype analyses were performed for both angiotensinogen-6 and TGFbeta1 codon 25.

RESULTS

Angiotensinogen-6 AA genotype was significantly associated with Crohn's disease (p = 0.007, OR = 2.38, CI = 1.32-4.32) in cohort 1, but not in the smaller cohort 2 (p = 0.19). The association remained significant when the two cohorts were combined (p = 0.008), and in a TDT family analysis (p = 0.03). TGF 1 codon 25 was associated with stricturing Crohn's disease (p = 0.01, OR = 2.63, CI = 1.16-5.88) and a shorter time to intestinal resection (p = 0.06).

CONCLUSIONS

The association of the angiotensinogen-6 variant with Crohn's disease supports a potential role for angiotensin-converting enzyme inhibitors and angiotensin II receptor antagonists in disease treatment.

Chronic narcotic use in inflammatory bowel disease patients: prevalence and clinical characteristics

BACKGROUND

Narcotic addiction can be a significant problem in inflammatory bowel disease (IBD). However, there are few published reports about this problem.

METHODS

All patients prescribed narcotics chronically in the absence of demonstrable organic pathology were identified on the computerized Brisbane IBD Research Group database (n=332 patients with informative data as of 1 January 1999). Individual case records were reviewed with regard to clinical, psychiatric and social characteristics of these patients, and the prevalence of psychiatric disorders were compared with a control group of IBD patients.

RESULTS

Eleven patients were identified. Nine had complete datasets, eight with Crohn's disease (CD), of which six had previous stricturing ileal disease, and one patient had ulcerative colitis, making a prevalence of 2.7% of IBD patients and 5.1% of CD patients. A 67% prevalence of a psychiatric disorder in narcotic users was significantly greater than the 8% prevalence in the control group of IBD patients (odds ratio 22, 95% CI 3.24-177).

CONCLUSIONS

A significant proportion of IBD patients without demonstrable organic pathology were chronic narcotic users. Psychiatric disorders are common in this subgroup, as with chronic functional abdominal pain syndromes. It is suggested that inappropriate narcotic use in IBD patients can be reduced by appreciating that narcotics are a temporary therapy only for IBD patients, and awareness of pre-existing social and psychiatric disorders, which not only impact on clinical presentation of pain, but also help define the subgroup of patients who are at risk of narcotic misuse.

CD40 and CD86 upregulation with divergent CMRF44 expression on blood dendritic cells in inflammatory bowel diseases

OBJECTIVE

Dendritic cells (DC) are the only antigen-presenting cells that can activate naïve T lymphocytes and initiate a primary immune response. They are also thought to have a role in immune tolerance. DC traffic from the blood to peripheral tissue where they become activated. They then present antigen and the costimulating signals necessary to initiate an immune response. In this study, we investigated the number, subsets, and activation pattern of circulating and intestinal DC from patients with clinically mild ulcerative colitis (UC) or Crohn's disease.

METHODS

Patients were recruited, if they were not taking immunosuppressive therapy, and were assessed for clinical severity of their disease using for UC, the Clinical Activity Index, and for Crohn's disease, the Crohn's Disease Activity Index. Blood CD11c+ and CD11c- DC subsets, expression of costimulatory antigens, CD86 and CD40, and the early differentiation/activation antigen, CMRF44, were enumerated by multicolor flow cytometry of lineage negative (lin- = CD3-, CD19-, CD14-, CD16-) HLA-DR+ DC. These data were compared with age-matched healthy and the disease control groups of chronic noninflammatory GI diseases (cGI), acute noninflammatory GI diseases (aGI), and chronic non-GI inflammation (non-GI). In addition, cryostat sections of colonoscopic biopsies from healthy control patients and inflamed versus noninflamed gut mucosa of inflammatory bowel disease (IBD) patients were examined for CD86+ and CD40+ lin- cells.

RESULTS

Twenty-one Crohn's disease and 25 UC patients, with mean Crohn's Disease Activity Index of 98 and Clinical Activity Index of 3.1, and 56 healthy controls, five cGI, five aGI, and six non-GI were studied. CD11c+ and CD11c- DC subsets did not differ significantly between Crohn's, UC, and healthy control groups. Expression of CD86 and CD40 on freshly isolated blood DC from Crohn's patients appeared higher (16.6%, 31%) and was significantly higher in UC (26.6%, 46.3%) versus healthy controls (5.5%, 25%) (p = 0.004, p = 0.012) and non-GI controls (10.2%, 22.8%) (p = 0.012, p = 0.008), but not versus cGI or aGI controls. CD86+ and CD40+ DC were also present in inflamed colonic and ileal mucosa from UC and Crohn's patients but not in noninflamed IBD mucosa or normal mucosa. Expression of the CMRF44 antigen was low on freshly isolated DC, but it was upregulated after 24-h culture on DC from all groups, although significantly less so on DC from UC versus Crohn's or healthy controls (p = 0.024). The CMRF44+ antigen was mainly associated with CD11c+ DC, and in UC was inversely related to the Clinical Activity Index (r = -0.69, p = 0.0002).

CONCLUSIONS

There is upregulation of costimulatory molecules on blood DC even in very mild IBD but surprisingly, there is divergent expression of the differentiation/activation CMRF44 antigen. Upregulation of costimulatory molecules and divergent expression of CMRF44 in blood DC was also apparent in cGI and aGI but not in non-GI or healthy controls, whereas intestinal CD86+ and CD40+ DC were found only in inflamed mucosa from IBD patients. Persistent or distorted activation of blood DC or divergent regulation of costimulatory and activation antigens may have important implications for gut mucosal immunity and inflammation.

Early Australian experience with infliximab, a chimeric antibody against tumour necrosis factor-alpha, in the treatment of Crohn's disease: is its efficacy augmented by steroid-sparing immunosuppressive therapy? The Infliximab User Group

BACKGROUND

Tumour necrosis factor-alpha (TNF-alpha) plays an important role in the pathology of Crohn's disease. Infliximab, a chimeric antibody against TNF-alpha, has been shown in controlled clinical trials to be effective in two-thirds of patients with refractory or fistulating Crohn's disease. The factors that determine a clinical response in some patients but not others are unknown.

AIMS

To document the early Australian experience with infliximab treatment for Crohn's disease and to identify factors that may determine a beneficial clinical response.

METHODS

Gastroenterologists known to have used infliximab for Crohn's disease according to a compassionate use protocol were asked to complete a spreadsheet that included demographic information, Crohn's disease site, severity, other medical or surgical treatments and a global clinical assessment of Crohn's disease outcome, judged by participating physicians as complete and sustained (remission for the duration of the study), complete but unsustained (remission at 4 weeks but not for the whole study) or partial clinical improvement (sustained or unsustained).

RESULTS

Fifty-seven patients were able to be evaluated, with a median follow-up time of 16.4 (4-70) weeks, including 23 patients with fistulae. There were 21 adverse events, including four serious events. Fifty-one patients (89%) had a positive clinical response for a median duration (range) of 11 (2-70) weeks. Thirty patients (52%) had a remission at 4 weeks, 10 of whom had remission for longer than 12 weeks. Forty-two per cent of fistulae closed. Sustained remission (P = 0.065), remission at 4 weeks (P = 0.033) and a positive clinical response of any sort (P = 0.004) were more likely in patients on immunosuppressive therapy, despite there being more smokers in this group.

CONCLUSION

This review of the first Australian experience with infliximab corroborates the reported speed and efficacy of this treatment for Crohn's disease. The excellent response appears enhanced by the concomitant use of conventional steroid-sparing immunosuppressive therapy.

Shared and unique environmental factors determine the ecology of methanogens in humans and rats

OBJECTIVE

This study ascertains the relative contributions of genetics and environment in determining methane emission in humans and rats. There is considerable interest in the factors determining the microbial species that inhabit the colon. Methanogens. which are archaebacteria, are an easily detected colonic luminal bacteria because they respire methane. They are present in some but not all human colons and lower animal hindguts. Opinion varies on the nature of the factors influencing this ecology with some studies proposing the existence of host genetic influences.

METHODS

Methane emission was measured in human twin pairs by gas chromatography, and structural equation modeling was used to determine the proportion of genetic and environmental determinants. The importance of the timing of environmental effects and rat strain on the trait of methane emission were ascertained by experiments with cohabiting methanogenic and nonmethanogenic rats.

RESULTS

Analysis of breath samples from 274 adolescent twin pairs and their families indicated that the major influences on the trait of methane emission are the result of shared (53%, 95% confidence interval 39-61) and unique environmental (47%, 95% confidence interval 38-56) effects. No significant autosomal genetic effects were detected, but as observed in other studies, men (37%) were less likely to excrete methane in their breath than women (63%). Investigation of methane emission in rats indicated that environmental effects in this animal are most potent during the weaning period, with stable gut microbial ecology thereafter for some but not all rat strains.

CONCLUSIONS

These results are consistent with shared and unique environmental factors being the main determinants of the ecology of this colonic microbe.

Treatment of joint pain in Crohn's patients with budesonide controlled ileal release

1. Joint pain is a frequent manifestation of Crohn's disease. Budesonide controlled ileal release (CIR) is a predominantly topically acting glucocorticosteroid, which is effective in treating active ileal or ileocaecal Crohn's disease. 2. Therefore, it was of interest to study the effect of this predominantly topically acting therapy on the treatment of an extraintestinal symptom of Crohn's disease by analysing data collected from budesonide CIR (Entocort; Astra Draco AB, Lund, Sweden) trials. 3. Three large studies of budesonide CIR treatment in active Crohn's disease provided a reliable source of clinical data. Of the 611 patients treated in the prospective double-blind controlled trials, 291 had joint pain (arthritis/arthralgia) at entry, which was recorded as part of the Crohn's Disease Activity Index. Statistical analysis was based on all patients treated, provided that the patient had joint pain at the start of treatment. 4. Daily oral budesonide CIR (9mg) resulted in clinical remission of joint pain in 74% (95% confidence intervals (CI) 67-82%) of patients. This outcome was nearly twice as good as placebo (41%; 95% CI 34-57%) and as good as the outcome effected by daily oral prednisolone (40mg; 72%; 95% CI 60-84%). The favourable response to budesonide CIR (9 mg) did not correlate with glucocorticosteroid-associated side effects or with adrenal suppression, which were half those in the prednisolone (40 mg/day) group. 5. The favourable outcome may relate to restitution of normal intestinal immune function.

Alkyl halides, super hydrogen production and the pathogenesis of pneumatosis cystoides coli

BACKGROUND AND AIMS

The colons of patients with pneumatosis cystoides coli produce excessive H2. Exposure to alkyl halides could explain this. Six consecutive patients who had pneumatosis cystoides coli while taking chloral hydrate (1-5+ g/day) are reported. Patients 2 and 3 were investigated after they had ceased chloral hydrate treatment. One produced methane, the other did not. (Pneumatosis cystoides coli patients are non-methanogenic according to the literature.) Both had overnight fasting breath H2 of less than 10 ppm. A literature review disclosed just one patient who was using chloral at the time of diagnosed pneumatosis cystoides coli, but an epidemic of the disease in workers exposed to trichloroethylene.

METHODS

(i) In vitro experiments with human faeces: chloral or closely related alkyl halides were added to anaerobic faecal cultures derived from four methane-producing and three non-methanogenic human subjects. H2 and CH4 gases were measured. (ii) In vivo animal experiment: chloral hydrate was added to drinking water of four Wistar rats, and faecal H2 compared with control rats.

RESULTS

Alkyl halides increased H2 up to 900 times in methanogenic and 10 times in non-methanogenic faecal cultures. The Ki of chloral was 0.2 mM. Methanogenesis was inhibited in concert with the increase in net H2. In the rat experiment, chloral hydrate increased H2 10 times, but did not cause pneumatosis.

CONCLUSIONS

Chloral and trichloroethylene are alkyl halides chemically similar to chloroform, a potent inhibitor of H2 consumption by methanogens and acetogens. These bacteria are the most important H2-consuming species in the colon. It is postulated that exposure to these alkyl halides increases net H2 production, which sets the scene for "counterperfusion supersaturation" and the formation of gas cysts. In recent times, very low prescribing rates for chloral have caused primary pneumatosis cystoides to become extremely rare. As with primary pneumatosis, secondary pneumatosis cystoides, which occurs if there is small bowel bacterial overgrowth distal to a proximally located gut obstruction, is predicted by counterperfusion supersaturation. "Inherent unsaturation" due to metabolism of O2 is a safety factor, which could explain why gas bubbles do not form more often in tissue with high H2 tension.

The effect of C5a and U46619 on the isolated, perfused human placental lobule: development of a method for the online estimation of tissue fluid accumulation

A method for the automatic and simultaneous determination of perfusion pressure and fluid accumulation in the isolated, perfused human placental lobule is described. We demonstrated that the inflammatory mediator, C5a, a C5a agonist analogue peptide, and the thromboxane mimetic U46619 caused increased fetal perfusion pressure and increased tissue weight when administered via the fetal arterial circulation. Occlusion of the fetal venous effluent tubing caused significantly greater increases in tissue weight than the pharmacological agents. Detectable increases in tissue weight occurred within 47 +/- 3 sec (n = 21) following pressure increases caused by the pharmacological agents. In each case, the increase in tissue weight was accompanied by an increased permeability of the materno-fetal barrier, shown by the transfer of Evans blue albumin from the fetal circulation to the maternal compartment.

Inhibition of methanogenesis by human bile

The factors that regulate methanogenesis in humans have not been established. The presence of bile acid, which is lost into the colon from the small intestine, may be an important regulatory factor of methanogenesis. To examine this possibility, the effect of human bile on methane production by faecal cultures, and the in vivo effect of biliary diversion on breath methane excretion in a methanogenic choledochostomy patient, were investigated. Faecal suspensions (0.1%) from five methanogenic humans were incubated anaerobically with bile (0.3-30%) from three choledochostomy patients, and headspace methane measured by gas chromatography. All biles inhibited headspace methane. Inhibition of methanogenesis was dose dependent, plateaued at 10-30% bile concentration, and was abolished by 0.6% cholestyramine. The maximum inhibition by bile, median (range), was 38 (0.9-56)% of control methane values. Reversal of the bile fistula in the fourth choledochostomy patient converted that subject from methanogenic to 'non-methanogenic' status, It is concluded that inhibition of methanogens in the caecum by bile acid could significantly reduce the number of methanogens in the colon. This and the effect of transit time could explain much of the known epidemiology of 'non-methanogenesis', which has been related to obesity, (comparatively) fast colonic transit in healthy persons, and to small intestinal Crohn's disease.

Does counterperfusion supersaturation cause gas cysts in pneumatosis cystoides coli, and can breathing heliox reduce them?

The pathogenesis of pneumatosis cystoides coli remains obscure in the absence of an explanation for why pockets of gas should form in the first place and why they should be maintained in the wall and mesentery of the colon. Counterperfusion supersaturation could explain the formation and location of the gas cysts, which occur mostly near blood vessels on the mesenteric border of the colon, and the absence of methane gas in them. The hypothesis can be tested by treating patients with pneumatosis cystoides coli with heliox.

Reversibility of tachyphylaxis to C5A in guinea pig tissues, perfused human placental lobule, and umbilical artery

The spasmogenic effect of C5a is mediated by histamine and/or eicosanoids. Tachyphylaxis to this effect of C5a occurs rapidly, but the spasmogenic effects of C5a on a guinea pig lung parenchymal strips, field-stimulated ventricular papillary muscle, and human umbilical artery were completely restored by a 1-h period of drug-free rest, whereas that of guinea pig ileum was not. Perfusion of the isolated human placental lobule with C5a caused a transient pressor response that was largely abolished by indomethacin (5 microM), indicating mediation by cyclooxygenase metabolites. This pressor response to C5a was also completely restored following a 1-h rest period. The results show that tissue rest reverses tachyphylaxis to the spasmogenic effects of C5a in tissues where the response is mediated by cyclooxygenase metabolites. Where the response is mediated by histamine released by mast cells, restoration does not occur, presumably because of the catastrophic nature of mast cell degranulation. Histamine released in guinea pig papillary muscle by C5a may be from non-mast-cell sources.

Pressor effect of ethanol in the isolated perfused human placental lobule

Pharmacologically relevant concentrations of ethanol (0.01-0.3 g/%) were perfused via the fetal circulation in isolated human placental lobules. This resulted in a dose-related rise in fetal arterial pressure, which at 0.3 g/% ethanol, was 10.1 +/- 1.1 mmHg above the pre-drug baseline. The pressor responses to ethanol were (i) rapid in onset, reaching a stable plateau within 5-10 min following administration, (ii) readily reversible by perfusion with drug-free media, (iii) non-tachyphylactic and (iv) largely inhibited by the cyclo-oxygenase inhibitor, inhibitor, indomethacin (5 microM). This pressor action of ethanol in the fetal circulation may contribute to the pathogenesis of the fetal alcohol syndrome as well as represent an underlying mechanism of ethanol-induced hypertension.

A possible role for bile acid in the control of methanogenesis and the accumulation of hydrogen gas in the human colon

This study investigated a possible role for primary bile acid in the control of methanogenesis in the human colon. Production of hydrogen and methane was measured in anaerobic faecal cultures derived from faeces of six 'non-methanogenic' and three methanogenic healthy humans. Using a sensitive technique for gas measurement, methane was detected in all faecal cultures, including those from 'non-methanogenic' humans. Bile acid inhibited methanogenesis in a dose-response fashion in the in vitro 'non-methanogenic' and methanogenic faecal cultures. Inhibition was significant at bile acid concentrations > 0.05%. Methanogenesis correlated with methanogen (methanogenic bacteria) numbers. If this inhibition occurs in vivo, then it would explain much of the epidemiology of non-methanogenesis in humans. From an analysis of net hydrogen production by the faecal cultures, it is inferred that bile acid inhibits other hydrogen-consuming bacteria in addition to methanogens. These in vitro data suggest a major role for bile acid in the accumulation of hydrogen gas in the colon. Possible links between bile acid induced accumulation of gas and irritable bowel syndrome are discussed.

Active chronic peptic ulcer disease complicated by gastric outlet obstruction in pregnancy

A case of active peptic ulcer disease in a primigravida at 29 weeks' gestation is presented, with a literature review. This particular case was complicated by gastric outlet obstruction, a complication which has not been previously reported in the obstetric literature. Although an uncommon diagnosis in pregnancy, the investigations for peptic ulcer disease should be actively pursued. Treatment can prevent serious complications.

Hydrogen sulphide and total acid-volatile sulphide in faeces, determined with a direct spectrophotometric method

Hydrogen sulphide may be important in human bowel pathophysiology. Available methods for determination of hydrogen sulphide and total sulphide have not been validated for faeces. This paper reports on a method for direct determination of sulphide in faecal homogenates, and techniques for collecting faeces to permit determination of both hydrogen sulphide and total sulphide. Mean total sulphide and mean hydrogen sulphide concentrations were 0.66 and 0.17 mumol/g wet faeces, respectively. These concentrations are much higher than previous estimates. There was no significant difference between methanogenic and non-methanogenic faeces. Significant sulphidogenesis occurred in both methanogenic and non-methanogenic in vitro faecal incubations, with both sulphate and cysteine sources. These results do not support previous claims that sulphidogenesis occurs only in non-methanogenic faeces.