G R van den Brink

Treatment of bile duct lesions after laparoscopic cholecystectomy.

From January 1990 to June 1994, 53 patients who sustained bile duct injuries during laparoscopic cholecystectomy were treated at the Amsterdam Academic Medical Centre. There were 16 men and 37 women with a mean age of 47 years. Follow up was established in all patients for a median of 17 months. Four types of ductal injury were identified. Type A (18 patients) had leakage from cystic ducts or peripheral hepatic radicles, type B (11 patients) had major bile duct leakage, type C (nine patients) had an isolated ductal stricture, and type D (15 patients) had complete transection of the bile duct. Endoscopic retrograde cholangiopancreatography (ERCP) established the diagnosis in all type A, B, and C lesions. In type D lesions percutaneous cholangiography was required to delineate the proximal extent of the injury. Initial treatment (until resolution of symptoms and discharge from hospital) comprised endoscopy in 36 patients and surgery in 26 patients. Endoscopic treatment was possible and successful in 16 of 18 of type A lesions, five of seven of type B lesions, and three of nine of type C lesions. Most failures resulted from inability to pass strictures or leaks at the initial endoscopy. During initial treatment additional surgery was required in seven patients. Fourteen patients underwent percutaneous or surgical drainage of bile collections, or both. After endoscopic treatment early complications occurred in three patients, with a fatal outcome in two (not related to the endoscopic therapy). During follow up six patients developed late complications. All 15 patients with complete transection and four patients with major bile duct leakage were initially treated surgically. During initial treatment additional endoscopy was required in two patients. Early complications occurred in eight patients. During follow up seven patients developed stenosis of the anastomosis or bile duct. Reconstructive surgery in the early postoperative phase was associated with more complications than elective reconstructive surgery. Most type A and B bile duct injuries after laparoscopic cholecystectomy (80%) can be treated endoscopically. In patients with more severe ductal injury (type C and D) reconstructive surgery is eventually required in 70%. Multidisciplinary approach to these lesions is advocated and algorithms for treatment are proposed.

Sonic hedgehog expression correlates with fundic gland differentiation in the adult gastrointestinal tract

Background: Sonic hedgehog (Shh) is an important endodermal morphogenetic signal during the development of the vertebrate gut. It controls gastrointestinal patterning in general, and gastric gland formation in particular. We have previously shown that Shh regulates gastric gland proliferation in the adult but detailed analysis of its expression along the adult gastrointestinal tract has never been undertaken. We therefore studied Shh expression along the normal human and rodent adult gastrointestinal tract as well as in intestinal metaplasia of the stomach, gastric and intestinal metaplasia of the oesophagus, and gastric heterotopia in Meckel’s diverticulum. Methods: The studies were performed with in situ hybridisation and by immunohistochemistry using an antibody that recognises the Shh precursor form. Results: We found that in the normal gastrointestinal tract, high levels of Shh were expressed in the fundic glands of the stomach. Shh expression was also found in fundic gland metaplasia and heterotopia. However, Shh expression was lost in intestinal metaplasia of the stomach. Conclusion: We found a strong correlation between Shh expression and fundic gland differentiation. Our current study therefore provides evidence that in addition to its role in gastric epithelial development, Shh plays a unique role in gastric epithelial differentiation in adults.

H pylori colocalises with MUC5AC in the human stomach

BACKGROUND The bacterium Helicobacter pyloriis able to adhere to and to colonise the human gastric epithelium, yet the primary gene product responsible as a receptor for its adherence has not been identified. AIMS To investigate the expression of the gastric mucins MUC5AC and MUC6 in the gastric epithelium in relation to H pyloricolonisation in order to examine their possible roles in the binding of H pylori. PATIENTS Seventy two consecutive patients suspected of having H pylori infection. METHODS MUC5AC, MUC6, and H pylori were detected in single sections of antral biopsy specimens using immunohistochemical triple staining. RESULTS MUC5AC was expressed in the superficial epithelium and the upper part of the gastric pits. MUC6 expression was detected in the lower part of the gastric pits. The expression of both mucins in the epithelium was complementary. In each patient, there was a sharply delineated transition between MUC5AC and MUC6 producing cell populations. In allH pylori positive patients there was a striking colocalisation of H pylori and MUC5AC; more than 99% of the bacteria were associated with either extracellular MUC5AC or the apical domain of MUC5AC producing cells. CONCLUSIONS H pylori is very closely associated with extracellular MUC5AC and epithelial cells that produce MUC5AC. This indicates that MUC5AC, but not MUC6, plays a role in the adhesion ofH pylori to the gastric mucosa.

Effect of aspirin on the Wnt/beta-catenin pathway is mediated via protein phosphatase 2A.

Nonsteroidal anti-inflammatory drugs show chemopreventive efficacy in colon cancer, but the mechanism behind this remains unclear. Elucidating this mechanism is seen as vital to the development of new chemopreventive agents. We studied the effects of aspirin on the oncogenic Wnt/β-catenin pathway activity in colorectal cancer cell lines and observed that aspirin dose-dependently decreased the activity of this pathway, as judged by TCF-driven luciferase activity, reduced Wnt target gene expression and increased phosphorylation of β-catenin by immunoblotting. Furthermore, the ubiquitination and cytoplasmic levels of β-catenin were assessed by immunoblotting, and also the localization of β-catenin was shown by green fluorescent protein-tagged β-catenin and time-lapse fluorescent imaging. Importantly, aspirin treatment caused increased phosphorylation of protein phosphatase 2A (PP2A), an event associated with inhibition of PP2A enzymatic activity, which was confirmed by a reduction in enzymatic PP2A activity. Moreover, this inhibition of PP2A enzymatic activity was essential for the effects of aspirin on the Wnt/β-catenin pathway as shown by transient transfection with PP2A constructs. The findings in this article provide a molecular explanation for the efficacy of aspirin in chemoprevention of colorectal cancer and shows biochemical evidence that PP2A is an important regulator of Wnt/β-catenin pathway activity in these cells.

Endogenous c-Myc is essential for p53-induced apoptosis in response to DNA damage in vivo

Recent studies have suggested that C-MYC may be an excellent therapeutic cancer target and a number of new agents targeting C-MYC are in preclinical development. Given most therapeutic regimes would combine C-MYC inhibition with genotoxic damage, it is important to assess the importance of C-MYC function for DNA damage signalling in vivo. In this study, we have conditionally deleted the c-Myc gene in the adult murine intestine and investigated the apoptotic response of intestinal enterocytes to DNA damage. Remarkably, c-Myc deletion completely abrogated the immediate wave of apoptosis following both ionizing irradiation and cisplatin treatment, recapitulating the phenotype of p53 deficiency in the intestine. Consistent with this, c-Myc-deficient intestinal enterocytes did not upregulate p53. Mechanistically, this was linked to an upregulation of the E3 Ubiquitin ligase Mdm2, which targets p53 for degradation in c-Myc-deficient intestinal enterocytes. Further, low level overexpression of c-Myc, which does not impact on basal levels of apoptosis, elicited sustained apoptosis in response to DNA damage, suggesting c-Myc activity acts as a crucial cell survival rheostat following DNA damage. We also identify the importance of MYC during DNA damage-induced apoptosis in several other tissues, including the thymus and spleen, using systemic deletion of c-Myc throughout the adult mouse. Together, we have elucidated for the first time in vivo an essential role for endogenous c-Myc in signalling DNA damage-induced apoptosis through the control of the p53 tumour suppressor protein.

Rage signalling promotes intestinal tumourigenesis

Development of colon cancer is a multistep process that is regulated by intrinsic and extrinsic cellular signals. Extrinsic factors include molecular patterns that are derived from either pathogens (PAMPs) or cellular damage (DAMPs). These molecules can promote tumourigenesis by activation of the innate immune system, but the individual contribution of ligands and their receptors remains elusive. The receptor for advanced glycation end products (Rage) is a pattern recognition receptor that binds multiple ligands derived from a damaged cell environment such as Hmgb1 and S100 protein. Here we show that Rage signalling has a critical role in sporadic development of intestinal adenomas, as ApcMin/+ Rage−/− mice are protected against tumourigenesis.

Altered bone morphogenetic protein signalling in the Helicobacter pylori-infected stomach

Morphogens regulate epithelial cell fate decisions in the adult gastrointestinal tract. The authors hypothesized that influx of inflammatory cells into the lamina propria may disturb the normal expression gradients of morphogens (morphogenetic landscape) in gastrointestinal epithelia. Changes in the activity of the bone morphogenetic protein (BMP) pathway in normal and Helicobacter pylori‐infected gastric mucosa were therefore examined. It is shown that BMP receptors, the activated (phosphorylated) form of the intracellular BMP signal transduction protein SMAD1, and BMP target ID2 all localize to gastric epithelial cells that are at the end of the axis of epithelial renewal in normal mucosa. Colonization of human gastric mucosa with H. pylori was associated with an increase in BMP2 expression due to influx of inflammatory cells that produce BMP2. Furthermore, whereas no BMP4 was detected in the normal antrum, focal infiltrates of BMP4‐expressing cells were found in the H. pylori‐infected stomach. This influx of BMP‐expressing cells was associated with an increase in epithelial BMP signalling. Interestingly, a shift in activity of the BMP pathway was observed towards the precursor cell compartment (isthmus) of the gastric units. Thus, H. pylori infection results in an influx of inflammatory cells that disturb the normal activity gradient of a morphogenetic pathway with an established role in epithelial cell fate regulation. The data suggest that morphological changes in epithelial histology may result from alterations in the morphogenetic landscape secondary to changes in the cellular composition of the lamina propria. Copyright

Hedgehog Wnteraction in colorectal cancer

The Hedgehog pathway was recently shown to antagonise constitutive activity of the Wnt pathway that drives proliferation of colorectal cancer cells. Studies in this issue of Gut refine our understanding of the underlying mechanism and provide evidence for such antagonism in colorectal cancers in vivo The mucosa of the colon is covered by a single layer of epithelial cells that is replaced once every 3–7 days. New cells are produced by a pool of progenitor cells that lie at the base of small mucosal invaginations called crypts. It has been estimated that these progenitor cells generate approximately 10 billion new cells per day in the human colon.1 Homeostasis in such a massive process of regeneration can only be achieved if the behaviour of cells in the system is not regulated at the level of the individual cell (intrinsic). Instead, the fate of individual epithelial cells must be determined by extra cellular (extrinsic) signals that are generated at the population level. It is now becoming clear that these extrinsic signals are provided by morphogens, a class of molecules that has been identified by developmental biologists who studied patterning events during embryogenesis.2 Morphogens are soluble proteins that form long range concentration gradients and act in a dose dependent manner to induce distinct cellular responses on their target cells. In this way, cellular fate is determined by the distance of a target cell from the source of the morphogen. Several morphogens have now been identified as regulators of cell fate in the adult colon. The Wnt pathway (fig 1) was the first morphogenetic pathway that was implicated in colonic epithelial homeostasis when it was found that adenomatous polyposis coli (APC) acts as an important regulator of Wnt signalling.3 APC had initially been identified as the gene mutated in patients with …

Oral tolerance is inefficient in neonatal mice due to a physiological Vitamin A deficiency

Increased risk of allergy during early life indicates deficient immune regulation in this period of life. To date, the cause for inefficient neonatal immune regulation has never been elucidated. We aimed to define the ontogeny of oral tolerance and to identify necessary conditions specific for this stage of life. Ovalbumin (OVA) was administered orally to mice through breast milk and efficiency of systemic tolerance to OVA was assessed in adulthood using a model of allergic airway inflammation. Oral tolerance induction was fully efficient starting third week of life. Inefficiency in neonates was a consequence of abnormal antigen transfer across the gut barrier and retinaldehyde dehydrogenase expression by mesenteric lymph node CD103+ neonatal dendritic cells, resulting in inefficient T-cell activation. Neonates’ serum retinol levels were three times lower than in adult mice, and vitamin A supplementation was sufficient to rescue neonatal defects and allow tolerance induction from birth. The establishment of oral tolerance required the differentiation of Th1 lymphocytes in both vitamin A-supplemented neonates and 3-week-old unsupplemented mice. This knowledge should guide the design of interventions for allergy prevention that are adapted to the neonatal stage of life such as vitamin A supplementation.

The BMP pathway either enhances or inhibits the Wnt pathway depending on the SMAD4 and p53 status in CRC

Background:Constitutive Wnt activation is essential for colorectal cancer (CRC) initiation but also underlies the cancer stem cell phenotype, metastasis and chemosensitivity. Importantly Wnt activity is still modulated as evidenced by higher Wnt activity at the invasive front of clonal tumours termed the β-catenin paradox. SMAD4 and p53 mutation status and the bone morphogenetic protein (BMP) pathway are known to affect Wnt activity. The combination of SMAD4 loss, p53 mutations and BMP signalling may integrate to influence Wnt signalling and explain the β-catenin paradox.Methods:We analysed the expression patterns of SMAD4, p53 and β-catenin at the invasive front of CRCs using immunohistochemistry. We activated BMP signalling in CRC cells in vitro and measured BMP/Wnt activity using luciferase reporters. MTT assays were performed to study the effect of BMP signalling on CRC chemosensitivity.Results:Eighty-four percent of CRCs with high nuclear β-catenin staining are SMAD4 negative and/or p53 aberrant. BMP signalling inhibits Wnt signalling in CRC only when p53 and SMAD4 are unaffected. In the absence of SMAD4, BMP signalling activates Wnt signalling. When p53 is lost or mutated, BMP signalling no longer influences Wnt signalling. The cytotoxic effects of 5-FU are influenced in a similar manner.Conclusions:The BMP signalling pathway differentially modulates Wnt signalling dependent on the SMAD4 and p53 status. The use of BMPs in cancer therapy, as has been proposed by previous studies, should be targeted to individual cancers based on the mutational status of p53 and SMAD4.