Cameron J. Bell

Prolonged colonic epithelial hyporesponsiveness after colitis: role of inducible nitric oxide synthase

Colonic epithelial secretion is an important host defense mechanism. We examined whether a bout of colitis would produce long-lasting changes in epithelial function that persisted after resolution of mucosal inflammation. Colitis was induced in rats with intracolonic trinitrobenzenesulfonic acid. Six weeks later, colonic damage and inducible nitric oxide synthase (iNOS) mRNA expression and activity were measured. Segments of distal colon were mounted in Ussing chambers for measurement of permeability and responsiveness to secretory stimuli. Basal electrolyte transport parameters and permeability were not different from untreated controls. Despite normal macroscopic and histological appearance, secretory responses to electrical field stimulation (EFS), isobutylmethylxanthine (IBMX), and carbachol were significantly depressed (by 60-70%) relative to controls. iNOS mRNA expression and enzyme activity were significantly elevated. Dexamethasone reversed epithelial hyporesponsiveness and significantly reduced iNOS mRNA expression. A selective iNOS inhibitor normalized the secretory responses to EFS and IBMX but not to carbachol. These data suggest that ongoing synthesis of nitric oxide by iNOS contributes to chronic suppression of epithelial secretory function after episodes of colitis.Colonic epithelial secretion is an important host defense mechanism. We examined whether a bout of colitis would produce long-lasting changes in epithelial function that persisted after resolution of mucosal inflammation. Colitis was induced in rats with intracolonic trinitrobenzenesulfonic acid. Six weeks later, colonic damage and inducible nitric oxide synthase (iNOS) mRNA expression and activity were measured. Segments of distal colon were mounted in Ussing chambers for measurement of permeability and responsiveness to secretory stimuli. Basal electrolyte transport parameters and permeability were not different from untreated controls. Despite normal macroscopic and histological appearance, secretory responses to electrical field stimulation (EFS), isobutylmethylxanthine (IBMX), and carbachol were significantly depressed (by 60-70%) relative to controls. iNOS mRNA expression and enzyme activity were significantly elevated. Dexamethasone reversed epithelial hyporesponsiveness and significantly reduced iNOS mRNA expression. A selective iNOS inhibitor normalized the secretory responses to EFS and IBMX but not to carbachol. These data suggest that ongoing synthesis of nitric oxide by iNOS contributes to chronic suppression of epithelial secretory function after episodes of colitis.

THE EFFECT OF ENTEROHEMORRHAGIC ESCHERICHIA-COLI O157-H7 ON INTESTINAL STRUCTURE AND SOLUTE TRANSPORT IN RABBITS

BACKGROUND The effect of enterohemorrhagic Escherichia coli O157:H7 infection on intestinal morphology and solute transport was examined. METHODS New Zealand white rabbits, aged 10 days, were infected with E. coli strain EDL933 (O157:H7 containing the 60-megadalton plasmid-encoding adhesion factors VT1 and VT2) and compared with controls. Small and large intestinal histology and solute transport were studied 5 days after inoculation. Ion transport in the distal colon was also examined in animals infected with different strains encoding a combination of pathogenic factors. RESULTS Infection with EDL933 induced diarrhea and mucosal disease in the colon, inhibited colonic Na+ absorption, and stimulated of Cl- secretion, but had no impact on the small intestine. Infection with strains A7785-C3A (O157:H7, plasmid-, VT1+, VT2+) and 85-170 (O157:H7, plasmid+, VT-) induced similar transport changes to EDL933. C600/1 (E. coli K-12, plasmid+, VT1+) decreased Na+ and Cl- absorption only. CONCLUSIONS Abnormalities of colonic structure and ion transport could account for diarrhea production, but pathogenic factors other than the 60-megadalton plasmid-encoding adhesion factor and verotoxins appear to be involved in enterohemorrhagic E. coli infection.

Modulation of host response to Escherichia coll 0157:H7 infection by anti-CD18 antibody in rabbits

BACKGROUND/AIMS Escherichia coli O157:H7 infection induces diarrhea, severe colitis, and colonic electrolyte transport abnormalities characterized by decreased Na absorption and Cl secretion. The aim of this study was to examine the role of the host inflammatory response in inducing distal colonic transport changes during infection with E. coli O157:H7. METHODS New Zealand white rabbits aged 10 days were infected with E. coli O157:H7 strain EDL933 (plasmid+, verotoxin 1+, verotoxin 2+). Studies were performed daily from day 1 to day 5 postinfection and compared with uninfected controls (10 days old). Distal colonic ion transport was studied in vitro under short-circuited conditions in Ussing chambers, and tissue inflammation was assessed by mucosal myeloperoxidase activities and mucosal neutrophil (polymorphonuclear neutrophil [PMN]) counts. In a second study, PMN infiltration was inhibited by an anti-CD18 (leukocyte adhesion molecule) monoclonal antibody, IB4, and histology and transport were studied on day 5 postinfection. RESULTS Infection with O157:H7 induced diarrhea and inhibition of Na absorption by day 3. CI secretion occurred on day 5, coincident with tissue infiltration with PMN. Pretreatment with IB4 prevented histological damage and tissue infiltration with PMN, and it inhibited the transport abnormalities induced by infection alone. CONCLUSIONS Infection with O157:H7 reduces Na absorption and stimulates Cl secretion in the distal colon. Disruption of the epithelium and changes in colonic electrolyte transport during enterohemorrhagic E. coli are mediated by the host inflammatory response.

Proteomic profiling of cholangiocarcinoma: diagnostic potential of SELDI-TOF MS in malignant bile duct stricture.

Proteomic techniques promise to improve the diagnosis of cholangiocarcinoma (CC) in both tissue and serum as histological diagnosis and existing serum markers exhibit poor sensitivities. We explored the use of surface‐enhanced laser desorption/ionization time‐of‐flight mass spectrometry (SELDI‐TOF MS) to identify potential protein biomarkers of CC. Twenty‐two resected CC samples were compared with adjacent noninvolved bile duct tissue. Serum from patients with CC (n = 20) was compared with patients with benign disease (n = 20), and healthy volunteers (n = 25). Samples were analyzed on hydrophobic protein chips via SELDI‐TOF MS, and classification models were developed using logistic regression and cross‐validation analysis. Univariate analysis revealed 14 individual peaks differentially expressed between CC and bile duct tissue, 4 peaks between CC and benign disease, and 12 peaks between CC and sera of healthy volunteers. The 4,462 mass‐to‐charge serum peak had superior discriminatory ability to carbohydrate antigen 19.9 (CA19.9) and carcinoembryonic antigen (CEA) (P = .004; receiver operating characteristic [ROC] area under the curve [AUC] = 0.76, 0.73, and 0.70, respectively). The training models developed panels of peaks that distinguished CC from bile duct tissue (92.5% sensitivity, 92.3% specificity; ROC AUC = 0.96), CC from benign serum (65.0% sensitivity, 70.0% specificity; ROC AUC = 0.83), and CC from sera of healthy volunteers (75.0% sensitivity, 100% specificity; ROC AUC = 0.92). Serum results were further improved with the inclusion of CA19.9 and CEA (ROC AUC = 0.86 and 0.99 for CC vs benign and healthy volunteer serum, respectively). In conclusion, biomarker panels are capable of distinguishing CC from nonmalignant tissue; serum markers have important diagnostic implications for unknown bile duct stricture. (HEPATOLOGY 2006;44:658–666.)

GASTRODUODENAL MUCOSAL DEFENSE

Significant advances in our understanding of a number of facets of the physiology and pathophysiology of mucosal defense have been made in the past year. The modulation of bicarbonate secretion by the gastroduodenal epithelium is becoming well characterized, with increasing evidence that this secretion is under neurohumoral control. The importance of mucosal blood flow in providing a supply of bicarbonate to the surface epithelium, particularly after superficial injury, has also been demonstrated. Through the use of pharmacologic probes such as capsaicin, the underlying mechanism for the reactive hyperemia that follows exposure of the mucosa to an irritant is becoming more clearly understood. Clinical evidence supporting a role for epidermal growth factor in mucosal defense and repair is now emerging and is consistent with earlier animal studies. Similarly, a role for polyamines and ornithine decarboxylase in mucosal repair has been supported by recent experimental evidence.

Cyclic AMP-dependent anion secretion in human small and large intestine

Cyclic AMP‐dependent Cl secretion is the major secretion pathway in human intestine. The aim of the present study was to examine mechanisms involved in cAMP‐dependent anion secretion in human small and large intestine. Surgical resection specimens from both jejunum and distal colon were studied under short circuited conditions. Addition of the phosphodiesterase inhibitor IBMX induced an increase in the short‐circuit current (Isc) equivalent to the net increase in Cl secretion. The Isc was inhibited by diphenylamine decarboxylate (DPC; Cl channel blocker), bumetanide (basolateral Na+/K+/2Cl cotransporter), BaCl2 (basolateral K+ channel) and Cl free buffer in both segments and indomethacin (cyclo‐oxygenase inhibitor) in colon alone. Diphenylamine decarboxylate appears to directly inhibit secretion in jejunum, although its inhibitory effect is possibly mediated by inhibition of cyclo‐oxygenase in the colon. A small component of IBMX‐stimulated Isc was inhibited by acetazolamide. Cyclic AMP‐dependent secretion is largely apical Cl secretion, although a small component appears to be HCO3. Secretion is dependent on basolateral K+ channels and Na+/K+/2Cl cotransporters and, in the colon, is inhibited by indomethacin, implying a role for cyclo‐oxygenase metabolites. The chloride channel blocker DPC inhibits secretion in both areas. This class of compounds may have potential for treatment of secretory diarrhoea.

One hundred and seventy-eight consecutive pancreatoduodenectomies without mortality: role of the multidisciplinary approach

BACKGROUND Pancreatoduodenectomy offers the only chance of cure for patients with periampullary cancers. This, however, is a major undertaking in most patients and is associated with a significant morbidity and mortality. A multidisciplinary approach to the workup and follow-up of patients undergoing pancreatoduodenectomy was initiated at our institution to improve the diagnosis, resection rate, mortality and morbidity. We undertook the study to assess the effect of this approach on diagnosis, resection rates and short-term outcomes such as morbidity and mortality. METHODS A prospective database of patients presenting with periampullary cancers to a single surgeon between April 2004 and April 2010 was reviewed. All cases were discussed at a multidisciplinary meeting comprising surgeons, gastroenterologists, radiologists, oncologists, radiation oncologists, pathologists and nursing staff. A standardized investigation and management algorithm was followed. Complications were graded according to the Clavien-Dindo classification. RESULTS A total of 295 patients with a periampullary lesion were discussed and 178 underwent pancreatoduodenectomy (resection rate 60%). Sixty-one patients (34%) required either a vascular or an additional organ resection. Eighty-nine patients experienced complications, of which the commonest was blood transfusion (12%). Thirty-four patients (19%) had major complications, i.e. grade 3 or above. There was no in-hospital, 30-day or 60-day mortality. CONCLUSIONS Pancreatoduodenectomy can safely be performed in high-volume centers with very low mortality. The surgeons role should be careful patient selection, intensive preoperative investigations, use of a team approach, and an unbiased discussion at a multidisciplinary meeting to optimize the outcome in these patients.

Inflammatory bowel disorders: current and future drugs that modulate adhesion molecules.

SummaryInfiltration of leucocytes into the mucosa is a hallmark feature of a number of inflammatory bowel disorders, most notably Crohn’s disease and ulcerative colitis. The interactions between circulating leucocytes and the vascular endothelium that permit leucocyte migration to a site of injury or infection are mediated via a variety of adhesion molecules. There is now ample evidence for alterations in adhesion molecule expression and function in inflammatory bowel disorders. This raises the possibility that adhesion molecules could be targets for novel therapies. Indeed, many existing anti-inflammatory drugs are capable of modulating adhesion molecule expression or function. Moreover, intensive research is under way to develop more selective and effective modulators of adhesion molecules, in the hope that they will be useful for treating various inflammatory disorders.

Complications of sphincter of Oddi manometry: Biliary-like pain versus acute pancreatitis

Objective Although acute pancreatitis is the most significant complication of sphincter of Oddi manometry (SOM), acute biliary-like abdominal pain – similar or identical to the patients usual recurrent acute episodes of pain and not fulfilling clinical criteria for acute pancreatitis – can also be provoked by SOM. The aim of the article is to determine and compare the relative frequency of occurrence of, and risk factors for, post-manometry biliary-like abdominal pain and post-manometry pancreatitis. Material and methods The clinical and laboratory features, the manometric recordings from the sphincter of Oddi, and the immediate post-manometry outcomes, were examined in 234 consecutive patients undergoing sphincter of Oddi manometry at our Unit. Results Post-manometry pancreatitis occurred in 9% of patients, and was associated with two risk factors on multivariate analysis: a history of post-ERCP pancreatitis (odds ratio [OR] 5.9) and a raised basal sphincter pressure (≥40 mmHg) at SOM (OR 3.5). An increased sphincter phasic wave frequency (≥7/min) at SOM was identified as a significant (p<0.05) risk factor on univariate testing only. Post-manometry biliary-like pain occurred in 12% of patients, and was associated with 3 different risk factors on multivariate analysis: age below 50 years (OR 4.6); less than a 2-year history of recurrent abdominal pain (OR 3.0); and ERCP and/or ES carried out during the SOM procedure (OR 9.3). Conclusions Provocation of biliary-like pain following SOM, without clinical evidence of pancreatitis, occurs at least as frequently as post-manometry acute pancreatitis. In contrast to post-manometry pancreatitis, post-manometry biliary-like pain occurs more often in younger patients with a shorter duration of symptoms and does not appear related to the manometric features of the sphincter documented at SOM; we propose that this clinical entity may reflect the presence of bile duct or duodenal hypersensitivity/hyperalgesia.

Lumiracoxib-induced cholestatic liver injury.

Lumiracoxib is a novel cyclo-oxygenase 2 inhibitor with gastrointestinal safety benefits over conventional non-steroidal anti-inflammatories. The Australian Therapeutic Goods Administration (TGA) approved lumiracoxib at 200-mg and 400-mg doses; however, clinical efficacy is not dose dependent with therapeutic equivalency shown between 50-mg, 200-mg and 400-mg doses. Hinz et al. also suggested that hepatotoxicity can be avoided at a lower dose of 50 mg with preserved clinical efficacy. This case report looks at a cholestatic pattern of liver injury with lumiracoxib and reviews available histological information to date from the Australian TGA. An 83-year-old woman was referred for assessment of progressive, cholestatic liver enzyme abnormalities. She was of good health, with no significant smoking or drinking history. Her past history included hysterectomy, cholecystectomy, appendicectomy, segmental colectomy for an extensive polyp, hypertension, osteoporosis, gastro-oesophageal reflux, chronic bronchitis, trigeminal neuralgia and osteoarthritis of left knee. There was no past or familial liver disease. The patient was initiated on lumiracoxib from November 2006 to September 2007 by her local practitioner for osteoarthritis. This was in addition to a regular medication list taken over >2 years of risedronate, irbesartan, omeprazole, fish oil, paracetamol, glucosamine, simvastatin and psyllium husks, with no recent antibiotic use. Her liver enzymes were then noted to be progressively cholestatic over an 8-month period between mid-2007 and early 2008. Liver enzymes were normal in May 2006, with isolated elevation of gamma-glutamyl transpeptidase (gGT) to 86 u/L (normal range 0–45 u/L) first noticed in June 2007. Worsening of liver function tests followed with an asymptomatic clinical picture and preserved liver function (alkaline phosphatase 1174 u/L gGT 2114 u/L alanine transaminase 208 u/L and aspartate transaminase 186 U/L). Physical examination was normal. A full liver screening panel was ordered to exclude autoimmune, infectious and metabolic causes. These tests were normal, with the exception of anti-nuclear antibody 1:80 and cytoplasmic anti-neutrophil cytoplasmic antibody 1:20. Simvastatin was ceased without an improvement to her hepatic test results. Computer tomography scanning of the abdomen found prominence of the common bile duct, and the patient referred for endoscopic retrograde cholangiopancreatogram (ERCP). ERCP was normal, with a temporary 10-Fr plastic stent placed into a 9-mm common bile duct. This failed to improve her liver function tests (LFT), and the stent was removed 8 weeks after. A percutaneous liver biopsy was done in August 2008. The biopsy showed preserved hepatic lobular architecture without necrosis, mild expansion of all portal tracts and ductular proliferation with occasional ductopaenia. These portal tracts had heavy inflammatory cell infiltrates, predominantly of neutrophils and lymphocytes with occasional eosinophils and plasma cells (Fig. 1). There was no lymphocytic piecemeal necrosis. Granulomas were not present. The biopsy was consistent with a cholestatic drug-induced liver injury correlating with a predominantly cholestatic liver function test. The chronology of drug use and the complete normalisation of the patient’s LFT following drug discontinuation suggest the presentation to be a probable hepatotoxic reaction to lumiracoxib. The Australian TGA to date had documented 53 cases of adverse drug reactions for lumiracoxib, of which 44 were classified possible adverse drug reactions and nine probable. Histology was available only in four; the first poorly documented; the second a chronic active hepatitis with piecemeal necrosis, extensive cholestasis, cirrhosis and abundant polymorphonuclear cells; the third a severe acute hepatitis with extensive multi-acinar dropout and lastly a chronic active hepatitis with mononuclear cells in abundance. Only one was deemed a probable adverse drug reaction with a predominant acinar injury pattern observed. Between lumiracoxib’s approval in 2006 and market withdrawal in August 2007, five patients had developed life-threatening hepatotoxicity, with two dead and three receiving a liver transplant. Although significant hepatotoxicity has been noted for lumiracoxib, there is a paucity of histopathological Figure 1 The portal tract is expanded and inflamed, with prominent ductular proliferation at its margin. A damaged bile duct is present centrally. The hepatocytes show little abnormality. bs_bs_banner