Cyclic AMP-mediated chloride secretion is induced by prostaglandin F2alpha in human isolated colon.

BACKGROUND AND PURPOSE: Prostaglandin F(2alpha) (PGF(2alpha)) is implicated in the pathogenesis of inflammatory bowel disease and colorectal cancer. This study investigates the effects of PGF(2alpha) on electrophysiological parameters in isolated human colonic mucosa. EXPERIMENTAL APPROACH: Ion transport was measured as changes in short-circuit current across human colonic epithelia mounted in Ussing chambers. Colonic crypts were isolated by calcium chelation and cyclic adenosine monophosphate (cAMP) was measured by ELISA. KEY RESULTS: PGF(2alpha) stimulated chloride secretion in a concentration-dependent manner with an EC(50) of 130 nM. The PGF(2alpha) induced increase in chloride secretion was inhibited by AL8810 (10 microM), a specific PGF(2alpha) receptor antagonist. In addition, PGF(2alpha) (1 microM) significantly increased levels of cAMP in isolated colonic crypts. CONCLUSIONS AND IMPLICATIONS: PGF(2alpha) stimulated chloride secretion in samples of human colon in vitro through a previously unrecognizd cAMP-mediated mechanism. These findings have implications for inflammatory states.

Bradykinin regulates human colonic ion transport in vitro.

BACKGROUND AND PURPOSE: Kinins are acknowledged as important regulators of intestinal function during inflammation; however, their effects on human intestinal ion transport have not been reported. Here, we used muscle-stripped human colonic tissue and cultured T(84)-cell monolayers to study bradykinin (BK) actions on human intestinal ion transport. EXPERIMENTAL APPROACH: Ion transport was measured as changes in short-circuit current (I(sc)) across colonic epithelia mounted in Ussing chambers. KEY RESULTS: In intact tissue, there was a distinct polarity to BK-elicited I(sc) responses. Whereas basolateral BK stimulated sustained responses (EC(50)=0.5+/-0.1 microM), those to apical BK were more rapid and transient (EC(50)=4.1+/-1.2 nM). In T(84) cells, responses to both apical and basolateral BK were similar to those seen upon apical addition to intact tissues. Cross-desensitization between apical and basolateral domains was not observed. BK-induced responses were largely due to Cl(-) secretion as shown by their sensitivity to bumetanide and removal of Cl(-) from the bathing solution. Studies using selective agonists and antagonists indicate responses to BK are mediated by B(2) receptors. Finally, responses to basolateral BK in intact tissues were inhibited by tetrodotoxin (1 microM), atropine (1 microM), capsaicin (100 microM) and piroxicam (10 microM). BK-stimulated prostaglandin (PG)E(2) release from colonic tissue. CONCLUSIONS: BK stimulates human colonic Cl(-) secretion by activation of apical and basolateral B(2) receptors. Responses to apical BK reflect a direct action on epithelial cells, whereas those to basolateral BK are amplified by stimulation of enteric nerves and PG synthesis.

Increased risk of myocardial infarction as first manifestation of ischaemic heart disease and nonselective nonsteroidal anti-inflammatory drugs.

AIMS: Selective cyclooxygenase (COX)-2 inhibitors have recently been implicated as enhancing risk of myocardial infarction (MI). Nonselective nonsteroidal anti-inflammatory drugs (NSAIDs) are also effective COX-2 inhibitors, so we investigated the hypothesis that they too increase risk of MI. METHODS: We conducted a case-control study with direct structured interview of cases and controls. Cases were all subjects (N = 205) with a first nonfatal MI who had no previously recognized cardiovascular disease. Community controls (N = 258) were randomly selected from the same practice as the index case. Hospital controls (N = 205) were those admitted at the same time as index cases for nonmyocardial conditions not influenced by NSAID use. The effects of aspirin, NSAIDs and previously recognized influences on MI were investigated by unconditional logistic regression analysis. RESULTS: NSAID use was associated with an increase risk of MI with an odds ratio of 1.77 (1.03, 3.03) vs. community controls and 2.61 (1.38, 4.95) vs. hospital controls. These values were 5.00 (1.18, 21.28) and 7.66 (0.87, 67.48), respectively, in aspirin users. Results were similar when naproxen was grouped with aspirin. Odds ratios for smoking and for use of antidiabetic medication were 3.91 (2.52, 6.04) and 3.92 (1.25, 12,33), respectively, vs. community controls. CONCLUSIONS: Like selective COX-2 inhibitors, non-selective NSAIDs [corrected] are associated with an increased risk of MI. The extent to which this reflects interference with aspirin warrants further investigation.

Prevalence and incidence of gastroduodenal ulcers during treatment with vascular protective doses of aspirin.

BACKGROUND: Aspirin is valuable for preventing vascular events, but information about ulcer frequency is necessary to inform risk-benefit decisions in individual patients. AIM: To determine ulcer prevalence and incidence in a population representative of those given aspirin therapy and evaluate risk predictors. METHODS: Patients taking aspirin 75-325 mg daily were recruited from four countries. Exclusions included use of gastroprotectant drugs or other non-steroidal anti-inflammatory drugs. We measured point prevalence of endoscopic ulcers, after quantitating dyspeptic symptoms. Incidence was assessed 3 months later in those eligible to continue (no baseline ulcer or reason for gastroprotectants). RESULTS: In 187 patients, ulcer prevalence was 11% [95% confidence interval (CI) 6.3-15.1%]. Only 20% had dyspeptic symptoms, not significantly different from patients without ulcer. Ulcer incidence in 113 patients followed for 3 months was 7% (95% CI 2.4-11.8%). Helicobacter pylori infection increased the risk of a duodenal ulcer [odds ratio (OR) 18.5, 95% CI 2.3-149.4], as did age >70 for ulcers in stomach and duodenum combined (OR 3.3, 95% CI 1.3-8.7). CONCLUSIONS: Gastroduodenal ulcers are found in one in 10 patients taking low-dose aspirin, and most are asymptomatic; this needs considering when discussing risks/benefits with patients. Risk factors include older age and H. pylori (for duodenal ulcer).

Dual COX inhibition and upper gastrointestinal damage.

Aspirin and non-aspirin NSAIDs injure the gastrointestinal tract principally as a result of their inhibition of prostaglandin synthesis. This is mediated via abrogation of the secretion of mucus and bicarbonate and by reduction in mucosal blood flow. Topical injury and inhibition of platelet thromboxane may also contribute respectively to damage and ulcer bleeding. Recognition of a second cyclooxygenase, COX-2, enabled drugs to be developed that selectively target this enzyme which is expressed in inflamed joints. These have proved to be effective treatments whilst causing little or no acute gastroduodenal injury and reduced ulcers and their complications. Future strategies may capitalise upon the phenomenon of substrate diversion of lipoxygenase products. Balanced cyclooxygenase/lipoxygenase inhibition maybe less harmful than cyclooxygenase inhibition. Also, nitric oxide can subserve many of the protective effects of prostaglandins and NO-donating NSAIDs are under evaluation.

Gastrointestinal safety of AZD3582, a cyclooxygenase inhibiting nitric oxide donator: proof of concept study in humans.

BACKGROUND: Cyclooxygenase inhibiting nitric oxide donators (CINODs) are a new class of anti-inflammatory and analgesic drugs that may minimise gastrointestinal toxicity compared with standard non-steroidal anti-inflammatory drugs (NSAIDs) by virtue of nitric oxide donation. METHODS: A proof of concept study of the gastrointestinal safety of AZD3582, the first CINOD available for human testing, was conducted. Thirty one subjects were randomised to receive placebo, naproxen 500 mg twice daily, or its nitroxybutyl derivative AZD3582 in an equimolar dose (750 mg twice daily) for 12 days in a double blind three period crossover volunteer study. At the start and end of each dosing period, gastroduodenal injury was assessed by endoscopy and small bowel permeability by differential urinary excretion of lactulose and L-rhamnose. Pharmacokinetic profiles were assessed at steady state. RESULTS: On naproxen, the mean total number of gastroduodenal erosions was 11.5 (and one subject developed an acute ulcer) versus 4.1 on AZD3582 (p<0.0001). More than half of the subjects had no erosions on AZD3582. Differences were seen for both the stomach and duodenum. Naproxen increased intestinal permeability (lactulose:L-rhamnose ratio 0.030 before v 0.040 after treatment) whereas AZD3582 (0.029 before, 0.029 after; p=0.006 v naproxen) and placebo (0.030 before, 0.028 after; p<0.001 v naproxen) did not. The steady state bioavailability of naproxen metabolised from AZD3582 was 95% (95% confidence interval 87-101%) of that after naproxen administration. CONCLUSIONS: This human study supports animal data showing reduced gastrointestinal toxicity with the CINOD AZD3582. The potential combination of effective pain relief and gastrointestinal protection offered by AZD3582 warrants further evaluation in human clinical studies.

COX-LOX inhibition: current evidence for an emerging new therapy.

Safe and effective drug treatment is an important objective of all doctors. In the treatment of arthritis, non-steroidal anti-inflammatory drugs offer effective treatment but safety is significantly limited, largely due to gastrointestinal toxicity. Attention has recently focused on exploiting increased knowledge of metabolism of arachidonic acid to allow the development of safer anti-inflammatory drugs. Dual inhibitors of cyclo-oxygenase and lipoxygenase are planned. These drugs may inhibit formation of both prostaglandins and leukotrienes. This review outlines the salient features of cyclo-oxygenase and lipoxygenase metabolism of arachidonic acid. The role of the eicosanoids in mediating inflammation and gastrointestinal integrity is delineated. Evidence is presented regarding action of licofelone, one COX/LOX inhibitor that is currently in advanced stages of clinical trials. This review examines the hypothesis that licofelone is an effective anti-inflammatory agent that does not cause peptic damage.

Gastrointestinal safety of selective COX-2 inhibitors.

It appears that selective Cox-2 inhibitors do not affect the gastro duodenal mucosa whilst having anti-inflammatory and analgesic efficacy similar to non-selective NSAIDs. Two broad categories of drugs are Cox-2 selective: coxibs and a number of pre-existing NSAIDs retrospectively found to have selectivity. Cox-2 inhibitors cause less dyspepsia than NSAIDs. They spare gastrointestinal mucosal generation of prostaglandins (PGs) and PG-dependent bicarbonate secretion. Coxibs cause no acute mucosal injury in endoscopic ulcers compared to NSAID comparators. In the VIGOR study all upper GI events were reduced from 4.5 per 100 patient years to 2.1 per 100 patient years with supra-therapeutic doses of rofecoxib compared with naproxen. In the CLASS study, over a period of 3 days to 6 months, incidence of ulcer complications was 0.76% with celecoxib and 1.45% for ibuprofen or diclofenac. The less substantial reduction in events in the CLASS study compared with the VIGOR may be due, at least in part, to the fact that 21% of the patients were also on low dose aspirin. However it is premature to say that the benefit of Cox-2 inhibitors is lost in patients taking aspirin. There is continuing debate on the role of Cox-2 inhibitors in patients who have other risk factors for complicated ulcer disease e.g. patients who are elderly, on aspirin or corticosteroids, have a previous ulcer or have H. pylori infection.

Findings on liver biopsy to investigate abnormal liver function tests in the absence of diagnostic serology.

BACKGROUND/AIMS: The significance of abnormal liver function tests in the absence of diagnostic serology is unclear. The aim of this study was to report liver biopsy findings in a large group of patients with unexplained abnormal liver biochemistry. METHODS: Histological findings were examined in 354 patients who underwent liver biopsy to investigate abnormal liver function tests. RESULTS: Six percent of patients had a normal liver biopsy while 26% were found to have some degree of fibrosis and 6% were cirrhotic. Thirty four and 32% of biopsies suggested non-alcoholic steatohepatits or fatty liver respectively. Other diagnoses included cryptogenic hepatitis, drug toxicity, primary and secondary biliary cirrhosis, autoimmune hepatits, alcohol-related liver disease, primary sclerosing cholangitis, haemochromatosis, amyloid and glycogen storage disease. Patient management was directly altered in 18% of patients due to liver biopsy findings and three families were entered into screening programmes for inheritable liver disease. CONCLUSIONS: The finding of abnormal liver function tests in the absence of diagnostic serology may indicate significant liver disease. Liver biopsy yields a range of liver diseases of diverse nature and extent. Liver diseases may be uncovered for which specific treatment is indicated.

Real-time gait event detection for paraplegic FES walking.

A real-time method for the detection of gait events that occur during the electrically stimulated locomotion of paraplegic subjects is described. It consists of a two-level algorithm for the processing of sensor signals and the determination of gait event times. Sensor signals and information about the progression of the stimulator though its pre-specified stimulation "pattern" are processed by a machine intelligence (fuzzy logic) algorithm to determine an initial estimate of the patient's current phase of gait. This is then reviewed and modified by a second algorithm that removes spurious gait estimates, and determines gait event times. These gait event times are known to the system within approximately one-half of a gait cycle. The resulting gait event detection system was successfully evaluated on three subjects. Detection accuracy is not adversely affected by day-to-day gait variability. This work resolved technical and practical issues that previously limited the real time application of these methods. In particular, cosmetically acceptable insole force transducers were used. This gait event detector is designed for use in a real time controller for the automatic adjustment of the intensity and timing of stimulation while the subject is walking using functional electrical stimulation (FES).

Oxygen metabolites in immune- stimulated ion transport in rat colon: modulation by taurine.

BACKGROUND/AIMS: Activation of cells within the lamina propria can cause electrogenic chloride secretion across intestinal epithelia by release and/or synthesis of mediator molecules, including reactive oxygen metabolites (ROMs). In this investigation we examined whether indirect (immune) stimulation of ion transport across rat colon was ROM-mediated. METHODS: Paired segments of rat colon, stripped of underlying smooth muscle, were mounted on Ussing chambers in order to measure electrogenic ion transport. Changes in short circuit current (SCC) were used as a measure of net electrogenic ion transport measured in response to the bacterial tri-peptide formyl-Met-Leu-Phe (fMLP) which was used to activate lamina propria neutrophils. The effect of the established anti-oxidants catalase and diethyldithiocarbamate (DDTC) and the putative anti-oxidant taurine upon immune-stimulated ion transport was examined. RESULTS: The anti-oxidant DDTC but not catalase significantly attenuated ion transport responses to fMLP. Taurine applied basolaterally reduced ion transport response to fMLP but not to the directly acting secretagogues forskolin. Taurine applied apically enhanced ion transport responses to fMLP. CONCLUSION: Anti-oxidants, including taurine, may be useful in treatment of colitis. The enhancement of effect seen when taurine was applied apically may have negative implications regarding the therapeutic usefulness of taurine administration to the lumenal compartment.

Smoking and hepato-biliary disease.

The effect of cigarette smoking has been assessed in several hepato-biliary diseases, although in only a few was smoking the main focus of the study. Other than in primary sclerosing cholangitis, the relationships found are not strong and it remains unclear whether any are causal in nature - particularly in the absence of clearly demonstrated biological mechanisms. Nevertheless, many studies have found a modest but definite association between smoking and gallstone disease. As smoking is so prevalent in many countries, the public health impact of even a weak causal relationship would be considerable.

Berberine inhibits ion transport in human colonic epithelia.

The effects of berberine on ion transport in both human colonic mucosal epithelia and an intestinal epithelial cell line (T84) were examined. Berberine (concentration range 0-500 microM) reduced both basal and stimulated ion transport responses in human colonic mucosae in a manner which was non-specific for Ca2+ -or cAMP-mediated signals. Similarly, in cultured intestinal epithelial monolayers, berberine inhibited Ca2+ -and cAMP-mediated responses indicating an inhibitory activity directly at the level of the epithelium rather than an indirect effect through other mucosal element(s). Berberine did not alter the rate of generation of cAMP by adenylyl cyclase or the activity of protein kinase A, the effector enzyme of the cAMP pathway. Berberine inhibited carbachol-stimulated 86Rb+ efflux from T84 monolayers. Berberine also inhibited K+ conductance in apically-permeabilised re-sected mucosae. These results indicate i) that berberine exerts an anti-secretory action directly upon epithelial cells and ii) the mechanism of action may be at the level of blockade of K+ channels.

Urokinase-type plasminogen activator in colorectal cancer: relationship with clinicopathological features and patient outcome.

Urokinase-type plasminogen activator (u-PA) is a serine protease that has been implicated in cancer invasion and metastasis. We quantitated u-PA levels in normal colorectal mucosa, adenomatous polyps, and colorectal cancers and correlated these levels with clinicopathological features and patient survival. Detergent extracts were prepared from 133 colorectal cancers, 133 corresponding colorectal mucosal samples, and 15 synchronous adenomatous polyps. u-PA levels were determined using an ELISA, and a cancer:normal u-PA ratio was calculated for each case. u-PA levels were higher in cancers than in normal tissues, whereas adenomas had intermediate levels (P < 0.0001). u-PA levels were unrelated to clinical or pathological features. Survival was decreased in patients with a high cancer:normal u-PA ratio (P = 0.007). Multivariate survival analysis of patients undergoing curative surgery confirmed that the u-PA cancer:normal ratio was related to outcome (relative risk, 2.67; P = 0.02) and was independent of tumor stage (relative risk, 2.26; P = 0.03). Our study suggests that a high ratio of cancer to normal mucosal u-PA indicates an increased risk of colorectal cancer progression. Measurement of u-PA may provide useful prognostic information in patients undergoing curative surgery for colorectal cancer. The aggressive behavior of colorectal cancers with a high u-PA ratio suggests that the protease might be a suitable target for the development of therapeutic agents to prevent invasion and metastasis.

Long-term outcome following curative surgery for malignant large bowel obstruction.

This study determined whether the long-term outcome of patients with obstructing colorectal cancer could be related to conventional pathological prognostic variables or to other clinical, operative or histological features. Ninety-eight patients with bowel obstruction who had undergone potentially curative surgery and survived the postoperative period were studied. Features related to poor long-term outcome after a median follow-up of 5 years included bowel perforation at initial operation (P = 0.007), advanced tumour stage (P < 0.001), poor tumour differentiation (P = 0.02), mucin production by tumour (P = 0.004) and the presence of vascular (P = 0.08) and neural (P = 0.004) invasion. Outcome was not significantly related to the seniority of the operating surgeon (P = 0.52), even when this was adjusted for potentially confounding variables (adjusted hazard rate ratio for trainee surgeons 1.4 (95 per cent confidence interval 0.9-2.4), P = 0.16). Conventional prognostic features may help to identify the majority of patients with obstructed colorectal cancer at high risk of tumour recurrence and death.