The effect of naloxone-3-glucuronide on colonic transit time in healthy men after acute morphine administration: a placebo-controlled double-blinded crossover preclinical volunteer study

BACKGROUND: Constipation is a significant side effect of opioid therapy. We have previously demonstrated that naloxone-3-glucuronide (NX3G) antagonizes the motility-lowering-effect of morphine in the rat colon. AIM: To find out whether oral NX3G is able to reduce the morphine-induced delay in colonic transit time (CTT) without being absorbed and influencing the analgesic effect. METHODS: Fifteen male volunteers were included. Pharmacokinetics: after oral administration of 0.16 mg/kg NX3G, blood samples were collected over a 6-h period. Pharmacodynamics: NX3G or placebo was then given at the start time and every 4 h thereafter. Morphine (0.05 mg/kg) or placebo was injected s.c. 2 h after starting and thereafter every 6 h for 24 h. CTT was measured over a 48-h period by scintigraphy. Pressure pain threshold tests were performed. RESULTS: Neither NX3G nor naloxone was detected in the venous blood. The slowest transit time was observed during the morphine phase, which was significantly different from morphine with NX3G and placebo. The pain perception was not significantly influenced by NX3G. CONCLUSIONS: Orally administered NX3G is able to reverse the morphine-induced delay of CTT in humans without being detected in peripheral blood samples. Therefore, NX3G may improve symptoms of constipation in-patients using opioid medication without affecting opioid-analgesic effects.

Systemic prokinetic pharmacologic treatment for postoperative adynamic ileus following abdominal surgery in adults

BACKGROUND: Postoperative adynamic bowel atony interferes with recovery following abdominal surgery. Prokinetic pharmacologic drugs are widely used to accelerate postoperative recovery. OBJECTIVES: To evaluate the benefits and harms of systemic acting prokinetic drugs to treat postoperative adynamic ileus in patients undergoing abdominal surgery. SEARCH STRATEGY: Trials were identified by computerised searches of the Cochrane Central Register of Controlled Trials, MEDLINE, EMBASE, and the Cochrane Colorectal Cancer Group specialised register. The reference lists of included trials and review articles were tracked and authors contacted. SELECTION CRITERIA: Randomised controlled parallel-group trials (RCT) comparing the effect of systemically acting prokinetic drugs against placebo or no intervention. DATA COLLECTION AND ANALYSIS: Four reviewers independently extracted the data and assessed trial quality. Trial authors were contacted for additional information if needed. MAIN RESULTS: Thirty-nine RCTs met the inclusion criteria contributing a total of 4615 participants. Most trials enrolled a small number of patients and showed moderate to poor (reporting of) methodological quality, in particular regarding allocation concealment and intention-to-treat analysis. Fifteen systemic acting prokinetic drugs were investigated and ten comparisons could be summarized. Six RCTs support the effect of Alvimopan, a novel peripheral mu receptor antagonist. However, the trials do not meet reporting guidelines and the drug is still in an investigational stage. Erythromycin showed homogenous and consistent absence of effect across all included trials and outcomes. The evidence is insufficient to recommend the use of cholecystokinin-like drugs, cisapride, dopamine-antagonists, propranolol or vasopressin. Effects are either inconsistent across outcomes, or trials are too small and often of poor methodological quality. Cisapride has been withdrawn from the market due to adverse cardiac events in many countries. Intravenous lidocaine and neostigmine might show a potential effect, but more evidence on clinically relevant outcomes is needed. Heterogeneity among included trials was seen in 10 comparisons. No major adverse drug effects were evident. AUTHORS' CONCLUSIONS: Alvimopan may prove to be beneficial but proper judgement needs adherence to reporting standards. Further trials are needed on intravenous lidocaine and neostigmine. The remaining drugs can not be recommended due to lack of evidence or absence of effect.

CX3CR1+ cells facilitate the activation of CD4 T cells in the colonic lamina propria during antigen-driven colitis

Dendritic cells (DCs) and macrophages populate the intestinal lamina propria to initiate immune responses required for the maintenance of intestinal homeostasis. To investigate whether CX3CR1(+) phagocytes communicate with CD4 T cells during the development of transfer colitis, we established an antigen-driven colitis model induced by the adoptive transfer of DsRed OT-II cells in CX3CR1(GFP/+) × RAG(-/-) recipients challenged with Escherichia coli expressing ovalbumin (OVA) fused to a cyan fluorescent protein (CFP). After colonization of CX3CR1(GFP/+) × RAG(-/-) animals with red fluorescent E. coli pCherry-OVA, colonic CX3CR1(+) cells but not CD103(+) DCs phagocytosed E. coli pCherry-OVA. Degraded bacterial-derived antigens are transported by CD103(+) DCs to mesenteric lymph nodes (MLNs), where CD103(+) DCs prime naive T cells. In RAG(-/-) recipients reconstituted with OT II cells and gavaged with OVA-expressing E. coli, colonic CX3CR1(+) phagocytes are in close contact with CD4 T cells and presented bacterial-derived antigens to CD4 T cells to activate and expand effector T cells.

Epithelial NAIPs protect against colonic tumorigenesis.

NLR family apoptosis inhibitory proteins (NAIPs) belong to both the Nod-like receptor (NLR) and the inhibitor of apoptosis (IAP) families. NAIPs are known to form an inflammasome with NLRC4, but other in vivo functions remain unexplored. Using mice deficient for all NAIP paralogs (Naip1-6(Δ/Δ)), we show that NAIPs are key regulators of colorectal tumorigenesis. Naip1-6(Δ/Δ) mice developed increased colorectal tumors, in an epithelial-intrinsic manner, in a model of colitis-associated cancer. Increased tumorigenesis, however, was not driven by an exacerbated inflammatory response. Instead, Naip1-6(Δ/Δ) mice were protected from severe colitis and displayed increased antiapoptotic and proliferation-related gene expression. Naip1-6(Δ/Δ) mice also displayed increased tumorigenesis in an inflammation-independent model of colorectal cancer. Moreover, Naip1-6(Δ/Δ) mice, but not Nlrc4-null mice, displayed hyper-activation of STAT3 and failed to activate p53 18 h after carcinogen exposure. This suggests that NAIPs protect against tumor initiation in the colon by promoting the removal of carcinogen-elicited epithelium, likely in a NLRC4 inflammasome-independent manner. Collectively, we demonstrate a novel epithelial-intrinsic function of NAIPs in protecting the colonic epithelium against tumorigenesis.

Incidence of Gallstone Formation and Cholecystectomy 10 Years After Bariatric Surgery.

PURPOSE Rapid weight loss is a risk factor for gallstone formation, and postoperative treatment options for gallstone formation are still part of scientific discussion. No prospective studies monitored the incidence for gallstone formation and subsequent cholecystectomy after bariatric surgery longer than 5 years. The aim of the study was to determine the incidence of gallstone formation and cholecystectomy in bariatric patients over 10 years. MATERIALS AND METHODS One hundred nine patients were observed over 10 years after laparoscopic gastric banding or gastric bypass/gastric sleeve. The incidence of gallstone formation and cholecystectomy was correlated to longitudinal changes in anthropometric parameters. RESULTS In total, 91 female and 18 male patients were examined. Nineteen patients had postoperative gallstone formation, and 12 female patients required cholecystectomy. The number needed to harm for gallstone formation was 7.1 and 2.3 cases in the banding group and gastric bypass/gastric sleeve group, respectively. The number needed to harm for cholecystectomy was 11.6 and 2.5 cases in the banding group and the gastric bypass/gastric sleeve group, respectively. Weight loss was higher in patients requiring subsequent cholecystectomy. Mean follow-up to cholecystectomy was 21.5 months with the latest operation after 51 months. CONCLUSION Female gender and rapid weight loss were major risk factors for postoperative cholelithiasis. Ultrasound examinations within 2 to 5 years are recommended in every patient, independent of bariatric procedure. Pharmacologic treatment should be considered in high risk patients within 2 to 5 years to prevent postoperative cholelithiasis. This helps to optimize patient care and lowers postoperative morbidity.

Prevalence and determinants of colonic polyps in children undergoing colonoscopy: A large hospital-based cross-sectional study

Background. Colorectal polyps are abnormal growths in the wall of the colon including the rectum. The study aims to estimate the prevalence and type of colonic polyps in children undergoing colonoscopic examination at Texas Children's Hospital (TCH) in Houston, Texas during 2000-2007. Also, to examine the factors associated with colonic polyps and the potential determinants of colonic polyps in children undergoing colonoscopy and compare those who had colonic polyps with those who did not on colonoscopy, and determine the significant risk factors of colonic polyps in these children. ^ Methods. We conducted a cross sectional study to analyze data collected at TCH. We obtained demographic, clinical, and histopathology information on consecutive patients who underwent colonoscopy during 2000-2007 from endoscopic records contained in the PEDS-CORI registry (Pediatric Endoscopy Database System-Clinical Outcomes Research Initiative), and abstracted data from the accompanying histopathology reports. ^ Results. We identified 2,693-unique patients, under 18 years of age, who underwent colonoscopy. Approximately 65.5% were white non-Hispanic, and 10.8% African-American. The mean age was 8.7 years and 51.8% were female patients. Polyps were present in 174 patients (6.5%). The most common two histological types were juvenile (60.6%), inflammatory (17.4%). We found that the prevalence of polyps was higher in younger aged children (12.9% in 0-5 years) than in older aged children (4% in 15-17 years), and slightly higher in males than in females (7.9% and 5.4% respectively). For males only, the odds of polyps were statistically significantly higher in Blacks and Hispanics compared to white non Hispanics (OR of 2.2 and 2.1, respectively, and 95% CI of 1.3, 3.9 and 1.3, 3.5 respectively). The indications for colonoscopy were different for children with polyps compared to those without polyps, i.e., 47.0% vs. 19.8% respectively for lower GI bleeding, 2.7% vs. 21.4% respectively for abdominal pain/bloating, and, or 0.9% vs. 9.6% respectively for diarrhea. ^ Conclusion. Colorectal polyps occur in about 1 in 15 children and adolescents undergoing first colonoscopy. The demographic variable of younger age is strongly associated with having polyps irrespective of ethnicity. Lower GI bleeding is strongly related to the presence of colorectal polyps in children and adolescents undergoing colonoscopy.^

Expression of p53, {\it * ras\/} and PCNA in human colonic neoplasms: Possible biomarkers of malignant potential

Colorectal cancer is a leading cause of cancer mortality and early detection can significantly improve the clinical outcome. Most colorectal cancers arise from benign neoplastic lesions recognized as adenomas. Only a small percentage of all adenomas will become malignant. Thus, there is a need to identify specific markers of malignant potential. Studies at the molecular level have demonstrated an accumulation of genetic alterations, some hereditary but for the most occurring in somatic cells. The most common are the activation of ras, an oncogene involved in signal transduction, and the inactivation of p53, a tumor suppressor gene implicated in cell cycle regulation. In this study, 38 carcinomas, 95 adenomas and 20 benign polyps were analyzed by immunohistochemistry for the abnormal expression of p53 and ras proteins. An index of cellular proliferation was also measured by labeling with PCNA. A general overexpression of p53 was immunodetected in 66% of the carcinomas, while 26% of adenomas displayed scattered individual positive cells or a focal high concentration of positive cells. This later was more associated with severe dysplasia. Ras protein was detected in 37% of carcinomas and 32% of adenomas mostly throughout the tissue. p53 immunodetection was more frequent in adenomas originating in colons with synchronous carcinomas, particularly in patients with familial adenomatous polyposis and it may be a useful marker in these cases. Difference in the frequency of p53 and ras alterationbs was related to the location of the neoplasm. Immunodetection of p53 protein was correlated to the presence of a mutation in p53 gene at exon 7 and 5 in 4/6 carcinomas studied and 2 villous adenomas. Thus, we characterized in adenomas the abnormal expression of two proteins encoded by the most commonly altered genes in colorectal cancer. p53 alteration appears to be more specifically associated with transition to malignancy than ras. By using immunohistochemistry, a technique that keeps the architecture of the tissue intact, it was possible to correlate these alterations to histopathological characteristics that were associated with higher risks for transformation: villous content, dysplasia and size of adenoma. ^

Effects of p53 mutations on apoptosis in mouse intestinal and human colonic adenomas

We have examined the effects of inactivation of the p53 tumor suppressor gene on the incidence of apoptotic cell death in two stages of the adenoma-to-carcinoma progression in the intestine: in early adenomas where p53 mutations are rare and in highly dysplastic adenomas where loss of p53 occurs frequently. Homozygosity for an inactivating germ-line mutation of p53 had no effect on the incidence or the rate of progression of ApcMin/+-induced adenomas in mice and also did not affect the frequency of apoptosis in the cells of these adenomas. To examine the effect of p53 loss on apoptosis in late-stage adenomas, we compared the incidence of apoptotic cell death before and after the appearance of highly dysplastic cells in human colonic adenomas. The appearance of highly dysplastic cells, which usually coincides during colon tumor progression with loss of heterozygosity at the p53 locus, did not correlate with a reduction in the incidence of apoptosis. These studies suggest that p53 is only one of the genes that determine the incidence of apoptotic in colon carcinomas and that wild-type p53 retards the progression of many benign colonic adenoma to malignant carcinomas by mechanism(s) other than the promotion of apoptosis.

Does the colonic H,K-ATPase also act as an Na,K-ATPase?

We previously have demonstrated that the colonic P-ATPase α subunit cDNA encodes an H,K-ATPase when expressed in Xenopus laevis oocytes. Besides its high level of amino acid homology (75%) with the Na,K-ATPase, the colonic H,K-ATPase also shares a common pharmacological profile with Na,K-ATPase, because both are ouabain-sensitive and Sch 28080-insensitive. These features raise the possibility that an unrecognized property of the colonic H,K-ATPase would be Na+ translocation. To test this hypothesis, ion-selective microelectrodes were used to measure the intracellular Na+ activity of X. laevis oocytes expressing various combinations of P-ATPase subunits. The results show that expression in oocytes of the colonic H,K-ATPase affects intracellular Na+ homeostasis in a way similar to the expression of the Bufo marinus Na,K-ATPase; intracellular Na+ activity is lower in oocytes expressing the colonic H,K-ATPase or the B. marinus Na,K-ATPase than in oocytes expressing the gastric H,K-ATPase or a β subunit alone. In oocytes expressing the colonic H,K-ATPase, the decrease in intracellular Na+ activity persists when diffusive Na+ influx is enhanced by functional expression of the amiloride-sensitive epithelial Na+ channel, suggesting that the decrease is related to increased active Na+ efflux. The Na+ decrease depends on the presence of K+ in the external medium and is inhibited by 2 mM ouabain, a concentration that inhibits the colonic H,K-ATPase. These data are consistent with the hypothesis that the colonic H,K-ATPase may transport Na+, acting as an (Na,H),K-ATPase. Despite its molecular and functional characterization, the physiological role of the colonic (Na,H),K-ATPase in colonic and renal ion homeostasis remains to be elucidated.

A neurotensin antagonist, SR 48692, inhibits colonic responses to immobilization stress in rats.

We previously reported that short-term immobilization stress of rats causes increased colonic mucin release, goblet cell depletion, prostaglandin E2 secretion, and colonic mast cell activation, as well as increased colonic motility. The purpose of this study was to investigate whether neurotensin (NT), a peptide expressed in both brain and digestive tract, participates in these responses. Rats were pretreated with SR 48692 (1 mg/kg, i.p.), an NT antagonist, 15 min before immobilization (30 min). The administration of the antagonist significantly inhibited stress-mediated secretion of colonic mucin, prostaglandin E2, and a product of rat mast cells, rat mast cell protease II (P < 0.05), but did not alter the increase in fecal pellet output caused by immobilization stress. Immobilization stress also resulted in a quantifiable decrease in the abundance of NT receptor mRNA in rat colon compared with that in colonic tissues from nonimmobilized rats as measured by densitometric analysis of in situ hybridization studies (P < 0.03). We conclude that the peptide NT is involved in colonic goblet cell release and mucosal mast cell activation after immobilization stress.

An apical permeability barrier to NH3/NH4+ in isolated, perfused colonic crypts.

Fermentation of nonabsorbed nutrients in the colon generates high concentrations of NH3/NH4+ in the colonic lumen. NH3 is a small, lipophilic neutral weak base that readily permeates almost all cell membranes, whereas its conjugate weak acid NH4+ generally crosses membranes much more slowly. It is not known how colonocytes maintain intracellular pH in the unusual acid-base environment of the colon, where permeant acid-base products of fermentation exist in high concentration. To address this issue, we hand dissected and perfused single, isolated crypts from rabbit proximal colon, adapting techniques from renal-tubule microperfusion. Crypt perfusion permits control of solutions at the apical (luminal) and basolateral (serosal) surfaces of crypt cells. We assessed apical- vs. basolateral-membrane transport of NH3/NH4+ by using fluorescent dyes and digital imaging to monitor intracellular pH of microvacuolated crypt cells as well as luminal pH. We found that, although the basolateral membranes have normal NH3/NH4+ permeability properties, there is no evidence for transport of either NH3 or NH4+ across the apical borders of these crypt cells. Disaggregating luminal mucus did not increase the transport of NH3/NH4+ across the apical border. We conclude that, compared to the basolateral membrane, the apical border of crypt colonocytes has a very low permeability-area product for NH3/NH4+. This barrier may represent an important adaptation for the survival of crypt cells in the environment of the colon.

Lith1, a major gene affecting cholesterol gallstone formation among inbred strains of mice.

The prevalence of cholesterol gallstones differs among inbred strains of mice fed a diet containing 15% (wt/wt) dairy fat, 1% (wt/wt) cholesterol, and 0.5% (wt/wt) cholic acid. Strains C57L, SWR, and A were notable for a high prevalence of cholelithiasis; strains C57BL/6, C3H, and SJL had an intermediate prevalence; and strains SM, AKR, and DBA/2 exhibited no cholelithiasis after consuming the diet for 18 weeks. Genetic analysis of the difference in gallstone prevalence rates between strains AKR and C57L was carried out by using the AKXL recombinant inbred strain set and (AKR x C57L)F1 x AKR backcross mice. Susceptibility to gallstone formation was found to be a dominant trait determined by at least two genes. A major gene, named Lith1, mapped to mouse chromosome 2. When examined after 6 weeks on the lithogenic diet, the activity of hepatic 3-hydroxy-3-methylglutaryl-CoA reductase (EC 1.1.1.88) was downregulated as expected in the gallstone-resistant strains, AKR and SJL, but this enzyme failed to downregulate in C57L and SWR, the gallstone-susceptible strains. This suggests that regulation of the rate-limiting enzyme in cholesterol biosynthesis may be pivotal in determining the occurrence and severity of cholesterol hypersecretion and hence lithogenicity of gallbladder bile. These studies indicate that genetic factors are critical in determining gallstone formation and that the genetic resources of the mouse model may permit these factors to be identified.

Extracellular pH regulation in microdomains of colonic crypts: effects of short-chain fatty acids.

It has been suggested that transepithelial gradients of short-chain fatty acids (SCFAs; the major anions in the colonic lumen) generate pH gradients across the colonic epithelium. Quantitative confocal microscopy was used to study extracellular pH in mouse distal colon with intact epithelial architecture, by superfusing tissue with carboxy SNARF-1 (a pH-sensitive fluorescent dye). Results demonstrate extracellular pH regulation in two separate microdomains surrounding colonic crypts: the crypt lumen and the subepithelial tissue adjacent to crypt colonocytes. Apical superfusion with (i) a poorly metabolized SCFA (isobutyrate), (ii) an avidly metabolized SCFA (n-butyrate), or (iii) a physiologic mixture of acetate/propionate/n-butyrate produced similar results: alkalinization of the crypt lumen and acidification of subepithelial tissue. Effects were (i) dependent on the presence and orientation of a transepithelial SCFA gradient, (ii) not observed with gluconate substitution, and (iii) required activation of sustained vectorial acid/base transport by SCFAs. Results suggest that the crypt lumen functions as a pH microdomain due to slow mixing with bulk superfusates and that crypts contribute significant buffering capacity to the lumen. In conclusion, physiologic SCFA gradients cause polarized extracellular pH regulation because epithelial architecture and vectorial transport synergize to establish regulated microenvironments.