Different bile acids exhibit distinct biological effects: the tumor promoter deoxycholic acid induces apoptosis and the chemopreventive agent ursodeoxycholic acid inhibits cell proliferation

Treatment options for primary sclerosing cholangitis

Primary sclerosing cholangitis is a cholestatic liver disease characterized by inflammation and fibrosis of intra-/extrahepatic bile ducts, leading to multifocal strictures. Primary sclerosing cholangitis exhibits a progressive course resulting in cirrhosis and the need for liver transplantation over a median period of 12 years. The disease is frequently associated with inflammatory bowel disease and carries an increased risk of colorectal cancer and cholangiocarcinoma. Despite extensive research, there is currently no effective medical treatment. Multiple drugs are shown to be ineffective in halting disease progression, including ursodeoxycholic acid, the most widely evaluated drug. High-dose ursodeoxycholic acid (28-30 mg/kg/day) was recently shown to increase the adverse events rate. Endoscopic or radiological dilatation of a 'dominant' stricture may lead to symptomatic and biochemical improvement. However, liver transplantation is the only life-prolonging treatment for patients with end-stage disease. Studies with promising drugs, such as antibiotics, antifibrotic agents and bile acid derivatives, are eagerly awaited.

Ursodeoxycholic acid and chemoprevention of colorectal cancer

Colorectal cancer is respectively the third and second most common cancer among men and women in France. Interest in chemoprevention for colorectal cancer has increased over the last two decades. Beside non-steroidal anti-inflammatory drugs, ursodeoxycholic acid (UDCA) may have chemopreventive action in colorectal cancer with a likely better tolerance. In high-risk populations such as patients with inflammatory bowel disease or prior colorectal adenoma or carcinoma, retrospective and prospective studies have suggested a beneficial effect of UDCA. In azoxymethane model, UDCA inhibits tumor development by countering the tumor-promoting effects of secondary bile acids, such as deoxycholic acid (DCA). The opposing effects of UDCA and DCA on lipid raft composition may be central to their effects on colonic tumorigenesis. Differential effects of DCA and UDCA on growth factor and inflammatory signals involved in colorectal carcinogenesis, such as epidermal growth factor receptors (EGFR) signaling and Cox-2 expression, likely mediate their opposing effects on colonic tumor promotion and tumor inhibition, respectively.

Dietary bile acid supplementation improves intestinal integrity and survival in a murine model

PURPOSE

In vitro supplementation of the bile salt, taurodeoxycholic acid (TDCA), has been shown to stimulate proliferation and prevent intestinal apoptosis in IEC-6 cells. We hypothesize that addition of TDCA to a rodent liquid diet will be protective against induced intestinal injury.

METHODS

C57Bl6 mice were fed a liquid diet with or without 50-mg/(kg d) TDCA supplementation. After 6 days, the mice were injected with lipopolysaccharide (LPS) (10 mg/kg) to induce intestinal injury. Specimens were obtained 24 hours later and evaluated for intestinal apoptosis, crypt proliferation, and villus length. A separate cohort of animals was injected with LPS (25 mg/kg) and followed 7 days for survival.

RESULTS

Mice whose diet was supplemented with TDCA had significantly increased survival. After LPS-induced injury, mice supplemented with TDCA showed decreased intestinal apoptosis by both H&E and caspase-3. They also had increased intestinal proliferation by 5-bromo-2'deoxyuridine staining and increased villus length.

CONCLUSIONS

Dietary TDCA supplementation alleviates mucosal damage and improves survival after LPS-induced intestinal injury. Taurodeoxycholic acid is protective of the intestinal mucosa by increasing resistance to injury-induced apoptosis, stimulating enterocyte proliferation, and increasing villus length. Taurodeoxycholic acid supplementation also results in an increased survival benefit. Therefore, bile acid supplementation may potentially protect the intestine from injury or infection.

Bile acids as endogenous etiologic agents in gastrointestinal cancer

Bile acids are implicated as etiologic agents in cancer of the gastrointestinal (GI) tract, including cancer of the esophagus, stomach, small intestine, liver, biliary tract, pancreas and colon/rectum. Deleterious effects of bile acid exposure, likely related to carcinogenesis, include: induction of reactive oxygen and reactive nitrogen species; induction of DNA damage; stimulation of mutation; induction of apoptosis in the short term, and selection for apoptosis resistance in the long term. These deleterious effects have, so far, been reported most consistently in relation to esophageal and colorectal cancer, but also to some extent in relation to cancer of other organs. In addition, evidence is reviewed for an association of increased bile acid exposure with cancer risk in human populations, in specific human genetic conditions, and in animal experiments. A model for the role of bile acids in GI carcinogenesis is presented from a Darwinian perspective that offers an explanation for how the observed effects of bile acids on cells contribute to cancer development.

Deoxycholate induces COX-2 expression via Erk1/2-, p38-MAPK and AP-1-dependent mechanisms in esophageal cancer cells

Background

The progression from Barrett's metaplasia to adenocarcinoma is associated with the acquirement of an apoptosis-resistant phenotype. The bile acid deoxycholate (DCA) has been proposed to play an important role in the development of esophageal adenocarcinoma, but the precise molecular mechanisms remain undefined. The aim of this study was to investigate DCA-stimulated COX-2 signaling pathways and their possible contribution to deregulated cell survival and apoptosis in esophageal adenocarcinoma cells.

Methods

Following exposure of SKGT-4 cells to DCA, protein levels of COX-2, MAPK and PARP were examined by immunoblotting. AP-1 activity was assessed by mobility shift assay. DCA-induced toxicity was assessed by DNA fragmentation and MTT assay.

Results

DCA induced persistent activation of the AP-1 transcription factor with Fra-1 and JunB identified as the predominant components of the DCA-induced AP-1 complex. DCA activated Fra-1 via the Erk1/2- and p38 MAPK while Erk1/2 is upstream of JunB. Moreover, DCA stimulation mediated inhibition of proliferation with concomitant low levels of caspase-3-dependent PARP cleavage and DNA fragmentation. Induction of the anti-apoptotic protein COX-2 by DCA, via MAPK/AP-1 pathway appeared to balance the DCA mediated activation of pro-apoptotic markers such as PARP cleavage and DNA fragmentation. Both of these markers were increased upon COX-2 suppression by aspirin pretreatment prior to DCA exposure.

Conclusion

DCA regulates both apoptosis and COX-2-regulated cell survival in esophageal cells suggesting that the balance between these two opposing signals may determine the transformation potential of DCA as a component of the refluxate.

Growth suppression by ursodeoxycholic acid involves caveolin-1 enhanced degradation of EGFR

Ursodeoxycholic acid (UDCA) has been shown to prevent colon tumorigenesis in animal models and in humans. In vitro work indicates that this bile acid can suppress cell growth and mitogenic signaling suggesting that UDCA may be an anti-proliferative agent. However, the mechanism by which UDCA functions is unclear. Previously we showed that bile acids may alter cellular signaling by acting at the plasma membrane. Here we utilized EGFR as a model membrane receptor and examined the effects that UDCA has on its functioning. We found that UDCA promoted an interaction between EGFR and caveolin-1 and this interaction enhanced UDCA-mediated suppression of MAP kinase activity and cell growth. Importantly, UDCA treatment led to recruitment of the ubiquitin ligase, c-Cbl, to the membrane, ubiquitination of EGFR, and increased receptor degradation. Moreover, suppression of c-Cbl activity abrogated UDCA's growth suppression activities suggesting that receptor ubiquitination plays an important role in UDCA's biological activities. Taken together these results suggest that UDCA may act to suppress cell growth by inhibiting the mitogenic activity of receptor tyrosine kinases such as EGFR through increased receptor degradation.

Physical activity as a determinant of fecal bile acid levels

Physical activity is protective against colon cancer, whereas colonic bile acid exposure is a suspected risk factor. Although likely related, the association between physical activity and bile acid levels has not been well-studied. Furthermore, the effect of triglycerides, which are known to modify bile acid levels, on this relationship has not been investigated. We conducted a cross-sectional analysis of baseline fecal bile acid levels for 735 colorectal adenoma formers obtained from participants in a phase III ursodeoxycholic acid chemoprevention trial. Compared with the lowest quartile of recreational physical activity duration, the highest quartile was associated with a 17% lower fecal bile acid concentration, adjusted for age, sex, dietary fiber intake, and body mass index (P = 0.042). Furthermore, consistent with a previously established relationship between serum triglyceride levels and bile acid metabolism, we stratified by triglyceride level and observed a 34% lower fecal bile acid concentration (highest versus lowest quartiles of physical activity) in individuals with low triglycerides (<136 mg/dL; P = 0.002). In contrast, no association between physical activity and fecal bile acid concentration was observed for subjects with high triglycerides (> or =136 mg/dL). Our results suggest that the biological mechanism responsible for the protective effect of physical activity on the incidence of colon cancer may be partially mediated by decreasing colonic bile acid exposure. However, this effect may be limited to individuals with lower triglyceride levels.

Hydrophobic bile acids, genomic instability, Darwinian selection, and colon carcinogenesis

Sporadic colon cancer is caused predominantly by dietary factors. We have selected bile acids as a focus of this review since high levels of hydrophobic bile acids accompany a Western-style diet, and play a key role in colon carcinogenesis. We describe how bile acid-induced stresses cause cell death in susceptible cells, contribute to genomic instability in surviving cells, impose Darwinian selection on survivors and enhance initiation and progression to colon cancer. The most likely major mechanisms by which hydrophobic bile acids induce stresses on cells (DNA damage, endoplasmic reticulum stress, mitochondrial damage) are described. Persistent exposure of colon epithelial cells to hydrophobic bile acids can result in the activation of pro-survival stress-response pathways, and the modulation of numerous genes/proteins associated with chromosome maintenance and mitosis. The multiple mechanisms by which hydrophobic bile acids contribute to genomic instability are discussed, and include oxidative DNA damage, p53 and other mutations, micronuclei formation and aneuploidy. Since bile acids and oxidative stress decrease DNA repair proteins, an increase in DNA damage and increased genomic instability through this mechanism is also described. This review provides a mechanistic explanation for the important link between a Western-style diet and associated increased levels of colon cancer.

A rat model of chronic postinflammatory visceral pain induced by deoxycholic acid

BACKGROUND & AIMS

Chronic visceral hyperalgesia is considered an important pathophysiologic symptom in irritable bowel syndrome (IBS); previous gastrointestinal inflammation is a potent etiologic factor for developing IBS. Although there are several animal models of adult visceral hypersensitivity after neonatal perturbation or acute colonic irritation/inflammation, current models of postinflammatory chronic visceral hyperalgesia are unsatisfactory. The aim of this study was to establish a model of chronic visceral hyperalgesia after colonic inflammation in the rat.

METHODS

Deoxycholic acid (DCA) was instilled into the rat colon daily for 3 days and animals were tested for up to 4 weeks.

RESULTS

DCA induced mild, transient colonic inflammation within 3 days that resolved within 3 weeks. An exaggerated visceromotor response, referred pain to mechanical stimulation, increased spinal Fos expression, and colonic afferent and dorsal horn neuron activity were apparent by 1 week and persisted for at least 4 weeks, indicating chronic dorsal horn hyperexcitability and visceral hyperalgesia. There was no spontaneous pain, based on open field behavior. There was a significant increase in opioid-receptor activity.

CONCLUSIONS

DCA induces mild, transient colitis, resulting in persistent visceral hyperalgesia and referred pain in rats, modeling some aspects of postinflammatory IBS.

Akt-dependent NF-kappaB activation is required for bile acids to rescue colon cancer cells from stress-induced apoptosis

Conjugated secondary bile acids promote human colon cancer cell proliferation by activating EGF receptors (EGFR). We hypothesized that bile acid-induced EGFR activation also mediates cell survival by downstream Akt-regulated activation of NF-kappaB. Deoxycholyltaurine (DCT) treatment attenuated TNF-alpha-induced colon cancer cell apoptosis, and stimulated rapid and sustained NF-kappaB nuclear translocation and transcriptional activity (detected by NF-kappaB binding to an oligonucleotide consensus sequence and by activation of luciferase reporter gene constructs). Both DCT-induced NF-kappaB nuclear translocation and attenuation of TNF-alpha-stimulated apoptosis were dependent on EGFR activation. Inhibitors of nuclear translocation, proteosome activity, and IkappaBalpha kinase attenuated NF-kappaB transcriptional activity. Cell transfection with adenoviral vectors encoding a non-degradable IkappaBalpha 'super-repressor' blocked the actions of DCT on both NF-kappaB activation and TNF-alpha-induced apoptosis. Likewise, transfection with mutant akt and treatment with a chemical inhibitor of Akt attenuated effects of DCT on NF-kappaB transcriptional activity and TNF-alpha-induced apoptosis. Chemical inhibitors of Akt and NF-kappaB activation also attenuated DCT-induced rescue of H508 cells from ultraviolet radiation-induced apoptosis. Collectively, these observations indicate that, downstream of EGFR, bile acid-induced colon cancer cell survival is mediated by Akt-dependent NF-kappaB activation. These findings provide a mechanism whereby bile acids increase resistance of colon cancer to chemotherapy and radiation.

Colonic interposition in a woman with attenuated familial adenomatosis polyposis: does the location of the colon affect polyp formation?

Attenuated familial adenomatous polyposis (AFAP) is a rare but well-established cause of colorectal carcinoma and multiple polyps. The present paper describes a case of a woman diagnosed with colorectal cancer at 34 years of age and subsequently found to have AFAP by genetic testing. During infancy, the patient underwent surgical correction of esophageal atresia with colonic interposition. While she had developed adenomatous polyps in her native cecum, there was no evidence of polyps or cancer in the segment of large intestine interposed between her upper esophagus and stomach. Therefore, various environmental differences between the upper and lower gastrointestinal tract may play a role in the expression of AFAP phenotype.

Intestinal bile acid physiology and pathophysiology

Bile acids (BAs) have a long established role in fat digestion in the intestine by acting as tensioactives, due to their amphipathic characteristics. BAs are reabsorbed very efficiently by the intestinal epithelium and recycled back to the liver via transport mechanisms that have been largely elucidated. The transport and synthesis of BAs are tightly regulated in part by specific plasma membrane receptors and nuclear receptors. In addition to their primary effect, BAs have been claimed to play a role in gastrointestinal cancer, intestinal inflammation and intestinal ionic transport. BAs are not equivalent in any of these biological activities, and structural requirements have been generally identified. In particular, some BAs may be useful for cancer chemoprevention and perhaps in inflammatory bowel disease, although further research is necessary in this field. This review covers the most recent developments in these aspects of BA intestinal biology.

Bile acid induces expression of COX-2 through the homeodomain transcription factor CDX1 and orphan nuclear receptor SHP in human gastric cancer cells

The caudal-related homeobox gene, CDX1, encodes for an intestinal-specific transcription factor and is involved in the induction of intestinal metaplasia (IM) of the stomach in gastric cancer. Gastric IM induced by bile reflux is a precancerous gastric adenocarcinomal lesion and has been associated with the induction of cyclooxygenase-2 (COX-2). In this study, we demonstrate the molecular mechanisms underlying the transcriptional regulation of COX-2 by bile acid in gastric cells. We noted that the ectopic expression of CDX1 enhanced COX-2 gene expression and that bile acid was associated with the induction of CDX1 expression. Furthermore, the induction of CDX1 by bile acid was mediated by the orphan nuclear receptor, small heterodimer partner (SHP). Finally, it was verified that the expression of COX-2, CDX1, SHP and CCAAT element-binding protein beta messenger RNA in human IM lesions were significantly higher than in lesions associated with gastritis. Collectively, these results reveal that bile acid induces an increase in the gene expression of COX-2 via the sequential transcriptional induction of SHP and CDX1 in precancerous lesions of human gastric cancer.

A chenodeoxycholic derivative, HS-1200, induces apoptosis and cell cycle modulation via Egr-1 gene expression control on human hepatoma cells

We previously reported that HS-1200, a synthetic chenodeoxycholic acid derivative, has apoptosis-inducing activity in various human cancer cells. The present study was undertaken to examine whether HS-1200 had an anticancer effect on HepG2 (wild-type p53) and Hep3B (p53 deleted) human hepatoma cells. Treatment of both cells with HS-1200 resulted in growth inhibition and induction of apoptosis as measured by MTT assay, nuclear staining, DNA fragmentation and flow cytometry analysis. The increase in apoptosis was associated with the alteration in the ratio of Bcl-2/Bax protein expression. In addition, flow cytometry analysis indicated that HS-1200 induced G1 phase arrest in both cells. When analyzing the expression of cell cycle-related proteins, we found that HS-1200 reduced the expression levels of cyclin D1, cyclin A, and Cdk2. HS-1200 treatment also caused an increase in the expression levels of p21 WAF1/CIP1 in HepG2 cells in a p53-dependent manner and in Hep3B cells in a p53-independent manner. Moreover, the expression level of p27 KIP1 was increased in both cell lines. We also observed that HS-1200 decreased the levels of cyclooxygenase (COX)-2 mRNA and protein expression. Furthermore, HS-1200 treatment markedly induced the Egr-1 expression at an early time point, and the increased expression levels of p53, p21 WAF1/CIP1, p27 KIP1, and COX-2 after treatment with HS-1200 were completely inhibited in HepG2 cells and partially inhibited in Hep3B cells by silencing of Egr-1, respectively. Taken together, these findings provide important new insights into the possible molecular mechanisms of the anticancer activity of the synthetic bile acid derivative, HS-1200, through Egr-1 regulation.

Deoxycholyltaurine rescues human colon cancer cells from apoptosis by activating EGFR-dependent PI3K/Akt signaling

Recent studies indicate that secondary bile acids promote colon cancer cell proliferation but their role in maintaining cell survival has not been explored. We found that deoxycholyltaurine (DCT) markedly attenuated both unstimulated and TNF-alpha-stimulated programmed cell death in colon cancer cells by a phosphatidylinositol 3-kinase (PI3K)-dependent mechanism. To examine the role of bile acids and PI3K signaling in maintaining colon cancer cell survival, we explored the role of signaling downstream of bile acid-induced activation of the epidermal growth factor receptor (EGFR) in regulating both apoptosis and proliferation of HT-29 and H508 human colon cancer cells. DCT caused dose- and time-dependent Akt (Ser(473)) phosphorylation, a commonly used marker of activated PI3K/Akt signaling. Both EGFR kinase and PI3K inhibitors attenuated DCT-induced Akt phosphorylation and Akt activation, as demonstrated by reduced phosphorylation of a GSK-3-paramyosin substrate. Transfection of HT-29 cells with kinase-dead EGFR (K721M) reduced DCT-induced Akt phosphorylation. In HT-29 cells, EGFR and PI3K inhibitors as well as transfection with dominant negative AKT attenuated DCT-induced cell proliferation. DCT-induced PI3K/Akt activation resulted in downstream phosphorylation of GSK-3 (Ser(21/9)) and BAD (Ser(136)), and nuclear translocation (activation) of NF-kappaB, thereby confirming that DCT-induced activation of PI3K/Akt signaling regulates both proproliferative and prosurvival signals. Collectively, these results indicate that DCT-induced activation of post-EGFR PI3K/Akt signaling stimulates both colon cancer cell survival and proliferation.

Activation of MUC1 mucin expression by bile acids in human esophageal adenocarcinomatous cells and tissues is mediated by the phosphatidylinositol 3-kinase

BACKGROUND

In esophageal adenocarcinoma, MUC1 mucin expression increases in early stages of the carcinogenetic sequence, during which bile reflux has been identified as a major carcinogen. However, no link between MUC1 overexpression and the presence of bile acids in the reflux has been established so far, and molecular mechanisms regulating MUC1 expression during esophageal carcinogenetic sequence are unknown. Our aim was to identify (1) the bile acids able to upregulate MUC1 expression in esophageal cancer cells and mucosal samples, (2) the regulatory regions in MUC1 promoter responsive to bile acids, and (3) the signaling pathway(s) involved in this regulation.

METHODS

MUC1 mRNA and mucin expression were studied by the means of real-time reverse transcriptase polymerase chain reaction (RT-PCR) and immunohistochemistry, both in the human esophageal OE33 adenocarcinoma cell line and in an ex vivo explant model. MUC1 promoter was cloned and transcription regulation was studied by transient cell transfection to identify the bile acid-responsive regions. Signaling pathways involved were identified using specific pharmacologic inhibitors and siRNA approach.

RESULTS

Taurocholic, taurodeoxycholic, taurochenodeoxycholic, glycocholic, sodium glycocholate, and deoxycholic bile acids upregulated MUC1 mRNA and protein expression. The highest induction was obtained with deoxycholic and taurocholic acids in both cellular and explant models. The bile acid-mediated upregulation of MUC1 transcription occurs at the promoter level, with responsive elements located in the -1472/-234 region of the promoter, and involves the phosphatidylinositol 3-kinase signaling pathway.

CONCLUSIONS

Bile acids induce MUC1 mucin overexpression in human esophageal adenocarcinoma cells and tissues by activating its transcription through a process involving phosphatidylinositol 3-kinase.

Ursodeoxycholic acid: Mechanism of action and novel clinical applications

Ursodeoxycholic acid (UDCA) is used in the treatment of cholestatic liver diseases, gallstone dissolution, and for patients with hepatitis C virus infection to ameliorate elevated alanine aminotransferase levels. The efficacy of UDCA treatment has been debated and the mechanisms of action in humans have still not defined. Suggested mechanisms include the improvement of bile acid transport and/or detoxification, cytoprotection, and anti-apoptotic effects. In this review, we summarize the proposed molecular mechanisms for the action of UDCA, especially in hepatocytes, and also discuss the putative future clinical usage of this unique drug.

Ursodeoxycholic acid versus sulfasalazine in colitis-related colon carcinogenesis in mice

PURPOSE

Inflammation influences carcinogenesis. In the current study, we investigated whether ursodeoxycholic acid (UDCA) can inhibit colitis-related mouse colon carcinogenesis and compared it with the effects of sulfasalazine.

EXPERIMENTAL DESIGN

Male CD-1 mice were given a single i.p. injection of azoxymethane followed by 1-week oral exposure of 1% dextran sodium sulfate in drinking water. They are then maintained on a basal diet mixed with UDCA (0.016%, 0.08%, or 0.4%) or sulfasalazine (0.05%) for 17 weeks. At week 20, the tumor-inhibitory effects of both chemicals were assessed by counting the incidence and multiplicity of colonic neoplasms. The immunohistochemical expression of the proliferating cell nuclear antigen labeling index in colonic epithelial malignancies was also assessed. Finally, at week 5, the mRNA expressions for cyclooxygenase-2, inducible nitric oxide synthase, peroxisome proliferator-activated receptor-gamma, and tumor necrosis factor-alpha were measured in nontumorous mucosa.

RESULTS

Feeding the mice with UDCA at all doses significantly inhibited the multiplicity of colonic adenocarcinoma. The treatment also significantly lowered the proliferating cell nuclear antigen labeling index in the colonic malignancies. UDCA feeding reduced the expression of inducible nitric oxide synthase and tumor necrosis factor-alpha mRNA in the colonic mucosa, while not significantly affecting the expression of cyclooxygenase-2 mRNA and peroxisome proliferator-activated receptor-gamma mRNA. Sulfasalazine caused a nonsignificant reduction in the incidence and multiplicity of colonic neoplasia and did not affect these mRNA expression.

CONCLUSIONS

Our findings suggest that UDCA rather than sulfasalazine could serve as an effective suppressing agent in colitis-related colon cancer development in mice.

Chemoprophylaxis of colorectal cancer in inflammatory bowel disease: current concepts

Ulcerative colitis and Crohn's disease both confer an increased risk of developing colorectal cancer. The use of 5-aminosalicylate as a remission-inducing agent has been long accepted. Its use as a potential chemoprophylactic agent has been proposed and is used by some practitioners. This review examines the most recent data on 5-aminosalicylate as a chemoprophylactic drug as well as ursodeoxycholic acid, folic acid, azathioprine, and 6-mercaptopurine.

Influence of Camembert consumption on the composition and metabolism of intestinal microbiota: a study in human microbiota-associated rats

The objective of the present study was to evaluate the consequence of Camembert consumption on the composition and metabolism of human intestinal microbiota. Camembert cheese was compared with milk fermented by yoghurt starters andLactobacillus caseias a probiotic reference. The experimental model was the human microbiota-associated (HM) rat. HM rats were fed a basal diet (HMB group), a diet containing Camembert made from pasteurised milk (HMCp group) or a diet containing fermented milk (HMfm group). The level of micro-organisms from dairy products was measured in faeces using cultures on a specific medium and PCR–temporal temperature gradient gel electrophoresis. The metabolic characteristics of the caecal microbiota were also studied: SCFA, NH3, glycosidase and reductase activities, and bile acid degradations. The results showed that micro-organisms from cheese comprised 105–108bacteria/g faecal sample in the HMCp group.Lactobacillusspecies from fermented milk were detected in HMfm rats. Consumption of cheese and fermented milk led to similar changes in bacterial metabolism: a decrease in azoreductase activity and NH3concentration and an increase in mucolytic activities. However, specific changes were observed: in HMCp rats, the proportion of ursodeoxycholic resulting from chenodeoxycholic epimerisation was higher; in HMfm rats, α and β-galactosidases were higher than in other groups and both azoreductases and nitrate reductases were lower. The results show that, as for fermented milk, Camembert consumption did not greatly modify the microbiota profile or its major metabolic activities. Ingested micro-organisms were able to survive in part during intestinal transit. These dairy products exert a potentially beneficial influence on intestinal metabolism.

Ursodeoxycholic acid modulates histone acetylation and induces differentiation and senescence

Agents that can modulate colonic environment and control dysregulated signaling are being evaluated for their chemopreventive potential in colon cancer. Ursodeoxycholate (UDCA) has shown chemopreventive potential in preclinical and animal models of colon cancer, but the mechanism behind it remains unknown. Here biological effects of UDCA were examined to understand mechanism behind its chemoprevention in colon cancer. Our data suggests that UDCA can suppress growth in a wide variety of cancer cell lines and can induce low level of apoptosis in colon cancer cells. We also found that UDCA treatment induces alteration in morphology, increased cell size, upregulation of cytokeratin 8, 18 and 19 and E-cadherin, cytokeratin remodeling and accumulation of lipid droplets, suggesting that UDCA induces differentiation in colon carcinoma cells. Our results also suggest significant differences in UDCA and sodium butyrate induced functional differentiation. We also report for the first time that UDCA can induce senescence in colon cancer cells as assessed by flattened, spread out and vacuolated morphology as well as by senescence marker beta-galactosidase staining. We also found that UDCA inhibits the telomerase activity. Surprisingly, we found that UDCA is not a histone deacytylase inhibitor but instead induces hypoacetylation of histones unlike hyperacetylation induced by sodium butyrate. Our results also suggest that, although UDCA induced senescence is p53, p21 and Rb independent, HDAC6 appears to be important in UDCA induced senescence. In summary, our data shows that UDCA modulates chromatin by inducing histone hypoacetylation and induces differentiation and senescence in colon cancer cells.

Matrix metalloproteinase-7-catalyzed release of HB-EGF mediates deoxycholyltaurine-induced proliferation of a human colon cancer cell line

Prior evidence indicates that bile acids stimulate colon cancer cell proliferation by muscarinic receptor-induced transactivation of epidermal growth factor receptors (EGFR). To explore further the mechanism underlying this action, we tested the hypothesis that bile acids activate a matrix metalloproteinase (MMP) that catalyzes release of an EGFR ligand. Initial studies showed that non-selective MMP inhibitors blocked the actions of deoxycholyltaurine (DCT), thereby indicating a role for MMP-catalyzed release of an EGFR ligand. DCT-induced cell proliferation was reduced by increasing concentrations of EGFR kinase inhibitors, by antibodies to the ligand binding domain of EGFR, by neutralizing antibodies to heparin binding-EGF-like growth factor (HB-EGF) and by CRM197, an inhibitor of HB-EGF release. These findings and our observations with more selective MMP inhibitors suggested that MMP-7, an enzyme known to release HB-EGF, plays a key role in mediating bile acid-induced H508 colon cancer cell proliferation. We observed that recombinant HB-EGF and MMP-7 mimicked both the signaling and proliferative actions of bile acids. Strikingly, reducing MMP-7 expression with either neutralizing antibody or small interfering RNA attenuated the actions of DCT. MMP-7 expression in H508 cells was confirmed using quantitative reverse transcription PCR. DCT stimulated a greater than 10-fold increase in MMP-7 gene transcription. Co-localization of pro-MMP-7 and pro-HB-EGF at the cell surface (immunofluorescence microscopy) was demonstrated, indicating proximity of the enzyme to its substrate. These findings provide strong evidence that in H508 human colon cancer cells, DCT-induced transactivation of EGFR is mediated by MMP-7-catalyzed release of the EGFR ligand HB-EGF.

Cytotoxic activity of Apomine is due to a novel membrane-mediated cytolytic mechanism independent of apoptosis in the A375 human melanoma cell line

Apomine, a novel bisphosphonate ester, has demonstrated anticancer activity in a variety of cancer cell lines; however, its mechanism of cytotoxicity is not well understood. Previous work has demonstrated that Apomine induces cell death by activation of caspase-3 in several cancer cell types. However, we have demonstrated that Apomine induces cell death in the A375 human melanoma cell line through a novel membrane-mediated mechanism that is independent of caspase-3 activation. This mechanism of membrane lysis may apply to other bisphosphonates and may be an important mechanism for overcoming resistance to apoptosis. Interestingly, Apomine-mediated cell death in the A375 and UACC 3093 human melanoma cell lines is also independent of N-Ras farnesylation, which was a previously described mechanism of action for Apomine in other cancer cell types. These data suggest that Apomine induces cell death through a novel plasma membrane-mediated cytolytic pathway, independent of caspase-3 activation and N-Ras farnesylation.

Resistance to ursodeoxycholic acid-induced growth arrest can also result in resistance to deoxycholic acid-induced apoptosis and increased tumorgenicity

BACKGROUND

There is a large body of evidence which suggests that bile acids increase the risk of colon cancer and act as tumor promoters, however, the mechanism(s) of bile acids mediated tumorigenesis is not clear. Previously we showed that deoxycholic acid (DCA), a tumorogenic bile acid, and ursodeoxycholic acid (UDCA), a putative chemopreventive agent, exhibited distinct biological effects, yet appeared to act on some of the same signaling molecules. The present study was carried out to determine whether there is overlap in signaling pathways activated by tumorogenic bile acid DCA and chemopreventive bile acid UDCA.

METHODS

To determine whether there was an overlap in activation of signaling pathways by DCA and UDCA, we mutagenized HCT116 cells and then isolated cell lines resistant to UDCA induced growth arrest. These lines were then tested for their response to DCA induced apoptosis.

RESULTS

We found that a majority of the cell lines resistant to UDCA-induced growth arrest were also resistant to DCA-induced apoptosis, implying an overlap in DCA and UDCA mediated signaling. Moreover, the cell lines which were the most resistant to DCA-induced apoptosis also exhibited a greater capacity for anchorage independent growth.

CONCLUSION

We conclude that UDCA and DCA have overlapping signaling activities and that disregulation of these pathways can lead to a more advanced neoplastic phenotype.

Chemoprevention: risk reduction with medical therapy of inflammatory bowel disease

The ideal chemopreventative agent, in addition to being efficacious in the prevention of cancer, must be easily administered, affordable, safe, and well tolerated, with minimal side effects. In the past decade, a growing body of literature has emerged on the prevention of CRC in patients with long-standing CD and UC. The data are not definitive and consist almost exclusively of retrospective case-control and cohort studies rather than the more rigorous prospective RCTs. 5-ASA compounds have been most thoroughly studied, and most of the existing data support the use of 5-ASA in the prevention of CRC. Although the precise dose and duration are unclear, studies suggest that chronic systemic administration of 5-ASA at a dose of at least 1.2 g/d is most likely to be effective. A beneficial effect of folate, albeit not statistically significant, has been consistently shown in every study performed for this purpose. Folate supplementation, which is safe and affordable, should also be recommended for all patients with IBD, especially those taking sulfasalazine. UDCA has been shown to exert a protective effect in most studies on patients with UC and concomitant PSC. Because this patient population is at particularly high risk for CRC, it is advisable to consider UDCA in all patients with colitis complicated by PSC. For patients without PSC, sufficient data do not exist to recommend it for the purpose of cancer prevention. Five of the six corticosteroid studies have found a beneficial effect of systemic steroids, although most did not reach statistical significance. Regardless, given the frequent and serious adverse effects associated with chronic steroid use, systemic corticosteroids should not be prescribed for this indication. Budesonide, an oral corticosteroid with minimal systemic absorption, is a potential alternative, although it has not yet been studied as a chemopreventative agent. Similarly, until the long-term safety of chronic NSAID use can be demonstrated in patients with IBD, the role of NSAIDs in chemoprevention remains undefined. Although the data are conflicting, immune-modulating medications, such as AZA, do not seem to confer any reduction in the risk of dysplasia or CRC. The data on calcium supplementation and statin use are still too limited to endorse their use for the prevention of colitis-related CRC. Chemoprevention is an area that holds great promise in the reduction of morbidity and mortality associated with IBD. Further studies, including prospective trials when possible and cost-effectiveness analyses, need to be performed to develop an optimal strategy for the reduction of cancer risk in patients with IBD.

The calcium-binding domain of the stress protein SEP53 is required for survival in response to deoxycholic acid-mediated injury

Stress protein responses have evolved in part as a mechanism to protect cells from the toxic effects of environmental damaging agents. Oesophageal squamous epithelial cells have evolved an atypical stress response that results in the synthesis of a 53 kDa protein of undefined function named squamous epithelial-induced stress protein of 53 kDa (SEP53). Given the role of deoxycholic acid (DCA) as a potential damaging agent in squamous epithelium, we developed assays measuring the effects of DCA on SEP53-mediated responses to damage. To achieve this, we cloned the human SEP53 gene, developed a panel of monoclonal antibodies to the protein, and showed that SEP53 expression is predominantly confined to squamous epithelium. Clonogenic assays were used to show that SEP53 can function as a survival factor in mammalian cell lines, can attenuate DCA-induced apoptotic cell death, and can attenuate DCA-mediated increases in intracellular free calcium. Deletion of the highly conserved EF-hand calcium-binding domain in SEP53 neutralizes the colony survival activity of the protein, neutralizes the protective effects of SEP53 after DCA exposure, and permits calcium elevation in response to DCA challenge. These data indicate that the squamous cell-stress protein SEP53 can function as a modifier of the DCA-mediated calcium influx and identify a novel survival pathway whose study may shed light on mechanisms relating to squamous cell injury and associated cancer development.

Deoxycholic acid induces intracellular signaling through membrane perturbations

Secondary bile acids have long been postulated to be tumor promoters in the colon; however, their mechanism of action remains unclear. In this study, we examined the actions of bile acids at the cell membrane and found that they can perturb membrane structure by alteration of membrane microdomains. Depletion of membrane cholesterol by treating with methyl-beta-cyclodextrin suppressed deoxycholic acid (DCA)-induced apoptosis, and staining for cholesterol with filipin showed that DCA caused a marked rearrangement of this lipid in the membrane. Likewise, DCA was found to affect membrane distribution of caveolin-1, a marker protein that is enriched in caveolae membrane microdomains. Additionally, fluorescence anisotropy revealed that DCA causes a decrease in membrane fluidity consistent with the increase in membrane cholesterol content observed after 4 h of DCA treatment of HCT116 cells. Significantly, by using radiolabeled bile acids, we found that bile acids are able to interact with and localize to microdomains differently depending on their physicochemical properties. DCA was also found to induce tyrosine phosphorylation and activate the receptor tyrosine kinase epidermal growth factor receptor in a ligand-independent manner. In contrast, ursodeoxycholic acid did not exhibit any of these effects even though it interacted significantly with the microdomains. Collectively, these data suggest that bile acid-induced signaling is initiated through alterations of the plasma membrane structure and the redistribution of cholesterol.

Bile acid-induced proliferation of a human colon cancer cell line is mediated by transactivation of epidermal growth factor receptors

Although epidemiological studies indicate an association between elevations in fecal bile acids and the development of colorectal cancer, the cellular mechanism for the proliferative actions of bile acids is not clear. Studies from other laboratories indicate a paradoxical pro-apoptotic action of bile acids on cell culture lines. Our previous studies indicate that cholinergic agonist-induced proliferation of colon cancer cells that express M3 muscarinic receptors (M3R) is mediated by transactivation of the epidermal growth factor receptor (EGFR) and that bile acids stimulate proliferation of colon cancer cells that express M3R. In the present study, we investigated the effects of bile acids on cell signaling and proliferation of a human colon cancer cell line (H508 cells) that abundantly expresses M3R and EGFR. Treatment with taurine and glycine conjugates of lithocholic and deoxycholic acids stimulated reversible activation of the p44/42 MAP kinase signaling cascade and proliferation of H508 cells. Bile acids did not stimulate proliferation of SNU-C4 colon cancer cells that express EGFR but not muscarinic receptors. Atropine, a muscarinic receptor inverse agonist, blocked bile acid-induced H508 cell proliferation. At concentrations that stimulate cell proliferation, conjugated bile acids did not activate caspase-3, a key mediator of apoptosis. Conjugated bile acids stimulated phosphorylation of EGFR Tyr992, thereby implicating EGFR transactivation in the cellular mechanism underlying their proliferative actions. This was confirmed by observing that inhibitors of EGFR activation and antibodies to the ligand-binding domain of EGFR blocked both the signaling and proliferative actions of bile acids. Collectively, these results suggest that in this colon cancer cell line, bile acid-induced colon cancer cell proliferation is M3R-dependent and is mediated by transactivation of EGFR.

Effect of Bile Acids on Butyrate-Sensitive and -Resistant Human Colon Adenocarcinoma Cells

A controlled balance among cell proliferation, differentiation, and apoptosis is required for the maintenance of gastrointestinal mucosa; these processes are influenced by luminal components, such as butyrate and bile acids. Using butyrate-sensitive (BCS-TC2) and butyrate-resistant (BCS-TC2.BR2) human colon carcinoma cells, we wanted to establish whether colon carcinoma cells that acquire resistance to butyrate-induced apoptosis are also resistant to the cytotoxic effect of certain bile acids, contributing, in this way, to the progression of colon carcinogenesis. The effect of bile acids on BCS-TC2 cell viability is dose and time dependent and highly stereospecific. Quantification of the relative percentage of apoptotic cells and caspase-3 activity reveals that deoxycholic acid (DCA) and chenodeoxycholic acid (CDCA) induce apoptosis in BCS-TC2 cells. BCS-TC2.BR2 cells are consistently less sensitive to their cytotoxic effects, requiring concentrations to induce 50% inhibition (IC50) in cell viability of 740 microM and >1 mM for CDCA and DCA, respectively, compared with IC50 values of 310 and 540 microM for BCS-TC2 cells. DCA-treated BCS-TC2.BR2 cells show few apoptotic signs and no caspase-3 activation. On the other hand, CDCA-treated BCS-TC2.BR2 cells show caspase-3 activation and apoptotic features, although to a lower extent than BCS-TC2 cells. Our results, in an in vitro model system, point out that acquisition of butyrate resistance is accompanied by a partial resistance to the cytotoxic effects of bile acids, which may enhance the survival of tumorigenic cells.

Serum bile acids, programmed cell death and cell proliferation in the mucosa of patients with colorectal adenomas

BACKGROUND

Deoxycholic acid induced programmed cell death and an imbalance with cell proliferation may favour colorectal tumourigenesis according to 'in vitro' studies, but information is lacking on the relationships occurring 'in vivo' in humans.

AIMS

To evaluate whether serum deoxycholic acid is associated with programmed cell death and cell proliferation in colonic mucosa.

METHODS

In 10 patients with colorectal adenomas, we measured fasting serum levels of bile acids; and, in normal colonic mucosa, programmed cell death by the TUNEL technique and cell proliferation by immunohistochemical staining with anti-Ki67. Total and compartmental indices for both activities were calculated.

RESULTS

Among serum bile acids, only total deoxycholic acid (median: 0.89 micromol/L +/- 0.54 95% CI), showed a significant positive correlation with the total and basal compartments PCD Index (r = 0.68, p < 0.05). Total proliferation index showed no correlation with either total PCD Index, or bile acids. Within the median compartment of the crypt, cell proliferation was negatively associated with all unconjugated bile acids.

CONCLUSIONS

The positive association between deoxycholic acid and programmed cell death in the basal compartment of the crypt, and the negative association of cell proliferation and unconjugated bile acids in the median compartment, do not seem to support the co-carcinogenic effect of deoxycholic acid.

Phase III trial of ursodeoxycholic acid to prevent colorectal adenoma recurrence

BACKGROUND

Ursodeoxycholic acid (UDCA) treatment is associated with a reduced incidence of colonic neoplasia in preclinical models and in patients with conditions associated with an increased risk for colon cancer. We conducted a phase III, double-blind placebo-controlled trial of UDCA to evaluate its ability to prevent colorectal adenoma recurrence.

METHODS

We randomly assigned 1285 individuals who had undergone removal of a colorectal adenoma within the past 6 months to daily treatment with UDCA (8-10 mg/kg of body weight; 661 participants) or with placebo (624 participants) for 3 years or until follow-up colonoscopy. Recurrence rates (number of recurrent adenomas per unit time) were compared by use of a Huber-White variance estimator. Proportions of participants with one or more recurrent adenomas were compared with a Pearson chi-square statistic; adjusted odds ratios (ORs) were obtained by logistic regression. All statistical tests were two-sided.

RESULTS

We observed a non-statistically significant 12% reduction in the adenoma recurrence rate associated with UDCA treatment, compared with placebo treatment. However, UDCA treatment was associated with a statistically significant reduction (P = .03) in the recurrence of adenomas with high-grade dysplasia (adjusted OR = 0.61, 95% confidence interval = 0.39 to 0.96). We observed no statistically significant differences between UDCA and placebo groups in recurrence with regard to adenoma size, villous histology, or location.

CONCLUSIONS

UDCA treatment was associated with a non-statistically significant reduction in total colorectal adenoma recurrence but with a statistically significant 39% reduction in recurrence of adenomas with high-grade dysplasia. Because severely dysplastic lesions have a high risk of progression to invasive colorectal carcinoma, this finding indicates that future chemoprevention trials of UDCA in individuals with such lesions should be considered.

Review article: current management of primary sclerosing cholangitis

The management of primary sclerosing cholangitis (PSC) is hindered by incomplete understanding of the pathogenesis of the disease and the lack of good prognostic models. Few large randomized controlled trials of drug therapy have been published. Best practice in the management of PSC is currently based therefore on careful interpretation of the available evidence, close observation of individual patients and clinical experience of the disease. Drug therapy is useful for alleviating symptoms. Ursodeoxycholic acid may slow progression of the disease and reduce the frequency of complications. Consensus is emerging on the issues of screening for the malignant complications of PSC and the indications for liver transplantation are becoming broader and encompassing the earliest stages of cholangiocarcinoma. In view of the rarity of the disease in the general population, large international collaborations to study PSC are necessary to provide clearer answers in areas of uncertainty, and these are now beginning to emerge.

Bile acids as carcinogens in human gastrointestinal cancers

Bile acids were first proposed to be carcinogens in 1939 and 1940. On the basis of later work with rodent models, bile acids came to be regarded as cancer promoters rather than carcinogens. However, considerable indirect evidence, obtained more recently, supports the view that bile acids are carcinogens in humans. At least 15 reports, from 1980 through 2003, indicate that bile acids cause DNA damage. The mechanism is probably indirect, involving induction of oxidative stress and production of reactive oxygen species that then damage DNA. Repeated DNA damage likely increases the mutation rate, including the mutation rate of tumor suppressor genes and oncogenes. Additional reports, from 1994 through 2002, indicate that bile acids, at the increased concentrations accompanying a high fat diet, induce frequent apoptosis. Those cells within the exposed population with reduced apoptosis capability tend to survive and selectively proliferate. That bile acids cause DNA damage and may select for apoptosis-resistant cells (both leading to increased mutation), indicates that bile acids are likely carcinogens. In humans, an increased incidence of cancer of the laryngopharyngeal tract, esophagus, stomach, pancreas, the small intestine (near the Ampulla of Vater) and the colon are associated with high levels of bile acids. The much larger number of cell generations in the colonic (and, likely, other gastrointestinal) epithelia of humans compared to rodents may allow time for induction and selection of mutations leading to cancer in humans, although not in rodents.

Synthetic bile acid derivatives induce apoptosis through a c-Jun N-terminal kinase and NF-kappaB-dependent process in human cervical carcinoma cells

Recently, we have reported that a synthetic derivative of ursodeoxycholic acid (UDCA), HS-1183, and those of chenodeoxycholic acid (CDCA), HS-1199 and HS-1200, induced apoptosis in human breast carcinoma cells through a p53-independent pathway. Here, we present that the synthetic bile acid derivatives induce apoptosis in SiHa human cervical carcinoma cells as well. The parental compounds, UDCA and CDCA, exhibited no significant effect on the cell viability at the concentration ranges tested. However, their synthetic bile acid derivatives significantly decreased cell viability in a concentration dependent manner. Characteristic manifestations of apoptosis including DNA fragmentation, an increased level of proapoptotic protein Bax, and cleavage of poly(ADP-ribose) polymerase were shown when the cells were treated with these synthetic compounds. Nuclear translocation of nuclear transcription factor NF-kappaB was increased and this suggests that the synthetic compounds induce apoptosis in a NF-kappaB dependent pathway. Phosphorylations of p38 and extracellular signal-regulated kinase were not affected, whereas c-Jun N-terminal kinase (JNK) was activated along with an increased level of transcription factor c-Jun. Our studies demonstrate that the newly synthesized bile acids are capable of inhibiting cell proliferation and inducing apoptosis in SiHa cells through activation of JNK and NF-kappaB.

Ursodeoxycholic Acid Can Suppress Deoxycholic Acid-Induced Apoptosis by Stimulating Akt/PKB-Dependent Survival Signaling

The nontoxic bile acid ursodeoxycholic acid (UDCA) is reported to be an anti-apoptotic agent with efficacy against a variety of death stimuli including the cytotoxic bile acid deoxycholic acid (DCA). To gain insight into this anti-apoptotic property, we tested UDCA for its ability to protect the colon carcinoma-derived cell line HCT116 against DCA-induced apoptosis. We found that UDCA could suppress DCA-induced apoptosis in a time- and dose-dependent manner and that this effect correlated with Akt phosphorylation. Importantly, UDCA lost its ability to protect cells from DCA-induced cell death when Akt activity was suppressed genetically using a dominant negative Akt mutant or when PI3K activity was inhibited pharmacologically. These results suggest that UDCA can protect HCT116 cells against DCA-induced apoptosis by stimulating Akt-dependent survival signaling.

Ursodiol Use Is Possibly Associated with Lower Incidence of Hepatocellular Carcinoma in Hepatitis C Virus–Associated Liver Cirrhosis

In a previous study of patients with hepatitis C virus (HCV)–associated liver cirrhosis (HCV-LC), we showed that increased liver inflammation, as assessed by higher serum alanine aminotransferase (ALT), was associated with increased risk for the development of hepatocellular carcinoma (HCC). This suggested that suppression of inflammation might inhibit HCC development in HCV-LC. Several agents have been suggested to possess chemopreventive potential against the development of HCC in chronic HCV-associated liver disease, including herbal medicines, such as Stronger-Neo-Minophagen C (glycyrrhizin) and Sho-saiko-to (TJ-9). Ursodiol [ursodeoxycholic acid (UDCA)], a bile acid widely used to treat cholestatic liver diseases, also possesses anti-inflammatory properties in liver disease. We hypothesized that suppression of liver inflammation, as assessed by decreases in serum ALT, might inhibit HCC occurrence in patients with HCV-LC. In this study, the preventive effect of UDCA on HCC was examined in patients with early-stage HCV-LC. One hundred two patients with HCV-LC (Child stage A) were treated with anti-inflammatory drugs, Stronger-Neo-Minophagen C,Sho-saiko-to, or UDCA, with the goal of lowering the average serum ALT level to &lt;80 IU. Iftheaverage ALT level did not remain &lt;80 IU after treatment with one agent, multiagent therapy was initiated. The patients were followed up for &gt;5 years and were retrospectively subdivided into two groups: 56 UDCA users (group A) and 46 UDCA nonusers (group B). The mean ± SD dosage of UDCA administered in group A was 473.7 ± 183.0 mg/d. The average duration of UDCA administration in group A was 37.3 ± 15.9 months over the 5-year study period. The cumulative incidence of HCC was recorded. The 5-year incidence of HCC in group A was 17.9% (10 of 56) and was significantly lower than that in group B (39.1%, 18 of 46; P = 0.025). The risk for HCC incidence, calculated by a logistic regression model, showed that the administration of UDCA significantly decreased hepatocarcinogenesis (P = 0.036). The herbal medicines used were comparable in dosage and treatment duration in the UDCA and non-UDCA groups. In conclusion, UDCA might prevent HCC development in HCV-LC. Interestingly, because the serum ALT trends over time were nearly the same in both groups, the chemopreventive effectiveness of UDCA was not accompanied by greater reductions in ALT compared with the UDCA nonusers.

A Nonenzymatic Modification of the Amino-terminal Domain of Histone H3 by Bile Acid Acyl Adenylate

Although it has been proposed that the secondary bile acids, deoxycholic acid and lithocholic acid, increase the number of aberrant crypt foci in the colon and may act as colon tumor promoters, there is little evidence detailing their mechanism of action. Histones play an important role in controlling gene expression, and the posttranslational modification of histones plays a role in regulation of intracellular signal transduction. In particular, the amino-terminal tail domain of histone H3 is sensitive to several posttranslational modifications, and acetylation of this domain changes its electrostatic environment and results in the loss of native folding. Therefore, we studied the modification of epsilon-amino groups on human histone H3 by deoxycholyl adenylate, which is an active intermediate in deoxycholyl thioester biosynthesis. After incubation of recombinant human histone H3 with a smaller amount of acyl adenylate, followed by enzymatic digestion, the peptide fragment mixtures were analyzed by matrix-assisted laser desorption ionization mass spectrometry. These data showed the formation of only one adduct fragment, which corresponded to amino acids 3-8 with a deoxycholate adduct, suggesting that the epsilon-amino group of Lys(4) had the highest reactivity. This novel modification, formation of a bile acid adduct on the histone H3 amino-terminal tail domain through an active acyl adenylate, may relate to the carcinogenesis-promoting effects of secondary bile acids.

Dietary fiber–rich colloids from apple pomace extraction juices do not affect food intake and blood serum lipid levels, but enhance fecal excretion of steroids in rats

The aim of this study was to investigate the effects of colloids isolated from apple pomace extraction juices (so-called B-juices) produced by enzymatic liquefaction on food intake, levels of blood serum lipids, and fecal excretion of bile acids (BA) and neutral sterols (NS) in vivo. Ten male Wistar rats per group were fed diets containing either no apple dietary fiber (DF) (control), a 5% supplementation with juice colloids, or an alcohol-insoluble substance (AIS) from apples for 6 weeks. Apple DF in diets led to lower weight gain in rats fed with B-juice colloids (P< 0.05). For these rats, food intake was not affected but was highest with feeding AIS (10% more than control) to cover energy requirements. The supplementation of diet with apple DF from extraction juices or AIS had minor effects on blood serum lipids. In rats fed either juice colloids or AIS, up to 30% (5.31 micromol/g dry weight) and 88% (7.69 micromol/g dry weight) more primary BA were excreted in feces, respectively, as compared to that in the control group (4.10 micromol/g dry weight) (P < 0.05). In cecal contents, a 15% (juice colloids) to 37% (AIS) increase in primary BA was found. In contrast, concentrations of secondary BA were lower in feces of test groups (P < 0.05). Excretion of total BA and NS was higher in rats fed apple DF (P < 0.05). Our study is the first to prove that there are beneficial physiologic effects of apple DF isolated from pomace extraction juices produced by enzymatic liquefaction. These results may help to develop such innovative juice products that are rich in DF of fruit origin for diminishing the lack of DF intake.

Liver transplantation for primary sclerosing cholangitis; predictors and consequences of hepatobiliary malignancy

BACKGROUND/AIMS

Hepatobiliary malignancies are frequently seen in primary sclerosing cholangitis (PSC) and they complicate the evaluation of patients and timing of liver transplantation.

METHODS

Data from all Nordic PSC patients listed for liver transplantation during 1990-2001 were recorded prospectively. Predictors of hepatobiliary malignancy and patient survival rates have been analysed.

RESULTS

Hepatobiliary malignancy was found in 52/255 (20%) patients accepted to the waiting list. Recent diagnosis of PSC, no ursodeoxycholic acid (UDCA) treatment, clinical suspicion and previous colorectal-cancer were predictors of malignancy. Among 89 patients with a strong suspicion of malignancy prior to acceptance, 35 (39%) had confirmed malignancy. A clinical suspicion had been raised in 35/52 (67%) patients with malignancy. Malignancy was found in 31/223 patients who received a liver allograft. The 1-, 3- and 5-year patient survival rates following transplantation for patients with PSC and cholangiocarcinoma were 65, 35 and 35%, respectively.

CONCLUSIONS

Hepatobiliary malignancy is suspected in 1/3 of the PSC patients and found in 1/5. Although cholangiocarcinoma is regarded as a contraindication to liver transplantation (LTX), PSC patients with cholangiocarcinoma had a 35% 5-year survival following transplantation.

Results of a Phase I Multiple-Dose Clinical Study of Ursodeoxycholic Acid

Background: The hydrophilic bile acid, ursodeoxycholic acid (UDCA), may indirectly protect against colon carcinogenesis by decreasing the overall proportion of the more hydrophobic bile acids, such as deoxycholic acid (DCA), in aqueous phase stool. In the AOM rat model, treatment with UDCA resulted in a significant decrease in adenoma formation and colorectal cancer. It was hypothesized that there is a dose-response relationship between treatment with the more hydrophilic bile acid, UDCA, and a reduction in the proportion of the more hydrophobic bile acid, DCA, in the aqueous stool phase, suggesting the potential of UDCA as a chemopreventive agent. Methods: Eighteen participants were randomized to 300, 600, or 900 mg/day UDCA for 21 days in this multiple-dose, double-blinded study. Seventy-two-hour stool samples were collected pretreatment and on days 18–20 of UDCA treatment for bile acid measurements. Pharmacokinetics were performed and blood bile acids were measured at days 1 and 21 of UDCA treatment. Results: There were no serious adverse events associated with UDCA treatment. There was a dose-response increase in the posttreatment to baseline ratio of UDCA to DCA from the 300 mg/day to the 600 mg/day group, but not between the 600 and the 900 mg/day groups, in both aqueous and solid phase stool. This posttreatment increase was statistically significant in aqueous phase stool for the 300 and 600 mg/day treatment groups (P = 0.038 and P = 0.014, respectively), but was only marginally significant in the 900 mg/day treatment group (P = 0.057). Following the first dose administration, a dose-dependent increase in plasma ursodeoxycholic concentrations was observed in fasting subjects; however, when these levels were measured postprandially following 3 weeks of treatment, the areas under the plasma concentration-time profile (AUC) were not statistically different and remained relatively unchanged over time. Conclusions: UDCA treatment did not decrease the quantity of DCA in fecal water or solids; however, it did decrease the proportion of DCA in fecal water and solids in relation to UDCA. Thus, 3 weeks of UDCA treatment resulted in an overall increase in hydrophilicity of bile acids in the aqueous phase stool, with a peak effect observed with a daily dose of 600 mg/day. Much larger studies are needed to determine the effect of ursodeoxycholic administration on deoxycholic concentration, overall hydrophilicity of stool bile acids, and the long-term effects on intermediate biomarkers of cellular damage.

Synthetic CDCA derivatives-induced apoptosis of stomach cancer cell line SNU-1 cells

PURPOSE

This study was conducted to explore whether CDCA derivatives induce apoptosis in a stomach cancer cell line, and to dissect the detailed mechanism underlying apoptosis.

MATERIALS AND METHODS

The human stomach cancer cell line, SNU-1, cells were treated with the synthetic CDCA derivatives, HS-1199 and HS-1200. DNA and mitochondrial stains were used to detect apoptotic cells by fluorescence imaging or flow cytometry. The caspase-3 activity was measured by Western blotting.

RESULTS

Both the HS-1199 and HS-1200 induced decreased viabilities of the SNU-1 cells, in time-dependent manners. The CDCA derivatives demonstrated various apoptosis hallmarks, such as mitochondrial changes (reduction of MMP, cytochrome c release, and Smac/ DIABLO translocation), activation of caspase-3 (resulting in the degradation of PARP and DFF45), DNA fragmentation and nuclear condensation.

CONCLUSION

The CDCA derivatives, HS-1199 and HS-1200, both induced apoptosis of the SNU-1 gastric cancer cells in caspase- and mitochondria-dependent fashions. Many important issues relating to their therapeutic applications remain to be elucidated.

Taurodeoxycholate increases intestinal epithelial cell proliferation through c-myc expression

BACKGROUND

Bile salts have been shown to modulate gastrointestinal epithelial restitution, differentiation, and other functions. Prior studies have shown that the bile salt taurodeoxycholate increases cell migration after injury. The purpose of this experiment was to determine the effect that taurodeoxycholate has on intestinal epithelial cell growth, c-myc expression and function.

METHODS

IEC-6 or Caco-2 cells were treated with varying concentrations of taurodeoxycholate (.05 to 1 mmol/L) and proliferation determined. Apoptosis was measured by use of DNA fragmentation assay and nuclear staining. Cell phase was determined with propidium iodide flow cytometry. C-myc expression was determined by Northern and Western blot analysis, and c-myc function was inhibited by specific c-myc antisense.

RESULTS

There was no change in cell structure. Apoptosis was not induced. Six days after exposure to taurodeoxycholate, IEC-6 cell proliferation was significantly increased. Flow cytometry showed a significant increase in S-phase concentration and a significant decrease in G1-phase concentration of the cell cycle. Taurodeoxycholate also increased c-myc protein and mRNA expression, and inhibition of c-myc function prevented taurodeoxycholate-induced cell proliferation.

CONCLUSIONS

Exposure to physiological concentrations of the bile salt taurodeoxycholate increases intestinal epithelial cell proliferation. This effect is at least partially mediated through a c-myc-dependent mechanism. Bile salts can have a beneficial effect on the intestinal mucosa.

Ursodeoxycholic acid (UDCA) can inhibit deoxycholic acid (DCA)-induced apoptosis via modulation of EGFR/Raf-1/ERK signaling in human colon cancer cells

Ursodeoxycholic acid (UDCA), a hydrophilic bile acid, is known as a cytoprotective agent. UDCA prevents apoptosis induced by a variety of stress stimuli including cytotoxic bile acids such as deoxycholic acid (DCA). Here we examined the molecular mechanism by which UDCA can antagonize DCA-induced apoptosis in human colon cancer cells. UDCA pretreatment decreases the number of apoptotic cells caused by exposure to DCA and UDCA. Further studies of the signaling pathway showed that UDCA pretreatment suppressed DNA binding activity of activator protein-1 and this was accompanied by downregulation of both extracellular signal-regulated kinase (ERK) and Raf-1 kinase activities stimulated by exposure to DCA. DCA was also found to activate epidermal growth factor receptor (EGFR) activity and UDCA inhibited this. Collectively, these findings suggest that the inhibitory effect of UDCA in DCA-induced apoptosis is partly mediated by modulation of EGFR/Raf-1/ERK signaling.