Taurodeoxycholate increases intestinal epithelial cell proliferation through c-myc expression

Role of microencapsulated Lactobacillus plantarum in alleviating intestinal inflammatory damage through promoting epithelial proliferation and differentiation in layer chicks

The alleviating effects of Lactobacillus plantarum in microencapsulation (LPM) on lipopolysaccharide (LPS)-induced intestinal inflammatory injury were investigated in layer chicks. A total of 252 healthy Hy-Line Brown layer chicks were randomly divided into six groups. Birds were injected with saline or LPS except for the control, and the diets of birds subjected to LPS were supplemented with nothing, L. plantarum, LPM, and wall material of LPM, respectively. The viable counts of LPM reached 109 CFU/g, and the supplemental levels of L. plantarum, LPM, and WM were 0.02 g (109 CFU), 1.0 g, and 0.98 g, per kilogram feed, respectively. LPS administration caused intestinal damage in layer chicks, evidenced by increased proinflammatory factors accompanied by poor intestinal development and morphology (p < 0.05). LPM/LPS significantly increased body weight, small intestine weight and length, villus height, villus height/crypt depth, and mRNA relative expression of tight junction protein genes (p < 0.05) and performed better than free L. plantarum. These findings could be attributed to the significant increase in viable counts of L. plantarum in the small intestine (p < 0.05), as well as the enhanced levels of Actinobacteriota, Lactobacillaceae, and Lactobacillus in intestinal microbiota (p < 0.05). Such results could further significantly increase goblet and PCNA+ cell percentage (p < 0.05); the mRNA relative expressions of epithelial cell, fast-cycling stem cell, quiescent stem cell, endocrine cell, and Paneth cell; and goblet and proliferative cell marker genes, including E-cadherin, Lgr-5, Bmi-1, ChA, Lysozome, Mucin-2, and PCNA (p < 0.05). Furthermore, the mRNA relative expressions of key genes involved in epithelial cell proliferation, namely, c-Myc, Cyclin-1, Wnt-3, Lrp-5, and Olfm-4, exhibited significant upregulation compared with the LPS treatment, as well as the differentiating genes Notch-1 and Hes-1 (p < 0.05). To sum up, microencapsulated L. plantarum supplementation could alleviate intestinal injury in layer chicks induced by LPS by promoting the proliferation and differentiation of intestinal epithelial cells, which could be attributed to the increase in viable count of L. plantarum in the gut and optimization in intestinal microbial flora.

Deoxynivalenol Exposure Induced Colon Damage in Mice Independent of the Gut Microbiota

SCOPE

To investigate whether deoxynivalenol (DON) can induce intestinal damage through gut microbiota in mice.

METHODS AND RESULTS

Mice are orally administered DON (1 mg kg-1 bw day-1 ) for 4 weeks, and then recipient mice receive fecal microbiota transplantation (FMT) from DON-exposed mice after antibiotic treatment. Furthermore, the mice are orally treated with DON (1 mg kg-1 bw day-1 ) for 4 weeks after antibiotic treatment. Histological damage, disruption of tight junction protein expression, and increased oxidative stress and apoptosis in the colon as well as higher serum lipopolysaccharides are observed after DON exposure. Moreover, DON exposure changes the composition and diversity of the gut microbiota as well as the contents of fecal metabolites (mainly bile acids). Differential metabolic pathways may be related to mitochondrial metabolism, apoptosis, and inflammation following DON exposure. However, only a decrease in mRNA levels of occludin and claudin-3 is observed in the colon of recipient mice after FMT. After depleting the gut microbiota in mice, DON exposure can also cause histological damage, disorders of tight junction protein expression, and increased oxidative stress and apoptosis in the colon.

CONCLUSIONS

DON exposure can induce colon damage in mice independent of the gut microbiota.

The inhibition of enterocyte proliferation by lithocholic acid exacerbates necrotizing enterocolitis through downregulating the Wnt/β-catenin signalling pathway

Objectives

Necrotizing enterocolitis (NEC) is a catastrophic gastrointestinal emergency in preterm infants, whose exact aetiology remains unknown. The role of lithocholic acid (LCA), a key component of secondary bile acids (BAs), in NEC is unclear.

Methods

Clinical data were collected to analyse the changes of BAs in NEC patients. In vitro studies, the cell proliferation and cell death were assessed. In vivo experiments, the newborn rats were administered with low or high dose of LCA and further induced NEC.

Results

Clinically, compared with control group, total BAs in the NEC patients were significantly higher when NEC occurred. In vitro, LCA treatment significantly inhibited the cell proliferation through arresting cell cycle at G1/S phase without inducing apoptosis or necroptosis. Mechanistically, the Wnt/β‐catenin pathway was involved. In vivo, LCA inhibited intestinal cell proliferation leading to disruption of intestinal barrier, and thereby increased the severity of NEC. Specifically, LCA supplementation caused higher levels of FITC‐labelled dextran in serum, reduced PCNA expression and inhibited the activity of Wnt/β‐catenin pathway in enterocytes. The LC–MS/MS test found that LCA was significantly higher in intestinal tissue of NEC group, and more obviously in the NEC‐L and NEC‐H group compared with the DM group.

Conclusion

LCA exacerbates NEC by inhibiting intestinal cell proliferation through downregulating the Wnt/β‐catenin pathway.

Fecal microbiota from children with vitamin A deficiency impair colonic barrier function in germ-free mice: The possible role of alterative bile acid metabolites

OBJECTIVE

This study explores the effects of fecal microbiota from children with vitamin A (VA) deficiency on colonic mucosal barrier function.

METHODS

The composition of gut microbes was identified in children with different VA levels, then feces from children with normal VA or VA deficiency was collected separately and transplanted into germ-free (GF) mice, respectively. Three weeks after transplantation, the colon morphology, colonic tight junction proteins, gut microbes, and metabolites were evaluated.

RESULTS

In children, Bifidobacterium and Bacteroides were positively correlated with VA levels. Colonization of VA deficiency fecal microbiota markedly impaired colonic development in GF mice, down-regulated colonic tight junction-related proteins occludin and claudin-1, and reduced immunoglobulin A secretion. Furthermore, fecal microbiota transplantation with different VA levels altered composition of gut microbes and bile acid metabolism pathways in GF mice.

CONCLUSION

These data suggest that fecal microbiota from children with VA deficiency attenuates colonic barrier function in GF mice, which may be achieved by changing the bile acid metabolic pathways.

Role and significance of bile acid membrane receptor GPBAR1 in pathogenesis of obstructive jaundice

GPBAR1 is the first confirmed G protein coupled bile acid membrane receptor, which is widely expressed in the liver, gallbladder, kidney, intestine, and the nervous and cardiovascular systems. During the development of obstructive jaundice (OJ), GPBAR1 is activated by bile acid signal and mediates different signal transduction pathways, thus playing a corresponding role in the pathogenesis of OJ. GPBAR1 may be a potential therapeutic target for the treatment of OJ by controlling inflammation, regulating the function of bile duct epithelial barrier, inhibiting renal oxidative stress, and regulating intestinal mucosal barrier and intestinal flora, pruritus and sensory disturbance, and cardiovascular function. This article reviews the role and signficance of GPBAR1 in the pathogenesis of OJ.

Identification and Characterization of MAPK Signaling Pathway Genes and Associated lncRNAs in the Ileum of Piglets Infected by Clostridium perfringens Type C

Clostridium perfringens type C (C. perfringens type C) is one of the main microbial pathogens responsible for piglet diarrhea worldwide, causing substantial economic losses for pig-rearing industries. The mitogen-activated protein kinase (MAPK) signaling pathway is a key regulator of inflammatory bowel disease, especially necrotic enteritis. However, whether and how the MAPK signaling pathway is involved in regulating the process of piglet diarrhea when challenged by C. perfringens type C are still unknown. Here, we screened 38 differentially expressed genes (DEGs) in piglets' ileum tissues experimentally infected with C. perfringens type C that were enriched in the Sus scrofa MAPK signaling pathway, based on our previous transcriptome data. Of these DEGs, 12 genes (TRAF2, MAPK8, and GADD45G, among others) were upregulated whereas 26 genes (MAPK1, TP53, and CHUK, among others) were downregulated in the infected group. Our results showed that MAPK1, TP53, MAPK8, MYC, and CHUK were in the core nodes of the PPI network. Additionally, we obtained 35 lncRNAs from the sequencing data, which could be trans-targeted to MAPK signaling pathway genes and were differentially expressed in the ileum tissues infected with C. perfringens. We used qRT-PCR to verify the expression levels of genes and lncRNAs related to the MAPK signaling pathway; their expression patterns were consistent with RNA sequencing data. Our results provide strong support for deeply exploring the role of the MAPK signaling pathway in diarrhea caused by C. perfringens type C.

Genistein Combined Polysaccharide (GCP) Can Inhibit Intracrine Androgen Synthesis in Prostate Cancer Cells

Our group and others have previously shown that genistein combined polysaccharide (GCP), an aglycone isoflavone-rich extract with high bioavailability and low toxicity, can inhibit prostate cancer (CaP) cell growth and survival as well as androgen receptor (AR) activity. We now elucidate the mechanism by which this may occur using LNCaP and PC-346C CaP cell lines; GCP can inhibit intracrine androgen synthesis in CaP cells. UPLC-MS/MS and qPCR analyses demonstrated that GCP can mediate a ~3-fold decrease in testosterone levels (p < 0.001) and cause decreased expression of intracrine androgen synthesis pathway enzymes (~2.5-fold decrease of 3βHSD (p < 0.001), 17βHSD (p < 0.001), CYP17A (p < 0.01), SRB1 (p < 0.0001), and StAR (p < 0.01)), respectively. Reverse-phase HPLC fractionation and bioassay identified three active GCP fractions. Subsequent NMR and LC-MS analysis of the fraction with the highest level of activity, fraction 40, identified genistein as the primary active component of GCP responsible for its anti-proliferative, pro-apoptotic, and anti-AR activity. GCP, fraction 40, and genistein all mediated at least a ~2-fold change in these biological activities relative to vehicle control (p < 0.001). Genistein caused similar decreases in the expression of 17βHSD and CYP17A (2.5-fold (p < 0.001) and 1.5-fold decrease (p < 0.01), respectively) compared to GCP, however it did not cause altered expression of the other intracrine androgen synthesis pathway enzymes; 3βHSD, SRB1, and StAR. Our combined data indicate that GCP and/or genistein may have clinical utility and that further pre-clinical studies are warranted.

Hyodeoxycholic acid (HDCA) suppresses intestinal epithelial cell proliferation through FXR-PI3K/AKT pathway, accompanied by alteration of bile acids metabolism profiles induced by gut bacteria

Bile acids (BAs) have been implicated in regulation of intestinal epithelial signaling and function. This study aimed to investigate the effects of hyodeoxycholic acid (HDCA) on intestinal epithelial cell proliferation and explore the underlying mechanisms. IPEC-J2 cells and weaned piglets were treated with HDCA and the contributions of cellular signaling pathways, BAs metabolism profiles and gut bacteria were assessed. In vitro, HDCA suppressed IPEC-J2 proliferation via the BAs receptor FXR but not TGR5. In addition, HDCA inhibited the PI3K/AKT pathway, while knockdown of FXR or constitutive activation of AKT eliminated the inhibitory effects of HDCA, suggesting that FXR-dependent inhibition of PI3K/AKT pathway was involved in HDCA-suppressed IPEC-J2 proliferation. In vivo, dietary HDCA inhibited intestinal expression of proliferative markers and PI3K/AKT pathway in weaned piglets. Meanwhile, HDCA altered the BAs metabolism profiles, with decrease in primary BA and increase in total and secondary BAs in feces, and reduction of conjugated BAs in serum. Furthermore, HDCA increased abundance of the gut bacteria associated with BAs metabolism, and thereby induced BAs profiles alternation, which might indirectly contribute to HDCA-suppressed cell proliferation. Together, HDCA suppressed intestinal epithelial cell proliferation through FXR-PI3K/AKT signaling pathway, accompanied by alteration of BAs metabolism profiles induced by gut bacteria.

Protective effect of rhubarb against intestinal mucosal barrier injury in rats with obstructive jaundice

Objective: To investigate the effects of raw rhubarb (RR) on the intestinal barrier dysfunction and endotoxemia in rat models with obstructive jaundice (OJ).

Methods: Twenty-seven Sprague–Dawley rats were randomly allocated to four groups: control ([Formula: see text]), sham operation ([Formula: see text]), model ([Formula: see text]), and treatment ([Formula: see text]). Rat models with OJ were used in the model and treatment groups. In the treatment group, rats were intragastrically administered with RR granular solution. After treatment, serum endotoxin (ET), serum alanine aminotransferase (ALT), aspartate aminotransferase (AST), and total bilirubin (TB) levels were determined. The liver tissue, bile duct tissue above the obstruction bile duct site, and parts of the ileum and colon tissues were stained with hematoxylin and eosin and observed by light microscopy, and the histopathological changes in the ileum were observed by electron microscopy.

Results: Fourteen days after the rats in the treatment group were intragastrically administered with RR granular solution, the ALT, AST, and TB levels showed no significant difference between the control and sham operation groups ([Formula: see text]). Serum ET level was significantly lower in the treatment group than in the model group ([Formula: see text]). Histopathology of the liver and bile duct revealed that RR might alleviate OJ-associated hepatocyte degeneration/necrosis, infiltration of inflammatory cells, and hepatic fibrosis, and reduce the damage to parietal cells and bile duct mucosa. In OJ rats, RR might also have a protective effect against colonic wall edema and necrosis and infiltration of inflammatory cells.

Conclusions: RR may improve the structural changes in the intestinal mucosa caused by OJ and decrease serum ET level in OJ rats.

Role of Farnesoid X Receptor and Bile Acids in Hepatic Tumor Development

Hepatocellular carcinoma (HCC) is a leading cause of cancer deaths worldwide, and an association between altered bile acid (BA) metabolism, down‐regulation of farnesoid X receptor (FXR), which is a master regulator of BA metabolism, and hepatocarcinogenesis has been documented. While global FXR deficiency in mice results in spontaneous HCC with aging, the contribution of tissue‐specific FXR deficiency to hepatocarcinogenesis remains unclear. In this study, the prevalence of hepatic tumors, expression of genes related to tumorigenesis, and serum/liver BA levels were compared among male whole‐body Fxr‐null, hepatocyte‐specific Fxr‐null (Fxr^∆Hep), and enterocyte‐specific Fxr‐null (Fxr^∆IE) mice at the age of 3, 14, and 20 months. More than 90% of 20‐month‐old whole‐body Fxr‐null mice had hepatic tumors with enhanced hepatic expression of myelocytomatosis oncogene (Myc) and cyclin‐dependent kinase 4 (Cdk4) messenger RNAs (mRNAs) and elevated serum taurocholate (TCA) and tauromuricholate (TMCA) and their respective unconjugated derivatives. The incidence of hepatic tumors was significantly lower in Fxr^∆Hep and Fxr^∆IE mice (20% and 5%, respectively), and the increases in Myc and Cdk4 mRNA or serum BA concentrations were not detected in these mice compared to Fxr^{floxed [fl]/fl} mice; a similar tendency was observed in 14‐month‐old mice. However, increased hepatic c‐Myc protein expression was found only in Fxr‐null mice at the age of 3, 14, and 20 months. Treatment with TCA induced Myc expression in Fxr‐null cultured primary mouse hepatocytes but not in wild‐type (WT) mouse hepatocytes, demonstrating that the combination of hepatocyte FXR disruption with elevated TCA is required for Myc induction and ensuing age‐dependent hepatocarcinogenesis in Fxr‐null mice. Conclusion: There is a relatively low risk of hepatic tumors by inhibition of FXR in enterocytes, likely due to the lack of increased TCA and Myc induction.

Bile acid receptor TGR5 overexpression is associated with decreased intestinal mucosal injury and epithelial cell proliferation in obstructive jaundice

Bile acids stimulate intestinal epithelial proliferation in vitro. We sought to investigate the role of the bile acid receptor TGR5 in the protection of intestinal epithelial proliferation in obstructive jaundice. Intestinal tissues and serum samples were obtained from patients with malignant obstructive jaundice and from bile duct ligation (BDL) rats. Intestinal permeability and morphological changes in the intestinal mucosa were observed. The functions of TGR5 in cell proliferation in intestinal epithelial injury were determined by overexpression or knockdown studies in Caco-2 and FHs 74 Int cells pretreated with lipopolysaccharide (LPS). Internal biliary drainage was superior to external biliary drainage in recovering intestinal permeability and mucosal histology in patients with obstructive jaundice. In BDL rats, feeding of chenodeoxycholic acid (CDCA) decreased intestinal mucosa injury. The levels of PCNA, a marker of proliferation, increased in response to CDCA feeding and were paralleled by elevated TGR5 expression. CDCA upregulated TGR5 expression and promoted proliferation in Caco-2 and FHs 74 Int cells pretreated with LPS. Overexpression of TGR5 resulted in increased PCNA, cell viability, EdU incorporation, and the proportion of cells in S phase, whereas knockdown of TGR5 had the opposite effect. Our data indicate that bile acids promote intestinal epithelial cell proliferation and decrease mucosal injury by upregulating TGR5 expression in obstructive jaundice.

Intestinal barrier integrity and function in infants with cholestasis

Background/Aims

The safety of the human body is maintained by effective monitoring of the mucosal surface integrity and protection against potentially harmful compounds. This function of the gut called intestinal barrier function can be affected by cholestasis and the absence of bile in the intestinal lumen. We aimed to determine whether the gut barrier integrity is impaired in infants with cholestasis by evaluation of the intestinal fatty acid binding proteins (I-FABP) and ileal bile acid binding protein (I-BABP) as markers of intestinal epithelial cell damage and plasma D-lactate level as a marker of gut wall permeability.

Methods

This case-control study included 53 infants with cholestasis and 29 controls. Serum levels of I-FABP, I-BABP, and D-lactate were measured in all subjects.

Results

Both groups of patients with neonatal hepatitis and biliary atresia showed significantly higher levels of I-FABP and I-BABP than the controls. There were no differences in the serum D-lactate level between the cases and controls. There was no difference between the two groups of patients (I and II) regarding any of the parameters studied. No significant correlations between serum levels of I-FABP, I-BABP, or D-lactate and total or direct bilirubin levels were found in the cholestatic infants.

Conclusions

The intestinal epithelial barrier integrity is breached nearly in all parts of the intestine in infants with cholestasis. Further research is recommended to determine the impact of this finding on the management of these infants. The relationship between physical intestinal barrier damage and its functional failure remains subject for further research.

Systematic review: bile acids and intestinal inflammation-luminal aggressors or regulators of mucosal defence?

BACKGROUND

Inflammatory bowel diseases (IBD), comprising Crohn's disease and ulcerative colitis (UC), are chronic conditions attributed to an aberrant immune response to luminal triggers. Recently, published work suggests a pathogenic role for bile acids in this context.

AIM

To perform a systematic review of studies investigating the role of bile acids in intestinal inflammation and present potentially relevant clinical implications.

METHODS

Pubmed search for English language articles published up to May 2015. Terms used were: 'bile', 'bile acid', 'barrier', 'small bowel injury', 'Crohn's' and 'colitis'.

RESULTS

Experimental studies support a variable role for bile acids in intestinal barrier homoeostasis. This may be attributed to different physicochemical properties, variable effects on epithelia and immune cells via bile acids-specific receptors, or through a cross-talk with the gut microbiome. A reduction in the bile acids pool, with lower concentrations of secondary forms, has been recognised for some time in Crohn's disease and associated to ileal dysfunction and bile acids malabsorption. Recent work suggests that these changes, including an increase in sulphated forms, are related to inflammatory activity in both Crohn's disease and UC. The detrimental effects of 'western diet' elements such as emulsifiers and fat, which have been implicated in the development of the current IBD and obesity epidemics, may also be bile acid-mediated.

CONCLUSIONS

Although there are only a few observational clinical studies to support an interaction, in vivo human and animal studies support an association between bile acids metabolism, the gut microbiome and intestinal inflammation. This may well prove to have significant diagnostic and therapeutic implications.

Effect of different biliary drainage methods on intestinal barrier function in rats with obstructive jaundice

AIM: To investigate the effect of different biliary drainage methods on intestinal barrier function in rats with obstructive jaundice.

METHODS: Sixty healthy SD rats were divided into four groups: sham-operation (SO) group, obstructive jaundice (OJ) group, internal drainage (ID) group, and external drainage (ED) group. One week after surgery, specimens from the rats of the SO and OJ groups were collected. Biliary drainage was performed using different methods in the ID and ED groups, and the specimens were harvested seven days after drainage. The levels of alanine aminotransferase (ALT), total bilirubin (TBIL), direct bilirubin (DBIL), and total bile acide (TBA) in serum, and sIgA in intestine mucus were determined and compared between different groups.

RESULTS: Serum levels of ALT, TBIL, DBIL, and TBA were significantly higher in the OJ group than in the SO, ID, and ED groups. The levels of sIgA in intestine mucus were significantly higher in the ID group than in the OJ and ED groups (0.272 ± 0.182 vs 0.160 ± 0.150, 0.191 ± 0.113, both P < 0.05).

CONCLUSION: Both ID and ED effectively relieve biliary obstruction and improve liver function. ID significantly increases intestinal mucus sIgA. The effect of ID on intestinal barrier function is better than that of ED.

Bile salts increase epithelial cell proliferation through HuR-induced c-Myc expression

BACKGROUND

Bile salts increase intestinal mucosal proliferation through an increase in c-Myc, a transcription factor that controls the expression of numerous translation regulatory proteins. HuR is an RNA-binding protein that regulates translation of target mRNAs. RNA-binding proteins can control mRNA stability by binding to AU- and U-rich elements located in the 3'-untranslated regions (3'-UTRs) of target mRNAs.

AIM

To determine how bile salt-induced c-Myc stimulates enterocyte proliferation.

METHODS

Enterocyte proliferation was measured both in vivo using C57Bl6 mice and in vitro using IEC-6 cells after taurodeoxycholate (TDCA) supplementation. HuR and c-Myc protein expression was determined by immunoblot. c-Myc mRNA expression was determined by PCR. HuR expression was inhibited using specific small interfering RNA. HuR binding to c-Myc mRNA was determined by immunoprecipitation.

RESULTS

TDCA increased enterocyte proliferation in vivo and in vitro. TDCA stimulates translocation of HuR from the nucleus to the cytoplasm. Cytoplasmic HuR regulates c-Myc translation by HuR binding to the 3'-UTR of c-Myc mRNA. Increased TDCA-induced c-Myc increases enterocyte proliferation.

CONCLUSIONS

Bile salts have beneficial effects on the intestinal epithelial mucosa, which are important in maintaining intestinal mucosal integrity and function. These data further support an important beneficial role of bile salts in regulation of mucosal growth and repair. Decreased enterocyte exposure to luminal bile salts, as occurs during critical illness, liver failure, starvation, and intestinal injury, may have a detrimental effect on mucosal integrity.

Polysaccharides from Capsosiphon fulvescens stimulate the growth of gastrointestinal cells

Capsosiphon fulvescens is a green alga that is abundant along the southwest coast of South Korea. Although it is consumed for its purported health-enhancing properties, particularly as a treatment for stomach disorders and hangovers, the health effects of dietary C. fulvescens remain unclear. Polysaccharides extracted from C. fulvescens (Cf-PS) are investigated for their effects on the proliferation of rat small intestinal epithelial IEC-6 cells. Cf-PS stimulated IEC-6 cell proliferation in a dose-dependent manner. Further, Cf-PS treatment induced the translocation of β-catenin, an effector of the Wnt signaling pathway, from the cytosol to the nucleus and increased the expression of cyclinD1 and c-myc. Cf-PS also induced ERK1/2 phosphorylation, which is activated by mitogenic and proliferative stimuli such as growth factors, but the phosphorylation of JNK and p38 was not enhanced. Therefore, this chapter discusses the effect of Cf-PS on the growth of gastrointestinal cells.

Polysaccharides from Capsosiphon fulvescens stimulate the growth of IEC-6 Cells by activating the MAPK signaling pathway

Seaweed extracts show diverse bioactivities, such as antioxidant and antitumor activity. Capsosiphon fulvescens is a green alga that is abundant along the southwest coast of South Korea. Although it is consumed for its purported health-enhancing properties, particularly as a treatment for stomach disorders and hangovers, the health effects of dietary C. fulvescens remain unclear. We extracted polysaccharides from C. fulvescens (Cf-PS), investigated their effects on the proliferation of rat small intestinal epithelial IEC-6 cells, and determined the signaling cascade involved. We cultured IEC-6 cells in the presence of Cf-PS, which stimulated cell proliferation in a dose-dependent manner, and analyzed the Wnt and MAPK signaling pathways, which are related to cell proliferation. Cf-PS treatment induced the translocation of β-catenin, an effector of the Wnt signaling pathway, from the cytosol to the nucleus and increased the expression of cyclinD1 and c-myc. Cf-PS also induced ERK1/2 phosphorylation, which is activated by mitogenic and proliferative stimuli such as growth factors, but the phosphorylation of JNK and p38 was not enhanced. Our results show that Cf-PS regulates proliferation via stimulating the nuclear translocation of β-catenin and ERK1/2 activation in intestinal epithelial cells.

Intestinal epithelial cell proliferation, apoptosis and expression of tight junction proteins in patients with obstructive jaundice

BACKGROUND

Intestinal hyperpermeability has been repeatedly confirmed in patients with obstructive jaundice and is considered a pivotal factor in the development of septic and renal complications in these patients. However, little is known on the mechanism(s) leading to this phenomenon. This study was undertaken to investigate the cellular and subcellular intestinal alterations in patients with obstructive jaundice.

DESIGN

Sixteen patients with obstructive jaundice of malignant (n = 8, group A) or benign (n = 8, group B) aetiology, without concomitant cholangitis, and eight healthy controls (group C) were subjected to duodenal biopsy distal to the ampulla of Vater. Specimens were examined histologically and the apoptotic activity in the cryptal epithelium was recorded. Epithelial proliferation was evaluated by immunohistochemical expression of Ki67 antigen. The expression of the tight junction (TJ) proteins occludin, claudin-1, claudin-4 and claudin-7 in the intestinal epithelium was also evaluated by immunohistochemistry.

RESULTS

Patients with malignant or benign obstructive jaundice presented significantly decreased intestinal epithelial cell proliferation rates compared with controls (P < 0·05), whereas no differences were detected in apoptotic activity. In a semiquantitative analysis of TJ protein expression, occludin, claudin-1 and -7 were significantly decreased (P < 0·001), whereas claudin-4 was significantly increased (P < 0·01) in jaundiced patients and their distribution was altered. No differences were detected between patients with malignant or benign obstructive jaundice for all intestinal barrier parameters studied.

CONCLUSION

Decreased enterocyte proliferation and altered TJ protein expression might represent important mechanisms for intestinal barrier dysfunction and hyperpermeability in patients with extrahepatic cholestasis. The potential pharmacological modulation of these factors may lead to better control of intestinal permeability in the jaundiced patient with improved clinical outcome.

Pathophysiology of increased intestinal permeability in obstructive jaundice

Despite advances in preoperative evaluation and postoperative care, intervention, especially surgery, for relief of obstructive jaundice still carries high morbidity and mortality rates, mainly due to sepsis and renal dysfunction. The key event in the pathophysiology of obstructive jaundice-associated complications is endotoxemia of gut origin because of intestinal barrier failure. This breakage of the gut barrier in obstructive jaundice is multi-factorial, involving disruption of the immunologic, biological and mechanical barrier. Experimental and clinical studies have shown that obstructive jaundice results in increased intestinal permeability. The mechanisms implicated in this phenomenon remain unresolved, but growing research interest during the last decade has shed light in our knowledge in the field. This review summarizes the current concepts in the pathophysiology of obstructive jaundice-induced gut barrier dysfunction, analyzing pivotal factors, such as altered intestinal tight junctions expression, oxidative stress and imbalance of enterocyte proliferation and apoptosis. Clinicians handling patients with obstructive jaundice should not neglect protecting the intestinal barrier function before, during and after intervention for the relief of this condition, which may improve their patients' outcome.

Pathophysiology of increased intestinal permeability in obstructive jaundice

Despite advances in preoperative evaluation and postoperative care, intervention, especially surgery, for relief of obstructive jaundice still carries high morbidity and mortality rates, mainly due to sepsis and renal dysfunction. The key event in the pathophysiology of obstructive jaundice-associated complications is endotoxemia of gut origin because of intestinal barrier failure. This breakage of the gut barrier in obstructive jaundice is multi-factorial, involving disruption of the immunologic, biological and mechanical barrier. Experimental and clinical studies have shown that obstructive jaundice results in increased intestinal permeability. The mechanisms implicated in this phenomenon remain unresolved, but growing research interest during the last decade has shed light in our knowledge in the field. This review summarizes the current concepts in the pathophysiology of obstructive jaundice-induced gut barrier dysfunction, analyzing pivotal factors, such as altered intestinal tight junctions expression, oxidative stress and imbalance of enterocyte proliferation and apoptosis. Clinicians handling patients with obstructive jaundice should not neglect protecting the intestinal barrier function before, during and after intervention for the relief of this condition, which may improve their patients’ outcome.

Intestinal capacity to digest and absorb carbohydrates is maintained in a rat model of cholestasis

Cholestasis is associated with systemic accumulation of bile salts and with deficiency of bile in the intestinal lumen. During the past years bile salts have been identified as signaling molecules that regulate lipid, glucose, and energy metabolism. Bile salts have also been shown to activate signaling routes leading to proliferation, apoptosis, or differentiation. It is unclear, however, whether cholestasis affects the constitution and absorptive capacity of the intestinal epithelium in vivo. We studied small intestinal morphology, proliferation, apoptosis, expression of intestine-specific genes, and carbohydrate absorption in cholestatic (1 wk bile duct ligation), bile-deficient (1 wk bile diversion), and control (sham) rats. Absorptive capacity was assessed by determination of plasma [(2)H]- and [(13)C]glucose concentrations after intraduodenal administration of [(2)H]glucose and naturally enriched [(13)C]sucrose, respectively. Small intestinal morphology, proliferation, apoptosis, and gene expression of intestinal transcription factors (mRNA levels of Cdx-2, Gata-4, and Hnf-1alpha, and Cdx-2 protein levels) were similar in cholestatic, bile-deficient, and control rats. The (unlabeled) blood glucose response after intraduodenal administration was delayed in cholestatic animals, but the absorption over 180 min was quantitatively similar between the groups. Plasma concentrations of [(2)H]glucose and [(13)C]glucose peaked to similar extents in all groups within 7.5 and 30 min, respectively. Absorption of [(2)H]glucose and [(13)C]glucose in plasma was similar in all groups. The present data indicate that neither accumulation of bile salts in the body, nor their intestinal deficiency, two characteristic features of cholestasis, affect rat small intestinal proliferation, differentiation, apoptosis, or its capacity to digest and absorb carbohydrates.

Bile salts induce resistance to apoptosis through NF-kappaB-mediated XIAP expression

Apoptosis plays a critical role in intestinal mucosal homeostasis. We previously showed that the bile salt taurodeoxycholate has a beneficial effect on the intestinal mucosa through an increase in resistance to apoptosis mediated by nuclear factor (NF)-kappaB. The current study further characterizes the effect of bile salts on intestinal epithelial cell susceptibility to apoptosis and determines if the X-linked inhibitor of apoptosis protein (XIAP) regulates bile salt-induced resistance to apoptosis. Exposure of normal intestinal epithelial cells (IEC-6) to the conjugated bile salts taurodeoxycholate (TDCA) and taurochenodeoxycholate (TCDCA) resulted in an increase in resistance to tumor necrosis factor (TNF)-alpha and cycloheximide (CHX)-induced apoptosis, and NF-kappaB activation. Treatment with TDCA and TCDCA resulted in an increase in XIAP expression. Specific inhibition of NF-kappaB by infection with an adenoviral vector that expresses the IkappaBalpha super-repressor (IkappaBSR) prevented the induction of XIAP expression and the bile salt-mediated resistance to apoptosis. Treatment with the specific XIAP inhibitor Smac also overcame this increase in enterocyte resistance to apoptosis. Bile salts inhibited formation of the active caspase-3 from its precursor procaspase-3. Smac prevented the inhibitory effect of bile salts on caspase-3 activation. These results indicate that bile salts increase intestinal epithelial cell resistance to apoptosis through NF-kappaB-mediated XIAP expression. Bile salt-induced XIAP mediates resistance to TNF-alpha/CHX-induced apoptosis, at least partially, through inhibition of caspase-3 activity. These data support an important beneficial role of bile salts in regulation of mucosal integrity. Decreased enterocyte exposure to luminal bile salts, as occurs during starvation and parenteral nutrition, may have a detrimental effect on mucosal integrity.

Spontaneous hepatocarcinogenesis in farnesoid X receptor-null mice

The farnesoid X receptor (FXR) controls the synthesis and transport of bile acids (BAs). Mice lacking expression of FXR, designated Fxr-null, have elevated levels of serum and hepatic BAs and an increase in BA pool size. Surprisingly, at 12 months of age, male and female Fxr-null mice had a high incidence of degenerative hepatic lesions, altered cell foci and liver tumors including hepatocellular adenoma, carcinoma and hepatocholangiocellular carcinoma, the latter of which is rarely observed in mice. At 3 months, Fxr-null mice had increased expression of the proinflammatory cytokine IL-1beta mRNA and elevated beta-catenin and its target gene c-myc. They also had increased cell proliferation as revealed by increased PCNA mRNA and BrdU incorporation. These studies reveal a potential role for FXR and BAs in hepatocarcinogenesis.

Characterization of fasted-state human intestinal fluids collected from duodenum and jejunum

The solubility of drugs in the gastrointestinal tract is very challenging to simulate with artificial media due to the high complexity of human intestinal fluid (HIF). In particular, bile salt composition, pH and buffer capacity are very important characteristics of HIF, since they determine the solubility of drugs in-vivo. In this study, we have measured the concentrations of individual bile salts in human intestinal fluids (n=6) collected from two different locations (duodenum and jejunum) in the fasted state. Total bile salt concentrations ranged from 570 to 5,137 microM in the duodenum and from 829 to 5,470 microM in the jejunum. The following rank order of relative bile salt concentration in duodenum was observed: taurocholic acid > glycocholate >or= glycochenodeoxycholate > glycodeoxycholate > taurochenodeoxycholate > taurodeoxycholate. Cholic acid, tauroursodeoxycholate, chenodeoxycholic acid, and deoxycholic acid represented less than 1% of bile salts present in the samples. Ursodeoxycholate could not be detected in HIF. No statistically significant difference between bile salt composition of duodenal and jejunal aspirates was observed. The buffer capacity of HIF was compared with other media commonly used for solubility/dissolution determinations, indicating a relatively low buffer capacity of HIF (4-13 mmol L(-1)/pH). This low buffer capacity was reflected in the change in pH (between 4 and 9.5) that occurred in HIF after addition of model compounds covering a broad pK(a) range. Interindividual variability in pH, buffer capacity and bile salt contents of HIF will contribute to differences in the rate and extent of absorption of compounds for which dissolution/solubility is the rate limiting step. The variability observed warrants further research to explore the impact of intraluminal conditions on drug solubility.

Bile salt exposure increases proliferation through p38 and ERK MAPK pathways in a non-neoplastic Barrett's cell line

Bile reflux has been implicated in the neoplastic progression of Barrett's esophagus (BE). Bile salts increase proliferation in a Barrett's-associated adenocarcinoma cell line (SEG-1 cells) by activating ERK and p38 MAPK pathways. However, it is not clear that these findings in cancer cells are applicable to non-neoplastic cells of benign BE. We examined the effect of bile salts on three human cell lines: normal esophageal squamous (NES) cells, non-neoplastic Barrett's cells (BAR cells), and SEG-1 cells. We hypothesized that bile salt exposure activates proproliferative and antiapoptotic pathways to promote increased growth in BE. NES, BAR, and SEG-1 cells were exposed to glycochenodeoxycholic acid (GCDA) at a neutral pH for 5 min. Proliferation was measured by Coulter counter cell counts and a 5-bromo-2'-deoxyuridine (BrdU) incorporation assay. GCDA-induced MAPK activation was examined by Western blot analysis for phosphorylated ERK and p38. Apoptosis was measured by TdT-mediated dUTP nick-end labeling and annexin V staining after GCDA and UV-B exposure. Statistical significance was determined by ANOVA. NES cells exposed to 5 min of GCDA did not increase cell number. In BAR cells, GCDA exposure increased cell number by 31%, increased phosphorylated p38 and ERK levels by two- to three-fold, increased BrdU incorporation by 30%, and decreased UV-induced apoptosis by 15-20%. In conclusion, in a non-neoplastic Barrett's cell line, GCDA exposure induces proliferation by activation of both ERK and p38 MAPK pathways. These findings suggest a potential mechanism whereby bile reflux may facilitate the neoplastic progression of BE.