Glycochenodeoxycholic acid induces stemness and chemoresistance via the STAT3 signaling pathway in hepatocellular carcinoma cells

The poor prognosis of hepatocellular carcinoma (HCC) is primarily attributed to its high frequency of recurrence and resistance to chemotherapy. Epithelial-to-mesenchymal transition (EMT) and the acquisition of cancer stem cells (CSCs) are the fundamental drivers of chemoresistance in HCC. Glycochenodeoxycholic acid (GCDC), a component of bile acid (BA), has been reported to induce necrosis in primary human hepatocytes. In the present work, we investigated the function of GCDC in HCC chemoresistance. We found that GCDC promoted chemoresistance in HCC cells by down-regulating and up-regulating the expression of apoptotic and anti-apoptotic genes, respectively. Furthermore, GCDC induced the EMT phenotype and stemness in HCC cells and activated the STAT3 signaling pathway. These findings reveal that GCDC promotes chemoresistance in HCC by inducing stemness via the STAT3 pathway and could be a potential target in HCC chemotherapy.

Direct Amplification of Tissue Factor:Factor VIIa Procoagulant Activity by Bile Acids Drives Intrahepatic Coagulation

OBJECTIVE

Regulation of TF (tissue factor):FVIIa (coagulation factor VIIa) complex procoagulant activity is especially critical in tissues where plasma can contact TF-expressing cells. One example is the liver, where hepatocytes are routinely exposed to plasma because of the fenestrated sinusoidal endothelium. Although liver-associated TF contributes to coagulation, the mechanisms controlling the TF:FVIIa complex activity in this tissue are not known. Approach and Results: Common bile duct ligation in mice triggered rapid hepatocyte TF-dependent intrahepatic coagulation coincident with increased plasma bile acids, which occurred at a time before observable liver damage. Similarly, plasma TAT (thrombin-antithrombin) levels increased in cholestatic patients without concurrent hepatocellular injury. Pathologically relevant concentrations of the bile acid glycochenodeoxycholic acid rapidly increased hepatocyte TF-dependent procoagulant activity in vitro, independent of de novo TF synthesis and necrotic or apoptotic cell death. Glycochenodeoxycholic acid increased hepatocyte TF activity even in the presence of the phosphatidylserine-blocking protein lactadherin. Interestingly, glycochenodeoxycholic acid and taurochenodeoxycholic acid increased the procoagulant activity of the TF:FVIIa complex relipidated in unilamellar phosphatidylcholine vesicles, which was linked to an apparent decrease in the K_m for FX (coagulation factor X). Notably, the zwitterionic detergent 3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonate, a bile acid structural analog, did not increase relipidated TF:FVIIa activity. Bile acids directly enhanced factor X activation by recombinant soluble TF:FVIIa complex but had no effect on FVIIa alone.

CONCLUSIONS

The results indicate that bile acids directly accelerate TF:FVIIa-driven coagulation reactions, suggesting a novel mechanism whereby elevation in a physiological mediator can directly increase TF:FVIIa procoagulant activity.

Reflux induces DNA strand breaks and expression changes of MMP1+9+14 in a human miniorgan culture model

Gastroesophageal reflux disease has been implicated in the pathogenesis of adenocarcinoma of the oesophagus. The same applies to laryngopharyngeal reflux (LPR) and squamous cell cancer of the head and neck, but so far, this link has not been proven. The impact of low pH and bile acids has not been studied extensively in cells other than oesophageal cancer cell lines and tissue. The aims of this study were to investigate the pathogenic potential of reflux and its single components on the mucosa of the upper respiratory tract. We measured DNA stability in human miniorgan cultures (MOCs) and primary epithelial cell cultures (EpCs) in response to reflux by the alkaline comet assay. As matrix metalloproteinases (MMPs) are involved in extracellular matrix remodelling processes and may contribute to cancer progression, we studied the expression of MMP1, -9, and -14 in MOCs, EpC, UM-SCC-22B, and FADUDD. DNA strand breaks (DNA-SBs) increased significantly at low pH and after incubation with human or artificial gastric juice. Single incubation with glycochenodeoxycholic acid also showed a significant increase in DNA-SBs. In epithelial cell cultures, human gastric juice increased the number of DNA-SBs at pH 4.5 and 5.5. Artificial gastric juice significantly up regulated the gene expression of MMP9. Western blot analysis confirmed the results of gene expression analysis, but the up regulation of MMP1, -9, and -14 was donor-specific. Reflux has the ability to promote genomic instability and may contribute to micro environmental changes suitable for the initiation of malignancy. Further functional gene analysis may elucidate the role of laryngopharyngeal reflux in the development of head neck squamous cell carcinoma (HNSCC).

Differential activation of the human farnesoid X receptor depends on the pattern of expressed isoforms and the bile acid pool composition

The farnesoid X receptor (FXR) is a key sensor in bile acid homeostasis. Although four human FXR isoforms have been identified, the physiological role of this diversity is poorly understood. Here we investigated their subcellular localization, agonist sensitivity and response of target genes. Measurement of mRNA revealed that liver predominantly expressed FXRα1(+/-), whereas FXRα2(+/-) were the most abundant isoforms in kidney and intestine. In all cases, the proportion of FXRα(1/2)(+) and FXRα(1/2)(-) isoforms, i.e., with and without a 12bp insert, respectively, was approximately 50%. When FXR was expressed in liver and intestinal cells the magnitude of the response to GW4064 and bile acids differs among FXR isoforms. In both cell types the strongest response was that of FXRα1(-). Different efficacy of bile acids species to activate FXR was found. The four FXR isoforms shared the order of sensitivity to bile acids species. When in FXR-deficient cells FXR was transfected, unconjugated, but not taurine- and glycine-amidated bile acids, were able to activate FXR. In contrast, human hepatocytes and cell lines showing an endogenous expression of FXR were sensitive to both unconjugated and conjugated bile acids. This suggests that to activate FXR conjugated, but not unconjugated, bile acids require additional component(s) of the intracellular machinery not related with uptake processes, which are missing in some tumor cells. In conclusion, cell-specific pattern of FXR isoforms determine the overall tissue sensitivity to FXR agonists and may be involved in the differential response of FXR target genes to FXR activation.

Progressive stages of mitochondrial destruction caused by cell toxic bile salts

The cell-toxic bile salt glycochenodeoxycholic acid (GCDCA) and taurochenodeoxycholic acid (TCDCA) are responsible for hepatocyte demise in cholestatic liver diseases, while tauroursodeoxycholic acid (TUDCA) is regarded hepatoprotective. We demonstrate the direct mitochondrio-toxicity of bile salts which deplete the mitochondrial membrane potential and induce the mitochondrial permeability transition (MPT). The bile salt mediated mechanistic mode of destruction significantly differs from that of calcium, the prototype MPT inducer. Cell-toxic bile salts initially bind to the mitochondrial outer membrane. Subsequently, the structure of the inner boundary membrane disintegrates. And it is only thereafter that the MPT is induced. This progressive destruction occurs in a dose- and time-dependent way. We demonstrate that GCDCA and TCDCA, but not TUDCA, preferentially permeabilize liposomes containing the mitochondrial membrane protein ANT, a process resembling the MPT induction in whole mitochondria. This suggests that ANT is one decisive target for toxic bile salts. To our knowledge this is the first report unraveling the consecutive steps leading to mitochondrial destruction by cell-toxic bile salts.

Carbon metabolism-mediated myogenic differentiation

The role of nutrients and metabolism in cellular differentiation is poorly understood. Using RNAi screening, metabolic profiling and small-molecule probes, we discovered that the knockdown of three metabolic enzymes-phosphoglycerate kinase (Pgk1), hexose-6-phosphate dehydrogenase (H6pd) and ATP citrate lyase (Acl)-induces differentiation of mouse C2C12 myoblasts even in the presence of mitogens. These enzymes and the pathways they regulate provide new targets for the control of myogenic differentiation in myoblasts and rhabdomyosarcoma cells.