Biliatresone induces cholangiopathy in C57BL/6J neonates.

Exposure to plant toxins or microbiota that are able to digest common food ingredients to toxic structures might be responsible for biliary atresia (BA). An isoflavonoid, biliatresone is known to effectively alter the extrahepatic bile duct (EHBD) development in BALB/c mice. Biliatresone causes a reduction of Glutathione (GSH) levels, SOX17 downregulation and is effectively countered with N-Acetyl-L-cysteine treatment in vitro. Therefore, reversing GSH-loss appears to be a promising treatment target for a translational approach. Since BALB/c mice have been described as sensitive in various models, we evaluated the toxic effect of biliatresone in robust C57BL/6J mice and confirmed its toxicity. Comparison between BALB/c and C57BL/6J mice revealed similarity in the toxic model. Affected neonates exhibited clinical symptoms of BA, such as jaundice, ascites, clay-colored stools, yellow urine and impaired weight gain. The gallbladders of jaundiced neonates were hydropic and EHBD were twisted and enlarged. Serum and histological analysis proved cholestasis. No anomalies were seen in the liver and EHBD of control animals. With our study we join a chain of evidence confirming that biliatresone is an effective agent for cross-lineage targeted alteration of the EHBD system.

The synthetic toxin biliatresone causes biliary atresia in mice.

Exposure to environmental toxins may be responsible for biliary atresia. The focus of this study was to investigate the effect of biliatresone on the development of the hepatobiliary system in mice. We successfully synthesized biliatresone with a purity of 98% and confirmed its biliary toxicity. Exposure to high doses of biliatresone caused abortion or death in pregnant mice. Neonatal mice injected with biliatresone developed clinical signs of biliary obstruction, and dysplasia or the absence of extrahepatic biliary tract lumen, which confirmed the occurrence of biliary atresia. In the portal tract of biliary atresia mice, signs of infiltration of inflammatory cells and liver fibrosis were observed. The signature of extrahepatic biliary gene expression in these mice mainly involved the cell adhesion process, and hepatic RNA-seq was highly linked to transcriptional evidence of oxidative stress. When compared with the control group, hepatic glutathione levels were markedly reduced after biliatresone injection. Taken together, these data confirm that biliatresone causes severe developmental abnormalities of the hepatobiliary system in mice. Furthermore, decreased levels of glutathione may play a mechanistic role in the pathogenesis of liver fibrosis in biliatresone-induced experimental biliary atresia.

Impaired Redox and Protein Homeostasis as Risk Factors and Therapeutic Targets in Toxin-Induced Biliary Atresia.

BACKGROUND & AIMS: Extrahepatic biliary atresia (BA) is a pediatric liver disease with no approved medical therapy. Recent studies using human samples and experimental modeling suggest that glutathione redox metabolism and heterogeneity play a role in disease pathogenesis. We sought to dissect the mechanistic basis of liver redox variation and explore how other stress responses affect cholangiocyte injury in BA. METHODS: We performed quantitative in situ hepatic glutathione redox mapping in zebrafish larvae carrying targeted mutations in glutathione metabolism genes and correlated these findings with sensitivity to the plant-derived BA-linked toxin biliatresone. We also determined whether genetic disruption of HSP90 protein quality control pathway genes implicated in human BA altered biliatresone toxicity in zebrafish and human cholangiocytes. An in vivo screening of a known drug library was performed to identify novel modifiers of cholangiocyte injury in the zebrafish experimental BA model, with subsequent validation. RESULTS: Glutathione metabolism gene mutations caused regionally distinct changes in the redox potential of cholangiocytes that differentially sensitized them to biliatresone. Disruption of human BA-implicated HSP90 pathway genes sensitized zebrafish and human cholangiocytes to biliatresone-induced injury independent of glutathione. Phosphodiesterase-5 inhibitors and other cyclic guanosine monophosphate signaling activators worked synergistically with the glutathione precursor N-acetylcysteine in preventing biliatresone-induced injury in zebrafish and human cholangiocytes. Phosphodiesterase-5 inhibitors enhanced proteasomal degradation and required intact HSP90 chaperone. CONCLUSION: Regional variation in glutathione metabolism underlies sensitivity to the biliary toxin biliatresone and may account for the reported association between BA transplant-free survival and glutathione metabolism gene expression. Human BA can be causatively linked to genetic modulation of protein quality control. Combined treatment with N-acetylcysteine and cyclic guanosine monophosphate signaling enhancers warrants further investigation as therapy for BA.

Toll-like receptor 7 agonist induces hypoplasia of the biliary system in a neonatal mouse model.

BACKGROUND/PURPOSE: Viral infections and innate immunity signaling, especially Toll-like receptor 7 (TLR7) have been implicated in the pathogenesis of biliary atresia (BA). Administration of rhesus rotavirus-type A to newborn Balb/c mice produces inflammatory obstruction of bile ducts, which resembles human BA. However, whether activation of TLR7 signaling plays a role in neonatal hepatobiliary injury remains to be investigated. METHODS: TLR7 agonist, imiquimod (R837), was intraperitoneally administered to Balb/c mice within 24 hours of birth and then every other day. Morphological and histological injuries of liver and gallbladder were examined at 2 weeks. Hepatic messenger RNA expression of TLR7 signaling was studied. Terminal deoxynucleotidyl transferase 2'-deoxyuridine 5'-triphosphate nick end labeling staining was used to delineate hepatobiliary apoptosis upon TLR7 stimulation. RESULTS: TLR7 agonist, imiquimod, induced hypoplasia of the biliary system of neonatal Balb/c mice both in atrophic gallbladder and in paucity of intrahepatic bile ducts. There was significantly higher hepatic expression of TLR7 and downstream innate immunity-mediated interferon regulatory factor 7, interferon-α, and tumor necrosis factor-α. In addition, terminal deoxynucleotidyl transferase 2'-deoxyuridine 5'-triphosphate nick end labeling-positive cells in the liver were increased after injections of TLR7 agonist. CONCLUSION: The results demonstrate that TLR7 activation may trigger innate immunity pathways and induce apoptosis and hypoplasia of neonatal biliary trees in Balb/c mice. The novel findings give an implication of pathogenesis of infantile cholestasis, such as BA.

The toxin biliatresone causes mouse extrahepatic cholangiocyte damage and fibrosis through decreased glutathione and SOX17.

UNLABELLED: Biliary atresia, the most common indication for pediatric liver transplantation, is a fibrotic disease of unknown etiology affecting the extrahepatic bile ducts of newborns. The recently described toxin biliatresone causes lumen obstruction in mouse cholangiocyte spheroids and represents a new model of biliary atresia. The goal of this study was to determine the cellular changes caused by biliatresone in mammalian cells that ultimately lead to biliary atresia and extrahepatic fibrosis. We treated mouse cholangiocytes in three-dimensional (3D) spheroid culture and neonatal extrahepatic duct explants with biliatresone and compounds that regulate glutathione (GSH). We examined the effects of biliatresone on SOX17 levels and determined the effects of Sox17 knockdown on cholangiocytes in 3D culture. We found that biliatresone caused disruption of cholangiocyte apical polarity and loss of monolayer integrity. Spheroids treated with biliatresone had increased permeability as shown by rhodamine efflux within 5 hours compared with untreated spheroids, which retained rhodamine for longer than 12 hours. Neonatal bile duct explants treated with the toxin showed lumen obstruction with increased subepithelial staining for α-smooth muscle actin and collagen, consistent with fibrosis. Biliatresone caused a rapid and transient decrease in GSH, which was both necessary and sufficient to mediate its effects in cholangiocyte spheroid and bile duct explant systems. It also caused a significant decrease in cholangiocyte levels of SOX17, and Sox17 knockdown in cholangiocyte spheroids mimicked the effects of biliatresone. CONCLUSION: Biliatresone decreases GSH and SOX17 in mouse cholangiocytes. In 3D cell systems, this leads to cholangiocyte monolayer damage and increased permeability; in extrahepatic bile duct explants, it leads to disruption of the extrahepatic biliary tree and subepithelial fibrosis. This mechanism may be important in understanding human biliary atresia. (Hepatology 2016;64:880-893).

Glutathione antioxidant pathway activity and reserve determine toxicity and specificity of the biliary toxin biliatresone in zebrafish.

UNLABELLED: Biliatresone is an electrophilic isoflavone isolated from Dysphania species plants that has been causatively linked to naturally occurring outbreaks of a biliary atresia (BA)-like disease in livestock. Biliatresone has selective toxicity for extrahepatic cholangiocytes (EHCs) in zebrafish larvae. To better understand its mechanism of toxicity, we performed transcriptional profiling of liver cells isolated from zebrafish larvae at the earliest stage of biliatresone-mediated biliary injury, with subsequent comparison of biliary and hepatocyte gene expression profiles. Transcripts encoded by genes involved in redox stress response, particularly those involved in glutathione (GSH) metabolism, were among the most prominently up-regulated in both cholangiocytes and hepatocytes of biliatresone-treated larvae. Consistent with these findings, hepatic GSH was depleted at the onset of biliary injury, and in situ mapping of the hepatic GSH redox potential using a redox-sensitive green fluorescent protein biosensor showed that it was significantly more oxidized in EHCs both before and after treatment with biliatresone. Pharmacological and genetic manipulation of GSH redox homeostasis confirmed the importance of GSH in modulating biliatresone-induced injury given that GSH depletion sensitized both EHCs and the otherwise resistant intrahepatic cholangiocytes to the toxin, whereas replenishing GSH level by N-acetylcysteine administration or activation of nuclear factor erythroid 2-like 2 (Nrf2), a transcriptional regulator of GSH synthesis, inhibited EHC injury. CONCLUSION: These findings strongly support redox stress as a critical contributing factor in biliatresone-induced cholangiocyte injury, and suggest that variations in intrinsic stress responses underlie the susceptibility profile. Insufficient antioxidant capacity of EHCs may be critical to early pathogenesis of human BA. (Hepatology 2016;64:894-907).

Development of an animal model of fibrous cholangitis in pigs.

INTRODUCTION: The aim of this study was to develop a model of fibrous cholangitis in the offspring of gravid domestic pigs through the administration of 1,4-phenylene diisothiocyanate (DITC). MATERIAL AND METHODS: Six young domestic pigs and two gravid pigs with their offspring (21 pigs) were used as experimental models and six wild-type animals were used as controls. All pigs were divided into five main groups and five subgroups, according to their developmental stage and time of exposure to DITC. The following histopathological characteristics were quantitatively evaluated on a scale of 0-5: ductal proliferation, periportal fibrosis, inflammatory infiltration, periductal fibrosis and edema, intraluminal fibrosis, duct wall thickening, epithelial apoptosis, and arterial hyperplasia/hypertrophy. RESULTS: Statistically significant differences were observed for most of the histopathological markers between the group of pigs' offspring that received DITC at early gestation and their control group. Moreover, the group of animals that were exposed to the agent at early gestation exhibited significant differences for all histopathological characteristics compared to the animals that were exposed at late gestation. On the other hand, no statistically significant differences were observed between the group of animals that received the agent at late gestation and their healthy controls. CONCLUSIONS: Administration of DITC to domestic pigs in early pregnancy may induce histopathological patterns of fibrous cholangitis to their offspring imitating biliary atresia. This model may provide insight to the pathogenesis of the obstructive cholangitis in pigs.

Intrahepatic biliary ablation with pure ethanol: an experimental model of biliary atresia.

PURPOSE: We describe a new rat model of biliary atresia, induced by biliary ablation with pure ethanol. METHODS: A catheter was inserted and fixed in the common bile duct of male rats. Saline or pure ethanol was injected through the catheter and the animals were monitored for 8 weeks thereafter. We measured total bilirubin (T-Bil), aspartate aminotransferase (AST), alanine transaminase (ALT), and hyaluronic acid (HA) and examined liver biopsy specimens immunohistochemically for α-smooth muscle actin staining (α-SMA) and transforming growth factor-ß1 (TGF-ß1). RESULTS: The ethanol injection group animals were further divided into a temporary and a persistent liver dysfunction group. In the persistent group, T-Bil, AST, ALT and HA levels were significantly higher after 8 weeks in the persistent group than in the control group and the temporary group. In the ethanol injection group, α-SMA expression was prominent in the surrounding proliferative bile ducts and portal areas. The distribution of TGF-ß1 was found prominently in hepatocytes in the center of nodules and in ductular epithelial cells. CONCLUSIONS: This study characterizes the effects of ethanol-induced bile duct injury in rats, resulting in sclerosing cholangitis and its secondary effects. We believe that this experimental model will prove useful in the study of biliary atresia.

Gastrointestinal malformations in two infants born to women with hyperthyroidism untreated in the first trimester.

We report two infants with gastrointestinal anomalies: one with esophageal atresia and tracheo-esophageal fistula and the other with biliary tree atresia, born to hyperthyroid women diagnosed and treated with methimazole after 14 weeks' gestation. Euthyroidism was documented in both infants. These cases raise the issue of whether untreated hyperthyroidism and not methimazole intake is the teratogen.

[Paucity of interlobular bile ducts in twins and maternal abuse of psychopharmaceuticals during pregnancy]. / Paucità delle vie biliari interlobulari in due gemelli ed assunzione materna di psicofarmaci in gravidanza.

We report the case of twins with intrahepatic cholestasis in "paucity of interlobular bile ducts". Both the children presented an associated cardiac defect even if dissimilar and a transient tubulopathy. Despite the presence of these alterations we suppose that these cases can be included among the group of rare nonsyndromic paucity of interlobular bile ducts. The different extent of the pathology in the two patients suggest a toxic etiology which could have struck more severely the twin who were less protected by the utero-placental barrier. In the literature reports we found some cases of extrahepatic biliary atresia related with maternal amphetamine addiction, but no cases of intrahepatic atresia. As during pregnancy the mother had abused of a number of drugs and in particular of amphetamine, we suppose that the amphetamine addiction can account for the hepatic pathology.