Early Preview of Basic Science Review: Biliatresone

Generally, one of the best lectures at our national meeting is the “Basic Science Year in Review.”  I would be surprised if a recent study (O Waisbourd-Zinman et al. Hepatology 2016; 64: 880-93) does not get some attention during this review.

Even though biliary atresia (BA) remains the leading cause of pediatric liver transplantation, the exact reasons for its development have not been elucidated.  There are data “implicating both immune dysregulation and genetic factors in human BA.  Toxin-induced BA is not inconsistent with these findings and may represent a primary injury, with immune dysregulation representing a secondary insult.”

One of the reasons for suspecting a toxin dates back to outbreaks of a BA-like disease in newborn lambs that occurred in New South Wales in 1964 and 1988. During both these periods, severe droughts led to pregnant livestock grazing on atypical flora.  Ultimately, a plant toxin termed “biliatresone” was isolated from Australian plants (Dysphania species).

Here’s how this study advanced the science on biliatresone:

  • The authors treated mouse cholangiocytes in 3D spheroid culture and neonatal extrahepatic duct exlplants with biliatresone and compounds that regluate glutathione (GSH)
  • The authors determined the effects of biliatresone on SOX17 levels and the effects of Sox17 knockdown on cholangiocytes in 3D culture

Key findings:

  • “Biliatresoe caused disrupton of cholangiocyte apical polarity and loss of monolayer integrity.”
  • “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…and caused a significant decrease in cholangiocyte SOX17, and Sox17 knockdown in cholangiocyte spheroids mimicked the effects of biliatresone.”
  • These findings are easiest to appreciate in their figures, particularly Figure 4 and 5.

While pregnant women are not likely exposed to biliatresone, the authors showed that the effects of the toxin on lowering GSH was sufficient for cholangiocyte injury.; in addition, they showed that “SOX17 is required to maintain the epithelial architecture of the gallbladder and the cystic duct.”  Thus, there are likely other exposures that could lead to similar outcomes

My take: I will let Dr. Barnard explain the elegant experiments.  This study strongly supports maternal dietary factors as a contributing role in the pathophysiology of BA.  Now identifying these teratogens is crucial.

Also noted: X Zhao et al. Hepatology 2016; 64: 894-907. This study “strongly support redox stress as a critical contributing factor in biliatresone-induced cholangioctye injury” in Zebrafish.  Specifically, the authors identified that gene transcripts involved in redox stress, particularly regarding glutathione were upregulated after exposure to biliatresone.

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