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

Abstract

BACKGROUND and AIMS: Extra-hepatic 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 screen 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 (PDE5i) and other cGMP signaling activators worked synergistically with the glutathione precursor Nacetylcysteine (NAC) in preventing biliatresone-induced injury in zebrafish and human cholangiocytes. PDE5i enhanced proteasomal degradation and required intact HSP90 chaperone. CONCLUSION: Regional variation in glutathione metabolism underlies sensitivity to the biliary toxin biliatresone, and mirrors recently reported BA risk stratification linked to glutathione metabolism gene expression. Human BA can be causatively linked to genetic

HIF-1alpha-pathway activation in cholangiocytes of patients with biliary atresia: An immunohistochemical/molecular exploratory study

“…A limitation of this study was the small sample size, which precluded confirmative statistical evidence for two of our hypotheses: first, the existence of a correlation between HIF-nuclear positivity in cholangiocytes and decreased early native liver survival; and second, that reduced native liver survival might have resulted from the loss of the protective role of GSR against oxidative stress, as observed in an experimental model of BA [60]. However, given the small size of the sample, for both these correlations we were only able to detect a trend for statistical significance (SDC2 Table 5…”

The HSP90 inhibitor 17‐DMAG alleviates primary biliary cholangitis via cholangiocyte necroptosis prevention

“…22,23 The inhibition of HSP90 can also prevent LPS-induced liver injury by decreasing proinflammatory cytokines in mice. 24 Besides, HSP90 might be involved in the injury of cholangiocytes in patients with biliary atresia 25 and is a potential biomarker for the diagnosis of biliary atresia. 26 In this study, we found that a high expression of HSP90 could mediate cholangiocyte necroptosis.…”

Biliary Atresia: A Complex Hepatobiliary Disease with Variable Gene Involvement, Diagnostic Procedures, and Prognosis

“…In fact, it seems to be multifactorial. Other than a viral involvement with sporadic cases including reovirus, rotavirus, Epstein-Barr virus, and cytomegalovirus, a decreased Treg subset of the CD4 positive T lymphocytes [ 70 , 71 ], environmental factors, such as biliatresone [ 59 , 72 , 73 , 74 , 75 ], and ADP-ribosylation factor 6 (ARF6) have been actively investigated [ 76 ].…”