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.

HDR syndrome in a Japanese girl with biliary atresia: a case report.

BACKGROUND: Hypoparathyroidism, sensorineural deafness, and renal dysplasia (HDR) syndrome is an autosomal dominant disorder. We report the first detailed case of hypoparathyroidism complicated by biliary atresia. CASE PRESENTATION: A 1-year-old Japanese girl was admitted to our hospital for living donor liver transplantation. She suffered from obstructive jaundice owing to biliary atresia. She also had persistent hypocalcemia. Despite oral calcium and abundant vitamin D supplementation, a laboratory test showed hypocalcemia (1.4 mmol/l) and hyperphosphatemia (2.6 mmol/l). The intact parathyroid hormone level was normal (66 ng/l) with severe vitamin D deficiency (25-hydroxy vitamin D: undetectable levels). There were no rachitic changes in metaphysis on X-rays. Her family history showed that her mother had sensorineural deafness, a low serum calcium level (2.1 mmol/l), hypoplastic left kidney, and a past history of an operation for right vesicoureteral reflux. We suspected that this patient and her mother have hypoparathyroidism, sensorineural deafness, and renal dysplasia syndrome. A heterozygous GATA3 gene mutation (c.736delGinsAT) was found in this patient and her mother, but not in her father. CONCLUSION: This familial case confirms the importance of family history in the diagnosis of HDR syndrome. Regardless of marked vitamin D deficiency, the complication of hypoparathyroidism prevented the onset of vitamin D deficiency rickets in our patient.

Liver hepcidin and stainable iron expression in biliary atresia.

Hepcidin is a proposed mammalian host defense peptide that was identified on the basis of its antimicrobial activity, but it was later shown to be a crucial regulator of iron homeostasis and a mediator of the anemia of chronic inflammation. Hepcidin and stainable iron expression in biliary atresia (BA) were investigated in this study. Fresh liver tissues were obtained from 10 patients in the early stage of BA when they underwent Kasai's procedure, 9 in the late stage of BA when they received liver transplantation and 5 controls receiving liver resection for benign lesions other than cholestasis or fibrosis. Real-time quantitative reverse-transcription PCR (QRT-PCR), immunohistochemical staining and ELISA were performed to gauge hepcidin mRNA and protein expression in liver and plasma. Archival liver specimens from patients in the early and late stages of BA were treated with Perls' acid ferrocyanide technique for hepatic stainable iron. The results demonstrated that liver hepcidin mRNA expression was 100-fold lower in late-stage BA than in the early stage by QRT-PCR. Significantly weaker liver hepcidin immunostaining and lower plasma hepcidin levels were found in late-stage BA than in the early stage. There was also significantly lower stainable iron in the liver of late-stage BA. The major site of stainable iron was in Kupffer cells. The results support a role for hepcidin as a key regulator of mammalian iron metabolism and chronic inflammation, whose expression correlates with the degree of stainable iron in BA.