Biology subjects

Kriegermeier, A.

Publications and source records attributed to Kriegermeier, A..

3 recordsLinked to original sources

bioRxiv2022

The inositol-requiring enzyme 1α/X-box protein 1 (IRE1α/XBP1) pathway of the unfolded protein response is impaired in pediatric cholestatic liver disease explants

Background/AimsCholestatic liver diseases (CLD) are the leading indication for pediatric liver transplantation. Increased intrahepatic bile acid concentrations cause endoplasmic reticulum (ER) stress and the unfolded protein response (UPR) is activated to maintain homeostasis. UPR dysregulation, including the inositol-requiring enzyme 1/X-box protein 1 (IRE1/XBP1) pathway, is associated with several adult liver diseases. We evaluated hepatic UPR expression in pediatric patients with end-stage CLD and hypothesize that an inability to appropriately activate the hepatic IRE1/XBP1 pathway is associated with the pathogenesis of CLD. MethodsWe evaluated 34 human liver explants. Cohorts included: pediatric CLD (Alagille, ALGS, and progressive familial intrahepatic cholestasis, PFIC), pediatric non-cholestatic liver disease controls (autoimmune hepatitis, AIH), adult CLD, and normal controls. We performed RNA-seq, quantitative PCR, and western blotting to measure expression differences of the hepatic UPR and other signaling pathways. ResultsMetascape pathway analysis demonstrated that the KEGG protein processing in ER pathway was downregulated in pediatric CLD compared to normal controls. Pediatric CLD had decreased hepatic IRE1/XBP1 pathway gene expression and decreased protein expression of p-IRE1 compared to normal controls. These CLD changes were not disease-specific to ALGS or PFIC. IRE1/XBP1 pathway gene expression was decreased in pediatric CLD compared to AIH disease controls. ConclusionPediatric CLD explants have decreased gene and protein expression of the protective IRE1/XBP1 pathway and down-regulated KEGG protein processing in the ER pathways. IRE1/XBP1 pathway expression differences occur when compared to both normal and non-cholestatic disease controls. Attenuated expression of the IRE1/XBP1 pathway is associated with cholestatic diseases and could be targeted to treat pediatric CLD.

cell biology↗

bioRxiv2022

Hepatic Deletion of X-box Binding Protein 1 in Farnesoid X Receptor Null Mice Leads to Enhanced Liver Injury

Background & AimsFarnesoid X receptor (FXR) regulates bile acid metabolism and FXR null (Fxr-/-) mice have elevated bile acid levels and progressive liver injury. The inositol-requiring enzyme 1 (IRE1)/X-box binding protein 1 (XBP1) pathway is a protective pathway of the unfolded protein response (UPR) that is activated in response to ER stress. In this study we sought to determine the role of the UPR in Fxr-/- mice. Approach & ResultsWe examined hepatic UPR gene and protein expression in 10- and 24-week-old wild type (WT) and Fxr-/- mice. Hepatic XBP1 and other UPR pathways were activated in 24-week-old Fxr-/- mice, but not WT mice. To further determine the role of the liver UPR activation in Fxr-/- mice, we generated mice with FXR and liver-specific XBP1 double knockout (DKO, Fxr-/-Xbp1LKO) and Fxr-/- Xbp1fl/fl single knockout (SKO) mice and characterized their phenotypes at different ages. DKO mice demonstrated enhanced liver injury, apoptosis and fibrosis compared with SKO mice. RNA-seq revealed increased gene expression in apoptosis, inflammation and cell proliferation pathways in DKO mice. The proapoptotic C/EBP-homologous protein (CHOP) pathway was activated in DKO mice. At age 60 weeks, all DKO mice and no SKO mice spontaneously developed liver tumors. ConclusionsThe hepatic XBP1 pathway is activated in older Fxr-/- mice and has a protective role. The potential interaction between XBP1 and FXR signaling may be important in modulating the hepatocellular cholestatic stress responses.

molecular biology↗

bioRxiv2019

Coordinated development of the mouse extrahepatic bile duct: implications for neonatal susceptibility to biliary injury

Background & AimsThe extrahepatic bile duct is the primary tissue initially affected by the cholangiopathy biliary atresia. Biliary atresia affects neonates exclusively and current animal models suggest that the developing bile duct is uniquely susceptible to damage. In this study, we aimed to define the anatomical and functional differences between the neonatal and adult mouse extrahepatic bile ducts.\n\nMethodsWe studied mouse passaged cholangiocytes, mouse BALB/c neonatal and adult primary cholangiocytes and isolated extrahepatic bile ducts, and a collagen reporter mouse. Methods included transmission electron microscopy, lectin staining, immunostaining, rhodamine uptake assays, bile acid toxicity assays, and in vitro modeling of the matrix.\n\nResultsThe cholangiocyte monolayer of the neonatal extrahepatic bile duct was immature, lacking the uniform apical glycocalyx and mature cell-cell junctions typical of adult cholangiocytes. Functional studies showed that the glycocalyx protected against bile acid injury and that neonatal cholangiocyte monolayers were more permeable than adult monolayers. In adult ducts, the submucosal space was filled with collagen I, elastin, hyaluronic acid, and proteoglycans. In contrast, the neonatal submucosa had little collagen I and elastin, although both increased rapidly after birth. In vitro modeling suggested that the composition of the neonatal submucosa relative to the adult submucosa led to increased diffusion of bile. A Col-GFP reporter mouse showed that cells in the neonatal but not adult submucosa were actively producing collagen.\n\nConclusionWe identified four key differences between the neonatal and adult extrahepatic bile duct. We showed that these features may have functional implications, suggesting the neonatal extrahepatic bile ducts are particularly susceptible to injury and fibrosis.\n\nLay SummaryBiliary atresia is a disease that affects newborns and is characterized by extrahepatic bile duct injury and obstruction with resulting liver injury. We identify four key differences between the epithelial and submucosal layers of the neonatal and adult extrahepatic bile duct and show that these may render the neonatal duct particularly susceptible to injury.\n\nHighlightsO_LIThe apical glycocalyx is thin and patchy in neonatal compared to adult cholangiocytes\nC_LIO_LINeonatal cholangiocytes have immature cell-cell junctions and increased permeability\nC_LIO_LIThe neonatal submucosal space has minimal collagen I or elastin\nC_LIO_LIThe neonatal submucosal space contains many actively collagen-secreting cells\nC_LI\n\nGraphical abstract\n\nO_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=95 SRC=\"FIGDIR/small/576256_ufig1.gif\" ALT=\"Figure 1\">\nView larger version (27K):\norg.highwire.dtl.DTLVardef@1685e52org.highwire.dtl.DTLVardef@1086478org.highwire.dtl.DTLVardef@1fc3f55org.highwire.dtl.DTLVardef@1a20a5f_HPS_FORMAT_FIGEXP M_FIG C_FIG

physiology↗