Project description:Polycystic liver disease (PLD) is a group of genetic disorders characterized by bile duct dilatation and/or progressive development of multiple intrahepatic fluid-filled biliary cysts (>10), which are the main cause of morbidity. Current surgical and/or pharmacological therapies exert short-term and modest benefits, and thus liver transplantation represents the only curative option. Recently, novel PLD-causative genes, encoding for endoplasmic reticulum (ER)-resident proteins involved in protein biogenesis and transport, were identified. Here, we hypothesized that aberrant proteostasis contributes to PLD pathogenesis, representing a potential therapeutic target. In this regard, ER stress was assessed at transcriptional (qPCR), proteomic (mass spectrometry), morphological (transmission electron microscopy; TEM) and functional (20S proteasome activity) levels in different models of PLD (i.e., human and rat). Moreover, PCK rat (animal model of PLD) was employed to determine the effects of ER stress inhibitors [4-phenylbutyric acid (4-PBA)] and/or inducers [tunicamycin (TM)] in hepatic cytogenesis and, consequently, in the progression of the disease. Likewise, the impact of the aforementioned ER stress modulators was also analyzed on the expression of unfolded protein response (UPR) factors, the 20S proteasome activity, the mechanisms involved in the maintenance of ER proteostasis and the cell fate decisions (i.e., survival/apoptosis). Interestingly, the expression levels of the UPR factors were markedly upregulated in liver tissue from PLD patients and PCK rats, as well as in primary cultures of human and rat cystic cholangiocytes, compared to normal controls. Additionally, cystic cholangiocytes showed altered proteomic profiles, mainly related to proteostasis (i.e., synthesis, folding, trafficking and degradation of nascent proteins), marked enlargement of the ER lumen (by TEM), and hyperactivation of the 20S proteasome. Notably, chronic treatment of PCK rats with 4-PBA decreased liver weight, as well as both liver and cystic volumes, of animals under baseline or TM administration compared to control groups. In vitro, 4-PBA downregulated the expression (mRNA) of UPR effectors, normalized, at least in part, proteomic profiles related to protein synthesis, folding, trafficking and degradation, and reduced the proteasome hyperactivity in cystic cholangiocytes, reducing their hyperproliferation and apoptosis. Conclusion: Restoration of proteostasis in cystic cholangiocytes with 4-PBA halts hepatic cystogenesis, emerging as a novel and promising therapeutic strategy.

Project description:Background & Aims: Rapid induction of beta-PDGF receptor (beta-PDGFR) is a core feature of hepatic stellate cell activation, the hallmark of liver fibrogenesis. However, biological consequences of the induction are not well characterized. We aimed to determine the involvement of beta-PDGFR-mediated molecular pathway activation on hepatic stellate cells in liver injury, fibrogenesis, and carcinogenesis in vivo. Methods: Loss and constitutive activation of beta-PDGFR were assessed in mouse models with either a stellate cell-specific beta-PDGFR knockout or the expression of an autoactivating mutation respectively. Liver injury and fibrosis were induced in two mechanistically distinct models: carbontetrachloride (CCl4) treatment and ligation of the common bile duct. Hepatocarcinogenesis with underlying liver injury/fibrosis was assessed by a single dose of diethylnitrosamine (DEN) followed by repeated injections of CCl4. Genome-wide expression profiling was performed isolated stellate cells from these models to determine deregulated pathways. Results: Depletion of beta-PDGFR in hepatic stellate cells led to decreased histological liver injury, serum transaminases, collagen alpha 1(I) and alpha smooth muscle actin expression, and collagen deposition. Stellate cell proliferation was significantly reduced after acute hepatic injury in vivo. In contrast, autoactivation of beta-PDGFR in stellate cells accelerated liver fibrosis, most prominently after 6 weeks of CCl4 induced injury. There was no difference in development of DEN-induced pre-neoplastic loci according to the status of beta-PDGFR. Conclusions: Depletion of beta-PDGFR in hepatic stellate cells attenuated the development of liver injury, fibrosis, and stellate cell proliferation in multiple animal models, whereas the constitutive activation of beta-PDGFR enhanced fibrosis. However, manipulation of beta-PDGFR alone did not reduce development of dysplastic nodules. These findings indicate that titration of receptor beta-PDGFR expression on stellate cells parallels fibrosis and injury, but may not impact the development of hepatic neoplasia alone. Hepatic stellate cells were isolated from liver of beta-PDGFR-wild-type or knockout mice, and treated with beta-PDGF ligand or vehicle control.

Project description:Background & Aims: Rapid induction of beta-PDGF receptor (beta-PDGFR) is a core feature of hepatic stellate cell activation, the hallmark of liver fibrogenesis. However, biological consequences of the induction are not well characterized. We aimed to determine the involvement of beta-PDGFR-mediated molecular pathway activation on hepatic stellate cells in liver injury, fibrogenesis, and carcinogenesis in vivo. Methods: Loss and constitutive activation of beta-PDGFR were assessed in mouse models with either a stellate cell-specific beta-PDGFR knockout or the expression of an autoactivating mutation respectively. Liver injury and fibrosis were induced in two mechanistically distinct models: carbontetrachloride (CCl4) treatment and ligation of the common bile duct. Hepatocarcinogenesis with underlying liver injury/fibrosis was assessed by a single dose of diethylnitrosamine (DEN) followed by repeated injections of CCl4. Genome-wide expression profiling was performed isolated stellate cells from these models to determine deregulated pathways. Results: Depletion of beta-PDGFR in hepatic stellate cells led to decreased histological liver injury, serum transaminases, collagen alpha 1(I) and alpha smooth muscle actin expression, and collagen deposition. Stellate cell proliferation was significantly reduced after acute hepatic injury in vivo. In contrast, autoactivation of beta-PDGFR in stellate cells accelerated liver fibrosis, most prominently after 6 weeks of CCl4 induced injury. There was no difference in development of DEN-induced pre-neoplastic loci according to the status of beta-PDGFR. Conclusions: Depletion of beta-PDGFR in hepatic stellate cells attenuated the development of liver injury, fibrosis, and stellate cell proliferation in multiple animal models, whereas the constitutive activation of beta-PDGFR enhanced fibrosis. However, manipulation of beta-PDGFR alone did not reduce development of dysplastic nodules. These findings indicate that titration of receptor beta-PDGFR expression on stellate cells parallels fibrosis and injury, but may not impact the development of hepatic neoplasia alone.

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Comparative hepatic transcriptome analyses revealed possible pathogenic mechanisms of fasiglifam (TAK-875)-induced acute liver injury in mice

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