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Proteostasis disturbances and endoplasmic reticulum stress contribute to polycystic liver disease: New therapeutic targets.

ABSTRACT: BACKGROUND & AIMS:Polycystic liver diseases (PLDs) are genetic disorders characterized by progressive development of multiple biliary cysts. Recently, novel PLD-causative genes, encoding for endoplasmic reticulum (ER)-resident proteins involved in protein biogenesis and transport, were identified. We hypothesized that aberrant proteostasis contributes to PLD pathogenesis, representing a potential therapeutic target. METHODS:ER stress was analysed at transcriptional (qPCR), proteomic (mass spectrometry), morphological (transmission electron microscopy, TEM) and functional (proteasome activity) levels in different PLD models. The effect of ER stress inhibitors [4-phenylbutyric acid (4-PBA)] and/or activators [tunicamycin (TM)] was tested in polycystic (PCK) rats and cystic cholangiocytes in vitro. RESULTS:The expression levels of unfolded protein response (UPR) components were 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. Cystic cholangiocytes showed altered proteomic profiles, mainly related to proteostasis (ie synthesis, folding, trafficking and degradation of proteins), marked enlargement of the ER lumen (by TEM) and hyperactivation of the 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 conditions or after TM administration compared to controls. In vitro, 4-PBA downregulated the expression (mRNA) of UPR effectors, normalized proteomic profiles related to protein synthesis, folding, trafficking and degradation and reduced the proteasome hyperactivity in cystic cholangiocytes, reducing their hyperproliferation and apoptosis. CONCLUSIONS:Restoration of proteostasis in cystic cholangiocytes with 4-PBA halts hepatic cystogenesis, emerging as a novel therapeutic strategy.

SUBMITTER: Santos-Laso A

PROVIDER: S-EPMC7370945 | biostudies-literature | 2020 Jul

REPOSITORIES: biostudies-literature

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Proteostasis disturbances and endoplasmic reticulum stress contribute to polycystic liver disease: New therapeutic targets.

Santos-Laso Alvaro A Izquierdo-Sanchez Laura L Rodrigues Pedro M PM Huang Bing Q BQ Azkargorta Mikel M Lapitz Ainhoa A Munoz-Garrido Patricia P Arbelaiz Ander A Caballero-Camino Francisco J FJ Fernández-Barrena Maite G MG Jimenez-Agüero Raul R Argemi Josepmaria J Aragon Tomas T Elortza Felix F Marzioni Marco M Drenth Joost P H JPH LaRusso Nicholas F NF Bujanda Luis L Perugorria Maria J MJ Banales Jesus M JM

Liver international : official journal of the International Association for the Study of the Liver 20200506 7

<h4>Background & aims</h4>Polycystic liver diseases (PLDs) are genetic disorders characterized by progressive development of multiple biliary cysts. Recently, novel PLD-causative genes, encoding for endoplasmic reticulum (ER)-resident proteins involved in protein biogenesis and transport, were identified. We hypothesized that aberrant proteostasis contributes to PLD pathogenesis, representing a potential therapeutic target.<h4>Methods</h4>ER stress was analysed at transcriptional (qPCR), proteom ...[more]

PMID: 32378324

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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.

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Proteostasis disturbances and endoplasmic reticulum stress contribute to polycystic liver disease: New therapeutic targets.

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Proteostasis disturbances and endoplasmic reticulum stress contribute to polycystic liver disease: New therapeutic targets.

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