title: PNPLA3 overexpression results in reduction of proteins predisposing to fibrosis.
abstract: Liver fibrosis is a pathological scarring response to chronic hepatocellular injury and hepatic stellate cells (HSCs) are key players in this process. PNPLA3 I148M is a common variant robustly associated with liver fibrosis but the mechanisms underlying this association are unknown. We aimed to examine a) the effect of fibrogenic and proliferative stimuli on PNPLA3 levels in HSCs and b) the role of wild type and mutant PNPLA3 overexpression on markers of HSC activation and fibrosis.Here, we show that PNPLA3 is upregulated by the fibrogenic cytokine transforming growth factor-beta (TGF-β), but not by platelet-derived growth factor (PDGF), and is involved in the TGF-β-induced reduction in lipid droplets in primary human HSCs. Furthermore, we show that retinol release from human HSCs ex vivo is lower in cells with the loss-of-function PNPLA3 148M compared with 148I wild type protein. Stable overexpression of PNPLA3 148I wild type, but not 148M mutant, in human HSCs (LX-2 cells) induces a reduction in the secretion of matrix metallopeptidase 2 (MMP2), tissue inhibitor of metalloproteinase 1 and 2 (TIMP1 and TIMP2), which is mediated by retinoid metabolism. In conclusion, we show a role for PNPLA3 in HSC activation in response to fibrogenic stimuli. Moreover, we provide evidence to indicate that PNPLA3-mediated retinol release may protect against liver fibrosis by inducing a specific signature of proteins involved in extracellular matrix remodelling.
authors.affiliation: Department of Molecular and Clinical Medicine, University of Gothenburg, Sweden.
authors.forename: Piero
authors.initials: P
authors.lastname: Pingitore
authors.affiliation: Internal Medicine, Fondazione IRCCS Ca' Granda Ospedale Policlinico Milano, Milan, Italy.
authors.forename: Paola
authors.initials: P
authors.lastname: Dongiovanni
authors.affiliation: Department of Molecular and Clinical Medicine, University of Gothenburg, Sweden.
authors.forename: Benedetta Maria
authors.initials: BM
authors.lastname: Motta
authors.affiliation: Department of Pathophysiology and Transplantation, Università degli Studi di Milano, Milan, Italy.
authors.forename: Marica
authors.initials: M
authors.lastname: Meroni
authors.affiliation: Clinical Nutrition Unit, Department of Medical and Surgical Sciences, Magna Graecia University, Catanzaro, Italy.
authors.forename: Saverio Massimo
authors.initials: SM
authors.lastname: Lepore
authors.affiliation: Department of Molecular and Clinical Medicine, University of Gothenburg, Sweden.
authors.forename: Rosellina Margherita
authors.initials: RM
authors.lastname: Mancina
authors.affiliation: Internal Medicine, Fondazione IRCCS Ca' Granda Ospedale Policlinico Milano, Milan, Italy.
authors.forename: Serena
authors.initials: S
authors.lastname: Pelusi
authors.affiliation: Clinical Nutrition Unit, Department of Medical and Surgical Sciences, Magna Graecia University, Catanzaro, Italy.
authors.forename: Cristina
authors.initials: C
authors.lastname: Russo
authors.affiliation: Department of Molecular and Clinical Medicine, University of Gothenburg, Sweden.
authors.forename: Andrea
authors.initials: A
authors.lastname: Caddeo
authors.affiliation: Department of Pathophysiology and Transplantation, Università degli Studi di Milano, Milan, Italy.|Liver Surgery and Transplant Unit, Fondazione IRCCS Ca' Granda Ospedale Policlinico Milano, Milan, Italy.
authors.forename: Giorgio
authors.initials: G
authors.lastname: Rossi
authors.affiliation: Clinical Nutrition Unit, Department of Medical and Surgical Sciences, Magna Graecia University, Catanzaro, Italy.
authors.forename: Tiziana
authors.initials: T
authors.lastname: Montalcini
authors.affiliation: Clinical Nutrition Unit, Department of Medical and Surgical Sciences, Magna Graecia University, Catanzaro, Italy.
authors.forename: Arturo
authors.initials: A
authors.lastname: Pujia
authors.affiliation: Department of Molecular and Clinical Medicine, University of Gothenburg, Sweden.|Cardiology Department, Sahlgrenska University Hospital, Gothenburg, Sweden.
authors.forename: Olov
authors.initials: O
authors.lastname: Wiklund
authors.affiliation: Internal Medicine, Fondazione IRCCS Ca' Granda Ospedale Policlinico Milano, Milan, Italy.|Department of Pathophysiology and Transplantation, Università degli Studi di Milano, Milan, Italy.
authors.forename: Luca
authors.initials: L
authors.lastname: Valenti
authors.affiliation: Department of Molecular and Clinical Medicine, University of Gothenburg, Sweden.|Clinical Nutrition Unit, Department of Medical and Surgical Sciences, Magna Graecia University, Catanzaro, Italy.|Cardiology Department, Sahlgrenska University Hospital, Gothenburg, Sweden.
authors.forename: Stefano
authors.initials: S
authors.lastname: Romeo
mesh_terms: D005786:Gene Expression Regulation / Q000235:genetics; D005838:Genotype; D055166:Hepatic Stellate Cells / Q000378:metabolism* / Q000473:pathology; D006801:Humans; D008049:Lipase / Q000096:biosynthesis / Q000235:genetics*; D050356:Lipid Metabolism / Q000235:genetics*; D008103:Liver Cirrhosis / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D020778:Matrix Metalloproteinase 2 / Q000096:biosynthesis; D008565:Membrane Proteins / Q000096:biosynthesis / Q000235:genetics*; D010982:Platelet-Derived Growth Factor / Q000235:genetics / Q000378:metabolism; D061251:Primary Cell Culture; D019715:Tissue Inhibitor of Metalloproteinase-1 / Q000096:biosynthesis; D019716:Tissue Inhibitor of Metalloproteinase-2 / Q000096:biosynthesis; D016212:Transforming Growth Factor beta / Q000235:genetics / Q000378:metabolism; D014801:Vitamin A / Q000008:administration & dosage* / Q000378:metabolism; D000217:Acyltransferases; D054512:Phospholipases A2, Calcium-Independent
chemical_list: D008049:Lipase; D020778:Matrix Metalloproteinase 2; D008565:Membrane Proteins; D010982:Platelet-Derived Growth Factor; D019715:Tissue Inhibitor of Metalloproteinase-1; D019716:Tissue Inhibitor of Metalloproteinase-2; D016212:Transforming Growth Factor beta; D014801:Vitamin A; C560822:TIMP1 protein, human; C560823:TIMP2 protein, human; C075278:platelet-derived growth factor A; C533682:PNPLA3 protein, human; D000217:Acyltransferases; D054512:Phospholipases A2, Calcium-Independent; C522361:MMP2 protein, human