title: Cellular cholesterol accumulation modulates high fat high sucrose (HFHS) diet-induced ER stress and hepatic inflammasome activation in the development of non-alcoholic steatohepatitis.
abstract: Non-alcoholic steatohepatitis (NASH), is the form of non-alcoholic fatty liver disease posing risk to progress into serious long term complications. Human and pre-clinical models implicate cellular cholesterol dysregulation playing important role in its development. Mouse model studies suggest synergism between dietary cholesterol and fat in contributing to NASH but the mechanisms remain poorly understood. Our laboratory previously reported the primary importance of hepatic endoplasmic reticulum cholesterol (ER-Chol) in regulating hepatic ER stress by comparing the responses of wild type, Ldlr-/-xLcat+/+ and Ldlr-/-xLcat-/- mice, to a 2% high cholesterol diet (HCD). Here we further investigated the roles of ER-Chol and ER stress in HFHS diet-induced NASH using the same strains. With HFHS diet feeding, both WT and Ldlr-/-xLcat+/+ accumulate ER-Chol in association with ER stress and inflammasome activation but the Ldlr-/-xLcat-/- mice are protected. By contrast, all three strains accumulate cholesterol crystal, in correlation with ER-Chol, albeit less so in Ldlr-/-xLcat-/- mice. By comparison, HCD feeding per se (i) is sufficient to promote steatosis and activate inflammasomes, and (ii) results in dramatic accumulation of cholesterol crystal which is linked to inflammasome activation in Ldlr-/-xLcat-/- mice, independent of ER-Chol. Our data suggest that both dietary fat and cholesterol each independently promote steatosis, cholesterol crystal accumulation and inflammasome activation through distinct but complementary pathways. In vitro studies using palmitate-induced hepatic steatosis in HepG2 cells confirm the key roles by cellular cholesterol in the induction of steatosis and inflammasome activations. These novel findings provide opportunities for exploring a cellular cholesterol-focused strategy for treatment of NASH.
authors.affiliation: Keenan Research Centre, Li Ka Shing Knowledge Institute, Department of Medicine, St Michael's Hospital, Toronto, Canada; Department of Physiology, Faculty of Medicine, University of Toronto, Toronto, Canada.
authors.forename: Amir
authors.initials: A
authors.lastname: Bashiri
authors.affiliation: Keenan Research Centre, Li Ka Shing Knowledge Institute, Department of Medicine, St Michael's Hospital, Toronto, Canada.
authors.forename: Dinushan
authors.initials: D
authors.lastname: Nesan
authors.affiliation: Keenan Research Centre, Li Ka Shing Knowledge Institute, Department of Medicine, St Michael's Hospital, Toronto, Canada.
authors.forename: Ghazaleh
authors.initials: G
authors.lastname: Tavallaee
authors.affiliation: Keenan Research Centre, Li Ka Shing Knowledge Institute, Department of Medicine, St Michael's Hospital, Toronto, Canada.
authors.forename: Ian
authors.initials: I
authors.lastname: Sue-Chue-Lam
authors.affiliation: Keenan Research Centre, Li Ka Shing Knowledge Institute, Department of Medicine, St Michael's Hospital, Toronto, Canada.
authors.forename: Kevin
authors.initials: K
authors.lastname: Chien
authors.affiliation: Keenan Research Centre, Li Ka Shing Knowledge Institute, Department of Medicine, St Michael's Hospital, Toronto, Canada.
authors.forename: Graham F
authors.initials: GF
authors.lastname: Maguire
authors.affiliation: Molecular Structure and Function Program, Research Institute, The Hospital for Sick Children, Toronto, Ontario, Canada.
authors.forename: Mark
authors.initials: M
authors.lastname: Naples
authors.affiliation: Molecular Structure and Function Program, Research Institute, The Hospital for Sick Children, Toronto, Ontario, Canada.
authors.forename: Jing
authors.initials: J
authors.lastname: Zhang
authors.affiliation: Faculty of Pharmacy, University of Toronto, Toronto, Canada.
authors.forename: Lilia
authors.initials: L
authors.lastname: Magomedova
authors.affiliation: Molecular Structure and Function Program, Research Institute, The Hospital for Sick Children, Toronto, Ontario, Canada.
authors.forename: Khosrow
authors.initials: K
authors.lastname: Adeli
authors.affiliation: Faculty of Pharmacy, University of Toronto, Toronto, Canada.
authors.forename: Carolyn L
authors.initials: CL
authors.lastname: Cummins
authors.affiliation: Keenan Research Centre, Li Ka Shing Knowledge Institute, Department of Medicine, St Michael's Hospital, Toronto, Canada; Department of Physiology, Faculty of Medicine, University of Toronto, Toronto, Canada; Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, Canada. Electronic address: ngd@smh.ca.
authors.forename: Dominic S
authors.initials: DS
authors.lastname: Ng
mesh_terms: D000818:Animals; D002791:Cholesterol, Dietary / Q000009:adverse effects / Q000378:metabolism*; D059305:Diet, High-Fat / Q000009:adverse effects; D004195:Disease Models, Animal; D059865:Endoplasmic Reticulum Stress / Q000187:drug effects* / Q000235:genetics; D005260:Female; D005786:Gene Expression Regulation; D056945:Hep G2 Cells; D006801:Humans; D058847:Inflammasomes / Q000187:drug effects / Q000378:metabolism; D007863:Lecithin Cholesterol Acyltransferase Deficiency / Q000235:genetics / Q000378:metabolism; D050356:Lipid Metabolism / Q000235:genetics; D008099:Liver / Q000378:metabolism* / Q000473:pathology; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D065626:Non-alcoholic Fatty Liver Disease / Q000209:etiology / Q000235:genetics* / Q000378:metabolism / Q000503:physiopathology; D010084:Oxidation-Reduction; D019308:Palmitic Acid / Q000494:pharmacology; D007862:Phosphatidylcholine-Sterol O-Acyltransferase / Q000235:genetics* / Q000378:metabolism; D011973:Receptors, LDL / Q000172:deficiency / Q000235:genetics*; D015398:Signal Transduction
chemical_list: D002791:Cholesterol, Dietary; D058847:Inflammasomes; D011973:Receptors, LDL; D019308:Palmitic Acid; D007862:Phosphatidylcholine-Sterol O-Acyltransferase
keywords: Cholesterol crystal; ER cholesterol; ER stress; Inflammasome; LCAT knockout mice; NASH