title: Cholesterol crystallization within hepatocyte lipid droplets and its role in murine NASH.
abstract: We recently reported that cholesterol crystals form in hepatocyte lipid droplets (LDs) in human and experimental nonalcoholic steatohepatitis. Herein, we assigned WT C57BL/6J mice to a high-fat (15%) diet for 6 months, supplemented with 0%, 0.25%, 0.5%, 0.75%, or 1% dietary cholesterol. Increasing dietary cholesterol led to cholesterol loading of the liver, but not of adipose tissue, resulting in fibrosing steatohepatitis at a dietary cholesterol concentration of ≥0.5%, whereas mice on lower-cholesterol diets developed only simple steatosis. Hepatic cholesterol crystals and crown-like structures also developed at a dietary cholesterol concentration ≥0.5%. Crown-like structures consisted of activated Kupffer cells (KCs) staining positive for NLRP3 and activated caspase 1, which surrounded and processed cholesterol crystal-containing remnant LDs of dead hepatocytes. The KCs processed LDs at the center of crown-like structures in the extracellular space by lysosomal enzymes, ultimately transforming into lipid-laden foam cells. When HepG2 cells were exposed to LDL cholesterol, they developed cholesterol crystals in LD membranes, which caused activation of THP1 cells (macrophages) grown in coculture; upregulation ofTNF-alpha,NLRP3,and interleukin 1beta (IL1β) mRNA; and secretion of IL-1beta. In conclusion, cholesterol crystals form on the LD membrane of hepatocytes and cause activation and cholesterol loading of KCs that surround and process these LDs by lysosomal enzymes.
authors.affiliation: Division of Gastroenterology, Department of Medicine, Veterans Affairs Puget Sound Health Care System, Seattle, WA georgei@medicine.washington.edu.|Division of Gastroenterology, University of Washington, Seattle, WA.
authors.forename: George N
authors.initials: GN
authors.lastname: Ioannou
authors.affiliation: Division of Metabolism, Endocrinology and Nutrition, University of Washington, Seattle, WA.
authors.forename: Savitha
authors.initials: S
authors.lastname: Subramanian
authors.affiliation: Division of Metabolism, Endocrinology and Nutrition, University of Washington, Seattle, WA.
authors.forename: Alan
authors.initials: A
authors.lastname: Chait
authors.affiliation: Division of Gastroenterology, Department of Medicine, Veterans Affairs Puget Sound Health Care System, Seattle, WA.
authors.forename: W Geoffrey
authors.initials: WG
authors.lastname: Haigh
authors.affiliation: Department of Pathology, University of Washington, Seattle, WA.
authors.forename: Matthew M
authors.initials: MM
authors.lastname: Yeh
authors.affiliation: Liver Research Group, Australian National University Medical School at the Canberra Hospital, Garran, ACT, Australia.
authors.forename: Geoffrey C
authors.initials: GC
authors.lastname: Farrell
authors.affiliation: Division of Gastroenterology, University of Washington, Seattle, WA.
authors.forename: Sum P
authors.initials: SP
authors.lastname: Lee
authors.affiliation: Division of Gastroenterology, Department of Medicine, Veterans Affairs Puget Sound Health Care System, Seattle, WA.|Division of Gastroenterology, University of Washington, Seattle, WA.
authors.forename: Christopher
authors.initials: C
authors.lastname: Savard
mesh_terms: D000818:Animals; D002784:Cholesterol / Q000737:chemistry*; D002791:Cholesterol, Dietary / Q000494:pharmacology; D003460:Crystallization; D059305:Diet, High-Fat / Q000009:adverse effects; D004305:Dose-Response Relationship, Drug; D004789:Enzyme Activation / Q000187:drug effects; D056945:Hep G2 Cells; D022781:Hepatocytes / Q000737:chemistry*; D006801:Humans; D007728:Kupffer Cells / Q000187:drug effects / Q000378:metabolism; D066292:Lipid Droplets / Q000737:chemistry*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D065626:Non-alcoholic Fatty Liver Disease / Q000378:metabolism* / Q000473:pathology*; D000074084:THP-1 Cells
chemical_list: D002791:Cholesterol, Dietary; D002784:Cholesterol
keywords: cholesterol crystal; fatty liver; lipotoxicity; nonalcoholic steatohepatitis