Fatty acid and endotoxin activate inflammasomes in mouse hepatocytes that release danger signals to stimulate immune cells
UMass Chan Affiliations
Office of Medical EducationDepartment of Medicine, Division of Gastroenterology
Document Type
Journal ArticlePublication Date
2011-07-01Keywords
AnimalsApoptosis
Caspase 1
Choline Deficiency
Dietary Fats
Disease Models, Animal
Endotoxins
Fatty Acids
Fatty Liver
Female
Hepatocytes
Immune System
Inflammasomes
Interleukin-1beta
Methionine
Mice
Mice, Inbred C57BL
Tumor Necrosis Factor-alpha
Animal Experimentation and Research
Cells
Digestive System Diseases
Gastroenterology
Hemic and Immune Systems
Immunology and Infectious Disease
Lipids
Macromolecular Substances
Metadata
Show full item recordAbstract
The pathogenesis of nonalcoholic steatohepatitis (NASH) and inflammasome activation involves sequential hits. The inflammasome, which cleaves pro-interleukin-1β (pro-IL-1β) into secreted IL-1β, is induced by endogenous and exogenous danger signals. Lipopolysaccharide (LPS), a toll-like receptor 4 ligand, plays a role in NASH and also activates the inflammasome. In this study, we hypothesized that the inflammasome is activated in NASH by multiple hits involving endogenous and exogenous danger signals. Using mouse models of methionine choline-deficient (MCD) diet-induced NASH and high-fat diet-induced NASH, we found up-regulation of the inflammasome [including NACHT, LRR, and PYD domains-containing protein 3 (NALP3; cryopyrin), apoptosis-associated speck-like CARD-domain containing protein, pannexin-1, and pro-caspase-1] at the messenger RNA (mRNA) level increased caspase-1 activity, and mature IL-1β protein levels in mice with steatohepatitis in comparison with control livers. There was no inflammasome activation in mice with only steatosis. The MCD diet sensitized mice to LPS-induced increases in NALP3, pannexin-1, IL-1β mRNA, and mature IL-1β protein levels in the liver. We demonstrate for the first time that inflammasome activation occurs in isolated hepatocytes in steatohepatitis. Our novel data show that the saturated fatty acid (FA) palmitic acid (PA) activates the inflammasome and induces sensitization to LPS-induced IL-1β release in hepatocytes. Furthermore, PA triggers the release of danger signals from hepatocytes in a caspase-dependent manner. These hepatocyte-derived danger signals, in turn, activate inflammasome, IL-1β, and tumor necrosis factor α release in liver mononuclear cells. CONCLUSION: Our novel findings indicate that saturated FAs represent an endogenous danger in the form of a first hit, up-regulate the inflammasome in NASH, and induce sensitization to a second hit with LPS for IL-β release in hepatocytes. Furthermore, hepatocytes exposed to saturated FAs release danger signals that trigger inflammasome activation in immune cells. Thus, hepatocytes play a key role in orchestrating tissue responses to danger signals in NASH.Source
Hepatology. 2011 Jul;54(1):133-44. doi: 10.1002/hep.24341. Link to article on publisher's site
DOI
10.1002/hep.24341Permanent Link to this Item
http://hdl.handle.net/20.500.14038/49197PubMed ID
21488066Related Resources
ae974a485f413a2113503eed53cd6c53
10.1002/hep.24341