Fatty Acid and Endotoxin Activate Inflammasomes in Mouse Hepatocytes that Release Danger Signals to Stimulate Immune Cells

By T. Csák, M. Ganz, Justin Pespisa, K. Kodys, A. Dolganiuc, G. Szabo. Hepatology, 2011

660 citations recorded by the source corpus.

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. (HEPATOLOGY 2011;)

Subfields: Epidemiology, Molecular Biology, Nutrition and Dietetics

View Paper: https://www.semanticscholar.org/paper/478608d47d4c0a8570b1687bfa2dc19a14d47d40

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In Epidemiology

1. M. Pinzani
2. E. Tsochatzis
3. Natascha Roehlen
4. E. Crouchet
5. E. Buzzetti
6. Ali Canbay
7. T. Baumert

In Molecular Biology

1. Kate Schroder
2. S. Masters

In Nutrition and Dietetics

1. Kate Schroder

Citations in the corpus

• The multiple-hit pathogenesis of non-alcoholic fatty liver disease (NAFLD). (2016, background): “[62] Csak T, Ganz M, Pespisa J, et al.”
• Intestinal microbiota in patients with nonalcoholic fatty liver disease (2013, neutral): “Insulin (pmol/L) 21 (15-61) 33 (15-465) 97 (29-437)”
• NLRP3 inflammasome activation results in hepatocyte pyroptosis, liver inflammation and fibrosis (2014, background): “appears to be mediated through the NLRP3 inflammasome.(15-17) These studies demonstrate that Casp1 plays an important role in inflammation and fibrosis during NASH and ASH development.”
• NLRP3 inflammasome blockade reduces liver inflammation and fibrosis in experimental NASH in mice (2017, background): “* Contributed equally to this work and are deemed equal first authors Short title: MCC950 reverses NASH Key words: NAFLD, NLRP3, inflammasome, cholesterol crystals, Kupffer cells, hepatocytes, interleukin-1, fibrosis.”
• Liver Fibrosis: Mechanistic Concepts and Therapeutic Perspectives (2020, background): “Even if NLRP3 inflammasome activation in different cell types has not been completely elucidated, several evidences demonstrated that accumulation of toxic lipids and DAMPs- and PAMPS-mediated TLR signaling activates NLRP3 inflammasome [45,163,165].”