The innate immune receptor TREM-1 promotes liver injury and fibrosis
Anh Thu Nguyen-Lefebvre, Ashwin Ajith, Vera Portik-Dobos, Daniel David Horuzsko, Ali Syed Arbab, Amiran Dzutsev, Ramses Sadek, Giorgio Trinchieri, Anatolij Horuzsko
Anh Thu Nguyen-Lefebvre, Ashwin Ajith, Vera Portik-Dobos, Daniel David Horuzsko, Ali Syed Arbab, Amiran Dzutsev, Ramses Sadek, Giorgio Trinchieri, Anatolij Horuzsko
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Research Article Hepatology Inflammation

The innate immune receptor TREM-1 promotes liver injury and fibrosis

Abstract

Inflammation occurs in all tissues in response to injury or stress and is the key process underlying hepatic fibrogenesis. Targeting chronic and uncontrolled inflammation is one strategy to prevent liver injury and fibrosis progression. Here, we demonstrate that triggering receptor expressed on myeloid cells 1 (TREM-1), an amplifier of inflammation, promotes liver disease by intensifying hepatic inflammation and fibrosis. In the liver, TREM-1 expression was limited to liver macrophages and monocytes and was highly upregulated on Kupffer cells, circulating monocytes, and monocyte-derived macrophages in a mouse model of chronic liver injury and fibrosis induced by carbon tetrachloride (CCl4) administration. TREM-1 signaling promoted proinflammatory cytokine production and mobilization of inflammatory cells to the site of injury. Deletion of Trem1 reduced liver injury, inflammatory cell infiltration, and fibrogenesis. Reconstitution of Trem1-deficient mice with Trem1-sufficient Kupffer cells restored the recruitment of inflammatory monocytes and the severity of liver injury. Markedly increased infiltration of liver fibrotic areas with TREM-1–positive Kupffer cells and monocytes/macrophages was found in patients with hepatic fibrosis. Our data support a role of TREM-1 in liver injury and hepatic fibrogenesis and suggest that TREM-1 is a master regulator of Kupffer cell activation, which escalates chronic liver inflammatory responses, activates hepatic stellate cells, and reveals a mechanism of promotion of liver fibrosis.

Authors

Anh Thu Nguyen-Lefebvre, Ashwin Ajith, Vera Portik-Dobos, Daniel David Horuzsko, Ali Syed Arbab, Amiran Dzutsev, Ramses Sadek, Giorgio Trinchieri, Anatolij Horuzsko

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Figure 5

Deletion of Trem1 reduces inflammatory cell infiltration at early stages of liver fibrogenesis.

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Deletion of Trem1 reduces inflammatory cell infiltration at early stages...
(A) Flow cytometric dot plots of liver cells from control WT and Trem1–/– mice (oil-injected, n = 3/group) and WT and Trem1–/– mice 12 hours and 72 hours after CCl4 injury (n = 7 mice/time point/group). Cells were stained with anti-F4/80, anti-CD11b, anti-CCR2, anti-CX3CR1, anti–IL-1β, anti-TNF, and anti–TGF-β1 antibodies. Liver cells from WT mice were stained and analyzed 72 hours after CCl4 injection for the expression of CCR2 and CX3CR1 (n = 5 mice) and for the intracellular expression of IL-1β, TNF, and TGF-β1 (n = 7 mice). Flow cytometric histograms represent cells gated on a F4/80+CD11b+ population. Control staining was performed with IgG isotype (gray histograms). (B–D) Percentage of CD11b+ cells, neutrophils, and inflammatory monocyte–derived macrophages in liver from WT and Trem1–/– mice quantified after 12 hours and 72 hours of oil injection (n = 3 mice/time point/group) or CCl4 treatment (n = 7 mice/time point/group). Results are displayed as the mean ± SEM. *P < 0.05, **P < 0.01, ***P < 0.001, and ****P < 0.0001, by 2-tailed Student’s t test (B, C, and D).