Hepatic macrophage migration and differentiation critical for liver fibrosis is mediated by the chemokine receptor C-C motif chemokine receptor 8 in mice

Abstract

Chemokines critically control the infiltration of immune cells upon liver injury, thereby promoting hepatic inflammation and fibrosis. The chemokine receptor CCR8 can affect trafficking of monocytes/macrophages, monocyte-derived dendritic cells (DCs) and T-helper cell (Th) subsets, but its role in liver diseases is currently unknown. To investigate the functional role of CCR8 in liver diseases, ccr8−/− and wild-type (WT) mice were subjected to chronic experimental injury models of carbon tetrachloride (CCl4) administration and surgical bile duct ligation (BDL). CCR8 was strongly up-regulated in the injured liver. Ccr8−/− mice displayed attenuated liver damage (e.g., ALT, histology, and TUNEL) compared to WT mice and were also protected from liver fibrosis in two independent injury models. Flow cytometry revealed reduced infiltrates of liver macrophages, neutrophils and natural killer cells, whereas hepatic CD4+ T cells increased. The main CCR8-expressing cells in the liver were hepatic macrophages, and CCR8 was functionally necessary for CCL1-directed migration of inflammatory but not for nonclassical monocytes into the liver. Moreover, the phenotype of liver macrophages from injured ccr8−/− animals was altered with increased expression of DC markers and enhanced expression of T-cell-attracting chemokine macrophage inflammatory protein 1-alpha (MIP-1α/CCL3). Correspondingly, hepatic CD4+ T cells showed increased Th1 polarization and reduced Th2 cells in CCR8-deficient animals. Liver fibrosis progression, but also subsequent T-cell alterations, could be restored by adoptively transferring CCR8-expressing monocytes/macrophages into ccr8−/− mice during experimental injury. Conclusions CCR8 critically mediates hepatic macrophage recruitment upon injury, which subsequently shapes the inflammatory response in the injured liver, affecting macrophage/DC and Th differentiation. CCR8 deficiency protects the liver against injury, ameliorating initial inflammatory responses and hepatic fibrogenesis. Inhibition of CCR8 or its ligand, CCL1, might represent a successful therapeutic target to limit liver inflammation and fibrosis progression.

Time course of gene expression during mouse skeletal muscle hypertrophy

“…The number of canonical pathways that were significantly (P Ͻ 0.001) enriched was the highest at d1 (29) and then progressively decreased at each subsequent time point (20,19,13,11, and 9 at d3, d5, d7, d10, and d14, respectively). In Fig.…”

“…There were four pathways that were enriched across all three gene expression patterns of the time course: hepatic fibrosis/hepatic stellate cell activation, T-helper cell differentiation, LPS/IL-1-mediated inhibition of retinoid X receptor (RXR) function and liver X receptor (LXR)/RXR activation. The exact role of these pathways in the hypertrophic response in skeletal muscle is not readily apparent, as they have been primarily shown in the liver to regulate the production of connective tissue (hepatic fibrosis/hepatic stellate cell activation and T-helper cell differentiation) (10, 11), cholesterol metabolism (LPS/IL-1 mediated inhibition of RXR function and LXR/RXR activation) (3,34), and inflammation (T-helper cell differentiation) (11).…”

Chemokine Receptor CXCR6-Dependent Hepatic NK T Cell Accumulation Promotes Inflammation and Liver Fibrosis

“…390439; MP Biomedicals, Solon, OH) (8). Biochemical assays and gene and protein expression studies were performed as described previously (8,24,25).…”

“…Total leukocytes from spleen were subjected to CXCL16-dependent migration assays (100 ng/ml; eBioscience, San Diego, CA) through a semipermeable membrane (pore size, 5 mm) (24). The migrated population was analyzed using FACS.…”

“…Circulating and intrahepatic leukocytes were isolated and subjected to FACS analysis as described previously (24). Multicolor stainings were conducted using monoclonal Abs: F4/80 (Serotec, Raleigh, NC), CD115, CD4, CD11b (all eBioscience), CD45, CD146, Gr1/Ly6C, Ly6G, CD19, NK1.1, CD8 and CD3 (all BD, Heidelberg, Germany), CD1d tetramer loaded with aGalCer (ProImmune, Oxford, U.K.).…”