Regulation of the macrophage-hepatic stellate cell interaction by targeting macrophage peroxisome proliferator-activated receptor gamma to prevent non-alcoholic steatohepatitis progression in mice.

Macrophages display remarkable plasticity and can interact with surrounding cells to affect hepatic immunity and tissue remodelling during the progression of liver diseases. Peroxisome proliferator-activated receptor gamma (PPARγ) plays a critical role in macrophage maturation, polarization and metabolism. In this study, we investigated the role of PPARγ in macrophage-hepatic stellate cell (HSC) interaction during non-alcoholic steatohepatitis (NASH) development. Wild-type, Ppargfl/fl and PpargΔLyz2 mice were fed a methionine- and choline-deficient (MCD) diet to induce NASH. Depletion of macrophages was performed using an injection of gadolinium chloride intraperitoneally. PPARγ-overexpressing or PPARγ-knockout macrophages were stimulated with saturated fatty acid (SFA) and cocultured with HSCs in a conditioned medium or the transwell coculture system. Depletion of macrophages inhibited HSC activation and ameliorated NASH progression in MCD diet-fed mice. Coculturing HSCs with macrophages or culturing HSCs in a macrophage-conditioned medium-facilitated HSC activation, and this effect was magnified when macrophages were metabolically activated by SFA. Moreover, the absence of PPARγ in macrophages enhanced metabolic activation, promoting the migration and activation of HSCs through IL-1β and CCL2. In contrast, overexpression of PPARγ in macrophages obtained the opposite effects. In vivo, macrophage-specific PPARγ knockout affected the phenotype of hepatic macrophages and HSCs, involving the MAPK and NLRP3/caspase-1/IL-1β signalling pathways. Infiltrating hepatic monocyte-derived macrophages became the predominant macrophages in NASH liver, especially in PpargΔLyz2 mice, paralleling with aggravated inflammation and fibrosis. Regulating macrophage PPARγ affected the metabolic activation of macrophages and their interaction with HSCs. Macrophage-specific PPARγ may be an attractive therapeutic target for protecting against NASH-associated inflammation and fibrosis.

Ni XX ，Ji PX ，Chen YX ，Li XY ，Sheng L ，Lian M ，Guo CJ ，Hua J ... -  《-》

Role of XBP1 in regulating the progression of non-alcoholic steatohepatitis.

Non-alcoholic steatohepatitis (NASH) is associated with the dysregulation of lipid metabolism and hepatic inflammation, though the underlying mechanisms remain unclear. We aimed to investigate the role of X-box binding protein-1 (XBP1) in the progression of NASH. Human liver tissues obtained from patients with NASH and controls were used to assess XBP1 expression. NASH models were developed in hepatocyte-specific Xbp1 knockout (Xbp1ΔHep), macrophage-specific Xbp1 knockout (Xbp1ΔMf), macrophage-specific Nlrp3 knockout, and wild-type (Xbp1FL/FL or Nlrp3FL/FL) mice fed with a high-fat diet for 26 weeks or a methionine/choline-deficient diet for 6 weeks. The expression of XBP1 was significantly upregulated in liver samples from patients with NASH. Hepatocyte-specific Xbp1 deficiency inhibited the development of steatohepatitis in mice fed the high-fat or methionine/choline-deficient diets. Meanwhile, macrophage-specific Xbp1 knockout mice developed less severe steatohepatitis and fibrosis than wild-type Xbp1FL/FL mice in response to the high-fat or methionine/choline-deficient diets. Macrophage-specific Xbp1 knockout mice showed M2 anti-inflammatory polarization. Xbp1-deleted macrophages reduced steatohepatitis by decreasing the expression of NLRP3 and secretion of pro-inflammatory cytokines, which mediate M2 macrophage polarization in macrophage-specific Xbp1 knockout mice. Steatohepatitis was less severe in macrophage-specific Nlrp3 knockout mice than in wild-type Nlrp3FL/FL mice. Xbp1-deleted macrophages prevented hepatic stellate cell activation by decreasing expression of TGF-β1. Less fibrotic changes were observed in macrophage-specific Xbp1 knockout mice than in wild-type Xbp1FL/FL mice. Inhibition of XBP1 suppressed the development of NASH. XBP1 regulates the development of NASH. XBP1 inhibitors protect against steatohepatitis. Thus, XBP1 is a potential target for the treatment of NASH. XBP1 is a transcription factor that is upregulated in liver tissues of patients with non-alcoholic steatohepatitis (NASH). Conditional knockout of Xbp1 in hepatocytes resulted in decreased lipid accumulation in mice, while genetic deletion of Xbp1 in macrophages ameliorated nutritional steatohepatitis and fibrosis in mice. Pharmacological inhibition of XBP1 protects against steatohepatitis and fibrosis, highlighting a promising therapeutic strategy for NASH.

Wang Q ，Zhou H ，Bu Q ，Wei S ，Li L ，Zhou J ，Zhou S ，Su W ，Liu M ，Liu Z ，Wang M ，Lu L ... -  《-》

Regulation of peroxisome proliferator-activated receptor-gamma activity affects the hepatic stellate cell activation and the progression of NASH via TGF-β1/Smad signaling pathway.

Ni XX ，Li XY ，Wang Q ，Hua J ... -  《-》

Peroxisome proliferator-activated receptors gamma reverses hepatic nutritional fibrosis in mice and suppresses activation of hepatic stellate cells in vitro.

Nonalcoholic steatohepatitis with fibrosis is a more severe form of nonalcoholic fatty liver disease, one of the most common liver diseases. We have previously shown that peroxisome proliferator-activated receptors gamma (PPARgamma) ligand, rosiglitazone, prevented the development of the methionine choline deficient (MCD) diet-induced fibrosing steatohepatitis. We have now tested whether overexpression of PPARgamma ameliorates established steatohepatitis and fibrosis. Male C57BL6 mice fed with MCD diet for 8 weeks developed hepatic fibrosis with increased hepatic expression of collagen1alpha(I), inhibitors of fibrosis reversal-1, regulator involved in matrix degradation-9 and connective tissue growth factor. After 2 weeks of transduction of PPARgamma through an adenovirus-expressing PPARgamma (Ad-PPARgamma), expression of these genes was reduced in a manner that paralleled the reduction in activated hepatic stellate cells (HSCs) and resolution of liver fibrosis. On the in vitro study, PPARgamma is expressed in primary quiescent HSC, but depleted in culture activated HSC. Conversely, ectopic expression of PPARgamma in activated HSC achieved the phenotypic reversal to the quiescent cell. Such induction markedly suppressed cell viability and cell proliferation, downregulated proliferating cell nuclear antigen, and caused cell cycle arrest at G0/G1 phase. Further, introduction of PPARgamma in HSC increased cell apoptosis, this was confirmed by enhanced expression of FasL, cleaved caspase-3, cleaved caspase-7 and poly ADP-ribose polymerase, indicating an extrinsic apoptosis pathway. In conclusion, the present study shows that MCD diet-induced fibrosing steatohepatitis can be reversed by overexpression of PPARgamma. It is likely that PPARgamma reverses fibrosis by reducing HSCs proliferation, inducing cell cycle arrest and apoptosis.

Yu J ，Zhang S ，Chu ES ，Go MY ，Lau RH ，Zhao J ，Wu CW ，Tong L ，Zhao J ，Poon TC ，Sung JJ ... -  《-》

Honokiol attenuates diet-induced non-alcoholic steatohepatitis by regulating macrophage polarization through activating peroxisome proliferator-activated receptor γ.

Non-alcoholic steatohepatitis (NASH) may develop into hepatic cirrhosis. This study aimed to investigate whether honokiol could prevent NASH induced by high-cholesterol and high-fat (CL) diet in mice and the possible mechanism involved. Mice were fed with CL diet for 12 weeks to establish a NASH model; honokiol (0.02% w/w in diet) was added to evaluate its effect on NASH. Murine peritoneal macrophages, RAW264.7 and ANA-1 cells, were used to explore the possible mechanisms of honokiol on macrophage polarization. Mice developed NASH after fed with CL diet for 12 weeks. Honokiol supplementation alleviated insulin resistance, hepatic steatosis, inflammation, and fibrosis induced by CL diet. Immunohistochemistry showed that honokiol induced more M2 macrophages in livers compared with CL diet alone. Honokiol decreased M1 marker genes (TNFα and MCP-1) and increased M2 marker gene (YM-1, IL-10, IL-4R and IL-13) expression in mice liver compared with CL diet. Moreover, treatment with honokiol lowered alanine aminotransferase and aspartate aminotransferase in serum and preserved liver from lipid peroxidation, evidenced by lowered hepatic malondialdehyde level. Honokiol has antioxidant function, as honokiol upregulated hepatic glutathione and superoxide dismutase level and downregulated hepatic CYP2E1 protein level. Hepatic peroxisome proliferator-activated receptor γ (PPARγ) and its target genes were upregulated by honokiol. Furthermore, honokiol (10 μM) treatment in mouse peritoneal cells, RAW264.7 cells and ANA-1 cells, led to M2 macrophage polarization, whereas a PPARγ antagonist, GW9662, abolished this effect of honokiol. Honokiol can attenuate CL diet-induced NASH and the mechanism in which possibly is polarizing macrophages to M2 phenotype via PPARγ activation.

Zhong X ，Liu H 《-》