Immunomodulatory functions of hepatic non-parenchymal cells in the pathogenesis of alcoholic liver disease

Abstract

Part Ⅰ. Toll-like receptor 3 activation in Kupffer cells and stellate cells attenuates alcoholic liver injury by direct interleukin-10 production and decreased endocannabinoid production in mice

Background & Aims : Hepatic stellate cells (HSCs) and Kupffer cells are involved in development of alcoholic liver injuries such as steatosis and inflammation by producing endocannabinoids and inflammatory mediators, respectively. The important function of toll-like receptor (TLR) 4 on Kupffer cells and hepatic stellate cells (HSCs) has been well documented in alcoholic liver injury. However, little is known about the role of TLR3. Therefore, we tested whether TLR3 activation in HSCs and Kupffer cells could attenuate alcoholic liver injury in vivo, and investigated its possible mechanisms in vitro. Materials and Methods : Alcoholic liver injury was achieved by feeding wild type (WT), TLR3 knockout ($TLR3^{-/-}$) and interleukin (IL)-$10^{-/-}$ mice with high-fat diet plus binge ethanol drinking for 2 weeks. To activate TLR3, polyinosinic-polycytidylic acid (poly I:C) was injected into mice. For in vitro studies, freshly isolated HSCs and Kupffer cells were treated with poly I:C. Results : In WT mice, poly I:C treatment reduced alcoholic liver injury and fat accumulation by suppressing nuclear factor-$\kappa$ B activation and sterol response element-binding protein 1c expression in the liver. In addition, poly I:C treatment induced natural killer (NK) cell-mediated apoptosis of HSCs which responsible for the decreased fat deposition in hepatocytes. Furthermore, importantly, freshly isolated HSCs and Kupffer cells from poly I:C treated mice showed enhanced expression of IL-10 compared to controls. Infiltrated macrophage numbers and the expression of tumor necrosis $factor-\alpha$, monocyte chemoattractant protein-1 and IL-6 on these cells were decreased after poly I:C treatment. In vitro, poly I:C treatment enhanced the expression of IL-10 via a TLR3-dependent mechanism in HSCs and Kupffer cells. However, the protective effects of poly I:C on alcoholic liver injury were abrogated in $TLR3^{-/-}$ and $IL-10^{-/-}$ mice. Conclusions : TLR3 activation ameliorates alcoholic liver injury via the stimulation of IL-10 production in HSCs and Kupffer cells, and suppression of HSCs by increased NK cell cytotoxicity. Our findings suggest that targeting the TLR3 activation could be a novel therapeutic ways for the treatment of alcoholic liver injury.

Part Ⅱ. Ginsenoside F2 treatment ameliorates alcoholic liver injury by increased regulatory T cells and IL-10 production in mice Background & Aims : It has been reported recently that an intestinal metabolites of ginsenoside has diverse protective effects against liver injury. However, specific mechanism how ginsenoside metabolites attenuated liver injury was still unclear, especially in alcohol-mediated liver injury. Here, we explored the possibility whether ginsenoside F2, a ginsenoside metabolites, treatment could be a preventing way in the progression of alcoholic liver injury. Materials and Methods : Alcoholic liver injury was achieved by feeding wild type (WT) mice with binge ethanol drinking for 2 weeks with or without ginsenoside F2. Hepatic mononuclear cells, Kupffer cells, stellate cells (HSCs) and regulatory T cells (Tregs) were isolated, and subjected to in vitro study. Results : Alcoholic liver injury was attenuated by gindenoside F2. Ginsenoside F2 treatment reduced infiltrating macrophages/Kupffer cells and granulocytes in the liver. Activation of Kupffer cells and HSCs was decreased, and IL-10 induction was increased in ex vivo isolated .Kupffer cells and HSCs. We further confirm the increased IL-10 in both cells in vitro. Tregs population and its total counts in liver was increased by ginsenoside treatment, however, coculture with HSC suppress the activity of Tregs directly. Reduced fat accumulation was related to decreased endocannabinoid-producing gene expression by ginsenoside F2 treatment. All the preventive effect of ginsenoside was abrogated in more chronic model of 4 weeks mice. We investigated the possibility of ginsenoside F2 as a therapeutics for attenuating alcoholic liver injury in mice.