Interleukin-22 (IL-22) is known to play a key role in promoting antimicrobial immunity, inflammation, and tissue repair at barrier surfaces by binding to the receptors IL-10R2 and IL-22R1. IL-22R1 is generally thought to be expressed exclusively in epithelial cells. In this study, we identified high levels of IL-10R2 and IL-22R1 expression on hepatic stellate cells (HSCs), the predominant cell type involved in liver fibrogenesis in response to liver damage. In vitro treatment with IL-22 induced the activation of signal transducer and activator of transcription 3 (STAT3) in primary mouse and human HSCs. IL-22 administration prevented HSC apoptosis in vitro and in vivo, but surprisingly, the overexpression of IL-22 via either gene targeting (IL-22 transgenic mice) or exogenous administration of adenovirus expressing IL-22 reduced liver fibrosis and accelerated the resolution of liver fibrosis during recovery. Furthermore, IL-22 overexpression or treatment increased the number of senescence-associated β-galactosidase-positive HSCs and decreased α-smooth muscle actin expression in fibrotic livers in vivo and cultured HSCs in vitro. Deletion of STAT3 prevented IL-22-induced HSC senescence in vitro, whereas the overexpression of a constitutively activated form of STAT3 promoted HSC senescence via p53- and p21-dependent pathways. Finally, IL-22 treatment upregulated suppressor of cytokine signaling 3 expression in HSCs. Immunoprecipitation analyses revealed that SOCS3 bound p53 and subsequently increased the expression of p53 and its target genes, contributing to IL-22-mediated HSC senescence. Conclusion IL-22 induces the senescence of HSCs, which express both IL-10R2 and IL-22R1, thereby ameliorating liver fibrogenesis. The anti-fibrotic effect of IL-22 is likely mediated via the induction of HSC senescence in addition to the previously discovered hepatoprotective functions of IL-22.

Endoplasmic reticulum (ER) stress promotes tumor cell escape from immunosurveillance. However, the underlying mechanisms remain unknown. We hypothesized that ER stress induces hepatocellular carcinoma (HCC) cells to release exosomes, which attenuate antitumor immunity by modulating the expression of programmed death ligand 1 (PD‐L1) in macrophages. In this study, we demonstrated that expression of several ER stress markers (glucose‐regulated protein 78, activating transcription factor 6, protein kinase R–like ER kinase, and inositol‐requiring enzyme 1α) was up‐regulated in HCC tissues and negatively correlated with the overall survival and clinicopathological scores in patients with HCC. Expression of ER stress–related proteins positively correlated with CD68+ macrophage recruitment and PD‐L1 expression in HCC tissues. High‐throughput sequencing analysis identified miR‐23a‐3p as one of the most abundant microRNAs in exosomes derived from tunicamycin (TM)‐treated HCC cells (Exo‐TMs). miR‐23a‐3p levels in HCC tissues negatively correlated with overall survival. Treatment with Exo‐TMs up‐regulated the expression of PD‐L1 in macrophages in vitro and in vivo. Bioinformatics analysis suggests that miR‐23a‐3p regulates PD‐L1 expression through the phosphatase and tensin homolog (PTEN)–phosphatidylinositol 3‐kinase–protein kinase B (AKT) pathway. This notion was confirmed by in vitro transfection and coculture experiments, which revealed that miR‐23a‐3p inhibited PTEN expression and subsequently elevated phosphorylated AKT and PD‐L1 expression in macrophages. Finally, coculture of T cells with Exo‐TM–stimulated macrophages decreased CD8+ T‐cell ratio and interleukin‐2 production but increased T‐cell apoptosis in vitro. Conclusion: ER‐stressed HCC cells release exosomes to up‐regulate PD‐L1 expression in macrophages, which subsequently inhibits T‐cell function through an exosome miR‐23a–PTEN–AKT pathway. Our findings provide insight into the mechanism how tumor cells escape from antitumor immunity.

Obesity and alcohol consumption often coexist and work synergistically to promote steatohepatitis; however, the underlying mechanisms remain obscure. Here, we demonstrated that feeding mice a high-fat diet (HFD) for as little as 3 days markedly exacerbated acute ethanol binge-induced liver neutrophil infiltration and injury. Feeding mice with a HFD for 3 months plus a single binge of ethanol induced much more severe steatohepatitis. Moreover, 3-day or 3-month HFD-plus-ethanol binge (3d-HFD+ethanol or 3m-HFD+ethanol) treatment markedly upregulated the hepatic expression of several chemokines, including chemokine (C-X-C motif) ligand 1 (Cxcl1), which showed the highest fold (approximately 20-fold and 35-fold, respectively) induction. Serum CXCL1 protein levels were markedly elevated after the HFD+ethanol treatment. Blockade of CXCL1 with a CXCL1 neutralizing antibody or genetic deletion of the Cxcl1 gene reduced the HFD+ethanol-induced hepatic neutrophil infiltration and injury; whereas overexpression of the Cxcl1 exacerbated steatohepatitis in HFD-fed mice. Furthermore, the expression of Cxcl1 mRNA was upregulated in hepatocytes, hepatic stellate cells and endothelial cells isolated from HFD+ethanol-fed mice compared to mice that were only given a HFD, with the highest fold induction observed in hepatocytes. In vitro stimulation of hepatocytes with palmitic acid upregulated the expression of Cxcl1 mRNA, and this upregulation was attenuated after treatment with ERK1/2, JNK, or NF-κB inhibitors. In addition, hepatic or serum levels of free fatty acids (FFAs) were higher in HFD+ethanol-fed mice than in the control groups. In conclusion, a HFD combined with acute ethanol consumption synergistically induces acute liver inflammation and injury via the elevation of hepatic or serum FFAs and subsequent upregulation of hepatic CXCL1 expression and promotion of hepatic neutrophil infiltration.