Lamina propria interleukin 17 A aggravates natural killer T-cell activation in autoimmune hepatitis

Natural Killer T (NKT) Cells in Autoimmune Hepatitis: Current Evidence from Basic and Clinical Research

Natural killer T (NKT) cells are unconventional T cells that are activated by glycolipid antigens. They can produce a variety of inflammatory and regulatory cytokines and, therefore, modulate multiple aspects of the immune response in different pathological settings, including autoimmunity. NKT cells have also been implicated in the immunopathogenesis of autoimmune hepatitis, and in this review we summarize and analyze the main studies investigating the involvement and/or homeostasis of NKT cells in this disease. In detail, the evidence from both basic and clinical research has been specifically analyzed. Even though the experimental murine models supported a relevant role of NKT cells in immune-mediated hepatic injury, very few studies specifically investigated NKT cell homeostasis in patients with autoimmune hepatitis; however, these initial studies reported some alterations of NKT cells in these patients, which may also correlate with the disease activity to some extent. Further clinical studies are needed to investigate the potential role and use of NKT cell analysis as a disease marker of clinical relevance, and to better understand the precise cellular and molecular mechanisms by which NKT cells contribute to the pathogenesis of autoimmune hepatitis.

M1 macrophage-derived exosomes promote autoimmune liver injury by transferring long noncoding RNA H19 to hepatocytes

Exosomes mediate intercellular communication by transmitting active molecules. The function of long noncoding RNA (lncRNA) H19 in autoimmune liver injury is unclear. Concanavalin A (ConA)-induced liver injury is well-characterized immune-mediated hepatitis. Here, we showed that lncRNA H19 expression was increased in the liver after ConA treatment, accompanied by increased exosome secretion. Moreover, injection of AAV-H19 aggravated ConA-induced hepatitis, with an increase in hepatocyte apoptosis. However, GW4869, an exosome inhibitor, alleviated ConA-induced liver injury and inhibited the upregulation of lncRNA H19. Intriguingly, lncRNA H19 expression in the liver was significantly downregulated, after macrophage depletion. Importantly, the lncRNA H19 was primarily expressed in type I macrophage (M1) and encapsulated in M1-derived exosomes. Furthermore, H19 was transported from M1 to hepatocytes via exosomes, and exosomal H19 dramatically induced hepatocytes apoptosis both in vitro and vivo. Mechanistically, H19 upregulated the transcription of hypoxia-inducible factor-1 alpha (HIF-1α), which accumulated in the cytoplasm and mediated hepatocyte apoptosis by upregulating p53. M1-derived exosomal lncRNA H19 plays a pivotal role in ConA-induced hepatitis through the HIF-1α-p53 signaling pathway. These findings identify M1 macrophage-derived exosomal H19 as a novel target for the treatment of autoimmune liver diseases.

zVAD alleviates experimental autoimmune hepatitis in mice by increasing the sensitivity of macrophage to TNFR1-dependent necroptosis

BACKGROUND & AIMS

Autoimmune hepatitis (AIH) is characterized by hepatocyte destruction, leading to lymphocyte and macrophage accumulation in the liver. Macrophages are key drivers of AIH. A membrane-permeable pan-caspase inhibitor, Z-Val-Ala-DL-Asp-fluoromethylketone (zVAD), induces macrophage necroptosis in response to certain stimuli. However, the function of zVAD in the pathogenesis of autoimmune hepatitis remains elusive. In this study, we aimed to evaluate the effect and explore the underlying mechanisms of zVAD against AIH.

METHODS

Murine acute autoimmune liver injury was established by concanavalin A (ConA) injection. Bone marrow-derived macrophages (BMDMs) were used in adoptive cell transfer experiments. The mechanism of action of zVAD was examined using macrophage cell lines and BMDMs. Phosphorylation of mixed lineage kinase domain-like proteins was used as a marker of necroptosis.

RESULTS

Treatment with zVAD increased necroptosis, reduced inflammatory cytokine production, and alleviated liver injury in a ConA-induced liver injury mouse model. Regardless of zVAD treatment, macrophage deletion resulted in reduced neutrophil accumulation and relieved ConA-induced liver injury. In vitro studies have shown that zVAD pretreatment promotes lipopolysaccharide-induced macrophage necroptosis and leads to reduced pro-inflammatory cytokine and chemokine secretion. Transferring zVAD-pretreated BMDMs in mice notably reduced ConA-associated liver inflammation and injury, resulting in lower mortality than that observed after transferring normal BMDMs. Mechanistically, zVAD treatment increased the expression of tumour necrosis factor receptor (TNFR)-1 and interleukin (IL)-10 in macrophages. TNFR1 expression decreased upon transfection with IL-10-specific small interfering RNAs and blocking of TNFR1 decreased macrophage necroptosis.

CONCLUSIONS

We found that zVAD alleviated ConA-induced liver injury by increasing the sensitivity of macrophages to necroptosis via IL-10-induced TNFR1 expression. This study provides new insights into the treatment of autoimmune hepatitis via zVAD-induced macrophage necroptosis.