Immunoregulatory role of the IL-33/amphiregulin axis in acute immune-mediated liver disease

Introduction Autoimmune hepatitis is an inflammatory liver disease that is characterized by destruction of liver tissue by autoreactive T cells. Consequently, interleukin 33 (IL-33) is released from necrotic hepatocytes and binds to the IL-33 receptor ST2 thereby activating group 2 innate lymphoid cells (ILC2) and regulatory T cells (Tregs). We have previously shown that IL-33 pre-treatment ameliorated concanavalin A (ConA)-induced immune-mediated hepatitis but the underlying mechanisms remain unknown. Following activation, ILC2 and Tregs express amphiregulin (AREG). Since AREG is associated with tissue repair and immunosuppressive functions, we aimed at investigating the role of ILC2- and Treg-derived AREG in the regulation of hepatic inflammation.

Methods For induction of immune-mediated hepatitis, C57BL/6 (WT) and Areg -/- mice received i.v. ConA and were analysed 24 hours later. To study the effect of IL-33 on immune cell phenotype and liver disease pathology, mice received i.p. recombinant murine IL-33 on three consecutive days followed by ConA challenge. Liver damage was quantified by measurement of serum activities of alanine transaminase (ALT) and immune cell phenotype was determined by flow cytometry.

Results In ConA-induced immune-mediated hepatitis, severe liver damage was associated with elevated Il33 and Areg tissue mRNA, as well as AREG serum protein levels. The release of IL-33 resulted in an increased frequency of hepatic ILC2 expressing the activation marker KLRG1, the effector cytokines IL-5 and IL-13 as well as AREG. In contrast, the expression of the co-inhibitory receptor PD-1 was downregulated. Moreover, the frequency of hepatic AREG+ Tregs was elevated. IL-33 treatment prior ConA application protected WT mice from immune-mediated hepatitis, enhanced ILC2 frequency and activation as well as expansion and AREG expression of ST2+ Tregs compared to ConA-treated mice. Furthermore, we induced immune-mediated hepatitis in Areg-/- mice to investigate its immuno-modulatory function in acute liver injury. Interestingly, these mice developed more severe hepatitis than WT mice. Hepatic ILC2 cells were more activated while the frequency of ST2+ Tregs was significantly reduced.

Conclusion The alarmin IL-33 plays a critical role in the alleviation of immune-mediated hepatitis. This immunoregulatory function might be driven by expansion and activation of ST2+ ILC2 and Tregs as well as induction of AREG expression in these cell populations.

Publication History

Article published online:
04 January 2021