In vitro antigen-specific induction of IL-22 in human subjects that resolved HCV infection

Pathological Roles of Interleukin-22 in the Development of Recurrent Hepatitis C after Liver Transplantation

OBJECTIVE

The aim of this study was to longitudinally evaluate and analyze the role of interleukin-22-producing CD4 positive cells (IL-22) in the pathogenesis of Hepatitis C Virus recurrence after Orthotopic Liver Transplantation (HCV-OLT).

METHODS

15 HCV-OLT, 15 age- and gender- matched non-HCV post-OLT (OLT) and 15 hepatitis C virus infected (HCV) patients were enrolled into our study from the liver transplantation and research center at Beijing 302 Hospital. We determined the frequencies of IL-22 using flow cytometry and expression of IL-22 mRNA using PCR in peripheral blood and liver tissue. We also divided HCV-OLT patients into rapid fibrosis progression (RFP) and slow fibrosis progression (SFP), examined IL-22 cells and analyzed the correlations between IL-22 frequencies and liver injury, fibrosis and clinical parameters. Moreover, we investigated the role of IL-22 in Human Hepatic Stellate Cells (HSCs).

RESULTS

The levels of serum IL-22, frequencies of IL-22 producing cells in peripheral blood mononuclear cells, and expression of IL-22 mRNA and protein in the liver in the HCV-OLT group were significantly higher than that in the HCV and OLT groups. Furthermore, eight (53.3%) patients developed RFP after two years; another three patients were diagnosed liver cirrhosis. The frequencies of IL-22 were much higher in RFP compared with SFP, while no significant difference existed between OLT and SFP. Intrahepatic IL-22 positive cells were located in fibrotic areas and significantly correlated with α-smooth muscle actin (α-SMA) and fibrosis staging scores, not with grading scores and HCRVNA. In vitro, IL-22 administration prevented HSCs apoptosis, promoted HSCs proliferation and activation, up-regulated the expression of HSC-sourced growth factors including α-SMA, TGF-β and TIMP-1, and increased the production of liver fibrosis markers including laminin, hyaluronic acid and collagen type IV.

CONCLUSION

Peripheral and intrahepatic IL-22 is up-regulated and plays a pathological role in exacerbating liver fibrosis by activating HSCs in HCV-OLT patients, which may predict RFP and serve as an attractive target for anti-fibrotic therapy.

The role of the IL-22/IL-22R1 axis in cancer

Interleukin-22 (IL-22) is an IL-10 family cytokine produced by T cells and innate lymphoid cells. The IL-22 signaling pathway orchestrates mucosal immune defense and tissue regeneration through pleiotropic effects including pro-survival signaling, cell migration, dysplasia and angiogenesis. While these functions can prevent initial establishment of tumors, they can also be hijacked by aggressive cancers to enhance tumor growth and metastasis. Thus, the role of the IL-22/IL-22R1 axis in cancer is complex and context-specific. Evidence of IL-22 involvement manifests as dysregulation of IL-22 expression and signaling in patients with many common cancers including those of the gut, skin, lung and liver. Unlike other cancer-associated cytokines, IL-22 has restricted tissue specificity as its unique receptor IL-22R1 is exclusively expressed on epithelial and tissue cells, but not immune cells. This makes it an attractive target for therapy as there is potential achieve anti-tumor immunity with fewer side effects. This review summarizes current findings on functions of IL-22 in association with general mechanisms for tumorigenesis as well as specific contributions to particular cancers, and ponders how best to approach further research in the field.