Expression of inflammatory, immune regulatory and tissue restorative genes by both Ly6Chi and Ly6Cint/- monocyte/macrophage subsets in acute and chronic liver injury in mice

Background Autoimmune liver diseases (AILD) may lead to flares and chronic liver inflammation mediated by the innate and the adaptive immune system. Here we phenotypically characterized monocyte/macrophage subsets in murine models of AILD, based on previous definitions of inflammatory M1 (Ly6Chi/CCR2+) and anti-inflammatory/restorative M2 (Ly6Cint/low/CX3CR1+) subsets, to analyse monocyte/macrophage differentiation during acute and chronic phases of inflammatory liver injury.

Methods To induce anti-inflammatory/restorative monocyte/macrophage subsets, C57BL/6 mice were treated with IL-33 on three consecutive days. Acute immune-mediated liver injury was induced by administration of ConA to C57BL/6 mice. Mdr2-/- mice develop sclerosing cholangitis and served as chronic model. Simultaneous analysis of mRNA and protein expression by flow cytometry was performed using the PrimeFlow RNA assay.

Results IL-33 pre-treatment prevented acute hepatitis and resulted in elevated frequencies of Ly6Cint monocytes/macrophages expressing genes associated with anti-inflammatory/restorative function (Mmp9, Chil3, Tgfb1). However, all subsets showed increased expression of the M1 marker CCR2. In acute hepatitis, frequencies of Ly6Chi and Ly6Cint monocytes/macrophages increased. Both subsets expressed inflammation-associated (Nos2, Tnf) as well as anti-inflammatory/restorative genes (Il10, Arg1, Chil3, Tgfb1). In Mdr2-/- mice, Ly6Cint and Ly6C- macrophages were increased while Ly6Chi monocytes were decreased. They exhibited an un-specific gene expression profile by up-regulating Il12, Tnf, Il10, Chil3 and Areg.

Conclusion M1/M2 classification based on expression of Ly6Chi/CCR2+ and Ly6Cint/low/CX3CR1+ seems not to be appropriate for characterization of hepatic monocyte/macrophage subsets in acute versus chronic liver inflammation as they expressed a mixed pro- and anti-inflammatory/restorative gene profile.

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Artikel online veröffentlicht:
26. Januar 2022