Novel RORγt inverse agonists limit IL-17-mediated liver inflammation and fibrosis

Abstract

Liver fibrosis is a global health problem. IL-17A has proven profibrogenic properties in liver disease making it an interesting therapeutic target. IL-17A is regulated by RORγt and produced by Th17 CD4+ and γδ-T cells. We hypothesized that blocking IL-17A production will limit fibrosis progression by reducing recruitment of inflammatory cells. Herein, we tested the therapeutic potential of 2 novel RORγt inverse agonists (2,3 derivatives of 4,5,6,7-tetrahydro-benzothiophene) in a mouse model of CCl4-induced liver injury. C57BL/6 mice received 2 weekly injections of CCl4 for 4 weeks. As of week 3, mice were treated with the 2 novel inverse agonists (TF-S10 and TF-S14) and GSK805 as a positive control. Mice treated with the inverse agonists showed reduced immune cells infiltrate around the portal and central veins. TF-S14 significantly reduced AST levels (P < 0.05), and all inhibitors led to an improvement in relative liver weight (liver index). Flow cytometry analysis demonstrated that all inhibitors reduced the numbers of intrahepatic lymphocytes (CD4+, CD8+, and γδ-T cells, P < 0.05), and myeloid (CD11b+) cells (P = 0.04), most significantly eosinophils (P < 0.05). Furthermore, IL-17A production by CD4+ and γδ-T cells was diminished (P < 0.05 and P < 0. 01, respectively). Finally, livers from inhibitors-treated mice showed decreased markers of hepatic stellate cell activation (desmin and ɑ-smooth muscle actin [ɑ-SMA]) and significantly reduced expression of the profibrogenic genes (Col1a1, Acta, Loxl2, and Tgfβ) (P < 0.001). This was accompanied by diminished collagen deposition as measured by Picrosirius Red staining (P < 0.001). In conclusion, our results suggest that inhibition of the IL-17A pathway could be a promising therapeutic strategy for liver fibrosis.

Keywords: IL-17A; RORγt; inflammation; inverse agonist; liver fibrosis.