Diverse potential of secretome from natural killer cells and monocyte-derived macrophages in activating stellate cells.

Chronic liver diseases, such as non-alcoholic steatohepatitis (NASH)-induced cirrhosis, are characterized by an increasing accumulation of stressed, damaged, or dying hepatocytes. Hepatocyte damage triggers the activation of resident immune cells, such as Kupffer cells (KC), as well as the recruitment of immune cells from the circulation toward areas of inflammation. After infiltration, monocytes differentiate into monocyte-derived macrophages (MoMF) which are functionally distinct from resident KC. We herein aim to compare the in vitro signatures of polarized macrophages and activated hepatic stellate cells (HSC) with ex vivo-derived disease signatures from human NASH. Furthermore, to shed more light on HSC activation and liver fibrosis progression, we investigate the effects of the secretome from primary human monocytes, macrophages, and NK cells on HSC activation. Interleukin (IL)-4 and IL-13 treatment induced transforming growth factor beta 1 (TGF-ß1) secretion by macrophages. However, the supernatant transfer did not induce HSC activation. Interestingly, PMA-activated macrophages showed strong induction of the fibrosis response genes COL10A1 and CTGF, while the supernatant of IL-4/IL-13-treated monocytes induced the upregulation of COL3A1 in HSC. The supernatant of PMA-activated NK cells had the strongest effect on COL10A1 induction in HSC, while IL-15-stimulated NK cells reduced the expression of COL1A1 and CTGF. These data indicate that other factors, aside from the well-known cytokines and chemokines, might potentially be stronger contributors to the activation of HSCs and induction of a fibrotic response, indicating a more diverse and complex role of monocytes, macrophages, and NK cells in liver fibrosis progression.

Antifibrotic Drug Nintedanib Inhibits CSF1R to Promote IL-4-associated Tissue Repair Macrophages.

Profibrotic and prohomeostatic macrophage phenotypes remain ill-defined, both in vivo and in vitro, impeding the successful development of drugs that reprogram macrophages as an attractive therapeutic approach to manage fibrotic disease. The goal of this study was to reveal profibrotic and prohomeostatic macrophage phenotypes that could guide the design of new therapeutic approaches targeting macrophages to treat fibrotic disease. This study used nintedanib, a broad kinase inhibitor approved for idiopathic pulmonary fibrosis, to dissect lung macrophage phenotypes during fibrosis-linked inflammation by combining in vivo and in vitro bulk and single-cell RNA-sequencing approaches. In the bleomycin model, nintedanib drove the expression of IL-4/IL-13-associated genes important for tissue regeneration and repair at early and late time points in lung macrophages. These findings were replicated in vitro in mouse primary bone marrow-derived macrophages exposed to IL-4/IL-13 and nintedanib. In addition, nintedanib promoted the expression of IL-4/IL-13 pathway genes in human macrophages in vitro. The molecular mechanism was connected to inhibition of the colony stimulating factor 1 (CSF1) receptor in both human and mouse macrophages. Moreover, nintedanib counterbalanced the effects of TNF on IL-4/IL-13 in macrophages to promote expression of IL-4/IL-13-regulated tissue repair genes in fibrotic contexts in vivo and in vitro. This study demonstrates that one of nintedanib's antifibrotic mechanisms is to increase IL-4 signaling in macrophages through inhibition of the CSF1 receptor, resulting in the promotion of tissue repair phenotypes.