TGF-β-Induced CCR8 Promoted Macrophage Transdifferentiation into Myofibroblast-Like Cells

Abstract Background: Idiopathic pulmonary fibrosis (IPF) is an unknown interstitial disease characterized by tissue fibrosis for which there currently is no effective treatment. Macrophages, as the main immune cells in lung tissue, are involved in the whole process of pulmonary fibrosis. In recent years, intercellular transformation has been widespread concerned in pulmonary fibrosis researchers. The macrophages which have flexible heterogeneity and plasticity participate in different physiological processes of the body. Cell chemokine receptor 8 (CCR8) expressed in a variety of cells plays a significant chemotactic role in inducing cell activation and migration. And it could also promote the differentiation of macrophages under certain environmental conditions. The current study is intended to explore the role of CCR8 in macrophage transdifferentiation into myofibroblast cells in idiopathic pulmonary fibrosis.Methods: We conducted experiments using Ccr8-specific small interfering RNA (siRNA), autophagy inhibitor (3-methyladenine,3-MA) and agonist (rapamycin) to explore the underlying mechanisms of macrophage transdifferentiation into myofibroblast cells in TGF-β induced pulmonary fibrosis. Results: The results indicated that TGF-β treatment increased the CCR8 protein level in a time- and a dose-dependent manner in MH-S, as well as macrophage transdifferentiation-related markers, including Vimentin, Collagen 1, and a-SMA, and cell migration. In addition, levels of autophagy were enhanced in macrophages treated with TGF-β. We found that 3-MA, an autophagy inhibitor decreased the expression levels of macrophage transdifferentiation-related markers and attenuated the cell migration. Furthermore, inhibition of CCR8 through using Ccr8-specific siRNA reduced the levels of autophagy and macrophage transdifferentiation-related markers, and inhibited the cell migration. Enhancing autophagy with rapamycin attenuated the inhibition effect of Ccr8-specific siRNA on macrophage migration and the increase of myofibroblast marker proteins.Conclusions: Our findings showed that the macrophages exposed to TGF-β had the potential to transdifferentiate into myofibroblasts and CCR8 was involved in the process. The effect of CCR8 in TGF-β-induced macrophage transdifferentiation occurs mainly through autophagy. Targeting the CCR8 may become a novel therapeutic strategy for the treatment of IPF.