Panoply™ Human CCR4 Knockdown Stable Cell Line

Pulmonary fibrosis (PF) is a fatal respiratory disease with limited treatment options and a poor prognosis. The chemokine CCL17 plays a crucial role in the pathogenesis of immune diseases. CCL17 levels in bronchoalveolar lavage fluid (BALF) are significantly higher in patients with idiopathic pulmonary fibrosis (IPF) than in healthy volunteers. However, the source and function of CCL17 in PF remain unclear. Here, researchers demonstrate that CCL17 levels are elevated in the lungs of IPF patients and mice with bleomycin (BLM)-induced PF. Specifically, CCL17 is upregulated in alveolar macrophages (AMs), and antibody blockade of CCL17 protects mice from BLM-induced fibrosis and significantly reduces fibroblast activation. Mechanistic studies indicate that CCL17 interacts with the fibroblast receptor CCR4, thereby activating the TGF-β/Smad signaling pathway, promoting fibroblast activation and tissue fibrosis. Furthermore, knockdown of CCR4 by CCR4-siRNA or blockade of CCR4 with the CCR4 antagonist C-021 ameliorated pulmonary fibrosis pathology in mice. In conclusion, the CCL17-CCR4 axis is involved in the progression of pulmonary fibrosis, and targeting CCL17 or CCR4 could inhibit fibroblast activation and tissue fibrosis and may benefit patients with fibroproliferative lung diseases.

Transwell assays demonstrated enhanced migration of MRC5 cells following CCL17 induction (Figure 1A). However, this effect was abolished in CCR4 knockdown MRC5 cells (Figure 1A). CCR4 knockdown significantly reduced the expression of α-SMA and COL1 in CCL17-treated fibroblasts (Figure 1B and C). Similar data were obtained in MRC5 cells following α-SMA immunostaining (Figure 1D). CCL17 treatment did not increase the phosphorylation of Smad2 and Smad3 in CCR4 knockdown cells (Figure 1E). Furthermore, inhibition of CCR4 with the potent CCR4 antagonist C-021 abolished the CCL17-induced enhancement of SBE4-luciferase reporter gene activity (Figure 1F). Collectively, these results suggest that CCL17 signals through CCR4 to mediate fibroblast activation.

Figure 1. CCL17 activates fibroblasts in a CCR4-dependent manner. (Wang Q, et al., 2023)