Macrophages are paracrine signalers that regulate tissular responses to injury through interactions with parenchymal cells. Connexin hemichannels have recently been shown to mediate efflux of ATP by macrophages, with resulting cytosolic calcium responses in adjacent cells. Here we report that lung macrophages with deletion of connexin 43 (MacΔCx43) had decreased ATP efflux into the extracellular space and induced a decreased cytosolic calcium response in co-cultured fibroblasts compared to WT macrophages. Furthermore, MacΔCx43 mice had decreased lung fibrosis after bleomycin-induced injury. Interrogating single cell data for human and mouse, we found that P2rx4 was the most highly expressed ATP receptor and calcium channel in lung fibroblasts and that its expression was increased in the setting of fibrosis. Fibroblast-specific deletion of P2rx4 in mice decreased lung fibrosis and collagen expression in lung fibroblasts in the bleomycin model. Taken together, these studies reveal a Cx43-dependent profibrotic effect of lung macrophages and support development of fibroblast P2rx4 as a therapeutic target for lung fibrosis.
Connexin 43 , Idiopathic Pulmonary Fibrosis , Adenosine Triphosphate/metabolism , Animals , Bleomycin/pharmacology , Calcium/metabolism , Connexin 43/genetics , Connexin 43/metabolism , Fibroblasts/metabolism , Idiopathic Pulmonary Fibrosis/metabolism , Macrophages/metabolism , Mice , Mice, Knockout
Cx3cr1+ monocyte-derived macrophages (moMacs) are recruited to tissues after injury and are known to have profibrotic effects, but the cell-cell interactions and specific pathways that regulate this polarization and function are incompletely understood. Here we investigate the role of moMac-derived Pdgfa in bleomycin-induced lung fibrosis in mice. Deletion of Pdgfa with Cx3cr1-CreERT2 decreased bleomycin-induced lung fibrosis. Among a panel of in vitro macrophage polarizing stimuli, robust induction of Pdgfa was noted with IL10 in both mouse and human moMacs. Likewise, analysis of single-cell data revealed high expression of the receptor IL10RA in moMacs from human fibrotic lungs. Studies with IL10-GFP mice revealed that IL10-expressing cells were increased after injury in mice and colocalized with moMacs. Notably, deletion of IL10ra with Csf1r-Cre: IL10ra fl/fl mice decreased both Pdgfa expression in moMacs and lung fibrosis. Taken together, these findings reveal a novel, IL10-dependent mechanism of macrophage polarization leading to fibroblast activation after injury.
Interleukin-10/metabolism , Lung Injury , Pulmonary Fibrosis , Animals , Bleomycin/pharmacology , Interleukin-10/genetics , Lung/metabolism , Lung Injury/pathology , Macrophages/metabolism , Mice , Mice, Inbred C57BL , Pulmonary Fibrosis/chemically induced , Pulmonary Fibrosis/genetics , Pulmonary Fibrosis/metabolism
