YAP/TAZ are Crucial Regulator of Macrophage-mediated Pulmonary Inflammation and Fibrosis after Bleomycin-induced Injury

Pulmonary fibrosis (PF) is the most prevalent and severe form of end-stage interstitial lung disease. Macrophages are crucial players in inflammation-induced PF, but the mechanisms driving macrophage polarization and their specific roles in PF pathogenesis remain poorly understood. Here, we demonstrate that both YAP and TAZ are activated in lung macrophages from patients with PF as well as in mice with bleomycin-induced PF. Myeloid-specific Yap/Taz deletion resulted in reduced recruitment of monocyte-derived alveolar macrophages (Mo-AMs), impaired inflammatory responses, decreased PF, and enhanced alveolar epithelial cell regeneration following bleomycin treatment. Conversely, the expression of a constitutively active YAP mutant (YAP 5SA ) exacerbated bleomycin-induced PF by increasing Mo-AM recruitment, elevating expression of proinflammatory and profibrotic markers, and impairing alveolar epithelial cell regeneration. We demonstrate that YAP/TAZ-CCL2 signaling plays a crucial role in bleomycin-induced PF, as blocking CCL2 with a neutralizing antibody effectively abrogated the YAP 5SA -induced recruitment of Mo-AMs, inflammatory and fibrotic responses. Additionally, we reveal that the YAP/TAZ-MBD2-TGFβ1-pSMAD2 signaling axis is crucial not only for profibrotic macrophage polarization but also for their crosstalk with lung fibroblasts, driving the fibroblast-to-myofibroblast transition. Collectively, these findings suggest that targeting aberrant YAP/TAZ activity to modulate inflammatory and fibrotic response could be a promising strategy for the prevention and treatment of PF.