The mechanosensitive PIEZO1 channel promotes CD54+/iNOS+ neutrophil expansion in pulmonary fibrosis

Pulmonary fibrosis (PF) represents the common end-stage outcome of a broad range of interstitial lung diseases. The shared pathophysiologic mechanisms remain poorly understood. Here, we identify two phenotypically distinct neutrophil subsets in PF: a pro-inflammatory subset characterized by CD54 (human) or iNOS (mouse) expression, and an alternative subset marked by Arg1 expression. Notably, CD54+ and iNOS+ neutrophils were markedly expanded in PF patients and mice with bleomycin-induced PF, respectively. Adoptive transfer of iNOS+ neutrophils exacerbated fibrosis in bleomycin-induced PF, whereas transfer of Arg1+ neutrophils had no significant effect. Further, the expression of PIEZO1, a mechanically activated ion channel, is predominantly upregulated in CD54+ neutrophils from PF patients or iNOS+ neutrophils from PF mice. Piezo1 ablation in neutrophils selectively impairs iNOS+ neutrophil differentiation, thereby attenuating fibrosis progression. Mechanistically, PIEZO1 promotes the differentiation of these pro-inflammatory subsets through the transcription factor IRF4 in a calcium-dependent manner. We further identify the JAK/STAT pathway as an upstream regulator of PIEZO1 expression in neutrophils. Consequently, PIEZO1 expression and CD54+ neutrophils are markedly decreased in patients treated with JAK inhibitor baricitinib. Importantly, combined inhibition of JAK/STAT and calcium signaling exerts synergistic suppression on the iNOS+ neutrophil expansion and PF progression. Together, our findings reveal a mechanism in which PIEZO1 promotes PF by specifically driving the expansion of CD54+/iNOS+ neutrophils. Neutrophils have been shown to be involved in pulmonary fibrosis (PF). Here, the authors identify an expanded pro-inflammatory neutrophil state marked by CD54 in human PF and by iNOS in murine PF, demonstrate that iNOS+ neutrophils promote PF whilst Arg+ neutrophils are less effective, and show that mechanical activation of the PIEZO1 channel contributes to the promotion of PF by CD54 + /iNOS+ neutrophils.