Pyroptosis of pulmonary fibroblasts through NLRC4 inflammasome leads to acuterespiratory failure

The NAIP-NLRC4 inflammasome plays a pivotal role in the defense against bacterial infections. Thus far, the in vivo physiological function of the NAIP-NLRC4 inflammasome is acknowledged primarily as a driving force of inflammation and limited to immune cells. Acute lung injury and its severe manifestation, acute respiratory failure (ARF), are the leading cause of mortality in septic patients. Here we identify that the NAIP/NLRC4 inflammasome is highly and specifically expressed in pulmonary fibroblasts and that pyroptosis of pulmonary fibroblasts play a critical role in acute lung injury. We found that mice challenged with Gram-negative bacteria or flagellin developed lethal ARF, evident by a reduction in blood oxygen saturation, disruption of lung barrier function, and escalated inflammation. Flagellin-induced ARF was protected in caspase-1 or fibroblast-specific GSDMD deficient mice. These findings not only expand our knowledge on the (patho)physiological function of the NAIP-NLRC4 inflammasome, but also demonstrate an underappreciated role of inflammasome activation and pyroptosis in the development of ARF during sepsis. Overall design: To detect the types of cells changing during inflammasome-dependent acute lung injury, we performed single-cell RNA sequencing of lung cells. C57BL/6 were divided into PBS and LFn-flagellin/PA treated groups. We then performed gene expression profiling using data from RNA-seq of these two group.