Aberrant ceramide accumulation fuels eosinophilic inflammation by promoting eosinophil extracellular trap formation and release in chronic rhinosinusitis with nasal polyps.

Abstract

Eosinophilic inflammation represents a hallmark pathologic feature of chronic rhinosinusitis with nasal polyps (CRSwNP). Although ceramides, the central sphingolipid metabolites, are implicated in asthma pathogenesis, their mechanistic contributions to CRSwNP remain poorly elucidated. We sought to investigate the functions and associated mechanisms of ceramide in the pathogenesis of CRSwNP. Immunofluorescence and absolute quantitative lipidomics analysis were performed to evaluate the levels of ceramide and its species in nasal biopsy samples. In vitro culture and stimulation of purified eosinophils from human peripheral blood to validate the function of ceramides. Small interfering RNA transfection and inhibition assays to determine the molecular mechanism. The expression levels of ceramide and its binding protein were enriched in eosinophilic CRSwNP. Increased Cer(18:1_24:1) was related with eosinophil extracellular trap (EET) counts and disease severity in patients with eosinophilic CRSwNP. Cer(18:1_24:1) potently induced eosinophils activation by promoting EET formation and release. Mechanistically, Cer(18:1_24:1)-induced elevated levels of reactive oxygen species (ROS)/mitochondrial ROS (mROS) promoted EET formation by upregulating PAD4/CitH3 on one hand, and drove the oligomerization of the N terminal of gasdermin D (GSDMD-N) and membrane pore formation to facilitate the EET release on the other hand. Furthermore, ceramide-binding protein PP2AC inhibition blocked EET formation and release by reduction of ROS/mROS production. Interestingly, selenium supplementation mitigated Cer(18:1_24:1)-induced EET production and release by decreasing production of ROS/mROS. Aberrant ceramide accumulation fuels eosinophilic inflammation by promoting EET formation and release through the PP2AC-ROS/mROS-GSDMD-N pathway, which may contribute to the severity and progression of eosinophilic CRSwNP. These mechanistic insights may provide novel therapeutic strategies for eosinophil-driven inflammatory disorders.