Very-long-chain Ceramide Cer24:1 Alleviates LPS-induced Airway Inflammation in Neutrophilic Asthma by Inhibiting Th17 Differentiation

<bold>Background:</bold> Th17 cells and IL-17A play important roles in the pathogenesis of neutrophilic airway inflammation. Metabolomics has revealed the vital role of sphingolipid in asthma, but the biological function of ceramides remains unclear. <bold>Objective:</bold> This study investigated the effect of very-long-chain ceramide (VLCC) on Th17 differentiation and airway inflammation in neutrophilic asthma. <bold>Methods:</bold> In this study, we first included patients with asthma and analyzed phospholipids in exhaled breath condensate (EBC) and plasma. In addition, the effect of Cer24:1 on airway inflammation and lung Th17 was investigated in a Lipopolysaccharides(LPS)-induced neutrophilic asthma mouse model. Flow cytometry was used to detect the effect of Cer24:1 on Th17 differentiation, and RNA sequencing was performed to explore the possible mechanisms of Cer 24:1. <bold>Results:</bold> The abundance of Cer24:1, a type of VLCC in EBC and plasma, was significantly reduced in patients with neutrophilic asthma and negatively correlated with Th17 in blood and neutrophil in sputum. In mice with neutrophilic asthma, Cer24:1 was decreased in the lung and bronchoalveolar lavage fluid. After Cer24:1 injection, airway resistance and lung inflammation were alleviated and Th17 in the lung were significantly reduced. Cer24:1 also effectively inhibited Th17 differentiation in vitro. Thus, Cer24:1 may act by binding to the PIP4K2C and inhibit Th17 differentiation through the JAK2-STAT3 pathway. <bold>Conclusions:</bold> This study found reduced Cer24:1 in patients with neutrophilic asthma, indicating that Cer24:1 may inhibit Th17 differentiation and ameliorate airway inflammation in neutrophilic asthma.