CerS6 orchestrates mitochondrial-immune crosstalk via BNIP3-dependent mitophagy suppression and mtDNA-STING/NLRP3 activation in acute lung injury.

Acute lung injury (ALI) is characterized by impaired alveolar epithelial barrier function and mitochondrial dysfunction in type II alveolar epithelial cells (AT2 cells). Ceramide synthase 6 (CerS6), a key enzyme in sphingolipid metabolism responsible for generating C16:0 ceramide, has not previously been implicated in ALI. This study reveals that CerS6 expression is significantly upregulated in AT2 cells during lipopolysaccharide (LPS)- and cecal ligation and puncture (CLP)-induced ALI. Specific knockout of CerS6 in AT2 cells attenuates apoptosis, inflammation, oxidative stress, and barrier disruption in an ALI mouse model while preserving mitochondrial function. Mechanistically, CerS6 directly interacts with the mitophagy receptor BNIP3, disrupting its binding to LC3 and thereby inhibiting mitophagy. The impaired mitochondrial clearance mechanism promotes cytoplasmic release of mtDNA and activates the STING/NLRP3 signaling cascade. RNA-Seq further confirmed that CerS6 knockdown suppressed the STING/NLRP3 pathway and upregulated BNIP3. Notably, CerS6 metabolite C16:0 ceramide also participated in these effects, reinforcing the pivotal role of sphingolipid metabolism in linking mitochondrial stress to innate immune activation. In summary, this study establishes CerS6 as a core driver of mitochondrial dysfunction and redox imbalance in acute lung injury, and indicates that both CerS6 and C16:0 ceramide may serve as potential therapeutic targets.