Sphingomyelin Synthase 2 Deletion Mitigates Oxidative Stress-Induced NF-κB Activation via Lipid Metabolic Reprogramming in Dry Eye Disease.

Purpose: To investigate the pathogenetic role of sphingomyelin synthase 2 (SMS2) in dry eye disease (DED). Methods: Human corneal epithelial cells (HCECs) were exposed to oxidative stress (H₂O₂), hyperosmolarity, or inflammatory stimuli to evaluate SMS2 expression. SMS2 was silenced via small interfering RNA, with cell viability and lipid peroxidation markers assessed under stress. Multi-omics identified key pathways, validated by Western blot, quantitative real-time PCR (qRT-PCR), and immunofluorescence. A benzalkonium chloride (BAC)-induced DED mouse model was established, with corneal damage, tear secretion, goblet cell density, and MUC5AC expression analyzed. SMS2 knockout (KO) and wild-type mice were compared, lipid peroxidation markers were measured, and NF-κB-associated cytokines were quantified via ELISA/qRT-PCR. Results: In HCECs, H₂O₂ time-dependently upregulated SMS2, while its silencing reduced cytotoxicity and decreased the accumulation of malondialdehyde (MDA) and 4-hydroxynonenal (4-HNE). Lipidomics revealed H₂O₂-induced accumulation of sphingomyelins and unsaturated triglycerides, suppressed by SMS2 knockdown. Multiomics highlighted NF-κB pathway inhibition with SMS2 deficiency, showing impaired IκBα degradation, reduced p65 nuclear translocation, and downregulated IL-1β, IL-6, and IL-8. In BAC-induced DED mice, SMS2 was upregulated in corneal/conjunctival epithelia, accompanied by increased ocular tissue MDA/4-HNE levels. SMS2-KO mice exhibited reduced lipid peroxidation, milder corneal damage, increased tear secretion, restored goblet cell density, and elevated MUC5AC expression. NF-κB-dependent cytokines were reduced in SMS2-KO tissues at transcriptional and protein levels. Conclusion: SMS2 promotes DED progression by driving oxidative stress-induced lipid dysregulation and NF-κB activation. SMS2 deficiency attenuates ocular surface damage, restores tear function, and suppresses inflammation, identifying SMS2 as a therapeutic target for DED.