Ly93 Inhibits Sphingomyelin Synthesis and Attenuates Inflammation and Injury in Dry Eye Conjunctival Organoids

We aimed to investigate the pathogenic role of sphingomyelin (SM) in dry eye disease (DED) and evaluate Ly93, an SM synthase inhibitor, as a potential therapy for DED-associated inflammation.

Tear samples from DED patients and healthy participants were analyzed for SM concentrations using liquid chromatography-tandem mass spectrometry. Correlations between SM levels and clinical parameters were evaluated. The effects of SM on normal conjunctival organoids and the therapeutic efficacy of Ly93 on hyperosmolarity-induced DED conjunctival organoids were investigated. SM levels after treatment with Ly93 were also measured. The inflammatory cytokines (IL-1β, IL-6, and MMP-9), signaling pathways (STAT1, nuclear factor-κB, and PI3K), apoptosis (caspase-3 and caspase-9), ferroptosis (Fe2+, GPX4, TFR, and 4-HNE) were analyzed.

Tear SM concentrations were significantly elevated in DED patients and positively correlated with disease severity. Exogenous SM upregulated STAT1, IL-1β, IL-6, and inducible nitric oxide synthase expression in conjunctival organoids. Hyperosmolarity-induced DED conjunctival organoids exhibited elevated MMP-9 and IL-1β, activated signaling pathways (nuclear factor-κB, STAT1, and PI3K), increased apoptosis (caspase-3 and caspase-9), and ferroptosis (elevated Fe2+, TFR, and 4-HNE, and decreased GPX4). Ly93 treatment effectively reduced SM levels and attenuated inflammation, apoptosis, and ferroptosis in the DED organoid model.

Our study demonstrates that elevated SM promotes ocular surface inflammation and cellular injury. Inhibition of SM synthase by Ly93 alleviates DED-associated inflammation and injury, suggesting that targeting SM metabolism represents a promising therapeutic strategy.