Sodium butyrate modulates ocular surface microbiome and attenuates inflammation of meibomian gland dysfunction in ApoE-/- mice.

BACKGROUND: The ocular surface microbiome (OSM) in patients with meibomian gland dysfunction (MGD) differs from that of healthy individuals. However, the precise role of OSM in MGD remains unknown. Therefore, we aimed to investigate the mechanism of OSM in the inflammation of MGD and the effects of topical sodium butyrate (SB) treatment in ApoE-/- mice. METHODS: ApoE-/- (n = 36) and wild-type C57BL/6J (n = 16) mice served as MGD models and healthy controls, respectively. MGD mice were treated with safety-confirmed concentrations of SB (1, 5, and 10 mM) and PBS for 3 weeks. OSM was analyzed by 16S rRNA gene sequencing (V3-V4). The slit-lamp biomicroscopy, tear cytokines, histopathology (oil red O/PAS/TUNEL staining), and TLR4/MyD88/NF-κB signaling (RT-qPCR, immunohistochemistry, and Western blotting) were evaluated. RESULTS: Five-month-old ApoE-/- mice exhibited typical clinical and histological features of MGD. These mice exhibited elevated tear levels of inflammatory cytokines and activation of the TLR4/NF-κB signaling pathway in the MGs and conjunctivae. Treatment with SB improved the corneal fluorescein staining score of MGD. The ApoE-/- mice demonstrated dysbiosis of OSM, characterized by an increase in Proteobacteria and a decrease in Bacteroidota. Additionally, the relative abundance of Muribacter and Muribacter muris increased in ApoE-/- mice, while that of Staphylococcus and Staphylococcus lentus decreased, and these alterations were restored by SB treatment. SB also reduced the expression of the TLR4/NF-κB p65 signaling pathway, inflammatory cytokines, and apoptosis in MGs and conjunctival tissues. CONCLUSION: ApoE-/- mice exhibited characteristic features of MGD, accompanied by dysbiosis of OSM. Topical administration of SB modulated the OSM and reduced MGD-associated inflammation. Video Abstract.