[Causal associations between immune cell phenotypes and Ménière's disease: a bidirectional two-sample Mendelian randomization study and validation in mice].

objectivesTo explore the causal relationship between 731 immune cell phenotypes and Ménière's disease (MD) using Mendelian randomization (MR) analysis and experimental validation in mice.

methodsBased on GWAS data and with immune cell phenotypes and MD as the exposure and outcome variables respectively, we conducted MR analysis using inverse variance weighting (IVW) supplemented by MR-Egger and weighted median methods. Heterogeneity, pleiotropy and leave-one-out sensitivity analyses were performed. Thirty C57BL/6 mice were randomly divided into control, model and anti-CD20 mAb groups, and in the latter two groups, endolymphatic hydrops models were established by LPS injection behind the ear; treatment with the anti-CD20 mAb was administered via tail vein injection before modeling. Auditory and vestibular functions of the mice were evaluated by auditory brainstem response (ABR), water maze and open field tests. HE staining, immunofluorescence, qPCR, Western blotting, immunohistochemistry and ELISA were used to examine inner ear pathology, expressions of immune markers, TLR4/NF-κB pathway, AQP3, and ZO-1, and serum levels of inflammatory factors.

resultsMR analysis identified CD19⁺B cells, CD27⁺IgD⁻CD38⁺B cells and CD3⁺T cells as the major risk factors, and CD39⁺CD4⁺T cells as the core protective factor. Sensitivity analysis confirmed robustness of the results without heterogeneity, pleiotropy or reverse causality. The mouse models of endolymphatic hydrops showed obvious auditory/vestibular dysfunction, endolymphatic hydrops, upregulated CD19, CD27 and CD3 expressions, downregulated CD39, AQP3 and ZO-1 expressions, activated TLR4/NF-κB pathway, and elevated serum levels of inflammatory factors. All these abnormalities were significantly improved in anti-CD20 mAb treatment group.

conclusionsImmune cell phenotype abnormality is causally associated with MD, and B cell activation-mediated immune imbalance contributes to MD via the TLR4/NF-κB pathway, inducing inner ear inflammation and abnormal fluid/barrier function. Anti-CD20 mAb ameliorates MD pathology and dysfunction by depleting activated B cells, which provides new evidence for MD immunotherapy.