Synergistic Interaction Between MALAT1/miR‐30b‐5p/BAFF Axis and Inflammatory Cytokines Underlies Rituximab‐Refractory NMOSD

BACKGROUND AND OBJECTIVE: Despite achieving complete peripheral B cell deletion after over 6 months of rituximab therapy, a clinically significant minority of neuromyelitis optica spectrum disorder (NMOSD) patients experience breakthrough relapses, yet the underlying mechanism remains unclear. Our study aims to explore the underlying mechanism-the contribution of the MALAT1/miR-30b-5p/BAFF axis activation in monocytes to NMOSD disease attacks and relapses resistant to rituximab therapy. METHODS: To investigate immune dysregulation in NMOSD, we established clinical groups comprising peripheral blood mononuclear cells (PBMCs) and serum from NMOSD patients: onset cases (PBMCs: n = 10; serum: n = 23) and rituximab-treated cases subdivided into remission (n = 26) and rituximab-refractory relapse (n = 13), along with healthy controls (n = 15). To profile the MALAT1/miR-30b-5p/BAFF axis and inflammatory mediators, we quantified MALAT1, miR-30b-5p, BAFF, and cytokine levels using qPCR, ELISA, and Western Blot and validated molecular interactions via dual-luciferase reporter assays. To characterize cellular heterogeneity, single-cell RNA sequencing (scRNA-seq) was performed on PBMCs from two rituximab-refractory relapsed NMOSD patients, two rituximab-remission NMOSD patients, and two healthy controls. For mechanistic validation, THP-1 cells were transfected with MALAT1 overexpression constructs or miR-30b-5p mimics, followed by functional assessments to determine their roles in monocyte activation and cytokine production. RESULTS: Significant activation of the MALAT1/miR-30b-5p/BAFF axis was observed in NMOSD patients at disease onset compared to healthy controls. Moreover, this axis correlated with rituximab-refractory NMOSD, featuring monocyte-specific MALAT1 upregulation and elevated serum BAFF in rituximab-refractory relapse patients. In THP-1 cells, the overexpression of MALAT1 downregulated miR-30b-5p, resulting in increased BAFF expression and pro-inflammatory cytokines secretion (IL-1β, IL-8, TNF-α), while also accelerating cell proliferation. Significantly, transfection with miR-30b-5p mimics reversed the MALAT1-driven upregulation of BAFF and pro-inflammatory cytokines, supporting the MALAT1/miR-30b-5p/BAFF axis as a regulatory circuit underlying inflammatory dysregulation in NMOSD. CONCLUSION: We identify the MALAT1/miR-30b-5p axis as a driver of NMOSD pathogenesis and rituximab-refractory relapse. Upregulation of monocytic MALAT1 suppresses miR-30b-5p, leading to increased BAFF and pro-inflammatory cytokines secretion, thereby promoting inflammatory responses. Targeting this pathway may offer therapeutic potential for relapse prevention.