miRNA-34b overexpression alleviates neuromyelitis optica spectrum disorders by regulating the TIA-1-stress granule pathway

Abstract: Background: Neuromyelitis optica spectrum disorders (NMOSD) are autoimmune demyelinating diseases of the central nervous system. The role of microRNA-34b (miR-34b) in NMOSD pathogenesis remains unclear. This study investigates the expression and functional mechanism of miR-34b in NMOSD, specifically its regulation of the TIA-1-stress granule pathway. Objectives: To determine the expression level of miR-34b in NMOSD tissues and cell lines and to elucidate whether miR-34b suppresses cell proliferation and promotes apoptosis by directly targeting the TIA-1-stress granule pathway. Methods: Real-time PCR was used to detect miR-34b expression in 25 NMOSD tissue specimens obtained from a hospital laboratory (13 early-stage, 12 chronic-stage) and 10 normal control tissues, as well as in RGC-5 cells. RGC-5 cells were transfected with miR-34b mimics, inhibitors or negative controls. Cell proliferation was assessed by MTT assay and cell cycle distribution and apoptosis was analyzed by flow cytometry (PI staining and Annexin V-FITC/PI double staining, respectively). The direct binding between miR-34b and the 3'-UTR of TIA-1 mRNA was validated using a dual-luciferase reporter assay. Protein expression levels of TIA-1, SG, HuR, CDK2 and BCL-2 were measured by Western blot. A rescue experiment was performed by co-transfecting miR-34b mimics with a TIA-1 overexpression plasmid. Results: miR-34b was lower in NMOSD vs controls (0.32 ± 0.08 vs. 1.00 ± 0.12, P<0.01), especially in the chronic stage. miR-34b mimics inhibited proliferation, induced G0/G1 arrest (68.5% vs. 52.1%, P<0.01) and increased apoptosis (22.6% vs. 8.3%, P<0.001). miR-34b inhibitor had opposite effects. miR-34b directly bound TIA-1 3'-UTR and downregulated TIA-1, SG, HuR. TIA-1 overexpression partially reversed miR-34b effects. Conclusions: miR-34b is downregulated in NMOSD. Overexpression of miR-34b suppresses proliferation and promotes apoptosis by targeting the TIA-1-stress granule pathway. Restoring miR-34b may be a therapeutic strategy for NMOSD.