METTL3 mitigates age-related hearing loss by inhibiting NF-κB-mediated inflammatory responses through the m⁶A...

Age-related hearing loss (ARHL) is a prevalent and debilitating sensory deficit in the elderly, with chronic inflammation being a key pathogenic driver. The RNA methyltransferase METTL3, a primary mediator of N6-methyladenosine (m6A) modification, has been implicated in various aging-related diseases; however, its functional role and mechanism in ARHL remain poorly defined. ARHL models were established using 12-month-old C57BL/6 mice and by treating HEI-OC1 auditory cells with LPS and D-galactose. Auditory function and cochlear pathology were assessed through auditory brainstem response (ABR) thresholds and hematoxylin-eosin (H&E) staining, respectively. Inflammatory cytokine levels, gene and protein expression, were measured using ELISA, qPCR, Western blotting, and immunofluorescence. The molecular mechanism of METTL3 in inflammation was investigated using m6A RNA methylation quantification kit, RIP-qPCR analysis, and RNA stability assay. We found that both NFKBIA and METTL3 were significantly downregulated in the cochleae of ARHL mice. In HEI-OC1 cells, overexpression of NFKBIA suppressed the NLRP3 inflammasome and the pro-inflammatory NF-κB/IL-6/STAT3 axis. Furthermore, METTL3 overexpression mitigated NF-κB-mediated inflammation, an effect that was significantly attenuated upon NFKBIA knockdown. Mechanistically, METTL3 directly bound to NFKBIA mRNA and enhanced its stability through m6A modification. Critically, in ARHL mice, METTL3 overexpression restored NFKBIA levels, ameliorated hearing loss and cochlear damage, and suppressed the activation of the NLRP3 inflammasome and the NF-κB/IL-6/STAT3 pathway. Collectively, METTL3 mitigated ARHL by downregulating the NF-κB/IL-6/STAT3/NLRP3-mediated inflammatory responses through the enhancement of NFKBIA m6A modification.