NSUN2 enhances the stability of PTPRD mRNA via m5C methylation to aggravate astrocyte activation

This study attempts to investigate the functional role of NOP2/Sun RNA methyltransferase 2 (NSUN2) in astrocyte activation and inflammatory response following traumatic brain injury (TBI), and explore its mechanism in regulating A1 astrocyte phenotype activation through m⁵C methylation-mediated stabilization of protein tyrosine Phosphatase receptor type D (PTPRD) mRNA. Astrocyte-specific knockdown of NSUN2 and PTPRD overexpression mouse models were established, followed by TBI modeling. Neurological function and neuronal loss were evaluated, while ELISA measured inflammatory factors and m⁵C levels. Bioinformatics analysis identified m⁵C-related proteins associated with TBI and astrocytes. RT-qPCR detected NSUN2 expression, and immunofluorescence examined NSUN2-glial fibrillary acidic protein (GFAP) colocalization. In vitro experiments included m⁵C level detection, RNA immunoprecipitation, and RNA stability assays. Flow cytometry analyzed the ratios of GFAP⁺ and C3⁺ to GFAP⁺ and S100A10⁺ cells. Neuronal toxicity was assessed by TUNEL after astrocyte-neuron co-culture. TBI models showed significantly decreased Garcia scores, impaired balance beam performance, deficits in spatial memory, reduced Nissl bodies, and elevated inflammatory factors, confirming successful TBI modeling. NSUN2 expression and m⁵C levels were significantly increased in TBI models, with strong colocalization with GFAP. NSUN2 knockdown markedly attenuated TBI-induced brain damage, suppressed A1 astrocyte activation, reduced pro-inflammatory factor release, and decreased GFAP⁺C3⁺/GFAP⁺S100A10⁺ ratios, while PTPRD overexpression reversed the inhibitory effects of NSUN2 knockdown on A1 phenotype activation. In vivo validation demonstrated NSUN2 promoted A1 astrocyte activation via PTPRD, exacerbating TBI-induced brain injury. NSUN2 exacerbates A1 astrocyte activation and subsequent inflammation-mediated tissue damage following TBI through m⁵C methylation-enhanced stabilization of PTPRD mRNA.

Astrocyte; M(5)C methylation; NSUN2; PTPRD; TBI.