Mechanism of Mettl14 regulating AIM2 inflammasome activation and neuronal apoptosis and pyroptosis in spinal cord injury by mediating PPARγ m6A methylation.

Abstract

Spinal cord injury (SCI) represents a destructive pathological and neurological state. Methyltransferase-like 14 (Mettl14)-mediated m6A modification links to spinal cord injury (SCI), and we explored its mechanism. SCI mouse models were subjected to si-Mettl14 and si-negative control treatments and mouse behavior, pathological condition and apoptosis assessments. The oxygen/glucose deprivation (OGD)-induced spinal cord neuronal cell models were processed with si-Mettl14 and si-peroxisome proliferator-activated receptor γ (PPARγ) plasmids, and pcDNA3.1-YTHDF2 or synthetic dsDNA Poly(dA: dT), followed by viability and apoptosis evaluation by MTT and flow cytometry. Levels of Mettl14, PPARγ, and YTHDF2 mRNAs and proteins, AIM2 inflammasome activation-associated and pyroptosis marker proteins, PPARγ m6A methylation and pyroptosis-related inflammatory factors were determined by RT-qPCR, Western blot, Me-RIP and ELISA, with PPARγ mRNA stability and YTHDF2-PPARγ interaction assessed. Mettl14 and PPARγ m6A modification levels rose in SCI spinal cord tissues, while PPARγ levels dropped. Mettl14 knockdown dampened m6A modification, up-regulated PPARγ levels, weakened neuronal apoptosis, and ameliorated SCI in mice. OGD down-regulated PPARγ and accelerated OGD-induced neuronal apoptosis and pyroptosis via inducing Mettl14-mediated m6A modification. Mettl14 amplified PPARγ mRNA degradation and down-regulated PPARγ by mediating m6A methylation via the YTHDF2-dependent pathway. Mettl14 silencing-mediated PPARγ m6A methylation mitigated OGD-induced neuronal apoptosis and pyroptosis by inactivating AIM2 inflammasome. Mettl14 triggered activated AIM2 inflammasomes, promoted neuronal apoptosis and pyroptosis, and worsened SCI in SCI mice via mediating PPARγ m6A methylation. Mettl14 regulates AIM2 inflammasome activation, and redounds to spinal cord neuronal apoptosis and pyroptosis in SCI by mediating m6A methylation of PPARγ.