YTHDF2-dependent m⁶A modification of FOXO3 mRNA mediates TIMP1 expression and contributes to intervertebral disc...

The accumulation of reactive oxygen species (ROS) significantly contributes to intervertebral disc degeneration (IDD), but the mechanisms behind this phenomenon remain unclear. This study revealed elevated ROS levels in the intervertebral discs (IVDs) of aged mice compared to those of younger mice. The local application of hydrogen peroxide (H₂O₂) near lumbar discs also induced ROS accumulation and IDD. Isobaric tags for relative and absolute quantitation (iTRAQ) analysis of discs from aged and H₂O₂-injected mice showed increased levels of YTH N6-methyladenosine RNA binding protein F2 (YTHDF2) and matrix metallopeptidase 1/3/7/9 (MMP1/3/7/9), along with decreased levels of forkhead box O3 (FOXO3) and TIMP1 (tissue inhibitor of metalloproteinases 1). Our experiments indicated that in nucleus pulposus (NP) cells and young mouse IVDs that were not exposed to ROS, FOXO3 recruited histone acetyltransferase CBP (CREB binding protein) and mediator complex subunit 1 (Med1) to activate TIMP1 expression, which inhibited MMP activity and prevented disc degeneration. However, ROS exposure activated YTHDF2 and promoted the degradation of m⁶A-modified FOXO3 mRNA, impairing FOXO3's ability to activate TIMP1. This degradation exacerbated MMP activity and contributed to the degradation of the IVD extracellular matrix. Notably, administration of the YTHDF2 inhibitor DC-Y13-27 in older and H₂O₂-treated mice significantly enhanced FOXO3 and TIMP1 expression, reduced MMP activity, and mitigated IVD degeneration. Together, this study uncovers a novel ROS-regulated pathway in IDD, centered on the YTHDF2/FOXO3/TIMP1/MMPs axis, suggesting that targeting YTHDF2 may represent a promising therapeutic strategy for combating the progression of IDD.