DDIT3 drives nucleus pulposus cell PANoptosis and intervertebral disc degeneration progression

Intervertebral disc degeneration (IDD) is closely linked to nucleus pulposus (NP) cell death exhibiting a PANoptotic phenotype-concurrent activation of apoptosis, necroptosis, and pyroptosis-yet its molecular regulators remain unclear. Here we identify DNA damage-inducible transcript 3 (DDIT3) as a key mediator of inflammatory PANoptosis. RNA sequencing of TNF-α-treated human NP cells revealed robust DDIT3 upregulation, consistent with observations in degenerated human discs and a rat needle-puncture IDD model. In vitro, DDIT3 knockdown (siRNA) reduced PANoptosis markers (NLRP3, caspase-1 p20, Bax, cleaved caspase-3, MLKL, p-MLKL), inflammatory cytokines (IL-1β, IL-18), and reactive oxygen species (ROS), whereas DDIT3 overexpression produced the opposite effects. Mechanistically, transcriptomics and luciferase assays indicated that DDIT3 transactivates CUL3; direct promoter binding was corroborated by chromatin immunoprecipitation and electrophoretic mobility shift assays. Molecular docking (predictive) together with co-immunoprecipitation supported a CUL3-caspase-8 interaction, and CUL3-dependent polyubiquitination enhanced caspase-8 activation. In vivo, lentiviral DDIT3 silencing mitigated disc degeneration in rat puncture models, preserved aggrecan/collagen II, and reduced PANoptotic readouts, whereas DDIT3 overexpression accelerated matrix loss. Collectively, these findings position the DDIT3-CUL3-caspase-8 axis as a central regulator of inflammatory PANoptosis in NP cells and a potential therapeutic target for halting IDD progression.