Pterostilbene mitigates intervertebral disc degeneration via dual regulation of mitophagy and NLRP3 ubiquitination to inhibit nucleus pulposus cell pyroptosis

BACKGROUND: Intervertebral disc degeneration (IVDD) is a major contributor to low back pain and is characterized by mitochondrial dysfunction, inflammation, and regulated cell death in nucleus pulposus (NP) cells. NLRP3 inflammasome-mediated pyroptosis plays a pivotal role in disc degeneration, whereas mitophagy limits mitochondrial damage and inflammasome activation. Emerging evidence indicates that pterostilbene (PTE) exhibits diverse pharmacological activities; however, its role in attenuating IVDD remains insufficiently understood. OBJECTIVE: To investigate whether PTE attenuates IVDD by regulating mitophagy and NLRP3 inflammasome-mediated pyroptosis, and to elucidate the underlying molecular mechanisms. STUDY DESIGN: This study combined network pharmacology analysis, in vitro cellular experiments, and an in vivo rat IVDD model to evaluate the therapeutic effects and mechanisms of PTE. METHODS: Network pharmacology was used to predict the cytoprotective potential of PTE. In vitro, LPS-stimulated NP cells were employed to evaluate inflammation, extracellular matrix degradation, pyroptosis, mitochondrial function, and mitophagic flux. Pharmacological inhibitors were used to interrogate mitophagy-dependent mechanisms, while Western blotting, co-immunoprecipitation, and related assays were performed to assess signaling pathways, protein stability, and ubiquitination. In vivo, a rat IVDD model was established to evaluate the therapeutic effects of PTE through radiological and histopathological analyses. RESULTS: PTE attenuated LPS-induced inflammatory responses and extracellular matrix degradation in NP cells. It suppressed NLRP3 inflammasome-mediated pyroptosis and restored mitochondrial function by enhancing mitophagic flux, whereas inhibition of mitophagy partially reversed these protective effects. Mechanistically, PTE activated the AMPK/mTOR/ULK1 signaling pathway to promote mitophagy. In parallel, PTE facilitated ubiquitination and proteasomal degradation of NLRP3, predominantly through K48-linked polyubiquitination, while K63-linked modification may contribute to regulatory signaling. Notably, this ubiquitination-mediated degradation occurred independently of mitophagy. In vivo, PTE significantly alleviated disc degeneration, reduced NLRP3, caspase-1, and p-mTOR expression, and increased collagen II, SOX9, PINK1, LC3, and p-AMPK levels. CONCLUSION: PTE attenuates IVDD progression by coordinately enhancing mitophagy and promoting K48-linked ubiquitin-proteasome-dependent degradation of NLRP3. These two mechanisms operate independently yet synergistically to suppress inflammasome activation, providing mechanistic insight into PTE as a potential disease-modifying therapeutic strategy for IVDD.