The role and mechanism of autophagy-regulated Keap1/Nrf2 pathway in oxidative stress-induced cartilage endplate cell apoptosis.

BACKGROUND

Intervertebral disc degeneration (IVDD), a leading cause of chronic low back pain, involves oxidative stress, impaired autophagy, and apoptosis. However, the dynamic crosstalk among Kelch-like ECH-associated protein 1/Nuclear factor erythroid 2-related factor 2 (Keap1/Nrf2) antioxidant signaling, autophagy, and cell death during IVDD progression remains unclear.

METHODS

Degenerated disc tissues from patients were examined using histology, transmission electron microscopy (TEM), and Western blot. A rat IVDD model was established to assess temporal changes (12 weeks vs. 24 weeks). In vitro, oxidative stress was induced in chondrocytes by H₂O₂. Autophagy was modulated via pharmacological inhibitors [3-methyladenine (3-MA), bafilomycin A1 (Baf-A1), chloroquine (CQ)] and genetic tools (siRNA targeting BECN-1/Atg7, p62 overexpression, BECN-1 overexpression). Markers of Keap1/Nrf2 signaling, autophagy, apoptosis, and matrix metabolism were evaluated.

RESULTS

Clinical IVDD tissues showed disrupted structure, suppressed autophagy (reduced BECN-1/Atg7/LC3-II, elevated p62), weakened Nrf2 signaling (low Nrf2/p-Nrf2/SOD1/SOD2), and increased apoptosis. In rats, autophagy was transiently enhanced at 12 weeks but declined at 24 weeks. Autophagy inhibition exacerbated H₂O₂-induced damage by suppressing Nrf2 signaling. BECN-1 overexpression restored autophagy, reactivated Nrf2, and alleviated apoptosis and matrix degradation. In vivo BECN-1 therapy reduced apoptosis, restored autophagic flux, and improved disc structure.

CONCLUSION

Autophagy sustains disc homeostasis by regulating Keap1/Nrf2-mediated antioxidant defense. Impaired autophagy accelerates IVDD via oxidative stress and apoptosis, while BECN-1 overexpression offers therapeutic potential by restoring autophagy-Nrf2 crosstalk.