The protective up-regulation of metallothionein-2A in intervertebral disc degeneration inhibits nucleus pulposus cell ferroptosis through activation of the PI3K/AKT/mTOR pathway

Intervertebral disc degeneration (IVDD) is a major contributor to low back pain, influenced by various factors including cellular senescence, apoptosis, oxidative stress, and inflammation. Metallothionein-2A (MT2A), due to its unique metal-binding and antioxidant capacity, plays a critical role in various diseases. This research sought to clarify how MT2A inhibits the progression of IVDD. Single-cell sequencing analysis revealed that ferroptosis was involved in IVDD, and MT2A was significantly upregulated in the degenerated nucleus pulposus tissue. In vitro, Tert-Butyl Hydroperoxide (TBHP) treatment induced MT2A expression. Knockdown of MT2A exacerbated TBHP-induced ferroptosis, whereas MT2A overexpression or treatment with ferrostatin-1 reversed ferroptosis, lipid peroxidation, and mitochondrial damage. In vivo, AAV-mediated MT2A overexpression significantly alleviated puncture-induced IVDD in rats. Mechanistically, MT2A overexpression activated PI3K/AKT/mTOR pathway, and this protective effect was significantly attenuated upon treatment with specific pathway inhibitors. In Conclusion, our findings demonstrate that MT2A is protectively upregulated in IVDD and mitigates ferroptosis of NP cells and IVDD progression through activation of the PI3K/AKT/mTOR pathway, which designates MT2A as a promising target for therapy in IVDD.