CircZNF418 Prevents Intervertebral Disc Degeneration by Targeting the HuR/SIRT6 Axis to Protect Against Oxidative Stress-Induced Ferroptosis and Senescence

Abstract

Intervertebral disc degeneration (IVDD) is a common degenerative disorder affecting the spine. Ferroptosis and cellular senescence are key pathological features driving IVDD progression, but the mechanisms involved in their regulation remain incompletely understood. While circular RNAs (circRNAs) have been implicated in nucleus pulposus cells (NPCs) function, the specific role of circZNF418 in IVDD has not been explored. In this study, we aimed to investigate the function and mechanism of circZNF418 in IVDD, focusing on its impact on oxidative stress-induced ferroptosis and senescence in NPCs. NPCs were treated with tert-butyl hydroperoxide to mimic oxidative stress during IVDD progression. The levels of malondialdehyde (MDA) and glutathione (GSH) were quantified using commercial kits, and senescence was assessed using SA-β-gal staining. Gene and protein expression was analyzed using qPCR, Western blotting, immunofluorescence, and immunohistochemistry. RNA pull-down and immunoprecipitation were used to examine interactions among circZNF418, HuR, and SIRT6. circZNF418 levels were found to be lower in degenerative nucleus pulposus tissues, associated with increased ferroptosis and cellular senescence. circZNF418 expression declined in response to oxidative stress and was correlated with increased NPC senescence and ferroptosis. Overexpression of circZNF418 protected NPCs from oxidative damage, while its knockdown exacerbated senescence and ferroptosis. Silencing of SIRT6 partially reversed the protective effects of circZNF418 overexpression. Additionally, both circZNF418 and SIRT6 were shown to bind to HuR, with circZNF418 promoting SIRT6 expression, which was reversed by HuR silencing. The findings indicate that circZNF418 regulates NPC senescence and ferroptosis by upregulating SIRT6. A novel signaling pathway, the novel circZNF418/HuR/SIRT6 axis, was identified, showing its potential in IVDD therapy, while circZNF418 was identified as a potential target, thus providing new diagnostic biomarkers and the development of effective treatments for IVDD.