Magnolol protects against oxidative stress induced senscence of rat nucleus pulposus cells via SIRT1/PGC-1α signaling pathway

Background In the context of intervertebral disc degeneration (IDD), the apoptosis of nucleus pulposus cells (NPCs) is a pivotal factor that contributes to disease progression. Magnolol, a natural compound extracted from the bark of Magnolia officinalis, has been extensively investigated for its potential to mitigate aging processes and function as a potent antioxidant. Consequently, our research aimed to elucidate the biological role of magnolol and to examine the potential mechanisms that may be associated with the progression of intervertebral disc degeneration, particularly concerning cellular senescence. Material and Methods To investigate the functions of magnolol in disc degeneration and elucidate its underlying mechanisms, a series of experiments were conducted to examine the impact of varying levels of hydrogen peroxide (H ₂ O ₂ ) on rat neural progenitor cells. To explore the influence of magnolol at different concentrations, both magnolol alone and its combination with EX527 were introduced into the experimental culture. The survival of cells was assessed using the CCK-8 assay and cellular senescence was evaluated through immunohistochemical analysis utilising the β-galactosidase staining method. Cell death analysis was performed using Annexin V-EGEP/PI dual staining. The MitoSOTM Red assay kit was utilised to specifically measure mitochondrial reactive oxygen species (ROS), providing a targeted approach for assessing oxidative stress within cellular mitochondria. Mitochondrial membrane potential (MMP) was evaluated using a fluorescence microscope following JC-1 staining. Age-related indicators (P16, P21, P53, MMP-3, and P-Rb) and apoptosis-related proteins (Bax, Bcl-2) were analysed. Furthermore, the expression levels of the signalling pathways involving Caspase-3, PARP-1, SIRT1, and PGC-1α were comprehensively assessed using western blot techniques. Results The experimental results reveal that Magnolol exhibited no significant cytotoxic effects at concentrations up to 60 µM in rat NP cells after exposure for either 12 or 24 hours. The use of magnolol as a pre-treatment agent significantly alleviated the harmful effects of H₂O₂-induced apoptosis in various cellular models. Magnolol shows promise in mitigating the adverse consequences of H ₂ O ₂ -induced mitochondrial dysfunction by reducing elevated levels of reactive oxygen species (ROS) and enhancing mitochondrial membrane potential (MMP). Additionally, pre-treatment with magnolol significantly decreased the senescence rate in rat neuronal progenitor cells (NPCs), as indicated by a decline in senescence-related markers. Prior to exposing NPCs to 300 µM H ₂ O ₂ , the cells were treated with 10 µM EX527, a specific inhibitor of SIRT1. This study illustrated that the previously observed inhibitory effect of magnolol on programmed cell death was effectively reversed, indicating a restoration of normal apoptotic pathways in the treated cells. Conclusion The findings of the study suggest that magnolol may protect mitochondrial integrity and diminish cellular senescence in rat nucleus pulposus (NPCs) subjected to hydrogen peroxide, through the SIRT1/PGC-1α signalling cascade. It is now clear that magnolol presents considerable potential as a novel therapeutic agent in the clinical setting, specifically aimed at addressing and alleviating the progression of disc degeneration.