Inhibition of ERK1/2 mediated activation of Drp1 alleviates intervertebral disc degeneration via suppressing pyroptosis and apoptosis in nucleus pulposus cells

Objective

Dynamin-related protein 1 (Drp1) plays a crucial role in various inflammatory and degenerative diseases, yet its involvement in intervertebral disc degeneration (IVDD) remains poorly understood. This study aims to elucidate the mechanism by which Drp1 contributes to IVDD and to identify the efficacy of the Drp1 inhibitor Mdivi-1 on IVDD.

Methods

Tert-butyl hydroperoxide (TBHP) is utilized to induce an oxidative stress microenvironment in vitro. In vivo, IVDD model is constructed in 8-week old rats through puncture operation. The therapeutic effect of Mdivi-1 is evaluated through X-ray, MRI and histological analysis. A comprehensive set of experiments, including single-cell sequencing analysis, western blot, flow cytometry and immunofluorescence staining, are conducted to investigate the role and underlying mechanisms of Drp1 in vitro.

Results

Our study demonstrates that the expression of Drp1 and phosphorylated Drp1 (p-Drp1) are up-regulated in degenerative nucleus pulposus cells (NPCs), which are accompanied with increased pyroptosis and apoptosis. In vivo, both si-Drp1-mediated Drp1 knockdown and the pharmacological inhibitor Mdivi-1 alleviate puncture-induced IVDD in rats. In vitro, si-Drp1 or Mdivi-1 inhibits mitochondria-dependent apoptosis and pyroptosis triggered by TBHP. Mechanistically, Mdivi-1 reduces p-Drp1 levels, inhibits excessive mitochondrial fission, and mitigates mitochondrial dysfunction. Drp1 phosphorylation-based Drp1 mitochondrial translocation and subsequent apoptosis and pyroptosis are regulated by ERK1/2 phosphorylation in NPCs under oxidative stress condition.

Conclusion

This study highlights the involvement of Drp1 in the pathological progression of degenerative NPCs in IVDD, which is regulated by ERK1/2. Pharmacological inhibition of Drp1 with Mdivi-1 protects NPCs by promoting mitochondrial function and attenuating apoptosis and pyroptosis. These findings suggest that Mdivi-1 is a promising therapeutic candidate for IVDD treatment.

Translational Potential

By offering experimental evidence on the role and mechanism of Drp1 in IVDD, this study underscores the potential of Mdivi-1 as a therapeutic strategy for IVDD.