Custom-Made Ce–Mn Bimetallic Nanozyme for the Treatment of Intervertebral Disc Degeneration by Inhibiting Oxidative Stress and Modulating Macrophage M1/M2 Polarization

Intervertebral disc degeneration (IDD)-induced lower back pain (LBP) brings heavy burden worldwide. In the degenerated intervertebral disc, there is an increase in the accumulation of reactive oxygen species (ROS) and the infiltration of M1 macrophages, which leads to abnormal local inflammatory microenvironment and exacerbates IDD. In this study, we developed a novel injectable polyethylene glycol (PEG)-capped cerium ion–manganese ion (Ce–Mn) bimetallic nanozyme (CeMn-PEG) with strong ROS scavenging and M2-type macrophage polarizing abilities to efficiently alleviate IDD. In vitro experiments demonstrated that CeMn-PEG effectively scavenged excess ROS in both nucleus pulposus (NP) and RAW264.7 cells. In addition, we found that CeMn-PEG markedly protected NP cells from H2O2-induced overproduction of inflammatory cytokines, excessive cell apoptosis and autophagy, and imbalance between extracellular matrix (ECM) degradation. Moreover, CeMn-PEG induced macrophages to transition from the M1 phenotype to the M2 phenotype and the increased M2-type macrophages could alleviate H2O2-induced ECM degradation and cell apoptosis in NP cells. In a puncture-induced mouse IDD model, CeMn-PEG treatment could effectively ameliorate the progression of disc degeneration and mitigate puncture-induced mechanical hyperalgesia. Thus, our study demonstrated the effectiveness of CeMn-PEG as a novel treatment strategy for the treatment of IDD and a range of other inflammatory diseases.