Oxidative Damage Induces Apoptosis and Promotes Calcification in Disc Cartilage Endplate Cell Through ROS/MAPK/NF-κB Pathway: Implications for Disc Degeneration

Cartilage endplate (CEP) cell calcification and apoptosis play a vital role in the intervertebral disc degeneration (IVDD). Oxidative stress is a key factor in inducing programmed cell death and cartilage calcification. However, the cell death and calcification of cartilage endplate cells under oxidative stress have never been described. The present study investigated the apoptosis and calcification in the cartilage endplate cell under oxidative stress induced by HO to understand the underlying mechanism of IVDD. The cartilage endplate cells isolated from human lumbar discs were subjected to different concentrations of HO for various time periods. The cell viability was determined by CCK-8 assay, whereas Western blot, immunofluorescence, and Alcian blue, Alizarin red, and Von Kossa staining evaluated the apoptosis and calcification. The level of mitochondria-specific reactive oxygen species (ROS) was quantified with an oxygen radical-sensitive probe-MitoSOX. The potential signaling pathways were investigated by Western blot after the addition of N-acetyl-l-cysteine (NAC). We found that the oxidative stress induced by HO increased the apoptosis and subsequently the calcification in the cartilage endplate cells through the ROS/p38/ERK/p65 pathway. The apoptosis and the calcification of the cartilage endplate cells induced by HO can be abolished by NAC. These results suggested that regulating the apoptosis and the calcification in the cartilage endplate cells under oxidative stress should be advantageous for the survival of cells and might delay the process of disc degeneration.