Emodin protects against apoptosis and inflammation by regulating reactive oxygen species-mediated NF-κB signaling in interleukin-1β-stimulated human nucleus pulposus cells

Intervertebral disc degeneration (IDD) is a complex degradative disorder associated with inflammation. Emodin, an anthraquinone derivative, possesses strong anti-inflammatory activity. This study focused on the in vitro therapeutic action of emodin in a cellular model of IDD. Human nucleus pulposus cells (NPCs) were stimulated with interleukin-1 beta (IL-1 beta) to induce inflammation. Cell Counting Kit-8 and terminal deoxynucleotidyl transferase dUTP nick end labeling staining assays were performed to evaluate the viability and apoptosis of NPCs, respectively. Caspase-3 activity was measured to indirectly assess cell apoptosis. Western blot analysis was performed to detect protein expression levels. Reverse transcription-polymerase chain reaction was performed for the detection of relative mRNA levels of tumor necrosis factor-alpha (TNF-alpha) and IL-6. Enzyme-linked immunosorbent assay was performed to analyze TNF-alpha and IL-6 secretion. Our results showed that emodin treatment mitigated IL-1 beta -induced reduction of cell viability in NPCs. Moreover, the increase in reactive oxygen species (ROS) production, apoptotic rate, and caspase-3 activity in IL-1 beta -stimulated NPCs was reduced by emodin treatment. Treatment with emodin also abolished IL-1 beta -induced inflammation in NPCs, as indicated by reduced secretion of IL-6 and TNF-alpha. Besides, the increase in expression levels of phosphorylated p65 and nuclear p65 in IL-1 beta -stimulated NPCs was suppressed by emodin treatment. Furthermore, inhibition of nuclear factor kappa B (NF-kappa B) activation with pyrrolidine dithiocarbamate aggravated the protective effects of emodin. These results suggested that emodin protected NPCs against IL-1 beta -induced apoptosis and inflammation via inhibiting ROS-mediated activation of NF-kappa B.