Neural precursor cell expressed developmentally downregulated 4–mediated phosphatase and tensin homolog ubiquitination alleviates senescence and apoptosis of nucleus pulposus cells under interleukin-1 beta conditions
Yang Lin, Cheng Li, Xuehui Chang, Ye Wang, Shiying JiaObjective
Increasing evidence indicates that aging and apoptosis of nucleus pulposus cells are closely associated with the pathogenesis of intervertebral disc degeneration. This study investigated the role of E3 ubiquitin ligase neural precursor cell expressed developmentally downregulated gene 4 (NEDD4) in the interleukin-1 beta-induced aging and apoptosis of human nucleus pulposus cells and evaluated whether NEDD4 mediates these effects by promoting the ubiquitination and degradation of phosphatase and tensin homolog (PTEN).
Methods
Two commercially available immortalized human nucleus pulposus cells were used for in vitro experiments, without involving human participants or collecting human tissues. The cells were treated with interleukin-1 beta (10 ng/mL for 24 h) to establish an inflammatory model of intervertebral disc degeneration. Transfection of overexpressed NEDD4 and/or PTEN was performed in the model cells. Cell viability, apoptosis, senescence, oxidative stress, inflammatory mediators, and extracellular matrix–related proteins were assessed. The interactions between NEDD4 and PTEN and the stability of the PTEN protein were investigated using co-immunoprecipitation, actinomycin D tracking, MG132 treatment, and intracellular ubiquitination experiments.
Results
Interleukin-1 beta treatment downregulated NEDD4 expression in nucleus pulposus cells to 2.3-fold of the baseline level (
Conclusions
This study preliminarily demonstrated that the overexpression of NEDD4 can alleviate the interleukin-1 beta-induced apoptosis and senescence phenomena of nucleus pulposus cells. This effect may be partially mediated by promoting the ubiquitination of PTEN and the proteasome degradation pathway. However, further functional deficiency experiments and in vivo validations are warranted to establish the causal relationship and therapeutic relevance.