Nutrient deprivation induces apoptosis of nucleus pulposus cells via activation of the BNIP3/AIF signalling pathway.

Nutrient deprivation (ND)-induced nucleus pulposus (NP) cell death serves an important role in intervertebral disc degeneration disease. However, the underlying mechanisms have yet to be thoroughly elucidated. The present study created a cell culture model under ND conditions to investigate the roles of the nutrient-sensitive protein B-cell lymphoma 2/adenovirus E1B 19 kDa-interacting protein (BNIP3) and the mitochondrial pro-death protein apoptosis-inducing factor (AIF) in the death pathway of NP cells. The present study demonstrated that cells subjected to ND for up to 72 h exhibited a time-dependent increase in cell death and decrease in mitochondrial membrane potential (Δψm), as compared with cells cultured under normal conditions. The results of western blotting demonstrated that BNIP3 expression was significantly upregulated in NP cells subjected to ND for 24 h, which coincided with AIF translocation to the cell nucleus and alterations in cell viability and Δψm. Furthermore, BNIP3 overexpression increased ND-induced NP cell death, whereas knockdown of BNIP3 or AIF abolished ND-induced NP cell death. In addition, BNIP3 overexpression increased AIF expression and BNIP3 knockdown decreased AIF expression in NP cells subjected to ND. In conclusion, ND induced NP cell death partially via activation of the BNIP3/AIF signalling pathway. These findings provide novel insights into the potential mechanisms underlying ND-induced death of NP cells during disc degeneration.

营养剥夺（ND）诱导的髓核（NP）细胞死亡在椎间盘退变疾病中起重要作用。然而，其潜在机制尚未完全阐明。本研究在营养剥夺条件下创建了细胞培养模型，以研究营养敏感蛋白B细胞淋巴瘤2/腺病毒E1B 19 kDa相互作用蛋白（BNIP3）和线粒体促死亡蛋白凋亡诱导因子（AIF）在NP细胞死亡通路中的作用。本研究表明，与在正常条件下培养的细胞相比，接受营养剥夺长达72小时的细胞表现出细胞死亡的时间依赖性增加以及线粒体膜电位（Δψm）的降低。蛋白质印迹结果表明，在营养剥夺24小时的NP细胞中，BNIP3表达显著上调，这与AIF向细胞核的转位以及细胞活力和Δψm的改变同时发生。此外，BNIP3过表达增加了营养剥夺诱导的NP细胞死亡，而BNIP3或AIF的敲低则消除了营养剥夺诱导的NP细胞死亡。另外，在营养剥夺的NP细胞中，BNIP3过表达增加了AIF表达，而BNIP3敲低则降低了AIF表达。总之，营养剥夺部分通过激活BNIP3/AIF信号通路诱导NP细胞死亡。这些发现为椎间盘退变过程中营养剥夺诱导NP细胞死亡的潜在机制提供了新的见解。