Promoting Nrf2/Sirt3‐Dependent Mitophagy Suppresses Apoptosis in Nucleus Pulposus Cells and Protects against Intervertebral Disc Degeneration

Abstract

One of the causes of intervertebral disc degeneration (IVDD) is nucleus pulposus cell (NPC) death, possibly apoptosis. In this study, we explored the role of the Nrf2/Sirt3 pathway and tert-butylhydroquinone (t-BHQ) in IVDD and elucidated the potential working mechanism. Reactive oxygen species (ROS) assay kits and malondialdehyde (MDA) assay kits were used to assess oxidative stress. Western blot and TUNEL staining were used to examine apoptosis. After siRNA against Nrf2 or lentivirus against Sirt3 was transfected into NPCs, the mechanism of the effect of the Nrf2/Sirt3 pathway on NPCs was assessed. The interaction between t-BHQ and its potential interacting protein NRF2 was further investigated through protein docking analysis. ChIP examined the binding affinity between Nrf2 and Sirt3 promoter. In vivo experiments, X-ray, hematoxylin-eosin (HE) staining, Safranin O staining, and immunohistochemistry were used to evaluate IVDD grades. The results demonstrated that activation of the Nrf2/Sirt3 pathway inhibited tert-butyl hydroperoxide- (TBHP-) induced apoptosis and mitochondrial dysfunction in vitro. In addition to apoptosis, upregulation of the Nrf2/Sirt3 pathway induced by t-BHQ restored TBHP-induced autophagic flux disturbances. However, its protective effect was reversed by chloroquine and Si-ATG5. Furthermore, t-BHQ ameliorated IVDD development in a rat model. In conclusion, our findings indicate that the Nrf2/Sirt3 pathway and its agonist represent a potential candidate for treating IVDD.

Oxidative Stress and Intervertebral Disc Degeneration: Pathophysiology, Signaling Pathway, and Therapy

“…In autophagy-deficient cells, H 2 O 2 -induced oxidative stress aggravates the production of ROS, which indicate the protective effect of autophagy on oxidative stress damage [ 6 ]. Moreover, the antioxidant Keap1-Nrf2-ARE pathway can restore autophagic flux disturbances caused by TBHP and further alleviate apoptosis [ 65 ]. Therefore, autophagy is a double-edged sword in IDD caused by oxidative stress, excessive autophagy can boost the death of cell, but appropriate autophagy can increase the survival of cell.…”

“…Tang et al found that H 2 O 2 -induced excessive accumulation of Nrf2 can protect cell from oxidative stress through Keap1-Nrf2-p62 autophagic pathway [ 6 ]. Moreover, the upregulation of Nrf2/Sirt3 pathway can alleviate the apoptosis and mitochondrial dysfunction in TBHP-induced rat IDD NP cell, and the upregulation of Nrf2/Sirt3 pathway also restored the disturbed autophagy in this model [ 65 ]. In addition to NP cell, Nrf2 plays an important role in endplate chondrocytes.…”

Scientific literature landscape analysis of researches on oxidative stress in intervertebral disc degeneration in web of science

“…1456 authors, 352 organizations, and 30 countries contributed to this field. Table 2 showed the top author with the most publications was Wang K ( n = 17) from Tongji Medical College ( Yin et al, 2021 ), the second was Shao ZW ( n = 16) from Tongji Medical College ( Chen S. et al, 2020 ), followed by Wang XY ( n = 15) from The Second Affiliated Hospital of Wenzhou Medical University ( Hu S. et al, 2021 ), Yang C ( n = 12) from Tongji Medical College ( Song et al, 2021 ), Zhang Y ( n = 12) from Third Military Medical University ( Xu et al, 2021 ). Of the 352 organizations, Huazhong University of Science Technology, Shanghai Jiao Tong University, Wenzhou Medical University, Zhejiang University, and Sun Yat Sen University had contributed 31, 21, 20, 15, and 12 publications, respectively.…”

Optineurin-mediated mitophagy as a potential therapeutic target for intervertebral disc degeneration

“…We speculate that short-term oxidative stress causes cells to undergo stress, which promotes mitophagy to counteract the damaging stimulus, resulting in elevated OPTN expression, whereas long-term stress causes oxidative and antioxidant dysregulation, resulting in mitophagy failure. Moreover, OPTN is not the only protein involved in protection against mitochondrial damage, and other proteins, such as NRF2 ( Hu et al, 2021b ), Sirt3 ( Wang J et al, 2018 ) and Parkin ( Zhang et al, 2018 ), are also involved in mitochondrial damage-related responses. Therefore, different cells may activate different types of proteins to regulate oxidative stress.…”