Sirtuin 3-dependent mitochondrial redox homeostasis protects against AGEs-induced intervertebral disc degeneration

Abstract

Intervertebral disc (IVD) degeneration contributes largely to pathoanatomical and degenerative changes of spinal structure that increase the risk of low back pain. Apoptosis in nucleus pulposus (NP) can aggravate IVD degeneration, and increasing studies have shown that interventions targeting NP cell apoptosis can ameliorate IVD degeneration, exhibiting their potential for use as therapeutic strategies. Recent data have shown that advanced glycation end products (AGEs) accumulate in NP tissues in parallel with the progression of IVD degeneration and form a microenvironment of oxidative stress. This study examined whether AGEs accumulation aggravates NP cell apoptosis and IVD degeneration, and explored the mechanisms underlying these effects. We observed that the viability and proliferation of human NP cells were significantly suppressed by AGEs treatment, mainly due to apoptosis. Furthermore, activation of the mitochondrial apoptosis pathway was detected after AGEs treatment. In addition, the molecular data showed that AGEs could significantly aggravate the generation of mitochondrial reactive oxygen species and prolonged activation of the mitochondrial permeability transition pore, as well as the increased level of Bax protein and decreased level of Bcl-2 protein in mitochondria. These effects could be reduced by antioxidant (2-(2,2,6,6-Tetramethylpiperidin-1-oxyl-4-ylamino)-2-oxoethyl) triphenylphosphonium chloride (MitoTEMPO) and Visomitin (SKQ1). Importantly, we identified that impairment of Sirtuin3 (SIRT3) function and the mitochondrial antioxidant network were vital mechanisms in AGEs-induced oxidative stress and secondary human NP cell apoptosis. Finally, based on findings that nicotinamide mononucleotide (NMN) could restore SIRT3 function and rescue human NP cell apoptosis through adenosine monophosphate-activated protein kinase and peroxisome proliferator-activated receptor-γ coactivator 1α (AMPK-PGC-1α) pathway in vitro, we confirmed its protective effect on AGEs-induced IVD degeneration in vivo. In conclusion, our data demonstrate that SIRT3 protects against AGEs-induced human NP cell apoptosis and IVD degeneration. Targeting SIRT3 to improve mitochondrial redox homeostasis may represent a potential therapeutic strategy for attenuating AGEs-associated IVD degeneration.

Impaired calcium homeostasis via advanced glycation end products promotes apoptosis through endoplasmic reticulum stress in human nucleus pulposus cells and exacerbates intervertebral disc degeneration in rats

“…Furthermore, we confirmed our in vitro findings by utilizing a previously described AGEs-induced IVD-degeneration model to characterize the role of ER Ca 2+ homeostasis in vivo [14]. At 4-week after establishing the model, we observed severe IVD-degenerative changes in the AGEs-injected group, with these alterations partially ameliorated by administration of calcium antagonists.…”

“…As shown previously [14], AGEs treatment induces mitochondria-dependent apoptosis in NP cells; however, the underlying mechanisms are not fully elucidated. To investigate the role of ER stress in AGEs-induced NP-cell apoptosis, NP cells were cultured in the presence of 200 lgÁmL À1 AGEs in the presence or absence of the specific ER-stress inhibitor 4-phenylbutyric acid (4-PBA).…”

“…Therefore, AGEs accumulation in the IVD potentially plays a crucial pathological role in the onset and progression of disc degeneration. Based on our previous results , this study represents a further investigation of correlations between AGEs and apoptosis.…”

“…Advanced glycation end products (AGEs) represent a heterogeneous group of irreversible compounds formed by nonenzymatic glucose-protein condensation (the Maillard reaction) reactions and that accumulate in tissues concomitant with increased age [10]. Our and others previous studies demonstrate that AGEs also accumulate in the IVD with age and advanced degeneration, especially in diabetic individuals, leading to decreased proteoglycan production and increased catabolism, inflammation, and apoptosis [11][12][13][14]. Therefore, AGEs accumulation in the IVD potentially plays a crucial pathological role in the onset and progression of disc degeneration.…”

Dexamethasone promotes mesenchymal stem cell apoptosis and inhibits osteogenesis by disrupting mitochondrial dynamics

“…Mitochondrial membrane potential was detected by JC-1 (C2006; Beyotime) assay kits according to our previous study [21]. In brief, cells were cocultured with dexamethasone of different concentrations for 24 h; then the cells were centrifuged and collected.…”