SIRT1 protects against apoptosis by promoting autophagy in degenerative human disc nucleus pulposus cells

Jiang, Wei; Zhang, Xuemei; Hao, Jie; Shen, Jieliang; Ji, Fang; Dong, Wen; Da-wu, Wang; Zhang, Xiaojun; Shui, Wei; Luo, Yi; Lin, Liangbo; Qiu, Quanhe; Liu, Bin; Hu, Zhenming

doi:10.1038/srep07456

Cited by 122 publications

(107 citation statements)

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“…76,77 An altered level of autophagy during intervertebral disc degeneration and aging has been reported. [37][38][39][40]78 Our studies clearly show evidence of MTOR-independent, noncanonical autophagy in NP cells. In addition, hypoxic induction of autophagy is independent of HIF1 as well as increased oxidative stress.…”

Section: Discussionmentioning

confidence: 66%

“…Although the causative relationship between disc degeneration and autophagy is not yet clear, alterations in the level of autophagy have been observed in degenerated IVDs, IVDs of aged or diabetic rats [37][38][39] and NP cells derived from degenerative human discs. 40 In addition, various stresses such as high glucose, 41,42 aberrant mechanical compression, 43 lactate overload, 44 glucosamine, 45 and reactive oxygen species (ROS), 43 activate autophagy in NP cells, further implicating autophagy modulation as a possible contributor to disc pathologies. However, studies investigating the mechanisms of how basal autophagy is controlled in NP cells and the role of physiological stimuli in this process are mostly lacking.…”

Section: Introductionmentioning

confidence: 99%

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Hypoxia promotes noncanonical autophagy in nucleus pulposus cells independent of MTOR and HIF1A signaling

et al. 2016

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Nucleus pulposus (NP) cells reside in the avascular and hypoxic microenvironment of intervertebral discs. Importantly, many activities related to survival and function of NP cells are controlled by the HIF-family of transcription factors. We hypothesize that NP cells adapt to their hypoxic niche through modulation of macroautophagy/autophagy. In various cell types, hypoxia induces autophagy in a HIF1A-dependent fashion; however, little is known about hypoxic regulation of autophagy in NP cells. Hypoxia increases the number of autophagosomes as seen by TEM analysis and LC3-positive puncta in NP cells. Hypoxic induction of autophagy was also demonstrated by a significantly higher number of autophagosomes and smaller change in autolysosomes in NP cells expressing tandem-mCherry-EGFP-LC3B. Increased LC3-II levels were not accompanied by a concomitant increase in BECN1 or the ATG12-ATG5 complex. In addition, ULK1 phosphorylation at Ser757 and Ser777 responsive to MTOR and AMPK, respectively, was not affected in hypoxia. Interestingly, when MTOR activity was inhibited by rapamycin or Torin1, LC3-II levels did not change, suggesting a novel MTOR-independent regulation. Noteworthy, while silencing of HIF1A affected hypoxic induction of BNIP3, it did not affect LC3-II levels, indicating hypoxia-induced autophagy is HIF1-independent. Importantly, there was no change in the number of LC3-positive autophagosomes in NP-specific Hif1a null mice. Finally, inhibition of autophagic flux did not affect the glycolytic metabolism of NP cells, suggesting a possible nonmetabolic role of autophagy. Taken together, our study for the first time shows that NP cells regulate autophagy in a noncanonical fashion independent of MTOR and HIF1A signaling.

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Section: Discussionmentioning

confidence: 66%

Section: Introductionmentioning

confidence: 99%

Hypoxia promotes noncanonical autophagy in nucleus pulposus cells independent of MTOR and HIF1A signaling

et al. 2016

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“…Although a causal relationship between autophagy defects and IDD has not yet been established, our findings showed that FOXO function promotes NP cell survival under oxidative and inflammatory stresses, major drivers of NP cell apoptosis and aging‐related IDD (Nasto et al, 2013; Wang et al, 2013; Yang et al, 2014), and thus suggest that activation of FOXO in aged IVD could increase autophagy and protect NP cells from stress‐induced apoptosis. Further supporting this hypothesis, various studies have shown that autophagy activation can protect NP cells against different apoptotic insults (Jiang, Jin, Wang, Jiang, & Dong, 2014; Jiang, Zhang, et al, 2014). …”

Section: Discussionmentioning

confidence: 72%

FOXO are required for intervertebral disk homeostasis during aging and their deficiency promotes disk degeneration

et al. 2018

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Intervertebral disk (IVD) degeneration is a prevalent age‐associated musculoskeletal disorder and a major cause of chronic low back pain. Aging is the main risk factor for the disease, but the molecular mechanisms regulating IVD homeostasis during aging are unknown. The aim of this study was to investigate the function of FOXO, a family of transcription factors linked to aging and longevity, in IVD aging and age‐related degeneration. Conditional deletion of all FOXO isoforms (FOXO1, 3, and 4) in IVD using the Col2a1Cre and AcanCreER mouse resulted in spontaneous development of IVD degeneration that was driven by severe cell loss in the nucleus pulposus (NP) and cartilaginous endplates (EP). Conditional deletion of individual FOXO in mature mice showed that FOXO1 and FOXO3 are the dominant isoforms and have redundant functions in promoting IVD homeostasis. Gene expression analyses indicated impaired autophagy and reduced antioxidant defenses in the NP of FOXO‐deficient IVD. In primary human NP cells, FOXO directly regulated autophagy and adaptation to hypoxia and promoted resistance to oxidative and inflammatory stress. Our findings demonstrate that FOXO are critical regulators of IVD homeostasis during aging and suggest that maintaining or restoring FOXO expression can be a therapeutic strategy to promote healthy IVD aging and delay the onset of IVD degeneration.

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“…The protein extracts were then electrophoretically resolved by SDS-PAGE (10-20 mg protein/lane) and transferred onto PVDF membranes for immunoblot analysis. The blots were processed (19)(20)(21) and then probed with the indicated antibodies. The after antibodies were used for b-actin (47778; Santa Cruz Biotechnology, TX, USA), a2tubulin (T5168; Sigma-Aldrich), SIRT1 (07-131; EMD-Millipore), Ac-H3K9/14 (A-4021-050; EMDMillipore), 2MeH3K9 (07441; EMD-Millipore), MMP13 (sc-81547; Santa Cruz Biotechnology), LEF1 (2230; Cell Signaling Technology ), and b-catenin (ab16051; Abcam, Cambridge, United Kingdom).…”

Section: Protein and Immunoblot Analysesmentioning

confidence: 99%

“…Correspondingly, additional in vivo studies (14) demonstrated that Sirt1 exerts an anti-inflammatory effect in cartilage during OA. Moreover, mechanistic studies have provided further support that SIRT1 promotes chondrocyte survival through various pathways (15)(16)(17)(18)(19)-in particular, deacetylation of p65/ RelA-which reduces iNOS gene expression after IL-1b challenge of chondrocytes (20). Despite the wealth of information regarding the beneficial effects exerted by SIRT1 in maintaining chondrocyte survival and attenuating inflammation, very little is known about the impact of SIRT1 on cartilage destruction during OA.…”

mentioning

confidence: 99%

LEF1‐mediated MMP13 gene expression is repressed by SIRT1 in human chondrocytes

et al. 2017

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Reduced SIRT1 activity and levels during osteoarthritis (OA) promote gradual loss of cartilage. Loss of cartilage matrix is accompanied by an increase in matrix metalloproteinase (MMP) 13, partially because of enhanced LEF1 transcriptional activity. In this study, we assessed the role of SIRT1 in LEF1-mediated MMP13 gene expression in human OA chondrocytes. Results showed that MMP13 protein levels and enzymatic activity decreased significantly during SIRT1 overexpression or activation by resveratrol. Conversely, MMP13 gene expression was reduced in chondrocytes transfected with SIRT1 siRNA or treated with nicotinamide (NAM), a sirtuin inhibitor. Chondrocytes challenged with IL-1b, a cytokine involved in OA pathogenesis, enhanced LEF1 protein levels and gene expression, resulting in increased MMP13 gene expression; however, overexpression of SIRT1 during IL-1b challenge impeded LEF1 levels and MMP13 gene expression. Previous reports showed that LEF1 binds to the MMP13 promoter and transactivates its expression, but we observed that SIRT1 repressed LEF1 protein and mRNA expression, ultimately reducing LEF1 transcriptional activity, as judged by luciferase assay. Finally, mouse articular cartilage from Sirt1 2/2 presented increased LEF1 and MMP13 protein levels, similar to human OA cartilage. Thus, demonstrating for the first time that SIRT1 represses MMP13 in human OA chondrocytes, which appears to be mediated, at least in part, through repression of the transcription factor LEF1, a known modulator of MMP13 gene expression.-Elayyan, J., Lee, E.-J., Gabay, O., Smith, C. A., Qiq, O., Reich, E., Mobasheri, A., Henrotin, Y., Kimber, S. J., Dvir-Ginzberg, M. LEF1-mediated MMP13 gene expression is repressed by SIRT1 in human chondrocytes. FASEB J. 31, 3116-3125 (2017). www.fasebj.orgArticular cartilage undergoes age-related degenerative changes leading to the joint disease osteoarthritis (OA). Gradual loss of hyaline joint cartilage during OA is evoked through chronic synovitis, which involves the accumulation of proinflammatory cytokines, as IL1b, TNF-a, and IL6 within the joint (1-5), subsequently leading to a steady increase in matrix metalloproteinases (MMPs) and a disintegrin and MMP with thrombospondin motifs (ADAMTS) proteins, which further promote cartilage destruction (6-12). Recent experimental attempts ABBREVIATIONS: ACAN, aggrecan gene; ADAMTS, a disintegrin and metalloproteinase with thrombospondin-like motifs; BMP, bone morphogenic protein; ChIP, chromatin immunoprecipitation; COL2A1, collagen-2 a-1 gene; FBS, fetal bovine serum; FGF, fibroblast growth factor; GDF, growth differentiation factor; GSK3b, glycogen synthase kinase-3b; hESC, human embryonic stem cell; KO, knockout; LEF, lymphoid enhancer factor; MMP, matrix metalloproteinase; NAM, nicotinamide adenine mononucleotide; OA, osteoarthritis; Res, resveratrol; qPCR, quantitative PCR; siRNA, small interfering RNA; SIRT1, silent mating type information regulation 2 homolog 1 (sirtuin-1); SOX9, sex-determining-region-on-the-Y-chromosome-relate...

show abstract

SIRT1 protects against apoptosis by promoting autophagy in degenerative human disc nucleus pulposus cells

Cited by 122 publications

References 50 publications

Hypoxia promotes noncanonical autophagy in nucleus pulposus cells independent of MTOR and HIF1A signaling

Hypoxia promotes noncanonical autophagy in nucleus pulposus cells independent of MTOR and HIF1A signaling

FOXO are required for intervertebral disk homeostasis during aging and their deficiency promotes disk degeneration

LEF1‐mediated MMP13 gene expression is repressed by SIRT1 in human chondrocytes

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