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Apigenin Alleviates Intervertebral Disc Degeneration via Restoring Autophagy Flux in Nucleus Pulposus Cells.

ABSTRACT: Oxidative stress-induced apoptosis and senescence of nucleus pulposus (NP) cells play a crucial role in the progression of intervertebral disc degeneration (IVDD). Accumulation of studies has shown that activated autophagy and enhanced autophagic flux can alleviate IVDD. In this study, we explored the effects of apigenin on IVDD in vitro and in vivo. Apigenin was found to inhibit tert-butyl hydroperoxide (TBHP)-induced apoptosis, senescence, and ECM degradation in NP cells. In addition, apigenin treatment can restore the autophagic flux blockage caused by TBHP. Mechanistically, we found that TBHP may induce autophagosome and lysosome fusion interruption and lysosomal dysfunction, while apigenin alleviates these phenomena by promoting the nuclear translocation of TFEB via the AMPK/mTOR signaling pathway. Furthermore, apigenin also exerts a protective effect against the progression of IVDD in the puncture-induced rat model. Taken together, these findings indicate that apigenin protects NP cells against TBHP-induced apoptosis, senescence, and ECM degradation via restoration of autophagic flux in vitro, and it also ameliorates IVDD progression in rats in vivo, demonstrating its potential for serving as an effective therapeutic agent for IVDD.

SUBMITTER: Xie C

PROVIDER: S-EPMC8795835 | biostudies-literature | 2021

REPOSITORIES: biostudies-literature

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Apigenin Alleviates Intervertebral Disc Degeneration via Restoring Autophagy Flux in Nucleus Pulposus Cells.

Xie Chenglong C Shi Yifeng Y Chen Zuoxi Z Zhou Xin X Luo Peng P Hong Chenxuan C Tian Naifeng N Wu Yaosen Y Zhou Yifei Y Lin Yan Y Dou Haicheng H Wu Aimin A Huang Qishan Q Zhang Xiaolei X Wang Xiangyang X

Frontiers in cell and developmental biology 20220114

Oxidative stress-induced apoptosis and senescence of nucleus pulposus (NP) cells play a crucial role in the progression of intervertebral disc degeneration (IVDD). Accumulation of studies has shown that activated autophagy and enhanced autophagic flux can alleviate IVDD. In this study, we explored the effects of apigenin on IVDD in vitro and in vivo. Apigenin was found to inhibit tert-butyl hydroperoxide (TBHP)-induced apoptosis, senescence, and ECM degradation in NP cells. In addi ...[more]

PMID: 35096819

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Project description:Background/objectiveIntervertebral disc (IVD) degeneration (IVDD) that greatly affected by regional biomechanical environment is a major cause of low back pain. Injectable hydrogels have been commonly studied for treatment of IVDD due to their capability of mimicking extracellular matrix structure to support cellular behavior and clinical prospects in minimally invasive treatment. However, most hydrogels suffer from complicated chemistry, potential uncertainty and toxicity from in-situ gelation, and mismatch with IVD mechanical environment that limit their therapeutic effects or clinical translation in IVDD or intervertebral disc defect repair. For IVD lesion repair, the study aims to develop a novel hydrogel with shear-thinning enabled injectability, high bio-safety, and mechanical properties adaptable to the IVD environment, using a simple chemistry and method. And therapeutic efficacy of the novel hydrogel in the treatment of IVDD or intervertebral disc defect will be revealed.MethodsA glycerol cross-linked PVA gel (GPG) was synthesized based on multiple H-bonds formation between glycerol molecules and PVA chains. The rheological and mechanical properties were tested. The swelling ratio was measured. The micro-architecture was observed through scanning and transmission electron microscopes. Nucleus pulposus (NP) cells were cultured in GPG-coated plates or silicone chambers treated under hydrostatic or dynamic loading in vitro, and examined for proliferation, vitality, apoptosis, expression of catabolic and anabolic markers. GPG was injected in needle puncture (IDD) or NP discectomy (NPD) models in vivo, and examined through magnetic resonance imaging, micro-computed tomography scanning and histological staining.ResultsGPG had a highly porous structure consisting of interconnected pores. Meanwhile, the GPG had NP-like viscoelastic property, and was able to withstand the cyclic deformation while exhibiting a prominent energy-dissipating capability. In vitro cell tests demonstrated that, the hydrogel significantly down-regulated the expression of catabolic markers, maintained the level of anabolic markers, preserved cell proliferation and vitality, reduced apoptotic rate of NP cells under pathologically hydrostatic and dynamic loading environments compared to cells cultured on untreated plate or silicone chamber. In vivo animal studies revealed that injection of GPG efficiently maintained NP structural integrity, IVD height and relative water content in IDD models, and stimulated the fibrous repair in NPD models.ConclusionThis study showed that GPG, with high injectability, NP-like viscoelastic characteristics, good energy-dissipating properties and swelling capacities, preserved NP cells vitality against pathological loading, and had therapeutic effects on IVD repair in IDD and NPD models.The translational potential of this articleEffective clinical strategy for treatment of intervertebral disc degeneration (IVDD) is still lacking. This study demonstrates that injection of a hydrogel with nucleus pulposus-matched viscoelastic property could remarkably prevent the IVDD progress. Prepared with simple chemistry and procedure, the cell/drug-free GPG with high bio-safety and shear-thinning enabled injectability bears great translational potential for the clinical treatment of IVDD via a minimally invasive approach.

Project description:The nucleus pulposus (NP) plays a vital role in intervertebral disc degeneration (IVDD). Previous studies have revealed cellular heterogeneity in NP tissue during IVDD progression. However, the cellular and molecular alterations of diverse cell clusters during IVDD remain to be fully elucidated. NP tissues were isolated from patients with different grades of IVDD undergoing discectomy, and then subjected to single-cell RNA sequencing (scRNA-seq). Cell subsets were identified based on unbiased clustering of gene expression profiles. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analyses were performed to determine the molecular features of diverse cell clusters. Monocle analysis was used to illustrate the differentiation trajectories of chondrocytes. Additionally, CellPhoneDB analysis revealed potential interactions between chondrocytes and other cells during IVDD. Based on the expression profiles of 47,610 individual cells, eight putative clusters including chondrocytes, endothelial cells, fibroblasts, macrophages, mural cells, osteoclasts, proliferating stromal cells and T cells were identified. The chondrocyte cluster was classified into three subsets, C1-C3, which were associated with stress-resistance, fibrosis and inflammatory responses, respectively. Pseudo-time trajectories suggested that chondrocytes gradually differentiated into fibroblasts during IVDD. Immune cells including cDC2s, macrophages and monocytes were identified. Further analysis showed that chondrocytes might communicate with immune cells via the MIF, TNFSF9, SPP1 and CCL4L2 signaling pathways. In addition, we found that invading endothelial cells might interact with chondrocytes through the COL4A1, CXCL12, VEGFA and SEMA3E signaling pathways. Our results reveal the cellular complexity and phenotypic characteristics of NP tissues at single-cell resolution, which will contribute to the in-depth investigation of preventative and regenerative strategies for IVDD.

Project description:Background contextLow back pain, affecting nearly 40% of adults, mainly results from intervertebral disc degeneration (IVDD), while the pathogenesis of IVDD is still not fully elucidated. Recently, some researches have revealed that necroptosis, a programmed necrosis, participated in the progression of IVDD, nevertheless, the underlying mechanism remains unclear.PurposeTo study the mechanism of necroptosis of Nucleus Pulposus (NP) cells in IVDD, focusing on the role of MyD88 signaling.Study designThe expression and co-localization of necroptotic indicators and MyD88 were examined in vivo, and MyD88 inhibitor was applied to determine the role of MyD88 signaling in necroptosis of NP cells in vitro.MethodsHuman disc specimens were collected from patients receiving diskectomy for lumbar disc herniation (LDH) or traumatic lumbar fractures after MRI scanning. According to the Pfirrmann grades, they were divided into normal (Grades 1, 2) and degenerated groups (4, 5). Tissue slides were prepared for immunofluorescence to assess the co-localization of necroptotic indicators (RIP3, MLKL, p-MLKL) and MyD88 histologically. The combination of TNFα, LPS and Z-VAD-FMK was applied to induce necroptosis of NP cells. Level of ATP, reactive oxygen species (ROS), live-cell staining and electron microscope study were employed to study the role of MyD88 signaling in necroptosis of NP cells.ResultsIn vivo, the increased expression and co-localization of necroptotic indicators (RIP3, MLKL, p-MLKL) and MyD88 were found in NP cells of degenerated disc, while very l low fluorescence intensity in tissue of traumatic lumbar fractures. In vitro, the MyD88 inhibitor effectively rescued the necroptosis of NP cells, accompanied by increased viability, ATP level, and decreased ROS level. The effect of MyD88 inhibition on necroptosis of NP cells was further confirmed by ultrastructure of mitochondria shown by Transmission Electron Microscope (TEM).ConclusionOur results indicated that the involvement of MyD88 signaling in the necroptosis of NP cells in IVDD, which will replenish the pathogenesis of IVDD and provide a novel potential therapeutic target for IVDD.

Project description:Intervertebral Disc degeneration (IDD) is one of the leading causes of disability, and current therapies are ineffective. Phosphodiesterase 4B (PDE4B) plays an essential role in regulating the activation of nuclear factor E2-related factor 2 (Nrf2), while Nrf2 regulates ferroptosis. However, it is still unknown whether PDE4B is involved in the development of IDD. In this study, we explored the role of PDE4B on ferroptosis and Nrf2 in IDD pathogenesis by in vivo and in vitro experiments. The findings suggested that the expressions of PDE4B, ASCL4, and TRFC were significantly upregulated, and the expression of Nrf2 was significantly downregulated in nucleus pulposus (NP) tissues from human IDD patients dependent on IDD degeneration. Overexpression of PDE4B (PDE4B-OE) in NP cells upregulated the expression of ASCL4 and TRFC, and downregulated the expression of Nrf2. Meanwhile, the level of cytokine and oxidative stress were upregulated. Ferroptosis inhibitor Fer-1 or Nrf2 activator dimethyl fumarate (DMF) suppressed the effect of PDE4B-OE, while ferroptosis inducer elastin enhanced the effect of PDE4B-OE. In the IDD rat model, PDE4 inhibitor roflumilast, ferroptosis inhibitor Fer-1, or Nrf2 activator dimethyl fumarate (DMF) delayed IDD pathogenesis. While administration of ferroptosis inducer elastin enhanced IDD pathogenesis. Combination with PDE4B inhibitor and ferroptosis inhibitor Fer-1 significantly synergistic reversed IDD pathogenesis. While combination with PDE4B inhibitor or Nrf2 activator and elastin also decreased the degree of the IDD. The IHC suggested PDE4 inhibitor downregulated the expression of ASCL4 and TRFC. However, the combination effect of the Nrf2 activator was not obvious. Our study suggested that aberrant PDE4B activation in NP tissues induces pathological changes in IDD mediated by ferroptosis, and PDE4 inhibitor reveres the process of IDD by suppressing ferroptosis, and has a synergic effect with ferroptosis inhibitor. So PDE4B inhibition may be a potential therapeutic strategy for IDD.

Dataset Information

Apigenin Alleviates Intervertebral Disc Degeneration via Restoring Autophagy Flux in Nucleus Pulposus Cells.

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Apigenin Alleviates Intervertebral Disc Degeneration <i>via</i> Restoring Autophagy Flux in Nucleus Pulposus Cells.

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