Aug 2026· Advancement of science· 0 citations· 29 references
Medicine
TL;DR
It is demonstrated that CMA activity is downregulated in nucleus pulposus cells from IDD patients and IL‐1β‐induced rat intervertebral disc cell models, causing cytoplasmic accumulation of a novel CMA substrate, Midnolin (MIDN).
Abstract
ABSTRACT Intervertebral disc degeneration (IDD) is a leading cause of low back pain with incompletely understood mechanisms. Although autophagy dysfunction is a documented contributor to IDD, the precise pathobiological role of chaperone‐mediated autophagy (CMA) remains poorly understood. Here, we demonstrate that CMA activity is downregulated in nucleus pulposus cells (NPCs) from IDD patients and IL‐1β‐induced rat intervertebral disc cell models, causing cytoplasmic accumulation of a novel CMA substrate, Midnolin (MIDN). Accumulated MIDN bypasses the ubiquitin‐proteasome system and directly binds to Tuberous Sclerosis Complex 2 (TSC2), mediating its degradation. TSC2 loss relieves mechanistic target of rapamycin complex 1 (mTORC1) inhibition, resulting in mTORC1 hyperactivation, which drives cellular senescence, senescence‐associated secretory phenotype (SASP), and extracellular matrix (ECM) degradation in NPCs. In vitro and in a rat caudal needle puncture model, MIDN knockdown (shRNA), CMA activation (LAMP2A overexpression), or mTORC1 inhibition (Rapamycin) significantly attenuated IL‐1β or MIDN overexpression‐induced senescence and disc degeneration. Our findings reveal an “Impaired CMA–MIDN accumulation–TSC2 degradation–mTORC1 activation” axis central to IDD pathogenesis, offering potential therapeutic targets.
ABSTRACT Intervertebral disc degeneration (IVDD) constitutes a leading contributor to the development of low back pain, yet its epigenetic regulation remains unclear. Here, we identify a mechanism by which N6‐methyladenosine (m6A) RNA modification contributes to lysosomal membrane permeabilization (LMP) in IVDD. Single‐cell transcriptomic analysis of human nucleus pulposus (NP) tissues shows an enrichment of lysosomal pathway genes in severely degenerated NP cells, along with LMP and disrupted mitophagy flux. We further show that interleukin‐1β (IL‐1β) induces LMP, disrupts mitophagic flux, and causes mitochondrial dysfunction in NP cells. IL‐1β enhances WTAP, a key part of the m6A methyltransferase complex, essential for m6A methylation of ACSL4 mRNA. The m6A reader IGF2BP2 then binds and stabilizes the modified transcripts, leading to increased ACSL4 expression. Consequently, lysosomal lipid peroxidation is promoted through accumulation of arachidonic acid‐containing phospholipids, resulting in LMP. In a rat model, intradiscal delivery of AAV9‐shWTAP attenuates disc degeneration, with preserved disc height, improved extracellular matrix synthesis, and restored lysosomal function and mitophagy. Our study reveals the WTAP/ACSL4/IGF2BP2 axis as a mediator of IL‐1β‐induced LMP via m6A‐dependent lipid peroxidation, highlighting a potential therapeutic target for IVDD.
Shu Jia, Xu Gao, Laimin Zhu et al.· Advancement of science· 0 citations
Intervertebral disc degeneration (IVDD) is a predominant contributor to low back pain, characterized by nucleus pulposus cell (NPC) senescence, extracellular matrix (ECM) metabolic dysfunction, and chronic inflammation. Excessive mitochondrial fission contributes to IVDD, yet the underlying regulatory mechanisms remain unclear. Herein, we identified ETS proto-oncogene 1 (ETS1) as a critical regulator of mitochondrial fission in human NPCs. ETS1 was upregulated in severe human IVDD and correlated with disc degeneration severity and NPC senescence. Mechanistically, inflammatory cytokines induced ETS1 upregulation, which directly bound to the dynamin 1-like (DNM1L, encoding DRP1) promoter and activated its transcription. Increased DRP1 triggered excessive mitochondrial fission, leading to reactive oxygen species accumulation, NPC senescence, and ECM catabolism. Inhibition of ETS1 via AAV5-mediated RNA interference or targeting DRP1 with CRISPR/dCas9-KRAB system or Mdivi-1 alleviated mitochondrial dysfunction, cellular senescence, ECM degradation, and attenuated IVDD progression. Collectively, our findings revealed the ETS1/DRP1 axis as a novel pathogenic mechanism and a potential therapeutic target in IVDD.
Pengfei Li, Yichen Que, Shuhao Zhang et al.· Cellular Signalling· 0 citations
This study clarifies the molecular mechanism by which the USP5/MATN3 axis regulates cellular senescence and affects IVDD progression, opening up new potential targets for the intervention strategy of IVDD.
Chunyang Fan, Jie-yun Xia, Yao Zhang et al.· Cellular Signalling· 0 citations
Abstract Background The pathology of intervertebral disc degeneration (IDD) is characterized by metabolic dysregulation within nucleus pulposus (NP) cells. TRIM25 has been implicated in diverse tumors and pathological processes, yet its precise role in mediating mitochondrial function and metabolic alterations during IDD progression remains unclear. Methods Transcriptome sequencing was performed to analyze gene expression changes during IDD progression. Molecular biology techniques including co‐immunoprecipitation and ubiquitination assays were used to investigate the interaction between TRIM25 and the glycolytic enzyme ENO1 and its regulatory mechanism. Cellular and in vivo animal models were employed to validate the effects of the TRIM25‐USP7‐ENO1 axis on glycolysis, mitochondrial function, ATP levels, and extracellular matrix degradation. Results Transcriptome sequencing revealed that glycolysis‐related pathways and TRIM25 were significantly upregulated during IDD progression. Mechanistically, TRIM25 interacted with ENO1. Contrary to its typical E3 ligase function, TRIM25 overexpression stabilized ENO1 by reducing its K48‐linked polyubiquitination. Furthermore, TRIM25 enhanced the interaction between USP7 and ENO1, leading to USP7‐mediated deubiquitination and stabilization of ENO1. Disruption of the TRIM25‐USP7‐ENO1 axis suppressed glycolysis, improved mitochondrial function, elevated ATP levels, and inhibited extracellular matrix degradation. In vivo, modulation of this axis correspondingly accelerated or ameliorated IDD progression. Conclusion We identified a novel TRIM25‐USP7‐ENO1 axis, through which TRIM25 stabilizes ENO1 by promoting USP7‐ENO1 interaction and subsequent USP7‐dependent deubiquitination. This non‐canonical function expands the known role of TRIM25 and highlights a promising therapeutic target for restoring mitochondrial dysfunction and metabolic homeostasis in IDD. Key points TRIM25 recruits the deubiquitinating enzyme USP7 to collaboratively enhance the deubiquitination and stability of the key glycolytic enzyme ENO1, establishing a new regulatory pathway linking inflammation and metabolism. This regulatory axis exacerbates glycolysis, impairs mitochondrial function, disrupts cellular energy homeostasis, and ultimately leads to extracellular matrix degradation, systematically explaining a new pathological mechanism of IDD. Both cellular and animal models confirm that intervention in the TRIM25/USP7/ENO1 axis effectively reverses metabolic imbalance and degenerative progression, offering a promising new therapeutic strategy for IDD. This study extends TRIM25's role from immune regulation to metabolic processes and is the first to report USP7's involvement in glycolytic enzyme regulation, providing a new paradigm for studying “non‐canonical” functions of E3 ligases and deubiquitinating enzymes.
Xiao-Ming Liu, Wen-Yu Zhang, Hang Feng et al.· Clinical and Translational M...· 0 citations
Abstract Nucleus pulposus (NP) cell quiescence maintains intervertebral disc homeostasis, while mTORC1 regulates autophagy–lysosomal function and inflammatory secretion to preserve quiescence—rapamycin specifically targets mTORC1. Herein, we fabricated rapamycin‐nanoliposomes (rapa‐lipos) via ultrasonic dispersion, thin‐film dispersion, and filtration to improve rapamycin bioavailability, investigating their role in inhibiting the senescence phenotype of NP cells through β‐gal staining, lysosomal staining, transmission electron microscopy, ELISA, and cell cycle inhibitors. The mechanistic effects of rapa‐lipos on mTORC1, NLRP3/Caspase‐1 pathway (NCP) and autophagy–lysosomal pathway (ALP) were also analyzed by western blotting, immunofluorescence (IF), Si‐RNA (raptor), and PCR. In vivo, rapa‐lipos were injected into rat intervertebral disc with IL‐1β‐induced degeneration, assessed via HE staining, x‐ray, MRI, and IF. Rapa‐lipos exhibited high encapsulation efficiency, favorable drug loading, uniform particle size, and controlled release, suppressing NP cell senescence‐related phenotypes (morphological changes, elevated IL‐1β/TNF‐α secretion, increased β‐gal activity, lysosomal dysfunction, upregulated P21/P16 and reduced P27 expression). Mechanistically, rapa‐lipos targeted‐inhibited mTORC1, then blocked NCP and activated ALP to maintain NP cell quiescence. In vivo, x‐ray, MRI and histological evaluation confirmed rapa‐lipos mitigated intervertebral disc degeneration. Collectively, rapa‐lipos target mTORC1‐mediated NCP and ALP to inhibit NP cell senescence, offering a promising strategy for intervertebral disc degeneration prevention.
Hui Xing, Miao Yu, Jiabin Liu et al.· Bioengineering & Translation...· 0 citations
Intervertebral disc degeneration pathogenesis involves chronic inflammation and cell death, highlighting the need for targeted therapeutic strategies. Extracellular vesicles (EVs) have emerged as promising bioactive materials for designing therapeutic approach. In this study, we demonstrate that youthful-state EVs (Y-EVs) outperform aged donor-derived EVs (O-EVs) in resolving inflammatory cascades within nucleus pulposus (NP) cells. EVs from young rats significantly suppressed TNF-α-induced inflammation in NP cells by reducing pro-inflammatory cytokine secretion, inhibiting extracellular matrix catabolism, and ameliorating rat disc degeneration in vivo. Mechanistically, CD55 enrichment in Y-EVs attenuated NF-κB pathway activation, thereby disrupting inflammatory transcriptional programs. CD55 knockdown abrogated the anti-inflammatory efficacy of Y-EV, confirming its functional necessity. Besides, we identified thioredoxin (TRX) as a critical suppressor of NLRP1 inflammasome activation via direct protein binding, which inhibited NP cell pyroptosis. Crucially, CD55 in Y-EVs facilitated TRX-mediated NLRP1 suppression, whereas O-EVs failed to upregulate TRX or suppress the NLRP1 inflammasome. This study highlights the age-dependent functional divergence of EV bioactivity and establishes CD55 as a key determinant of their therapeutic superiority. The TRX–NLRP1 interaction represents a novel target for disc degeneration intervention, positioning youthful-state EVs as an optimized bioactive material for disc regeneration strategies.
Zhiwei Liao, Kun Wang, M. Lei et al.· Biomedical Materials· 0 citations
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