Urolithin A improves mitochondrial health, reduces cartilage degeneration, and alleviates pain in osteoarthritis

Long COVID as a Disease of Accelerated Biological Aging: An Opportunity to Translate Geroscience Interventions

It has been four years since long COVID-the protracted consequences that survivors of COVID-19 face-was first described. Yet, this entity continues to devastate the quality of life of an increasing number of COVID-19 survivors without any approved therapy. Furthermore, there remains a paucity of clinical trials addressing the biological root causes of this disease. Notably, the symptoms of long COVID-including but not limited to exercise intolerance, cognitive impairment, orthostasis, and functional decline-are typically seen with advancing age. Leveraging this similarity, we posit that Geroscience-which aims to target the biological drivers of aging to prevent age-associated conditions as a group-could offer promising therapeutic avenues for long COVID. Bearing this in mind, this review presents a framework for studying long COVID as a state of effectively accelerated biological aging. Thus, we comprehensively review here the role of biological hallmarks of aging in long COVID, identifying research gaps and proposing directions for future preclinical and clinical studies.

Mitophagy in relation to chronic inflammation/ROS in aging

Various assaults on mitochondria occur during the human aging process, contributing to mitochondrial dysfunction. This mitochondrial dysfunction is intricately connected with aging and diseases associated with it. In vivo, the accumulation of defective mitochondria can precipitate inflammatory and oxidative stress, thereby accelerating aging. Mitophagy, an essential selective autophagy process, plays a crucial role in managing mitochondrial quality control and homeostasis. It is a highly specialized mechanism that systematically removes damaged or impaired mitochondria from cells, ensuring their optimal functioning and survival. By engaging in mitophagy, cells are able to maintain a balanced and stable environment, free from the potentially harmful effects of dysfunctional mitochondria. An ever-growing body of research highlights the significance of mitophagy in both aging and age-related diseases. Nonetheless, the association between mitophagy and inflammation or oxidative stress induced by mitochondrial dysfunction remains ambiguous. We review the fundamental mechanisms of mitophagy in this paper, delve into its relationship with age-related stress, and propose suggestions for future research directions.

Mitochondria-Related Gene MAOB is a Key Biomarker of Osteoarthritis and Inhibition of Its Expression Reduces LPS-induced Chondrocyte Damage

The mitochondria are an important organelle in cells responsible for producing energy, and its abnormal function is closely related to the occurrence and development of osteoarthritis. Finding key genes associated with mitochondrial dysfunction in osteoarthritis can provide new ideas for the study of its pathogenesis. Firstly, 371 differential expressed genes (DEGs) were obtained through bioinformatics analysis of the GSE12021 and GSE55235 datasets in the GEO database, and 24 mitochondria-related DEGs (Mito-DEGs) were obtained by crossing differential genes with mitochondrial related genes. Next, KEGG and GO analysis of Mito-DEGs showed that upregulated Mito-DEGs were mainly enriched in small molecule catabolic process and tryptophan metabolism, while downregulated Mito-DEGs were mainly enriched in acetyl-CoA metabolic process and fatty acid biosynthesis. Furthermore, the key genes ME2 and MAOB were obtained through protein-protein interaction network analysis and lasso cox analysis of the 24 Mito-DEGs. In addition, the comparison results of immune cell scores showed differences between T cells CD4 memory resting, T cells regulatory (Tregs), Mast cells resting, and Mast cells activated in the OA group and the control group. More importantly, the potential regulatory mechanisms of key genes were studied through GSEA analysis and their correlation with immune infiltrating cells, immune checkpoints, m6A, and ferroptosis. Finally, in LPS-induced C28/I2 cells, silencing MAOB reduced inflammation injury and inhibited mitochondrial damage. Our research findings suggest that MAOB may hold potential as a target for the diagnosis and treatment of osteoarthritis.

The role and intervention of mitochondrial metabolism in osteoarthritis

Osteoarthritis (OA), a prevalent degenerative joint disease, affects a substantial global population. Despite the elusive etiology of OA, recent investigations have implicated mitochondrial dysfunction as a significant factor in disease pathogenesis. Mitochondria, pivotal cellular organelles accountable for energy production, exert essential roles in cellular metabolism. Hence, mitochondrial dysfunction can exert broad-ranging effects on various cellular processes implicated in OA development. This comprehensive review aims to provide an overview of the metabolic alterations occurring in OA and elucidate the diverse mechanisms through which mitochondrial dysfunction can contribute to OA pathogenesis. These mechanisms encompass heightened oxidative stress and inflammation, perturbed chondrocyte metabolism, and compromised autophagy. Furthermore, this review will explore potential interventions targeting mitochondrial metabolism as means to impede or decelerate the progression of OA. In summary, this review offers a comprehensive understanding of the involvement of mitochondrial metabolism in OA and underscores prospective intervention strategies.

Lubricating Microneedles System with Multistage Sustained Drug Delivery for the Treatment of Osteoarthritis

Osteoarthritis (OA) is a typical joint degenerative disease that is prevalent worldwide and significantly affects the normal activities of patients. Traditional treatments using diclofenac (DCF) as an anti-inflammatory drug by oral administration and transdermal delivery have many inherent deficiencies. In this study, a lubricating microneedles (MNs) system for the treatment of osteoarthritis with multistage sustained drug delivery and great reduction in skin damage during MNs penetration is developed. The bilayer dissolvable MNs system, namely HA-DCF@PDMPC, is prepared by designating the composite material of hyaluronic acid (HA) and covalently conjugated drug compound (HA-DCF) as the MNs tips and then modifying the surface of MNs tips with a self-adhesive lubricating copolymer (PDMPC). The MNs system is designed to achieve sustained drug release of DCF via ester bond hydrolysis, physical diffusion from MNs tips, and breakthrough of lubrication coating. Additionally, skin damage is reduced due to the presence of the lubrication coating on the superficial surface. Therefore, the lubricating MNs with multistage sustained drug delivery show good compliance as a transdermal patch for OA treatment, which is validated from anti-inflammatory cell tests and therapeutic animal experiments, down-regulating the expression levels of pro-inflammatory factors and alleviating articular cartilage destruction.

Increased Glycolytic Activity Is Part of Impeded M1(LPS) Macrophage Polarization in the Presence of Urolithin A

Urolithin A is a gut metabolite of ellagitannins and reported to confer health benefits, e.g., by increased clearance of damaged mitochondria by macroautophagy or curbed inflammation. One targeted cell type are macrophages, which are plastic and able to adopt pro- or anti-inflammatory polarization states, usually assigned as M1 and M2 macrophages, respectively. This flexibility is tightly coupled to characteristic shifts in metabolism, such as increased glycolysis in M1 macrophages, and protein expression upon appropriate stimulation. This study aimed at investigating whether the anti-inflammatory properties of U: rolithin A may be driven by metabolic alterations in cultivated murine M1(lipopolysaccharide) macrophages. Expression and extracellular flux analyses showed that urolithin A led to reduced il1β, il6, and nos2 expression and boosted glycolytic activity in M1(lipopolysaccharide) macrophages. The pro-glycolytic feature of UROLITHIN A: occurred in order to causally contribute to its anti-inflammatory potential, based on experiments in cells with impeded glycolysis. Mdivi, an inhibitor of mitochondrial fission, blunted increased glycolytic activity and reduced M1 marker expression in M1(lipopolysaccharide/UROLITHIN A: ), indicating that segregation of mitochondria was a prerequisite for both actions of UROLITHIN A: . Overall, we uncovered a so far unappreciated metabolic facet within the anti-inflammatory activity of UROLITHIN A: and call for caution about the simplified notion of increased aerobic glycolysis as an inevitably proinflammatory feature in macrophages upon exposure to natural products.

Mitochondrial DNA drives neuroinflammation through the cGAS-IFN signaling pathway in the spinal cord of neuropathic pain mice

Neuroinflammation is pivotal in the development of neuropathic pain (NeP). While mitochondrial deoxyribonucleic acid (mtDNA) and cyclic GMP-AMP synthase (cGAS) are recognized for inducing inflammation in various neurological disorders, their involvement in NeP remains ambiguous. In this study, we examined: (1) the changes in mtDNA and cGAS in mice with NeP induced by chronic constriction injury (CCI) of the sciatic nerve, whether mtDNA triggers inflammation via the cGAS signaling; (2) the effects of RU.521, a cGAS antagonist, on CCI-induced nociception (allodynia and hyperalgesia) and relative inflammatory protein expression; (3) the activation of microglia and the cGAS-IFN pathway mediated by mtDNA in BV2 cell; (4) the effect of RU.521 on mtDNA-induced inflammatory response in BV2 cells. Results revealed reduced mtDNA levels in the sciatic nerve but increased levels in the spinal cord of CCI mice, along with elevated cGAS expression and inflammatory factors. RU.521 alleviated nociceptive behaviors in CCI mice, possibly by normalizing cGAS levels and suppressing inflammation. Neuron-derived mtDNA provoked cellular activation and upregulated cGAS signaling in BV2 cells. Additionally, RU.521 and DNase I effectively inhibited cGAS-induced inflammation. These findings underscore the critical role of mtDNA accumulation and mtDNA-mediated cGAS signaling in NeP development after peripheral nerve injury.

The metabolic characteristics and changes of chondrocytes in vivo and in vitro in osteoarthritis

Osteoarthritis (OA) is an intricate pathological condition that primarily affects the entire synovial joint, especially the hip, hand, and knee joints. This results in inflammation in the synovium and osteochondral injuries, ultimately causing functional limitations and joint dysfunction. The key mechanism responsible for maintaining articular cartilage function is chondrocyte metabolism, which involves energy generation through glycolysis, oxidative phosphorylation, and other metabolic pathways. Some studies have shown that chondrocytes in OA exhibit increased glycolytic activity, leading to elevated lactate production and decreased cartilage matrix synthesis. In OA cartilage, chondrocytes display alterations in mitochondrial activity, such as decreased ATP generation and increased oxidative stress, which can contribute to cartilage deterioration. Chondrocyte metabolism also involves anabolic processes for extracellular matrix substrate production and energy generation. During OA, chondrocytes undergo considerable metabolic changes in different aspects, leading to articular cartilage homeostasis deterioration. Numerous studies have been carried out to provide tangible therapies for OA by using various models in vivo and in vitro targeting chondrocyte metabolism, although there are still certain limitations. With growing evidence indicating the essential role of chondrocyte metabolism in disease etiology, this literature review explores the metabolic characteristics and changes of chondrocytes in the presence of OA, both in vivo and in vitro. To provide insight into the complex metabolic reprogramming crucial in chondrocytes during OA progression, we investigate the dynamic interaction between metabolic pathways, such as glycolysis, lipid metabolism, and mitochondrial function. In addition, this review highlights prospective future research directions for novel approaches to diagnosis and treatment. Adopting a multifaceted strategy, our review aims to offer a comprehensive understanding of the metabolic intricacies within chondrocytes in OA, with the ultimate goal of identifying therapeutic targets capable of modulating chondrocyte metabolism for the treatment of OA.

Exosomes derived from miR-146a-overexpressing fibroblast-like synoviocytes in cartilage degradation and macrophage M1 polarization: a novel protective agent for osteoarthritis?

Introduction

Pathological changes in the articular cartilage (AC) and synovium are major manifestations of osteoarthritis (OA) and are strongly associated with pain and functional limitations. Exosome-derived microRNAs (miRNAs) are crucial regulatory factors in intercellular communication and can influence the progression of OA by participating in the degradation of chondrocytes and the phenotypic transformation in the polarization of synovial macrophages. However, the specific relationships and pathways of action of exosomal miRNAs in the pathological progression of OA in both cartilage and synovium remain unclear.

Methods

This study evaluates the effects of fibroblast-like synoviocyte (FLS)-derived exosomes (FLS-Exos), influenced by miR-146a, on AC degradation and synovial macrophage polarization. We investigated the targeted relationship between miR-146a and TRAF6, both in vivo and in vitro, along with the involvement of the NF-κB signaling pathway.

Results

The expression of miR-146a in the synovial exosomes of OA rats was significantly higher than in healthy rats. In vitro, the upregulation of miR-146a reduced chondrocyte apoptosis, whereas its downregulation had the opposite effect. In vivo, exosomes derived from miR-146a-overexpressing FLSs (miR-146a-FLS-Exos) reduced AC injury and chondrocyte apoptosis in OA. Furthermore, synovial proliferation was reduced, and the polarization of synovial macrophages shifted from M1 to M2. Mechanistically, the expression of TRAF6 was inhibited by targeting miR-146a, thereby modulating the Toll-like receptor 4/TRAF6/NF-κB pathway in the innate immune response.

Discussion

These findings suggest that miR-146a, mediated through FLS-Exos, may alleviate OA progression by modulating cartilage degradation and macrophage polarization, implicating the NF-κB pathway in the innate immune response. These insights highlight the therapeutic potential of miR-146a as a protective agent in OA, underscoring the importance of exosomal miRNAs in the pathogenesis and potential treatment of the disease.

Intrauterine hyperglycemia induces SIRT3-mediated mitochondrial dysfunction: the fetal origin pathogenesis of precocious osteoarthritis

OBJECTIVE

Diabetes and other metabolic and inflammatory comorbidities are highly associated with osteoarthritis (OA). However, whether early-life hyperglycemia exposure affects susceptibility to long-term OA is still unknown. The purpose of this study was to explore the fetal origins of OA and provide insights into early-life safeguarding for individual health.

METHOD

This study utilized streptozotocin to induce intrauterine hyperglycemia and performed destabilization of the medial meniscus surgery on the knee joints of the offspring mice to induce accelerated OA. Cartilage degeneration-related markers, as well as the expression levels of mitochondrial respiratory chain complexes and mitophagy genes in the adult offspring mice, were investigated. In vitro, mitochondrial function and mitophagy of chondrocyte C28/I2 cells stimulated under high glucose conditions were also evaluated. The methylation levels of the sirt3 gene promoter region in the articular cartilage of intrauterine hyperglycemia-exposed offspring mice were further analyzed.

RESULTS

In this study, we found that the intrauterine hyperglycemic environment could lead to an increase in individual susceptibility to OA in late adulthood, mainly due to persistently low levels of Sirt3 expression. Downregulation of Sirt3 causes impaired mitophagy in chondrocytes and abnormal mitochondrial respiratory function due to a failure to clear aged and damaged mitochondria in a timely manner. Overexpressing Sirt3 at the cellular level or using Sirt3 agonists like Honokiol in mouse models can partially rescue mitophagy disorders caused by the hyperglycemic environment and thus alleviate the progression of OA.

CONCLUSION

Our study revealed a significantly increased susceptibility to OA in the gestational diabetes mellitus offspring, which is partly attributed to exposure to adverse factors in utero and ultimately to the onset of disease via epigenetic modulation.

Integration of metabolomics and transcriptomics provides insights into the molecular mechanism of temporomandibular joint osteoarthritis

The deficiency of clinically specific biomarkers has made it difficult to achieve an accurate diagnosis of temporomandibular joint osteoarthritis (TMJ-OA) and the insufficient comprehension of the pathogenesis of the pathogenesis of TMJ-OA has posed challenges in advancing therapeutic measures. The combined use of metabolomics and transcriptomics technologies presents a highly effective method for identifying vital metabolic pathways and key genes in TMJ-OA patients. In this study, an analysis of synovial fluid untargeted metabolomics of 6 TMJ-OA groups and 6 temporomandibular joint reducible anterior disc displacement (TMJ-DD) groups was conducted using liquid and gas chromatography mass spectrometry (LC/GC-MS). The differential metabolites (DMs) between TMJ-OA and TMJ-DD groups were analyzed through multivariate analysis. Meanwhile, a transcriptomic dataset (GSE205389) was obtained from the GEO database to analyze the differential metabolism-related genes (DE-MTGs) between TMJ-OA and TMJ-DD groups. Finally, an integrated analysis of DMs and DE-MTGs was carried out to investigate the molecular mechanisms associated with TMJ-OA. The analysis revealed significant differences in the levels of 46 DMs between TMJ-OA and TMJ-DD groups, of which 3 metabolites (L-carnitine, taurine, and adenosine) were identified as potential biomarkers for TMJ-OA. Collectively, differential expression analysis identified 20 DE-MTGs. Furthermore, the integration of metabolomics and transcriptomics analysis revealed that the tricarboxylic acid (TCA) cycle, alanine, aspartate and glutamate metabolism, ferroptosis were significantly enriched. This study provides valuable insights into the metabolic abnormalities and associated pathogenic mechanisms, improving our understanding of TMJOA etiopathogenesis and facilitating potential target screening for therapeutic intervention.

Amyloid β accelerates age-related proteome-wide protein insolubility

Loss of proteostasis is a highly conserved feature of aging across model organisms and results in the accumulation of insoluble protein aggregates. Protein insolubility is also a unifying feature of major age-related neurodegenerative diseases, including Alzheimer's Disease (AD), in which hundreds of insoluble proteins associate with aggregated amyloid beta (Aβ) in senile plaques. Despite the connection between aging and AD risk, therapeutic approaches to date have overlooked aging-driven generalized protein insolubility as a contributing factor. However, proteins that become insoluble during aging in model organisms are capable of accelerating Aβ aggregation in vitro and lifespan in vivo. Here, using an unbiased proteomics approach, we questioned the relationship between Aβ and age-related protein insolubility. Specifically, we uncovered that Aβ expression drives proteome-wide protein insolubility in C. elegans, even in young animals, and this insoluble proteome is highly similar to the insoluble proteome driven by normal aging, this vulnerable sub-proteome we term the core insoluble proteome (CIP). We show that the CIP is enriched with proteins that modify Aβ toxicity in vivo, suggesting the possibility of a vicious feedforward cycle in the context of AD. Importantly, using human genome-wide association studies (GWAS), we show that the CIP is replete with biological processes implicated not only in neurodegenerative diseases but also across a broad array of chronic, age-related diseases (CARDs). This provides suggestive evidence that age-related loss of proteostasis could play a role in general CARD risk. Finally, we show that the geroprotective, gut-derived metabolite, Urolithin A, relieves Aβ toxicity, supporting its use in clinical trials for dementia and age-related diseases.

Novel insights into the role of ubiquitination in osteoarthritis

Ubiquitination (Ub) and deubiquitination are crucial post-translational modifications (PTMs) that precisely regulate protein degradation. Under the catalysis of a cascade of E1-E2-E3 ubiquitin enzymes, ubiquitination extensively regulates protein degradation exerting direct impact on various cellular processes, while deubiquitination opposes the effect of ubiquitination and prevents proteins from degradation. Notably, such dynamic modifications have been widely investigated to be implicated in cell cycle, transcriptional regulation, apoptosis and so on. Therefore, dysregulation of ubiquitination and deubiquitination could lead to certain diseases through abnormal protein accumulation and clearance. Increasing researches have revealed that the dysregulation of catalytic regulators of ubiquitination and deubiquitination triggers imbalance of cartilage homeostasis that promotes osteoarthritis (OA) progression. Hence, it is now believed that targeting on Ub enzymes and deubiquitinating enzymes (DUBs) would provide potential therapeutic pathways. In the following sections, we will summarize the biological role of Ub enzymes and DUBs in the development and progression of OA by focusing on the updating researches, with the aim of deepening our understanding of the underlying molecular mechanism of OA pathogenesis concerning ubiquitination and deubiquitination, so as to explore novel potential therapeutic targets of OA treatment.

TGF-β3 mediates mitochondrial dynamics through the p-Smad3/AMPK pathway

It is well recognized that mitochondrial dynamics plays a vital role in cartilage physiology. Any perturbation in mitochondrial dynamics could cause disorders in cartilage metabolism and even lead to the occurrence of cartilage diseases such as osteoarthritis (OA). TGF-β3, as an important growth factor that appears in the joints of OA disease, shows its great potential in chondrocyte growth and metabolism. Nevertheless, the role of TGF-β3 on mitochondrial dynamics is still not well understood. Here we aimed to investigate the effect of TGF-β3 on mitochondrial dynamics of chondrocytes and reveal its underlying bio-mechanism. By using transmission electron microscopy (TEM) for the number and morphology of mitochondria, western blotting for the protein expressions, immunofluorescence for the cytoplasmic distributions of proteins, and RNA sequencing for the transcriptome changes related to mitochondrial dynamics. We found that TGF-β3 could increase the number of mitochondria in chondrocytes. TGF-β3-enhanced mitochondrial number was via promoting the mitochondrial fission. The mitochondrial fission induced by TGF-β3 was mediated by AMPK signaling. TGF-β3 activated canonical p-Smad3 signaling and resultantly mediated AMPK-induced mitochondrial fission. Taken together, these results elucidate an understanding of the role of TGF-β3 on mitochondrial dynamics in chondrocytes and provide potential cues for therapeutic strategies in cartilage injury and OA disease in terms of energy metabolism.

Koumine inhibits IL-1β-induced chondrocyte inflammation and ameliorates extracellular matrix degradation in osteoarthritic cartilage through activation of PINK1/Parkin-mediated mitochondrial autophagy

Osteoarthritis (OA) is a degenerative joint disease, Increasingly, mitochondrial autophagy has been found to play an important regulatory role in the prevention and treatment of osteoarthritis. Koumine is a bioactive alkaloid extracted from the plant Gelsemium elegans. In previous research, Koumine was found to have potential in improving the progression of OA in rats. However, the specific mechanism of its action has not been fully explained. Therefore, the aim of this study was to investigate whether Koumine can alleviate OA in rats by influencing mitochondrial autophagy. In the in vitro study, rat chondrocytes (RCCS-1) were induced with IL-1β (10 ng/mL) to induce inflammation, and Koumine (50 μg/mL) was co-treated. In the in vivo study, a rat OA model was established by intra-articular injection of 2% papain, and Koumine was administered orally (1 mg/kg, once daily for two weeks). It was found that Koumine effectively reduced cartilage erosion in rats with osteoarthritis. Additionally, it decreased the levels of inflammatory factors such as IL-1β, IL-6, and extracellular matrix (ECM) components MMP13 and ADAMTS5 in chondrocytes and articular cartilage tissue, while increasing the level of Collagen II.Koumine inhibited the production of reactive oxygen species (ROS) in cartilage tissue and increased the number of autophagosomes in chondrocytes and articular cartilage tissue. Additionally, it upregulated the expression of mitochondrial autophagy proteins LC3Ⅱ/Ⅰ, PINK1, Parkin, and Drp1. The administration of Mdivi-1 (50 μM) reversed the enhanced effect of Koumine on mitochondrial autophagy, as well as its anti-inflammatory and anti-ECM degradation effects in rats with OA. These findings suggest that Koumine can alleviate chondrocyte inflammation and improve the progression of OA in rats by activating PINK1/Parkin-mediated mitochondrial autophagy.

The NLRX1-SLC39A7 complex orchestrates mitochondrial dynamics and mitophagy to rejuvenate intervertebral disc by modulating mitochondrial Zn2+ trafficking

Intervertebral disc degeneration (IDD) is the most critical pathological factor in the development of low back pain. The maintenance of nucleus pulposus (NP) cell and intervertebral disc integrity benefits largely from well-controlled mitochondrial quality, surveilled by mitochondrial dynamics (fission and fusion) and mitophagy, but the outcome is cellular context-dependent that remain to be clarified. Our studies revealed that the loss of NLRX1 is correlated with NP cell senescence and IDD progression, which involve disordered mitochondrial quality. Further using animal and in vitro tissue and cell models, we demonstrated that NLRX1 could facilitate mitochondrial quality by coupling mitochondrial dynamic factors (p-DNM1L, L-OPA1:S-OPA1, OMA1) and mitophagy activity. Conversely, mitochondrial collapse occurred in NLRX1-defective NP cells and switched on the compensatory PINK1-PRKN pathway that led to excessive mitophagy and aggressive NP cell senescence. Mechanistically, NLRX1 was originally shown to interact with zinc transporter SLC39A7 and modulate mitochondrial Zn2+ trafficking via the formation of an NLRX1-SLC39A7 complex on the mitochondrial membrane of NP cells, subsequently orchestrating mitochondrial dynamics and mitophagy. The restoration of NLRX1 function by gene overexpression or pharmacological agonist (NX-13) treatment showed great potential for regulating mitochondrial fission with synchronous fusion and mitophagy, thus sustaining mitochondrial homeostasis, ameliorating NP cell senescence and rejuvenating intervertebral discs. Collectively, our findings highlight a working model whereby the NLRX1-SLC39A7 complex coupled mitochondrial dynamics and mitophagy activity to surveil and target damaged mitochondria for degradation, which determines the beneficial function of the mitochondrial surveillance system and ultimately rejuvenates intervertebral discs.Abbreviations: 3-MA: 3-methyladenine; Baf-A1: bafilomycin A1; CDKN1A/p21: cyclin dependent kinase inhibitor 1A; CDKN2A/p16: cyclin dependent kinase inhibitor 2A; DNM1L/DRP1: dynamin 1 like; EdU: 5-Ethynyl-2'-deoxyuridine; HE: hematoxylin-eosin; IDD: intervertebral disc degeneration; IL1B/IL-1β: interleukin 1 beta; IL6: interleukin 6; MAP1LC3B/LC3B: microtubule associated protein 1 light chain 3 beta; MKI67/Ki67: marker of proliferation Ki-67; LBP: low back pain; MMP: mitochondrial membrane potential; MFN1: mitofusin 1; MFN2: mitofusin 2; MFF: mitochondrial fission factor; NP: nucleus pulposus; NLRX1: NLR family member X1; OMA1: OMA1 zinc metallopeptidase; OPA1: OPA1 mitochondrial dynamin like GTPase; PINK1: PTEN induced kinase 1; PRKN: parkin RBR E3 ubiquitin protein ligase; ROS: reactive oxidative species; SASP: senescence-associated secretory phenotype; SA-GLB1/β-gal: senescence-associated galactosidase beta 1; SO: safranin o; TBHP: tert-butyl hydroperoxide; TP53/p53: tumor protein p53; SLC39A7/ZIP7: solute carrier family 39 member 7; TOMM20: translocase of outer mitochondrial membrane 20; TIMM23: translocase of inner mitochondrial membrane 23.

Alpha 2-adrenoceptor participates in anti-hyperalgesia by regulating metabolic demand

The α2-adrenoceptor agonist dexmedetomidine is a commonly used drug for sedatives in clinics and has analgesic effects; however, its mechanism of analgesia in the spine remains unclear. In this study, we systematically used behavioural and transcriptomic sequencing, pharmacological intervention, electrophysiological recording and ultrasound imaging to explore the analgesic effects of the α2-adrenoceptor and its molecular mechanism. Firstly, we found that spinal nerve injury changed the spinal transcriptome expression, and the differential genes were mainly related to calcium signalling and tissue metabolic pathways. In addition, α2-adrenoceptor mRNA expression was significantly upregulated, and α2-adrenoceptor was significantly colocalised with markers, particularly neuronal markers. Intrathecal dexmedetomidine suppressed neuropathic pain and acute inflammatory pain in a dose-dependent manner. The transcriptome results demonstrated that the analgesic effect of dexmedetomidine may be related to the modulation of neuronal metabolism. Weighted gene correlation network analysis indicated that turquoise, brown, yellow and grey modules were the most correlated with dexmedetomidine-induced analgesic effects. Bioinformatics also annotated the involvement of metabolic processes and neural plasticity. A cardiovascular-mitochondrial interaction was found, and ultrasound imaging revealed that injection of dexmedetomidine significantly enhanced spinal cord perfusion in rats with neuropathic pain, which might be regulated by pyruvate dehydrogenase kinase 4 (pdk4), cholesterol 25-hydroxylase (ch25 h) and GTP cyclohydrolase 1 (gch1). Increasing the perfusion doses of dexmedetomidine significantly suppressed the frequency and amplitude of spinal nerve ligation-induced miniature excitatory postsynaptic currents. Overall, dexmedetomidine exerts analgesic effects by restoring neuronal metabolic processes through agonism of the α2-adrenoceptor and subsequently inhibiting changes in synaptic plasticity.

(Poly)phenol-related gut metabotypes and human health: an update

Dietary (poly)phenols have received great interest due to their potential role in the prevention and management of non-communicable diseases. In recent years, a high inter-individual variability in the biological response to (poly)phenols has been demonstrated, which could be related to the high variability in (poly)phenol gut microbial metabolism existing within individuals. An interplay between (poly)phenols and the gut microbiota exists, with (poly)phenols being metabolised by the gut microbiota and their metabolites modulating gut microbiota diversity and composition. A number of (poly)phenol metabolising phenotypes or metabotypes have been proposed, however, potential metabotypes for most (poly)phenols have not been investigated, and the relationship between metabotypes and human health remains ambiguous. This review presents updated knowledge on the reciprocal interaction between (poly)phenols and the gut microbiome, associated gut metabotypes, and subsequent impact on human health.

Advances in the study of mitophagy in osteoarthritis

Osteoarthritis (OA), characterized by cartilage degeneration, synovial inflammation, and subchondral bone remodeling, is among the most common musculoskeletal disorders globally in people over 60 years of age. The initiation and progression of OA involves the abnormal metabolism of chondrocytes as an important pathogenic process. Cartilage degeneration features mitochondrial dysfunction as one of the important causative factors of abnormal chondrocyte metabolism. Therefore, maintaining mitochondrial homeostasis is an important strategy to mitigate OA. Mitophagy is a vital process for autophagosomes to target, engulf, and remove damaged and dysfunctional mitochondria, thereby maintaining mitochondrial homeostasis. Cumulative studies have revealed a strong association between mitophagy and OA, suggesting that the regulation of mitophagy may be a novel therapeutic direction for OA. By reviewing the literature on mitophagy and OA published in recent years, this paper elaborates the potential mechanism of mitophagy regulating OA, thus providing a theoretical basis for studies related to mitophagy to develop new treatment options for OA.

Cellulose nanocrystals-reinforced dual crosslinked double network GelMA/hyaluronic acid injectable nanocomposite cryogels with improved mechanical properties for cartilage tissue regeneration

Improvement of mechanical properties of injectable tissue engineering scaffolds is a current challenge. The objective of the current study is to produce a highly porous injectable scaffold with improved mechanical properties. For this aim, cellulose nanocrystals-reinforced dual crosslinked porous nanocomposite cryogels were prepared using chemically crosslinked methacrylated gelatin (GelMA) and ionically crosslinked hyaluronic acid (HA) through the cryogelation process. The resulting nanocomposites showed highly porous structures with interconnected porosity (>90%) and mean pore size in the range of 130-296 μm. The prepared nanocomposite containing 3%w/v of GelMA, 20 w/w% of HA, and 1%w/v of CNC showed the highest Young's modulus (10 kPa) and excellent reversibility after 90% compression and could regain its initial shape after injection by a 16-gauge needle in the aqueous media. The in vitro results demonstrated acceptable viability (>90%) and migration of the human chondrocyte cell line (C28/I2), and chondrogenic differentiation of human adipose stem cells. A two-month in vivo assay on a rabbit's ear model confirmed that the regeneration potential of the prepared cryogel is comparable to the natural autologous cartilage graft, suggesting it is a promising alternative for autografts in the treatment of cartilage defects.

Sirtuin 4 (Sirt4) downregulation contributes to chondrocyte senescence and osteoarthritis via mediating mitochondrial dysfunction

Chondrocyte senescence has recently been proposed as a key pathogenic mechanism in the etiology of osteoarthritis (OA). Nevertheless, the precise molecular mechanisms underlying chondrocyte senescence remain poorly understood. To address this knowledge gap, we conducted an investigation into the involvement of Sirtuin 4 (Sirt4) in chondrocyte senescence. Our experimental findings revealed a downregulation of Sirt4 expression in TBHP-induced senescent chondrocytes in vitro, as well as in mouse OA cartilage. Additionally, we observed that the knockdown of Sirt4 in chondrocytes promoted cellular senescence and cartilage degradation, while the overexpression of Sirt4 protected the cells against TBHP-mediated senescence of chondrocytes and cartilage degradation. Moreover, our findings revealed elevated levels of reactive oxygen species (ROS), abnormal mitochondrial morphology, compromised mitochondrial membrane potential, and reduced ATP production in Sirt4 knockdown chondrocytes, indicative of mitochondrial dysfunction. Conversely, Sirt4 overexpression successfully mitigated TBHP-induced mitochondrial dysfunction. Further analysis revealed that Sirt4 downregulation impaired the cellular capacity to eliminate damaged mitochondria by inhibiting Pink1 in chondrocytes, thereby enhancing the accumulation of ROS and facilitating chondrocyte senescence. Notably, the overexpression of Pink1 counteracted the effects of Sirt4 knockdown on mitochondrial dysfunction. Importantly, our study demonstrated the promise of gene therapy employing a lentiviral vector encoding mouse Sirt4, as it successfully preserved the integrity of articular cartilage in mouse models of OA. In conclusion, our findings provide compelling evidence that the overexpression of Sirt4 enhances mitophagy, restores mitochondrial function, and protects against chondrocyte senescence, thereby offering a novel therapeutic target and potential strategy for the treatment of OA.

Natural Activators of Autophagy

Autophagy is the process by which cell contents, such as aggregated proteins, dysfunctional organelles, and cell structures are sequestered by autophagosome and delivered to lysosomes for degradation. As a process that allows the cell to get rid of non-functional components that tend to accumulate with age, autophagy has been associated with many human diseases. In this regard, the search for autophagy activators and the study of their mechanism of action is an important task for treatment of many diseases, as well as for increasing healthy life expectancy. Plants are rich sources of autophagy activators, containing large amounts of polyphenolic compounds in their composition, which can be autophagy activators in their original form, or can be metabolized by the intestinal microbiota to active compounds. This review is devoted to the plant-based autophagy activators with emphasis on the sources of their production, mechanism of action, and application in various diseases. The review also describes companies commercializing natural autophagy activators.

Mitophagy Activation by Urolithin A to Target Muscle Aging

The age-related loss of skeletal muscle function starts from midlife and if left unaddressed can lead to an impaired quality of life. A growing body of evidence indicates that mitochondrial dysfunction is causally involved with muscle aging. Muscles are tissues with high metabolic requirements, and contain rich mitochondria supply to support their continual energy needs. Cellular mitochondrial health is maintained by expansing of the mitochondrial pool though mitochondrial biogenesis, by preserving the natural mitochondrial dynamic process, via fusion and fission, and by ensuring the removal of damaged mitochondria through mitophagy. During aging, mitophagy levels decline and negatively impact skeletal muscle performance. Nutritional and pharmacological approaches have been proposed to manage the decline in muscle function due to impaired mitochondria bioenergetics. The natural postbiotic Urolithin A has been shown to promote mitophagy, mitochondrial function and improved muscle function across species in different experimental models and across multiple clinical studies. In this review, we explore the biology of Urolithin A and the clinical evidence of its impact on promoting healthy skeletal muscles during age-associated muscle decline.

Moxibustion ameliorates osteoarthritis by regulating gut microbiota via impacting cAMP-related signaling pathway

BACKGROUND

Osteoarthritis (OA) is a prevalent progressive disorder. Moxibustion has found widespread use in clinical practice for OA, while its underlying mechanism remains elusive.

OBJECTIVE

To investigate whether moxibustion can ameliorate OA by influencing the metabolic processes in OA and to elucidate the specific metabolic mechanisms involved.

METHODS

C57BL/6J WT mice were randomly assigned to one of three groups: the SHAM group, the ACLT group, and the ACLT+M group. In the ACLT+M group, mice underwent moxibustion treatment at acupoints Shenshu (BL23) and Zusanli (ST36) for a continuous period of 28 days, with each session lasting 20 min. We conducted a comprehensive analysis to assess the impact of moxibustion on OA, focusing on pathological changes, intestinal flora composition, and serum metabolites.

RESULTS

Moxibustion treatment effectively mitigated OA-related pathological changes. Specifically, moxibustion treatment resulted in the amelioration of articular cartilage damage, synovial inflammation, subchondral bone sclerosis when compared to the ACLT group. Moreover, 16S rDNA sequencing analysis revealed that moxibustion treatment positively influenced the composition of the flora, making it more similar to that of the SHAM group. Notably, moxibustion treatment led to a reduction in the abundance of Ruminococcus and Proteobacteria in the intestine. In addition, non-targeted metabolomics analysis identified 254 significantly different metabolites between the groups. Based on KEGG pathway analysis and the observed impact of moxibustion on OA-related inflammation, moxibustion therapy is closely associated with the cAMP-related signaling pathway.

CONCLUSION

Moxibustion can relieve OA by regulating intestinal flora and via impacting cAMP-related signaling pathway.

Amyloid β accelerates age-related proteome-wide protein insolubility

Loss of proteostasis is a highly conserved feature of aging across model organisms and typically results in the accumulation of insoluble protein aggregates. Protein insolubility is a central feature of major age-related neurodegenerative diseases, including Alzheimer's Disease (AD), where hundreds of insoluble proteins associate with aggregated amyloid beta (Aβ) in senile plaques. Moreover, proteins that become insoluble during aging in model organisms are capable of accelerating Aβ aggregation in vitro. Despite the connection between aging and AD risk, therapeutic approaches to date have overlooked aging-driven protein insolubility as a contributory factor. Here, using an unbiased proteomics approach, we questioned the relationship between Aβ and age-related protein insolubility. We demonstrate that Aβ expression drives proteome-wide protein insolubility in C. elegans and this insoluble proteome closely resembles the insoluble proteome driven by normal aging, suggesting the possibility of a vicious feedforward cycle of aggregation in the context of AD. Importantly, using human genome-wide association studies (GWAS), we show that the CIP is replete with biological processes implicated not only in neurodegenerative diseases but also across a broad array of chronic, age-related diseases (CARDs). This provides suggestive evidence that age-related loss of proteostasis could play a role in general CARD risk. Finally, we show that the CIP is enriched with proteins that modulate the toxic effects of Aβ and that the gut-derived metabolite, Urolithin A, relieves Aβ toxicity, supporting its use in clinical trials for dementia and other age-related diseases.

New insight of the pathogenesis in osteoarthritis: the intricate interplay of ferroptosis and autophagy mediated by mitophagy/chaperone-mediated autophagy

Ferroptosis, characterized by iron accumulation and lipid peroxidation, is a form of iron-driven cell death. Mitophagy is a type of selective autophagy, where degradation of damaged mitochondria is the key mechanism for maintaining mitochondrial homeostasis. Additionally, Chaperone-mediated autophagy (CMA) is a biological process that transports individual cytoplasmic proteins to lysosomes for degradation through companion molecules such as heat shock proteins. Research has demonstrated the involvement of ferroptosis, mitophagy, and CMA in the pathological progression of Osteoarthritis (OA). Furthermore, research has indicated a significant correlation between alterations in the expression of reactive oxygen species (ROS), adenosine monophosphate (AMP)-activated protein kinase (AMPK), and hypoxia-inducible factors (HIFs) and the occurrence of OA, particularly in relation to ferroptosis and mitophagy. In light of these findings, our study aims to assess the regulatory functions of ferroptosis and mitophagy/CMA in the pathogenesis of OA. Additionally, we propose a mechanism of crosstalk between ferroptosis and mitophagy, while also examining potential pharmacological interventions for targeted therapy in OA. Ultimately, our research endeavors to offer novel insights and directions for the prevention and treatment of OA.

FUNDC1/PFKP-mediated mitophagy induced by KD025 ameliorates cartilage degeneration in osteoarthritis

Osteoarthritis (OA) is the most common joint disease, but no disease-modifying drugs have been approved for OA treatment. Mitophagy participates in mitochondrial homeostasis regulation by selectively clearing dysfunctional mitochondria, which might contribute to cartilage degeneration in OA. Here, we provide evidence of impaired mitophagy in OA chondrocytes, which exacerbates chondrocyte degeneration. Among the several classic mitophagy-regulating pathways and receptors, we found that FUNDC1 plays a key role in preserving chondrocyte homeostasis by inducing mitophagy. FUNDC1 knockdown in vitro and knockout in vivo decreased mitophagy and exacerbated mitochondrial dysfunction, exacerbating chondrocyte degeneration and OA progression. FUNDC1 overexpression via intra-articular injection of adeno-associated virus alleviated cartilage degeneration in OA. Mechanistically, our study demonstrated that PFKP interacts with and dephosphorylates FUNDC1 to induce mitophagy in chondrocytes. Further analysis identified KD025 as a candidate drug for restoring chondrocyte mitophagy by increasing the FUNDC1-PFKP interaction and thus alleviating cartilage degeneration in mice with DMM-induced OA. Our study highlights the role of the FUNDC1-PFKP interaction in chondrocyte homeostasis via mitophagy induction and identifies KD025 as a promising agent for treating OA by increasing chondrocyte mitophagy.

Mitophagy in human health, ageing and disease

Maintaining optimal mitochondrial function is a feature of health. Mitophagy removes and recycles damaged mitochondria and regulates the biogenesis of new, fully functional ones preserving healthy mitochondrial functions and activities. Preclinical and clinical studies have shown that impaired mitophagy negatively affects cellular health and contributes to age-related chronic diseases. Strategies to boost mitophagy have been successfully tested in model organisms, and, recently, some have been translated into clinics. In this Review, we describe the basic mechanisms of mitophagy and how mitophagy can be assessed in human blood, the immune system and tissues, including muscle, brain and liver. We outline mitophagy's role in specific diseases and describe mitophagy-activating approaches successfully tested in humans, including exercise and nutritional and pharmacological interventions. We describe how mitophagy is connected to other features of ageing through general mechanisms such as inflammation and oxidative stress and forecast how strengthening research on mitophagy and mitophagy interventions may strongly support human health.

Retuning Mitochondrial Apoptosis/Mitophagy Balance via SIRT3-Energized and Microenvironment-Modulated Hydrogel Microspheres to Impede Osteoarthritis

Full-range therapeutic regimens for osteoarthritis (OA) should consider organs (joints)-tissues (cartilage)-cells (chondrocytes)-organelles cascade, of which the subcellular mitochondria dominate eukaryotic cells' fate, and thus causally influence OA progression. However, the dynamic regulation of mitochondrial rise and demise in impaired chondrocytes and the exact role of mitochondrial metronome sirtuins 3 (SIRT3) is not clarified. Herein, chondrocytes are treated with SIRT3 natural agonist dihydromyricetin (DMY) or chemical antagonist 3-TYP, respectively, to demonstrate the positive action of SIRT3 on preserving cartilage extracellular matrix (ECM). Molecular mechanical investigations disclose that SIRT3-induced chondroprotection depended on the repression of mitochondrial apoptosis (mtApoptosis) and the activation of mitophagy. Inspired by the high-level matrix proteinases and reactive oxygen species (ROS) in the OA environment, by anchoring gelatin methacrylate (GelMA) and benzenediboronic acid (PBA) to hyaluronic acid methacrylate (HAMA) with microfluidic technology, a dual-responsive hydrogel microsphere laden with DMY is tactfully fabricated and named as DMY@HAMA-GelMA-PBA (DMY@HGP). In vivo injection of DMY@HGP ameliorated cartilage abrasion and subchondral bone sclerosis, as well as promoted motor function recovery in post-traumatic OA (PTOA) model via recouping endogenous mtApoptosis and mitophagy balance. Overall, this study unveils a novel mitochondrial dynamic-oriented strategy, holding great promise for the precision treatment of OA.

Pharmacological Effects of Urolithin A and Its Role in Muscle Health and Performance: Current Knowledge and Prospects

Urolithin A (UA) is a naturally occurring compound derived from the metabolism of gut microbiota, which has attracted considerable research attention due to its pharmacological effects and potential implications in muscle health and performance. Recent studies have demonstrated that Urolithin A exhibits diverse biological activities, encompassing anti-inflammatory, antioxidant, anti-tumor, and anti-aging properties. In terms of muscle health, accumulating evidence suggests that Urolithin A may promote muscle protein synthesis and muscle growth through various pathways, offering promise in mitigating muscle atrophy. Moreover, Urolithin A exhibits the potential to enhance muscle health and performance by improving mitochondrial function and regulating autophagy. Nonetheless, further comprehensive investigations are still warranted to elucidate the underlying mechanisms of Urolithin A and to assess its feasibility and safety in human subjects, thereby advancing its potential applications in the realms of muscle health and performance.

Atractylenolide-III alleviates osteoarthritis and chondrocyte senescence by targeting NF-κB signaling

Atractylenolide-III (AT-III) is well known as its role in antioxidant and anti-inflammatory. Present study was aimed to figure out its effects on osteoarthritis and potential mechanisms. Rat model, human osteoarthritis cartilage explants as well as rat/human chondrocyte cultures were prepared to test AT-III's effects on osteoarthritis progression and chondrocyte senescence. Potential targeted molecules of AT-III were predicted using network pharmacology and molecular docking, assessed by Western blotting and then verified with rescue experiments. AT-III treatment alleviated osteoarthritis severity (shown by OARSI grading score and micro-CT) and chondrocyte senescence (indexed by levels of SA-β-gal, P16, P53, MMP13, ROS and ratio of healthy/collapsed mitochondrial membrane potentials). Network pharmacology and molecular docking suggested that AT-III might play role through NF-κB pathway. Further experiments revealed that AT-III reduced phosphorylation of IKKα/β, IκBα and P65 in NF-κB pathway. As well as nuclear translocation of p65. Both in vivo and in vitro experiments indicated that AT-III's effects on osteoarthritis and anti-senescence were reversed by an NF-κB agonist. AT-III could alleviate osteoarthritis by inhibiting chondrocyte senescence through NF-κB pathway, which indicated that AT-III is a prospective drug for osteoarthritis treatment.

Oxidative stress as a key modulator of cell fate decision in osteoarthritis and osteoporosis: a narrative review

During aging and after traumatic injuries, cartilage and bone cells are exposed to various pathophysiologic mediators, including reactive oxygen species (ROS), damage-associated molecular patterns, and proinflammatory cytokines. This detrimental environment triggers cellular stress and subsequent dysfunction, which not only contributes to the development of associated diseases, that is, osteoporosis and osteoarthritis, but also impairs regenerative processes. To counter ROS-mediated stress and reduce the overall tissue damage, cells possess diverse defense mechanisms. However, cellular antioxidative capacities are limited and thus ROS accumulation can lead to aberrant cell fate decisions, which have adverse effects on cartilage and bone homeostasis. In this narrative review, we address oxidative stress as a major driver of pathophysiologic processes in cartilage and bone, including senescence, misdirected differentiation, cell death, mitochondrial dysfunction, and impaired mitophagy by illustrating the consequences on tissue homeostasis and regeneration. Moreover, we elaborate cellular defense mechanisms, with a particular focus on oxidative stress response and mitophagy, and briefly discuss respective therapeutic strategies to improve cell and tissue protection.

Mitophagy disorder mediates cardiac deterioration induced by severe hypoglycemia in diabetic mice

Severe hypoglycemia is closely related to adverse cardiovascular outcomes in patients with diabetes; however, the specific mechanism remains unclear. We previously found that severe hypoglycemia aggravated myocardial injury and cardiac dysfunction in diabetic mice, and that the mechanism of damage was related to mitochondrial oxidative stress and dysfunction. Based on the key regulatory role of mitophagy in mitochondrial quality control, this study aimed to further explore whether the myocardial damage caused by severe hypoglycemia is related to insufficient mitophagy and to clarify their underlying regulatory relationship. After severe hypoglycemia, mitochondrial reactive oxygen species increased, mitochondrial membrane potential and ATP content decreased, and pathological mitochondrial damage was aggravated in the myocardium of diabetic mice. This was accompanied by decreased mitochondrial biosynthesis, increased fusion, and downregulated PTEN-induced kinase 1 (PINK1)/Parkin-dependent mitophagy. Treating diabetic mice with the mitophagy activator and polyphenol metabolite urolithin A activated PINK1/Parkin-dependent mitophagy, reduced myocardial oxidative stress and mitochondrial damage associated with severe hypoglycemia, improved mitochondrial function, alleviated myocardial damage, and ultimately improved cardiac function. Thus, we provide insight into the prevention and treatment of diabetic myocardial injury caused by hypoglycemia to reduce adverse cardiovascular outcomes in patients with diabetes.

Gut microbiota and intervertebral disc degeneration: a bidirectional two-sample Mendelian randomization study

BACKGROUND

Although previous studies have suggested a close association between gut microbiota (GM) and intervertebral disc degeneration (IVDD), the causal relationship between them remains unclear. Hence, we thoroughly investigate their causal relationship by means of a two-sample Mendelian randomization (MR) study, aiming to determine the impact of gut microbiota on the risk of developing intervertebral disc degeneration.

METHODS

Summary data from genome-wide association studies of GM (the MiBioGen) and IVDD (the FinnGen biobank) have been acquired. The inverse variance weighted (IVW) method was utilized as the primary MR analysis approach. Weighted median, MR-Egger regression, weighted mode, and simple mode were used as supplements. The Mendelian randomization pleiotropy residual sum and outlier (MR-PRESSO) and MR-Egger regression were performed to assess horizontal pleiotropy. Cochran's Q test evaluated heterogeneity. Leave-one-out sensitivity analysis was further conducted to determine the reliability of the causal relationship. A reverse MR analysis was conducted to assess potential reverse causation.

RESULTS

We identified nine gut microbial taxa that were causally associated with IVDD (P < 0.05). Following the Benjamini-Hochberg corrected test, the association between the phylum Bacteroidetes and a higher risk of IVDD remained significant (IVW FDR-corrected P = 0.0365). The results of the Cochrane Q test did not indicate heterogeneity (P > 0.05). Additionally, both the MR-Egger intercept test and the MR-PRESSO global test revealed that our results were not influenced by horizontal pleiotropy (P > 0.05). Furthermore, the leave-one-out analysis substantiated the reliability of the causal relationship. In the reverse analysis, no evidence was found to suggest that IVDD has an impact on the gut microbiota.

CONCLUSION

Our results validate the potential causal impact of particular GM taxa on IVDD, thus providing fresh insights into the gut microbiota-mediated mechanism of IVDD and laying the groundwork for further research into targeted preventive measures.

Current aspects of small extracellular vesicles in pain process and relief

Small extracellular vesicles (sEVs) have been identified as a noteworthy paracrine mechanism of intercellular communication in diagnosing and managing neurological disorders. Current research suggests that sEVs play a pivotal role in the pathological progression of pain, emphasizing their critical function in the pathological progression of pain in acute and chronic pain models. By facilitating the transfer of diverse molecules, such as proteins, nucleic acids, and metabolites, sEVs can modulate pain signaling transmission in both the central and peripheral nervous systems. Furthermore, the unique molecules conveyed by sEVs in pain disorders indicate their potential as diagnostic biomarkers. The application of sEVs derived from mesenchymal stem cells (MSCs) in regenerative pain medicine has emerged as a promising strategy for pain management. Moreover, modified sEVs have garnered considerable attention in the investigation of pathological processes and therapeutic interventions. This review presents a comprehensive overview of the current knowledge regarding the involvement of sEVs in pain pathogenesis and treatment. Nevertheless, additional research is imperative to facilitate their clinical implementation. Schematic diagram of sEVs in the biogenesis, signal transmission, diagnosis, and treatment of pain disorders. Small extracellular vesicles (sEVs) are secreted by multiple cells, loading with various biomolecules, such as miRNAs, transmembrane proteins, and amino acids. They selectively target other cells and regulating pain signal transmission. The composition of sEVs can serve as valuable biomarkers for pain diagnosis. In particular, mesenchymal stem cell-derived sEVs have shown promise as regenerative medicine for managing multiple pain disorders. Furthermore, by modifying the structure or contents of sEVs, they could potentially be used as a potent analgesic method.

SkQ1 Improves Immune Status and Normalizes Activity of NADPH-Generating and Antioxidant Enzymes in Rats with Adjuvant-Induced Rheumatoid Arthritis

Rheumatoid arthritis (RA) is a severe systemic autoimmune inflammatory disease. Oxidative stress and excessive formation of reactive oxygen species (ROS) by the mitochondria are considered as the central pathogenetic mechanisms of connective tissue destruction and factors responsible for a highly active inflammatory process and autoimmune response. The aim of this work was to evaluate the effect of mitochondria-targeted antioxidant 10-(6'-plastoquinonyl)decyltriphenylphosphonium (SkQ1) on the immune status, intensity of free radical-induced oxidation, and functioning of the antioxidant system (AOS) and NADPH-generating enzymes in rats with the adjuvant-induced RA. Laboratory animals were divided into 4 groups: control group; animals with RA; animals injected intraperitoneally with SkQ1 at the doses of 1250 and 625 nmol/kg, respectively, every 24 h for 8 days starting from day 7 of RA development. Tissue samples for analysis were collected on day 15 of the experiment. Erythrocyte sedimentation rate, the content of circulating immune complexes, and the concentration of class A, M, and G immunoglobulins were determined by enzyme immunoassay. The intensity of free radical-induced oxidation was evaluated based on the assessment of the iron-induced biochemiluminescence, diene conjugate content, and activity of aconitate hydratase. Enzymatic activity and metabolite content in the tissue samples were analyzed spectrophotometrically. It was shown that the development of RA was associated with an increase in the manifestation of immune response markers and intensity of free radical-induced oxidation, as well as with disruption of the AOS functioning and activation of NADPH-generating enzymes. SkQ1 administration resulted in a dose-dependent changes in the oxidative status indicators towards the control values and normalization of the immune status parameters. SkQ1 decreased the level of mitochondrial ROS, resulting in the suppression of the inflammatory response, which might cause inhibition of free radical generation by immunocompetent cells and subsequent mitigation of the oxidative stress severity in the tissues.

Urolithin A as a Potential Agent for Prevention of Age-Related Disease: A Scoping Review

The aging of an organism is hallmarked by systemic loss of functional tissue, resulting in increased fragility and eventual development of age-related neurodegenerative, musculoskeletal, cardiovascular, and neoplastic diseases. Growing scientific evidence points to mitochondrial dysfunction as a key contributor in the aging process and subsequent development of age-related pathologies. Under normal physiologic conditions, the body removes dysfunctional mitochondria via an autophagic process known as mitophagy. Urolithin A (UA), a metabolite produced when gut microflora digests the polyphenol compounds ellagitannin and ellagic acid, is a known inducer of mitophagy via several identified mechanisms of action. The primary objective of this scoping review is to identify and summarize the clinical relevance of UA supplementation in the prevention of age-related pathology and diseases. A computer-assisted literature review was performed using PubMed and EMBASE for primary source research articles examining UA supplementation and aging-related pathologies. A total of 293 articles were initially identified from a database search, and 15 articles remained for inclusion in this review, based on predetermined criteria. Analysis of the 15 identified publications demonstrated that UA holds potential as a dietary intervention for slowing the progression of aging and preventing the development of age-related disease. This review also illustrates the potential role that mitochondrial health and inflammation play in the progression of age-related pathology. Identifying the clinical relevance of UA supplementation in the prevention of age-related pathology and diseases will help further the focus of research on treatments that may improve the longevity and quality of life in patients at risk for these comorbidities.

Silibinin alleviates ferroptosis of rat islet β cell INS-1 induced by the treatment with palmitic acid and high glucose through enhancing PINK1/parkin-mediated mitophagy

Type 2 diabetes (T2DM) is induced by the abundance of glucose and lipids, which causes glucolipotoxicity to the pancreatic β-cells. Silibinin is a natural flavonoid possessing the regulatory activity on insulin production and therapeutic activity in diabetic mice; however, its effect on glucolipotoxicity is not fully explained. This in vitro study investigates the effects of silibinin on palmitic acid (PA) and high glucose (HG)-induced cell loss and ferroptosis of rat insulinoma INS-1 cells. In the cells treated with PA and HG, expressions of glucose transporter 4 (Glut4) and carnitine acyltransferase I (CPT1) for β-oxidation of fatty acids are reduced. Mitochondria are the metabolic organelles for glucose and fatty acids. The mitochondrial membrane potential (MMP) and ATP production were decreased, while the ROS level was elevated in the cells treated with PA and HG, indicating an induction of mitochondrial disorder. Cell loss was partially rescued by ferroptosis inhibition, suggesting an involvement of ferroptosis in the cells treated with PA and HG. More importantly, the increases in total iron, lipid ROS, MDA and COX-2, and the decrease in ferroptosis inhibitory molecules GSH, GPX4 and FSP1 appeared in the cells treated with PA and HG, confirming the occurrence of ferroptosis. Moreover, PINK1/parkin-mediated mitophagy, a vital process for selective elimination of damaged mitochondria, was blocked. Interestingly, silibinin rescued the mitochondria, restricted the ferroptosis and restored the mitophagy. By using the pharmacological stimulator and inhibitor of mitophagy, and si-RNA transfection to silence PINK1 expression, silibinin's protective effect against ferroptosis caused by PA and HG treatment was found to depend on mitophagy. Collectively, our current study reveals the new mechanisms for the protection of silibinin against the injury of INS-1 cells treated with PA and HG, elucidates the participation of ferroptosis in glucolipotoxicity, highlighting the involvement of mitophagy in defense against ferroptotic cell death.

Mitochondrion: A bridge linking aging and degenerative diseases

Aging is a natural process, characterized by progressive loss of physiological integrity, impaired function, and increased vulnerability to death. For centuries, people have been trying hard to understand the process of aging and find effective ways to delay it. However, limited breakthroughs have been made in anti-aging area. Since the hallmarks of aging were summarized in 2013, increasing studies focus on the role of mitochondrial dysfunction in aging and aging-related degenerative diseases, such as neurodegenerative diseases, osteoarthritis, metabolic diseases, and cardiovascular diseases. Accumulating evidence indicates that restoring mitochondrial function and biogenesis exerts beneficial effects in extending lifespan and promoting healthy aging. In this paper, we provide an overview of mitochondrial changes during aging and summarize the advanced studies in mitochondrial therapies for the treatment of degenerative diseases. Current challenges and future perspectives are proposed to provide novel and promising directions for future research.

Cellular rejuvenation: molecular mechanisms and potential therapeutic interventions for diseases

The ageing process is a systemic decline from cellular dysfunction to organ degeneration, with more predisposition to deteriorated disorders. Rejuvenation refers to giving aged cells or organisms more youthful characteristics through various techniques, such as cellular reprogramming and epigenetic regulation. The great leaps in cellular rejuvenation prove that ageing is not a one-way street, and many rejuvenative interventions have emerged to delay and even reverse the ageing process. Defining the mechanism by which roadblocks and signaling inputs influence complex ageing programs is essential for understanding and developing rejuvenative strategies. Here, we discuss the intrinsic and extrinsic factors that counteract cell rejuvenation, and the targeted cells and core mechanisms involved in this process. Then, we critically summarize the latest advances in state-of-art strategies of cellular rejuvenation. Various rejuvenation methods also provide insights for treating specific ageing-related diseases, including cellular reprogramming, the removal of senescence cells (SCs) and suppression of senescence-associated secretory phenotype (SASP), metabolic manipulation, stem cells-associated therapy, dietary restriction, immune rejuvenation and heterochronic transplantation, etc. The potential applications of rejuvenation therapy also extend to cancer treatment. Finally, we analyze in detail the therapeutic opportunities and challenges of rejuvenation technology. Deciphering rejuvenation interventions will provide further insights into anti-ageing and ageing-related disease treatment in clinical settings.

The physiological metabolite α-ketoglutarate ameliorates osteoarthritis by regulating mitophagy and oxidative stress

Osteoarthritis (OA) is an age-related metabolic disease. Low-grade inflammation and oxidative stress are the last common pathway of OA. α-ketoglutarate (α-KG) is an essential physiological metabolite from the mitochondrial tricarboxylic acid (TCA) cycle, with multiple functions, including anti-inflammation and antioxidation, and exhibits decreased serum levels with age. Herein, we aimed to investigate the effect and mechanism of α-KG on OA. We first quantified the α-KG levels in human cartilage tissue and osteoarthritic chondrocytes induced by IL-1β. Besides, IL-1β-induced osteoarthritic chondrocytes were treated with different concentrations of α-KG. Chondrocyte proliferation and apoptosis, synthesis and degradation of extracellular matrix, and inflammation mediators were analyzed. RNA sequencing was used to explore the mechanism of α-KG, and mitophagy and oxidative stress levels were further detected. These results were verified in an anterior cruciate ligament transection (ACLT) induced age-related OA rat model. We found that α-KG content decreased by 31.32% in damaged medial cartilage than in normal lateral cartilage and by 36.85% in IL-1β-induced human osteoarthritic chondrocytes compared to control. α-KG supplementation reversed IL-1β-induced chondrocyte proliferation inhibition and apoptosis, increased the transcriptomic and proteinic expression of ACAN and COL2A1 in vivo and in vitro, but inhibited the expression of MMP13, ADAMTS5, IL-6, and TNF-α. In mechanism, α-KG promoted mitophagy and inhibited ROS generation, and these effects could be prevented by Mdivi-1 (a mitophagy inhibitor). Overall, α-KG content decreased in human OA cartilage and IL-1β-induced osteoarthritic chondrocytes. Moreover, α-KG supplementation could alleviate osteoarthritic phenotype by regulating mitophagy and oxidative stress, suggesting its potential as a therapeutic target to ameliorate OA.

Role of reactive oxygen species and mitochondrial damage in rheumatoid arthritis and targeted drugs

Rheumatoid arthritis (RA) is an autoimmune disease characterized by synovial inflammation, pannus formation, and bone and cartilage damage. It has a high disability rate. The hypoxic microenvironment of RA joints can cause reactive oxygen species (ROS) accumulation and mitochondrial damage, which not only affect the metabolic processes of immune cells and pathological changes in fibroblastic synovial cells but also upregulate the expression of several inflammatory pathways, ultimately promoting inflammation. Additionally, ROS and mitochondrial damage are involved in angiogenesis and bone destruction, thereby accelerating RA progression. In this review, we highlighted the effects of ROS accumulation and mitochondrial damage on inflammatory response, angiogenesis, bone and cartilage damage in RA. Additionally, we summarized therapies that target ROS or mitochondria to relieve RA symptoms and discuss the gaps in research and existing controversies, hoping to provide new ideas for research in this area and insights for targeted drug development in RA.

An update on animal models of intervertebral disc degeneration and low back pain: Exploring the potential of artificial intelligence to improve research analysis and development of prospective therapeutics

Animal models have been invaluable in the identification of molecular events occurring in and contributing to intervertebral disc (IVD) degeneration and important therapeutic targets have been identified. Some outstanding animal models (murine, ovine, chondrodystrophoid canine) have been identified with their own strengths and weaknesses. The llama/alpaca, horse and kangaroo have emerged as new large species for IVD studies, and only time will tell if they will surpass the utility of existing models. The complexity of IVD degeneration poses difficulties in the selection of the most appropriate molecular target of many potential candidates, to focus on in the formulation of strategies to effect disc repair and regeneration. It may well be that many therapeutic objectives should be targeted simultaneously to effect a favorable outcome in human IVD degeneration. Use of animal models in isolation will not allow resolution of this complex issue and a paradigm shift and adoption of new methodologies is required to provide the next step forward in the determination of an effective repairative strategy for the IVD. AI has improved the accuracy and assessment of spinal imaging supporting clinical diagnostics and research efforts to better understand IVD degeneration and its treatment. Implementation of AI in the evaluation of histology data has improved the usefulness of a popular murine IVD model and could also be used in an ovine histopathological grading scheme that has been used to quantify degenerative IVD changes and stem cell mediated regeneration. These models are also attractive candidates for the evaluation of novel anti-oxidant compounds that counter inflammatory conditions in degenerate IVDs and promote IVD regeneration. Some of these compounds also have pain-relieving properties. AI has facilitated development of facial recognition pain assessment in animal IVD models offering the possibility of correlating the potential pain alleviating properties of some of these compounds with IVD regeneration.

Urolithin A alleviates neuropathic pain and activates mitophagy

Neuropathic pain (NP) occurs frequently in the general population and has a negative impact on the quality of life. There is no effective therapy available yet owing to the complex pathophysiology of NP. In our previous study, we found that urolithin A (UA), a naturally occurring microflora-derived metabolite, could relieve NP in mice by inhibiting the activation of microglia and release of inflammation factors. Here in this study, we sought to investigate whether mitophagy would be activated when UA alleviated NP in mice. We showed that the autophagy flow was blocked in the spinal dorsal horn of the chronic constriction injury (CCI) mice when the most obvious pain behavior occurs. Intraperitoneal injection of UA markedly activated the mitophagy mediated by PTEN-induced kinase 1/Parkin, promoted mitobiogenesis in both neurons and microglia, and alleviated NP in the CCI mice. In summary, our data suggest that UA alleviates NP in mice and meanwhile induces mitophagy activation, which highlights a therapeutic potential of UA in the treatment of NP.