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

Deficiency of FUN14 domain-containing 1 enhances the migration and invasion of fibroblast-like synoviocytes in rheumatoid arthritis through mitochondrial dysregulation

BACKGROUND

Fibroblast-like synoviocytes (FLS) display aggressive phenotypes contributing to synovitis and joint destruction in rheumatoid arthritis (RA). Disrupted mitochondrial homeostasis has been proposed to aggravate the RA pathogenesis, however, the underlying mechanism remains to be elucidated. This study aimed to elucidate the role of mitophagy receptor FUN14 domain-containing 1 (FUNDC1) on RA-FLS migration and invasion.

METHODS

We analyzed the correlation of synovial FUNDC1 expression with joint destruction and disease activity in RA patients. Single cell sequencing data analysis combined with immunofluorescence indicated the specific expression and localization of FUNDC1 in synovial tissue and RA-FLS. The roles of FUNDC1 in the migration, invasion, and cytokine secretion of RA-FLS were examined by patient-derived primary culture as well as SCID mouse models. We investigated the effects and mechanism of FUNDC1 on mitophagy and mitochondrial quality control network in primary RA-FLS.

RESULTS

We found that the FUNDC1 was mainly expressed in FLS and exhibited a decreased level in RA synovium, which was correlated with severe joint destruction. Deficiency of FUNDC1 enhanced migration, invasion as well as secretion of matrix metalloproteinases in RA-FLS. On the contrary, overexpression of FUNDC1 in RA-FLS with low FUNDC1 inhibited the migration, invasion and secretion capacity of RA-FLS. Mechanistically, repressed FUNDC1 level in RA-FLS impaired mitophagy, imbalanced mitochondrial quality control, and increased mitochondrial reactive oxygen species (mtROS) production, leading to the overactivation of the MAPK pathway. Treatment with mtROS scavenger mtTEMPO can reverse this process and diminish the invasiveness of RA-FLS.

CONCLUSIONS

Deficiency of FUNDC1 dysregulates mitochondrial quality-control system and induces aggressive phenotype of RA-FLS, resulting in joint destruction during RA progression.

Chuanxiong-Danggui herb pair alleviated cognitive deficits of APP/PS1 mice by promoting mitophagy

ETHNOPHARMACOLOGICAL RELEVANCE

Disruption of receptor-mediated mitophagy contributes to neuronal damage in Alzheimer's disease (AD). Chuanxiong-Danggui herb pair (CDHP) is classic herbal pair applied to treating neurodegenerative diseases including AD, Amyotrophic Lateral Sclerosis, Parkinson's disease. Though studies have demonstrated the neuroprotective effects of CDHP, the underlying mechanisms by which CDHP attenuates neuronal impairment of AD remains to be elucidated.

AIM OF THE STUDY

The objective of this work was to investigate the anti-AD mechanism of CDHP in APP/PS1 mice.

MATERIALS AND METHODS

Behavioral assessments were conducted on C57BL/6J and APP/PS1 mice following CDHP treatment, alongside an evaluation of neuronal morphology in the hippocampal region. In vitro, HT-22 cells were induced by Aβ25-35 before being treated with CDHP. The mechanisms of CDHP were investigated using transmission electron microscopy, Golgi staining, immunofluorescence, and Western blot analysis.

RESULTS

Results from the passive avoidance test and the Morris water maze (MWM) indicated that CDHP significantly mitigated cognitive deficits of APP/PS1 mice, accompanied by a reduction of pathological damage in the CA1 and CA3 regions of hippocampus. Further testing found that a significant reduction in dendritic spines density was rescued by CDHP. Synaptophysin (SYN) and postsynaptic density protein 95 (PSD-95) were elevated in the CDHP group, while β-amyloid (Aβ) plaques deposition was significantly reduced. Simultaneously, CDHP markedly inhibited neuronal apoptosis through a decrease of the levels of Cleaved Caspase-12 and enhanced expression of Bcl-2/Bax, both in vivo and in vitro. Additionally, CDHP improved mitochondrial morphology and function in the AD model by decreasing abnormal mitochondria and increasing the expression of COXIV. Transmission electron microscopy (TEM) revealed that clear mitophagy-autophagosomes were nearly absent in APP/PS1 mice, while the expression of p62 and LC3B were elevated following CDHP treatment. Furthermore, CDHP increased the expression of the FUNDC1 and PGAM5 in APP/PS1 mice and AD-like cell models.

CONCLUSION

These findings suggest that CDHP mitigated cognitive dysfunction in APP/PS1 mice by enhancing mitophagy to reduce neuronal injury.

Chondrocyte Mitochondrial Quality Control: A Novel Insight into Osteoarthritis and Cartilage Regeneration

Significance: Osteoarthritis (OA), one of the most prevalent joint diseases affecting more than 240 million people, strongly influences human health and reduces life quality. This review aims to fill the current research gap regarding the application and potential of mitochondrial quality control (MQC) based therapies in the treatment of OA, thereby providing guidance for future research and clinical practice. Recent Advances: Chondrocytes respond to the inflammatory microenvironment via an array of signaling pathways and thus are critical in cartilage degeneration and OA progression. Mitochondria, as an important metabolic center in chondrocytes, play a vital role in responding to inflammatory stimuli. Multiple MQC mechanisms, including mitochondrial antioxidant defense, mitochondrial protein quality control, mitochondrial DNA repair, mitochondrial dynamics, mitophagy, and mitochondrial biogenesis, sustain mitochondrial homeostasis under pathological conditions. Critical Issues: Despite extensive OA research, effective therapies remain limited. Elucidating MQC mechanisms in disease progression and post-traumatic cartilage repair is crucial. While preclinical studies demonstrate potential, clinical translation requires addressing protocol standardization, patient stratification, and long-term efficacy, as well as safety validation. Future Directions: Future research should focus on developing personalized MQC-based OA therapies guided by biomarker profiling and signaling pathway modulation. However, translational challenges persist, particularly regarding pervasive off-target effects, inadequate OA-specific targeting capacity, interpatient heterogeneity, and reliable evaluation of long-term therapeutic efficacy. Strategic prioritization of OA-specific MQC targets coupled with delivery system optimization may significantly improve both clinical translatability and therapeutic outcomes.

Anti-arthritis Effect of Anti-chitinase-3-like 1 Antibody Through Inhibition of MMP3

Chitinase-3-like 1 (CHI3L1) is a key factor in regulating inflammatory processes and development of rheumatoid arthritis (RA) since is highly produced by synoviocytes and macrophages in the development RA. Collagen-induced arthritis (CIA) model is the most widely used because its pathogenesis is similar to human RA. Thus, we aimed to investigate if anti-CHI3L1 antibody could reduce RA development in the CIA model. To induce CIA, DBA1/J mice were immunized with a type II bovine collagen emulsion in complete Freund's adjuvant, and boosted type II bovine collagen. THP-1 and MH7A cells were used for pro-inflammation responses. Anti-CHI3L1 Ab treatment reduced the RA clinical score and paw thickness of mice. Inflammation-induced matrix metalloproteinase 3 (MMP3) expression was reduced by inhibiting CHI3L1, and MMP3 knockdown suppressed the expression of RA-related inflammatory cytokines in LPS-treated THP-1 and MH7A cells. Our findings suggest that anti-CHI3L1 Ab showed significant anti-arthritic effects by inhibiting MMP3 expression.

SIRT3-PINK1-PKM2 axis prevents osteoarthritis via mitochondrial renewal and metabolic switch

Maintaining mitochondrial homeostasis is critical for preserving chondrocyte physiological conditions and increasing resistance against osteoarthritis (OA). However, the underlying mechanisms governing mitochondrial self-renewal and energy production remain elusive. In this study, we demonstrated mitochondrial damage and aberrant mitophagy in OA chondrocytes. Genetically overexpressing PTEN-induced putative kinase 1 (PINK1) protects against cartilage degeneration by removing defective mitochondria. PINK1 knockout aggravated cartilage damage due to impaired mitophagy. SIRT3 directly deacetylated PINK1 to promote mitophagy and cartilage anabolism. Specifically, PINK1 phosphorylated PKM2 at the Ser127 site, preserving its active tetrameric form. This inhibited nuclear translocation and the interaction with β-catenin, resulting in a metabolic shift and increased energy production. Finally, a double-knockout mouse model demonstrated the role of the SIRT3-PINK1-PKM2 axis in safeguarding the structural integrity of articular joints and improving motor functions. Overall, this study provides a novel insight into the regulation of mitochondrial renewal and metabolic switches in OA.

JP4-039 protects chondrocytes from ferroptosis to attenuate osteoarthritis progression by promoting Pink1/Parkin-dependent mitophagy

Background

Osteoarthritis (OA) is the most common degenerative joint disease, and its main pathological mechanism is articular cartilage degeneration. The purpose of this study was to investigate the role of mitophagy in the pathogenesis of chondrocyte ferroptosis in OA.

Methods

The expressions of ferroptosis related proteins (GPX4, FTH1, COX2) and ubiquitin-dependent mitophagy related proteins (PARKIN, PINK1) in the intact and injured areas of OA cartilage were analyzed. Nitro oxide JP4-039, a mitochondrial targeting antioxidant, has bifunctional role of targeting mitochondria. Then we evaluated the potential protective effect of JP4-039 in OA using the destabilization of medial meniscus (DMM)-induced OA model, as well as tert-butyl hydrogen peroxide (TBHP)-treated primary mouse chondrocytes and human cartilage explants.

Results

The concentrations of iron and lipid peroxidation and the expression of ferroptosis drivers in the damaged areas of human OA cartilages were significantly higher than those in the intact cartilage. Pink1/Parkin-dependent mitophagy decreased in the injured area of human OA cartilage and was negatively correlated with ferroptosis. Then, the toxicity and effectiveness of JP4-039 are tested to determine its working concentration. Next, at the molecular biological level, we found that JP4-039 showed the effect of anti-chondrocyte ferroptosis. Moreover, it was verified on DMM-induced OA model mice, that JP4-039 could delay the progression of OA. Finally, JP4-039 was re-verified in vivo and in vitro to inhibit chondrocyte ferroptosis and delay the progression of OA by promoting Pink1/Parkin-dependent mitophagy.

Conclusion

JP4-039 inhibits ferroptosis of chondrocytes by promoting Pink1/Parkin-dependent mitophagy and delays OA progression.

m7G-modified mt-tRF3b-LeuTAA regulates mitophagy and metabolic reprogramming via SUMOylation of SIRT3 in chondrocytes

N7-methylguanosine (m7G) modification is one of the most prevalent RNA modifications, and methyltransferase-like protein-1 (METTL1) is a key component of the m7G methyltransferase complex. METTL1-catalyzed m7G as a new RNA modification pathway that regulates RNA structure, biogenesis, and cell migration. Increasing evidence indicates that m7G modification has been implicated in the pathophysiological process of osteoarthritis (OA). However, the underlying molecular mechanisms of m7G modification remains incompletely elucidated during the progression of OA. Here we found that METTL1 and m7G levels were markedly increased in OA chondrocytes. In addition, METTL1-mediated m7G modification upregulated mt-tRF3b-LeuTAA expression to exacerbate chondrocyte degeneration. Mechanistically, mt-tRF3b-LeuTAA decreased the SUMO-specific protease 1 (SENP1) protein expression and upregulated the level of sirtuin 3 (SIRT3) SUMOylation to inhibit PTEN induced kinase 1 (PINK1)/Parkin-mediated mitochondrial mitophagy. Intra-articular injection of PMC-tRF3b-LeuTAA inhibitor (Polyamidoamine-polyethylene glycol surface-modified with Minimal self-peptides and Chondrocyte-affinity peptides, PMC) attenuated destabilization of the medial meniscus (DMM) mouse cartilage degeneration in vivo. Our study demonstrates that METTL1/m7G/mt-tRF3b-LeuTAA axis accelerate cartilage degradation by inhibiting mitophagy and promoting mitochondrial dysfunction through SIRT3 SUMOylation, and suggest that targeting METTL1 and its downstream signaling axis could be a promising therapeutic target for OA treatment.

Role of mitophagy in intervertebral disc degeneration: A narrative review

OBJECTIVE

The pivotal role of mitophagy in the initiation and progression of intervertebral disc (IVD) degeneration (IDD) has become increasingly apparent due to a growing body of research on its pathogenesis. This review summarizes the role of mitophagy in IDD and the therapeutic potential of targeting this process.

DESIGN

This narrative review is divided into three parts: the regulatory mechanisms of mitophagy, the role of mitophagy in IDD, and the applications and prospects of mitophagy for the treatment of IDD.

RESULTS

Mitophagy protects cells against harmful external stimuli and plays a crucial protective role by promoting extracellular matrix (ECM) production, inhibiting ECM degradation, and reducing apoptosis, senescence, and cartilage endplate calcification. However, excessive mitophagy is often detrimental to cells. Currently, the regulatory mechanisms governing appropriate and excessive mitophagy remain unclear.

CONCLUSIONS

Proper mitophagy effectively maintains IVD cell homeostasis and slows the progression of IDD. Conversely, excessive mitophagy may accelerate IDD development. Further research is needed to elucidate the regulatory mechanisms underlying appropriate and excessive mitophagy, which could provide new theoretical support for the application of mitophagy targeting to the treatment of IDD.

Mitochondria in skeletal system-related diseases

Skeletal system-related diseases, such as osteoporosis, arthritis, osteosarcoma and sarcopenia, are becoming major public health concerns. These diseases are characterized by insidious progression, which seriously threatens patients' health and quality of life. Early diagnosis and prevention in high-risk populations can effectively prevent the deterioration of these patients. Mitochondria are essential organelles for maintaining the physiological activity of the skeletal system. Mitochondrial functions include contributing to the energy supply, modulating the Ca2+ concentration, maintaining redox balance and resisting the inflammatory response. They participate in the regulation of cellular behaviors and the responses of osteoblasts, osteoclasts, chondrocytes and myocytes to external stimuli. In this review, we describe the pathogenesis of skeletal system diseases, focusing on mitochondrial function. In addition to osteosarcoma, a characteristic of which is active mitochondrial metabolism, mitochondrial damage occurs during the development of other diseases. Impairment of mitochondria leads to an imbalance in osteogenesis and osteoclastogenesis in osteoporosis, cartilage degeneration and inflammatory infiltration in arthritis, and muscle atrophy and excitationcontraction coupling blockade in sarcopenia. Overactive mitochondrial metabolism promotes the proliferation and migration of osteosarcoma cells. The copy number of mitochondrial DNA and mitochondria-derived peptides can be potential biomarkers for the diagnosis of these disorders. High-risk factor detection combined with mitochondrial component detection contributes to the early detection of these diseases. Targeted mitochondrial intervention is an effective method for treating these patients. We analyzed skeletal system-related diseases from the perspective of mitochondria and provided new insights for their diagnosis, prevention and treatment by demonstrating the relationship between mitochondria and the skeletal system.

Mitophagy in Cell Death Regulation: Insights into Mechanisms and Disease Implications

Mitophagy, a selective form of autophagy, plays a crucial role in maintaining optimal mitochondrial populations, normal function, and intracellular homeostasis by monitoring and removing damaged or excess mitochondria. Furthermore, mitophagy promotes mitochondrial degradation via the lysosomal pathway, and not only eliminates damaged mitochondria but also regulates programmed cell death-associated genes, thus preventing cell death. The interaction between mitophagy and various forms of cell death has recently gained increasing attention in relation to the pathogenesis of clinical diseases, such as cancers and osteoarthritis, neurodegenerative, cardiovascular, and renal diseases. However, despite the abundant literature on this subject, there is a lack of understanding regarding the interaction between mitophagy and cell death. In this review, we discuss the main pathways of mitophagy, those related to cell death mechanisms (including apoptosis, ferroptosis, and pyroptosis), and the relationship between mitophagy and cell death uncovered in recent years. Our study offers potential directions for therapeutic intervention and disease diagnosis, and contributes to understanding the molecular mechanism of mitophagy.

Exploring the Mechanism of Ferroptosis Induction by Sappanone A in Cancer: Insights into the Mitochondrial Dysfunction Mediated by NRF2/xCT/GPX4 Axis

Non-small cell lung cancer (NSCLC), a major subtype of lung cancer, encompasses squamous cell carcinoma, adenocarcinoma, and large cell carcinoma. Compared to small cell lung cancer, NSCLC cells grow and divide more slowly, and their metastasis occurs at a later stage. Currently, chemotherapy is the primary treatment for this disease. Sappanone A (SA) is a flavonoid compound extracted from the plant Caesalpinia sappan, known for its antitumor, redox-regulating, and anti-inflammatory properties. Recent studies have investigated the interaction of SA with mitochondrial pathways in regulating cell death through the Nrf-2/GPX-4/xCT axis. This study specifically explores the mechanism by which SA affects mitochondrial morphology and structure through the regulation of mitophagy and mitochondrial biogenesis in tumor cells. The study primarily utilizes second-generation transcriptomic sequencing data and molecular docking techniques to elucidate the role of SA in regulating programmed cell death in tumor cells. The omics results indicate that SA treatment significantly targets genes involved in oxidative phosphorylation, mitophagy, mitochondrial dynamics, and oxidative stress. Further findings confirmed that the Nrf-2/GPX4/xCT pathway serves as a crucial target of SA in the treatment of NSCLC. Knockdown of Nrf-2 (si-Nrf-2) and Nrf-2 overexpression (ad-Nrf-2) were shown to modulate the therapeutic efficacy of SA to varying degrees. Additionally, modifications to the GPX4/xCT genes significantly affected the regulatory effects of SA on mitochondrial autophagy, biogenesis, and energy metabolism. These regulatory mechanisms may be mediated through the caspase pathway and ferroptosis-related signaling. Molecular biology experiments have demonstrated that SA intervention further inhibits the phosphorylation of FUNDC1 at Tyr18 and downregulates TOM20 expression. SA treatment was found to reduce the expression of PGC1α, Nrf-1, and Tfam, resulting in a decrease in mitochondrial respiration and energy metabolism. Overexpression of Nrf-2 was shown to counteract the regulatory effects of SA on mitophagy and mitochondrial biogenesis. Confocal microscopy experiments further revealed that SA treatment increases mitochondrial fragmentation, subsequently inducing mitochondrial pathway-mediated programmed cell death. However, genetic modification of the Nrf-2/GPX4/xCT pathway significantly altered the regulatory effects of SA on tumor cells. In conclusion, SA has been identified as a promising therapeutic agent for NSCLC. The mitochondrial pathway-mediated apoptosis and ferroptosis may represent key mechanisms in regulating tumor cell death. Targeting the Nrf-2/GPX-4/xCT axis offers a novel therapeutic approach for maintaining mitochondrial homeostasis within the cellular microenvironment.

Machine learning algorithm-based biomarker exploration and validation of mitochondria-related diagnostic genes in osteoarthritis

The role of mitochondria in the pathogenesis of osteoarthritis (OA) is significant. In this study, we aimed to identify diagnostic signature genes associated with OA from a set of mitochondria-related genes (MRGs). First, the gene expression profiles of OA cartilage GSE114007 and GSE57218 were obtained from the Gene Expression Omnibus. And the limma method was used to detect differentially expressed genes (DEGs). Second, the biological functions of the DEGs in OA were investigated using Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis. Wayne plots were employed to visualize the differentially expressed mitochondrial genes (MDEGs) in OA. Subsequently, the LASSO and SVM-RFE algorithms were employed to elucidate potential OA signature genes within the set of MDEGs. As a result, GRPEL and MTFP1 were identified as signature genes. Notably, GRPEL1 exhibited low expression levels in OA samples from both experimental and test group datasets, demonstrating high diagnostic efficacy. Furthermore, RT-qPCR analysis confirmed the reduced expression of Grpel1 in an in vitro OA model. Lastly, ssGSEA analysis revealed alterations in the infiltration abundance of several immune cells in OA cartilage tissue, which exhibited correlation with GRPEL1 expression. Altogether, this study has revealed that GRPEL1 functions as a novel and significant diagnostic indicator for OA by employing two machine learning methodologies. Furthermore, these findings provide fresh perspectives on potential targeted therapeutic interventions in the future.

Network pharmacology combined with experimental validation to investigate the effect of Rongjin Niantong Fang on chondrocyte apoptosis in knee osteoarthritis

Knee osteoarthritis (KOA) is a chronic degenerative disease that affects the quality of life of middle‑aged and elderly individuals, and is one of the major factors leading to disability. Rongjin Niantong Fang (RJNTF) can alleviate the clinical symptoms of patients with KOA, but the molecular mechanism underlying its beneficial effects on KOA remains unknown. Using pharmacological analysis and in vitro experiments, the active components of RJNTF were analyzed to explore their potential therapeutic targets and mechanisms in KOA. The potential targets and core signaling pathways by which RJNTF exerts its effects on KOA were obtained from databases such as Gene Expression Omnibus, Traditional Chinese Medicine Systems Pharmacology and Analysis Platform. Subsequently, chondrocyte apoptosis was modeled using hydrogen peroxide (H2O2). Cell Counting Kit‑8 assay involving a poly [ADP‑ribose] polymerase‑1 (PARP1) inhibitor, DAPI staining, reverse transcription‑quantitative PCR, Annexin V‑FITC/PI staining and flow cytometry, western blotting and co‑immunoprecipitation analysis were used to determine the therapeutic efficacy of RJNTF on KOA and to uncover the molecular mechanism. It was found that PARP1‑knockdown lentivirus, incubation with PARP1 inhibitor PJ34, medium and high doses of RJNTF significantly reduced H2O2‑induced chondrocyte apoptosis. Medium and high doses of RJNTF downregulated the expression of cleaved caspase‑3, cleaved PARP1 and PAR total proteins, as well as nucleus proteins of apoptosis‑inducing factor (AIF) and migration inhibitory factor (MIF), and upregulated the expression of caspase‑3, PARP1 total protein, as well as the cytoplasmic expression of AIF and MIF, suggesting that RJNTF may inhibit chondrocyte apoptosis through the PARP1/AIF signaling pathway.

WITHDRAWN: The dysregulated autophagy in osteoarthritis: Revisiting molecular profile

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