Spermidine rescues the deregulated autophagic response to oxidative stress of osteoarthritic chondrocytes

Potential role of gut-related factors in the pathology of cartilage in osteoarthritis

Osteoarthritis (OA) is a common progressive degenerative disease. Gut microbiota (GM) and their metabolites have been closely associated with the onset, progression, and pathology of OA. GM and their metabolites may influence the cartilage directly, or indirectly by affecting the gut, the immune system, and the endocrine system. They function through classical pathways in cartilage metabolism and novel pathways that have recently been discovered. Some of them have been used as targets for the prevention and treatment of OA. The current study sought to describe the major pathological signaling pathways in OA chondrocytes and the potential role of gut-related factors in these pathways.

IKKα affects the susceptibility of primary human osteoarthritis chondrocytes to oxidative stress-induced DNA damage by tuning autophagy

The functional derangement affecting human chondrocytes during osteoarthritis (OA) onset and progression is sustained by the failure of major homeostatic mechanisms. This makes them more susceptible to oxidative stress (OS), which can induce DNA damage responses and exacerbate stress-induced senescence. The knockdown (KD) of IκB kinase α (IKKα), a dispensable protein in healthy articular cartilage physiology, was shown to increase the survival and replication potential of human primary OA chondrocytes. Our recent findings showed that the DNA Mismatch Repair pathway only partially accounts for the reduced susceptibility to OS of IKKαKD cells. Here we therefore investigated other ROS-mediated DNA damage and repair mechanisms. We exposed IKKαWT and IKKαKD chondrocytes to sub-cytotoxic hydrogen peroxide and evaluated the occurrence of double-strand breaks (DSB), 8-oxo-2'-deoxyguanosine (8-oxo-dG) and telomere shortening. ROS exposure was able to significantly increase the number of γH2AX foci (directly related to the number of DSB) in both cell types, but IKKα deficient cells undergoing cell division were able to better recover compared to their IKKα proficient counterpart. 8-oxo-dG signal proved to be the highest DNA damage signal among those investigated, located in the mitochondria and with a slightly higher intensity in IKKα proficient cells immediately after OS exposure. Furthermore, ROS significantly reduced telomere length both in IKKαWT and IKKαKD, with the former showing more pervasive effects, especially in dividing cells. Assessment of the HIF-1α>Beclin-1>LC3B axis after recovery from OS showed that IKKα deficient cells exhibited a more efficient autophagic machinery that allowed them to better cope with oxidative stress, possibly through the turnover of damaged mitochondria. Higher Beclin-1 levels likely helped in rescuing dividing cells (identified by coupled cell cycle analysis) because of Beclin-1's involvement in both autophagy and mitotic spindle organization. Therefore, our data further confirm the higher capacity of IKKαKD chondrocytes to cope with oxidative stress-induced DNA damage.

The role of ferroptosis in osteoarthritis: Progress and prospects

Osteoarthritis (OA) is the most prevalent degenerative joint disease, marked by cartilage degeneration, synovitis, and subchondral bone changes. The absence of effective drugs and treatments to decelerate OA's progression highlights a significant gap in clinical practice. Ferroptosis, an iron-dependent cell death driven by lipid peroxidation, has emerged as a research focus in osteoarthritic chondrocytes. This form of cell death is characterized by imbalances in iron and increased lipid peroxidation within osteoarthritic chondrocytes. Key antioxidant mechanisms, such as Glutathione Peroxidase 4 (GPX4) and the Nuclear Factor Erythroid 2-Related Factor 2 (NRF2) pathway, are vital in countering ferroptosis in osteoarthritic chondrocytes. This review collates recent findings on ferroptosis in osteoarthritic chondrocytes, emphasizing iron regulation, lipid peroxidation, and antioxidative responses. It also explores emerging therapeutics aimed at mitigating OA by targeting ferroptosis in chondrocytes.

Alpha-ketoglutarate ameliorates age-related and surgery induced temporomandibular joint osteoarthritis via regulating IKK/NF-κB signaling

Recent studies have shed light on the important role of aging in the pathogenesis of joint degenerative diseases and the anti-aging effect of alpha-ketoglutarate (αKG). However, whether αKG has any effect on temporomandibular joint osteoarthritis (TMJOA) is unknown. Here, we demonstrate that αKG administration improves condylar cartilage health of middle-aged/aged mice, and ameliorates pathological changes in a rat model of partial discectomy (PDE) induced TMJOA. In vitro, αKG reverses IL-1β-induced/H2O2-induced decrease of chondrogenic markers (Col2, Acan and Sox9), and inhibited IL-1β-induced/ H2O2-induced elevation of cartilage catabolic markers (ADAMTS5 and MMP13) in condylar chondrocytes. In addition, αKG downregulates senescence-associated (SA) hallmarks of aged chondrocytes, including the mRNA/protein level of SA genes (p16 and p53), markers of nuclear disorders (Lamin A/C) and SA-β-gal activities. Mechanically, αKG decreases the expressions of p-IKK and p-NF-κB, protecting TMJ from inflammation and senescence-related damage by regulating the NF-κB signaling. Collectively, our findings illuminate that αKG can ameliorate age-related TMJOA and PDE-induced TMJOA, maintain the homeostasis of cartilage matrix, and exert anti-aging effects in chondrocytes, with a promising therapeutic potential in TMJOA, especially age-related TMJOA.

Spermidine attenuates chondrocyte inflammation and cellular pyroptosis through the AhR/NF-κB axis and the NLRP3/caspase-1/GSDMD pathway

Introduction

Osteoarthritis (OA) is a prevalent chronic degenerative disease, marked by a complex interplay of mechanical stress, inflammation, and metabolic imbalances. Recent studies have highlighted the potential of spermidine (SPD), a naturally occurring polyamine known for its anti-inflammatory and antioxidant properties, as a promising therapeutic agent for OA. This study delves into the therapeutic efficacy and mechanistic pathways of SPD in mitigating OA symptoms.

Methods

Forty Sprague-Dawley rats were randomly assigned to four groups, including the CG (sham operation), model (anterior cruciate ligament transection [ACLT], and treatment (ACLT + two different doses of SPD) groups. In vivo, correlations between OA severity and different interventions were assessed by ELISA, X-rays, CT imaging, histological staining, and immunohistochemistry. In vitro, IL-1β was used to trigger chondrocyte inflammation, and SPD's cytotoxicity was assessed in primary rat chondrocytes. Next, inflammatory markers, extracellular matrix (ECM) proteins, and pathway marker proteins were detected in chondrocytes administered IL-1β alone, SPD, or aryl hydrocarbon receptor (AhR) silencing, by qRT-PCR, Griess reaction, ELISA, Western blot, and immunofluorescence. Morphological alterations and pyroptosis in chondrocytes were examined by transmission electron microscopy (TEM) and flow cytometry.

Results

Our research reveals that SPD exerts significant anti-inflammatory and antipyroptotic effects on IL-1β-treated chondrocytes and in anterior cruciate ligament transection (ACLT) rat models of OA, primarily through interaction with the Aryl hydrocarbon receptor (AhR). Specifically, SPD's binding to AhR plays a crucial role in modulating the inflammatory response and cellular pyroptosis by inhibiting both the AhR/NF-κB and NLRP3/caspase-1/GSDMD signaling pathways. Furthermore, the knockdown of AhR was found to negate the beneficial effects of SPD, underscoring the centrality of the AhR pathway in SPD's action mechanism. Additionally, SPD was observed to promote the preservation of cartilage integrity and suppress ECM degradation, further supporting its potential as an effective intervention for OA.

Discussion

Collectively, our findings propose SPD as a novel therapeutic approach for OA treatment, targeting the AhR pathway to counteract the disease's progression and highlighting the need for further clinical evaluation to fully establish its therapeutic utility.

Spermidine protects cartilage from IL-1β-mediated ferroptosis

Rheumatoid arthritis is characterized by a burst of inflammation, the destruction of cartilage and the abundant release of inflammatory factors such as IL-1β. Thus, the effect of IL-1β on cartilage was examined in this study. IL-1β could cause lipid peroxidation and disturbances in iron metabolism by increasing the expression of NCOA4 and decreasing the expression of FTH, which also induced ferritinophagy. In addition, the expression of the key antioxidant proteins SLC7A11 and GPX4 was inhibited by IL-1β, resulting in ferroptosis in chondrocytes. Spermidine (SPD), a low-molecular-weight aliphatic nitrogen-containing compound that widely exists in animals, has been reported to be an antioxidant. In our study, we found that SPD could inhibit ferritinophagy and reverse the decrease in the expression of SLC7A11 and GPX4. Therefore, we uncovered one of the molecular mechanisms of cartilage destruction and inflammation and provide a potential polyamine for the treatment of RA.

Natural Autophagy Activators to Fight Age-Related Diseases

The constant increase in the elderly population presents significant challenges in addressing new social, economic, and health problems concerning this population. With respect to health, aging is a primary risk factor for age-related diseases, which are driven by interconnected molecular hallmarks that influence the development of these diseases. One of the main mechanisms that has attracted more attention to aging is autophagy, a catabolic process that removes and recycles damaged or dysfunctional cell components to preserve cell viability. The autophagy process can be induced or deregulated in response to a wide range of internal or external stimuli, such as starvation, oxidative stress, hypoxia, damaged organelles, infectious pathogens, and aging. Natural compounds that promote the stimulation of autophagy regulatory pathways, such as mTOR, FoxO1/3, AMPK, and Sirt1, lead to increased levels of essential proteins such as Beclin-1 and LC3, as well as a decrease in p62. These changes indicate the activation of autophagic flux, which is known to be decreased in cardiovascular diseases, neurodegeneration, and cataracts. The regulated administration of natural compounds offers an adjuvant therapeutic alternative in age-related diseases; however, more experimental evidence is needed to support and confirm these health benefits. Hence, this review aims to highlight the potential benefits of natural compounds in regulating autophagy pathways as an alternative approach to combating age-related diseases.

Spermidine as an epigenetic regulator of autophagy in neurodegenerative disorders

Autophagy is an abnormal protein degradation and recycling process that is impaired in various neurological diseases like Alzheimer's disease (AD), Parkinson's disease (PD), and Huntington's disease. Spermidine is a natural polyamine found in various plant- and meat-based diets that can induce autophagy, and is decreased in various neurodegenerative diseases. It acts on epigenetic enzymes like E1A-binding protein p300, HAT enzymes like Iki3p and Sas3p, and α-tubulin acetyltransferase 1 that modulate autophagy. Histone modifications like acetylation, phosphorylation, and methylation could influence autophagy. Autophagy is epigenetically regulated in various neurodegenerative disorders with many epigenetic enzymes and miRNAs. Polyamine regulation plays an essential role in the disease pathogenesis of AD and PD. Therefore, in this review, we discuss various enzymes and miRNAs involved in the epigenetic regulation of autophagy in neurodegenerative disorders and the role of spermidine as an autophagy enhancer. The alterations in spermidine-mediated regulation of Beclin-1, LC3-II, and p62 genes in AD and other PD-associated enzymes could impact the process of autophagy in these neurodegenerative diseases. With the ever-growing data and such promising effects of spermidine in autophagy, we feel it could be a promising target in this area and worth further detailed studies.

Non-coding RNAs as regulators of autophagy in chondrocytes: Mechanisms and implications for osteoarthritis

Osteoarthritis (OA) is a chronic degenerative joint disease with multiple causative factors such as aging, mechanical injury, and obesity. Autophagy is a complex dynamic process that is involved in the degradation and modification of intracellular proteins and organelles under different pathophysiological conditions. Autophagy, as a cell survival mechanism under various stress conditions, plays a key role in regulating chondrocyte life cycle metabolism and cellular homeostasis. Non-coding RNAs (ncRNAs) are heterogeneous transcripts that do not possess protein-coding functions, but they can act as effective post-transcriptional and epigenetic regulators of gene and protein expression, thus participating in numerous fundamental biological processes. Increasing evidence suggests that ncRNAs, autophagy, and their crosstalk play crucial roles in OA pathogenesis. Therefore, we summarized the complex role of autophagy in OA chondrocytes and focused on the regulatory role of ncRNAs in OA-associated autophagy to elucidate the complex pathological mechanisms of the ncRNA-autophagy network in the development of OA, thus providing new research targets for the clinical diagnosis and treatment of OA.

Gubi decoction mitigates knee osteoarthritis via promoting chondrocyte autophagy through METTL3-mediated ATG7 m6A methylation

Knee osteoarthritis (KOA) is a chronic joint disease that significantly affects the health of the elderly. As an herbal remedy, Gubi decoction (GBD) has been traditionally used for the treatment of osteoarthritis-related syndromes. However, the anti-KOA efficacy and mechanism of GBD remain unclear. This study aimed to experimentally investigate the anti-KOA efficacy and the underlying mechanism of GBD. The medial meniscus (DMM) mice model and IL-1β-stimulated chondrocytes were, respectively, constructed as in vivo and in vitro models of KOA to evaluate the osteoprotective effect and molecular mechanism of GBD. The UPLC-MS/MS analysis showed that GBD mainly contained pinoresinol diglucoside, rehmannioside D, hesperidin, liquiritin, baohuoside I, glycyrrhizic acid, kaempferol and tangeretin. Animal experiment showed that GBD could alleviate articular cartilage destruction and recover histopathological alterations in DMM mice. In addition, GBD inhibited chondrocyte apoptosis and restored DMM-induced dysregulated autophagy evidenced by the upregulation of ATG7 and LC3 II/LC3 I but decreased P62 level. Mechanistically, METTL3-mediated m6A modification decreased the expression of ATG7 in DMM mice, as it could be significantly attenuated by GBD. METTL3 overexpression significantly counteracted the protective effect of GBD on chondrocyte autophagy. Further research showed that GBD promoted proteasome-mediated ubiquitination degradation of METLL3. Our findings suggest that GBD could act as a protective agent against KOA. The protective effect of GBD may result from its promotion on chondrocyte autophagy by suppressing METTL3-dependent ATG7 m6A methylation.

Attenuating intervertebral disc degeneration through spermidine-delivery nanoplatform based on polydopamine for persistent regulation of oxidative stress

As one of the most widespread musculoskeletal diseases worldwide, intervertebral disc degeneration (IVDD) remains an intractable clinical problem. Currently, oxidative stress has been widely considered as a significant risk factor in the IVDD pathological changes, and targeting oxidative stress injury to improve the harsh microenvironment may provide a novel and promising strategy for disc repair. It is evident that spermidine (SPD) has the ability to attenuate oxidative stress across several disease models. However, limited research exists regarding its impact on oxidative stress within the intervertebral disc. Moreover, enhancing the local utilization rate of SPD holds great significance in IVDD management. This study aimed to develop an intelligent biodegradable mesoporous polydopamine (PDA) nanoplatform for sustained release of SPD. The obtained PDA nanoparticles with spherical morphology and mesoporous structure released loaded-therapeutic molecules under low pH and H2O2. Combined treatment with SPD loaded into PDA nanoparticles (SPD/PDA) resulted in better therapeutic potential than those with SPD alone on oxidative stress injury. Furthermore, both SPD and SPD/PDA could induce anti-inflammatory M2 macrophage polarization. Upon injection into degenerative IVDs, the SPD/PDA group achieved a good repair efficacy with a long-term therapeutic effect. These findings indicated that the synergized use of SPD with responsive drug delivery nanocarriers may steadily scavenge reactive oxygen species and provide an effective approach toward the treatment of IVDD.

Spermidine ameliorates osteoarthritis via altering macrophage polarization

OBJECTIVE

Spermidine (SPD) is an anti-aging natural substance, and it exerts effects through anti-apoptosis and anti-inflammation. However, the specific protective mechanism of SPD in osteoarthritis (OA) remains unclear. Here, we explored the role of SPD on the articular cartilage and the synovial tissue, and tested whether the drug would regulate the polarization of synovial macrophages by in vivo and in vitro experiments.

METHODS

By constructing an OA model in mice, we preliminarily explored the protective effect of SPD on the articular cartilage and the synovial tissue. Meanwhile, we isolated and cultured human primary chondrocytes and bone marrow-derived macrophages (BMDMs), and prepared a conditioned medium (CM) to explore the specific protective effect of SPD in vitro.

RESULTS

We found that SPD alleviated cartilage degeneration and synovitis, increased M2 polarization and decreased M1 polarization in synovial macrophages. In vitro experiments, SPD inhibited ERK MAPK and p65/NF-κB signaling in macrophages, and transformed macrophages from M1 to M2 subtypes. Interestingly, SPD had no direct protective effect on chondrocytes in vitro; however, the conditioned medium (CM) from M1 macrophages treated with SPD promoted the anabolism and inhibited the catabolism of chondrocytes. Moreover, this CM markedly suppressed IL-1β-induced p38/JNK MAPK signaling pathway activation in chondrocytes.

CONCLUSIONS

This work provides new perspectives on the role of SPD in OA. SPD does not directly target chondrocytes, but can ameliorate the degradation of articular cartilage through regulating M1/M2 polarization of synovial macrophages. Hence, SPD is expected to be the potential therapy for OA.

The Molecular Role of Polyamines in Age-Related Diseases: An Update

Polyamines (Pas) are short molecules that exhibit two or three amine groups that are positively charged at a physiological pH. These small molecules are present in high concentrations in a wide variety of organisms and tissues, suggesting that they play an important role in cellular physiology. Polyamines include spermine, spermidine, and putrescine, which play important roles in age-related diseases that have not been completely elucidated. Aging is a natural process, defined as the time-related deterioration of the physiological functions; it is considered a risk factor for degenerative diseases such as cardiovascular, neurodegenerative, and musculoskeletal diseases; arthritis; and even cancer. In this review, we provide a new perspective on the participation of Pas in the cellular and molecular processes related to age-related diseases, focusing our attention on important degenerative diseases such as Alzheimerߣs disease, Parkinsonߣs disease, osteoarthritis, sarcopenia, and osteoporosis. This new perspective leads us to propose that Pas function as novel biomarkers for age-related diseases, with the main purpose of achieving new molecular alternatives for healthier aging.

Spermidine suppresses oxidative stress and ferroptosis by Nrf2/HO-1/GPX4 and Akt/FHC/ACSL4 pathway to alleviate ovarian damage

AIMS

Oxidative stress is considered to be one of the culprits of ovarian dysfunction. Spermidine (SPD) is a natural aliphatic polyamine that is widely present in living organisms and has been shown to exert preventive effects on various ageing-related diseases. This study seeks to investigate the potential preventive and protective effects of SPD on ovarian oxidative damage.

MAIN METHODS

Ovarian oxidative stress model in C57BL/6 mice was established by 3-nitropropionic acid. Female mice were administrated 10 mg/kg or 15 mg/kg SPD. The estrous cycle, serum hormone levels and mating test were measured to evaluate ovarian function. Follicle counts and AMH levels to assess ovarian reserve. Masson's trichrome to assess ovarian fibrosis. TUNEL analysis to evaluate follicular granulosa cells (GCs) apoptosis. Oxidative stress and autophagy indicators (Nrf2, HO-1, GPX4, LC3B, P62) were measured in vivo and in vitro. RNA-sequencing was performed on SPD-treated GC to study the effects of SPD on Akt and FHC/ACSL4 signaling.

KEY FINDINGS

SPD supplementation improved ovarian endocrine function and reproductive capacity in oxidative stress mice. SPD regularized the estrous cycle and alleviated oxidative stress. Furthermore, SPD increased the ovarian reserve, reducing GC apoptosis by activating the Nrf2/HO-1/GPX4 pathway. RNA-sequencing showed that SPD induced 230 genes changes in porcine GC, which were mainly involved in oocyte meiosis, arginine biosynthesis and glutathione metabolism pathways. SPD attenuated H2O2-induced ferroptosis by regulating Akt/FHC/ACSL4 signaling.

SIGNIFICANCE

SPD alleviates oxidative stress and ferroptosis by regulating the Nrf2/HO-1/GPX4 and Akt/FHC/ACSL4 pathway, which may be a novel potential strategy to protect ovarian oxidative damage.

Human Osteoblasts' Response to Biomaterials for Subchondral Bone Regeneration in Standard and Aggressive Environments

Osteochondral lesions, when not properly treated, may evolve into osteoarthritis (OA), especially in the elderly population, where altered joint function and quality are usual. To date, a collagen/collagen-magnesium-hydroxyapatite (Col/Col-Mg-HAp) scaffold (OC) has demonstrated good clinical results, although suboptimal subchondral bone regeneration still limits its efficacy. This study was aimed at evaluating the in vitro osteogenic potential of this scaffold, functionalized with two different strategies: the addition of Bone Morphogenetic Protein-2 (BMP-2) and the incorporation of strontium (Sr)-ion-enriched amorphous calcium phosphate (Sr-ACP) granules. Human osteoblasts were seeded on the functionalized scaffolds (OC+BMP-2 and OC+Sr-ACP, compared to OC) under stress conditions reproduced with the addition of H2O2 to the culture system, as well as in normal conditions, and evaluated in terms of morphology, metabolic activity, gene expression, and matrix synthesis. The OC+BMP-2 scaffold supported a better osteoblast morphology and stimulated scaffold colonization, cell activity, and extracellular matrix secretion, especially in the stressed culture environment but also in normal culture conditions, with increased expression of genes related to osteoblast differentiation. In conclusion, the incorporation of BMP-2 into the Col/Col-Mg-HAp scaffold also represents an improvement of the osteochondral scaffold in more challenging conditions, supporting further preclinical studies to optimize it for use in clinical practice.

BRG1 mediates protective ability of spermidine to ameliorate osteoarthritic cartilage by Nrf2/KEAP1 and STAT3 signaling pathway

BACKGROUND

Spermidine (SPD) is a natural polyamine that shows beneficial effects on osteoarthritis (OA). However, the effect of SPD on cartilage inflammation remains unknown. This study aimed to investigate the potential mechanisms underlying the protective effect of SPD against OA-induced articular cartilage degradation.

METHOD

SW1353 human chondrocytes were treated with hydrogen peroxide and lipopolysaccharide to induce models of inflammation and oxidative stress, followed by different dose of SPD intervention. Moreover, mice that underwent anterior cruciate ligament transection were bred and treated with SPD. The effects of SPD were observed using a CCK-8 kit, real-time polymerase chain reaction, immunoblotting, and immunofluorescent assays.

RESULT

SPD significantly increased the expression of antioxidant proteins, chondrogenic genes, and inflammatory factors both in vivo and in vitro. And injury of the mouse cartilage was also reduced by SPD. Moreover, SPD activated the Nrf2/KEAP1 pathway and inhibited STAT3 phosphorylation. BRG1 expression was decreased in osteoarthritic mouse cartilage, whereas SPD treatment caused an upregulation. However, when BRG1 was specifically inhibited by an adeno-associated virus and small interfering RNA, the antioxidant and anti-inflammatory effects of SPD were significantly diminished both in vitro and in vivo.

CONCLUSION

We found that SPD ameliorated cartilage damage in OA by activating the BRG1-mediated Nrf2/KEAP1 pathway. SPD and BRG1 may provide new therapeutic options or targets for the treatment of OA.

Spermidine alleviating oxidative stress and apoptosis by inducing autophagy of granulosa cells in Sichuan white geese

Spermidine have been reported a role in antioxidative, antiaging, and antiinflammatory. Oxidative stress causes granulosa cell (GC) apoptosis, follicular atresia, and impairs poultry reproductive functions. Studies have found that autophagy is the protective mechanism against antioxidant stress and apoptosis in cells. However, the relationship between spermidine-induced autophagy, oxidative stress, and apoptosis in goose GCs remains unclear. In this study, we investigated the autophagy mechanism to mediate spermidine effects on the alleviation of oxidative stress and apoptosis in goose GCs. Follicular GCs were treated with spermidine combination with 3-Nitropropanoic acid (3-NPA), rapamycin (RAPA), and chloroquine (CQ) or with hydrogen peroxide, RAPA, and CQ. Spermidine upregulated the ratio of LC3-II/I, inhibited the accumulation of p62 protein, and induced autophagy. 3-NPA treatment significantly increased ROS production, MDA content, SOD activity, cleaved CASPASE-3 protein expression, and decreased BCL-2 protein expression in follicular GCs. Spermidine inhibited oxidative stress and apoptosis induced by 3-NPA. In addition, hydrogen peroxide-induced oxidative stress was inhibited by spermidine. However, the inhibitory effect of spermidine was eliminated under chloroquine. Our results demonstrated that spermidine relieved oxidative stress and apoptosis of GCs by inducing autophagy, indicating that spermidine has a great potential to maintain proteostasis and sustain granulosa cell viability in geese.

PPARγ activation suppresses chondrocyte ferroptosis through mitophagy in osteoarthritis

BACKGROUND

Osteoarthritis (OA) is a prevalent disease plaguing the elderly. Recently, chondrocyte ferroptosis has been demonstrated to promote the progression of OA. Peroxisome proliferator-activated receptor-γ (PPARγ) is an important factor in maintaining cartilage health. However, the relationship between PPARγ and chondrocyte ferroptosis in OA and its mechanism is completely unclear.

METHODS

We established a surgically induced knee OA rat model to investigate PPARγ and chondrocyte ferroptosis in OA. Rat knee specimens were collected for Safranin O/Fast Green staining and immunohistochemical staining after administered orally placebo or pioglitazone (PPARγ agonist) for 4 weeks. We used RSL3 to establish a chondrocyte ferroptosis model cultured in vitro to study the role of PPARγ activation toward ferroptosis, mitochondrial function, and PTEN-induced putative kinase 1 (Pink1)/Parkin-dependent mitophagy. GW9662 (PPARγ antagonist), Mdivi-1 (mitophagy inhibitor), and chloroquine (mitophagy inhibitor) were employed to investigate the mechanism of PPARγ-Pink1/Parkin-dependent mitophagy in the inhibition of ferroptosis.

RESULTS

We found that PPARγ activation by pioglitazone attenuated not only OA but also inhibited the expression of the ferroptosis marker acyl-CoA synthetase long-chain family member 4 (ACSL4) at the same time in rats. Furthermore, in vivo and in vitro data indicated that PPARγ activation restored Pink1/Parkin-dependent mitophagy, improved mitochondrial function, inhibited chondrocyte ferroptosis, and delayed the progression of OA.

CONCLUSIONS

The present study demonstrated that PPARγ activation attenuates OA by inhibiting chondrocyte ferroptosis, and this chondroprotective effect was achieved by promoting the Pink1/Parkin-dependent mitophagy pathway.

Cardamonin alleviates chondrocytes inflammation and cartilage degradation of osteoarthritis by inhibiting ferroptosis via p53 pathway

Osteoarthritis (OA) is a common degenerative joint disease, mainly presented by the deterioration of articular cartilage. Amounts of data demonstrated this deterioration is composed of oxidative stress, pro-inflammation and chondrocyte death events. Ferroptosis is a novel form of cell death that differs from apoptosis and autophagy, recent studies have shown that chondrocyte ferroptosis contributes to the development of osteoarthritis. Cardamonin (CAD) has been demonstrated to possess antioxidant and anti-inflammatory properties in several diseases, whether CAD may influence the OA progression is still obscure. Therefore, we aimed to determine whether CAD alleviates chondrocyte ferroptosis and its effect on OA with potential mechanism. In this study, we found that inflammation, cartilage degradation and ferroptosis induced by interleukin-1β (IL-1β) were significantly alleviated by CAD. Moreover, the administration of the ferroptosis inhibitor, Deferoxamine (DFO) reversed the inflammatory and cartilage degradation effects of IL-1β as well. Chondrocyte mitochondrial morphology and function were alleviated by both CAD and DFO. We found that CAD increased collagen II, p53, SLC7A11 GPX4 expression and decreased MMP13, iNOS, COX2 expression in chondrocytes, further investigation showed that the P53 signaling pathway was involved. In vivo, intra-articular injection of CAD significantly ameliorated cartilage damage in a rat OA model, induced collagen II and SLC7A11 expression by immunohistochemistry. Our study proves that CAD ameliorated OA cartilage degradation by regulating ferroptosis via P53 signaling pathway, suggesting a potential role of CAD in OA treatment.

Daurisoline attenuates H2O2-induced chondrocyte autophagy by activating the PI3K/Akt/mTOR signaling pathway

BACKGROUND

Osteoarthritis (OA) is a chronic degenerative joint disease characterized by cartilage degeneration and intra-articular inflammation. Daurisoline (DAS) is an isoquinoline alkaloid isolated from Rhizoma Menispermi, whose antitumor and anti-inflammatory pharmacological effects have been demonstrated, but the effects of DAS on OA have rarely been researched. In this study, we aimed to explore the potential role of DAS in OA and its partial mechanism.

MATERIALS AND METHODS

The cytotoxicity of H₂O₂ and DAS toward chondrocytes was detected by the Cell Counting Kit-8 assay. Safranin O staining was used to detect chondrocyte phenotype changes. Cell apoptosis was measured by both flow cytometry and quantitative analysis of the protein levels of the apoptosis-related factors Bax, Bcl-2 and cleaved caspase-3 by western blot. Western blotting and immunofluorescence were used to assess the expression of the autophagy-related proteins LC3, Beclin-1 and p62. In addition, key signal pathway targets and matrix-degrading indicators were measured by western blot.

RESULTS

Our results indicated that H₂O₂ induced human chondrocyte apoptosis and activated autophagy in a dose-dependent manner. DAS treatment dose-dependently reversed the expression of apoptosis-related proteins (Bax, Bcl-2 and cleaved caspase3) and the apoptosis rate induced by H₂O₂. Western blot and immunofluorescence analyses showed that DAS decreased the H₂O₂-induced upregulation of the autophagy marker Beclin-1 and the LC3 II/LC3 I ratio and upregulated the p62 protein level. Mechanistically, DAS inhibited autophagy through the activation of the classical PI3K/AKT/mTOR signaling pathway and protected chondrocytes from apoptosis. In addition, DAS alleviated the H₂O₂-induced degradation of type II collagen and the high expression of matrix metalloproteinase 3 (MMP3) and MMP13.

CONCLUSION

Our research demonstrated that DAS alleviated chondrocyte autophagy caused by H₂O₂ through activation of the PI3K/AKT/mTOR signaling pathway and protected chondrocytes from apoptosis and matrix degradation. In conclusion, these findings suggest that DAS may serve as a promising therapeutic strategy for OA.

NOTCH1: A Novel Player in the Molecular Crosstalk Underlying Articular Chondrocyte Protection by Oleuropein and Hydroxytyrosol

Osteoarthritis (OA) is the most common joint disease, but no effective and safe disease-modifying treatment is available. Risk factors such as age, sex, genetics, injuries and obesity can concur to the onset of the disease, variably triggering the loss of maturational arrest of chondrocytes further sustained by oxidative stress, inflammation and catabolism. Different types of nutraceuticals have been studied for their anti-oxidative and anti-inflammatory properties. Olive-derived polyphenols draw particular interest due to their ability to dampen the activation of pivotal signaling pathways in OA. Our study aims to investigate the effects of oleuropein (OE) and hydroxytyrosol (HT) in in vitro OA models and elucidate their possible effects on NOTCH1, a novel therapeutic target for OA. Chondrocytes were cultured and exposed to lipopolysaccharide (LPS). Detailed analysis was carried out about the OE/HT mitigating effects on the release of ROS (DCHF-DA), the increased gene expression of catabolic and inflammatory markers (real time RT-PCR), the release of MMP-13 (ELISA and Western blot) and the activation of underlying signaling pathways (Western blot). Our findings show that HT/OE efficiently attenuates LPS-induced effects by firstly reducing the activation of JNK and of the NOTCH1 pathway downstream. In conclusion, our study provides molecular bases supporting the dietary supplementation of olive-derived polyphenols to revert/delay the progression of OA.

Isorhynchophylline alleviates cartilage degeneration in osteoarthritis by activating autophagy of chondrocytes

CONTEXT

Osteoarthritis is a common degenerative disease, the cause of it is still unknown, and the treatment mainly focuses on improving symptoms. Studies have found that Isorhynchophylline (Isorhy) has antioxidant, anti-inflammatory, antiproliferative and neuroprotective effects.

OBJECTIVE

This study investigates the role and mechanism of Isorhy in OA.

METHODS

The destabilized medial meniscus model was used to mimic OA. Fifteen male Sprague Dawley rats were partitioned into three portions: Normal group, OA group (surgery; normal saline treatment) and OA + Isorhy group (surgery; 50 μM Isorhy treatment) were performed on the first day of every week from the 5th to the 8th week after surgery. After 4 weeks of drug treatment, the rats have been processed without debridement of the knee specimens and fixed using 4% paraformaldehyde for two days. The morphological analysis was performed by H&E, Safranin O-Fast green staining and micro-CT analysis. The specimens were researched employing Micro-CT. In the part of the aggregate methods that were evaluated by qRT-PCR and western blot of the following proteins LC3II/LC3I, Beclin-1, ATG5, ATG7, MMP3 andMMP13. Akt/PI3K signaling related proteins (p-AKT, AKT, p-PI3K, PI3K, p-mTOR, mTOR) were detected by Western blot. BECLIN1 and MMP3 were detected by Immunofluorescence assay.

RESULTS

In this present research, it was proved that autophagy-related and cartilage matrix-related proteins in osteoarthritis could be regulated by Isorhynchophylline treatment. The transcriptome sequencing results suggested the regulation was closely associated with PI3K/AKT/mTOR pathway, thereby alleviating osteoarticular inflammation. In-depth study showed that Isorhy could also affect OA in rat OA models, that was indicated by H&E, Safranin O-Fast green staining, and also micro-CT analysis.

CONCLUSION

Our findings indicated that Isorhy could be regarded as a prospective candidate for OA treatment.

Tannic acid antagonizes atrazine exposure-induced autophagy and DNA damage crosstalk in grass carp hepatocytes via NO/iNOS/NF-κB signaling pathway to maintain stable immune function

Atrazine (ATR) is a herbicide widely used in grass crops. The pollution of the soil and water environment is extremely harmful to aquatic animals and their offspring. iNOS/NO upregulation, DNA damage and cellular autophagy affect the immune function of fish liver cells. The effects of ATR at exposure doses on grass carp hepatocytes in terms of autophagy and DNA damage effects in genotoxicity, as well as the antagonistic effects of TAN on the above phenotypes and the internal mechanisms are not known. Therefore, we constructed control (Con group), ATR exposure (ATR group), TAN exposure (TAN group) and mixed group (ATR + TAN group) models on grass carp hepatocytes. Validation was performed by comet assay, MDC staining, qRT-PCR and protein blotting assay as well as iNOS/NO indicator levels and expression of immune factors as these experimental methods. Our data indicate that iNOS/NO assay kit measured that ATR treatment resulted in a significant increase in iNOS/NO activity and levels in grass carp hepatocytes (p < 0.05). We also found that NO/iNOS/NF-κB pathway genes were significantly activated (p < 0.05) at the exposure dose of ATR (3 μg mL-1). In addition, the proportion of cells that died due to DNA damage, autophagy, and immunotoxic effects was significantly increased at the exposure dose of ATR. Comet assay protein blotting detected increased DNA damage in cells at the ATR exposure dose (p < 0.05). MDC staining and qRT-PCR and protein blotting to detect the proportion of autophagic cells and autophagy-related genes also appeared upregulated at the exposed dose of ATR (p < 0.05). In brief, this study showed that ATR exposure caused cellular DNA damage and autophagy via the NO/iNOS/NF-κB axis, which led to immunotoxic effects and eventual death of grass carp hepatocytes. The present study facilitates the demonstration of the molecular mechanism of TAN alleviation of ATR cytotoxicity from the perspective of NO-mediated iNOS/NF-κB axis. It provides insights into the protection of farmed fish from agricultural contaminants and opens up new horizons in the use of natural plant-derived monomers for the clinical treatment of antagonistic triazine pesticide poisoning.

Mitophagy-A New Target of Bone Disease

Bone diseases are usually caused by abnormal metabolism and death of cells in bones, including osteoblasts, osteoclasts, osteocytes, chondrocytes, and bone marrow mesenchymal stem cells. Mitochondrial dysfunction, as an important cause of abnormal cell metabolism, is widely involved in the occurrence and progression of multiple bone diseases, including osteoarthritis, intervertebral disc degeneration, osteoporosis, and osteosarcoma. As selective mitochondrial autophagy for damaged or dysfunctional mitochondria, mitophagy is closely related to mitochondrial quality control and homeostasis. Accumulating evidence suggests that mitophagy plays an important regulatory role in bone disease, indicating that regulating the level of mitophagy may be a new strategy for bone-related diseases. Therefore, by reviewing the relevant literature in recent years, this paper reviews the potential mechanism of mitophagy in bone-related diseases, including osteoarthritis, intervertebral disc degeneration, osteoporosis, and osteosarcoma, to provide a theoretical basis for the related research of mitophagy in bone diseases.

Research Progress and Potential Applications of Spermidine in Ocular Diseases

Spermidine, a natural polyamine, exists in almost all human tissues, exhibiting broad properties like anti-aging, autophagy induction, anti-inflammation, anti-oxidation, cell proliferation activation, and ion channel regulation. Considering that spermidine is already present in human nutrition, recent studies targeting supplementing exogenous sources of this polyamine appear feasible. The protective role of spermidine in various systems has been illuminated in the literature, while recent progress of spermidine administration in ocular diseases remains to be clarified. This study shows the current landscape of studies on spermidine and its potential to become a promising therapeutic agent to treat ocular diseases: glaucoma, optic nerve injury, age-related macular degeneration (AMD), cataracts, dry eye syndrome, and bacterial keratitis. It also has the potential to become a potent biomarker to predict keratoconus (KC), cataracts, uveitis, glaucoma, proliferative diabetic retinopathy (PDR), proliferative vitreoretinopathy (PVR), and retinopathy of prematurity (ROP). We also summarize the routes of administration and the effects of spermidine at different doses.

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

Osteoarthritis (OA) is the most common age‐related joint disorder with no effective therapy. According to the World Health Organization, OA affects over 500 million people and is characterized by degradation of cartilage and other joint tissues, severe pain, and impaired mobility. Mitochondrial dysfunction contributes to OA pathology. However, interventions to rescue mitochondrial defects in human OA are not available. Urolithin A (Mitopure) is a natural postbiotic compound that promotes mitophagy and mitochondrial function and beneficially impacts muscle health in preclinical models of aging and in elderly and middle‐aged humans. Here, we showed that Urolithin A improved mitophagy and mitochondrial respiration in primary chondrocytes from joints of both healthy donors and OA patients. Furthermore, Urolithin A reduced disease progression in a mouse model of OA, decreasing cartilage degeneration, synovial inflammation, and pain. These improvements were associated with increased mitophagy and mitochondrial content, in joints of OA mice. These findings indicate that UA promotes joint mitochondrial health, alleviates OA pathology, and supports Urolithin A's potential to improve mobility with beneficial effects on structural damage in joints.

CDDO-Im ameliorates osteoarthritis and inhibits chondrocyte apoptosis in mice via enhancing Nrf2-dependent autophagy

Osteoarthritis (OA) is the most prevalent chronic degenerative joint disease with few treatment options. The pathogenesis of OA is characterized by sustained inflammation, oxidative stress and chondrocyte apoptosis that eventually lead to cartilage degradation and joint dysfunction. In the present study, we identified a synthetic triterpenoid CDDO-Im(1-[2-cyano-3,12-dioxooleana-1,9(11)-dien-28-oyl] imidazole) as an activator of Nrf2 (nuclear factor erythroid 2-related factor 2) that displayed strong anti-OA effects. We showed that CDDO-Im (20 nM) significantly alleviated TNF-α-induced apoptosis of primary human chondrocytes and extracellular matrix degradation. In a mouse OA model incurred by DMM (destabilization of medial meniscus), administration of CDDO-Im (2.5 mg/kg, ip, every other day for 8 weeks) effectively reduced knee joint cartilage erosion and serum levels of inflammatory cytokines IL-1β and IL-6. We revealed that CDDO-Im (20 nM) significantly enhanced autophagy activities in chondrocytes, whereas the autophagy inhibition by chloroquine (CQ, 50 μM) or 3-methyladenine (3-MA, 5 mM) abrogated the anti-apoptosis and chondroprotective effects of CDDO-Im in TNF-α-treated chondrocytes. Moreover, we confirmed that CDDO-Im (1-20 nM) dose-dependently activated Nrf2 pathway in TNF-α-treated chondrocytes, and its chondroprotective and autophagy-enhancing effects were significantly diminished when Nrf2 signaling was blocked by Nrf2 inhibitor ML385 (20 μM) or siRNA-mediated Nrf2 knockdown. Together, our results demonstrate that CDDO-Im exhibits prominent chondroprotective and anti-OA activities owing to its Nrf2 activation and autophagy-enhancing properties, which might provide new insights into the strategies of OA clinical prevention and treatment.

Evidence for adduction of biologic amines with reactive metabolite of 8-epidiosbulbin E acetate in vitro and in vivo

Dioscorea bulbifera L. (DBL) is one of traditional Chinese medicines and has been used for the treatment of goiter, tumor and carbuncles. However, clinic application of the herbal medicine has been limited, due to reported severe hepatotoxicity. 8-Epidiosbulbin E acetate (EEA), one of the major components of DBL, can cause severe liver damage. The furan ring of EEA is metabolized by CYP3A4 to a cis-enedial reactive intermediate prone to react amino and/or thiol groups of amino acid residues. In this study, we investigated the interaction of the reactive intermediate with biologic amines. EEA-derived biologic amine adducts, including spermidine, spermine, putrescine, ornithine, lysine and glutamine were detected in cultured mouse primary hepatocytes treated with EEA. Only spermidine adduct was observed in bile of mice given EEA. The detection of the adducts was established by labeling with bromobenzyl mercaptan and LC-MS/MS analysis. Exposure of EEA resulted in concentration dependent cytotoxicity in hepatocytes. Pretreatment with spermidine attenuated the susceptibility of cells to the cytotoxicity of EEA, because of the compensation of the depleted spermidine.

Geroprotectors and Skeletal Health: Beyond the Headlines

Osteoporosis and osteoarthritis are the most common age-related diseases of the musculoskeletal system. They are responsible for high level of healthcare use and are often associated with comorbidities. Mechanisms of ageing such as senescence, inflammation and autophagy are common drivers for both diseases and molecules targeting those mechanisms (geroprotectors) have potential to prevent both diseases and their co-morbidities. However, studies to test the efficacy of geroprotectors on bone and joints are scant. The limited studies available show promising results to prevent and reverse Osteoporosis-like disease. In contrast, the effects on the development of Osteoarthritis-like disease in ageing mice has been disappointing thus far. Here we review the literature and report novel data on the effect of geroprotectors for Osteoporosis and Osteoarthritis, we challenge the notion that extension of lifespan correlates with extension of healthspan in all tissues and we highlight the need for more thorough studies to test the effects of geroprotectors on skeletal health in ageing organisms.

Identification of Hub Genes and Pathways Associated with Oxidative Stress of Cartilage in Osteonecrosis of Femoral Head Using Bioinformatics Analysis

OBJECTIVE

This study aimed to identify the hub genes and pathways of genes related to oxidative stress of cartilage in osteonecrosis of femoral head (ONFH), and to predict the transcription factors of the hub genes.

METHODS

The GSE74089 was obtained from the Gene Expression Omnibus (GEO) database, including 4 necrotic tissues and 4 normal tissues, and the differentially expressed genes (DEGs) were identified by limma package in R language. Simultaneously, we searched for the genes related to oxidative stress in the Gene Ontology (GO) database. GO and signaling pathways analysis were performed using DAVID, Metascape, and GSEA. Protein-protein interaction (PPI) network was constructed using the STRING database, and the Degree algorithm of Cytoscape software was used to screen for hub genes. Finally, the NetworkAnalyst web tool was used to find the hub genes' transcriptional factors (TFs).

RESULTS

In total, 440 oxidative stress-related genes were found in GSE74089 and GO database, and 88 of them were significantly differentially expressed. These genes were mainly involved in several signaling pathways, such as MAPK signaling pathway, PI3K-AKT-mTOR signaling pathway, FOXO signaling pathway. The top 10 hub genes were JUN, FOXO3, CASP3, JAK2, RELA, EZH2, ABL1, PTGS2, FBXW7, MCL1. Besides, TFAP2A, GATA2, SP1, and E2F1 may be the key regulatory factors of hub genes.

CONCLUSIONS

We identified some hub genes and signaling pathways associated with oxidative stress in ONFH through a series of bioinformatics analyses.

p62 works as a hub modulation in the ageing process

p62 (also known as SQSTM1) is widely used as a predictor of autophagic flux, a process that allows the degradation of harmful and unnecessary components through lysosomes to maintain protein homeostasis in cells. p62 is also a stress-induced scaffold protein that resists oxidative stress. The multiple domains in its structure allow it to be connected with a variety of vital signalling pathways, autophagy and the ubiquitin proteasome system (UPS), allowing p62 to play important roles in cell proliferation, apoptosis and survival. Recent studies have shown that p62 is also directly or indirectly involved in the ageing process. In this review, we summarize in detail the process by which p62 regulates ageing from multiple ageing-related signs with the aim of providing new insight for the study of p62 in ageing.

New Insights into the Roles and Mechanisms of Spermidine in Aging and Age-Related Diseases

High incidences of morbidity and mortality associated with age-related diseases among the elderly population are a socio-economic challenge. Aging is an irreversible and inevitable process that is a risk factor for pathological progression of diverse age-related diseases. Spermidine, a natural polyamine, plays a critical role in molecular and cellular interactions involved in various physiological and functional processes. Spermidine has been shown to modulate aging, suppress the occurrence and severity of age-related diseases, and prolong lifespan. However, the precise mechanisms through which spermidine exerts its anti-aging effects have not been established. In this review, we elucidate on the mechanisms and roles underlying the beneficial effects of spermidine in aging from a molecular and cellular perspective. Moreover, we provide new insights into the promising potential diagnostic and therapeutic applications of spermidine in aging and age-related diseases.

Paeonol Induces Protective Autophagy in Retinal Photoreceptor Cells

Background: Retinal photoreceptor (RP) cells are widely involved in retina-related diseases, and oxidative stress plays a critical role in retinal secondary damage. Herein, we investigated the effectiveness and potential mechanisms of autophagy of paeonol (Pae) in terms of oxidation resistance. Methods: The animal model was induced by light damage (LD) in vivo, whereas the in vitro model was established by H₂O₂ stimulation. The effectiveness of Pae was evaluated by hematoxylin and eosin, terminal deoxynucleotidyl transferase dUTP nick end labeling assay, immunofluorescence, transmission electron microscopy, electroretinogram, and Western blot analysis in vivo, and the underlying mechanisms of Pae were assessed by Cell Counting Kit-8 assay, reactive oxygen species (ROS) assay, and Western blot analysis in 661W cells. We mainly evaluated the effects of Pae on apoptosis and autophagy. Results: Increased apoptosis of the LD-induced and decreased autophagy of RPs were mitigated by Pae treatment. Pea, which increased the expression of mitochondrial functional protein cytochrome c, reversed the decreased cell viability and autophagy induced by oxidative stress in 661W cells. Experiments showed that autophagy was downregulated in PINK1/Parkin dependent and the BNIP3L/Nix dependent pathways under H₂O₂ stimulation and was upregulated by Pae treatment. Pae increased the cell viability and reduced ROS levels through autophagy. Conclusion: Pretreatment with Pae preserved RP cells by enhancing autophagy, which protected retinal function.

Oxidative stress-induced DNA damage and repair in primary human osteoarthritis chondrocytes: focus on IKKα and the DNA Mismatch Repair System

During osteoarthritis development, chondrocytes are subjected to a functional derangement. This increases their susceptibility to stressful conditions such as oxidative stress, a characteristic of the aging tissue, which can further provoke extrinsic senescence by DNA damage responses. It was previously observed that IκB kinase α knockdown increases the replicative potential of primary human OA chondrocytes cultured in monolayer and the survival of the same cells undergoing hypertrophic-like differentiation in 3-D. In this paper we investigated whether IKKα knockdown could modulate oxidative stress-induced senescence of OA chondrocytes undergoing a DDR and particularly the involvement in this process of the DNA mismatch repair system, the principal mechanism for repair of replicative and recombinational errors, devoted to genomic stability maintenance in actively replicating cells. This repair system is also implicated in oxidative stress-mediated DNA damage repair. We analyzed microsatellite instability and expression of the mismatch repair components in human osteoarthritis chondrocytes after IKKα knockdown and H₂O₂ exposure. Only low MSI levels and incidence were detected and exclusively in IKKα proficient cells. Moreover, we found that IKKα proficient and deficient chondrocytes differently regulated MMR proteins after oxidative stress, both at mRNA and protein level, suggesting a reduced susceptibility of IKKα deficient cells. Our data suggest an involvement of the MMR system in the response to oxidative stress that tends to be more efficient in IKKαKD cells. This argues for a partial contribution of the MMR system to the better ability to recover DNA damage already observed in these cells.

Inhibition of HDAC6 by Tubastatin A reduces chondrocyte oxidative stress in chondrocytes and ameliorates mouse osteoarthritis by activating autophagy

The aim of this study was to determine the effect of HDAC6 inhibition using the selective inhibitor Tubastatin A (TubA) on the regulation of tert-butyl hydroperoxide (TBHP)-treated chondrocytes and a mouse OA model. Using conventional molecular biology methods, our results showed that the level of HDAC6 increases both in the cartilage of osteoarthritis (OA) mice and TBHP-treated chondrocytes in vitro. TubA treatment effectively inhibits the expression of HDAC6, attenuates oxidative stress, reduces the level of apoptotic proteins to maintain chondrocyte survival, and suppresses the extracellular matrix (ECM) degradation. In addition, our results also revealed that HDAC6 inhibition by TubA activates autophagy in chondrocytes, whereas the protective effects of TubA were abolished by autophagy inhibitor intervention. Subsequently, the positive effects of HDAC6 inhibition by TubA were also found in a mouse OA model. Therefore, our study provide evidence that HDAC6 inhibition prevents OA development, and HDAC6 could be applied as a potential therapeutic target for OA management.

Punicalagin Inhibits Tert-Butyl Hydroperoxide-Induced Apoptosis and Extracellular Matrix Degradation in Chondrocytes by Activating Autophagy and Ameliorates Murine Osteoarthritis

Background

Osteoarthritis (OA) is a prevalent articular disorder and has no entirely satisfactory treatment. Punicalagin (PUG) is a polyphenol which has shown multiple pharmacological effects on various diseases. However, the role of PUG in the treatment of OA has not been well defined.

Methods

The effects of PUG on anti-oxidative stress, anti-apoptosis, extracellular matrix (ECM) degradation and autophagy were evaluated in chondrocytes through Western blot and immunofluorescence (IF) staining. Meanwhile, the effects of PUG on destabilization of the medial meniscus (DMM) model were also assessed in vivo by performing histopathologic analysis and IF staining.

Results

In vitro, PUG treatment not only increased the level of HO-1 and SOD1 against oxidative stress but also suppressed the expression of apoptotic proteins and inhibited ECM degradation. Meanwhile, PUG treatment activated autophagy and restores autophagic flux in chondrocytes after tert-butyl hydroperoxide (TBHP) insult, inhibition of autophagy by 3-methyladenine (3-MA) partly abrogated the protective effects of PUG on chondrocytes. In vivo, degeneration of the articular cartilage following DMM was also ameliorated by PUG treatment.

Conclusion

PUG prevents the progression of OA through inhibition of apoptosis, oxidative stress and ECM degradation in chondrocytes, which mediated by the activation of autophagy.

Nutrients and Pathways that Regulate Health Span and Life Span

Both life span and health span are influenced by genetic, environmental and lifestyle factors. With the genetic influence on human life span estimated to be about 20–25%, epigenetic changes play an important role in modulating individual health status and aging. Thus, a main part of life expectance and healthy aging is determined by dietary habits and nutritional factors. Excessive or restricted food consumption have direct effects on health status. Moreover, some dietary interventions including a reduced intake of dietary calories without malnutrition, or a restriction of specific dietary component may promote health benefits and decrease the incidence of aging-related comorbidities, thus representing intriguing potential approaches to improve healthy aging. However, the relationship between nutrition, health and aging is still not fully understood as well as the mechanisms by which nutrients and nutritional status may affect health span and longevity in model organisms. The broad effect of different nutritional conditions on health span and longevity occurs through multiple mechanisms that involve evolutionary conserved nutrient-sensing pathways in tissues and organs. These pathways interacting each other include the evolutionary conserved key regulators mammalian target of rapamycin, AMP-activated protein kinase, insulin/insulin-like growth factor 1 pathway and sirtuins. In this review we provide a summary of the main molecular mechanisms by which different nutritional conditions, i.e., specific nutrient abundance or restriction, may affect health span and life span.

Dietary Mitophagy Enhancer: A Strategy for Healthy Brain Aging?

Recently, nutritional interventions have received attention as promising approaches to promote human health during a lifespan. The Mediterranean and Okinawan diets have been associated with longevity and decreasing risk for age-related diseases in contrast to the Western diet. The effect might be due to several antioxidative bioactive compounds highly consumed in both diets, namely, resveratrol, hydroxytyrosol, oleuropein, curcumin, and spermidine. This review aims to address the underlying mechanisms of these compounds to enhance mental fitness throughout life with a focus on brain mitophagy. Mitophagy is the autophagic clearance of dysfunctional, redundant, and aged mitochondria. In aging and neurodegenerative disorders, mitophagy is crucial to preserve the autophagy mechanism of the whole cell, especially during oxidative stress. Growing evidence indicates that curcumin, astaxanthin, resveratrol, hydroxytyrosol, oleuropein, and spermidine might exert protective functions via antioxidative properties and as well the enhanced induction of mitophagy mediators. The compounds seem to upregulate mitophagy and thereby alleviate the clearance of dysfunctional and aged mitochondria as well as mitogenesis. Thus, the Mediterranean or Okinawan diet could represent a feasible nutritional approach to reduce the risk of developing age-related cognitive impairment and corresponding disorders via the stimulation of mitophagy and thereby ensure a balanced redox state of brain cells.

Mitophagy in degenerative joint diseases

Mitochondrial dysfunction is involved in aging and multiple degenerative diseases, including intervertebral disc degeneration (IVDD) and osteoarthritis (OA). Thus, the maintenance of mitochondria homeostasis and function is important. Mitophagy, a process that selectively clears damaged or dysfunctional mitochondria through autophagic machinery, functions to maintain mitochondrial quality control and homeostasis. IVDD and OA are similar joint diseases involving the degradation of cartilaginous tissues that are mainly caused by oxidative stress, cell apoptosis and extracellular matrix (ECM) degradation. Over the past decade, accumulating evidence indicates the essential role of mitophagy in the pathogenesis of IVDD and OA. Importantly, strategies by the regulation of mitophagy exert beneficial effects in the pre-clinical experiments. Given the importance and novelty of mitophagy, we provide an overview of mitophagy pathways and discuss the roles of mitophagy in IVDD and OA. We also highlight the potential of targeting mitophagy for the treatment of degenerative joint diseases.

Abbreviations: AD: Alzheimer disease; AF: annulus fibrosus; ADORA2A/A2AR: adenosine A2a receptor; AMBRA1: autophagy and beclin 1 regulator 1; BMSCs: bone marrow mesenchymal stem cells; BNIP3: BCL2 interacting protein 3; BNIP3L/NIX: BCL2/adenovirus E1B interacting protein 3-like; CDH6: cadherin 6; CEP: cartilaginous endplates; circRNA: circular RNA; DNM1L/DRP1: dynamin 1-like; ECM: extracellular matrix; HIF1A: hypoxia inducible factor 1: alpha subunit; IL1B: interleukin 1 beta; IMM: inner mitochondrial membranes; IVDD: intervertebral disc degeneration; MAPK8/JNK: mitogen-activated protein kinase 8; MFN1: mitofusin 1; MFN2: mitofusin 2; MIA: monosodium iodoacetate; RHOT/MIRO: ras homolog family member T; MMP: mitochondrial transmembrane potential; CALCOCO2/NDP52: calcium binding and coiled-coil domain 2; NFE2L2: nuclear factor: erythroid 2 like 2; NP: nucleus pulposus; OA: osteoarthritis; OPA1: OPA1: mitochondrial dynamin like GTPase; OPTN: optineurin; PRKN: parkin RBR E3 ubiquitin protein ligase; PD: Parkinson disease; PGAM5: PGAM family member 5; PPARGC1A/PGC-1A: peroxisome proliferator activated receptor: gamma: coactivator 1 alpha; PHF23: PHD finger protein 23; PINK1: PTEN induced putative kinase 1; ROS: reactive oxygen species; SfMSCs: synovial fluid MSCs; SIRT1: sirtuin 1; SIRT2: sirtuin 2; SIRT3: sirtuin 3; SQSTM1/p62: sequestosome 1; TNF: tumor necrosis factor; Ub: ubiquitin; UBL: ubiquitin-like; VDAC: voltage-dependent anion channel.

Irisin Mitigates Oxidative Stress, Chondrocyte Dysfunction and Osteoarthritis Development through Regulating Mitochondrial Integrity and Autophagy

Compromised autophagy and mitochondrial dysfunction downregulate chondrocytic activity, accelerating the development of osteoarthritis (OA). Irisin, a cleaved form of fibronectin type III domain containing 5 (FNDC5), regulates bone turnover and muscle homeostasis. Little is known about the effect of Irisin on chondrocytes and the development of osteoarthritis. This study revealed that human osteoarthritic articular chondrocytes express decreased level of FNDC5 and autophagosome marker LC3-II but upregulated levels of oxidative DNA damage marker 8-hydroxydeoxyguanosine (8-OHdG) and apoptosis. Intra-articular administration of Irisin further alleviated symptoms of medial meniscus destabilization, like cartilage erosion and synovitis, while improved the gait profiles of the injured legs. Irisin treatment upregulated autophagy, 8-OHdG and apoptosis in chondrocytes of the injured cartilage. In vitro, Irisin improved IL-1β-mediated growth inhibition, loss of specific cartilage markers and glycosaminoglycan production by chondrocytes. Irisin also reversed Sirt3 and UCP-1 pathways, thereby improving mitochondrial membrane potential, ATP production, and catalase to attenuated IL-1β-mediated reactive oxygen radical production, mitochondrial fusion, mitophagy, and autophagosome formation. Taken together, FNDC5 loss in chondrocytes is correlated with human knee OA. Irisin repressed inflammation-mediated oxidative stress and extracellular matrix underproduction through retaining mitochondrial biogenesis, dynamics and autophagic program. Our analyses shed new light on the chondroprotective actions of this myokine, and highlight the remedial effects of Irisin on OA development.

Permanent cystathionine-β-Synthase gene knockdown promotes inflammation and oxidative stress in immortalized human adipose-derived mesenchymal stem cells, enhancing their adipogenic capacity

In the present study, we aimed to investigate the impact of permanent cystathionine-β-Synthase (CBS) gene knockdown in human telomerase reverse transcriptase (hTERT) immortalized human adipose-derived mesenchymal stem cells (ASC52telo) and in their capacity to differentiate into adipocytes. CBS gene KD in ASC52telo cells led to increased cellular inflammation (IL6, CXCL8, TNF) and oxidative stress markers (increased intracellular reactive oxygen species and decreased reduced glutathione levels) in parallel to decreased H₂S production and rejuvenation (LC3 and SIRT1)-related gene expression. In addition, CBS gene KD in ASC52telo cells resulted in altered mitochondrial respiratory function, characterised by decreased basal respiration (specifically proton leak) and spare respiratory capacity, without significant effects on cell viability and proliferation. In this context, shCBS-ASC52telo cells displayed enhanced adipogenic (FABP4, ADIPOQ, SLC2A4, CEBPA, PPARG)-, lipogenic (FASN, DGAT1)- and adipocyte (LEP, LBP)-related gene expression markers, decreased expression of proinflammatory cytokines, and increased intracellular lipid accumulation during adipocyte differentiation compared to control ASC52telo cells. Otherwise, the increased adipogenic potential of shCBS-ASC52telo cells was detrimental to the ability to differentiate into osteogenic linage. In conclusion, this study demonstrated that permanent CBS gene KD in ASC52telo cells promotes a cellular senescence phenotype with a very increased adipogenic potential, promoting a non-physiological enhanced adipocyte differentiation with excessive lipid storage.

Nutraceutical Activity in Osteoarthritis Biology: A Focus on the Nutrigenomic Role

Osteoarthritis (OA) is a disease associated to age or conditions that precipitate aging of articular cartilage, a post-mitotic tissue that remains functional until the failure of major homeostatic mechanisms. OA severely impacts the national health system costs and patients' quality of life because of pain and disability. It is a whole-joint disease sustained by inflammatory and oxidative signaling pathways and marked epigenetic changes responsible for catabolism of the cartilage extracellular matrix. OA usually progresses until its severity requires joint arthroplasty. To delay this progression and to improve symptoms, a wide range of naturally derived compounds have been proposed and are summarized in this review. Preclinical in vitro and in vivo studies have provided proof of principle that many of these nutraceuticals are able to exert pleiotropic and synergistic effects and effectively counteract OA pathogenesis by exerting both anti-inflammatory and antioxidant activities and by tuning major OA-related signaling pathways. The latter are the basis for the nutrigenomic role played by some of these compounds, given the marked changes in the transcriptome, miRNome, and methylome. Ongoing and future clinical trials will hopefully confirm the disease-modifying ability of these bioactive molecules in OA patients.