Autophagy Protects Advanced Glycation End Product-Induced Apoptosis and Expression of MMP-3 and MMP-13 in Rat Chondrocytes

Liraglutide, a glucagon-like peptide-1 receptor agonist, ameliorates inflammation and apoptosis via inhibition of receptor for advanced glycation end products signaling in AGEs induced chondrocytes

BACKGROUND

This study aimed to investigate functions of GLP-1R agonist by liraglutide (LIRA) and revealing the mechanism related to AGEs/RAGE in chondrocytes.

METHODS

To illustrate potential effect of GLP-1R agonist on AGEs induced chondrocytes, chondrocytes were administrated by AGEs with LIRA and GLP-1R inhibitor exendin. Inflammatory factors were assessed using ELISA. Real-time PCR was used to evaluate the catabolic activity MMPs and ADAMTS mRNA level, as well as anabolic activity (aggrecan and collagen II). RAGE expression was investigated by Western blotting. TUNEL, caspase3 activity and immunofluorescence were performed to test the apoptotic activity.

RESULTS

Our results showed that treatment with LIRA at > 100 nM attenuated the AGE-induced chondrocyte viability. Western bolt demonstrated that GLP-1R activation by LIRA treatment reduced RAGE protein expression compared with the AGEs groups. ELISA showed that LIRA hindered the AGEs-induced production of inflammatory cytokines (IL-6, IL-12 and TNF-α) in primary chondrocytes. AGEs induced catabolism levels (MMP-1, -3, -13 and ADAMTS-4, 5) are also attenuated by LIRA, causing the retention of more extracellular matrix (Aggrecan and Collagen II). TUNEL, caspase3 activity and immunofluorescence results indicated that LIRA inhibited the AGEs-induced production of inflammatory cytokines in primary chondrocytes and attenuated the caspase 3 level, leading to the reduced apoptotic activity. All the protective effects are reversed by exendin (GLP-1R blockers).

CONCLUSIONS

The present study demonstrates for the first time that LIRA, an agonist for GLP-1R which is commonly used in type 2 diabetes reverses AGEs induced chondrocyte inflammation and apoptosis through suppressing RAGE signaling, contributing to reduced catabolism and retention of more extracellular matrix. The above results indicate the possible effect of GLP-1R agonist on treating OA.

Human Skin Aging and the Anti-Aging Properties of Retinol

The skin is the most-extensive and -abundant tissue in the human body. Like many organs, as we age, human skin experiences gradual atrophy in both the epidermis and dermis. This can be primarily attributed to the diminishing population of epidermal stem cells and the reduction in collagen, which is the primary structural protein in the human body. The alterations occurring in the epidermis and dermis due to the aging process result in disruptions to the structure and functionality of the skin. This creates a microenvironment conducive to age-related skin conditions such as a compromised skin barrier, slowed wound healing, and the onset of skin cancer. This review emphasizes the recent molecular discoveries related to skin aging and evaluates preventive approaches, such as the use of topical retinoids. Topical retinoids have demonstrated promise in enhancing skin texture, diminishing fine lines, and augmenting the thickness of both the epidermal and dermal layers.

Strategic outline of interventions targeting extracellular matrix for promoting healthy longevity

The extracellular matrix (ECM), composed of interlinked proteins outside of cells, is an important component of the human body that helps maintain tissue architecture and cellular homeostasis. As people age, the ECM undergoes changes that can lead to age-related morbidity and mortality. Despite its importance, ECM aging remains understudied in the field of geroscience. In this review, we discuss the core concepts of ECM integrity, outline the age-related challenges and subsequent pathologies and diseases, summarize diagnostic methods detecting a faulty ECM, and provide strategies targeting ECM homeostasis. To conceptualize this, we built a technology research tree to hierarchically visualize possible research sequences for studying ECM aging. This strategic framework will hopefully facilitate the development of future research on interventions to restore ECM integrity, which could potentially lead to the development of new drugs or therapeutic interventions promoting health during aging.

Identification of MMP9 as a Novel Biomarker to Mitochondrial Metabolism Disorder and Oxidative Stress in Calcific Aortic Valve Stenosis

Calcific aortic valve stenosis (CAVS) is the most common heart valve disorder among humans. To date, no effective method has been identified to prevent this disease. Herein, we aimed to identify novel diagnostic and mitochondria-related biomarkers of CAVS, based on two machine learning algorithms. We further explored their association with infiltrating immune cells and studied their potential function in CAVS. The GSE12644, GSE51472, and GSE83453 expression profiles were downloaded from the Gene Expression Omnibus (GEO) repository. The GSE12644 and GSE51472 datasets were integrated to identify differentially expressed genes (DEGs). GSE12644 contains 10 normal and 10 CAVS samples, whereas GSE51472 contains 5 normal and 10 CAVS samples. GO and KEGG assays of DEGs were conducted, and the correlation between matrix metalloproteinase 9 (MMP9) expression and immune cell infiltration was explored, using CIBERSORT. The LASSO regression model and SVM-RFE analysis were used to identify diagnostic genes. The expression of MMP9 in CAVS and non-CAVS samples was measured using RT-PCR, western blotting and immunohistochemistry. A series of functional experiments were performed to explore the potential role of MMP9 in mitochondrial metabolism and oxidative stress during CAVS progression. Twenty-two DEGs were identified, of which six genes (SCG2, PPBP, TREM1, CCL19, WIF1, and MMP9) were ultimately distinguished as diagnostic genes in CAVS. Of these, MMP9 was indicated as a mitochondria-related gene, the expression and diagnostic value of which were further confirmed in the GSE83453 dataset. Correlation analysis revealed a positive correlation between MMP9 and infiltrating immune cells. In our cohort, MMP9 expression was distinctly increased in CAVS samples, and its inhibition attenuated the calcification of valve interstitial cells (VICs) by suppressing mitochondrial damage and oxidative stress. Taken together, our findings suggest MMP9 as a novel mitochondrial dysfunction biomarker and therapeutic target for CAVS.

The role of AGEs in pathogenesis of cartilage destruction in osteoarthritis

Osteoarthritis (OA) is a degenerative disease resulting from progressive joint destruction caused by many factors. Its pathogenesis is complex and has not been elucidated to date. Advanced glycation end products (AGEs) are a series of irreversible and stable macromolecular complexes formed by reducing sugar with protein, lipid, and nucleic acid through a non-enzymatic glycosylation reaction (Maillard reaction). They are an important indicator of the degree of ageing. Currently, it is considered that AGEs accumulation in vivo is a molecular basis of age-induced OA, and AGEs production and accumulation in vivo is one of the important reasons for the induction and acceleration of the pathological changes of OA. In recent years, it has been found that AGEs are involved in a variety of pathological processes of OA, including extracellular matrix degradation, chondrocyte apoptosis, and autophagy. Clearly, AGEs play an important role in regulating the expression of OA-related genes and maintaining the chondrocyte phenotype and the stability of the intra-articular environment. This article reviews the latest research results of AGEs in a variety of pathological processes of OA, to provide a new direction for the study of OA pathogenesis and a new target for prevention and treatment.

Cite this article: Bone Joint Res 2022;11(5):292–300.

Chondroprotective effects of purple corn anthocyanins on advanced glycation end products induction through suppression of NF-κB and MAPK signaling

Formation of advanced glycation end products (AGEs), which are associated with diabetes mellitus, contributes to prominent features of osteoarthritis, i.e., inflammation-mediated destruction of articular cartilage. Among the phytochemicals which play a role in anti-inflammatory effects, anthocyanins have also been demonstrated to have anti-diabetic properties. Purple corn is a source of three major anthocyanins: cyanidin-3-O-glucoside, pelargonidin-3-O-glucoside and peonidin-3-O-glucoside. Purple corn anthocyanins have been demonstrated to be involved in the reduction of diabetes-associated inflammation, suggesting that they may have a beneficial effect on diabetes-mediated inflammation of cartilage. This investigation of the chondroprotective effects of purple corn extract on cartilage degradation found a reduction in glycosaminoglycans released from AGEs induced cartilage explants, corresponding with diminishing of uronic acid loss of the cartilage matrix. Investigation of the molecular mechanisms in human articular chondrocytes showed the anti-inflammatory effect of purple corn anthocyanins and the metabolite, protocatechuic acid (PCA) on AGEs induced human articular chondrocytes via inactivation of the NFκb and MAPK signaling pathways. This finding suggests that purple corn anthocyanins and PCA may help ameliorate AGEs mediated inflammation and diabetes-mediated cartilage degradation.

Bcl-xL expression following articular cartilage injury and its effects on the biological function of chondrocytes

This study aimed to investigate the expression of B-cell lymphoma-extra large (Bcl-xL) in cartilage tissues following articular cartilage injury and to determine its effects on the biological function of chondrocytes. A total of 25 necrotic cartilage tissue samples and 25 normal tissue samples were collected from patients diagnosed with osteoarthritis at our hospital from December 2015 to December 2018. The mRNA expression levels of Bcl-xL, caspase-3, and matrix metalloproteinase-3 (MMP-3) in the normal and necrotic tissues were examined via quantitative polymerase chain reaction, and their protein expression levels were detected via western blotting. The expression levels of Bcl-xL, insulin-like growth factor-1 (IGF-1), and bone morphogenetic protein (BMP) were significantly lower but those of caspase-3, MMP-3, interleukin-1β (IL-1β), and chemokine-like factor 1 (CKLF1) levels were markedly higher in necrotic cartilage tissues than in normal tissues. Following cell transfection, the expression levels of Bcl-xL, IGF-1, and BMP were remarkably higher but those of caspase-3, MMP-3, IL-1β, and CKLF1 were notably lower in the Si-Bcl-xL group than in the NC group. The Si-Bcl-xL group showed significantly lower cell growth and noticeably higher apoptosis rate than the NC group (normal control group). The expression of Bcl-xL is reduced following articular cartilage injury, and this reduction promotes the proliferation and inhibits the apoptosis of chondrocytes. Therefore, Bcl-xL could serve as a relevant molecular target in the clinical practice of osteoarthritis and other diseases causing cartilage damage.

Down-regulated ciRS-7/up-regulated miR-7 axis aggravated cartilage degradation and autophagy defection by PI3K/AKT/mTOR activation mediated by IL-17A in osteoarthritis

Osteoarthritis (OA) is one of the most painful and widespread chronic degenerative joint diseases and is characterized by destructed articular cartilage and inflamed joints. Previously, our findings indicated that circular RNA ciRS-7 (ciRS-7)/microRNA 7 (miR-7) axis is abnormally expressed in OA, and regulates proliferation, inflammatory responses, and apoptosis of interleukin-1β (IL-1β)-stimulated chondrocytes. However, its underlying role in OA remains unknown.

In this study, we first validated cartilage degradation and defection of autophagy in samples of OA patients. IL-1β initially stimulated autophagy of chondrocytes, and ultimately significantly suppressed autophagy. Upregulated ciRS-7/down-regulated miR-7 aggravated IL-1β-induced cartilage degradation, and restrained autophagy in vitro. Gene sequencing and bioinformatics analysis performed on a control group, IL-1β group, and IL-1β+miR-7-mimics group demonstrated that seven of the most significant mRNA candidates were enriched in the interleukin-17 (IL-17) signaling pathway. Increased IL-17A levels were also observed by qRT-PCR and ELISA. In addition, it was revealed that the ciRS-7/miR-7 axis ameliorated cartilage degradation and defection of autophagy by PI3K/AKT/mTOR activation in IL-1β-induced chondrocytes. Furthermore, an OA model was established in rats with medial meniscus destabilization. miR-7-siRNA-expressing lentiviruses alleviated surgical resection-induced cartilage destruction of OA mice, whereas miR-7 mimics worsened the effects. Thus, these findings revealed that the mechanism of the ciRS-7/miR-7 axis involved regulating OA progression and provided valuable directions for OA treatment.

Tectorigenin Alleviates Inflammation, Apoptosis, and Ossification in Rat Tendon-Derived Stem Cells via Modulating NF-Kappa B and MAPK Pathways

Tendinopathy is a common musculoskeletal disorder that mainly affects athletes and people of older age. Tumor necrosis factor-α (TNF-α) plays an important role in initiating tendinopathy. Tectorigenin, an extract component of Belam-canda Chinesis, possesses anti-inflammatory and anti-apoptosis activity. The present study was established to investigate the role of tectorigenin against the pathogenetic effects of TNF-α on tendon-derived stem cells (TDSCs) in vivo and in vitro. The findings indicated that TNF-α is able to induce TDSC inflammation, apoptosis, and ossification, as well as activate nuclear factor-kappa B and mitogen-activated protein kinase (MAPK). Furthermore, the results confirmed that tectorigenin is able to inhibit the TNF-α-induced inflammation, apoptosis, and ossification. Tectorigenin treatment decreases activation of NF-kappa B and MAPK signaling in TDSCs. Tectorigenin ameliorates tendinopathy in the in vivo rat model. Thus, these data reveal that tectorigenin can serve as a potential treatment for tendinopathy.

Rapamycin protects chondrocytes against IL-18-induced apoptosis and ameliorates rat osteoarthritis

Interleukin 18 (IL-18) promotes inflammation and apoptosis in chondrocytes, thereby contributing to the development and progression of osteoarthritis (OA). Here, we investigated the effects of IL-18 treatment and inhibition in rat chondrocytes in vitro and in vivo. We used RT-PCR and Western blotting to measure the mRNA and protein levels of the chondrocyte-specific genes Collagen II and Aggrecan as well as the protein levels of apoptosis-related (Bax, Bcl2, Caspase3/9), autophagy-related (Atg5, Atg7, Beclin1, LC3), and mTOR pathway-related genes (PI3K, Akt, mTOR). We observed a decrease in Collagen II and Aggrecan mRNA and protein levels, upregulation of chondrocyte apoptosis, downregulation of chondrocyte autophagy, and activation of the PI3K/Akt/mTOR pathway upon IL-18 treatment. PI3K/Akt/mTOR pathway activation and inhibition tests using rat 740Y-P (PI3K activator), SC79 (AKT activator), 3BDO (mTOR activator), or LY294002 (PI3K inhibitor) revealed that activation of the PI3K/Akt/mTOR pathway enhances chondrocyte-specific gene degradation induced by IL-18, while its inhibition has protective effects on chondrocytes. We also found that treatment with rapamycin (a selective mTOR inhibitor) also exerts chondro-protective effects that ameliorate OA by promoting autophagy. These results suggest that inhibition of the mTOR pathway could be exploited for therapeutic benefits in the treatment of OA.

Pioglitazone attenuates advanced glycation end products-induced apoptosis and calcification by modulating autophagy in tendon-derived stem cells

Diabetes mellitus (DM) is one of the prominent risk factors for pathological development and progression of tendinopathy. One feature of DM-related changes in tendinopathy is accumulation of advanced glycation end products (AGEs) in affected tendons. Pioglitazone (Pio), a peroxisome proliferator-activated receptor γ agonist, performs a protective effect against AGEs. The present study aimed to investigate the pathogenetic role of AGEs on tendon-derived stem cells (TDSCs) and to determine the effect of Pio on AGEs-induced TDSC dysfunctions. Results indicated that AGEs induced TDSC apoptosis as well as compensatory activation of autophagy. Pharmacologic activation/inhibition of autophagy leaded to alleviate/exacerbate apoptosis induced by AGEs. We further confirmed the effect of Pio on autophagy, which ameliorated apoptosis and abnormal calcification caused by AGEs both in vitro and in vivo. Thus, we suggest that Pio ameliorates the dysfunctions of TDSCs against AGEs by promoting autophagy, and we also reveal that Pio is a potential pharmacological choice for tendinopathy.

Inhibition of P2Y11R ameliorated TNF-α-induced degradation of extracellular matrix in human chondrocytic SW1353 cells

Osteoarthritis is a major global health burden. Joint destruction resulting from excessive degradation of type II collagen and aggrecan in the articular extracellular matrix by metalloproteinases and aggrecanases, respectively, is a major pathological hallmark of osteoarthritis. However, the exact mechanisms remain poorly understood. Currently, there are few non-invasive therapies capable of slowing or halting the progression of the disease. In the present study, we investigated the involvement of the P2Y₁₁ purinergic protein and its receptor P2Y11R in TNF-α-mediated degradation of the extracellular matrix in SW1353 cell line chondrocytes using the novel P2Y11R antagonist NF157. To our knowledge, this is the first study to explore the effects of NF157 in OA. Our results indicate that P2Y11R may indeed play a role in TNF-α-induced degradation of extracellular matrix in OA as treatment with NF157 significantly reduced expression of metalloproteinase (MMP)-3, MMP-13, a disintegrin and metalloproteinase with thrombospondin motifs (ADAMTS)-4 and ADAMTS-5, and ameliorated degradation of type II collagen and aggrecan in SW1353 chondrocytes in a dose-dependent manner. Furthermore, we show that treatment with NF157 significantly reduced nuclear translocation of p65 and subsequent activation of nuclear factor κB (NF-κB).

Role of the Inflammation-Autophagy-Senescence Integrative Network in Osteoarthritis

Osteoarthritis is the most common musculoskeletal disease causing chronic disability in adults. Studying cartilage aging, chondrocyte senescence, inflammation, and autophagy mechanisms have identified promising targets and pathways with clinical translatability potential. In this review, we highlight the most recent mechanistic and therapeutic preclinical models of aging with particular relevance in the context of articular cartilage and OA. Evidence supporting the role of metabolism, nuclear receptors and transcription factors, cell senescence, and circadian rhythms in the development of musculoskeletal system degeneration assure further translational efforts. This information might be useful not only to propose hypothesis and advanced models to study the molecular mechanisms underlying joint degeneration, but also to translate our knowledge into novel disease-modifying therapies for OA.

Protective effects of PI3K/Akt signal pathway induced cell autophagy in rat knee joint cartilage injury

As the major reason for limb dysfunction, osteoarthritis (OA) is closely correlated with the level of cellular autophagy. PI3K/Akt is a classical signaling pathway which regulates autophagy, but with unclear roles in OA related cartilage injury. Studying PI3K/Akt induced autophagy in rat knee joint cartilage injury and possible functional mechanism is of critical importance for clinical treatment. This study established a rat knee joint cartilage injury model, in which Akt agonist IGF-1 or autophagy inducer Rapamycin was administrated. Western blot was used to detect the expression level of AKT, phosphorylated AKT, Beclin-1 and LC3-II/I. Formation of autophagosome and lysosome was assessed by transmission electron microscopy. HE, safranin O and toluidine blue staining was used to evaluate cartilage injury. TUNEL staining was performed to measure cell apoptosis. Real-time quantitative PCR measured the expression of cartilage injury indexes such as Aggrecan, Collagen II and MMP13. Compared with normal group, iodacetic acid treatment group showed cartilage injury, whereas AKT activation and autophagy induction groups had significant improvement. mRNA analysis showed enhanced degradation of Aggrecan and Collagen II in AKT activation and autophagy groups with decreased MMP13 mRNA level (P<0.05). Western blot results showed that after AKT activation and autophagy induction, protein levels of Beclin-1 and LC3-II/I were remarkably elevated (P<0.05). TUNEL assay showed significant inhibition of cell apoptosis. In conclusion, activation of PI3K/Akt signal pathway can improve iodacetic acid induced rat knee joint cartilage injury through inducing cell autophagy.