Requirement of the phosphatidylinositol 3-kinase/Akt signaling pathway for the effect of nicotine on interleukin-1beta-induced chondrocyte apoptosis in a rat model of osteoarthritis

The Mechanism by Which Cyperus rotundus Ameliorates Osteoarthritis: A Work Based on Network Pharmacology

Background

Cyperus rotundus (CR) is widely used in traditional Chinese medicine to prevent and treat a variety of diseases. However, its functions and mechanism of action in osteoarthritis (OA) has not been elucidated. Here, a comprehensive strategy combining network pharmacology, molecular docking, molecular dynamics simulation and in vitro experiments was used to address this issue.

Methods

The bioactive ingredients of CR were screened in TCMSP database, and the potential targets of these ingredients were obtained through Swiss Target Prediction database. Genes in OA pathogenesis were collected through GeneCards, OMIM and DisGeNET databases. Gene Ontology (GO) analysis and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis were performed using DAVID database. STRING database and Cytoscape 3.10 software were used to construct "component-target-pathway" network, and predict the core targets affected by CR. The binding affinity between bioactive components and the core targets was evaluated by molecular docking and molecular dynamics simulation. The therapeutic activity of kaempferol on chondrocytes in inflammatory conditions was verified by in vitro experiments.

Results

Fifteen CR bioactive ingredients were obtained, targeting 192 OA-related genes. A series of biological processes, cell components, molecular functions and pathways were predicted to be modulated by CR components. The core targets of CR in OA treatment were AKT serine/threonine kinase 1 (AKT1), interleukin 1 beta (IL1B), SRC proto-oncogene, non-receptor tyrosine kinase (SRC), BCL2 apoptosis regulator (BCL2), signal transducer and activator of transcription 3 (STAT3), epidermal growth factor receptor (EGFR), hypoxia-inducible factor 1 subunit alpha (HIF1A), matrix metallopeptidase 9 (MMP9), estrogen receptor 1 (ESR1) and PPARG orthologs from vertebrates (PPARG), and the main bioactive ingredients of CR showed good binding affinity with these targets. In addition, kaempferol, one of the CR bioactive components, weakens the effects of IL-1β on the viability, apoptosis and inflammation of chondrocytes.

Conclusion

Theoretically, CR has great potential to ameliorate the symptoms and progression of OA, via multiple components, multiple targets, and multiple downstream pathways.

Ginsenoside-Rb1 prevents bone cartilage destruction through down-regulation of p-Akt, p-P38, and p-P65 signaling in rabbit

BACKGROUND

Osteoarthritis (OA) is the most common joint complaint resulting in pain, disability, and loss of quality of life. On the other hand, ginsenoside-Rb1 is a plant product derived from ginseng that possesses immune-regulation and anti-inflammatory activities. However, it has been reported that different rout of administration but hydrogel-based Ginsenoside-Rb1 in an OA rabbit model has not been investigated.

PURPOSE

The aim of this study was to investigate the potential effects of ginsenoside-Rb1 such as anti-arthritic activity in a rabbit knee OA model via NF- κB, PI3K/Akt, and P38/(MAPK) pathways.

STUDY DESIGN

In the current study, rabbit osteoarthritis was induced by hollow trephine on the femur trochlea and the hydrogel-based Ginsenoside-Rb1 sheets were inserted on the rabbit knee to assess the anti-arthritis activity of ginsenoside-Rb1 which is sustained release.

METHODS

After the hydrogel-based Rb1 sheet insert on the rabbit knee, macroscopic and micro CT was performed for investigation of chondroprotective effect. Matrix metalloproteinases (MMPs) and apoptotic expression were assessed through Immunohistochemistry and RT-PCR assay. In addition, the flow cytometry technique was used for the investigation of intracellular reactive oxygen species (ROS) production and histological changes were examined by HE, safranin O, and Masson trichrome staining method. Furthermore, the NF- κB, PI3K/Akt, and P38/(MAPK) pathways were investigated using Western blot analysis.

RESULTS

Macroscopic and micro CT investigation of hydrogel-Rb1 treatment showed a dose-dependent chondroprotective effect. Immunohistochemistry and RT-PCR revealed that expression of matrix metalloproteinases (MMPs) and apoptotic markers TNF-α, caspase-3, and bax are down-regulated in a dose-dependent fashion following implantation of hydrogel-Rb. Higher levels of intracellular reactive oxygen species (ROS) were observed in the OA group. In histopathological investigation of hydrogel-Rb1 exhibited larger amounts of chondro cells, glycosaminoglycan's, and collagen compared to the defect group. Furthermore, the NF- κB, PI3K/Akt, and P38/(MAPK) pathways were downregulated by hydrogel-Rb1 while the disease model showed upstream. In the meantime, MMP expression level was considerably down-regulated.

CONCLUSIONS

Our results indicate the protective effect of ginsenoside-Rb1 against OA pathogenesis through prevention of apoptosis with suppression of ROS production and activation of NF-κB signaling through downregulation of the MAPK and PI3K/Akt signaling pathways.

CircRNA-miRNA networks in regulating bone disease

Circular RNA (circRNA) is a class of endogenous noncoding RNA (ncRNA), presenting as a special covalent closed loop without a 5' cap or 3' tail, maintaining resistance to RNA exonuclease and keeping high stability. Although lowly expressed in most situations, circRNA makes an active difference in regulating physiological or pathological processes by modulating gene expression by regulation of transcription, protein, and miRNA functions through various mechanisms in particular tissues. Recent studies have demonstrated the roles of the miRNA-circRNA network in the development of several bone diseases such as osteoporosis, a multiple-mechanism disease resulting from defective bone quality and low bone mass, osteoarthritis, whose main pathomechanism is inflammation and articular cartilage degradation, as well as osteosarcoma, known as one of the most common bone cancers. However, the specific mechanism of how circRNA along with miRNA influences those diseases is not well documented, showing potential for the development of new therapies for those bone diseases.

PRMT1 promotes extracellular matrix degradation and apoptosis of chondrocytes in temporomandibular joint osteoarthritis via the AKT/FOXO1 signaling pathway

Temporomandibular joint osteoarthritis (TMJOA) is a chronic degenerative joint disease characterized by extracellular matrix (ECM) degradation and chondrocyte apoptosis. The aim of this study was to investigate the role of PRMT1 in TMJOA pathogenesis and its underlying molecular mechanism. Compared to the control group, PRMT1 was highly expressed in IL-1β-treated chondrocytes and articular cartilage following MIA injection into rat TMJs. Furthermore, knocking down PRMT1 considerably inhibited ECM degradation and apoptosis induced by IL-1β. Mechanistic analyses further revealed that PRMT1 knockdown activated the PI3K/AKT signaling pathway and prevented FOXO1 from translocating to the nucleus. Moreover, an inhibitor of AKT (LY294002) rescued the effect of PRMT1 knockdown on IL-1β-induced ECM degradation and apoptosis, and AMI-1, a selective inhibitor of PRMT1, inhibited PRMT1 expression and reversed the pathological progress of TMJOA. Thus, our findings suggest that PRMT1 plays an essential role in ECM degradation and chondrocyte apoptosis in TMJOA via the AKT/FOXO1 signaling pathway.

The role of the cholinergic anti-inflammatory pathway in autoimmune rheumatic diseases

The cholinergic anti-inflammatory pathway (CAP) is a classic neuroimmune pathway, consisting of the vagus nerve, acetylcholine (ACh)-the pivotal neurotransmitter of the vagus nerve-and its receptors. This pathway can activate and regulate the activities of immune cells, inhibit cell proliferation and differentiation, as well as suppress cytokine release, thereby playing an anti-inflammatory role, and widely involved in the occurrence and development of various diseases; recent studies have demonstrated that the CAP may be a new target for the treatment of autoimmune rheumatic diseases. In this review, we will summarize the latest progress with the view of figuring out the role of the cholinergic pathway and how it interacts with inflammatory reactions in several autoimmune rheumatic diseases, and many advances are results from a wide range of experiments performed in vitro and in vivo.

Repurposing pentosan polysulfate sodium as hyaluronic acid linked polyion complex nanoparticles for the management of osteoarthritis: A potential approach

Osteoarthritis is still a disease burden for pharmaceutical scientists and strategy makers. It is associated with the chronic inflammation of joints especially weight-bearing joints like knee, hip, backbone, and phalanges. NSAIDs that are used for the management of inflammation associated with osteoarthritis have high side effects related to gastric upset, gastric ulcer, and long term treatment associated with liver and kidney damage. Nanotechnology has gained a huge scope for the management of arthritis as it can reach out to the deep inside the cell and alter cellular physiology as desired. The present study hypothesizes the use of polyion complex nanoparticles of hyaluronic acid linked Pentosan polysulfate sodium, a disease-modifying agent for the treatment of osteoarthritis administered through transdermal route. The hypothesis involves the use of drug repurposing as the drug was initially approved for interstitial cystitis, a condition of the urinary bladder associated with pain and swelling. Being very low oral bioavailability and gastric irritation profile, the transdermal route would be beneficial. To overcome the problem associated with the oral route, there is a need for the targeted approach that will particularly reach at inflammatory sites. Thereby transdermal delivery of hyaluronic acid linked Pentosan polysulfate sodium through polyion complex nanoparticle therapy will be a novel therapeutic approach to combat osteoarthritis.

Research Progress on the Antiosteoarthritic Mechanism of Action of Natural Products

Background

Osteoarthritis (OA) is a clinical joint degenerative disease, the pathogenic factors of which include age, obesity, and mechanical injury. Its main pathological features include cartilage loss, narrowing of joint space, and osteophyte formation. At present, there are a variety of treatment methods for OA. Natural products, which are gradually being applied in the treatment of OA, are advantageous as they present with low toxicity and low costs and act on multiple targets.

Methods

The terms “natural products,” “osteoarthritis,” and “chondrocytes” were searched in PubMed to screen the related literature in the recent 10 years.

Results

We comprehensively introduced 62 published papers on 48 natural products involving 6, 3, 5, 12, 4, and 5 kinds of terpenoids, polysaccharides, polyphenols, flavonoids, alkaloids, and saponins, respectively (and others).

Conclusion

The mechanisms of their anti-OA action mainly involve reducing the production of inflammatory factors, reducing oxidative stress, regulating the metabolism of chondrocytes, promoting the proliferation of chondrocytes, or inhibiting chondrocyte apoptosis. This article summarizes the anti-OA activity of natural products in the last 10 years and provides candidate monomers for further study for use in OA treatment.

IGF-1 Facilitates Cartilage Reconstruction by Regulating PI3K/AKT, MAPK, and NF-kB Signaling in Rabbit Osteoarthritis

Purpose

The pathogenesis of osteoarthritis (OA) is characterized by joint degeneration. The pro-inflammatory cytokine interleukin (IL)-1β plays a vital role in the pathogenesis of OA by stimulation of specific signaling pathways like NF-κB, PI3K/Akt, and MAPKs pathways. The catabolic role of growth factors in the OA may be inhibited cytokine-activated pathogen. The purpose of this study was to investigate the potential effects of insulin-like growth factor-1 (IGF-1) on IL-1β-induced apoptosis in rabbit chondrocytes in vitro and in an in vivo rabbit knee OA model.

Methods

In the present study, the OA developed in chondrocyte with the treatment of IL-1β and articular cartilage ruptures by removal of cartilage from the rabbit knee femoral condyle. After IGF-1 treatment, immunohistochemistry and qRT-PCR were identified OA expression with changes in MMPs (matrix metalloproteinases). The production of ROS (intracellular reactive oxygen species) in the OA was detected by flow cytometry. Further, the disease progression was microscopically investigated and pathophysiological changes were analyzed using histology. The NF-κB, PI3K/Akt and P38 (MAPK) specific pathways that are associated with disease progression were also checked using the Western blot technique.

Results

The expression of MMPs and various apoptotic markers are down-regulated following administration of IGF-1 in a dose-dependent fashion while significantly up-regulation of TIMP-1. The results showed that higher levels of ROS were observed upon treatment of chondrocytes and chondral OA with IL-1β. Collectively, our results indicated that IGF-1 protected NF-κB pathway by suppression of PI3K/Akt and MAPKs specific pathways. Furthermore, the macroscopic and pathological investigation showed that it has a chondroprotective effect by the formation of hyaline cartilage.

Conclusion

Our results indicate a protective effect of IGF-1 against OA pathogenesis by inhibition of NF-κB signaling via regulation of the MAPK and PI3K/Akt signaling pathways and prevention of apoptosis by suppression of ROS production.

WISP1 Protects Against Chondrocyte Senescence and Apoptosis by Regulating αvβ3 and PI3K/Akt Pathway in Osteoarthritis

Our study aimed at validating the effect of WISP1 on osteoarthritis (OA) and the pathway involved in the WISP1-induced protection against OA. The expression of WISP1 was measured by immunohistochemical analyses. We found that WISP1 expression was shown to be upregulated within human OA cartilage compared with controls. WISP1 expression was related to knee OA severity. rhWISP1 inhibited OA chondrocyte senescence and apoptosis in vitro, which was reversed by the αvβ3 antibody and PI3K/Akt inhibitor LY294002. WISP1 overexpression induced by knee injection of LiCI could also prevent the senescence and apoptosis of rat chondrocytes. Safranin-O staining and Mankin score revealed that WISP1 overexpression can protect rat chondrocytes from degeneration. Nearly opposite results were obtained in the treatment of ICG-001 and siRNA-WISP1 in vivo. These data strongly suggest that WISP1 can protect against the senescence and apoptosis of chondrocytes via modulating the αvβ3 receptor and PI3K/Akt signaling pathway within OA. Therefore, the development of specific activators of WISP1 may present the value of an underlying OA treatment.

Berberine and musculoskeletal disorders: The therapeutic potential and underlying molecular mechanisms

BACKGROUND

Musculoskeletal disorders are a group of disorders that affect the joints, bones, and muscles, causing long-term disability. Berberine, an isoquinoline alkaloid, has been previously established to exhibit beneficial properties in preventing various diseases, including musculoskeletal disorders.

PURPOSE

This review article aims to recapitulate the therapeutic potential of berberine and its mechanism of action in treating musculoskeletal disorders.

METHODS

A wide range of literature illustrating the effects of berberine in ameliorating musculoskeletal disorders was retrieved from online electronic databases (PubMed and Medline) and reviewed.

RESULTS

Berberine may potentially retard the progression of osteoporosis, osteoarthritis and rheumatoid arthritis. Limited studies reported the effects of berberine in suppressing the proliferation of osteosarcoma cells. These beneficial properties of berberine are mediated in part through its ability to target multiple signaling pathways, including PKA, p38 MAPK, Wnt/β-catenin, AMPK, RANK/RANKL/OPG, PI3K/Akt, NFAT, NF-κB, Hedgehog, and oxidative stress signaling. In addition, berberine exhibited anti-apoptotic, anti-inflammatory, and immunosuppressive properties.

CONCLUSION

The current evidence indicates that berberine may be effective in preventing musculoskeletal disorders. However, findings from in vitro and in vivo investigations await further validation from human clinical trial.

Osteopontin inhibits osteoarthritis progression via the OPN/CD44/PI3K signal axis

Chondrocyte degeneration and extracellular matrix component loss are the primary causes of osteoarthritis (OA). OA can be treated by inhibiting chondrocyte degeneration and increasing extracellular matrix component secretion. Osteopontin (OPN), a multifunctional protein, has gained immense attention with regard to its involvement in OA. This study aimed to explore the therapeutic value and mechanism of action of OPN in OA treatment. Results of the histomorphological analysis revealed a worn-off OA cartilage tissue surface, cartilage matrix layer deterioration, and calcium salt deposition. Compared to that in normal chondrocytes, in OA chondrocytes, the OPN, CD44, and PI3K protein and mRNA expression was upregulated. Further, siOPN, rhOPN, and rhOPN plus LS-C179404 interfered with OA chondrocytes. As verified in mice, OPN directly inhibited the expression level of PI3K in OA chondrocytes by binding with CD44. Morphological analysis of the knee joints demonstrated that OPN effectively inhibited OA progression via the OPN/CD44/PI3K signal axis. In conclusion, OPN activates intracellular PI3K signaling molecules by binding to CD44 on the cell surface to cause downstream cascading effects, thereby delaying chondrocyte degeneration and reducing cartilage matrix component loss; therefore, OPN is a potential therapeutic agent for OA.

Proinflammatory cytokines and lipopolysaccharides up regulate MMP-3 and MMP-13 production in Asian elephant (Elephas maximus) chondrocytes: attenuation by anti-arthritic agents

Background

Osteoarthritis (OA), the most common form of arthritic disease, results from destruction of joint cartilage and underlying bone. It affects animals, including Asian elephants (Elephas maximus) in captivity, leading to joint pain and lameness. However, publications regarding OA pathogenesis in this animal are still limited. Therefore, this study aimed to investigate the effect of proinflammatory cytokines, including interleukin-1 beta (IL-1β), IL-17A, tumor necrosis factor-alpha (TNF-α), and oncostatin M (OSM), known mediators of OA pathogenesis, and lipopolysaccharides on the expression of cartilaginous degrading enzymes, matrix metalloproteinase (MMP)-3 and MMP-13, in elephant articular chondrocytes (ELACs) cultures. Anti-arthritic drugs and the active compounds of herbal plants were tested for their potential attenuation against overproduction of these enzymes.

Results

Among the used cytokines, OSM showed the highest activation of MMP3 and MMP13 expression, especially when combined with IL-1β. The combination of IL-1β and OSM was found to activate phosphorylation of the mitogen-activated protein kinase (MAPK) pathway in ELACs. Lipopolysaccharides or cytokine-induced expressions were suppressed by pharmacologic agents used to treat OA, including dexamethasone, indomethacin, etoricoxib, and diacerein, and by three natural compounds, sesamin, andrographolide, and vanillylacetone.

Conclusions

Our results revealed the cellular mechanisms underlying OA in elephant chondrocytes, which is triggered by proinflammatory cytokines or lipopolysaccharides and suppressed by common pharmacological or natural medications used to treat human OA. These results provide a more basic understanding of the pathogenesis of elephant OA, which could be useful for adequate medical treatment of OA in this animal.

FAM3A protects chondrocytes against interleukin-1β-induced apoptosis through regulating PI3K/Akt/mTOR pathway

Chondrocyte death due to apoptosis is central for osteoarthritis (OA) pathogenesis. The family with sequence similarity 3A (FAM3A) is a mitochondrial protein that plays an important role for cellular adaptation to stress and cell survival. Yet, whether FAM3A is associated with chondrocyte apoptosis and OA pathogenesis remains uncharacterized. In this study, we found that FAM3A expression was downregulated in cartilage tissue from an experimental OA mouse model. Besides, FAM3A expression was also reduced in chondrocytes treated with interleukin-1β (IL-1β), an inflammatory cytokine that promotes cartilage degradation. Moreover, we discovered that FAM3A attenuated chondrocyte apoptosis induced by IL-1β treatment in vitro, suggesting a protective effect of FAM3A against chondrocyte apoptosis. Moreover, mechanistically, FAM3A activated PI3K/Akt/mTOR pathway in IL-1β-treated chondrocytes, and blockade of PI3K/Akt/mTOR pathway with specific inhibitors, wortmannin and LY294002, diminished FAM3A effect on IL-1β-induced chondrocyte apoptosis, hence demonstrating that FAM3A attenuates IL-1β-induced chondrocyte apoptosis through activating the pro-survival PI3K/Akt/mTOR pathway. In conclusion, our study may identify FAM3A as a potential regulator of chondrocyte apoptosis involved in OA pathogenesis.

Estrogen reverses nicotine-induced inflammation in chondrocytes via reducing the degradation of ECM

PROBLEM

Osteoarthritis (OA) is a chronic disease with a very high incidence and the pathology of which is quite complex. Epidemiological investigation showed that OA may be related to smoking and estrogen levels, but there are few studies focused on the cross-effect of these two factors. This research aims to investigate the molecular mechanism of nicotine and estrogen effects on chondrocytes to study the effect of smoking on the incidence of osteoarthritis in women.

METHOD OF THE STUDY

Nicotine was added to obtain inflammatory supernatants of macrophages, which were used to induce chondrocyte inflammation. Toluidine staining and immunohistochemistry were used to detect the extracellular matrix (ECM) of chondrocytes, while the important proteins in the metabolism of chondrocytes were detected by Western blot.

RESULTS

Nicotine-induced inflammatory supernatant promoted the degradation of ECM, such as type II collagen, aggrecan and proteoglycan 4. While in the presence of physiological concentrations of estrogen, this destructive effect is reversed. On the molecular level, estrogen (17β-estradiol, 1 nmol/L) can inhibit the matrix degrading enzymes and promote the transforming growth factor (TGF)-β1 pathway which is involved in matrix synthesis. However, in the presence of inflammatory induction, although estrogen could still inhibit the expression of matrix degrading enzymes, it inhibited the TGF-β1 pathway. Moreover, the different inflammatory factors in the inflammatory supernatant, mainly tumor necrosis factor-α, interleukin-1β, had different effects on the metabolic processes of chondrocytes.

CONCLUSION

Estrogen reverses nicotine-induced inflammation mainly via reducing the degradation of ECM. The cross-effect of estrogen and inflammatory factor inhibitors can be a potential clinical reference for OA patients.

Transient receptor potential ankyrin 1 (trpa1) mediates il-1β-induced apoptosis in rat chondrocytes via calcium overload and mitochondrial dysfunction

Background

Chondrocyte apoptosis is a central feature in the progression of osteoarthritis (OA), and would be triggered by sustained elevation of intracellular calcium ion (Ca²⁺), also known as a cellular second messenger. Transient receptor potential ankyrin 1 (TRPA1) is a membrane-associated cation channel, and the activation of which causes an influx of cation ions, in particularly Ca²⁺, into the activated cells. Therefore, we investigate the potential role of TRPA1 in mediating Ca²⁺ influx to promote chondrocyte apoptosis in OA.

Methods

The expression of TRPA1 in interleukin (IL)-1β-treated rat chondrocytes was assessed by Polymerase chain reaction (PCR) and Western blot (WB), and the functionality of TRPA1 channel by Ca²⁺ influx measurements. Meanwhile, the chondrocyte apoptosis in IL-1β-treated cells was measured by TUNEL assay and flow cytometry. The measurement of mitochondrial membrane potential and apoptosis-associated proteins after inhibition of TRPA1 were also performed in IL-1β-treated rat chondrocytes.

Results

After being induced by IL-1β, the gene and protein expression of TRPA1 was increased in the dose-dependent manner. Meanwhile, Ca²⁺ influx mediated by TRPA1 in rat chondrocytes was also enhanced. Pharmacological inhibition of TRPA1 downregulated the apoptotic rate in IL-1β-treated rat chondrocytes. In addition, the membrane potential depolarization was improved and significantly increased expression of apoptosis-associated proteins also reduced by the TRPA1 antagonist.

Conclusions

We found the IL-1β caused the increased functional expression of TRPA1, the activation of which involved IL-1β-induced apoptosis in rat chondrocytes. The potential mechanism may be linked to the intracellular calcium overload mediated by TRPA1 and attendant mitochondrial dysfunction.

Curcumin improves age-related and surgically induced osteoarthritis by promoting autophagy in mice

Reduced autophagy has been implied in chondrocyte death and osteoarthritis. Curcumin (Cur) owns therapeutic effect against osteoarthritis (OA) and enhances autophagy in various tumor cells. Whether the cartilage protection of curcumin is associated with autophagy promotion and the potential signaling pathway involved remains unclear. The present study aimed to investigate the role of autophagy in the anti-OA activity of curcumin using spontaneous and surgically induced OA mice model. Spontaneous and surgically induced OA mice model was established and treated with Cur. Articular cartilage destruction and proteoglycan loss were scored through Safranin O/Fast green staining. Apoptotic cell death was detected with TUNEL (terminal deoxynucleotidyl transferase-mediated dTUP-biotin nick end labeling assay) staining and Western blot for caspase-3, Bcl-2 associated X protein (Bax), and Bcl-2 (B-cell lymphoma-2). Light chain 3 (LC3) immunohistochemistry was used to evaluate autophagy. In vitro, primary chondrocytes were treated with interleukin 1 beta (IL-1β) and Cur. Autophagy was inhibited using 3-methyladenine. Apoptosis and autophagy were detected using flow cytometry and Western blotting assay. Curcumin treatment enhanced autophagy, reduced apoptosis, and cartilage loss in both OA models. In vitro, curcumin treatment improved IL-1β induced autophagy inhibition, cell viability decrease, and apoptosis. Mechanistically, in vivo studies suggested curcumin promoted autophagy through regulating Akt/mTOR pathway. In conclusion, our results demonstrate that curcumin-induced autophagy via Akt/mTOR signaling pathway contributes to the anti-OA effect of curcumin.

Paeoniflorin inhibits IL-1β-induced chondrocyte apoptosis by regulating the Bax/Bcl-2/caspase-3 signaling pathway

Apoptosis serves a pivotal role in the pathogenesis of osteoarthritis (OA). Increasing evidence has demonstrated that paeoniflorin exerts key properties (including anticancer, anti-inflammation and neuroprotective) for clinical applications. However, the precise role of paeoniflorin in articular cartilage apoptosis remains unknown. The present study explored the effects and potential molecular mechanism of paeoniflorin on rat chondrocyte apoptosis. Rat articular chondrocytes were cultured in monolayers. The lactate dehydrogenase (LDH) release rate of cells was determined by an LDH release assay. Annexin V-fluorescein isothiocyanate and propidium iodide staining were performed to detect early and advanced apoptotic cells by flow cytometry. The activity of caspase-3 in chondrocytes was determined using a caspase-3 activity assay. The expression of B-cell lymphoma 2 (Bcl-2)/Bcl-2-associated X protein (Bax) was examined by reverse transcription‑quantitative polymerase chain and western blotting. The present study also examined the protein kinase B (Akt) signaling pathway by western blotting. Treatment with 25 or 50 µM paeoniflorin markedly decreased the release of LDH and the ratio of apoptotic cells in interleukin (IL)-1β-induced rat chondrocytes. Paeoniflorin treatment decreased the mRNA and protein levels of Bax, and increased the level of Bcl-2. Paeoniflorin also reduced the activity of caspase-3 in chondrocytes. Furthermore, paeoniflorin was determined to regulate the Akt signaling pathway by increasing Akt phosphorylation. Therefore, paeoniflorin may exert its protective effect by inhibiting apoptosis in IL-1β-induced rat chondrocytes and thus, may be an effective agent in the prevention and treatment of OA.

The inhibition of PLCγ1 protects chondrocytes against osteoarthritis, implicating its binding to Akt

Previous studies have addressed the involvement of phosphoinositide-specifc phospholipase γ1 (PLCγ1) and protein kinase B (PKB/Akt) in osteoarthritis (OA) pathogenesis, but it is not ascertained the possibility of them to be potential targets for OA therapy. Here, through local intra-articular injection of PLCγ or Akt inhibitor in a rat OA model induced by anterior cruciate ligament transaction plus medial meniscus resection, the architecture of chondrocyte and matrix organization of articular cartilage were observed using histopathological assays and Aggrecan, Col2, PLCγ1, and Akt levels were detected using immunohistochemistry assays. By treatment of Akt or PLCγ inhibitor and transfection of different PLCγ1- or Akt-expressing vectors in rat OA model chondrocytes, Aggrecan, Col2, PLCγ1, p-PLCγ1, Akt, and p-Akt levels were detected using western blotting analysis. The binding between PLCγ1 and Akt was assessed with co-immunoprecipitation assays in human OA chondrocytes. These results showed that PLCγ inhibition protected chondrocytes against OA, but Akt inhibition did not dramatically aggravate OA progression. There were mutual antagonism and binding between PLCγ1 and Akt that could be regulated by their phosphorylation levels. Consequently, the data reveal that the inhibition of PLCγ1 may provide an attractive therapeutic target for OA therapy, implicating its binding to Akt.

Peroxiredoxin 4 inhibits IL-1β-induced chondrocyte apoptosis via PI3K/AKT signaling

BACKGROUND

Chondrocytes apoptosis induced by reactive oxygen species (ROS) plays a critical role in the pathogenesis of osteoarthritis (OA). Peroxiredoxin 4 (PRDX4), a member of the PRDX family, is essential for removing metabolic free radicals and reducing intracellular ROS. In this study, we sought to investigate the roles of PRDX4 on interleukin 1β (IL-1β)-induced chondrocyte apoptosis.

METHODS

Primary chondrocytes were isolated from the articular cartilage of Sprague-Dawley rats, infected with PRDX4 overexpressing lentivirus and treated with IL-1β (10ng/mL). Cell apoptosis and ROS production identified by flow cytometry. Protein expression levels was evaluated by Western blotting analysis. Nitric oxide (NO) production and Caspase-3/9 activation were assessed by the Griess reaction method and colorimetric assay kit, respectively.

RESULTS

PRDX4 overexpression in chondrocytes significantly decreased IL-1β-induced apoptosis. It also reversed the activity of IL-1β that increased ROS and NO production. PRDX4 overexpression reversed the activity of IL-1β that reduced the levels of Bcl-2, p-AKT and p-PRAS40, as well as increased Bax levels and Caspase-3/9 activation. More importantly, pre-treated with AKT inhibitor (AZD5363) significantly reduced the protective effects of PRDX4.

CONCLUSIONS

Our data demonstrated that the regulatory effects of PRDX4 on IL-1β-induced chondrocyte apoptosis can be partially attributed to phosphatidylinositol 3-kinase/AKT signaling. These results indicate that PRDX4 might play a protective role in OA cartilage degeneration.

Insights into the Action Mechanisms of Traditional Chinese Medicine in Osteoarthritis

Osteoarthritis (OA) is a chronic degenerative joint disease characterized by articular cartilage destruction, synovial inflammation, and osteophyte formation. No effective treatments are available. The current pharmacological medications such as nonsteroidal anti-inflammatory drugs (NSAIDs) and analgesics, accompanied by possible adverse effects, might ameliorate OA symptoms. But they do not arrest the progression of OA. Traditional Chinese medicine (TCM) provides medical value by modification of disease and symptoms in OA. Valuable work on exploring TCM merits for OA patients has been investigated using modern technologies, although the complicated interacting network among the numerous components indicates the uncertainty of target specification. This review will provide an overview of the action mechanism of TCM in the last 5 years, discussing the TCM activities of anti-inflammation, antiapoptosis, antioxidation, anticatabolism, and proliferation in OA. TCM is a proposed medical option for OA treatment.

Protection of carboxymethylated chitosan on chondrocytes from nitric oxide-induced apoptosis by regulating phosphatidylinositol 3-kinase/Akt signaling pathway

Chondrocyte apoptosis is the most important element of development and progression of osteoarthritis (OA). Nitric oxide (NO) was used as the agent to induce chondrocyte apoptosis. Carboxymethylated chitosan (CMCS) has anti-apoptosis effect on many cell types in vitro. This study was designed to investigate the protective effect of CMCS on NO-induced chondrocyte apoptosis and the probable molecular mechanisms. The newborn Sprague-Dawley (SD) rats were used in this study for isolation of chondrocytes. The cell viability was determined by cell counting kit (CCK-8), cell apoptosis was detected by Annexin-V/PI double staining assay kit. The levels of phosphorylated-PI3K (p-PI3K), phosphorylated-Akt (p-Akt), Bcl-2 and Bax were determined by Western blot analysis. The caspase-3 activity was determined by a quantitative colorimetric assay. Results showed that pretreatment with CMCS could inhibit the apoptosis induced by NO. CMCS could decrease the activity of NO and decrease the expression of Bcl-2, p-PI3K and p-Akt, increase the expression of Bax, cytochrome c and caspase-3. CMCS also could reverse the effect of NO that prompted matrix metalloproteinase-13 (MMP-13) and inhibited tissue inhibitor of metalloproteinase-1 (TIMP-1) activity. All the present results indicated that CMCS can protect NO induced chondrocytes apoptosis by activate PI3K/Akt signaling pathway.

Chondro-Protective and Antiarthritic Effects of Sulfonamido-Based Gallate-ZXHA-TC in Vitro and in Vivo

The effects of gallic acid (GA) on arthritis are limited by weak antioxidant effects and inferior biological properties of GA. We recently described a new series of synthesized GA derivatives by coupling with sulfonamides. Among these analogs, a novel compound synthesized from GA and sulfadimoxine (SDM) named ZXHA-TC exhibited the most robust anti-inflammatory potential. In this current study, the chondro-protective and antiarthritic effects of ZXHA-TC were investigated both in vitro and in vivo. In the in vitro study, ZXHA-TC exerted chondro-protective effects as evidenced by promoting cell proliferation and the maintaining of the phenotype of articular chondrocytes treated with interleukin-1-beta (IL-1β). The potential of ZXHA-TC to slow the progress of osteoarthritis (OA) was suggested by a reduction in matrix metalloproteinases (MMPs) and the up-regulation of the tissue inhibitor of metalloproteinase-1 (TIMP-1). In a rabbit anterior cruciate ligament transaction (ACLT) model of OA, ZXHA-TC exerted a protective effect on arthritis as assessed by macroscopic scores, histological, qRT-PCR, and immunohistochemical analyses. The effects of ZXHA-TC on inhibiting the production of inflammatory mediators in OA may be mediated partly by the suppression of the PI3K/AKT pathway or MAPK cascades, leading to NF-κB inactivation. Thus, this study indicates that ZXHA-TC may be developed as a potential therapeutic agent for OA.

Overexpression of microRNA-634 suppresses survival and matrix synthesis of human osteoarthritis chondrocytes by targeting PIK3R1

Osteoarthritis (OA) is a degenerative disease characterized by deterioration of articular cartilage. Recent studies have demonstrated the importance of some microRNAs in cartilage damage. The aim of this study was to identify and characterize the expression of microRNA-634 (miR-634) in normal and OA chondrocytes, and to determine its role in OA pathogenesis. Human normal and OA chondrocytes obtained from patients were cultured in vitro. Transfection with miR-634 mimic or inhibitor was employed to investigate the effect of miR-634 on chondrocyte survival and matrix synthesis, and to identify miR-634 target. The results indicated that miR-634 was expressed at lower level in high grade OA chondrocyte compared with normal chondrocytes. Overexpression of miR-634 could inhibit cell survival and matrix synthesis in high grade OA chondrocytes. Furthermore, miR-634 targeted PIK3R1 gene that encodes the regulatory subunit 1 of class I PI3K (p85α) and exerted its inhibitory effect on the phosphorylation of Akt, mTOR, and S6 signal molecules in high grade OA chondrocytes. Therefore, the data suggested that miR-634 could suppress survival and matrix synthesis of high grade OA chondrocytes through targeting PIK3R1 gene to modulate the PI3K/Akt/S6 and PI3K/Akt/mTOR/S6 axes, with important implication for validating miR-634 as a potential target for OA therapy.

DAG/PKCδ and IP3/Ca²⁺/CaMK IIβ Operate in Parallel to Each Other in PLCγ1-Driven Cell Proliferation and Migration of Human Gastric Adenocarcinoma Cells, through Akt/mTOR/S6 Pathway

Phosphoinositide specific phospholipase Cγ (PLCγ) activates diacylglycerol (DAG)/protein kinase C (PKC) and inositol 1,4,5-trisphosphate (IP3)/Ca²⁺/calmodulin-dependent protein kinase II (CaMK II) axes to regulate import events in some cancer cells, including gastric adenocarcinoma cells. However, whether DAG/PKCδ and IP3/Ca²⁺/CaMK IIβ axes are simultaneously involved in PLCγ1-driven cell proliferation and migration of human gastric adenocarcinoma cells and the underlying mechanism are not elucidated. Here, we investigated the role of DAG/PKCδ or CaMK IIβ in PLCγ1-driven cell proliferation and migration of human gastric adenocarcinoma cells, using the BGC-823 cell line. The results indicated that the inhibition of PKCδ and CaMK IIβ could block cell proliferation and migration of BGC-823 cells as well as the effect of inhibiting PLCγ1, including the decrease of cell viability, the increase of apoptotic index, the down-regulation of matrix metalloproteinase (MMP) 9 expression level, and the decrease of cell migration rate. Both DAG/PKCδ and CaMK IIβ triggered protein kinase B (Akt)/mammalian target of rapamycin (mTOR)/S6 pathway to regulate protein synthesis. The data indicate that DAG/PKCδ and IP3/Ca²⁺/CaMK IIβ operate in parallel to each other in PLCγ1-driven cell proliferation and migration of human gastric adenocarcinoma cells through Akt/mTOR/S6 pathway, with important implication for validating PLCγ1 as a molecular biomarker in early gastric cancer diagnosis and disease surveillance.

Protein kinase B and extracellular signal-regulated kinase contribute to the chondroprotective effect of morroniside on osteoarthritis chondrocytes

Despite extensive studies on the multifaceted roles of morroniside, the main active constituent of iridoid glycoside from Corni Fructus, the effect of morroniside on osteoarthritis (OA) chondrocytes remains poorly understood. Here, we investigated the influence of morroniside on cultured human OA chondrocytes and a rat experimental model of OA. The results showed that morroniside enhanced the cell viability and the levels of proliferating cell nuclear antigen expression (PCNA), type II collagen and aggrecan in human OA chondrocytes, indicating that morroniside promoted chondrocyte survival and matrix synthesis. Furthermore, different doses of morroniside activated protein kinase B (AKT) and extracellular signal-regulated kinase (ERK) in human OA chondrocytes, and in turn, triggered AKT/S6 and ERK/P70S6K/S6 pathway, respectively. The PI3K/AKT inhibitor LY294002 or the MEK/ERK inhibitor U0126 attenuated the effect of morroniside on human OA chondrocytes, indicating that the activation of AKT and ERK contributed to the regulation of morroniside in human OA chondrocytes. In addition, the intra-articular injection of morroniside elevated the level of proteoglycans in cartilage matrix and the thickness of articular cartilage in a rat experimental model of OA, with the increase of AKT and ERK activation. As a consequence, morroniside has chondroprotective effect on OA chondrocytes, and may have the therapeutic potential for OA treatment.

Protection of ginsenoside Rg1 on chondrocyte from IL-1β-induced mitochondria-activated apoptosis through PI3K/Akt signaling

Chondrocyte apoptosis is closely related to the development and progression of osteoarthritis. Ginsenoside Rg1 protects cells by antagonizing apoptosis. This study aimed to investigate the protective effect of Rg1 on interleukin 1β (IL-1β)-induced chondrocyte apoptosis and the underlying molecular mechanisms. Chondrocytes were harvested from the joints of 1-week-old Sprague-Dawley rats. After treated with 10 μg/mL Rg1 for 2 h, the chondrocytes were cultured with 10 ng/mL IL-1β to induce cytotoxicity. Cell viability was assessed with MTT assays. Annexin V/propidium iodide staining and terminal deoxynucleotidyl transferase dUTP nick-end labeling were used to detect chondrocyte apoptosis. The contents of total Akt, phosphorylated Akt (p-Akt), Bcl-2, Bax, and cytochrome C (Cyt c) were determined by Western blotting assay. A quantitative colorimetric assay was used to determine caspase-3 activity. Our present findings have shown that pre-treatment of chondrocytes with Rg1 reduces IL-1β induced cytotoxicity/apoptosis. Rg1 pretreatment also decreases the activity of IL-1β that reduces expression of Bcl-2 and level of p-Akt, and increases Bax activity, Cyt c release, and caspase-3 activation. It also reverses the activity of IL-1β that reduces the expression of tissue inhibitor of metalloproteinase-1 expression and increased the synthesis of matrix metalloproteinase-13, with the net effect of inhibiting extracellular matrix degradation. These results indicate that Rg1 may protect chondrocytes from IL-1β-induced apoptosis via the phosphatidylinositol 3-kinase/protein kinase B signaling pathway, through preventing caspase-3 release.

Berberine ameliorates cartilage degeneration in interleukin-1β-stimulated rat chondrocytes and in a rat model of osteoarthritis via Akt signalling

Berberine, a plant alkaloid used in Chinese medicine, has broad cell-protective functions in a variety of cell lines. Chondrocyte apoptosis contributes to the pathogenesis of cartilage degeneration in osteoarthritis (OA). However, little is known about the effect and underlying mechanism of berberine on OA chondrocytes. Here, we assessed the effects of berberine on cartilage degeneration in interleukin-1β (IL-1β)-stimulated rat chondrocytes and in a rat model of OA. The results of an MTT assay and western blotting analysis showed that berberine attenuated the inhibitory effect of IL-1β on the cell viability and proliferating cell nuclear antigen expression in rat chondrocytes. Furthermore, berberine activated Akt, which triggered p70S6K/S6 pathway and up-regulated the levels of aggrecan and Col II expression in IL-1β-stimulated rat chondrocytes. In addition, berberine increased the level of proteoglycans in cartilage matrix and the thickness of articular cartilage, with the elevated levels of Col II, p-Akt and p-S6 expression in a rat OA model, as demonstrated by histopathological and immunohistochemistry techniques. The data thus strongly suggest that berberine may ameliorate cartilage degeneration from OA by promoting cell survival and matrix production of chondrocytes, which was partly attributed to the activation of Akt in IL-1β-stimulated articular chondrocytes and in a rat OA model. The resultant chondroprotective effects indicate that berberine merits consideration as a therapeutic agent in OA.