Nitric oxide and inflammatory mediators in the perpetuation of osteoarthritis

Nuciferine ameliorates osteoarthritis: An in vitro and in vivo study

Osteoarthritis (OA) is the most common musculoskeletal disease and a leading cause of pain and disability. A key hallmark of OA is cartilage degradation, which occurs due to an imbalance between the synthesis and degradation of the extracellular matrix (ECM). Interleukin-1β(IL-1β) has been reported to regulate ECM metabolism. Nuciferine (Nuc), a natural peptide extracted from the lotus leaf, possesses several significant pharmacological properties. However, the anti-inflammation of Nuc in OA has not been reported. In this study, ELISA and Western blot analyses were used to measure the production of inflammatory mediators in IL-1β-Induced mouse chondrocytes. Additionally, mice with or without surgical destabilization of the medial meniscus (DMM) were treated with intra-articular injection of Nuc. We found that Nuc significantly reduces the level of iNOS, PEG2, and IL-6 in IL-1β-induced chondrocytes. Furthermore, Nuc can ameliorate the development of OA in mice. Mechanistically, we found that the chondrocyte-protective effects of Nuc occur via the PTEN/NF-κB pathway. These findings suggest that Nuc could be a potential therapeutic agent for improving OA development.

Amentoflavone maintaining extracellular matrix homeostasis and inhibiting subchondral bone loss in osteoarthritis by inhibiting ERK, JNK and NF-κB signaling pathways

Amentoflavone (AF), a plant biflavone isolated from Selaginella sinensis ethanol extract, is characterized by anti-inflammatory and anti-oxidant properties. According to previous studies, inflammation and oxidative stress are closely related to the pathophysiology of osteoarthritis (OA). However, the effects and mechanisms of AF on OA have not been elucidated.To investigate the inhibitory effects and its molecular mechanism of AF on extracellular matrix (ECM) degradation stimulated by IL-1β as well as subchondral bone loss induced by RANKL in mice chondrocytes. Quantitative PCR was used to detect the mRNA expression of genes related to inflammation, ECM, and osteoclast differentiation. Protein expression level of iNOS, COX-2, MMP13, ADAMTS5, COL2A1, SOX9, NFATc1, c-fos, JNK, ERK, P65, IκBα was measured by western blotting. The levels of TNF-α and IL-6 in the supernatants were measured by ELISA. The amount of ECM in chondrocytes was measured using toluidine blue staining. The levels of Aggrecan and Col2a1 in chondrocytes were measured using immunofluorescence. Tartrate-resistant acid phosphatase (TRAP) staining, F-actin staining and immunofluorescence were used to detect the effect of AF on osteoclast differentiation and bone resorption. The effect of AF on destabilization of the medial meniscus (DMM)-induced OA mice can be detected in hematoxylin-eosin (H&E) staining, Safranin O green staining and immunohistochemistry.AF might drastically attenuated IL-1β-stimulated inflammation and reduction of ECM formation by blocking ERK and NF-κB signaling pathways in chondrocytes. Meanwhile, AF suppressed the formation of osteoclasts and the resorption of bone function induced by RANKL. In vivo, AF played a protective role by stabilizing cartilage ECM and inhibiting subchondral bone loss in destabilization of the medial meniscus (DMM)-induced OA mice, further proving its protective effect in the development of OA. Our study show that AF alleviated OA by suppressing ERK, JNK and NF-κB signaling pathways in OA models in vitro and DMM-induced OA mice, suggesting that AF might be a potential therapeutic agent in the treatment of OA.

Protective effects of polydatin against bone and joint disorders: the in vitro and in vivo evidence so far

Polydatin is an active polyphenol displaying multifaceted benefits. Recently, growing studies have noticed its potential therapeutic effects on bone and joint disorders (BJDs). Therefore, this article reviews recent in vivo and in vitro progress on the protective role of polydatin against BJDs. An insight into the underlying mechanisms is also presented. It was found that polydatin could promote osteogenesis in vitro, and symptom improvements have been disclosed with animal models of osteoporosis, osteosarcoma, osteoarthritis and rheumatic arthritis. These beneficial effects obtained in laboratory could be mainly attributed to the bone metabolism-regulating, anti-inflammatory, antioxidative, apoptosis-regulating and autophagy-regulating functions of polydatin. However, studies on human subjects with BJDs that can lead to early identification of the clinical efficacy and adverse effects of polydatin have not been reported yet. Accordingly, this review serves as a starting point for pursuing clinical trials. Additionally, future emphasis should also be devoted to the low bioavailability and prompt metabolism nature of polydatin. In summary, well-designed clinical trials of polydatin in patients with BJD are in demand, and its pharmacokinetic nature must be taken into account.

Urolithin B reduces cartilage degeneration and alleviates osteoarthritis by inhibiting inflammation

Osteoarthritis is the most prevalent degenerative joint disease reported worldwide. Conventional treatment strategies mainly focus on medication and involve surgical joint replacement. The use of these therapies is limited by gastrointestinal complications and the lifespan of joint prostheses. Hence, safe and efficacious drugs are urgently needed to impede the osteoarthritis progression. Urolithin B, a metabolite of ellagic acid in the gut, exhibits anti-inflammatory and antioxidant properties; however, its role in osteoarthritis remains unclear. In this study, we demonstrated that urolithin B efficiently inhibits the inflammatory factor-induced production of matrix metalloproteinases (MMP3 and MMP13) in vitro and upregulates the expression of type II collagen and aggrecan. Urolithin B alleviates cartilage erosion and osteophyte formation induced by anterior cruciate ligament transections. Moreover, urolithin B inhibits the activation of the NF-κB pathway by reducing the phosphorylation of Iκb-α and the nuclear translocation of P65. In summary, urolithin B significantly inhibits inflammation and alleviates osteoarthritis. Hence, urolithin B can be considered a potential agent suitable for the effective treatment of osteoarthritis in the future.

5-aminosalicylic acid suppresses osteoarthritis through the OSCAR-PPARγ axis

Osteoarthritis (OA) is a progressive and irreversible degenerative joint disease that is characterized by cartilage destruction, osteophyte formation, subchondral bone remodeling, and synovitis. Despite affecting millions of patients, effective and safe disease-modifying osteoarthritis drugs are lacking. Here we reveal an unexpected role for the small molecule 5-aminosalicylic acid (5-ASA), which is used as an anti-inflammatory drug in ulcerative colitis. We show that 5-ASA competes with extracellular-matrix collagen-II to bind to osteoclast-associated receptor (OSCAR) on chondrocytes. Intra-articular 5-ASA injections ameliorate OA generated by surgery-induced medial-meniscus destabilization in male mice. Significantly, this effect is also observed when 5-ASA was administered well after OA onset. Moreover, mice with DMM-induced OA that are treated with 5-ASA at weeks 8-11 and sacrificed at week 12 have thicker cartilage than untreated mice that were sacrificed at week 8. Mechanistically, 5-ASA reverses OSCAR-mediated transcriptional repression of PPARγ in articular chondrocytes, thereby suppressing COX-2-related inflammation. It also improves chondrogenesis, strongly downregulates ECM catabolism, and promotes ECM anabolism. Our results suggest that 5-ASA could serve as a DMOAD.

Pachymic acid suppresses the inflammatory response of chondrocytes and alleviates the progression of osteoarthritis via regulating the Sirtuin 6/NF-κB signal axis

Articular cartilage degeneration is a characteristic pathological change of osteoarthritis (OA). Pachymic acid (PA) is an active ingredient found in Poria cocos. Previous studies have shown that PA has anti-inflammatory effects on a variety of diseases. However, the role of PA in OA and its underlying mechanisms has not been clearly elucidated. In this study, we investigated potential protective effect of PA on OA through cell experiments in vitro and animal experiments in vivo. PA inhibited interleukin-1β-induced inflammatory mediator production in chondrocytes, which includes nitric oxide, inducible nitric oxide synthase, prostaglandin E2, cyclooxygenase-2, tumor necrosis factor alpha and interleukin-6. Meanwhile, PA also reversed the up-regulation of matrix metalloproteinase-3 and thrombospondin motifs 5, and the down-regulation of collagen type II and aggrecan in IL-1β-treated chondrocytes. Mechanistically, our findings revealed that PA-mediated overexpression of SIRT6 inhibited the NF-κB signaling pathway. In vivo, PA contributes to improve cartilage damage in the mouse OA model. In summary, PA inhibited IL-1β-induced inflammation and extracellular matrix degeneration by promoting SIRT6 expression and inhibiting the NF-κB signaling pathway, which indicates that PA is beneficial for the treatment of OA.

The Role of Genetics and Epigenetic Regulation in the Pathogenesis of Osteoarthritis

Osteoarthritis (OA) is progressive disease characterised by cartilage degradation, subchondral bone remodelling and inflammation of the synovium. The disease is associated with obesity, mechanical load and age. However, multiple pro-inflammatory immune mediators regulate the expression of metalloproteinases, which take part in cartilage degradation. Furthermore, genetic factors also contribute to OA susceptibility. Recent studies have highlighted that epigenetic mechanisms may regulate the expression of OA-associated genes. This review aims to present the mechanisms of OA pathogenesis and summarise current evidence regarding the role of genetics and epigenetics in this process.

Connection between Osteoarthritis and Nitric Oxide: From Pathophysiology to Therapeutic Target

Osteoarthritis (OA), a disabling joint inflammatory disease, is characterized by the progressive destruction of cartilage, subchondral bone remodeling, and chronic synovitis. Due to the prolongation of the human lifespan, OA has become a serious public health problem that deserves wide attention. The development of OA is related to numerous factors. Among the factors, nitric oxide (NO) plays a key role in mediating this process. NO is a small gaseous molecule that is widely distributed in the human body, and its synthesis is dependent on NO synthase (NOS). NO plays an important role in various physiological processes such as the regulation of blood volume and nerve conduction. Notably, NO acts as a double-edged sword in inflammatory diseases. Recent studies have shown that NO and its redox derivatives might be closely related to both normal and pathophysiological joint conditions. They can play vital roles as normal bone cell-conditioning agents for osteoclasts, osteoblasts, and chondrocytes. Moreover, they can also induce cartilage catabolism and cell apoptosis. Based on different conditions, the NO/NOS system can act as an anti-inflammatory or pro-inflammatory agent for OA. This review summarizes the studies related to the effects of NO on all normal and OA joints as well as the possible new treatment strategies targeting the NO/NOS system.

Cerium oxide nanoparticles protect against chondrocytes and cartilage explants from oxidative stress via Nrf2/HO-1 pathway in temporomandibular joint osteoarthritis

Oxidative stress is closely linked to the etiology of temporomandibular joint osteoarthritis. (TMJ-OA) and is an important therapeutic target. Cerium oxide nanoparticles (CNPs) have been broadly studied owing to their powerful antioxidant properties and potential preventive and therapeutic effects against chronic diseases. The current study was designed to explore the protective effects of CNPs on the progression of TMJ-OA and their potential mechanisms. We detected the ability of CNPs to eliminate reactive oxygen species (ROS) in chondrocytes. Moreover, their protective effects on chondrocytes were detected in the level of gene and protein. Furthermore, TUNEL assay, histology and safranin O-fast green staining were used to detect the beneficial effects of CNPs on cartilage explants. The mechanism of CNPs, protecting condylar cartilage by reducing inflammation, was further explored by knocking down the Nuclear factor-erythroid 2-related factor (Nrf2) gene. CNPs could reduce the ROS levels in chondrocytes and cartilage explants and reverse the IL-1β-induced imbalance of cartilage matrix metabolism and apoptosis. The protective effects of CNPs on cartilage were lost after key antioxidant factors including Nrf2 and heme-oxygenase 1(HO-1) were significantly reduced. In conclusion, this study demonstrated for the first time that activating the Nrf2/HO-1 signaling pathway by CNPs might have therapeutic potential for TMJ-OA.

Stevioside targets the NF-κB and MAPK pathways for inhibiting inflammation and apoptosis of chondrocytes and ameliorates osteoarthritis in vivo

Osteoarthritis (OA) is a joint disease that is characterized by articular cartilage degeneration and destruction. Stevioside (SVS) is a diterpenoid glycoside extracted from Stevia rebaudiana Bertoni with some specific effects against inflammatory and apoptotic, whereas it is still unclear what function SVS has in osteoarthritis. This study focuses on the anti-inflammatory and anti-apoptosis functions of SVS on chondrocytes induced by interleukin (IL)-1beta, and the role of SVS in an osteoarthritis model for mice. We can detect the production of inflammatory factors such as nitric oxide (NO) and prostaglandin E2 (PGE2) using real-time quantitative polymerase chain reaction (RT-qPCR), the Griess reaction, and enzyme linked immunosorbent assay (ELISA). On the basis of Western blot, we have observed the protein expressions of cartilage matrix metabolism, inflammatory factors, and apoptosis of chondrocytes. Simultaneously, the pharmacological effects of SVS in mice were evaluated by hematoxylin and eosin (HE), toluidine blue, Safranin O, and immunohistochemical staining. The results show that SVS slows extracellular matrix degradation and chondrocyte apoptosis. In addition, SVS mediates its cellular effect by inhibiting the activation of mitogen-activated protein kinase (MAPK) and nuclear factor kappa B (NF-κB) signaling pathways. Meanwhile, molecular docking studies revealed that SVS has excellent binding capabilities to p65, extracellular signal-regulated kinase (ERK), p38, and c-Jun N-terminal kinase (JNK). The study suggests that SVS can be developed as a potential osteoarthritis treatment.

Anti-Inflammatory and Chondro-Protective Effects of Acidic Polysaccharide from Enteromorpha Prolifera in Experimental Models of Osteoarthritis In-Vitro and In-Vivo

OBJECTIVE

Osteoarthritis (OA) progression has been shown to increase the expression of inflammatory cytokines in joints, leading to the destruction of cartilage matrix. Interleukin (IL)-1β is a potent inflammatory cytokine associated with osteoarthritic synovial fluid. The protective effects of polysaccharides from Enteromorpha prolifera against acute hepatic injury was reported.

DESIGN

In this study, we examined the effects of Enteromorpha polysaccharide extracts (EPEs) in the treatment of OA. The effects of the EPEs were assessed using an IL-1β-stimulated SW1353 and SW982 cells. The expression levels of specific mRNA and proteins were evaluated using semi-quantitative reverse transcription polymerase chain reaction (sqRT-PCR) and western immunoblotting. An OA animal study involving C57BL/6J mice was also conducted to assess the effects on tactile sensitivity and anterior cruciate ligament transection (ACLT).

RESULTS

Acidic polysaccharide extract (APE) was shown to significantly reduce cytokine and chemokine mRNA levels in IL-1β-stimulated SW1353 and SW982 cells and attenuate the expression of proinflammatory cytokines and p38/AP-1 in SW1353 cells. APE was also shown to minimize the effect of osteolytic lesions in the knee joints of ACLT-induced osteoarthritic mice.

CONCLUSIONS

APE is a potent inhibitor of joint degeneration associated with OA.

Interleukin 1β and lipopolysaccharides induction dictate chondrocyte morphological properties and reduce cellular roughness and adhesion energy comparatively

Osteoarthritis (OA) is a whole joint disease marked by the degradation of the articular cartilage (AC) tissue, chronic inflammation, and bone remodeling. Upon AC's injury, proinflammatory mediators including interleukin 1β (IL1β) and lipopolysaccharides (LPS) play major roles in the onset and progression of OA. The objective of this study was to mechanistically detect and compare the effects of IL1β and LPS, separately, on the morphological and nanomechanical properties of bovine chondrocytes. Cells were seeded overnight in a full serum medium and the next day divided into three main groups: A negative control (NC) of a reduced serum medium and 10 ng/ml IL1ß or 10 ng/ml LPS-modified media. Cells were induced for 24 h. Nanomechanical properties (elastic modulus and adhesion energy) and roughness were quantified using atomic force microscopy. Nitric oxide, prostaglandin 2 (PGE2), and matrix metalloproteinases 3 (MMP3) contents; viability of cells; and extracellular matrix components were quantified. Our data revealed that viability of the cells was not affected by inflammatory induction and IL1ß induction increased PGE2. Elastic moduli of cells were similar among IL1β and NC while LPS significantly decreased the elasticity compared to NC. IL1ß induction resulted in least cellular roughness while LPS induction resulted in least adhesion energy compared to NC. Our images suggest that IL1ß and LPS inflammation affect cellular morphology with cytoskeleton rearrangements and the presence of stress fibers. Finally, our results suggest that the two investigated inflammatory mediators modulated chondrocytes' immediate responses to inflammation in variable ways.

Glutamine exerts a protective effect on osteoarthritis development by inhibiting the Jun N-terminal kinase and nuclear factor kappa-B signaling pathways

Strategies for treating osteoarthritis (OA) have become a research focus because an effective treatment for OA is unavailable. The objective of this study was to explore the effects and underlying mechanisms of glutamine (Gln) in OA. First, the chondrocytes were identified and a standard IL-1β-induced OA model was established. After treatment with Gln or saline, the viability and apoptosis of chondrocytes were evaluated using a CCK-8 assay and flow cytometry analysis, which revealed that Gln can improve the IL-1β-induced OA cells. Meanwhile, Gln can enhance the expression of aggrecan and collagen II, which are protective proteins for articular cartilage. Instead, Gln inhibited the expression of matrix metalloproteinase-1 (MMP-1) and matrix metalloproteinase-13 (MMP-13), which can degrade cartilage. To better understand the underlying mechanisms of Gln in IL-1β-induced chondrocytes, the classical OA pathways of JNK and NF-κB were examined at the protein and mRNA levels using western blot and qRT-PCR analyses. We found that JNK and NF-κB were downregulated gradually depending on the Gln dose and protective and destructive factors changed based on changes of JNK and NF-κB. The effects of high-dose Gln were more effective than low-dose. Moreover, Gln was applied to the animal OA model to check the effects in vivo. The results showed that Gln attenuated cartilage degeneration and decreased OARSI scores, which demonstrated that Gln can improve OA. The experiments showed that Gln can benefit mice with OA by inhibiting the JNK and NF-κB signaling pathways.

SEMA6D, Negatively Regulated by miR-7, Contributes to C28/I2 chondrocyte's Catabolic and Anabolic Activities via p38 Signaling Pathway

MiR-7 has been recognized as an osteoarthritis (OA-)-promoting factor, but the specific downstream pathway of miR-7 still remains unknown. Further investigation of the molecular regulatory mechanism of miR-7 might help develop a novel therapeutic method for OA. In this study, we revealed that Semaphorin 6D (SEMA6D) was a direct target gene of miR-7 and presented a negative regulatory relation with SEMA6D in vitro and in vivo. SEMA6D could improve OA in rat OA models, as indicated by H&E and Safranin O-Fast green staining, and also μCT analysis. Further evaluation of SEMA6D suggested that SEMA6D promotes the anabolism and reduces the catabolism of C28/I2 chondrocytes via inhibiting the activation of the p38 pathway. The present research illustrated that SEMA6D is a negatively regulatory factor of miR-7 and a pivotal mediator of catabolism and anabolism in C28/I2 chondrocytes. SEMA6D exerts its function via inhibiting the activation of the p38 pathway.

The protective effect of kirenol in osteoarthritis: an in vitro and in vivo study

BACKGROUND

Osteoarthritis (OA) is a chronic degenerative disease, its main characteristic involves articular cartilage destruction and inflammation response, absent of effective medical treatment. Our current research aimed to explore anti-inflammatory effect of kirenol, a diterpenoid natural product compound, in the development of OA and its potential molecular mechanism through in vitro and in vivo study.

METHODS

In vitro, chondrocytes were pretreated with kirenol for 2 h before IL-1β stimulation. Production of NO, PGE2, TNF-α, IL-6, aggrecan, collagen-II, MMP13and ADAMTS5 were evaluated by the Griess reaction and ELISAs. The mRNA (aggrecan and collagen-II) and protein expression (COX-2, iNOS, P65, IκB, PI3K, AKT) were measured by qRT-PCR and Western blot respectively. Immunofluorescence was used to assess the expression of collagen-II and P65. The in vivo effect of kirenol was evaluated in mice OA models induced by destabilization of the medial meniscus (DMM).

RESULTS

We found that kirenol inhibited IL-1β-induced expression of NO, PGE2, TNF-α, IL-6, COX-2, iNOS, ADAMTS-5. Besides, kirenol remarkably decreased IL-1β-induced degradation of aggrecan and collagen-II. Furthermore, kirenol significantly inhibited IL-1β-induced phosphorylation of PI3K/Akt and NF-κB signaling. In vivo, the cartilage in kirenol-treated mice exhibited less cartilage degradation and lower OARSI scores.

CONCLUSIONS

Taken together, the results of this study provide potent evidence that kirenol could be utilized as a potentially therapeutic agent in prevention and treatment of OA.

Sex-Specific Reduction in Inflammation of Osteoarthritic Human Chondrocytes and Nutraceutical-Dependent Extracellular Matrix Formation

Introduction

The aim of this study was to investigate the ability of osteoarthritic human chondrocytes to produce articular cartilage (AC) tissues with a reduced inflammatory environment in response to 4 anti-inflammatory nutraceuticals: alpha-tocopherol (Alpha), gallic acid (G), ascorbic acid (AA), and catechin hydrate (C).

Methods

Chondrocytes isolated from patients who underwent total knee arthroplasty surgeries were divided into groups (9 male; mean age, 66.2 ± 3.5 years and 11 female; mean age, 64.2 ± 3.1 years). Cells were cultured based on sex and supplemented with either a negative control (NC) medium or NC plus one of the nutraceuticals at a concentration of 50 μM. At day 21, cultures were characterized histologically, biochemically, and for gene expression of vital markers.

Results

At day 21, 62.3% and 66.2% reduction in nitric oxide (NO) content was evident for female and male cells, respectively. G-treatment of female cells resulted in the lowest expression of nitric oxide synthase-2 (NOS2), matrix metalloproteinase-13 (MMP13), and collagen type-10 (COL10). Alpha-treatment of male cells resulted in the lowest expression of NOS2, bone morphogenic protein-2, MMP13, COL10 and tumor necrosis factor alpha induced protein-6 (TNFAIP6) relative to NC. AA and Alpha treatment resulted in the highest glycosaminoglycan (GAG) content for female and male cultures, respectively.

Conclusion

A sex-dependent response of osteoarthritic chondrocytes to nutraceutical treatment was evident. Our results suggest the use of G for female cells and Alpha for male cells in OA applications seems to be favorable in reducing inflammation and enhancing chondrocytes' ability to form AC tissues.

Betulin Alleviates the Inflammatory Response in Mouse Chondrocytes and Ameliorates Osteoarthritis via AKT/Nrf2/HO-1/NF-κB Axis

Osteoarthritis (OA) is a common degenerative joint disease featuring the degeneration, destruction, and ossification of cartilage. Inflammation which may facilitate OA occurrence and development is considered as the main pathological factor. Betulin, a natural product extracted from birch bark, has been commonly used for inflammation treatment; however, its role in OA remains unclear. This study is aimed to explore whether betulin can suppress IL-1β–induced inflammation in chondrocytes and alleviate OA in vitro and in vivo. In in vitro studies, the generation of pro-inflammatory factors, such as interleukin-6 (IL-6), tumor necrosis factor alpha (TNF-α), prostaglandin E2 (PGE2), and nitric oxide (NO), was assessed using the enzyme-linked immunosorbent assay (ELISA) and Griess reaction. As revealed by results, betulin inhibited the expression of pro-inflammatory mediators. In addition, the protein expressions of inducible nitric oxide synthase (iNOS), cyclooxygenase-2 (COX-2), matrix metalloproteinase (MMP-13), thrombospondin motifs 5 (ADAMTS5), Collagen II, and Aggrecan were quantified using Western blot analysis. We found that betulin could inhibit the generation of COX-2 and iNOS induced by IL-1β, indicating that betulin has anti-inflammatory effects in chondrocytes. Furthermore, betulin downregulates the expression of MMP-13 and ADAMTS-5 and upregulates the expression of Collagen II and Aggrecan, indicating that it can inhibit the degradation of the extracellular matrix. In mechanism, betulin activated the AKT/Nrf2 pathway and inhibited the phosphorylation of p65. In in vivo studies, administration of betulin in vivo could inhibit cartilage destruction and inflammatory progression. Therefore, these findings suggest that betulin may alleviate IL-1β–induced OA via the AKT/Nrf2/HO-1/NF-κB signal axis, and betulin may be a potential drug for the treatment of OA.

Extracellular vesicles as novel approaches for the treatment of osteoarthritis: a narrative review on potential mechanisms

Osteoarthritis (OA) is a progressive degeneration of articular cartilage with involvement of synovial membrane, and subchondral bone. Current treatment approaches have focused on controlling the OA symptoms, pain, and inflammation. Recently, cell-based therapies, including the application of stem cells such as mesenchymal stem cells (MSCs), have been introduced for restoration of the articular cartilage. Despite promising outcomes, there are some limitations in the application of MSCs for OA treatment. It has been demonstrated that the regenerative potential of stem cells is related to the production of paracrine factors. Extracellular vehicles (EVs), the main component of cell secretome, are membrane-bounded structures that deliver biologically active agents. The delivery of molecules (e.g., nucleic acids, proteins, and lipids) leads to cell-to-cell communication and the alteration of cell functions. In this review, general characteristics of EVs, as well as their potential mechanisms in the prevention and treatment of OA were considered. Based on in vitro and in vivo studies, EVs have shown to contribute to cartilage regeneration via suppression of degenerative factors and regulation of chondrocyte function in the synthesis of extracellular matrix components. Also, they inhibit the progression of OA or protect the cartilage from degradation via their impact on inflammatory cytokines. The different signaling pathways of EVs against the pathologic features of OA were summarized in this review. According to the results obtained from several investigations, more investigations should be design to prove the safety and effectiveness of EVs in the treatment and prevention of OA progression.

β-Hydroxyisovalerylshikonin inhibits IL-1β-induced chondrocyte inflammation via Nrf2 and retards osteoarthritis in mice

Osteoarthritis is a chronic degenerative disease characterized by cartilage destruction. It is the fourth most disabling disease worldwide and is currently incurable. Inflammation and extracellular matrix (ECM) degradation are considered to be substantial reasons for accelerating the progression of OA. β-Hydroxyisoamylshikonin (β-HIVS) is a natural naphthoquinone compound with anti-inflammatory and antioxidant activity. However, the effect of β-HIVS on OA is still unclear. In this study, we found that β-HIVS can down-regulate the expression of NO, PEG2, IL-6, TNF-α, COX-2, and iNOS, suggesting its anti-inflammatory effects in chondrocytes; we also found that β-HIVS may down-regulate the expression of ADAMTS5 and MMP13 and up-regulate the expression of aggrecan and collagen II to inhibit the degradation of ECM. Mechanistically, β-HIVS inhibited the NFκB pathway by activating the Nrf2/HO-1 axis, thereby exerting its anti-inflammatory and inhibitory effects on ECM degradation. In vivo experiments also proved the therapeutic effects of β-HIVS on OA in mice, and Nrf2 is the target of β-HIVS. These findings indicate that β-HIVS may become a new drug for the treatment of OA.

Maltol inhibits the progression of osteoarthritis via the nuclear factor-erythroid 2-related factor-2/heme oxygenase-1 signal pathway in vitro and in vivo

Osteoarthritis (OA) is a common degenerative joint disease characterized by articular cartilage degeneration and inflammation. Currently, there is hardly any effective treatment for OA due to its complicated pathology and the severe side effects of the treatment drugs used. It has been reported that maltol, a Maillard reaction product derived from ginseng, inhibits inflammation and oxidative stress in several animal models. However, the potential anti-inflammatory effects of maltol in OA treatment are unknown. This study aimed to evaluate the anti-inflammatory effects of maltol on interleukin (IL)-1β-induced mouse chondrocytes and protective effects of maltol on these chondrocytes in medial meniscus destabilization (DMM) OA mouse models. Mice, randomly divided into maltol (n = 15), vehicle (n = 15) and control (n = 15) groups were treated with the same dose of maltol or saline, respectively. The cartilage tissues were extracted for histological analysis 8 weeks postoperative. For the in vitro studies, chondrocytes were treated with 10 ng mL-1 IL-1β combined with maltol at different concentrations. In vitro assays showed that the maltol pre-treatment significantly inhibited the expressions of multiple inflammatory factors induced by IL-1β, such as inducible nitric oxide synthase (iNOS), cyclooxygenase-2 (COX-2), prostaglandin E2 (PGE2), nitric oxide (NO), interleukin-6 (IL-6) and tumor necrosis factor (TNF-α). In addition, maltol alleviated the degradation of the extracellular matrix (ECM) by inhibiting the expressions of matrix metalloproteinase-13 (MMP13) and thrombospondin motif 5 (ADAMTS5), as well as reversing the degradation of aggrecan and collagen II. Moreover, maltol suppressed nuclear factor kappa B (NF-κB) signaling by activating the nuclear factor-erythroid 2-related factor-2 (Nrf2) in in vitro and in vivo studies. These findings indicate that maltol reduces the inflammation induced by IL-1β in chondrocytes. Therefore, the results of this study indicated that maltol may be a potential drug for the effective treatment of OA.

Ferulic acid suppresses interleukin-1β-induced degeneration of chondrocytes isolated from patients with osteoarthritis through the SIRT1/AMPK/PGC-1α signaling pathway

Background

Interleukin‐1β (IL‐1β) is involved in osteoarthritis pathogenesis and mediates a series of toxic processes including the production of matrix metalloproteinase and inflammatory regulators which are suppressed by activation of silent information regulator 1 (SIRT1). We aimed to determine the effects of ferulic acid (FA) on IL‐1β‐induced osteoarthritis chondrocyte degeneration.

Methods

We examined the effects of FA on osteoarthritis chondrocyte viability and SIRT1 activation. The impact of FA on IL‐1β‐induced osteoarthritis chondrocyte toxicity was determined by prostaglandin E2 (PGE₂), nitrite, IL‐6, components of the extracellular matrix, and markers of oxidative stress. Finally, we determined whether these effects were mediated through SIRT1 by inhibiting SIRT1 activity using SIRT1 inhibitor Sirtinol.

Results

We found that FA activated SIRT1/AMPK/PGC‐1α signaling pathway and attenuated IL‐1β‐induced osteoarthritis chondrocyte degeneration by suppressing the production of IL‐6, PGE₂, nitrite, Collagen I, Runx‐2, MMP‐1, MMP‐3, and MMP‐13, enhancing Collagen II and Aggrecan expression and inhibiting oxidative stress. Inhibition of SIRT1 by Sirtinol attenuated the protective effects of FA.

Conclusion

Our findings reveal that FA prevents IL‐1β‐induced osteoarthritis chondrocyte toxicity, which suggests that FA may be a potential therapy for osteoarthritis and warrants further investigation for its clinical application.

Hydrogen sulfide protects against IL-1β-induced inflammation and mitochondrial dysfunction-related apoptosis in chondrocytes and ameliorates osteoarthritis

The inflammatory environment and excessive chondrocyte apoptosis have been demonstrated to play crucial roles in the onset of osteoarthritis (OA). Hydrogen sulfide (H2 S), a gaseous signalling molecule, exerts an inhibitory effect on inflammation and apoptosis in several degenerative diseases. However, the protective effect of H2 S against OA has not been fully clarified, and its underlying mechanism should be examined further. In the current study, the role of endogenous H2 S in the pathogenesis of OA and its protective effects on interleukin (IL)-1β-induced chondrocytes were identified. Our data revealed decreased H2 S expression in both human degenerative OA cartilage tissue and IL-1β-induced chondrocytes. Pretreatment with the H2 S donor sodium hydrosulfide (NaHS) dramatically attenuated IL-1β-induced overproduction of inflammatory cytokines and improved the balance between anabolic and catabolic chondrocyte capacities, and these effects were dependent on PI3K/AKT pathway-mediated inhibition of nuclear factor kappa B (NF-κB). Moreover, mitochondrial dysfunction-related apoptosis was significantly reversed by NaHS in IL-1β-stimulated chondrocytes. Mechanistically, NaHS partially suppressed IL-1β-induced phosphorylation of the mitogen-activated protein kinase (MAPK) cascades. Furthermore, in the destabilization of the medial meniscus mouse model, OA progression was ameliorated by NaHS administration. Taken together, these results suggest that H2 S may antagonize IL-1β-induced inflammation and mitochondrial dysfunction-related apoptosis via selective suppression of the PI3K/Akt/NF-κB and MAPK signalling pathways, respectively, in chondrocytes and may be a potential therapeutic agent for the treatment of OA.

Cardamonin Attenuates Inflammation and Oxidative Stress in Interleukin-1β-Stimulated Osteoarthritis Chondrocyte through the Nrf2 Pathway

Osteoarthritis (OA) is a chronic degenerative joint disease characterized by the deterioration of articular cartilage. The progression of OA leads to an increase in inflammatory mediators in the joints, thereby promoting the destruction of the cartilage matrix. Recent studies have reported on the anti-inflammatory and antioxidant properties of cardamonin, which also appears to interact with cellular targets, such as nuclear erythroid 2-related factor 2 (Nrf2), extracellular signal-regulated kinase (ERK), and mammalian target of rapamycin (mTOR) during the progression of tumors. To date, few studies have investigated the effects of cardamonin on chondrocyte inflammation. In the current study, we determined that treating interleukin-1 beta (IL-1β-stimulated chondrocyte cells) with cardamonin significantly reduced the release of nitric oxide (NO) and prostaglandin E2 (PGE2) and significantly inhibited the expression of pro-inflammatory proteins, including inducible nitric oxide synthase (iNOS) and cyclooxygenase 2 (COX2). Cardamonin was also shown to: (1) inhibit the activation and production of matrix metalloproteinases (MMPs), (2) suppress the nuclear factor-κB (NF-κB) signaling pathway, (3) suppress the expression of toll-like receptor proteins, (4) activate the Nrf2 signaling pathway, and (5) increase the levels of antioxidant proteins heme oxygenase-1 (HO-1) and NAD(P)H:quinone oxidoreductase 1 (NQO1). The increase in antioxidant proteins led to corresponding antioxidant effects (which were abolished by Nrf2 siRNA). Our findings identify cardamonin as a candidate Nrf2 activator for the treatment and prevention of OA related to inflammation and oxidative stress.

Decursin alleviates the aggravation of osteoarthritis via inhibiting PI3K-Akt and NF-kB signal pathway

Osteoarthritis (OA) is a common joint disease that takes joint degeneration or aging as its pathological basis, and joint swelling, pain or dysfunction as its main clinical manifestations. Decursin (DE), the major active component isolated from Angelica gigas Nakai, has been demonstrated to possess anti-inflammatory effect in many diseases. But, the specific physiological mechanism of DE on OA is not clear yet. Therefore, the object of this study was to assess the therapeutic effect of DE on OA, and to explore its potential anti-inflammatory mechanisms. In vitro cell experiments, the inflammatory response in chondrocytes is mediated via interleukin-1β (IL-1β), which led to abnormal secretion of pro-inflammatory factors, such as prostaglandin E2 (PGE₂), interleukin-6 (IL-6), tumor necrosis factor alpha (TNF-α), cyclooxygenase-2 (COX-2), nitric oxide (NO) and inducible nitric oxide synthase (iNOS). These cytokines were all decreased by the preconditioning of DE in a dose-dependent form of 1, 5, and 10 µM. Moreover, DE could restrain IL-1β-mediated inflammatory reaction and the collapse of extracellular matrix (ECM) via reducing the secretion of ADAMTS (a disintegrin and metalloproteinase with thrombospondin motifs) and MMPs (matrix metalloproteinases). In short, DE restrained IL-1β-mediated abnormal excitation of PI3K/AKT/NF-κB axis. Furthermore, molecular docking analysis showed that DE has a strong binding affinity with the inhibitory targets of PI3K. In vivo animal studies, DE treatment could helped to improve destruction of articular cartilage and decreased the serum inflammatory factor levels in an operationally induced mouse OA model. To sum up, these data obtained from the experiment indicate that DE has good prospects for the treatment of osteoarthritis.

Puerarin suppresses inflammation and ECM degradation through Nrf2/HO-1 axis in chondrocytes and alleviates pain symptom in osteoarthritic mice

Osteoarthritis (OA) is the most common degenerative joint disorder with no effective drugs. Puerarin is a dietary supplement that has wide-ranging pharmacological effects. This study aimed to investigate the effects of Puerarin on OA. The effects of Puerarin on apoptosis, extracellular matrix (ECM) metabolism, and inflammation-related factors were assessed; also, the nuclear factor-κB (NF-κB) signaling pathway and Nrf2/HO-1 (nuclear factor (erythroid-derived 2)-like 2/heme oxygenase-1) axis were evaluated to elucidate the working mechanism of Puerarin. Mice were fed with Puerarin to evaluate the therapeutic effect of Puerarin on Osteoarthritis in vivo. The results showed that Puerarin suppressed inflammatory mediators and apoptosis induced by IL-1β treatment in chondrocytes, it may also suppress ECM degradation in IL-1β treated chondrocytes. The mechanism study revealed that Nrf2/HO-1 pathway is involved in Puerarin induced inhibition of NF-κB signaling pathway. Finally, in vivo study demonstrated that Puerarin could postpone the progression of OA in mice and relieve the symptoms of pain. In conclusion, Puerarin may potentially alleviate OA progression, and the mechanism may relate to the Nrf2/HO-1 pathway regulation.

The protective effect of hesperetin in osteoarthritis: an in vitro and in vivo study

Osteoarthritis (OA), a progressive joint disorder, is principally characterized by the degeneration and destruction of articular cartilage. Previous research studies demonstrated that inflammation and ECM degradation play a major role in OA development. Hesperetin, the aglycone of neohesperidin found in the peel of Citrus aurantium L. (Rutaceae), demonstrated in several studies potential anti-inflammatory activity in a variety of diseases. However, the mechanisms by which hesperetin plays a protective role in osteoarthritis (OA) are not completely understood. In this study, we found the anti-inflammatory effects of hesperetin in the progression of OA in both in vitro and in vivo experiments. In vitro, IL-1β-induced expression of inducible nitric oxide synthase (iNOS), cyclooxygenase-2 (COX-2), nitric oxide (NO), tumor necrosis factor alpha (TNF-α), prostaglandin E2 (PGE2), and interleukin-6 (IL-6) were inhibited by hesperetin. Moreover, hesperetin down-regulated the IL-1β-stimulated matrix metalloproteinase-13 (MMP-13) and thrombospondin motifs 5 (ADAMTS-5) while up-regulating collagen type II and aggrecan. Mechanistically, we revealed that hesperetin suppressed nuclear factor kappa B (NF-κB) signaling by activating the nuclear factor (erythroid-derived 2)-like 2 (Nrf2) in IL-1β-induced chondrocytes. Hesperetin-induced repression of OA development is shown using a DMM model. Taken together, our findings suggest that hesperetin may be a novel potential therapeutic agent for repressing the development of OA.

Maltol prevents the progression of osteoarthritis by targeting PI3K/Akt/NF-κB pathway: In vitro and in vivo studies

Osteoarthritis (OA), a prevalent degenerative arthritis disease, principle characterized by the destruction of cartilage and associated with the inflammatory response. Maltol, a product formed during the processing of red ginseng (Panax ginseng, CA Meyer), has been reported to have the potential effect of anti-inflammatory. However, its specific mechanisms are not demonstrated. We investigated the protective effect of maltol in the progression of OA both in vitro and in vivo experiments. Human chondrocytes were pre-treated with maltol (0, 20, 40, 60 μM, 24 hours) and incubated with IL-1β (10 ng/mL, 24 hours) in vitro. Expression of PGE2, TNF-α and NO was measured by the ELISA and Griess reaction. The expression of iNOs, COX-2, aggrecan, ADAMTS-5, MMP-13, IκB-α, p65, P-AKT, AKT, PI3K and P-PI3K was analysed by Western blotting. The expression of collagen II and p65-active protein was detected by immunofluorescence. Moreover, the serious level of OA was evaluated by histological analysis in vivo. We identified that maltol could suppress the IL-1β-stimulated generation of PGE2 and NO. Besides, maltol not only suppressed the production of COX-2, iNOs, TNF-α, IL-6, ADAMTS-5, MMP-13, but also attenuated the degradation of collagen II and aggrecan. Furthermore, maltol remarkably suppressed the phosphorylation of PI3K/AKT and NF-κB induced by IL-1β in human OA chondrocytes. Moreover, maltol could block the cartilage destroy in OA mice in vivo. To date, all data indicate maltol is a potential therapeutic agent by inhibiting inflammatory response via the regulation of NF-κB signalling for OA.

Amentadione from the Alga Cystoseira usneoides as a Novel Osteoarthritis Protective Agent in an Ex Vivo Co-Culture OA Model

Osteoarthritis (OA) remains a prevalent chronic disease without effective prevention and treatment. Amentadione (YP), a meroditerpenoid purified from the alga Cystoseira usneoides, has demonstrated anti-inflammatory activity. Here, we investigated the YP anti-osteoarthritic potential, by using a novel OA preclinical drug development pipeline designed to evaluate the anti-inflammatory and anti-mineralizing activities of potential OA-protective compounds. The workflow was based on in vitro primary cell cultures followed by human cartilage explants assays and a new OA co-culture model, combining cartilage explants with synoviocytes under interleukin-1β (IL-1β) or hydroxyapatite (HAP) stimulation. A combination of gene expression analysis and measurement of inflammatory mediators showed that the proposed model mimicked early disease stages, while YP counteracted inflammatory responses by downregulation of COX-2 and IL-6, improved cartilage homeostasis by downregulation of MMP3 and the chondrocytes hypertrophic differentiation factors Col10 and Runx2. Importantly, YP downregulated NF-κB gene expression and decreased phosphorylated IkBα/total IkBα ratio in chondrocytes. These results indicate the co-culture as a relevant pre-clinical OA model, and strongly suggest YP as a cartilage protective factor by inhibiting inflammatory, mineralizing, catabolic and differentiation processes during OA development, through inhibition of NF-κB signaling pathways, with high therapeutic potential.

Astilbin prevents osteoarthritis development through the TLR4/MD-2 pathway

Osteoarthritis has become one of the main diseases affecting the life of many elderly people with high incidence of disability, and local chronic inflammation in the joint cavity is the most crucial pathological feature of osteoarthritis. Astilbin is the main active component in a variety of natural plants such as Hypericum perforatum and Sarcandra glabra, which possess antioxidant and anti‐inflammatory effects. At present, there is no study about the protective effect of Astilbin for osteoarthritis. The purpose of this study was to investigate the effect of Astilbin in human OA chondrocytes and mouse OA model, which was established by surgery‐mediated destabilization of the medial meniscus (DMM). In vitro, we found that Astilbin pre‐treatment inhibited lipopolysaccharide (LPS)‐induced overproduction of inflammation‐correlated cytokines such as nitric oxide (NO), prostaglandin E2 (PGE2), tumour necrosis factor α (TNF‐α) and interleukin 6 (IL‐6), and suppressed overexpression of inflammatory enzymes such as inducible nitric oxide synthase (iNOS) and cyclooxygenase 2 (COX‐2). Astilbin, on the other hand, prevented the LPS‐induced degradation of extracellular matrix (ECM) by down‐regulating MMP13 (matrix metalloproteinases 13) and ADAMTS5 (a disintegrin and metalloproteinase with thrombospondin motifs 5). Moreover, by inhibiting the formation of the TLR4/MD‐2/LPS complex, Astilbin blocked LPS‐induced activation of TLR4/NF‐κB signalling cascade. In vivo, Astilbin showed the chondro‐protective effect in the surgical‐induced OA mouse models. In conclusion, our findings provided evidence that develops Astilbin as a potential therapeutic drug for OA patients.

In Vitro and In Vivo Anti-inflammatory Activity of Bovine Milkfat Globule (MFGM)-derived Complex Lipid Fractions

Numerous health related properties have been reported for bovine milk fat globule membrane (MFGM) and its components. Here we present novel data on the in vitro and in vivo anti-inflammatory activity of various MFGM preparations which confirm and extend the concept of MFGM as a dietary anti-inflammatory agent. Cell-based assays were used to test the ability of MFGM preparations to modulate levels of the inflammatory mediators IL-1β, nitric oxide, superoxide anion, cyclo-oxygenase-2, and neutrophil elastase. In rat models of arthritis, using MFGM fractions as dietary interventions, the phospholipid-enriched MFGM isolates were effective in reducing adjuvant-induced paw swelling while there was a tendency for the ganglioside-enriched isolate to reduce carrageenan-induced rat paw oedema. These results indicate that the anti-inflammatory activity of MFGM, rather than residing in a single component, is contributed to by an array of components acting in concert against various inflammatory targets. This confirms the potential of MFGM as a nutritional intervention for the mitigation of chronic and acute inflammatory conditions.

Anti-inflammatory and analgesic effect of LD-RT and some novel thiadiazole derivatives through COX-2 inhibition

Generally, highly selective COX-2 inhibitors cause cardiovascular side effects. Celecoxib is the highly marketed coxib, so there is still a need for the synthesis of COX-2 inhibitors with less adverse effects. Moreover, low-dose radiotherapy (LD-RT) is clinically used for the treatment of inflammatory diseases. The present study aimed to investigate the analgesic and anti-inflammatory activity of a novel series of 1,3,4-thiadiazole derivatives alone or combined with LD-RT with a single dose of 0.5 Gy. Initially, in vitro COX-1/COX-2 inhibition assays were performed, identifying the sulfonamide-containing compounds 5-10 as the most potent candidates, with IC₅₀ values in the range of 0.32-0.37 µM and the highest selectivity indices. These compounds and celecoxib were subjected to in vivo examination after their safety was assessed through the acute toxicity test. Treatment with compounds 5-10 inhibited carrageenan-induced edema by nearly 47-56%, which was nearly equivalent to celecoxib. Compounds 7 and 8 and celecoxib showed an analgesic activity of 64.15%, 49.05%, and 84.90%, respectively, whereas compounds 5, 6, 9, and 10 did not show any analgesic activity unless combined with LD-RT. Ulcerogenic activity, histological paw examination, and docking studies were performed. Compounds 5-10 were nearly similar to celecoxib, showing normal histological features with no ulcerogenic activity.

Imperatorin suppresses IL-1β-induced iNOS expression via inhibiting ERK-MAPK/AP1 signaling in primary human OA chondrocytes

Joint inflammation is a key player in the pathogenesis of osteoarthritis (OA). Imperatorin, a plant-derived small molecule has been reported to have anti-inflammatory properties; however, its effect on chondrocytes is not known. Here, we investigated the effects of Imperatorin on interleukin-1β (IL-1β) induced expression of inducible nitric oxide synthase (iNOS) and nitric oxide production in primary human OA chondrocytes and cartilage explants culture under pathological conditions and explored the associated signaling pathways. We pretreated chondrocytes or explants with Imperatorin (50 μM) followed by IL-1β (1 ng/ml), and the culture supernatant was used to determine the levels of nitrite production by Griess assay and chondrocytes were harvested to prepare cell lysate or RNA for gene expression analysis of iNOS by Western blot or qPCR and in explants by immunohistochemistry (IHC). Pretreatment of primary chondrocytes and cartilage explants with Imperatorin suppressed IL-1β induced expression of iNOS and NO production. Imperatorin blocked the IL-1β-induced phosphorylation of ERK-MAPK/AP1 signaling pathway to suppress iNOS expression. The role of ERK in the regulation of iNOS expression was verified by using ERK inhibitor. Interestingly, we also found that Imperatorin binds to iNOS protein and inhibits its activity in vitro. Our data demonstrated that Imperatorin possess strong anti-inflammatory activity and may be developed as a therapeutic agent for the management of OA.

The protective effect of myricitrin in osteoarthritis: An in vitro and in vivo study

Osteoarthritis (OA) is a long-term, chronic, progressive joint condition caused by a pathology characterized by the deterioration of joint cartilage and proliferation of subchondral bone. Myricitrin (Myr) is a flavonoid compound extracted from myrica rubra with potent anti-inflammatory properties, as demonstrated in various studies. However, the mechanisms by which Myr plays a protective role in OA are not completely understood. In this study, the anti-inflammatory properties and potential mechanisms of Myr on mouse chondrocytes treated with interleukin (IL) -1beta (β) were explored in vitro and the role of Myr in a mouse model of OA in vivo. The production of pro-inflammatory factors, such as IL-6, tumor necrosis factor alpha (TNF-α), prostaglandin E2 (PGE2) and nitric oxide (NO) were assessed by enzyme linked immunosorbent assay (ELISA) and the Griess reaction. Protein expression of inducible nitric oxide synthase (iNOS), cyclooxygenase-2 (COX-2), Collagen-II, matrix metalloproteinase(MMP)-13, MMP-3, thrombospondin motifs 5(ADAMTS5), inhibitor ofnuclear factor kappa-B (IκB), p-IκB, p65, p-p65, c-jun-terminal kinase (JNK), p-JNK, extracellular regulated protein kinases (ERK), p-ERK, p38 and p-p38 were quantified using Western blot analysis. In the present study, we found that Myr inhibited IL-1β-induced production of NO and PGE2, expression of MMP-13, MMP-3 and ADAMTS5 and degradation of collagen-II in mouse chondrocytes. Mechanistically, Myr inhibited the activation of mitogen-activated protein kinase (MAPK) and nuclear factor kappa-B (NF-κB) treated with IL-1β in mouse chondrocytes. In vivo, Myr decreased OA Research Society International (OARSI) scores in a surgically-induced mouse model of OA. These data suggest that Myr could be developed as a potential therapyfor OA.

Undenatured Type II Collagen (UC-II) in Joint Health and Disease: A Review on the Current Knowledge of Companion Animals

OA is quite common in companion animals, especially in large breed dogs and horses. Collagen, the most abundant protein of mammals, has specific connective tissue types for skin, bones, reticulate, basal lamina, bones, cell surfaces, while type II collagen (UC-II) forms the main structure of cartilage tissue. Even at the smaller dosages, UC-II has also been reported to be more effective than the glucosamine and chondroitin sulfate supplements, which are the supplements most frequently used in the market. In this review, we summarize the effects of UC-II on joint health and function in health and disease conditions in companion animals.

Eklund K. Osteoarthritis and Toll-Like Receptors: When Innate Immunity Meets Chondrocyte Apoptosis

Osteoarthritis (OA) has long been viewed as a degenerative disease of cartilage, but accumulating evidence indicates that inflammation has a critical role in its pathogenesis. In particular, chondrocyte-mediated inflammatory responses triggered by the activation of innate immune receptors by alarmins (also known as danger signals) are thought to be involved. Thus, toll-like receptors (TLRs) and their signaling pathways are of particular interest. Recent reports suggest that among the TLR-induced innate immune responses, apoptosis is one of the critical events. Apoptosis is of particular importance, given that chondrocyte death is a dominant feature in OA. This review focuses on the role of TLR signaling in chondrocytes and the role of TLR activation in chondrocyte apoptosis. The functional relevance of TLR and TLR-triggered apoptosis in OA are discussed as well as their relevance as candidates for novel disease-modifying OA drugs (DMOADs).

Ginsenoside Rb1 inhibits monoiodoacetate-induced osteoarthritis in postmenopausal rats through prevention of cartilage degradation

Background

Ginsenoside Rb1 (G-Rb1), one of the major active compounds in Panax ginseng, has already been shown to reduce inflammation in various diseases. Osteoarthritis (OA) has traditionally been considered a degenerative disease with degradation of joint articular cartilage. However, recent studies have shown the association of inflammation with OA. In the present study, we investigated whether Rb1 had an antiinflammatory effect on monoiodoacetate (MIA)-induced OA in ovariectomized rats as a model of postmenopausal arthritis.

Methods

G-Rb1 at a dosage of 3 and 10 μg/kg body weight was administered every 3 days intraarticularly for a period of 4 weeks to observe antiarthritic effects. Diclofenac (10 mg/kg) served as a positive control.

Results

The administration of Rb1 significantly ameliorated OA inflammatory symptoms and reduced serum levels of inflammatory cytokines. Furthermore, G-Rb1 administration considerably enhanced the expression of bone morphogenetic protein-2 and collagen 2A and reduced the levels of matrix metalloproteinase-13 genes, indicating a chondroprotective effect of G-Rb1. G-Rb1 also significantly reduced the expression of several inflammatory cytokines/chemokines (interferon gamma (IFN-γ), monocyte chemoattractant protein-1 (MCP-1)/CCL-2, interleukin [IL]-1β, and IL-6). Histological analysis demonstrated that G-Rb1 significantly attenuated the pathological changes in MIA-induced OA in ovariectomized rats. Safranin O and toluidine blue staining further demonstrated that G-Rb1 effectively prevented the degradation of cartilage and glycosaminoglycans, respectively.

Conclusion

Overall, our results suggest that G-Rb1 exerts cartilage protective effect on MIA-induced ovariectomized OA rats, by inhibiting inflammatory mediators such as IL-6, IL-1β, MCP-1/CCL-2, cyclooxygenase-2 (COX-2), and prostaglandin E₂ (PGE2). These results shed a light on possible therapeutic application of G-Rb1 in OA.

FSTL1 promotes nitric oxide-induced chondrocyte apoptosis via activating the SAPK/JNK/caspase3 signaling pathway

OBJECTIVE

Previous studies have shown that follistatin-like protein 1 (FSTL1) is elevated in the synovial fluid of osteoarthritis and is associated with disease activity. The experiment was performed to stuy the effect and mechanism of FSTL1 on chondrocyte apoptosis in osteoarthritis.

DESIGN

After the isolation of human normal and osteoarthritis (OA) chondrocytes, the expression of FSTL1 was detected by Q-PCR and western blot analyses. Chondrocytes were pre-transfected with FSTL1 overexpression plasmids then treated with SNP, and chondrocyte viability and apoptosis levels were detected by MTS and flow cytometry, respectively. Cartilage matrix gene expression was measured by Q-PCR and signal pathway-related proteins were assessed by western blot.

RESULTS

The expression of FSTL1 in OA chondrocytes was markedly up-regulated compared with normal human chondrocytes (P < 0.05). The apoptosis rate of chondrocytes in the FSTL1 overexpression groups was highly elevated in the comparison with the negative control groups (P < 0.05). Additionally, FSTL1 potentiated protein abundances of MMP1, MMP3, MMP-9, and Bax as well as reduced Coll2a1 and Aggrecan and Bcl-2 expression. Furthermore, western blot results showed that the SAPK/JNK/Caspase3 signal pathway was significantly activated and the Ac-DEVD-FMK impaired FSTL1 induced chondrocyte apoptosis.

CONCLUSION

FSTL1 promoted SNP-induced chondrocytes apoptosis by activating the SAPK/JNK/Caspase3 signal pathway.

Akebia Saponin D suppresses inflammation in chondrocytes via the NRF2/HO-1/NF-κB axis and ameliorates osteoarthritis in mice

Akebia Saponin D promotes the translocation of NRF2 into nucleus, activates NRF2/HO-1 pathway and inhibits NF-κB pathway in chondrocytes, and ultimately alleviates osteoarthritis development.

Protectin DX attenuates IL-1β-induced inflammation via the AMPK/NF-κB pathway in chondrocytes and ameliorates osteoarthritis progression in a rat model

Protectin DX (PDX) has been reported to have extensive anti-inflammatory effects. However, it is unknown whether PDX acts as an anti-inflammatory agent in the context of osteoarthritis (OA). This study aimed to evaluate the anti-inflammatory activity of PDX in vitro and in vivo in a model of OA. Primary rat chondrocytes were preincubated with PDX 1 h prior to IL-1β treatment for 24 h. We found that PDX was nontoxic, and pretreatment with PDX increased cell viability in IL-1β-induced chondrocytes. Preincubation with PDX also efficiently inhibited the degradation of type II collagen dose-dependently. Additionally, the expression of MMP-3, MMP-13, ADAMTS4, iNOS, COX-2, NO, and PGE2 decreased after IL-1β stimulation when cells were preincubated with PDX. Moreover, PDX inhibited the increase in phosphorylated NF-κB p65 and IκBα upon IL-1β stimulation, and the negative effects of IL-1β on chondrocytes were partially blocked by treatment with pyrrolidine dithiocarbamate (PDTC), a selective NF-κB inhibitor. In addition, we found that PDX increased AMPK phosphorylation in IL-1β-mediated chondrocytes. The phosphorylation of AMPK could be inhibited by compound C, a classic AMPK inhibitor. Compound C also remarkably reversed the decrease in p65 phosphorylation and MMP-13 expression caused by PDX. Furthermore, nuclear translocation of NF-κB was visible by immunofluorescence after PDX-induced AMPK activation. Additionally, we verified that PDX ameliorated cartilage degradation in monosodium iodoacetate (MIA)-induced OA rats through histological evaluation and ELISA of TNF-α in the serum and intra-articular lavage fluid. In conclusion, we have shown that PDX suppresses inflammation in chondrocytes in vitro and in vivo, likely through the AMPK/NF-κB signaling pathway. Our results suggest that PDX could be a useful novel therapeutic agent for OA treatment.

Mangiferin: Possible uses in the prevention and treatment of mixed osteoarthritic pain

Osteoarthritis (OA) pain has been proposed to be a mixed pain state, because in some patients, central nervous system factors are superimposed upon the more traditional peripheral factors. In addition, a considerable amount of preclinical and clinical evidence has shown that, accompanying the central neuroplasticity changes and partially driven by a peripheral nociceptive input, a real neuropathic component occurs that are particularly linked to disease severity and progression. Hence, innovative strategies targeting neuroprotection and particularly neuroinflammation to prevent and treat OA pain could be introduced. Mangiferin (MG) is a glucosylxanthone that is broadly distributed in higher plants, such as Mangifera indica L. Previous studies have documented its analgesic, anti-inflammatory, antioxidant, neuroprotective, and immunomodulatory properties. In this paper, we propose its potential utility as a multitargeted compound for mixed OA pain, even in the context of multimodal pharmacotherapy. This hypothesis is supported by three main aspects: the cumulus of preclinical evidence around this xanthone, some preliminary clinical results using formulations containing MG in clinical musculoskeletal or neuropathic pain, and by speculations regarding its possible mechanism of action according to recent advances in OA pain knowledge.

Urate and osteoarthritis: Evidence for a reciprocal relationship

Hyperuricemia is a common condition, and in a subset of patients leads to gout, the most common inflammatory arthritis. Osteoarthritis is the most common form of arthritis overall, and gout and osteoarthritis frequently coexist in the same patient. However, the relationship between the two remains poorly defined. More particularly, the impact of osteoarthritis on the development of gout, and the impact of gout on the development of osteoarthritis, remain to be determined. Additionally, whether hyperuricemia mediates osteoarthritis in the absence of gout is uncertain. Here, we review the evidence linking gout and osteoarthritis, with a special focus on the role of hyperuricemia in the presence or absence of gout. Since disease modifying agents are currently available for hyperuricemia and gout but not for osteoarthritis, a contributory role for urate in the pathogenesis of osteoarthritis could have important clinical implications.

Inhibiting the PI3K/AKT/NF-κB signal pathway with nobiletin for attenuating the development of osteoarthritis: in vitro and in vivo studies

Osteoarthritis (OA), an age-related degenerative disease, is characterized by progressive degradation of the articular cartilage. There is increasing evidence that nobiletin (NOB) exerts special biological functions in a variety of diseases. However, whether it protects against OA remains unknown. In this study, we investigated the anti-inflammatory and chondroprotective effects of NOB on IL-1β-induced human OA chondrocytes and in the surgical DMM mice OA models. In vitro, NOB treatment completely suppressed the overproduction of pro-inflammatory mediators, including PGE2, NO, COX-2, iNOS, TNF-α and IL-6 in IL-1β-induced human OA chondrocytes. Moreover, NOB exerted a potent inhibitory effect on the expression of MMP-13 and ADAMTS-5 as well as the degradation of aggrecan and collagen-II, which leads to the degradation of the extracellular matrix. Furthermore, NOB dramatically suppressed the IL-1β-stimulated phosphorylation of PI3K/Akt and activation of NF-κB in human OA chondrocytes. In addition, treatment with NOB not only prevented the destruction of cartilage and the thickening of subchondral bone but also relieved synovitis in mice OA models. In conclusion, our study suggests that NOB holds novel therapeutic potential for the treatment of OA.

Mangiterpenes A-C and 2',3'-seco-manginoid C, four sesquiterpene/monoterpene-shikimate-conjugated spirocyclic meroterpenoids from Guignardia mangiferae

Mangiterpenes A-C and 2',3'-seco-manginoid C, four undescribed sesquiterpene/monoterpene-shikimate-conjugated meroterpenoids with spiro ring systems, were isolated from Guignardia mangiferae. The structures and absolute configurations of these compounds were established by comprehensive spectroscopic analyses and electronic circular dichroism (ECD) calculations. Mangiterpenes A-C represent the first examples of sesquiterpene-shikimate-conjugated spirocyclic meroterpenoids, and 2',3'-seco-manginoid C features an unexpected 2',3'-seco-manginoids skeleton. Mangiterpene C strongly inhibited the production of NO inducted by LPS, with an IC₅₀ value of 5.97 μM. It showed an anti-inflammatory effect by means of blocking in the NF-κB signaling pathway and decreasing the expression of inflammatory mediators.