Cyclooxygenase-2 and prostaglandins in articular tissues

Integration of serum pharmacochemistry and metabolomics to reveal the underlying mechanism of shaoyao-gancao-fuzi decoction to ameliorate rheumatoid arthritis

ETHNOPHARMACOLOGICAL RELEVANCE

For centuries, Shaoyao-Gancao-Fuzi decoction (SGFD) has been a reliable traditional Chinese medicine for treating rheumatoid arthritis (RA). Despite its long history of use, the specific active components and underlying mechanisms of its therapeutic effects have yet to be fully understood.

AIM OF THE STUDY

The aim of this study was to investigate the active ingredients and therapeutic effects of SGFD on RA, and to further understand its underlying mechanism.

MATERIALS AND METHODS

The chemical constituents in SGFD extract and in rat serum after oral administration of SGFD were identified and evaluated using ultra-performance liquid chromatography quadrupole-time-flight mass spectrometry (UPLC-Q-TOF/MS) together with various data-processing methods, respectively. The efficacy of SGFD was assessed by using an adjuvant-induced arthritis (AIA) rat model and lipopolysaccharide-stimulated RAW 264.7 cell. Subsequently, cell metabolomic was conducted to clarify the potential biomarkers and pathways. ELISA, RT-qPCR, and WB were used to verify the anti-arthritis mechanism of SGFD.

RESULTS

A total of 65 chemical constituents were identified in SGFD. 17 active components were distinguished in rat serum samples, of which 13 may be the main active ingredients for SGFD treatment of RA. The remarkable efficacy of SGFD in reducing the symptoms of RA is evident through its ability to alleviate the redness and swelling of the affected paws, as well as reduce the infiltration of inflammatory cells. Cell experiments revealed that rat serum of SGFD reduced IL-1β, IL-6, and TNF-α secretion in RAW 264.7 cells. 27 potential biomarkers were identified through cell metabolomics analysis. The arachidonic acid (AA) metabolism signaling pathway was activated in RA, which could be reversed by rat serum of SGFD. SGFD effectively inhibited the expression and transformation of AA by downregulating the expression of key enzymes, including phospholipase A and cyclooxygenase.

CONCLUSION

SGFD may ameliorate RA symptoms by regulating the AA-PGH2-PGE2/PGF2α pathway. The main active components include songorine, fuziline, neoline, albiflorin, paeoniflorin, liquiritin, benzoylmesaconine, isoformononetin, liquiritigenin, isoliquiritigenin, formononetin, glycyrrhizic acid, and glycyrrhetinic acid.

Skeletal interoception in osteoarthritis

The interoception maintains proper physiological conditions and metabolic homeostasis by releasing regulatory signals after perceving changes in the internal state of the organism. Among its various forms, skeletal interoception specifically regulates the metabolic homeostasis of bones. Osteoarthritis (OA) is a complex joint disorder involving cartilage, subchondral bone, and synovium. The subchondral bone undergoes continuous remodeling to adapt to dynamic joint loads. Recent findings highlight that skeletal interoception mediated by aberrant mechanical loads contributes to pathological remodeling of the subchondral bone, resulting in subchondral bone sclerosis in OA. The skeletal interoception is also a potential mechanism for chronic synovial inflammation in OA. In this review, we offer a general overview of interoception, specifically skeletal interoception, subchondral bone microenviroment and the aberrant subchondral remedeling. We also discuss the role of skeletal interoception in abnormal subchondral bone remodeling and synovial inflammation in OA, as well as the potential prospects and challenges in exploring novel OA therapies that target skeletal interoception.

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

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

Sesquiterpene Lactones with Anti-Inflammatory Activity from the Halophyte Sonchus brachyotus DC

There were five sesquiterpene lactones, belonging to the eudesmanolide class, isolated from the halophyte Sonchus brachyotus DC. The structures of the compounds were determined using spectroscopic methods, including 1D and 2D NMR spectra, MS data, and optical rotation values. Compounds 4 and 5 were characterized by the position of p-hydroxyphenylacetyl group in the sugar moiety. In the evaluation of anti-inflammatory effects on LPS-activated RAW264.7 macrophages, compound 1, 5α,6βH-eudesma-3,11(13)-dien-12,6α-olide, potently suppressed the expression of iNOS and COS-2, as well as the production of TNF-α, IL-6, and IL-10. Treatment of 1 regulates the Nrf2/HO-1 pathway.

The Interplay of Biomechanical and Biological Changes Following Meniscus Injury

PURPOSE OF REVIEW

Meniscus injury often leads to joint degeneration and post-traumatic osteoarthritis (PTOA) development. Therefore, the purpose of this review is to outline the current understanding of biomechanical and biological repercussions following meniscus injury and how these changes impact meniscus repair and PTOA development. Moreover, we identify key gaps in knowledge that must be further investigated to improve meniscus healing and prevent PTOA.

RECENT FINDINGS

Following meniscus injury, both biomechanical and biological alterations frequently occur in multiple tissues in the joint. Biomechanically, meniscus tears compromise the ability of the meniscus to transfer load in the joint, making the cartilage more vulnerable to increased strain. Biologically, the post-injury environment is often characterized by an increase in pro-inflammatory cytokines, catabolic enzymes, and immune cells. These multi-faceted changes have a significant interplay and result in an environment that opposes tissue repair and contributes to PTOA development. Additionally, degenerative changes associated with OA may cause a feedback cycle, negatively impacting the healing capacity of the meniscus. Strides have been made towards understanding post-injury biological and biomechanical changes in the joint, their interplay, and how they affect healing and PTOA development. However, in order to improve clinical treatments to promote meniscus healing and prevent PTOA development, there is an urgent need to understand the physiologic changes in the joint following injury. In particular, work is needed on the in vivo characterization of the temporal biomechanical and biological changes that occur in patients following meniscus injury and how these changes contribute to PTOA development.

Skeletal interoception in bone homeostasis and pain

Accumulating evidence indicates that interoception maintains proper physiological status and orchestrates metabolic homeostasis by regulating feeding behaviors, glucose balance, and lipid metabolism. Continuous skeletal remodeling consumes a tremendous amount of energy to provide skeletal scaffolding, support muscle movement, store vital minerals, and maintain a niche for hematopoiesis, which are processes that also contribute to overall metabolic balance. Although skeletal innervation has been described for centuries, recent work has shown that skeletal metabolism is tightly regulated by the nervous system and that skeletal interoception regulates bone homeostasis. Here, we provide a general discussion of interoception and its effects on the skeleton and whole-body metabolism. We also discuss skeletal interoception-mediated regulation in the context of pathological conditions and skeletal pain as well as future challenges to our understanding of these process and how they can be leveraged for more effective therapy.

Analysis of the Anti-Inflammatory and Anti-Osteoarthritic Potential of Flonat Fast®, a Combination of Harpagophytum Procumbens DC. ex Meisn., Boswellia Serrata Roxb., Curcuma longa L., Bromelain and Escin (Aesculus hippocastanum), Evaluated in In Vitro Models of Inflammation Relevant to Osteoarthritis

Osteoarthritis (OA) is a joint disease characterized by inflammation of the synovium, angiogenesis, cartilage degradation, and osteophyte formation. Harpagophytum Procumbens DC. ex Meisn., Boswellia Serrata Roxb., Curcuma longa L., Bromelain and Escin (Aesculus hippocastanum) are plants which extracts, together to Bromelain and Escin (Aesculus hippocastanum) are traditionally used in OA. However, their mechanistic role remains unclear. We aimed to investigate whether these bioactives alone or in combination (as in Flonat Fast^®) can suppress TNF-α-induced inflammation, angiogenesis, and osteophyte formation using two cell models involved in OA: endothelial cells and monocytes. Each plant extract was evaluated for its polyphenol content, antioxidant activity, and toxicity. In endothelial cells and monocytes, expression of genes involved in OA was assessed, functional assays for inflammation and angiogenesis were performed, and impairment of reactive oxygen species production (ROS) was evaluated. Exposure of cells to the bioactives alone and in combination before cytokine stimulation resulted in differential counterregulation of several gene and protein expressions, including those for cyclooxygenases-2, metalloproteinase-9, transforming growth factor β1, and bone morphogenic protein-2. We demonstrated that these bioactives modulated monocyte adhesion to endothelial cells as well as cell migration and endothelial angiogenesis. Consistent with radical scavenging activity in the cell-free system, the bioactives curbed TNF-α-stimulated intracellular ROS production. We confirmed the potential anti-inflammatory and antiangiogenic effects of the combination of Harpagophytum procumbens, Boswellia, Curcuma, Bromelain, and Escin and provided new mechanistic evidence for their use in OA. However, further clinical studies are needed to evaluate the true clinical utility of these bioactives as supportive, preventive, and therapeutic agents.

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.

Evaluation of the Anti-Inflammatory and Chondroprotective Effect of Celecoxib on Cartilage Ex Vivo and in a Rat Osteoarthritis Model

OBJECTIVE

The potential chondroprotective effect of celecoxib, a nonsteroidal anti-inflammatory drug and selective cyclooxygenase-2 inhibitor used to reduce pain and inflammation in knee osteoarthritis patients, is disputed. This study aimed at investigating the chondroprotective effects of celecoxib on (1) human articular cartilage explants and (2) in an in vivo osteoarthritis rat model.

DESIGN

Articular cartilage explants from 16 osteoarthritis patients were cultured for 24 hours with celecoxib or vehicle. Secreted prostaglandins (prostaglandin E₂, prostaglandin F_2α, prostaglandin D₂) and thromboxane B2 (TXB2) concentrations were determined in medium by ELISA, and protein regulation was measured with label-free proteomics. Cartilage samples from 7 of these patients were analyzed for gene expression using real-time quantitative polymerase chain reaction. To investigate the chondroprotective effect of celecoxib in vivo, 14 rats received an intra-articular injection of celecoxib or 0.9% NaCl after osteoarthritis induction by anterior cruciate ligament transection and partial medial meniscectomy (ACLT/pMMx model). Histopathological scoring was used to evaluate osteoarthritis severity 12 weeks after injection.

RESULTS

Secretion of prostaglandins, target of Nesh-SH3 (ABI3BP), and osteonectin proteins decreased, whereas tissue inhibitor of metalloproteinase 2 (TIMP-2) increased significantly after celecoxib treatment in the human (ex vivo) explant culture. Gene expression of a disintegrin and metalloproteinase with thrombospondin motifs 4 and 5 (ADAMTS4/5) and metalloproteinase 13 (MMP13) was significantly reduced after celecoxib treatment in human cartilage explants. Cartilage degeneration was reduced significantly in an in vivo osteoarthritis knee rat model.

CONCLUSIONS

Our data demonstrated that celecoxib acts chondroprotective on cartilage ex vivo and a single intra-articular bolus injection has a chondroprotective effect in vivo.

Aberrant Expression of COX-2 and FOXG1 in Infrapatellar Fat Pad-Derived ASCs from Pre-Diabetic Donors

Osteoarthritis (OA) is a degenerative joint disease resulting in limited mobility and severe disability. Type II diabetes mellitus (T2D) is a weight-independent risk factor for OA, but a link between the two diseases has not been elucidated. Adipose stem cells (ASCs) isolated from the infrapatellar fat pad (IPFP) may be a viable regenerative cell for OA treatment. This study analyzed the expression profiles of inflammatory and adipokine-related genes in IPFP-ASCs of non-diabetic (Non-T2D), pre-diabetic (Pre-T2D), and T2D donors. Pre-T2D ASCs exhibited a substantial decrease in levels of mesenchymal markers CD90 and CD105 with no change in adipogenic differentiation compared to Non-T2D and T2D IPFP-ASCs. In addition, Cyclooxygenase-2 (COX-2), Forkhead box G1 (FOXG1) expression and prostaglandin E2 (PGE2) secretion were significantly increased in Pre-T2D IPFP-ASCs upon stimulation by interleukin-1 beta (IL-1β). Interestingly, M1 macrophages exhibited a significant reduction in expression of pro-inflammatory markers TNFα and IL-6 when co-cultured with Pre-T2D IPFP-ASCs. These data suggest that the heightened systemic inflammation associated with untreated T2D may prime the IPFP-ASCs to exhibit enhanced anti-inflammatory characteristics via suppressing the IL-6/COX-2 signaling pathway. In addition, the elevated production of PGE2 by the Pre-T2D IPFP-ASCs may also suggest the contribution of pre-diabetic conditions to the onset and progression of OA.

Systematic Review: Targeted Molecular Imaging of Angiogenesis and Its Mediators in Rheumatoid Arthritis

Extensive angiogenesis is a characteristic feature in the synovial tissue of rheumatoid arthritis (RA) from a very early stage of the disease onward and constitutes a crucial event for the development of the proliferative synovium. This process is markedly intensified in patients with prolonged disease duration, high disease activity, disease severity, and significant inflammatory cell infiltration. Angiogenesis is therefore an interesting target for the development of new therapeutic approaches as well as disease monitoring strategies in RA. To this end, nuclear imaging modalities represent valuable non-invasive tools that can selectively target molecular markers of angiogenesis and accurately and quantitatively track molecular changes in multiple joints simultaneously. This systematic review summarizes the imaging markers used for single photon emission computed tomography (SPECT) and/or positron emission tomography (PET) approaches, targeting pathways and mediators involved in synovial neo-angiogenesis in RA.

Immunopotentiators improve the antioxidant defense, apoptosis, and immune response in Shaoxing ducklings

The abuse of antibiotics for agricultural purposes has been under scrutiny. Therefore, there is an urgent need to find antibiotic substitutes in animal production. The effects of chlorogenic acid, β-D-Glucan, astragalus flavone, CpG-DNA, and chicken IgG on spleen antioxidant capacity, apoptosis, and the immune response in Shaoxing ducklings were investigated in this study. The ducklings treated with β-D-Glucan, astragalus flavone, CpG-DNA, and chicken IgG showed significant reduction in catalase and superoxide dismutase activities. The five immunopotentiators facilitated caspase 3 expression and reduced Bcl2 expression in the spleen. Compared to the control group, the protein level of COX2 was significantly upregulated in the chlorogenic acid, CpG-DNA, and chicken IgG groups. The protein level of iNOS expression was significantly improved in all immunopotentiator groups, except for the astragalus flavone group. The five immunopotentiators induced IL-1β, IFN-α, IFN-β, TNF-α, RIG-I, TLR3, and TLR7 gene expression. In summary, chlorogenic acid, β-D-Glucan, astragalus flavone, CpG-DNA, and chicken IgG, as immunopotentiators, improved the innate immune response in the ducklings, which not only provides a new avenue for the development of efficient approaches to prevent pathogen infections, but also offers an alternative to antibiotics in animal production.

Metabolomics combined with network pharmacology to study the mechanism of Shentong Zhuyu decoction in the treatment of rheumatoid arthritis

ETHNOPHARMACOLOGICAL RELEVANCE

Shentong Zhuyu decoction (STZYD) was first recorded in the classic of "Yilin Gaicuo" written by Wang Qingren, and recognized by the Chinese National Administration of Traditional Chinese Medicine as one of the 100 classic formulas. The formula has been widely used in the treatment of rheumatoid arthritis (RA) with significant clinical effects. However, its mechanism of action is not completely clear.

AIM OF THE STUDY

This study aimed to explore the mechanism of STZYD in the treatment of RA by network pharmacology and metabolomics.

MATERIALS AND METHODS

The effects of STZYD anti-RA were investigated by paw swelling, arthritis score, cytokine level, histopathological and micro-CT analysis in adjuvant-induced arthritis (AIA) rats. The chemical constituents of STZYD and absorbed constituents in AIA rat serum were analyzed by UPLC-Q-Exactive MS/MS. Based on the characterized chemical components, the network pharmacology was used to find potential targets and signaling pathways of STZYD in RA treatment. Meanwhile, the predicted pathway was determined by the Western blot (WB). Subsequently, non-targeted metabolomics of serum was performed to analyze metabolic profiles, potential biomarkers, and metabolic pathways of STZYD in the treatment of RA based on LC-MS technology.

RESULTS

STZYD significantly alleviated RA symptoms by improving paw redness and swelling, bone and cartilage damage, synovial hyperplasia, and infiltration of inflammatory cells, and decreased the generation of pro-inflammatory cytokines IL-1β, IL-6, IL-17A and TNF-α in AIA rats. Totally, 59 chemical components of STZYD and 24 serum migrant ingredients were identified. A total of 655 genes of potential bioactive components in STZYD and 1025 related genes of RA were obtained. TNF signaling pathway was considered to one of the main signaling pathways of STZYD anti-RA by KEGG analysis, including a wide range intracellular signaling pathways. NF-κB signaling pathway regulates inflammation and immunity in the TNF signaling pathway. STZYD markedly inhibited the expression of NF-κB signaling pathway. Ten potential biomarkers were found in metabolomics based on LC-MS technology. Alanine, aspartate and glutamate metabolism, arachidonic acid metabolism are the most related pathways of STZYD anti-RA.

CONCLUSION

The study based on serum pharmacochemistry, network pharmacology and metabolomics indicated that STZYD can improve RA through regulating inflammation and immunity related pathways, and provided a new possibility for treatment of RA.

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

OBJECTIVE

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Do Pomegranate Hydrolyzable Tannins and Their Derived Metabolites Provide Relief in Osteoarthritis? Findings from a Scoping Review

Osteoarthritis (OA) is the most common form of arthritis affecting both the elderly and the middle-aged population. Although various therapeutics have been developed to arrest the structural deterioration of cartilage, the current treatments are limited to delay the progress of OA clinically. Therefore, it is pivotal to study new therapeutic agents for chondroprotection and the prevention of cartilage degeneration. Hydrolyzable tannin (HT)-containing foods aroused considerable interest in recent years for their relevant anti-inflammatory effects. The focus of this scoping review is to provide an overview of the evidence of the therapeutic potential of HTs and their metabolites in preventing or alleviating the course of OA. A broad search of PubMed and Scopus databases on this topic resulted in 156 articles. After the exclusion of reviews and not relevant records, 31 articles were retrieved. Although only some papers did not consider the biotransformation of HTs, most recent studies also have investigated the effect of HT metabolites. Further larger clinical trials, with an in-deep analysis of HT metabolization, are still needed to unravel the potential benefits of these compounds in OA, paving the way towards the development of a dietary strategy for the improvement of pro-inflammatory cytokine-induced chondrocyte dysfunctions and injuries.

Hyperosmolar Ionic Solutions Modulate Inflammatory Phenotype and sGAG Loss in a Cartilage Explant Model

OBJECTIVE

The objective of this study was to compare the effects of hyperosmolar sodium (Na+), lithium (Li+) and potassium (K+) on catabolic and inflammatory osteoarthritis (OA) markers and sulfated glycosaminoglycan (sGAG) loss in TNF-α-stimulated cartilage explants.

METHODS

Explants from bovine stifle joints were stimulated with TNF-α for 1 day to induce cartilage degradation followed by supplementation with 50 mM potassium chloride (KCl), 50 mM lithium chloride (LiCl), 50 mM sodium chloride (NaCl), or 100 nM dexamethasone for an additional 6 days. We assessed the effect of TNF-α stimulation and hyperosmolar ionic treatment on sGAG loss and expression of OA-associated proteins: ADAMTS-5, COX-2, MMP-1, MMP-13, and VEGF.

RESULTS

TNF-α treatment increased sGAG loss (P < 0.001) and expression of COX-2 (P = 0.018), MMP-13 (P < 0.001), and VEGF (P = 0.017) relative to unstimulated controls. Relative to activated controls, LiCl and dexamethasone treatment attenuated sGAG loss (P = 0.008 and P = 0.042, respectively) and expression of MMP-13 (P = 0.005 and P = 0.036, respectively). In contrast, KCl treatment exacerbated sGAG loss (P = 0.032) and MMP-1 protein expression (P = 0.010). NaCl treatment, however, did not alter sGAG loss or expression of OA-related proteins. Comparing LiCl and KCl treatment shows a potent reduction (P < 0.05) in catabolic and inflammatory mediators following LiCl treatment.

CONCLUSION

These results suggest that these ionic species elicit varying responses in TNF-α-stimulated explants. Cumulatively, these findings support additional studies of hyperosmolar ionic solutions for potential development of novel intraarticular injections targeting OA.

Melatonin Maintains Anabolic-Catabolic Equilibrium and Regulates Circadian Rhythm During Osteoarthritis Development in Animal Models: A Systematic Review and Meta-analysis

Background: The driving force behind osteoarthritis (OA) pathogenesis is an anabolic-catabolic (a/c) imbalance. Melatonin (MT) is a key player in maintaining a/c stability and mitigates OA pathogenesis, but mechanisms underlying its effects remain poorly understood.

Objectives: We performed a systematic review analyzing the experimental data that support the clinical applicability of MT in the treatment of OA pathogenesis, placing particular emphasis on the regulation of circadian rhythms and a/c balance.

Methods: Major electronic databases and grey literature were used to identify related original articles. Methodological quality of all selected studies was evaluated using the SYRCLE risk of bias tool. Pooled mean differences (MDs)/standardized mean differences (SMDs) with 95% confidence intervals (CIs) were calculated to estimate the effect size.

Results: Eleven trials were included in this systematic review. Compared with the control group, MT significantly decreased the levels of interleukin-1β (IL-1β; SMD = −5.45; 95% CI [−6.78, −4.12]; p < 0.00001, and histological grading scale (SMD = −3.46; 95% CI, [−5.24, −1.68]; p < 0.0001). MT significantly increased the transforming growth factor-β1 (TGF-β1; SMD = 1.17; 95% CI [0.31, 2.03]; p < 0.0007). Furthermore, core circadian clock genes Per2 and Cry1 mRNA levels were regulated by MT treatment in OA progression.

Conclusion: MT may maintain a/c balance and regulate circadian rhythms during OA development. MT could be used in as adjunct with other interventions to manage pain and OA severity.

Responses to an intra-articular lipopolysaccharide challenge following dietary supplementation of Saccharomyces cerevisiae fermentation product in young horses

Dietary intervention may be a valuable strategy to optimize the intra-articular environment in young horses to prolong their performance career. To test the hypothesis that dietary supplementation of a Saccharomyces cerevisiae fermentation product would reduce markers of joint inflammation and increase markers of cartilage metabolism following a single inflammatory insult, Quarter Horse yearlings (mean ± SD; 9 ± 1.0 mo) were balanced by age, sex, body weight (BW), and farm of origin and randomly assigned to the following treatment groups: 1.25% BW/d (dry matter basis) custom-formulated concentrate only (CON; n = 9) or concentrate top-dressed with 21 g/d S. cerevisiae fermentation product (SCFP; n = 10) for 98 d. Horses had ad libitum access to Coastal bermudagrass hay. On day 84, one randomly selected radial carpal joint from each horse was injected with 0.5 ng lipopolysaccharide (LPS) solution. The remaining carpal joint was injected with sterile lactated Ringer’s solution as a contralateral control. Synovial fluid obtained before supplementation (day 0) and on day 84 at preinjection hour 0 and 6, 12, 24, 168, and 336 h postinjection was analyzed for prostaglandin E₂ (PGE₂), carboxypropeptide of type II collagen (CPII), and collagenase cleavage neopeptide (C2C) by commercial assays. Rectal temperature, heart rate, respiration rate, carpal surface temperature, and carpal circumference were recorded prior to each sample collection and for 24 h postinjection. Data were analyzed using linear models with repeated measures. From day 0 to 84, synovial C2C declined (P ≤ 0.01) and the CPII:C2C ratio increased (P ≤ 0.01) in all horses with no effect of diet. In response to intra-articular LPS, synovial PGE₂ increased by hour 6 (P ≤ 0.01) and returned to baseline by hour 336; CPII increased by hour 12, remained elevated through hour 168 (P ≤ 0.01), and returned to baseline by hour 336; and C2C increased by hour 6 (P ≤ 0.01) but did not return to baseline through hour 336 (P ≤ 0.01). Post-intra-articular injection, PGE₂ levels were lower in SCFP than CON horses (P = 0.01) regardless of injection type. Synovial CPII and the CPII:C2C ratio demonstrated stability during the LPS challenge in SCFP compared with CON horses (P ≤ 0.01). Clinical parameters were not influenced by diet but increased in response to repeated arthrocentesis (P ≤ 0.01). Dietary SCFP may favorably modulate intra-articular inflammation following an acute stressor and influence cartilage turnover in young horses.

Cyclooxygenase-2 regulates PTHrP transcription in human articular chondrocytes and is involved in the pathophysiology of osteoarthritis in rats

Background

Cyclooxygenase-2 (COX-2) inhibitors are prescribed for the management of osteoarthritis (OA)-associated pain and inflammation. However, the role of COX-2 in normal and osteoarthritic articular chondrocytes has not been well investigated. We hypothesize that COX-2 plays a role in articular chondrocytes under normal conditions and during OA progression.

Methods

In vivo COX-2 levels in articular cartilage of normal and papain-induced osteoarthritic rats were compared. The role of COX-2 in human articular chondrocytes (HACs) was tested in vitro by COX-2 overexpression or activity inhibition. The levels of COX-2 and marker gene for normal function or articular cartilage degeneration were evaluated: mRNA by qRT-PCR; proteins by western blotting or immunohistochemistry; and glycosaminoglycan (GAG) by Safranin O-fast green staining. Parathyroid hormone-related protein (PTHrP) promoter activity was detected with luciferase reporter assays.

Results

In the OA rat study, COX-2 and PTHrP were simultaneously increased in osteoarthritic rat chondrocytes, while increased PTHrP levels were reduced by celecoxib, a COX-2 selective inhibitor. The levels of normal cartilage matrices, GAG and type II collagen decreased, while markers of degeneration, collagen type X and MMP13 were elevated in osteoarthritic articular chondrocytes. Celecoxib rescued the loss of GAG and the increased collagen type X and MMP13 levels. In vitro, COX-2 overexpression in HACs significantly increased Col2a1, Col10a1, PTHrP and MMP13 mRNA expression, which was decreased when COX-2 activity was suppressed. More importantly, COX-2 overexpression upregulated the PTHrP transcription, mRNA expression and protein levels.

Conclusion

COX-2 plays a pathophysiological role by preventing terminal differentiation of articular chondrocytes by upregulating PTHrP expression at the early stage of OA progression.

The Translational potential of this article

COX2 up-regulates PTHrP expression in normal and OA articular chondrocytes.

Targeting Toll-like Receptor (TLR) Pathways in Inflammatory Arthritis: Two Better Than One?

Inflammatory arthritis is a cluster of diseases caused by unregulated activity of the immune system. The lost homeostasis is followed by the immune attack of one’s self, what damages healthy cells and tissues and leads to chronic inflammation of various tissues and organs (e.g., joints, lungs, heart, eyes). Different medications to control the excessive immune response are in use, however, drug resistances, flare-reactions and adverse effects to the current therapies are common in the affected patients. Thus, it is essential to broaden the spectrum of alternative treatments and to develop disease-modifying drugs. In the last 20 years, the involvement of the innate immune receptors TLRs in inflammatory arthritis has been widely investigated and targeting either the receptor itself or the proteins in the downstream signalling cascades has emerged as a promising therapeutic strategy. Yet, concerns about the use of pharmacological agents that inhibit TLR activity and may leave the host unprotected against invading pathogens and toxicity issues amid inhibition of downstream kinases crucial in various cellular functions have arisen. This review summarizes the existing knowledge on the role of TLRs in inflammatory arthritis; in addition, the likely druggable related targets and the developed inhibitors, and discusses the pros and cons of their potential clinical use.

Inflammation and ROS in arthritis: management by Ayurvedic medicinal plants

Chronic joint inflammatory disorders like osteoarthritis and rheumatoid arthritis, which are manifested by joint dysfunction, show an upsurge in inflammation and oxidative stress. Although conventional anti-arthritic drugs are being used to relieve pain from arthritic symptoms, they usually cause severe side effects. Traditionally used Ayurvedic medicinal plants are a promising alternative for the management of arthritic symptoms, as they are safe and effective. Ayurvedic medicinal plants improve arthritic symptoms by reducing joint tenderness, joint pain, swelling, bone and cartilage damage, and increasing knee flexion, walking distance and sports activities. These beneficial effects of Ayurvedic medicinal plants on arthritis are mediated through various cellular mechanisms including inhibition of the inflammatory markers NF-κB, cytokines, adipokines, PGE2, NO, iNOS, COX-2, and MMPs and induction of antioxidant status by decreasing free radicals, lipid peroxidation, and myeloperoxidase, and increasing antioxidant enzymes, Nrf2, and HO-1. Thus, a strategy requires using these Ayurvedic medicinal plants to treat arthritis. This article describes the status of inflammation and oxidative stress in arthritic conditions. We also provide evidence that Ayurvedic medicinal plants and their bioactive components are highly effective in improving arthritic symptoms.

Solanum xanthocarpum fruit extract promotes chondrocyte proliferation in vitro and protects cartilage damage in collagenase induced osteoarthritic rats (article reference number: JEP 114028)

ETHNOPHARMACOLOGICAL RELEVANCE

Osteoarthritis (OA), a degenerative joint disease, is characterized by cartilage erosion and matrix degradation. Solanum xanthocarpum Schrad. & Wendl. fruits (SXF) and leaves have long been used as folk remedy in the treatment of pain in rheumatism.

AIM OF THE STUDY

This study was aimed to investigate the phytochemical components and protective benefits of SXF on in vitro chondrocytes proliferation, and in vivo suppression of collagenase-induced OA.

MATERIALS AND METHODS

Phytochemical components in ethanolic SXF extract were evaluated using gas chromatography-mass spectrometry (GC-MS). Effect of SXF on in vitro cell proliferation of primary chondrocytes was determined by cell proliferation assay and cell cycle analysis by flow cytometry. OA was induced in the right knees of rats through intra-articular injection of collagenase type-II. To evaluate in vivo preventive function of SXF, body weight, blood ALP, histopathological changes in the knee joint, proteoglycan, and collagen content were determined. The mRNA expression of COL-2, MMP-3 and COX-2 genes through qRT-PCR was studied. Antioxidant activities, total phenolics and flavonoid contents of SXF were also examined.

RESULTS

GC-MS analysis revealed that SXF constitutes 28 phytochemicals including flavonoids (3-methoxy apigenin, quercetin, luteolin), tannin (quinic acid), terpenes (oleanolic acid, lupeol, psi.psi carotene), phytosterols (campesterol, stigmasterol, β-sitosterol), and ascorbic acid. In vitro studies demonstrated that SXF enhanced the cell proliferation in a dose-dependent manner and has no cytotoxic effect on primary chondrocytes. In vivo study suggests that SXF protects the cartilage destruction induced by collagenase. The histological study revealed that SXF restored the synthesis of collagen and proteoglycan, vital factors for cartilage restoration, and reduced the arthritic score. An up-regulation in COL-2 expression and suppression of MMP-3 and COX-2 were detected by qRT-PCR analysis. Thus, in vivo study suggests the protective effects of SXF on cartilage destruction induced by collagenase.

CONCLUSIONS

Our results imply that SXF benefits and ameliorates OA by enhancing the chondrocytes proliferation and preventing the articular cartilage damage through the restoration of their structural molecules, arthritic score reduction, suppression of MMP-3 and COX-2 expression level and up regulation of COL-2 genes expression. These results suggest that SXF could be a promising alternative treatment candidate for osteoarthritis.

Inhibition of cyclooxygenase-2 enhanced intestinal epithelial homeostasis via suppressing β-catenin signalling pathway in experimental liver fibrosis

The intestinal barrier dysfunction is crucial for the development of liver fibrosis but can be disturbed by intestinal chronic inflammation characterized with cyclooxygenase‐2 (COX‐2) expression. This study focused on the unknown mechanism by which COX‐2 regulates intestinal epithelial homeostasis in liver fibrosis. The animal models of liver fibrosis induced with TAA were established in rats and in intestinal epithelial–specific COX‐2 knockout mice. The impacts of COX‐2 on intestinal epithelial homeostasis via suppressing β‐catenin signalling pathway were verified pharmacologically and genetically in vivo. A similar assumption was tested in Ls174T cells with goblet cell phenotype in vitro. Firstly, disruption of intestinal epithelial homeostasis in cirrhotic rats was ameliorated by celecoxib, a selective COX‐2 inhibitor. Then, β‐catenin signalling pathway in cirrhotic rats was associated with the activation of COX‐2. Furthermore, intestinal epithelial–specific COX‐2 knockout could suppress β‐catenin signalling pathway and restore the disruption of ileal epithelial homeostasis in cirrhotic mice. Moreover, the effect of COX‐2/PGE2 was dependent on the β‐catenin signalling pathway in Ls174T cells. Therefore, inhibition of COX‐2 may enhance intestinal epithelial homeostasis via suppression of the β‐catenin signalling pathway in liver fibrosis.

Potential role of bioactive lipids in rheumatoid arthritis

Rheumatoid arthritis (RA) is a chronic inflammatory autoimmune disease, which involves a pathological inflammatory response against articular cartilage in multiple joints throughout the body. It is a complex disorder associated with comorbidities such as depression, lymphoma, osteoporosis and cardiovascular disease (CVD), which significantly deteriorate patients' quality of life and prognosis. This has ignited a large initiative to elucidate the physiopathology of RA, aiming to identify new therapeutic targets and approaches in its multidisciplinary management. Recently, various lipid bioactive products have been proposed to have an essential role in this process; including eicosanoids, specialized pro-resolving mediators, phospholipids/sphingolipids, and endocannabinoids. Dietary interventions using omega-3 polyunsaturated fatty acids or treatment with synthetic endocannabinoids agonists have been shown to significantly ameliorate RA symptoms. Indeed, the modulation of lipid metabolism may be crucial in the pathophysiology and treatment of autoimmune diseases.

How Aconiti Radix Cocta can Treat Gouty Arthritis Based on Systematic Pharmacology and UPLC-QTOF-MS/MS

Background: Gouty arthritis (GA) is a common metabolic disease caused by a long-term disorder of purine metabolism and increased serum levels of uric acid. The processed product of dried root of Aconitum carmichaeli Debeaux (Aconiti Radix cocta, ARC) is used often in traditional Chinese medicine (TCM) to treat GA, but its specific active components and mechanism of action are not clear.

Methods: First, we used ultra-performance liquid chromatography-quadrupole/time-of-flight tandem mass spectrometry to identify the chemical spectrum of ARC. Based on this result, we explored the active components of ARC in GA treatment and their potential targets and pathways. Simultaneously, we used computer simulations, in vitro cell experiments and animal experiments to verify the prediction results of systems pharmacology. In vitro, we used aurantiamide acetate (AA) to treat monosodium urate (MSU)-stimulated THP-1 cells and demonstrated the reliability of the prediction by western blotting and real-time reverse transcription-quantitative polymerase chain reaction (RT-qPCR). ELISAs kit were used to measure changes in levels of proinflammatory factors in rats with GA induced by MSU to demonstrate the efficacy of ARC in GA treatment.

Results: Forty-three chemical constituents in ARC were identified. ARC could regulate 65 targets through 29 active components, and then treat GA, which involved 1427 Gene Ontology (GO) terms and 146 signaling pathways. Signaling pathways such as proteoglycans in cancer, C-type lectin receptor signaling pathway, and TNF signaling pathway may have an important role in GA treatment with ARC. In silico results showed that the active components songoramine and ignavine had high binding to mitogen-activated protein kinase p38 alpha (MAPK14) and matrix metallopeptidase (MMP)9, indicating that ARC treatment of GA was through multiple components and multiple targets. In vitro experiments showed that AA in ARC could effectively reduce expression of MAPK14, MMP9, and cyclooxygenase2 (PTGS2) in THP-1 cells stimulated by MSU, whereas it could significantly inhibit the mRNA expression of Caspase-1, spleen tyrosine kinase (SYK), and PTGS2. Animal experiments showed that a ARC aqueous extract could significantly reduce expression of tumor necrosis factor (TNF)-α, interleukin (IL)-1β, and intereleukin (IL)-18 in the serum of GA rats stimulated by MSU. Hence, ARC may inhibit inflammation by regulating the proteoglycans in cancer-associated signaling pathways.

Conclusion: ARC treatment of GA may have the following mechanisms, ARC can reduce MSU crystal-induced joint swelling, reduce synovial tissue damage, and reduce the expression of inflammatory factors in serum. AA in ARC may inhibit inflammation by regulating the protein expression of MAPK14, MMP9, and PTGS2 and the mRNA expression of caspase-1, SYK, and PTGS2.

Arrabidaea chica Verlot fractions reduce MIA-induced osteoarthritis progression in rat knees

This study aims to investigate the activity of n-hexane, ethyl acetate and butanol fractions obtained from Arrabidaea chica Verlot against MIA-induced osteoarthritis (OA). The antinociceptive potentials of each fraction were evaluated through a cyclooxygenase (COX) 1 and 2 inhibition test and an in vivo OA-model. In addition, toxicity assessments in the liver, spleen and kidney, as well as radiographic and histopathological knee analyses, were performed. The chemical composition of the n-hexane fraction was elucidated, and a molecular docking protocol was carried out to identify which compounds are associated with the detected bioactivity. The n-hexane A. chica fraction preferentially inhibits COX-2, with 90% inhibition observed at 10 µg/mL. The fractions also produced significant improvements in OA incapacity, motor activity and hyperalgesia parameters and in radiological knee conditions. However, concerning the histopathological evaluations, these improvements were only significant in the hexane and ethyl acetate fraction treatments, which resulted in better average scores, suggesting that these fractions slow OA-promoted joint injury progression. Histopathological organ analyses indicate that the fractions are not toxic to animals. Twenty compounds were identified in the n-hexane fraction, comprising fatty acids, terpenes and phytosterols. In silico analyses indicate the presence of favourable interactions between some of the identified compounds and the COX-2 enzyme, mainly concerning alpha-tocopherol (Vitamin E), squalene and beta-sitosterol. The findings indicate that A. chica fractions display analgesic, anti-inflammatory properties, are non-toxic and are able to slow OA progression, and may, therefore, be prioritized as natural products in OA human clinical trials.

Histone Modifications and Chondrocyte Fate: Regulation and Therapeutic Implications

The involvement of histone modifications in cartilage development, pathology and regeneration is becoming increasingly evident. Understanding the molecular mechanisms and consequences of histone modification enzymes in cartilage development, homeostasis and pathology provides fundamental and precise perspectives to interpret the biological behavior of chondrocytes during skeletal development and the pathogenesis of various cartilage related diseases. Candidate molecules or drugs that target histone modifying proteins have shown promising therapeutic potential in the treatment of cartilage lesions associated with joint degeneration and other chondropathies. In this review, we summarized the advances in the understanding of histone modifications in the regulation of chondrocyte fate, cartilage development and pathology, particularly the molecular writers, erasers and readers involved. In addition, we have highlighted recent studies on the use of small molecules and drugs to manipulate histone signals to regulate chondrocyte functions or treat cartilage lesions, in particular osteoarthritis (OA), and discussed their potential therapeutic benefits and limitations in preventing articular cartilage degeneration or promoting its repair or regeneration.

Mesenchymal stem/stromal cells as a valuable source for the treatment of immune-mediated disorders

Over recent years, mesenchymal stem/stromal cells (MSCs) and their potential biomedical applications have received much attention from the global scientific community in an increasing manner. Firstly, MSCs were successfully isolated from human bone marrow (BM), but in the next steps, they were also extracted from other sources, mostly from the umbilical cord (UC) and adipose tissue (AT). The International Society for Cellular Therapy (ISCT) has suggested minimum criteria to identify and characterize MSCs as follows: plastic adherence, surface expression of CD73, D90, CD105 in the lack of expression of CD14, CD34, CD45, and human leucocyte antigen-DR (HLA-DR), and also the capability to differentiate to multiple cell types including adipocyte, chondrocyte, or osteoblast in vitro depends on culture conditions. However, these distinct properties, including self-renewability, multipotency, and easy accessibility are just one side of the coin; another side is their huge secretome which is comprised of hundreds of mediators, cytokines, and signaling molecules and can effectively modulate the inflammatory responses and control the infiltration process that finally leads to a regulated tissue repair/healing or regeneration process. MSC-mediated immunomodulation is a direct result of a harmonic synergy of MSC-released signaling molecules (i.e., mediators, cytokines, and chemokines), the reaction of immune cells and other target cells to those molecules, and also feedback in the MSC-molecule-target cell axis. These features make MSCs a respectable and eligible therapeutic candidate to be evaluated in immune-mediated disorders, such as graft versus host diseases (GVHD), multiple sclerosis (MS), Crohn's disease (CD), and osteoarthritis (OA), and even in immune-dysregulating infectious diseases such as the novel coronavirus disease 2019 (COVID-19). This paper discussed the therapeutic applications of MSC secretome and its biomedical aspects related to immune-mediated conditions. Sources for MSC extraction, their migration and homing properties, therapeutic molecules released by MSCs, and the pathways and molecular mechanisms possibly involved in the exceptional immunoregulatory competence of MSCs were discussed. Besides, the novel discoveries and recent findings on immunomodulatory plasticity of MSCs, clinical applications, and the methods required for their use as an effective therapeutic option in patients with immune-mediated/immune-dysregulating diseases were highlighted.

Robust COX-2-mediated prostaglandin response may drive arthralgia and bone destruction in patients with chronic inflammation post-chikungunya

Patients following infection by chikungunya virus (CHIKV) can suffer for months to years from arthralgia and arthritis. Interestingly, methotrexate (MTX) a major immune-regulatory drug has proved to be of clinical benefit. We have previously shown that CHIKV can persist in the joint of one patient 18 months post-infection and plausibly driving chronic joint inflammation but through ill-characterized mechanisms. We have pursued our investigations and report novel histological and in vitro data arguing for a plausible role of a COX-2-mediated inflammatory response post-CHIKV. In the joint, we found a robust COX-2 staining on endothelial cells, synovial fibroblasts and more prominently on multinucleated giant cells identified as CD11c+ osteoclasts known to be involved in bone destruction. The joint tissue was also strongly stained for CD3, CD8, CD45, CD14, CD68, CD31, CD34, MMP2, and VEGF (but not for NO synthase and two B cell markers). Dendritic cells were rarely detected. Primary human synovial fibroblasts were infected with CHIKV or stimulated either by the synthetic molecule polyriboinosinic:polyribocytidylic acid (PIC) to mimic chronic viral infection or cytokines. First, we found that PIC and CHIKV enhanced mRNA expression of COX-2. We further found that PIC but not CHIKV increased the mRNA levels of cPLA2α and of mPGES-1, two other central enzymes in PGE2 production. IFNβ upregulated cPLA2α and COX-2 transcription levels but failed to modulated mPGES-1 mRNA expression. Moreover, PIC, CHIKV and IFNβ decreased mRNA expression of the PGE2 degrading enzyme 15-PGDH. Interestingly, MTX failed to control the expression of all these enzymes. In sharp contrast, dexamethasone was able to control the capacity of pro-inflammatory cytokines, IL-1β as well as TNFα, to stimulate mRNA levels of cPLA2α, COX-2 and mPGES-1. These original data argue for a concerted action of CHIKV (including viral RNA) and cytokines plausibly released from recruited leukocytes to drive a major COX-2-mediated PGE2 proinflammatory responses to induce viral arthritis.

It is important to have a better understanding of the immuno-pathogenesis of Chikungunya virus (CHIKV) and particularly focusing on the chronic phase associated to arthralgia and arthritis. Benefiting from our prospective cohort studies, we herein provide novel in vivo data identifying for the first time the implication of COX-2 and several other enzymes involved in prostaglandin biosynthesis and the persistence of the virus on the joint. Prostaglandin has major activities in inflammation and joint destruction. In vitro, we have used a model of human synovial fibroblasts to decipher the regulatory mechanisms of prostaglandin biosynthesis pathway. We have made important observations showing that the virus itself as well as major inflammatory cytokines can dramatically control the expression of all enzymes involved in the metabolism of prostaglandin. Interestingly, pharmacological investigations further revealed that dexamethasone, but not methotrexate (currently used to treat patients with chikungunya) may be of clinical values.

Apoptosis in the Extraosseous Calcification Process

Extraosseous calcification is a pathologic mineralization process occurring in soft connective tissues (e.g., skin, vessels, tendons, and cartilage). It can take place on a genetic basis or as a consequence of acquired chronic diseases. In this last case, the etiology is multifactorial, including both extra- and intracellular mechanisms, such as the formation of membrane vesicles (e.g., matrix vesicles and apoptotic bodies), mitochondrial alterations, and oxidative stress. This review is an overview of extraosseous calcification mechanisms focusing on the relationships between apoptosis and mineralization in cartilage and vascular tissues, as these are the two tissues mostly affected by a number of age-related diseases having a progressively increased impact in Western Countries.

Pathophysiological Perspective of Osteoarthritis

Osteoarthritis (OA) is the most well-known degenerative disease among the geriatric and is a main cause of significant disability in daily living. It has a multifactorial etiology and is characterized by pathological changes in the knee joint structure including cartilage erosion, synovial inflammation, and subchondral sclerosis with osteophyte formation. To date, no efficient treatment is capable of altering the pathological progression of OA, and current therapy is broadly divided into pharmacological and nonpharmacological measures prior to surgical intervention. In this review, the significant risk factors and mediators, such as cytokines, proteolytic enzymes, and nitric oxide, that trigger the loss of the normal homeostasis and structural changes in the articular cartilage during the progression of OA are described. As the understanding of the mechanisms underlying OA improves, treatments are being developed that target specific mediators thought to promote the cartilage destruction that results from imbalanced catabolic and anabolic activity in the joint.

Prostanoid Receptor Subtypes and Its Endogenous Ligands with Processing Enzymes within Various Types of Inflammatory Joint Diseases

A complex inflammatory process mediated by proinflammatory cytokines and prostaglandins commonly occurs in the synovial tissue of patients with joint trauma (JT), osteoarthritis (OA), and rheumatoid arthritis (RA). This study systematically investigated the distinct expression profile of prostaglandin E2 (PGE2), its processing enzymes (COX-2), and microsomal PGES-1 (mPGES-1) as well as the corresponding prostanoid receptor subtypes (EP1-4) in representative samples of synovial tissue from these patients (JT, OA, and RA). Quantitative TaqMan®-PCR and double immunofluorescence confocal microscopy of synovial tissue determined the abundance and exact immune cell types expressing these target molecules. Our results demonstrated that PGE2 and its processing enzymes COX-2 and mPGES-1 were highest in the synovial tissue of RA, followed by the synovial tissue of OA and JT patients. Corresponding prostanoid receptor, subtypes EP3 were highly expressed in the synovium of RA, followed by the synovial tissue of OA and JT patients. These proinflammatory target molecules were distinctly identified in JT patients mostly in synovial granulocytes, in OA patients predominantly in synovial macrophages and fibroblasts, whereas in RA patients mainly in synovial fibroblasts and plasma cells. Our findings show a distinct expression profile of EP receptor subtypes and PGE2 as well as the corresponding processing enzymes in human synovium that modulate the inflammatory process in JT, OA, and RA patients.

Characterization of Synovial Cytokine Patterns in Bucket-Handle and Posterior Horn Meniscal Tears

The specific etiology of meniscal tears, including the mechanism of lesion, location, and orientation, is considered for its contribution to subsequent joint cytokine responsiveness, healing outcomes, and by extension, appropriate lesion-specific surgical remediation. Meniscal repair is desirable to reduce the probability of development of posttraumatic osteoarthritis (PTOA) which is strongly influenced by the coordinate generation of pro- and anti-inflammatory cytokines by the injured cartilage. We now present biochemical data on variation in cytokine levels arising from two particular meniscal tears: bucket-handle (BH) and posterior horn (PH) isolated meniscal tears. We selected these two groups due to the different clinical presentations. We measured the concentrations of TNF-α, IL-1β, IL-6, IL-8, and IL-10 in knee synovial fluid of 45 patients with isolated meniscal lesions (BH tear, n = 12; PH tear, n = 33). TNF-α levels were significantly (p < 0.05) greater in the BH group compared with the PH group, whereas IL-1β levels were significantly greater (p < 0.05) in the PH group compared with the BH group. Both BH and PH groups were consistent in presenting a positive correlation between concentrations of IL-6 and IL-1β. A fundamental difference in IL-10 responsiveness between the two groups was noted; specifically, levels of IL-10 were positively correlated with IL-6 in the BH group, whereas in the PH group, levels of IL-10 were positively correlated with IL-1β. Collectively, our data suggest a possible influence of the meniscal tear pattern to the articular cytokine responsiveness. This differential expression of inflammatory cytokines may influence the risk of developing PTOA in the long term.

Chondroprotective Actions of Selective COX-2 Inhibitors In Vivo: A Systematic Review

Knee osteoarthritis (OA) is a condition mainly characterized by cartilage degradation. Currently, no effective treatment exists to slow down the progression of OA-related cartilage damage. Selective COX-2 inhibitors may, next to their pain killing properties, act chondroprotective in vivo. To determine whether the route of administration is important for the efficacy of the chondroprotective properties of selective COX-2 inhibitors, a systematic review was performed according to the PRISMA guidelines. Studies investigating OA-related cartilage damage of selective COX-2 inhibitors in vivo were included. Nine of the fourteen preclinical studies demonstrated chondroprotective effects of selective COX-2 inhibitors using systemic administration. Five clinical studies were included and, although in general non-randomized, failed to demonstrate chondroprotective actions of oral selective COX-2 inhibitors. All of the four preclinical studies using bolus intra-articular injections demonstrated chondroprotective actions, while one of the three preclinical studies using a slow release system demonstrated chondroprotective actions. Despite the limited evidence in clinical studies that have used the oral administration route, there seems to be a preclinical basis for considering selective COX-2 inhibitors as disease modifying osteoarthritis drugs when used intra-articularly. Intra-articularly injected selective COX-2 inhibitors may hold the potential to provide chondroprotective effects in vivo in clinical studies.

Purinergic System Signaling in Metainflammation-Associated Osteoarthritis

Inflammation triggered by metabolic imbalance, also called metainflammation, is low-grade inflammation caused by the components involved in metabolic syndrome (MetS), including central obesity and impaired glucose tolerance. This phenomenon is mainly due to excess nutrients and energy, and it contributes to the pathogenesis of osteoarthritis (OA). OA is characterized by the progressive degeneration of articular cartilage, which suffers erosion and progressively becomes thinner. Purinergic signaling is involved in several physiological and pathological processes, such as cell proliferation in development and tissue regeneration, neurotransmission and inflammation. Adenosine and ATP receptors, and other members of the signaling pathway, such as AMP-activated protein kinase (AMPK), are involved in obesity, type 2 diabetes (T2D) and OA progression. In this review, we focus on purinergic regulation in osteoarthritic cartilage and how different components of MetS, such as obesity and T2D, modulate the purinergic system in OA. In that regard, we describe the critical role in this disease of receptors, such as adenosine A2A receptor (A2AR) and ATP P2X7 receptor. Finally, we also assess how nucleotides regulate the inflammasome in OA.

L-Theanine Reduced the Development of Knee Osteoarthritis in Rats via Its Anti-Inflammation and Anti-Matrix Degradation Actions: In Vivo and In Vitro Study

The etiology of osteoarthritis (OA) is multifactorial, with no effective disease-modifying-drugs. L-theanine has been reported to inhibit inflammatory responses in some diseases and this study aimed to investigate the effect of L-theanine on Interleukin-1(IL-1)β-stimulated chondrocytes, and in an injury-induced OA rat model. Primary chondrocytes were stimulated by IL-1β (10 ng/mL) for 24 h and then co-cultured with L-theanine for 24 h. The effects of L-theanine on IL-1β-stimulated expression of pro-inflammatory cytokines and hydrolytic enzyme were analyzed using Western blotting, quantitative polymerase chain reaction (q-PCR) and enzyme-linked immunosorbent assay (ELISA) kits. An immunofluorescence assay was used to detect nuclear factor kappa B (NF-κB) phosphorylation. OA was induced by anterior cruciate ligament transection (ACLT) surgery in rats and celecoxib was used as a positive control. OA severity was measured using the Osteoarthritis Research Society International (OARSI) grading system to describe histological changes. The results showed that L-theanine decreased the expression of pro-inflammatory mediators, including cyclooxygenase-2 (COX-2), prostaglandin E2 (PGE-2), inducible nitric oxide synthase (iNOS), and nitric oxide (NO), both in vivo and in vitro. L-theanine treatment inhibited IL-1β-induced upregulation of matrix metalloproteinases (MMP)-3 and MMP-13, as well as inhibited NF-κB p65 activation. In vivo animal model showed that L-theanine administration (200 mg/kg) significantly alleviated OA lesions and decreased OARSI score. Our data indicated that L-theanine decreased inflammatory cytokines and protected extracellular matrix degradation through inhibition of the NF-κB pathway, and L-theanine may be considered a promising therapeutic strategy in OA prevention.

Transcriptional profiling of murine macrophages stimulated with cartilage fragments revealed a strategy for treatment of progressive osteoarthritis

Accumulating evidence suggests that synovitis is associated with osteoarthritic process. Macrophages play principal role in development of synovitis. Our earlier study suggests that interaction between cartilage fragments and macrophages exacerbates osteoarthritic process. However, molecular mechanisms by which cartilage fragments trigger cellular responses remain to be investigated. Therefore, the current study aims at analyzing molecular response of macrophages to cartilage fragments. To this end, we analyzed the transcriptional profiling of murine macrophages exposed to cartilage fragments by RNA sequencing. A total 153 genes were differentially upregulated, and 105 genes were down-regulated in response to cartilage fragments. Bioinformatic analysis revealed that the most significantly enriched terms of the upregulated genes included scavenger receptor activity, integrin binding activity, TNF signaling, and toll-like receptor signaling. To further confirm our results, immunohistochemical staining was performed to detected regulated molecules in synovial tissues of OA patients. In consistence with RNA-seq results, MARCO, TLR2 and ITGα5 were mainly detected in the intima lining layer of synovial tissues. Moreover, blockade of TLR2 or ITGα5 but not Marco using specific antibody significantly reduced production of TNF-α in stimulated macrophages by cartilage fragments. Our data suggested that blocking TLR2 or ITGα5 might be promising therapeutic strategy for treating progressive osteoarthritis.

Identifying effector molecules, cells, and cytokines of innate immunity in OA

Inflammatory changes are observed in affected joints of osteoarthritis (OA) patients and are thought to be involved in the pathology that develops along OA progression. This narrative review provides an overview of the various cell types that are present in the joint during OA and which alarmins, cytokines, chemokines, growth factors, and other mediators they produce. Moreover, the involvement of more systemic processes like inflammaging and its associated cellular senescence in the context of OA are discussed.

Theobromine mitigates IL-1β-induced oxidative stress, inflammatory response, and degradation of type II collagen in human chondrocytes

Osteoarthritis is one of the major causes of disability in elderly adults. Chondrocytes are responsible for the formation and remodeling of articular cartilage in joint tissue. The dysfunction of chondrocytes is a significant factor in the development of osteoarthritis. In the current study, we found that theobromine, a constituent of the cacao plant, possesses a preventive effect against interleukin (IL)-1β-induced chondrocyte dysfunction. Theobromine ameliorates IL-1β-induced production of cellular reactive oxygen species (ROS) and inflammatory mediators including cyclooxygenase-2 (COX-2) and prostaglandin E2 (PGE2). The presence of theobromine suppresses IL-1β-induced inducible nitro oxide synthase (iNOS) expression and cellular nitro oxide (NO) production. Theobromine also suppresses IL-1β-induced production of the pro-inflammatory cytokines tumor necrosis factor-α (TNF-α) and monocyte chemoattractant protein-1 (MCP-1), as well as matrix metalloproteinases (MMP)-3 and MMP-13. Additionally, theobromine mitigates IL-1β-induced type II collagen degradation. Mechanistically, we show that theobromine inhibits IL-1β-induced IκBα activation, nuclear factor-κB (NF-κB) protein p65 accumulation, and transfected NF-κB promoter activity, indicating that theobromine suppresses the NF-κB pathway in chondrocytes. Collectively, our study demonstrates that the natural molecule theobromine has a protective effect to counter cytokine-induced chondrocyte dysfunction, implying its beneficial effect in the prevention of osteoarthritis.

The Effect of Aqueous Extract of Trachyspermum ammi Seeds and Ibuprofen on Inflammatory Gene Expression in the Cartilage Tissue of Rats with Collagen-Induced Arthritis

Background and Objectives

Rheumatoid arthritis (RA) is an inflammatory disease treated with nonsteroidal anti–inflammatory drugs that have different side effects. One of the plants used for this purpose in the traditional medicine is Trachyspermum ammi. The present study aimed at investigating the anti–inflammatory effect of this plant on type II collagen-induced arthritis (CIA) in Wistar rats.

Materials and Methods

The study was performed on 35 male Wistar rats. Seven rats were considered as the healthy control group (normal group), and CIA was stablished in the rest. The rats with a model of inflammatory arthritis were divided into four groups. One group did not receive any treatment and three groups were treated orally with ibuprofen (15 mg/kg), aqueous extract of the T. ammi seeds (100 mg/kg), or their combination for 30 days. The effect of different treatments was investigated on the paw thickness, arthritis score, and mRNA level of COX2 and iNOS genes.

Results

CIA increased paw thickness, arthritis score, and COX2 and iNOS mRNA levels compared to those of the normal group. Treatment with ibuprofen and aqueous extract alone or in combination reduced the studied variables. Reduction in the paw thickness, arthritis score, and iNOS mRNA level was more in the ibuprofen-treated group than the T. ammi extract-treated group, but treatment with T. ammi extract reduced COX2 mRNA level more than ibuprofen.

Conclusion

It seems that the aqueous extract of T. ammi can be used alone or in combination with ibuprofen to treat RA.

A representative metalloprotease induces PGE2 synthesis in fibroblast-like synoviocytes via the NF-κB/COX-2 pathway with amplification by IL-1β and the EP4 receptor

Inflammatory joint conditions are characterized by synovial inflammation, which involves activation of fibroblast-like synoviocytes (FLSs) and production of inflammatory mediators and matrix metalloproteases (MMPs) in joints. This study showed that the snake venom metalloprotease (SVMP) BaP1 activates FLSs to produce PGE₂ by a mechanism dependent on COX-2, mPGES-1 and iPLA₂s. BaP1 also induces IL-1β release, which up-regulates the production of PGE₂ at a late stage of the stimulation. Expression of COX-2 and mPGES-1 are induced by BaP1 via activation of NF-κB pathway. While NF-κB p50 and p65 subunits are involved in up-regulation of COX-2 expression, only p65 is involved in BaP1-induced mPGES-1 expression. In addition, BaP1 up-regulates EP4 receptor expression. Engagement of this receptor by PGE₂ triggers a positive feedback loop for its production by up-regulating expression of key components of the PGE₂ biosynthetic cascade (COX-2, mPGES-1 and the EP4 receptor), thus contributing to amplification of BaP1-induced effects in FLSs. These data highlight the importance of FLS as a target for metalloproteases in joint inflammation and provide new insights into the roles of MMPs in inflammatory joint diseases. Moreover, our results may give insights into the importance of the catalytic domain, of MMPs for the inflammatory activity of these enzymes.

Curcumin attenuates MSU crystal-induced inflammation by inhibiting the degradation of IκBα and blocking mitochondrial damage

BACKGROUND

Gouty arthritis is characterized by the deposition of monosodium urate (MSU) within synovial joints and tissues due to increased urate concentrations. In this study, we explored the effect of the natural compound curcumin on the MSU crystal-stimulated inflammatory response.

METHODS

THP-1-derived macrophages and murine RAW264.7 macrophages were pretreated with curcumin for 1 h and then stimulated with MSU suspensions for 24 h. The protein level of TLR4, MyD88, and IκBα, the activation of the NF-κB signaling pathway, the expression of the NF-κB downstream inflammatory cytokines, and the activity of NLRP3 inflammasome were measured by western blotting and ELISA. THP-1 and RAW264.7 cells were loaded with MitoTracker Green to measure mitochondrial content, and MitoTracker Red to detect mitochondrial membrane potential. To measure mitochondrial reactive oxygen species (ROS) levels, cells were loaded with MitoSOX Red, which is a mitochondrial superoxide indicator. The effects of curcumin on mouse models of acute gout induced by the injection of MSU crystals into the footpad and synovial space of the ankle, paw and ankle joint swelling, lymphocyte infiltration, and MPO activity were evaluated.

RESULTS

Curcumin treatment markedly inhibited the degradation of IκBα, the activation of NF-κB signaling pathway, and the expression levels of the NF-κB downstream inflammatory genes such as IL-1β, IL-6, TNF-α, COX-2, and PGE2 in the MSU-stimulated THP-1-derived macrophages. Curcumin administration protected THP-1 and RAW264.7 cells from MSU induced mitochondrial damage through preventing mitochondrial membrane potential reduction, decreasing mitochondria ROS, and then inhibited the activity of NLRP3 inflammasome. Intraperitoneal administration of curcumin alleviated MSU crystal-induced paw and ankle joint swelling, inflammatory cell infiltration, and MPO activity in mouse models of acute gout. These results correlated with the inhibition of the degradation of IκBα, the phosphorylation levels of NF-κB subunits (p65 and p50), and the activity of NLRP3 inflammasome.

CONCLUSION

Curcumin administration effectively alleviated MSU-induced inflammation by suppressing the degradation of IκBα, the activation NF-κB signaling pathway, the damage of mitochondria, and the activity of NLRP3 inflammasome. Our results provide a new strategy in which curcumin therapy may be helpful in the prevention of acute episodes of gout.

CP-25 reverses prostaglandin E4 receptor desensitization-induced fibroblast-like synoviocyte dysfunction via the G protein-coupled receptor kinase 2 in autoimmune arthritis

Paeoniflorin-6'-O-benzene sulfonate (CP-25) is a novel compound derived from paeoniflorin that has been demonstrated to have therapeutic effects in a rat model of rheumatoid arthritis (RA). However, the underlying mechanism has not been elucidated to date. We explored this mechanism in the present study by treating rats with adjuvant arthritis (AA) with CP-25. We found that the membrane EP4 protein level was downregulated; whereas, GRK2 was upregulated, in fibroblast-like synoviocyte (FLS)s of AA rats. Prostaglandin (PGE)2 stimulated FLS proliferation and enhanced the membrane EP4 receptor protein level; the latter was reversed by the administration of an EP4 receptor agonist, whereas the membrane GRK2 protein level gradually increased. The changes in the EP4 receptor and GRK2 expression were enhanced by TNF-α, and the former was accompanied by an alteration in the cyclic (c)AMP level. The EP4 receptor agonist stimulation increased the association between GRK2 and the EP4 receptor. GRK2 knockdown abrogated the abnormalities in FLS proliferation. The CP-25 treatment (100 mg/kg) suppressed joint inflammation with an efficacy that was similar to that of methotrexate. This finding was associated with EP4 upregulation and GRK2 downregulation in FLSs. Thus, GRK2 plays an important role in the abnormal FLS proliferation observed in AA possibly by promoting EP4 receptor desensitization and decreasing the cAMP level. Our results demonstrate that CP-25 has therapeutic potential for the treatment of human RA via GRK2 regulation.

Structural characterization and anti-inflammatory activity evaluation of chemical constituents in the extract of Trifolium repens L

The chemical constituents in Trifolium repens L. were comprehensively studied by UPLC in this work, and a total number of 308 compounds were detected with 169 ones identified. The possible fragmentation pathways were proposed and fragmentation rules were summarized. On the basis of the concluded strategies, the characterized compounds could be classified into organic acids and their derivatives, alkaloids, amino acids, peptides, flavonoids, oligosaccharides, coumarins, and other types of compounds. This approach provided a rapid way for the identification of constituents in T. repens L., and even in other complex analytes. Among the separation and identification of the constituents, three compounds of great amount were isolated and characterized by NMR. The expression of iNOS and COX-2 in LPS-induced RAW 264.7 cells was suppressed by the pretreatment with three isolated constituents. The results implied they may potentially serve as a remedy for the therapy of inflammation. PRACTICAL APPLICATIONS: This work provided a rapid method for the identification of the complex analyte, which could be used in TCM, natural food and so on. The summarized fragmentation rule could be applied for the analysis of several types of compounds, such as organic acids and their derivatives, alkaloids, amino acids and peptides, flavonoids, oligosaccharides, coumarins, and so on. Most of natural plants contain these kinds of compounds, so these rules could have wide applications. Except the phytochemical investigation, T. repens L. displayed anti-inflammation activity according to the reported literature, and the three isolated constituents may potentially serve as a remedy for the therapy of inflammation referring to the result of this research.

Cysteinyl leukotriene receptor antagonism: a promising pharmacological strategy for lowering the severity of arthritis

BACKGROUND AND AIMS

Though cyclooxygenase inhibitors are employed in rheumatoid arthritis treatment, modulators of leukotrienes are underexplored. We investigated the therapeutic potential of montelukast, a known cysteinyl leukotriene receptor-1 (CysLT1) inhibitor in an experimental rat model of arthritis.

METHODS

Arthritis was induced in rats, and montelukast (5 mg/kg body wt.) was administered prophylactically (PAM) and therapeutically (TAM) through oral route.

RESULTS AND DISCUSSION

Blood and joint tissue markers of oxidative stress (lipid peroxidation, protein carbonyls, and nitric oxides) were significantly (p < 0.05) reduced in montelukast administered rats. Paw inflammation, RA markers (RF and CRP), eicosanoids (PGE₂, LTB₄, and LTC₄), cytokines (IL-1β and MCP-1), activity of hydrolytic enzymes (collagenase, elastase, and hyaluronidase), expression of matrix metalloproteinases (MMP), and EP-4 receptor were significantly (p < 0.05) reduced in montelukast administered rats. This study established that leukotriene inhibition through montelukast lowered the severity of arthritis and thus a potential strategy for reducing the severity of arthritis.

Therapeutic effects of the total lignans from Vitex negundo seeds on collagen-induced arthritis in rats

BACKGROUND

The seeds of Vitex negundo, with rich lignans metabolites, have been widely used as a traditional Chinese medicine and Ayurvedic herbal medicine for the treatment of rheumatism and joint inflammation. The total lignans of Vitex negundo seeds (TOV) were suggested to play an important role in the treatment of arthritis.

PURPOSE

The aim of the study was designed to investigate the anti-arthritic effects of TOV on collagen-induced arthritis (CIA) in rats as well as its possible mechanisms.

METHODS

TOV was prepared by combined macroporous resin and polyamide column chromatography, and constituents of TOV were analyzed by HPLC. CIA model in rats was established by immunization with chicken type II collagen and then the rats were intragastrically administrated with TOV for 30 days. Rat arthritis was evaluated by measurements of hind paw edema, arthritis index score, weight growth and indices of thymus and spleen, and by histological examination. Levels of serum MMP-2, MMP-3, MMP-9, IL-1β, IL-6, IL-8, IL-10, IL-17A and TNF-α were also examined. In addition, the expression of COX-2, iNOS and IκB, p-IκB in synovial tissues was evaluated by western blotting. The analgesic and anti-inflammatory effects of TOV were also evaluated in acetic acid-induced writhing and xylene-induced ear edema in mice, respectively. In addition, acute toxicity test was employed to preliminarily assess the safety of TOV.

RESULTS

TOV significantly inhibited the paw edema and decreased the arthritis index, with no influence on the body weight and the indices of thymus and spleen of CIA rats. Meanwhile, TOV dose-dependently reduced the infiltration of inflammatory cells, synovial hyperplasia and attenuated cartilage damage. Additionally, the serum levels of IL-1β, IL-6, IL-8, IL-17A, TNF-α, MMP-3 and MMP-9 were markedly decreased, while the level of serum IL-10 was increased in TOV-treated rats. The significant reduction of the expression of COX-2, iNOS and p-IκB and the notable increase of IκB in synovial tissues were also observed in TOV-treated animals. TOV also significantly inhibited acetic acid-induced writhing and decreased xylene-induced ear edema in mice. Finally, the maximal tolerable dose (MTD) of TOV was determined to be 16.0 g/kg.

CONCLUSION

These results suggest that TOV has significant anti-arthritic effects on collagen-induced arthritis in rats, which may be attributed to the inhibition of the levels of IL-1β, IL-6, IL-8, IL-17A, TNF-α, MMP-3 and MMP-9, and the increase of IL-10 in serum as well as down-regulation of the protein expression of COX-2 and iNOS in synovial tissues via suppressing the phosphorylation and degradation of IκB. Due to its high efficacy and safety, TOV can be regarded as a promising drug candidate for rheumatoid arthritis treatment.

Regulatory effects of paeoniflorin-6'-O-benzene sulfonate (CP-25) on dendritic cells maturation and activation via PGE2-EP4 signaling in adjuvant-induced arthritic rats

Rheumatoid arthritis (RA) is a chronic, systemic autoimmune disease. Dendritic cells (DCs) are one of the most powerful antigen-presenting cells, and they play an important role in RA pathogenesis. Prostaglandin E2 (PGE2) is a potent lipid mediator that can regulate the maturation and activation of DCs, but the molecular mechanisms have not been elucidated. In this study, both in vitro and in an RA rat model, we investigated the mechanisms involved by focusing on PGE2-mediated signaling and using a novel anti-inflammatory compound, paeoniflorin-6'-O-benzene sulfonate (CP-25). PGE2 combined with tumor necrosis factor-α promoted DC maturation and activation through EP4-cAMP signaling. Treatment with CP-25 increased the endocytic capacity of DCs induced by PGE2. CP-25 inhibited the potency of DCs induced by the EP4 receptor agonist, CAY10598, to stimulate allogeneic T cells. Consistent with these findings, the CAY10598-induced upregulation of DC surface activation markers and production of IL-23 was significantly inhibited by CP-25 in a concentration-dependent manner. In vivo administration of CP-25 alleviated adjuvant arthritis (AA) in rats through inhibition of DC maturation and activation. Our results indicate that PGE2-EP4-cAMP signal hyperfunction can lead to abnormal activation of DC functions, which correlates with the course of disease in AA rats and provides a possible treatment target. The inhibition of DC maturation and activation by CP-25 interference of the PGE2-EP4 pathway may significantly contribute to the immunoregulatory profile of CP-25 when used to treat RA and other immune cell-mediated disorders.

Glycogen synthase kinase-3 inhibitor as a multi-targeting anti-rheumatoid drug

Rheumatoid arthritis (RA) is a chronic inflammatory joint disease that causes swelling, bone erosion, and joint disorder. Patients with RA therefore suffer from pain and physiological disability, and have a decreased quality of life. During the progression of RA, many different types of cells and inflammatory factors influence each other with an important role. A better understanding of the pathology of RA should therefore lead to the development of effective anti-rheumatoid drugs, such as the anti-TNFα antibody. Glycogen synthase kinase-3 (GSK-3) is a cytoplasmic serine/threonine protein kinase that is involved in a large number of key cellular processes and is dysregulated in a wide variety of diseases, including inflammation and osteoporosis. The accumulated evidence has suggested that GSK-3 could be involved in multiple steps in the progression of RA. In the present review, the mechanisms of the pathogenesis of RA are summarized, and recent developments and potential new drugs targeting GSK-3 are discussed.