Inflammatory Response In Chondrocytes Research Articles

Novel Insights into the Links between N6-Methyladenosine and Regulated Cell Death in Musculoskeletal Diseases.

Musculoskeletal diseases (MSDs), including osteoarthritis (OA), osteosarcoma (OS), multiple myeloma (MM), intervertebral disc degeneration (IDD), osteoporosis (OP), and rheumatoid arthritis (RA), present noteworthy obstacles associated with pain, disability, and impaired quality of life on a global scale. In recent years, it has become increasingly apparent that N6-methyladenosine (m6A) is a key regulator in the expression of genes in a multitude of biological processes. m6A is composed of 0.1-0.4% adenylate residues, especially at the beginning of 3'-UTR near the translation stop codon. The m6A regulator can be classified into three types, namely the "writer", "reader", and "eraser". Studies have shown that the epigenetic modulation of m6A influences mRNA processing, nuclear export, translation, and splicing. Regulated cell death (RCD) is the autonomous and orderly death of cells under genetic control to maintain the stability of the internal environment. Moreover, distorted RCDs are widely used to influence the course of various diseases and receiving increasing attention from researchers. In the past few years, increasing evidence has indicated that m6A can regulate gene expression and thus influence different RCD processes, which has a central role in the etiology and evolution of MSDs. The RCDs currently confirmed to be associated with m6A are autophagy-dependent cell death, apoptosis, necroptosis, pyroptosis, ferroptosis, immunogenic cell death, NETotic cell death and oxeiptosis. The m6A-RCD axis can regulate the inflammatory response in chondrocytes and the invasive and migratory of MM cells to bone remodeling capacity, thereby influencing the development of MSDs. This review gives a complete overview of the regulatory functions on the m6A-RCD axis across muscle, bone, and cartilage. In addition, we also discuss recent advances in the control of RCD by m6A-targeted factors and explore the clinical application prospects of therapies targeting the m6A-RCD in MSD prevention and treatment. These may provide new ideas and directions for understanding the pathophysiological mechanism of MSDs and the clinical prevention and treatment of these diseases.

Micro-current stimulation could inhibit IL-1β-induced inflammatory responses in chondrocytes and protect knee bone cartilage from osteoarthritis

Micro-current stimulation could inhibit IL-1β-induced inflammatory responses in chondrocytes and protect knee bone cartilage from osteoarthritis

Inflammatory Response Modulation by Low-Dose Anti-inflammatory Drugs Treatment in an In Vitro Osteoarthritis Cellular Model.

Low-dose-medicine is based on the administration of low doses of biological regulators to restore the immunologic balance altered in the disease. Cytokines are pivotal regulators of cellular and tissue functions and impaired crosstalk, due to an imbalance between specific cytokines, it is fundamental in acute inflammation and diseases correlated to low-grade chronic inflammation. Osteoarthritis is the most prevalent arthritic disease and a leading cause of disability. In the treatment of muscle- skeletal pathologies, the therapeutic integration of conventional medicine with homotoxicology, or low-dose-medicine appears to be beneficial. This study aims to get more insights into the role of inflammatory cytokines and chemokines during the development of osteoarthritis and to evaluate a possible blocking strategy using anti-inflammatory molecules, we resort to an in vitro experimental model using an established human chondrosarcoma cell line that underwent to a well known pro-inflammatory stimulus as bacterial lipopolysaccharide. We tested the production of inflammatory-related cytokines and chemokines, and the efficacy of low-dose (LD) administration of anti-inflammatory compounds, namely IL-10 and anti-IL-1, to block inflammatory cellular pathways. Following an inflammatory insult, chondrocytes upregulated the expression of several pro-inflammatory cyto-/chemokines and this induction could be counteracted by LD IL-10 and anti-IL-1. We reported that these effects could be ascribed to an interfering effect of LD drugs with the NF-κB signaling. Our results provided a good indication that LD drugs can be effective in inhibiting the inflammatory response in chondrocytes opening the way to new therapies for the treatment of diseases such as osteoarthritis.

Gentiopicroside ameliorates the lipopolysaccharide-induced inflammatory response and hypertrophy in chondrocytes

PurposeThis study aimed to evaluate the protective effects of gentiopicroside against lipopolysaccharide-induced chondrocyte inflammation.MethodsSW 1353 chondrosarcoma cells were stimulated with LPS (5 μg/ml) for 24 h and treated with different concentrations of gentiopicroside (GPS) for 24 h. The toxic effects of GPS on chondrocytes were determined using a CCK-8 assay and EdU staining. Western blotting, qPCR, and immunofluorescence analysis were used to examine the protective effect of GPS against the inflammatory response in chondrocytes induced by lipopolysaccharide (LPS). One-way ANOVA was used to compare the differences between the groups (significance level of 0.05).ResultsThe CCK-8 results showed that 10, 20 and 40 μM GPS had no significant toxic effects on chondrocytes; GPS effectively reduced the production of IL-1β and PGE2, reversed LPS-induced extracellular matrix degradation in cartilage by inhibiting the Stat3/Runx2 signaling pathway, and suppressed the hypertrophic transformation of SW 1353 chondrosarcoma cells.ConclusionOur study demonstrated that GPS significantly inhibited the LPS-induced inflammatory response and hypertrophic cellular degeneration in SW 1353 chondrosarcoma cells and is a valuable traditional Chinese medicine for the treatment of knee osteoarthritis.

FSTL1 Accelerates Nucleus Pulposus Cell Senescence and Intervertebral Disc Degeneration Through TLR4/NF-κB Pathway.

Intervertebral disc degeneration (IVDD) is a major contributor to low back pain (LBP), and inflammatory factors play crucial roles in its pathogenesis. Follistatin-like 1 (FSTL1) has been reported to induce an inflammatory response in chondrocytes, microglia and preadipocytes, but its role in the pathogenesis of nucleus pulposus cell (NPC) degeneration remains unclear. In this study, we mainly utilized an acidosis-induced NPC degeneration model and a rabbit puncture IVDD model to investigate the role of FSTL1 in IVDD both in vitro and in vivo. We confirmed that FSTL1 expression significantly increased in nucleus pulposus (NP) tissues from IVDD patients and rabbit puncture IVDD models. The expression levels of FSTL1 were significantly increased in all three models of NPC degeneration under harsh microenvironments. In addition, recombinant human FSTL1 (rh-FSTL1) was found to upregulate the expression of p16 and p21, increase the number of senescence-associated β-galactosidase (SA-β-gal)-positive cells, induce senescence-related secretory phenotypes (SASP), and downregulate extracellular matrix (ECM) protein expressions, leading to an imbalance in ECM metabolism destructions. Conversely, silencing of FSTL1 by small interfering RNA (siRNA) ameliorated senescence of NPCs associated with inflammation in IVDD. Furthermore, Toll-like receptor 4/nuclear factor-κB (TLR4/NF-κB) pathway plays a crucial role in regulating NPC senescence through FSTL1 regulation. Inhibition of TLR4 expression partly reversed the effects of rh-FSTL1 on NPC senescence-associated inflammation. Finally, rabbit IVDD model experiments demonstrated that the specific FSTL1 siRNA markedly repressed the development of IVDD. These findings may offer a therapeutic approach for mitigating inflammation-induced senescence associated with IVDD.

Anti-Inflammatory Activity of APPA (Apocynin and Paeonol) in Human Articular Chondrocytes.

Osteoarthritis (OA) is a chronic joint disease leading to cartilage loss and reduction in the joint space which results in pain. The current pharmacological treatment of OA is inadequate and pharmacological interventions focus on symptom management. APPA, a combination of apocynin (AP) and paeonol (PA), is a potential drug for treating OA. The aim of this study was to analyze the effects of APPA on the modulation of the inflammatory response in chondrocytes. Samples were incubated with IL-1β and APPA, and their responses to proinflammatory cytokines, catabolic mediators and redox responses were then measured. The effect of APPA on mitogenesis was also evaluated. Results show that APPA attenuated the expression of IL-8, TNF-α, MMP-3, MMP-13, SOD-2 and iNOS, resulting in the protection of human articular cartilage. APPA decreased PGC-1α gene expression induced by IL-1β. APPA did not modulate the gene expression of Mfn2, Sirt-1 or Sirt-3. The overall findings indicate that APPA may be an effective treatment for OA by targeting several of the pathways involved in OA pathogenesis.

Hexabromocyclododecane (HBCD) induced PANoptosis of chondrocytes via activation of the NLRP3 inflammasome and decreased the exercise ability of mice in vivo

Hexabromocyclododecane (HBCD) is a persistent organic pollutant (POP). HBCD is found in the blood and tissues of most populations and causes a range of toxicological damage to tissues and cells. However, the toxicological effects of HBCD on chondrocytes are not fully understood. Here, we evaluated the toxicological effects of HBCD on chondrocytes and cartilaginous tissue. For this, a model of primary cartilage cells was established. Chondrocytes were exposed to different concentrations of HBCD. Western blot, indirect immunofluorescence, ELISA and other biochemical experiments were performed to analyze the toxicological effects of HBCD on chondrocytes/articular cartilage tissue. Cell proliferation assays showed that HBCD caused a reduction in the proliferative capacity of chondrocytes, and further work indicated that HBCD induces chondrocyte death. Further experiments demonstrated that HBCD caused an inflammatory response in chondrocytes by evaluating the levels of inflammatory factors. We found that HBCD led to PANoptosis in chondrocytes by detecting panapoptosis-related marker molecules, and experimental data indicated that apoptosis markers (cleaved caspase-3/7), pyroptosis markers (caspase-1/GSDMD-N) and necroptosis markers (pMLKL/RIPK3) were upregulated after HBCD treatment. Subsequent experiments illustrated that HBCD activated the DAMP sensor NLRP3, which then mediated ZBP1-induced PANoptosis. In the in vivo model, the experimental animals were administered HBCD at 25, 50 and 100 µg/kg/week for 15 weeks. We found that HBCD led to an inflammatory response in articular cartilage tissue. The safranin O-fast green assay showed a certain degree of damage to cartilage tissue under HBCD treatment. Furthermore, HBCD resulted in an increase in MMP13 expression and a downregulation of COL2 expression in chondrocytes/cartilaginous tissues. HBCD decreased the exercise ability of mice in vivo. These data indicate that HBCD leads to chondrocyte damage. In summary, this study lays the foundation for further exploration of the toxicological effects of HBCD on bone and joints.

THU471 Resolution Of Elevated Alkaline Phosphatase After Joint Replacement In Severe Osteoarthritis

Abstract Disclosure: J. Rakholiya: None. S. Nagaraj: None. P. Sharma: None. Introduction: Alkaline phosphatase (ALP) elevation is commonly seen in hepatobiliary disorders. Conditions of high turnover such as healing fractures, hyperparathyroidism, Pagets’ disease of the bone, also lead to ALP elevation (1). Osteoarthritis (OA), characterised by degeneration of articular cartilage, joint space narrowing, and osteophyte formation, rarely causes ALP elevation. We present a case of ALP elevation that resolved after the arthritic joint was replaced. Case Presentation: A 60-year-old female with history of bilateral knee OA presented to the endocrinology clinic due to elevated ALP for over a year. She reported chronic fatigue, sleep disturbance, dry skin, hair loss, inability to lose weight and anxiety. ALP level at presentation was 165 U/L. An extensive work-up showed unremarkable serum and ionized calcium, serum phosphorus, parathyroid hormone, vitamin D 25-OH, calcitriol, 24-hour urine calcium, serum protein electrophoresis, and 24-hour urine protein electrophoresis. Dual x-ray absorptiometry (DXA) scan was normal with Fracture risk assessment tool (FRAX) score 5.9% for major osteoporotic fracture and 0.2% for hip fracture. Patient underwent total left knee arthroplasty following which ALP improved from 165 U/L to 135 U/L within 9 weeks of the procedure. Five months later, ALP was elevated (164 U/L) again. She then underwent right knee arthroplasty and ALP dropped to normal level (114 U/L) within 1 week post-surgery. Discussion: We report the rare phenomenon of ALP elevation in severe OA, that resolved after joint replacement. OA is characterised by inflammation mediated cartilage destruction, subchondral bone change, osteophyte formation, and alterations of ligaments and meniscuses. Bone change in severe OA is associated with increased synovial fluid ALP level. However, there is a paucity of literature studying the association of ALP with OA. A cross-sectional study of 3060 patients demonstrated higher serum ALP with symptomatic knee OA. Another study showed higher ALP levels with increased joint stiffness. The ALP elevation was attributed to low grade inflammation causing an inflammatory response in chondrocytes, and osteoarthritic pain. There is a need for more studies to evaluate the utility of serum ALP as a biomarker for severe OA. Presentation: Thursday, June 15, 2023

Bergapten exerts a chondroprotective effect in temporomandibular joint osteoarthritis by combining intestinal flora alteration and reactive oxygen species reduction

Bergapten, a furanocoumarin naturally occurring in bergamot essential oil, has been demonstrated to have the potential to alleviate osteoarthritis-related symptoms via its anti-inflammatory activity. Although its systemic bioavailability is limited, its precise mechanisms of action and effects on temporomandibular joint osteoarthritis (TMJOA) and its relationship with the intestinal flora remain unclear. Here, we explored the anti-TMJOA effect of BGT combined with the interleukin-1β-induced inflammatory response of chondrocytes in a monosodium iodoacetate (MIA)-induced TMJOA rat model. It was confirmed that BGT effectively reduced proinflammatory mediators and increased type II collagen, bone volume, and trabecular number of condyles in TMJOA rats. Importantly, the oral administration of BGT altered the intestinal flora of rats by increasing the relative abundances of nine prebiotic species and decreasing the relative abundance of one potential species. In addition, BGT considerably reduced reactive oxygen species (ROS) levels by suppressing glutathione, oxidized glutathione, and superoxide dismutase in the serum and malondialdehyde in urine. These results suggest that BGT exerts a chondroprotective effect, most likely by improving the intestinal flora and reducing ROS production associated with TMJOA in rats. This finding indicates a novel beneficial effect of BGT on the prevention and treatment of TMJOA.

SPRED2 promotes autophagy and attenuates inflammatory response in IL-1β induced osteoarthritis chondrocytes via regulating the p38 MAPK signaling pathway

Osteoarthritis (OA) is an age-related degenerative disease primarily characterized by articular cartilage degeneration. Many inflammatory mediators are upregulated in OA patients. Mitogen-activated protein kinase (MAPK) and nuclear factor-κB (NF-κB) pathways play a role in the regulation of inflammatory response. Autophagy appears to exhibit a protective mechanism, and alleviate the symptoms of OA in rats. Dysregulation of SPRED2 is associated with various diseases involving inflammatory response. However, the role of SPRED2 in OA development remains to be investigated. The present work demonstrated that SPRED2 promoted autophagy and attenuated inflammatory response in IL-1β induced osteoarthritis chondrocytes via regulating the p38 MAPK signaling pathway. SPRED2 was downregulated in human knee cartilage tissues of OA patients and in IL-1β-induced chondrocytes. SPRED2 enhanced chondrocyte proliferation and prevented cell apoptosis induced by IL-1β. SPRED2 prevented IL-1β-induced chondrocytes autophagy and inflammatory response in chondrocytes. SPRED2 inhibited the activation of p38 MAPK signaling pathway and ameliorated OA injury of cartilage. Thus, SPRED2 promoted autophagy and inhibited inflammatory response by regulation of p38 MAPK signaling pathway in vivo.

BuShen JianGu Fang alleviates cartilage degeneration via regulating multiple genes and signaling pathways to activate NF-κB/Sox9 axis

BackgroundOsteoarthritis (OA) is an inflammatory response in chondrocytes, causing extracellular matrix (ECM) degradation and cartilage destruction, affecting millions of people worldwide. Chinese herbal formulae BuShen JianGu Fang (BSJGF) has been clinically applied for treating OA-related syndromes, but the underlying mechanism still unclear. MethodsThe components of BSJGF were analyzed by liquid chromatography-mass spectrometry (LC-MS). To make a traumatic OA model, the anterior cruciate ligament of 6-8-week-old male SD rats were cut and then the 0.4 mm metal was used to destroy the knee joint cartilage. OA severity was assessed by histological and Micro-CT. Mouse primary chondrocytes were utilized to investigate the mechanism of BSJGF alleviate osteoarthritis, which was examined by RNA-seq technology combined with a series of functional experiments. ResultsA total 619 components were identified by LC-MS. In vivo, BSJGF treatment result in a higher articular cartilage tissue area compared to IL-1β group. Treatment also significantly increased Tb.Th, BV/TV and BMD of subchondral bone (SCB), which implied a protective effect on maintaining the stabilization of SCB microstructure. In vitro results indicated BSJGF promoted chondrocyte proliferation, increased the expression level of cartilage-specific genes (Sox9, Col2a1, Acan) and synthesized acidic polysaccharide, while inhibiting the release of catabolic enzymes and production of reactive oxygen species (ROS) induced by IL-1β. Transcriptome analysis showed that there were 1471 and 4904 differential genes between IL-1β group and blank group, BSJGF group and IL-1β group, respectively, including matrix synthesis related genes (Col2a1, H19, Acan etc.), inflammation related genes (Comp, Pcsk6, Fgfr3 etc.) and oxidative stress related genes (Gm26917, Bcat1, Sod1 etc.). Furthermore, KEGG analysis and validation results showed that BSJGF reduces OA-mediated inflammation and cartilage damaged due to modulation of NF-κB/Sox9 signaling axis. ConclusionThe innovation of the present study was the elucidation of the alleviating cartilage degradation effect of BSJGF in vivo and in vitro and discovery of its mechanism through RNA-seq combined with function experiments, which provides a biological rationale for the clinical application of BSJGF for OA treatment.

HMGA1 Aggravates Oxidative Stress Injury and Inflammatory Responses in IL-1β-Induced Primary Chondrocytes through the JMJD3/ZEB1 Axis

Introduction: Osteoarthritis (OA) is associated with oxidative stress injury (OSI) and inflammatory responses in chondrocytes. This study sought to explore the mechanism of high mobility group A1 (HMGA1) in interleukin-1beta (IL-1β)-induced OSI and inflammatory responses in primary chondrocytes. Methods: Primary chondrocytes were cultured and treated with IL-1β to establish an OA-cell model. Levels of HMGA1, Jumonji domain-containing 3 (JMJD3), and ZEB1 in cells were determined by real-time quantitative polymerase chain reaction and Western blot analysis. Cell viability, contents of tumor necrosis factor-α, IL-6, and IL-10, reactive oxygen species level, and glutathione peroxidase activity were assessed by the cell counting kit-8 assay, enzyme-linked immunosorbent assay, and assay kits. Enrichment levels of HMGA1 on the JMJD3 promoter and enrichment levels of JMJD3 and trimethylated histone H3 at lysine 27 (H3K27me3) on the ZEB1 promoter region were determined by chromatin immunoprecipitation. Functional rescue experiments were performed to analyze the impact of ZEB1 and JMJD3 on IL-1β-induced chondrocytes. Results: IL-1β treatment induced HMGA1 upregulation, OSI, and inflammatory responses in chondrocytes. HMGA1 downregulation reduced IL-1β-induced OSI and inflammatory responses in chondrocytes. Mechanically, HMGA1 was bound to the JMJD3 promoter to promote JMJD3 transcription, and JMJD3 induced demethylation of H3K27me3 on the ZEB1 promoter to promote ZEB1 transcription. Overexpression of JMJD3 or ZEB1 neutralized the protective role of silencing HMGA1 in IL-1β-induced chondrocytes. Conclusion: HMGA1 aggravated IL-1β-induced OSI and inflammatory responses in chondrocytes through the promotion of JMJD3 and ZEB1.

Glutamine metabolism modulates chondrocyte inflammatory response.

Osteoarthritis is the most common joint disease in the world with significant societal consequences but lacks effective disease-modifying interventions. The pathophysiology consists of a prominent inflammatory component that can be targeted to prevent cartilage degradation and structural defects. Intracellular metabolism has emerged as a culprit of the inflammatory response in chondrocytes, with both processes co-regulating each other. The role of glutamine metabolism in chondrocytes, especially in the context of inflammation, lacks a thorough understanding and is the focus of this work. We display that mouse chondrocytes utilize glutamine for energy production and anabolic processes. Furthermore, we show that glutamine deprivation itself causes metabolic reprogramming and decreases the inflammatory response of chondrocytes through inhibition of NF-κB activity. Finally, we display that glutamine deprivation promotes autophagy and that ammonia is an inhibitor of autophagy. Overall, we identify a relationship between glutamine metabolism and inflammatory signaling and display the need for increased study of chondrocyte metabolic systems.

Circ_0043947 contributes to interleukin 1\u03b2-induced injury in chondrocytes by sponging miR-671-5p to up-regulate RTN3 expression in osteoarthritis pathology

ObjectiveOsteoarthritis (OA) is a chronic joint disease featured by articular cartilage degeneration and damage. Accumulating evidence have demonstrated the pivotal regulatory roles of circular RNAs in OA pathology. However, the role of circ_0043947 in OA progression and its associated mechanism remain largely unknown.MethodsThe expression of RNA and protein was determined by reverse transcription-quantitative polymerase chain reaction and Western blot assay. Cell viability was assessed by 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Cell proliferation was analyzed by 5-Ethynyl-2′-deoxyuridine (EdU) assay and flow cytometry. Cell apoptosis was assessed by flow cytometry. Enzyme linked immunosorbent assay was conducted to analyze the release of pro-inflammatory cytokines. Dual-luciferase reporter assay and RNA immunoprecipitation assay were performed to confirm the target interaction between microRNA-671-5p (miR-671-5p) and circ_0043947 or reticulon 3 (RTN3).ResultsInterleukin 1β (IL-1β) stimulation up-regulated the expression of circ_0043947 in chondrocytes. IL-1β treatment restrained the viability and proliferation and induced the apoptosis, extracellular matrix degradation and inflammatory response of chondrocytes partly by up-regulating circ_0043947. Circ_0043947 interacted with miR-671-5p, and miR-671-5p silencing largely reversed circ_0043947 knockdown-mediated protective effects in IL-1β-induced chondrocytes. miR-671-5p interacted with the 3′ untranslated region (3′UTR) of RTN3. miR-671-5p overexpression attenuated IL-1β-induced injury in chondrocytes, and these protective effects were largely overturned by the overexpression of RTN3. Circ_0043947 acted as a molecular sponge for miR-671-5p to up-regulate RTN3 level in chondrocytes.ConclusionCirc_0043947 silencing alleviated IL-1β-induced injury in chondrocytes by targeting miR-671-5p/RTN3 axis.

Glaucocalyxin A Attenuates IL-1β-Induced Inflammatory Response and Cartilage Degradation in Osteoarthritis Chondrocytes via Inhibiting the Activation of NF-κB Signaling Pathway.

Glaucocalyxin A (GLA) is a bioactive natural compound with anti-inflammatory activity. Herein, the role of GLA in osteoarthritis (OA) was evaluated. Our results demonstrated that the IL-1β-induced inducible nitric oxide synthase (iNOS) and cyclooygenase-2 (COX-2) expression, two enzymes resulting in the release of nitric oxide (NO) and PGE2, were also prevented by GLA in chondrocytes. Moreover, GLA suppressed inflammatory cytokines production in chondrocytes. In addition, the elevated expressions of MMPs and ADAMTSs and the degradation of aggrecan and collagen II were reversed by GLA in chondrocytes. Furthermore, GLA decreased p-p65 level and suppressed the nuclear p65 accumulation in the nucleus of chondrocytes. Collectively, we concluded that GLA attenuated inflammatory response in chondrocytes via NF-κB pathway. These findings suggested that GLA might become an effective agent for OA treatment.

Curcumin ameliorates H2O2-induced inflammatory response in chondrocytes by inducing autophagy activation.

Relapsing polychondritis (RP) is a clinical disease characterized by inflammation of cartilage tissue and chondrocytes. The principal curcuminoid curcumin is the most active component in turmeric and has been reported to have a chondroprotective effect, including anti-inflammatory activity, which is vitally important for mitigating RP symptoms and prognosis. However, the mechanisms underlying these actions have remained to be fully elucidated. In the present study, the chondroprotective mechanisms of curcumin on hydrogen peroxide (H2O2)-treated primary chondrocytes were examined in vitro. The viability of chondrocytes treated with H2O2 was significantly reduced in a dose- and time-dependent manner. Cotreatment of curcumin with H2O2 significantly decreased growth inhibition. It was observed that curcumin inhibited the expression levels of the inflammatory mediators interleukin (IL)-1β, IL-6 and inducible nitric oxide synthase and induced autophagy activation. Curcumin increased the protein levels of the autophagy marker beclin-1 and light chain 3-II and decreased the expression levels of P62 in H2O2-treated chondrocytes. The curcumin-induced anti-inflammatory effects were markedly abrogated by the autophagy inhibitor 3-methyladenine. In conclusion, the present study suggested that curcumin regulates inflammatory factors by activating autophagy in chondrocytes. The protective role of curcumin in chondrocytes was demonstrated, suggesting that it should be explored for the prophylactic treatment of RP in the clinic in the future.

Timosaponin B-II alleviates osteoarthritis-related inflammation and extracellular matrix degradation through inhibition of mitogen-activated protein kinases and nuclear factor-κB pathways in vitro

ABSTRACT Osteoarthritis (OA), an inflammatory response in chondrocytes, leads to extracellular matrix (ECM) degradation and cartilage destruction. Timosaponin B-II (TB-II) is the main bioactive component of Rhizoma Anemarrhenae with reported antioxidant and anti-inflammatory effects. This study investigated the anti-OA function and mechanism of TB-II on IL-1β-stimulated SW1353 cells and primary rat chondrocytes. We firstly screened the concentration of TB-II in SW1353 cells and primary rat chondrocytes using CCK-8 assay. Thereafter, SW1353 cells and chondrocytes were, respectively, pretreated with TB-II (20 and 40 μg/mL) and TB-II (10 and 30 μg/mL) for 24 h and then stimulated with interleukin 1β (IL-1β, 10 ng/mL) for another 24 hours. Results showed that TB-II suppressed the production of reactive oxygen species, the protein levels of inducible nitric oxide synthase and cyclooxygenase-2 in IL-1β-stimulated SW1353 cells and chondrocytes. IL-1β-induced high secretion levels of nitric oxide and prostaglandin 2, TNF-α, IL-6 and MCP-1 were down-regulated by TB-II treatment, indicating an anti-inflammatory effect of TB-II on OA in vitro condition. Moreover, TB-II weakened the mRNA and protein expression of (matrix metalloproteinase) MMPs including MMP-1, MMP-3, and MMP-13, indicating the protection of TB-II against ECM degradation. Mechanically, TB-II suppressed MAPKs and NF-κB pathways under IL-1β stimulation evidenced by the down-regulated protein expression of p-ERK, p-p38, p-JNK, p-p65 and the reduced translocation of p65 subunit to the nucleus. The present study demonstrated that TB-II might become a novel therapeutic agent for OA treatment through repressing IL-1β-stimulated inflammation, oxidative stress and ECM degradation via suppressing the MAPKs and NF-κB pathways.

Polygonatum sibiricum polysaccharide inhibits IL-1β-induced inflammation in human chondrocytes

Osteoarthritis (OA) is a degenerative joint disease associated with inflammation. Polygonatum sibiricum polysaccharide (PSP) is a major group of active components isolated from Polygonatum sibiricum with broad activities including anti-inflammatory effect. However, the role of PSP in OA is unclear. In the present study, we aimed to investigate the effects of PSP on IL-1β-induced inflammatory response in primary human OA chondrocytes. The results showed that PSP improved cell viability of chondrocytes in response to IL-1β induction. The increased levels of several inflammatory mediators including nitric oxide (NO), prostaglandin E2 (PGE2), inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) in IL-1β-induced chondrocytes were attenuated by PSP in a dose-dependent manner. The IL-1β-induced production of pro-inflammatory cytokines, TNF-α and IL-6, were mitigated by PSP in chondrocytes. Besides, PSP also suppressed the production of matrix metalloproteinases (MMPs), including MMP-1, MMP-3 and MMP-13 in IL-1β-stimulated chondrocytes. Furthermore, the IL-1β-induced activation of NF-κB signaling pathway in chondrocytes was also prevented by PSP. These findings suggested that PSP alleviated IL-1β-induced inflammatory response in chondrocytes via inhibiting NF-κB signaling pathway.

Cedrol alleviates the apoptosis and inflammatory response of IL-1β-treated chondrocytes by promoting miR-542-5p expression.

Cedrol has been shown to exert anti-tumor, anti-inflammatory, and anti-oxidative effects, but its role in osteoarthritis (OA) is unclear. This study aimed to explore the effect of cedrol in OA. Chondrocytes were isolated from newborn rats and cultured in Dulbecco's modified Eagle's medium (DMEM). Then, Alcian blue staining was used to identify the chondrocytes. IL-1β and cedrol were used to treat chondrocytes. Cell viability and apoptosis were measured by MTT and flow cytometry assays, respectively. The expressions of miR-542-5p, miR-26b-5p, miR-572, miR-138-5p, miR-328-3p, miR-1254, Bcl-2, Bax, iNOS, COX-2, and MMP-13 were detected by quantitative reverse transcription polymerase chain reaction (qRT-PCR) or western blot. NO and PGE2 levels were detected by ELISA. All the cells extracted from the newborn rats were dyed blue, indicating that the cells were chondrocytes. IL-1β could reduce the viability and promote apoptosis and inflammatory response of chondrocytes, while cedrol could reverse the effect of IL-1β. In addition, cedrol could significantly increase the expression of miR-542-5p in IL-1β-treated chondrocytes. Moreover, miR-542-5p inhibitor could partly reverse the effect of cedrol in the apoptosis and inflammation response of chondrocytes. Cedrol alleviated IL-1β-induced apoptosis and inflammatory response of chondrocytes by promoting miR-542-5p expression.

DNA methyltransferase 3 beta mediates the methylation of the microRNA-34a promoter and enhances chondrocyte viability in osteoarthritis

ABSTRACT Osteoarthritis (OA) is characterized by destruction of articular cartilage with an imbalance between synthesis and degradation of extracellular matrix (ECM). In the current study, we explored the role of microRNA-34a (miR-34a) and the behind epigenetic mechanism in the degradation of ECM in OA. Using miRNA-based microarray analysis, we found that miR-34a was overexpressed in cartilage tissues of OA patients relative to patients with acute traumatic amputations. Moreover, its expression was positively correlated with the ECM degradation and inflammation. Mechanistically, miR-34a targeted MCL1, and possible target genes of miR-34a were enriched in the PI3K/AKT pathway. Furthermore, DNMT3B inhibited miR-34a by promoting miR-34a methylation. Functional experiments using CCK-8, flow cytometry, Safranin O staining, RT-qPCR, ELISA, Western blot, and HE staining revealed that miR-34a inhibitor suppressed ECM degradation and inflammatory response of chondrocytes and cartilage tissues. By contrast, downregulation of DNMT3B and MCL1 reversed the repressive effects of miR-34a inhibitor in vitro and in vivo. Altogether, our findings establish that silencing of miR-34a by DNMT3B could effectively reduce chondrocyte ECM degradation and inflammatory response in mice by targeting MCL1 and mediating the downstream PI3K/AKT pathway. This present study revealed that miR-34a knockdown might develop a novel intervention for OA treatment.