Response In Human Osteoarthritis Chondrocytes Research Articles

UFL1 attenuates IL-1β-induced inflammatory response in human osteoarthritis chondrocytes

Osteoarthritis (OA) is a chronic inflammatory joint disease characterized by degradation of articular cartilage. Ubiquitin-fold modifier 1 (UFM1)-specific ligase 1 (UFL1) is an UFM1 E3 ligase that has been identified as a regulator of inflammatory response. However, the role of UFL1 in OA remains unknown. The aim of the present study was to explore the function of UFL1 in an in vitro OA system in chondrocytes. Our results showed that UFL1 was lowly expressed in both OA articular tissues and chondrocytes with IL-1β induction. Ectopic expression of UFL1 improved cell viability of IL-1β-induced chondrocytes. UFL1 suppressed the production of NO and PGE2, as well the expression levels of iNOS and COX-2 in IL-1β-induced chondrocytes. The IL-1β-induced increases in TNF-α and IL-6 levels were attenuated by UFL1. Ectopic expression of UFL1 inhibited the production of extracellular matrix (ECM) degrading enzymes including matrix metalloproteinase 3 (MMP-3), MMP-13, ADAMTS-4 and ADAMTS-5 in chondrocytes with IL-1β induction. Additionally, UFL1 suppressed IL-1β-induced activation of NF-κB signaling pathway in chondrocytes. In conclusion, these findings indicated that UFL1 exerted protective effect on IL-1β-induced chondrocytes. Thus, UFL1 might be a potential target for the treatment of OA.

Regulation of Inflammatory Response in Human Osteoarthritic Chondrocytes by Novel Herbal Small Molecules.

In this study, 34 Traditional Chinese Medicine (TCM) compounds were screened for potential anabolic and anti-inflammatory properties on human osteoarthritic (OA) chondrocytes. The anabolic effects were assessed by measuring the glycosaminoglycan (GAG) relative to the DNA content using a 3D pellet culture model. The most chondrogenic compounds were tested in an inflammatory model consisting of 3 days of treatment with cytokines (IL-1β/TNF-α) with or without supplementation of TCM compounds. The anti-inflammatory effects were assessed transcriptionally, biochemically and histologically. From the 34 compounds, Vanilic acid (VA), Epimedin A (Epi A) and C (Epi C), 2′′-O-rhamnosylicariside II (2-O-rhs II), Icariin, Psoralidin (PS), Protocatechuicaldehyde (PCA), 4-Hydroxybenzoic acid (4-HBA) and 5-Hydroxymethylfurfural (5-HMF) showed the most profound anabolic effects. After induction of inflammation, pro-inflammatory and catabolic genes were upregulated, and GAG/DNA was decreased. VA, Epi C, PS, PCA, 4-HBA and 5-HMF exhibited anti-catabolic and anti-inflammatory effects and prevented the up-regulation of pro-inflammatory markers including metalloproteinases and cyclooxygenase 2. After two weeks of treatment with TCM compounds, the GAG/DNA ratio was restored compared with the negative control group. Immunohistochemistry and Safranin-O staining confirmed superior amounts of cartilaginous matrix in treated pellets. In conclusion, VA, Epi C, PS, PCA, 4-HBA and 5-HMF showed promising anabolic and anti-inflammatory effects.

Astragaloside inhibits IL-1β-induced inflammatory response in human osteoarthritis chondrocytes and ameliorates the progression of osteoarthritis in mice

Background: Osteoarthritis (OA) is a chronic joint-degeneration disease and accounts for the most frequent arthritis in aging people. OA is characterized by the degeneration of articular cartilage, subchondral bone sclerosis and synovitis. Inflammation as an important role in OA progression, in that anti-inflammatory agents could effectively inhibit the development of OA with minimal side effects, therefore developing a nature anti-inflammatory compound will be a promising therapy for treating OA.Methods: We treated patient-derived chondrocytes and mouse models of OA with astragaloside, an effective component of astragalus membranaceus, and measured its effect on pro-inflammatory cytokines and OA progression in mice.Results: In vitro, astragaloside induced a dose-dependent inhibition of IL-1β-induced the production of inflammatory factors, including interleukin-6 (IL-6), tumor necrosis factor-α (TNF-α), nitric oxide (NO), prostaglandin E2 (PGE2), expression of MMP 13 and ADAMTS-5, and the activation of NF-κB signaling. In vivo, astragaloside ameliorate the degeneration of cartilage in mouse model of OA.Conclusion: Astragaloside potentially serve as a promising and effective therapeutic agent for treating OA patients.

Isofraxidin inhibits interleukin-1β induced inflammatory response in human osteoarthritis chondrocytes

Osteoarthritis (OA) is the most prevalent disease of knee especially in the aged people. Isofraxidin (IF) is a coumarin compound refined from traditional Chinese medicines with potential anti-inflammatory ability. This study aimed to evaluate protective anti-inflammatory effects of IF in human OA chondrocytes. The chondrocytes were isolated from OA patients and pretreated with IF before treatment with IL-1β. The results showed that IF blocked IL-1β-stimulated production of NO and PGE2. In addition, IF inhibited the expression of COX-2, iNOs, MMP-1, MMP-3, MMP-13, ADAMTS-4 and ADAMTS-5, and increased the levels of aggrecan and collagen-II. Mechanistically, IF suppressed IL-1β-induced IκB-α degradation and NF-κB activation. In conclusion, our results demonstrate that IF inhibits inflammation in OA via the regulation of NF-κB signaling, and suggest that IF may be a potential therapeutic agent for OA.

Eriodictyol inhibits IL-1β-induced inflammatory response in human osteoarthritis chondrocytes

Osteoarthritis (OA) is a degenerative disease of joints, which is closely associated with cartilage degradation. Eriodictyol, a natural flavonoid compound, has been reported to have anti-inflammatory and anti-osteoclastogenic effects. However, the effect of eriodictyol on inflammatory response in OA has not been investigated. Our results showed that eriodictyol attenuated the inhibition of cell viability in IL-1β-stimulated chondrocytes. In addition, eriodictyol inhibited the expressions of inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2), and the production of prostaglandin E2 (PGE2) and nitric oxide (NO), which were induced by IL-1β. The induction of inflammatory cytokines and matrix metalloproteinases (MMPs) caused by IL-1β stimulation was also attenuated by eriodictyol. Furthermore, eriodictyol pretreatment inhibited IκBα degradation and the level of p-p65, and enhanced the up-regulation of nuclear factor (erythroid-derived 2)-like 2 (Nrf2) and heme oxygenase 1 (HO-1) in IL-1β-stimulated chondrocytes. Si-Nrf2 treatment significantly inhibited the expressions of Nrf2 and HO-1 in chondrocytes. Additionally, si-Nrf2 transfection also abolished the anti-inflammatory effects of eriodictyol in chondrocytes. These findings indicated that eriodictyol exhibited anti-inflammatory effect in IL-1β-stimulated chondrocytes. The effect was mediated by inhibiting NF-κB via activating the Nrf2/HO-1 signaling pathway.

Scoparone prevents IL-1β-induced inflammatory response in human osteoarthritis chondrocytes through the PI3K/Akt/NF-κB pathway

Osteoarthritis (OA) is a degenerative joint disease that is commonly accompanied by inflammation. Scoparone is a biologically active constituent isolated from Artemisia capillaris and possesses anti-inflammatory activity. However, the effect of scoparone on inflammatory response in OA has not been authenticated. The aim of this study was to evaluate the role of scoparone in OA in vitro. Our results showed that IL-1β treatment significantly inhibited the cell viability of chondrocytes, whereas the inhibition effect was attenuated by scoparone in a dose-dependent manner. IL-1β also efficiently induced the production of nitric oxide (NO), prostaglandin E2 (PGE2), MMP-3, MMP-13, ADAMTS-4 and ADAMTS-5 in chondrocytes. However, scoparone dose-dependently suppressed the induction. In addition, scoparone repressed IL-1β-induced the expression of iNOS and COX-2 in chondrocytes. Furthermore, the activation of the PI3K/Akt/NF-κB pathway induced by IL-1β was diminished by scoparone treatment. Taken together, these findings indicated that scoparone inhibited the expression of inflammatory mediators in IL-1β-induced chondrocytes via regulating the PI3K/Akt/NF-κB pathway. Thus, scoparone may be used as a new therapeutic agent for the treatment of OA.

Nrf2/ARE pathway attenuates oxidative and apoptotic response in human osteoarthritis chondrocytes by activating ERK1/2/ELK1-P70S6K-P90RSK signaling axis.

Nrf2, a redox regulated transcription factor, has recently been shown to play a role in cartilage integrity but the mechanism remains largely unknown. Osteoarthritis (OA) is a multifactorial disease in which focal degradation of cartilage occurs. Here, we studied whether Nrf2 exerts chondroprotective effects by suppressing the oxidative stress and apoptosis in IL-1β stimulated human OA chondrocytes. Expression of Nrf2 and its target genes HO-1, NQO1 and SOD2 was significantly high in OA cartilage compared to normal cartilage and was also higher in damaged area compared to smooth area of OA cartilage of the same patient. Human chondrocytes treated with IL-1β resulted in robust Nrf2/ARE reporter activity, which was inhibited by pretreatment with antioxidants indicating that Nrf2 activity was due to IL-1β-induced ROS generation. Ectopic expression of Nrf2 significantly suppressed the IL-1β-induced generation of ROS while Nrf2 knockdown significantly increased the basal as well as IL-1β-induced ROS levels in OA chondrocytes. Further, Nrf2 activation significantly inhibited the IL-1β-induced activation of extrinsic and intrinsic apoptotic pathways as determined by inhibition of DNA fragmentation, activation of Caspase-3,-8,-9, cleavage of PARP, release of cytochrome-c, suppression of mitochondrial dysfunction and mitochondrial ROS production in OA chondrocytes. Nrf2 over-expression in OA chondrocytes increased the expression of anti-apoptotic proteins while pro-apoptotic proteins were suppressed. Importantly, Nrf2 over-expression activated ERK1/2 and its downstream targets-ELK1, P70S6K and P90RSK and suppressed the IL-1β-induced apoptosis whereas inhibition of ERK1/2 activation abrogated the protective effects of Nrf2 in OA chondrocytes. Taken together, our data demonstrate that Nrf2 is a stress response protein in OA chondrocytes with anti-oxidative and anti-apoptotic function and acts via activation of ERK1/2/ELK1-P70S6K-P90RSK signaling axis. These activities of Nrf2 make it a promising candidate for the development of novel therapies for the management of OA.

Polydatin inhibits the IL-1β-induced inflammatory response in human osteoarthritic chondrocytes by activating the Nrf2 signaling pathway and ameliorates murine osteoarthritis.

Osteoarthritis (OA), which is characterized by progressive degradation of the articular cartilage, is the most prevalent form of human arthritis. Accumulating evidence has shown that polydatin (PD) exerts special biological functions in a variety of diseases. However, whether it protects against OA development has remained unknown. Here, we investigated the anti-inflammatory and chondroprotective effects of PD on interleukin (IL)-1β-induced human osteoarthritic chondrocytes and in the surgical destabilization of medial meniscus mouse (DMM) OA models. In vitro, PD treatment completely suppressed the over-production of pro-inflammatory mediators, including prostaglandin E2 (PGE2), tumor necrosis factor-α (TNF-α), nitric oxide (NO), cyclooxygenase-2 (COX-2), inducible nitric oxide synthase (iNOS), and IL-6 in IL-1β-induced human OA chondrocytes. Moreover, PD exerted a suppressive effect on the expression of matrix-degrading proteases, including matrix metalloproteinase 13 (MMP13) and thrombospondin motifs 5 (ADAMTS-5), which leads to the degradation of the extracellular matrix (ECM). Meanwhile, specific inhibition of the nuclear factor (erythroid-derived 2)-like 2 (Nrf2) level by short-interfering RNA (siRNA) strongly reversed the anti-inflammatory and chondroprotective effects of PD in human OA chondrocytes. The protective effects of PD were also observed in vivo. In conclusion, our studies demonstrate that PD holds novel therapeutic potential for the development of OA.

Gypenoside inhibits interleukin-1β-induced inflammatory response in human osteoarthritis chondrocytes.

Gypenoside (GP), the main active ingredient of Gynostemma pentaphyllum, possesses a variety of pharmacological capacities including anti-inflammation, anti-oxidation, and anti-tumor. However, the effects of GP on IL-1β-stimulated human osteoarthritis (OA) chondrocytes are still unknown. Therefore, this study aimed to investigate the anti-inflammatory effects of GP on IL-1β-stimulated human OA chondrocytes and explore the possible mechanism. Our results showed that GP dose-dependently inhibited IL-1β-induced NO and PGE2 production in human OA chondrocytes. In addition, treatment of GP inhibited the expression of MMP3 and MMP13, which was increased by IL-1β. Finally, we found that pretreatment of GP obviously suppressed NF-κB activation in IL-1β-stimulated human OA chondrocytes. Taken together, the results demonstrated that GP has chondro-protective effects, at least in part, through inhibiting the activation of NF-κB signaling pathway in human OA chondrocytes. Thus, these findings suggest that GP may be considered as an alternative therapeutic agent for the management of OA patients.

Tormentic Acid Inhibits IL-1β-Induced Inflammatory Response in Human Osteoarthritic Chondrocytes

Tormentic Acid Inhibits IL-1β-Induced Inflammatory Response in Human Osteoarthritic Chondrocytes

Fisetin inhibits IL-1β-induced inflammatory response in human osteoarthritis chondrocytes through activating SIRT1 and attenuates the progression of osteoarthritis in mice

Osteoarthritis (OA) is a degenerative joint disease characterized by cartilage degradation and inflammation. Fisetin, a polyphenol extracted from fruits and vegetables, has been reported to have anti-inflammatory effects. Our study aimed to investigate the effect of fisetin on OA both in vitro and in vivo. In vitro, chondrocytes were pretreated with fisetin alone or fisetin combined with sirtinol (an inhibitor of SIRT1) for 2h before IL-1β stimulation. Production of NO, PGE2, TNF-α and IL-6 were evaluated by the Griess reaction and ELISAs. The mRNA (COX-2, iNOS, MMP-3, MMP-13, ADAMTS-5, Sox-9, aggrecan and collagen-II) and protein expression (COX-2, iNOS, MMP-3, MMP-13, ADAMTS-5 and SIRT1) were measured by qRT-PCR and Western blot respectively. Immunofluorescence was used to assess the expression of collagen-II and SIRT1. SIRT1 activity was quantified with SIRT1 fluorometric assay kit. The in vivo effect of fisetin was evaluated by gavage in mice OA models induced by destabilization of the medial meniscus (DMM). We found that fisetin inhibited IL-1β-induced expression of NO, PGE2, TNF-α, IL-6, COX-2, iNOS, MMP-3, MMP-13, ADAMTS-5. Besides, fisetin remarkably decreased IL-1β-induced degradation of Sox-9, aggrecan and collagen-II. Furthermore, fisetin significantly inhibited IL-1β-induced SIRT1 decrease and inactivation. However, the inhibitory effect of fisetin was obvious abolished by sirtinol, suggesting that fisetin exerts anti-inflammatory effects through activating SIRT1. In vivo, fisetin-treated mice exhibited less cartilage destruction and lower OARSI scores. Moreover, fisetin reduced subchondral bone plate thickness and alleviated synovitis. Taken together, these findings indicate that fisetin may be a potential agent in the treatment of OA.

Plumbagin Prevents IL-1β-Induced Inflammatory Response in Human Osteoarthritis Chondrocytes and Prevents the Progression of Osteoarthritis in Mice.

Inflammation and inflammatory cytokines have been reported to play vital roles in the development of osteoarthritis (OA). Plumbagin, a quinonoid compound extracted from the roots of medicinal herbs of the Plumbago genus, has been reported to have anti-inflammatory effects. However, the anti-inflammatory effects of plumbagin on OA have not been reported. This study aimed to assess the effects of plumbagin on human OA chondrocytes and in a mouse model of OA induced by destabilization of the medial meniscus (DMM). In vitro, human OA chondrocytes were pretreated with plumbagin (2, 5, 10μM) for 2h and subsequently stimulated with IL-1β for 24h. Production of NO, PGE2, MMP-1, MMP-3, and MMP-13 was evaluated by the Griess reagent and ELISAs. The messenger RNA (mRNA) expression of COX-2, iNOS, MMP-1, MMP-3, MMP-13, aggrecan, and collagen-II was measured by real-time PCR. The protein expression of COX-2, iNOS, p65, p-p65, IκBα, and p-IκBα was detected by Western blot. The protein expression of collagen-II was evaluated by immunofluorescence. In vivo, the severity of OA was determined by histological analysis. We found that plumbagin significantly inhibited the IL-1β-induced production of NO and PGE2; expression of COX-2, iNOS, MMP-1, MMP-3, and MMP-13; and degradation of aggrecan and collagen-II. Furthermore, plumbagin dramatically suppressed IL-1β-stimulated NF-κB activation. In vivo, treatment of plumbagin not only prevented the destruction of cartilage and the thickening of subchondral bone but also relieved synovitis in mice OA models. Taken together, these results suggest that plumbagin may be a potential agent in the treatment of OA.

Piceatannol inhibits the IL-1β-induced inflammatory response in human osteoarthritic chondrocytes and ameliorates osteoarthritis in mice by activating Nrf2.

Osteoarthritis (OA) is a complex process, to which an inflammatory environment contributes markedly. Piceatannol exerts anti-inflammatory effects on several diseases. In the current study, we explored the protective effects of piceatannol on the progression of OA and investigated its molecular target. In vitro, piceatannol not only attenuated the over-production of inflammatory mediators and cytokines-such as nitric oxide (NO), prostaglandin E2 (PGE2), tumor necrosis factor alpha (TNF-α), and interleukin-6 (IL-6)-but also suppressed the expression of cyclooxygenase-2 (COX-2) and inducible nitric oxide synthase (iNOS) at both the mRNA and protein levels. Piceatannol also decreased the expression of metalloproteinase 13 (MMP13) and thrombospondin motifs 5 (ADAMTS5), which mediate extracellular matrix degradation. Mechanistically, we found that piceatannol inhibited IL-1β-induced nuclear factor kappa B (NF-κB) activation by activating the nuclear factor (erythroid-derived 2)-like 2 (Nrf2)/heme oxygenase 1 (HO-1) pathway. Furthermore, piceatannol exerted protective effects in a mouse model of OA. Taken together, these findings indicate that piceatannol may be a potential therapeutic agent for OA.

Sesamin inhibits IL-1β-stimulated inflammatory response in human osteoarthritis chondrocytes by activating Nrf2 signaling pathway.

Sesamin, a bioactive component extracted from sesame, has been reported to exert anti-inflammatory and anti-oxidant effects. In this study, we evaluated the anti-inflammatory effects of sesamin on IL-1β-stimulated human osteoarthritis chondrocytes and investigated the possible mechanism. Results demonstrated that sesamin treatment significantly inhibited PGE2 and NO production induced by IL-1β. Sesamin inhibited MMP1, MMP3, and MMP13 production in IL-1β-stimulated chondrocytes. Sesamin also inhibited IL-1β-induced phosphorylation of NF-κB p65 and IκBa. Meanwhile, sesamin was found to up-regulate the expression of Nrf2 and HO-1. However, Nrf2 siRNA reversed the anti-inflammatory effects of sesamin. In conclusion, our results suggested that sesamin showed anti-inflammatory effects in IL-1β-stimulated chondrocytes by activating Nrf2 signaling pathway.

Butein inhibits IL-1β-induced inflammatory response in human osteoarthritis chondrocytes and slows the progression of osteoarthritis in mice

Osteoarthritis (OA) is a progressive degenerative disease characterized by irreversible articular cartilage destruction. Butein, a polyphenolic compound isolated from the stem bark of cashews and Rhus verniciflua Stokes, has been reported to have anti-inflammatory effects. This study aimed to assess the effect of butein on human OA chondrocytes and mice OA models induced by destabilization of the medial meniscus (DMM). In vitro, human OA chondrocytes were pretreated with butein at 10, 50μM and subsequently stimulated with IL-1β (10ng/ml) for 24h. Production of NO, PGE2, TNF-α and IL-6 was evaluated by the Griess reaction and ELISAs. The mRNA expression of COX-2, iNOS, TNF-α, IL-6, MMP-1, MMP-3, MMP-13, ADAMTS-4, ADAMTS-5, COL-2 and SOX-9 were measured by real-time PCR. The protein expression of COX-2, iNOS, MMP-13, COL-2, SOX-9, p65 and IκB-α were detected by Western blot. P65 nuclear translocation was detected by immunofluorescence. In vivo, the severity of OA was determined by histological analysis. We found that butein significantly inhibited the IL-1β-induced production of NO and PGE2, expression of COX-2, iNOS, TNF-α, IL-6 and MMP-13, degradation of COL-2 and SOX-9 at mRNA and protein levels as well as MMP-1, MMP-3, ADAMTS-4 and ADAMTS-5 gene expression. Furthermore, butein dramatically suppressed IL-1β-stimulated IκB-α degradation and NF-kB p65 activation. In vivo, the cartilage in butein-treated mice exhibited less Safranin O loss, cartilage erosion and lower OARSI scores. Butein also reduced subchondral bone plate thickness and alleviated synovitis. Taken together, these findings indicate that butein may be a potential agent in the treatment of OA.

Effects of platycodin D on IL-1β-induced inflammatory response in human osteoarthritis chondrocytes

Platycodin D (PYD), a major saponin derived and isolated from the roots of Platycodon grandiflorum, has been reported to have anti-inflammatory and anti-tumor effects. The present study aimed to investigate the effects of PYD on IL-1β-stimulated human osteoarthritis chondrocytes. Chondrocytes were treated with PYD 1h before IL-1β treatment. The levels of MMP1, MMP13, IL-8, RANTES, PGE2, and NO were measured in this study. The expression of LXRα, NF-κB, and IκBα were detected by western blot analysis. The results showed that PYD significantly inhibited IL-1β-induced MMP1, MMP13, IL-8, RANTES, PGE2, and NO production. PYD also suppressed IL-1β-induced NF-κB activation. Furthermore, the expression of LXRα was up-regulated by PYD in a dose-dependent manner. In addition, LXRα siRNA inhibited the effects of PYD on MMP1, MMP13, PGE2, and NO production in human osteoarthritis chondrocytes. In conclusion, these results suggested that PYD attenuated IL-1β-induced inflammatory response in osteoarthritis chondrocyte by activating LXRα.

Mangiferin Inhibits IL-1β-Induced Inflammatory Response by Activating PPAR-γ in Human Osteoarthritis Chondrocytes.

Inflammation has been reported to play critical roles in the development of osteoarthritis. In the present study, we investigated whether mangiferin (MFN) had anti-inflammatory effects in IL-1β-stimulated human osteoarthritis chondrocytes. The cells were treated with various concentrations of MFN in the presence or absence of IL-1β. The production of MMP-1, MMP-3, PGE2, and NO was measured in this study. The expression of NF-kB and PPAR-γ was detected by western blot analysis. MFN inhibited IL-1β-induced inflammatory mediators PGE2 and NO production. MFN also inhibited IL-1β-induced MMP1 and MMP3 production. IL-1β-induced NF-kB activation was significantly inhibited by MFN. In addition, MFN was found to up-regulate the expression of PPAR-γ in human osteoarthritis chondrocytes. PPAR-γ inhibitor GW9662 significantly reversed the anti-inflammatory effects of MFN. These results suggest that MFN inhibits IL-1β-induced inflammatory response in human osteoarthritis chondrocytes by activating PPAR-γ.

Tormentic Acid Inhibits IL-1β-Induced Inflammatory Response in Human Osteoarthritic Chondrocytes.

The pro-inflammatory cytokine interleukin-1beta (IL-1β) plays critical roles in pathogenesis of osteoarthritis (OA). Tormentic acid (TA), a triterpene isolated from Rosa rugosa, has anti-inflammatory activity. However, the anti-inflammatory effect of TA on OA is still unclear. So, in the present study, we examined the effect of TA on IL-1β-induced inflammatory response in primary human OA chondrocytes. Our results demonstrated that TA significantly decreased the IL-1β-stimulated expression of matrix metalloproteinase-3 (MMP-3) and MMP-13. It also inhibited the IL-1β-induced expression of inducible nitric oxide (NO) synthase (iNOS) and cyclooxygenase-2 (COX-2), as well as the production of NO and prostaglandin E2 (PGE2) in human OA chondrocytes. Furthermore, TA greatly inhibited the IL-1β-induced NF-κB activation. In conclusion, this study is the first to demonstrate the anti-inflammatory activity of TA in human OA chondrocytes. TA significantly inhibits the IL-1β-induced inflammatory response by suppressing the NF-κB signaling pathway. Thus, TA may be a potential agent in the treatment of OA.

Long Intergenic Noncoding RNAs Mediate the Human Chondrocyte Inflammatory Response and Are Differentially Expressed in Osteoarthritis Cartilage.

ObjectiveTo identify long noncoding RNAs (lncRNAs), including long intergenic noncoding RNAs (lincRNAs), antisense RNAs, and pseudogenes, associated with the inflammatory response in human primary osteoarthritis (OA) chondrocytes and to explore their expression and function in OA.MethodsOA cartilage was obtained from patients with hip or knee OA following joint replacement surgery. Non‐OA cartilage was obtained from postmortem donors and patients with fracture of the neck of the femur. Primary OA chondrocytes were isolated by collagenase digestion. LncRNA expression analysis was performed by RNA sequencing (RNAseq) and quantitative reverse transcriptase–polymerase chain reaction. Modulation of lncRNA chondrocyte expression was achieved using LNA longRNA GapmeRs (Exiqon). Cytokine production was measured with Luminex.ResultsRNAseq identified 983 lncRNAs in primary human hip OA chondrocytes, 183 of which had not previously been identified. Following interleukin‐1β (IL‐1β) stimulation, we identified 125 lincRNAs that were differentially expressed. The lincRNA p50‐associated cyclooxygenase 2–extragenic RNA (PACER) and 2 novel chondrocyte inflammation–associated lincRNAs (CILinc01 and CILinc02) were differentially expressed in both knee and hip OA cartilage compared to non‐OA cartilage. In primary OA chondrocytes, these lincRNAs were rapidly and transiently induced in response to multiple proinflammatory cytokines. Knockdown of CILinc01 and CILinc02 expression in human chondrocytes significantly enhanced the IL‐1–stimulated secretion of proinflammatory cytokines.ConclusionThe inflammatory response in human OA chondrocytes is associated with widespread changes in the profile of lncRNAs, including PACER, CILinc01, and CILinc02. Differential expression of CILinc01 and CIinc02 in hip and knee OA cartilage, and their role in modulating cytokine production during the chondrocyte inflammatory response, suggest that they may play an important role in mediating inflammation‐driven cartilage degeneration in OA.

Diabetes-induced osteoarthritis: role of hyperglycemia in joint destruction

Recent epidemiologic and experimental data reinforced the concept that diabetes mellitus (DM) is an independent risk factor for osteoarthritis (OA). Besides a systemic inflammatory response that can affect joint tissues and contribute to OA pathogenesis, direct effects of hyperglycaemia have been shown to cause cell damage and induce inflammation by various mechanisms in several tissues associated to diabetic complications. Whether and how glucose directly affects joint tissues and cells is just beginning to be unraveled. Indirect effects of high glucose can result from enhanced formation of advanced glycation end products (AGEs) which accumulate in OA cartilage in an age-dependent manner and play a pro-inflammatory and pro-catabolic role mediated by activation of their specific receptor, RAGE, on chondrocytes and synovial cells. Some direct effects of high glucose have also been demonstrated, namely induction of IGF-1 resistance[1] and inhibition of dehydroascorbate transport which can compromise collagen synthesis[2]. Our studies have been aimed at determining whether and how hyperglycemia affects chondrocyte functions and contributes to OA development and progression. The results obtained showed that high and low glucose concentrations regulate the availability of facilitative glucose transporter (GLUT) isoforms and the glucose transport capacity of human chondrocytes. High glucose concentrations decrease the transport capacity and GLUT-1 protein content without affecting its mRNA levels, but this ability to adjust glucose transport capacity as a function of its availability is compromised in aged/OA chondrocytes leading to its intracellular accumulation[3]. The consequences of this are increased and prolonged ROS production[3] and expression of metalloproteinases (MMP)-1 and -13[4], IL-1β, TNF-α, inducible nitric oxide (NO) synthase (iNOS) and NO production, mediated by high glucose-induced NF-κB activation[5], as well as decreased responsiveness to TGF-β[4] and impaired autophagy[5]. High glucose is thus sufficient to induce an inflammatory and catabolic response in human OA chondrocytes. Furthermore, it potentiates pro-inflammatory effects of IL-1β, namely IL-6, cyclooxygenase 2 (Cox)-2, prostaglandin E2 (PGE2) and NO production[6]. The pro-inflammatory effects of high glucose in human chondrocytes and diabetic mice, namely induction of Cox-2, IL-6 and MMP-13 and production of PGE2, as well as decreased production of Collagen II, have also been shown to involve impairment of anti-inflammatory pathways, namely by decreasing PPAR-γ expression[7]. Elucidating how high glucose modulates joint tissue homeostasis will identify novel targets for development of innovative strategies both to identify diagnostic and prognostic biomarkers of OA and to effectively modify disease progression.