Reversal of autocrine and paracrine effects of interleukin 1 (IL-1) in human arthritis by type II IL-1 decoy receptor. Potential for pharmacological intervention

Benzophenone-3 exposure induced apoptosis via impairing mitochondrial function in human chondrocytes

Osteoarthritis (OA) is a chronic joint disease affecting millions of adults worldwide, characterized by degeneration of articular cartilage. Many environmental risk factors contribute to OA development. Benzophenone-3 (BP-3), a commonly used ultraviolet filter in personal care products, has been positively associated with OA risk. However, it remains unclear whether and how BP-3 induces toxic effects on articular chondrocytes and promote OA development. This study aims to investigate the damage of BP-3 at environmentally relevant concentrations to human chondrocytes, as well as potential mechanisms linking BP-3 with injury of chondrocytes. Notably, BP-3 significantly inhibited cell viability, induced apoptosis, and up-regulated matrix metalloproteinase (MMP) 1 and 13 which mediated cartilage degradation in C28/I2 human normal chondrocytes. Moreover, the function of mitochondria was impaired and oxidative stress occurred in BP-3 exposure groups, evidenced by elevation of reactive oxygen species (ROS) generation, reduction of mitochondrial membrane potential, decrease of ATP production and inhibition of mitochondrial respiratory chain complex I, II, III and IV. Meanwhile, BP-3 caused mitochondrial cristae vague and formation of autophagosomes. PTEN induced putative kinase 1/E3 ubiquitin protein ligase (PINK1/Parkin) pathway was also activated by BP-3. Addition of autophagy inhibitor, 3-Methyladenine (3-MA), suppressed PINK1/Parkin-mediated mitophagy, but increased BP-3-induced expression of MMP1 and 13, as well as exacerbated BP-3-induced apoptosis, suggesting mitophagy may exert a chondroprotective effect and partially alleviate apoptosis induced by this compound. In brief, BP-3 exposure may increase OA risk via inducing apoptosis and increasing breakdown of extracellular matrix in chondrocytes, and mitochondrial dysfunction and mitophagy may play a crucial role in the mechanisms of BP-3-induced toxicity to articular chondrocytes.

Interleukin-21 Influences Glioblastoma Course: Biological Mechanisms and Therapeutic Potential

Brain tumors represent a heterogeneous group of neoplasms involving the brain or nearby tissues, affecting populations of all ages with a high incidence worldwide. Among the primary brain tumors, the most aggressive and also the most common is glioblastoma (GB), a type of glioma that falls into the category of IV-grade astrocytoma. GB often leads to death within a few months after diagnosis, even if the patient is treated with available therapies; for this reason, it is important to continue to discover new therapeutic approaches to allow for a better survival rate of these patients. Immunotherapy, today, seems to be one of the most innovative types of treatment, based on the ability of the immune system to counteract various pathologies, including cancer. In this context, interleukin 21 (IL-21), a type I cytokine produced by natural killer (NK) cells and CD4+ T lymphocytes, appears to be a valid target for new therapies since this cytokine is involved in the activation of innate and adaptive immunity. To match this purpose, our review deeply evaluated how IL-21 could influence the progression of GB, analyzing its main biological processes and mechanisms while evaluating the potential use of the latest available therapies.

Interleukins, growth factors, and transcription factors are key targets for gene therapy in osteoarthritis: A scoping review

Objective

Osteoarthritis (OA) is the most common degenerative joint disease, characterized by a progressive loss of cartilage associated with synovitis and subchondral bone remodeling. There is however no treatment to cure or delay the progression of OA. The objective of this manuscript was to provide a scoping review of the preclinical and clinical studies reporting the effect of gene therapies for OA.

Method

This review followed the JBI methodology and was reported in accordance with the PRISMA-ScR checklist. All research studies that explore in vitro, in vivo, or ex vivo gene therapies that follow a viral or non-viral gene therapy approach were considered. Only studies published in English were included in this review. There were no limitations to their date of publication, country of origin, or setting. Relevant publications were searched in Medline ALL (Ovid), Embase (Elsevier), and Scopus (Elsevier) in March 2023. Study selection and data charting were performed by two independent reviewers.

Results

We found a total of 29 different targets for OA gene therapy, including studies examining interleukins, growth factors and receptors, transcription factors and other key targets. Most articles were on preclinical in vitro studies (32 articles) or in vivo animal models (39 articles), while four articles were on clinical trials related to the development of TissueGene-C (TG-C).

Conclusion

In the absence of any DMOAD, gene therapy could be a highly promising treatment for OA, even though further development is required to bring more targets to the clinical stage.

Exercise induced meteorin-like protects chondrocytes against inflammation and pyroptosis in osteoarthritis by inhibiting PI3K/Akt/NF-κB and NLRP3/caspase-1/GSDMD signaling

The production of metrnl, a novel adipomyokine, is induced upon exercise in adipose tissue and skeletal muscle. In this study, we investigated the anti-inflammatory and antipyroptotic effects of exercise-induced metrnl producted in rats in vitro and in vivo. Forty Sprague-Dawley rats were divided randomly into five groups: control (CG), osteoarthritis (OA) with sedentary lifestyle (OAG), OA with low intensity exercise (OAL), OA with moderate intensity exercise (OAM), and OA with high intensity exercise (OAH). The correlation between the level of metrnl and OA degree was detected using ELISA, X-ray imaging, histology, and immunohistochemistry in vivo. Primary chondrocytes were preincubated with recombinant metrnl before interleukin-1β administration to verify the anti-inflammatory and antipyroptotic effects of metrnl. Western blotting and quantitative reverse transcription (qRT)-PCR were used to evaluate the differences in protein and mRNA expression between groups, respectively. Reactive oxygen species (ROS) assay, immunofluorescence, transmission electron microscopy (TEM), and flow cytometry were used to evaluate morphological changes and pyroptosis in chondrocytes. In the moderate-intensity treadmill exercise group, the severity of OA showed maximum relief and the metrnl levels had the most significant increase. Metrnl exerted its anti-inflammatory effect through the suppression of the PI3K/Akt/NF-κB pathway in IL-1β-induced OA chondrocytes, which was accompanied with the recovery of collagen II expression and the attenuation of MMP13 and ADAMTS5. Moreover, metrnl ameliorated chondrocyte pyroptosis by inhibiting the activation of the nod-like receptor protein-3/caspase-1/gasdermin D cascade. In conclusion, moderate-intensity exercise improves inflammation and pyroptosis by increasing metrnl release, which inhibits the PI3K/Akt/NF-κB and further NLRP3/caspase-1/GSDMD signaling pathways.

Negative Regulation of the IL-1 System by IL-1R2 and IL-1R8: Relevance in Pathophysiology and Disease

Interleukin-1 (IL-1) is a primary cytokine of innate immunity and inflammation. IL-1 belongs to a complex family including ligands with agonist activity, receptor antagonists, and an anti-inflammatory cytokine. The receptors for these ligands, the IL-1 Receptor (IL-1R) family, include signaling receptor complexes, decoy receptors, and negative regulators. Agonists and regulatory molecules co-evolved, suggesting the evolutionary relevance of a tight control of inflammatory responses, which ensures a balance between amplification of innate immunity and uncontrolled inflammation. IL-1 family members interact with innate immunity cells promoting innate immunity, as well as with innate and adaptive lymphoid cells, contributing to their differentiation and functional polarization and plasticity. Here we will review the properties of two key regulatory receptors of the IL-1 system, IL-1R2, the first decoy receptor identified, and IL-1R8, a pleiotropic regulator of different IL-1 family members and co-receptor for IL-37, the anti-inflammatory member of the IL-1 family. Their complex impact in pathology, ranging from infections and inflammatory responses, to cancer and neurologic disorders, as well as clinical implications and potential therapeutic exploitation will be presented.

Effects of adenovirus-mediated knockdown of IRAK4 on synovitis in the osteoarthritis rabbit model

BACKGROUND

The use of interleukin-1 receptor-associated kinase 4 (IRAK4) inhibitor as a treatment for the inflammatory joint disease is a promising method. However, its underlying mechanism in osteoarthritis (OA) remains unclear. The purpose of this study is to look into the effects of adenovirus-mediated knockdown of IRAK4 on synovitis in the OA rabbit model.

METHODS

Ad-shIRAK4 was injected two weeks after anterior cruciate ligament resection. Six weeks later, the rabbits were killed. The expression of IRAK4, TNFR-associated factor 6(TRAF6), TGF-activated kinase 1(TAK1), p-IKB kinase (p-IKK), p-nuclear factor kappa-B (p-NFκB), p38, and p-p38 in the synovial membrane was detected by western blot, qRT-PCR, and immunohistochemistry analysis. Immunohistochemistry was to detect the expression of IRAK4 proteins in articular cartilage. H&E staining was to assess the pathological changes of synovium and cartilage. The levels of interleukin (IL)-1β, tumor necrosis factor-α(TNF-α), and MMP-13 in the synovial fluid were measured by ELISA. X-ray and micro-computerized tomography (μCT) scans were used to assess knee joint conditions and microstructure of subchondral bone.

RESULTS

IRAK4 expression levels in synovial tissues of the OA model group exhibited a significant upward trend. Ad-shIRAK4 significantly reduced IRAK4 mRNA expression in synovium tissues. Notably, Ad-shIRAK4 suppressed the Toll-like receptor/interleukin-1 receptor (TLR/IL-1R) signaling. In addition, in the Ad-shIRAK4 treatment group, we can see less inflammatory cell infiltration and reduced hyperplasia and angiogenesis. The levels of IL-1β, TNF-α, and MMP-13 in the synovial fluid in the OA model group were significantly higher than that in the control group, which were reduced by Ad-shIRAK4 treatment. Finally, Results of HE stains, immunohistochemistry, and μCT showed that Ad-shIRAK4 treatment has a protective effect on cartilage damage.

CONCLUSIONS

IRAK4 is significantly upregulated in the synovium from the osteoarthritis rabbit model. In addition, Ad-shIRAK4 reduced the expression of IRAK4 and suppressed TLR/IL-1R signaling in the synovium from the osteoarthritis rabbit model. Ad-shIRAK4 could alleviate synovitis and cartilage degradation in the osteoarthritis rabbit model, and thus alleviate the symptoms of OA and prevent the progression of OA.

Autophagy promotion enhances the protective effect of Morroniside on human OA chondrocyte

Morroniside plays a therapeutic role in knee osteoarthritis (OA) by protecting chondrocytes. PI3K/AKT signaling is involved in the regulation of chondrocytes by Morroniside. PI3K/AKT suppresses autophagy through downstream signaling. However, the regulation of chondrocyte autophagy by Morroniside and the significance of the above effect on protecting chondrocytes aren't clear. The results showed that Morroniside inhibited the autophagiy of human OA chondrocytes. Besides, both PI3K inhibitors and mTOR inhibitors significantly reversed the autophagy reduced by Morroniside, but had no effect on the protective effect of Morroniside on chondrocytes. However, the enhanced autophagy caused by overexpression of autophagic genes enhanced the protective effect of Morroniside on chondrocytes. In conclusion, Morroniside represses the autophagy of human OA chondrocyte, which is related to PI3K/mTOR pathway. Moreover, the upregulation of autophagy further promoted the role of Morroniside in treating chondrocytes. Our data present a potential clue for the therapeutic strategies of Morroniside in treating OA.

Interleukin 1 receptor antagonist (IL1RN) gene variants predict radiographic severity of knee osteoarthritis and risk of incident disease

OBJECTIVE

In these studies, we examined the association of single nucleotide polymorphisms (SNPs) of the IL1RN gene with radiographic severity of symptomatic knee osteoarthritis (SKOA) and the risk of incident OA. We also explored these genetic polymorphisms in patients with new onset rheumatoid arthritis (RA).

METHODS

Over 1000 subjects who met American College of Rheumatology criteria for tibiofemoral OA were selected from three independent, National Institute of Health (NIH)-funded cohorts. CTA and TTG haplotypes formed from three SNPs of the IL1RN gene (rs419598, rs315952, rs9005) were assessed for association with radiographic severity, and risk for incident radiographic OA (rOA) in a nested case-control cohort. These IL1RN haplotypes were also assessed for association with disease activity (DAS28) and plasma inflammatory markers in patients with RA.

RESULTS

Carriage of the IL1RN TTG haplotype was associated with increased odds of more severe rOA compared with age-matched, sex-matched and body mass index-matched individuals. Examination of the osteoarthritis initiative Incidence Subcohort demonstrated that carriage of the TTG haplotype was associated with 4.1-fold (p=0.001) increased odds of incident rOA. Plasma IL-1Ra levels were lower in TTG carriers, while chondrocytes from TTG carriers exhibited decreased secretion of IL-1Ra. In patients with RA, the TTG haplotype was associated with increased DAS28, decreased plasma IL-1Ra and elevations of plasma inflammatory markers (hsCRP, interleukin 6 (IL-6)).

CONCLUSION

Carriage of the IL1RN TTG haplotype is associated with more severe rOA, increased risk for incident OA, and increased evidence of inflammation in RA. These data suggest that the IL1RN TTG risk haplotype, associated with decreased IL-1Ra plasma levels, impairs endogenous 'anti-inflammatory' mechanisms.

WITHDRAWN: MicroRNA-107 regulates autophagy and apoptosis of osteoarthritis chondrocytes by targeting TRAF3

This article has been withdrawn: please see Elsevier Policy on Article Withdrawal (http://www.elsevier.com/locate/withdrawalpolicy). This article has been withdrawn at the request of the editor and publisher. The publisher regrets that an error occurred which led to the premature publication of this paper. This error bears no reflection on the article or its authors. The publisher apologizes to the authors and the readers for this unfortunate error.

Interleukin-1β signaling in osteoarthritis - chondrocytes in focus

Osteoarthritis (OA) can be regarded as a chronic, painful and degenerative disease that affects all tissues of a joint and one of the major endpoints being loss of articular cartilage. In most cases, OA is associated with a variable degree of synovial inflammation. A variety of different cell types including chondrocytes, synovial fibroblasts, adipocytes, osteoblasts and osteoclasts as well as stem and immune cells are involved in catabolic and inflammatory processes but also in attempts to counteract the cartilage loss. At the molecular level, these changes are regulated by a complex network of proteolytic enzymes, chemokines and cytokines (for review: [1]). Here, interleukin-1 signaling (IL-1) plays a central role and its effects on the different cell types involved in OA are discussed in this review with a special focus on the chondrocyte.

Tuning inflammation and immunity by the negative regulators IL-1R2 and IL-1R8

Interleukin-1 receptor family members (ILRs) and Toll-Like Receptors (TLRs) are key players in immunity and inflammation and are tightly regulated at different levels. Most cell types, including cells of the innate and adaptive immune system express ILRs and TLRs. In addition, IL-1 family members are emerging as key players in the differentiation and function of innate and adaptive lymphoid cells. IL-1R2 and IL-1R8 (also known as TIR8 or SIGIRR) are members of the ILR family acting as negative regulators of the IL-1 system. IL-1R2 binds IL-1 and the accessory protein IL-1RAcP without activating signaling and can be released as a soluble form (sIL-1R2), thus modulating IL-1 availability for the signaling receptor. IL-1R8 dampens ILR- and TLR-mediated cell activation and it is a component of the receptor recognizing human IL-37. Here, we summarize our current understanding of the structure and function of IL-1R2 and IL-1R8, focusing on their role in different pathological conditions, ranging from infectious and sterile inflammation, to autoimmunity and cancer-related inflammation. We also address the emerging evidence regarding the role of IL-1R8 as a crucial checkpoint molecule in NK cells in anti-cancer and antiviral activity and the potential therapeutic implications of IL-1R8 blockade in specific pathological contexts.

Novel protein therapeutic joint retention strategy based on collagen-binding Avimers

Designing drugs to treat diseases associated with articular joints, particularly those targeting chondrocytes, is challenging due to unique local environmental constraints including the avascular nature of cartilage, the absence of a closed joint compartment, and a highly cross-linked extracellular matrix. In an effort to address these challenges, we developed a novel strategy to prolong residence time of intra-articularly administered protein therapeutics. Avimer domains are naturally found in membrane polypeptides and mediate diverse protein-protein interactions. Screening of a phage Avimer domain library led to identification of several low affinity type II collagen-binding Avimers. Following several rounds of mutagenesis and reselection, these initial hits were transformed to high affinity, selective type II collagen-binding Avimers. One such Avimer (M26) persisted in rat knees for at least 1 month following intra-articular administration. Fusion of this Avimer to a candidate therapeutic payload, IL-1Ra, yielded a protein construct which simultaneously bound to type II collagen and to IL-1 receptor. In vitro, IL-1Ra_M26 bound selectively to cartilage explants and remained associated even after extensive washing. Binding appeared to occur preferentially to pericellular regions surrounding chondrocytes. An acute intra-articular IL-1-induced IL-6 challenge rat model was employed to assess in vivo pharmacodynamics. Whereas both IL-1Ra_M26 and native IL-1Ra inhibited IL-6 output when co-administered with the IL-1 challenge, only IL-1Ra_M26 inhibited when administered 1 week prior to IL-1 challenge. Collagen-binding Avimers thus represent a promising strategy for enhancing cartilage residence time of protein therapeutics. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:1238-1247, 2018.

Different roles of Akt and mechanistic target of rapamycin in serum‑dependent chondroprotection of human osteoarthritic chondrocytes

Despite various animal serums being used widely to culture chondrocytes, the regulatory mechanism of serum on chondrocyte activities has not been elucidated. In the present study, human osteoarthritis (OA) chondrocytes were used to perform in vitro investigations on the effect of different concentrations of bovine fetal serum on extracellular matrix synthesis, cell proliferation and autophagy using the Cell Counting Kit‑8 analysis, a laser‑scanning confocal microscope, and western blot analysis. The results demonstrated that 5% serum exerted a chondroprotective effect more than the other concentrations of serum, as it simultaneously promoted cell proliferation, autophagy, and ECM synthesis in human OA chondrocytes. Furthermore, the decreased mechanistic target of rapamycin (mTOR) and increased Akt were observed in 5% serum‑treated OA chondrocytes. Either mTOR or Akt inhibitor influenced the effect of 5% serum on cell proliferation and autophagy in human OA chondrocytes, which was associated with LC‑3B or B‑cell lymphoma-2 (Bcl‑2) signal molecules. Consistent with previous studies, the present study proposes that 5% serum promotes cell proliferation via the Akt/Bcl‑2 axis and induces autophagy via the mTOR/LC‑3B axis in human OA chondrocytes. Furthermore, the different roles of Akt and mTOR in the cell processes of human OA chondrocytes require consideration for preclinical and clinical therapy of OA.

Gout and Osteoarthritis: Associations, Pathophysiology, and Therapeutic Implications

Osteoarthritis (OA), the most common type of arthritis worldwide, is a degenerative disease of diarthrodial joints resulting in pain, reduced quality of life, and socioeconomic burden. Gout, the most common form of inflammatory arthritis, is a consequence of persistently elevated levels of urate and the formation of proinflammatory monosodium urate crystals in joints. Clinicians have long noted a predilection for both diseases to occur in the same joints. In this review, we provide an overview into research elucidating possible biochemical, mechanical, and immunological relationships between gout and OA. We additionally consider the potential implications of these relationships for OA treatment.

Revisiting the Role of Interleukin-1 Pathway in Osteoarthritis: Interleukin-1α and -1β, and NLRP3 Inflammasome Are Not Involved in the Pathological Features of the Murine Menisectomy Model of Osteoarthritis

Background: Innate immune response components such as toll-like receptors (TLRs) and NLRP3-inflammasome act in concert to increase IL-1α/β secretion by synovial macrophages. Previous results suggest that IL-1α/β could be an important mediator involved in the pathogenesis of osteoarthritis (OA). Objectives: The aim of our study was to evaluate the role of NLRP3, IL-1β, and IL-1α in the menisectomy (MNX) model of murine OA. Methods: Murine chondrocytes (CHs) and bone marrow-derived machrophages (BMDM) were stimulated with hydroxyapatite (HA) crystals, a form of calcium-containing crystal found in human OA, and IL-1β and IL-6 secretion assayed by ELISA.Conversely, the ability of IL-1β and IL-6 to induce CHs calcification was assessed in vitro by Alizarin red staining. Knees from 8 to 10 weeks old C57Bl/6J wild-type (WT) (n = 7), NLRP3^-/- (n = 9), IL-1α^-/- (n = 5), and IL-1β^-/- (n = 5) mice were menisectomized, using the sham-operated contralateral knee as control. 8 weeks later, knee cartilage degradation and synovial inflammation were evaluated by histology. In addition, apoptotic chondrocytes, metalloproteases activity, and collagen-type 2 expression were evaluated in all mice. Joint calcification and subchondral bone parameters were quantified by CT-scan in WT and IL-1β^-/- menisectomized knees. Results:In vitro, HA crystals induced significant increased IL-6 secretion by CHs, while IL-1β remained undetectable.Conversely, both IL-6 and IL-1β were able to increase chondrocytes mineralization. In vivo, operated knees exhibited OA features compared to sham-operated knees as evidenced by increased cartilage degradation and synovial inflammation. In menisectomized KO mice, severity and extent of cartilage lesions were similar (IL-1α^-/- mice) or exacerbated (IL-1β^-/- and NLRP3^-/- mice) compared to that of menisectomized WT mice. Metalloproteases activity, collagen-type 2 expression, chondrocytes apoptosis, and synovial inflammation were similar between KO and WT mice menisectomized knees. Moreover, the extent of joint calcification in osteoarthritic knees was comparable between IL-1β^-/- and WT mice. Conclusions: MNX knees recapitulated features of OA, i.e, cartilage destruction, synovial inflammation, cell death, and joint calcification. Deficiency of IL-1α did not impact on the severity of these features, whereas deficiency of IL-1β or of NLRP3 led to increased cartilage erosion. Our results suggest that IL-1α and IL-1β are not key mediators in this murine OA model and may explain the inefficiency of IL-1 targeted therapies in OA.

Inflammasomes in the lung

Innate immune responses act as first line defences upon exposure to potentially noxious stimuli. The innate immune system has evolved numerous intracellular and extracellular receptors that undertake surveillance for potentially damaging particulates. Inflammasomes are intracellular innate immune multiprotein complexes that form and are activated following interaction with these stimuli. Inflammasome activation leads to the cleavage of pro-IL-1β and release of the pro-inflammatory cytokine, IL-1β, which initiates acute phase pro-inflammatory responses, and other responses are also involved (IL-18, pyroptosis). However, excessive activation of inflammasomes can result in chronic inflammation, which has been implicated in a range of chronic inflammatory diseases. The airways are constantly exposed to a wide variety of stimuli. Inflammasome activation and downstream responses clears these stimuli. However, excessive activation may drive the pathogenesis of chronic respiratory diseases such as severe asthma and chronic obstructive pulmonary disease. Thus, there is currently intense interest in the role of inflammasomes in chronic inflammatory lung diseases and in their potential for therapeutic targeting. Here we review the known associations between inflammasome-mediated responses and the development and exacerbation of chronic lung diseases.

Cytokine decoy and scavenger receptors as key regulators of immunity and inflammation

IL-1R2 was the first decoy receptor to be described. Subsequently receptors which act as pure decoys or scavengers or trigger dampening of cytokine signaling have been described for cytokines and chemokines. Here we review the current understanding of the mode of action and significance in pathology of the chemokine atypical receptor ACKR2, the IL-1 decoy receptor IL-1R2 and the atypical IL-1 receptor family IL-1R8. Decoy and scavenger receptors with no or atypical signaling have emerged as a general strategy conserved in evolution to tune the action of cytokines, chemokines and growth factors.

Trichostatin A increases the TIMP-1/MMP ratio to protect against osteoarthritis in an animal model of the disease

The histone deacetylase inhibitor trichostatin A (TSA) has been demonstrated to alleviate certain symptoms associated with osteoarthritis (OA). However, the exact mechanisms underlying this protective effect remain to be elucidated. The present study therefore examined the effects of TSA on the expression levels of interleukin-1β (IL-1β)-induced matrix metalloproteinases (MMPs) and tissue inhibitor of metalloproteinases-1 (TIMP-1) in vitro and in vivo. In vitro, reverse transcription-quantitative polymerase chain reaction was performed to investigate alterations in mRNA expression levels in TSA-treated chondrocytes in the presence or absence of IL-1β; in addition, protein expression and acetylation levels were assessed by western blotting. In vivo, TSA was administered to rats by intra-articular injection, following which the mRNA and protein expression levels were analyzed. In addition, macroscopic and histological observations were conducted. Chondrocytes treated with IL-1β demonstrated increased mRNA and protein expression levels of MMP-1, MMP-3 and MMP-13, and decreased expression levels of TIMP-1 mRNA and protein; these alterations were significantly attenuated by TSA treatment. In addition, increased MMPs and decreased TIMP-1 expression levels were observed in vivo in the OA rat model. TSA treatment demonstrated in vivo efficacy through the attenuation of various OA-associated molecular and physiological changes. Taken together, the results of the present study suggest that TSA has potential therapeutic value for the treatment of OA.

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

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

The Involvement of Mutual Inhibition of ERK and mTOR in PLCγ1-Mediated MMP-13 Expression in Human Osteoarthritis Chondrocytes

The issue of whether ERK activation determines matrix synthesis or degradation in osteoarthritis (OA) pathogenesis currently remains controversial. Our previous study shows that PLCγ1 and mTOR are involved in the matrix metabolism of OA cartilage. Investigating the interplays of PLCγ1, mTOR and ERK in matrix degradation of OA will facilitate future attempts to manipulate ERK in OA prevention and therapy. Here, cultured human normal chondrocytes and OA chondrocytes were treated with different inhibitors or transfected with expression vectors, respectively. The levels of ERK, p-ERK, PLCγ1, p-PLCγ1, mTOR, p-mTOR and MMP-13 were then evaluated by Western blotting analysis. The results manifested that the expression level of ERK in human OA chondrocytes was lower than that in human normal articular chondrocytes, and the up-regulation of ERK could promote matrix synthesis, including the decrease in MMP-13 level and the increase in Aggrecan level in human OA chondrocytes. Furthermore, the PLCγ1/ERK axis and a mutual inhibition of mTOR and ERK were observed in human OA chondrocytes. Interestingly, activated ERK had no inhibitory effect on MMP-13 expression in PLCγ1-transformed OA chondrocytes. Combined with our previous study, the non-effective state of ERK activation by PLCγ1 on MMP-13 may be partly attributed to the inhibition of the PLCγ1/mTOR axis on the PLCγ1/ERK axis. Therefore, the study indicates that the mutual inhibition of ERK and mTOR is involved in PLCγ1-mediated MMP-13 expression in human OA chondrocytes, with important implication for the understanding of OA pathogenesis as well as for its prevention and therapy.

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

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

Cyclin-dependent kinase 9 inhibition protects cartilage from the catabolic effects of proinflammatory cytokines

OBJECTIVE

Cyclin-dependent kinase 9 (CDK-9) controls the activation of primary inflammatory response genes. The purpose of this study was to determine whether CDK-9 inhibition protects cartilage from the catabolic effects of proinflammatory cytokines.

METHODS

Human chondrocytes were challenged with different proinflammatory stimuli (interleukin-1β [IL-1β], lipopolysaccharides, and tumor necrosis factor α) in the presence or absence of either the CDK-9 inhibitor flavopiridol or small interfering RNA (siRNA). The expression of messenger RNA (mRNA) for inflammatory mediator genes, catabolic genes, and anabolic genes were determined by real-time quantitative reverse transcription-polymerase chain reaction (qRT-PCR) analysis. Cartilage explants were incubated for 6 days with IL-1β in the presence or absence of flavopiridol. Cartilage matrix degradation was assessed by the release of glycosaminoglycan (GAG) and cleaved type II collagen (COL2A) peptides.

RESULTS

CDK-9 inhibition by flavopiridol or knockdown by siRNA effectively suppressed the induction of mRNA for inducible nitric oxide synthase by all 3 proinflammatory stimuli. Results from NF-κB-targeted PCR array analysis showed that flavopiridol suppressed IL-1β induction of a broad range of inflammatory mediator genes (59 of 67 tested). CDK-9 inhibition also suppressed the induction of catabolic genes (matrix metalloproteinase 1 [MMP-1], MMP-3, MMP-9, MMP-13, ADAMTS-4, and ADAMTS-5), but did not affect the basal expression of anabolic genes (COL2A, aggrecan, and cartilage oligomeric matrix protein) and housekeeping genes. Flavopiridol had no apparent short-term cytotoxicity, as assessed by G6PDH activity. Finally, in IL-1β-treated cartilage explants, flavopiridol reduced the release of the matrix degradation product GAG and cleaved COL2A peptides, but did not affect long-term chondrocyte viability.

CONCLUSION

CDK-9 activity is required for the primary inflammatory response in chondrocytes. Flavopiridol suppresses the induction of inflammatory mediator genes and catabolic genes to protect cartilage from the deleterious effects of proinflammatory cytokines, without affecting cell viability and functions.

Disruption of phosphoinositide-specific phospholipases Cγ1 contributes to extracellular matrix synthesis of human osteoarthritis chondrocytes

Osteoarthritis (OA) is a degenerative joint disease characterized by articular cartilage degradation including extracellular matrix (ECM) degradation and cell loss. It is known that phosphoinositide-specific phospholipase γ1 (PLCγ1) can trigger several signaling pathways to regulate cell metabolism. However, whether this kinase is expressive and active in human OA chondrocytes and its role in the pathological progression of OA have not been investigated. The current study was designed to investigate the PLCγ1 expression in human OA cartilage, and whether PLCγ1 was involved in the ECM synthesis had been further explored using cultured human OA chondrocytes. Our results indicated that PLCγ1 was highly expressed in human OA chondrocytes. In our further study using the cultured human OA chondrocytes, the results demonstrated that the disruption of PLCγ1 by its inhibitor, U73122, and siRNA contributed to the ECM synthesis of human OA chondrocytes through regulating the expression of ECM-related signaling molecules, including MMP-13, Col II, TIMP1, Sox-9, and AGG. Furthermore, PLCγ1/IP3/Ca2+/CaMK II signaling axis regulated the ECM synthesis of human chondrocytes through triggering mTOR/P70S6K/S6 pathway. In summary, our results suggested that PLC-γ1 activities played an important role in the ECM synthesis of human OA chondrocytes, and may serve as a therapeutic target for treating OA.

Genomic analysis and differential expression of HMG and S100A family in human arthritis: upregulated expression of chemokines, IL-8 and nitric oxide by HMGB1

We applied global gene expression arrays, quantitative real-time PCR, immunostaining, and functional assays to untangle the role of High Mobility Groups proteins (HMGs) in human osteoarthritis (OA)-affected cartilage. Bioinformatics analysis showed increased mRNA expression of Damage-Associated Molecular Patterns (DAMPs): HMGA, HMGB, HMGN, SRY, LEF1, HMGB1, MMPs, and HMG/RAGE-interacting molecules (spondins and S100A4, S100A10, and S100A11) in human OA-affected cartilage as compared with normal cartilage. HMGB2 was down-regulated in human OA-affected cartilage. Immunohistological staining identified HMGB1 in chondrocytes in the superficial cartilage. Cells of the deep cartilage and subchondral bone showed increased expression of HMGB1 in OA-affected cartilage. HMGB1 was expressed in the nucleus, cytosol, and extracellular milieu of chondrocytes in cartilage. Furthermore, HMGB1 was spontaneously released from human OA-affected cartilage in ex vivo conditions. The effects of recombinant HMGB1 was tested on human cartilage and chondrocytes in vitro. HMGB1 stimulated mRNA of 2 NFκB gene enhancers (NFκB1 and NFκB2), 16 CC and CXC chemokines (IL-8, CCL2, CCL20, CCL3, CCL3L1, CCL3L3, CCL4, CCL4L1, CCL4L2, CCL5, CCL8, CXCL1, CXCL10, CXCL2, CXCL3, and CXCL6) by ≥10-fold. Furthermore, HMGB1 and IL-1β and/or tumor necrosis factor α (but not HMGI/Y) also significantly induced inducible nitric oxide synthase, NO, and interleukin (IL)-8 production in human cartilage and chondrocytes. The recombinant HMGB1 utilized in this study shows properties that are similar to disulfide-HMGB1. The differential, stage and/or tissue-specific expression of HMGB1, HMGB2, and S100A in cartilage was associated with regions of pathology and/or cartilage homeostasis in human OA-affected cartilage. Noteworthy similarities in the expression of mouse and human HMGB1 and HMGB2 were conserved in normal and arthritis-affected cartilage. The multifunctional forms of HMGB1 and S100A could perpetuate damage-induced cartilage inflammation in late-stage OA-affected joints similar to sterile inflammation. The paracrine effects of HMGB1 can induce chemokines and NO that are perceived to change cartilage homeostasis in human OA-affected cartilage.

Negative regulatory receptors of the IL-1 family

The IL-1 family of ligands and receptors has a central role in both innate and adaptive immune responses and is tightly controlled by antagonists, decoy receptors, scavengers, dominant negative molecules, miRNAs and other mechanisms, acting extracellularly or intracellularly. During evolution, the development of multiple mechanisms of negative regulation reveals the need for tight control of the biological consequences of IL-1 family ligands in order to balance local and systemic inflammation and limit immunopathology. Indeed, studies with gene targeted mice for negative regulators and genetic studies in humans provide evidence for their non-redundant role in controlling inflammation, tissue damage and adaptive responses. In addition, studies have revealed the need of negative regulation of the IL-1 family not only in disease, but also in homeostatic conditions. In this review, the negative regulation mediated by decoy receptors are presented and include IL-1R2 and IL-IL-18BP as well as atypical receptors, which include TIR8/SIGIRR, IL-1RAcPb, TIGIRR-1 and IL-1RAPL. Particular emphasis is given to IL-1R2, since its discovery is the basis for the formulation of the decoy paradigm, now considered a general strategy to counter the primary inflammatory activities of cytokines and chemokines. Emphasis is also given to TIR8, a prototypical negative regulatory receptor having non-redundant roles in limiting inflammation and adaptive responses.

Decoys and Regulatory "Receptors" of the IL-1/Toll-Like Receptor Superfamily

Members of the IL-1 family play a key role in innate and adaptive immunity and in the pathogenesis of diverse diseases. Members of IL-1R like receptor (ILR) family include signaling molecules and negative regulators. The latter include decoy receptors (IL-1RII; IL-18BP) and “receptors” with regulatory function (TIR8/SIGIRR; IL-1RAcPb; DIGIRR). Structural considerations suggest that also TIGIRR-1 and IL-1RAPL may have regulatory function. The presence of multiple pathways of negative regulation of members of the IL-1/IL-1R family emphasizes the need for a tight control of members of this fundamental system.

Synovial fluid concentrations and relative potency of interleukin-1 alpha and beta in cartilage and meniscus degradation

Cartilage degeneration with osteoarthritis (OA) is believed to involve the activities of interleukin-1 (IL-1), which exists as alpha and beta isoforms. The goal of this study was to measure the concentrations of both isoforms of IL-1 in the synovial fluid of normal and spontaneously osteoarthritic porcine knees, and to test the hypothesis that physiologic concentrations of IL-1α and IL-1β exhibit different potencies in activating calcium signaling, the production of matrix metalloproteinases and nitric oxide, and the loss of proteoglycans and tissue mechanical properties in cartilage and meniscus. Median concentrations of IL-1α were 0.043 ng/ml with mild OA and 0.288 ng/ml with moderate OA, whereas IL-1β concentrations were 0.109 ng/ml with mild OA and 0.122 ng/ml with moderate OA. Both isoforms induced calcium signaling in chondrocytes and meniscal cells at all concentrations. Overall, cartilage and meniscus catabolism was significantly more sensitive to IL-1α than IL-1β at concentrations of 1 ng/ml or less, while few differences were observed between the two forms at 10 ng/ml. These data provide a range of physiologic IL-1 concentrations that can serve as a framework for the comparison of various in vitro studies, as well as providing further insight for the development of anti-cytokine therapies for OA.

Alcohol-induced IL-1β in the brain is mediated by NLRP3/ASC inflammasome activation that amplifies neuroinflammation

Alcohol-induced neuroinflammation is mediated by proinflammatory cytokines, including IL-1β. IL-1β production requires caspase-1 activation by inflammasomes-multiprotein complexes that are assembled in response to danger signals. We hypothesized that alcohol-induced inflammasome activation contributes to increased IL-1β in the brain. WT and TLR4-, NLRP3-, and ASC-deficient (KO) mice received an ethanol-containing or isocaloric control diet for 5 weeks, and some received the rIL-1ra, anakinra, or saline treatment. Inflammasome activation, proinflammatory cytokines, endotoxin, and HMGB1 were measured in the cerebellum. Expression of inflammasome components (NLRP1, NLRP3, ASC) and proinflammatory cytokines (TNF-α, MCP-1) was increased in brains of alcohol-fed compared with control mice. Increased caspase-1 activity and IL-1β protein in ethanol-fed mice indicated inflammasome activation. TLR4 deficiency protected from TNF-α, MCP-1, and attenuated alcohol-induced IL-1β increases. The TLR4 ligand, LPS, was not increased in the cerebellum. However, we found up-regulation of acetylated and phosphorylated HMGB1 and increased expression of the HMGB1 receptors (TLR2, TLR4, TLR9, RAGE) in alcohol-fed mice. NLRP3- or ASC-deficient mice were protected from caspase-1 activation and alcohol-induced IL-1β increase in the brain. Furthermore, in vivo treatment with rIL-1ra prevented alcohol-induced inflammasome activation and IL-1β, TNF-α, and acetylated HMGB1 increases in the cerebellum. Conversely, intracranial IL-1β administration induced TNF-α and MCP-1 in the cerebellum. In conclusion, alcohol up-regulates and activates the NLRP3/ASC inflammasome, leading to caspase-1 activation and IL-1β increase in the cerebellum. IL-1β amplifies neuroinflammation, and disruption of IL-1/IL-1R signaling prevents alcohol-induced inflammasome activation and neuroinflammation. Increased levels of acetylated and phosphorylated HMGB1 may contribute to alcoholic neuroinflammation.

Osteoimmunology and the influence of pro-inflammatory cytokines on osteoclasts

Bone and immune system are functionally interconnected. Immune and bone cells derive from same progenitors in the bone marrow, they share a common microenvironment and are being influenced by similar mediators. The evidence on increased bone resorption associated with inappropriate activation of T cells such as during inflammation, is well established. However, the molecular mechanisms beyond this clinical observation have begun to be intensively studied with the advancement of osteoimmunology. Now days, we have firm evidence on the influence of numerous proinflammatory cytokines on bone cells, with the majority of data focused on osteoclasts, the bone resorbing cells. It has been shown that some proinflammatory cytokines could possess osteoclastogenic and/or anti-osteoclastogenic properties and can target osteoclasts directly or via receptor activator of nuclear factor κB (RANK)/RANK ligand(RANKL)/osteoprotegerin (OPG) system. Several studies have reported opposing data regarding (anti)osteoclastogenic properties of these cytokines.

Therefore, the first part of this review is summarizing current evidence on the influence of pro-inflammatory cytokines on osteoclasts and thus on bone resorption. In the second part, the evidence on the role of pro-inflammatory cytokines in osteoporosis and osteoarthritis is reviewed to show that unravelling the mechanisms beyond such complex bone diseases, is almost impossible without considering skeletal and immune systems as an indivisible integrated system.

Hydrodynamics-based delivery of an interleukin-1 receptor II fusion gene ameliorates rat autoimmune myocarditis by inhibiting IL-1 and Th17 cell polarization

Type II interleukin-1 receptor (IL-1RII) is a non-signaling decoy receptor that blocks the activity of interleukin-1 (IL-1), a pro-inflammatory cytokine involved in experimental autoimmune myocarditis (EAM). The aim of this study was to examine the effects of hydrodynamics-based delivery of a recombinant plasmid encoding IL-1RII-Ig and to elucidate the role of IL-1RII in EAM rats. Rats were immunized on day 0 and injected with a recombinant plasmid encoding IL-1RII-Ig or pCAGGS-SP-Ig (control plasmid) on day 6. IL-1RII-Ig gene therapy effectively controlled EAM as indicated by a decreased heart weight-to-body weight ratio, reduced areas of myocarditis, reduced expression of genes encoding atrial natriuretic peptide and brain natriuretic peptide in the heart, and improved cardiac function. IL-1RII-Ig significantly inhibited the expression of IL-1-related cytokines such as IL-1β, prostaglandin E2 synthase, cyclooxygenase, and monocyte chemotactic protein-1 in EAM hearts. Furthermore, the effect of serum containing IL-1RII-Ig on the expression of immune-related genes in IL-1-stimulated splenocytes cultured from EAM rats was examined. The results showed that the expression of IL-6, transforming growth factor-β, retinoic acid-related orphan nuclear receptor (RORγt) and IL-17, was significantly decreased upon exposure to serum containing IL-1RII-Ig. In conclusion, hydrodynamics-based delivery of a recombinant plasmid encoding IL-1RII-Ig effectively prevented progression of left ventricular remodeling and myocardial damage in EAM rats. Moreover, IL-1RII may ameliorate experimental autoimmune myocarditis by blocking IL-1 and inhibiting production of the cytokines important for the polarization of T cells toward a Th17 phenotype.

Matrilin-3 induction of IL-1 receptor antagonist is required for up-regulating collagen II and aggrecan and down-regulating ADAMTS-5 gene expression

Introduction

Deletion or mutation of the gene encoding the cartilage extracellular matrix (ECM) protein matrilin-3 (MATN3) results in the early onset of osteoarthritis (OA), suggesting chondroprotective properties of MATN3. To understand the mechanisms underlying these properties, we determined the effects of MATN3 protein on the expression of several key anabolic and catabolic genes involved in chondrocyte homeostasis, and the dependence of such regulation on the anti-inflammatory cytokine: IL-1 receptor antagonist (IL-1Ra).

Methods

The effects of recombinant human (rh) MATN3 protein were examined in C28/I2 immortalized human chondrocytes, primary human chondrocytes (PHCs), and primary mouse chondrocytes (PMCs). Messenger RNA levels of IL-1Ra, COL2A1, ACAN, MMP-13, and ADAMTS-4 and -5 were determined using real-time RT-PCR. Knocking down IL-1Ra was achieved by siRNA gene silencing. IL-1Ra protein levels were quantified by ELISA and the Bio-Plex Suspension Array System. COL2A1 protein level was quantified using Western blot analysis. Statistic analysis was done using the two-tailed t-test or one-way ANOVA.

Results

rhMATN3 protein induced gene expression of IL-1Ra in C28/I2 cells, PHCs, and PMCs in a dose- and time-dependent manner. Treatment of C28/I2 cells and PHCs with MATN3 protein stimulated gene expression of COL2A1 and ACAN. Conversely, mRNA levels of COL2A1 and ACAN were decreased in MATN3 KO mice. MATN3 protein treatment inhibited IL-1β-induced MMP-13, ADAMTS-4 and ADAMTS-5 in C28/I2 cells and PHCs. Knocking down IL-1Ra abolished the MATN3-mediated stimulation of COL2A1 and ACAN and inhibition of ADAMTS-5, but had no effect on MATN3 inhibition of MMP-13 mRNA.

Conclusion

Our findings point to a novel regulatory role of MATN3 in cartilage homeostasis due to its capacity to induce IL-1Ra, to upregulate gene expression of the major cartilage matrix components, and to downregulate the expression of OA-associated matrix-degrading proteinases in chondrocytes. The chondroprotective properties of endogenous MATN3 depend partly on its induction of IL-1Ra. Our findings raise a possibility to use rhMATN3 protein for anti-inflammatory and chondroprotective therapy.

Perturbation of nuclear lamin A causes cell death in chondrocytes

OBJECTIVE

Mutations in LMNA encoding the A-type lamins cause several diseases, including those with features of premature aging and skeletal abnormalities. The aim of this study was to examine the expression of lamin A in cartilage from patients with osteoarthritis (OA) and the effects of its overexpression on chondrocyte senescence and apoptosis.

METHODS

Human chondrocyte-like cells (SW-1353) were used. RNA isolated from human OA and non-OA cartilage was used for profiling messenger RNA expression, using Affymetrix microarray analysis. The effects of lamin A overexpression on mitochondrial function and apoptosis were examined by assessing mitochondrial membrane potential, ATP levels, and cytochrome c release, and with a TUNEL assay. Western blotting was performed to determine protein expression.

RESULTS

Lamin A expression was markedly elevated in OA cartilage samples compared with non-OA control samples. Western blot analysis confirmed increased expression of lamin A in OA compared with non-OA cartilage. Interleukin-1β treatment inhibited lamin A accumulation, whereas treatment with prostaglandin E(2) (PGE(2) ) caused a marked increase in lamin A accumulation. These effects of exogenous PGE(2) on lamin A expression were mediated via the EP(2) /EP(4) receptors. Transfected chondrocytes that expressed lamin A displayed markers of early senescence/apoptosis.

CONCLUSION

The results of this study suggest that lamin A is up-regulated in OA chondrocytes, and that increased nuclear accumulation of lamin A in response to catabolic stress may account for the premature aging phenotype and apoptosis of OA chondrocytes.

Anabolic/Catabolic balance in pathogenesis of osteoarthritis: identifying molecular targets

Osteoarthritis is the most common degenerative musculoskeletal disease. In healthy cartilage, a low turnover of extracellular matrix molecules occurs. Proper balance of anabolic and catabolic activities is thus crucial for the maintenance of cartilage tissue integrity and for the repair of molecular damages sustained during daily usage. In persons with degenerative diseases such as osteoarthritis, this balance of anabolic and catabolic activities is compromised, and the extent of tissue degradation predominates over the capacity of tissue repair. This mismatch eventually results in cartilage loss in persons with osteoarthritis. Tissue homeostasis is controlled by coordinated actions and crosstalk among a number of proanabolic and antianabolic and procatabolic and anticatabolic factors. In osteoarthritis, an elevation of antianabolic and catabolic factors occurs. Interestingly, anabolic activity is also increased, but this response fails to repair the tissue because of both quantitative and qualitative insufficiency. This review presents an overview of the anabolic and catabolic activities involved in cartilage degeneration and the interplay among different signaling and metabolic factors. Understanding the basic molecular mechanisms responsible for tissue degeneration is critical to identifying and developing means to efficiently block or reverse the pathobiological symptoms of osteoarthritis.

Regulation of MMP-3 expression and secretion by the chemokine eotaxin-1 in human chondrocytes

BACKGROUND

Osteoarthritis (OA) is characterized by the degradation of articular cartilage, marked by the breakdown of matrix proteins. Studies demonstrated the involvement of chemokines in this process, and some may potentially serve as diagnostic markers and therapeutic targets; however, the underlying signal transductions are not well understood.

METHODS

We investigated the effects of the CC chemokine eotaxin-1 (CCL11) on the matrix metalloproteinase (MMP) expression and secretion in the human chondrocyte cell line SW1353 and primary chondrocytes.

RESULTS

Eotaxin-1 significantly induced MMP-3 mRNA expression in a dose-dependent manner. Inhibitors of extracellular signal-regulated kinase (ERK) and p38 kinase were able to repress eotaxin-1-induced MMP-3 expression. On the contrary, Rp-adenosine-3',5'-cyclic monophosphorothioate (Rp-cAMPs), a competitive cAMP antagonist for cAMP receptors, and H-89, a protein kinase A (PKA) inhibitor, markedly enhanced eotaxin-1-induced MMP-3 expression. These results suggest that MMP-3 expression is specifically mediated by the G protein-coupled eotaxin-1 receptor activities. Interestingly, little amount of MMP-3 protein was detected in the cell lysates of eotaxin-1-treated SW1353 cells, and most of MMP-3 protein was in the culture media. Furthermore we found that the eotaxin-1-dependent MMP-3 protein secretion was regulated by phospholipase C (PLC)-protein kinase C (PKC) cascade and c-Jun N-terminal kinase (JNK)/mitogen-activated protein (MAP) kinase pathways. These data indicate a specific regulation of MMP-3 secretion also by eotaxin-1 receptor activities.

CONCLUSIONS

Eotaxin-1 not only induces MMP-3 gene expression but also promotes MMP-3 protein secretion through G protein-coupled eotaxin-1 receptor activities. Chemokines, such as eotaxin-1, could be a potential candidate in the diagnosis and treatment of arthritis.

Glatiramer acetate (GA), the immunomodulatory drug, inhibits inflammatory mediators and collagen degradation in osteoarthritis (OA) cartilage

OBJECTIVE

Glatiramer acetate (GA), the generic name for Copaxone, an immunomodulatory agent, has been shown to induce interleukin-1 receptor antagonist (IL-1Ra) production in macrophages. We therefore tested the effects of GA on the catabolic activities of osteoarthritis (OA) chondrocytes.

DESIGN

Primary human chondrocytes and OA cartilage explants were utilized in this study. IL-1Ra, pro-matrix metalloproteinase-13 (proMMP-13) and prostaglandin E(2) (PGE(2)) were estimated in the cell culture supernatants and in vitro MMP-13 activity was measured using fluorogenic substrate. TaqMan Real-Time quantitative polymerase chain reaction (RT-qPCR) was performed to estimate relative expression levels of genes.

RESULTS

GA treatment significantly increased transcription and production of sIL-1Ra (P=0.001) in both culture models. Furthermore, addition of GA (100 μg) inhibited: (1) spontaneous collagen degradation as assayed by CTX II enzyme-linked immunosorbent assay (ELISA) [mean CTX II (ng/g cartilage)] in control was 7.79 [95% confidence interval (CI) 2.57-13.02]-3.415 (95% CI 0.81-6.02) (P=0.0286); (2) spontaneous proMMP-13 secretion [mean MMP-13 (ng/g cartilage)] in control was 16.98 (95% CI 7.739-26.23)-6.973 (95% CI 1.632-12.31) (P=0.0286); (3) production of IL-1β-induced inflammatory mediators such as nitric oxide (NO) [mean NO (μM)] in IL-1 cultures was 11.47 (95% CI 7.10-15.83)-0.87 (95% CI 0.18-1.56) (P=0.0022); and (4) recombinant MMP-13 in vitro activity (15-25%; P=0.004).

CONCLUSIONS

These data suggest that GA effects may be due to upregulation of IL-1Ra as well as direct inhibition of MMP-13 activity. Based on these studies, we propose that GA has potential for disease modifying properties in OA and should be evaluated in vivo in animal studies.

Increased interleukin-1β gene expression in peripheral blood leukocytes is associated with increased pain and predicts risk for progression of symptomatic knee osteoarthritis

OBJECTIVE

To evaluate whether gene expression profiles could serve as biomarkers of symptomatic knee osteoarthritis (OA) by examining gene expression profiles in peripheral blood leukocytes (PBLs) from patients with OA compared with those from non-OA controls, and to determine whether candidate genomic biomarkers (PBL expression of inflammatory genes) predict an increased risk of disease progression in patients with symptomatic radiographic knee OA.

METHODS

Three independent cohorts of patients with knee OA and non-OA control subjects were studied. Two cohorts (a learning cohort and a validation cohort) were recruited at New York University Hospital for Joint Diseases (NYUHJD), and 1 cohort (a validation cohort) was recruited at Duke University Medical Center. PBL gene expression was assessed using Affymetrix microarray and was confirmed by quantitative polymerase chain reaction (qPCR). Radiographic progression at 2 years was assessed in 86 patients.

RESULTS

We identified 173 genes that were significantly up-regulated or down-regulated (≥1.5-fold change) in OA PBLs, at a false discovery rate of 5%. Cluster analysis revealed 2 distinct subgroups among the patients with OA: those in whom the expression of interleukin-1β (IL-1β) was increased ≥2-fold compared with controls, and those in whom the expression of IL-1β was comparable with that in controls. Overexpression of IL-1β in these OA subclasses was validated using qPCR in all 3 cohorts. Patients with the inflammatory "IL-1β signature" had higher pain scores and decreased function and were at higher risk of radiographic progression of OA.

CONCLUSION

PBLs from patients with symptomatic knee OA display a characteristic transcriptome profile. Moreover, increased expression of IL-1β identifies a subset of patients with OA who have increased pain and are at higher risk of radiographic progression of OA.

Anti-Inflammatory mechanisms of the proteinase-activated receptor 2-inhibiting peptide in human synovial cells

Background

Osteoarthritis (OA) is a degenerative joint disease which affects the entire joint structure, including the synovial membrane. Disease progression was shown to involve inflammatory changes mediated by proteinase-activated receptor (PAR)-2. Previous studies demonstrated that PAR-2 messenger (m)RNA and protein levels increased in OA synovial cells, suggesting that PAR-2 is a potential therapeutic target of the disease.

Methods

We designed a PAR-2-inhibiting peptide (PAR2-IP) by changing an isoleucine residue in the PAR-2-activating peptide (PAR2-AP), SLIGKV, to alanine, generating the SLAGKV peptide. We used it to test PAR-2-mediated inflammatory responses, including the expressions of cyclooxygenase (COX)-2 and matrix metalloproteinase (MMP)-1 and activation of nuclear factor (NF)-κB in human synovial cells. As a control, expressions of COX-2 and MMP-1 were induced by trypsin at both the mRNA and protein levels.

Results

The PAR2-AP increased the expression of COX-2 more dramatically than that of MMP-1. When we treated cells with the designed PAR2-IP, the trypsin-induced COX-2 level was completely inhibited at a moderate concentration of the PAR2-IP. With further examination of trypsin-induced NF-κB activation, we observed sufficient inhibitory effects of the PAR2-IP in synoviosarcoma cells and primary synovial cells from OA patients.

Conclusions

Our study suggests that the PAR2-IP inhibits trypsin-induced NF-κB activation, resulting in a reduction in inflammatory COX-2 expression in synovial cells. Application of PAR2-IP is suggested as a potential therapeutic strategy for OA.

The role of synovial fluid markers of catabolism and anabolism in osteoarthritis, rheumatoid arthritis and asymptomatic organ donors

Introduction

The purpose of this study was to correlate the level of anabolic and catabolic biomarkers in synovial fluid (SF) from patients with rheumatoid arthritis (RA), patients with osteoarthritis (OA) and asymptomatic organ donors.

Methods

SF was collected from the knees of 45 OA, 22 RA patients and 20 asymptomatic organ donors. Eight biomarkers were selected and analyzed by using an enzyme-linked immunosorbent assay: interleukin (IL)-1, IL-6, IL-8 and IL-11; leukemia-inhibitory factor (LIF); cartilage oligomeric protein (COMP); osteocalcin; and osteogenic protein 1 (OP-1). Data are expressed as medians (interquartile ranges). The effects of sex and disease activity were assessed on the basis of the Western Ontario and McMaster Universities index score for patients with OA and on the basis of white blood cell count, erythrocyte sedimentation rate and C-reactive protein level for patients with RA.

Results

The mean ages (± SD) of the patients were as follows: 53 ± 9 years for patients with OA, 54 ± 11 years for patients with RA and 52 ± 7 years for asymptomatic organ donors. No effect of participants' sex was identified. In the SF of patients with RA, four of five cytokines were higher than those in the SF of patients with OA and those of asymptomatic organ donors. The most significant differences were found for IL-6 and IL-8, where IL-6 concentration in SF of patients with RA was almost threefold higher than that in patients with OA and fourfold higher than that in asymptomatic donor controls: 354.7 pg/ml (1,851.6) vs. 119.4 pg/ml (193.2) vs. 86.97 pg/ml (82.0) (P < 0.05 and P < 0.05, respectively). IL-8 concentrations were higher in SF of patients with RA than that in patients with OA as well as that in asymptomatic donor controls: 583.6 pg/ml (1,086.4) vs. 429 pg/ml (87.3) vs. 451 pg/ml (170.1) (P < 0.05 and P < 0.05, respectively). No differences were found for IL-11 in the SF of patients with RA and that of patients with OA, while a 1.4-fold difference was detected in the SF of patients with OA and that of asymptomatic donor controls: 296.2 pg/ml (257.2) vs. 211.6 pg/ml (40.8) (P < 0.05). IL-1 concentrations were the highest in the SF of RA patients (9.26 pg/ml (11.1)); in the SF of asymptomatic donors, it was significantly higher than that in patients with OA (9.083 pg/ml (1.6) vs. 7.76 pg/ml (2.6); P < 0.05). Conversely, asymptomatic donor control samples had the highest LIF concentrations: 228.5 pg/ml (131.6) vs. 128.4 pg/ml (222.7) in the SF of patients with RA vs. 107.5 pg/ml (136.9) in the SF of patients with OA (P < 0.05). OP-1 concentrations were twofold higher in the SF of patients with RA than those in patients with OA and threefold higher than those in asymptomatic donor control samples (167.1 ng/ml (194.8) vs. 81.79 ng/ml (116.0) vs. 54.49 ng/ml (29.3), respectively; P < 0.05). The differences in COMP and osteocalcin were indistinguishable between the groups, as were the differences between active and inactive OA and RA.

Conclusions

Activation of selected biomarkers corresponds to the mechanisms that drive each disease. IL-11, LIF and OP-1 may be viewed as a cluster of biomarkers significant for OA; while profiling of IL-1, IL-6, IL-8, LIF and OP-1 may be more significant in RA. Larger, better-defined patient cohorts are necessary to develop a biomarker algorithm for prognostic use.

Uric acid is a danger signal of increasing risk for osteoarthritis through inflammasome activation

Uric acid (UA) is known to activate the NLRP3 (Nacht, leucine-rich repeat and pyrin domain containing protein 3) inflammasome. When activated, the NLRP3 (also known as NALP3) inflammasome leads to the production of IL-18 and IL-1β. In this cohort of subjects with knee osteoarthritis (OA), synovial fluid uric acid was strongly correlated with synovial fluid IL-18 and IL-1β. Synovial fluid uric acid and IL-18 were strongly and positively associated with OA severity as measured by both radiograph and bone scintigraphy, and synovial fluid IL-1β was associated with OA severity but only by radiograph. Furthermore, synovial fluid IL-18 was associated with a 3-y change in OA severity, on the basis of the radiograph. We conclude that synovial fluid uric acid is a marker of knee OA severity. The correlation of synovial fluid uric acid with the two cytokines (IL-18 and IL-1β) known to be produced by uric acid-activated inflammasomes and the association of synovial fluid IL-18 with OA progression, lend strong support to the potential involvement of the innate immune system in OA pathology and OA progression.

Cartilage biology, pathology, and repair

Osteoarthritis is one of the most common forms of musculoskeletal disease and the most prominent type of arthritis encountered in all countries. Although great efforts have been made to investigate cartilage biology and osteoarthritis pathology, the treatment has lagged behind that of other arthritides, as there is a lack of effective disease-modifying therapies. Numerous approaches for dealing with cartilage degradation have been tried, but enjoyed very little success to develop approved OA treatments with not only symptomatic improvement but also structure-modifying effect. In this review we discuss the most recent findings regarding the regulation of cartilage biology and pathology and highlight their potential therapeutic values.

Dynamic loading enhances integrative meniscal repair in the presence of interleukin-1

OBJECTIVE

Meniscal tears are a common knee injury and increased levels of interleukin-1 (IL-1) have been measured in injured and degenerated joints. Studies have shown that IL-1 decreases the shear strength, cell accumulation, and tissue formation in meniscal repair interfaces. While mechanical stress and IL-1 modulate meniscal biosynthesis and degradation, the effects of dynamic loading on meniscal repair are unknown. The purpose of this study was to determine the effects of mechanical compression on meniscal repair under normal and inflammatory conditions.

EXPERIMENTAL DESIGN

Explants were harvested from porcine medial menisci. To simulate a full-thickness defect, a central core was removed and reinserted. Explants were loaded for 4h/day at 1 Hz and 0%-26% strain for 14 days in the presence of 0 or 100 pg/mL of IL-1. Media were assessed for matrix metalloproteinase (MMP) activity, aggrecanase activity, sulfated glycosaminoglycan (S-GAG) release, and nitric oxide (NO) production. After 14 days, biomechanical testing and histological analyses were performed.

RESULTS

IL-1 increased MMP activity, S-GAG release, and NO production, while decreasing the shear strength and tissue repair in the interface. Dynamic loading antagonized IL-1-mediated inhibition of repair at all strain amplitudes. Neither IL-1 treatment nor strain altered aggrecanase activity. Additionally, strain alone did not alter meniscal healing, except at the highest strain magnitude (26%), a level that enhanced the strength of repair.

CONCLUSIONS

Dynamic loading blocked the catabolic effects of IL-1 on meniscal repair, suggesting that joint loading through physical therapy may be beneficial in promoting healing of meniscal lesions under inflammatory conditions.

Radiographic severity of knee osteoarthritis is conditional on interleukin 1 receptor antagonist gene variations

BACKGROUND

A lack of biomarkers that identify patients at risk for severe osteoarthritis (OA) complicates development of disease-modifying OA drugs.

OBJECTIVE

To determine whether inflammatory genetic markers could stratify patients with knee OA into high and low risk for destructive disease.

METHODS

Genotype associations with knee OA severity were assessed in two Caucasian populations. Fifteen single nucleotide polymorphisms (SNPs) in six inflammatory genes were evaluated for association with radiographic severity and with synovial fluid mediators in a subset of the patients.

RESULTS

Interleukin 1 receptor antagonist (IL1RN) SNPs (rs419598, rs315952 and rs9005) predicted Kellgren-Lawrence scores independently in each population. One IL1RN haplotype was associated with lower odds of radiographic severity (OR=0.15; 95% CI 0.065 to 0.349; p<0.0001), greater joint space width and lower synovial fluid cytokine levels. Carriage of the IL1RN haplotype influenced the age relationship with severity.

CONCLUSION

IL1RN polymorphisms reproducibly contribute to disease severity in knee OA and may be useful biomarkers for patient selection in disease-modifying OA drug trials.

The antioxidant resveratrol protects against chondrocyte apoptosis via effects on mitochondrial polarization and ATP production

OBJECTIVE

To determine the effects of the antioxidant resveratrol on the functions of human chondrocytes in osteoarthritis (OA).

METHODS

Chondrocytes and cartilage explants were isolated from OA patients undergoing knee replacement surgery. Effects of resveratrol in the presence or absence of interleukin-1beta (IL-1beta) stimulation were assessed by measurement of prostaglandin E(2) (PGE(2)) and leukotriene B(4) (LTB(4)) synthesis, cyclooxygenase (COX) activity, matrix metalloproteinase (MMP) expression, and proteoglycan production. To explore the mechanisms of action of resveratrol, its effects on mitochondrial function and apoptosis were examined by assessing mitochondrial membrane potential, ATP levels, cytochrome c release, and annexin V staining.

RESULTS

Resveratrol inhibited both spontaneous and IL-1beta-induced PGE(2) production by >20% (P < 0.05) and by 80% (P < 0.001), respectively; similarly, LTB(4) production was reduced by >50% (P < 0.05). The production of PGE(2) was inhibited via a 70-90% suppression of COX-2 expression and enzyme activity (P < 0.05). Resveratrol also promoted anabolic effects in OA explant cultures, by elevating proteoglycan synthesis and decreasing production of MMPs 1, 3, and 13. Pretreatment of OA chondrocytes with resveratrol blocked mitochondrial membrane depolarization, loss of mitochondrial biomass, and IL-1beta-induced ATP depletion. Similarly, IL-1beta-mediated induction of the apoptotic markers cytochrome c and annexin V was also inhibited by resveratrol. Exogenous addition of PGE(2) abolished the protective effects of resveratrol on mitochondrial membrane integrity, ATP levels, expression of apoptotic markers, and DNA fragmentation.

CONCLUSION

Resveratrol protects against IL-1beta-induced catabolic effects and prevents chondrocyte apoptosis via its inhibition of mitochondrial membrane depolarization and ATP depletion. These beneficial effects of resveratrol are due, in part, to its capacity to inhibit COX-2-derived PGE(2) synthesis. Resveratrol may therefore protect against oxidant injury and apoptosis, which are main features of progressive OA.

Interleukin-1 region meta-analysis with osteoarthritis phenotypes

OBJECTIVE

Several research groups have examined osteoarthritis (OA) association with Interleukin-1 (IL-1) region markers and haplotypes. The results have been suggestive for hand OA, negative for knee OA, and conflicting for hip OA.

DESIGN

Our aim was to address conflicts employing meta-analytical methods on data from 1238 European-descent cases with various OA phenotypes and 1269 European-descent controls from four study centers. We imputed some missing genotype data and reconstructed IL-1 region extended haplotypes. A previously reported 7-marker IL1A-IL1B-IL1RN extended risk haplotype was tested for association with each specific index phenotype.

RESULTS

For hip OA, data from three centers showed heterogeneity of extended-risk-haplotype effect, two panels showing trend toward risk and another showing protection, with overall odds ratio (OR) 1.24 (95% Confidence interval (CI) 0.45-3.41, P 0.67). The heterogeneity fell partly along control ascertainment lines, chiefly between controls ascertained as spouses of arthroplasty patients and controls identified through population radiographic survey. For knee OA, the results showed no heterogeneity and no significant extended-risk-haplotype effect. For hand OA, the results showed little heterogeneity and a modest trend toward positive association (summary OR 1.34, 95% CI 0.83-2.17 P 0.23). Using a Bayesian partition modeling approach, the 7-marker extended haplotypes showed no significant effect on any OA phenotype examined. A 3-single-nucleotide polymorphism (SNP) IL1B-IL1RN haplotype rs1143627-rs16944-rs419598 showed a trend toward hand OA association (posterior probability of association 0.72) with the most prominent feature being protection from a specific haplotype representing a partial mirror image of the extended risk haplotype (OR estimated at 0.46).

CONCLUSIONS

The meta-analysis data do not confirm but only suggest that some hand and hip OA risk could be associated with the IL-1 region, particularly centered in IL1B and possibly also IL1RN.

Brief focal cerebral ischemia that simulates transient ischemic attacks in humans regulates gene expression in rat peripheral blood

Blood gene expression profiles of very brief (5 and 10 mins) focal ischemia that simulates transient ischemic attacks in humans were compared with ischemic stroke (120 mins focal ischemia), sham, and naïve controls. The number of significantly regulated genes after 5 and 10 mins of cerebral ischemia was 39 and 160, respectively (fold change >/=mid R:1.5mid R: and P<0.05). There were 103 genes common to brief focal ischemia and ischemic stroke. Ingenuity pathway analysis showed that genes regulated in the 5 mins group were mainly involved in small molecule biochemistry. Genes regulated in the 10 mins group were involved in cell death, development, growth, and proliferation. Such genes were also regulated in the ischemic stroke group. Genes common to ischemia were involved in the inflammatory response, immune response, and cell death-indicating that these pathways are a feature of focal ischemia, regardless of the duration. These results provide evidence that brief focal ischemia differentially regulates gene expression in the peripheral blood in a manner that could distinguish brief focal ischemia from ischemic stroke and controls in rats. We postulate that this will also occur in humans.

Prostaglandin E2 exerts catabolic effects in osteoarthritis cartilage: evidence for signaling via the EP4 receptor

Elevated levels of PGE(2) have been reported in synovial fluid and cartilage from patients with osteoarthritis (OA). However, the functions of PGE(2) in cartilage metabolism have not previously been studied in detail. To do so, we cultured cartilage explants, obtained from patients undergoing knee replacement surgery for advanced OA, with PGE(2) (0.1-10 muM). PGE(2) inhibited proteoglycan synthesis in a dose-dependent manner (maximum 25% inhibition (p < 0.01)). PGE(2) also induced collagen degradation, in a manner inhibitable by the matrix metalloproteinase (MMP) inhibitor ilomastat. PGE(2) inhibited spontaneous MMP-1, but augmented MMP-13 secretion by OA cartilage explant cultures. PCR analysis of OA chondrocytes treated with PGE(2) with or without IL-1 revealed that IL-1-induced MMP-13 expression was augmented by PGE(2) and significantly inhibited by the cycolooygenase 2 selective inhibitor celecoxib. Conversely, MMP-1 expression was inhibited by PGE(2), while celecoxib enhanced both spontaneous and IL-1-induced expression. IL-1 induction of aggrecanase 5 (ADAMTS-5), but not ADAMTS-4, was also enhanced by PGE(2) (10 muM) and reversed by celecoxib (2 muM). Quantitative PCR screening of nondiseased and end-stage human knee OA articular cartilage specimens revealed that the PGE(2) receptor EP4 was up-regulated in OA cartilage. Moreover, blocking the EP4 receptor (EP4 antagonist, AH23848) mimicked celecoxib by inhibiting MMP-13, ADAMST-5 expression, and proteoglycan degradation. These results suggest that PGE(2) inhibits proteoglycan synthesis and stimulates matrix degradation in OA chondrocytes via the EP4 receptor. Targeting EP4, rather than cyclooxygenase 2, could represent a future strategy for OA disease modification.