Oxygen radicals as effectors of cartilage destruction. Direct degradative effect on matrix components and indirect action via activation of latent collagenase from polymorphonuclear leukocytes

(Chemical) Roles of HOCl in Rheumatic Diseases

Chronic rheumatic diseases such as rheumatoid arthritis (RA) are characterized by a dysregulated immune response and persistent inflammation. The large number of neutrophilic granulocytes in the synovial fluid (SF) from RA patients leads to elevated enzyme activities, for example, from myeloperoxidase (MPO) and elastase. Hypochlorous acid (HOCl), as the most important MPO-derived product, is a strong reactive oxygen species (ROS) and known to be involved in the processes of cartilage destruction (particularly regarding the glycosaminoglycans). This review will discuss open questions about the contribution of HOCl in RA in order to improve the understanding of oxidative tissue damaging. First, the (chemical) composition of articular cartilage and SF and the mechanisms of cartilage degradation will be discussed. Afterwards, the products released by neutrophils during inflammation will be summarized and their effects towards the individual, most abundant cartilage compounds (collagen, proteoglycans) and selected cellular components (lipids, DNA) discussed. New developments about neutrophil extracellular traps (NETs) and the use of antioxidants as drugs will be outlined, too. Finally, we will try to estimate the effects induced by these different agents and their contributions in RA.

Superoxide dismutase-loaded porous polymersomes as highly efficient antioxidant nanoparticles targeting synovium for osteoarthritis therapy

Oxidative stress and the reactive oxygen species (ROS) have important roles in osteoarthritis (OA) development and progression. Scavenging ROS by exogenous antioxidant enzymes could be a promising approach for OA treatment. However, the direct use of antioxidant enzymes, such as superoxide dismutase (SOD), is challenging due to a lack of effective drug delivery system to knee joints. This study utilized a highly efficient antioxidative nanoparticle based on SOD-loaded porous polymersome nanoparticles (SOD-NPs) for delivery of SOD to mouse knee joints. The resultant SOD-NPs had prolonged mouse joint retention time with predominant accumulation in synovium but not in articular cartilage. Examining human synovial explants revealed that SOD-NPs minimize oxidative damages induced by OA-like insults. Intra-articular injections of SOD-NPs in mice receiving OA surgery were effective in attenuating OA initiation and preventing its further progression. Mechanistically, SOD-NPs reduced ROS production and the synthesis of catabolic proteases in both articular cartilage and synovium. Hence, our work demonstrates the therapeutic potential of SOD-NPs and indicate that targeting synovium holds a great promise for OA therapy.

A Comprehensive Review of Viscosupplementation in Osteoarthritis of the Knee

PURPOSE OF REVIEW

The purpose of this systematic review is to discuss emerging evidence in the field of viscosupplementation for chronic knee pain secondary to Osteoarthritis (OA). This review focuses on types of viscosupplementation that are clinically available currently, evidence to support their use, contraindications, and adverse events.

RECENT FINDINGS

OA, also known as degenerative joint disease, is the most common form of arthritis in the United States, affecting 54.4 million, or 22.7% of the adult population. The knee is the most common joint affected in OA, with up to 41% involvement, 30% in the hands, and 19% in the hips. The pathophysiology of OA is complex, with contributing factors including mechanical stress to the joint, as well as many person-specific factors such as genetic susceptibility, ethnicity, nutrition, and sex. Treatment modalities include weight control, exercise, non-steroidal and steroidal anti-inflammatory drugs, opioids, intra-articular platelet-rich plasma, placebo, corticosteroid injection, intra-articular viscosupplementation, and surgery. Viscosupplementation consists of injection of hyaluronic acid (HA) into affected joints, intending to restore the physiologic viscoelasticity in the synovial fluid (SF) in the absence of inflammation. HA has also been shown to downregulate pro-inflammatory factors, such as PGE2 and NFkB, and proteases and proteinases known to break down the joint matrix.The contraindications for HA injection are similar to any other injection therapy, and adverse events are usually mild, local, and transient. Viscosupplementation (VS) is effective over placebo and more effective than NSAIDs and corticosteroids in pain reduction and improved functionality; however, guidelines recommend neither for nor against its use, demonstrating variability in the existing evidence base.Current VS options divide primarily into native vs. cross-linked and low-molecular-weight vs. high-molecular-weight. Current treatment options include Hylan g-f-20, Sodium Hyaluronate preparations (Suparts Fx, Euflexxa, Gelsyn-3, Durolane, Hyalgen), single-use agents (Gel-One, Synvisc-One, Monovisc), and Hyaluronan (Orthovisc, Monovisc, Hymovic). They share a common safety profile, and all have evidence supporting their efficacy. Their specific details are reviewed here.

SUMMARY

OA is the most common form of arthritis. It is a chronic, debilitating illness with a high impact on the functionality and quality of life of a significant part of the population in the western world. Treatments include medical management, physical therapy, activity modification, injection, and surgery. VS effectively reduces pain, increases functionality, and delays surgery in the knee to treat osteoarthritis. While previous studies have demonstrated variable results, more evidence is becoming available generally supportive of the benefit of VS in the treatment of knee OA.

The glyco-redox interplay: Principles and consequences on the role of reactive oxygen species during protein glycosylation

Reactive oxygen species (ROS) carry out prime physiological roles as intracellular signaling agents, yet pathologically high concentrations of ROS cause irreversible damage to biomolecules, alter cellular programs and contribute to various diseases. While decades of intensive research have identified redox-related patterns and signaling pathways, very few addressed how the glycosylation machinery senses and responds to oxidative stress. A common trait among ROS and glycans residing on glycoconjugates is that they are both highly dynamic, as they are quickly fine-tuned in response to stressors such as inflammation, cancer and infectious diseases. On this account, the delicate balance of the redox potential, which is tightly regulated by dozens of enzymes including NOXs, and the mitochondrial electron transport chain as well as the fluidity of glycan biosynthesis resulting from the cooperation of glycosyltransferases, glycosidases, and nucleotide sugar transporters, is paramount to cell survival. Here, we review the broad spectrum of the interplay between redox changes and glycosylation with respect to their principle consequences on human physiology.

Neutrophils in the Pathogenesis of Rheumatoid Arthritis and Systemic Lupus Erythematosus: Same Foe Different M.O

Dysregulated neutrophil activation contributes to the pathogenesis of autoimmune diseases including rheumatoid arthritis (RA) and systemic lupus erythematosus (SLE). Neutrophil-derived reactive oxygen species (ROS) and granule proteases are implicated in damage to and destruction of host tissues in both conditions (cartilage in RA, vascular tissue in SLE) and also in the pathogenic post-translational modification of DNA and proteins. Neutrophil-derived cytokines and chemokines regulate both the innate and adaptive immune responses in RA and SLE, and neutrophil extracellular traps (NETs) expose nuclear neoepitopes (citrullinated proteins in RA, double-stranded DNA and nuclear proteins in SLE) to the immune system, initiating the production of auto-antibodies (ACPA in RA, anti-dsDNA and anti-acetylated/methylated histones in SLE). Neutrophil apoptosis is dysregulated in both conditions: in RA, delayed apoptosis within synovial joints contributes to chronic inflammation, immune cell recruitment and prolonged release of proteolytic enzymes, whereas in SLE enhanced apoptosis leads to increased apoptotic burden associated with development of anti-nuclear auto-antibodies. An unbalanced energy metabolism in SLE and RA neutrophils contributes to the pathology of both diseases; increased hypoxia and glycolysis in RA drives neutrophil activation and NET production, whereas decreased redox capacity increases ROS-mediated damage in SLE. Neutrophil low-density granulocytes (LDGs), present in high numbers in the blood of both RA and SLE patients, have opposing phenotypes contributing to clinical manifestations of each disease. In this review we will describe the complex and contrasting phenotype of neutrophils and LDGs in RA and SLE and discuss their discrete roles in the pathogenesis of each condition. We will also review our current understanding of transcriptomic and metabolomic regulation of neutrophil phenotype in RA and SLE and discuss opportunities for therapeutic targeting of neutrophil activation in inflammatory auto-immune disease.

Medical ozone therapy in facet joint syndrome: an overview of sonoanatomy, ultrasound-guided injection techniques and potential mechanism of action

Facet joint osteoarthritis is the most prevalent source of facet joint pain and represents a significant cause of low back pain. Oxygen-ozone therapy has been shown to have positive results in acute and chronic spinal degeneration diseases and it could be a safe and efficacious alternative to traditional facet joint conservative treatments. This review article explains the interventional facet joint management with ultrasound-guided oxygen-ozone therapy, providing an anatomy/sonoanatomy overview of lumbar facet joints and summarizing the potential mechanism of action of oxygen-ozone in the treatment of facet joint osteoarthritis, not yet fully understood.

Redox and NF-κB signaling in osteoarthritis

Human cells have to deal with the constant production of reactive oxygen species (ROS). Although ROS overproduction might be harmful to cell biology, there are plenty of data showing that moderate levels of ROS control gene expression by maintaining redox signaling. Osteoarthritis (OA) is the most common joint disorder with a multi-factorial etiology including overproduction of ROS. ROS overproduction in OA modifies intracellular signaling, chondrocyte life cycle, metabolism of cartilage matrix and contributes to synovial inflammation and dysfunction of the subchondral bone. In arthritic tissues, the NF-κB signaling pathway can be activated by pro-inflammatory cytokines, mechanical stress, and extracellular matrix degradation products. This activation results in regulation of expression of many cytokines, inflammatory mediators, transcription factors, and several matrix-degrading enzymes. Overall, NF-κB signaling affects cartilage matrix remodeling, chondrocyte apoptosis, synovial inflammation, and has indirect stimulatory effects on downstream regulators of terminal chondrocyte differentiation. Interaction between redox signaling and NF-κB transcription factors seems to play a distinctive role in OA pathogenesis.

Neutrophils and redox stress in the pathogenesis of autoimmune disease

Polymorphonuclear leukocytes, or neutrophils, are specialist phagocytic cells of the innate immune system. Their primary role is host defence against micro-organisms, which they kill via phagocytosis, followed by release of reactive oxygen species (ROS) and proteolytic enzymes within the phagosome. ROS are generated via the action of the NADPH oxidase (also known as NOX2), in a process termed the 'Respiratory Burst'. This process consumes large amounts of oxygen, which is converted into the highly-reactive superoxide radical O₂^- and H₂O₂. Subsequent activation of myeloperoxidase (MPO) generates secondary oxidants and chloroamines that are highly microbiocidal in nature, which together with proteases such as elastase and gelatinase provide a toxic intra-phagosomal environment able to kill a broad range of micro-organisms. However, under certain circumstances such as during an auto-immune response, neutrophils can be triggered to release ROS and proteases extracellularly causing damage to host tissues, modification of host proteins, lipids and DNA and dysregulation of oxidative homeostasis. This review describes the range of ROS species produced by human neutrophils with a focus on the implications of neutrophil redox products in autoimmune inflammation.

Hemoglobin stimulates the expression of ADAMTS-5 and ADAMTS-9 by synovial cells: a possible cause of articular cartilage damage after intra-articular hemorrhage

Background

ADAMTS (a disintegrin and metalloprotease with thrombospondin motifs) proteins play an important pathological role in matrix degeneration. Aggrecan degradation is a significant and critical event in early-stage osteoarthritis. To determine the effect of hemoglobin (Hb) on the ability of synovial tissues to produce ADAMTS family members, we examined the influence of Hb by synovial cells in an in vitro experimental system.

Methods

Synovial tissues were obtained from five young patients with meniscal injury under arthroscopic surgery. Primary cultures of human knee synovial cells were treated with different doses of human Hb (0, 25, 50, 100 μg/ml). The culture media were collected 24 h after Hb-treatment. In the time-course studies, cells were treated with and without 100 μg/ml Hb, and culture media were taken at 6, 12, and 24 h. To identify the proteins responsible for aggrecanase activity, Western blot analysis using antibodies against human ADAMTS-5, −8, −9, and −10; enzyme-linked immunosorbent assay (ELISA); and gene expression for ADAMTS-5 and -9 were examined. Statistical comparisons between each group were performed using paired t-tests.

Results

Western blot analysis revealed that Hb-treatment resulted in the expression of ADAMTS-5 and -9. Neither control group nor Hb-treated medium showed immunoreactivity against ADAMTS-8 or −10. In a dose-dependency study, the Hb-treated group showed significantly higher levels of ADAMTS-5 and -9 compared with the control (p < 0.05). There was no significant difference between 25, 50, and 100 μg/ml Hb-treated groups. In a time-course study, the ADAMTS-5 and -9 levels in the conditioned medium had significantly increased expression at 6, 12, and 24 h in the Hb-treated group (p < 0.05). Hb evoked significant expression of ADAMTS-9 mRNA at 12 and 24 h (p < 0.05).

Conclusions

These findings indicate that Hb induces the expression of ADAMTS-5 and -9 by synovial cells at low doses, even at an acute phase, and suggests a possible role for Hb in cartilage damage after intra-articular hemorrhage. The results also suggest a new potential therapeutic target by inhibiting the activities of ADAMTS-5 and -9 to prevent cartilage damage after intra-articular hemorrhage.

The Signaling Pathways Involved in Chondrocyte Differentiation and Hypertrophic Differentiation

Chondrocytes communicate with each other mainly via diffusible signals rather than direct cell-to-cell contact. The chondrogenic differentiation of mesenchymal stem cells (MSCs) is well regulated by the interactions of varieties of growth factors, cytokines, and signaling molecules. A number of critical signaling molecules have been identified to regulate the differentiation of chondrocyte from mesenchymal progenitor cells to their terminal maturation of hypertrophic chondrocytes, including bone morphogenetic proteins (BMPs), SRY-related high-mobility group-box gene 9 (Sox9), parathyroid hormone-related peptide (PTHrP), Indian hedgehog (Ihh), fibroblast growth factor receptor 3 (FGFR3), and β-catenin. Except for these molecules, other factors such as adenosine, O₂ tension, and reactive oxygen species (ROS) also have a vital role in cartilage formation and chondrocyte maturation. Here, we outlined the complex transcriptional network and the function of key factors in this network that determine and regulate the genetic program of chondrogenesis and chondrocyte differentiation.

ROS/oxidative stress signaling in osteoarthritis

Osteoarthritis is the most common joint disorder with increasing prevalence due to aging of the population. Its multi-factorial etiology includes oxidative stress and the overproduction of reactive oxygen species, which regulate intracellular signaling processes, chondrocyte senescence and apoptosis, extracellular matrix synthesis and degradation along with synovial inflammation and dysfunction of the subchondral bone. As disease-modifying drugs for osteoarthritis are rare, targeting the complex oxidative stress signaling pathways would offer a valuable perspective for exploration of potential therapeutic strategies in the treatment of this devastating disease.

Berberine attenuates CCN2-induced IL-1β expression and prevents cartilage degradation in a rat model of osteoarthritis

Connective tissue growth factor (CTGF; also known as CCN2) is an inflammatory mediator that is abundantly expressed in osteoarthritis (OA). Interleukin-1β (IL-1β) plays a pivotal role in OA pathogenesis. Berberine exhibits an anti-inflammatory effect, but the mechanisms by which it modulates CCN2-induced IL-1β expression in OA synovial fibroblasts (OASFs) remain unknown. We showed that CCN2-induced IL-1β expression is mediated by the activation of αvβ3/αvβ5 integrin-dependent reactive oxygen species (ROS) generation, and subsequent activation of apoptosis signal-regulating kinase 1 (ASK1), p38/JNK, and nuclear factor-κB (NF-κB) signaling pathways. This IL-1β expression in OASFs is attenuated by N-acetylcysteine (NAC), inhibitors of ASK1, p38, or JNK, or treatment with berberine. Furthermore, berberine also reverses cartilage damage in an experimental model of collagenase-induced OA (CIOA). We observed that CCN2 increased IL-1β expression via αvβ3/αvβ5 integrins, ROS, and ASK1, p38/JNK, and NF-κB signaling pathways. Berberine was found to inhibit these signaling components in OASFs in vitro and prevent cartilage degradation in vivo. We suggest a novel therapeutic strategy of using berberine for managing OA.

Glycosaminoglycan degradation by selected reactive oxygen species

SIGNIFICANCE

Inflammatory diseases (such as arthritis) of the extracellular matrix (ECM) are of considerable socioeconomic significance. There is clear evidence that reactive oxygen species (ROS) and nitrogen species released by, for instance, neutrophils contribute to the degradation of the ECM. Here we will focus on the ROS-induced degradation of the glycosaminoglycans, one important component of the ECM.

RECENT ADVANCES

The recently developed "anti-TNF-α" therapy is primarily directed against neutrophilic granulocytes that are powerful sources of ROS. Therefore, a more detailed look into the mechanisms of the reactions of these ROS is reasonable.

CRITICAL ISSUES

Since both enzymes and ROS contribute to the pathogenesis of inflammatory diseases, it is very difficult to estimate the contributions of the individual species in a complex biological environment. This particularly applies as many products are not stable but only transient products that decompose in a time-dependent manner. Thus, the development of suitable analytical methods as well as the establishment of useful biomarkers is a challenging aspect.

FUTURE DIRECTIONS

If the mechanisms of ECM destruction are understood in more detail, then the development of suitable drugs to treat inflammatory diseases will be hopefully much more successful.

Oxidative stress and status of antioxidant enzymes in children with Kashin-Beck disease

OBJECTIVES

To clarify whether there is oxidative stress in Kashin-Beck disease (KBD) and if cartilage damage from reactive oxygen species (ROS) and oxidative stress mediate the chondral necrosis in articular cartilage of KBD.

METHODS

We recruited 64 KBD patients, 46 healthy children from severely affected KBD regions, 81 healthy children from a non-severely affected KBD endemic regions, and 91 healthy control children from a non-KBD region. Ten patients with KBD from the non-severely affected KBD regions were included in the experiment. The 2,3-DAN fluorescence technique was used to test selenium in the hair and blood. The biochemical techniques used to test the indicators of oxidative stress included thiobarbituric acid reactive substances (TBARS) levels, and antioxidant enzyme activities in serum samples. Histochemical staining was used to detect proteoglycans in cartilage sections. The 4-hydroxy-2-nonenal (4-HNE) and 8-hydroxydeoxyguanisine (8-OHdG) were localized by immunohistochemistry.

RESULTS

The levels of TBARS in serum were significantly increased in KBD children. The levels of antioxidants in serum were significantly higher in both KBD and normal children from KBD regions than in the normal children from non-KBD regions. The percentage of chondrocytes staining for 4-HNE and 8-OHdG in KBD patients was significantly higher than in controls. Staining for 4-HNE and 8-OHdG in KBD patients was prominent in all zones of articular cartilage, especially in the necrotic chondrocytes of the deep zone.

CONCLUSION

KBD is an oxidative stress-related disease, and the oxidative stress in cartilage contributes to the pathology of cartilage damage in KBD.

Modulation of inflammation and oxidative stress in canine chondrocytes

OBJECTIVE

To determine whether oxidative stress could be induced in canine chondrocytes in vitro.

SAMPLE

Chondrocytes obtained from healthy adult mixed-breed dogs.

PROCEDURES

Harvested chondrocytes were maintained at 37°C with 5% CO2 for 24 hours. To assess induction of oxidative stress, 2 stimuli were used: hydrogen peroxide and a combination of interleukin-1β (IL-1β) and tumor necrosis factor-α (TNF-α). To determine the effect of hydrogen peroxide, a set of chondrocyte-seeded plates was incubated with control medium alone or hydrogen peroxide (100, 200, or 300μM) for 24 hours. For inhibition of oxidative stress, cells were incubated for 24 hours with N-acetylcysteine (NAC; 10mM) before exposure to hydrogen peroxide. Another set of chondrocyte-seeded plates was incubated with control medium alone or with IL-1β (10 ng/mL) and TNF-α (1 ng/mL) for 24 hours. Supernatants were obtained for measurement of prostaglandin E2 production, and cell lysates were used for measurement of superoxide dismutase (SOD) activity and reduced-glutathione (GSH) concentration.

RESULTS

Chondrocytes responded to the oxidative stressor hydrogen peroxide with a decrease in SOD activity and GSH concentration. Exposure to the antioxidant NAC caused an increase in SOD activity in hydrogen peroxide-stressed chondrocytes to a degree comparable with that in chondrocytes not exposed to hydrogen peroxide. Similarly, NAC exposure induced significant increases in GSH concentration. Activation with IL-1β and TNF-α also led to a decrease in SOD activity and increase in prostaglandin E2 production.

CONCLUSIONS AND CLINICAL RELEVANCE

Canine chondrocytes responded to the oxidative stress caused by exposure to hydrogen peroxide and cytokines. Exposure to oxidative stress inducers could result in perturbation of chondrocyte and cartilage homeostasis and could contribute to the pathophysiology of osteoarthritis. Use of antioxidants, on the other hand, may be helpful in the treatment of arthritic dogs.

Association of NADPH oxidase p22phox gene C242T, A640G and -930A/G polymorphisms with primary knee osteoarthritis in the Greek population

Osteoarthritis (OA) is the most common form of arthritis with still unknown pathogenic etiology and considerable contribution of genetic factors. Recently, a new emerging role of oxidative stress in the pathology of OA has been reported, lacking however elucidation of the underlying mechanism. Nicotinamide adenine dinucleotide phosphate (NADPH) oxidase being a complex enzyme produced by chondrocytes, presents the major source of reactive oxygen species and main contributor of increased oxidative stress. The present study aims to evaluate the association of NADPH oxidase p22phox gene C242T, A640G and -A930G polymorphisms with primary knee OA in the Greek population. One hundred fifty five patients with primary symptomatic knee OA participated in the study along with 139 matched controls. Genotypes were determined using polymerase chain reaction and restriction fragment length polymorphism technique. Allelic and genotypic frequencies were compared between both study groups. NADPH p22phox -A930G polymorphism was significantly associated with knee OA in the crude analysis (P = 0.018). No significant difference was detected for C242T and A640G polymorphisms (P > 0.05). The association between -A930G polymorphism and knee OA disappeared when the results were adjusted for obesity (P = 0.078, odds ratio 0.54, 95 % CI 0.272-1.071). The interaction between all three polymorphisms was not significant. The present study shows that NADPH oxidase p22phox gene C242T, A640G and -A930G polymorphisms are not risk factors for knee OA susceptibility in the Greek population. Further studies are needed to give a global view of the importance of this polymorphism in the pathogenesis of OA.

The effect of ketorolac tromethamine, methylprednisolone, and platelet-rich plasma on human chondrocyte and tenocyte viability

PURPOSE

The purpose of this study was to evaluate the effect on cell viability of the isolated and combined use of allogeneic platelet-rich plasma (PRP) and ketorolac tromethamine on human chondrocytes and tenocytes in a highly controlled in vitro environment.

METHODS

PRP was produced from 8 subjects. Human chondrocytes (Lonza, Hopkinton, MA) and tenocytes isolated from samples of the long head of the biceps tendons were treated in culture with PRP, ketorolac tromethamine, and methylprednisolone, both alone and in combination. Control samples were treated in media containing 2% or 10% fetal bovine serum (FBS). Cells were exposed for 1 hour. Luminescence assays were obtained to examine cell viability after 24 hours and long-term effects on cell viability after 120 hours. Radioactive thymidine assay was used to measure proliferation after 120 hours.

RESULTS

For chondrocytes, cell viability (120 hours) increased significantly with the treatment of PRP alone (43,949 ± 28,104 cells; P < .001) and with the combination of ketorolac tromethamine and PRP (43,276 ± 31,208; P < .001), compared with the 2% FBS group (7,397 ± 470). Cell viability decreased significantly after exposure to methylprednisolone (1,323 ± 776; P < .001) and its combination with PRP (4,381 ± 5,116; p < .001). For tenocytes, cell viability (120 hours) was significantly higher with the treatment of PRP (61,287 ± 23,273; P < .001) and the combined treatment of ketorolac tromethamine and PRP (52,025 ± 17,307; P < .001), compared with the 2% FBS group (23,042 ± 2,973). Cell viability decreased significantly after exposure to methylprednisolone (3,934 ± 1,791; P = .001) and its combination with PRP (5,201 ± 2,834; P = .003), compared with 2% FBS.

CONCLUSIONS

Tendon and cartilage cells showed increased cell viability after an exposure to allogeneic PRP and ketorolac tromethamine. Exposure to methylprednisolone alone decreased cell viability, and addition of PRP could partially reverse this negative effect.

CLINICAL RELEVANCE

Intra-articular injections of pain-modifying or anti-inflammatory drugs are routinely given in orthopaedic practice. Among the many agents available for intra-articular injection, corticosteroids and local anesthetics are the most common in clinical practice. Potential detrimental side effects of intra-articular injections of corticosteroids and local anesthetics have prompted investigation into alternative treatment options such as combinations of PRP and ketorolac tromethamine. In vitro evaluation of their effect on cell viability might build a basis for further translational research and clinical application.

Over-expression of extracellular superoxide dismutase in mouse synovial tissue attenuates the inflammatory arthritis

Oxidative stress such as reactive oxygen species (ROS) within the inflamed joint have been indicated as being involved as inflammatory mediators in the induction of arthritis. Correlations between extracellular-superoxide dismutase (EC-SOD) and inflammatory arthritis have been shown in several animal models of RA. However, there is a question whether the over-expression of EC-SOD on arthritic joint also could suppress the progression of disease or not. In the present study, the effect on the synovial tissue of experimental arthritis was investigated using EC-SOD over-expressing transgenic mice. The over-expression of EC-SOD in joint tissue was confirmed by RT-PCR and immunohistochemistry. The degree of the inflammation in EC-SOD transgenic mice was suppressed in the collagen-induced arthritis model. In a cytokine assay, the production of pro-inflammatory cytokines such as, IL-1β, TNFα, and matrix metalloproteinases (MMPs) was decreased in fibroblast-like synoviocyte (FLS) but not in peripheral blood. Histological examination also showed repressed cartilage destruction and bone in EC-SOD transgenic mice. In conclusion, these data suggest that the over-expression of EC-SOD in FLS contributes to the activation of FLS and protection from joint destruction by depressing the production of the pro-inflammatory cytokines and MMPs. These results provide EC-SOD transgenic mice with a useful animal model for inflammatory arthritis research.

Oxidant damage in Kashin-Beck disease and a rat Kashin-Beck disease model by employing T-2 toxin treatment under selenium deficient conditions

Kashin-Beck disease (KBD) is an endemic degenerative osteoarthropathy, but the mechanisms underlying its pathogenesis remains unclear. This study compares antioxidant capacity and lipid peroxidation using a novel model, in which rats were administered a selenium-deficient diet for 4 weeks prior to their exposure to T-2 toxin for 4 weeks. Changes in cell morphology and empty chondrocyte lacunae indicative of cell death, as well as cartilage proteoglycan loss in the deep zone of articular cartilage of knee joints were observed in rats with selenium-deficient diet plus T-2 toxin treatment. These changes were similar to those observed previously in KBD. The levels of thiobarbituric acid reactive substances (TBARS), indicative of lipid peroxidation in serum and cartilage, were significantly increased in all experimental groups compared to the normal diet group, while the levels of antioxidants, measured as total antioxidant capacity (T-AOC), catalase (CAT), superoxide dismutase (SOD), and glutathione peroxidases (GPX), in serum and cartilage were significantly lower than that in the normal diet group. The mRNA expression of those antioxidants in cartilage tissue was significantly reduced by T-2 toxin alone or by selenium-deficient diet plus T-2 toxin treatment. These results indicate that increasing TBARS and decreasing antioxidants in serum and cartilage by T-2 toxin treatment with a selenium-deficient nutritional status may alter oxidative stress in joint tissues and contribute to the pathological process of cartilage damage in KBD.

The effect of antioxidants on the production of pro-inflammatory cytokines and orthodontic tooth movement

Orthodontic force causes gradual compression of the periodontal ligament tissues, which leads to local hypoxia in the compression side of the tissues. In this study, we investigated whether antioxidants exert a regulatory effect on two factors: the expression of pro-inflammatory cytokines in human periodontal ligament fibroblasts (PDLFs) that were exposed to mechanical compression and hypoxia and the rate of orthodontic tooth movement in rats. Exposure of PDLFs to mechanical compression (0.5-3.0 g/cm(2)) or hypoxic conditions increased the production of intracellular reactive oxygen species. Hypoxic treatment for 24 h increased the mRNA levels of IL-1β, IL-6 and IL-8 as well as vascular endothelial growth factor (VEGF) in PDLFs. Resveratrol (10 nM) or N-acetylcysteine (NAC, 20 mM) diminished the transcriptional activity of hypoxiainducible factor-1 and hypoxia-induced expression of VEGF. Combined treatment with mechanical compression and hypoxia significantly increased the expression levels of IL-1β, IL-6, IL-8, TNF-α and VEGF in PDLFs. These levels were suppressed by NAC and resveratrol. The maxillary first molars of rats were moved mesially for seven days using an orthodontic appliance. NAC decreased the amount of orthodontic tooth movement compared to the vehicle-treated group. The results from immunohistochemical staining demonstrated that NAC suppressed the expression of IL-1β and TNF-α in the periodontal ligament tissues compared to the vehicle-treated group. These results suggest that antioxidants have the potential to negatively regulate the rate of orthodontic tooth movement through the down-regulation of pro-inflammatory cytokines in the compression sides of periodontal ligament tissues.

Heme oxygenase-1 induction modulates microsomal prostaglandin E synthase-1 expression and prostaglandin E(2) production in osteoarthritic chondrocytes

Pro-inflammatory cytokines such as interleukin-1beta (IL-1beta) may participate in the pathogenesis of cartilage damage in osteoarthritis (OA) through the production of catabolic enzymes and inflammatory mediators. Induction of heme oxygenase-1 (HO-1) has previously been shown to exert anti-inflammatory effects in different cell types. We have investigated whether HO-1 induction may modify chondrocyte viability and the production of relevant mediators such as oxidative stress and prostaglandin E(2) (PGE(2)) elicited by IL-1beta in OA chondrocytes. Chondrocytes were isolated from OA cartilage and used in primary culture. Cells were stimulated with IL-1beta in the absence or presence of the HO-1 inducer cobalt protoporphyrin IX (CoPP). Gene expression was assessed by quantitative real-time PCR, protein levels by ELISA and Western blot, apoptosis by laser scanning cytometry using annexin V-FITC and TUNEL assays, and oxidative stress by LSC with dihydrorhodamine 123. HO-1 induction by CoPP enhanced chondrocyte viability and aggrecan content while inhibiting apoptosis and oxidative stress generation. PGE(2) is produced in OA chondrocytes stimulated by IL-1beta by the coordinated induction of cyclooxygenase-2 and microsomal PGE synthase 1 (mPGES-1). The production of PGE(2) was decreased by HO-1 induction as a result of diminished mPGES-1 protein and mRNA expression. Transfection with HO-1 small interfering RNA counteracted CoPP effects. In addition, the activation of nuclear factor-kappaB and early growth response-1 was significantly reduced by CoPP providing a basis for its anti-inflammatory effects. These results confirm the protective role of HO-1 induction in OA chondrocytes and suggest the potential interest of this strategy in degenerative joint diseases.

The Therapeutic Effect of Extracellular Superoxide Dismutase (EC-SOD) Mouse Embryonic Fibroblast (MEF) on Collagen-Induced Arthritis (CIA) Mice

Rheumatoid arthritis is a chronic inflammatory disease. The generation of reactive oxygen species (ROS) within an inflamed joint has been suggested as playing a significant pathogenic role. Extracellular superoxide dismutase (EC-SOD) is a major scavenger enzyme of ROS, which has received growing attention for its therapeutic potential. To investigate the therapeutic effect of EC-SOD in mice with collagen-induced arthritis (CIA), we used mouse embryonic fibroblast (MEF) of transgenic mice that overexpresses EC-SOD on the skin by using hK14 promoter. DBA/1 mice that had been treated with bovine type II collagen were administrated subcutaneous injections of EC-SOD transgenic MEF (each at 1.4 × 106 cells) on days 28, 35, and 42 after primary immunization. To test EC-SOD activity, blood samples were collected in each group on day 49. The EC-SOD activity was nearly 1.5-fold higher in the transgenic MEF-treated group than in the non-transgenic MEF-treated group (p < 0.05). The severity of arthritis in mice was scored in a double-blind manner, with each paw being assigned a separate clinical score. The severity of arthritis in EC-SOD transgenic MEF-treated mice was significantly suppressed in the arthritic clinical score (p < 0.05). To investigate the alteration of cytokine levels, ELISA was used to measure blood samples. Levels of IL-1β and TNF-α were reduced in the transgenic MEF-treated group (p < 0.05). Abnormalities of the joints were examined by H&E staining. There were no signs of inflammation except for mild hyperplasia of the synovium in the transgenic MEF-treated group. The proliferation of CII-specific T cells was lower in the transgenic MEF-treated mice than in those in the other groups. The transfer of EC-SOD transgenic MEF has shown a therapeutic effect in CIA mice and this approach may be a safer and more effective form of therapy for rheumatoid arthritis.

Estrogen and testosterone attenuate extracellular matrix loss in collagen-induced arthritis in rats

Rheumatoid arthritis (RA) is a sexually dimorphic, autoimmune inflammatory disorder affecting the joints. Joint disability in RA results primarily from loss of matrix components (collagen and glycosoaminoglycan) in the cartilage and synovium. This study was carried out to understand the effect of physiological levels of testosterone, estrogen, and progesterone on oxidative stress-induced changes in matrix composition in rat synovium in arthritis. Arthritis induction in castrated and ovariectomized rats resulted in enhanced oxidative stress and this was assessed by lipid peroxidation levels and depletion of antioxidants. This, in turn, led to significantly (p < 0.01) increased levels of TNF-alpha and matrix metalloproteinase-2 (MMP-2), subsequently resulting in loss of collagen, elastin, and glycosoaminoglycan (GAG) and disorganization of reticulin as evidenced by biochemical quantitation and also by staining for collagen, reticulin, and elastin. Treatment with physiological doses of dihydrotestosterone (25 mg topically) and estrogen (5 microg/0.1 ml subcutaneously) restored the antioxidant levels significantly (p < 0.05) and reduced the levels of TNF-alpha and MMP-2, with estrogen exhibiting a higher potency. This, in turn, attenuated the damage to reticulin organization as well as the loss of collagen and GAG in the articular tissues. However, elastin loss could not be attenuated by either treatment. Progesterone (2 mg/0.1 ml subcutaneously) was not shown to have any significance in disease modification, and on the contrary, it inhibited the protective effects of estrogen. However, progesterone contributed to increased collagen levels in the tissues.

Oxidative damage to extracellular matrix and its role in human pathologies

The extracellular compartments of most biological tissues are significantly less well protected against oxidative damage than intracellular sites and there is considerable evidence for such compartments being subject to a greater oxidative stress and an altered redox balance. However, with some notable exceptions (e.g., plasma and lung lining fluid) oxidative damage within these compartments has been relatively neglected and is poorly understood. In particular information on the nature and consequences of damage to extracellular matrix is lacking despite the growing realization that changes in matrix structure can play a key role in the regulation of cellular adhesion, proliferation, migration, and cell signaling. Furthermore, the extracellular matrix is widely recognized as being a key site of cytokine and growth factor binding, and modification of matrix structure might be expected to alter such behavior. In this paper we review the potential sources of oxidative matrix damage, the changes that occur in matrix structure, and how this may affect cellular behavior. The role of such damage in the development and progression of inflammatory diseases is discussed.

A capsular incision leads to a fast osteoarthritic response, but also elevated levels of activated osteogenic protein-1 in rabbit knee joint cartilage

We studied whether a small capsular incision alone, or combined with meniscectomy could induce early osteoarthritic changes in the rabbit knee. Thirty-one rabbits were operated on with a capsular incision in the left knee and meniscectomy in the right knee. Another 12 rabbits were used as controls. The rabbits were killed 3, 6 and 12 weeks after surgery. Osteoarthritic changes in the articular cartilage were evaluated by the modified Mankin score. The subchondral bone was evaluated by scintimetry ((99m)Tc-HDP) and semiquantitative grading of histological changes. Osteogenic protein (OP-1) in its mature and pro-form was examined by immunohistochemistry. Both a capsular incision and meniscectomy induced articular cartilage fibrillation and increased bone metabolic activity during the initial weeks after surgery. Capsular incision led to lesser changes than meniscectomy. Mature OP-1 was elevated, and its pro-form reduced, in meniscectomized knees. A similar pattern was observed in knees with capsular incision. Already 3 weeks after surgery, the articular cartilage and subchondral bone showed typical signs of early osteoarthritis (OA), and a reparative response was suggested by increased intensity of OP-1 staining. As these signs were also found in knees with capsular incision only, it appears that trauma-related factors such as increased bleeding and inflammation are critical for the development of OA.

Pathogenesis of haemophilic arthropathy

The pathogenetic mechanism of haemophilic arthropathy is multifactorial and includes degenerative cartilage-mediated and inflammatory synovium-mediated components. Intra-articular blood first has a direct effect on cartilage, as a result of the iron-catalysed formation of destructive oxygen metabolites (resulting in chondrocyte apoptosis), and subsequently affects the synovium, in addition to haemosiderin-induced synovial triggering. Both processes occur in parallel, and while they influence each other they probably do not depend on each other. This concept resembles degenerative joint damage as found in osteoarthritis as well as inflammatory processes in rheumatoid arthritis. These processes finally result in a fibrotic and destroyed joint.

Production of lipid peroxidation products in osteoarthritic tissues: new evidence linking 4-hydroxynonenal to cartilage degradation

OBJECTIVE

The lipid peroxidation product 4-hydroxynonenal (HNE) is prominently produced in osteoarthritic (OA) synovial cells, but its specific contribution to cartilage destruction is not understood. This study was designed to test whether HNE signaling and binding are involved in OA cartilage degradation through type II collagen (CII) and matrix metalloproteinase 13 (MMP-13) modulation.

METHODS

HNE levels in synovial fluid and in isolated OA chondrocytes treated with free radical donors were determined by enzyme-linked immunosorbent assay. The formation of the HNE/CII adducts was measured in cartilage explants by immunoprecipitation. Levels of CII and MMP-13 messenger RNA and protein were determined by reverse transcription-polymerase chain reaction, Western blotting, and by the use of commercial kits.

RESULTS

Levels of HNE/protein adducts were higher in OA synovial fluid compared with normal synovial fluid and were higher in OA chondrocytes treated with free radical donors compared with untreated cells. In cartilage explants, HNE induced CII cleavage, as established by the generation of neoepitopes. The level of HNE/CII adducts was increased in OA cartilage explants incubated with free radical donors. Modification of CII by HNE accelerated its degradation by active MMP-13. In isolated OA chondrocytes, HNE inhibited the expression of CII and tissue inhibitor of metalloproteinases 1 and induced MMP-13 mainly through activation of p38 MAPK. In vitro, HNE binding to MMP-13 activated this enzyme at a molar ratio of 1:100 (MMP-13 to HNE).

CONCLUSION

The increased level of HNE in OA cartilage and the ability of HNE to induce transcriptional and posttranslational modifications of CII and MMP-13 suggest that this aldehyde could play a role in OA.

Extracellular superoxide dismutase and oxidant damage in osteoarthritis

OBJECTIVE

To use human cartilage samples and a mouse model of osteoarthritis (OA) to determine whether extracellular superoxide dismutase (EC-SOD) is a constituent of cartilage and to evaluate whether there is a relationship between EC-SOD deficiency and OA.

METHODS

Samples of human cartilage were obtained from femoral heads at the time of joint replacement surgery for OA or femoral neck fracture. Samples of mouse tibial cartilage obtained from STR/ort mice and CBA control mice were compared at 5, 15, and 35 weeks of age. EC-SOD was measured by enzyme-linked immunosorbent assay, Western blotting, and immunohistochemistry techniques. Real-time quantitative reverse transcription-polymerase chain reaction was used to measure messenger RNA for EC-SOD and for endothelial cell, neuronal, and inducible nitric oxide synthases. Nitrotyrosine formation was assayed by Western blotting in mouse cartilage and by fluorescence immunohistochemistry in human cartilage.

RESULTS

Human articular cartilage contained large amounts of EC-SOD (mean +/- SEM 18.8 +/- 3.8 ng/gm wet weight of cartilage). Cartilage from patients with OA had an approximately 4-fold lower level of EC-SOD compared with cartilage from patients with hip fracture. Young STR/ort mice had decreased levels of EC-SOD in tibial cartilage before histologic evidence of disease occurred, as well as significantly more nitrotyrosine formation at all ages studied.

CONCLUSION

EC-SOD, the major scavenger of reactive oxygen species in extracellular spaces, is decreased in humans with OA and in an animal model of OA. Our findings suggest that inadequate control of reactive oxygen species plays a role in the pathophysiology of OA.

Comparative effects of IL-1beta and hydrogen peroxide (H2O2) on catabolic and anabolic gene expression in juvenile bovine chondrocytes

OBJECTIVE

To compare the effects of hydrogen peroxide (H(2)O(2)) to those of interleukin-1beta (IL-1beta) on gene expression in juvenile bovine articular chondrocytes (BAC). The study analyses the activation of nuclear factor-kappa B (NF-kappaB) and activator protein-1 (AP-1) transcription factors, and the mRNA steady-state levels of the type II collagen, aggrecan core protein matrix, metalloproteinases (MMP-1, -3), and transforming growth factor-beta1 (TGF-beta1) genes.

METHODS

Confluent BAC cultures were treated for 3 and 24h with IL-1beta and/or different concentrations of H(2)O(2) (Protocol 1). Following initial treatment, a part of the cells was further subjected to another 24h with medium, in the presence of IL-1beta, to determine the effect of the cytokine on H(2)O(2) pre-treated cells (Protocol 2). Total RNA and nuclear protein extractions were performed to study mRNA steady-state levels (real-time polymerase chain reaction) and AP-1/NF-kappaB DNA binding (Electrophoretic Mobility Shift Assays), respectively.

RESULTS

IL-1beta enhanced both AP-1 and NF-kappaB binding, whereas H(2)O(2) only activated AP-1. H(2)O(2) pre-treatment decreased the IL-1beta activation of NF-kappaB. Both H(2)O(2) and IL-1beta down-regulated type II collagen and aggrecan expression and increased that of MMP-1 and -3. When cells were pre-treated with H(2)O(2), followed by IL-1beta, the effects were the same as those observed with H(2)O(2) alone. However, although H(2)O(2) and IL-1beta were capable of increasing TGF-beta1 expression separately, subsequent incubation with both factors led to a partial or total abolition of TGF-beta1 up-regulation.

CONCLUSION

The different regulation of NF-kappaB and AP-1 by H(2)O(2) and IL-1beta underlines the distinct roles played by the two transcription factors in the regulation of gene expression. H(2)O(2) and IL-1beta exert similar effects on matrix, MMPs and TGF-beta1 gene expression. However, the association of H(2)O(2) and IL-1beta does not cause synergic effect, and rather leads, in some cases, to an opposite effect. These data provide further insights into the respective roles of reactive oxygen species and cytokine in the pathophysiology of joint diseases.

Hemoglobin stimulates the expression of matrix metalloproteinases, MMP-2 and MMP-9 by synovial cells: a possible cause of joint damage after intra-articular hemorrhage

Intra-articular bleeding causes degradation of articular cartilage leading to joint disorders, but the mechanisms is not well understood. The present study examined the effect of hemoglobin on the ability of synovial tissues to produce plasminogen activators and matrix metalloproteinases that play important roles in the degradation of articular cartilage. Human Hb added to primary cultures of human knee synovial cells markedly increased fibrinolytic activity and gelatinolytic activity. The fibrinolytic activity was due to an increase in uPA activity. Western blot analysis and gelatin zymography indicated that the increased gelatinolytic activity was due to increased MMP-2 and -9. In order to know whether the effect of Hb on cultured synovial tissue is also true in in vivo system or not, rabbit hemoglobin was injected into rabbit knee joints. Coinciding with in vitro study, hemoglobin elicited considerable increase in fibrinolytic and gelatinolytic activity. The level of proteoglycan fragments in the hemoglobin-treated joint fluid was significantly elevated, indicating cartilage matrix degradation. Cartilage damage after hemoglobin treatment was also confirmed by histological study. These findings suggest that hemoglobin stimulates the secretion of uPA, MMP-2 and MMP-9 by synovial tissues, and raise a possible role of hemoglobin in joint damage after intra-articular bleeding.

Enhancement of collagen-induced arthritis in mice genetically deficient in extracellular superoxide dismutase

OBJECTIVE

To examine the influence of superoxide on the severity of collagen-induced arthritis (CIA) in mice.

METHODS

CIA was induced in DBA/1J mice lacking the extracellular superoxide dismutase (EC-SOD) gene (knockout [KO]) and in normal DBA/1J mice (wild-type [WT]).

RESULTS

The clinical disease activity score was significantly higher in EC-SOD-KO mice than in WT mice between days 36 and 53, and the histologic scores for joint damage on day 53 increased 2-fold or more in the EC-SOD-KO mice. There were no significant differences between the 2 groups of mice in proliferation indices of spleen or lymph node cells in vitro after stimulation with type II collagen. Although both IgG1 and IgG2a anticollagen antibody levels increased in both groups of mice between days 21 and 53, there were no significant differences between the 2 groups. Lipopolysaccharide-stimulated spleen cells from EC-SOD-KO mice produced greater levels of tumor necrosis factor alpha (TNFalpha) over 48 hours in culture compared with cells from WT mice. Increased steady-state levels of messenger RNA (mRNA) for interferon-gamma (IFNgamma), TNFalpha, and interleukin-1beta (IL-1beta), and lower levels of IL-1 receptor antagonist (IL-1Ra) mRNA were present in the joints of the EC-SOD-KO mice compared with the WT mice.

CONCLUSION

The absence of EC-SOD leads to more severe CIA, which may be accompanied by enhanced production of the proinflammatory cytokines IFNgamma, TNFalpha, and IL-1beta, and decreased production of the antiinflammatory cytokine IL-1Ra in the joints.

Nutrient supplementation with polyunsaturated fatty acids and micronutrients in rheumatoid arthritis: clinical and biochemical effects

OBJECTIVE

To investigate in a double-blind placebo-controlled, parallel group study, the effects of a nutrient supplement, containing, among other ingredients, the omega-3 fatty acids eicosapentaenoic acid (1.4 g EPA), docosahexaenoic acid (0.211 g DHA), omega-6 fatty acid gamma-linolenic acid (0.5 g GLA) and micronutrients in patients with active rheumatoid arthritis (RA).

DESIGN, SUBJECTS AND INTERVENTION

RA patients were randomized to receive either daily liquid nutrient supplementation or placebo for 4 months. The primary end point was the change in tender joint count at 2 and 4 months. Other clinical variables included swollen joint count, visual analogue scales for pain and disease activity, grip strength, functionality score and morning stiffness. Biochemical parameters included plasma concentrations of PUFA and vitamins C and E.

SETTING

Outpatient university clinic.

RESULTS

In all, 66 patients enrolled, 55 completed the study. No significant change from baseline in tender joint count or any of the other clinical parameters was detected in either group. Patients receiving nutrient supplementation, but not those receiving placebo, had significant increases in plasma concentrations of vitamin E (P=0.015), and EPA, DHA and docosapentaenoic acid concomitant with decreases of arachidonic acid (P=0.01). Intergroup differences for PUFA and vitamin E were significantly different (P=0.01 and 0.03, respectively).

CONCLUSIONS

This double-blind, placebo-controlled study in RA patients did not show superior clinical benefit of daily nutrient supplementation with EPA, GLA and micronutrients at the doses tested as compared to placebo. The study adds information regarding doses of omega-3 fatty acids, below which anti-inflammatory effects in RA are not seen.

The role of reactive oxygen species in homeostasis and degradation of cartilage

OBJECTIVES

The metabolism of cells in articular joint tissues in normal and pathological conditions is subject to a complex environmental control. In addition to soluble mediators such as cytokines and growth factors, as well as mechanical stimuli, reactive oxygen species (ROS) emerge as major factors in this regulation. ROS production has been found to increase in joint diseases, such as osteoarthritis and rheumatoid arthritis, but their role in joint diseases initiation and progression remains questionable.

METHOD

This review is focused on the role of ROS, mainly nitric oxide, peroxynitrite and superoxide anion radicals, in the signaling mechanisms implied in the main cellular functions, including synthesis and degradation of matrix components. The direct effects of ROS on cartilage matrix components as well as their inflammatory and immunomodulatory effects are also considered.

RESULTS

Some intracellular signaling pathways are redox sensitive and ROS are involved in the regulation of the production of some biochemical factors involved in cartilage degradation and joint inflammation. Further, ROS may cause damage to all matrix components, either by a direct attack or indirectly by reducing matrix components synthesis, by inducing apoptosis or by activating latent metalloproteinases. Finally, we have highlighted the uncoupling effect of ROS on tissue remodeling and synovium inflammation, suggesting that antioxidant therapy could be helpful to treat structural changes but not to relieve symptoms.

CONCLUSIONS

This review of the literature supports the concept that ROS are not only deleterious agents involved in cartilage degradation, but that they also act as integral factors of intracellular signaling mechanisms. Further investigation is required to support the concept of antioxidant therapy in the management of joint diseases.

Activated PMNs lead to oxidative stress on chondrocytes: a study of swine knees

Using an in vitro model, based on primary cultured chondrocytes, we examined possible oxidative injury caused by activated polymorphonuclear neutrophil granulocytes (PMNs), which are thought to be part of the pathomechanism of hemarthrosis. Chondrocytes were isolated from swine knee joints and divided into three groups. Pure chondrocytes acted as the control population (group I). PMNs from the systemic circulation, and hydrogen peroxide (as an artificial source of reactive oxygen species (ROS)) were added to groups II and III, respectively. All cultures were incubated for 6 hours. After the experiment, lipid membrane degradation by ROS was assessed by monitoring changes in the levels of malondialdehyde (MDA) and 4-hydroxyalkenal contents of the chondrocyte specimens. Changes in the endogenous scavenger status of the chondrocytes were characterized by measuring of reductions in glutathione (GSH) concentration and superoxide dismutase (SOD) activity. Significant increases in MDA/4-hydroxyalkenal levels and SOD activity as well as an expressive reduction in intracellular GSH content were highlighted by comparing the control to the PMN- or H2O2-treated cell populations. These findings confirm previous suggestions that PMN-derived ROS contribute to degradation of cartilage in hemarthrosis.

Aggrecanases and cartilage matrix degradation

The loss of extracellular matrix macromolecules from the cartilage results in serious impairment of joint function. Metalloproteinases called 'aggrecanases' that cleave the Glu373-Ala374 bond of the aggrecan core protein play a key role in the early stages of cartilage destruction in rheumatoid arthritis and in osteoarthritis. Three members of the ADAMTS family of proteinases, ADAMTS-1, ADAMTS-4 and ADAMTS-5, have been identified as aggrecanases. Matrix metalloproteinases, which are also found in arthritic joints, cleave aggrecans, but at a distinct site from the aggrecanases (i.e. Asn341-Phe342). The present review discuss the enzymatic properties of the three known aggrecanases, the regulation of their activities, and their role in cartilage matrix breakdown during the development of arthritis in relation to the action of matrix metalloproteinases.

Depletion of pulmonary EC-SOD after exposure to hyperoxia

Extracellular superoxide dismutase (EC-SOD) is highly expressed in lung tissue. EC-SOD contains a heparin-binding domain that is sensitive to proteolysis. This heparin-binding domain is important in allowing EC-SOD to exist in relatively high concentrations in specific regions of the extracellular matrix and on cell surfaces. EC-SOD has been shown to protect the lung against hyperoxia in transgenic and knockout studies. This study tests the hypothesis that proteolytic clearance of EC-SOD from the lung during hyperoxia contributes to the oxidant-antioxidant imbalance that is associated with this injury. Exposure to 100% oxygen for 72 h resulted in a significant decrease in EC-SOD levels in the lungs and bronchoalveolar lavage fluid of mice. This correlated with a significant depletion of EC-SOD from the alveolar parenchyma as determined by immunofluorescence and immunohistochemistry. EC-SOD mRNA was unaffected by hyperoxia; however, there was an increase in the ratio of proteolyzed to uncut EC-SOD after hyperoxia, which suggests that hyperoxia depletes EC-SOD from the alveolar parenchyma by cutting the heparin-binding domain. This may enhance hyperoxic pulmonary injury by altering the oxidant-antioxidant balance in alveolar spaces.

Cartilage degradation by stimulated human neutrophils: elastase is mainly responsible for cartilage damage

Although neutrophilic granulocytes are assumed to contribute to cartilage degradation during rheumatic diseases, there is still a discussion whether reactive oxygen species (ROS) or proteolytic enzymes that are both released by the neutrophils are most relevant to cartilage degradation. To gain further insight into these processes, an in vitro approach to study the interaction between the products of stimulated neutrophilic granulocytes and cartilage was used: Neutrophils from the blood of healthy volunteers were treated with different stimulators (e.g., Ca(2+) ionophores) in order to induce degranulation. Supernatants of neutrophils were afterward incubated with thin slices of pig articular cartilage. Some experiments were also performed in the presence of selected enzyme inhibitors. Supernatants of cartilage were subsequently assayed by one- and two-dimensional high-resolution proton NMR spectroscopy, and the content of soluble carbohydrates in the supernatant was additionally determined by biochemical methods. The selective inhibition of elastase decreased most significantly the extent of cartilage degradation, whereas all other inhibitors had much smaller effects. These results were additionally confirmed by measuring the effect of isolated elastase on articular cartilage in the absence and presence of different inhibitors. It is concluded that elastase released [EC 3.4.21.37] by neutrophils is the most relevant enzyme for cartilage degradation.

Treatment of murine collagen-induced arthritis by ex vivo extracellular superoxide dismutase gene transfer

OBJECTIVE; Superoxide dismutase (SOD) is a potent antiinflammatory enzyme that has received growing attention for its therapeutic potential. This study was undertaken to examine the efficacy of extracellular SOD (EC-SOD) gene therapy in murine collagen-induced arthritis.

METHODS

Embryonic DBA/1 mouse fibroblasts were infected with a recombinant retrovirus expressing human EC-SOD. DBA/1 mice that had been treated with type II collagen were administered subcutaneous injections of 2 x 10(7) EC-SOD-expressing fibroblasts on day 29, when symptoms of arthritis were already present. The severity of arthritis in individual mice was evaluated in a double-blind manner; each paw was assigned a separate clinical score, and hind paw thickness was measured with a caliper. Mice were killed on day 50 for histologic examination of the joints.

RESULTS

High serum concentrations of EC-SOD were maintained for at least 7 days. Mice treated with the transgene exhibited significant suppression of clinical symptoms such as disabling joint swelling, deformity, and hind paw thickness, compared with the untreated group (mean +/- SD maximum clinical score in the untreated and the transgene-treated groups 2.71 +/- 1.08 and 1.35 +/- 1.22, respectively; P < 0.01, and hind paw thickness 3.04 +/- 0.18 mm and 2.56 +/- 0.12 mm, respectively; P < 0.05). Histologic abnormalities, including destruction of cartilage and bone, infiltration of mononuclear cells, and proliferation of synovial cells, were also markedly improved in the EC-SOD-treated mice compared with the control group (histopathologic score 7.50 +/- 1.13 and 4.13 +/- 1.88 in the untreated and transgene-treated groups, respectively; P < 0.05).

CONCLUSION

These results indicate that EC-SOD gene transfer may be an effective form of therapy for rheumatoid arthritis.

In vitro study of the antioxidant properties of nimesulide and 4-OH nimesulide: effects on HRP- and luminol-dependent chemiluminescence produced by human chondrocytes

OBJECTIVES

Reactive oxygen species (ROS) are now recognized to play an important role in the pathogenesis of rheumatic diseases and constitute an interesting therapeutic target for drugs. This in vitro study was designed to evaluate the antioxidant properties of nimesulide (NIM), a nonsteroidal antiinflammatory drug of the sulfonanilide class, and its main metabolite 4-OH nimesulide (4-OHNIM).

METHODS

The scavenging effects of NIM and 4-OH NIM on hydroxyl radical ((.)OH) and superoxide anions (O(minusd)(2)) were investigated by electron spin resonance (ESR), using 5, 5-dimethylpyrroline-N-oxide (DMPO) as the spin trap agent. The quenching properties of these drugs on hypochlorite anion was studied by luminol enhanced chemiluminescence. Finally, the effects of NIM and 4-OHNIM on the reactive oxygen species production by human articular chondrocytes were recorded by HRP and luminol-enhanced chemiluminescence.

RESULTS

By this method it has been demonstrated that NIM and 4-OHNIM, at concentrations ranging from 10 to 100 microM, are potent scavengers of(.)OH whereas only 4-OHNIM was capable to scavenge O(minusd)(2). Chemiluminescence generated by HOCl was also significantly and dose-dependently inhibited by both NIM and 4-OHNIM. Nevertheless, at each concentration tested, the inhibitory effect of 4-OHNIM was significantly more marked, even at the highest concentration (100 microM). Furthermore, when chondrocytes were pre-incubated for 48-96 h with NIM or 4-OHNIM, the luminol- and HRP-dependent CL produced by the cells was significantly inhibited in a dose-dependent manner.

CONCLUSIONS

NIM and 4-OHNIM may protect cartilage against oxidative stress, not only by scavenging ROS but also by inhibiting their production by chondrocytes.

In vitro study of the antioxidant properties of non steroidal anti-inflammatory drugs by chemiluminescence and electron spin resonance (ESR)

OBJECTIVES

To determine the antioxidant activities of nonsteroidal anti-inflammatory drugs (NSAIDS), we examined by chemiluminescence (CL) and electron spin resonance (ESR) their scavenging properties towards lipid peroxides, hypochlorous acid and peroxynitrite.

METHODS

The antioxidant properties of nimesulide (NIM), 4-hydroxynimesulide (4-HONIM), aceclofenac (ACLO), 4-hydroxyaceclofenac (4-HOA-CLO), diclofenac (DICLO) and indomethacin (INDO) were tested on four different reactive oxygen species (ROS) generating systems: (I) phorbol-myristate acetate (PMA)-activated neutrophils, (II) Fe2+/ascorbate-induced lipid peroxidation, (III) HOCl-induced light emission, (IV) the kinetics of ONOO- decomposition followed by spectrophotometry. ROS production was monitored by luminol-enhanced CL or by ESR using two different spin traps.

RESULTS

At 10 microM, ACLO, NIM, 4-HONIM, 4-HOA-CLO, and DICLO decreased luminol-enhanced CL generated by PMA-activated neutrophils. Inversely, INDO increased the luminol enhanced CL. Interestingly, hydroxylated metabolites were more potent antioxidants than the parent drugs. Furthermore, all drugs tested, excepted ACLO, lowered lipid peroxidation induced by Fe2+/ascorbate system. ACLO and DICLO, even at the highest concentration tested (100 microM), did not significantly lower HOCl induced CL, whereas the other drugs were potent scavengers. Finally, all the NSAIDS accelerated decomposition of ONOO-, suggesting a potential capacity of the molecules to scavenge peroxynitrite.

CONCLUSION

The NSAIDs possess variable degrees of antioxidant activities, linked to their ability to react with HOCl, lipid peroxides or ONOO-. These antioxidant activities could offer interesting targeted side-effects in the treatment of joint inflammatory diseases.

Superoxide regulation of endothelin-converting enzyme

Reactive oxygen species (ROS) act as signaling molecules in the cardiovascular system, regulating cellular proliferation and migration. However, an excess of ROS can damage cells and alter endothelial cell function. We hypothesized that endogenous mechanisms protect the vasculature from excess levels of ROS. We now show that superoxide can inhibit endothelin-converting enzyme activity (ECE) and decrease endothelin-1 synthesis. Superoxide inhibits ECE but hydrogen peroxide and nitric oxide do not. Superoxide inhibits ECE by ejecting zinc from the enzyme, and the addition of exogenous zinc restores enzymatic activity. Superoxide may inhibit other zinc metalloproteinases by a similar mechanism and may thus play an important role in regulating the biology of blood vessels.

Cartilage degradation by stimulated human neutrophils: reactive oxygen species decrease markedly the activity of proteolytic enzymes

BACKGROUND

Although neutrophilic granulocytes clearly contribute to cartilage degradation in rheumatic diseases, it is unclear if reactive oxygen species (ROS) or proteolytic enzymes are the most important components in cartilage degradation and how they interact.

RESULTS

Neutrophils were stimulated by chemicals conferring a different degree of ROS formation and enzyme release. Supernatants of neutrophils were incubated with thin slices of pig articular cartilage. Supernatants of cartilage were assayed by NMR spectroscopy, MALDI-TOF mass spectrometry and relevant biochemical methods. Stimulation conditions of neutrophils correlated well with the extent of cartilage degradation. Due to the release of different enzymes, cartilage degradation could be best monitored by NMR since mainly low-mass degradation products were formed. Astonishingly, the suppression of the formation of ROS resulted in decreased cartilage degradation.

CONCLUSION

ROS formed by neutrophils are not directly involved in cartilage degradation but influence the activity of proteolytic enzymes, which are the main effectors of cartilage degradation.