An experimental model for hydrogen peroxide-induced tissue damage. Effects of a single inflammatory mediator on (peri)articular tissues

Of rodents, research and relationships: a pharmacological odyssey

This article is an autobiographical account of a research career in inflammatory diseases, mechanisms and pharmacotherapy, drug research and development, in academia and industry in various European countries spanning the last 55 years. The author describes how tenacity and independent thought, learned in formative years, and tempered later by the development of good relationships with colleagues have guided his career. This has spanned research, among other fields, on prostaglandins as pro-and anti-inflammatory mediators, oxidative stress and antioxidants, phospholipid mediators, cytokines, innate and adaptive immune responses and the establishment of various inflammatory and immunological models. The author has helped discover and develop novel therapeutic approaches to pain, arthritic, dermatological, respiratory, and autoimmune disorders and contributed to bringing eight drug candidates to clinical trials. He has helped establish new research labs in four different centres and been involved in teaching undergraduate and mature students in three different universities. With extensive experience in scientific publishing and several international awards, he emphasises that without good teamwork, little can be achieved in scientific research.

Oxidative Stress Mediated Therapy in Patients with Rheumatoid Arthritis: A Systematic Review and Meta-Analysis

OBJECTIVE

The aim of this meta-analysis is to explore all the available literature to obtain updated data about the potential use of antioxidants in the treatment of rheumatoid arthritis (RA) and its ability to reduce disease progression and cardiovascular risk.

METHODS

This systematic review and meta-analysis was performed strictly in accordance with the PRISMA guidelines. English and Chinese databases were searched with a retrieval time up to March 2023. These databases included the PubMed, Embase, Medline Complete, Web of Sciences and Cochrane Collaboration, Wanfang, China National Knowledge Infrastructure, and VIP databases. This literature search was formulated by the two researchers independently. The search strategy consists of reading, collecting the literature, and conducting the preliminary screening. After that, they provide the final selection of the literature according to the inclusion criteria and data extraction. Also, for all studies, the risk bias was assessed to evaluate the quality of the included references. The content of the risk assessment of bias included the following criteria: random allocation method, allocation plan hiding, blind method, completeness of result data, and selectivity of reporting of results, as well as other biases. The main outcomes were clinical efficiency of antioxidant therapy (C-reactive protein, DAS28 score, HAQ, Number of tender joints, etc.) and oxidative stress indicators (catalase, superoxide dismutase, or total antioxidant capacity).

RESULTS

We observed, in most of the studies, the small or moderate effects of antioxidant treatment. The mean effect size is 0.525, and that means that moderate effects were observed in 30 selected RCTs. Also, this effect is confirmed in the 1652 patients with RA with the mean confidence interval of 0.276 (lower limit) and 0.983 (upper limit). Cohen coefficient was calculated at 0.05.

CONCLUSION

The existing evidence is that antioxidants can reduce systemic and local oxidative stress and can reduce damage as the main agent involved in autoimmune diseases such as rheumatoid arthritis.

Fabrication of Electrochemical-Based Bioelectronic Device and Biosensor Composed of Biomaterial-Nanomaterial Hybrid

The field of bioelectronics has paved the way for the development of biochips, biomedical devices, biosensors and biocomputation devices. Various biosensors and biomedical devices have been developed to commercialize laboratory products and transform them into industry products in the clinical, pharmaceutical, environmental fields. Recently, the electrochemical bioelectronic devices that mimicked the functionality of living organisms in nature were applied to the use of bioelectronics device and biosensors. In particular, the electrochemical-based bioelectronic devices and biosensors composed of biomolecule-nanoparticle hybrids have been proposed to generate new functionality as alternatives to silicon-based electronic computation devices, such as information storage, process, computations and detection. In this chapter, we described the recent progress of bioelectronic devices and biosensors based on biomaterial-nanomaterial hybrid.

Peroxidase-immobilized porous silica particles for in situ formation of peroxidase-free hydrogels with attenuated immune responses

Enzymatic crosslinking chemistry using horseradish peroxidase (HRP) has been widely utilized as an effective approach to fabricating injectable hydrogels with high efficiency under mild reaction conditions. However, their clinical applications are limited by the immunogenicity of the plant-derived enzyme. Herein we report the design, synthesis and characterization of HRP-immobilized porous silica particles (HRP-particles) and their use for in situ formation of HRP-free hydrogels. HRP was immobilized on aminopropyl-modified porous silica particles of 70-140 µm in diameter via poly(ethylene glycol) spacers of different molecular weights by reductive amination reaction. Two different HRP-free hydrogels based on dextran-tyramine and gelatin-hydroxyphenylpropionic acid (GHPA) conjugates were produced by passing a solution containing the conjugates and H₂O₂ through a syringe packed with HRP-particles. The storage modulus and gelation rate of both hydrogels were tunable by varying the contact time between the polymer solution and HRP-particles. Our in vitro study revealed that HRP-free GHPA hydrogel was less stimulatory to activated mouse macrophages than HRP-containing GHPA hydrogel with the same stiffness. Furthermore, HRP-free GHPA hydrogel exhibited remarkably lower levels of local and systemic inflammation than HRP-containing one upon subcutaneous injection in immunocompetent C57BL/6J mice. The attenuated immunogenicity of HRP-free GHPA hydrogels makes them an attractive platform for tissue engineering applications. STATEMENT OF SIGNIFICANCE: The immunogenicity of HRP is a significant issue for clinical application of HRP-catalyzed in situ forming hydrogels. HRP-particles are developed to overcome the safety concerns by fabricating HRP-free hydrogels. The porosity of silica particles and molecular weight of poly(ethylene glycol) spacers are discovered as important factors determining the catalytic ability of HRP-particles to induce the in situ crosslinking of polymer-phenol conjugates. Although several articles speculate the potential of HRP to trigger immune responses when administered as a part of hydrogel formulation, no literature has attempted to investigate the immunogenicity of HRP-containing hydrogels in comparison with HRP-free hydrogels. Our findings suggest that the immunogenicity issue should be carefully considered before clinical translation of HRP-containing hydrogels.

Metabolic syndrome and the decreased levels of uric acid by leflunomide favor redox imbalance in patients with rheumatoid arthritis

Oxidative stress plays a role in the pathophysiology of rheumatoid arthritis (RA). The aim of the present study was to verify the influence of metabolic syndrome (MetS) and disease-modifying antirheumatic drugs on nitrosative and oxidative biomarkers in patients with RA. A total of 177 patients with RA and 150 healthy volunteers participated in this study, which measured lipid hydroperoxides, advanced oxidation protein products (AOPP), nitric oxide metabolites (NOx), carbonyl protein, total radical-trapping antioxidant parameter (TRAP), uric acid (UA), and C-reactive protein (CRP). NOx and the NOx/TRAP ratio were significantly increased in RA, while no significant differences in lipid hydroperoxides, AOPP, UA, and TRAP levels were found between both groups. Treatment with leflunomide was associated with increased levels of carbonyl protein, and lowered levels in TRAP and UA, while the NOx/TRAP ratio further increased. NOx and the NOx/TRAP ratio were significantly higher in women than in men, while TRAP and UA were significantly lower in women. MetS was accompanied by increased AOPP and UA levels. RA was best predicted by increased NOx/TRAP ratio, CRP, and BMI. In conclusion, our data demonstrated that NOx and NOx/TRAP are strongly associated with RA physiopathology. Our findings suggest that inhibition of iNOS may become an interesting therapeutic approach for the treatment of RA. In addition, the presence of MetS and a decrease in levels of UA by leflunomide favor redox imbalance in RA patients. More studies are needed to evaluate the impact of antioxidant capacity reduction on RA progression.

Electrochemical Biosensor Composed of Silver Ion-Mediated dsDNA on Au-Encapsulated Bi2 Se3 Nanoparticles for the Detection of H2 O2 Released from Breast Cancer Cells

A newly developed electrochemical biosensor composed of a topological insulator (TI) and metallic DNA (mDNA) is fabricated. The bismuth selenide nanoparticle (Bi₂ Se₃ NP) is synthesized and sandwiched between the gold electrode and another Au-deposited thin layer (Bi₂ Se₃ @Au). Then, eight-silver-ion mediated double-stranded DNA (mDNA) is immobilized onto the substrate (Bi₂ Se₃ @Au-mDNA) for the further detection of hydrogen peroxide. The Bi₂ Se₃ NP acts as the electrochemical-signal booster, while unprecedentedly its encapsulation by the Au thin layer keeps the TI surface states protected, improves its electrochemical-signal stability and provides an excellent platform for the subsequent covalent immobilization of the mDNA through Au-thiol interaction. Electrochemical results show that the fabricated biosensor represents much higher Ag⁺ redox current (≈10 times) than those electrodes prepared without Bi₂ Se₃ @Au. The characterization of the Bi₂ Se₃ @Au-mDNA film is confirmed by atomic force microscopy, scanning tunneling microscopy, and cyclic voltammetry. The proposed biosensor shows a dynamic range of 00.10 × 10^-6 m to 27.30 × 10^-6 m, very low detection limit (10 × 10^-9 m), unique current response (1.6 s), sound H₂ O₂ recovery in serum, and substantial capability to classify two breast cancer subtypes (MCF-7 and MDA-MB-231) based on their difference in the H₂ O₂ generation, offering potential applications in the biomedicine and pharmacology fields.

Horseradish and radish peroxidases eaten with fish could help explain observed associations between fish consumption and protection from age-related dementia

A juxtaposition of regional cuisines and recent prospective studies of fish consumption in China and Japan points to fresh horseradish and/or radish (HRR) as possible contributors to delaying age-related dementia. The hypothesis is that the inverse association found sometimes between fish intake and cognitive decline is partially due to exposure of the oral cavity to active peroxidases from HRR served in conjunction with fish. This hypothesis can be tested by specifically looking at whether HRR is consumed with fish and whether such HRR is prepared in a way that preserves activity of HRR peroxidases. It is possible that by putting active HRR peroxidases in their mouths, elderly people supplement their age-diminished salivary antioxidant capacity and break down additional hydrogen peroxide (H₂O₂) in the oral cavity before it can migrate into the brain, thus decreasing the incidence of brain cell death induction by chronically-elevated H₂O₂. Intentional exposure of the oral cavity to active HRR peroxidases could be a prophylactic for delaying dementia. Because vegetable peroxidases are inactivated by gastric juices, it will be difficult to obtain benefit from HRR peroxidases' antioxidant effect via ingestion in encapsulated dietary supplements.

Progress does not just come in giant leaps: adapting techniques for the study of inflammation to novel applications

INTRODUCTION

Discussion of the relevance of suitable experimental models for the effective translation of drug effects to clinical inflammatory diseases has a long history. Much emphasis is placed these days on genetically transformed mice, which may have developmental drawbacks. But are established models redundant?

FINDINGS

Drawn from personal experience, examples are provided of the success of tinkering with technology in the context of inflammation. These include the use of specific dietary deficiency conditions, the development of new applications for established drugs and the introduction of a variety of readouts to assess outcome in studies on established disease models. Such approaches have been used to demonstrate inflammation-modulating effects of prostaglandin E, in the development of ebselen, for the introduction of immunomodulatory macrolide drugs and in new approaches to the therapy of multiple sclerosis.

CONCLUSION

Fine tuning of experimental approaches and evaluation technologies can often still provide innovative, clinically relevant insights into the potential beneficial effects of drugs and pharmacological agents.

The oxidative stress theory of disease: levels of evidence and epistemological aspects

The theory that oxidative stress (OS) is at the root of several diseases is extremely popular. However, so far, no antioxidant has been recommended or offered by healthcare systems neither has any been approved as therapy by regulatory agencies that base their decisions on evidence-based medicine. This is simply because, so far, despite many preclinical and clinical studies indicating a beneficial effect of antioxidants in many disease conditions, randomised clinical trials have failed to provide the evidence of efficacy required for drug approval. In this review, we discuss the levels of evidence required to claim causality in preclinical research on OS, the weakness of the oversimplification associated with OS theory of disease and the importance of the narrative in its popularity. Finally, from a more translational perspective, we discuss the reasons why antioxidants acting by scavenging ROS might not only prevent their detrimental effects but also interfere with essential signalling roles. We propose that ROS have a complex metabolism and are generated by different enzymes at diverse sites and at different times. Aggregating this plurality of systems into a single theory of disease may not be the best way to develop new drugs, and future research may need to focus on specific oxygen-toxifying pathways rather than on non-specific ROS scavengers. Finally, similarly to what is nowadays required for clinical trials, we recommend making unpublished data available in repositories (open data), as this will allow big data approaches or meta-analyses, without the drawbacks of publication bias.

LINKED ARTICLES

This article is part of a themed section on Redox Biology and Oxidative Stress in Health and Disease. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v174.12/issuetoc.

Anti-apoptotic Activity of Ginsenoside Rb1 in Hydrogen Peroxide-treated Chondrocytes: Stabilization of Mitochondria and the Inhibition of Caspase-3

Chondrocyte apoptosis has been recognized as an important factor in the pathogenesis of osteoarthritis (OA). Hydrogen peroxide (H₂O₂), which produces reactive oxygen species, reportedly induces apoptosis in chondrocytes. The ginsenoside Rb₁ (GRb₁) is the principal component in ginseng and has been shown to have a variety of biological activities, such as anti-arthritis, anti-inflammation, and anti-tumor activities. In this study, we evaluated the effects of G-Rb₁ on the mitochondrial permeability transition (MPT) and caspase-3 activity of chondrocyte apoptosis induced by H₂O₂. Cultured rat articular chondrocytes were exposed to H₂O₂ with or without G-Rb₁ and assessed for viability, MPT, Bcl-xL/Bax expression, caspase-3 activity, and apoptosis. The co-treatment with G-Rb₁ showed an inhibition of MPT, caspase-3 activity, and cell death. Additionally, the levels of the apoptotic protein Bax were significantly lower and the levels of the anti-apoptotic protein Bcl-xL were higher compared with H₂O₂ treatment alone. The results of this study demonstrate that G-Rb₁ protects chondrocytes against H₂O₂-induced apoptosis, at least in part via the inhibition of MPT and caspase-3 activity. These results demonstrate that G-Rb₁ is a potentially useful drug for the treatment of OA patients.

Geranylgeranylacetone suppresses hydrogen peroxide-induced apoptosis of osteoarthritic chondrocytes

BACKGROUND

Osteoarthritis (OA) is a common disease, afflicting many sufferers with both pain and functional disorders. Various therapies have been attempted for OA, but no fully effective treatment has been established yet. Apoptosis of chondrocytes caused by reactive oxygen species (ROS) has been considered important in the pathogenesis of OA. The progression of OA may be prevented by suppressing apoptosis of chondrocytes. Geranylgeranylacetone (GGA) has been used as an anti-ulcer drug in Japan for more than 20 years. Several recent studies have shown that GGA can induce heat shock protein (HSP) and exert cytoprotective actions on a large variety of cells and tissues. In this study, we investigated the effects of GGA on the apoptosis of OA chondrocytes induced by hydrogen peroxide (H(2)O(2)).

METHODS

Human isolated OA chondrocytes were cultured in the absence or presence of GGA. Cell viability, caspase 3/7 and 9 activities, HSP70 mRNA and protein expressions were examined, and morphological analyses were conducted after exposure of cells to H(2)O(2) to induce apoptosis.

RESULTS

Geranylgeranylacetone dose-dependently reversed the H(2)O(2)-induced decrease in cell viability. It was recognized that GGA rendered OA chondrocytes resistant to H(2)O(2)-induced apoptosis from Hoechst 33342 staining and TUNEL staining. Caspases 3 and 9 were activated by addition of H(2)O(2), and GGA suppressed this H(2)O(2)-induced activation of both caspases. H(2)O(2)-induced induction of HSP70 was enhanced in OA chondrocytes by pretreatment with GGA. The results showed that GGA can suppress apoptosis of chondrocytes and enhance production of HSP70.

CONCLUSIONS

This study is the first, to our knowledge, to demonstrate that GGA protects OA chondrocytes from H(2)O(2)-induced apoptosis, at least in part by enhancing HSP70 production. These results indicate that GGA is a potentially useful drug for the treatment of OA.

The chondroprotective effects of ferulic acid on hydrogen peroxide-stimulated chondrocytes: inhibition of hydrogen peroxide-induced pro-inflammatory cytokines and metalloproteinase gene expression at the mRNA level

OBJECTIVE

The objective of the study is to evaluate the effect of ferulic acid (FA), an antioxidant from the Chinese herb Dong-Gui [Chinese angelica, Angelica sinensis (Oliv.) Diels], on the regulation of various genes in hydrogen peroxide-stimulated porcine chondrocytes at the mRNA level.

METHODS

The effect of FA and the effective concentration of FA on porcine chondrocytes was evaluated by the lactate dehydrogenase, WST-1, crystal violet assay, and a chemical luminescence assay. Gene expression in hydrogen peroxide-stimulated chondrocytes either pre- or post-treated with FA was evaluated by real-time PCR.

RESULTS

Chondrocytes pre-treated with 40 microM FA decreased the hydrogen peroxide-induced interleukin-1beta (IL-1beta), tumor necrosis factor-alpha (TNF-alpha), and MMP-1 and partially restored SOX9 gene expression. Post-treatment with 40 microM FA also decreased the expression of MMP-1 and MMP-13.

CONCLUSION

FA decreased the hydrogen peroxide-induced IL-1beta, TNF-alpha, MMP-1 and MMP-13 and increased SOX9 gene expression. These findings suggest that FA may prove to be important in the treatment of osteoarthritis. Further research is needed.

Oxidative stress induces expression of osteoarthritis markers procollagen IIA and 3B3(-) in adult bovine articular cartilage

OBJECTIVE

Oxidative stress occurs when the metabolic balance of a cell is disrupted through exposure to excess pro-oxidant. Whilst it is known that unregulated production or exposure to exogenous sources of pro-oxidants induces chondrocyte cell death and degrades matrix components in vitro, relatively little is known of the effects of pro-oxidants on articular cartilage in situ. The objective of this study was to determine if a single exposure to the pro-oxidant hydrogen peroxide (H(2)O(2)) induces a degenerative phenotype.

METHODS

Articular cartilage explants were obtained from skeletally mature bovine steers and exposed to a single dose of hydrogen peroxide (0.1-1.0 mM) and cultured for up to 21 days. Cell death, and sulfated glycosaminoglycan loss into the medium and gene expression were quantitatively determined. Adoption of an abnormal chondrocyte phenotype was analyzed through the expression of 3B3(-), nitrotyrosine and procollagen type IIA epitopes in cartilage explants.

RESULTS

Cell death occurred primarily at the surface zone of cartilage in a dose-dependent manner in H(2)O(2) treated explants, and supplementation of standard serum-free medium with insulin-selenium-transferrin significantly reduced cell death (>fourfold). Nitric oxide synthase-2 gene expression and proteoglycan loss increased in oxidant treated explants in a concentration-dependent manner. Antibody labeling to 3B3(-), procollagen type IIA and nitrotyrosine was present in all treated explants but absent in untreated explants.

CONCLUSIONS

This study demonstrates that a single exposure to high levels of pro-oxidant causes the expression of genes and antibody epitopes that are associated with early degenerative changes observed in experimental osteoarthritis.

Etanercept reduces the oxidative stress marker levels in patients with rheumatoid arthritis

This study was performed to evaluate the effects of the TNF-alpha inhibitor etanercept on oxidation stress markers representing DNA damage, lipid peroxidation, and protein glycosylation. Twenty-two rheumatoid arthritis (RA) patients underwent etanercept treatment. The levels of serum total, urinary total, and urinary free pentosidine, which is an advanced glycation end-product (AGE), of urinary N(epsilon)-hexanoyl lysine (N(epsilon)-HEL), and of 8-hydroxy-deoxy guanosine (8-OHdG) were measured at baseline and at 3 and 6 months after the initial treatment with etanercept. Serum total and urinary total pentosidine levels were reduced at 6 months after the initial treatment with etanercept, and urinary free pentosidine levels were reduced at 3 and 6 months. Urinary N(epsilon)-HEL levels were also reduced at 3 and 6 months, and urinary 8-OHdG levels were reduced at 6 months. Serum total and urinary total pentosidine levels in RA patients correlated with the number of swelling joints and tender joints, and urinary total pentosidine levels correlated with the Disease Activity Score using 28 joints (DAS28). This study demonstrated that etanercept acts as a regulator against pentosidine formation, oxidative DNA damage, and lipid peroxidation in RA patients.

Thioredoxin protects against joint destruction in a murine arthritis model

Thioredoxin (TRX) is an oxidative stress-inducible biological antioxidant that is highly expressed in the synoviocytes of rheumatoid arthritis (RA) patients. There is much evidence that oxidative stress plays a key role in the inflammation and destruction of RA joints; the functional relationship between TRX and RA remains unknown, however. We therefore investigated the role played by TRX in the inflammatory and joint-damaging processes of RA using a murine model in which arthritis was induced by administering a mixture of anti-type II collagen monoclonal antibodies (mAb) and lipopolysaccharide (LPS). In Wt mice mAb/LPS injection induced neutrophil infiltration, cartilage destruction, and chondrocyte apoptosis within the joints, all of which were dramatically suppressed in TRX transgenic (TRX-Tg) mice. Moreover, the 8-hydoxy-2'-deoxyguanosine (8-OHdG) expression seen in Wt mice after mAb/LPS injection was almost completely inhibited in TRX-Tg mice. The administration of recombinant TRX also suppressed mAb/LPS-induced joint swelling in Wt mice. Taken together, these results suggest that TRX protects against arthritis and is a plausible candidate with which to develop novel therapies for the treatment of RA.

Vulnerability to ROS-induced cell death in ageing articular cartilage: the role of antioxidant enzyme activity

OBJECTIVES

To test the hypothesis that age-related loss of chondrocytes in cartilage is associated with impaired reactive oxygen species (ROS) homeostasis resulting from reduced antioxidant defence.

METHODS

Cell numbers: The total number of chondrocytes in the articular cartilage of the femoral head of young, mature and old rats was estimated using an unbiased stereological method. ROS quantification: Fluorescence intensity in chondrocytes was quantified using the oxygen free radical sensing probe dihydrorhodamine 123 (DHR 123), confocal laser scanning microscopy and densitometric image analysis. In order to delineate the reactive species, explants were pre-treated with N-acetylcysteine (NAC) or N(G)-nitro-l-arginine methyl ester (l-NAME) prior to ROS quantification. Induction of intracellular ROS: Explants were incubated in the redox-cycling drug menadione after which they underwent ROS quantification and cell-viability assay. Antioxidant enzyme activity: The activity of catalase, superoxide dismutase (SOD) and glutathione peroxidase (GPX) was measured.

RESULTS

Chondrocyte numbers: A significant and progressive loss of chondrocytes was observed with ageing. Cellular ROS levels: A significant age-related increase in cellular ROS-induced fluorescence was demonstrated. NAC significantly reduced ROS levels in old chondrocytes only. Induction of intracellular ROS: Menadione increased cellular ROS levels dose-dependently in young and old chondrocytes, with a greater effect in the latter. Old chondrocytes were more vulnerable to menadione-induced cytotoxicity. Antioxidant enzymes: Catalase activity declined significantly in aged cartilage whilst SOD and GPX activities were unaltered.

CONCLUSIONS

Substantial loss of chondrocytes occurs in rat articular cartilage which may result from increased vulnerability to elevated intracellular ROS levels, consequent upon a decline in antioxidant defence.

Antioxidant activity of the methanol fraction of Pluchea indica root extract

Studies were carried out to evaluate the influence of the methanol fraction of Pluchea indica Less root extract (PIRE), the dual inhibitors (BW 755C and phenidone) and vitamin on both in vivo and in vitro free radical-scavenging activities, CCl(4)-induced lipid peroxidation and the metabolism of arachidonic acid by lipoxygenase. PIRE produced significant antiinflammatory activity against glucose oxidase-induced paw oedema (in vivo), inhibited hydroxyl radical and superoxide generation, lysis of erythrocytes induced by hydrogen peroxide, CCl(4)-induced lipid peroxidation and also dioxygenase activity of lipoxygenase (both in the presence and absence of hydrogen peroxide). Significantly higher free radical-scavenging activity was observed with BW 755C and phenidone compared with PIRE. However, both BW 755C and phenidone stimulated hydroxyl radical generation compared with the observed inhibitory effects of PIRE and vitamin E.

Ebselen suppresses late airway responses and airway inflammation in guinea pigs

Although ebselen, a seleno-organic compound, inhibits inflammation in various animal models, its efficacy as an anti-asthma drug remains to be clarified. In this study, we investigated the inhibitory effect of ebselen on a guinea pig asthma model. Ebselen was orally administered at dosages of 1-20 mg/kg 2 h before an ovalbumin (OA) challenge, and then airway responses, airway inflammation, the generation of superoxide, H(2)O(2), and nitrotyrosine, and the induction of inducible nitric oxide synthase (iNOS) were evaluated. Sensitized animals challenged with OA aerosol showed dual airflow limitations, i.e., immediate and late airway responses (IAR and LAR). Ebselen significantly inhibited LAR at dosages greater than 10 mg/kg, but did not inhibit IAR at any dosage. Bronchoalveolar lavage (BAL) examination showed that airway inflammation was significantly suppressed by ebselen at 10 mg/kg. The generation of superoxide and H(2)O(2) occurred on endothelial cells of LAR bronchi, and was inhibited by 10 mg/kg of ebselen. Superoxide generation was inhibited by diphenyleneiodonium chloride (DPI), a NAD(P)H oxidase inhibitor, but not by allopurinol, a xanthine oxidase inhibitor. Immunoreactivities for iNOS and nitrotyrosine were also observed on endothelial cells of LAR bronchi and were abolished in ebselen-treated animals. The present findings suggest that ebselen can be applied as a new therapeutic agent for asthma. The possible mechanisms by which ebselen inhibits LAR likely involve suppression of oxidant formation and iNOS induction in endothelial cells.

Dietary vitamins and selenium diminish the development of mechanically induced osteoarthritis and increase the expression of antioxidative enzymes in the knee joint of STR/1N mice

OBJECTIVE

To study the influence of dietary vitamins and selenium on mechanically-induced osteoarthritis (OA) and the expression of antioxidative enzymes in male STR/1N and Balb/c mice. Male STR/1N mice are prone to develop OA caused by a varus deformity-induced mechanical overload of the medial tibial plateau.

METHODS

After 12 months of feeding (special diet supplemented with the vitamins E, C, A, B6, B2, and selenium) serial histological sections of the knee joints were evaluated for development of osteoarthritic changes (grade 0-4). Serum glutathione peroxidase activity (GSH-px) was measured photometrically. Expression of antioxidative enzymes was demonstrated by immunohistochemistry.

RESULTS

All control STR/1N mice showed OA lesions (grade 3-4) while the special diet decreased OA incidence significantly down to approximately 65% (mostly grade 2). Even in Balb/c mice the incidence was decreased by the special diet from approximately 21% (control animals; grade 1) to approximately 14%. Serum GSH-px activity increased diet-dependently in both mouse strains but was generally higher in Balb/c mice. In both mouse strains the special diet increased the expression of GSH-px and Cu/Zn-SOD in articular cartilage while there was no expression of Mn-SOD. There was also a special diet-dependent increase in expression of GSH-px in the synovium of both mouse strains while an increase in expression of Mn-SOD and Cu/Zn-SOD could only be seen in the synovium of STR/1N mice.

CONCLUSIONS

A diet supplemented with vitamins/selenium might be important in prevention or therapy of mechanically induced OA. We hypothesize that free oxygen radical species might be involved in the mechanical induction of OA.

Antioxidants and fatty acids in the amelioration of rheumatoid arthritis and related disorders

The generation of reactive oxygen species (free radicals) is an important factor in the development and maintenance of rheumatoid arthritis in humans and animal models. One source of free radicals is nitric oxide produced within the synoviocytes and chondrocytes and giving rise to the highly toxic radical peroxynitrite. Several cytokines, including tumour necrosis factor-alpha (TNFalpha) are involved in the formation of free radicals, partly by increasing the activity of nitric oxide synthase. Indeed, nitric oxide may mediate some of the deleterious effects of cytokines on bone resorption. Aspirin, tetracyclines, steroids and methotrexate can suppress nitric oxide synthase. Dietary antioxidants include ascorbate and the tocopherols and beneficial effects of high doses have been reported especially in osteoarthritis. There is also evidence for beneficial effects of beta-carotene and selenium, the latter being a component of the antioxidant enzyme glutathione peroxidase. The polyunsaturated fatty acids (PUFA) include the n-3 compounds, some of which are precursors of eicosanoid synthesis, and the n-6 group which can increase formation of the pro-inflammatory cytokines TNFalpha and interleukin-6, and of reactive oxygen species. Some prostaglandins, however, suppress cytokine formation, so that n-3 PUFA often oppose the inflammatory effects of some n-6-PUFA. gamma-linolenic acid (GLA) is a precursor of prostaglandin E1, a fact which may account for its reported ability to ameliorate arthritic symptoms. Fish oil supplements, rich in n-3 PUFA such as eicosapentaenoic acid have been claimed as beneficial in rheumatoid arthritis, possibly by suppression of the immune system and its cytokine repertoire. Some other oils of marine origin (e.g. from the green-lipped mussel) and a range of vegetable oils (e.g. olive oil and evening primrose oil) have indirect anti-inflammatory actions, probably mediated via prostaglandin E1. Overall, there is a growing scientific rationale for the use of dietary supplements as adjuncts in the treatment of inflammatory disorders such as rheumatoid arthritis and osteoarthritis.

Reactive oxygen species participation in experimentally induced arthritis of the temporomandibular joint in rats

In the temporomandibular joint (TMJ), it has been hypothesized that mechanical stresses lead to the oxidative stress of articular tissues. It has also been postulated that cells pertinent to arthritis-including endothelial cells and synovial cells-when stimulated by mechanical stresses and/or pro-inflammatory cytokines, promote oxidative damage. To determine the involvement of reactive oxygen species (ROS) in the diseased joint, we studied the generation of ROS in synovial fluid (SF) from interleukin-1alpha (IL-1alpha)-induced TMJ arthritis by electron spin resonance (ESR) spectroscopy, using the spin trap 5,5-dimethyl-1-pyrroline N-oxide (DMPO). The TMJ arthritis was experimentally induced in rats by the injection of human recombinant IL-1alpha into the TMJ; control rats were treated with normal saline solution. We found that the detected radicals in the collected SF were identified as a 1:2:2:1 quartet, characteristic of the hydroxyl radical-DMPO spin adduct. The ESR signal intensity of the hydroxyl radical-DMPO spin adduct in the SF from IL-1-treated rats was significantly higher than that from the control rats (P < 0.01). The results of ESR study also showed that hydroxyl radical (HO*) was increased in a time-dependent fashion in the presence of superoxide anion radical (O2*-) scavenger superoxide dismutase (SOD); the formation of DMPO-HO* was strongly inhibited by the iron chelater deferoxamine. We could measure higher levels of free iron (Fe2- and Fe3-) in the SF from TMJ arthritis than in that from controls (P < 0.05). Analysis of the data obtained from the present study suggests that the HO* radical detected in SF from IL-1-induced TMJ arthritis is generated via a modified Haber-Weiss reaction (biological Fenton reaction) in which O2*- can subsequently result in the production of H2O2 through dismutation reaction by SOD. Thus, HO* may be generated from the reaction of resultant H2O2 with free iron ions. The results presented here provide the first evidence of involvement of ROS in IL-1-induced TMJ arthritis.

Protective effects of Orostachys japonicus A. Berger (Crassulaceae) on H2O2-induced apoptosis in GT1-1 mouse hypothalamic neuronal cell line

Oxidative stress is a major cause of neurodegenerative diseases, so the protection of neuronal cells from reactive oxygen species can be beneficial for the prevention and treatment of these diseases. Methanol extract of Orostachys japonicus A. Berger (Crassulaceae), a traditional oriental medical herb, was shown to have a protective effect on H2O2-induced apoptosis in GT1-1 mouse hypothalamic neuronal cell line which was detected by flow cytometry after propidium iodide staining. Among fractions of O. japonicus, chloroform fraction had the highest protective effect, and water fraction had no protective effect suggesting that the active ingredients might be hydrophobic compounds.

Hydroxyl radical generation by rheumatoid blood and knee joint synovial fluid

OBJECTIVE

To demonstrate directly that highly reactive hydroxyl radicals (OH.) can be generated in patients with rheumatoid arthritis and contribute to joint damage, and to examine the ability of blood to cause OH. generation.

METHODS

The sensitive and specific technique of hydroxylation of aromatic compounds (salicylate and phenylalanine) was used to measure OH.. Synovial fluid and blood from patients with active rheumatoid arthritis were aspirated and immediately added to tubes containing salicylate and phenylalanine as detectors of OH., or to tubes containing saline as a control. Levels of specific products of attack of OH. upon salicylate (2,3- and 2,5-dihydroxybenzoates) and phenylalanine (ortho- and meta-tyrosines) were measured by high performance liquid chromatography.

RESULTS

Synovial fluid samples aspirated into saline never contained ortho- or meta-tyrosines or 2,3-dihydroxybenzoate. Of 53 patients examined, synovial fluid and blood from 36 caused formation of ortho- and meta-tyrosines when aspirated into solutions containing phenylalanine. Repeated sampling from three "positive" patients showed consistent evidence of these hydroxylation products. Similarly, of 22 patients examined, synovial fluid and blood from 18 caused formation of 2,3- and 2,5-dihydroxybenzoates when aspirated into salicylate solutions. Further evidence for the role of OH. was provided by inhibition of the hydroxylation by the specific OH. scavengers mannitol and sodium formate.

CONCLUSIONS

Aspirated knee joint fluids and blood from rheumatoid arthritis patients can generate OH., consistent with current views on the importance of this radical as a cytotoxic agent in rheumatoid disease. The ability of body fluids to cause OH. formation is not correlated with simple laboratory indices of disease activity, but is reproducible on sequential sampling from the same patients. The mechanism and significance of the phenomenon in rheumatoid arthritis pathology remain to be established.

Susceptibility of mice to bacterial and fungal infections after intragastric administration of ebselen

The seleno-organic compound ebselen (2-phenyl-1,2-benzisoselenazol-3(2H)-one) has anti-inflammatory activity and exhibits glutathione peroxidase-like activity in-vitro. Ebselen inhibited candidacidal activity over the same range of concentrations as it inhibited the production of microbicidal H2O2 by human neutrophils and macrophage-like cells. Therefore, the long-term administration of ebselen might be expected to induce an immunocompromised state in the host. To examine such a possibility, mice (5-weeks-old ddY, male) were given daily intragastric doses of 0, 10 or 100 mg/kg-1 ebselen for 21 days and then infected intraperitoneally with Candida albicans (10(8) cells/mouse), Pseudomonas aeruginosa (1.5 x 10(7) cells/mouse) or methicillin-resistant Staphylococcus aureus (5 x 10(8) cells/mouse). Ebselen at none of the tested doses affected the increase in body weight of mice during administration of the drug. No evidence was obtained that mice became more susceptible to the various microorganisms after the administration of ebselen at any tested dose.

Neutrophil oxygen metabolite inhibition of cultured chinchilla middle ear epithelial cell growth

Middle ear inflammation in acute bacterial otitis media is characterized by accumulation of neutrophils in middle ear effusion. Since neutrophils release products that may injure surrounding tissues, we studied the effect of neutrophil metabolic products on middle ear epithelial cells (MEECs) in vitro. Chinchilla MEECs were incubated with phorbol myristate acetate (PMA)-activated human neutrophils or with hydrogen peroxide (H2O2). Cell growth, which was measured by 3H-thymidine incorporation, was inhibited by activated neutrophils and by H2O2. Unstimulated neutrophils, PMA alone, and catalase alone did not affect the viability of MEECs. Catalase, an enzyme that reduces H2O2, partially blocked the inhibitory effect of activated neutrophils and completely blocked the inhibitory effect of H2O2. Inhibition of MEEC metabolism by neutrophil-reactive oxygen species may contribute to epithelial injury, which may prolong the middle ear inflammatory response and lead to chronic tissue damage.

The effect of ebselen on T-lymphocyte migration to arthritic joints and dermal inflammatory reactions in the rat

We have previously observed that ebselen (PZ 51, 2-Phenyl-1,2-Bensoisoselenazol-3-(2H)-one) can inhibit human polymorphonuclear leukocyte (PMNL) transendothelial migration in vitro and PMNL migration to arthritic joints and dermal inflammatory reactions in rats. In this study, we investigated the effect of ebselen on T-lymphocyte migration to the inflamed joints in rats with adjuvant arthritis (AA) and to dermal inflammation induced by cytokines (IFN gamma, mTNF alpha), cytokine inducing stimuli (poly I:C and LPS), or a delayed type hypersensitivity (DTH) reaction. Treatment of rats with AA with ebselen (100 mg/kg/day) p.o. for three days significantly reduced accumulation of 111In-labelled spleen T-cells (SPLT) in the arthritic joints, including forepaws, carpal joints, hindpaws and talar joints, and in all the above dermal inflammatory reactions. The inhibitory effect of ebselen on SPLT cell accumulation was greater than with indomethacin (2 mg/kg/day) and was observed within 3 h of initiation of ebselen treatment. Ebselen also inhibited SPLT migration to mandibular, axillary and mesenteric lymph nodes, and to the spleen. The results suggest that not only does ebselen inhibit SPLT migration to inflamed joints and to dermal inflammation but it also may inhibit lymphocyte homing and recirculation. Whether these effects of ebselen are related to its reported inhibition of cellular activation and intracellular signalling requires further investigation. However, the inhibition of T-lymphocyte migration reported here and of PMNL migration reported previously may both be beneficial in the treatment of human arthritis.

The effect of ebselen on polymorphonuclear leukocyte migration to joints in rats with adjuvant arthritis

We have previously reported that ebselen (PZ 51,2-Phenyl-1,2- Benzoisoselenazol-3-(2H)-one), a selinyl organic compound with anti-inflammatory properties, inhibited human polymorphonuclear leukocyte (PMNL) adhesion to and migration through cytokine-activated human umbilical vein endothelium in vitro. Here we investigated the in vivo effect of ebselen on PMNL migration into arthritic joints and dermal inflammation in rats with adjuvant arthritis. The rats were immunized with adjuvant (Mycobacteriaum butyricum in mineral oil) and 13 days later, when arthritis was fully developed, treatment (p.o.) with ebselen, indomethacin or vehicle was initiated. The migration of 51Cr-labelled blood PMNL purified from arthritic donors and extravasation of 125I-labelled HSA in arthritic joints and dermal inflammatory reactions was quantitatively measured. Treatment of rats with 100 mg/kg/day ebselen for 3 days, inhibited by 72-79% the PMNL migration into arthritic joints and tail (spondylitis) and by 50-60% into dermal inflammatory reactions induced with zymosan-activated rat serum (ZAS; C5adesArg), endotoxin (LPS) or IL-1 alpha. The inhibitory effect of ebselen was dose-dependent, because treatment of rats with 100 mg/kg/day ebselen caused significantly more inhibition of PMNL migration than did 30 mg/kg/day, although this dose was still effective. Ebselen inhibited PMNL migration into arthritic joints and dermal inflammation within 3 h of initial oral administration (100 mg/kg). However, ebselen did not suppress plasma albumin extravasation into arthritic joints and dermal inflammatory reactions. Compared to ebselen, treatment with indomethacin (2 mg/kg/day) was significantly less effective in inhibiting PMNL accumulation in joints, but in contrast to ebselen, indomethacin did inhibit plasma albumin extravasation into carpal and talar joints. The results suggest that ebselen effectively and rapidly inhibits PMNL migration in vivo, as also observed in vitro, and that it has anti-inflammatory actions distinct from classic nonsteroidal anti-inflammatory drugs such as indomethacin.

The effect of ebselen on polymorphonuclear leukocyte and lymphocyte migration to inflammatory reactions in rats

Ebselen, a selinyl organic compound with anti-inflammatory properties was found by us previously to inhibit in vitro human polymorphonuclear leukocyte (PMNL) adhesion to and migration through umbilical vein endothelium monolayers. Here we investigated in rats the effect of ebselen on PMNL and spleen T lymphocyte (SPLT) migration to inflamed joints induced by intra-articular (i.a) injection of recombinant murine tumor necrosis factor alpha (mTNF alpha) and to dermal inflammatory reactions. Inflammation was induced in the carpal and talar joints of rats by intra-articular (i.a.) injection (100 ng) of mTNF alpha once daily for 2 days. Corresponding joints in the opposite limb received diluent. Simultaneously, the rats were treated p.o. with either ebselen (100 mg/kg/day) or indomethacin (2 mg/kg/day) or vehicle for 2 days. Dermal inflammation was induced by intradermal injection (0.05 ml) of inflammatory stimuli. Accumulation of 51Cr-labelled rat blood PMNL, 111In-labeled SPLT, and extravasation of 125I-labelled human serum albumin (HSA) in the joints and in skin sites were measured. Treatment of rats with ebselen inhibited by 33-65% PMNL migration to the mTNF alpha inflamed joints, and to dermal inflammation induced by zymosan activated serum (ZAS; containing C5adesArg), endotoxin (LPS), mIL-1 beta and mTNF alpha. Migration of SPLT to dermal inflammation induced by interferon gamma (IFN gamma), poly-inosine-cytosine (poly I:C) and LPS was also significantly inhibited (22-33%), but SPLT migration into the inflamed joints was not effected by ebselen. Indomethacin treatment of rats also inhibited PMNL migration into the inflamed joints, but unlike ebselen, indomethacin inhibited only ZAS induced dermal PMNL accumulation. In contrast to ebselen, indomethacin inhibited SPLT migration into the inflamed joints as well as to the dermal inflammation induced by poly I:C and a delayed-type hypersensitivity reaction (DTH). In addition, treatment of rats with indomethacin significantly inhibited plasma protein (125I-HSA) extravasation in the inflamed joints and the dermal inflammatory reaction induced by ZAS, but ebselen had no such effect. In conclusion, ebselen appears to have a distinct antiinflammatory mechanism of action from indomethacin and the PMNL findings are consistent with a direct inhibitory action on PMNL activation and PMNL transendothelial migration as observed previously in vitro.

Ebselen, a selenoorganic compound as glutathione peroxidase mimic

The selenoorganic compound ebselen, 2-phenyl-1,2-benzisoselenazol-3(2H)-one, exhibits activity as an enzyme mimic. The reaction catalyzed is that of a glutathione (GSH) peroxidase (i.e., the reduction of a hydroperoxide at the expense of thiol). The specificity for substrates ranges from hydrogen peroxide and smaller organic hydroperoxides to membrane-bound phospholipid and cholesterol hydroperoxides. In addition to glutathione, the thiol reductant cosubstrate can be dithioerythritol, N-acetylcysteine or dihydrolipoate, or other suitable thiol compounds. Ebselen also has properties such as free radical and singlet oxygen quenching. Model experiments in vitro with liposomes, microsomes, isolated cells, and organs show that the protection against oxidative challenge afforded by ebselen can be explained largely by the activity as GSH peroxidase mimic. Whether this also explains the known preliminary results in clinical settings is yet open. The metabolism and disposition of ebselen is presented in this review. The main point is that the selenium is not bioavailable, explaining the extremely low toxicity observed in animal studies. The occurrence of natural GPx mimics, ovothiol and related compounds, is briefly mentioned.

Disease-modifying anti-rheumatic drugs: strategies for screening

Rheumatoid arthritis, a disease of unknown aetiology, has a multifactorial pathogenesis which may result in irreversible connective tissue destruction and loss of joint function. The search for drugs which offer more than symptomatic relief is a long term, largely unachieved aim of many pharmaceutical companies. This review briefly outlines those features of the aetiopathogenesis which appear to offer targets for therapeutic intervention and the structured strategy and test systems that can be used to detect drugs which may be capable of halting disease progression.

Effect of Ebselen on polymorphonuclear leukocyte adhesion to and migration through cytokine-activated vascular endothelium

Ebselen (PZ51, 2-Phenyl-1, 2-Benzoisoselenazol-3-(2H)-one) is a selinyl organic compound with anti-inflammatory properties. Some of its pharmacological effects are thought to result from its peroxidase activity. Here we examined the effects of Ebselen on polymorphonuclear leukocyte (PMNL) adhesion to umbilical vein endothelium and transendothelial migration in a modified Boyden chamber in which both PMNL-dependent and endothelial-dependent (IL-1, TNF alpha) PMNL adhesion and migration can be measured. Ebselen was found to dose dependently inhibit the adhesion of PMNL to IL-1 activated endothelium and to inhibit transendothelial PMNL migration induced by IL-1 alpha, and TNF alpha with an IC50 value of 28 microM. Transendothelial migration induced by the PMNL chemotactic agents C5adesArg and N-formyl-norleu-leu-phe was also inhibited at slightly higher concentrations. The effect of Ebselen was not on endothelial cell activation but on PMNL activation for adhesion and migration. This effect on PMNL was irreversible for the duration of the assay period (75 min). The results suggest that the anti-inflammatory activity of Ebselen may, in part, be due to direct inhibition of PMNL adhesion to vascular endothelium and transendothelial migration in response to a variety of inflammatory mediators.

The selective protection afforded by ebselen against lipid peroxidation in an ROS-dependent model of inflammation

The effects of an experimental model of hydrogen-peroxide-induced foot pad oedema on indices of oxidative damage to biomolecules have been investigated. We have demonstrated increased levels of fluorescent protein and lipid peroxides occurring in plasma at 24 and 48 h post-injection. In addition, a decrease in the degree of galactosylation of IgG was observed which kinetically related the degree of inflammation and to the increase in protein autofluorescence (a specific index of oxidative damage). The effects of ebselen, a novel organoselenium compound which protects against oxidative tissue injury in a glutathione-peroxidase-like manner, have also been examined in this model. Pretreatment of animals with a dose of 50 mg/kg ebselen afforded significant and selective protection against lipid peroxidation only. This effect may contribute to the anti-inflammatory effect of this agent in hydroperoxide-linked tissue damage.

Ebselen affects calcium homeostasis in human platelets

Ebselen (PZ 51, 2-phenyl-1,2-benzoisoselenazol-3-(2H)-one) is a selenoorganic compound with anti-inflammatory properties. Its pharmacological action is thought to originate from its peroxidase activity which could lower the peroxide tonus required for cyclooxygenase and lipoxygenase activations. From experiments with aspirin-treated human platelets we now present evidence that ebselen also affects intracellular calcium homeostasis by inhibiting the agonist-triggered increase in intracellular calcium. Using Mn2+ entry to quench the fura-2 fluorescence after cell stimulation, we could exclude an interaction of ebselen with receptor-operated calcium channels and therefore an inhibition of extracellular calcium influx. It became evident from whole cell experiments and by using isolated platelet microsomal vesicles that ebselen inhibits the inositol 1,4,5-trisphosphate (IP3) induced calcium release. Besides this inhibitory effect of ebselen on the calcium release higher concentrations of the compound (greater than or equal to 5 microM) induced a calcium release from our microsomal vesicles which also could be reversed by dithiothreitol. An activation of inflammatory cells is usually associated with increased cytosolic calcium concentrations. An inhibition of such calcium movements by ebselen may account for an up to now unidentified anti-inflammatory mechanism of ebselen action which is linked to a direct effect of this compound rather than to its peroxidase-like activity.