The role of nitric oxide in osteoarthritis

Potential directions for drug development for osteoarthritis

BACKGROUND

Osteoarthritis (OA) is a frustrating disease for both patient and physician because neither cause nor cure is known and there are currently no disease-modifying drugs.

OBJECTIVE

To review current therapeutic approaches as well as new findings regarding OA pathoetiology that could form the basis of future direction for the development of drugs to prevent or slow down disease progression.

METHODS

After reviewing disease progression in human OA, as demonstrated by histological analyses, the reasons for cartilage erosion are explored and possible therapeutic approaches are highlighted.

RESULTS/CONCLUSIONS

OA may be an epigenetic disease. This new concept can explain many aspects of the disease and provide reasons why therapeutic approaches until now have met with little success.

Effect of kramecyne on the inflammatory response in lipopolysaccharide-stimulated peritoneal macrophages

Kramecyne is a new peroxide, it was isolated from Krameria cytisoides, methanol extract, and this plant was mostly found in North and South America. This compound showed potent anti-inflammatory activity; however, the mechanisms by which this compound exerts its anti-inflammatory effect are not well understood. In this study, we examined the effects of kramecyne on inflammatory responses in mouse lipopolysaccharide- (LPS-) induced peritoneal macrophages. Our findings indicate that kramecyne inhibits LPS-induced production of tumor necrosis factor (TNF-α) and interleukin- (IL-) 6. During the inflammatory process, levels of cyclooxygenase- (COX-) 2, nitric oxide synthase (iNOS), and nitric oxide (NO) increased in mouse peritoneal macrophages; however, kramecyne suppressed them significantly. These results provide novel insights into the anti-inflammatory actions and support its potential use in the treatment of inflammatory diseases.

Down-regulation of protein kinase Cδ inhibits inducible nitric oxide synthase expression through IRF1

In inflammation, pro-inflammatory cytokines and bacterial products induce the production of high amounts of NO by inducible nitric oxide synthase (iNOS) in inflammatory and tissue cells. NO is an effector molecule in innate immunity, and it also has regulatory and pro-inflammatory/destructive effects in the inflammatory process. Protein kinase Cδ (PKCδ) is an important signaling protein regulating B lymphocyte functions, but less is known about its effects in innate immunity and inflammatory gene expression. In the present study we investigated the role of PKCδ in the regulation of iNOS expression in inflammatory conditions. NO production and iNOS expression were induced by LPS or a combination of cytokines IFNγ, IL-1β, and TNFα. Down-regulation of PKCδ by siRNA and inhibition of PKCδ by rottlerin suppressed NO production and iNOS expression in activated macrophages and fibroblasts. PKCδ directed siRNA and inhibition of PKCδ by rottlerin suppressed also the expression of transcription factor IRF1, possibly through inhibition of STAT1 activation. Accordingly, down-regulation of IRF1 by siRNA reduced iNOS expression in response to inflammatory stimuli. In addition, inhibition of PKCδ showed anti-inflammatory effects in carrageenan induced paw inflammation in mice as did iNOS inhibitor L-NIL. These results suggest that inhibitors of PKCδ have anti-inflammatory effects in disease states complicated by enhanced NO production through iNOS pathway.

Effect of iNOS inhibitor S-methylisothiourea in monosodium iodoacetate-induced osteoathritic pain: implication for osteoarthritis therapy

Much information is available on the role of nitric oxide (NO) in osteoarthritis (OA). However, its role has not been studied in the monosodium iodoacetate (MIA)-induced model of osteoarthritic pain. The present study was undertaken in rats to investigate the effect of iNOS inhibitor S-methylisothiourea (SMT) in MIA-induced osteoathritic pain and disease progression in rats. Osteoarthritis was produced by single intra-articular injection of the MIA in the right knee joint on day 0. Treatment groups were orally gavazed with different doses of SMT (10, 30 and 100mg/kg) and etoricoxib (10mg/kg) daily for 21 days. On days 0, 3, 7, 14 and 21, pain was measured and histopathology of right knee joint was done on day 21. SMT produced analgesia in a dose-dependent manner as shown by mechanical, heat hyperalgesia, knee vocalization, knee squeeze test, and spontaneous motor activity test. SMT reduced NO production in synovial fluid. Histopathological findings indicated that SMT reduced disease progression as evident from complete cartilage formation in rats treated with SMT at 30 mg/kg. In conclusion, the results indicate that SMT attenuates the MIA-induced pain and histopathological changes in the knee joint. The antinociceptive and antiarthritic effects of SMT were mediated by inhibiting cartilage damage and suppression of NO in synovial fluid. It is suggested that SMT has potential as a therapeutic modality in the treatment of osteoarthritis.

Suppression of lipopolysaccharide-induced expression of inflammatory indicators in RAW 264.7 macrophage cells by extract prepared from Ginkgo biloba cambial meristematic cells

CONTEXT

Ginkgo biloba L. (Ginkgoaceae) leaves have been used as an herbal medicine that has a complex range of biological activities. However, when we consider that biological activity of plant extracts is highly variable according to the source, location, and harvest season, technology to obtain the natural products with homogeneity is extremely important.

OBJECTIVE

We established the technology to obtain the cambial meristematic cells (CMCs) of Ginkgo biloba, which were expanded in vitro with homogeneity through a suspension culture and then determined the anti-inflammatory activity of fractionated samples prepared from the ethanol extract of CMCs.

MATERIALS AND METHODS

We determined the anti-inflammatory activity of samples using lipopolysaccharide (LPS)-stimulated RAW 264.7 macrophage cells. Especially, influence of sample treatment on the expression of various indicators, such as nitric oxide (NO), inducible nitric oxide synthase (iNOS), cyclooxygenase (COX)-2, mitogen-activated protein (MAP) kinases, transcription factor, and cytokines, involved in inflammatory activity was assessed.

RESULTS

A fractionated sample demonstrated 53.4% inhibition of LPS-induced NO production from the cells. Additionally, when fractionated samples were treated, iNOS and COX-2 expressions were almost completely suppressed. Fractionated samples also inhibited the phosphorylation of LPS-induced extracellular signal-regulated (ERK) and p38 MAP kinases more than 60%. IκB phosphorylation and subsequent nuclear factor (NF)-κB activation were also suppressed by fractionated samples. The expression of pro-inflammatory cytokines, IL-6 and tumor necrosis factor (TNF)-α, was significantly inhibited by the sample treatment.

DISCUSSION AND CONCLUSION

Fractionated samples from the ethanol extract of Ginkgo biloba CMCs could potentially be the source of a powerful anti-inflammatory substance.

Suppressive effects of PG201, an antiarthritic botanical formulation, on lipopolysaccharide-induced inflammatory mediators in Raw264.7 cells

PG201, an ethanol extract from a mixture of 12 herbs, has strong antiarthritic activity. To understand the molecular mechanisms underlying its anti-inflammatory effects, PG201-mediated suppression of inflammatory mediators was studied in Raw264.7, a mouse macrophage cell line. PG201 decreased the expression of interleukin (IL)-1β, IL-6 and CC chemokine ligand-2, but not tumor necrosis factor-α, at the protein and mRNA levels in lipopolysaccharide-stimulated Raw264.7 cells. Results from a gel retardation assay indicated that PG201 substantially reduced the DNA-binding activity of the activator protein-1 and cyclic adenosine monophosphate-responsive element-binding protein transcription factors, but not nuclear factor-κB. Western blot and Northern blot analyses showed that PG201 reduced inducible nitric oxide synthase and cytosolic phospholipase A(2) (cPLA(2)) protein expression, but did not affect mRNA expression, ultimately resulting in decreased nitric oxide and prostaglandin E(2). The protein expression of cPLA(2) was decreased by PG201 in the presence of cycloheximide, an inhibitor of translation, suggesting that PG201 may facilitate the degradation of cPLA(2). Taken together, these results suggest that PG201 selectively affects the expression of proteins that play key roles in the inflammatory response at transcriptional and post-translational levels.

Adiponectin associates with markers of cartilage degradation in osteoarthritis and induces production of proinflammatory and catabolic factors through mitogen-activated protein kinase pathways

Introduction

Adiponectin is an adipokine that regulates energy metabolism and insulin sensitivity, but recent studies have pointed also to a role in inflammation and arthritis. The purpose of the present study was to investigate the association and effects of adiponectin on inflammation and cartilage destruction in osteoarthritis (OA).

Methods

Cartilage and blood samples were collected from 35 male OA patients undergoing total knee replacement surgery. Preoperative radiographs were evaluated using Ahlbäck classification criteria for knee OA. Circulating concentrations of adiponectin and biomarkers of OA, that is, cartilage oligomeric matrix protein (COMP) and matrix metalloproteinase 3 (MMP-3), were measured. Cartilage samples obtained at the time of surgery were cultured ex vivo, and the levels of adiponectin, nitric oxide (NO), IL-6, MMP-1 and MMP-3 were determined in the culture media. In addition, the effects of adiponectin on the production of NO, IL-6, MMP-1 and MMP-3 were studied in cartilage and in primary chondrocyte cultures.

Results

Plasma adiponectin levels and adiponectin released from OA cartilage were higher in patients with the radiologically most severe OA (Ahlbäck grades 4 and 5) than in patients with less severe disease (Ahlbäck grades 1 to 3). Plasma adiponectin concentrations correlated positively with biomarkers of OA, that is, COMP (r = 0.55, P = 0.001) and MMP-3 (r = 0.34, P = 0.046). Adiponectin was released by OA cartilage ex vivo, and it correlated positively with production of NO (r = 0.43, P = 0.012), IL-6 (r = 0.42, P = 0.018) and MMP-3 (r = 0.34, P = 0.051). Furthermore, adiponectin enhanced production of NO, IL-6, MMP-1 and MMP-3 in OA cartilage and in primary chondrocytes in vitro in a mitogen-activated protein kinase (MAPK)-dependent manner.

Conclusions

The findings of this study show that adiponectin is associated with, and possibly mediates, cartilage destruction in OA.

Rose hip and its constituent galactolipids confer cartilage protection by modulating cytokine, and chemokine expression

Background

Clinical studies have shown that rose hip powder (RHP) alleviates osteoarthritis (OA). This might be due to anti-inflammatory and cartilage-protective properties of the complete RHP or specific constituents of RHP. Cellular systems (macrophages, peripheral blood leukocytes and chondrocytes), which respond to inflammatory and OA-inducing stimuli, are used as in vitro surrogates to evaluate the possible pain-relief and disease-modifying effects of RHP.

Methods

(1) Inflammatory processes were induced in RAW264.7 cells or human peripheral blood leukocytes (PBL) with LPS. Inflammatory mediators (nitric oxide (NO), prostaglandin E₂ (PGE₂) and cytokines/chemokines) were determined by the Griess reaction, EIA and multiplex ELISA, respectively. Gene expression was quantified by RT-PCR. RHP or its constituent galactolipid, GLGPG (galactolipid (2S)-1, 2-di-O-[(9Z, 12Z, 15Z)-octadeca-9, 12, 15-trienoyl]-3-O-β-D-galactopyranosyl glycerol), were added at various concentrations and the effects on biochemical and molecular parameters were evaluated. (2) SW1353 chondrosarcoma cells and primary human knee articular chondrocytes (NHAC-kn) were treated with interleukin (IL)-1β to induce in vitro processes similar to those occurring during in vivo degradation of cartilage. Biomarkers related to OA (NO, PGE₂, cytokines, chemokines, metalloproteinases) were measured by multiplex ELISA and gene expression analysis in chondrocytes. We investigated the modulation of these events by RHP and GLGPG.

Results

In macrophages and PBL, RHP and GLGPG inhibited NO and PGE₂ production and reduced the secretion of cytokines (TNF-α, IFN-γ, IL-1β, IL-6, IL-12) and chemokines (CCL5/RANTES, CXCL10/IP-10). In SW1353 cells and primary chondrocytes, RHP and GLGPG diminished catabolic gene expression and inflammatory protein secretion as shown by lower mRNA levels of matrix metalloproteinases (MMP-1, MMP-3, MMP-13), aggrecanase (ADAMTS-4), macrophage inflammatory protein (MIP-2, MIP-3α), CCL5/RANTES, CXCL10/IP-10, IL-8, IL-1α and IL-6. The effects of GLGPG were weaker than those of RHP, which presumably contains other chondro-protective substances besides GLGPG.

Conclusions

RHP and GLGPG attenuate inflammatory responses in different cellular systems (macrophages, PBLs and chondrocytes). The effects on cytokine production and MMP expression indicate that RHP and its constituent GLGPG down-regulate catabolic processes associated with osteoarthritis (OA) or rheumatoid arthritis (RA). These data provide a molecular and biochemical basis for cartilage protection provided by RHP.

Dual specificity phosphatase 1 regulates human inducible nitric oxide synthase expression by p38 MAP kinase

The role of dual specificity phosphatase 1 (DUSP1) in inducible nitric oxide synthase (iNOS) expression in A549 human pulmonary epithelial cells, J774 mouse macrophages and primary mouse bone marrow-derived macrophages (BMMs) was investigated. iNOS expression was induced by a cytokine mixture (TNF, IFNγ and IL-1β) in A549 cells and by LPS in J774 cells, and it was inhibited by p38 MAPK inhibitors SB202190 and BIRB 796. Stimulation with cytokine mixture or LPS enhanced also DUSP1 expression. Down-regulation of DUSP1 by siRNA increased p38 MAPK phosphorylation and iNOS expression in A549 and J774 cells. In addition, LPS-induced iNOS expression was enhanced in BMMs from DUSP1^(−/−) mice as compared to that in BMMs from wild-type mice. The results indicate that DUSP1 suppresses iNOS expression by limiting p38 MAPK activity in human and mouse cells. Compounds that enhance DUSP1 expression or modulate its function may be beneficial in diseases complicated with increased iNOS-mediated NO production.

Effect of nitric oxide on mitochondrial activity of human synovial cells

Background

Nitric oxide (NO) is a messenger implicated in the destruction and inflammation of joint tissues. Cartilage and synovial membrane from patients with rheumatoid arthritis (RA) and osteoarthritis (OA) have high levels of NO. NO is known to modulate various cellular pathways and, thus, inhibit the activity of the mitochondrial respiratory chain (MRC) of chondrocytes and induce the generation of reactive oxygen species (ROS) and cell death in multiple cell types. For these reasons, and because of the importance of the synovial membrane in development of OA pathology, we investigated the effects of NO on survival, mitochondrial function, and activity of fibroblastic human OA synovial cells.

Methods

Human OA synovia were obtained from eight patients undergoing hip joint replacement. Sodium nitroprusside (SNP) was used as a NO donor compound and cell viability was evaluated by MTT assays. Mitochondrial function was evaluated by analyzing the mitochondrial membrane potential (Δψm) with flow cytometry using the fluorofore DePsipher. ATP levels were measured by luminescence assays, and the activities of the respiratory chain complexes (complex I: NADH CoQ₁ reductase, complex II: succinate dehydrogenase, complex III: ubiquinol-cytochrome c reductase, complex IV: cytochrome c oxidase) and citrate synthase (CS) were measured by enzymatic assay. Protein expression analyses were performed by western blot.

Results

SNP at a concentration of 0.5 mM induced cell death, shown by the MTT method at different time points. The percentages of viable cells at 24, 48 and 72 hours were 86.11 ± 4.9%, 74.31 ± 3.35%, and 43.88 ± 1.43%, respectively, compared to the basal level of 100% (*p < 0.05). SNP at 0.5 mM induced depolarization of the mitochondrial membrane at 12 hours with a decrease in the ratio of polarized cells (basal = 2.48 ± 0.28; SNP 0.5 mM = 1.57 ± 0.11; *p < 0.01). The time course analyses of treatment with SNP at 0.5 mM demonstrated that treatment reliably and significantly reduced intracellular ATP production (68.34 ± 14.3% vs. basal = 100% at 6 hours; *p < 0.05). The analysis of the MRC at 48 hours showed that SNP at 0.5 mM increased the activity of complexes I (basal = 36.47 ± 3.92 mol/min/mg protein, SNP 0.5 mM = 58.08 ± 6.46 mol/min/mg protein; *p < 0.05) and III (basal = 63.87 ± 6.93 mol/min/mg protein, SNP 0.5 mM = 109.15 ± 30.37 mol/min/mg protein; *p < 0.05) but reduced CS activity (basal = 105.06 ± 10.72 mol/min/mg protein, SNP at 0.5 mM = 66.88 ± 6.08 mol/min/mg protein.; *p < 0.05), indicating a decrease in mitochondrial mass. Finally, SNP regulated the expression of proteins related to the cellular cycle; the NO donor decreased bcl-2, mcl-1 and procaspase-3 protein expression.

Conclusions

This study suggests that NO reduces the survival of OA synoviocytes by regulating mitochondrial functionality, as well as the proteins controlling the cell cycle.

Cartilage destruction is partly induced by the internal proteolytic enzymes and apoptotic phenomenon of chondrocytes in relapsing polychondritis

OBJECTIVE

We analyzed 9 cases by immunohistochemical studies in order to elucidate the mechanisms of cartilage destruction in relapsing polychondritis (RP), which often involves the external auricle and respiratory tract through immunological disorder.

METHODS

Cartilage tissues were obtained during surgical operations. Cell species in the granulation tissues, especially near the cartilage, were identified by cell-surface markers [CD3, CD4, CD8, CD20, CD45 (LCA), and CD68]. The proteolytic enzymes expressed in the cells in the perichondral granulation and in chondrocytes themselves were analyzed by immunohistochemical studies using anti-matrix metalloproteinase (MMP) -1, -3, -8, -9, and -13, and cathepsin D, K, L, and elastase antibodies. Apoptosis and nitric oxide (NO), an apoptosis-related factor, were also examined using ApopTag and antinitrotyrosine antibody, respectively.

RESULTS

Among cell species that infiltrated in perichondral granulation, LCA, CD68 (monocytes/macrophages), and CD4 cells were dominant in number; MMP-8, MMP-9, and elastase were expressed only in the perichondral granulation; whereas MMP-3 and cathepsin K and L were detected in both chondrocytes and granulations. Out of 9 cases examined, 6 revealed apoptotic cells in excess of 50% of chondrocytes. There was a strong correlation between the number of apoptotic cells and the number of MMP-3-positive (r = 0.83) and cathepsin K-positive cells (r = 0.92). Abundant NO-expressing cells were observed in the chondrocytes in degenerated cartilage, similar to apoptosis.

CONCLUSION

Cartilage destruction in polychondritis is induced not only by perichondral inflammation, but also by intrinsic factors expressed in chondrocytes themselves, including certain kinds of proteolytic enzymes and apoptosis.

Tormentic acid, a triterpenoid saponin, isolated from Rosa rugosa, inhibited LPS-induced iNOS, COX-2, and TNF-α expression through inactivation of the nuclear factor-κb pathway in RAW 264.7 macrophages

We previously reported that extract of Rosa rugosa root and its active triterpenoids constituents exhibit anti-nociceptive and anti-inflammatory effects in animal models. However, little is known about the effects and the molecular mechanism of the 19α-hydroxyursane-type triterpenoids. Among the tested 19α-hydroxyursane-type triterpenoids (kaji-ichigoside F(1), rosamultin, euscaphic acid, tormentic acid (TA)), TA was found to most potently inhibit the production of nitric oxide (NO) in RAW 264.7 cells. We investigated the anti-inflammatory effects and its underlying molecular mechanisms of TA in lipopolysaccaride (LPS)-stimulated RAW 264.7 cells. TA dose-dependently reduced the productions of NO, prostaglandin E(2) (PGE(2)), and tumor necrosis factor-α (TNF-α) induced by LPS. In addition, TA significantly suppressed the LPS-induced expressions of inducible nitric oxide synthase (iNOS), cyclooxygenase-2 (COX-2), and TNF-α at the mRNA and protein levels. Moreover, treatment with TA decreased LPS-induced DNA binding of nuclear factor-kappa B (NF-κB) and nuclear translocation of p65 and p50 subunits of NF-κB. Consistent with these findings, TA also suppressed the LPS-stimulated degradation and phosphorylation of inhibitor of kappa B-α (IκB-α). Taken together, these results suggest that the anti-inflammatory activity of TA is associated with the down-regulation of iNOS, COX-2, and TNF-α through the negative regulation of the NF-κB pathway in RAW 264.7 cells.

Osteoarthritis: another component of metabolic syndrome?

Osteoarthritis (OA) has become a major public health problem not only because of its increasing prevalence worldwide but also because of its frequent association with cardiovascular disease, the leading cause of death in industrialized countries. There is growing evidence that OA is not simply a disease related to aging or mechanical stress of joints but rather a "metabolic disorder" in which various interrelated lipid, metabolic, and humoral mediators contribute to the initiation and progression of the disease process. Indeed, OA has been linked not only to obesity but also to other cardiovascular risk factors, namely, diabetes, dyslipidemia, hypertension, and insulin resistance.

Cartilage biology, pathology, and repair

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

Pharmacologic therapy for osteoarthritis--the era of disease modification

Osteoarthritis (OA) is a prevalent and disabling condition for which few safe and effective therapeutic options are available. Current approaches are largely palliative and in an effort to mitigate the rising tide of increasing OA prevalence and disease impact, modifying the structural progression of OA has become a focus of drug development. This Review describes disease modification and discusses some of the challenges involved in the discovery and development of disease-modifying OA drugs (DMOADs). A variety of targeted agents are in mature phases of development; specific agents that are beyond preclinical development in phase II and III trials and show promise as potential DMOADs are discussed. A research agenda with respect to disease modification in OA is also provided, and some of the future challenges we face in this field are discussed.

Anti-inflammatory potential of Phaseolus calcaratus Roxburgh, a oriental medicine, on LPS-stimulated RAW 264.7 macrophages

Objectives

The seed of Phaseolus calcaratus Roxburgh (PHCR) has traditionally been used as a herbal medicine, considered to have anti-inflammatory potential. Here we examined the ability of PHCR seed extract to inhibit inflammatory responses of macrophages to bacterial toxin and the mechanism involved.

Methods

In the present study, we prepared four fractions from an ethanol extract of PHCR seed and investigated their effects on the production of nitric oxide and cytokines, and the expression of inducible nitric oxide synthase (iNOS) in lipopolysaccharide (LPS)-stimulated RAW 264.7 macrophage cells.

Key findings

The fractions inhibited LPS-induced nitric oxide production and cyclooxygenase-2 (COX-2) expression in the cells. The ethyl acetate fraction at 100 µg/ml almost completely suppressed NO production, iNOS and COX-2 expression, and TNF-α and IL-6 secretion in cells stimulated with LPS. The fraction also inhibited phosphorylation of extracellular signal-regulated kinase (ERK) and p38 in LPS-stimulated cells with the attendant suppression of IκBα nuclear translocation and nuclear factor (NF)-κB activation. Furthermore, PHCR seed extracts contained a large number of phenolic compounds having antioxidant potentials against 1,1-diphenyl-2-picrylhydrazyl (DPPH) radicals and hydroxyl radicals. We identified catechin-7-O-β-d-glucopyranoside as one of the active compounds responsible for the biological activity of PHCR seed extract.

Conclusions

These results suggest for the first time that ethanol extracts from PHCR seed have anti-inflammatory potential on LPS-stimulated macrophages through the down-regulation of ERK/p38- and NF-κB-mediated signalling pathways.

Enhanced reactivity to malondialdehyde-modified proteins by systemic lupus erythematosus autoantibodies

OBJECTIVE

Evaluation of the reactivity of autoantibodies of systemic lupus erythematosus (SLE) patients directed against malondialdehyde (MDA)-modified catalase, superoxide dismutase (SOD), and different Hep2 protein fractions (hydrophobic, hydrophilic, and nuclear).

METHOD

Thiol groups and MDA-protein adducts were first assessed among 65 SLE patients and 60 healthy controls. Then, the reactivities of SLE immunoglobulin (Ig)G autoantibodies towards MDA-modified and unmodified proteins were compared using a standard enzyme-linked immunosorbent assay (ELISA).

RESULTS

An increase in the levels of MDA-modified proteins and a decrease in the concentration of thiol groups among SLE patients (p < 0.05) were observed. IgG circulating autoantibodies in the sera of SLE patients exhibited a significant enhanced reactivity (p < 0.05) against catalase and SOD-modified proteins. The same data were observed in the different protein fractions extracted from cultured cells (p < 0.05).

CONCLUSION

These data reinforce the role of oxidative stress and especially lipid peroxidation products in the progression of SLE disease.

Differential effect of molecular mass hyaluronan on lipopolysaccharide-induced damage in chondrocytes

Hyaluronan is a biological polysaccharide that may exist in different degrees of polymerization. Several investigations reported that low molecular mass hyaluronan may have pro-inflammatory activity, while high molecular mass hyaluronan can exert beneficial effects. Starting from these data, the aim of this study was to investigate the effect of hyaluronan of different molecular mass in mouse articular chondrocyte cultures stimulated with lipopolysaccharide (LPS). Inflammation was induced in chondrocytes by acute treatment with 2.0 microg/ml LPS. High levels of tumour necrosis factor (TNF)-alpha, interleukin (IL)-1beta, IL-6, interferon (IFN)-gamma and iNOS gene expression and their related proteins were found in chondrocytes 24 h after treatment with LPS. High concentrations of NO, NF-kappaB activation, IkappaBalpha phosphorylation and apoptosis, evaluated by the increase in caspase-3 expression and its related protein amount were also produced by LPS stimulation. In contrast, LPS reduced aggrecan and collagen type II (Col2A) expression and their protein production. The treatment of chondrocytes with hyaluronan of different molecular mass produced the following effects: (i) low molecular mass hyaluronan exerted a slight inflammatory effect in untreated chondrocytes, while in LPS-treated chondrocytes it enhanced cytokine production and decreased aggrecan and Col2A compared with cells treated with LPS alone; (ii) no effect was exerted on LPS-induced apoptosis and NO production; (iii) medium molecular mass hyaluronan did not exert any inflammatory/anti-inflammatory activity in LPS-untreated/treated cells and failed to reduce apoptosis; and (iv) high molecular mass hyaluronan had no inflammatory effect in LPS-untreated cells while it was able to reduce all the detrimental effects stimulated by LPS treatment. These data confirm the multifactorial role played by hyaluronan and suggest, in particular, that hyaluronan may modulate inflammation during pathologies by its different degrees of polymerization.

Leptin enhances synthesis of proinflammatory mediators in human osteoarthritic cartilage--mediator role of NO in leptin-induced PGE2, IL-6, and IL-8 production

Obesity is an important risk factor for osteoarthritis (OA) in weight-bearing joints, but also in hand joints, pointing to an obesity-related metabolic factor that influences on the pathogenesis of OA. Leptin is an adipokine regulating energy balance, and it has recently been related also to arthritis and inflammation as a proinflammatory factor. In the present paper, the effects of leptin on human OA cartilage were studied. Leptin alone or in combination with IL-1 enhanced the expression of iNOS and COX-2, and production of NO, PGE₂, IL-6, and IL-8. The results suggest that the effects of leptin are mediated through activation of transcription factor nuclear factor κB (NF-κB) and mitogen-activated protein kinase (MAPK) pathway c-Jun NH₂-terminal kinase (JNK). Interestingly, inhibition of leptin-induced NO production with a selective iNOS inhibitor 1400 W inhibited also the production of IL-6, IL-8, and PGE₂, and this was reversed by exogenously added NO-donor SNAP, suggesting that the effects of leptin on IL-6, IL-8, and PGE₂ production are dependent on NO. These findings support the idea of leptin as a factor enhancing the production of proinflammatory factors in OA cartilage and as an agent contributing to the obesity-associated increased risk for osteoarthritis.

In vitro and in vivo modulation of cartilage degradation by a standardized Centella asiatica fraction

Osteoarthritis (OA) is a degenerative joint disease in which focal cartilage destruction is one of the primary features. The present study aims to evaluate the effect of a Centella asiatica fraction on in vitro and in vivo cartilage degradation. Bovine cartilage explants and bovine chondrocytes cultured in alginate were stimulated with IL-1 beta in the presence or absence of different concentrations (2, 5 and 10 microg/ml) of a standardized Centella asiatica triterpenes (CAT) fraction. The CAT fraction inhibited the IL-1 beta-induced proteoglycan (PG) release and nitric oxide (NO) production by cartilage explants in a dose-dependent manner. The IL-1 beta-induced reduction in PG synthesis and proliferation of chondrocytes cultured in alginate were counteracted by the CAT fraction at a concentration of 10 microg/ml. In a zymosan-induced acute arthritis model, the CAT fraction inhibited PG depletion without modulating joint swelling and inflammatory cell infiltration. In conclusion, the present study demonstrated for the first time that the tested Centella asiatica fraction was able to inhibit the zymosan-induced cartilage degradation in vivo without affecting the zymosan-induced inflammatory cell infiltration and joint swelling. The in vitro data indicate that the cartilage protective activity might at least partially be induced by the inhibition of NO production. The overall results indicate a possible disease modifying osteoarthritic activity of the Centella asiatica fraction.

Inflammatory response in patients with active and inactive osteoarthritis

In the present study, we have investigated comparatively the inflammatory response of patients with active and inactive osteoarthritis. The sera from 31 healthy individuals, 37 patients with active OA, and 19 patients with inactive OA were assayed for TNF-alpha, IL-6, sRANKL, RANTES, and MRP8 using ELISA in order to evaluate their potential as markers of disease activity. Also, the spontaneous and LSP-induced release of TNF-alpha and IL-6 by peripheral blood neutrophils was determined. The activation of OA is associated with elevated TNF-alpha, IL-6, and RANTES serum levels while sRANKL and MRP8 appeared to be increased in both active and inactive OA. The neutrophil spontaneous and up-regulated by LPS cytokine release can contribute to the exacerbation of OA.

Nitric oxide and cardiovascular effects: new insights in the role of nitric oxide for the management of osteoarthritis

Nitric oxide (NO) is an important mediator in both health and disease. In addition to its effects on vascular tone and platelet function, it plays roles in inflammation and pain perception that may be of relevance in osteoarthritis. Many patients with osteoarthritis take nonsteroidal anti-inflammatory drugs (NSAIDs) long term for pain control. Over recent years concern has been raised about the possible cardiovascular side effects of NSAIDs. The reasons for this possible increased cardiovascular risk with NSAIDs are not yet entirely clear, although changes in blood pressure, renal salt handling and platelet function may contribute. Recently, drugs that chemically link a NSAID with a NO donating moiety (cyclo-oxygenase-inhibiting NO-donating drugs [CINODs]) were developed. NO is an important mediator of endothelial function, acting as a vasodilator and an inhibitor of platelet aggregation, and having anti-inflammatory properties. The potential benefits of CINODs include the combination of effective analgesic and anti-inflammatory actions with NO release, which might counterbalance any adverse cardiovascular effects of NSAIDs. Effects of CINODs in animal studies include inhibition of vasopressor responses, blood pressure reduction in hypertensive rats and inhibition of platelet aggregation. CINODs may also reduce ischemic damage to compromised myocardial tissue. In addition, endothelial dysfunction is a recognized feature of inflammatory arthritides, and therefore a drug that might provide slow release of NO to the vasculature while treating pain is an attractive prospect in these conditions. Further studies of the effects of CINODs in humans are required, but these agents represent a potential exciting advance in the management of osteoarthritis.

Porphyromonas gingivalis, gamma interferon, and a proapoptotic fibronectin matrix form a synergistic trio that induces c-Jun N-terminal kinase 1-mediated nitric oxide generation and cell death

During infection and inflammation, bacterial and inflammatory proteases break down extracellular matrices into macromolecular fragments. Fibronectin fragments are associated with disease severity in arthritis and periodontitis. The mechanisms by which these fragments contribute to disease pathogenesis are unclear. One likely mechanism is that fibronectin fragments induce apoptosis of resident cells, which can be further modulated by nitric oxide. Nitric oxide levels are increased at inflammatory sites in periodontitis patients. The aim of this study was to examine whether a proapoptotic fibronectin matrix (AFn) exerts its action by inducing nitric oxide and whether priming by bacterial and inflammatory components exacerbates this mechanism. Our data demonstrate that AFn increased the levels of nitric oxide and inducible nitric oxide synthase (iNOS) dose and time dependently in periodontal ligament (PDL) cells. These effects and apoptosis were inhibited by iNOS suppression and enhanced by iNOS overexpression. Nitric oxide and iNOS induction were paralleled by increased c-Jun N-terminal kinase 1 (JNK-1) phosphorylation. JNK-1 overexpression enhanced the expression of nitric oxide and iNOS, whereas inhibiting JNK-1 by small interfering RNA or a kinase mutant reversed these findings. Priming PDL cells with Porphyromonas gingivalis, its lipopolysaccharide (LPS), or gamma interferon (IFN-gamma) further increased nitric oxide levels and apoptosis. Escherichia coli and Streptococcus mutans induced lesser effects. Gingival fibroblasts and neutrophils responded to a lesser degree to these stimuli, whereas keratinocytes were resistant to apoptosis. Thus, proapoptotic matrices trigger nitric oxide release via JNK-1, promoting further apoptosis in host cells. LPS and IFN-gamma accentuate this mechanism, suggesting that during inflammation, the affected matrices and bacterial and inflammatory components combined exert a greater pathogenic effect on host cells.

Effects of levo- and dextrosimendan on NF-kappaB-mediated transcription, iNOS expression and NO production in response to inflammatory stimuli

BACKGROUND AND PURPOSE

Levosimendan is used in the treatment of decompensated heart failure. It increases the contractility of the myocardium by sensitizing troponin C to calcium. In addition, levosimendan has been reported to have beneficial effects in experimental models of septic shock. Because heart failure and sepsis have been associated with excessive nitric oxide (NO) production through inducible NOS (iNOS), we investigated the effects of the simendans on NO production and iNOS expression and on generation of pro-inflammatory cytokines.

EXPERIMENTAL APPROACH

Macrophages and fibroblasts were exposed to inflammatory stimuli to induce iNOS expression. Proteins were measured by western blot and mRNA expression was determined by quantitative RT-PCR. Promoter activity and nuclear factor-kappaB (NF-kappaB) and the gamma-activated site (GAS; binding site for signal transducer and activator of transcription 1; STAT1)-mediated transcription were investigated using luciferase reporter constructs. Cytokines tumour necrosis factor-alpha (TNF-alpha) and interleukin-6 (IL-6) were measured by ELISA.

KEY RESULTS

Levosimendan and dextrosimendan decreased NO production in a dose-dependent manner in cells exposed to inflammatory stimuli. The simendans decreased iNOS protein and mRNA expression but did not affect iNOS mRNA decay. These compounds decreased iNOS promoter activity and inhibited NF-kappaB-mediated transcription but not that mediated by STAT1/GAS. The simendans reduced IL-6 production slightly but they had no effect on TNF-alpha synthesis.

CONCLUSIONS AND IMPLICATIONS

The simendans downregulated NF-kappaB-dependent transcription and decreased iNOS promoter activity, iNOS expression and NO production. These mechanisms may contribute to their beneficial clinical effects.

Purified human plasma glycosaminoglycans reduced NF-kappaB activation, pro-inflammatory cytokine production and apoptosis in LPS-treated chondrocytes

INTRODUCTION

There have been several cases reporting a significant increase in chondroitin sulphate plasma levels in patients with different types of disease, such as systemic lupus erythematosus, rheumatoid arthritis, and liver disease. At present, the precise role of chondroitin sulphate molecules in blood is unclear. Previous investigations have shown that the addition of purified human plasma glycosaminoglycans (GAGs), containing a high percentage of chondroitin-4-sulphate (C4S) was able to inhibit lipid peroxidation and to protect cells from reactive oxygen species damage, suggesting antioxidant activity. Starting from these reports, the aim of this study was to evaluate the effectiveness of GAG structures purified from normal human plasma in reducing inflammation using a model of lipopolysaccharide (LPS)-induced increase of pro-inflammatory cytokines in mouse articular chondrocyte cultures.

RESULTS

Chondrocyte stimulation with LPS (50 microg/ml) for 24 h enhanced gene expression of tumor necrosis factor alpha (TNF-alpha), interleukin-1 beta (IL-1beta), interleukin 6 (IL-6), interferon gamma (IFN-gamma), inducible nitric oxide synthase (iNOS) and increases in their related protein levels, as well as NF-kappaB activation, IkappaBalpha phosphorylation and apoptosis evaluated by the increase in caspase-3 expression and its related protein amount. LPS treatment also generated a high amount of nitric oxide (NO). The addition of different doses of purified human GAGs to LPS-stimulated chondrocytes reduced inflammatory cytokines and iNOS both at mRNA and protein levels, blocked NF-kappaB activation and cytoplasmic IkappaBalpha phosphorylation, limited cell death by inhibiting apoptosis, and reduced NO concentrations.

CONCLUSIONS

These results further support the hypothesis that plasma GAGs may function as immunomodulators and their increased release and degradation could be a biological response acting to modulate inflammation during disease.

Beneficial effects of Ajuga decumbens on osteoporosis and arthritis

Extract of the whole plant, Ajuga decumbens (KE) has long been used in China as a medication for the relief of joint pain. Previously, we proved that KE up-regulated the synthesis of collagen in false aged model rats. In this paper we examined the effects of KE on nitric oxide (NO) production, expression of inducible nitric oxide synthase (iNOS), osteoblast and osteoclast activity. We also investigated whether KE had any anti-osteoporosis or anti-arthritic activity by using ovariectmized mice and adjuvant induced arthritic rats. KE exhibited down-regulation of differentiation into osteoclast and up-regulation of mineralization in osteoblast-like MC3T3-E1 cells in a concentration-dependent manner. NO synthesized by iNOS plays important roles in inflammatory disease and imbalance between bone resorption and bone formation caused by estrogen depletion. KE inhibited expression of iNOS which caused concentration dependent inhibition of NO production. Furthermore, KE prevented brittle bones in ovariectomized mice and swelling of the left hind ankle in adjuvant induced arthritic rats. Therefore, KE improved the balance of bone resorption and bone formation, showing anti-inflammatory effects. Consequently, KE is beneficial for sufferers of bone and joint disease.

The chemical biology of nitric oxide--an outsider's reflections about its role in osteoarthritis

Excess formation of nitric oxide (NO) has been invoked in the development of osteoarthritis and blamed for triggering chondrocyte apoptosis and matrix destruction. Much of the evidence for a deleterious role of NO in disease progression has been obtained indirectly and inferred from the measurement of nitrite/nitrate and nitrotyrosine concentrations as well as iNOS expression in biopsy specimen, cartilage explants and cytokine-stimulated cells in culture. While these results clearly indicate an involvement of NO and suggest additional contributions from oxidative stress-related components they do not necessarily establish a cause/effect relationship. Many NO metabolites are not mere dosimeters of local NO production but elicit potent down-stream effects in their own right. Moreover, oxygen tension and other experimental conditions typical of many in vitro studies would seem to be at odds with the particular situation in the joint. Recent insight into the chemical biology of NO, in particular with regard to cellular redox-regulation, mitochondrial signaling and nitration reactions, attest to a much richer network of chemical transformations and interactions with biological targets than hitherto assumed. In conjunction with the emerging biology of nitrite and nitrate this information challenges the validity of the long-held view that "too much NO" is contributing to disease progression. Instead, it suggests that part of the problem is a shift from NO to superoxide-dominated chemistries triggering changes in thiol-dependent redox signaling, hypoxia-induced gene expression and mitochondrial function. This essay aims to provide a glimpse into research areas that may hold promise for future investigations into the underlying causes of osteoarthritis.

Janus kinase 3 inhibitor WHI-P154 in macrophages activated by bacterial endotoxin: differential effects on the expression of iNOS, COX-2 and TNF-alpha

Bacterial endotoxin is a potent inducer of inflammatory response, including the induction of inducible nitric oxide synthase (iNOS) expression and nitric oxide (NO) production, and the expression of cyclo-oxygenase (COX)-2 and tumor necrosis factor (TNF)-alpha in inflammatory cells. In the present study, we investigated the effects of pharmacological inhibition of Janus kinase (JAK) 3 on the production of these proinflammatory molecules in macrophages exposed to bacterial endotoxin (lipopolysaccharide; LPS). JAK3 inhibitors WHI-P154 (4-(3'-bromo-4'-hydroxylphenyl)-amino-6,7-dimethoxyquinazoline) and its derivative WHI-P131 inhibited LPS-induced iNOS expression and NO production in a dose-dependent manner. WHI-P154 inhibited the activation of signal transducer and activator of transcription (STAT) 1 and the expression of iNOS mRNA but it had no effect on iNOS mRNA decay when determined by actinomycin D assay. The JAK3 inhibitor had no effect on COX-2 expression, and TNF-alpha production was slightly inhibited only at higher drug concentrations (30 microM). In addition, WHI-P154 inhibited iNOS expression and NO production also in human epithelial cells. Our results suggest that JAK3 inhibition modulates human and murine iNOS expression and NO production in response to inflammatory stimuli.