Role of mitogen-activated protein kinases and tyrosine kinases on IL-1-Induced NF-kappaB activation and iNOS expression in bovine articular chondrocytes

The protective effect of 3-indolepropanoic acid on aflatoxin B1-induced systemic perturbation of the liver and kidney function in rats

Aflatoxin B1 (AFB1) is known to derange the hepatorenal system by redox, DNA adduct formation and apoptotic networks. Endogenous 3-indole propionic acid (3-IPA) is a metabolite of tryptophan metabolism by gut microbiota that can protect against redox imbalance, inflammation and cellular lipid damage. We investigated the beneficial effect of 3-IPA against AFB1-mediated organ toxicity in male rats post 28 days of consecutive treatment. The 3-IPA (25 and 50 mg/kg) was orally administered alongside AFB1 (50 μg/kg) treatment. Biochemical and enzyme-linked immunosorbent assays were utilised to examine biomarkers of hepatorenal function, oxidative status and inflammation. DNA damage and apoptosis were also assessed, and histological staining techniques were used to investigate hepatorenal tissues for pathological indicators. The 3-IPA supplementation abated AFB1-mediated increases in biomarkers of hepatic and renal dysfunction in rat serum. Co-administration of 3-IPA further reduced AFB1-induced redox imbalance (by upregulating antioxidant mediators and enzymes [GSH, TSH, Trx, Trx-R, SOD, CAT, GPx and GST]; reducing reactive oxygen species, lipid peroxidation and DNA adduct [RONS, LPO and 8-OH-dG] formation; suppressing pro-inflammatory and apoptotic mediators [XO, MPO, NO, IL-1β and Casp -9 and -3]; and upregulating the level of interleukin 10 (IL-10). Moreover, treatment with 3-IPA lessened hepatorenal tissue injuries. These findings suggest that augmenting 3-IPA endogenously from tryptophan metabolism may provide a novel strategy to forestall xenobiotics-mediated hepatorenal toxicity, including AFB1.

Prevention of Oxidative Stress and Diseases by Antioxidant Supplementation

Excessive and uncontrolled oxidative stress can damage biomacromolecules, such as lipids, proteins, carbohydrates, and DNA, by free radical and oxidant overproduction. In this review, we critically discuss the main properties of free radicals, their implications in oxidative stress, and specific pathological conditions. In clinical medicine, oxidative stress can play a role in several chronic noncommunicable diseases, such as diabetes mellitus, cardiovascular, inflammatory, neurodegenerative diseases, and tumours. Antioxidant supplements can theoretically prevent or stop the progression of diseases, but a careful literature analysis finds that more evidence is needed to dissect the ultimate beneficial effect of antioxidants versus reactive oxygen species in several diseases.

Recent Advances in Reactive Oxygen Species (ROS)-Responsive Polyfunctional Nanosystems 3.0 for the Treatment of Osteoarthritis

Osteoarthritis (OA) is an inflammatory and degenerative joint disease with severe effects on individuals, society, and the economy that affects millions of elderly people around the world. To date, there are no effective treatments for OA; however, there are some treatments that slow or prevent its progression. Polyfunctional nanosystems have many advantages, such as controlled release, targeted therapy and high loading rate, and have been widely used in OA treatment. Previous mechanistic studies have revealed that inflammation and ROS are interrelated, and a large number of studies have demonstrated that ROS play an important role in different types of OA development. In this review article, we summarize third-generation ROS-sensitive nanomaterials that scavenge excessive ROS from chondrocytes and osteoclasts in vivo. We only focus on polymer-based nanoparticles (NPs) and do not review the effects of drug-loaded or heavy metal NPs. Mounting evidence suggests that polyfunctional nanosystems will be a promising therapeutic strategy in OA therapy due to their unique characteristics of being sensitive to changes in the internal environment.

Pentosan polysulfate inhibits IL-1β-induced iNOS, c-Jun and HIF-1α upregulation in canine articular chondrocytes

Osteoarthritic (OA) chondrocytes are shown to express inducible nitric oxide synthase (iNOS) which produces high concentrations of nitric oxide (NO), particularly when stimulated with proinflammatory cytokines. NO is involved in OA cartilage degradation. On the other hand, c-Jun N-terminal Kinase (JNK) pathway mediates the activation and transcription of c-Jun, which is required for interleukin-1 (IL-1)-induction of matrix metalloproteinases-13 (MMP-13) in OA pathogenesis. Therefore, the selective inhibition of iNOS and c-Jun is a promising target for treatment and prevention of OA. The purpose of the study was to investigate the inhibitory effects of pentosan polysulfate (PPS) on IL-1β-induced iNOS, c-Jun and HIF-α isoforms upregulation in canine articular chondrocytes (CACs). Primary (P0) chondrocytes were isolated and cultured from femoral head cartilages of three (3) dogs. First passage (P1) chondrocytes were preincubated with 0, 1, 5, 15 and 40 μg/mL of PPS for 4 hr before treatment with 10 ng/mL rhIL-1β for a further 8 hr. In addition, we evaluated the effects of single and multiple cytokine with or without LPS on iNOS protein induction. PPS significantly inhibited (P < 0.05) IL-1β-induced iNOS, c-Jun and HIF-1α mRNA upregulation in a dose-dependent pattern. iNOS mRNA was significantly inhibited at 15 and 40 μg/mL whereas c-Jun and HIF-1α were significantly downregulated at 5, 15 and 40 μg/mL of PPS compared to chondrocytes treated with only rhIL-1β. Intriguingly, CACs were recalcitrant to single IL-1β, TNF-α or LPS-induction of iNOS protein including to a combination of IL-1β+TNF-α, IL-1β+LPS except to TNF-α+LPS and IL-1β+TNF-α+LPS suggestive of a protective mechanism from iNOS detrimental effects on perpetuating OA. IL-1β+TNF-α+LPS-induced iNOS protein expression was significantly abrogated by PPS. We demonstrate for the first time that PPS is a novel inhibitor of IL-1β-induced iNOS, c-Jun, and HIF-1α mRNA upregulation and iNOS protein induction which may be beneficial for prevention and treatment OA.

Glaucomatous Optic Neuropathy: When Glia Misbehave

The loss of vision in the human eye disease, glaucoma, is due to degeneration of the axons of the retinal ganglion cells. In glaucoma, reactive astrocytes in the optic nerve head contain inducible nitric oxide synthase, which apparently produces excessive nitric oxide that damages the axons. The astrocytes respond to the elevated intraocular pressure that is characteristic of the disease. An important signal transduction pathway for the induction of nitric oxide synthase in response to pressure is the epidermal growth factor receptor tyrosine kinase. Pharmacological inhibition of the activity or the induction of inducible nitric oxide synthase may provide neuroprotection for the treatment of glaucoma.

Differential effects of the essential oils of Lavandula luisieri and Eryngium duriaei subsp. juresianum in cell models of two chronic inflammatory diseases

CONTEXT

Effective drugs to treat osteoarthritis (OA) and inflammatory bowel disease (IBD) are needed.

OBJECTIVE

To identify essential oils (EOs) with anti-inflammatory activity in cell models of OA and IBD.

MATERIALS AND METHODS

EOs from Eryngium duriaei subsp. juresianum (M. Laínz) M. Laínz (Apiaceae), Laserpitium eliasii subsp. thalictrifolium Sennen & Pau (Apiaceae), Lavandula luisieri (Rozeira) Rivas-Martínez (Lamiaceae), Othantus maritimus (L.) Hoff. & Link (Asteraceae), and Thapsia villosa L. (Apiaceae) were analyzed by GC and GC/MS. The anti-inflammatory activity of EOs (5-200 μg/mL) was evaluated by measuring inducible nitric oxide synthase (iNOS) and nuclear factor-κB (NF-κB) activation (total and phosphorylated IκB-α), in primary human chondrocytes and the intestinal cell line, C2BBe1, stimulated with interleukin-1β (IL-1β) or interferon-γ (IFN-γ), IL-1β and tumor necrosis factor-α (TNF-α), respectively.

RESULTS

The EO of L. luisieri significantly reduced iNOS (by 54.9 and 81.0%, respectively) and phosphorylated IκB-α (by 87.4% and 62.3%, respectively) in both cell models. The EO of E. duriaei subsp. juresianum caused similar effects in human chondrocytes, but was inactive in intestinal cells, even at higher concentrations. The EOs of L. eliasii subsp. thalictrifolium and O. maritimus decreased iNOS expression by 45.2 ± 8.7% and 45.2 ± 6.2%, respectively, in C2BBe1 cells and were inactive in chondrocytes. The EO of T. villosa was inactive in both cell types.

DISCUSSION AND CONCLUSION

This is the first study showing anti-inflammatory effects of the EOs of L. luisieri and E. duriaei subsp. juresianum. These effects are specific of the cell type and may be valuable to develop new therapies or as sources of active compounds with improved efficacy and selectivity towards OA and IBD.

Combination of diacerhein and antiepileptic drugs after local peripheral, and oral administration in the rat formalin test

Preclinical Research The present study was designed to evaluate the possible antinociceptive interaction between diacerhein and some antiepileptic drugs (carbamazepine, topiramate and gabapentin) on formalin-induced nociception. Diacerhein, each of the antiepileptics or a fixed dose-ratio combination of these drugs was assessed after local peripheral and oral administration in rats. lsobolographic analyses were used to define the interaction between drugs. Diacerhein, antiepileptic drugs (carbamazepine, topiramate and gabapentin) or their combinations yielded a dose-dependent antinociceptive effect when administered by both routes. Theoretical ED30 values for the combination estimated from the isobolograms were obtained as follows: diacerhein-carbamazepine (85.99 ± 7.07 μg/paw; 56.53 ± 4.56 mg/kg po), diacerhein-topiramate (197.97 ± 22.90 μg/paw; 13.06 ± 2.44 mg/kg po) and diacerhein-gabapentin (96.87 ± 17.73 μg/paw; 17.90 ± 4.70 mg/kg p.o.) for the local peripheral and oral administration routes, respectively. These values were significantly higher than the experimentally obtained ED30 values: diacerhein-carbamazepine (49.33 ± 3.37 μg/paw; 35.49 ± 7.91 mg/kg po), diacerhein-topiramate (133.00 ± 39.10 μg/paw; 8.87 ± 1.46 mg/kg po) and diacerhein-gabapentin (70.98 ± 14.73 μg/paw; 10.95 ± 3.23 mg/kg po). The combinations produced their antinociceptive effects without motor impairment in the rotarod test indicating synergistic interactions with a good side effect profile.

Ameliorating ER-stress attenuates Aeromonas hydrophila-induced mitochondrial dysfunctioning and caspase mediated HKM apoptosis in Clarias batrachus

Endoplasmic reticulum (ER)-stress and unfolding protein response (UPR) has not been implied in Aeromonas hydrophila-pathogenicity. We report increased expression of the ER-stress markers: CHOP, BiP and phospho-eIF2α in A. hydrophila-infected headkidney macrophages (HKM) in Clarias batrachus. Pre-treatment with ER-stress inhibitor, 4-PBA alleviated ER-stress and HKM apoptosis suggesting ER-UPR critical for the process. The ER-Ca(2+) released via inositol-triphosphate and ryanodine receptors induced calpain-2 mediated superoxide ion generation and consequent NF-κB activation. Inhibiting NF-κB activation attenuated NO production suggesting the pro-apoptotic role of NF-κB on HKM pathology. Calpain-2 activated caspase-12 to intensify the apoptotic cascade through mitochondrial-membrane potential (ψm) dissipation and caspase-9 activation. Altered mitochondrial ultra-structure consequent to ER-Ca(2+) uptake via uniporters reduced ψm and released cytochrome C. Nitric oxide induced the cGMP/PKG-dependent activation of caspase-8 and truncated-Bid formation. Both the caspases converge onto caspase-3 to execute HKM apoptosis. These findings offer a possible molecular explanation for A. hydrophila pathogenicity.

Sphingosine 1-phosphate counteracts the effects of interleukin-1β in human chondrocytes

OBJECTIVE

The lipid mediator sphingosine 1-phosphate (S1P) is found in the synovial fluid of osteoarthritis (OA) patients. S1P protects bovine cartilage by counteracting the effects of interleukin-1β (IL-1β). This study was undertaken to examine the interaction of S1P and IL-1β in human OA chondrocytes.

METHODS

Human cartilage was obtained from patients undergoing total knee joint replacement. Chondrocytes were cultured in monolayer and treated with IL-1β and S1P. Expression of S1P receptor subtypes and genes involved in cartilage degradation was evaluated using real-time polymerase chain reaction, immunohistochemistry, and Western blotting. S1P signaling was evaluated using inhibitors of S1P receptors and small interfering RNA (siRNA) knockdown of the S1P2 receptor. Phosphorylation of MAP kinases and NF-κB in response to IL-1β and S1P was detected by Western blotting.

RESULTS

S1P2 was identified as the most prevalent S1P receptor subtype in human OA cartilage and chondrocytes in vitro. S1P reduced expression of inducible nitric oxide synthase (iNOS) in IL-1β-treated chondrocytes. Reduction of ADAMTS-4 and matrix metalloproteinase 13 expression by S1P correlated with S1P2 expression. Pharmacologic inhibition of the S1P2 receptor, but not the S1P1 and S1P3 receptors, abrogated the inhibition of iNOS expression. Similar results were observed using siRNA knockdown. S1P signaling inhibited IL-1β-induced phosphorylation of p38 MAPK.

CONCLUSION

In human chondrocytes, S1P reduces the induction of catabolic genes in the presence of IL-1β. Activation of the S1P2 receptor counteracts the detrimental phosphorylation of p38 MAPK by IL-1β.

Diacerein decreases visceral pain through inhibition of glutamatergic neurotransmission and cytokine signaling in mice

The present study evaluated the antinociceptive effect of the pro-inflammatory cytokines inhibitor diacerein in mice and its possible mechanism of action. The antinociception produced by diacerein was tested at different sites of action, moreover selective antagonists or agonists were used to identify the mechanism that may be involved in its antinociceptive action against acetic acid-induced visceral pain. Diacerein administered systemically (intraperitoneal [i.p.] or intra-gastric [i.g.] routes), supra-spinally (i.c.v.), spinally (i.t.) or peripherally (in association with the irritant agent) inhibited the visceral nociception induced by acetic acid in mice. Interestingly, diacerein treatment (25 mg/kg, i.p. or 50 mg/kg, i.g.) produced long-lasting (for up to 4 h) inhibition of acetic acid-induced nociception. Intraperitoneal treatment of mice with diacerein (25.0 mg/kg) inhibited somatic nociception induced by i.t. injection of glutamate, NMDA, kainate, and trans-ACPD but not that caused by AMPA. Diacerein (5.0-25.0 mg/kg) also produced dose related inhibition of interleukin-1β (IL-1β) and tumor necrosis factor alpha (TNF-α) induced nociception. These results indicate that diacerein produces antinociception by inhibiting glutamatergic transmission through both ionotropic and metabotropic receptors as well as activity of pro-inflammatory cytokines.

Mechanistic aspects of inducible nitric oxide synthase-induced lung injury in burn trauma

INTRODUCTION

Although the beneficial effects of inducible nitric oxide synthase (iNOS) inhibition in acute lung injury secondary to cutaneous burn and smoke inhalation were previously demonstrated, the mechanistic aspects are not completely understood. The objective of the present study is to describe the mechanism(s) underlying these favourable effects. We hypothesised that iNOS inhibition prevents formation of excessive reactive nitrogen species and attenuates the activation of poly(ADP) (poly(adenosine diphosphate)) ribose polymerase, thus mitigating the severity of acute lung injury in sheep subjected to combined burn and smoke inhalation.

METHODS

Adult ewes were chronically instrumented for a 24-h study and allocated to groups: sham: not injured, not treated, n = 6; control: injured, not treated, n = 6; and BBS-2: injured treated with iNOS dimerisation inhibitor BBS-2, n = 6. Control and BBS-2 groups received 40% total body surface area 3rd-degree cutaneous burn and cotton smoke insufflation into the lungs under isoflurane anaesthesia.

RESULTS

Treatment with iNOS inhibitor BBS-2 significantly improved pulmonary gas exchange (partial pressure of oxygen in the blood/fraction of inspired oxygen (PaO₂/FiO₂) 409 ± 43 mmHg vs. 233 ± 50 mmHg in controls, p < 0.05) and reduced airway pressures (peak pressure 20 ± 1 cm H₂O vs. 28 ± 2 cm H₂O in controls, p < 0.05) and lung water content (lung wet-to-dry ratio 4.1 ± 0.3 vs. 5.2 ± 0.2 in controls, p < 0.05) 24h after the burn and smoke injury. BBS-2 significantly reduced the increases in lung lymph nitrite/nitrate (10 ± 3 μM vs. 26 ± 6 μM in controls, p < 0.05) and 3-nitrotyrosine (109 ± 11 (densitometry value) vs. 151 ± 18 in controls, p < 0.05). Burn/smoke-induced increases in lung tissue nitrite/nitrate, poly(ADP)ribose polymerase, nuclear factor-κB (NF-κB) activity, myeloperoxidase activity and malondialdehyde formation and interleukin (IL)-8 expression were also attenuated with BBS-2.

CONCLUSIONS

The results provide strong evidence that BBS-2 ameliorated acute lung injury by inhibiting the inducible nitric oxide synthase/reactive nitrogen species/poly(ADP-ribose) polymerase (iNOS/RNS/PARP) pathway.

Differential effects of p38MAP kinase inhibitors on the expression of inflammation-associated genes in primary, interleukin-1beta-stimulated human chondrocytes

BACKGROUND AND PURPOSE

A main challenge in the therapy of osteoarthritis (OA) is the development of drugs that will modify the disease. Reliable test systems are necessary to enable an efficient screening of therapeutic substances. We therefore established a chondrocyte-based in vitro cell culture model in order to characterize different p38MAPK inhibitors.

EXPERIMENTAL APPROACH

Interleukin-1beta (IL-1beta)-stimulated human OA chondrocytes were treated with the p38MAPK inhibitors Birb 796, pamapimod, SB203580 and the new substance CBS-3868. Birb 796- and SB203580-treated cells were analysed in a genome-wide microarray analysis. The efficacy of all inhibitors was characterized by quantitative gene expression analysis and the quantification of PGE(2) and NO release.

KEY RESULTS

Microarray analysis revealed inhibitor-specific differences in gene expression. Whereas SB203580 had a broad effect on chondrocytes, Birb 796 counteracted the IL-1beta effect more specifically. All p38MAPK inhibitors significantly inhibited the IL-1beta-induced gene expression of COX-2, mPGES1, iNOS, matrix metalloproteinase 13 (MMP13) and TNFRSF11B, as well as PGE(2) release. Birb 796 and CBS-3868 showed a higher efficacy than SB203580 and pamapimod at inhibiting the expression of COX-2 and MMP13 genes, as well as PGE(2) release. In the case of mPGES1 and TNFRSF11B gene expression, CBS-3868 exceeded the efficacy of Birb 796.

CONCLUSIONS AND IMPLICATIONS

Our test system could differentially characterize inhibitors of the same primary pharmaceutical target. It reflects processes relevant in OA and is based on chondrocytes that are mainly responsible for cartilage degradation. It therefore represents a valuable tool for drug screening in between functional in vitro testing and in vivo models.

Glucosamine sulfate reduces experimental osteoarthritis and nociception in rats: association with changes of mitogen-activated protein kinase in chondrocytes

OBJECTIVE

To study the effects of oral glucosamine sulfate on the development of osteoarthritis (OA) and to examine concomitant changes in the nociceptive behavior of rats.

METHODS

OA was induced in Wistar rats by anterior cruciate ligament transection (ACLT) of the right knee; the left knee was untreated. The OA+glucosamine group received oral glucosamine sulfate (250 mg/kg/day) in a 2-g wafer once a day for 10 consecutive weeks starting at week 5 after ACLT. The OA group was treated as above with 2-g wafers (placebo). The control group of naïve rats received 2-g wafers only. The glucosamine alone group comprised naïve rats receiving glucosamine sulfate only. Nociceptive behavior (mechanical allodynia and weight-bearing distribution of hind paws) during OA development was analyzed pre- and 3, 6, 9, 12, 15, and 18 weeks post-ACLT. Macroscopic and histologic studies were then performed on the cartilage and synovia. Immunohistochemical analysis was performed to examine the effect of glucosamine on expression of mitogen-activated protein kinases (MAPKs) in the articular cartilage chondrocytes.

RESULTS

OA rats receiving glucosamine showed a significantly lower degree of cartilage degeneration than the rats receiving placebo. Glucosamine treatment also suppressed synovitis. Mechanical allodynia and weight-bearing distribution studies showed significant improvement in the OA+glucosamine group as compared to the OA group. Moreover, glucosamine attenuated p38 and c-Jun N-terminal kinase (JNK) but increased extracellular signal-regulated kinase 1/2 (ERK) expression in OA-affected cartilage.

CONCLUSION

Our results indicate that treatment with oral glucosamine sulfate in a rat OA model (1) attenuates the development of OA, (2) concomitantly reduces nociception, and (3) modulates chondrocyte metabolism, possibly through inhibition of cell p38 and JNK and increase of ERK expression.

Muscone protects vertebral end-plate degeneration by antiinflammatory property

Most chronic neck pain is the result of degeneration of the cervical spine. IL-1beta may play an important role in intervertebral disc degeneration. This being the case, inhibiting IL-1beta could provide a therapeutic approach for reducing or preventing disc degeneration. Muscone reportedly relieves pain and suppresses inflammation. Therefore, we asked whether muscone, a potent antiinflammatory agent, could reduce proinflammatory cytokines in vitro (end-plate cartilage cultures) and end-plate degeneration in vivo (a rat model that induces intervertebral disc degeneration). In vitro, muscone reversed IL-1beta-induced upregulation of IL-1beta, tumor necrosis factor alpha, cyclooxygenase 2, inducible nitric oxide synthase, matrix metalloproteinase 13, aggrecanase 2, and nitric oxide and downregulation of Col2alpha1 and aggrecan. Pretreatment with muscone (6.25, 12.5, 25 mumol/L) inhibited the IL-1beta-induced phosphorylation of extracellular signal-regulated kinases 1/2 and c-Jun N-terminal kinase in a dose-dependent manner. In vivo, muscone inhibited the expression of prostaglandin E2, 6-keto-prostaglandin F1alpha, IL-1beta, and tumor necrosis factor alpha and recovered the structural distortion of the degenerative disc. Our findings suggest muscone is a promising agent for treating intervertebral disc degeneration through its antiinflammatory effects.

Anti-inflammatory and antinociceptive effects of Baccharis dracunculifolia DC (Asteraceae) in different experimental models

AIM OF THE STUDY

The aerial parts of Baccharis dracunculifolia D.C., popularly known as "alecrim do campo", are used in folk medicine as anti-inflammatory. The aim of the present study was to evaluate the anti-inflammatory and antinociceptive activities of the crude hydroalcoholic extract obtained from leaves of Baccharis dracunculifolia (BdE), which have not been reported.

MATERIALS AND METHODS

BdE was analyzed by HPLC and in vivo evaluated (doses ranging from 50 to 400mg/kg, p.o.) by using the acetic acid-induced abdominal constrictions, paw oedema induced by carrageenan or histamine, overt nociception models using capsaicin, glutamate or phorbol myristate acetate (PMA), formalin-induced nociception and mechanical hypernociception induced by carrageenan or complete Freund adjuvant (CFA). As positive controls it was used paracetamol in both acetic acid and formalin tests; dipyrone in capsaicin, glutamate and PMA-induced nociception; indomethacin in CFA and carrageenan-induced hypernociception models. In addition, the in vitro effects of BdE on COX-2 activity and on the activation of NF-kappaB were also evaluated.

RESULTS

BdE (50-400mg/kg, p.o.) significantly diminished the abdominal constrictions induced by acetic acid, glutamate and CFA. Furthermore, BdE also inhibited the nociceptive responses in both phases of formalin-induced nociception. BdE, administered orally, also produced a long-lasting anti-hypernociceptive effect in the acute model of inflammatory pain induced by carrageenan. It was also observed the inhibition of COX-2 activity by BdE.

CONCLUSION

In summary, the data reported in this work confirmed the traditional anti-inflammatory indications of Baccharis dracunculifolia leaves and provided biological evidences that Baccharis dracunculifolia, like Brazilian green propolis, possess antinociceptive and anti-inflammatory activities.

Increased expression of lipocalin-type prostaglandin D2 synthase in osteoarthritic cartilage

Introduction

Prostaglandin D synthase (PGDS) is responsible for the biosynthesis of PGD and J series, which have been shown to exhibit anti-inflammatory and anticatabolic effects. Two isoforms have been identified: hematopoietic- and lipocalin-type PGDS (H-PGDS and L-PGDS, respectively). The aims of this study were to investigate the expressions of H-PGDS and L-PGDS in cartilage from healthy donors and from patients with osteoarthritis (OA) and to characterize their regulation by interleukin-1-beta (IL-1β) in cultured OA chondrocytes.

Methods

The expressions of H-PGDS and L-PGDS mRNA and protein in cartilage were analyzed by real-time reverse transcriptase-polymerase chain reaction (RT-PCR) and immunohistochemistry, respectively. Chondrocytes were stimulated with IL-1β, and the expression of L-PGDS was evaluated by real-time RT-PCR and Western blotting. The roles of de novo protein synthesis and of the signalling pathways mitogen-activated protein kinases (MAPKs), nuclear factor-kappa-B (NF-κB), and Notch were evaluated using specific pharmacological inhibitors.

Results

L-PGDS and H-PGDS mRNAs were present in both healthy and OA cartilage, with higher levels of L-PGDS than H-PGDS (> 20-fold). The levels of L-PGDS mRNA and protein were increased in OA compared with healthy cartilage. Treatment of chondrocytes with IL-1β upregulated L-PGDS mRNA and protein expressions as well as PGD₂ production in a dose- and time-dependent manner. The upregulation of L-PGDS by IL-1β was blocked by the translational inhibitor cycloheximide, indicating that this effect is indirect, requiring de novo protein synthesis. Specific inhibitors of the MAPK p38 (SB 203580) and c-jun N-terminal kinase (JNK) (SP600125) and of the NF-κB (SN-50) and Notch (DAPT) signalling pathways suppressed IL-1β-induced upregulation of L-PGDS expression. In contrast, an inhibitor of the extracellular signal-regulated kinase (ERK/MAPK) (PD98059) demonstrated no significant influence. We also found that PGD₂ prevented IL-1β-induced upregulation of L-PGDS expression.

Conclusions

This is the first report demonstrating increased levels of L-PGDS in OA cartilage. IL-1β may be responsible for this upregulation through activation of the JNK and p38 MAPK and NF-κB signalling pathways. These data suggest that L-PGDS might have an important role in the pathophysiology of OA.

Interleukin-1beta and interleukin-6 disturb the antioxidant enzyme system in bovine chondrocytes: a possible explanation for oxidative stress generation

OBJECTIVE

Beside matrix metalloproteinases, reactive oxygen species (ROS) are the main biochemical factors of cartilage degradation. To prevent ROS toxicity, chondrocytes possess a well-coordinated enzymatic antioxidant system formed principally by superoxide dismutases (SODs), catalase (CAT) and glutathione peroxidase (GPX). This work was designed to assess the effects of interleukin (IL)-1beta and IL-6 on the enzymatic activity and gene expression of SODs, CAT and GPX in bovine chondrocytes.

METHODS

Bovine chondrocytes were cultured in monolayer for 4-96 h in the absence or in the presence of IL-1beta (0.018-1.8ng/ml) or IL-6 (10-100 ng/ml). To study signal transduction pathway, inhibitors of mitogen-activated protein kinases (MAPK) (PD98059, SB203580 and SP600125) (5-20 microM) and nuclear factor (NF)-kappaB inhibitors [BAY11-7082 (1-10 microM) and MG132 (0.1-10 microM)] were used. SODs, CAT and GPX enzymatic activities were evaluated in cellular extract by using colorimetric enzymatic assays. Mn SODs, Cu/Zn SOD, extracellular SOD (EC SOD), CAT and GPX gene expressions were quantified by real-time and quantitative polymerase chain reaction (PCR).

RESULTS

Mn SOD and GPX activities were dose and time-dependently increased by IL-1beta. In parallel, IL-1beta markedly enhanced Mn SOD and GPX gene expressions, but decreased Cu/Zn SOD, EC SOD and CAT gene expressions. Induction of SOD enzymatic activity and Mn SOD mRNA expression were inhibited by NF-kappaB inhibitors but not by MAPK inhibitors. IL-6 effects were similar but weaker than those of IL-1beta.

CONCLUSIONS

In conclusion, IL-1beta, and to a lesser extend IL-6, dysregulates enzymatic antioxidant defenses in chondrocyte. These changes could lead to a transient accumulation of H(2)O(2) in mitochondria, and consequently to mitochondria damage. These changes contribute to explain the mitochondrial dysfunction observed in osteoarthritis chondrocytes.

IL-1beta regulates FHL2 and other cytoskeleton-related genes in human chondrocytes

In osteoarthritis (OA), cartilage destruction is associated not only with an imbalance of anabolic and catabolic processes but also with alterations of the cytoskeletal organization in chondrocytes, although their pathogenetic origin is largely unknown so far. Therefore, we have studied possible effects of the proinflammatory cytokine IL-1beta on components of the cytoskeleton in OA chondrocytes on gene expression level. Using a whole genome array, we found that IL-1beta is involved in the regulation of many cytoskeleton-related genes. Apart from well-known cytoskeletal components, the expression and regulation of four genes coding for LIM proteins were shown. These four genes were previously undescribed in the chondrocyte context. Quantitative PCR analysis confirmed significant downregulation of Fhl1, Fhl2, Lasp1, and Pdlim1 as well as Tubb and Vim by IL-1beta. Inhibition of p38 mitogen-activated protein kinase (MAPK) by SB203580 counteracted the influence of IL-1beta on Fhl2 and Tubb expression, indicating partial involvement of this signaling pathway. Downregulation of the LIM-only protein FHL2 was confirmed additionally on the protein level. In agreement with these results, IL-1beta induced changes in the morphology of chondrocytes, the organization of the cytoskeleton, and the cellular distribution of FHL2. We conclude that L-1beta is involved in the regulation of various cytoskeletal components in human chondrocytes including the multifunctional protein FHL2. This might be relevant for the pathogenesis of OA.

Peroxisome proliferator-activated receptor gamma1 expression is diminished in human osteoarthritic cartilage and is downregulated by interleukin-1beta in articular chondrocytes

Peroxisome proliferator-activated receptor γ (PPARγ) is a nuclear receptor involved in the regulation of many cellular processes. We and others have previously shown that PPARγ activators display anti-inflammatory and chondroprotective properties in vitro and improve the clinical course and histopathological features in an experimental animal model of osteoarthritis (OA). However, the expression and regulation of PPARγ expression in cartilage are poorly defined. This study was undertaken to investigate the quantitative expression and distribution of PPARγ in normal and OA cartilage and to evaluate the effect of IL-1β, a prominent cytokine in OA, on PPARγ expression in cultured chondrocytes. Immunohistochemical analysis revealed that the levels of PPARγ protein expression were significantly lower in OA cartilage than in normal cartilage. Using real-time RT-PCR, we demonstrated that PPARγ1 mRNA levels were about 10-fold higher than PPARγ2 mRNA levels, and that only PPARγ1 was differentially expressed: its levels in OA cartilage was 2.4-fold lower than in normal cartilage (p < 0.001). IL-1 treatment of OA chondrocytes downregulated PPARγ1 expression in a dose- and time-dependent manner. This effect probably occurred at the transcriptional level, because IL-1 decreases both PPARγ1 mRNA expression and PPARγ1 promoter activity. TNF-α, IL-17, and prostaglandin E₂ (PGE₂), which are involved in the pathogenesis of OA, also downregulated PPARγ1 expression. Specific inhibitors of the mitogen-activated protein kinases (MAPKs) p38 (SB203580) and c-Jun N-terminal kinase (SP600125), but not of extracellular signal-regulated kinase (PD98059), prevented IL-1-induced downregulation of PPARγ1 expression. Similarly, inhibitors of NF-κB signaling (pyrrolidine dithiocarbamate, MG-132, and SN-50) abolished the suppressive effect of IL-1. Thus, our study demonstrated that PPARγ1 is downregulated in OA cartilage. The pro-inflammatory cytokine IL-1 may be responsible for this downregulation via a mechanism involving activation of the MAPKs (p38 and JNK) and NF-κB signaling pathways. The IL-1-induced downregulation of PPARγ expression might be a new and additional important process by which IL-1 promotes articular inflammation and cartilage degradation.

Chondroitin sulfate inhibits the nuclear translocation of nuclear factor-kappaB in interleukin-1beta-stimulated chondrocytes

Chondroitin sulfate is referred as a symptomatic slow-acting drug for osteoarthritis because it improves articular function, and reduces joint swelling and effusion. In addition, chondroitin sulfate prevents joint space narrowing of the knee. We hypothesized that the anti-inflammatory effect of chondroitin sulfate is associated to a decrease in the activation of mitogen-activated protein kinases (MAPK) and of the transcription factors nuclear factor-kappaB (NF-kappaB) and activator protein-1 (AP-1). Cultured rabbit chondrocytes were stimulated with interleukin-1beta (IL-1beta) in presence of chondroitin sulfate. Nuclear translocation of NF-kappaB and AP-1, and nitrite concentrations (as an index for nitric oxide) was assessed 48 hr later. The effect of chondroitin sulfate on IL-1beta activation of extracellular signal-regulated kinase 1/2 (Erk1/2) and p38MAPK was documented by immunoblot. The effect of chondroitin sulfate on sodium nitroprusside-induced apoptosis was evaluated with the terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labelling assay. Chondroitin sulfate reduced IL-1beta-induced NF-kappaB nuclear translocation, but not AP-1 translocation, it decreased IL-1beta-induced phosphorylation of Erk1/2 and abrogated p38MAPK phosphorylation, but did not prevent IL-1beta-induced increase in nitrite. Finally, chondroitin sulfate decreased nitroprusside-induced apoptosis of the chondrocytes. These results suggest that some of the biological activities of chondroitin sulfate may be associated to the reduction in Erk1/2 and p38MAPK phosphorylation and nuclear transactivation of NF-kappaB.

Oestrogens inhibit interleukin 1beta-mediated nitric oxide synthase expression in articular chondrocytes through nuclear factor-kappa B impairment

OBJECTIVES

To investigate the presence and functionality of oestrogen receptor alpha (ERalpha) in interleukin (IL)1beta-treated rabbit articular chondrocytes in culture, and to determine the mechanisms of 17beta oestradiol (E2) effects on IL1beta-induced inducible nitric oxide synthase (iNOS) expression.

METHODS

The presence and functionality of ERalpha were investigated by immunocytochemistry and transient expression of an E2-responsive reporter construct. iNOS expression and production were determined by transient expression of a chimeric iNOS promoter-luciferase construct and protein immunoblotting. Nitric oxide (NO) production was determined by the Griess reaction. DNA-binding activities of nuclear factor-kappaB (NF-kappaB) and activated protein 1 were determined by electrophoretic mobility shift assay (EMSA)-ELISA assays. Nuclear translocation of p65 was studied by immunocytochemistry.

RESULTS

ERalpha was identified in the nucleus of chondrocytes. ERalpha efficiently transactivated a transiently expressed E2-responsive construct. On IL1beta treatment, ERalpha partially diffused from its nuclear localisation into the cytoplasm and its transactivation ability was impaired. Nevertheless, E2, tamoxifen and raloxifene efficiently inhibited IL1beta-induced NO production (-34%, -31% and -36%, respectively). E2 decreased IL1beta-induced iNOS protein expression (-40%). Transient expression of an iNOS promoter construct strongly suggested that iNOS expression was inhibited at the transcriptional level, and EMSA-ELISA assays showed that E2 reduced (-60%) the IL1beta-induced p65 DNA-binding capacity. Finally, the p65 nuclear translocation induced by IL1beta was also strongly decreased by E2.

CONCLUSIONS

Our data support a reciprocal antagonism between oestrogens and IL1beta, ultimately resulting in the decrease of cytokine-dependent NO production through transcriptional inhibition of iNOS expression. This effect was associated with selective inhibition of p65 DNA binding and nuclear translocation.

Differential regulation of cyclooxygenase-2 and inducible nitric oxide synthase by 4-hydroxynonenal in human osteoarthritic chondrocytes through ATF-2/CREB-1 transactivation and concomitant inhibition of NF-κB signaling cascade

4-hydroxynonenal (HNE), a lipid peroxidation end product, is produced abundantly in osteoarthritic (OA) articular tissues and was recently identified as a potent catabolic factor in OA cartilage. In this study, we provide additional evidence that HNE acts as an inflammatory mediator by elucidating the signaling cascades targeted in OA chondrocytes leading to cyclooxygenase-2 (COX-2) and inducible nitric oxide synthase (iNOS) gene expression. HNE induced COX-2 protein and mRNA levels with accompanying increases in prostaglandin E2 (PGE(2)) production. In contrast, HNE had no effect on basal iNOS expression or nitric oxide (NO) release. However, HNE strongly inhibited IL-1beta-induced iNOS or NO production. Transient transfection experiments revealed that the ATF/CRE site (-58/-53) is essential for HNE-induced COX-2 promoter activation and indeed HNE induced ATF-2 and CREB-1 phosphorylation as well as ATF/CRE binding activity. Overexpression of p38 MAPK enhanced the HNE-induced ATF/CRE luciferase reporter plasmid activation, COX-2 synthesis and promoter activity. HNE abrogated IL-1beta-induced iNOS expression and promoter activity mainly through NF-kappaB site (-5,817/-5,808) possibly via suppression of IKKalpha-induced IkappaBalpha phosphorylation and NF-kappaB/p65 nuclear translocation. Upon examination of upstream signaling components, we found that IKKalpha was inactivated through HNE/IKKalpha adduct formation. Taken together, these findings illustrate the central role played by HNE in the regulation of COX-2 and iNOS in OA. The aldehyde induced selectively COX-2 expression via ATF/CRE activation and inhibited iNOS via IKKalpha inactivation.

IL-1beta, an immediate early protein secreted by activated microglia, induces iNOS/NO in C6 astrocytoma cells through p38 MAPK and NF-kappaB pathways

In the present study we sought to examine cell-cell interactions by investigating the effects of factors released by stimulated microglia on inducible nitric oxide (NO) synthase (iNOS) induction in astrocytoma cells. After examining the temporal profiles of proinflammatory molecules induced by lipopolysaccharide (LPS) stimulation in BV2 microglial cells, iNOS and IL-1beta were observed to be the first immediate-response molecules. Removal of LPS after 3 hr stimulation abrogated NO release, whereas a full induction of IL-1beta was retained in BV2 cells. We observed consistently that conditioned medium (CM) from activated microglia resulted in the induction of iNOS in C6 cells, and IL-1beta was shown to be a key regulator of iNOS induction. An IL-1beta-neutralizing antibody diminished NO induction. Incubation with recombinant IL-1beta stimulated NO release to a lesser extent compared to microglial CM; co-treatment of LPS and IL-1beta had a potent, synergistic effect on NO release from C6 cells. Transient transfection with MEK kinase 1 (MEKK1) or nuclear factor-kappa B (NF-kappaB) expression plasmids induced iNOS, and IL-1beta further enhanced the MEKK1 response. Furthermore, IL-1beta-mediated NO release from C6 cells was significantly suppressed by inhibition of p38 mitogen activated protein kinase (MAPK) or NF-kappaB by specific chemical inhibitors. Both IL-1beta and MEKK1 stimulated p38 and JNK MAPKs, as well as the NF-kappaB pathway, to induce iNOS in C6 cells. Microglia may represent an anti-tumor response in the central nervous system, which is potentiated by the local secretion of immunomodulatory factors that in turn affects astrocytoma (glioma) cells. A better understanding of microglia-glioma or microglia-astrocyte interactions will help in the design of novel immune-based therapies for brain tumors or neuronal diseases.

Angiotensin II type 2 receptor-bradykinin B2 receptor functional heterodimerization

Angiotensin II type 2 (AT2R) or bradykinin B2 (B2R) receptor activation enhances NO production. Recently, we demonstrated enhancement of NO production when AT2R and B2R are simultaneously activated in vivo. However, the mechanism involved in this enhancement is unknown. Using confocal fluorescence resonance energy transfer microscopy, we report the distance between the AT2R and B2R in PC12W cell membranes to be 50+/-5 A, providing evidence and quantification of receptor heterodimerization as the mechanism for enhancing NO production. The rate of AT2R-B2R heterodimer formation is largely a function of the degree of AT2R-B2R expression. The physical association between the dimerized receptors initiates changes in intracellular phosphoprotein signaling activities leading to phosphorylation of c-Jun terminal kinase, phosphotyrosine phosphatase, inhibitory protein kappaBalpha, and activating transcription factor 2; dephosphorylation of p38 and p42/44 mitogen-activated protein kinase and signal transducer inhibitor of transcription 3; and enhancing production of NO and cGMP. Controlling the expression of AT2R-B2R, consequently influencing their biologically active dimerization, presents a potential therapeutic target for the treatment of hypertension and other cardiovascular and renal disorders.

Peroxynitrite-modified collagen-II induces p38/ERK and NF-kappaB-dependent synthesis of prostaglandin E2 and nitric oxide in chondrogenically differentiated mesenchymal progenitor cells

OBJECTIVE

Peroxynitrite (ONOO(-)) is formed in the inflamed and degenerating human joint. Peroxynitrite-modified collagen-II (PMC-II) was recently discovered in the serum of patients with osteoarthritis (OA) and rheumatoid arthritis (RA). Therefore we investigated the cellular effects of PMC-II on human mesenchymal progenitor cells (MPCs) as a model of cartilage and cartilage repair cells in the inflamed and degenerating joint.

DESIGN

MPCs were isolated from the trabecular bone of patients undergoing reconstructive surgery and were differentiated into a chondrogenic lineage. Cells were exposed to PMC-II and levels of the proinflammatory mediators nitric oxide (*NO) and prostaglandin E(2) (PGE(2)) measured. Levels of inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2), phosphorylated mitogen activated protein kinases (MAPKs) and nuclear factor kappa B (NF-kappaB) activation were measured by enzyme linked immunosorbent assay (ELISA) together with specific MAPK and NF-kappaB inhibitors.

RESULTS

PMC-II induced ()NO and PGE(2) synthesis through upregulation of iNOS and COX-2 proteins. PMC-II also lead to the phosphorylation of MAPKs, extracellularly regulated kinase 1/2 (ERK1/2) and p38 [but not c-Jun NH(2)-terminal kinase (JNK1/2)] and the activation of proinflammatory transcription factor NF-kappaB. Inhibitors of p38, ERK1/2 and NF-kappaB prevented PMC-II induced ()NO and PGE(2) synthesis, iNOS and COX-2 protein expression and NF-kappaB activation.

CONCLUSION

iNOS, COX-2, NF-kappaB and MAPK are known to be activated in the joints of patients with OA and RA. PMC-II induced iNOS and COX-2 synthesis through p38, ERK1/2 and NF-kappaB dependent pathways suggesting a previously unidentified pathway for the synthesis of the proinflammatory mediators, ()NO and PGE(2), further suggesting that inhibitors of these pathways may be therapeutic in the inflamed and degenerating human joint.

The effects of diacerhein on mechanical allodynia in inflammatory and neuropathic models of nociception in mice

In this study we analyzed the systemic antiallodynic properties of diacerhein, a drug used to treat osteoarthritis, in inflammatory and neuropathic models of nociception in mice. The effects of diacerhein were compared with those of gabapentin, a drug used clinically for the management of neuropathic pain. Similar to gabapentin, diacerhein was able to significantly reverse the mechanical allodynia induced by carrageenan. A significant inhibition of carrageenan-induced nociception was also observed when diacerhein was administered by the intrathecal but not by the intraplantar route. The treatment with diacerhein or with gabapentin also inhibited the mechanical allodynia induced by complete Freund's adjuvant (CFA) or after the partial ligation of the sciatic nerve (PLSN). In the same range of doses, diacerhein or gabapentin did not affect the locomotor activity, motor coordination, or body temperature of the animals. The present results indicate that diacerhein produces marked antiallodynic effects in carrageenan and CFA nociception models and also inhibits the neuropathic pain after PLSN, with an efficacy similar to that observed for gabapentin. Diacerhein may be a potentially interesting tool for the management of inflammatory and neuropathic pain.

Octacalcium phosphate crystals directly stimulate expression of inducible nitric oxide synthase through p38 and JNK mitogen-activated protein kinases in articular chondrocytes

Basic calcium phosphate (BCP) crystals, including hydroxyapatite, octacalcium phosphate (OCP) and carbonate-apatite, have been associated with severe osteoarthritis and several degenerative arthropathies. Most studies have considered the chondrocyte to be a bystander in the pathogenesis of calcium crystal deposition disease, assuming that synovial cell cytokines were the only triggers of chondrocyte activation. In the present study we identified direct activation of articular chondrocytes by OCP crystals, which are the BCP crystals with the greatest potential for inducing inflammation. OCP crystals induced nitric oxide (NO) production and inducible nitric oxide synthase (NOS) mRNA expression by isolated articular chondrocytes and cartilage fragments, in a dose-dependent manner and with variations over time. OCP crystals also induced IL-1β mRNA expression. Using pharmacological and cytokine inhibitors, we observed that OCP crystals induced NO production and inducible NOS mRNA activation were regulated at both the transcriptional and the translational levels; were independent from IL-1β gene activation; and involved p38 and c-Jun amino-terminal kinase (JNK) mitogen-activated protein kinase (MAPK) pathways, as further confirmed by OCP crystal-induced p38 and JNK MAPK phosphorylation. Taken together, our data suggest that the transcriptional inducible NOS response to OCP crystals involved both the p38 and the JNK MAPK pathways, probably under the control of activator protein-1. NO, a major mediator of cartilage degradation, can be directly produced by BCP crystals in chondrocytes. Together with synovial activation, this direct mechanism may be important in the pathogenesis of destructive arthropathies triggered by microcrystals.

Signalling pathway involved in nitric oxide synthase type II activation in chondrocytes: synergistic effect of leptin with interleukin-1

The objective of the present study was to investigate the effect of leptin, alone or in combination with IL-1, on nitric oxide synthase (NOS) type II activity in vitro in human primary chondrocytes, in the mouse chondrogenic ATDC5 cell line, and in mature and hypertrophic ATDC5 differentiated chondrocytes. For completeness, we also investigated the signalling pathway of the putative synergism between leptin and IL-1. For this purpose, nitric oxide production was evaluated using the Griess colorimetric reaction in culture medium of cells stimulated over 48 hours with leptin (800 nmol/l) and IL-1 (0.025 ng/ml), alone or combined. Specific pharmacological inhibitors of NOS type II (aminoguanidine [1 mmol/l]), janus kinase (JAK)2 (tyrphostin AG490 and Tkip), phosphatidylinositol 3-kinase (PI3K; wortmannin [1, 2.5, 5 and 10 micromol/l] and LY294002 [1, 2.5, 5 and 10 micromol/l]), mitogen-activated protein kinase kinase (MEK)1 (PD098059 [1, 5, 10, 20 and 30 micromol/l]) and p38 kinase (SB203580 [1, 5, 10, 20 and 30 micromol/l]) were added 1 hour before stimulation. Nitric oxide synthase type II mRNA expression in ATDC5 chondrocytes was investigated by real-time PCR and NOS II protein expression was analyzed by western blot. Our results indicate that stimulation of chondrocytes with IL-1 results in dose-dependent nitric oxide production. In contrast, leptin alone was unable to induce nitric oxide production or expression of NOS type II mRNA or its protein. However, co-stimulation with leptin and IL-1 resulted in a net increase in nitric oxide concentration over IL-1 challenge that was eliminated by pretreatment with the NOS II specific inhibitor aminoguanidine. Pretreatment with tyrphostin AG490 and Tkip (a SOCS-1 mimetic peptide that inhibits JAK2) blocked nitric oxide production induced by leptin/IL-1. Finally, wortmannin, LY294002, PD098059 and SB203580 significantly decreased nitric oxide production. These findings were confirmed in mature and hypertrophic ATDC5 chondrocytes, and in human primary chondrocytes. This study indicates that leptin plays a proinflammatory role, in synergy with IL-1, by inducing NOS type II through a signalling pathway that involves JAK2, PI3K, MEK-1 and p38 kinase.

Effect of hypoxia and reoxygenation on gene expression and response to interleukin-1 in cultured articular chondrocytes

OBJECTIVE

To determine the effects of hypoxia and reoxygenation on the metabolism of chondrocytes and their response to interleukin-1beta (IL-1beta). The study included activation of hypoxia-inducible factor 1 (HIF-1), NF-kappaB, and activator protein 1 (AP-1) transcription factors, expression of matrix components and metalloproteases and transforming growth factor beta (TGFbeta) and TGFbeta receptors, and production of nitric oxide (NO) and prostaglandin E(2) (PGE(2)).

METHODS

Bovine articular chondrocytes (BACs) were cultured to confluency in either 5% O(2) (hypoxia) or 21% O(2) (normoxia) in media supplemented with 10% fetal calf serum (FCS). BACs were preincubated for 18 hours in media with 1% FCS only and then incubated for 24 hours in the presence of IL-1beta. For reoxygenation experiments, cells were treated in the same way in 5% O(2), except that cultures were transferred to normal atmospheric conditions and used after 4 hours for RNA extraction or after 30 minutes for cytoplasmic or nuclear protein extraction.

RESULTS

In hypoxic and reoxygenated chondrocytes, we observed strong DNA binding of HIF-1. IL-1beta-induced DNA binding of NF-kappaB and AP-1 was significantly higher in hypoxic and reoxygenated cultures than in normoxia. Greater activation of the MAPKs was also observed with IL-1beta treatment in hypoxia compared with normoxia. Steady-state levels of type II collagen and aggrecan core protein messenger RNA (mRNA) were decreased by IL-1beta in all instances. Matrix metalloprotease 1 (MMP-1) and MMP-3 mRNA were increased by IL-1beta in normoxia and hypoxia, whereas only MMP-3 mRNA was enhanced in reoxygenated cultures. The MMP-2 mRNA level was not significantly affected by IL-1beta in normoxia or hypoxia, whereas it was enhanced in reoxygenated cultures. MMP-9 mRNA was dramatically decreased by IL-1beta only in low oxygen tension. Tissue inhibitor of metalloproteinases 1 (TIMP-1) message was significantly enhanced by the cytokine in most instances, whereas TIMP-2 message was markedly decreased by IL-1beta in reoxygenated cultures. Stimulation of TGFbeta1 expression by IL-1beta was observed only in normal atmospheric conditions. One of the more striking findings of the study was the greater stimulating effect of IL-1beta on NO production observed in hypoxia, which was much higher than in normoxia, whereas the reverse was observed for IL-1beta-induced PGE(2) production.

CONCLUSION

Oxygen level and reoxygenation stress significantly modulate gene expression and the response of articular chondrocytes to cytokines such as IL-1beta. In hypoxic conditions, which mimic the in vivo condition of cartilage, the effects of IL-1beta on both synthesis and degradative processes are significantly different from those in normoxia, conditions that are unlikely encountered by chondrocytes in a normal state. In low oxygen tension, high IL-1beta-induced NO production is associated with a significant decrease in PGE(2) synthesis. These data should influence our concept of the role of oxygen in the pathophysiology of joint disease and may help define the best conditions in which to develop bioartificial cartilage.

Dexamethasone-induced and estradiol-induced CREB activation and annexin 1 expression in CCRF-CEM lymphoblastic cells: evidence for the involvement of cAMP and p38 MAPK

AIMS

Annexin 1 (ANXA1), a member of the annexin family of calcium-binding and phospholipid-binding proteins, is a key mediator of the anti-inflammatory actions of steroid hormones. We have previously demonstrated that, in the human lymphoblastic CCRF-CEM cell line, both the synthetic glucocorticoid hormone, dexamethasone (Dex), and the estrogen hormone, 17beta-estradiol (E2beta), induce the synthesis of ANXA1, by a mechanism independent of the activation of their nuclear receptors. Recently, it was reported that the gene coding for ANXA1 contains acAMP-responsive element (CRE). In this work, we investigated whether Dex and E2beta were able to induce the activation of CRE binding proteins (CREB) in the CCRF-CEM cells. Moreover, we studied the intracellular signalling pathways involved in CREB activation and ANXA1 synthesis in response to Dex and E2beta; namely, the role of cAMP and the p38 mitogen activated protein kinase (MAPK).

RESULTS

The results show that Dex and E2beta were as effective as the cAMP analogue, dBcAMP, in inducing CREB activation. On the contrary, dBcAMP induced ANXA1 synthesis as effectively as these steroid hormones. Furthermore, the cAMP antagonist, Rp-8-Br-cAMPS, and the specific p38 MAPK inhibitor,SB203580, effectively prevented both Dex-induced, E2beta-induced and dBcAMP-induced CREB activation and ANXA1 synthesis.

CONCLUSIONS

Taken together, our results suggest that,in CCRF-CEM cells, Dex-induced and E2beta-inducedANXA1 expression requires the activation of the transcription factor CREB, which in turn seems to be mediated by cAMP and the p38 MAPK. These findings also suggest that, besides the nuclear steroid hormone receptors, other transcription factors, namely CREB, may play important roles in mediating the anti-inflammatory actions of glucocorticoids and oestrogen hormones.

Regulation of metalloproteinases and NF-kappaB activation in rabbit synovial fibroblasts via E prostaglandins and Erk: contrasting effects of nabumetone and 6MNA

1 Nabumetone is a prodrug that is converted in vivo into 6-methoxy-2-naphthylacetic acid (6MNA), a cyclooxygenase inhibitor with anti-inflammatory properties. We tested the effects of nabumetone and 6MNA on the inflammatory responses of synovial fibroblasts (SFs). 2 Brief exposures to 6MNA (50-150 microm) had no effect on IL-1beta/TNF-alpha (each 20 ng ml(-1))-stimulated Erk activation. Longer exposures depleted prostaglandin E1 (PGE1) as much as 70%, and stimulated Erk as much as 300%. Nabumetone (150 microm) inhibited Erk activation by 60-80%. 6MNA (50-150 microm) stimulated (approximately 200%) and nabumetone (150 microm) inhibited (approximately 50%) matrix metalloproteinase (MMP)-1, but not MMP-13 secretion from SFs. 3 6MNA stimulation of MMP-1 secretion was inhibited approximately 30% by PGE1 (1 microm) and approximately 80% by the Erk pathway inhibitor UO126 (10 microm), confirming that PGE depletion and Erk activation mediate MMP-1 secretion by 6MNA. 4 Consistent with its role as an Erk inhibitor, nabumetone (150 microm) abrogated 6MNA enhancement of MMP-1 secretion. 5 UO126 (10 microm) and nabumetone (150 microm) inhibited (approximately 70 and 40%, respectively), but 6MNA (150 microm) enhanced (approximately 40%), NF-kappaB activation. 6 Our data indicate that 6MNA shares with other COX inhibitors several proinflammatory effects on synovial fibroblasts. In contrast, nabumetone demonstrates anti-inflammatory and potentially arthroprotective effects that have not been previously appreciated.

Rhein inhibits interleukin-1 beta-induced activation of MEK/ERK pathway and DNA binding of NF-kappa B and AP-1 in chondrocytes cultured in hypoxia: a potential mechanism for its disease-modifying effect in osteoarthritis

In the present report, we show that bovine articular chondrocytes cultured in low oxygen tension, i.e. in conditions mimicking their hypoxic in vivo environment, respond to IL-1beta (10 ng/mL) by an increased DNA binding activity of NF-kappaB and AP-1 transcription factors. Incubation of the cells with 10(-5) M rhein for 24 h was found to reduce this activity, particularly in the case of AP-1. Mitogen activated kinases (ERK-1 and ERK-2) were activated by exposure of the chondrocytes to 1-h treatment with IL-1beta. This effect was greater in hypoxia (3% O2) than in normoxia (21% O2). Rhein was capable of reducing the IL-1beta-stimulated ERK1/ERK2 pathway whatever the tension of oxygen present in the environment. The level of c-jun protein, an element of AP-1 complex, was increased by exposure of the chondrocytes to IL-1beta after 2, 6, and 24 h. Addition of rhein at 10(-5) M for 24 h did not reduce the c-jun protein amount. The mRNA steady-state levels of collagen type II (COL2A1) and aggrecan core protein were found to be significantly increased by a 24-h treatment with 10(-5) M rhein. This stimulating effect was also observed in the presence of IL-1beta, suggesting that the drug could prevent or reduce the IL-1beta-induced inhibition of extracellular matrix synthesis. IL-1-induced collagenase (MMPI) expression was significantly decreased by rhein in the same conditions. In conclusion, rhein can effectively inhibit the IL-1-activated MAPK pathway and the binding of NF-kappaB and AP-1 transcription factors, two key factors involved in the expression of several proinflammatory genes by chondrocytes. In addition, the drug can reduce the procatabolic effect of the cytokine, by reducing the MMPI synthesis, and enhance the synthesis of matrix components, such as type II collagen and aggrecan. These results may explain the antiosteoarthritic properties of rhein and its disease-modifying effects on OA cartilage, in spite of absence of inhibition at prostaglandin level.

Proline-rich tyrosine kinase 2 and Src kinase signaling transduce monosodium urate crystal-induced nitric oxide production and matrix metalloproteinase 3 expression in chondrocytes

OBJECTIVE

Articular deposition of monosodium urate monohydrate (MSU) crystals may promote cartilage and bone erosion. Therefore, the aim of this study was to determine how MSU crystals stimulate chondrocytes.

METHODS

Nitric oxide (NO) release, and expression of inducible nitric oxide synthase (iNOS) and matrix metalloproteinase 3 (MMP-3) were assessed in cultured chondrocytes treated with MSU. MSU-induced functional signaling by specific protein kinases (p38, Src, and the focal adhesion kinase [FAK] family members proline-rich tyrosine kinase 2 [Pyk-2] and FAK) was also examined using selective pharmacologic inhibitors and transfection of kinase mutants.

RESULTS

MSU induced MMP-3 and iNOS expression and NO release in chondrocytes in a p38-dependent manner that did not require interleukin-1 (IL-1), as demonstrated by using IL-1 receptor antagonist. MSU induced rapid tyrosine phosphorylation of Pyk-2 and FAK, their adaptor protein paxillin, and interacting kinase c-Src. Pyk-2 and c-Src signaling both mediated p38 MAPK activation in response to MSU. Pyk-2 and c-Src signaling played a major role in transducing MSU-induced NO production and MMP-3 expression. But, despite the observed FAK phosphorylation, a selective pharmacologic FAK inhibitor and a FAK dominant-negative mutant both failed to block MSU-induced NO release or MMP-3 expression in parallel experiments.

CONCLUSION

In chondrocytes, MSU crystals activate a signaling kinase cascade typically employed by adhesion receptors that involves upstream Src and FAK family activation and downstream p38 activation. In this cascade, Pyk-2, Src, and p38 kinases transduce MSU-induced NO production and MMP-3 expression. Our results identify Pyk-2 and c-Src as novel sites for potential therapeutic intervention in cartilage degradation in chronic gout.

Apoptosis and the loss of chondrocyte survival signals contribute to articular cartilage degradation in osteoarthritis

Apoptotic death of articular chondrocytes has been implicated in the pathogenesis of osteoarthritis (OA). Apoptotic pathways in chondrocytes are multi-faceted, although some cascades appear to play a greater in vivo role than others. Various catabolic processes are linked to apoptosis in OA cartilage, contributing to the reduction in cartilage integrity. Recent studies suggest that beta1-integrin mediated cell-matrix interactions provide survival signals for chondrocytes. The loss of such interactions and the inability to respond to IGF-1 stimulation may be partly responsible for the hypocellularity and matrix degradation that characterises OA. Here we have reviewed the literature in this area of cartilage cell biology in an effort to consolidate the existing information into a plausible hypothesis regarding the involvement of apoptosis in the pathogenesis of OA. Understanding of the interactions that promote chondrocyte apoptosis and cartilage hypocellularity is essential for developing appropriately targeted therapies for inhibition of chondrocyte apoptosis and the treatment of OA.

Differential roles of hydrogen peroxide and superoxide in mediating IL-1-induced NF-kappa B activation and iNOS expression in bovine articular chondrocytes

Our previous studies showed that reactive oxygen species (ROS) are required for the pro-inflammatory cytokine interleukin-1 beta (IL-1) to induce the activity of the Nuclear transcription Factor-kappa B (NF-kappa B) and the expression of the inducible isoform of the nitric oxide synthase (iNOS) in bovine articular chondrocytes. This study aimed at elucidating the role of hydrogen peroxide (H(2)O(2)) and the superoxide radical, two major ROS, in mediating those IL-1-induced responses. The results obtained show that chondrocytes produce both H(2)O(2) and superoxide radical in response to IL-1. Treatment of the chondrocyte cultures with H(2)O(2) alone did not induce NF-kappa B activation or iNOS expression. Addition of H(2)O(2) simultaneously with IL-1 did neither enhance nor inhibit NF-kappa B activation and iNOS expression, relatively to treatment with IL-1 alone. Accordingly, treatment with catalase did not inhibit those IL-1-induced responses. Treatment with superoxide dismutase, however, effectively prevented IL-1-induced I kappa B-alpha degradation and iNOS expression. Taken together, the results obtained indicate that superoxide mediates IL-1-induced I kappa B-alpha degradation and the consequent NF-kappa B activation and iNOS expression in chondrocytes, whereas H(2)O(2) does not seem to participate in those IL-1-induced responses. In conclusion, the present study identifies the superoxide radical as the ROS involved in mediating the IL-1-induced signaling pathway that leads to NF-kappa B activation and to the expression of NF-kappa B-dependent genes in bovine articular chondrocytes.

Comparison of the signal transduction pathways for the induction of gene expression of nitric oxide synthase-2 in response to two different stimuli

Human optic nerve astrocytes induce nitric oxide synthase-2 (NOS-2) in vitro in response to cytokines (interferon-gamma/interleukin-1beta) and elevated hydrostatic pressure. Using relatively specific inhibitors, we have compared induction of NOS-2 in response to these two stimuli to determine whether the same or different signal transduction pathways participate in the responses. Using SN50 and CAGE, which inhibit the NFkappaB pathway, the induction of NOS-2 in response to both cytokines and elevated hydrostatic pressure was blocked. Using SB202190 and SB203580, which inhibit p38 mitogen-activated protein kinase, only the response to cytokines was blocked. In contrast, when inhibitors of epidermal growth factor receptor tyrosine kinase AG 82 and AG 18 were used, the induction of NOS-2 in response to pressure, but not in response to cytokines, was blocked. Signal transduction pathways presumably regulate the synthesis of NOS-2 through downstream events that induce transcription of the NOS-2 gene. Our data suggest that activation of different sites in the promoter region of the NOS-2 gene is needed for these different stimuli to induce NOS-2.

Diacerhein and rhein prevent interleukin-1beta-induced nuclear factor-kappaB activation by inhibiting the degradation of inhibitor kappaB-alpha

Diacerhein and rhein are anthraquinone compounds that ameliorate the course of osteoarthritis. Recent reports also suggest that these compounds may have antiinflammatory properties, but the cellular mechanisms by which they exert antiosteoarthritic and possibly antiinflammatory effects are still incompletely understood. The purpose of this study was to investigate the ability of diacerhein and rhein to inhibit the activation of the transcription factor nuclear factor kappaB, induced by the proinflammatory cytokine interleukin-1beta, in primary monolayer cultures of bovine articular chondrocytes. We also studied the ability of diacerhein and rhein to prevent the expression of the inducible nitric oxide synthase gene, which is driven by nuclear factor-kappaB. We observed that interleukin-1beta induced the degradation of the inhibitor kappaB-alpha protein and the translocation of the protein p65 (a member of the nuclear factor-kappaB family) to the nucleus, which were inhibited by diacerhein and rhein, in a dose-dependent manner. Interleukin-1beta-induced nuclear factor-kappaB binding to a specific (gamma-(32)P)-labelled oligonucleotide probe was also inhibited by treatment of chondrocytes with diacerhein or rhein, as revealed by electrophoretic mobility shift assay. Inducible nitric oxide synthase mRNA and protein synthesis and nitric oxide production were also inhibited by diacerhein and rhein, in a dose-dependent manner. The half-maximal inhibitory concentrations of diacerhein and rhein, relative to nitric oxide production, were 8.2 microM ;and 7.7 microM, respectively. These results suggest that diacerhein and rhein inhibit nuclear factor-kappaB activation and, consequently, the expression of nuclear factor-kappaB-dependent genes, such as the inducible nitric oxide synthase gene, which can explain their antiosteoarthritic and antiinflammatory effects.