3-nitrotyrosine and Osteoarthritis

Osteoarthritic chondrocytes show an over-activity of inflammatory catabolic mediators, and olive products have attracted attention because they were discovered to have some benefits on osteoarthritis patients. We investigated the mechanisms of action of olive leaf polyphenolic compounds in osteoarthritic chondrocytes (OACs) using a standardized leaf extract, ZeyEX, and its main phenolic component, oleuropein, also compared with anti-inflammatory drug ibuprofen. OACs, isolated from joint-cartilages of Grade 4 OA patients, were found to express COMP and MMP-9 throughout their culture period. ZeyEX, oleuropein, and ibuprofen increased cell viability at concentrations of 1-100 nM, did not change at 500 nM-50 μM, but inhibited at ≥100 μM. The adherence profile of OACs increased with 1 μM of ibuprofen or ZeyEX and 10 nM-1 μM oleuropein. Although the markers for oxidative and nitrosative stresses (ROS and 3-NT) generally inhibited by three agents, the inhibitory effect of ZeyEX on 3-NT emerged dramatically (1 nM-10 μM). Lipid-hydroperoxides and HNE-adducts were also inhibited by each agent, but AGE-adducts unchanged by oleuropein while reduced by ZeyEX and ibuprofen. Inflammatory biomarkers, IL-1β, IL-6, Casp-1/ICE, and TNF-α, were inhibited by three agents, however osteopontin and GM-CSF by only ZeyEX and ibuprofen. A decreased COMP, TLR4, and RAGE expression levels were observed by three agents, but only the effects of ZeyEX was concentration-dependent. In particular, ZeyEX and oleuropein improved COL2, inhibited p-JNK/JNK, and increased GPx. COX2 was only inhibited by ibuprofen. The results indicate that polyphenolic-olive compounds counteract redox-sensitive inflammatory aggressions in osteoarthritic chondrocytes that may stop the progression of pathology and allow regeneration.

Topics: Aged; Aldehydes; Biomarkers; Cartilage, Articular; Cell Adhesion; Cell Survival; Chondrocytes; Female; Glycation End Products, Advanced; Humans; Ibuprofen; Inflammation Mediators; JNK Mitogen-Activated Protein Kinases; Lipid Peroxides; Male; Middle Aged; Olea; Osteoarthritis; Oxidation-Reduction; Phenol; Phosphorylation; Reactive Oxygen Species; Receptor for Advanced Glycation End Products; Toll-Like Receptor 4; Tyrosine

To evaluate the role of synovial oxidative stress on joint pathology in a spontaneous mouse model of osteoarthritis (OA) by intra-articular (IA) delivery of recombinant adeno-associated virus (rAAV) expressing anti-oxidant protein heme oxygenase-1 (HO-1).. Joint transduction by rAAV vectors was evaluated with serotype 1, 2, 5 and 8 capsids carrying LacZ gene administered by IA injections into STR/ort mice. Transduced cell types were identified by β-galactosidase staining in sectioned joints. Effect of oxidative stress on AAV transduction of primary synoviocytes in vitro was quantitated by fluorescence-activated cell sorting (FACS) analysis. In vivo, the efficacy of rAAV1/HO-1 was tested by IA administration into STR/ort mice followed by histopathological scoring of cartilage. Levels of 3-nitrotyrosine (3-NT) and HO-1 were assessed by immunohistochemistry (IHC) of joint sections.. Administration of a rAAV1 based vector into OA mouse joints resulted in transduction of the synovium, joint capsule, adipocytes and skeletal muscle while none of the serotypes showed significant cartilage transduction. All OA joints exhibited significantly elevated levels of oxidative stress marker, 3-NT, in the synovium compared to OA-resistant CBA-strain of mice. In vitro studies demonstrated that AAV transgene expression in primary synoviocytes was augmented by oxidative stress induced by H(2)O(2) and that a rAAV expressing HO-1 reduced the levels of oxidative stress. In vivo, HO-1 was increased in the synovium of STR/ort mice. However, delivery of rAAV1/HO-1 into OA joints did not reduce cartilage degradation.. AAV-mediated HO-1 delivery into OA joints during active disease was not sufficient to improve cartilage pathology in this model.

Topics: Animals; Bone Remodeling; Dependovirus; Disease Models, Animal; Gene Transfer Techniques; Heme Oxygenase-1; Hydrogen Peroxide; In Vitro Techniques; Injections, Intra-Articular; Joints; Male; Membrane Proteins; Mice; Mice, Inbred CBA; Mice, Inbred Strains; Mice, Mutant Strains; Osteoarthritis; Oxidative Stress; Synovial Membrane; Transduction, Genetic; Tyrosine

Osteoarthritis (OA) is an age-related joint disease that is characterized by degeneration of articular cartilage and chronic pain. Oxidative stress is considered one of the pathophysiological factors in the progression of OA. We investigated the effects of grape seed proanthocyanidin extract (GSPE), which is an antioxidant, on monosodium iodoacetate (MIA)-induced arthritis of the knee joint of rat, which is an animal model of human OA. GSPE (100 mg/kg or 300 mg/kg) or saline was given orally three times per week for 4 weeks after the MIA injection. Pain was measured using the paw withdrawal latency (PWL), the paw withdrawal threshold (PWT) and the hind limb weight bearing ability. Joint damage was assessed using histological and microscopic analysis and microcomputerized tomography. Matrix metalloproteinase-13 (MMP13) and nitrotyrosine were detected using immunohistochemistry. Administration of GSPE to the MIA-treated rats significantly increased the PWL and PWT and this resulted in recovery of hind paw weight distribution (P < 0.05). GSPE reduced the loss of chondrocytes and proteoglycan, the production of MMP13, nitrotyrosine and IL-1β and the formation of osteophytes, and it reduced the number of subchondral bone fractures in the MIA-treated rats. These results indicate that GSPE is antinociceptive and it is protective against joint damage in the MIA-treated rat model of OA. GSPE could open up novel avenues for the treatment of OA.

Topics: Analgesics; Animals; Antioxidants; Bone Resorption; Disease Models, Animal; Gene Expression Regulation; Humans; Interleukin-1beta; Iodoacetates; Knee Joint; Male; Matrix Metalloproteinase 13; Osteoarthritis; Pain; Plant Extracts; Proanthocyanidins; Rats; Rats, Wistar; Seeds; Tomography, Emission-Computed; Tyrosine; Vitis

The contribution of inducible nitric oxide synthase (iNOS) to oxidative/nitrative stress is well-documented in inflammation, but difficult to quantify. Using a novel, recently developed assay for 3-nitrotyrosine (3-NT), we characterized iNOS activity and its inhibition in preclinical models of inflammation. In particular, we utilized the 3-NT assay to assess the role of iNOS in the disease pathology as well as for proof of pharmacology of iNOS inhibitors in an acute endotoxin challenge model, in models of rheumatoid arthritis (RA) such as rat adjuvant- and collagen-induced arthritis (AIA and CIA) and a model of osteoarthritis (OA) such as rat sodium monoiodoacetate-induced arthritis (MIA). Quantification of nitrotyrosine was performed using immuno-affinity 2-D LC-MS/MS assay. This assay is a very specific and reproducible and is amenable to a number of biological fluids. Plasma levels of 3-NT were significantly elevated in an acute model of inflammation (rat LPS) and in models of rheumatoid arthritis (adjuvant- and collagen-induced arthritis), and osteoarthritis (monoiodoacetate-induced arthritis). Plasma 3-NT correlated with the severity of the inflammatory response; thus, a 20-fold increase was observed in the rat LPS model, a 10-fold increase in AIA, and only a 2.5-fold elevation in CIA. Pharmacological intervention with iNOS inhibitors decreased 3-NT levels and associated pathology. 3-NT determination allowed for better elucidation of the role of iNOS in RA and OA disease pathology and provided proof of pharmacology for NOS inhibitors in animal models of RA and OA.

Topics: Animals; Arthritis, Experimental; Arthritis, Rheumatoid; Biomarkers; Disease Models, Animal; Enzyme Inhibitors; Inflammation; Nitric Oxide Synthase Type II; Osteoarthritis; Rats; Severity of Illness Index; Tyrosine

To investigate the in vitro and in vivo effects of interleukin (IL)-4 on mechanical stress-induced nitric oxide (NO) expression by chondrocytes, and destruction of cartilage and NO production in an instability-induced osteoarthritis (OA) model in rat knee joints, respectively.. Cyclic tensile stress (CTS; 0.5Hz and 7% elongation) was applied to cultured normal rat chondrocytes with or without pre-incubation with recombinant rat IL-4 (rrIL-4). Inducible NO synthase (iNOS) mRNA expression and NO production were examined with real-time polymerase chain reaction and the Griess reaction, respectively. OA was induced in rat knee joints by transection of the anterior cruciate and medial collateral ligaments and resection of the medial meniscus. rrIL-4 (10, 50, and 100 ng/joint/day) was injected intra-articularly, and knee joint samples were collected 2, 4, and 6 weeks after surgery. Cartilage destruction was evaluated by the modified Mankin score and Osteoarthritis Research Society International scoring system on paraffin-embedded sections stained with safranin O. Cleavage of aggrecan and NO production were examined by immunohistochemistry for aggrecan neoepitope (NITEGE) and of nitrotyrosine (NT), respectively.. rrIL-4 down-regulated CTS-induced iNOS mRNA expression and NO production by chondrocytes. The intra-articular injection of rrIL-4 gave rise to a limited, but significant amelioration of cartilage destruction, prevention of loss of aggrecan, and decrease in the number of NT-positive chondrocytes, an effect that was not dose-dependent.. The present study suggests that IL-4 may exert chondroprotective properties against mechanical stress-induced cartilage destruction, at least in part, by inhibiting NO production by chondrocytes.

Topics: Aggrecans; Animals; Arthritis, Experimental; Cells, Cultured; Chondrocytes; Dose-Response Relationship, Drug; Femur; Gene Expression Regulation, Enzymologic; Injections, Intra-Articular; Interleukin-4; Mechanotransduction, Cellular; Nitric Oxide; Nitric Oxide Synthase Type II; Osteoarthritis; Rats; Rats, Wistar; Recombinant Proteins; Reverse Transcriptase Polymerase Chain Reaction; RNA, Messenger; Stress, Mechanical; Tyrosine

We recently reported that methionine-loaded human umbilical vein endothelial cells (HUVECs) exported homocysteine (Hcy) and were associated with hydroxyl radical generation and oxidation of lipids in LDL. Herein we have analysed the Hcy-induced posttranslational modifications (PTMs) of LDL protein. PTMs have been characterised using electrophoretic mobility shift, protein carbonyl ELISA, HPLC with electrochemical detection and Western blotting of 3-nitrotyrosine, and LDL uptake by scavenger receptors on monocyte/macrophages. We have also analysed PTMs in LDL isolated from rheumatoid (RA) and osteo-(OA) arthritis patients with cardiovascular disease (CVD). While reagent Hcy (< 50 microM) promoted copper-catalysed LDL protein oxidation, Hcy released from methionine-loaded HUVECs promoted LDL protein nitration. In addition, LDL nitration was associated with enhanced monocyte/macrophage uptake when compared with LDL oxidation. LDL protein nitration and uptake by monocytes, but not carbonyl formation, was elevated in both RA and OA patients with CVD compared with disease-matched patients that had no evidence of CVD. Moreover, a direct correlation between plasma total Hcy (tHcy) and LDL uptake was observed. The present studies suggest that elevated plasma tHcy may promote LDL nitration and increased scavenger receptor uptake, providing a molecular mechanism that may contribute to the clinical link between CVD and elevated plasma tHcy.

Topics: Adult; Aged; Arthritis, Rheumatoid; Blotting, Western; Cardiovascular Diseases; Case-Control Studies; Cells, Cultured; Chromatography, High Pressure Liquid; Copper; Electrophoretic Mobility Shift Assay; Endothelium, Vascular; Enzyme-Linked Immunosorbent Assay; Female; Homocysteine; Humans; Lipoproteins, LDL; Male; Methionine; Middle Aged; Nitrites; Osteoarthritis; Receptors, Scavenger; Tyrosine; Umbilical Veins

Increased reactive nitrogen species (RNS) production has been suggested in the pathogenesis of rheumatoid arthritis (RA), osteoarthritis (OA) as well as in systemic lupus erythematosus (SLE). They are known to have direct toxicity to cells. High concentrations of serum nitrite/nitrate and elevated urinary nitrate:creatine ratio has been found in patients with RA, OA and SLE. Reactive nitrogen species play a role in the chronicity of inflammatory reaction such as cartilage and bone destruction seen in patients with RA and OA. Arthritis is also associated with increased intra-articular formation of 3-nitrotyrosine (3-NT), which may contribute to joint damage. There is growing evidence that nitrative injury plays an important role in oxidative stress in the etiology and pathogenesis of SLE. 3-nitrotyrosine is thought to be a relatively specific marker of nitrosative damage mediated by nitric oxide (NO) and its by-products.. Commercially available poly l-tyrosine was exposed to nitrating species resulting in the formation of 3-nitrotyrosine. Antibodies present in synovial fluid and sera of 30 patients with rheumatoid arthritis, 15 patients with osteoarthritis and 15 patients with SLE were studied for their recognition of 3-NT by direct binding ELISA.. IgG from the synovial fluid (SF) of RA and OA patients, purified on protein A-Sepharose matrix, exhibited increased recognition of 3-NT, than the IgG isolated from the sera of RA and OA patients in competitive ELISA, whereas IgG isolated from the sera of SLE patients exhibited increased recognition of 3-NT, than the IgG isolated from the synovial fluid. There was a higher prevalence of antibodies against 3-NT in the synovial fluid than in the sera of patients with RA and OA. Higher level of anti-3-NT antibodies were found in the synovial fluid in the later stages of SLE when compared to the early stages but was not more than that found in the sera.. The RNS may be produced within the inflamed joints of RA and OA patients but not in SLE patients. The 3-NT levels also correlated directly with disease activity.

Topics: Arthritis, Rheumatoid; Enzyme-Linked Immunosorbent Assay; Humans; Immunoglobulin G; Lupus Erythematosus, Systemic; Osteoarthritis; Spectrum Analysis; Synovial Fluid; Tyrosine

Because nitric oxide related species have been found in the inflamed joints of patients with arthritis, we investigated whether protein nitrotyrosine (a marker of tissue exposure to peroxynitrite) is present in their synovial tissues.. Protein nitrotyrosine was detected immunohistochemically and by Western blot analysis. Synovial tissues removed surgically from 12 patients with rheumatoid arthritis (RA) (mean age 63.7 yrs) and 20 with osteoarthritis (OA) (mean age 66.6 yrs) were studied.. Nitrated proteins were detected immunohistochemically in all of 18 tissues examined. Diffuse staining of the stroma was seen in all patients, with more extensive staining in RA than OA (p = 0.008). Intense staining was detected in some lymphocytes, but not in others, even within a single lymphoid aggregate. Neutrophils did not stain for nitrotyrosine. Vascular endothelial cells stained for nitrotyrosine but adjoining smooth muscle cells did not. Both cytoplasmic and nuclear staining was seen in macrophages, endothelial cells, and lymphocytes. Numerous bands of nitrated proteins were detected by Western blot analysis of 15 synovial tissue extracts. Inducible nitric oxide synthase (iNOS) was detected immunohistochemically in endothelial cells, macrophages, vascular smooth muscle cells, and synoviocytes.. Nitrotyrosine-containing proteins were found in essentially all synovia from RA and OA patients. The most prominent site of nitration in all cases was the stroma. iNOS, the likely source of the nitrating species, was found in a variety of cell types.

Topics: Aged; Aged, 80 and over; Arthritis, Rheumatoid; Blotting, Western; Female; Humans; Immunohistochemistry; Male; Middle Aged; Osteoarthritis; Peroxynitrous Acid; Staining and Labeling; Synovial Membrane; Tyrosine

Osteoarthritis (OA) is the most common joint disease in horses. Chondrocyte apoptosis has been implicated as a major pathological OA change in humans and experimental animals but no studies have been performed on equine OA. Articular cartilage was collected from three normal and five OA horses. Histopathological changes were scored by a modified Mankin grading system. A terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL) assay was performed to identify chondrocyte apoptosis. Nitric oxide (NO) production from chondrocytes was indirectly evaluated by immunohistochemistry with polyclonal antibody to nitrotyrosine. The histopathological score and percentage of chondrocyte apoptosis from the OA cartilages were significantly higher than from normal cartilages. There was a significant correlation between histopathological grade and the percentage of chondrocyte apoptosis. OA cartilages exhibited stronger immunoreactivity to nitrotyrosine than normal cartilage. Topographical distributions of chondrocyte apoptosis, cartilage matrix degeneration, and NO production overlapped in equine OA cartilages, suggesting that these pathological phenomena are closely interrelated.

Topics: Animals; Apoptosis; Cartilage, Articular; Chondrocytes; Horse Diseases; Horses; Immunohistochemistry; In Situ Nick-End Labeling; Nitric Oxide; Osteoarthritis; Tyrosine

To determine whether oxidative damage to cartilage proteins can be detected in aging and osteoarthritic (OA) cartilage, and to correlate the results with the local production of interleukin-1beta (IL-1beta) and the responsiveness of isolated chondrocytes to stimulation with insulin-like growth factor 1 (IGF-1).. The presence of nitrotyrosine was used as a measure of oxidative damage. Histologic sections of knee articular cartilage, obtained from young adult and old adult cynomolgus monkeys, which develop age-related, naturally occurring OA, were evaluated. Each cartilage section was graded histologically on a scale of 0-7 for the presence of OA-like changes, and serial sections were immunostained using antibodies to nitrotyrosine and IL-1beta. Chondrocytes isolated and cultured from cartilage adjacent to the sections used for immunostaining were tested for their response to IGF-1 stimulation by measuring sulfate incorporation in alginate cultures. For comparison with the monkey tissues, cartilage sections from human tissue donors and from tissue removed at the time of OA-related joint replacement surgery were also immunostained for nitrotyrosine and IL-1beta.. The presence of nitrotyrosine was associated with aging and with the development of OA in cartilage samples from both monkeys and humans. All sections that were highly positive for IL-1beta also showed staining for nitrotyrosine. However, in a few sections from older adult monkeys and humans, nitrotyrosine was present but IL-1beta was absent, suggesting that some age-related oxidative damage is independent of IL-1beta. In chondrocytes that were isolated from monkey cartilage positive for nitrotyrosine or IL-1beta, the response to stimulation with IGF-1 was significantly reduced. In some samples from older adult monkeys, IGF-1 resistance was seen in cells isolated from tissue that did not stain for nitrotyrosine or IL-1beta.. Oxidative damage due to the concomitant overproduction of nitric oxide and other reactive oxygen species is present in both aging and OA cartilage. This damage can contribute to the resistance of chondrocytes to IGF-1 stimulation, but it is unlikely to be the sole cause of IGF-1 resistance in these chondrocytes.

Topics: Aging; Animals; Cartilage, Articular; Cells, Cultured; Chondrocytes; Drug Resistance; Humans; Insulin-Like Growth Factor I; Interleukin-1; Macaca fascicularis; Osteoarthritis; Oxidation-Reduction; Tyrosine

To clarify the involvement of the caspase family in the pathway of NO-induced chondrocyte apoptosis, osteoarthritis (OA) cartilage obtained from 8 patients undergoing total hip arthroplasty were used for histopathological study. Cartilage samples taken from non-fibrillated areas of femoral head resected during surgery for femoral neck fracture were used for comparison. DNA fragmentation of chondrocytes was detected by the nick end-labeling (TUNEL) method. Apoptosis was further confirmed by transmission electron microscopy. The distributions of nitrotyrosine (NT), caspase-3, and -9 were examined immunohistochemically. The populations of apoptotic as well as NT-, caspase-3-, and -9-positive cells were quantified by counting the number of cells in the superficial, middle, and deep layers, respectively. The TUNEL-positive cells were observed primarily in superficial proliferating chondrocytes, clustering chondrocytes, and deep-layer chondrocytes of OA cartilage. Few positive cells were seen in the proliferating chondrocytes in the middle layer. Positive reactions for caspase-3 and -9 were observed in chondrocytes in similar areas. Histological OA grade showed significant correlations with the mean populations of apoptotic chondrocytes (% apoptosis) over the 3 areas. The populations of NT-positive cells (% NT) over the same areas also showed significant correlation with OA grade. Positivity for caspase-3 closely correlated with the OA grade, % apoptosis and %NT. It was concluded that caspase-3 and -9 could play a role in NO-induced chondrocyte apoptosis in OA cartilage.

Topics: Aged; Aged, 80 and over; Apoptosis; Cartilage, Articular; Caspase 3; Caspase 9; Caspases; Chondrocytes; Humans; Immunohistochemistry; In Situ Nick-End Labeling; Microscopy, Electron; Middle Aged; Osteoarthritis; Tyrosine

In inflammatory arthritis, there is evidence indicating that the affected tissues produce large amounts of oxygen-free radicals and NO. Herein, we examine the biologic effects of exposure of IgG to hypochlorous acid (HOCl) and peroxynitrite (ONOO). The concentrations of IgG modified by chlorination and nitrosation were measured in synovial fluids from inflammatory and noninflammatory arthritis. Human IgG was exposed to increasing concentrations of HOCl and ONOO, and the resulting products were tested for complement component binding; binding to FcgammaRI; activation of polymorphonuclear neutrophils; effect on the Ab-combining site of Abs; and in vivo inflammatory activity in a rabbit model of acute arthritis. Rheumatoid synovial fluids contained significantly greater concentrations of nitrosated and chlorinated IgG compared with ostearthritic specimens. In vitro exposure of human IgG to HOCl and ONOO resulted in a concentration-dependent decrease in C3 and C1q fixation. The decrease in Fc domain-dependent biologic functions was confirmed by competitive binding studies to the FcgammaRI of U937 cells. HOCl-treated IgG monomer was 10 times less effective in competing for binding compared with native IgG, and ONOO-treated IgG was 2.5 times less effective. The modified IgGs were also ineffective in inducing synthesis of H(2)O(2) by human PMN. The Ag-binding domains of IgG also showed a concentration-dependent decrease in binding to Ag. The ability of the modified IgGs to induce acute inflammation in rabbit knees decreased 20-fold as gauged by the intensity of the inflammatory cell exudates. These studies clarify the modulating role of biological oxidants in inflammatory processes in which Ag-autoantibody reactions and immune complex pathogenesis may play an important role.

Topics: Acute Disease; Animals; Arthritis, Experimental; Arthritis, Rheumatoid; Binding Sites, Antibody; Complement C1q; Complement C3; Female; Free Radicals; Gout; Humans; Hydrogen Peroxide; Hypochlorous Acid; Immunoglobulin G; Male; Neutrophils; Nitrates; Osteoarthritis; Oxidation-Reduction; Oxygen; Rabbits; Receptors, IgG; Serum Albumin, Bovine; Synovial Fluid; Tyrosine

We used the experimental dog model of osteoarthritis (OA) to examine the in vivo effects of N-iminoethyl-L-lysine (L-NIL), a selective inhibitor of the inducible nitric oxide synthase (iNOS), on the tissue level and distribution of interleukin-1beta (IL-1beta), collagenase-1, stromelysin-1, cyclooxygenase-2 (COX-2), iNOS and nitrotyrosine, through immunohistochemical and morphometric analysis.. Cartilage and synovial membrane specimens were obtained from 3 experimental groups of dogs: Group I--unoperated dogs that received no treatment; Group II--dogs subjected to a sectioning of the anterior cruciate ligament of the right knee and given no treatment; and Group III--operated dogs that received oral treatment with L-NIL (10 mg/kg twice daily/po) for 10 weeks starting immediately after surgery. The operated dogs were killed 10 weeks post-surgery. The tissue distributions of IL-1beta, metalloproteases (MMP), COX-2, iNOS and nitrotyrosine were documented by immunohistochemistry using specific antibodies, and quantified by morphometric analysis.. In cartilage, the cell scores (percentage of chondrocytes staining positive for the antigen) for iNOS and 3-nitrotyrosine were dramatically enhanced in OA specimens compared to normal (p < 0.0001). However, the cartilage of dogs treated with L-NIL showed significantly lower cell scores for iNOS (p<0.0001, condyle; p<0.001, plateau), nitrotyrosine (p<0.0004; p<0.0001) and COX-2 (p<0.0001; p<0.001) compared to that of untreated OA dogs. Similar findings were observed for collagenase-1 and stromelysin-1, where the increased cell scores of these 2 MMP in OA cartilage were reduced after treatment with L-NIL (collagenase: p<0.002, condyle; p<0.0003, plateau; stromelysin: p<0.006; p<0.0001). The increased cell scores for the IL-1beta, COX-2, iNOS and nitrotyrosine found in the synovial lining and mononuclear cell infiltrate of operated animals were also found to be markedly reduced in dogs treated with L-NIL.. Our study demonstrates for the first time in vivo in an experimental model of OA, that a selective inhibition of iNOS by L-NIL and the subsequent decreased production of NO also results in a marked decrease in production of major catabolic factors such as MMP, IL-1beta and peroxynitrite, as well as a reduction in COX-2 expression.

Topics: Animals; Cartilage, Articular; Culture Techniques; Cyclooxygenase 2; Disease Models, Animal; Dogs; Dose-Response Relationship, Drug; Immunohistochemistry; Interleukin-1; Isoenzymes; Lysine; Metalloendopeptidases; Nitric Oxide; Nitric Oxide Synthase; Osteoarthritis; Prostaglandin-Endoperoxide Synthases; Sensitivity and Specificity; Statistics, Nonparametric; Synovial Membrane; Tyrosine

To examine the pathologic changes in meniscus tissue during experimental osteoarthritis (OA) and to determine the relationship between nitric oxide (NO) synthesis, apoptosis, and meniscus degradation.. OA was induced in rabbits by anterior cruciate ligament (ACL) transection. Knees were harvested after 9 weeks and assessed for OA severity. Menisci were subjected to histologic, immunohistochemical, and electron microscopic analyses for the presence of nitrotyrosine and apoptosis. Menisci were also cultured for analysis of NO production.. All menisci from joints with ACL transection demonstrated degenerative changes. A high number of apoptotic cells was present in the medial part of menisci, which contains chondrocytic cells. Menisci from nonoperated contralateral knees contained only small numbers of cells in apoptosis. Conditioned media from meniscus cultures contained similarly elevated levels of nitrite as cartilage cultures from the same arthritic knees. Nitrotyrosine immunoreactivity, an indicator of in vivo NO production, was prominent in menisci from knees with ACL transection. In addition, menisci from normal knees produced high levels of NO in response to in vitro stimulation with interleukin-1beta or lipopolysaccharide.. These observations suggest that pathologic changes in menisci are a regular feature of experimentally induced OA and are associated with NO production and meniscus cell apoptosis.

Topics: Animals; Apoptosis; Cells, Cultured; Menisci, Tibial; Nitric Oxide; Osteoarthritis; Rabbits; Tyrosine