Cytokines and other mediators in rheumatoid arthritis

New and promising type of leukotriene B4 (LTB4) antagonists based on the 1,4-benzodioxine structure

New leukotriene B4 (LTB4) antagonists have been synthesized that can be considered as potential anti-inflammatory drugs. Structures containing the dioxygenated nucleus of 1,4-benzodioxine constitute a potential group of leukotriene B4 (LTB4) antagonists. The objective of this study was to access efficient and selective LTB4 antagonists as a way to elucidate the role of LTB4 in inflammatory processes and therefore allow the development of new types of structures based on 1,4-benzodioxine. Forty-one new 1,4-benzodioxine molecules substituted at different positions of the heterocyclic nucleus were synthesized to determine the minimum structural requirements by studying structure-activity relationships. Eighteen of them were tested in vitro and in vivo for their anti-inflammatory activity related to the antagonist character of LTB4. Pharmacological tests have shown satisfactory in vitro activity for compounds 24b, 24c and 24e with IC50's of 288, 439, 477 nM respectively. The results of the in vivo tests, carried out with the compound that presented greater activity in the in vitro tests 24b, have shown significant anti-inflammatory properties.

Drug-Bearing Supramolecular Filament Hydrogels as Anti-Inflammatory Agents

We report here on the covalent conversion of the anti-inflammatory agent ketoprofen into self-assembling prodrugs that enable the effective purification of ketoprofen enantiomers, the improved selectivity and potency of ketoprofen, as well as the formation of one-component drug-bearing supramolecular hydrogels. We found that the ketoprofen hydrogelator could exhibit much-enhanced selectivity for cyclooxygenase 2 (COX-2) over COX-1, reduce the concentration of inflammatory cytokines (IL-1 and TNFα), and induce apoptosis in fibroblast-like synoviocytes while maintaining biocompatibility with healthy chondrocytes. In addition, these anti-inflammatory agent-containing hydrogels demonstrated the ability to retain the therapeutic within a joint cavity after intra-articular injection, exhibiting a slow, steady release into the plasma. We believe that upon further optimization these drug-based injectable supramolecular hydrogels could provide the basis for a local treatment strategy for rheumatoid arthritis and similar conditions.

Studies of synthetic chalcone derivatives as potential inhibitors of secretory phospholipase A2, cyclooxygenases, lipoxygenase and pro-inflammatory cytokines

Arachidonic acid metabolism leads to the generation of key lipid mediators which play a fundamental role during inflammation. The inhibition of enzymes involved in arachidonic acid metabolism has been considered as a synergistic anti-inflammatory effect with enhanced spectrum of activity. A series of 1,3-diphenyl-2-propen-1-one derivatives were investigated for anti-inflammatory related activities involving inhibition of secretory phospholipase A2, cyclooxygenases, soybean lipoxygenase, and lipopolysaccharides-induced secretion of interleukin-6 and tumor necrosis factor-alpha in mouse RAW264.7 macrophages. The results from the above mentioned assays exhibited that the synthesized compounds were effective inhibitors of pro-inflammatory enzymes and cytokines. The results also revealed that the chalcone derivatives with 4-methlyamino ethanol substitution seem to be significant for inhibition of enzymes and cytokines. Molecular docking experiments were carried out to elucidate the molecular aspects of the observed inhibitory activities of the investigated compounds. Present findings increase the possibility that these chalcone derivatives might serve as a beneficial starting point for the design and development of improved anti-inflammatory agents.

Pharmacological evaluation and docking studies of α,β-unsaturated carbonyl based synthetic compounds as inhibitors of secretory phospholipase A₂, cyclooxygenases, lipoxygenase and proinflammatory cytokines

Arachidonic acid and its metabolites have generated high level of interest among researchers due to their vital role in inflammation. The inhibition of enzymes involved in arachidonic acid metabolism has been considered as synergistic anti-inflammatory effect. A series of novel α,β-unsaturated carbonyl based compounds were synthesized and evaluated for their inhibitory activity on secretory phospholipase A₂ (sPLA₂), cyclooxygenases (COX), soybean lipoxygenase (LOX) in addition to proinflammatory cytokines comprising IL-6 and TNF-α. Six α,β-unsaturated carbonyl based compounds (2, 3, 4, 12, 13 and 14) exhibited strong inhibition of sPLA₂ activity, with IC₅₀ values in the range of 2.19-8.76 μM. Nine compounds 1-4 and 10-14 displayed inhibition of COX-1 with IC₅₀ values ranging from 0.37 to 1.77 μM (lower than that of reference compound), whereas compounds 2, 10, 13 and 14 strongly inhibited the COX-2. The compounds 10-14 exhibited strong inhibitory activity against LOX enzyme. All compounds were evaluated for the inhibitory activities against LPS-induced TNF-α and IL-6 release in the macrophages. On the basis of screening results, five active compounds 3, 4, 12, 13 and 14 were found strong inhibitors of TNF-α and IL-6 release in a dose-dependent manner. Molecular docking experiments were performed to clarify the molecular aspects of the observed COX and LOX inhibitory activities of the investigated compounds. Present findings increases the possibility that these α,β-unsaturated carbonyl based compounds might serve as beneficial starting point for the design and development of improved anti-inflammatory agents.

The Discovery of Orally Active Triaminotriazine Aniline Amides as Inhibitors of p38 MAP Kinase

A new structural class of triaminotriazine aniline amides possessing potent p38 enzyme activity has been discovered. The initial hit (compound 1a) was identified through screening the Pharmacopeia ECLiPS compound collection. SAR modification led to the identification of a short acting triaminotriazine aniline methoxyamide (compound 1m) possessing in vitro and in vivo oral activity in animal models of acute and chronic inflammatory disease. An X-ray crystal structure of compound 1m in this class, cocrystallized with unactivated p38 alpha protein, indicates that these compounds bind to the ATP binding pocket and possess key H-bonding interactions within a deeper cleft. Hydrogen bonding between one of the triazine nitrogens and the backbone NH of the Met109 residue occurs through a water molecule. The methoxyamide NH and carbonyl oxygen are within H-bonding distance of Glu71 and Asp168.

Inflammatory cytokines released from the facet joint tissue in degenerative lumbar spinal disorders

STUDY DESIGN

A prospective study of surgical cases of degenerative lumbar spinal disorders demonstrated inflammatory cytokines in the facet joint tissue.

OBJECTIVE

To quantify various inflammatory cytokines released from the facet joint tissue in surgical cases of degenerative lumbar spinal disorders.

SUMMARY OF BACKGROUND DATA

In degenerative lumbar spinal disorders, pain is often caused by osteoarthritis of a facet joint. There are inflammatory mediators such as prostaglandins and leukotrienes in facet joint tissue in lumbar spinal degeneration. However, no reports have studied if there are also inflammatory cytokines in the facet joint, which generated arthropathic changes in degenerative lumbar spinal disorder and if pain is caused by chemical factors associated with inflammation such as inflammatory cytokines.

METHODS

Forty patients with degenerative lumbar disorders who had undergone operative treatment were included in this study. Fifty-five joint cartilages and 67 synovia were harvested from the lumbar facet joints in responsible intervertebral levels of patients. There were 24 male and 16 female subjects with average ages of 50 and 67 years, respectively, in 11 cases of lumbar disc herniation and 29 cases of lumbar spinal canal stenosis. Using ELISA and CLEIA methods, joint cartilage and synovial tissues were harvested during surgery from the facet joint at the responsible upper levels to measure IL-1beta, TNF-alpha, and IL-6 in individual tissues.

RESULTS

IL-1beta was detected in joint cartilage and synovium in both groups and its positive reaction rate was higher in LSCS than in LDH. There was no difference in IL-1beta concentration in cartilage tissue between the two groups. There was TNF-alpha in the synovium of LSCS. IL-6 was high in joint cartilage and synovium in both groups. The concentration was significantly higher in LSCS than in LDH.

CONCLUSIONS

There are inflammatory cytokines in facet joint tissue at high levels in degenerative lumbar spinal disorders. Inflammatory cytokines have a higher concentration rate in lumbar spinal canal stenosis than in lumbar disc herniation. This finding suggests that inflammatory cytokines in degenerated facet joints may have some relation to the cause of pain in degenerative lumbar disorders.

Synthesis and Structure−Activity Relationship of Aminobenzophenones. A Novel Class of p38 MAP Kinase Inhibitors with High Antiinflammatory Activity

We wish to report the synthesis and structure-activity relationship (SAR) of a series of 4-aminobenzophenones, as a novel compound class with high antiinflammatory activity. Our initial lead, (4-[(2-aminophenyl)amino]phenyl)(phenyl)methanone (3), was systematically optimized and resulted in compounds that potently inhibited the release of the proinflammatory cytokines IL-1beta and TNF-alpha in human peripheral blood mononuclear cells stimulated by LPS. One of the most potent compounds, among others, was (4-[(2-aminophenyl)amino]-2-chlorophenyl)(2-methylphenyl)methanone (45) with IC(50) values of 14 and 6 nM for the inhibition of IL-1beta and TNF-alpha, respectively. Furthermore, we found these types of compounds to be potent and selective p38 MAP kinase inhibitors, e.g. 45 had an IC(50) value of 10 nM. Molecular modeling was used to rationalize our SAR data and to propose a model for the interaction of compound 45 with the p38 MAP kinase. The model involved a favorable hydrogen bond between the carbonyl group of the benzophenone and the NH of Met-109, positioning ring A in the hydrophobic pocket I of the enzyme. Good antiinflammatory effects were demonstrated in two murine models of dermatitis after topical application (oxazolone and TPA model).

Tryptophan catabolism in synovial fluid of various arthropathies and its relationship with inflammatory cytokines

Synovial fluids (SF) from patients with rheumatoid arthritis (RA), psoriatic arthritis (PsA), gout, and osteoarthritis (OA) were investigated for the levels of interleukin (IL)-1 beta, IL-6 and IL-8, tryptophan (Trp) and indoleamine 2,3-dioxygenase (IDO) activity. Significant differences exist in the levels of IL-1 beta between inflammatory arthritides RA, PsA and gout and non inflammatory arthritis, such as OA. The highest concentration of IL-1 beta was found in RA, that showed high levels also of IL-6 and IL-8. In the same disease we also found the highest IDO activity and the lowest Trp concentration. In addition, IDO activity seems to be related with the decrease in Trp, as demonstrated by the inverse correlation found between these two substances in the SF of all patients.

Methotrexate suppresses the interleukin-6 induced generation of reactive oxygen species in the synoviocytes of rheumatoid arthritis

Various cytokines and reactive oxygen species (ROS) play a fundamental role in the inflammatory and immunologic processes of rheumatoid arthritis (RA). Methotrexate (MTX) is one of the disease-modifying anti-rheumatic drugs and its effect may be partly due to the modulation of immunologic or inflammatory reactions by some cytokines. In the present study, we investigated the effects of MTX on the gene expression and synthesis of interleukin-6 (IL-6), and the proliferative activity and the production of ROS in the fibroblast-like synoviocytes (FLSs) obtained from the patient of RA. The expression or production of IL-6 was induced spontaneously, and augmented by the addition of recombinant human IL-6 or recombinant human IL-1 beta and TNF-alpha in FLSs. These spontaneous and augmented IL-6 expressions or productions were suppressed by treatment with low-concentration of MTX (1 microg/ml). Also, IL-6 stimulated the proliferation of FLSs, and this IL-6 driven proliferation was inhibited with the treatment of MTX or N-acetylcysteine (NAC, 1 mM). Furthermore, ROS production in FLSs was increased significantly by IL-6, and its effect was also abrogated in the presence of MTX or NAC. These results suggest that inflammatory reaction in the synovium of RA patients could be augmented by the autocrine or other cytokine-induced production of IL-6 with subsequent generation of ROS in the synoviocytes, and the modulations of IL-6 synthesis and ROS production may contribute to the therapeutic effects of MTX for RA.

Disease-modifying activity of SB 242235, a selective inhibitor of p38 mitogen-activated protein kinase, in rat adjuvant-induced arthritis

OBJECTIVE

To evaluate the effects of SB 242235, a potent and selective inhibitor of p38 mitogen-activated protein (MAP) kinase, on joint integrity in rats with adjuvant-induced arthritis (AIA).

METHODS

Male Lewis rats with AIA were orally treated either prophylactically (days 0-20) or therapeutically (days 10-20) with SB 242235. Efficacy was determined by measurements of paw inflammation, dual-energy x-ray absorptiometry for bone-mineral density (BMD), magnetic resonance imaging (MRI), microcomputed tomography (CT), and histologic evaluation. Serum tumor necrosis factor alpha (TNFalpha) in normal (non-AIA) rats and serum interleukin-6 (IL-6) levels in rats with AIA were measured as markers of the antiinflammatory effects of the compound.

RESULTS

SB 242235 inhibited lipopolysaccharide-stimulated serum levels of TNFalpha in normal rats, with a median effective dose of 3.99 mg/kg. When SB 242235 was administered to AIA rats prophylactically on days 0-20, it inhibited paw edema at 30 mg/kg and 10 mg/kg per day by 56% and 33%, respectively. Therapeutic administration on days 10-20 was also effective, and inhibition of paw edema was observed at 60, 30, and 10 mg/kg (73%, 51%, and 19%, respectively). Significant improvement in joint integrity was demonstrated by showing normalization of BMD and also by MRI and micro-CT analysis. Protection of bone, cartilage, and soft tissues was also shown histologically. Serum IL-6 levels were decreased in AIA rats treated with the 60 mg/kg dose of compound.

CONCLUSION

Symptoms of AIA in rats were significantly reduced by both prophylactic and therapeutic treatment with the p38 MAP kinase inhibitor, SB 242235. Results from measurements of paw inflammation, assessment of BMD, MRI, and micro-CT indicate that this compound exerts a protective effect on joint integrity, and thus appears to have disease-modifying properties.

Role of cytokines in the pathogenesis of anemia of chronic disease in rheumatoid arthritis

The aim of our study was to evaluate the role of proinflammatory cytokines: tumor necrosis factor alpha (TNFalpha), interleukin-1beta (IL-1beta), and interleukin-6 (IL-6), as well as the possible contribution of interleukin-10 (IL-10) in anemia of chronic disease (ACD) of rheumatoid arthritis (RA) patients. We measured the serum levels of TNFalpha, IL-1beta, and IL-6 in 105 anemic and 127 nonanemic RA patients. We also investigated the effects of the above cytokines on the development of burst-forming units-erythroid (BFUe) and colony-forming units-erythroid (CFUe) in bone marrow cultures. Anemic patients had significantly higher serum levels of TNFalpha, IL-1beta, and IL-6 compared to nonanemics. Serum IL-10 levels were low and there was no significant difference in IL-10 concentrations between anemic and nonanemic patients. Proinflammatory cytokines inhibited proliferation of BFUe and CFUe. IL-10 did not decrease the erythroid colony growth. Proinflammatory cytokines may play a role in the pathogenesis of ACD in RA patients. Low levels of IL-10 possibly contribute to the development of ACD.

Interleukin-1alpha and tumor necrosis factor alpha synergistically stimulate prostaglandin E2-dependent production of interleukin-11 in rheumatoid synovial fibroblasts

OBJECTIVE

Interleukin-11 (IL-11), an IL-6-type cytokine, is thought to be involved in bone resorption via osteoclast differentiation. Here, we characterized the combined effect of IL-1alpha and tumor necrosis factor alpha (TNFalpha), major cytokines in the rheumatoid synovium, on the production of IL-11 by cultured rheumatoid synovial fibroblasts (RSFs).

METHODS

The amounts of IL-11, IL-6, and prostaglandin E2 (PGE2) were measured by enzyme-linked immunosorbent assay. IL-11 messenger RNA (mRNA) levels were determined by Northern blotting. Protein expression of cytosolic phospholipase A2 (cPLA2), cyclooxygenase 2 (COX-2), and protein kinase C (PKC) isoforms were determined by Western blotting.

RESULTS

IL-1alpha and TNFalpha synergistically stimulated RSFs to produce IL-11 at both the mRNA and protein levels. This synergistic effect was completely inhibited by indomethacin. The inhibition was prevented by PGE2, indicating that the synergistic effect of IL-1alpha and TNFalpha was PGE2-mediated. The cooperative effects of these 2 cytokines were also observed in the production of PGE2 and the expression of 2 regulatory enzymes in PGE2 production, cPLA2 and COX-2. The synergistic induction of IL-11 by IL-1alpha and TNFalpha was completely inhibited by a potent inhibitor of all isoforms of PKC, GF109203X. In contrast, phorbol myristate acetate, which induced a down-regulation of PKC, degrading all PKC isoforms except atypical PKC, did not affect the induction of IL-11.

CONCLUSION

These findings suggest that IL-1alpha and TNFalpha synergistically stimulate the production of IL-11 via their effects on PGE2 production in the rheumatoid joint, and that atypical PKC may be another target for down-regulation of IL-11, the bone resorption-associated cytokine.

Effects of interferon-gamma and tumor necrosis factor alpha on the expression of the genes encoding aggrecan, biglycan, and decorin core proteins in cultured human chondrocytes

OBJECTIVE

To determine the effects of interferon-gamma (IFN gamma) and tumor necrosis factor alpha (TNF alpha), alone or in combination, on the expression of aggrecan, biglycan, and decorin core protein genes in human chondrocytes.

METHODS

Isolated human chondrocytes were cultured on poly(2-hydroxyethyl methacrylate)-coated plastic dishes to prevent the loss of cartilage-specific phenotype, and the effects of IFN gamma and TNF alpha, alone or in combination, on aggrecan, biglycan, and decorin core protein gene transcription and steady-state messenger RNA (mRNA) levels were examined.

RESULTS

The addition of IFN gamma (1.5 pM) or TNF alpha (0.3 pM) caused a decrease in the steady-state level of aggrecan mRNA (-25% and -15%, respectively), and the combination of these low-concentration cytokines caused a potent inhibition (-66%). These effects were the result of a decrease (-50%) in the transcription rate of the corresponding gene. At the concentrations used, IFN gamma did not alter the levels of biglycan mRNA or the transcription rates of the biglycan core protein gene. In contrast, TNF alpha decreased biglycan steady-state mRNA levels (-62%) and the biglycan core protein gene transcription rate (-18%). The combination of IFN gamma and TNF alpha resulted in a potentiation of the inhibitory effects of TNF alpha on biglycan mRNA levels (-79%) and transcription rate of the biglycan core protein gene (-46%). IFN gamma produced a modest decrease in decorin mRNA levels (-23%) and decorin core protein gene transcription rate (-17%). In contrast, TNF alpha resulted in a marked increase in decorin mRNA levels (+260%) that was not the result of transcriptional regulation. Notably, the combination of IFN gamma and TNF alpha potentiated the inhibitory effects of IFN gamma on decorin mRNA (-80%) and on the transcription of the corresponding gene (-43%). Similar results were obtained in fetal and adult articular chondrocytes.

CONCLUSION

These data demonstrate that 1) the expression of the core protein genes encoding the cartilage proteoglycans aggrecan, biglycan, and decorin is differentially regulated by IFN gamma and TNF alpha; 2) these effects are mediated by transcriptional and posttranscriptional mechanisms; and 3) the combination of the 2 cytokines causes a potent inhibitory effect on the expression of the genes for the core proteins of these 3 proteoglycans, which occurs largely at the transcriptional level. The inhibition of aggrecan, decorin, and biglycan core protein gene expression by the combination of IFN gamma and TNF alpha may contribute to the cartilage destruction that is characteristic of inflammatory joint diseases.

Effects of interferon-gamma and tumor necrosis factor alpha on the expression of the genes encoding aggrecan, biglycan, and decorin core proteins in cultured human chondrocytes

OBJECTIVE

To determine the effects of interferon-gamma (IFN gamma) and tumor necrosis factor alpha (TNF alpha), alone or in combination, on the expression of aggrecan, biglycan, and decorin core protein genes in human chondrocytes.

METHODS

Isolated human chondrocytes were cultured on poly(2-hydroxyethyl methacrylate)-coated plastic dishes to prevent the loss of cartilage-specific phenotype, and the effects of IFN gamma and TNF alpha, alone or in combination, on aggrecan, biglycan, and decorin core protein gene transcription and steady-state messenger RNA (mRNA) levels were examined.

RESULTS

The addition of IFN gamma (1.5 pM) or TNF alpha (0.3 pM) caused a decrease in the steady-state level of aggrecan mRNA (-25% and -15%, respectively), and the combination of these low-concentration cytokines caused a potent inhibition (-66%). These effects were the result of a decrease (-50%) in the transcription rate of the corresponding gene. At the concentrations used, IFN gamma did not alter the levels of biglycan mRNA or the transcription rates of the biglycan core protein gene. In contrast, TNF alpha decreased biglycan steady-state mRNA levels (-62%) and the biglycan core protein gene transcription rate (-18%). The combination of IFN gamma and TNF alpha resulted in a potentiation of the inhibitory effects of TNF alpha on biglycan mRNA levels (-79%) and transcription rate of the biglycan core protein gene (-46%). IFN gamma produced a modest decrease in decorin mRNA levels (-23%) and decorin core protein gene transcription rate (-17%). In contrast, TNF alpha resulted in a marked increase in decorin mRNA levels (+260%) that was not the result of transcriptional regulation. Notably, the combination of IFN gamma and TNF alpha potentiated the inhibitory effects of IFN gamma on decorin mRNA (-80%) and on the transcription of the corresponding gene (-43%). Similar results were obtained in fetal and adult articular chondrocytes.

CONCLUSION

These data demonstrate that 1) the expression of the core protein genes encoding the cartilage proteoglycans aggrecan, biglycan, and decorin is differentially regulated by IFN gamma and TNF alpha; 2) these effects are mediated by transcriptional and posttranscriptional mechanisms; and 3) the combination of the 2 cytokines causes a potent inhibitory effect on the expression of the genes for the core proteins of these 3 proteoglycans, which occurs largely at the transcriptional level. The inhibition of aggrecan, decorin, and biglycan core protein gene expression by the combination of IFN gamma and TNF alpha may contribute to the cartilage destruction that is characteristic of inflammatory joint diseases.

Tumor necrosis factor enhances the capsaicin sensitivity of rat sensory neurons

The capacity of the proinflammatory cytokines, tumor necrosis factor alpha (TNF alpha) and interleukin 1 beta (IL-1 beta), to modulate the sensitivity of isolated sensory neurons grown in culture to the excitatory chemical agent capsaicin was examined. Alterations in capsaicin sensitivity were assessed by quantifying the number of neurons labeled with cobalt after exposure to capsaicin and by recording the whole-cell response from a single neuron to the focal application of capsaicin. A 24 hr pretreatment of the neuronal cultures with TNF alpha (10 or 50 ng/ml), but not IL-1 beta (10 or 50 ng/ml), produced a concentration-dependent increase in the number of cobalt-labeled neurons after exposure to 100 nM capsaicin. The peak increase in the number of labeled neurons was attained after a 4 hr treatment with 10 ng/ml TNF alpha. Similarly, pretreatment with TNF alpha (10 ng/ml for 4, 12, and 24 hr) produced a greater than twofold increase in the average peak amplitude of the inward current evoked by 100 nM capsaicin. Both the TNF alpha-induced increase in labeling and current amplitude were blocked by treating the neuronal cultures with indomethacin before the addition of TNF alpha. Enhancement of the capsaicin-evoked current also was blocked by the specific cyclo-oxygenase-2 inhibitor SC-236. These results indicate that TNF alpha can enhance the sensitivity of sensory neurons to the excitation produced by capsaicin and that this enhancement likely is mediated by the neuronal production of prostaglandins. Isolated sensory neurons grown in culture may prove to be a useful model system in which to explore how prolonged exposure to mediators associated with chronic inflammation alter the regulatory pathways that modulate the excitability of the nervous system.

The new collagenase, collagenase-3, is expressed and synthesized by human chondrocytes but not by synoviocytes. A role in osteoarthritis

Recently, a new human collagenase, collagenase-3 has been identified. Since collagen changes are of particular importance in cartilage degeneration, we investigated if collagenase-3 plays a role in osteoarthritis (OA). Reverse transcriptase-PCR analysis revealed that in articular tissues collagenase-3 was expressed by the chondrocytes but not by the synoviocytes. Northern blot analysis of the chondrocyte mRNA revealed the presence of two major gene transcripts of 3.0 and 2.5 kb, and a third one of 2.2 kb was occasionally present. Compared to normal, OA showed a significantly higher (3.0 kb, P < or = 0.05; 2.5 kb, P < or = 0.03) level of collagenase-3 mRNA expression. Collagenase-3 had a higher catalytic velocity tate (about fivefold) than collagenase-1 on type II collagen. With the use of two specific antibodies, we showed that human chondrocytes had the ability to produce collagenase-3 as a proenzyme and as a glycosylated doublet. The chondrocyte collagenase-3 protein is produced in a significantly higher (P < or = 0.04) level in OA (approximately 9.5-fold) than in normal. The synthesis and expression of this new collagenase could also be modulated by two proinflammatory cytokines, IL-1 beta and TNF-alpha, in a time- and dose-dependent manner. This study provides novel and interesting data on collagenase-3 expression and synthesis in human cartilage cells and suggest its involvement in human OA cartilage patho-physiology.

Collagen induces cytokine production by synovial fluid mononuclear cells in rheumatoid arthritis

Synovial fluid (SF) mononuclear cells (MNC) from 13 patients with rheumatoid arthritis (RA) and 12 patients with other arthritic diseases (OD) including osteoarthritis (OA), gout and spondyloarthritis (SA) were cultured in the presence of collagen types I and II or lipopolysaccharide (LPS) for 24 h. Interleukin-1 (IL-1), IL-6 and tumor necrosis factor-alpha (TNF-alpha) in the SF and culture supernatants were assayed using ELISA. The results showed that one-half of the RA patients with high SF monocyte count had high SF IL-6 levels that coincided with the high spontaneous release of IL-6 by SF MNC. In the other RA patients with lower SF monocyte count, type II collagen induced significantly higher IL-1 beta than the medium control levels by SF MNC (P < 0.01) or that of the other diseases (P < 0.01). Similarly, type II collagen-induced IL-6 and TNF-alpha production rose significantly (P < 0.01) from SF MNC of RA but less from OD (P < 0.05). In addition, type I collagen could also induce IL-1, IL-6 and TNF-alpha in these samples from RA and OD patients but was less potent than type II collagen. Our results indicate that collagen-induced cytokines may be important in the pathogenesis of the disease.

Effect of etodolac on prostaglandin E2 biosynthesis, active oxygen generation and bradykinin formation

The inhibitory actions of etodolac on prostaglandin (PG) E2 biosynthesis, active oxygen generation and bradykinin formation were compared with those of indomethacin, diclofenac Na, piroxicam, naproxen, ketoprofen and aspirin. The inhibitory action (IC50 5.35 x 10(-8) M) of etodolac on PGE2 biosynthesis in rabbit articular chondrocytes stimulated by interleukin-1 (IL-1) beta was about 1/5 that of indomethacin. The inhibitory action of etodolac on spontaneous PGE2 biosynthesis in rabbit gastric epithelial cells (RGEs) (IC50 2.27 x 10(-5) M) and Madin-Darby canine kidney cells (MDCKs) (IC50 4.54 x 10(-7) M) was much less than that in rabbit articular chondrocytes stimulated by IL-1 beta and about 1/19 and 1/9 that of indomethacin in rabbit gastric epithelial cells (RGEs) and Madin-Darby canine kidney cells (MDCKs), respectively. The inhibitory action of etodolac on active oxygen generation was similar to that of indomethacin and piroxicam, and more potent than that of naproxen, ketoprofen and aspirin. The inhibitory action of etodolac on bradykinin formation was the most potent among the seven anti-inflammatory drugs tested. Both etodolac and bromelain inhibited the inflammatory pain in concanavalin A-treated paws of rats in a dose-dependent manner, but indomethacin did not. These results indicate that etodolac is an anti-inflammatory drug which suppress IL-1 beta-stimulated PGE2 biosynthesis in rabbit articular chondrocytes, active oxygen generation and bradykinin formation. It has less suppressive action against spontaneous PGE2 biosynthesis in RGEs and MDCKs. Thus, etodolac is considered to be a safe anti-inflammatory drug for clinical use.

Effects of glucocorticoids in rheumatoid arthritis. Diminished glucocorticoid receptors do not result in glucocorticoid resistance

OBJECTIVE

Lymphocytes of patients with rheumatoid arthritis (RA) have diminished receptor density; thus, patients with RA should show partial resistance to glucocorticoids. We investigated the glucocorticoid sensitivity of lymphocytes in RA patients compared with healthy subjects.

METHODS

We determined the effects of glucocorticoids on lymphocyte proliferation and cytokine release.

RESULTS

Proliferation and cytokine release were inhibited in RA patients to the same extent as in healthy controls.

CONCLUSION

Diminished receptor density in RA patients does not result in glucocorticoid resistance.

Basement membrane proteins in synovial membrane: distribution in rheumatoid arthritis and synthesis by fibroblast-like cells

Rheumatoid arthritis is a complex disease of unknown origin. In consequence of some immunological reactions, proliferative invading synovial tissue leads to destruction of normal joint architecture. The aim of this study was to investigate qualitative changes in extracellular matrix distribution of proliferating rheumatoid synovium and their cellular origin. Synovial tissues from 57 clinically indicated arthrotomies were investigated with immunofluorescence, using specific antibodies against extracellular matrix proteins in tissue slides and cultured cells, which were also studied for collagen biosynthesis. Results indicated that synovial fibroblast-like cells synthesize and secrete basement membrane proteins laminin and collagen type IV as e.g. endothelial cells or organogenic fibroblasts. Laminin and collagen type IV were specifically demonstrated pericellularly in the hyperplastic lining layer of active rheumatoid synovitis. These findings are discussed with respect to the possible implication of altered cell-matrix interactions in rheumatoid synovial proliferation.

Prostaglandin E2 antagonizes gingival fibroblast proliferation stimulated by interleukin-1 beta

Treatment of human gingival fibroblasts with prostaglandin E2 (PGE2) resulted in significant concentration-dependent inhibition in deoxyribonucleic acid (DNA) synthesis (8.40-37.89%), while indomethacin (INDO) (PG inhibitor), interleukin-1 beta (IL-1 beta) or IL-1 beta+INDO caused a significant and dose-dependent increase in DNA synthesis. Addition of PGE2 to culture media containing IL-1 beta and INDO caused a significant concentration-dependent reduction in IL-1 beta- and INDO-induced stimulation of DNA synthesis. The findings suggest that IL-1 beta and PGE2, which are also produced by fibroblasts, could play an important role in regulation of gingival tissue development and wound healing, and their modulation may have therapeutic potential.

Transcriptional modulation of cartilage-specific collagen gene expression by interferon gamma and tumour necrosis factor alpha in cultured human chondrocytes

To examine the possibility that cytokines produced in inflamed joint tissues may contribute to the loss of articular cartilage by causing inhibition of synthesis of cartilage-specific matrix macromolecules, we studied the effects of interferon gamma (IFN gamma) and tumour necrosis factor alpha (TNF alpha), alone and in combination, on the expression of the genes for types-II, -IX and -XI collagens in cultured human chondrocytes. Chondrocytes isolated from human fetal epiphyseal cartilage by sequential enzymic digestions were cultured in the presence of IFN gamma (30 pM), TNF alpha (15 pM) or a combination of suboptimal concentrations of both cytokines (1.5 pM IFN gamma plus 0.3 pM TNF alpha). IFN gamma caused a maximal decrease of 23.3-32.6% in the biosynthesis of collagen by chondrocytes. TNF alpha was a more potent inhibitor causing a 42.8-45.3% decrease at one-half the concentration of IFN gamma. A synergistic inhibitory effect of 58.2% was observed with the combination of 1.5 pM IFN gamma plus 0.3 pM TNF alpha. Electrophoretic analysis of the biosynthesized proteins showed a co-ordinate decrease in the production of the three cartilage-specific collagen types II, IX and XI. These effects were accompanied by parallel changes in the steady-state levels of their corresponding mRNAs. In vitro transcription assays showed that the collagen inhibitory effects of the cytokines occurred largely at the transcriptional level. Similar effects of the cytokines were observed on biosynthesis of types-II, -IX and -XI collagens and steady-state mRNA levels for type-II collagen by chondrocytes obtained from adult articular cartilage. These observations indicate that IFN gamma and TNF alpha can induce a synergistic inhibition of the synthesis of cartilage-specific collagens by fetal and adult human chondrocytes and suggest that these effects may contribute to the articular cartilage loss that occurs in inflammatory joint diseases.

Contrasting levels of in vitro cytokine production by rheumatoid synovial tissues demonstrating different patterns of mononuclear cell infiltration

Synovial membrane samples obtained at knee arthroplasty from 22 patients with rheumatoid arthritis (RA) were characterized histologically. Two groups were identified. Tissue samples from 15 patients demonstrated multiple focal lymphoid aggregates of mononuclear cells (group A). Samples from the remaining seven patients demonstrated diffuse mononuclear cell infiltration (group B). Samples of each synovial membrane (0.25 g) were cultured for cytokine production. The highest levels of IL-1 beta and IL-6 were produced by group A tissues: 19.1 +/- 19.6 ng/ml IL-1 beta (mean +/- s.d.) and 264.4 +/- 301.9 ng/ml IL-6, versus 3.8 +/- 6.6 ng/ml and 54.7 +/- 42.6 ng/ml respectively. Small quantities of IL-2 and IL-4 were measured in both groups: the levels of IL-2 in group A cultures were highest (P = 0.04). Moreover, using MoAbs, the most intense cytokine staining in the tissues was detected in group A. Similar total numbers of each cell subpopulation and similar quantities of immunoglobulin and rheumatoid factor synthesis were measured in both groups. It is suggested that the presence of multiple focal lymphoid aggregates associated with higher levels of cytokine production observed in group A represent a greater degree of immunological activation, and may represent a subgroup of patients with a greater potential for articular destruction.

UVA-induced autocrine stimulation of fibroblast-derived-collagenase by IL-6: a possible mechanism in dermal photodamage?

Like other cytokines, IL-6 has been reported to stimulate collagenase. In this study we were interested in whether IL-6 is involved in the ultraviolet (UV) mediated up-regulation of fibroblast-derived collagenase. Confluent fibroblast monolayers were irradiated under standardized conditions. Following UVA irradiation the bioactivity of IL-6 increased up to fiftyfold in the supernatants of irradiated compared to mock-irradiated fibroblasts. As determined by Northern blot analysis this was also reflected on the pre-translational level by a tenfold increase of IL-6-specific mRNA following UVA irradiation. Induction of IL-6-specific mRNA was maximal at 6 h post-irradiation, thus clearly preceding the maximal induction of collagenase mRNA at 24 h post-irradiation. To elucidate the regulatory role of IL-6 in the UVA induction of fibroblast-derived collagenase, monospecific polyclonal neutralizing antibodies directed against recombinant human IL-6 and antisense oligonucleotides specifically inhibiting the translation of IL-6 mRNA were used at various concentrations. The amount of UVA-induced collagenase mRNA was reduced in a dose-dependent manner when antibodies or specific antisense oligonucleotides were present during and after irradiation. Taken together our data provide first evidence that UVA enhances IL-6 synthesis and secretion in fibroblasts. IL-6 induces via an autocrine mechanism collagenase and may thus contribute to the actinic damage of the dermis.

Cytokine regulation of human lung fibroblast hyaluronan (hyaluronic acid) production. Evidence for cytokine-regulated hyaluronan (hyaluronic acid) degradation and human lung fibroblast-derived hyaluronidase

We characterized the mechanisms by which recombinant (r) tumor necrosis factor (TNF), IFN-gamma, and IL-1, alone and in combination, regulate human lung fibroblast hyaluronic acid (HA) production. Each cytokine stimulated fibroblast HA production. The combination of rTNF and rIFN-gamma resulted in a synergistic increase in the production of high molecular weight HA. This was due to a synergistic increase in hyaluronate synthetase activity and a simultaneous decrease in HA degradation. In contrast, when rTNF and rIL-1 were combined, an additive increase in low molecular weight HA was noted. This was due to a synergistic increase in hyaluronate synthetase activity and a simultaneous increase in HA degradation. Human lung fibroblasts contained a hyaluronidase that, at pH 3.7, depolymerized high molecular weight HA to 10-40 kD end products of digestion. However, hyaluronidase activity did not correlate with fibroblast HA degradation. Instead, HA degradation correlated with fibroblast-HA binding, which was increased by rIL-1 plus rTNF and decreased by rIFN-gamma plus rTNF. Recombinant IL-1 and rTNF weakly stimulated and rIL-1 and rTNF in combination further augmented the levels of CD44 mRNA in lung fibroblasts. In contrast, rIFN-gamma did not significantly alter the levels of CD44 mRNA in unstimulated or rTNF stimulated cells. These studies demonstrate that rIL-1, rTNF, and rIFN-gamma have complex effects on biosynthesis and degradation which alter the quantity and molecular weight of the HA produced by lung fibroblasts. They also show that fibroblast HA degradation is mediated by a previously unrecognized lysosomal-type hyaluronidase whose function may be regulated by altering fibroblast-HA binding. Lastly, they suggest that the CD44 HA receptor may be involved in this process.

Serum levels of interleukin-1b, tumour necrosis factor-a and interleukin-2 in rheumatoid arthritis. Correlation with disease activity

Cytokines are potent immunoregulatory factors and may be directly involved in the disordered immunoregulation found in chronic rheumatic diseases. Interleukin-1b (IL-1b), Interleukin-2 (IL-2) and Tumour Necrosis Factor-a (TNF-a) have been implicated in the pathogenesis of rheumatoid arthritis (RA) as mediators of chronic inflammation. Serum levels of IL-1b and TNF-a measured by radioimmunoassay were significantly higher in patients with RA than in healthy controls of similar sex and age while serum levels of IL-2 were significantly lower in the same patients. Further IL-1b and TNF-a were significantly elevated in RA patients with active disease and IL-2 was significantly reduced when compared with patients with low active disease. Serum IL-1b and TNF-a appear to correlate with systemic inflammation, and systemic features of RA may result from dissemination of cytokines produced in the synovium. The role of IL-2 in RA remains controversial. Reduced levels of IL-2 may be an expression of a deficiency of T-cells to produce IL-2 in the active phases of RA or may be due to a possible absorption of IL-2 by lymphocyte receptors.

Direct stimulation of cytokines (IL-1 beta, TNF-alpha, IL-6, IL-2, IFN-gamma and GM-CSF) in whole blood. I. Comparison with isolated PBMC stimulation

Production of interleukin 1 beta (IL-1 beta), interleukin 6 (IL-6), tumor necrosis factor alpha (TNF-alpha), interleukin 2 (IL-2), interferon gamma (IFN-gamma) and granulocyte-macrophage colony-stimulating factor (GM-CSF) after stimulation by lipopolysaccharide (LPS) and phytohemagglutinin (PHA) was studied in 1/10 diluted whole blood (WB) culture and in peripheral blood mononuclear cell (PBMC) culture. Cytokines IL-1 beta, TNF-alpha and IL-6 are preferentially stimulated by LPS whereas IL-2, IFN-gamma and GM-CSF are stimulated by PHA. Combination of 5 micrograms/ml PHA and 25 micrograms/ml LPS gave the most reliable production of the six cytokines studied. IL-1 beta, TNF-alpha and IL-6 represent a homogeneous group of early-produced cytokines positively correlated among themselves and with the number of monocytes in the culture (LeuM3). Furthermore, IL-1 beta was negatively correlated with the number of T8 lymphocytes. IL-2, IFN-gamma and GM-CSF represent a group of late-produced cytokines. Kinetics and production levels of IL-6 and GM-CSF are similar in WB and PBMC cultures. In contrast, production levels of TNF-alpha and IFN-gamma are higher in WB than in PBMC whereas production levels of IL-6 and IL-2 are lower in WB than in PBMC. Individual variation in responses to PHA + LPS was always higher in PBMC cultures than in WB cultures. The capacity of cytokine production in relation to the number of mononuclear cells is higher in WB, or in PBMC having the same mononuclear cell concentration as WB, than in conventional cultures of concentrated PBMC (10(6)/ml). Because it mimics the natural environment, diluted WB culture may be the most appropriate milieu in which to study cytokine production in vitro.

Interleukin-1 beta stimulates cytosolic phospholipase A2 in rheumatoid synovial fibroblasts

Phospholipase A2 (PLA2) activities in rheumatoid synovial fibroblasts (RSF) stimulated with interleukin-1 beta (IL-1 beta) were investigated. RSF incubated in the presence of IL-1 beta (120 pg/ml) for 18 h secreted 35 fold more PGE2 than did those incubated without IL-1 beta. IL-1 beta treatment did not increase the level of secretory PLA2 (sPLA2) activity or sPLA2 protein in the conditioned medium or subcellular fractions of lysed RSF. In contrast, the cell-associated PLA2 activity increased 3 to 4 fold in IL-1 beta stimulated RSF when compared with the control. The IL-1 beta stimulated, cell-associated PLA2 required submicromolar concentrations of calcium for activity, a characteristic consistent with the calcium sensitivity of cytosolic PLA2 (cPLA2) activity reported in other cell types, such as U937 cells. These findings demonstrate that an elevation in a cytosolic PLA2, rather than a sPLA2, is associated with increased PGE2 production in IL-1 beta stimulated RSF.

Synovial membrane histology and immunopathology in rheumatoid arthritis and osteoarthritis. In vivo effects of antirheumatic drugs

We examined the histologic and immunopathologic features of the synovial membrane of 18 patients with rheumatoid arthritis (RA) and 12 patients with osteoarthritis (OA) who had undergone total knee arthroplasty. Patients were classified into 5 groups according to therapeutic regimen and disease: RA treated with nonsteroidal antiinflammatory drugs (NSAIDs), RA treated with NSAIDs and prednisone, RA treated with NSAIDs and methotrexate (MTX), OA treated with analgesics, and OA treated with NSAIDs. There were no significant between-group differences in the percentages or the distribution pattern of the infiltrating T cell subsets (CD4, CD8), HLA-DR, or interleukin-2 receptor-bearing cells. However, inflammatory indices, which included the thickness of the lining cell layer and the density of the mononuclear cell infiltrate, were significantly higher in the RA patients treated with prednisone and those treated with MTX (P less than 0.05). Similarly, fibrosis was markedly reduced in these 2 groups. The RA patients treated with NSAIDs alone and the 2 groups of patients with OA demonstrated similar profiles. These data suggest that prednisone and MTX may inhibit the development of fibrosis without altering the subsets of the inflammatory cell population. This observation raises the possibility that the action of these 2 drugs may be partly mediated by the suppression of inflammatory mediators that are responsible for fibroblast activation.

Modulation of the effects of interleukin-1 on glycosaminoglycan synthesis by the urine-derived interleukin-1 inhibitor, but not by interleukin-6

Interleukin-1 (IL-1) has been shown to regulate glycosaminoglycan (GAG) synthesis. We therefore investigated whether an IL-1 inhibitor or IL-6 modulates IL-1 biologic activities in human synovial cells and cultured articular cartilage. We found that in the presence of a constant amount of IL-1 beta, stimulation of hyaluronic acid (HA) synthesis by the IL-1 inhibitor was inhibited in a dose-dependent manner. Similarly, the decrease in sulfated GAG synthesis induced by IL-1 was reversed by the addition of the IL-1 inhibitor. In contrast, IL-6 did not affect the production of HA, prostaglandin E2, or collagenase in synovial cells, nor did it affect GAG in organ cultures when tested in the presence or absence of IL-1 beta. Hence, IL-6 was ineffective in modulating IL-1 bioactivities on HA or sulfated GAG synthesis. These results emphasize the importance of IL-1 and IL-1 inhibitor in connective tissue destruction and raise questions concerning the role of IL-6 in this pathogenesis.

Detection of interleukin 8 biological activity in synovial fluids from patients with rheumatoid arthritis and production of interleukin 8 mRNA by isolated synovial cells

The presence of neutrophils in the synovial joint of patients with rheumatoid arthritis (RA) is thought to be due to the activity of chemotactic factors released by activated cells in the joint. We have shown in this report, for the first time, the abundance of one such factor, interleukin 8 (IL 8), in the synovial fluid of patients both with RA and other non-RA joint diseases, and the spontaneous production of IL 8 mRNA by RA synovial cells in culture. There was no correlation between the levels of chemotactic activity and IL 8 protein, suggesting that other factors with similar neutrophil chemotactic activity are also present in the synovial fluid exudate. In support of this concept neither the level of chemotactic activity nor IL 8 protein levels correlated with neutrophil or leukocyte infiltration, indicating that the mechanism of migration into the inflammatory environment of the joint is complex. Such migration is likely to be due to a number of chemotactic signals in addition to IL 8, which may either synergize with, or inhibit, the action of IL 8.

Two-dimensional electrophoresis of synovial tissue, synovial fluid and serum in patients with rheumatoid arthritis and related diseases

Using the technique of two-dimensional (2D) electrophoresis with consecutive silver staining, we investigated samples of serum, synovial fluid and synovial tissue obtained from 19 patients suffering from rheumatoid arthritis (RA) or non-RA arthritis. From these experiments we have drawn the following conclusions. 2D electrophoresis of serum, synovial fluid and synovial tissue extracts taken from patients suffering from joint diseases is a reproducible method. Repeated runs of the same sample reveal an essentially constant protein spot pattern. The time period between surgery and tissue preparation did not influence the number of protein spots when less than 15 h was involved. The protein spot number is always lower in synovial fluid than in either synovial tissue or serum in RA and non-RA patients. The mean value for the number of spots is 68 for the inflamed tissue irrespective of the cause of arthritis (RA and non-RA group taken together) and 47 for the control group. This difference is significant. We were able to definitely identify 7 spots in the tissue extract. We did not find RA-specific protein spots in either serum, synovial fluid or tissue extracts from the synovial membrane. The only significant difference between RA patients and either non-RA or control group patients concerning the protein spot pattern is the increased size of the immunoglobulin spot (mainly IgG) in RA. In addition, we discuss possible reasons for failure of the 2D electrophoresis technique to detect disease-specific protein patterns.

Detection of transforming growth factor-beta in rheumatoid arthritis synovial tissue: lack of effect on spontaneous cytokine production in joint cell cultures

The presence of transforming growth factor-beta (TGF-beta) in inflammatory joint disease was investigated. Synovial fluid from patients with rheumatoid arthritis (RA) and patients with other non-autoimmune inflammatory joint diseases contained high levels of both active and latent TGF-beta. Levels of active TGF-beta did not correlate with drug regimen in either patient group or with the recovery period in the individuals with non-RA joint disease. Freshly isolated synovial cells from individuals with RA were shown by Northern blotting to express the mRNA for TGF-beta 1 and to secrete latent TGF-beta protein which could be neutralized by antibodies to TGF-beta 1 and TGF-beta 2. Lipopolysaccharide-stimulated peripheral blood mononuclear cells from normal donors produced interleukin-1 (IL-1) and tumour necrosis factor-alpha (TNF-alpha) which was inhibited by pretreatment of these cells with recombinant TGF-beta. Cytokine production was not inhibited if the addition of TGF-beta was used after the inducing stimulus, suggesting that in activated cells cytokine production cannot be inhibited. This was confirmed by the observation that neither TGF-beta 1 or TGF-beta 2 inhibited spontaneous IL-1 or TNF-alpha production by rheumatoid synovial mononuclear cells in culture. These findings show that despite the presence of active TGF-beta in RA synovial joints and the spontaneous production of latent (potentially active) TGF-beta by RA cells in culture, additional TGF-beta did not inhibit ongoing cytokine synthesis in vitro. This suggests that TGF-beta may not inhibit cytokine production in the rheumatoid joint although it cannot be ruled out that in vivo TGF-beta already has an immunosuppressive effect which cannot be further increased in vitro by exogenous protein.

Measurement of interleukin-1 alpha and -1 beta in gingival crevicular fluid: implications for the pathogenesis of periodontal disease

Samples of gingival crevicular fluid (GCF) were harvested from sites manifesting features characteristic of active disease including inflammation, periodontal attachment loss, and radiographic signs of alveolar bone destruction in untreated patients with advanced periodontitis. The presence and concentrations of interleukin-1 alpha (IL-1 alpha) and interleukin-1 beta (IL-1 beta) were measured using ELISAs specific for these cytokine molecules. IL-1 alpha and/or IL-1 beta were identified in the GCF of 15 of 15 patients having untreated periodontitis. Ninety percent (71 of 79) of the sites tested contained measureable amounts of IL-1, with IL-1 beta as the more frequently occurring form. IL-1 alpha levels ranged from 0.23 nM to 13.9 nM in the GCFs. IL-1 beta levels were between 0.04 nM and 5.28 nM. Marked reductions of total IL-1 levels were observed following effective treatment. Both forms of IL-1 messenger RNA (mRNA) were detected in 17 of 17 gingival tissue samples from 6 patients. These results demonstrate that IL-1 is produced and released locally in periodontal disease at concentrations sufficient to mediate tissue inflammation and bone resorption. IL-1 may serve as a marker of periodontal tissue destruction.

Cytokines and cytokine inhibitors or antagonists in rheumatoid arthritis

This review has summarized some of the evidence suggesting that cytokines may play an important role in mediating pathophysiologic events in RA. However, these proteins are capable of mediating both stimulatory (agonist) and inhibitory (antagonist) effects in the rheumatoid synovium. GM-CSF, IL-1, TNF alpha, and PDGF are all produced in the rheumatoid synovium and may function to induce inflammation, enzyme release, fibroblast proliferation, and tissue destruction. Local release of IL-6 may alter the effects of IL-1 and TNF alpha, as well as induce Ig production and hepatic synthesis of acute-phase proteins. However, specific inhibitors of IL-1 and TNF alpha exist, which, if also released into the synovium, may antagonize the proinflammatory effects of these cytokines. In addition, IL-1 may have antiinflammatory effects, such as the induction of the synthesis of collagen and enzyme inhibitors by chondrocytes and synovial fibroblasts. Stimulation of these latter cells by TGF beta also may result in decreased matrix degradation and increased formation of scar tissue. The developing scenario is one of cell-cell interactions that are influenced in positive and negative manners by the local release of various mediators. A further understanding of cytokines and cytokine inhibitors in the rheumatoid synovium may lead to the development of more specific and effective therapeutic agents.

Interleukin-1 release by rat synovial cells is dependent on sequential treatment with gamma-interferon and lipopolysaccharide

To determine the potential regulatory mechanisms involved in synovial cell interleukin-1 (IL-1) release, the ability of gamma-interferon (gamma-IFN) to influence IL-1 release was assessed. Rat synovial cells cultured in the presence of a variety of stimuli, including lipopolysaccharide (LPS), failed to release IL-1. However, pretreatment of synovial cells with gamma-IFN, followed by LPS stimulation, resulted in increased levels of intracellular IL-1 as well as release of IL-1 from the cell. The level of IL-1 release was dependent on the concentration of both gamma-IFN and LPS, and on length of exposure to the gamma-IFN. The kinetic and dose requirements for gamma-IFN-dependent IL-1 release were similar to those for Ia antigen expression, but LPS was necessary for IL-1 messenger RNA induction, intracellular IL-1 accumulation, and IL-1 release. In addition, sequential treatment, i.e., gamma-IFN followed by LPS, was essential for IL-1 induction. Substitution of phorbol ester or calcium ionophore for gamma-IFN did not result in similar IL-1 release. In addition, induction of IL-1 messenger RNA by another stimulus was not sufficient to result in IL-1 release following LPS treatment. These results suggest that release of IL-1 by rat synovial cells requires the production of a regulatory signal, which is inducible by gamma-IFN.

Localization of collagenase mRNA in rheumatoid arthritis synovium by in situ hybridization histochemistry

Collagenase has been implicated as playing an important role in the connective tissue destruction that is a major feature of rheumatoid arthritis. Numerous cell types in the hyperplastic rheumatoid synovium are capable of synthesizing collagenase. Past studies have used predominantly synovial fibroblasts in culture as a model system for the regulation of collagenase production, but the major cellular source of the enzyme in vivo has not been determined. Using the techniques of in situ hybridization histochemistry and indirect immunofluorescence, we determined the cellular source of collagenase in frozen sections of human synovium. Collagenase mRNA production was localized to cells along the synovial lining layer in rheumatoid arthritis. These were identified as the macrophage-like Type A synovial lining cells by immunofluorescence with antibody LeuM3. Endothelial cells, fibroblasts, and T and B lymphocytes were devoid of detectable collagenase mRNA. Synovial tissue sections from patients with osteoarthritis and trauma did not contain detectable collagenase mRNA. These data identify the Type A macrophage-like synovial lining cell as the primary source of collagenase mRNA in vivo in the rheumatoid arthritis synovium and, potentially, as a major effector cell in the tissue destruction of the disease.

The effect of the anabolic steroid, stanozolol, on the production of procollagenase by human synovial and skin fibroblasts in vitro

The ability of the anabolic steroid, stanozolol, to stimulate procollagenase production by human synovial and skin fibroblasts was examined in an in vitro assay system. Stanozolol is used therapeutically to treat a variety of connective tissue and vascular disorders and its clinical effects suggest that it can modulate connective tissue breakdown. The results showed that stanozolol was capable, in a dose dependent manner, of significantly stimulating procollagenase production by skin fibroblasts. However, in three synovial fibroblast lines no evidence was found of increased collagenase production following treatment with stanozolol; although the synovial fibroblasts secreted significantly increased amounts of procollagenase in response to IL-1. These results may shed some light on the mechanism of action in vivo of stanozolol in the treatment of connective tissue disorders.

Activation of macrophages in an experimental rat model of arthritis induced by Erysipelothrix rhusiopathiae infection

Infection of Lewis rats with Erysipelothrix rhusiopathiae represents an experimental model system of acute and chronic arthritis. We studied here the acute inflammatory phase with respect to stimulation of macrophages and lymphocytes. Intragluteal injection of viable E. rhusiopathiae (10(2) to 10(4) bacteria) rapidly induced generalized inflammation, loss of body weight, hind leg arthritis, and systemic macrophage activation within 2 to 3 days. The same symptoms could also be evoked by injection of dead E. rhusiopathiae. Ex vivo, peritoneal macrophages released large amounts of tumor necrosis factor alpha on day 2 and interleukin-1 on day 3, whereas production of prostaglandin E2 was delayed to days 5 to 7 and appeared to counteract tumor necrosis factor alpha synthesis. The inflammatory response and development of arthritis were strongly dependent on T lymphocytes, as evidenced by the following findings: (i) lymphocytes released lymphokines that activated macrophages to enhanced mediator release; (ii) treatment of rats with cyclosporin A reduced infection-induced macrophage activation; (iii) mitogen-stimulated thymocyte proliferation was enhanced, indicating an infection-induced maturation-differentiation process in the thymus; and (iv) in T-cell-deficient nude rats, a higher dose of bacteria was required for infection, the inflammatory response was less severe, and only mild, but not chronic, arthritis developed. Thus, an E. rhusiopathiae-induced inflammation in rats provides a useful tool to characterize activated macrophages and T lymphocytes during the development of acute arthritis and its transition into the chronic form.

Cytokine production in culture by cells isolated from the synovial membrane

Cytokine expression was investigated in synovial cell cultures isolated from diseased joints of patients with rheumatoid arthritis (RA) and osteoarthritis (OA). Tumour necrosis factor alpha (TNF alpha) was produced spontaneously at high levels by both RA and OA synovial cells. There was no correlation between cell composition and level of TNF alpha produced. In contrast, lymphotoxin (LT) and Interferon gamma (IFN gamma) (greater than 50 pg/ml) were not found. This was further investigated in the RA cultures at both the mRNA and protein level. The results indicated that high levels of mRNA were produced spontaneously by these cells, but the relevant protein was undetectable. The presence of inhibitors and/or shed receptor is unlikely to account for undetectable LT as most of the recombinant LT added to the cultures could be recovered. In addition, in some cases this resulted in an increase in IL-1 production indicating that LT is biologically active in this system. It is not clear at this stage why the protein for these mediators (produced by activated T cells) are not found in the rheumatoid cultures, although it may be due to a post-transcriptional mechanism. This possibility is currently being investigated in addition to the development of more sensitive assays for these cytokines.

Interleukin-1 induces interleukin-1 alpha and interleukin-1 beta gene expression in synovial fibroblasts and peripheral blood monocytes

Cellular interactions involved in the chronic inflammatory response, characteristic of those found in the joints of rheumatoid arthritis patients, were investigated by examining the effect of interleukin-1 (IL-1), tumor necrosis factor alpha, and gamma-interferon on the regulation of IL-1 gene expression and production by synovial fibroblasts. Biologically active IL-1 was detected in lysates of IL-1-treated rat and human fibroblasts that had been isolated from synovial tissue by collagenase digestion. Northern blot analysis of RNA isolated from these cells revealed the expression of IL-1 alpha and IL-1 beta transcripts. Neither the IL-1 transcripts nor the biologic activity of IL-1 was found in untreated synovial fibroblasts. The messenger RNA induction in synovial cells was followed by a time- and dose-dependent expression of intracellular IL-1 activity. Human monocytes and human skin fibroblasts also responded to IL-1 treatment by producing IL-1-specific transcripts. These observations suggest that IL-1 plays a key role in stimulating immune and inflammatory responses and in sustaining those responses through continued production at sites of inflammation.