Serum protein signatures detect early radiographic osteoarthritis

OBJECTIVE

To test the hypothesis that early knee and hand osteoarthritis (OA) development is characterized by detectable changes in serum proteins relevant to inflammation, cell growth, activation, and metabolism several years before OA becomes radiographically evident.

METHODS

Using microarray platforms that simultaneously test 169 proteins relevant to inflammation, cell growth, activation and metabolism, we conducted a case-control study nested within the Baltimore Longitudinal Study of Aging (BLSA). Subjects included 22 incident cases of OA and 66 age-, sex- and body mass index (BMI)-matched controls. Serum samples tested were obtained at the time of radiographic classification as either case or control, and up to 10 years earlier at a time when all participants were free of radiographic OA. Proteins with mean signal intensities fourfold higher than background were compared between cases and controls using multivariate techniques.

RESULTS

Sixteen proteins were different between OA cases compared to controls. Four of these proteins [matrix metalloproteinase (MMP)-7, interleukin (IL)-15, plasminogen activator inhibitor (PAI)-1 and soluble vascular adhesion protein (sVAP)-1] were already different in samples obtained 10 years before radiographic classification and remained different at the time of diagnosis. Six additional proteins were only associated with subsequent OA development and not with established OA.

CONCLUSIONS

Changes in serum proteins implicated in matrix degradation, cell activation, inflammation and bone collagen degradation products accompany early OA development and can precede radiographic detection by several years.

Radiographic changes in rheumatoid arthritis patients attaining different disease activity states with methotrexate monotherapy and infliximab plus methotrexate: the impacts of remission and tumour necrosis factor blockade

OBJECTIVE

To examine the association of radiographic progression and disease activity states in patients with rheumatoid arthritis (RA) treated with methotrexate with or without infliximab.

METHODS

Patients (n = 1049) with active RA for 3 years or less and no previous methotrexate treatment were randomly assigned (4 : 5 : 5) to receive methotrexate plus placebo or methotrexate plus infliximab 3 or 6 mg/kg at weeks 0, 2 and 6, and every 8 weeks thereafter to week 46. Disease activity was classified by the simplified disease activity index as remission (< or =3.3), low (>3.3 to < or =11), moderate (>11 to < or =26), high (>26). Radiographic progression was measured as a change from baseline to week 54 in total Sharp score.

RESULTS

At weeks 14 and 54, more patients receiving methotrexate plus infliximab than methotrexate plus placebo were in remission (10.7% versus 2.8% week 14; 21.3% versus 12.3% week 54; p<0.001 for both). Methotrexate plus placebo halted radiographic progression only if patients achieved remission within 3 months, whereas methotrexate plus infliximab also halted or minimised progression in patients with low or moderate activity, respectively. Patients with persistently high disease activity levels had much less progression of joint damage if treated with methotrexate plus infliximab versus methotrexate monotherapy. Even with infliximab plus methotrexate there was a direct relationship between disease activity and radiographic changes, although the slope was deflected when compared with methotrexate monotherapy.

CONCLUSION

With methotrexate, joint damage progresses even at low and moderate disease activity levels, whereas methotrexate plus infliximab inhibits radiographic progression across all disease activity states.

The Early Rheumatoid Arthritis (ERA) trial comparing the efficacy and safety of etanercept and methotrexate

The Early Rheumatoid Arthritis (ERA) trial compared monotherapy with etanercept or methotrexate in patients with early erosive rheumatoid arthritis. Over the initial period of 12, and subsequently 24, months both treatments were associated with a profound reduction in radiographic progression of joint damage, as well as a reduction in signs and symptoms of disease. Etanercept showed slight superiority to methotrexate in reducing subsequent radiographic erosions and in the rapidity of the clinical response. Both therapies proved to be safe and well tolerated and, importantly, the relative safety and tolerance of a rapidly escalated dosing regimen for methotrexate was demonstrated. In summary, early aggressive treatment of RA is associated with clinical and radiographic benefit that can be demonstrated after a relatively short period of treatment.

A comparison of etanercept and methotrexate in patients with early rheumatoid arthritis

BACKGROUND

Etanercept, which blocks the action of tumor necrosis factor, reduces disease activity in patients with long-standing rheumatoid arthritis. Its efficacy in reducing disease activity and preventing joint damage in patients with active early rheumatoid arthritis is unknown.

METHODS

We treated 632 patients with early rheumatoid arthritis with either twice-weekly subcutaneous etanercept (10 or 25 mg) or weekly oral methotrexate (mean, 19 mg per week) for 12 months. Clinical response was defined as the percent improvement in disease activity according to the criteria of the American College of Rheumatology. Bone erosion and joint-space narrowing were measured radiographically and scored with use of the Sharp scale. On this scale, an increase of 1 point represents one new erosion or minimal narrowing.

RESULTS

As compared with patients who received methotrexate, patients who received the 25-mg dose of etanercept had a more rapid rate of improvement, with significantly more patients having 20 percent, 50 percent, and 70 percent improvement in disease activity during the first six months (P<0.05). The mean increase in the erosion score during the first 6 months was 0.30 in the group assigned to receive 25 mg of etanercept and 0.68 in the methotrexate group (P= 0.001), and the respective increases during the first 12 months were 0.47 and 1.03 (P=0.002). Among patients who received the 25-mg dose of etanercept, 72 percent had no increase in the erosion score, as compared with 60 percent of patients in the methotrexate group (P=0.007). This group of patients also had fewer adverse events (P=0.02) and fewer infections (P= 0.006) than the group that was treated with methotrexate.

CONCLUSIONS

As compared with oral methotrexate, subcutaneous [corrected] etanercept acted more rapidly to decrease symptoms and slow joint damage in patients with early active rheumatoid arthritis.

Prevalence of significant knee pain among older Americans: results from the Third National Health and Nutrition Examination Survey

OBJECTIVE

To assess the prevalence of persistent knee pain among older adults in the US.

DESIGN

A nationally representative cross-sectional survey with an in-person interview and medical examination

SETTING AND PARTICIPANTS

Between 1988 and 1994, 6596 adults aged 60 to 90+ years were examined as part of the National Health and Nutrition Examination Survey III. Mexican Americans and non-Hispanic blacks were over-sampled to produce reliable estimates for these groups.

MAIN OUTCOME MEASUREMENTS

Participants were asked to report whether they had experienced knee pain on most days for the 6 weeks preceding their medical exam.

RESULTS

Overall, 18.1% of US men and 23.5% of US women aged 60 years and older reported knee pain. Sixty- to ninety-year-old men reported knee pain less frequently than their age-matched female counterparts. There was a trend for reports of knee pain to increase steadily as these adults aged from 60 to 85 years. The highest prevalence of knee pain was reported among 85- to 90-year-old men (23.7%) and women (30.0%). Among non-Hispanic white adults older than age 60, 18.4% of men and 22.0% of women reported knee pain. Reports of knee pain among non-Hispanic black men and Mexican American men were similar to those of their non-Hispanic white counterparts. In contrast, 26.4% of Mexican American women and 32.8% of non-Hispanic black women reported knee pain. We also found that difficulty in performing physical functioning activities was associated with a higher prevalence of knee pain.

CONCLUSIONS

Many US adults older than age 60 years report knee pain, and the prevalence is higher in older adults. Reports of knee pain are highest among non-Hispanic black women and the oldest Americans. Intervention strategies are needed to prevent and better manage knee pain among older US adults to stem the adverse health consequences and diminished quality of life associated with this common problem.

Comparison of the responses of B1 and B2 kinin receptors to agonist stimulation

The human B2 kinin receptor (B2KR), stably expressed in Chinese hamster ovary cells, responded to bradykinin stimulation with rapid (within minutes) ligand internalization and loss of cell surface receptors (sequestration). By contrast, B1 kinin receptors (B1KR) showed almost no ligand internalization or receptor sequestration upon stimulation with des-Arg10-Kallidin (DAK). The ability of the B2KR to internalize and sequester is conferred by information in the cytoplasmic tail of the receptor. It is normally impossible to determine receptor affinity at 37 degrees C because of internalization and sequestration processes. We created a mutant B2KR, truncated at K315 of the cytoplasmic tail, that was no longer able to internalize or sequester, and compared the affinity of this mutant, and of the B1KR, at 0 degrees C and 37 degrees C. The B1KR receptor showed the same affinity (Kd = 0.4 nM) at both 0 degrees C and 37 degrees C. By contrast, the K315 mutant of the B2KR showed a lower affinity (Kd = 2.9 nM) at 37 degrees C than at 0 degrees C (Kd = 1.4 nM), indicating more rapid ligand dissociation at 37 degrees C. After ligand exposure, clones expressing B1KR exhibited a very slow dissociation of DAK, even at 37 degrees C. Although both kinin receptor subtypes induce the generation of inositol phosphates, functional responses showed clear differences. The response to stimulation of the B2KR comprises a rapid loss of functional responses, receptor sequestration, and ligand dissociation, and, upon long term stimulation, downregulation. By contrast, ligand stimulation of the B1KR, once this receptor is expressed de novo under pathological conditions, results in persistent signaling due to lack of ligand dissociation, desensitization and receptor sequestration. Moreover, long term stimulation of this receptor actually leads to increased expression.

Coupling of the PTH/PTHrP receptor to multiple G-proteins. Direct demonstration of receptor activation of Gs, Gq/11, and Gi(1) by [alpha-32P]GTP-gamma-azidoanilide photoaffinity labeling

Parathyroid hormone (PTH) elicits many of its physiological effects by activating distinct, G-protein-coupled signaling cascades that lead to synthesis of cyclic AMP and hydrolysis of phosphatidylinositol 4,5-bisphosphate. Using the nonhydrolyzable photo-reactive GTP analog [alpha-32P]GTP-gamma-azidoanilide (GTP-AA) and peptide antisera raised against G-protein alpha-subunits, we studied coupling of the PTH receptor to G-proteins in rat osteoblast-like cells (ROS 17/2.8), and in human embryonal kidney cells expressing the cloned human PTH/parathyroid hormone-related peptide (PTHrP) receptor at 40,000 receptors/cell (C20) or 400,000 receptors/cell (C21). Incubation of C21 membranes (but not C20 membranes) with [Nle8,18, Tyr34]-bovine PTH(1-34) amide (bPTH[1-34]) led to concentration-dependent incorporation of GTP-AA into the two isoforms of G alpha s, into G alpha q/11, and to a much lesser extent into G alpha i(1). In ROS 17/2.8 cells, bPTH(1-34) increased the incorporation of GTP-AA into G alpha s, but not into G alpha q/11 or G alpha i. The ability of bPTH(1-34) to increase labeling of G alpha s and G alpha q/11 was correlated with the receptor-dependent sensitivity of the adenylyl cyclase and phospholipase C signaling pathways to the hormone.

Osteoarthritis in older adults

OBJECTIVE

This review highlights the clinical and pathophysiologic features of osteoarthritis (OA) of the peripheral joints and discusses the current and future management options for this common but potentially disabling disease. This article also addresses the contribution of osteoarthritis to falls and functional impairment in older people.

DESIGN

A critical assessment of current data regarding the pathogenesis of osteoarthritis, current and future therapies, and the potential role of OA in falls and functional impairment in older people.

CONCLUSIONS

Osteoarthritis is the most prevalent articular disease in older adults. Disease markers that will detect early disease and allow early intervention with pharmacologic agents that modify, if not halt, disease progression are much needed, but they are presently unavailable. Current management should include safe and adequate pain relief using systemic and local therapies and should also include medical and rehabilitative interventions to prevent, or at least compensate for, functional deficits. Although OA can result in impaired mobility and lower extremity function, its contribution as a cause of recurrent falls or impaired self-care, relative to other comorbid conditions, remains ill-defined. Further analysis of the determinants of disability, loss of mobility and falls in older patients with OA is needed.

Soluble recombinant neutral endopeptidase (CD10) as a potential antiinflammatory agent

Several endogenous peptides, including bradykinin and substance P, have potent inflammatory effects in the joint. Levels of these peptides are regulated by plasma and cell-associated peptide degrading enzymes. One of these peptidases, neutral endopeptidase-24.11 (NEP-24.11), is expressed constitutively and in high density on human synovial cells and is presumed to play a critical role in local regulation of peptide levels in the joint. We examined the role of endogenous NEP-24.11 in regulating bradykinin-mediated effects in an articular model, and investigated the ability of soluble, recombinant human NEP-24.11 to augment the effects of the endogenous enzyme. Our studies demonstrate that endogenous synovial NEP-24.11 does not significantly modulate inflammatory peptide effects on cells when competing with colocalizing peptide receptors expressed in high density. Administration of excess, soluble recombinant NEP-24.11 can overcome this problem, however. Furthermore, the activity of the recombinant enzyme was not compromised in the presence of oxidants or inflammatory joint fluids. Recombinant NEP-24.11 holds promise as a novel therapeutic strategy for the treatment of inflammatory arthritis.

Influence of the cytosolic carboxyl termini of human B1 and B2 kinin receptors on receptor sequestration, ligand internalization, and signal transduction

To determine the role of the cytoplasmic carboxyl termini of human B1 and B2 kinin receptors (B1KR and B2KR, respectively) in the internalization of their respective ligands, des-Arg10-kallidin and bradykinin (BK), both wild type receptors, as well as truncated B2KRs, a mutated B2KR, and chimeric receptors were stably expressed in Chinese hamster ovary cells. Incubation of [3H]BK at 37 degrees C with cells expressing wild type B2KR resulted in pronounced and rapid ligand internalization ( approximately 80% after 10 min). By contrast, incubation of 3H-labeled des-Arg10-kallidin with cells expressing B1KR resulted in a modest, slow internalization of the ligand (<20% after 10 min). Replacement, from Cys324, of the cytoplasmic carboxyl terminus of the B2KR with that of the B1KR from Cys330 (both Cys residues are putative palmitoylation sites) greatly reduced ligand internalization ( approximately 40% after 10 min) without significantly altering Kd or ligand-induced signal activation. By marked contrast, the corresponding replacement, of the sequence from Cys330 of the cytoplasmic carboxyl terminus of the B1KR with the segment of the B2KR, led to a striking increase of ligand internalization ( approximately 75% within 10 min) without altering Kd or ligand-induced signal activation. Truncation of the B2KR to within three amino acids of Cys324 (truncation at Gly327) led to strongly reduced ligand internalization ( approximately 40% after 10 min). Truncation of the B2KR up to Lys315 almost completely abolished internalization of [3H]BK (10% after 10 min). This additional reduction is apparently not caused by the loss of the potential palmitoylation site at Cys324, since a B2KR with a point mutation of Cys324 to Ala internalized [3H]BK as rapidly as the wild type B2KR. From these results we conclude that the cytoplasmic carboxyl terminus of the human B2KR contains sequences that are necessary and sufficient to permit rapid ligand-induced sequestration of human kinin receptors and internalization of their agonists.

Stable expression of the human kinin B1 receptor in Chinese hamster ovary cells. Characterization of ligand binding and effector pathways

To delineate ligand binding and functional characteristics of the human B1 kinin receptor, a stable clone of Chinese hamster ovary cells expressing a single class of binding sites for [3H]des-Arg10-lysylbradykinin with a Kd of 0.3 nM and a Bmax of 38 fmol/mg protein ( approximately 40,000 receptors/cell) was isolated. Studies with peptide analogs showed that a lysine residue at position 1 (based on the lysylbradykinin sequence) of ligands was essential for high affinity binding to the human B1 receptor. In marked contrast to cloned Chinese hamster ovary cells expressing the human kinin B2 receptor, which internalized approximately 80% of the ligand within 5 min upon exposure to 2 nM [3H]bradykinin, exposure of cells expressing the B1 receptor to 1 nM [3H]des-Arg10-lysylbradykinin resulted in minimal ligand internalization. Stimulation of the B1 receptor led to inositol phosphate generation and transient increases in intracellular calcium, confirming coupling to phospholipase C, while immunoprecipitation of photoaffinity-labeled G-proteins from membranes indicated specific coupling of the receptor to Galphaq/11 and Galphai1,2. The B1, unlike the B2, receptor does not desensitize (as demonstrated by continuous phosphoinositide hydrolysis), enhancing the potential role of this receptor during inflammatory events.

Mechanisms of prostanoid synthesis in human synovial cells: cytokine-peptide synergism

Bradykinin (BK)2 and interleukin-1 (IL-1) interact synergistically to stimulate prostaglandin synthesis in human synovial fibroblast-like cells. The effect of BK is rapid and correlates with its capacity to elevate cytosolic levels of calcium ([Ca2+]i), while IL-1's effect is slow and s dependent upon de novo protein synthesis. The mechanism of this synergistic interaction was investigated. In the basal state, high levels of arachidonic acid (AA) were spontaneously released from synovial cells but near absent levels of cyclooxygenase activity prevented metabolism of AA to prostanoid. BK was a potent stimulus for elevating AA, but not prostaglandins, above basal levels. IL-1, in contrast, increased prostaglandins but not AA, above basal levels. IL-1 treatment was not associated with a loss or redistribution of AA among phospholipid classes. These results are consistent with high basal phospholipase activity in synovial cells and demonstrate the ability of BK, presumably via its ability to raise [Ca2+]i, to further elevate this activity(ies). Metabolism of AA to prostanoid is minimal in resting and BK-stimulated synovial cells, however, without the concomitant induction of cyclooxygenase activity by IL-1. These studies clarify the different, but synergistic, mechanisms of action of a peptide and cytokine in stimulating prostanoid synthesis in synovial cells. In addition, these data extend the results of previous investigations in demonstrating that basal phospholipase activity provides sufficient AA substrate for IL-1 induced prostanoid synthesis without invoking the concomitant induction of phospholipase activity by IL-1.

Inhibition of the response to nasal provocation with bradykinin by HOE-140: efficacy and duration of action

The present studies were undertaken as a first step to evaluate the potential usefulness of the bradykinin antagonist HOE-140 in delineating the role of kinins in the pathogenesis of chronic rhinitis. Intranasal single-dose administration of HOE-140, at doses up to 500 micrograms, was safe and well tolerated. Bradykinin-induced symptoms and increased vascular permeability could be inhibited, in a dose-dependent manner, by preadministration of HOE-140 5 min prior to kinin challenge. The results of dose-ranging experiments suggested that bradykinin and HOE-140 were approximately equipotent at bradykinin receptors. Preadministration of HOE-140 2 h before kinin challenge caused a significant but much weaker level of inhibition than that seen with 5-min preadministration. Comparison of data with those obtained during dose-ranging studies suggested that more than 90% of the administered HOE-140 was lost during this 2-h period. We conclude that topical HOE-140 is an effective inhibitor of the effects of bradykinin on the nasal mucosa but that the short duration of action of this drug may severely limit the utility of HOE-140 in delineating the role of kinins in the pathogenesis of chronic rhinitis.

Bradykinin is a potent and relatively selective stimulus for cytosolic calcium elevation in human synovial cells

Previously, we have shown that bradykinin elicits the production of prostaglandin E2 (PGE2) in human synovial cells only after pre-exposure of the cells to IL-1. The observation that calcium ionophores, but not a variety of physiologic receptor-mediated agonists, can mimic bradykinin in its synergy with IL-1 led us to hypothesize that the ability of bradykinin to induce prostanoid synthesis was a result of its selective ability (among physiologic agonists) to raise the cytosolic free ionized calcium concentration ([Ca2+]i) levels of synovial cells. Extending this hypothesis, it follows that the relative potency of an agonist in inducing PGE2 production from IL-1-treated cells should be dependent on its ability to raise [Ca2+]i. In these studies, we have confirmed the potent ability of bradykinin to elevate [Ca2+]i in resting human synovial cells. That the effect of bradykinin on [Ca2+]i was mediated through the previously described synovial cell kinin receptor was confirmed by a pharmacologic profile consistent with a high affinity B2 kinin receptor. Furthermore, the relative specificity and potency of the PGE2 response of bradykinin in IL-1-treated cells was paralleled, in resting cells, by a similar pattern in the [Ca2+]i response. Finally, IL-1 had no direct effect on [Ca2+]i levels, nor did it alter agonist-induced elevations in [Ca2+]i. We conclude that the potency of a receptor-mediated agonist in inducing prostanoid synthesis in synovial cells is dependent on its ability to raise [Ca2+]i. However, this effect is not enough, in and of itself, to induce prostanoid synthesis; the concomitant induction by IL-1 of a PG-generating enzyme is also required.

Bradykinin is a potent and relatively selective stimulus for cytosolic calcium elevation in human synovial cells

Previously, we have shown that bradykinin elicits the production of prostaglandin E2 (PGE2) in human synovial cells only after pre-exposure of the cells to IL-1. The observation that calcium ionophores, but not a variety of physiologic receptor-mediated agonists, can mimic bradykinin in its synergy with IL-1 led us to hypothesize that the ability of bradykinin to induce prostanoid synthesis was a result of its selective ability (among physiologic agonists) to raise the cytosolic free ionized calcium concentration ([Ca2+]i) levels of synovial cells. Extending this hypothesis, it follows that the relative potency of an agonist in inducing PGE2 production from IL-1-treated cells should be dependent on its ability to raise [Ca2+]i. In these studies, we have confirmed the potent ability of bradykinin to elevate [Ca2+]i in resting human synovial cells. That the effect of bradykinin on [Ca2+]i was mediated through the previously described synovial cell kinin receptor was confirmed by a pharmacologic profile consistent with a high affinity B2 kinin receptor. Furthermore, the relative specificity and potency of the PGE2 response of bradykinin in IL-1-treated cells was paralleled, in resting cells, by a similar pattern in the [Ca2+]i response. Finally, IL-1 had no direct effect on [Ca2+]i levels, nor did it alter agonist-induced elevations in [Ca2+]i. We conclude that the potency of a receptor-mediated agonist in inducing prostanoid synthesis in synovial cells is dependent on its ability to raise [Ca2+]i. However, this effect is not enough, in and of itself, to induce prostanoid synthesis; the concomitant induction by IL-1 of a PG-generating enzyme is also required.

Type VI collagen-specific messenger RNA is expressed constitutively by cultured human synovial fibroblasts and is suppressed by interleukin-1

OBJECTIVE

Type VI collagen is a prominent constituent of the synovial extracellular matrix. The cellular source of this matrix protein and the identity of local factor sin synovium that may regulate its expression have not been delineated, however. We examined the capacity of human fibroblast-like synovial cells to synthesize type VI collagen as well as the effect of interleukin-1 (IL-1) on this expression.

METHODS

RNA was extracted from cultured human synovial cells derived from patients with rheumatoid arthritis (RA) and osteoarthritis (OA). Northern blots were analyzed using sequence-specific probes, and steady-state messenger RNA (mRNA) levels of the 3 alpha (VI) procollagen chains were measured. The effect of IL-1 treatment on these levels was determined.

RESULTS

Abundant expression of 3 characteristic mRNA transcripts, corresponding to the alpha 1 (4.2-kb), alpha 2 (3.5-kb), and alpha 3 (8.5-kb) chains of type VI procollagen, was observed in untreated cells derived from RA and OA patients. IL-1 treatment consistently suppressed steady-state mRNA levels for all 3 alpha (VI) procollagen chains in a time- and dose-dependent manner. Tumor necrosis factor alpha induced a response similar to that of IL-1, while IL-2 was ineffective in this regard. Indomethacin partially restored alpha (VI) mRNA expression in IL-1--treated cells.

CONCLUSION

These studies provide novel data demonstrating abundant steady-state levels of mRNA transcripts coding for all 3 type VI procollagen polypeptides in human synovial fibroblast-like cells, as well as coordinated down-regulation of these transcripts by IL-1. Local production of IL-1 may thus constitute an important means in vivo of regulating the production of type VI collagen.

Bradykinin effects in guinea pig tracheal epithelial cells are mediated through a B2 kinin receptor and can be inhibited by the selective antagonist Hoe 140

Attempts to evaluate the role of kinins in airway inflammation in humans using the bradykinin receptor antagonist [DArg0-Hyp3-DPhe7]-bradykinin (NPC 567) were unsuccessful, possibly because of the low potency and poor stability of this compound. Recently, [DArg0-Hyp3-Thi5-DTic7-Oic8]-bradykinin (Hoe 140), a novel antagonist that seems to overcome these weaknesses, has been developed. The present study was performed to compare the potency and efficacy of Hoe 140 to those of NPC 567 and another antagonist, [DArg0-Hyp3-DPhe7-Ile8]-bradykinin (B7418), on kinin receptors on guinea pig tracheal epithelial cells. Radioligand binding studies showed the presence of two types of B2 kinin receptors on guinea pig tracheal epithelial cells: a high-affinity site with a Kd of 0.44 nM and Bmax of 12.1 fmol/10(6) cells (4000 sites/cell), and a lower affinity site with a Kd of 10 nM and Bmax of 16 fmol/10(6) cells (9600 sites/cell). Bradykinin-induced prostaglandin E2 production seemed to be associated primarily with the lower affinity site. All three B2 receptor antagonists displaced labeled bradykinin from both classes of binding sites and inhibited bradykinin-induced prostaglandin E2 production, but Hoe 140 was up to 40-fold more potent than NPC 567 and showed an affinity comparable to that of bradykinin for both binding sites. This higher potency of Hoe 140, and its stability against peptidases, suggests that this compound will be useful in evaluating the role of bradykinin in inflammatory diseases of the airways.

Cultured human synovial fibroblasts rapidly metabolize kinins and neuropeptides

Kinins and substance P have been implicated in the pathogenesis of inflammatory arthritis by virtue of their abilities to induce vasodilation, edema, and pain. The relative biological potencies of these peptides in vivo would depend at least in part upon their rates of catabolism in the joint. We hypothesized that human synovial lining cells may regulate intraarticular levels of kinins and neuropeptides via degradation by cell surface-associated peptidases. We exposed intact human synovial fibroblasts to kinins and substance P, in the presence or absence of specific peptidase inhibitors, and measured the amount of intact substrate remaining and degradation product(s) generated over time. Aminopeptidase M (AmM; EC 3.4.11.2), neutral endopeptidase-24.11 (NEP-24.11; EC 3.4.24.11), and dipeptidyl(amino)peptidase IV (DAP IV; EC 3.4.14.5) were identified on the cell surface of synovial cells. Bradykinin degradation was due entirely to NEP-24.11 (1.39 +/- 0.29 nmol/min per well). Lysylbradykinin was also degraded by NEP-24.11 (0.80 +/- 0.19 nmol/min per well); however, in the presence of phosphoramidon, AmM-mediated conversion to bradykinin (3.74 +/- 0.46 nmol/min per well) could be demonstrated. The combined actions of NEP-24.11 (0.93 +/- 0.15 nmol/min per well) and DAP IV (0.84 +/- 0.18 nmol/min per well) were responsible for the degradation of substance P. AmM (2.44 +/- 0.33 nmol/min per well) and NEP-24.11 (1.30 +/- 0.45 nmol/min per well) were responsible for the degradation of the opioid peptide, [Leu5]enkephalin. The identity of each of the three peptidases was confirmed via synthetic substrate hydrolysis, inhibition profile, and immunological identification. The profiles of peptidase enzymes identified in cells derived from rheumatoid and osteoarthritic joints were identical. These data demonstrate the human synovial fibroblast to be a rich source of three specific peptidases and suggest that it may play a prominent role in regulating peptide levels in the joint.

Characterization of kinin receptors on human synovial cells and upregulation of receptor number by interleukin-1

Bradykinin has been implicated in the pathogenesis of inflammatory arthritis by virtue of its potent proinflammatory properties. We have previously shown bradykinin to be a potent stimulus for the release of prostanoids from interleukin-1 (IL-1)-treated, but not untreated, human synovial cells. We hypothesize that one mechanism by which IL-1 induces responsiveness to bradykinin is by upregulation of number or affinity of kinin receptors on human synovial cells. We performed [3H]bradykinin binding studies in intact human synovial tissue and in cultured human synovial cells. Specific, saturable [3H]bradykinin binding sites in intact synovia were identified by autoradiographic localization and were present in much higher density in rheumatoid, than in osteoarthritis, synovia. In untreated human synovial cells in culture, a single (B2) class of kinin binding sites with a Kd of 2.3 nM and Bmax of 58 +/- 9 fmol/10(6) cells was demonstrated. In matched experiments, IL-1 treatment enhanced specific [3H]bradykinin binding 1.5- to 2.0-fold above that observed in untreated cells. This enhancement was attributable to an increase in Bmax (53 +/- 4 vs. 105 +/- 24 fmol/10(6) cells in untreated and IL-1-treated cells, respectively), rather than an alteration in Kd (1.7 and 1.4 nM, respectively). The potencies of a series of kinin analogs and antagonists and unrelated peptides in displacing [3H]bradykinin from IL-1-treated cells correlated well with their abilities to induce prostanoid release. These studies provide novel information regarding the nature of kinin receptors in intact human synovia and in cultured human synovial cells, their regulation by IL-1 and their role in IL-1-treated cells in kinin-mediated prostaglandin E2 production.

Anti-histone antibodies in the serum of autoimmune MRL and NZB/NZW1 F1 mice

Anti-histone antibodies have been reported in a number of human autoimmune diseases, most notably idiopathic and drug-induced lupus erythematosus. In the current study, anti-histone antibody activity was detected using ELISA and electroblotting techniques in sera from autoimmune NZB/W, MRL-lpr, and MRL-(+)/+ mice. Anti-histone activity increased with age, maturing earlier in females, in both NZB/W and MRL-lpr mice. Testosterone treatment decreased anti-histone activity in NZB/W mice and estrogen treatment from 2 weeks of age increased anti-histone activity in MRL-lpr mice, suggesting that gonadal hormones modified the expression of autoantibodies recognizing these protein antigens. Estrogen also increased serum IgG levels in MRL-lpr mice. Sex hormones affected expression of antibodies recognizing soy milk proteins but not ovalbumin in a similar manner. Nitrocellulose Western blots of SDS gels probed with sera from both types of autoimmune mice most often demonstrated reactivity with histone1. Some mice, usually mature females, also recognized histone4, histone3, and histone2.

Preincubation of human synovial cells with IL-1 modulates prostaglandin E2 release in response to bradykinin

Kinins are vasoactive peptides whose potent inflammatory and bone resorbing properties suggest a role for these autacoids in the pathogenesis of inflammatory arthritis. We used cultured human synovial cells as a model to evaluate the effects of bradykinin on articular tissue. In resting synovial cells, bradykinin was a relatively ineffective stimulus for PGE2 production. However, after a period of preincubation with the cytokine, IL-1, which is itself a stimulus for PGE2 production, synovial cells exhibited a further striking time- and dose-dependent response to bradykinin. Maximal release of PGE2 was observed in response to 10(-7) to 10(-6) M bradykinin after first pretreating the cells for 24 h with 5 to 10 U/ml of IL-1. rIL-1 alpha and IL-1 beta, as well as rTNF-alpha, induced a similar response to bradykinin in synovial cells, whereas recombinant IL-2 did not. The bradykinin analog, lysylbradykinin, was equipotent in inducing PGE2 release from IL-1 pretreated synovial cells, whereas des(Arg9) bradykinin, substance P, and neurokinins A and B were ineffective in this regard in both IL-1-pretreated and in resting cells. Synovial cells derived from patients with rheumatoid arthritis and osteoarthritis responded similarly to bradykinin. The synergistic response in PGE2 production induced by IL-1 and bradykinin was significantly inhibited by pretreatment with 1 microM indomethacin or dexamethasone (96 and 94% inhibition, respectively). In addition, the response was abrogated by pretreatment with 10 micrograms/ml of cycloheximide or actinomycin D (81 and 97% inhibition, respectively). These data provide the first description of synergism of IL-1 with a noncytokine peptide in human synovial cells. The ability of IL-1 to increase the responsiveness of synovial tissues to bradykinin may play an important role in potentiating inflammatory responses within the joint.

Preincubation of human synovial cells with IL-1 modulates prostaglandin E2 release in response to bradykinin

Kinins are vasoactive peptides whose potent inflammatory and bone resorbing properties suggest a role for these autacoids in the pathogenesis of inflammatory arthritis. We used cultured human synovial cells as a model to evaluate the effects of bradykinin on articular tissue. In resting synovial cells, bradykinin was a relatively ineffective stimulus for PGE2 production. However, after a period of preincubation with the cytokine, IL-1, which is itself a stimulus for PGE2 production, synovial cells exhibited a further striking time- and dose-dependent response to bradykinin. Maximal release of PGE2 was observed in response to 10(-7) to 10(-6) M bradykinin after first pretreating the cells for 24 h with 5 to 10 U/ml of IL-1. rIL-1 alpha and IL-1 beta, as well as rTNF-alpha, induced a similar response to bradykinin in synovial cells, whereas recombinant IL-2 did not. The bradykinin analog, lysylbradykinin, was equipotent in inducing PGE2 release from IL-1 pretreated synovial cells, whereas des(Arg9) bradykinin, substance P, and neurokinins A and B were ineffective in this regard in both IL-1-pretreated and in resting cells. Synovial cells derived from patients with rheumatoid arthritis and osteoarthritis responded similarly to bradykinin. The synergistic response in PGE2 production induced by IL-1 and bradykinin was significantly inhibited by pretreatment with 1 microM indomethacin or dexamethasone (96 and 94% inhibition, respectively). In addition, the response was abrogated by pretreatment with 10 micrograms/ml of cycloheximide or actinomycin D (81 and 97% inhibition, respectively). These data provide the first description of synergism of IL-1 with a noncytokine peptide in human synovial cells. The ability of IL-1 to increase the responsiveness of synovial tissues to bradykinin may play an important role in potentiating inflammatory responses within the joint.

Inflammatory central nervous system involvement in rheumatoid arthritis

We describe a patient with seropositive rheumatoid arthritis who developed pachymeningitis resulting in optic atrophy. Clinical, histopathologic, and radiologic findings in 18 additional cases of inflammatory CNS disease associated with rheumatoid arthritis are reviewed. The three characteristic neuropathologic findings were rheumatoid nodules, pachymeningitis or leptomeningitis, and vasculitis. In most cases, more than one of these histopathologic processes were found. The typical host was middle-aged with long-standing severe nodular disease. However, contrary to previous reports, CNS disease occurred in a significant number of patients without active synovitis and extracranial vasculitis and nodules. Although no correlation between specific neurologic symptoms and neuropathology was noted, patients with CNS nodules tended to be asymptomatic more often than patients with vasculitis or meningitis. CSF analysis and computed axial tomography were helpful diagnostic tools, but diagnosis was ultimately made only by directed biopsy or at autopsy. Treatment with surgical decompression and/or corticosteroids has proved beneficial in several cases. Inflammatory CNS involvement in rheumatoid arthritis should be considered in any patient with neurologic symptoms in whom infectious and malignant processes are ruled out. An aggressive, invasive approach for diagnostic biopsies seems warranted.