Activation of synovial cell p38 MAP kinase by macrophage migration inhibitory factor

OBJECTIVE

Macrophage migration inhibitory factor (MIF) is a proinflammatory cytokine important in animal models of rheumatoid arthritis (RA). We investigated the utilization by MIF of mitogen activated protein (MAP) kinase signalling pathways in the stimulation of fibroblast-like synoviocytes (FLS), cyclooxygenase-2 (COX-2), prostaglandin E(2) (PGE(2)), and interleukin 6 (IL-6) and IL-8 expression.

METHODS

Cultured human RA FLS were treated with recombinant MIF. Activation of MAPK was measured by Western blotting and blocked using specific inhibitors. The expression of COX-2, PGE(2), IL-6, and IL-8 were measured using flow cytometry, ELISA, and real-time polymerase chain reaction.

RESULTS

MIF induced the phosphorylation of FLS p38 and extracellular-signal regulated kinase (ERK) MAP kinase. MIF significantly induced COX-2 and IL-6 protein and mRNA expression as well as PGE(2) and IL-8 production. Antagonism of p38 MAP kinase inhibited MIF induction of COX-2, PGE(2), and IL-6. In contrast, antagonism of ERK had no effect on COX-2, PGE(2), or IL-6. Neither antagonist inhibited MIF-induced IL-8.

CONCLUSION

MIF activates RA FLS COX-2 and IL-6 expression via p38 MAP kinase activation and induces IL-8 via p38 and ERK MAP kinase-independent pathways.

Modulation of inflammation and response to dexamethasone by Annexin 1 in antigen-induced arthritis

OBJECTIVE

Annexin 1 (Anx-1) is a putative mediator of the antiinflammatory actions of glucocorticoids (GCs). This study investigated the role of Anx-1 in experimental arthritis and in GC-mediated inhibition of inflammation, using antigen-induced arthritis (AIA) in Anx-1 knockout (Anx-1(-/-)) mice.

METHODS

Arthritis was induced by intraarticular injection of methylated BSA (mBSA) in mice preimmunized with mBSA. Disease was assessed after 7 days by histologic examination of the knee joints. Serum levels of anti-mBSA IgG were determined by enzyme-linked immunosorbent assay. Cytokine messenger RNA (mRNA) expression was detected by real-time polymerase chain reaction.

RESULTS

A significant exacerbation of arthritis was observed in the Anx-1(-/-) mice compared with wild-type (WT) mice. This was associated with increased mRNA expression of synovial interleukin-1 beta, tumor necrosis factor alpha, interleukin-6, and macrophage migration inhibitory factor. Dexamethasone significantly reduced the histologic severity of synovitis and bone damage in the WT mice, but exerted no inhibitory effects in the Anx-1(-/-) mice, and also significantly reduced the serum levels of anti-mBSA IgG and the numbers of peripheral blood neutrophils and lymphocytes in WT mice, but had no such effect in Anx-1(-/-) mice.

CONCLUSION

Anx-1 exerts endogenous antiinflammatory effects on AIA via the regulation of cytokine gene expression, and also mediates the antiinflammatory actions of dexamethasone in AIA.

Macrophage migration inhibitory factor in systemic lupus erythematosus

OBJECTIVE

To examine associations between serum macrophage migration inhibitory factor (MIF) and disease-related variables and corticosteroid use in patients with systemic lupus erythematosus (SLE).

METHODS

Serum MIF concentration was measured by ELISA in 90 female patients with SLE and 279 healthy controls. Univariate and multivariate regression analyses were used to examine the associations between serum MIF concentration and disease-related indices of SLE and corticosteroid use.

RESULTS

Serum MIF concentrations were positively associated with SLE disease damage (SLICC/ACR index), and indices of disease damage were greater in SLE patients with serum MIF concentrations above the normal median value. Serum MIF concentration was also observed to be significantly greater in patients with SLICC/ACR damage index (DI) scores >/= 3. Serum MIF was also positively associated with current corticosteroid dose. Significantly higher SLICC/ACR DI scores were observed in patients with values of serum MIF above the normal median, and this remained significant after adjusting for corticosteroid dose. Serum MIF concentration was also predictive of SLICC/ACR index after 3 years of followup, but this association was partly confounded by corticosteroid dose. Serum MIF was also negatively associated with serum creatinine concentration, independent of disease damage and corticosteroid dose.

CONCLUSION

MIF is overexpressed in patients with SLE. While this can be partly explained by corticosteroid use, there is evidence of an association between MIF and lupus-related disease damage.

Is macrophage migration inhibitory factor a therapeutic target in systemic lupus erythematosus?

Systemic lupus erythematosus (SLE) is the prototype of a cluster of diseases that are characterized by a loss of self tolerance and chronic inflammation in organs including skin, kidney, brain and joints. Researchers have long debated the varying contributions of the components of the immune system to the pathogenesis of SLE, but the emigration of leucocytes from the microcirculation, and the subsequent tissue inflammation mediated by these inflammatory cells, are key features of chronic inflammation seen in SLE. Macrophage migration inhibitory factor (MIF) is a broad-spectrum pro-inflammatory cytokine. We hypothesize that MIF is an important inflammatory mediator in the perpetuation of immune activation in SLE, via its effects on activation of T and B cells, and endothelial and effector cells. As MIF exerts anti-apoptotic effects, it may also play a role in promoting abnormal survival of autoreactive lymphocytes, thus perpetuating autoimmune reactivity. In addition, MIF has a unique relationship with glucocorticoids, in that MIF can override the effects of glucocorticoids and may be important in steroid resistance. By virtue of its pluripotent functions, we propose that MIF may be a critical mediator of inflammation and damage in SLE, and that targeting of MIF may offer therapeutic benefits in this disease.

Regulation of p53 by macrophage migration inhibitory factor in inflammatory arthritis

OBJECTIVE

To study the capacity of macrophage migration inhibitory factor (MIF) to regulate proliferation, apoptosis, and p53 in an animal model of rheumatoid arthritis (RA) and in fibroblast-like synoviocytes (FLS) from humans with RA.

METHODS

Antigen-induced arthritis (AIA) was induced in MIF(-/-) mice and littermate controls. FLS were obtained from patients with RA. Western blotting and immunohistochemistry were used to measure p53 in cells and tissues. Apoptosis was detected in cells by flow cytometry using TUNEL and annexin V/propidium iodide labeling. Apoptosis in tissue was detected using TUNEL. Proliferation was assessed in cultured cells and tissue by (3)H-thymidine incorporation and Ki-67 immunostaining, respectively.

RESULTS

MIF inhibited p53 expression in human RA FLS. Levels of p53 were correspondingly increased in MIF(-/-) mouse tissues and cells. Spontaneous and sodium nitroprusside-induced apoptosis were significantly increased in MIF(-/-) cells. In vitro exposure of FLS to MIF reduced apoptosis and significantly induced FLS proliferation. Synoviocyte proliferation in MIF(-/-) mice was correspondingly reduced. A decrease in the severity of AIA in MIF(-/-) mice was associated with an increase in p53 and apoptosis in synovium. Evidence of in situ proliferation was scant in this model, and no difference in in situ proliferation was detectable in MIF(-/-) mice compared with wild-type mice.

CONCLUSION

These results indicate a role for MIF in the regulation of p53 expression and p53-mediated events in the inflamed synovium and support the hypothesis that MIF is of critical importance in the pathogenesis of RA.

Macrophage migration inhibitory factor in rheumatoid arthritis: clinical correlations

OBJECTIVE

Cytokines play an important role in the pathology of rheumatoid arthritis (RA). Macrophage migration inhibitory factor (MIF) is a cytokine with a broad spectrum of actions, including induction of monocyte tumour necrosis factor alpha (TNF-alpha). Evidence of the expression and proinflammatory activity of MIF has recently been demonstrated in RA synovium and in animal models of RA. We wished to assess the relationship between MIF expression in synovium and clinical disease.

METHODS

Computer-assisted analysis of the cytokine content of arthroscopically obtained biopsies of RA synovium, using paired samples from eight patients with active and inactive/treated disease, was compared with documented clinical parameters.

RESULTS

Synovial MIF immunostaining correlated strongly with disease activity as measured by CRP concentration. Reductions in clinical disease parameters, including CRP, tender and swollen joint counts, were accompanied by significant reductions in synovial MIF. Synovial TNF-alpha, transforming growth factor beta (TGF-beta) and interleukin (IL) 10 also showed a significant reduction in association with reduced disease activity, while IL-1 beta and IL-1 receptor agonist did not.

CONCLUSION

The correlation of synovial MIF with disease activity corroborates existing evidence of the role of this cytokine in RA. The demonstration that only MIF and TNF-alpha show significant variation in synovial cytokine content with clinical remission suggests that MIF is an important member of the cytokine hierarchy in RA.

Hypothalamic-pituitary-adrenal axis regulation of inflammation in rheumatoid arthritis

The profound anti-inflammatory effects of glucocorticoids in drug therapy are reflected in the effects in vivo of endogenous glucocorticoids produced by the adrenals. The production of adrenal glucocorticoids is driven by the hypothalamus and pituitary, which in turn are responsive to circulating products of the inflammatory response, especially cytokines. That inflammation can drive the production of anti-inflammatory glucocorticoids denotes the hypothalamic-pituitary-adrenal (HPA)-immune axis as a classic negative feedback control loop. Defects in HPA axis function are implicated in susceptibility to, and severity of, animal models of rheumatoid arthritis (RA), and are hypothesized to contribute to the human disease. In this paper, data supporting the concept of the HPA axis as a regulator of the inflammatory response in animal models of arthritis are reviewed, along with data from studies in humans. Taken together, these data support the hypothesis that the HPA axis provides one of the key mechanisms for inhibitory regulation of the inflammatory response. Manipulation of HPA axis-driven endogenous anti-inflammatory responses may provide new methods for the therapeutic control of inflammatory diseases.

Regulation of synoviocyte phospholipase A2 and cyclooxygenase 2 by macrophage migration inhibitory factor

OBJECTIVE

Macrophage migration inhibitory factor (MIF) is a proinflammatory cytokine with known actions in macrophage and T cell activation. MIF also has the unique capacity to reverse the inhibitory effects of glucocorticoids on these cells. We have recently demonstrated MIF expression in human rheumatoid arthritis (RA) synovium and cultured fibroblast-like synoviocytes (FLS), as well as the ability of FLS-derived MIF to induce monocyte release of tumor necrosis factor alpha. We investigated the effects of MIF on aspects of RA FLS activation, including the induction of phospholipase A2 (PLA2) and cyclooxygenase (COX).

METHODS

PLA2 activity was measured by 3H-arachidonic acid released from treated FLS supernatants. COX activity was measured by prostaglandin E2 enzyme-linked immunosorbent assay. Cytosolic PLA2 (cPLA2) and COX-2 messenger RNA (mRNA) were determined using semiquantitative reverse transcriptase-polymerase chain reaction.

RESULTS

Constitutive PLA2 activity was detected in RA FLS. Recombinant human MIF up-regulated PLA2 activity (P < 0.01) and cPLA2 mRNA expression, but had no effect on secretory PLA2. Recombinant human MIF up-regulated COX activity (P < 0.05) and COX-2 mRNA, but had no observable effect on COX-1. Interleukin-1beta (IL-1beta) significantly up-regulated PLA2 activity (P < 0.005) and cPLA2 mRNA expression while anti-MIF monoclonal antibody (mAb) significantly inhibited this IL-1beta-induced PLA2 activity (P < 0.02). Anti-MIF mAb significantly reduced IL-1beta-induced COX activity (P < 0.05) and COX-2 mRNA expression.

CONCLUSION

MIF exerts a proinflammatory effect on key aspects of RA FLS activation. That anti-MIF mAb inhibited IL-1beta up-regulation of FLS indicates an additional cofactor role for MIF in IL-1beta-induced FLS activation. These data suggest that MIF antagonism has important therapeutic potential in RA.

Role of macrophage migration inhibitory factor (MIF) in murine antigen-induced arthritis: interaction with glucocorticoids

(MIF) is a broad-spectrum proinflammatory cytokine implicated in human rheumatoid arthritis. The synthesis of MIF by synovial cells is stimulated by glucocorticoids, and previous studies suggest that MIF antagonizes the anti-inflammatory effects of glucocorticoids. This has not been established in a model of arthritis. We wished to test the hypothesis that MIF can act to reverse the anti-inflammatory effects of glucocorticoids in murine antigen-induced arthritis (AIA). Cutaneous DTH reactions and AIA were induced by intradermal injection and intra-articular injection, respectively, of methylated bovine serum albumin in presensitized mice. Animals were treated with anti-MIF MoAbs, recombinant MIF, and/or dexamethasone (DEX). Skin thickness of DTH reactions was measured with callipers and arthritis severity was measured by blinded quantitative histological assessment of synovial cellularity. Cutaneous DTH to the disease-initiating antigen was significantly inhibited by anti-MIF MoAb treatment (P < 0.001). AIA was also significantly inhibited by anti-MIF MoAb (P < 0.02). DEX treatment induced a dose-dependent inhibition of AIA, which was significant at 0.2 mg/kg (P < 0.05). MIF treatment reversed the effect of therapeutic DEX on AIA (P < 0.001). DEX also significantly inhibited DTH reactions (P < 0.05) but rMIF had no effect on this effect of DEX. DTH and AIA are MIF-dependent models of inflammation and arthritis. The reversal of glucocorticoid suppression of AIA by MIF supports the concept that MIF is a counter-regulator of glucocorticoid control of synovial inflammation. Although DTH was observed to be MIF-dependent and glucocorticoid-sensitive, rMIF had no reversing effect on the suppression of DTH by glucocorticoids. This suggests that inflammatory processes in specific tissues may respond differently to MIF in the presence of glucocorticoids.

Annexin I surface binding sites and their regulation on human fibroblast-like synoviocytes

OBJECTIVE

Annexin I is a glucocorticoid-inducible protein whose expression in rheumatoid synovium and inhibitory actions in animal models of arthritis suggests its involvement in human arthritis. The present study explored the potential for annexin I to mediate its antiinflammatory actions via specific cell-surface binding sites on human fibroblast-like synoviocytes (FLS).

METHODS

Annexin I binding sites on cultured FLS from patients with osteoarthritis (OA) and rheumatoid arthritis (RA) were determined by ligand-binding flow cytometry. Phospholipase A2 (PLA2) activity was determined by arachidonic acid release.

RESULTS

FLS exhibited saturable, concentration-dependent cell-surface annexin I binding, with >99% of the OA FLS exhibiting binding at an annexin I concentration of 10 microM. Annexin I binding of RA FLS was significantly lower than that of OA FLS. FLS annexin I binding sites were not affected by elastase or a specific elastase inhibitor, and elastase release did not differ between RA and OA cells. In contrast, collagenase significantly increased annexin I binding sites on OA FLS and approached a significant effect on RA FLS. Tumor necrosis factor alpha increased annexin I binding sites on OA and RA FLS. Similarly, interleukin-1beta significantly increased annexin I binding on OA FLS; but the increased binding on RA FLS was not significant. Dexamethasone exerted no significant effect on OA or RA FLS annexin I binding sites. Treatment of RA FLS with an annexin I N-terminal peptide significantly inhibited RA FLS PLA2 activity.

CONCLUSION

This is the first description of the expression, regulation, and function of cell surface annexin I binding sites on FLS. Reduced annexin I binding sites in RA FLS may impair the sensitivity of certain proinflammatory events to glucocorticoids.

Corticosteroids in the treatment of rheumatologic diseases

The year 2000 marks the fiftieth anniversary of the awarding of the Nobel Prize for Medicine to Hench, Kendall, and Reichstein for their discovery of glucocorticoid treatment of rheumatic diseases. The efficacy and toxicity of glucocorticoids has remained a matter of contention ever since, with debate continuing over their place in the therapeutic armamentarium of rheumatologists. Few if any rheumatologists would not prescribe glucocorticoids, however, and review of new data on their use, efficacy, and toxicity remains topical. Perceived advances in the ability to manage osteoporosis arising from glucocorticoid use has allowed focus to shift onto other toxicities, including vascular disease, but important advances in our understanding of the mechanism of action of glucocorticoids are still lacking.

Regulation of macrophage migration inhibitory factor by endogenous glucocorticoids in rat adjuvant-induced arthritis

OBJECTIVE

To explore the regulation of macrophage migration inhibitory factor (MIF) by endogenous glucocorticoids in adjuvant-induced arthritis (AIA).

METHODS

Adrenalectomy or sham operation was performed 2 days prior to adjuvant arthritis induction. Synovial explant supernatant levels of MIF and tumor necrosis factor alpha (TNFalpha) were measured by enzyme-linked immunosorbent assay (ELISA). Synovial MIF immunostaining was detected by 3-layer immunohistochemistry. Serum MIF levels were measured by Western blotting. Pituitary MIF release was measured by ELISA. Anti-MIF monoclonal antibody (mAb) or isotype-matched control antibody was administered to adrenalectomized (ADX) animals throughout AIA development.

RESULTS

Compared with sham operation, adrenalectomy was associated with significant exacerbation of clinical disease parameters (P < 0.05). Adrenalectomy was associated with significantly reduced levels of synovial MIF, but not TNFalpha. In contrast, adrenalectomy was associated with increased serum MIF levels. Concomitant increased pituitary MIF levels were observed in ADX rats, consistent with the pituitary being the principal source of this increase. The administration of specific anti-MIF mAb conferred 100% protection from lethality during arthritis development and decreased arthritis disease expression.

CONCLUSION

These findings provide the first in vivo confirmation of the observation that endogenous glucocorticoids are involved in the regulation of MIF in a site of inflammation, and that local and systemic MIF production are differentially regulated in this setting. The reversal of disease in ADX rats by anti-MIF mAb suggests that balance between glucocorticoids and MIF may influence the expression of inflammatory disease.

Annexin I and dexamethasone effects on phospholipase and cyclooxygenase activity in human synoviocytes

Annexin I is a glucocorticoid-induced mediator with anti-inflammatory activity in animal models of arthritis. We studied the effects of a bioactive annexin I peptide, ac 2-26, dexamethasone (DEX), and interleukin-1beta (IL-1beta) on phospholipase A2 (PLA2) and cyclooxygenase (COX) activities and prostaglandin E2 (PGE2) release in cultured human fibroblast-like synoviocytes (FLS). Annexin I binding sites on human osteoarthritic (OA) FLS were detected by ligand binding flow cytometry. PLA2 activity was measured using 3H-arachidonic acid release, PGE2 release and COX activity by ELISA, and COX2 content by flow cytometry. Annexin I binding sites were present on human OA FLS. Annexin I peptide ac 2-26 exerted a significant concentration-dependent inhibition of FLS constitutive PLA2 activity, which was reversed by IL-1beta. In contrast, DEX inhibited IL-1beta-induced PLA2 activity but not constitutive activity. DEX but not annexin I peptide inhibited IL-1beta-induced PGE2 release. COX activity and COX2 expression were significantly increased by IL-1beta. Annexin I peptide demonstrated no inhibition of constitutive or IL-1beta-induced COX activity. DEX exerted a concentration-dependent inhibition of IL-1beta-induced but not constitutive COX activity. Uncoupling of inhibition of PLA2 and COX by annexin I and DEX support the hypothesis that COX is rate-limiting for PGE2 synthesis in FLS. The effect of annexin I but not DEX on constitutive PLA2 activity suggests a glucocorticoid-independent role for annexin I in autoregulation of arachidonic acid production. The lack of effect of annexin I on cytokine-induced PGE2 production suggests PGE2-independent mechanisms for the anti-inflammatory effects of annexin I in vivo.

Endogenous glucocorticoids modulate experimental anti-glomerular basement membrane glomerulonephritis

The influence of endogenous glucocorticoids (GC) on glomerular injury was studied in a rat model of heterologous anti-glomerular basement membrane (GBM) glomerulonephritis (GN). Sprague-Dawley rats underwent adrenalectomy (ADX) or sham-operation 3 days prior to i.v. administration of both nephritogenic (100 microgram/g) and subnephritogenic (50 microgram/g) doses of sheep anti-rat GBM globulin. Administration of a subnephritogenic dose of anti-GBM globulin resulted in GN in adrenalectomized animals only. Similarly, ADX performed prior to administration of anti-GBM in the nephritogenic dose range resulted in exacerbation of GN compared with sham-operated animals (24 h protein excretion: 190.8 +/- 32.8 versus 42.5 +/- 2.6 mg/24 h; P < 0.005). In ADX animals receiving subnephritogenic doses of anti-GBM injury was manifested by abnormal proteinuria (62.7 +/- 5.8 mg/24 h), accumulation of neutrophils which peaked at 6 h (7.2 +/- 1.37 neutrophils per glomerular cross-section (neut/gcs)) and macrophage accumulation in glomeruli at 24 h (6.8 +/- 1.2 macrophages/gcs). Sham-adrenalectomized animals given the same dose of anti-GBM globulin developed minimal or no glomerular injury: urinary protein excretion (8.7 +/- 1.5 mg/24 h, P < 0.001); neutrophils (0.2 +/- 0.04 neutrophils/gcs, P < 0.001); macrophages (1.2 +/- 0.5 macrophages/gcs, P < 0.001). The increased cellular recruitment to glomeruli in adrenalectomized animals was associated with glomerular endothelial P-selectin expression. P-selectin expression was not detected in sham-operated rats after anti-GBM injection. Complement deposition in glomeruli was minimal in both groups. Physiologic GC replacement of ADX rats receiving subnephritogenic-dose anti-GBM reversed the observed susceptibility to GN development, with urinary protein excretion (7.8 +/- 1.12, P < 0.005) and no detectable P-selectin expression or leucocyte accumulation in glomeruli. These results suggest that endogenous GC modulate heterologous anti-GBM nephritis in rats and that this may be attributable, in part, to regulation of P-selectin expression.

Glucocorticoid regulation of inflammation: the plot thickens

While glucocorticoids are widely used in the suppression of immune-inflammatory diseases, much remains unknown about the contribution of endogenous adrenal glucocorticoids to inflammatory regulation. It is now well understood that glucocorticoids are increased by inflammatory stress and provide for responsive limitation of inflammation. It is self-evident that the immune response in healthy animals takes place in a milieu characterised by background levels of glucocorticoids. It is less well appreciated, however, that basal levels of glucocorticoids may in fact be a requirement for a normal immune response. In fact, extensive data exist supporting the hypothesis that glucocorticoids interact with the immune-inflammatory system in a biphasic, concentration dependent fashion. No mechanistic explanation for this apparent paradox has previously existed. Recently, the cytokine macrophage migration inhibitory factor (MIF), while possessing pleiotropic pro-inflammatory properties, has been demonstrated to be glucocorticoid-inducible. This observation has the potential to explain key aspects of the biphasic regulation of inflammatory response by endogenous glucocorticoids.

Macrophage migration inhibitory factor in rheumatoid arthritis: evidence of proinflammatory function and regulation by glucocorticoids

OBJECTIVE

Macrophage migration inhibitory factor (MIF) is a proinflammatory cytokine whose involvement in tumor necrosis factor alpha (TNFalpha) synthesis and T cell activation suggests a role in the pathogenesis of rheumatoid arthritis (RA). Antagonism of MIF is associated with marked inhibition of animal models of RA. Uniquely, MIF is inducible by low concentrations of glucocorticoids. We sought to investigate the expression of MIF in RA synovial tissue.

METHODS

MIF was demonstrated in human RA synovium by immunohistochemistry, flow cytometry, enzyme-linked immunosorbent assay (ELISA), and reverse transcription-polymerase chain reaction (RT-PCR). Regulation of MIF expression was investigated by treatment of cultured fibroblast-like synoviocytes (FLS) with interleukin-1beta (IL-1beta), TNFalpha, or interferon-gamma (IFNgamma), and dexamethasone (DEX). Mononuclear cell TNFalpha release after exposure to FLS-conditioned medium was measured by ELISA.

RESULTS

MIF was present in RA synovial lining CD14+ macrophages and FLS. Constitutive MIF messenger RNA (mRNA) expression was demonstrated by RT-PCR of RNA from unstimulated cultured RA FLS, which also released abundant MIF. Serum, synovial fluid, and FLS intracellular MIF were significantly higher in RA patients than in controls. Synoviocyte MIF was not increased by IL-1beta, TNFalpha, or IFNgamma. In contrast, DEX 10(-7)M significantly reduced synoviocyte MIF, while DEX 10(-10)-10(-12)M induced a significant increase in MIF and MIF mRNA. Peripheral blood mononuclear cell TNFalpha release was induced by culture in RA FLS-conditioned medium, and this induction was significantly abrogated by monoclonal anti-MIF antibody, suggesting that MIF is an upstream regulator of TNFalpha release.

CONCLUSION

These data represent the first demonstration of the cytokine MIF in human autoimmune disease and suggest MIF as a potential therapeutic target in RA.

Macrophage migration inhibitory factor in rheumatoid arthritis: evidence of proinflammatory function and regulation by glucocorticoids

OBJECTIVE

Macrophage migration inhibitory factor (MIF) is a proinflammatory cytokine whose involvement in tumor necrosis factor alpha (TNFalpha) synthesis and T cell activation suggests a role in the pathogenesis of rheumatoid arthritis (RA). Antagonism of MIF is associated with marked inhibition of animal models of RA. Uniquely, MIF is inducible by low concentrations of glucocorticoids. We sought to investigate the expression of MIF in RA synovial tissue.

METHODS

MIF was demonstrated in human RA synovium by immunohistochemistry, flow cytometry, enzyme-linked immunosorbent assay (ELISA), and reverse transcription-polymerase chain reaction (RT-PCR). Regulation of MIF expression was investigated by treatment of cultured fibroblast-like synoviocytes (FLS) with interleukin-1beta (IL-1beta), TNFalpha, or interferon-gamma (IFNgamma), and dexamethasone (DEX). Mononuclear cell TNFalpha release after exposure to FLS-conditioned medium was measured by ELISA.

RESULTS

MIF was present in RA synovial lining CD14+ macrophages and FLS. Constitutive MIF messenger RNA (mRNA) expression was demonstrated by RT-PCR of RNA from unstimulated cultured RA FLS, which also released abundant MIF. Serum, synovial fluid, and FLS intracellular MIF were significantly higher in RA patients than in controls. Synoviocyte MIF was not increased by IL-1beta, TNFalpha, or IFNgamma. In contrast, DEX 10(-7)M significantly reduced synoviocyte MIF, while DEX 10(-10)-10(-12)M induced a significant increase in MIF and MIF mRNA. Peripheral blood mononuclear cell TNFalpha release was induced by culture in RA FLS-conditioned medium, and this induction was significantly abrogated by monoclonal anti-MIF antibody, suggesting that MIF is an upstream regulator of TNFalpha release.

CONCLUSION

These data represent the first demonstration of the cytokine MIF in human autoimmune disease and suggest MIF as a potential therapeutic target in RA.

Inhibitory effect of annexin I on synovial inflammation in rat adjuvant arthritis

OBJECTIVE

Annexin I is an endogenous antiinflammatory mediator, expressed in rheumatoid arthritis (RA) synovium, the contribution of which to autoregulation of the synovial inflammatory response has not been examined in models of RA. We investigated the antiinflammatory role of annexin I in rat adjuvant arthritis.

METHODS

Rats with adjuvant-induced arthritis (AIA) were treated with a specific anti-annexin I monoclonal antibody (mAb), isotype control IgG, and/or dexamethasone. Clinical outcomes and synovial synthesis of tumor necrosis factor alpha (TNFalpha), prostaglandin E2 (PGE2), and nitric oxide were examined, and annexin I expression was assessed by flow cytometry and reverse transcription-polymerase chain reaction.

RESULTS

Anti-annexin I mAb reversed the effects of dexamethasone on the clinical features of AIA and exacerbated AIA in the absence of exogenous glucocorticoid. Clinical exacerbation of AIA by anti-annexin I mAb was accompanied by significantly increased synovial TNFalpha and PGE2, suggesting that annexin I tonically inhibits the production of these mediators. Anti-annexin I mAb treatment was associated with significantly reduced leukocyte intracellular annexin I, despite increased annexin I messenger RNA expression, consistent with a depletion effect of extracellular mAb via the cell surface.

CONCLUSION

Annexin I is a key endogenous inhibitory mediator of arthritis via mechanisms that include inhibition of cytokine and effector molecule production. Moreover, a synthesis-independent depletion of intracellular annexin I by extracellular antibody supports the hypothesis that externalization of annexin I is involved in its mode of action.

Three year follow-up of body composition changes in pre-menopausal women with systemic lupus erythematosus

OBJECTIVES

To measure the change in body composition in a pre-menopausal female systemic lupus erythematosus (SLE) population over 3 yr, and to identify predictors of change in body composition including the effects of disease-, corticosteroid (CS)- and patient-related variables.

METHODS

All 55 pre-menopausal females with SLE who participated in a cross-sectional study of body composition in 1994 were invited to undergo interview, examination, medical record review, and body composition assessment by dual-energy X-ray absorptiometry (DXA).

RESULTS

Twenty-eight subjects participated with a mean (S.E.M.) age of 34.4 (1.6) yr, duration of SLE of 6.8 (0.8) yr and mean (range) time to follow-up of 3.2 (2.9-3.4) yr. Seventeen subjects were exposed to CS during the study period with a mean (range) daily dose of prednisolone of 12.0 (2.8-22.9) mg. There was a significant increase in body mass index (BMI) (24.53+/-0.83 vs 25.37+/-1.04, P = 0.03) and fat-free mass (41.04+/-0.83 vs 41.53+/-0.92, P = 0.05) over the 3 yr period. Univariate analysis revealed that change in fat-free mass was significantly associated with change in total body bone mineral density (BMD) (P = 0.03). Stepwise multiple linear regression analysis revealed a significant independent association of disease activity with increases in both BMI (r2 = 0.41, P = 0.006) and fat mass (r2 = 0.39, P = 0.007), and of exercise and Modified Health Assessment Questionnaire with an increase in fat-free mass (r2 = 0.51, P = 0.007). Age at SLE diagnosis and smoking were significant independent predictors for loss of total body BMD, while CS duration was predictive of an increase in total body BMD (r2 = 0.80, P < 0.0001).

CONCLUSION

In this SLE population, disease activity was predictive of deleterious changes in body composition, including increases in BMI and fat mass. Patient-related variables were also important predictors of body composition change with exercise independently predicting an increase in fat-free mass, and smoking predictive of loss of total body BMD. In contrast, CS-related variables were not found to have harmful effects on body composition. Change in fat-free mass, and not fat mass, was predictive of change in total body BMD.

Urinary excretion of the pyridinium cross-links of collagen in systemic lupus erythematosus

The aim of this study was to measure the urinary excretion of the pyridinium cross-links of collagen and to determine their usefulness as markers of reduced bone mineral density in systemic lupus erythematosus (SLE). All female SLE patients managed at a single centre were invited to participate in a cross-sectional study of urinary pyridinium cross-links excretion (HPLC), bone mineral density (DXA), and SLE-related variables. Ninety-one women with SLE were studied, 35 of whom were postmenopausal. Pyridinoline/Creatinine (Pyd/Cr) and deoxypyridinoline/Cr (Dpd/Cr) levels in postmenopausal women were significantly increased compared with premenopausal values (p = 0.010 and p = 0.004, respectively). Univariate linear regression analysis revealed a significant association of Dpd/Cr with reduced femoral neck and lumbar spine BMD (p = 0.001, p<0.001), and of Pyd/Cr with reduced femoral neck BMD (p = 0.020). In addition, the association of Pyd/Cr with reduced lumbar spine BMD approached significance (p = 0.055). Stepwise multiple linear regression analysis adjusting for other variables confirmed a significant association of Dpd/Cr with reduced lumbar spine BMD (p = 0.006), and a significant association of both Pyd/Cr and Dpd/Cr with postmenopausal status (p = 0.003, p<0.001). It was concluded that in this SLE population, the urinary excretion of Dpd/Cr was a useful marker of reduced BMD at the lumbar spine. Menopausal status was a major predictor of cross-links excretion in SLE.

Endogenous glucocorticoids modulate neutrophil migration and synovial P-selectin but not neutrophil phagocytic or oxidative function in experimental arthritis

Pharmacologic glucocorticoids are powerful inhibitors of the inflammatory response at many levels, including leucocyte trafficking and function. The adhesion molecule P-selectin is a key participant in polymorphonuclear neutrophil (PMN) migration to sites of inflammation. The extent to which endogenous glucocorticoids influence PMN migration and activation is not clear. We used the glucocorticoid receptor antagonist RU486 to examine the effect of endogenous glucocorticoid blockade on PMN migration and function in carrageenan monoarthritis in the rat. Arthritis was induced by intraarticular injection of carrageenan and disease severity measured by PMN count in synovial lavage fluid. Decalcified frozen sections of injected joints were analysed for expression of P-selectin by immunohistochemistry. Adrenal glucocorticoid action was blocked in vivo with RU486 20 mg/kg. PMN phagocytosis and reactive oxygen species synthesis were measured by flow cytometry. Carrageenan injection was associated with severe arthritis (synovial lavage PMN 5.9 +/- 0.7 x 10(6), P < 0.01 versus control) which was dose-dependent. P-selectin was not detected in normal joints but was abundant in joints injected with 500 microg carrageenan. RU486 resulted in exacerbation of carrageenan arthritis (9.7 +/- 0.8 x 10(6), P < 0.05). RU486 also altered the threshold for disease induction, in that most RU486-treated animals were susceptible to arthritis at a dose of carrageenan (2.5 microg) which did not induce arthritis in most control-treated animals (P < 0.05), denoting an altered threshold for arthritis induction. RU486 treatment was associated with increased synovial P-selectin expression. Activation status as measured by PMN phagocytic and oxidative function were not influenced by endogenous glucocorticoid blockade. These findings suggest that endogenous glucocorticoids selectively influence PMN migration to inflamed joints via P-selectin expression, but have no effect on PMN activation status.