The role of adhesion molecules in the pathogenesis of rheumatoid arthritis

Increased CEACAM1 expression on peripheral blood neutrophils in patients with rheumatoid arthritis

Altered expression of adhesion molecules in immune cells has been demonstrated in rheumatoid arthritis (RA). Carcinoembryonic-antigen-related cell-adhesion molecule 1 (CEACAM1) is an adhesion molecule that acts as a coinhibitory receptor in the immune system. We investigated the role of CEACAM1 in immune cell subsets of patients with RA. Peripheral blood was obtained from 37 patients with RA and 20 healthy controls (HC). The expression of CEACAM1 and T-cell immunoglobulin mucin domain molecule (TIM) -3 on peripheral blood mononuclear cells and neutrophils was analyzed by flow cytometry. Intracellular TIM-3 expression was analyzed using cellular lysates by Western blot analysis. Serum levels of soluble CEACAM1 (sCEACAM1) were estimated by an enzyme-linked immunosorbent assay. CEACAM1 expression was not detected in peripheral blood mononuclear cells, including in CD14(+) monocytes and CD3(+) lymphocytes isolated from patients with RA or HC. However, substantial cell-surface expression of CEACAM1 was detected in peripheral blood neutrophils, and it was significantly elevated in samples from patients with RA without remission compared to those in remission. There was no significant difference in serum levels of sCEACAM1 between patients with RA and HC. Cell-surface expression of TIM-3 was not detected in peripheral blood neutrophils from patients with RA or HC but was seen in CD14(+) monocytes. However, there was no significant difference in TIM-3 expression on monocytes between patients with RA and HC. Our data indicate that cell-surface expression of CEACAM1 on peripheral blood neutrophils are higher in patients with RA and that it is associated with rheumatoid inflammation. Further studies are needed to explore the potential role of CEACAM1 in rheumatoid inflammatory pathways.

The complement system drives local inflammatory tissue priming by metabolic reprogramming of synovial fibroblasts

Arthritis typically involves recurrence and progressive worsening at specific predilection sites, but the checkpoints between remission and persistence remain unknown. Here, we defined the molecular and cellular mechanisms of this inflammation-mediated tissue priming. Re-exposure to inflammatory stimuli caused aggravated arthritis in rodent models. Tissue priming developed locally and independently of adaptive immunity. Repeatedly stimulated primed synovial fibroblasts (SFs) exhibited enhanced metabolic activity inducing functional changes with intensified migration, invasiveness and osteoclastogenesis. Meanwhile, human SF from patients with established arthritis displayed a similar primed phenotype. Transcriptomic and epigenomic analyses as well as genetic and pharmacological targeting demonstrated that inflammatory tissue priming relies on intracellular complement C3- and C3a receptor-activation and downstream mammalian target of rapamycin- and hypoxia-inducible factor 1α-mediated metabolic SF invigoration that prevents activation-induced senescence, enhances NLRP3 inflammasome activity, and in consequence sensitizes tissue for inflammation. Our study suggests possibilities for therapeutic intervention abrogating tissue priming without immunosuppression.

Characterisation of fibroblast-like synoviocytes from a murine model of joint inflammation

Introduction

Fibroblast-like synoviocytes (FLS) play a central role in defining the stromal environment in inflammatory joint diseases. Despite a growing use of FLS isolated from murine inflammatory models, a detailed characterisation of these cells has not been performed.

Methods

In this study, FLS were isolated from inflamed joints of mice expressing both the T cell receptor transgene KRN and the MHC class II molecule Ag7 (K/BxN mice) and their purity in culture determined by immunofluorescence and real-time reverse transcription polymerase chain reaction (real-time RT-PCR). Basal expression of proinflammatory genes was determined by real-time RT-PCR. Secreted interleukin 6 (IL-6) was measured by enzyme-linked immunosorbent assay (ELISA), and its regulation by tumor necrosis factor-alpha (TNF-α and corticosterone (the major glucocorticoid in rodents) measured relative to other mesenchymal cell populations.

Results

Purity of FLS culture was identified by positive expression of fibronectin, prolyl 4-hydroxylase, cluster of differentiation 90.2 (CD90.2) and 248 (CD248) in greater than 98% of the population. Cultured FLS were able to migrate and invade through matrigel, a process enhanced in the presence of TNF-α. FLS isolated from K/BxN mice possessed significantly greater basal expression of the inflammatory markers IL-6, chemokine ligand 2 (CCL-2) and vascular cell adhesion molecule 1 (VCAM-1) when compared to FLS isolated from non-inflamed tissue (IL-6, 3.6 fold; CCL-2, 11.2 fold; VCAM-1, 9 fold; P < 0.05). This elevated expression was abrogated in the presence of corticosterone at 100 nmol/l. TNF-α significantly increased expression of all inflammatory markers to a much greater degree in K/BxN FLS relative to other mesenchymal cell lines (K/BxN; IL-6, 40.8 fold; CCL-2, 1343.2 fold; VCAM-1, 17.8 fold; ICAM-1, 13.8 fold; P < 0.05), with secreted IL-6 mirroring these results (K/BxN; con, 169 ± 29.7 versus TNF-α, 923 ± 378.8 pg/ml/1 × 10⁵ cells; P < 0.05). Dose response experiments confirmed effective concentrations between 10 and 100 nmol/l for corticosterone and 1 and 10 ng/ml for TNF-α, whilst inflammatory gene expression in FLS was shown to be stable between passages four and seven.

Conclusions

This study has established a well characterised set of key inflammatory genes for in vitro FLS culture, isolated from K/BxN mice and non-inflamed wild-type controls. Their response to both pro- and anti-inflammatory signalling has been assessed and shown to strongly resemble that which is seen in human FLS culture. Additionally, this study provides guidelines for the effective characterisation, duration and treatment of murine FLS culture.

Integrins and their ligands in rheumatoid arthritis

Integrins play an important role in cell adhesion to the extracellular matrix and other cells. Upon ligand binding, signaling is initiated and several intracellular pathways are activated. This leads to a wide variety of effects, depending on cell type. Integrin activation has been linked to proliferation, secretion of matrix-degrading enzymes, cytokine production, migration, and invasion. Dysregulated integrin expression is often found in malignant disease. Tumors use integrins to evade apoptosis or metastasize, indicating that integrin signaling has to be tightly controlled. During the course of rheumatoid arthritis, the synovial tissue is infiltrated by immune cells that secrete large amounts of cytokines. This pro-inflammatory milieu leads to an upregulation of integrin receptors and their ligands in the synovial tissue. As a consequence, integrin signaling is enhanced, leading to enhanced production of matrix-degrading enzymes and cytokines. Furthermore, in analogy to invading tumors, synovial fibroblasts start invading and degrading cartilage, thereby generating extracellular matrix debris that can further activate integrins.

Cold and heat pattern of rheumatoid arthritis in traditional Chinese medicine: distinct molecular signatures indentified by microarray expression profiles in CD4-positive T cell

The research is aimed to explore the distinct molecular signatures in discriminating the rheumatoid arthritis patients with traditional Chinese medicine (TCM) cold pattern and heat pattern. Twenty patients with typical TCM cold pattern and heat pattern were included. Microarray technology was used to reveal gene expression profiles in CD4+ T cells. The signal intensity of each expressed gene was globally normalized using the R statistics program. The ratio of cold pattern to heat pattern in patients with RA at more or less than 1:2 was taken as the differential gene expression criteria. Protein-protein interaction information for these genes from databases was searched, and the highly connected regions were detected by IPCA algorithm. The significant pathways were extracted from these subnetworks by Biological Network Gene Ontology tool. Twenty-nine genes differentially regulated between cold pattern and heat pattern were found. Among them, 7 genes were expressed significantly more in cold pattern. Biological network of protein-protein interaction information for these significant genes were searched and four highly connected regions were detected by IPCA algorithm to infer significant complexes or pathways in the biological network. Particularly, the cold pattern was related to Toll-like receptor signaling pathway. The following related pathways in heat pattern were included: Calcium signaling pathway; cell adhesion molecules; PPAR signaling pathway; fatty acid metabolism. These results suggest that better knowledge of the main biological processes involved at a given pattern in TCM might help to choose the most appropriate treatment.

Involvement of MAPKs and NF-kappaB in tumor necrosis factor alpha-induced vascular cell adhesion molecule 1 expression in human rheumatoid arthritis synovial fibroblasts

OBJECTIVE

To investigate the roles of MAPKs and NF-kappaB in tumor necrosis factor alpha (TNFalpha)-induced expression of vascular cell adhesion molecule 1 (VCAM-1) in human rheumatoid arthritis synovial fibroblasts (RASFs).

METHODS

Human RASFs were isolated from synovial tissue obtained from patients with RA who underwent knee or hip surgery. The involvement of MAPKs and NF-kappaB in TNFalpha-induced VCAM-1 expression was investigated using pharmacologic inhibitors and transfection with short hairpin RNA (shRNA) and measured using Western blot, reverse transcriptase-polymerase chain reaction, and gene promoter assay. NF-kappaB translocation was determined by Western blot and immunofluorescence staining. The functional activity of VCAM-1 was evaluated by lymphocyte adhesion assay.

RESULTS

TNFalpha-induced VCAM-1 expression, phosphorylation of p42/p44 MAPK, p38 MAPK, and JNK, and translocation of NF-kappaB were attenuated by the inhibitors of MEK-1/2 (U0126), p38 (SB202190), JNK (SP600125), and NF-kappaB (helenalin) or by transfection with their respective shRNA. TNFalpha-stimulated translocation of NF-kappaB into the nucleus and NF-kappaB promoter activity were blocked by Bay11-7082, but not by U0126, SB202190, or SP600125. VCAM-1 promoter activity was enhanced by TNFalpha in RASFs transfected with VCAM-1-Luc, and this promoter activity was inhibited by Bay11-7082, U0126, SB202190, and SP600125. Moreover, up-regulation of VCAM-1 increased the adhesion of lymphocytes to the RASF monolayer, and this adhesion was attenuated by pretreatment with helenalin, U0126, SP600125, or SB202190 prior to exposure to TNFalpha or by anti-VCAM-1 antibody before the addition of lymphocytes.

CONCLUSION

In RASFs, TNFalpha-induced VCAM-1 expression is mediated through activation of the p42/p44 MAPK, p38 MAPK, JNK, and NF-kappaB pathways. These results provide new insights into the mechanisms underlying cytokine-initiated joint inflammation in RA and may inspire new targeted therapeutic approaches.

Anabolic and catabolic function of chondrocyte ex vivo is reflected by the metabolic processing of type II collagen

OBJECTIVE

The aim of the present study was to investigate collagen metabolism after anabolic and catabolic stimulation of chondrocytes ex vivo.

DESIGN

Metabolic activities in ex vivo bovine cartilage explants were stimulated with insulin-like growth factor I (IGF-I) or a combination of tumor necrosis factor alpha (TNFalpha) and oncostatin M (OSM). Supernatants were assessed for changes in biochemical markers, N-terminal propeptide of type II (PIINP) collagen and fragments of C-telopeptide of type II collagen (CTX-II). Matrix metalloproteinases (MMP) were added to metabolic inactivated cartilage and evaluated by the two biochemical markers for formation or degradation, respectively. Finally, urinary CTX-II and PIINP were evaluated for assessment of type II collagen turnover in patients with rheumatoid arthritis (RA).

RESULTS

In the bovine articular cartilage explants, IGF-I induced an increase in PIINP level up to 4.8+/-1.1[ng/ml]/mg cartilage whereas CTX-II remained below 0.1+/-0.1[ng/ml]/mg cartilage. In the catabolic stimulated explants both PIINP and CTX-II were released to the supernatant, reaching concentrations of 9.0+/-1.4 and 9.1+/-2.2[ng/ml]/mg cartilage, respectively. RA patients had significantly lower serum concentrations of PIINP (3.4+/-3.7 ng/ml) compared with those healthy individuals (18.7+/-12.41 ng/ml, P<0.001). In contrast, RA patients had significantly higher urinary CTX-II (0.8+/-0.8 mg/mmol) compared to the healthy controls (0.1+/-0.08 mg/mmol, P=0.004).

CONCLUSIONS

This study is the first to demonstrate that precursors and degradation products of type II collagen released into the supernatant can effectively reflect the anabolic and catabolic activities of stimulated cartilage explants.

AGIX-4207 [2-[4-[[1-[[3,5-bis(1,1-dimethylethyl)-4-hydroxyphenyl]thio]-1-methylethyl]thio]-2,6-bis(1,1-dimethylethyl)phenoxy]acetic acid], a novel antioxidant and anti-inflammatory compound: cellular and biochemical characterization of antioxidant activity and inhibition of redox-sensitive inflammatory gene expression

The pathogenesis of chronic inflammatory diseases, including rheumatoid arthritis, is regulated, at least in part, by modulation of oxidation-reduction (redox) homeostasis and the expression of redox-sensitive inflammatory genes including adhesion molecules, chemokines, and cytokines. AGIX-4207 [2-[4-[[1-[[3,5-bis(1,1-dimethylethyl)-4-hydroxyphenyl]thio]-1-methylethyl]thio]-2,6-bis(1,1-dimethylethyl)phenoxy]acetic acid] is a novel, orally active, phenolic antioxidant and anti-inflammatory compound with antirheumatic properties. To elucidate its anti-inflammatory mechanisms, we evaluated AGIX-4207 for a variety of cellular, biochemical, and molecular properties. AGIX-4207 exhibited potent antioxidant activity toward lipid peroxides in vitro and displayed enhanced cellular uptake relative to a structurally related drug, probucol. This resulted in potent inhibition of cellular levels of reactive oxygen species in multiple cell types. AGIX-4207 selectively inhibited tumor necrosis factor (TNF)-alpha-inducible levels of the redox-sensitive genes, vascular cell adhesion molecule-1 and monocyte chemoattractant protein-1, with less inhibition of E-selectin, and no effect on intracellular adhesion molecule-1 expression in endothelial cells. In addition, AGIX-4207 inhibited cytokine-induced levels of monocyte chemoattractant protein-1, interleukin (IL)-6, and IL-8 from endothelial cells and human fibroblast-like synoviocytes as well as lipopolysaccharide-induced release of TNF-alpha, IL-1beta, and IL-6 from human peripheral blood mononuclear cells. AGIX-4207 did not inhibit TNF-alpha-induced nuclear translocation of nuclear factor of the kappa-enhancer in B cells (NF-kappaB), suggesting that the mechanism of action is independent of this redox-sensitive transcription factor. Taken together, these results provide a mechanistic framework for understanding the anti-inflammatory and antirheumatic activity of AGIX-4207 and provide further support for the view that inhibition of redox-sensitive inflammatory gene expression is an attractive approach for the treatment of chronic inflammatory diseases.

Association of intercellular adhesion molecule-1 with clinical manifestations and interleukin-18 in patients with active, untreated adult-onset Still's disease

OBJECTIVE

To investigate the association of intercellular adhesion molecule 1 (ICAM-1) with clinical manifestations and interleukin-18 (IL-18) levels in patients with active untreated adult-onset Still's disease (AOSD).

METHODS

We determined serum soluble ICAM-1 (sICAM-1) levels by enzyme-linked immunosorbent assay in 50 patients with active untreated AOSD, 20 patients with active rheumatoid arthritis (RA), and 20 healthy controls. The levels of ICAM-1 messenger RNA expression in IL-18-stimulated peripheral blood mononuclear cells (PBMCs) and in biopsy specimens obtained from AOSD patients with Still's rash or synovitis were investigated using real-time quantitative polymerase chain reaction.

RESULTS

Significantly higher serum levels of sICAM-1 were observed in patients with active untreated AOSD compared with those with active RA and healthy controls. Serum sICAM-1 levels were significantly correlated with the clinical activity score (r = 0.565, P < 0.001), ferritin values (r = 0.462, P < 0.005), and IL-18 levels (r = 0.462, P < 0.005) in patients with AOSD. The serum sICAM-1 level was identified as a predictor of hepatic dysfunction (odds ratio [OR] 1.016, P = 0.011) and disseminated intravascular coagulation (DIC) (OR 1.013, P = 0.023). Up-regulation of ICAM-1 gene expression was demonstrated in IL-18-stimulated PBMCs from patients with AOSD. Increased levels of ICAM-1 transcripts were observed in the biopsy specimens obtained from AOSD patients with Still's rash or synovitis compared with healthy skin and patients with osteoarthritis.

CONCLUSION

The serum sICAM-1 level may be used as a clinical marker to assess disease activity and may predict the occurrence of hepatic dysfunction and DIC in AOSD. IL-18-up-regulated gene expression of ICAM-1 may contribute to the inflammatory response in AOSD.

Rolipram inhibits polarization and migration of human T lymphocytes

Phosphodiesterase inhibitors possess anti-inflammatory and immunomodulatory properties and seem to have a great potential in the treatment of inflammatory skin diseases; however, an overall study on the effects of specific phosphodiesterase inhibitors, such as rolipram on the processes involved in the extravasation of lymphoid cells has not been performed. In this work we have assessed the effect of rolipram on the adhesion, polarization, and migration of normal human T lymphocytes. We found that low concentrations of rolipram were able to inhibit significantly the adhesion of T cells to the beta1 and beta2 integrin ligands vascular cell adhesion molecule-1 and intercellular adhesion molecule-1. Rolipram also interfered with the activation of integrins, and significantly inhibited the homotypic aggregation of T lymphocytes induced by anti-beta1 and anti-alpha4 integrin chain monoclonal antibodies. In addition, rolipram had a downregulatory effect on the activation of T cells, and significantly diminished the expression of the activation antigens CD69, CD25, and CD98 induced by phytohemagglutinin. Finally, this drug inhibited the polarization and transendothelial migration of T lymphocytes induced by the chemokine CXCL12 (SDF-1) and the chemotactic cytokine interleukin-15. The results indicate that rolipram, at low concentrations, exerts an important anti-inflammatory and immunomodulatory effect, and suggest that this selective phosphodiesterase inhibitor may be an effective tool for the therapy of immune-mediated diseases.

NF-kappa B regulates VCAM-1 expression on fibroblast-like synoviocytes

Expression of VCAM-1 on synovial fibroblasts is a clinical hallmark of rheumatoid arthritis. The interaction of VCAM-1 and its integrin receptor very late Ag-4 is believed to be critically involved in the recruitment and retention of immune cells in the inflamed joints. To study the regulation of VCAM-1 in synovial fibroblasts, fibroblast-like synoviocytes (FLS) were isolated from the knee joints of normal mice and passaged repeatedly to obtain a homogeneous cell population. We have found that VCAM-1 is constitutively expressed on mouse FLS (mFLS) and that its surface expression is further increased after exposure to TNF-alpha. Nuclear translocation of transcription factor NF-kappa B including P50/P50 homodimer and P65/P50 heterodimer was activated by TNF-alpha treatment. In mFLS stably expressing a dominant-negative mutant of the inhibitory protein I-kappa B alpha- (mI-kappa B), which does not undergo proteolytic degradation, NF-kappa B remains in the cytosol and its activation in response to TNF-alpha is abolished. VCAM-1 protein expression after TNF-alpha stimulation was blocked in cells expressing the mI-kappa B. This effect is likely due to the loss of NF-kappa B-mediated transcription of VCAM-1, because the 5-fold increase in mRNA levels in response to TNF-alpha is absent in the mutant cells. To confirm these findings, we transduced mFLS with an adenoviral vector containing the mI-kappa B transgene. VCAM-1 expression was also blocked by mI-kappa B in this system, whereas cells transduced with a control adenoviral vector remained responsive to TNF-alpha. These results indicate that NF-kappa B mediates TNF-alpha-induced VCAM-1 expression on mFLS.

A role for angiogenesis in rheumatoid arthritis

Rheumatoid arthritis (RA) is a chronic debilitating disease characterized by distinct autoimmune, inflammatory and fibrovascular components which lead to synovial proliferation and joint destruction. However, existing treatments specifically target only autoimmune and inflammatory components despite the fact that neovascularization of the inflamed synovium is a hallmark of rheumatoid arthritis. Angiogenesis may contribute to synovial growth, leukocyte recruitment and tissue remodeling, thus potentiating disease progression. Although no therapies currently target angiogenesis, several existing therapies have anti-angiogenic activity. Recent advances in anti-angiogenic strategies in oncology, including the identification of integrin alpha v beta 3 as a crucial effector of angiogenesis, suggest a means to assess the role of angiogenesis in rheumatoid arthritis. Synovial endothelial cells have been shown to express integrin alpha v beta 3, suggesting that these cells may be targeted for angiogenesis inhibition. Prior studies in rat arthritis models have shown benefit after the addition of broad spectrum integrin antagonists. However, formal assessment of integrin-targeted anti-angiogenic activity is now underway. These controlled studies will be important in assessing the efficacy of therapies which target angiogenesis in RA.

Tyrosine phosphorylated proteins in synovial cells of rheumatoid arthritis

Two of the key events in the pathogenesis of rheumatoid arthritis are the synovial cell proliferation and lymphocyte infiltration into the synovium. The resulting synovitis is longlasting and leads to destructive arthritis, which is a hallmark of rheumatoid arthritis. Accumulating evidence suggests that one of the key biochemical events in the altered cell function of RA is phosphorylation of the tyrosine residues of proteins. In this paper we review the cellular components participating in the chronic inflammation of RA joints. We present the results of analyzing tyrosine phosphorylated proteins of synovial cells from RA patients and discuss a possible pathogenic role of non-receptor tyrosine kinase in RA.

Matrix valency regulates integrin-mediated lymphoid adhesion via Syk kinase

Lymphocytes accumulate within the extracellular matrix (ECM) of tumor, wound, or inflammatory tissues. These tissues are largely comprised of polymerized adhesion proteins such as fibrin and fibronectin or their fragments. Nonactivated lymphoid cells attach preferentially to polymerized ECM proteins yet are unable to attach to monomeric forms or fragments of these proteins without previous activation. This adhesion event depends on the appropriate spacing of integrin adhesion sites. Adhesion of nonactivated lymphoid cells to polymeric ECM components results in activation of the antigen receptor-associated Syk kinase that accumulates in adhesion-promoting podosomes. In fact, activation of Syk by antigen or agonists, as well as expression of an activated Syk mutant in lymphoid cells, facilitates their adhesion to monomeric ECM proteins or their fragments. These results reveal a cooperative interaction between signals emanating from integrins and antigen receptors that can serve to regulate stable lymphoid cell adhesion and retention within a remodeling ECM.

Pentoxifylline Inhibits Adhesion and Activation of Human T Lymphocytes

We have herein studied the effect of pentoxifylline (PTX) on the adhesion and activation of human T lymphocytes. We found that PTX inhibited the adhesion of T cells to the β1 and β2 integrin ligands VCAM-1 and ICAM-1; this inhibitory activity was dose dependent, with a maximal effect from 12 to 24 h. We also found that PTX was able to interfere with the activation of β1 integrins induced by intracellular signals; however, the conformational change of β1 integrins induced by extracellular stimuli (e.g., activating mAbs, or Mn2+) was not significantly affected by this drug. In addition, the homotypic aggregation of T cells induced by anti-β1 and -β2 integrin chain mAbs was also inhibited by PTX. PTX had a significant inhibitory effect on the T lymphocyte expression of the activation Ags CD25 (IL-2Rα-chain), CD69 (activation-inducer molecule), and CD98 (4F2) induced by PHA. Accordingly, PTX also interfered with early cell activation events such as the rise in intracellular Ca2+ and the activation of the Na+/H+ antiporter induced by PHA and phorbol esters, respectively. Furthermore, this drug inhibited both the cell cycle progression and cell proliferation of T cells induced through the CD3/TCR complex. However, this drug did not show any effect on the cell activation/proliferation induced by PMA plus ionomycin. Our results indicate that PTX interferes efficiently with the activation and cell adhesion of human T lymphocytes. These effects may be of relevance for the clinical uses of this drug.

Modulation of MMP-2 (gelatinase A) and MMP-9 (gelatinase B) by interferon-gamma in a human salivary gland cell line

Gelatinases have been shown to be regulated by many cytokines and growth factors, and have been implicated in the pathogenesis of certain autoimmune diseases via tissue destruction. High levels of several cytokines, including IFN-gamma and TNF-alpha, have been demonstrated in the salivary gland microenvironment of patients with Sjogren's syndrome (SS). How these cytokines may be contributing to the pathogenesis of this disease is not well understood. We hypothesized that IFN-gamma with or without (+/-) TNF-alpha could be playing a role in the pathogenesis of SS via the regulation of matrix metalloproteinase (MMP) levels. This study examined the role of IFN-gamma and (+) TNF-alpha in the regulation of the matrix metalloproteinases, MMP-2 (72 kD gelatinase A) and MMP-9 (92 kD gelatinase B). A human salivary gland cell line (HSG) has been used as a possible in vitro model to study the role of IFN-gamma + TNF-alpha in the pathogenesis of SS. The HSG cell line, in the presence of IFN +/- TNF-alpha, displays increased MMP-2 and MMP-9 gelatinolytic activity, protein and RNA levels. The increase in MMP activity was partially blocked with an antibody against the IFN-gamma receptor, and this was associated with a complete inhibition of the previously described IFN-gamma +/- TNF-alpha antiproliferative effect. However, incubation of IFN-gamma treated HSG cells with the synthetic MMP inhibitor BB94 did not alleviate this antiproliferative effect. In addition, we demonstrate that there are very high levels of MMP-9 in the saliva of patients with SS when compared to healthy control subjects. These data suggest that cytokines could be regulating MMP production by salivary epithelial cells and thus indicate a potential role for these cells in the pathogenesis of SS.

Rheumatoid arthritis synovial fibroblast and U937 macrophage/monocyte cell line interaction in cartilage degradation

OBJECTIVE

To examine the interaction between synovial fibroblasts and macrophages in the context of cartilage degradation.

METHODS

An in vitro model of human cartilage degradation was used, in which purified populations of fibroblasts and macrophages were added to a radiolabeled cartilage disc. Cartilage destruction was measured by the percentage of radiolabel release.

RESULTS

Fibroblasts, obtained from either rheumatoid arthritis (RA) or osteoarthritis synovial tissue, could mediate cartilage degradation if cocultured with the U937 macrophage cell line. Skin and RA bone marrow fibroblasts had no degradative effect on cartilage. Fibroblast-macrophage contact was not required for cartilage degradation. Cartilage degradation by synovial fibroblasts was inhibited by antibodies to tumor necrosis factor alpha (TNF alpha), interleukin-1 beta (IL-1 beta), and IL-6. Cartilage degradation was almost completely abrogated by a combination of antibodies to TNF alpha and IL-1 beta. Contact between fibroblasts and cartilage was shown to be essential. Antibodies to CD44, but not to intercellular adhesion molecule 1, markedly inhibited cartilage degradation.

CONCLUSION

TNF alpha, IL-1 beta, and IL-6 were involved in the activation of synovial fibroblasts to cause cartilage degradation. Cartilage degradation occurred only when fibroblasts were in contact with cartilage. CD44 was demonstrated to be involved in the fibroblast-cartilage interaction.

Leukocyte migration in the leg in response to experimental venous hypertension

PURPOSE

Leukocyte trapping and activation in the microcirculation of the legs may play an important role in causing skin damage in venous disease. Leukocyte emigration from the microcirculation and subsequent locomotion in response to venous hypertension was studied in a group of 12 normal volunteers using a "skin window" technique.

METHODS

Two 0.5-cm square dermal abrasions were made with a dental stone over the gaiter area of the leg and the flexor aspect of the forearm (control), which were covered with moist micropore membranes. The volunteers lay supine for 30 minutes, and then stood supported for 30 minutes to raise the venous pressure in the leg, and then lay supine again for 30 minutes. The experiment was repeated in six volunteers who lay supine for the whole period. The membranes were changed and collected every 15 minutes, fixed in formal saline solution, and dual-stained for monocytes and polymorphonuclear leukocytes. The type and numbers of cells that emigrated and the furthest distance traveled (leading front) by the cells through the membrane were measured.

RESULTS

Both in arms and legs, the vast majority of cells that emigrated were neutrophils, with very few monocytes (arm, 93% neutrophils and 7% monocytes; leg, 97% neutrophils and 3% monocytes). In the 30 minutes after venous hypertension, leukocyte migration significantly decreased in the leg (median leukocyte locomotion: basal, 75.3 microns; standing, 73.5 microns; after hypertension, 62.9 microns; p = 0.012, Wilcoxon matched pairs signed rank test), but not in the arm (basal, 86.2 microns; standing, 84.4 microns; after hypertension, 85.5 microns; p = NS) or when the experiment was repeated with the volunteers lying supine for the entire period (basal, 91.5 microns; standing, 89.4 microns; after hypertension, 92.6 microns; p = NS).

CONCLUSIONS

Leukocyte migration is decreased immediately after experimental venous hypertension, which may be a result of the release of factors that inhibit migration.

Inhibition of lymphocyte adhesion to cytokine-activated synovial fibroblasts by glucocorticoids involves the attenuation of vascular cell adhesion molecule 1 and intercellular adhesion molecule 1 gene expression

OBJECTIVE

The aim of this study was to evaluate the ability of glucocorticoids to inhibit lymphocyte adhesion to human synovial fibroblasts.

METHODS

Adhesion of lymphocytes to cultured synovial fibroblasts was measured by counting the number of cells bound to fibroblasts. Surface expression of intercellular adhesion molecule 1 (ICAM-1) was measured by enzyme-linked immunosorbent assay, while vascular cell adhesion molecule 1 (VCAM-1) surface expression was measured by flow cytometry. ICAM-1 and VCAM-1 messenger RNA (mRNA) levels were assessed by Northern blot analysis.

RESULTS

Stimulation of synovial fibroblasts by the proinflammatory cytokines tumor necrosis factor alpha, interleukin-1beta, and interferon-gamma resulted in a dose-dependent increase in lymphocyte adhesion to synovial fibroblasts. This response was inhibited by preincubation of the cells with the synthetic glucocorticoid dexamethasone. Since lymphocyte adhesion to synovial fibroblasts is known to be mediated by VCAM-1 and ICAM-1, we examined the modulation of VCAM-1 and ICAM-1 expression in these cells. All 3 cytokines stimulated VCAM-1 and ICAM-1 surface and mRNA expression. Dexamethasone inhibited both VCAM-1 and ICAM-1 surface and mRNA expression in a dose-dependent manner, which correlated with the inhibition of lymphocyte adhesion.

CONCLUSION

Taken together, these results suggest that glucocorticoids may reduce inflammatory responses at extravascular sites by inhibiting the expression of these adhesion molecules, thereby reducing the adhesion of lymphocytes to connective tissue cells.

Adhesion molecules in autoimmune disease

Leukocyte activation, circulation, and localization to inflammatory sites are dependent on adherence to molecules on other cells or to extracellular matrix ligands. Adhesion molecule expression and interactions are probably involved in initiation and propagation of autoimmune diseases. Adhesion molecules pertinent to the development of autoimmunity are the subject of this review. Material in this review was generated by a manual and a computerized search of medical literature pertaining to adhesion molecules and specific autoimmune diseases. Topics covered include adhesion molecule classification, regulation of adhesion, and characterization of adhesion receptors in specific autoimmune diseases, including rheumatoid arthritis (RA), systemic lupus erythematosus, Sjögren's syndrome, autoimmune thyroid disease, multiple sclerosis, and diabetes mellitus. Adhesion molecules are classified into selectin, integrin, and immunoglobulin supergene family groups. Increased adhesion molecule expression and avidity changes occurring with cellular activation are the principal methods regulating leukocyte adhesion. Tumor necrosis factor-alpha (TNF alpha), interferon-gamma (IFN-gamma), and interleukin-1 (IL-1) stimulate adhesion receptor expression on lymphoid and nonlymphoid tissues. Although differences between specific autoimmune diseases exist, key interactions facilitating the development of autoimmune inflammation appear to include L-selectin/P-selectin/E-selectin, lymphocyte function-associated antigen-1 (LFA-1)/intercellular adhesion molecule-1 (ICAM-1), very late antigen-4 (VLA-4)/vascular cell adhesion molecule-1 (VCAM-1), and alpha 4B7/MadCAM or VCAM-1 adhesion. Administration of anti-adhesion molecule antibodies in experimental animal models of autoimmunity and in a preliminary trial with RA patients has been successful in preventing or reducing autoimmune disease severity. A vast array of adhesive interactions occurs between immunocompetent cells, endothelium, extracellular matrix, and target tissues during the evolution of an autoimmune disease. Further characterization of leukocyte migration patterns and adherence should clarify pathogenic processes in specific autoimmune diseases and identify potential therapeutic targets for their treatment.