beta2-microglobulin induces MMP-1 but not TIMP-1 expression in human synovial fibroblasts

High-Molecular-Weight Hyaluronic Acid Inhibits IL-1β-Induced Synovial Inflammation and Macrophage Polarization through the GRP78-NF-κB Signaling Pathway

Recent evidence has suggested that synovial inflammation and macrophage polarization were involved in the pathogenesis of osteoarthritis (OA). Additionally, high-molecular-weight hyaluronic acid (HMW-HA) was often used clinically to treat OA. GRP78, an endoplasmic reticulum (ER) stress chaperone, was suggested to contribute to the hyperplasia of synovial cells in OA. However, it was still unclear whether HMW-HA affected macrophage polarization through GRP78. Therefore, we aimed to identify the effect of HMW-HA in primary synovial cells and macrophage polarization and to investigate the role of GRP78 signaling. We used IL-1β to treat primary synoviocytes to mimic OA, and then treated them with HMW-HA. We also collected conditioned medium (CM) to culture THP-1 macrophages and examine the changes in the phenotype. IL-1β increased the expression of GRP78, NF-κB (p65 phosphorylation), IL-6, and PGE2 in primary synoviocytes, accompanied by an increased macrophage M1/M2 polarization. GRP78 knockdown significantly reversed the expression of IL-1β-induced GRP78-related downstream molecules and macrophage polarization. HMW-HA with GRP78 knockdown had additive effects in an IL-1β culture. Finally, the synovial fluid from OA patients revealed significantly decreased IL-6 and PGE2 levels after the HMW-HA treatment. Our study elucidated a new form of signal transduction for HMW-HA-mediated protection against synovial inflammation and macrophage polarization and highlighted the involvement of the GRP78-NF-κB signaling pathway.

HLA-C: An Accomplice in Rheumatic Diseases

Human leukocyte antigen c (HLA-C) is a polymorphic membrane protein encoded by the HLA-C gene in the class I major histocompatibility complex. HLA-C plays an essential role in protection against cancer and viruses but has also been implicated in allograft rejection, preeclampsia, and autoimmune disease. This review summarizes reports and proposed mechanisms for the accessory role of HLA-C in rheumatic diseases. Historically, contributions of HLA-C to rheumatic diseases were eclipsed by the stronger association with HLA-DRB1 alleles containing the "shared epitope" with rheumatoid arthritis. Larger genetic association studies and more powerful analytical approaches have revealed independent associations of HLA-C with rheumatic disease-associated phenotypes, including development of anticitrullinated peptide antibodies. HLA-C functions by presenting antigens to T cells and by binding activatory and inhibitory receptors on natural killer (NK) cells, but the exact mechanisms by which the HLA-C locus contributes to autoimmunity are largely undefined. Studies have suggested that HLA-C and NK cell receptor polymorphisms may predict responsiveness to pharmacotherapy. Understanding the mechanisms of the role of HLA-C in rheumatic disease could uncover therapeutic targets or guide precision pharmacologic treatments.

Proteomic analysis of synovial fluid in osteoarthritis using SWATH‑mass spectrometry

The lack of early diagnostic maneuvers and effective pharmacotherapy for osteoarthritis (OA) is predominantly attributed to current limited understanding of its pathogenesis. In the present study, the alteration of synovial fluid (SF) proteome in OA were analyzed using SWATH-mass spectrometry (SWATH-MS) to further elucidate the pathogenesis of OA. SF samples were collected from 10 OA and 10 rheumatoid arthritis (RA) patients undergoing arthroplasty and 10 patients undergoing arthroscopy for traumatic arthritis (meniscus injury without cartilage lesion). According to the Kellgren-Lawrence (KL) radiographic grading criteria, all the OA and RA patients were classified as KL grade 4. SWATH-MS was applied to identify differentially expressed proteins specifically regulated in OA. Differentially expressed proteins identified by SWATH-MS were subjected to gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway annotation. Proteins of interest were quantified by enzyme-linked immunosorbent assay (ELISA) following identification. With the use of SWATH-MS, 131 proteins were identified to be differentially expressed in OA, of which 93 corresponded to upregulation and 38 to downregulation. Complement C1r was the most significantly upregulated protein in OA. Twenty-eight out of the 131 proteins were specifically regulated in OA, of which 17 were upregulated and 11 were downregulated. Dickkopf-related protein 2 (DKK2) was one of the proteins specifically upregulated in OA. Furthermore, KEGG pathway annotation indicated that differentially expressed proteins in OA were enriched in complement and coagulation cascades. ELISA indicated that OA severity was positively correlated with the levels of complement C1r (r=0.549; P<0.001) and DKK2 (r=0.79; P<0.001) in the SF. The results indicate that complement and coagulation cascades are involved in the pathogenesis of OA. Differentially expressed proteins, including complement C1r and DKK2 may be used as potential biomarkers or drug targets, which may facilitate with intervention of OA.

Perlecan/HSPG2 and matrilysin/MMP-7 as indices of tissue invasion: tissue localization and circulating perlecan fragments in a cohort of 288 radical prostatectomy patients

Prostate cancer (PCa) cells use matrix metalloproteinases (MMPs) to degrade tissue during invasion. Perlecan/HSPG2 is degraded at basement membranes, in reactive stroma and in bone marrow during metastasis. We previously showed MMP-7 efficiently degrades perlecan. We now analyzed PCa tissue and serum from 288 prostatectomy patients of various Gleason grades to decipher the relationship between perlecan and MMP-7 in invasive PCa. In 157 prostatectomy specimens examined by tissue microarray, perlecan levels were 18% higher than their normal counterparts. In Gleason grade 4 tissues, MMP-7 and perlecan immunostaining levels were highly correlated with each other (average correlation coefficient of 0.52) in PCa tissue, regardless of grade. Serial sections showed intense, but non-overlapping, immunostaining for MMP-7 and perlecan at adjacent borders, reflecting the protease-substrate relationship. Using a capture assay, analysis of 288 PCa sera collected at prostatectomy showed elevated levels of perlecan fragments, with most derived from domain IV. Perlecan fragments in PCa sera were associated with overall MMP-7 staining levels in PCa tissues. Domain IV perlecan fragments were present in stage IV, but absent in normal, sera, suggesting perlecan degradation during metastasis. Together, perlecan fragments in sera and MMP-7 in tissues of PCa patients are measures of invasive PCa.

[Doxycycline or how to create new with the old?]

Tetracyclines are broad-spectrum antibiotics that interfere with protein synthesis. They were first widely prescribed by dermatologists in the early 1950s in the treatment of acne. More recently, their biological actions on inflammation, proteolysis, angiogenesis, apoptosis, metal chelation, ionophoresis, and bone metabolism were studied. Matrix metalloproteinases (MMPs) are a family of proteolytic enzymes that degrade components of the extracellular matrix (ECM). MMPs have direct or indirect effects on the vascular endothelium and the vascular relaxation/contraction system. The therapeutic effects of tetracyclines and analogues were studied in rosacea, bullous dermatoses, neutrophilic diseases, pyoderma gangrenosum, sarcoidosis, aortic aneurysms, cancer metastasis, periodontitis and autoimmune diseases autoimmune diseases such as rheumatoid arthritis and scleroderma. In addition, downregulation of MMP using doxycycline could be beneficial in reducing vascular dysfunction mediated by MMPs and progressive damage of the vascular wall. We review the nonantibiotic properties of doxycycline and its potential clinical applications.

Matrix metalloproteinase, vitamin A and methylprednisolone effects on experimentally induced amyloid arthropathy

We evaluated the role of some matrix metalloproteinases (MMPs) in enhancing the effect of vitamin A and the inhibiting effect of methylprednisolone on amyloid arthropathy in brown layer chicks. We used 100 one-day-old Isa brown layer chicks. The chicks were allocated to one of four groups as follows: negative control group (I), vitamin A group (II), positive control group (III) and methylprednisolone group (IV). Amyloid arthropathy was induced by injections of complete Freund's adjuvant into the left intertarsal joints of the chicks. Serum vitamin A and tissue MMP (MMP-1, MMP-2, MMP-9) levels were measured and differences among the groups were investigated. Serum vitamin A rates (μg/dl) were: 63.57 ± 4.10, 47.13 ± 10.62, 53.26 ± 10.79, 98.48 ± 8.20 in groups I, II, III and IV, respectively (p < 0.001). MMP-1, MMP-2 and MMP-9 levels were evaluated in tissues from the chickens with amyloid arthropathy. Methylprednisolone significantly suppressed the release of MMP-1 and MMP-2, and increased the release of MMP-9 in birds with amyloid arthropathy. In addition, vitamin A significantly increased the release of MMP-1, MMP-2 and MMP-9.

Matrix metalloproteinase-1 of gingival fibroblasts influenced by advanced glycation end products (AGEs) and their association with receptor for AGEs and nuclear factor-κB in gingival connective tissue

BACKGROUND

The effect of advanced glycation end products (AGEs) on gingival inflammation has not been fully elucidated. This study aims to investigate the hypothesis that AGEs may enhance the expression of matrix metalloproteinase-1 (MMP-1) of human gingival fibroblasts (HGFs) and to explore whether the signal pathway receptor for AGE (RAGE)/nuclear factor-κB (NF-κB) are involved in the expression of MMP-1 in HGFs.

METHODS

Cultured HGFs from 12 healthy gingival human tissue samples were coincubated with AGEs for the detection of MMP-1 protein and mRNA. Thirty-six gingival samples were collected and treated for the determination of RAGE, NF-κB, and MMP-1 mRNA level in gingival connective tissues from the participants with chronic periodontitis, diabetes-associated periodontitis, and healthy controls. Enzyme-linked immunosorbent assay and real-time fluorescence reverse transcription-polymerase chain reaction were used for the measurement of protein and mRNA level, respectively. In addition, clinical periodontal parameters were also checked.

RESULTS

AGEs strongly induced MMP-1 mRNA and protein expression in HGFs and in a time- and concentration-dependent manner (P <0.05). In gingival connective tissue, the level of both RAGE mRNA and NF-κB mRNA were higher in patients with periodontitis than in healthy controls (P <0.05). There was significant correlation between the level of RAGE mRNA and NF-κB mRNA (R(2) = 0.90, P <0.05).

CONCLUSIONS

Accumulation of AGEs may upregulate the expression of MMP-1 by HGFs, which may play a role in the development of diabetes-associated periodontitis, and RAGE/NF-κB pathway may be involved in metabolism of MMP-1 in HGFs.

Cartilage biomarkers in hemodialysis patients and the effect of beta2-microglobulin on articular chondrocytes

OBJECTIVE

Dialysis-related amyloidosis (DRA) is a severe complication of maintenance hemodialysis (HD). Given the predominant deposition of beta(2)-microglobulin (beta2m) fibrils on articular cartilage in early DRA, we investigated the significance of beta2m and its relationship to distinct cartilage biomarkers in early DRA diagnosis in HD patients. Furthermore, we assessed the effects of beta2m on articular chondrocytes in vitro.

METHODS

Serum samples from 133 patients were collected before and after HD. Type II collagen cleavage product (C2C), procollagen II c-propeptide (CPII), aggrecan chondroitin sulfate 846 epitope (CS-486) and cartilage oligomeric matrix protein (COMP) levels were determined by enzyme-linked immunosorbent assay. Primary bovine articular chondrocytes were cultured as monolayers and incubated with beta2m at 1.5mg/l and 20mg/l. Cartilage glucosaminoglycan synthesis was measured by [(35)S]sulfate incorporation. mRNA expression of interleukin (IL)-1beta, matrix metalloproteinases (MMPs)-3 and -9 was measured by reverse-transcriptase polymerase chain reaction (RT-PCR).

RESULTS

Incubation with beta2m at 20mg/l significantly decreased matrix biosynthesis. PCR analysis revealed an increase of IL-1beta, as well as MMPs-3 and -9 on the mRNA level. C2C/CPII, CS-486 and COMP levels were increased only in a subset of patients without a significant correlation with beta2m concentrations. A subgroup analysis elucidated an increase in type II collagen degradation during the first years of HD, as shown by the elevation of C2C/CPII ratio.

CONCLUSION

beta2m exerted anti-anabolic effects on articular chondrocytes in vitro and might be involved in cartilage degradation in HD patients. beta2m serum levels, however, did not reflect cartilage degradation in DRA. The assessment of C2C/CPII, CS-486 or COMP concentrations apparently has minor relevance in DRA diagnosis in HD patients. However, the increased type II collagen breakdown within 5 years after HD onset possibly mirrors the early stages of DRA. Thus, the C2C/CPII ratio could be employed in longitudinal studies, since it may reflect a risk for DRA related arthropathy development in a subset of patients.

Clinical and histopathological features of progressive-type familial amyloidotic polyneuropathy with TTR Lys54

The purpose of this study was to evaluate the clinical and pathological features in patients with progressive-type familial amyloidotic polyneuropathy (FAP) using autopsy and biopsy specimens. A proband is a 33-year-old man with FAP type I who developed motor, sensory and autonomic impairments with neuropathy, heart failure, and anorexia. Genetic findings of transthyretin (TTR) revealed G to A transition in codon 54 causing a rare mutation of TTR Lys54. He died of pneumonia and severe cardiac failure 4 years after onset. Autopsy showed heavy amyloid deposition in the heart, peripheral nerves, thyroid, skin, fat tissue, prostate and testis, moderate in the sympathetic nerve trunk, vagal nerve, celiac plexus, pelvic plexus, bladder, gastrointestinal tract, tongue, pancreas, lung, pituitary, blood vessel, gall bladder, adrenals and muscles, and free in the central nervous system, liver, kidney and spleen. Sural nerve biopsy in a sibling confirmed TTR amyloidosis immunohistochemically. Electronmicroscopic findings of amyloid fibrils were similar to that of FAP Met30. Immunoelectronmicroscopic findings indicated the relationship between amyloid fibrils or non-fibrillar structure and collagen fibers. The distribution of amyloid deposition, heavy in the heart and lacking in the kidney, is a characteristic feature and reflected severity of FAP with TTR Lys54.

Efferent vagal nerve stimulation induces tissue inhibitor of metalloproteinase-1 in myocardial ischemia-reperfusion injury in rabbit

Vagal nerve stimulation has been suggested to ameliorate left ventricular (LV) remodeling in heart failure. However, it is not known whether and to what degree vagal nerve stimulation affects matrix metalloproteinase (MMP) and tissue inhibitor of MMP (TIMP) in myocardium, which are known to play crucial roles in LV remodeling. We therefore investigated the effects of electrical stimulation of efferent vagal nerve on myocardial expression and activation of MMPs and TIMPs in a rabbit model of myocardial ischemia-reperfusion (I/R) injury. Anesthetized rabbits were subjected to 60 min of left coronary artery occlusion and 180 min of reperfusion with (I/R-VS, n = 8) or without vagal nerve stimulation (I/R, n = 7). Rabbits not subjected to coronary occlusion with (VS, n = 7) or without vagal stimulation (sham, n = 7) were used as controls. Total MMP-9 protein increased significantly after left coronary artery occlusion in I/R-VS and I/R to a similar degree compared with VS and sham values. Endogenous active MMP-9 protein level was significantly lower in I/R-VS compared with I/R. TIMP-1 mRNA expression was significantly increased in I/R-VS compared with the I/R, VS, and sham groups. TIMP-1 protein was significantly increased in I/R-VS and VS compared with the I/R and sham groups. Cardiac microdialysis technique demonstrated that topical perfusion of acetylcholine increased dialysate TIMP-1 protein level, which was suppressed by coperfusion of atropine. Immunohistochemistry demonstrated a strong expression of TIMP-1 protein in cardiomyocytes around the dialysis probe used to perfuse acetylcholine. In conclusion, in a rabbit model of myocardial I/R injury, vagal nerve stimulation induced TIMP-1 expression in cardiomyocytes and reduced active MMP-9.

Effects of nifedipine and interleukin-1alpha on the expression of collagen, matrix metalloproteinase-1, and tissue inhibitor of metalloproteinase-1 in human gingival fibroblasts

BACKGROUND AND OBJECTIVE

Nifedipine-induced gingival overgrowth is known to be characterized by fibrosis and some degree of inflammation. However, the molecular mechanism of the fibrosis is not fully understood. The purpose of this study was to investigate in vitro the effects of nifedipine and interleukin-1alpha on the molecules involved in fibrosis, namely type I collagen, matrix metalloproteinase-1 (MMP-1), and tissue inhibitor of metalloproteinase-1 (TIMP-1).

MATERIAL AND METHODS

Four human gingival fibroblast strains, derived from four healthy volunteers, were cultured in media containing nifedipine (1 microg/ml), with or without interleukin-1alpha (0.05 ng/ml). The mRNAs of type I collagen, MMP-1, and TIMP-1 were measured by reverse transcription-polymerase chain reaction (RT-PCR). The proteins of MMP-1 and TIMP-1 were examined by enzyme-linked immunosorbent assay (ELISA), and the ratios of MMP-1 to TIMP-1 proteins were calculated.

RESULTS

The mRNA expression of type I collagen showed no significant change. Both mRNA expression and protein production of MMP-1 were up-regulated by interleukin-1alpha, either alone or in combination with nifedipine, whereas those of TIMP-1 were up-regulated by nifedipine alone or in combination with interleukin-1alpha. The ratio of MMP-1 to TIMP-1 was not changed by nifedipine alone, but it was increased by interleukin-1alpha alone or in combination with nifedipine. However, in two of the four cell strains tested, nifedipine reduced the ratio of MMP-1 to TIMP-1 compared with that for interleukin-1alpha alone.

CONCLUSION

These results suggest that nifedipine may predispose to fibrosis in some individuals in situations where interleukin-1 levels are raised.

Development of a novel 2D proteomics approach for the identification of proteins secreted by primary chondrocytes after stimulation by IL-1 and oncostatin M

OBJECTIVES

To develop a proteomics approach to study changes in the secreted protein levels of primary human chondrocytes after stimulation by the pro-inflammatory cytokines interleukin-1 and oncostatin M.

METHODS

Using both the primary human articular and bovine nasal chondrocyte-conditioned mediums, methods were investigated to enable the separation of proteins by two-dimensional (2D) gel electrophoresis. Differentially regulated proteins were identified using tandem electrospray mass spectrometery.

RESULTS

We discovered that proteoglycans and glycosylaminoglycans (GAGs) secreted by chondrocytes significantly interfered with 2D gel focusing. Several different methods for GAG removal were attempted including enzymic digestion, cetyl pyridinium chloride precipitation and anion exchange in high salt. The anion exchange proved to be the most effective. Even from these initial gels, we were able to identify eight proteins produced by human chondrocytes: matrix metalloproteinase (MMP)-1, MMP-3, YKL40, cyclophilin A, beta2-microglobulin, transthyretin, S100A11, peroxidine 1 and cofilin. MMP-1, MMP-3, YKL40 and cyclophilin A were all identified as processed, smaller peptide fragments.

CONCLUSIONS

We were able to develop a novel sample preparation protocol to allow the reproducible sample preparation of secreted proteins from human chondrocytes. From the initial data, we were able to show that at least some of the proteins produced were cleaved to smaller fragments as a result of proteolysis. Therefore, this technique provides valuable information about protein processing which gene-based arrays do not.

Histological analysis of the ligamentum flavum of patients with dialysis-related spondyloarthropathy

Dialysis-related spondyloarthropathy (DRS) is a severe complication of long-term hemodialysis that ultimately leads to functional disability of the upper and lower extremities. Although the cause of this disease is still unknown, it is thought that amyloid deposits are involved. beta2-Microglobulin (beta2M) is a major component of amyloid fibrils, some of which are modified with the advanced glycation end-product (AGE). To clarify the pathophysiology of DRS we histologically examined the ligamentum flavum of the cervical spine in 15 patients with DRS. The mean duration of hemodialysis was 20 years (12-27 years). In addition to the congo red stain for amyloid, beta2M and AGE were detected by immunohistochemical methods. Macrophages were stained with CD68 antibody. Amyloid deposits were found in tissues, although the extent of the stained area differed among the patients. Part of the amyloid deposit area was positively immunostained for beta2M and AGE. In 10 cases macrophages positive for CD68 infiltrated around the amyloid deposits. Comparing these histological findings with the dialysis duration, more positive staining areas for beta2M and AGE were found in the tissue from patients with long-term dialysis. These findings suggest that both beta2M and AGE play roles in the pathogenesis of DRS.

Beta-2 microglobulin in ESRD: an in-depth review

Beta-2 microglobulin is the most widely studied low-molecular-weight protein in end-stage renal disease. It is known to cause dialysis-related amyloidosis (DRA), by virtue of its retention when renal function fails, its deposition in tissues, its aggregation into fibrils, and its ability to become glycosylated. The onset of DRA may be protracted by the use of noncellulosic membranes, especially when high-volume hemodiafiltration is used in the treatment of renal failure. Adsorptive methods have been developed to improve the removal of beta-2 microglobulin. There seems to be a relative risk reduction in mortality when patients are treated with dialysis membranes that have a higher clearance of beta-2 microglobulin.

Ankylosing spondylitis: a beta2m-deposition disease?

To explain the strong association between HLA-B27 and ankylosing spondylitis, we suggest that the release of beta(2)-microglobulin (beta(2)m) from a subpopulation of cell surface-expressed HLA-B27 molecules leads to beta(2)m-deposition within synovia and to the initiation of an inflammatory process, which culminates in destructive spondyloarthropathy.

Microarray analysis reveals the involvement of beta-2 microglobulin (B2M) in human osteoarthritis

OBJECTIVE

To assess whether beta-2 microglobulin (B2M) has effects on articular chondrocytes that would implicate B2M involvement in osteoarthritis (OA) pathogenesis.

METHODS

The mRNA levels of B2M in fetal and osteoarthritic chondrocytes were detected by RT-PCR. B2M levels in synovial fluid and tissue cultured media from cartilage explants were tested using B2M ELISA kit. Primary cultured chondrocytes were used for proliferation and microarray experiments.

RESULTS

The average B2M level in OA synovial fluid is significantly higher than that found in normal synovial fluid. However, there was no significant difference in B2M synovial fluid levels amongst differing OA stages. The release of B2M by osteoarthritic cartilage was detectable after 24h in culture and continued to increase during the 72 h study period. B2M had an inhibitory effect on chondrocyte growth at 1.0 microg/ml, and became significantly inhibitory at 10.0 microg/ml. Genes regulated by B2M were detected through microarray technology. Twenty genes were found to be up-regulated by B2M, including collagen type III which is known to be up-regulated in OA. Eleven genes were found to be down-regulated at least two-fold by B2M.

CONCLUSION

These results indicate that B2M is highly expressed in OA cartilage and synovial fluid compared to normal, and suggest that B2M may have effects on chondrocyte function that could contribute to OA pathogenesis. Published by Elsevier Science Ltd.

Beta 2-microglobulin amyloidosis: role of monocytes/macrophages

PURPOSE OF REVIEW

Macrophage infiltration is a distinctive histological characteristic of beta2-microglobulin amyloidosis. Studies reported during the past years have helped to clarify the role of monocytes/macrophages in the fibrillar precipitation of beta2-microglobulin and in the pathogenesis of osteoarticular pathology.

RECENT FINDINGS

Contrary to the original view, macrophage infiltration is more likely a secondary phenomenon of amyloidosis rather than an initiating event. The observation that macrophages are associated with a later stage of beta2-microglobulin amyloidosis suggests a possible role of these cells in transformation of clinical silent deposits into symptomatic osteoarticular destruction. Accumulating evidence suggests that beta2-microglobulin modified with advanced glycation end products plays a key role in recruitment and activation of macrophages through an advanced glycation end products receptor-mediated pathway, and thus may contribute to the development of local cellular inflammation in beta2-microglobulin amyloidosis.

SUMMARY

Beta 2-microglobulin amyloidosis arthropathies may result from progressive accumulation of advanced glycation end products in long-lived amyloid linked to a heightened cellular response. Antagonism of the interaction between advanced glycation end products and their receptor may be a relevant strategy for cellular inflammation in beta2-microglobulin amyloidosis.

Receptor for advanced glycation end products on human synovial fibroblasts: role in the pathogenesis of dialysis-related amyloidosis

An important component of amyloid fibrils in dialysis-related amyloidosis (DRA) is beta(2)-microglobulin (beta(2)m) modified with advanced glycation end products (AGE). The amyloid deposits are located principally in joint structures, with adjacent chronic inflammatory reaction characterized by monocyte infiltration. This study examined the interaction of AGE-beta(2)m with human synovial fibroblasts and investigated the proinflammatory effects of that interaction. It was demonstrated that human synovial fibroblasts constitutively expressed the receptor for AGE (RAGE). RAGE expression was detected mainly in synovial intima and was upregulated in DRA synovium. (125)I-AGE-beta(2)m bound to immobilized human synovial fibroblasts in a specific, dose-dependent manner (K(d) of approximately 138.0 nM), and binding was inhibited by anti-RAGE IgG. Incubation of human synovial fibroblasts with AGE-beta(2)m induced degradation of this AGE-modified protein, as well as increased monocyte chemoattractant protein-1 (MCP-1) mRNA and protein expression. The amount of MCP-1 produced by AGE-beta(2)m-stimulated human synovial fibroblasts was sufficient to induce the chemotaxis of monocytes. MCP-1 synthesis resulted from engagement of RAGE, because the increase in MCP-1 synthesis was attenuated by preincubation of human synovial fibroblasts with anti-RAGE IgG. These data provide evidence of RAGE-mediated perturbation of human synoviocytes, which may be involved in the pathogenesis of inflammatory processes associated with DRA.

Signal transduction of beta2m-induced expression of VCAM-1 and COX-2 in synovial fibroblasts

BACKGROUND

beta2 microglobulin (beta2m) amyloidosis is a destructive articular disease affecting dialysis patients. We have demonstrated that beta2m increases the expression of vascular cell adhesion molecule (VCAM-1) and cyclooxygenase-2 (COX-2) in human osteoarthritic synovial fibroblasts (SFLs).

METHODS

To determine the cell signaling pathways, SFLs were incubated with beta2m in the presence or absence of various inhibitors for 24 hours. Intracellular calcium ([Ca2+]i) was measured by fluorometric techniques and vascular cell adhesion molecule-1 (VCAM-1) and cyclooxygenase-2 (COX-2) expression was determined by immunohistochemistry and Western blotting.

RESULTS

beta2m increased [Ca2+]i levels in a dose dependent manner (P < 0.05) in SFLs. BAPTA-AM, a [Ca2+]i chelator, completely inhibited beta2m-induced expression of VCAM-1 and COX-2. U73122 [phospholipase C (PLC) inhibitor] or 2-APB [specific inhibitor of inositol 1,4,5-trisphosphate (IP3)-induced [Ca2+]i release] completely blocked the beta2m-induced increase in [Ca2+]i and the up-regulation of VCAM-1 and COX-2. However, pretreatment with staurosporin, a protein kinase C inhibitor, had no effect. Disruption of the actin cytoskeleton by treatment with cytochalasin D or latrunculin A blocked beta2m up-regulation of VCAM-1 and COX-2. Finally, cells treated with phosphatidylinositol-3 kinase (PI-3 kinase) inhibitors wortmannin or LY294002 also failed to express VCAM-1 and COX-2.

CONCLUSIONS

These results demonstrate that IP3-mediated [Ca2+]i release, PI-3 kinase, and actin cytoskeleton reorganization are involved in beta2m-induced expression of VCAM-1 and COX-2 in human SFLs. Understanding the potential pathways by which beta2m exerts its inflammatory-like effects may lead to the development of future therapies.

β2-Microglobulin Amyloidosis: Effects of Ultrapure Dialysate and Type of Dialyzer Membrane

ABSTRACT. The available data on the pathophysiology of β2-microglobulin amyloidosis (β2mA) suggest that this progressive disease associated with end-stage renal failure develops in several consecutive phases. First, declining kidney function leads to retention of β2 microglobulin (β2m) and its deposition preferentially in the synovial tissue of bigger joints such as wrists, shoulders, and hips. Second, at the site of deposition, formation of unique amyloid fibrils, whose major component is β2m, takes place. Deposition and fibril formation occur in the absence of modification of β2mA by advanced glycoxidation end products and also in the absence of a local inflammatory response. It is later, in the third phase, that advanced glycoxidation end product modification of β2m induces a local inflammatory response by attracting macrophages chemotactically and by stimulating these cells to produce and release proinflammatory cytokines. In addition, unmodified β2m itself induces inflammatory activities such as upregulation of cyclooxygenase-2 and metalloproteinase-1. The severity of the local inflammation seems to determine the degree of the destructive processes in tissue and bone accompanying β2mA.

Synovial fluid gelatinase concentrations and matrix metalloproteinase and cytokine expression in naturally occurring joint disease in horses

OBJECTIVES

To determine concentrations of matrix metalloproteinase (MMP)-2 and -9 in synovial fluid; and mRNA expression of MMP-1, -13, and -3; interleukin[IL]-1alpha and beta; and tumor necrosis factor (TNF)-alpha in synovial membrane and articular cartilage from horses with naturally occurring joint disease.

SAMPLE POPULATION

Synovial fluid (n = 76), synovial membrane (59), and articular cartilage (45) from 5 clinically normal horses and 55 horses with joint disease categorized as traumatic (acute [AT] or chronic [CT]), osteochondritis dissecans (OCD), or septic (S).

PROCEDURE

Synovial fluid gelatinase concentrations were analyzed, using zymography. Synovial membrane and articular cartilage mRNA expression for MMP-1, -3, and -13, IL-1alpha and beta, TNF-alpha, type-II collagen, and aggrecan were analyzed, using quantitative reverse transcriptase-polymerase chain reaction.

RESULTS

Synovial fluid pro-MMP-2 concentration was significantly higher in diseased joints than normal joints. Septic joints had significantly higher concentrations of pro and active MMP-9. Stromelysin-1 was expressed in > or = 80% of synovial membrane and articular cartilage samples and was strongly influenced by age. Collagenases were rarely expressed, with MMP-13 expressed only in diseased joints. Interleukin-1beta expression was significantly higher in all OCD samples and was influenced by age. Tumor necrosis factor-alpha expression was significantly higher in cartilage from joints with AT and OCD. There was no correlation between MMP or cytokines and type-II collagen or aggrecan expression.

CONCLUSIONS AND CLINICAL RELEVANCE

Matrix metalloproteinase-2 and -3 are abundant in naturally occurring joint disease and normal joints. Interleukin-1beta and TNF-alpha may be important in the pathogenesis of OCD. Age affects MMP and IL-1beta concentrations.

Accumulation of advanced glycation end products decreases collagen turnover by bovine chondrocytes

The integrity of the collagen network is essential for articular cartilage to fulfill its function in load support and distribution. Damage to the collagen network is one of the first characteristics of osteoarthritis. Since extensive collagen damage is considered irreversible, it is crucial that chondrocytes maintain a functional collagen network. We investigated the effects of advanced glycation end products (AGEs) on the turnover of collagen by articular cartilage chondrocytes. Increased AGE levels (by culturing in the presence of ribose) resulted in decreased collagen synthesis (P < 0.05) and decreased MMP-mediated collagen degradation (P < 0.02). The latter could be attributed to increased resistance of the collagen network to MMPs (P < 0.05) as well as the decreased production of MMPs by chondrocytes (P < 0.02). Turnover of a protein is determined by its synthesis and degradation rates and therefore these data indicate that collagen turnover is decreased at enhanced AGE levels. Since AGE levels in human cartilage increase approximately 50 fold between age 20 and 80, cartilage collagen turnover likely decreases with increasing age. Impaired collagen turnover adversely affects the capacity of chondrocytes to remodel and/or repair its extracellular matrix. Consequently, age-related accumulation of AGE (via decreased collagen turnover) may contribute to the development of cartilage damage in osteoarthritis.

beta(2)-Microglobulin increases the expression of vascular cell adhesion molecule on human synovial fibroblasts

BACKGROUND

beta(2)-Microglobulin (beta(2)m) amyloidosis is a destructive articular disease that affects patients on dialysis. The disease presentation is similar to other forms of arthritis in which adhesion molecules are felt to be pathogenic. Therefore, we hypothesized that beta(2)m directly increases the expression of vascular cell adhesion molecule-1 (VCAM-1) by synovial fibroblasts. We also examined the effect of alteration of beta(2)m by advanced glycation end products on this cellular response.

METHODS

Human synovial fibroblasts were isolated and incubated with beta(2)m with and without alteration with advanced glycation end products. VCAM-1 expression was determined by immunohistochemistry, flow cytometry, and Western blot and Northern blot analyses.

RESULTS

beta(2)m increased the protein expression of VCAM-1 by synovial fibroblasts in a dose-dependent manner. beta(2)m altered with advanced glycation end products had no effect. However, all forms of beta(2)m increased VCAM-1 mRNA. beta(2)m also increased the adhesion of peripheral blood mononuclear cells to synovial fibroblasts.

CONCLUSION

beta2m directly increases the expression of VCAM-1 by synovial fibroblasts, indicating that synovial fibroblasts may play a key role in the pathogenesis of beta(2)m amyloidosis.

Pathogenesis of beta(2)-microglobulin amyloidosis: role of monocytes/macrophages

beta(2)-microglobulin (beta(2)M) amyloidosis (A beta(2)M) is a serious, often incapacitating complication for patients undergoing long-term hemodialysis. Amyloid deposits composed of beta(2)M fibrils as the major constituent protein are mainly localized in joints and periarticular bone and lead to chronic arthralgias, carpal tunnel syndrome, and eventually destructive arthropathy. Although recent histologic studies have shown the accumulation of monocytes/macrophages around amyloid deposits, the factor(s) causing their infiltration and pathologic involvement have yet to be fully elucidated. Immunohistochemical staining reveals that macrophages in tenosynovial tissues express CD13, CD14, CD33, HLA-DR, and CD68 antigens on their surfaces and express interleukin (IL)-1 beta, tumor necrosis factor (TNF)-alpha, and IL-6. Many of these cells also express LFA-1 (CD11a/CD18), Mac-1 (CD11b/CD18), and VLA-4 (CD49d/CD29) on their surfaces. AGE-modified beta(2)M enhances chemotaxis of monocytes and stimulates macrophages to release bone-resorbing cytokines, such as IL-1 beta, TNF-alpha and IL-6. Via a RAGE-mediated pathway, AGE-modified, but not unmodified beta(2)M, significantly delays constitutive apoptosis of human peripheral blood monocytes. Monocytes survival in an advanced glycation end product (AGE) beta(2)M-containing microenvironment is associated with their phenotypic alteration into macrophage-like cells that generate more reactive oxygen species and elaborate greater quantities of IL-1 beta and TNF-alpha. Thus through regulation of their survival and differentiation, AGE beta(2)M in amyloid deposits may be able to influence the presence and quantity of infiltrated monocytes, and hence their biologic effects.

Dynamic of beta(2)-microglobulin fibril formation and reabsorption: the role of proteolysis

Dialysis-related amyloidosis (DRA) is caused by the deposition, in target tissues, of beta(2)-microglobulin (beta(2)M) in fibrillar conformation. Several reports indicate that fibrillar beta(2)M is chemically heterogeneous and such heterogeneity is partially related to the presence of truncated species of the protein. In association with the full-length species, a beta(2)M isoform lacking six N-terminal residues is present in all the samples of our collection of ex vivo fibrils. The pattern of proteolytic cleavage in amyloidosis and in other diseases is completely different, as demonstrated by the absence in fibrillar beta(2)M of the cleavage at lysine 58, which is contrary to that described in rheumatoid arthritis and other diseases. The role of limited proteolysis of beta(2)M in the pathogenesis of the disease is uncertain. However, we have shown that the apparently minor modification of the intact protein, such as the removal of N-terminal hexapeptide, is capable of dramatically affecting its stability, protection from proteolytic digestion, and enhance its capacity to make in vitro amyloid fibrils. The structure, folding dynamic, and function of the truncated species of beta(2)M, peculiar of DRA, could shed new light on the mechanism of beta(2)M fibril formation and reabsorption.

The role of the synovium and cartilage in the pathogenesis of beta(2)-microglobulin amyloidosis

The predilection for beta(2)-microglobulin (beta(2)M) amyloid deposition in articular structures is unique compared to other forms of amyloid; this article focuses on possible pathogenic mechanisms. The synovium and/or cartilage appear to be important in the pathogenesis of beta(2)M amyloidosis (A beta(2)M), as amyloid is not found in the shafts of long bones. The concentration of beta(2)M in the joint fluid parallels that in serum. Once in the joint space, evidence suggests that the beta(2)M binds to collagen in cartilage as the initial site of deposition. This binding may serve as the first step in subsequent amyloid formation, although this remains to be proven. beta(2)M has been shown to have many direct effects on synovial fibroblasts, including induction of the release of cytokines, metalloproteinases, cyclooxygenase-2, and vascular cell adhesion molecule-1 (VCAM-1). The release of these inflammatory mediators that lead to tissue degradation is also observed in other forms of arthritis. Thus beta(2)M itself may elicit the release of inflammatory mediators from synovial fibroblasts even in the absence of cellular infiltrates.