Evolving concepts of rheumatoid arthritis

De novo carcinogenesis promoted by chronic inflammation is B lymphocyte dependent

Chronic inflammation predisposes tissue to cancer development; however, regulatory mechanisms underlying recruitment of innate leukocytes toward developing neoplasms are obscure. We report that genetic elimination of mature T and B lymphocytes in a transgenic mouse model of inflammation-associated de novo epithelial carcinogenesis, e.g., K14-HPV16 mice, limits neoplastic progression to development of epithelial hyperplasias that fail to recruit innate immune cells. Adoptive transfer of B lymphocytes or serum from HPV16 mice into T and B cell-deficient/HPV16 mice restores innate immune cell infiltration into premalignant tissue and reinstates necessary parameters for full malignancy, e.g., chronic inflammation, angiogenic vasculature, hyperproliferative epidermis. These findings support a model in which B lymphocytes are required for establishing chronic inflammatory states that promote de novo carcinogenesis.

Kappa and delta opioid receptors are expressed but down-regulated in fibroblast-like synoviocytes of patients with rheumatoid arthritis and osteoarthritis

OBJECTIVE

To investigate the expression and regulation of the kappa-opioid receptor (KOR) and the delta-opioid receptor (DOR) in fibroblast-like synoviocytes (FLS) from patients with osteoarthritis (OA) and rheumatoid arthritis (RA), and to explore the potential antiarthritic mechanisms of peripheral KORs.

METHODS

FLS isolated from synovial tissues of 6 OA patients, 8 RA patients, and 2 healthy individuals were exposed to the selective KOR agonist U69593, the selective DOR agonist SNC 80, and kappa-opioid dynorphin A in the presence or absence of the KOR antagonist nor-binaltorphimine, the DOR antagonist naltrindole, and the proinflammatory cytokines tumor necrosis factor alpha (TNFalpha) and interleukin-1beta (IL-1beta). The expression of KOR and DOR in OA and RA FLS was evaluated on the messenger RNA (mRNA) and protein levels with TaqMan real-time reverse transcriptase-polymerase chain reaction and immunofluorescence staining, respectively. KOR/DOR-mediated activation of ERK-1 and ERK-2 was investigated by Western blotting.

RESULTS

We detected functional KOR and DOR in normal FLS and observed a reduction of both receptors in OA and RA FLS, which was more distinct in RA FLS. U69593 enhanced KOR mRNA expression in both OA and RA FLS in a KOR antagonist-reversible manner. However, the dose required for maximal enhancement in RA FLS was 10 times higher than that required in OA FLS. TNFalpha and IL-1beta both suppressed the expression of DOR and KOR mRNA in both OA and RA FLS.

CONCLUSION

DOR and KOR are constitutively present in normal FLS and are suppressed under inflammatory conditions, such as RA and OA. Most interestingly, the KOR agonist U69593 may exert an antiarthritic effect via up-regulation of KOR in OA and RA FLS.

Somatic mutations in the mitochondria of rheumatoid arthritis synoviocytes

Somatic mutations have a role in the pathogenesis of a number of diseases, particularly cancers. Here we present data supporting a role of mitochondrial somatic mutations in an autoimmune disease, rheumatoid arthritis (RA). RA is a complex, multifactorial disease with a number of predisposition traits, including major histocompatibility complex (MHC) type and early bacterial infection in the joint. Somatic mutations in mitochondrial peptides displayed by MHCs may be recognized as non-self, furthering the destructive immune infiltration of the RA joint. Because many bacterial proteins have mitochondrial homologues, the immune system may be primed against these altered peptides if they mimic bacterial homologues. In addition, somatic mutations may be influencing cellular function, aiding in the acquirement of transformed properties of RA synoviocytes. To test the hypothesis that mutations in mitochondrial DNA (mtDNA) are associated with RA, we focused on the MT-ND1 gene for mitochondrially encoded NADH dehydrogenase 1 (subunit one of complex I – NADH dehydrogenase) of synoviocyte mitochondria from RA patients, using tissue from osteoarthritis (OA) patients for controls. We identified the mutational burden and amino acid changes in potential epitope regions in the two patient groups. RA synoviocyte mtDNA had about twice the number of mutations as the OA group. Furthermore, some of these changes had resulted in potential non-self MHC peptide epitopes. These results provide evidence for a new role for somatic mutations in mtDNA in RA and predict a role in other diseases.

Characterization of histopathology and gene-expression profiles of synovitis in early rheumatoid arthritis using targeted biopsy specimens

The disease category of early rheumatoid arthritis (RA) has been limited with respect to clinical criteria. Pathological manifestations of synovitis in patients whose disease is clinically classified as early RA seem to be heterogeneous, with regular variations. To clarify the relation between the molecular and histopathological features of the synovitis, we analyzed gene-expression profiles in the synovial lining tissues to correlate them with histopathological features. Synovial tissues were obtained from knee joints of 12 patients with early RA by targeted biopsy under arthroscopy. Surgical specimens of long-standing RA (from four patients) were examined as positive controls. Each histopathological parameter characteristic of rheumatoid synovitis in synovial tissues was scored under light microscopy. Total RNAs from synovial lining tissues were obtained from the specimens selected by laser capture microdissection and the mRNAs were amplified by bacteriophage T7 RNA polymerase. Their cDNAs were analyzed in a cDNA microarray with 23,040 cDNAs, and the levels of gene expression in multilayered lining tissues, compared with those of normal-like lining tissues in specimens from the same person, were determined to estimate gene-expression profiles characteristic of the synovial proliferative lesions in each case. Based on cluster analysis of all cases, gene-expression profiles in the lesions in early RA fell into two groups. The groups had different expression levels of genes critical for proliferative inflammation, including those encoding cytokines, adhesion molecules, and extracellular matrices. One group resembled synovitis in long-standing RA and had high scores for some histopathological features – involving accumulations of lymphocytes and plasma cells – but not for other features. Possible differences in the histopathogenesis and prognosis of synovitis between the two groups are discussed in relation to the candidate genes and histopathology.

A functional variant in FCRL3, encoding Fc receptor-like 3, is associated with rheumatoid arthritis and several autoimmunities

Rheumatoid arthritis is a common autoimmune disease with a complex genetic etiology. Here we identify a SNP in the promoter region of FCRL3, a member of the Fc receptor-like family, that is associated with susceptibility to rheumatoid arthritis (odds ratio = 2.15, P = 0.00000085). This polymorphism alters the binding affinity of nuclear factor-kappaB and regulates FCRL3 expression. We observed high FCRL3 expression on B cells and augmented autoantibody production in individuals with the disease-susceptible genotype. We also found associations between the SNP and susceptibility to autoimmune thyroid disease and systemic lupus erythematosus. FCRL3 may therefore have a pivotal role in autoimmunity.

Early rheumatoid arthritis is characterized by a distinct and transient synovial fluid cytokine profile of T cell and stromal cell origin

Pathological processes involved in the initiation of rheumatoid synovitis remain unclear. We undertook the present study to identify immune and stromal processes that are present soon after the clinical onset of rheumatoid arthritis (RA) by assessing a panel of T cell, macrophage, and stromal cell related cytokines and chemokines in the synovial fluid of patients with early synovitis. Synovial fluid was aspirated from inflamed joints of patients with inflammatory arthritis of duration 3 months or less, whose outcomes were subsequently determined by follow up. For comparison, synovial fluid was aspirated from patients with acute crystal arthritis, established RA and osteoarthritis. Rheumatoid factor activity was blocked in the synovial fluid samples, and a panel of 23 cytokines and chemokines measured using a multiplex based system. Patients with early inflammatory arthritis who subsequently developed RA had a distinct but transient synovial fluid cytokine profile. The levels of a range of T cell, macrophage and stromal cell related cytokines (e.g. IL-2, IL-4, IL-13, IL-17, IL-15, basic fibroblast growth factor and epidermal growth factor) were significantly elevated in these patients within 3 months after symptom onset, as compared with early arthritis patients who did not develop RA. In addition, this profile was no longer present in established RA. In contrast, patients with non-rheumatoid persistent synovitis exhibited elevated levels of interferon-γ at initiation. Early synovitis destined to develop into RA is thus characterized by a distinct and transient synovial fluid cytokine profile. The cytokines present in the early rheumatoid lesion suggest that this response is likely to influence the microenvironment required for persistent RA.

Hypoxia inducible factor (HIF) in rheumatology: low O2! See what HIF can do!

Maintenance of oxygen homoeostasis is the basic principle in cell proliferation, differentiation, survival, and function in all higher organisms. The transcription factor, HIF (hypoxia inducible factor) has a central role in oxygen homoeostasis, and is indispensably linked to energy metabolism. Abnormally reduced oxygen concentrations leading to dysfunctional cell metabolism are found in rheumatoid arthritis and hence, knowledge of the molecular adaptive responses to hypoxia and the involvement of HIF in the pathogenesis of RA are interesting.

Circulating CD26 is negatively associated with inflammation in human and experimental arthritis

Dipeptidyl peptidase IV (DPPIV, CD26), a protease-cleaving N-terminal X-Pro dipeptide from selected proteins including some chemokines, is expressed both as a soluble form in plasma and on the cell surface of various immune and nonimmune cell types. To gain insights into the pathophysiological role of CD26 in arthritis, we explored DPPIV/CD26 expression during murine antigen-induced arthritis (AIA), an experimental model of arthritis. AIA induction led to reduced plasma DPPIV activity. In CD26-deficient mice, the severity of AIA was increased as assessed by enhanced technetium uptake and by increased histological parameters of inflammation (synovial thickness and exudate). We demonstrated that CD26 controls the in vivo half-life of the intact active form of the proinflammatory chemokine stromal cell-derived factor-1 (SDF-1). CD26-deficient mice exhibited increased levels of circulating active SDF-1, associated with increased numbers of SDF-1 receptor (CXCR4)-positive cells infiltrating arthritic joints. In a clinical study, plasma levels of DPPIV/CD26 from rheumatoid arthritis patients were significantly decreased when compared to those from osteoarthritis patients and inversely correlate with C-reactive protein levels. In conclusion, decreased circulating CD26 levels in arthritis may influence CD26-mediated regulation of the chemotactic SDF-1/CXCR4 axis.

Interleukin 12 (IL12B) and interleukin 12 receptor (IL12RB1) gene polymorphisms in rheumatoid arthritis

The aim of this study was to assess the possible association between the IL12B and the IL12RB1 gene polymorphisms and the systemic autoimmune disease rheumatoid arthritis (RA). Our study population consisted of 545 patients with RA and 393 healthy subjects. All the individuals were of white Spanish origin. Genotyping of the IL12B (IL12Bpro and IL12B 3' untranslated region) and IL12RB1 (641A-->G, 1094T-->C, and 1132G-->C) polymorphisms was performed by polymerase chain reaction-restriction fragment length polymorphism and polymerase chain reaction-fluorescent methods. No statistically significant differences in the distribution of the IL12B and the IL12RB1 genotypes and alleles between patients with RA and control subjects were observed. In addition, no association was found between the above-mentioned polymorphisms with any of the demographic and clinical parameters tested in patients with RA. These results suggest that IL12B and IL12RB1 genes may not play a relevant role in the susceptibility or severity of RA in the Spanish population.

LIGHT is involved in the pathogenesis of rheumatoid arthritis by inducing the expression of pro-inflammatory cytokines and MMP-9 in macrophages

Macrophages play a crucial role in the perpetuation of inflammation and irreversible cartilage damage during the development of rheumatoid arthritis (RA). LIGHT (TNFSF14) and its receptor TR2 (TNFRSF14) are known to have pro-inflammatory activities in foam cells of atherosclerotic plaques. We tested a hypothesis that LIGHT and TR2 are involved in activation of monocyte/macrophages in RA synovium. Immunohistochemical analysis of RA synovial tissue samples revealed that both LIGHT and TR2 are expressed in CD68 positive macrophages. In contrast, synovial tissue samples from osteoarthritis (OA) patients failed to reveal the expression of LIGHT. Expression of TR2 in RA synovial macrophages was also detected using flow cytometry analysis. To identify the role of LIGHT in the functioning of macrophages in RA, we isolated macrophage enriched cells from RA synovial fluid and stimulated them with LIGHT. LIGHT induced expression of matrix metalloproteinase-9 and pro-inflammatory cytokines such as tumor necrosis factor (TNF)-alpha, interleukin (IL)-6, and IL-8. These data indicate that LIGHT and TR2 expressed in macrophages are involved in the pathogenesis of RA by inducing the expression pro-inflammatory cytokines and matrix degrading enzymes.

Interleukin-32: a cytokine and inducer of TNFalpha

We describe the gene structure, regulation, signal transduction. and functions of a cytokine, interleukin (IL)-32. An IL-18 unresponsive cell was converted to a responsive cell by transfection of the IL-18 receptor beta chain, and IL-18-induced microarray revealed high expression of a cytokine-like gene. Although IL-32 does not share sequence homology with known cytokine families, IL-32 induces various cytokines, human TNFalpha, and IL-8 in THP-1 monocytic cells as well as mouse TNFalpha and MIP-2 in Raw macrophage cells. IL-32 activates typical cytokine signal pathways of nuclear factor-kappa B (NF-kappaB) and p38 mitogen-activated protein kinase. IL-32 mRNA is highly expressed in immune tissue rather than other tissues. Human IL-32 exists as four splice variants, and IL-32 from other species were found as expressed sequence tag clones in the databank. Induced in human peripheral lymphocyte cells after mitogen stimulation, in human epithelial cells by IFNgamma, and in NK cells after exposure to the combination of IL-12 plus IL-18, IL-32 may play a role in inflammatory/autoimmune diseases.

A HEV-restricted sulfotransferase is expressed in rheumatoid arthritis synovium and is induced by lymphotoxin-alpha/beta and TNF-alpha in cultured endothelial cells

BACKGROUND

The recruitment of lymphocytes to secondary lymphoid organs relies on interactions of circulating cells with high endothelial venules (HEV). HEV are exclusive to these organs under physiological conditions, but they can develop in chronically-inflamed tissues. The interaction of L-selectin on lymphocytes with sulfated glycoprotein ligands on HEV results in lymphocyte rolling, which represents the initial step in lymphocyte homing. HEV expression of GlcNAc6ST-2 (also known as HEC-GlcNAc6ST, GST-3, LSST or CHST4), an HEV-restricted sulfotransferase, is essential for the elaboration of L-selectin functional ligands as well as a critical epitope recognized by MECA-79 mAb.

RESULTS

We examined the expression of GlcNAc6ST-2 in relationship to the MECA-79 epitope in rheumatoid arthritis (RA) synovial vessels. Expression of GlcNAc6ST-2 was specific to RA synovial tissues as compared to osteoarthritis synovial tissues and localized to endothelial cells of HEV-like vessels and small flat-walled vessels. Double MECA-79 and GlcNAc6ST-2 staining showed colocalization of the MECA-79 epitope and GlcNAc6ST-2. We further found that both TNF-alpha and lymphotoxin-alphabeta induced GlcNAc6ST-2 mRNA and protein in cultured human umbilical vein endothelial cells.

CONCLUSION

These observations demonstrate that GlcNAc6ST-2 is induced in RA vessels and provide potential cytokine pathways for its induction. GlcNAc6ST-2 is a novel marker of activated vessels within RA ectopic lymphoid aggregates. This enzyme represents a potential therapeutic target for RA.

Non-thyroid autoantibodies in autoimmune thyroid disease

Autoimmune thyroid disease is frequently accompanied by other organ-specific and non-organ-specific diseases, most likely because there is sharing of genetic and possibly environmental susceptibility factors. These associations are well recognized in the autoimmune polyglandular syndromes; autoimmune thyroid disease is one of the three major endocrinopathies in the type 2 syndrome and occurs in around 4% of type 1 patients. This review considers the frequency of disease-specific autoantibodies in patients with thyroid autoimmunity and briefly examines the role of such antibodies in performing screening for the associated conditions. Recommendations are made for using such autoantibody tests in the setting of patients with autoimmune thyroid disorders, and also for the utility of screening for thyroid autoimmunity in patients with pernicious anaemia, Addison's disease, coeliac disease, primary biliary cirrhosis, myasthenia gravis, lymphocytic hypophysitis, systemic lupus erythematosus and rheumatoid arthritis. At present, however, there are no large-scale trials that have shown the cost-benefit ratio of autoantibody screening for autoimmunity screening, and clinicians must use individual judgement combined with heightened awareness to identify who to test.

Epitope spreading initiates in the CNS in two mouse models of multiple sclerosis

Introduction

Mouse models of rheumatoid arthritis (RA) have proven critical for identifying genetic and cellular mechanisms of the disease. Upon discovering mice in our breeding colony that had spontaneously developed inflamed joints reminiscent of RA, we established the novel IIJ (inherited inflamed joints) strain. The purpose of this study was to characterize the histopathological, clinical, genetic and immunological properties of the disease.

Methods

To begin the IIJ strain, an arthritic male mouse was crossed with SJL/J females. Inheritance of the phenotype was then tracked by intercrossing, backcrossing and outcrossing to other inbred strains. The histopathology of the joints and extraarticular organ systems was examined. Serum cytokines and immunoglobulins (Igs) were measured by ELISA and cytometric bead array. Transfer experiments tested whether disease could be mediated by serum alone. Finally, the cellular joint infiltrate and the composition of secondary lymphoid organs were examined by immunohistochemistry and flow cytometry.

Results

After nine generations of intercrossing, the total incidence of arthritis was 33% (304 of 932 mice), with females being affected more than males (38% vs. 28%; P < 0.001). Swelling, most notably in the large distal joints, typically became evident at an early age (mean age of 52 days). In addition to the joint pathology, which included bone and cartilage erosion, synovial hyperproliferation and a robust cellular infiltration of mostly Gr-1⁺ neutrophils, there was also evidence of systemic inflammation. IL-6 was elevated in the sera of recently arthritic mice, and extraarticular inflammation was observed histologically in multiple organs. Total serum Ig and IgG1 levels were significantly elevated in arthritic mice, and autoantibodies such as rheumatoid factor and Ig reactive to joint components (collagen type II and joint homogenate) were also detected. Nevertheless, serum failed to transfer disease. A high percentage of double-negative (CD4^-CD8^-) CD3⁺ TCRα/β⁺ T cells in the lymphoid organs of arthritic IIJ mice suggested significant disruption in the T-cell compartment.

Conclusions

Overall, these data identify the IIJ strain as a new murine model of inflammatory, possibly autoimmune, arthritis. The IIJ strain is similar, both histologically and serologically, to RA and other murine models of autoimmune arthritis. It may prove particularly useful for understanding the female bias in autoimmune diseases.

Circadian melatonin and cortisol levels in rheumatoid arthritis patients in winter time: a north and south Europe comparison

BACKGROUND

Altered functioning of the hypothalamic-pituitary-adrenal axis and altered melatonin production might modulate the circadian symptoms in patients with rheumatoid arthritis.

OBJECTIVE

To investigate the influence of different winter photoperiods on the circadian rhythms of serum melatonin, cortisol, tumour necrosis factor alpha (TNFalpha), and interleukin 6 (IL6) in patients with rheumatoid arthritis from a north Europe country (Estonia) and a south Europe country (Italy).

METHODS

The patients from Estonia (n = 19) and Italy (n = 7) had similar disease severity and duration and were compared with healthy age and sex matched controls in the two countries. Blood samples were collected during the period January to February at 8 pm, 10 pm, midnight, 2 am, 4 am, 6 am, 8 am, and 3 pm. Melatonin was measured by radioimmunoassay using (125)I-melatonin. Serum cortisol, TNFalpha, and IL6 cytokines were assayed by standard methods.

RESULTS

Higher circadian melatonin concentrations from 10 pm and an earlier peak were observed in Estonian patients than in their age and sex matched controls (p<0.01). Starting from midnight, melatonin concentrations were significantly higher in the Estonian patients than in the Italian patients. No significant differences were observed for serum cortisol. Serum TNFalpha was higher (p<0.05) in Estonian patients than in their controls and was correlated with the melatonin levels.

CONCLUSIONS

In a north European country (Estonia), the circadian rhythm of serum concentrations of melatonin and TNFalpha in patients with rheumatoid arthritis were significantly higher than in matched controls or in rheumatoid patients from a south Europe country (Italy).

Association of a functional single-nucleotide polymorphism of PTPN22, encoding lymphoid protein phosphatase, with rheumatoid arthritis and systemic lupus erythematosus

OBJECTIVE

To assess the possible association between the PTPN22 gene 1858C-->T polymorphism and the predisposition and clinical expression of 2 systemic autoimmune diseases, rheumatoid arthritis (RA) and systemic lupus erythematosus (SLE).

METHODS

Our study population consisted of 826 RA patients, 338 SLE patients, and 1,036 healthy subjects. All subjects were of Spanish Caucasian origin. Genotyping of the PTPN22 gene 1858C-->T polymorphism was performed by real-time polymerase chain reaction technology, using the TaqMan 5'-allele discrimination assay.

RESULTS

The overall distribution of genotypes in the RA patients was significantly different from that in the controls (P = 0.005, by chi-square test with 2 x 3 contingency tables). We observed a statistically significant difference in the distribution of the PTPN22 1858T allele between healthy subjects (7.4%), and RA patients (10.4%) (P = 0.001, odds ratio [OR] 1.45 [95% confidence interval (95% CI) 1.15-1.83]). In addition, PTPN22 1858 C/T and T/T genotypes were present at a significantly higher frequency in SLE patients than in controls (P = 0.02, OR 1.55 [95% CI 1.05-2.29]). Differences were also observed when allele frequencies were compared, with the PTPN22 1858T allele being present at a higher frequency among SLE patients (P = 0.03, OR 1.45 [95% CI 1.01-2.09]).

CONCLUSION

These results suggest that the PTPN22 1858T allele may confer differential susceptibility to RA and SLE in the Spanish population.

Wnt signalling in rheumatoid arthritis

Rheumatoid arthritis (RA) is a symmetrical polyarticular disease of unknown aetiology that affects primarily the diarthrodial joints. Characteristic features of RA pathogenesis are synovial hyperplasia and inflammation accompanied by cartilage loss and joint destruction. Synovial hyperplasia and inflammation are a consequence of an increase in the macrophage-like and fibroblast-like synoviocytes of the synovial intimal lining associated with infiltration of leucocytes into the subintimal space. Although therapeutic interventions are available, the disease persists despite therapy in a significant fraction of patients. Several lines of evidence have substantiated a crucial role of activated fibroblast-like synoviocytes (FLS) during RA pathogenesis. The hyperplastic FLS population potentially promotes leucocyte infiltration and retention. The rheumatoid synovium eventually transforms into a pannus that destroys articular cartilage and bone. There are no approved drugs that are known to target the FLS in RA, and the underlying mechanisms driving FLS activation remain unresolved. In this review, the importance of Wnt-frizzled (Fz)-mediated signalling in the autonomous activation of FLS is discussed. Anti-Wnt/anti-Fz antibodies, Fz receptor antagonists or small-molecule inhibitors of Wnt-Fz signalling might be useful for therapeutic interventions in refractory RA.

The induction of matrix metalloproteinase and cytokine expression in synovial fibroblasts stimulated with immune cell microparticles

Rheumatoid arthritis is a chronic inflammatory disease characterized by destruction of cartilage and bone that is mediated by synovial fibroblasts. To determine the mechanisms by which these cells are activated to produce matrix metalloproteinases (MMPs), the effects of microparticles were investigated. Microparticles are small membrane-bound vesicles whose release from immune cells is increased during activation and apoptosis. Because microparticles occur abundantly in the synovial fluid in rheumatoid arthritis, they could represent novel stimulatory agents. Microparticles derived from T cells and monocytes strongly induced the synthesis of MMP-1, MMP-3, MMP-9, and MMP-13 in fibroblasts. The induction was time-dependent, with effects primarily observed after 36 h; under these conditions, MMP-2, MMP-14, and tissue inhibitor of MMP-1 (TIMP-1), TIMP-2, and TIMP-3 were not induced. Microparticles also increased the synthesis of inflammatory mediators including IL-6, IL-8, monocyte chemoattractant protein 1 (MCP-1), and MCP-2. In Ikappa-B-transfected synovial fibroblasts, MMPs were less inducible by microparticles compared with wild-type fibroblasts. Blocking of TNFalpha and IL-1beta with antibodies against TNFalpha and with IL-1 receptor antagonist did not abrogate stimulation by microparticles. These data provide evidence for a novel mechanism by which vesicles derived from activated or apoptotic immune cells can promote the destructive activity of synovial fibroblasts in rheumatoid arthritis.

Increased proviral load in HTLV-1-infected patients with rheumatoid arthritis or connective tissue disease

BACKGROUND

Human T-lymphotropic virus type 1 (HTLV-1) proviral load is related to the development of HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP) and has also been shown to be elevated in the peripheral blood in HTLV-1-infected patients with uveitis or alveolitis. Increased proliferation of HTLV-1-infected cells in, or migration of such cells into, the central nervous system is also seen in HAM/TSP. In the present study, we evaluated the proviral load in a cohort of HTLV-1-infected patients with arthritic conditions.

RESULTS

HTLV-1 proviral load in the peripheral blood from 12 patients with RA and 6 patients with connective tissue disease was significantly higher than that in matched asymptomatic HTLV-1 carriers, but similar to that in matched HAM/TSP controls. HAM/TSP was seen in one-third of the HTLV-1-infected patients with RA or connective tissue disease, but did not account for the higher proviral load compared to the asymptomatic carrier group. The proviral load was increased in the synovial fluid and tissue from an HTLV-1-infected patient with RA, the values suggesting that the majority of infiltrated cells were HTLV-1-infected. In the peripheral blood from HTLV-1-infected patients with RA or connective tissue disease, HTLV-1 proviral load correlated with the percentages of memory CD4+ T cells and activated T cells, and these percentages were shown to be markedly higher in the synovial fluid than in the peripheral blood in an HTLV-1-infected patient with RA.

CONCLUSIONS

These biological findings are consistent with a role of the retrovirus in the development of arthritis in HTLV-1-infected patients. A high level of HTLV-1-infected lymphocytes in the peripheral blood and their accumulation in situ might play a central role in the pathogenesis of HTLV-1-associated inflammatory disorders. Alternatively, the autoimmune arthritis, its etiological factors or treatments might secondarily enhance HTLV-1 proviral load.

NF-kappaB-regulated expression of cellular FLIP protects rheumatoid arthritis synovial fibroblasts from tumor necrosis factor alpha-mediated apoptosis

OBJECTIVE

Little apoptosis has been observed in rheumatoid arthritis (RA) synovial tissues. Tumor necrosis factor alpha (TNFalpha) is expressed in the joints of patients with RA, yet RA synovial fibroblasts are relatively resistant to apoptosis induced by TNFalpha. Recently, we demonstrated that FLIP is highly expressed in the RA joint. These studies were performed to determine if TNFalpha-induced NF-kappaB controls the expression of FLIP long (FLIP(L)) and FLIP short (FLIP(S)) in RA synovial fibroblasts and to determine the role of FLIP in the control of TNFalpha-induced apoptosis.

METHODS

RA synovial fibroblasts were isolated from RA synovial tissues and used between passages 3 and 9. RA synovial or control fibroblasts were sham infected or infected with a control adenovirus vector or one expressing the super-repressor IkappaBalpha (srIkappaBalpha). The cells were stimulated with TNFalpha or a control vehicle, and expression of FLIP(L) and FLIP(S) was determined by isoform-specific real-time polymerase chain reaction and Western blot analysis. Cell viability was determined by XTT cleavage, and apoptosis was determined by annexin V staining, DNA fragmentation, and activation of caspases 8 and 3.

RESULTS

TNFalpha induced the expression of both isoforms of FLIP messenger RNA (mRNA) in RA synovial fibroblasts; however, FLIP(L) was the dominant isoform detected by Western blot analysis. In control fibroblasts, TNFalpha induced the expression of FLIP(L) and FLIP(S) mRNA and protein. The TNFalpha-induced, but not the basal, expression of FLIP was regulated by NF-kappaB. When NF-kappaB activation was suppressed by the expression of srIkappaBalpha, TNFalpha-mediated apoptosis was induced. TNFalpha-induced apoptotic cell death was mediated by caspase 8 activation and was prevented by the ectopic expression of FLIP(L) or the caspase 8 inhibitor CrmA.

CONCLUSION

The TNFalpha-induced, but not the basal, expression of FLIP is regulated by NF-kappaB in RA synovial fibroblasts. The resistance of RA synovial fibroblasts to TNFalpha-induced apoptosis is mediated by the NF-kappaB-regulated expression of FLIP. These observations support the role of NF-kappaB and FLIP as attractive therapeutic targets in RA.

The cytolethal distending toxin induces receptor activator of NF-kappaB ligand expression in human gingival fibroblasts and periodontal ligament cells

Actinobacillus actinomycetemcomitans is associated with localized aggressive periodontitis, a disease characterized by rapid loss of the alveolar bone surrounding the teeth. Receptor activator of NF-kappaB Ligand (RANKL) and osteoprotegerin (OPG) are two molecules that regulate osteoclast formation and bone resorption. RANKL induces osteoclast differentiation and activation, whereas OPG blocks this process by acting as a decoy receptor for RANKL. The purpose of this study was to investigate the effect of A. actinomycetemcomitans on the expression of RANKL and OPG in human gingival fibroblasts and periodontal ligament cells. RANKL mRNA expression was induced in both cell types challenged by A. actinomycetemcomitans extract, whereas OPG mRNA expression remained unaffected. Cell surface RANKL protein was also induced by A. actinomycetemcomitans, whereas there was no change in OPG protein secretion. A cytolethal distending toxin (Cdt) gene-knockout strain of A. actinomycetemcomitans did not induce RANKL expression, in contrast to its wild-type strain. Purified Cdt from Haemophilus ducreyi alone, or in combination with extract from the A. actinomycetemcomitans cdt mutant strain, induced RANKL expression. Pretreatment of A. actinomycetemcomitans wild-type extract with Cdt antiserum abolished RANKL expression. In conclusion, A. actinomycetemcomitans induces RANKL expression in periodontal connective tissue cells. Cdt is crucial for this induction and may therefore be involved in the pathological bone resorption during the process of localized aggressive periodontitis.

Endogenous interleukin-6, but not tumor necrosis factor α, contributes to the development of toll-like receptor 4/myeloid differentiation factor 88-mediated acute arthritis in mice

OBJECTIVE

To generate a mouse model of reactive arthritis (ReA), an aseptic synovitis that develops in joints distant from the primary bacterial infection site, to examine roles for Toll-like receptors (TLRs) that recognize bacterial components involved in the development of this arthritis, and to identify the cytokine(s) relevant to this arthritis.

METHODS

Mice were treated with cell wall extract from Escherichia coli (ECW) gram-negative bacterium by injection into the footpads. Seven days later, the mice were challenged with lipopolysaccharide (LPS), a TLR-4 ligand, which was injected into the knee joint cavity. To investigate the cytokine(s) involved in this arthritis, mice deficient in various arthritogenic cytokines, such as interleukin-6 (IL-6), IL-12, IL-18, interferon-gamma, and tumor necrosis factor alpha (TNFalpha), were sequentially treated with ECW and LPS.

RESULTS

ECW-primed mice manifested acute severe arthritis after intraarticular challenge with ECW or LPS, while unprimed mice exhibited modest changes after these challenges. Mutant mice lacking functional TLR-4 or myeloid differentiation factor 88 (MyD88), an adaptor molecule of TLR-4 signaling, were resistant to this arthritis. Although both TNFalpha and IL-6 were equally expressed in the joint after LPS challenge, Il6(-/-) mice, but not Tnf(-/-) mice, were resistant to ECW/LPS-induced arthritis.

CONCLUSION

Our present results clearly indicate the importance of priming with ECW and the requirement of TLR-4/MyD88-mediated IL-6, but not TNFalpha, for the development of ECW/LPS-induced arthritis. LPS-induced IL-6, in the absence of TNFalpha, mediates LPS-induced arthritis. These results suggest that IL-6 is a rational target for therapeutic regimens for inflammatory arthritis, including ReA and rheumatoid arthritis.

Regulation of arthritis by p53: Critical role of adaptive immunity

OBJECTIVE

The p53 tumor-suppressor protein is expressed in rheumatoid arthritis synovium, and loss of p53 function through somatic mutation can occur in longstanding disease. Previous studies demonstrated that p53 is protective in murine collagen-induced arthritis (CIA). To determine if adaptive immune responses or synovial effector functions are responsible for this effect, passive models of arthritis were studied in p53 wild-type and knockout mice.

METHODS

Models of passive CIA, passive K/BxN serum transfer arthritis, and active CIA were induced in DBA/1 p53(-/-) or p53(+) mice. Hind paws were evaluated for histologic evidence of inflammation and joint destruction. Synovial interleukin-6 and matrix metalloproteinases 3 and 13 gene expression was analyzed by real-time quantitative polymerase chain reaction. To evaluate T cell function in p53(-/-) mice, draining lymph node (LN) cells from mice immunized with type II collagen (CII) were evaluated in vitro.

RESULTS

Increased disease severity in p53(-/-) mice was confirmed in the standard CIA model. However, clinical arthritis, joint destruction, and synovial gene expression in the passive CIA and K/BxN serum transfer arthritis models were similar in p53(-/-) and p53(+) mice. To determine if the p53 effect was related to T cell function, LN cells from CII-immunized mice were isolated and stimulated with antigen in vitro. CII-stimulated T cell proliferation and interferon-gamma production were significantly higher in p53(-/-) mice. An independent assessment of Th1 function using the cutaneous delayed-type hypersensitivity model confirmed that p53(-/-) mice have enhanced T cell responses in vivo.

CONCLUSION

Adaptive immune responses, rather than antibody-mediated responses, in p53(-/-) mice account for increased disease severity in the active CIA model.

Prophylactic adenovirus-mediated human kallistatin gene therapy suppresses rat arthritis by inhibiting angiogenesis and inflammation

OBJECTIVE

Kallistatin has been shown to be an angiogenesis inhibitor. In this study, we investigated whether adenovirus-mediated kallistatin gene delivery has a prophylactic effect in a rat arthritis model.

METHODS

Adenovirus containing the human kallistatin gene (AdHKBP) was injected intraarticularly into ankle joints before the onset of arthritis in a rat model. The effect of kallistatin gene transfer on endothelial cell proliferation in joint extracts was assayed. The response to kallistatin treatment was determined according to clinical parameters, including ankle circumference, articular index, and radiographic scores. Hematoxylin and eosin staining was performed in order to score joint tissues and count neutrophil numbers. In addition, small vessels were quantified by identification of von Willebrand factor-positive endothelial cells. The inflammatory responses were determined by measuring tumor necrosis factor alpha (TNFalpha) and interleukin-1beta (IL-1beta) levels in ankle homogenates.

RESULTS

The expression of recombinant human kallistatin in rat ankle joints after gene transfer was identified by immunohistochemical analysis and Western blotting. Significant reductions in the ankle circumference, articular index, and radiographic score were observed in AdHKBP-treated rats compared with control rats treated with the adenoviral plasmid carrying green fluorescent protein. Kallistatin gene transfer also significantly ameliorated the histologic scores in ankle joints and reduced vessel density and neutrophil numbers. The inhibitory effect of kallistatin on the accumulation of inflammatory cells in ankle joints was accompanied by reduced TNFalpha and IL-1beta levels in joint homogenates. Furthermore, an in vitro experiment showed that the proliferation of endothelial cells was markedly inhibited by the addition of AdHKBP-treated joint extract to the culture media, supporting a role of kallistatin in inhibiting angiogenesis.

CONCLUSION

This study demonstrates that kallistatin gene therapy has a prophylactic effect in inhibiting arthritis in the rat ankle. Kallistatin inhibits arthritis through its antiangiogenesis and antiinflammation activities. These results implicate potential therapeutic applications for suppression of arthritis by kallistatin gene therapy.

Roles for NF-kappaB and c-Fos in osteoclasts

NF-kappaB and c-Fos are transcription factors that are activated in immune cells and in most other cell types following stimulation by a variety of factors, including cytokines, growth factors, and hormones. They regulate the expression of a large number of genes, and both are activated in osteoclast precursors after RANKL, IL-1, or TNF bind to their respective receptors. However, of these cytokines, only RANKL is required for the induction of osteoclast formation in vivo. Nevertheless, it is likely that IL-1, TNF, and other cytokines participate in the upregulation of osteoclast formation seen in a variety of conditions that affect the skeleton in which cytokine production is increased, including estrogen deficiency and inflammatory bone diseases. In this review, the RANKL/ OPG/RANK system and roles for NF-kappaB and c-Fos in osteoclasts are reviewed along with our current understanding of how this system may be disrupted in common bone diseases, such as postmenopausal osteoporosis, inflammatory arthritis, and Paget's disease.

Chemokine receptor expression in rat adjuvant-induced arthritis

OBJECTIVE

Chemokine receptors mediate leukocyte migration into inflamed rheumatoid arthritis (RA) synovial tissue (ST). Knowledge of their distribution is crucial for understanding the evolution of the inflammatory process. In this study, we used rat adjuvant-induced arthritis (AIA), a model for RA, to define the temporospatial expression of chemokine receptors.

METHODS

ST from rats with AIA was immunostained, the percentage of cells expressing each receptor was determined, and findings were correlated with levels of inflammation. Chemokine receptor expression was evaluated on rat macrophages in vitro.

RESULTS

CCR1, a receptor for macrophage inflammatory protein 1alpha (MIP-1alpha)/CCL3 and RANTES/CCL5, exhibited high constitutive expression on macrophages in AIA. CCR5, binding MIP-1alpha/CCL3 and RANTES/CCL5, was up-regulated on ST macrophages during the course of AIA, correlating with macrophage expression of CCR2, a receptor for monocyte chemoattractant protein 1/CCL2. Endothelial cell (EC) CCR2 was down-regulated as arthritis progressed, inversely correlating with inflammation. CCR3, another RANTES/CCL5 receptor, was constitutively high on macrophages in vivo and in vitro, with down-regulation during AIA. CXCR4, a receptor for stromal cell-derived factor 1/CXCL12), was prominently up-regulated on ECs, preceding the peak of inflammation.

CONCLUSION

These findings show that 1) constitutive expression of CCR1 on macrophages remains high during AIA; 2) CCR2 and CCR3 may play a role in initial recruitment of leukocytes to ST in AIA; 3) macrophage expression of CCR2 and CCR5 may be important for sustaining inflammatory changes; and 4) EC CXCR4 may be a harbinger of inflammatory changes. Our results may help guide chemokine receptor blockade-targeting treatment strategies in inflammatory arthritis.

Mast cells and innate cytokines are associated with susceptibility to autoimmune heart disease following coxsackievirus B3 infection

The development of autoimmune disease involves a combination of genetic and environmental factors. Many autoimmune diseases are believed to be triggered by viral infections. Since the early, natural immune response to infection can determine the later development of the adaptive immune response, innate immunity likely influences the progression from viral immunity to autoimmunity. To investigate the role of the innate immune response on susceptibility to autoimmune disease, we compared the early cytokine response of mice susceptible or resistant to the development of autoimmune heart disease following viral infection. We found that susceptible BALB/c mice produced elevated levels of TNF-alpha, IL-1beta, and IL-4 within hours of Coxsackievirus B3 (CB3) infection. These cytokines are known to be critical for the development of autoimmune heart disease, and are also rapidly produced from activated mast cells (MC). Degranulating MC were observed as early as 6 h following CB3 infection in the heart, and significantly higher numbers of MC were found in the spleen of susceptible BALB/c mice at this time. Thus, susceptibility to autoimmune heart disease can be determined as early as 6 h following viral infection in susceptible strains of mice.

C1q governs deposition of circulating immune complexes and leukocyte Fcgamma receptors mediate subsequent neutrophil recruitment

Inflammation induced by circulating immunoglobulin G–immune complexes (ICs) characterizes many immune-mediated diseases. In this work, the molecular requirements for the deposition of circulating ICs and subsequent acute leukocyte recruitment in mice were elucidated. We show that after intravenous injection, preformed soluble ICs are rapidly deposited in the postcapillary venules of the cremaster microcirculation, secondary to increased vascular permeability. This deposition is dependent on complement C1q. IC deposition is associated with leukocyte recruitment. Leukocyte rolling, which is mediated by P-selectin in the exteriorized cremaster muscle, is not further increased in response to ICs. In contrast, leukocyte rolling velocity is significantly decreased and leukocyte adhesion is significantly increased in the presence of ICs. The IC-mediated slow leukocyte rolling velocity and subsequent adhesion and emigration are dependent on Fcγ receptors (FcγRs), particularly FcγRIII, with complement C3 and C5 having no detectable role. These studies suggest a regulatory mechanism of IC deposition and leukocyte trafficking in IC-mediated inflammation requiring C1q and FcγRs in sequential, noninteracting roles.

Is rheumatoid arthritis premature osteoarthritis with fetal-like healing?

Rheumatoid arthritis is now known to share many pathogenetic features with osteoarthritis including synovial activation with release of pro-inflammatory cytokines into the synovial fluid. As premature chondrocyte aging and dedifferentiation is increasingly accepted as integral to OA pathogenesis, premature aging of chondrocytes and perhaps subchondral bone may underlie RA. This hypothesis explains many otherwise enigmatic features of RA joint pathology such as the homing of pannus to cartilage. In addition, the surprising finding of mesenchymal precursor cells in RA joints has led to speculation that some aspect of RA pathogenesis involves an attempt to recapitulate the embryonic limb development program. In its totality, RA seems to consist of an attempt to regenerate damaged cartilage and subchondral bone in an adult organism. Since this is impossible, the best the pannus can do is to crawl through empty cartilage lacunae and replace the cartilage and subchondral bone with scar tissue. As opposed to fetal healing, inflammation is necessary to sustain and control the fibroproliferation. Two recently-discovered blood cell types seem to maintain and regulate fibroplastic states in humans: (1) CD34+ and/or monocytoid stem-cell precursors replace aging mesenchymal cells, and (2) regulatory-type adherent CD4+CD28-T cells control growth of those increasingly apoptosis-resistant mesenchymal cells. Such cells occur at multiple sites in AID patients.

Platelet-derived growth factor-AA increases IL-1beta and IL-8 expression and activates NF-kappaB in rheumatoid fibroblast-like synoviocytes

The effect of platelet-derived growth factor (PDGF)-AA on the inflammation in rheumatoid arthritis (RA) and osteoarthritis (OA) was investigated using cultured fibroblast-like synoviocytes (FLS) obtained from RA and OA patients as well as control nonarthritic (NA) individuals. PDGF-AA increased the mRNA and protein expressions of proinflammatory cytokines, interleukin (IL)-1beta and IL-8 in RA FLS. Biological activity of IL-1 in the culture supernatant of RA FLS was also increased by PDGF-AA stimulation. Interestingly, PDGF-AA synergized with tumour necrosis factor (TNF)-alpha to upregulate the protein expressions of IL-1beta and IL-8. PDGF-induced enhancement of the IL-1beta and IL-8 mRNA expressions was also observed in OA FLS. However, the expression of these proinflammatory cytokines in NA FLS did not change by PDGF treatment, suggesting that the inflammatory condition might have modified the biological effects of PDGF. In accordance with the enhanced expression of inflammatory cytokines, the activity of nuclear factor kappaB was also induced in response to PDGF-AA in RA FLS. These results suggest that PDGF-AA plays an important role in the progression of RA inflammation, and inhibiting PDGF activity may be useful for the effective RA treatment.

Local expression of matrix metalloproteinases, cathepsins, and their inhibitors during the development of murine antigen-induced arthritis

Cartilage and bone degradation, observed in human rheumatoid arthritis (RA), are caused by aberrant expression of proteinases, resulting in an imbalance of these degrading enzymes and their inhibitors. However, the role of the individual proteinases in the pathogenesis of degradation is not yet completely understood. Murine antigen-induced arthritis (AIA) is a well-established animal model of RA. We investigated the time profiles of expression of matrix metalloproteinase (MMP), cathepsins, tissue inhibitors of matrix metalloproteinases (TIMP) and cystatins in AIA. For primary screening, we revealed the expression profile with Affymetrix oligonucleotide chips. Real-time polymerase chain reaction (PCR) analyses were performed for the validation of array results, for tests of more RNA samples and for the completion of the time profile. For the analyses at the protein level, we used an MMP fluorescence activity assay and zymography. By a combination of oligonucleotide chips, real-time PCR and zymography, we showed differential expressions of several MMPs, cathepsins and proteinase inhibitors in the course of AIA. The strongest dysregulation was observed on days 1 and 3 in the acute phase. Proteoglycan loss analysed by safranin O staining was also strongest on days 1 and 3. Expression of most of the proteinases followed the expression of pro-inflammatory cytokines. TIMP-3 showed an expression profile similar to that of anti-inflammatory interleukin-4. The present study indicates that MMPs and cathepsins are important in AIA and contribute to the degradation of cartilage and bone.

CC and CXC chemokine receptors mediate migration, proliferation, and matrix metalloproteinase production by fibroblast-like synoviocytes from rheumatoid arthritis patients

OBJECTIVE

To explore the potential involvement of the chemokine system in synoviocyte-mediated tissue destruction in rheumatoid arthritis (RA), we studied the expression profile of chemokine receptors and their function in the migration, proliferation, and matrix metalloproteinase (MMP) production of cultured fibroblast-like synoviocytes (FLS) from RA patients.

METHODS

The presence of CC and CXC chemokine receptors on cultured FLS was studied at the messenger RNA (mRNA) level by reverse transcriptase-polymerase chain reaction and at the cell surface expression level by flow cytometry. Variations in cytosolic calcium influx induced by chemokine stimulation were assessed by flow cytometry on Fura Red-preloaded FLS. Two-compartment transwell chambers were used for FLS chemotaxis assays. Cell growth was measured by a fluorescence-based proliferation assay. Gelatinase and collagenase activities were determined by a fibril degradation assay and zymography.

RESULTS

FLS constitutively expressed the receptors CCR2, CCR5, CXCR3, and CXCR4, both at the cell surface and mRNA levels, but failed to express CCR3 and CCR6. Significant intracytosolic calcium influx was observed on FLS challenged with monocyte chemotactic protein 1 (MCP-1), stromal cell-derived factor 1alpha (SDF-1alpha), and interferon-inducible protein 10 (IP-10). Stimulation with MCP-1, SDF-1alpha, IP-10, and monokine induced by interferon-gamma enhanced the migration and proliferation of FLS. These chemokines, in addition to RANTES, increased in a dose- and time-dependent manner the gelatinase and collagenase activities in cell-free supernatants of cultured FLS. Interestingly, the chemokine-mediated up-regulation of MMP activities was significantly abrogated by the presence of anti-interleukin-1beta, but not anti-tumor necrosis factor alpha, blocking antibodies.

CONCLUSION

These data suggest that through modulation of the migration, proliferation, and MMP production by FLS, the chemokine system may play a more direct role in the destructive phase of RA than is currently suspected, and thus emphasize the relevance of chemokines and their receptors as potential therapeutic targets in this disease.

Defining a role for fibroblasts in the persistence of chronic inflammatory joint disease

The most surprising feature of the inflammatory response in rheumatoid arthritis is not that it occurs but that it does not resolve. The persistence of the chronic inflammatory response in conjunction with ongoing joint destruction is an all too familiar finding in many patients with rheumatoid arthritis. Despite the use of effective anti-inflammatory agents and disease modifying drugs, a significant proportion of patients with rheumatoid arthritis continue to have resistant disease. Complete clinical remission is unusual for more than six months and a formal cure of the disease remains elusive. In this report we focus on how attempts to address the question of why rheumatoid arthritis persists have led to a different interpretation of the pathogenesis of rheumatoid disease; one in which alterations in stromal cells such as fibroblasts play an important role in the switch from resolving to persistent disease.

Synovial tissue macrophages: a sensitive biomarker for response to treatment in patients with rheumatoid arthritis

BACKGROUND

Previous work identified synovial sublining macrophage numbers as a potential biomarker for clinical efficacy in rheumatoid arthritis.

OBJECTIVE

To investigate the association between changes in infiltration of synovial macrophages and clinical improvement after antirheumatic treatment.

METHODS

88 patients who participated in various clinical trials were studied. All patients underwent serial arthroscopy before initiation of treatment and after different time intervals. Immunohistochemical and digital image analysis were performed according to standardised procedures to detect changes in CD68+ synovial sublining macrophages in relationship to changes in the 28 joint count Disease Activity Score (DAS28). Statistical analysis was performed using one way analysis of variance, the independent samples t test, linear regression, and the standardised response mean (SRM).

RESULTS

For good, moderate, and non-responders, according to the DAS28 response criteria, there was a significant difference in the change in sublining macrophages (mean (SEM) cells/mm(2) -643 (124), -270 (64), and -95 (60), respectively; p<0.0003). There was a significant correlation between the change in the number of macrophages and the change in DAS28 (Pearson correlation 0.874, p<0.01). The change in sublining macrophages explained 76% of the variation in the change in DAS28 (p<0.02). The sensitivity to change of the biomarker was high in patients treated actively (SRM >0.8), whereas the ability to detect changes in placebo treated patients was weak (SRM <0.3).

CONCLUSION

The results suggest that changes in synovial sublining macrophages can be used to predict possible efficacy of antirheumatic treatment.

Methotrexate enhances prostaglandin D2-stimulated heat shock protein 27 induction in osteoblasts

As for the pathogenesis of rheumatoid arthritis (RA), prostaglandins (PGs) act as important mediators of inflammation and joint destruction. Among them, PGD2 is well recognized as a potent regulator of osteoblastic functions. We previously showed that PGD2 stimulates the induction of heat shock protein 27 (HSP27) via protein kinase C (PKC)-dependent p38 mitogen-activated protein (MAP) kinase and p44/p42 MAP kinase in osteoblast-like MC3T3-E1 cells. Therefore, it is a current topic to clarify how HSP27 plays a role for regulating osteoblastic functions in the lesion of RA. On the other hand, methotrexate (MTX) is one of the most effective medicines for the treatment of RA. Here, we examined the effect of MTX on PGD2-stimulated HSP27 induction in MC3T3-E1 cells. The cells were pretreated with various doses of MTX including therapeutic dosage for RA, and then stimulated by PGD2. MTX significantly enhanced the PGD2- increased levels of HSP27 in a dose-dependent manner, although MTX alone had no effect on the levels of HSP27. In addition, MTX amplified the PGD2-increased levels of HSP27 mRNA. On the contrary, MTX had little effect on PGD2-induced formation of inositol phosphates, PKC activation and phosphorylations of MAP kinases. Our results strongly suggest that MTX enhances PGD2-stimulated HSP27 induction at a point downstream from MAP kinases in osteoblasts.

Interaction between RANKL and HLA-DRB1 genotypes may contribute to younger age at onset of seropositive rheumatoid arthritis in an inception cohort

OBJECTIVE

To determine whether the RANKL and HLA-DRB1 "shared epitope" (SE) genotypes contribute to the development of rheumatoid arthritis (RA).

METHODS

We studied 237 patients with early RA (within 15 months of symptom onset) who were seropositive for rheumatoid factor. HLA-DRB1 genotyping was performed using the polymerase chain reaction (PCR)-based oligonucleotide probe assay. RANKL polymorphisms were analyzed using PCR pyrosequencing for SNP1 and fluorescence-based PCR for the presence or absence of the TAAA insertion.

RESULTS

The presence of SE-containing DRB1*04 alleles was associated with an earlier age at RA onset (mean +/- SD 47 +/- 12.7 years versus 53 +/- 12.5 years in SE- patients; P = 0.0004). The 2 novel RANKL polymorphisms were in strong linkage disequilibrium (P < 0.0001) and were associated with earlier ages at disease onset (e.g., for the CC versus CT/TT genotypes, 44 +/- 13.5 years versus 51 +/- 12.7 years; P = 0.0080). The mean age at disease onset in SE+ patients with the RANKL-CC genotype (35 +/- 7.2 years) was a mean of 18 years younger than in SE- patients with RANKL-CT/TT (53 +/- 12.5 years; P < 0.0001) and was 17 years younger than in SE- patients with RANKL-CC (52 +/- 13.2 years; P = 0.0005). The proportion of patients with both the SE and RANKL risk alleles was highest (23%) in those who developed RA during their third decade of life (ages 20-30 years), with a declining trend among those who developed RA during their fourth (16%), fifth (5%), and sixth or later (0%) decades. Interestingly, 92% of the patients diagnosed as having RA between ages 20 and 30 years carried at least 1 of the RA-associated DRB1*04 alleles, suggesting a strong influence of the SE in the early onset of RA. The majority of patients who developed RA symptoms in their third to fifth decades (74 of 119 [62%]) carried at least 1 copy of the DRB1*04 alleles; in contrast, fewer than half of the patients who developed RA in their sixth decade or later (50 of 118 [42%]) had DRB1*04 alleles. RANKL genotypes were not associated with erosive disease at baseline or with the yearly progression rate of radiographic joint damage.

CONCLUSION

This study provides the first evidence that novel RANKL polymorphisms were associated with an earlier age at RA onset in SE+, but not SE-, patients and that an interaction between SE-containing HLA-DRB1 and RANKL polymorphisms increased the disease penetrance, resulting in a mean age at RA onset that was 18-20 years younger. Our results also suggested genetic differences between patients with early-onset and those with late-onset RA.

Proinflammatory cytokine genes are constitutively overexpressed in the heart in experimental systemic lupus erythematosus: a brief communication

The heart is one of a number of organs that may be affected in systemic lupus erythematosus (SLE), a prototypic autoimmune disease. Potential anatomical sites of involvement include the myocardium, pericardium, endocardium, valves, conduction system and blood vessels that subserve the heart. Typically, the severity of cardiovascular disease in lupus correlates with the degree of systemic inflammation, which is mirrored by the level of C-reactive protein (CRP) in the plasma. C-reactive protein, in turn is regulated by proinflammatory cytokines, such as interleukins (ILs) 1beta and 6. These cytokines have been found in functionally and/or structurally damaged areas of the heart and have been implicated in disease pathogenesis. It has been assumed that the source of these putatively pathogenetically relevant cytokines in the compromised heart is infiltrating mononuclear cells. This study tests the hypothesis that cardiomyocytes per se may contribute to proinflammatory cytokine production in the setting of systemic inflammation. Using as the experimental model MRL/MpJ-Tnfrs6(lpr) (MRL-lpr/lpr) mice, which spontaneously manifest an autoimmune syndrome that has clinical features of SLE, we show that ventricular homogenates and ventricular cardiomyocytes constitutively overexpress genes encoding the proinflammatory cytokines IL-1beta, IL-6, IL-10, and gamma interferon. The results suggest the possibility that proinflammatory cytokines emanating from the heart may actually contribute to the high levels of CRP that appear to aid in predicting subsequent cardiac events. Viewed in this setting, CRP becomes a footprint of an ongoing pathogenic process mediated, in part, by the heart muscle itself.

Glucose-6-phosphate isomerase variants play a key role in the generation of anti-GPI antibodies: possible mechanism of autoantibody production

Glucose-6-phosphate isomerase (GPI), recognized as an autoantigen in the K/BxN arthritis model, is a ubiquitous cytoplasmic enzyme. Anti-GPI antibodies (Abs) are also detected in the serum of patients with arthritic diseases including rheumatoid arthritis (RA). So far, 24 GPI variants have been reported and most of these variants relate to non-spherocytic hemolytic disease. To understand the mechanisms of anti-GPI Ab production, cDNAs from peripheral blood mononuclear cells of subjects with or without anti-GPI Abs were cloned and sequenced. We identified 39 new GPI variants (57-1596 bp). The frequency of GPI variants in healthy control subjects (HS) with anti-GPI Abs (27/73, 31.5%) was significantly higher than that in anti-GPI Ab-negative HS (5/78, 6.4%, p < 0.001). The frequency of GPI variants in anti-GPI Ab-positive RA patients (22/77, 28.6%) was more significantly higher than in anti-GPI Ab-negative patients (1/63, 1.6%, p < 0.0001). Our results suggest that GPI variants may play a crucial role in the production of autoantibodies against ubiquitous GPI autoantigens.

Mast cells in inflammatory arthritis

Mast cells are present in limited numbers in normal human synovium, but in rheumatoid arthritis and other inflammatory joint diseases this population can expand to constitute 5% or more of all synovial cells. Recent investigations in a murine model have demonstrated that mast cells can have a critical role in the generation of inflammation within the joint. This finding highlights the results of more than 20 years of research indicating that mast cells are frequent participants in non-allergic immune responses as well as in allergy. Equipped with a diversity of surface receptors and effector capabilities, mast cells are sentinels of the immune system, detecting and delivering a first response to invading bacteria and other insults. Accumulating within inflamed tissues, mast cells produce cytokines and other mediators that may contribute vitally to ongoing inflammation. Here we review some of the non-allergic functions of mast cells and focus on the potential role of these cells in murine and human inflammatory arthritis.

Fas Ligand as a Tool for Immunosuppression and Generation of Immune Tolerance

The role of Fas ligand (FasL) in physiologically limiting immune responses and maintaining immune-privileged sites has led to a body of research aiming to confer protection to allogeneic grafts by expressing FasL on the allogeneic tissue or by administrating FasL-transduced donor dendritic cells. In addition, several studies have used FasL to abrogate autoimmune responses. This review presents the results of these studies and discusses the problems associated with FasL usage.

p53 tumor suppressor gene mutations in fibroblast-like synoviocytes from erosion synovium and non-erosion synovium in rheumatoid arthritis

Abnormalities in the p53 tumor suppressor gene have been detected in rheumatoid arthritis (RA) and could contribute to the pathogenesis of chronic disease. To determine whether synoviocytes from invasive synovium in RA have an increased number of mutations compared with non-erosion synoviocytes, p53 cDNA subclones from fibroblast-like synoviocytes (FLS) derived from erosion and non-erosion sites of the same synovium were examined in patients requiring total joint replacement. Ten erosion FLS lines and nine non-erosion FLS lines were established from nine patients with RA. Exons 5–10 from 209 p53 subclones were sequenced (114 from erosion FLS, 95 from non-erosion FLS). Sixty percent of RA FLS cell lines and 8.6% of the p53 subclones isolated from FLS contained p53 mutations. No significant differences were observed between the erosion and non-erosion FLS with regard to the frequency or type of p53 mutation. The majority of the mutations were missense transition mutations, which are characteristic of oxidative damage. In addition, paired intact RA synovium and cultured FLS from the same joints were evaluated for p53 mutations. Matched synovium and cultured synoviocytes contained p53 mutations, although there was no overlap in the specific mutations identified in the paired samples. Clusters of p53 mutations in subclones were detected in some FLS, including one in codon 249, which is a well-recognized 'hot spot' associated with cancer. Our data are consistent with the hypothesis that p53 mutations are randomly induced by genotoxic exposure in small numbers of RA synoviocytes localized to erosion and non-erosion regions of RA synovium. The determining factor for invasiveness might be proximity to bone or cartilage rather than the presence of a p53 mutation.

Proinflammatory mediators elicit secretion of the intracellular B-lymphocyte stimulator pool (BLyS) that is stored in activated neutrophils: implications for inflammatory diseases

We have recently shown that granulocyte-colony-stimulating factor (G-CSF)- and interferon-gamma (IFN-gamma)-activated human neutrophils accumulate and release remarkable amounts of soluble B-lymphocyte stimulator (BLyS) in vitro. In this study, we provide evidence that neutrophils migrating into skin window exudates (SWEs) developed in healthy volunteers and in patients with rheumatoid arthritis (RA), synthesized, and released BLyS in response to locally produced G-CSF. Accordingly, the concentrations of soluble BLyS in SWEs were significantly more elevated than in serum. Because the levels of SWE BLyS, but not SWE G-CSF, were higher in patients with RA than in healthy subjects, we examined the effect of CXCL8/IL-8, C5a, and other proinflammatory mediators that dramatically accumulate in RA SWEs and in inflamed synovial fluids. We show that CXCL1/GROalpha, CXCL8/IL-8, C5a, immune complexes, tumor necrosis factor-alpha (TNF-alpha), leukotriene B4, N-formyl-methionyl-leucyl-phenylalanine (fMLP), and lipopolysaccharide (LPS), which by themselves do not induce BLyS de novo synthesis, act as potent secretagogues for BLyS, which is mainly stored in Golgi-related compartments within G-CSF-treated neutrophils, as determined by immunogold electron microscopy. This action is pivotal in greatly amplifying neutrophil-dependent BLyS release in SWEs of patients with RA compared with healthy subjects. Collectively, our data uncover a novel mechanism that might dramatically exacerbate the release of BLyS by neutrophils during pathologic inflammatory responses.

T-cell large granular lymphocyte leukemia and related disorders

T-cell large granular lymphocyte (LGL) leukemia is a clonal proliferation of cytotoxic T cells, which causes neutropenia, anemia, and/or thrombocytopenia. This condition is often associated with autoimmune disorders, especially rheumatoid arthritis, and other lymphoproliferative disorders. The diagnosis is suggested by flow cytometry demonstrating an expansion of CD8(+)CD57(+) T cells and is confirmed by T-cell receptor gene rearrangement studies. Mounting evidence suggests that LGL leukemia is a disorder of dysregulation of apoptosis through abnormalities in the Fas/Fas ligand pathway. In most patients, this is an indolent disorder, and significant improvement of cytopenias can be achieved with immunosuppressive agents such as steroids, methotrexate, cyclophosphamide, and cyclosporin A. This review provides a concise, up-to-date summary of LGL leukemia and the related, more aggressive, malignancies of cytotoxic T cells and natural killer cells.

Rap1 signaling is required for suppression of Ras-generated reactive oxygen species and protection against oxidative stress in T lymphocytes

Transient production of reactive oxygen species (ROS) plays an important role in optimizing transcriptional and proliferative responses to TCR signaling in T lymphocytes. Conversely, chronic oxidative stress leads to decreased proliferative responses and enhanced transcription of inflammatory gene products, and is thought to underlie the altered pathogenic behavior of T lymphocytes in some human diseases, such as rheumatoid arthritis (RA). Although the signaling mechanisms regulating ROS production in T lymphocytes has not been identified, activation of the small GTPase Ras has been shown to couple agonist stimulation to ROS production in other cell types. We find that Ras signaling via Ral stimulates ROS production in human T lymphocytes, and is required for TCR and phorbol ester-induced ROS production. The related small GTPase Rap1 suppresses agonist, Ras and Ral-dependent ROS production through a PI3K-dependent pathway, identifying a novel mechanism by which Rap1 can distally antagonize Ras signaling pathways. In synovial fluid T lymphocytes from RA patients we observed a high rate of endogenous ROS production, correlating with constitutive Ras activation and inhibition of Rap1 activation. Introduction of dominant-negative Ras into synovial fluid T cells restored redox balance, providing evidence that deregulated Ras and Rap1 signaling underlies oxidative stress and consequent altered T cell function observed in RA.

A missense single-nucleotide polymorphism in a gene encoding a protein tyrosine phosphatase (PTPN22) is associated with rheumatoid arthritis

Rheumatoid arthritis (RA) is the most common systemic autoimmune disease, affecting approximately 1% of the adult population worldwide, with an estimated heritability of 60%. To identify genes involved in RA susceptibility, we investigated the association between putative functional single-nucleotide polymorphisms (SNPs) and RA among white individuals by use of a case-control study design; a second sample was tested for replication. Here we report the association of RA susceptibility with the minor allele of a missense SNP in PTPN22 (discovery-study allelic P=6.6 x 10(-4); replication-study allelic P=5.6 x 10(-8)), which encodes a hematopoietic-specific protein tyrosine phosphatase also known as "Lyp." We show that the risk allele, which is present in approximately 17% of white individuals from the general population and in approximately 28% of white individuals with RA, disrupts the P1 proline-rich motif that is important for interaction with Csk, potentially altering these proteins' normal function as negative regulators of T-cell activation. The minor allele of this SNP recently was implicated in type 1 diabetes, suggesting that the variant phosphatase may increase overall reactivity of the immune system and may heighten an individual carrier's risk for autoimmune disease.