Holm Häntzschel

Chemokine Secretion of Rheumatoid Arthritis Synovial Fibroblasts Stimulated by Toll-Like Receptor 2 Ligands

To analyze the role of Toll-like receptors (TLR) in the pathogenesis of rheumatoid arthritis, we have assessed the effects of stimulation of cultured synovial fibroblasts by the TLR-2 ligand bacterial peptidoglycan. By using high density oligonucleotide microarray analysis we identified 74 genes that were up-regulated >2.5-fold. Fourteen CC and CXC chemokine genes were among the genes with the highest up-regulation. Quantitative real-time PCR analysis confirmed up-regulation of granulocyte chemotactic protein (GCP)-2, RANTES, monocyte chemoattractant protein (MCP)-2, IL-8, growth-related oncogene-2, and to a lesser extent, macrophage-inflammatory protein 1α, MCP-1, EXODUS, and CXCL-16. GCP-2, RANTES, and MCP-2 were detected in culture supernatants of synovial fibroblasts stimulated with peptidoglycan. Chemokine secretion induced by stimulation of rheumatoid arthritis synovial fibroblasts via TLR-2 was functionally relevant as demonstrated by chemotaxis assays. GCP-2 and MCP-2 expression, which have not been reported previously in rheumatoid arthritis, was demonstrated in synovial tissue sections of patients diagnosed with rheumatoid arthritis but not in those with osteoarthritis. Correspondingly, synovial fluid levels were significantly higher in patients diagnosed with rheumatoid arthritis as compared with osteoarthritis. Thus, we present evidence for an induction of chemokine secretion by activation of synovial fibroblasts via TLR-2, possibly contributing to the formation of inflammatory infiltrates characteristically found in rheumatoid arthritis joints.

Association of PTPN22 1858 single-nucleotide polymorphism with rheumatoid arthritis in a German cohort: higher frequency of the risk allele in male compared to female patients

The functional single-nucleotide polymorphism (SNP) of the gene PTPN22 is a susceptibility locus for rheumatoid arthritis (RA). The study presented here describes the association of the PTPN22 1858T allele with RA in a German patient cohort; 390 patients with RA and 349 controls were enrolled in the study. For 123 patients, clinical and radiographic documentation over 6 years was available from the onset of disease. Genotyping of the PTPN22 1858 SNP was performed using an restriction fragment length polymorphism PCR-based genotyping assay. The odds ratio to develop RA was 2.57 for carriers of the PTPN22 1858T allele (95% confidence interval (CI) 1.85–3.58, p < 0.001), and 5.58 for homozygotes (95% CI 1.85–16.79). The PTPN22 1858T allele was significantly associated not only with rheumatoid factor (RF) and anti-cyclic citrullinated peptide (CCP) positive RA, but also with RF and anti-CCP negative disease. The frequency of the PTPN22 1858T allele was increased disproportionately in male patients (53.8% compared to 33.0% in female patients, p < 0.001), and the resulting odds ratio for male carriers was increased to 4.47 (95% CI 2.5–8.0, p < 0.001). Moreover, within the male patient population, the rare allele was significantly associated with the HLA-DRB1 shared epitope (p = 0.01). No significant differences in disease activity or Larsen scores were detected. The results provide further evidence that the PTPN22 1858T allele is associated with RA irrespective of autoantibody production. The increased frequency of the risk allele in male patients and its association with the shared epitope indicate that the genetic contribution to disease pathogenesis might be more prominent in men.

Interaction between Transmembrane TNF and TNFR1/2 Mediates the Activation of Monocytes by Contact with T Cells

Monocytes and monocytic cells produce proinflammatory cytokines upon direct cell contact with activated T cells. In the autoimmune disease rheumatoid arthritis, the pivotal role of TNF-α implies that the interaction between transmembrane TNF-α (mTNF) and the TNF receptors (TNFR1 and TNFR2) might participate in the T cell contact-dependent activation of monocytes. Accordingly, treatment of rheumatoid arthritis by administration of a TNF-α-blocking Ab was found to significantly decrease TNF-α production by monocytes. Several lines of evidence indicated that signaling through TNFR1/2 and through mTNF (reverse signaling) is involved in TNF-α production by monocytes after T cell contact: 1) blocking mTNF on activated T cells leads to a significant reduction in TNF-α production; 2) down-regulation of TNFR1/2 on monocytes by transfection with small interfering RNA results in diminished TNF-α production; 3) blocking or down-regulating TNFR2 on activated T cells inhibits TNF-α production, indicating that mTNF on the monocyte surface mediates signaling; 4) ligation of mTNF on monocytes by surface TNFR2 transfected into resting T cells induces TNF-α production due to reverse signaling by mTNF; and 5) ligation of mTNF on monocytes by a soluble TNFR2:Ig receptor construct induces TNF-α production due to reverse signaling. In conclusion, we identified mTNF and TNFR1/2 as interaction partners contributing to TNF-α production in monocytes. Both pathways initiated by mTNF-TNFR interaction are likely to be inhibited by treatment with anti-TNF-α Abs.

Clonally expanded CD4+CD28null T cells in rheumatoid arthritis use distinct combinations of T cell receptor BV and BJ elements

Clonally expanded, autoreactive CD4+CD28null cells can be found in the peripheral blood of patients with rheumatoid arthritis and have been shown to be associated with severeextra‐articular disease manifestations. We investigated the size of the CD4+CD28null compartment and the TCR β chain repertoire of expanded CD4+ clonotypes in 94 rheumatoid arthritis patients by complementarity‐determining region 3 (CDR3) length analysis (spectratyping) in the BV6 and BV14 TCR families, with primers specific for three arbitrarily chosen β chain joining elements (BJ1S2, BJ2S3 and BJ2S7). The spectratyping results showed a strong correlation of the size of the CD4+CD28null compartment with the detected number of BV14 clonotypes, whereas no association with BV6 oligoclonality was found. Only clones using the BV14–BJ1S2 and BV14–BJ2S3 combinations contributed to this correlation, however, whereas BV14–BJ2S7 clones did not. This preferential correlation implies a role for the TCR β chain in stimulating clonal outgrowth and argues against the previously suggested superantigenic stimulation of in‐vivo‐expanded clones. Instead, since no evidence for shared antigen specificity could be detected, clonal expansion of T cells in rheumatoid arthritis might be influenced by the BJ elements because of changes in the flexibility of the protein backbone of the β‐chain.

Persistent high serum levels of cartilage oligomeric matrix protein in a subgroup of patients with traumatic knee injury

Abstract The objective was to assess whether changes of cartilage oligomeric matrix protein (COMP) serum levels can predict the development of osteoarthritis following traumatic knee injury. Sera and synovial fluids were acquired at surgery (T0) and postoperatively during the first (T1) and second (T2) year from 30 knee-injured patients. COMP levels and anti-COMP autoantibodies were quantified by ELISA. Radiographs and patient questionnaires were used to assess outcomes. At T0, compared with controls (1.6±1.6 μg/ml), the serum COMP concentration was significantly elevated (6.5±2.8 μg/ml) with a tendency to further increase (T0 vs. T1, P=0.076) and subsequently decrease (T1 vs. T2, P=0.074). However, individual variations are observed, e.g. persistently high (8/30) or increasing (T0 to T2, 8/30) serum COMP. Ten of these patients have elevated COMP at T2 that increased from T0. COMP levels in serum and synovial fluid correlated significantly (P=0.012). Interestingly, some patients who revealed increasing serum levels of COMP from T0 to T2 displayed anti-COMP autoantibodies. These data suggest that local immune response could contribute to further joint damage. The subgroup of 10 patients (33%) with elevated and increasing serum COMP levels and in particular the patients with antibodies against cartilage matrix molecules appear at increased risk for developing posttraumatic osteoarthritis.

Failure of catecholamines to shift T-cell cytokine responses toward a Th2 profile in patients with rheumatoid arthritis

To further understand the role of neuro-immunological interactions in the pathogenesis of rheumatoid arthritis (RA), we studied the influence of sympathetic neurotransmitters on cytokine production of T cells in patients with RA. T cells were isolated from peripheral blood of RA patients or healthy donors (HDs), and stimulated via CD3 and CD28. Co-incubation was carried out with epinephrine or norepinephrine in concentrations ranging from 10-5 M to 10-11 M. Interferon (IFN)-γ, tumour necrosis factor (TNF)-α, interleukin (IL)-4, and IL-10 were determined in the culture supernatant with enzyme-linked immunosorbent assay. In addition, IFN-γ and IL-10 were evaluated with intracellular cytokine staining. Furthermore, basal and agonist-induced cAMP levels and catecholamine-induced apoptosis of T cells were measured. Catecholamines inhibited the synthesis of IFN-γ, TNF-α, and IL-10 at a concentration of 10-5 M. In addition, IFN-γ release was suppressed by 10-7 M epinephrine. Lower catecholamine concentrations exerted no significant effect. A reduced IL-4 production upon co-incubation with 10-5 M epinephrine was observed in RA patients only. The inhibitory effect of catecholamines on IFN-γ production was lower in RA patients as compared with HDs. In RA patients, a catecholamine-induced shift toward a Th2 (type 2) polarised cytokine profile was abrogated. Evaluation of intracellular cytokines revealed that CD8-positive T cells were accountable for the impaired catecholaminergic control of IFN-γ production. The highly significant negative correlation between age and catecholamine effects in HDs was not found in RA patients. Basal and stimulated cAMP levels in T-cell subsets and catecholamine-induced apoptosis did not differ between RA patients and HDs. RA patients demonstrate an impaired inhibitory effect of catecholamines on IFN-γ production together with a failure to induce a shift of T-cell cytokine responses toward a Th2-like profile. Such an unfavorable situation is a perpetuating factor for inflammation.

Ex Vivo Homeostatic Proliferation of CD4+ T Cells in Rheumatoid Arthritis Is Dysregulated and Driven by Membrane-Anchored TNFα

The systemic CD4+ T cell compartment in patients with rheumatoid arthritis (RA) is characterized by TCR repertoire contraction, shortened telomere lengths, and decreased numbers of recent thymic emigrants, suggesting a disturbed CD4+ T cell homeostasis. In mice, homeostatic proliferation of peripheral CD4+ T cells is regulated by TCR interaction with self peptide-MHC complexes (pMHC) and can be reproduced in vitro. We have established an ex vivo model of homeostatic proliferation, in which self-replication of human CD4+ T cells is induced by cell-cell contact with autologous monocytes. In healthy individuals, blockade of TCR-pMHC class II contact resulted in decreased CD4+ T cell division. In contrast, homeostatic proliferation in RA patients was not inhibited by pMHC blockade, but increased during the initial culture period. The anti-TNF-α Ab cA2 inhibited homeostasis-driven ex vivo proliferation in healthy controls and in RA patients. In addition, treatment of RA patients with infliximab decreased the ex vivo rate of homeostatic proliferation of CD4+ T cells. Our results suggest a disturbed regulation of CD4+ T cell homeostasis leading to the repertoire aberrations reported in RA. Membrane-anchored TNF-α appears to be a cell-cell contact-dependent stimulus of homeostatic proliferation of CD4+ T cells, possibly favoring self-replication of autoreactive CD4+ T cells in patients with RA.

Immunopathogenesis of Rheumatic Diseases in the Context of Neuroendocrine Interactions

Abstract: Growing evidence supports the hypothesis that alterations of the stress response and interactions between the neuroendocrine and immune systems contribute to the pathogenesis of rheumatic diseases such as rheumatoid arthritis (RA). In particular, the hypothalamus‐pituitary‐adrenal (HPA) axis and the autonomic nervous system (ANS) are of special interest. Polymorphisms of the corticotropin‐releasing hormone (CRH)‐regulating region have been described recently. These polymorphisms are differentially distributed in RA patients and healthy subjects of various ethnic origin, thus supporting the hypothesis that they represent a new genetic marker for RA susceptibility. The decreased expression of β2‐adrenergic receptors (β2‐R) on lymphatic cells in rheumatic diseases like RA, together with an impaired influence of catecholamines on immune function in these patients, further underlines the concept of a dysfunction of the ANS in rheumatic diseases. Results from work in this field will provide more insight into the pathogenesis of RA and help to establish novel therapies for this chronic rheumatic disease.

The contact-mediated response of peripheral-blood monocytes to preactivated T cells is suppressed by serum factors in rheumatoid arthritis

Stimulation of monocytes/macrophages after cell contact with preactivated T cells has been suggested to contribute to the excessive TNF-α production in rheumatoid arthritis (RA). In this study, T cell-contact-dependent TNF-α production by peripheral-blood monocytes in vitro was investigated and found to be significantly lower in treated and untreated patients with RA than in healthy controls. This suppression was not due to a general deficiency of monocytes to respond, because responses to lipopolysaccharide were comparable in patients and controls. In agreement with the pivotal role of TNF-α in RA, T cell-dependent induction of TNF-α in synovial macrophages was fivefold to tenfold higher than in peripheral-blood monocytes from either patients or controls. The decreased response of peripheral-blood monocytes from patients with RA was found to be mediated by inhibitory serum factors, because the addition of patient sera to monocytes from healthy controls suppressed TNF-α response in the co-culture assay. Preincubation of monocytes from healthy controls with RA serum was sufficient to suppress the subsequent TNF-α response in T cell co-cultures, indicating that inhibitory factors do indeed bind to monocyte surfaces, which might represent a regulatory counter-action of the immune system to the long-standing and consuming autoimmune process in RA. There are some indications that apolipoprotein A-1 might be part of this regulatory system.

Sequence variants of the CRH 5'-flanking region : Effects on DNA-protein interactions studied by EMSA in PC12 cells

Abstract:  Recently, studies in adult rheumatoid arthritis patients have shown an association with four single‐nucleotide polymorphisms (SNPs) in the 3.7‐kb regulatory region of human corticotropin‐releasing hormone (hCRH) gene located at positions −3531, −3371, −2353, and −684 bp. Three of these novel polymorphisms are in absolute linkage disequilibrium, resulting in three combined alleles, named A1B1, A2B1, and A2B2. To study whether the described polymorphic nucleotide sequences in the 5′ region of the hCRH gene interfere with binding of nuclear proteins, an electric mobility shift assay (EMSA) was performed. At position −2353 bp, a specific DNA protein complex was detected for the wild‐type sequence only, possibly interfering with a binding site for the activating transcription factor 6 (ATF6). In contrast, no difference could be detected for the other SNPs. However, at position −684, a quantitative difference in protein binding due to cAMP incubation could be observed. To further investigate whether these SNPs in the CRH promoter are associated with an altered regulation of the CRH gene, we performed a luciferase reporter gene assay with transiently transfected rat pheochromocytoma cells PC12. Incubation with 8‐Br‐cAMP alone or in combination with cytokines enhanced significantly the promoter activity in PC12 cells. The promoter haplotypes studied exhibited a differential capacity to modulate CRH gene expression. In all our experiments, haplotype A1B1 showed the most pronounced influence on promoter activity. Taken together, our results demonstrate a differential binding capacity of nuclear proteins of the promoter polymorphisms resulting in a different gene regulation. Most probably the SNP at position −2,353 plays a major role in mediating these differences.