Overexpression of human homologs of the bacterial DnaJ chaperone in the synovial tissue of patients with rheumatoid arthritis

Characteristics of the (Auto)Reactive T Cells in Rheumatoid Arthritis According to the Immune Epitope Database

T cells are known to be involved in the pathogenesis of rheumatoid arthritis (RA). Accordingly, and to better understand T cells' contribution to RA, a comprehensive review based on an analysis of the Immune Epitope Database (IEDB) was conducted. An immune CD8+ T cell senescence response is reported in RA and inflammatory diseases, which is driven by active viral antigens from latent viruses and cryptic self-apoptotic peptides. RA-associated pro-inflammatory CD4+ T cells are selected by MHC class II and immunodominant peptides, which are derived from molecular chaperones, host extra-cellular and cellular peptides that could be post-translationally modified (PTM), and bacterial cross-reactive peptides. A large panel of techniques have been used to characterize (auto)reactive T cells and RA-associated peptides with regards to their interaction with the MHC and TCR, capacity to enter the docking site of the shared epitope (DRB1-SE), capacity to induce T cell proliferation, capacity to select T cell subsets (Th1/Th17, Treg), and clinical contribution. Among docking DRB1-SE peptides, those with PTM expand autoreactive and high-affinity CD4+ memory T cells in RA patients with an active disease. Considering original therapeutic options in RA, mutated, or altered peptide ligands (APL) have been developed and are tested in clinical trials.

Heat Shock Protein 70 as a Double Agent Acting Inside and Outside the Cell: Insights into Autoimmunity

Heat shock proteins (Hsp) are a diverse group of constitutive and/or stress-induced molecules that are categorized into several classes on the basis of their molecular weight. Mammalian Hsp have been mostly regarded as intracellular chaperones that mediate a range of essential cellular functions, including proper folding of newly synthesized polypeptides, refolding of denatured proteins, protein transport, and stabilization of native proteins' structures. The well-characterized and highly evolutionarily conserved, stress-inducible 70-kDa heat shock protein (Hsp70), is a key molecular chaperone that is overexpressed in the cell in response to stress of various origin. Hsp70 exhibits an immunosuppressive activity via, e.g., downregulation of the nuclear factor-kappa B (NF-κB) activation, and pharmacological induction of Hsp70 can ameliorate the autoimmune arthritis development in animal models. Moreover, Hsp70 might be passively or actively released from the necrotic or stressed cells, respectively. Highly immunogenic extracellular Hsp70 has been reported to impact both the innate and adaptive immune responses, and to be implicated in the autoimmune reaction. In addition, preclinical studies revealed that immunization with highly conserved Hsp70 peptides could be regarded as a potential treatment target for autoimmune arthritis, such as the rheumatoid arthritis, via induction of antigen-specific regulatory T helper cells (also called Treg). Here, a dual role of the intra- and extracellular Hsp70 is presented in the context of the autoimmune reaction.

Targeting of tolerogenic dendritic cells to heat-shock proteins in inflammatory arthritis

Background

Autologous tolerogenic dendritic cells (tolDC) are a promising therapeutic strategy for inflammatory arthritis (IA) as they can regulate autoantigen-specific T cell responses. Here, we investigated two outstanding priorities for clinical development: (i) the suitability of using heat-shock proteins (HSP), abundant in inflamed synovia, as surrogate autoantigens to be presented by tolDC and (ii) identification of functional biomarkers that confirm tolDC regulatory activity.

Methods

Cell proliferation dye-labelled human peripheral blood mononuclear cells of IA (rheumatoid arthritis (RA) and psoriatic arthritis (PsA)) patients or healthy donors were cultured with HSP40-, HSP60- and HSP70-derived peptides or recall antigens (e.g. tuberculin purified protein derivative (PPD)) in the presence or absence of tolDC or control DC for 9 days. Functional characteristics of proliferated antigen-specific T-cells were measured using flow cytometry, gene expression profiling and cytokine secretion immunoassays. Repeated measures analysis of variance (ANOVA) with Bonferroni correction for comparisons between multiple groups and paired Student t test for comparisons between two groups were used to determine significance.

Results

All groups showed robust CD4⁺ T-cell responses towards one or more HSP-derived peptide(s) as assessed by a stimulation index > 2 (healthy donors: 78%, RA: 73%, PsA: 90%) and production of the cytokines IFNγ, IL-17A and GM-CSF. Addition of tolDC but not control DC induced a type 1 regulatory (Tr1) phenotype in the antigen-specific CD4⁺ T-cell population, as identified by high expression of LAG3, CD49b and secretion of IL-10. Furthermore, tolDC inhibited bystander natural killer (NK) cell activation in a TGFβ dependent manner.

Conclusions

HSP-specific CD4⁺ T-cells are detectable in the majority of RA and PsA patients and can be converted into Tr1 cells by tolDC. HSP-loaded tolDC may therefore be suitable for directing T regulatory responses to antigens in inflamed synovia of IA patients. Tr1 markers LAG3, CD49b and IL-10 are suitable biomarkers for future tolDC clinical trials.

Targeting of tolerogenic dendritic cells towards heat-shock proteins: a novel therapeutic strategy for autoimmune diseases?

Tolerogenic dendritic cells (tolDCs) are a promising therapeutic tool to restore immune tolerance in autoimmune diseases. The rationale of using tolDCs is that they can specifically target the pathogenic T-cell response while leaving other, protective, T-cell responses intact. Several ways of generating therapeutic tolDCs have been described, but whether these tolDCs should be loaded with autoantigen(s), and if so, with which autoantigen(s), remains unclear. Autoimmune diseases, such as rheumatoid arthritis, are not commonly defined by a single, universal, autoantigen. A possible solution is to use surrogate autoantigens for loading of tolDCs. We propose that heat-shock proteins may be a relevant surrogate antigen, as they are evolutionarily conserved between species, ubiquitously expressed in inflamed tissues and have been shown to induce regulatory T cells, ameliorating disease in various arthritis mouse models. In this review, we provide an overview on how immune tolerance may be restored by tolDCs, the problem of selecting relevant autoantigens for loading of tolDCs, and why heat-shock proteins could be used as surrogate autoantigens.

Rheumatoid Arthritis, Immunosenescence and the Hallmarks of Aging

Age is the most important risk factor for the development of infectious diseases, cancer and chronic inflammatory diseases including rheumatoid arthritis (RA). The very act of living causes damage to cells. A network of molecular, cellular and physiological maintenance and repair systems creates a buffering capacity against these damages. Aging leads to progressive shrinkage of the buffering capacity and increases vulnerability. In order to better understand the complex mammalian aging processes, nine hallmarks of aging and their interrelatedness were recently put forward.

RA is a chronic autoimmune disease affecting the joints. Although RA may develop at a young age, the incidence of RA increases with age. It has been suggested that RA may develop as a consequence of premature aging (immunosenescence) of the immune system. Alternatively, premature aging may be the consequence of the inflammatory state in RA. In an effort to answer this chicken and egg conundrum, we here outline and discuss the nine hallmarks of aging, their contribution to the pre-aged phenotype and the effects of treatment on the reversibility of immunosenescence in RA.

Human Hsp40 proteins, DNAJA1 and DNAJA2, as potential targets of the immune response triggered by bacterial DnaJ in rheumatoid arthritis

Hsp40 proteins of bacterial and human origin are suspected to be involved in the pathogenesis of rheumatoid arthritis (RA). It has been shown that sera of RA patients contain increased levels of antibodies directed to bacterial and human Hsp40s. The aim of this work was to explore immunological similarities between the bacterial (DnaJ) and human (DNAJA1 and DNAJA2) Hsp40 proteins in relation to their possible involvement in the RA. Using polyclonal antibodies directed against a full-length DnaJ or its domains, against DNAJA1 and DNAJA2, as well as monoclonal anti-DnaJ antibodies, we found immunological similarities between the bacterial and human Hsp40s. Both ELISA and Western blotting showed that these similarities were not restricted to the conserved J domains but were also present in the C-terminal variable regions. We also found a positive correlation between the levels of the anti-DnaJ and anti-DNAJA1 antibodies in the sera of RA patients. This finding supports the molecular mimicry hypothesis that human Hsp40 could be the targets of antibodies originally directed against bacterial DnaJ in RA.

Hsp40 proteins modulate humoral and cellular immune response in rheumatoid arthritis patients

Recent research on the heat shock proteins (Hsps) in chronic inflammatory diseases indicates that Hsps may have disease-suppressive activities. Our aim was to characterize immune response directed to bacterial (DnaJ) and human Hsp40s in patients with rheumatoid arthritis (RA). We found elevated levels of anti-DnaJ, anti-Hdj2, and anti-Hdj3 (but not ant-Hdj1) serum antibodies in the RA patients (P < or = 0.001) compared to healthy controls. In peripheral blood mononuclear cells (PBMCs) culture, all tested Hsp40 proteins significantly inhibited the divisions of CD4+ and CD8+ T cells of the RA patients but not those of the controls. Both DnaJ and Hdj2 stimulated secretion of the main anti-inflammatory cytokine IL-10 by PBMCs of the RA patients (P < 0.05), and of IL-6 by PBMCs of the RA (P < 0.001) and control (P < 0.01) groups. DnaJ reduced TNFalpha secretion (P < 0.05) by both groups of PBMCs. Our results show for the first time that the RA patients have an increased humoral response to human Hsp40 proteins Hdj2 and Hdj3. This is also the first description of immunomodulatory effect of human Hsp40s on T cells and cytokine secretion in RA, suggesting that Hsp40s act as natural anti-inflammatory agents in RA.

Hsp70 expression and induction as a readout for detection of immune modulatory components in food

Stress proteins such as heat shock proteins (Hsps) are up-regulated in cells in response to various forms of stress, like thermal and oxidative stress and inflammation. Hsps prevent cellular damage and increase immunoregulation by the activation of anti-inflammatory T-cells. Decreased capacity for stress-induced Hsp expression is associated with immune disorders. Thus, therapeutic boosting Hsp expression might restore or enhance cellular stress resistance and immunoregulation. Especially food- or herb-derived phytonutrients may be attractive compounds to restore optimal Hsp expression in response to stress. In the present study, we explored three readout systems to monitor Hsp70 expression in a manner relevant for the immune system and evaluated novel Hsp co-inducers. First, intracellular staining and analysis by flow cytometry was used to detect stress and/or dietary compound induced Hsp70 expression in multiple rodent cell types efficiently. This system was used to screen a panel of food-derived extracts with potent anti-oxidant capacity. This strategy yielded the identity of several new enhancers of stress-induced Hsp70 expression, among them carvacrol, found in thyme and oregano. Second, CD4(+) T-cell hybridomas were generated that specifically recognized an immunodominant Hsp70 peptide. These hybridomas were used to show that carvacrol enhanced Hsp70 levels increased T-cell activation. Third, we generated a DNAJB1-luc-O23 reporter cell line to show that carvacrol increased the transcriptional activation of a heat shock promoter in the presence of arsenite. These assay systems are generally applicable to identify compounds that affect the Hsp level in cells of the immune system.

The involvement of heat-shock proteins in the pathogenesis of autoimmune arthritis: a critical appraisal

OBJECTIVES

To review the literature on the role of heat-shock proteins (HSPs) in the pathogenesis of autoimmune arthritis in animal models and patients with rheumatoid arthritis (RA).

METHODS

The published literature in Medline (PubMed), including our published work on the cell-mediated as well as humoral immune response to various HSPs, was reviewed. Studies in the preclinical animal models of arthritis as well as RA were examined critically and the data are presented.

RESULTS

In experimental arthritis, disease induction by different arthritogenic stimuli, including an adjuvant, led to immune response to mycobacterial HSP65 (BHSP65). However, attempts to induce arthritis by a purified HSP have not met with success. There are several reports of a significant immune response to HSP65 in RA patients. However, the issue of cause and effect is difficult to address. Nevertheless, several studies in animal models and a couple of clinical trials in RA patients have shown the beneficial effect of HSPs against autoimmune arthritis.

CONCLUSIONS

There is a clear association between immune response to HSPs, particularly HSP65, and the initiation and propagation of autoimmune arthritis in experimental models. The correlation is relatively less convincing in RA patients. In both cases, the ability of HSPs to modulate arthritis offers support, albeit an indirect one, for the involvement of these antigens in the disease process.

Identification of intra-group, inter-individual, and gene-specific variances in mRNA expression profiles in the rheumatoid arthritis synovial membrane

Introduction

Rheumatoid arthritis (RA) is a chronic inflammatory and destructive joint disease characterized by overexpression of pro-inflammatory/pro-destructive genes and other activating genes (for example, proto-oncogenes) in the synovial membrane (SM). The gene expression in disease is often characterized by significant inter-individual variances via specific synchronization/desynchronization of gene expression. To elucidate the contribution of the variance to the pathogenesis of disease, expression variances were tested in SM samples of RA patients, osteoarthritis (OA) patients, and normal controls (NCs).

Method

Analysis of gene expression in RA, OA, and NC samples was carried out using Affymetrix U133A/B oligonucleotide arrays, and the results were validated by real-time reverse transcription-polymerase chain reaction. For the comparison between RA and NC, 568 genes with significantly different variances in the two groups (P ≤ 0.05; Bonferroni/Holm corrected Brown-Forsythe version of the Levene test) were selected. For the comparison between RA and OA, 333 genes were selected. By means of the Kyoto Encyclopedia of Genes and Genomes, the pathways/complexes significantly affected by higher gene expression variances were identified in each group.

Results

Ten pathways/complexes significantly affected by higher gene expression variances were identified in RA compared with NC, including cytokine–cytokine receptor interactions, the transforming growth factor-beta pathway, and anti-apoptosis. Compared with OA, three pathways with significantly higher variances were identified in RA (for example, B-cell receptor signaling and vascular endothelial growth factor signaling). Functionally, the majority of the identified pathways are involved in the regulation of inflammation, proliferation, cell survival, and angiogenesis.

Conclusion

In RA, a number of disease-relevant or even disease-specific pathways/complexes are characterized by broad intra-group inter-individual expression variances. Thus, RA pathogenesis in different individuals may depend to a lesser extent on common alterations of the expression of specific key genes, and rather on individual-specific alterations of different genes resulting in common disturbances of key pathways.

[Immunogenetics--HLA-association, molecular chaperones and "related" diseases]

The association of rheumatoid arthritis (RA) with the HLA complex has been well established since 1978. But what does that mean? After reminding the reader of some existing immunological interpretations, a more recent variant is introduced. Antigens and molecular chaperones of the HSP70 family form complexes, which interact with HLA-DR beta-chains, especially of the DRB1*0401 genotype, which is the most common among patients with RA in our region. This mechanism might bring *0401(+) persons an advantage in defence against microorganisms, but a disadvantage concerning autoimmunity. Chaperone machines are upregulated in synovial tissue of RA patients. As their number and variety is huge in humans, there exist many possibilities for function, reaching from antigen presentation to immune regulation. In addition to the HLA complex, the "genetic background" plays an important role for the development of an autoimmune disease. This is demonstrated in families of patients with RA or scleroderma, where a high percentage of first degree relatives suffer from a "related" disease.

Continuous enhanced expression of Hsc70 but not Hsp70 in rheumatoid arthritis synovial tissue

OBJECTIVE

To investigate the expression of constitutive and inducible members of the Hsp70 protein family in synovial tissue of patients with rheumatoid arthritis (RA) or osteoarthritis (OA).

METHODS

Frozen sections of synovial tissue and isolated synovial adherent cells obtained from 17 RA patients, 5 OA patients, and 1 patient with carpal tunnel syndrome (CTS) were analyzed with specific monoclonal antibodies, by immunohistochemistry, immunocytochemistry, and immunoblotting.

RESULTS

Expression of the constitutive chaperone Hsc70 was increased in synovial tissue from 9 of 9 patients with RA, but was faint or undetectable in 3 of 3 samples from patients with OA. In RA samples, cells mainly of the synovial lining stained intensely for Hsc70 as well as for HLA-DR, CD14, and CD68. Also, in vitro-cultured synovial adherent cells from 8 of 9 RA patients overexpressed Hsc70 (specimens from 1 RA patient were used in both the immunochemistry and the in vitro culture studies). On immunoblots of protein extracts, the synovial and HeLa cell molecules appeared identical in size. The inducible chaperone Hsp70 was not detected in samples from any of the same 17 RA patients, except for rare, isolated cells in 3. Samples from 4 of 5 OA patients also were negative for the inducible chaperone Hsp70, and the fifth was very weakly positive. In addition, tissue from 1 patient with CTS was analyzed 10 months before diagnosis of RA. Synovial tissue from this patient showed extreme overexpression of both Hsc70 and Hsp70.

CONCLUSION

In RA, synovial lining cells continuously overexpress Hsc70 but not Hsp70. Hsc70 may be up-regulated due to the high activity of these cells in several respects, including antigen processing and presentation.

Characterization of the anti-DnaJ monoclonal antibodies and their use to compare immunological properties of DnaJ and its human homologue HDJ-1

Escherichia coli DnaJ (Hsp40) is suspected to participate in rheumatoid arthritis (RA) pathogenesis in humans by an autoimmune process. In this work a set of 6 anti-DnaJ monoclonal antibodies (mAbs) was raised and localization of the epitopes recognized by the mAbs was investigated. Western blotting and enzyme-linked immunosorbent assay (ELISA) experiments showed that the mAbs efficiently bound only native antigen. Using DnaJ mutant proteins with deletions of specified domains and ELISA, we found that AC11 mAb reacted with the best conserved in evolution N-terminal J domain, whereas BB3, EE11, CC5, CC8, and DC7 bound to the C-terminal part after residue 200. Mapping performed with the use of a random peptide library displayed by filamentous phage indicated that (1) AC11 mAb bound to a region between residues 33-48, including D-34 which belongs to the HPD triad, present in all DnaJ homologues, (2) BB3 recognized residues localized in the 204-224 region, (3) EE11 recognized the 291-309 region, (4) CC5--the region 326-359, and (5) CC8--the 346-366 region. All these mAbs, as well as the polyclonal antibodies against the N- or C-terminal domain, bound efficiently to HDJ-1, human Hsp40. These results show the presence of a significant immunological similarity between bacterial DnaJ and human HDJ-1, which is not restricted to the evolutionarily conserved parts of the proteins, and suggest that HDJ-1 could be a possible target of immune response triggered by DnaJ.

Major differences in antigen-processing correlate with a single Arg71<-->Lys substitution in HLA-DR molecules predisposing to rheumatoid arthritis and with their selective interactions with 70-kDa heat shock protein chaperones

Several HLA-DR alleles are genetically associated with rheumatoid arthritis. DRB1*0401 predominates in Northern Europe and has a characteristic (70)QKRAA motif. This sequence contacts bound peptides and the TCR. Further interactions have been suggested with additional proteins during Ag loading. We explored the much stronger processing/presentation of full-length recombinant human acetylcholine receptor alpha subunit to a specific T cell clone by APC from DRB1*0401+ than *0408+ donors. Using DR*04 transfectants, we show that this difference results largely from the single Lys71<-->Arg interchange (0401<-->0408), which scarcely affects epitope binding, rather than from any other associated polymorphism. Furthermore, we proved our recombinant polypeptides to contain the Escherichia coli 70-kDa heat shock protein molecule DnaK and its requirement for efficient processing and presentation of the epitope by DRB1*0401+ cells. According to a recent report, 70-kDa heat shock protein chaperones preferentially bind to the QKRAA, rather than the QRRAA, motif. Variations between the shared epitope motifs QKRAA and QRRAA are emphasized by underlining. We propose that such interactions enhance the intracellular epitope loading of *0401 molecules. They may thus broaden immune responses to pathogens and at least partially explain the distinct contributions of DRB1*0401 and other alleles to disease predisposition.

The human endoplasmic reticulum molecular chaperone BiP is an autoantigen for rheumatoid arthritis and prevents the induction of experimental arthritis

Rheumatoid arthritis (RA) is the most common, crippling human autoimmune disease. Using Western blotting and tandem mass spectroscopy, we have identified the endoplasmic reticulum chaperone BiP, a 78-kDa glucose-regulated protein, as a possible autoantigen. It preferentially stimulated increased proliferation of synovial T cells from patients with RA but not from patients with other arthritides. Mice with established collagen- or pristane-induced arthritis developed IgG Abs to BiP. Although BiP injected in CFA failed to induce arthritis in several strains of rats and mice, including HLA-DR4(+/-)- and HLA-DR1(+/+)-transgenic animals, it completely inhibited the development of arthritis when given i.v. 1 wk before the injection of type II collagen arthritis. Preimmunization with BiP suppressed the development of adjuvant arthritis in Lewis rats in a similar manner. This is the first report of a mammalian chaperone that is an autoantigen in human RA and in experimental arthritis and that can also prevent the induction of experimental arthritis. These findings may stimulate the development of new immunotherapies for the treatment of RA.

Inflamed shoulder structures in polymyalgia rheumatica with normal erythrocyte sedimentation rate

OBJECTIVE

To investigate the inflammatory involvement of shoulder articular and extraarticular structures in polymyalgia rheumatica (PMR) patients with a normal erythrocyte sedimentation rate (ESR) at diagnosis.

METHODS

This was a case-control study. All consecutive, untreated new outpatients diagnosed as having PMR with a normal ESR (<40 mm/hour) during a 6-month period were included in the study (case patients). Controls were 12 consecutive, untreated PMR outpatients with an ESR of >40 mm/hour who were observed after the case patients. Before starting corticosteroid therapy, all case patients and controls underwent bilateral shoulder ultrasonography (US) and magnetic resonance imaging (MRI). US and MRI scans were evaluated independently by two radiologists who were blinded to the reciprocal results.

RESULTS

Six case patients (4 men and 2 women) and 12 controls (4 men and 8 women) were studied. Both US and MRI demonstrated bilateral subacromial/subdeltoid bursitis in all 6 case patients and in 11 of the 12 (92%) controls (P not significant [NS]). One control had unilateral bursitis. Glenohumeral joint synovitis was found in 4 of 6 case patients (67%) by MRI and in 3 of 6 case patients (50%) by US (P NS), as well as in 8 of 12 controls (67%) by MRI and in 7 of 12 controls (58%) by US (P NS). Both MRI and US detected biceps tenosynovitis in 5 of 6 case patients (83%) and in 8 of 12 controls (67%) (P NS). The severity of bursitis did not differ significantly between the groups. US was as effective as MRI in detecting inflammatory changes of the shoulder.

CONCLUSION

MRI and US studies showed that PMR patients with normal or high ESRs have similar inflammatory shoulder lesions. Moreover, bilateral subacromial/subdeltoid bursitis represents the imaging hallmark in PMR patients with a high or normal ESR. MRI or US of the shoulder may facilitate the proper diagnosis in patients with the typical proximal symptoms of PMR who also have normal ESRs.