Stress (heat shock) proteins and rheumatic disease. New advance or just another band wagon?

Role and regulation of intestinal epithelial heat shock proteins in health and disease

Mucosal injury and inflammation are cardinal manifestations of inflammatory bowel diseases (IBD), arising when the effects of cytotoxic factors and conditions overwhelm the cell's capacity for defense (i.e. cytoprotection) or repair. To date, most research in this area has focused primarily on agents and processes involved in producing tissue injury, with less consideration given to inherent mechanisms of cytoprotection and cellular repair. Therapeutic approaches to IBD reflect this bias, being largely directed towards down-regulating the inflammatory process by inhibiting the production of immune and inflammatory mediators. This review will focus on the cell's inherent ability to defend itself against cellular stress and injury through the production of evolutionarily conserved stress proteins called heat shock proteins (HSP). The physiological role of these proteins in maintaining intestinal epithelial cell structure and function will be reviewed, with emphasis on studies that examine the role of HSP in IBD. A clearer understanding of the innate cytoprotective mechanisms inherent in intestinal epithelial cells will foster the development of new insights into basic epithelial cell biology, which ultimately can be used to establish target-specific therapies directed at reducing or alleviating mucosal injury, thereby promoting tissue healing and repair.

Mediators of stress effects in inflammatory bowel disease: not the usual suspects

Empirical efforts to prove or disprove an association between stress and the course of inflammatory bowel disease (IBD) have had inconsistent results. Direct study of mediators of stress-related physiological processes may clarify this important area.

METHODS

candidate mediators were selected based on evidence that they have a role in the pathophysiology of IBD. Medline searches for original articles addressing each putative mediator and psychological stress were conducted. Articles were reviewed with goals of synthesis and hypothesis generation.

RESULTS

there is evidence that substance P (SP), vasoactive intestinal protein (VIP), tumour necrosis factor alpha (TNFalpha), oxidant molecules, endogenous glucocorticoids and heat shock proteins (HSPs) are involved in the stress response.

DISCUSSION

two principles emerge which should inform efforts to investigate stress in IBD. First, stress effects are regulated by highly interdependent systems. Second, the effects of mediators are highly specific to the location of their activity, and so, investigations in IBD are likely to require direct investigation of inflamed and unaffected gut tissue.

Stress proteins as targets for anti-inflammatory therapies

Microbial heat shock proteins (HSPs) are ubiquitous and highly immunogenic. In healthy humans, B- and T-cells with specificity for self-HSP can be easily detected. In patients with chronic inflammatory diseases, raised levels of antibodies and T-cells with reactivity to self-HSP have been observed. Based on this and other evidence, this raised immune reactivity might be the result of stress-induced upregulation of self-HSP during inflammation and is possibly caused by tissue destruction. More importantly, immunization with conserved sequences of microbial-HSP increases resistance to the induction of autoimmune disease. Together, it appears that immune reactivity directed towards self-HSP can be part of a regulatory immune effector mechanism that contributes to maintenance of self-tolerance and has anti-inflammatory activity. Boosting of such anti-inflammatory effector mechanisms by artificial immunization offers attractive immunotherapeutic possibilities.

Effect of hyperthermia on the extracellular matrix. I. Heat enhances hyaluronan and inhibits sulphated glycosaminoglycan synthesis

The synthesis of sulphated glycosaminoglycans (GAG) and hyaluronan (HA) was studied in 3 cell strains incubated at 37 degrees C or 42 degrees C. Cells were labelled with [3H]glucosamine and [35S]sulphate. No incorporation of [35S]sulphate was observed at 42 degrees C. Cellulose acetate electrophoresis of GAGs synthesized at 42 degrees C showed only one [3H]glucosamine-labelled band completely digested with Streptomyces hyaluronidase. The quantification of [3H]glucosamine-labelled GAGs before and after hyaluronidase treatment indicated an increased rate of HA synthesis at 42 degrees C as compared to the rate of synthesis at 37 degrees C. These results suggest that hyperthermia stimulates HA synthesis and inhibits sulphated GAG synthesis in several cell strains which in turn may contribute to the modification of extracellular environment in inflammation.

Spinal fluid lymphocytes from a subgroup of multiple sclerosis patients respond to mycobacterial antigens

Immune responses to heat shock or stress proteins are observed in several chronic autoimmune diseases. Such proteins are major antigens of many bacteria, especially mycobacteria. To determine whether immune responses to stress proteins occur in chronic inflammatory diseases of the central nervous system such as multiple sclerosis (MS) we measured proliferative responses of lymphocytes from spinal fluids and bloods of patients with MS and other neurological diseases to a sonicate of M. tuberculosis, an acetone extract of M. tuberculosis, a recombinant 65-kd heat shock protein of M. leprae, and tetanus toxoid as a control recall antigen. Significantly increased spinal fluid lymphocyte responses to mycobacterial sonicate, relative to responses from paired peripheral blood lymphocytes, were present in 14 of 20 specimens from patients with MS (p < 0.025) and 2 of 9 specimens from patients with other neurological diseases. Spinal fluid lymphocytes also responded to tetanus toxoid, but differences between blood and spinal fluid were not statistically significant. Lymphocytes from 1 patient with MS responded only to M. leprae. There were no proliferative responses to the M. tuberculosis acetone extract. When patients with MS were classified according to duration of disease (< 2- or > 2-yr duration) 9 of 10 patients with recent onset had cerebrospinal fluid cells that responded to M. tuberculosis compared with 5 of 10 with longer duration symptoms (p < 0.012). Our data suggest a selective recruitment and/or expansion of mycobacterial reactive cells to the central nervous system of a subpopulation of patients with MS.(ABSTRACT TRUNCATED AT 250 WORDS)

Surface expression of heat shock protein 90 by blood mononuclear cells from patients with systemic lupus erythematosus

Previous studies have indicated that blood mononuclear cells from 15-20% of patients with systemic lupus erythematosus (SLE) carry elevated levels of hsp90, a heat shock protein associated with steroid receptors in cells. We analysed surface expression of hsp90 on mononuclear cells (lymphocytes and monocytes) from patients with SLE by monoclonal antibody AC88 and flow cytometry. Whilst all blood mononuclear cells have intracellular hsp90, a significant proportion of patients with SLE expressed hsp90 on lymphocyte and monocyte surfaces. This was significantly higher on SLE lymphocytes than in laboratory controls and was positively correlated with disease activity. Comparison of total hsp90 with surface hsp90 in the same SLE patients' blood mononuclear samples indicated a correlation with a subgroup of patients. There was no correlation with expression of surface hsp90 by lymphocytes and activation markers. Patients with Sjögren's syndrome, rheumatoid arthritis, dermatomyositis and scleroderma were studied as disease controls and increased levels of shsp90 were detected in only three of the 53 patients studied. It is concluded that surface hsp90 expression is a feature of about 20% of patients with SLE and is correlated with high disease activity. The exposure of this hsp on the surface of some lymphocytes suggests that it is a candidate autoantigen in SLE.

Antibody to a 63 kilodalton insect protein in ankylosing spondylitis

Ankylosing spondylitis (AS) is associated with antibodies to a heat shock puff on drosophila chromosomes. This observation was investigated by immunoblotting using extracts of the Schneider insect cell line and HeLa cells, before and after heat shock. An insect protein of 63 kilodaltons (but no equivalent human protein) was recognised by 21 (46%) of 46 serum samples from patients with AS, one of two patients with Reiter's syndrome, four (7%) of 60 patients with systemic lupus erythematosus, and two (4%) of 50 control subjects, but not by serum samples from patients with rheumatoid arthritis (RA). Previous heat shock did not appear to affect the strength of reaction, but ML-30, a monoclonal antibody to the mycobacterial 65 kilodalton heat shock protein (hsp65), also recognised an insect protein of 63 kilodaltons by immunoblotting. Antibodies to recombinant mycobacterial hsp65 were measured by enzyme linked immunosorbent assay (ELISA) in serum samples from patients with AS and RA. IgA binding to hsp65 was increased in 41% of AS and 19% of RA serum samples, but there was no correlation with detection of antibody to the insect 63 kilodalton protein.

The search for laboratory measures of outcome in rheumatoid arthritis

A large number of laboratory tests have been developed within the past decade to measure factors involved in the immune inflammation of RA. These can be divided into genetic markers, general measures of inflammation, autoantibodies and tissue-specific markers. In general, it is simpler to prove the power of a certain test to measure the disease process than to predict outcome. Apart from RF positivity and CRP/ESR, few, if any, tests have proven to be of importance in independent studies from different centres. Among the promising candidates for future work are detailed analysis of the HLA-D region genes, sulphoxidation status, the autoantibody against RA33 nuclear antigen, soluble IL-2 receptor measuring lymphocyte activity, hyaluronate/hyaluronan or PIIINP from synovial tissue, the combined use of COMP and proteoglycan epitope tests for cartilage matrix, and pyrodinoline cross-linking for collagen from bone and cartilage. The ideal setting for testing such markers are prospective cohort studies starting early in the disease, and since many such studies have been initiated recently, one can expect much new information in coming years. Attention needs to be devoted to the kinetics of marker metabolism, since many are degraded or removed at very fast rates from the circulation, making serum assays less informative.

Immune responses to 18.6 and 30-kDa mycobacterial antigens in rheumatoid patients, and V beta usage by specific synovial T-cell lines and fresh T cells

We have investigated both the humoral and the cellular immune responses of patients with juvenile rheumatoid arthritis (JRA) and rheumatoid arthritis (RA) to mycobacterial antigens. The JRA group was not Bacillus Calmette Guerin (BCG) vaccinated whilst the majority of the RA group was. As determined by immunoblotting, 79% of sera from patients with JRA reacted mainly with a 18.6-kDa protein (P18.6), whilst 70% of sera from patients with RA reacted mainly with a 30-kDa protein (P30) of BCG, M. tuberculosis and M. kansasii. In contrast, only a moderate proportion of the control sera (25% of adult and 20% of children) showed reactivity to P30, and none of the samples had significant reactivity with the P18.6 antigen. Furthermore, T-cell proliferation to the P18.6 and P30 antigens was detected in the majority of JRA and RA patients, and was nearly always higher in synovial fluid (SF) than in the peripheral blood (PB). We also investigated the usage of V beta family genes in P18.6 and P30 antigen-specific T-cell lines established from the SF of one patient with active RA. We showed that V beta 2, -4, -5, -6, -7, -14, -17, -18 and V beta 19 were over-represented compared with other known V beta families. We also noted that the proportion of V beta 14 was higher in freshly isolated SF mononuclear cells compared with the blood in this patient and in 2 out of 4 other RA patients examined. Other V beta families such as V beta 6, V beta 8, V beta 16, V beta 18 and V beta 19 were also over-represented in the SF compared with the blood in some patients. Taken together our results provide more information concerning the role of mycobacterial antigens in RA and suggest that there may be an in vivo clonal expansion of T lymphocytes in the synovium.

Oxygen free radicals and human diseases

Free radicals and other reactive oxygen species are constantly formed in the human body. Many of them serve useful physiological functions, but they can be toxic when generated in excess and this toxicity is often aggravated by the presence of ions of such transition metals as iron or copper. Excess generation of reactive oxygen species within tissues can damage DNA, lipids, proteins and carbohydrates. Which of these is the most important target of damage depends upon the cell type subjected to the oxidative stress and upon how it is imposed.

Stress proteins, autoimmunity, and autoimmune disease

At birth, the immune system is biased toward recognition of microbial antigens in order to protect the host from infection. Recent data suggest that an important initial line of defense in this regard involves autologous stress proteins, especially conserved peptides of hsp60, which are presented to T cells bearing gamma delta receptors by relatively nonpolymorphic class lb molecules. Natural antibodies may represent a parallel B cell mechanism. Through an evolving process of "physiological" autoreactivity and selection by immunodominant stress proteins common to all prokaryotes, B and T cell repertoires expand during life to meet the continuing challenge of infection. Because stress proteins of bacteria are homologous with stress proteins of the host, there exists in genetically susceptible individuals a constant risk of autoimmune disease due to failure of mechanisms for self-nonself discrimination. That stress proteins actually play a role in autoimmune processes is supported by a growing body of evidence which, collectively, suggests that autoreactivity in chronic inflammatory arthritis involves, at least initially, gamma delta cells which recognize epitopes of the stress protein hsp60. Alternate mechanisms for T cell stimulation by stress proteins undoubtedly also exist, e.g., molecular mimicry of the DR beta third hypervariable region susceptibility locus for rheumatoid arthritis by a DnaJ stress protein epitope in gram-negative bacteria. While there still is confusion with respect to the most relevant stress protein epitopes, a central role for stress proteins in the etiology of arthritis appears likely. Furthermore, insight derived from the work thus far in adjuvant-induced arthritis already is stimulating analyses of related phenomena in autoimmune diseases other than those involving joints. Only limited data are available in the area of humoral autoimmunity to stress proteins. Autoantibodies to a number of stress proteins have been identified in SLE and rheumatoid arthritis, but their pathogenetic significance remains to be established. Nevertheless, the capacity of certain stress proteins to bind to multiple proteins in the nucleus and cytoplasm both physiologically and during stress or injury to cells, suggests that stress proteins may be important elements in the "immunogenic particle" concept of the origin of antinuclear and other autoantibodies. In short, this fascinating group of proteins, so mysterious only a few years ago, has impelled truly extraordinary new lines of investigation into the nature of autoimmunity and autoimmune disease.