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Heat shock protein B1-deficient mice display impaired wound healing.
There is large literature describing in vitro experiments on heat shock protein (hsp)B1 but understanding of its function in vivo is limited to studies in mice overexpressing human hspB1 protein. Experiments in cells have shown that hspB1 has chaperone activity, a cytoprotective role, regulates inflammatory gene expression, and drives cell proliferation. To investigate the function of the protein in vivo we generated hspB1-deficient mice. HspB1-deficient fibroblasts display increased expression of the pro-inflammatory cytokine, interleukin-6, compared to wild-type cells, but reduced proliferation. HspB1-deficient fibroblasts exhibit reduced entry into S phase and increased expression of cyclin-dependent kinase inhibitors p27(kip1) and p21(waf1). The expression of hspB1 protein and mRNA is also controlled by the cell cycle. To investigate the physiological function of hspB1 in regulating inflammation and cell proliferation we used an excisional cutaneous wound healing model. There was a significant impairment in the rate of healing of wounds in hspB1-deficient mice, characterised by reduced re-epithelialisation and collagen deposition but also increased inflammation. HspB1 deficiency augments neutrophil infiltration in wounds, driven by increased chemokine (C-X-C motif) ligand 1 expression. This appears to be a general mechanism as similar results were obtained in the air-pouch and peritonitis models of acute inflammation.
Nimesulide improves the symptomatic and disease modifying effects of leflunomide in collagen induced arthritis.
Nimesulide is a COX-2 inhibitor used for symptomatic relief of rheumatoid arthritis. Leflunomide is an anti-pyrimidine used to manage the progression of rheumatoid arthritis. Herein we studied the influence of nimesulide and leflunomide combination in terms of disease symptoms and progression using collagen-induced arthritis model in mice, as a model for rheumatoid arthritis. Collagen induced arthritis was induced by immunization with type II collagen. Assessment of joint stiffness and articular hyperalgesia were evaluated using a locomotor activity cage and the Hargreaves method, respectively. Disease progression was assessed via arthritic index scoring, X-ray imaging, myeloperoxidase enzyme activity and histopathologic examination. Nimesulide induced only transient symptomatic alleviation on the top of decreased leucocytic infiltration compared to arthritis group. However, nimesulide alone failed to induce any significant improvement in the radiological or pathological disease progression. Leflunomide alone moderately alleviates the symptoms of arthritis and moderately retarded the radiological and pathological disease progression. Combination of nimesulide and leflunomide significantly improved symptomatic (analgesia and joint stiffness) and arthritic disease progression (radiological, pathological and Myeloperoxidase enzyme activity) in collagen induced arthritis animal model.
Exploitation of the IDO Pathway in the Therapy of Rheumatoid Arthritis.
Indoleamine 2,3-dioxygenase (IDO) is the first and rate-limiting step along the kynurenine pathway and is thought to play a key role in immune homeostasis through depletion of tryptophan and accumulation of kynurenines. In this review we summarize recent research into the possibility of harnessing the IDO pathway for the therapy of rheumatoid arthritis. Inhibition of IDO activity, or knockout of the gene encoding IDO, was shown to cause an increase in the severity of collagen-induced arthritis, an animal model of rheumatoid arthritis. The increased severity of disease was associated with elevated numbers of pathogenic Th1 and Th17 cells in the joints and draining lymph nodes. In another study, analysis of the kinetics of expression of downstream kynurenine pathway enzymes during the course of arthritis revealed a potential role for tryptophan metabolites in resolution of arthritis. Furthermore, the therapeutic administration of L-kynurenine or [3,4-dimethoxycinnamonyl]-anthranilic acid (a synthetic derivative of 3-hydroxy-anthranilic acid) significantly reduced both clinical and histological progression of experimental arthritis. These findings raise the possibility of exploiting the IDO pathway for the therapy of autoimmune disease.
Inhibitor of kappa B epsilon (IκBε) is a non-redundant regulator of c-Rel-dependent gene expression in murine T and B cells.
Inhibitors of kappa B (IκBs) -α, -β and -ε effect selective regulation of specific nuclear factor of kappa B (NF-κB) dimers according to cell lineage, differentiation state or stimulus, in a manner that is not yet precisely defined. Lymphocyte antigen receptor ligation leads to degradation of all three IκBs but activation only of subsets of NF-κB-dependent genes, including those regulated by c-Rel, such as anti-apoptotic CD40 and BAFF-R on B cells, and interleukin-2 (IL-2) in T cells. We report that pre-culture of a mouse T cell line with tumour necrosis factor-α (TNF) inhibits IL-2 gene expression at the level of transcription through suppressive effects on NF-κB, AP-1 and NFAT transcription factor expression and function. Selective upregulation of IκBε and suppressed nuclear translocation of c-Rel were very marked in TNF-treated, compared to control cells, whether activated via T cell receptor (TCR) pathway or TNF receptor. IκBε associated with newly synthesised c-Rel in activated cells and, in contrast to IκBα and -β, showed enhanced association with p65/c-Rel in TNF-treated cells relative to controls. Studies in IκBε-deficient mice revealed that basal nuclear expression and nuclear translocation of c-Rel at early time-points of receptor ligation were higher in IκBε-/- T and B cells, compared to wild-type. IκBε-/- mice exhibited increased lymph node cellularity and enhanced basal thymidine incorporation by lymphoid cells ex vivo. IκBε-/- T cell blasts were primed for IL-2 expression, relative to wild-type. IκBε-/- splenic B cells showed enhanced survival ex vivo, compared to wild-type, and survival correlated with basal expression of CD40 and induced expression of CD40 and BAFF-R. Enhanced basal nuclear translocation of c-Rel, and upregulation of BAFF-R and CD40 occurred despite increased IκBα expression in IκBε-/- B cells. The data imply that regulation of these c-Rel-dependent lymphoid responses is a non-redundant function of IκBε.
Paradoxical effects of tumour necrosis factor-alpha in adjuvant-induced arthritis.
Anti-tumour necrosis factor (TNF)alpha therapy is highly effective in rheumatoid arthritis and it is surprising, therefore, that a recent study showed that intraperitoneal administration of recombinant TNFalpha reduced the severity of adjuvant-induced arthritis and decreased IFNgamma expression in cultured draining lymph node cells. Furthermore, in untreated arthritic rats, maximal TNFalpha expression in draining lymph node cells coincided with spontaneous disease remission, suggesting a role for endogenous TNFalpha in recovery from arthritis. If confirmed in further studies, these findings suggest that, in addition to its well-established pro-inflammatory properties, TNFalpha may also play a disease-limiting role in this model of rheumatoid arthritis by suppressing effector T cell responses.
Collagen-induced arthritis in mice: a major role for tumor necrosis factor-alpha.
Collagen-induced arthritis is the most widely used animal model for the evaluation of novel therapeutic strategies for rheumatoid arthritis. The disease is induced by immunization of genetically susceptible strains of mice or rats with type II collagen in adjuvant. Susceptibility to collagen-induced arthritis is associated with major histocompatibility complex (MHC) class II genes, although non-MHC genes also play a role. Both B- and T-lymphocytes are important in the pathogenesis of collagen-induced arthritis, with the peak of the T-cell response occurring around the time of disease onset. Histopathological assessment of the joints of animals with collagen-induced arthritis reveal a proliferative synovitis with infiltration of polymorphonuclear and mononuclear cells, the formation of an erosive pannus, cartilage degradation, and fibrosis. As in human rheumatoid arthritis, a number of both pro- and anti-inflammatory cytokines are expressed in the joints of mice with collagen-induced arthritis, including tumor necrosis factor-alpha (TNFalpha) and interleukin (IL)-1beta, IL-6, IL-1Ra, IL-10, and transforming growth factor beta. The use transgenic and knockout strains of mice, as well as biological inhibitors, have revealed important pathological roles for multiple cytokines. Of these, TNFalpha emerged as a valid therapeutic target for rheumatoid arthritis and this led to the setting up of clinical trials of anti-TNFalpha antibody therapy. Three anti-TNFalpha biologics(infliximab, etanercept, and adalimumab) are now approved for use and TNFalpha blockade therefore represents an important advance in our ability to treat rheumatoid arthritis.
Collagen-induced arthritis in mice.
Collagen-induced arthritis in mice has been widely used to address questions of disease pathogenesis and to validate therapeutic targets for human rheumatoid arthritis. Arthritis is normally observed about 3 wk after immunization with autologous or heterologous type II collagen in complete Freund's adjuvant and susceptibility to the disease is strongly associated with major histocompatibility complex class II genes. The development of collagen-induced arthritis is associated with strong T- and B-cell responses to type II collagen and the chief pathological features of the disease include a proliferative synovitis with infiltration of polymorphonuclear and mononuclear cells, pannus formation, cartilage degradation, erosion of bone and fibrosis. Proinflammatory cytokines, such as tumor necrosis factor-alpha and interleukin--1beta, are abundantly expressed in the arthritic joints of mice with collagen-induced arthritis and, as in human rheumatoid arthritis, blockade of these molecules is effective in reducing the severity of disease.
Pathogenesis and therapy of rheumatoid arthritis.
Rheumatoid arthritis is a chronic disabling disease affecting at least 1% of the population on a worldwide basis. Research aimed at understanding the pathogenesis of this disease led to the identification of TNFalpha as a major pro-inflammatory cytokine expressed in the inflamed joints of patients with rheumatoid arthritis. Subsequently, in vitro studies provided evidence to suggest that TNFalpha played an important role in driving the expression of additional pro-inflammatory cytokines, such as IL-1, GM-CSF, IL-6, and IL-8, in synovial cell cultures. Another important finding that confirmed the pathological significance of TNFalpha was that mice genetically engineered to overexpress TNFalpha spontaneously developed arthritis. Subsequently, the therapeutic effect TNFalpha blockade was tested in animal models prior to clinical trials in human patients, which provided unequivocal verification of the validity of TNFalpha as a therapeutic target. Anti-TNFalpha therapy is now accepted as a fully-validated treatment modality for rheumatoid arthritis.
Anti-TNF therapy: where have we got to in 2005?
The blockade of TNF has had significant impact on the therapy of a number of chronic autoimmune diseases. In this chapter we review the concepts leading up to this therapy in rheumatoid arthritis (RA), how it spreads into other autoimmune diseases, and how greater understanding of its use has led to augmented therapeutic benefit. There are still many limitations, but the prospects for the future are intriguing.
Collagen-induced arthritis as a model for rheumatoid arthritis.
Collagen-induced arthritis (CIA) is an animal model of rheumatoid arthritis (RA) that is widely used to address questions of disease pathogenesis and to validate therapeutic targets. Arthritis is normally induced in mice or rats by immunization with autologous or heterologous type II collagen in adjuvant. Susceptibility to collagen-induced arthritis is strongly associated with major histocompatibility complex class II genes, and the development of arthritis is accompanied by a robust T- and B-cell response to type II collagen. The chief pathological features of CIA include a proliferative synovitis with infiltration of polymorphonuclear and mononuclear cells, pannus formation, cartilage degradation, erosion of bone, and fibrosis. As in RA, pro-inflammatory cytokines, such as tumor necrosis factor alpha(TNFalpha) and interleukin (IL)-1beta, are abundantly expressed in the arthritic joints of mice with CIA, and blockade of these molecules results in a reduction of disease severity.
Tumour necrosis factor alpha as a therapeutic target for immune-mediated inflammatory diseases.
Preclinical studies have identified and validated tumour necrosis factor alpha (TNFalpha) as a key disease molecule and therapeutic target for immunotherapeutic intervention in many immune-mediated inflammatory diseases. Clinical indications include rheumatoid arthritis, Crohn's disease, ankylosing spondylitis and psoriasis. Recent clinical findings indicate that many chronic inflammatory disorders share certain pathogenic pathways, whereas others are limited to particular disease phenotypes. Better understanding of these pathogenic pathways will inform the development of new therapeutic approaches leading to more complete and sustained disease remissions.
Kynurenine metabolism in health and disease.
Kynurenine is a small molecule derived from tryptophan when this amino acid is metabolised via the kynurenine pathway. The biological activity of kynurenine and its metabolites (kynurenines) is well recognised. Therefore, understanding the regulation of the subsequent biochemical reactions is essential for the design of therapeutic strategies which aim to interfere with the kynurenine pathway. However, kynurenine concentration in the body may not only be determined by the efficiency of kynurenine synthesis but also by the rate of kynurenine clearance. In this review, current knowledge about the mechanisms of kynurenine production and routes of its clearance is presented. In addition, the involvement of kynurenine and its metabolites in the biology of different T cell subsets (including Th17 cells and regulatory T cells) and neuronal cells is discussed.
Remission of collagen-induced arthritis is associated with high levels of transforming growth factor-beta expression in the joint.
Immunization of genetically susceptible strains of mice with heterologous type II collagen leads to the induction of a self-limiting polyarthritis that begins to subside around 10 days after onset of clinical disease. The aims of this study were to compare pro- and anti-inflammatory cytokine expression in the joints during the course of arthritis in order to identify cytokines involved in spontaneous remission of arthritis. DBA/1 mice were immunized with type II collagen and an immunohistochemical analysis of expression of proinflammatory cytokines [tumour necrosis factor (TNF)-alpha, interleukin (IL)-1beta and IL-6] and anti-inflammatory cytokines [IL-10, IL-1ra, transforming growth factor (TGF)-beta1, TGF-beta2 and TGF-beta3] in joints was carried out over the course of the disease. Both pro- and anti-inflammatory cytokines were found to be expressed in early arthritis. However, around 10 days after onset of arthritis, the level of expression of proinflammatory cytokines declined while the level of expression of anti-inflammatory cytokines, particularly TGF-beta1 and TGF-beta2, increased. Surprisingly, TNF-alpha continued to be expressed at low levels during the period of disease remission (30 days after onset). Blockade of TNF-alpha during the period of disease remission had no effect on TGF-beta expression. This study confirms that the level of inflammation in arthritis correlates strongly with the balance of pro- and anti-inflammatory cytokine expression in the joints. Of the anti-inflammatory cytokines studied, TGF-beta1 and TGF-beta2 predominate during the time of disease remission, suggesting that these cytokines are involved in regulating disease activity.