Rheumatoid Arthritis: Clark JM

Nagy G, Clark JM, Buzás EI, Gorman CL, Cope AP. · Department of Rheumatology, Semmelweis University, Medical School, Arpád fejedelem u.7, 1023 Budapest, Hungary. · Immunol Lett. · Pubmed #17568690 No free full text.

Abstract: Whilst many physiological functions of nitric oxide (NO) have been revealed so far, recent evidence proposes an essential role for NO in T lymphocyte activation and signal transduction. NO acts as a second messenger, activating soluble guanyl cyclase and participating in signal transduction pathways involving cyclic GMP. NO modulates mitochondrial events that are involved in apoptosis and regulates mitochondrial biogenesis in many cell types, including lymphocytes. Several studies undertaken on patients with RA and SLE have documented increased endogenous NO synthesis, although the effects of NO may be distinct. Here, we discuss recent evidence that NO contributes to T cell dysfunction in both SLE and RA by altering multiple signaling pathways in T cells. Although NO may play a physiological role in lymphocyte cell signaling, its overproduction may perturb T cell activation, differentiation and effector responses, each of which may contribute in different ways to the pathogenesis of autoimmunity.

Zhang Z, Gorman C, Clark JM, Cope AP. · Kennedy Institute of Rheumatology Division, Faculty of Medicine, Imperial College, London, United Kingdom. · Wien Med Wochenschr. · Pubmed #16465609 No free full text.

Abstract: Technology has advanced to the stage where it is now possible to identify genes that confer low to moderate risk of developing autoimmune diseases such as rheumatoid arthritis (RA). This has been facilitated by the growing appreciation that these hard to detect genetic signals can only be defined in large cohorts of well characterized patients. In RA, the association between disease susceptibility and genes encoded within the MHC has been known for decades. Recent studies have identified several new candidate genes that provide further insights into the molecular nature of aberrant immune responses in chronic inflammatory diseases. Here, we describe some of these new genes. Based on their known functions we propose that in a subgroup of patients with RA inheritance of allelic variants at distinct loci could lead to dysregulation of adaptive immune responses characterized by chronic, low-amplitude signaling transduced by antigen T cell receptors.

Isomäki P, Clark JM, Panesar M, Cope AP. · Institute of Medical Technology, Tampere University and Department of Internal Medicine, Tampere University Hospital, Tampere, Finland. · Curr Drug Targets Inflamm Allergy. · Pubmed #16101535 No free full text.

Abstract: Immune and inflammatory responses are governed by antigen-specific T cells, whose activation, differentiation and effector function are induced by signals delivered via the T cell antigen receptor (TCR) and by costimulatory and cytokine receptors. The molecular events leading to the activation of naïve T cells have been extensively studied and are well characterized. Much less is known about the molecular and biochemical events regulating the activation of T cells in chronic inflammatory diseases such as rheumatoid arthritis (RA). This review examines the current state of knowledge of T cell activation in chronic inflammation, focusing on RA, and summarizes experimental data which indicate that the chronic inflammatory process may profoundly affect TCR and cytokine signal transduction pathways. We present evidence suggesting that in chronic inflammation, the antigen-driven TCR-mediated processes are attenuated, while cytokine-driven effector responses are sustained or even enhanced. The possible implications of this inbalance are discussed.

Nagy G, Clark JM, Buzas E, Gorman C, Pasztoi M, Koncz A, Falus A, Cope AP. · Department of Rheumatology, Semmelweis University, Medical School, Budapest, Hungary. · Immunol Lett. · Pubmed #18396335 No free full text.

Abstract: Experimental and clinical evidence for T cell involvement in the pathology of rheumatoid arthritis (RA) is compelling, and points to a local dysregulation of T cell function in the inflamed joint. Nitric oxide (NO) has been shown to regulate T cell function under physiological conditions, but overproduction of NO may contribute to lymphocyte dysfunction characteristic of RA. Several investigations in patients with RA have documented evidence of increased NO synthesis, but these studies have focused largely on macrophage-derived NO and its impact on innate immune and inflammatory responses. In this study, we set out to explore the contribution that T cells make to NO production. We find that T cells from RA patients produce >2.5 times more NO than healthy donor T cells (p<0.001). Although NO is an important physiological mediator of mitochondrial biogenesis, mitochondrial mass is similar in RA and control T cells. In contrast, increased NO production is associated with increased cytoplasmic Ca(2+) concentrations in RA T cells (p<0.001). In vitro treatment of human peripheral blood lymphocytes, or Jurkat cells with TNF increases NO production (p=0.006 and p=0.001, respectively), whilst infliximab treatment in RA patients decreases T cell derived NO production within 6 weeks of the first infusion (p=0.005). Together, these data indicate that TNF induced NO production in T lymphocytes may contribute to perturbations of immune homeostasis in RA.