The JAK inhibitor tofacitinib suppresses synovial JAK1-STAT signalling in rheumatoid arthritis
Ann Rheum Dis. 2014 Nov 14. pii: annrheumdis-2014-206028. doi: 10.1136/annrheumdis-2014-206028. [Epub ahead of print]
Targeting intracellular pathways such as JAK/STAT represents a novel approach to the treatment of RA. Tofacitinib is an oral JAK inhibitor, proven to be effective in the treatment of RA, yet the pathways affected by tofacitinib and the effects on gene expression in situ are unknown. In this study, Boyle et al. tested the hypothesis that tofacitinib targets cytokine signalling critical to the pathogenesis of rheumatoid synovitis by investigating tofacitinib effects on synovial pathobiology.
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July 2014
Nociceptive sensory neurons drive interleukin-23-mediated psoriasiform skin inflammation
Nature. 2014;510(7503):157–161.
The abnormal activation of skin immune cells, such as dermal dendritic cells (DDCs) and interleukin (IL)-17-producing γδ T (γδT17) cells, by IL-23 is known to provoke psoriasis-type inflammation. What is less well known is how peripheral nerves regulate cutaneous immune responses. In this study, IL-23-dependent psoriasis-like inflammation was induced in mice to help determine the precise molecular mechanism of neuroimmune communication in the skin. Findings indicate nocic...
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June 2014
Differential regulation of anti-inflammatory genes by p38 MAP kinase kinase 6
Journal of Inflammation 2014, 11:14
Several p38α inhibitors have been developed and evaluated in RA. However, despite pre-clinical data showing promise, the compounds have been shown to have little therapeutic efficacy. Previous studies have suggested this may be a result of inhibitors blocking the role of p38 in limiting inflammation. Previous studies by the same authors have shown that the targeting of MKK3 or MKK 6, which are the upstream activators of p38, may be superior to p38 blockade as the anti-inflammatory effects ...
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Alternative p38 MAPKs Are Essential for Collagen-Induced Arthritis
Arthritis and Rheumatology Vol66, No. 5, May2014 pp 1208-1217
MAPK family proteins are regulatory proteins, affecting processes such as synthesis and release of proinflammatory molecules which contribute to the pathogenesis of RA. In particular, the p38 MAPK protein family is central to proinflammatory cytokine production. There are four member of the p38 group; p38α, p38β, p38γ and p38δ. This study sought to evaluate p38γ and p38δ deficiency in mice CIA model. In p38γ-/- or p38δ-/- mice, the percentage of mic...
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Mechanism of Activation of Protein Kinase JAK2 by the Growth Hormone Receptor
Science 344, 2014; doi: 10.1126/science.1249783
Class I cytokine receptors are key regulators of many processes within the body. The receptors use the JAK-STAT signalling pathway, the deregulation of which causes it to become an important pathway in oncogenesis. Despite this, the processes responsible for JAK2 activation by class I receptors remains elusive. Previous studies using growth hormone and its receptor have led to a model of receptor activation where hormone induced receptor dimerization resulted in close proximity of the receptor i...
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Structure of the pseudokinase-kinase domains from protein kinase TYK2 reveals a mechanism for Janus kinase (JAK) autoinhibition
Proc Natl Acad Sci U S A. 2014 May 19. pii: 201401180. [Epub ahead of print]
The JAK family of kinases (JAK1, JAK2, JAK3 and TYK2) are receptor-associated tyrosine kinases that act downstream of many cytokines and interferons. Recent studies have provided structural information about the kinase and pseudokinase domains of JAKs however the molecular mechanism by which JAK activity is regulated by the pseudokinase domain is poorly understood. This study builds on a recent finding that the N terminus of the JAK1 pseudokinase group may act as a switch for kinase activation b...
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Structural basis for the recognition of interferon-α receptor by tyrosine kinase 2
Nat Struct Mol Biol. 2014 May;21(5):443-8. doi: 10.1038/nsmb.2807. Epub 2014 Apr 6
Janus kinases, JAKs, are essential in the mediation of cytokine and interferon signalling whilst also being crucial to body processes such as immune function, hematopoeises, metabolism and cellular growth. However, it is not known is how the four members of the JAK family interact with and are activated by over 30 cytokine receptors with near perfect affinity and specificity. Currently, there are no crystal structures available for any JAK bound to a cytokine receptor. This study sought address ...
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May 2014
JAK2-STAT3 Blockade by AG490 Suppresses Autoimmune Arthritis in Mice via Reciprocal Regulation of Regulatory T cells and Th17 cells
J Immunol 2014; 192:4417-4424
In this study, Park et al sought to investigate the effects of the JAK2 inhibitor, AG490 in RA. Using murine CIA models, both preventative and therapeutic models were investigated. In the preventative model, CIA mice treated with AG490 showed a significantly lower incidence rate of arthritis and arthritic scores when compared to mice injected with vehicle. In the therapeutic model, as in the preventative, AG490 treated mice exhibited less severe arthritis. Through further experiments, it was dem...
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Blocking the janus-activated kinase pathway reduces tumor necrosis factor alpha-induced interlukin-18 bioactivity by caspase-1 inhibition
Arthritis Research and Therapy 2014,16:R102
IL-18, a member of the IL-1 family, has been shown to play an important role in immune response and is involved in the pathogenesis of RA. The study objective was to examine the role of the JAK pathway in modulating TNFa-induced-IL18 bioactivity by reducing caspase-1 function. Caspase-1 is the protease that cleaves pro-IL-18 to IL-18, thereby activating it. In testing it was noted that by blocking the JAK pathway significantly decreased caspase-1 transcription, expression and activity showing th...
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Btk inhibition suppresses agonist-induced human macrophage activation and inflammatory gene expression in RA synovial tissue explants
Ann Rheum Dis Published Online First 24 April 2014 doi:10.1136/annrheumdis-2013-204143
Bruton’s tyrosine kinase, a downstream target of PI3K signalling, has been shown to be crucial in the B lymphocyte and myeloid cell contribution to murine models of arthritis. Synovial tissue samples were taken from biologically naïve RA (n=16) and PsA (n=12) patients in order to assess the expression of BTK. Separate RA synovial explants (n=8) were used to assess the effects of the specific BTK inhibitor RN486. BTK was expressed at equivalent levels in both RA and PsA synovial tissue, however e...