Rheumatoid Arthritis Support

It is now widely accepted that atherosclerosis is a result of cellular and molecular events characteristic of inflammation. Vascular inflammation can be caused by upregulation of Ang-II which is produced locally by inflammed vessels and induces synthesis and secretion of IL-6, a cytokine responsible for induction of angiotensinogen synthesis in liver through JAK/STAT3 pathway, which gets activated through high affinity membrane protein receptors on target cells, termed IL-6R-chain recruiting gp-130 which is associated with tyrosine kinases (Jaks 1/2, and Tyk2 kinase). Cytokines IL-4 and IL-13 gets elevated in lungs of chronically suffered asthmatics. Signalling through IL-4/IL-13 complexes is thought to occur through IL-4Rα-chain which is responsible for activation of JAK-1 and Tyk2 kinases. A role of Tyk2 in rheumatoid arthritis is directly observed in Tyk2 deficient mice which were resistant to experimental arthritis. Tyk2-/- mice displayed a lack of responsiveness to a small amount of IFN-α, but they respond normally to a high concentration of IFN-α/β. Additionally, these mice respond normally to IL-6 and IL-10, suggesting that Tyk2 is dispensable for mediating for IL-6 and IL-10 signaling and does not play a major role in IFN-α signaling. Although Tyk2-/- mice are phenotypically normal, they exhibit abnormal responses to inflammatory challenges in a variety of cells isolated from Tyk2-/- mice. The most remarkable phenotype observed in Tyk2-deficient macrophages was lack of nitric oxide production upon stimulation with LPS. Further elucidation of molecular mechanisms of LPS signaling, showed that Tyk2 and IFN-β deficiency leads resistance to LPS-induced endotoxin shock, whereas STAT1-deficient mice are susceptible. Development of a Tyk2 inhibitor appears to be a rational approach in the drug discovery.


Adapted from the Wikipedia article Tyrosine kinase 2, under the G. N. U. Free Documentation License. Please also see http://en.wikipedia.org/wiki