Three families of cell-adhesion molecules (CAMs) have been implicated in mediating interactions of platelets, endothelial cells, and leukocytes: the selectins, the integrins and the immunoglobulin superfamily. The selectin family of molecules comprising E-, L-, and P-selectin act in concert with other cell adhesion molecules to effect adhesive interactions of platelets, endothelial cells, and leukocytes. Extensive literature is available implicating cell adhesion molecules in diverse disease processes including reperfusion injury, cancer, coronary heart disease, atherosclerosis, restenosis after coronary angioplasty, and chronic inflammatory diseases like asthma and IBD.
The emigration of white blood cells to inflammatory sites requires at least four steps: leukocyte rolling along activated endothelium, leukocyte activation, firm adhesion and transendothelial migration. Interaction of the selectins with their carbohydrate ligands seems to be important for the initial binding of the leukocytes to the endothelium under conditions of fluid shear stress. Subsequent firm adhesion and extravasation seems to be mediated by another family of molecules, the β2 (CD 18)-integrins. A number of soluble mediators like IL-1β, TNF, endotoxin, thrombin and histamine can up regulate one or more endothelial adhesion molecules. The major adhesion receptors and ligands regulating leukocyte-endothelium interactions include ICAM-1, ICAM-2/LFA-1; VCAM/VLA-4; L-selectin/GlyCAM-1; CD 34, MAdCAM-1; E-selectin/ESL-1, PSGL-1; P-selectin/PSGL1
Genetic experiments involving construction and testing of mice deficient in each of these selectins suggest that they provide overlapping, but crucial contributions to leukocyte recruitment in inflammation. Mice lacking each of these selectins exhibit defects in neutrophil rolling and extravasation. Further, mice deficient in both E and P selectin present extreme leukocytosis, elevated cytokine levels and alterations in haematopoesis.
Platelet P-selectin may also play a very important role in both hemostasis and the ensuing inflammatory reaction. Platelets are rapidly recruited to the site of the vascular injury to prevent excessive bleeding. The interaction of platelets with the vessel wall is a crucial event leading to the formation of a hemostatic plug. The role of platelet P-selectin in hemostasis was confirmed in a recent study which showed that platelets roll on stimulated endothelium expressing P-selectin in vivo. Furthermore, bleeding time was prolonged by 40% in P-selectin deficient mice.
Today the treatment of inflammatory conditions include treatment using steroids which negatively affect the immuno defence system and leads to a total inhibition of the inflammation, where it is of interest and importance to control the inflammatory regulating system.
WO 96/01115 relates to pyrimidine nucleotide precursors for treatment of systemic inflammation and encompasses uridine. The systemic inflammations are caused by bacterial sepsis.
Inflammation is a common feature in the pathogenesis of numerous diseases. Inflammation is normally localized defensive response to invasion of the host by foreign material. Inflammation can be caused by a wide variety of agents including mechanical trauma, toxins, and neoplasia and is not a response reserved exclusively for basal infections. The accumulation and subsequent activation of leukocytes are, however, central events in the pathogenesis of virtually all forms of inflammation.
The knowledge of a protective effect of uridine in bacterial sepsis does not automatically lead to the deduction that uridine could benefit in inflammation caused by other agents. Similarly, although it is known that bacterial sepsis can lead to coagulation problems, a number of bleeding disorders are associated with platelet dysfunction without a concomitant bacterial infection. Since bacteria are not involved in the etiology of a number of diseases. covered by the present use including reperfusion injury, cancer, coronary heart disease. arteriosclerosis, restenosis after coronary angioplasty, and chronic inflammatory diseases like asthma, rheumatoidal diseases like rheumatoid arthritis, and IBD.
Rational Behind Random In Vitro Screening
Since initial binding of leukocytes to endothelium initiates the inflammatory process, it has been utilised in an vitro system to study the adhesion of various cells to human umbilical cord endothelial cells. The method is well established and has been successfully utilised by a number of research groups. This in vitro static adhesion assay has been used herein for random screening of substances that can block leukocyte adhesion to endothelial cells. A variety of substances were tested as literature has shown that a number of, both, carbohydrate and non-carbohydrate structures can block interaction of selectins with cognate ligands. Substances that can block interaction of endothelial adhesion molecules with cognate ligands on leukocytes have potential as novel, selective inhibitors of acute and chronic inflammatory reactions and ischemia reperfusion states, without risk of general immuno suppression.