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Pathway Description
Azelastine H1 Antihistamine Smooth Muscle Relaxation Action Pathway
Homo sapiens
Drug Action Pathway
Azelastine is a histamine H1-receptor antagonist used intranasally to treat allergic and vasomotor rhinitis and in an ophthalmic solution to treat allergic conjunctivitis. H1-antihistamines interfere with the agonist action of histamine at the H1 receptor and are administered to attenuate inflammatory process in order to treat conditions such as allergic rhinitis, allergic conjunctivitis, and urticaria. H1-antihistamines act on H1 receptors in T-cells to inhibit the immune response, in blood vessels to constrict dilated blood vessels, and in smooth muscles of lungs and intestines to relax those muscles.
H1-antihistamines interfere with the agonist action of histamine at the H1 receptor and are administered to attenuate inflammatory process in order to treat conditions such as allergic rhinitis, allergic conjunctivitis, and urticaria. H1-antihistamines act on H1 receptors in T-cells to inhibit the immune response, in blood vessels to constrict dilated blood vessels, and in smooth muscles of lungs and intestines to relax those muscles. Allergies causes blood vessel dilation which causes swelling (edema) and fluid leakage. Azelastine also inhibits the H1 histamine receptor on bronchiole smooth muscle myocytes. This normally activates the Gq signalling cascade which activates phospholipase C which catalyzes the production of Inositol 1,4,5-trisphosphate (IP3) and Diacylglycerol (DAG). Because of the inhibition, IP3 doesn't activate the release of calcium from the sarcoplasmic reticulum, and DAG doesn't activate the release of calcium into the cytosol of the endothelial cell. This causes a low concentration of calcium in the cytosol, and it, therefore, cannot bind to calmodulin.Calcium bound calmodulin is required for the activation of myosin light chain kinase. This prevents the phosphorylation of myosin light chain 3, causing an accumulation of myosin light chain 3. This causes muscle relaxation, opening up the bronchioles in the lungs, making breathing easier.
References
Azelastine H1 Antihistamine Smooth Muscle Relaxation Pathway References
Wishart DS, Feunang YD, Guo AC, Lo EJ, Marcu A, Grant JR, Sajed T, Johnson D, Li C, Sayeeda Z, Assempour N, Iynkkaran I, Liu Y, Maciejewski A, Gale N, Wilson A, Chin L, Cummings R, Le D, Pon A, Knox C, Wilson M: DrugBank 5.0: a major update to the DrugBank database for 2018. Nucleic Acids Res. 2018 Jan 4;46(D1):D1074-D1082. doi: 10.1093/nar/gkx1037.
Pubmed: 29126136
Overington JP, Al-Lazikani B, Hopkins AL: How many drug targets are there? Nat Rev Drug Discov. 2006 Dec;5(12):993-6. doi: 10.1038/nrd2199.
Pubmed: 17139284
Imming P, Sinning C, Meyer A: Drugs, their targets and the nature and number of drug targets. Nat Rev Drug Discov. 2006 Oct;5(10):821-34. doi: 10.1038/nrd2132.
Pubmed: 17016423
Dorsch W, Hintschich C, Neuhauser J, Weber J: Sequential histamine inhalations cause increased bronchial histamine reactivity in guinea pigs: role of platelets, thromboxanes and prostacyclin. Naunyn Schmiedebergs Arch Pharmacol. 1984 Sep;327(2):148-55. doi: 10.1007/BF00500910.
Pubmed: 6387510
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