The role of prostaglandins in allergic inflammation

: Prostaglandins likewise leukotriens are proinflammatory mediators resulting from metabolic degradation of the arachidonic acid originating from membrane phospholipids. The most important products of enzyme cyclooxygenation of arachidonic acid are prostaglandins D2, E2, F2a, tromboxane A2 and prostacyclin. Prostaglandins express their tissue effects via the five basic receptor types. Within the allergic inflammation activated mast cell synthesizes prostaglandin D2 (first lipid mediator) which has bronchoconstrictive and vasodilating effects and attracts neutrophilic leukocytes. Moreover, it also participates in the late phase reactions, six hours subsequent to the exposure to the allergen. This mediator is also important in pathogenesis of urticaria, allergic rhinitis and allergic bronchial asthma. In addition to prostaglandin D2, prostaglandin F2a and tromboxane A2 also have bronchoconstrictive actions, while prostacyclin and prostaglandin E have bronchodilating effects. Inhalation of prostaglandin E prevents asthmatic attacks caused by allergens, strain, metabisulfite and ameliorates attacks of aspirin asthma, which confirms the hypothesis that aspirin asthma is based on cyclooxigenase inhibition and increased leukotriene production. In patients with atopic dermatitis, prostaglandin E has suppressive effects on Interferon gamma production by Th1 helper cells and increases production of Interleukin 4 by the Th2 cells. Tromboxane A2 plays a certain role in the development of bronchial hyperreactivity and late asthmatic response. Prostaglandins are also important mediators in the pathogenesis of allergic conjunctivitis. Most of nonsteroidal antiinflammatory drugs inhibit the enzyme cyclooxygenase and thus also prostaglandin biosynthesis and release.