[Mode of action of corticoids in asthma]

Generally speaking, corticosteroids exert their effects on cells through genomic and non genomic mechanisms. They both suppress and enhance numerous biological phenomena. In asthma, corticosteroids act at different levels. They: inhibit chemical mediators, whether these are performed, like histamine, or newly formed, like arachidonic acid metabolites (prostaglandins and leukotrienes) or the platelet-activating factor (PAF); restore the sensitivity of beta-adrenergic receptors to sympathomimetic drugs; exert a powerful anti-inflammatory effect, notably reducing bronchial mucus secretion; reduce bronchial hyperreactivity and modify the bronchial response to bronchoconstrictors; act on respiratory function and gas exchanges. Many effects of corticosteroids in asthma involve the synthesis of proteins, such as lipomodulin (or macrocortin) which inhibits phospholipase A2, a key-enzyme in the synthesis of numerous chemical mediators derived from membrane phospholipids. The multiple effects of corticosteroids account for their broad spectrum of activity and their effectiveness against both acute and chronic manifestations of asthma.