[Mechanism of action and effects of corticoids in asthma]

The value of oral or inhaled glucocorticoids (GCS) in asthma is well recognized. Their use has remained empirical for a long time. However, some progress has been achieved recently in the understanding of their general mode of action and of their bronchial effects suggesting that in the near future ther may be some new therapeutic perspectives. The fundamental action of GCS involves a close intracellular interaction between the specific glucocorticoid hormone receptor and the cellular genome which results in the activation of the genes coding the proteins responsible for the phenotypic response of the cell and thus for their biological action. The place of the extra-genomic mechanisms remains ill understood. The immunomodulating action of GCS is difficult to dissociate from their anti-inflammatory and anti-allergic effects which seem to predominate in asthma. They inhibit all stages of the inflammatory reaction in acting on the key mediators of the inflammatory response, the pharmacologically active lipids (LPA: prostaglandins, leukotrienes, PAF-acether) which are a result of the catabolism of arachidonic acid which occurs during the course of membrane activation. The phospholipid A2 (PLA2), a membrane enzyme responsible for the splitting of the phospholipids in the presence of calcium and leading to the liberation of LPA is the driving force of the reaction in such a way that the products of the nuclear activation subsequently reactivated. GCS is considered as a natural modulator of inflammation, inducing the synthesis of lipocortin, an inhibitory protein of PLA2, which explains the blockage in the generation of LPA and thus the inflammatory reaction. The regulation of the activity of these or of the lipocortin seems to lead to the intervention of the phosphorylation. But numerous questions remain concerning the precise action of PLO2, the existence of endogenous lipocortin, their secretion and their extra-cellular action. In spite of these unknown facts it is not impossible to envisage a clinical potential for lipocortin, once sequenced and produced, when the pharmacological and immunological problems have been surmounted. In asthma the effect of GCS essentially involve: the inhibition of all the bronchial components of inflammation: the synthesis, liberation and peripheral action of the mediators; the oedema and mucous congestion.(ABSTRACT TRUNCATED AT 400 WORDS)