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Research Article Free access | 10.1172/JCI114101
Unité de Pharmacologie Cellulaire associée Unité Institut Nationale de la Santé et de la Recherche Medicale U285, Paris, France.
Find articles by Maridonneau-Parini, I. in: JCI | PubMed | Google Scholar
Unité de Pharmacologie Cellulaire associée Unité Institut Nationale de la Santé et de la Recherche Medicale U285, Paris, France.
Find articles by Errasfa, M. in: JCI | PubMed | Google Scholar
Unité de Pharmacologie Cellulaire associée Unité Institut Nationale de la Santé et de la Recherche Medicale U285, Paris, France.
Find articles by Russo-Marie, F. in: JCI | PubMed | Google Scholar
Published June 1, 1989 - More info
Glucocorticoids inhibit superoxide (O2-) generation by phagocytes through a mechanism that remains unclear. We investigated this effect by using dexamethasone on guinea pig alveolar macrophages. O2- generation was induced either by the calcium ionophore A23187, a potent stimulus of phospholipase A2, or by the protein kinase C activator, phorbol myristate acetate (PMA). Dexamethasone inhibited O2- generation initiated by A23187 by 50-55%. This inhibition required: (a) more than 45 min incubation and was maximal after 2 h; (b) glucocorticoid receptor occupancy; and (c) protein synthesis. The inhibitory effect of dexamethasone could not be explained by an interaction with the respiratory burst enzyme NADPH oxidase since O2- generation was only weakly affected upon PMA stimulation. Lipocortin I, a glucocorticoid inducible and phospholipase A2 inhibitory protein, inhibited O2- generation initiated by A23187 but failed to modulate the respiratory burst activated by PMA. These results were obtained with lipocortin I purified from mouse lungs, human blood mononuclear cells, and with human recombinant lipocortin I. We propose that lipocortin I is capable of inhibiting the activation of NADPH oxidase only when membrane signal transduction involves phospholipase A2. By mimicking the effect of dexamethasone, lipocortin I may extend its potential anti-inflammatory action to the partial control of the formation of oxygen reactive species by phagocytes.