Glucocorticoids and stress: permissive and suppressive actions.

Protection against stress by glucocorticoids is discussed in relation to their permissive and suppressive actions. Evidence from the last decade is summarized regarding the physiological nature of the suppressive actions, and the hypothesis that they prevent stress-activated defense mechanisms from overshooting and damaging the organism. Support for this hypothesis has come from observations on how endogenous or administered glucocorticoids control inflammatory and immune responses, protect in endotoxic and hemorrhagic shock, regulate central nervous system responses to stimuli, and moderate many defense reactions through suppression of cytokines and other mediators. Studies showing that glucocorticoids permissively induce receptors for several mediators that they suppress have led to a model in which stimulated activity of a mediator system is increased permissively through induction of mediator receptors and decreased through suppression of mediator production.