Steroids and asthma

Antigen-induced bronchial anaphylaxis in actively sensitized SD rats. Effects of glucocorticoid treatment

We examined the effects of glucocorticosteroids (GCS) on antigen-induced bronchial anaphylactic reactions (BAR) in SD rats immunized with ovalbumin (OA) and alum. The animals were treated with vehicle, budesonide (BUD), dexamethasone (DEX), or hydrocortisone (HC) at various times before intravenous (i.v.) antigen challenge. The drugs were administered either intraperitoneally (i.p.) or intratracheally (i.t.); the BAR was elicited by a low or by a high challenge dose of antigen. A BAR elicited by a low challenge dose of antigen was reduced in a dose-dependent way by all GCS after i.p. administration; at 1 mg/kg, BUD and DEX significantly reduced BAR and at 50 mg/kg all three of the examined compounds inhibited the BAR by 50% or more. For BUD, maximum effect was recorded when it was given 12 h before test. There was only a slight variation in the inhibitory effects of the GCS with immunization conditions of test animals. I.t. instillation of the drugs did not markedly increase their inhibitory capacity as compared to i.p. administration. BAR elicited by a high antigen dose was at best marginally affected by the GCS when given either i.p. or i.t. Thus, antigen-induced airway reactivity in rats can be reduced by GCS treatment provided that this is performed sufficiently long before the test and that the challenge dose of antigen is not too high.

Glucocorticosteroid effects on dog and rat serum complement

Inhibiting properties of glucocorticosteroids in vivo on the complement system are not fully recognized. Dexamethasone and prednisolone (10(-7)-10(-3)mol/l.) have no direct effects on serum complement of the dog, rat, human and guinea pig. Yet after subcutaneous application of dexamethasone (0.4 mg/kg) on two consecutive days to healthy beagle dogs the total functional complement is reduced to about 60% of the normal level within the next three days. This effect could be shown to be dose-dependent in male beagle dogs. Partial recovery of the depressed complement level (CH50 U/ml) occurs after the 6th day without treatment. In parallel a decrease in serum C3 is observed. The qualitative serum protein pattern documented by cellulose acetate film electrophoresis (CAF) reflects the decrease of C3 by a reduced beta 1-beta 2 level with a concomitant increase of the alpha 2 serum proteins. In contrast, serum complement, C3 and the serum CAF pattern in rats are not much altered by prednisolone (2 X 15 mg/kg s.c.) or dexamethasone (2 X 2 mg/kg s.c.). Thus the rat appears relatively insensitive to humoral changes induced by steroid alone. Altered liver protein synthesis of complement and other acute phase proteins appear responsible for the profound steroid effects observed in the dog.

Inhibitory effect of glucocorticosteroids on anti-IgE-induced histamine release from human basophilic leukocytes: evidence for a dual mechanism of action

Anti-IgE-induced histamine release from human leukocytes is inhibited when the cells before challenge are cultured overnight in the presence of glucocorticoids (GCSs). The present report suggests that the GCSs might exert their effect by at least a dual mechanism of action. Histamine release was induced by a suboptimum concentration of anti-IgE. When the release recorded in the presence of the steroid is plotted against the release recorded in its absence, the data points of several experiments fit a regression line characterized by two parameters: its slope and its intercept with the abscissa. Structure-activity examination with selected GCSs indicates that the orders of potency for affecting these two parameters are not identical. Furthermore, pulse experiments suggest that the cells require different times of contact with the steroid to express inhibition according to the two parameters. The removal of adherent cells or platelets did not markedly affect the degree of leukocyte histamine release or its inhibition by a given GCS, suggesting that the steroid interacts directly with the basophil. Finally, steroid-induced inhibition was not affected by the putative phospholipase A2-inhibitor p-bromophenacylbromide (BPB) or the 5-lipoxygenase inhibitor nordihydroguaiaretic acid (NDGA).