EFFECTS OF DIRITHROMYCIN AND ERYTHROMYCYLAMINE ON HUMAN NEUTROPHIL DEGRANULATION

Dirithromycin and, to a lesser extent, erythromycylamine and erythromy cin directly induced the release of three intragranular enzymes (lysoz yme, lactoferrin, and beta-glucuronidase) from unstimulated human neut rophils. Macrolide-induced enzyme release was dependent upon the incub ation time (30 to 180 min) and drug concentration. Dirithromycin was t he most effective. At 120 min, release of lysozyme, beta-glucuronidase , and lactoferrin by macrolide (100 mu g/ml)-treated cells, expressed as a percentage of total enzyme content, was, respectively, 58% +/- 8. 3%, 52% +/- 10.7%, and 35% +/- 5.1% (dirithromycin); 42% +/- 3.9%, 28% +/- 5.8%, and 10% +/- 2.2% (erythromycylamine); and 35% +/- 4.0%, 19% +/- 4.3%, and 10% +/- 5.2% (erythromycin) (mean +/- standard error of the mean of three to eight experiments). The lowest macrolide concent rations which induced significant enzyme release were 10, 100, and 25 mu g/ml, respectively, for dirithromycin, erythromycylamine, and eryth romycin. Furthermore, we obtained evidence of a link between the prode granulation effects of dirithromycin and erythromycylamine and the int ragranular location of these drugs. Indeed, cell associated drug level s increased for up to 60 min and then plateaued and declined substanti ally. Increasing the pH from 7 to 9 resulted in a parallel increase in drug uptake and the prodegranulation effect. Finally, when macrolide- treated neutrophils were disrupted by sonication and centrifuged, a co rrelation was found between lysozyme and beta-glucuronidase activities (both granule markers) and pellet-associated macrolide levels, Taken together, our results suggest that dirithromycin and erythromycylamine concentrate within neutrophil granules and then induce degranulation.