Augmentation of apoptosis in bronchial exuded rat eosinophils by cyclosporin A

The effect of cyclosporin A on apoptosis in eosinophils was examined to clarify the inhibitory mechanisms of cyclosporin A on allergen-induced eosinophilia in the airway. Eosinophils in bronchoalveolar lavage fluid from sensitized rats after inhaling an allergen were used. More than 50% of the eosinophils that died spontaneously by apoptosis within 24 hour incubation in RPMI 1640 medium contained 10% fetal calf serum. The addition of cyclosporin A or dexamethasone significantly enhanced the eosinophils apoptosis at concentrations of more than 0.1 microM. Apoptosis in eosinophils was considerably suppressed in the presence of culture supernatant of activated splenocytes as a source of various cytokines. Even in the presence of culture supernatant of activated splenocytes, cyclosporin A or dexamethasone facilitated apoptosis in eosinophils. These results suggest that apoptotic death of activated eosinophils is augmented with cyclosporin A and that accelerated apoptosis in eosinophils of the airway may account for the inhibitory effect of cyclosporin A on eosinophilia.