510 Caspase-9 is Involved in CD30 Activation Induced Eosinophil Apoptosis

Abstract

BackgroundWe evaluated whether ligation of CD30 incite the apoptosis, and investigated the mechanisms of CD30 induced eosinophil apoptosis is dependent on caspase activation.MethodsWe purified eosinophils using MACS system. Expression of CD30 on eosinophils were measured and eosinophils were cultured in the wells pretreated with anti-CD30 mAb and isotype control IgG1, IL-5 and dexamethasone in RPMI 1640 media supplemented with 10% FBS, and the apoptotic rate were measured using flow cytometry. To evaluate whether caspase-9 is involved in CD30- induced eosinophil apoptosis, the apoptotic rate was evaluated with addition of caspase-9 inhibitor and the expression of procaspase-9 was also measured using Western blot.ResultsThe apoptotic rates of eosinophils cultured in the presence of anti-CD30 mAb were significantly increased to 29.1 ± 6.1% and 47.3% ± 4.7% compared with 17.1 ± 6.7% and 29.4 ± 9.2% of the control at 4 and 24 hours, respectively (both P < 0.05). Caspase-9 inhibitor suppressed the mAb induced eosinophil apoptosis from 54.8 ± 6.9% and 71.5 ± 11.6% to 24.5 ± 6.0% and 47.8 ± 11.4% at 18 and 36 hours, respectively (both P < 0.001). We also showed the expression of procaspase-9 with the mAb was diminished compared with that of the control and of IL-5.ConclusionsThis study showed CD30 activation enhances the eosinophil apoptosis and the effect is mediated by Caspase-9 activation.