ABSTRACT
BACKGROUND AND OBJECTIVE: Eosinophil is a major inflammatory cell in allergic diseases and parasitic infestations. Various cytokines such as GM-CSF, IL-3 and IL-5 are known to activate eosinophils and prolong their survival. Among them, IL-5 is the most potent stimulator of eosinophil survival. Recently, it was reported that increased expression of Bcl-2 is related to prolonged survival of IL-5 stimulated eosinophil. Theophylline is a useful drug in bronchial asthma, due not only to bronchial dilation but also to its anti-inflammatory effects. It has been suggested that anti inflammatory action of theophylline derives from the reduction of inflammatory cells in the airways which is mechated by stimulat on of apoptosis of inflammatory cells. In this study, we investigated, by measuring Bcl-2 expression of IL-5 stimulated eosinophil, the effect of theophylline on apoptosis as one of the anti-inflammatory action. MATERIAL AND METHOD: Peripheral eosinophils were isolated from atopic patients by using Perco- 11 discontinuous gradient and purified by negative selection technique using MACS. Eosinophil viability and apoptosis were measured by FACscan. Expression of Bcl-2 protein in eosinophils was detected by Western blot and ELISA. RESULTS: IL-5 increased the percentage of viable eosinophils and reduced the apoptosis of eosinophils in a dose dependent manner. The increased survival of IL-5 stimulated eosinophils was reduced by theophylline via activation of apoptosis. Bcl-2 was increased when eosinophils were cultured with IL-5 only, but when theophylline was cocultured, reduced Bcl-2 was seen with Western blot and ELISA. CONCLUSION: IL-5 increases the survival of eosinophil through the enhanced expression of Bcl- 2. Theophylline has counter action against IL-5 via inhibition of Bcl-2 induced by IL-5. Inhibiting the prolongation of eosinophil survival caused by IL-5 might be one possible mechanism of antiinflammatory effects of theophylline.