Suppressive Effect of Tranilast on Interleukin-5 Prolonged Eosinophils Survival via Apoptosis

Tranilast has long been used clinically to treat allergic diseases such as bronchial asthma. To further clarify the antiinflammatory machanism, we examined the ability of tranilast to counteract the prolongation of eosinophil survival induced by interleukin (IL)-5. Tranilast reduced the IL-5 prolonged survival of eosinophils at the concentration range of 30 μg/ml to 100 μg/ml. The DNA extracted from eosinophils cultured with tranilast showed signs of fragmentation that was comparable with apoptosis. Electron-microscopic analysis of activated eosinophils cultured with 100 μg/ml of tranilast also revealed morphologic features of apoptosis. These data suggest that tranilast may act in vivo on activated eosinophils to reduce inflammation in allergic diseases.