Prevention of IL-3 Deprivation Induced Apoptosis in Mast Cells by LPS

Jeong, Seung Hun; Kim, Tae Hyun; Kim, Hyung Min; Shibayama, Hirohiko; Yoo, Young Hyun

Abstract

Mast cells play a protective role in host defense against bacteria, and are found in high number at the host-environment interface. Stimulation of mast cells by bacterial cell wall components is essential for their protective effects against entero-bacterial infection. Mast cells have an extraordinarily long longevity in peripheral tissues compared to other types of blood cells. We undertook this study to reveal the mechanism underlying the prevention on IL-3 deprivation-induced apoptosis in mast cells by LPS. Bone marrow derived mast cells (BMMCs) were obtained from femurs of BALB/c mice and cultured under IL-3 stimulation for 4-6 weeks. At the same point when IL-3 was depleted, BMMCs were treated with LPS. To examine the effect of LPS, DNA electrophoresis, Western blotting, immunoflourescense staining, confocal microscopy, RT-PCR and immunoprecipitation were conducted. IL-3 deprivation reduced cellular viability and induced nuclear condensation and translocation of apoptosisassociated factors. However, LPS treatment prevented these IL-3 deprivation-induced apoptotic events. IL-3 deprivation downregulated representative antiapoptotic factors such as XIAP, 14-3-3, Bcl-2 and Bcl-xL. Expression level of these factors was maintained in BMMCs treated by LPS, which was similar to the level in the control cells. The Bim to Bcl-2 interaction was increased in IL-3 depleted cells, which was prevented by LPS treatment. It was also demonstrated that LPS induced the new expression of a cytokine-induced antiapoptotic factor anamorsin gene in BMMCs under IL-3 deprived condition. Taken together, LPS prevents IL-3 deprivation induced apoptosis in BMMCs via several antiapoptotic factors. This preventive mechanism of LPS on BMMCs apoptosis may contribute the long longevity of mast cells in the peripheral tissue.