Function of bcl-X proteins in Nitric Oxide-induced Apoptosis in RAW 264.7 Macrophages

Paik, Sang Gi; Kim, Young Sang; Im, Joo Young; Yoon, Jeong Heon

Abstract

LPS and IFN-r induce nitric oxide synthase in macrophages and the resultant NO causes apoptotic cell death in the activated macrophages. NO production and apoptosis were inhibited by N-monomethyl L-arginine (NMMA), a competitive inhibitor of NO synthase. To study the role of BCL-X proteins, RAW 264.7 cells were transfected with the expression vectors with human bcl-Xl or bcl-Xs cDNAs, respectively. Stable transfectants were selected and confirmed by RT-PCR. NO production in response to LPS and IFN-r caused apoptosis in RAW 264.7 cells and vector transfected control cells within 24 hr. Both NO production and apoptosis were inhibited by N(G)-monomethyl L-arginine (NMMA). In contrast, bcl-Xs transfectant appeared slightly susceptible and bcl-X(L)< transfectant appeared slightly resistant, although NO production was similar to control cells. These results suggest that bcl-X proteins play roles in both positive and negative regulation of apoptosis induced by NO.