NITRIC-OXIDE INDUCED POLY(ADP-RIBOSE) POLYMERASE CLEAVAGE IN RAW-264.7 MACROPHAGE APOPTOSIS IS BLOCKED BY BCL-2

Endogenously generated or exogenously supplied nitric oxide causes cle avage of poly(ADP-ribose) polymerase (PARP) and apoptotic cell death i n RAW 264.7 macrophages. With the use of NO donors such as S-nitrosogl utathione or spermine-NO we established that PARP digestion occurs in parallel with DNA fragmentation, and is preceded by accumulation of th e tumor suppressor gene product p53. PARR cleavage in response to lipo polysaccharide and interferon-gamma treatment is prevented by N-G-mono methyl-L-arginine, thus proving a NO requirement. Endogenous NO genera tion, p53 accumulation, and PARP degradation occurred prior to the det ection of significant chromatin condensation. In contrast, in stable B cl-2 transfected cells, NO-initiated PARP cleavage was almost complete ly blocked. Our data implicate PARP as a proteolytic substrate during NO-mediated apoptotic cell death in RAW 264.7 macrophages and establis h Bcl-2 as an efficient signal terminator in this process.