title: Bcl-2 protein inhibits bufalin-induced apoptosis through inhibition of mitogen-activated protein kinase activation in human leukemia U937 cells.
abstract: In a previous study, we demonstrated that bufalin, which is an active principle of Chinese medicine, chan'su, caused apoptosis in human leukemia U937 cells by anomalous activation of mitogen-activated protein kinase (MAPK) via the signaling pathway of Ras, Raf-1, and MAPK kinase-1. Here, we report the effect of overexpression of bcl-2 in U937 cells on the signaling pathway of apoptosis that is induced by bufalin. The results indicated that the apoptosis induced by bufalin in U937 cells was significantly inhibited by overexpression of the Bcl-2 protein. No significant difference was detected in the activation of MAPK kinase-1 that is induced by bufalin in wild-type or Bcl-2-overexpressed U937 cells; however, the activation of MAPK by bufalin was significantly attenuated in the cells overexpressing Bcl-2. Bufalin treatment activated activator protein-1 transcriptional activity; however, this activation was decreased to 40% in bcl-2-overexpressed U937 cells. These results indicate that Bcl-2 acts downstream of MAPK kinase-1 but upstream of MAPK and suggest that, in the signaling pathway of the apoptotic process induced by bufalin, the transcriptional activity of activator protein-1 may be down-regulated through the inhibition of MAPK activity by Bcl-2.
authors.affiliation: Laboratory of Biological Chemistry, School of Pharmaceutical Sciences, Showa University, Shinagawa-ku, Tokyo, Japan.
authors.forename: M
authors.initials: M
authors.lastname: Watabe
authors.forename: N
authors.initials: N
authors.lastname: Kawazoe
authors.forename: Y
authors.initials: Y
authors.lastname: Masuda
authors.forename: S
authors.initials: S
authors.lastname: Nakajo
authors.forename: K
authors.initials: K
authors.lastname: Nakaya
mesh_terms: D000970:Antineoplastic Agents / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects*; D002018:Bufanolides / Q000494:pharmacology*; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism*; D015870:Gene Expression; D006801:Humans; D007938:Leukemia / Q000201:enzymology; D020929:Mitogen-Activated Protein Kinase Kinases; D009000:Monocytes / Q000201:enzymology; D011494:Protein Kinases / Q000378:metabolism; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000235:genetics / Q000502:physiology*; D012333:RNA, Messenger / Q000032:analysis; D018808:Transcription Factor AP-1 / Q000378:metabolism; D014162:Transfection; D014407:Tumor Cells, Cultured
chemical_list: D000970:Antineoplastic Agents; D002018:Bufanolides; D019253:Proto-Oncogene Proteins c-bcl-2; D012333:RNA, Messenger; D018808:Transcription Factor AP-1; D011494:Protein Kinases; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D020929:Mitogen-Activated Protein Kinase Kinases; C022777:bufalin