2-Methoxyestradiol-induced apoptosis in human leukemia cells proceeds through a reactive oxygen species and Akt-dependent process.
The effects of 2-Methoxyestradiol (2ME)-induced apoptosis was examined in human leukemia cells (U937 and Jurkat) in relation to mitochondrial injury, oxidative damage, and perturbations in signaling pathways. 2ME induced apoptosis in these cells in a dose-dependent manner associated with release of mitochondrial proteins (cytochrome c, AIF), generation of reactive oxygen species (ROS), downregulation of Mcl-1 and XIAP, and inactivation (dephosphorylation) of Akt accompanied by activation of JNK. In these cells, enforced activation of Akt by a constitutively active myristolated Akt construct prevented 2ME-mediated mitochondrial injury, XIAP and Mcl-1 downregulation, JNK activation, and apoptosis, but not ROS generation. Conversely, 2ME lethality was potentiated by the phosphatidylinositol 3-kinase (PI3K) inhibitor LY294002. Furthermore, in U937 cells, the hydrogen peroxide scavenger catalase and a superoxide dismutase (SOD) mimetic, TBAP, blocked these events, as well as Akt inactivation. Interruption of the JNK pathway by pharmacologic or genetic (e.g. siRNA) means attenuated 2ME-induced mitochondrial injury, XIAP and Mcl-1 downregulation, and apoptosis. Collectively, these findings suggest a hierarchical model of 2ME-related apoptosis induction in human leukemia cells in which 2ME-induced oxidative injury represents a primary event resulting in Akt inactivation, leading, in turn, to JNK activation, and culminating in XIAP and Mcl-1 downregulation, mitochondrial injury, and apoptosis. They also suggest that in human leukemia cells, the Akt pathway plays a critical role in mediating the response to oxidative stress induced by 2ME.
Gao
Ning
N
Department of Medicine, Virginia Commonwealth University/Medical College of Virginia, Richmond, VA 23298, USA.
Rahmani
Mohamed
M
Dent
Paul
P
Grant
Steven
S
D000077584:2-Methoxyestradiol; D000873:Anthracenes / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects*; D002867:Chromones / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004958:Estradiol / Q000031:analogs & derivatives* / Q000494:pharmacology*; D006801:Humans; D048031:JNK Mitogen-Activated Protein Kinases / Q000378:metabolism; D019169:Jurkat Cells; D009025:Morpholines / Q000494:pharmacology; D019869:Phosphatidylinositol 3-Kinases; D017346:Protein Serine-Threonine Kinases / Q000502:physiology*; D011506:Proteins / Q000037:antagonists & inhibitors; D011518:Proto-Oncogene Proteins / Q000502:physiology*; D051057:Proto-Oncogene Proteins c-akt; D017382:Reactive Oxygen Species / Q000378:metabolism*; D020298:U937 Cells; D051636:X-Linked Inhibitor of Apoptosis Protein
D000077584:2-Methoxyestradiol; D000873:Anthracenes; D002867:Chromones; D004958:Estradiol; D048031:JNK Mitogen-Activated Protein Kinases; D009025:Morpholines; D019869:Phosphatidylinositol 3-Kinases; D017346:Protein Serine-Threonine Kinases; D011506:Proteins; D011518:Proto-Oncogene Proteins; D051057:Proto-Oncogene Proteins c-akt; D017382:Reactive Oxygen Species; D051636:X-Linked Inhibitor of Apoptosis Protein; C496866:XIAP protein, human; C432165:pyrazolanthrone; C085911:2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one; C494918:AKT1 protein, human