Sodium orthovanadate potentiates EGCG-induced apoptosis that is dependent on the ERK pathway.
Epigallocatechin-3-gallate (EGCG) is a potent chemopreventive agent in many test systems and has been shown to inhibit tumor promotion and induce apoptosis. In the present study, we determined the effect of vanadate, a potent inhibitor of tyrosine phosphatase, on EGCG-induced apoptosis. Investigation of the mechanism of EGCG or vanadate-induced apoptosis revealed induction of caspase 3 activity and cleavage of phospholipase-gamma1 (PLC-gamma1). Furthermore, vanadate potentiated EGCG-induced apoptosis by mitogen-activated protein kinase (MAPK) signaling pathway. Treatment with EGCG plus vanadate for 24h produced morphological features of apoptosis and DNA fragmentation in U937 cells. This was associated with cytochrome c release, caspase 3 activation, and PLC-gamma1 degradation. EGCG plus vanadate activates multiple signal transduction pathways involved in coordinating cellular responses to stress. We demonstrate a requirement for extracellular signal-regulated protein kinase (ERK), a member of the mitogen-activated protein kinase family in EGCG plus vanadate-induced apoptosis in U937 cells. Elevated ERK activity that contributed to apoptosis by EGCG plus vanadate was supported by PD98059 and U0126, chemical inhibitor of MEK/ERK signaling pathway, prevented apoptosis. Taken together, our finding suggests that ERK activation plays an active role in mediating EGCG plus vanadate-induced apoptosis of U937 cells and functions upstream of caspase activation to initiate the apoptotic signal.
Choi
Yun-Jung
YJ
Department of Immunology, School of Medicine, Keimyung University, 194 DongSan-Dong Jung-Gu, Taegu 700-712, South Korea.
Lim
Sung-Yup
SY
Woo
Ju-Hyung
JH
Kim
Young-Ho
YH
Kwon
Young Kyu
YK
Suh
Seong-Il
SI
Lee
Sung-Hee
SH
Choi
Wha-Youl
WY
Kim
Jong-Guk
JG
Lee
In-Seon
IS
Park
Jong-Wook
JW
Kwon
Taeg-Kyu
TK
D016588:Anticarcinogenic Agents / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects; D053148:Caspase 3; D020169:Caspases / Q000378:metabolism; D002392:Catechin / Q000031:analogs & derivatives* / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D003574:Cytochrome c Group / Q000378:metabolism; D004357:Drug Synergism; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D005419:Flavonoids / Q000494:pharmacology; D006801:Humans; D020935:MAP Kinase Signaling System; D020929:Mitogen-Activated Protein Kinase Kinases / Q000037:antagonists & inhibitors; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D017027:Protein Tyrosine Phosphatases / Q000037:antagonists & inhibitors; D011506:Proteins / Q000378:metabolism; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism; D020298:U937 Cells; D014638:Vanadates / Q000037:antagonists & inhibitors / Q000494:pharmacology*
D016588:Anticarcinogenic Agents; D003574:Cytochrome c Group; D004791:Enzyme Inhibitors; D005419:Flavonoids; D011506:Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D014638:Vanadates; D002392:Catechin; C045651:epigallocatechin gallate; D020928:Mitogen-Activated Protein Kinases; D020929:Mitogen-Activated Protein Kinase Kinases; D017027:Protein Tyrosine Phosphatases; C505407:CASP3 protein, human; D053148:Caspase 3; D020169:Caspases; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one