Epigallocatechin gallate protects nerve growth factor differentiated PC12 cells from oxidative-radical-stress-induced apoptosis through its effect on phosphoinositide 3-kinase/Akt and glycogen synthase kinase-3.
The effects of epigallocatechin gallate (EGCG) on the phosphoinositide 3-kinase (PI3K)/Akt and glycogen synthase kinase-3 (GSK-3) pathway during oxidative-stress-induced injury were studied using H2O2-treated PC12 cells, which were differentiated by nerve growth factor (NGF). Following 100 microM H2O2 exposure, the viability of differentiated PC12 cells (EGCG or z-VAD-fmk pretreated vs. not pretreated) was evaluated the number of viable cell with Trypan blue and 3,4,5-dimethylthiazol-2-yl (MTT). Additionally, expression of cytochrome c, caspase-3, poly(ADP-ribose) polymerase (PARP), PI3K/Akt and GSK-3 was examined using Western blot analyses. EGCG or z-VAD-fmk-pretreated PC12 cells showed an increase of viability compared to untreated PC12 cells, and pretreatment of PC12 cells with either agent induced a dose-dependent inhibition of caspase-3 activation and PARP cleavage. However, inhibition of cytochrome c release was only detected in EGCG-pretreated cells. Upon examination of the PI3K/Akt and GSK-3 upstream pathway, Western blots of EGCG pretreated cells showed decreased immunoreactivity (IR) of Akt and GSK-3 and increased IR of p85a PI3K, phosphorylated Akt and phosphorylated GSK-3. In contrast, no changes were seen in z-VAD-fmk-pretreated cells. These results show that EGCG affects the PI3K/Akt, GSK-3 pathway as well as downstream signaling, including the cytochrome c and caspase-3 pathways. Therefore, it is suggested that EGCG-mediated activation of PI3K/Akt and inhibition of GSK-3 could be a new potential therapeutic strategy for neurodegenerative diseases associated with oxidative injury.
Koh
Seong-Ho
SH
Department of General Toxicology, National Institute of Toxicological Research, KFDA, Seoul, South Korea.
Kim
Seung H
SH
Kwon
Hyugsung
H
Park
Younjoo
Y
Kim
Ki Sok
KS
Song
Chi Won
CW
Kim
Juhan
J
Kim
Myung-Ho
MH
Yu
Hyun-Jeung
HJ
Henkel
Jenny S
JS
Jung
Hai Kwan
HK
D000818:Animals; D017209:Apoptosis / Q000187:drug effects* / Q000502:physiology; D053148:Caspase 3; D061945:Caspase Inhibitors; D020169:Caspases / Q000378:metabolism; D002392:Catechin / Q000031:analogs & derivatives* / Q000494:pharmacology*; D002454:Cell Differentiation / Q000187:drug effects / Q000502:physiology; D002470:Cell Survival / Q000187:drug effects / Q000502:physiology; D045304:Cytochromes c / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004791:Enzyme Inhibitors / Q000494:pharmacology; D038362:Glycogen Synthase Kinase 3 / Q000037:antagonists & inhibitors / Q000378:metabolism; D020932:Nerve Growth Factor / Q000494:pharmacology; D019636:Neurodegenerative Diseases / Q000188:drug therapy / Q000201:enzymology / Q000517:prevention & control*; D018696:Neuroprotective Agents / Q000494:pharmacology*; D018384:Oxidative Stress / Q000187:drug effects* / Q000502:physiology; D016716:PC12 Cells; D019869:Phosphatidylinositol 3-Kinases / Q000187:drug effects / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D000071137:Poly (ADP-Ribose) Polymerase-1; D011065:Poly(ADP-ribose) Polymerases; D017346:Protein Serine-Threonine Kinases; D011506:Proteins / Q000378:metabolism; D011518:Proto-Oncogene Proteins / Q000187:drug effects / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt; D051381:Rats
D053148:Caspase 3; D061945:Caspase Inhibitors; D020169:Caspases; D002392:Catechin; D045304:Cytochromes c; D004791:Enzyme Inhibitors; D038362:Glycogen Synthase Kinase 3; D020932:Nerve Growth Factor; D018696:Neuroprotective Agents; D019869:Phosphatidylinositol 3-Kinases; D000071137:Poly (ADP-Ribose) Polymerase-1; D011065:Poly(ADP-ribose) Polymerases; D017346:Protein Serine-Threonine Kinases; D011506:Proteins; D011518:Proto-Oncogene Proteins; D051057:Proto-Oncogene Proteins c-akt; C499322:Parp1 protein, rat; C494920:Akt1 protein, rat; C505410:Casp3 protein, rat; C057580:gallocatechol