Induction of apoptosis by esculetin in human leukemia U937 cells through activation of JNK and ERK.
Esculetin is a phenolic compound that is found in various natural plant products and induces apoptosis in several types of human cancer cells. However, the underlying mechanisms of its action are not completely understood. In the present study, we used human leukemia cells to gain further insight into the mechanism of esculetin-induced anti-proliferative action and apoptosis. It was found that esculetin inhibits cell viability by inducing apoptosis, as evidenced by the formation of apoptotic bodies, DNA fragmentation, and the accumulation of cells in the sub-G1 phase. Esculetin-induced apoptosis was correlated with mitochondrial dysfunction, leading to the release of cytochrome c from the mitochondria to the cytosol, as well as the proteolytic activation of caspases. The z-DEVD-fmk caspase-3 inhibitor and the ectopic expression of anti-apoptotic Bcl-2 significantly inhibited esculetin-induced apoptosis, demonstrating the important role of caspase-3 and mitochondrial proteins in the observed cytotoxic effect. Furthermore, esculetin selectively increased the phosphorylation of extracellular-regulated kinase (ERK) and c-Jun N-terminal kinase (JNK), but not that of other kinases such as Akt and p38 activation. In addition, an ERK-specific inhibitor, PD98059, and a JNK-specific inhibitor, SP600125, showed inhibited sub-G1 phase DNA content, DNA fragmentation, caspase activation, and mitochondrial dysfunction induced by esculetin treatment. These results indicated that the JNK and ERK pathways were key regulators of apoptosis in response to esculetin in human leukemia U937 cells.
Park
Cheol
C
Division of Biological Sciences, College of Natural Science, Pusan National University, Busan 609-735, South Korea.
Jin
Cheng-Yun
CY
Kim
Gi-Young
GY
Choi
Il-Whan
IW
Kwon
Taeg Kyu
TK
Choi
Byung Tae
BT
Lee
Su Jae
SJ
Lee
Won Ho
WH
Choi
Yung Hyun
YH
D000975:Antioxidants / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects*; D015153:Blotting, Western; D061945:Caspase Inhibitors; D002453:Cell Cycle / Q000187:drug effects; D002467:Cell Nucleus / Q000187:drug effects / Q000648:ultrastructure; D049109:Cell Proliferation / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D045304:Cytochromes c / Q000378:metabolism; D053938:DNA Fragmentation / Q000187:drug effects; D048049:Extracellular Signal-Regulated MAP Kinases / Q000502:physiology*; D019254:Genes, bcl-2 / Q000235:genetics; D006801:Humans; D007202:Indicators and Reagents; D048031:JNK Mitogen-Activated Protein Kinases / Q000502:physiology*; D020782:Matrix Metalloproteinases / Q000378:metabolism; D009842:Oligopeptides / Q000494:pharmacology; D051966:Phospholipase C gamma / Q000378:metabolism; D020298:U937 Cells; D014468:Umbelliferones / Q000494:pharmacology*
D000975:Antioxidants; D061945:Caspase Inhibitors; D007202:Indicators and Reagents; D009842:Oligopeptides; D014468:Umbelliferones; C110772:benzoylcarbonyl-aspartyl-glutamyl-valyl-aspartyl-fluoromethyl ketone; D045304:Cytochromes c; D048049:Extracellular Signal-Regulated MAP Kinases; D048031:JNK Mitogen-Activated Protein Kinases; D051966:Phospholipase C gamma; D020782:Matrix Metalloproteinases; C007628:esculetin