Induction of apoptosis via mitogen-activated protein kinase pathway by a K vitamin analog in rat hepatocytes.
OBJECTIVE
Compound 5 (Cpd 5), a vitamin K analog, inhibits rat hepatocyte DNA synthesis and hepatoma cell growth. The aim of this study was to determine if the inhibitory effect of Cpd 5 on cell growth was related to apoptosis.


METHODS
Isolated rat hepatocytes were cultured with Cpd 5, and mitogen-activated signaling pathway and apoptosis pathway were investigated using Western blot analysis.


RESULTS
When rat hepatocytes were cultured with Cpd 5 for 48 h, apoptosis was evident, which included characteristic morphological changes, DNA fragmentation, and the activation of caspase 3 (CPP 32)-like protease. Examination of upstream events of apoptosis pathway showed that the expression of Bax was induced and bcl-2 was inhibited by Cpd 5 treatment. Concomitant with the induction of apoptosis, Cpd 5 activated the extracellular signal-regulated kinase (ERK) signaling pathway. PD 98059, a mitogen-activated protein kinase kinase inhibitor, and glutathione, an anti-thiol-oxidant, not only blocked Cpd 5-induced ERK phosphorylation, but also antagonized the activation of CPP-32, the altered Bcl-2/Bax expression, and DNA fragmentation.


CONCLUSIONS
The data suggest that the ERK signaling pathway may be involved in the regulation of rat hepatocyte apoptosis induced by Cpd 5.
Wang
Ziqiu
Z
Thomas E. Starzl Transplantation Institute, Department of Surgery, University of Pittsburgh School of Medicine, E 1552 Biomedical Science Tower, 200 Lothrop Street, Pittsburgh, PA 15213, USA.
Nishikawa
Yuji
Y
Wang
Meifang
M
Carr
Brian I
BI
D000818:Animals; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology*; D053148:Caspase 3; D020169:Caspases / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005419:Flavonoids / Q000494:pharmacology; D005978:Glutathione / Q000494:pharmacology; D006131:Growth Inhibitors / Q000494:pharmacology*; D022781:Hepatocytes / Q000166:cytology*; D020935:MAP Kinase Signaling System / Q000187:drug effects* / Q000502:physiology; D008297:Male; D011518:Proto-Oncogene Proteins / Q000096:biosynthesis; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000096:biosynthesis; D051381:Rats; D011916:Rats, Inbred F344; D014812:Vitamin K / Q000031:analogs & derivatives / Q000494:pharmacology*; D051028:bcl-2-Associated X Protein
C446520:2-(2-hydroxyethylsulfanyl)-3-methyl-1,4-naphthoquinone; C494828:Bax protein, rat; D004791:Enzyme Inhibitors; D005419:Flavonoids; D006131:Growth Inhibitors; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D051028:bcl-2-Associated X Protein; D014812:Vitamin K; C505410:Casp3 protein, rat; D053148:Caspase 3; D020169:Caspases; D005978:Glutathione; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one