| Title | Effect of sulforaphane on metallothionein expression and induction of apoptosis in human hepatoma HepG2 cells. | | Author(s) | Yeh CT, Yen GC | | Institution | Department of Food Science and Biotechnology, National Chung Hsing University, Taichung 40227, Taiwan. | | Source | Carcinogenesis 2005 Dec; 26(12):2138-48. | | MeSH | Anticarcinogenic Agents
Apoptosis
Blotting, Western
Carcinoma, Hepatocellular
Caspases
Extracellular Signal-Regulated MAP Kinases
Humans
JNK Mitogen-Activated Protein Kinases
Liver Neoplasms
Metallothionein
Mitogen-Activated Protein Kinases
NF-E2-Related Factor 2
Poly(ADP-ribose) Polymerases
Proto-Oncogene Proteins c-bcl-2
RNA, Messenger
Research Support, Non-U.S. Gov't
Reverse Transcriptase Polymerase Chain Reaction
Signal Transduction
Thiocyanates
Tumor Cells, Cultured
bcl-2-Associated X Protein
bcl-X Protein
p38 Mitogen-Activated Protein Kinases
| | Abstract | The molecular mechanism of sulforaphane on the induction of metallothionein (MT) genes in HepG2 cells and the antiproliferative effects of sulforaphane were investigated in this study. Treatment of the cells with sulforaphane at non-toxicity concentration (0-20 microM) resulted in coordinate increases in the induction of MT-I and MT-II mRNA, followed by corresponding increases in MT protein expression. Western blot analysis revealed the increased level of the transcription factor, Nrf2 in a time-dependent manner from sulforaphane-treated cells. Furthermore, sulforaphane activated the extracellular signal-regulated protein kinase (ERK), p38 and c-Jun N-terminal kinase (JNK) mitogen-activated protein kinase (MAPK) pathways. SB203580, a specific inhibitor of p38 and PD98059, a specific inhibitor of ERK, abolished sulforaphane-induced MT protein expression, whereas SP600125, a specific inhibitor of JNK, had no significant effect. At relatively high concentration (30-100 microM), sulforaphane is a cell growth modulator, as it induced apoptotic cell death characterized by internucleosomal DNA fragmentation and caused a rapid induction of caspase 3 activity, according to the appearance of the caspase 3 fragments and stimulated proteolytic cleavage of poly (ADP-ribose) polymerase in a time-dependent manner. Moreover, sulforaphane-induced apoptotic cell death was accompanied by upregulation of Bax and downregulation of Bcl-2 and Bcl-X(l) protein. Sulforaphane-induced DNA fragmentation was blocked by the N-acetyl-L-cysteine and catalase, suggesting that the death signaling was triggered by oxidative stress. Taken together these results strongly suggest that at low concentrations of sulforaphane, activation of MAPKs, such as ERK and p38 pathway, lead to Nrf2-mediated MT gene expression. Whereas at a higher concentration, sulforaphane is an effective apoptosis inducer in HepG(2) cells through regulation of Bcl-2 family molecular and activation of ICE/Ced-3 protease (caspase 3) cascade. The results from this study may provide more evidence for its chemopreventive function. | | Language | eng | | Pub Type(s) | Journal Article
| | PubMed ID | 16033772 |
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