TY - JOUR
T1 - Involvement of p38 MAPK and Nrf2 in phenolic acid-induced P-form phenol sulfotransferase expression in human hepatoma HepG2 cells
AU - Yeh, Chi Tai
AU - Yen, Gow Chin
N1 - Funding Information:
This research work was partially supported by the National Science Council, the Republic of China, under the grant NSC92-2313-B005-067.
PY - 2006/5
Y1 - 2006/5
N2 - Phenolic acids have significant biological and pharmacological properties and some have demonstrated remarkable ability to alter sulfate conjugation. However, the modulation mechanisms of phenolic acids on phenol sulfotransferase expression have not been described. In the present study, we investigated the effects of phenolic acids on the expression of the Phase II P-form of phenol sulfotransferase (PST-P) in human hepatoma HepG2 cells. RT-PCR and western blot data revealed that gallic acid induced increase in PST-P expression at the mRNA and protein levels, respectively. This induction was also marked by an increase in PST-P activity. Actinomycin D and cycloheximide inhibited gallic acid-responsive PST-P mRNA expression, indicating that gallic acid is a requirement for transcription and de novo protein synthesis. Transient transfection of HepG2 cells with a reporter plasmid of the upstream region of the human PST gene caused a significant increase in reporter gene activity after gallic acid exposure. Moreover, gallic acid increased the nuclear levels of Nrf2, a transcription factor governing antioxidant response element (ARE). Electrophoretic mobility shift assay showed increased binding of nuclear proteins to ARE consensus sequence after treatment with gallic acid. While investigating the signaling pathways responsible for PST-P induction, we observed that gallic acid activated the p38 mitogen-activated protein kinase (MAPK) pathway. SB203580, a specific inhibitor of p38 MAPK, abolished gallic acid-induced PST-P protein expression. Similarly, gallic acid also caused an accumulation of Nrf2. Moreover, the protective effects of gallic acid on tert-butyl hydroperoxide-induced toxicity was partially blocked by p38 MAPK and PST-P inhibitors, further demonstrating that gallic acid attenuates oxidative stress through a pathway that involves p38 MAPK and PST-P. These results indicate that gallic acid is a potent inducer of PST-P and that PST-P induction is responsible for the gallic acid-mediated cytoprotection against oxidative damage.
AB - Phenolic acids have significant biological and pharmacological properties and some have demonstrated remarkable ability to alter sulfate conjugation. However, the modulation mechanisms of phenolic acids on phenol sulfotransferase expression have not been described. In the present study, we investigated the effects of phenolic acids on the expression of the Phase II P-form of phenol sulfotransferase (PST-P) in human hepatoma HepG2 cells. RT-PCR and western blot data revealed that gallic acid induced increase in PST-P expression at the mRNA and protein levels, respectively. This induction was also marked by an increase in PST-P activity. Actinomycin D and cycloheximide inhibited gallic acid-responsive PST-P mRNA expression, indicating that gallic acid is a requirement for transcription and de novo protein synthesis. Transient transfection of HepG2 cells with a reporter plasmid of the upstream region of the human PST gene caused a significant increase in reporter gene activity after gallic acid exposure. Moreover, gallic acid increased the nuclear levels of Nrf2, a transcription factor governing antioxidant response element (ARE). Electrophoretic mobility shift assay showed increased binding of nuclear proteins to ARE consensus sequence after treatment with gallic acid. While investigating the signaling pathways responsible for PST-P induction, we observed that gallic acid activated the p38 mitogen-activated protein kinase (MAPK) pathway. SB203580, a specific inhibitor of p38 MAPK, abolished gallic acid-induced PST-P protein expression. Similarly, gallic acid also caused an accumulation of Nrf2. Moreover, the protective effects of gallic acid on tert-butyl hydroperoxide-induced toxicity was partially blocked by p38 MAPK and PST-P inhibitors, further demonstrating that gallic acid attenuates oxidative stress through a pathway that involves p38 MAPK and PST-P. These results indicate that gallic acid is a potent inducer of PST-P and that PST-P induction is responsible for the gallic acid-mediated cytoprotection against oxidative damage.
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U2 - 10.1093/carcin/bgi281
DO - 10.1093/carcin/bgi281
M3 - Article
C2 - 16308312
AN - SCOPUS:33646196955
SN - 0143-3334
VL - 27
SP - 1008
EP - 1017
JO - Carcinogenesis
JF - Carcinogenesis
IS - 5
ER -