title: Docosahexaenoic acid downregulates phenobarbital-induced cytochrome P450 2B1 gene expression in rat primary hepatocytes via the c-Jun NH2-terminal kinase mitogen-activated protein kinase pathway.
abstract: Mitogen-activated protein kinase (MAPK) pathways play central roles in the transduction of extracellular stimuli into cells and the regulation of expression of numerous genes. Docosahexaenoic acid (DHA) was shown to be involved in the regulation of expression of drug metabolizing enzymes (DMEs) in rat primary hepatocytes in response to xenobiotics. Cytochrome P450 2B1 (CYP 2B1) is a DME that is dramatically induced by phenobarbital-type inducers. The constitutive androstane receptor (CAR) plays a critical role in regulating the expression of DMEs, and the phosphorylation/dephosphorylation of CAR is an important event in CYP 2B1 expression. In the present study, we determined the effect of DHA on MAPK transactivation and its role in CYP 2B1 expression induced by phenobarbital. c-Jun NH2-terminal kinase (JNK) JNK1/2 and ERK1/2 were activated by phenobarbital in a dose-dependent manner. DHA (100 muM) inhibited JNK1/2 and ERK2 activation induced by phenobarbital in a time-dependent manner. Both SP600125 (a JNK inhibitor) and SB203580 (a p38 MAPK inhibitor) inhibited CYP 2B1 protein and mRNA expression induced by phenobarbital. SB203580 significantly increased the intracellular 3'-5'-cyclic adenosine monophosphate (cAMP) concentration compared with a control group (p < 0.05). Our results suggest that inhibition of JNK activation by DHA is at least part of the mechanisms of DHA's downregulation of CYP 2B1 expression induced by phenobarbital.
authors.affiliation: Department of Nutrition, Chung Shan Medical University, Taichung, Taiwan, ROC.
authors.forename: Chia-Yang
authors.initials: CY
authors.lastname: Lu
authors.forename: Chien-Chun
authors.initials: CC
authors.lastname: Li
authors.forename: Kai-Li
authors.initials: KL
authors.lastname: Liu
authors.forename: Chong-Kuei
authors.initials: CK
authors.lastname: Lii
authors.forename: Haw-Wen
authors.initials: HW
authors.lastname: Chen
mesh_terms: D000818:Animals; D002478:Cells, Cultured; D000242:Cyclic AMP / Q000032:analysis; D019362:Cytochrome P-450 CYP2B1 / Q000037:antagonists & inhibitors / Q000235:genetics*; D004281:Docosahexaenoic Acids / Q000494:pharmacology*; D015536:Down-Regulation / Q000187:drug effects*; D004789:Enzyme Activation / Q000187:drug effects; D004790:Enzyme Induction / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology; D015870:Gene Expression / Q000187:drug effects; D022781:Hepatocytes / Q000737:chemistry / Q000201:enzymology*; D048031:JNK Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D008297:Male; D020928:Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D010634:Phenobarbital / Q000494:pharmacology*; D012333:RNA, Messenger / Q000032:analysis; D051381:Rats; D017207:Rats, Sprague-Dawley
chemical_list: D004791:Enzyme Inhibitors; D012333:RNA, Messenger; D004281:Docosahexaenoic Acids; D000242:Cyclic AMP; D019362:Cytochrome P-450 CYP2B1; D048031:JNK Mitogen-Activated Protein Kinases; D020928:Mitogen-Activated Protein Kinases; D010634:Phenobarbital