title: Coactivator PGC-1alpha regulates the fasting inducible xenobiotic-metabolizing enzyme CYP2A5 in mouse primary hepatocytes.
abstract: The nutritional state of organisms and energy balance related diseases such as diabetes regulate the metabolism of xenobiotics such as drugs, toxins and carcinogens. However, the mechanisms behind this regulation are mostly unknown. The xenobiotic-metabolizing cytochrome P450 (CYP) 2A5 enzyme has been shown to be induced by fasting and by glucagon and cyclic AMP (cAMP), which mediate numerous fasting responses. Peroxisome proliferator-activated receptor gamma coactivator (PGC)-1alpha triggers many of the important hepatic fasting effects in response to elevated cAMP levels. In the present study, we were able to show that cAMP causes a coordinated induction of PGC-1alpha and CYP2A5 mRNAs in murine primary hepatocytes. Furthermore, the elevation of the PGC-1alpha expression level by adenovirus mediated gene transfer increased CYP2A5 transcription. Co-transfection of Cyp2a5 5' promoter constructs with the PGC-1alpha expression vector demonstrated that PGC-1alpha is able to activate Cyp2a5 transcription through the hepatocyte nuclear factor (HNF)-4alpha response element in the proximal promoter of the Cyp2a5 gene. Chromatin immunoprecipitation assays showed that PGC-1alpha binds, together with HNF-4alpha, to the same region at the Cyp2a5 proximal promoter. In conclusion, PGC-1alpha mediates the expression of Cyp2a5 induced by cAMP in mouse hepatocytes through coactivation of transcription factor HNF-4alpha. This strongly suggests that PGC-1alpha is the major factor mediating the fasting response of CYP2A5.
authors.affiliation: Department of Pharmacology and Toxicology, University of Oulu, Oulu, Finland.
authors.forename: Satu
authors.initials: S
authors.lastname: Arpiainen
authors.forename: Sanna-Mari
authors.initials: SM
authors.lastname: Järvenpää
authors.forename: Aki
authors.initials: A
authors.lastname: Manninen
authors.forename: Pirkko
authors.initials: P
authors.lastname: Viitala
authors.forename: Matti A
authors.initials: MA
authors.lastname: Lang
authors.forename: Olavi
authors.initials: O
authors.lastname: Pelkonen
authors.forename: Jukka
authors.initials: J
authors.lastname: Hakkola
mesh_terms: D000256:Adenoviridae / Q000235:genetics; D000818:Animals; D001189:Aryl Hydrocarbon Hydroxylases / Q000096:biosynthesis* / Q000235:genetics; D018929:Cell Culture Techniques; D002478:Cells, Cultured; D006152:Cyclic GMP / Q000378:metabolism; D065637:Cytochrome P-450 CYP2A6; D000072467:Cytochrome P450 Family 2; D004790:Enzyme Induction; D005215:Fasting / Q000378:metabolism*; D005822:Genetic Vectors; D051557:Hepatocyte Nuclear Factor 4 / Q000378:metabolism; D022781:Hepatocytes / Q000201:enzymology*; D008297:Male; D051379:Mice; D008811:Mice, Inbred DBA; D000071248:Peroxisome Proliferator-Activated Receptor Gamma Coactivator 1-alpha; D011401:Promoter Regions, Genetic; D012333:RNA, Messenger / Q000096:biosynthesis; D015398:Signal Transduction; D013997:Time Factors; D015534:Trans-Activators / Q000235:genetics / Q000378:metabolism*; D014157:Transcription Factors; D015533:Transcriptional Activation; D014162:Transfection; D015854:Up-Regulation; D015262:Xenobiotics / Q000378:metabolism*
chemical_list: D051557:Hepatocyte Nuclear Factor 4; C496593:Hnf4a protein, mouse; D000071248:Peroxisome Proliferator-Activated Receptor Gamma Coactivator 1-alpha; C485290:Ppargc1a protein, mouse; D012333:RNA, Messenger; D015534:Trans-Activators; D014157:Transcription Factors; D015262:Xenobiotics; D001189:Aryl Hydrocarbon Hydroxylases; C585520:Cyp2a5 protein, mouse; D065637:Cytochrome P-450 CYP2A6; D000072467:Cytochrome P450 Family 2; D006152:Cyclic GMP