title: Mitochondrial genome depletion dysregulates bile acid- and paracetamol-induced expression of the transporters Mdr1, Mrp1 and Mrp4 in liver cells.
abstract: OBJECTIVE
  Mitochondria are involved in the toxicity of several compounds, retro-control of gene expression and apoptosis activation. The effect of mitochondrial genome (mtDNA) depletion on changes in ABC transporter protein expression in response to bile acids and paracetamol was investigated.
  
  
  METHODS
  Hepa 1-6 mouse hepatoma cells with 70% decrease in 16S/18S rRNA ratio (Rho cells) were obtained by long-term treatment with ethidium bromide.
  
  
  RESULTS
  Spontaneous apoptosis and reactive oxygen species (ROS) generation were decreased in Rho cells. Following glycochenodeoxycholic acid (GCDCA) or paracetamol, Rho cells generated less ROS and were more resistant to cell death. Apoptosis induced by GCDCA and Fas was also reduced. The basal expression of Mdr1 was significantly enhanced, but this was not further stimulated by GCDCA or paracetamol, as observed in wild-type (WT) cells. Basal expression of Mrp1 and Mrp4 was similar in WT and Rho cells, whereas they were up-regulated only in WT cells after GCDCA or paracetamol, along with the transcription factors Shp and Nrf2, but not Fxr or Pxr. Increased expression of Nrf2 was accompanied by its enhanced nuclear translocation. Glycoursodeoxycholic acid failed to cause any of the effects observed for GCDCA or paracetamol.
  
  
  CONCLUSIONS
  The Nrf2-mediated pathway is partly independent of ROS production. Nuclear translocation of Nrf2 is insufficient to up-regulate Mdr1, Mrp1 and Mrp4, which requires the participation of other regulatory element(s) whose activation in response to GCDCA and paracetamol is impaired in Rho cells and hence probably sensitive to ROS.
authors.affiliation: Research Unit, University Hospital, Salamanca, 37007 Salamanca, Spain.
authors.forename: M J
authors.initials: MJ
authors.lastname: Perez
authors.forename: E
authors.initials: E
authors.lastname: Gonzalez-Sanchez
authors.forename: A
authors.initials: A
authors.lastname: Gonzalez-Loyola
authors.forename: J M
authors.initials: JM
authors.lastname: Gonzalez-Buitrago
authors.forename: J J G
authors.initials: JJ
authors.lastname: Marin
mesh_terms: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000378:metabolism*; D000082:Acetaminophen / Q000494:pharmacology; D018712:Analgesics, Non-Narcotic / Q000494:pharmacology; D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D006528:Carcinoma, Hepatocellular / Q000378:metabolism; D045744:Cell Line, Tumor; D005786:Gene Expression Regulation / Q000187:drug effects; D054629:Genome, Mitochondrial; D005999:Glycochenodeoxycholic Acid / Q000494:pharmacology; D008099:Liver / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D051379:Mice; D027425:ATP-Binding Cassette, Sub-Family C Proteins / Q000187:drug effects* / Q000378:metabolism; D051267:NF-E2-Related Factor 2 / Q000378:metabolism; D012335:RNA, Ribosomal / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism; D014580:Ursodeoxycholic Acid / Q000031:analogs & derivatives / Q000494:pharmacology
chemical_list: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D000082:Acetaminophen; D018712:Analgesics, Non-Narcotic; D005999:Glycochenodeoxycholic Acid; D027425:ATP-Binding Cassette, Sub-Family C Proteins; D051267:NF-E2-Related Factor 2; D012335:RNA, Ribosomal; D017382:Reactive Oxygen Species; D014580:Ursodeoxycholic Acid; C489540:Abcc4 protein, mouse; C495636:Nfe2l2 protein, mouse; C024033:glycoursodeoxycholic acid; C421109:multidrug resistance-associated protein 1