Genomic consequences of cytochrome P450 2C9 overexpression in human hepatoma cells

Chem Res Toxicol. 2009 May;22(5):779-87. doi: 10.1021/tx800417u.

Abstract

Cytochrome P450 2C9 (P450 2C9) is one of the most important P450 isoforms in the human liver, as it metabolizes numerous exogenous and endogenous substrates. Moreover, it is inducible by several compounds, such as rifampicin, phenobarbital, and NSAIDs (nonsteroidal anti-inflammatories). The aim of this study was to investigate the global cellular consequences of P450 2C9 overexpression at the transcriptional level using an untargeted approach: pangenomic microarrays. Recombinant adenovirus was used to express P450 2C9 instead of an inducer to prevent a per se effect of inducer or its metabolites. P450 2C9 overexpression induced endoplasmic reticulum (ER) stress and regulated genes implicated in the unfolded protein response (UPR) as heat shock protein (HSP) (we studied particurlarly HSPA5 and HSPB1) and in the endoplasmic reticulum associated degradation (ERAD) system as Sec61 and ubiquitin and proteasome pathways. UPR and ERAD are two mechanisms of adaptative response to ER stress. Moreover, activation of Akt was observed in HepG2 cells that overexpress P450 2C9 and might participate in the cellular adaptive response to stress, thus leading to the activation of cell survival pathways. UPR and ERAD should be caused by accumulation of native and misfolded P450 2C9 protein. Our results indicated that P450 2C9 overexpression did not lead to toxicity but induced an ER stress due to protein overexpression rather than mono-oxygenase activity. The ER stress triggered activation of the adaptative response and of pathways leading to cell survival.

MeSH terms

  • Aryl Hydrocarbon Hydroxylases / genetics
  • Aryl Hydrocarbon Hydroxylases / metabolism*
  • Carcinoma, Hepatocellular
  • Cell Survival
  • Cytochrome P-450 CYP2C9
  • Endoplasmic Reticulum / genetics
  • Endoplasmic Reticulum / metabolism
  • Gene Expression Profiling*
  • HSP27 Heat-Shock Proteins / genetics
  • HSP27 Heat-Shock Proteins / metabolism
  • Heat-Shock Proteins / genetics
  • Heat-Shock Proteins / metabolism
  • Humans
  • Membrane Proteins / genetics
  • Membrane Proteins / metabolism
  • Proteasome Endopeptidase Complex / genetics
  • Proteasome Endopeptidase Complex / metabolism
  • SEC Translocation Channels
  • Transcription, Genetic
  • Tumor Cells, Cultured
  • Ubiquitin / genetics
  • Ubiquitin / metabolism

Substances

  • HSP27 Heat-Shock Proteins
  • HSPB1 protein, human
  • Heat-Shock Proteins
  • Membrane Proteins
  • SEC Translocation Channels
  • Ubiquitin
  • CYP2C9 protein, human
  • Cytochrome P-450 CYP2C9
  • Aryl Hydrocarbon Hydroxylases
  • Proteasome Endopeptidase Complex
  • molecular chaperone GRP78