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Extent and character of phenobarbital-mediated changes in gene expression in the liver
F W Frueh1, U M Zanger, U A Meyer
1Department of Pharmacology, Biozentrum, University of Basel, Switzerland.
Abstract:
Phenobarbital elicits pleiotropic effects in the liver, including induction of enzymes involved in xenobiotic metabolism. The spectrum of this response was analyzed by differential display of a large population (approximately 7500) of mRNAs in chicken embryo liver treated in vivo with phenobarbital. We identified 29 cDNA fragments that reproducibly and significantly changed in intensity after a 48-hr in ovo treatment. Eighteen of these (62%) were increased, whereas 11 (38%) were decreased. Twenty strongly regulated cDNA fragments were subcloned and further analyzed. Nucleotide sequence analysis revealed three types of genes: (a) those previously described to be regulated by phenobarbital, including CYP2H1, glutathione S-transferase, and uridine diphosphate-glucuronosyltransferase; (b) genes reported herein for the first time to be regulated by phenobarbital, including fibrinogen beta-chain and gamma-chain, retinal glutamine synthetase, apolipoprotein B, two gene products with homologies to elongation factor 1delta and complement factor H, respectively, and (c) several novel genes with hitherto unknown functions. If these data are extrapolated to the entire population of mRNAs of a liver cell, phenobarbital seems to significantly modulate the expression of more than 50 different genes. Our results also demonstrate that a large fraction of genes is negatively regulated by drug treatment.
Insights
Phenobarbital significantly alters gene expression in chicken embryo liver, affecting over 50 genes involved in various functions. This drug treatment notably downregulates a substantial portion of these genes.
Area of Science:
- Hepatology
- Molecular Biology
- Pharmacogenomics
Background:
- Phenobarbital is known to induce liver enzymes crucial for metabolizing foreign compounds (xenobiotics).
- Understanding the full scope of phenobarbital's effects on gene expression in the liver is essential for comprehending its pleiotropic actions.
Purpose of the Study:
- To comprehensively analyze the spectrum of messenger RNA (mRNA) changes in chicken embryo liver following phenobarbital treatment.
- To identify novel genes regulated by phenobarbital and characterize the overall impact on gene expression.
Main Methods:
- Differential display was employed to screen approximately 7500 mRNAs in chicken embryo liver after 48-hour in ovo phenobarbital exposure.
- Selected cDNA fragments with significant expression changes were subcloned and analyzed using nucleotide sequencing.
Main Results:
- 29 cDNA fragments showed reproducible and significant changes in expression (18 increased, 11 decreased).
- Sequencing identified known phenobarbital-regulated genes (e.g., CYP2H1, glutathione S-transferase) and newly identified targets (e.g., fibrinogen chains, apolipoprotein B).
- Several novel genes with unknown functions were also found to be regulated.
Conclusions:
- Phenobarbital significantly modulates the expression of a wide array of genes in the liver, potentially exceeding 50 different genes.
- A substantial fraction of genes identified in this study were negatively regulated by phenobarbital treatment.
- These findings reveal a broader impact of phenobarbital on liver gene expression than previously recognized.