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Effects of oltipraz and related chemoprevention compounds on gene expression in rat liver
L Anderson1, V K Steele, G J Kelloff
1Large Scale Biology Corporation, Rockville, MD 20850, USA.
Abstract:
One promising approach to cancer chemoprevention involves the induction of phase II xenobiotic metabolism enzymes. Since this approach requires drugs specifically intended to alter tissue gene expression patterns over long periods, it will be important to determine experimentally which proteins are increased or decreased by treatment, and how such alterations may (or may not) be related to the postulated chemopreventive mechanism. We have employed two-dimensional electrophoresis to detect and quantitate gene expression effects of candidate chemoprevention compounds in the livers of treated rats. Oltipraz, an inducer of several phase II enzymes, affected a series of at least 26 proteins, most of which were slightly decreased by treatment. Several proteins were increased, the prime example being rat liver spot 693, which was induced more than 7-fold by oltipraz. This protein was excised from multiple 2-D gels and subjected to in situ tryptic digestion followed by microchemical sequence analysis. The resulting multiple peptide sequences match perfectly with the cDNA-derived sequence of rat aflatoxin B1 aldehyde reductase (AFAR). Using quantitative measurements of AFAR from 2-D gels, we compared a series of dose regimens. Oltipraz administration by gavage or in diet appeared equally effective, while recovery studies indicated a half-time of 5.5 days for disappearance of the AFAR protein.(ABSTRACT TRUNCATED AT 250 WORDS)
Insights
Oltipraz, a cancer chemoprevention drug, significantly increases aflatoxin B1 aldehyde reductase (AFAR) protein levels in rat livers. This finding helps understand how chemopreventive compounds alter gene expression for cancer prevention.
Area of Science:
- Biochemistry
- Molecular Biology
- Toxicology
Background:
- Cancer chemoprevention strategies often target the induction of phase II xenobiotic metabolism enzymes.
- Understanding drug-induced changes in protein expression is crucial for evaluating chemopreventive mechanisms.
- Long-term administration of chemopreventive agents necessitates detailed analysis of their effects on tissue gene expression.
Purpose of the Study:
- To investigate the protein expression changes in rat livers induced by the chemoprevention compound oltipraz.
- To identify specific proteins affected by oltipraz treatment and correlate these changes with its chemopreventive potential.
Main Methods:
- Two-dimensional electrophoresis (2-D electrophoresis) was used to detect and quantify protein expression alterations in rat liver samples.
- Proteins of interest were isolated, subjected to in situ tryptic digestion, and analyzed using microchemical sequence analysis.
- Quantitative measurements of specific proteins were performed using 2-D gel data.
Main Results:
- Oltipraz treatment affected at least 26 proteins, with most showing slight decreases, but one significant increase.
- Rat liver spot 693, identified as aflatoxin B1 aldehyde reductase (AFAR), showed a more than 7-fold induction by oltipraz.
- Oltipraz administration via gavage or diet yielded similar efficacy, and AFAR protein levels exhibited a half-life of 5.5 days post-treatment.
Conclusions:
- Oltipraz significantly induces the expression of aflatoxin B1 aldehyde reductase (AFAR) in rat livers.
- The study identifies AFAR as a key protein modulated by oltipraz, contributing to the understanding of its chemopreventive mechanism.
- These findings provide valuable insights into the molecular effects of chemopreventive agents on xenobiotic metabolism.