Clofibrate-induced gene expression changes in rat liver: a cross-laboratory analysis using membrane cDNA arrays

Area of Science:

• Toxicology
• Genomics
• Molecular Biology

Background:

• Microarrays offer potential for identifying toxic hazards through mechanism-based toxicity markers.
• Assessing reliability and interlaboratory reproducibility of microarray data is crucial for risk assessment.
• The International Life Sciences Institute (ILSI) Health and Environmental Science Institute (HESI) Technical Committee investigated genomics in risk assessment.

Purpose of the Study:

• To investigate the biological response in rats to the hepatotoxin clofibrate using gene expression profiling.
• To determine the reliability and reproducibility of microarray data in a toxicological context.
• To identify mechanistically relevant markers of toxicity.

Main Methods:

• Rats were treated with clofibrate (high/low doses) for 1, 3, or 7 days in two laboratories.
• Clinical chemistry, histopathology, and cDNA microarray analysis were performed.
• Quantitative real-time polymerase chain reaction (qPCR) was used to validate gene expression changes.

Main Results:

• Gene expression changes in pathways related to fatty acid metabolism, cell proliferation, and oxidation were detected, consistent with clofibrate's hepatotoxicity mechanism.
• Gene expression levels correlated with the observed biological responses.
• High concordance was observed between pooled and individual RNA samples, though some variability in quantitative data was noted due to experimental and data analysis procedures.

Conclusions:

• Gene expression profiling using microarrays shows promise for identifying toxic hazards by detecting mechanistically relevant markers.
• The study highlights the potential of transcriptomics in mechanism-based risk assessment.
• Standardization of experimental and data analysis protocols is important for improving microarray data reproducibility.