Gene expression changes induced by the tumorigenic pyrrolizidine alkaloid riddelliine in liver of Big Blue rats

Nan Mei,Lei Guo,Tao Chen,Ruqing Liu,James C Fuscoe

doi:10.1186/1471-2105-8-s7-s4

Abstract

BackgroundPyrrolizidine alkaloids (PAs) are probably the most common plant constituents that poison livestock, wildlife, and humans worldwide. Riddelliine is isolated from plants grown in the western United States and is a prototype of genotoxic PAs. Riddelliine was used to investigate the genotoxic effects of PAs via analysis of gene expression in the target tissue of rats in this study. Previously we observed that the mutant frequency in the liver of rats gavaged with riddelliine was 3-fold higher than that in the control group. Molecular analysis of the mutants indicated that there was a statistically significant difference between the mutational spectra from riddelliine-treated and control rats.ResultsRiddelliine-induced gene expression profiles in livers of Big Blue transgenic rats were determined. The female rats were gavaged with riddelliine at a dose of 1 mg/kg body weight 5 days a week for 12 weeks. Rat whole genome microarray was used to perform genome-wide gene expression studies. When a cutoff value of a two-fold change and a P-value less than 0.01 were used as gene selection criteria, 919 genes were identified as differentially expressed in riddelliine-treated rats compared to the control animals. By analysis with the Ingenuity Pathway Analysis Network, we found that these significantly changed genes were mainly involved in cancer, cell death, tissue development, cellular movement, tissue morphology, cell-to-cell signaling and interaction, and cellular growth and proliferation. We further analyzed the genes involved in metabolism, injury of endothelial cells, liver abnormalities, and cancer development in detail.ConclusionThe alterations in gene expression were directly related to the pathological outcomes reported previously. These results provided further insight into the mechanisms involved in toxicity and carcinogenesis after exposure to riddelliine, and permitted us to investigate the interaction of gene products inside the signaling networks.

Highlights

Pyrrolizidine alkaloids (PAs) are probably the most common plant constituents that poison livestock, wildlife, and humans worldwide
Samples and DNA microarray data analysis Liver samples used in this study were from a previous report [14] in which female Big Blue rats were treated with a carcinogenic dose (1 mg/kg, 5 days per week) of riddelliine for 12 weeks
After data normalized by Quantile normalization which is recommended by the manufacturer, the intensities of the whole rat gene data were analyzed by Principal Components Analysis (PCA, Figure 1)

Summary

Introduction

Pyrrolizidine alkaloids (PAs) are probably the most common plant constituents that poison livestock, wildlife, and humans worldwide. Pyrrolizidine alkaloids (PAs) are common constituents of thousands of plant species around the world and PA-containing plants are probably the most common poisonous plants affecting livestock, wildlife, and humans. Riddelliine is a representative genotoxic PA, and is present in plants growing in the rangelands of the western United States [5,6,7]. These plants containing riddelliine appear to enter the human food chain since riddelliine residues have been detected in meat, milk, and honey [7]. Riddelliine was nominated by the U.S Food and Drug Administration to the National Toxicology Program (NTP) for genotoxicity and carcinogenicity testing due to the potential for human exposure [5]

Methods

Results

Conclusion