Proteomic Analysis of Hepatic Protein Profiles in Rare Minnow (Gobiocypris rarus) Exposed to Perfluorooctanoic Acid

Perfluorooctanoic acid (PFOA) is a ubiquitous contaminant that has been shown to lead to hepatoxicity and is implicated in the incidence of liver tumors in mammals. A number of previous studies have described the toxic effects of PFOA based on conventional toxicological indices and transcriptional data. However, little evidence on protein levels is available. To further our understanding of mechanisms of action and identify the potential protein biomarkers for PFOA exposure, two-dimensional electrophoresis coupled with mass spectrometry has been used to identify proteins differentially expressed in the livers of rare minnow (Gobiocypris rarus) following PFOA exposure of 3, 10, and 30 mg/L. After comparison of the protein profiles from treated and control groups, 34 and 48 protein spots were found altered in abundance (>2-fold) from males and females, respectively. Matrix-assisted laser desorption/ ionization (MALDI) tandem time-of-flight mass spectrometry (TOF/TOF) analysis allowed the unambiguous identification of 25 spots, corresponding to 22 different proteins. These proteins were involved in intracellular fatty acid transport, oxidative stress, macromolecule catabolism, the cell cycle, maintenance of intracellular Ca²⁺ homeostasis, and mitochondrial function. In addition, marked gender differences in response to PFOA have been well-described from the comparison of the male and female protein profiles. Transcriptional analysis of nine mRNAs encoding proteins altered by PFOA in the proteome analysis was determined by real-time PCR. The consistent and discrepant results between mRNA and protein levels suggested that complicated regulatory mechanisms of gene expression were implicated in the response to PFOA exposure.