Differential Expression Profiling of the Hepatic Proteome in a Rat Model of Dioxin Resistance

Abstract

One characteristic feature of acute 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) toxicity is dramatic interspecies and interstrain variability in sensitivity. This complicates dioxin risk assessment for humans. However, this variability also provides a means of characterizing mechanisms of dioxin toxicity. Long-Evans (Turku/AB) rats are orders of magnitude more susceptible to TCDD lethality than Han/Wistar (Kuopio) rats, and this difference constitutes a very useful model for identifying mechanisms of dioxin toxicity. We adopted a proteomic approach to identify the differential effects of TCDD exposure on liver protein expression in Han/Wistar rats as compared with Long-Evans rats. This allows determination of which, if any, protein markers are indicative of differences in dioxin susceptibility and/or responsible for conferring resistance. Differential protein expression in total liver protein was assessed using two-dimensional gel electrophoresis, computerized gel image analysis, in-gel digestion, and mass spectrometry. We observed significant changes in the abundance of several proteins, which fall into three general classes: (i) TCDD-independent and exclusively strain-specific (e.g. isoforms of the protein-disulfide isomerase A3, regucalcin, and agmatine ureohydrolase); (ii) strain-independent and only dependent on TCDD exposure (e.g. aldehyde dehydrogenase 3A1 and rat selenium-binding protein 2); (iii) dependent on both TCDD exposure and strain (e.g. oxidative stress-related proteins, apoptosis-inducing factor, and MAWD-binding protein). By integrating transcriptomic (microarray) data and genomic data (computational search of regulatory elements), we found that protein expression levels were mainly controlled at the level of transcription. These results reveal, for the first time, a subset of hepatic proteins that are differentially regulated in response to TCDD in a strain-specific manner. Some of these differential responses may play a role in establishing the major differences in TCDD response between these two strains of rats. As such, our work is expected to lead to new insights into the mechanism of TCDD toxicity and resistance. Molecular & Cellular Proteomics 5:882-894, 2006.

Insoluble Mutant SOD1 Is Partly Oligoubiquitinated in Amyotrophic Lateral Sclerosis Mice

“…The mass spectra were internally calibrated with trypsin or V8 autolysis fragments, routinely obtaining accuracy better than 30 ppm. For the detection of additional post-translational modifications of SOD1, liquid chromatography-MS/MS analysis was done on a reverse phase microbore liquid chromatography Suveyor system coupled to an ion trap mass spectrometer LCQ Deca XP Plus (Thermo Finningan), as described (28).…”

CYP1A/Regucalcin Gene Expression and Edema Formation in Zebrafish Embryos Exposed to 2,3,7,8-Tetrachlorodibenzo-p-dioxin

“…Our results indicated there was no significant difference in RC mRNA expression at each selected time compared to the control. Similarly, TCDD did not alter the abundance of RC transcripts or proteins in rat model (Pastorelli et al 2006). So taken together, there may be some other Ca 2+ -regulated protein rather than RC which would be involved in TCDDinduced edema.…”

“…TCDD exposure to lake trout eggs produces a dose-related induction of CYP1A in vascular endothelial cells of embryos and sac fry, which correlates with yolk sac edema, hemodynamic dysfunction, and subsequent sac fry mortality (Guiney et al 1997). On the other hand, exposure to TCDD substantially increases the intracellular free Ca 2+ level in several cell types (Puga et al 1997;Canga et al 1993), and regucalcin (RC), a Ca 2+ -binding protein, plays a role in the maintenance of intracellular Ca 2+ homeostasis by activating Ca 2+ pump enzymes, was also studied in rat model to evaluate the risk posed by TCDD (Takahashi and Yamaguchi 1997;Pastorelli et al 2006). In this study, mortality, heart rates, edema severity, CYP1A, and RC gene expressions were studied to investigate low dose of TCDD-induced toxicity in zebrafish during the early life stage.…”

Sex-dependent compensated oxidative stress in the mouse liver upon deletion of catechol O-methyltransferase

“…In iron loaded hepatic cells, a decrease in ALDH2 activity [55] and expression [56] pumping activity [58]. Pastorelli and co-workers [57] also speculate that the elevated basal levels of regucalcin may confer to the TCDD-resistant strain a protection against disruption of calcium homeostasis as might be mediated by TCDD. Therefore, the decrease of the levels of ALDH2 and regucalcin in the COMT disrupted liver may not be compensatory in nature, but on the contrary, these changes might make the liver more vulnerable to the cellular environment under COMT disruption..…”