In vitro screening for population variability in chemical toxicity - PubMed (original) (raw)

In vitro screening for population variability in chemical toxicity

Shannon H O'Shea et al. Toxicol Sci. 2011 Feb.

Abstract

Immortalized human lymphoblastoid cell lines have been used to demonstrate that it is possible to use an in vitro model system to identify genetic factors that affect responses to xenobiotics. To extend the application of such studies to investigative toxicology by assessing interindividual and population-wide variability and heritability of chemical-induced toxicity phenotypes, we have used cell lines from the Centre d'Etude du Polymorphisme Humain (CEPH) trios assembled by the HapMap Consortium. Our goal is to aid in the development of predictive in vitro genetics-anchored models of chemical-induced toxicity. Cell lines from the CEPH trios were exposed to three concentrations of 14 environmental chemicals. We assessed ATP production and caspase-3/7 activity 24 h after treatment. Replicate analyses were used to evaluate experimental variability and classify responses. We show that variability of response across the cell lines exists for some, but not all, chemicals, with perfluorooctanoic acid (PFOA) and phenobarbital eliciting the greatest degree of interindividual variability. Although the data for the chemicals used here do not show evidence for broad-sense heritability of toxicity response phenotypes, substantial cell line variation was found, and candidate genetic factors contributing to the variability in response to PFOA were investigated using genome-wide association analysis. The approach of screening chemicals for toxicity in a genetically defined yet diverse in vitro human cell-based system is potentially useful for identification of chemicals that may pose a highest risk, the extent of within-species variability in the population, and genetic loci of interest that potentially contribute to chemical susceptibility.

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Figures

FIG. 1.

FIG. 1.

Interindividual variability in response to toxicants in a panel of human lymphoblast cell lines. Production of ATP (A) and activation of caspase-3/7 (B) were assessed 24 h after treatment with phenobarbital (○, 3000μM), PFOA (□, 100mM), rifampin (▴, 100μM), or propiconazole (◊, 100μM). Percent change over the baseline (vehicle, 1% DMSO) in each cell line is shown. Cell lines are ordered (in each panel separately) according to the response to phenobarbital. Cell lines were considered responders (filled symbols) if percent change was exceeding the significance threshold (see Materials and Methods section ).

FIG. 2.

FIG. 2.

Population-wide variability in response to 14 model toxicants. Production of ATP (A and C) and activation of caspase-3/7 (B and D) in a panel of human lymphoblast cells were assessed 24 h after treatment with the highest dose (see Supplementary fig. 1) of each compound. Box and whiskers plots (A and B) were used to exhibit the variability in responses across the population. Bar graphs (C and D) demonstrate the number of cell lines with a significant response above (light bars) or below (dark bars) the vehicle control.

FIG. 3.

FIG. 3.

Within-assay correlation map of compound activity across the population. Correlations between compounds with respect to their population-wide effects in the ATP production (bottom left) or caspase-3/7 activation (upper right) assays are shown as a heat map using Spearman correlation coefficient values (see sidebar scale for reference). Only DE 71 and Rifampin (Caspase 3/7 activation) showed negative correlation.

FIG. 4.

FIG. 4.

Correlation of responses between chemicals and individuals. Heat maps were generated by clustering (average linkage on the correlation metric) the data on percent ATP production and percent caspase activation at highest dose across all chemicals and individuals. The heat maps are ordered both vertically and horizontally with the most correlated participants and chemicals being displayed near to one another. Data were mean centered and transformed as indicated in the corresponding histograms.

FIG. 5.

FIG. 5.

Genome-wide association scan of ATP production response to PFOA. (A) Genome-wide plot of SNPs and their degree of association with PFOA-elicited ATP production phenotype. Arrows indicate the loci with highest association. (B and C) Loci (500 kb) on chromosomes 4 and 14 flanking SNPs that are highly associated (p < 0.000001) with PFOA-elicited phenotype. Genes located in these loci are shown as well as gene networks for CPSF2 (D) and RIN3 (E). Shaded symbols (IGHM, RAB5A and RAB5B) indicate genes that have been identified as responsive to PFOA treatment in rat and chicken liver (Guruge et al., 2006; Yeung et al., 2007).

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