Cell-Based Metabolomics for Untargeted Screening and Prioritization of Vertebrate-Active Stressors in Streams Across the United States

Abstract

The U.S. Geological Survey and the U.S. Environmental Protection Agency have assessed contaminants in 38 streams across the U.S., using an extensive suite of target-chemical analysis methods along with a variety of biological effects tools. Here, we report zebrafish liver (ZFL) cell-culture based NMR metabolomic analysis of these split stream samples. We used this untargeted approach to evaluate the sites according to overall impact on the ZFL metabolome and found that neither the total number of organics detected at the sites, nor their cumulative concentrations, were good predictors of these impacts. Further, we used partial least squares regression to compare ZFL endogenous metabolite profiles to values for 455 potential stressors (organics, inorganics, and physical properties) measured in these waters and found that the profiles covaried with at most 280 of the stressors, which were subsequently ranked into quartiles based on the strength of their covariance. While contaminants of emerging concern (CECs) were well represented in the top, most strongly covarying quartilesuggesting considerable potential for eliciting biological responses at these sitesthere was even higher representation of various well-characterized legacy contaminants (e.g., PCBs). These results emphasize the importance of complementing chemical analysis with untargeted bioassays to help focus regulatory efforts on the most significant ecosystem threats.

Pathway‐Based Approaches for Assessing Biological Hazards of Complex Mixtures of Contaminants: A Case Study in the Maumee River

“…One approach involves studying changes in specific metabolites or suites of metabolites to identify biological pathways affected by a given individual test chemical (e.g., Collette et al 2010; Ekman et al 2012; Davis et al 2017). The second approach employs changes in metabolite profiles to provide inferences about the nature of the complex chemical mixture associated with observed biological effects (e.g., Davis et al 2013, 2016; Collette et al 2019). As an illustration of this second type of application, Davis et al (2013) described a caged fish study in which comparative metabolite profiles enabled definition of the contribution of pulp and paper mill influent to the biological effects of a WWTP effluent by conducting measurements in fish exposed before, during, and after a scheduled shutdown of the mill.…”

“…As an illustration of this second type of application, Davis et al (2013) described a caged fish study in which comparative metabolite profiles enabled definition of the contribution of pulp and paper mill influent to the biological effects of a WWTP effluent by conducting measurements in fish exposed before, during, and after a scheduled shutdown of the mill. To build on this approach, we subsequently developed a more direct way to associate changes in endogenous metabolite profiles with individual contaminants in complex mixtures using PLS regression (Davis et al 2016; Collette et al 2019). For the present study, we employed this PLS‐based method to identify contaminants in the measured mixtures that covaried with hepatic metabolomic changes, to highlight (or possibly eliminate) chemicals of potential concern.…”

“…We used partial least‐squares (PLS) regression (SIMCA‐13.0; Umetrics) to compare changes in endogenous metabolite profiles with concentrations of detected organic contaminants, and to screen out those contaminants whose concentrations did not significantly covary with metabolite changes. We have previously used this modeling approach to identify environmental stressors that have (or do not have) a significant biological impact on endogenous metabolites, and full modeling details can be found in these earlier studies (Davis et al 2016; Collette et al 2019). Briefly, for the upstream batch, we first constructed a “global” PLS model that included all 87 organic contaminants detected in at least one of the samples from the upstream sites.…”

The Eco‐Exposome Concept: Supporting an Integrated Assessment of Mixtures of Environmental Chemicals

“…The eco-exposome concept-Environmental Toxicology and Chemistry, 2022;41:30-45 eco-and human exposome research (Collette et al, 2019;Jeong et al, 2018;Rappaport, 2012;Zheng et al, 2020). For example, Collette et al (2019) used PLS combined with crossvalidated predictive residuals analyses to identify stressors related to endogenous metabolite profiles in a zebrafish cell line exposed to water sample extracts from 38 different US streams.…”

Untargeted Lipidomics for Determining Cellular and Subcellular Responses in Zebrafish (Danio rerio) Liver Cells Following Exposure to Complex Mixtures in U.S. Streams

“…The ZFL cell line was chosen due to the extensive use of zebrafish as a model for both human and ecological health-related toxicological research 18 and its demonstrated use for monitoring biological effects of complex mixtures of contaminants in surface water. 19 We sought first to assess the potential of the ZFL lipidome for environmental monitoring and, second, to identify potentially useful lipid-based biomarkers for identifying adverse cellular and subcellular effects.…”