Grantee Research Project Results
2023 Progress Report: Assessment of Underlying Molecular Mechanisms Promoting Adipogenic Outcomes in Complex Mixtures
EPA Grant Number: R840459Title: Assessment of Underlying Molecular Mechanisms Promoting Adipogenic Outcomes in Complex Mixtures
Investigators: Kassotis, Christopher Dennis , Ghosh, Samiran , Korzeniewski, Steven
Institution: Wayne State University
EPA Project Officer: Aja, Hayley
Project Period: September 1, 2022 through August 31, 2025
Project Period Covered by this Report: September 1, 2022 through August 31,2023
Project Amount: $598,487
RFA: Development of Innovative Approaches to Assess the Toxicity of Chemical Mixtures Request for Applications (RFA) (2022) RFA Text | Recipients Lists
Research Category: Safer Chemicals , Early Career Awards , Health Effects , Human Health , Chemical Safety for Sustainability , New Approach Methods (NAMs) , Mixtures , Non-Vertebrate Animal Testing , CSS
Objective:
Aim 1. We will evaluate mixtures of increasing complexity for ability to promote adipogenesis. Specifically, we will examine mixtures of increasing complexity for their deviations from expected adipogenic effects using concentration addition and independent action models. We hypothesize that mixtures of increasing complexity will shift towards independent action, but that the most complex mixtures will not be well predicted by either model. We will also develop an effect-based model to predict adipogenic activity based on component bioactivities, which we hypothesize will provide a chemical agnostic approach to risk assessments of realistic environmental mixtures.
Aim 2. This proposed research program will rigorously assess available mixture models through controlled assessments of contaminants acting through shared, distinct, and mixed mechanisms. We will utilize in silico approaches to select chemicals predicted to promote adipogenesis through distinct mechanisms. We will use in vitro and in vivo models of metabolic health disruption to assess both individual chemicals and their mixtures and compare with predicted outcomes based on concentration addition and independent action. (3) Our results will promote a greater functional understanding of complex mixture effects that can be utilized to bolster risk assessments of diverse contaminant exposures. By using this stepwise approach of increasing mixture complexity, we expect a primary output of clearly describing the weaknesses and strengths of these standard mixture models. Through our testing of dust extracts, we expect that we can support a new method of mixture risk assessments through using component mechanistic effect levels to determine cooperative effects on complex health endpoints and/or outcomes.
Progress Summary:
The first mixture (Aim 1A) was tested both in vitro and in vivo for all measured outcomes. Each of the chemicals and the mixture were able to activate the peroxisome proliferator activated receptor gamma and each of the chemicals and the mixture were pro-adipogenic in the human mesenchymal stem cell model. The concentration addition predicted responses well matched the observed data and demonstrated as-anticipated additive responses. The independent action models demonstrated responses that were orders of magnitude different than the observed responses, supporting our hypothesis that the single mechanism of action mixture tested here would conform best to the concentration addition model. This mixture represents a simple mixture acting through a shared (single) mode of action on metabolic disruption endpoints. These pro-adipogenic findings suggest that 1) metabolism disrupting chemicals are considerably more widespread in the environment, with a number of these contaminants being reported as active on metabolic health for the first time. 2) that the mixture exhibited lower magnitude of effect than expected in the zebrafish model. This may be due to the reported differences in human versus zebrafish PPARg ligand binding domain. While rosiglitazone does not activate zebrafish PPARg, it robustly activates human PPARg; this has not been well explored for other PPARg-activating chemicals, though we present evidence that these ligand binding domain differences might affect a number of chemicals’ responses. While determinations of synergy are rare and not observed here, additivity is a common phenomenon and are entirely ignored by current federal chemical regulations. Moreover, we provide additional data supporting that single mechanism mixtures are more accurately predicted via concentration addition than via independent action. This tool can be used for risk assessment for mixtures operating through shared mechanism of action. We anticipate that our next aims will help to identify which models work best when multiple mechanisms are involved in the outcomes of interest.
Future Activities:
The next year of the funding period will include writing and submission of manuscript on Aim 1A by end of 2023 or start of 2024. We will also present this project at one or more conferences during the year two period. We will complete all in vitro and in vivo testing for Aim 1B, analyze results, and prepare this manuscript for submission by end of Year 2. We are currently in the process of completing our final zebrafish exposure experiment and will finish analyzing this data in early 2024. In vitro testing is ongoing, with reporter gene assays and hMSC assays complete by the middle of year two of the grant. Results will be presented at one or more meetings during year two. We will initiate both in vitro and in vivo testing for Aim 2A by the end of year two, with a goal of at least 50% complete by the end of the second year. We will also acquire our dust samples for Aim 2B testing by the end of the second year of this award.
Supplemental Keywords:
Adipogenesis; Metabolic Health; Obesogen; Mixture; Dust; Chemicals; Organics; Cumulative Effects; Organism; Cellular; AnimalRelevant Websites:
The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.