Carolinas Research Day 2021

Biomedical Studies

05 Exposure to the Environmental Endocrine Disruptor Tolylfluanid During Cerebral Brain Development Significantly Alters Cortical Neuron Gene Expression

Amar Patel, Ken Nguyen, Rachel Winstead, Olivia Mattner, Rebecca Beaudry, Katherine Baumgarner, Bradley Baumgarner, PhD2, and Stephan Brown, MD, PhD

Edward Via College of Osteopathic Medicine-Carolinas, Gibbs Cancer Institute, University of South Carolina Upstate

Introduction: Tolylfluanid (TF), (the active ingredient in agricultural pesticides) is an endocrine disruptor that has been shown to increase anaerobic glycolysis and reduce oxygen consumption in human cells. Both gene expression and environmental input are essential for normal brain development, and disruption of either can fundamentally alter neural outcomes [1]. Brain formation begins with the development of neural progenitor cells, which are derived from the ectodermal germ layer [2]. The ensuing period of fetal development extends through the end of gestation. During this time there is rapid growth and elaboration of both cortical and subcortical structures, including the rudiments of the major fiber pathways (Kostovic and Jovanov-Milosevic 2006). Similar to pluripotent stem cells, neural progenitors rely almost exclusively on anaerobic glycolysis to meet their energy needs [4]. The differentiation of neural progenitor cells into functional cortical neurons coincides with a transition from anaerobic glycolysis to oxidative phosphorylation [4-5]. Neural differentiation increases the expression of genes associated with

mitochondrial metabolism while simultaneously decreasing the expression of glycolysis-related genes [5]. TF is an environmental EDC that has been shown to reduce glucose oxidation in mammalian cells [10]. Chen et al. [10] discovered that TF reduced glucose oxidation in human adipocytes by directly inhibiting the mitochondrial pyruvate carrier (MPC). A previous investigation by Vacanti et al. [11] revealed that pharmacological inhibition (similar to TF) or genetic deletion of MPC significantly reduced glucose oxidation in human skeletal muscle cells, which increased mitochondrial fatty acid glutamine oxidation [11]. Therefore, it appears that by blocking mitochondrial pyruvate uptake, TF can increase the utilization of other oxidative fuels. However, the potential impact of TF exposure on cellular glycolytic capacity has yet to be fully investigated. Hypothesis: TF deceases glucose oxidation in developing neurons causing metabolic stress. This constant stress alters neuron metabolism leading to gene expression alterations.

We propose to determine whether TF exposure during central nervous system development could significantly alter fully differentiated human brain organoids. The central nervous system forms in the third week of fetal development and is derived from neuroectodermal germ tissue (1). In the brain, most of the glucose is oxidized to produce the vast amounts of ATP required to maintain cellular processes (2). The availability of energy to neuronal progenitor cells could limit the brain’s size and activity (3). Conclusions: Results reveal that treating induced- pluripotent stem cell derived cerebral organoids with TF throughout differentiation significantly altered organoid development and particularly effected subpopulations of neurons (ie. Dopaminergic neurons and cortical) differently than other neural cell types. Metabolic studies showed reduces the glycolytic rate of fully differentiated cortical neurons under basal and compensatory (anaerobic) conditions when compared to vehicle treated cells.

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