Grantee Research Project Results
2016 Progress Report: Establishing an AOP for the Role of the Vitamin D Receptor in Developmental Neurotoxicity
EPA Grant Number: R835541Title: Establishing an AOP for the Role of the Vitamin D Receptor in Developmental Neurotoxicity
Investigators: Kullman, Seth W. , Levin, Edward D , Slotkin, Theodore
Institution: Duke University Medical Center , North Carolina State University
EPA Project Officer: Aja, Hayley
Project Period: July 1, 2013 through June 30, 2016 (Extended to January 31, 2018)
Project Period Covered by this Report: July 1, 2015 through June 30,2016
Project Amount: $799,496
RFA: Development and Use of Adverse Outcome Pathways that Predict Adverse Developmental Neurotoxicity (2012) RFA Text | Recipients Lists
Research Category: Chemical Safety for Sustainability , Human Health
Objective:
Recent evidence suggests a linkage between exposure to environmental neurotoxic chemicals and the marked increase in neurodevelopmental disorders including learning disabilities, attention deficit and hyperactivity disorder, autism spectrum disorders, and Parkinson’s disease. Neurotoxic chemical exposure during development can have adverse functional effects expressed either during the process of neurobehavioral development or later in life. Vitamin D receptors are critical regulators for neurodevelopment and interruption of vitamin signaling during ontogeny can have important consequences on neural differentiation and the development of neural circuitry, particularly with regard to dopaminergic innervation. Here we provide an adverse outcome pathway to test the hypothesis that modulation of the vitamin D neuroendocrine axis is associated with developmental neurotoxicity and may play a pathophysiological role in adult neurobehavioral disorders. Our AOP is based upon four specific aims: Aim 1. Identify and validate VDR as a nuclear receptor target for chemical agents identified in the EPA’s ToxCast and Tox21 chemical libraries; Aim 2. Establish integrative neuronal cell response to select VDR agonists/antagonists; Aim 3. Utilize the zebrafish vivo model to assess xenobiotic induced modulation of dopaminergic neurons though alterations in tyrosine hydroxylase expression and activity; and Aim 4. Establish a linkage between developmental exposures, modulation of VDR signaling and adult neural behavioral consequence in zebrafish.
Progress Summary:
To date we have made significant accomplishments on each of the defined aims and goals. Multiple Tox21/ToxCast VDR agonists/antagonists have been screened using validated orthogonal nuclear receptor assays with both human and zebrafish VDR. Through this process we have confirmed transactivation activities and the ability of ligands to initiate key protein:protein interactions with essential VDR co-regulators. We have used select cell based assays in hepatic, kidney, monocytes and neuronal cell lines to demonstrate the ability of VDR agonists/antagonists to enhance transcriptional activation of endogenous transcriptional targets. We have localized VDR expression in zebrafish and medaka brain, and extending experiments to examine how VDR agonists/antagonists (dys)regulate select neural targets in developing and adult zebrafish brain. Finally, we have screened selective VDR agonists/antagonists to identify how VDR signaling or disruption there in, modulates behavioral outcomes of larval and adult zebrafish. Overall, data derived in year three is consistent with stated aims of the proposal. Aims of the project have not changed from the original application. Additionally, to aid in facilitating proof of principle we have developed models of vitamin D deficient (D-) and vitamin D sufficient (D+) lines of zebrafish that can be used as a positive control supporting our initial hypothesis regarding the role of vitamin D in neurodevelopment. In this line of investigation, we have established a F0 population(s) of fish that are either D+ and D-. Compared to D+ animals, D- animals display multiple phenotypes including visceral fat/lipid accumulation, corneal thickening and altered oocyte development in addition to select neuro-phenotypes. Both D+ and D- lines are reproductively active and we are in process of collecting D+ and D- F1’s. To date we illustrate that both D- F0 adults and D- F1s exhibit differential behavioral functions, altered levels of neurogenic markers, and metabolic differences compared to D+ animals. These studies are ongoing and will greatly facilitate our understanding of the role(s) vitamin D sufficiency or deficiency plays in early neurodevelopment and possible adult neurodegenerative disease. Our AOP is designed to facilitate prediction of a chemical’s potential for developmental neurotoxicity in a manner that is both informative of mechanisms and relevant to human health risk assessment. These studies are directed at establishing the adverse outcome pathway for toxicant actions on vitamin D receptors causing neurobehavioral impairment. The intent is to define a screening system to enable testing large chemical libraries for receptor activities in relation to developmental neurotoxicity and implement predictive strategies for human risk based upon evaluation of mechanistic and apical data derived from a linked series of in vitro and in vivo responses.
Journal Articles:
No journal articles submitted with this report: View all 24 publications for this projectSupplemental Keywords:
Vitamin D, developmental neurotoxicity, dopamine, zebrafishProgress and Final Reports:
Original AbstractThe 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.