Vitamin D2 and Calcipotriol (psoriasis drug) increase Vitamin D3 getting to cells – June 2018

Confirmation of high-throughput screening data and novel mechanistic insights into VDR-xenobiotic interactions by orthogonal assays

(Nature) Scientific Reports | (2018) 8:8883 | DOI:10.1038/s41598-018-27055-3

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Endogenous CYP24A1 induction in HL-60 cells by compounds in the presence of 3nM Vitamin D3:

Improves the Vitamin D Receptor Response

(a) VDR agonists: as % increase of D3
    Note: Calcipotriol treats Psoriasis - by increasing the D3 getting to cells

% of Vitamin D Receptor Response relative to D3

Example: Cadmium (toxic) reduces response to just 12% of normal

Debabrata Mahapatra1, Jill A. Franzosa5, Kyle Roell2, Melaine Agnes Kuenemann2, Keith A. Houck 5, David M. Reif 2, Denis Fourches2 & Seth W. Kullman3,4 swkullma at ncsu.edu
1 Comparative Biomedical Sciences, College of Veterinary Medicine, North Carolina State University, Raleigh, North Carolina, USA.
2 Department of Chemistry, Bioinformatics Research Center, North Carolina State University, Raleigh, North Carolina, USA.
3 Department of Biological Sciences, North Carolina State University, Raleigh, North Carolina, USA.
^Program in Environmental and Molecular Toxicology, North Carolina State University, Raleigh, North Carolina, USA.
5 National Center for Computational Toxicology, Office of Research and Development, U.S. Environmental Protection Agency, RTP, Raleigh, North Carolina, USA.

High throughput screening (HTS) programs have demonstrated that the Vitamin D receptor (VDR) is activated and/or antagonized by a wide range of structurally diverse chemicals. In this study, we examined the Tox21 qHTS data set generated against VDR for reproducibility and concordance and elucidated functional insights into VDR-xenobiotic interactions. Twenty-one potential VDR agonists and 19 VDR antagonists were identified from a subset of >400 compounds with putative VDR activity and examined for VDR functionality utilizing select orthogonal assays. Transient transactivation assay (TT) using a human VDR plasmid and Cyp24 luciferase reporter construct revealed 20/21 active VDR agonists and 18/19 active VDR antagonists. Mammalian-2-hybrid assay (M2H) was then used to evaluate VDR interactions with co-activators and co-regulators. With the exception of a select few compounds, VDR agonists exhibited significant recruitment of co-regulators and co-activators whereas antagonists exhibited considerable attenuation of recruitment by VDR. A unique set of compounds exhibiting synergistic activity in antagonist mode and no activity in agonist mode was identified. Cheminformatics modeling of VDR-ligand interactions were conducted and revealed selective ligand VDR interaction. Overall, data emphasizes the molecular complexity of ligand-mediated interactions with VDR and suggest that VDR transactivation may be a target site of action for diverse xenobiotics.