AUTHOR=Meyer Vanessa , Saccone Donovan Sean , Tugizimana Fidele , Asani Furaha Florence , Jeffery Tamsyn Jacki , Bornman Liza 

TITLE=Methylation of the Vitamin D Receptor (VDR) Gene, Together with Genetic Variation, Race, and Environment Influence the Signaling Efficacy of the Toll-Like Receptor 2/1-VDR Pathway

JOURNAL=Frontiers in Immunology

VOLUME=8

YEAR=2017

URL=https://www.frontiersin.org/journals/immunology/articles/10.3389/fimmu.2017.01048

DOI=10.3389/fimmu.2017.01048

ISSN=1664-3224

ABSTRACT=<sec id="ST1"><title>Background</title><p>The disparity in prevalence of infectious diseases across the globe is common knowledge. Vitamin D receptor (VDR)-mediated toll-like receptor (TLR) 2/1 signaling produces antimicrobial peptides, which is critical as a first line of defense in innate immunity. Numerous studies disclosed the independent role of genetic polymorphisms in this pathway, vitamin D status or season and more recently epigenetics, as factors contributing to infectious disease predisposition. Few studies address the interaction between environment, genetics, and epigenetics. Here, we hypothesized that VDR-mediated TLR2/1 signaling is influenced by a combination of environment, epigenetics and genetics, collectively influencing differential innate immunity.</p></sec><sec id="ST2"><title>Methods</title><p>Healthy Black and White South Africans (<italic>n</italic> = 100) donated blood, while ultraviolet index (UVI) was recorded for the duration of the study. LC-MS/MS supported 25(OH)D<sub>3</sub> quantification. Monocyte/macrophage cultures, supplemented with/without 1,25(OH)<sub>2</sub>D<sub>3</sub>, were activated with the TLR2/1 elicitor, Pam<sub>3</sub>CSK<sub>4</sub>. <italic>VDR</italic>, cathelicidin antimicrobial peptide, hCAP-18, and 25-hydroxyvitamin D<sub>3</sub>-24-hydroxylase expression were quantified by RT-qPCR or flow cytometry. Pyrosequencing facilitated <italic>VDR</italic> methylation analysis and single-nucleotide polymorphism (SNP) genotyping in regions pinpointed through a bioinformatics workflow.</p></sec><sec id="ST3"><title>Results</title><p>Season interacted with race showing 25(OH)D<sub>3</sub> deficiency in Blacks. UVI correlated with 25(OH)D<sub>3</sub> and <italic>VDR</italic> methylation, likely influencing race differences in the latter. Regarding the TLR2/1 pathway, race differences in SNP genotype distribution were confirmed and functional analysis of VDR-mediated signaling showed interaction between race, season, and 25(OH)D<sub>3</sub> status. Multivariate OPLS-DA mirrored several interactions between UVI, 25(OH)D<sub>3</sub> status, DNA sequence, and methylation variants. Methylation of the third cytosine-phosphate-guanine dinucleotide (CpG) in the promoter CpG island (CGI) 1062, CGI 1062 CpG 3, significantly discriminated a 5.7-fold above average mean in VDR protein level upon TLR2/1 elicitation, the variation of which was further influenced by 25(OH)D<sub>3</sub> status and the <italic>VDR</italic> SNP <italic>Taq</italic>I.</p></sec><sec id="ST4"><title>Conclusion</title><p>Regulation of VDR-mediated TLR2/1 signaling is multifactorial, involving interaction between environment [UVI and consequent 25(OH)D<sub>3</sub> status], epigenetics (<italic>VDR</italic> methylation at key regulatory sites), and genetics (<italic>TLR1, TIRAP</italic>, and <italic>VDR</italic> SNPs).</p></sec>