Gene expression profiles in dendritic cells conditioned by 1α,25-dihydroxyvitamin D₃ analog

Inhibition of dendritic cell (DC) maturity is an important immunomodulatory effect of 1α,25-dihydroxyvitamin D₃ (1α,25(OH) ₂D₃) and related analogs (D₃ analogs). The mechanisms underlying 1α,25(OH)₂D₃-mediated DC modulation are Vitamin D receptor (VDR)-dependent and likely involve direct or indirect regulation of multiple genes. Gene expression profiles of bone marrow-derived DCs (BMDCs) generated in the absence or presence of a potent D₃ analog were analyzed using microarray technology. Results for D₃ analog-conditioned DCs were also compared with glucocorticoid-conditioned BMDCs and with BMDCs conditioned with D₃ analog and glucocorticoid combined. Of ∼12,000 gene products assayed, 52% were considered to have detectable expression in unconditioned BMDCs. Based on relative expression levels, 5.3% of these expressed genes were "silenced" or "suppressed" in D₃ analog-conditioned BMDCs and 2.1% were "augmented". In addition, 1.7% of gene products undetectable in control BMDCs were "induced" by D₃ analog. Functional grouping of modulated genes demonstrated important effects of D₃ analog on immunoreceptors, on chemokines and chemokine receptors, on growth factors/cytokines and related receptors, and on neuroendocrine hormones and related receptors. Many of these gene products were unaffected or differently regulated by glucocorticoid suggesting specific VDR-mediated regulatory effects. Confirmation of microarray analysis results for two differentially regulated chemokines (MIP-1α and RANTES) was obtained by RT-PCR and ELISA. The methodology provides novel insights into DC gene regulation by 1α,25(OH)₂D₃ agonists.