Regulation of IL-6 and calcitonin gene-related peptide (CGRP) expression by vitamin (VD) in transformed dorsal root ganglion (DRG) cells

Summary: Abstract Body: IL-6 and the neuropeptide CGRP promote generation of Th17 helper T cells and Th17-type immunity is involved in several autoimmune disorders including psoriasis. Some evidence implicates CGRP in the pathogenesis of psoriasis. Also, there is evidence that sensory nerves play a role in Th17-type immunity and inflammation, including in psoriasis. Our preliminary experiments have shown that 25-hydroxyvitamin D3 [25(OH)D3] inhibits production of IL-6 by murine transformed DRG neurons (MED17.11 cells) as a surrogate for primary DRG neurons. MED 17.11 cells were derived from DRG cells from an Immortomouse and express the temperature-sensitive SV40 large T antigen. They express markers of committed sensory neuron progenitors and, when cultured in differentiation medium (containing interferon gamma, fibroblast growth factor 2, dibutyryl cAMP, forskolin, nerve growth factor, Y-27632 and glial cell derived neurotrophic factor), they express markers of mature DRG neurons. Lymph nodes are innervated, so IL-6 and CGRP released from nerves is anatomically situated to influence Th17 cell generation. We have now asked if the active form of VD, 1,25-dihydroxyvitamin D3 [1,25(OH)2D3], similarly regulates IL-6 expression and whether VD also regulates CGRP expression. MED 17.11 cells were cultured (105/ml) in differentiation medium for 48 hrs to induce differentiation. Then, medium in each well was replaced with differentiation medium containing a range of concentrations of 25(OH)D3 or 1,25(OH)2D3. Twenty-four and 48 hrs later supernatants and cells were harvested and cells lysed. IL-6 and CGRP content of supernatants and lysates was assessed by ELISA. Both 25(OH)D3 and 1,25(OH)2D3 significantly inhibited IL-6 content of supernatants and CGRP content of lysates in a dose-dependent manner with 1,25(OH)2D3 more potent. Interestingly, very little IL-6 could be detected in lysates and CGRP could not be reliably detected in supernatants. VD may beneficially affect disorders involving Th17-type immunity (such as psoriasis) by decreasing expression of IL-6 and CGRP by DRG nerves. Wanhong Ding¹, Lori Stohl¹, Richard D. Granstein¹ 1. Weill Cornell Medicine, New York, NY, United States. Adaptive and Auto-Immunity