Oral Presentation International Veterinary Immunology Symposium 2016

The role of nutrition in the regulation of the porcine immune response; the regulatory actions of vitamin A and vitamin D on cell signaling pathways in epithelial cells and macrophages (#26)

Harry Dawson 1 , Celine Chen 1 , Joseph F Urban 1
  1. ARS, USDA, Beltsville, MD, United States

Previously we demonstrated that the most bioactive vitamin A metabolite, all-trans retinoic acid (ATRA) increased T helper 2-associated responses induced by Ascaris infection of pigs. We also demonstrated, on a limited basis, that ATRA potentiated the mRNA expression of several IL-4 induced chemokines associated with alternative activation (M2a) in porcine macrophages in vitro. Herein, we describe several mechanisms whereby ATRA affects IL-4 signaling and extend these findings to epithelial cells and to other cell signaling pathways. Treatment of primary explanted pig alveolar macrophages and several pig myeloid cell lines with ATRA alone induced expression of additional markers of M2a activation, and reduced the expression of classically activated (M1)-associated macrophage markers, as shown by next generation sequencing (NGS), real-time RT-PCR analysis and protein expression. NGS also showed that ATRA regulated an abundance of genes in the vitamin D3 (1,25- dihydroxyvitamin D3 (VD3) receptor (VDR) pathway. Treatment with both ATRA and VD3 differentially affected the expression of M1 and M2a macrophage markers. ATRA-treatment also reduced the induction of TNF mRNA and protein expression in response to LPS/interferon-g treatment. In two intestinal epithelial cell lines, we observed that ATRA increased RNA and protein for the IL-4 receptor alpha chain and the VDR. ATRA increased IL-4 induced phosphorylation of signal transducer and activator of transcription 6 (STAT6) and mRNA expression of the chloride channel, calcium activated, family member 1 (CLCA1), important for mucus formation, and chemokine (C-C motif) ligand 26 (CCL26) a potent eosinophil chemoattractant. ATRA also increased VD3 induced gene expression. Thus, in intestinal epithelial cells and macrophages, ATRA increased signaling in response to IL-4 and VD3. Given the prevalence of allergic and parasitic diseases worldwide and the close similarities in the porcine and human immune responses, these findings have important implications for the nutritional regulation of inflammation at mucosal surfaces.