Location: Diet, Genomics and Immunology Laboratory
2014 Annual Report
Objectives
Objective 1: Determine whether bioactive food components, such as vitamins A and D or lycopene, acting via vitamin A and D-receptor-mediated pathways and nuclear factor-kappaB signaling, exhibit dose-dependent inhibitory effects on macrophage-mediated remodeling of adipose tissue toward a pro-inflammatory phenotype in response to high fat diets in a swine model. [NP 107 Component 3, Problem Statement 3B].
Objective 2: Determine whether bioactives from food, including selenium, vitamin A, and thiol compounds, alter the immune response to model infectious organisms in mice through epigenetic changes, redox sensitive signaling pathways, and tissue remodeling by controlling cellular thiol levels, redox tone, and/or mitochondrial function. Compare responses of wild-type and genetically engineered mice with altered expression of one or more selenoproteins or proteins important for vitamin A or redox function, to identify specific proteins or pathways important for the effect of the nutrients under study on immune function and tissue remodeling. [NP 107 Component 3, Problem Statement 3B]
Approach
For Objective 1, in vitro and in vivo porcine models will be used to test the hypothesis that vitamin A or vitamin D or metabolites of dietary compounds that signal through retinoic acid receptor signaling pathways, such as lycopene, will promote an anti-inflammatory phenotype of adipose tissue macrophages and inhibit pro-inflammatory responses of adipose tissue macrophages to inflammatory ligands via inhibition of NF-kappaB signaling and epigenetic regulation of macrophage polarization.
For Objective 2, a mouse model will be used to test the hypothesis that bioactives from food, including selenium, vitamin A, and thiol compounds, alter the immune response to model infectious organisms in mice through epigenetic changes, redox-sensitive signaling pathways, and tissue remodeling by controlling cellular thiol levels, redox tone, and/or mitochondrial function. Responses of wild-type and genetically engineered mice with altered expression of one or more selenoproteins or proteins important for vitamin A or redox function, will be used to identify specific proteins or pathways important for the effect of the nutrients under study on immune function and tissue remodeling.
Progress Report
This is a new project plan replacing and expanding on 1235-51000-055-00D. Several porcine adipose tissue macrophage isolations were performed to optimize yield and viability. Based upon these results, the lab has tested and purchased an automated magnetic bead isolation unit. Several human and monocyte blood isolations were performed to determine the best time course for addition of macrophage polarizing ligands such as retinoic acid and interleukin-4.
Progress was made in identifying candidate selenoprotein genes affected by selenium deficiency and associated with the rebound in immunity upon re-feeding adequate diet. The expression of selenoproteins GPX2 and GPX3 is increased by infection. However, GPX2 activity is further enhanced by selenium deficiency while GPX3 expression is decreased by selenium deficiency. Re-feeding adequate diet decreases expression of GPX2 but increases expression of GPX3. GPX1 activity also rapidly rebounds after re-feeding adequate diet. Thioredoxin reductase and selenophosphate synthase 2 expression is decreased by infection but to a lesser extent in selenium deficient mice and this trend starts to reverse upon re-feeding. Cyst formation is a STAT6-dependent process and knock-out of IL-13 produces a cyst phenotype similar to that seen in selenium deficient mice where IL-13 expression is decreased, suggesting a role for IL-13. Several thiol compounds were tested including N-acetyl cysteine, 2-mercaptoethanol, lipoic acid, and Co-enzyme Q10, for their ability to alter the pathogenesis of C. rodetnium infection. Both Co-Q10 and 2-ME reduced the level of colonization in the colon and these results will be pursued further. Preliminary studies on the effect of Vitamin A (VA) deficiency on immunity were completed and demonstrate that VA deficiency increases the colonization of the colon, and causes barrier function disruption, but only in the presence of pathogenic bacteria. Th1/Th17 cytokine production was blunted by VA deficiency but not chemokine production. There was severe damage to the colonic epithelial layer and disruption of crypt architecture. In addition, goblet cells were enlarged in VA deficient mice and stained more heavily for mucins, raising the possibility that export of mucins into the intestinal lumen is impaired in VA deficient mice.
Accomplishments
1. Vitamin A is critical for immunity to gastrointestinal bacterial infections. Vitamin A deficiency remains a significant problem in developing countries and sub-clinical deficiencies may exist in at-risk populations such as low-income children or the elderly in the U.S. We demonstrated that vitamin A deficiency impairs the ability to mount an effective immune response to bacterial infection in mice that is very similar to E. coli infections in humans and supports epidemiological studies showing more frequent and severe diarrheal disease in vitamin A individuals. These results highlight the need of health care workers to evaluate the diets of at risk populations to insure that adequate levels of vitamin A are being consumed for optimal immune function.
