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A Vitamin D-cAMP Anti-Inflammatory Axis in Asthmatic Airway Epithelium
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A1198 - A Vitamin D-cAMP Anti-Inflammatory Axis in Asthmatic Airway Epithelium
Author Block: D. M. Mansell1, C. E. Hoptay2, B. Harmon3, K. Authelet4, D. K. Pillai5, R. J. Freishtat6; 1Microbiology, College of Medicine, Howard University, Northwest, DC, United States, 2Center of Genetic Medicine, Children's National Medical Center, Washington, DC, United States, 3Children s National Health System, Washington, DC, United States, 4Children s National Medical Center, Washington, DC, United States, 5Childrens National Medical Center, Washington, DC, United States, 6Pediatrics, Children's National Med Ctr, Washington, DC, United States.
Abstract
RATIONALE: We and others have shown that vitamin D insufficiency is related to asthma pathology. The mechanisms underlying this interaction are not clear, but one possibility is that vitamin D acts like other fat-soluble vitamins (e.g. vitamin E) that are known to induce anti-inflammatory cAMP. Therefore, we hypothesize that vitamin D (25(OH)D) induces cAMP production in airway epithelial cells.
METHODS: Nasal epithelial cells and demographic data were collected as part of the AsthMaP2 cohort of urban youth between six and 20 years with physician-diagnosed asthma for >1 year. Nasal epithelial cells were cultured for 90 minutes ex vivo with 25(OH)D and/or dexamethasone (DEX). mRNA was profiled using Illumina and validated using NanoString. Network and functional analyses were performed using Ingenuity Pathway Analysis. Confirmatory experiments were performed on human asthmatic and non-asthmatic tracheal bronchial epithelial cells exposed to 25(OH)D with or without DEX. Intracellular proteins were measured with ELISA.
RESULTS: Of 214 AsthMaP2 participants, 53% were male and (97%) had persistent asthma. The mean (SE) age=10.9(0.4) years, BMI percentile for age=72.1(3)%, and serum 25(OH)D=19.5(0.9) ng/mL. Whole transcriptome analyses of nasal epithelial cells (n=7) showed 34 transcripts differentially expressed across conditions (p≤0.01). Pathways analysis identified cAMP signaling as a top activated pathway impacted by 25(OH)D. Intracellular cAMP levels were 10-fold higher in asthmatic (n=3) vs. non-asthmatic (n=3) tracheal bronchial epithelial cells at baseline (p=0.009). While this difference persisted through 15 minutes of exposure to vitamin D with or without DEX, there were no significant changes in intracellular cAMP from baseline.
CONCLUSIONS: Our data show that asthmatic epithelial cells constitutively express higher levels of cAMP than non-asthmatic epithelial cells. Interestingly, low cAMP levels in dendritic cells have been shown to induce Th2 responses. Vitamin D’s predicted effects are not demonstrated in our small confirmatory sample. Additional experiments are required to rule in or out the proposed vitamin D-cAMP relationship in asthma.
Author Block: D. M. Mansell1, C. E. Hoptay2, B. Harmon3, K. Authelet4, D. K. Pillai5, R. J. Freishtat6; 1Microbiology, College of Medicine, Howard University, Northwest, DC, United States, 2Center of Genetic Medicine, Children's National Medical Center, Washington, DC, United States, 3Children s National Health System, Washington, DC, United States, 4Children s National Medical Center, Washington, DC, United States, 5Childrens National Medical Center, Washington, DC, United States, 6Pediatrics, Children's National Med Ctr, Washington, DC, United States.
Abstract
RATIONALE: We and others have shown that vitamin D insufficiency is related to asthma pathology. The mechanisms underlying this interaction are not clear, but one possibility is that vitamin D acts like other fat-soluble vitamins (e.g. vitamin E) that are known to induce anti-inflammatory cAMP. Therefore, we hypothesize that vitamin D (25(OH)D) induces cAMP production in airway epithelial cells.
METHODS: Nasal epithelial cells and demographic data were collected as part of the AsthMaP2 cohort of urban youth between six and 20 years with physician-diagnosed asthma for >1 year. Nasal epithelial cells were cultured for 90 minutes ex vivo with 25(OH)D and/or dexamethasone (DEX). mRNA was profiled using Illumina and validated using NanoString. Network and functional analyses were performed using Ingenuity Pathway Analysis. Confirmatory experiments were performed on human asthmatic and non-asthmatic tracheal bronchial epithelial cells exposed to 25(OH)D with or without DEX. Intracellular proteins were measured with ELISA.
RESULTS: Of 214 AsthMaP2 participants, 53% were male and (97%) had persistent asthma. The mean (SE) age=10.9(0.4) years, BMI percentile for age=72.1(3)%, and serum 25(OH)D=19.5(0.9) ng/mL. Whole transcriptome analyses of nasal epithelial cells (n=7) showed 34 transcripts differentially expressed across conditions (p≤0.01). Pathways analysis identified cAMP signaling as a top activated pathway impacted by 25(OH)D. Intracellular cAMP levels were 10-fold higher in asthmatic (n=3) vs. non-asthmatic (n=3) tracheal bronchial epithelial cells at baseline (p=0.009). While this difference persisted through 15 minutes of exposure to vitamin D with or without DEX, there were no significant changes in intracellular cAMP from baseline.
CONCLUSIONS: Our data show that asthmatic epithelial cells constitutively express higher levels of cAMP than non-asthmatic epithelial cells. Interestingly, low cAMP levels in dendritic cells have been shown to induce Th2 responses. Vitamin D’s predicted effects are not demonstrated in our small confirmatory sample. Additional experiments are required to rule in or out the proposed vitamin D-cAMP relationship in asthma.
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