Allergic Airway Disease is Dependent on Methylene-Tetrahydrofolate Reductase (expression)

RATIONALE: The development and progression of asthma are strongly influenced by environmental exposures. We have demonstrated that mice exposed to a diet enriched with methyl donors during vulnerable periods of fetal development can enhance the heritable risk of allergic airway disease through epigenetic changes. OBJECTIVES: Since there is conflicting evidence on the role of folate in modifying allergic airway disease risk, we hypothesized that blocking folate metabolism through the loss of methylene-tetrahydrofolate reductase (MTHFR) activity would reduce the allergic airway disease phenotype. METHODS: Using a house dust mite (HDM) induced model of allergic airway disease, we tested the effect of MTHFR on disease severity. MEASUREMENTS AND MAIN RESULTS: Loss of MTHFR alters single carbon metabolite levels in the lung and serum including elevated homocysteine and cystathionine and reduced methionine. HDM-treated C57BL/6MTHFR-/- mice demonstrate significantly less airway hyerreactivity (AHR) compared to HDM-treated C57BL/6 mice. Furthermore, HDM-treated C57BL/6MTHFR-/- mice compared to HDM-treated C57BL/6 mice have reduced whole lung lavage (WLL) cellularity, eosinophilia, and IL-4/IL-5 cytokine concentrations. The effect of MTHFR loss on HDM-induced allergic airway disease was reversed by betaine supplementation. 737 genes are differentially expressed and 146 regions are differentially methylated in lung tissue from HDM-treated C57BL/6MTHFR-/- mice and HDM-treated C57BL/6 mice. Additionally, analysis of methylation/expression relationships identified 503 significant correlations. CONCLUSION: Collectively, these findings indicate that single carbon metabolism warrants further investigation as a disease modifier in allergic airway disease. Gene expression profiles of lung in MTHFR-/- mice treated with house dust mite (HDM, n = 9) or saline (n = 5) or wild-type (WT) mice treated with house dust mite (HDM, n = 9) or saline (n = 6)