The effects of folic acid as model methyl donor on epigenetic modification in human CD4+ in vitro

Introduction: Over the past few decades, the incidence of allergic diseases such as asthma has been increasing in children. This increase is been suggested to be of an environment basis and might be triggered by epigenetical modification. Furthermore, there is increasing evidence that different pregnancy supplementation like folic acid and vitamin B12 play a very important role in the development of fetus. Folic acid plays a very important role in DNA repair as well as in DNA methylation in different loci. The goal of this study is to investigate the effect of different concentrations of folic acid in different time points on the DNA methylation as well as histone acetylation/methylation at cytokine promoters.

Methods: Human CD4+ cells were isolated from peripheral blood of different donors and chromatin immunoprecipitation was performed and validated in order to study the histone modification (acetylation and methylation) in different loci. After establishing the method, the effect of different concentrations of folic acid (1ng, 10ng, 100ng, 1µg, 4µg and 10µg) on the histone modification in CD4+ cells was investigated. Furthermore, DNA methylation, mRNA expression and cytokine production were also investigated to have a hint on the correlation of both DNA methylation and histone modification with both mRNA expression and cytokine production. Morever, cell proliferation was measured using 5-Bromo-2-desoxy-Uridine (BrdU).

Results: Different folic acid concentrations lead to different cell proliferation as well as mRNA expression and cytokine production. The highest concentration of cytokines as well as cell proliferation was observed at 4µg, which is the concentration usually used in cell culture media. Different concentrations caused different activity on mRNA, cytokine levels as well as cell proliferation. These changes can be reflected on DNA methylation and histone modification which will be tested in the following experiments.

Conclusion: Folic acid seems to have a strong effect on the immunological activity of CD4+ cells and this effect varies according to the folic acid concentration. Wheather this variation in vitro is comparable to the in vivo prenatal situation of CD4+ cell activity, needs further investigated.