Effect of different environmental factors on epigenetic modification in allergy and asthma
In this study chromatin immunoprecipitation was established for using the method in cohort studies were only small amount of cells are available and the samples are routinely frozen and stored at low temperature. Additionally, the method was validated for that purpose. This method was validated usin...
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|Summary:||In this study chromatin immunoprecipitation was established for using the method in cohort studies were only small amount of cells are available and the samples are routinely frozen and stored at low temperature. Additionally, the method was validated for that purpose. This method was validated using different well known validation protocols. Three different cohorts were analyzed using this method with three different perspectives.
In the first cohort, the effect of folate status during pregnancy upon acetylation of Th1, TH2, Treg and TH17 cell loci in cord blood CD4+ T cells was investigated. For that purpose the two extremes very low vs. very high folate levels in maternal blood were picked and both DNA methylation and histone acetylation were investigated.. GATA3 and IL9 were significantly more acetylated at both histones H3 and H4 in the high folate group compared to the low folate group. This suggests that folate status during pregnancy can modify the epigenome toward a more Th2 phenotype supporting the development of allergic disease later in life.
On the other hand, supplementation with fish oil during pregnancy showed adversary effects to what folate showed by causing the reduction in acetylation at the IL13 locus at both H3 and H4 histones. Parallel to that there was a reduction in the histone acetylation in H3 histone at the TBX21 locus. This proves to be consistent with the protein and mRNA data obtained from the same individual 11 years ago (Dunstan et al. 2003). Fish oil proves once again that it can attenuate inflammatory process through ω-3 fatty acids contained in it. Fatty acids in general cause a general DNA hypermethylation which can regulate different genes including inflammatory cytokines and genes (Burdge and Lillycrop 2014). Whether histone acetylation is affected through the same mechanisms illustrated earlier is still to be revealed.
In the same fashion, a comparison between allergic asthmatics with healthy controls was explored. This picture looks more complex. It is not a single factor that causes these epigenetic modifications. Not all the allergy/asthma related genes were influenced in that scenario but there was susceptible gene, among them were IL13 and FOXP3 (FOXP3 data are courtesy of Diana Raedler PhD thesis). Both were significantly more acetylated at histone H3 in asthmatic children in comparison with healthy controls. Moreover, the acetylation at histone H4 for IL13 locus was as well increased in the asthmatic children compared to their fellow healthy controls.
The effect of environmental factors on the development of allergic disease through the development and alteration of the human epigenome is now a major mechanism of disease development. How these effects and what are the most important marks are, is still an open question.
There are still some open questions to be answered and they are of a great importance for future planning.
1- Folate is considered a methyl donor and affects DNA methylation. In this study we have seen another effect of folate comprising histone acetylation as a key factor driving the Th2 machinery. How folate as a methyl donor does affect histone acetylation remains to be clarified.
2- Fish oil with all the different ω-3 fatty acids is considered with different publications a protector against development of allergic disease. In this study we were able to show that fish oil supplementation is associated with histone acetylation and this was further correlated to allergic disease development later in life. The remaining question is how a fatty acid that is usually incorporated into cell membrane alters the epigenome of an individual causing the silencing or activation of certain genes.
3- It has been shown by many investigators that epigenetic modifications work not lonely but are interlinked with each other. Several studies showed interacted mechanisms between different epigenetic modifications. It is very important to have more detailed studies to shed more light on that prospective to understand more the complexity of the human genome.
At the end, in this study one small step toward a better understanding of our complexity has been made and how does a small part of the human epigenome work has been revealed.|
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