Hyperhomocysteinemia during aortic aneurysm, a plausible role of epigenetics

Hyperhomocysteinemia is associated with aortic aneurysm, however, the mechanisms are unclear. We hypothesize that the expression level of genes involved in extracellular matrix (ECM) remodeling, oxidative stress, and enzymes involved in homocysteine metabolism pathway in aortic aneurysm and hyperhomocysteinemia are differentially regulated by DNA methylation. We studied the mRNA levels of MTHFR, SAHH, MMP-1, -9, TIMP-1, -4, peroxiredoxin, NOX-2, -3 (NAPDH oxidase subunits), collagen and elastin in normal and aortic aneurysm tissues from humans and aorta tissue from HHcy (Cystathionine beta synthase heterozygote knockout, CBS+/-) mice treated with high methionine diet. The total RNA was extracted using Trizol method and RT-PCR was performed. Protein expression of MTHFR, H3K9 (trimethyl) and TIMP4 were studied in mice using immunohistochemistry. MTHFR and TIMP4 expression was seen to be increasing in both human aneurysm samples as well as HHcy CBS+/- mice. There was increased expression of MMP9, peroxiredoxin and decreased expression of MMP1, Collagen I and IV was noted in thoracic aortic aneurysm samples. Increased Collagen IV and decreased Collagen I levels were seen in CBS +/- HHcy mice compared to their wild type controls. Since DNA methylation regulates gene expression of enzymes in Hcy metabolism pathway, we also measured the mRNA levels of DNMTs, MBD2 and H3K9. The results suggest an increase in the levels of DNMT1, 3a, MBD2 and H3K9 in CBS +/- aorta compared to their wild type controls. Our findings suggest a possible role of methylation in regulation of expression of genes involved in matrix remodeling and homocysteine metabolism.