DNA Methylation Polymorphisms Precede Any Histological Sign of Atherosclerosis in Mice Lacking Apolipoprotein E

Abstract

The present work investigates the occurrence and significance of aberrant DNA methylation patterns during early stages of atherosclerosis. To this end, we asked whether the genetically atherosclerosis-prone APOEnull mice show any changes in DNA methylation patterns before the appearance of histologically detectable vascular lesion. We exploited a combination of various techniques: DNA fingerprinting, in vitro methyl-accepting assay, 5-methylcytosine quantitation, histone posttranslational modification analysis, Southern blotting, and PCR. Our results show that alterations in DNA methylation profiles, including both hyper-and hypomethylation, were present in aortas and PBMC of 4-week-old mutant mice with no detectable atherosclerotic lesion. Sequencing and expression analysis of 60 leukocytic polymorphisms revealed that epigenetic changes involve transcribed genic sequences, as well as repeated interspersed elements. Furthermore, we showed for the first time that atherogenic lipoproteins promote global DNA hypermethylation in a human monocyte cell line. Taken together, our results unequivocally show that alterations in DNA methylation profiles are early markers of atherosclerosis in a mouse model and may play a causative role in atherogenesis.Atherosclerosis and its complications are a major cause of death and disability in the developed world. The disease is characterized by infiltration of lipid particles in the arterial wall, accompanied by the recruitment of inflammatory and immune cells, migration and proliferation of smooth muscle cells (SMC), 1 and synthesis of extracellular matrix. These processes eventually result in the gradual development of an elevated lipid-rich, fibrocellular lesion (1).In mammals, DNA methyltransferases use S-adenosyl methionine (SAM) as a methyl group donor to methylate the carbon in position 5 of cytosine residues in a CpG dinucleotide (CG) context (2). DNA methylation regulates fundamental biological phenomena such as gene expression, genome stability, mutation rate, genomic imprinting, and X chromosome inactivation (3-6). Both global and gene-specific alterations in DNA methylation are associated with abnormal phenotypes in disease (7,8). For example, cancer cells show global genomic hypomethylation and dense hypermethylation of CpG islands, which are normally unmethylated (9). The identification of cancer type-and stage-specific changes in DNA methylation has justified hopes for novel diagnostic and therapeutic avenues (10).Two general observations suggest that alterations in DNA methylation patterns are involved in atherogenesis (11-13). First, global hypomethylation and dense hypermethylation of certain CpG islands are associated with aging, a major risk factor for atherosclerosis (14). Second, hyperhomocysteinemia and the subsequent decreased production or bioavailability of SAM is associated with an increased risk of cardiovascular disease (15). Accordingly, mice with genetically reduced levels of methylenetetrahydrofolate reductase, a key enzyme in the pathway generating ...

Extensive demethylation of normally hypermethylated CpG islands occurs in human atherosclerotic arteries

“…As for atherosclerosis, potentially predisposing abnormal DNA methylation patterns have been detected in animal models prior to the appearance of vascular lesions (3). Furthermore, human and animal studies consistently indicate that global DNA hypomethylation accompanies advanced atherosclerosis (3,4). Importantly, 2 recent human studies have indicated that circulating levels of inflammation markers and exposure to environmental risk factors for atherosclerosis were associated with hypomethylation of highly repeated elements of leukocyte DNA (5,6).…”

“…Accordingly, elegant animal models offer proof of principle for the idea that simple dietary interventions can have a significant impact on DNA methylation (2). As for atherosclerosis, potentially predisposing abnormal DNA methylation patterns have been detected in animal models prior to the appearance of vascular lesions (3). Furthermore, human and animal studies consistently indicate that global DNA hypomethylation accompanies advanced atherosclerosis (3,4).…”

Tissue-specific Changes in H19 Methylation and Expression inMice withHyperhomocysteinemia

“…Recent evidence suggests that DNA methylation may play a role in the pathology of cardiovascular disease. Global DNA hypomethylation has been observed in advanced atherosclerotic lesions of humans, rabbits, and mice (2)(3)(4). Apolipoprotein E-deficient mice have been found to have aberrant DNA methylation patterns involving both hypo-and hypermethylation of DNA in aorta and peripheral blood mononuclear cells but not in liver and skeletal muscle (4).…”

Association of the methylenetetrahydrofolate reductase C677T polymorphism and fracture risk in Chinese postmenopausal women

“…DNA methylation is a critical epigenetic mechanism, which involves the initiation of chromatin remodeling and gene expression regulation [28]. Aberrant DNA methylation is believed to play an important role in promotion of a number of diseases [29][30][31]. Recently, several reports have shown that individuals carrying the MTHFR 677TT genotype experience significantly decreased DNA methylation [32,33].…”