Local hypomethylation in atherosclerosis found in rabbit ec-sod gene

Extracellular superoxide dismutase (EC-SOD) protects arteries against delet erious effects of superoxide anions and the development of atherosclerosis. In this study, we cloned and characterized rabbit ec-sod gene. We identifi ed 6 rabbit C-elements and 5 CpG clusters in the cloned sequence. One of th e CpG clusters is located on the coding sequence. Because CpG clusters are potential sites for methylation acid may explain the occurrence of mutation s, methylation status of each of the CpG dimers located in the coding seque nce CpG cluster was characterized using direct genomic sequencing, Unexpect edly, a marked reduction in the amount of methylated CPG dinucleotides in e c-sod gene was detected in atherosclerotic aortas as compared with normal a ortic intima-media. Although alterations in DNA methylation are well charac terized in malignant tumors, the presence of methylation changes in atheros clerosis has not been studied even though both diseases are characterized b y excess cellular proliferation and alterations in gene expression. Further analysis of the whole genomic methylation by high-pressure liquid chromato graphy in normal and atherosclerotic aortas revealed a tendency for a decre ased 5-methylcytosine (5-mC) content in atherosclerotic aortas as compared with normal arteries. Hypomethylation in atherosclerotic aortas occurred at the same level as has been reported from malignant tumors. Although a caus al relationship between the methylation level and expression of EC-SOD cann ot be proven, our results show that ec-sod hypomethylation is associated wi th the development of atherosclerosis and suggest that it may affect struct ure and function of ec-sod and other genes possibly involved in the develop ment of atherosclerotic lesions.