Hyperhomocysteinemia induces cardiac injury by up-regulation of p53-dependent Noxa and Bax expression through the p53 DNA methylation in ApoE-/- mice

Hyperhomocysteinemia （HHcy） is a risk factor for cardiovas- cular disease and has a strong correlation with heart failure. However, the effects of HHcy on cardiac tissue remain less well understood. To elucidate the role of p53-dependent apoptosis in HHcy-induced cardiac injury, we fed ApoE-/- mice with high methionine diet to establish HHcy model. Serum Hcy, cardiac enzymes, and lipids were measured. The protein levels of Noxa, DNMT1, caspases-3/9, and p53 were determined by enzyme-linked immunosorbent assay. Bcl-2 and Bax proteins were detected by immunohistochemistry staining. S-adenosyl methionine and S-adenosyl homocyst- eine concentrations were determined by high-performance liquid chromatography. The mRNA levels of p53 and DNMT1 were analyzed by real-time polymerase chain reac- tion （PCR） and the methylation levels of p53 were analyzed by nested methylation-specific-PCR. Our data showed that the concentrations of serum Hcy and lipids were increased in Meth group compared with the N-control group, which indicated that the model was established successfully. The expres- sion levels of p53 and Noxa were increased in Meth group, while the methylation status of p53 was hypomethylation. The activities of caspase-3/9 were increased in Meth group compared with the N-control group. In addition, immunohistochemistry staining showed that the expression of Bax was significantly increased in Meth and Meth-F group compared with the N-control group. In summary, HHcy induces cardiac injury by up-regulation of p53-dependent pro-apop- totic related genes Noxa and Bax, while p53 DNA hypo- methylation is a key molecular mechanism in pathological process induced by HHcy.