Objective: To investigate the similarities and differences of homocysteine and cysteine on pathogenesis of As in cultured human vascular smooth muscle cells (HVSMCs).
Methods: Cultured HVSMCs were treated by different concentrations of Hcy and Cys for 24 h. (1) The SOD activity and MDA contents were measured by chromatometry. (2) The rates of apoptosis of HVSMCs were detected by flow cytometry. The expression of caspases-3 mRNA in HVSMCs was detected by reverse-trascription polymerase chain reaction (RT-PCR). (3) The proliferative activities of HVSMCs were examined by MTT assay. (4) HVSMCs were incubated with 1000 micromol/L Hcy and Cys for 24, 48 and 72h respectively, then the DNA methylation status were assayed by nested methylation-specific polymerase chain reaction , and the expressions of ERa mRNA of HVSMCs were detected by RT-PCR.
Results: (1) Hey significantly increased the MDA contents and SOD activities in a dose-dependent manner, but the increase of MDA contents and SOD activities were much weaker induced by Cys (P < 0.01). (2) The results of flow cytometry, expression of caspases-3 mRNA, and MTU test showed that the effects of Hey and Cys on rate of apoptosis and proliferation of HVSMCs were not much different. (3) Hey obviously induced de novo methylation in the promoter region of the ERa gene in HVSMCs, and the expressions of ERalpha mRNA were correspondingly down-regulated. The Cys had no effect on methylation modification of ERalpha gene, and very mild effect on ERalpha mRNA expression.
Conclusion: The oxidative stress and the methylative modification induced by Hcy may have the top position in its pathogenic mechanism of pro-atherosclerosis. The pro-apoptotic and proliferation-promoting effects of Hcy were similar with Cys, which suggested that these two effects might just play mild roles in its pro-atherosclerotic traits.