These results further suggest that downregulation of CuZn-SOD and Mn-SOD expression is likely the consequence of hypermethylation of H3K9 in placental trophoblasts in preeclampsia, and inhibition of H3K9 methyltransferases eliminated the repression effect of methylated H3K9 on CuZn-SOD and Mn-SOD genes. The gene discussed is SOD2; the disease is preeclampsia.