In order to investigate the influence of silencing soluble epoxide hydrolase (sEH) with double-stranded small interfering RNA (siRNA) on cardiomyocytes apoptosis induced by doxorubicin (DOX),two plasmids containing siRNA sequences specific to sEH were constructed and transfected into the primary cultured cardiomyocytes by using FuGENE HD transfection agents.The mRNA and protein expression levels of sEH were detected by semiquantitative RT-PCR and Western blotting respectively,and the plasmids that silenced sEH most significantly were selected,and renamed EH-R.The plasmids carrying a nonspecific siRNA coding sequence (PCN) served as the negative control.Cardiomyocytes were divided into four groups:control group,DOX group,PCN+DOX group,and EH-R+DOX group.Apoptosis of cardiomyocytes was induced by DOX at a concentration of l μmol/L.Apoptosis rate of cardiomyocytes was determined by flow cytometery.The protein expression levels of Bcl-2 and Bax were detected by Western blotting.The results showed that the expression of sEH was down-regulated by EH-R plasmid.The expression levels of sEH mRNA and protein in the EH-R+DOX group were significantly decreased as compared with other groups (P＜0.01).As compared with the control group,the apoptosis rate of cardiomyocytes in three DOX-treated groups was obviously increased,the expression levels of Bax increased,and those of Bcl-2 decreased (P＜0.01).However,the expression levels of Bax were decreased,those of Bcl-2 increased and the apoptosis rate of cardiomyocytes obviously decreased in EH-R+DOX group when compared with those in the DOX group and the PCN+DOX group (P＜0.01 for each).It was concluded that the recombinant plasmids could be successfully constructed,and transfected into the primary cultured cardiomyocytes.They could ameliorate the DOX-induced cardiomyocytes apoptosis by selectively inhibiting the expression of sEH with RNAi and increasing the expression of Bcl-2.