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OBJECTIVE:To evaluate whether endothelial dysfunction and hypertension are prevented by trans-cinnamaldehyde (tCA) through the activation of endothelial nitric oxide synthase (eNOS).METHODS.:Human umbilical vein endothelial cells (HUVECs) were cultured in vitro and stimulated with tCA to determine cell viability using the methyl thiazolyl tetrazolium assay.The effect of tCA on nitric oxide (NO) production was determined by diaminofluorescein-dyes in the absence or presence of inhibitors of eNOS,AMPK,PKA,and AKT.The effect of tCA on blood pressure was determined by the tail-cuff method in obesity spontaneous hypertension (SHR.Cg-Leprcp/NDmcr) rats.The phosphorylation of eNOS and protein expression of the insulin-signaling pathway (InsR-IRS1-PI3K-AKT) were measured by west blot.RESULTS:tCA at concentrations less than 100 μM did not affect cell viability in cultured HUVECs.Stimulation with tCA promoted NO release in a time-dependent manner compared with the control group.tCA-treated HUVECs also significantly increased AKT-Ser473 and eNOS-Ser1 177 phosphorylation.In SHR-CP rats,treatment with tCA at a dose of 40 mg/kg/day for 6 weeks markedly reduced the systolic blood pressure and diastolic blood pressure,increased the phosphorylation of AKT and eNOS,and increased urinary nitric oxidation.CONCLUSION:tCA attenuated endothelial dysfunction and reduced blood pressure in SHR-CP rats.The underlying mechanisms may involve the increase in AKT and eNOS phosphorylation and the release of eNOS-derived NO.