ABSTRACT
AIM:To investigate whether angiotensin Ⅱ (Ang Ⅱ)/angiotensin Ⅱ type 1 receptor (AT1 R)pathway down-regulates endothelial nitric oxide synthase (eNOS) Ser1177 phosphorylation level in human umbilical vein endothelial cells by activating protein phosphatase 2A (PP2A).METHODS:Human umbilical vein endothelial cells were randomly divided into normal control (control) group,Ang Ⅱ group,candesartan (CAN;specific AT1R blocker) group and CAN pretreatment + Ang Ⅱ group.The protein levels of total eNOS,p-eNOS (Ser1177),PP2Ac,IPP2A2 and p-PP2Ac (Tyr307) were determined by Western blot.The content of NO in the cell culture medium was detected by chemical colorimetry.RESULTS:Compared with control group,the level of p-eNOS (Ser1177) and the content of NO decreased (P ＜0.05).Compared with the same concentration of Ang Ⅱ group,CAN pretreatment increased the level of p-eNOS (Ser1177) and the content of NO (P ＜ 0.05),but the protein expression of eNOS showed no significant difference.Compared with control group,the levels of p-PP2Ac (Tyr307) and IPP2A2 decreased (P ＜ 0.05).Compared with the same concentration of Ang Ⅱ group,CAN pretreatment increased the levels of p-PP2Ac (Tyr307) and IPP2A2 (P ＜ 0.05),but the protein expression of PP2Ac showed no significant difference.CONCLUSION:Ang Ⅱ down-regulates the level of p-eNOS (Ser1177),and decreases the production of NO in human umbilical vein endothelial cells via AT1 R pathway.This effect may be related to the reduction of p-PP2Ac (Tyr307) and protein expression of IPP2A2,which results in the enhancement of PP2A2 activity.Pretreatment with AT1 R blocker CAN increases p-PP2Ac (Tyr307) level and IPP2A2 protein expression,thus reducing the PP2A activity,and ultimately restoring eNOS Ser1177 phosphorylation level and eNOS activity.
ABSTRACT
AIM:To investigate whether angiotensin Ⅱ (Ang Ⅱ)/angiotensin Ⅱ type 1 receptor (AT1 R)pathway down-regulates endothelial nitric oxide synthase (eNOS) Ser1177 phosphorylation level in human umbilical vein endothelial cells by activating protein phosphatase 2A (PP2A).METHODS:Human umbilical vein endothelial cells were randomly divided into normal control (control) group,Ang Ⅱ group,candesartan (CAN;specific AT1R blocker) group and CAN pretreatment + Ang Ⅱ group.The protein levels of total eNOS,p-eNOS (Ser1177),PP2Ac,IPP2A2 and p-PP2Ac (Tyr307) were determined by Western blot.The content of NO in the cell culture medium was detected by chemical colorimetry.RESULTS:Compared with control group,the level of p-eNOS (Ser1177) and the content of NO decreased (P ＜0.05).Compared with the same concentration of Ang Ⅱ group,CAN pretreatment increased the level of p-eNOS (Ser1177) and the content of NO (P ＜ 0.05),but the protein expression of eNOS showed no significant difference.Compared with control group,the levels of p-PP2Ac (Tyr307) and IPP2A2 decreased (P ＜ 0.05).Compared with the same concentration of Ang Ⅱ group,CAN pretreatment increased the levels of p-PP2Ac (Tyr307) and IPP2A2 (P ＜ 0.05),but the protein expression of PP2Ac showed no significant difference.CONCLUSION:Ang Ⅱ down-regulates the level of p-eNOS (Ser1177),and decreases the production of NO in human umbilical vein endothelial cells via AT1 R pathway.This effect may be related to the reduction of p-PP2Ac (Tyr307) and protein expression of IPP2A2,which results in the enhancement of PP2A2 activity.Pretreatment with AT1 R blocker CAN increases p-PP2Ac (Tyr307) level and IPP2A2 protein expression,thus reducing the PP2A activity,and ultimately restoring eNOS Ser1177 phosphorylation level and eNOS activity.