Mechanism Of Low Shear Stress Represses Endothelial Cell Antio Xidant Response By Keap1/Nrf2 Pathway

Objective:Low shear stress(LSS)can induce oxidative stress and injury in vascular endothelial cells,but its specific mechanism is still not completely clear.The purpose of this study is to investigate the relationship between LSS and endothelial cell antioxidant response and its potential mechanism.Methods:The LSS and high shear stress(HSS)were applied to human umbilical vein endothelial cells(HUVECs)by using a parallel plate flow chamber.Keap1,Nrf2 and antioxidant response element NQO1,HO-1 total protein level and transcription level were measured by q RT-PCR and Western Blot,including the nuclear and cytoplasmic protein level of Keap1 and Nrf2 apart.The distribution of Nrf2 in cytosol and nucleus was observed by immunofluorescence staining.Results:(1)Compared to HSS,the transcription level of Keap1(p>0.05)and Nrf2(p>0.05)showed no statistically significant in HUVECs under LSS.The total protein level of Keap1 under LSS was higher than HSS(p<0.05)when Nrf2 was reduced(p<0.05).(2)By the nuclear and cytoplasmic protein extraction,the cytoplasmic protein levels of Keap1(p<0.05)and Nrf2(p<0.001)were up-regulated under LSS.In nuclear,the Keap1(p<0.01)and Nrf2(p<0.001)protein levels under LSS were much lower than HSS.(3)Immunofluorescence staining showed that Keap1 and Nrf2 distributed in the cytoplasm mainly under LSS.Exposed to HSS,the Keap1 and Nrf2 translocated in the nuclear.(4)Compared to HSS,the transcription levels of HO-1(p<0.01)and NQO1(p<0.01)were decreased when the protein levels of them were also down-regulated.Conclusion:In summary,the present study provided that low shear stress inhibited the Keap1/Nrf2 signaling pathway and repressed the translocation of Nrf2 into the nucleus,which may be a molecular mechanism of the decreased antioxidant response capacity of endothelial cells.