Fluid Shear Stress Mediates The Expression Of Monocyte Chemotactic Protein-1 By Vascular Endothelial Cells And Its Signaling Pathway

Objective:The outcome of patients with end stage renal disease depends on functional vascular access.Arteriovenous fistula is the foremost vascular access for patients.But the patency rate of arteriovenous fistula is low.The fluid dynamics and biological environment have changed after vascular anastomosis that may lead to intimal hyperplasia,venous stenosis and influence maturation and patency rate of arteriovenous fistula.The study investigated the mechanism of fluid shear stress on intimal hyperplasia,and provided the evidence for improving maturation and patency rate of arteriovenous fistula.Methods:(1)We established the parallel plate flow chamber,in which human umbilical vein endothelial cells(HUVECs)were exposed to laminar shear stress or oscillating shear stress.Using computational fluid dynamics(CFD)models computed fluid shear stress and mapped its spatial distribution in the parallel plate flow chamber.(2)We established the parallel plate flow chamber,in which HUVECs were exposed to laminar shear stress or oscillatory shear stress.The laminar shear stress included low shear stress(4dyn/cm~2),physiological shear stress(12dyn/cm~2),and high shear stress(20dyn/cm~2),and oscillatory shear stress(0±5dyn/cm~2),and the action time were 0 h,6 h,12 h and 24 h.Immunofluorescence was applicated to detect the receptor of MCP-1(CCR2)and caveolin-1(Cav-1).Western blotting was used to analysis the expression of MCP-1,CCR2,Cav-1,ERK1/2 and NF-?B.In order to definite the possible signaling pathways in intimal hyperplasia induced by fluid shear stress,disruption of caveolae by cholesterol depletion with M?CD and the inhibitor of ERK were used separately.(3)To simulate uremic environment,some uremic serum was added to culture medium.We established the parallel plate flow chamber,in which HUVEC were exposed to laminar shear stress or oscillating shear stress.Western blotting was used to analysis the expression of MCP-1,CCR2,Cav-1,ERK1/2 and NF-?B.Results:(1)The flow in the parallel plate flow chamber was drivied by pressure.There was no significant difference between the pressure distribution of flow field in X and Z direction,and the pressure gradually decreased along flow direction.In the mode of steady flow,the steady flow moved along X axis,and showed parabolic distribution,the extreme value was in the center.The fluid in the parallel plate flow chamber was typical Poiseuille flow.The flow was steady,rapid and uniform in most of the middle area,and the wall shear stress was proportional to the velocity gradient In the mode of unsteady flow,the wall shear stress was positively correlated to the flow,and the change of wall shear stress showed sinusoidal period along with flow.(2)The expression of MCP-1,CCR2,ERK1/2 and NF-?B increased,and Cav-1decreased in HUVECs exposed to low laminar shear stress or oscillating shear stress.The expression of MCP-1,CCR2,ERK1/2 and NF-?B decreased,and Cav-1increased in HUVECs exposed to high laminar shear stress.The expression of MCP-1,CCR2,ERK1/2,and NF-?B increased,and Cav-1 decrease with time-dependent.M?CD inhibited the expression of Cav-1,meanwhile,the expression of MCP-1,CCR2,ERK1/2 and NF-?B increased.ERK inhibitor blunted the levels of NF-?B and MCP-1.(3)The expression of MCP-1,CCR2,ERK1/2 and NF-?B increased,and Cav-1 decreased in HUVECs exposed to low laminar shear stress or oscillating shear stress.The changes of the above proteins were more significant than physiological environment.The expression of MCP-1,CCR2,ERK1/2 and NF-?B decreased,and Cav-1 increased in HUVECs exposed to high laminar shear stress,which were different from physiological environment significantly.Conclusion:Low laminar shear stress or oscillating shear stress reduced the expression of Cav-1,activated ERK pathway,and increased the level of MCP-1 and CCR2.High laminar shear stress leaded to opposite direction.The expression of MCP-1,CCR2,ERK1/2,and NF-?B increased,and Cav-1 decrease with time-dependent.Low laminar shear stress or oscillating shear stress may influence intimal hyperplasia by Cav-1//MCP-1-CCR2/ERK pathway.