Aim To investigate the effect of angiotensin Ⅱ(AngⅡ)on the expression of monocyte chemoattractant protein-1(MCP-1)receptor CCR2 and therapeutic effect of losartan on atherosclerosis.Methods Human monocytoid cell(THP-1)were treated with AngⅡ(10-7 mol/L)for 24 h in the absence or presence of losartan(10-7,10-6,10-5 mol/L).The level of MCP-1 in the medium,the adhesion of monocytes to endothelial cell and the expression of CCR2 mRNA were determined.Results Compared with control,incubation of THP-1 with AngⅡ(10-7 mol/L)for 24 h significantly elevated the concentrations of MCP-1(26.46 ±3.58 ng/L vs.10.56 ±2.34 ng/L,p<0.01),increased the number of monocytes binding to endothelial cell(596±27 vs.268±16,p<0.01)and upregulated the expression of CCR2 mRNA.Treatment with losartan decreased the levels of MCP-1,inhibited monocytic binding to endothelial cell,and downregulated the expression of CCR2 mRNA by AngⅡ.Conclusions These data suggest that treatment with losartan in vitro inhibits monocytic activation via downregulation of MCP-1 receptor CCR2 genetic expression.