Aim To explore the effect of stromal cell derived factor 1α—CXCR4(SDF-1α—CXCR4)on THP-1 cells chemotaxis,the influence of oxidized low density lipoprotein(ox-LDL)on THP-1 cells migration exposed to SDF-1α,and the effect of ox-LDL on the expression of CXCR4 in THP-1 cell.Methods THP-1 cells chemotaxis was examined with transwell permeable supports.CXCR4 mRNA and protein was revealed by RT-PCR and Western blot respectively in THP-1 cells incubated with different concentrations/time of ox-LDL.Results SDF-1α induced a pronounced migration of input cells in a concentration-related manner,but this effect was obviously inhibited by the antibody to CXCR4.After pretreated with different concentration of ox-LDL for 48 h,THP-1 cells were exposed to 10 μg/L SDF-1α,ox-LDL enhanced THP-1 cells migration in a concentration-dependent manner and 50 mg/L ox-LDL support 11 fold higher of cells migration.CXCR4 was constitutionally expressed in THP-1 cells.Compared with the control group,a four-to-five fold induction of CXCR4 occurred in THP-1 treated with 50 mg/L ox-LDL.The up-regulation effect was monitored within 6 h,it was peaked at 12 h,then followed with a decline,which mirrored the expression pattern of CXCR4 in monocyte.Conclusions SDF-1α/CXCR4 is implicated in chemotaxis of THP-1 cell and chemotactic response of monocyte to SDF-1α is enhanced by ox-LDL;ox-LDL up-regulates CXCR4 expression.