Abstract 658: Lentiviral Blockade of the SDF-1/CXCR4 Pathway in Leukocytes Aggravates Atherosclerotic Lesion Development
The chemokine SDF-1α and its receptor CXCR4 have been shown to be highly expressed in advanced atherosclerotic lesions. To delineate the effect of blockade of the SDF-1α/CXCR4 pathway in leukocytes on plaque development, we generated a lentivirus expressing a SDF-1 antagonist (LV.SDF(P2>G) and one containing a CXCR4 degrakine (LV.CXCR4degrakine), which leads to targeted lysosomal degradation of CXCR4 protein. Irradiated female LDLr−/− mice were transplanted with LDLr−/− bone marrow that was infected with LV.Empty control, LV.SDF(P2>G) or LV.CXCR4degrakine. After 6 weeks, the mice were placed on Western-type diet for 10 weeks, after which lesions in the aortic root were quantified. Blockade of SDF-1α signalling by either LV.SDF(P2>G) or by LV.CXCR4degrakine in vitro resulted in reduced migration and proliferation of FDCP progenitor cells in response to SDF-1α (100 ng/ml, P<0.005), indicating that infection with either lentivirus indeed resulted in blockade of the SDF-1α/CXCR4 pathway. Also, SDF-1α stimulated migration of RAW macrophages was reduced after infection with LV.SDF(P2>G) (P=0.005). In vivo, transplantation of bone marrow infected with LV.CXCR4degrakine resulted in a sustained reduction of CXCR4 protein levels on T-cells, B-cells and macrophages, while the blood cell distribution was not altered. Plaque size in the aortic root was increased from 4.6 ± 0.7*105 μm2 in LV.Empty control mice to 6.7 ± 0.7*105 μm2 in LV.SDF(P2>G) mice (P=0.06, 145%) and to 8.0 ± 0.6*105 μm2 in the LV.CXCR4degrakine mice (P=0.002, 172%). No difference was observed in macrophage content of the lesions, while that of smoothelin-1 (SMCs) was reduced in the antagonist and degrakine group. Also, a trend was observed towards increased iron levels in these treatment groups. Adhesion of FDCP cells, infected with either antagonist or degrakine virus, to atherosclerotic plaques was significantly reduced compared to control cells (−52% and −68% respectively, P<0.05), suggesting a protective role for progenitor cells. In conclusion, blockade of the SDF-1α/CXCR4 pathway results in a marked increase in atherosclerotic lesion development, which has important clinical implications as CXCR4 is considered as therapeutic target for the treatment of HIV infection and cancer.