Monocyte chemoattractant protein 1 and fractalkine play opposite roles in angiogenesis via recruitment of different macrophage subtypes

Abstract

AIM: To explore the interaction between macrophages and chemokines [monocyte chemoattractant protein 1 (MCP-1/CCL2) and fractalkine/CX3CL1] and the effects of their interaction on neovascularization. METHODS: Human peripheral blood mononuclear cells, donated by healthy volunteers, were separated and cultured in RPMI-1640 medium containing 10% fetal bovine serum, then induced into macrophages by stimulation with 30 μg/L granulocyte macrophage-colony stimulating factor (GM-CSF). The expression of CCR2 and/or CX3CR1 in the macrophages was examined using flow cytometry. Macrophages were then stimulated with recombinant human CCL2 (rh-CCL2) or recombinant human CX3CL1 (rh-CX3CL1). The expression of angiogenesis-related genes, including VEGF-A, THBS-1 and ADAMTS-1 were examined using real-time quantitative polymerase chain reaction (PCR). Supernatants from stimulated macrophages were used in an assay of human retinal endothelial cell (HREC) proliferation. Finally, stimulated macrophages were co-cultured with HREC in a migration assay. RESULTS: The expression rate of CCR2 in macrophages stimulated by GM-CSF was 42%±1.9%. The expression rate of CX3CR1 was 71%±3.3%. Compared with vehicle-treated groups, gene expression of VEGF-A in the macrophages was greater in 150 mg/L CCL2-treated groups (P<0.05), while expression of THBS-1 and ADAMTS-1 was significantly lower (P<0.05). By contrast, compared with vehicle-treated groups, expression of VEGF-A in 150 mg/L CX3CL1-treated groups was significantly lower (P<0.05), while expression of THBS-1 and ADAMTS-1 was greater (P<0.05). Supernatants from CCL2 treated macrophages promoted proliferation of HREC (P<0.05), while supernatants from CX3CL1-treated macrophages inhibited the proliferation of HREC (P<0.05). HREC migration increased when co-cultured with CCL2-treated macrophages, but decreased with CX3CL1-treated macrophages (P<0.05). CONCLUSION: CCL2 and CX3CL1 exert different effects in regulation of macrophage in expression of angiogenesis-related factors, including VEGF-A, THBS-1 and ADAMTS-1. Our findings suggest that CCL2 and CX3CL1 may be candidate proteins for further exploration of novel targets for treatment of ocular neovascularization.

Keywords

• 222
• chemokine
• macrophage
• proliferation
• migration
• angiogenesis