Evidence for the involvement of SDF‐1 and CXCR4 in the disruption of endothelial cell‐branching morphogenesis and angiogenesis by TNF‐α and IFN‐γ

Vigorous inflammatory responses are associated with tissue damage, particularly when toxic levels of inflammatory cytokines are produced. Despite proangiogenic factors being present early at sites of inflammation, vascular repair occurs toward the end of the inflammatory response, suggesting modulation of the proangiogenic response. Endogenous inhibitors of angiogenesis induced during acute inflammation are poorly characterized. Here, we looked for endothelial cell‐derived modulators of angiogenesis that may account for delayed neovascularization during inflammation. Gene profiling of endothelial cells showed that the inflammatory cytokines tumor necrosis factor α (TNF‐α) and interferon‐γ (IFN‐γ) selectively promote expression of the antiangiogenic molecules, IFN‐inducible protein‐10, monokine induced by IFN‐γ, tryptophanyl‐tRNA synthetase, and tissue inhibitor of metalmetalloproteinase‐1, and inhibit expression of the proangiogenic molecules, platelet‐endothelial cell adhesion molecule‐1, vascular endothelial growth factor receptor‐2, stromal cell‐derived factor‐1 (SDF‐1), collagen type IV, endothelial cell growth factor‐1, and carcinoembryonic antigen‐related cell adhesion molecule‐1. Reduced endothelial cell expression of SDF‐1 protein by TNF‐α and IFN‐γ disrupts extracellular matrix‐dependent endothelial cell tube formation, an in vitro morphogenic process that recapitulates critical steps in angiogenesis. Replacement of SDF‐1 onto the endothelial cell surface reconstitutes this morphogenic process. In vivo, TNF‐α and IFN‐γ inhibit growth factor‐induced angiogenesis and SDF‐1 expression in endothelial cells. These results demonstrate that SDF‐1/CXC chemokine receptor‐4 constitutes a TNF‐α‐ and IFN‐γ‐regulated signaling system that plays a critical role in mediating angiogenesis inhibition by these inflammatory cytokines.