The CXC Chemokine Receptor 2, CXCR2, Is the Putative Receptor for ELR+ CXC Chemokine-Induced Angiogenic Activity

TLDR

ELR+ CXC chemokines such as IL‑8, GROα/β/γ, and ENA‑78 can induce angiogenesis independently of inflammation, yet the endothelial receptor mediating this effect had not been identified. The authors hypothesized that CXCR2 serves as the endothelial receptor for ELR+ CXC chemokine–driven angiogenesis. They examined CXCR2 expression in cultured human microvascular endothelial cells and assessed its functional role in chemotaxis using anti‑CXCR2 antibodies, pertussis toxin, and in vivo corneal assays in rats and CXCR2‑deficient mice. CXCR2 was expressed at the protein level, its blockade inhibited ELR+ CXC chemokine–induced chemotaxis and angiogenesis, and CXCR2‑null mice failed to respond to these chemokines, confirming CXCR2 as the receptor responsible for ELR+ CXC chemokine–mediated angiogenesis.

Abstract

Abstract We have previously shown that members of the ELR+ CXC chemokine family, including IL-8; growth-related oncogenes α, β, and γ; granulocyte chemotactic protein 2; and epithelial neutrophil-activating protein-78, can mediate angiogenesis in the absence of preceding inflammation. To date, the receptor on endothelial cells responsible for chemotaxis and neovascularization mediated by these ELR+ CXC chemokines has not been determined. Because all ELR+ CXC chemokines bind to CXC chemokine receptor 2 (CXCR2), we hypothesized that CXCR2 is the putative receptor for ELR+ CXC chemokine-mediated angiogenesis. To test this postulate, we first determined whether cultured human microvascular endothelial cells expressed CXCR2. CXCR2 was detected in human microvascular endothelial cells at the protein level by both Western blot analysis and immunohistochemistry using polyclonal Abs specific for human CXCR2. To determine whether CXCR2 played a functional role in angiogenesis, we determined whether this receptor was involved in endothelial cell chemotaxis. We found that microvascular endothelial cell chemotaxis in response to ELR+ CXC chemokines was inhibited by anti-CXCR2 Abs. In addition, endothelial cell chemotaxis in response to ELR+ CXC chemokines was sensitive to pertussis toxin, suggesting a role for G protein-linked receptor mechanisms in this biological response. The importance of CXCR2 in mediating ELR+ CXC chemokine-induced angiogenesis in vivo was also demonstrated by the lack of angiogenic activity induced by ELR+ CXC chemokines in the presence of neutralizing Abs to CXCR2 in the rat corneal micropocket assay, or in the corneas of CXCR2−/− mice. We thus conclude that CXCR2 is the receptor responsible for ELR+ CXC chemokine-mediated angiogenesis.