VEGF attenuates lung injury by inducing homing of CD133⁺ progenitors via VEGFR1.

Although vascular endothelial growth factor (VEGF) promotes vascular permeability and results in edema, studies have suggested it may protect the lung from inflammatory injury via poorly understood mechanisms. Using a mouse model of extracorporeal circulation (ECC), we found that levels of intravenous VEGF increased in lung tissue and inhibited inflammation, thereby attenuating lung injury. These effects could be obtained by intravenous injection or inhalation of VEGF, and they were abolished by treatment with anti-VEGF antibody. Detailed analyses using immunofluorescence and flow cytometry showed that VEGF increased the homing of CD133⁺ VEGFR1⁺ progenitors to lung tissue, and this homing could be mimicked in a dose-dependent manner by treatment with VEGF receptor 1 (VEGFR1) agonist and blocked by treatment with anti-VEGFR1 antibody. Interestingly, we found that exposing pulmonary monocytes in vitro to VEGF did not inhibit ECC-induced inflammation. Our results suggest that VEGF enters lung tissues from the circulation and that it attenuates lung injury not by directly inhibiting release of pro-inflammatory factors but by binding to VEGFR1 to recruit CD133⁺ progenitors. These progenitors then inhibit local inflammation.

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