VEGF-A rapidly induces recruitment of circulating neutrophils to tissue in a VEGFR1- and VEGFR2-dependent manner. VEGF-A-induced leukocyte (A) intravascular adhesion and (B) emigration occur within 30 minutes after onset of VEGF-A superperfusion of the cremaster muscle (control [0 nM], n = 4; VEGF-A 0.2 nM, n = 4; VEGF-A 0.4 nM, n = 4; VEGF-A 2 nM, n = 6; and VEGF-A 20 nM, n = 6). #P < .05 compared with basal values within the same group; *P < .05 compared with control group at the same time point. Leukocyte subsets were differentiated by using CX₃CR1^GFP/GFP mice and fluorescently tagged anti-Ly6G mAb (clone 1A8). (C) One frame from time 30 minutes in a video recording is shown. Scale bar = 30 μm. Postcapillary venule outlined with dashed lines. (D) The leukocytes recruited after 90 minutes of VEGF-A (2 nM) superperfusion were neutrophils (Ly6G⁺) and not monocytes (CX₃CR1⁺; control, n = 3; VEGF-A, n = 6). The VEGF-A-induced neutrophil recruitment to muscle was completely inhibited by neutralizing antibodies directed toward either VEGFR1 (clone MF1) or VEGFR2 (clone DC101). (E) Adherent cells and (F) emigrated cells (n = 5 per treatment group). *P < .05 compared with control group at the same time point. (G) Mouse peripheral blood neutrophils expressed levels of VEGFR1 transcripts similar to those in endothelial cells. Relative expression of mRNA presented in arbitrary units (A.U.). Semiquantitative reverse-transcription polymerase chain reaction (n = 11 mice) from 3 independent trials. (H) VEGFR1 and VEGFR2 protein expressions were confirmed on circulating human neutrophils (n = 8) by flow cytometry (isotype in black). (I) Direct stimulation of human neutrophils by either VEGF-A (2 nM) or VEGF-B (5 nM) induced signal transduction via VEGFR1 (phosphorylation of ERK [pERK] compared to total Erk [tErk]; western blot from 4 independent trials).