CXCR2 and CXCR4 antagonistically regulate neutrophil trafficking from murine bone marrow
Kyle J. Eash, … , Priya K. Gopalan, Daniel C. Link
Kyle J. Eash, … , Priya K. Gopalan, Daniel C. Link
Published June 1, 2010
Citation Information: J Clin Invest. 2010;120(7):2423-2431. https://doi.org/10.1172/JCI41649.
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Research Article Immunology

CXCR2 and CXCR4 antagonistically regulate neutrophil trafficking from murine bone marrow

Abstract

Neutrophils are a major component of the innate immune response. Their homeostasis is maintained, in part, by the regulated release of neutrophils from the bone marrow. Constitutive expression of the chemokine CXCL12 by bone marrow stromal cells provides a key retention signal for neutrophils in the bone marrow through activation of its receptor, CXCR4. Attenuation of CXCR4 signaling leads to entry of neutrophils into the circulation through unknown mechanisms. We investigated the role of CXCR2-binding ELR+ chemokines in neutrophil trafficking using mouse mixed bone marrow chimeras reconstituted with Cxcr2–/– and WT cells. In this context, neutrophils lacking CXCR2 were preferentially retained in the bone marrow, a phenotype resembling the congenital disorder myelokathexis, which is characterized by chronic neutropenia. Additionally, transient disruption of CXCR4 failed to mobilize Cxcr2–/– neutrophils. However, neutrophils lacking both CXCR2 and CXCR4 displayed constitutive mobilization, showing that CXCR4 plays a dominant role in neutrophil trafficking. With regard to CXCR2 ligands, bone marrow endothelial cells and osteoblasts constitutively expressed the ELR+ chemokines CXCL1 and CXCL2, and CXCL2 expression was induced in endothelial cells during G-CSF–induced neutrophil mobilization. Collectively, these data suggest that CXCR2 signaling is a second chemokine axis that interacts antagonistically with CXCR4 to regulate neutrophil release from the bone marrow.

Authors

Kyle J. Eash, Adam M. Greenbaum, Priya K. Gopalan, Daniel C. Link

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Figure 4

CXCR2 and CXCR4 signals interact antagonistically to regulate neutrophil release.

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CXCR2 and CXCR4 signals interact antagonistically to regulate neutrophil...
(A) Representative dot plots show cell surface CXCR4 expression of WT and Cxcr2–/– Gr-1+SSChi bone marrow cells from a Cxcr2–/– mixed chimera (right), and cells treated with an isotype-matched antibody (left), shown as controls. Bar graphs show CXCR4 MFI and percent CXCR4+ cells from n = 5 mice. White bars, WT; black bars, Cxcr2–/–. (B) Cxcr2–/– mixed chimeras (n = 5) were given a single subcutaneous injection of AMD3100 (5 mg/kg), and neutrophils were quantified at the indicated times. (C and D) Number of neutrophils in the bone marrow and spleen (C) and NDI (D) at 1 hour after AMD3100 administration (n = 3). (E and F) MKO (n = 10) and DKO (n = 4) mixed chimeras were established as described in Figure 1. Blood, bone marrow, and spleen neutrophils (E) and NDI (F) were quantified 7 weeks after transplantation. ***P < 0.001, 1-way ANOVA. (G) MKO mixed chimeras (n = 3) were given a subcutaneous injection of GROβ (100 μg/kg), and the number of WT and Cxcr4–/– neutrophils in the blood was measured after 30 minutes. (B and G) †P < 0.05, ‡P < 0.01 versus time 0; **P < 0.01, ***P < 0.001 versus WT at the same time point; 2-way ANOVA.