Heart-resident CCR2+ macrophages promote neutrophil extravasation through TLR9/MyD88/CXCL5 signaling
Wenjun Li, … , Kory J. Lavine, Daniel Kreisel
Wenjun Li, … , Kory J. Lavine, Daniel Kreisel
Published August 4, 2016
Citation Information: JCI Insight. 2016;1(12):e87315. https://doi.org/10.1172/jci.insight.87315.
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Research Article Inflammation Transplantation

Heart-resident CCR2+ macrophages promote neutrophil extravasation through TLR9/MyD88/CXCL5 signaling

Abstract

It is well established that maladaptive innate immune responses to sterile tissue injury represent a fundamental mechanism of disease pathogenesis. In the context of cardiac ischemia reperfusion injury, neutrophils enter inflamed heart tissue, where they play an important role in potentiating tissue damage and contributing to contractile dysfunction. The precise mechanisms that govern how neutrophils are recruited to and enter the injured heart are incompletely understood. Using a model of cardiac transplant–mediated ischemia reperfusion injury and intravital 2-photon imaging of beating mouse hearts, we determined that tissue-resident CCR2+ monocyte–derived macrophages are essential mediators of neutrophil recruitment into ischemic myocardial tissue. Our studies revealed that neutrophil extravasation is mediated by a TLR9/MyD88/CXCL5 pathway. Intravital 2-photon imaging demonstrated that CXCL2 and CXCL5 play critical and nonredundant roles in guiding neutrophil adhesion and crawling, respectively. Together, these findings uncover a specific role for a tissue-resident monocyte-derived macrophage subset in sterile tissue inflammation and support the evolving concept that macrophage ontogeny is an important determinant of function. Furthermore, our results provide the framework for targeting of cell-specific signaling pathways in myocardial ischemia reperfusion injury.

Authors

Wenjun Li, Hsi-Min Hsiao, Ryuji Higashikubo, Brian T. Saunders, Ankit Bharat, Daniel R. Goldstein, Alexander S. Krupnick, Andrew E. Gelman, Kory J. Lavine, Daniel Kreisel

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Figure 7

CXCL2 and CXCL5 regulate neutrophil chemotaxis and trafficking of neutrophils in heart grafts.

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CXCL2 and CXCL5 regulate neutrophil chemotaxis and trafficking of neutro...
Neutrophil trafficking in WT hearts after administration of (A) isotype control antibodies (see Supplemental Video 13; n = 4 mice) or (B) CXCL2-neutralizing antibody (see Supplemental Video 14; n = 4 mice). Relative time is displayed in hrs:min:sec. Scale bars: 50 μm. (C) Percentage of neutrophils that entered myocardial tissue during imaging period was significantly lower after neutralization of CXCL2 compared with mice that received isotype control antibodies. (D) Neutrophil rolling velocities were significantly higher in coronary veins of cardiac grafts after neutralization of CXCL2 compared with mice that received isotype control antibodies. (E) Due to a small number of adherent neutrophils, crawling velocities could not be evaluated when CXCL2 was neutralized. Neutrophil trafficking in (F) WT and (G) CXCL5-deficient cardiac grafts (see Supplemental Videos 5 and 15, respectively; Isotype control, n = 4; CXCL2-neutralizing antibody, n = 4; CXCL5-deficient heart grafts, n = 5. Relative time is displayed in hrs:min:sec. Scale bars: 50 μm. (H) Percentage of neutrophils that entered myocardial tissue during imaging period was significantly lower when cells in the hearts were unable to produce CXCL5 compared with WT cardiac grafts. (I) Neutrophil rolling velocities were significantly higher in coronary veins of cardiac grafts when hearts lacked expression of CXCL5 compared with WT cardiac grafts. (J) Intraluminal crawling velocities of neutrophils were significantly lower when hearts lacked expression of CXCL5 compared with WT cardiac grafts. *P < 0.05; **P < 0.01; ***P < 0.001 (t test). Data in C–E and H–J are derived from 4–5 mice for each experimental group as indicated above. For C–E and H–J, symbols represent averages obtained from individual mice with over 30 neutrophils examined per mouse, horizontal bars denote means, and error bars denote ±SEM.