Distinct Compartmentalization of the Chemokines CXCL1 and CXCL2 and the Atypical Receptor ACKR1 Determine Discrete Stages of Neutrophil Diapedesis

Abstract

Summary Neutrophils require directional cues to navigate through the complex structure of venular walls and into inflamed tissues. Here we applied confocal intravital microscopy to analyze neutrophil emigration in cytokine-stimulated mouse cremaster muscles. We identified differential and non-redundant roles for the chemokines CXCL1 and CXCL2, governed by their distinct cellular sources. CXCL1 was produced mainly by TNF-stimulated endothelial cells (ECs) and pericytes and supported luminal and sub-EC neutrophil crawling. Conversely, neutrophils were the main producers of CXCL2, and this chemokine was critical for correct breaching of endothelial junctions. This pro-migratory activity of CXCL2 depended on the atypical chemokine receptor 1 (ACKR1), which is enriched within endothelial junctions. Transmigrating neutrophils promoted a self-guided migration response through EC junctions, creating a junctional chemokine “depot” in the form of ACKR1-presented CXCL2 that enabled efficient unidirectional luminal-to-abluminal migration. Thus, CXCL1 and CXCL2 act in a sequential manner to guide neutrophils through venular walls as governed by their distinct cellular sources.

Chemokine-triggered microtubule polymerization promotes neutrophil chemotaxis and invasion but not transendothelial migration

“…Once extravasating, neutrophils interact with inflamed pericytes via two key components, namely, the CXCR2 ligand CXCL1 and the β2 integrin ligand ICAM‐1 . We therefore next tested if taxol inhibition of neutrophils interferes with chemokinetic neutrophil motility on a substrate coated with CXCL1 alone.…”

“…Experiment in C is a representative of 5. ns = nonsignificant integrin ligand ICAM-1. [36][37][38][39][40] We therefore next tested if taxol inhibition of neutrophils interferes with chemokinetic neutrophil motility on a substrate coated with CXCL1 alone. This locomotion was confirmed to be both CXCL1 and CXCR2 dependent (Supplemental Fig.…”

Local microvascular leakage promotes trafficking of activated neutrophils to remote organs

“…The sequence of molecular and cellular events that guide neutrophils from the vascular lumen to the interstitial tissue is well established and described by the leukocyte adhesion cascade (3). Here, it is considered that chemokines immobilized on the luminal aspect of blood vessels trigger the local arrest of neutrophils (3) with sequential, compartmentalized, and locally presented chemotactic cues within venular walls promoting luminal-to-abluminal diapedesis (6). Although glycosaminoglycans (GAGs) are considered to provide the principal mode of retaining chemokines on the luminal aspect of blood vessels, the retention of chemokines within EC junctions is likely mediated by binding to the atypical chemokine receptor ACKR1 that is enriched at these sites (6,37).…”

“…In addition, we recently demonstrated the importance of retaining directional cues within EC junctions in facilitating luminal-toabluminal neutrophil breaching of the endothelium (6).…”

Estrogen exacerbates mammary involution through neutrophil dependent and independent mechanism

“…Thus, Mirt2 regulation by E2B in neutrophils indicates its involvement 190 in the moderation of the inflammatory response during mammary involution.191Next, the study investigated the mechanism of estrogen-induced neutrophils infiltration. 192 S100A8, S100A9, CXCL1, and CXCL2 are known neutrophil chemoattractants that promote 193 12 neutrophil migration during inflammation [23][24][25]. S100A8 and S100A9 are small calcium-194 binding proteins that activate calcium-dependent signalling through receptor for advanced 195 glycation endproducts (RAGE) or toll-like receptor 4 (TLR4).…”