Neutrophil chemorepulsion in defined interleukin-8 gradients in vitro and in vivo

TLDR

Robust neutrophil chemorepulsion in microfluidic IL‑8 gradients depended on chemokine concentration, CXCR2, and involved polarization of cytoskeletal elements and signaling molecules linked to chemotaxis and leading‑edge formation. Chemorepulsion is pertussis toxin‑sensitive, PI3K‑ and RhoGTPase‑dependent, can be modulated by cAMP and PKC to alter directionality, and was confirmed in a rat inflammation model, thereby extending the neutrophil migration paradigm.

Abstract

Abstract We report for the first time that primary human neutrophils can undergo persistent, directionally biased movement away from a chemokine in vitro and in vivo, termed chemorepulsion or fugetaxis. Robust neutrophil chemorepulsion in microfluidic gradients of interleukin-8 (IL-8; CXC chemokine ligand 8) was dependent on the absolute concentration of chemokine, CXC chemokine receptor 2 (CXCR2), and was associated with polarization of cytoskeletal elements and signaling molecules involved in chemotaxis and leading edge formation. Like chemoattraction, chemorepulsion was pertussis toxin-sensitive and dependent on phosphoinositide-3 kinase, RhoGTPases, and associated proteins. Perturbation of neutrophil intracytoplasmic cyclic adenosine monophosphate concentrations and the activity of protein kinase C isoforms modulated directional bias and persistence of motility and could convert a chemorepellent to a chemoattractant response. Neutrophil chemorepulsion to an IL-8 ortholog was also demonstrated and quantified in a rat model of inflammation. The finding that neutrophils undergo chemorepulsion in response to continuous chemokine gradients expands the paradigm by which neutrophil migration is understood and may reveal a novel approach to our understanding of the homeostatic regulation of inflammation.