title: Deficient CX3CR1 signaling promotes recovery after mouse spinal cord injury by limiting the recruitment and activation of Ly6Clo/iNOS+ macrophages.
abstract: Macrophages exert divergent effects in the injured CNS, causing either neurotoxicity or regeneration. The mechanisms regulating these divergent functions are not understood but can be attributed to the recruitment of distinct macrophage subsets and the activation of specific intracellular signaling pathways. Here, we show that impaired signaling via the chemokine receptor CX3CR1 promotes recovery after traumatic spinal cord injury (SCI) in mice. Deficient CX3CR1 signaling in intraspinal microglia and monocyte-derived macrophages (MDMs) attenuates their ability to synthesize and release inflammatory cytokines and oxidative metabolites. Also, impaired CX3CR1 signaling abrogates the recruitment or maturation of MDMs with presumed neurotoxic effects after SCI. Indeed, in wild-type mice, Ly6C(lo)/iNOS(+)/MHCII(+)/CD11c(-) MDMs dominate the lesion site, whereas CCR2(+)/Ly6C(hi)/MHCII(-)/CD11c(+) monocytes predominate in the injured spinal cord of CX3CR1-deficient mice. Replacement of wild-type MDMs with those unable to signal via CX3CR1 resulted in anatomical and functional improvements after SCI. Thus, blockade of CX3CR1 signaling represents a selective anti-inflammatory therapy that is able to promote neuroprotection, in part by reducing inflammatory signaling in microglia and MDMs and recruitment of a novel monocyte subset.
authors: Center for Brain and Spinal Cord Repair, The Ohio State University, Columbus, Ohio 43210, USA.
authors: Dustin J
authors: DJ
authors: Donnelly
authors: Erin E
authors: EE
authors: Longbrake
authors: Todd M
authors: TM
authors: Shawler
authors: Kristina A
authors: KA
authors: Kigerl
authors: Wenmin
authors: W
authors: Lai
authors: C Amy
authors: CA
authors: Tovar
authors: Richard M
authors: RM
authors: Ransohoff
authors: Phillip G
authors: PG
authors: Popovich
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D000950:Antigens, Ly / Q000378:metabolism*; D018845:CD11 Antigens / Q000378:metabolism; D000073883:CX3C Chemokine Receptor 1; D002478:Cells, Cultured; D054360:Chemokine CXCL1 / Q000235:genetics / Q000378:metabolism; D004195:Disease Models, Animal; D005434:Flow Cytometry; D005786:Gene Expression Regulation / Q000235:genetics; D049452:Green Fluorescent Proteins / Q000235:genetics; D008264:Macrophages / Q000378:metabolism*; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D009043:Motor Activity / Q000235:genetics / Q000502:physiology; D004676:Myelin Basic Protein / Q000378:metabolism; D009569:Nitric Oxide / Q000378:metabolism; D052247:Nitric Oxide Synthase Type II / Q000378:metabolism*; D019707:Receptors, Chemokine / Q000172:deficiency*; D020127:Recovery of Function / Q000235:genetics*; D015398:Signal Transduction / Q000235:genetics / Q000502:physiology*; D013119:Spinal Cord Injuries / Q000235:genetics / Q000473:pathology* / Q000503:physiopathology*
chemical_list: D000950:Antigens, Ly; D018845:CD11 Antigens; D000073883:CX3C Chemokine Receptor 1; D054360:Chemokine CXCL1; C471885:Cx3cr1 protein, mouse; C475895:Cxcl1 protein, mouse; C494192:Ly-6C antigen, mouse; D004676:Myelin Basic Protein; D019707:Receptors, Chemokine; D049452:Green Fluorescent Proteins; D009569:Nitric Oxide; D052247:Nitric Oxide Synthase Type II