Macrophages migrate in an activation-dependent manner to chemokines involved in neuroinflammation

Daphne Ys Vogel,Anton Tj Tool,Christine D Dijkstra,Sandra Amor,Marjolein Breur,Helga E De Vries,Priscilla Dam Heijnen

doi:10.1186/1742-2094-11-23

Abstract

BackgroundIn neuroinflammatory diseases, macrophages can play a dual role in the process of tissue damage, depending on their activation status (M1 / M2). M1 macrophages are considered to exert damaging effects to neurons, whereas M2 macrophages are reported to aid regeneration and repair of neurons. Their migration within the central nervous system may be of critical importance in the final outcome of neurodegeneration in neuroinflammatory diseases e.g. multiple sclerosis (MS). To provide insight into this process, we examined the migratory capacity of human monocyte-derived M1 and M2 polarised macrophages towards chemoattractants, relevant for neuroinflammatory diseases like MS.MethodsPrimary cultures of human monocyte-derived macrophages were exposed to interferon gamma and lipopolysaccharide (LPS) to evoke proinflammatory (M1) activation or IL-4 to evoke anti-inflammatory (M2) activation. In a TAXIScan assay, migration of M0, M1 and M2 towards chemoattractants was measured and quantified. Furthermore the adhesion capacity and the expression levels of integrins as well as chemokine receptors of M0, M1 and M2 were assessed. Alterations in cell morphology were analysed using fluorescent labelling of the cytoskeleton.ResultsSignificant differences were observed between M1 and M2 macrophages in the migration towards chemoattractants. We show that M2 macrophages migrated over longer distances towards CCL2, CCL5, CXCL10, CXCL12 and C1q compared to non-activated (M0) and M1 macrophages. No differences were observed in the adhesion of M0, M1 and M2 macrophages to multiple matrix components, nor in the expression of integrins and chemokine receptors. Significant changes were observed in the cytoskeleton organization upon stimulation with CCL2, M0, M1 and M2 macrophages adopt a spherical morphology and the cytoskeleton is rapidly rearranged. M0 and M2 macrophages are able to form filopodia, whereas M1 macrophages only adapt a spherical morphology.ConclusionsTogether our results indicate that the alternative activation status of macrophages promotes their migratory properties to chemoattractants relevant for neuroinflammatory diseases like MS. Conversely, classically activated, proinflammatory macrophages have reduced migratory properties. Based on our results, we postulate that the activation status of the macrophage influences the capacity of the macrophages to rearrange their cytoskeleton. This is the first step in understanding how modulation of macrophage activation affects macrophage migration in neuroinflammatory diseases like MS.

Highlights

Infiltration of circulating monocytes is a pathological hallmark of injury to the central nervous system (CNS)
It was shown in mice that upon mechanical spinal cord injury, the recruitment of M1 and M2 macrophages in the CNS differs; M1 macrophages were found to derive from monocytes that entered the traumatized spinal cord dependent on Chemokine C-C motif ligand (CCL)2 through the adjacent spinal cord leptomeninges, whereas the M2 polarised cells were derived from monocytes that trafficked through the brain-ventricular choroid plexus [8]
To investigate the migration capacities of differently activated macrophages, we examined the rate of migration towards a chemoattractant, their ability to adhere to Migration we investigated the migratory capacities of M0, M1 and M2 macrophages, by assessing both spontaneous motility and directed migration towards CXCL10, CXCL12, CCL5, CCL2 and C1q

Summary

Introduction

Infiltration of circulating monocytes is a pathological hallmark of injury to the central nervous system (CNS). Once in the CNS, blood-derived macrophages are thought to contribute to tissue damage and repair in yet unidentified ways [1,2,3]. It was shown in mice that upon mechanical spinal cord injury, the recruitment of M1 and M2 macrophages in the CNS differs; M1 macrophages were found to derive from monocytes that entered the traumatized spinal cord dependent on Chemokine C-C motif ligand (CCL) through the adjacent spinal cord leptomeninges, whereas the M2 polarised cells were derived from monocytes that trafficked through the brain-ventricular choroid plexus [8]. M1 macrophages are considered to exert damaging effects to neurons, whereas M2 macrophages are reported to aid regeneration and repair of neurons Their migration within the central nervous system may be of critical importance in the final outcome of neurodegeneration in neuroinflammatory diseases e.g. multiple sclerosis (MS). To provide insight into this process, we examined the migratory capacity of human monocyte-derived M1 and M2 polarised macrophages towards chemoattractants, relevant for neuroinflammatory diseases like MS

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