Evaluation of the effect of GM-CSF blocking on the phenotype and function of human monocytes

Noushin Lotfi,Guang-Xian Zhang,Abdolmohamad Rostami,Nafiseh Esmaeil

doi:10.1038/s41598-020-58131-2

Abstract

Granulocyte-macrophage colony-stimulating factor (GM-CSF) is a multipotent cytokine that prompts the proliferation of bone marrow-derived macrophages and granulocytes. In addition to its effects as a growth factor, GM-CSF plays an important role in chronic inflammatory autoimmune diseases such as multiple sclerosis and rheumatoid arthritis. Reports have identified monocytes as the primary target of GM-CSF; however, its effect on monocyte activation has been under-estimated. Here, using flow cytometry and ELISA we show that GM-CSF induces an inflammatory profile in human monocytes, which includes an upregulated expression of HLA-DR and CD86 molecules and increased production of TNF-α and IL-1β. Conversely, blockage of endogenous GM-CSF with antibody treatment not only inhibited the inflammatory profile of these cells, but also induced an immunomodulatory one, as shown by increased IL-10 production by monocytes. Further analysis with qPCR, flow cytometry and ELISA experiments revealed that GM-CSF blockage in monocytes stimulated production of the chemokine CXCL-11, which suppressed T cell proliferation. Blockade of CXCL-11 abrogated anti-GM-CSF treatment and induced inflammatory monocytes. Our findings show that anti-GM-CSF treatment induces modulatory monocytes that act in a CXCL-11-dependent manner, a mechanism that can be used in the development of novel approaches to treat chronic inflammatory autoimmune diseases.

Highlights

Granulocyte-macrophage colony-stimulating factor (GM-CSF) is a multipotent cytokine that stimulates the proliferation of bone marrow-derived macrophages and granulocytes
We show that CXCL-11 is a monocyte-derived modulatory chemokine that is suppressed explicitly by GM-CSF
We showed that GM-CSF-treated monocytes increased the expression of critical antigen-presenting molecules such as HLA-DR and CD86 as compared with the control group

Summary

Introduction

Granulocyte-macrophage colony-stimulating factor (GM-CSF) is a multipotent cytokine that stimulates the proliferation of bone marrow-derived macrophages and granulocytes. GM-CSF signaling affects the survival and activation of myeloid cells, dendritic cell (DC) differentiation and M1 macrophage phenotype polarization; it boosts antigen presentation, induces phagocytosis, recruits monocytes and other myeloid populations from bone marrow to circulation and promotes chemotaxis[9,10]. It has been recently demonstrated that CCR2+Ly6Chi inflammatory monocytes are a target of GM-CSF in CNS autoimmunity by stimulating inflammatory monocytes and their conversion into pathogenic macrophage-derived dendritic cells[11,12,13]. GM-CSF-activated monocytes migrate across the blood-brain barrier (BBB) and mediate BBB rupture by increasing expression of the endothelial adhesion molecules ICAM-1 and VCAM-114,15. In EAE and MS, the CCR2-CCL2 axis has been previously shown to be a significant driver of inflammatory leukocyte infiltration into the CNS, and its activity positively correlates with disease pathogenesis[16,17,18]. CXCL-11 is upregulated in MS patients after IFN-β therapy and the decrease in the number of relapses may be linked to the increase in CXCR3 ligands in the serum of IFN-β-treated MS patients[25]

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Results

Conclusion