Deletion of astroglial CXCL10 delays clinical onset but does not affect progressive axon loss in a murine autoimmune multiple sclerosis model.

Emily Mills Ko,Athena M Soulika,Travis Burns,Eunyoung Lee,Joyce H Ma,Laird Miers,Jiho Sohn,Fuzheng Guo,David Pleasure,Peter Bannerman,David Ko

doi:10.1186/1742-2094-11-105

Abstract

Multiple sclerosis (MS) is characterized by central nervous system (CNS) inflammation, demyelination, and axonal degeneration. CXCL10 (IP-10), a chemokine for CXCR3+ T cells, is known to regulate T cell differentiation and migration in the periphery, but effects of CXCL10 produced endogenously in the CNS on immune cell trafficking are unknown. We created floxed cxcl10 mice and crossed them with mice carrying an astrocyte-specific Cre transgene (mGFAPcre) to ablate astroglial CXCL10 synthesis. These mice, and littermate controls, were immunized with myelin oligodendrocyte glycoprotein peptide 35-55 (MOG peptide) to induce experimental autoimmune encephalomyelitis (EAE). In comparison to the control mice, spinal cord CXCL10 mRNA and protein were sharply diminished in the mGFAPcre/CXCL10fl/fl EAE mice, confirming that astroglia are chiefly responsible for EAE-induced CNS CXCL10 synthesis. Astroglial CXCL10 deletion did not significantly alter the overall composition of CD4+ lymphocytes and CD11b+ cells in the acutely inflamed CNS, but did diminish accumulation of CD4+ lymphocytes in the spinal cord perivascular spaces. Furthermore, IBA1+ microglia/macrophage accumulation within the lesions was not affected by CXCL10 deletion. Clinical deficits were milder and acute demyelination was substantially reduced in the astroglial CXCL10-deleted EAE mice, but long-term axon loss was equally severe in the two groups. We concluded that astroglial CXCL10 enhances spinal cord perivascular CD4+ lymphocyte accumulation and acute spinal cord demyelination in MOG peptide EAE, but does not play an important role in progressive axon loss in this MS model.

Highlights

Multiple sclerosis (MS) is a neuroinflammatory and neurodegenerative disease that affects more than one million people worldwide
Evaluation of astroglial CXCL10 deletion To delete astroglial CXCL10, we developed a line of mice in which CXCL10WT alleles were replaced by CXCL10fl alleles, and crossed them with mice carrying mGFAPcre (Figure 1A)
In astroglial CXCL10 knockout mice, while CXCL10 was undetectable in astrocytes, the overall CXCL10 immunoreactivity in whole spinal cord sections was diminished by half, and remaining positive signal colocalized primarily with infiltrating cells. qRT/PCR showed that spinal cord CXCL10 mRNA levels on days 7 and 14 post-MOG peptide immunization were substantially reduced in astroglial CXCL10 knockout mice (Figure 1D), whereas the level of mRNA encoding CXCL9, a chemokine that, like CXCL10, activates CXCR3, was not altered at these time-points in astroglial CXCL10 knockout mice (Figure 1E)

Summary

Introduction

Multiple sclerosis (MS) is a neuroinflammatory and neurodegenerative disease that affects more than one million people worldwide. MS and its murine model, experimental autoimmune encephalomyelitis (EAE), are mediated by activated autoreactive T lymphocytes which traffic to the central nervous system (CNS), where they are reactivated and release pro-inflammatory cytokines and chemokines, resulting in CNS recruitment and activation of innate immune cells including monocytederived macrophages and microglia [1,2,3]. Antibody-mediated systemic blockade of CXCL10 signaling has been reported to prevent recruitment of activated CD4+ T cells to the CNS parenchyma, and to diminish severity in an EAE passive transfer model [5]. Antibody blockade of CXCL10 signaling has been reported to exacerbate EAE in an active immunization model [7], and a later study of antibody blockade of passive transfer EAE failed to confirm a diminution in disease severity [8]. Immunization with myelin oligodendrocyte glycoprotein peptide (MOG peptide) of mice in which CXCL10

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