Pathogenesis – Neurodegeneration Poster Presentation

P0999 - The role of neuronal CXCL13 chemokine expression in Multiple Sclerosis Pathology (ID 907)

Speakers
  • R. James
Authors
  • R. James
  • H. Jacobs
  • X. Zhang
  • R. Reynolds
Presentation Number
P0999
Presentation Topic
Pathogenesis – Neurodegeneration

Abstract

Background

Chemokine CXCL13 is suggested as a potential prognostic marker for patient outcomes. Cerebrospinal fluid (CSF) levels of CXCL13 are increased at all stages of MS and correlate with CSF B-cell counts, disability, cortical thinning and markers of neurodegeneration. A recent GWAS study identified a SNP in the promoter region of its receptor CXCR5 (rs630923) was a MS susceptibility loci. However, little is known concerning its expression pattern or mechanisms of action within the CNS.

Objectives

We aimed to study the expression of CXCL13 and its receptor CXCR5 in the grey matter (GM) of post-mortem SPMS brains and how this might contribute to cortical pathology and clinical outcomes. To investigate the occurrence of the rs630923 SNP in 240 cases in the MS tissue bank ask whether having either the common (C:C) or minor (A:C) 'protective' genotype correlated to CXCL13 or CXCR5 levels or with any clinical outcomes

Methods

Levels of CXCL13 and CXCR5 were assessed in cortical GM from 50 MS post-mortem brains using ELISA and western blotting and immunofluorescence with cell specific markers. We examined the role of CXCL13 and CXCR5 expression in primary cultures of rat neurons and astrocytes. Finally, we used a rat model of cortical pathology in which LTα and IFNγ are chronically over-expressed in the cortical subarachnoid space of DA rats.

Results

Protein levels for both CXCL13 and CXCR5 were increased in MS GM and correlated with the extent of GM demyelination and neuronal loss. Patients with the shortest disease duration had the highest GM CXCL13 levels. CXCL13 was expressed primarily by neurons in layers II/III and IV. CXCR5 was expressed in neurons and astrocytes, mainly in the subpial layers and in deep layer VI near the white matter. Patients with C:C allele had significantly shorted time to progressive than A:C genotypes. Both CXCL13 protein in tissue and CSF and CXCR5 tissue levels are higher in C:C genotype than A:C. Chronic overexpression of LTα and IFNγ in the rat meninges increased the neuronal expression of CXCL13, suggesting CSF cytokines can influence parenchymal CXCL13 expression. Stimulation of primary neurons with LTα, TNF or IFNγ lead to an increase in CXCL13 gene and protein expression. Recombinant CXCL13 alone was not toxic to neurons, but it increased the level of cell death when added to neuronal cultures together with L-glutamate. This was accompanied by increased levels of caspase-8/9 mRNA and was inhibited by a caspase inhibitor Z-VAD-FMK. Protein arrays of primary astrocyte cultures stimulated with CXCL13 showed increased expression of CCL5, CCL3, CCL20, CXCL10 and CXCL5.

Conclusions

We suggest that neuronal expression of CXCL13 is stimulated by cytokines present in the GM and CSF and may signal through CXCR5 receptors on astrocytes to increase production of chemokines linked to MS progression. Neuronally produced or CSF derived CXCL13 may act on CXCR5 on neurons making them more vulnerable to cell death when they are exposed to stressors.

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