Blood–brain barrier disruption in CCL2 transgenic mice during pertussis toxin-induced brain inflammation

Angela E Schellenberg,Trevor Owens,Reza Khorooshi,Henrik Toft-Hansen,James Peeling,Marc R Del Bigio,Richard Buist

doi:10.1186/2045-8118-9-10

Abstract

BackgroundThe chemokine CCL2 has an important role in the recruitment of inflammatory cells into the central nervous system (CNS). A transgenic mouse model that overexpresses CCL2 in the CNS shows an accumulation of leukocytes within the perivascular space surrounding vessels, and which infiltrate into the brain parenchyma following the administration of pertussis toxin (PTx).MethodsThis study used contrast-enhanced magnetic resonance imaging (MRI) to quantify the extent of blood–brain barrier (BBB) disruption in this model pre- and post-PTx administration compared to wild-type mice. Contrast-enhanced MR images were obtained before and 1, 3, and 5 days after PTx injection in each animal. After the final imaging session fluorescent dextran tracers were administered intravenously to each mouse and brains were examined histologically for cellular infiltrates, BBB leakage and tight junction protein.ResultsBBB breakdown, defined as a disruption of both the endothelium and glia limitans, was found only in CCL2 transgenic mice following PTx administration and seen on MR images as focal areas of contrast enhancement and histologically as dextrans leaking from blood vessels. No evidence of disruption in endothelial tight junctions was observed.ConclusionGenetic and environmental stimuli were needed to disrupt the integrity of the BBB in this model of neuroinflammation.

Highlights

The chemokine CCL2 has an important role in the recruitment of inflammatory cells into the central nervous system (CNS)
One transgenic mouse that received an initial dose of 20 μg/kg pertussis toxin (PTx) died under anesthetic during imaging on day 3 and a second transgenic mouse that received an initial dose of 10 μg/kg PTx died on day 5
MR imaging Focal areas of enhancement on contrast-enhanced MR images were scattered throughout coronal brain slices of CCL2 transgenic mice that had been injected with PTx (Figures 3, 4)

Summary

Introduction

The chemokine CCL2 has an important role in the recruitment of inflammatory cells into the central nervous system (CNS). Leukocytes accumulate in the perivascular space between the endothelium and glia limitans (formed by astrocytic foot processes) in transgenic mice that overexpress CCL2 in the CNS [17,18] This transgenic mouse model is a unique experimental system for studying the infiltration of inflammatory cells across the endothelium and glia limitans of the BBB, which is not possible in EAE [19]. These mice show infiltration of leukocytes across the BBB following pertussis toxin (PTx) administration along with an upregulation of proinflammatory cytokines and metalloproteinase genes [18]. PTx increases the permeability of the BBB in animal models of EAE and results in a more severe disease course [20]

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Discussion

Conclusion