A β-Lactam Antibiotic Dampens Excitotoxic Inflammatory CNS Damage in a Mouse Model of Multiple Sclerosis

Nico Melzer,Martin Stangel,Christoph Fahlke,Heinz Wiendl,Alexandra Kotsiari,Alla L Zozulya,Sven G Meuth,Christian Weidenfeller,Stefan Bittner,Delany Torres-Salazar,Marco Prinz

doi:10.1371/journal.pone.0003149

Abstract

In multiple sclerosis (MS) and its animal model experimental autoimmune encephalomyelitis (EAE), impairment of glial “Excitatory Amino Acid Transporters” (EAATs) together with an excess glutamate-release by invading immune cells causes excitotoxic damage of the central nervous system (CNS). In order to identify pathways to dampen excitotoxic inflammatory CNS damage, we assessed the effects of a β-lactam antibiotic, ceftriaxone, reported to enhance expression of glial EAAT2, in “Myelin Oligodendrocyte Glycoprotein” (MOG)-induced EAE. Ceftriaxone profoundly ameliorated the clinical course of murine MOG-induced EAE both under preventive and therapeutic regimens. However, ceftriaxone had impact neither on EAAT2 protein expression levels in several brain areas, nor on the radioactive glutamate uptake capacity in a mixed primary glial cell-culture and the glutamate-induced uptake currents in a mammalian cell line mediated by EAAT2. Moreover, the clinical effect of ceftriaxone was preserved in the presence of the EAAT2-specific transport inhibitor, dihydrokainate, while dihydrokainate alone caused an aggravated EAE course. This demonstrates the need for sufficient glial glutamate uptake upon an excitotoxic autoimmune inflammatory challenge of the CNS and a molecular target of ceftriaxone other than the glutamate transporter. Ceftriaxone treatment indirectly hampered T cell proliferation and proinflammatory INFγ and IL17 secretion through modulation of myelin-antigen presentation by antigen-presenting cells (APCs) e.g. dendritic cells (DCs) and reduced T cell migration into the CNS in vivo. Taken together, we demonstrate, that a β-lactam antibiotic attenuates disease course and severity in a model of autoimmune CNS inflammation. The mechanisms are reduction of T cell activation by modulation of cellular antigen-presentation and impairment of antigen-specific T cell migration into the CNS rather than or modulation of central glutamate homeostasis.

Highlights

Multiple sclerosis (MS) is considered a paradigmatic autoimmune inflammatory disorder of the central nervous system (CNS) [1,2]
Glutamate excitotoxicity is a dominant feature contributing to lesion pathogenesis and neuronal degeneration in multiple sclerosis [10,11,12]
In 2005 Rothstein et al proposed that b-lactam antibiotics such as ceftriaxone exert a profound neuroprotective effect in pathological CNS conditions involving glutamate excitotoxicity by functionally up-regulating glial glutamate transporter expression [14]

Summary

Introduction

Multiple sclerosis (MS) is considered a paradigmatic autoimmune inflammatory disorder of the central nervous system (CNS) [1,2]. Activated autoreactive T- and B-lymphocytes together with granulocytes and macrophages cross the blood-brain-barrier and migrate into the CNS parenchyma. This is followed by formation of inflammatory plaques in the CNS, that are mainly but not exclusively located in white matter [1]. Resulting excessive extracellular glutamate levels cause prolonged activation of calcium-permeable ionotropic glutamate receptors on neuronal and glial cells leading to excitotoxic CNStissue damage [10,11]. Ionotropic glutamate receptor antagonists have proven to be effective in ameliorating the clinical course and CNS-tissue damage in EAE [10,11,12], making glutamate-mediated excitotoxicity an attractive target for future therapy of MS [13]

Methods

Results

Conclusion