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

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.

Small-molecule activator of glutamate transporter EAAT2 translation provides neuroprotection

“…EAAT2 upregulation, we note that not all studies have confirmed that EAAT2 can be upregulated by ceftriaxone (39,40). Similarly, our study found only marginal upregulation of EAAT2 with ceftriaxone administration to mice ( Figure 3F).…”

Regulation of Glial Glutamate Transporters by C-terminal Domains

“…Transport currents that are due to electrogenic glutamate transport were therefore determined by subtracting whole-cell currents before application of 0.5 mM L-glutamate from currents measured in the same cell after substrate application (Fig. 1B, inset) (5,34,35). These current components required internal K ϩ (12) and were blocked by external TBOA (data not shown).…”

Stromal Interaction Molecules 1 and 2 Are Key Regulators of Autoreactive T Cell Activation in Murine Autoimmune Central Nervous System Inflammation

“…For functional analysis, dentritic cells (DCs) from wt or Stim2 2/2 mice were prepared from BM cells flushed from femur and tibia bones as described before (19). BM-derived DCs were harvested on day 8, and 2 3 10 6 cells in 1 ml splenocyte complete medium were incubated with 50 mg/ml MOG 35-55 for 6 h. Thereafter MOG 35-55 -loaded DCs (1 3 10 5 ) were cocultured with MACS isolated CD4 + T cells (5 3 10 5 ) (Miltenyi Biotec, Bergisch Gladbach, Germany) for 3 d, and supernatants were assessed for IFN-g and IL-17 levels by ELISA.…”