Blood Glutamate Scavenger as a Novel Neuroprotective Treatment in Spinal Cord Injury

Neurotrauma causes immediate elevation of extracellular glutamate (Glu) levels, which creates excitotoxicity and facilitates inflammation, glial scar formation, and consequently neuronal death. Finding factors that reduce the inflammatory response and glial scar formation, and increase neuronal survival and neurite outgrowth, are of major importance for improving the outcome after spinal cord injury (SCI). In the present study, we evaluated a new treatment aiming to remove central nervous system (CNS) Glu into the systemic blood circulation by intravenous (IV) administration of blood Glu scavengers (BGS) such as the enzyme recombinant glutamate-oxaloacetate transaminase 1 (rGOT1) and its co-substrate. In this study we induced in mice an SCI (hemisection), and 1 h post-injury started administering BGS treatment for 5 consecutive days. The treatment reduced the expression levels of p-p38, which regulates apoptosis and increased the expression of p-Akt, which mediates cell survival. Moreover, this treatment decreased pro-inflammatory cytokine expression and microglia activation, reduced astrocytes' reactivity, and facilitated expression of radial glia markers such as Pax6 and nestin. BGS treatment increased the survival of neurons at lesion site and enabled axonal regeneration into the injury site. These effects were correlated with improved functional recovery of the left paretic hindlimb. Thus, early pharmacological intervention with BGS following SCI may be neuroprotective and create a pro-regenerative environment by modulating glia cell response. In light of our results, the availability of the method to remove excess Glu from CNS without the need to deliver drugs across the blood-brain barrier (BBB) and with minimal or no adverse effects may provide a major therapeutic asset.