TNF-α potentiates glutamate-induced spinal cord motoneuron death via NF-κB

Besides glutamate excitotoxicity, the neuroinflammatory response is emerging as a relevant contributor to motoneuron loss in amyotrophic lateral sclerosis (ALS). In this regard, high levels of circulating proinflammatory cytokines such as tumor necrosis factor-alpha (TNF-alpha) have been shown both in human patients and in animal models of ALS. The aim of this work was to study the effects of TNF-alpha on glutamate-induced excitotoxicity in spinal cord motoneurons. In rat spinal cord organotypic cultures chronic glutamate excitotoxicity, induced by the glutamate-uptake inhibitor threohydroxyaspartate (THA), resulted in motoneuron loss that was associated with a neuroinflammatory response. In the presence of TNF-alpha. THA-induced excitotoxic motoneuron death was potentiated. Co-exposure to TNF-alpha and THA also resulted in down-regulation of the astroglial glutamate transporter 1 (GLT-1) and in increased extracellular glutamate levels, which were prevented by nuclear factor-kappaB (NF-kappa B) inhibition. Furthermore, TNF-alpha and THA also cooperated in the induction of oxidative stress in a mechanism involving the NF-kappa B signalling pathway as well. The inhibition of this pathway abrogated the exacerbation of glutamate-mediated motoneuron death induced by TNF-alpha. These data link two important pathogenic mechanisms. excitotoxicity and neuroinflammation, suggested to play a role in ALS and, to our knowledge, this is the first time that TNF-alpha-induced NF-kappa B activation has been reported to potentiate glutamate excitotoxicity on motononeurons. (C) 2010 Elsevier Inc. All rights reserved.