Multiple sclerosis and glutamate excitotoxicity

The previous understanding of multiple sclerosis was solely related to neuroinflammation and its harmful effects; however, countless data indicate the importance of some inflammation-independent, neurodegenerative mechanisms associated with mitochondria malfunction, iron deposition and oxidative stress. Recently, it has been postulated that glutamate excitotoxicity, a phenomenon that takes place when an excessive amount of glutamate overactivates its cellular receptors and induces cell death, could be a missing link between inflammatory and neurodegenerative processes evident in multiple sclerosis. Glutamate is the major excitatory neurotransmitter of the central nervous system, which has been proven to have a central role in a complex communication network established between all residential brain cells, including neurons, astrocytes, oligodendrocytes and microglia. Thus, the disturbance of glutamate homeostasis could affect practically all physiological functions and interactions of brain cells, leading to heterogeneity of pathological events. The understanding of glutamate excitotoxicity as a valid mechanism of central nervous system damage in multiple sclerosis, requires the revision of the current knowledge about a source of elevated extracellular glutamate, glutamate receptor alterations, alterations of glutamate transporters and metabolizing enzymes, as well as molecular mechanism of excitotoxic damage.