Oral fingolimod rescues the functional deficits of synapses in experimental autoimmune encephalomyelitis

BACKGROUND AND PURPOSE Alterations of glutamate-mediated synaptic transmission occur early during neuroinflammatory insults, and lead to degenerative neuronal damage in multiple sclerosis (MS) and also in experimental autoimmune encephalomyelitis (EAE), which is a murine model of MS. Fingolimod is an effective orally active agent for the treatment of MS, affecting lymphocyte invasion of the brain. However, it is still unclear if fingolimod can be neuroprotective in this disorder. EXPERIMENTAL APPROACH Using neurophysiological recordings and morphological evaluation of dendritic integrity, we evaluated the effects of oral fingolimod on the clinical score of EAE mice in order to determine whether the compound was associated with preservation of synaptic transmission. KEY RESULTS Oral fingolimod prevented and reversed the pre- and postsynaptic alterations of glutamate transmission in EAE mice. These effects were associated with a clear amelioration of the clinical deterioration seen in EAE mice, and with a significant inhibition of neuronal dendritic pathology. Fingolimod did not alter the spontaneous excitatory postsynaptic currents in control animals, suggesting that only the pathological processes behind the inflammation-induced defects in glutamate transmission were modulated by this compound. CONCLUSIONS AND IMPLICATIONS The beneficial effects of fingolimod on the clinical, synaptic and dendritic abnormalities of murine EAE might correlate with the neuroprotective actions of this agent, as observed in MS patients.