IMPACT OF COMPLEMENT OVER-ACTIVATION ON GLUTAMATE RELEASE IN THE CORTEX OF EAE MOUSE MODEL

Growing evidence implicates complement activation in the progression of multiple sclerosis (MS), including direct effects within the central nervous system. This study aimed to investigate the contribution of the complement components C1q and C3 to synaptic dysfunction in experimental autoimmune encephalomyelitis (EAE), a mouse model of progressive MS, with particular emphasis on their impact on glutamate release from cortical neuronal terminals (synaptosomes) and astrocytic processes (gliosomes) during the acute phase of the disease. EAE was induced in female C57BL/6J mice by immunization with MOG₃₅–₅₅ and compared with age-sex-matched control animals. Complement-dependent glutamate release was evaluated using up–down superfusion experiments, with [³H]D-aspartate employed as a non-metabolizable analogue of glutamate. Western blot analysis of cortical tissue revealed increased expression of astrocytic and microglial activation markers in total lysates, together with elevated levels of C1q and C3 in isolated synaptosomes and gliosomes. Meanwhile, cortical synaptosomes displayed reduced expression of the glutamate transporter EAAT2, whereas gliosomes exhibited increased EAAT1 levels. These molecular alterations were associated with decreased complement-evoked glutamate release from synaptosomes and enhanced release from gliosomes, consistent with a reversal of EAAT-mediated transport. Overall, these findings identify a noncanonical role of complement in perturbing glutamate homeostasis and synaptic function in EAE, providing mechanistic insight into MS pathophysiology and supporting complement modulation as a potential therapeutic strategy.