Stroke results from the occlusion of a cerebral artery by a fibrin clot. Currently, the only approved treatment for stroke is the use of tPA (tissue-type Plasminogen Activator) as a thrombolytic agent1. Although tPA is beneficial in the vascular compartment, tPA is deleterious in the cerebral parenchyma by modifying properties of the NMDA receptor. Indeed, tPA cleaves the NR1 subunit of the NMDA receptor leading to a potentiation of the NMDA-induced calcium influx2. Based on these observations, we have investigated whether neuroserpin (NS), a brain-derived tPA inhibitor3, could prevent this deleterious pro-excitotoxic activity of tPA. By using cultured cortical neurons, we have tested whether recombinant NS could influence excitotoxicity induced by NMDA or AMPA, two glutamatergic agonists. Although NS failed to alter AMPA-induced necrosis, it displayed a dose-dependent neuroprotective activity (up to 50%) against NMDA receptor-mediated neuronal death. By using calcium videomicroscopy imaging, we evidenced that NS decreases NMDA-induced calcium influx in neurons. Moreover, preliminary results show that NS reduces the lesion induced by the striatal injection of NMDA. These data suggest that promoting NS expression in the brain of stroke patients could prevent the deleterious effect of tPA in the brain parenchyma (potentiation of excitotoxic neuronal death) without affecting the beneficial thrombolytic activity of tPA in the vascular compartment. To address this question, we are investigating the regulation of NS expression by using luciferase gene reporter, real time PCR and immunoblotting to identify new ways to control the production of endogenous NS.
