Urokinase-type Plasminogen Activator Induces Neurorepair in the Ischemic Brain

Urokinase-type plasminogen activator (uPA) is a serine proteinase that upon binding to its receptor (uPAR) catalyzes the conversion of plasminogen into plasmin on the cell surface. Recent studies indicate that neurons but not astrocytes release uPA during the recovery phase from an ischemic injury, and that binding of uPA to uPAR promotes neurorepair in the ischemic brain by a mechanism that does not require plasmin generation. A combined approach of in vitro and in vivo studies has shown that uPA binding to uPAR induces the reorganization of the actin cytoskeleton in dendritic spines and axons that have suffered an ischemic injury. Furthermore, recent data indicate that uPA-uPAR binding induces astrocytic activation and a crosstalk between activated astrocytes and the injured neuron that triggers a sequence of biochemical events that promote the repair of synapses injured by the ischemic insult. The translational relevance of these observations is noteworthy because following its intravenous administrations recombinant uPA (ruPA) reaches the ischemic tissue, thus raising the question of whether treatment with ruPA is an effective therapeutic strategy to promote neurorepair functional recovery among ischemic stroke survivors.