Abstract P70: SPAK/OSR1 Signaling as a Novel Target for Post-Stroke Oxidative Stress Brain Injury

Abstract

Stroke is the second leading cause of death worldwide, and ischemic stroke accounts for the vast majority of stroke cases. Currently, recombinant tissue plasminogen activator and endovascular thrombectomy are the two primary therapy strategies for acute ischemic stroke patients. Reactive oxygen species (ROS)-mediated oxidative stress can cause brain injury during reperfusion. We have shown that the Ste20/SPS1-related proline-alanine-rich protein kinase/oxidative stress-responsive kinase-1 (SPAK/OSR1) are activated in ischemic stroke brains, resulting in worsened outcomes in murine stroke models. SPAK activation induces the production of pro-inflammatory cytokines. Post-stroke administration of a novel SPAK inhibitor ZT-1a attenuates cerebral edema and protects against brain damage in in vivo model of ischemic stroke. However, whether ROS mediated oxidative stress directly activate SPAK/OSR1 pathway and induces SPAK pro-inflammatory cytokine production in ischemic brains remains unknown. In our extended study, we examined activation of SPAK/OSR1 and its substrate Na-K-Cl cotransporter (NKCC1) in cultured mouse primary neurons in response to hydrogen peroxide (H 2 O 2 )-mediated oxidative stress. We found that exposure of neurons to H 2 O 2 for 24 hrs triggered upregulation of protein expression and phosphorylation activation of SPAK/OSR1 and NKCC1 ( p < 0.05), which are accompanied with an increase in intracellular Na + concentration and neuronal death ( p < 0.01). These changes were blocked by an ROS scavenger ebselen. Interestingly, both novel SPAK inhibitor ZT-1a and NKCC1 inhibitor bumetanide are able to block H 2 O 2 -induced neuronal damage. We are in the process to assess effects of SPAK inhibitor ZT-1a in reducing ROS-mediated inflammation and brain injury in in vivo model of ischemic stroke. Together, our study suggests that ROS can activate SPAK/OSR1 complex during reperfusion injury and the therapeutic potentials of SPAK inhibitor ZT-1a for ischemic stroke.