Abstract W P210: Plasma Kallikrein Induces Ischemic Brain Damage Through Cleavage-Dependent Activation of NMDA Receptors
Background and Purpose: Ischemic stroke ultimately leads to brain dysfunction and neurological deficits. However, the mechanisms that contribute to neuronal injury and dysfunction in ischemic stroke are not fully understood. Recent studies have shown that pharmacological inhibition of the serine protease plasma kallikrein (PK) reduced neuron death and neurological impairment in ischemic brain in mice. In this study, we examine the effects of PK on the neuronal cell death and brain damage in mice and investigate the molecular mechanism of PK-induced neuronal cell death in ischemic stroke.
Methods: Ischemia was produced in wild-type (WT) and PK knockout mice by permanent middle cerebral artery occlusion (pMCAO). Infarct volume was quantified by TTC staining and brain function was evaluated by neurological scoring. The effect of PK on neuron cell death in cell culture was determined by lactate dehydrogenase (LDH) release. NMDA receptor function was measured by patch clamp and Ca2+ imaging. NR1 cleavage was detected by western blot. The effect of systemic PK inhibition on pMCAO-induced infarct volume was evaluated in mice treated with the PK inhibitor (BPCCB) or vehicle alone delivered using subcutaneously implanted osmotic pumps.
Results: We show that PK deficiency in mice decreased MCAO-induced infarct volume by 39.8% (P<0.01) and improved neurological function compared responses in WT mice. Addition of PK to cell culture media enhanced NMDA-induced cell death of cortical neurons. We further show that PK induced cleavage of NR1 and identify the cleavage site in the extracellular N-terminal domain of NR1. The truncated form of NR1 displayed enhanced NMDA-stimulated current and calcium influx. Treatment of mice with a PK inhibitor reduced MCAO-induced brain damage and neuronal injury.
Conclusions: PK enhances NMDA receptor-mediated excitotoxicity and ischemic neuronal death. These findings suggest that PK may serve as a potential therapeutic target for treatment of ischemic stroke.
Author Disclosures: G. wu: None. L. Wu: None. D. Clapham: None. E. Feener: None.
- © 2014 by American Heart Association, Inc.