Abstract TP144: Preclinical Translation and Validation of C3a Receptor Antagonist in Thromboembolic Stroke

Abstract

Background: Activation of complement component C3 and expression of cerebro-endothelial C3a receptor (C3aR) occur after stroke regardless of the dynamics of cerebral blood flow (CBF) changes. Moreover, intravenous tissue plasminogen activator (IVT) cleaves C3 to generate C3a anaphylatoxin which promotes hemorrhagic transformation. We reported that C3aR antagonist (C3aRA) therapy is neuroprotective in a model of mechanical reperfusion simulating ET (endovascular thromboectomy) but is not beneficial following permanent ischemia. Although the majority of ischemic strokes are thromboembolic (TE), C3aRA has not been tested in TE-stroke models. Hypothesis: We hypothesized that TE-stroke upregulates the C3a/C3aR axis to exacerbate stroke injury, and C3aRA therapy is neuroprotective with and without IVT in TE-stroke. Methods: Plasma C3a level and brain C3aR expression were assessed following TE-stroke induced either with photothrombosis (PT) in young C57/B6 male mice or with a ~1-cm long partially humanized embolic thrombus (eMCAo) in C57/B6 aged male mice. Post-ischemic C3aRA therapy was tested in both models, as well as with late IVT (4-hrs) after eMCAo. Behavioral outcome, infarct volume and HT were assessed. Results: Plasma C3a and brain C3aR expression levels were significantly elevated acutely in both PT- and eMCAo stroke models. Interestingly, brain C3aR remained chronically elevated 4-wks after TE-stroke. Flow cytometry demonstrated that C3aR expression was primarily increased in cerebro-endothelial cells following eMCAo. When administered 1-hr after PT-stroke, C3aRA improved sensorimotor function as determined by the adhesive tape removal and corner tests, reduced infarction volume, and suppressed inflammatory responses. Furthermore, late IVT 4-hrs after eMCAo does not reduce infarction volume but worsens neurological deficit score likely due to increased HT. C3aRA therapy given 2-hr after eMCAo prior to IVT improved neurological outcomes and reduced both infarction volume and HT. Conclusion: C3aRA represents a promising adjuvant therapy with or without IVT following TE-stroke. These findings must be extended to comorbid TE-stroke and through chronic treatment to prevent post-stroke vascular dementia.