Abstract WMP115: Rapid Vascular Complement Activation: A Key Driver of Blood-Brain Barrier Disruption in Ischemic Stroke With Acute Hyperglycemia

Background: Acute hyperglycemia, which occurs in over 40% of ischemic stroke patients irrespective of pre-existing diabetes, exacerbates stroke injury. Understanding its mechanisms is vital for innovative treatments. Here we investigate the role of complement in hyperglycemia-exacerbated damage after stroke.

Method: Male C57/BL6 mice (10-11 weeks) underwent 30-min suture-induced middle cerebral artery occlusion followed by reperfusion, resembling clinical thrombectomy. Acute hyperglycemia was induced 10 min pre-stroke via glucose injection. Mice were sacrificed at 4.5h and 24h post-stroke to analyze brain swelling, blood-brain barrier (BBB) leakage and hemorrhagic transformation (HT). Mortality, neurological deficits, and motor-sensory functions were assessed at 14 days post-stroke. Complement activation was visualized via C3d immunostaining. Complement C3's role was examined using knock-out mice and the targeted complement inhibitor CR2-Crry fusion protein.

Result: Hyperglycemia rapidly worsens BBB leakage (p<0.0001), brain swelling (p<0.05), and HT (p<0.0001) at 4.5 hr after stroke. Hyperglycemic stroke mice exhibit higher mortality (100% vs 25%, p=0.0008), body weight loss, and behavior impairment at the sub-acute phase compared to normoglycemic mice. Notably, acute hyperglycemia rapidly increased plasma C3 levels at 1hr after stroke (p<0.01), accompanied by rapid and time-dependent activation of C3 in ischemic brain vessels, as marked by increased vascular C3d; and this co-localized with autoantibody (IgM/IgG) vessel buildup and vessel leakage. Additionally, C3d levels positively correlated with brain swelling and HT (p<0.01). Vascular C3d and leakage into parenchyma were markedly reduced in the absence of reperfusion. Blocking complement via C3 knock-out or post-reperfusion systemic injection of C3 inhibitor CR2-Crry mitigates hyperglycemia's detrimental effects, including BBB leakage.

Conclusion: Rapid vascular activation of complement C3 is a significant driver of hyperglycemic-exacerbated pathology in experimental stroke. Inhibiting C3 activation could be a potential therapeutic approach to improve hyperglycemic stroke outcome.