Abstract 3261: Vascular Protection Mediates Neuroprotection: Role of VEGF-A and B

Abstract

Introduction: Neuroprotection remains an elusive goal for the treatment of stroke patients. Vascular protection is achievable in humans and may result in reduced brain injury. Our recent preclinical studies demonstrated robust protective effects of angiotensin II receptor type-1 blockers (ARBs), leading to improved stroke outcome. These effects were associated with increased VEGF production and an enhanced proangiogenic state. Purpose: To remove the possibility of a protective effect with blood pressure lowering alone, we determined whether ARBs exert neuro- and vascular protective effects in isolated brain cells. Methods: Human cerebral microvascular endothelial cells (hCMEC) and mouse hippocampal neuronal cells (HT-22) were treated with clinically relevant concentrations of candesartan (0.1 and 1.6 µg/ml) and losartan (0.05 and 0.2 µg/ml). Angiogenic response was assessed using wound healing and Matrigel tube formation assays. Cell proliferation and viability were assessed by BrdU incorporation and MTT assays respectively. Western blotting was used to measure the levels of VEGF isoforms in hCMEC and apoptotic markers in the neurons. Results: Treatment with ARBs increased endothelial cell migration (45, 32, 39 and 27% increase in percent migration after 18 hours of treatment with candesartan 0.1, candesartan 1.6, losartan 0.05 and losartan 0.2 µg/ml respectively, p<0.05) and tube formation (4 and 10 fold increase after 48 and 72 hours of treatment with candesartan 1.6 µg/ml respectively, p<0.05). This was accompanied by an increased expression of VEGF-A and B both in the cell lysate and the conditioned media after 24 hours of treatment (90 and 65% increase in VEGF-A and B respectively). Direct application of candesartan did not salvage neurons after 24 hours of serum starvation. However, conditioned media collected from endothelial cells treated with candesartan decreased the expression of apoptotic markers in the neurons by 25%. Conclusion: ARBs exert a neuroprotective effect that is mediated through vasculature-secreted VEGF A and B. Translational Impact: This work demonstrates, for the first time, that the neuroprotective effects of ARBs are mediated through effects on the vasculature. Vascular protection represents an exciting new therapeutic avenue for the treatment of ischemic stroke patients.