Background & purposes: Although there were a number of studies that apply angiotensin II (Ang II) peptide vaccine to treat hypertension, no therapeutic attempt has been made to show efficacy of Ang II peptide vaccine for ischemia stroke. The purpose of this study is to investigate whether pre-exposure Ang II vaccination exhibits the cerebroprotective effects after permanent middle cerebral artery occlusion (p-MCAo) in rats.
Methods: After subcutaneous injection of Ang II peptide vaccine (10μg/200μl) or saline (200μl) to Wistar rats (male, 4week-old) at the time point of 4, 6 and 7 week-old, MCAo or sham surgery was performed at 8 week-old. Neurological function was evaluated at 24 hours of MCAo using Neurological Severity Score (NSS). The plasma Ang II antibody titer or brain parenchymal Ang II antibody level was quantified using ELISA. Serial sections were stained with cresyl violet to measure infarction volume. Neuronal degeneration and oxidative stress were evaluated using Fluoro Jade B (FJB) and 4-Hydroxynonenal (4-HNE) staining. The expression of brain renin-angiotensin-system (RAS) components or NOX2 was quantified using real-time PCR.
Results: Systemic blood pressure was not affected by vaccination. Infarction volume 24 hours after MCAo was reduced not in plasma low-titer (Lo) group (OD50%<6000) but in plasma high-titer (Hi) group (OD50%≧6000) compared with saline (S) group, thus Hi group was defined as vaccine treated (V) group. Parenchymal anti-Ang II antibody level in the ischemic hemisphere was significantly higher in Hi group compared with Lo group. Both FJB positive neurons and 4-HNE positive cells were significantly decreased in V group. The expression of brain AngII type 1 receptor mRNA and brain NOX2 mRNA were less in V group compared with S group. Amelioration on neurological function was observed because of low score of neurological severity score in V group.
Conclusions: Prior vaccination ameliorates ischemic injury and neurological function in p-MCAo rats. The inhibitory effects against brain RAS and /or its anti-oxidative effects in the ischemic lesion were the suggested mechanisms of Ang II peptide vaccine in cerebral ischemia. Therapeutic vaccination targeting Ang II may provide a new approach to treat cerebral ischemia.