Abstracts

T-CELL EXTRAVASATION IS NOT REQUIRED FOR THE DEVELOPMENT OF ACUTE SEIZURES IN RESPONSE TO BLOOD-BRAIN BARRIER DISRUPTION IN A PIG MODEL

Abstract number : 3.132
Submission category : 1. Translational Research
Year : 2009
Submission ID : 10226
Source : www.aesnet.org
Presentation date : 12/4/2009 12:00:00 AM
Published date : Aug 26, 2009, 08:12 AM

Authors :
Qingshan Teng, N. Marchi, L. Franic, M. Nguyen, T. Masaryk, P. Rasmussen and D. Janigro

Rationale: The relationship between blood-brain barrier disruption (BBBD) and seizures has been an area of dispute in seizure/epilepsy research. We previously demonstrated that BBBD mediated by intra-arterial hyperosmotic mannitol infusion causes electroencephalographic (EEG) changes in a pig model. We have now characterized the cerebrovascular events occurring at the time of acute seizures after blood-brain barrier disruption with hyperosmotic mannitol. Methods: Adult pigs (n=3) were placed under anesthesia using isofluorane. An injection catheter was threaded into the internal carotid artery (ICA) via femoral artery under angiographic guidance. A hyperosmotic solution of mannitol (1.4 M, 40-100 mL) was injected into the ICA to hemispherically disrupt the BBB. Immediately after the injection of mannitol to disrupt blood-brain barrier, gadolinium-loaded CD8 T lymphocytes were injected through the catheter to visualized the passage of cells across leaky BBB. by MRI. EEG, brain blood flow measured by Transcranial Doppler (TCD) and Immunohistochemical staining (Cresyl Violet and CD8 staining of extravasated cells) were performed. Results: Our study confirmed that injection of hyperosmotic mannitol caused disruption of the BBB leading to fast generalizing acute electrographic and behavioral seizures in 25% of animals. We again confirmed that propensity to seizures depends on the degree of BBBD. In other words, unsuccessful BBBD did not cause seizures. TCD demonstrated no significant brain perfusion changes during the BBBD procedure, ruling out the possibility that brain ischemia might be responsible for the EEG changes. Gd++ positive signal were detected by MRI in the ICA territory indicating T lymphocyte extravasation. In addition, cresyl violet staining of the brain tissues revealed that the accumulation of T lymphocyte was restricted to perivascular space. Immunohistochemical staining for CD8 was performed to further confirm the perivascular segregation of cell extravasation. Quantification of lymphocyte distribution (intravascular, perivascular and brain parenchymal) indicated modest parenchymal spreading of the lymphocyte, while the majority of the cells were either intravascular or perivascular in location. MRI was negative in the contralateral side of the brain (non-BBBD) and histological examination of the brain showed minimal extravasation of WBCs in the non-BBBD hemisphere. Furthermore, a low dose of mannitol (40 ml) did not lead to the disruption of the BBB, did not induced EEG-behavioral changes and did not lead to perivascular accumulation of lymphocytes. Conclusions: Our data demonstrate that intravascular injection of hyperosmotic mannitol induced BBBD resulting in the perivascular accumulation of Gd++-loaded lymphocytes. We confirmed that BBB disruption induced EEG and behavioral seizures which are not due to alteration of cerebral blood flow. These findings demonstrated that for the development of acute seizures in response to BBBD T-cell extravasation is not required.
Translational Research