Expression of MAL is necessary for ETX induced BBB permeability.
Mal+/+ and Mal-/- mice were injected via IP with 5ng of active ETX per gram of body weight; saline treated animals were used as controls. After 1 hour, all animals were intravenously injected with FITC-Na for ten minutes then sacrificed. Brains were harvested and the amount of FITC-Na per gram of brain was calculated using spectrometry. Results are normalized to individual genotype controls and expressed as FITC-Na extravasation (% CT). Results expressed as Mean ± SEM, *p<0.05 determined by ANOVA, n = 3–5 mice per group. (B) Alternatively, ETX or saline treated Mal+/+ and Mal-/- mice were intravenously injected with 70kDA FITC-dextran for ten minutes one our after treatment. Brains were harvested, cryoprotected, and sectioned. 70kDA FITC-dextran extravasation into the brain parenchyma was determined by fluorescent microscopy. Dashed line identifies corpus callosum (CC). OB, olfactory bulb. CB, Cerebellum. Sections are approximately 1 to 1.5 millimeters to the left of the mid-sagittal plane. (C) Higher magnification of pericallosal white matter in ETX treated Mal+/+ mice identify ovoid shaped lesions (white ovals) perpendicular to corpus callosum (CC, width denoted with white dotted lines). White arrows point to shadows in FITC-dextran halos presumed to be central veins. (D) Sagittal sections of perfused control or ETX treated Mal+/+ stained for endogenous mouse IgG (red). FITC-BSL1 (green) was used to identify microvasculature. Dashed lines identify width of corpus callosum (CC). In control treated mice, limited IgG extravasation was observed, even around large vessels (white arrows), presumed to be deep medullary veins. In ETX treated mice, IgG extravasation is very prominent, especially around large vessels (white arrowheads), presumed to be deep medullary veins.