The role of p53 in brain edema after 24 h of experimental subarachnoid hemorrhage in a rat model.

Our previous study demonstrated that p53 plays an orchestrating role in the vasospasm and apoptotic cell death after subarachnoid hemorrhage (SAH). We now hypothesize that p53 also plays an important role in brain edema by up-regulating the expression of MMP-9 via the NF-kappaB molecular signaling pathway. Adult male rats (300-350 g) were divided into five groups (n=20 each): Sham, SAH treatment with DMSO or PFT-alpha (0.2 mg/kg and 2.0 mg/kg), intraperitoneally. The monofilament puncture model was used to induce SAH and animals were subsequently sacrificed at 24 h. The blood-brain barrier (BBB) disruption, brain water content, MMP-9 activity, immunohistochemistry, treble fluorescence labeling, Western blot, and ultra-structural observations were performed. Evans blue extravagation, BBB diffuse leakage of IgG protein and brain water content were significantly reduced by PFT-alpha treatment; and the expression of p53, NF-kappaB and MMP-9 were significantly increased. The tight junction protein (Occludin) in endothelia cells and Collage IV in basal lamina were decreased in the brain of SAH rats, and were also modified by PFT-alpha treatment. Ultra-structural changes included disruption of endothelial tight junction and widening of the inter-endothelial spaces. Treble labeling showed p53 colocalized with NF-kappaB and MMP-9 in cerebral endothelia cells. We thus conclude that the level of p53 in cerebral microvasculature significantly affects the BBB permeability and brain edema after 24 h of SAH in rats. This can be at least partially ascribed to p53 inducing a significant up-regulation of MMP-9 via NF-kappaB in the endothelium, which in turn opened the tight junction by degrading Occludin and disrupting the basal lamina by degrading collagen IV.