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Aims Inflammation and apoptosis play important roles in increasing vascular permeability following subarachnoid hemorrhage (SAH). The objective of this study was to evaluate whether urinary trypsin inhibitor (UTI), a serine protease inhibitor, attenuates vascular permeability by its antiinflammatory and antiapoptotic effects after experimental SAH. Methods Subarachnoid hemorrhage models were established in adult male Sprague-Dawley rats by endovascular perforation. UTI was administered by intraperitoneal injection immediately following SAH. Brain edema was assessed by magnetic resonance imaging (MRI) at 24 h after SAH. Neurological deficits, brain water content, vascular permeability, malondialdehyde (MDA) concentration, and myeloperoxidase (MPO) activity were evaluated. Immunohistochemical staining and Western blot were used to explore the underlying protective mechanism of UTI. Results Urinary trypsin inhibitor 50,000 U/kg significantly attenuated brain edema and neurological deficits and reduced vascular permeability at 24 h after SAH. MDA concentration and MPO activity in hippocampus were significantly decreased with UTI treatment. Furthermore, the levels of phosphorylated JNK, NF-κB (p65), tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6) and proapoptotic protein p53, caspase-3 were elevated in the microvascular endothelial cells of the hippocampus after SAH, which were alleviated with UTI treatment. Conclusion Urinary trypsin inhibitor reduced vascular permeability after SAH through its antiinflammatory and antiapptotic effects via blocking the activity of JNK, NF-κB, and p53. [ABSTRACT FROM AUTHOR]

SUMMARY Aims: To investigate the mechanism behind cytotoxic edema formation following subarachnoid hemorrhage (SAH). Methods: We explored the role of aquaporin-4 (AQP4), inwardly rectifying K+ 4.1 (Kir4.1) channels and their upstream orchestrators p53 and p38MAPK in this process. A p53 inhibitor, pifithrin-α (PFT-α) was administered intraperitoneally to rats undergoing SAH by endovascular perforation. Totally, 98 male SD rats were categorized into sham, SAH, SAH+ dimethyl sulfoxide (DMSO), SAH+ 0.2 or 2.0 mg/kg PFT-α groups. At 24 h after SAH, MRI (diffusion-weighted imaging [DWI]), immunohistochemistry, and Western blot were used. Results: MRI (DWI) showed a significant cytotoxic edema in the brain following SAH with PFT-α therapy reducing it. Immunohistochemistry and Western blot showed an increased level of p53, phosphorylated-p38MAPK and AQP4 and a reduced level of Kir4.1; all of which could be reversed following PFT-α treatment. Treble labeling staining revealed colocalization of p53 with phosphorylated-p38MAPK and unmatched expression of AQP4 and Kir4.1 within astrocyte cells. Conclusion: These results indicated p53 mediates the formation of cytotoxic edema in the brain following SAH; an uncoupling expression of AQP4 and Kir4.1 on astrocytic end feets orchestrated by p38MAPK was partly responsible. [ABSTRACT FROM AUTHOR]