Einfluss der neutrophilen Granulozyten auf die Blut- Hirn- Schranken- Störung in einem experimentellen Modell der Subarachnoidalblutung

Abstract

unclear. In the pathophysiology of other diseases, a neutrophil-induced disruption of the blood-brain barrier (BBB) was shown to play a major role. We therefore examined the effect of neutrophils on the BBB in the first 24 hours after SAH in a murine endovascular filament perforation model of SAH.

Methods SAH was induced in C57BL/6N mice by endovascular filament perforation. Neutropenia was induced by anti-Ly6G antibody injection 12 h prior to surgery, successful induction of neutropenia was verified by differential leukocyte counts at the end of the experiment. Animals were sacrificed at 15 min, 3 h, and 24 h after SAH. The brains were dissected and frozen in powdered dry ice, cryosections were obtained, and IgG fluorescence staining was performed. Positive IgG fluorescence was taken as a surrogate parameter for BBB disruption. The area with BBB disruption was determined for the left hemisphere. Data are expressed in percent relative to the ipsilateral hemisphere. The Mann-Whitney U test was used for statistical analysis with p < 0.05 considered as statistically significant.

Results 51 animals were assigned to either sham surgery or SAH induction with or without prior induction of neutropenia. SAH induction without prior induction of neutropenia induced a sharp increase in the area with BBB disruption (SAH, 15 min: 6,27 ± 3,35%, 3 h: 16,02 ± 6,35%, 24 h: 21,71 ± 5,58%), which was not present after sham surgery (sham, 15 min: 5,16 ± 1,64%, 3 h: 5,93 ± 4,18%, 24 h: 6,65 ± 6,71%). After induction of neutropenia, SAH-induced disruption of the BBB was attenuated compared to SAH alone (SAH and neutropenia, 15 min: 2,36 ± 2%, 3 h: 8,66 ± 5,83%, 24 h: 5,42 ± 3,84%), which reached statistical significance at 24 h post-SAH.

Conclusion Already in the first hours after SAH, neutrophils induce a disruption of the BBB. Targeting neutrophil function or neutrophil interaction with the neurovascular unit could therefore be a promising strategy to mitigate BBB disruption after SAH. More studies are needed to examine whether the early neutrophil-induced BBB disruption is the critical phenomenon that leads to activation of cerebral inflammation in the weeks after SAH.