gms | German Medical Science

Objective: Despite decades of research, processes leading to the intravascular inflammatory response accompanying subarachnoid hemorrhage (SAH) remain elusive. The herein presented study focusses on investigating the extent and the progression of blood-brain barrier (BBB) disruption through the loss of BBB-specific tight and adherens junction (TJ and AJ) molecules in a mouse model of SAH.

Method: SAH was induced in mice by filament perforation. The localization of barrier maintaining molecules was achieved by immune-fluorescence techniques on day 1, 2, 4 and 7 in SAH versus sham operated mice on the respetive days. Moreover, an analysis of the gene expression of brain endothelial TJs and AJs, and of selected pro-inflammatory mediators was examined in freshly isolated cerebral capillaries employing real-time qPCR.

Results: Our analysis revealed a firm time-dependent decrease of the transcript level and distribution of barrier tightening molecules: claudin-1, -5 and -12, occludin, VE-cadherin and ZO-1 (0.4 ± 0.1-fold on day 1, 0.3 ± 0.1-fold on day 2, 0.6 ± 0.2-fold on day 1, 0.6 ± 0.2-fold on day 7, 0.6 ± 0.1-fold on day 1 and 0.5 ± 0.1-fold gene expression on day 7, respectively, as compared to the sham control set as 1) subsequently to an induction of claudin-3 (11.0 ± 0.3-fold on day 2 compared to sham) post SAH. Additionally, tumor necrosis factor alpha (TNFα), interleukin-1 beta (IL-1β) and IL-6 (3.6 ± 0.6-fold on day 7, 2.6 ± 0.8-fold on day 1 and 3.0 ± 0.8-fold gene expression on day 7, respectively) being pro-inflammatory mediators were strongly elevated in brain capillaries after SAH as opposed to the respective controls.

Conclusions: The strong inflammatory response within brain endothelial cells following SAH depicted by an increased expression of pro-inflammatory cytokines is accompanied by a progressive reduction of important barrier tightening molecules. The dynamics observed in the localization and gene expression of individual TJs nominate these proteins as important targets for clarifying the mechanisms of BBB regulation post SAH.