Perihematomal endothelin-1 level is associated with an increase in blood-brain barrier permeability in a rabbit model of intracerebral hematoma.

BACKGROUND

Endothelin-1 (ET-1) has deleterious effects on water homeostasis, cerebral edema, and blood-brain barrier (BBB) integrity. Highly expressed ET-1 was observed after intracerebral hemorrhage (ICH); however, ET-1 changes and their relationship with BBB disruption within 24 hours of ICH have not been thoroughly investigated. The aim of the present study was to observe the changes in perihematomal ET-1 levels in various phases of ICH and their correlation with the BBB integrity in a rabbit model of ICH.

METHODS

Twenty-five rabbits (3.2-4.3 kg body weight) were randomly divided into a normal control group (five rabbits) and a model group (20 rabbits). Animals in the model group were equally divided into four subgroups (five rabbits each to be sacrificed at 6, 12, 18, and 24 hours following ICH establishment). An ICH model was prepared in the model group by infusing autologous arterial blood into the rabbit brain. ET-1 expression in perihematomal brain tissues was determined using immunohistochemistry and color image analysis, and the permeability of the BBB was assayed using the Evan's Blue (EB) method. A repeated measures analysis of variance was used to make comparisons of the ET-1 and EB content across the entire time series.

RESULTS

The number of perihematomal endothelial cells with ET-1 positive expressions following 6, 12, 18, and 24 hours ICH model establishment was 9.32, 13.05, 15.90, and 20.44, respectively, but as low as 6.67 in the control group. The average transmittance of ET-1-positive cell bodies at 6, 12, 18, and 24 hours after ICH was 99.10, 97.40, 85.70, and 80.80, respectively, but 100.12 in the control group. These data reveal that the expression of ET-1 was significantly increased at 6, 12, 18, and 24 hours after ICH compared with the control group, and a marked decrease in the average transmittance of ET-1-positive cell bodies was noted (P < 0.05). Similarly, the perihematomal EB content at 6, 12, 18, and 24 hours after ICH was 29.39 ± 1.16, 32.20 ± 0.73, 33.63 ± 1.08, and 35.26 ± 1.12, respectively, in the model group and 28.06 ± 0.80 in the control group. The results indicate that a significant increase in the EB content in the model group was observed compared with that of the control group (P < 0.05). Moreover, a positive correlation between the number of ET-1-positive endothelial cells and BBB permeability was observed (r = 0.883, P < 0.05).

CONCLUSIONS

High levels of ET-1 are closely associated with BBB disruption. ET-1 may play an important role in the pathogenesis of secondary brain injury after ICH.