Article
Haem degradation products and their pathogenetic role in cerebral vasospasm after subarachnoid haemorrhage
Hämdegradationsprodukte und deren Rolle in der Entstehung des zerebralen Vasospasmus nach einer Subarachnoidalblutung
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Published: | May 8, 2019 |
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Objective: Delayed cerebral ischemia (DCI) caused by symptomatic cerebral vasospasm is supposed to be the most common determinant of mortality and prognosis in patients suffering from subarachnoid haemorrhage (SAH). Actually, the guideline-based recommendations of vasospasm treatment fail to improve the clinical outcome. We hypothesize that haem degradation products (HDPs), originating from the intracranial haematoma surrounding the ruptured aneurysm, are involved in vasospasm pathogenesis by BKCa potassium channel inhibition. HDPs, comprising propentdyopents (PDPs) and bilirubin oxidation products (BOXes), are present in the cerebrospinal fluid of SAH patients and induce a short-onset vasoconstrictive effect on mouse cerebral arterioles.
Methods: To study the long-term effect of HDPs on cerebral perfusion, SAH was experimentally induced in adult wildtype and BK channel deficient mice (FVB/N) by the subarachnoid injection of autologous blood or PDP and BOX isomers into the cisterna magna, followed by temporally high-resolution echo-planar MR perfusion imaging series at 9.4T until the postinterventional day 14. Subsequent to MRI, vessel wall morphology of cerebral arteries was analyzed by immunofluorescence microscopy of PFA-fixed brain slices stained with anti-CD31 and anti-smooth muscle actin.
Results: The subarachnoid injection of venous autologous blood (30 µl, n=5) or PDP isomers (30 µl, 1 µM, n=5) induced a significant (p<0.05) reversible cortical perfusion delay in adult wildtype mice on postinterventional days 3 and 7 in comparison to control (injection of artificial cerebrospinal fluid, n=4). This perfusion disturbance was absent in PDP-treated BK knockout mice (30 µl, 1 µM, n=4). In contrast, subarachnoidally injected BOX isomers (30 µl, 1 µM, n=5) failed to induce cerebral perfusion deficits (p>0.05). Two weeks after subarachnoid PDP injection (1 µM), basal cerebral arteries of wildtype mice were affected by a significant (p<0.001) increase of smooth muscle wall thickness (12.8±1.5 µm) in comparison to controls (n=4, 6.1±0,9 µm).
Conclusion: Besides the short-onset vasoactivity, our data demonstrate a long-term effect of PDPs on cerebral perfusion for the first time which correlates with the onset of delayed vasospasm in SAH patients. In addition, PDPs induce changes in arterial vessel wall morphology. These findings may promote novel strategies for vasospasm treatment.