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J Am Heart Assoc. 2014 Aug 28;3(4). pii: e001220. doi: 10.1161/JAHA.114.001220.

Impact of heme and heme degradation products on vascular diameter in mouse visual cortex.

Author information

1
Hans-Berger Department of Neurology, University Hospital Jena, Germany (A.J., S.G.W., A.W., K.K., O.W.W., K.H.).
2
Institute of Inorganic and Analytical Chemistry, Friedrich-Schiller University, Jena, Germany (R.A.S., M.K., M.K., G.P., M.W.) Department of Anesthesiology and Intensive Care Medicine/Center for Sepsis Control and Care, University Hospital, Friedrich Schiller University, Jena, Germany (R.A.S.).
3
Institute of Inorganic and Analytical Chemistry, Friedrich-Schiller University, Jena, Germany (R.A.S., M.K., M.K., G.P., M.W.).

Abstract

BACKGROUND:

Delayed cerebral vasospasm is the most common cause of mortality and severe neurological impairment in patients who survive subarachnoid hemorrhage. Despite improvements in the field of diagnostic imaging, options for prevention and medical treatment-primarily with the calcium channel antagonist nimodipine or hemodynamic manipulations-are insufficient. Previous studies have suggested that heme and bilirubin oxidation end products, originating from degraded hemoglobin around ruptured blood vessels, are involved in the development of vasospasm by inhibiting large conductance BKC a potassium channels in vascular smooth muscle cells. In this study, we identify individual heme degradation products regulating arteriolar diameter in dependence of BKC a channel activity.

METHODS AND RESULTS:

Using differential interference contrast video microscopy in acute brain slices, we determined diameter changes of intracerebral arterioles in mouse visual cortex. In preconstricted vessels, the specific BKC a channel blockers paxilline and iberiotoxin as well as iron-containing hemin caused vasoconstriction. In addition, the bilirubin oxidation end product Z-BOX A showed a stronger vasoconstrictive potency than its regio-isomer Z-BOX B. Importantly, Z-BOX A had the same vasoconstrictive effect, independent of its origin from oxidative degradation or chemical synthesis. Finally, in slices of Slo1-deficient knockout mice, paxilline and Z-BOX A remained ineffective in changing arteriole diameter.

CONCLUSIONS:

We identified individual components of the oxidative bilirubin degradation that led to vasoconstriction of cerebral arterioles. The vasoconstrictive effect of Z-BOX A and Z-BOX B was mediated by BKC a channel activity that might represent a signaling pathway in the occurrence of delayed cerebral vasospasm in subarachnoid hemorrhage patients.

KEYWORDS:

bilirubin oxidation end products; cerebral vasospasm; potassium ion channels; subarachnoid hemorrhage

PMID:
25169792
PMCID:
PMC4310418
DOI:
10.1161/JAHA.114.001220
[Indexed for MEDLINE]
Free PMC Article

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