Propentdyopents as Heme Degradation Intermediates Constrict Mouse Cerebral Arterioles and Are Present in the Cerebrospinal Fluid of Patients With Subarachnoid Hemorrhage

Abstract

Rationale: Delayed ischemic neurological deficit is the most common cause of neurological impairment and unfavorable prognosis in patients with subarachnoid hemorrhage (SAH). Despite the existence of neuroimaging modalities that depict the onset of the accompanying cerebral vasospasm, preventive and therapeutic options are limited and fail to improve outcome owing to an insufficient pathomechanistic understanding of the delayed perfusion deficit. Previous studies have suggested that BOXes (bilirubin oxidation end products), originating from released heme surrounding ruptured blood vessels, are involved in arterial vasoconstriction. Recently, isolated intermediates of oxidative bilirubin degradation, known as PDPs (propentdyopents), have been considered as potential additional effectors in the development of arterial vasoconstriction. Objective: To investigate whether PDPs and BOXes are present in hemorrhagic cerebrospinal fluid and involved in the vasoconstriction of cerebral arterioles. Methods and Results: Via liquid chromatography/mass spectrometry, we measured increased PDP and BOX concentrations in cerebrospinal fluid of SAH patients compared with control subjects. Using differential interference contrast microscopy, we analyzed the vasoactivity of PDP isomers in vitro by monitoring the arteriolar diameter in mouse acute brain slices. We found an arteriolar constriction on application of PDPs in the concentration range that occurs in the cerebrospinal fluid of patients with SAH. By imaging arteriolar diameter changes using 2-photon microscopy in vivo, we demonstrated a short-onset vasoconstriction after intrathecal injection of either PDPs or BOXes. Using magnetic resonance imaging, we observed a long-term PDP-induced delay in cerebral perfusion. For all conditions, the arteriolar narrowing was dependent on functional big conductance potassium channels and was absent in big conductance potassium channels knockout mice. Conclusions: For the first time, we have quantified significantly higher concentrations of PDP and BOX isomers in the cerebrospinal fluid of patients with SAH compared to controls. The vasoconstrictive effect caused by PDPs in vitro and in vivo suggests a hitherto unrecognized pathway contributing to the pathogenesis of delayed ischemic deficit in patients with SAH.

Haptoglobin administration into the subarachnoid space prevents hemoglobin-induced cerebral vasospasm

“…Additionally, Hb, heme, and heme-degradation products can exert vascular effects via NO-independent mechanisms. Oxidation of bilirubin, the ultimate heme-metabolism product, results in the accumulation of bilirubin oxidation products (BOXes) and propentdyopents in patient CSF (58)(59)(60). Heme, BOXes, and propentdyopents can all promote vasoconstriction by acting on large conductance BK Ca potassium channels in astrocytes and vascular smooth muscle cells (60)(61)(62).…”

“…Oxidation of bilirubin, the ultimate heme-metabolism product, results in the accumulation of bilirubin oxidation products (BOXes) and propentdyopents in patient CSF (58)(59)(60). Heme, BOXes, and propentdyopents can all promote vasoconstriction by acting on large conductance BK Ca potassium channels in astrocytes and vascular smooth muscle cells (60)(61)(62). Finally, oxyHb can stimulate production of the potent vasoconstrictor, endothelin (63,64), and alter expression of calcium and potassium channels in cerebral arteries (65)(66)(67).…”

Pyrrolic and Dipyrrolic Chlorophyll Degradation Products in Plants and Herbivores

“…This is in accordance with the overall lower concentration of those products in heme degradation. There, PDPs as intermediates usually occurred in 20–80 times higher amounts than BOXes . In contrast, BOX C occurred in higher amounts compared to PDPs in the leaves.…”

“…Both isomers of each group are in an equilibrium and are proven intermediates to BOXes . Those oxidative heme degradation products were quantified in nano‐ to micromolar concentrations with a 20–80 times higher abundance for PDPs compared to BOXes in bile, gallstones and the cerebrospinal fluid of stroke patients . Heme degradation products are involved in vessel constrictions as stroke complication and act as effectors in the liver …”

BOX A-type monopyrrolic heterocycles modified via the Suzuki-Miyaura cross-coupling reaction

“…The oxidative in vitro degradation of bilirubin with hydrogen peroxide in highly alkaline solution yields BOXes A [9], B [9] and C [10] with extremely poor yields allowing characterization of these derivatives but impeding studies with respect to biological activity and fate. Therefore we developed strategies for the total syntheses of these BOXes A [11], B [12], C and D [13] to elucidate their effects on biological tissues [7,9,[14][15][16]. Here we report our investigation on the Suzuki-Miyaura crosscoupling reaction to modify the substitution pattern of BOX A-type derivatives for labeling and future investigations on the influence of certain substituents on biological activity.…”