Acute bilirubin ditaurate exposure attenuates ex vivo platelet reactive oxygen species production, granule exocytosis and activation

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Author(s)
Pennell, Evan Noel
Wagner, Karl-Heinz
Mosawy, Sapha
Bulmer, Andrew Cameron
Griffith University Author(s)
Year published
2019
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Background:
Bilirubin, a by-product of haem catabolism, possesses potent endogenous antioxidant and platelet inhibitory properties. These properties may be useful in inhibiting inappropriate platelet activation and ROS production; for example, during storage for transfusion. Given the hydrophobicity of unconjugated bilirubin (UCB), we investigated the acute platelet inhibitory and ROS scavenging ability of a water-soluble bilirubin analogue, bilirubin ditaurate (BRT) on ex vivo platelet function to ascertain its potential suitability for inclusion during platelet storage.
Methods:
The inhibitory potential of BRT (10–100 μM) ...
View more >Background: Bilirubin, a by-product of haem catabolism, possesses potent endogenous antioxidant and platelet inhibitory properties. These properties may be useful in inhibiting inappropriate platelet activation and ROS production; for example, during storage for transfusion. Given the hydrophobicity of unconjugated bilirubin (UCB), we investigated the acute platelet inhibitory and ROS scavenging ability of a water-soluble bilirubin analogue, bilirubin ditaurate (BRT) on ex vivo platelet function to ascertain its potential suitability for inclusion during platelet storage. Methods: The inhibitory potential of BRT (10–100 μM) was assessed using agonist induced platelet aggregation, dense granule exocytosis and flow cytometric analysis of P-selectin and GPIIb/IIIa expression. ROS production was investigated by analysis of H2DCFDA fluorescence following agonist simulation while mitochondrial ROS production investigated using MitoSOX™ Red. Platelet mitochondrial membrane potential and viability was assessed using TMRE and Zombie Green™ respectively. Results: Our data shows ≤35 μM BRT significantly inhibits both dense and alpha granule exocytosis as measured by ATP release and P-selectin surface expression, respectively. Significant inhibition of GPIIb/IIIa expression was also reported upon ≤35 μM BRT exposure. Furthermore, platelet exposure to ≤10 μM BRT significantly reduces platelet mitochondrial ROS production. Despite the inhibitory effect of BRT, platelet viability, mitochondrial membrane potential and agonist induced aggregation were not perturbed. Conclusions: These data indicate, for the first time, that BRT, a water-soluble bilirubin analogue, inhibits platelet activation and reduces platelet ROS production ex vivo and may, therefore, may be of use in preserving platelet function during storage.
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View more >Background: Bilirubin, a by-product of haem catabolism, possesses potent endogenous antioxidant and platelet inhibitory properties. These properties may be useful in inhibiting inappropriate platelet activation and ROS production; for example, during storage for transfusion. Given the hydrophobicity of unconjugated bilirubin (UCB), we investigated the acute platelet inhibitory and ROS scavenging ability of a water-soluble bilirubin analogue, bilirubin ditaurate (BRT) on ex vivo platelet function to ascertain its potential suitability for inclusion during platelet storage. Methods: The inhibitory potential of BRT (10–100 μM) was assessed using agonist induced platelet aggregation, dense granule exocytosis and flow cytometric analysis of P-selectin and GPIIb/IIIa expression. ROS production was investigated by analysis of H2DCFDA fluorescence following agonist simulation while mitochondrial ROS production investigated using MitoSOX™ Red. Platelet mitochondrial membrane potential and viability was assessed using TMRE and Zombie Green™ respectively. Results: Our data shows ≤35 μM BRT significantly inhibits both dense and alpha granule exocytosis as measured by ATP release and P-selectin surface expression, respectively. Significant inhibition of GPIIb/IIIa expression was also reported upon ≤35 μM BRT exposure. Furthermore, platelet exposure to ≤10 μM BRT significantly reduces platelet mitochondrial ROS production. Despite the inhibitory effect of BRT, platelet viability, mitochondrial membrane potential and agonist induced aggregation were not perturbed. Conclusions: These data indicate, for the first time, that BRT, a water-soluble bilirubin analogue, inhibits platelet activation and reduces platelet ROS production ex vivo and may, therefore, may be of use in preserving platelet function during storage.
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Journal Title
Redox Biology
Volume
26
Copyright Statement
© 2019 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/BY-NC-ND/4.0/).
Subject
Biochemistry and cell biology
Medical biochemistry and metabolomics
Haematology
Pharmacology and pharmaceutical sciences