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PO3-3-50

Biased activation of soluble guanylyl cyclase by quinones causes contractions of isolated arteries: Role of NADPH: quinone oxidoreductase-1

[Speaker] Susan WS Leung:1
[Co-author] Charlotte Ms Detremmerie:1, Paul M Vanhoutte:1
1:Department of Pharmacology and Pharmacy, University of Hong Kong, Hong Kong

Background Previous experiments in isolated arteries indicate that quinones, including thymoquinone (a para-quinone) and β-lapachone [an ortho-quinone and high-affinity substrate of NADPH:quinone oxidoreductase-1 (NQO-1)], causes augmentations of contraction. The augmentation depends on the activation of soluble guanylyl cyclase (sGC) to generate cyclic inosine monophosphate (cIMP) rather than the canonical cyclic guanosine monophosphate (cGMP). The present study aims to identify cellular target of the quinones in mediating the biased activation of sGC.
Methods Arteries (aortae and mesenteric arteries) were isolated from male Sprague Dawley rats (12 to 16 weeks of age) and studied in organ chamber for the measurement of isometric tension. They were contracted with phenylephrine followed by exposure to increasing concentrations of β-lapachone in the absence or presence of different pharmacological agents. Some of the preparations were used to measure the activity and protein presence, respectively, with enzyme assay kits and Western immunoblotting, of NQO-1.
Results β-lapachone augmented contractions of aortae and mesenteric arteries with endothelium. This augmentation was inhibited by endothelium-removal and inhibitors of endothelial NO synthase (eNOS), sGC or NQO-1. In preparations without endothelium or treated with an eNOS-inhibitor, the augmentations were restored by the NO-donor detaNONOate; they were inhibited by inhibitors of NQO-1. In preparation without endothelium, the augmentations to β-lapachone were also partially restored by exogenous inosine triphosphate (the substrate of sGC for cIMP production) or exogenous cIMP. The activity, but not the protein presence, of NQO-1 in aortae was increased by β-lapachone and inhibited by NQO-1 inhibitors.
Conclusions These results indicate that the potential detrimental augmentations observed with quinones are mediated by the activation of NQO-1, which in turn interferes with the sGC-pathway, biasing the activity of the latter to produce cyclic IMP.

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