Oleoyl-lysophosphatidylcholine limits endothelial nitric oxide bioavailability by induction of reactive oxygen species.

Andrijana Kozina,Saša Frank,Michael Sze Ka Wong,Seth Hallström,Katrin Schröder,Kurt Schmidt,Roland Malli,Stefan Opresnik,Wolfgang F Graier

doi:10.1371/journal.pone.0113443

Andrijana Kozina, Saša Frank + Show 7 more

Open Access

https://doi.org/10.1371/journal.pone.0113443

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Abstract

Previously we reported modulation of endothelial prostacyclin and interleukin-8 production, cyclooxygenase-2 expression and vasorelaxation by oleoyl- lysophosphatidylcholine (LPC 18:1). In the present study, we examined the impact of this LPC on nitric oxide (NO) bioavailability in vascular endothelial EA.hy926 cells. Basal NO formation in these cells was decreased by LPC 18:1. This was accompanied with a partial disruption of the active endothelial nitric oxide synthase (eNOS)- dimer, leading to eNOS uncoupling and increased formation of reactive oxygen species (ROS). The LPC 18:1-induced ROS formation was attenuated by the superoxide scavenger Tiron, as well as by the pharmacological inhibitors of eNOS, NADPH oxidases, flavin-containing enzymes and superoxide dismutase (SOD). Intracellular ROS-formation was most prominent in mitochondria, less pronounced in cytosol and undetectable in endoplasmic reticulum. Importantly, Tiron completely prevented the LPC 18:1-induced decrease in NO bioavailability in EA.hy926 cells. The importance of the discovered findings for more in vivo like situations was analyzed by organ bath experiments in mouse aortic rings. LPC 18:1 attenuated the acetylcholine-induced, endothelium dependent vasorelaxation and massively decreased NO bioavailability. We conclude that LPC 18:1 induces eNOS uncoupling and unspecific superoxide production. This results in NO scavenging by ROS, a limited endothelial NO bioavailability and impaired vascular function.

Highlights

Nitric oxide (NO) is a crucial endothelial factor for the maintenance of cardiovascular homeostasis, reflected by its growth regulatory, anti-inflammatory and antithrombotic activities, along with the capacity to promote relaxation of vascular smooth muscle cells and concomitant vasodilation [1, 2]
In previous studies we found a profound capacity of LPC 18:1 to induce endothelial prostacyclin production [30], interleukin-8 [31] and cyclooxygenase-2 [32] expression as well as potency of attenuating vasorelaxation [29]
To examine the impact of acute, short exposure of cells to LPC 18:1 on NO bioavailability, cells were incubated with this LPC or PBS at concentration of 60 mM in the presence of 5% fetal bovine serum (FBS) for 15 min

Summary

Introduction

Nitric oxide (NO) is a crucial endothelial factor for the maintenance of cardiovascular homeostasis, reflected by its growth regulatory, anti-inflammatory and antithrombotic activities, along with the capacity to promote relaxation of vascular smooth muscle cells and concomitant vasodilation [1, 2]. In vascular endothelium NO is produced by endothelial nitric oxide synthase (eNOS) during conversion of L-arginine to L-citrulline. Decreased availability of endothelium-derived NO and increased production of reactive oxygen species (ROS), such as superoxide, hydrogen peroxide or hydroxyl radicals are hallmarks of endothelial dysfunction [4]. Increased cellular superoxide, generated by NADPH oxidase [5], xanthine oxidase [6], cyclooxygenases [7] or mitochondria [8] reacts with NO to form peroxynitrite, a reactive molecule capable of oxidizing the essential cofactor of eNOS, tetrahydrobiopterin (BH4) [9]. This, together with depletion of L-arginine and accumulation of asymmetric dimethyl-L-arginine leads to eNOS uncoupling [1]. Uncoupled eNOS generates superoxide instead of NO, resulting in oxidative stress and NO depletion [10]

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