Molecular Biomarkers of Vascular Dysfunction in Obstructive Sleep Apnea

Elzbieta Kaczmarek,Christiane Ferran,Atul Malhotra,Douglas N Clarke,Christopher P O'Donnell,Aristidis Veves,Eva Csizmadia,Jessie P Bakker,Olivier Kocher,Francesco Tecilazich,Shawn E Bearden

doi:10.1371/journal.pone.0070559

Abstract

Untreated and long-lasting obstructive sleep apnea (OSA) may lead to important vascular abnormalities, including endothelial cell (EC) dysfunction, hypertension, and atherosclerosis. We observed a correlation between microcirculatory reactivity and endothelium-dependent release of nitric oxide in OSA patients. Therefore, we hypothesized that OSA affects (micro)vasculature and we aimed to identify vascular gene targets of OSA that could possibly serve as reliable biomarkers of severity of the disease and possibly of vascular risk. Using quantitative RT-PCR, we evaluated gene expression in skin biopsies of OSA patients, mouse aortas from animals exposed to 4-week intermittent hypoxia (IH; rapid oscillations in oxygen desaturation and reoxygenation), and human dermal microvascular (HMVEC) and coronary artery endothelial cells (HCAEC) cultured under IH. We demonstrate a significant upregulation of endothelial nitric oxide synthase (eNOS), tumor necrosis factor-alpha-induced protein 3 (TNFAIP3; A20), hypoxia-inducible factor 1 alpha (HIF-1α?? and vascular endothelial growth factor (VEGF) expression in skin biopsies obtained from OSA patients with severe nocturnal hypoxemia (nadir saturated oxygen levels [SaO2]<75%) compared to mildly hypoxemic OSA patients (SaO2 75%–90%) and a significant upregulation of vascular cell adhesion molecule 1 (VCAM-1) expression compared to control subjects. Gene expression profile in aortas of mice exposed to IH demonstrated a significant upregulation of eNOS and VEGF. In an in vitro model of OSA, IH increased expression of A20 and decreased eNOS and HIF-1α expression in HMVEC, while increased A20, VCAM-1 and HIF-1αexpression in HCAEC, indicating that EC in culture originating from distinct vascular beds respond differently to IH stress. We conclude that gene expression profiles in skin of OSA patients may correlate with disease severity and, if validated by further studies, could possibly predict vascular risk in OSA patients.

Highlights

Symptomatic obstructive sleep apnea (OSA) is a breathing disorder that affects 6–13% of the adult Western population [1]
Our results indicate that endothelium-dependent microvascular reactivity in response to ACh was significantly decreased in severely hypoxemic OSA patients compared to controls (Fig. 1A)
In this study, using a minimally invasive skin biopsy method, we demonstrate, for the first time, that expression levels of several genes relevant to endothelial cell (EC) function are modulated in OSA patients in a way that correlates with disease severity, and possibly vascular risk

Summary

Introduction

Symptomatic obstructive sleep apnea (OSA) is a breathing disorder that affects 6–13% of the adult Western population [1]. Untreated OSA induces oxidative stress, inflammation, and endothelial cell (EC) dysfunction [3], which have been confirmed in animal models of OSA [4]. These abnormalities are linked to impaired activity of endothelial nitric oxide synthase (eNOS), an enzyme that generates nitric oxide (NO), and whose bioavailability is required for normal function of the endothelium [5,6]. Intermittent hypoxia-induced increase in HIF-1a protein levels has been suggested as an adaptive response to OSA [12,14,15]; negative effects of HIF-1a activation, such as hypertension and ischemic injury, have been reported in animal models of OSA [16]

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Conclusion