Oxidative Stress and Sleep Apnea-Hypopnea Syndrome

Endothelial dysfunction and circulating microparticles from patients with obstructive sleep apnea

Endothelial dysfunction is involved in vascular complications of obstructive sleep apnea (OSA). In this study, circulating microparticles (MPs) from patients with OSA-induced nocturnal desaturations were characterized and their effects on endothelial function were evaluated. Two age-matched groups of patients undergoing polysomnography for OSA were compared: 35 desaturators with a 3% oxyhemoglobin desaturation index (ODI) > or = 10 events per hour of sleep and 27 nondesaturators with ODI <10 events per hour. MPs were characterized by flow cytometry and then either used to treat in vitro human endothelial cells or to study endothelial function in mice. Circulating MPs did not differ between groups, but MPs from granulocytes and activated leukocytes (CD62L(+)) were found at higher levels in desaturators. In vitro, MPs from desaturators reduced endothelial nitric oxide (NO) production by enhancing phosphorylation of endothelial NO synthase at the site of inhibition and expression of caveolin-1. CD62L(+) MPs positively correlated with ODI. Endothelial NO production negatively correlated with both CD62L(+) MPs and ODI. MPs from desaturators increased expression of endothelial adhesion molecules including E-selectin, ICAM-1 and ITGA5, and cyclooxygenase 2. Moreover, injection of MPs from desaturators into mice impaired endothelium-dependent relaxation in aorta and flow-induced dilation in small mesenteric arteries. This study demonstrates an association between endothelial dysfunction and increased circulating levels of CD62L(+) MPs. This may initiate atherogenic processes in patients with OSA and severe nighttime hypoxia.

Nasal continuous positive airway pressure treatment reduces systemic oxidative stress in patients with severe obstructive sleep apnea syndrome

OBJECTIVE

To evaluate whether nasal continuous positive airway pressure (nCPAP) reduces oxidative stress in patients with severe obstructive sleep apnea (OSA) syndrome.

MATERIALS AND METHODS

Forty-six patients with severe OSA (AHI> or =30) requiring nasal CPAP treatment and 46 controls (subjects without OSA and with mild OSA as defined by an AHI<15) were enrolled. Oxidative stress was evaluated in blood samples with a commercially available automated spectrophotometric assay (D-ROMs test, Diacron, Grosseto, Italy). Blood samples were collected the evening before (10:00 p.m.) and the morning after (07:00 a.m.) a diagnostic polysomnography. Patients with severe OSA syndrome were subsequently submitted to a second polysomnography with nasal CPAP titration the following night. Using the same schedule we collected blood samples from the patients the morning after the nCPAP titration and after two months of nCPAP treatment.

RESULTS

Patients with severe OSA presented higher levels of oxidative stress than patients with AHI<15 in the evening and in the morning (357.57+/-13.07 UCarr vs. 319.28+/-12.66 UCarr, p=0.038, and 371.83+/-12.83 UCarr vs. 328.09+/-11.76 UCarr, p=0.014, respectively). Patients with severe OSA presented a significant reduction the levels of oxidative stress the morning after the nCPAP titration study (371.83+/-12.83 UCarr vs. 298.21+/-9.62 UCarr, p=0.001) and this reduction was further preserved after a period of two months of nCPAP treatment (293.72+/-6.55 UCarr, p=0.001 vs. baseline). Statistically significant correlations were observed between levels of oxidative stress and nocturnal polysomnography (NPSG) markers as oxygen desaturation index (ODI), arousal index (AI), lowest oxygen saturation of hemoglobin, and mean oxygen saturation of hemoglobin.

CONCLUSIONS

Patients with severe OSA syndrome presented increased systemic oxidative stress. A single night of nCPAP treatment significantly reduced the levels of oxidative stress in patients with severe OSA syndrome, and this reduction was maintained at least after two months of nCPAP treatment.