Obstructive Sleep Apnea May Lead to Endothelial Cell Death

Key Point

Circulating apoptotic endothelial cells, which correlate with abnormal vascular function, are increased in patients with obstructive sleep apnea.

Researchers have found that patients with obstructive sleep apnea (OSA) have higher levels of apoptotic endothelial cells circulating in their bloodstream than people who do not have OSA. The finding may help explain why those with OSA are at higher risk for cardiovascular disease (CVD).

According to the researchers, reporting in the June 1 issue of the American Journal of Respiratory and Critical Care Medicine, “levels of apoptotic endothelial cells are correlated with abnormal endothelial vasorelaxation, a precursor of atherosclerosis-related events,” and treatment with nasal continuous positive airway pressure (nasal CPAP) can reduce levels of circulating apoptotic endothelial cells in OSA patients.

In a released statement, lead researcher Ali El Solh, MD, MPH, of the University at Buffalo in New York, said the study was conducted “to explain why patients with OSA had a higher risk of cardiovascular morbidity and mortality.” He added that “the increased levels of circulating apoptotic endothelial cells would mean less production of nitric oxide that is crucial to artery vasodilatation. The less nitric oxide, the higher potentially is the risk of hypertension and acute heart attack. CPAP treatment would likely restore the physiologic function of the lining of the blood vessels.”

The study involved 14 men with OSA who were nonsmokers, had no coexisting diseases, and did not use medications. Ten healthy nonsmokers served as controls.

The OSA patients were given polysomnographic testing to verify the diagnosis. The men were comparable in age, blood pressure, and metabolic profile, but the OSA patients had a higher BMI (though the difference was not statistically significant) and had more apoptotic cells circulating in their bloodstream. Furthermore, OSA patients were more likely than controls to have vasomotor dysfunction.

The OSA patients were given nasal CPAP treatment for eight weeks. Use of CPAP ranged from four to seven hours per night. At the end of the study, the patients’ vascular reactivity and levels of circulating endothelial apoptotic cells were reevaluated. There were no significant differences from baseline in body measurements or metabolism, but among the OSA patients, the number of circulating endothelial apoptotic cells was reduced significantly from 39.2 to 22.3 cells/mL, which correlated to marked improvements in brachial artery vascular reactivity.

More research is needed before these results can be applied clinically, according to Dr. El Solh. He added that statins, angiotensin-converting enzyme inhibitors, and vitamin C reduce endothelial apoptosis, but it is not known if these agents could help patients with OSA.      

Reference
El Solh AA, Akinnusi ME, Baddoura FH, Manowski CR.
Endothelial cell apoptosis in obstructive sleep apnea: a link to endothelial dysfunction. Am J Respir Crit Care Med. 2007;175(11);1186-1191.

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