Nocturnal hypoxic stress activates invasive ability of monocytes in patients with obstructive sleep apnea syndrome

Abstract

Backgrounds: Obstructive sleep apnea syndrome (OSAS) is known to be a risk factor of cardiovascular events. However, the precise mechanism has not been fully elucidated. OSAS-induced hypoxic stress may promote the production of inflammatory cytokines and chemokines by monocytes, which has a crucial role in the development of atherosclerosis. In addition, adhesion to the vascular endothelium and transendothelial migration of monocytes are considered to induce atherosclerosis. The aim of this study was to investigate the effects of hypoxic stress on the invasive ability of monocytes in OSAS. Methods; Twenty-one male OSAS patients and 17 male healthy control subjects, age- and body mass index-matched, were enrolled. Venous blood samples were collected not only before and after sleep but also after CPAP titration for the purpose of monocyte isolation. The invasive ability of monocytes was evaluated by counting the number of invasive cells using a BD BioCoat Matrigel Invasion Chamber. Results; The number of cells which represents invasive ability was significantly higher in OSAS patients as compared to control subjects in the early morning (p<0.001). Invasive ability in the early morning was significantly elevated as compared to that before sleep in OSAS patients (p<0.001), and it was positively correlated with oxygen desaturation index (p<0.05). CPAP titration led to alleviation of the invasive ability (p<0.001). Conclusions; The results indicate that OSAS-induced hypoxic stress activates the invasive ability of monocytes, and that this phenomenon observed during sleep may contribute to the development of atherosclerosis in OSAS.