Intermittent hypoxia-associated vascular and extravascular changes; improvement of endothelial function under application of anti-inflammatory and anti-oxidative drugs

Background: Obstructive sleep apnoea is associated with atherosclerosis. In order to examine the pathomechanisms linking these both diseases, we sought to assess the influence of intermittent hypoxia on the endothelial function and endothelial progenitor cells as well as to check the reversibility of hypoxia-induced changes under the administration of anti-inflammatory and anti-oxidative drugs.

Methods: 36 ApoE-/- mice under high-cholesterol diet were divided into 4 groups: the first three groups underwent intermittent hypoxia treatment (33 cycles of oxygen concentration changes between 21% and 5%, 8 hours/day for 6 weeks). Additionally, the second and third group were injected i.p. with anti-inflammatory anti-TNFalpha antibody infliximab (10 µg/kg, 1x week) and anti-oxidative compound L-glutathione (250 µg/kg, 3x week), respectively. The last group under normoxia served as a control. Endothelial function was measured by means of an organ bath technique. Sca1/flk1+ endothelial progenitor cells in bone marrow and blood and CD31/Annexin V+ endothelial microparticles in blood were analyzed by flow cytometry.

Results: Endothelial function was significantly impaired under hypoxic conditions (73 ± 6% of maximal vasoconstriction vs. control: 45 ± 6%). The treatment with infliximab and L-glutathione improved endothelial function to the level of control (47 ± 6%, 47 ± 9%; resp.). Consistent with this result, the levels of endothelial microparticles increased under hypoxia compared to the remaining groups (0,28 ± 0,13% vs. 0,16 ± 0,06%, 0,16 ± 0,07%, 0,17 ± 0,09%; resp., p < 0,05). The number of sca1/flk1+ cells was higher in bone marrow in hypoxia than in a control group (2,2 ± 0,4%, 1,3 ± 0,2%; resp., p < 0,05); both drugs reduced the percentage of bone marrow sca1/flk1+ cells to that of a control (1,2 ± 0,1%, 1,1 ± 0,2%; resp.). In contrast, sca1/flk1+ cells in blood were less frequent under hypoxia vs. control and drug groups (2,3 ± 0,5% vs. 5,5 ± 1,5%, 5,3 ± 1,2%, 5,1 ± 1,1%; resp., p < 0,05).

Conclusions: Obstructive sleep apnoea impairs endothelial function. Despite elevated production of endothelial progenitor cells in bone marrow, the peripheral repair capacity is attenuated under intermittent hypoxia. Infliximab and L-glutathione normalize hypoxia-induced vascular and extravascular changes.