ABSTRACT
<p><b>OBJECTIVE</b>To investigate the effect of different patterns of intermittent hypoxia on the levels of interleukin-6 (IL-6) and interleukin-8 (IL-8) of vascular endothelial cell.</p><p><b>METHODS</b>The human umbilical vein endothelial cells of the line ECV304 were used to set up the cells model. The experiment cell strains contained one control group and eight experimental groups, 1 constance normoxia group (control group), 3 different intermittent hypoxia (IH) degree groups (10% O₂ group, 1.5% O₂ group, 0.5% O₂ group with 12 times/h), 4 different IH frequency groups (40 times/h, 20 times/h, 12 times/h, 9 times/h and 6 times/h with 0.5%O2). The specimen were put into a program-controlled gas delivery system with different level and frequency of IH respectively. Then enzyme linked immunosorbent assay (ELISA) was used to examine the levels of IL-6 and IL-8.</p><p><b>RESULTS</b>Higher level of IL-6 and IL-8 were found in 3 different IH degree groups than in control group (F were 1961.100 and 103.855 respectively, P all < 0.001). The level of IL-6 and IL-8 was gradually increased with the decreasing of IH degree. The difference of IL-6 and IL-8 levels between each two different groups in IH degree was significant (P all < 0.05). The level of IL-6 and IL-8 groups was significantly different in severe IH exposure (F were 544.396 and 149.328 respectively, P all < 0.001 in both groups). There was a trend as the IH frequency decreased, the level of IL-6 and IL-8 was tenderly increased in 20/hour group (P < 0.05), highest in 12/hour group (P < 0.05), decreased in 9/hour group (P < 0.05), and decreased further in 6/hour group (P < 0.05) in severe IH expose. There was statistical significance between each two different frequency IH groups (P < 0.05).</p><p><b>CONCLUSIONS</b>Intermittent hypoxia caused significant inflammatory reaction in vascular endothelial cells. The secreted level of IL-6 and IL-8 depended on the degree of hypoxia. There was a trend as the level of IH frequency decreased, the level of IL-6 and IL-8 gradually increased at first, and then decreased in the same way.</p>