Mechanisms of vascular endothelial cell injury in response to intermittent and/or continuous hypoxia exposure and protective effects of anti-inflammatory and anti-oxidant agents.

Abstract

Hypoxia induces vascular endothelial injuries; however, the mechanisms involved and effects of interventions remain unclear. Investigate the inflammatory response and oxidative stress in co-cultured neutrophils and vascular endothelial cells, apoptotic changes in endothelial cells, and effects of the antioxidant, Tempol, or the NF-êB inflammatory channel blocker, pyrrolidine dithiocarbamate (PDTC), upon endothelial cells under conditions of intermittent and/or continuous hypoxic exposure. Polymorphonuclear neutrophils co-cultured with human umbilical vein endothelial cells were subjected to the following conditions: intermittent normoxia (IN), intermittent hypoxia (IH), continuous hypoxia (CH), intermittent with continuous hypoxia (OS), OS+Tempol (OS+T), or OS+PDTC (OS+P) for 2, 5, or 8h. Inflammatory factors, TNF-α and IL-6, the adhesion molecule, ICAM-1, CAT activity, and MDA concentrations in supernatants from the co-culture as well as pro- (Bak) and anti- (Bcl-xl) apoptotic gene expression levels in the endothelial cells were determined. Inflammatory factors, adhesion molecules, oxidative stress, and apoptosis genes in all groups showed significant, time-dependent increases as compared with the IN group. TNF-α, IL-6, ICAM-1, and MDA levels in the OS group were increased, while CAT was decreased as compared with that observed in the IH, CH, OS+T, and OS+P groups. Bcl-x1 expression and Bcl-x1/BAK ratios were decreased and BAX increased in the OS versus IH, CH, OS+T, or OS+P groups. Both pro- and anti-apoptotic proteins showed time-dependent increases, while the Bcl-x1/BAK ratio decreased over these times. Tempol and PDTC partially prevented these effects. Inflammation, oxidative stress, and apoptosis are all involved in vascular endothelial injury induced by OS. Anti-inflammatory and anti-oxidative interventions can partially improve effects of OS.