Endothelial Dysfunction In Emphysematous Rats Exposed To Intermittent Hypoxia And Interventional Effect Of Tempol

Objective:Chronic obstructive pulmonary disease?COPD?and obstructive sleep apnea?OSA?are independent risk factors for cardiovascular diseases,where hypoxia is the common pathophysiological feature.Their coexist as an overlap syndrome?OS?.Compared with pure COPD or OSA,OS has greater degree of nocturnal hypoxemia,hypercapnia and pulmonary hypertension,then earlier and greater risk of cardiovascular diseases,that result in the increasing risk of death.Vascular endothelial injury is the first step in the development of atherosclerotic disease,which can cause the occurrence of cardiovascular events.The potential mechanisms of cardiovascular complications in OS are not fully understood,but is likely to be related to the hypoxia-induced inflammation and apoptosis involving endothelial injury.We developed an overlap syndrome rat model to assess systemic inflammatory status and endothelial cell apoptosis levels,and explore whether antioxidant intervention can protect the vascular endothelium by inhibiting inflammation and endothelial cell apoptosis.It may contribute to provide a new strategies and experimental basis for the prevention and treatment of OS-related cardiovascular complications.Methods:Male Wistar rats?n=66?were randomly distributed into 6 groups:normal oxygen control?NC?,intermittent hypoxia?IH?,cigarette exposed hypoxia?CH?,exposure to cigarette smoke and IH?OS?,exposure to OS and treated with tempol?OST?and exposure to OS and treated with NaCl?OSN?.In the preliminary experiment,arterial blood gas?ABG?of 18 rats?3 from each of the 6 groups?was measured to monitor their oxygen partial pressure?PaO₂?,carbon dioxide partial pressure?PaCO₂?and oxygen saturation?SaO₂?.After an 8-week challenge,pathologic pictures were obtained from the rats in each group,and were stained with hematoxylin/eosin?H/E?for the measurement of mean alveolar number?MAN?and mean linear intercept?MLI?.Serum concentrations of intracellular adhesion molecule-1?ICAM-1?and vascular cellular adhesion molecule-1?VCAM-1?were detected by enzyme-linked immunosorbent assay?ELISA?,and the apoptotic rate of circulating endothelial cells?CECs?were analysed by flow cytometry.Results:?1?The PH values of ABG in all groups were within the normal range.The PaO2 of IH group,OS group,OSN group and OST group were respectively 56.83±2.10,50.92±1.58,51.01±1.27 and 65.45±2.17mmHg in the hypoxia phase,91.78±1.12,79.58±0.62,80.12±1.12 and 84.27±1.97 mmHg in the reoxygenation phase.PaO2 was decreased and returned to normal periodically with the filling of N₂and compressed air.MAN was significantly decreased while MLI was increased in CH or OS group.Moreover,the intervention of tempol can increase MAN and decrease MLI.?2?The ICAM-1 and VCAM-1 levels in the peripheral blood of the rats were the highest in OS group and the lowest in the NC group.The serum ICAM-1 and VCAM-1 levels in IH group were higher than in CH group.?3?The CECs apoptosis was the highest in OS group and the lowest in NC group.The apoptosis rate of CECs in IH group were higher than in CH group.?4?The ICAM-1 and VCAM-1 levels in the peripheral blood of the rats were lower in OST group than those in OS and OSN groups,were higher than those in NC group.There were no statistical difference when compared ICAM-1 and VCAM-1 levels between OS and OSN groups.?5?The CECs apoptosis was lower in OST group than those in OS and OSN groups,was higher than those in NC group.There were no statistical difference when compared CECs apoptosis between OS and OSN groups.Conclusions:?1?The pathological changes of lung and blood gas analysis results showed that emphysema exposed to IH model was established successfully.The lung injury and hypoxia were more serious when they were overlapped.?2?When emphysema is combined with IH,it may aggravate systemic inflammation and accelerate endothelial cell apoptosis synergistically.Compared with emphysema or IH,inflammatory response and endothelial cell apoptosis are more significant after overlapping,which may lead to more serious vascular endothelial injury.?3?After intervention with antioxidant tempol,the levels of ICAM-1,VCAM-1 and CECs apoptosis in the peripheral blood of rats were significantly lower than those in OS group,suggesting that the antioxidants can extenuate intercellular adhesion abnormally by decreasing expression of adhesion molecules and reduce apoptosis of endothelial cells,and that play an important role in the protection of vascular endothelium.?4?After intervention with antioxidant tempol,the levels of ICAM-1,VCAM-1 and CECs in peripheral blood of rats were significantly higher than those in normoxic control group,suggesting that the overlap of emphysema and IH may induce inflammation and endothelial cell apoptosis through a variety of ways.Tempol can only partly improve endothelial injury when emphysema combined with IH.