Systematic And Endothelial Inflammation And The EPC Levels In Emphysematous Rats Exposed To Intermittent Hypoxia

Objective: Chronic obstructive pulmonary disease(COPD) and obstructive sleep apnea(OSA) are known to increase the risk of systemic inflammation and cardiovascular diseases. Their coexistence, which is denominated "Overlap Syndrome", has greater degree of hypoxemia and hypercapnia and greater risk of cardiovascular death than either OSA or COPD alone. To develop a intermittent hypoxia(IH) combined with emphysema rat model and to explore whether IH combined with emphysema results in severe inflammation in lung, liver, pancreas,carotid artery and whole blood, and whether the inflammation changes levels of coagulant/anticoagulant factors synthesized in the liver.Method: Sixty male Wistar rats were put into 4 groups: control group, treated with sham smoke exposure(16 weeks) and sham IH exposure(21%O2); IH group, sham smoke exposure and true IH exposure(the flow(5 L/min) of nitrogen(N2, IH phase)or clean air(air, ROX phase) alternatively delivered into a customized IH housing chamber to maintain a designated hypoxia(30 s) and ROX phase(90 s, normoxia)cycles of alternations per minute, 9 AM to 5 PM in every day, from the start of the13 th week to the end of the 16 th week for 4 weeks); emphysema group, true smoke exposure(exposed to the smoke of 15 commercial unfiltered cigarettes for 30 minutes twice daily, in the morning(before 9 AM) and in the evening(after 5 PM), for 16weeks) and sham IH exposure; and Overlap group, true smoke exposure and true IH exposure. Arterial blood gas(ABG) data was obtained from 5 rats randomly selected in each group during preliminary tests. In the rest 10 rats in each group, we obtained bronchoalveolar lavage fluid(BALF) for routine tests and blood samples for apoptosis of T lymphocytes and neutrophil and endothelial progenitor cells(EPC)counts. Tumor necrosis factor(TNF)-α, interleukins(IL-6)-plasma concentrations and liver coagulant/anticoagulant factors(antithrombin(AT), fibrinogen(FIB), Factor VIII(F VIII) and von Willebrand factor(v WF)) were evaluated. We also obtained tissue blocks of lung, liver, pancreas, and right carotid artery for pathologic scoring and measurements of liver oxidative stress(measuring hepatic oxidative stress enzymes, superoxide dismutase(SOD) activity, catalase(CAT) activity and malondialdehyde(MDA) concentration). SPSS 11.5 software was used for statistical analysis.Result:(1) MLI is significantly increased while MAN is decreased in Emphysema or Overlap group compared with IH or Control group. In addition, pathological scores show higher levels in Emphysema or Overlap group compared with IH group or Control group, suggesting the emphysematous rat model has been established.(2) Neutrophil apoptosis and CD3+CD8+ T lymphocyte apoptosis are the highest in Control group, lowest in Overlap group when that in Emphysema group is more than IH group. CD3+CD4+ T lymphocyte apoptosis level is the least in Control group, the most in Overlap group when that in IH group is more than Emphysema group.(3) EPC level in whole blood is the least in Control group, the most in Overlap group when that in IH group is more than Emphysema group.(4) The serum levels of TNF-α and IL-6 are the lowest in Control group, highest in Overlap group when those in Emphysema group are higher than IH group when that in Emphysema group is more than IH group.(5) Histological inflammatory scores of lung, liver, pancreas, and right carotid artery are the lowest in Control group, highest in Overlap group when those in Emphysema group are higher than IH group.(6) The percentage of macrophages is significantly lower in Overlap or IH group than in Emphysema or Control group. The percentage of neutrophils is the most in Emphysema group when there is no statistical difference among other groups. The percentage of lymphocytes is significantly higher in Overlap or IH group than in Emphysema or Control group and that is the least in Emphysema group.(7) FIB, FVIII and v WF are the highest in Overlap group, the lowest in Control group,when those values are higher in Emphysema group than IH group. AT is the least in Overlap group, the most in Control group, when this is less in Emphysema group than IH group.(8) MAD is the highest in Overlap group, the lowest in Control group, when this value is higher in Emphysema group than IH group. SOD and CAT are the least in Overlap group, the most in Control group, when those are less in Emphysema group than IH group.Conclusions:(1) The higher pathological score and pathological morphology of lung and blood gas analysis results suggest that our OS model established successfully.Lymphocytes play an important role in the process of IH and Overlap lung injury.Neuthrophils play an important role in the process of Emphysema lung injury.(2) In model animals, when IH is combined with emphysema, there will be a more severe or an “overlapped” systemic/multiple organic inflammation, oxidative stress and hyper-coagulability.(3) The pro-inflammatory and pro-thrombotic status resulted from “OS” exposure may elicit a robust EPC mobilization, which needs further investigation.