The role of nuclear factor-κB in endothelial cell inflammatory injury by intermittent hypoxia in rat with emphysema

Abstract

To investigate mechanism underlying the role of nuclear factor Kappa B (NF-κB) which induced inflammatory injury and functional lesions of aortic endothelial cells in rat with emphysema and intermittent hypoxia. Sixty male Wistar rats were divided randomly into 4 experimental groups (n = 15 each group): control group, emphysema group, intermittent hypoxia (IH) group, emphysema with intermittent hypoxia group. The rats in control group had ad libitum access to food and water under normal circumstance. The rats in the emphysema group were exposed to cigarette smoke twice daily (30 min each time). As for IH group, the rats were exposed to intermittent hypoxia circumstance (8 h/day). Both cigarette smoke twice a day (30 min each time) and intermittent hypoxia circumstance (8 h/day) were imposed on the rats in emphysema with intermittent hypoxia group. All the rats were exposed for 8 weeks. Five rats were randomly selected from each group to measure the blood gas on the ninth week. We collected lung and endothelial tissues of thoracic aorta from the rest sacrificed rats, and observed the pathological changes of lung tissue through HE staining. The levels of ET-1, TNF-α and IL-8 in rat endothelial tissues of thoracic aorta were measured by ELISA testing. Nitrate reductase was used to measure the levels of NO, and RT-PCR to detect the levels of NF-κB mRNA, ICAM-1 mRNA, MMP-9 mRNA and eNOS mRNA. Lung pathology and blood gas results showed that the rat model of emphysema with intermittent hypoxia was established successfully. The levels of ET-1, TNF-α, IL-8 in emphysema with intermittent hypoxia group were (172.4 ± 1.6) ng/L, (104.1 ± 1.4) ng/L, (272.1 ± 3.6) ng/L respectively, significantly higher than the control group, emphysema group and intermittent hypoxia group (all P < 0.05). The level of NO was (27.07 ± 0.57) µmol/L, which was significant reduced; the expression of NF-κB mRNA, ICAM-1 mRNA, MMP-9 mRNA in emphysema with intermittent hypoxia group was significantly upregulated compared with the control goup, emphysema group and intermittent hypoxia group (all P < 0.05). The levels of eNOS mRNA expression were significantly lower than other three groups. The expression of NF-κB mRNA was positively correlated with MMP-9 mRNA level (r = 0.572, P < 0.001) and the expression of NF-κB mRNA was negatively correlated with eNOS mRNA level (r = 0.534, P < 0.001); there was no statistical difference in levels of NF-κB mRNA and eNOS mRNA expression between intermittent hypoxia and emphysema group (P > 0.05). Compared with only emphysema or intermittent hypoxia exposure, inflammatory injury of aortic endothelial cells of rats induced by emphysema with intermittent hypoxia was more serious, and may result in more serious cardiovascular complications. The activation of NF-κB pathway may be an important mechanism of its inflammatory response.