兔未成熟肺缺血再灌注损伤的实验研究

The experimental study on infant rabbit lung injury induced by ischemia-reperfusion

目的探讨未成熟肺缺血再灌注损伤的特点及其可能的机制。方法选用新西兰成熟和幼白兔各24只，随机分为成熟对照组、成熟缺血再灌注组、幼兔对照组、幼兔缺血再灌注组。建立Sakuma模型，肺门阻断1h后，开放再灌注4h。设定阻断1h、开放1、2和4h4个时间点，收集血样。ELISA法检测血液中IL-1β、TNF-α水平；术毕收集肺组织分别进行MDA、ROS-HR浓度及SOD、GSH-PX活性测定；Westernblot检测肺组织中MyD88和NF-κB水平；光镜和电镜观察损伤后的肺组织病理改变。结果幼兔组肺组织损伤性变化明显。光镜观察有更多的粒细胞浸润，组织肿胀、肺泡腔渗液、肺泡腔塌陷明显；电镜观察可见部分肺泡上皮细胞及内皮细胞脱落，线粒体肿胀明显，嵴破裂，甚至消失。MDA、ROS-HR浓度升高，SOD、GSH-PX活性下降；各时间点的IL-1β、TNF-α水平有不同程度升高，特别是再灌注后的2、4h（P〈0．01）；再灌注后肺组织中MyD88和NF-κB表达也显著升高。结论幼兔未成熟肺缺血再灌注损伤严重，可能与其相对低的抗氧化能力和产生更多的ROS有关。

Objective To explore the characteristics of ischemia-reperfusion induced intant lung damage and the poten- tial mechanisms of the injuried. Methods Both infant （ 15 -21 days old） and adult （5 -6 months old） rabbits were subjec- ted to either ischemia-reperfusion or sham operation. Ischemia-reperfusion was induced by clamping the right pulmonary hilum for 1 hour and then removal of the clamp tor 4 hours under anesthesia. The lung tissue were sampled for histological examination by light and electron microcopies and for biological evaluation of mitochondrial alterations. Production and expression of free radical species-hydroxyl radical （ROS-HR）, malondialdehyde （MDA）, superoxide dismutase （SOD）, glutathione peroxidase （GSH-PX）, myeloid difterentiation factor-88 （MyD-88） , and nuclear factor-κB （NF-KB） in the lung tissue were also exam- ined. In addition, circulating levels of interleukin-1β and tumor necrosis factor-α were measured during the ischemia-reperfu- sion process. Results In comparison to adult lungs, the infant lungs had more increased neutrophil infiltration, edema, swelled alveolar epithelial and endothelial cells, and severer mitochondrial impairment reflected by damage of the inner mem- brane as well as decrease in the membrane potential afler ischemia-reperfusion. The lungs in infant animals subjected to sham operation displayed higher levels of ROS-HR and MDA and lower levels of SOD and GSH-PX than those in adult controls. The lungs in infants with ischemia-reperfusion were found to further produce more ROS-HR, and MDA, and less SOD and GSH-PX than the ischemia-reperfused adult lungs. Moreover, the circulating levels of interleukin-1β and tumor necrosis factor-α were elevated during the period of ischemia-reperfusion, particularly in the infant animals, which appeared to be associated with the expression of MyD-88 and NF-κB in the lungs. Conclusion Lung ischemia-reperfusion causes more severe lung damage in in- fants than in adults, probably due to combination of low antioxidant capacity and overproduction of ROS in infants.