中性粒细胞凋亡延迟在脂多糖所致大鼠急性肺损伤发病机制中的作用

目的 探讨急性肺损伤时肺组织及外周血中性粒细胞（PMN）凋亡和坏死的发生规律及其与肺损伤的关系。以及可能涉及的机制。方法 Wistar大鼠50只，腹腔注射脂多糖（LPS，O55B5，3mg/kg)造成大鼠急性肺损伤，分为LPS注射后2h组、4h组、8h组，12h组及正常对照组。于预定时相取血及支气管灌洗液，密度梯度离心分离PMN，用流式细胞仪测定凋亡，坏死细胞比例及呼吸焊发功能，同时测定乳酸脱氢酶（LDH）含量，肺通透指数，肿瘤坯 煞费苦心因子（TNF）、白细胞介素（IL）1β、IL-6含量和Ca^2 浓度。结果 ALI大鼠肺灌洗液中PMN凋亡，坏死比例的变化与外周血不同，主要表现为存活细胞比例增加，凋亡延迟，肺灌洗液中TNF、IL-1β、IL-6含量明显高于外周血，且持续时间较长，同时，肺灌洗液LDH明显升高，肺通透指数显著增加。结论 肺组织中高浓度的细胞因子和短暂升高的Ca^2 使游出的PMN的正常凋亡途径发生障碍，造成PMN持续处于激活状态及毒性内容物的持续释放，与肺组织损伤有密切关系。

The role of PMN apoptosis delay in acute lung injury induced by administrating LPS

OBJECTIVE: To investigate the law of apoptosis and necrosis of the peripheral PMN and the PMN extravasated into pulmonary tissue, and its relationship with lung injury and the mechanisms involved. METHODS: Fifty rats were subjected to acute lung injury by administrating intraperitoneally LPS (O(55)B(5), 3 mg/kg). Blood was harvested and bronchoalveoli was lavaged pre-LPS and 2, 4, 8, 12 h after LPS administration. PMNs were isolated by density gradient centrifugation and apoptosis, necrosis and respiratory burst were detected by flow cytometry. LDH activity, TNF, IL-1beta, IL-6, and lung permeability index were also measured. RESULTS: Viable PMN in bronchoalveolar lavage fluid (BLF) increased and apoptosis was delayed compared with that in peripheral blood. Meanwhile, TNF, IL-1beta and IL-6 in BLF were obviously higher and endured longer compared with those in peripheral blood. Moreover, the LDH activity in BLF and the lung permeability index were also remarkably increased. CONCLUSION: Retention of PMN in tissues and the abnormality in apoptotic pathway inevitably caused by higher level cytokines and temporal increased of intracellular free Ca(2+) generate persistent activation of PMN and excessive release of toxic substances, resulting in tissue injury.