【作者】 张新日；

【导师】 徐永健；

【作者基本信息】 华中科技大学 ， 呼吸内科， 2005， 博士

【摘要】 机械通气对于临床救治危重症患者具有其他疗法所无可替代的作用。然而，机械通气本身也可作为一种损伤因素诱发或加重肺损伤，称为呼吸机所致肺损伤（ventilator induced lung injury，VILI）。VILI是机械通气过程中的一个严重并发症，也是促使患者病情加重和死亡的重要原因。因此，机械通气如使用不当不但起不到应有的治疗作用，还会酿成严重后果，导致通气治疗失败，给人民生命财产造成巨大损失。大量研究已经证明机械通气压力过高、潮气量过大可诱发和加重肺损伤。然而在临床上，虽然我们不可能给患者设置过大的、足以引起肺组织损伤的潮气量，但常规潮气量通气是否绝对安全，对正常肺组织能否造成炎症性损伤目前尚有争议。动物实验表明，高气道峰压（PIP）和大潮气量（V_T）通气可使中性粒细胞（PMN）激活。PMN活化后不但能释放多种细胞因子和炎症介质，还可生成大量氧自由基和蛋白水解酶等，这是造成肺组织炎症性损伤的主要原因。然而在VILI的发病过程中，PMN并非是唯一的参与细胞，也不是引起肺组织炎症性损伤的始动细胞，其活化依赖于肺内其他前炎细胞因子的释放。巨噬细胞炎症蛋白（MIP）是1988年Wolpe等用LPS刺激巨噬细胞系（RAW264.7），在其上清液中首次发现的新型蛋白质，包括MIP-1、MIP-2、MIP-3、MIP-4和MIP-5。其中MIP-1和MIP-2与呼吸系统疾病关系密切，具有广泛的生物学活性，不但参与机体炎症反应和免疫反应，还具有抗肿瘤作用、促进造血功能和损伤修复作用。Murch等对30例ARDS患儿行支气管肺泡灌洗，发现其BALF上清液中MIP-1α浓度明显高于对照组，经地塞米松治疗12～24小时后其浓度明显降低。但MIP-1α在VILI的发生中是否也具有类似作用，目前尚未见到文献报道。核因子-κB（NF-κB）是近年来发现的一种调控靶基因转录表达的特异性DNA结合蛋白，是由Rel蛋白家族中两个亚单位构成的二聚体复合物，其中由p65和p50组成的异源二聚体最有代表性。正常时NF-κB存在于细胞浆内，并与抑制性亚基I-κB结合处于失活状态。在各种致病因素作用下，I-κB发生磷酸化而与NF-κB脱离，即可导致NF-κB激活。后者异位进入细胞核，与DNA上特异位点相结合，从而调控靶基因的转录。研究表明，NF-κB可通过调控肺部多种细胞因子和粘附分子如白介素-1β（IL-1β）、TNF-α、IL-6、IL-8、ICAM-1和选择素E等基因的转录和表达，参与机体的免疫及炎症反应。但NF-κB是否参与调控VILI时肺部MIP-1α基因的转录表达目前尚无定论，有待进一步研究。肺泡巨噬细胞（AM）是肺内局部炎症反应的主要始动细胞，不但具有强大的吞噬功能，激活后还能合成和分泌多种炎性介质及细胞因子，从而导致肺脏局部炎症反应失控，是造成ALI的重要原因。Takata等通过在体家兔肺损伤模型研究发现，AM活化并释放TNF-α、IL-1β及IL-8等前炎细胞因子在中性粒细胞活化中起重要作用。Hirani等研究表明，在参与ALI／ARDS发病的众多细胞因子中，IL-8是中性粒细胞向肺内募集最强的趋化因子，它可由AM产生，也可由其他细胞产生，并受局部组织氧合状态调节。但AM在VILI的发病中究竟扮演什么角色，目前尚不清楚。鉴于当前VILI的研究基础与现状，本研究将通过肉眼、光镜和电镜对不同潮气量机械通气大鼠的肺组织进行观察，并测定其动脉血气分析，测定BALF中性粒细胞计数、髓过氧化物酶（MPO）活性以及MIP-1α和蛋白含量，同时采用免疫组织化学染色和原位分子杂交技术测定其肺组织和肺泡巨噬细胞MIP-1α和NF-κB基因及其蛋白表达水平，以从分子水平上探讨不同潮气量机械通气致大鼠急性肺损伤的发生机制，从而为VILI的临床防治提供新的线索。一、研究内容本研究内容包括3部分：第一部分：呼吸机所致大鼠急性肺损伤的病理学改变第二部分：中性粒细胞活化在呼吸机致大鼠急性肺损伤中的作用第三部分：巨噬细胞炎症蛋白-1α在呼吸机致大鼠急性肺损伤中的作用二、研究方法1．Wistar大鼠32只（山西医科大学动物中心提供），体重300～310g，随机分为4组：①对照组：未行机械通气；②小潮气量组：V_T 7ml／kg；③常规潮气量组：V_T 12ml／kg；④大潮气量组：V_T 40ml／kg。2．在肉眼、光镜和电镜下对不同潮气量机械通气致大鼠急性肺损伤的病理改变进行观察。3．测定各组大鼠肺湿／干重比值（W／D）。4．用全自动血气分析仪测定各组大鼠动脉血气分析。5．在光镜下行支气管肺泡灌洗液（BALF）WBC及PMN计数。6．按罗武生等的方法测定血浆和BALF中髓过氧化物酶（MPO）活性。7．用双缩脲法测定血浆蛋白含量，用考马斯亮兰法测定BALF蛋白含量。8．采用ELISA法测定血浆及BALF中MIP-1α含量。9．采用免疫组织化学染色法检测肺组织MIP-1α蛋白表达水平。10．采用原位分子杂交法检测肺组织MIP-1αmRNA表达水平。11．采用免疫组织化学染色法检测肺组织NF-κB p65蛋白表达水平。12．采用免疫细胞化学染色法检测肺泡巨噬细胞MIP-1α及NF-κB p65蛋白表达水平。三、研究结果（一）各组大鼠肺脏病理学改变结果显示，小潮气量组大鼠肺脏外观基本正常，光镜下仅见少量炎性细胞浸润，电镜下观察与对照组无明显差别。常规潮气量组大鼠肺脏外观略显肿胀，但表面色泽基本正常，光镜下可见不同程度肺间质水肿和炎症细胞浸润，电镜下可见肺泡隔内有大量电子密度较低的液状物质聚集。大潮气量组大鼠肺脏外观明显肿胀，表面可见点状出血，光镜下可见弥漫性肺间质水肿和炎症细胞浸润，电镜下可见肺泡上皮细胞之间以及毛细血管内皮细胞之间的连接受损，中性粒细胞呈功能激活状态，表面伸出许多棘状突起，胞浆颗粒外释，呈空泡变。（二）各组大鼠肺湿／干重比值（W／D）和动脉血气分析测定结果结果显示，大潮气量组和常规潮气量组肺湿／干重比值（W／D）明显高于对照组和小潮气量组（P＜0.01），而动脉血氧分压（PaO₂）明显低于对照组和小潮气量组（P＜0.01，P＜0.05）；小潮气量组与对照组各项指标间比较差异均无统计学意义（P＞0.05）。（三）各组大鼠BALF中白细胞及中性粒细胞计数测定结果结果显示，常规潮气量组和大潮气量组大鼠BALF中白细胞及中性粒细胞计数均明显高于对照组和小潮气量组（P＜0.001），对照组和小潮气量组间比较差异无统计学意义（P＞0.05）。（四）各组大鼠血浆及BALF中MPO活性测定结果结果显示，常规潮气量组和大潮气量组大鼠BALF中MPO活性均明显高于对照组和小潮气量组（P＜0.01，P＜0.05）；大潮气量组大鼠BALF中MPO活性明显高于常规潮气量组（P＜0.01）；对照组和小潮气量组间比较差异无统计学意义（P＞0.05）。各组大鼠血浆MPO活性间比较差异均无统计学意义（P＞0.05）。（五）各组大鼠血浆及BALF中蛋白含量测定结果结果显示，常规潮气量组和大潮气量组大鼠BALF中蛋白含量均明显高于对照组和小潮气量组（P＜0.01）；大潮气量组大鼠BALF中蛋白含量明显高于常规潮气量组（P＜0.01）；对照组和小潮气量组间比较差异无统计学意义（P＞0.05）。各组大鼠血浆蛋白含量间比较差异均无统计学意义（P＞0.05）。（六）各组大鼠血浆和BALF中MIP-1α含量测定结果结果显示，常规潮气量组和大潮气量组大鼠BALF中MIP-1α含量均明显高于小潮气量组和对照组（P＜0.01）；小潮气量组与对照组比较以及常规潮气量组与大潮气量组比较，差异均无统计学意义（P＞0.05）。各组大鼠血浆中MIP-1α含量间比较差异无统计学意义（P＞0.05）。相关分析结果表明，各组大鼠BALF中MIP-1α含量与MPO活性及PMN计数间均呈正相关（r=0.454，P＜0.05：r=0.431，P＜0.05）。（七）各组大鼠肺组织MIP-1α免疫组织化学染色结果结果显示，大潮气量组和常规潮气量组细支气管和肺泡上皮细胞MIP-1α蛋白表达水平均比小潮气量组与对照组明显增高（P＜0.01）；小潮气量组细支气管及肺泡上皮细胞MIP-1α蛋白表达水平与对照组比较差异均无统计学意义（P＞0.05）。除细支气管上皮和肺泡上皮细胞外，血管内皮细胞、平滑肌细胞也可见少量MIP-1α蛋白阳性表达。（八）各组大鼠肺组织MIP-1αmRNA原位杂交及NF-κB p65蛋白免疫组织化学染色结果结果显示，大潮气量组和常规潮气量组细支气管上皮MIP-1αmRNA阳性表达细胞百分比，以及NF-κB p65蛋白表达阳性细胞百分比均明显高于小潮气量组和对照组（P＜0.01）；小潮气量组与对照组比较差异无统计学意义（P＞0.05）。相关分析结果表明，各组大鼠细支气管上皮MIP-1αmRNA阳性表达细胞百分比与NF-κB p65蛋白表达阳性细胞百分比之间呈正相关（r=0.482、P＜0.05）。（九）各组大鼠BALF中肺泡巨噬细胞MIP-1α及NF-κB p65蛋白免疫细胞化学染色测定结果结果表明，大潮气量组和常规潮气量组大鼠BALF中肺泡巨噬细胞MIP-1α及NF-κB p65蛋白表达阳性细胞百分比均明显高于小潮气量组和对照组（P＜0.01）；小潮气量组与对照组比较差异无统计学意义（P＞0.05）。相关分析结果表明，各组大鼠BALF中肺泡巨噬细胞MIP-1α染色阳性细胞百分比与NF-κB p65蛋白核染色阳性细胞百分比之间呈正相关（r=0.457，P＜0.05）。四、研究结论1．小潮气量通气对正常肺组织无明显损伤作用。常规潮气量通气对正常肺组织造成的损伤虽然在肉眼下不太明显，但在光镜和电镜下可以显示出来。大潮气量通气对正常肺组织所造成的损伤不仅在肉眼和光镜下明显可见，而且在超微结构上也有特殊改变。提示没有任何肺保护措施的大潮气量和常规潮气量机械通气对正常肺组织有不同程度损伤作用。常规潮气量通气所引起的肺损伤虽不如大潮气量通气严重，但绝对不能轻视。2．肺内中性粒细胞募集、活化在呼吸机所致肺损伤中起重要作用，而且潮气量越大，中性粒细胞数目越多、活性越高，对肺组织造成的损伤就越严重。测定血浆及BALF中蛋白含量，并计算肺泡膜通透指数（BALF蛋白含量／血浆蛋白含量）在一定程度上可反映肺组织的损伤程度，而且测定方法简单可靠，有一定实用价值。各组大鼠血浆中MPO活性及蛋白含量之间比较无明显差异，说明呼吸机所致肺损伤在一定程度上主要表现在肺脏局部，而对全身影响较小。3．巨噬细胞炎症蛋白-1α（MIP-1α）与VILI发生有密切关系，MIP-1α通过化学激动和化学趋化作用促使中性粒细胞在肺内聚集和活化，是导致VILI发病的重要原因之一。在VILI发病过程中，MIP-1α的来源是多途径的，除肺泡巨噬细胞外，其他肺组织细胞也可表达MIP-1α。4．在VILI的发生过程中，肺组织细胞释放MIP-1α在一定程度上可能受NF-κB的调控。机械刺激→NF-κB→细胞因子信号通路可能是VILI发生过程中细胞内信号传导途径。因此，通过阻断NF-κB活化、减少MIP-1α释放和抑制中性粒细胞活性等多个环节入手进行干预和治疗，可作为VILI防治的一个新方向。5．肺泡巨噬细胞（AM）是引起VILI的始动细胞之一。AM活化并释放MIP-1α是导致VILI发生的一个重要因素，其过程可能受NF-κB的调控。AM可直接或间接感受机械刺激信号，使细胞内NF-κB发生活化。细胞内NF-κB活化既是AM激活的关键步骤，也是AM激活的重要标志。更多还原

【Abstract】 Mechanical ventilation （MV） which has unique curing effects on the serious illnesses, can’t be replaced by other therapies. MV itself, however, may also act as a damaging factor to induce or aggravate lung injury which is called ventilator-induced lung injury （VILI）. VILI is one of the serious complications in the process of mechanical ventilation, and is also an important factor in deteriorating patient’s health, even to death. Therefore, mechanical ventilation, if misused, will fail in any supposed therapeutic effects and also subject people’s life and property to a heavy loss.Many research have proved that high airway pressure or large volume ventilation can initiate or aggravate lung injury. Of course, clinically it is impossible for us to setting such high tidal volume which is high enough to induce lung injury. However, it remains controversial whether conventional tidal volume ventilation is absolutely safe without initiating inflammatory lung injury.Animal experiment studies have indicated that MV with high PIP and large V_T may activate neutrophils （PMN）. After activation, PMN can release not only various kinds of cytokines and inflammatory mediators but also a lot of oxyradicals and proteinases, which are the chief causes of the inflammatory lung injury. However, PMN is neither the only cell nor the starting cell to evoke inflammatory lung injury in the process of VILI and its activation depends on the release of other preinflammatory factors.Macrophage inflammatory proteins （MIP） which were discovered first by Wolpe and colleagues in 1988 in the supernatant derived from irritating macrophagic system （RAW 264.7） with LPS are new proteins including MIP-1、 MIP-2、 MIP-3、 MIP-4 and MIP-5. MIP-1 and MIP-2 have extensive biological activities and are related to respiratory disease closely. They not only take part in inflammatory and immunological reactions, but also have effects on tumor resisting, hematogenesis promoting and impairment restoring. By executing bronchoalveolar lavage for 30 ARDS children, Murch and colleagues found that the concentration of MlP-1α in BALF supernatant was significantly higher than that of the control group and was obviously decreased after being treated with Dexamethasone for 12 to 24 hours. However, whether MIP-1α has similar effects on the process of VILI, so far there are not related articles published.NF-κB regulating the transcription of target genes is a kind of specific DNA binding protein discovered in recent years. As a dimer compounds, NF-κB is composed of two subunits from Rel protein-family, among which the heterodimer composed of p65 and p50 is of the most representative. Normally, NF-κB binding with I-κB resides in cytoplasm in the state of deactivation. After being stimulated by various etiological factors I-κB can be phosphorylated and separated from NF-κB, thus NF-κB is activated. The latter enters the nucleus, binds with the specific site in DNA and regulates the transcription of target genes. It has been proved that NF-κB can participate in the immune and inflammatory reactions in the lungs by regulating the genetic expression of numerous cytokines and adhesion molecules, such as IL-1β, TNF-α, IL-6, IL-8, ICAM-1, selectin E etc. However, whether NF-κB takes part in regulating MIP-1α gene transcription there are still no final conclusions and it needs to be investigated further.Alveolar macrophages （AM） are the major starting cells of the local imflammation in the lungs. They not only possess powerful phagocytosis but also can synthesize and secrete many kinds of inflammatory mediators and cytokines when activated, which leads to local imflammation in the lungs losing control and is an important cause of ALL Studying with in vivo rabbit lung injury models, Takata and colleagues discovered that AM activated and released proinflammatory cytokines, such as TNF-α、 IL-1β and IL-8 etc, might play an important role in activating PMN. Hirani and colleagues demonstrated that among numerous cytokines participating in ALI/ARDS, IL-8 was the strongest chemotatic factor causing PMN to recruit towards lung tissues. IL-8_could be produced by AM or other cells and could be adjusted by local oxygenation state. However, what roles AM has played in the pathogenesis of VILI has not been understood so far.In view of the present researches on VILI, this study will observe the lung injury induced by different volume ventilation in rats under macroscopy, light and electron microscope, then test their arterial blood gas, activity of MPO and the level of MIP-1α, protein content and PMN count in BALF. Simultaneously, the genetic and their protein expression of MIP-1α and NF-κB in lung tissue and alveolar macrophage will be detected with immunohistochemistry and in situ molecular hybridization technique, so as to explore the effects of different tidal volume ventilation on acute lung injury in rats at molecular level and provide a new clue to the prevention and treatment of VILI.CONTENTSThe study includes three parts:Part 1: Pathology of acute lung injury induced by ventilator in rats.Part 2: Effects of neutrophil’s activation on acute lung injury induced by ventilator in rats.Part 3: Effects of macrophage inflammatory protein-1α （MIP-1α） on acute lung injury induced by ventilator in rats.METHODS1. Thirty-two healthy male Wistar rats （provided by Experimental Animal Center ofShanxi Medical University） weighing 300-310g were randomly divided into 4 groups: ① control group: without mechanical ventilation; ② low tidal volume group （L-V_T） : V_T 7ml/kg; ③ conventional tidal volume group （C-V_T） : V_T 12ml/kg; ④ high tidal volume group （H-V_T） :V_T40ml/kg.2. Observe the pathologic alteration of lung injury induced by different volume ventilation in rats under macroscopy, light and electron microscope.3. Test lung wet/dry weight ratio （W/D）.4. Carry out blood gas analysis by automatic blood gas analyzer.5. Count the white blood cells （WBC） and PMN in BALF with light microscope.6. Measure the activities of myeloperoxidase （MPO） in BALF with the method of Luo Wusheng.. 7. Measure the levels of protein in plasma with biuret detection and measure the levels of protein in BALF with Coomassie brilliant blue G-250 detection respectively.8. Detect the content of MIP-α in plasma and BALF with ELISA9. Detect the expression of MIP-1α protein in lung tissue with immunohistochemical staining.10. Detect the expression of MIP-1α mRNA in lung tissue with situ hybridization technique.11. Detect the expression of NF-κB p65 protein in lung tissue with immunohistochemical staining.12. Detect the expression of MIP-1α and NF-κB p65 protein in alveolar macrophage with immunohistochemical staining.RESULTS 1. Pathological changes of the rat lungsOf the low tidal volume group, the appearance of the lungs was normal under macroscopy. Though there were a few neutrophils infiltration under light microscope, the lung tissue structures were not obviously different from that of control group under transmission electron microscope. Of the conventional tidal volume group, the appearance of the lungs was swollen slightly, but their colour and lustre were almost the same as the control group. Under light microscope the interstitial edema and neutrophils infiltration could be found, and under electron microscope there were a great quantity of low electronic density liquid materials congregated in interalveolar septum. Of the high tidal volume group, the lungs were swollen obviously and the spotty hemorrhages could be found on their surface. There were widespread interstitial edema and massive neutrophils infiltration under light microscope. Under electron microscope, the conjunctions between the alveolar epithelial cells and between the capillary endothelial cells were injured with gaps. The neutrophils were in activated state protruding many spine-like processes and their granules contents released with many vacuoles left.2. Results of lung wet/dry weight ratio （W/D） and blood gas analysisThe results showed that W/D of the high and conventional tidal volume group was significantly higher than those of the low tidal volume group and the control group （P<0.01）, PaO₂ of the high and conventional tidal volume group were significantly lower than those of the low tidal volume group and the control group （P<0.01,P<0.05）. However, no statistical difference could be found between the low tidal volume group and the control group （P>0.05）.3. Results of WBC and PMN in BALFThe results showed that WBC and PMN counts in BALF were significantly higher in rats ventilated with high and conventional tidal volume than in those ventilated with low tidal volume and control group （P<0.001）, but no significant difference could be found between low tidal volume group and control group （P>0.05）.4. Results of MPO in plasma and BALFThe results showed that the activity of MPO in BALF was significantly higher in rats ventilated with high and conventional tidal volume than in those ventilated with low tidal volume and control group （P<0.01, P<0.05）. The activity of MPO in BALF of the high tidal volume group was significantly higher than that of the conventional tidal volume group （P<0.01）, but no significant difference could be seen between low tidal volume group and control group （P>0.05）. Of the activity of MPO in plasma there was no statistical difference existed among all rat groups （P>0.05）.5. Results of protein levels in plasma and BALFThe results showed that the protein levels in BALF were significantly higher in rats ventilated with high and conventional tidal volume than in those ventilated with low tidal volume and control group （P<0.01）, the protein levels of the high tidal volume group were significantly higher than that of the conventional tidal volume group （P<0.01）. However, no significant difference could be found between the low tidal volume group and the control group （P>0.05）. Of the protein levels in plasma there was no statistical difference existed among all rat groups （P>0.05）.6. Results of MlP-1α content in plasma and BALFThe results showed that MlP-1α in BALF were significantly higher in rats ventilated with high and conventional tidal volume than in those ventilated with low tidal volume and control group （P<0.01）. No significant difference could be found either between the low tidal volume group and the control group or between the conventional tidal volume group and the high tidal volume group in BALF （P>0.05）. Of the MIP-1α content in plasma no statistical difference could be found among all rat groups （P>0.05）. Correlation study showed that there was a positive correlation existed either between MIP-1α content and MPO or between MIP-1α content and PMN in BALF respectively （r=0.454, P<0.05; r=0.431, P<0.05）.7. Result of MIP-1α expression in lung tissue detected with immunohistochemical stainingThe results showed that MIP-α expression in bronchiole and alveolar epithelial cells were significantly higher in rats ventilated with high and conventional tidal volume than in those ventilated with low tidal volume and control group （P<0.01）, but no significant difference could be found between the low tidal volume group and the control group （P>0.05）. Besides the bronchiole and alveolar epithelial cells a little MlP-1α protein was also expressed in vascular endothelial cells and smooth muscle cells.8. Results of MIP-1α-mRNA detected with hybridization in situ and NF-κB p65 detected with immunohistochemical staining in lung tissueThe results showed that both MIP-1α mRNA and NF-κB p65 protein positive bronchiole epithelial cell percentage of rats ventilated with high and conventional tidal volume were significantly higher than those ventilated with low tidal volume and control group （P<0.01）, but no significant difference could be found between the low tidal volume group and the control group （P>0.05）. Correlation study showed that there was a positive correlation existed between the MIP-1α mRNA positive bronchiole epithelial cell percentage and the NF-κB p65 protein positive bronchiole epithelial cell percentage （r=0.482, P<0.05）.9. Results of MIP-1α and NF-κB p65 of alveolar macrophage in BALF detected with immunohistochemical stainingThe results showed that the positive alveolar macrophage percentage of MIP-1α and NF-κB p65 in BALF were significantly higher in rats ventilated with high and conventional tidal volume than in those ventilated with low tidal volume and control group （P<0.01）, but no significant difference could be found between the low tidal volume group and the control group （P>0.05）. Correlation study showed that there was a positive correlation existed between the MIP-1α positive alveolar macrophage percentage and the NF-κB p65 positive alveolar macrophage percentage （r=0.457, P<0.05）.CONCLUSIONS1. Low tidal volume ventilation does not have obvious damaging effects on the normal lung tissues. Of the conventional tidal volume ventilation, although no obvious lung injuries can be seen under macroscopy they can be displayed under light and electron microscope. Injuries caused by high tidal volume ventilation not only are obvious under macroscopy and light microscope, but also have special alterations in ultramicrostructure. All of these indicate that high and conventional tidal volume ventilation without any protecting procedures can produce injuries to the normal lung tissue. Although the injuries caused by conventional tidal volume ventilation is not as serious as those caused by high tidal volume ventilation, it shall not be ignored absolutly.2. Recruitment and activation of the neutrophils in the lung tissues might play an important role in the pathogenesis of VILI. The more the tidal volume is, the more the number and activity of neutrophils are, and the more the lung injury happens. Measuring the protein levels in plasma and BALF and calculating the permeation index of alveolar membrane can reflect the degree of lung injury to some extent, which is not only simple and reliable, but also useful as a practical method. Of the MPO activity and the protein levels in plasma there is no statistical difference existed between any groups, which indicates that VILI chiefly occurs in local lung tissues and has few effects on the whole body.3. MIP-1α is related closely to VILI. MIP-1α evokes PMN to be recruited and activated in the lungs through chemical agitation and chemical chemotaxis, which may be one of the important accesses to VILI. In the process of VILI, the sources of MIP-1α are multiple. Except for AM, other cells in the lung tissues can also express MlP-la.4. In the process of VILI, MIP-1α delivery from lung tissues may be regulated by NF-κB to some extent. The chain of mechanical stimulation →NF-κB→cytokines may be an important pathway in the occurrence of VILI. Therefore, it may be viewed as a new direction to prevent and treat VILI by multiple interventions, such as blocking NF-κB activation, reducing MIP-1α delivery and suppressing PMN activation and so on.5. Alveolar macrophage （AM） is one of the starting cells to VILI. AM’s activating and releasing MIP-1α is an important factor leading to VILI, which may be regulated by NF-κB. AM can receive the signals from the mechanical stimulation directly or indirectly and make NF-κB in the cells activated. The activation of intra-cellular NF-κB is both the critical step and the important mark for AM’s activation.更多还原