Microvesicles as crucial mediators of cytokine-dependent perioperative lung injury induced by mechanical ventilation

每年，全世界有超过3.1亿例重大手术。在大多数情况下，患者使用呼吸机或“呼吸机”维持生命，确保氧气输送到肺部。肺部并发症在手术后很常见，严重者可导致残疾或死亡。这些并发症可能是由呼吸机拉伸肺细胞使其发炎引起的，但我们目前对这背后的机制的理解很差，导致没有有效的治疗方法。肺部炎症是由各种各样的物质控制的，如“细胞因子”。肿瘤坏死因子（TNF）是一种在呼吸机相关肺损伤中起关键作用的细胞因子。这可以以各种形式发现，但我们不知道哪种类型的TNF在这种疾病中最重要。当细胞被激活或损伤时，它们会释放出被称为微泡（MV）的微小颗粒，这些颗粒可以携带TNF等货物，在细胞之间传递信息。越来越多的证据表明这些MV在几种肺部疾病中起着至关重要的作用，特别是与它们相关的细胞因子。我们进行了初步实验，表明如果呼吸机过度拉伸小鼠的肺部，一种已知刺激MV产生的物质（ATP）会释放出来，含有TNF的MV数量会增加;如果在实验室中拉伸肺细胞，也会发生这种情况。此外，当肺细胞由于细胞拉伸或感染而发炎时，MV和细胞之间的相互作用增加，导致细胞变得更加受伤。最后，我们研究了肺移植手术的患者，发现在手术后低氧水平的患者中有更多的肺MV，突出了肺MV的重要性。因此，我们提出，呼吸机引起的肺过度伸展引发了物质的释放，导致含麻黄碱的MV的产生。这些MV然后与伸展的肺细胞相互作用，引起肺部炎症，可能导致手术后肺部并发症。我们的主要目标是确定与MV相关的细胞因子在呼吸机上引起肺部炎症的作用。为此，我们将进行详细的实验室实验（使用从病人身上采集的样本），以达到以下目的：1）鉴定在由呼吸机引起的肺过度牵张后细胞因子包装在MV内的机制，2）研究MV与静息或牵张的肺细胞之间的相互作用，3）了解如果细胞被拉伸，MV对肺细胞的生物学效应是否会增强。我们将在实验室中使用不同类型的细胞复制肺环境，然后使用机器拉伸。我们将深入研究这些条件下MV的产生和细胞因子的分布。此外，我们将评估这些MV对肺细胞的生物学效应，并观察它们的效应是否会因细胞拉伸而增强。为了观察我们的实验室研究结果是否能在人类身上复制，我们将研究接受“食管切除术”的患者，这是一种切除食道癌的大手术。由于这种复杂手术所需的特殊类型的通气，这些患者暴露于肺过度拉伸。我们将使用肺液和血液样本动态评估MV产生、各种形式的细胞因子的分布以及肺部炎症/损伤。我们还将评估MV数量或与其相关的细胞因子是否可以预测哪些患者在手术后会出现肺部并发症。最后，我们将结合联合收割机从患者身上提取的MV，在实验室中与拉伸/非拉伸肺细胞一起评估MV的生物学效应和相互作用。我们希望这项工作能够在未来尝试预防肺部炎症和后续并发症，为手术期间或需要重症监护的呼吸机患者提供帮助，这有可能大大改善预后。

Each year, over 310 million major operations are performed worldwide. In most cases, patients are kept alive using a breathing machine or 'ventilator', ensuring oxygen is delivered to the lungs. Lung complications are common after an operation which in severe cases can lead to disability or death. These complications can be caused by the ventilator stretching the lung cells making them become inflamed but our current understanding of the mechanisms behind this is poor leading to no effective treatments.Lung inflammation is controlled by a wide variety of substances such as "cytokines". One cytokine shown to be crucial in lung injury related to being on a ventilator is tumour necrosis factor (TNF). This can be found in various forms, but we do not know which type of TNF is most important in this disease. When cells are activated or injured, they release tiny particles known as microvesicles (MV) which can carry cargo such as TNF within them, delivering information between cells. There is increasing evidence that these MVs play a vital role in several lung diseases, specifically the cytokines associated with them.We performed preliminary experiments that show if a ventilator over-stretches the lungs of mice, a substance known to stimulate MV production (ATP) is released and there is an increase in MV numbers that contain TNF; this also happens if you stretch lung cells in the laboratory. Also, when lung cells are inflamed due to cell stretch or infection, the interaction between MVs and the cells increases, causing the cells to become even more injured. Finally, we studied patients having lung transplant surgery and found more lung MVs in those patients that suffered from low oxygen levels after the operation, highlighting the importance of lung MVs.Therefore, we propose that over-stretch of the lungs caused by a ventilator initiates the release of substances that leads to the production of cytokine-containing MVs. These MVs then interact with stretched lung cells causing lung inflammation, possibly leading to lung complications after surgery.Our primary objective is to identify the role of cytokines associated with MVs that cause lung inflammation when on a ventilator. To do this, we will perform detailed laboratory experiments (using samples taken from patients) to achieve the following aims: 1) Identify the mechanisms by which cytokines are packaged within MVs following lung overstretch caused by a ventilator, 2) Investigate the interaction between MVs and resting or stretched lung cells, 3) Understand if the biological effect of MVs on lung cells is enhanced if the cells are stretched.We will replicate the lung environment in the laboratory using different types of cells which will then be stretched using a machine. We will thoroughly study the production of MVs and the distribution of cytokines in these conditions. Additionally, we will assess the biological effects of these MVs on lung cells and see if their effects are enhanced by cell stretch. To see if our laboratory findings are replicated in humans, we will study patients undergoing 'oesophagectomy', a major operation to remove cancer of the gullet. These patients are exposed to lung overstretch due to a special type of ventilation necessary for this complex operation. We will dynamically assess MV production, the distribution of cytokines in various forms and lung inflammation/ injury using lung fluid and blood samples. We will also assess if MV numbers or the cytokines associated with them can predict which patient will have a lung complication after surgery. Finally, we will combine MVs taken from patients, with stretched/non-stretched lung cells in the laboratory to assess the MVs biological effects and interactions.We hope this work enables future attempts to prevent lung inflammation and subsequent complications for patients on a ventilator during an operation or needing intensive care, which has the potential to vastly improve outcomes.