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

每年，全球进行的大型手术超过3.1亿次。在大多数情况下，患者通过呼吸机或呼吸机维持生命，确保氧气被输送到肺部。肺部并发症在手术后很常见，在严重的情况下可能会导致残疾或死亡。这些并发症可能是由呼吸机拉伸肺细胞使其发炎引起的，但目前我们对其背后的机制了解很少，导致没有有效的治疗方法。肺部炎症由多种物质控制，如“细胞因子”。与使用呼吸机相关的肺损伤中，有一种细胞因子被证明是至关重要的，那就是肿瘤坏死因子。这可以以各种形式发现，但我们不知道哪种类型的肿瘤坏死因子在这种疾病中最重要。当细胞被激活或受伤时，它们会释放被称为微泡(MV)的微小颗粒，这种颗粒可以携带肿瘤坏死因子等货物，在细胞之间传递信息。越来越多的证据表明，这些MV在几种肺部疾病中发挥着至关重要的作用，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，一种已知的刺激MV产生的物质(ATP)会释放出来，含有肿瘤坏死因子的MV数量会增加；如果你在实验室拉伸肺细胞，也会发生这种情况。此外，当肺细胞因细胞伸展或感染而发炎时，MVS与细胞之间的相互作用增加，导致细胞受到更严重的伤害。最后，我们对接受肺移植手术的患者进行了研究，发现术后低氧患者肺MVS较多，突出了肺MVS的重要性。因此，我们认为呼吸机引起的肺过度伸展会启动物质的释放，导致含有细胞因子的MVS的产生。然后，这些MV与拉伸的肺细胞相互作用，导致肺部炎症，可能导致手术后的肺部并发症。我们的主要目标是确定与MV相关的细胞因子在使用呼吸机时导致肺部炎症的作用。为此，我们将进行详细的实验室实验(使用患者的样本)以实现以下目标：1)确定呼吸机引起的肺过度拉伸后MVS内包装细胞因子的机制；2)研究MVS与静息或拉伸的肺细胞之间的相互作用；3)了解如果细胞拉伸，MVS对肺细胞的生物学效应是否会增强。我们将在实验室使用不同类型的细胞复制肺环境，然后使用机器拉伸这些细胞。我们将深入研究在这些条件下MVS的产生和细胞因子的分布。此外，我们将评估这些微血管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。为了验证我们的实验室研究结果是否也适用于人类，我们将研究正在接受“食道切除术”的患者，这是一种切除食道癌的主要手术。这些患者暴露于肺过度伸展，因为这种复杂的手术需要一种特殊类型的通风。我们将使用肺液和血液样本来动态评估MV的产生、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数值或与其相关的细胞因子是否可以预测哪位患者会在手术后出现肺部并发症。最后，我们将结合患者的MVS和实验室中拉伸/非拉伸的肺细胞来评估MVS的生物学效应和相互作用。我们希望这项工作能够使未来的尝试能够预防患者在手术或需要重症监护期间使用呼吸机时的肺部炎症和后续并发症，这有可能极大地改善结果。

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.