MICA: Mitochondrial dysfunction in macrophages and impaired bacterial clearance in chronic obstructive pulmonary disease (COPD)

慢性阻塞性肺疾病（COPD）是一种由炎症和小气道狭窄引起的进行性肺部疾病，导致呼吸困难。慢性阻塞性肺病是由吸烟引发的，但戒烟后炎症仍然存在，并导致疾病进展。确定引发炎症的原因至关重要，因为没有任何治疗可以阻止炎症的发展。频繁的细菌性胸部感染与COPD症状恶化有关。我们认为，呼吸道细菌的无效清除导致COPD的进展。我们和其他研究人员发现，在慢性阻塞性肺病患者中，肺部气囊中的免疫细胞对细菌表现出错误的反应，这些细菌通常会导致胸部感染，导致细菌持续存在于气道中。这些细胞被称为肺泡巨噬细胞（AM），它们在COPD患者中吞噬和杀死细菌的能力较差。我们将研究为什么会发生这种情况。细胞（如AM）产生能量（代谢）的过程根据细胞功能（如杀死细菌）动态变化。我们的初步结果表明，COPD AM不能根据需要调节其代谢，这阻碍了细菌的清除。细胞中参与新陈代谢的关键部分是线粒体。正常情况下，巨噬细胞吞噬细菌后，其线粒体的功能从代谢转变为产生杀死细菌的物质（线粒体活性氧；“mROS”）。这需要线粒体分裂成更小的单位（“线粒体裂变”）。我们的研究表明，慢性阻塞性肺病AM通常会产生过多的mROS，因此不能增加产生以杀死细菌。我们认为，在COPD中，AM线粒体在试图杀死细菌时适应其功能的能力较差，导致对感染的易感性。然而，这些过程如何正常发挥作用或在COPD中出现问题的确切细节尚不完全清楚。需要更好地了解以确定新的治疗方法来加强COPD的这些过程。我们将确定在健康人群中有效杀死细菌所需的巨噬细胞代谢、mROS产生和线粒体裂变的关键变化，并确定COPD如何改变这种反应。为此，我们将从健康的非吸烟者、健康的当前吸烟者和COPD患者的血液或肺部研究AM。我们将通过支气管镜从肺中分离AM，在支气管镜中，将一根光纤管插入气道，并用液体冲洗肺的一部分以获得细胞。我们还将使用感染和气道疾病的小鼠模型。首先，我们将通过分离AM并标记化学物质以跟踪代谢（“质谱”）来详细描述AM对感染的代谢反应。我们将测量参与对细菌反应的基因和蛋白质的模式，以确定感染期间参与的代谢途径。我们将在健康AM中确认这些代谢反应，然后确定它们在COPD中如何改变。接下来，我们将测量mROS的产生，并研究它是如何在感染后和COPD AM中产生的。我们还将研究在这些条件下线粒体裂变的时间和机制。我们目前的研究结果提出了几种mROS产生和裂变的潜在机制，我们对代谢和基因表达的分析将有助于确定测试哪种理论。来自人类细胞的关键发现将在小鼠模型中得到验证。我们还将使用从影响线粒体功能的遗传缺陷的人的细胞中提取的巨噬细胞来验证研究结果。我们将在细胞中使用化学和基因编辑技术来修改我们已经确定在COPD中改变的影响细菌反应的途径。最后，为了开发潜在的治疗方法，我们将筛选药物库，以确定改善关键反应的方法。这些将在小鼠模型和患者样本中进行测试，以帮助确定未来COPD试验的优先方法。

Chronic obstructive pulmonary disease (COPD) is a progressive lung disease caused by inflammation and narrowing of the small airways, leading to breathlessness. COPD is triggered by cigarette smoke, but inflammation persists after stopping smoking and causes disease progression. Identifying what drives inflammation is vital since no treatment can stop progression. Frequent bacterial chest infections are associated with worsening COPD symptoms. We believe that ineffective clearance of bacteria from the airways causes COPD progression. We and others have found that in COPD, immune cells in the air sacs in the lung display faulty responses to bacteria that commonly cause chest infections resulting in bacteria persisting in the airway. These cells, termed alveolar macrophages (AM), are less able to eat and kill bacteria in people with COPD. We will examine why this happens.The process by which cells, such as AM, produce energy (metabolism) changes dynamically based on the cells function (e.g. killing bacteria). Our preliminary results suggest that COPD AM are less able to adjust their metabolism as needed, and this prevents bacterial clearance. Key parts of the cell involved in metabolism are mitochondria. Normally, after macrophages have eaten bacteria, the function of their mitochondria changes away from metabolism and towards producing substances to kill bacteria (mitochondrial reactive oxygen species; "mROS"). This requires the mitochondria to break up into smaller units ("mitochondrial fission"). Our work suggests that COPD AM normally produce too much mROS so cannot increase production to kill bacteria. We believe that in COPD, AM mitochondria are less able to adapt their function when trying to kill bacteria, leading to susceptibility to infection. However, the precise details of how these processes normally function, or go wrong in COPD, are not fully understood. A better understanding is needed to identify new treatments to enhance these processes in COPD. We will determine the key changes in metabolism, production of mROS and mitochondrial fission in macrophages required to kill bacteria effectively in healthy people and determine how COPD alters this response.To do this, we will study AM from the blood or lungs of healthy non-smokers, healthy current smokers, and people with COPD. We will isolate AM from the lungs by bronchoscopy, where a fibre-optic tube is passed into the airways and a segment of the lung is flushed with fluid to obtain the cells. We will also use mouse models of infection and airway disease. First, we will characterise in detail the metabolic response of AM to infection by isolating AM and labelling them with chemicals to track metabolism ("mass spectrometry"). We will measure patterns of genes and proteins involved in responding to bacteria, to identify metabolic pathways engaged during infection. We will confirm these metabolic responses in healthy AM and then determine how they are altered in COPD. Next, we will measure mROS production and investigate how it is produced following infection and in COPD AM. We will also examine the timing and mechanism of mitochondrial fission in these conditions. Our current findings suggest several potential mechanisms for mROS production and fission, and our analyses of metabolism and gene expression here will help determine which theories to test. Key findings from human cells will be validated in mouse models. We will also validate findings using macrophages derived from cells from people with genetic defects impacting mitochondrial function. We will use chemical and gene editing techniques in cells to modify pathways we have identified as altered in COPD that impact bacterial responses. Finally, to develop potential treatments we will screen libraries of drugs to identify ways of improving key responses. These will be tested in mouse models and patient samples to help prioritise approaches for future trials in COPD.