Lipid and Protein Effects on Monolayer Stability

急性呼吸窘迫综合征（ARDS）是一种弥漫性、炎症性肺部疾病， 血管通透性增加，肺顺应性降低，以及充气组织损失，影响200，000例 美国每年有40%的死亡率。在过去，新冠肺炎感染显著增加了这些数字 年ARDS发生的机制以及宿主因素如何增加发生ARDS的风险， 严重的疾病仍不清楚。已知基础疾病引起的炎症与ARDS有关 进展和严重程度。我们推测，脂肪酶催化的病原体磷脂降解， 可溶性溶血脂和游离脂肪酸可导致称为“拉普拉斯不稳定性”的机械肺不稳定性 通过使健康的肺表面活性剂失活。拉普拉斯不稳定性的发生是因为肺泡内压力 随着拉普拉斯压力的增加，Δε = 2λ/ε;在以下情况下，半径较小的肺泡中的Δ ε高于较大的肺泡𝑃 𝛾表面张力是恒定的。这将导致较小的肺泡收缩并充满液体，而较大的肺泡则会收缩并充满液体。 肺泡扩张，这两种症状都是ARDS。为了防止这种情况，必须随着肺泡的减少而减少 半径，使得2（）−> 0，其中（）=（）（）是弹性模量。𝜕𝛾𝜔𝐸𝛾𝜔𝐸为了健康的肺 表面活性剂2-羟基-g >> 0.然而，在炎症过程中，溶血脂质浓度增加的顺序是： 由于脂肪酶作用于病原体膜，肺泡液中的浓度增加。我们发现 溶血棕榈酰磷脂酰胆碱浓度高于其临界胶束浓度（CMC）时，𝜔𝐸 肺表面活性物质单层急剧减少，导致在呼吸频率下2（≤0，𝜔 可能导致拉普拉斯不稳定性并损害均匀的肺充气。理论模型显示，𝐸 由于单层和相邻流体中的胶束之间的溶血脂的扩散交换而降低。 该项目将使用实验和理论相结合的方法来了解病原体是如何产生的 具有广泛变化的CMC的影响力的溶血脂，使得化学或物理干预可能是𝜔𝐸 是为了扭转拉普拉斯不稳定性而发展起来的。在目标1中，我们将使用开发的独特实验技术 在我们的实验室中，以确定肺表面活性物质的溶解性质如何由于与溶血脂质接触而发生变化， 代表浓度高于和低于CMC的各种病原体。我们将确定影响 研究了肺泡上皮细胞（E. coli）对模型肺泡表面动力学的影响，以及这如何导致生理功能障碍。在目标2中， 我们将检查临床和模型肺表面活性剂的液-固域形态，以了解其作用 胆固醇和界面曲率在修改域的形状和大小，以最大限度地提高LS再扩展期间 吸入和最小化溶解脂质吸附。这些首次的实验和基本的理论 方法应该确定最佳的肺表面活性物质组成， 提供了一种新的稳定ARDS肺的方法。

Acute respiratory distress syndrome (ARDS) is a diffuse, inflammatory lung disease characterized by increased vascular permeability, decreased lung compliance, and loss of aerated tissue affecting 200,000 in the US annually with 40% mortality. Covid-19 infections have significantly increased these numbers over the past year. The mechanisms through which ARDS arises and how host factors confer an increased risk of developing severe disease remain unclear. It is known that inflammation due to underlying disease is linked to ARDS progression and severity. We hypothesize that lipase-catalyzed degradation of pathogen phospholipids to soluble lysolipids and free fatty acids can lead to a mechanical lung instability known as the “Laplace Instability by inactivating healthy lung surfactant. The Laplace Instability occurs because the intra-alveolar pressure is increased by the Laplace pressure, ∆𝑃 = 2𝛾⁄𝑅 ; ∆𝑃 is higher in alveoli with smaller radii, 𝑅, than larger alveoli if 𝛾, the surface tension, is constant. This would cause smaller alveoli to deflate and fill with fluid, while the larger alveolar become distended, both symptoms of ARDS. To prevent this, 𝛾 must decrease with decreasing alveolar radius such that 2𝐸∗(𝜔) − 𝛾 > 0 in which 𝐸∗(𝜔) = 𝐴(𝜔)(𝜕𝛾⁄𝜕𝐴) is the dilatational modulus. For healthy lung surfactant 2𝐸∗(𝜔) -g >> 0. However, during inflammation, lysolipid concentrations increase by orders of magnitude in the alveolar fluids due to lipases acting on pathogen membranes. We find that lysopalmitoylphosphatidylcholine concentrations above its critical micelle concentration (CMC) cause 𝐸∗(𝜔) of lung surfactant monolayers to decrease dramatically leading to 2𝐸∗(𝜔) − 𝛾 ≤ 0 at breathing frequencies, which can lead to the Laplace Instability and compromise uniform lung inflation. Theoretical models show 𝐸∗ decreases due to diffusive exchange of lysolipids between the monolayer and the micelles in the adjacent fluid. This project will use a combined experimental and theoretical approach to understand how pathogen derived lysolipids with widely varying CMC’s influence 𝐸∗(𝜔) so that chemical or physical interventions might be developed to reverse the Laplace Instability. In Aim 1, we will use the unique experimental techniques developed in our labs to establish how the dilatational properties of lung surfactant change due to contact with lysolipids representative of various pathogens at concentrations above and below the CMC. We will determine the impact of 𝐸∗(𝜔) on the dynamics of model alveolar surfaces, and how this leads to physiological dysfunction. In Aim 2, we will examine the liquid-solid domain morphology of clinical and model lung surfactants to understand the role of cholesterol and interfacial curvature in modifying domain shapes and sizes to maximize LS respreading during inhalation and minimize lysolipid adsorption. These first of their kind experiments and fundamental theoretical approaches should determine the optimal lung surfactant composition that is resistant to lysolipid adsorption and provide a new way of stabilizing the ARDS lung.