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，其特征是 血管通透性增加，肺顺应性降低，充气组织丢失，影响了200,000人 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的发生机制以及宿主因素如何增加发生的风险 严重疾病仍不清楚。众所周知，潜在疾病引起的炎症与ARDS有关。 进展和严重程度。我们假设脂肪酶催化的病原菌磷脂降解为 可溶性溶质脂和游离脂肪酸可导致被称为“拉普拉斯不稳定性”的机械性肺不稳定 通过灭活健康的肺表面活性物质。拉普拉斯不稳定性的发生是因为肺泡内压 随着拉普拉斯压力的增加，半径较小的肺泡的∆𝑃=2𝛾⁄𝑅；∆𝑃比较大的肺泡的𝑅高 表面张力𝛾是恒定的。这会导致较小的肺泡放气并充满液体，而较大的肺泡 肺泡扩张，这都是急性呼吸窘迫综合征的症状。为了防止这种情况，𝛾必须随着肺泡的减少而减少 半径为2𝐸∗(𝜔)−𝛾；0，其中𝐸∗(𝜔)=𝐴(𝜔)(𝜕𝛾⁄𝜕𝐴)是膨胀系数。为了健康的肺部 表面活性剂2𝐸∗(𝜔)-g&gt；&gt；0。然而，在炎症期间，溶菌脂浓度增加了数量级 由于脂肪酶作用于病原体膜，肺泡液中的大小。我们发现 溶血磷脂酰胆碱浓度高于其临界胶束浓度会引起𝐸∗(𝜔 肺表面活性物质单分子层急剧减少，导致呼吸频率为2𝐸∗(𝜔)−𝛾≤0，这 可导致拉普拉斯不稳，影响均匀的肺充气。理论模型显示𝐸∗ 由于溶质脂在单层和相邻流体中的胶束之间的扩散交换而减少。 这个项目将使用实验和理论相结合的方法来理解病原体是如何 具有很大变化的cmc影响的溶固体脂𝐸∗(𝜔)，以便化学或物理干预可能是 发展起来是为了扭转拉普拉斯不稳定性。在目标1中，我们将使用开发的独特实验技术 以确定肺表面活性物质与溶菌脂接触后的扩张特性如何变化 代表浓度高于和低于CMC的各种病原体。我们将确定影响 𝐸∗(𝜔)对模型肺泡表面动力学的研究，以及这如何导致生理功能障碍。在目标2中， 我们将检查临床肺表面活性物质和模型肺表面活性物质的液-固结构域形态以了解其作用。 在修改区域形状和大小以最大化LS再扩散过程中胆固醇和界面曲率的影响 吸入并最大限度地减少溶菌脂的吸收。这些是他们的第一个同类实验和基本理论 方法应确定最优的肺表面活性物质的组成，以抵抗溶菌素吸附和 为ARDS肺的稳定提供了一种新的方法。

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.