Lipid and Protein Effects on Monolayer Stability

肺表面活性物质（LS）在降低肺泡气液界面表面张力γ方面具有良好的作用 知道的我们假设LS的第二个基本功能是防止拉普拉斯不稳定性， 将气体从较小的肺泡排出并进入较大的肺泡，导致肺泡去募集、肺不张和肺功能丧失。 肺顺应性这些是急性呼吸窘迫综合征（ARDS）的核心症状， 在美国有15万人患病死亡率高达40%我们假设， LS单分子层面积的变化可以逆转拉普拉斯不稳定性。弹性模量，ε=εε，𝜕𝛾 将表面张力的变化γ与界面面积的变化A联系起来。对于2ε−γ >0，拉普拉斯压力 随着半径的减小而减小，从而抑制了拉普拉斯不稳定性。然而，如果2ε−γ < 0， 充气驱动较小肺泡的塌陷，导致肺泡溢流和肺顺应性降低。 我们的初步工作表明，血清蛋白和溶血脂，增加肺泡液中， ARDS诱导的炎症通过竞争性吸附到肺泡界面而增加γ。这些抑制剂 也由于它们与亚相的扩散交换而显著地降低结晶模量， 特别是在低界面面积应变率（ΔA（t）/A）下。这种情况出现在肺的受损区域， 不良的气体交换和高水平的炎症产物，并在2ε−γ < 0时引起拉普拉斯不稳定性。 这会导致肺部受伤区域的进一步损伤，并建立一个负反馈回路， 对目前ARDS治疗的无效性负责。 为了解决这一假设，我们建立了一种新型的毛细管压力显微张力计，以测量ε（ω） LS、血清蛋白和溶血脂首次。我们将绘制出临床和模型肺表面活性剂的ε（ω） 作为表面活性剂组成、形态、表面压力和频率的函数，以确定影响 饱和与不饱和脂质部分、结构域形态和肺表面活性蛋白SP-B和SP-C， 胆固醇和脂肪酸级分。我们将研究ε（ω）如何由于亚相组成而变化， 溶血脂、白蛋白和纤维蛋白原，所有这些在ARDS肺中具有升高的水平。这是他们第一次 测量结果应该为我们提供一张拉普拉斯不稳定性起作用的条件图 在ARDS的发展过程中。逆转拉普拉斯不稳定性需要了解如何防止抑制剂 到达肺泡界面，或去除吸附的抑制剂。从我们对ε（ω）的新理解来看， 我们将创造具有最佳流变性能的LS配方，以促进LS再扩展。我们也 建议最大限度地减少LS中的阴离子脂质部分并加入低浓度的聚乙二醇 (PEG)和来自佐剂如明矾的三价阳离子，将提供静电和渗透帮助， 促进LS吸附。最小化抑制剂浓度和最大化LS将降低γ，增加ε（ω）， 并逆转导致拉普拉斯不稳定性的条件，从而恢复适当的肺功能。

The role of Lung Surfactant (LS) in lowering the surface tension, γ, at the alveolar air-liquid interface is well known. We hypothesize that a second essential function of LS is to prevent the Laplace instability, which drives gas out of smaller alveoli and into larger ones, leading to alveolar de-recruitment, atelectasis and loss of lung compliance. These are the core symptoms of Acute Respiratory Distress Syndrome (ARDS), which afflicts 150,000 people in the US with a 40% mortality rate. We hypothesize that the dynamic resistance of the LS monolayer to changes in area can reverse the Laplace instability. The dilatational modulus, 𝜀 = 𝐴 𝜕𝛾 𝜕𝐴 , relates the change in surface tension, γ, to the change in interfacial area, A. For 2ε−γ >0, the Laplace pressure decreases with decreasing radius, suppressing the Laplace Instability. However, if 2ε−γ < 0, variations in lung inflation drive collapse of smaller alveoli, leading to the alveolar flooding and decreased lung compliance. Our preliminary work shows that serum proteins and lysolipids, which increase in the alveolar fluids during ARDS-induced inflammation, increase γ by competitively adsorbing to the alveolar interface. These inhibitors also dramatically decrease the dilatational modulus due to their diffusional exchange with the subphase, especially at low interfacial area strain rates (ΔA(t)/A). Such conditions arise in damaged areas of the lung with poor gas exchange and high levels of inflammation products and provoke the Laplace instability as 2ε−γ < 0. This leads to further damage in injured areas of the lung and a negative feedback loop is established that may be responsible for the ineffectiveness of current ARDS treatments. To address this hypothesis, we have built a novel capillary pressure microtensiometer to measure ε(ω) of LS, serum proteins, and lysolipids for the first time. We will map out ε(ω) for clinical and model lung surfactants as a function of surfactant composition, morphology, surface pressure and frequency to determine the effects of saturated vs. unsaturated lipid fraction, domain morphology, and lung surfactant proteins SP-B and SP-C, cholesterol and fatty acid fractions. We will examine how ε(ω) changes due to subphase compositions of lysolipids, albumin, and fibrinogen, all of which have elevated levels in the ARDS lung. These first of their kind measurements should provide us with a map of the conditions under which the Laplace instability plays a role in the progression of ARDS. Reversing the Laplace instability requires understanding how to prevent inhibitors from reaching the alveolar interface, or removing inhibitors that do adsorb. From our new understanding of ε(ω) we will create LS formulations with optimized rheological properties to promote LS respreading. We also propose that minimizing the anionic lipid fraction in LS and adding low concentrations of polyethylene glycol (PEG) and trivalent cations from adjuvants such as alum, will provide an electrostatic and osmotic assist to promote LS adsorption. Minimizing the inhibitor concentration and maximizing LS would lower γ, increase ε(ω) and reverse the conditions leading to the Laplace instability, thereby restoring proper lung function.