Department of Chemical Engineering, University of California, Santa Barbara, CA, USA
Department of Chemical Engineering, University of California, Santa Barbara, CA, USA.
J R Soc Interface. 2018 Apr;15(141). doi: 10.1098/rsif.2017.0895.
All mammals depend on lung surfactant (LS) to reduce surface tension at the alveolar interface and facilitate respiration. The inactivation of LS in acute respiratory distress syndrome (ARDS) is generally accompanied by elevated levels of fibrinogen and other blood plasma proteins in the alveolar space. Motivated by the mechanical role fibrinogen may play in LS inactivation, we measure the interfacial rheology of mixed monolayers of fibrinogen and dipalmitoylphosphatidylcholine (DPPC), the main constituent of LS, and compare these to the single species monolayers. We find DPPC to be ineffective at displacing preadsorbed fibrinogen, which gives the resulting mixed monolayer a strongly elastic shear response. By contrast, how effectively a pre-existing DPPC monolayer prevents fibrinogen adsorption depends upon its surface pressure. At low DPPC surface pressures, fibrinogen penetrates DPPC monolayers, imparting a mixed viscoelastic shear response. At higher initial DPPC surface pressures, this response becomes increasingly viscous-dominated, and the monolayer retains a more fluid, DPPC-like character. Fluorescence microscopy reveals that the mixed monolayers exhibit qualitatively different morphologies. Fibrinogen has a strong, albeit preparation-dependent, mechanical effect on phospholipid monolayers, which may contribute to LS inactivation and disorders such as ARDS.
所有哺乳动物都依赖肺表面活性剂（LS）来降低肺泡界面的表面张力，从而促进呼吸。在急性呼吸窘迫综合征（ARDS）中，LS 的失活通常伴随着肺泡空间中纤维蛋白原和其他血浆蛋白水平的升高。鉴于纤维蛋白原在 LS 失活中可能发挥的机械作用，我们测量了纤维蛋白原和二棕榈酰磷脂酰胆碱（DPPC）混合单层的界面流变特性，DPPC 是 LS 的主要成分，并将这些与单种单层进行了比较。我们发现 DPPC 对预吸附的纤维蛋白原没有置换作用，这使得所得混合单层具有强烈的弹性剪切响应。相比之下，预先存在的 DPPC 单层对纤维蛋白原吸附的阻止效果取决于其表面压力。在 DPPC 表面压力较低时，纤维蛋白原渗透 DPPC 单层，赋予混合粘弹性剪切响应。在较高的初始 DPPC 表面压力下，这种响应变得越来越粘性主导，单层保留了更具流动性、类似 DPPC 的特性。荧光显微镜显示混合单层表现出不同的形态。纤维蛋白原对磷脂单层具有强烈的、尽管取决于制备的机械作用，这可能有助于 LS 失活和 ARDS 等疾病。
