Edelson J D
St. Michael's Hospital Health Sciences Research Centre, University of Toronto, ON, Canada.
New Horiz. 1995 May;3(2):229-39.
More than a quarter century has passed since Ashbaugh and colleagues postulated that abnormalities of surfactant are causally related to the abrupt and severe organ dysfunction that occurs in individuals with acute lung injury (ALI). In this time, much progress has been made in expanding our understanding of the normal functions of the alveolar epithelium and how these functions may be disrupted in the context of ALI. Alveolar epithelial cells are a key structural component of the spatial separation of gas and plasma, essential for normal gas exchange in the lung. In addition, alveolar epithelial cells synthesize, secrete, and take up surfactant, which, by reducing surface tension, is a key determinant of intra-alveolar pressure. Surfactant is qualitatively and quantitatively abnormal in lung injury due to changes in synthesis, secretion, intra-alveolar metabolism, and biophysical inhibition by protein and lipid inhibitors. Alveolar epithelial cells also subserve additional host defense functions, such as modulation of lymphocyte, macrophage, and neutrophil function; production of prostanoids, complement proteins, and nitric oxide; and display of major histocompatibility complex II molecules and intracellular adhesion molecule-1. Although the physiologic and pathogenic significance of some these functions is not absolutely clear, they are of potential relevance in the context of lung injury, wherein they may participate in the process of alveolar injury and repair.
自阿什baugh及其同事提出表面活性剂异常与急性肺损伤（ALI）患者发生的急性、严重器官功能障碍存在因果关系以来，已过去25年有余。在此期间，我们在拓展对肺泡上皮细胞正常功能的理解以及这些功能在ALI情况下如何被破坏方面取得了很大进展。肺泡上皮细胞是气体与血浆空间分隔的关键结构组成部分，对肺内正常气体交换至关重要。此外，肺泡上皮细胞合成、分泌并摄取表面活性剂，表面活性剂通过降低表面张力，是肺泡内压的关键决定因素。由于合成、分泌、肺泡内代谢的变化以及蛋白质和脂质抑制剂的生物物理抑制作用，肺损伤时表面活性剂在质量和数量上均异常。肺泡上皮细胞还发挥其他宿主防御功能，如调节淋巴细胞、巨噬细胞和中性粒细胞功能；产生前列腺素、补体蛋白和一氧化氮；以及表达主要组织相容性复合体II类分子和细胞间黏附分子-1。尽管其中一些功能的生理和致病意义尚不完全清楚，但它们在肺损伤情况下可能具有潜在相关性，在肺损伤过程中它们可能参与肺泡损伤和修复过程。
