Kalina M, Blau H, Riklis S, Kravtsov V
Department of Cell Biology and Histology, Sackler School of Medicine, Tel Aviv University, Israel.
Am J Physiol. 1995 Jan;268(1 Pt 1):L144-51. doi: 10.1152/ajplung.1995.268.1.L144.
Cultured alveolar type II cells and alveolar macrophages were found to secrete colony-stimulating factors (CSF) into the medium. Surfactant protein A (SP-A; 0.1-5 micrograms/ml) and bacterial lipopolysaccharide (LPS; 10-20 micrograms/ml) were found to upregulate the secretion of CSF (seven-fold) from these cells. However, a reversal of the stimulatory effect was observed when the two agents were added simultaneously to the cells. SP-A-enhanced phagocytosis of bacteria by alveolar macrophages was also inhibited by simultaneous addition of SP-A and LPS. Thus some biological activities attributed to either SP-A or LPS are inhibited in the simultaneous presence of the two agents. We therefore investigated the possibility of interaction and binding between SP-A and LPS molecules. Our biochemical data that include immunoblots and enzyme-linked immunosorbent assay support the notion that SP-A is capable of binding LPS, and this interaction is time and concentration dependent. The binding was partially inhibited (60%) by antibody to SP-A. The binding was calcium independent and was not affected by excess carbohydrates such as methyl alpha-D-mannopyranoside or heparin. Lipid A, the hydrophobic component of LPS, however, inhibited the SP-A-LPS interaction and also caused a partial reversal of the binding. Thus these results indicate that lipid A is associated with this binding. The biological implication of SP-A-LPS interaction, especially during inflammatory responses, is discussed.
研究发现，培养的肺泡Ⅱ型细胞和肺泡巨噬细胞可向培养基中分泌集落刺激因子（CSF）。表面活性蛋白A（SP-A；0.1 - 5微克/毫升）和细菌脂多糖（LPS；10 - 20微克/毫升）可上调这些细胞CSF的分泌（7倍）。然而，当将这两种物质同时添加到细胞中时，观察到刺激作用发生了逆转。同时添加SP-A和LPS也会抑制SP-A增强的肺泡巨噬细胞对细菌的吞噬作用。因此，在两种物质同时存在时，一些归因于SP-A或LPS的生物学活性会受到抑制。我们因此研究了SP-A和LPS分子之间相互作用及结合的可能性。我们包括免疫印迹和酶联免疫吸附测定在内的生化数据支持SP-A能够结合LPS这一观点，且这种相互作用具有时间和浓度依赖性。SP-A抗体可部分抑制（60%）这种结合。这种结合不依赖钙，且不受过量碳水化合物如α-D-甲基甘露糖苷或肝素的影响。然而，LPS的疏水成分脂多糖A可抑制SP-A-LPS相互作用，也会导致结合的部分逆转。因此，这些结果表明脂多糖A与这种结合有关。本文讨论了SP-A-LPS相互作用的生物学意义，尤其是在炎症反应期间。
