Effect of bacterial endotoxin on the transmembrane electrical potential and plasma membrane fluidity of human monocytes.
Effect of bacterial endotoxin on the transmembrane electrical potential and plasma membrane fluidity of human monocytes.
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细菌内毒素对人单核细胞跨膜电位和质膜流动性的影响。
DOI：
10.1016/0005-2736(85)90466-3
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发表时间：
1985
期刊：
影响因子：
--
通讯作者：
Sullivan,R
中科院分区：
文献类型：
--
作者：
Larsen,NE;Enelow,RI;Simons,ER;Sullivan,R
为了深入了解细菌内毒素与人类单核细胞表面的物理相互作用，我们研究了伤寒沙门氏菌内毒素和脂质A对这些细胞质膜两个功能特性的影响：(1)跨膜电位和(2)脂质双分子层的流动性。利用荧光亲脂性阳离子探针3,3 ' -二丙基硫代二碳菁（dii - s - c3(5)）监测跨膜电位，我们发现内毒素和脂质A都没有诱导单核细胞的质膜去极化，也没有阻碍其对肉豆酸酯酚的去极化反应。通过将悬挂在含有增加浓度钾离子（K+）的培养基中的di-S-C3(5)标记的细胞暴露于缬霉素中，分析单核细胞的静息跨膜电位，对照细胞和内毒素预处理细胞的反应没有差异。接下来，我们通过监测1,6-二苯基-1,3,5-己三烯的荧光强度来检测内毒素和脂质A对单核细胞质膜流动性的影响。通过量化该薄膜探针在8 ~ 56°C之间发射的平行和垂直偏振光的强度，分子各向异性测量用于鉴定质膜碳氢化合物区域内温度依赖的相变，并估计细胞暴露于内毒素或脂质a之前和之后脂质双分子层的相对微粘度。单核细胞与内毒素或脂质A的预孵育似乎增加了细胞膜的表观微粘度和脂质双分子层的秩序，这反映在其流动活化能的降低上。我们的数据表明，当内毒素分子接触单核细胞表面时，脂质A片段似乎被合并到质膜中，增加了脂质双分子层的微粘度，而不会显著改变其离子渗透性。因此，我们得出结论，内毒素对单核细胞的代谢激活与膜去极化无关，也不是由膜去极化引起的。
In order to gain insight into the physical interaction between bacterial endotoxins and the surface of human monocytes, we investigated the effects ofSalmonella typhiendotoxin and lipid A on two functional properties of the plasma membrane of these cells: (1) the transmembrane electrical potential and (2) the fluidity of the lipid bilayer. Using the fluorescent lipophilic cationic probe 3,3′-dipropylthiodicarbocyanine (di-S-C3(5)) to monitor the transmembrane electrical potential, we found that neither endotoxin nor lipid A induced depolarization of the monocyte's plasma membrane or impeded its ability to undergo depolarization in response to phorbol myristate acetate. When the resting transmembrane potential of the monocyte was analyzed by exposing di-S-C3(5)-labeled cells suspended in media containing incremental concentrations of potassium ion (K+) to valinomycin, no difference between the response of control cells and cells pretreated with endotoxin was noted. We next examined the effect of endotoxin and lipid A on the fluidity of the monocyte's plasma membrane by monitoring the intensity of the fluorescence of 1,6-diphenyl-1,3,5-hexatriene. By quantifying the intensity of parallel and perpendicular polarized light emitted by this membrane-embedded probe between 8 and 56°C, measurements of molecular anisotropy were used to identify temperature-dependent phase transitions within the hydrocarbon region of the plasma membrane and to estimate the relative microviscosity of the lipid bilayer before and after exposing the cells to endotoxin or lipid A. Although the temperature at which phase transitions occurred was the same in all experimental groups of cells, preincubation of monocytes with either endotoxin or lipid A appeared to increase both the apparent microviscosity of the cell membrane and the order of the lipid bilayer as reflected by a decrease in its flow-activation energy. Our data indicate that when endotoxin molecules contact the surface of the monocyte, the lipid A moiety appears to become incorporated into the plasma membrane, increasing the microviscosity of the lipid bilayer without significantly altering its ionic permeability. We therefore conclude that the metabolic activation of monocytes by endotoxin is not coupled to, or initiated by, membrane depolarization.