Benatti Carlos R, Lamy M Teresa, Epand Richard M
Instituto de Física, Universidade de S. Paulo, CP 66318, CEP 05315-970, S. Paulo, SP, Brazil.
Biochim Biophys Acta. 2008 Apr;1778(4):844-53. doi: 10.1016/j.bbamem.2007.12.011. Epub 2007 Dec 23.
Cationic amphiphiles used for transfection can be incorporated into biological membranes. By differential scanning calorimetry (DSC), cholesterol solubilization in phospholipid membranes, in the absence and presence of cationic amphiphiles, was determined. Two different systems were studied: 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC)+cholesterol (1:3, POPC:Chol, molar ratio) and 1-palmitoyl-2-oleoyl-sn-glycero-3-[phospho-l-serine] (POPS)+cholesterol (3:2, POPS:Chol, molar ratio), which contain cholesterol in crystallite form. For the zwitterionic lipid POPC, cationic amphiphiles were tested, up to 7 mol%, while for anionic POPS bilayers, which possibly incorporate more positive amphiphiles, the fractions used were higher, up to 23 mol%. 1,2-dioleoyl-3-trimethylammonium-propane (DOTAP) and DOTAP in methyl sulfate salt form (DOTAPmss) were found to cause a small decrease on the enthalpy of the cholesterol transition of pure cholesterol aggregates, possibly indicating a slight increase on the cholesterol solubilization in POPC vesicles. With the anionic system POPS:Chol, the cationic amphiphiles dramatically change the cholesterol crystal thermal transition, indicating significant changes in the cholesterol aggregates. For structural studies, phospholipids spin labeled at the 5th or 16th carbon atoms were incorporated. In POPC, at the bilayer core, the cationic amphiphiles significantly increase the bilayer packing, decreasing the membrane polarity, with the cholesterol derivative 3 beta-[N-(N',N'-dimethylaminoethane)-carbamoyl]-cholesterol (DC-chol) displaying a stronger effect. In POPS and POPS:Chol, DC-chol was also found to considerably increase the bilayer packing. Hence, exogenous cationic amphiphiles used to deliver nucleic acids to cells can change the bilayer packing of biological membranes and alter the structure of cholesterol crystals, which are believed to be the precursors to atherosclerotic lesions.
用于转染的阳离子两亲物可整合到生物膜中。通过差示扫描量热法（DSC），测定了在不存在和存在阳离子两亲物的情况下磷脂膜中胆固醇的溶解情况。研究了两种不同的体系：1-棕榈酰-2-油酰-sn-甘油-3-磷酸胆碱（POPC）+胆固醇（1:3，POPC:胆固醇，摩尔比）和1-棕榈酰-2-油酰-sn-甘油-3-[磷酰-L-丝氨酸]（POPS）+胆固醇（3:2，POPS:胆固醇，摩尔比），它们含有微晶形式的胆固醇。对于两性离子脂质POPC，测试了高达7摩尔%的阳离子两亲物，而对于可能掺入更多正性两亲物的阴离子POPS双层膜，使用的比例更高，高达23摩尔%。发现1,2-二油酰-3-三甲基铵丙烷（DOTAP）和硫酸甲酯盐形式的DOTAP（DOTAPmss）会使纯胆固醇聚集体的胆固醇转变焓略有降低，这可能表明POPC囊泡中胆固醇的溶解度略有增加。在阴离子体系POPS:胆固醇中，阳离子两亲物显著改变了胆固醇晶体的热转变，表明胆固醇聚集体有显著变化。为了进行结构研究，掺入了在第5或16个碳原子处自旋标记的磷脂。在POPC中，在双层核心处，阳离子两亲物显著增加了双层堆积，降低了膜极性，胆固醇衍生物3β-[N-（N'，N'-二甲基氨基乙烷）-氨基甲酰]-胆固醇（DC-胆固醇）显示出更强的效果。在POPS和POPS:胆固醇中，也发现DC-胆固醇显著增加了双层堆积。因此，用于将核酸递送至细胞的外源性阳离子两亲物可改变生物膜的双层堆积并改变胆固醇晶体的结构，而胆固醇晶体被认为是动脉粥样硬化病变的前体。
