Simberg Dmitri, Weiss Aryeh, Barenholz Yechezkel
Laboratory of Membrane and Liposome Research, Department of Biochemistry, Hebrew University-Hadassah Medical School, Jerusalem 91120, Israel.
Hum Gene Ther. 2005 Sep;16(9):1087-96. doi: 10.1089/hum.2005.16.1087.
There are many indications that interaction of serum proteins with intravenously injected cationic lipoplexes disturbs lipofection in vitro and in vivo. However, transfection with certain lipid compositions such as N-[1- (2,3-dioleoyloxy)propyl]-N,N,N-trimethylammonium chloride (DOTAP)/cholesterol appears to be more resistant to serum and more efficacious. We investigated the mechanism of interaction between fluorescently labeled lipoplexes of the above composition and fluorescently labeled serum proteins. Fluorescence resonance energy transfer measurements in vitro indicate that serum proteins interact instantly and closely with the DOTAP/cholesterol lipoplexes. In accord with this, preinjection of fluorescently labeled serum into mice before injection of lipoplexes showed an immediate association of proteins with lipoplexes. Serum proteins colocalized with the lipoplexes in the lung vasculature; however, they dissociated from the cationic lipid as soon as 1 hr postinjection, probably because of displacement of serum proteins from lipoplexes by extracellular proteoglycans. Indeed, this displacement was imitated by heparin, a typical glycosaminoglycan, and could be explained by the inability of weakly acidic serum proteins to neutralize the DOTAP/cholesterol electrical surface potential psi0. The stability of the cationic lipid psi0 in serum could be a key reason for the high lung association and transfection efficiency with this formulation.
有许多迹象表明，血清蛋白与静脉注射的阳离子脂质体复合物之间的相互作用会在体外和体内干扰脂质转染。然而，用某些脂质组合物如N-[1-(2,3-二油酰氧基)丙基]-N,N,N-三甲基氯化铵（DOTAP）/胆固醇进行转染似乎对血清更具抗性且更有效。我们研究了上述组合物的荧光标记脂质体复合物与荧光标记血清蛋白之间的相互作用机制。体外荧光共振能量转移测量表明，血清蛋白与DOTAP/胆固醇脂质体复合物立即紧密相互作用。与此一致的是，在注射脂质体之前向小鼠预先注射荧光标记血清显示蛋白与脂质体立即结合。血清蛋白在肺血管系统中与脂质体共定位；然而，注射后1小时它们就与阳离子脂质解离，这可能是由于细胞外蛋白聚糖将血清蛋白从脂质体上置换下来。事实上，肝素（一种典型的糖胺聚糖）模拟了这种置换，并且可以通过弱酸性血清蛋白无法中和DOTAP/胆固醇的表面电势ψ0来解释。阳离子脂质ψ0在血清中的稳定性可能是该制剂具有高肺结合率和转染效率的关键原因。
