Kerdous Rachid, Heuvingh Julien, Bonneau Stéphanie
Université Pierre et Marie Curie, ANBioΦ, FRE3207 CNRS, 4 place Jussieu, Paris, France.
Biochim Biophys Acta. 2011 Dec;1808(12):2965-72. doi: 10.1016/j.bbamem.2011.08.002. Epub 2011 Aug 8.
Photochemical internalization is a drug delivery technology employing a photo-destabilization of the endosomes and the photo-controlled release of endocyted macromolecules into the cytosol. This effect is based on the ability of some photosensitizers to interact with endosomal membranes and to photo-induce damages leading to its breakdown. The permeabilization efficiency is not quantitatively related to the importance of the damages, but to their asymmetric repartition within the leaflets. Using unilamellar vesicles and a chlorin, we studied the effect of the membrane's cholesterol content on its photo-permeabilization. First, the affinity of the chlorin for membranes was studied. Then, we asymmetrically oxidized the membranes. For DOPC/CHOL GUVs, we observed different shape transitions, in accordance with an increase followed by a decrease of the membrane effective curvature. These modifications are delayed by the cholesterol. Finally, the photo-permeabilization of GUVs occurs, corresponding to a pore formation due to the membrane tension, resulting from vesicles buddings. Cholesterol-rich GUVs permeabilization occurs after a lag, and is less important. These results are interpreted regarding both (i) the cholesterol-induced tightening of the lipids, its consequences on physical parameters of the membrane and on oxidation rate and (ii) the suggested ability of cholesterol to flip rapidly and then to relax the differential density-based stress accumulated during membrane bending.
光化学内化是一种药物递送技术，它利用内体的光不稳定作用以及将内吞的大分子光控释放到细胞质中。这种效应基于某些光敏剂与内体膜相互作用并光诱导损伤导致其破裂的能力。通透效率与损伤的程度没有定量关系，而是与它们在小叶内的不对称分布有关。我们使用单层囊泡和二氢卟吩研究了膜胆固醇含量对其光通透作用的影响。首先，研究了二氢卟吩对膜的亲和力。然后，我们对膜进行不对称氧化。对于二油酰磷脂酰胆碱/胆固醇巨型单层囊泡（DOPC/CHOL GUVs），我们观察到不同的形状转变，这与膜有效曲率先增加后降低一致。这些修饰被胆固醇延迟。最后，GUVs发生光通透作用，这对应于由于囊泡出芽导致的膜张力而形成的孔。富含胆固醇的GUVs通透作用在有延迟后发生，且程度较小。这些结果从以下两方面进行了解释：（i）胆固醇引起的脂质收紧、其对膜物理参数和氧化速率的影响；（ii）胆固醇快速翻转并随后缓解膜弯曲过程中积累的基于密度差异的应力的假定能力。
