Horowitz A T, Barenholz Y, Gabizon A A
Department of Oncology, Hadassah University Hospital, Jerusalem, Israel.
Biochim Biophys Acta. 1992 Aug 24;1109(2):203-9. doi: 10.1016/0005-2736(92)90084-y.
We have investigated the in vitro cytotoxicity of free doxorubicin (DOX) and liposome-entrapped DOX (L-DOX) against a human ovarian carcinoma cell line (OV-1063) using a colorimetric assay. DOX was encapsulated in the inner water phase of liposomes by an ammonium sulfate-generated proton gradient. Liposomes varied in phospholipid composition but were of a similar size. It was found that the cytotoxic activity of L-DOX is substantially decreased when liposomes containing phospholipids of high phase-transition temperature (Tm) are used. The type of negatively charged headgroup did not have any significant influence on the cytotoxicity observed. Experiments using resin beads that bind free and protein-bound DOX, but do not interact with L-DOX, indicated that the cytotoxic effect is mediated by the release of drug from the liposomes into the extracellular medium; no evidence was found for direct cellular uptake of liposome-encapsulated drug. The use of the ionophore nigericin to induce the release of DOX from high-Tm liposomes increased cytotoxicity to a level comparable to free DOX, suggesting that 'remote release' techniques may substantially improve the efficiency of liposome-mediated drug delivery and allow for the full exploitation of the favorable pharmacokinetic properties of specific high-Tm formulations.
我们使用比色法研究了游离阿霉素（DOX）和脂质体包裹的阿霉素（L-DOX）对人卵巢癌细胞系（OV-1063）的体外细胞毒性。通过硫酸铵产生的质子梯度将DOX包裹在脂质体的内水相中。脂质体的磷脂组成不同，但大小相似。结果发现，当使用含有高相变温度（Tm）磷脂的脂质体时，L-DOX的细胞毒性活性会大幅降低。带负电荷的头基类型对观察到的细胞毒性没有任何显著影响。使用能结合游离和与蛋白质结合的DOX但不与L-DOX相互作用的树脂珠进行的实验表明，细胞毒性作用是由药物从脂质体释放到细胞外介质介导的；没有发现脂质体包裹药物直接被细胞摄取的证据。使用离子载体尼日利亚菌素诱导DOX从高Tm脂质体中释放，可使细胞毒性增加到与游离DOX相当的水平，这表明“远程释放”技术可能会显著提高脂质体介导的药物递送效率，并充分利用特定高Tm制剂有利的药代动力学特性。
