Ahmad I, Perkins W R, Lupan D M, Selsted M E, Janoff A S
Liposome Company Inc., Princeton, NJ 08540, USA.
Biochim Biophys Acta. 1995 Jul 26;1237(2):109-14. doi: 10.1016/0005-2736(95)00087-j.
Indolicidin, a cationic tridecapeptide amide isolated from the granules of bovine neutrophils, has been found to possess potent antimicrobial activity in vitro but its nonselective toxicity could restrict its therapeutic utility. We found that the concentration at which indolicidin disrupts washed human red blood cell membranes coincided with the concentration at which indolicidin self associates. Because of a preponderance of hydrophobic residues, we believed that indolicidin would partition into liposomes which would restrict its exchange with biological tissues and consequently reduce its toxicity. Fluorescence spectroscopy of indolicidin added to 100 nm liposomes comprised of POPC, POPC/cholesterol (60:40 mol%), DPPC, or DPPC/cholesterol (60:40) revealed a large blue-shift and an increase in intensity of the emission profile indicating insertion into the bilayer. Of the lipids tested, POPC exhibited the highest degree of indolicidin binding as determined by fluorescence and encapsulation efficiency. By sequestering indolicidin within the lipid bilayer of 100 nm POPC liposomes we significantly reduced its toxicity to CHO/K1 cells. Likewise, the systemic toxicity of liposomal indolicidin in Balb/c mice was decreased dramatically relative to aqueous solutions; the maximum dose at which no deaths occurred was 0.4 mg/kg for free indolicidin versus 40 mg/kg for indolicidin-POPC. Because of this decrease in toxicity, we were able to administer liposomally encapsulated material at significantly higher concentrations than unencapsulated aqueous material and achieve efficacy in treating animals systemically infected with Aspergillus fumigatus. Liposomal but not free indolicidin was found to be effective in obtaining cures. This report is the first description of the in vivo therapeutic activity of a neutrophil-derived antimicrobial peptide and suggests that liposomal treatment modalities will provide effective strategies for endowing this class of compounds with pharmacological utility.
吲哚杀菌素是一种从牛中性粒细胞颗粒中分离出的阳离子十三肽酰胺，已发现它在体外具有强大的抗菌活性，但其非选择性毒性可能会限制其治疗用途。我们发现，吲哚杀菌素破坏洗涤过的人红细胞膜的浓度与其自身缔合的浓度一致。由于疏水残基占优势，我们认为吲哚杀菌素会分配到脂质体中，这将限制其与生物组织的交换，从而降低其毒性。添加到由POPC、POPC/胆固醇（60:40摩尔%）、DPPC或DPPC/胆固醇（60:40）组成的100纳米脂质体中的吲哚杀菌素的荧光光谱显示，发射谱有很大的蓝移且强度增加，表明其插入了双层膜中。在所测试的脂质中，通过荧光和包封效率测定，POPC表现出最高程度的吲哚杀菌素结合。通过将吲哚杀菌素隔离在100纳米POPC脂质体的脂质双层内，我们显著降低了其对CHO/K1细胞的毒性。同样，相对于水溶液，脂质体吲哚杀菌素在Balb/c小鼠中的全身毒性显著降低；无死亡发生的最大剂量，游离吲哚杀菌素为0.4毫克/千克，而吲哚杀菌素-POPC为40毫克/千克。由于毒性降低，我们能够以比未包封的水性材料显著更高的浓度给予脂质体包封的材料，并在治疗全身感染烟曲霉的动物中取得疗效。发现脂质体而非游离的吲哚杀菌素能有效治愈疾病。本报告首次描述了中性粒细胞衍生的抗菌肽的体内治疗活性，并表明脂质体治疗方式将为赋予这类化合物药理效用提供有效的策略。
