Chemical Sciences Division, Saha Institute of Nuclear Physics, 1/AF, Bidhannagar, Kolkata-700064, India.
Langmuir. 2011 Dec 20;27(24):15054-64. doi: 10.1021/la2030186. Epub 2011 Nov 16.
Membrane fusion is an essential process guiding many important biological events, which most commonly requires the aid of proteins and peptides as fusogenic agents. Small drug induced fusion at low drug concentration is a rare event. Only three drugs, namely, meloxicam (Mx), piroxicam (Px), and tenoxicam (Tx), belonging to the oxicam group of non steroidal anti-inflammatory drugs (NSAIDs) have been shown by us to induce membrane fusion successfully at low drug concentration. A better elucidation of the mechanism and the effect of different parameters in modulating the fusion process will allow the use of these common drugs to induce and control membrane fusion in various biochemical processes. In this study, we monitor the effect of lipid headgroup size mismatch in the bilayer on oxicam NSAIDs induced membrane fusion, by introducing dimyristoylphosphatidylethanolamine (DMPE) in dimyristoylphosphatidylcholine (DMPC) small unilamellar vesicles (SUVs). Such headgroup mismatch affects various lipid parameters which includes inhibition of trans-bilayer motion, domain formation, decrease in curvature, etc. Changes in various lipidic parameters introduce defects in the membrane bilayer and thereby modulate membrane fusion. SUVs formed by DMPC with increasing DMPE content (10, 20, and 30 mol %) were used as simple model membranes. Transmission electron microscopy (TEM) and differential scanning calorimetry (DSC) were used to characterize the DMPC-DMPE mixed vesicles. Fluorescence assays were used to probe the time dependence of lipid mixing, content mixing, and leakage and also used to determine the partitioning of the drugs in the membrane bilayer. How the inhibition of trans-bilayer motion, heterogeneous distribution of lipids, decrease in vesicle curvature, etc., arising due to headgroup mismatch affect the fusion process has been isolated and identified here. Mx amplifies these effects maximally followed by Px and Tx. This has been correlated to the enhanced partitioning of the hydrophobic Mx compared to the more hydrophilic Px and Tx in the mixed bilayer.
膜融合是指导许多重要生物事件的基本过程，通常需要蛋白质和肽作为融合剂的帮助。在低药物浓度下，药物诱导的小融合是一种罕见的事件。只有三种药物，即美洛昔康（Mx）、吡罗昔康（Px）和替诺昔康（Tx），属于非甾体抗炎药（NSAIDs）的昔康类，已被证明可在低药物浓度下成功诱导膜融合。更好地阐明机制和不同参数对融合过程的影响将允许使用这些常见药物来诱导和控制各种生化过程中的膜融合。在这项研究中，我们通过在二肉豆蔻酰磷脂酰胆碱（DMPC）小单层囊泡（SUV）中引入二肉豆蔻酰磷脂酰乙醇胺（DMPE），监测双层脂质头基大小不匹配对昔康 NSAIDs 诱导的膜融合的影响。这种头基不匹配会影响各种脂质参数，包括跨双层运动的抑制、域形成、曲率降低等。各种脂质参数的变化会在膜双层中产生缺陷，从而调节膜融合。用含有越来越多的 DMPE（10、20 和 30 mol%）的 DMPC 形成 SUV，作为简单的模型膜。使用透射电子显微镜（TEM）和差示扫描量热法（DSC）来表征 DMPC-DMPE 混合囊泡。荧光分析用于探测脂质混合、内容混合和泄漏的时间依赖性，并用于确定药物在膜双层中的分配。由于头基不匹配而导致的跨双层运动抑制、脂质不均匀分布、囊泡曲率降低等如何影响融合过程在这里被分离和确定。与更亲水的 Px 和 Tx 相比，Mx 抑制跨双层运动的能力最强，随后是 Px 和 Tx。这与疏水性 Mx 在混合双层中的分配增强有关，而 Px 和 Tx 的分配增强。
