Abdollahpour Nooshin, Soheili Vahid, Saberi Mohammad Reza, Chamani Jamshidkhan
Department of Biology, Faculty of Sciences, Young Researchers and Elite Club, Islamic Azad University-Mashhad Branch, Mashhad, Iran.
Department of Drug Control, School of Pharmacy, Mashhad University of Medical Sciences, Mashhad, Iran.
Eur J Drug Metab Pharmacokinet. 2016 Dec;41(6):705-721. doi: 10.1007/s13318-015-0297-y.
Human serum albumin (HSA) is the most frequent protein in blood plasma. Albumin transports various compounds, preserves osmotic pressure, and buffers pH. A unique feature of albumin is its ability to bind drugs and other bioactive molecules. However, it is important to consider binary and ternary systems of two pharmaceuticals to estimate the effect of the first drug on the second one and physicochemical properties.
Different techniques including time-resolved, second-derivative and anisotropy fluorescence spectroscopy, resonance light scattering (RLS), critical induced aggregation concentration (C ), particle size, zeta potential and stability analysis were employed in this assessment to elucidate the binding behavior of Amlodipine and Aspirin to HSA. Moreover, isothermal titration calorimetric techniques were performed and the QSAR properties were applied to analyze the hydration energy and log P. Multiple sequence alignments were also used to predict the structure and biological characteristics of the HSA binding site.
Time-resolved fluorescence spectroscopy showed interaction of both drugs to HSA based on a static quenching mechanism. Subsequently, second-derivative fluorescence spectroscopy presented different values of parameter H in binary and ternary systems, which were suggested that tryptophan was in a more polar environment in the ternary system than in a binary system. Moreover, the polydispersity index and results from mean number measurements revealed that the presence of the second drug caused a decrease in the stability of systems and increased the heterogeneity of complex. It is also, observed that the gradual addition of HSA has led to a marked increase in fluorescence anisotropy (r) of Amlodipine and Aspirin which can be suggested that the drugs were located in a restricted environment of the protein as confirmed by Red Edge Excitation Shift (REES) studies. The isothermal titration calorimetric technique demonstrated that the interaction of the drugs with HSA was an enthalpically-driven process.
The present experiment showed that the binding of Amlodipine and Aspirin to HSA induced a conformational change of HSA. It was also identified that the protein binding of the first drug could be affected by the second drug. Such results can be of great use for understanding the pharmacokinetic and pharmacodynamic mechanisms of drugs.
人血清白蛋白（HSA）是血浆中最常见的蛋白质。白蛋白运输各种化合物，维持渗透压并缓冲pH值。白蛋白的一个独特特性是其结合药物和其他生物活性分子的能力。然而，考虑两种药物的二元和三元体系以评估第一种药物对第二种药物的影响以及物理化学性质非常重要。
本评估采用了不同的技术，包括时间分辨、二阶导数和各向异性荧光光谱、共振光散射（RLS）、临界诱导聚集浓度（C）、粒径、zeta电位和稳定性分析，以阐明氨氯地平和阿司匹林与HSA的结合行为。此外，进行了等温滴定量热技术，并应用定量构效关系（QSAR）性质分析水合能和log P。还使用了多序列比对来预测HSA结合位点的结构和生物学特征。
时间分辨荧光光谱显示两种药物基于静态猝灭机制与HSA相互作用。随后，二阶导数荧光光谱在二元和三元体系中呈现出不同的参数H值，这表明在三元体系中色氨酸所处的环境比二元体系中更具极性。此外，多分散指数和平均数量测量结果表明，第二种药物的存在导致体系稳定性降低，复合物的异质性增加。还观察到，逐渐加入HSA导致氨氯地平和阿司匹林的荧光各向异性（r）显著增加，这表明药物位于蛋白质的受限环境中，红边激发位移（REES）研究证实了这一点。等温滴定量热技术表明，药物与HSA的相互作用是一个焓驱动的过程。
本实验表明，氨氯地平和阿司匹林与HSA的结合诱导了HSA的构象变化。还发现第一种药物的蛋白质结合可能受到第二种药物的影响。这些结果对于理解药物的药代动力学和药效学机制可能非常有用。
