Wang Yi-run, Fang Qing, Hu Tao-ying, Liu Ying
Guang Pu Xue Yu Guang Pu Fen Xi. 2016 Nov;36(11):3789-95.
Isonicotinic acid hydrazide (Isoniazid, INH) is one of the most commonly used first-line anti-tuberculosis drugs, which has been reported that the high concentration of INH in human body can lead to epilepsy, liver function failure, and even death. Therefore, studying the potential binding effects of INH on the structure and activity of human serum albumin (HSA) and catalase (CAT) is very essential for evaluating its toxicity and side effect. In this paper, multi-spectroscopic and molecular docking methods were used to elucidate the patterns of INH to HSA and CAT under imitated physiological conditions. The inner filter effect of all fluorescence data in the paper was eliminated to get accurate binding parameters. The Stern-Volmer quenching constants (KSV) of both HSA-INH system and CAT-INH system inversely correlated with temperatures, demonstrating that INH quench the intrinsic fluorescence of HSA and CAT via static quenching. The conformational investigation of HSA and CAT through UV-visible absorption spectroscopy, synchronous fluorescence and circular dichroism (CD) showed that INH could change the micro-environment of tryptophan residues and reduced the α-helix content of protein. These results demonstrated that the binding of INH may lead to the loosening of protein skeleton, which which may affect its physiological function. The results of molecular docking revealed that the INH was located in Sudlow’s site I of HSA. And INH bound to CAT at a cavity among the wrapping domain helical domain and β-barrel, which resulted in the inhibition of CAT activity. In addition, Levofloxacin (LVFX) is a new effective and safe second-line anti-tuberculosis drugs and can improve the curative effect on anti-TB by using with other anti-TB drugs, the result of Hill’s coefficients (nH) about synergy between INH and proved that LVFX promoted the interaction of HSA with INH. Moreover, according to the CD spectra, synergy between INH and LVFX changed the conformation of HSA and the amount of α-helix decreased about 7.9%. This work will provide important insights into the binding and toxicity mechanism of INH to HSA and CAT in vivo and is expected to be helpful in evaluating the essential information for using the INH safely.
异烟肼（Isoniazid，INH）是最常用的一线抗结核药物之一，据报道，人体中高浓度的异烟肼会导致癫痫、肝功能衰竭，甚至死亡。因此，研究异烟肼对人血清白蛋白（HSA）和过氧化氢酶（CAT）的结构和活性的潜在结合作用，对于评估其毒性和副作用非常重要。本文采用多光谱和分子对接方法，阐明了在模拟生理条件下异烟肼与HSA和CAT的作用模式。消除了本文中所有荧光数据的内滤效应，以获得准确的结合参数。HSA-INH体系和CAT-INH体系的斯特恩-沃尔默猝灭常数（KSV）均与温度呈负相关，表明异烟肼通过静态猝灭作用猝灭了HSA和CAT的内源荧光。通过紫外可见吸收光谱、同步荧光和圆二色性（CD）对HSA和CAT的构象研究表明，异烟肼可以改变色氨酸残基的微环境，并降低蛋白质的α-螺旋含量。这些结果表明，异烟肼的结合可能导致蛋白质骨架的松弛，这可能会影响其生理功能。分子对接结果表明，异烟肼位于HSA的Sudlow位点I。异烟肼在包裹结构域、螺旋结构域和β-桶之间的一个腔中与CAT结合，从而导致CAT活性受到抑制。此外，左氧氟沙星（LVFX）是一种新型有效且安全的二线抗结核药物，与其他抗结核药物联合使用可提高抗结核疗效，关于异烟肼与左氧氟沙星协同作用的希尔系数（nH）结果证明，左氧氟沙星促进了HSA与异烟肼的相互作用。此外，根据CD光谱，异烟肼与左氧氟沙星的协同作用改变了HSA的构象，α-螺旋含量减少了约7.9%。这项工作将为异烟肼在体内与HSA和CAT的结合及毒性机制提供重要见解，有望有助于评估安全使用异烟肼的必要信息。
