DDAB (6,8-dichloro-9,9-dimethyl-7-oxo-7,9-dihydroacridin-2-yl benzoate) is a newly developed near-infrared fluorescent probe for human carboxylesterase 2 (hCE2), exhibiting high specificity and good reactivity for real-time monitoring the enzymatic activities of hCE2 in complex biological systems. In order to explore the applicability of DDAB in commonly used animal species, the interspecies difference in DDAB hydrolysis was carefully investigated by using liver microsomes from human and five experimental animals including mouse, rat, dog, minipig and monkey. Metabolite profiling demonstrated that DDAB hydrolysis could be catalyzed by all tested liver microsomes from different animals but displayed significant difference in the reaction rate. Chemical inhibition assays demonstrated that carboxylesterases (CEs) were the major enzymes involved in DDAB hydrolysis in all tested liver microsomes, indicating that DDAB was a selective substrate of CEs in a variety of mammals. However, the differential effects of loperamide (LPA, a specific inhibitor against hCE2) on DDAB hydrolysis among various species were observed. The apparent kinetic parameters and the maximum intrinsic clearances (CLmax) for DDAB hydrolysis in liver microsomes from different animals were determined, and the order of CLmax values for the formation of DDAO was CyLM>MLM≈PLM>RLM>HLM≈DLM. These findings were helpful for the rational use of DDAB as an imaging tool for CE2 in different mammals, as well as for translational researches on the function of mammalian CEs and CE2-associated drug-drug interactions.

中文翻译：

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不同物种肝脏微粒体中DDAO苯甲酸酯的比较代谢。

DDAB（6,8-dichloro-9,9-dimethyl-7-oxo-7,9-dihydroacridin-2-yl benzoate）是一种新开发的针对人羧酸酯酶2（hCE2）的近红外荧光探针，具有很高的特异性和实时监测复杂生物系统中hCE2酶活性的良好反应性。为了探索DDAB在常用动物物种中的适用性，使用人和五种实验动物（包括小鼠，大鼠，狗，小型猪和猴子）的肝微粒体仔细研究了DDAB水解的种间差异。代谢物谱分析表明，来自不同动物的所有测试肝微粒体均可以催化DDAB水解，但反应速率存在显着差异。化学抑制分析表明，在所有测试的肝微粒体中，羧酸酯酶（CEs）是参与DDAB水解的主要酶，这表明DDAB是多种哺乳动物中CEs的选择性底物。但是，观察到了洛哌丁胺（LPA，一种针对hCE2的特异性抑制剂）对DDAB水解的不同影响。确定了不同动物肝脏微粒体中DDAB水解的表观动力学参数和最大内在清除率（CLmax），形成DDAO的CLmax值的顺序为CyLM>MLM≈PLM> RLM>HLM≈DLM。这些发现有助于合理使用DDAB作为CE2在不同哺乳动物中的成像工具，以及对哺乳动物CEs的功能和与CE2相关的药物相互作用的转化研究。