Tianjin Key Laboratory of Environment, Nutrition and Public Health, Tianjin 300070, PR China; Department of Occupational and Environmental Health, School of Public Health, Tianjin Medical University, Tianjin 300070, PR China; National Demonstration Center for Experimental Preventive Medicine Education (Tianjin Medical University), Tianjin 300070, PR China.
Department of Toxicology and Sanitary Chemistry, School of Public Health, Tianjin Medical University, Tianjin 300070, PR China.
Environ Pollut. 2020 Aug;263(Pt B):114521. doi: 10.1016/j.envpol.2020.114521. Epub 2020 Apr 5.
Polycyclic aromatic hydrocarbons (PAHs) are known as one of the ubiquitous environmental pollutants caused by unavoidable combustion of by-products. Despite decades of research on adverse health effects towards humans, the effects of PAHs and their hydroxylated metabolites (OH-PAHs) on UDP-glucuronosyltransferases (UGTs) remain unclear. This study aimed to investigate inhibitory effects with structure-dependence of 14 PAHs and OH-PAHs towards the activity of 7 isoforms of UGTs using in vitro recombinant UGTs-catalyzed glucuronidation of 4-methylumbelliferone (4-MU) as the probe reaction. PAHs and OH-PAHs showed inhibitory effects towards different UGT isoforms with different extents. For inhibition kinetics determination, 1-HONAP, 4-HOPHE, 9-HOPHE, and 1-HOPYR were utilized as the representative compounds, and UGT1A6, UGT1A9 and UGT2B7 were chosen as the three representative UGT isoforms. The inhibitory effects of 4-HOPHE, 9-HOPHE and 1-HOPYR on three above UGT isoforms were the same: UGT1A9>UGT1A6>UGT2B; for 1-HONAP, that is UGT1A6>UGT1A9>UGT2B. Molecular docking methods were utilized to find the activity cavity of UGT1A9 and UGT2B7 binding with 1-HONAP and 1-HOPYR. Hydrogen bonds and hydrophobic contacts were mainly contributors to their interactions. In vitro-in vivo extrapolation (IVIVE) showed that high in vivo inhibition possibility exists for the inhibition of OH-PAHs on UGTs. All the results provide a novel viewpoint for an explanation of the toxicity of PAHs and OH-PAHs.
多环芳烃（PAHs）是一种普遍存在的环境污染物，由不可避免的副产品燃烧产生。尽管已经对其对人类健康的不良影响进行了数十年的研究，但 PAHs 及其羟基化代谢物（OH-PAHs）对尿苷二磷酸葡萄糖醛酸转移酶（UGTs）的影响仍不清楚。本研究旨在通过体外重组 UGT 催化 4-甲基伞形酮（4-MU）的葡萄糖醛酸化反应，用探针反应，研究 14 种 PAHs 和 OH-PAHs 的结构依赖性对 7 种 UGT 同工酶活性的抑制作用。PAHs 和 OH-PAHs 对不同的 UGT 同工酶表现出不同程度的抑制作用。为了确定抑制动力学，选择 1-HONAP、4-HOPHE、9-HOPHE 和 1-HOPYR 作为代表性化合物，选择 UGT1A6、UGT1A9 和 UGT2B7 作为三种代表性 UGT 同工酶。4-HOPHE、9-HOPHE 和 1-HOPYR 对三种以上 UGT 同工酶的抑制作用相同：UGT1A9>UGT1A6>UGT2B；对于 1-HONAP，是 UGT1A6>UGT1A9>UGT2B。利用分子对接方法找到了 UGT1A9 和 UGT2B7 与 1-HONAP 和 1-HOPYR 结合的活性腔。氢键和疏水接触是它们相互作用的主要贡献者。体外-体内外推（IVIVE）表明，OH-PAHs 对 UGTs 的抑制作用在体内具有很高的抑制可能性。所有结果为解释 PAHs 和 OH-PAHs 的毒性提供了一个新的视角。
