New mechanistic insights into halogen-dependent cytotoxic pattern of monohaloacetamide disinfection byproducts
Shaoyang Hu, Xiangxiang Li, Tingting Gong, Guang Tian, Shuqi Guo, Chengqian Huo, Jingqiang Wan, Rutao Liu
Abstract
As highly toxic nitrogenous disinfection byproducts (DBPs), monohaloacetamides (monoHAcAms) generally exhibited a cytotoxic rank order of iodoacetamide ˃ bromoacetamide ˃ chloroacetamide . However, the mechanisms underlying the halogen-dependent cytotoxic pattern remain largely veiled as yet. In this work, oxidative stress/damage levels in monoHAcAm-treated Chinese hamster ovary cells were thoroughly analyzed, and binding interactions between monoHAcAms and antioxidative enzyme Cu/Zn-superoxide dismutase (Cu/Zn-SOD) were investigated by multiple spectroscopic techniques and molecular docking . Upon exposure to monoHAcAms, the intracellular levels of key biomarkers associated with oxidative stress/damage, including reactive oxygen species , malondialdehyde , lactate dehydrogenase , 8-hydroxy-2-deoxyguanosine, cell apoptosis , and G 1 cell cycle arrest, were all significantly increased in a dose-response manner with the same halogen-dependent rank order as their cytotoxicity. Moreover, this rank order was also determined to be applicable to the monoHAcAm-induced alterations in the conformation, secondary structure , and activity of Cu/Zn-SOD, the microenvironment surrounding aromatic amino acid residues in Cu/Zn-SOD, as well as the predicted binding energy of SOD-monoHAcAm interactions. Our results revealed that the halogen-dependent cytotoxic pattern of monoHAcAms was attributed to their differential capacity to induce oxidative stress/damage and their interaction with antioxidative enzyme , which contribute to a better understanding of the halogenated DBP-induced toxicological mechanisms .