文献类型：期刊文献

英文题名：Nitroreductase Increases Menadione-Mediated Oxidative Stress in Aspergillus nidulans

作者：Zhou, Yao[1];Lv, Hangya[1];Li, Haoxiang[1];Li, Jingyi[1];Yan, Yunfeng[1];Liu, Feiyun[1];Hao, Wenliang[2];Zhou, Zhemin[2];Wang, Ping[1];Zhou, Shengmin[1]

机构：[1]East China Univ Sci & Technol, Sch Biotechnol, State Key Lab Bioreactor Engn, Shanghai, Peoples R China;[2]Jiangnan Univ, Key Lab Ind Biotechnol, Minist Educ, Sch Biotechnol, Wuxi, Jiangsu, Peoples R China

年份：2021

卷号：87

期号：24

外文期刊名：APPLIED AND ENVIRONMENTAL MICROBIOLOGY

收录：;EI(收录号：20215011330330);WOS:【SCI-EXPANDED(收录号:WOS:000722388800022)】；

基金：This study was funded by the International S&T Innovation Cooperation Key Project (2017YFE0129600), the National Natural Science Foundation of China (21672065, 22077032, and 21636003), the National Major Science and Technology Projects of China (2019ZX09739001), the Fundamental Research Funds for the Central Universities (22221818014), and the 111 Project (B18022).

语种：英文

外文关键词：Aspergillus nidulans; menadione; nitroreductase; oxidative stress; ROS resistance

摘要：Nitroreductases (NTRs) catalyze the reduction of a wide range of nitrocompounds and quinones using NAD(P)H. Although the physiological functions of these enzymes remain obscure, a tentative function of resistance to reactive oxygen species (ROS) via the detoxification of menadione has been proposed. This suggestion is based primarily on the transcriptional or translational induction of an NTR response to menadione rather than on convincing experimental evidence. We investigated the performance of a fungal NTR from Aspergillus nidulans (AnNTR) exposed to menadione to address the question of whether NTR is really an ROS defense enzyme. We confirmed that AnNTR was transcriptionally induced by external menadione. We observed that menadione treatment generated cytotoxic levels of O-2(center dot-), which requires well-known antioxidant enzymes such as superoxide dismutase, catalase, and peroxiredoxin to protect A. nidulans against menadione-derived ROS stress. However, AnNTR was counterproductive for ROS defense, since knocking out AnNTR decreased the intracellular O-2(center dot-) levels, resulting in fungal viability higher than that of the wild type. This observation implies that AnNTR may accelerate the generation of O-2(center dot-) from menadione. Our in vitro experiments indicated that AnNTR uses NADPH to reduce menadione in a single-electron reaction, and the subsequent semiquinone-quinone redox cycling resulted in O-2(center dot-) generation. We demonstrated that A. nidulans nitroreductase should be an ROS generator, but not an ROS scavenger, in the presence of menadione. Our results clarified the relationship between nitroreductase and menadione-derived ROS stress, which has long been ambiguous. IMPORTANCE Menadione is commonly used as an O-2(center dot-) generator in studies of oxidative stress responses. However, the precise mechanism through which menadione mediates cellular O-2(center dot-) generation, as well as the way in which cells respond, remains unclear. Elucidating these events will have important implications for the use of menadione in biological and medical studies. Our results show that the production of Aspergillus nidulans nitroreductase (AnNTR) was induced by menadione. However, the accumulated AnNTR did not protect cells but instead increased the cytotoxic effect of menadione through a single-electron reduction reaction. Our finding that nitroreductase is involved in the menadione-mediated O-2(center dot-) generation pathway has clarified the relationship between nitroreductase and menadione-derived ROS stress, which has long been ambiguous.