Effect of genetic variation on human cytochrome p450 reductase-mediated paraquat cytotoxicity.
Paraquat (1,1'-dimethyl-4,4'-bipyridylium dichloride) is a widely used herbicide and is highly toxic to human and animals. The mechanisms of paraquat toxicity involve the generation of superoxide anion through the process of redox cycling. NADPH-cytochrome P450 oxidoreductase (POR) has been reported to be a major enzyme for one-electron reduction of paraquat that initiates the redox cycling. Recently, a total of six missense variants of human POR have been identified in patients with discorded steroidogenesis. However, the effect of these genetic variations on POR-mediated paraquat toxicity is not known. Using the Flp-In Chinese hamster ovary (CHO) cells stably expressing either mouse or human POR and the cells with POR knockdown by siRNA, we confirmed that POR is responsible for paraquat-induced cytotoxicity. We further used this validated system to compare paraquat-induced toxicity among the cells that stably expressed wild-type human POR and its natural variants. While there was no difference in paraquat-induced toxicity between the cells expressing wild-type human POR and the Cys569Tyr variant, the toxicity in cells expressing all the other variants (Tyr181Asp, Ala287Pro, Arg457His, Val492Glu, and Val608Phe) was significantly decreased. Our results provide further evidence on the important role of POR in paraquat-induced toxicity and suggest that individuals carrying the functional variant POR alleles may have an altered susceptibility to paraquat exposure.
School of Public Health/Environmental and Occupational Health Sciences Institute, University of Medicine and Dentistry of New Jersey, Piscataway, New Jersey 08854, USA.
Jing-Fen
JF
Han
Shou-Lin
SL
Wang
Xiao-Yang
XY
He
Chun-Yong
CY
Liu
Jun-Yan
JY
Hong
D000483:Alleles; D000818:Animals; D016466:CHO Cells; D003001:Cloning, Molecular; D006224:Cricetinae; D014644:Genetic Variation; D006540:Herbicides / Q000633:toxicity*; D006801:Humans; D051379:Mice; D009251:NADPH-Ferrihemoprotein Reductase / Q000235:genetics / Q000378:metabolism*; D010269:Paraquat / Q000633:toxicity*; D034741:RNA, Small Interfering; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction
D006540:Herbicides; D034741:RNA, Small Interfering; D011994:Recombinant Proteins; D009251:NADPH-Ferrihemoprotein Reductase; D010269:Paraquat