Xenometabolome of Early-Life Stage Salmonids Exposed to 6PPD-Quinone

Abstract N -(1,3-Dimethylbutyl)- N′ -phenyl- p -phenylenediamine-quinone (6PPD-Q) is a ubiquitous transformation product (TP) derived from the rubber tire antioxidant N -(1,3-Dimethylbutyl)- N′ -phenyl- p -phenylenediamine (6PPD) and is acutely toxic to certain species of Salmonidae . Not all salmonids are sensitive to acute lethality caused by 6PPD-Q, with 6PPD-Q potency varying by several orders of magnitude among teleosts. The main driver(s) of species sensitivity differences is (are) a pressing question, with one area of interest examining whether differences in teleosts ability to biotransform and detoxify 6PPD-Q could be a key factor. This study utilized liquid-chromatography high-resolution mass spectrometry (LC-HRMS) to assess biotransformation and metabolome-wide effects of 6PPD-Q on early-life stage salmonids, including two sensitive species, rainbow trout ( Oncorhynchus mykiss ) and lake trout ( Salvelinus namaycush ), and one tolerant species, brown trout ( Salmo trutta ). Three phase I TPs and seven phase II TPs were detected, with differences in peak areas revealing that brown trout had the greatest ability to detoxify 6PPD-Q. Monohydroxylated TPs were verified using co-developed analytical standards that will be of use for future biomonitoring and exposure assessment. Several endogenous metabolites were found to be dysregulated in rainbow and lake trout, indicative of mitochondrial dysfunction, altered metabolism, and disrupted membrane permeability. Results of this study indicate a difference in the biotransformation capability of 6PPD-Q among Salmonidae fish species and subsequent unique metabolome responses. Graphical Abstract Synopsis Inter-species salmonid differences in the biotransformation capability of 6PPD-Q leads to sensitivity variability and subsequent unique metabolome responses.