Mechanistic Understanding of the Synergistic Potential of Azole Fungicides in the Aquatic Invertebrate Gammarus pulex

Abstract

Azole fungicides are known inhibitors of the important enzyme class cytochrome P450 monooxygenases (CYPs), thereby influencing the detoxification of co-occurring substances via biotransformation. This synergism in mixtures containing an azole has mostly been studied by effect measurements, while the underlying mechanism has been less well investigated. In this study, six azole fungicides (cyproconazole, epoxiconazole, ketoconazole, prochloraz, propiconazole, and tebuconazole) were selected to investigate their synergistic potential and their CYP inhibition strength in the aquatic invertebrate Gammarus pulex. The strobilurin fungicide azoxystrobin was chosen as co-occurring substrate, and the synergistic potential was measured in terms of internal concentrations of azoxystrobin and associated biotransformation products (BTPs). Azoxystrobin is biotransformed by various reactions, and 18 BTPs were identified. By measuring internal concentrations of azoxystrobin and its BTPs with high-resolution tandem mass spectrometry in the presence and absence of azole fungicides followed by toxicokinetic modeling, we showed that the inhibition of CYP-catalyzed biotransformation reactions indeed played a role for the observed synergism. However, synergism was only observed for prochloraz at environmentally realistic concentrations. Increased uptake rate constants, an increase in the total internal concentration of azoxystrobin and its BTPs, in vivo assays for measuring CYP activities, and G. pulex video-tracking suggested that the 2-fold increase in bioaccumulation, and, thereby, the raised toxicity of azoxystrobin in the presence of prochloraz is not only caused by inhibited biotransformation but even more by increased azoxystrobin uptake induced by hyperactivity.

Imidacloprid induces adverse effects on fish early life stages that are more severe in Japanese medaka (Oryzias latipes) than in zebrafish (Danio rerio)

“…The sample preparation was based on the method by Rosch et al (2017). In general, 100 µL of 100 µg/L imidacloprid_d 4 , 500 µL MeOH, and 300 mg of 1 mm zirconia/silica beads (BioSpec Products, Inc., U.S.A.) were added to the frozen organisms, followed by homogenization and extraction using a FastPrep bead beater (MP Biomedicals, Switzerland) in two cycles (15 s, 6 m/s).…”

Oxidation Behavior of Insecticide Azoxystrobin and its Voltammetric Determination Using Boron‐doped Diamond Electrode

“…The first two‐electron wave corresponds to oxidation of vinyl methyl ether portion of the β ‐methoxyacrylate moiety of the AS molecule yielding to a hydroxyl aldehyde functionality of the oxidation product. It is worth mentioning that the β ‐methoxyacrylate moiety is the toxophore of the azoxystrobin molecule and, at the same time, a reactive centre prone to oxidative metabolism catalysed by cytochrome P450 enzymes .…”

Size‐dependent sensitivity of stream amphipods indicates population‐level responses to chemical pollution

“…DEET) containing N, Ndiethyl‐m‐toluamide (Pennetier et al., 2005). Furthermore, complex toxic interactions on oxidative stress, detoxification and neurotoxicity biomarkers have been recorded in amphipods and insect larvae exposed to combined pesticides (Corbel et al., 2006; Demirci et al., 2018; Rösch et al., 2017). However, we only included one insecticide (the organophosphate diazinon) and one azole fungicide (the triazole tebuconazol) in our MP mixture, and in general, synergistic interactions may be relatively uncommon in mixtures of pesticides and other MPs including metals and antifoulants (Cedergreen, 2014).…”