title: Hepatotoxic effects of (tri)azole fungicides in a broad dose range.
abstract: The toxicological relevance of effects observed at molecular stage, which occur at dose levels well below classical no-observed adverse effect levels is currently subject to controversial scientific debate. While the importance of molecular effects for the identification of a mode of action or an adverse outcome pathway is undisputed, their impact for other regulatory purposes remains uncertain. Here, we report the results of a 28-day rat-feeding study including three widely used hepatotoxic (tri)azole fungicides (cyproconazole, epoxiconazole and prochloraz) administered individually at five dose levels, ranging from slightly above the reference values to a clear toxic effect dose. Parameters analysed included pathology, histopathology, clinical chemistry and particularly effects on the molecular level. Since azole fungicides are considered to cause liver toxicity by a mechanism involving the constitutive androstane receptor (CAR), a known CAR activator (phenobarbital, PB) was administered to investigate potential similarities between triazoles and PB-mediated liver toxicity by pathway-focused gene expression analysis. Our results show an increase in liver weights and additionally histopathological changes (hepatocellular hypertrophy) for all substances at the top dose levels. The effects on liver weight were most pronounced for cyproconazole by which also the animals receiving the next lower dose were affected. In addition, vacuolisation of hepatocytes was observed at the top dose level. No such findings were obtained with any substance at lower doses to which consumers and operators might be exposed to. In contrast, the expression of sensitive marker genes (like some cytochrome-P-450 isoforms) was significantly affected also at the lower dose levels. While some of these changes, like the induction of genes related to fatty acid and phospholipid metabolism (e.g. Fasn, Fat/Cd36, Ppargc1a) or xenobiotic metabolism (Cyp1a1, Cyp2b1, Cyp3a2), could be associated with high dose effects like hepatocellular vacuolisation or hypertrophy, a histopathological correlate was lacking for others.
authors.affiliation: Federal Institute for Risk Assessment (BfR), Berlin, Germany.
authors.forename: T
authors.initials: T
authors.lastname: Heise
authors.affiliation: Federal Institute for Risk Assessment (BfR), Berlin, Germany.
authors.forename: F
authors.initials: F
authors.lastname: Schmidt
authors.affiliation: Federal Institute for Risk Assessment (BfR), Berlin, Germany.
authors.forename: C
authors.initials: C
authors.lastname: Knebel
authors.affiliation: Federal Institute for Risk Assessment (BfR), Berlin, Germany.
authors.forename: S
authors.initials: S
authors.lastname: Rieke
authors.affiliation: Institute for Animal Pathology, Berlin, Germany.
authors.forename: W
authors.initials: W
authors.lastname: Haider
authors.affiliation: Federal Institute for Risk Assessment (BfR), Berlin, Germany.
authors.forename: R
authors.initials: R
authors.lastname: Pfeil
authors.affiliation: Federal Institute for Risk Assessment (BfR), Berlin, Germany.
authors.forename: C
authors.initials: C
authors.lastname: Kneuer
authors.affiliation: Federal Institute for Risk Assessment (BfR), Berlin, Germany.
authors.forename: L
authors.initials: L
authors.lastname: Niemann
authors.affiliation: Federal Institute for Risk Assessment (BfR), Berlin, Germany. Philip.marx-stoelting@bfr.bund.de.
authors.forename: P
authors.initials: P
authors.lastname: Marx-Stoelting
mesh_terms: D000818:Animals; D056486:Chemical and Drug Induced Liver Injury / Q000209:etiology* / Q000473:pathology; D000090702:Constitutive Androstane Receptor; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004852:Epoxy Compounds / Q000008:administration & dosage / Q000633:toxicity*; D005659:Fungicides, Industrial / Q000008:administration & dosage / Q000633:toxicity*; D005786:Gene Expression Regulation / Q000187:drug effects; D022781:Hepatocytes / Q000187:drug effects; D007093:Imidazoles / Q000008:administration & dosage / Q000633:toxicity*; D008297:Male; D010634:Phenobarbital / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D018160:Receptors, Cytoplasmic and Nuclear / Q000378:metabolism; D014230:Triazoles / Q000008:administration & dosage / Q000633:toxicity*
chemical_list: D000090702:Constitutive Androstane Receptor; D004852:Epoxy Compounds; D005659:Fungicides, Industrial; D007093:Imidazoles; D018160:Receptors, Cytoplasmic and Nuclear; D014230:Triazoles; C093628:cyproconazole; D003577:Cytochrome P-450 Enzyme System; C045362:prochloraz; C109476:epoxiconazole; D010634:Phenobarbital
keywords: Adverse outcome pathway; Liver; Low dose; Phenobarbital; Triazole