Related Experiment Video
Updated: Jun 27, 2026
Broth Microdilution In Vitro Screening: An Easy and Fast Method to Detect New Antifungal Compounds
Published on: February 14, 2018
New Approach Methods for Hazard Identification: A Case Study with Azole Fungicides Affecting Molecular Targets
Constanze Knebel1, Roderich D Süssmuth2, Helen S Hammer3
1Department Food Safety, German Federal Institute for Risk Assessment, Max-Dohrn-Street 8-10, 10589 Berlin, Germany.
Abstract:
Triazole fungicides such as propiconazole (Pi) or tebuconazole (Te) show hepatotoxicity in vivo, e.g., hypertrophy and vacuolization of liver cells following interaction with nuclear receptors such as PXR (pregnane-X-receptor) and CAR (constitutive androstane receptor). Accordingly, azoles affect gene expression associated with these adverse outcomes in vivo but also in human liver cells in vitro. Additionally, genes indicative of liver cholestasis are affected in vivo and in vitro. We therefore analyzed the capability of Pi and Te to cause cholestasis in an adverse outcome pathway (AOP)-driven approach in hepatic cells of human origin in vitro, considering also previous in vivo studies. Bile salt export pump (BSEP) activity assays confirmed that both azoles are weak inhibitors of BSEP. They alternate the expression of various cholestasis-associated target genes and proteins as well as the mitochondrial membrane function. Published in vivo data, however, demonstrate that neither Pi nor Te cause cholestasis in rodent bioassays. This discrepancy can be explained by the in vivo concentrations of both azoles being well below their EC50 for BSEP inhibition. From a regulatory perspective, this illustrates that toxicogenomics and human in vitro models are valuable tools to detect the potential of a substance to cause a specific type of toxicity. To come to a sound regulatory conclusion on the in vivo relevance of such a finding, results will have to be considered in a broader context also including toxicokinetics in a weight-of-evidence approach.
Insights
Triazole fungicides like propiconazole and tebuconazole can affect liver cells. While they show potential for cholestasis in vitro, in vivo studies indicate no significant risk at relevant concentrations.
Area of Science:
- Toxicology
- Hepatotoxicity
- Environmental Health
Background:
- Triazole fungicides, including propiconazole (Pi) and tebuconazole (Te), are known to cause liver toxicity (hepatotoxicity) in vivo.
- Hepatotoxicity is linked to interactions with nuclear receptors like PXR and CAR, affecting gene expression and potentially leading to liver cholestasis.
Purpose of the Study:
- To investigate the potential of propiconazole (Pi) and tebuconazole (Te) to induce cholestasis using an adverse outcome pathway (AOP)-driven approach in human hepatic cells in vitro.
- To reconcile in vitro findings with existing in vivo data regarding the cholestatic potential of these azole fungicides.
Main Methods:
- Utilized human liver cells in vitro for toxicogenomic analysis.
- Performed bile salt export pump (BSEP) activity assays.
- Assessed expression of cholestasis-associated genes and proteins.
- Evaluated mitochondrial membrane function.
Main Results:
- Propiconazole and tebuconazole were identified as weak inhibitors of BSEP.
- These azoles altered the expression of cholestasis-related genes and proteins and affected mitochondrial membrane potential.
- In vivo studies in rodents did not show evidence of cholestasis for either fungicide.
Conclusions:
- The discrepancy between in vitro and in vivo results for cholestasis is attributed to in vivo concentrations being below the EC50 for BSEP inhibition.
- Toxicogenomics and human in vitro models are valuable for identifying potential toxicity.
- Regulatory assessment requires a weight-of-evidence approach, integrating toxicokinetics and in vivo data for a comprehensive conclusion on in vivo relevance.
More Related Videos
Related Concept Videos
01:19Pharmacovigilance
This process, termed pharmacovigilance, aims to detect, evaluate, and minimize harmful effects related to medication use. The data collection for pharmacovigilance depends on spontaneous reporting systems, where healthcare professionals or patients voluntarily report suspected ADRs.
In some cases, there...
01:23Types of Biopharmaceutical Studies: Controlled and Non-Controlled Approaches
Non-controlled studies, commonly employed for initial exploration, lack a control group, rendering them susceptible to biases and external influences. In contrast, controlled...
01:29Pharmacogenomics: Identification of New Drug Targets
01:15Impact of Pharmacokinetic–Pharmacodynamic Models: Regulatory Decisions
01:15Antifungal Agents