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MC-LR detoxication in human and rats: inter-organ and inter-species differences
Verdiana Malandrucco1, Nicoletta Santori1, Jean-Lou C M Dorne2
1Istituto Superiore di Sanità, Environment & Health Dept, Viale Regina Elena, Rome 299, Italy.
Toxicology Letters
|June 8, 2026
Summary
This study reveals how glutathione conjugation by specific enzymes detoxifies Microcystin-LR (MC-LR). Enzyme activity and availability influence toxin levels, crucial for risk assessment and physiologically based kinetic (PBK) modeling.
Area of Science:
- Toxicology and Pharmacology
- Biochemical Kinetics
- Risk Assessment Methodologies
Background:
- Next-Generation Risk Assessment (NGRA) necessitates human-relevant data for physiologically based kinetic (PBK) modeling.
- Microcystin-LR (MC-LR), a cyanobacterial toxin, poses risks to food and feed safety.
- Understanding MC-LR detoxification pathways is critical for accurate risk assessment.
Purpose of the Study:
- To investigate the isoform-specific and extrahepatic glutathione (GSH) conjugation of MC-LR.
- To characterize kinetic parameters and intrinsic clearance (Cli) of MC-LR by various glutathione S-transferase (GST) isoforms and cytosols.
- To provide quantitative data for PBK model development in NGRA.
Main Methods:
- Incubation of recombinant human GSTs and pooled human/rat intestinal and kidney cytosols with MC-LR (1-60µM).
- Characterization of kinetic parameters (e.g., Vmax, Km) and intrinsic clearance (Cli).
- Comparison of spontaneous vs. GST-mediated conjugation and assessment of inter-organ/interspecies differences.
Main Results:
- GST isoforms P1 and T1 exhibited the highest MC-LR conjugation activity, with varying kinetic behaviors across substrate concentrations.
- Human intestinal and renal cytosols showed significant GST-mediated metabolic efficiency, comparable to hepatic data due to high GSTP1/T1 expression.
- Hepatic enzymatic conjugation capacity exceeded extrahepatic in humans; rat hepatic detoxification was significantly more efficient than human.
- Spontaneous conjugation was dominant in vitro but GST-mediated conjugation became critical under GSH depletion or scaled hepatic volume.
Conclusions:
- GST isoform distribution, polymorphism, and GSH availability significantly impact inter-organ, interspecies, and inter-individual variability in MC-LR detoxification.
- Extrahepatic detoxification plays a notable role, particularly in humans, influencing overall MC-LR clearance.
- The study provides essential kinetic parameters for refining PBK models and advancing NGRA for MC-LR risk assessment.
Keywords:
Extrahepatic metabolismGlutathione conjugationIn vitro biotransformationMicrocystin LRSpecies differences, NGRAMore Related Videos
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