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Updated: Sep 20, 2026
Isolation of Primary Mouse Hepatocytes for Nascent Protein Synthesis Analysis by Non-radioactive L-azidohomoalanine Labeling Method
Published on: October 23, 2018
Cylindrospermopsin-induced protein synthesis inhibition and its dissociation from acute toxicity in mouse hepatocytes
Suzanne M Froscio1, Andrew R Humpage, Philip C Burcham
1Department of Clinical and Experimental Pharmacology, University of Adelaide, Adelaide, South Australia 5005, Australia. suzanne.froscio@rmit.edu.au
Abstract:
The toxicology of the cyanobacterial alkaloid cylindrospermopsin (CYN), a potent inhibitor of protein synthesis, appears complex and is not well understood. In exposed mice the liver is the main target for the toxic effects of CYN. In this study primary mouse hepatocyte cultures were used to investigate the mechanisms involved in CYN toxicity. The results show that 1-5 microM CYN caused significant concentration-dependent cytotoxicity (52%-82% cell death) at 18 h. Protein synthesis inhibition was a sensitive, early indicator of cellular responses to CYN. Following removal of the toxin, the inhibition of protein synthesis could not be reversed, showing behavior similar to that of the irreversible inhibitor emetine. In contrast to the LDH leakage, protein synthesis was maximally inhibited by 0.5 microM CYN. No protein synthesis occurred over 4-18 h at or above this concentration. Inhibition of cytochrome P450 (CYP450) activity with 50 microM proadifen or 50 microM ketoconazole diminished the toxicity of CYN but not the effects on protein synthesis. These findings imply a dissociation of the two events and implicate the involvement of CYP450-derived metabolites in the toxicity process, but not in the impairment of protein synthesis. Thus, the total abolition of protein synthesis may exaggerate the metabolite effects but cannot be considered a primary cause of cell death in hepatocytes over an acute time frame. In cell types deficient in CYP450 enzymes, protein synthesis inhibition may play a more crucial role in the development of cytotoxicity.
Insights
Cylindrospermopsin (CYN) causes liver cell death by inhibiting protein synthesis and through CYP450 metabolites. Protein synthesis inhibition is an early indicator but not the primary cause of CYN toxicity in hepatocytes.
Area of Science:
- Toxicology
- Cell Biology
- Environmental Health
Background:
- Cylindrospermopsin (CYN) is a cyanobacterial alkaloid with complex and poorly understood toxicology.
- CYN is a potent inhibitor of protein synthesis, and the liver is a primary target organ in exposed animals.
Purpose of the Study:
- To investigate the mechanisms of CYN toxicity in primary mouse hepatocytes.
- To elucidate the roles of protein synthesis inhibition and cytochrome P450 (CYP450) activity in CYN-induced cytotoxicity.
Main Methods:
- Primary mouse hepatocyte cultures were exposed to varying concentrations of CYN.
- Cytotoxicity was assessed by measuring cell death and lactate dehydrogenase (LDH) leakage.
- Protein synthesis inhibition and CYP450 activity were evaluated using specific assays and inhibitors (proadifen, ketoconazole).
Main Results:
- CYN induced concentration-dependent cytotoxicity and irreversible protein synthesis inhibition in hepatocytes.
- Protein synthesis inhibition occurred at lower CYN concentrations than LDH leakage.
- Inhibition of CYP450 activity reduced CYN toxicity but did not affect protein synthesis inhibition, suggesting a dissociation of these effects.
Conclusions:
- CYN toxicity involves both direct effects on protein synthesis and the action of CYP450-derived metabolites.
- While protein synthesis inhibition is an early indicator, it is not the primary driver of acute hepatocyte cell death.
- CYP450 metabolites play a significant role in CYN-induced liver toxicity.
