CYP2E1-mediated modulation of valproic acid-induced hepatocytotoxicity.
OBJECTIVE
To determine the cytotoxicity of valproic acid (VPA) and its metabolite, 4-ene-valproic acid (4-ene-VPA) in human hepatoblastoma cells (Hep G2), and to study the modulatory effect of cytochrome P450 2E1 induction in this model.


METHODS
Cells were exposed to VPA or 4-ene-VPA in the presence of either ethanol (EtOH), or EtOH combined with disulphiram (DS). Some cells were exposed to alpha-fluoro-VPA or to alpha-fluoro-4-ene-VPA in the absence of CYP2E1 inducers. Apoptosis and necrosis were measured by analyzing 6000 cells per sample using transmission electron microscopy, while cytokine release and apoptosis were quantitated by ELISA.


RESULTS
VPA + EtOH increased VPA cytotoxicity. 4-ene-VPA + EtOH significantly increased toxicity, while DS + EtOH significantly reduced this toxicity. Alpha-fluorinated analogues reduced cytotoxicity compared to the corresponding VPA compounds. Neither VPA nor alpha-fluorinated VPA increased the release of IL-6 or TNF-alpha in media. A significant increase in the release of TNF-alpha was observed in cells exposed to 4-ene-VPA that further increased with EtOH exposure.


CONCLUSIONS
Cells exposed to 4-ene-VPA experience greater cytotoxicity than those treated with VPA. Cytochrome P450 2E1 inducers enhance toxicity in VPA-exposed cells, while alpha-fluorination of VPA diminishes cytotoxicity by directly interfering with the beta-oxidation of the 4-ene-VPA metabolite.
Neuman
M G
MG
Division of Clinical Pharmacology, Sunnybrook & Women's College Health Sciences Centre and Department of Pathology, Toronto Health Network, Canada. manuela@sten.sunnybrook.utoronto.ca
Shear
N H
NH
Jacobson-Brown
P M
PM
Katz
G G
GG
Neilson
H K
HK
Malkiewicz
I M
IM
Cameron
R G
RG
Abbott
F
F
D000927:Anticonvulsants / Q000633:toxicity*; D017209:Apoptosis; D002470:Cell Survival / Q000187:drug effects; D019392:Cytochrome P-450 CYP2E1 / Q000096:biosynthesis / Q000378:metabolism*; D004790:Enzyme Induction; D006801:Humans; D015850:Interleukin-6 / Q000378:metabolism; D008099:Liver / Q000187:drug effects* / Q000201:enzymology / Q000378:metabolism / Q000648:ultrastructure; D008854:Microscopy, Electron; D014407:Tumor Cells, Cultured; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism; D014635:Valproic Acid / Q000633:toxicity*
D000927:Anticonvulsants; D015850:Interleukin-6; D014409:Tumor Necrosis Factor-alpha; D014635:Valproic Acid; D019392:Cytochrome P-450 CYP2E1