Mechanism of Impila (Callilepis laureola)-induced cytotoxicity in Hep G2 cells.
OBJECTIVE
To determine the mechanism(s) of Impila (Callilepis laureola)-induced toxicity in human hepatoblastoma Hep G2 cells in vitro and the possible prevention of this toxicity by N-acetylcysteine (NAC).


METHODS
Cells were treated with an aqueous extract of Impila (10 mg/mL) for up to 24 h. NAC (5 mM) was administered either concomitantly with Impila or one hour post Impila treatment. Cytotoxicity was quantitated spectrophotometrically by the metabolism of the tetrazolium dye MTT. Total glutathione (GSH) was measured using the Tietze assay.


RESULTS
Impila produced cytotoxicity and depleted GSH in a concentration- and time-dependent manner. A significant depletion in GSH was observed after 15 min (p < 0.0001 vs. control), whereas significant cytotoxicity was only observed after at least 3 h (p < 0.0001 vs. control). Both concomitant and posttreatment with NAC prevented Impila-induced GSH depletion and resulted in a significant decrease in Impila-induced cytotoxicity (p < 0.001 vs. NAC-untreated cells).


CONCLUSIONS
Our results suggest the mechanism of Impila-induced cytotoxicity in Hep G2 cells in vitro involves depletion of cellular GSH. Preventing GSH depletion by supplementing cells with NAC reduces cytotoxicity.
Popat
Alpa
A
Division of Clinical Pharmacology, Sunnybrook and Women's College Health Sciences Centre, Toronto, Ontario, Canada.
Shear
Neil H
NH
Malkiewicz
Izabella
I
Thomson
Stuart
S
Neuman
Manuela G
MG
D000111:Acetylcysteine / Q000494:pharmacology; D002455:Cell Division / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D005562:Formazans; D005978:Glutathione / Q000378:metabolism*; D018197:Hepatoblastoma / Q000188:drug therapy* / Q000378:metabolism; D006801:Humans; D008113:Liver Neoplasms / Q000188:drug therapy* / Q000378:metabolism; D016488:Medicine, African Traditional; D010936:Plant Extracts / Q000633:toxicity*; D010946:Plants, Medicinal / Q000633:toxicity*; D013778:Tetrazolium Salts; D013997:Time Factors; D014407:Tumor Cells, Cultured / Q000187:drug effects / Q000378:metabolism
D005562:Formazans; D010936:Plant Extracts; D013778:Tetrazolium Salts; C079782:MTT formazan; D005978:Glutathione; D000111:Acetylcysteine