The role of oxidative stress on the effect of 1,4,7,10,13,16-hexathiacyclooctadecane on copper and zinc toxicity in HepG2 cells.
Experiments have shown that 1,4,7,10,13,16-hexathiacyclooctadecane (L3) increased the Cu2+ toxicity on HepG2 cells, whereas the combination Zn(2+)/L3 was less toxic relative to the metal control. In all cases, glutathione (GSH) levels were decreased and vitamins C and E supplementation partially counteracted the increased toxicity in the Cu(2+)/L3-treated cells. The previously observed effects of this hexathiamacrocyclic ligand (L3) on the Cu2+ and Zn2+ toxicity were further investigated by first depleting the intracellular GSH levels by means of L-buthionine S,R-sulphoximine. Combined treatment with Cu(2+)/L3 resulted in complete cell death, whereas for Zn(2+)/L3 no severe effects were observed. Direct measurement of reactive oxygen species (ROS) revealed that Cu2+ induced a high degree of oxidative stress on the cells. This was not the case for Zn2+. The results proved a previously proposed mechanism in which GSH is used to conjugate the metal-ligand complex, but as a result of this, GSH is no longer available for inactivation of ROS. Also, both the intracellular copper and zinc content were determined for each experiment by means of inductively coupled plasma-atomic emission spectroscopy. According to these data, zinc is depleted in Cu(2+)/L3-treated cells, which could have consequences on superoxide dismutase and as a result of this on the amount of oxidative stress.
Smet
P W
PW
Scientific Institute of Public Health, Division Toxicology, Laboratory of Biochemical Toxicology, J Wytsmanstraat 16, 1050 Brussels, Belgium. peter.smet@iph.fgov.be
Elskens
M
M
Bolle
F
F
Dierickx
P J
PJ
D019328:Buthionine Sulfoximine / Q000494:pharmacology; D006528:Carcinoma, Hepatocellular; D003300:Copper / Q000032:analysis / Q000633:toxicity*; D004305:Dose-Response Relationship, Drug; D004338:Drug Combinations; D005978:Glutathione / Q000172:deficiency; D022781:Hepatocytes / Q000187:drug effects* / Q000378:metabolism; D006573:Heterocyclic Compounds, 1-Ring / Q000633:toxicity*; D006801:Humans; D018384:Oxidative Stress / Q000502:physiology*; D017382:Reactive Oxygen Species / Q000378:metabolism; D013054:Spectrophotometry, Atomic; D013440:Sulfides / Q000633:toxicity*; D014407:Tumor Cells, Cultured; D015032:Zinc / Q000032:analysis / Q000633:toxicity*
D004338:Drug Combinations; D006573:Heterocyclic Compounds, 1-Ring; D017382:Reactive Oxygen Species; D013440:Sulfides; D019328:Buthionine Sulfoximine; C408082:1,4,7,10,13,16-hexathiacyclooctadecane; D003300:Copper; D005978:Glutathione; D015032:Zinc