A search for cellular and molecular mechanisms involved in depleted uranium (DU) toxicity.
Addition of U(VI) (uranyl acetate) to isolated rat hepatocytes results in rapid glutathione oxidation, reactive oxygen species (ROS) formation, lipid peroxidation, decreased mitochondrial membrane potential, and lysosomal membrane rupture before hepatocyte lysis occurred. Cytotoxicity was prevented by ROS scavengers, antioxidants, and glutamine (ATP generator). Hepatocyte dichlorofluorescein oxidation was inhibited by mannitol (a hydroxyl radical scavenger) or butylated hydroxyanisole and butylated hydroxytoluene (antioxidants). Glutathione depleted hepatocytes were resistant to U(VI) toxicity and much less dichlorofluorescein oxidation occurred. Reduction of U(VI) by glutathione or cysteine in vitro was also accompanied by oxygen uptake and was inhibited by Ca(II) (a U(IV) or U(VI) reduction inhibitor). U(VI)-induced cytotoxicity and ROS formation was also inhibited by Ca(II), which suggests that U(IV) and U(IV) GSH mediate ROS formation in isolated hepatocytes. The U(VI) reductive mechanism required for toxicity has not been investigated. Cytotoxicity was also prevented by cytochrome P450 inhibitors, particularly CYP 2E1 inhibitors, but not inhibitors of DT diaphorase or glutathione reductase. This suggests that P450 reductase and reduced cytochrome P450 contributes to U(VI) reduction to U(IV). In conclusion, U(VI) cytotoxicity is associated with mitochondrial/lysosomal toxicity by the reduced biological metabolites and ROS.
Pourahmad
Jalal
J
Faculty of Pharmacy and Pharmaceutical Research Center, Shaheed Beheshti University of Medical Sciences, Tehran, Iran. j.pourahmadjaktaji@utoronto.ca
Ghashang
Monireh
M
Ettehadi
Hossein Ali
HA
Ghalandari
Ruhollah
R
D000818:Animals; D000975:Antioxidants / Q000494:pharmacology; D002478:Cells, Cultured; D065607:Cytochrome P-450 Enzyme Inhibitors; D004705:Endocytosis / Q000187:drug effects; D005978:Glutathione / Q000378:metabolism; D022781:Hepatocytes / Q000187:drug effects; D015227:Lipid Peroxidation / Q000187:drug effects; D008297:Male; D053078:Membrane Potential, Mitochondrial / Q000187:drug effects; D008954:Models, Biological; D009942:Organometallic Compounds / Q000037:antagonists & inhibitors / Q000633:toxicity*; D010084:Oxidation-Reduction / Q000187:drug effects; D018384:Oxidative Stress / Q000187:drug effects; D051381:Rats; D017207:Rats, Sprague-Dawley; D017382:Reactive Oxygen Species / Q000037:antagonists & inhibitors / Q000378:metabolism
D000975:Antioxidants; D065607:Cytochrome P-450 Enzyme Inhibitors; D009942:Organometallic Compounds; D017382:Reactive Oxygen Species; C005460:uranyl acetate; D005978:Glutathione