The cytoprotective effect of N-acetyl-L-cysteine against ROS-induced cytotoxicity is independent of its ability to enhance glutathione synthesis.
2,3,5-Tris(glutathion-S-yl)-hydroquinone (TGHQ), a metabolite of hydroquinone, is toxic to renal proximal tubule epithelial cells. TGHQ retains the ability to redox cycle and create an oxidative stress. To assist in elucidating the contribution of reactive oxygen species (ROS) to TGHQ-induced toxicity, we determined whether the antioxidant, N-acetyl-L-cysteine (NAC), could protect human kidney proximal tubule epithelial cells (HK-2 cell line) against TGHQ-induced toxicity. NAC provided remarkable protection against TGHQ-induced toxicity to HK-2 cells. NAC almost completely inhibited TGHQ-induced cell death, mitochondrial membrane potential collapse, as well as ROS production. NAC also attenuated TGHQ-induced DNA damage and the subsequent activation of poly (ADP-ribose) polymerase and ATP depletion. Moreover, NAC significantly attenuated c-Jun NH2-terminal kinase and p38 mitogen-activated protein kinase phosphorylation induced by TGHQ. In contrast, NAC itself markedly increased extracellular regulated kinase1/2 (ERK1/2) activation, and the upstream mitogen-activated protein/extracellular signal-regulated kinase kinase inhibitor, PD-98059, only partially inhibited this activation, suggesting that NAC can directly activate ERK1/2 activity. However, although NAC is frequently utilized as a glutathione (GSH) precursor, the cytoprotection afforded by NAC in HK-2 cells was not a consequence of increased GSH levels. We speculate that NAC exerts its protective effect in part by directly scavenging ROS and in part via ERK1/2 activation.
Department of Pharmacology and Toxicology, College of Pharmacy, University of Arizona Health Science Center, Tucson, Arizona 85721, USA.
Fengjiao
F
Zhang
Serrine S
SS
Lau
Terrence J
TJ
Monks
D000111:Acetylcysteine / Q000494:pharmacology*; D000255:Adenosine Triphosphate / Q000378:metabolism; D000975:Antioxidants / Q000494:pharmacology*; D015153:Blotting, Western; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects; D019610:Cytoprotection / Q000187:drug effects*; D004847:Epithelial Cells / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D005434:Flow Cytometry; D005978:Glutathione / Q000031:analogs & derivatives / Q000096:biosynthesis* / Q000633:toxicity; D006801:Humans; D006873:Hydroquinones / Q000633:toxicity; D007687:Kidney Tubules, Proximal / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D053078:Membrane Potential, Mitochondrial / Q000187:drug effects; D018384:Oxidative Stress / Q000187:drug effects; D017382:Reactive Oxygen Species / Q000378:metabolism*
D000975:Antioxidants; D006873:Hydroquinones; D017382:Reactive Oxygen Species; C078765:2,3,5-(triglutathion-S-yl)hydroquinone; D000255:Adenosine Triphosphate; D005978:Glutathione; D000111:Acetylcysteine