Journal of Clinical Toxicology
Open Access
ISSN: 2161-0495
ISSN: 2161-0495
Nan Mei, Xiaoqing Guo, Zuhong Zhang, Stacey L Dial, Vasily N Dobrovolsky, Si Chen and Lei Guo
National Center for Toxicological Research, USA
Scientific Tracks Abstracts: J Clin Toxicol
The biological consequences of exposure to piperidine nitroxides is a concern, given their widespread use in manufacturing processes and their potential use in clinical applications. Previously, we have demonstrated that TEMPO (2,2,6,6-tetramethylpiperidine- 1-oxyl), a low molecular weight free radical, can induce cytotoxicity and genotoxicity in mammalian cells. Extending this earlier work, the present study investigates the underlying mechanisms of TEMPO-associated oxidative stress and genotoxicity, particularly the roles of reactive oxygen species (ROS) and mitogen-activated protein kinase (MAPK) signaling. Our results demonstrate that TEMPO induced time- and concentration-dependent intracellular ROS production and glutathione depletion in mouse lymphoma L5178Y cells. TEMPO also induced apoptosis as demonstrated by increased caspase-3/7 activity, an increased proportion of annexin V stained cells, and decreased expression of anti-apoptotic proteins including Bcl-2, Bcl-xL and Mcl-1. N-acetylcysteine, a ROS scavenger, attenuated the ROS production and apoptosis induced by TEMPO. Moreover, Western blot analyses revealed that TEMPO activated �?³-H2A.X, a hallmark of DNA damage, and c-Jun N-terminal kinases (JNK); a key member in the mitogenactivated protein kinase (MAPK) signaling pathway. Addition of SP600125, a JNK-specific inhibitor, blocked TEMPO-mediated JNK phosphorylation and also attenuated TEMPO-induced apoptosis. These findings indicate that TEMPO-induced apoptosis and toxicity are, at least in part, mediated by oxidative stress and activation of JNK in the MAPK pathway.
Nan Mei after graduating from Hebei Medical University, China in 1984, started his scientific career in clinical cancer research and diagnosis as a Physician in a university hospital. In 1997, he received his PhD degree from the University of Occupational and Environmental Health, Japan. He then extended his training on assessing DNA damage as a Post-doctoral Fellow at the Cross Cancer Institute, Canada. In 2002, he joined the US FDA/NCTR. Currently his research focuses on genetic toxicology and toxicogenomics. He has published more than 80 peer-reviewed research articles in prestigious journals and 11 book chapters.
Email: Nan.Mei@fda.hhs.gov