Involvement of Oxidative Stress and Poly(ADP-ribose) Polymerase Activation in 3-Nitropropionic Acid-induced Cytotoxicity in Human Neuroblastoma Cells
Eunjoo Nam1, Young Jae Lee2, Young Ah Oh1,Jin Ah Jung1, Hye In Im1, Seong Eun Koh3, Sungho Maeng1,Wan Seok Joo1, andYong Sik Kim1
1Department of Pharmacology, Seoul National University College of Medicine and Neuroscience Research Institute, Medical Research Center, Seoul 110－799, Korea; 2Maria Infertility Hospital, Biomedical Research Institute, Seoul 130－110, Korea; 3Department of Rehabilitation Medicine, Konkuk University College of Medicine, Seoul 143－914, Korea
3-Nitropropionic acid (3-NP) inhibits electron transport in mitochondria, leading to a metabolic failure. In order to elucidate the mechanism underlying this toxicity, we examined a few biochemical changes possibly involved in the process, such as metabolic inhibition, generation of reactive oxygen species (ROS), DNA strand breakage, and activation of Poly(ADP-ribose) polymerase (PARP). Exposure of SK-N-BE(2)C neuroblastoma cells to 3-NP for 48 h caused actual cell death, while inhibition of mitochondrial function was readily observed when exposed for 24 h to low concentrations (0.2∼2 mM) of 3-NP. The earliest biochemical change detected with low concentration of 3-NP was an accumulation of ROS (4 h after 3-NP exposure) followed by degradation of DNA. PARP activation by damaged DNA was also detectable, but at a later time. The accumulation of ROS and DNA strand breakage were suppressed by the addition of glutathione or N-acetyl-L-cysteine (NAC), which also partially restored mitochondrial function and cell viability. In addition, inhibition of PARP also reduced the 3-NP-induced DNA strand breakage and cytotoxicity. These results suggest that oxidative stress and activation of PARP are the major factors in 3-NP-induced cytotoxicity,and that the inhibition of these factors may be useful in protecting neuroblastoma cells from 3-NP-induced toxicity.