Oxidative stress-mediated inhibition of brain creatine kinase activity by methylmercury

• Published in: Neurotoxicology (Park Forest South) 2010-09, Vol.31 (5), p.454-460
• Main Authors: Glaser, Viviane, Leipnitz, Guilhian, Straliotto, Marcos Raniel, Oliveira, Jade, dos Santos, Vanessa Valgas, Wannmacher, Clóvis Milton Duval, de Bem, Andreza Fabro, Rocha, João Batista Teixeira, Farina, Marcelo, Latini, Alexandra
• Format: Article
• Language: English
• Subjects: Analysis of Variance; Animals; Astrocytoma - pathology; Biological and medical sciences; Blood-brain barrier; Brain - drug effects; Brain - enzymology; Cell Line, Tumor; Chemical and industrial products toxicology. Toxic occupational diseases; Creatine kinase; Creatine Kinase - metabolism; Dose-Response Relationship, Drug; Enzyme Activation - drug effects; Gene Expression Regulation, Enzymologic - drug effects; Male; Medical sciences; Metals and various inorganic compounds; Methylmercury; Methylmercury Compounds - pharmacology; Mice; Neurotoxicity; Oxidative Stress - drug effects; Protein Carbonylation - drug effects; Reactive Oxygen Species - metabolism; Tetrazolium Salts; Thiazoles; Time Factors; Toxicology
• ISSN: 0161-813X; 1872-9711
• DOI: 10.1016/j.neuro.2010.05.012

Methylmercury (MeHg), a potent neurotoxicant, easily passes through the blood–brain barrier and accumulates in brain causing severe irreversible damage. However, the underlying neurotoxic mechanisms elicited by MeHg are still not completed defined. In this study, we aimed to investigate the in vitro toxic effects elicited by crescent concentrations (0–1500 μM) of MeHg on creatine kinase (CK) activity, thiol content (NPSH) and protein carbonyl content (PCC) in mouse brain preparations. In addition, CK activity, MTT reduction and DCFH-DA oxidation (reactive oxygen species (ROS) formation) were also measured in C6 glioma cell linage. CK activity was severely reduced by MeHg treatment in mouse brain preparations. This inhibitory effect was positively correlated to the MeHg-induced reduction of NPSH levels and increment in PCC. Moreover, the positive correlation between brain CK activity and NPSH levels was observed at either 15 or 60 min of MeHg pre-incubation. In addition, MeHg-treated C6 cells showed also a significant inhibition of CK activity at MeHg concentrations, as low as, 50 μM in parallel to reduced mitochondrial function and increased ROS production. Taking together, these data demonstrate that MeHg severely affects CK activity, an essential enzyme for brain energy buffering to maintain cellular energy homeostasis. This effect appears to be mediated by oxidation of thiol groups that might cause subsequent oxidative stress.