Manganese-induced oxidative DNA damage in neuronal SH-SY5Y cells: Attenuation of thymine base lesions by glutathione and N-acetylcysteine

Abstract

Manganese (Mn) is an essential trace element required for normal function and development. However, exposure to this metal at elevated levels may cause manganism, a progressive neurodegenerative disorder with neurological symptoms similar to idiopathic Parkinson’s disease (IPD). Elevated body burdens of Mn from exposure to parental nutrition, vapors in mines and smelters and welding fumes have been associated with neurological health concerns. The underlying mechanism of Mn neurotoxicity remains unclear. Accordingly, the present study was designed to investigate the toxic effects of Mn2+ in human neuroblastoma SH-SY5Y cells. Mn2+ caused a concentration dependent decrease in SH-SY5Y cellular viability compared to controls. The LD50 value was 12.98 μM Mn2+ (p <0.001 for control vs. 24h Mn treatment). Both TUNEL and annexin V/propidium iodide apoptosis assays confirmed the induction of apoptosis in the cells following exposure to Mn2+ (2 μM, 62 μM or 125 μM). In addition, Mn2+ induced both the formation and accumulation of DNA single strand breaks (via alkaline comet assay analysis) and oxidatively modified thymine bases (via gas chromatography/mass spectrometry analysis). Pre-incubation of the cells with characteristic antioxidants, either 1 mM N-acetylcysteine or 1 mM glutathione reduced the level of DNA strand breaks and the formation of thymine base lesions, suggesting protection against oxidative cellular damage. Our findings indicate that 1) exposure of SH-SY5Y cells to Mn promotes both the formation and accumulation of oxidative DNA nucleotide base damage, 2) SH-SY5Y cells with accumulated DNA damage are more likely to die via an apoptotic pathway and 3) the accumulated levels of DNA damage can be abrogated by the addition of exogenous chemical antioxidants. This is the first known report of Mn2+-induction and antioxidant protection of thymine lesions in this SH-SY5Y cell line and contributes new information to the potential use of antioxidants as a therapeutic strategy for protection against Mn2+-induced oxidative DNA damage.

High extracellular levels of potassium and trace metals in human brain abscess

“…ROS formation is also thought to be the cause of the pro-apoptotic effect of Cu on neurons (Chen et al, 2009) and its pro-necrotic effect in astrocytes (Scheiber et al, 2010) at concentrations seen in pus in the present study. Formation of ROS may also be stimulated by Mn (Stephenson et al, 2013) and Cr (Bagchi et al, 2002;Davidson et al, 2007) at low micromolar concentration, but the concentration of these ions in pus in the present study was submicromolar, so it is difficult to evaluate their importance for symptom generation in our patients.…”

Developmental exposure to manganese induces lasting motor and cognitive impairment in rats

“…5E and G). Oxidative stress has been implicated in Mn neurotoxicity (Milatovic et al, 2009;Herná ndez et al, 2011;Stephenson et al, 2013), and it has been reported that Mn induces production of H 2 O 2 in vitro (Posser et al, 2009) and hydroxyl radical in vivo (Bałasz et al, 2015). This result demonstrates that the hippocampus is susceptible to oxidative stress induced by perinatal Mn exposure and the effects of excessive levels of Mn in this region have consequences for the antioxidant defense system in rats that last into adulthood (PND70).…”

DNA Damage Induced by Manganese

“…15 Exposure of neuroblastoma SH-SY5Y cells to low, subcytotoxic, MnCl 2 concentrations (2 mM) resulted in an eight-fold increase in DNA damage. 20 In human leukocytes, Mn exposure did not increase the amount of strand breaks or cross-links. 21 Potassium permanganate has been shown to cause DNA strand breaks in human peripheral blood lymphocytes.…”