Lipid peroxides and glutathione status in human progenitor mononuclear (U937) cells following exposure to low doses of nickel and copper

Abstract

Effects of Cu²⁺, Ni²⁺ or Cu²⁺ + Ni²⁺ on lipid peroxide and glutathione (GSH) levels in U937 cells were investigated. Cells were treated with 0, 5, 10, and 20 µM of Cu²⁺ and/or Ni²⁺ and H₂O₂ (0.01 mM) and incubated for 24 hours at 37°C. Lipid peroxides were measured by the thiobarbituric acid assay (TBA). GSH intracellular levels were assayed by the GSH assay kit from EMD/Calbiochem (San Diego, California, USA). Cu²⁺ or Ni²⁺ significantly (P < 0.01) increased lipid peroxides in a dose-dependent manner, compared to controls. The effect was more pronounced for Cu²⁺, compared to the Ni²⁺-treated samples. Cu²⁺ + Ni²⁺ increased lipid peroxides in a significant (P < 0.001), dose-dependent manner, compared to Cu²⁺ or Ni²⁺ alone (i.e., ratio of 2.5:1-fold for combined versus single treatments, respectively). Cu²⁺ or Ni²⁺ significantly decreased GSH levels in U937 cells, with the effect being pronounced for Cu²⁺. Cu²⁺ + Ni²⁺ metal ions significantly (P < 0.001) depleted cells of GSH in a dose-dependent manner. Ethylene diamine tetraacetic acid (EDTA) at 50 or 100 µM moderately reduced the Cu²⁺- or Ni²⁺-induced effects on GSH levels. Interestingly, GSH levels generally decreased to half (except for the combined metal dose of 20 µM at 100 µM EDTA) of its level at the highest metal concentration tested for both the single or combined treatments. In conclusion, multiple exposures of cells to metal ions may be lethal to cells, compared to their single treatments.

Keywords::

• Copper
• glutathione
• lipid peroxides
• nickel
• thiobarbituric acid assay
• U937 cells

Acknowledgment

The authors thank Dr. Gary McCollum of Vanderbilt University for reading and offering his constructive criticisms and suggestions. This study did not involve the use of humans or experimental animals.

Declaration of interest

This study was supported with grants from Tennessee State University through the “EARDA” program, NIAMS Grant no. RO3AR46384-02 to Samuel E. Adunyah of Meharry Medical College, MBRS SCORE Grant no. SO6GM08037-29, an NCI supplementary grant to Meharry Medical College through VICC, and NIH-NCRR RCMI Grant no. 2G12RRO3032-16 to Meharry Medical College, and the financial support of the Samuel P. Massey Chair of Excellence for Environmental studies chaired by Dr. Lonnie Sharpe at Tennessee State University. Dr. Samuel E. Adunyah is also supported by 5 U54 RR026140-03 (NCRR) / 8 U54 MD007593-03 (NIMHD) and NCI 1 U54 CA163069-01 grants.