Mercury-induced apoptosis and necrosis in murine macrophages: role of calcium-induced reactive oxygen species and p38 mitogen-activated protein kinase signaling

Toxicol Appl Pharmacol. 2004 Apr 1;196(1):47-57. doi: 10.1016/j.taap.2003.11.020.

Abstract

The current study characterizes the mechanism by which mercury, a toxic metal, induces death in murine macrophages. The cytotoxic EC(50) of mercury ranged from 62.7 to 81.1 microM by various assays in J774A.1 cultures; accordingly, we employed 70 microM of mercuric chloride in most experiments. Mercury-induced intracellular calcium modulated reactive oxygen species (ROS) production, which resulted in both cell apoptosis and necrosis indicated by annexin V binding and caspase-3 activity, and propidium-iodide binding. Calcium antagonists abolished ROS production. Mercury stimulated p38 mitogen-activated protein kinase (MAPK) and additively stimulated lipopolysaccharide-activated p38. Mercury-activated p38 was decreased by pretreatment of cells with antioxidants, N-acetylcysteine (NAC) and silymarin, indicating that mercury-induced ROS were involved in p38 activation. Mercury increased the expression of tumor necrosis factor alpha (TNFalpha); antioxidants and a specific p38 inhibitor decreased this effect. Pretreatment with antioxidants, p38 inhibitor, and anti-TNFalpha antibody decreased mercury-induced necrosis; however, anti-TNFalpha antibody did not decrease mercury-induced apoptosis. Results suggest that mercury-induced macrophage death is a mix of apoptosis and necrosis employing different pathways. P38-mediated caspase activation regulates mercury-induced apoptosis and p38-mediated TNFalpha regulates necrosis in these cells. Calcium regulates ROS production and mercury-induced ROS modulate downstream p38 that regulates both apoptosis and necrosis.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Apoptosis / drug effects*
  • Calcium / metabolism*
  • Cell Survival / drug effects
  • Cells, Cultured
  • Enzyme Activation
  • Macrophages / drug effects*
  • Macrophages / metabolism
  • Macrophages / pathology
  • Mercuric Chloride / toxicity*
  • Mice
  • Mice, Inbred BALB C
  • Mitogen-Activated Protein Kinases / metabolism*
  • Necrosis
  • Reactive Oxygen Species / metabolism*
  • Signal Transduction / drug effects
  • p38 Mitogen-Activated Protein Kinases

Substances

  • Reactive Oxygen Species
  • Mercuric Chloride
  • Mitogen-Activated Protein Kinases
  • p38 Mitogen-Activated Protein Kinases
  • Calcium