Mercury-induced apoptosis and necrosis in murine macrophages: role of calcium-induced reactive oxygen species and p38 mitogen-activated protein kinase signaling.
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.
Kim
Sang Hyun
SH
Interdisciplinary Program in Toxicology, Department of Physiology and Pharmacology, College of Veterinary Medicine, The University of Georgia, Athens, GA 30602-7389, USA.
Sharma
Raghubir P
RP
D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D002118:Calcium / Q000378:metabolism*; D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D004789:Enzyme Activation; D008264:Macrophages / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D008627:Mercuric Chloride / Q000633:toxicity*; D051379:Mice; D008807:Mice, Inbred BALB C; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D009336:Necrosis; D017382:Reactive Oxygen Species / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects; D048051:p38 Mitogen-Activated Protein Kinases
D017382:Reactive Oxygen Species; D008627:Mercuric Chloride; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; D002118:Calcium