Mechanisms of Mg2+ inhibition of BzATP-dependent Ca2+ responses in THP-1 monocytes

Brain Res. 2012 Mar 9;1442:1-8. doi: 10.1016/j.brainres.2012.01.004. Epub 2012 Jan 11.

Abstract

We have recently reported effects of Mg2+ to confer neuroprotection against toxicity of purinergic stimulated microglia and THP-1 monocytes. To examine mechanisms underlying neuroprotection, we have studied Mg2+ modulation of transient changes in intracellular Ca2+ ([Ca2+]i) in THP-1 cells induced by P2X7R agonist 2',3'-[benzoyl-4-benzoyl]-ATP (BzATP). Application of BzATP caused a rapid transient increase in [Ca2+]i followed by a prolonged component. The time course of the secondary slower phase was significantly reduced with Ca2+-free extracellular solution, with treatment of THP-1 cells by the P2X7R antagonist, oxATP or with exposure of cells to the store-operated channel (SOC) inhibitor, SKF96365. These results suggest that Ca2+ influx, mediated by both the P2X7R or by SOC, contribute to the slow component of [Ca2+]i. Treatment of THP-1 cells with 10 mMMg2+ was highly effective in reducing the time course of BzATP-induced Ca2+ decay; unlike the other modulatory protocols, Mg2+ markedly inhibited the amplitudes of slow and rapid components. In addition, acute application of Mg2+ during BzATP-induced responses elicited in the presence of either oxATP or SKF96365 to block respective P2X7R and SOC contributions, rapidly attenuated [Ca2+]i to baseline levels. Priming of cells with the inflammatory stimulus LPS/IFN-γ markedly enhanced the slower, but not rapid, phase of BzATP-induced [Ca2+]i with application of 10 mMMg2+ inhibiting both components of response. A model is proposed to account for BzATP stimulation of both ionotropic P2XR and metabotropic P2YR which provides a mechanistic basis for elevated Mg2+ anti-inflammatory and neuroprotective actions in inflamed brain.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adenosine Triphosphate / analogs & derivatives
  • Adenosine Triphosphate / metabolism
  • Adenosine Triphosphate / pharmacology
  • Calcium / metabolism*
  • Cell Line, Tumor
  • Humans
  • Imidazoles / pharmacology
  • Interferon-gamma / immunology
  • Lipopolysaccharides / immunology
  • Magnesium / pharmacology*
  • Models, Biological
  • Monocytes / immunology
  • Monocytes / metabolism*
  • Purinergic P2X Receptor Agonists / pharmacology
  • Purinergic P2X Receptor Antagonists / pharmacology
  • Receptors, Purinergic P2X7 / metabolism
  • Receptors, Purinergic P2Y / metabolism

Substances

  • Imidazoles
  • Lipopolysaccharides
  • Purinergic P2X Receptor Agonists
  • Purinergic P2X Receptor Antagonists
  • Receptors, Purinergic P2X7
  • Receptors, Purinergic P2Y
  • 3'-O-(4-benzoyl)benzoyladenosine 5'-triphosphate
  • 2',3'-dialdehyde ATP
  • Interferon-gamma
  • Adenosine Triphosphate
  • Magnesium
  • 1-(2-(3-(4-methoxyphenyl)propoxy)-4-methoxyphenylethyl)-1H-imidazole
  • Calcium