Inhibitory effects of U73122 and U73343 on Ca2+ influx and pore formation induced by the activation of P2X7 nucleotide receptors in mouse microglial cell line

Biochim Biophys Acta. 2005 Nov 15;1726(2):177-86. doi: 10.1016/j.bbagen.2005.08.001. Epub 2005 Aug 15.

Abstract

P2X7 receptors are ATP-gated ion channels and play important roles in microglial functions in the brain. Activation of P2X7 receptors by ATP or its agonist BzATP induces Ca2+ influx from extracellular space, followed by the formation of non-selective membrane pores that is permeable to larger molecules, such as fluorescent dye. To determine whether phospholipase C (PLC) is involved in the activation of P2X7 receptors in microglial cells, U73122, a specific inhibitor of PLC, and its inactive analogue U73343 were examined on ATP and BzATP-induced channel and pore formation in an immortalized C57BL/6 mouse microglial cell line (MG6-1). ATP induced both a transient and a sustained increase in the intracellular Ca2+ concentration ([Ca2+]i) in MG6-1 cells, whereas BzATP evoked only a sustained increase. U73122, but not U73343, inhibited the transient [Ca2+]i increase involving Ca2+ release from intracellular stores through PLC activation. In contrast, both U73122 and U73343 inhibited the sustained [Ca2+]i increase either prior or after the activation of P2X7 receptor channels by ATP and BzATP. In addition, these U-compounds inhibited the influx of ethidium bromide induced by ATP and BzATP, suggesting possible PLC-independent blockage of the process of P2X7-associated channel and pore formations by U-compounds in C57BL/6 mouse microglial cells.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adenosine Triphosphate / analogs & derivatives
  • Adenosine Triphosphate / pharmacology
  • Animals
  • Brain / metabolism
  • Calcium / metabolism*
  • Calcium Signaling / drug effects
  • Cell Line
  • Estrenes / pharmacology*
  • Ethidium
  • Fluorescent Dyes / pharmacology
  • Membrane Transport Proteins / metabolism
  • Mice
  • Microglia / metabolism*
  • Nuclear Pore / metabolism*
  • Phosphodiesterase Inhibitors / pharmacology*
  • Pyrrolidinones / pharmacology*
  • Receptors, Purinergic P2 / metabolism*
  • Receptors, Purinergic P2X7
  • Type C Phospholipases / metabolism

Substances

  • Estrenes
  • Fluorescent Dyes
  • Membrane Transport Proteins
  • P2rx7 protein, mouse
  • Phosphodiesterase Inhibitors
  • Pyrrolidinones
  • Receptors, Purinergic P2
  • Receptors, Purinergic P2X7
  • 1-(6-((3-methoxyestra-1,3,5(10)-trien-17-yl)amino)hexyl)-1H-pyrrole-2,5-dione
  • U 73343
  • 3'-O-(4-benzoyl)benzoyladenosine 5'-triphosphate
  • Adenosine Triphosphate
  • Type C Phospholipases
  • Ethidium
  • Calcium