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.
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.
Takenouchi
Takato
T
Department of Molecular Biology and Immunology, National Institute of Agrobiological Sciences, Kannondai 3-1-5, Tsukuba, Ibaraki 305-8602, Japan.
Ogihara
Kazumasa
K
Sato
Mitsuru
M
Kitani
Hiroshi
H
D000255:Adenosine Triphosphate / Q000031:analogs & derivatives / Q000494:pharmacology; D000818:Animals; D001921:Brain / Q000378:metabolism; D002118:Calcium / Q000378:metabolism*; D020013:Calcium Signaling / Q000187:drug effects; D002460:Cell Line; D004963:Estrenes / Q000494:pharmacology*; D004996:Ethidium; D005456:Fluorescent Dyes / Q000494:pharmacology; D026901:Membrane Transport Proteins / Q000378:metabolism; D051379:Mice; D017628:Microglia / Q000378:metabolism*; D022022:Nuclear Pore / Q000378:metabolism*; D010726:Phosphodiesterase Inhibitors / Q000494:pharmacology*; D011760:Pyrrolidinones / Q000494:pharmacology*; D018048:Receptors, Purinergic P2 / Q000378:metabolism*; D058486:Receptors, Purinergic P2X7; D010738:Type C Phospholipases / Q000378:metabolism
D004963:Estrenes; D005456:Fluorescent Dyes; D026901:Membrane Transport Proteins; C546469:P2rx7 protein, mouse; D010726:Phosphodiesterase Inhibitors; D011760:Pyrrolidinones; D018048:Receptors, Purinergic P2; D058486:Receptors, Purinergic P2X7; C060229:1-(6-((3-methoxyestra-1,3,5(10)-trien-17-yl)amino)hexyl)-1H-pyrrole-2,5-dione; C074854:U 73343; C033901:3'-O-(4-benzoyl)benzoyladenosine 5'-triphosphate; D000255:Adenosine Triphosphate; D010738:Type C Phospholipases; D004996:Ethidium; D002118:Calcium