Heterogeneity and potentiation of AMPA type of glutamate receptors in rat cultured microglia.
alpha-amino-hydroxy-5-methyl-isoxazole-4-propionate (AMPA) receptor in rat cultured microglia were analyzed precisely using flop- and flip-preferring allosteric modulators of AMPA receptors, 4-[2-(phenylsulfonylamino)ethylthio]-2,6-difluoro-phenoxyacetamide (PEPA) and cyclothiazide (CTZ), respectively. Glutamate (Glu)- or kainite (KA)-induced currents were completely inhibited by a specific blocker of AMPA receptor, LY300164, indicating that functional Glu-receptors in cultured microglia are mostly AMPA receptor but not KA receptor in many cells. Glu- and KA-induced currents were potentiated by PEPA and CTZ in a concentration-dependent manner. The ratio of the potentiation by PEPA to the potentiation by cyclothiazide varied with cells between 0.1 and 0.9, suggesting cell-to-cell heterogeneity of AMPA receptor subunits expressed in microglia. Quantitative RT-PCR revealed that GluR1-3 mainly occurred in the flip forms, which agreed with the stronger potentiation of receptor currents by CTZ vs. PEPA. Finally, the potentiation of microglial AMPA receptors by PEPA and CTZ inhibited the Glu-induced release of tumor necrosis factor-alpha (TNF-alpha) unpredictably. The increase in TNF-alpha release by Glu or KA required extracellular Na+ and Ca2+ ions but not mitogen-activated protein kinase (MAPK), suggesting the effects of PEPA and CTZ were not due to the inhibition of MAPK. These results suggest that potentiation of microglial AMPA receptors serves as a negative feedback mechanism for the regulation of TNF-alpha release and may contribute to the ameliorating effects of allosteric modulators of AMPA receptors.
Hagino
Yukiko
Y
Laboratory of Pathophysiology, Graduate School of Pharmaceutical Sciences, Kyushu University, Fukuoka, Japan.
Kariura
Yukihiro
Y
Manago
Yoshimasa
Y
Amano
Taiju
T
Wang
Bing
B
Sekiguchi
Masayuki
M
Nishikawa
Kaori
K
Aoki
Shunsuke
S
Wada
Keiji
K
Noda
Mami
M
D000494:Allosteric Regulation / Q000187:drug effects / Q000502:physiology; D000818:Animals; D000831:Animals, Newborn; D002118:Calcium / Q000378:metabolism; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism*; D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D018683:Excitatory Amino Acid Agents / Q000494:pharmacology; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D025461:Feedback, Physiological / Q000187:drug effects / Q000502:physiology; D018698:Glutamic Acid / Q000378:metabolism*; D020935:MAP Kinase Signaling System / Q000187:drug effects / Q000502:physiology; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D017628:Microglia / Q000187:drug effects / Q000378:metabolism*; D018408:Patch-Clamp Techniques; D021122:Protein Subunits / Q000187:drug effects / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D018091:Receptors, AMPA / Q000187:drug effects / Q000378:metabolism*; D012964:Sodium / Q000378:metabolism; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism
D018683:Excitatory Amino Acid Agents; D018691:Excitatory Amino Acid Antagonists; D021122:Protein Subunits; D018091:Receptors, AMPA; D014409:Tumor Necrosis Factor-alpha; D018698:Glutamic Acid; D012964:Sodium; D002118:Calcium