Physiological mechanisms of lysophosphatidylcholine-induced de-ramification of murine microglia.
Activation of microglial cells, the resident macrophages of the brain, occurs rapidly following brain injury. De-ramification, i.e. transformation from ramified into amoeboid morphology is one of the earliest manifestations of microglial activation. In the present study, we identified the physiological mechanisms underlying microglial de-ramification induced by lysophosphatidylcholine (LPC). Patch-clamp experiments revealed activation of non-selective cation currents and Ca(2+)-dependent K(+) currents by extracellular LPC. LPC-activated non-selective cation channels were permeable for monovalent and divalent cations. They were inhibited by Gd(3+), La(3+), Zn(2+) and Grammostola spatulata venom, but were unaffected by diltiazem, LOE908MS, amiloride and DIDS. Ca(2+) influx through non-selective cation channels caused sustained increases in intracellular Ca(2+) concentration. These Ca(2+) increases were sufficient to elicit charybdotoxin-sensitive Ca(2+)-dependent K(+) currents. However, increased [Ca(2+)](i) was not required for LPC-induced morphological changes. In LPC-stimulated microglial cells, non-selective cation currents caused transient membrane depolarization, which was followed by sustained membrane hyperpolarization induced by Ca(2+)-dependent K(+) currents. Furthermore, LPC elicited K(+) efflux by stimulating electroneutral K(+)-Cl(-) cotransporters, which were inhibited by furosemide and DIOA. LPC-induced microglial de-ramification was prevented by simultaneous inhibition of non-selective cation channels and K(+)-Cl(-) cotransporters, suggesting their functional importance for microglial activation.
Schilling
Tom
T
Institute of Physiology, Humboldt University, Tucholskystr. 2, D-10117 Berlin, Germany.
Lehmann
Frank
F
Rückert
Berit
B
Eder
Claudia
C
D000465:Algorithms; D000818:Animals; D000831:Animals, Newborn; D002118:Calcium / Q000378:metabolism; D002463:Cell Membrane Permeability / Q000187:drug effects / Q000502:physiology; D002478:Cells, Cultured; D004594:Electrophysiology; D005456:Fluorescent Dyes; D016257:Fura-2; D007473:Ion Channels / Q000187:drug effects* / Q000502:physiology*; D008244:Lysophosphatidylcholines / Q000494:pharmacology*; D008262:Macrophage Activation / Q000187:drug effects / Q000502:physiology; D008564:Membrane Potentials / Q000502:physiology; D051379:Mice; D017628:Microglia / Q000187:drug effects* / Q000502:physiology* / Q000648:ultrastructure; D018408:Patch-Clamp Techniques; D011188:Potassium / Q000378:metabolism; D024681:Potassium Channels, Calcium-Activated / Q000187:drug effects; D027981:Symporters / Q000378:metabolism; D000096922:K Cl- Cotransporters
D002118:Calcium; D005456:Fluorescent Dyes; D016257:Fura-2; D007473:Ion Channels; D008244:Lysophosphatidylcholines; D011188:Potassium; D024681:Potassium Channels, Calcium-Activated; D027981:Symporters; D000096922:K Cl- Cotransporters