Secreted phospholipase A2 potentiates glutamate-induced calcium increase and cell death in primary neuronal cultures.
Secreted phospholipases A2 (sPLA2s) modulate neuronal survival and neurotransmitter release. Here we show that sPLA2 (group III) synergistically increases glutamate-induced cell death and intracellular calcium ([Ca2+]i) in cultured primary cortical and hippocampal neurons. Whereas 1 microM glutamate elicited transient [Ca2+]i increases in all neurons that recovered 66% to baseline, 25 ng/ml sPLA2 pretreatment resulted in sustained [Ca2+]i increases, with only 5% recovery. At 250 nM glutamate, 25% of neurons failed to respond, and the average recovery time was 101 +/- 12 sec; sPLA2 increased recovery time to 158 +/- 6 sec, and only 2% of cells failed to respond. Both the noncompetitive N-methyl-D-aspartate (NMDA) receptor antagonist MK-801 and the calcium-channel blocker cobalt inhibited this effect. Experiments with the glutamate uptake inhibitor L-trans-pyrollidine-2,4-dicarboxylic acid (2.5 microM) indicated that glutamate uptake sites are not a likely modulation point by sPLA2, whereas arachidonic acid (AA) potentiated calcium responses to glutamate. Thus the enhancement of glutamate-induced [Ca2+]i increases by sPLA2 may be due to modulation at NMDA receptors and/or calcium channels by AA. These results indicate that sPLA2 affects neuronal responses to both nontoxic (0.1-10 microM) and toxic (=25 microM) concentrations of glutamate, implicating this enzyme in neuronal functions in pathology.
DeCoster
Mark A
MA
Neuroscience Center, LSU Health Sciences Center, New Orleans, Louisiana 70112, USA.
Lambeau
Gerard
G
Lazdunski
Michel
M
Bazan
Nicolas G
NG
D000818:Animals; D016587:Antimutagenic Agents / Q000494:pharmacology; D016718:Arachidonic Acid / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000187:drug effects / Q000378:metabolism; D020013:Calcium Signaling / Q000187:drug effects / Q000502:physiology*; D016923:Cell Death / Q000187:drug effects / Q000502:physiology*; D002478:Cells, Cultured; D002540:Cerebral Cortex / Q000187:drug effects / Q000378:metabolism; D003035:Cobalt / Q000494:pharmacology; D003998:Dicarboxylic Acids / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D018698:Glutamic Acid / Q000378:metabolism* / Q000494:pharmacology; D006624:Hippocampus / Q000187:drug effects / Q000378:metabolism; D007424:Intracellular Fluid / Q000187:drug effects / Q000378:metabolism; D009474:Neurons / Q000187:drug effects / Q000201:enzymology*; D014179:Neurotransmitter Uptake Inhibitors / Q000494:pharmacology; D010741:Phospholipases A / Q000378:metabolism* / Q000494:pharmacology; D054467:Phospholipases A2; D011759:Pyrrolidines / Q000494:pharmacology; D051381:Rats; D016194:Receptors, N-Methyl-D-Aspartate / Q000187:drug effects / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology
D016587:Antimutagenic Agents; D015220:Calcium Channels; D003998:Dicarboxylic Acids; D018691:Excitatory Amino Acid Antagonists; D014179:Neurotransmitter Uptake Inhibitors; D011759:Pyrrolidines; D016194:Receptors, N-Methyl-D-Aspartate; D016718:Arachidonic Acid; D003035:Cobalt; D018698:Glutamic Acid; C083486:pyrrolidine-2,4-dicarboxylic acid; D010741:Phospholipases A; D054467:Phospholipases A2; C018021:cobaltous chloride; D002118:Calcium