Group IIA secretory phospholipase A2 stimulates exocytosis and neurotransmitter release in pheochromocytoma-12 cells and cultured rat hippocampal neurons

• Published in: Neuroscience 2003, Vol.121 (4), p.891-898
• Main Authors: WEI, S, ONG, W. Y, THWIN, M. M, FONG, C. W, FAROOQUI, A. A, GOPALAKRISHNAKONE, P, HONG, W
• Format: Article
• Language: English
• Subjects: Animals; Animals, Newborn; Biological and medical sciences; Calcium Signaling - drug effects; Calcium Signaling - physiology; Cell Membrane - drug effects; Cell Membrane - enzymology; Cells, Cultured; Central nervous system; Central neurotransmission. Neuromudulation. Pathways and receptors; Chelating Agents - pharmacology; Enzyme Inhibitors - pharmacology; Exocytosis - drug effects; Exocytosis - physiology; Fundamental and applied biological sciences. Psychology; Group II Phospholipases A2; Hippocampus - drug effects; Hippocampus - enzymology; Kainic Acid - pharmacology; Membrane Fusion - drug effects; Membrane Fusion - physiology; Membrane Potentials - drug effects; Membrane Potentials - physiology; Nerve Degeneration - chemically induced; Nerve Degeneration - enzymology; Neurons - drug effects; Neurons - enzymology; Neurons - metabolism; Neurotransmitter Agents - metabolism; Patch-Clamp Techniques; PC12 Cells; Phospholipases A - metabolism; Phospholipases A - pharmacology; Phospholipases A2; Presynaptic Terminals - drug effects; Presynaptic Terminals - enzymology; Rats; Rats, Wistar; Synaptic Vesicles - drug effects; Synaptic Vesicles - enzymology; Synaptic Vesicles - metabolism; Vertebrates: nervous system and sense organs
• ISSN: 0306-4522; 1873-7544
• DOI: 10.1016/s0306-4522(03)00525-6

Recent evidence shows that secretory phospholipase A2 (sPLA2) may play a role in membrane fusion and fission, and may thus affect neurotransmission. The present study therefore aimed to elucidate the effects of sPLA2 on vesicle exocytosis. External application of group IIA sPLA2 (purified crotoxin subunit B or purified human synovial sPLA2) caused an immediate increase in exocytosis and neurotransmitter release in pheochromocytoma-12 (PC12) cells, detected by carbon fiber electrodes placed near the cells, or by changes in membrane capacitance of the cells. EGTA and a specific inhibitor of sPLA2 activity, 12-epi-scalaradial, abolished the increase in neurotransmitter release, indicating that the effect of sPLA2 was dependent on calcium and sPLA2 enzymatic activity. A similar increase in neurotransmitter release was also observed in hippocampal neurons after external application of sPLA2, as detected by changes in membrane capacitance of the neurons. In contrast to external application, internal application of sPLA2 to PC12 cells and neurons produced blockade of neurotransmitter release. Our recent studies showed high levels of sPLA2 activity in the normal rat hippocampus, medulla oblongata and cerebral neocortex. The sPLA2 activity in the hippocampus was significantly increased, after kainate-induced neuronal injury. The observed effects of sPLA2 on neurotransmitter release in this study may therefore have a physiological, as well as a pathological role.