Porcine pancreatic group IB secretory phospholipase A2 potentiates Ca2+ influx through L-type voltage-sensitive Ca2+ channels.
Secretory phospholipase A(2) (sPLA(2)) exhibits neurotoxicity in the central nervous system. There are high-affinity binding sites of the porcine pancreatic group IB sPLA(2) (sPLA(2)-IB) in the brain. sPLA(2)-IB causes neuronal cell death via apoptosis in the rat cerebral cortex. Although apoptosis is triggered by an influx of Ca(2+) into neurons, it has not yet been ascertained whether the Ca(2+) influx is associated with the neurotoxicity of sPLA(2)-IB. We thus examined the possible involvement of Ca(2+) in the neurotoxicity of sPLA(2)-IB in the primary culture of rat cortical neurons. sPLA(2)-IB induced neuronal cell death in a concentration- and time-dependent manner. This death was accompanied by condensed chromatin and fragmented DNA, exhibiting apoptotic features. Before apoptosis, sPLA(2)-IB markedly enhanced the influx of Ca(2+) into neurons. A calcium chelator suppressed neurons from sPLA(2)-IB-induced neuronal cell death in a concentration-dependent manner. An L-type voltage-sensitive Ca(2+) channel (L-VSCC) blocker significantly protected the sPLA(2)-IB-potentiated influx of Ca(2+). On the other hand, blockers of N-VSCC and P/Q-VSCC did not. An L-VSCC blocker protected neurons from sPLA(2)-IB-induced neuronal cell death. In addition, the L-VSCC blocker ameliorated the apoptotic features of sPLA(2)-IB-treated neurons. Neither an N-VSCC blocker nor P/Q-VSCC blockers affected the neurotoxicity of the enzyme. In conclusion, these findings demonstrate that the influx of Ca(2+) into neurons play an important role in the neurotoxicity of sPLA(2)-IB. Furthermore, the present study suggests that L-VSCC contribute to the sPLA(2)-IB-potentiated influx of Ca(2+) into neurons.
Yagami
Tatsurou
T
Discovery Research Laboratories, Shionogi and Co Ltd, 12-4 Sagisu 5-Chome, Fukushima-ku, Osaka 553-0002, Japan. tatsurou.yagami@shionogi.co.jp
Ueda
Keiichi
K
Asakura
Kenji
K
Sakaeda
Toshiyuki
T
Hata
Satoshi
S
Kuroda
Takayuki
T
Sakaguchi
Gaku
G
Itoh
Naohiro
N
Hashimoto
Yutaka
Y
Hori
Yozo
Y
D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D002118:Calcium / Q000378:metabolism*; D002121:Calcium Channel Blockers / Q000494:pharmacology; D020746:Calcium Channels, L-Type / Q000187:drug effects*; D016923:Cell Death / Q000187:drug effects; D002467:Cell Nucleus / Q000187:drug effects / Q000378:metabolism; D002478:Cells, Cultured; D053938:DNA Fragmentation / Q000187:drug effects; D005260:Female; D054500:Group IB Phospholipases A2; D020287:In Situ Nick-End Labeling; D008856:Microscopy, Fluorescence; D009474:Neurons / Q000187:drug effects*; D009498:Neurotoxins / Q000494:pharmacology / Q000633:toxicity; D009553:Nimodipine / Q000494:pharmacology; D010179:Pancreas / Q000201:enzymology*; D010741:Phospholipases A / Q000494:pharmacology* / Q000633:toxicity; D054467:Phospholipases A2; D011247:Pregnancy; D051381:Rats; D017207:Rats, Sprague-Dawley; D013268:Stimulation, Chemical; D013552:Swine
D002121:Calcium Channel Blockers; D020746:Calcium Channels, L-Type; D009498:Neurotoxins; D009553:Nimodipine; D010741:Phospholipases A; D054500:Group IB Phospholipases A2; D054467:Phospholipases A2; C516204:Pla2g1b protein, rat; D002118:Calcium