title: The Na+/Ca2+ exchanger-mediated Ca2+ influx triggers nitric oxide-induced cytotoxicity in cultured astrocytes.
abstract: Nitric oxide (NO) is involved in many pathological conditions including neurodegenerative disorders. We have previously found that sodium nitroprusside (SNP), an NO donor, stimulates mitogen-activated protein kinases (MAPKs) such as extracellular signal-regulating kinase (ERK), c-jun N-terminal protein kinase (JNK) and p38 MAPK, leading to caspase-independent apoptosis in cultured astrocytes. In view of the previous observation that NO stimulates the activity of the Na(+)/Ca(2+) exchanger (NCX), this study examines the involvement of NCX in cytotoxicity. The specific NCX inhibitor SEA0400 blocked SNP-induced phosphorylation of ERK, JNK and p38 MAPK, and decrease in cell viability. SNP-induced phosphorylation of ERK, JNK and p38 MAPK was blocked by removal of external Ca(2+), and SNP treatment caused an increase in (45)Ca(2+) influx. This increase in (45)Ca(2+) influx was blocked by SEA0400, but not the Ca(2+) channel blocker nifedipine. In addition, SNP-induced (45)Ca(2+) influx and cytotoxicity were reduced in NCX1-deficient cells which were transfected with NCX1 siRNA. Inhibitors of intracellular Ca(2+)-dependent proteins such as calpain and calmodulin blocked SNP-induced ERK phosphorylation and decrease in cell viability. Furthermore, the guanylate cyclase inhibitor LY83583 and the cGMP-dependent protein kinase inhibitor KT5823 blocked SNP-induced cytotoxicity. These findings suggest that NCX-mediated Ca(2+) influx triggers SNP-induced apoptosis in astrocytes, which may be mediated by a cGMP-dependent pathway.
authors.affiliation: Laboratory of Medicinal Pharmacology, Graduate School of Pharmaceutical Sciences, Osaka University, Suita, Osaka 565-0871, Japan.
authors.forename: Tatsuya
authors.initials: T
authors.lastname: Kitao
authors.forename: Kazuhiro
authors.initials: K
authors.lastname: Takuma
authors.forename: Toshiyuki
authors.initials: T
authors.lastname: Kawasaki
authors.forename: Yuriko
authors.initials: Y
authors.lastname: Inoue
authors.forename: Aki
authors.initials: A
authors.lastname: Ikehara
authors.forename: Tetsuaki
authors.initials: T
authors.lastname: Nashida
authors.forename: Yukio
authors.initials: Y
authors.lastname: Ago
authors.forename: Toshio
authors.initials: T
authors.lastname: Matsuda
mesh_terms: D000818:Animals; D001253:Astrocytes / Q000187:drug effects / Q000378:metabolism* / Q000473:pathology; D001693:Biological Transport, Active / Q000187:drug effects / Q000502:physiology; D002118:Calcium / Q000378:metabolism* / Q000633:toxicity*; D020013:Calcium Signaling / Q000187:drug effects / Q000502:physiology; D016923:Cell Death / Q000187:drug effects / Q000502:physiology; D002478:Cells, Cultured; D006152:Cyclic GMP / Q000502:physiology; D020030:Nitric Oxide Donors / Q000633:toxicity*; D009599:Nitroprusside / Q000633:toxicity; D051381:Rats; D017208:Rats, Wistar; D015398:Signal Transduction / Q000502:physiology; D019831:Sodium-Calcium Exchanger / Q000037:antagonists & inhibitors / Q000235:genetics / Q000502:physiology*
chemical_list: D020030:Nitric Oxide Donors; D019831:Sodium-Calcium Exchanger; C110374:sodium-calcium exchanger 1; D009599:Nitroprusside; D006152:Cyclic GMP; D002118:Calcium