Oxidative stress and cyclooxygenase-2 induction mediate cyanide-induced apoptosis of cortical cells.
Cyanide (KCN)-induced generation of reactive oxygen species (ROS) involves cyclooxygenase-2 (COX-2)-mediated reactions in some neurons. The present study examines the extent to which COX isoforms are involved in KCN-induced apoptotic cell death processes of cultured cortical cells. After treatment with KCN (10-300 microM), COX-2 was expressed in a time- and concentration-dependent manner increasing markedly over a 4-h period. However, no significant changes were observed in COX-1 levels at any cyanide concentration. Correlated with COX-2 up-regulation, KCN induced a time-dependent apoptotic death. TUNEL staining showed that the COX-2 inhibitor NS-398 (30 microM) blocked KCN-induced apoptosis, whereas the selective COX-1 inhibitor valeryl salicylate did not affect the level of apoptotic cell death. Exposure of cells to KCN (300 microM) for 24 h resulted in DNA fragmentation, which was also reduced by NS-398. Prostaglandin E(2) (PGE(2)) accumulation in cell culture supernatants was increased by KCN and NS-398 blocked PGE(2) generation. PCR studies further confirmed that COX-2 expression was increased by KCN. Antioxidants phenyl-N-test-butylnitrone, superoxide dismutase, and catalase significantly inhibited KCN-induced COX-2 up-regulation and subsequent apoptosis. N(G)-nitro-L-arginine methylester an inhibitor of nitric oxide synthase, blocked KCN-induced PGE(2) production and apoptosis, but not COX-2 expression. Increased nitric oxide levels caused by cyanide may directly activate the COX-2 enzyme. These data show that cyanide treatment of cortical cells involves increased COX-2 expression, PGE(2) accumulation, and ROS generation, resulting in apoptotic cell death.
Li
L
L
Neurotoxicology Laboratory, Department of Medical Chemisstry and Molecular Chemistry and Molecular Pharmacology, Purdue University, West Lafayette, Indiana 47907-1333, USA.
Prabhakaran
K
K
Shou
Y
Y
Borowitz
J L
JL
Isom
G E
GE
D000818:Animals; D000975:Antioxidants / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects*; D002540:Cerebral Cortex / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D051546:Cyclooxygenase 2; D052246:Cyclooxygenase 2 Inhibitors; D016861:Cyclooxygenase Inhibitors / Q000494:pharmacology; D015232:Dinoprostone / Q000096:biosynthesis; D004790:Enzyme Induction / Q000187:drug effects; D007527:Isoenzymes / Q000096:biosynthesis*; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D018384:Oxidative Stress; D011190:Potassium Cyanide / Q000633:toxicity*; D011451:Prostaglandin-Endoperoxide Synthases / Q000096:biosynthesis*; D051381:Rats; D017207:Rats, Sprague-Dawley
D000975:Antioxidants; D052246:Cyclooxygenase 2 Inhibitors; D016861:Cyclooxygenase Inhibitors; D007527:Isoenzymes; D051546:Cyclooxygenase 2; D011451:Prostaglandin-Endoperoxide Synthases; D015232:Dinoprostone; D011190:Potassium Cyanide; D019331:NG-Nitroarginine Methyl Ester