Neoechinulin a imparts resistance to acute nitrosative stress in PC12 cells: a potential link of an elevated cellular reserve capacity for pyridine nucleotide redox turnover with cytoprotection.
Treatment of PC12 cells with fungus-derived alkaloid neoechinulin A for more than 12 h renders the cells resistant to subsequent superoxide (O₂⁻)/nitric oxide (NO) insults derived from 3-morpholinosydnonimine (SIN-1). However, the underlying mechanism(s) remains largely unclear. To elucidate the mechanism(s), we assessed the specificity of the cytoprotection afforded by neoechinulin A treatment using other cytocidal stressors and also clarified the resulting cellular alterations, focusing on the antioxidant and metabolic enzymes systems. Neoechinulin A treatment for more than 12 h endowed PC12 cells with significant resistance to transient NO toxicity, but not persistent NO toxicity, bolus H₂O₂ toxicity, or oxidative insult from the redox cycling quinone menadione. Cellular antioxidant system profiling revealed no substantial potentiation of the activity of any antioxidant enzyme in lysate from the neoechinulin A-treated cells excluding glutathione (GSH) content, which was significantly decreased (>50%), resulting in a proportional compromise in the thiol-reducing activity of the intact cells. In addition, no differences were observed in the activity for any nicotinamide adenine dinucleotide (phosphate) reduced form (NAD(P)H)-generating enzyme, steady-state NAD(P)H/nicotinamide adenine dinucleotide (phosphate) oxidized form (NAD(P)⁺) ratios, or the levels of total NAD(P)H. Nevertheless, the neoechinulin A-treated intact cells exhibited increased NAD(P)H redox turnover when driven by extracellular tetrazolium. The structurally inactive analog preechinulin failed to protect cells against NO toxicity or induce these alterations, suggesting their link with the cytoprotective mechanism. These results suggest that neoechinulin A, despite disabling the GSH defense system, confers cytoprotection against nitrosative stresses by elevating the cellular reserve capacity for NAD(P)H generation, which could offset crippling of energy-supplying systems due to nitrosative stress.
Department of Applied Biological Science, Faculty of Science and Technology, Tokyo University of Science, Chiba 278-8510, Japan.
Soichiro
S
Akashi
Kyo
K
Shirai
Tatsumi
T
Okada
Kanako
K
Konishi
Toshifumi
T
Takeuchi
Kouji
K
Kuramochi
Muneaki
M
Takahashi
Tomoya
T
Nakagawa
Yuki
Y
Ogura
Satoshi
S
Fujieda
Yasushi
Y
Shibata
Fumio
F
Sugawara
Susumu
S
Kobayashi
Nobuo
N
Watanabe
Takao
T
Arai
D000818:Animals; D002470:Cell Survival / Q000187:drug effects; D019610:Cytoprotection / Q000187:drug effects* / Q000502:physiology; D005978:Glutathione / Q000378:metabolism; D026121:Indole Alkaloids / Q000494:pharmacology*; D008981:Molsidomine / Q000031:analogs & derivatives / Q000494:pharmacology; D009569:Nitric Oxide / Q000633:toxicity*; D009574:Nitro Compounds / Q000494:pharmacology; D010084:Oxidation-Reduction; D018384:Oxidative Stress / Q000187:drug effects; D010088:Oxidoreductases / Q000378:metabolism; D016716:PC12 Cells; D010879:Piperazines / Q000494:pharmacology*; D051381:Rats; D000254:Sodium-Potassium-Exchanging ATPase / Q000037:antagonists & inhibitors; D014166:Transferases / Q000378:metabolism
D026121:Indole Alkaloids; D009574:Nitro Compounds; D010879:Piperazines; C490266:neoechinulin A; D009569:Nitric Oxide; C002385:linsidomine; C061872:FK 409; D008981:Molsidomine; D010088:Oxidoreductases; D014166:Transferases; D000254:Sodium-Potassium-Exchanging ATPase; D005978:Glutathione