Interaction of cyanide with a dopamine metabolite: formation of a cyanohydrin adduct and its implications for cyanide-induced neurotoxicity.
Incubation of rat pheochromocytoma (PC12) cells with cyanide (1-10 mM) for 30 min produced a compound which eluted between dopamine (DA) and 3,4-dihydroxyphenylacetic acid in HPLC-EC analysis. Generation of the compound was rapid, concentration-dependent and blocked by pretreatment with clorgyline, a monoamine oxidase A inhibitor. In cell free incubation, the compound formed rapidly when cyanide was added to a mixture of monoamine oxidase and DA, but was not detected when cyanide was included with DA alone. The compound was radiolabelled when 14C-KCN was added to the incubation mixture. Based on these results, it is proposed that the deaminated metabolite of DA, 3,4-dihydroxyphenylacetaldehyde (DOPAL), reacts non enzymatically with cyanide to form the cyanohydrin adduct 2-hydroxy-3-(3,4-dihydroxyphenyl) propionitrile (HPN). HPN was confirmed by spectral analysis and co-elution with synthetic HPN. Incubation of mouse brain slices with cyanide (1 mM) generated 0.98 ng HPN/100 mg wet wt. over a 10 min period and HPN was detected in brains of mice after injection of cyanide (15.6 micrograms) into the lateral brain ventricle. Repeated doses of KCN (6 mg/kg, s.c., five times) produced 0.14 +/- 0.03 ng/100 mg of tissue in striatum. Incubation of PC12 cells for 60 min with 500 microM HPN killed 23% of the cells and increased DA release from the cells by 39.8% over untreated cells. Uptake of HPN into the cells was partially blocked by the catecholamine uptake inhibitor imipramine. These results indicate cyanide reacts with the DA metabolite DOPAL to generate a biologically active cyanohydrin adduct which may contribute to the neurotoxic response to cyanide.
Kanthasamy
A G
AG
Department of Pharmacology and Toxicology, Purdue University, West Lafayette, Indiana 47907-1334, USA.
Rathinavelu
A
A
Borowitz
J L
JL
Isom
G E
GE
D015102:3,4-Dihydroxyphenylacetic Acid / Q000737:chemistry / Q000378:metabolism; D000818:Animals; D002851:Chromatography, High Pressure Liquid; D003486:Cyanides / Q000633:toxicity*; D004298:Dopamine / Q000031:analogs & derivatives / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D051379:Mice; D009498:Neurotoxins; D016716:PC12 Cells; D051381:Rats
D003486:Cyanides; D009498:Neurotoxins; D015102:3,4-Dihydroxyphenylacetic Acid; D004298:Dopamine