Paradoxical effects of two oximes on nitric oxide production by purified NO synthases, in cell culture and in animals.
We have studied the impact of two novel compounds TO-85 (2,6-di-(alpha-aziridino-alpha-hydroxyiminomethyl)pyridine and TO-133 (bis-(diaziridinoglyoximato)copper), designed as NO donors, on nitrite production by cell cultures, NO production in rat tissues and their ability to inhibit purified NO synthases (NOS). Both substances induced considerable increase of nitrite production in cell cultures. When NO production was assayed in rat organs by means of ESR using Fe(DETC) as a spin trap the anticipated NO-increasing activity of TO-85 was observed only in kidneys; the NO level increasing almost 10-fold. Treatment of rats with TO-133, decreased the NO concentration in brain cortex, cerebellum and liver. When the drugs were administered to animals with high level of iNOS expression induced by LPS, TO-85 did not significantly modify the LPS-induced NO production; administration of TO-133 caused a significant decrease of NO production in blood, brain cortex and cerebellum. Only high concentrations of TO-85 were capable of inhibiting iNOS (IC50=7 mM), the substance inhibited eNOS at lower concentrations (IC50=250 microM). Inhibitory activities of TO-85 on nNOS were dependent on BH4 concentrations, suggesting eventual competition of TO-85 with BH4 when the substance interacts with nNOS. TO-133 reduced eNOS activity with IC50=200 microM, nNOS activity with IC50=200 microM, iNOS activity was not much affected by this substance. Thus, the two tested compounds manifest opposite effects on NO production by purified enzymes and in cell culture. The pattern of the NO synthesis modification in a living animal appears to be even more complex. Our results stress the importance of direct measurements of NO in the tissues using the ESR method.
Sjakste
N
N
Latvian Institute of Organic Synthesis, Aizkraukles Street 21, Riga LV1006, Latvia. Nikolajs.Sjakste@lu.lv
Andrianov
V G
VG
Boucher
J-L
JL
Shestakova
I
I
Baumane
L
L
Dzintare
M
M
Meirena
D
D
Kalvinsh
I
I
D000818:Animals; D001120:Arginine / Q000378:metabolism; D001388:Aziridines / Q000494:pharmacology; D001708:Biopterins / Q000031:analogs & derivatives / Q000378:metabolism; D045744:Cell Line, Tumor; D019343:Citric Acid; D004050:Ditiocarb / Q000737:chemistry; D004578:Electron Spin Resonance Spectroscopy; D005296:Ferrous Compounds / Q000737:chemistry; D006801:Humans; D008070:Lipopolysaccharides / Q000494:pharmacology; D008297:Male; D051379:Mice; D015394:Molecular Structure; D009569:Nitric Oxide / Q000037:antagonists & inhibitors / Q000097:blood / Q000378:metabolism*; D019001:Nitric Oxide Synthase / Q000378:metabolism*; D052248:Nitric Oxide Synthase Type I / Q000037:antagonists & inhibitors / Q000378:metabolism; D052247:Nitric Oxide Synthase Type II / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000378:metabolism; D052250:Nitric Oxide Synthase Type III / Q000037:antagonists & inhibitors / Q000378:metabolism; D010091:Oximes / Q000494:pharmacology*; D051381:Rats; D017208:Rats, Wistar; D019097:Spin Trapping / Q000379:methods
D001388:Aziridines; D005296:Ferrous Compounds; D008070:Lipopolysaccharides; D010091:Oximes; D001708:Biopterins; D019343:Citric Acid; D009569:Nitric Oxide; C016600:ferrous citrate; D001120:Arginine; D004050:Ditiocarb; D019001:Nitric Oxide Synthase; D052248:Nitric Oxide Synthase Type I; D052247:Nitric Oxide Synthase Type II; D052250:Nitric Oxide Synthase Type III; C003402:sapropterin