N-Aryl N'-hydroxyguanidines, a new class of NO-donors after selective oxidation by nitric oxide synthases: structure-activity relationship.
The formation of nitric oxide (NO) was followed during the oxidation of 37 N-hydroxyguanidines or related derivatives, including 18 new N-aryl N'-hydroxyguanidines, by recombinant inducible nitric oxide synthase (NOS II). Several N-aryl N'-hydroxyguanidines bearing a relatively small, electron-donating para subtituent, such as H, F, Cl, CH(3), OH, OCH(3), and NH(2), led to NO formation rates between 8 and 41% of that of NO formation from the natural NOS substrate, N(omega)-hydroxy-L-arginine (NOHA). The characteristics of these reactions were very similar to those previously reported for the oxidation of NOHA by NOS:(i) the strict requirement of NOS containing (6R)-5,6,7,8-tetrahydro-L-biopterin, reduced nicotinamide adenine dinucleotide phosphate, and O(2) for the oxidation to occur, (ii) the formation of NO and the corresponding urea in a 1:1 molar ratio, and (iii) a strong inhibitory effect of the classical NOS inhibitors such as N(omega)-nitro-L-arginine and S-ethyl-iso-thiourea. Structure-activity relationship studies showed that two structural factors are crucial for NO formation from compounds containing a C(triple bond)NOH function. The first one is the presence of a monosubstituted N-hydroxyguanidine function, since disubstituted N-hydroxyguanidines, amidoximes, ketoximes, and aldoximes failed to produce NO. The second one is the presence of a N-phenyl ring bearing a relatively small, not electron-withdrawing para substituent that could favorably interact with a hydrophobic cavity close to the NOS catalytic site. The k(cat) value for NOS II-catalyzed oxidation of N-para-fluorophenyl N'-hydroxyguanidine was 80% of that found for NOHA, and its k(cat)/K(m) value was only 9-fold lower than that of NOHA. Interestingly, the K(m) value found for NOS II-catalyzed oxidation of N-(3-thienyl) N'-hydroxyguanidine was 25 microM, almost identical to that of NOHA. Recombinant NOS I and NOS III also oxidize several N-aryl N'-hydroxyguanidines with the formation of NO, with a clearly different substrate specificity. The best substrates of the studied series for NOS I and NOS III were N-(para-hydroxyphenyl) and N-(meta-aminophenyl) N'-hydroxyguanidine, respectively. Among the studied compounds, the para-chlorophenyl and para-methylphenyl derivatives were selective substrates of NOS II. These results open the way toward a new class of selective NO donors after in situ oxidation by each NOS family.
Renodon-Cornière
Axelle
A
Laboratoire de Chimie et Biochimie Pharmacologiques et Toxicologiques, UMR 8601 CNRS, Université Paris V, 45 Rue des Saints Pères, 75270 Paris Cedex 06, France.
Dijols
Sylvie
S
Perollier
Céline
C
Lefevre-Groboillot
David
D
Boucher
Jean-Luc
JL
Attias
Roger
R
Sari
Marie-Agnes
MA
Stuehr
Dennis
D
Mansuy
Daniel
D
D002384:Catalysis; D002851:Chromatography, High Pressure Liquid; D006146:Guanidines / Q000138:chemical synthesis* / Q000737:chemistry; D007700:Kinetics; D009249:NADP / Q000737:chemistry; D020030:Nitric Oxide Donors / Q000138:chemical synthesis* / Q000737:chemistry; D019001:Nitric Oxide Synthase / Q000737:chemistry*; D052248:Nitric Oxide Synthase Type I; D052247:Nitric Oxide Synthase Type II; D052250:Nitric Oxide Synthase Type III; D010084:Oxidation-Reduction; D010100:Oxygen / Q000737:chemistry; D010108:Oxyhemoglobins / Q000737:chemistry; D013329:Structure-Activity Relationship
D006146:Guanidines; D020030:Nitric Oxide Donors; D010108:Oxyhemoglobins; D009249:NADP; D019001:Nitric Oxide Synthase; D052248:Nitric Oxide Synthase Type I; D052247:Nitric Oxide Synthase Type II; D052250:Nitric Oxide Synthase Type III; D010100:Oxygen