NO Biosynthesis (no + biosynthesis)

Distribution by Scientific Domains

Selected Abstracts

The alpha-amino group of l -arginine mediates its antioxidant effect

S. Wallner
Antioxidant effects may constitute part of the possible antiatherogenic effects of the amino acid l -arginine. These antioxidant properties were further characterized in a model of lipoprotein oxidation. Oxidation of lipoproteins in unfractionated human serum was continuously monitored by a fluorescent probe. The antioxidant effects of l -arginine, N -,-acetyl-arginine and vitamin E in combination with l -arginine were measured after initiation of free radical generation with either copper or 2,2,-azobis(2-amidinopropane) hydrochloride (AAPH). The half-time of the fast propagation rate for copper-induced lipoprotein oxidation increased after incubation with l -arginine in a dose-dependent manner (P < 0·01). N -,-acetyl-arginine did not show such effects. Vitamin E and l -arginine show different effects on copper-induced oxidation, the former increasing only lag-time, the latter increasing only propagation rate, and do not have reciprocal effects. In contrast to copper-induced oxidation, l -arginine increased the lag-time of AAPH-induced lipoprotein oxidation (P < 0·01), with no effect on the propagation rate at physiological concentrations. Again, N -,-acetyl-arginine did not show any antioxidant effects. Our experiments provide further evidence that mechanisms other than serving as a substrate for the NO-synthase could be involved in the antiatherosclerotic effect of l -arginine. In addition, our experiments clearly show, that the antioxidant effect of l -arginine is due to a chemical moiety different from that serving as the substrate for NO biosynthesis. [source]

NF-,B involvement in the induction of high affinity CAT-2 in lipopolysaccharide-stimulated rat lungs

C.-J. Huang
Background:, Endotoxemia stimulates nitric oxide (NO) biosynthesis through induction of inducible NO synthase (iNOS). Cellular uptake of l -arginine, the sole substrate for iNOS, is an important mechanism regulating NO biosynthesis by iNOS. The isozymes of type-2 cationic amino acid transporters, including CAT-2, CAT-2A, and CAT-2B, constitute the most important pathways responsible for trans -membrane l -arginine transportation. Therefore, regulation of CAT-2 isozymes expression may constitute one of the downstream regulatory pathways that control iNOS activity. We investigated the time course of enzyme induction and the role of nuclear factor-,B (NF-,B) in CAT-2 isozymes expression in lipopolysaccharide-(LPS) treated rat lungs. Methods:, Adult male Sprague,Dawley rats were randomly given intravenous injections of normal saline (N/S), LPS, LPS plus NF-,B inhibitor pre-treatment (PDTC, dexamethasone, or salicylate), or an NF-,B inhibitor alone. The rats were sacrificed at different times after injection and enzyme expression and lung injury were examined. Pulmonary and systemic NO production were also measured. Results:, LPS co-induced iNOS, CAT-2, and CAT-2B but not CAT-2A expression in the lungs. Furthermore, NF-,B actively participated in LPS-induction of iNOS, CAT-2, and CAT-2B. LPS induced pulmonary and systemic NO overproduction and resulted in lung injuries. Attenuation of LPS-induced iNOS, CAT-2, and CAT-2B induction significantly inhibited NO biosynthesis and lessened lung injury. Conclusion:, NF-,B actively participates in the induction of CAT-2 and CAT-2B in intact animals. Our data further support the idea that CAT-2 and CAT-2B are crucial in regulating iNOS activity. [source]

Arylazoamidoximes and Related Compounds as NO-modulators

Alexander Schröder
Abstract Three amidinoarylhydrazines 1, three arylazoamidines 2, and nine arylazoamidoximes 3 have been synthesized and investigated for their potential to function as nitric oxide (NO) modulators. In-vitro studies demonstrated that 2 and 3 inhibited platelet aggregation (2c, IC50 = 3 ,M) which could also be shown in vivo by inhibition of thrombus formation in arterioles (3a, 22%). Moreover, for all compounds antihypertensive effects were examined in vivo with SHR rats, with 2a being the most potent candidate by lowering blood pressure by 19%. However, no common underlying mechanism of action could be shown. Some of these compounds released HNO non-enzymatically. Incubations with NO synthase isoforms (NOSs) revealed, that compounds 1 to 3 were weak substrates for NOSs but arylazoamidoximes 3 remarkably elevated the NOSs activity in the presence of L -arginine (3h, up to fivefold). In addition, we examined effects on arginase and dimethylarginine dimethylaminohydrolase (DDAH), two further enzymes involved in the complex regulation of NO biosynthesis, to elucidate whether the observed in-vivo effects can be traced back to their modulation. Furthermore, the metabolic fate of arylazoamidoximes 3 was addressed by investigation of a possible N -reductive biotransformation. In summary, novel NO-modulating compound classes are presented, among which arylazoamidoximes 3 are potent activators of NOS isoforms, and arylazoamidines 2 exert in-vivo effects by unknown mechanisms. [source]

Antinociceptive effect of a ruthenium complex in mice

M. P. Cristiano
Summary 1,The ruthenium complexes are important tools in inorganic chemistry. Different biological properties are found in the presence of distinct coordinate ligands, which offer a variety of potential clinical and pharmacological uses. 2,The aim of this work was to evaluate the antinociceptive and behavioural effects of the ruthenium complex, trans -[RuCl2(i-dinic)4]Cl, in mice. 3,The potential analgesic activity was tested using the formalin and hot plate tests and the behavioural effect was evaluated using the rotarod and spontaneous locomotor tests. The complex was administered at concentrations of 1.3, 4.5 and 18.0 ,mol kg,1 i.p. Morphine (6.0 mg kg,1, i.p.) and diclofenac sodium (20.0 mg kg,1, i.p.) were used as reference drugs. 4,The compound had no sedative activity on motor ataxia in the behavioural and analgesic tests. No significant effect was observed in the first phase of the formalin test, however, an effect was observed in the second phase. 5,The complex studied was probably more powerful than the reference drugs as an antinociceptive agent, as this mechanism also involved the nitric oxide (NO) pathway. From this perspective, further experimental studies will be useful to understand the effect of these compounds on NO and the relationship between prostaglandin and NO biosynthesis. [source]