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Inhibitors of kynurenine hydroxylase and kynureninase increase cerebral formation of kynurenate and have sedative and anticonvulsant activities. 1994

R Carpenedo, and A Chiarugi, and P Russi, and G Lombardi, and V Carlà, and R Pellicciari, and L Mattoli, and F Moroni
Department of Preclinical and Clinical Pharmacology, University of Florence, Italy.

Kynurenate is an endogenous antagonist of the ionotropic glutamate receptors. It is synthesized from kynurenine, a tryptophan metabolite, and a significant increase in its brain concentration could be useful in pathological situations. We attempted to increase its neosynthesis by modifying kynurenine catabolism. Several kynurenine analogues were synthesized and tested as inhibitors of kynurenine hydroxylase (E.C.1.14.13.9) and of kynureninase (E.C.3.7.1.3), the two enzymes which catalyse the conversion of kynurenine to excitotoxin quinolinate. Among these analogues we observed that nicotinylalanine, a compound whose pharmacological properties have previously been reported, had an IC50 of 900 +/- 180 microM as inhibitor of kynurenine hydroxylase and of 800 +/- 120 microM as inhibitor of kynureninase. In the search for more potent molecules we noticed that meta-nitrobenzoylalanine had an IC50 of 0.9 +/- 0.1 microM as inhibitor of kynurenine hydroxylase and of 100 +/- 12 microM as inhibitor of kynureninase. When administered to rats meta-nitrobenzoylalanine (400 mg/kg) significantly increased the concentration of kynurenine (up to 10 times) and kynurenate (up to five times) in the brain. Similar results were obtained in the blood and in the liver. Furthermore meta-nitrobenzoylalanine increased in a dose dependent, long lasting (up to 13 times and up to 4 h) manner the concentration of kynurenate in the hippocampal extracellular fluid, as evaluated with a microdialysis technique. This increase was associated with a decrease in the locomotor activity and with protection from maximal electroshock-induced seizures in rats or from audiogenic seizures in DBA/2 mice. The conclusions drawn from the present study are: (i) meta-nitrobenzoylalanine is a potent inhibitor of kynurenine hydroxylase also affecting kynureninase; (ii) the inhibition of these enzymes causes a significant increase in the brain extracellular concentration of kynurenate; (iii) this increase is associated with sedative and anticonvulsant actions, suggesting a functional antagonism of the excitatory amino acid receptors.

UI MeSH Term Description Entries
D006993 Hypnotics and Sedatives Drugs used to induce drowsiness or sleep or to reduce psychological excitement or anxiety. Hypnotic,Sedative,Sedative and Hypnotic,Sedatives,Hypnotic Effect,Hypnotic Effects,Hypnotics,Sedative Effect,Sedative Effects,Sedatives and Hypnotics,Effect, Hypnotic,Effect, Sedative,Effects, Hypnotic,Effects, Sedative,Hypnotic and Sedative
D007736 Kynurenic Acid A broad-spectrum excitatory amino acid antagonist used as a research tool. Kynurenate,Acid, Kynurenic
D007737 Kynurenine A metabolite of the essential amino acid tryptophan metabolized via the tryptophan-kynurenine pathway.
D008297 Male Males
D009043 Motor Activity Body movements of a human or an animal as a behavioral phenomenon. Activities, Motor,Activity, Motor,Motor Activities
D009457 Neuroglia The non-neuronal cells of the nervous system. They not only provide physical support, but also respond to injury, regulate the ionic and chemical composition of the extracellular milieu, participate in the BLOOD-BRAIN BARRIER and BLOOD-RETINAL BARRIER, form the myelin insulation of nervous pathways, guide neuronal migration during development, and exchange metabolites with neurons. Neuroglia have high-affinity transmitter uptake systems, voltage-dependent and transmitter-gated ion channels, and can release transmitters, but their role in signaling (as in many other functions) is unclear. Bergmann Glia,Bergmann Glia Cells,Bergmann Glial Cells,Glia,Glia Cells,Satellite Glia,Satellite Glia Cells,Satellite Glial Cells,Glial Cells,Neuroglial Cells,Bergmann Glia Cell,Bergmann Glial Cell,Cell, Bergmann Glia,Cell, Bergmann Glial,Cell, Glia,Cell, Glial,Cell, Neuroglial,Cell, Satellite Glia,Cell, Satellite Glial,Glia Cell,Glia Cell, Bergmann,Glia Cell, Satellite,Glia, Bergmann,Glia, Satellite,Glial Cell,Glial Cell, Bergmann,Glial Cell, Satellite,Glias,Neuroglial Cell,Neuroglias,Satellite Glia Cell,Satellite Glial Cell,Satellite Glias
D009525 Niacin A water-soluble vitamin of the B complex occurring in various animal and plant tissues. It is required by the body for the formation of coenzymes NAD and NADP. It has PELLAGRA-curative, vasodilating, and antilipemic properties. Nicotinic Acid,3-Pyridinecarboxylic Acid,Enduracin,Induracin,Lithium Nicotinate,Niacin Aluminum Salt,Niacin Ammonium Salt,Niacin Calcium Salt,Niacin Cobalt (2+) Salt,Niacin Copper (2+) Salt,Niacin Hydrochloride,Niacin Iron (2+) Salt,Niacin Lithium Salt,Niacin Lithium Salt, Hemihydrate,Niacin Magnesium Salt,Niacin Manganese (2+) Salt,Niacin Potassium Salt,Niacin Sodium Salt,Niacin Tartrate,Niacin Tosylate,Niacin Zinc Salt,Nicamin,Nico-400,Nicobid,Nicocap,Nicolar,Nicotinate,Wampocap,3 Pyridinecarboxylic Acid,Aluminum Salt, Niacin,Hydrochloride, Niacin,Nico 400,Nico400,Nicotinate, Lithium,Potassium Salt, Niacin,Sodium Salt, Niacin,Tartrate, Niacin,Tosylate, Niacin
D001923 Brain Chemistry Changes in the amounts of various chemicals (neurotransmitters, receptors, enzymes, and other metabolites) specific to the area of the central nervous system contained within the head. These are monitored over time, during sensory stimulation, or under different disease states. Chemistry, Brain,Brain Chemistries,Chemistries, Brain
D004597 Electroshock Induction of a stress reaction in experimental subjects by means of an electrical shock; applies to either convulsive or non-convulsive states. Electroconvulsive Shock,Electroconvulsive Shocks,Electroshocks,Shock, Electroconvulsive,Shocks, Electroconvulsive
D006867 Hydrolases Any member of the class of enzymes that catalyze the cleavage of the substrate and the addition of water to the resulting molecules, e.g., ESTERASES, glycosidases (GLYCOSIDE HYDROLASES), lipases, NUCLEOTIDASES, peptidases (PEPTIDE HYDROLASES), and phosphatases (PHOSPHORIC MONOESTER HYDROLASES). EC 3. Hydrolase

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