Pharmacodynamic Effects of a d-Amino Acid Oxidase Inhibitor Indicate a Spinal Site of Action in Rat Models of Neuropathic Pain
01 Jun 2013-Journal of Pharmacology and Experimental Therapeutics (American Society for Pharmacology and Experimental Therapeutics)-Vol. 345, Iss: 3, pp 502-511
TL;DR: Results indicate that inhibition of DAAO in peripheral afferent spinal circuits reduced spontaneous neuronal activity to attenuate pain-related behaviors in rat models of neuropathic and inflammatory pain.
Abstract: Inhibition of d-amino acid oxidase (DAAO) activity is a potential target for the treatment of chronic pain. Here we characterized the effects of systemic administration of the DAAO inhibitor 4H-furo[3,2-b]pyrrole-5-carboxylic acid (SUN) in rat models of neuropathic and inflammatory pain. Oral administration of SUN dose dependently attenuated tactile allodynia induced by ligation of the L5 spinal nerve (SNL) and similarly reversed thermal hyperalgesia produced by chronic constriction injury. In addition, SUN was efficacious against complete Freund's adjuvant-induced thermal hyperalgesia. In these models, maximal reversal of pain-related behaviors corresponded with maximum rates of increase in brain and plasma d-serine concentrations, indicative of full inhibition of DAAO activity. To investigate the possible site(s) of action, we recorded spontaneous nerve activity and mechanically evoked responses of central spinal cord dorsal horn neurons and compared these with spontaneous activity of peripheral dorsal root filaments in anesthetized SNL model animals. Oral SUN reduced spontaneous activity in both central and peripheral recordings at doses and pretreatment times that corresponded to reduced mechanical allodynia in behavioral experiments. After intravenous administration of SUN, the onset of action for this central effect was rapid (maximal effects within 30 minutes), but was abolished by severing afferent inputs to the dorsal horn. Overall, these results indicate that inhibition of DAAO in peripheral afferent spinal circuits reduced spontaneous neuronal activity to attenuate pain-related behaviors in rat models of neuropathic and inflammatory pain.
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TL;DR: The known properties of human DAAO suggest that its activity must be finely tuned to fulfill a main physiological function such as the control of D-serine levels in the brain as well as the role of post-translational modifications on its main biochemical properties at the cellular level.
Abstract: D-Amino acid oxidase (DAAO) is an FAD-containing flavoenzyme that catalyzes with absolute stereoselectivity the oxidative deamination of all natural D-amino acids, the only exception being the acidic ones. This flavoenzyme plays different roles during evolution and in different tissues in humans. Its three-dimensional structure is well conserved during evolution: minute changes are responsible for the functional differences between enzymes from microorganism sources and those from humans. In recent years several investigations focused on human DAAO, mainly because of its role in degrading the neuromodulator D-serine in the central nervous system. D-Serine is the main coagonist of N-methyl D-aspartate receptors, i.e., excitatory amino acid receptors critically involved in main brain functions and pathologic conditions. Human DAAO possesses a weak interaction with the FAD cofactor; thus, in vivo it should be largely present in the inactive, apoprotein form. Binding of active-site ligands and the substrate stabilizes flavin binding, thus pushing the acquisition of catalytic competence. Interestingly, the kinetic efficiency of the enzyme on D-serine is very low. Human DAAO interacts with various proteins, in this way modulating its activity, targeting, and cell stability. The known properties of human DAAO suggest that its activity must be finely tuned to fulfill a main physiological function such as the control of D-serine levels in the brain. At present, studies are focusing on the epigenetic modulation of human DAAO expression and the role of post-translational modifications on its main biochemical properties at the cellular level.
59 citations
TL;DR: Comparison of QUE with morphine and gabapentine has revealed significant effects of this agent in the current chronic constriction injury model, and QUE was significantly superior to Gabapentin and morphine in terms of alleviating mechanical and thermal hypersensitivity.
Abstract: Flavonoids are popular substances in the literature, with proven effects on cardiovascular, neoplastic and neurodegenerative diseases. Antioxidant effect is the most pronounced and studied one. Among thousands of flavonoids, quercetin (QUE) is a prototype with significant antioxidant effects. This study aims to demonstrate the effects of QUE in an experimental rat model of chronic constriction injury (CCI). A two-level study was designed with 42 adult Wistar rats that were randomly assigned to different groups. In the first part, animals in sham, control, quercetin, morphine and gabapentine groups received chronic constriction injury to their sciatic nerves and received a single dose of QUE, morphine and gabapentine. In the second part, different dose regimens of QUE were administered to different groups of animals. Pre-injury and post-injury assessments for mechanical hypersensitivity, thermal sensitivity, locomotor activity and anxiety were recorded and statistical comparisons were performed between different groups. Comparison of QUE with morphine and gabapentine has revealed significant effects of this agent in the current chronic constriction injury model. QUE was significantly superior to Gabapentine and morphine in terms of alleviating mechanical and thermal hypersensitivity. Additionally, pre-injury administration of QUE for 4 days demonstrated long-term effectiveness on mechanical hypersensitivity. This preliminary report the on effects of QUE in a chronic constriction injury model proved significant effects of the agent, which should be supplemented with different studies using different dose regimens.
33 citations
TL;DR: Results show that neuropathic pain depends upon glial d-serine that co-activates spinal NMDA receptors and that upregulated serine racemase expression was upregulated in astrocyte processes in neuropathic rats compared to sham rats.
33 citations
TL;DR: These findings demonstrate for the first time that the activation of Sig-1Rs increases the expression of Srr and d-serine in astrocytes and ultimately affects dorsal horn neurons that are involved in the development of MA in neuropathic mice.
32 citations
Cites background from "Pharmacodynamic Effects of a d-Amin..."
...inhibitor, which increased D-serine concentrations in brain and plasma,reduced spontaneous neuronal activity in both central and peripheral recordings and alsoattenuated pain behaviors in rat models of neuropathic and inflammatory pain[34]....
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TL;DR: The results confirm previous hypotheses regarding active-site lid flexibility of mammalian D-amino acid oxidases and could assist in the design of the next generation of hDAAO inhibitors.
Abstract: The NMDAR (N-methyl-D-aspartate receptor) is a central regulator of synaptic plasticity and learning and memory. hDAAO (human D-amino acid oxidase) indirectly reduces NMDAR activity by degrading the NMDAR co-agonist D-serine. Since NMDAR hypofunction is thought to be a foundational defect in schizophrenia, hDAAO inhibitors have potential as treatments for schizophrenia and other nervous system disorders. Here, we sought to identify novel chemicals that inhibit hDAAO activity. We used computational tools to design a focused, purchasable library of compounds. After screening this library for hDAAO inhibition, we identified the structurally novel compound, ‘compound 2’ [3-(7-hydroxy-2-oxo-4-phenyl-2H-chromen-6-yl)propanoic acid], which displayed low nM hDAAO inhibitory potency (Ki=7 nM). Although the library was expected to enrich for compounds that were competitive for both D-serine and FAD, compound 2 actually was FAD uncompetitive, much like canonical hDAAO inhibitors such as benzoic acid. Compound 2 and an analog were independently co-crystalized with hDAAO. These compounds stabilized a novel conformation of hDAAO in which the active-site lid was in an open position. These results confirm previous hypotheses regarding active-site lid flexibility of mammalian D-amino acid oxidases and could assist in the design of the next generation of hDAAO inhibitors.
30 citations
References
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TL;DR: DAO activity was noticeably low or absent in the nucleus of the solitary tract, ventrolateral medulla and intramediolateral cell column of the spinal cord, indicative of a neuromodulatory role for endogenous D-serine (at the NMDA-glycine site) in in the central control of blood pressure.
24 citations
"Pharmacodynamic Effects of a d-Amin..." refers background in this paper
...DAAO also has been reported to be expressed in the spinal cord of rats (Kappor and Kapoor, 1997), with localization including the dorsal horn....
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Patent•
02 Jul 2007TL;DR: In this article, the authors provided novel inhibitors of the enzyme D-amino acid oxidase as well as pharmaceutical compositions including the compounds of the invention, and also provided methods for the treatment and prevention of neurological disorders, such as neuropsychiatric and neurodegenerative diseases, and pain, ataxia and convulsion.
Abstract: This invention provides novel inhibitors of the enzyme D-amino acid oxidase as well as pharmaceutical compositions including the compounds of the invention. Also provided are methods for the treatment and prevention of neurological disorders, such as neuropsychiatric and neurodegenerative diseases, as well as pain, ataxia and convulsion. The compounds of the invention have the general structure wherein Q is a member selected from O, S, CR1 and N, X and Y are members independently selected from CR2, O, S, N and NR3.
21 citations
TL;DR: The utility of lentiviruses to deliver RNAi to glial cells within the cerebellum, and the role of DAO in D-serine metabolism are confirmed, provide a tool to investigate DAO, an enzyme currently of considerable interest in the pathophysiology and therapy of schizophrenia.
21 citations
"Pharmacodynamic Effects of a d-Amin..." refers background in this paper
...Increases in cerebellum D-serine concentrations have also been reported after cerebellar DAAO activity was inhibited by RNAi (Burnet et al., 2011)....
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TL;DR: It is suggested that under physiological conditions, glycine sites in the spinal cord were available but became saturated following peripheral inflammation, and increased endogenous d-serine or glycine may be involved in nociceptive transmission by modulating NMDA receptor activities.
11 citations
"Pharmacodynamic Effects of a d-Amin..." refers background in this paper
...In fact, reports with intrathecal administration would suggest pronociceptive effects of spinal D-serine (Kolhekar et al., 1994; Guo et al., 2006)....
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Patent•
28 Dec 2004
TL;DR: In this article, the authors present methods for increasing D-Serine concentration and reducing concentration of the toxic products of D- Serine oxidation, for enhancing learning, memory and/or cognition, or for treating schizophrenia, Alzheimer's disease, ataxia, or neuropathic pain, or preventing loss in neuronal function characteristic of neurodegenerative diseases.
Abstract: Methods for increasing D-Serine concentration and reducing concentration of the toxic products of D- Serine oxidation, for enhancing learning, memory and/or cognition, or for treating schizophrenia, Alzheimer's disease, ataxia, or neuropathic pain, or preventing loss in neuronal function characteristic of neurodegenerative diseases involve administering to a subject in need of treatment a therapeutic amount of a compound of formula I, or a pharmaceutically acceptable salt or solvate thereof: I wherein Z1 is N or CR3; Z2 is N or CR4; Z3 is O or S; A is hydrogen, alkyl or M+; M is aluminum, calcium, lithium, magnesium, potassium, sodium, zinc or a mixture thereof; R1, R2, R3 and R4 are independently selected from hydrogen, alkyl, hydroxy alkoxy, aryl, acyl, halo, cyano, haloalkyl, NHCOOR5 and SO2NH2; R5 is aryl, arylalkyl, heteroaryl or heteroarylalkyl; at least one of R1, R2, R3 and R4 is other than hydrogen; and at least one of Z1 and Z2 is other than N.
4 citations