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Ecto-5 '-Nucleotidase (CD73) Inhibits Nociception by Hydrolyzing AMP to Adenosine in Nociceptive Circuits

Department of Cell and Molecular Physiology, UNC Neuroscience Center and Curriculum in Neurobiology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, USA.
The Journal of Neuroscience : The Official Journal of the Society for Neuroscience (Impact Factor: 6.75). 02/2010; 30(6):2235-44. DOI: 10.1523/JNEUROSCI.5324-09.2010
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ABSTRACT Ecto-5'-nucleotidase (NT5E, CD73) is a membrane-anchored protein that hydrolyzes extracellular adenosine 5'-monophosphate (AMP) to adenosine in diverse tissues but has not been directly studied in nociceptive neurons. We found that NT5E was located on peptidergic and nonpeptidergic nociceptive neurons in dorsal root ganglia (DRG) and on axon terminals in lamina II (the substantia gelatinosa) of spinal cord. NT5E was also located on epidermal keratinocytes, cells of the dermis, and on nociceptive axon terminals in the epidermis. Following nerve injury, NT5E protein and AMP histochemical staining were coordinately reduced in lamina II. In addition, AMP hydrolytic activity was reduced in DRG neurons and spinal cord of Nt5e(-/-) mice. The antinociceptive effects of AMP, when combined with the adenosine kinase inhibitor 5-iodotubericidin, were reduced by approximately 50% in Nt5e(-/-) mice and were eliminated in Adenosine A(1) receptor (A(1)R, Adora1) knock-out mice. Additionally, Nt5e(-/-) mice displayed enhanced sensitivity in the tail immersion assay, in the complete Freund's adjuvant model of inflammatory pain and in the spared nerve injury model of neuropathic pain. Collectively, our data indicate that the ectonucleotidase NT5E regulates nociception by hydrolyzing AMP to adenosine in nociceptive circuits and represents a new molecular target for the treatment of chronic pain. Moreover, our data suggest NT5E is well localized to regulate nucleotide signaling between skin cells and sensory axons.

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    • "yed by Wachstein and Meisel for histochemical characterization of hepatic phosphatases ( Wachstein & Meisel , 1957 ) . Using this approach , tissue and cellular localization as well as substrate specificity of different purinergic enzymes has been char - acterized in the murine brain ( Langer et al . , 2008 ) , dorsal root ganglion , spinal cord ( Sowa et al . , 2010 ; Street et al . , 2013 ; Zylka et al . , 2008 ) and other neurogenic zones ( Langer et al . , 2007 ) , rat liver ( Fausther et al . , 2012 ) , murine pancreas , salivary glands , gastrointestinal tract ( Kittel et al . , 2004a ; Lavoie et al . , 2011 ) and thoracic aortas ( Kauffenstein et al . , 2010 ; Mercier et al . , 2012 ) , mouse"
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    Critical Reviews in Biochemistry and Molecular Biology 11/2014; 49(6):473-97. DOI:10.3109/10409238.2014.953627 · 5.81 Impact Factor
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    • "The role of peripheral adenosine systems, and specifically activation of A1Rs on peripheral sensory nerves in inhibiting pain, is now receiving renewed attention. This reflects several developments including: (1) identification of nucleotidases (CD73, PAP) that generate endogenous adenosine from nucleotides in nociceptive circuits (Zylka et al., 2008; Sowa et al., 2010b); (2) implication of peripheral adenosine (and nucleotides) in acupuncture analgesia in mice (Goldman et al., 2010) and in humans (Takano et al., 2012); (3) peripheral administration of PAP into acupoints leads to long-lasting antinociception (several days) that is dependent on A1Rs (Hurt and Zylka, 2012); (4) exercise regimens that produce analgesia in a model of neuropathic pain involve A1Rs (peripheral adenosine levels increase due to increased ATP utilization in muscle) (Martins et al., 2013). Several strategies may potentially recruit this peripheral system: (1) topical administration of small molecule drugs that directly or indirectly activate peripheral A1Rs; (2) optimizing acupuncture by augmenting adenosine production or inhibiting adenosine metabolism; (3) novel delivery techniques such as localized delivery of nucleotidases to acupuncture sites (Zylka, 2011; Hurt and Zylka, 2012; Sawynok, 2013). "
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    ABSTRACT: Topical analgesics applied locally to skin or to specialized compartments modify pain by actions on sensory nerve endings and/or adjacent cellular elements. With this approach, there are low systemic drug levels, good tolerability and few drug interactions, and combination with oral formulations is feasible. The goal of this review is to provide an overview of the potential for topical analgesics to contribute to improved management of neuropathic pain. Mechanistic and preclinical studies indicate much potential for development of novel topical analgesics for neuropathic pain. In humans, two topical analgesics are approved for use in post-herpetic neuralgia (lidocaine 5% medicated plaster, capsaicin 8% patch), and there is evidence for efficacy in other neuropathic pain conditions. Comparative trials indicate similar efficacy between topical and oral analgesics. Not all individuals respond to topical analgesics, and there is interest in determining factors (patient factors, sensory characteristics) which might predict responsiveness to topical analgesics. There is a growing number of controlled trials and case reports of investigational agents (vasodilators, glutamate receptor antagonists, α2-adrenoreceptor agonists, antidepressants, centrally acting drugs), including combinations of several agents, indicating these produce pain relief in neuropathic pain. There is interest in compounding topical analgesics for neuropathic pain, but several challenges remain for this approach. Topical analgesics have the potential to be a valuable additional approach for the management of neuropathic pain.
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    • "Ecto-5'-nucleotidase (NT5E) is an enzyme located in the cell membrane that catalyzes the extracellular conversion of adenosine monophosphate (AMP) into adenosine in several tissues, included dorsal root ganglia (DRG) and substantia gelatinosa (Zylka, 2011). Recent studies have demonstrated that the analgesic effect of AMP combined with an AK inhibitor halved in NT5E knockout animals and is totally reversed in A 1R knockout animals (Sowa et al., 2010a). These results inspired another study that evaluated whether exogenous supply of NT5E (increases supply of adenosine) could induce a long lasting analgesic effect. "
    Pharmacology, 03/2012; , ISBN: 978-953-51-0222-9
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