Functional interactions between NMDA receptors and TRPV1 in trigeminal sensory neurons mediate mechanical hyperalgesia in the rat masseter muscle

University of Maryland School of Dentistry, Department of Neural and Pain Sciences, Program in Neuroscience, Baltimore, MD 21201, USA.
Pain (Impact Factor: 5.21). 05/2012; 153(7):1514-24. DOI: 10.1016/j.pain.2012.04.015
Source: PubMed


The NMDA and TRPV1 receptors that are expressed in sensory neurons have been independently demonstrated to play important roles in peripheral pain mechanisms. In the present study, we investigated whether the 2 receptor-channel systems form a functional complex that provides the basis for the development of mechanical hyperalgesia. In the masseter muscle, direct application of NMDA induced a time-dependent increase in mechanical sensitivity, which was significantly blocked when the muscle was pretreated with a specific TRPV1 antagonist, AMG9810. The NR1 subunit of the NMDA receptor and TRPV1 were coexpressed in 32% of masseter afferents in trigeminal ganglia (TG). Furthermore, NR1 and NR2B formed protein-protein complexes with TRPV1 in TG as demonstrated by coimmunoprecipitation experiments. Calcium imaging analyses further corroborated that NMDA and TRPV1 receptors functionally interact. In TG culture, application of NMDA resulted in phosphorylation of serine, but not threonine or tyrosine, residues of TRPV1 in a time course similar to that of the development of NMDA-induced mechanical hyperalgesia. The NMDA-induced phosphorylation was significantly attenuated by CaMKII and PKC inhibitors, but not by a PKA inhibitor. Consistent with the biochemical data, the NMDA-induced mechanical hyperalgesia was also effectively blocked when the muscle was pretreated with a CaMKII or PKC inhibitor. Thus, NMDA receptors and TRPV1 functionally interact via CaMKII and PKC signaling cascades and contribute to mechanical hyperalgesia. These data offer novel mechanisms by which 2 ligand-gated channels in sensory neurons interact and reinforce the notion that TRPV1 functions as a signal integrator under pathological conditions.

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Available from: Jin Y Ro, Jun 16, 2015
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    • "both TRPV1 and TRPA1. ATP or glutamate-induced mechanical hypersensitivity is prevented when either PKC or CaMKII is inhibited, and the inhibition of TRPV1 similarly suppressed the muscular hypersensitivity (Lee et al., 2012b; Saloman et al., 2013). Both P2X 3 and NMDAR activation induces phosphorylation of TRPV1, including serine 800 site, which is the major underlying mechanism for TRPV1 sensitization (Lee et al., 2012a). "
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    ABSTRACT: TRPA1 is expressed in muscle afferents and direct activation of these receptors induces acute mechanical hypersensitivity. However, the functional role of TRPA1 under pathological muscle pain conditions and mechanisms by which TRPA1 mediate muscle pain and hyperalgesia are not clearly understood. Two rodent behavioral models validated to assess craniofacial muscle pain conditions were used to study ATP- and NMDA-induced acute mechanical hypersensitivity and complete Freund's adjuvant (CFA)-induced persistent mechanical hypersensitivity. The rat grimace scale was utilized to assess inflammation-induced spontaneous muscle pain. Behavioral pharmacology experiments were performed to assess the effects of AP18, a selective TRPA1 antagonist under these conditions. TRPA1 expression levels in trigeminal ganglia were examined before and after CFA treatment in the rat masseter muscle. Pre-treatment of the muscle with AP18 dose-dependently blocked the development of acute mechanical hypersensitivity induced by NMDA and αβmeATP, a specific agonist for NMDA and P2X3 receptor, respectively. CFA-induced mechanical hypersensitivity and spontaneous muscle pain responses were significantly reversed by post-treatment of the muscle with AP18 when CFA effects were most prominent. CFA-induced myositis was accompanied by significant up-regulation of TRPA1 expression in TG. Our findings showed that TRPA1 in muscle afferents plays an important role in the development of acute mechanical hypersensitivity and in the maintenance of persistent muscle pain and hypersensitivity. Our data suggested that TRPA1 may serve as a downstream target of pro-nociceptive ion channels, such as P2X3 and NMDA receptors in masseter afferents, and that increased TRPA1 expression under inflammatory conditions may contribute to the maintenance of persistent muscle pain and mechanical hyperalgesisa. Mechanistic studies elucidating transcriptional or post-translational regulation of TRPA1 expression under pathological pain conditions should provide important basic information to further advance the treatment of craniofacial muscle pain conditions.
    Neuroscience 09/2015; 310. DOI:10.1016/j.neuroscience.2015.09.042 · 3.36 Impact Factor
    • "In addition, potential patho(physio)logic consequences of permanently increased CaMKIIa activity in sensory neurons include: nociceptive hypersensitivity and mechanical hyperalgesia through a modulation of TRPV1 activity and its interaction with NMDA receptors (Price et al., 2005; Lee et al., 2012), or activation of purinergic P2X 3 receptors (Nair et al., 2010); as well as mediation of reactive oxygen species increase and cell damage (Kim et al., 2011; Nishio et al., 2012). "
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    ABSTRACT: The activity of calcium/calmodulin-dependent protein kinase II alpha (CaMKIIα) may play a critical role in the modulation of nociceptor activity and plasticity of primary sensory trigeminal neurons. The aim of this study was to investigate the immunoreactivity of phosphorylated CaMKIIα (pCaMKIIα) in subpopulations of trigeminal ganglion (TG) neurons in rat models of early diabetes type 1 (dm1) and 2 (dm2). DM1 model was induced with intraperitoneally (i.p.) injected streptozotocin (STZ) (55mg/kg). DM2 rats were fed with the high fat diet (HFD) for two weeks and then received 35mg/kg of STZ i.p. Two weeks and 2 months after the STZ-diabetes induction, rats were sacrificed and immunohistocemical analysis for detection of pCaMKIIα immunoreactivity and double immunoflorescence labeling with isolectin (IB4) was performed. Increased intensity of pCaMKIIα immunofluorescence, restricted to IB4-negative small-diameter neurons, was seen in TG neurons two months after STZ-DM1 induction. DM1 model, as well as the obesity (control dm2 groups) resulted in neuronal impaired growth while dm2 model led to neuron hypertrophy in TG. Observed changes may play a critical role in the modulation of nociceptor activity and plasticity of primary sensory trigeminal neurons. In future, innovative strategies for modulation of CaMKIIα activity in specific subpopulations of neurons could be a novel approach in therapy of diabetic trigeminal neuropathy. Copyright © 2015. Published by Elsevier B.V.
    Journal of Chemical Neuroanatomy 02/2015; 64. DOI:10.1016/j.jchemneu.2015.02.003 · 1.50 Impact Factor
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    • "More recent studies have uncovered the involvement of TRPV1 in the central mechanical nociception together in connection with the other TRP channel – TRPA1 [47]. Other studies speculate that the central mechanical hyperalgesia could be induced by the functional interaction between P2X3 [48] or NMDA receptor [49] and TRPV1. These studies provide the evidence that TRPV1 channels are important not only for the peripheral pain sensation, but they can also play an important role in the central mechanical nociception. "
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    ABSTRACT: Cyclin-dependent kinase 5 (Cdk5) is a unique member of the serine/threonine kinase family. This kinase plays an important role in neuronal development and deregulation of its activity leads to neurodegenerative disorders. Cdk5 also serves an important function in the regulation of nociceptive signaling. Our previous studies revealed that the expression of Cdk5 and its activator, p35, is upregulated in nociceptive neurons during peripheral inflammation. The aim of the present study was to characterize the involvement of Cdk5 in orofacial pain. Since mechanical hyperalgesia is the distinctive sign of many orofacial pain conditions, we adapted an existing orofacial stimulation test to assess the behavioral responses to mechanical stimulation in the trigeminal region of the transgenic mice with either reduced or increased Cdk5 activity. Mice overexpressing or lacking p35, an activator of Cdk5, showed altered phenotype in response to noxious mechanical stimulation in the trigeminal area. Mice with increased Cdk5 activity displayed aversive behavior to mechanical stimulation as indicated by a significant decrease in reward licking events and licking time. The number of reward licking/facial contact events was significantly decreased in these mice as the mechanical intensity increased. By contrast, mice deficient in Cdk5 activity displayed mechanical hypoalgesia. Collectively, our findings demonstrate for the first time the important role of Cdk5 in orofacial mechanical nociception. Modulation of Cdk5 activity in primary sensory neurons makes it an attractive potential target for the development of novel analgesics that could be used to treat multiple orofacial pain conditions.
    Molecular Pain 12/2013; 9(1):66. DOI:10.1186/1744-8069-9-66 · 3.65 Impact Factor
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