NMP-7 inhibits chronic inflammatory and neuropathic pain via block of Cav3.2 T-type calcium channels and activation of CB2 receptors.
TL;DR: This work shows that NMP-7 mediates a significant analgesic effect in a model of persistent inflammatory and chronic neuropathic pain by way of T-type channel modulation and CB2 receptor activation, and provides a novel therapeutic avenue for managing chronic pain conditions via mixed CB ligands/T-type channels.
Abstract: Background: T-type calcium channels and cannabinoid receptors are known to play important roles in chronic pain, making them attractive therapeutic targets. We recently reported on the design, synthesis and analgesic properties of a novel T-type channel inhibitor (NMP-7), which also shows mixed agonist activity on CB1 and CB2 receptors in vitro. Here, we analyzed the analgesic effect of systemically delivered NMP-7 (intraperitoneal (i.p.) or intragstric (i.g.) routes) on mechanical hypersensitivity in inflammatory pain induced by Complete Freund’s Adjuvant (CFA) and neuropathic pain induced by sciatic nerve injury. Results: NMP-7 delivered by either i.p. or i.g. routes produced dose-dependent inhibition of mechanical hyperalgesia in mouse models of inflammatory and neuropathic pain, without altering spontaneous locomotor activity in the open-field test at the highest active dose. Neither i.p. nor i.g. treatment reduced peripheral inflammation per se ,a s evaluated by examining paw edema and myeloperoxidase activity. The antinociception produced by NMP-7 in the CFA test was completely abolished in CaV3.2-null mice, confirming CaV 3.2 as ak ey target. The analgesic action of intraperitoneally delivered NMP-7 was not affected by pretreatment of mice with the CB1 antagonist AM281, but was significantly attenuated by pretreatment with the CB2 antagonist AM630, suggesting that CB2 receptors, but not CB1 receptors are involved in the action of NMP-7 in vivo. Conclusions: Overall, our work shows that NMP-7 mediates a significant analgesic effect in a model of persistent inflammatory and chronic neuropathic pain by way of T-type channel modulation and CB2 receptor activation. Thus, this study provides a novel therapeutic avenue for managing chronic pain conditions via mixed CB ligands/ T-type channel blockers.
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TL;DR: An overview of calcium channels as drug targets for nervous system disorders is provided, and potential challenges and opportunities for the development of new clinically effective calcium channel inhibitors are discussed.
Abstract: Voltage-gated calcium channels are important regulators of brain, heart and muscle functions, and their dysfunction can give rise to pathophysiological conditions ranging from cardiovascular disorders to neurological and psychiatric conditions such as epilepsy, pain and autism. In the nervous system, calcium channel blockers have been used successfully to treat absence seizures, and are emerging as potential therapeutic avenues for pathologies such as pain, Parkinson disease, addiction and anxiety. This Review provides an overview of calcium channels as drug targets for nervous system disorders, and discusses potential challenges and opportunities for the development of new clinically effective calcium channel inhibitors.
301 citations
TL;DR: It is suggested that drugs that affect multiple processes, rather than a single specific target, show the greatest promise for future therapeutic development.
Abstract: Injury to or disease of the nervous system can invoke chronic and sometimes intractable neuropathic pain. Many parallel, interdependent, and time-dependent processes, including neuroimmune interactions at the peripheral, supraspinal, and spinal levels, contribute to the etiology of this "disease of pain." Recent work emphasizes the roles of colony-stimulating factor 1, ATP, and brain-derived neurotrophic factor. Excitatory processes are enhanced, and inhibitory processes are attenuated in the spinal dorsal horn and throughout the somatosensory system. This leads to central sensitization and aberrant processing such that tactile and innocuous thermal information is perceived as pain (allodynia). Processes involved in the onset of neuropathic pain differ from those involved in its long-term maintenance. Opioids display limited effectiveness, and less than 35% of patients derive meaningful benefit from other therapeutic approaches. We thus review promising therapeutic targets that have emerged over the last 20 years, including Na+, K+, Ca2+, hyperpolarization-activated cyclic nucleotide-gated channels, transient receptor potential channel type V1 channels, and adenosine A3 receptors. Despite this progress, the gabapentinoids retain their status as first-line treatments, yet their mechanism of action is poorly understood. We outline recent progress in understanding the etiology of neuropathic pain and show how this has provided insights into the cellular actions of pregabalin and gabapentin. Interactions of gabapentinoids with the α2δ-1 subunit of voltage-gated Ca2+ channels produce multiple and neuron type-specific actions in spinal cord and higher centers. We suggest that drugs that affect multiple processes, rather than a single specific target, show the greatest promise for future therapeutic development.
240 citations
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...2 channels (Berger et al., 2014)....
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TL;DR: Recent developments in the discovery of novel classes of T‐type calcium channel blockers, and their analgesic effects in animal models of pain and in clinical trials are reviewed.
Abstract: Cav3.2 T-type calcium channels are important regulators of pain signals in afferent pain pathway, and their activities are dysregulated during various chronic pain states. Therefore it stands to reason that inhibiting T-type calcium channels in dorsal root ganglion neurons and in the spinal dorsal horn can be targeted for pain relief. This is supported by early pharmacological studies with T-type channel blockers such as ethosuximide, and by analgesic effects of siRNA depletion of Cav3.2 channels. In the past five years, considerable effort has been applied towards identifying novel classes of T-type calcium channel blockers. Here we review recent developments in the discovery of novel classes of T-type calcium channel blockers, and their analgesics effects in animal models of pain and in clinical trials.
86 citations
Cites background from "NMP-7 inhibits chronic inflammatory..."
...More recently, a series of novel DHP derivatives with a condensed hexahydroquinoline 1,4-DHP ring system were identified (Bladen et al., 2014)....
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TL;DR: It is concluded that activation of CB2R ameliorates DSS-induced colitis through enhancing autophagy that may inhibit NLRP3 inflammasome activation in macrophages and it is demonstrated that AMPK-mTOR-P70S6K signaling pathway was involved in thisCB2R-mediated process.
Abstract: Activation of cannabinoid receptor 2 (CB2R) ameliorates inflammation, but the underlying mechanism remains unclear. In the present study, we examined whether activation of CB2R could suppress the nucleotide-binding domain and leucine-rich repeat protein 3 (NLRP3) inflammasome. In peritoneal macrophages isolated from C57BL/6 mice, LPS/DSS challenge for 24 h increased the expression of the components of NLRP3 inflammasome NLRP3, Casp-1 p20/Casp-1 p45 ratio, proIL-1β and IL-1β and also enhanced autophagy (LC3-II/LC3-I ratio, Beclin-1 and SQSTM1). Pretreatment of peritoneal macrophages with HU 308, a selective CB2R agonist, attenuated LPS/DSS-induced NLRP3 inflammasome activation, but further enhanced autophagy. In comparison with wild-type (WT) control, peritoneal macrophages from CB2R knockout (KO) mice had more robust NLRP3 inflammasome activation and attenuated autophagy upon LPS/DSS challenge. Knockdown autophagy-related gene 5 (Atg5) with a siRNA in peritoneal macrophages attenuated the inhibitory effects of HU 308 on LPS/DSS-induced NLRP3 inflammasome activation in vitro. In vivo, HU308 treatment attenuated DSS-induced colitis mice associated with reduced colon inflammation and inhibited NLRP3 inflammasome activation in wild-type mice. In CB2R KO mice, DSS-induced inflammation and NLRP3 inflammasome activation were more pronounced than those in WT control. Finally, we demonstrated that AMPK-mTOR-P70S6K signaling pathway was involved in this CB2R-mediated process. We conclude that activation of CB2R ameliorates DSS-induced colitis through enhancing autophagy that may inhibit NLRP3 inflammasome activation in macrophages.
67 citations
TL;DR: The anatomical physiology, underlying mechanisms of neuropathic pain is overviewed to provide a better understanding in the initiation, development, maintenance, and modulation of this pervasive disease, and inspire research in the unclear mechanisms as well as potential targets.
46 citations
Cites background from "NMP-7 inhibits chronic inflammatory..."
...2 blocker SNI model analgesic effect (Berger et al., 2014) Suramin and the flavonoid gossypetin USP5-Cav3....
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...2 T-type channel blocker, was shown to mediate a significant analgesic effect in the model of neuropathic pain (Berger et al. , 2014)....
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References
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TL;DR: The combined antinociceptive and anxiolytic-like profiles of lamotrigine, gabapentin and riluzole suggests that these compounds likely modulate both sensory and affective dimensions of pain.
96 citations
"NMP-7 inhibits chronic inflammatory..." refers background in this paper
...knockdown [7,8] or inhibition of the T-type calcium channel by T-type channel modulators produce significant antinociceptive effects in vivo [9-13]....
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...Inhibition of T-type channels or in vivo antisense-mediated knockdown produces antinociception in these and other models of chronic pain [7-16]....
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TL;DR: This work sought to determine whether NADA and the prototypic arachidonoyl amino acid, N‐arachidonoysl glycine (NAGly) modulate T‐type ICa, which is expressed by many excitable cells, including neurons involved in pain detection and processing.
Abstract: Background and purpose: N-arachidonoyl dopamine (NADA) has complex effects on nociception mediated via cannabinoid CB1 receptors and the transient receptor potential vanilloid receptor 1 (TRPV1). Anandamide, the prototypic CB1/TRPV1 agonist, also inhibits T-type voltage-gated calcium channel currents (ICa). These channels are expressed by many excitable cells, including neurons involved in pain detection and processing. We sought to determine whether NADA and the prototypic arachidonoyl amino acid, N-arachidonoyl glycine (NAGly) modulate T-type ICa
Experimental approach: Human recombinant T-type ICa (CaV3 channels) expressed in HEK 293 cells and native mouse T-type ICa were examined using standard whole-cell voltage clamp electrophysiology techniques.
Key results: N-arachidonoyl dopamine completely inhibited CaV3 channels with a rank order of potency (pEC50) of CaV3.3 (6.45) ≥ CaV3.1 (6.29) > CaV3.2 (5.95). NAGly (10 µmol·L−1) inhibited CaV3 ICa by approximately 50% or less. The effects of NADA and NAGly were voltage- but not use-dependent, and both compounds produced significant hyperpolarizing shifts in CaV3 channel steady-state inactivation relationships. By contrast with anandamide, NADA and NAGly had modest effects on CaV3 channel kinetics. Both NAGly and NADA inhibited native T-type ICa in mouse sensory neurons.
Conclusions and implications: N-arachidonoyl dopamine and NAGly increase the steady-state inactivation of CaV3 channels, reducing the number of channels available to open during depolarization. These effects occur at NADA concentrations at or below to those affecting CB1 and TRPV1 receptors. Together with anandamide, the arachidonoyl neurotransmitter amides, NADA and NAGly, represent a new family of endogenous T-type ICa modulators.
67 citations
"NMP-7 inhibits chronic inflammatory..." refers background in this paper
...Additionally, both Δ(9)-THC and cannabidiol [21] or the endogenous cannabinoid anandamide and its derivatives [20-22] inhibit T-type channel activity....
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TL;DR: The results suggest that T-type Ca2+ channels are potential therapeutic targets for the treatment of spinal nerve ligation-induced neuropathic pain.
Abstract: STUDY DESIGN Painful behavior testing, whole-cell patch clamp recordings, and PCR analysis were served to test the influence of T-type Ca channels in spinal nerve-injured rats. OBJECTIVE To determine the changes of T-type Ca channels in dorsal root ganglion (DRG) neurons of different sizes and the contribution to neuronal firing and painful behavior in neuropathic pain induced by nerve injury. SUMMARY OF BACKGROUND DATA T-type and high-voltage-activated Ca channels play an important role in the transmission of nociceptive signals, especially in neuronal hyperexcitability in neuropathic pain. However, little is known about how nerve injury affects T-type Ca channels in DRG neurons of different sizes. METHODS The effect of intrathecal administration of mibefradil in nerve-ligated rats was examined by painful behavior testing and current clamp. The changes of T-type Ca channels in DRG neurons caused by spinal nerve ligation were determined by RT-PCR analysis and voltage clamp. RESULTS Spinal nerve injury significantly increased current density of T-type Ca channels in small DRG neurons. In addition, nerve injury significantly increased the percentage of T-type Ca channels in medium and large DRG neurons. Nerve injury significantly increased the mRNA levels of Cav3.2 and Cav3.3 in DRGs. Block of T-type Ca channels on mibefradil administration significantly normalized painful behavior and hyperexcitability in neuronal firing in spinal nerve-injured rats. CONCLUSION Our study first indicated the upregulation of functional T-type Ca channels in DRG neurons of different sizes and the changes in different subtypes of T-type Ca channels by spinal nerve injury. Considering the effect of blocking T-type Ca channels in painful behavior and abnormal neuronal firing in rats with nerve injury, our results suggest that T-type Ca channels are potential therapeutic targets for the treatment of spinal nerve ligation-induced neuropathic pain.
64 citations
TL;DR: This article attempts to cover pragmatic clinical considerations involved in the use of cannabinergic medicines in pain practice, including geographical and historical considerations, pharmacokinetics, pharmacodynamics, adverse effects, drug interactions, indications, and contraindications.
Abstract: Objectives:This article attempts to cover pragmatic clinical considerations involved in the use of cannabinergic medicines in pain practice, including geographical and historical considerations, pharmacokinetics, pharmacodynamics, adverse effects, drug interactions, indications, and contraindication
59 citations
"NMP-7 inhibits chronic inflammatory..." refers background in this paper
...The antinociceptive effects of the cannabinoid system make it an attractive target for relief of chronic pain, and randomized-controlled trials have indeed shown that cannabis use results in significant analgesia [18]....
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TL;DR: This work shows that both T-type channels as well as CB2 receptors play a role in the antinociceptive action of NMP-181, and also provides a novel avenue for suppressing chronic pain through novel mixed T- type/cannabinoid receptor ligands.
Abstract: Cannabinoid receptors and T-type calcium channels are potential targets for treating pain. Here we report on the design, synthesis and analgesic properties of a new mixed cannabinoid/T-type channel ligand, NMP-181. NMP-181 action on CB1 and CB2 receptors was characterized in radioligand binding and in vitro GTPγ[35S] functional assays, and block of transiently expressed human Cav3.2 T-type channels by NMP-181 was analyzed by patch clamp. The analgesic effects and in vivo mechanism of action of NMP-181 delivered spinally or systemically were analyzed in formalin and CFA mouse models of pain. NMP-181 inhibited peak CaV3.2 currents with IC50 values in the low micromolar range and acted as a CB2 agonist. Inactivated state dependence further augmented the inhibitory action of NMP-181. NMP-181 produced a dose-dependent antinociceptive effect when administered either spinally or systemically in both phases of the formalin test. Both i.t. and i.p. treatment of mice with NMP-181 reversed the mechanical hyperalgesia induced by CFA injection. NMP-181 showed no antinocieptive effect in CaV3.2 null mice. The antinociceptive effect of intrathecally delivered NMP-181 in the formalin test was reversed by i.t. treatment of mice with AM-630 (CB2 antagonist). In contrast, the NMP-181-induced antinociception was not affected by treatment of mice with AM-281 (CB1 antagonist). Our work shows that both T-type channels as well as CB2 receptors play a role in the antinociceptive action of NMP-181, and also provides a novel avenue for suppressing chronic pain through novel mixed T-type/cannabinoid receptor ligands.
43 citations
"NMP-7 inhibits chronic inflammatory..." refers background or methods in this paper
...Mouse ambulatory behavior was assessed in an open-field test as described previously [23]....
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...The use of such mixed CB/T-type calcium channel interacting compounds may provide a strategy for the development of better analgesics [23]....
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