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Shieh CC, Petrini MF, Dwyer TM, Farley JM. Effects of Elevated Cytosolic
Calcium on ACh-Induced Swine
Tracheal Smooth Muscle
Contraction. J Biomed Sci 2017. [DOI: 10.1159/000456939] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
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Shieh CC, Petrini MF, Dwyer TM, Farley JM. Calcium Mobilization and Muscle Contraction Induced by Acetylcholine in Swine Trachealis. J Biomed Sci 2017. [DOI: 10.1159/000456865] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
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Trumbull JD, Maslana ES, Mckenna DG, Nemcek TA, Niforatos W, Pan JY, Parihar AS, Shieh CC, Wilkins JA, Briggs CA, Bertrand D. High Throughput Electrophysiology Using a Fully Automated, Multiplexed Recording System. ACTA ACUST UNITED AC 2011. [DOI: 10.3109/10606820308252] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
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Kort ME, Atkinson RN, Thomas JB, Drizin I, Johnson MS, Secrest MA, Gregg RJ, Scanio MJ, Shi L, Hakeem AH, Matulenko MA, Chapman ML, Krambis MJ, Liu D, Shieh CC, Zhang X, Simler G, Mikusa JP, Zhong C, Joshi S, Honore P, Roeloffs R, Werness S, Antonio B, Marsh KC, Faltynek CR, Krafte DS, Jarvis MF, Marron BE. Subtype-selective Nav1.8 sodium channel blockers: Identification of potent, orally active nicotinamide derivatives. Bioorg Med Chem Lett 2010; 20:6812-5. [DOI: 10.1016/j.bmcl.2010.08.121] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2010] [Accepted: 08/24/2010] [Indexed: 12/19/2022]
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Scanio MJC, Shi L, Drizin I, Gregg RJ, Atkinson RN, Thomas JB, Johnson MS, Chapman ML, Liu D, Krambis MJ, Liu Y, Shieh CC, Zhang X, Simler GH, Joshi S, Honore P, Marsh KC, Knox A, Werness S, Antonio B, Krafte DS, Jarvis MF, Faltynek CR, Marron BE, Kort ME. Discovery and biological evaluation of potent, selective, orally bioavailable, pyrazine-based blockers of the Na(v)1.8 sodium channel with efficacy in a model of neuropathic pain. Bioorg Med Chem 2010; 18:7816-25. [PMID: 20965738 DOI: 10.1016/j.bmc.2010.09.057] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2010] [Revised: 09/16/2010] [Accepted: 09/22/2010] [Indexed: 11/29/2022]
Abstract
Na(v)1.8 (also known as PN3) is a tetrodotoxin-resistant (TTx-r) voltage-gated sodium channel (VGSC) that is highly expressed on small diameter sensory neurons. It has been implicated in the pathophysiology of inflammatory and neuropathic pain, and we envisioned that selective blockade of Na(v)1.8 would be analgesic, while reducing adverse events typically associated with non-selective VGSC blocking therapeutic agents. Herein, we describe the preparation and characterization of a series of 6-aryl-2-pyrazinecarboxamides, which are potent blockers of the human Na(v)1.8 channel and also block TTx-r sodium currents in rat dorsal root ganglia (DRG) neurons. Selected derivatives display selectivity versus human Na(v)1.2. We further demonstrate that an example from this series is orally bioavailable and produces antinociceptive activity in vivo in a rodent model of neuropathic pain following oral administration.
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Abstract
P2X receptors belong to a superfamily of ligand-gated ion channels that conduct the influx of Ca(2+), Na(+) and K(+) cations following activation by extracellular nucleotides such as ATP. Molecular cloning studies have identified seven subunits, namely P2X(1-7), that share approximately 40 - 50% identity in amino acid sequences within the subfamily. Using gene-silencing, pharmacological and electrophysiological approaches, recent studies have revealed roles for P2X(2), P2X(3), P2X(4) and P2X(7) receptors in nociceptive signalling. Homomeric P2X(3) and heteromeric P2X(2/3) receptors are highly localised in the peripheral sensory afferent neurons that conduct nociceptive sensory information to the spinal chord and brain. The discovery of A-317491, a selective and potent non-nucleotide P2X(3) antagonist, provided a pharmacological tool to determine the site and mode of action of P2X(3)-containing receptors in different pain behaviours, including neuropathic, inflammatory and visceral pain. Other P2X receptors (P2X(4) and P2X(7)) that are predominantly expressed in microglia, macrophages and cells of immune origin can trigger the release of cytokines, such as IL-1-beta and TNF-alpha. Genetic disruption of P2X(4) and P2X(7) signalling has been demonstrated to reduce inflammatory and neuropathic pain, suggesting that these two receptors might serve as integrators of neuroinflammation and pain. This article provides an overview of recent scientific literature and patents focusing on P2X(3), P2X(4) and P2X(7) receptors, and the identification of small molecule ligands for the potential treatment of neuropathic and inflammatory pain.
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Drizin I, Gregg RJ, Scanio MJC, Shi L, Gross MF, Atkinson RN, Thomas JB, Johnson MS, Carroll WA, Marron BE, Chapman ML, Liu D, Krambis MJ, Shieh CC, Zhang X, Hernandez G, Gauvin DM, Mikusa JP, Zhu CZ, Joshi S, Honore P, Marsh KC, Roeloffs R, Werness S, Krafte DS, Jarvis MF, Faltynek CR, Kort ME. Discovery of potent furan piperazine sodium channel blockers for treatment of neuropathic pain. Bioorg Med Chem 2008; 16:6379-86. [PMID: 18501613 DOI: 10.1016/j.bmc.2008.05.003] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2008] [Revised: 04/30/2008] [Accepted: 05/02/2008] [Indexed: 11/18/2022]
Abstract
The synthesis and pharmacological characterization of a novel furan-based class of voltage-gated sodium channel blockers is reported. Compounds were evaluated for their ability to block the tetrodotoxin-resistant sodium channel Na(v)1.8 (PN3) as well as the Na(v)1.2 and Na(v)1.5 subtypes. Benchmark compounds from this series possessed enhanced potency, oral bioavailability, and robust efficacy in a rodent model of neuropathic pain, together with improved CNS and cardiovascular safety profiles compared to the clinically used sodium channel blockers mexiletine and lamotrigine.
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Kort ME, Drizin I, Gregg RJ, Scanio MJC, Shi L, Gross MF, Atkinson RN, Johnson MS, Pacofsky GJ, Thomas JB, Carroll WA, Krambis MJ, Liu D, Shieh CC, Zhang X, Hernandez G, Mikusa JP, Zhong C, Joshi S, Honore P, Roeloffs R, Marsh KC, Murray BP, Liu J, Werness S, Faltynek CR, Krafte DS, Jarvis MF, Chapman ML, Marron BE. Discovery and biological evaluation of 5-aryl-2-furfuramides, potent and selective blockers of the Nav1.8 sodium channel with efficacy in models of neuropathic and inflammatory pain. J Med Chem 2008; 51:407-16. [PMID: 18176998 DOI: 10.1021/jm070637u] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Nav1.8 (also known as PN3) is a tetrodotoxin-resistant (TTx-r) voltage-gated sodium channel (VGSC) that is highly expressed on small diameter sensory neurons and has been implicated in the pathophysiology of inflammatory and neuropathic pain. Recent studies using an Nav1.8 antisense oligonucleotide in an animal model of chronic pain indicated that selective blockade of Nav1.8 was analgesic and could provide effective analgesia with a reduction in the adverse events associated with nonselective VGSC blocking therapeutic agents. Herein, we describe the preparation and characterization of a series of 5-substituted 2-furfuramides, which are potent, voltage-dependent blockers (IC50 < 10 nM) of the human Nav1.8 channel. Selected derivatives, such as 7 and 27, also blocked TTx-r sodium currents in rat dorsal root ganglia (DRG) neurons with comparable potency and displayed >100-fold selectivity versus human sodium (Nav1.2, Nav1.5, Nav1.7) and human ether-a-go-go (hERG) channels. Following systemic administration, compounds 7 and 27 dose-dependently reduced neuropathic and inflammatory pain in experimental rodent models.
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Donnelly-Roberts D, McGaraughty S, Shieh CC, Honore P, Jarvis MF. Painful purinergic receptors. J Pharmacol Exp Ther 2007; 324:409-15. [PMID: 18042830 DOI: 10.1124/jpet.106.105890] [Citation(s) in RCA: 131] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Multiple P2 receptor-mediated mechanisms exist by which ATP can alter nociceptive sensitivity following tissue injury. Evidence from a variety of experimental strategies, including genetic disruption studies and the development of selective antagonists, has indicated that the activation of P2X receptor subtypes, including P2X(3), P2X(2/3), P2X(4) and P2X(7), and P2Y (e.g., P2Y(2)) receptors, can modulate pain. For example, administration of a selective P2X(3) antagonist, A-317491, has been shown to effectively block both hyperalgesia and allodynia in different animal models of pathological pain. Intrathecally delivered antisense oligonucleotides targeting P2X(4) receptors decrease tactile allodynia following nerve injury. Selective antagonists for the P2X(7) receptor also reduce sensitization in animal models of inflammatory and neuropathic pain, providing evidence that purinergic glial-neural interactions are important modulators of noxious sensory neurotransmission. Furthermore, activation of P2Y(2) receptors leads to sensitization of polymodal transient receptor potential-1 receptors. Thus, ATP acting at multiple purinergic receptors, either directly on neurons (e.g., P2X(3), P2X(2/3), and P2Y receptors) or indirectly through neural-glial cell interactions (P2X(4) and P2X(7) receptors), alters nociceptive sensitivity. The development of selective antagonists for some of these P2 receptors has greatly aided investigations into the nociceptive role of ATP. This perspective highlights some of the recent advances to identify selective P2 receptor ligands, which has enhanced the investigation of ATP-related modulation of pain sensitivity.
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Jarvis MF, Honore P, Shieh CC, Chapman M, Joshi S, Zhang XF, Kort M, Carroll W, Marron B, Atkinson R, Thomas J, Liu D, Krambis M, Liu Y, McGaraughty S, Chu K, Roeloffs R, Zhong C, Mikusa JP, Hernandez G, Gauvin D, Wade C, Zhu C, Pai M, Scanio M, Shi L, Drizin I, Gregg R, Matulenko M, Hakeem A, Gross M, Johnson M, Marsh K, Wagoner PK, Sullivan JP, Faltynek CR, Krafte DS. A-803467, a potent and selective Nav1.8 sodium channel blocker, attenuates neuropathic and inflammatory pain in the rat. Proc Natl Acad Sci U S A 2007; 104:8520-5. [PMID: 17483457 PMCID: PMC1895982 DOI: 10.1073/pnas.0611364104] [Citation(s) in RCA: 404] [Impact Index Per Article: 22.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
Activation of tetrodotoxin-resistant sodium channels contributes to action potential electrogenesis in neurons. Antisense oligonucleotide studies directed against Na(v)1.8 have shown that this channel contributes to experimental inflammatory and neuropathic pain. We report here the discovery of A-803467, a sodium channel blocker that potently blocks tetrodotoxin-resistant currents (IC(50) = 140 nM) and the generation of spontaneous and electrically evoked action potentials in vitro in rat dorsal root ganglion neurons. In recombinant cell lines, A-803467 potently blocked human Na(v)1.8 (IC(50) = 8 nM) and was >100-fold selective vs. human Na(v)1.2, Na(v)1.3, Na(v)1.5, and Na(v)1.7 (IC(50) values >or=1 microM). A-803467 (20 mg/kg, i.v.) blocked mechanically evoked firing of wide dynamic range neurons in the rat spinal dorsal horn. A-803467 also dose-dependently reduced mechanical allodynia in a variety of rat pain models including: spinal nerve ligation (ED(50) = 47 mg/kg, i.p.), sciatic nerve injury (ED(50) = 85 mg/kg, i.p.), capsaicin-induced secondary mechanical allodynia (ED(50) approximately 100 mg/kg, i.p.), and thermal hyperalgesia after intraplantar complete Freund's adjuvant injection (ED(50) = 41 mg/kg, i.p.). A-803467 was inactive against formalin-induced nociception and acute thermal and postoperative pain. These data demonstrate that acute and selective pharmacological blockade of Na(v)1.8 sodium channels in vivo produces significant antinociception in animal models of neuropathic and inflammatory pain.
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Joshi SK, Mikusa JP, Hernandez G, Baker S, Shieh CC, Neelands T, Zhang XF, Niforatos W, Kage K, Han P, Krafte D, Faltynek C, Sullivan JP, Jarvis MF, Honore P. Involvement of the TTX-resistant sodium channel Nav 1.8 in inflammatory and neuropathic, but not post-operative, pain states. Pain 2006; 123:75-82. [PMID: 16545521 DOI: 10.1016/j.pain.2006.02.011] [Citation(s) in RCA: 141] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2005] [Revised: 01/05/2006] [Accepted: 02/06/2006] [Indexed: 10/24/2022]
Abstract
Antisense (AS) oligodeoxynucleotides (ODNs) targeting the Nav 1.8 sodium channel have been reported to decrease inflammatory hyperalgesia and L5/L6 spinal nerve ligation-induced mechanical allodynia in rats. The present studies were conducted to further characterize Nav 1.8 AS antinociceptive profile in rats to better understand the role of Nav 1.8 in different pain states. Consistent with earlier reports, chronic intrathecal Nav 1.8 AS, but not mismatch (MM), ODN decreased TTX-resistant sodium current density (by 60.5+/-10.2% relative to MM; p<0.05) in neurons from L4 to L5 dorsal root ganglia and significantly attenuated mechanical allodynia following intraplantar complete Freund's adjuvant. In addition, 10 days following chronic constriction injury of the sciatic nerve, Nav 1.8 AS, but not MM, ODN also attenuated mechanical allodynia (54.3+/-8.2% effect, p<0.05 vs. MM) 2 days after initiation of ODN treatment. The anti-allodynic effects remained for the duration of the AS treatment, and CCI rats returned to an allodynic state 4 days after discontinuing AS. In contrast, Nav 1.8 AS ODN failed to reduce mechanical allodynia in the vincristine chemotherapy-induced neuropathic pain model or a skin-incision model of post-operative pain. Finally, Nav 1.8 AS, but not MM, ODN treatment produced a small but significant attenuation of acute noxious mechanical sensitivity in naïve animals (17.6+/-6.2% effect, p<0.05 vs. MM). These data demonstrate a greater involvement of Nav 1.8 in frank nerve injury and inflammatory pain as compared to acute, post-operative or chemotherapy-induced neuropathic pain states.
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MESH Headings
- Animals
- Behavior, Animal
- Drug Evaluation, Preclinical
- Freund's Adjuvant/toxicity
- Hyperalgesia/drug therapy
- Hyperalgesia/etiology
- Hyperalgesia/physiopathology
- Inflammation/physiopathology
- Injections, Spinal
- Ion Transport
- Ligation
- Male
- NAV1.8 Voltage-Gated Sodium Channel
- Nerve Tissue Proteins/antagonists & inhibitors
- Nerve Tissue Proteins/drug effects
- Nerve Tissue Proteins/genetics
- Nerve Tissue Proteins/physiology
- Neuralgia/chemically induced
- Neuralgia/physiopathology
- Neurons, Afferent/drug effects
- Neurons, Afferent/physiology
- Oligodeoxyribonucleotides, Antisense/pharmacology
- Oligodeoxyribonucleotides, Antisense/therapeutic use
- Pain, Postoperative/physiopathology
- Patch-Clamp Techniques
- Pressure/adverse effects
- Rats
- Rats, Sprague-Dawley
- Sciatic Nerve/injuries
- Sodium/physiology
- Sodium Channels/drug effects
- Sodium Channels/genetics
- Sodium Channels/physiology
- Spinal Nerves/injuries
- Stress, Mechanical
- Tetrodotoxin/pharmacology
- Vincristine/toxicity
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Fryer RM, Rakestraw PA, Preusser LC, Brune ME, Carroll WA, Buckner SA, Shieh CC, King LL, Marsh KC, Gopalakrishnan M, Cox BF, Reinhart GA. Pharmacological characterization of the novel dihydropyridine potassium channel opener, (9R)-9-(3-iodo-4-methylphenyl)-5,9-dihydro-3H-furo[3,4-b]pyrano[4,3-e]pyridine-1,8(4H,7H)-dione (A-325100), and the regulation of cardiovascular function in conscious and anesthetized beagle dogs. J Cardiovasc Pharmacol 2005; 46:232-40. [PMID: 16044036 DOI: 10.1097/01.fjc.0000171755.28317.85] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
The pharmacological profile of the novel dihydropyridine K channel opener (KCO), (9R)-9-(3-iodo-4-methylphenyl)-5,9-dihydro-3H-furo[3,4-b]pyrano[4,3-e]pyridine-1,8(4H,7H)-dione (A-325100), is described in numerous in vitro assays. Furthermore, the cardiovascular effects of A-325100 are characterized in both the anesthetized and conscious dog. In vitro, A-325100 selectively activated KATP currents and potently relaxed vascular smooth muscle (IC50 between 7.69x10 M and 7.78x10 M), an effect that was abolished by glyburide. Moreover, A-325100 did not interact with L-type Ca2+ channels at concentrations up to 30 microM. In anesthetized dogs A-325100 produced a dose-dependent reduction in systemic vascular resistance and mean arterial pressure concomitant with dose-dependent increases in dP/dtmax and heart rate. In conscious telemetry-instrumented dogs oral administration of A-325100 produced a similar response profile, including dose-dependent reductions in MAP and increases in heart rate and dP/dtmax. When concentration-dependent changes in MAP, heart rate, and dP/dtmax were compared relative to circulating plasma concentrations, A-325100 produced similar effects in both the anesthetized and conscious dog. In conclusion, the present study provides the first pharmacological description of the novel and selective tricyclic dihydropyridine KCO, A-325100. When studied in vivo, A-325100 produced similar concentration-dependent cardiovascular effects in both models consistent with its mode of action and independent of route of administration. Thus, these data demonstrate that the hemodynamic effects of vasoactive compounds, such as KCOs, can be effectively profiled in both the conscious and anesthetized dog.
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Zhang XF, Han P, Faltynek CR, Jarvis MF, Shieh CC. Functional expression of P2X7 receptors in non-neuronal cells of rat dorsal root ganglia. Brain Res 2005; 1052:63-70. [PMID: 16005856 DOI: 10.1016/j.brainres.2005.06.022] [Citation(s) in RCA: 68] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2005] [Revised: 06/01/2005] [Accepted: 06/05/2005] [Indexed: 11/21/2022]
Abstract
The P2X7 receptor is an ATP-sensitive ligand-gated cation channel, expressed predominantly in cells with immune origin. Recent studies have demonstrated that P2X7 may play an important role in pain signaling. In the present study, the expression of P2X7 receptors in non-neuronal cells and neurons isolated from dorsal root ganglia was characterized using patch clamp, pharmacological and confocal microscopy approaches. In small diameter DRG neurons, 100 microM 2', 3'-O-(4-benzoylbenzoyl)-ATP (BzATP) evoked an inward current, which was inhibited completely by 1 microM A-317491, a potent and selective P2X3 receptor antagonist. In contrast, BzATP evoked concentration-dependent increases in inward currents in non-neuronal DRG cells with an EC50 value of 26 +/- 0.14 microM, which were resistant to the blockade by A-317491. The activity to evoke cationic currents by P2X receptor agonists in non-neuronal cells showed a rank order of BzATP > ATP > alpha,beta-meATP. Pyridoxal-phosphate-6-azophenyl-,2',4'-disulphonic acid (PPADS) and Mg2+ produced concentration-dependent inhibition of BzATP-evoked currents in non-neuronal cells. Confocal microscopy revealed positive immunoreactivity of anti-P2X7 receptor antibodies on non-neuronal cells. No anti-P2X7 immunoreactivity was observed on DRG neurons. Further electrophysiological studies showed that prolonged agonist activation of P2X7 receptors in non-neuronal cells did not lead to cytolytic pore formation. Taken together, the present study demonstrated functional expression of P2X7 receptors in non-neuronal but not in small diameter neurons from rat DRG. Modulation of P2X7 receptors in non-neuronal cells might have impact on peripheral sensory transduction under normal and pathological states.
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Gopalakrishnan M, Shieh CC. Potassium channel subtypes as molecular targets for overactive bladder and other urological disorders. Expert Opin Ther Targets 2005; 8:437-58. [PMID: 15469394 DOI: 10.1517/14728222.8.5.437] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
Potassium channels have re-emerged as attractive targets for overactive bladder and other urological diseases in recent years, in part due to an enhanced understanding of their molecular heterogeneity, tissue distribution, functional roles and regulation in physiological and pathological states. Cloning and heterologous expression analysis, coupled with the advancement of improved high-throughput screening techniques, have enabled expeditious identification of selective small-molecule openers and blockers for ATP-sensitive K+ channels, Ca2+-activated K+ channels and voltage-dependent K+ channel-KQT-like subfamily (KCNQ) members, and has paved the way in the assessment of efficacy and adverse effects in preclinical models. This review focuses on the rationale for molecular targeting of K+ channels, the current status of target validation, including preclinical proof-of-concept studies, and provides perspectives on the limitations and hurdles to be overcome in realising the potential of these targets for diverse urological indications such as overactive bladder, erectile dysfunction and prostate diseases.
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Gopalakrishnan M, Buckner SA, Shieh CC, Fey T, Fabiyi A, Whiteaker KL, Davis-Taber R, Milicic I, Daza AV, Scott VES, Castle NA, Printzenhoff D, London B, Turner SC, Carroll WA, Sullivan JP, Coghlan MJ, Brune ME. In vitro and in vivo characterization of a novel naphthylamide ATP-sensitive K+ channel opener, A-151892. Br J Pharmacol 2004; 143:81-90. [PMID: 15302680 PMCID: PMC1575269 DOI: 10.1038/sj.bjp.0705908] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2004] [Revised: 06/03/2004] [Accepted: 06/09/2004] [Indexed: 11/08/2022] Open
Abstract
1. Openers of ATP-sensitive K(+) channels are of interest in several therapeutic indications including overactive bladder and other lower urinary tract disorders. This study reports on the in vitro and in vivo characterization of a structurally novel naphthylamide N-[2-(2,2,2-trifluoro-1-hydroxy-1-trifluoromethyl-ethyl)-naphthalen-1-yl]-acetamide (A-151892), as an opener of the ATP-sensitive potassium channels. 2. A-151892 was found to be a potent and efficacious potassium channel opener (KCO) as assessed by glibenclamide-sensitive whole-cell current and fluorescence-based membrane potential responses (-log EC(50)=7.63) in guinea-pig bladder smooth muscle cells. 3. Evidence for direct interaction with KCO binding sites was derived from displacement of binding of the 1,4-dihydropyridine opener [(125)I]A-312110. A-151892 displaced [(125)I]A-312110 binding to bladder membranes with a -log Ki value of 7.45, but lacked affinity against over 70 neurotransmitter receptor and ion channel binding sites. 4. In pig bladder strips, A-151892 suppressed phasic, carbachol-evoked and electrical field stimulus-evoked contractility in a glibenclamide-reversible manner with -log IC(50) values of 8.07, 7.33 and 7.02 respectively, comparable to that of the potencies of the prototypical cyanoguanidine KCO, P1075. The potencies to suppress contractions in thoracic aorta (-log IC(50)=7.81) and portal vein (-log IC(50)=7.98) were not substantially different from those observed for suppression of phasic contractility of the bladder smooth muscle. 5. In vivo, A-151892 was found to potently suppress unstable bladder contractions in obstructed models of unstable contractions in both pigs and rats with pED(35%) values of 8.05 and 7.43, respectively. 6. These results demonstrate that naphthylamide analogs exemplified by A-151892 are novel K(ATP) channel openers and may serve as chemotypes to exploit additional analogs with potential for the treatment of overactive bladder and lower urinary tract symptoms.
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Parihar AS, Groebe DR, Scott VE, Feng J, Zhang XF, Warrior U, Gopalakrishnan M, Shieh CC. Functional analysis of large conductance Ca2(+)-activated K(+) channels: ion flux studies by atomic absorption spectrometry. Assay Drug Dev Technol 2004; 1:647-54. [PMID: 15090237 DOI: 10.1089/154065803770381002] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Although techniques such as (86)Rb(+) flux provide a sensitive measure of K(+) channel activity, the relatively short half-life and high-energy emission, together with the quantities of radioactive material generated, hinder the usefulness of flux-based formats in high throughput screening efforts. This study elaborates on the utilization of flame atomic absorption spectrometry (AAS) techniques for a nonradioactive rubidium efflux assay for large conductance Ca(2+)-activated K(+) channels (BK(Ca)) channels. Utilizing human embryonic kidney (HEK293) cells expressing the BK(Ca) alpha subunit, a 96-well cell-based nonradioactive rubidium efflux screen for channel openers and inhibitors was established. Known BK(Ca) channel openers, including NS1608, NS1619, and NS-8, activated rubidium efflux with EC(50) values ranging from 1 to 4 microM in both radioactive and nonradioactive efflux formats. Compounds such as iberiotoxin, paxilline, and charybdotoxin inhibited rubidium efflux responses evoked by the BK(Ca) channel opener NS1608 in both radioactive and nonradioactive efflux formats. The IC(50) values of the inhibitors in AAS format were comparable to those derived from (86)Rb(+) efflux assays. The present studies show that the pharmacological profiles of BK(Ca) channels assessed by AAS compare well with those obtained using the (86)Rb(+) efflux assay, and support the utility of nonradioactive efflux format for higher throughput screening campaigns for novel K(+) channel modulators.
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Zhang XF, Zhu CZ, Thimmapaya R, Choi WS, Honore P, Scott VE, Kroeger PE, Sullivan JP, Faltynek CR, Gopalakrishnan M, Shieh CC. Differential action potentials and firing patterns in injured and uninjured small dorsal root ganglion neurons after nerve injury. Brain Res 2004; 1009:147-58. [PMID: 15120592 DOI: 10.1016/j.brainres.2004.02.057] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 02/21/2004] [Indexed: 01/12/2023]
Abstract
The profile of tetrodotoxin sensitive (TTX-S) and resistant (TTX-R) Na(+) channels and their contribution to action potentials and firing patterns were studied in isolated small dorsal root ganglion (DRG) neurons after L5/L6 spinal nerve ligation (SNL). Total TTX-R Na(+) currents and Na(v) 1.8 mRNA were reduced in injured L5 DRG neurons 14 days after SNL. In contrast, TTX-R Na(+)currents and Na(v) 1.8 mRNA were upregulated in uninjured L4 DRG neurons after SNL. Voltage-dependent inactivation of TTX-R Na(+) channels in these neurons was shifted to hyperpolarized potentials by 4 mV. Two types of neurons were identified in injured L5 DRG neurons after SNL. Type I neurons (57%) had significantly lower threshold but exhibited normal resting membrane potential (RMP) and action potential amplitude. Type II neurons (43%) had significantly smaller action potential amplitude but retained similar RMP and threshold to those from sham rats. None of the injured neurons could generate repetitive firing. In the presence of TTX, only 26% of injured neurons could generate action potentials that had smaller amplitude, higher threshold, and higher rheobase compared with sham rats. In contrast, action potentials and firing patterns in uninjured L4 DRG neurons after SNL, in the presence or absence of TTX, were not affected. These results suggest that TTX-R Na(+) channels play important roles in regulating action potentials and firing patterns in small DRG neurons and that downregulation in injured neurons and upregulation in uninjured neurons confer differential roles in shaping electrogenesis, and perhaps pain transmission, in these neurons.
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Shieh CC, Trumbull JD, Sarthy JF, McKenna DG, Parihar AS, Zhang XF, Faltynek CR, Gopalakrishnan M. Automated Parallel Oocyte Electrophysiology Test Station (POETs™): A Screening Platform for Identification of Ligand-Gated Ion Channel Modulators. Assay Drug Dev Technol 2003; 1:655-63. [PMID: 15090238 DOI: 10.1089/154065803770381011] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Ligand-gated ion channels (LGICs) play important roles in the regulation of cellular function and signaling and serve as excellent drug targets. However, fast desensitization of most LGICs limits the choice of reliable methods to identify agonists, antagonists, and/or modulators in a high throughput manner. In this study, automated Parallel Oocyte Electrophysiology Test station (POETs) was used to screen a directed compound library against a rapidly desensitizing LGIC and to characterize further the pharmacological properties of the hits. POETs allows up to six two-electrode voltage-clamp experiments to be performed in parallel by automatically loading of the oocytes into flowcells, assessing individual oocyte behavior prior to initiating experiments. Oocytes injected with cRNA were transferred from a chilled 96-well plate into flowcells by the instrument, where they were impaled under software control by two independent electrodes. Expression was tested by measuring current responses to rapid application of agonists. Compounds, prepared in a 96-well format, were tested for effects by coapplication with agonist at a single concentration of 30 microM over 2 s. After compound application, oocytes were washed for a minimum of 30 s, and used repeatedly if the test compounds had no significant effect on the control response. Typical throughput could reach approximately 14 plates/day depending on the protocol. Pilot library screening revealed a hit rate of 0.06%, with active compounds having IC(50) values of 4-40 microM. Hits were also confirmed in native neurons using patch-clamp techniques. We conclude that automated POETs serves as a suitable platform for screening and expedient identification of LGIC modulators.
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Trumbull JD, Maslana ES, McKenna DG, Nemcek TA, Niforatos W, Pan JY, Parihar AS, Shieh CC, Wilkins JA, Briggs CA, Bertrand D. High throughput electrophysiology using a fully automated, multiplexed recording system. RECEPTORS & CHANNELS 2003; 9:19-28. [PMID: 12825295] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 03/03/2023]
Abstract
The drug discovery process centers around finding and optimizing novel compounds active at therapeutic targets. This process involves direct and indirect measures of how compounds affect the behavior of the target in question. The sheer number of compounds that must be tested poses problems for classes of ion channel targets for which direct functional measurements (e.g., traditional patch-clamping) are too cumbersome and indirect measurements (e.g., Ca(2+)-sensitive dyes) lack sufficient sensitivity or require unacceptable compromises. We present an optimized process for obtaining large numbers of direct electrophysiological measurements (two-electrode voltage-clamp) from Xenopus oocytes using a combination of automated oocyte handling, efficient and flexible liquid delivery, parallel operation, and powerful integrated data analysis. These improvements have had a marked impact, increasing the contribution electrophysiology makes in optimizing lead compound series and the discovery of new ones. The design of the system is detailed along with examples of data generated in support of lead optimization and discovery.
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Davis-Taber R, Molinari EJ, Altenbach RJ, Whiteaker KL, Shieh CC, Rotert G, Buckner SA, Malysz J, Milicic I, McDermott JS, Gintant GA, Coghlan MJ, Carroll WA, Scott VE, Gopalakrishnan M. [125I]A-312110, a novel high-affinity 1,4-dihydropyridine ATP-sensitive K+ channel opener: characterization and pharmacology of binding. Mol Pharmacol 2003; 64:143-53. [PMID: 12815170 DOI: 10.1124/mol.64.1.143] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Although ATP-sensitive K+ channels continue to be explored for their therapeutic potential, developments in high-affinity radioligands to investigate native and recombinant KATP channels have been less forthcoming. This study reports the identification and pharmacological characterization of a novel iodinated 1,4-dihydropyridine KATP channel opener, [125I]A-312110 [(9R)-9-(4-fluoro-3-125iodophenyl)-2,3,5,9-tetrahydro-4H-pyrano[3,4-b]thieno[2,3-e]pyridin-8(7H)-one-1,1-dioxide]. Binding of [125I]A-312110 to guinea pig cardiac (KD = 5.8 nM) and urinary bladder (KD = 4.9 nM) membranes were of high affinity, saturable, and to a single set of binding sites. Displacement of [125I]A-312110 by structurally diverse potassium channel openers (KCOs) indicated a similar rank order of potency in both guinea pig cardiac and bladder membranes (Ki, heart): A-312110 (4.3 nM) > N-cyano-N'-(1,1-dimethylpropyl)-N"-3-pyridylguanidine (P1075) > (-)-N-(2-ethoxyphenyl)-N'-(1,2,3-trimethylpropyl)-2-nitroethene-1,1-diamine (Bay X 9228) > pinacidil > (-)-cromakalim > N-(4-benzoyl phenyl)-3,3,3-trifluro-2-hydroxy-2-methylpropionamine (ZD6169) > 9-(3-cyanophenyl)-3,4,6,7,9,10-hexahydro-1,8-(2H,5H)-acridinedione (ZM244085) >> diazoxide (16.7 microM). Displacement by KATP channel blockers, the sulfonylurea glyburide, and the cyanoguanidine N-[1-(3-chlorophenyl)cyclobutyl]-N'-cyano-N"-3-pyridinyl-guanidine (PNU-99963) were biphasic in the heart but monophasic in bladder with about a 100- to 500-fold difference in Ki values between high- and low-affinity sites. Good correlations were observed between cardiac or bladder-binding affinities of KCOs with functional activation as assessed by their respective potencies to either suppress action potential duration (APD) in Purkinje fibers or to relax electrical field-stimulated bladder contractions. Collectively, these results demonstrate that [125I]A-312110 binds with high affinity and has an improved activity profile compared with other radiolabeled KCOs. [125I]A-312110 is a useful tool for investigation of the molecular and functional properties of the KATP channel complex and for the identification, in a high throughput manner, of both novel channel blockers and openers that interact with cardiac/smooth muscle-type KATP channels.
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Shieh CC, Gopalakrishnan M. Electrophysiological analysis of ATP-sensitive potassium channels in mammalian cells and Xenopus oocytes. CURRENT PROTOCOLS IN PHARMACOLOGY 2003; Chapter 11:Unit11.6. [PMID: 21956803 DOI: 10.1002/0471141755.ph1106s21] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
This unit describes general methodologies for the characterization of ATP-sensitive K+ channels and the study of ligand-channel interactions in native tissues and clonal cell lines by electrophysiological techniques. Detailed protocols on how to establish patch-clamp single-channel and whole-cell current recording are presented. Two-electrode voltage clamp techniques for studying ATP-sensitive K+ channels expressed in Xenopus oocytes are also included.
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Parihar AS, Coghlan MJ, Gopalakrishnan M, Shieh CC. Effects of intermediate-conductance Ca2+-activated K+ channel modulators on human prostate cancer cell proliferation. Eur J Pharmacol 2003; 471:157-64. [PMID: 12826234 DOI: 10.1016/s0014-2999(03)01825-9] [Citation(s) in RCA: 85] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
The effects of 1-ethyl-2-benzimidazolinone (1-EBIO) and riluzole on human prostate cancer cells, LNCaP and PC-3, were evaluated using rubidium (86Rb(+)) efflux and proliferation assays. 1-EBIO and riluzole evoked concentration-dependent increases in 86Rb(+) efflux from LNCaP and PC-3 cells that were sensitive to inhibition by intermediate-conductance Ca(2+)-activated K(+) channel (IK(Ca)) blockers clotrimazole and charybdotoxin. Blockers of large-conductance Ca(2+)-activated K(+) (BK(Ca)) channel, iberiotoxin, or small-conductance Ca(2+)-activated K(+) (SK(Ca)) channel, apamin or scyllatoxin, had no effect. Concurrently, both 1-EBIO and riluzole evoked concentration-dependent increases in proliferation from human prostate cancer cell lines (LNCaP and PC-3 cells). Clotrimazole and charybdotoxin, but not iberiotoxin, apamin or scyllatoxin, inhibited 1-EBIO- and riluzole-evoked increases in proliferation from LNCaP and PC-3 cells. N-(3-(trifluoromethyl)phenyl)-N'-(2-hydroxy-5-chlorophenyl)urea (NS-1608) and 2-amino-5-(2-fluorophenyl)-4-methyl-1H-pyrrole-3-carbonitrile (NS-8), BK(Ca) channel openers had no effect on LNCaP and PC-3 proliferation. These results demonstrate that IK(Ca) channels play an important role in the regulation of human prostate cancer cell proliferation.
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Turner SC, Carroll WA, White TK, Gopalakrishnan M, Coghlan MJ, Shieh CC, Zhang XF, Parihar AS, Buckner SA, Milicic I, Sullivan JP. The discovery of a new class of large-conductance Ca2+-activated K+ channel opener targeted for overactive bladder: synthesis and structure-activity relationships of 2-amino-4-azaindoles. Bioorg Med Chem Lett 2003; 13:2003-7. [PMID: 12781183 DOI: 10.1016/s0960-894x(03)00324-x] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
2-Amino-4-azaindoles have been identified as a structurally novel class of BK(Ca) channel openers. Their synthesis from 2-chloro-3-nitropyridine is described together with their in vitro properties assessed by 86Rb(+) efflux and whole-cell patch-clamp assays using HEK293 cells stably transfected with the BK(Ca) alpha subunit. In vitro functional characterization of BK(Ca) channel opening activity was also assessed by measurement of relaxation of smooth muscle tissue strips obtained from Landrace pig bladders. The preliminary SAR data indicate the importance of steric bulk around the 2-amino substituent.
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