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Siddiqui S, Wenzel SE, Bozik ME, Archibald DG, Dworetzky SI, Mather JL, Killingsworth R, Ghearing N, Schwartz JT, Ochkur SI, Jacobsen EA, Busse WW, Panettieri RA, Prussin C. Safety and Efficacy of Dexpramipexole in Eosinophilic Asthma (EXHALE): A randomized controlled trial. J Allergy Clin Immunol 2023; 152:1121-1130.e10. [PMID: 37277072 DOI: 10.1016/j.jaci.2023.05.014] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2023] [Revised: 04/07/2023] [Accepted: 05/01/2023] [Indexed: 06/07/2023]
Abstract
BACKGROUND There is a need for new and effective oral asthma therapies. Dexpramipexole, an oral eosinophil-lowering drug, has not previously been studied in asthma. OBJECTIVE We sought to evaluate the safety and efficacy of dexpramipexole in lowering blood and airway eosinophilia in subjects with eosinophilic asthma. METHODS We performed a randomized, double-blind, placebo-controlled proof-of-concept trial in adults with inadequately controlled moderate to severe asthma and blood absolute eosinophil count (AEC) greater than or equal to 300/μL. Subjects were randomly assigned (1:1:1:1) to dexpramipexole 37.5, 75, or 150 mg BID (twice-daily) or placebo. The primary end point was the relative change in AEC from baseline to week 12. Prebronchodilator FEV1 week-12 change from baseline was a key secondary end point. Nasal eosinophil peroxidase was an exploratory end point. RESULTS A total of 103 subjects were randomly assigned to dexpramipexole 37.5 mg BID (N = 22), 75 mg BID (N = 26), 150 mg BID (N = 28), or placebo (N = 27). Dexpramipexole significantly reduced placebo-corrected AEC week-12 ratio to baseline, in both the 150-mg BID (ratio, 0.23; 95% CI, 0.12-0.43; P < .0001) and the 75-mg BID (ratio, 0.34; 95% CI, 0.18-0.65; P = .0014) dose groups, corresponding to 77% and 66% reductions, respectively. Dexpramipexole reduced the exploratory end point of nasal eosinophil peroxidase week-12 ratio to baseline in the 150-mg BID (median, 0.11; P = .020) and the 75-mg BID (median, 0.17; P = .021) groups. Placebo-corrected FEV1 increases were observed starting at week 4 (nonsignificant). Dexpramipexole displayed a favorable safety profile. CONCLUSIONS Dexpramipexole demonstrated effective eosinophil lowering and was well tolerated. Additional larger clinical trials are needed to understand the clinical efficacy of dexpramipexole in asthma.
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Affiliation(s)
- Salman Siddiqui
- National Heart and Lung Institute, Imperial College, London, United Kingdom
| | - Sally E Wenzel
- University of Pittsburgh School of Public Health, Environmental & Occupational Health, Pittsburgh, Pa
| | | | | | | | | | | | - Natasha Ghearing
- Division of Allergy and Immunology, University of Cincinnati College of Medicine, Cincinnati, Ohio
| | - Justin T Schwartz
- Division of Allergy and Immunology, University of Cincinnati College of Medicine, Cincinnati, Ohio
| | - Sergei I Ochkur
- Division of Allergy, Asthma and Clinical Immunology, Scottsdale, Ariz; Department of Medicine, Mayo Clinic Arizona, Scottsdale, Ariz
| | - Elizabeth A Jacobsen
- Division of Allergy, Asthma and Clinical Immunology, Scottsdale, Ariz; Department of Medicine, Mayo Clinic Arizona, Scottsdale, Ariz
| | - William W Busse
- Division of Allergy, Pulmonary and Critical Care Medicine, Department of Medicine, University of Wisconsin School of Medicine and Public Health, Madison, Wis
| | - Reynold A Panettieri
- Rutgers Institute for Translational Medicine and Science, The State University of New Jersey, New Brunswick, NJ
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Laidlaw TM, Prussin C, Panettieri RA, Lee S, Ferguson BJ, Adappa ND, Lane AP, Palumbo ML, Sullivan M, Archibald D, Dworetzky SI, Hebrank GT, Bozik ME. Dexpramipexole depletes blood and tissue eosinophils in nasal polyps with no change in polyp size. Laryngoscope 2018; 129:E61-E66. [DOI: 10.1002/lary.27564] [Citation(s) in RCA: 47] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2018] [Accepted: 08/20/2018] [Indexed: 12/12/2022]
Affiliation(s)
- Tanya M. Laidlaw
- Brigham and Women's Hospital, Division of Rheumatology, Immunology, and Allergy; Boston Massachusetts
| | | | | | | | | | | | - Andrew P. Lane
- Department of Otolaryngology-Head and Neck Surgery; Johns Hopkins University School of Medicine; Baltimore Maryland U.S.A
| | - Marina L. Palumbo
- Brigham and Women's Hospital, Division of Rheumatology, Immunology, and Allergy; Boston Massachusetts
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Dworetzky SI, Hebrank GT, Archibald DG, Reynolds IJ, Farwell W, Bozik ME. The targeted eosinophil-lowering effects of dexpramipexole in clinical studies. Blood Cells Mol Dis 2017; 63:62-65. [PMID: 28178599 DOI: 10.1016/j.bcmd.2017.01.008] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2016] [Accepted: 01/14/2017] [Indexed: 12/13/2022]
Abstract
Dexpramipexole, an orally bioavailable small molecule previously under clinical development in amyotrophic lateral sclerosis, was observed during routine safety hematology monitoring to demonstrate pronounced, dose- and time-dependent eosinophil-lowering effects, with minor reductions on other leukocyte counts. Analysis of hematology lab values across two double-blind, randomized placebo-controlled clinical trials at total daily doses ranging from 50mg to 300mg demonstrated that dexpramipexole consistently and markedly lowered peripheral blood eosinophils. This effect developed after 1month on treatment, required 3-4months to reach its maximum, remained constant throughout treatment, and partially recovered to baseline levels upon drug withdrawal. All doses tested were well tolerated. The overall adverse event rate was similar for dexpramipexole and placebo, and notably with no increase in infection-related adverse events associated with eosinophil-lowering effects. Given the reliance on and insufficiency of off-label chronic corticosteroid therapy for hypereosinophilic syndromes and other eosinophilic-associated diseases (EADs), a need exists for less toxic, more effective, targeted therapeutic alternatives. Further clinical studies are underway to assess the eosinophil-lowering effect of dexpramipexole in the peripheral blood and target tissues of EAD patients and whether such reductions, if observed, produce clinically important benefits.
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Burris KD, Dworetzky SI. JBS Special Issue: Innovative Screening Methodologies to Identify New Compounds for the Treatment of Central Nervous System Disorders. ACTA ACUST UNITED AC 2016; 21:425-6. [PMID: 27206854 DOI: 10.1177/1087057116644231] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2016] [Accepted: 03/22/2016] [Indexed: 11/15/2022]
Affiliation(s)
- Kevin D Burris
- Lilly Research Laboratories, Quantitative Biology, Indianapolis, IN, USA
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5
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Alavian KN, Dworetzky SI, Bonanni L, Zhang P, Sacchetti S, Li H, Signore AP, Smith PJS, Gribkoff VK, Jonas EA. The mitochondrial complex V-associated large-conductance inner membrane current is regulated by cyclosporine and dexpramipexole. Mol Pharmacol 2014; 87:1-8. [PMID: 25332381 DOI: 10.1124/mol.114.095661] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Inefficiency of oxidative phosphorylation can result from futile leak conductance through the inner mitochondrial membrane. Stress or injury may exacerbate this leak conductance, putting cells, and particularly neurons, at risk of dysfunction and even death when energy demand exceeds cellular energy production. Using a novel method, we have recently described an ion conductance consistent with mitochondrial permeability transition pore (mPTP) within the c-subunit of the ATP synthase. Excitotoxicity, reactive oxygen species-producing stimuli, or elevated mitochondrial matrix calcium opens the channel, which is inhibited by cyclosporine A and ATP/ADP. Here we show that ATP and the neuroprotective drug dexpramipexole (DEX) inhibited an ion conductance consistent with this c-subunit channel (mPTP) in brain-derived submitochondrial vesicles (SMVs) enriched for F1FO ATP synthase (complex V). Treatment of SMVs with urea denatured extramembrane components of complex V, eliminated DEX- but not ATP-mediated current inhibition, and reduced binding of [(14)C]DEX. Direct effects of DEX on the synthesis and hydrolysis of ATP by complex V suggest that interaction of the compound with its target results in functional conformational changes in the enzyme complex. [(14)C]DEX bound specifically to purified recombinant b and oligomycin sensitivity-conferring protein subunits of the mitochondrial F1FO ATP synthase. Previous data indicate that DEX increased the efficiency of energy production in cells, including neurons. Taken together, these studies suggest that modulation of a complex V-associated inner mitochondrial membrane current is metabolically important and may represent an avenue for the development of new therapeutics for neurodegenerative disorders.
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Affiliation(s)
- Kambiz N Alavian
- Department of Internal Medicine (K.N.A., P.Z., S.S., H.L., E.A.J.) and Department of Neurobiology (E.A.J.), Yale University School of Medicine, New Haven, Connecticut; Division of Brain Sciences, Department of Medicine, Imperial College London, London, United Kingdom (K.N.A.); Department of Neuroscience, Imaging and Clinical Sciences, University G.d'Annunzio of Chieti-Pescara, Chieti-Pescara, Italy (L.B.); Knopp Biosciences LLC, Pittsburgh, Pennsylvania (S.I.D., A.P.S., V.K.G.); and Biocurrents Research Center, Marine Biological Laboratory, Woods Hole, Massachusetts (P.J.S.S.)
| | - Steven I Dworetzky
- Department of Internal Medicine (K.N.A., P.Z., S.S., H.L., E.A.J.) and Department of Neurobiology (E.A.J.), Yale University School of Medicine, New Haven, Connecticut; Division of Brain Sciences, Department of Medicine, Imperial College London, London, United Kingdom (K.N.A.); Department of Neuroscience, Imaging and Clinical Sciences, University G.d'Annunzio of Chieti-Pescara, Chieti-Pescara, Italy (L.B.); Knopp Biosciences LLC, Pittsburgh, Pennsylvania (S.I.D., A.P.S., V.K.G.); and Biocurrents Research Center, Marine Biological Laboratory, Woods Hole, Massachusetts (P.J.S.S.)
| | - Laura Bonanni
- Department of Internal Medicine (K.N.A., P.Z., S.S., H.L., E.A.J.) and Department of Neurobiology (E.A.J.), Yale University School of Medicine, New Haven, Connecticut; Division of Brain Sciences, Department of Medicine, Imperial College London, London, United Kingdom (K.N.A.); Department of Neuroscience, Imaging and Clinical Sciences, University G.d'Annunzio of Chieti-Pescara, Chieti-Pescara, Italy (L.B.); Knopp Biosciences LLC, Pittsburgh, Pennsylvania (S.I.D., A.P.S., V.K.G.); and Biocurrents Research Center, Marine Biological Laboratory, Woods Hole, Massachusetts (P.J.S.S.)
| | - Ping Zhang
- Department of Internal Medicine (K.N.A., P.Z., S.S., H.L., E.A.J.) and Department of Neurobiology (E.A.J.), Yale University School of Medicine, New Haven, Connecticut; Division of Brain Sciences, Department of Medicine, Imperial College London, London, United Kingdom (K.N.A.); Department of Neuroscience, Imaging and Clinical Sciences, University G.d'Annunzio of Chieti-Pescara, Chieti-Pescara, Italy (L.B.); Knopp Biosciences LLC, Pittsburgh, Pennsylvania (S.I.D., A.P.S., V.K.G.); and Biocurrents Research Center, Marine Biological Laboratory, Woods Hole, Massachusetts (P.J.S.S.)
| | - Silvio Sacchetti
- Department of Internal Medicine (K.N.A., P.Z., S.S., H.L., E.A.J.) and Department of Neurobiology (E.A.J.), Yale University School of Medicine, New Haven, Connecticut; Division of Brain Sciences, Department of Medicine, Imperial College London, London, United Kingdom (K.N.A.); Department of Neuroscience, Imaging and Clinical Sciences, University G.d'Annunzio of Chieti-Pescara, Chieti-Pescara, Italy (L.B.); Knopp Biosciences LLC, Pittsburgh, Pennsylvania (S.I.D., A.P.S., V.K.G.); and Biocurrents Research Center, Marine Biological Laboratory, Woods Hole, Massachusetts (P.J.S.S.)
| | - Hongmei Li
- Department of Internal Medicine (K.N.A., P.Z., S.S., H.L., E.A.J.) and Department of Neurobiology (E.A.J.), Yale University School of Medicine, New Haven, Connecticut; Division of Brain Sciences, Department of Medicine, Imperial College London, London, United Kingdom (K.N.A.); Department of Neuroscience, Imaging and Clinical Sciences, University G.d'Annunzio of Chieti-Pescara, Chieti-Pescara, Italy (L.B.); Knopp Biosciences LLC, Pittsburgh, Pennsylvania (S.I.D., A.P.S., V.K.G.); and Biocurrents Research Center, Marine Biological Laboratory, Woods Hole, Massachusetts (P.J.S.S.)
| | - Armando P Signore
- Department of Internal Medicine (K.N.A., P.Z., S.S., H.L., E.A.J.) and Department of Neurobiology (E.A.J.), Yale University School of Medicine, New Haven, Connecticut; Division of Brain Sciences, Department of Medicine, Imperial College London, London, United Kingdom (K.N.A.); Department of Neuroscience, Imaging and Clinical Sciences, University G.d'Annunzio of Chieti-Pescara, Chieti-Pescara, Italy (L.B.); Knopp Biosciences LLC, Pittsburgh, Pennsylvania (S.I.D., A.P.S., V.K.G.); and Biocurrents Research Center, Marine Biological Laboratory, Woods Hole, Massachusetts (P.J.S.S.)
| | - Peter J S Smith
- Department of Internal Medicine (K.N.A., P.Z., S.S., H.L., E.A.J.) and Department of Neurobiology (E.A.J.), Yale University School of Medicine, New Haven, Connecticut; Division of Brain Sciences, Department of Medicine, Imperial College London, London, United Kingdom (K.N.A.); Department of Neuroscience, Imaging and Clinical Sciences, University G.d'Annunzio of Chieti-Pescara, Chieti-Pescara, Italy (L.B.); Knopp Biosciences LLC, Pittsburgh, Pennsylvania (S.I.D., A.P.S., V.K.G.); and Biocurrents Research Center, Marine Biological Laboratory, Woods Hole, Massachusetts (P.J.S.S.)
| | - Valentin K Gribkoff
- Department of Internal Medicine (K.N.A., P.Z., S.S., H.L., E.A.J.) and Department of Neurobiology (E.A.J.), Yale University School of Medicine, New Haven, Connecticut; Division of Brain Sciences, Department of Medicine, Imperial College London, London, United Kingdom (K.N.A.); Department of Neuroscience, Imaging and Clinical Sciences, University G.d'Annunzio of Chieti-Pescara, Chieti-Pescara, Italy (L.B.); Knopp Biosciences LLC, Pittsburgh, Pennsylvania (S.I.D., A.P.S., V.K.G.); and Biocurrents Research Center, Marine Biological Laboratory, Woods Hole, Massachusetts (P.J.S.S.)
| | - Elizabeth A Jonas
- Department of Internal Medicine (K.N.A., P.Z., S.S., H.L., E.A.J.) and Department of Neurobiology (E.A.J.), Yale University School of Medicine, New Haven, Connecticut; Division of Brain Sciences, Department of Medicine, Imperial College London, London, United Kingdom (K.N.A.); Department of Neuroscience, Imaging and Clinical Sciences, University G.d'Annunzio of Chieti-Pescara, Chieti-Pescara, Italy (L.B.); Knopp Biosciences LLC, Pittsburgh, Pennsylvania (S.I.D., A.P.S., V.K.G.); and Biocurrents Research Center, Marine Biological Laboratory, Woods Hole, Massachusetts (P.J.S.S.)
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6
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Wu YJ, Conway CM, Sun LQ, Machet F, Chen J, Chen P, He H, Bourin C, Calandra V, Polino JL, Davis CD, Heman K, Gribkoff VK, Boissard CG, Knox RJ, Thompson MW, Fitzpatrick W, Weaver D, Harden DG, Natale J, Dworetzky SI, Starrett JE. Discovery of (S,E)-3-(2-fluorophenyl)-N-(1-(3-(pyridin-3-yloxy)phenyl)ethyl)-acrylamide as a potent and efficacious KCNQ2 (Kv7.2) opener for the treatment of neuropathic pain. Bioorg Med Chem Lett 2013; 23:6188-91. [PMID: 24070783 DOI: 10.1016/j.bmcl.2013.08.092] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2013] [Accepted: 08/26/2013] [Indexed: 12/21/2022]
Abstract
Acrylamide (S)-6, a potent and efficacious KCNQ2 (Kv7.2) opener, demonstrated significant activity in two models of neuropathic pain and in the formalin test, suggesting that KCNQ2 openers may be useful in the treatment of neuropathic pain including diabetic neuropathy.
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Affiliation(s)
- Yong-Jin Wu
- Research and Development, Bristol-Myers Squibb Company, 5 Research Parkway, Wallingford, CT 06492, USA.
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7
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McDonald IM, Mate RA, Zusi FC, Huang H, Post-Munson DJ, Ferrante MA, Gallagher L, Bertekap RL, Knox RJ, Robertson BJ, Harden DG, Morgan DG, Lodge NJ, Dworetzky SI, Olson RE, Macor JE. Discovery of a novel series of quinolone α7 nicotinic acetylcholine receptor agonists. Bioorg Med Chem Lett 2013; 23:1684-8. [DOI: 10.1016/j.bmcl.2013.01.070] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2012] [Revised: 01/11/2013] [Accepted: 01/16/2013] [Indexed: 11/25/2022]
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8
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Alavian KN, Dworetzky SI, Bonanni L, Zhang P, Sacchetti S, Mariggio MA, Onofrj M, Thomas A, Li H, Mangold JE, Signore AP, Demarco U, Demady DR, Nabili P, Lazrove E, Smith PJS, Gribkoff VK, Jonas EA. Effects of dexpramipexole on brain mitochondrial conductances and cellular bioenergetic efficiency. Brain Res 2012; 1446:1-11. [PMID: 22364637 DOI: 10.1016/j.brainres.2012.01.046] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2012] [Accepted: 01/18/2012] [Indexed: 02/01/2023]
Abstract
Cellular stress or injury can result in mitochondrial dysfunction, which has been linked to many chronic neurological disorders including amyotrophic lateral sclerosis (ALS) and Parkinson's disease (PD). Stressed and dysfunctional mitochondria exhibit an increase in large conductance mitochondrial membrane currents and a decrease in bioenergetic efficiency. Inefficient energy production puts cells, and particularly neurons, at risk of death when energy demands exceed cellular energy production. Here we show that the candidate ALS drug dexpramipexole (DEX; KNS-760704; ((6R)-4,5,6,7-tetrahydro-N6-propyl-2,6-benzothiazole-diamine) and cyclosporine A (CSA) inhibited increases in ion conductance in whole rat brain-derived mitochondria induced by calcium or treatment with a proteasome inhibitor, although only CSA inhibited calcium-induced permeability transition in liver-derived mitochondria. In several cell lines, including cortical neurons in culture, DEX significantly decreased oxygen consumption while maintaining or increasing production of adenosine triphosphate (ATP). DEX also normalized the metabolic profile of injured cells and was protective against the cytotoxic effects of proteasome inhibition. These data indicate that DEX increases the efficiency of oxidative phosphorylation, possibly by inhibition of a CSA-sensitive mitochondrial conductance.
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Affiliation(s)
- Kambiz N Alavian
- Department of Internal Medicine, Yale University School of Medicine, New Haven, CT, USA
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9
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Romine JL, Martin SW, Meanwell NA, Gribkoff VK, Boissard CG, Dworetzky SI, Natale J, Moon S, Ortiz A, Yeleswaram S, Pajor L, Gao Q, Starrett JE. 3-[(5-Chloro-2-hydroxyphenyl)methyl]-5-[4-(trifluoromethyl)phenyl ]-1,3,4-oxadiazol-2(3H)-one, BMS-191011: opener of large-conductance Ca(2+)-activated potassium (maxi-K) channels, identification, solubility, and SAR. J Med Chem 2007; 50:528-42. [PMID: 17266205 DOI: 10.1021/jm061006n] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Compound 8a (BMS-191011), an opener of the cloned large-conductance, Ca2+-activated potassium (maxi-K) channel, demonstrated efficacy in in vivo stroke models, which led to its nomination as a candidate for clinical evaluation. Its maxi-K channel opening properties were consistent with its structural topology, being derived by combining elements from other known maxi-K openers. However, 8a suffered from poor aqueous solubility, which complicated elucidation of SAR during in vitro evaluation. The activity of 8a in in vivo stroke models and studies directed toward improving its solubility are reported herein. Enhanced solubility was achieved by appending heterocycles to the 8a scaffold, and a notable observation was made that inclusion of a simple amino group (anilines 8k and 8l) yielded excellent in vitro maxi-K ion channel opening activity and enhanced brain-to-plasma partitioning compared to the appended heterocycles.
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Affiliation(s)
- Jeffrey L Romine
- Bristol-Myers Squibb Pharmaceutical Research Institute, 5 Research Parkway, Wallingford, Connecticut 06492, USA.
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10
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Vrudhula VM, Dasgupta B, Qian-Cutrone J, Kozlowski ES, Boissard CG, Dworetzky SI, Wu D, Gao Q, Kimura R, Gribkoff VK, Starrett JE. Atropisomeric 3-(β-hydroxyethyl)-4-arylquinolin-2-ones as Maxi-K Potassium Channel Openers. J Med Chem 2007; 50:1050-7. [PMID: 17274609 DOI: 10.1021/jm061093j] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The synthesis of a series of 3-beta-hydroxyethyl-4-arylquinolin-2-ones is described. These compounds contain hydrophilic and hydrophobic substituents ortho to the phenolic OH in the C ring of the quinolinone. Electrophysiological evaluation of the panel of compounds revealed that 11 and 16 with an unbranched ortho substituent retain activity as maxi-K ion channel openers. Members of this series of compounds can exist as stable atropisomers. Calculated estimates of the energy barrier for rotation around the aryl-aryl single bond in 3 is 31 kcal/mol. The atropisomers of (+/-)-3, (+/-)-4, and (+/-)-11 were separated by chiral HPLC and tested for their effect on maxi-K mediated outward current in hSlo injected X. laevis oocytes. The (-) isomer in each case was found to be more active than the corresponding (+) isomer, suggesting that the ion channel exhibits stereoselective activation. X-ray crystallographic structures of (+)-3 and (+)-11 were determined. Evaluation of the stability of (-)-3 at 80 degrees C in n-butanol indicated a 19.6% conversion to (+)-3 over 72 h. In human serum at 37 degrees C (-)-3 did not racemize over the course of the 30 h study.
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Affiliation(s)
- Vivekananda M Vrudhula
- Bristol-Myers Squibb Pharmaceutical Research Institute, 5 Research Parkway, Wallingford, Connecticut 06492, USA.
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11
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Yang B, Gribkoff VK, Pan J, Damagnez V, Dworetzky SI, Boissard CG, Bhattacharjee A, Yan Y, Sigworth FJ, Kaczmarek LK. Pharmacological activation and inhibition of Slack (Slo2.2) channels. Neuropharmacology 2006; 51:896-906. [PMID: 16876206 DOI: 10.1016/j.neuropharm.2006.06.003] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2006] [Accepted: 06/01/2006] [Indexed: 10/24/2022]
Abstract
The Slack (Sequence like a calcium-activated K channel) (Slo2.2) gene is abundantly expressed in the mammalian brain and encodes a sodium-activated K+ (KNa) channel. Although the specific roles of Slack channel subunits in neurons remain to be identified, they may play a role in the adaptation of firing rate and in protection against ischemic injury. In the present study, we have generated a stable cell line expressing the Slack channel, and have analyzed the pharmacological properties of these channels in these cells and in Xenopus oocytes. Two known blockers of KNa channels, bepridil and quinidine, inhibited Slack currents in a concentration-dependent manner and decreased channel activity in excised membrane patches. The inhibition by bepridil was potent, with an IC50 of 1.0 microM for inhibition of Slack currents in HEK cells. In contrast, bithionol was found to be a robust activator of Slack currents. When applied to the extracellular face of excised patches, bithionol rapidly induced a reversible increase in channel opening, suggesting that it acts on Slack channels relatively directly. These data establish an important early characterization of agents that modulate Slack channels, a process essential for the experimental manipulation of Slack currents in neurons.
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Affiliation(s)
- Bo Yang
- Department of Pharmacology, Yale University School of Medicine, 333 Cedar Street, New Haven, CT 06520, USA
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12
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L'Heureux A, Martel A, He H, Chen J, Sun LQ, Starrett JE, Natale J, Dworetzky SI, Knox RJ, Harden DG, Weaver D, Thompson MW, Wu YJ. (S,E)-N-[1-(3-heteroarylphenyl)ethyl]-3-(2-fluorophenyl)acrylamides: synthesis and KCNQ2 potassium channel opener activity. Bioorg Med Chem Lett 2005; 15:363-6. [PMID: 15603955 DOI: 10.1016/j.bmcl.2004.10.065] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2004] [Revised: 10/20/2004] [Accepted: 10/21/2004] [Indexed: 10/26/2022]
Abstract
Replacement of the morpholinyl moiety in (S,E)-N-[1-(3-morpholinophenyl)ethyl]-3-phenylacrylamide (1) with heteroaryl groups led to the identification of (S,E)-N-1-[3-(6-fluoropyridin-3-yl)phenyl]ethyl-3-(2-fluorophenyl)acrylamide (5) as a potent KCNQ2 potassium channel opener. Among this series of heteroaryl substituted acrylamides, (S,E)-N-1-[3-(1H-pyrazol-1-yl)phenyl]ethyl-3-(2-fluorophenyl)acrylamide (9) exhibits balanced potency and efficacy. The syntheses and the KCNQ2 opener activity of this series of acrylamides are described.
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Affiliation(s)
- Alexandre L'Heureux
- Department of Medicinal Chemistry, Bristol-Myers Squibb Pharmaceutical Research Institute, 100 de l'Industrie Blvd., Candiac, Quebec, Canada, J5R 1J1
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13
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Boy KM, Guernon JM, Sit SY, Xie K, Hewawasam P, Boissard CG, Dworetzky SI, Natale J, Gribkoff VK, Lodge N, Starrett JE. 3-Thio-quinolinone maxi-K openers for the treatment of erectile dysfunction. Bioorg Med Chem Lett 2005; 14:5089-93. [PMID: 15380205 DOI: 10.1016/j.bmcl.2004.07.080] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2004] [Revised: 07/29/2004] [Accepted: 07/29/2004] [Indexed: 10/26/2022]
Abstract
A series of Maxi-K openers for the treatment of erectile dysfunction based on the 3-thio-quinolinone core is described. Significant levels of channel opening (up to 550% of control) are seen in transfected oocytes. Functional activity in rabbit corpus cavernosum tissue strips confirms the potential to effect therapy for ED, the effect being maximal for the 3-amino-2-hydroxy thiol side chain.
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Affiliation(s)
- Kenneth M Boy
- Bristol-Myers Squibb Pharmaceutical Research Institute, 5 Research Parkway, Wallingford, CT 06492, USA.
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14
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Wu YJ, Sun LQ, He H, Chen J, Starrett JE, Dextraze P, Daris JP, Boissard CG, Pieschl RL, Gribkoff VK, Natale J, Knox RJ, Harden DG, Thompson MW, Fitzpatrick W, Weaver D, Wu D, Gao Q, Dworetzky SI. Synthesis and KCNQ2 opener activity of N-(1-benzo[1,3]dioxol-5-yl-ethyl, N-[1-(2,3-dihydro-benzofuran-5-yl)-ethyl, and N-[1-(2,3-dihydro-1H-indol-5-yl)-ethyl acrylamides. Bioorg Med Chem Lett 2005; 14:4533-7. [PMID: 15357987 DOI: 10.1016/j.bmcl.2004.06.035] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2004] [Revised: 06/10/2004] [Accepted: 06/10/2004] [Indexed: 10/26/2022]
Abstract
Bioisosteric replacement studies led to the identification of N-(1-benzo[1,3]dioxol-5-yl-ethyl)-3-(2-chloro-phenyl)-acrylamide ((S)-3) as a highly potent KCNQ2 opener, and 3-(2,6-difluoro-phenyl)-N-[1-(2,3-dihydro-benzofuran-5-yl)-ethyl]-acrylamide ((S)-4), and N-[1-(2,3-dihydro-1H-indol-5-yl)-ethyl]-3-(2-fluoro-phenyl)-acrylamide ((S)-5) as highly efficacious KCNQ2 openers. In contrast, their respective R enantiomers showed significantly less or no appreciable KCNQ2 opener activity even at the highest concentration tested (10 microM). Because of its high potency and moderate efficacy as well as its convenient synthesis, (+/-)-3 was selected as a reference compound for analyzing efficacies of KCNQ openers in electrophysiology studies. Compounds (S)-4 and (S)-5 demonstrated significant activity in reducing neuronal hyperexcitability in rat hippocampal slices. The synthesis and the KCNQ2 opener activity of these acrylamides are described.
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Affiliation(s)
- Yong-Jin Wu
- Department of Neuroscience Chemistry, Bristol-Myers Squibb Pharmaceutical Research Institute, 5 Research Parkway, Wallingford, CT 06492, USA.
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15
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Abstract
During the past five years, several members of the KCNQ potassium channel gene family have been identified with a high degree of CNS specificity. Within the KCNQ family, the combination of the KCNQ2/KCNQ3 proteins, and the KCNQ5/KCNQ3 arrangement has been identified as the molecular correlates of the different M-currents. Several lines of evidence are emerging demonstrating the importance of these channels in regulating neuronal excitability; for example, determination of the excitability threshold, firing properties, and responsiveness of neurons to synaptic inputs. Recent studies have shown that KCNQ openers have potential for the treatment of several CNS disorders characterized by neuronal hyperexcitability, such as migraine, epilepsy and neuropathic pain. This article reviews the recent developments of KCNQ potassium channel openers.
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Affiliation(s)
- Yong-Jin Wua
- Department of Neuroscience Chemistry, Bristol-Myers Squibb Pharmaceutical Research Institute, 5 Research Parkway, Wallingford, Connecticut 06492, USA.
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16
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Weaver CD, Harden D, Dworetzky SI, Robertson B, Knox RJ. A thallium-sensitive, fluorescence-based assay for detecting and characterizing potassium channel modulators in mammalian cells. SLAS Discovery 2005; 9:671-7. [PMID: 15634793 DOI: 10.1177/1087057104268749] [Citation(s) in RCA: 132] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Potassium channels have been identified as targets for a large number of therapeutic indications. The ability to use a high-throughput functional assay for the detection and characterization of small-molecule modulators of potassium channels is very desirable. However, present techniques capable of screening very large chemical libraries are limited in terms of data quality, temporal resolution, ease of use, and requirements for specialized instrumentation. To address these issues, the authors have developed a fluorescence-based thallium flux assay. This assay is capable of detecting modulators of both voltage and ligand-gated potassium channels expressed in mammalian cells. The thallium flux assay can use instruments standard to most high-throughput screening laboratories, and using such equipment has been successfully employed to screen large chemical libraries consisting of hundreds of thousands of compounds.
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Affiliation(s)
- C David Weaver
- Vanderbilt Institute of Chemical Biology and Department of Pharmacology, 812 Robinson Research Building, Nashville, TN 37232-6600, USA.
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17
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Wu YJ, Boissard CG, Chen J, Fitzpatrick W, Gao Q, Gribkoff VK, Harden DG, He H, Knox RJ, Natale J, Pieschl RL, Starrett JE, Sun LQ, Thompson M, Weaver D, Wu D, Dworetzky SI. (S)-N-[1-(4-cyclopropylmethyl-3,4-dihydro-2H-benzo[1,4]oxazin-6-yl)-ethyl]-3-(2-fluoro-phenyl)-acrylamide is a potent and efficacious KCNQ2 opener which inhibits induced hyperexcitability of rat hippocampal neurons. Bioorg Med Chem Lett 2004; 14:1991-5. [PMID: 15050644 DOI: 10.1016/j.bmcl.2004.01.069] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2003] [Revised: 01/09/2004] [Accepted: 01/14/2004] [Indexed: 11/22/2022]
Abstract
(S)-N-[1-(4-Cyclopropylmethyl-3,4-dihydro-2H-benzo[1,4]oxazin-6-yl)-ethyl]-3-(2-fluoro-phenyl)-acrylamide ((S)-2) was identified as a potent and efficacious KCNQ2 opener. This compound demonstrated significant activity in reducing neuronal hyperexcitability in rat hippocampal slices, and the inhibition mediated by (S)-2 was reversed by the KCNQ blocker linopirdine.
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Affiliation(s)
- Yong-Jin Wu
- Department of Neuroscience Chemistry, Bristol-Myers Squibb Pharmaceutical Research Institute, 5 Research Parkway, Wallingford, CT 06492, USA.
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18
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Wu YJ, He H, Sun LQ, L'Heureux A, Chen J, Dextraze P, Starrett JE, Boissard CG, Gribkoff VK, Natale J, Dworetzky SI. Synthesis and structure-activity relationship of acrylamides as KCNQ2 potassium channel openers. J Med Chem 2004; 47:2887-96. [PMID: 15139767 DOI: 10.1021/jm0305826] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
A new class of acrylamides was synthesized, and the effects of these analogues on outward potassium current were evaluated by using two electrode voltage clamp recordings from Xenopus laevis oocytes expressing cloned mKCNQ2 channels. SAR studies indicated that the pharmacophore of the acrylamide series includes the (S) absolute configuration at the (1-phenyl)ethyl moiety and the alpha,beta-unsaturated acrylamide functionality with a free NH. This study identified (S)-N-[1-(3-morpholin-4-yl-phenyl)-ethyl]-3-phenyl-acrylamide ((S)-1) and (S)-N-[1-(4-fluoro-3-morpholin-4-yl-phenyl)-ethyl]-3-(4-fluoro-phenyl)-acrylamide ((S)-2) as KCNQ2 openers for further electrophysiological evaluations. These two acrylamides demonstrated significant activity in the cortical spreading depression model of migraine as we reported previously.
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Affiliation(s)
- Yong-Jin Wu
- Bristol-Myers Squibb Pharmaceutical Research Institute, 5 Research Parkway, Wallingford, Connecticut 06492, USA.
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19
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Hewawasam P, Chen N, Ding M, Natale JT, Boissard CG, Yeola S, Gribkoff VK, Starrett J, Dworetzky SI. The synthesis and structure–activity relationships of 3-amino-4-benzylquinolin-2-ones. Bioorg Med Chem Lett 2004; 14:1615-8. [PMID: 15026035 DOI: 10.1016/j.bmcl.2004.01.073] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2004] [Accepted: 01/23/2004] [Indexed: 11/18/2022]
Abstract
3-amino-4-benzylquinolin-2-ones have been identified as a novel class of KCNQ2 channel openers. Synthesis and SAR is described along with their electrophysiological evaluation as activators of the cloned mKCNQ2 channel expressed in Xenopus laevis oocytes. The preliminary SAR data suggest the importance of both the trifluoromethylsulfonamido group and electron-withdrawing substituents on the quinolone nucleus for expression of KCNQ2 channel opening properties.
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Affiliation(s)
- Piyasena Hewawasam
- Department of Chemistry, The Bristol-Myers Squibb Pharmaceutical Research Institute, 5 Research Parkway, Wallingford, CT 06492, USA.
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20
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Wu YJ, Boissard CG, Greco C, Gribkoff VK, Harden DG, He H, L'Heureux A, Kang SH, Kinney GG, Knox RJ, Natale J, Newton AE, Lehtinen-Oboma S, Sinz MW, Sivarao DV, Starrett JE, Sun LQ, Tertyshnikova S, Thompson MW, Weaver D, Wong HS, Zhang L, Dworetzky SI. (S)-N-[1-(3-morpholin-4-ylphenyl)ethyl]- 3-phenylacrylamide: an orally bioavailable KCNQ2 opener with significant activity in a cortical spreading depression model of migraine. J Med Chem 2003; 46:3197-200. [PMID: 12852750 DOI: 10.1021/jm034073f] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
(S)-N-[1-(3-Morpholin-4-ylphenyl)ethyl]-3-phenylacrylamide (2) was synthesized as an orally bioavailable KCNQ2 potassium channel opener. In a rat model of migraine, 2 demonstrated significant oral activity in reducing the total number of cortical spreading depressions induced by potassium chloride.
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Affiliation(s)
- Yong-Jin Wu
- Bristol-Myers Squibb Pharmaceutical Research Institute, 5 Research Parkway, Wallingford, Connecticut 06492, USA.
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21
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Hewawasam P, Fan W, Ding M, Flint K, Cook D, Goggins GD, Myers RA, Gribkoff VK, Boissard CG, Dworetzky SI, Starrett JE, Lodge NJ. 4-Aryl-3-(hydroxyalkyl)quinolin-2-ones: novel maxi-K channel opening relaxants of corporal smooth muscle targeted for erectile dysfunction. J Med Chem 2003; 46:2819-22. [PMID: 12825925 DOI: 10.1021/jm030005h] [Citation(s) in RCA: 83] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Novel 4-aryl-3-(hydroxyalkyl)quinoline-2-one derivatives were prepared and evaluated as openers of the cloned maxi-K channel hSlo expressed in Xenopus laevis oocytes by utilizing electrophysiological methods. The effect of these maxi-K openers on corporal smooth muscle was studied in vitro using isolated rabbit corpus cavernosum. From this study, a potent maxi-K opener was identified as an effective relaxant of rabbit corporal smooth muscle and shown to be active in an in vivo animal model of male erectile function.
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Affiliation(s)
- Piyasena Hewawasam
- Department of Chemistry, The Bristol-Myers Squibb Pharmaceutical Research Institute, 5 Research Parkway, Wallingford, Connecticut 06492, USA.
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22
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Li Y, Johnson G, Romine JL, Meanwell NA, Martin SW, Dworetzky SI, Boissard CG, Gribkoff VK, Starrett JE. Novel openers of Ca2+-dependent large-conductance potassium channels: symmetrical pharmacophore and electrophysiological evaluation of bisphenols. Bioorg Med Chem Lett 2003; 13:1437-9. [PMID: 12668007 DOI: 10.1016/s0960-894x(03)00156-2] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Electrophysiological evaluation of symmetrical analogues of the known maxi-K opener NS-004 (1) led to the discovery of bisphenols 2a, 3a and 4a as openers of cloned maxi-K channels expressed in oocytes.
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Affiliation(s)
- Yi Li
- Computer-Assisted Drug Design, The Bristol-Myers Squibb Pharmaceutical Research Institute, 5 Research Parkway, Wallingford, CT 06492, USA.
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23
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Romine JL, Martin SW, Gribkoff VK, Boissard CG, Dworetzky SI, Natale J, Li Y, Gao Q, Meanwell NA, Starrett JE. 4,5-diphenyltriazol-3-ones: openers of large-conductance Ca(2+)-activated potassium (maxi-K) channels. J Med Chem 2002; 45:2942-52. [PMID: 12086481 DOI: 10.1021/jm010569q] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
A series of diphenyl-substituted heterocycles were synthesized and evaluated by electrophysiological techniques as openers of the cloned mammalian large-conductance, Ca(2+)-activated potassium (maxi-K) channel. The series was designed from deannulation of known benzimidazolone maxi-K opener NS-004 (2) thereby providing an effective template for obtaining structure-activity-related information. The triazolone ring system was the most studied wherein 4,5-diphenyltriazol-3-one 6d (maxi-K = 158%) was identified as the optimal maxi-K channel opener.
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Affiliation(s)
- Jeffrey L Romine
- Bristol-Myers Squibb Pharmaceutical Research Institute, 5 Research Parkway, Wallingford, CT 06492, USA.
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24
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Hewawasam P, Gribkoff VK, Pendri Y, Dworetzky SI, Meanwell NA, Martinez E, Boissard CG, Post-Munson DJ, Trojnacki JT, Yeleswaram K, Pajor LM, Knipe J, Gao Q, Perrone R, Starrett JE. The synthesis and characterization of BMS-204352 (MaxiPost) and related 3-fluorooxindoles as openers of maxi-K potassium channels. Bioorg Med Chem Lett 2002; 12:1023-6. [PMID: 11909708 DOI: 10.1016/s0960-894x(02)00101-4] [Citation(s) in RCA: 132] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
3-Aryl-3-fluorooxindoles can be efficiently synthesized in two steps by the addition of an aryl Grignard to an isatin, followed by treatment with DAST. Oxindole 1 (BMS-204352; MaxiPost) can be isolated using chiral HPLC or prepared by employing chiral resolution. Cloned maxi-K channels are opened by 1, which demonstrates a brain/plasma ratio >9 in rats.
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Affiliation(s)
- Piyasena Hewawasam
- Department of Chemistry, Bristol-Myers Squibb Pharmaceutical Research Institute, 5 Research Parkway, Wallingford, CT 06492, USA
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25
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Gribkoff VK, Starrett JE, Dworetzky SI, Hewawasam P, Boissard CG, Cook DA, Frantz SW, Heman K, Hibbard JR, Huston K, Johnson G, Krishnan BS, Kinney GG, Lombardo LA, Meanwell NA, Molinoff PB, Myers RA, Moon SL, Ortiz A, Pajor L, Pieschl RL, Post-Munson DJ, Signor LJ, Srinivas N, Taber MT, Thalody G, Trojnacki JT, Wiener H, Yeleswaram K, Yeola SW. Targeting acute ischemic stroke with a calcium-sensitive opener of maxi-K potassium channels. Nat Med 2001; 7:471-7. [PMID: 11283675 DOI: 10.1038/86546] [Citation(s) in RCA: 254] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
During ischemic stroke, neurons at risk are exposed to pathologically high levels of intracellular calcium (Ca++), initiating a fatal biochemical cascade. To protect these neurons, we have developed openers of large-conductance, Ca++-activated (maxi-K or BK) potassium channels, thereby augmenting an endogenous mechanism for regulating Ca++ entry and membrane potential. The novel fluoro-oxindoles BMS-204352 and racemic compound 1 are potent, effective and uniquely Ca++-sensitive openers of maxi-K channels. In rat models of permanent large-vessel stroke, BMS-204352 provided significant levels of cortical neuroprotection when administered two hours after the onset of occlusion, but had no effects on blood pressure or cerebral blood flow. This novel approach may restrict Ca++ entry in neurons at risk while having minimal side effects.
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Affiliation(s)
- V K Gribkoff
- Neuroscience Drug Discovery, Bristol-Myers Squibb Pharmaceutical Research Institute, Wallingford, Connecticut, USA.
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26
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Gribkoff VK, Starrett JE, Dworetzky SI. Maxi-K potassium channels: form, function, and modulation of a class of endogenous regulators of intracellular calcium. Neuroscientist 2001; 7:166-77. [PMID: 11496927 DOI: 10.1177/107385840100700211] [Citation(s) in RCA: 96] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Large-conductance calcium-activated (maxi-K, BK) potassium channels are widely distributed in the brain. Maxi-K channels function as neuronal calcium sensors and contribute to the control of cellular excitability and the regulation of neurotransmitter release. Little is currently known of any significant role of maxi-K channels in the genesis of neurological disease. Recent advances in the molecular biology and pharmacology of these channels have revealed sources of phenotypic variability and demonstrated that they can be successfully modulated by pharmacological agents. A potential role is suggested in the treatment of conditions such as ischemic stroke and cognitive disorders.
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Affiliation(s)
- V K Gribkoff
- Neuroscience and Genitourinary Drug Discovery, Bristol-Myers Squibb Pharmaceutical Research Institute, Wallingford, Connecticut 06492, USA
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27
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Joiner WJ, Tang MD, Wang LY, Dworetzky SI, Boissard CG, Gan L, Gribkoff VK, Kaczmarek LK. Formation of intermediate-conductance calcium-activated potassium channels by interaction of Slack and Slo subunits. Nat Neurosci 1998; 1:462-9. [PMID: 10196543 DOI: 10.1038/2176] [Citation(s) in RCA: 138] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Large-conductance calcium-activated potassium channels (maxi-K channels) have an essential role in the control of excitability and secretion. Only one gene Slo is known to encode maxi-K channels, which are sensitive to both membrane potential and intracellular calcium. We have isolated a potassium channel gene called Slack that is abundantly expressed in the nervous system. Slack channels rectify outwardly with a unitary conductance of about 25-65 pS and are inhibited by intracellular calcium. However, when Slack is co-expressed with Slo, channels with pharmacological properties and single-channel conductances that do not match either Slack or Slo are formed. The Slack/Slo channels have intermediate conductances of about 60-180 pS and are activated by cytoplasmic calcium. Our findings indicate that some intermediate-conductance channels in the nervous system may result from an interaction between Slack and Slo channel subunits.
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Affiliation(s)
- W J Joiner
- Department of Pharmacology, Yale University School of Medicine, New Haven, Connecticut 06520, USA
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28
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Hewawasam* P, Meanwell NA, Gribkoff VK, Dworetzky SI, Boissard CG. DISCOVERY OF A NOVEL CLASS OF BK CHANNEL OPENERS: ENANTIOSPECIFIC SYNTHESIS AND BK CHANNEL OPENING ACTIVITY OF 3-(5-CHLORO-2-HYDROXYPHENYL)-1,3-DIHYDRO-3-HYDROXY-6-(TRIFLUOROMETHYL)-2H-INDOL-2-ONE. Bioorg Med Chem Lett 1997. [DOI: 10.1016/s0960-894x(97)00202-3] [Citation(s) in RCA: 68] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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29
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Chang CP, Dworetzky SI, Wang J, Goldstein ME. Differential expression of the alpha and beta subunits of the large-conductance calcium-activated potassium channel: implication for channel diversity. Brain Res Mol Brain Res 1997; 45:33-40. [PMID: 9105668 DOI: 10.1016/s0169-328x(96)00230-6] [Citation(s) in RCA: 71] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
In addition to the large alpha subunits that conduct selective ion currents, many native voltage-gated ion channels contain associated proteins which modulate the channel activity. Recently, a beta subunit of the large-conductance calcium-activated K+ (BK) channel has been cloned and functionally characterized. In this report, we studied the tissue distribution of the alpha and beta subunits of rat BK channels by nuclease protection analyses and in situ hybridization. BK alpha mRNA is widely distributed but is especially enriched in the brain. In the adult brain, BK alpha expression is robust and widespread throughout all areas of the neo-, olfactory and hippocampal cortices, habenula and cerebellum. Other prominent sites of BK alpha expression include thalamus and amygdala. In marked contrast to the expression pattern of BK alpha mRNA, the expression of BK beta mRNA is relatively low and preferentially in the periphery. In rat brains, BK beta mRNA occurs only in a few discrete populations of neurons that also express BK alpha messages. These results indicate that the major type of BK channels in the brain, unlike the alpha beta channel type in aortic and tracheal smooth muscle, is devoid of the beta subunit. These observations provide a structural basis for the BK channel diversity observed in a variety of tissues.
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Affiliation(s)
- C P Chang
- Central Nervous System Drug Discovery, Bristol-Myers Squibb Pharmaceutical Research Institute, Wallingford, CT 06492, USA.
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30
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Dworetzky SI, Boissard CG, Lum-Ragan JT, McKay MC, Post-Munson DJ, Trojnacki JT, Chang CP, Gribkoff VK. Phenotypic alteration of a human BK (hSlo) channel by hSlobeta subunit coexpression: changes in blocker sensitivity, activation/relaxation and inactivation kinetics, and protein kinase A modulation. J Neurosci 1996; 16:4543-50. [PMID: 8764643 PMCID: PMC6579031] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/1996] [Revised: 05/03/1996] [Accepted: 05/07/1996] [Indexed: 02/02/2023] Open
Abstract
A human homolog of the large-conductance calcium-activated potassium (BK) channel beta subunit (hSlobeta) was cloned, and its effects on a human BK channel (hSlo) phenotype are reported. Coexpression of hSlo and hSlobeta, in both oocytes and human embryonic kidney 293 cells, resulted in increased Ca2+ sensitivity, marked slowing of BK channel activation and relaxation, and significant reduction in slow inactivation. In addition, coexpression changed the pharmacology of the BK channel phenotype: hSlo-mediated currents in oocytes were more sensitive to the peptide toxin iberiotoxin than were hSlo + hSlobeta currents, and the potency of blockade by the alkaloid BK blocker tetrandrine was much greater on hSlo + hSlobeta- mediated currents compared with hSlo currents alone. No significant differences in the response to charybdotoxin or the BK channel opener NS1619 were observed. Modulation of BK channel activity by phosphorylation was also affected by the presence of the hSlobeta subunit. Application of cAMP-dependent protein kinase increased P(OPEN) of hSlo channels, but decreased P(OPEN)of most hSlo + hSlobeta channels. Taken together, these altered characteristics may explain some of the wide diversity of BK channel phenotypes observed in native tissues.
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Affiliation(s)
- S I Dworetzky
- Central Nervous System Drug Discovery, Bristol-Myers Squibb Pharmaceutical Research Institute, Wallingford, Connecticut 06492, USA
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31
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Kozlowski ES, Johnson G, Dischino DD, Dworetzky SI, Boissard CG, Gribkoff VK. Synthesis and biological evaluation of an iodinated iberiotoxin analogue, [mono-iodo-Tyr5, Phe36]-iberiotoxin. Int J Pept Protein Res 1996; 48:194-9. [PMID: 8872538 DOI: 10.1111/j.1399-3011.1996.tb00831.x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
The synthesis and iodination of a structural analogue of the specific large-conductance calcium-activated potassium (BK) channel blocker, iberiotoxin (IbTX), a 37-amino acid scorpion neurotoxin, is reported. The synthesis of this analogue, [Tyr5, Phe36]-IbTX, was accomplished using standard solid-phase Fmoc (9-fluorenylmethoxycarbonyl) chemistry protocols. The linear peptide was cyclized via the formation of three intramolecular disulfide bridges and subsequently iodinated at the Tyr5 position. Upon purification, the iodinated analogue, [mono-iodo-Tyr5, Phe36]-IbTX, exhibited comparable biological activity to native IbTX in blocking BK-mediated currents. These findings suggest the synthesis and use of an 125I labelled IbTX analogue for BK channel localization in autoradiography experiments.
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Affiliation(s)
- E S Kozlowski
- Department of Central Nervous System Chemistry, Richard L. Gelb Center for Pharmaceutical Research and Development, Bristol-Myers Squibb, Wallingford, Connecticut, USA
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Starrett Jr. JE, Dworetzky SI, Gribkoff VK. Modulators of Large-Conductance Calcium-Activated Potassium (BK) Channels as Potential Therapeutic Targets. Curr Pharm Des 1996. [DOI: 10.2174/1381612802666220926184514] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
BK channels are large conductance calcium-activated potassium channels that are found in many tissues, including excitable cells such as myocytes and neurons. The high conductance and dependence on calcium of BK channels suggests that modulation of these channels may have a pronounced effect on tissues in which they are expressed. Within the past four years, a variety of small molecules and natural product-derived modulators of BK channels have been described. This review will focus on compounds which are openers and blockers of BK channels and their therapeutic potential, with introductory sections covering the biophysics, pharmacology and molecular biology of BK channels.
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Affiliation(s)
- John E. Starrett Jr.
- Division of Central Chemistry, Bristol-Myers Squibb Pharmaceutical Research Institute, 5 Research Parkway, Wallingford, 5 Research Parkway, Wallingford, USA
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Gribkoff VK, Lum-Ragan JT, Boissard CG, Post-Munson DJ, Meanwell NA, Starrett JE, Kozlowski ES, Romine JL, Trojnacki JT, Mckay MC, Zhong J, Dworetzky SI. Effects of channel modulators on cloned large-conductance calcium-activated potassium channels. Mol Pharmacol 1996; 50:206-17. [PMID: 8700114] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
Through expression of the cloned mouse (mSlo) or human (hSlo) large-conductance (BK) Ca(2+)-activated K+ channel in Xenopus laevis oocytes and HEK 293 cells, we characterized the effects of reported blockers and openers of BK channels to initiate the study of the molecular determinants of BK channel modulation. In oocytes, iberiotoxin and charybdotoxin, peptidyl scorpion toxins, were both equally effective blockers of BK current, although iberiotoxin was significantly more potent than charybdotoxin. The structurally related peptide kaliotoxin was not a potent blocker of BK current. Paxilline, a fungal tremorgenic alkaloid, was an effective but complex blocker of BK current. Tetrandrine, a putative blocker of type II BK channels, and ketamine were relatively ineffective. The putative BK openers NS004 and NS1619, phloretin, niflumic acid, flufenamic acid, and 5-nitro-2-(3-phenylpropylamino)benzoic acid (NPPB) increased BK current in oocytes at microM concentrations; many of these produced biphasic concentration-response relationships. Coapplication of representative blockers and openers revealed several patterns of interaction, including competitive and noncompetitive antagonism. NS1619, niflumic acid, and phloretin were tested by using excised inside-out membrane patches from HEK 293 cells and were found to increase the activity of hSlo BK channels and produce a leftward shift in the G/Gmax-versus-voltage relationship of these channels. These results represent the first comprehensive examination of the molecular pharmacology of BK channels.
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Affiliation(s)
- V K Gribkoff
- Central Nervous System Drug Discovery, Bristol-Myers Squibb Pharmaceutical Research Institute, Wallingford, Connecticut 06492, USA.
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Gribkoff VK, Starrett JE, Dworetzky SI. The pharmacology and molecular biology of large-conductance calcium-activated (BK) potassium channels. Adv Pharmacol 1996; 37:319-48. [PMID: 8891106 DOI: 10.1016/s1054-3589(08)60954-0] [Citation(s) in RCA: 66] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Affiliation(s)
- V K Gribkoff
- Bristol-Myers Squibb Pharmaceutical Research Institute Wallingford, Connecticut 06492, USA
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Dworetzky SI, Trojnacki JT, Gribkoff VK. Cloning and expression of a human large-conductance calcium-activated potassium channel. Brain Res Mol Brain Res 1994; 27:189-93. [PMID: 7877450 DOI: 10.1016/0169-328x(94)90203-8] [Citation(s) in RCA: 114] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
A putative BK channel gene was cloned from a human brain (substantia nigra) cDNA library by hybridization screening. The sequence of the full length clone shows high homology with the mSlo gene, suggesting that this cDNA is the human homologue (hSlo). The hSlo clone does not contain either alternative exon A or B at its splice sites; and similar to mSlo, it has a long string of serines at its 5' end. Reverse transcription coupled with the PCR technique demonstrated the differences in expression of the isoforms among the CNS and the periphery. Expression of hSlo in Xenopus oocytes showed a family of outward currents, induced by step depolarizations, that were blocked by iberiotoxin and activated by the compound NS004, a known opener of native and cloned maxi-K channels. Single channel recordings of hSlo channels showed a high degree of voltage- and Ca(2+)-dependence, and an average single channel conductance of 285.9 pS.
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Affiliation(s)
- S I Dworetzky
- Central Nervous System Drug Discovery, Dept., Bristol-Myers Squibb Pharmaceutical Research Institute, Wallingford, CT 06492
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McKay MC, Dworetzky SI, Meanwell NA, Olesen SP, Reinhart PH, Levitan IB, Adelman JP, Gribkoff VK. Opening of large-conductance calcium-activated potassium channels by the substituted benzimidazolone NS004. J Neurophysiol 1994; 71:1873-82. [PMID: 8064354 DOI: 10.1152/jn.1994.71.5.1873] [Citation(s) in RCA: 55] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
1. We used electrophysiological techniques to examine the effects of 5-trifluoromethyl-1-(5-chloro-2-hydroxyphenyl)-1,3-dihydro-2H-benzimidaz ole- 2-one (NS004) on large-conductance calcium-activated potassium (BK) channels. 2. We used recordings from excised membrane patches (cell-attached and inside-out single-channel configurations) and whole-cell patch-clamp recordings to examine the effects of NS004 on single BK channels and whole-cell outward currents, respectively, in rat GH3 clonal pituitary tumor cells. We also tested NS004 on voltage-clamped BK channels isolated from rat brain plasma membrane preparations and reconstituted into planar lipid bilayers. Finally, we used two-electrode voltage-clamp techniques to study the effects of NS004 on currents expressed in Xenopus laevis oocytes by the recently described Slo BK clone from Drosophila. 3. In GH3 cells and in Xenopus oocytes expressing the Slo gene product NS004 produced an increase in an iberiotoxin- or tetraethylammonium-sensitive whole-cell outward current, respectively. NS004 produced a significant increase in the activity of single GH3 cell BK channels and rat brain BK channels reconstituted into planar lipid bilayers. In both systems this was characterized by an increase in channel mean open time, a decrease in interburst interval, and an apparent increase in channel voltage/calcium sensitivity. 4. These data indicate that NS004 could be useful for investigating the biophysical and molecular properties of BK channels and for determining the functional consequences of the opening of BK channels.
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Affiliation(s)
- M C McKay
- Department of Biophysics, Bristol-Myers Squibb Pharmaceutical Research Institute, Wallingford, Connecticut 06492
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Gribkoff VK, Champigny G, Barbry P, Dworetzky SI, Meanwell NA, Lazdunski M. The substituted benzimidazolone NS004 is an opener of the cystic fibrosis chloride channel. J Biol Chem 1994; 269:10983-6. [PMID: 7512555] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
Cystic fibrosis is a major inherited disorder involving abnormalities of fluid and electrolyte transport in a number of different organs. Epithelial cells of cystic fibrosis patients have a decreased capacity to secrete chloride in response to cAMP-mobilizing agents because of the mutation of a single gene. The gene product, the cystic fibrosis transmembrane conductance regulator or CFTR, is a chloride channel. The most frequent mutation is a deletion of phenylalanine in position 508 (delta F508-CFTR) that reduces both the expression of the CFTR protein at the cell surface, and the activity of the Cl- channel. This work presents the properties of NS004, a substituted benzimidazolone, which is the first activator of normal and mutant CFTR-associated chloride channels to be described. NS004 activated CFTR and delta F508-CFTR Cl- channels expressed in Xenopus oocytes, and increased 125I efflux (via the Cl- channel) from Vero cells expressing CFTR and delta F508-CFTR. Application of NS004 to the external side of outside-out patches excised from these CFTR- and delta F508-CFTR-expressing cells induced a marked and reversible increase in channel activity.
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Affiliation(s)
- V K Gribkoff
- Department of Central Nervous System Biophysics and Molecular Biology, Bristol-Myers Squibb Pharmaceutical Research Institute, Wallingford, Connecticut 06492
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Lindner MD, Dworetzky SI, Sampson C, Loy R. Relationship of APP mRNA transcripts and levels of NGF and low-affinity NGF receptors to behavioral measures of age-related cognitive dysfunction. J Neurosci 1994; 14:2282-9. [PMID: 8158269 PMCID: PMC6577152] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
This study was designed to examine the relationship between cognitive function and endogenous levels of NGF, low-affinity NGF receptor (LNGFR), and amyloid precursor protein (APP) mRNAs. Using 3 month (n = 5), 18 month (n = 40), and 29 month (n = 17) Fischer-344 male rats, cognitive function was assessed with the Morris water maze, reverse transcription and polymerase chain reaction were used to quantify APP mRNAs, and NGF and LNGFR levels were determined with an ELISA. Cognitive function declined progressively with age from 3 months to 18 months, and from 18 months to 29 months, but only RNA content in the tissue declined significantly from 3 months to 18 months. Between 18 month and 29 month rats were small but statistically significant decreases only for Kunitz protease inhibitor (KPI)-inclusive mRNAs and cortical NGF levels. There was a small but statistically significant correlation between cognitive function and %KPI (the amount of KPI APP mRNAs relative to the total amount of APP mRNA), with lower %KPI related to more impaired spatial learning. No other statistically significant correlation or linear relationship could be detected between cognitive function and any of the other neurological measures or any combination of these measures (i.e., hippocampal levels of APP 695 mRNA, cortical and hippocampal levels of NGF, and cortical, hippocampal, and basal forebrain levels of LNGFR).(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- M D Lindner
- University of Rochester School of Medicine, Monroe Community Hospital, New York 14620
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Dworetzky SI, Wright KL, Fey EG, Penman S, Lian JB, Stein JL, Stein GS. Sequence-specific DNA-binding proteins are components of a nuclear matrix-attachment site. Proc Natl Acad Sci U S A 1992; 89:4178-82. [PMID: 1570345 PMCID: PMC525656 DOI: 10.1073/pnas.89.9.4178] [Citation(s) in RCA: 101] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
We have identified a nuclear matrix-attachment region within an upstream element of a human H4 histone gene promoter. Nuclear matrix proteins, isolated and solubilized from HeLa S3 cells, were found to interact with sequence specificity at this matrix-attachment region. Several types of assays for protein-DNA interaction showed that the minimal sequence for the nuclear matrix protein-DNA interaction was 5'-TGACGTCCATG-3'; the underlined region corresponds to the core consensus sequence for ATF transcription factor binding. Two proteins with molecular masses of 43 and 54 kDa were identified by UV-crosslinking analysis as integral components of this protein-DNA complex. The molecular masses of these proteins and the ATF-binding site consensus sequence suggest that these proteins are members of the ATF family. Our results provide direct evidence for nuclear matrix localization of sequence-specific DNA-binding factors for an actively transcribed gene. The proximity of a strong positive transcriptional regulatory element to the matrix-attachment region of this gene suggests that the nuclear matrix may serve to localize and concentrate trans-acting factors that facilitate regulation of gene expression.
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Affiliation(s)
- S I Dworetzky
- Department of Cell Biology, University of Massachusetts Medical Center, Worcester 01655
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Stein GS, Lian JB, Dworetzky SI, Owen TA, Bortell R, Bidwell JP, van Wijnen AJ. Regulation of transcription-factor activity during growth and differentiation: involvement of the nuclear matrix in concentration and localization of promoter binding proteins. J Cell Biochem 1991; 47:300-5. [PMID: 1795014 DOI: 10.1002/jcb.240470403] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Several lines of evidence are presented which support involvement of the nuclear matrix in regulating the transcription of two genes, histone and osteocalcin, that are reciprocally expressed during development of the osteoblast phenotype. In the 5' regulatory region of an H4 histone gene, which is expressed in proliferating osteoblasts early during the developmental/differentiation sequence, a dual role is proposed for the nuclear matrix binding domain designated NMP-1 (-589 to -730 upstream from the transcription start site). In addition to functioning as a nuclear matrix attachment site, the sequences contribute to the upregulation of histone gene transcription, potentially facilitated by concentration and localization of an 84kD ATF DNA binding protein. A homologous nuclear matrix binding domain was identified in the promoter of the osteocalcin gene, which is expressed in mature osteoblasts in an extracellular matrix undergoing mineralization. The NMP binding domain in the osteocalcin gene promoter resides contiguous to the vitamin D responsive element. Together with gene and transcription factor localization, a model is proposed whereby nuclear matrix-associated structural constraints on conformation of the osteocalcin gene promoter facilitates vitamin D responsiveness mediated by cooperativity at multiple regulatory elements.
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Affiliation(s)
- G S Stein
- Department of Cell Biology, University of Massachusetts Medical Center, Worcester 01655
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Dworetzky SI, Fey EG, Penman S, Lian JB, Stein JL, Stein GS. Progressive changes in the protein composition of the nuclear matrix during rat osteoblast differentiation. Proc Natl Acad Sci U S A 1990; 87:4605-9. [PMID: 2352938 PMCID: PMC54165 DOI: 10.1073/pnas.87.12.4605] [Citation(s) in RCA: 151] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Primary cultures of fetal rat calvarial osteoblasts undergo a developmental sequence with respect to the temporal expression of genes encoding osteoblast phenotypic markers. Based on previous suggestions that gene-nuclear matrix associations are involved in regulating cell- and tissue-specific gene expression, we investigated the protein composition of the nuclear matrix during this developmental sequence by using high-resolution two-dimensional gel electrophoresis. The nuclear matrix was isolated at times during a 4-week culture period that represent the three principal osteoblast phenotypic stages: proliferation, extracellular matrix (ECM) maturation, and mineralization. The most dramatic changes in the nuclear matrix protein patterns occurred during transitions from the proliferation to the ECM maturation stage and from ECM maturation to the mineralization period, with only minor variations in the profiles within each period. These stage-specific changes, corresponding to the major transition points in gene expression, indicate that the nuclear matrix proteins reflect the progressive differentiation of the bone cell phenotype. Subcultivation of primary cells delays mineralization, and a corresponding delay was observed for the nuclear matrix protein patterns. Thus, the sequential changes in protein composition of the nuclear matrix that occur during osteoblast differentiation represent distinct stage-specific markers for maturation of the osteoblast to an osteocytic cell in a bone-like mineralized ECM. These changes are consistent with a functional involvement of the nuclear matrix in mediating modifications of developmental gene expression.
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Affiliation(s)
- S I Dworetzky
- Department of Cell Biology, University of Massachusetts Medical Center, Worcester 01655
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Abstract
To determine if the number of targeting signals affects the transport of proteins into the nucleus, Xenopus oocytes were injected with colloidal gold particles, ranging in diameter from 20 to 280 A, that were coated with BSA cross-linked with synthetic peptides containing the SV-40 large T-antigen nuclear transport signal. Three BSA conjugate preparations were used; they had an average of 5, 8, and 11 signals per molecule of carrier protein. In addition, large T-antigen, which contains one signal per monomer, was used as a coating agent. The cells were fixed at various times after injection and subsequently analyzed by electron microscopy. Gold particles coated with proteins containing the SV-40 signal entered the nucleus through central channels located within the nuclear pores. Analysis of the intracellular distribution and size of the tracers that entered the nucleus indicated that the number of signals per molecule affect both the relative uptake of particles and the functional size of the channels available for translocation. In control experiments, gold particles coated with BSA or BSA conjugated with inactive peptides similar to the SV-40 transport signal were virtually excluded from the nucleus. Gold particles coated with nucleoplasmin, an endogenous karyophilic protein that contains five targeting signals per molecule, was transported through the nuclear pores more effectively than any of the BSA-peptide conjugates. Based on a correlation between the peri-envelope density of gold particles and their relative uptake, it is suggested that the differences in the activity of the two targeting signals is related to their binding affinity for envelope receptors. It was also determined, by performing coinjection experiments, that individual pores are capable of recognizing and transporting proteins that contain different nuclear targeting signals.
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Affiliation(s)
- S I Dworetzky
- Department of Anatomy and Cell Biology, University of Florida, College of Medicine, Gainesville 32610
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Affiliation(s)
- C M Feldherr
- Department of Anatomy and Cellular Biology, School of Medicine, University of Florida, Gainesville 32610
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Abstract
In the present study, various sized gold particles coated with tRNA, 5S RNA, or poly(A) were used to localize and characterize the pathways for RNA translocation to the cytoplasm. RNA-coated gold particles were microinjected into the nucleus of Xenopus oocytes. The cells were fixed after 15, 60 min, or 6 h, and the particle distribution was later observed by electron microscopy. Similar results were obtained with all classes of RNA used. After nuclear injection, particles ranging from 20-230 A in diameter were observed within central channels of the nuclear pores and in the cytoplasm immediately adjacent to the pores. Particles of this size would not be expected to diffuse through the pores, suggesting that some form of mediated transport occurred. In addition, it was found that the translocation process is saturable. At least 97% of the pores analyzed appeared to be involved in the translocation process. Gold coated with nonphysiological polynucleotides (poly[I] or poly[dA]) were also translocated. When nuclei were injected with either BSA-, ovalbumin-, polyglutamic acid-, or PVP-coated gold, the particles were essentially excluded from the pores. These results indicate that the accumulation of RNA-gold within the pores and adjacent cytoplasm was not due to non-specific effects. We conclude that the translocation sites for gold particles coated with different classes of RNA are located in the centers of the nuclear pores and that particles at least 230 A in diameter can cross the envelope. Tracer particles injected into the cytoplasm were observed within the nuclear pores in areas near the site of injection. However, only a small percentage of the particles actually entered the nucleus. It was also determined, by performing double injection experiments, that individual pores are bifunctional, that is, capable of transporting both proteins and RNA.
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Affiliation(s)
- S I Dworetzky
- Department of Anatomy and Cell Biology, University of Florida, College of Medicine, Gainesville 32610
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