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Sanderson L, da Silva M, Sekhar GN, Brown RC, Burrell-Saward H, Fidanboylu M, Liu B, Dailey LA, Dreiss CA, Lorenz C, Christie M, Persaud SJ, Yardley V, Croft SL, Valero M, Thomas SA. Drug reformulation for a neglected disease. The NANOHAT project to develop a safer more effective sleeping sickness drug. PLoS Negl Trop Dis 2021; 15:e0009276. [PMID: 33857146 PMCID: PMC8078842 DOI: 10.1371/journal.pntd.0009276] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2020] [Revised: 04/27/2021] [Accepted: 02/26/2021] [Indexed: 01/16/2023] Open
Abstract
Background Human African trypanosomiasis (HAT or sleeping sickness) is caused by the
parasite Trypanosoma brucei sspp. The disease has two
stages, a haemolymphatic stage after the bite of an infected tsetse fly,
followed by a central nervous system stage where the parasite penetrates the
brain, causing death if untreated. Treatment is stage-specific, due to the
blood-brain barrier, with less toxic drugs such as pentamidine used to treat
stage 1. The objective of our research programme was to develop an
intravenous formulation of pentamidine which increases CNS exposure by some
10–100 fold, leading to efficacy against a model of stage 2 HAT. This target
candidate profile is in line with drugs for neglected diseases inititative
recommendations. Methodology To do this, we evaluated the physicochemical and structural characteristics
of formulations of pentamidine with Pluronic micelles (triblock-copolymers
of polyethylene-oxide and polypropylene oxide), selected candidates for
efficacy and toxicity evaluation in vitro, quantified
pentamidine CNS delivery of a sub-set of formulations in vitro and
in vivo, and progressed one pentamidine-Pluronic formulation
for further evaluation using an in vivo single dose brain
penetration study. Principal Findings Screening pentamidine against 40 CNS targets did not reveal any major
neurotoxicity concerns, however, pentamidine had a high affinity for the
imidazoline2 receptor. The reduction in insulin secretion in
MIN6 β-cells by pentamidine may be secondary to pentamidine-mediated
activation of β-cell imidazoline receptors and impairment of cell viability.
Pluronic F68 (0.01%w/v)-pentamidine formulation had a similar inhibitory
effect on insulin secretion as pentamidine alone and an additive
trypanocidal effect in vitro. However, all Pluronics tested
(P85, P105 and F68) did not significantly enhance brain exposure of
pentamidine. Significance These results are relevant to further developing block-copolymers as
nanocarriers, improving BBB drug penetration and understanding the side
effects of pentamidine. Sleeping sickness or human African Trypanosomiasis (HAT) is a disease caused by a
parasite, which is transferred to humans by the bite of an infected tsetse fly.
There are two disease stages: the first stage is the blood-based stage of the
disease and the second stage affects the brain. It is fatal if left untreated.
The blood-brain barrier (BBB) makes the brain stage difficult to treat because
it prevents 99% of all drugs from entering the brain from the blood. Those
anti-HAT drugs that do enter the brain are toxic and have serious side effects.
Pentamidine is a less toxic blood stage drug, which our research has shown has a
limited ability to cross the BBB due to its removal by proteins called
transporters. The objective of this study was to use Pluronic to improve
pentamidine delivery to target sites, whilst reducing its side effects. Pluronic
is a polymer, which can assemble into micelles and encapsulate the drug. Thus,
prolonging its circulation time and protecting it. Our study indicated that the
selected Pluronics did not increase the brain delivery of pentamidine. However.
Pluronic-pentamidine formulations were identified that harboured trypanocidal
activity and did not increase safety concerns compared to unformulated
pentamidine.
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Affiliation(s)
- Lisa Sanderson
- King’s College London, Institute of Pharmaceutical Science,
Franklin-Wilkins Building, Stamford Street, London, United
Kingdom
| | - Marcelo da Silva
- King’s College London, Institute of Pharmaceutical Science,
Franklin-Wilkins Building, Stamford Street, London, United
Kingdom
| | - Gayathri N. Sekhar
- King’s College London, Institute of Pharmaceutical Science,
Franklin-Wilkins Building, Stamford Street, London, United
Kingdom
| | - Rachel C. Brown
- King’s College London, Institute of Pharmaceutical Science,
Franklin-Wilkins Building, Stamford Street, London, United
Kingdom
| | - Hollie Burrell-Saward
- Faculty of Infectious and Tropical Diseases, London School of Hygiene and
Tropical Medicine, London, United Kingdom
| | - Mehmet Fidanboylu
- King’s College London, Institute of Pharmaceutical Science,
Franklin-Wilkins Building, Stamford Street, London, United
Kingdom
| | - Bo Liu
- King’s College London, Department of Diabetes, School of Life Course
Sciences, Faculty of Life Sciences & Medicine, London, United
Kingdom
| | - Lea Ann Dailey
- King’s College London, Institute of Pharmaceutical Science,
Franklin-Wilkins Building, Stamford Street, London, United
Kingdom
| | - Cécile A. Dreiss
- King’s College London, Institute of Pharmaceutical Science,
Franklin-Wilkins Building, Stamford Street, London, United
Kingdom
| | - Chris Lorenz
- King’s College London, Theory & Simulation of Condensed Matter Group,
Department of Physics, Strand, London, United Kingdom
| | - Mark Christie
- King’s College London, Institute of Pharmaceutical Science,
Franklin-Wilkins Building, Stamford Street, London, United
Kingdom
| | - Shanta J. Persaud
- King’s College London, Department of Diabetes, School of Life Course
Sciences, Faculty of Life Sciences & Medicine, London, United
Kingdom
| | - Vanessa Yardley
- Faculty of Infectious and Tropical Diseases, London School of Hygiene and
Tropical Medicine, London, United Kingdom
| | - Simon L. Croft
- Faculty of Infectious and Tropical Diseases, London School of Hygiene and
Tropical Medicine, London, United Kingdom
| | - Margarita Valero
- Physical Chemistry Department, Faculty of Pharmacy, University of
Salamanca, Salamanca, Spain
| | - Sarah A. Thomas
- King’s College London, Institute of Pharmaceutical Science,
Franklin-Wilkins Building, Stamford Street, London, United
Kingdom
- * E-mail:
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Amisten S, Duner P, Asplund O, Mohammed Al-Amily I, Groop L, Salehi A. Activation of imidazoline receptor I 2, and improved pancreatic β-cell function in human islets. J Diabetes Complications 2018; 32:813-818. [PMID: 29996974 DOI: 10.1016/j.jdiacomp.2018.06.010] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/21/2018] [Revised: 05/28/2018] [Accepted: 06/19/2018] [Indexed: 12/22/2022]
Abstract
AIM The impact of BL11282, an imidazoline receptor (NISCH) agonist, on potentiation of glucose-stimulated insulin secretion (GSIS) from isolated human non-diabetic (ND) and type 2 diabetic (T2D) islets was investigated. METHODS Analysis of mRNA was performed by RNA-sequencing and qPCR. Insulin and cAMP by RIA and ELISA respectively. RESULTS RNA-sequencing data revealed that NISCH is highly expressed in fat tissues, islets, liver and muscles, with eight detectable splice variants of transcripts in islets. NISCH had a positive correlation with GLP-1 (GLP1R) and GIP (GIPR) receptor transcripts. The expression of NISCH was confirmed by qPCR in human islets. NISCH and GLP1R were comparably higher expressed in mouse islets compared to human islets. GSIS was dose-dependently potentiated by BL11282 from incubated islets of ND and T2D human islet donors. The insulinotropic action of BL11282 was associated with increased cAMP. While the harmful effect of high glucose on reductive capacity of islet cells was enhanced by glibenclamide during long-term culture, it was counteracted by BL11282 or Bt2-cAMP. BL11282 also increased proliferation of INS-1 cells during long-time culture. CONCLUSION Our data suggest that BL11282 potentiates GSIS by an action involving cAMP/PKA system and BL11282 could be an attractive insulinotropic and β-cell protective agent.
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Affiliation(s)
- Stefan Amisten
- Department of Clinical Science, SUS, Division of Islet Cell Physiology, University of Lund, Sweden
| | - Pontus Duner
- Experimental Cardiovascular Research, University of Lund, Sweden
| | - Olof Asplund
- Diabetes and Endocrinology, University of Lund, Sweden
| | - Israa Mohammed Al-Amily
- Department of Clinical Science, SUS, Division of Islet Cell Physiology, University of Lund, Sweden
| | - Leif Groop
- Diabetes and Endocrinology, University of Lund, Sweden
| | - Albert Salehi
- Department of Clinical Science, SUS, Division of Islet Cell Physiology, University of Lund, Sweden; Department of Neuroscience and Physiology, Metabolic Research Unit, University of Goteborg, Goteborg, Sweden.
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Holstein GR, Friedrich VL, Martinelli GP. Imidazoleacetic acid-ribotide in vestibulo-sympathetic pathway neurons. Exp Brain Res 2016; 234:2747-60. [PMID: 27411812 DOI: 10.1007/s00221-016-4725-2] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2016] [Accepted: 07/06/2016] [Indexed: 02/06/2023]
Abstract
Imidazole-4-acetic acid-ribotide (IAARP) is a putative neurotransmitter/modulator and an endogenous regulator of sympathetic drive, notably systemic blood pressure, through binding to imidazoline receptors. IAARP is present in neurons and processes throughout the CNS, but is particularly prevalent in regions that are involved in blood pressure control. The goal of this study was to determine whether IAARP is present in neurons in the caudal vestibular nuclei that participate in the vestibulo-sympathetic reflex (VSR) pathway. This pathway is important in modulating blood pressure upon changes in head position with regard to gravity, as occurs when humans rise from a supine position and when quadrupeds climb or rear. Sinusoidal galvanic vestibular stimulation was used to activate the VSR and cfos gene expression in VSR pathway neurons of rats. These subjects had previously received a unilateral FluoroGold tracer injection in the rostral or caudal ventrolateral medullary region. The tracer was transported retrogradely and filled vestibular neuronal somata with direct projections to the injected region. Brainstem sections through the caudal vestibular nuclei were immunostained to visualize FluoroGold, cFos protein, IAARP and glutamate immunofluorescence. The results demonstrate that IAARP is present in vestibular neurons of the VSR pathway, where it often co-localizes with intense glutamate immunofluorescence. The co-localization of IAARP and intense glutamate immunofluorescence in VSR neurons may represent an efficient chemoanatomical configuration, allowing the vestibular system to rapidly up- and down-modulate the activity of presympathetic neurons in the ventrolateral medulla, thereby altering blood pressure.
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Affiliation(s)
- Gay R Holstein
- Department of Neurology, Icahn School of Medicine at Mount Sinai, Box 1140, One Gustave L. Levy Place, New York, NY, 10029, USA.
- Department of Neuroscience, Icahn School of Medicine at Mount Sinai, New York, NY, USA.
- Department of Anatomy/Functional Morphology, Icahn School of Medicine at Mount Sinai, New York, NY, USA.
| | - Victor L Friedrich
- Department of Neuroscience, Icahn School of Medicine at Mount Sinai, New York, NY, USA
| | - Giorgio P Martinelli
- Department of Neurology, Icahn School of Medicine at Mount Sinai, Box 1140, One Gustave L. Levy Place, New York, NY, 10029, USA
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The insulin secretory action of novel polycyclic guanidines: Discovery through open innovation phenotypic screening, and exploration of structure–activity relationships. Bioorg Med Chem Lett 2014; 24:1031-6. [DOI: 10.1016/j.bmcl.2014.01.021] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2013] [Revised: 01/06/2014] [Accepted: 01/08/2014] [Indexed: 11/18/2022]
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Martir JF, Bozdagi O, Martinelli GP, Friedrich VL, Holstein GR. Imidazoleacetic acid-ribotide in the rodent striatum: a putative neurochemical link between motor and autonomic deficits in Parkinson's disease. ACTA BIOLOGICA HUNGARICA 2012; 63 Suppl 1:5-18. [PMID: 22453739 DOI: 10.1556/abiol.63.2012.suppl.1.3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
We have previously demonstrated that imidazole-4-acetic acid-ribotide (IAA-RP) is present in the mammalian brain and is an endogenous ligand at imidazoline binding sites. In the present study, we used a polyclonal antiserum to visualize IAA-RP-containing neurons in the rat caudoputamen. We observe IAA-RP-immunostained neurons scattered throughout the dorsal and ventral striatum. Most of these cells co-localize GABA, but none are parvalbumin-immunoreactive. In contrast, approximately 50% of the calbindin D28k-immunopositive striatal neurons co-localize IAA-RP. Electrophysiological studies using corticostriatal slices demonstrated that bath application of IAA-RP reversibly depresses the synaptically mediated component of field potentials recorded in the striatum by stimulation of cortical axons. Addition of competitive glutamate receptor antagonists completely blocks the response, confirming its association with glutamatergic transmission. Using paired-pulse stimuli, IAA-RP was shown to exert, at least in part, a presynaptic effect, but blockade of GABAA receptor-mediated transmission did not alter the response. Lastly, we show that this effect is attributable to imidazoline-1 receptors, and not to α2 adrenergic receptors. Since IAA-RP is an endogenous central regulator of blood pressure, and cardiovascular dysfunction is a common symptom associated with Parkinson's disease (PD), we speculate that IAA-RP-related abnormalities may underlie some of the autonomic dysfunction that occurs in PD.
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Affiliation(s)
- J F Martir
- Department of Neurology, Functional Morphology Mount Sinai School of Medicine, New York, NY 10029, USA
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Bozdagi O, Wang XB, Martinelli GP, Prell G, Friedrich VL, Huntley GW, Holstein GR. Imidazoleacetic acid-ribotide induces depression of synaptic responses in hippocampus through activation of imidazoline receptors. J Neurophysiol 2011; 105:1266-75. [PMID: 21228308 DOI: 10.1152/jn.00263.2010] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Imidazole-4-acetic acid-ribotide (IAA-RP), an endogenous agonist at imidazoline receptors (I-Rs), is a putative neurotransmitter/regulator in mammalian brain. We studied the effects of IAA-RP on excitatory transmission by performing extracellular and whole cell recordings at Schaffer collateral-CA1 synapses in rat hippocampal slices. Bath-applied IAA-RP induced a concentration-dependent depression of synaptic transmission that, after washout, returned to baseline within 20 min. Maximal decrease occurred with 10 μM IAA-RP, which reduced the slope of field extracellular postsynaptic potentials (fEPSPs) to 51.2 ± 5.7% of baseline at 20 min of exposure. Imidazole-4-acetic acid-riboside (IAA-R; 10 μM), the endogenous dephosphorylated metabolite of IAA-RP, also produced inhibition of fEPSPs. This effect was smaller than that produced by IAA-RP (to 65.9 ± 3.8% of baseline) and occurred after a further 5- to 8-min delay. The frequency, but not the amplitude, of miniature excitatory postsynaptic currents was decreased, and paired-pulse facilitation (PPF) was increased after application of IAA-RP, suggesting a principally presynaptic site of action. Since IAA-RP also has low affinity for α(2)-adrenergic receptors (α(2)-ARs), we tested synaptic depression induced by IAA-RP in the presence of α(2)-ARs, I(1)-R, or I(3)-R antagonists. The α(2)-AR antagonist rauwolscine (100 nM), which blocked the actions of the α(2)-AR agonist clonidine, did not affect either the IAA-RP-induced synaptic depression or the increase in PPF. In contrast, efaroxan (50 μM), a mixed I(1)-R and α(2)-AR antagonist, abolished the synaptic depression induced by IAA-RP and abolished the related increase in PPF. KU-14R, an I(3)-R antagonist, partially attenuated responses to IAA-RP. Taken together, these data support a role for IAA-RP in modulating synaptic transmission in the hippocampus through activation of I-Rs.
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Affiliation(s)
- O Bozdagi
- Department of Neurology, Mount Sinai School of Medicine, One Gustave Levy Place, New York, NY 10029, USA
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Holstein GR, Martinelli GP, Friedrich VL. Anatomical observations of the caudal vestibulo-sympathetic pathway. J Vestib Res 2011; 21:49-62. [PMID: 21422542 PMCID: PMC3570023 DOI: 10.3233/ves-2011-0395] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
The vestibular system senses the movement and position of the head in space and uses this information to stabilize vision, control posture, perceive head orientation and self-motion in three-dimensional space, and modulate autonomic and limbic activity in response to locomotion and changes in posture. Most vestibular signals are not consciously perceived and are usually appreciated through effector pathways classically described as the vestibulo-ocular, vestibulo-spinal, vestibulo-collic and vestibulo-autonomic reflexes. The present study reviews some of the recent data concerning the connectivity and chemical anatomy of vestibular projections to autonomic sites that are important in the sympathetic control of blood pressure.
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Affiliation(s)
- Gay R Holstein
- Department of Neurology, Mount Sinai School of Medicine, New York, NY 10029, USA.
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Lechin F, van der Dijs B, Pardey-Maldonado B, Rivera JE, Baez S, Lechin ME. Anorexia nervosa depends on adrenal sympathetic hyperactivity: opposite neuroautonomic profile of hyperinsulinism syndrome. Diabetes Metab Syndr Obes 2010; 3:311-7. [PMID: 21437100 PMCID: PMC3047992 DOI: 10.2147/dmsott.s10744] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
OBJECTIVE The aim of our study was to determine the central and peripheral autonomic nervous system profiles underlying anorexia nervosa (AN) syndrome, given that affected patients present with the opposite clinical profile to that seen in the hyperinsulinism syndrome. DESIGN We measured blood pressure and heart rate, as well as circulating neurotransmitters (noradrenaline, adrenaline, dopamine, plasma serotonin, and platelet serotonin), using high-performance liquid chromatography with electrochemical detection, during supine resting, one minute of orthostasis, and after five minutes of exercise. In total, 22 AN patients (12 binge-eating/purging type and 10 restricting type) and age-, gender-, and race-matched controls (70 ± 10.1% versus 98 ± 3.0% of ideal body weight) were recruited. RESULTS We found that patients with AN had adrenal sympathetic overactivity and neural sympathetic underactivity, demonstrated by a predominance of circulating adrenaline over noradrenaline levels, not only during the supine resting state (52 ± 2 versus 29 ± 1 pg/mL) but also during orthostasis (67 ± 3 versus 32 ± 2 pg/mL, P < 0.05) and after exercise challenge (84 ± 4 versus 30 ± 3 pg/mL, P < 0.01). CONCLUSION Considering that this peripheral autonomic nervous system disorder depends on the absolute predominance of adrenomedullary C1 adrenergic nuclei over A5 noradrenergic pontine nucleus, let us ratify the abovementioned findings. The AN syndrome depends on the predominance of overwhelming adrenal sympathetic activity over neural sympathetic activity. This combined central and autonomic nervous system profile contrasts with that registered in patients affected by hyperinsulinism, hypoglycemia, and bulimia syndrome which depends on the absolute predominance of neural sympathetic activity.
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Affiliation(s)
- Fuad Lechin
- Department of Pathophysiology, Sections of Neuroendocrinology, Neuropharmacology, and Neurochemistry, Instituto de Medicina Experimental, Faculty of Medicine, Universidad Central de Venezuela, Caracas
- Instituto de Vias Digestivas Caracas, Centro Clínico Profesional, Caracas, Venezuela
- Correspondence: Fuad Lechin, Apartado 80 983, Caracas 1080-A, Venezuela, Tel +58 212 961 1048, Fax +58 212 961 0172, Email
| | - Bertha van der Dijs
- Department of Pathophysiology, Sections of Neuroendocrinology, Neuropharmacology, and Neurochemistry, Instituto de Medicina Experimental, Faculty of Medicine, Universidad Central de Venezuela, Caracas
- Instituto de Vias Digestivas Caracas, Centro Clínico Profesional, Caracas, Venezuela
| | - Betty Pardey-Maldonado
- Department of Pathophysiology, Sections of Neuroendocrinology, Neuropharmacology, and Neurochemistry, Instituto de Medicina Experimental, Faculty of Medicine, Universidad Central de Venezuela, Caracas
| | - Jairo E Rivera
- Department of Pathophysiology, Sections of Neuroendocrinology, Neuropharmacology, and Neurochemistry, Instituto de Medicina Experimental, Faculty of Medicine, Universidad Central de Venezuela, Caracas
| | - Scarlet Baez
- Department of Pathophysiology, Sections of Neuroendocrinology, Neuropharmacology, and Neurochemistry, Instituto de Medicina Experimental, Faculty of Medicine, Universidad Central de Venezuela, Caracas
| | - Marcel E Lechin
- Department of Internal Medicine, Texas A and M Health Science Center, College of Medicine, Texas, USA
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Hatlapatka K, Wienbergen A, Kühne C, Jörns A, Willenborg M, Rustenbeck I. Selective Enhancement of Nutrient-Induced Insulin Secretion by ATP-Sensitive K+ Channel-Blocking Imidazolines. J Pharmacol Exp Ther 2009; 331:1033-41. [DOI: 10.1124/jpet.109.152751] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
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Bahekar RH, Jain MR, Jadav PA, Prajapati VM, Patel DN, Gupta AA, Sharma A, Tom R, Bandyopadhya D, Modi H, Patel PR. Synthesis and antidiabetic activity of 2,5-disubstituted-3-imidazol-2-yl-pyrrolo[2,3-b]pyridines and thieno[2,3-b]pyridines. Bioorg Med Chem 2007; 15:6782-95. [PMID: 17723306 DOI: 10.1016/j.bmc.2007.08.005] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2007] [Revised: 07/31/2007] [Accepted: 08/01/2007] [Indexed: 10/23/2022]
Abstract
In the present investigation, two series of 2,5-disubstituted-3-imidazol-2-yl-pyrrolo[2,3-b]pyridines (2a-l) and thieno[2,3-b]pyridines (3a-l) were designed as analogs of BL 11282 (1). The in vitro glucose dependent insulinotropic activity of all the test compounds was evaluated using RIN5F cell based assay and all the test compounds showed glucose and concentration dependent insulin secretion. The in vivo antidiabetic activities of most potent compounds from each series (2c and 3c) were assessed in C57BL/6J mice. Compounds 2c and 3c showed dose dependent insulin secretion and significant glucose reduction in vivo. In general, compounds 2c and 3c were found to be equipotent at all the three different doses selected and with respect to BL 11282, both the test compounds were found to be more potent, at all the time points.
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Affiliation(s)
- Rajesh H Bahekar
- Zydus Research Centre, Cadila Healthcare Ltd, Sarkhej-Bavala N H 8A, Moraiya, Ahmedabad, India.
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Martinelli GP, Friedrich VL, Prell GD, Holstein GR. Vestibular neurons in the rat contain imidazoleacetic acid-ribotide, a putative neurotransmitter involved in blood pressure regulation. J Comp Neurol 2007; 501:568-81. [PMID: 17278132 DOI: 10.1002/cne.21271] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
A substantial body of research has led to the recognition that the vestibular system participates in blood pressure modulation during active movements and changes in posture, and that this modulation is effected at least partly by the caudal vestibular nuclei. The I-4 isomer of imidazoleacetic acid-ribotide (IAA-RP) is a putative neurotransmitter/modulator that is thought to be an endogenous regulator of general sympathetic drive, particularly systemic blood pressure. The present study employed immunofluorescence and light and electron microscopic immunocytochemistry to visualize IAA-RP in the vestibular nuclei of adult male rats. The results demonstrate IAA-RP immunolabeling of subpopulations of vestibular neurons in the descending nucleus and the caudal half of the medial nucleus, with scattered immunostained vestibular neurons also present more rostrally. On the basis of double immunofluorescence staining for IAA-RP and calbindin, many of these ribotide-immunoreactive neurons appear to be innervated by cerebellar Purkinje cell afferents. Ultrastructural observations in the caudal vestibular nuclei confirm the IAA-RP immunolocalization in cell bodies and dendritic processes, and in some myelinated axons and presynaptic boutons. The regional distribution of IAA-RP immunoreactivity corresponds to the location of vestibular neurons involved in autonomic functions. The presence of IAA-RP in those neurons suggests that they participate specifically in vestibulo-autonomic regulation of blood pressure. The localization of immunostain in processes and terminals suggests that vestibulo-autonomic activity is subject to local feedback control. Overall, the observations offer a chemoanatomic basis for understanding the vestibular side effects commonly experienced by patients treated with clonidine and other imidazoline-related drugs.
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Affiliation(s)
- Giorgio P Martinelli
- Department of Neurology, Mount Sinai School of Medicine, New York, New York 10029, USA
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Friedrich VL, Martinelli GP, Prell GD, Holstein GR. Distribution and cellular localization of imidazoleacetic acid-ribotide, an endogenous ligand at imidazol(in)e and adrenergic receptors, in rat brain. J Chem Neuroanat 2007; 33:53-64. [PMID: 17210242 PMCID: PMC1907380 DOI: 10.1016/j.jchemneu.2006.11.002] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2006] [Revised: 11/21/2006] [Accepted: 11/23/2006] [Indexed: 10/23/2022]
Abstract
Imidazoleacetic acid-ribotide (IAA-RP) is a putative neurotransmitter/modulator recently discovered in mammalian brain. The present study examines the distribution of IAA-RP in the rat CNS using a highly specific antiserum raised in rabbit against IAA-RP with immunostaining of aldehyde-fixed rat CNS. IAA-RP-immunoreactive neurons were present throughout the neuraxis; neuroglia were not labeled. In each region, only a subset of the neuronal pool was immunostained. In the forebrain, ribotide-immunolabeled neurons were common in neocortex, in hippocampal formation, and in subcortical structures including basal ganglia, thalamus and hypothalamus. Labeling was prominent in limbic areas including olfactory bulb, basal forebrain, pyriform cortex and amygdala. In the mid- and hindbrain, immunolabeled neurons were concentrated in specific nuclei and, in some areas, in specific subregions of those nuclei. Structures of the motor system, including cranial nerve motor nuclei, precerebellar nuclei, the substantia nigra, and the red nucleus were clearly labeled. Staining was intense in cells and/or puncta in the rostral and caudal ventrolateral medullary reticular formation, nucleus tractus solitarius and the caudal vestibular nuclear complex. Within neurons, the ribotide was found predominantly in somata and dendrites; some myelinated axons and occasional synaptic terminals were also immunostained. These data indicate that IAA-RP contributes to the neurochemical phenotype of many neuronal populations and further supports our suggestion that, in autonomic structures, IAA-RP may serve as a chemical mediator in complex circuits involved in blood pressure regulation and, more generally, sympathetic drive.
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Affiliation(s)
- Victor L. Friedrich
- Department of Neuroscience, Mount Sinai School of Medicine, One Gustave Levy Place, New York, NY 10029
| | - Giorgio P. Martinelli
- Department of Neurology, Mount Sinai School of Medicine, One Gustave Levy Place, New York, NY 10029
| | - George D. Prell
- Department of Pharmacology, Mount Sinai School of Medicine, One Gustave Levy Place, New York, NY 10029
| | - Gay R. Holstein
- Department of Neuroscience, Mount Sinai School of Medicine, One Gustave Levy Place, New York, NY 10029
- Department of Neurology, Mount Sinai School of Medicine, One Gustave Levy Place, New York, NY 10029
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Wienbergen A, Bleck C, Lackmann TG, Rustenbeck I. Antagonism of the insulinotropic action of first generation imidazolines by openers of KATP channels. Biochem Pharmacol 2007; 73:94-102. [PMID: 17056015 DOI: 10.1016/j.bcp.2006.09.017] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2006] [Revised: 09/13/2006] [Accepted: 09/15/2006] [Indexed: 10/24/2022]
Abstract
The antagonism between K(ATP) channel-blocking insulinotropic imidazolines - phentolamine, alinidine, idazoxan and efaroxan - and K(ATP) channel openers, diazoxide and nucleoside diphosphates, was studied in mouse pancreatic islets and B-cells. In inside-out patches from B-cells, 500muM MgGDP abolished the inhibitory effect of the imidazolines. 300muM diazoxide further increased channel activity. The depolarizing effect of all imidazolines (100muM) on the B-cell membrane potential was practically completely antagonized by 300muM diazoxide. In contrast, diazoxide was unable to decrease the cytosolic Ca(2+) concentration ([Ca(2+)](i)) which was elevated by phentolamine, whereas the [Ca(2+)](i) increases induced by the other imidazolines were promptly antagonized. The effects on [Ca(2+)](i) were reflected by the secretory activity in that the stimulatory effects of alinidine, idazoxan and efaroxan, but not that of phentolamine were antagonized by diazoxide. Metabolic inhibition of intact B-cells by 250muM NaCN, most likely by a decrease of the ATP/ADP ratio, significantly diminished the K(ATP) channel-blocking effect of a low concentration of alinidine (10muM), whereas efaroxan proved to be susceptible even at a highly effective concentration (100muM). This may explain the oscillatory pattern of the [Ca(2+)](i) increase typically produced by efaroxan in pancreatic B-cells. In conclusion, the inhibitory effect of imidazolines on K(ATP) channels, which is exerted at the pore-forming subunit, Kir6.2, is susceptible to the action of endogenous and exogenous K(ATP) channel openers acting at the regulatory subunit SUR, which confers tissue specificity. With intact cells this antagonism can be obscured, possibly by intracellular accumulation of some imidazolines.
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Affiliation(s)
- Antje Wienbergen
- Institute of Pharmacology and Toxicology, Technical University of Braunschweig, D-38106 Braunschweig, Germany
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Bour S, Iglesias-Osma MC, Marti L, Duro P, Garcia-Barrado MJ, Pastor MF, Prévot D, Visentin V, Valet P, Moratinos J, Carpéné C. The imidazoline I2-site ligands BU 224 and 2-BFI inhibit MAO-A and MAO-B activities, hydrogen peroxide production, and lipolysis in rodent and human adipocytes. Eur J Pharmacol 2006; 552:20-30. [PMID: 17056035 DOI: 10.1016/j.ejphar.2006.09.021] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2006] [Revised: 09/07/2006] [Accepted: 09/11/2006] [Indexed: 12/31/2022]
Abstract
Numerous imidazolinic agents exhibit antihyperglycaemic properties and have been described to promote insulin secretion, however their effects on adipose tissue development have been poorly investigated. Since white adipose tissue (WAT) plays an important role in glucose homeostasis and expresses imidazoline (I(2)) binding sites abundantly, this work aimed at studying extrapancreatic actions of two I(2)-site ligands, BU 224 and 2-BFI in adipocytes. Interaction with monoamine oxidase (MAO) was investigated by measuring the ability to modulate [(14)C]tyramine oxidation and hydrogen peroxide production. Direct influence on glucose uptake or on lipolytic activity was tested on mouse, rat, rabbit and human adipocytes. BU 224 and 2-BFI behaved as reversible inhibitors of both MAO-A and -B, as demonstrated by total inhibition of tyramine oxidation in human adipocytes and platelets or in liver from rats previously treated with selective MAO-inhibitors. Moreover, they weakly inhibited semicarbazide-sensitive amine oxidase. Like classical MAO-inhibitors, they were unable to produce hydrogen peroxide and to activate glucose uptake but prevented tyramine to do so in rodent or human adipocytes. BU 224 and 2-BFI also differed from MAO-inhibitors since they inhibited lipolysis at millimolar concentrations via a still undefined pathway independent of alpha(2)-adrenoceptor stimulation, beta-adrenergic antagonism and MAO activation. However, chronic treatment of obese Zucker rats with 2-BFI did not modify the maximal lipolytic capacity or the mild insulin resistance status of their adipocytes. Taken together, our observations demonstrate on WAT novel effects of BU 224 and 2-BFI different from their already reported actions on brain or endocrine pancreas.
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Affiliation(s)
- Sandy Bour
- Inserm, U586, Unité de Recherches sur les Obésités, Université Paul Sabatier, IFR31, CHU Rangueil, Toulouse, F-31432, France
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17
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Bleck C, Wienbergen A, Rustenbeck I. Essential role of the imidazoline moiety in the insulinotropic effect but not the KATP channel-blocking effect of imidazolines; a comparison of the effects of efaroxan and its imidazole analogue, KU14R. Diabetologia 2005; 48:2567-75. [PMID: 16283242 DOI: 10.1007/s00125-005-0031-4] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/18/2005] [Accepted: 07/18/2005] [Indexed: 10/25/2022]
Abstract
AIMS/HYPOTHESIS Imidazolines are a class of investigational antidiabetic drugs. It is still unclear whether the imidazoline ring is decisive for insulinotropic characteristics. MATERIALS AND METHODS We studied the imidazoline efaroxan and its imidazole analogue, KU14R, which is currently classified as an imidazoline antagonist. The effects of both on stimulus secretion-coupling in normal mouse islets and beta cells were compared by measuring KATP channel activity, plasma membrane potential, cytosolic calcium concentration ([Ca2+]c) and dynamic insulin secretion. RESULTS In the presence of 10 mmol/l but not of 5 mmol/l glucose, efaroxan (100 micromol/l) strongly enhanced insulin secretion by freshly isolated perifused islets, whereas KU14R (30, 100 or 300 micromol/l) was ineffective at both glucose concentrations. Surprisingly, the insulinotropic effect of efaroxan was not antagonised by KU14R. KATP channels were blocked by efaroxan (IC50 8.8 micromol/l, Hill slope -1.1) and by KU14R (IC50 31.9 micromol/l, Hill slope -1.5). Neither the KATP channel-blocking effect nor the depolarising effect of efaroxan was antagonised by KU14R. Rather, both compounds strongly depolarised the beta cell membrane potential and induced action potential spiking. However, KU14R was clearly less efficient than efaroxan in raising [Ca2+]c in single beta cells and whole islets at 5 mmol/l glucose. The increase in [Ca2+]c induced by 10 mmol/l glucose was affected neither by efaroxan nor by KU14R. Again, KU14R did not antagonise the effects of efaroxan. CONCLUSIONS/INTERPRETATION The presence of an imidazole instead of an imidazoline ring leads to virtually complete loss of the insulinotropic effect in spite of a preserved ability to block KATP channels. The imidazole compound is less efficient in raising [Ca2+]c; in particular, it lacks the ability of the imidazoline to potentiate the enhancing effect of energy metabolism on Ca2+-induced insulin secretion.
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Affiliation(s)
- C Bleck
- Institute of Pharmacology and Toxicology, Technical University of Brunswick, Brunswick, Germany
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18
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Enantioselective synthesis of 2-ethyl-2,3-dihydrobenzofuran carboxylic acid, direct precursor of (+)-efaroxan, from a Baylis–Hillman adduct. Tetrahedron Lett 2005. [DOI: 10.1016/j.tetlet.2005.07.099] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Prell GD, Martinelli GP, Holstein GR, Matulić-Adamić J, Watanabe KA, Chan SLF, Morgan NG, Haxhiu MA, Ernsberger P. Imidazoleacetic acid-ribotide: an endogenous ligand that stimulates imidazol(in)e receptors. Proc Natl Acad Sci U S A 2004; 101:13677-82. [PMID: 15365189 PMCID: PMC518812 DOI: 10.1073/pnas.0404846101] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2004] [Indexed: 11/18/2022] Open
Abstract
We identified the previously unknown structures of ribosylated imidazoleacetic acids in rat, bovine, and human tissues to be imidazole-4-acetic acid-ribotide (IAA-RP) and its metabolite, imidazole-4-acetic acid-riboside. We also found that IAA-RP has physicochemical properties similar to those of an unidentified substance(s) extracted from mammalian tissues that interacts with imidazol(in)e receptors (I-Rs). ["Imidazoline," by consensus (International Union of Pharmacology), includes imidazole, imidazoline, and related compounds. We demonstrate that the imidazole IAA-RP acts at I-Rs, and because few (if any) imidazolines exist in vivo, we have adopted the term "imidazol(in)e-Rs."] The latter regulate multiple functions in the CNS and periphery. We now show that IAA-RP (i) is present in brain and tissue extracts that exhibit I-R activity; (ii) is present in neurons of brainstem areas, including the rostroventrolateral medulla, a region where drugs active at I-Rs are known to modulate blood pressure; (iii) is present within synaptosome-enriched fractions of brain where its release is Ca(2+)-dependent, consistent with transmitter function; (iv) produces I-R-linked effects in vitro (e.g., arachidonic acid and insulin release) that are blocked by relevant antagonists; and (v) produces hypertension when microinjected into the rostroventrolateral medulla. Our data also suggest that IAA-RP may interact with a novel imidazol(in)e-like receptor at this site. We propose that IAA-RP is a neuroregulator acting via I-Rs.
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Affiliation(s)
- George D Prell
- Department of Pharmacology and Biological Chemistry, Mount Sinai School of Medicine, New York, NY 10029, USA.
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Rustenbeck I, Krautheim A, Jörns A, Steinfelder HJ. β-Cell toxicity of ATP-sensitive K+ channel-blocking insulin secretagogues. Biochem Pharmacol 2004; 67:1733-41. [PMID: 15081872 DOI: 10.1016/j.bcp.2004.01.016] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2003] [Accepted: 01/16/2004] [Indexed: 11/27/2022]
Abstract
A prolonged exposure of isolated pancreatic islets to insulin secretagogues, the imidazolines phentolamine, alinidine and idazoxan (100microM each), the sulfonylurea tolbutamide (500microM), or the alkaloid quinine (100microM) resulted in morphological damage of 4-18% of beta-cells compared to less than 2% in controls. Thus, the question arose whether K(ATP) channel-blocking insulin secretagogues are beta-cell toxic as has already been suggested for sulfonylureas. The concentration- and time-dependency of the secretagogue-associated toxicity was documented by viability assays in insulin-secreting HIT T15 cells. Treatment for 24h with idazoxan reduced MTT conversion by 50% at 100microM and by 98% at 1000microM. Phentolamine and quinine reduced viability comparably at 1000microM, but were less toxic at 100microM. On the other hand, the imidazoline alinidine and the sulfonylurea tolbutamide were only moderately toxic (less than 40% viability loss at 1000microM). The imidazoline efaroxan appeared even to be non-toxic. Apoptotic DNA fragmentation and DEVD-caspase activation was observed at 100microM of idazoxan and phentolamine, whereas at 1000microM signs of necrosis predominated. Alinidine, tolbutamide and quinine treatment did not increase markers of apoptotic cell death. Blocking Ca(2+) influx by D600 did not diminish secretagogue-associated toxicity. Electron microscopy confirmed the validity of these observations for beta-cells in intact mouse islets. In summary, beta-cell toxicity of the tested insulin secretagogues varied widely and did not depend on a prolonged Ca(2+) influx via L-type Ca(2+) channels. Thus, secretagogue-mediated closure of K(ATP) channels is apparently not per se beta-cell toxic.
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Affiliation(s)
- Ingo Rustenbeck
- Institute of Pharmacology and Toxicology, Technical University of Braunschweig, D-38106 Braunschweig, Germany.
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Rustenbeck I, Dickel C, Grimmsmanns T. Desensitization of insulin secretory response to imidazolines, tolbutamide, and quinine. II. Electrophysiological and fluorimetric studies. Biochem Pharmacol 2001; 62:1695-703. [PMID: 11755123 DOI: 10.1016/s0006-2952(01)00793-6] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Prolonged in vitro exposure (18 h) of pancreatic islets to insulin secretagogues that block ATP-dependent K(+) channels (K(ATP) channels), such as sulfonylureas, imidazolines, and quinine, induced a desensitization of insulin secretion (Rustenbeck et al., pages 1685-1694, this issue). To elucidate the underlying mechanisms, K(ATP) channel activity, plasma membrane potential and the cytosolic Ca(2+) concentration ([Ca(2+)](i)) were measured in mouse single B-cells. In B-cells desensitized by phentolamine or quinine (100 microM each) K(ATP) channel activity was virtually absent and could not be elicited by diazoxide. Desensitization by alinidine (100 microM) induced a marked reduction of K(ATP) channel activity, which could be reversed by diazoxide, whereas exposure to idazoxan (100 microM) or tolbutamide (500 microM) had no lasting effect on K(ATP) channel activity. Correspondingly, phentolamine-, alinidine-, and quinine-desensitized B-cells were markedly depolarized, whereas B-cells that had been exposed to tolbutamide or idazoxan had an unchanged resting membrane potential. The increase in [Ca(2+)](i) normally elicited by phentolamine and alinidine was suppressed after desensitization by these compounds, whereas the [Ca(2+)](i) increase by re-exposure to quinine was markedly reduced and that by tolbutamide only minimally affected as compared with control-cultured B-cells. The increase in [Ca(2+)](i) elicited by a K(+) depolarization was diminished in secretagogue-pretreated B-cells, the extent depending on the secretagogue. This effect was closely correlated with the degree of depolarization after pretreatment with the respective secretagogue. In conclusion, the apparently uniform desensitization of secretion by K(ATP) channel blockers is due to different effects at two stages located distally in the stimulus-secretion coupling: either at the stage of [Ca(2+)](i) regulation, where the increase is depressed as a consequence of a persistent depolarization (e.g. in the case of phentolamine or alinidine) and/or at the stage of exocytosis, which responds only weakly to substantial increases in [Ca(2+)](i) (in the case of tolbutamide).
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Affiliation(s)
- I Rustenbeck
- Institute of Clinical Biochemistry, Hannover Medical School, D-30623, Hannover, Germany.
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Clews PJ, Ramsden CA, Morgan NG. Preparation of novel 2-(benzo[b]furan-2-yl)-1H-imidazolines for photoaffinity labelling and affinity isolation of imidazoline binding. J Heterocycl Chem 2001. [DOI: 10.1002/jhet.5570380237] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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