1
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Shayan M, Eslami F, Khosravi A, Rashidian A, Jafari RM, Maroufi SF, Golroudbari HT, Dehpour AR. The Possible Protective Effects of Ondansetron and Tropisetron on Optic Nerve Crush Injury in Rats. Drug Res (Stuttg) 2023; 73:88-94. [PMID: 36423625 DOI: 10.1055/a-1969-4600] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
BACKGROUND This study aimed to evaluate the potential neuroprotective effect of cyclosporine - a calcineurin inhibitor-, ondansetron, and tropisetron-5-hydroxytryptamine (serotonin) 3 receptor (5-HT3R) antagonists-, on optic nerve crush (ONC) injury in rats. Moreover, underlying signaling activities of their beneficial neuroprotective effects were studied. METHODS Adult male rats were treated with the intravitreal administration of cyclosporine (1.6 mM), ondansetron (100 nM), and tropisetron (100 nM) immediately after the induction of ONC. Subsequently, on 7th day after surgery, the rats' retinas were extracted, and the expression of apoptotic regulators (Bax and Bcl-2) and calcineurin were studied by western blot analysis. RESULTS The induction of ONC injury was associated to higher expression of Bax and calcineurin, while Bcl-2 expression was considerably decreased in these animals. Intravitreal treatment with cyclosporine (1.6 mM), ondansetron (100 nM), and tropisetron (100 nM) significantly attenuated the increased expression of Bax and calcineurin. Moreover, the treatment with these agents resulted in an elevated expression of Bcl-2 in the retina. CONCLUSION Our findings indicate that cyclosporine, ondansetron, and tropisetron protect against ONC injury in rats, possibly via the suppression of apoptosis and modulation of calcineurin activity directly and via 5-HT3 receptors. Moreover, immunoblotting showed that tropisetron was more effective as opposed to ondansetron. Further studies are needed to evaluate the precise mechanism behind cyclosporine, ondansetron, and tropisetron activities.
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Affiliation(s)
- Maryam Shayan
- Experimental Medicine Research Center, Tehran University of Medical Sciences, Tehran, Iran.,Department of Pharmacology, School of Medicine, Tehran University of Medical Sciences, Tehran, Iran
| | - Faezeh Eslami
- Experimental Medicine Research Center, Tehran University of Medical Sciences, Tehran, Iran.,Department of Pharmacology, School of Medicine, Tehran University of Medical Sciences, Tehran, Iran
| | - Ayda Khosravi
- Experimental Medicine Research Center, Tehran University of Medical Sciences, Tehran, Iran.,Department of Pharmacology, School of Medicine, Tehran University of Medical Sciences, Tehran, Iran
| | - Amir Rashidian
- Experimental Medicine Research Center, Tehran University of Medical Sciences, Tehran, Iran.,Department of Pharmacology, School of Medicine, Tehran University of Medical Sciences, Tehran, Iran
| | - Razie Mohammad Jafari
- Experimental Medicine Research Center, Tehran University of Medical Sciences, Tehran, Iran.,Department of Pharmacology, School of Medicine, Tehran University of Medical Sciences, Tehran, Iran
| | - Seyed Farzad Maroufi
- Experimental Medicine Research Center, Tehran University of Medical Sciences, Tehran, Iran.,Department of Pharmacology, School of Medicine, Tehran University of Medical Sciences, Tehran, Iran
| | - Hasti Tashak Golroudbari
- Experimental Medicine Research Center, Tehran University of Medical Sciences, Tehran, Iran.,Department of Pharmacology, School of Medicine, Tehran University of Medical Sciences, Tehran, Iran
| | - Ahmad Reza Dehpour
- Experimental Medicine Research Center, Tehran University of Medical Sciences, Tehran, Iran.,Department of Pharmacology, School of Medicine, Tehran University of Medical Sciences, Tehran, Iran
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Yu D, Gong X, Zhang Y, Li Q, Zhang M. Tropisetron Preconditioning Decreases Myocardial Biomarkers in Patients Undergoing Heart Valve Replacement Surgery. Front Med (Lausanne) 2022; 9:690272. [PMID: 35425785 PMCID: PMC9002259 DOI: 10.3389/fmed.2022.690272] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2021] [Accepted: 03/01/2022] [Indexed: 12/01/2022] Open
Abstract
Background Cardioplegic arrest during the heart valve replacement surgery frequently leads to myocardial damage. Tropisetron (TRP) has been demonstrated to reduce myocardial ischemia-reperfusion injury and inflammation in animals. We examined the efficacy of TRP in lowering myocardial biomarkers in patients undergoing heart valve replacement surgery. Methods A total of seventy-five patients, scheduled for elective heart valve replacement surgery, were randomly chosen to receive either 10 ml of normal saline or 10 mg/10 ml of TRP immediately after anesthesia induction. Blood samples for the measurement of cardiac troponin I (cTnI), creatine kinase (CK-MB), lactate dehydrogenase (LDH), tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), and interleukin-10 (IL-10) were taken before anesthesia, as well as 4, 12, and 24 h after aortic cross-clamp release to evaluate myocardial injury using two-way ANOVA for repeated measurements. The study was registered at www.chictr.org.cn (number, ChiCTR-1800018681). Results Treatment with TRP decreased the increment of cTnI (Fgroup = 4.911, p = 0.030; Ftime = 55.356, p = 0.001; Fgroup × time = 5.340, p = 0.002) at 12 and 24 h; of CK-MB (Fgroup = 6.552, p = 0.013; Ftime = 49.276, p = 0.001; Fgroup × time = 7.627, p = 0.003) at 4, 12, and 24 h; of TNF-α (Fgroup = 4.153, p = 0.046; Ftime = 28.244, p = 0.002; Fgroup × time = 4.692, p = 0.006) at 4 and 12 h; and of LDH (Fgroup = 4.275, p = 0.043; Ftime = 63.225, p = 0.001; Fgroup × time = 2.501, p = 0.083) at 24 h after the release of the aortic cross-clamp. It increased IL-10 (Fgroup = 5.958, p = 0.018; Ftime = 31.226, p = 0.002; Fgroup × time = 1.464, p = 0.236) at 12 h after the release of the aortic cross-clamp. Multiple linear regression analysis showed that cardiopulmonary bypass (CPB) time was a risk factor, and that TRP treatment was a protective factor for postoperative cTNI change (β = 4.449, 95% CI [0.97–7.92], p = 0.013 for CPB time; and β = −381, 95% CI [−613.4 to −148.5], p = 0.002 for TRP treatment). Conclusions Tropisetron had cardioprotective and anti-inflammatory effects in patients undergoing heart valve replacement surgery with cardioplegic arrest. The addition of TRP and reduction of CPB time should be considered for myocardial protection in heart valve replacement surgery. Clinical Trial Registration [www.chictr.org.cn/index.aspx], identifier [ChiCTR1800018681].
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Affiliation(s)
- Di Yu
- Department of Anesthesiology, Taihe Hospital, Hubei University of Medicine, Shiyan, China.,Hubei No. 3 People's Hospital of Jianghan University, Wuhan, China
| | - Xingrui Gong
- Department of Anesthesiology, Xiangyang Central Hospital, Hubei University of Arts and Science, Xiangyang, China
| | - Yufei Zhang
- Department of Anesthesiology, Taihe Hospital, Hubei University of Medicine, Shiyan, China
| | - Qing Li
- Department of Anesthesiology, Taihe Hospital, Hubei University of Medicine, Shiyan, China
| | - Mazhang Zhang
- Department of Anesthesiology, Shanghai Children' Medical Central, Shanghai Jiao Tong University School of Medicine, Shanghai, China
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3
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Abstract
The α7-type nicotinic acetylcholine receptor is one of the most unique and interesting of all the members of the cys-loop superfamily of ligand-gated ion channels. Since it was first identified initially as a binding site for α-bungarotoxin in mammalian brain and later as a functional homomeric receptor with relatively high calcium permeability, it has been pursued as a potential therapeutic target for numerous indications, from Alzheimer disease to asthma. In this review, we discuss the history and state of the art for targeting α7 receptors, beginning with subtype-selective agonists and the basic pharmacophore for the selective activation of α7 receptors. A key feature of α7 receptors is their rapid desensitization by standard "orthosteric" agonist, and we discuss insights into the conformational landscape of α7 receptors that has been gained by the development of ligands binding to allosteric sites. Some of these sites are targeted by positive allosteric modulators that have a wide range of effects on the activation profile of the receptors. Other sites are targeted by direct allosteric agonist or antagonists. We include a perspective on the potential importance of α7 receptors for metabotropic as well as ionotropic signaling. We outline the challenges that exist for future development of drugs to target this important receptor and approaches that may be considered to address those challenges. SIGNIFICANCE STATEMENT: The α7-type nicotinic acetylcholine receptor (nAChR) is acknowledged as a potentially important therapeutic target with functional properties associated with both ionotropic and metabotropic signaling. The functional properties of α7 nAChR can be regulated in diverse ways with the variety of orthosteric and allosteric ligands described in this review.
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Affiliation(s)
- Roger L Papke
- Departments of Pharmacology and Therapeutics (R.L.P) and Chemistry (N.A.H.), University of Florida, Gainesville, FL
| | - Nicole A Horenstein
- Departments of Pharmacology and Therapeutics (R.L.P) and Chemistry (N.A.H.), University of Florida, Gainesville, FL
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4
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Stegemann A, Böhm M. Targeting the α7 nicotinic acetylcholine receptor-A novel road towards the future treatment of skin diseases. Exp Dermatol 2020; 29:924-931. [PMID: 32780438 DOI: 10.1111/exd.14173] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2020] [Revised: 08/05/2020] [Accepted: 08/07/2020] [Indexed: 12/11/2022]
Abstract
Nicotinic acetylcholine receptors (nAChRs) are members of the superfamily of neurotransmitter-gated ion channels. The natural ligand for nAChRs is the endogenous neurotransmitter acetylcholine. Among the nAChRs is the α7nAChR. It is not only expressed by neural tissues but also in the skin. A number of different resident cutaneous cell types including epidermal keratinocytes, sebocytes and dermal fibroblasts express functional α7nAChR. Moreover, cells of the immune system such as lymphocytes, macrophages and monocytes, playing an important role in skin homeostasis, also express α7nAChR. Translational research focusing on the exploitation of the α7nAChR in dermatology has revealed that this neuroendocrine receptor could be promising target for the treatment of inflammatory skin diseases. For example, α7nAChR agonists can counteract transforming growth factor-β1-mediated responses in dermal fibroblasts, key effector cells in scleroderma. In accordance with this α7nAChR, agonists are effective in both inflammation and non-inflammation-driven models of experimentally induced skin fibrosis. Moreover, α7nAChR agonists can modulate expression of proinflammatory cytokines in epidermal keratinocytes that are crucially involved in the pathogenesis of psoriasis and other inflammatory skin diseases. Finally, the capability of α7nAChR agonists to suppress ultraviolet light A/B-induced responses, for example production of proinflammatory cytokines and oxidative stress, the latter crucially involved in dermal photoageing, points to a potential of such agents in the prevention of extrinsic skin ageing. Therefore, emphasis on translational research targeting the α7nAChR in skin may lead to the development of new treatment and prevention modalities against fibrosclerotic skin diseases, psoriasis vulgaris, atopic dermatitis, acne, photodermatoses and extrinsic skin ageing.
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Affiliation(s)
| | - Markus Böhm
- Dept. of Dermatology, University of Münster, Germany
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5
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Papke RL, Lindstrom JM. Nicotinic acetylcholine receptors: Conventional and unconventional ligands and signaling. Neuropharmacology 2020; 168:108021. [PMID: 32146229 PMCID: PMC7610230 DOI: 10.1016/j.neuropharm.2020.108021] [Citation(s) in RCA: 66] [Impact Index Per Article: 16.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2019] [Revised: 02/05/2020] [Accepted: 02/25/2020] [Indexed: 12/28/2022]
Abstract
Postsynaptic nAChRs in the peripheral nervous system are critical for neuromuscular and autonomic neurotransmission. Pre- and peri-synaptic nAChRs in the brain modulate neurotransmission and are responsible for the addictive effects of nicotine. Subtypes of nAChRs in lymphocytes and non-synaptic locations may modulate inflammation and other cellular functions. All AChRs that function as ligand-gated ion channels are formed from five homologous subunits organized to form a central cation channel whose opening is regulated by ACh bound at extracellular subunit interfaces. nAChR subtype subunit composition can range from α7 homomers to α4β2α6β2β3 heteromers. Subtypes differ in affinities for ACh and other agonists like nicotine and in efficiencies with which their channels are opened and desensitized. Subtypes also differ in affinities for antagonists and for positive and negative allosteric modulators. Some agonists are "silent" with respect to channel opening, and AChRs may be able to signal metabotropic pathways by releasing G-proteins independent of channel opening. Electrophysiological studies that can resolve single-channel openings and molecular genetic approaches have allowed characterization of the structures of ligand binding sites, the cation channel, and the linkages between them, as well as the organization of AChR subunits and their contributions to function. Crystallography and cryo-electron-microscopy are providing increasing insights into the structures and functions of AChRs. However, much remains to be learned about both AChR structure and function, the in vivo functional roles of some AChR subtypes, and the development of better pharmacological tools directed at AChRs to treat addiction, pain, inflammation, and other medically important issues. This article is part of the special issue on 'Contemporary Advances in Nicotine Neuropharmacology'.
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Affiliation(s)
- Roger L Papke
- Department of Pharmacology and Therapeutics, University of Florida, P.O. Box 100267, Gainesville, FL, 32610-0267, USA.
| | - Jon M Lindstrom
- Department of Neuroscience, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA, USA
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6
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Basak S, Gicheru Y, Kapoor A, Mayer ML, Filizola M, Chakrapani S. Molecular mechanism of setron-mediated inhibition of full-length 5-HT 3A receptor. Nat Commun 2019; 10:3225. [PMID: 31324772 PMCID: PMC6642186 DOI: 10.1038/s41467-019-11142-8] [Citation(s) in RCA: 37] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2019] [Accepted: 06/23/2019] [Indexed: 12/27/2022] Open
Abstract
Serotonin receptor (5-HT3AR) is the most common therapeutic target to manage the nausea and vomiting during cancer therapies and in the treatment of irritable bowel syndrome. Setrons, a class of competitive antagonists, cause functional inhibition of 5-HT3AR in the gastrointestinal tract and brainstem, acting as effective anti-emetic agents. Despite their prevalent use, the molecular mechanisms underlying setron binding and inhibition of 5-HT3AR are not fully understood. Here, we present the structure of granisetron-bound full-length 5-HT3AR solved by single-particle cryo-electron microscopy to 2.92 Å resolution. The reconstruction reveals the orientation of granisetron in the orthosteric site with unambiguous density for interacting sidechains. Molecular dynamics simulations and electrophysiology confirm the granisetron binding orientation and the residues central for ligand recognition. Comparison of granisetron-bound 5-HT3AR with the apo and serotonin-bound structures, reveals key insights into the mechanism underlying 5-HT3AR inhibition.
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Affiliation(s)
- Sandip Basak
- Department of Physiology and Biophysics, Case Western Reserve University, Cleveland, OH, 44106-4970, USA
| | - Yvonne Gicheru
- Department of Physiology and Biophysics, Case Western Reserve University, Cleveland, OH, 44106-4970, USA
| | - Abhijeet Kapoor
- Department of Pharmacological Sciences, Icahn School of Medicine at Mount Sinai, New York, NY, USA
| | - Megan L Mayer
- Division of CryoEM and Bioimaging, SSRL, SLAC National Accelerator Laboratory, Stanford University, Menlo Park, CA, 94025, USA
| | - Marta Filizola
- Department of Pharmacological Sciences, Icahn School of Medicine at Mount Sinai, New York, NY, USA
| | - Sudha Chakrapani
- Department of Physiology and Biophysics, Case Western Reserve University, Cleveland, OH, 44106-4970, USA.
- Department of Neuroscience, School of Medicine, Case Western Reserve University, Cleveland, OH, 44106-4970, USA.
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7
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Stegemann A, Böhm M. Tropisetron via α7 nicotinic acetylcholine receptor suppresses tumor necrosis factor-α-mediated cell responses of human keratinocytes. Exp Dermatol 2019; 28:276-282. [DOI: 10.1111/exd.13883] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2018] [Revised: 12/17/2018] [Accepted: 01/11/2019] [Indexed: 12/12/2022]
Affiliation(s)
- Agatha Stegemann
- Department of Dermatology; University of Münster; Münster Germany
| | - Markus Böhm
- Department of Dermatology; University of Münster; Münster Germany
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8
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Peripheral 5-HT3 Receptors Are Involved in the Antinociceptive Effect of Bunodosine 391. Toxins (Basel) 2017; 10:toxins10010012. [PMID: 29280949 PMCID: PMC5793099 DOI: 10.3390/toxins10010012] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2017] [Revised: 12/06/2017] [Accepted: 12/20/2017] [Indexed: 12/27/2022] Open
Abstract
Bunodosine 391 (BDS 391), a low molecular weight compound isolated from the sea anemone Bunodosoma cangicum, increases the nociceptive threshold and inhibits inflammatory hyperalgesia. Serotonin receptors are involved in those effects. In this study, we have expanded the characterization of the antinociceptive effect of BDS 391 demonstrating that, in rats: (a) the compound inhibits (1.2–12 ng/paw) overt pain, in the formalin test, and mechanical hyperalgesia (0.6–6.0 ng/paw) detected in a model of neuropathic pain; (b) intraplantar administration of ondansetron, a selective 5-HT3 receptor antagonist, blocks the effect of BDS 391, whereas ketanserin, a 5-HT2 receptor antagonist, partially reversed this effect, indicating the involvement of peripheral 5-HT2 and 5-HT3 receptors in BDS 391 antinociception; and (c) in binding assay studies, BDS 391 was not able to displace the selective 5-HT receptor antagonists, suggesting that this compound does not directly bind to these receptors. The effect of biguanide, a selective 5-HT3 receptor agonist, was also evaluated. The agonist inhibited the formalin’s nociceptive response, supporting an antinociceptive role for 5-HT3 receptors. Our study is the first one to show that a non-peptidic low molecular weight compound obtained from a sea anemone is able to induce antinociception and that activation of peripheral 5-HT3 receptors contributes to this effect.
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9
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The current agonists and positive allosteric modulators of α7 nAChR for CNS indications in clinical trials. Acta Pharm Sin B 2017; 7:611-622. [PMID: 29159020 PMCID: PMC5687317 DOI: 10.1016/j.apsb.2017.09.001] [Citation(s) in RCA: 85] [Impact Index Per Article: 12.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2017] [Revised: 08/02/2017] [Accepted: 08/25/2017] [Indexed: 01/06/2023] Open
Abstract
The alpha-7 nicotinic acetylcholine receptor (α7 nAChR), consisting of homomeric α7 subunits, is a ligand-gated Ca2+-permeable ion channel implicated in cognition and neuropsychiatric disorders. Enhancement of α7 nAChR function is considered to be a potential therapeutic strategy aiming at ameliorating cognitive deficits of neuropsychiatric disorders such as Alzheimer's disease (AD) and schizophrenia. Currently, a number of α7 nAChR modulators have been reported and several of them have advanced into clinical trials. In this brief review, we outline recent progress made in understanding the role of the α7 nAChR in multiple neuropsychiatric disorders and the pharmacological effects of α7 nAChR modulators used in clinical trials.
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Key Words
- 5-CSRTT, five-choice serial reaction time task
- 5-HT, serotonin
- ACh, acetylcholine
- AD, Alzheimer's disease
- ADHD, attention deficit hyperactivity disorder
- Acetylcholine
- Alpha7
- Alzheimer's disease
- Aβ, amyloid-β peptide
- CNS, central nervous system
- DMTS, delayed matching-to-sample
- ECD, extracellular domain
- GABA, γ-aminobutyric acid
- Ion channel
- MLA, methyllycaconitine
- NOR, novel object recognition
- PAMs, positive allosteric modulators
- PCP, neonatal phencyclidine
- PD, Parkinson's disease
- PPI, prepulse inhibition
- Positive allosteric modulators
- SAR, structure–activity relationship
- Schizophrenia
- TMD, transmembrane domains
- nAChR
- nAChR, nicotinic acetylcholine receptor
- α-Btx, α-bungarotoxin
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10
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Yin XJ, Geng CA, Chen XL, Sun CL, Yang TH, Li TZ, Zhou J, Zhang XM, Chen JJ. Synthesis and Cytotoxicity Evaluation of Tropinone Derivatives. NATURAL PRODUCTS AND BIOPROSPECTING 2017; 7:215-223. [PMID: 28321792 PMCID: PMC5397392 DOI: 10.1007/s13659-017-0124-z] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/19/2016] [Accepted: 03/12/2017] [Indexed: 06/06/2023]
Abstract
Sixteen tropinone derivatives were prepared, and their antitumor activities against five human cancer cells (HL-60, A-549, SMMC-7721, MCF-7 and SW480) were evaluated with MTS [3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxy methoxyphenyl)-2-(4-sulfopheny)-2H-tetrazolium] assay. Most of the derivatives exhibited better activities compared with tropinone at the concentration of 40 μM. Particularly, derivative 6 showed significant activities with IC50 values of 3.39, 13.59, 6.65, 13.09 and 12.38 μM respectively against HL-60, A-549, SMMC-7721, MCF-7 and SW480 cells, which suggested more potent activities than that of cis-dichlorodiamineplatinum (DDP).
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Affiliation(s)
- Xiu-Juan Yin
- State Key Laboratory of Phytochemistry and Plant Resources in West China, Kunming Institute of Botany, Chinese Academy of Sciences, Kunming, 650201, China
- University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Chang-An Geng
- State Key Laboratory of Phytochemistry and Plant Resources in West China, Kunming Institute of Botany, Chinese Academy of Sciences, Kunming, 650201, China
- Yunnan Key Laboratory of Natural Medicinal Chemistry, Kunming Institute of Botany, Chinese Academy of Sciences, Kunming, 650201, China
| | - Xing-Long Chen
- State Key Laboratory of Phytochemistry and Plant Resources in West China, Kunming Institute of Botany, Chinese Academy of Sciences, Kunming, 650201, China
- University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Chang-Li Sun
- State Key Laboratory of Phytochemistry and Plant Resources in West China, Kunming Institute of Botany, Chinese Academy of Sciences, Kunming, 650201, China
| | - Tong-Hua Yang
- State Key Laboratory of Phytochemistry and Plant Resources in West China, Kunming Institute of Botany, Chinese Academy of Sciences, Kunming, 650201, China
- Yunnan Key Laboratory of Natural Medicinal Chemistry, Kunming Institute of Botany, Chinese Academy of Sciences, Kunming, 650201, China
| | - Tian-Ze Li
- State Key Laboratory of Phytochemistry and Plant Resources in West China, Kunming Institute of Botany, Chinese Academy of Sciences, Kunming, 650201, China
- Yunnan Key Laboratory of Natural Medicinal Chemistry, Kunming Institute of Botany, Chinese Academy of Sciences, Kunming, 650201, China
| | - Jun Zhou
- State Key Laboratory of Phytochemistry and Plant Resources in West China, Kunming Institute of Botany, Chinese Academy of Sciences, Kunming, 650201, China
| | - Xue-Mei Zhang
- State Key Laboratory of Phytochemistry and Plant Resources in West China, Kunming Institute of Botany, Chinese Academy of Sciences, Kunming, 650201, China
- Yunnan Key Laboratory of Natural Medicinal Chemistry, Kunming Institute of Botany, Chinese Academy of Sciences, Kunming, 650201, China
| | - Ji-Jun Chen
- State Key Laboratory of Phytochemistry and Plant Resources in West China, Kunming Institute of Botany, Chinese Academy of Sciences, Kunming, 650201, China.
- Yunnan Key Laboratory of Natural Medicinal Chemistry, Kunming Institute of Botany, Chinese Academy of Sciences, Kunming, 650201, China.
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11
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Ruepp MD, Wei H, Leuenberger M, Lochner M, Thompson AJ. The binding orientations of structurally-related ligands can differ; A cautionary note. Neuropharmacology 2017; 119:48-61. [PMID: 28137449 PMCID: PMC5464333 DOI: 10.1016/j.neuropharm.2017.01.023] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2016] [Revised: 01/13/2017] [Accepted: 01/24/2017] [Indexed: 11/19/2022]
Abstract
Crystal structures can identify ligand-receptor interactions and assist the development of novel therapeutics, but experimental challenges sometimes necessitate the use of homologous proteins. Tropisetron is an orthosteric ligand at both 5-HT3 and α7 nACh receptors and its binding orientation has been determined in the structural homologue AChBP (pdbid: 2WNC). Co-crystallisation with a structurally-related ligand, granisetron, reveals an almost identical orientation (pdbid; 2YME). However, there is a >1000-fold difference in the affinity of tropisetron at 5-HT3 versus α7 nACh receptors, and α7 nACh receptors do not bind granisetron. These striking pharmacological differences prompt questions about which receptor the crystal structures most closely represent and whether the ligand orientations are correct. Here we probe the binding orientation of tropisetron and granisetron at 5-HT3 receptors by in silico modelling and docking, radioligand binding on cysteine-substituted 5-HT3 receptor mutants transiently expressed in HEK 293 cells, and synthetic modification of the ligands. For 15 of the 23 cysteine substitutions, the effects on tropisetron and granisetron were different. Structure-activity relationships on synthesised derivatives of both ligands were also consistent with different orientations, revealing that contrary to the crystallographic evidence from AChBP, the two ligands adopt different orientations in the 5-HT3 receptor binding site. Our results show that even quite structurally similar molecules can adopt different orientations in the same binding site, and that caution may be needed when using homologous proteins to predict ligand binding. The drugs granisetron and tropisetron are structurally similar. Crystals of them bound to AChBP suggest they have similar binding orientations. At 5-HT3R, the effects of mutagenesis indicate that their orientations differ. SAR on both of these drugs also supports different orientations.
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Affiliation(s)
- Marc-David Ruepp
- Department of Chemistry and Biochemistry, University of Bern, Bern, Switzerland
| | - Hao Wei
- Department of Pharmacology, University of Cambridge, Cambridge, UK
| | - Michele Leuenberger
- Department of Chemistry and Biochemistry, University of Bern, Bern, Switzerland
| | - Martin Lochner
- Department of Chemistry and Biochemistry, University of Bern, Bern, Switzerland; Institute of Biochemistry and Molecular Medicine, University of Bern, Bern, Switzerland.
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12
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Yin XJ, Geng CA, Huang XY, Chen H, Ma YB, Chen XL, Sun CL, Yang TH, Zhou J, Zhang XM, Chen JJ. Bioactivity-guided synthesis of tropine derivatives as new agonists for melatonin receptors. RSC Adv 2016. [DOI: 10.1039/c6ra06748d] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Twenty-three tropine derivatives as new melatonin receptor (MT1 and MT2) agonists were synthesized and evaluated on HEK293 cells in vitro.
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13
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Teodoro R, Scheunemann M, Deuther-Conrad W, Wenzel B, Fasoli FM, Gotti C, Kranz M, Donat CK, Patt M, Hillmer A, Zheng MQ, Peters D, Steinbach J, Sabri O, Huang Y, Brust P. A Promising PET Tracer for Imaging of α₇ Nicotinic Acetylcholine Receptors in the Brain: Design, Synthesis, and in Vivo Evaluation of a Dibenzothiophene-Based Radioligand. Molecules 2015; 20:18387-421. [PMID: 26473809 PMCID: PMC6332508 DOI: 10.3390/molecules201018387] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2015] [Revised: 09/25/2015] [Accepted: 09/28/2015] [Indexed: 01/22/2023] Open
Abstract
Changes in the expression of α7 nicotinic acetylcholine receptors (α7 nAChRs) in the human brain are widely assumed to be associated with neurological and neurooncological processes. Investigation of these receptors invivo depends on the availability of imaging agents such as radioactively labelled ligands applicable in positron emission tomography (PET). We report on a series of new ligands for α7 nAChRs designed by the combination of dibenzothiophene dioxide as a novel hydrogen bond acceptor functionality with diazabicyclononane as an established cationic center. To assess the structure-activity relationship (SAR) of this new basic structure, we further modified the cationic center systematically by introduction of three different piperazine-based scaffolds. Based on invitro binding affinity and selectivity, assessed by radioligand displacement studies at different rat and human nAChR subtypes and at the structurally related human 5-HT3 receptor, we selected the compound 7-(1,4-diazabicyclo[3.2.2]nonan-4-yl)-2-fluorodibenzo-[b,d]thiophene 5,5-dioxide (10a) for radiolabeling and further evaluation invivo. Radiosynthesis of [18F]10a was optimized and transferred to an automated module. Dynamic PET imaging studies with [18F]10a in piglets and a monkey demonstrated high uptake of radioactivity in the brain, followed by washout and target-region specific accumulation under baseline conditions. Kinetic analysis of [18F]10a in pig was performed using a two-tissue compartment model with arterial-derived input function. Our initial evaluation revealed that the dibenzothiophene-based PET radioligand [18F]10a ([18F]DBT-10) has high potential to provide clinically relevant information about the expression and availability of α7 nAChR in the brain.
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Affiliation(s)
- Rodrigo Teodoro
- Helmholtz-Zentrum Dresden-Rossendorf, Institute of Radiopharmaceutical Cancer Research, Permoserstraße 15, Leipzig 04318, Germany.
| | - Matthias Scheunemann
- Helmholtz-Zentrum Dresden-Rossendorf, Institute of Radiopharmaceutical Cancer Research, Permoserstraße 15, Leipzig 04318, Germany.
| | - Winnie Deuther-Conrad
- Helmholtz-Zentrum Dresden-Rossendorf, Institute of Radiopharmaceutical Cancer Research, Permoserstraße 15, Leipzig 04318, Germany.
| | - Barbara Wenzel
- Helmholtz-Zentrum Dresden-Rossendorf, Institute of Radiopharmaceutical Cancer Research, Permoserstraße 15, Leipzig 04318, Germany.
| | - Francesca Maria Fasoli
- Consiglio Nazionale delle Ricerche, Institute of Neuroscience, Biometra-Institute University of Milan, Via Luigi Vanvitelli 32, Milano 20129, Italy.
| | - Cecilia Gotti
- Consiglio Nazionale delle Ricerche, Institute of Neuroscience, Biometra-Institute University of Milan, Via Luigi Vanvitelli 32, Milano 20129, Italy.
| | - Mathias Kranz
- Helmholtz-Zentrum Dresden-Rossendorf, Institute of Radiopharmaceutical Cancer Research, Permoserstraße 15, Leipzig 04318, Germany.
| | - Cornelius K Donat
- Helmholtz-Zentrum Dresden-Rossendorf, Institute of Radiopharmaceutical Cancer Research, Permoserstraße 15, Leipzig 04318, Germany.
| | - Marianne Patt
- Department of Nuclear Medicine, University Hospital Leipzig, Liebigstraße 18, Leipzig 04103, Germany.
| | - Ansel Hillmer
- PET Center, Yale University, P.O. Box 208048, 801 Howard Avenue, New Haven, CT 06520-8048, USA.
| | - Ming-Qiang Zheng
- PET Center, Yale University, P.O. Box 208048, 801 Howard Avenue, New Haven, CT 06520-8048, USA.
| | - Dan Peters
- Dan PET AB, Rosenstigen 7, Malmö SE-21619, Sweden.
| | - Jörg Steinbach
- Helmholtz-Zentrum Dresden-Rossendorf, Institute of Radiopharmaceutical Cancer Research, Permoserstraße 15, Leipzig 04318, Germany.
| | - Osama Sabri
- Department of Nuclear Medicine, University Hospital Leipzig, Liebigstraße 18, Leipzig 04103, Germany.
| | - Yiyun Huang
- PET Center, Yale University, P.O. Box 208048, 801 Howard Avenue, New Haven, CT 06520-8048, USA.
| | - Peter Brust
- Helmholtz-Zentrum Dresden-Rossendorf, Institute of Radiopharmaceutical Cancer Research, Permoserstraße 15, Leipzig 04318, Germany.
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Bertrand D, Lee CHL, Flood D, Marger F, Donnelly-Roberts D. Therapeutic Potential of α7 Nicotinic Acetylcholine Receptors. Pharmacol Rev 2015; 67:1025-73. [DOI: 10.1124/pr.113.008581] [Citation(s) in RCA: 108] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
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15
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Fakhfouri G, Mousavizadeh K, Mehr SE, Dehpour AR, Zirak MR, Ghia JE, Rahimian R. From Chemotherapy-Induced Emesis to Neuroprotection: Therapeutic Opportunities for 5-HT3 Receptor Antagonists. Mol Neurobiol 2014; 52:1670-1679. [DOI: 10.1007/s12035-014-8957-5] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2014] [Accepted: 10/21/2014] [Indexed: 01/11/2023]
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16
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Papke RL. Merging old and new perspectives on nicotinic acetylcholine receptors. Biochem Pharmacol 2014; 89:1-11. [PMID: 24486571 PMCID: PMC4755309 DOI: 10.1016/j.bcp.2014.01.029] [Citation(s) in RCA: 137] [Impact Index Per Article: 13.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2013] [Revised: 01/17/2014] [Accepted: 01/22/2014] [Indexed: 01/02/2023]
Abstract
This review covers history underlying the discovery of the molecular mediators of nicotine's effects in the brain and the diversity of the nicotinic acetylcholine receptor (nAChR) subtypes. Models are presented for both their structure and their function as mediators of signal transduction, with special consideration of the differences between the two main subtypes: heteromeric receptors, which are specialized for rapid electrochemical signal transduction, and homomeric α7 receptors, which have come to be implicated in both ionotropic and metabotropic signaling. This review presents perspectives on the pharmacology and therapeutic targeting of nAChRs for the treatment of nicotine dependence or disease.
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Affiliation(s)
- Roger L Papke
- Department of Pharmacology and Therapeutics, University of Florida, College of Medicine, PO Box 100267, 1200 Newell Drive, Gainesville, FL 32610-0267, USA.
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17
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Swartz MM, Linn DM, Linn CL. Tropisetron as a neuroprotective agent against glutamate-induced excitotoxicity and mechanisms of action. Neuropharmacology 2013; 73:111-21. [PMID: 23727438 DOI: 10.1016/j.neuropharm.2013.05.020] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2012] [Revised: 04/23/2013] [Accepted: 05/07/2013] [Indexed: 11/30/2022]
Abstract
The objective of this study was to determine the neuroprotective role of tropisetron on retinal ganglion cells (RGCs) as well as to explore the possible mechanisms associated with alpha7 nAChR-induced neuroprotection. Adult pig RGCs were isolated from all other retinal tissue using a two-step panning technique. Once isolated, RGCs were cultured for 3 days under control untreated conditions, in the presence of 500 μM glutamate to induce excitotoxicity, and when tropisetron was applied before glutamate to induce neuroprotection. 500 μM glutamate decreased RGC survival by an average of 62% compared to control conditions. However, RGCs pretreated with 100 nM tropisetron before glutamate increased cell survival to an average of 105% compared to controls. Inhibition studies using the alpha7 nAChR antagonist, MLA (10 nM), support the hypothesis that tropisetron is an effective neuroprotective agent against glutamate-induced excitotoxicity; mediated by α7 nAChR activation. ELISA studies were performed to determine if signaling cascades normally associated with excitotoxicity and neuroprotection were up- or down-regulated after tropisetron treatment. Tropisetron had no discernible effects on pAkt levels but significantly decreased p38 MAPK levels associated with excitotoxicity from an average of 15 ng/ml to 6 ng/ml. Another mechanism shown to be associated with neuroprotection involves internalization of NMDA receptors. Double-labeled immunocytochemistry and electrophysiology studies provided further evidence that tropisetron caused internalization of NMDA receptor subunits. The findings of this study suggest that tropisetron could be an effective therapeutic agent for the treatment of degenerative disorders of the central nervous system that involves excitotoxicity.
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Affiliation(s)
- Michael M Swartz
- Western Michigan University, Department of Biological Sciences, Kalamazoo, MI 49008, USA
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18
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Stegemann A, Sindrilaru A, Eckes B, del Rey A, Heinick A, Schulte JS, Müller FU, Grando SA, Fiebich BL, Scharffetter-Kochanek K, Luger TA, Böhm M. Tropisetron suppresses collagen synthesis in skin fibroblasts via α7 nicotinic acetylcholine receptor and attenuates fibrosis in a scleroderma mouse model. ACTA ACUST UNITED AC 2013; 65:792-804. [PMID: 23440693 DOI: 10.1002/art.37809] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2012] [Accepted: 11/20/2012] [Indexed: 01/23/2023]
Abstract
OBJECTIVE There is increasing evidence that serotonin (5-hydroxytryptamine [5-HT]) and distinct 5-HT receptors are involved in the pathogenesis of systemic sclerosis. The aim of this study was to test the hypothesis that tropisetron, a routinely used antiemetic agent previously characterized as a 5-HT(3/4) receptor-modulating agent, can directly affect collagen synthesis in vitro and attenuate experimentally induced fibrosis in vivo. METHODS Functional in vitro studies were performed using human dermal fibroblasts (HDFs). Signal transduction studies included immunofluorescence analysis, Western immunoblotting, promoter reporter assays, cAMP/Ca(2+) measurements, and use of pharmacologic activators and inhibitors. Gene silencing was performed using small interfering RNA. Putative receptors of tropisetron were detected by semiquantitative reverse transcription-polymerase chain reaction (RT-PCR) and immunofluorescence. The murine model of bleomycin-induced scleroderma was used to assess the antifibrogenic and antifibrotic effects of tropisetron in vivo. Collagen expression in vitro, ex vivo, and in situ was determined by real-time RT-PCR analysis, Western immunoblotting, sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and immunohistochemical analysis. RESULTS Tropisetron suppressed collagen synthesis induced by transforming growth factor β1 (TGFβ1). This effect was independent of 5-HT(3/4) receptor but was mediated via α7 nicotinic acetylcholine receptor (α7nAChR). Suppression of TGFβ1-induced collagen synthesis occurred via an unknown molecular mechanism not involving modulation of the Smad, cAMP, Akt, c-Jun, or MAPK pathway. In vivo, tropisetron not only prevented skin fibrosis but also reduced the collagen content in established dermal fibrosis induced by bleomycin. CONCLUSION Tropisetron directly reduces collagen synthesis in HDFs via an α7nAChR-dependent mechanism. The antifibrogenic and antifibrotic effects of this agent observed in a mouse model of bleomycin- induced scleroderma indicate the future potential of tropisetron in the treatment of fibrotic diseases such as scleroderma.
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19
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Thompson AJ. Recent developments in 5-HT3 receptor pharmacology. Trends Pharmacol Sci 2013; 34:100-9. [DOI: 10.1016/j.tips.2012.12.002] [Citation(s) in RCA: 56] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2012] [Revised: 12/07/2012] [Accepted: 12/10/2012] [Indexed: 12/19/2022]
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20
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Shi C, Yu R, Shao S, Li Y. Partial activation of α7 nicotinic acetylcholine receptors: insights from molecular dynamics simulations. J Mol Model 2012; 19:871-8. [PMID: 23086458 DOI: 10.1007/s00894-012-1618-6] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2012] [Accepted: 09/30/2012] [Indexed: 10/27/2022]
Abstract
Nicotinic acetylcholine receptors (nAChRs) are drug targets for neuronal disorders and diseases. Partial agonists for nAChRs are currently being developed as drugs for the treatment of neurological diseases for their relative safety originated from reduced excessive stimulation. In the current study, molecular docking, molecular dynamics simulations and binding energy calculations were performed to theoretically investigate the interactions between the partial agonists, 4-OH-DMXBA and tropisetron with α7-nAChR. The results suggest that the partial agonists 4-OH-DMXBA and tropisetron bind with α7-nAChR in a binding mode similar to that with AChBP. The non-conserved residues in the binding sites contribute to the orientation deviation of these partial agonists from their orientation in AChBP. Energy calculation and decomposition using MM-GB/SA suggests that the van der Waals term (ΔE(VDW)) is the main driving force for the binding of the partial agonists to α7-nAChR. The molecular dynamics simulations showed that the opening of the C-loop binding with the partial agonists is in-between the openings for the binding with the full agonist and in the apo state. This conformation difference for the C-loop sheds light on the partial agonism of nAChR.
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Affiliation(s)
- Caijuan Shi
- Key Laboratory of Systems Bioengineering, Ministry of Education, Department of Pharmaceutical Engineering, School of Chemical Engineering and Technology, Tianjin University, Tianjin, 300072, China
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21
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Olincy A, Freedman R. Nicotinic mechanisms in the treatment of psychotic disorders: a focus on the α7 nicotinic receptor. Handb Exp Pharmacol 2012:211-32. [PMID: 23027417 PMCID: PMC3692393 DOI: 10.1007/978-3-642-25758-2_8] [Citation(s) in RCA: 63] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Nicotine is heavily abused by persons with schizophrenia. Nicotine better enables people with schizophrenia to filter out extraneous auditory stimuli. Nicotine also improves prepulse inhibition when compared to placebo. Nicotine similarly increases the amplitude of patients' duration mismatch negativity. The 15q13-14 region of the genome coding for the α7 nicotinic receptor is linked to schizophrenia. Multiple single nucleotide polymorphisms have been identified in this 15q13-14 gene promoter region that are more frequently present in people with schizophrenia than in normal controls. Abnormalities in expression and regulation of central nicotinic cholinoceptors with decreased α7 binding in multiple brain regions are also present. Nicotine enhances cognition in schizophrenia. Alternative agents that activate the nicotinic receptor have been tested including 3-[2,4-dimethoxybenzylidene]anabaseine (DMXB-A). This compound improved attention, working memory, and negative symptoms in an add-on study in nonsmoking patients with schizophrenia. There are multiple other nicotinic agents, including positive allosteric modulators, in the preclinical stages of development. Finally, the effects of varenicline and clozapine and their relation to smoking cessation are discussed.
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Affiliation(s)
- Ann Olincy
- Department of Psychiatry, University of Colorado, Denver, 13001 East 17th Place, Mail Stop, F546, Aurora, CO 80045, USA
| | - Robert Freedman
- Department of Psychiatry, University of Colorado, Denver, 13001 East 17th Place, Mail Stop, F546, Aurora, CO 80045, USA
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22
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Nemecz Á, Taylor P. Creating an α7 nicotinic acetylcholine recognition domain from the acetylcholine-binding protein: crystallographic and ligand selectivity analyses. J Biol Chem 2011; 286:42555-42565. [PMID: 22009746 DOI: 10.1074/jbc.m111.286583] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Determining the structure of the ligand-binding domain of the nicotinic acetylcholine receptor (nAChR) has been a long standing goal in the design of selective drugs useful in implicated diseases for this prevalent receptor family. Acetylcholine-binding proteins have proven to be valuable surrogates with structural similarity and sequence identity to the extracellular domain of the nicotinic receptor, yet these soluble proteins have their unique features and do not serve as exact replicates of the nAChRs of interest. Here we systematically modify the sequence of these proteins toward the homomeric human α7 nAChR. These chimeric proteins exhibit a shift in affinities to reflect α7 binding characteristics yet maintain expression levels and stability conducive for crystallization. We also present a pentameric humanoid nAChR extracellular domain with the structural determination of the α7 nAChR glycosylation site.
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Affiliation(s)
- Ákos Nemecz
- Departments of Chemistry and Biochemistry, University of California, San Diego, La Jolla, California 92093-0650; Department of Pharmacology, Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California, San Diego, La Jolla, California 92093-0650
| | - Palmer Taylor
- Department of Pharmacology, Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California, San Diego, La Jolla, California 92093-0650.
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23
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Li J, Mathieu SL, Harris R, Ji J, Anderson DJ, Malysz J, Bunnelle WH, Waring JF, Marsh KC, Murtaza A, Olson LM, Gopalakrishnan M. Role of α7 nicotinic acetylcholine receptors in regulating tumor necrosis factor-α (TNF-α) as revealed by subtype selective agonists. J Neuroimmunol 2011; 239:37-43. [PMID: 21911260 DOI: 10.1016/j.jneuroim.2011.08.007] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2011] [Revised: 06/25/2011] [Accepted: 08/10/2011] [Indexed: 12/28/2022]
Abstract
Immunological responses to protect against excessive inflammation can be regulated by the central nervous system through the cholinergic anti-inflammatory pathway wherein acetylcholine released from vagus nerves can inhibit inflammatory cytokines. Although a role for the α7 nicotinic acetylcholine receptor (α7 nAChR) in mediating this pathway has been suggested, pharmacological modulation of the pathway by selective agonists remains to be further elucidated. In this study, the role of α7 nAChRs in the regulation of TNF-α release was investigated using high affinity and selective α7 nAChR agonists in mouse peritoneal macrophage and human whole blood in vitro, and in mouse serum in vivo. In mouse peritoneal macrophages, LPS-induced TNF-α release in vitro was inhibited by a selective α7 nAChR agonist, A-833834 (5-[6-(5-Methyl-hexahydro-pyrrolo[3,4-c]pyrrol-2-yl)-pyridazin-3-yl]-1H-indole), and that effect was attenuated by α7 nAChR antagonist methyllycaconitine. The inhibitory effect of A-833834 on LPS-induced TNF-α release was also observed in human whole blood in vitro. I.v. LPS-induced TNF-α release in mouse serum was attenuated following i.p. administration of A-833834. Similarly, i.v. LPS-induced TNF-α release in mouse serum was also attenuated following i.p. administration of A-585539, another α7 nAChR agonist with limited brain penetration, suggesting that these effects are mediated by peripheral α7 nAChRs. A-833834 was also efficacious in suppressing TNF-α release in mouse serum following oral administration in zymosan-induced peritonitis. These studies collectively demonstrate that selectively targeting α7 nAChRs could offer a novel therapeutic modality to treat acute and chronic inflammatory disease states.
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Affiliation(s)
- Jinhe Li
- Neuroscience Research, Global Pharmaceutical Research and Development, Abbott Laboratories, 100 Abbott Park Road, Abbott Park, IL 60064, United States
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Williams DK, Wang J, Papke RL. Investigation of the molecular mechanism of the α7 nicotinic acetylcholine receptor positive allosteric modulator PNU-120596 provides evidence for two distinct desensitized states. Mol Pharmacol 2011; 80:1013-32. [PMID: 21885620 DOI: 10.1124/mol.111.074302] [Citation(s) in RCA: 96] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Although α7 nicotinic acetylcholine receptors are considered potentially important therapeutic targets, the development of selective agonists has been stymied by the α7 receptor's intrinsically low probability of opening (P(open)) and the concern that an agonist-based therapeutic approach would disrupt endogenous cholinergic function. Development of α7 positive allosteric modulators (PAMs) holds promise of avoiding both issues. N-(5-Chloro-2,4-dimethoxyphenyl)-N'-(5-methyl-3-isoxazolyl)-urea (PNU-120596) is one of the most effective α7 PAMs, with a mechanism associated, at least in part, with the destabilization of desensitized states. We studied the mechanism of PNU-120596 potentiation of α7 receptors expressed in Xenopus laevis oocytes and outside-out patches from BOSC 23 cells. We identify two forms of α7 desensitization: one is destabilized by PNU-120596 (D(s)), and the other is induced by strong episodes of activation and is stable in the presence of the PAM (D(i)). Our characterization of prolonged bursts of single-channel currents that occur with PNU-120596 provide a remarkable contrast to the behavior of the channels in the absence of the PAM. Individual channels that avoid the D(i) state show a 100,000-fold increase in P(open) compared with receptors in the nonpotentiated state. In the presence of PNU-120596, balance between D(s) and D(i) is dynamically regulated by both agonist and PAM binding, with maximal ion channel activity at intermediate levels of binding to both classes of sites. In the presence of high agonist concentrations, competitive antagonists may have the effect of shifting the balance in favor of D(s) and increasing ion channel currents.
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Affiliation(s)
- Dustin K Williams
- Department of Pharmacology and Therapeutics, College of Medicine, University of Florida, Gainesville, FL 32610-0267, USA
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25
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Lee RHC, Liu YQ, Chen PY, Liu CH, Chen MF, Lin HW, Kuo JS, Premkumar LS, Lee TJF. Sympathetic α₃β₂-nAChRs mediate cerebral neurogenic nitrergic vasodilation in the swine. Am J Physiol Heart Circ Physiol 2011; 301:H344-54. [PMID: 21536845 DOI: 10.1152/ajpheart.00172.2011] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The α(7)-nicotinic ACh receptor (α(7)-nAChR) on sympathetic neurons innervating basilar arteries of pigs crossed bred between Landrace and Yorkshire (LY) is known to mediate nicotine-induced, β-amyloid (Aβ)-sensitive nitrergic neurogenic vasodilation. Preliminary studies, however, demonstrated that nicotine-induced cerebral vasodilation in pigs crossbred among Landrace, Yorkshire, and Duroc (LYD) was insensitive to Aβ and α-bungarotoxin (α-BGTX). We investigated nAChR subtype on sympathetic neurons innervating LYD basilar arteries. Nicotine-induced relaxation of porcine isolated basilar arteries was examined by tissue bath myography, inward currents on nAChR-expressing oocytes by two-electrode voltage recording, and mRNA and protein expression in the superior cervical ganglion (SCG) and middle cervical ganglion (MCG) by reverse transcription PCR and Western blotting. Nicotine-induced basilar arterial relaxation was not affected by Aβ, α-BGTX, and α-conotoxin IMI (α(7)-nAChR antagonists), or α-conotoxin AuIB (α(3)β(4)-nAChR antagonist) but was inhibited by tropinone and tropane (α(3)-containing nAChR antagonists) and α-conotoxin MII (selective α(3)β(2)-nAChR antagonist). Nicotine-induced inward currents in α(3)β(2)-nAChR-expressing oocytes were inhibited by α-conotoxin MII but not by α-BGTX, Aβ, or α-conotoxin AuIB. mRNAs of α(3)-, α(7)-, β(2)-, and β(4)-subunits were expressed in both SCGs and MCGs with significantly higher mRNAs of α(3)-, β(2)-, and β(4)-subunits than that of α(7)-subunit. The Aβ-insensitive sympathetic α(3)β(2)-nAChR mediates nicotine-induced cerebral nitrergic neurogenic vasodilation in LYD pigs. The different finding from Aβ-sensitive α(7)-nAChR in basilar arteries of LY pigs may offer a partial explanation for different sensitivities of individuals to Aβ in causing diminished cerebral nitrergic vasodilation in diseases involving Aβ.
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Affiliation(s)
- Reggie Hui-Chao Lee
- Institutes of Medical Sciences, College of Medicine, Tzu Chi University, Hualien, Taiwan
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Yamauchi JG, Nemecz Á, Nguyen QT, Muller A, Schroeder LF, Talley TT, Lindstrom J, Kleinfeld D, Taylor P. Characterizing ligand-gated ion channel receptors with genetically encoded Ca2++ sensors. PLoS One 2011; 6:e16519. [PMID: 21305050 PMCID: PMC3030600 DOI: 10.1371/journal.pone.0016519] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2010] [Accepted: 12/21/2010] [Indexed: 11/23/2022] Open
Abstract
We present a cell based system and experimental approach to characterize agonist and antagonist selectivity for ligand-gated ion channels (LGIC) by developing sensor cells stably expressing a Ca2+ permeable LGIC and a genetically encoded Förster (or fluorescence) resonance energy transfer (FRET)-based calcium sensor. In particular, we describe separate lines with human α7 and human α4β2 nicotinic acetylcholine receptors, mouse 5-HT3A serotonin receptors and a chimera of human α7/mouse 5-HT3A receptors. Complete concentration-response curves for agonists and Schild plots of antagonists were generated from these sensors and the results validate known pharmacology of the receptors tested. Concentration-response relations can be generated from either the initial rate or maximal amplitudes of FRET-signal. Although assaying at a medium throughput level, this pharmacological fluorescence detection technique employs a clonal line for stability and has versatility for screening laboratory generated congeners as agonists or antagonists on multiple subtypes of ligand-gated ion channels. The clonal sensor lines are also compatible with in vivo usage to measure indirectly receptor activation by endogenous neurotransmitters.
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Affiliation(s)
- John G. Yamauchi
- Department of Pharmacology, Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California San Diego, La Jolla, California, United States of America
- Biomedical Sciences Graduate Program, University of California San Diego, La Jolla, California, United States of America
| | - Ákos Nemecz
- Department of Pharmacology, Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California San Diego, La Jolla, California, United States of America
- Department of Chemistry and Biochemistry, University of California San Diego, La Jolla, California, United States of America
| | - Quoc Thang Nguyen
- Department of Physics, University of California San Diego, La Jolla, California, United States of America
| | - Arnaud Muller
- Department of Physics, University of California San Diego, La Jolla, California, United States of America
| | - Lee F. Schroeder
- Department of Physics, University of California San Diego, La Jolla, California, United States of America
| | - Todd T. Talley
- Department of Pharmacology, Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California San Diego, La Jolla, California, United States of America
| | - Jon Lindstrom
- Department of Neurosciences, School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America
| | - David Kleinfeld
- Department of Physics, University of California San Diego, La Jolla, California, United States of America
| | - Palmer Taylor
- Department of Pharmacology, Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California San Diego, La Jolla, California, United States of America
- * E-mail:
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Uphouse L, Heckard D, Hiegel C, Guptarak J, Maswood S. Tropisetron increases the inhibitory effect of mild restraint on lordosis behavior of hormonally primed, ovariectomized rats. Behav Brain Res 2011; 219:221-6. [PMID: 21238491 DOI: 10.1016/j.bbr.2011.01.006] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2010] [Revised: 12/28/2010] [Accepted: 01/10/2011] [Indexed: 01/19/2023]
Abstract
Ovariectomized rats, hormonally primed with 10 μg estradiol benzoate and 500 μg progesterone are resistant to the lordosis-inhibiting effects of a 5 min restraint experience. However, modulation of the serotonergic (5-HT) system alters this resistance to stress. In the following experiment, ovariectomized Fischer inbred rats were hormonally primed with 10 μg estradiol benzoate and 500 μg progesterone. The effect of 5 min restraint on sexual behavior was examined after bilateral hypothalamic infusion or intraperitoneal (ip) treatment with the 5-HT(3) receptor antagonist, 3-tropanylindole-3-carboxylate hydrochloride (tropisetron). Infusion with 50 or 100 ng tropisetron inhibited lordosis behavior. When rats were infused with 10 or 25 ng tropisetron, rats showed normal lordosis behavior. However, when infusion with 10 or 25 ng tropisetron was combined with 5 min restraint, lordosis behavior was inhibited. These findings are consistent with prior work that has implicated hypothalamic serotonin in control of lordosis behavior and in the effect of mild restraint on the behavior. In contrast to the effects of the intracranial infusion, intraperitoneal injection with 1.0 or 2.0 mg/kg tropisetron did not amplify the effects of restraint.
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Affiliation(s)
- Lynda Uphouse
- Department of Biology, Texas Woman's University, Denton, TX 76204, United States.
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Therapeutic targets for neuroprotection and/or enhancement of functional recovery following traumatic brain injury. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2011; 98:85-131. [PMID: 21199771 DOI: 10.1016/b978-0-12-385506-0.00003-x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Traumatic brain injury (TBI) is a significant public health concern. The number of injuries that occur each year, the cost of care, and the disabilities that can lower the victim's quality of life are all driving factors for the development of therapy. However, in spite of a wealth of promising preclinical results, clinicians are still lacking a therapy. The use of preclinical models of the primary mechanical trauma have greatly advanced our knowledge of the complex biochemical sequela that follow. This cascade of molecular, cellular, and systemwide changes involves plasticity in many different neurochemical systems, which represent putative targets for remediation or attenuation of neuronal injury. The purpose of this chapter is to highlight some of the promising molecular and cellular targets that have been identified and to provide an up-to-date summary of the development of therapeutic compounds for those targets.
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Li T, Bunnelle WH, Ryther KB, Anderson DJ, Malysz J, Helfrich R, Grønlien JH, Håkerud M, Peters D, Schrimpf MR, Gopalakrishnan M, Ji J. Syntheses and structure–activity relationship (SAR) studies of 2,5-diazabicyclo[2.2.1]heptanes as novel α7 neuronal nicotinic receptor (NNR) ligands. Bioorg Med Chem Lett 2010; 20:3636-9. [DOI: 10.1016/j.bmcl.2010.04.105] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2010] [Revised: 04/22/2010] [Accepted: 04/23/2010] [Indexed: 10/19/2022]
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Bartman ME, Wilkerson JER, Johnson SM. 5-HT3 receptor-dependent modulation of respiratory burst frequency, regularity, and episodicity in isolated adult turtle brainstems. Respir Physiol Neurobiol 2010; 172:42-52. [PMID: 20399913 DOI: 10.1016/j.resp.2010.04.008] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2009] [Revised: 04/10/2010] [Accepted: 04/11/2010] [Indexed: 11/19/2022]
Abstract
To determine the role of central serotonin 5-HT(3) receptors in respiratory motor control, respiratory motor bursts were recorded from hypoglossal (XII) nerve rootlets on isolated adult turtle brainstems during bath-application of 5-HT(3) receptor agonists and antagonists. mCPBG and PBG (5-HT(3) receptor agonists) acutely increased XII burst frequency and regularity, and decreased bursts/episode. Tropisetron and MDL72222 (5-HT(3) antagonists) increased bursts/episode, suggesting endogenous 5-HT(3) receptor activation modulates burst timing in vitro. Tropisetron blocked all mCPBG effects, and the PBG-induced reduction in bursts/episode. Tropisetron application following mCPBG application did not reverse the long-lasting (2h) mCPBG-induced decrease in bursts/episode. We conclude that endogenous 5-HT(3) receptor activation regulates respiratory frequency, regularity, and episodicity in turtles and may induce a form of respiratory plasticity with the long-lasting changes in respiratory regularity.
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Affiliation(s)
- Michelle E Bartman
- Department of Comparative Biosciences, School of Veterinary Medicine, University of Wisconsin, 2015 Linden Drive, Madison, WI 53706, USA
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31
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Hibbs RE, Sulzenbacher G, Shi J, Talley TT, Conrod S, Kem WR, Taylor P, Marchot P, Bourne Y. Structural determinants for interaction of partial agonists with acetylcholine binding protein and neuronal alpha7 nicotinic acetylcholine receptor. EMBO J 2009; 28:3040-51. [PMID: 19696737 DOI: 10.1038/emboj.2009.227] [Citation(s) in RCA: 130] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2009] [Accepted: 07/14/2009] [Indexed: 11/09/2022] Open
Abstract
The pentameric acetylcholine-binding protein (AChBP) is a soluble surrogate of the ligand binding domain of nicotinic acetylcholine receptors. Agonists bind within a nest of aromatic side chains contributed by loops C and F on opposing faces of each subunit interface. Crystal structures of Aplysia AChBP bound with the agonist anabaseine, two partial agonists selectively activating the alpha7 receptor, 3-(2,4-dimethoxybenzylidene)-anabaseine and its 4-hydroxy metabolite, and an indole-containing partial agonist, tropisetron, were solved at 2.7-1.75 A resolution. All structures identify the Trp 147 carbonyl oxygen as the hydrogen bond acceptor for the agonist-protonated nitrogen. In the partial agonist complexes, the benzylidene and indole substituent positions, dictated by tight interactions with loop F, preclude loop C from adopting the closed conformation seen for full agonists. Fluctuation in loop C position and duality in ligand binding orientations suggest molecular bases for partial agonism at full-length receptors. This study, while pointing to loop F as a major determinant of receptor subtype selectivity, also identifies a new template region for designing alpha7-selective partial agonists to treat cognitive deficits in mental and neurodegenerative disorders.
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Affiliation(s)
- Ryan E Hibbs
- Department of Pharmacology, Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California, San Diego, La Jolla, CA, USA
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Abstract
Voltage-clamp techniques are typically used to study the plasma membrane proteins, such as ion channels and transporters that control bioelectrical signals. Many of these proteins have been cloned and can now be studied as potential targets for drug development. The two approaches most commonly used for heterologous expression of cloned ion channels and transporters involve either transfection of the genes into small cells grown in tissue culture or the injection of the genetic material into larger cells. The standard large cells used for the expression of cloned cDNA or synthetic RNA are the egg progenitor cells (oocytes) of the African frog, Xenopus laevis. Until recently, cellular electrophysiology was performed manually by a single operator, one cell at a time. However, methods of high throughput electrophysiology have been developed which are automated and permit data acquisition and analysis from multiple cells in parallel. These methods are breaking a bottleneck in drug discovery, useful in some cases for primary screening as well as for thorough characterization of new drugs. Increasing throughput of high-quality functional data greatly augments the efficiency of academic research and pharmaceutical drug development. Some examples of studies that benefit most from high throughput electrophysiology include pharmaceutical screening of targeted compound libraries, secondary screening of identified compounds for subtype selectivity, screening mutants of ligand-gated channels for changes in receptor function, scanning mutagenesis of protein segments, and mutant-cycle analysis. We describe here the main features and potential applications of OpusXpress, an efficient commercially available system for automated recording from Xenopus oocytes. We show some types of data that have been gathered by this system and review realized and potential applications.
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Affiliation(s)
- Roger L Papke
- Department of Pharmacology and Therapeutics, University of Florida College of Medicine, Gainesville, Florida, USA.
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Horenstein NA, Leonik FM, Papke RL. Multiple pharmacophores for the selective activation of nicotinic alpha7-type acetylcholine receptors. Mol Pharmacol 2008; 74:1496-511. [PMID: 18768388 DOI: 10.1124/mol.108.048892] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The activation of heteromeric and homomeric nicotinic acetylcholine receptors was studied in Xenopus laevis oocytes to identify key structures of putative agonist molecules associated with the selective activation of homomeric alpha7 receptors. We observed that selectivity between alpha7 and alpha4beta2 was more readily obtained than selectivity between alpha7 and alpha3beta4. Based on structural comparisons of previously characterized selective and nonselective agonists, we hypothesize at least three chemical motifs exist that, when present in molecules containing an appropriate cationic center, could be associated with the selective activation of alpha7 receptors. We identify the three distinct structural motifs based on prototypical drugs as the choline motif, the tropane motif, and the benzylidene motif. The choline motif involves the location of an oxygen-containing polar group such as a hydroxyl or carbonyl separated by two carbons from the charged nitrogen. The tropane motif provides alpha7-selectivity based on the addition of multiple small hydrophobic groups positioned away from the cationic center in specific orientations. We show that this motif can convert the nonselective agonists quinuclidine and ethyltrimethyl-ammonium to the alpha7-selective analogs methyl-quinuclidine and diethyldimethyl-ammonium, respectively. We have shown previously that the benzylidene group of 3-2,4, dimethoxy-benzylidene anabaseine (GTS-21) converts anabaseine into an alpha7-selective agonist. The benzylidene motif was also applied to quinuclidine to generate another distinct family of alpha7-selective agonists. Our results provide insight for the further development of nicotinic therapeutics and will be useful to direct future experiments with protein structure-based modeling and site-directed mutagenesis.
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Affiliation(s)
- Nicole A Horenstein
- Department of Pharmacology and Therapeutics, University of Florida, Gainesville, Florida 32610-0267, USA
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Alzoubi KH, Aleisa AM, Alkadhi KA. Expression of gLTP in sympathetic ganglia of obese Zucker rats in vivo: molecular evidence. J Mol Neurosci 2008; 35:297-306. [PMID: 18563301 DOI: 10.1007/s12031-008-9110-6] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2008] [Accepted: 05/21/2008] [Indexed: 12/20/2022]
Abstract
Long-term potentiation in sympathetic ganglia (gLTP) is similar to LTP of the hippocampal area CA1 in that its expression involves similar changes in signaling molecules. We have shown previously that the stress-prone, hypertensive obese Zucker rats (OZR) expressed gLTP in sympathetic ganglia and that high blood pressure was reduced by treatment with 5-HT(3) receptor antagonists. In the present study, we present additional electrophysiological evidence for the pre-expression of gLTP in sympathetic ganglia from OZR indicated by failure of repetitive stimulation to express gLTP in isolated superior cervical ganglia (SCG) and inhibition of baseline ganglionic transmission by a 5-HT(3) receptor antagonist. We have also investigated the role of key signaling molecules in the expression of gLTP in the hypertensive OZR. Immunoblot analysis showed a significant increase in the levels of phosphorylated (P-)CaMKII and protein kinase C gamma (PKCgamma) in SCG from OZR. The ratio of P-CaMKII to the total CaMKII was markedly increased in OZR ganglia, suggesting increased phosphorylation of this molecule. Additionally, there was a significant decrease in the levels of calcineurin in ganglia. Furthermore, the neural nitric oxide synthase and hemeoxygenase II, which are essential for the expression of gLTP, were significantly elevated in OZR ganglia. The present findings confirm that ganglia from OZR have expressed gLTP and that synaptic plasticity in sympathetic ganglia may involve a molecular cascade similar to that of LTP of the brain hippocampal area CA1.
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Affiliation(s)
- K H Alzoubi
- Department of Clinical Pharmacy, Faculty of Pharmacy, Jordan University of Science and Technology, Irbid, Jordan
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35
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Lightfoot AP, Kew JNC, Skidmore J. Alpha7 nicotinic acetylcholine receptor agonists and positive allosteric modulators. PROGRESS IN MEDICINAL CHEMISTRY 2008; 46:131-71. [PMID: 18381125 DOI: 10.1016/s0079-6468(07)00003-3] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Affiliation(s)
- Andrew P Lightfoot
- Medicinal Chemistry, Psychiatry CEDD, GlaxoSmithKline, New Frontiers Science Park, Third Avenue, Harlow, Essex, CM19 5AW, UK
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36
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Olincy A, Stevens KE. Treating schizophrenia symptoms with an alpha7 nicotinic agonist, from mice to men. Biochem Pharmacol 2007; 74:1192-201. [PMID: 17714692 PMCID: PMC2134979 DOI: 10.1016/j.bcp.2007.07.015] [Citation(s) in RCA: 100] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2007] [Revised: 07/07/2007] [Accepted: 07/11/2007] [Indexed: 10/23/2022]
Abstract
Current antipsychotic treatments fail to fully address the range of symptoms of schizophrenia, particularly with respect to social and occupational dysfunctions. Recent work has highlighted the role of nicotinie in both cognitive and attentional deficits as well as deficient processing of repetitive sensory information. The predilection for schizophrenia patients to be extremely heavy cigarette smokers may be related to their attempt to compensate for a reduction in hippocampal alpha7 nicotinic cholinergic receptors by delivering exogenous ligand to the remaining receptors. Studies in rodent models of both learning and memory deficits and deficits in sensory inhibition have confirmed a role for the alpha7 subtype of the nicotinic cholinergic receptor in these processes. Rodent studies also demonstrated the efficacy of a selective partial alpha7 nicotinic agonist, DMXBA, to improve these deficits. Subsequent human clinical trials demonstrated improved sensory inhibition in 12 schizophrenia patients and showed improvement in several subtests of the RBANS learning and memory assessment instrument. These data suggest that therapeutic agents selected for alpha7 nicotinic activity may have utility in treating certain symptoms of schizophrenia.
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Affiliation(s)
- Ann Olincy
- Department of Psychiatry, University of Colorado at Denver and Health Sciences Center, Denver, CO 80262, USA.
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37
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Romanelli MN, Gratteri P, Guandalini L, Martini E, Bonaccini C, Gualtieri F. Central Nicotinic Receptors: Structure, Function, Ligands, and Therapeutic Potential. ChemMedChem 2007; 2:746-67. [PMID: 17295372 DOI: 10.1002/cmdc.200600207] [Citation(s) in RCA: 145] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
The growing interest in nicotinic receptors, because of their wide expression in neuronal and non-neuronal tissues and their involvement in several important CNS pathologies, has stimulated the synthesis of a high number of ligands able to modulate their function. These membrane proteins appear to be highly heterogeneous, and still only incomplete information is available on their structure, subunit composition, and stoichiometry. This is due to the lack of selective ligands to study the role of nAChR under physiological or pathological conditions; so far, only compounds showing selectivity between alpha4beta2 and alpha7 receptors have been obtained. The nicotinic receptor ligands have been designed starting from lead compounds from natural sources such as nicotine, cytisine, or epibatidine, and, more recently, through the high-throughput screening of chemical libraries. This review focuses on the structure of the new agonists, antagonists, and allosteric ligands of nicotinic receptors, it highlights the current knowledge on the binding site models as a molecular modeling approach to design new compounds, and it discusses the nAChR modulators which have entered clinical trials.
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Affiliation(s)
- M Novella Romanelli
- Laboratory of Design, Synthesis, and Study of Biologically Active Heterocycles (HeteroBioLab), Department of Pharmaceutical Sciences, University of Florence, via Ugo Schiff 6, 50019 Sesto Fiorentino, Italy.
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38
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Faerber L, Drechsler S, Ladenburger S, Gschaidmeier H, Fischer W. The neuronal 5-HT3 receptor network after 20 years of research — Evolving concepts in management of pain and inflammation. Eur J Pharmacol 2007; 560:1-8. [PMID: 17316606 DOI: 10.1016/j.ejphar.2007.01.028] [Citation(s) in RCA: 164] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2006] [Accepted: 01/09/2007] [Indexed: 11/19/2022]
Abstract
The 5-HT3 receptor is a pentameric ligand-gated cation channel which is found in the central and peripheral nervous system and on extraneuronal locations like lymphocytes, monocytes and fetal tissue. Five monomer subtypes, the 5-HT(3A-E) subunits, have been identified which show differences in the amino-terminal and the transmembrane region. The functional relevance of different receptor compositions is not yet clarified. 5-HT3 receptors are located predominantly in CNS regions that are involved in the integration of the vomiting reflex, pain processing, the reward system and anxiety control. The preferential localization on nerve endings is consistent with a physiological role of 5-HT3 receptors in the control of neurotransmitter release such as dopamine, cholecystokinin, glutamate, acetylcholine, GABA, substance P, or serotonin itself. 5-HT3-receptor agonists cause unpleasant effects like nausea and anxiety, and no clinical use has been considered. In contrast, the introduction of 5-HT3-receptor antagonists for chemotherapy-induced vomiting was extremely successful. After development of other gastrointestinal indications like postoperative vomiting and diarrhea-predominant irritable bowel syndrome recent research focuses on rheumatological indications such as fibromyalgia, rheumatoid arthritis and tendinopathies. Positive effects have also been observed for pain syndromes such as chronic neuropathic pain and migraine. These effects seem to be related to substance P-mediated inflammation and hyperalgesia. Furthermore, antiinflammatory and immunomodulatory properties have been observed for 5-HT3-receptor antagonists which might explain promising findings in systemic sclerosis and other immunological conditions. For all of these innovative indications the optimal dosing schedule is a crucial issue, since a bell-shaped dose-response curve has been observed repeatedly for 5-HT3-receptor antagonists, particularly in CNS effects.
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Affiliation(s)
- Lothar Faerber
- Department of Pharmacology, Regensburg Medical School, Universitaetsstr. 31, 93053 Regensburg, Germany.
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39
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Feuerbach D, Nozulak J, Lingenhoehl K, McAllister K, Hoyer D. JN403, in vitro characterization of a novel nicotinic acetylcholine receptor alpha7 selective agonist. Neurosci Lett 2007; 416:61-5. [PMID: 17314009 DOI: 10.1016/j.neulet.2007.01.045] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2006] [Revised: 01/15/2007] [Accepted: 01/21/2007] [Indexed: 11/30/2022]
Abstract
This report describes the in vitro features of a novel selective nicotinic acetylcholine receptor (nAChR) alpha7 agonist, JN403, (S)-(1-Aza-bicyclo[2.2.2]oct-3-yl)-carbamic acid (S)-1-(2-fluoro-phenyl)-ethyl ester. JN403 was evaluated in a number of in vitro systems of different species, at recombinant receptors using radioligand binding, signal transduction and electrophysiological studies. When using [(125)I] alpha-bungarotoxin (alpha-BTX) as a radioligand, JN403 has high affinity for human recombinant nAChR alpha7 (pK(D)=6.7). Functionally, JN403 is a partial and potent agonist at human nAChR alpha7. The compound stimulates calcium influx in GH3 cells recombinantly expressing the human nAChR with an pEC(50) of 7.0 and an E(max) of 85% (compared to the full agonist epibatidine). In Xenopus oocytes expressing human nAChR alpha7 JN403 induces inward currents with an pEC(50) of 5.7 and an E(max) of 55%. In both recombinant systems JN403 is a partial agonist and the agonistic effects are blocked after pre-administration of methyllycaconitine (MLA, 100nM), a nAChR alpha7 antagonist. In functional calcium influx assays, JN403 displays a significantly lower potency for other subtypes of human nAChRs like alpha4beta2, alpha3beta4, alpha1beta1gammadelta as well as 5HT(3) receptors when tested functionally as an antagonist (pIC(50)<4.8) and is devoid of agonistic activity (pEC(50)<4). Similarly, JN403 shows low binding activity at a wide panel of neurotransmitter receptors. Thus, JN403 is a potent and selective nAChR alpha7 agonist and will be a useful tool for the characterization of nAChR alpha7 mediated effects both in vitro and in vivo.
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Affiliation(s)
- Dominik Feuerbach
- Neuroscience Research, Novartis Institutes for BioMedical Research, Basel, Switzerland.
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40
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Leonik FM, Papke RL, Horenstein NA. Quinuclidines as selective agonists for alpha-7 nicotinic acetylcholine receptors. Bioorg Med Chem Lett 2007; 17:1520-2. [PMID: 17276680 DOI: 10.1016/j.bmcl.2007.01.003] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2006] [Revised: 12/16/2006] [Accepted: 01/03/2007] [Indexed: 11/20/2022]
Abstract
The alpha7 subtype of the neuronal nicotinic acetylcholine receptors (nAChRs) was targeted for the design of selective agonists deriving from the quinuclidine scaffold. Arylidene groups at the 3-position and N-methyl quinuclidine were found to be selective agonists with EC(50)s of 1.5 and 40 microM, respectively.
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Affiliation(s)
- Fedra M Leonik
- Department of Chemistry, University of Florida, Gainesville, FL 32611-7200, USA
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41
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Martin LF, Freedman R. Schizophrenia and the alpha7 nicotinic acetylcholine receptor. INTERNATIONAL REVIEW OF NEUROBIOLOGY 2007; 78:225-46. [PMID: 17349863 DOI: 10.1016/s0074-7742(06)78008-4] [Citation(s) in RCA: 167] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/05/2022]
Abstract
In addition to the devastating symptoms of psychosis, many people with schizophrenia also suffer from cognitive impairment. These cognitive symptoms lead to marked dysfunction and can impact employability, treatment adherence, and social skills. Deficits in P50 auditory gating are associated with attentional impairment and may contribute to cognitive symptoms and perceptual disturbances. This nicotinic cholinergic-mediated inhibitory process represents a potential new target for therapeutic intervention in schizophrenia. This chapter will review evidence implicating the nicotinic cholinergic, and specifically, the alpha7 nicotinic receptor system in the pathology of schizophrenia. Impaired auditory sensory gating has been linked to the alpha7 nicotinic receptor gene on the chromosome 15q14 locus. A majority of persons with schizophrenia are heavy smokers. Although nicotine can acutely reverse diminished auditory sensory gating in people with schizophrenia, this effect is lost on a chronic basis due to receptor desensitization. The alpha7 nicotinic agonist 3-(2,4 dimethoxy)benzylidene-anabaseine (DMXBA) can also enhance auditory sensory gating in animal models. DMXBA is well tolerated in humans and a new study in persons with schizophrenia has found that DMXBA enhances both P50 auditory gating and cognition. alpha7 Nicotinic acetylcholine receptor agonists appear to be viable candidates for the treatment of cognitive disturbances in schizophrenia.
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Affiliation(s)
- Laura F Martin
- Research Service, VA Eastern Colorado Health Care System, Denver, Colorado 80220, USA
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42
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Hogg RC, Bertrand D. Partial agonists as therapeutic agents at neuronal nicotinic acetylcholine receptors. Biochem Pharmacol 2006; 73:459-68. [PMID: 16979139 DOI: 10.1016/j.bcp.2006.08.010] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2006] [Revised: 08/04/2006] [Accepted: 08/10/2006] [Indexed: 11/30/2022]
Abstract
Improved understanding of how brain function is altered in neurodegenerative disease states, pain and conditions, such as schizophrenia and attention deficit disorder, has highlighted the role of nicotinic acetylcholine receptors (nAChRs) in these conditions and identified them as promising therapeutic targets. nAChRs are widely expressed throughout the peripheral and central nervous system, and this widespread nature underlines the need for new ligands with different selectivities and pharmacological profiles if we are to avoid the adverse side effects associated with many of the nAChR modulators currently identified. Partial agonists have the unique property of being able to act both as agonists or antagonists depending on the concentration of endogenous neurotransmitter. Moreover, the agonist action of partial agonists has a 'ceiling' effect, giving them a large safety margin and making them an attractive proposition for therapeutic molecules. Partial agonists of nAChRs are currently being developed as a nicotine replacement therapy for smoking cessation and for the treatment of a number of neurological diseases associated with a loss of cholinergic function. This commentary will discuss the pharmacological properties of partial agonists and review recent research developments in the field of partial agonists acting at nicotinic receptors.
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Affiliation(s)
- Ron C Hogg
- Department of Neurosciences, Medical Faculty, CMU, 1 rue Michel Servet, CH-1211 Geneva 4, Switzerland.
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43
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Papke RL. Estimation of both the potency and efficacy of alpha7 nAChR agonists from single-concentration responses. Life Sci 2005; 78:2812-9. [PMID: 16343553 DOI: 10.1016/j.lfs.2005.11.009] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2005] [Accepted: 11/02/2005] [Indexed: 11/27/2022]
Abstract
The assessment of functional properties is a crucial step in the screening of potential new drug candidates. The development of moderate to high throughput electrophysiological recording systems such as OpusXpress (Molecular Devices) has facilitated the process of testing new drugs to a large degree. However, while the simple screening of multiple drugs at a single concentration identifies "hits" and "misses", the generation of full concentration-response studies is still a bottleneck in drug development. The alpha7 nicotinic acetylcholine receptor displays a unique concentration dependence of response kinetics which permits estimates of EC50 and Imax values for experimental drugs to be generated from single-concentration responses. This method is based on the analysis of 13 different concentration-response studies utilizing either human or rat alpha7 nAChR. Each experimental response was first normalized to an ACh control, and then a transformation of the pooled data was generated which, based on the relationship between the net charge and peak current to their respective EC50 values defined the "functional concentration" (the test concentration relative to the EC50 for the given agonist). At low functional concentrations, net charge is large relative to peak current amplitude and at higher functional concentration this relationship reverses. For any single-concentration response, the ratio of net charge to peak current can be used to estimate functional concentration. Efficacy can then be estimated by comparing the observed (net charge) response to the expected value for a full agonist at the estimated functional concentration. This extended analysis, combined with automated recording methods, should greatly increase the efficiency with which promising new drug candidates can be characterized.
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Affiliation(s)
- Roger L Papke
- Pharmacology and Therapeutics 100267 JHMHSC, 1600 SW Archer Rd. University of Florida, College of Medicine Gainesville, FL 32610, USA.
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44
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Papke RL, Zheng G, Horenstein NA, Dwoskin LP, Crooks PA. The characterization of a novel rigid nicotine analog with alpha7-selective nAChR agonist activity and modulation of agonist properties by boron inclusion. Bioorg Med Chem Lett 2005; 15:3874-80. [PMID: 16005216 PMCID: PMC3593044 DOI: 10.1016/j.bmcl.2005.05.118] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2005] [Revised: 05/26/2005] [Accepted: 05/26/2005] [Indexed: 11/30/2022]
Abstract
The alpha7 nAChR subtype is of particular interest as a potential therapeutic target since it has been implicated as a mediator of both cognitive and neuroprotective activity. The rigid nicotine analog ACME and the N-cyanoborane conjugate ACME-B are selective partial agonists of rat alpha7 receptors expressed in Xenopus oocytes, with no significant activation of either alpha3beta4 or alpha4beta2 receptors. ACME-B is both more potent and efficacious than ACME. The efficacies of ACME-B and ACME are approximately 26% and 10% of the efficacy of ACh, respectively. Similar N-conjugation of S(-)nicotine with cyanoborane decreased efficacy for alpha3beta4 and alpha4beta2 receptors, as well as for alpha7 nAChR. Structural comparison of ACME with the benzylidene anabaseines, another class of previously identified alpha7-selective agonists, suggests that they share a similar structural motif that may be applicable to other alpha7-selective agonists.
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Affiliation(s)
- Roger L Papke
- University of Florida, College of Medicine, 1600 SW Archer Road, Gainesville, FL 32610, USA.
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Placzek AN, Grassi F, Meyer EM, Papke RL. An α7 Nicotinic Acetylcholine Receptor Gain-of-Function Mutant That Retains Pharmacological Fidelity. Mol Pharmacol 2005; 68:1863-76. [PMID: 16186249 DOI: 10.1124/mol.105.016402] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The alpha7-type nicotinic acetylcholine receptor (nAChR) has been recognized as a potential therapeutic target for the treatment of a variety of pathologic conditions, including schizophrenia, Alzheimer's disease, and peripheral inflammation. A unique feature of alpha7 nAChRs that tends to complicate functional assays intended to identify selective drugs for these receptors is the strong concentration-dependent desensitization of their agonist-evoked responses. At low agonist concentrations, voltage-clamp responses are small but tend to closely follow the solution exchange profile, whereas higher agonist concentrations produce responses that peak and then decay very rapidly, usually before the full drug concentration has been achieved. In this article, we report that an alpha7 T245S mutant, which has a point mutation at the sixth position in the alpha7 second transmembrane domain (T6'S), demonstrates a significant gain of function, sustaining current when exposed to relatively high agonist concentrations when expressed in Xenopus laevis oocytes and larger peak currents when expressed in mammalian GH4C1 cells. At the single-channel level, the T6'S mutant has a unitary conductance of 61.7 +/- 5.8 pS, similar to that reported for wild-type alpha7, but a vastly longer average open duration. In addition, channel burst activity indicates a greater than 40% probability of channel re-opening in the sustained presence of 30 muM acetylcholine, consistent with a greater overall open probability relative to wild-type alpha7. Unlike the alpha7 L248T gain-of-function mutant, the T6'S mutant exhibits a pharmacological profile that is remarkably similar to the wild-type alpha7 receptor, implicating it as a potentially useful tool for identifying therapeutic agents.
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Affiliation(s)
- Andon N Placzek
- Department of Pharmacology and Therapeutics, P. O. Box 100267, University of Florida, Gainesville, Florida 32610-0267, USA
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