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Yoo ES, Li L, Jia L, Lord CC, Lee CE, Birnbaum SG, Vianna CR, Berglund ED, Cunningham KA, Xu Y, Sohn JW, Liu C. Gα i/o-coupled Htr2c in the paraventricular nucleus of the hypothalamus antagonizes the anorectic effect of serotonin agents. Cell Rep 2021; 37:109997. [PMID: 34788630 PMCID: PMC8636014 DOI: 10.1016/j.celrep.2021.109997] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2021] [Revised: 09/28/2021] [Accepted: 10/21/2021] [Indexed: 01/19/2023] Open
Abstract
The anorexigenic effect of serotonergic compounds has largely been attributed to activation of serotonin 2C receptors (Htr2cs). Using mouse genetic models in which Htr2c can be selectively deleted or restored (in Htr2c-null mice), we investigate the role of Htr2c in forebrain Sim1 neurons. Unexpectedly, we find that Htr2c acts in these neurons to promote food intake and counteract the anorectic effect of serotonergic appetite suppressants. Furthermore, Htr2c marks a subset of Sim1 neurons in the paraventricular nucleus of the hypothalamus (PVH). Chemogenetic activation of these neurons in adult mice suppresses hunger, whereas their silencing promotes feeding. In support of an orexigenic role of PVH Htr2c, whole-cell patch-clamp experiments demonstrate that activation of Htr2c inhibits PVH neurons. Intriguingly, this inhibition is due to Gαi/o-dependent activation of ATP-sensitive K+ conductance, a mechanism of action not identified previously in the mammalian nervous system. Yoo et al. show that Htr2c, the target of a former weight loss drug, can inhibit and promote food intake by coupling with distinct intracellular signaling events in different hypothalamic neurons. These findings may help explain the rather modest anti-obesity effects of Htr2c agonists.
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Affiliation(s)
- Eun-Seon Yoo
- Department of Biological Sciences, Korea Advanced Institute of Science and Technology, Daejeon 34141, Korea
| | - Li Li
- Center for Hypothalamic Research, Department of Internal Medicine, UT Southwestern Medical Center, Dallas, TX 75390, USA
| | - Lin Jia
- Center for Hypothalamic Research, Department of Internal Medicine, UT Southwestern Medical Center, Dallas, TX 75390, USA; Department of Biological Sciences, The University of Texas at Dallas, Richardson, TX 75080, USA
| | - Caleb C Lord
- Center for Hypothalamic Research, Department of Internal Medicine, UT Southwestern Medical Center, Dallas, TX 75390, USA
| | - Charlotte E Lee
- Center for Hypothalamic Research, Department of Internal Medicine, UT Southwestern Medical Center, Dallas, TX 75390, USA
| | - Shari G Birnbaum
- Department of Psychiatry, UT Southwestern Medical Center, Dallas, TX 75390, USA; Peter O'Donnell Jr. Brain Institute, UT Southwestern Medical Center, Dallas, TX 75390, USA
| | - Claudia R Vianna
- Center for Hypothalamic Research, Department of Internal Medicine, UT Southwestern Medical Center, Dallas, TX 75390, USA
| | - Eric D Berglund
- Center for Hypothalamic Research, Department of Internal Medicine, UT Southwestern Medical Center, Dallas, TX 75390, USA
| | - Kathryn A Cunningham
- Center for Addiction Research and Department of Pharmacology and Toxicology, University of Texas Medical Branch, Galveston, TX 77555, USA
| | - Yong Xu
- Children's Nutrition Research Center, Department of Pediatrics, Baylor College of Medicine, Houston, TX 77030, USA; Department of Molecular and Cellular Biology, Baylor College of Medicine, Houston, TX 77030, USA
| | - Jong-Woo Sohn
- Department of Biological Sciences, Korea Advanced Institute of Science and Technology, Daejeon 34141, Korea.
| | - Chen Liu
- Center for Hypothalamic Research, Department of Internal Medicine, UT Southwestern Medical Center, Dallas, TX 75390, USA; Department of Neuroscience, UT Southwestern Medical Center, Dallas, TX 75390, USA; Peter O'Donnell Jr. Brain Institute, UT Southwestern Medical Center, Dallas, TX 75390, USA.
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Sharma V, Nair SV, Jaitley P, Nakade UP, Sharma A, Choudhury S, Garg SK. ATP-sensitive and maxi potassium channels regulate BRL 37344-induced tocolysis in buffaloes-an in vitro study. Theriogenology 2017; 107:194-202. [PMID: 29172176 DOI: 10.1016/j.theriogenology.2017.10.044] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2017] [Revised: 10/26/2017] [Accepted: 10/30/2017] [Indexed: 11/17/2022]
Abstract
Cellular coupling of beta3-adrenoceptors (β3-ADR) to potassium channels in myometrium is largely unknown. In vitro study was undertaken to unravel the presence of β3-adrenergic receptors (ADR) and the role of K+-channels in mediating β3-ADR-induced relaxation in isolated myometrial strips from cyclic non-pregnant water buffaloes. Isometric tension was recorded in isolated myometrial strips using data acquisition system based physiograph. Compared to SR 59230A, BRL 37344 was found to be more potent in inducing β3-dependent myometrial relaxation which was significantly (p < 0.05) inhibited in the presence of β3 antagonist, SAR 150640. The immunoreactive protein to β3-ADR was also detected in membrane fraction of myometrial protein. Further, incubation with BRL 37344 (10 μM) significantly (p < 0.05) increased c-AMP accumulation (37.58 ± 9.52 pmol/mg protein; n = 4) in the myometrial strips compared to basal c-AMP level (16.85 ± 3.87 pmol/mg protein; n = 4). The concentration response curves (CRC) of BRL 37344 were significantly (p < 0.05) shifted towards right in the presence of KATP channels specific blocker, glibenclamide (10 μM) and maxi K+-channels (BKCa) specific blocker, iberiotoxin (100 nM), with decrease in both efficacy and potency as compared to control. However, 4-aminopyridine (4-AP), a specific blocker of the voltage gated K+-channels (Kv), failed to alter the CRC of BRL 37344. Existence of immunoreactive protein to Kir6.1, α-subunit of BKCa and Kv1.1 channels were also detected in the membrane fraction of myometrial protein. Based on the above findings, it can be concluded that BRL 37344 is a potent stimulator of β3-adrenoceptors in buffalo myometrium and besides mediating their effect through rise in c-AMP, they are coupled to KATP and BKCa channels in inducing tocolytic effects.
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Affiliation(s)
- Vipin Sharma
- Smooth Muscle & Molecular Pharmacology Laboratory, Department of Veterinary Pharmacology & Toxicology, College of Veterinary Science and Animal Husbandry, U.P. Pandit Deen Dayal Upadhyaya Pashu Chikitsa Vigyan Vishwavidyalaya Evam, Go-Anusandhan Sansthan, Mathura 281001, India
| | - Sooraj V Nair
- Smooth Muscle & Molecular Pharmacology Laboratory, Department of Veterinary Pharmacology & Toxicology, College of Veterinary Science and Animal Husbandry, U.P. Pandit Deen Dayal Upadhyaya Pashu Chikitsa Vigyan Vishwavidyalaya Evam, Go-Anusandhan Sansthan, Mathura 281001, India
| | - Pooja Jaitley
- Smooth Muscle & Molecular Pharmacology Laboratory, Department of Veterinary Pharmacology & Toxicology, College of Veterinary Science and Animal Husbandry, U.P. Pandit Deen Dayal Upadhyaya Pashu Chikitsa Vigyan Vishwavidyalaya Evam, Go-Anusandhan Sansthan, Mathura 281001, India
| | - Udayraj P Nakade
- Smooth Muscle & Molecular Pharmacology Laboratory, Department of Veterinary Pharmacology & Toxicology, College of Veterinary Science and Animal Husbandry, U.P. Pandit Deen Dayal Upadhyaya Pashu Chikitsa Vigyan Vishwavidyalaya Evam, Go-Anusandhan Sansthan, Mathura 281001, India
| | - Abhishek Sharma
- Smooth Muscle & Molecular Pharmacology Laboratory, Department of Veterinary Pharmacology & Toxicology, College of Veterinary Science and Animal Husbandry, U.P. Pandit Deen Dayal Upadhyaya Pashu Chikitsa Vigyan Vishwavidyalaya Evam, Go-Anusandhan Sansthan, Mathura 281001, India
| | - Soumen Choudhury
- Smooth Muscle & Molecular Pharmacology Laboratory, Department of Veterinary Pharmacology & Toxicology, College of Veterinary Science and Animal Husbandry, U.P. Pandit Deen Dayal Upadhyaya Pashu Chikitsa Vigyan Vishwavidyalaya Evam, Go-Anusandhan Sansthan, Mathura 281001, India.
| | - Satish Kumar Garg
- Smooth Muscle & Molecular Pharmacology Laboratory, Department of Veterinary Pharmacology & Toxicology, College of Veterinary Science and Animal Husbandry, U.P. Pandit Deen Dayal Upadhyaya Pashu Chikitsa Vigyan Vishwavidyalaya Evam, Go-Anusandhan Sansthan, Mathura 281001, India
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Ouyang Z, Wang X, Meng Q, Feng L, Sun Y, Wu X, Xu Q. Suppression of adenosine monophosphate-activated protein kinase selectively triggers apoptosis in activated T cells and ameliorates immune diseases. Biochem Biophys Res Commun 2017; 487:223-229. [PMID: 28412370 DOI: 10.1016/j.bbrc.2017.04.038] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2017] [Accepted: 04/10/2017] [Indexed: 01/10/2023]
Abstract
Deficient apoptosis of activated T cells can result in immunological disorders. Molecules associated with energy and metabolisms are suggested to be involved in pathogenesis of immune diseases, but remain uninvestigated. In the present study we reported that glibenclamide exerted a new pharmacological effect on inflammatory responses by selectively triggering apoptosis of activated T cells. Glibenclamide demonstrated an inhibition on activated T lymphocytes, whereas showed no toxicity in the naive cells. This effect was mainly related with its ability to facilitate apoptosis in activated T cells with an up-regulation of cleaved-caspases and cleaved-PARP. Glibenclamide enhanced Fas expression and suppressed the expression of antiapoptotic cellular FLICE-inhibitory protein. The underlying mechanism of glibenclamide was not associated with its classical inhibitory effect on ATP-sensitive potassium channels, but due to a unique suppression on the phosphorylation of 5' adenosine monophosphate-activated protein kinase, which was augmented during T cell activation. An in vivo experiment further demonstrated that glibenclamide ameliorated T-cell-mediated contact hypersensitivity in mice. Altogether, these results suggest that AMPK inhibition by glibenclamide can regulate the survival and death of T lymphocytes and be beneficial for the treatment of autoimmune diseases.
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Affiliation(s)
- Zijun Ouyang
- State Key Laboratory of Pharmaceutical Biotechnology, School of Life Sciences, Nanjing University, 22 Hankou Road, Nanjing 210093, China
| | - Xingqi Wang
- State Key Laboratory of Pharmaceutical Biotechnology, School of Life Sciences, Nanjing University, 22 Hankou Road, Nanjing 210093, China
| | - Qianqian Meng
- State Key Laboratory of Pharmaceutical Biotechnology, School of Life Sciences, Nanjing University, 22 Hankou Road, Nanjing 210093, China
| | - Lili Feng
- State Key Laboratory of Pharmaceutical Biotechnology, School of Life Sciences, Nanjing University, 22 Hankou Road, Nanjing 210093, China
| | - Yang Sun
- State Key Laboratory of Pharmaceutical Biotechnology, School of Life Sciences, Nanjing University, 22 Hankou Road, Nanjing 210093, China
| | - Xuefeng Wu
- State Key Laboratory of Pharmaceutical Biotechnology, School of Life Sciences, Nanjing University, 22 Hankou Road, Nanjing 210093, China.
| | - Qiang Xu
- State Key Laboratory of Pharmaceutical Biotechnology, School of Life Sciences, Nanjing University, 22 Hankou Road, Nanjing 210093, China.
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Freitas ACN, Silva GC, Pacheco DF, Pimenta AMC, Lemos VS, Duarte IDG, de Lima ME. The synthetic peptide PnPP-19 induces peripheral antinociception via activation of NO/cGMP/K ATP pathway: Role of eNOS and nNOS. Nitric Oxide 2017; 64:31-38. [PMID: 28087360 DOI: 10.1016/j.niox.2017.01.004] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2016] [Revised: 01/06/2017] [Accepted: 01/09/2017] [Indexed: 01/19/2023]
Abstract
BACKGROUND and purpose: The peptide PnPP-19, derived from the spider toxin PnTx2-6 (renamed as δ-CNTX-Pn1c), potentiates erectile function by activating the nitrergic system. Since NO has been studied as an antinociceptive molecule and PnPP-19 is known to induce peripheral antinociception, we intended to evaluate whether PnPP-19 could induce peripheral antinociception through activation of this pathway. EXPERIMENTAL APPROACH Nociceptive thresholds were measured by paw pressure test. PGE2 (2 μg/paw) was administered intraplantarly together with PnPP-19 and inhibitors/blockers of NOS, guanylyl cyclase and KATP channels. The nitrite concentration was accessed by Griess test. The expression and phosphorylation of eNOS and nNOS were determined by western blot. KEY RESULTS PnPP-19 (5, 10 and 20 μg/paw) induced peripheral antinociception in rats. Administration of NOS inhibitor (L-NOarg), selective nNOS inhibitor (L-NPA), guanylyl cyclase inhibitor (ODQ) and the blocker of KATP (glibenclamide) partially inhibited the antinociceptive effect of PnPP-19 (10 μg/paw). Tissue nitrite concentration increased after PnPP-19 (10 μg/paw) administration. Expression of eNOS and nNOS remained the same in all tested groups, however the phosphorylation of nNOS Ser852 (inactivation site) increased and phosphorylation of eNOS Ser1177 (activation site) decreased after PGE2 injection. Administration of PnPP-19 reverted this PGE2-induced effect. CONCLUSIONS AND IMPLICATIONS The peripheral antinociceptive effect induced by PnPP-19 is resulting from activation of NO-cGMP-KATP pathway. Activation of eNOS and nNOS might be required for such effect. Our results suggest PnPP-19 as a new drug candidate to treat pain and reinforce the importance of nNOS and eNOS activation, as well as endogenous NO release, for induction of peripheral antinociception.
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Affiliation(s)
- A C N Freitas
- Departamento de Bioquímica e Imunologia, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Belo Horizonte, M.G., Brazil
| | - G C Silva
- Departamento Farmacologia, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Belo Horizonte, M.G., Brazil
| | - D F Pacheco
- Departamento de Bioquímica e Imunologia, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Belo Horizonte, M.G., Brazil; Departamento Farmacologia, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Belo Horizonte, M.G., Brazil
| | - A M C Pimenta
- Departamento de Bioquímica e Imunologia, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Belo Horizonte, M.G., Brazil
| | - V S Lemos
- Departamento Farmacologia, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Belo Horizonte, M.G., Brazil
| | - I D G Duarte
- Departamento Farmacologia, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Belo Horizonte, M.G., Brazil
| | - M E de Lima
- Departamento de Bioquímica e Imunologia, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Belo Horizonte, M.G., Brazil.
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Dadak S, Beall C, Vlachaki Walker JM, Soutar MPM, McCrimmon RJ, Ashford MLJ. Oleate induces K ATP channel-dependent hyperpolarization in mouse hypothalamic glucose-excited neurons without altering cellular energy charge. Neuroscience 2017; 346:29-42. [PMID: 28087336 PMCID: PMC5346158 DOI: 10.1016/j.neuroscience.2016.12.053] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2016] [Accepted: 12/29/2016] [Indexed: 11/29/2022]
Abstract
Oleate and low glucose hyperpolarize and inhibit GT1-7 and mouse GE neurons by activation of KATP. Oleate inhibition of GT1-7 neuron activity is not mediated by AMPK or fatty acid oxidation. Activation of KATP by oleate requires ATP hydrolysis but does not reduce the levels ATP or the ATP:ADP ratio. GT1-7 hyperpolarization by oleate is not dependent on UCP2. Oleate and low glucose depolarize a subpopulation of hypothalamic GI neurons.
The unsaturated fatty acid, oleate exhibits anorexigenic properties reducing food intake and hepatic glucose output. However, its mechanism of action in the hypothalamus has not been fully determined. This study investigated the effects of oleate and glucose on GT1-7 mouse hypothalamic cells (a model of glucose-excited (GE) neurons) and mouse arcuate nucleus (ARC) neurons. Whole-cell and perforated patch-clamp recordings, immunoblotting and cell energy status measures were used to investigate oleate- and glucose-sensing properties of mouse hypothalamic neurons. Oleate or lowered glucose concentration caused hyperpolarization and inhibition of firing of GT1-7 cells by the activation of ATP-sensitive K+ channels (KATP). This effect of oleate was not dependent on fatty acid oxidation or raised AMP-activated protein kinase activity or prevented by the presence of the UCP2 inhibitor genipin. Oleate did not alter intracellular calcium, indicating that CD36/fatty acid translocase may not play a role. However, oleate activation of KATP may require ATP metabolism. The short-chain fatty acid octanoate was unable to replicate the actions of oleate on GT1-7 cells. Although oleate decreased GT1-7 cell mitochondrial membrane potential there was no change in total cellular ATP or ATP/ADP ratios. Perforated patch and whole-cell recordings from mouse hypothalamic slices demonstrated that oleate hyperpolarized a subpopulation of ARC GE neurons by KATP activation. Additionally, in a separate small population of ARC neurons, oleate application or lowered glucose concentration caused membrane depolarization. In conclusion, oleate induces KATP-dependent hyperpolarization and inhibition of firing of a subgroup of GE hypothalamic neurons without altering cellular energy charge.
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Affiliation(s)
- Selma Dadak
- Division of Molecular and Clinical Medicine, School of Medicine, Ninewells Hospital and Medical School, University of Dundee, Dundee DD1 9SY, UK
| | - Craig Beall
- Division of Molecular and Clinical Medicine, School of Medicine, Ninewells Hospital and Medical School, University of Dundee, Dundee DD1 9SY, UK; Institute of Biomedical and Clinical Sciences, University of Exeter Medical School, RILD Building, Barrack Road, Exeter EX2 5DW, UK
| | - Julia M Vlachaki Walker
- Institute of Biomedical and Clinical Sciences, University of Exeter Medical School, RILD Building, Barrack Road, Exeter EX2 5DW, UK
| | - Marc P M Soutar
- Division of Molecular and Clinical Medicine, School of Medicine, Ninewells Hospital and Medical School, University of Dundee, Dundee DD1 9SY, UK
| | - Rory J McCrimmon
- Division of Molecular and Clinical Medicine, School of Medicine, Ninewells Hospital and Medical School, University of Dundee, Dundee DD1 9SY, UK
| | - Michael L J Ashford
- Division of Molecular and Clinical Medicine, School of Medicine, Ninewells Hospital and Medical School, University of Dundee, Dundee DD1 9SY, UK.
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Yee AG, Freestone PS, Bai JZ, Lipski J. Paradoxical lower sensitivity of Locus Coeruleus than Substantia Nigra pars compacta neurons to acute actions of rotenone. Exp Neurol 2016; 287:34-43. [PMID: 27771354 DOI: 10.1016/j.expneurol.2016.10.010] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2016] [Revised: 10/14/2016] [Accepted: 10/18/2016] [Indexed: 12/21/2022]
Abstract
Parkinson's disease (PD) is not only associated with degeneration of dopaminergic (DAergic) neurons in the Substantia Nigra, but also with profound loss of noradrenergic neurons in the Locus Coeruleus (LC). Remarkably, LC degeneration may exceed, or even precede the loss of nigral DAergic neurons, suggesting that LC neurons may be more susceptible to damage by various insults. Using a combination of electrophysiology, fluorescence imaging and electrochemistry, we directly compared the responses of LC, nigral DAergic and nigral non-dopaminergic (non-DAergic) neurons in rat brain slices to acute application of rotenone, a mitochondrial toxin used to create animal and in vitro models of PD. Rotenone (0.01-5.0μM) dose-dependently inhibited the firing of all three groups of neurons, primarily by activating KATP channels. The toxin also depolarised mitochondrial potential (Ψm) and released reactive oxygen species (H2O2). When KATP channels were blocked, rotenone (1μM) increased the firing of LC neurons by activating an inward current associated with dose-dependent increase of cytosolic free Ca2+ ([Ca2+]i). This effect was attenuated by blocking oxidative stress-sensitive TRPM2 channels, and by pre-treatment of slices with anti-oxidants. These results demonstrate that rotenone inhibits the activity of LC neurons mainly by activating KATP channels, and increases [Ca2+]ivia TRPM2 channels. Since the responses of LC neurons were smaller than those of nigral DAergic neurons, our study shows that LC neurons are paradoxically less sensitive to acute effects of this parkinsonian toxin.
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Affiliation(s)
- Andrew G Yee
- Faculty of Medical and Health Sciences, University of Auckland, Auckland, New Zealand
| | - Peter S Freestone
- Faculty of Medical and Health Sciences, University of Auckland, Auckland, New Zealand
| | - Ji-Zhong Bai
- Faculty of Medical and Health Sciences, University of Auckland, Auckland, New Zealand
| | - Janusz Lipski
- Faculty of Medical and Health Sciences, University of Auckland, Auckland, New Zealand.
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Haythorne E, Hamilton DL, Findlay JA, Beall C, McCrimmon RJ, Ashford MLJ. Chronic exposure to K ATP channel openers results in attenuated glucose sensing in hypothalamic GT1-7 neurons. Neuropharmacology 2016; 111:212-222. [PMID: 27618741 DOI: 10.1016/j.neuropharm.2016.09.008] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2016] [Revised: 07/06/2016] [Accepted: 09/07/2016] [Indexed: 10/21/2022]
Abstract
Individuals with Type 1 diabetes (T1D) are often exposed to recurrent episodes of hypoglycaemia. This reduces hormonal and behavioural responses that normally counteract low glucose in order to maintain glucose homeostasis, with altered responsiveness of glucose sensing hypothalamic neurons implicated. Although the molecular mechanisms are unknown, pharmacological studies implicate hypothalamic ATP-sensitive potassium channel (KATP) activity, with KATP openers (KCOs) amplifying, through cell hyperpolarization, the response to hypoglycaemia. Although initial findings, using acute hypothalamic KCO delivery, in rats were promising, chronic exposure to the KCO NN414 worsened the responses to subsequent hypoglycaemic challenge. To investigate this further we used GT1-7 cells to explore how NN414 affected glucose-sensing behaviour, the metabolic response of cells to hypoglycaemia and KATP activity. GT1-7 cells exposed to 3 or 24 h NN414 exhibited an attenuated hyperpolarization to subsequent hypoglycaemic challenge or NN414, which correlated with diminished KATP activity. The reduced sensitivity to hypoglycaemia was apparent 24 h after NN414 removal, even though intrinsic KATP activity recovered. The NN414-modified glucose responsiveness was not associated with adaptations in glucose uptake, metabolism or oxidation. KATP inactivation by NN414 was prevented by the concurrent presence of tolbutamide, which maintains KATP closure. Single channel recordings indicate that NN414 alters KATP intrinsic gating inducing a stable closed or inactivated state. These data indicate that exposure of hypothalamic glucose sensing cells to chronic NN414 drives a sustained conformational change to KATP, probably by binding to SUR1, that results in loss of channel sensitivity to intrinsic metabolic factors such as MgADP and small molecule agonists.
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Affiliation(s)
- Elizabeth Haythorne
- Division of Molecular and Clinical Medicine, School of Medicine, Ninewells Hospital & Medical School, University of Dundee, Dundee, UK.
| | - D Lee Hamilton
- Division of Molecular and Clinical Medicine, School of Medicine, Ninewells Hospital & Medical School, University of Dundee, Dundee, UK.
| | - John A Findlay
- Division of Molecular and Clinical Medicine, School of Medicine, Ninewells Hospital & Medical School, University of Dundee, Dundee, UK.
| | - Craig Beall
- Division of Molecular and Clinical Medicine, School of Medicine, Ninewells Hospital & Medical School, University of Dundee, Dundee, UK.
| | - Rory J McCrimmon
- Division of Molecular and Clinical Medicine, School of Medicine, Ninewells Hospital & Medical School, University of Dundee, Dundee, UK.
| | - Michael L J Ashford
- Division of Molecular and Clinical Medicine, School of Medicine, Ninewells Hospital & Medical School, University of Dundee, Dundee, UK.
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Levin MD, Zhang H, Uchida K, Grange DK, Singh GK, Nichols CG. Electrophysiologic consequences of KATP gain of function in the heart: Conduction abnormalities in Cantu syndrome. Heart Rhythm 2015; 12:2316-24. [PMID: 26142302 PMCID: PMC4624040 DOI: 10.1016/j.hrthm.2015.06.042] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/05/2015] [Indexed: 11/21/2022]
Abstract
BACKGROUND Gain-of-function (GOF) mutations in the KATP channel subunits Kir6.1 and SUR2 cause Cantu syndrome (CS), a disease characterized by multiple cardiovascular abnormalities. OBJECTIVE The purpose of this study was to better determine the electrophysiologic consequences of such GOF mutations in the heart. METHODS We generated transgenic mice (Kir6.1-GOF) expressing ATP-insensitive Kir6.1[G343D] subunits under α-myosin heavy chain (α-MHC) promoter control, to target gene expression specifically in cardiomyocytes, and performed patch-clamp experiments on isolated ventricular myocytes and invasive electrophysiology on anesthetized mice. RESULTS In Kir6.1-GOF ventricular myocytes, KATP channels showed decreased ATP sensitivity but no significant change in current density. Ambulatory ECG recordings on Kir6.1-GOF mice revealed AV nodal conduction abnormalities and junctional rhythm. Invasive electrophysiologic analyses revealed slowing of conduction and conduction failure through the AV node but no increase in susceptibility to atrial or ventricular ectopic activity. Surface ECGs recorded from CS patients also demonstrated first-degree AV block and fascicular block. CONCLUSION The primary electrophysiologic consequence of cardiac KATP GOF is on the conduction system, particularly the AV node, resulting in conduction abnormalities in CS patients who carry KATP GOF mutations.
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Affiliation(s)
- Mark D Levin
- Center for the Investigation of Membrane Excitability Diseases, Washington University School of Medicine, St. Louis, Missouri; Department of Pediatrics, Washington University School of Medicine, St. Louis, Missouri
| | - Haixia Zhang
- Center for the Investigation of Membrane Excitability Diseases, Washington University School of Medicine, St. Louis, Missouri; Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, Missouri
| | - Keita Uchida
- Center for the Investigation of Membrane Excitability Diseases, Washington University School of Medicine, St. Louis, Missouri; Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, Missouri
| | - Dorothy K Grange
- Center for the Investigation of Membrane Excitability Diseases, Washington University School of Medicine, St. Louis, Missouri; Department of Pediatrics, Washington University School of Medicine, St. Louis, Missouri
| | - Gautam K Singh
- Center for the Investigation of Membrane Excitability Diseases, Washington University School of Medicine, St. Louis, Missouri; Department of Pediatrics, Washington University School of Medicine, St. Louis, Missouri
| | - Colin G Nichols
- Center for the Investigation of Membrane Excitability Diseases, Washington University School of Medicine, St. Louis, Missouri; Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, Missouri.
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Lazarenko R, Geisler J, Bayliss D, Larner J, Li C. D-chiro-inositol glycan stimulates insulin secretion in pancreatic β cells. Mol Cell Endocrinol 2014; 387:1-7. [PMID: 24530497 PMCID: PMC4366192 DOI: 10.1016/j.mce.2014.02.004] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/06/2013] [Revised: 01/30/2014] [Accepted: 02/07/2014] [Indexed: 12/25/2022]
Abstract
Insulin has been shown to act on pancreatic β cells to regulate its own secretion. Currently the mechanism underlying this effect is unclear. INS-2, a novel inositol glycan pseudo-disaccharide containing D-chiro-inositol and galactosamine, has been shown to function as an insulin mimetic and a putative insulin mediator. In the present study we found that INS-2 stimulates insulin secretion in MIN6 β cells and potentiates glucose stimulated insulin secretion in isolated mouse islets. Importantly, INS-2 failed to potentiate insulin secretion induced by tolbutamide, which stimulates insulin release by closing ATP sensitive potassium channels (KATP). Electrophysiological studies showed that INS-2 inhibited sulfonylurea-sensitive KATP conductance. The effect of INS-2 on inhibiting KATP channel is mediated by protein phosphatase 2C (PP2C), as knocking down PP2C expression in MIN6 cells by PP2C small hairpin RNA completely abolished the effect of INS-2 on KATP and consequently attenuated INS-2 induced insulin secretion. In conclusion, the present study identifies a novel mechanism involving PP2C in regulating KATP channel activity and consequently insulin secretion.
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Affiliation(s)
- Roman Lazarenko
- Department of Pharmacology, University of Virginia Health System, Charlottesville, VA, United States
| | - Jessica Geisler
- Department of Pharmacology, University of Virginia Health System, Charlottesville, VA, United States
| | - Douglas Bayliss
- Department of Pharmacology, University of Virginia Health System, Charlottesville, VA, United States
| | - Joseph Larner
- Department of Pharmacology, University of Virginia Health System, Charlottesville, VA, United States
| | - Chien Li
- Department of Pharmacology, University of Virginia Health System, Charlottesville, VA, United States.
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Negrette-Guzmán M, Huerta-Yepez S, Tapia E, Pedraza-Chaverri J. Modulation of mitochondrial functions by the indirect antioxidant sulforaphane: a seemingly contradictory dual role and an integrative hypothesis. Free Radic Biol Med 2013; 65:1078-1089. [PMID: 23999506 DOI: 10.1016/j.freeradbiomed.2013.08.182] [Citation(s) in RCA: 72] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/22/2013] [Revised: 08/21/2013] [Accepted: 08/22/2013] [Indexed: 01/25/2023]
Abstract
The chemotherapeutic isothiocyanate sulforaphane (SFN) was early linked to anticarcinogenic and antiproliferative activities. Soon after, this compound, derived from cruciferous vegetables, became an excellent and useful trial for anti-cancer research in experimental models including growth tumor, metastasis, and angiogenesis. Many subsequent reports showed modifications in mitochondrial signaling, functionality, and integrity induced by SFN. When cytoprotective effects were found in toxic and ischemic insult models, seemingly contradictory behaviors of SFN were discovered: SFN was inducing deleterious changes in cancer cell mitochondria that eventually would carry the cell to death via apoptosis and also was protecting noncancer cell mitochondria against oxidative challenge, which prevented cell death. In both cases, SFN exhibited effects on mitochondrial redox balance and phase II enzyme expression, mitochondrial membrane potential, expression of the family of B cell lymphoma 2 homologs, regulation of proapoptotic proteins released from mitochondria, activation/inactivation of caspases, mitochondrial respiratory complex activities, oxygen consumption and bioenergetics, mitochondrial permeability transition pore opening, and modulation of some kinase pathways. With the ultimate findings related to the induction of mitochondrial biogenesis by SFN, it could be considered that SFN has effects on mitochondrial dynamics that explain some divergent points. In this review, we list the reports involving effects on mitochondrial modulation by SFN in anti-cancer models as well as in cytoprotective models against oxidative damage. We also attempt to integrate the data into a mechanism explaining the various effects of SFN on mitochondrial function in only one concept, taking into account mitochondrial biogenesis and dynamics and making a comparison with the theory of reactive oxygen species threshold of cell death. Our interest is to achieve a complete view of cancer and protective therapies based on SFN that can be extended to other chemotherapeutic compounds with similar characteristics. The work needed to test this hypothesis is quite extensive.
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Affiliation(s)
- Mario Negrette-Guzmán
- Departamento de Biología, Facultad de Química, Universidad Nacional Autónoma de México, 04510 Mexico City, DF, Mexico
| | - Sara Huerta-Yepez
- Unidad de Investigación en Enfermedades Oncológicas, Hospital Infantil de México Federico Gómez, Mexico City, DF, Mexico
| | - Edilia Tapia
- Laboratorio de Patología Renal, Departamento de Nefrología, Instituto Nacional de Cardiología Ignacio Chávez, Mexico City, DF, Mexico
| | - José Pedraza-Chaverri
- Departamento de Biología, Facultad de Química, Universidad Nacional Autónoma de México, 04510 Mexico City, DF, Mexico.
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Ghaly H, Jörns A, Rustenbeck I. Effect of fluoroquinolones on mitochondrial function in pancreatic beta cells. Eur J Pharm Sci 2013; 52:206-14. [PMID: 24284031 DOI: 10.1016/j.ejps.2013.11.011] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2013] [Revised: 11/04/2013] [Accepted: 11/12/2013] [Indexed: 11/19/2022]
Abstract
Hyper- and hypoglycaemias are known side effects of fluoroquinolone antibiotics, resulting in a number of fatalities. Fluoroquinolone-induced hypoglycaemias are due to stimulated insulin release by the inhibition of the KATP channel activity of the beta cell. Recently, it was found that fluoroquinolones were much less effective on metabolically intact beta cells than on open cell preparations. Thus the intracellular effects of gatifloxacin, moxifloxacin and ciprofloxacin were investigated by measuring NAD(P)H- and FAD-autofluorescence, the mitochondrial membrane potential, and the adenine nucleotide content of isolated pancreatic islets and beta cells. 100 μM of moxifloxacin abolished the NAD(P)H increase elicited by 20mM glucose, while gatifloxacin diminished it and ciprofloxacin had no significant effect. This pattern was also seen with islets from SUR1 Ko mice, which have no functional KATP channels. Moxifloxacin also diminished the glucose-induced decrease of FAD-fluorescence, which reflects the intramitochondrial production of reducing equivalents. Moxifloxacin, but not ciprofloxacin or gatifloxacin significantly reduced the effect of 20mM glucose on the ATP/ADP ratio. The mitochondrial hyperpolarization caused by 20mM glucose was partially antagonized by moxifloxacin, but not by ciprofloxacin or gatifloxacin. Ultrastructural analyses after 20 h tissue culture showed that all three compounds (at 10 and 100 μM) diminished the number of insulin secretory granules and that gatifloxacin and ciprofloxacin, but not moxifloxacin induced fission/fusion configurations of the beta cell mitochondria. In conclusion, fluoroquinolones affect the function of the mitochondria in pancreatic beta cells which may diminish the insulinotropic effect of KATP channel closure and contribute to the hyperglycaemic episodes.
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Affiliation(s)
- Hany Ghaly
- Institute of Pharmacology and Toxicology, University of Braunschweig, D-38106 Braunschweig, Germany
| | - Anne Jörns
- Institute of Clinical Biochemistry, Hannover Medical School, 30623 Hannover, Germany
| | - Ingo Rustenbeck
- Institute of Pharmacology and Toxicology, University of Braunschweig, D-38106 Braunschweig, Germany.
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Zhang HX, Silva JR, Lin YW, Verbsky JW, Lee US, Kanter EM, Yamada KA, Schuessler RB, Nichols CG. Heterogeneity and function of K(ATP) channels in canine hearts. Heart Rhythm 2013; 10:1576-83. [PMID: 23871704 DOI: 10.1016/j.hrthm.2013.07.020] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/18/2013] [Indexed: 01/08/2023]
Abstract
BACKGROUND The concept that pore-forming Kir6.2 and regulatory SUR2A subunits form cardiac ATP-sensitive potassium (K(ATP)) channels is challenged by recent reports that SUR1 is predominant in mouse atrial K(ATP) channels. OBJECTIVE To assess SUR subunit composition of K(ATP) channels and consequence of K(ATP) activation for action potential duration (APD) in dog hearts. METHODS Patch-clamp techniques were used on isolated dog cardiomyocytes to investigate K(ATP) channel properties. Dynamic current clamp, by injection of a linear K(+) conductance to simulate activation of the native current, was used to study the consequences of K(ATP) activation on APD. RESULTS Metabolic inhibitor (MI)-activated current was not significantly different from pinacidil (SUR2A-specific)-activated current, and both currents were larger than diazoxide (SUR1-specific)-activated current in both the atrium and the ventricle. Mean K(ATP) conductance (activated by MI) did not differ significantly between chambers, although, within the ventricle, both MI-induced and pinacidil-induced currents tended to decrease from the epicardium to the endocardium. Dynamic current-clamp results indicate that myocytes with longer baseline APDs are more susceptible to injected K(ATP) current, a result reproduced in silico by using a canine action potential model (Hund-Rudy) to simulate epicardial and endocardial myocytes. CONCLUSIONS Even a small fraction of K(ATP) activation significantly shortens APD in a manner that depends on existing heterogeneity in K(ATP) current and APD.
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Affiliation(s)
- Hai Xia Zhang
- Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, Missouri; Center for the Investigation of Membrane Excitability Diseases, Washington University School of Medicine, St. Louis, Missouri
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Priestley JR, Buelow MW, McEwen ST, Weinberg BD, Delaney M, Balus SF, Hoeppner C, Dondlinger L, Lombard JH. Reduced angiotensin II levels cause generalized vascular dysfunction via oxidant stress in hamster cheek pouch arterioles. Microvasc Res 2013; 89:134-45. [PMID: 23628292 DOI: 10.1016/j.mvr.2013.04.004] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2013] [Revised: 03/19/2013] [Accepted: 04/18/2013] [Indexed: 11/23/2022]
Abstract
OBJECTIVES We investigated the effect of suppressing plasma angiotensin II (ANG II) levels on arteriolar relaxation in the hamster cheek pouch. METHODS Arteriolar diameters were measured via television microscopy during short-term (3-6days) high salt (HS; 4% NaCl) diet and angiotensin converting enzyme (ACE) inhibition with captopril (100mg/kg/day). RESULTS ACE inhibition and/or HS diet eliminated endothelium-dependent arteriolar dilation to acetylcholine, endothelium-independent dilation to the NO donor sodium nitroprusside, the prostacyclin analogs carbacyclin and iloprost, and the KATP channel opener cromakalim; and eliminated arteriolar constriction during KATP channel blockade with glibenclamide. Scavenging of superoxide radicals and low dose ANG II infusion (25ng/kg/min, subcutaneous) reduced oxidant stress and restored arteriolar dilation in arterioles of HS-fed hamsters. Vasoconstriction to topically-applied ANG II was unaffected by HS diet while arteriolar responses to elevation of superfusion solution PO2 were unaffected (5% O2, 10% O2) or reduced (21% O2) by HS diet. CONCLUSIONS These findings indicate that sustained exposure to low levels of circulating ANG II leads to widespread dysfunction in endothelium-dependent and independent vascular relaxation mechanisms in cheek pouch arterioles by increasing vascular oxidant stress, but does not potentiate O2- or ANG II-induced constriction of arterioles in the distal microcirculation of normotensive hamsters.
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