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Birnbaum F, Eguchi A, Pardon G, Chang ACY, Blau HM. Tamoxifen treatment ameliorates contractile dysfunction of Duchenne muscular dystrophy stem cell-derived cardiomyocytes on bioengineered substrates. NPJ Regen Med 2022; 7:19. [PMID: 35304486 PMCID: PMC8933505 DOI: 10.1038/s41536-022-00214-x] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2021] [Accepted: 02/15/2022] [Indexed: 02/06/2023] Open
Abstract
Duchenne muscular dystrophy (DMD) is a progressive genetic myopathy that leads to heart failure from dilated cardiomyopathy by early adulthood. Recent evidence suggests that tamoxifen, a selective estrogen receptor modulator widely used to treat breast cancer, ameliorates DMD cardiomyopathy. However, the mechanism of action of 4-hydroxytamoxifen, the active metabolite of tamoxifen, on cardiomyocyte function remains unclear. To examine the effects of chronic 4-hydroxytamoxifen treatment, we used state-of-the-art human-induced pluripotent stem cell-derived cardiomyocytes (iPSC-CMs) and a bioengineered platform to model DMD. We assessed the beating rate and beating velocity of iPSC-CMs in monolayers and as single cells on micropatterns that promote a physiological cardiomyocyte morphology. We found that 4-hydroxytamoxifen treatment of DMD iPSC-CMs decreased beating rate, increased beating velocity, and ameliorated calcium-handling deficits, leading to prolonged viability. Our study highlights the utility of a bioengineered iPSC-CM platform for drug testing and underscores the potential of repurposing tamoxifen as a therapy for DMD cardiomyopathy.
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Affiliation(s)
- Foster Birnbaum
- Baxter Laboratory for Stem Cell Biology, Department of Microbiology and Immunology, Stanford University School of Medicine, Stanford University, Stanford, CA, USA
| | - Asuka Eguchi
- Baxter Laboratory for Stem Cell Biology, Department of Microbiology and Immunology, Stanford University School of Medicine, Stanford University, Stanford, CA, USA.,Stanford Cardiovascular Institute, Stanford University School of Medicine, Stanford, CA, USA
| | - Gaspard Pardon
- Baxter Laboratory for Stem Cell Biology, Department of Microbiology and Immunology, Stanford University School of Medicine, Stanford University, Stanford, CA, USA.,Stanford Cardiovascular Institute, Stanford University School of Medicine, Stanford, CA, USA
| | - Alex C Y Chang
- Baxter Laboratory for Stem Cell Biology, Department of Microbiology and Immunology, Stanford University School of Medicine, Stanford University, Stanford, CA, USA. .,Stanford Cardiovascular Institute, Stanford University School of Medicine, Stanford, CA, USA. .,Department of Cardiology and Shanghai Institute of Precision Medicine, Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China.
| | - Helen M Blau
- Baxter Laboratory for Stem Cell Biology, Department of Microbiology and Immunology, Stanford University School of Medicine, Stanford University, Stanford, CA, USA. .,Stanford Cardiovascular Institute, Stanford University School of Medicine, Stanford, CA, USA.
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Tran QK. Reciprocality Between Estrogen Biology and Calcium Signaling in the Cardiovascular System. Front Endocrinol (Lausanne) 2020; 11:568203. [PMID: 33133016 PMCID: PMC7550652 DOI: 10.3389/fendo.2020.568203] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/31/2020] [Accepted: 08/19/2020] [Indexed: 12/30/2022] Open
Abstract
17β-Estradiol (E2) is the main estrogenic hormone in the body and exerts many cardiovascular protective effects. Via three receptors known to date, including estrogen receptors α (ERα) and β (ERβ) and the G protein-coupled estrogen receptor 1 (GPER, aka GPR30), E2 regulates numerous calcium-dependent activities in cardiovascular tissues. Nevertheless, effects of E2 and its receptors on components of the calcium signaling machinery (CSM), the underlying mechanisms, and the linked functional impact are only beginning to be elucidated. A picture is emerging of the reciprocality between estrogen biology and Ca2+ signaling. Therein, E2 and GPER, via both E2-dependent and E2-independent actions, moderate Ca2+-dependent activities; in turn, ERα and GPER are regulated by Ca2+ at the receptor level and downstream signaling via a feedforward loop. This article reviews current understanding of the effects of E2 and its receptors on the cardiovascular CSM and vice versa with a focus on mechanisms and combined functional impact. An overview of the main CSM components in cardiovascular tissues will be first provided, followed by a brief review of estrogen receptors and their Ca2+-dependent regulation. The effects of estrogenic agonists to stimulate acute Ca2+ signals will then be reviewed. Subsequently, E2-dependent and E2-independent effects of GPER on components of the Ca2+ signals triggered by other stimuli will be discussed. Finally, a case study will illustrate how the many mechanisms are coordinated to moderate Ca2+-dependent activities in the cardiovascular system.
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Nagy S, Hafner P, Schmidt S, Rubino-Nacht D, Schädelin S, Bieri O, Fischer D. Tamoxifen in Duchenne muscular dystrophy (TAMDMD): study protocol for a multicenter, randomized, placebo-controlled, double-blind phase 3 trial. Trials 2019; 20:637. [PMID: 31752977 PMCID: PMC6869203 DOI: 10.1186/s13063-019-3740-6] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2019] [Accepted: 09/21/2019] [Indexed: 12/25/2022] Open
Abstract
Background Duchenne muscular dystrophy (DMD) is an inherited neuromuscular disorder of childhood with a devastating disease course. Several targeted gene therapies and molecular approaches have been or are currently being tested in clinical trials; however, a causative therapy is still not available and best supportive care is limited to oral glucocorticoids with numerous long-term side effects. Tamoxifen is a selective estrogen receptor regulator, and shows antioxidant actions and regulatory roles in the calcium homeostasis besides its antitumor activity. In a mouse model of DMD, oral tamoxifen significantly improved muscle strength and reduced muscle fatigue. This multicenter, randomized, double-blind, placebo-controlled phase III trial aims to demonstrate safety and efficacy of tamoxifen over placebo in pediatric patients with DMD. After completion of the double-blind phase, an open-label extension of the study will be offered to all participants. Methods/design At least 71 ambulant and up to 20 nonambulant patients with DMD are planned to be enrolled at multiple European sites. Patients will be randomly assigned to receive either tamoxifen 20 mg or placebo daily over 48 weeks. In the open-label extension phase, all patients will be offered tamoxifen for a further 48 weeks. The primary endpoint of the double-blind phase is defined as the change of the D1 domain of the motor function measure in ambulant patients or a change of the D2 domain in nonambulant patients under tamoxifen compared to placebo. Secondary outcome measures include change in timed function tests, quantitative muscle testing, and quantitative magnetic resonance imaging of thigh muscles. Laboratory analyses including biomarkers of tamoxifen metabolism and muscle dystrophy will also be assessed. Discussion The aim of the study is to investigate whether tamoxifen can reduce disease progression in ambulant and nonambulant patients with DMD over 48 weeks. Motor function measures comprise the primary endpoint, whereas further clinical and radiological assessments and laboratory biomarkers are performed to provide more data on safety and efficacy. An adjacent open-label extension phase is planned to test if earlier initiation of the treatment with tamoxifen (verum arm of double-blind phase) compared to a delayed start can reduce disease progression more efficiently. Trial registration ClinicalTrials.gov, NCT03354039. Registered on 27 November 2017.
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Affiliation(s)
- Sara Nagy
- Division of Developmental- and Neuropaediatrics, University Children's Hospital Basel (UKBB), University of Basel, Spitalstrasse 33, Postfach, 4031, Basel, Switzerland. .,Department of Neurology, University Hospital Basel, University of Basel, Petersgraben 4, 4031, Basel, Switzerland.
| | - Patricia Hafner
- Division of Developmental- and Neuropaediatrics, University Children's Hospital Basel (UKBB), University of Basel, Spitalstrasse 33, Postfach, 4031, Basel, Switzerland
| | - Simone Schmidt
- Division of Developmental- and Neuropaediatrics, University Children's Hospital Basel (UKBB), University of Basel, Spitalstrasse 33, Postfach, 4031, Basel, Switzerland
| | - Daniela Rubino-Nacht
- Division of Developmental- and Neuropaediatrics, University Children's Hospital Basel (UKBB), University of Basel, Spitalstrasse 33, Postfach, 4031, Basel, Switzerland
| | - Sabine Schädelin
- Clinical Trial Unit, University of Basel, Schanzenstrasse 55, 4056, Basel, Switzerland
| | - Oliver Bieri
- Department of Radiology, Division of Radiological Physics, University Hospital Basel, University of Basel, Petersgraben 4, 4031, Basel, Switzerland
| | - Dirk Fischer
- Division of Developmental- and Neuropaediatrics, University Children's Hospital Basel (UKBB), University of Basel, Spitalstrasse 33, Postfach, 4031, Basel, Switzerland
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Getter T, Suh S, Hoang T, Handa JT, Dong Z, Ma X, Chen Y, Blackshaw S, Palczewski K. The selective estrogen receptor modulator raloxifene mitigates the effect of all- trans-retinal toxicity in photoreceptor degeneration. J Biol Chem 2019; 294:9461-9475. [PMID: 31073029 DOI: 10.1074/jbc.ra119.008697] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2019] [Revised: 05/08/2019] [Indexed: 12/19/2022] Open
Abstract
The retinoid cycle is a metabolic process in the vertebrate retina that continuously regenerates 11-cis-retinal (11-cisRAL) from the all-trans-retinal (atRAL) isomer. atRAL accumulation can cause photoreceptor degeneration and irreversible visual dysfunction associated with incurable blinding retinal diseases, such as Stargardt disease, retinitis pigmentosa (RP), and atrophic age-related macular degeneration (AMD). The underlying cellular mechanisms leading to retinal degeneration remain uncertain, although previous studies have shown that atRAL promotes calcium influx associated with cell apoptosis. To identify compounds that mitigate the effects of atRAL toxicity, here we developed an unbiased and robust image-based assay that can detect changes in intracellular calcium levels in U2OS cells. Using our assay in a high-throughput screen of 2,400 compounds, we noted that selective estrogen receptor modulators (SERMs) potently stabilize intracellular calcium and thereby counteract atRAL-induced toxicity. In a light-induced retinal degeneration mouse model (Abca4 -/- Rdh8 -/-), raloxifene (a benzothiophene-type scaffold SERM) prevented the onset of photoreceptor apoptosis and thus protected the retina from degeneration. The minor structural differences between raloxifene and one of its derivatives (Y 134) had a major impact on calcium homeostasis after atRAL exposure in vitro, and we verified this differential impact in vivo In summary, the SERM raloxifene has structural and functional neuroprotective effects in the retina. We propose that the highly sensitive image-based assay developed here could be applied for the discovery of additional drug candidates preventing photoreceptor degeneration.
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Affiliation(s)
- Tamar Getter
- From the Gavin Herbert Eye Institute, Department of Ophthalmology, University of California, Irvine, California 92697, .,the Department of Pharmacology, Case Western Reserve University, Cleveland, Ohio 44106
| | - Susie Suh
- From the Gavin Herbert Eye Institute, Department of Ophthalmology, University of California, Irvine, California 92697.,the Department of Pharmacology, Case Western Reserve University, Cleveland, Ohio 44106
| | - Thanh Hoang
- the Solomon H. Snyder Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205
| | - James T Handa
- the Wilmer Eye Institute, Department of Ophthalmology, Johns Hopkins University School of Medicine, Baltimore, Maryland 21287
| | | | - Xiuli Ma
- Polgenix Inc., Irvine, California 92617
| | - Yuanyuan Chen
- the Department of Ophthalmology, School of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, and.,the McGowan Institute of Regenerative Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania 15213
| | - Seth Blackshaw
- the Solomon H. Snyder Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205
| | - Krzysztof Palczewski
- From the Gavin Herbert Eye Institute, Department of Ophthalmology, University of California, Irvine, California 92697, .,the Department of Pharmacology, Case Western Reserve University, Cleveland, Ohio 44106
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Wittnich C, Wallen J, Belanger M. The Role of 17β-Estradiol in Myocardial Hypertrophy in Females in the Presence and Absence of Hypertension. Cardiovasc Drugs Ther 2016; 29:347-53. [PMID: 26109517 DOI: 10.1007/s10557-015-6603-8] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
PURPOSE There are gender-differences in the development of cardiac hypertrophy, which appear to be related, in part, to sex hormones. This report gives an overview of this relationship and reports on original data assessing how varying levels of plasma 17β-estradiol determine relative heart size, in vivo function, in hypertensive versus normotensive rats. METHODS Female spontaneously hypertensive rats (SHR) and normotensive Wistar-Kyoto (WKY) rats were either surgically neutered or sham operated at 21 days of age. A subgroup of neutered females received 17β-estradiol replacement. At 6 months, in vivo heart function was measured, the heart/body weight ratio (mg/g) was assessed as a measure of hypertrophy and correlated with plasma 17β-estradiol. RESULTS There was a significant positive relationship between plasma 17β-estradiol and heart/body weight ratio in both WKY (R = 0.509, P = 0.011) and SHR females (R = 0.359, P = 0.032). Interestingly, the slope of this relationship was 2-fold steeper in the WKY females, suggesting a blunted effect in the SHR, whose hearts also had 35 % lower ERβ content. With increasing plasma estradiol levels, WKY females showed improved LV function while SHR females showed impaired LV relaxation. CONCLUSIONS Plasma estradiol modulates relative heart mass in both normotensive and hypertensive female rats. With any increase in plasma 17β-estradiol, hypertensive females show a blunted response compared with the normotensive females, which may be related to a reduced estrogen receptor expression in the presence of hypertension. In contrast to normotensive females, hypertensive females showed impaired function with increases in plasma 17β-estradiol.
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Affiliation(s)
- Carin Wittnich
- From the Departments of Physiology (J.W., C.W., M.B) and Surgery (C.W.) and The Cardiovascular Sciences Collaborative Program (W.J.W., C.W.), University of Toronto, 1 King's College Circle, Medical Sciences Bldg. Room 7256, Toronto, Ontario, Canada, M5S 1A8,
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Cho E, Zhang Y, Pruznak A, Kim HM. Effect of tamoxifen on fatty degeneration and atrophy of rotator cuff muscles in chronic rotator cuff tear: An animal model study. J Orthop Res 2015; 33:1846-53. [PMID: 26121952 DOI: 10.1002/jor.22964] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/09/2015] [Accepted: 06/03/2015] [Indexed: 02/04/2023]
Abstract
Fatty degeneration of the rotator cuff muscles is an irreversible change resulting from chronic rotator cuff tear and is associated with poor clinical outcomes following rotator cuff repair. We evaluated the effect of Tamoxifen, a competitive estrogen receptor inhibitor, on fatty degeneration using a mouse model for chronic rotator cuff tear. Sixteen adult mice were divided into two diet groups (Tamoxifen vs. Regular) and subjected to surgical creation of a large rotator cuff tear and suprascapular nerve transection in their left shoulder with the right shoulder serving as a control. The rotator cuff muscles were harvested at 16 weeks and subjected to histology and RT-PCR for adipogenic and myogenic markers. Histology showed substantially decreased atrophy and endomysial inflammation in Tamoxifen group, but no significant differences in the amount of intramuscular adipocytes and lipid droplets compared to the Regular group. With RT-PCR, the operated shoulders showed significant upregulation of myogenin and PPAR-γ, and downregulation of myostatin compared to the nonsurgical shoulder. No significant differences of gene expression were found between the two diet groups. Our study demonstrated that tamoxifen diet leads to decreased muscle atrophy and inflammatory changes following chronic rotator cuff tear, but has no apparent effect on adipogenesis.
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Affiliation(s)
- Edward Cho
- Department of Orthopaedics and Rehabilitation, Penn State College of Medicine, Hershey, Pennsylvania
| | - Yue Zhang
- Department of Orthopaedics and Rehabilitation, Penn State College of Medicine, Hershey, Pennsylvania
| | - Anne Pruznak
- Cellular and Molecular Physiology, Penn State College of Medicine, Hershey, Pennsylvania
| | - H Mike Kim
- Department of Orthopaedics and Rehabilitation, Penn State College of Medicine, Hershey, Pennsylvania
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Jennings P, Schwarz M, Landesmann B, Maggioni S, Goumenou M, Bower D, Leonard MO, Wiseman JS. SEURAT-1 liver gold reference compounds: a mechanism-based review. Arch Toxicol 2014; 88:2099-133. [DOI: 10.1007/s00204-014-1410-8] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2014] [Accepted: 10/01/2014] [Indexed: 12/20/2022]
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Dorchies OM, Reutenauer-Patte J, Dahmane E, Ismail HM, Petermann O, Patthey- Vuadens O, Comyn SA, Gayi E, Piacenza T, Handa RJ, Décosterd LA, Ruegg UT. The anticancer drug tamoxifen counteracts the pathology in a mouse model of duchenne muscular dystrophy. THE AMERICAN JOURNAL OF PATHOLOGY 2013; 182:485-504. [PMID: 23332367 DOI: 10.1016/j.ajpath.2012.10.018] [Citation(s) in RCA: 61] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/18/2012] [Revised: 09/17/2012] [Accepted: 10/07/2012] [Indexed: 12/18/2022]
Abstract
Duchenne muscular dystrophy (DMD) is a severe disorder characterized by progressive muscle wasting,respiratory and cardiac impairments, and premature death. No treatment exists so far, and the identification of active substances to fight DMD is urgently needed. We found that tamoxifen, a drug used to treat estrogen-dependent breast cancer, caused remarkable improvements of muscle force and of diaphragm and cardiac structure in the mdx(5Cv) mouse model of DMD. Oral tamoxifen treatment from 3 weeks of age for 15 months at a dose of 10 mg/kg/day stabilized myofiber membranes, normalized whole body force, and increased force production and resistance to repeated contractions of the triceps muscle above normal values. Tamoxifen improved the structure of leg muscles and diminished cardiac fibrosis by~ 50%. Tamoxifen also reduced fibrosis in the diaphragm, while increasing its thickness,myofiber count, and myofiber diameter, thereby augmenting by 72% the amount of contractile tissue available for respiratory function. Tamoxifen conferred a markedly slower phenotype to the muscles.Tamoxifen and its metabolites were present in nanomolar concentrations in plasma and muscles,suggesting signaling through high-affinity targets. Interestingly, the estrogen receptors ERa and ERb were several times more abundant in dystrophic than in normal muscles, and tamoxifen normalized the relative abundance of ERb isoforms. Our findings suggest that tamoxifen might be a useful therapy for DMD.
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MESH Headings
- Animals
- Antineoplastic Agents/pharmacology
- Antineoplastic Agents/therapeutic use
- Behavior, Animal/drug effects
- Biomarkers/metabolism
- Biomechanical Phenomena/drug effects
- Body Weight/drug effects
- Creatine Kinase/blood
- Diaphragm/pathology
- Diaphragm/physiopathology
- Disease Models, Animal
- Feeding Behavior/drug effects
- Fibrosis
- Mice
- Muscle Contraction/drug effects
- Muscle Fibers, Skeletal/drug effects
- Muscle Fibers, Skeletal/pathology
- Muscular Dystrophy, Animal/blood
- Muscular Dystrophy, Animal/drug therapy
- Muscular Dystrophy, Animal/pathology
- Muscular Dystrophy, Animal/physiopathology
- Muscular Dystrophy, Duchenne/blood
- Muscular Dystrophy, Duchenne/drug therapy
- Muscular Dystrophy, Duchenne/pathology
- Muscular Dystrophy, Duchenne/physiopathology
- Myocardium/pathology
- Organ Size/drug effects
- Receptors, Estrogen/metabolism
- Tamoxifen/blood
- Tamoxifen/pharmacology
- Tamoxifen/therapeutic use
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Affiliation(s)
- Olivier M Dorchies
- Department of Pharmacology, University of Geneva and University of Lausanne, Geneva, Switzerland.
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Wittnich C, Tan L, Wallen J, Belanger M. Sex differences in myocardial metabolism and cardiac function: an emerging concept. Pflugers Arch 2013; 465:719-29. [DOI: 10.1007/s00424-013-1232-1] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2013] [Accepted: 01/30/2013] [Indexed: 12/29/2022]
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Tamoxifen promotes superoxide production in platelets by activation of PI3-kinase and NADPH oxidase pathways. Thromb Res 2011; 129:36-42. [PMID: 21875743 DOI: 10.1016/j.thromres.2011.08.010] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2011] [Revised: 07/06/2011] [Accepted: 08/03/2011] [Indexed: 12/31/2022]
Abstract
BACKGROUND Tamoxifen is a selective estrogen receptor antagonist that is widely used for treatment and prevention of breast cancer. However, tamoxifen use can lead to an increased incidence of thrombotic events. The reason for this adverse event remains unknown. Previous studies showed that tamoxifen and its active metabolite Z-4-hydroxytamoxifen rapidly increased intracellular free calcium ([Ca(2+)](i)) in human platelets by a non-genomic mechanism that involved the activation of phospholipase C. Platelets play a pivotal role in thrombosis and Ca(2+) elevation is a central event in platelet activation. Therefore the mechanism by which tamoxifen activated Ca(2+) entry into platelets was investigated. METHODS [Ca(2+)](i) was measured using the fluorescent indicator fura-2 and reactive oxygen species were measured using lucigenin in isolated human platelets. RESULTS Tamoxifen analogs E-4-hydroxytamoxifen, with weak activity at the nuclear estrogen receptor and Z-4-hydroxytamoxifen, with strong activity at nuclear estrogen receptor, were equally active at increasing [Ca(2+)](i) and synergizing with ADP and thrombin to increase [Ca(2+)](i) in platelets. This result suggests that the effects of tamoxifen and E- and Z-4-hydroxytamoxifen to increase [Ca(2+)](i) are not mediated by the classical genomic estrogen receptor. The effects of tamoxifen to increase [Ca(2+)](i) were strongly inhibited by apocynin and apocynin dimer. This suggests that tamoxifen activates NADPH oxidase which leads to superoxide generation and in turn caused an increase in [Ca(2+)](i). Free radical scavengers TEMPO and TEMPOL also inhibited tamoxifen-induced [Ca(2+)](i) elevation. Inhibition of phosphoinositide-3-kinase (PI3-kinase), an upstream effector of NADPH oxidase with wortmannin and LY-294,002 also caused substantial inhibition of tamoxifen-induced elevation of [Ca(2+)](i). CONCLUSION Tamoxifen increases [Ca(2+)](i) in human platelets by a non-genomic mechanism. Tamoxifen activates phospholipase Cγ as well as PI3-kinase and NADPH oxidase pathway to generate superoxide which causes the release of Ca(2+) from the endoplasmic reticulum, and promotes Ca(2+) influx into the platelets.
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Huang CC, Huang CJ, Cheng JS, Liu SI, Chen IS, Tsai JY, Chou CT, Lin MC, Jan CR. Effect of clomiphene on [Ca2+]irises and cell viability in rabbit corneal epithelial cells. Drug Dev Res 2008. [DOI: 10.1002/ddr.20253] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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Beca S, Pavlov E, Kargacin ME, Aschar-Sobbi R, French RJ, Kargacin GJ. Inhibition of a cardiac sarcoplasmic reticulum chloride channel by tamoxifen. Pflugers Arch 2008; 457:121-35. [PMID: 18458943 DOI: 10.1007/s00424-008-0510-9] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2007] [Revised: 03/21/2008] [Accepted: 03/25/2008] [Indexed: 11/25/2022]
Abstract
Anion and cation channels present in the sarcoplasmic reticulum (SR) are believed to be necessary to maintain the electroneutrality of SR membrane during Ca(2+) uptake by the SR Ca(2+) pump (SERCA). Here we incorporated canine cardiac SR ion channels into lipid bilayers and studied the effects of tamoxifen and other antiestrogens on these channels. A Cl(-) channel was identified exhibiting multiple subconductance levels which could be divided into two primary conductance bands. Tamoxifen decreases the time the channel spends in its higher, voltage-sensitive band and the mean channel current. The lower, voltage-insensitive, conductance band is not affected by tamoxifen, nor is a K(+) channel present in the cardiac SR preparation. By examining SR Ca(2+) uptake, SERCA ATPase activity, and SR ion channels in the same preparation, we also estimated SERCA transport current, SR Cl(-) and K(+) currents, and the density of SERCA, Cl(-), and K(+) channels in cardiac SR membranes.
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Affiliation(s)
- Sanja Beca
- Department of Physiology and Biophysics, University of Calgary, Calgary, Alberta, T2N 4N1, Canada
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Wray S, Noble K. Sex hormones and excitation-contraction coupling in the uterus: the effects of oestrous and hormones. J Neuroendocrinol 2008; 20:451-61. [PMID: 18266942 DOI: 10.1111/j.1365-2826.2008.01665.x] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
In this review, we examine how far the increased understanding that we have of the events in excitation contraction can explain the effects of the oestrous cycle and sex hormones on uterine function. Observational studies of electrical and mechanical activity in the rat myometrium have shown a relative quiescence during pro-oestrous, with little propagation of any electrical events. Thus, uterine activity can be said to approximately inversely reflect plasma 17beta-oestradiol concentrations. We show that Ca(2+) signalling and mechanical activity are greatest in metoestrous and dioestrous compared to pro-oestrous and oestrous. These data are discussed in terms of hormonal effects on Ca(2+) and K(+) channels. Finally, the influence of sex hormones on lipid rafts and caveolae are considered and discussed in relation to recent findings on their role in uterine signalling and contractility, and cholesterol levels and obesity.
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Affiliation(s)
- S Wray
- The Physiological Department, School of Biomedical Sciences, University of Liverpool, Liverpool, UK.
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In silico elucidation of the molecular mechanism defining the adverse effect of selective estrogen receptor modulators. PLoS Comput Biol 2007; 3:e217. [PMID: 18052534 PMCID: PMC2098847 DOI: 10.1371/journal.pcbi.0030217] [Citation(s) in RCA: 73] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2007] [Accepted: 09/26/2007] [Indexed: 12/12/2022] Open
Abstract
Early identification of adverse effect of preclinical and commercial drugs is crucial in developing highly efficient therapeutics, since unexpected adverse drug effects account for one-third of all drug failures in drug development. To correlate protein–drug interactions at the molecule level with their clinical outcomes at the organism level, we have developed an integrated approach to studying protein–ligand interactions on a structural proteome-wide scale by combining protein functional site similarity search, small molecule screening, and protein–ligand binding affinity profile analysis. By applying this methodology, we have elucidated a possible molecular mechanism for the previously observed, but molecularly uncharacterized, side effect of selective estrogen receptor modulators (SERMs). The side effect involves the inhibition of the Sacroplasmic Reticulum Ca2+ ion channel ATPase protein (SERCA) transmembrane domain. The prediction provides molecular insight into reducing the adverse effect of SERMs and is supported by clinical and in vitro observations. The strategy used in this case study is being applied to discover off-targets for other commercially available pharmaceuticals. The process can be included in a drug discovery pipeline in an effort to optimize drug leads and reduce unwanted side effects. Early identification of the side effects of preclinical and commercial drugs is crucial in developing highly efficient therapeutics, as unexpected side effects account for one-third of all drug failures in drug development and lead to drugs being withdrawn from the market. Compared with the experimental identification of off-target proteins that cause side effects, computational approaches not only save time and costs by providing a candidate list of potential off-targets, but also provide insight into understanding the molecular mechanisms of protein–drug interactions. In this paper we describe an integrated approach to identifying similar drug binding pockets across protein families that have different global shapes. In a case study, we elucidate a possible molecular mechanism for the observed side effects of selective estrogen receptor modulators (SERMs), which are widely used to treat and prevent breast cancer and other diseases. The prediction provides molecular insight into reducing the side effects of SERMs and is supported by clinical and biochemical observations. The strategy used in this case study is being applied to discover off-targets for other commercially available pharmaceuticals and to repurpose existing safe pharmaceuticals to treat different diseases. The process can be included in a drug discovery pipeline in an effort to optimize drug leads, reduce unwanted side effects, and accelerate development of new drugs.
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Geraldes P, Gosselin H, Tanguay JF, Clément R, Calderone A. Tamoxifen treatment of myocardial infarcted female rats exacerbates scar formation. Pflugers Arch 2007; 454:385-93. [PMID: 17285298 DOI: 10.1007/s00424-007-0215-5] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2006] [Accepted: 01/15/2007] [Indexed: 12/01/2022]
Abstract
Hormonal replacement therapy in postmenopausal women was associated with an increased incidence of nonfatal myocardial infarction. Selective estrogen receptor modulators were considered an alternative pharmacological approach. However, selective estrogen receptor modulators acting via estrogen receptor-dependent and receptor-independent mechanisms may negatively influence cardiac remodeling. The present study tested the hypothesis that tamoxifen (TAM) treatment after coronary artery ligation compromised scar formation. TAM administration (10 mg kg(-1) day(-1) for 3 weeks) to postmyocardial infarcted (MI) female adult rats significantly increased scar surface area (TAM+MI = 0.67 +/- 0.08 vs MI = 0.45 +/- 0.06 cm(2)) and weight (TAM+MI = 0.071 +/- 0.007 vs MI = 0.050 +/- 0.006 grams). In the infarct region, a significant decrease (p < 0.05) of small calibre vessels (lumen diameter <50 microm) was observed in TAM treated post-MI rats (4.5 +/- 0.8 vessels/mm(2)), as compared to untreated MI rats (7 +/- 0.7 vessels/mm(2)). Consistent with the latter finding, 4-OH TAM caused a dose-dependent suppression of vascular endothelial growth factor (VEGF)-stimulated (10(-9) mol/l) capillarity-like tubule formation by rat aortic endothelial cells in vitro via an estrogen receptor-independent mechanism. These data have demonstrated that TAM treatment of post-MI female rats exacerbated scar formation and may have occurred at least in part via the attenuation of new vessel formation in the infarct region.
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Affiliation(s)
- Pedro Geraldes
- Research Centre, Montreal Heart Institute, 5000 Belanger Street East, Montreal, Quebec, H1T 1C8, Canada
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16
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Olson ML, Kargacin ME, Honeyman TW, Ward CA, Kargacin GJ. Effects of Phytoestrogens on Sarcoplasmic/Endoplasmic Reticulum Calcium ATPase 2a and Ca2+Uptake into Cardiac Sarcoplasmic Reticulum. J Pharmacol Exp Ther 2005; 316:628-35. [PMID: 16227472 DOI: 10.1124/jpet.105.092940] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Phytoestrogens are naturally occurring estrogenic compounds found in plants and plant products. These compounds are also known to exert cellular effects independent of their interactions with estrogen receptors. We studied the effects of the phytoestrogens phloretin, phloridzin, genistein, and biochanin A on Ca(2+) uptake into the cardiac muscle sarcoplasmic reticulum (SR). Genistein and biochanin A did not affect SR Ca(2+) uptake. On the other hand, phloretin and phloridzin decreased the maximum velocity of SR Ca(2+) uptake but did not affect the Hill coefficient or the Ca(2+) sensitivity of uptake. Measurements of the ATPase activity of the cardiac SR Ca(2+) pump (SERCA2a) revealed direct inhibitory effects of phloretin and phloridzin on SERCA2a. Neither compound induced a detectable change in the permeability of the SR membrane to Ca(2+). These results indicate that phloretin and phloridzin inhibit cardiac SR Ca(2+) uptake by directly inhibiting SERCA2a.
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Affiliation(s)
- Marnie L Olson
- Department of Physiology and Biophysics, University of Calgary, Canada
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17
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Willett MC, Dluzen DE. Tamoxifen increases methamphetamine-evoked dopamine output from superfused striatal tissue fragments of male mice. Brain Res 2004; 1029:186-94. [PMID: 15542073 DOI: 10.1016/j.brainres.2004.09.043] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/29/2004] [Indexed: 11/16/2022]
Abstract
The antiestrogen, tamoxifen (TMX), has been shown to function as a neuroprotectant against the nigrostriatal dopaminergic (NSDA) neurotoxin, methamphetamine (MA), within male mice. In the present report, we examined the effects of a combined infusion of TMX and MA within superfused striatal tissue fragments of male mice as an approach to understand some of the bases for TMX to function as a NSDA neuroprotectant within male mice. In Experiment 1, a coinfusion of TMX at 1, 10, or 100 pg/ml were all equally effective in increasing MA-evoked dopamine (DA) output as compared with a 0 pg/ml (control) dose. In Experiment 2, we tested whether this effect of TMX was specific for MA-evoked DA output by coinfusing TMX with a depolarizing concentration of potassium chloride (K+ -30 mM). No statistically significant differences were obtained between superfusions of striatal tissue fragments stimulated with K+ in the presence or absence of TMX (100 pg/ml). In Experiment 3, we assessed whether these effects of TMX may be exerted upon the dopamine transporter (DAT) by coinfusing DA (1 microM) in the presence or absence of TMX (100 pg/ml). No differences in DA recovery rates were obtained between superfusions performed in the presence or absence of TMX. Taken together, these results show that the striatum of male mice is very sensitive to the modulatory effects of TMX upon MA-evoked DA output. These effects of TMX appear to be relatively specific for MA-evoked DA output, as K+ -stimulated DA was not altered by TMX, and do not appear to exert these effects by altering dopamine transporter function.
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Affiliation(s)
- Matthew C Willett
- Department of Anatomy, Northeastern Ohio Universities College of Medicine (NEOUCOM), 4209 State Route 44, PO Box 95, Rootstown, OH 44272-0095, USA
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18
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Yuill KH, Borg JJ, Ridley JM, Milnes JT, Witchel HJ, Paul AA, Kozlowski RZ, Hancox JC. Potent inhibition of human cardiac potassium (HERG) channels by the anti-estrogen agent clomiphene—without QT interval prolongation. Biochem Biophys Res Commun 2004; 318:556-61. [PMID: 15120636 DOI: 10.1016/j.bbrc.2004.04.063] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2004] [Indexed: 10/26/2022]
Abstract
The acquired form of the long-QT syndrome (LQTS) is a major safety consideration for the development and subsequent use of both cardiac and non-cardiac drugs; it is usually associated with pharmacological inhibition of cardiac HERG-encoded potassium channels. Clomiphene is an anti-estrogen agent used extensively in the treatment of infertility and is not associated with a risk of QT interval prolongation, in contrast to a structurally related compound tamoxifen. We describe here a potent inhibitory effect (IC(50) = 0.18 microM) of clomiphene on HERG ionic current (I(HERG)) recorded from a mammalian cell line expressing HERG channels. Inhibition of I(HERG) by clomiphene showed voltage-dependence and developed quickly following membrane depolarisation, indicating contingency of block on HERG channel gating. At 100 nM, clomiphene and the related anti-estrogen tamoxifen produced similar levels of I(HERG) blockade (p > 0.05). Experiments on guinea-pig isolated perfused hearts revealed that, despite its inhibitory action on I(HERG), clomiphene produced no significant effect at 1 microM on uncorrected QT interval (p > 0.1) nor on rate-corrected QT interval (QT(c); p > 0.1 for QT(c) determined using Van de Water's formula). The disparity between clomiphene's potent I(HERG) inhibition and its lack of effect on the QT interval underscores the notion that I(HERG) pharmacology may best be used alongside other screening methods when investigating the QT-prolonging tendency and related cardiotoxicity of non-cardiac drugs.
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Affiliation(s)
- Kathryn H Yuill
- Department of Physiology and Cardiovascular Research Laboratories, School of Medical Sciences, University Walk, Bristol BS8 1TD, UK
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19
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Brasier G, Tikellis C, Xuereb L, Craigie J, Casley D, Kovacs CS, Fudge NJ, Kalnins R, Cooper ME, Wookey PJ. Novel hexad repeats conserved in a putative transporter with restricted expression in cell types associated with growth, calcium exchange and homeostasis. Exp Cell Res 2004; 293:31-42. [PMID: 14729055 DOI: 10.1016/j.yexcr.2003.10.002] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
A transport protein is described with 12 transmembrane spans. Within the cytoplasmic amino-terminal domain, several novel hexad repeats are conserved in human, mouse, rat and pig, four to six of which had the canonical form PS_S_H(+). In the carboxyl-terminal domain, a polyglutamate sequence (5-8) is conserved. Restricted expression of the transporter was identified in acidophil cells of the adult pituitary that secrete growth hormone and prolactin. In the fetus, expression was restricted to osteoclasts, chondrocytes, thyroid, pituitary, central nervous system, eye, liver and heart. In particular, expression was found in structures associated with rapid calcium exchange including the retina, cardiomyocytes and in the intraplacental yolk sac that expresses calcitropic molecules. Furthermore, expression found in osteoclasts and kidney, within the distal portions of nephrons and collecting ducts, was consistent with a role in calcium homeostasis. In human pituitary, four mRNA transcripts, and in mouse kidney, three mRNA transcripts were expressed. In developing mouse kidney, the amount of each transcript varied that suggested the multiple transcripts might be differentially expressed in different physiological states. We propose that the transporter is specific for a calcium-chelator complex and is important for growth and calcium metabolism.
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Affiliation(s)
- Geoffrey Brasier
- Department of Medicine, University of Melbourne, Parkville, Victoria, Australia
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20
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Borg JJ, Hancox JC, Hogg DS, James AF, Kozlowski RZ. Actions of the anti-oestrogen agent clomiphene on outward K+ currents in rat ventricular myocytes. Clin Exp Pharmacol Physiol 2004; 31:86-95. [PMID: 14756690 DOI: 10.1111/j.1440-1681.2004.03956.x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
1. The effects of clomiphene (CLM) on cardiac outward K+ current components from rat isolated ventricular myocytes were investigated using the whole-cell patch-clamp technique. Clomiphene (10 micromol/L) significantly inhibited both peak (Ipeak) and end-pulse (Ilate) outward currents (elicited by a 500 msec voltage step from -40 to +50 mV in the presence of K+-containing intracellular and extracellular solutions) by approximately 37% (n = 6; P < 0.01) and 49% (n = 6; P < 0.01), respectively. In contrast, CLM had no effect on outward currents when K+-free solutions were used. 2. A double-pulse protocol and Boltzmann fitting were used to separate individual K+ current components on the basis of their voltage-dependent inactivation properties. At potentials positive to -80 mV, two inactivating transient outward components (Ito) and (IKx) and a non-inactivating steady state component (Iss) could be distinguished. 3. Clomiphene inhibited both Ito and Iss. The maximal block of Ito and Iss induced by CLM (100 micromol/L) was approximately 61% (n = 5) and 43% (n = 5) with IC50 values of 1.54 +/- 0.39 and 2.2 +/- 0.4 micromol/L, respectively. In contrast, the peak magnitude of IKx was unaltered by CLM, although its time-course of inactivation was accelerated. 4. Further experiments whereby myocytes were superfused with the vasoactive peptide endothelin (ET)-1 (20 nmol/L) revealed that CLM (10 micro mol/L) completely abolished the ET-1-sensitive component of Iss. 5. Our findings demonstrate, for the first time, the effects of CLM on distinct cardiac K+ current components and show that CLM modulates the voltage-gated K+ current components Ito and IKx and inhibits the steady state outward current Iss in rat ventricular myocytes.
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Affiliation(s)
- John J Borg
- Department of Pharmacology, School of Medical Sciences, University of Bristol, University Walk, Bristol BS8 1TD, UK
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21
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González-Pérez J, Crespo MJ. Acute effects of toremifene on the vasculature of intact and menopause-induced rats. Vascul Pharmacol 2003; 40:205-11. [PMID: 14746827 DOI: 10.1016/j.vph.2003.06.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Clinical studies have shown that cardiovascular performance in postmenopausal women could be modified by treatment with selective estrogen receptor modulators (SERM). However, the mechanisms by which these drugs act on the cardiovascular system have not been elucidated. This work evaluates the effect of toremifene, a new member of the SERM family, on the vasculature of intact and ovariectomized adult Sprague-Dawley rats. The responsiveness of rings from the thoracic aorta to norepinephrine, potassium chloride, acetylcholine and sodium nitroprusside was assessed before and after 15 min of incubation with 1.0-microM toremifene. Toremifene displaced the concentration-response curve for norepinephrine-induced contractions to the right in both groups of animals. Moreover, the EC(50) values for the curves increased from 154+/-31 to 754+/-162 nM (P<.05) in intact rats and from 88+/-11 to 230+/-71 nM (P<.05) in ovariectomized rats. Toremifene also reduced contractile responses to potassium chloride (10-120 mM), displacing the entire curve to the right in both groups of animals without modifying the EC(50) values. The drug shifted the concentration-response curve for the acetylcholine-induced relaxation to the left and significantly increased E(max) values (18% for ovariectomized rats vs. 16% for controls) without affecting EC(50) values in either group tested. In addition, toremifene potentiated the relaxing responses to physiological doses (0.1-1.0 nM) of sodium nitroprusside in both groups, suggesting a direct effect at the level of the vascular smooth muscle. Acute toremifene incubation increased basal relaxation in aortic rings from both intact and ovariectomized rats. These results suggest that toremifene, by improving the functional status of the endothelium-smooth muscle unit, may have a beneficial effect on the cardiovascular status of menopause-induced rats.
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Affiliation(s)
- Jorge González-Pérez
- Department of Biology, University of Puerto Rico-Rio Piedras, San Juan, Puerto Rico
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22
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Curl CL, Wendt IR, Canny BJ, Kotsanas G. Effects of ovariectomy and 17 beta-oestradiol replacement on [Ca2+]i in female rat cardiac myocytes. Clin Exp Pharmacol Physiol 2003; 30:489-94. [PMID: 12823264 DOI: 10.1046/j.1440-1681.2003.03864.x] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
1. The present study investigated the effects of ovariectomy (OVX) and 17beta-oestradiol replacement on [Ca2+]i in rat freshly isolated cardiac myocytes. 2. Myocytes were isolated from the hearts of sham, OVX and OVX + 17beta-oestradiol-replaced female rats by enzymatic digestion with collagenase. Changes in [Ca2+]i in response to varied extracellular [Ca2+] were measured using the Ca2+-sensitive dye fura-2, with the contractile responses of each cell measured as cell shortening. 3. Increasing extracellular [Ca2+] resulted in increased [Ca2+]i in all three groups. Peak [Ca2+]i and the amplitude of the Ca2+ transient were significantly greater (P < 0.01) in cells from OVX animals compared with cells from both sham and 17beta-oestradiol-replaced OVX animals. 4. The time-course of decay of the Ca2+ transient was significantly faster (P < 0.02) in OVX cells compared with both sham and 17beta-oestradiol-replaced cells. In addition, time to 50% relaxation was significantly faster (P < 0.04) and extent of shortening significantly greater (P < 0.01) in OVX cells than in either sham or 17beta-oestradiol cells. 5. These data demonstrate clear differences in peak [Ca2+]i and the amplitude of the Ca2+ transient between OVX female rat cardiac myocytes compared with intact and 17beta-oestradiol-replaced OVX female rat cardiac myocytes. This suggests that oestrogen may play a long-term role in limiting Ca2+ entry into the cardiac myocyte.
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Affiliation(s)
- Claire L Curl
- Department of Physiology, Monash University, Melbourne, Victoria, Australia
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23
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Jan CR, An-Jen C, Chang HT, Roan CJ, Lu YC, Jiann BP, Ho CM, Huang JK. The anti-breast cancer drug tamoxifen alters Ca2+ movement in Chinese hamster ovary (CHO-K1) cells. Arch Toxicol 2003; 77:160-6. [PMID: 12632256 DOI: 10.1007/s00204-002-0420-0] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2002] [Accepted: 10/17/2002] [Indexed: 10/20/2022]
Abstract
The anti-breast cancer drug tamoxifen has recently been shown to cause an increase in intracellular free-Ca(2+) concentrations ([Ca(2+)](i)) in renal tubular cells, breast cells and bladder cells. Because tamoxifen is known to alter ovary function in human patients and in rats, the present study was aimed at exploring whether tamoxifen could alter Ca(2+) movement in Chinese hamster ovary (CHO-K1) cells. Cytosolic free-Ca(2+) levels in populations of cells have been explored by using fura-2 as a fluorescent Ca(2+) indicator. Tamoxifen at concentrations above 1 micro M increased [Ca(2+)](i) in a concentration-dependent manner with an EC(50) value of 8 micro M. The Ca(2+) signal was reduced by removing extracellular Ca(2+), but was not affected by nifedipine, verapamil, diltiazem or ICI 182,780 (an estrogen receptor antagonist). Pretreatment with 1 micro M thapsigargin (an endoplasmic reticulum Ca(2+) pump inhibitor) to deplete the endoplasmic reticulum Ca(2+) abolished 10 micro M tamoxifen-induced Ca(2+) release. Neither inhibition of phospholipase C with 2 micro M U73122 nor depletion of ryanodine-sensitive Ca(2+) stores with 50 micro M ryanodine affected tamoxifen-induced Ca(2+) release. Cell proliferation assays using ELISA revealed that overnight incubation with 5-10 micro M tamoxifen inhibited cell proliferation by 20%, and 20 micro M tamoxifen killed all cells. Together, the results suggest that, in CHO-K1 cells, tamoxifen induced a [Ca(2+)](i) increase by causing store-Ca(2+) release from the endoplasmic reticulum in an phospholipase C-independent manner, and by inducing Ca(2+) influx. The action of tamoxifen appears to be dissociated from estrogen receptor activation. Longer incubation with tamoxifen (>5 micro M) was cytotoxic.
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Affiliation(s)
- Chung-Ren Jan
- Department of Medical Education and Research, Kaohsiung Veterans General Hospital, 813, Kaohsiung, Taiwan.
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24
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Borg JJ, Yuill KH, Hancox JC, Spencer IC, Kozlowski RZ. Inhibitory effects of the antiestrogen agent clomiphene on cardiac sarcolemmal anionic and cationic currents. J Pharmacol Exp Ther 2002; 303:282-92. [PMID: 12235262 DOI: 10.1124/jpet.102.038901] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The aim of this study was to determine the effects of the antiestrogen agent clomiphene on cardiac anionic and cationic sarcolemmal ion channels. Whole-cell recordings were made from rat and guinea pig ventricular myocytes. Clomiphene inhibited the volume-regulated chloride current [I(Cl,vol), activated by cell swelling after hypotonic shock (approximately 145 mOsM)] with an IC(50) value of approximately 9.4 microM. In contrast, at concentrations up to 100 microM, clomiphene failed to inhibit both the chloride current activated by cyclic AMP (I(Cl,cAMP)) and the anionic background current (I(AB)). At 10 microM, clomiphene blocked the voltage-gated fast sodium current and the L-type calcium current (I(Ca,L)) in both species. The voltage-independent fractional block of I(Ca,L) induced by clomiphene (10 microM) was approximately 82%, this concentration also inhibited the inwardly rectifying K(+) current with a fractional current block of approximately 26% at -90 mV. Fractional block of outward current at +70 mV in rat was approximately 25%, implying that delayed rectifying K(+) channels were also affected by clomiphene. We conclude that clomiphene shows selectivity for I(Cl,vol) over I(Cl,cAMP) and I(AB) and therefore represents a useful tool for studying chloride conductances in isolated ventricular myocytes with interfering currents blocked. However, due to its effects on cation conductances it would be of little value in this regard for other types of in vitro or in vivo experiments.
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Affiliation(s)
- John J Borg
- Department of Pharmacology, School of Medical Sciences, University of Bristol, United Kingdom
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25
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Picard L, Côté K, Teijeira J, Greentree D, Rousseau E. Sarcoplasmic reticulum K(+) channels from human and sheep atrial cells display a specific electro-pharmacological profile. J Mol Cell Cardiol 2002; 34:1163-72. [PMID: 12392890 DOI: 10.1006/jmcc.2002.2041] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
It has recently been proposed that the Ca(2+) uptake by the SR is inhibited by blocking Cl(-) and/or K(+) movements across this intracellular membrane. We have characterised the functional and pharmacological profile of the SR K(+) channel derived from human and sheep atrial cells. Mammalian atrial SR preparations were subjected to [(3)H]-ryanodine binding assays, SDS-PAGE analysis and channel protein reconstitution into planar lipid bilayers. Assessment of [(3)H]-ryanodine binding on the SR Ca(2+) release channel revealed that it was inhibited by both Ruthenium Red and Mg(2+) with IC(50) values of 4.11 microM and 9.12 m M, respectively. In crude populations as well as in all SR-enriched fractions, activity of K(+) selective channels was recorded. This channel displayed a high conductance value of 193 and 185 pS for human and sheep preparations respectively. Gating and conducting behaviours of this channel were unaffected by the addition of up to 5m M 4-Aminopyridine (4-AP), 100 n M Iberiotoxin (IbTX), 10 microM E-4031 and 30 microM amiodarone. However, 100n M Dendrotoxin (gamma-DTX) largely increase the occurrence of the SR K(+) channel subconducting states without an effect on the main unitary conductance. These results demonstrate that the SR K(+) channel, present in all mammalian atrial SR membranes tested (as assessed by [(3)H]-ryanodine binding and its typical inhibition by ruthenium red and the magnesium), displays different properties than those classically described for cardiac sarcolemmal K(+) channels. Despite the fact that the biophysical properties of the SR K(+) channel are well known, its molecular identity remains to be ascertained.
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Affiliation(s)
- Luc Picard
- Le Bilarium, Département de Physiologie et Biophysique, Faculté de Médecine, Université de Sherbrooke, Sherbrooke, QC, J1H 5N4, Canada
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26
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Lu YC, Jiann BP, Chang HT, Huang JK, Chen WC, Su W, Jan CR. Effect of the anti-breast cancer drug tamoxifen on Ca(2+) movement in human osteosarcoma cells. PHARMACOLOGY & TOXICOLOGY 2002; 91:34-9. [PMID: 12193259 DOI: 10.1034/j.1600-0773.2002.910106.x] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
The anti-breast cancer drug tamoxifen has recently been shown to cause an increase in [Ca(2+)]i in renal tubular cells, breast cells and bladder cells. Because tamoxifen is known to interact with oestrogens leading to modulation of bone metabolism, the present study was aimed at exploring whether tamoxifen could alter Ca(2+) signaling in human osteoblast-like MG63 cells. Cytosolic free Ca(2+) levels were recorded by using the Ca(2+)-sensitive dye fura-2. Tamoxifen induced a sustained [Ca(2+)]i increase at concentrations above 1 microM with an EC(50) of 8 microM. Removal of extracellular Ca(2+) reduced the response by 40%, suggesting that tamoxifen induced both Ca(2+) influx and store Ca(2+) release. Tamoxifen-induced Ca(2+) influx was confirmed as tamoxifen caused Mn(2+) influx-induced quench of fura-2 fluorescence. In Ca(2+)-free medium, pretreatment with 10 microM tamoxifen abolished the [Ca(2+)]i increase induced by 1 microM thapsigargin (an endoplasmic reticulum Ca(2+) pump inhibitor), and by 2 microM carbonylcyanide m-chlorophenylhydrazone (a mitochondrial uncoupler). Conversely, pretreatment with thapsigargin and carbonylcyanide m-chlorophenylhydrazone only reduced 64% of tamoxifen-induced [Ca(2+)]i increases. Addition of 2 microM U73122 to inhibit phospholipase C activity abolished the [Ca(2+)]i increase induced by 1 microM histamine, a phospholipase C-dependent Ca(2+) mobilizer, without affecting 10 microM tamoxifen-induced Ca(2+) release. The [Ca(2+)]i increase induced by 10 microM tamoxifen was not altered by 10 microM of nifedipine, verapamil and diltiazem. Together, the data show that tamoxifen induced a lasting increase in [Ca(2+)]i in human osteoblast-like cells by causing Ca(2+) influx and releasing Ca(2+) from multiple stores in a phospholipase C-independent manner.
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Affiliation(s)
- Yih-Chau Lu
- Department of Orthopaedic Surgery, Kaohsiung Veterans General Hospital, Kaohsiung, Taiwan 813
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27
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Chao YY, Jan CR, Ko YC, Chen JJ, Jiann BP, Lu YC, Chen WC, Su W, Chen IS. Effect of lignans isolated from Hernandia nymphaeifolia on estrogenic compounds-induced calcium mobilization in human neutrophils. Life Sci 2002; 70:3109-21. [PMID: 12008094 DOI: 10.1016/s0024-3205(02)01570-9] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
The effect of five lignans isolated from Hernandia nymphaeifolia on estrogenic compounds (17beta-estradiol, tamoxifen and clomiphene)-induced Ca(2+) mobilization in human neutrophils was investigated. The five lignans were epi-yangambin, epi-magnolin, epi-aschantin, deoxypodophyllotoxin and yatein. In Ca(2+)-containing medium, the lignans (50-100 microM) inhibited 10 microM 17beta-estradiol- and 5 microM tamoxifen-induced increases in intracellular free Ca(2+) levels ([Ca(2+)](i)) without changing 25 microM clomiphene-induced [Ca(2+)](i) increase. 17beta-estradiol and tamoxifen increased [Ca(2+)](i) by causing Ca(2+) influx and Ca(2+) release because their responses were partly reduced by removing extracellular Ca(2+). In contrast, clomiphene solely induced Ca(2+) release. The effect of the lignans on these two Ca(2+) movement pathways underlying 17beta-estradiol- and tamoxifen-induced [Ca(2+)](i) increases was explored. All the lignans (50-100 microM) inhibited 10 microM 17beta-estradiol-and 5 microM tamoxifen-induced Ca(2+) release, and 17beta-estradiol-induced Ca(2+) influx. However, only 100 microM epi-aschantin was able to reduce tamoxifen-induced Ca(2+) influx while the other lignans had no effect. Collectively, this study shows that the lignans altered estrogenic compounds-induced Ca(2+) signaling in human neutrophils in a multiple manner.
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Affiliation(s)
- Yu-Ying Chao
- Graduate Institute of Pharmaceutical Sciences, Kaohsiung Medical University, 807, Kaohsiung, Taiwan
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28
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Jiann BP, Lu YC, Chang HT, Huang JK, Jan CR. Effect of clomiphene on Ca(2+) movement in human prostate cancer cells. Life Sci 2002; 70:3167-78. [PMID: 12008099 DOI: 10.1016/s0024-3205(02)01574-6] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
The effect of clomiphene, an ovulation-inducing agent, on cytosolic free Ca(2+) levels ([Ca(2+)](i)) in populations of PC3 human prostate cancer cells was explored by using fura-2 as a Ca(2+) indicator. Clomiphene at concentrations between 10-50 microM increased [Ca(2+)](i) in a concentration-dependent manner. The [Ca(2+)](i) signal was biphasic with an initial rise and a slow decay. Ca(2+) removal inhibited the Ca(2+) signal by 41%. Adding 3 mM Ca(2+) increased [Ca(2+)](i) in cells pretreated with clomiphene in Ca(2+)-free medium, confirming that clomiphene induced Ca(2+) entry. In Ca(2+)-free medium, pretreatment with 50 microM brefeldin A (to permeabilize the Golgi complex), 1 microM thapsigargin (to inhibit the endoplasmic reticulum Ca(2+) pump), and 2 microM carbonylcyanide m-chlorophenylhydrazone (to uncouple mitochondria) inhibited 25% of 50 microM clomiphene-induced store Ca(2+) release. Conversely, pretreatment with 50 microM clomiphene in Ca(2+)-free medium abolished the [Ca(2+)](i) increase induced by brefeldin A, thapsigargin or carbonylcyanide m-chlorophenylhydrazone. The 50 microM clomiphene-induced Ca(2+)release was unaltered by inhibiting phospholipase C with 2 microM 1-(6-((17beta-3-methoxyestra-1,3,5(10)-trien-17-yl)amino)hexyl)-1H-pyrrole-2,5-dione (U73122). Trypan blue exclusion assay suggested that incubation with clomiphene (50 microM) for 2-15 min induced time-dependent decrease in cell viability by 10-50%. Collectively, the results suggest that clomiphene induced [Ca(2+)](i) increases in PC3 cells by releasing store Ca(2+) from multiple stores in an phospholipase C-independent manner, and by activating Ca(2+) influx; and clomiphene was of mild cytotoxicity.
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Affiliation(s)
- Bang-Ping Jiann
- Department of Surgery, Kaohsiung Veterans General Hospital, Kaohsiung 813, Taiwan
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