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Guimaraes DA, Aquino NSS, Rocha-Resende C, Jesus ICG, Silva MM, Scalzo SA, Fonseca RC, Durand MT, Pereira V, Tezini GCSV, Oliveira A, Prado VF, Stefanon I, Salgado HC, Prado MAM, Szawka RE, Guatimosim S. Neuronal cholinergic signaling constrains norepinephrine activity in the heart. Am J Physiol Cell Physiol 2022; 322:C794-C801. [PMID: 35264016 DOI: 10.1152/ajpcell.00031.2022] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
It is well known that cholinergic hypofunction contributes to cardiac pathology; yet, the mechanisms involved remain unclear. Our previous publication has shown that genetically engineered model of cholinergic deficit, the vesicular acetylcholine transporter knockdown homozygous (VAChT KDHOM) mice exhibit pathological cardiac remodeling and a gradual increase in cardiac mass with aging. Given that an increase in cardiac mass is often caused by adrenergic hyperactivity, we hypothesized that VAChT KDHOM mice might have an increase in cardiac norepinephrine (NE) levels. We thus investigated the temporal changes in NE content in the heart from 3, 6 and 12 month-old VAChT mutants. Interestingly, mice with cholinergic hypofunction showed a gradual elevation in cardiac NE content, which was already increased at 6 months of age. Consistent with this finding, 6 month-old VAChT KDHOM mice showed enhanced sympathetic activity and a greater abundance of tyrosine hydroxylase positive sympathetic nerves in the heart. VAChT mutants exhibited an increase in peak calcium transient, and mitochondrial oxidative stress in cardiomyocytes along with enhanced GRK5 and NFAT staining in the heart. These are known targets of adrenergic signaling in the cell. Moreover, vagotomized-mice displayed an increase in cardiac NE content confirming the data obtained in VAChT KDHOM mice. Establishing a causal relationship between acetylcholine and NE, VAChT KDHOM mice treated with pyridostigmine, a cholinesterase inhibitor, showed reduced cardiac NE content, rescuing the phenotype. Our findings unveil a yet unrecognized role of cholinergic signaling as a modulator of cardiac NE, providing novel insights into the mechanisms that drive autonomic imbalance.
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Affiliation(s)
- Diogo A Guimaraes
- Department of Physiology and Biophysics, Institute of Biological Sciences, Universidade Federal de Minas Gerais, Belo Horizonte, Minas Gerais, Brazil
| | - Nayara S S Aquino
- Department of Physiology and Biophysics, Institute of Biological Sciences, Universidade Federal de Minas Gerais, Belo Horizonte, Minas Gerais, Brazil
| | - Cibele Rocha-Resende
- Department of Physiology and Biophysics, Institute of Biological Sciences, Universidade Federal de Minas Gerais, Belo Horizonte, Minas Gerais, Brazil
| | - Itamar C G Jesus
- Department of Physiology and Biophysics, Institute of Biological Sciences, Universidade Federal de Minas Gerais, Belo Horizonte, Minas Gerais, Brazil
| | - Mário Morais Silva
- Department of Physiology and Biophysics, Institute of Biological Sciences, Universidade Federal de Minas Gerais, Belo Horizonte, Minas Gerais, Brazil
| | - Sergio A Scalzo
- Department of Physiology and Biophysics, Institute of Biological Sciences, Universidade Federal de Minas Gerais, Belo Horizonte, Minas Gerais, Brazil
| | - Roberta Cristelli Fonseca
- Department of Physiology and Biophysics, Institute of Biological Sciences, Universidade Federal de Minas Gerais, Belo Horizonte, Minas Gerais, Brazil
| | - Marina T Durand
- Universidade de Ribeirão Preto, Ribeirão Preto, São Paulo, Brazil
| | - Vanessa Pereira
- Department of Physiology and Biophysics, Institute of Biological Sciences, Universidade Federal de Minas Gerais, Belo Horizonte, Minas Gerais, Brazil
| | | | - André Oliveira
- Department of Physiology and Biophysics, Institute of Biological Sciences, Universidade Federal de Minas Gerais, Belo Horizonte, Minas Gerais, Brazil
| | - Vânia F Prado
- Robarts Research Institute, The University of Western Ontario, Department of Physiology 1and Pharmacology, Department of Anatomy and Cell Biology, Schulich School of Medicine and Dentistry, University of Western Ontario, London, Canada
| | - Ivanita Stefanon
- Department of Physiological Sciences, Universidade Federal do Espírito Santo, Vitória, Espirito Santo, Brazil
| | - Helio C Salgado
- Faculdade de Medicina de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, São Paulo, Brazil
| | - Marco Antonio Máximo Prado
- Robarts Research Institute, The University of Western Ontario, Department of Physiology 1and Pharmacology, Department of Anatomy and Cell Biology, Schulich School of Medicine and Dentistry, University of Western Ontario, London, Canada
| | - Raphael E Szawka
- Department of Physiology and Biophysics, Institute of Biological Sciences, Universidade Federal de Minas Gerais, Belo Horizonte, Minas Gerais, Brazil
| | - Silvia Guatimosim
- Department of Physiology and Biophysics, Institute of Biological Sciences, Universidade Federal de Minas Gerais, Belo Horizonte, Minas Gerais, Brazil
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2
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Teixeira VP, Miranda K, Scalzo S, Rocha-Resende C, Silva MM, Tezini GCSV, Melo MB, Souza-Neto FP, Silva KSC, Jesus ICG, Santos AK, de Oliveira M, Szawka RE, Salgado HC, Prado MAM, Poletini MO, Guatimosim S. Increased cholinergic activity under conditions of low estrogen leads to adverse cardiac remodeling. Am J Physiol Cell Physiol 2021; 320:C602-C612. [PMID: 33296286 DOI: 10.1152/ajpcell.00142.2020] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2020] [Accepted: 12/03/2020] [Indexed: 02/07/2023]
Abstract
Cholinesterase inhibitors are used in postmenopausal women for the treatment of neurodegenerative diseases. Despite their widespread use in the clinical practice, little is known about the impact of augmented cholinergic signaling on cardiac function under reduced estrogen conditions. To address this gap, we subjected a genetically engineered murine model of systemic vesicular acetylcholine transporter overexpression (Chat-ChR2) to ovariectomy and evaluated cardiac parameters. Left-ventricular function was similar between Chat-ChR2 and wild-type (WT) mice. Following ovariectomy, WT mice showed signs of cardiac hypertrophy. Conversely, ovariectomized (OVX) Chat-ChR2 mice evolved to cardiac dilation and failure. Transcript levels for cardiac stress markers atrial natriuretic peptide (ANP) and B-type natriuretic peptide (BNP) were similarly upregulated in WT/OVX and Chat-ChR2/OVX mice. 17β-Estradiol (E2) treatment normalized cardiac parameters in Chat-ChR2/OVX to the Chat-ChR2/SHAM levels, providing a link between E2 status and the aggravated cardiac response in this model. To investigate the cellular basis underlying the cardiac alterations, ventricular myocytes were isolated and their cellular area and contractility were assessed. Myocytes from WT/OVX mice were wider than WT/SHAM, an indicative of concentric hypertrophy, but their fractional shortening was similar. Conversely, Chat-ChR2/OVX myocytes were elongated and presented contractile dysfunction. E2 treatment again prevented the structural and functional changes in Chat-ChR2/OVX myocytes. We conclude that hypercholinergic mice under reduced estrogen conditions do not develop concentric hypertrophy, a critical compensatory adaptation, evolving toward cardiac dilation and failure. This study emphasizes the importance of understanding the consequences of cholinesterase inhibition, used clinically to treat dementia, for cardiac function in postmenopausal women.
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MESH Headings
- Acetylcholine/metabolism
- Animals
- Cholinergic Fibers/metabolism
- Estradiol/pharmacology
- Estrogen Replacement Therapy
- Estrogens/deficiency
- Female
- Heart/innervation
- Heart Rate
- Hypertrophy, Left Ventricular/metabolism
- Hypertrophy, Left Ventricular/pathology
- Hypertrophy, Left Ventricular/physiopathology
- Hypertrophy, Left Ventricular/prevention & control
- Mice, Inbred C57BL
- Mice, Transgenic
- Myocardial Contraction
- Myocytes, Cardiac/drug effects
- Myocytes, Cardiac/metabolism
- Myocytes, Cardiac/pathology
- Ovariectomy
- Signal Transduction
- Ventricular Dysfunction, Left/metabolism
- Ventricular Dysfunction, Left/pathology
- Ventricular Dysfunction, Left/physiopathology
- Ventricular Dysfunction, Left/prevention & control
- Ventricular Function, Left/drug effects
- Ventricular Remodeling/drug effects
- Vesicular Acetylcholine Transport Proteins/genetics
- Vesicular Acetylcholine Transport Proteins/metabolism
- Mice
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Affiliation(s)
- Vanessa P Teixeira
- Department of Physiology and Biophysics, Institute of Biological Sciences, Universidade Federal de Minas Gerais, Belo Horizonte, Minas Gerais, Brazil
| | - Kiany Miranda
- Department of Physiology and Biophysics, Institute of Biological Sciences, Universidade Federal de Minas Gerais, Belo Horizonte, Minas Gerais, Brazil
| | - Sergio Scalzo
- Department of Physiology and Biophysics, Institute of Biological Sciences, Universidade Federal de Minas Gerais, Belo Horizonte, Minas Gerais, Brazil
| | - Cibele Rocha-Resende
- Department of Physiology and Biophysics, Institute of Biological Sciences, Universidade Federal de Minas Gerais, Belo Horizonte, Minas Gerais, Brazil
| | - Mário Morais Silva
- Department of Physiology and Biophysics, Institute of Biological Sciences, Universidade Federal de Minas Gerais, Belo Horizonte, Minas Gerais, Brazil
| | - Geisa C S V Tezini
- Ribeirão Preto Medical School, Universidade de São Paulo, Riberão Preto, São Paulo, Brazil
| | - Marcos B Melo
- Department of Physiology and Biophysics, Institute of Biological Sciences, Universidade Federal de Minas Gerais, Belo Horizonte, Minas Gerais, Brazil
| | - Fernando Pedro Souza-Neto
- Department of Physiology and Biophysics, Institute of Biological Sciences, Universidade Federal de Minas Gerais, Belo Horizonte, Minas Gerais, Brazil
| | - Kaoma S C Silva
- Department of Physiology and Biophysics, Institute of Biological Sciences, Universidade Federal de Minas Gerais, Belo Horizonte, Minas Gerais, Brazil
| | - Itamar C G Jesus
- Department of Physiology and Biophysics, Institute of Biological Sciences, Universidade Federal de Minas Gerais, Belo Horizonte, Minas Gerais, Brazil
| | - Anderson K Santos
- Department of Physiology and Biophysics, Institute of Biological Sciences, Universidade Federal de Minas Gerais, Belo Horizonte, Minas Gerais, Brazil
| | - Mauro de Oliveira
- Ribeirão Preto Medical School, Universidade de São Paulo, Riberão Preto, São Paulo, Brazil
| | - Raphael E Szawka
- Department of Physiology and Biophysics, Institute of Biological Sciences, Universidade Federal de Minas Gerais, Belo Horizonte, Minas Gerais, Brazil
| | - Helio C Salgado
- Ribeirão Preto Medical School, Universidade de São Paulo, Riberão Preto, São Paulo, Brazil
| | - Marco Antonio Máximo Prado
- Robarts Research Institute, Department of Physiology and Pharmacology and Department of Anatomy and Cell Biology, University of Western Ontario, London, Ontario, Canada
| | - Maristela O Poletini
- Department of Physiology and Biophysics, Institute of Biological Sciences, Universidade Federal de Minas Gerais, Belo Horizonte, Minas Gerais, Brazil
| | - Silvia Guatimosim
- Department of Physiology and Biophysics, Institute of Biological Sciences, Universidade Federal de Minas Gerais, Belo Horizonte, Minas Gerais, Brazil
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3
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Queiroz CM, Tiba PA, Moreira KM, Guidine PAM, Rezende GHS, Moraes MFD, Prado MAM, Prado VF, Tufik S, Mello LE. Sleep pattern and learning in knockdown mice with reduced cholinergic neurotransmission. Braz J Med Biol Res 2013; 46:844-54. [PMID: 24141612 PMCID: PMC3854314 DOI: 10.1590/1414-431x20133102] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2013] [Accepted: 07/22/2013] [Indexed: 11/22/2022] Open
Abstract
Impaired cholinergic neurotransmission can affect memory formation and influence sleep-wake cycles (SWC). In the present study, we describe the SWC in mice with a deficient vesicular acetylcholine transporter (VAChT) system, previously characterized as presenting reduced acetylcholine release and cognitive and behavioral dysfunctions. Continuous, chronic ECoG and EMG recordings were used to evaluate the SWC pattern during light and dark phases in VAChT knockdown heterozygous (VAChT-KDHET, n=7) and wild-type (WT, n=7) mice. SWC were evaluated for sleep efficiency, total amount and mean duration of slow-wave, intermediate and paradoxical sleep, as well as the number of awakenings from sleep. After recording SWC, contextual fear-conditioning tests were used as an acetylcholine-dependent learning paradigm. The results showed that sleep efficiency in VAChT-KDHET animals was similar to that of WT mice, but that the SWC was more fragmented. Fragmentation was characterized by an increase in the number of awakenings, mainly during intermediate sleep. VAChT-KDHET animals performed poorly in the contextual fear-conditioning paradigm (mean freezing time: 34.4±3.1 and 44.5±3.3 s for WT and VAChT-KDHET animals, respectively), which was followed by a 45% reduction in the number of paradoxical sleep episodes after the training session. Taken together, the results show that reduced cholinergic transmission led to sleep fragmentation and learning impairment. We discuss the results on the basis of cholinergic plasticity and its relevance to sleep homeostasis. We suggest that VAChT-KDHET mice could be a useful model to test cholinergic drugs used to treat sleep dysfunction in neurodegenerative disorders.
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Affiliation(s)
- C M Queiroz
- Universidade Federal de São Paulo, Departamento de Fisiologia, São Paulo,SP, Brasil
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4
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de Castro BM, Pereira GS, Magalhães V, Rossato JI, De Jaeger X, Martins-Silva C, Leles B, Lima P, Gomez MV, Gainetdinov RR, Caron MG, Izquierdo I, Cammarota M, Prado VF, Prado MAM. Reduced expression of the vesicular acetylcholine transporter causes learning deficits in mice. Genes Brain Behav 2008; 8:23-35. [PMID: 18778400 DOI: 10.1111/j.1601-183x.2008.00439.x] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Storage of acetylcholine in synaptic vesicles plays a key role in maintaining cholinergic function. Here we used mice with a targeted mutation in the vesicular acetylcholine transporter (VAChT) gene that reduces transporter expression by 40% to investigate cognitive processing under conditions of VAChT deficiency. Motor skill learning in the rotarod revealed that VAChT mutant mice were slower to learn this task, but once they reached maximum performance they were indistinguishable from wild-type mice. Interestingly, motor skill performance maintenance after 10 days was unaffected in these mutant mice. We also tested whether reduced VAChT levels affected learning in an object recognition memory task. We found that VAChT mutant mice presented a deficit in memory encoding necessary for the temporal order version of the object recognition memory, but showed no alteration in spatial working memory, or spatial memory in general when tested in the Morris water maze test. The memory deficit in object recognition memory observed in VAChT mutant mice could be reversed by cholinesterase inhibitors, suggesting that learning deficits caused by reduced VAChT expression can be ameliorated by restoring ACh levels in the synapse. These data indicate an important role for cholinergic tone in motor learning and object recognition memory.
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Affiliation(s)
- B M de Castro
- Program in Molecular Pharmacology, ICB and Núcleo de Neurociências, Departamento de Fisiologia e Biofísica, Universidade Federal de Minas Gerais, Belo Horizonte, MG, Brazil
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5
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Massote PD, Pinheiro ACN, Fonseca CG, Prado MAM, Guimarães ALS, Massensini AR, Gomez MV. Protective effect of retinal ischemia by blockers of voltage-dependent calcium channels and intracellular calcium stores. Cell Mol Neurobiol 2008; 28:847-56. [PMID: 18196453 DOI: 10.1007/s10571-007-9243-0] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2007] [Accepted: 11/17/2007] [Indexed: 01/13/2023]
Abstract
In the present study, the neuroprotective effect of blockers of voltage-dependent calcium channels (VDCC) and intracellular calcium stores on retinal ischemic damage induced by oxygen deprivation-low glucose insult (ODLG) was investigated. Retinal damage induced by ODLG was dependent on the calcium concentration in the perfusion medium. When incubated in medium containing 2.4 mM CaCl(2), cell death in ischemic retinal slices treated with blockers of VDCC, omega-conotoxin GVIA (1.0 microM), omega-conotoxin MVIIC (100 nM) and nifedipine (1.0 microM), was reduced to 62 +/- 2.3, 46 +/- 4.3 and 47 +/- 3.9%, respectively. In the presence of blockers of intracellular calcium stores, dantrolene (100 microM) and 2-APB (100 microM), the cell death was reduced to 46 +/- 3.2 and 55 +/- 2.9%, respectively. Tetrodotoxin (1.0 microM), reducing the extent of the membrane depolarization reduces the magnitude of calcium influx trough VDCC causing a reduction of the cell death to 55 +/- 4.3. Lactate dehydrogenase content of untreated ischemic retinal slices was reduced by 37% and treatment of ischemic slices with BAPTA-AM (100 microM) or 2-APB (100 microM) abolished the leakage of LDH. Dantrolene (100 microM) and nifedipine (1.0 microM) partially blocked the induced reduction on the LDH content of retinal ischemic slices. Histological analysis of retinal ischemic slices showed 40% reduction of ganglion cells that was prevented by BAPTA-AM or dantrolene. 2-APB partially blocked this reduction whilst nifedipine had no effect, p > 0.95. Conclusion Blockers of VDCC and intracellular calcium-sensitive receptors exert neuroprotective effect on retinal ischemia.
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6
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Macêdo CDS, DaRocha WD, Mortara RA, Prado MAM, Teixeira SMR. Characterization of a Trypanosoma cruzi antigen with homology to intracellular mammalian lectins. Int J Parasitol 2006; 36:1473-84. [PMID: 17027760 DOI: 10.1016/j.ijpara.2006.08.010] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2006] [Revised: 08/10/2006] [Accepted: 08/15/2006] [Indexed: 01/23/2023]
Abstract
Two cDNAs, isolated from a Trypanosoma cruzi amastigote library immunoscreened with sera from patients with Chagas disease, encode proteins with sequence homology to eukaryotic components of the cellular sorting and recycling machinery. These proteins, denominated TcAGL, present an N-terminal lectin domain and a C-terminal region containing repetitive amino acids and a poly-glutamine tract. They are products of polymorphic alleles of a single copy gene constitutively expressed during the parasite life cycle. Polyclonal antibodies obtained from mice immunized with the recombinant antigen recognize proteins with apparent molecular weight ranging from 95 to 120 kDa in cell lysates from all three life stages and in various strains of the parasite. Sera from Chagas disease patients recognize the recombinant antigen in ELISA and immunoprecipitation assays but not in Western blot assays under denaturing conditions. Consistent with its proposed role in the glycoprotein secreting pathway, immunofluorescence analyses and expression of a green fluorescent protein-tagged TcAGL protein indicate a sub-cellular localization in the vicinity of the flagellar pocket membrane and the Golgi complex of the parasite.
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Affiliation(s)
- C D S Macêdo
- Departamento de Bioquímica e Imunologia, ICB, Universidade Federal de Minas Gerais, Belo Horizonte, MG 31270-010, Brazil
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7
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Pinheiro ACN, Gomez RS, Guatimosim C, Silva JH, Prado MAM, Gomez MV. The effect of sevoflurane on intracellular calcium concentration from cholinergic cells. Brain Res Bull 2006; 69:147-52. [PMID: 16533663 DOI: 10.1016/j.brainresbull.2005.11.016] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2005] [Revised: 11/10/2005] [Accepted: 11/23/2005] [Indexed: 11/28/2022]
Abstract
The mechanism of action of volatile anesthetics is not completely understood. Calcium release from internal stores may alter signaling pathways that influence neurotransmission. Abnormalities of the regulation of intracellular calcium concentration ([Ca2+]i) from patients with malignant hyperthermia is a hallmark of this syndrome indicating the potential of these agents to interact with proteins involved in Ca2+ signaling. In the present study, a cholinergic cell line (SN56) was used to examine whether the release of calcium from intracellular stores occurs in the presence of sevoflurane. Changes in [Ca2+]i were measured using fluo-4, a fluorescent calcium sensitive dye and laser scanning confocal microscopy. Sevoflurane induced an increase on [Ca2+]i from SN56 cells. The sevoflurane-induced increase on [Ca2+]i remained even when the cells were perfused with medium lacking extracellular calcium. However, this effect was abolished by BAPTA-AM, a chelator of intracellular calcium, suggesting the involvement of intracellular Ca2+ stores. Using cyclopiazonic acid, an inhibitor of sarcoplasmic/endoplasmic reticulum Ca(2+)-ATPase, we investigated whether the depletion of intracellular Ca2+ stores interfered with the effect of sevoflurane. In the presence of this agent, sevoflurane caused a small but not significant rise on [Ca2+]i of the SN56 cells. Dantrolene, an inhibitor of ryanodine-sensitive calcium stores did not modify the sevoflurane increase on [Ca2+]i. Carbachol, a drug that releases Ca2+ from the IP3 pool, abolished the effect of sevoflurane. In addition, xestospongin D, a cell-permeant IP3 receptor antagonist, decreased significantly the sevoflurane increase on [Ca2+]i. Our data suggest that the sevoflurane-induced increase on [Ca2+]i from SN56 cells occurs through the release of calcium from IP3-sensitive calcium stores.
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8
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Fernandes VMV, Romano-Silva MA, Gomes DA, Prado MAM, Santos TM, Gomez MV. Dopamine release evoked by beta scorpion toxin, tityus gamma, in prefrontal cortical slices is mediated by intracellular calcium stores. Cell Mol Neurobiol 2005; 24:757-67. [PMID: 15672678 DOI: 10.1007/s10571-004-6917-8] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
1. We have investigated the effect of tityus gamma (TiTX gamma) scorpion toxin on the release of [3H]dopamine in rat brain prefrontal cortical slices. The stimulatory effect of TiTX gamma on the release of [3H]dopamine was dose/time-dependent with an EC50 of 0.01 microM. 2. Tetrodotoxin blocked the TiTX gamma-induced release of [3H]dopamine, indicating the dependency for Na+ channels. 3. EGTA had no effect on the TiTX gamma-induced release of [3H]dopamine, indicating the process is independent of extracellular calcium. Release of [3H]dopamine evoked by TiTX gamma was inhibited by 57% by BAPTA, a chelator of intracellular calcium. 4. Xestospongin and 2-APB, putative blockers of IP3-sensitive release of intracellular calcium stores, caused an equal and significant inhibition of 24% of the TiTX gamma-induced release of [3H]dopamine, while the slight inhibition evoked by dantrolene, a putative blocker of ryanodine-sensitive calcium store was not significant. 5. Nomifensine and ascorbic acid, blockers of dopamine transporter (DAT), caused an inhibition of 27 and 29%, respectively, on the toxin-induced release of [3H]dopamine suggesting that most of the TiTX gamma-induced release of dopamine is not due to the reversal of Na+ gradient. 6. In conclusion the majority of the TiTX gamma-induced release of [3H]dopamine is exocytotic and mobilizes calcium from the intracellular IP3-sensitive calcium stores.
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9
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Ribeiro FM, Alves-Silva J, Volknandt W, Martins-Silva C, Mahmud H, Wilhelm A, Gomez MV, Rylett RJ, Ferguson SSG, Prado VF, Prado MAM. The hemicholinium-3 sensitive high affinity choline transporter is internalized by clathrin-mediated endocytosis and is present in endosomes and synaptic vesicles. J Neurochem 2003; 87:136-46. [PMID: 12969261 DOI: 10.1046/j.1471-4159.2003.01974.x] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Synthesis of acetylcholine depends on the plasma membrane uptake of choline by a high affinity choline transporter (CHT1). Choline uptake is regulated by nerve impulses and trafficking of an intracellular pool of CHT1 to the plasma membrane may be important for this regulation. We have generated a hemagglutinin (HA) epitope tagged CHT1 to investigate the organelles involved with intracellular trafficking of this protein. Expression of CHT1-HA in HEK 293 cells establishes Na+-dependent, hemicholinium-3 sensitive high-affinity choline transport activity. Confocal microscopy reveals that CHT1-HA is found predominantly in intracellular organelles in three different cell lines. Importantly, CHT1-HA seems to be continuously cycling between the plasma membrane and endocytic organelles via a constitutive clathrin-mediated endocytic pathway. In a neuronal cell line, CHT1-HA colocalizes with the early endocytic marker green fluorescent protein (GFP)-Rab 5 and with two markers of synaptic-like vesicles, VAMP-myc and GFP-VAChT, suggesting that in cultured cells CHT1 is present mainly in organelles of endocytic origin. Subcellular fractionation and immunoisolation of organelles from rat brain indicate that CHT1 is present in synaptic vesicles. We propose that intracellular CHT1 can be recruited during stimulation to increase choline uptake in nerve terminals.
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Affiliation(s)
- F M Ribeiro
- Laboratório de Neurobiologia Molecular, Departamento de Bioquímica-Imunologia, ICB, Universidade Federal de Minas Gerais, Belo Horizonte, Brazil
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10
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Carneiro AMD, Kushmerick C, Koenen J, Arndt MHL, Cordeiro MN, Chavez-Olortegui C, Diniz CR, Gomez MV, Kalapothakis E, Prado MAM, Prado VF. Expression of a functional recombinant Phoneutria nigriventer toxin active on K+ channels. Toxicon 2003; 41:305-13. [PMID: 12565753 DOI: 10.1016/s0041-0101(02)00292-1] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
PnTx3-1 is a peptide isolated from the venom of the spider Phoneutria nigriventer that specifically inhibits A-type K(+) currents (I(A)) in GH(3) cells. Here we used a bacterial expression system to produce an NH(2)-extended mutant of PnTx3-1 (ISEF-PnTx3-1) and tested whether the toxin is functional. The recombinant toxin was purified from bacterial extracts by a combination of affinity and ion-exchange chromatography. The recombinant toxin blocked A-type K(+) currents in GH(3) cells in a fashion similar to that observed with the wild-type toxin purified from the spider venom. These results suggest that recombinant cDNA methods provide a novel source for the production of functional Phoneutria toxins. The recombinant ISEF-PnTx3-1 should be useful for further understanding of the role of A-type K(+) currents in biological processes.
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Affiliation(s)
- A M D Carneiro
- Departamento de Bioquímica-Imunologia, ICB, Universidade Federal de Minas Gerais, Av Antonio Carlos, 6627, Belo Horizonte, 31270-901, Minas Gerais, Brazil
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11
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Bicalho AFX, Guatimosim C, Prado MAM, Gomez MV, Romano-Silva MA. Investigation of the modulation of glutamate release by sodium channels using neurotoxins. Neuroscience 2002; 113:115-23. [PMID: 12123690 DOI: 10.1016/s0306-4522(02)00139-2] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The modulation of neurotransmitter release by calcium channels is well established, yet, sodium channels were regarded mainly as charge carriers. Many lines of evidence suggest a more fine-tuning role played by sodium channels. Using rat cerebrocortical isolated nerve endings (synaptosomes) and two toxins that have separate sites of action on sodium channels and provoke distinct changes in channel kinetics, we were able to show that depending on the rate of increase in channel conductance, the outcome in terms of neurotransmitter release and calcium channel types coupled to that event are different. Mainly, our study focused on veratridine, an alkaloid from lilaceous plants that binds to sodium channel toxin site 2, and tityustoxin, a toxin purified from the venom of the Brazilian yellow scorpion Tityus serrulatus that binds to site 3. Veratridine induces a slower increase in intrasynaptosomal sodium and calcium concentrations, slower depolarization, delayed exocytosis and a slower and predominantly calcium-independent glutamate release, when compared to tityustoxin.Thus, we have used these two toxins to investigate the events that start with sodium entry and culminate with the release of glutamate in isolated nerve endings (synaptosomes) from rat cerebral cortex. With that in mind we measured intrasynaptosomal free sodium concentration [Na(+)](i), intrasynaptosomal free calcium concentration [Ca(2+)](i), membrane potential, exocytosis and glutamate release using fluorescent probes.
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Affiliation(s)
- A F X Bicalho
- Laboratório de Neurofarmacologia, Departamento de Farmacologia, ICB, Universidade Federal de Minas Gerais, Av. Antonio Carlos 6627, Belo Horizonte 31270-901, MG, Brazil
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Nicolato R, Fernandes VMV, Moraes-Santos T, Gomez RS, Prado MAM, Romano-Silva MA, Gomez MV. Release of gamma-[(3)H]aminobutyric acid in rat brain cortical slices by alpha-scorpion toxin. Neurosci Lett 2002; 325:155-8. [PMID: 12044644 DOI: 10.1016/s0304-3940(02)00177-5] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
In this paper, the effect of the alpha-scorpion toxin tityustoxin (TsTX) in the release of gamma-[(3)H]aminobutyric acid ([(3)H]GABA) from rat brain cortical slices is described. The TsTX-stimulatory effect on the release of [(3)H]GABA was dependent on incubation time and TsTX concentration, having an EC(50) of 0.33 microM. Tetrodotoxin (TTX) completely inhibited the TsTX action on [(3)H]GABA release. The scorpion toxin effect was calcium-dependent and involves P/Q calcium channels. beta-Alanine also induces the release of [(3)H]GABA that was not inhibited by TTX but was additive in the presence of TsTX. The data suggest a neuronal origin for the release of [(3)H]GABA by TsTX.
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Affiliation(s)
- R Nicolato
- Laboratório de Neurofarmacologia, Departamento de Farmacologia, ICB-UFMG, Avenida Antonio Carlos 6627, Pampulha, 31270-901 Belo Horizonte MG, Brazil
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Abstract
Protein kinase C (PKC) is a signal transducing enzyme that is an important regulator of multiple physiologic processes and a potential molecular target for volatile anaesthetic actions. However, the effects of these agents on PKC activity are not yet fully understood. Volatile anaesthetics increase intracellular calcium concentration ([Ca(2+)](i)) in a variety of cells, thus their effects on PKC activity may be indirect due to [Ca(2+)](i) increase. Alternatively, the anaesthetics could directly stimulate PKC activity. In order to distinguish these two possibilities in intact cells, we used a fully functional green fluorescent protein conjugated PKCbetaII (GFP-PKCbetaII) and confocal microscopy to evaluate the dynamic redistribution of PKC in living SN56 cells, a cholinergic cell line, in response to halothane. Halothane induced PKC translocation in SN56 cells transfected with GFP-PKCbetaII. This effect was not suppressed by dantrolene, a drug that blocks halothane-induced Ca(2+) release from intracellular stores in these cells. These findings indicate that halothane induces PKC translocation in SN56 cells independently of its ability to release calcium from internal stores.
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Affiliation(s)
- R S Gomez
- Departamento de Cirurgia, Faculdade de Medicina da UFMG, Belo Horizonte-Minas Gerais, Brazil.
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