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Sipido KR, Willems R, Claus P, Mubagwa K, Kelly-Laubscher R, Katz AA, Gwanyanya A. Matthew Amoni (March 13, 1991-October 3, 2022). Heart Rhythm 2023; 20:793-794. [PMID: 37120289 DOI: 10.1016/j.hrthm.2023.03.012] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/02/2023] [Accepted: 03/02/2023] [Indexed: 05/01/2023]
Affiliation(s)
- Karin R Sipido
- Experimental Cardiology, Department of Cardiovascular Sciences, KU Leuven, Leuven, Belgium.
| | - Rik Willems
- Experimental Cardiology, Department of Cardiovascular Sciences, KU Leuven, Leuven, Belgium; Division of Cardiology, University Hospitals Leuven, Leuven, Belgium
| | - Piet Claus
- Imaging and Cardiovascular Dynamics, Department of Cardiovascular Sciences, KU Leuven, Leuven, Belgium
| | - Kanigula Mubagwa
- Experimental Cardiology, Department of Cardiovascular Sciences, KU Leuven, Leuven, Belgium; Department of Basic Sciences, Université Catholique de Bukavu, Bukavu, Democratic Republic of Congo
| | - Roisin Kelly-Laubscher
- Department of Pharmacology and Therapeutics, College of Medicine and Health, University College Cork, Cork, Ireland
| | - Arieh A Katz
- Division of Biochemistry and Structural Biology, University of Cape Town, Cape Town, South Africa
| | - Asfree Gwanyanya
- Department of Human Biology, University of Cape Town, Cape Town, South Africa
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Menzele A, Aboalgasm H, Ballo R, Gwanyanya A. Hyperglycaemia-induced impairment of the autorhythmicity and gap junction activity of mouse embryonic stem cell-derived cardiomyocyte-like cells. Histochem Cell Biol 2022; 159:329-337. [PMID: 36547741 DOI: 10.1007/s00418-022-02170-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 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] [Accepted: 11/22/2022] [Indexed: 12/24/2022]
Abstract
Diabetes mellitus with hyperglycaemia is a major risk factor for malignant cardiac dysrhythmias. However, the underlying mechanisms remain unclear, especially during the embryonic developmental phase of the heart. This study investigated the effect of hyperglycaemia on the pulsatile activity of stem cell-derived cardiomyocytes. Mouse embryonic stem cells (mESCs) were differentiated into cardiac-like cells through embryoid body (EB) formation, in either baseline glucose or high glucose conditions. Action potentials (APs) were recorded using a voltage-sensitive fluorescent dye and gap junction activity was evaluated using scrape-loading lucifer yellow dye transfer assay. Molecular components were detected using immunocytochemistry and immunoblot analyses. High glucose decreased the spontaneous beating rate of EBs and shortened the duration of onset of quinidine-induced asystole. Furthermore, it altered AP amplitude, but not AP duration, and had no impact on neither the expression of the hyperpolarisation-activated cyclic nucleotide-gated isoform 4 (HCN4) channel nor on the EB beating rate response to ivabradine nor isoprenaline. High glucose also decreased both the intercellular spread of lucifer yellow within an EB and the expression of the cardiac gap junction protein connexin 43 as well as upregulated the expression of transforming growth factor beta 1 (TGF-β1) and phosphorylated Smad3. High glucose suppressed the autorhythmicity and gap junction conduction of mESC-derived cardiomyocytes, via mechanisms probably involving TGF-β1/Smad3 signalling. The results allude to glucotoxicity related proarrhythmic effects, with potential clinical implications in foetal diabetic cardiac disease.
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Affiliation(s)
- Amanda Menzele
- Department of Human Biology, Faculty of Health Sciences, University of Cape Town, Observatory, Cape Town, 7925, South Africa
| | - Hamida Aboalgasm
- Department of Human Biology, Faculty of Health Sciences, University of Cape Town, Observatory, Cape Town, 7925, South Africa
| | - Robea Ballo
- Department of Human Biology, Faculty of Health Sciences, University of Cape Town, Observatory, Cape Town, 7925, South Africa
| | - Asfree Gwanyanya
- Department of Human Biology, Faculty of Health Sciences, University of Cape Town, Observatory, Cape Town, 7925, South Africa.
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Andriulė I, Pangonytė D, Gwanyanya A, Karčiauskas D, Mubagwa K, Mačianskienė R. Detection of TRPM6 and TRPM7 Proteins in Normal and Diseased Cardiac Atrial Tissue and Isolated Cardiomyocytes. Int J Mol Sci 2022; 23:ijms232314860. [PMID: 36499188 PMCID: PMC9736228 DOI: 10.3390/ijms232314860] [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] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2022] [Revised: 11/24/2022] [Accepted: 11/25/2022] [Indexed: 12/02/2022] Open
Abstract
Magnesium-sensitive transient receptor potential melastatin (TRPM) ion channels, TRPM6 and TRPM7, are present in several organs, but their roles in the heart remain unclear. Therefore, here, we studied the expression patterns of TRPM6 and TRPM7 in normal and diseased myocardium. Cardiac atrial tissue and cardiomyocytes were obtained from healthy pigs and undiseased human hearts as well as from hearts of patients with ischemic heart disease (IHD) or atrial fibrillation (AF). Immunofluorescence and ELISA were used to detect TRP proteins. TRPM6 and TRPM7 immunofluorescence signals, localized at/near the cell surface or intracellularly, were detected in pig and human atrial tissues. The TRP channel modulators carvacrol (CAR, 100 µM) or 2-aminoethoxydiphenyl borate (2-APB, 500 µM) decreased the TRPM7 signal, but enhanced that of TRPM6. At a higher concentration (2 mM), 2-APB enhanced the signals of both proteins. TRPM6 and TRPM7 immunofluorescence signals and protein concentrations were increased in atrial cells and tissues from IHD or AF patients. TRPM6 and TRPM7 proteins were both detected in cardiac atrial tissue, with relatively similar subcellular localization, but distinctive drug sensitivity profiles. Their upregulated expression in IHD and AF suggests a possible role of the channels in cardiac atrial disease.
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Affiliation(s)
- Inga Andriulė
- Institute of Cardiology, Lithuanian University of Health Sciences, 50103 Kaunas, Lithuania
| | - Dalia Pangonytė
- Institute of Cardiology, Lithuanian University of Health Sciences, 50103 Kaunas, Lithuania
| | - Asfree Gwanyanya
- Department of Human Biology, Faculty of Health Sciences, University of Cape Town, Cape Town 7700, South Africa
| | - Dainius Karčiauskas
- Institute of Cardiology, Lithuanian University of Health Sciences, 50103 Kaunas, Lithuania
- Department of Cardiac, Thoracic and Vascular Surgery, Hospital of Lithuanian University of Health Sciences Kauno Klinikos, 50161 Kaunas, Lithuania
| | - Kanigula Mubagwa
- Department of Cardiovascular Sciences, Faculty of Medicine, KU Leuven, 3000 Leuven, Belgium
- Department of Basic Sciences, Faculty of Medicine, Université Catholique de Bukavu, Bukavu, Congo
| | - Regina Mačianskienė
- Institute of Cardiology, Lithuanian University of Health Sciences, 50103 Kaunas, Lithuania
- Correspondence:
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Gwanyanya A, Mubagwa K. Emerging role of transient receptor potential (TRP) ion channels in cardiac fibroblast pathophysiology. Front Physiol 2022; 13:968393. [PMID: 36277180 PMCID: PMC9583832 DOI: 10.3389/fphys.2022.968393] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [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: 06/13/2022] [Accepted: 09/20/2022] [Indexed: 11/13/2022] Open
Abstract
Cardiac fibroblasts make up a major proportion of non-excitable cells in the heart and contribute to the cardiac structural integrity and maintenance of the extracellular matrix. During myocardial injury, fibroblasts can be activated to trans-differentiate into myofibroblasts, which secrete extracellular matrix components as part of healing, but may also induce cardiac fibrosis and pathological cardiac structural and electrical remodeling. The mechanisms regulating such cellular processes still require clarification, but the identification of transient receptor potential (TRP) channels in cardiac fibroblasts could provide further insights into the fibroblast-related pathophysiology. TRP proteins belong to a diverse superfamily, with subgroups such as the canonical (TRPC), vanilloid (TRPV), melastatin (TRPM), ankyrin (TRPA), polycystin (TRPP), and mucolipin (TRPML). Several TRP proteins form non-selective channels that are permeable to cations like Na+ and Ca2+ and are activated by various chemical and physical stimuli. This review highlights the role of TRP channels in cardiac fibroblasts and the possible underlying signaling mechanisms. Changes in the expression or activity of TRPs such as TRPCs, TRPVs, TRPMs, and TRPA channels modulate cardiac fibroblasts and myofibroblasts, especially under pathological conditions. Such TRPs contribute to cardiac fibroblast proliferation and differentiation as well as to disease conditions such as cardiac fibrosis, atrial fibrillation, and fibroblast metal toxicity. Thus, TRP channels in fibroblasts represent potential drug targets in cardiac disease.
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Affiliation(s)
- Asfree Gwanyanya
- Department of Human Biology, University of Cape Town, Cape Town, South Africa
- *Correspondence: Asfree Gwanyanya,
| | - Kanigula Mubagwa
- Department of Cardiovascular Sciences, K U Leuven, Leuven, Belgium
- Department of Basic Sciences, Faculty of Medicine, Université Catholique de Bukavu, Bukavu, Democratic Republic of Congo
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Alatrag F, Amoni M, Kelly-Laubscher R, Gwanyanya A. Cardioprotective effect of fingolimod against calcium paradox-induced myocardial injury in the isolated rat heart. Can J Physiol Pharmacol 2022; 100:134-141. [PMID: 34559972 DOI: 10.1139/cjpp-2021-0381] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [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] [Indexed: 11/22/2022]
Abstract
Fingolimod (FTY720) inhibits Ca2+-permeable, Mg2+-sensitive channels called transient receptor potential melastatin 7 (TRPM7), but its effects on Ca2+ paradox (CP) - induced myocardial damage has not been evaluated. We studied the effect of FTY720 on CP-induced myocardial damage and used other TRPM7 channel inhibitors nordihydroguaiaretic acid (NDGA) and Mg2+ to test if any effect of FTY720 was via TRPM7 inhibition. Langendorff-perfused Wistar rat hearts were treated with FTY720 or NDGA and subjected to a CP protocol consisting of Ca2+ depletion followed by Ca2+ repletion. Hearts of rats pre-treated with MgSO4 were also subjected to CP. Hemodynamic parameters were measured using an intraventricular balloon, and myocardial infarct size was quantified using triphenyltetrazolium chloride stain. TRPM7 proteins in ventricular tissue were detected using immunoblot analysis. FTY720, but not NDGA, decreased CP-induced infarct size. Both FTY720 and NDGA minimized the CP-induced elevation of left ventricular end-diastolic pressure, but only FTY720 ultimately improved ventricular developed pressure. Mg2+ pre-treatment had no effect on CP-induced infarct size, nor hemodynamic parameters during CP, nor the level of TRPM7 protein expression in ventricular tissue. Overall, FTY720 attenuated CP-induced myocardial damage, with potential therapeutic implications on Ca2+-mediated cardiotoxicity; however, the cardioprotective mechanism of FTY720 seems to be unrelated to TRPM7 channel modulation.
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Affiliation(s)
- Fatma Alatrag
- Department of Human Biology, Faculty of Health Sciences, University of Cape Town, Observatory 7925, Cape Town, South Africa
| | - Matthew Amoni
- Department of Human Biology, Faculty of Health Sciences, University of Cape Town, Observatory 7925, Cape Town, South Africa
| | - Roisin Kelly-Laubscher
- Department of Pharmacology and Therapeutics, The College of Medicine and Health, University College Cork, Ireland
- Department of Biological Sciences, Faculty of Science, University of Cape Town, Rondebosch 7700, Cape Town, South Africa
| | - Asfree Gwanyanya
- Department of Human Biology, Faculty of Health Sciences, University of Cape Town, Observatory 7925, Cape Town, South Africa
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Gwanyanya A, Andriulė I, Istrate BM, Easmin F, Mubagwa K, Mačianskienė R. Modulation of the Cardiac Myocyte Action Potential by the Magnesium-Sensitive TRPM6 and TRPM7-like Current. Int J Mol Sci 2021; 22:ijms22168744. [PMID: 34445449 PMCID: PMC8395930 DOI: 10.3390/ijms22168744] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2021] [Revised: 08/04/2021] [Accepted: 08/12/2021] [Indexed: 01/08/2023] Open
Abstract
The cardiac Mg2+-sensitive, TRPM6, and TRPM7-like channels remain undefined, especially with the uncertainty regarding TRPM6 expression in cardiomyocytes. Additionally, their contribution to the cardiac action potential (AP) profile is unclear. Immunofluorescence assays showed the expression of the TRPM6 and TRPM7 proteins in isolated pig atrial and ventricular cardiomyocytes, of which the expression was modulated by incubation in extracellular divalent cation-free conditions. In patch clamp studies of cells dialyzed with solutions containing zero intracellular Mg2+ concentration ([Mg2+]i) to activate the Mg2+-sensitive channels, raising extracellular [Mg2+] ([Mg2+]o) from the 0.9-mM baseline to 7.2 mM prolonged the AP duration (APD). In contrast, no such effect was observed in cells dialyzed with physiological [Mg2+]i. Under voltage clamp, in cells dialyzed with zero [Mg2+]i, depolarizing ramps induced an outward-rectifying current, which was suppressed by raising [Mg2+]o and was absent in cells dialyzed with physiological [Mg2+]i. In cells dialyzed with physiological [Mg2+]i, raising [Mg2+]o decreased the L-type Ca2+ current and the total delayed-rectifier current but had no effect on the APD. These results suggest a co-expression of the TRPM6 and TRPM7 proteins in cardiomyocytes, which are therefore the molecular candidates for the native cardiac Mg2+-sensitive channels, and also suggest that the cardiac Mg2+-sensitive current shortens the APD, with potential implications in arrhythmogenesis.
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Affiliation(s)
- Asfree Gwanyanya
- Department of Cardiovascular Sciences, KU Leuven, 3000 Leuven, Belgium; (A.G.); (B.M.I.); (F.E.); (K.M.)
- Department of Human Biology, University of Cape Town, Cape Town 7925, South Africa
| | - Inga Andriulė
- Institute of Cardiology, Lithuanian University of Health Sciences, 50103 Kaunas, Lithuania;
| | - Bogdan M. Istrate
- Department of Cardiovascular Sciences, KU Leuven, 3000 Leuven, Belgium; (A.G.); (B.M.I.); (F.E.); (K.M.)
| | - Farjana Easmin
- Department of Cardiovascular Sciences, KU Leuven, 3000 Leuven, Belgium; (A.G.); (B.M.I.); (F.E.); (K.M.)
| | - Kanigula Mubagwa
- Department of Cardiovascular Sciences, KU Leuven, 3000 Leuven, Belgium; (A.G.); (B.M.I.); (F.E.); (K.M.)
- Department of Basic Sciences, Faculty of Medicine, Université Catholique de Bukavu, Bukavu, Congo
| | - Regina Mačianskienė
- Institute of Cardiology, Lithuanian University of Health Sciences, 50103 Kaunas, Lithuania;
- Correspondence:
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Aboalgasm H, Ballo R, Gwanyanya A. Organisational alteration of cardiac myofilament proteins by hyperglycaemia in mouse embryonic stem cell-derived cardiomyocytes. J Muscle Res Cell Motil 2021; 42:419-428. [PMID: 34387802 DOI: 10.1007/s10974-021-09607-9] [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] [Received: 06/02/2021] [Accepted: 08/04/2021] [Indexed: 11/28/2022]
Abstract
The exposure of the developing foetal heart to hyperglycaemia in mothers with diabetes mellitus is a major risk factor for foetal cardiac complications that lead to heart failure. We studied the effects of hyperglycaemia on the layout of cardiac myofilament proteins in stem cell-derived cardiomyocytes and their possible underlying mechanisms. Mouse embryonic stem cells (mESCs) were differentiated into cardiac-like cells and cultured in media containing baseline- or high glucose concentrations. Cellular biomarkers were detected using Western blot analysis, immunocytochemistry, 5-ethynyl-2'-deoxyuridine (EdU) cell proliferation assay, and terminal deoxynucleotidyl transferase dUTP nick-end labelling (TUNEL) assay. High glucose decreased the proportion of cardiac troponin T and α-actinin 2 positive mESCs as well as disrupted the α-actinin 2 striated pattern and the distribution of the cardiac myosin heavy chain α- and β isoforms. However, there was no alteration of the cellular EdU uptake nor the expression of the receptor of advanced glycation end-product (RAGE). High glucose also increased the presence of the oxidative stress marker nitrotyrosine as well as the number of TUNEL-stained nuclei in cardiac-like cells. Treatment with the antioxidant N-acetyl cysteine decreased the number of TUNEL-stained cells in high glucose and improved the α-actinin 2 striated pattern. Hyperglycaemia negatively impacted the expression and cellular organisation of cardiac myofilament proteins in mESC-derived cardiomyocytes through oxidative stress. The results add further insights into the pathophysiological mechanisms of cardiac contractile dysfunction in diabetic cardiac developmental disease.
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Affiliation(s)
- Hamida Aboalgasm
- Department of Human Biology, Faculty of Health Sciences, University of Cape Town, Observatory, 7925, Cape Town, South Africa
| | - Robea Ballo
- Department of Human Biology, Faculty of Health Sciences, University of Cape Town, Observatory, 7925, Cape Town, South Africa
| | - Asfree Gwanyanya
- Department of Human Biology, Faculty of Health Sciences, University of Cape Town, Observatory, 7925, Cape Town, South Africa.
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Aboalgasm H, Ballo R, Mkatazo T, Gwanyanya A. Hyperglycaemia-Induced Contractile Dysfunction and Apoptosis in Cardiomyocyte-Like Pulsatile Cells Derived from Mouse Embryonic Stem Cells. Cardiovasc Toxicol 2021; 21:695-709. [PMID: 33983555 DOI: 10.1007/s12012-021-09660-3] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/29/2021] [Accepted: 05/07/2021] [Indexed: 10/21/2022]
Abstract
Hyperglycaemia, a key metabolic abnormality in diabetes mellitus, is implicated in pathological cardiogenesis during embryological development. However, the underlying mechanisms and potential therapeutic targets remain unknown. We, therefore, studied the effect of hyperglycaemia on mouse embryonic stem cell (mESC) cardiac differentiation. The mESCs were differentiated via embryoid body (EB) formation and cultured under conditions with baseline (25 mM) or high (50 mM) glucose. Time-lapse microscopy images of pulsatile mESCs and Ca2+ transients were recorded. Biomarkers of cellular changes were detected using immunocytochemistry, terminal deoxynucleotidyl transferase dUTP nick-end labelling (TUNEL) assay, and Western blot analyses. Differentiated, spontaneously beating mESCs stained positive for cardiac troponin T, α-actinin 2, myosin heavy chain, and connexin 43. Hyperglycaemia decreased the EB diameter and number of beating EBs as well as the cellular amplitude of contraction, the Ca2+ transient, and the contractile response to caffeine (1 mM), but had no effect on the expression of the sarco-endoplasmic reticulum calcium transport ATPase 2 (SERCA 2). Furthermore, hyperglycaemia decreased the expression of B cell lymphoma 2 (Bcl-2) and increased the expression of cytoplasmic cytochrome c and the number of TUNEL-positive cells, but had no effect on the expression of one of the mitochondrial fusion regulatory proteins, optic atrophy protein 1 (OPA1). Overall, hyperglycaemia suppressed the mESC cardiomyocyte-like differentiation and induced contractile dysfunction. The results are consistent with mechanisms involving abnormal Ca2+ handling and mitochondrial-dependent apoptosis, factors which represent potential therapeutic targets in developmental diabetic cardiac disease.
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Affiliation(s)
- Hamida Aboalgasm
- Department of Human Biology, Faculty of Health Sciences, University of Cape Town, Observatory, Cape Town, 7925, South Africa
| | - Robea Ballo
- Department of Human Biology, Faculty of Health Sciences, University of Cape Town, Observatory, Cape Town, 7925, South Africa
| | - Thulisa Mkatazo
- Department of Human Biology, Faculty of Health Sciences, University of Cape Town, Observatory, Cape Town, 7925, South Africa
| | - Asfree Gwanyanya
- Department of Human Biology, Faculty of Health Sciences, University of Cape Town, Observatory, Cape Town, 7925, South Africa.
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Gwanyanya A, Godsmark CN, Kelly-Laubscher R. Ethanolamine: A Potential Promoiety with Additional Effects in the Brain. CNS Neurol Disord Drug Targets 2020; 21:108-117. [PMID: 33319663 DOI: 10.2174/1871527319999201211204645] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/24/2020] [Revised: 08/14/2020] [Accepted: 09/11/2020] [Indexed: 11/22/2022]
Abstract
Ethanolamine is a bioactive molecule found in several cells, including those in the central nervous system (CNS). In the brain, ethanolamine and ethanolamine-related molecules have emerged as prodrug moieties that can promote drug movement across the blood-brain barrier. This improvement in the ability to target drugs to the brain may also mean that in the process ethanolamine concentrations in the brain are increased enough for ethanolamine to exert its own neurological ac-tions. Ethanolamine and its associated products have various positive functions ranging from cell signaling to molecular storage, and alterations in their levels have been linked to neurodegenerative conditions such as Alzheimer's disease. This mini-review focuses on the effects of ethanolamine in the CNS and highlights the possible implications of these effects for drug design.
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Affiliation(s)
- Asfree Gwanyanya
- Department of Human Biology, Faculty of Health Sciences, University of Cape Town, Cape Town,. South Africa
| | - Christie Nicole Godsmark
- School of Public Health, College of Medicine and Health, University College Cork, Cork,. Ireland
| | - Roisin Kelly-Laubscher
- Department of Pharmacology and Therapeutics, School of Medicine, College of Medicine and Health, University College Cork, Cork,. Ireland
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Aboalgasm H, Petersen M, Gwanyanya A. Improvement of cardiac ventricular function by magnesium treatment in chronic streptozotocin-induced diabetic rat heart. Cardiovasc J Afr 2020; 32:141-148. [PMID: 33300932 DOI: 10.5830/cvja-2020-054] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2020] [Accepted: 11/11/2020] [Indexed: 11/06/2022] Open
Abstract
OBJECTIVE Chronic diabetes mellitus is associated with detrimental cardiovascular complications and electrolyte imbalances such as hypomagnesaemia. We investigated the effect of magnesium (Mg2+) on cardiac function and the possible role of histological and electrical alterations in chronic, streptozotocin-induced diabetic rats. METHODS Wistar rats were treated once intraperitoneally with streptozotocin or citrate, and then daily with MgSO4 or saline for four weeks. Cardiac contractile and electrocardiographic parameters were measured on Langendorff-perfused hearts. Other hearts were histologically stained or immunoblotted for the mitochondrial ATP synthase (ATP5A). RESULTS In diabetic hearts, Mg2+ prevented a diabetes-induced decrease in left ventricular developed pressure and improved contractility indices, as well as attenuated the reduction in heart rate and prolongation of QT interval, but not the QT interval corrected for heart rate (QTc). Histologically, there were neither differences in cardiomyocyte width nor interstitial collagen. The expression of ATP5A was not different among the treatment groups. CONCLUSIONS Mg2+ supplementation improved cardiac contractile activity in chronic diabetic hearts via mechanisms unrelated to electrocardiographic or histologically detectable myocardial alterations.
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Affiliation(s)
- Hamida Aboalgasm
- Department of Human Biology, Faculty of Health Sciences, University of Cape Town, Cape Town, South Africa
| | - Morea Petersen
- Department of Human Biology, Faculty of Health Sciences, University of Cape Town, Cape Town, South Africa
| | - Asfree Gwanyanya
- Department of Human Biology, Faculty of Health Sciences, University of Cape Town, Cape Town, South Africa.
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Araibi H, van der Merwe E, Gwanyanya A, Kelly-Laubscher R. The effect of sphingosine-1-phosphate on the endothelial glycocalyx during ischemia-reperfusion injury in the isolated rat heart. Microcirculation 2020; 27:e12612. [PMID: 32017300 DOI: 10.1111/micc.12612] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2019] [Revised: 01/24/2020] [Accepted: 01/30/2020] [Indexed: 12/25/2022]
Abstract
OBJECTIVE Sphingosine-1-phosphate is a natural metabolite that is cardioprotective, but its effects on endothelial glycocalyx damage during ischemia-reperfusion are unknown. Therefore, we investigated the effect of sphingosine-1-phosphate on the endothelial glycocalyx during ischemia-reperfusion. METHODS Isolated hearts from Wistar rats were perfused on a Langendorff system with Krebs-Henseleit buffer and pretreated with sphingosine-1-phosphate (10 nmol/L) before ischemia-reperfusion. Infarct size was measured by triphenyl tetrazolium chloride staining (n ≥ 6 per group). Cardiac edema was assessed by calculating total water content (n = 7 per group) and histologically quantifying the interstitial compartment (n ≥ 3 per group). The post-ischemic coronary release of syndecan-1 was quantified using ELISA. Syndecan-1 immunostaining intensity was assessed in perfusion-fixed hearts (n ≥ 3 per group). RESULTS Pretreatment with sphingosine-1-phosphate decreased infarct size in isolated hearts subjected to ischemia-reperfusion (P = .01 vs ischemia-reperfusion). However, sphingosine-1-phosphate had no effect on syndecan-1 levels in the coronary effluent or on the intensity of the syndecan-1 immunostaining signal in cardiac tissue. Heart total water content was not significantly different between control and ischemic groups but was significantly decreased in hearts treated with sphingosine-1-phosphate alone. CONCLUSION These results suggest that sphingosine-1-phosphate-induced cardioprotection against ischemia-reperfusion injury is not mediated by the maintenance of syndecan-1 in the endothelial glycocalyx.
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Affiliation(s)
- Hala Araibi
- Department of Human Biology, Faculty of Health Sciences, University of Cape Town, Cape Town, South Africa
| | - Elizabeth van der Merwe
- Department of Human Biology, Faculty of Health Sciences, University of Cape Town, Cape Town, South Africa
| | - Asfree Gwanyanya
- Department of Human Biology, Faculty of Health Sciences, University of Cape Town, Cape Town, South Africa
| | - Roisin Kelly-Laubscher
- Department of Human Biology, Faculty of Health Sciences, University of Cape Town, Cape Town, South Africa.,Department of Biological Sciences, Faculty of Science, University of Cape Town, Cape Town, South Africa.,Department of Pharmacology & Therapeutics, The College of Medicine and Health, University College Cork, Cork, Ireland
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Amoni M, Kelly-Laubscher R, Petersen M, Gwanyanya A. Cardioprotective and Anti-arrhythmic Effects of Magnesium Pretreatment Against Ischaemia/Reperfusion Injury in Isoprenaline-Induced Hypertrophic Rat Heart. Cardiovasc Toxicol 2017; 17:49-57. [PMID: 26696240 DOI: 10.1007/s12012-015-9355-6] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
The effects of magnesium (Mg2+) on ischaemic complications of pathological cardiac hypertrophy are unclear. In this study, we investigated effects of Mg2+ pretreatment on ischaemia/reperfusion (I/R) injury in isoprenaline (ISO)-induced hypertrophic hearts. Wistar rats were treated for 7 days with different combinations of ISO (1.25 mg/kg) subcutaneously, MgSO4 (270 mg/kg) intraperitoneally, or vehicle (saline). On the eighth day, hearts were either subjected to regional I/R during Langendorff perfusion or histologically stained with haematoxylin and eosin and Masson's trichrome. Haemodynamic and electrocardiographic parameters were recorded using the PowerLab data-acquisition system. Infarcts were identified by triphenyltetrazolium chloride staining. Plasma Mg2+ was measured using photometric assays. Mg2+ pretreatment significantly decreased I/R-induced infarct size (p = 0.001) and the overall arrhythmia score (p < 0.001) of I/R-induced ventricular ectopics, ventricular tachycardia, and ventricular fibrillation in hypertrophic hearts, but not non-hypertrophied hearts. Mg2+ also improved post-I/R left ventricular developed pressure in hypertrophic hearts. However, Mg2+ did not reverse the ISO-induced myocyte thickening and interstitial fibrosis or increases in heart weight. Plasma Mg2+ was not different among treatment groups. These results suggest that Mg2+ pretreatment may protect against I/R-induced injury and malignant arrhythmias in hypertrophic hearts, possibly via mechanisms unrelated to long-lasting changes in plasma Mg2+ or prevention of structural changes such as fibrosis.
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Affiliation(s)
- Matthew Amoni
- Department of Human Biology, Faculty of Health Sciences, University of Cape Town, Observatory, Cape Town, 7925, South Africa
| | - Roisin Kelly-Laubscher
- Department of Biological Sciences, Faculty of Science, University of Cape Town, Rondebosch, Cape Town, 7700, South Africa.,Academic Development Programme, Centre for Higher Education Development, University of Cape Town, Cape Town, South Africa
| | - Morea Petersen
- Department of Human Biology, Faculty of Health Sciences, University of Cape Town, Observatory, Cape Town, 7925, South Africa
| | - Asfree Gwanyanya
- Department of Human Biology, Faculty of Health Sciences, University of Cape Town, Observatory, Cape Town, 7925, South Africa.
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Amoni M, Kelly-Laubscher R, Blackhurst D, Gwanyanya A. Beneficial Effects of Magnesium Treatment on Heart Rate Variability and Cardiac Ventricular Function in Diabetic Rats. J Cardiovasc Pharmacol Ther 2016; 22:169-178. [PMID: 27276916 DOI: 10.1177/1074248416653831] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
BACKGROUND Diabetes mellitus induces life-threatening cardiovascular complications such as cardiac autonomic neuropathy and ventricular dysfunction and is associated with hypomagnesemia. In this study, we investigated the short-term effects of magnesium (Mg2+) treatment on streptozotocin (STZ)-induced diabetic cardiac complications. METHODS Adult Wistar rats were treated once with STZ (50 mg/kg, intraperitoneally [ip]) or vehicle (citrate) and then daily for 7 days with MgSO4 (270 mg/kg, ip) or saline. On the eighth day, in vivo tail-pulse plethysmography was recorded for heart rate variability (HRV) analysis, and ex vivo Langendorff-based left ventricular (LV) pressure-volume parameters were measured using an intraventricular balloon. Measurements of plasma lipid and Mg2+ levels as well as blood glucose and cardiac tissue Mg2+ levels were also performed. RESULTS Treatment with Mg2+ prevented diabetes-induced alterations in the standard deviation of the averages of normal-to-normal (NN) intervals (SDANN), root mean square differences of successive NN intervals (RMSSD), heart rate, and low-frequency (LF) power-high-frequency (HF) power ratio. In addition, Mg2+ restored orthostatic stress-induced changes in SDANN, RMSSD, and LF-HF ratio in diabetic rats. In isolated hearts, Mg2+ reversed the diabetes-induced decrease in LV end-diastolic elastance and the right shift of end-diastolic equilibrium volume intercept, without altering LV-developed pressure or end-systolic elastance. However, Mg2+ did not prevent the elevation in blood glucose, total cholesterol, and triglycerides or the decrease in high-density lipoprotein cholesterol in diabetes. Plasma- or cardiac tissue Mg2+ was not different among the treatment groups. CONCLUSION These results suggest that Mg2+ treatment may attenuate diabetes-induced reduction in HRV and improve LV diastolic distensibility, without preventing hyperglycemia and dyslipidemia. Thus, Mg2+ may have a modulatory role in the early stages of diabetic cardiovascular complications.
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Affiliation(s)
- Matthew Amoni
- 1 Department of Human Biology, University of Cape Town, Cape Town, South Africa
| | - Roisin Kelly-Laubscher
- 2 Department of Biological Sciences, University of Cape Town, Cape Town, South Africa.,3 Centre for Higher Education Development, University of Cape Town, Cape Town, South Africa
| | - Dee Blackhurst
- 4 Department of Pathology, University of Cape Town, Cape Town, South Africa
| | - Asfree Gwanyanya
- 1 Department of Human Biology, University of Cape Town, Cape Town, South Africa
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Garson C, Kelly-Laubscher R, Blackhurst D, Gwanyanya A. Lack of cardioprotection by single-dose magnesium prophylaxis on isoprenaline-induced myocardial infarction in adult Wistar rats. Cardiovasc J Afr 2015. [PMID: 26212925 PMCID: PMC4780018 DOI: 10.5830/cvja-2015-055] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [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] [Indexed: 12/03/2022] Open
Abstract
Aim Magnesium (Mg2+) is effective in treating cardiovascular disorders such as arrhythmias and pre-eclampsia, but its role during myocardial infarction (MI) remains uncertain. In this study, we investigated the effects of Mg2+ pre-treatment on isoprenaline (ISO)-induced MI in vivo. Methods Rats divided into four groups were each pre-treated with either MgSO4 (270 mg/kg intraperitoneally) or an equivalent volume of physiological saline, prior to the ISO (67 mg/kg subcutaneously) or saline treatments. One day post-treatment, the electrocardiogram and left ventricular blood pressures were recorded. Infarcts were determined using 2,3,5-triphenyltetrazolium chloride staining, and serum markers of lipid peroxidation were measured with spectrophotometric assays. Results Mg2+ pre-treatment neither altered the ISO-induced infarct size compared with ISO treatment alone (p > 0.05), nor reversed the low-voltage electrocardiogram or the prominent Q waves induced by ISO, despite a trend to decreased Q waves. Similarly, Mg2+ did not prevent the ISO-induced decrease in peak left ventricular blood pressure or the decrease in minimal rate of pressure change. Mg2+ did not reverse the ISO-induced gain in heart weight or loss of body weight. Neither ISO nor Mg2+ altered the concentrations of lipid peroxidation markers 24 hours post MI induction. Conclusion Although Mg2+ had no detrimental effects on electrical or haemodynamic activity in ISO-induced MI, the lack of infarct prevention may detract from its utility in MI therapy.
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Affiliation(s)
- Christie Garson
- Department of Human Biology, Faculty of Health Sciences, University of Cape Town, Cape Town, South Africa
| | - Roisin Kelly-Laubscher
- Department of Human Biology, Faculty of Health Sciences, University of Cape Town, Cape Town, South Africa
| | - Dee Blackhurst
- Department of Clinical Laboratory Sciences, Faculty of Health Sciences, University of Cape Town, Cape Town, South Africa
| | - Asfree Gwanyanya
- Department of Human Biology, Faculty of Health Sciences, University of Cape Town, Cape Town, South Africa.
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Gwanyanya A, Macianskiene R, Mubagwa K. Insights into the effects of diclofenac and other non-steroidal anti-inflammatory agents on ion channels. ACTA ACUST UNITED AC 2012; 64:1359-75. [PMID: 22943167 DOI: 10.1111/j.2042-7158.2012.01479.x] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
OBJECTIVES Diclofenac and other non-steroidal anti-inflammatory drugs (NSAIDs) are widely used in the treatment of inflammation and pain. Most effects of NSAIDs are attributed to the inhibition of cyclooxygenases (COX). However, many NSAIDs may have other effects not related to COX, including the modulation of various ion channels. The clinical implications of the effects on channels are not fully understood. This review outlines the effects of NSAIDs, with special attention to diclofenac, on ion channels and highlights the possible underlying mechanisms. KEY FINDINGS NSAIDs have effects on channels such as inhibition, activation or changes in expression patterns. The channels affected include voltage-gated Na(+) , Ca(2+) , or K(+) channels, ligand-gated K(+) channels, transient receptor potential and other cation channels as well as chloride channels in several types of cells. The mechanisms of drug actions not related to COX inhibition may involve drug-channel interactions, interference with the generation of second messengers, changes in channel expression, or synergistic/antagonist interactions with other channel modulators. SUMMARY The effects on ion channels may account for novel therapeutic actions of NSAIDs or for adverse effects. Among the NSAIDs, diclofenac may serve as a template for developing new channel modulators and as a tool for investigating the actions of other drugs.
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Affiliation(s)
- Asfree Gwanyanya
- Department of Human Biology, Faculty of Health Sciences, University of Cape Town, Cape Town, South Africa
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Gwanyanya A, Macianskiene R, Bito V, Sipido KR, Vereecke J, Mubagwa K. Inhibition of the calcium-activated chloride current in cardiac ventricular myocytes by N-(p-amylcinnamoyl)anthranilic acid (ACA). Biochem Biophys Res Commun 2010; 402:531-6. [PMID: 20971070 DOI: 10.1016/j.bbrc.2010.10.069] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2010] [Accepted: 10/17/2010] [Indexed: 12/01/2022]
Abstract
N-(p-amylcinnamoyl)anthranilic acid (ACA), a phospholipase A(2) (PLA(2)) inhibitor, is structurally-related to non-steroidal anti-inflammatory drugs (NSAIDs) of the fenamate group and may also modulate various ion channels. We used the whole-cell, patch-clamp technique at room temperature to investigate the effects of ACA on the Ca(2+)-activated chloride current (I(Cl(Ca))) and other chloride currents in isolated pig cardiac ventricular myocytes. ACA reversibly inhibited I(Cl(Ca)) in a concentration-dependent manner (IC(50)=4.2 μM, n(Hill)=1.1), without affecting the L-type Ca(2+) current. Unlike ACA, the non-selective PLA(2) inhibitor bromophenacyl bromide (BPB; 50 μM) had no effect on I(Cl(Ca)). In addition, the analgesic NSAID structurally-related to ACA, diclofenac (50 μM) also had no effect on I(Cl(Ca)), whereas the current in the same cells could be suppressed by chloride channel blockers flufenamic acid (FFA; 100 μM) or 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (DIDS;100 μM). Besides I(Cl(Ca)), ACA (50 μM) also suppressed the cAMP-activated chloride current, but to a lesser extent. It is proposed that the inhibitory effects of ACA on I(Cl(Ca)) are PLA(2)-independent and that the drug may serve as a useful tool in understanding the nature and function of cardiac anion channels.
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Affiliation(s)
- Asfree Gwanyanya
- Division of Experimental Cardiac Surgery, Department of Cardiovascular Diseases, University of Leuven, Leuven, Belgium
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Macianskiene R, Gwanyanya A, Sipido KR, Vereecke J, Mubagwa K. Induction of a novel cation current in cardiac ventricular myocytes by flufenamic acid and related drugs. Br J Pharmacol 2010; 161:416-29. [PMID: 20735425 PMCID: PMC2989592 DOI: 10.1111/j.1476-5381.2010.00901.x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [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: 02/01/2010] [Revised: 03/26/2010] [Accepted: 04/18/2010] [Indexed: 11/30/2022] Open
Abstract
BACKGROUND AND PURPOSE Interest in non-selective cation channels has increased recently following the discovery of transient receptor potential (TRP) proteins, which constitute many of these channels. EXPERIMENTAL APPROACH We used the whole-cell patch-clamp technique on isolated ventricular myocytes to investigate the effect of flufenamic acid (FFA) and related drugs on membrane ion currents. KEY RESULTS With voltage-dependent and other ion channels inhibited, cells that were exposed to FFA, N-(p-amylcinnamoyl)anthranilic acid (ACA), ONO-RS-082 or niflumic acid (NFA) responded with an increase in currents. The induced current reversed at +38 mV, was unaffected by lowering extracellular Cl(-) concentration or by the removal of extracellular Ca(2+) and Mg(2+), and its inward but not outward component was suppressed in Na(+)-free extracellular conditions. The current was suppressed by Gd(3+) but was resistant to 2-aminoethoxydiphenyl borate (2-APB) and to amiloride. It could not be induced by the structurally related non-fenamate anti-inflammatory drug diclofenac, nor by the phospholipase-A(2) inhibitors bromoenol lactone and bromophenacyl bromide. Muscarinic or alpha-adrenoceptor activation or application of diacylglycerol failed to induce or modulate the current. CONCLUSIONS AND IMPLICATIONS Flufenamic acid and related drugs activate a novel channel conductance, where Na(+) is likely to be the major charge carrier. The identity of the channel remains unclear, but it is unlikely to be due to Ca(2+)-activated (e.g. TRPM4/5), Mg(2+)-sensitive (e.g. TRPM7) or divalent cation-selective TRPs.
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Affiliation(s)
- R Macianskiene
- Division of Experimental Cardiac Surgery, Department of Cardiovascular Diseases, University of Leuven, Leuven, Belgium
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Macianskiene R, Gwanyanya A, Vereecke J, Mubagwa K. Inhibition of the magnesium-sensitive TRPM7-like channel in cardiac myocytes by nonhydrolysable GTP analogs: involvement of phosphoinositide metabolism. Cell Physiol Biochem 2008; 22:109-18. [PMID: 18769037 DOI: 10.1159/000149788] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/26/2008] [Indexed: 11/19/2022] Open
Abstract
BACKGROUND/AIMS A magnesium-inhibited, transient receptor potential melastatin 7 (TRPM7)-like channel is expressed in cardiac cell membranes. The role and regulation of this channel by intracellular nucleotides and membrane components remain unclear. METHODS We used the whole-cell voltage-clamp technique in pig isolated ventricular myocytes to investigate the effect of non-hydrolysable guanine nucleotides. RESULTS The TRPM7-like current, induced by intracellular dialysis with low [Mg(2+)], remained stable when the intracellular solution contained GTP. Substituting GTP by GTP-gamma-S or Gp-pNp, but not GDP-beta-S, induced a run-down of the current. Under dialysis with GTP-gamma-S, inhibiting phospholipase C by edelfosine or intracellularly adding exogenous phosphatidylinositol-4,5-bisphosphate (PIP(2)) decreased run-down, whereas extracellularly applying carbachol and phenylephrine accelerated it. Pretreatment of cells with pertussis toxin did not prevent the run-down induced by GTP-gamma-S. CONCLUSION Guanine nucleotides can modulate cardiac TRPM7-like channels via a mechanism linked to G proteins and to PIP(2) metabolism.
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Affiliation(s)
- Regina Macianskiene
- Department of Cardiovascular Diseases, Katholieke Universiteit Leuven, Leuven, Belgium
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Mubagwa K, Gwanyanya A, Zakharov S, Macianskiene R. Regulation of cation channels in cardiac and smooth muscle cells by intracellular magnesium. Arch Biochem Biophys 2007; 458:73-89. [PMID: 17123458 DOI: 10.1016/j.abb.2006.10.014] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.5] [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: 03/09/2006] [Revised: 10/16/2006] [Accepted: 10/16/2006] [Indexed: 01/06/2023]
Abstract
Magnesium regulates various ion channels in many tissues, including those of the cardiovascular system. General mechanisms by which intracellular Mg(2+) (Mg(i)(2+)) regulates channels are presented. These involve either a direct interaction with the channel, or an indirect modification of channel function via other proteins, such as enzymes or G proteins, or via membrane surface charges and phospholipids. To provide an insight into the role of Mg(i)(2+) in the cardiovascular system, effects of Mg(i)(2+) on major channels in cardiac and smooth muscle cells and the underlying mechanisms are then reviewed. Although Mg(i)(2+) concentrations are known to be stable, conditions under which they may change exist, such as following stimulation of beta-adrenergic receptors and of insulin receptors, or during pathophysiological conditions such as ischemia, heart failure or hypertension. Modifications of cardiovascular electrical or mechanical function, possibly resulting in arrhythmias or hypertension, may result from such changes of Mg(i)(2+) and their effects on cation channels.
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Affiliation(s)
- Kanigula Mubagwa
- Division of Experimental Cardiac Surgery, Department of Heart and Vessel Diseases, Katholieke Universiteit Leuven, Campus Gasthuisberg, Herestraat 49, B-3000 Leuven, Belgium.
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Gwanyanya A, Sipido KR, Vereecke J, Mubagwa K. ATP and PIP2 dependence of the magnesium-inhibited, TRPM7-like cation channel in cardiac myocytes. Am J Physiol Cell Physiol 2006; 291:C627-35. [PMID: 16707555 DOI: 10.1152/ajpcell.00074.2006] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.9] [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: 11/22/2022]
Abstract
The Mg(2+)-inhibited cation (MIC) current (I(MIC)) in cardiac myocytes biophysically resembles currents of heterologously expressed transient receptor potential (TRP) channels, particularly TRPM6 and TRPM7, known to be important in Mg(2+) homeostasis. To understand the regulation of MIC channels in cardiac cells, we used the whole cell voltage-clamp technique to investigate the role of intracellular ATP in pig, rat, and guinea pig isolated ventricular myocytes. I(MIC), studied in the presence or absence of extracellular divalent cations, was sustained for >or=50 min after patch rupture in ATP-dialyzed cells, whereas in ATP-depleted cells I(MIC) exhibited complete rundown. Equimolar substitution of internal ATP by its nonhydrolyzable analog adenosine 5'-(beta,gamma-imido)triphosphate failed to prevent rundown. In ATP-depleted cells, inhibition of lipid phosphatases by fluoride + vanadate + pyrophosphate prevented I(MIC) rundown. In contrast, under similar conditions neither the inhibition of protein phosphatases 1, 2A, 2B or of protein tyrosine phosphatase nor the activation of protein kinase A (forskolin, 20 microM) or protein kinase C (phorbol myristate acetate, 100 nM) could prevent rundown. In ATP-loaded cells, depletion of phosphatidylinositol 4,5-bisphosphate (PIP(2)) by prevention of its resynthesis (10 microM wortmannin or 15 microM phenylarsine oxide) induced rundown of I(MIC). Finally, loading ATP-depleted cells with exogenous PIP(2) (10 microM) prevented rundown. These results suggest that PIP(2), likely generated by ATP-utilizing lipid kinases, is necessary for maintaining cardiac MIC channel activity.
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Affiliation(s)
- Asfree Gwanyanya
- Experimental Cardiac Surgery, Heart and Vessel Diseases, Katholieke Universiteit Leuven, Leuven, Belgium
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Gwanyanya A, Amuzescu B, Zakharov SI, Macianskiene R, Sipido KR, Bolotina VM, Vereecke J, Mubagwa K. Magnesium-inhibited, TRPM6/7-like channel in cardiac myocytes: permeation of divalent cations and pH-mediated regulation. J Physiol 2004; 559:761-76. [PMID: 15272039 PMCID: PMC1665187 DOI: 10.1113/jphysiol.2004.067637] [Citation(s) in RCA: 77] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Cardiac tissue expresses several TRP proteins as well as a Mg2+ -inhibited, non-selective cation current (IMIC) that bears many characteristics of TRP channel currents. We used the whole-cell voltage clamp technique in pig and rat ventricular myocytes to characterize the permeation, blockage properties and regulation of the cardiac IMIC channels in order to compare them with TRP channels, in particular with Mg2+ -sensitive TRPM6 and TRPM7. We show that removing extracellular divalent cations unmasks large inward and outward monovalent currents, which can be inhibited by intracellular Mg2+. Inward currents are suppressed upon replacing extracellular Na+ by NMDG+. Divalent cations block monovalent IMIC and, at 10-20 mm, carry measurable currents. Their efficacy sequence in decreasing outward IMIC (Ni2+ = Mg2+ > Ca2+ > Ba2+) and in inducing inward IMIC (Ni2+ >> Mg2+ = Ca2+ approximately Ba2+), and their permeabilities calculated from reversal potentials are similar to those of TRPM6 and TRPM7 channels. The trivalent cations Gd3+ and Dy3+ also block IMIC in a voltage-dependent manner (delta = 0.4-0.5). In addition they inhibit the inward current carried by divalent cations. IMIC is regulated by pH. Decreasing or increasing extracellular pH decreased and increased IMIC, respectively (pH0.5 = 6.9, nH = 0.98). Qualitatively similar results were obtained on IMIC in rat basophilic leukaemia cells. These effects in cardiac myocytes were absent in the presence of high intracellular buffering by 40 mm Hepes. Our results suggest that IMIC in cardiac cells is due to TRPM channels, most probably to TRPM6 or TRPM7 channels or to their heteromultimeres.
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Affiliation(s)
- Asfree Gwanyanya
- Centre for Experimental Surgery & Anaesthesiology, Katholieke Universiteit, Leuven, Belgium
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