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Yang X, Na C, Wang Y. Angelica decursiva exerts antihypertensive activity by inhibiting L-type calcium channel. J Ethnopharmacol 2023; 313:116527. [PMID: 37088236 DOI: 10.1016/j.jep.2023.116527] [Citation(s) in RCA: 1] [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: 03/06/2023] [Revised: 04/15/2023] [Accepted: 04/18/2023] [Indexed: 05/03/2023]
Abstract
ETHNOPHARMACOLOGICAL RELEVANCE Angelica decursiva is a perennial herb that belongs to the Umbelliferae family. It is traditionally used to treat fever, upper respiratory tract infections, bleeding and hypertension. However, despite its extensive pharmacological potential, literature reports on its antihypertensive pharmacological properties are scarce. AIM OF THE STUDY In the study, crude extract from A. decursiva roots was examined for its antihypertensive activity and its molecular basis was explored. MATERIALS AND METHODS A. decursiva roots were extracted with ethanol, and isolated with silica gel normal-phase chromatography and reverse-phase high performance liquid chromatography. L-NAME-induced hypertensive mouse model was used to detect in vivo hypertensive activity. Thoracic aorta ring contraction activity and electrophysiology recordings were employed to evaluate in vitro antihypertensive activity and revealed an antihypertensive target, which was transiently expressed in HEK293T cells. RESULTS ADED exhibited significant antihypertensive effects in L-NAME-induced hypertension models and phenylephrine-induced vasoconstriction. Further screening revealed that demethylsuberosin is an essential component accounting for the antihypertension effects of A. decursiva. Voltage-gated calcium channel CaV1.2 is the likely target of A. decursiva for its antihypertension effects. CONCLUSION The study suggests that A. decursiva and demethylsuberosin may be effective antihypertensive agents in preclinical studies. It appears that A. decursiva and demethylsuberosin exert antihypertensive effects by inhibiting the CaV1.2 channel, which contributes to the vasodilatory effect. The present study provides experimental evidence that A. decursiva is an effective remedy for hypertension in folklore. Demethylsuberosin could be a lead molecule for antihypertension drug development.
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Affiliation(s)
- Xiaopei Yang
- Department of Basic Medicine, Chuxiong Medical College, Chuxiong, 675005, China.
| | - Chen Na
- Department of Pediatrics, Yanan Hospital Affiliated to Kunming Medical University, Kunming, Yunnan, 650000, China
| | - Yan Wang
- Department of Pediatrics, Yanan Hospital Affiliated to Kunming Medical University, Kunming, Yunnan, 650000, China.
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2
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Bartels P, Salveson I, Coleman AM, Anderson DE, Jeng G, Estrada-Tobar ZM, Man KNM, Yu Q, Kuzmenkina E, Nieves-Cintron M, Navedo MF, Horne MC, Hell JW, Ames JB. Half-calcified calmodulin promotes basal activity and inactivation of the L-type calcium channel Ca V1.2. J Biol Chem 2022; 298:102701. [PMID: 36395884 PMCID: PMC9764201 DOI: 10.1016/j.jbc.2022.102701] [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] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2022] [Revised: 10/30/2022] [Accepted: 10/31/2022] [Indexed: 11/17/2022] Open
Abstract
The L-type Ca2+ channel CaV1.2 controls gene expression, cardiac contraction, and neuronal activity. Calmodulin (CaM) governs CaV1.2 open probability (Po) and Ca2+-dependent inactivation (CDI) but the mechanisms remain unclear. Here, we present electrophysiological data that identify a half Ca2+-saturated CaM species (Ca2/CaM) with Ca2+ bound solely at the third and fourth EF-hands (EF3 and EF4) under resting Ca2+ concentrations (50-100 nM) that constitutively preassociates with CaV1.2 to promote Po and CDI. We also present an NMR structure of a complex between the CaV1.2 IQ motif (residues 1644-1665) and Ca2/CaM12', a calmodulin mutant in which Ca2+ binding to EF1 and EF2 is completely disabled. We found that the CaM12' N-lobe does not interact with the IQ motif. The CaM12' C-lobe bound two Ca2+ ions and formed close contacts with IQ residues I1654 and Y1657. I1654A and Y1657D mutations impaired CaM binding, CDI, and Po, as did disabling Ca2+ binding to EF3 and EF4 in the CaM34 mutant when compared to WT CaM. Accordingly, a previously unappreciated Ca2/CaM species promotes CaV1.2 Po and CDI, identifying Ca2/CaM as an important mediator of Ca signaling.
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Affiliation(s)
- Peter Bartels
- Department of Pharmacology, University of California, Davis, California, USA
| | - Ian Salveson
- Department of Chemistry, University of California, Davis, California, USA
| | - Andrea M Coleman
- Department of Pharmacology, University of California, Davis, California, USA; Department of Chemistry, University of California, Davis, California, USA
| | - David E Anderson
- Department of Chemistry, University of California, Davis, California, USA
| | - Grace Jeng
- Department of Pharmacology, University of California, Davis, California, USA
| | | | - Kwun Nok Mimi Man
- Department of Pharmacology, University of California, Davis, California, USA
| | - Qinhong Yu
- Department of Chemistry, University of California, Davis, California, USA
| | - Elza Kuzmenkina
- Center for Pharmacology, University of Cologne, Cologne, Germany
| | | | - Manuel F Navedo
- Department of Pharmacology, University of California, Davis, California, USA
| | - Mary C Horne
- Department of Pharmacology, University of California, Davis, California, USA.
| | - Johannes W Hell
- Department of Pharmacology, University of California, Davis, California, USA.
| | - James B Ames
- Department of Chemistry, University of California, Davis, California, USA.
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Han JW, Kang C, Kim Y, Lee MG, Kim JY. Isoproterenol-induced hypertrophy of neonatal cardiac myocytes and H9c2 cell is dependent on TRPC3-regulated Ca V1.2 expression. Cell Calcium 2020; 92:102305. [PMID: 33069962 DOI: 10.1016/j.ceca.2020.102305] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [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: 06/16/2020] [Revised: 09/24/2020] [Accepted: 09/25/2020] [Indexed: 02/07/2023]
Abstract
CaV1.2 and transient receptor potential canonical channel 3 (TRPC3) are two proteins known to have important roles in pathological cardiac hypertrophy; however, such roles still remain unclear. A better understanding of these roles is important for furthering the clinical understanding of heart failure. We previously reported that Trpc3-knockout (KO) mice are resistant to pathologic hypertrophy and that their CaV1.2 protein expression is reduced. In this study, we aimed to examine the relationship between these two proteins and characterize their role in neonatal cardiomyocytes. We measured CaV1.2 expression in the hearts of wild-type (WT) and Trpc3-/- mice, and examined the effects of Trpc3 knockdown and overexpression in the rat cell line H9c2. We also compared the hypertrophic responses of neonatal cardiomyocytes cultured from Trpc3-/- mice to a representative hypertrophy-causing drug, isoproterenol (ISO), and measured the activity of nuclear factor of activated T cells 3 (NFAT3) in neonatal cardiomyocytes (NCMCs). We inhibited the L-type current with nifedipine, and measured the intracellular calcium concentration using Fura-2 with 1-oleoyl-2-acetyl-sn-glycerol (OAG)-induced Ba2+ influx. When using the Trpc3-mediated Ca2+ influx, both intracellular calcium concentration and calcium influx were reduced in Trpc3-KO myocytes. Not only was the expression of CaV1.2 greatly reduced in Trpc3-KO cardiac lysate, but the size of the CaV1.2 currents in NCMCs was also greatly reduced. When NCMCs were treated with Trpc3 siRNA, it was confirmed that the expression of CaV1.2 and the intracellular nuclear transfer activity of NFAT decreased. In H9c2 cells, the ISO activated- and verapamil inhibited- Ca2+ influxes were dramatically attenuated by Trpc3 siRNA treatment. In addition, it was confirmed that both the expression of CaV1.2 and the size of H9c2 cells were regulated according to the expression and activation level of TRPC3. We found that after stimulation with ISO, cell hypertrophy occurred in WT myocytes, while the increase in size of Trpc3-KO myocytes was greatly reduced. These results suggest that not only the cell hypertrophy process in neonatal cardiac myocytes and H9c2 cells were regulated according to the expression level of CaV1.2, but also that the expression level of CaV1.2 was regulated by TRPC3 through the activation of NFAT.
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Affiliation(s)
- Jung Woo Han
- Department of Pharmacology and Brain Korea 21 PLUS Project for Medical Science, Yonsei University College of Medicine, Seoul 120-752, South Korea.
| | - Choeun Kang
- Department of Pharmacology and Brain Korea 21 PLUS Project for Medical Science, Yonsei University College of Medicine, Seoul 120-752, South Korea.
| | - Yonjung Kim
- Department of Pharmacology and Brain Korea 21 PLUS Project for Medical Science, Yonsei University College of Medicine, Seoul 120-752, South Korea.
| | - Min Goo Lee
- Department of Pharmacology and Brain Korea 21 PLUS Project for Medical Science, Yonsei University College of Medicine, Seoul 120-752, South Korea.
| | - Joo Young Kim
- Department of Pharmacology and Brain Korea 21 PLUS Project for Medical Science, Yonsei University College of Medicine, Seoul 120-752, South Korea.
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Moore SJ, Murphy GG. The role of L-type calcium channels in neuronal excitability and aging. Neurobiol Learn Mem 2020; 173:107230. [PMID: 32407963 DOI: 10.1016/j.nlm.2020.107230] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [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: 11/11/2019] [Revised: 03/09/2020] [Accepted: 04/12/2020] [Indexed: 12/11/2022]
Abstract
Over the last two decades there has been significant progress towards understanding the neural substrates that underlie age-related cognitive decline. Although many of the exact molecular and cellular mechanisms have yet to be fully understood, there is consensus that alterations in neuronal calcium homeostasis contribute to age-related deficits in learning and memory. Furthermore, it is thought that the age-related changes in calcium homeostasis are driven, at least in part, by changes in calcium channel expression. In this review, we focus on the role of a specific class of calcium channels: L-type voltage-gated calcium channels (LVGCCs). We provide the reader with a general introduction to voltage-gated calcium channels, followed by a more detailed description of LVGCCs and how they serve to regulate neuronal excitability via the post burst afterhyperpolarization (AHP). We conclude by reviewing studies that link the slow component of the AHP to learning and memory, and discuss how age-related increases in LVGCC expression may underlie cognitive decline by mediating a decrease in neuronal excitability.
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Affiliation(s)
- Shannon J Moore
- Michigan Neuroscience Institute, University of Michigan Medical School, 109 Zina Pitcher Place, Ann Arbor, MI 48109, United States; Department of Molecular and Integrative Physiology, University of Michigan Medical School, 109 Zina Pitcher Place, Ann Arbor, MI 48109, United States
| | - Geoffrey G Murphy
- Michigan Neuroscience Institute, University of Michigan Medical School, 109 Zina Pitcher Place, Ann Arbor, MI 48109, United States; Department of Molecular and Integrative Physiology, University of Michigan Medical School, 109 Zina Pitcher Place, Ann Arbor, MI 48109, United States.
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5
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Wang S, Li J, Liu Y, Zhang J, Zheng X, Sun X, Lei S, Kang Z, Chen X, Lei M, Hu H, Zeng X, Hao L. Distinct roles of calmodulin and Ca 2+/calmodulin-dependent protein kinase II in isopreterenol-induced cardiac hypertrophy. Biochem Biophys Res Commun 2020; 526:960-966. [PMID: 32303334 DOI: 10.1016/j.bbrc.2020.03.188] [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: 03/22/2020] [Accepted: 03/29/2020] [Indexed: 12/18/2022]
Abstract
Intracellular calcium is related to cardiac hypertrophy. The CaV1.2 channel and Ca2+/calmodulin-dependent protein kinase II (CaMKII) and CaM regulate the intracellular calcium content. However, the differences in CaMKII and CaM in cardiac hypertrophy are still conflicting and are worthy of studying as drug targets. Therefore, in this study, we aim to investigate the roles and mechanism of CaM and CaMKII on CaV1.2 in pathological myocardial hypertrophy. The results showed that ISO stimulation caused SD rat heart and cardiomyocyte hypertrophy. In vivo, the HW/BW, LVW/BW, cross-sectional area, fibrosis ratio and ANP expression were all increased. There were no differences in CaV1.2 channel expression in the in vivo model or the in vitro model, but the ISO stimulation induced channel activity, and the [Ca2+]i increased. The protein expression levels of CaMKII and p-CaMKII were all increased in the ISO group, but the CaM expression level decreased. AIP inhibited ANP, CaMKII and p-CaMKII expression, and ISO-induced [Ca2+]i increased. AIP also reduced HDAC4, p-HDAC and MEF2C expression. However, CMZ did not play a cardiac hypertrophy reversal role in vitro. In conclusion, we considered that compared with CaM, CaMKII may be a much more important drug target in cardiac hypertrophy reversal.
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Affiliation(s)
- Siqi Wang
- Department of Pharmaceutical Toxicology, School of Pharmacy, China Medical University, Shenyang, 110122, China
| | - Jingyuan Li
- Department of Pharmaceutical Toxicology, School of Pharmacy, China Medical University, Shenyang, 110122, China
| | - Yan Liu
- Department of Pharmaceutical Toxicology, School of Pharmacy, China Medical University, Shenyang, 110122, China
| | - Jie Zhang
- Department of Pharmaceutical Toxicology, School of Pharmacy, China Medical University, Shenyang, 110122, China
| | - Xi Zheng
- Department of Pharmaceutical Toxicology, School of Pharmacy, China Medical University, Shenyang, 110122, China
| | - Xuefei Sun
- Department of Pharmaceutical Toxicology, School of Pharmacy, China Medical University, Shenyang, 110122, China
| | - Shuai Lei
- Department of Pharmaceutical Toxicology, School of Pharmacy, China Medical University, Shenyang, 110122, China
| | - Ze Kang
- Department of Pharmaceutical Toxicology, School of Pharmacy, China Medical University, Shenyang, 110122, China
| | - Xiye Chen
- Department of Pharmaceutical Toxicology, School of Pharmacy, China Medical University, Shenyang, 110122, China
| | - Ming Lei
- Key Laboratory of Medical Electrophysiology of Ministry of Education, Collaborative Innovation Center for Prevention and Treatment of Cardiovascular Disease, Institute of Cardiovascular Research, Southwest Medical University, Luzhou, Sichuan, 646000, China
| | - Huiyuan Hu
- Department of Pharmaceutical Toxicology, School of Pharmacy, China Medical University, Shenyang, 110122, China
| | - Xiaorong Zeng
- Key Laboratory of Medical Electrophysiology of Ministry of Education, Collaborative Innovation Center for Prevention and Treatment of Cardiovascular Disease, Institute of Cardiovascular Research, Southwest Medical University, Luzhou, Sichuan, 646000, China.
| | - Liying Hao
- Department of Pharmaceutical Toxicology, School of Pharmacy, China Medical University, Shenyang, 110122, China.
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6
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Cao C, Oswald AB, Fabella BA, Ren Y, Rodriguiz R, Trainor G, Greenblatt MB, Hilton MJ, Pitt GS. The Ca V1.2 L-type calcium channel regulates bone homeostasis in the middle and inner ear. Bone 2019; 125:160-168. [PMID: 31121355 PMCID: PMC6615562 DOI: 10.1016/j.bone.2019.05.024] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/28/2019] [Revised: 05/01/2019] [Accepted: 05/18/2019] [Indexed: 02/07/2023]
Abstract
Bone remodeling of the auditory ossicles and the otic capsule is highly restricted and tightly controlled by the osteoprotegerin (OPG)/receptor activator of nuclear factor kappa-Β ligand (RANKL)/receptor activator of nuclear factor kappa-Β (RANK) system. In these bony structures, a pathological decrease in OPG expression stimulates osteoclast differentiation and excessive resorption followed by accrual of sclerotic bone, ultimately resulting in the development of otosclerosis, a leading cause of deafness in adults. Understanding the signaling pathways involved in maintaining OPG expression in the ear would shed light on the pathophysiology of otosclerosis and other ear bone-related diseases. We and others previously demonstrated that Ca2+ signaling through the L-type CaV1.2 Ca2+ channel positively regulates OPG expression and secretion in long bone osteoblasts and their precursor cells in vitro and in vivo. Whether CaV1.2 regulates OPG expression in ear bones has not been investigated. We drove expression of a gain-of-function CaV1.2 mutant channel (CaV1.2TS) using Col2a1-Cre, which we found to target osteochondral/osteoblast progenitors in the auditory ossicles and the otic capsule. Col2a1-Cre;CaV1.2TS mice displayed osteopetrosis of these bones shown by μCT 3D reconstruction, histological analysis, and lack of bone sculpting, findings similar to phenotypes seen in mice with an osteoclast defect. Consistent with those observations, we found that Col2a1-Cre;CaV1.2TS mutant mice showed reduced osteoclasts in the otic capsule, upregulated mRNA expression of Opg and Opg/Rankl ratio, and increased mRNA expression of osteoblast differentiation marker genes in the otic capsule, suggesting both an anti-catabolic and anabolic effect of CaV1.2TS mutant channel contributed to the observed morphological changes of the ear bones. Further, we found that Col2a1-Cre;CaV1.2TS mice experienced hearing loss and displayed defects of body balance in behavior tests, confirming that the CaV1.2-dependent Ca2+ influx affects bone structure in the ear and consequent hearing and vestibular functions. Together, these data support our hypothesis that Ca2+ influx through CaV1.2TS promotes OPG expression from osteoblasts, thereby affecting bone modeling/remodeling in the auditory ossicles and the otic capsule. These data provide insight into potential pathological mechanisms underlying perturbed OPG expression and otosclerosis.
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Affiliation(s)
- Chike Cao
- Cardiovascular Research Institute, Weill Cornell Medical College, 413 East 69th St., New York, NY 10021, USA.
| | - Aaron B Oswald
- Howard Hughes Medical Institute and Laboratory of Sensory Neuroscience, The Rockefeller University, 1230 York Avenue, New York, NY 10065, USA
| | - Brian A Fabella
- Howard Hughes Medical Institute and Laboratory of Sensory Neuroscience, The Rockefeller University, 1230 York Avenue, New York, NY 10065, USA
| | - Yinshi Ren
- Department of Orthopaedic Surgery, Duke University School of Medicine, 450 Research Drive, Durham, NC 27710, USA; Department of Cell Biology, Duke University School of Medicine, 450 Research Drive, Durham, NC 27710, USA
| | - Ramona Rodriguiz
- Mouse Behavioral and Neuroendocrine Analysis Core Facility, Duke University School of Medicine, 308 Research Drive, Durham, NC 27708, USA
| | - George Trainor
- Harrington Discovery Institute, Innovation Support Center, 2103 Cornell Road, Cleveland, OH 44106, USA
| | - Matthew B Greenblatt
- Department of Pathology and Laboratory Medicine, Weill Cornell Medical College, New York, NY 10021, USA; Research Division, Hospital for Special Surgery, New York, NY 10021, USA
| | - Matthew J Hilton
- Department of Orthopaedic Surgery, Duke University School of Medicine, 450 Research Drive, Durham, NC 27710, USA; Department of Cell Biology, Duke University School of Medicine, 450 Research Drive, Durham, NC 27710, USA
| | - Geoffrey S Pitt
- Cardiovascular Research Institute, Weill Cornell Medical College, 413 East 69th St., New York, NY 10021, USA
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Abstract
The first clinically used antiarrhythmic, antianginal and anti-hypertensive phenylalkylamine, verapamil's cardiovascular activity is inextricably linked to its ability to antagonize Ca2+ overload via blocking CaV1.2, a cardiac L-type Ca2+ channel of undisputed physiological and pharmacological importance in cardiovascular disorders such as myocardial ischemia-reperfusion injury. From a structural point of view, however, the action mechanism of verapamil is still elusive. Therefore, incorporating previous findings for verapamil and CaV1.2, this review article puts forward two experimental data-derived and -supported 3D structure models for CaV1.2's α1 subunit and its verapamil-bound form. Furthermore, this article suggests three biophysical mechanisms, namely competitive binding, steric hindrance and electrostatic repulsion, towards an atomic level understanding of how verapamil blocks the L-type Ca2+ current mediated by CaV1.2 in reality, which can be useful for the design and development of next-generation Ca2+ antagonists to provide safer and more effective treatment of cardiovascular diseases.
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Affiliation(s)
- Wei Li
- Department of Pharmacology, Shantou University Medical College, No. 22, Xinling Road, Shantou City, Guangdong Province, PR China
| | - Ganggang Shi
- Department of Pharmacology, Shantou University Medical College, No. 22, Xinling Road, Shantou City, Guangdong Province, PR China.
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Shimaoka T, Wang Y, Morishima M, Miyamoto S, Ono K. Hypomagnesemic down-regulation of L-type Ca(2+) channel in cardiomyocyte as an arrhythmogenic substrate in rats. ACTA ACUST UNITED AC 2015; 22:87-93. [PMID: 25701242 DOI: 10.1016/j.pathophys.2015.01.002] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [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: 01/13/2015] [Revised: 01/28/2015] [Accepted: 01/30/2015] [Indexed: 11/27/2022]
Abstract
The present study was designed to investigate the effect of magnesium (Mg) depletion on the expression of voltage-gated calcium (Ca(2+)) channels and Ca(2+) currents in the heart and thereby on hypomagnesemic arrhythmogenesis in adult male rats. Male Wistar rats were fed an Mg-free diet or a normal diet for up to 16 weeks. Serum Mg concentrations were significantly reduced at week 4 or later with an Mg-free diet, which experimentally represents hypomagnesemia. Myocardial Mg contents were also reduced at week 16 accompanied by myocardial hypertrophy. Telemetric ECG recordings revealed a long-term changes of ECG parameters in hypomagnesemic rats; RR shortening, QT prolongation and appreciable PR prolongation. At the same time, hypomagnesemic rats demonstrate various bradycardiac arrhythmias including ventricular premature beats, atrioventricular blocks and sinus arrest, which were never recoded in rats fed by a normal diet. Electrophysiological studies elucidated that the L-type Ca(2+) channel current was decreased in Mg-deficient cardiomyocytes, and these findings were consistent with down-regulation of CaV1.2-mRNA but not in levels of CaV1.3, CaV3.1 or CaV3.2. These findings provide novel insights into hypomagnesemic electrophysiological disorders in the heart, and should be considered when assessing the design of effective antiarrhythmic treatments in patients with hypomagnesemia.
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Affiliation(s)
- Toru Shimaoka
- Department of Pathophysiology, Oita University School of Medicine, Yufu, Oita 879-5593, Japan; Department of Cardiovascular Surgery, Oita University School of Medicine, Yufu, Oita 879-5593, Japan
| | - Yan Wang
- Department of Pathophysiology, Oita University School of Medicine, Yufu, Oita 879-5593, Japan
| | - Masaki Morishima
- Department of Pathophysiology, Oita University School of Medicine, Yufu, Oita 879-5593, Japan
| | - Shinji Miyamoto
- Department of Cardiovascular Surgery, Oita University School of Medicine, Yufu, Oita 879-5593, Japan
| | - Katsushige Ono
- Department of Pathophysiology, Oita University School of Medicine, Yufu, Oita 879-5593, Japan.
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Drum BML, Dixon RE, Yuan C, Cheng EP, Santana LF. Cellular mechanisms of ventricular arrhythmias in a mouse model of Timothy syndrome (long QT syndrome 8). J Mol Cell Cardiol 2013; 66:63-71. [PMID: 24215710 DOI: 10.1016/j.yjmcc.2013.10.021] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/31/2013] [Revised: 10/29/2013] [Accepted: 10/31/2013] [Indexed: 11/17/2022]
Abstract
Ca(2+) flux through l-type CaV1.2 channels shapes the waveform of the ventricular action potential (AP) and is essential for excitation-contraction (EC) coupling. Timothy syndrome (TS) is a disease caused by a gain-of-function mutation in the CaV1.2 channel (CaV1.2-TS) that decreases inactivation of the channel, which increases Ca(2+) influx, prolongs APs, and causes lethal arrhythmias. Although many details of the CaV1.2-TS channels are known, the cellular mechanisms by which they induce arrhythmogenic changes in intracellular Ca(2+) remain unclear. We found that expression of CaV1.2-TS channels increased sarcolemmal Ca(2+) "leak" in resting TS ventricular myocytes. This resulted in higher diastolic [Ca(2+)]i in TS ventricular myocytes compared to WT. Accordingly, TS myocytes had higher sarcoplasmic reticulum (SR) Ca(2+) load and Ca(2+) spark activity, larger amplitude [Ca(2+)]i transients, and augmented frequency of Ca(2+) waves. The large SR Ca(2+) release in TS myocytes had a profound effect on the kinetics of CaV1.2 current in these cells, increasing the rate of inactivation to a high, persistent level. This limited the amount of influx during EC coupling in TS myocytes. The relationship between the level of expression of CaV1.2-TS channels and the probability of Ca(2+) wave occurrence was non-linear, suggesting that even low levels of these channels were sufficient to induce maximal changes in [Ca(2+)]i. Depolarization of WT cardiomyocytes with a TS AP waveform increased, but did not equalize [Ca(2+)]i, compared to depolarization of TS myocytes with the same waveform. We propose that CaV1.2-TS channels increase [Ca(2+)] in the cytosol and the SR, creating a Ca(2+)overloaded state that increases the probability of arrhythmogenic spontaneous SR Ca(2+) release.
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Affiliation(s)
- Benjamin M L Drum
- Department of Physiology & Biophysics, University of Washington School of Medicine, Seattle, WA 98195, USA
| | - Rose E Dixon
- Department of Physiology & Biophysics, University of Washington School of Medicine, Seattle, WA 98195, USA
| | - Can Yuan
- Department of Physiology & Biophysics, University of Washington School of Medicine, Seattle, WA 98195, USA
| | - Edward P Cheng
- Department of Physiology & Biophysics, University of Washington School of Medicine, Seattle, WA 98195, USA
| | - Luis F Santana
- Department of Physiology & Biophysics, University of Washington School of Medicine, Seattle, WA 98195, USA.
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Meza U, Beqollari D, Romberg CF, Papadopoulos S, Bannister RA. Potent inhibition of L-type Ca2+ currents by a Rad variant associated with congestive heart failure. Biochem Biophys Res Commun 2013; 439:270-4. [PMID: 23973784 DOI: 10.1016/j.bbrc.2013.08.044] [Citation(s) in RCA: 9] [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: 08/11/2013] [Accepted: 08/13/2013] [Indexed: 10/26/2022]
Abstract
Ca(2+) influx via L-type voltage-gated Ca(2+) channels supports the plateau phase of ventricular action potentials and is the trigger for excitation-contraction (EC) coupling in the myocardium. Rad, a member of the RGK (Rem, Rem2, Rad, Gem/Kir) family of monomeric G proteins, regulates ventricular action potential duration and EC coupling gain through its ability to inhibit cardiac L-type channel activity. In this study, we have investigated the potential dysfunction of a naturally occurring Rad variant (Q66P) that has been associated with congestive heart failure in humans. Specifically, we have tested whether Rad Q66P limits, or even eliminates, the inhibitory actions of Rad on CaV1.2 and CaV1.3, the two L-type channel isoforms known to be expressed in the heart. We have found that mouse Rad Q65P (the murine equivalent of human Rad Q66P) inhibits L-type currents conducted by CaV1.2 or CaV1.3 channels as potently as wild-type Rad (>95% inhibition of both channels). In addition, Rad Q65P attenuates the gating movement of both channels as effectively as wild-type Rad, indicating that the Q65P substitution does not differentially impair any of the three described modes of L-type channel inhibition by RGK proteins. Thus, we conclude that if Rad Q66P contributes to cardiomyopathy, it does so via a mechanism that is not related to its ability to inhibit L-type channel-dependent processes per se. However, our results do not rule out the possibility that decreased expression, mistargeting or altered regulation of Rad Q66P may reduce the RGK protein's efficacy in vivo.
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Affiliation(s)
- U Meza
- Department of Medicine-Cardiology Division, University of Colorado Denver-Anschutz Medical Campus, 12700 East 19th Avenue, P15-8006, B-139, Aurora, CO 80045, USA; Departamento de Fisiología y Biofísica, Facultad de Medicina, Universidad Autónoma de San Luis Potosí, Venustiano Carranza #2405, San Luis Potosí, SLP 78210, México.
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