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Rajkovic J, Novakovic R, Grujic-Milanovic J, Ydyrys A, Ablaikhanova N, Calina D, Sharifi-Rad J, Al-Omari B. An updated pharmacological insight into calotropin as a potential therapeutic agent in cancer. Front Pharmacol 2023; 14:1160616. [PMID: 37138852 PMCID: PMC10149670 DOI: 10.3389/fphar.2023.1160616] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2023] [Accepted: 04/05/2023] [Indexed: 05/05/2023] Open
Abstract
Calotropin is a pharmacologically active compound isolated from milkweed plants like Calotropis procera, Calotropis gigantea, and Asclepias currasavica that belong to the Asclepiadaceae family. All of these plants are recognised as medical traditional plants used in Asian countries. Calotropin is identified as a highly potent cardenolide that has a similar chemical structure to cardiac glycosides (such as digoxin and digitoxin). During the last few years, cytotoxic and antitumor effects of cardenolides glycosides have been reported more frequently. Among cardenolides, calotropin is identified as the most promising agent. In this updated and comprehensive review, we aimed to analyze and discuss the specific mechanisms and molecular targets of calotropin in cancer treatment to open new perspectives for the adjuvant treatment of different types of cancer. The effects of calotropin on cancer have been extensively studied in preclinical pharmacological studies in vitro using cancer cell lines and in vivo in experimental animal models that have targeted antitumor mechanisms and anticancer signaling pathways. The analyzed information from the specialized literature was obtained from scientific databases until December 2022, mainly from PubMed/MedLine, Google Scholar, Scopus, Web of Science, and Science Direct databases using specific MeSH search terms. The results of our analysis demonstrate that calotropin can be a potential chemotherapeutic/chemopreventive adjunctive agent in cancer pharmacotherapeutic management.
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Affiliation(s)
- Jovana Rajkovic
- Institute for Pharmacology, Clinical Pharmacology and Toxicology, Faculty of Medicine, University of Belgrade, Belgrade, Serbia
| | - Radmila Novakovic
- Institute for Pharmacology, Clinical Pharmacology and Toxicology, Faculty of Medicine, University of Belgrade, Belgrade, Serbia
| | - Jelica Grujic-Milanovic
- Institute for Medical Research, National Institute of the Republic of Serbia, University of Belgrade, Belgrade, Serbia
| | - Alibek Ydyrys
- Biomedical Research Centre, Al-Farabi Kazakh National University, Almaty, Kazakhstan
| | - Nurzhanat Ablaikhanova
- Department of Biophysics, Biomedicine and Neuroscience, Al-Farabi Kazakh National University, Almaty, Kazakhstan
| | - Daniela Calina
- Department of Clinical Pharmacy, University of Medicine and Pharmacy of Craiova, Craiova, Romania
- *Correspondence: Daniela Calina, ; Javad Sharifi-Rad, ; Basem Al-Omari,
| | - Javad Sharifi-Rad
- Facultad de Medicina, Universidad del Azuay, Cuenca, Ecuador
- *Correspondence: Daniela Calina, ; Javad Sharifi-Rad, ; Basem Al-Omari,
| | - Basem Al-Omari
- Department of Epidemiology and Population Health, College of Medicine and Health Sciences, Khalifa University, Abu Dhabi, United Arab Emirates
- *Correspondence: Daniela Calina, ; Javad Sharifi-Rad, ; Basem Al-Omari,
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Monteiro DA, Lopes AG, Jejcic NU, da Silva Vasconcelos E, Kalinin AL, Rantin FT. Cardiac contractility of the African sharptooth catfish, Clarias gariepinus: role of extracellular Ca 2+, sarcoplasmic reticulum, and β-adrenergic stimulation. FISH PHYSIOLOGY AND BIOCHEMISTRY 2021; 47:1969-1982. [PMID: 34668117 DOI: 10.1007/s10695-021-01023-7] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/27/2020] [Accepted: 10/07/2021] [Indexed: 06/13/2023]
Abstract
This study investigated the dependence of contraction from extracellular Ca2+, the presence of a functional sarcoplasmic reticulum (SR), and the effects of β-adrenergic stimulation using isometric cardiac muscle preparations. Moreover, the expression of Ca2+-handling proteins such as SR-Ca2+-ATPase (SERCA), phospholamban (PLN), and Na+/Ca2+ exchanger (NCX) were also evaluated in the ventricular tissue of adult African sharptooth catfish, Clarias gariepinus, a facultative air-breathing fish. In summary, we observed that (1) contractility was strongly regulated by extracellular Ca2+; (2) inhibition of SR Ca2+-release by application of ryanodine reduced steady-state force production; (3) ventricular myocardium exhibited clear post-rest decay, even in the presence of ryanodine, indicating a decrease in SR Ca2+ content and NCX as the main pathway for Ca2+ extrusion; (4) a positive force-frequency relationship was observed above 60 bpm (1.0 Hz); (5) ventricular tissue was responsive to β-adrenergic stimulation, which caused significant increases in twitch force, kept a linear force-frequency relationship from 12 to 96 bpm (0.2 to Hz), and improved the cardiac pumping capacity (CPC); and (6) African catfish myocardium exhibited similar expression patterns of NCX, SERCA, and PLN, corroborating our findings that both mechanisms for Ca2+ transport across the SR and sarcolemma contribute to Ca2+ activator. In conclusion, this fish species displays great physiological plasticity of E-C coupling, able to improve the ability to maintain cardiac performance under physiological conditions to ecological and/or adverse environmental conditions, such as hypoxic air-breathing activity.
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Affiliation(s)
- Diana Amaral Monteiro
- Department of Physiological Sciences, Federal University of São Carlos (UFSCar), Via Washington Luís km 235, 13565-905 São Carlos, São Paulo, Brazil.
| | - André Guelli Lopes
- Department of Physiological Sciences, Federal University of São Carlos (UFSCar), Via Washington Luís km 235, 13565-905 São Carlos, São Paulo, Brazil
- Joint Graduate Program in Physiological Sciences, Federal University of São Carlos - UFSCar/São Paulo State University, UNESP Campus Araraquara, São Paulo, Brazil
| | - Nathalia Usun Jejcic
- Department of Physiological Sciences, Federal University of São Carlos (UFSCar), Via Washington Luís km 235, 13565-905 São Carlos, São Paulo, Brazil
| | - Eliton da Silva Vasconcelos
- Department of Physiological Sciences, Federal University of São Carlos (UFSCar), Via Washington Luís km 235, 13565-905 São Carlos, São Paulo, Brazil
- Joint Graduate Program in Physiological Sciences, Federal University of São Carlos - UFSCar/São Paulo State University, UNESP Campus Araraquara, São Paulo, Brazil
| | - Ana Lúcia Kalinin
- Department of Physiological Sciences, Federal University of São Carlos (UFSCar), Via Washington Luís km 235, 13565-905 São Carlos, São Paulo, Brazil
| | - Francisco Tadeu Rantin
- Department of Physiological Sciences, Federal University of São Carlos (UFSCar), Via Washington Luís km 235, 13565-905 São Carlos, São Paulo, Brazil
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Bazmi M, Escobar AL. Excitation-Contraction Coupling in the Goldfish ( Carassius auratus) Intact Heart. Front Physiol 2020; 11:1103. [PMID: 33041845 PMCID: PMC7518121 DOI: 10.3389/fphys.2020.01103] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2020] [Accepted: 08/10/2020] [Indexed: 12/17/2022] Open
Abstract
Cardiac physiology of fish models is an emerging field given the ease of genome editing and the development of transgenic models. Several studies have described the cardiac properties of zebrafish (Denio rerio). The goldfish (Carassius auratus) belongs to the same family as the zebrafish and has emerged as an alternative model with which to study cardiac function. Here, we propose to acutely study electrophysiological and systolic Ca2+ signaling in intact goldfish hearts. We assessed the Ca2+ dynamics and the electrophysiological cardiac function of goldfish, zebrafish, and mice models, using pulsed local field fluorescence microscopy, intracellular microelectrodes, and flash photolysis in perfused hearts. We observed goldfish ventricular action potentials (APs) and Ca2+ transients to be significantly longer when compared to the zebrafish. The action potential half duration at 50% (APD50) of goldfish was 370.38 ± 8.8 ms long, and in the zebrafish they were observed to be only 83.9 ± 9.4 ms. Additionally, the half duration of the Ca2+ transients was also longer for goldfish (402.1 ± 4.4 ms) compared to the zebrafish (99.1 ± 2.7 ms). Also, blocking of the L-type Ca2+ channels with nifedipine revealed this current has a major role in defining the amplitude and the duration of goldfish Ca2+ transients. Interestingly, nifedipine flash photolysis experiments in the intact heart identified whether or not the decrease in the amplitude of Ca2+ transients was due to shorter APs. Moreover, an increase in temperature and heart rate had a strong shortening effect on the AP and Ca2+ transients of goldfish hearts. Furthermore, ryanodine (Ry) and thapsigargin (Tg) significantly reduced the amplitude of the Ca2+ transients, induced a prolongation in the APs, and altogether exhibited the degree to which the Ca2+ release from the sarcoplasmic reticulum contributed to the Ca2+ transients. We conclude that the electrophysiological properties and Ca2+ signaling in intact goldfish hearts strongly resembles the endocardial layer of larger mammals.
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Affiliation(s)
- Maedeh Bazmi
- Quantitative Systems Biology Program, School of Natural Sciences, University of California, Merced, Merced, CA, United States
| | - Ariel L Escobar
- Department of Bioengineering, School of Engineering, University of California, Merced, Merced, CA, United States
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Zhong X, You N, Wang Q, Li L, Huang C. Reverse mode of sodium/calcium exchanger subtype 1 contributes to detrusor overactivity in rats with partial bladder outflow obstruction. Am J Transl Res 2018; 10:806-815. [PMID: 29636870 PMCID: PMC5883121] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2017] [Accepted: 02/06/2018] [Indexed: 06/08/2023]
Abstract
To investigate whether the reverse mode of sodium/calcium exchanger subtype 1 (NCX1) plays an important role in the excitability of detrusor cells in rats with partial bladder outflow obstruction (PBOO), PBOO was maintained for 6 weeks in forty female Wistar rats. Thirty of the animals exhibited non-voiding bladder contraction and comprised the DO group. An additional thirty sham-operated female Wistar rats were used as the control group. The expression levels of NCX1 were compared between the two groups by quantitative reverse transcriptase-polymerase chain reaction (RT-PCR), western blotting (WB), and double-label immunofluorescence. The contractions of detrusor strips in NCX reverse mode were measured in both groups using isometric tension. The role of NCX in the regulation of the intracellular Ca2+ concentration ([Ca2+]i) of smooth muscle cells was observed in reverse mode using confocal microscopy, and the current was evaluated in the presence of the antagonist KB-R7943 (5 μM and 10 μM) using the whole-cell patch-clamp technique. The expression of NCX1 was significantly higher in the DO group than in the control group, as assessed by qRT-PCR, WB analysis and immunofluorescence. The volume and rate of Ca2+ ion flux through the NCX, as well as the NCX currents, were higher in the DO group than in the control group in both modes. Increased NCX1 levels may contribute to the establishment of DO after PBOO by elevating [Ca2+]i in reverse mode under depolarization, potentially inducing cell excitability.
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Affiliation(s)
- Xiao Zhong
- Department of Urology, Second Affiliated Hospital, Third Military Medical UniversityChongqing 400037, P. R. China
| | - Nan You
- Department of Hepatobiliary Surgery, Second Affiliated Hospital, Third Military Medical UniversityChongqing 400037, P. R. China
| | - Qingqing Wang
- Department of Urology, Second Affiliated Hospital, Third Military Medical UniversityChongqing 400037, P. R. China
| | - Longkun Li
- Department of Urology, Second Affiliated Hospital, Third Military Medical UniversityChongqing 400037, P. R. China
| | - Chibing Huang
- Department of Urology, Second Affiliated Hospital, Third Military Medical UniversityChongqing 400037, P. R. China
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CHUGUN A, UCHIDE T, TSURIMAKI C, NAGASAWA H, SASAKI T, UENO S, TAKAGISHI K, HARA Y, TEMMA K. Mechanisms Responsible for Reduced Cardiotoxicity of Mitoxantrone Compared to Doxorubicin Examined in Isolated Guinea-Pig Heart Preparations. J Vet Med Sci 2008; 70:255-64. [DOI: 10.1292/jvms.70.255] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Affiliation(s)
- Akihito CHUGUN
- Laboratory of Veterinary Pharmacology, School of Veterinary Medicine, Kitasato University
| | - Tsuyoshi UCHIDE
- Laboratory of Toxicology, School of Veterinary Medicine, Kitasato University
| | - Chieko TSURIMAKI
- Laboratory of Toxicology, School of Veterinary Medicine, Kitasato University
| | - Hajime NAGASAWA
- Laboratory of Toxicology, School of Veterinary Medicine, Kitasato University
| | - Takushi SASAKI
- Laboratory of Toxicology, School of Veterinary Medicine, Kitasato University
| | - Shunji UENO
- Laboratory of Veterinary Public Health, School of Veterinary Medicine, Kitasato University
| | - Kiyohiko TAKAGISHI
- Laboratory of Cell and Molecular Biology, School of Veterinary Medicine, Kitasato University
| | - Yukio HARA
- Laboratory of Veterinary Pharmacology, School of Veterinary Medicine, Kitasato University
| | - Kyosuke TEMMA
- Laboratory of Toxicology, School of Veterinary Medicine, Kitasato University
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Palomeque J, Petroff MV, Sapia L, Gende OA, Mundiña-Weilenmann C, Mattiazzi A. Multiple alterations in Ca2+ handling determine the negative staircase in a cellular heart failure model. J Card Fail 2007; 13:143-54. [PMID: 17395056 DOI: 10.1016/j.cardfail.2006.11.002] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2006] [Revised: 10/13/2006] [Accepted: 11/03/2006] [Indexed: 11/27/2022]
Abstract
BACKGROUND The flat or negative force frequency relationship (FFR) is a hallmark of the failing heart. Either decreases in SERCA2a expression, increases in Na(+)/Ca(2+) exchanger (NCX) expression or elevated Na(+)(i) have been independently proposed as mediators of the negative FFR. METHODS AND RESULTS To determine whether each one of these mechanisms is sufficient to account for the negative FFR of the failing heart or on the contrary, various mechanisms, acting in concert are required. SERCA2a was pharmacologically inhibited with thapsigargin (TG) or cyclopiazonic acid (CPA) or by using siRNA technology; Na(+)(i) was increased with either ouabain (Oua) or monensin and NCX protein was overexpressed by gene transfer (Ad.NCX), to mimic in nonfailing cat myocytes the phenotype of the failing heart and examine their effect on the FFR. The positive FFR of healthy myocytes remained unaffected after either SERCA2a inhibition, Na(+)(i) elevation, or NCX overexpression. However, the combination of TG + Oua, Oua + Ad.NCX, or TG + Ad.NCX, converted the positive FFR to negative. Moreover, the FFR became negative at lower frequencies, when the 3 interventions were combined. CONCLUSIONS Ca(2+) handling has to be altered at several levels to explain the negative FFR of the failing heart. These anomalies in Ca(2+) homeostasis acting in synergy have additive effects.
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Affiliation(s)
- Julieta Palomeque
- Centro de Investigaciones Cardiovasculares, Facultad de Ciencias Médicas, Universidad Nacional de La Plata, La Plata 1900, Argentina
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Subramani S, Balakrishnan S, Jyoti T, Mohammed AA, Arasan S, Vijayanand C. Force-frequency relation in frog-ventricle is dependent on the direction of sodium/calcium exchange in diastole. ACTA ACUST UNITED AC 2006; 185:193-202. [PMID: 16218924 DOI: 10.1111/j.1365-201x.2005.01487.x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
AIM Force of contraction increases with stimulus-frequency in mammalian and amphibian hearts under control conditions. Here, we have analysed the mechanism of the force-frequency relation (FFR) in frog-ventricle. METHODS Circular strips of frog-ventricle were subjected to field-stimulation with frequencies in the range 0.03-0.2 Hz and force recorded on a chart-recorder. In another protocol, varying rest-periods were imposed while the preparation beat steadily at 0.2 Hz and the effect of rest on post-rest beat amplitude was noted. RESULTS Under control conditions, a positive FFR and a rest-induced decay of contraction amplitude (RID) were seen in the frequency range 0.03-0.2 Hz. With cadmium, nifedipine, nickel (40 micromol L(-1)), ryanodine and adrenaline (all drugs at 10 micromol L(-1) concentration, except nickel), the positive FFR and RID seen under control conditions persisted. When the bathing solution contained ouabain (10 micromol L(-1)) or low external sodium (40 mmol L(-1)), or high external calcium (5 mmol L(-1)), the FFR turned negative in the frequency range stated above and there were rest-induced potentiations (RIP). CONCLUSION When the conditions favour a net leak of calcium in diastole from intracellular stores via the calcium-extrusive mode of sodium-calcium exchanger (NCX), FFR is positive. An increase in frequency lessens the diastolic interval and therefore the diastolic calcium leak, thereby augmenting force. On the other hand, interventions which favour the calcium-acquisitive mode of NCX during diastole, changed the pattern of RID to RIP and converted FFR from positive to negative. With net diastolic calcium uptake, there is better store-filling and therefore higher force at lower frequencies.
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Affiliation(s)
- S Subramani
- Department of Physiology, Christian Medical College, Vellore 632002, Tamil nadu, India.
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Viatchenko-Karpinski S, Terentyev D, Jenkins LA, Lutherer LO, Györke S. Synergistic interactions between Ca2+ entries through L-type Ca2+ channels and Na+-Ca2+ exchanger in normal and failing rat heart. J Physiol 2005; 567:493-504. [PMID: 15975978 PMCID: PMC1474206 DOI: 10.1113/jphysiol.2005.091280] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
Abstract
We used confocal Ca2+ imaging and the patch-clamp technique to investigate the interplay between Ca2+ entries through L-type Ca2+ channels (LCCs) and reverse-mode Na+-Ca2+ exchange (NCX) in activating Ca2+-induced Ca2+ release (CICR) from the sarcoplasmic reticulum (SR) in cardiac myocytes from normal and failing rat hearts. In normal myocytes exposed to N(6),2'-O-dibutyryl adenosine-3',5'-cyclic monophosphate (db-cAMP, membrane-permeable form of cAMP), the bell-shaped voltage dependence of cytosolic Ca2+ transients was dramatically broadened due to activation of SR Ca2+ release at high membrane potentials (30-120 mV). This broadening of Ca2+-transient voltage dependence could be prevented by KB-R7943, an inhibitor of the reverse-mode NCX. Trans-sarcolemmal Ca2+ entries were measured fluorometrically in myocytes during depolarizing steps to high membrane potentials. The total Ca2+ entry (deltaF(Tot)) was separated into two Ca2+ entry components, LCC-mediated (deltaF(LCC)) and NCX-mediated (deltaF(NCX)), by exposing the cells to the specific inhibitors of LCCs and reverse-mode NCX, nifedipine and KB-R7943, respectively. In the absence of protein kinase A (PKA) stimulation the amplitude of the Ca2+-inflow signal (deltaF(Tot)) corresponded to the arithmetic sum of the amplitudes of the KB-R7943- and nifedipine-resistant components (deltaF(Tot)=deltaF(LCC)+deltaF(NCX)). PKA activation resulted in significant increases in deltaF(Tot) and deltaF(LCC). Paradoxically, deltaF(Tot) became approximately threefold larger than the sum of the deltaF(NCX) and deltaF(LCC) components. In myocytes from failing hearts, stimulation of PKA failed to induce a shift in Ca2+ release voltage dependence toward more positive membrane potentials. Although the total and NCX-mediated Ca2+ entries were increased again, deltaF(Tot) did not significantly exceed the sum of deltaF(LCC) and deltaF(NCX). We conclude that the LCC and NCX Ca2+-entry pathways interact synergistically to trigger SR Ca2+ release on depolarization to positive membrane potentials in PKA-stimulated cardiac muscle. In heart failure, this new form of Ca2+ release is diminished and may potentially account for the compromised contractile performance and reduced functional reserve in failing hearts.
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Affiliation(s)
- Serge Viatchenko-Karpinski
- Department of Physiology and Cell Biology, Davis Heart and Lung Research Institute, Ohio State University Medical Center, 473 West 12th Avenue, Columbus, OH 43210-1252, USA
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García-Rivello H, Taranda J, Said M, Cabeza-Meckert P, Vila-Petroff M, Scaglione J, Ghio S, Chen J, Lai C, Laguens RP, Lloyd KC, Hertig CM. Dilated cardiomyopathy in Erb-b4-deficient ventricular muscle. Am J Physiol Heart Circ Physiol 2005; 289:H1153-60. [PMID: 15863464 DOI: 10.1152/ajpheart.00048.2005] [Citation(s) in RCA: 105] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
The neuregulin receptor tyrosine kinase Erb-b4, initially linked to early cardiac development, is shown here to play a critical role in adult cardiac function. In wild-type mice, Erb-b4 protein localized to Z lines and to intercalated disks, suggesting a role in subcellular and intercellular communications of cardiomyocytes. Conditional inactivation of erb-b4 in ventricular muscle cells led to a severe dilated cardiomyopathy, characterized by thinned ventricular walls with eccentric hypertrophy, reduced contractility, and delayed conduction. This cardiac dysfunction may account for premature death in adult erb-b4-knockout mice. This study establishes a critical role for Erb-b4 in the maintenance of normal postnatal cardiac structure and function.
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Affiliation(s)
- Hernán García-Rivello
- Instituto de Investigaciones en Ingeniería Genética y Biología Molecular, INGEBI, Vuelta de Obligado 2490, 1428 Buenos Aires, Argentina
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Palomeque J, Vila Petroff MG, Mattiazzi A. Pacing Staircase Phenomenon in the Heart: From Bodwitch to the XXI Century. Heart Lung Circ 2004; 13:410-20. [PMID: 16352227 DOI: 10.1016/j.hlc.2004.08.006] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
The frequency of pacing is a fundamental physiological modulator of myocardial function. When the pacing rate increases there is normally an increase in contractility (a positive force-frequency relationship). However in small rodents, fish and end-stage failing myocardium, the force-frequency response has been found to be flat or even negative. The positive staircase is understood to be related with the increase in the intracellular Ca(2+) transient, mainly due to an enhanced sarcoplasmic reticulum Ca(2+) content at higher stimulation frequencies, resulting from an increase in Ca(2+) influx per unit time and reduced Ca(2+) efflux between beats. However, additional mechanisms, such as increased activity of Ca(2+)/calmodulin-dependent protein kinase or enhanced myofilament responsiveness to Ca(2+) may also play a role. Although an increase in contraction frequency has been shown to be associated with an increase in intracellular Na(+), several studies have shown a temporal dissociation between the increase in Na(i)(+) and the increase in force evoked by changes in pacing frequency. The way in which the Na(+)/Ca(2+) exchanger contributes to contraction frequency inotropy is still not well understood. The aim of this review is to examine the contribution of the fundamental components of cardiac excitation-contraction coupling to frequency inotropy in healthy and failing hearts.
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Affiliation(s)
- Julieta Palomeque
- Centro de Investigaciones Cardiovasculares, Facultad de Ciencias Médicas, Universidad Nacional de La Plata, 60 y 120, La Plata 1900, Argentina
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Valverde CA, Mundiña-Weilenmann C, Said M, Ferrero P, Vittone L, Salas M, Palomeque J, Petroff MV, Mattiazzi A. Frequency-dependent acceleration of relaxation in mammalian heart: a property not relying on phospholamban and SERCA2a phosphorylation. J Physiol 2004; 562:801-13. [PMID: 15528241 PMCID: PMC1665530 DOI: 10.1113/jphysiol.2004.075432] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
An increase in stimulation frequency causes an acceleration of myocardial relaxation (FDAR). Several mechanisms have been postulated to explain this effect, among which is the Ca(2+)-calmodulin-dependent protein kinase (CaMKII)-dependent phosphorylation of the Thr(17) site of phospholamban (PLN). To gain further insights into the mechanisms of FDAR, we studied the FDAR and the phosphorylation of PLN residues in perfused rat hearts, cat papillary muscles and isolated cat myocytes. This allowed us to sweep over a wide range of frequencies, in species with either positive or negative force-frequency relationships, as well as to explore the FDAR under isometric (or isovolumic) and isotonic conditions. Results were compared with those produced by isoprenaline, an intervention known to accelerate relaxation (IDAR) via PLN phosphorylation. While IDAR occurs tightly associated with a significant increase in the phosphorylation of Ser(16) and Thr(17) of PLN, FDAR occurs without significant changes in the phosphorylation of PLN residues in the intact heart and cat papillary muscles. Moreover, in intact hearts, FDAR was not associated with any significant change in the CaMKII-dependent phosphorylation of sarcoplasmic/endoplasmic Ca(2+) ATPase (SERCA2a), and was not affected by the presence of the CaMKII inhibitor, KN-93. In isolated myocytes, FDAR occurred associated with an increase in Thr(17) phosphorylation. However, for a similar relaxant effect produced by isoprenaline, the phosphorylation of PLN (Ser(16) and Thr(17)) was significantly higher in the presence of the beta-agonist. Moreover, the time course of Thr(17) phosphorylation was significantly delayed with respect to the onset of FDAR. In contrast, the time course of Ser(16) phosphorylation, the first residue that becomes phosphorylated with isoprenaline, was temporally associated with IDAR. Furthermore, KN-93 significantly decreased the phosphorylation of Thr(17) that was evoked by increasing the stimulation frequency, but failed to affect FDAR. Taken together, the results provide direct evidence indicating that CaMKII phosphorylation pathways are not involved in FDAR and that FDAR and IDAR do not share a common underlying mechanism. More likely, a CaMKII-independent mechanism could be involved, whereby increasing stimulation frequency would disrupt the SERCA2a-PLN interaction, leading to an increase in SR Ca(2+) uptake and myocardial relaxation.
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Affiliation(s)
- Carlos A Valverde
- Centro de Investigaciones Cardiovasculares, Facultad de Ciencias Médicas, Universidad Nacional de La Plata, 60 y 120, 1900 La Plata, Argentina
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Bölck B, Münch G, Mackenstein P, Hellmich M, Hirsch I, Reuter H, Hattebuhr N, Weig HJ, Ungerer M, Brixius K, Schwinger RHG. Na+/Ca2+ exchanger overexpression impairs frequency- and ouabain-dependent cell shortening in adult rat cardiomyocytes. Am J Physiol Heart Circ Physiol 2004; 287:H1435-45. [PMID: 15165985 DOI: 10.1152/ajpheart.00397.2003] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The Na(+)/Ca(2+) exchanger (NCX) may influence cardiac function depending on its predominant mode of action, forward mode or reverse mode, during the contraction-relaxation cycle. The intracellular Na(+) concentration ([Na(+)](i)) and the duration of the action potential as well as the level of NCX protein expression regulate the mode of action of NCX. [Na(+)](i) and NCX expression have been reported to be increased in human heart failure. Nevertheless, the consequences of altered NCX expression in heart failure are still a matter of discussion. We aimed to characterize the influence of NCX expression on intracellular Ca(2+) transport in rat cardiomyocytes by adenoviral-mediated gene transfer. A five- to ninefold (dose dependent) overexpression of NCX protein was achieved after 48 h by somatic gene transfer (Ad.NCX.GFP) versus control (Ad.GFP). NCX activity, determined by Na(+) gradient-dependent (45)Ca(2+)-uptake, was significantly increased. The protein expressions of sarco(endo)plasmic reticulum Ca(2+)-ATPase, phospholamban, and calsequestrin were unaffected by NCX overexpression. Fractional shortening (FS) of isolated cardiomyocytes was significantly increased at low stimulation rates in Ad.NCX.GFP. After a step-wise enhancing frequency of stimulation to 3.0 Hz, FS remained unaffected in Ad.GFP cells but declined in Ad.NCX.GFP cells. The positive inotropic effect of the cardiac glycoside ouabain was less effective in Ad.NCX.GFP cells, whereas the positive inotropic effect of beta-adrenergic stimulation remained unchanged. In conclusion, NCX overexpression results in a reduced cell shortening at higher stimulation frequencies as well as after inhibition of sarcolemmal Na(+)-K(+)-ATPase, i.e., in conditions with enhanced [Na(+)](i). At low stimulation rates, increased NCX expression enhances both intracellular systolic Ca(2+) and contraction amplitude.
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Affiliation(s)
- Birgit Bölck
- Laboratory of Muscle Research and Molecular Cardiology, Dept. of Internal Medicine III, Univ. of Cologne, Joseph-Stelzmann Strasse 9, 50924 Cologne, Germany
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Weiss M, Baek M, Kang W. Systems analysis of digoxin kinetics and inotropic response in the rat heart: effects of calcium and KB-R7943. Am J Physiol Heart Circ Physiol 2004; 287:H1857-67. [PMID: 15130880 DOI: 10.1152/ajpheart.01121.2003] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
To gain more insight into the mechanistic processes controlling the kinetics of inotropic response of digoxin in the perfused whole heart, an integrated kinetic model was developed incorporating digoxin uptake, receptor binding (Na(+)-K(+)-ATPase inhibition), and cellular events linking receptor occupation and response. The model was applied to data obtained in the single-pass Langendorff-perfused rat heart for external [Ca(2+)] of 0.5 and 1.5 mM under control conditions and in the presence of the reverse-mode Na(+)/Ca(2+) exchange inhibitor KB-R7943 (0.1 microM) in perfusate. Outflow concentration and left ventricular developed pressure data measured for three consecutive doses (15, 30, and 45 microg) in each heart were analyzed simultaneously. While disposition kinetics of digoxin was determined by interaction with a heterogeneous receptor population consisting of a high-affinity/low-capacity and a low-affinity/high- capacity binding site, response generation was >80% mediated by binding to the high-affinity receptor. Digoxin sensitivity increased at lower external [Ca(2+)] due to higher stimulus amplification. Coadministration of KB-R7943 significantly reduced the positive inotropic effect of digoxin at higher doses (30 and 45 microg) and led to a saturated and delayed receptor occupancy-response relationship in the cellular effectuation model. The results provide further evidence for the functional heterogeneity of the Na(+)-K(+)-ATPase and suggest that in the presence of KB-R7943 a reduction of the Ca(2+) influx rate via the reverse mode Na(+)/Ca(2+) exchanger might become the limiting factor in digoxin response generation.
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Affiliation(s)
- Michael Weiss
- Section of Pharmacokinetics, Dept. of Pharmacology, Martin Luther Univ. Halle-Wittenberg, D-06097 Halle, Germany.
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