Pub Date : 2002-06-28DOI: 10.1161/01.RES.0000024390.97889.C6
Tian Xue, E. Marbán, Ronald A. Li
If, a diastolic depolarizing current activated by hyperpolarization, is a key player in cardiac pacing. Despite the fact that If has been known for over 20 years, the encoding genes, namely HCN1 to 4, have only recently been identified. Functional data imply that different HCN isoforms may coassemble to form heteromeric channel complexes, but little direct evidence is available. Subunit stoichiometry is also unknown. Although the pore region of HCN channels contains the glycine-t yrosine-glycine (GYG) signature motif found in K+-selective channels, they permeate both Na+ and K+. In the present study, we probed the functional importance of the GYG selectivity motif in pacemaker channels by replacing this triplet in HCN1 with alanines (GYG349–351AAA or HCN1-AAA). HCN1-AAA did not yield functional currents; coexpression of HCN1-AAA with wild-type (WT) HCN1 suppressed normal channel activity in a dominant-negative manner (55.2±3.2%, 68.3±4.3%, 78.7±1.6%, 91.7±0.8%, and 97.9±0.2% current reduction at −140 mV for WT:AAA cRNA ratios of 4:1, 3:1, 2:1, 1:1, and 1:2, respectively) without affecting gating (steady-state activation, activation and deactivation kinetics) or permeation (reversal potential) properties. HCN1-AAA coexpression, however, did not alter the expressed current amplitudes of Kv1.4 and Kv2.1 channels, indicating that its suppressive effect was channel-specific. Statistical analysis reveals that a single HCN channel is composed of 4 monomeric subunits. Interestingly, HCN1-AAA also inhibited HCN2 in a dominant-negative manner with the same efficacy. We conclude that the GYG motif is a critical determinant of ion permeation for HCN channels, and that HCN1 and HCN2 readily coassemble to form heterotetrameric complexes.
{"title":"Dominant-Negative Suppression of HCN1- and HCN2-Encoded Pacemaker Currents by an Engineered HCN1 Construct: Insights Into Structure-Function Relationships and Multimerization","authors":"Tian Xue, E. Marbán, Ronald A. Li","doi":"10.1161/01.RES.0000024390.97889.C6","DOIUrl":"https://doi.org/10.1161/01.RES.0000024390.97889.C6","url":null,"abstract":"If, a diastolic depolarizing current activated by hyperpolarization, is a key player in cardiac pacing. Despite the fact that If has been known for over 20 years, the encoding genes, namely HCN1 to 4, have only recently been identified. Functional data imply that different HCN isoforms may coassemble to form heteromeric channel complexes, but little direct evidence is available. Subunit stoichiometry is also unknown. Although the pore region of HCN channels contains the glycine-t yrosine-glycine (GYG) signature motif found in K+-selective channels, they permeate both Na+ and K+. In the present study, we probed the functional importance of the GYG selectivity motif in pacemaker channels by replacing this triplet in HCN1 with alanines (GYG349–351AAA or HCN1-AAA). HCN1-AAA did not yield functional currents; coexpression of HCN1-AAA with wild-type (WT) HCN1 suppressed normal channel activity in a dominant-negative manner (55.2±3.2%, 68.3±4.3%, 78.7±1.6%, 91.7±0.8%, and 97.9±0.2% current reduction at −140 mV for WT:AAA cRNA ratios of 4:1, 3:1, 2:1, 1:1, and 1:2, respectively) without affecting gating (steady-state activation, activation and deactivation kinetics) or permeation (reversal potential) properties. HCN1-AAA coexpression, however, did not alter the expressed current amplitudes of Kv1.4 and Kv2.1 channels, indicating that its suppressive effect was channel-specific. Statistical analysis reveals that a single HCN channel is composed of 4 monomeric subunits. Interestingly, HCN1-AAA also inhibited HCN2 in a dominant-negative manner with the same efficacy. We conclude that the GYG motif is a critical determinant of ion permeation for HCN channels, and that HCN1 and HCN2 readily coassemble to form heterotetrameric complexes.","PeriodicalId":10314,"journal":{"name":"Circulation Research: Journal of the American Heart Association","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2002-06-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88331767","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2002-06-28DOI: 10.1161/01.RES.0000024262.11534.18
R. Loutzenhiser, A. Bidani, L. Chilton
The kinetic attributes of the afferent arteriole myogenic response were investigated using the in vitro perfused hydronephrotic rat kidney. Equations describing the time course for pressure-dependent vasoconstriction and vasodilation, and steady-state changes in diameter were combined to develop a mathematical model of autoregulation. Transfer functions were constructed by passing sinusoidal pressure waves through the model. These findings were compared with results derived using data from instrumented conscious rats. In each case, a reduction in gain and increase in phase were observed at frequencies of 0.2 to 0.3 Hz. We then examined the impact of oscillating pressure signals. The model predicted that pressure signals oscillating at frequencies above the myogenic operating range would elicit a sustained vasoconstriction the magnitude of which was dependent on peak pressure. These predictions were directly confirmed in the hydronephrotic kidney. Pressure oscillations presented at frequencies of 1 to 6 Hz elicited sustained afferent vasoconstrictions and the magnitude of the response depended exclusively on the peak pressure. Elevated systolic pressure elicited vasoconstriction even if mean pressure was reduced. These findings challenge the view that the renal myogenic response exists to maintain glomerular capillary pressure constant, but rather imply a primary role in protecting against elevated systolic pressures. Thus, the kinetic features of the afferent arteriole allow this vessel to adjust tone in response to changes in systolic pressures presented at the pulse rate. We suggest that the primary function of this mechanism is to protect the glomerulus from the blood pressure power that is normally present at the pulse frequency.
{"title":"Renal Myogenic Response: Kinetic Attributes and Physiological Role","authors":"R. Loutzenhiser, A. Bidani, L. Chilton","doi":"10.1161/01.RES.0000024262.11534.18","DOIUrl":"https://doi.org/10.1161/01.RES.0000024262.11534.18","url":null,"abstract":"The kinetic attributes of the afferent arteriole myogenic response were investigated using the in vitro perfused hydronephrotic rat kidney. Equations describing the time course for pressure-dependent vasoconstriction and vasodilation, and steady-state changes in diameter were combined to develop a mathematical model of autoregulation. Transfer functions were constructed by passing sinusoidal pressure waves through the model. These findings were compared with results derived using data from instrumented conscious rats. In each case, a reduction in gain and increase in phase were observed at frequencies of 0.2 to 0.3 Hz. We then examined the impact of oscillating pressure signals. The model predicted that pressure signals oscillating at frequencies above the myogenic operating range would elicit a sustained vasoconstriction the magnitude of which was dependent on peak pressure. These predictions were directly confirmed in the hydronephrotic kidney. Pressure oscillations presented at frequencies of 1 to 6 Hz elicited sustained afferent vasoconstrictions and the magnitude of the response depended exclusively on the peak pressure. Elevated systolic pressure elicited vasoconstriction even if mean pressure was reduced. These findings challenge the view that the renal myogenic response exists to maintain glomerular capillary pressure constant, but rather imply a primary role in protecting against elevated systolic pressures. Thus, the kinetic features of the afferent arteriole allow this vessel to adjust tone in response to changes in systolic pressures presented at the pulse rate. We suggest that the primary function of this mechanism is to protect the glomerulus from the blood pressure power that is normally present at the pulse frequency.","PeriodicalId":10314,"journal":{"name":"Circulation Research: Journal of the American Heart Association","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2002-06-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78824631","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2002-06-28DOI: 10.1161/01.RES.0000022200.71892.9F
I. Shiojima, K. Walsh
Akt is a serine/threonine protein kinase that is activated by a number of growth factors and cytokines in a phosphatidylinositol-3 kinase–dependent manner. Although antiapoptotic activity of Akt is well known, it also regulates other aspects of cellular functions, including migration, glucose metabolism, and protein synthesis. In this review, Akt signaling in endothelial cells and its critical roles in the regulation of vascular homeostasis and angiogenesis will be discussed.
{"title":"Role of Akt Signaling in Vascular Homeostasis and Angiogenesis","authors":"I. Shiojima, K. Walsh","doi":"10.1161/01.RES.0000022200.71892.9F","DOIUrl":"https://doi.org/10.1161/01.RES.0000022200.71892.9F","url":null,"abstract":"Akt is a serine/threonine protein kinase that is activated by a number of growth factors and cytokines in a phosphatidylinositol-3 kinase–dependent manner. Although antiapoptotic activity of Akt is well known, it also regulates other aspects of cellular functions, including migration, glucose metabolism, and protein synthesis. In this review, Akt signaling in endothelial cells and its critical roles in the regulation of vascular homeostasis and angiogenesis will be discussed.","PeriodicalId":10314,"journal":{"name":"Circulation Research: Journal of the American Heart Association","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2002-06-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84705907","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2002-06-14DOI: 10.1161/01.RES.0000022879.57270.11
T. Herron, K. McDonald
Myocardial performance is likely affected by the relative expression of the two myosin heavy chain (MyHC) isoforms, namely &agr;-MyHC and &bgr;-MyHC. The relative expression of each isoform is regulated developmentally and in pathophysiological states. Many pathophysiological states are associated with small shifts in the relative expression of each MyHC isoform, yet the functional consequence of these shifts remains unclear. The purpose of this study was to determine the functional effect of a small shift in the relative expression of &agr;-MyHC. To this end, power output was measured in rat cardiac myocyte fragments that expressed ≈12% &agr;-MyHC and in myocyte fragments that expressed ≈0% &agr;-MyHC, as determined in the same cells by SDS-PAGE analysis after mechanical experiments. Myocyte fragments expressing ≈12% &agr;-MyHC developed ≈52% greater peak normalized power output than myocyte fragments expressing ≈0% &agr;-MyHC. These results indicate that small amounts of &agr;-MyHC expression significantly augment myocyte power output.
{"title":"Small Amounts of &agr;-Myosin Heavy Chain Isoform Expression Significantly Increase Power Output of Rat Cardiac Myocyte Fragments","authors":"T. Herron, K. McDonald","doi":"10.1161/01.RES.0000022879.57270.11","DOIUrl":"https://doi.org/10.1161/01.RES.0000022879.57270.11","url":null,"abstract":"Myocardial performance is likely affected by the relative expression of the two myosin heavy chain (MyHC) isoforms, namely &agr;-MyHC and &bgr;-MyHC. The relative expression of each isoform is regulated developmentally and in pathophysiological states. Many pathophysiological states are associated with small shifts in the relative expression of each MyHC isoform, yet the functional consequence of these shifts remains unclear. The purpose of this study was to determine the functional effect of a small shift in the relative expression of &agr;-MyHC. To this end, power output was measured in rat cardiac myocyte fragments that expressed ≈12% &agr;-MyHC and in myocyte fragments that expressed ≈0% &agr;-MyHC, as determined in the same cells by SDS-PAGE analysis after mechanical experiments. Myocyte fragments expressing ≈12% &agr;-MyHC developed ≈52% greater peak normalized power output than myocyte fragments expressing ≈0% &agr;-MyHC. These results indicate that small amounts of &agr;-MyHC expression significantly augment myocyte power output.","PeriodicalId":10314,"journal":{"name":"Circulation Research: Journal of the American Heart Association","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2002-06-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86497100","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2002-06-14DOI: 10.1161/01.RES.0000020401.61826.EA
A. Csiszar, Z. Ungvari, J. Edwards, P. Kaminski, M. Wolin, A. Koller, G. Kaley
We aimed to elucidate the possible role of phenotypic alterations and oxidative stress in age-related endothelial dysfunction of coronary arterioles. Arterioles were isolated from the hearts of young adult (Y, 14 weeks) and aged (A, 80 weeks) male Sprague-Dawley rats. For videomicroscopy, pressure-induced tone of Y and A arterioles and their passive diameter did not differ significantly. In A, arterioles L-NAME (a NO synthase blocker)–sensitive flow-induced dilations were significantly impaired (Y: 41±8% versus A: 3±2%), which could be augmented by superoxide dismutase (SOD) or Tiron (but not l-arginine or the TXA2 receptor antagonist SQ29,548). For lucigenin chemiluminescence, O2·− generation was significantly greater in A than Y vessels and could be inhibited with SOD and diphenyliodonium. NADH-driven O2·− generation was also greater in A vessels. Both endothelial and smooth muscle cells of A vessels produced O2·− (shown with ethidium bromide fluorescence). For Western blotting, expression of eNOS and COX-1 was decreased in A compared with Y arterioles, whereas expressions of COX-2, Cu/Zn-SOD, Mn-SOD, xanthine oxidase, and the NAD(P)H oxidase subunits p47phox, p67phox, Mox-1, and p22phox did not differ. Aged arterioles showed an increased expression of iNOS, confined to the endothelium. Decreased eNOS mRNA and increased iNOS mRNA expression in A vessels was shown by quantitative RT-PCR. In vivo formation of peroxynitrite was evidenced by Western blotting, and immunohistochemistry showing increased 3-nitrotyrosine content in A vessels. Thus, aging induces changes in the phenotype of coronary arterioles that could contribute to the development of oxidative stress, which impairs NO-mediated dilations.
{"title":"Aging-Induced Phenotypic Changes and Oxidative Stress Impair Coronary Arteriolar Function","authors":"A. Csiszar, Z. Ungvari, J. Edwards, P. Kaminski, M. Wolin, A. Koller, G. Kaley","doi":"10.1161/01.RES.0000020401.61826.EA","DOIUrl":"https://doi.org/10.1161/01.RES.0000020401.61826.EA","url":null,"abstract":"We aimed to elucidate the possible role of phenotypic alterations and oxidative stress in age-related endothelial dysfunction of coronary arterioles. Arterioles were isolated from the hearts of young adult (Y, 14 weeks) and aged (A, 80 weeks) male Sprague-Dawley rats. For videomicroscopy, pressure-induced tone of Y and A arterioles and their passive diameter did not differ significantly. In A, arterioles L-NAME (a NO synthase blocker)–sensitive flow-induced dilations were significantly impaired (Y: 41±8% versus A: 3±2%), which could be augmented by superoxide dismutase (SOD) or Tiron (but not l-arginine or the TXA2 receptor antagonist SQ29,548). For lucigenin chemiluminescence, O2·− generation was significantly greater in A than Y vessels and could be inhibited with SOD and diphenyliodonium. NADH-driven O2·− generation was also greater in A vessels. Both endothelial and smooth muscle cells of A vessels produced O2·− (shown with ethidium bromide fluorescence). For Western blotting, expression of eNOS and COX-1 was decreased in A compared with Y arterioles, whereas expressions of COX-2, Cu/Zn-SOD, Mn-SOD, xanthine oxidase, and the NAD(P)H oxidase subunits p47phox, p67phox, Mox-1, and p22phox did not differ. Aged arterioles showed an increased expression of iNOS, confined to the endothelium. Decreased eNOS mRNA and increased iNOS mRNA expression in A vessels was shown by quantitative RT-PCR. In vivo formation of peroxynitrite was evidenced by Western blotting, and immunohistochemistry showing increased 3-nitrotyrosine content in A vessels. Thus, aging induces changes in the phenotype of coronary arterioles that could contribute to the development of oxidative stress, which impairs NO-mediated dilations.","PeriodicalId":10314,"journal":{"name":"Circulation Research: Journal of the American Heart Association","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2002-06-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86821369","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2002-06-14DOI: 10.1161/01.RES.0000020402.73609.F1
S. Yuan, Mack H. Wu, E. Ustinova, M. Guo, J. Tinsley, P. de Lanerolle, Wenjuan Xu
Neutrophil-induced coronary microvascular leakage represents an important pathophysiological consequence of ischemic and inflammatory heart diseases. The precise mechanism by which neutrophils regulate endothelial barrier function remains to be established. The aim of this study was to examine the microvascular endothelial response to neutrophil activation with a focus on myosin light chain kinase (MLCK)-mediated myosin light chain (MLC) phosphorylation, a regulatory process that controls cell contraction. The apparent permeability coefficient of albumin (Pa) was measured in intact isolated porcine coronary venules. Incubation of the vessels with C5a-activated neutrophils induced a time- and concentration-dependent increase in Pa. The hyperpermeability response was significantly attenuated during inhibition of endothelial MLC phosphorylation with the selective MLCK inhibitor ML-7 and transfection of a specific MLCK-inhibiting peptide. In contrast, transfection of constitutively active MLCK elevated Pa, which was abolished by ML-7. In addition to the vessel study, albumin transendothelial flux was measured in cultured bovine coronary venular endothelial monolayers, which displayed a hyperpermeability response to neutrophils and MLCK in a pattern similar to that in venules. Importantly, neutrophil stimulation caused MLC phosphorylation in endothelial cells in a time course closely correlated with that of the hyperpermeability response. Consistently, the MLCK inhibitors abolished neutrophil-induced MLC phosphorylation. Furthermore, immunohistochemical observation of neutrophil-stimulated endothelial cells revealed an increased staining for phosphorylated MLC in association with contractile stress fiber formation and intercellular gap development. Taken together, the results suggest that endothelial MLCK activation and MLC phosphorylation play an important role in mediating endothelial barrier dysfunction during neutrophil activation.
{"title":"Myosin Light Chain Phosphorylation in Neutrophil-Stimulated Coronary Microvascular Leakage","authors":"S. Yuan, Mack H. Wu, E. Ustinova, M. Guo, J. Tinsley, P. de Lanerolle, Wenjuan Xu","doi":"10.1161/01.RES.0000020402.73609.F1","DOIUrl":"https://doi.org/10.1161/01.RES.0000020402.73609.F1","url":null,"abstract":"Neutrophil-induced coronary microvascular leakage represents an important pathophysiological consequence of ischemic and inflammatory heart diseases. The precise mechanism by which neutrophils regulate endothelial barrier function remains to be established. The aim of this study was to examine the microvascular endothelial response to neutrophil activation with a focus on myosin light chain kinase (MLCK)-mediated myosin light chain (MLC) phosphorylation, a regulatory process that controls cell contraction. The apparent permeability coefficient of albumin (Pa) was measured in intact isolated porcine coronary venules. Incubation of the vessels with C5a-activated neutrophils induced a time- and concentration-dependent increase in Pa. The hyperpermeability response was significantly attenuated during inhibition of endothelial MLC phosphorylation with the selective MLCK inhibitor ML-7 and transfection of a specific MLCK-inhibiting peptide. In contrast, transfection of constitutively active MLCK elevated Pa, which was abolished by ML-7. In addition to the vessel study, albumin transendothelial flux was measured in cultured bovine coronary venular endothelial monolayers, which displayed a hyperpermeability response to neutrophils and MLCK in a pattern similar to that in venules. Importantly, neutrophil stimulation caused MLC phosphorylation in endothelial cells in a time course closely correlated with that of the hyperpermeability response. Consistently, the MLCK inhibitors abolished neutrophil-induced MLC phosphorylation. Furthermore, immunohistochemical observation of neutrophil-stimulated endothelial cells revealed an increased staining for phosphorylated MLC in association with contractile stress fiber formation and intercellular gap development. Taken together, the results suggest that endothelial MLCK activation and MLC phosphorylation play an important role in mediating endothelial barrier dysfunction during neutrophil activation.","PeriodicalId":10314,"journal":{"name":"Circulation Research: Journal of the American Heart Association","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2002-06-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84641365","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2002-06-14DOI: 10.1161/01.RES.0000022166.74073.F8
G. Hou, W. Vogel, M. Bendeck
Smooth muscle cell (SMC) interactions with collagen mediate cell migration during the pathogenesis of atherosclerosis and restenosis. Discoidin domain receptors (DDRs) have been identified as novel collagen receptors. We used aortic SMCs from wild-type and DDR1−/− mice to evaluate the function of the DDR1 in regulating migration. DDR1−/− SMCs exhibited impaired attachment to and migration toward a type I collagen substrate. Matrix metalloproteinase-2 (MMP-2) and MMP-9 activities were concomitantly reduced in these cells. Transfection of a full-length cDNA for DDR1b rescued these deficits, whereas kinase-dead mutants of DDR1 restored attachment but not migration and MMP production. These results suggest that active DDR1 kinase is a central mediator of SMC migration.
{"title":"Tyrosine Kinase Activity of Discoidin Domain Receptor 1 Is Necessary for Smooth Muscle Cell Migration and Matrix Metalloproteinase Expression","authors":"G. Hou, W. Vogel, M. Bendeck","doi":"10.1161/01.RES.0000022166.74073.F8","DOIUrl":"https://doi.org/10.1161/01.RES.0000022166.74073.F8","url":null,"abstract":"Smooth muscle cell (SMC) interactions with collagen mediate cell migration during the pathogenesis of atherosclerosis and restenosis. Discoidin domain receptors (DDRs) have been identified as novel collagen receptors. We used aortic SMCs from wild-type and DDR1−/− mice to evaluate the function of the DDR1 in regulating migration. DDR1−/− SMCs exhibited impaired attachment to and migration toward a type I collagen substrate. Matrix metalloproteinase-2 (MMP-2) and MMP-9 activities were concomitantly reduced in these cells. Transfection of a full-length cDNA for DDR1b rescued these deficits, whereas kinase-dead mutants of DDR1 restored attachment but not migration and MMP production. These results suggest that active DDR1 kinase is a central mediator of SMC migration.","PeriodicalId":10314,"journal":{"name":"Circulation Research: Journal of the American Heart Association","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2002-06-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83726874","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2002-06-14DOI: 10.1161/01.RES.0000022854.95998.5C
O. Berenfeld, A. Zaitsev, S. Mironov, A. Pertsov, J. Jalife
Atrial fibrillation (AF) may result from stationary reentry in the left atrium (LA), with fibrillatory conduction toward the right atrium (RA). We hypothesize that periodic input to the RA at an exceedingly high frequency results in disorganized wave propagation, compatible with fibrillatory conduction. Simultaneous endocardial and epicardial optical mapping (di-4-ANEPPS) was performed in isolated, coronary-perfused sheep RA. Rhythmic pacing of Bachmann’s bundle allowed well-controlled and realistic conditions for LA-driven RA. Pacing at increasingly higher frequencies (2.0 to 6.0 Hz) led to increasing delays in activation distal to major branching sites of the crista terminalis and pectinate bundles, culminating in spatially distributed intermittent blockade at or above ≈6.5 Hz. At this “breakdown frequency,” the direction of RA propagation became completely variable from beat to beat and thus transformed into fibrillatory conduction. Such frequency-dependent changes were independent of action potential duration. Rather, the spatial boundaries between proximal and distal frequencies correlated well with branch sites of the pectinate musculature. Thus, there exists a breakdown frequency in the sheep RA below which activity is periodic throughout the atrium and above which it is fibrillation-like. The data are consistent with the ideas that during AF, high-frequency activation initiated in the LA undergoes fibrillatory conduction toward the RA, and that sink-to-source effect at branch points of the crista terminalis and pectinate muscles is important in determining the complexity of the arrhythmia.
{"title":"Frequency-Dependent Breakdown of Wave Propagation Into Fibrillatory Conduction Across the Pectinate Muscle Network in the Isolated Sheep Right Atrium","authors":"O. Berenfeld, A. Zaitsev, S. Mironov, A. Pertsov, J. Jalife","doi":"10.1161/01.RES.0000022854.95998.5C","DOIUrl":"https://doi.org/10.1161/01.RES.0000022854.95998.5C","url":null,"abstract":"Atrial fibrillation (AF) may result from stationary reentry in the left atrium (LA), with fibrillatory conduction toward the right atrium (RA). We hypothesize that periodic input to the RA at an exceedingly high frequency results in disorganized wave propagation, compatible with fibrillatory conduction. Simultaneous endocardial and epicardial optical mapping (di-4-ANEPPS) was performed in isolated, coronary-perfused sheep RA. Rhythmic pacing of Bachmann’s bundle allowed well-controlled and realistic conditions for LA-driven RA. Pacing at increasingly higher frequencies (2.0 to 6.0 Hz) led to increasing delays in activation distal to major branching sites of the crista terminalis and pectinate bundles, culminating in spatially distributed intermittent blockade at or above ≈6.5 Hz. At this “breakdown frequency,” the direction of RA propagation became completely variable from beat to beat and thus transformed into fibrillatory conduction. Such frequency-dependent changes were independent of action potential duration. Rather, the spatial boundaries between proximal and distal frequencies correlated well with branch sites of the pectinate musculature. Thus, there exists a breakdown frequency in the sheep RA below which activity is periodic throughout the atrium and above which it is fibrillation-like. The data are consistent with the ideas that during AF, high-frequency activation initiated in the LA undergoes fibrillatory conduction toward the RA, and that sink-to-source effect at branch points of the crista terminalis and pectinate muscles is important in determining the complexity of the arrhythmia.","PeriodicalId":10314,"journal":{"name":"Circulation Research: Journal of the American Heart Association","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2002-06-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80801095","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2002-06-14DOI: 10.1161/01.RES.0000021115.24712.99
R. Yamasaki, Yiming Wu, M. Mcnabb, M. Greaser, S. Labeit, H. Granzier
&bgr;-Adrenergic stimulation of cardiac muscle activates protein kinase A (PKA), which is known to phosphorylate proteins on the thin and thick filaments of the sarcomere. Cardiac muscle sarcomeres contain a third filament system composed of titin, and here we demonstrate that titin is also phosphorylated by the &bgr;-adrenergic pathway. Titin phosphorylation was observed after &bgr;-receptor stimulation of intact cardiac myocytes and incubation of skinned cardiac myocytes with PKA. Mechanical experiments with isolated myocytes revealed that PKA significantly reduces passive tension. In vitro phosphorylation of recombinant titin fragments and immunoelectron microscopy suggest that PKA targets a subdomain of the elastic segment of titin, referred to as the N2B spring element. The N2B spring element is expressed only in cardiac titins, in which it plays an important role in determining the level of passive tension. Because titin-based passive tension is a determinant of diastolic function, these results suggest that titin phosphorylation may modulate cardiac function in vivo.
{"title":"Protein Kinase A Phosphorylates Titin’s Cardiac-Specific N2B Domain and Reduces Passive Tension in Rat Cardiac Myocytes","authors":"R. Yamasaki, Yiming Wu, M. Mcnabb, M. Greaser, S. Labeit, H. Granzier","doi":"10.1161/01.RES.0000021115.24712.99","DOIUrl":"https://doi.org/10.1161/01.RES.0000021115.24712.99","url":null,"abstract":"&bgr;-Adrenergic stimulation of cardiac muscle activates protein kinase A (PKA), which is known to phosphorylate proteins on the thin and thick filaments of the sarcomere. Cardiac muscle sarcomeres contain a third filament system composed of titin, and here we demonstrate that titin is also phosphorylated by the &bgr;-adrenergic pathway. Titin phosphorylation was observed after &bgr;-receptor stimulation of intact cardiac myocytes and incubation of skinned cardiac myocytes with PKA. Mechanical experiments with isolated myocytes revealed that PKA significantly reduces passive tension. In vitro phosphorylation of recombinant titin fragments and immunoelectron microscopy suggest that PKA targets a subdomain of the elastic segment of titin, referred to as the N2B spring element. The N2B spring element is expressed only in cardiac titins, in which it plays an important role in determining the level of passive tension. Because titin-based passive tension is a determinant of diastolic function, these results suggest that titin phosphorylation may modulate cardiac function in vivo.","PeriodicalId":10314,"journal":{"name":"Circulation Research: Journal of the American Heart Association","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2002-06-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89922550","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2002-06-14DOI: 10.1161/01.RES.0000020561.03244.7E
K. Egashira, Qingwei Zhao, C. Kataoka, Kisho Ohtani, M. Usui, I. Charo, K. Nishida, S. Inoue, M. Katoh, T. Ichiki, A. Takeshita
Neointimal hyperplasia is a major cause of restenosis after coronary intervention. Because vascular injury is now recognized to involve an inflammatory response, monocyte chemoattractant protein-1 (MCP-1) might be involved in underlying mechanisms of restenosis. In the present study, we demonstrate the important role of MCP-1 in neointimal hyperplasia after cuff-induced arterial injury. In the first set of experiments, placement of a nonconstricting cuff around the femoral artery of intact mice and monkeys resulted in inflammation in the early stages and subsequent neointimal hyperplasia at the late stages. We transfected with an N-terminal deletion mutant of the human MCP-1 gene into skeletal muscles to block MCP-1 activity in vivo. This mutant MCP-1 works as a dominant-negative inhibitor of MCP-1. This strategy inhibited early vascular inflammation (monocyte infiltration, increased expression of MCP-1, and inflammatory cytokines) and late neointimal hyperplasia. In the second set of experiments, the cuff-induced neointimal hyperplasia was found to be less in CCR2-deficient mice than in control CCR2+/+ mice. The MCP-1/CCR2 pathway plays a central role in the pathogenesis of neointimal hyperplasia in cuffed femoral artery of mice and monkeys. Therefore, the MCP-1/CCR2 pathway can be a therapeutic target for human restenosis after coronary intervention.
{"title":"Importance of Monocyte Chemoattractant Protein-1 Pathway in Neointimal Hyperplasia After Periarterial Injury in Mice and Monkeys","authors":"K. Egashira, Qingwei Zhao, C. Kataoka, Kisho Ohtani, M. Usui, I. Charo, K. Nishida, S. Inoue, M. Katoh, T. Ichiki, A. Takeshita","doi":"10.1161/01.RES.0000020561.03244.7E","DOIUrl":"https://doi.org/10.1161/01.RES.0000020561.03244.7E","url":null,"abstract":"Neointimal hyperplasia is a major cause of restenosis after coronary intervention. Because vascular injury is now recognized to involve an inflammatory response, monocyte chemoattractant protein-1 (MCP-1) might be involved in underlying mechanisms of restenosis. In the present study, we demonstrate the important role of MCP-1 in neointimal hyperplasia after cuff-induced arterial injury. In the first set of experiments, placement of a nonconstricting cuff around the femoral artery of intact mice and monkeys resulted in inflammation in the early stages and subsequent neointimal hyperplasia at the late stages. We transfected with an N-terminal deletion mutant of the human MCP-1 gene into skeletal muscles to block MCP-1 activity in vivo. This mutant MCP-1 works as a dominant-negative inhibitor of MCP-1. This strategy inhibited early vascular inflammation (monocyte infiltration, increased expression of MCP-1, and inflammatory cytokines) and late neointimal hyperplasia. In the second set of experiments, the cuff-induced neointimal hyperplasia was found to be less in CCR2-deficient mice than in control CCR2+/+ mice. The MCP-1/CCR2 pathway plays a central role in the pathogenesis of neointimal hyperplasia in cuffed femoral artery of mice and monkeys. Therefore, the MCP-1/CCR2 pathway can be a therapeutic target for human restenosis after coronary intervention.","PeriodicalId":10314,"journal":{"name":"Circulation Research: Journal of the American Heart Association","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2002-06-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"73415493","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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