Pub Date : 2002-08-23DOI: 10.1161/01.RES.0000030179.78135.FA
E. Schroder, K. Tobita, J. P. Tinney, J. Foldes, B. Keller
Abstract— Mechanical load regulates ventricular growth, function, and structure from the earliest stages of cardiac morphogenesis through senescence. Dramatic changes in cardiac form and function have been defined for developing cardiovascular systems, and changes in mechanical loading conditions can produce structural malformations such as left heart hypoplasia. To date, relatively little is known regarding the interactions between changes in mechanical load, morphogenesis, and the material properties of the embryonic heart. We tested the hypothesis that passive material properties in the embryonic heart change in response to altered mechanical load and that microtubules play an important role in this adaptive response. We measured biaxial passive stress-strain relations in left ventricular (LV) myocardial strips in chick embryos at Hamburger-Hamilton stage 27 following left atrial ligation (LAL) at stage 21 to reduce LV volume load and create left heart hypoplasia. Following LAL, myocardial stresses at given strains and circumferential stiffness increased versus control strips. Western blot analysis of LAL embryos showed an increase in both total and polymerized &bgr;-tubulin and confocal microscopy confirmed an increase in microtubule density in the LV compact layer versus control. Following colchicine treatment, LV stresses and stiffness normalized in LAL specimens and microtubule density following colchicine was similar in LAL to control. In contrast, Taxol treatment increased myocardial stresses and stiffness in control strips to levels beyond LAL specimens. Thus, the material properties of the developing myocardium are regulated by mechanical load and microtubules play a role in this adaptive response during cardiac morphogenesis.
{"title":"Microtubule Involvement in the Adaptation to Altered Mechanical Load in Developing Chick Myocardium","authors":"E. Schroder, K. Tobita, J. P. Tinney, J. Foldes, B. Keller","doi":"10.1161/01.RES.0000030179.78135.FA","DOIUrl":"https://doi.org/10.1161/01.RES.0000030179.78135.FA","url":null,"abstract":"Abstract— Mechanical load regulates ventricular growth, function, and structure from the earliest stages of cardiac morphogenesis through senescence. Dramatic changes in cardiac form and function have been defined for developing cardiovascular systems, and changes in mechanical loading conditions can produce structural malformations such as left heart hypoplasia. To date, relatively little is known regarding the interactions between changes in mechanical load, morphogenesis, and the material properties of the embryonic heart. We tested the hypothesis that passive material properties in the embryonic heart change in response to altered mechanical load and that microtubules play an important role in this adaptive response. We measured biaxial passive stress-strain relations in left ventricular (LV) myocardial strips in chick embryos at Hamburger-Hamilton stage 27 following left atrial ligation (LAL) at stage 21 to reduce LV volume load and create left heart hypoplasia. Following LAL, myocardial stresses at given strains and circumferential stiffness increased versus control strips. Western blot analysis of LAL embryos showed an increase in both total and polymerized &bgr;-tubulin and confocal microscopy confirmed an increase in microtubule density in the LV compact layer versus control. Following colchicine treatment, LV stresses and stiffness normalized in LAL specimens and microtubule density following colchicine was similar in LAL to control. In contrast, Taxol treatment increased myocardial stresses and stiffness in control strips to levels beyond LAL specimens. Thus, the material properties of the developing myocardium are regulated by mechanical load and microtubules play a role in this adaptive response during cardiac morphogenesis.","PeriodicalId":10314,"journal":{"name":"Circulation Research: Journal of the American Heart Association","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2002-08-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80022586","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 : 2002-08-23DOI: 10.1161/01.RES.0000031151.21145.59
M. Chandler, W. Stanley, H. Morita, G. Suzuki, Bridgette A. Roth, B. Blackburn, A. Wolff, H. Sabbah
The present study assesses whether ranolazine increases left ventricular (LV) function without an increase in myocardial oxygen consumption (M&OV0312;o2) and thus improves LV mechanical efficiency in dogs with heart failure (HF). Ranolazine did not change M&OV0312;o2 and LV mechanical efficiency increased (22.4±2.8% to 30.9±3.4% (P <0.05). In contrast, dobutamine significantly increased M&OV0312;o2 and did not improve mechanical efficiency. Thus, short-term treatment with ranolazine improved LV function without an increase in M&OV0312;o2, resulting in an increased myocardial mechanical efficiency in dogs with HF.
{"title":"Short-Term Treatment With Ranolazine Improves Mechanical Efficiency in Dogs With Chronic Heart Failure","authors":"M. Chandler, W. Stanley, H. Morita, G. Suzuki, Bridgette A. Roth, B. Blackburn, A. Wolff, H. Sabbah","doi":"10.1161/01.RES.0000031151.21145.59","DOIUrl":"https://doi.org/10.1161/01.RES.0000031151.21145.59","url":null,"abstract":"The present study assesses whether ranolazine increases left ventricular (LV) function without an increase in myocardial oxygen consumption (M&OV0312;o2) and thus improves LV mechanical efficiency in dogs with heart failure (HF). Ranolazine did not change M&OV0312;o2 and LV mechanical efficiency increased (22.4±2.8% to 30.9±3.4% (P <0.05). In contrast, dobutamine significantly increased M&OV0312;o2 and did not improve mechanical efficiency. Thus, short-term treatment with ranolazine improved LV function without an increase in M&OV0312;o2, resulting in an increased myocardial mechanical efficiency in dogs with HF.","PeriodicalId":10314,"journal":{"name":"Circulation Research: Journal of the American Heart Association","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2002-08-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86998442","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 : 2002-08-09DOI: 10.1161/01.RES.0000029969.39875.4B
Yuan Li, M. Anand-Srivastava
Abstract— We have previously shown that the enhanced expression of Gi proteins in spontaneously hypertensive rats (SHR) that precedes the development of high blood pressure may be one of the contributing factors in the pathogenesis of hypertension. In the present study, we demonstrate that the inactivation of Gi proteins by intraperitoneal injection of pertussis toxin (PT, 1.5 &mgr;g/100 g body wt) into 2-week-old prehypertensive SHR prevented the development of hypertension up to 4 weeks and that, thereafter, it started to increase and reached the same level found in untreated SHR after 6 weeks. A second injection of PT after 4 weeks delayed the increase in blood pressure for another week. The PT-induced decrease in blood pressure in 6-week-old SHR was associated with a decreased level of Gi&agr;-2 and Gi&agr;-3 proteins in the heart, as determined by in vitro ADP ribosylation and immunoblotting. The decreased level of Gi proteins was reflected in decreased Gi functions. Furthermore, an augmentation of blood pressure to the same level in PT-treated SHR as found in untreated SHR was associated with enhanced expression and function of Gi. These results indicate that the inactivation of Gi proteins by PT treatment in prehypertensive SHR attenuates the development of hypertension and suggest that the enhanced levels of Gi proteins that result in the decreased levels of cAMP and associated impaired cellular functions may be contributing factors in the pathogenesis of hypertension in SHR.
{"title":"Inactivation of Enhanced Expression of Gi Proteins by Pertussis Toxin Attenuates the Development of High Blood Pressure in Spontaneously Hypertensive Rats","authors":"Yuan Li, M. Anand-Srivastava","doi":"10.1161/01.RES.0000029969.39875.4B","DOIUrl":"https://doi.org/10.1161/01.RES.0000029969.39875.4B","url":null,"abstract":"Abstract— We have previously shown that the enhanced expression of Gi proteins in spontaneously hypertensive rats (SHR) that precedes the development of high blood pressure may be one of the contributing factors in the pathogenesis of hypertension. In the present study, we demonstrate that the inactivation of Gi proteins by intraperitoneal injection of pertussis toxin (PT, 1.5 &mgr;g/100 g body wt) into 2-week-old prehypertensive SHR prevented the development of hypertension up to 4 weeks and that, thereafter, it started to increase and reached the same level found in untreated SHR after 6 weeks. A second injection of PT after 4 weeks delayed the increase in blood pressure for another week. The PT-induced decrease in blood pressure in 6-week-old SHR was associated with a decreased level of Gi&agr;-2 and Gi&agr;-3 proteins in the heart, as determined by in vitro ADP ribosylation and immunoblotting. The decreased level of Gi proteins was reflected in decreased Gi functions. Furthermore, an augmentation of blood pressure to the same level in PT-treated SHR as found in untreated SHR was associated with enhanced expression and function of Gi. These results indicate that the inactivation of Gi proteins by PT treatment in prehypertensive SHR attenuates the development of hypertension and suggest that the enhanced levels of Gi proteins that result in the decreased levels of cAMP and associated impaired cellular functions may be contributing factors in the pathogenesis of hypertension in SHR.","PeriodicalId":10314,"journal":{"name":"Circulation Research: Journal of the American Heart Association","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2002-08-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"73783403","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 : 2002-08-09DOI: 10.1161/01.RES.0000029970.97247.57
K. Shinmura, R. Bolli, Siqi Liu, Xian-Liang Tang, E. Kodani, Y. Xuan, S. Srivastava, A. Bhatnagar
Abstract— Aldose reductase (AR), a member of the aldo-keto reductase superfamily, has been shown to metabolize toxic aldehydes generated by lipid peroxidation, suggesting that it may serve as an antioxidant defense. To investigate its role in the late phase of ischemic preconditioning (PC), conscious rabbits underwent 6 cycles of 4-minute coronary occlusion/4-minute reperfusion. Twenty-four hours later, there was a marked increase in AR protein and activity and in the myocardial content of sorbitol, a unique product of AR catalysis. Pretreatment with N&ohgr;-nitro-l-arginine, a nitric oxide synthase inhibitor, or chelerythrine, a protein kinase C inhibitor (both given at doses that block late PC in this model), prevented the increase in AR protein 24 hours later, demonstrating that ischemic PC upregulates AR via nitric oxide- and protein kinase C-dependent signaling pathways. The AR-selective inhibitors tolrestat and sorbinil prevented AR-mediated accumulation of sorbitol and abrogated the infarct-sparing effect of late PC, demonstrating that enhanced AR activity is necessary for this cardioprotective phenomenon to occur. Inhibition of AR did not affect infarct size or the myocardial accumulation of the lipid peroxidation product 4-hydroxy trans-2-nonenal (HNE) in nonpreconditioned rabbits. The accumulation of HNE was inhibited by late PC, and this effect was abrogated by sorbinil. Taken together, these results establish AR as an essential mediator of late PC. Furthermore, the data suggest that myocardial ischemia/reperfusion injury is due in part to the generation of lipid peroxidation products and that late PC diminishes this source of injury by upregulating AR.
{"title":"Aldose Reductase Is an Obligatory Mediator of the Late Phase of Ischemic Preconditioning","authors":"K. Shinmura, R. Bolli, Siqi Liu, Xian-Liang Tang, E. Kodani, Y. Xuan, S. Srivastava, A. Bhatnagar","doi":"10.1161/01.RES.0000029970.97247.57","DOIUrl":"https://doi.org/10.1161/01.RES.0000029970.97247.57","url":null,"abstract":"Abstract— Aldose reductase (AR), a member of the aldo-keto reductase superfamily, has been shown to metabolize toxic aldehydes generated by lipid peroxidation, suggesting that it may serve as an antioxidant defense. To investigate its role in the late phase of ischemic preconditioning (PC), conscious rabbits underwent 6 cycles of 4-minute coronary occlusion/4-minute reperfusion. Twenty-four hours later, there was a marked increase in AR protein and activity and in the myocardial content of sorbitol, a unique product of AR catalysis. Pretreatment with N&ohgr;-nitro-l-arginine, a nitric oxide synthase inhibitor, or chelerythrine, a protein kinase C inhibitor (both given at doses that block late PC in this model), prevented the increase in AR protein 24 hours later, demonstrating that ischemic PC upregulates AR via nitric oxide- and protein kinase C-dependent signaling pathways. The AR-selective inhibitors tolrestat and sorbinil prevented AR-mediated accumulation of sorbitol and abrogated the infarct-sparing effect of late PC, demonstrating that enhanced AR activity is necessary for this cardioprotective phenomenon to occur. Inhibition of AR did not affect infarct size or the myocardial accumulation of the lipid peroxidation product 4-hydroxy trans-2-nonenal (HNE) in nonpreconditioned rabbits. The accumulation of HNE was inhibited by late PC, and this effect was abrogated by sorbinil. Taken together, these results establish AR as an essential mediator of late PC. Furthermore, the data suggest that myocardial ischemia/reperfusion injury is due in part to the generation of lipid peroxidation products and that late PC diminishes this source of injury by upregulating AR.","PeriodicalId":10314,"journal":{"name":"Circulation Research: Journal of the American Heart Association","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2002-08-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90090597","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 : 2002-08-09DOI: 10.1161/01.RES.0000027530.58419.82
D. Michele, Carlen A. Gomez, Katie E. Hong, M. Westfall, J. Metzger
Abstract— Familial hypertrophic cardiomyopathy (FHC) has been linked to mutations in proteins of the cardiac contractile apparatus, including &agr;-tropomyosin (Tm). Mice expressing &agr;Tm in the heart were developed to determine the effects of FHC mutant Tm on cardiac structure and function from single cardiac myocytes to whole organ function in vivo. Expression of E180G mutant Tm did not produce cardiac hypertrophy or detectable changes in cardiac muscle morphology. However, E180G mutant Tm expression increased the Ca2+ sensitivity of force production in single cardiac myocytes in a transgene expression–dependent manner. Contractile dysfunction in single myocytes manifested organ level dysfunction, as conductance-micromanometry showed E180G Tm mice had significantly slowed relaxation (diastolic dysfunction) under physiological conditions. The diastolic dysfunction in E180G Tm mice was no longer evident during &bgr;-blockade because propranolol eliminated the effect of E180G Tm to slow myocardial relaxation. Cellular and organ level dysfunction were evident in E180G Tm mice in the absence of significant cardiac structural abnormalities normally associated with FHC. These findings therefore suggest that diastolic dysfunction in FHC may be a direct consequence of FHC mutant protein expression. In addition, because diastolic dysfunction in E180G Tm mice is dependent on inotropic status, cardiovascular stress may play an important role in FHC pathogenesis.
{"title":"Cardiac Dysfunction in Hypertrophic Cardiomyopathy Mutant Tropomyosin Mice Is Transgene-Dependent, Hypertrophy-Independent, and Improved by &bgr;-Blockade","authors":"D. Michele, Carlen A. Gomez, Katie E. Hong, M. Westfall, J. Metzger","doi":"10.1161/01.RES.0000027530.58419.82","DOIUrl":"https://doi.org/10.1161/01.RES.0000027530.58419.82","url":null,"abstract":"Abstract— Familial hypertrophic cardiomyopathy (FHC) has been linked to mutations in proteins of the cardiac contractile apparatus, including &agr;-tropomyosin (Tm). Mice expressing &agr;Tm in the heart were developed to determine the effects of FHC mutant Tm on cardiac structure and function from single cardiac myocytes to whole organ function in vivo. Expression of E180G mutant Tm did not produce cardiac hypertrophy or detectable changes in cardiac muscle morphology. However, E180G mutant Tm expression increased the Ca2+ sensitivity of force production in single cardiac myocytes in a transgene expression–dependent manner. Contractile dysfunction in single myocytes manifested organ level dysfunction, as conductance-micromanometry showed E180G Tm mice had significantly slowed relaxation (diastolic dysfunction) under physiological conditions. The diastolic dysfunction in E180G Tm mice was no longer evident during &bgr;-blockade because propranolol eliminated the effect of E180G Tm to slow myocardial relaxation. Cellular and organ level dysfunction were evident in E180G Tm mice in the absence of significant cardiac structural abnormalities normally associated with FHC. These findings therefore suggest that diastolic dysfunction in FHC may be a direct consequence of FHC mutant protein expression. In addition, because diastolic dysfunction in E180G Tm mice is dependent on inotropic status, cardiovascular stress may play an important role in FHC pathogenesis.","PeriodicalId":10314,"journal":{"name":"Circulation Research: Journal of the American Heart Association","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2002-08-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75732569","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 : 2002-08-09DOI: 10.1161/01.RES.0000028454.42385.8B
A. Kawakami, A. Tanaka, K. Nakajima, K. Shimokado, M. Yoshida
Abstract— Remnant lipoproteins have been reported to play a causative role in atherogenesis. We investigated the effect of remnant-like lipoprotein particles (RLPs) on monocyte-endothelial interaction and their potential regulation by atorvastatin. Monocytic U937 cells were incubated with RLPs isolated from hypertriglyceridemia subjects and their adhesion to human umbilical vein endothelial cells (HUVECs) was examined under flow conditions. Incubation of U937 cells with 15 &mgr;g protein/mL RLPs increased their adhesion to HUVECs activated with IL-1&bgr; (untreated: 6.8±1.6 cells/HPF versus RLPs: 16.2±3.3 cells/HPF, P <0.05). Flow cytometric analysis revealed that incubation with RLPs increased expression levels of CD11a, CD18, and CD49d in U937 cells. Moreover, RLP-induced RhoA activation as well as FAK activation was seen in U937 cells, and RLP-induced RhoA activation seemed to be involved with PKC-dependent signaling. To explore the effect of atorvastatin on RLP-induced U937 cell adhesion to HUVECs, U937 cells were incubated with RLPs in the presence of atorvastatin. Pretreatment of U937 cells with 10 &mgr;mol/L atorvastatin significantly decreased RLP-induced U937 cell adhesion to activated HUVECs (RLP 15.2±1.5 cells/HPF versus atorvastatin+RLP 10.2±1.0 cells/HPF;P <0.05) and decreased the enhanced integrin expression in RLP-treated U937 cells. Atorvastatin also inhibited RLP-induced RhoA activation and FAK activation in U937 cells. In summary, RLPs induced monocyte adhesion to vascular endothelium by sequential activation of PKC, RhoA, FAK, and integrins, indicating a role of remnant lipoproteins in vascular inflammation during atherogenesis. Atorvastatin attenuated this enhanced monocyte adhesion to HUVECs, suggesting an antiinflammatory role for this compound.
{"title":"Atorvastatin Attenuates Remnant Lipoprotein-Induced Monocyte Adhesion to Vascular Endothelium Under Flow Conditions","authors":"A. Kawakami, A. Tanaka, K. Nakajima, K. Shimokado, M. Yoshida","doi":"10.1161/01.RES.0000028454.42385.8B","DOIUrl":"https://doi.org/10.1161/01.RES.0000028454.42385.8B","url":null,"abstract":"Abstract— Remnant lipoproteins have been reported to play a causative role in atherogenesis. We investigated the effect of remnant-like lipoprotein particles (RLPs) on monocyte-endothelial interaction and their potential regulation by atorvastatin. Monocytic U937 cells were incubated with RLPs isolated from hypertriglyceridemia subjects and their adhesion to human umbilical vein endothelial cells (HUVECs) was examined under flow conditions. Incubation of U937 cells with 15 &mgr;g protein/mL RLPs increased their adhesion to HUVECs activated with IL-1&bgr; (untreated: 6.8±1.6 cells/HPF versus RLPs: 16.2±3.3 cells/HPF, P <0.05). Flow cytometric analysis revealed that incubation with RLPs increased expression levels of CD11a, CD18, and CD49d in U937 cells. Moreover, RLP-induced RhoA activation as well as FAK activation was seen in U937 cells, and RLP-induced RhoA activation seemed to be involved with PKC-dependent signaling. To explore the effect of atorvastatin on RLP-induced U937 cell adhesion to HUVECs, U937 cells were incubated with RLPs in the presence of atorvastatin. Pretreatment of U937 cells with 10 &mgr;mol/L atorvastatin significantly decreased RLP-induced U937 cell adhesion to activated HUVECs (RLP 15.2±1.5 cells/HPF versus atorvastatin+RLP 10.2±1.0 cells/HPF;P <0.05) and decreased the enhanced integrin expression in RLP-treated U937 cells. Atorvastatin also inhibited RLP-induced RhoA activation and FAK activation in U937 cells. In summary, RLPs induced monocyte adhesion to vascular endothelium by sequential activation of PKC, RhoA, FAK, and integrins, indicating a role of remnant lipoproteins in vascular inflammation during atherogenesis. Atorvastatin attenuated this enhanced monocyte adhesion to HUVECs, suggesting an antiinflammatory role for this compound.","PeriodicalId":10314,"journal":{"name":"Circulation Research: Journal of the American Heart Association","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2002-08-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76911457","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 : 2002-08-09DOI: 10.1161/01.RES.0000028455.36940.5E
D. Jiang, Bailong Xiao, Lin Zhang, S. Chen
Abstract— Mutations in the human cardiac Ca2+ release channel (ryanodine receptor, RyR2) gene have recently been shown to cause effort-induced ventricular arrhythmias. However, the consequences of these disease-causing mutations in RyR2 channel function are unknown. In the present study, we characterized the properties of mutation R4496C of mouse RyR2, which is equivalent to a disease-causing human RyR2 mutation R4497C, by heterologous expression of the mutant in HEK293 cells. [3H]ryanodine binding studies revealed that the R4496C mutation resulted in an increase in RyR2 channel activity in particular at low Ca2+ concentrations. This increased basal channel activity remained sensitive to modulation by caffeine, ATP, Mg2+, and ruthenium red. In addition, the R4496C mutation enhanced the sensitivity of RyR2 to activation by Ca2+ and by caffeine. Single-channel analysis showed that single R4496C mutant channels exhibited considerable channel openings at low Ca2+ concentrations. HEK293 cells transfected with mutant R4496C displayed spontaneous Ca2+ oscillations more frequently than cells transfected with wild-type RyR2. Substitution of a negatively charged glutamate for the positively charged R4496 (R4496E) further enhanced the basal channel activity, whereas replacement of R4496 by a positively charged lysine (R4496K) had no significant effect on the basal activity. These observations indicate that the charge and polarity at residue 4496 plays an essential role in RyR2 channel gating. Enhanced basal activity of RyR2 may underlie an arrhythmogenic mechanism for effort-induced ventricular tachycardia.
{"title":"Enhanced Basal Activity of a Cardiac Ca2+ Release Channel (Ryanodine Receptor) Mutant Associated With Ventricular Tachycardia and Sudden Death","authors":"D. Jiang, Bailong Xiao, Lin Zhang, S. Chen","doi":"10.1161/01.RES.0000028455.36940.5E","DOIUrl":"https://doi.org/10.1161/01.RES.0000028455.36940.5E","url":null,"abstract":"Abstract— Mutations in the human cardiac Ca2+ release channel (ryanodine receptor, RyR2) gene have recently been shown to cause effort-induced ventricular arrhythmias. However, the consequences of these disease-causing mutations in RyR2 channel function are unknown. In the present study, we characterized the properties of mutation R4496C of mouse RyR2, which is equivalent to a disease-causing human RyR2 mutation R4497C, by heterologous expression of the mutant in HEK293 cells. [3H]ryanodine binding studies revealed that the R4496C mutation resulted in an increase in RyR2 channel activity in particular at low Ca2+ concentrations. This increased basal channel activity remained sensitive to modulation by caffeine, ATP, Mg2+, and ruthenium red. In addition, the R4496C mutation enhanced the sensitivity of RyR2 to activation by Ca2+ and by caffeine. Single-channel analysis showed that single R4496C mutant channels exhibited considerable channel openings at low Ca2+ concentrations. HEK293 cells transfected with mutant R4496C displayed spontaneous Ca2+ oscillations more frequently than cells transfected with wild-type RyR2. Substitution of a negatively charged glutamate for the positively charged R4496 (R4496E) further enhanced the basal channel activity, whereas replacement of R4496 by a positively charged lysine (R4496K) had no significant effect on the basal activity. These observations indicate that the charge and polarity at residue 4496 plays an essential role in RyR2 channel gating. Enhanced basal activity of RyR2 may underlie an arrhythmogenic mechanism for effort-induced ventricular tachycardia.","PeriodicalId":10314,"journal":{"name":"Circulation Research: Journal of the American Heart Association","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2002-08-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81652947","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 : 2002-08-09DOI: 10.1161/01.RES.0000029080.15742.85
D. Bishop-Bailey, T. Hla, T. Warner
Abstract— Activation of the nuclear receptor/transcription factor, peroxisome proliferator-activated receptor &ggr; (PPAR&ggr;), is a newly defined target for limiting vascular pathologies. PPAR&ggr; is expressed in human and animal models of vascular disease, with particularly high levels being present in the cells of the neointimal microenvironment. In the present study, we show that intimal smooth muscle cells in vitro contain higher amounts of functional PPAR&ggr; than medial smooth muscle cells. The PPAR&ggr; ligand rosiglitazone more potently induced CD36 expression at low concentrations, and cell death by apoptosis at higher concentrations in intimal compared with medial smooth muscle cells. Intimal smooth muscle cells also contained high levels of cyclooxygenase-2 protein, and released a more diverse and larger amount of eicosanoids on arachidonic acid stimulation. Furthermore, when exogenous arachidonic acid was added, PPAR reporter gene activation was induced in a cyclooxygenase inhibitor–sensitive manner, an effect that correlated with an increase in CD36 expression. In summary, intimal smooth muscle cells contain functionally higher levels of PPAR&ggr;, PPAR&ggr; ligands have high- and low-potency targets in vascular smooth muscle cells, and cyclooxygenase can serve as a source of potential endogenous PPAR ligands. Intimal vascular smooth muscle cells therefore represent a potentially important target for the antiproliferative, and antiatherosclerotic actions of PPAR&ggr; ligands.
{"title":"Intimal Smooth Muscle Cells as a Target for Peroxisome Proliferator-Activated Receptor-&ggr; Ligand Therapy","authors":"D. Bishop-Bailey, T. Hla, T. Warner","doi":"10.1161/01.RES.0000029080.15742.85","DOIUrl":"https://doi.org/10.1161/01.RES.0000029080.15742.85","url":null,"abstract":"Abstract— Activation of the nuclear receptor/transcription factor, peroxisome proliferator-activated receptor &ggr; (PPAR&ggr;), is a newly defined target for limiting vascular pathologies. PPAR&ggr; is expressed in human and animal models of vascular disease, with particularly high levels being present in the cells of the neointimal microenvironment. In the present study, we show that intimal smooth muscle cells in vitro contain higher amounts of functional PPAR&ggr; than medial smooth muscle cells. The PPAR&ggr; ligand rosiglitazone more potently induced CD36 expression at low concentrations, and cell death by apoptosis at higher concentrations in intimal compared with medial smooth muscle cells. Intimal smooth muscle cells also contained high levels of cyclooxygenase-2 protein, and released a more diverse and larger amount of eicosanoids on arachidonic acid stimulation. Furthermore, when exogenous arachidonic acid was added, PPAR reporter gene activation was induced in a cyclooxygenase inhibitor–sensitive manner, an effect that correlated with an increase in CD36 expression. In summary, intimal smooth muscle cells contain functionally higher levels of PPAR&ggr;, PPAR&ggr; ligands have high- and low-potency targets in vascular smooth muscle cells, and cyclooxygenase can serve as a source of potential endogenous PPAR ligands. Intimal vascular smooth muscle cells therefore represent a potentially important target for the antiproliferative, and antiatherosclerotic actions of PPAR&ggr; ligands.","PeriodicalId":10314,"journal":{"name":"Circulation Research: Journal of the American Heart Association","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2002-08-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90251537","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 : 2002-08-09DOI: 10.1161/01.RES.0000027865.61704.32
K. Boheler, J. Czyż, D. Tweedie, Huang-Tian Yang, S. Anisimov, A. Wobus
Abstract— Embryonic stem (ES) cells have been established as permanent lines of undifferentiated pluripotent cells from early mouse embryos. ES cells provide a unique system for the genetic manipulation and the creation of knockout strains of mice through gene targeting. By cultivation in vitro as 3D aggregates called embryoid bodies, ES cells can differentiate into derivatives of all 3 primary germ layers, including cardiomyocytes. Protocols for the in vitro differentiation of ES cells into cardiomyocytes representing all specialized cell types of the heart, such as atrial-like, ventricular-like, sinus nodal–like, and Purkinje-like cells, have been established. During differentiation, cardiac-specific genes as well as proteins, receptors, and ion channels are expressed in a developmental continuum, which closely recapitulates the developmental pattern of early cardiogenesis. Exploitation of ES cell–derived cardiomyocytes has facilitated the analysis of early cardiac development and has permitted in vitro “gain-of-function” or “loss-of-function” genetic studies. Recently, human ES cell lines have been established that can be used to investigate cardiac development and the function of human heart cells and to determine the basic strategies of regenerative cell therapy. This review summarizes the current state of ES cell–derived cardiogenesis and provides an overview of how genomic strategies coupled with this in vitro differentiation system can be applied to cardiac research.
{"title":"Differentiation of Pluripotent Embryonic Stem Cells Into Cardiomyocytes","authors":"K. Boheler, J. Czyż, D. Tweedie, Huang-Tian Yang, S. Anisimov, A. Wobus","doi":"10.1161/01.RES.0000027865.61704.32","DOIUrl":"https://doi.org/10.1161/01.RES.0000027865.61704.32","url":null,"abstract":"Abstract— Embryonic stem (ES) cells have been established as permanent lines of undifferentiated pluripotent cells from early mouse embryos. ES cells provide a unique system for the genetic manipulation and the creation of knockout strains of mice through gene targeting. By cultivation in vitro as 3D aggregates called embryoid bodies, ES cells can differentiate into derivatives of all 3 primary germ layers, including cardiomyocytes. Protocols for the in vitro differentiation of ES cells into cardiomyocytes representing all specialized cell types of the heart, such as atrial-like, ventricular-like, sinus nodal–like, and Purkinje-like cells, have been established. During differentiation, cardiac-specific genes as well as proteins, receptors, and ion channels are expressed in a developmental continuum, which closely recapitulates the developmental pattern of early cardiogenesis. Exploitation of ES cell–derived cardiomyocytes has facilitated the analysis of early cardiac development and has permitted in vitro “gain-of-function” or “loss-of-function” genetic studies. Recently, human ES cell lines have been established that can be used to investigate cardiac development and the function of human heart cells and to determine the basic strategies of regenerative cell therapy. This review summarizes the current state of ES cell–derived cardiogenesis and provides an overview of how genomic strategies coupled with this in vitro differentiation system can be applied to cardiac research.","PeriodicalId":10314,"journal":{"name":"Circulation Research: Journal of the American Heart Association","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2002-08-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83314289","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 : 2002-08-09DOI: 10.1161/01.RES.0000029085.69891.F2
H. Patel, A. Hsu, J. Peart, G. Gross
Recently, the involvement of sarcolemmal KATP (sarcKATP) channels in ischemic and pharmacological preconditioning (IPC and PPC) has been minimized by numerous studies suggesting a primary role for mitochondrial KATP (mitoKATP) channels in early and delayed cardioprotection. Although the mitoKATP channel has clearly been shown to be a distal effector of delayed IPC and PPC, studies implicating it as a trigger of protection in delayed IPC are lacking. Accordingly, we characterized the role of cardiac KATP channels as triggers or distal effectors of delayed cardioprotection induced by opioids in rats, and the data suggest that the sarcKATP channel triggers and that the mitoKATP channel is a distal effector of opioid-induced delayed cardioprotection.
{"title":"Sarcolemmal KATP Channel Triggers Opioid-Induced Delayed Cardioprotection in the Rat","authors":"H. Patel, A. Hsu, J. Peart, G. Gross","doi":"10.1161/01.RES.0000029085.69891.F2","DOIUrl":"https://doi.org/10.1161/01.RES.0000029085.69891.F2","url":null,"abstract":"Recently, the involvement of sarcolemmal KATP (sarcKATP) channels in ischemic and pharmacological preconditioning (IPC and PPC) has been minimized by numerous studies suggesting a primary role for mitochondrial KATP (mitoKATP) channels in early and delayed cardioprotection. Although the mitoKATP channel has clearly been shown to be a distal effector of delayed IPC and PPC, studies implicating it as a trigger of protection in delayed IPC are lacking. Accordingly, we characterized the role of cardiac KATP channels as triggers or distal effectors of delayed cardioprotection induced by opioids in rats, and the data suggest that the sarcKATP channel triggers and that the mitoKATP channel is a distal effector of opioid-induced delayed cardioprotection.","PeriodicalId":10314,"journal":{"name":"Circulation Research: Journal of the American Heart Association","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2002-08-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80740986","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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