Sarcoplasmic reticulum-related changes in cytosolic calcium in pressure-overload-induced feline LV hypertrophy

1993 ◽  
Vol 265 (6) ◽  
pp. H2009-H2016 ◽  
Author(s):  
B. A. Bailey ◽  
S. R. Houser

Alterations in Ca2+ homeostasis that involve the sarcoplasmic reticulum (SR) were studied in feline left ventricular (LV) myocytes isolated from hearts with LV hypertrophy induced by slow, progressive pressure overload. At death, severe hypertrophy was evidenced by increased heart weight-to-body weight ratio (8.4 +/- 0.6 vs. 4.2 +/- 0.2 g/kg in controls). Steady-state Ca2+ transients (measured as. indo 1 fluorescence at 410 nm/480 nm; I410/I480) in LV hypertrophy (LVH) myocytes had diminished peak amplitudes (I410/I480 2.28 +/- 0.07 vs. 2.53 +/- 0.07 in controls) and prolonged durations (0.75 +/- 0.03 vs. 0.59 +/- 0.02 s in controls). The magnitude of shortening was reduced and the contractile duration was prolonged in LVH myocytes. The idea that changes in SR function are responsible for these alterations in the Ca2+ transient was tested by studying two aspects of SR-related Ca2+ homeostasis. Restitution of releasable SR Ca2+ was studied by measuring indo 1 transients and contractions during premature beats. The time course of restitution of both the indo 1 transient and contraction of hypertrophy myocytes was significantly slower than in controls. These data suggest that restitution of releasable SR Ca2+ is slowed in hypertrophy myocytes. The reduction of the indo 1 transient and contraction in beats following long rest periods (rest decay) was measured to determine the rate of Ca2+ loss from the SR. Rest decay was significantly (P < 0.05) more pronounced in hypertrophy myocytes, suggesting that Ca2+ loss from the SR is accelerated in these myocytes. (ABSTRACT TRUNCATED AT 250 WORDS)

1989 ◽  
Vol 256 (4) ◽  
pp. H1006-H1011 ◽  
Author(s):  
S. Kimura ◽  
A. L. Bassett ◽  
K. Saida ◽  
M. Shimizu ◽  
R. J. Myerburg

This study was designed to examine the Ca2+ sensitivity of the contractile system and the ability of the sarcoplasmic reticulum (SR) to accumulate and release Ca2+ in chemically (saponin) skinned cardiac fibers obtained from normal and pressure-overloaded hypertrophied rat left ventricles. Left ventricular pressure overload was induced by partial ligation of the abdominal aorta 6-8 wk before study. Age- and weight-matched normal rats served as controls. Pressure over-load increased the left ventricular weight-to-body weight ratio by 51%. There were no differences in the Ca2+-tension relationship between normal and hypertrophied preparations at Ca2+ concentrations of 10(-7) to 10(-4) M. Caffeine-induced Ca2+ release from the maximally Ca2+ -loaded SR was also not different between the two groups at caffeine concentrations of 0.5-30 mM. However, when the relative amount of Ca2+ accumulated in the SR with 10(-6), 3 x 10(-6), or 10(-5) M Ca2+ loading solutions for various loading periods was estimated by the area under the 25 mM caffeine-induced contraction, the accumulation of Ca2+ was significantly slower in hypertrophied fibers than in normal fibers. We conclude that depressed Ca2+ accumulation by the SR plays a role in modulation of contractile performance in this model of chronic pressure overload in rats.


1997 ◽  
Vol 272 (5) ◽  
pp. H2425-H2435 ◽  
Author(s):  
L. M. Delbridge ◽  
H. Satoh ◽  
W. Yuan ◽  
J. W. Bassani ◽  
M. Qi ◽  
...  

Alterations in cellular Ca2+ transport and excitation-contraction coupling may contribute to dysfunction in cardiac hypertrophy. Left ventricular myocytes were isolated from rat hearts after 15-18 wk of suprarenal abdominal aortic banding to evaluate the hypothesis that hypertrophy alters the relationship between Ca2+ current (ICa) and sarcoplasmic reticulum (SR) Ca2+ load during steady-state voltage-clamp depolarization. Mean arterial pressure (MAP) and heart weight-to-body weight ratio of banded (B) animals were significantly higher than in control or sham-operated animals (C). Isolated myocyte dimensions and volume increased in parallel with whole heart hypertrophy and elevation in MAP. However, the relationship between membrane surface area (measured by capacitance) and cell volume (measured by laser scanning confocal microscopy) was unaltered (C: 8.9 +/- 0.3; B: 8.5 +/- 0.4 pF/pl). No differences in the voltage dependence of ICa activation, steady-state inactivation, or recovery from inactivation were detected between C and B myocytes. Maximal ICa density for the two groups was also not different either under basal conditions (C: 4.28 +/- 0.98; B: 4.57 +/- 0.60 pA/pF) or in the presence of 1 microM isoproterenol (C: 16.6 +/- 2.3; B: 16.5 +/- 2.3 pA/pF). The fraction of Ca2+ released from the SR by a single twitch was 55.4 +/- 9.4% in C and 37.1 +/- 6.9% in B (not significantly different). Steady-state Ca2+ influx during a twitch was calculated in units of micromoles per liter of nonmitochondrial volume from the integral of ICa (C: 13.4 +/- 0.7 microM; B: 13.3 +/- 0.8 microM). The SR Ca2+ load was similarly calculated by integration of Na+/Ca2+ exchange current induced by rapid caffeine application (C: 140 +/- 9 microM; B: 169 +/- 18 microM). We conclude that significant cellular hypertrophy is associated with proportional increases in sarcolemmal ICa influx, SR Ca2+ loading, and the amount of SR Ca2+ released in this model of pressure overload.


1986 ◽  
Vol 60 (5) ◽  
pp. 1673-1679 ◽  
Author(s):  
S. N. Levine ◽  
G. T. Kinasewitz

To investigate potential mechanisms underlying the enhanced myocardial performance consequent to exercise training, the adrenergic receptors of myocardial tissue and Ca2+ uptake into sarcoplasmic reticulum-enriched fractions from exercise conditioned animals were compared with that of sedentary controls. Female Wistar rats were exercised by swimming 30 min (5 days/wk) for 12 wk. Exercise conditioning was effective in producing myocardial hypertrophy, as reflected by an increase in heart weight (1.179 +/- 0.022 vs. 1.031 +/- 0.020 g, P less than 0.001) and heart weight-to-body weight ratio (3.29 +/- 0.06 vs. 2.77 +/- 0.05 X 10(-3), P less than 0.001) but no difference in body weight. Despite the myocardial hypertrophy, neither the affinity nor the density of the alpha 1-adrenergic receptors or the beta-adrenergic receptors determined by Scatchard analysis of the ligands [3H]prazosin and [3H]dihydroalprenolol were significantly different between the two groups. The basal Ca2+ uptake into the sarcoplasmic reticulum was also similar (9.90 +/- 0.97 vs. 9.04 +/- 0.75 nmol/mg protein/min), but the addition of calmodulin produced a significantly greater increment in Ca2+ uptake into sarcoplasmic reticulum from the exercised-conditioned animals (1.90 +/- 0.23 vs. 1.21 +/- 0.19 nmol/mg protein/min, P less than 0.03). The adenosine triphosphatase (ATPase) activities of the sarcoplasmic reticulum-enriched fractions of the two groups were similar. We conclude that exercise conditioning produces an enhancement of calmodulin-mediated calcium uptake that is independent of any effect on Ca2+-ATPase.


2010 ◽  
Vol 299 (5) ◽  
pp. H1348-H1356 ◽  
Author(s):  
Craig A. Emter ◽  
Christopher P. Baines

Cardiac hypertrophy in response to hypertension or myocardial infarction is a pathological indicator associated with heart failure (HF). A central component of the remodeling process is the loss of cardiomyocytes via cell death pathways regulated by the mitochondrion. Recent evidence has indicated that exercise training can attenuate or reverse pathological remodeling, creating a physiological phenotype. The purpose of this study was to examine left ventricular (LV) function, remodeling, and cardiomyocyte mitochondrial function in aortic-banded (AB) sedentary (HFSED; n = 6), AB exercise-trained (HFTR, n = 5), and control sedentary ( n = 5) male Yucatan miniature swine. LV hypertrophy was present in both AB groups before the start of training, as indicated by increases in LV end-diastolic volume, LV end-systolic volume (LVESV), and LV end-systolic dimension (LVESD). Exercise training (15 wk) prevented further increases in LVESV and LVESD ( P < 0.05). The heart weight-to-body weight ratio, LV + septum-to-body weight ratio, LV + septum-to-right ventricle ratio, and cardiomyocyte cross-sectional area were increased in both AB groups postmortem regardless of training status. Preservation of LV function after exercise training, as indicated by the maintenance of fractional shortening, ejection fraction, and mean wall shortening and increased stroke volume, was associated with an attenuation of the increased LV fibrosis (23%) and collagen (36%) observed in HFSED animals. LV mitochondrial dysfunction, as measured by Ca2+-induced mitochondrial permeability transition, was increased in HFSED ( P < 0.05) but not HFTR animals. In conclusion, low-intensity interval exercise training preserved LV function as exemplified by an attenuation of fibrosis, maintenance of a positive inotropic state, and inhibition of mitochondrial dysfunction, providing further evidence of the therapeutic potential of exercise in a clinical setting.


1994 ◽  
Vol 266 (2) ◽  
pp. H749-H756
Author(s):  
F. Tomita ◽  
A. L. Bassett ◽  
R. J. Myerburg ◽  
S. Kimura

Sarcoplasmic reticulum (SR) Ca2+ uptake is reduced in the hypertrophied ventricle. To determine whether events initiated by beta-adrenergic stimulation are involved, we compared the effects of adenosine 3',5'-cyclic monophosphate (cAMP) on SR Ca2+ uptake between normal and pressure-overloaded hypertrophied hearts using saponin-skinned rat left ventricular muscles. Left ventricular pressure overload was induced by partial ligation of the abdominal aorta for 4–6 wk before study. Age-matched normal rats served as controls. Pressure overload increased the left ventricular weight-to-body weight ratio 60.8%. The SR was loaded by exposing the muscles to 10(-6) M Ca2+ solution; SR Ca2+ release was induced by 5 or 25 mM caffeine, and the amount of Ca2+ released from the SR was estimated by the area under the caffeine-induced transient contraction. Concomitant exposure to 10(-4) M cAMP did not influence caffeine-induced Ca2+ release in either normal or hypertrophied fibers. When 10(-4) M cAMP was applied during the Ca(2+)-loading periods, the amount of Ca2+ accumulated by the SR increased in both normal and hypertrophied fibers. However, the extent of increase was significantly smaller in hypertrophied fibers than in normal fibers [10.9 +/- 1.7 and 27.4 +/- 5.3% in 1 min of Ca2+ loading (P < 0.05), 12.2 +/- 3.2 and 24.7 +/- 3.8% in 4 min of Ca2+ loading (P < 0.05), respectively]. cAMP (10(-4) M) shifted the force-pCa relationship to the right similarly in normal and hypertrophied muscles, and there was no difference in the force-pCa relationship between the two groups either with or without cAMP.(ABSTRACT TRUNCATED AT 250 WORDS)


2019 ◽  
Vol 22 (6) ◽  
pp. E432-E437
Author(s):  
Zhixiang Xie ◽  
Shuyin Wang ◽  
Zijing Liang ◽  
Liangbo Zeng ◽  
Rongde Lai ◽  
...  

Objective: The aim of this study was to observe the impacts of the specific cyclooxygenase-2 inhibitor celecoxib on cardiac structures, functions, and inflammatory factors during the process of pressure overload–induced myocardial hypertrophy. Methods: Twenty-four male Sprague Dawley rats were randomly divided into 3 groups: the sham operation group, the surgery group, and the celecoxib group. The model was established according to the abdominal aortic coarctation method. Results: At 16 weeks, rats in the celecoxib group were fed a celecoxib-mixed diet (10 mg/kg) for 8 consecutive weeks. At week 24 after model establishment, the cardiac structures and functions were observed; changes in the levels of tumor necrosis factor (TNF)-α, transforming growth factor (TGF)-β, prostaglandin E2 (PGE2), C-reactive protein (CRP), and uric acid (UA) were detected; and the contents of Smad1/2/3 proteins (Smad1, Smad2, and Smad3)  were determined. Left ventricular mass index, the heart weight/body weight ratio, and TNF-α, TGF-β, PGE2, CRP, and UA levels of the celecoxib group were all significantly decreased relative to those of the surgery group (P < .05); moreover, the cardiac functions were significantly improved compared to those of the surgery group (P < .05). Conclusions: These results show that inflammatory factors are involved in the myocardial hypertrophy process and that celecoxib may reverse myocardial hypertrophy through a variety of pathways.


1991 ◽  
Vol 260 (5) ◽  
pp. H1612-H1618 ◽  
Author(s):  
N. Furukawa ◽  
A. L. Bassett ◽  
T. Furukawa ◽  
R. J. Myerburg ◽  
S. Kimura

The effects of D-myo-inositol 1,4,5-trisphosphate [Ins(1,4,5)P3] on the ability of the sarcoplasmic reticulum (SR) to accumulate and release Ca2+ and on the Ca2+ sensitivity of the contractile proteins were investigated using chemically (saponin) skinned cardiac fibers (60–120 microns diam) obtained from normal and pressure-overloaded hypertrophied rat left ventricles. Left ventricular pressure overload was induced by partial ligation of the abdominal aorta 3-6 wk before study. Age- and weight-matched normal rats served as controls. Pressure overload increased the left ventricular weight-to-body weight ratio by 45%. Ins(1,4,5)P3 at a concentration of 10 microM did not change the Ca(2+)-tension relationship at Ca2+ concentrations of 10(-7) to 10(-5) M in either normal or hypertrophied fibers. Ins(1,4,5)P3 also did not influence Ca2+ uptake by the SR in either normal or hypertrophied fibers. Ins(1,4,5)P3 did not induce Ca2+ release from the SR directly in either group. However, pretreatment with Ins(1,4,5)P3 enhanced the 5 mM caffeine-induced Ca2+ release by 80.5 +/- 22.7% in normal fibers enhances, rather than directly induces, SR Ca2+ release in normal rat hearts and that sustained pressure overload diminishes the response of the SR Ca(2+)-release system to Ins(1,4,5)P3, an action that may be partly responsible for contractile dysfunction in cardiac hypertrophy.


2010 ◽  
Vol 299 (3) ◽  
pp. H707-H712 ◽  
Author(s):  
Aziz Guellich ◽  
Shumin Gao ◽  
Chull Hong ◽  
Lin Yan ◽  
Thomas E. Wagner ◽  
...  

Adenylyl cyclase (AC) type 5 (AC5) and AC type 6 (AC6) are the two major AC isoforms in the heart. Cardiac overexpression of AC6 has been shown to be protective in response to several interventions. In this investigation, we examined the effects of chronic pressure overload in AC6 transgenic (TG) mice. In the absence of any stress, AC6 TG mice exhibited enhanced contractile function compared with their wild-type (WT) littermates, i.e., increased ( P < 0.05) left ventricular (LV) ejection fraction (EF) (75 ± 0.9 vs. 71 ± 0.5%) and LV dP/d t (7,850 ± 526 vs. 6,374 ± 315 mmHg/s). Forskolin (25 μg·kg−1·min−1 for 5 min) increased LVEF more ( P < 0.05) in AC6 TG mice (14.8 ± 1.0%) than in WT mice (7.7 ± 1.0%). Also, isoproterenol (0.04 μg·kg−1·min−1 for 5 min) increased LVEF more ( P < 0.05) in AC6 TG mice (18.0 ± 1.2%) than in WT mice (11.6 ± 2.1%). Pressure overload, induced by 4 wk of transverse aortic constriction (TAC), increased the LV weight-to-body weight ratio and myocyte cross-sectional area similarly in both groups, but reduced LVEF more in AC6 TG mice (22%) compared with WT mice (9%), despite the higher starting level of LVEF in AC6 TG mice. LV systolic wall stress increased more in AC6 TG mice than in WT mice, which could be responsible for the reduced LVEF in AC6 TG mice with chronic pressure overload. In addition, LV dP/d t was no longer elevated in AC6 TG mice after TAC compared with WT mice. LV end-diastolic diameter was also greater ( P < 0.05) in AC6 TG mice (3.8 ± 0.07 mm) than in WT mice (3.6 ± 0.05 mm) after TAC. Thus, in contrast to other interventions previously reported to be salutary with cardiac AC6 overpression, the response to chronic pressure overload was not; actually, AC6 TG mice fared worse than WT mice. The mechanism may be due to the increased LV systolic wall stress in AC6 TG mice with chronic pressure overload.


Circulation ◽  
2008 ◽  
Vol 118 (suppl_18) ◽  
Author(s):  
Hui Zhao ◽  
Yulin Liao ◽  
Tetsuo Minamino ◽  
Yoshihiro Asano ◽  
Masanori Asakura ◽  
...  

Background We previously reported that prolonged endoplasmic reticulum (ER) stress contributes to progression from cardiac hypertrophy to heart failure. Statins have an inhibitory effect on cholesterol synthesis, oxidative stresses, protein synthesis and production of inflammatory cytokines, all of which could be associated with ER stress. However, it is unknown whether statins can ameliorate ER stress in heart disease. This study was designed to investigate whether pravastatin could inhibit cardiac remodeling and ameliorate ER stress caused by pressure overload or tumor necrosis factor α (TNF α ). Methods and Results Cardiac hypertrophy was induced by transverse aortic constriction (TAC) for four weeks in C57BL/6 male mice. Either pravastatin (5 mg/kg/d, n=20, TAC+prava group) or its vehicle (n=20) was orally administered to mice. The ER stress signaling pathway was also studied in pressure-overloaded mice hearts and in cultured cardiomyocytes treated with TNF α (10ng/ml) for 24 hours. Four weeks after TAC, both heart-to-body weight ratio (8.68 ± 1.23 in TAC group, 6.92 ± 1.11 in TAC+prava group) and lung-to-body weight ratio (11.08 ± 2.58 in TAC group, 7.92± 3.56 in TAC+prava group) became significantly lower in pravastatin-treated mice than in the TAC group. Left ventricular fractional shortening and left ventricular ejection fraction (LVFS and LVEF) were larger in TAC+prava group (48.0±1.9 % and 80±1.9% respectively) compared with TAC group (LVFS and LVEF, 34.8 ±1.4% and 65 ±3%; P<0.01 VS TAC group each). Markers of ER stress such as an increase in ER chaperones and CHOP expressions and enhanced phosphorylation of eIF2 α were observed in the hearts of TAC mice, while pravastatin treatment significantly blunted these changes. Pravastatin-treated TAC mice also showed a decrease of cardiac apoptosis. Cardiac expression of TNF α was increased in TAC mice, and TNF α induced ER stress in cultured neonatal rat cardiomyocytes, either of which was significantly inhibited by pravastatin. Conclusions These findings indicate that pravastatin inhibits cardiac remodeling in mice subjected to pressure overload, and this action is associated with inhibition of the ER stress signaling pathway.


2019 ◽  
Vol 116 (1) ◽  
pp. 101-113 ◽  
Author(s):  
Hairuo Lin ◽  
Yang Li ◽  
Hailin Zhu ◽  
Qiancheng Wang ◽  
Zhenhuan Chen ◽  
...  

Abstract Aims Proton pump inhibitors (PPIs) are widely used in patients receiving percutaneous coronary intervention to prevent gastric bleeding, but whether PPIs are beneficial for the heart is controversial. Here, we investigated the effects of lansoprazole on cardiac hypertrophy and heart failure, as well as the underlying mechanisms. Methods and results Adult male C57 mice were subjected to transverse aortic constriction (TAC) or sham surgery and then were treated with lansoprazole or vehicle for 5 weeks. In addition, cultured neonatal rat ventricular cardiomyocytes and fibroblasts were exposed to angiotensin II in the presence or absence of lansoprazole. At 5 weeks after TAC, the heart weight/body weight ratio was lower in lansoprazole-treated mice than in untreated mice, as was the lung weight/body weight ratio, while left ventricular (LV) fractional shortening and the maximum and minimum rates of change of the LV pressure were higher in lansoprazole-treated mice, along with less cardiac fibrosis. In cultured cardiomyocytes, lansoprazole inhibited angiotensin II-induced protein synthesis and hypertrophy, as well as inhibiting proliferation of fibroblasts. Lansoprazole decreased myocardial levels of phosphorylated Akt, phosphorylated glycogen synthase kinase 3β, and active β-catenin in TAC mice and in angiotensin II-stimulated cardiomyocytes. After overexpression of active β-catenin or knockdown of H+/K+-ATPase α-subunit, lansoprazole still significantly attenuated myocyte hypertrophy. Conclusion Lansoprazole inhibits cardiac remodelling by suppressing activation of the Akt/GSK3β/β-catenin pathway independent of H+/K+-ATPase inhibition, and these findings may provide a novel insight into the pharmacological effects of PPIs with regard to alleviation of cardiac remodelling.


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