Zerumbone prevents pressure overload-induced left ventricular systolic dysfunction by inhibiting cardiac hypertrophy and fibrosis

BackgroundCardiac hypertrophy and fibrosis are hallmarks of cardiac remodeling and are involved functionally in the development of heart failure (HF). However, it is unknown whether Zerumbone (Zer) prevents left ventricular (LV) systolic dysfunction by inhibiting cardiac hypertrophy and fibrosis.PurposeThis study investigated the effect of Zer on cardiac hypertrophy and fibrosis in vitro and in vivo.Study Design/methodsIn primary cultured cardiac cells from neonatal rats, the effect of Zer on phenylephrine (PE)-induced hypertrophic responses and transforming growth factor beta (TGF-β)-induced fibrotic responses was observed. To determine whether Zer prevents the development of pressure overload-induced HF in vivo, a transverse aortic constriction (TAC) mouse model was utilized. Cardiac function was evaluated by echocardiography. The changes of cardiomyocyte surface area were observed using immunofluorescence staining and histological analysis (HE and WGA staining). Collagen synthesis and fibrosis formation were measured by scintillation counter and picrosirius staining, respectively. The total mRNA levels of genes associated with hypertrophy (ANF and BNP) and fibrosis (Postn and α-SMA) were measured by qRT-PCR. The protein expressions (Akt and α-SMA) were assessed by western blotting.ResultsZer significantly suppressed PE-induced increase in cell size, mRNA levels of ANF and BNP, and Akt phosphorylation in cardiomyocytes. The TGF-β-induced increase in proline incorporation, mRNA levels of Postn and α-SMA, and protein expression of α-SMA were decreased by Zer in cultured cardiac fibroblasts. In the TAC male C57BL/6 mice, echocardiography results demonstrated that Zer improved cardiac function by increasing LV fractional shortening and reducing LV wall thickness compared with the vehicle group. ZER significantly reduced the level of phosphorylated Akt both in cultured cardiomyocytes treated with PE and in the hearts of TAC. Finally, Zer inhibited the pressure overload-induced cardiac hypertrophy and cardiac fibrosis.ConclusionZer ameliorates pressure overload-induced LV dysfunction, at least in part by suppressing both cardiac hypertrophy and fibrosis.     

Association of interarm systolic blood pressure difference with atherosclerosis and left ventricular hypertrophy

An interarm systolic blood pressure (SBP) difference of 10 mmHg or more have been associated with peripheral artery disease and adverse cardiovascular outcomes. We investigated whether an association exists between this difference and ankle-brachial index (ABI), brachial-ankle pulse wave velocity (baPWV), and echocardiographic parameters. A total of 1120 patients were included in the study. The bilateral arm blood pressures were measured simultaneously by an ABI-form device. The values of ABI and baPWV were also obtained from the same device. Clinical data, ABI<0.9, baPWV, echocariographic parameters, and an interarm SBP difference ≥10 mmHg were compared and analyzed. We performed two multivariate forward analyses for determining the factors associated with an interarm SBP difference ≥10 mmHg [model 1: significant variables in univariate analysis except left ventricular mass index (LVMI); model 2: significant variables in univariate analysis except ABI<0.9 and baPWV]. The ABI<0.9 and high baPWV in model 1 and high LVMI in model 2 were independently associated with an interarm SBP difference ≥10 mmHg. Female, hypertension, and high body mass index were also associated with an interarm SBP difference ≥10 mmHg. Our study demonstrated that ABI<0.9, high baPWV, and high LVMI were independently associated with an interarm SBP difference of 10 mmHg or more. Detection of an interarm SBP difference may provide a simple method of detecting patients at increased risk of atherosclerosis and left ventricular hypertrophy.     

Relation between left ventricular cavity pressure and volume and systolic fiber stress and strain in the wall.

Pumping power as delivered by the heart is generated by the cells in the myocardial wall. In the present model study global left-ventricular pump function as expressed in terms of cavity pressure and volume is related to local wall tissue function as expressed in terms of myocardial fiber stress and strain. On the basis of earlier studies in our laboratory, it may be concluded that in the normal left ventricle muscle fiber stress and strain are homogeneously distributed. So, fiber stress and strain may be approximated by single values, being valid for the whole wall. When assuming rotational symmetry and homogeneity of mechanical load in the wall, the dimensionless ratio of muscle fiber stress (sigma f) to left-ventricular pressure (Plv) appears to depend mainly on the dimensionless ratio of cavity volume (Vlv) to wall volume (Vw) and is quite independent of other geometric parameters. A good (+/- 10%) and simple approximation of this relation is sigma f/Plv = 1 + 3 Vlv/Vw. Natural fiber strain is defined by ef = In (lf/lf,ref), where lf,ref indicates fiber length (lf) in a reference situation. Using the principle of conservation of energy for a change in ef, it holds delta ef = (1/3)delta In (1 + 3Vlv/Vw).     

Overexpression of ornithine decarboxylase decreases ventricular systolic function during induction of cardiac hypertrophy

Ornithine decarboxylase (ODC), the first enzyme of polyamine metabolism, is rapidly upregulated in response to agents that induce a pathological cardiac hypertrophy. Transgenic mice overexpressing ODC in the heart (MHC-ODC mice) experience a much more dramatic left ventricular hypertrophy in response to β-adrenergic stimulation with isoproterenol (ISO) compared to wild-type (WT) controls. ISO also induced arginase activity in transgenic hearts but not in controls. The current work studies the cooperation between the cardiac polyamines and L-arginine (L-Arg) availability in MHC-ODC mice. Although ISO-induced hypertrophy is well-compensated, MHC-ODC mice administered L-Arg along with ISO showed a rapid onset of systolic dysfunction and died within 48 h. Myocytes isolated from MHC-ODC mice administered L-Arg/ISO exhibited reduced contractility and altered calcium transients, suggesting an alteration in [Ca(2+)] homeostasis, and abbreviated action potential duration, which may contribute to arrhythmogenesis. The already elevated levels of spermidine and spermine were not further altered in MHC-ODC hearts by L-Arg/ISO treatment, suggesting alternative L-Arg utilization pathways lead to dysregulation of intracellular calcium. MHC-ODC mice administered an arginase inhibitor (Nor-NOHA) along with ISO died almost as rapidly as L-Arg/ISO-treated mice, while the iNOS inhibitor S-methyl-isothiourea (SMT) was strongly protective against L-Arg/ISO. These results point to the induction of arginase as a protective response to β-adrenergic stimulation in the setting of high polyamines. Further, NO generated by exogenously supplied L-Arg may contribute to the lethal consequences of L-Arg/ISO treatment. Since considerable variations in human cardiac polyamine and L-Arg content are likely, it is possible that alterations in these factors may influence myocyte contractility.     

Applications and limitations of end-systolic measures of ventricular performance

The usefulness of end-systolic measures of left ventricular performance as a load-independent method of assessing of ventricular contractility has been studied in intact, conscious dogs. The end-systolic pressure-chamber diameter (P-D) relation was shown to be linear, unaltered by preload changes, and shifted in a parallel fashion by inotropic stimulation, whereas the end-systolic pressure-volume relation appeared to increase in slope with increased contractility. A simplified measure of end-systolic relations that does not require measurement of chamber volume or diameter, the end-systolic pressure-wall thickness ( WTh ) relation, was also linear and shifted with acute changes in inotropic state. During regional ischemia, the regional end-systolic WTh relation also may provide a relatively load-independent means of detecting regional depression of myocardial contractility. With chronic pressure overload hypertrophy in dogs, the end-systolic P-D relation was markedly shifted upward and to the left, which indicates hyperfunction of the left ventricle; however, end-systolic wall stress-diameter relations were identical before and after the development of hypertrophy, which suggests that myocardial contractility was unaltered. These findings and clinical studies of mitral regurgitation imply that for assessing resting left ventricular contractility in certain chronic conditions, the use of wall stress rather than pressure may be appropriate in the end-systolic framework. Further experimental studies are needed in the intact circulation to better characterize end-systolic relations before their full potential in the clinical setting can be realized.     

Left ventricular systolic torsion correlates global cardiac performance during dyssynchrony and cardiac resynchronization therapy

Left ventricular (LV) systolic torsion is a primary mechanism contributing to stroke volume (SV). We hypothesized that change in LV torsion parallels changes in global systolic performance during dyssynchrony and cardiac resynchronization therapy (CRT). Seven anesthetized open chest dogs had LV pressure-volume relationship. Apical, basal, and mid-LV cross-sectional echocardiographic images were studied by speckle tracking analysis. Right atrial (RA) pacing served as control. Right ventricular (RV) pacing simulated left bundle branch block. Simultaneous RV-LV free wall and RV-LV apex pacing (CRTfw and CRTa, respectively) modeled CRT. Dyssynchrony was defined as the time difference in peak strain between earliest and latest segments. Torsion was calculated as the maximum difference between the apical and basal rotation. RA pacing had minimal dyssynchrony (52 ± 36 ms). RV pacing induced dyssynchrony (189 ± 61 ms, P < 0.05). CRTa decreased dyssynchrony (46 ± 36 ms, P < 0.05 vs. RV pacing), whereas CRTfw did not (110 ± 96 ms). Torsion during baseline RA was 6.6 ± 3.7°. RV pacing decreased torsion (5.1 ± 3.6°, P < 0.05 vs. control), and reduced SV, stroke work (SW), and dP/dt(max) compared with RA (21 ± 5 vs. 17 ± 5 ml, 252 ± 61 vs. 151 ± 64 mJ, and 2,063 ± 456 vs. 1,603 ± 424 mmHg/s, respectively, P < 0.05). CRTa improved torsion, SV, SW, and dP/dt(max) compared with RV pacing (7.7 ± 4.7°, 23 ± 3 ml, 240 ± 50 mJ, and 1,947 ± 647 mmHg/s, respectively, P < 0.05), whereas CRTfw did not (5.1 ± 3.6°, 18 ± 5 ml, 175 ± 48 mJ, and 1,699 ± 432 mmHg/s, respectively, P < 0.05). LV torsion changes covaried across conditions with SW (y = 0.94x+12.27, r = 0.81, P < 0.0001) and SV (y = 0.66x+0.91, r = 0.81, P < 0.0001). LV dyssynchrony changes did not correlate with SW or SV (r = -0.12, P = 0.61 and r = 0.08, P = 0.73, respectively). Thus, we conclude that LV torsion is primarily altered by dyssynchrony, and CRT that restores LV performance also restores torsion.     

Acute changes of biventricular gene expression in volume and right ventricular pressure overload

OBJECTIVE: We investigated the effects of acute volume and RV pressure overload on biventricular function and gene expression of BNP, pro-inflammatory cytokines (IL-6 and TNF-alpha), iNOS, growth factors (IGF-1, ppET-1), ACE and Ca2+-handling proteins (SERCA2a, phospholamban and calsequestrin). METHODS: Male Wistar rats (n=45) instrumented with pressure tip micromanometers in right (RV) and left ventricular (LV) cavities were assigned to one of three protocols: i) Acute RV pressure overload induced by pulmonary trunk banding in order to double RV peak systolic pressure, during 120 or 360 min; ii) acute volume overload induced by dextran40 infusion (5 ml/h), during 120 or 360 min; iii) Sham. RV and LV samples were collected for mRNA quantification. RESULTS: BNP upregulation was restricted to the overloaded ventricles. TNF-alpha, IL-6, ppET-1, SERCA2a and phospholamban gene activation was higher in volume than in pressure overload. IGF-1 overexpression was similar in both types of overload, but was limited to the RV. TNF-alpha and CSQ mRNA levels were increased in the non-overloaded LV after pulmonary trunk banding. No significant changes were detected in ACE or iNOS expression. RV end-diastolic pressures positively correlated with local expression of BNP, TNF-alpha, IL-6, IGF-1, ppET-1 and SERCA2a, while RV peak systolic pressures correlated only with local expression of IL-6, IGF-1 and ppET-1. CONCLUSIONS: Acute cardiac overload alters myocardial gene expression profile, distinctly in volume and pressure overload. These changes correlate more closely with diastolic than with systolic load. Nonetheless, gene activation is also present in the non-overloaded LV of selectively RV overloaded hearts.     

Effect of the mechanical ventilatory cycle on thermodilution right ventricular volumes and cardiac output.

The purpose of this study was to evaluate right ventricular (RV) loading and cardiac output changes, by using the thermodilution technique, during the mechanical ventilatory cycle. Fifteen critically ill patients on mechanical ventilation, with 5 cmH(2)O of positive end-expiratory pressure, mean respiratory frequency of 18 breaths/min, and mean tidal volume of 708 ml, were studied with help of a rapid-response thermistor RV ejection fraction pulmonary artery catheter, allowing 5-ml room-temperature 5% isotonic dextrose thermodilution measurements of cardiac index (CI), stroke volume (SV) index, RV ejection fraction (RVEF), RV end-diastolic volume (RVEDV), and RV end-systolic volume (RVESV) indexes at 10% intervals of the mechanical ventilatory cycle. The ventilatory modulation of CI and RV volumes varied from patient to patient, and the interindividual variability was greater for the latter variables. Within patients also, RV volumes were modulated more by the ventilatory cycle than CI and SV index. Around a mean value of 3.95 +/- 1.18 l. min(-1). m(-2) (= 100%), CI varied from 87.3 +/- 5.2 (minimum) to 114.3 +/- 5.1% (maximum), and RVESV index varied between 61.5 +/- 17.8 and 149.3 +/- 34.1% of mean 55.1 +/- 17.9 ml/m(2) during the ventilatory cycle. The variations in the cycle exceeded the measurement error even though the latter was greater for RVEF and volumes than for CI and SV index. For mean values, there was an inspiratory decrease in RVEF and increase in RVESV, whereas a rise in RVEDV largely prevented a fall in SV index. We conclude that cyclic RV afterloading necessitates multiple thermodilution measurements equally spaced in the ventilatory cycle for reliable assessment of RV performance during mechanical ventilation of patients.     

The "systolic volume balance" method for the noninvasive estimation of cardiac output based on pressure wave analysis

Cardiac output (CO) monitoring is essential for the optimal management of critically ill patients. Several mathematical methods have been proposed for CO estimation based on pressure waveform analysis. Most of them depend on invasive recording of blood pressure and require repeated calibrations, and they suffer from decreased accuracy under specific conditions. A new systolic volume balance (SVB) method, including a simpler empirical form (eSVB), was derived from basic physical principles that govern blood flow and, in particular, a volume balance approach for the conservation of mass ejected into and flowed out of the arterial system during systole. The formulas were validated by a one-dimensional model of the systemic arterial tree. Comparisons of CO estimates between the proposed and previous methods were performed in terms of agreement and accuracy using "real" CO values of the model as a reference. Five hundred and seven different hemodynamic cases were simulated by altering cardiac period, arterial compliance, and resistance. CO could be accurately estimated by the SVB method as follows: CO = C × PP(ao)/(T - P(sm) × T(s)/P(m)) and by the eSVB method as follows: CO = k × C × PP(ao)/T, where C is arterial compliance, PP(ao) is aortic pulse pressure, T is cardiac period, P(sm) is mean systolic pressure, T(s) is systolic duration, P(m) is mean pressure, and k is an empirical coefficient. SVB applied on aortic pressure waves did not require calibration or empirical correction for CO estimation. An empirical coefficient was necessary for brachial pressure wave analysis. The difference of SVB-derived CO from model CO (for brachial waves) was 0.042 ± 0.341 l/min, and the limits of agreement were -0.7 to 0.6 l/min, indicating high accuracy. The intraclass correlation coefficient and root mean square error between estimated and "real" CO were 0.861 and 0.041 l/min, respectively, indicating very good accuracy. eSVB also provided accurate estimation of CO. An in vivo validation study of the proposed methods remains to be conducted.     

Elevated oxidative stress and endothelial dysfunction in right coronary artery of right ventricular hypertrophy

Remodeling of right coronary artery (RCA) occurs during right ventricular hypertrophy (RVH) induced by banding of the pulmonary artery (PA). The effect of RVH on RCA endothelial function and reactive oxygen species (ROS) in vessel wall remains unclear. A swine RVH model (n = 12 pigs) induced by PA banding was used to study RCA endothelial function and ROS level. To obtain longitudinal coronary hemodynamic and geometric data, digital subtraction angiography was used during the progression of RVH. Blood flow in the RCA increased by 82% and lumen diameter of RCA increased by 22% over a 4-wk period of RVH. The increase in blood flow and the commensurate increase in diameter resulted in a constant wall shear stress in RCA throughout the RVH period. ROS was elevated by ～100% in RCA after 4 wk of PA banding. The expressions of p47(phox), NADPH oxidase (NOX1, NOX2, and NOX4) were upregulated in the range of 20-300% in RCA of RVH. The endothelial function was compromised in RCA of RVH as attributed to insufficient endothelial nitric oxide synthase cofactor tetrahydrobiopterin. In vivo angiographic analysis suggests an increased basal tone in the RCA during RVH. In conclusion, stretch due to outward remodeling of RCA during RVH (at constant wall shear stress), similar to vessel stretch in hypertension, appears to induce ROS elevation, endothelial dysfunction, and an increase in basal tone.     

Blockade of MyD88 attenuates cardiac hypertrophy and decreases cardiac myocyte apoptosis in pressure overload-induced cardiac hypertrophy in vivo

In this study, we evaluated whether blocking myeloid differentiation factor-88 (MyD88) could decrease cardiac myocyte apoptosis following pressure overload. Adenovirus expressing dominant negative MyD88 (Ad5-dnMyD88) or Ad5-green fluorescent protein (GFP) (Ad5-GFP) was transfected into rat hearts (n = 8/group) immediately followed by aortic banding for 3 wk. One group of rats (n = 8) was subjected to aortic banding for 3 wk without transfection. Sham surgical operation (n = 8) served as control. The ratios of heart weight to body weight (HW/BW) and heart weight to tibia length (HW/TL) were calculated. Cardiomyocyte size was examined by FITC-labeled wheat germ agglutinin staining of membranes. Cardiac myocyte apoptosis was determined by terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling assay, and myocardial interstitial fibrosis was examined by Masson's Trichrome staining. Aortic banding significantly increased the HW/BW by 41.0% (0.44 +/- 0.013 vs. 0.31 +/- 0.008), HW/TL by 47.2% (42.7 +/- 1.30 vs. 29.0 +/- 0.69), cardiac myocyte size by 49.6%, and cardiac myocyte apoptosis by 11.5%, and myocardial fibrosis and decreased cardiac function compared with sham controls. Transfection of Ad5-dnMyD88 significantly reduced the HW/BW by 18.2% (0.36 +/- 0.006 vs. 0.44 +/- 0.013) and HW/TL by 22.3% (33.2 +/- 0.95 vs. 42.7 +/- 1.30) and decreased cardiomyocyte size by 56.8%, cardiac myocyte apoptosis by 76.2%, as well as fibrosis, and improved cardiac function compared with aortic-banded group. Our results suggest that MyD88 is an important component in the Toll-like receptor-4-mediated nuclear factor-kappaB activation pathway that contributes to the development of cardiac hypertrophy. Blockade of MyD88 significantly reduced cardiac hypertrophy, cardiac myocyte apoptosis, and improved cardiac function in vivo.     

Effect of catecholamine-induced cardiac hypertrophy on the force-interval relationship

Cardiac hypertrophy was induced in adult female Wistar rats following 12 days of daily subcutaneous injections of isoproterenol (ISO). The left atria responded with a 13-14% increase in tissue growth, while the ventricles achieved a 34-39% increased tissue mass. Maximum force generation and twitch characteristics in 1.0 mM external Ca2+ for the left atria or the right papillary muscle were unchanged in the ISO-treated animals. The force-interval relation was determined at 26 degrees C between 0.5 and 120 s. The development of maximum force clearly passed through two phases identified as alpha and beta. To characterize these two processes the data were fitted to a two-term linear combination of exponentials (two-compartment model). The time constant and capacity of each process to contribute to the whole force-interval curve was determined by a four-parameter least square fit method. In control atrial muscle the time constants for the alpha and beta processes were 0.47 and 11.23 s, respectively. The contribution of each process to the total force curve in control atrial muscle was approximately 50% alpha and 50% beta. Following ISO-induced growth the time constants were 0.38 and 13.33 s with a shift of contributions towards 60% alpha and 40% beta. Control papillary muscle from the right ventricle had a similar alpha time constant of 0.49 s compared with atrial muscle but possessed a considerably slower beta time constant of 26.17 s. The contribution of each process to interval-dependent force development was 44.5 and 55.5%, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)     

The electrocardiogram of normal ferrets and ferrets with right ventricular hypertrophy

Sixty-eight electrocardiograms were recorded on ferrets (Mustela putorius furo). These represent 29 normal weanling males, 19 normal adult males and 20 adult males with right ventricular hypertrophy (RVH). Analyses of rate, rhythm, axis and total voltage were used to define the normal electrocardiogram (ECG) and to identify changes seen in RVH. The normal ferret has a heart rate of about 300 beats per minute and a mean electrical axis of + 86 degrees +/- 6.6 (SD). A 56% increase in right ventricular weight to body weight ratio was not associated with right axis deviation. The overall voltage produced on the ECG was increased in the group with RVH as compared to the normal group (p less than 0.030).