Basic & Clinical Pharmacology & Toxicology

Rosuvastatin Attenuates Heart Failure and Cardiac Remodelling in the Ageing Spontaneously Hypertensive Rat

Authors


Author for correspondence: Lindsay Brown, School of Biomedical Sciences, The University of Queensland, Brisbane, Qld 4072, Australia (fax +61 7 3365 1766, e-mail l.brown@uq.edu.au).

Abstract

Abstract:  3-hydroxy-3-methylglutaryl(HMG)-Coenzyme(Co)A reductase inhibitors such as rosuvastatin may improve clinical status in patients with hypertension and heart failure. The ageing spontaneously hypertensive rat (SHR) closely mimics the chronic heart failure disease process observed in humans. This study examined the structural and functional changes in the cardiovascular system of 15-month-old SHR and normotensive Wistar-Kyoto (WKY) rats treated with rosuvastatin (20 mg/kg/day perorally) for 24 weeks. Cardiovascular structure and function were monitored serially by echocardiography. At 21 months, ex vivo Langendorff, electrophysiological or histological studies were performed. Chronic rosuvastatin treatment attenuated elevations of left ventricular wet weight (mg/g body weight: 21-month WKY, 2.30 ± 0.04; 15-month SHR, 3.03 ± 0.08; 21-month SHR, 4.09 ± 0.10; 21-month SHR + rosuvastatin, 3.50 ± 0.13), myocardial extracellular matrix content (% left ventricular area: 21-month WKY, 7.6 ± 0.5; 15-month SHR, 13.2 ± 0.8; 21-month SHR 19.6 ± 1.0; 21-month SHR with rosuvastatin 14.6 ± 1.2) and diastolic stiffness (κ: 21-month WKY, 24.9 ± 0.6; 15-month SHR, 26.4 ± 0.4; 21-month SHR, 33.1 ± 0.8; 21-month SHR + rosuvastatin, 27.5 ± 0.6) as well as attenuating the deterioration of systolic and diastolic function (fractional shortening %: 21-month WKY, 66 ± 2; 15-month SHR, 51 ± 3; 21-month SHR, 38 ± 3; 21-month SHR + rosuvastatin, 52 ± 4). There was no effect on the increased systolic blood pressure, plasma low-density lipoprotein concentrations or the prolonged action potential duration. Thus, chronic rosuvastatin treatment may attenuate myocardial dysfunction in heart failure by preventing fibrosis.

Despite aggressive medical therapy, including angiotensin converting enzyme (ACE) inhibitors, β-adrenoceptor antagonists and diuretics, heart failure remains a major cause of morbidity and mortality worldwide [1]. The 3-hydroxy-3-methylglutaryl(HMG)-Coenzyme(Co)A reductase inhibitors or statins, introduced to lower blood cholesterol concentrations, have shown a range of pleiotropic effects which could be useful in the treatment of heart failure [2]. Statins lowered morbidity and mortality in coronary artery disease and other atherosclerotic vascular disease in large-scale clinical trials [3–6]. Additional analyses of these trials have shown that statin therapy also reduced the risk of developing heart failure [7,8]. Although these clinical trials generally excluded patients with symptomatic or severe heart failure, statins improved the survival and quality of life in patients with heart failure regardless of blood cholesterol concentrations, the aetiology of heart failure or other heart failure medications [9]. However, despite the reduction in plasma low-density lipoprotein and C-reactive peptide concentrations by rosuvastatin, the number of deaths from any cause in older patients with heart failure was not reduced after rosuvastatin therapy for a median of 32.8 months [10]. Further, low cholesterol concentrations were associated with less favourable outcomes in heart failure [11].

The young adult male spontaneously hypertensive rat (SHR) [12] aged 3–6 months has been studied extensively as a model of human essential hypertension. Chronic hypertension in these male SHR leads to progressive compensatory cardiac remodelling followed by decompensation and heart failure from about 15 months of age and so ageing SHR are considered to be a suitable rat model of human chronic hypertensive heart failure [13–16]. Rats also provide a model for studying the cardiovascular effects of statins that are independent of cholesterol lowering, as plasma low-density lipoprotein concentrations are normally low in rats (in contrast to humans) and statins usually do not modify their lipid profile [17]. In this study, we used the ageing male SHR model of heart failure to determine whether chronic administration of rosuvastatin prevents cardiac remodelling and dysfunction and the transition to heart failure.

Methods

Animal model and experimental protocol.  Male SHR and Wistar-Kyoto (WKY) rats were left to age to 15 months. Rats from both strains (15-month WKY, n = 30; 15-month SHR, n = 29) were killed at this age to obtain experimental baseline parameters. The remaining rats were then randomly assigned to either no further treatment (21-month WKY, n = 29; 21-month SHR, n = 33) or daily treatment by oral gavage with rosuvastatin (RSV, 20 mg/kg/day in 10% Tween 20) (WKY + RSV, n = 33; SHR + RSV, n = 36), for the following 24 weeks. This dose of rosuvastatin adequately inhibited HMG-CoA reductase in pre-clinical studies [18] and produced cardiovascular effects in chronic studies in rats [19–23]. Terminal experiments were performed in these rats at 21 months of age. All experimentation was approved by the Animal Experimentation Ethics Committee of The University of Queensland under the guidelines of the National Health and Medical Research Council of Australia.

Assessment of physiological parameters.  Systolic blood pressure was measured by tail-cuff plethysmography in rats lightly anaesthetized with intraperitoneal tiletamine (10 mg/kg) and zolazepam (10 mg/kg) within 15 min. after administration of the drugs. Rats were killed with pentobarbitone (100 mg/kg i.p.). Blood was taken from the abdominal vena cava, just caudal to the insertion of renal veins, centrifuged and the plasma immediately frozen. The heart was removed and the ventricles weighed immediately after death to be expressed as a ratio of the tissue weight (mg) to the total body weight (g). Plasma concentrations of total cholesterol, low density lipoprotein, high density lipoprotein and triglycerides were measured by The University of Queensland Veterinary Pathology Services, Brisbane, Australia. Plasma malondialdehyde concentrations as a measure of oxidative stress were determined in post-mortem blood by HPLC [24].

Echocardiography.  Echocardiography was performed at The Prince Charles Hospital Small Animal Theatre, Biological Research Facilities, Brisbane, Australia, by qualified sonographers. This non-invasive cardiac imaging technique was conducted on rats anaesthetized with intraperitoneal tiletamine (25 mg/kg) and zolazepam (25 mg/kg) (Zoletil®, Virbac Pty Ltd, Milperra, Australia) combined with xylazine (10 mg/kg) (Ilium Xylazil®, Troy Labs, Smithfield, Australia). Serial, in vivo left parasternal and left apical echocardiographic images of rats were obtained using the Hewlett Packard Sonos 5500 (12 MHz frequency foetal transducer; Melbourne, Australia) at an image depth of 3 cm using two focal zones [25]. Left ventricular M-mode measurements at the level of the papillary muscles included left ventricular end-diastolic dimensions, left ventricular end-systolic dimensions, interventricular septum and posterior wall thicknesses and fractional shortening. Cardiac output, ejection fraction and left ventricular mass were derived from these values [26]. Pulsed-wave Doppler analyses of mitral valve inflows were used as estimates of diastolic function.

Isolated Langendorff heart preparation.  Experiments were performed on rats anaesthetized with sodium pentobarbitone (100 mg/kg i.p.) as described previously [19,24]. Briefly, left ventricular developed pressure was measured using a balloon catheter inserted into the left ventricle through the mitral orifice of ex vivo hearts. Increments in balloon volume were applied to the heart with left ventricular end-diastolic pressure recorded at approximately 0, 5, 10, 15, 20 and 30 mmHg. At the end of the experiment, the atria and right ventricle were dissected away leaving the left ventricle and septum, which were blotted dry and then weighed. Myocardial diastolic stiffness was calculated as the diastolic stiffness constant (κ, dimensionless), the slope of the linear relation between tangent elastic modulus (E, dyne/cm2) and stress (σ, dyne/cm2) [19,24].

Microelectrode studies of isolated left ventricular papillary muscles.  Electrophysiological recordings of cardiac action potentials were obtained by microelectrode single cell impalements of ex vivo left ventricular papillary muscles, as described previously [19,24]. Action potential parameters measured were action potential duration (APD) at 20%, 50% and 90% of repolarization (APD20, ADP50 and APD90 respectively), action potential amplitude and resting membrane voltage.

Quantification of left ventricular collagen and cross-sectional area.  Collagen content was determined by image analysis of picrosirius red-stained sections of the hearts [19,24]. At least four areas from each heart were analysed and collagen levels expressed as a percentage of red area in each image. Cardiomyocyte cross-sectional area was measured as an average of at least 100 myocytes taken from five different sections of the left ventricle. Areas were acquired and averaged using image analysis software NIS-Elements (Nikon, Sydney, Australia).

Histological collagen results were confirmed by a modified hydroxyproline assay [27]. Approximately 5.0 mg samples of left ventricle were dried for 6 hr at 40°C. Tissues and standards were then hydrolysed in 6 M HCl at 107°C for 18 hr. The acid was blown off by compressed air and the hydrolysate reconstituted in distilled water. Chloramine T reagent was added to each sample for the oxidation step to progress, followed by Ehrlich’s reagent to enable chromophore development. The absorbance of each sample was read at 550 nm in a spectrophotometer and hydroxyproline content established from a standard curve.

Data analysis.  All results are given as mean ± S.E.M. These results were analysed by one-way analysis of variance followed by the Bonferroni post-test for multiple groups or a paired or unpaired Student’s t-test for two group comparisons. < 0.05 was considered statistically significant; *< 0.05 versus age-matched WKY control; < 0.05 versus 15-month SHR; < 0.05 versus age-matched SHR.

Results

Physiological parameters.

The final body weight was unchanged after the 24-week protocol for both treated and untreated SHR and WKY rats (table 1). Systolic blood pressure was elevated in untreated SHR rats in comparison with their age-matched WKY controls. Rosuvastatin treatment did not alter systolic blood pressure in either rat strain over the 6-month treatment period (fig. 1). Fifteen- and 21-month-old untreated SHRs also exhibited increased kidney, lung and liver wet weights normalized to body weight when compared with age-matched WKY rats. Rosuvastatin administration did not prevent this organ hypertrophy (table 1). There was no difference in plasma total cholesterol concentrations between 21-month SHR and WKY rats. Rosuvastatin therapy lowered plasma cholesterol concentrations in 21-month SHR but not in age-matched WKY rats (table 1). Concentrations of high-density lipoprotein, low-density lipoprotein and triglycerides were similar amongst treated and untreated 21-month old rats (table 1). Plasma malondialdehyde concentrations, as a measure of oxidative stress, were increased in 21-month SHR and lowered by rosuvastatin treatment in both WKY and SHRs (table 1).

Table 1. 
Physiological parameters of control and rosuvastatin (RSV)-treated WKY and SHR rats.
Data15-month WKY21-month WKY21-month WKY + RSV15-month SHR21-month SHR21-month SHR + RSV
  1. SBP, systolic blood pressure; NA, not available; LDL, low-density lipoprotein; HDL, high-density lipoprotein; LV, left ventricle; RV, right ventricle; CSA, cross-sectional area.

  2. *< 0.05 versus age-matched WKY control.

  3. < 0.05 versus 15-month SHR.

  4. < 0.05 versus age-matched SHR.

Initial body weight (g)NA440 ± 4 (n = 7)446 ± 7 (n = 12)NA413 ± 7 (n = 8)424 ± 7 (n = 15)
Final body weight (g)440 ± 4 (n = 7)446 ± 14 (n = 10)432 ± 8 (n = 12)413 ± 7 (n = 8)426 ± 13 (n = 11)405 ± 6 (n = 15)
LV + septum weight (mg/g)2.35 ± 0.03 (n = 7)2.30 ± 0.04 (n = 10)2.14 ± 0.05 (n = 12)3.03 ± 0.08* (n = 8)4.09 ± 0.10 (n = 11)3.50 ± 0.13†‡ (n = 15)
LV + septum weight (g/m tibial length)24.6 ± 0.2 (n = 7)24.7 ± 0.9 (n = 10)22.3 ± 0.3 (n = 12)29.7 ± 0.9* (n = 8)40.3 ± 1.3 (n = 11)33.9 ± 1.1†‡ (n = 15)
RV weight (mg/g)0.49 ± 0.02 (n = 7)0.51 ± 0.03 (n = 10)0.52 ± 0.02 (n = 12)0.48 ± 0.02 (n = 8)0.84 ± 0.06 (n = 11)0.66 ± 0.05 (n = 15)
RV weight (g/m tibial length)5.0 ± 0.1 (n = 7)5.1 ± 0.3 (n = 10)5.4 ± 0.2 (n = 12)4.7 ± 0.2 (n = 8)8.4 ± 0.8 (n = 11)6.4 ± 0.5 (n = 15)
Kidney weight (mg/g)5.79 ± 0.14 (n = 6)5.78 ± 0.14 (n = 10)5.78 ± 0.12 (n = 12)7.13 ± 0.32* (n = 8)7.10 ± 0.19* (n = 11)6.80 ± 0.08* (n = 15)
Lung weight (mg/g)3.30 ± 0.25 (n = 6)3.61 ± 0.25 (n = 10)3.83 ± 0.22 (n = 11)5.18 ± 0.18* (n = 8)6.31 ± 0.66* (n = 11)5.54 ± 0.37* (n = 15)
Liver weight (mg/g)24.9 ± 0.7 (n = 6)26.1 ± 0.4 (n = 10)29.5 ± 1.5 (n = 12)43.8 ± 1.8* (n = 8)40.8 ± 1.4* (n = 11)41.7 ± 1.6* (n = 15)
Plasma total cholesterol (mmol/l)NA3.6 ± 0.3 (n = 7)3.5 ± 0.2 (n = 7)NA3.0 ± 0.3 (n = 7)2.0 ± 0.1*‡ (n = 7)
Plasma LDL (mmol/l)NA0.23 ± 0.03 (n = 7)0.19 ± 0.01 (n = 7)NA0.23 ± 0.03 (n = 7)0.27 ± 0.03 (n = 6)
Plasma HDL (mmol/l)NA0.57 ± 0.03 (n = 7)0.53 ± 0.02 (n = 7)NA0.81 ± 0.11* (n = 7)0.74 ± 0.09* (n = 7)
Plasma triglycerides (mmol/l)NA0.80 ± 0.04 (n = 7)0.73 ± 0.03 (n = 7)NA1.16 ± 0.17 (n = 7)1.00 ± 0.12 (n = 7)
Plasma malondialdehyde (μmol/l)NA36.6 ± 3.3 (n = 6)25.5 ± 3.2 (n = 6)NA42.0 ± 4.0 (n = 6)31.0 ± 3.5 (n = 6)
LV interstitial collagen (% area)6.2 ± 0.6 (n = 7)7.6 ± 0.5 (n = 7)8.0 ± 0.7 (n = 8)13.2 ± 0.8* (n = 7)19.6 ± 1.0 (n = 7)14.6 ± 1.2*‡ (n = 8)
LV perivascular collagen (% area)23.7 ± 1.3 (n = 7)23.9 ± 1.7 (n = 7)24.7 ± 1.3 (n = 8)32.6 ± 1.3* (n = 7)33.9 ± 1.3 (n = 7)30.9 ± 1.4* (n = 8)
LV hydroxyproline content (mg/g)1.8 ± 0.1 (n = 10)1.7 ± 0.1 (n = 7)1.8 ± 0.1 (n = 8)2.3 ± 0.2* (n = 8)3.3 ± 0.3 (n = 11)2.5 ± 0.1*‡ (n = 11)
LV cardiomyocyte CSA (μm2)420 ± 9 (n = 7)495 ± 10 (n = 7)458 ± 8 (n = 8)757 ± 25* (n = 7)865 ± 20 (n = 7)738 ± 10* (n = 8)
Figure 1.

 Systolic blood pressure in WKY, spontaneously hypertensive rat (SHR) and rosuvastatin (RSV)-treated rats from 15 to 21 months of age (n = 6–15 for all groups).

The left ventricle plus septum wet weight was increased in SHRs when compared with their age-matched WKY rats. In addition, this parameter was significantly greater than in 15-month SHRs in both treated and untreated 21-month hypertensive rats. However, this indicator of left ventricular hypertrophy was attenuated in rosuvastatin-treated SHRs (table 1). Myocyte cross-sectional areas were markedly increased in SHR compared with WKY and this parameter increased with age; rosuvastatin treatment of SHR rats prevented this age-associated increase in myocyte cross-sectional areas in 21-month SHR (table 1). In contrast to the left ventrzicle, right ventricular wet weight was only augmented in the untreated 21-month SHR, with rosuvastatin therapy preventing this increase in organ weight (table 1). In comparison with age-matched WKY rats, left ventricular interstitial collagen area was significantly elevated in 15-month SHRs and even more so in untreated 21-month hypertensive rats. Further, rosuvastatin prevented the progressive interstitial fibrosis observed in these rats (table 1, fig. 2). Left ventricular perivascular collagen areas were similarly elevated in 15- and 21-month SHRs but this increase was unaffected by rosuvastatin (table 1). The hydroxyproline content of the left ventricle was elevated in hypertensive rats, significantly more so in 21-month untreated SHRs than in 15-month SHRs. In addition, 24 weeks of rosuvastatin treatment prevented this increase (table 1).

Figure 2.

 Representative picrosirius red-stained confocal images of left ventricular interstitial collagen from 15-month WKY (A), 21-month WKY (B), rosuvastatin (RSV)-treated WKY (C), 15-month spontaneously hypertensive rat (SHR) (D), 21-month SHR (E) and RSV-treated SHR (F) (magnification 40×). Graphical representation of left ventricular interstitial collagen area (n = 7-8 for all groups).

Echocardiographic parameters.

The interventricular septum at diastole was thickened in 18- and 21-month SHRs (treated and untreated) versus the age-matched WKY (table 2) but diastolic left ventricular posterior wall thickness and diastolic left ventricular internal diameter were unchanged in SHR rats (table 2). Two indicators of systolic function, fractional shortening and ejection fraction, were decreased in 15- and 21-month SHRs. Further, rosuvastatin treatment attenuated the decline in these two functional parameters at 19 and 21 months only (fig. 3, table 2). The E/A mitral flow rate ratio, an indicator of diastolic dysfunction, increased rapidly in hypertensive animals from 18 to 21 months of age. Administration of rosuvastatin prevented this rise in 19- and 20-month SHRs only (fig. 4). In addition, deceleration time of the E-wave was delayed in both treated and untreated 15- and 21-month SHR animals (table 2). The velocity of flow in the descending, but not ascending, aorta was reduced in 15-, 18- and 21-month SHRs. Further, 24 weeks of rosuvastatin treatment had no effect on this parameter (table 2). Lastly, the diameters of both the ascending and descending aortic arch were increased in hypertensive rats. In addition, the descending aortic arch diameter was greater in untreated 21-month SHRs than in 15-month SHRs, while rosuvastatin treatment prevented this progressive widening of the aortic lumen (table 2).

Table 2. 
Echocardiographic parameters of control and rosuvastatin (RSV)-treated WKY and SHR rats.
Data15-month WKY18-month WKY21-month WKY21-month WKY + RSV15-month SHR18-month SHR21-month SHR21-month SHR + RSV
  1. Note: IVSd, interventricular septum thickness at diastole; LVIDd, left ventricular internal diameter at diastole; LVPWd, left ventricular posterior wall thickness at diastole; Asc, ascending; Desc, descending.

  2. *< 0.05 versus age-matched WKY control. < 0.05 versus 15-month SHR

  3. < 0.05 versus age-matched SHR.

  4. Parameters were calculated as follows [20]: %FS = (LVIDd − LVIDs)/LVIDd × 100; Diastolic volume (ml) = 1.047 (LVIDd)3; Systolic volume (ml) = 1.047 (LVIDs)3; Stroke volume (ml) = diastolic volume − systolic volume; Ejection fraction (%) = (stroke volume/diastolic volume) × 100.

IVSd (cm)0.21 ± 0.01 (n = 10)0.20 ± 0.01 (n = 14)0.21 ± 0.01 (n = 10)0.19 ± 0.00 (n = 9)0.20 ± 0.01 (n = 10)0.27 ± 0.01† (n = 10)0.25 ± 0.01† (n = 8)0.25 ± 0.01† (n = 10)
LVIDd (cm)0.78 ± 0.05 (n = 10)0.85 ± 0.03 (n = 14)0.74 ± 0.02 (n = 10)0.70 ± 0.02 (n = 9)0.81 ± 0.02 (n = 10)0.70 ± 0.03 (n = 10)0.82 ± 0.04 (n = 8)0.87 ± 0.03 (n = 10)
LVPWd (cm)0.19 ± 0.02 (n = 10)0.17 ± 0.01 (n = 14)0.20 ± 0.01 (n = 10)0.18 ± 0.00 (n = 9)0.19 ± 0.01 (n = 10)0.22 ± 0.01 (n = 10)0.22 ± 0.01 (n = 8)0.23 ± 0.01 (n = 10)
Asc aorta flow velocity (m/sec.)1.17 ± 0.05 (n = 10)1.35 ± 0.03 (n = 14)1.20 ± 0.07 (n = 10)1.19 ± 0.05 (n = 9)1.13 ± 0.05 (n = 10)1.35 ± 0.05 (n = 10)1.30 ± 0.11 (n = 8)1.10 ± 0.05 (n = 10)
Desc aorta flow velocity (m/sec.)1.00 ± 0.11 (n = 10)1.25 ± 0.03 (n = 14)1.21 ± 0.06 (n = 10)1.10 ± 0.04 (n = 9)0.66 ± 0.03* (n = 10)0.70 ± 0.04* (n = 10)0.59 ± 0.04* (n = 8)0.62 ± 0.03* (n = 10)
Asc aortic arch diameter (cm)0.30 ± 0.01 (n = 10)0.32 ± 0.01 (n = 14)0.32 ± 0.01 (n = 10)0.29 ± 0.01 (n = 9)0.43 ± 0.01* (n = 10)0.42 ± 0.01* (n = 10)0.45 ± 0.01* (n = 8)0.44 ± 0.01* (n = 10)
Desc aortic arch diameter (cm)0.22 ± 0.01 (n = 10)0.26 ± 0.01 (n = 14)0.26 ± 0.01 (n = 10)0.21 ± 0.01 (n = 9)0.29 ± 0.01* (n = 10)0.33 ± 0.01* (n = 10)0.38 ± 0.02 (n = 8)0.32 ± 0.01* (n = 10)
Fractional shortening (%)63 ± 4 (n = 10)62 ± 4 (n = 14)66 ± 2 (n = 10)53 ± 2* (n = 9)51 ± 3 (n = 10)53 ± 3 (n = 10)38 ± 3* (n = 8)52 ± 4* (n = 10)
E/A mitral flow rate ratio1.81 ± 0.14 (n = 10)2.10 ± 0.11 (n = 10)2.00 ± 0.12 (n = 6)1.77 ± 0.06 (n = 8)1.76 ± 0.05 (n = 9)1.79 ± 0.11 (n = 8)4.04 ± 0.93 (n = 8)2.82 ± 0.33 (n = 7)
E wave deceleration time (msec.)65 ± 3 (n = 6)58 ± 2 (n = 10)72 ± 5 (n = 6)64 ± 3 (n = 8)49 ± 3* (n = 8)48 ± 3 (n = 7)43 ± 2* (n = 8)53 ± 4* (n = 7)
Figure 3.

 Cardiac ejection fraction in WKY, spontaneously hypertensive rat (SHR) and rosuvastatin (RSV)-treated rats from 15 to 21 months of age (n = 8–14 for all groups).

Figure 4.

 The E/A mitral flow rate ratio in WKY, spontaneously hypertensive rat (SHR) and rosuvastatin (RSV)-treated rats from 15 to 21 months of age (n = 6–13 for all groups).

Cardiac Langendorff and electrophysiological parameters.

The diastolic stiffness constant of isolated perfused hearts was elevated in 15-month SHRs when compared with age-matched WKYs. There was a further increase in this measure of myocardial stiffness in the untreated 21-month SHR, but rosuvastatin treatment prevented this increase (table 3). Other parameters of Langendorff heart function, such as developed pressure, the rate of contraction (max + dP/dt) and the rate of relaxation (max − dP/dt) were not different (table 3).

Table 3. 
Langendorff parameters of control and rosuvastatin (RSV)-treated WKY and SHR rats.
Data15-month WKY21-month WKY21-month WKY + RSV15-month SHR21-month SHR21-month SHR + RSV
  1. Note: dP/dt, rate of change of developed pressure.

  2. *< 0.05 versus age-matched WKY control.

  3. < 0.05 versus 15-month SHR.

  4. < 0.05 versus age-matched SHR.

Diastolic stiffness constant (κ)23.2 ± 0.8 (n = 9)24.9 ± 0.6 (n = 8)22.2 ± 0.6 (n = 10)26.4 ± 0.4* (n = 8)33.1 ± 0.8 (n = 11)27.5 ± 0.6 (n = 14)
Developed pressure (mmHg)121 ± 6 (n = 9)117 ± 10 (n = 6)122 ± 4 (n = 10)115 ± 5 (n = 8)97 ± 9 (n = 9)102 ± 9 (n = 14)
Max + dP/dt (mmHg/sec.)2150 ± 110 (n = 9)2220 ± 140 (n = 6)2180 ± 90 (n = 10)2050 ± 90 (n = 8)1610 ± 180 (n = 9)1810 ± 160 (n = 14)
Max − dP/dt (mmHg/sec.)−1340 ± 100 (n = 8)−1400 ± 70 (n = 6)−1360 ± 60 (n = 10)−1260 ± 70 (n = 8)−1110 ± 100 (n = 9)−1160 ± 110 (n = 14)

Electrophysiological studies of isolated papillary muscles revealed no difference in resting membrane potential or action potential amplitude but SHRs demonstrated a lengthening in APD (table 4). The action potentials of 15-month SHRs were prolonged at APD20, APD50 and APD90. Untreated 21-month SHR action potentials were even further prolonged at APD90 compared with the 15-month SHR. Rosuvastatin did not change this progressive electrical remodelling in hypertensive rats (table 4).

Table 4. 
Electrophysiological parameters of control and rosuvastatin (RSV)-treated WKY and SHR rats.
Data 15-month WKY (n = 7) 21-month WKY (n = 7) 21-month WKY + RSV (n = 8) 15-month SHR (n = 7) 21-month SHR (n = 8)21-month SHR + RSV (n = 7)
  1. Note: APD20, APD50 and APD90, action potential duration at 20%, 50% and 90% of repolarization respectively.

  2. *< 0.05 versus age-matched WKY control.

  3. < 0.05 versus 15-month SHR.

Resting membrane potential (mV)−67 ± 2 (n = 7)−72 ± 2 (n = 7)−70 ± 1 (n = 8)−72 ± 2 (n = 7)−67 ± 2 (n = 8)−69 ± 2 (n = 7)
Action potential amplitude (mV)82 ± 2 (n = 7)74 ± 4 (n = 7)77 ± 3 (n = 8)77 ± 4 (n = 7)83 ± 3 (n = 8)71 ± 5 (n = 7)
APD20 (msec.)8.0 ± 0.6 (n = 7)9.3 ± 1.1 (n = 7)6.6 ± 0.8 (n = 8)16.5 ± 2.2* (n = 7)22.8 ± 2.7* (n = 8)23.7 ± 2.4* (n = 7)
APD50 (msec.)16.2 ± 1.8 (n = 7)19.3 ± 2.9 (n = 7)14.1 ± 1.3 (n = 8)32.2 ± 2.6* (n = 7)45.5 ± 4.5* (n = 8)52.7 ± 5.1 (n = 7)
APD90 (msec.)47.1 ± 5.5 (n = 7)49.4 ± 6.8 (n = 7)54.6 ± 2.7 (n = 8)76.4 ± 4.8* (n = 7)129.3 ± 13.7 (n = 8)122.0 ± 9.5 (n = 7)

Discussion

Statins have proven effectiveness in lowering plasma cholesterol concentrations and subsequently preventing cardiovascular and cerebrovascular events [3–6] but their role in the treatment of human heart failure is equivocal [7–10]. Our study has used the ageing SHR [13–16] to show that rosuvastatin attenuated or delayed the functional (diastolic and systolic) and structural deterioration of the heart in this rodent model of hypertensive heart failure without significant changes in blood pressure, low-density lipoprotein cholesterol concentrations or action potential prolongation.

The effectiveness of the statins, including rosuvastatin, has generated many explanations involving so-called pleiotropic responses not related to lowering of low-density lipoprotein cholesterol concentrations [2]. Statins may be directly involved in a wide range of responses that could explain these pleiotropic responses in rats [28], including improving endothelial function, attenuating vascular remodelling and inhibiting vascular inflammatory responses. Decreased inflammatory cell infiltration into the myocardium could be associated with the decreased collagen deposition and cardiac stiffness, as previously shown with rosuvastatin in the DOCA-salt hypertensive rat [19]. The statins decreased plasma inflammatory markers in hyperlipidaemic patients [29]. The clinical relevance of pleiotropic responses with the statins has been critically reviewed [30].

The ageing male SHR from 15 to 21 months showed long-term hypertension with decreased contractile function, increased collagen deposition and cardiac stiffness, prolongation of the APD as well as right ventricular hypertrophy as signs of slowly developing heart failure, as in previous studies [13–16]. Rosuvastatin treatment reversed ventricular collagen deposition in the ageing SHR, consistent with previous studies with statins in rat models [31,32], including the SHR [33]. Decreased oxidative stress could be the possible mechanism for the antifibrotic response to rosuvastatin; oxidative stress has been associated with cardiac remodelling, especially hypertrophy and fibrosis [34]. The decreased cardiac stiffness is likely to reflect this decreased collagen deposition [35]; abnormal myocardial stiffness in senescent SHRs was reversible through pharmacological regression of cardiac fibrosis with the ACE inhibitor lisinopril [36]. The anti-fibrotic action of rosuvastatin may also underlie the attenuation of the decline in systolic and diastolic function as measured by echocardiography in the 21-month-old SHR. In patients with hypertensive heart disease, lisinopril produced regression of fibrosis and improvements in diastolic function [37].

Rosuvastatin did not decrease systolic blood pressure in ageing SHR, as also shown in l-NAME-treated WKY rats [20] and rats overexpressing the mouse renin gene [38] but in contrast to previous results in SHRs [20]. This may be age-related as decreased blood pressures were reported for rosuvastatin [20] and lovastatin [39] in 20-week-old SHRs. Further, rosuvastatin did not alter the action potential prolongation in ageing SHR hearts, the most common electrophysiological feature of the failing heart [40] which predisposes to dysrhythmias [41]. Compounds that improve survival in heart failure, such as the angiotensin II receptor blockers, ameliorated these electrophysiological changes in old SHRs [42].

Rosuvastatin lowered total plasma cholesterol concentrations in the ageing SHRs without changing low-density lipoprotein or high-density lipoprotein cholesterol concentrations. This suggests changes in other lipoprotein fractions, such as the very low or intermediate density lipoproteins, which were not measured in this study. As low-density lipoprotein and high-density lipoprotein concentrations were not changed by treatment, it seems unlikely that changes in total cholesterol concentrations are central to the attenuation of heart failure in the ageing SHR by rosuvastatin, but this cannot be ruled out.

The current study demonstrates that chronic rosuvastatin therapy during the transition from a compensated state to that of decompensation and failure attenuated both structural and functional deterioration of the heart in the SHR model of heart failure. Furthermore, these actions of rosuvastatin occurred together with decreases in collagen deposition but without changes in blood pressure, low-density lipoprotein or high-density lipoprotein cholesterol concentrations or action potential prolongation, suggesting that prevention of excessive collagen deposition plays an important role in delaying heart failure.

Acknowledgements

  We thank the sonographers of The Prince Charles Hospital, Ms Cathy West, Ms Katrine Quinn, Mr Chris Thomas and Mr Joe O’Sullivan and the manager of the Biological Research Facilities at The Prince Charles Hospital, Dr Kathleen Wilson, who assisted in monitoring rats during this procedure. This study was supported in part by a grant and drug from AstraZeneca, Macclesfield, Cheshire, UK.

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