Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “pressure overload”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 91 records · Page 5Linked to original sources
PubMed1977

Recuperative potential of cardiac muscle following relief of pressure overload hypertrophy and right ventricular failure in the cat.

This study examined the recuperative potential of cat hearts subjected to experimental right ventricular pressure overload (for a 10- to 14-day period) which provoked hypertrophy with and without congestive heart failure. Five groups of cats were studied: normal controls; one group with 70% pulmonary artery constriction which produced right ventricular hypertrophy (RVH); one group with an 87% constriction which also produced right ventricular hypertrophy but with congestive heart failure (CHF); and two groups which had been similarly subjected to pressure overload but which had been allowed a recovery period of 30 days after relief of the pressure overload. Both the 70% and 87% pulmonic constrictions were associated with extensive right ventricular hypertrophy, depression of myocardial contractile function, and severe redlction of cardiac norepinephrine stores (normal, 1.42 mug/g: RVH, 0.11 mug/g; CHF, 0.01 mug/g). After a 30-day period of relief from the pulmonic constriction normal hemodynamic function returned. In cats in which RVH had been relieved, right ventricular weight and contractile function were normal but catecholamine depletion persisted. Cats with relieved CHF showed depressed contractile function and depleted myocardial norepinephrine, and the right ventricular weight did not return to normal. Cardiac muscle of all pressure-overloaded nonrelieved hearts showed depressed velocity of shortening and depressed ability to sustain load. Cats with RVH alone regained normal muscle shortening velocity and load-bearing ability after relief. However, cardiac muscle from the CHF-relieved group recovered only unloaded shortening velocity while the ability to sustain load remained depressed. We conclude that the recuperative potential of myocardium damaged by pressure overload is adequate provided congestive heart failure has not occurred. Heart failure produces a persistent reduction in force-generating ability of the myocardium. Hypertrophy due to pressure overload, with or without CHF, leads to cardiac catecholamine depletion which is not readily reversed by relief of the overload.

Animals↗
PubMed2004

Effect of crocetin on cardiac hypertrophy induced by overloading pressure in rats.

AIM: To study the influence of crocetin on cardiac hypertrophy induced by overloading pressure in rats. METHODS: The model of cardiac hypertrophy was produced by overloading pressure in rats. The animals were divided into five groups: sham-operation group (0.5% CMC-Na, ig), model group (operation + 0.5% CMC-Na, ig), captopril group (operation + 50 mg x kg(-1), ig), crocetin I (100 mg x kg(-1), ig) and crocetin II (50 mg x kg(-1), ig). All animals were treated for 30 d by ig. Then, cardiac indexes were examined. The activity of ATPase and the hydroxyproline content in heart were assayed by colorimetric analysis. Matrix metalloproteinases (MMPs) activity was assayed by SDS-PAGE zymography. RESULTS: Compared with the model group, crocetin was found to significantly reduce the cardiac indexes and the content of hydroxyproline in heart, increase the activity of Na+ , K+ -ATPase, Ca2+, Mg2+ -ATPase and inhibit MMPs activity. CONCLUSION: The activity of MMPs may play a key role in the cardiac hypertrophy induced by overloading pressure, and proprably as a result of decreasing the activity of MMPs. Crocetin was shown to prevent remodeling of cardiac hypertrophy induced by overloading pressure.

Animals↗
PubMed2005

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.

Acute Disease↗
PubMed2002

Genetic alterations that inhibit in vivo pressure-overload hypertrophy prevent cardiac dysfunction despite increased wall stress.

BACKGROUND: A long-standing hypothesis has been that hypertrophy is compensatory and by normalizing wall stress acts to maintain normal cardiac function. Epidemiological data, however, have shown that cardiac hypertrophy is associated with increased mortality, thus casting doubt on the validity of this hypothesis. METHODS AND RESULTS: To determine whether cardiac hypertrophy is necessary to preserve cardiac function, we used 2 genetically altered mouse models that have an attenuated hypertrophic response to 8 weeks of pressure overload. End-systolic wall stress (sigma(es)) obtained by sonomicrometry after 1 week of pressure overload showed complete normalization of sigma(es) in pressure-overloaded wild-type mice (287+/-39 versus sham, 254+/-34 g/cm2), whereas the blunted hypertrophic response in the transgenic mice was inadequate to normalize sigma(es) (415+/-81 g/cm2, P<0.05). Remarkably, despite inadequate normalization of sigma(es), cardiac function as measured by serial echocardiography showed little deterioration in either of the pressure-overloaded genetic models with blunted hypertrophy. In contrast, wild-type mice with similar pressure overload showed a significant increase in chamber dimensions and progressive deterioration in cardiac function. Analysis of downstream signaling pathways in the late stages of pressure overload suggests that phosphoinositide 3-kinase may play a pivotal role in the transition from hypertrophy to heart failure. CONCLUSIONS: These data suggest that under conditions of pressure overload, the development of cardiac hypertrophy and normalization of wall stress may not be necessary to preserve cardiac function, as previously hypothesized.

Adenylyl Cyclases↗
PubMed1997

Role of angiotensin II in activation of the JAK/STAT pathway induced by acute pressure overload in the rat heart.

This study was designed to determine whether the JAK/STAT (indicating just another kinase/signal transducer and activator of transcription) pathway is activated in cardiac hypertrophy induced in vivo by pressure overload in rats and to demonstrate whether angiotensin II is involved in the activation of the JAK/STAT pathway. Acute pressure overload was produced by constricting the abdominal aorta of Wistar rats. Immunoprecipitation-Western blot analysis revealed that pressure overload activated JAK1, JAK2, and Tyk2 as early as 5 minutes and that STAT1, STAT2, and STAT3 were tyrosine-phosphorylated rapidly after exposure to the pressure overload. Phosphorylation of STAT1 and STAT2 peaked in the early stage at 5 to 15 minutes, whereas that of STAT3 peaked in the late stage at 60 minutes. Gel mobility shift of the interferon gamma activation site/interferon alpha-stimulating response element was observed immediately after the aortic banding, whereas the band of sis-inducing element was shifted in the late stage at 60 minutes. Both cilazapril (angiotensin II-converting enzyme inhibitor) and E4177 (angiotensin II type 1 [AT1] receptor antagonist) significantly suppressed the phosphorylation of Tyk2 and partially inhibited the phosphorylation of JAK2, but neither affected JAK1. Coimmunoprecipitation of the AT1 receptor with JAK2 or Tyk2 was clearly observed at 5 minutes and peaked at 15 minutes (20-fold the control value). These results indicate that the JAK/STAT pathway is activated by acute pressure overload in rats and that angiotensin II is involved in activating Tyk2, and partially activating JAK2, via the AT1 receptor. Both angiotensin II-dependent and -independent pathways take part in activating the JAK/STAT pathway in the pressure-overloaded rat heart.

Acute Disease↗
PubMed2005

Cardiac-specific attenuation of natriuretic peptide A receptor activity accentuates adverse cardiac remodeling and mortality in response to pressure overload.

Atrial (ANP) and brain (BNP) natriuretic peptides are hormones of myocardial cell origin. These hormones bind to the natriuretic peptide A receptor (NPRA) throughout the body, stimulating cGMP production and playing a key role in blood pressure control. Because NPRA receptors are present on cardiomyocytes, we hypothesized that natriuretic peptides may have direct autocrine or paracrine effects on cardiomyocytes or adjacent cardiac cells. Because both natriuretic peptides and NPRA gene expression are upregulated in states of pressure overload, we speculated that the effects of the natriuretic peptides on cardiac structure and function would be most apparent after pressure overload. To attenuate cardiomyocyte NPRA activity, transgenic mice with cardiac specific expression of a dominant-negative (DN-NPRA) mutation (HCAT D 893A) in the NPRA receptor were created. Cardiac structure and function were assessed (avertin anesthesia) in the absence and presence of pressure overload produced by suprarenal aortic banding. In the absence of pressure overload, basal and BNP-stimulated guanylyl cyclase activity assessed in cardiac membrane fractions was reduced. However, systolic blood pressure, myocardial cGMP, log plasma ANP levels, and ventricular structure and function were similar in wild-type (WT-NPRA) and DN-NPRA mice. In the presence of pressure overload, myocardial cGMP levels were reduced, and ventricular hypertrophy, fibrosis, filling pressures, and mortality were increased in DN-NPRA compared with WT-NPRA mice. In addition to their hormonal effects, endogenous natriuretic peptides exert physiologically relevant autocrine and paracrine effects via cardiomyocyte NPRA receptors to modulate cardiac hypertrophy and fibrosis in response to pressure overload.

Animals↗
PubMed2002

ECG determinants in adult patients with chronic right ventricular pressure overload caused by congenital heart disease: relation with plasma neurohormones and MRI parameters.

OBJECTIVE: To examine retrospectively the changes in ECG parameters over time and their correlation with other quantitative right ventricular (RV) function parameters in patients with chronic RV pressure overload caused by congenital heart disease. METHODS: 48 patients with chronic RV pressure overload caused by the following congenital heart diseases were studied: nine with congenitally corrected transposition of the great arteries (TGA), 12 with surgically corrected TGA, and 27 with a subpulmonary pressure overloaded RV. QRS duration and dispersion were measured manually from standard ECG recorded twice within five years. RV end diastolic volume (EDV) and RV mass were determined by magnetic resonance imaging. Brain natriuretic peptide (BNP) plasma concentrations were measured. RESULTS: QRS duration and QRS dispersion increased in all patient groups during the follow up period. QRS duration increased significantly in the congenitally corrected TGA (p = 0.04) and the subpulmonary pressure overloaded RV groups (p = 0.01). QRS dispersion increased significantly in patients with surgically corrected TGA (p = 0.03) and in the subpulmonary pressure overloaded RV group (p = 0.02). A significant correlation was found between QRS duration and RVEDV (r = 0.71, p < 0.0001). RV mass was significantly correlated with QRS duration in patients with tetralogy of Fallot (r = 0.67, p = 0.01). Mean (SD) plasma brain natriuretic peptide concentrations (6.6 (5.4) pmol/l) were increased compared with normal reference values but no correlation was found with ECG parameters or RV systolic pressure. No malignant arrhythmia or sudden death occurred. CONCLUSIONS: ECG parameters worsened gradually in asymptomatic or minimally symptomatic patients with chronic RV pressure overload, regardless of the nature of their congenital heart disease. In all patients, a significant positive correlation was found between QRS duration and RVEDV. In patients with tetralogy of Fallot there was also a correlation between QRS duration and RV mass.

Adult↗
PubMed1999

Cyclosporine attenuates pressure-overload hypertrophy in mice while enhancing susceptibility to decompensation and heart failure.

Left ventricular hypertrophy (LVH) is a compensatory mechanism to cope with pressure overload. Recently, a calcineurin pathway mediating LVH and its prevention by cyclosporine was reported. We examined whether calcineurin mediates LVH due to pressure overload in mice. Pressure overload was induced by aortic banding in 53 mice (32 treated with cyclosporine [25 mg. kg-1. d-1], 21 treated with vehicle). There were 17 sham-operated mice (9 treated with vehicle, 8 treated with cyclosporine). At 3 weeks after surgery, LV weight to body weight was greater in the nontreatment banded group (4.39+/-0. 16 mg/g) than in the cyclosporine-treated banded group (3.95+/-0.14 mg/g, P<0.05), with both groups being greater compared with the entire group of sham-operated mice (3.02+/-0.04 mg/g). The pressure gradient between the ascending and abdominal aorta was not different between the cyclosporine-treated (49.6+/-6.1 mm Hg) and nontreatment groups (48.7+/-4.6 mm Hg). Although LV systolic pressure was lower in the cyclosporine-treated banded animals, LV systolic wall stress was similar in the nontreatment banded group and in the cyclosporine-treated group. However, LV dP/dt was lower (P=0.05) in the cyclosporine-treated banded group (4774+/-656 mm Hg/s) than in the nontreatment banded group (6604+/-516 mm Hg/s). During the protocol, 23 of 32 mice in the cyclosporine-treated group and 9 of 21 mice in the nontreatment group died. All deaths occurred within 10 days after surgery. Deaths caused by heart failure were 7.2-fold higher (P<0.05) in the cyclosporine-treated group, whereas deaths due to other causes were not different between the 2 groups. In addition, LV function of mice was assessed at 48 hours after banding; LV ejection fraction measured with echocardiography was lower (P<0.05) in the cyclosporine-treated banded group (66+/-3.0%) than in the nontreatment banded group (79+/-1.5%), whereas LV systolic wall stresses were similar. Calcineurin phosphatase activity was depressed similarly in both cyclosporine-treated groups compared with both nontreatment groups. Thus, cyclosporine could attenuate, but not prevent, LVH at the expense of inhibiting an important compensatory mechanism in response to pressure overload, resulting in reduced LV wall stress and function and increased susceptibility to decompensation and heart failure.

Animals↗
PubMed2004

Brief pressure overload of the left ventricle preconditions rabbit myocardium against infarction.

BACKGROUND: Several nonischemic stimuli have been shown to precondition myocardium. We investigated cardioprotective effects and underlying mechanisms of brief pressure overload of the left ventricle in this study. METHODS: Brief pressure overload of the left ventricle was achieved by two 10-minute partial snaring of the ascending aorta so that systolic left ventricular pressure was raised 50% above the baseline value. Ischemic preconditioning was elicited by two 10-minute coronary artery occlusions. Ten minutes after different pretreatments, myocardial infarction was induced by a 60-minute coronary artery occlusion followed by 3-hour reperfusion. Area at risk and myocardial infarct was determined by blue dye injection and triphenyl tetrazolium chloride staining. RESULTS: The myocardial infarct size, expressed as percentage of area at risk, was significantly reduced in the pressure overload group (15.9% +/- 2.9%, p < 0.001, n = 9) as well as in the ischemic preconditioning group (14.9% +/- 1.9%, p < 0.001, n = 9) versus the control group (30.0% +/- 6.9%, n = 10). Pretreatment with a blocker of stretch-activated ion channels (gadolinium, 40 micromol/kg, intravenous) abolished the protection induced by pressure overload and ischemic preconditioning. Gadolinium itself did not alter the extent of infarct. There was no significant difference in hemodynamics, area at risk, and mortality among all groups of animals. CONCLUSIONS: Brief pressure overload of the left ventricle by partial snaring of the ascending aorta preconditioned rabbit myocardium against infarction. The underlying mechanism might be related to activation of stretch-activated ion channels.

Animals↗
PubMed1997

Age dependency of left ventricular diastolic function in pressure overload hypertrophy.

OBJECTIVES: We sought to evaluate whether age is a determinant of left ventricular (LV) pressure overload hypertrophy and whether diastolic function influenced the aging process. BACKGROUND: The adaptation of the left ventricle to chronic pressure overload is a complex process of hormonal, structural and hemodynamic factors. Different responses in the elderly patients have been described. METHODS: LV biplane cineangiography, micromanometry and endomyocardial biopsies were carried out in 57 patients with pure or predominant aortic stenosis. Patients were classified into a senior (< 60 years, mean age +/- SD 46 +/- 10 years, n = 35) and an elderly (< 65 years; mean age 70 +/- 4 years, n = 22) study group. LV systolic function was evaluated from biplane ejection fraction and midwall fractional shortening, whereas diastolic function was assessed from the time constant of LV pressure decay, peak filling rate and the constant of myocardial stiffness. Biopsy samples were examined morphometrically for interstitial fibrosis, fibrous content, muscle fiber diameter and volume fraction of myofibrils. RESULTS: Gender distribution and the severity of aortic stenosis were comparable in the two patient groups. LV peak systolic and end-diastolic pressures were significantly higher in the elderly than in the senior group. LV ejection fraction and midwall fractional shortening were comparable in the two groups. The time constant of relaxation and the myocardial stiffness constant were greater in the elderly than in the senior group whereas the early peak filling rate was significantly reduced in the elderly group. Interstitial fibrosis was increased, although not significantly (p < 0.06), and fibrous content was enhanced (p < 0.001) in elderly patients with respect to the senior group. There was a linear correlation between age and myocardial stiffness (r = 0.55), p < 0.0001) and an inverse relation between age and early peak filling rate (r = 0.52, p < 0.0001). CONCLUSIONS: In the presence of a comparable degree of aortic valve stenosis, elderly patients (> 65 years) present with more severe LV hypertrophy than do senior patients (< 60 years). Therefore elderly patients have a more pronounced impairment of LV diastolic function, whereas systolic function is preserved. Thus, there is an age dependency of LV pressure overload hypertrophy that can be explained by the longer duration of pressure overload or an exhaustion of the adaptation process in the elderly.

Adaptation, Physiological↗
PubMed1982

Altered myosin isozyme patterns from pressure-overloaded and thyrotoxic hypertrophied rabbit hearts.

Cardiac hypertrophy, induced by pressure overload, leads to a depression in the rate of force development, velocity of shortening, tension-dependent heat generation, and myosin ATPase activity, whereas cardiac hypertrophy, induced by thyroxine administration, leads to an increase in these parameters. These changes have been attributed, in part, to structural changes in myosin. In this study, we have investigated changes in the relative content of myosin isozymes and differences in primary structure of the isozymes in pressure-overloaded and thyrotoxic cardiac hypertrophy in the rabbit. Three myosin isozymic forms (V1 = fastest, V2 = intermediate, V3 = slowest mobility) were observed in pyrophosphate polyacrylamide gels from normal hearts with the V3 component being the predominant species. In the pressure-overloaded model, the V1 and V2 components disappeared or were present in reduced amounts leaving the V3 more predominant. The most striking difference was the isozymic profile produced in thyrotoxic hearts where the V1 became the predominant component and V2 and V3 the minor components. alpha-Chymotryptic digestion of myosin heavy chains produced characteristic, reproducible peptide patterns for each of the animal models, as did fluorographic analyses of alpha-chymotryptic digests of 14C-iodoacetamide (IAA)-labeled SH1 peptides of myosin. Our results suggest that altered proportions of myosin isozymes may be responsible for altered cardiac performance.

Adenosine Triphosphatases↗
PubMed1980

Myocardial blood flow and capillary density in chronic pressure overload of the feline left ventricle.

The effects of chronic pressure overload hypertrophy on myocardial blood flow and capillary density was measured in the feline left ventricle. Myocardial hypertrophy was produced by and 84% banding constriction of the ascending aorta 2.8 +/- 1.2 months before the experiments. In seven cats with aortic constriction, cardiac hypertrophy produced a 40% increase in left ventricular mass. Seven cats served as normals. Our findings show that, in chronic pressure overload hypertrophy, coronary blood flow at control (resting) levels is increased compared with normals. In both normal and hypertrophy cats endocardial/epicardial flow ratios were equal at the control level. In the hypertrophied hearts, coronary reserve, measured as the percentage increase in myocardial blood flow from control to near maximal flow during adenosine infusion, was reduced. In the hypertrophy group a shift in the transmural distribution of blood flow in the left ventricle was noticed, as indicated by a reduced endo/epi flow ratio, during adenosine infusion. A decreased capillary density in hypertrophy, most marked in endocardial tissue regions, was demonstrated by this study. These findings indicate that capillary growth does not parallel myofibre growth in the endocardium of pressure overload hypertrophied left ventricles. The resultant anatomical imbalance causes a compromise of flow reserve in the endocardium, making this region vulnerable to ischaemia.

Adenosine↗
PubMed2005

Sympathectomy or doxazosin, but not propranolol, blunt myocardial interstitial fibrosis in pressure-overload hypertrophy.

The adaptive changes that develop in the pressure-overloaded left ventricular (LV) myocardium include cardiomyocyte hypertrophy and interstitial fibrosis. Although the former is known to depend to a sizeable extent on sympathetic (over)activity, little information exists whether the same applies to the latter, ie, whether excess catecholamine exposure contributes to the imbalance between collagen deposition by fibroblasts and degradation by matrix metalloproteases (MMPs), eventually leading to LV collagen accumulation. Sprague-Dawley rats were subjected to abdominal aortic banding (B) or sham operation (S) and treated with beta-blockade (Bb, oral propranolol, 40 mg/kg per day), chemical sympathectomy (Sx, 6-hydroxydopamine, 150 mg/kg intraperitoneal twice per week) or vehicle (Vh). Ten weeks later, systolic blood pressure, LV weight, collagen abundance (computer-aided histology), zymographic matrix metalloproteinase (MMP)-2 activity and its specific tissue inhibitor concentration (TIMP-2) were measured. Both sympathectomy and beta-blockade failed to attenuate the banding-induced blood pressure elevation but significantly attenuated the attendant LV hypertrophy. As expected, pressure-overload hypertrophy was associated with interstitial fibrosis (collagen: 4.37+/-1.23% BVh versus 1.23+/-0.44% SVh, P<0.05), which was abolished by sympathectomy (2.55+/-1.31%, P=not significant versus SSx) but left unchanged by beta-blockade (4.11+/-1.23%, P<0.05 versus both SBb and BSx). beta-blockade, but not sympathectomy, was also associated with an increased TIMP-2/MMP-2 ratio (P<0.05), indicating reduced interstitial collagenolytic activity. In separate groups of banded and sham-operated rats, treatment with the alpha-receptor blocker doxazosin (10 mg/kg per day) displayed similar antifibrotic and biochemical effects as sympathectomy. Thus in the course of experimental pressure overload, the sympathetic nervous system plays a major pro-fibrotic role, which is mediated via alpha-adrenergic but not beta-adrenergic receptors.

Adrenergic alpha-Antagonists↗
PubMed2006

Pressure overload induces greater hypertrophy and mortality in female mice with p38alpha MAPK inhibition.

We examined pressure overload left ventricular (LV) hypertrophy (H) induced by aortic banding in transgenic mice with cardiac-specific expression of a dominant negative (DN) p38alpha (TG) and wild type controls (WT). In response to chronic pressure overload, induced by aortic constriction, LV/BW increased more, p<0.05, in female TG (6.4+/-0.2, n=7) than in WT female (5.1+/-0.2, n=10), or male TG or WT (5.0+/-0.2, n=10 vs. 5.5+/-0.2, n=8). Lung/BW, an index of LV decompensation, was significantly higher, p<0.05, in banded female TG (14+/-1.2 mg/g) than in WT females (9.0+/-0.8), or male TG or WT (8.2+/-0.7 vs. 9.3+/-1.3). This was associated with higher premature mortality, p<0.05, in banded female TG mice (42%) compared with banded WT females (10%), TG males (13%), or WT males (17%). In male, but not female, TG mice, the number of TUNEL-positive cells was smaller, p<0.05, compared with WT. Phospho-Akt kinase activity increased (p<0.05) in female TG after banding, but not in males. After ovariectomy, chronic pressure overload no longer induced greater mortality, greater LVH, or p-Akt levels in female TG mice, and like male TG mice, apoptosis was protected. DN-p38alpha enhanced estrogen-induced activation of Akt in cultured cardiac myocytes. Thus, inhibition of p38alpha MAPK paradoxically augments LVH resulting in cardiac decompensation and increased mortality in response to pressure overload more in female mice than male mice, which could be due to increased Akt activation and/or through cross-talk between p38alpha MAPK and Akt.

Animals↗
PubMed2002

Transforming growth factor-beta function blocking prevents myocardial fibrosis and diastolic dysfunction in pressure-overloaded rats.

BACKGROUND: Excessive myocardial fibrosis impairs cardiac function in hypertensive hearts. Roles of transforming growth factor (TGF)-beta in myocardial remodeling and cardiac dysfunction were examined in pressure-overloaded rats. METHODS AND RESULTS: Pressure overload was induced by a suprarenal aortic constriction in Wistar rats. Fibroblast activation (proliferation and phenotype transition to myofibroblasts) was observed after day 3 and peaked at days 3 to 7. Thereafter, myocyte hypertrophy and myocardial fibrosis developed by day 28. At day 28, echocardiography showed normal left ventricular fractional shortening, but the decreased ratio of early to late filling velocity of the transmitral Doppler velocity and hemodynamic measurement revealed left ventricular end-diastolic pressure elevation, indicating normal systolic but abnormal diastolic function. Myocardial TGF-beta mRNA expression was induced after day 3, peaked at day 7, and remained modestly increased at day 28. An anti-TGF-beta neutralizing antibody, which was administered intraperitoneally daily from 1 day before operation, inhibited fibroblast activation and subsequently prevented collagen mRNA induction and myocardial fibrosis, but not myocyte hypertrophy. Neutralizing antibody reversed diastolic dysfunction without affecting blood pressure and systolic function. CONCLUSIONS: TGF-beta plays a causal role in myocardial fibrosis and diastolic dysfunction through fibroblast activation in pressure-overloaded hearts. Our findings may provide an insight into a new therapeutic strategy to prevent myocardial fibrosis and diastolic dysfunction in pressure-overloaded hearts.

Animals↗
PubMed2006

Inhibition of Jak2 phosphorylation attenuates pressure overload cardiac hypertrophy.

RATIONALE: We examined the role of Jak2 kinase phosphorylation in the development of pressure overload hypertrophy in mice subjected to transverse aortic constriction (TAC) and treated with tyrphostin AG490, a pharmacological inhibitor of Jak2. METHODS: Control mice (sham), subjected to TAC for 15 days (TAC) or to TAC and treated with 48 microg/kg/day i.p. of tyrphostin AG490 (TAC+AG490) were evaluated for morphological, physiological, and molecular changes associated with pressure overload hypertrophy. RESULTS: Mice subjected to TAC alone developed concentric hypertrophy that accompanied activation of the components of the Jak/STAT signaling pathway manifested by an increase in phosphorylation of Jak2 and STAT3. We also observed increased phosphorylation of MAPK p44/p42, p38 MAPK and JNK in the TAC group, as well as, an increase in expression of MKP-1 phosphatase which negatively regulates MAPK kinases. Treatment of aortic constricted mice with tyrphostin AG490 failed to develop hypertrophy and showed a marked reduction in phosphorylation of Jak2 and STAT3. There was, however, in TAC and AG490 treated mice, a notable increase in the phosphorylation state of the MAPK p44/42, whereas MKP-1 phosphatase was downregulated. CONCLUSION: These findings suggest that Jak2 kinase plays an important role in left ventricular remodeling during pressure overload hypertrophy. Pharmacological inhibition of Jak2 kinase during pressure overload blocks the development of concentric hypertrophy.

Actins↗
PubMed1988

Right ventricular hypertrophy long after reversal of severe pressure overload in cats.

To test the hypothesis that alterations in ventricular size and function may persist long after reversal of a severe pressure overload, right ventricular (RV) hypertrophy was produced in cats by abrupt, severe constriction of the pulmonary artery (PA) for 8 wk, after which pressure overload was completely reversed by surgical removal of the PA band (group III). Despite debanding and recovery from pressure overload (RV peak systolic pressure = 22 +/- 4 vs. 66 +/- 20 mmHg before debanding and 25 +/- 4 mmHg in controls), parameters of hypertrophy 8-10 mo later remained substantially increased: e.g., RV/LV (left ventricular) mass ratio was 0.36 +/- 0.06 in group III vs. 0.24 +/- 0.03 in controls (group I) and 0.43 +/- 0.07 in a separate cohort (group II) studied after 8 wk of banding. Maximum RV stroke work during volume loading was computed from RV micromanometry and PA electromagnetic flow: 20 +/- 8 g-cm/g for group III vs. 51 +/- 14 for group I, P less than 0.05, and 21 +/- 7 for group II. Thus severe pressure overload of the RV may produce changes in size and function that are not fully reversed by complete removal of the overload.

Animals↗
PubMed1997

Etomoxir improves left ventricular performance of pressure-overloaded rat heart.

BACKGROUND: Numerous studies have demonstrated diverse abnormalities in subcellular structures of pressure-overloaded hypertrophied and failing heart. Long-term administration of etomoxir, a carnitine palmitoyltransferase-1 inhibitor, partially normalized the proportion of myosin isozyme V1 and number of active Ca2+ pumps in hypertrophied rat myocardium. METHODS AND RESULTS: To test the hypothesis that long-term etomoxir treatment improves the performance of hypertrophied ventricle, sham-operated rats and rats with ascending aorta constriction were treated with racemic etomoxir (15 mg/kg per day) for 12 weeks. Left ventricular geometry, dynamics of isovolumic contractions, as well as myosin isozymes as marker of etomoxir-induced phenotype changes were assessed. Etomoxir stimulated (P<.05) slight hypertrophic growth in right and left ventricles of sham-operated rats as well as in right ventricles but not in overloaded left ventricles of rats with aortic constriction. In all treated rats, etomoxir increased (P<.05) maximal developed pressure, left ventricular pressure-volume area, and +/- dP/dt(max). Enhanced values (P<.05) of derived indexes of myocardial performance (normalized stress-length area, maximal rate of wall stress rise, and decline) indicated that myocardial changes were responsible for the improved performance. The etomoxir treatment increased selectively (P<.05) the proportion of myosin V1 in pressure-overloaded left ventricles. CONCLUSIONS: The long-term treatment with etomoxir improved functional capacity of pressure-overloaded left ventricle, which can be attributed to an enhanced myocardial performance. Chronic carnitine palmitoyltransferase-1 inhibition may thus represent a candidate approach for developing novel agents that are useful in the prevention of undesirable consequences of pressure overload-induced cardiac hypertrophy.

Animals↗