Genetic Deletion of Galectin-3 Alters the Temporal Evolution of Macrophage Infiltration and Healing Affecting the Cardiac Remodeling and Function after Myocardial Infarction in Mice.

We studied the role of galectin-3 (Gal-3) in the expression of alternative activation markers (M2) on macrophage, cytokines, and fibrosis through the temporal evolution of healing, ventricular remodeling, and function after myocardial infarction (MI). C57BL/6J and Gal-3 knockout mice (Lgals3-/-) were subjected to permanent coronary ligation or sham. We studied i) mortality, ii) macrophage infiltration and expression of markers of alternative activation, iii) cytokine, iv) matrix metalloproteinase-2 activity, v) fibrosis, and vi) cardiac function and remodeling. At 1 week post-MI, lack of Gal-3 markedly attenuated F4/80+ macrophage infiltration and significantly increased the expression of Mrc1 and Chil1, markers of M2 macrophages at the MI zone. Levels of IL-10, IL-6, and matrix metalloproteinase-2 were significantly increased, whereas tumor necrosis factor-α, transforming growth factor-ß, and fibrosis were remarkably attenuated at the infarct zone. In Gal-3 knockout mice, scar thinning ratio, expansion, and cardiac remodeling and function were severely affected from the onset of MI. At 4 weeks post-MI, the natural evolution of fibrosis in Gal-3 knockout mice was also affected. Our results suggest that Gal-3 is essential for wound healing because it regulates the dynamics of macrophage infiltration, proinflammatory and anti-inflammatory cytokine expression, and fibrosis along the temporal evolution of MI in mice. The deficit of Gal-3 affected the dynamics of wound healing, thus aggravating the evolution of remodeling and function.

Galectin-1 as an Emerging Mediator of Cardiovascular Inflammation: Mechanisms and Therapeutic Opportunities.

Galectin-1 (Gal-1), an evolutionarily conserved ß-galactoside-binding lectin, controls immune cell homeostasis and tempers acute and chronic inflammation by blunting proinflammatory cytokine synthesis, engaging T-cell apoptotic programs, promoting expansion of T regulatory (Treg) cells, and deactivating antigen-presenting cells. In addition, this lectin promotes angiogenesis by co-opting the vascular endothelial growth factor receptor (VEGFR) 2 signaling pathway. Since a coordinated network of immunomodulatory and proangiogenic mediators controls cardiac homeostasis, this lectin has been proposed to play a key hierarchical role in cardiac pathophysiology via glycan-dependent regulation of inflammatory responses. Here, we discuss the emerging roles of Gal-1 in cardiovascular diseases including acute myocardial infarction, heart failure, Chagas cardiomyopathy, pulmonary hypertension, and ischemic stroke, highlighting underlying anti-inflammatory mechanisms and therapeutic opportunities. Whereas Gal-1 administration emerges as a potential novel treatment option in acute myocardial infarction and ischemic stroke, Gal-1 blockade may contribute to attenuate pulmonary arterial hypertension.

Cardiac-deleterious role of galectin-3 in chronic angiotensin II-induced hypertension.

Galectin-3 (Gal-3), a member of the ß-galactoside lectin family, has an important role in immune regulation. In hypertensive rats and heart failure patients, Gal-3 is considered a marker for an unfavorable prognosis. Nevertheless, the role and mechanism of Gal-3 action in hypertension-induced target organ damage are unknown. We hypothesized that, in angiotensin II (ANG II)-induced hypertension, genetic deletion of Gal-3 prevents left ventricular (LV) adverse remodeling and LV dysfunction by reducing the innate immune responses and myocardial fibrosis. To induce hypertension, male C57BL/6J and Gal-3 knockout (KO) mice were infused with ANG II (3 µg·min-1·kg-1 sc) for 8 wk. We assessed: 1) systolic blood pressure by plethysmography, 2) LV function and remodeling by echocardiography, 3) myocardial fibrosis by histology, 4) cardiac CD68+ macrophage infiltration by histology, 5) ICAM-1 and VCAM-1 expression by Western blotting, 6) plasma cytokines, including interleukin-6 (IL-6), by enzyme-linked immunosorbent assay, and 7) regulatory T (Treg) cells by flow cytometry as detected by their combined expression of CD4, CD25, and FOXP3. Systolic blood pressure and cardiac hypertrophy increased similarly in both mouse strains when infused with ANG II. However, hypertensive C57BL/6J mice suffered impaired ejection and shortening fractions. In these mice, the extent of myocardial fibrosis and macrophage infiltration was greater in histological sections, and cardiac ICAM-1, as well as plasma IL-6, expression was higher as assessed by Western blotting. However, all these parameters were blunted in Gal-3 KO mice. Hypertensive Gal-3 KO mice also had a higher number of splenic Treg lymphocytes. In conclusion, in ANG II-induced hypertension, genetic deletion of Gal-3 prevented LV dysfunction without affecting blood pressure or LV hypertrophy. This study indicates that the ANG II effects are, in part, mediated or triggered by Gal-3 together with the related intercellular signaling (ICAM-1 and IL-6), leading to cardiac inflammation and fibrosis.

Galectin-1 controls cardiac inflammation and ventricular remodeling during acute myocardial infarction.

Galectin-1 (Gal-1), an evolutionarily conserved ß-galactoside-binding lectin, plays essential roles in the control of inflammation and neovascularization. Although identified as a major component of the contractile apparatus of cardiomyocytes, the potential role of Gal-1 in modulating heart pathophysiology is uncertain. Here, we aimed to characterize Gal-1 expression and function in the infarcted heart. Expression of Gal-1 was substantially increased in the mouse heart 7 days after acute myocardial infarction (AMI) and in hearts from patients with end-stage chronic heart failure. This lectin was localized mainly in cardiomyocytes and inflammatory infiltrates in peri-infarct areas, but not in remote areas. Both simulated hypoxia and proinflammatory cytokines selectively up-regulated Gal-1 expression in mouse cardiomyocytes, whereas anti-inflammatory cytokines inhibited expression of this lectin or had no considerable effect. Compared with their wild-type counterpart, Gal-1-deficient (Lgals1(-/-)) mice showed enhanced cardiac inflammation, characterized by increased numbers of macrophages, natural killer cells, and total T cells, but reduced frequency of regulatory T cells, leading to impaired cardiac function at baseline and impaired ventricular remodeling 7 days after nonreperfused AMI. Treatment of mice with recombinant Gal-1 attenuated cardiac damage in reperfused AMI. Taken together, our results indicate a protective role for Gal-1 in normal cardiac homeostasis and postinfarction remodeling by preventing cardiac inflammation. Thus, Gal-1 treatment represents a potential novel strategy to attenuate heart failure in AMI.

N-acetyl-seryl-aspartyl-lysyl-proline reduces cardiac collagen cross-linking and inflammation in angiotensin II-induced hypertensive rats.

We have reported previously that Ac-SDKP (N-acetyl-seryl-aspartyl-lysyl-proline) reduces fibrosis and inflammation (in macrophages and mast cells). However, it is not known whether Ac-SDKP decreases collagen cross-linking and lymphocyte infiltration; lymphocytes modulate both collagen cross-linking and ECM (extracellular matrix) formation in hypertension. Thus we hypothesized that (i) in AngII (angiotensin II)-induced hypertension, Ac-SDKP prevents increases in cross-linked and total collagen by down-regulating LOX (lysyl oxidase), the enzyme responsible for cross-linking, and (ii) these effects are associated with decreased pro-fibrotic cytokine TGFß (transforming growth factor ß) and the pro-inflammatory transcription factor NF-κB (nuclear factor κB) and CD4+/CD8+ lymphocyte infiltration. We induced hypertension in rats by infusing AngII either alone or combined with Ac-SDKP for 3 weeks. Whereas Ac-SDKP failed to lower BP (blood pressure) or LV (left ventricular) hypertrophy, it did prevent AngII-induced increases in (i) cross-linked and total collagen, (ii) LOX mRNA expression and LOXL1 (LOX-like 1) protein, (iii) TGFß expression, (iv) nuclear translocation of NF-κB, (v) CD4+/CD8+ lymphocyte infiltration, and (vi) CD68+ macrophages infiltration. In addition, we found a positive correlation between CD4+ infiltration and LOXL1 expression. In conclusion, the effect of Ac-SDKP on collagen cross-linking and total collagen may be due to reduced TGFß1, LOXL1, and lymphocyte and macrophage infiltration, and its effect on inflammation could be due to lower NF-κB.

Unraveling the role of galectin-3 in cardiac pathology and physiology.

Galectin-3 (Gal-3) is a carbohydrate-binding protein with multiple functions. Gal-3 regulates cell growth, proliferation, and apoptosis by orchestrating cell-cell and cell-matrix interactions. It is implicated in the development and progression of cardiovascular disease, and its expression is increased in patients with heart failure. In atherosclerosis, Gal-3 promotes monocyte recruitment to the arterial wall boosting inflammation and atheroma. In acute myocardial infarction (AMI), the expression of Gal-3 increases in infarcted and remote zones from the beginning of AMI, and plays a critical role in macrophage infiltration, differentiation to M1 phenotype, inflammation and interstitial fibrosis through collagen synthesis. Genetic deficiency of Gal-3 delays wound healing, impairs cardiac remodeling and function after AMI. On the contrary, Gal-3 deficiency shows opposite results with improved remodeling and function in other cardiomyopathies and in hypertension. Pharmacologic inhibition with non-selective inhibitors is also protective in cardiac disease. Finally, we recently showed that Gal-3 participates in normal aging. However, genetic absence of Gal-3 in aged mice exacerbates pathological hypertrophy and increases fibrosis, as opposed to reduced fibrosis shown in cardiac disease. Despite some gaps in understanding its precise mechanisms of action, Gal-3 represents a potential therapeutic target for the treatment of cardiovascular diseases and the management of cardiac aging. In this review, we summarize the current knowledge regarding the role of Gal-3 in the pathophysiology of heart failure, atherosclerosis, hypertension, myocarditis, and ischemic heart disease. Furthermore, we describe the physiological role of Gal-3 in cardiac aging.

An Experimental Model of Myocardial Infarction for Studying Cardiac Repair and Remodeling in Knockout Mice.

Cardiovascular disease is the most prevalent cause of death in Western countries, with acute myocardial infarction (MI) being the most prevalent form. This paper describes a protocol for studying the role of galectin 3 (Gal-3) in the temporal evolution of cardiac healing and remodeling in an experimental animal model of MI. The procedures described include an experimental model of MI with a permanent coronary ligature in male C57BL/6J (control) and Gal-3 knockout (KO) mice, an echocardiography procedure to study cardiac remodeling and systolic function in vivo, a histological evaluation of interstitial myocardial fibrosis with picrosirius red-stained and rhodamine-conjugated lectin-stained sections for studying myocyte hypertrophy by the cross-sectional area (MCSA), and the quantification of infarct size and cardiac remodeling (scar thinning, septum thickness, and expansion index) by planimetry in slices stained with Masson's trichrome and triphenyl tetrazolium chloride. Gal-3 KO mice with MI showed disrupted cardiac remodeling and an increase in the scar thinning ratio and the expansion index. At the onset of MI, myocardial function and cardiac remodeling were also severely affected. At 4 weeks post MI, the natural evolution of fibrosis in infarcted Gal-3 KO mice was also affected. In summary, the experimental model of MI is a suitable model for studying the temporal evolution of cardiac repair and remodeling in mice with the genetic deletion of Gal-3 and other animal models. The lack of Gal-3 affects the dynamics of cardiac repair and disrupts the evolution of cardiac remodeling and function after MI.

Galectin-3 contributes to acute cardiac dysfunction and toxicity by increasing oxidative stress and fibrosis in doxorubicin-treated mice.

BACKGROUND: Doxorubicin (DOX) leads to cardiovascular toxicity through direct cardiomyocyte injury and inflammation. We aimed to study the role of Galectin-3 (Gal-3), a ß-galactosidase binding lectin associated with inflammation and fibrosis in DOX-induced acute cardiotoxicity in mice. METHODS: Male C57 and Gal-3 knockout (KO) mice were given a single dose of DOX (15 mg/kg, i.p) or placebo. Serum creatine phosphokinase (CPK), lactate dehydrogenase (LDH), aspartate aminotransferase (AST) and cardiac thiobarbituric acid-reactive substance (TBARS) were measured at 3 days to assess cardiac injury and oxidative stress. Cardiac remodeling and function were studied by echocardiography and catheterization at 7 days. Myocardial fibrosis was quantified in picrosirius red stained slices. RESULTS: Absence of Gal-3 tended to reduce the mortality after DOX. DOX significantly increased CPK, LDH, AST and TBARS while treated Gal-3 KO mice showed reduced injury and oxidative stress. After 7 days, adverse remodeling, fibrosis and dysfunction in treated-C57 mice were severely affected while those effects were prevented by absence of Gal-3. CONCLUSION: In summary, genetic deletion of Gal-3 prevented cardiac damage, adverse remodeling and dysfunction, associated with reduced cardiac oxidative stress and fibrosis. Understanding the contribution of GAL-3 to doxorubicin-induced cardiac toxicity reinforces its potential use as a therapeutic target in patients with several cancer types.

Treatment with N-acetyl-seryl-aspartyl-lysyl-proline prevents experimental autoimmune myocarditis in rats.

Myocarditis is commonly associated with cardiotropic infections and has been linked to development of autoimmunity. N-acetyl-seryl-aspartyl-lysyl-proline (Ac-SDKP) is a naturally occurring tetrapeptide that prevents inflammation and fibrosis in hypertension and other cardiovascular diseases; however, its effect on autoimmune-mediated cardiac diseases remains unknown. We studied the effects of Ac-SDKP in experimental autoimmune myocarditis (EAM), a model of T cell-mediated autoimmune disease. This study was conducted to test the hypothesis that Ac-SDKP prevents autoimmune myocardial injury by modulating the immune responses. Lewis rats were immunized with porcine cardiac myosin and treated with Ac-SDKP or vehicle. In EAM, Ac-SDKP prevented both systolic and diastolic cardiac dysfunction, remodeling as shown by hypertrophy and fibrosis, and cell-mediated immune responses without affecting myosin-specific autoantibodies or antigen-specific T cell responses. In addition, Ac-SDKP reduced cardiac infiltration by macrophages, dendritic cells, and T cells, pro-inflammatory cytokines [interleukin (IL)-1α, tumor necrosis factor-α, IL-2, IL-17] and chemokines (cytokine-induced neutrophil chemoattractant-1, interferon-γ-induced protein 10), cell adhesion molecules (intercellular adhesion molecule-1, L-selectin), and matrix metalloproteinases (MMP). Ac-SDKP prevents autoimmune cardiac dysfunction and remodeling without reducing the production of autoantibodies or T cell responses to cardiac myosin. The protective effects of Ac-SDKP in autoimmune myocardial injury are most likely mediated by inhibition of 1) innate and adaptive immune cell infiltration and 2) expression of proinflammatory mediators such as cytokines, chemokines, adhesion molecules, and MMPs.

The allometric model in chronic myocardial infarction.

BACKGROUND: An allometric relationship between different electrocardiogram (ECG) parameters and infarcted ventricular mass was assessed in a myocardial infarction (MI) model in New Zealand rabbits. METHODS: A total of fifteen animals were used, out of which ten underwent left anterior descending coronary artery ligation to induce infarction (7-35% area). Myocardial infarction (MI) evolved and stabilized during a three month-period, after which, rabbits were sacrificed and the injured area was histologically confirmed. Right before sacrifice, ECGs were obtained to correlate several of its parameters to the infarcted mass. The latter was normalized after combining data from planimetry measurements and heart weight. The following ECG parameters were studied: RR and PR intervals, P-wave duration (PD), QRS duration (QRSD) and amplitude (QRSA), Q-wave (QA), R-wave (RA) and S-wave (SA) amplitudes, T-wave peak amplitude (TA), the interval from the peak to the end of the T-wave (TPE), ST-segment deviation (STA), QT interval (QT), corrected QT and JT intervals. Corrected QT was analyzed with different correction formulae, i.e., Bazett (QTB), Framingham (QTFRA), Fridericia (QTFRI), Hodge (QTHO) and Matsunaga (QTMA) and compared thereafter. The former variables and infarcted ventricular mass were then fitted to the allometric equation in terms of deviation from normality, in turn derived after ECGs in 5 healthy rabbits. RESULTS: Six variables (JT, QTB, QA, SA, TA and STA) presented statistical differences among leads. QT showed the best allometric fit (r = 0.78), followed by TA (r = 0.77), STA (r = 0.75), QTFRA (r = 0.72), TPE (r = 0.69), QTFRI (r = 0.68) and QTMA (r = 0.68). Corrected QT's (QTFRA, QTFRI and QTMA) performed worse than the uncorrected counterpart (QT), the former scaling allometrically with similar goodness of fits. CONCLUSIONS: QT, TA, STA and TPE could possibly be used to assess infarction extent in an old MI event through the allometric model as a first approach. Moreover, the TPE also produced a good allometric scaling, leading to the potential existence of promising allometric indexes to diagnose malignant arrhythmias.

Angiotensin II-induced dilated cardiomyopathy in Balb/c but not C57BL/6J mice.

Balb/c mice, which are T-helper lymphocyte 2 (Th2) responders, are highly susceptible to infectious and non-infectious heart diseases, whereas C57BL/6 mice (Th1 responders) are not. Angiotensin II (Ang II) is not only a vasopressor but also a pro-inflammatory factor that leads to cardiac hypertrophy, fibrosis and dysfunction. We hypothesized that Ang II exacerbates cardiac damage in Balb/c but not in C57BL/6 mice even though both strains have a similar level of hypertension. Twelve-week-old male C57BL/6J and Balb/c mice received either vehicle or Ang II (1.4 mg kg(-1) day(-1), s.c. via osmotic minipump) for 8 weeks. At baseline, Balb/c mice exhibited the following: (1) a lower heart rate; (2) an enlarged left ventricular chamber; (3) a lower ejection fraction and shortening fraction; and (4) twice the left ventricular collagen deposition of age-matched C57BL/6J mice. Angiotensin II raised systolic blood pressure (to ∼150 mmHg) and induced cardiomyocyte hypertrophy in a similar manner in both strains. While C57BL/6J mice developed compensatory concentric hypertrophy and fibrosis in response to Ang II, Balb/c mice demonstrated severe left ventricular chamber dilatation, wall thinning and fibrosis, leading to congestive heart failure as evidenced by dramatically decreased ejection fraction and lung congestion (significant increase in lung weight), which are both characteristic of dilated cardiomyopathy. Our study suggests that the Th phenotype plays an active role in cardiac remodelling and function both in basal conditions and in hypertension. Angiotensin II-induced dilated cardiomyopathy in Balb/c mice is an ideal animal model for studying the impact of the adaptive immune system on cardiac remodelling and function and for testing strategies to prevent or treat hypertension-associated heart failure.

Cardiac Natriuretic Peptide Profiles in Chronic Hypertension by Single or Sequentially Combined Renovascular and DOCA-Salt Treatments.

The involvement of natriuretic peptides was studied during the hypertrophic remodeling transition mediated by sequential exposure to chronic hemodynamic overload. We induced hypertension in rats by pressure (renovascular) or volume overload (DOCA-salt) during 6 and 12 weeks of treatment. We also studied the consecutive combination of both models in inverse sequences: RV 6 weeks/DS 6 weeks and DS 6 weeks/RV 6 weeks. All treated groups developed hypertension. Cardiac hypertrophy and left ventricular ANP gene expression were more pronounced in single DS than in single RV groups. BNP gene expression was positively correlated with left ventricular hypertrophy only in RV groups, while ANP gene expression was positively correlated with left ventricular hypertrophy only in DS groups. Combined models exhibited intermediate values between those of single groups at 6 and 12 weeks. The latter stimulus associated to the second applied overload is less effective than the former to trigger cardiac hypertrophy and to increase ANP and BNP gene expression. In addition, we suggest a correlation of ANP synthesis with volume overload and of BNP synthesis with pressure overload-induced hypertrophy after a prolonged treatment. Volume and pressure overload may be two mechanisms, among others, involved in the differential regulation of ANP and BNP gene expression in hypertrophied left ventricles. Plasma ANP levels reflect a response to plasma volume increase and volume overload, while circulating BNP levels seem to be regulated by cardiac BNP synthesis and ventricular hypertrophy.

Nebivolol is more effective than atenolol for blood pressure variability attenuation and target organ damage prevention in L-NAME hypertensive rats.

ß-Adrenergic blockers are no longer recommended as first-line therapy due to the reduced cardioprotection of traditional ß-blockers compared with other antihypertensive drugs. It is unknown whether third-generation ß-blockers share the limitations of traditional ß-blockers. The aim of the present study was to compare the effects of nebivolol or atenolol on central and peripheral systolic blood pressure (SBP) and its variability and target organ damage (TOD) in N-nitro-L-arginine methyl ester (L-NAME) hypertensive rats. Male Wistar rats were treated with L-NAME for 8 weeks together with oral administration of nebivolol 30 mg/kg (n = 8), atenolol 90 mg/kg (n = 8), or vehicle (n = 8). The control group was composed of vehicle-treated Wistar rats. SBP and its variability, as well as echocardiographic parameters, were assessed during the last 2 weeks of treatment. Tissue levels of tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6) and transforming growth factor ß (TGF-ß), and histopathological parameters were evaluated in the left ventricle and aorta. Nebivolol had a greater ability than atenolol to decrease central SBP and mid-term and short-term blood pressure variability (BPV) in L-NAME rats. Echocardiographic analysis showed that nebivolol was more effective than atenolol on E/A wave ratio normalization. Compared with atenolol treatment, nebivolol had a greater protective effect on different TOD markers, inducing a decrease in collagen deposition and a reduction in the proinflammatory cytokines IL-6 and TNF-α in the left ventricle and aorta. Our findings suggest that the adverse hemodynamic profile and the reduced cardiovascular protection reported with traditional ß-blockers must not be carried forward to third-generation ß-blockers.

Ventricular function and natriuretic peptides in sequentially combined models of hypertension.

Hemodynamic parameters and natriuretic peptide levels were evaluated in cardiac hypertrophy produced by sequentially applied renovascular (RV) and deoxycorticosterone acetate-salt (DS) models of hypertension. We studied hypertensive rats by RV or DS treatment at 2 and 4 wk, as well as by the combination of 2 wk of each treatment in an inverse sequence: RV 2 wk/DS 2 wk (RV2/DS2) and DS 2 wk/RV 2 wk (DS2/RV2). The in vivo cardiac function, interstitial fibrosis, and synthesis and secretion of types A (ANP) and B (BNP) natriuretic peptides were monitored in hypertensive models compared with their corresponding sham (Sh2, Sh4). There were no differences in relaxation parameters among RV or DS groups and combined treatments. Left ventricular +dP/dt(max) increased only in RV4 (P < 0.01 vs. Sh4), and this increase was abolished in RV2/DS2. Interstitial collagen concentration increased after 4 wk in both RV4 and RV2/DS2 groups. Although there were no changes in collagen concentration in either DS2 or DS4 groups, clipping after 2 wk of DS (DS2/RV2) remarkably stimulated interstitial fibrosis (P < 0.01 vs. DS2). Plasma BNP increased in RV treatment at 4 wk (P < 0.001 vs. Sh4), but not in DS. Interestingly, RV applied after the 2 wk of DS treatment induced a marked increase in BNP levels (P < 0.001 vs. Sh4). In this regard, plasma BNP appears to be a reliable indicator of pressure overload. Our results suggest that the second stimulus of mechanical overload in combined models of hypertension determines the evolution of hypertrophy and synthesis and secretion of ANP and BNP.

Effects of third-generation ß-blockers, atenolol or amlodipine on blood pressure variability and target organ damage in spontaneously hypertensive rats.

BACKGROUND: ß-blockers are no longer considered as first-line antihypertensive drugs due to their lower cardioprotection. METHOD: Considering the differences in the pharmacological properties of ß-blockers, the present work compared the effects of third-generation ß-blockers - carvedilol and nebivolol - with a first-line agent - amlodipine - on hemodynamic parameters, including short-term blood pressure variability (BPV), and their ability to prevent target organ damage in spontaneously hypertensive rats (SHR). SHR rats were orally treated with carvedilol, nebivolol, atenolol, amlodipine or vehicle for 8 weeks. Wistar Kyoto rats treated with vehicle were used as normotensive group. Echocardiographic evaluation, BP, and short-term BPV measurements were performed. Left ventricle and thoracic aorta were removed for histological evaluations and to assess the expression of transforming growth factor ß (TGF-ß), tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6). RESULTS: Carvedilol, nebivolol or amlodipine induced a greater reduction of carotid BP, short-term BPV and echocardiography parameters than atenolol in SHR rats. Carvedilol, nebivolol and amlodipine were more effective than atenolol in the prevention of cardiac hypertrophy, and cardiac and aortic collagen deposit. Carvedilol and nebivolol, but not atenolol, reduced the expressions of fibrotic and inflammatory biomarkers - TGF-ß, TNF-α and IL-6 - in SHR rats to a similar extent to that of amlodipine. CONCLUSION: Chronic treatment with carvedilol or nebivolol attenuates carotid BP and short-term BPV, and reduces target organ damage in SHR to a greater extent than atenolol. Our findings suggest that the lower cardiovascular protection of nonvasodilating ß-blockers, as atenolol, in hypertension must not be translated to third-generation ß-blockers.

Effect of early versus late AT(1) receptor blockade with losartan on postmyocardial infarction ventricular remodeling in rabbits.

To characterize the temporal activation of the renin-angiotensin system after myocardial infarction (MI) in rabbits, we examined cardiac ANG II type 1 receptor (AT(1)R) expression and ANG II levels from 3 h to 35 days. The effects of losartan (12.5 mg.kg(-1).day(-1)) on functional and histomorphometric parameters when treatment was initiated early (3 h) and late (day 15) post-MI and maintained for different periods of time [short term (4 days), midterm (20 days), and long term (35 days)] were also studied. AT(1)R expression increased in the MI zone at 15 and 35 days (P < 0.05). ANG II levels increased (P < 0.05) in the non-MI zone at 24 h and in the MI zone as well as in plasma at 4 days and then progressively decreased until 35 days. The survival rate was significantly lower in untreated MI and early long-term-treated animals. Diastolic pressure-volume curves in MI at 35 and 56 days shifted to the right (P < 0.05). This shift was even more pronounced in long-term-treated groups (P < 0.05). Contractility decreased (P < 0.05 vs. sham) in the untreated and long-term-treated groups and was attenuated in the midterm-treated group. The early administration of losartan reduced RAM 11-positive macrophages from 4.15 +/- 0.05 to 3.05 +/- 0.02 cells/high-power field (HPF; P < 0.05) and CD45 RO-positive lymphocytes from 2.23 +/- 0.05 to 1.48 +/- 0.01 cells/HPF (P < 0.05) in the MI zone at 4 days. Long-term treatment reduced the scar collagen (MI: 70.50 +/- 2.35% and MI + losartan: 57.50 +/- 2.48, P < 0.05), determined the persistency of RAM 11-positive macrophages (3.02 +/- 0.13 cells/HPF) and CD45 RO-positive lymphocytes (2.77 +/- 0.58 cells/HPF, P < 0.05 vs. MI), and reduced the scar thinning ratio at 35 days (P < 0.05). Consequently, the temporal expressions of cardiac AT(1)R and ANG II post-MI in rabbits are different from those described in other species. Long-term treatment unfavorably modified post-MI remodeling, whereas midterm treatment attenuated this harmful effect. The delay in wound healing (early reduction and late persistency of inflammatory infiltrate) and adverse remodeling observed in long-term-treated animals might explain the unfavorable effect observed in rabbits.

Ribose treatment reduced the infarct size and improved heart function after myocardial infarction in rats.

OBJECTIVE: In this study the effect of ribose on heart function and infarct-size was analyzed 6 h after myocardial infarction (MI) in rats. METHODS: Continuous i.v.-infusion of NaCl or ribose (200 mg/kg/h) was started one day prior to induction of MI in female Sprague-Dawley rats which was done by ligation of the left coronary artery. Six hours after MI heart function was measured with 3F tip catheter, cardiac output by thermodilution method. Thereafter the ischemic area was delineated by Evans Blue infusion, and the infarct area was visualized by triphenyltetrazolium chloride staining. The mRNA expression of interleukin (IL)-1beta, IL-6, matrix-metalloproteinase (MMP)-8, and -9 was measured by ribonuclease protection assay. RESULTS: Heart function was severely depressed 6 hours after coronary artery occlusion, but recovered significantly under the influence of ribose. Left ventricular (LV) systolic pressure (LVSP) and contractility (LVdP/dtmax) were restored to the normal levels of sham-operated animals, while parameters of LV relaxation (LVdP/dtmin and time constant of relaxation tau) were impaired compared to sham-operated animals, but significantly improved by ribose treatment compared to sham-treated MI-rats. Moreover, the infarct size was significantly smaller in the ribose treated animals despite a comparable ischemic area at risk in all MI-rats. The cytokine mRNA expression after MI was significantly reduced after ribose treatment, while there were no differences regarding MMP expression. CONCLUSION: MI size was significantly reduced and LV function significantly improved by ribose treatment at 6 h after MI. This seemed to be based on slowing the velocity of the necrotic wave front across the LV wall after MI resulting in smaller infarcts.

Effects of overexpansion on stents' recoil, symmetry/asymmetry, and neointimal hyperplasia in aortas of hypercholesterolemic rabbits.

BACKGROUND: It is not known whether overexpansion modifies stent recoil, symmetric distribution of struts, and neointimal hyperplasia. OBJECTIVES: The objectives were (a) to evaluate whether stent overexpansion modifies the geometric configuration of the stent in the arterial wall, (b) to determine the relationship between overexpansion and stent recoil, and (c) to evaluate the relationship between the distribution of struts and neointimal hyperplasia. METHODS: Twenty tubular stainless steel 316L stents (3.0 and 3.5 mm in diameter) were implanted at 20 and 10 atm, respectively, in the abdominal aorta of New Zealand rabbits fed a hypercholesterolemic diet (1% cholesterol). Sham operations were also performed in seven animals. Eight weeks after implantation or sham operation, an intravascular ultrasound (IVUS) study was performed to measure stent recoil and aid in stent classification (symmetric or asymmetric) according to strut distribution. The degree of injury and neointimal hyperplasia were also evaluated in hematoxylin-eosin stained sections. RESULTS: The symmetry/asymmetry of stents assessed by IVUS, as well as the neointimal hyperplasia, was similar in both groups. Stent recoil was significantly greater in the 3.0-mm stent (overexpanded) group (0.28+/-0.02 mm), as compared with stent recoil in the 3.5-mm stent group (0.10+/-0.01 mm, P<.05). The neointimal hyperplasia in histological slices, independent of the implant technique, was predominantly in zones with higher strut concentration as compared with zones with fewer struts. CONCLUSIONS: Stent overexpansion enhanced stent recoil and did not modify symmetric and asymmetric strut distribution. Neointimal hyperplasia was not modified by the implant technique. Interestingly, significant hyperplasia was observed in locations with greater strut concentration, independent of overexpansion.

Atrial natriuretic peptide behaviour and myocyte hypertrophic profile in combined pressure and volume-induced cardiac hypertrophy.

OBJECTIVE: To investigate cardiomyocyte hypertrophy and hormonal profile in cardiac hypertrophy resulting from sequentially applied overloads. METHODS: We studied Sprague-Dawley rats with renovascular hypertension (RV), where pressure overload predominates, or deoxycorticosterone acetate (DOCA)-salt (DS), where volume overload predominates, at 2 and 4 weeks of treatment, and the combination of both models in inverse sequence: RV 2 weeks/DS 2 weeks (RV2/DS2) and DS 2 weeks/RV 2 weeks (DS2/RV2), and their sham controls (Sh). RESULTS: Blood pressure and cardiomyocyte diameter increased to a similar extent in RV and DS at 2 and 4 weeks and in combined models. Cardiomyocyte length increased remarkably in the DS4 group. Circulating atrial natriuretic peptide (ANP) was elevated in all hypertensive groups after 2 and 4 weeks. The RV2/DS2 group showed similar plasma ANP levels to RV4, but DS2/RV2 exhibited a three-fold increase in ANP levels (P<0.001 versus Sh4, DS2 and DS4). Atrial ANP mRNA remained unchanged in all groups. DS treatment alone or in combination with RV increased left ventricular ANP mRNA, meanwhile only RV treatment increased left ventricular B-type natriuretic peptide (BNP) mRNA. Ventricular ANP expression levels, but not circulating ANP, correlated with both cardiomyocyte diameter (r=0.859, P<0.01) and length (r=0.848, P<0.01). Renal expression of natriuretic peptide receptor C (NPR-C) was unchanged in RV4 but decreased to a similar extent in the DS4 group and both combined treatments. CONCLUSION: Morphometric patterns seem to be more related to the paracrine function of the heart than to the secretion of ANP and the endocrine function. Plasma ANP in the DS2/RV2 group could indicate a different evolution of the remodelling process. ANP expression seems to be a more sensitive marker for volume than for pressure overload.

Effects of carvedilol or amlodipine on target organ damage in L-NAME hypertensive rats: their relationship with blood pressure variability.

The aim of the study was to compare the effects of chronic oral treatment with carvedilol or amlodipine on blood pressure, blood pressure variability and target organ damage in N-nitro-l-arginine methyl ester (L-NAME) hypertensive rats. Wistar rats were treated with L-NAME administered in the drinking water for 8 weeks together with oral administration of carvedilol 30 mg/kg (n = 6), amlodipine 10 mg/kg (n = 6), or vehicle (n = 6). At the end of the treatment, echocardiographic evaluation, blood pressure, and short-term variability measurements were performed. Left ventricular and thoracic aortas were removed to assess activity of metalloproteinase 2 and 9 and expression levels of transforming growth factor ß, tumor necrosis factor α, and interleukin 6. Histological samples were prepared from both tissues. Carvedilol and amlodipine induced a comparable reduction of systolic and mean arterial pressure and its short-term variability in L-NAME rats. The expression of transforming growth factor ß, tumor necrosis factor α, and interleukin 6 decreased in both organs after carvedilol or amlodipine treatment and the activity of metalloproteinase was reduced in aortic tissue. Treatment with carvedilol or amlodipine completely prevented left ventricular collagen deposition and morphometric alterations in aorta. Oral chronic treatment with carvedilol or amlodipine significantly attenuates blood pressure variability and reduces target organ damage and biomarkers of tissue fibrosis and inflammation in L-NAME hypertensive rats.