Small guanine nucleotide-binding proteins and myocardial hypertrophy.

The small (21 kDa) guanine nucleotide-binding protein (small G protein) superfamily comprises 5 subfamilies (Ras, Rho, ADP ribosylation factors [ARFs], Rab, and Ran) that act as molecular switches to regulate numerous cellular responses. Cardiac myocyte hypertrophy is associated with cell growth and changes in the cytoskeleton and myofibrillar apparatus. In other cells, the Ras subfamily regulates cell growth whereas the Rho subfamily (RhoA, Rac1, and Cdc42) regulates cell morphology. Thus, the involvement of small G proteins in hypertrophy has become an area of significant interest. Hearts from transgenic mice expressing activated Ras develop features consistent with hypertrophy, whereas mice overexpressing RhoA develop lethal heart failure. In isolated neonatal rat cardiac myocytes, transfection or infection with activated Ras, RhoA, or Rac1 induces many of the features of hypertrophy. We discuss the mechanisms of activation of the small G proteins and the downstream signaling pathways involved. The latter may include protein kinases, particularly the mitogen-activated or Rho-activated protein kinases. We conclude that although there is significant evidence implicating Ras, RhoA, and Rac1 in hypertrophy, the mechanisms are not fully understood.

ESC Working Group on Myocardial Function Position Paper: how to study the right ventricle in experimental models

The right ventricle has become an increasing focus in cardiovascular research. In this position paper, we give a brief overview of the specific pathophysiological features of the right ventricle, with particular emphasis on functional and molecular modifications as well as therapeutic strategies in chronic overload, highlighting the differences from the left ventricle. Importantly, we put together recommendations on promising topics of research in the field, experimental study design, and functional evaluation of the right ventricle in experimental models, from non-invasive methodologies to haemodynamic evaluation and ex vivo set-ups.

Targeting myocardial remodelling to develop novel therapies for heart failure: a position paper from the Working Group on Myocardial Function of the European Society of Cardiology

The failing heart is characterized by complex tissue remodelling involving increased cardiomyocyte death, and impairment of sarcomere function, metabolic activity, endothelial and vascular function, together with increased inflammation and interstitial fibrosis. For years, therapeutic approaches for heart failure (HF) relied on vasodilators and diuretics which relieve cardiac workload and HF symptoms. The introduction in the clinic of drugs interfering with beta-adrenergic and angiotensin signalling have ameliorated survival by interfering with the intimate mechanism of cardiac compensation. Current therapy, though, still has a limited capacity to restore muscle function fully, and the development of novel therapeutic targets is still an important medical need. Recent progress in understanding the molecular basis of myocardial dysfunction in HF is paving the way for development of new treatments capable of restoring muscle function and targeting specific pathological subsets of LV dysfunction. These include potentiating cardiomyocyte contractility, increasing cardiomyocyte survival and adaptive hypertrophy, increasing oxygen and nutrition supply by sustaining vessel formation, and reducing ventricular stiffness by favourable extracellular matrix remodelling. Here, we consider drugs such as omecamtiv mecarbil, nitroxyl donors, cyclosporin A, SERCA2a (sarcoplasmic/endoplasmic Ca(2 +) ATPase 2a), neuregulin, and bromocriptine, all of which are currently in clinical trials as potential HF therapies, and discuss novel molecular targets with potential therapeutic impact that are in the pre-clinical phases of investigation. Finally, we consider conceptual changes in basic science approaches to improve their translation into successful clinical applications.

Transcriptomics and proteomics show that selenium affects inflammation, ctoskeleton, and cancer pathways in human rectal biopsies

Epidemiologic studies highlight the potential role of dietary selenium (Se) in colorectal cancer prevention. Our goal was to elucidate whether expression of factors crucial for colorectal homoeostasis is affected by physiologic differences in Se status. Using transcriptomics and proteomics followed by pathway analysis, we identified pathways affected by Se status in rectal biopsies from 22 healthy adults, including 11 controls with optimal status (mean plasma Se = 1.43 μM) and 11 subjects with suboptimal status (mean plasma Se = 0.86 μM). We observed that 254 genes and 26 proteins implicated in cancer (80%), immune function and inflammatory response (40%), cell growth and proliferation (70%), cellular movement, and cell death (50%) were differentially expressed between the 2 groups. Expression of 69 genes, including selenoproteins W1 and K, which are genes involved in cytoskeleton remodelling and transcription factor NFκB signaling, correlated significantly with Se status. Integrating proteomics and transcriptomics datasets revealed reduced inflammatory and immune responses and cytoskeleton remodelling in the suboptimal Se status group. This is the first study combining omics technologies to describe the impact of differences in Se status on colorectal expression patterns, revealing that suboptimal Se status could alter inflammatory signaling and cytoskeleton in human rectal mucosa and so influence cancer risk.

In Vivo Comparison of Hard Tissue Regeneration with Human Mesenchymal Stem Cells Processed with Either the FICOLL Method or the BMAC Method

Objective: To compare new bone formation in maxillary sinus augmentation procedures using biomaterial associated with mesenchymal stem cells (MSCs) separated by two different isolation methods. Background: In regenerative medicine open cell concentration systems are only allowed for clinical application under good manufacturing practice conditions. Methods: Mononuclear cells, including MSCs, were concentrated with either the synthetic poylsaccharid (FICOLL) method (classic open system-control group, n = 6 sinus) or the bone marrow aspirate concentrate (BMAC) method (closed system-test group, n = 12 sinus) and transplanted in combination with biomaterial. A sample of the cells was characterized by their ability to differentiate. After 4.1 months (SD +/- 1.0) bone biopsies were obtained and analyzed. Results: The new bone formation in the BMAC group was 19.9% (90% confidence interval [CI], 10.9-29), and in the FICOLL group was 15.5% (90% CI, 8.6-22.4). The 4.4% difference was not significant (90% CI, -4.6-13.5; p = 0.39). MSCs could be differentiated into osteogenic, chondrogenic, and adipogenic lineages. Conclusion: MSCs harvested from bone marrow aspirate in combination with bovine bone matrix particles can form lamellar bone and provide a reliable base for dental implants. The closed BMAC system is suited to substitute the open FICOLL system in bone regeneration procedures.

MODELING VERY LONG BASELINE INTERFEROMETRIC IMAGES WITH THE CROSS-ENTROPY GLOBAL OPTIMIZATION TECHNIQUE

We present a new technique for obtaining model fittings to very long baseline interferometric images of astrophysical jets. The method minimizes a performance function proportional to the sum of the squared difference between the model and observed images. The model image is constructed by summing N(s) elliptical Gaussian sources characterized by six parameters: two-dimensional peak position, peak intensity, eccentricity, amplitude, and orientation angle of the major axis. We present results for the fitting of two main benchmark jets: the first constructed from three individual Gaussian sources, the second formed by five Gaussian sources. Both jets were analyzed by our cross-entropy technique in finite and infinite signal-to-noise regimes, the background noise chosen to mimic that found in interferometric radio maps. Those images were constructed to simulate most of the conditions encountered in interferometric images of active galactic nuclei. We show that the cross-entropy technique is capable of recovering the parameters of the sources with a similar accuracy to that obtained from the very traditional Astronomical Image Processing System Package task IMFIT when the image is relatively simple (e. g., few components). For more complex interferometric maps, our method displays superior performance in recovering the parameters of the jet components. Our methodology is also able to show quantitatively the number of individual components present in an image. An additional application of the cross-entropy technique to a real image of a BL Lac object is shown and discussed. Our results indicate that our cross-entropy model-fitting technique must be used in situations involving the analysis of complex emission regions having more than three sources, even though it is substantially slower than current model-fitting tasks (at least 10,000 times slower for a single processor, depending on the number of sources to be optimized). As in the case of any model fitting performed in the image plane, caution is required in analyzing images constructed from a poorly sampled (u, v) plane.

Effects of exercise training on autonomic dysfunction management in an experimental model of menopause and myocardial infarction

Objective: The aim of this study was to investigate the effects of exercise training on cardiovascular autonomic dysfunction in ovariectomized rats submitted to myocardial infarction. Methods: Female Wistar rats were divided into the following ovariectomized groups: sedentary ovariectomized (SO), trained ovariectomized (TO), sedentary ovariectomized infarcted (SOI), and trained ovariectomized infarcted (TOI). Trained groups were submitted to an exercise training protocol on a treadmill (8 wk). Arterial baroreflex sensitivity was evaluated by heart rate responses to arterial pressure changes, and cardiopulmonary baroreflex sensitivity was tested by bradycardic and hypotension responses to serotonin injection. Vagal and sympathetic effects were calculated by pharmacological blockade. Results: Arterial pressure was reduced in the TO in comparison with the SO group and increased in the TOI in relation to the SOI group. Exercise training improved the baroreflex sensitivity in both the TO and TOI groups. The TOI group displayed improvement in cardiopulmonary reflex sensitivity compared with the SOI group at the 16 mu g/kg serotonin dose. Exercise training enhanced the vagal effect in both the TO (45%) and TOI (46%) animals compared with the SO and SOI animals and reduced the sympathetic effect in the TOI (38%) in comparison with the SOI animals. Significant correlations were obtained between bradycardic baroreflex responses and vagal (r = -0.7, P < 0.005) and sympathetic (r = 0.7, P < 0.001) effects. Conclusions: These results indicate that exercise training in ovariectomized rats submitted to myocardial infarction improves resting hemodynamic status and reflex control of the circulation, which may be due to an increase in the vagal component. This suggests a homeostatic role for exercise training in reducing the autonomic impairment of myocardial infarction in postmenopausal women.

Autonomic impairment after myocardial infarction: Role in cardiac remodelling and mortality

P>1. Impairmant of baroreflex sensitivity (BRS) has been implicated in the reduction of heart rate variability (HRV) and in the increased risk of death after myocardial infarction (MI). In the present study, we investigated whether the additional impairment in BRS induced by sinoaortic baroreceptor denervation (SAD) in MI rats is associated with changes in the low-frequency (LF) component of HRV and increased mortality rate. 2. Rats were randomly divided into four groups: control, MI, denervated (SAD) and SAD + MI rats. Left ventricular (LV) function was evaluated by echocardiography. Autonomic components were assessed by power spectral analysis and BRS. 3. Myocardial infarction (90 days) reduced ejection fraction (by similar to 42%) in both the MI and SAD + MI groups; however, an increase in LV mass and diastolic dysfunction were observed only in the SAD + MI group. Furthermore, BRS, HRV and the LF power of HRV were reduced after MI, with an exacerbated reduction seen in SAD + MI rats. The LF component of blood pressure variability (BPV) was increased in the MI, SAD and SAD + MI groups compared with the control group. Mortality was higher in the MI groups compared with the non-infarcted groups, with an additional increase in mortality in the SAD + MI group compared with the MI group. Correlations were obtained between BRS and the LF component of HRV and between LV mass and the LF component of BPV. 4. Together, the results indicate that the abolishment of BRS induced by SAD in MI rats further reduces the LF band of HRV, resulting in a worse cardiac remodelling and increased mortality in these rats. These data highlight the importance of this mechanism in the prognosis of patients after an ischaemic event.

Redox-sensitive prosurvival and proapoptotic protein expression in the myocardial remodeling post-infarction in rats

In this study, we investigated the oxidative stress influence in some prosurvival and proapoptotic proteins after myocardial infarction (MI). Male Wistar rats were divided in two groups: Sham-operated (control) and MI. MI was induced by left coronary artery occlusion. 28-days after surgery, echocardiographic, morphometric, and hemodynamic parameters were evaluated. Redox status (reduced to oxidized glutathione ratio, GSH/GSSG) and hydrogen peroxide levels (H(2)O(2)) were measured in heart tissue. The p-ERK/ERK, p-Akt/Akt, p-mTOR/mTOR and p-GSK-3 beta/GSK-3 beta ratios, as well as apoptosis-inducing factor (AIF) myocardial protein expression were quantified by Western blot. MI group showed an increase in cardiac hypertrophy (23%) associated with a decrease in ejection fraction (38%) and increase in left ventricular end-diastolic pressure (82%) when compared to control, characterizing ventricular dysfunction. Redox status imbalance was seen in MI animals, as evidenced by the decrease in the GSH/GSSG ratio (30%) and increased levels of H(2)O(2) (45%). This group also showed an increase in the ERK phosphorylation and a reduction of Akt and mTOR phosphorylation when compared to control. Moreover, we showed a reduction in the GSK-3 beta phosphorylation and an increase in AIF protein expression in MI group. Taken together, our results show increased H(2)O(2) levels and cellular redox imbalance associated to a higher p-ERK and AIF immunocontent, which would contribute to a maladaptive hypertrophy phenotype.

Granulocyte Colony-stimulating Factor Reduces Mortality by Suppressing Ventricular Arrhythmias in Acute Phase of Myocardial Infarction in Rats

Our aim was to evaluate the effects of granulocyte colony-stimulating factor (G-CSF) on early cardiac arrhythmias after myocardial infarction (MI) and the impact on survival. Male Wistar rats received repeated doses of 50 mu g/kg G-CSF (MI-GCSF group) or vehicle (MI group) at 7, 3, and 1 days before surgery. MI was induced by permanent occlusion of left corollary artery. The electrocardiogram was obtained before occlusion and then for 30 minutes after surgery. Events and duration of ventricular arrhythmias were analyzed. The levels of connexin43 (Cx43) were measured by Western blot immediately before MI production. Survival was significantly increased in MI-GCSF pretreated group (74% versus 52.0% MI. P < 0.05). G-CSF pretreatment also significantly reduced the ventricular premature beats when compared with the untreated-MI group (201 +/- 47 versus 679 +/- 117, P < 0.05). The number and the duration of ventricular tachycardia were smaller in the MI-G-CSF group, as well as the number of ventricular fibrillation episodes (10% versus 69% in NIL P < 0.05). Cx43 levels were significantly increased by G-CSF treatment (1.27 +/- 0.13 versus 0.86 +/- 0.11; P < 0.05). The MI size 24 hours after occlusion was reduced by G-CSF pretreatment (36 +/- 3% versus 44 +/- 2% of left ventricle in MI group; P < 0.05). The increase of Cx43 expression in the heart may explain the reduced incidence in ventricular arrhythmias in the early phases after coronary artery occlusion in rats, thus increasing survival after MI.

Hyperglycaemia protects the heart after myocardial infarction: aspects of programmed cell survival and cell death

Exposure to a high glucose medium or diabetes has been found to protect the heart against ischaemia. The activation of antiapoptotic and proliferative factors seems to be involved in this cardioprotection. This study was designed to evaluate the role of hyperglycaemia in cardiac function, programmed cell survival, and cell death in diabetic rats after myocardial infarction (MI). Male Wistar rats were divided into four groups (n = 8): control (C), diabetic (D), myocardial infarcted (MI), and diabetic myocardial infarcted (DI). The following measures were assessed in the left ventricle: size of MI, systolic and diastolic function by echocardiography, cytokines by ELISA (TNF-alpha, IL-1 beta, IL-6, and IL-10), gene expression by real-time PCR (Bax, Fas, p53, Bcl-2, HIF1-alpha, VEGF, and IL8r), caspase-3 activity by spectrofluorometric assay, glucose transporter type 1 and 4 (GLUT-1 and GLUT-4) protein expression by western blotting, and capillary density and fibrosis by histological analysis. Systolic function was improved by hyperglycaemia in the DI group, and this was accompanied by no improvement in diastolic dysfunction, a reduction of 36% in MI size, reduced proinflammatory cytokines, apoptosis activation, and an increase in cell survival factors (HIF1-alpha, VEGFa and IL8r) assessed 15 days post-MI. Moreover, hyperglycaemia resulted in angiogenesis (increased capillary density) before and after MI, accompanied by a reduction in fibrosis. Together, these results suggest that greater plasticity and cellular resistance to ischaemic injury result from chronic diabetic hyperglycaemia in rat hearts.

L-NAME Treatment Enhances Exercise-induced Content of Myocardial Heat Shock Protein 72 (Hsp72) in Rats

Background/Aim: Nitric oxide (NO) modulates the expression of the chaperone Hsp72 in the heart, and exercise stimulates both NO production and myocardial Hsp72 expression. The main purpose of the study was to investigate whether NO interferes with an exercise-induced myocardial Hsp72 expression. Methods: Male Wistar rats (70-100 days) were divided into control (C, n= 12), L-NAME-treated (L, n= 12), exercise (E, n= 13) and exercise plus L-NAME-treated (EL, n= 20) groups. L-NAME was given in drinking water (700 mg. L(-1)) and the exercise was performed on a treadmill (15-25 m.min(-1), 40-60 min. day(-1)) for seven days. Left ventricle (LV) protein Hsp content, NOS and phosphorylated-NOS (p-NOS) isoforms were measured using Western blotting. The activity of NOS was assayed in LV homogenates by the conversion of [(3)H] L-arginine to [(3)H] L-citrulline. Results: Hsp72 content was increased significantly (223%; p < 0.05) in the E group compared to the C group, but exercise alone did not alter the NOS content, p-NOS isoforms or NOS activity. Contrary to our expectation, L-NAME enhanced (p < 0.05) the exercise-induced Hsp72 content (EL vs. C, L and E groups = 1019%, 548% and 457%, respectively). Although the EL group had increased stimulatory p-eNOS(Ser1177) (over 200%) and decreased inhibitory p-nNOS(Ser852) (similar to 50%) compared to both the E and L groups (p < 0.05), NOS activity was similar in all groups. Conclusions: Our results suggest that exercise-induced cardiac Hsp72 expression does not depend on NO. Conversely, the in vivo L-NAME treatment enhances exercise-induced Hsp72 production. This effect may be due to an increase in cardiac stress. Copyright (C) 2011 S. Karger AG, Basel