[Show abstract][Hide abstract]ABSTRACT: S100A1, a Ca superset2+-binding protein of the EF-hand type, is preferentially expressed in myocardial tissue and has been shown to enhance cardiac contractile performance by regulating both sarcoplasmic reticulum (SR) Ca superset2+-handling and myofibrillar Ca superset2+-responsiveness. In cardiac disease, the expression of S100A1 is dynamically altered as it is significantly down-regulated in end stage human heart failure (HF), and it is up-regulated in compensated hypertrophy. Therefore, the delivery of a transgene encoding for S100A1 to the myocardium might be an attractive strategy for improving cardiac function in HF by replacing lost endogenous S100A1. In this study we sought to test whether exogenous S100A1 gene delivery to alter global cardiac function is feasible in the normal rabbit heart. An adenoviral S100A1 transgene (AdvS100A1) also containing the green fluorescent protein (GFP) was delivered using an intracoronary injection method with a dose of 5 x 10 superset11 total virus particles (tvp) (n = 8). Rabbits treated with either a GFP-only adenovirus (AdvGFP) or saline were used as control groups (n = 11 each). Seven days after global myocardial in vivo gene delivery hemodynamic parameters were assessed. S100A1 overexpression as a result of the intracoronary delivery of AdvS100A1 significantly increased left ventricular (LV) +dP/dt subsetmax, -dP/dt subsetmin and systolic ejection pressure (SEP) compared to both control groups after administration of isoproterenol (0.1, 0.5 and 1.0 microg/kgBW/min), while contractile parameters remained unchanged under basal conditions. These results demonstrate that global myocardial in vivo gene delivery is possible and that myocardial S100A1 overexpression can increase cardiac performance. Therefore, substitution of down-regulated S100A1 protein expression levels may represent a potential therapeutic strategy for improving the cardiac performance of the failing heart.
Full-text · Article · Nov 2006 · European journal of medical research
[Show abstract][Hide abstract]ABSTRACT: In human heart failure, increased expression of G protein-coupled receptor kinases (GRKs) causes the loss of beta-adrenergic receptor (betaAR) signaling and function. Mechanical unloading with a left ventricular assist device (LVAD) promotes reverse remodeling, which includes restoration of betaAR responsiveness. We tested the hypothesis that LVAD support of the failing human heart alters the expression and activity of GRKs and we sought to determine whether changes in myocardial GRKs could be tracked in lymphocytes.
Paired samples of human LV tissue (n = 12) and blood were obtained at the time of LVAD implantation (heart failure) and subsequent cardiac transplantation (LVAD). betaAR signaling was quantified by receptor density and adenylyl cyclase activity. Immunoblotting and real-time reverse transcription polymerase chain reaction were used to measure GRK2 and GRK5 protein and mRNA levels. Rhodopsin phosphorylation was used to assess total GRK activity. Consistent with reverse remodeling, betaAR density and signaling were restored to nonfailing levels after LVAD support. GRK2 protein levels were significantly reduced 55% after LVAD support and GRK2 mRNA was similarly reduced. In contrast, GRK5 protein and mRNA levels were unchanged. Total myocardial GRK activity was reduced similar to the drop in GRK2 expression. In lymphocytes, GRK2 protein levels were decreased after LVAD support and there was a significant positive correlation between myocardial and lymphocyte GRK2 levels in both heart failure and LVAD samples.
The changes in myocardial GRK2 expression and activity that are mirrored in lymphocytes provide a possible mechanism for the restoration of betaAR signaling and reverse remodeling after mechanical unloading in the failing heart. Moreover, lymphocytes may provide a surrogate marker of myocardial GRK2 in these patients.
No preview · Article · Jul 2006 · Journal of cardiac failure
[Show abstract][Hide abstract]ABSTRACT: A risk factor summation score was previously validated to successfully predict survival after insertion of a left ventricular assist device (LVAD). We investigated whether this scoring system also predicts clinical outcomes after eventual heart transplantation in LVAD recipients.
A retrospective review was performed on 153 consecutive patients who received an LVAD as a bridge to transplantation at 2 large-volume centers from 1996 to 2003. The scoring system was used to designate low- and high-scoring groups.
Thirty-day mortality and 5-year survival after transplantation were equivalent between groups (4.46% versus 7.32% and 76% versus 70%, respectively). No difference was seen in length of posttransplantation ventilator dependence (2.83 +/- 0.49 versus 3.3 +/- 0.72 days) or intensive care unit monitoring (6.38 +/- 0.77 versus 6.97 +/- 1.1 days). However, low-scoring patients had a significantly decreased duration of inotrope support (5.57 +/- 0.45 versus 7.74 +/- 1.0 days, P = .035).
A risk factor summation score may predict which LVAD patients will require prolonged inotropic support following heart transplantation. However, survival in high-risk (elevated score) LVAD patients following heart transplantation is comparable to low-risk groups, favoring the continued practice of LVAD implantation as a bridge to transplantation even in high-risk patients.
No preview · Article · Feb 2006 · Heart Surgery Forum
[Show abstract][Hide abstract]ABSTRACT: Approximately 50% of aortocoronary saphenous vein grafts are occluded 10 years after coronary revascularization surgery. Intimal hyperplasia, a critical component in saphenous vein graft failure, is defined by vascular smooth muscle cell proliferation, which is mediated in part by betagamma subunits of heterotrimeric G proteins (G(betagamma)) and downstream effectors such as mitogen-activated protein kinases. A peptide consisting of the carboxyl-terminus of the beta-adrenergic receptor kinase (betaARKct) binds G(betagamma), thereby inhibiting G(betagamma) signaling. Utilizing a recombinant adenovirus containing the coding sequence for the betaARKct peptide (AdbetaARKct), this study investigates whether treatment of the vein graft with AdbetaARKct reduces intimal hyperplasia in a large animal model of aortocoronary saphenous vein graft intimal hyperplasia.
Twenty-seven dogs (27-32 kg) underwent aortocoronary bypass grafting to the left anterior descending artery using autologous saphenous vein. Vein grafts were treated with saline (n = 8), an empty adenovirus (n = 8), or AdbetaARKct (n = 8). A subset of dogs (n = 3) were sacrificed on postoperative day 7 and betaARKct expression confirmed by Northern blotting.
Arteriograms performed on postoperative day 90 confirmed that saphenous vein grafts were patent. At postoperative day 90, AdbetaARKct-treated grafts demonstrated reduced intimal area compared to empty virus and saline treated animals (P < .05). Additionally, AdbetaARKct treatment of isolated vascular smooth muscle cells in vitro inhibited mitogen-activated protein kinase activation and decreased overall vascular smooth muscle cell proliferation.
This study demonstrates that betaARKct expression in aortocoronary saphenous vein grafts reduces intimal hyperplasia and decreases vascular smooth muscle cell proliferation in vitro via inhibition of G(betagamma)-mediated mitogen-activated protein kinase activation. Modulation of G(betagamma) via betaARKct may represent a novel therapy to reduce intimal hyperplasia and saphenous vein graft failure.
Full-text · Article · Dec 2005 · The Journal of thoracic and cardiovascular surgery
[Show abstract][Hide abstract]ABSTRACT: It is unclear if mild or moderate mitral valve regurgitation (MR) should be repaired at the time of coronary artery bypass grafting (CABG). We sought to determine the long-term effect of uncorrected MR, measured by intraoperative transesophageal echocardiography (TEE), in CABG patients.
Between May 1999 and September 2003, data were gathered for 3264 consecutive patients who underwent isolated CABG and had MR graded by intraoperative TEE. MR was graded on the following 5 levels: none, trace, mild, moderate, and severe. Patients who had severe MR or who underwent mitral valve surgery were eliminated from the analysis. The remaining patients were combined into the following 3 groups: none or trace, mild, and moderate MR. Preoperative and follow-up data were 99% complete. The median length of follow-up was 3.0 years. Multivariable analysis controlling for important preoperative risk factors was performed to determine predictors of death and death/hospitalization for heart failure. Increasing MR was a risk factor for death [hazard ratio (HR), 1.44; P<0.001] and death/heart failure hospitalization (HR, 1.34; P<0.01). When patients with moderate MR were eliminated from the analysis, mild MR was a risk factor for death (HR, 1.34; P=0.011) and death/hospitalization for heart failure (HR, 1.34; P<0.001).
Even mild MR, identified by intraoperative TEE, predicts worse outcomes after CABG. Revascularization alone did not eliminate the negative long-term effects of mild MR. CABG patients with uncorrected mild or moderate MR are at increased risk for death and heart-failure hospitalization; consideration for surgical repair or more aggressive medical management and follow-up is warranted.
[Show abstract][Hide abstract]ABSTRACT: Surgeons have adopted off-pump coronary artery bypass grafting (OPCAB) in an effort to reduce the morbidity of surgical revascularization. However, long-term outcome of OPCAB compared with conventional coronary artery bypass grafting (CABG) remains poorly defined.
Using logistic regression analysis and proportional hazards modeling, short-term and long-term outcomes (perioperative mortality and complications, risk-adjusted survival, and survival/freedom from revascularization) were investigated for patients who underwent OPCAB (641 patients) and CABG-cardiopulmonary bypass (5026 patients) from 1998 to 2003 at our institution. For these variables, follow-up was 98% complete. OPCAB patients were less likely to receive transfusion (odds ratio for OPCAB, 0.80; P=0.037), and there were trends toward improvement in other short-term outcomes compared with CABG-cardiopulmonary bypass. Long-term outcomes analysis demonstrated no difference in survival, but OPCAB patients were more likely to require repeat revascularization (OPCAB hazard ratio, 1.29; P=0.020).
OPCAB patients were less likely to receive transfusion during their hospitalization for surgery but had higher risk for revascularization in follow-up. These results highlight the need for a large randomized, controlled trial to compare these 2 techniques.
[Show abstract][Hide abstract]ABSTRACT: Fifty percent of human aortocoronary saphenous vein grafts are occluded after 10 years. Intimal hyperplasia is an initial step in graft occlusion and consists of vascular smooth muscle cell proliferation. Phosphatidylinositol 3-kinase and its downstream regulator, the inositol 3-phosphatase PTEN (phosphatase and tensin homolog deleted on chromosome 10), are important regulators of vascular smooth muscle cell proliferation, migration, and cell death. This study tests whether overexpression of PTEN in aortocoronary saphenous vein grafts can reduce intimal hyperplasia.
Adult dogs underwent aortocoronary bypass grafting to the left anterior descending artery by using the autologous saphenous vein. Saphenous vein grafts were treated with phosphate-buffered saline (n = 9), empty adenovirus (n = 8), or adenovirus encoding for PTEN (n = 8). Arteriography at 30 and 90 days assessed saphenous vein graft patency. A subset received saphenous vein grafts treated with a marker transgene (beta-galactosidase, n = 3), empty adenovirus (n = 4), or adenovirus encoding for PTEN (n = 4) and were killed on postoperative day 3 to confirm expression. Vascular smooth muscle cells were isolated from canine saphenous vein infected with adenovirus encoding for PTEN, and immunoblotting and proliferation assays were performed.
Saphenous vein graft transgene expression was confirmed by means of immunohistochemistry, immunoblotting, and polymerase chain reaction. Arteriograms revealed all saphenous vein grafts to be patent. Saphenous vein grafts treated with adenovirus encoding for PTEN demonstrated reduced intimal area compared with those treated with empty adenovirus and phosphate-buffered saline (1.39 +/- 0.11 vs 2.35 +/- 0.3 and 2.57 +/- 0.4 mm 2 , P < .05), and the intima/media ratio was lower in saphenous vein grafts treated with adenovirus encoding for PTEN (0.50 +/- 0.05 vs 1.43 +/- 0.18 and 1.11 +/- 0.14, P < .005). PTEN overexpression in vascular smooth muscle cells inhibited platelet-derived growth factor-induced phosphorylation of Akt, a downstream effector of phosphatidylinositol 3-kinase. PTEN-treated vascular smooth muscle cells demonstrated decreased basal, platelet-derived growth factor-stimulated, and serum-stimulated proliferation.
This study demonstrates that PTEN overexpression in aortocoronary saphenous vein grafts reduces intimal hyperplasia. The mechanism of this antiproliferative effect in vascular smooth muscle cells is likely due to inhibition of phosphatidylinositol 3-kinase signaling through Akt, with resultant decreases in vascular smooth muscle cell growth and survival. Therefore modulation of the phosphatidylinositol 3-kinase pathway through PTEN overexpression might represent a novel therapy to prevent saphenous vein graft intimal hyperplasia after coronary artery bypass grafting.
Preview · Article · Jul 2005 · Journal of Thoracic and Cardiovascular Surgery
[Show abstract][Hide abstract]ABSTRACT: Desensitization and downregulation of myocardial beta-adrenergic receptors (betaARs) are initiated by the increase in betaAR kinase 1 (betaARK1) levels. By interacting with betaARK1 through the phosphoinositide kinase (PIK) domain, phosphoinositide 3-kinase (PI3K) is targeted to agonist-stimulated betaARs, where it regulates endocytosis. We tested the hypothesis that inhibition of receptor-targeted PI3K activity would alter receptor trafficking and ameliorate betaAR signaling, ultimately improving contractility of failing cardiomyocytes.
To competitively displace PI3K from betaARK1, we generated mice with cardiac-specific overexpression of the PIK domain. Seven-day isoproterenol administration in wild-type mice induced desensitization of betaARs and their redistribution from the plasma membrane to early and late endosomes. In contrast, transgenic PIK overexpression prevented the redistribution of betaARs away from the plasma membrane and preserved their responsiveness to agonist. We further tested whether PIK overexpression could normalize already established betaAR abnormalities and ameliorate contractile dysfunction in a large animal model of heart failure induced by rapid ventricular pacing in pigs. Failing porcine hearts showed increased betaARK1-associated PI3K activity and marked desensitization and redistribution of betaARs to endosomal compartments. Importantly, adenoviral gene transfer of the PIK domain in failing pig myocytes resulted in reduced receptor-localized PI3K activity and restored to nearly normal agonist-stimulated cardiomyocyte contractility.
These data indicate that the heart failure state is associated with a maladaptive redistribution of betaARs away from the plasma membrane that can be counteracted through a strategy that targets the betaARK1/PI3K complex.
[Show abstract][Hide abstract]ABSTRACT: Heart failure (HF) represents one of the leading causes of morbidity and mortality in developed nations today. Although this disease process represents a final common endpoint for several entities, including hypertension, coronary artery disease, and cardiomyopathy, a predominant characteristic of end-stage HF is an altered beta-adrenergic receptor signaling cascade. In the heart, beta-adrenergic receptors (beta ARs), members of the superfamily of G-protein-coupled receptors (GPCRs), modulate cardiac function by controlling chronotropic, inotropic, and lusitropic responses to catecholamines of the sympathetic nervous system. In HF, beta ARs are desensitized and downregulated in a maladaptive response to chronic stimulation. This process is largely mediated by G-protein-coupled receptor kinases (GRKs), which phosphorylate GPCRs leading to functional uncoupling. The most abundant cardiac GRK, known as GRK2 or beta AR kinase 1 (beta ARK1), is increased in human HF, and has been implicated in the pathogenesis of dysfunctional cardiac beta AR signaling. The association of beta ARs and GRKs with impaired cardiac function has been extensively studied using transgenic mouse models, which have demonstrated that beta ARK1 plays a vital role in the regulation of myocardial beta AR signaling. These findings have caused beta ARs and GRKs to be regarded as potential therapeutic targets, and gene therapy strategies have been used to manipulate the beta AR signaling pathway in myocardium, leading to improved function in the compromised heart. Ultimately, these genetic modifications of the heart may represent new potential therapies for human HF.
No preview · Article · Aug 2004 · Journal of Molecular and Cellular Cardiology
[Show abstract][Hide abstract]ABSTRACT: Heart failure (HF) represents one of the leading causes of morbidity and mortality in developed nations today. Although this disease process represents a final common endpoint for several entities, including hypertension, coronary artery disease, and cardiomyopathy, a predominant characteristic of end-stage HF is an altered β-adrenergic receptor signaling cascade. In the heart, β-adrenergic receptors (βARs), members of the superfamily of G-protein-coupled receptors (GPCRs), modulate cardiac function by controlling chronotropic, inotropic, and lusitropic responses to catecholamines of the sympathetic nervous system. In HF, βARs are desensitized and downregulated in a maladaptive response to chronic stimulation. This process is largely mediated by G-protein-coupled receptor kinases (GRKs), which phosphorylate GPCRs leading to functional uncoupling. The most abundant cardiac GRK, known as GRK2 or βAR kinase 1 (βARK1), is increased in human HF, and has been implicated in the pathogenesis of dysfunctional cardiac βAR signaling. The association of βARs and GRKs with impaired cardiac function has been extensively studied using transgenic mouse models, which have demonstrated that βARK1 plays a vital role in the regulation of myocardial βAR signaling. These findings have caused βARs and GRKs to be regarded as potential therapeutic targets, and gene therapy strategies have been used to manipulate the βAR signaling pathway in myocardium, leading to improved function in the compromised heart. Ultimately, these genetic modifications of the heart may represent new potential therapies for human HF.
No preview · Article · May 2004 · Journal of Molecular and Cellular Cardiology
[Show abstract][Hide abstract]ABSTRACT: Failing human myocardium is characterized by an attenuated contractile response to beta-adrenergic receptor (betaAR) stimulation due to changes in this signaling cascade, including increased expression and activity of the beta-adrenergic receptor kinase (betaARK1). This leads to desensitization and downregulation of betaARs. Previously, expression of a peptide inhibitor of betaARK1 (betaARKct) has proven beneficial in several animal models of heart failure (HF).
To test the hypothesis that inhibition of betaARK1 could improve beta-adrenergic signaling and contractile function in failing human myocytes, the betaARKct was expressed via adenovirus-mediated (AdbetaARKct) gene transfer in ventricular myocytes isolated from hearts explanted from 10 patients with end-stage HF undergoing cardiac transplantation. AdbetaARKct also contained the marker gene, green fluorescent protein, and successful gene transfer was confirmed via fluorescence and immunoblotting. Compared with uninfected failing myocytes (control), the velocities of both contraction and relaxation in the AdbetaARKct-treated cells were increased in response to the beta-agonist isoproterenol (contraction: 57.5+/-6.6% versus 37.0+/-4.2% shortening per second, P<0.05; relaxation: 43.8+/-5.5% versus 27.5+/-3.9% lengthening per second, P<0.05). Fractional shortening was similarly enhanced (12.2+/-1.2% versus 8.0+/-0.9%, P<0.05). Finally, adenylyl cyclase activity in response to isoproterenol was also increased in AdbetaARKct-treated myocytes.
These results demonstrate that as in animal models of HF, expression of the betaARKct can improve contractile function and beta-adrenergic responsiveness in failing human myocytes. Thus, betaARK1 inhibition may represent a therapeutic strategy for human HF.
[Show abstract][Hide abstract]ABSTRACT: More than 50% of aortocoronary saphenous vein grafts are occluded 10 years after surgery. Intimal hyperplasia is an initial, critical step in the progression toward occlusion. To date, no clinically relevant large animal models of aortocoronary saphenous vein graft intimal hyperplasia have been fully characterized. Gene therapy holds promise as a novel treatment for aortocoronary saphenous vein graft intimal hyperplasia. The 2 objectives of this study are to characterize a canine model of aortocoronary saphenous vein graft intimal hyperplasia and to demonstrate that ex vivo gene delivery is possible in these grafts using adenoviral vectors.
Full-text · Article · Feb 2004 · Journal of Thoracic and Cardiovascular Surgery
[Show abstract][Hide abstract]ABSTRACT: Since beginning cardiac transplantation in 1985, Duke University Medical Center has performed 485 de novo heart transplants in adult recipients. Our program has broadened the access of patients to transplantation through the aggressive use of ventricular assist devices as bridge to transplant in patients with acute heart failure and shock, as well as through the introduction of an alternate list program for suboptimal transplant candidates. Despite this broadening of the recipient pool, our long-term outcomes have remained good, with 5-year survival of 75% and 10-year survival of 51%. Continued advances in immunosuppression and treatment for cardiac allograft vasculopathy seem likely to continue to improve long-term outcomes from cardiac transplantation. Expanding indications for VAD support (such as destination therapy) and continued improvements in this technology seem certain to impact patient selection and therefore the results of transplantation in the future. Appropriate triage of patients with advanced heart failure among available therapies will be the cornerstone of optimizing outcomes in this critically ill patient population.
No preview · Article · Feb 2004 · Clinical transplants