Transcoronary gene transfer of SERCA2a increases coronary blood flow and decreases cardiomyocyte size in a type 2 diabetic rat model

SERCA2a dysfunction in the pathophysiology of heart failure with preserved ejection fraction: a direct role is yet to be established

With rising incidence, mortality and limited therapeutic options, heart failure with preserved ejection fraction (HFpEF) remains one of the most important topics in cardiovascular medicine today. Characterised by left ventricular diastolic dysfunction partially due to impaired Ca2+ homeostasis, one ion channel in particular, SarcoEndoplasmic Reticulum Ca2+-ATPase (SERCA2a), may play a significant role in its pathophysiology. A better understanding of the complex mechanisms interplaying to contribute to SERCA2a dysfunction will help develop treatments targeting it and thus address the growing clinical challenge HFpEF poses. This review examines the conflicting evidence present for changes in SERCA2a expression and activity in HFpEF, explores potential underlying mechanisms, and finally evaluates the drug and gene therapy trials targeting SERCA2a in heart failure. Recent positive results from trials involving widely used anti-diabetic agents such as sodium-glucose co-transporter protein 2 inhibitors (SGLT2i) and glucagon-like peptide-1 (GLP-1) agonists offer advancement in HFpEF management. The potential interplay between these agents and SERCA2a regulation presents a novel angle that could open new avenues for modulating diastolic function; however, the mechanistic research in this emerging field is limited. Overall, the direct role of SERCA2a dysfunction in HFpEF remains undetermined, highlighting the need for well-designed pre-clinical studies and robust clinical trials.

Protective effect of SERCA2a-SUMOylation by SUMO-1 on diabetes-induced atherosclerosis and aortic vascular injury

Diabetes is a major risk factor for cardiovascular disease. However, the exact mechanism by which diabetes contributes to vascular damage is not fully understood. The aim of this study was to investigate the role of SUMO-1 mediated SERCA2a SUMOylation in the development of atherosclerotic vascular injury associated with diabetes mellitus. ApoE-/- mice were treated with streptozotocin (STZ) injection combined with high-fat feeding to simulate diabetic atherosclerosis and vascular injury. Human aortic vascular smooth muscle cells (HAVSMCs) were treated with high glucose (HG, 33.3 mM) and palmitic acid (PA, 200 µM) for 24 h to mimic a model of diabetes-induced vascular injury in vitro. Aortic vascular function, phenotypic conversion, migration, proliferation, intracellular Ca2+ concentration, the levels of small ubiquitin-like modifier type 1 (SUMO1), SERCA2a and SUMOylated SERCA2a were detected. Diabetes-induced atherosclerotic mice presented obvious atherosclerotic plaques and vascular injury, companied by significantly lower levels of SUMO1 and SERCA2a in aorta. HG and PA treatment in HAVSMCs reduced the expressions of SUMO1, SERCA2a and SUMOylated SERCA2a, facilitated the HAVSMCs phenotypic transformation, proliferation and migration, attenuated the Ca2+ transport, and increased the resting intracellular Ca2+ concentration. We also confirmed that SUMO1 directly bound to SERCA2a in HAVSMCs. Overexpression of SUMO1 restored the function and phenotypic contractile ability of HAVSMCs by upregulating SERCA2a SUMOylation, thereby alleviating HG and PA-induced vascular injury. These observations suggest an essential role of SUMO1 to protect diabetes-induced atherosclerosis and aortic vascular injury by the regulation of SERCA2a-SUMOylation and calcium homeostasis.

Cardiomyocyte-targeting exosomes from sulforaphane-treated fibroblasts affords cardioprotection in infarcted rats

BACKGROUND

Exosomes (EXOs), tiny extracellular vesicles that facilitate cell-cell communication, are being explored as a heart failure treatment, although the features of the cell source restrict their efficacy. Fibroblasts the most prevalent non-myocyte heart cells, release poor cardioprotective EXOs. A noninvasive method for manufacturing fibroblast-derived exosomes (F-EXOs) that target cardiomyocytes and slow cardiac remodeling is expected. As a cardioprotective isothiocyanate, sulforaphane (SFN)-induced F-EXOs (SFN-F-EXOs) should recapitulate its anti-remodeling properties.

METHODS

Exosomes from low-dose SFN (3 μM/7 days)-treated NIH/3T3 murine cells were examined for number, size, and protein composition. Fluorescence microscopy, RT-qPCR, and western blot assessed cell size, oxidative stress, AcH4 levels, hypertrophic gene expression, and caspase-3 activation in angiotensin II (AngII)-stressed HL-1 murine cardiomyocytes 12 h-treated with various EXOs. The uptake of fluorescently-labeled EXOs was also measured in cardiomyocytes. The cardiac function of infarcted male Wistar rats intramyocardially injected with different EXOs (1·10¹²) was examined by echocardiography. Left ventricular infarct size, hypertrophy, and capillary density were measured.

RESULTS

Sustained treatment of NIH/3T3 with non-toxic SFN concentration significantly enhances the release of CD81 + EXOs rich in TSG101 (Tumor susceptibility gene 101) and Hsp70 (Heat Shock Protein 70), and containing maspin, an endogenous histone deacetylase 1 inhibitor. SFN-F-EXOs counteract angiotensin II (AngII)-induced hypertrophy and apoptosis in murine HL-1 cardiomyocytes enhancing SERCA2a (sarcoplasmic/endoplasmic reticulum Ca²⁺ ATPase 2a) levels more effectively than F-EXOs. In stressed cardiomyocytes, SFN-F-EXOs boost AcH4 levels by 30% (p < 0.05) and significantly reduce oxidative stress more than F-EXOs. Fluorescence microscopy showed that mouse cardiomyocytes take in SFN-F-EXOs ~ threefold more than F-EXOs. Compared to vehicle-injected infarcted hearts, SFN-F-EXOs reduce hypertrophy, scar size, and improve contractility.

CONCLUSIONS

Long-term low-dose SFN treatment of fibroblasts enhances the release of anti-remodeling cardiomyocyte-targeted F-EXOs, which effectively prevent the onset of HF. The proposed method opens a new avenue for large-scale production of cardioprotective exosomes for clinical application using allogeneic fibroblasts.

Viral Vectors in Gene Therapy: Where Do We Stand in 2023?

Viral vectors have been used for a broad spectrum of gene therapy for both acute and chronic diseases. In the context of cancer gene therapy, viral vectors expressing anti-tumor, toxic, suicide and immunostimulatory genes, such as cytokines and chemokines, have been applied. Oncolytic viruses, which specifically replicate in and kill tumor cells, have provided tumor eradication, and even cure of cancers in animal models. In a broader meaning, vaccine development against infectious diseases and various cancers has been considered as a type of gene therapy. Especially in the case of COVID-19 vaccines, adenovirus-based vaccines such as ChAdOx1 nCoV-19 and Ad26.COV2.S have demonstrated excellent safety and vaccine efficacy in clinical trials, leading to Emergency Use Authorization in many countries. Viral vectors have shown great promise in the treatment of chronic diseases such as severe combined immunodeficiency (SCID), muscular dystrophy, hemophilia, β-thalassemia, and sickle cell disease (SCD). Proof-of-concept has been established in preclinical studies in various animal models. Clinical gene therapy trials have confirmed good safety, tolerability, and therapeutic efficacy. Viral-based drugs have been approved for cancer, hematological, metabolic, neurological, and ophthalmological diseases as well as for vaccines. For example, the adenovirus-based drug Gendicine® for non-small-cell lung cancer, the reovirus-based drug Reolysin® for ovarian cancer, the oncolytic HSV T-VEC for melanoma, lentivirus-based treatment of ADA-SCID disease, and the rhabdovirus-based vaccine Ervebo against Ebola virus disease have been approved for human use.

Gene Therapy Cargoes Based on Viral Vector Delivery

Viral vectors have been proven useful in a broad spectrum of gene therapy applications due to their possibility to accommodate foreign genetic material for both local and systemic delivery. The wide range of viral vectors has enabled gene therapy applications for both acute and chronic diseases. Cancer gene therapy has been addressed by the delivery of viral vectors expressing anti-tumor, toxic, and suicide genes for the destruction of tumors. Delivery of immunostimulatory genes such as cytokines and chemokines has also been applied for cancer therapy. Moreover, oncolytic viruses specifically replicating in and killing tumor cells have been used as such for tumor eradication or in combination with tumor killing or immunostimulatory genes. In a broad meaning, vaccines against infectious diseases and various cancers can be considered gene therapy, which has been highly successful, not the least for the development of effective COVID-19 vaccines. Viral vector-based gene therapy has also demonstrated encouraging and promising results for chronic diseases such as severe combined immunodeficiency (SCID), muscular dystrophy, and hemophilia. Preclinical gene therapy studies in animal models have demonstrated proof-of-concept for a wide range of disease indications. Clinical evaluation of drugs and vaccines in humans has showed high safety levels, good tolerance, and therapeutic efficacy. Several gene therapy drugs such as the adenovirus-based drug Gendicine® for non-small-cell lung cancer, the reovirus-based drug Reolysin® for ovarian cancer, lentivirus-based treatment of SCID-X1 disease, and the rhabdovirus-based vaccine Ervebo against Ebola virus disease, and adenovirus-based vaccines against COVID-19 have been developed.

Ca2+ mishandling and mitochondrial dysfunction: a converging road to prediabetic and diabetic cardiomyopathy

Diabetic cardiomyopathy is defined as the myocardial dysfunction that suffers patients with diabetes mellitus (DM) in the absence of hypertension and structural heart diseases such as valvular or coronary artery dysfunctions. Since the impact of DM on cardiac function is rather silent and slow, early stages of diabetic cardiomyopathy, known as prediabetes, are poorly recognized, and, on many occasions, cardiac illness is diagnosed only after a severe degree of dysfunction was reached. Therefore, exploration and recognition of the initial pathophysiological mechanisms that lead to cardiac dysfunction in diabetic cardiomyopathy are of vital importance for an on-time diagnosis and treatment of the malady. Among the complex and intricate mechanisms involved in diabetic cardiomyopathy, Ca2+ mishandling and mitochondrial dysfunction have been described as pivotal early processes. In the present review, we will focus on these two processes and the molecular pathway that relates these two alterations to the earlier stages and the development of diabetic cardiomyopathy.

Mechanisms underlying the vasodilatory effects of canagliflozin in the rabbit thoracic aorta: Involvement of the SERCA pump and Kv channels

AIMS

Canagliflozin is an anti-diabetic agent and sodium glucose co-transporter-2 inhibitor. Despite numerous clinical trials demonstrating its beneficial effects on blood pressure, the cellular mechanisms underlying the effects of canagliflozin on vascular reactivity have yet to be clarified. We investigated the vasodilatory effect of canagliflozin on aortic rings isolated from rabbits.

MAIN METHODS

We used rabbit thoracic aortic rings and its arterial tone was tested by using wire myography system.

KEY FINDINGS

Canagliflozin caused concentration-dependent vasodilation in aortic rings pre-constricted with phenylephrine or high K⁺. However, the degree of canagliflozin-induced vasodilation of the aortic rings pre-constricted with high K⁺ was less than that of rings pre-constricted with phenylephrine. Application of 4-aminopyridine, a voltage-dependent K⁺ (Kv) channel inhibitor, reduced canagliflozin-induced vasodilation. However, pre-incubation of an inwardly rectifying K⁺ channel inhibitor, a large-conductance Ca²⁺-activated K⁺ channel inhibitor, and an ATP-sensitive K⁺ inhibitor did not modulate the vasodilatory effects of canagliflozin. Indeed, canagliflozin increased Kv currents in aortic smooth muscle cells. Pre-treatment with thapsigargin or cyclopiazonic acid, a sarco/endoplasmic reticulum Ca²⁺-ATPase (SERCA) pump inhibitors, reduced the vasodilatory effects of canagliflozin. Conversely, pre-treatment with a Ca²⁺ channel inhibitor, adenylyl cyclase/PKA inhibitors, and guanylyl cyclase/PKG inhibitors did not modulate the vasodilatory effects of canagliflozin. Endothelium removal, and pre-treatment with the nitric oxide synthase inhibitor L-NAME, and small- and intermediate-conductance Ca²⁺-activated K⁺ channel inhibitor apamin and TRAM-34, did not diminish the vasodilatory effects of canagliflozin.

SIGNIFICANCE

Our results indicate that canagliflozin induces vasodilation, which is dependent on the robust SERCA activity and Kv channel activation.

Roles of sarcoplasmic reticulum Ca2+ ATPase pump in the impairments of lymphatic contractile activity in a metabolic syndrome rat model

The intrinsic lymphatic contractile activity is necessary for proper lymph transport. Mesenteric lymphatic vessels from high-fructose diet-induced metabolic syndrome (MetSyn) rats exhibited impairments in its intrinsic phasic contractile activity; however, the molecular mechanisms responsible for the weaker lymphatic pumping activity in MetSyn conditions are unknown. Several metabolic disease models have shown that dysregulation of sarcoplasmic reticulum Ca2+ ATPase (SERCA) pump is one of the key determinants of the phenotypes seen in various muscle tissues. Hence, we hypothesized that a decrease in SERCA pump expression and/or activity in lymphatic muscle influences the diminished lymphatic vessel contractions in MetSyn animals. Results demonstrated that SERCA inhibitor, thapsigargin, significantly reduced lymphatic phasic contractile frequency and amplitude in control vessels, whereas, the reduced MetSyn lymphatic contractile activity was not further diminished by thapsigargin. While SERCA2a expression was significantly decreased in MetSyn lymphatic vessels, myosin light chain 20, MLC20 phosphorylation was increased in these vessels. Additionally, insulin resistant lymphatic muscle cells exhibited elevated intracellular calcium and decreased SERCA2a expression and activity. The SERCA activator, CDN 1163 partially restored lymphatic contractile activity in MetSyn lymphatic vessel by increasing phasic contractile frequency. Thus, our data provide the first evidence that SERCA2a modulates the lymphatic pumping activity by regulating phasic contractile amplitude and frequency, but not the lymphatic tone. Diminished lymphatic contractile activity in the vessels from the MetSyn animal is associated with the decreased SERCA2a expression and impaired SERCA2 activity in lymphatic muscle.

Pathogenesis and pathophysiology of heart failure with reduced ejection fraction: translation to human studies

Heart failure represents the end result of different pathophysiologic processes, which culminate in functional impairment. Regardless of its aetiology, the presentation of heart failure usually involves symptoms of pump failure and congestion, which forms the basis for clinical diagnosis. Pathophysiologic descriptions of heart failure with reduced ejection fraction (HFrEF) are being established. Most commonly, HFrEF is centred on a reactive model where a significant initial insult leads to reduced cardiac output, further triggering a cascade of maladaptive processes. Predisposing factors include myocardial injury of any cause, chronically abnormal loading due to hypertension, valvular disease, or tachyarrhythmias. The pathophysiologic processes behind remodelling in heart failure are complex and reflect systemic neurohormonal activation, peripheral vascular effects and localised changes affecting the cardiac substrate. These abnormalities have been the subject of intense research. Much of the translational successes in HFrEF have come from targeting neurohormonal responses to reduced cardiac output, with blockade of the renin-angiotensin-aldosterone system (RAAS) and beta-adrenergic blockade being particularly fruitful. However, mortality and morbidity associated with heart failure remains high. Although systemic neurohormonal blockade slows disease progression, localised ventricular remodelling still adversely affects contractile function. Novel therapy targeted at improving cardiac contractile mechanics in HFrEF hold the promise of alleviating heart failure at its source, yet so far none has found success. Nevertheless, there are increasing calls for a proximal, 'cardiocentric' approach to therapy. In this review, we examine HFrEF therapy aimed at improving cardiac function with a focus on recent trials and emerging targets.

miR-146a Suppresses SUMO1 Expression and Induces Cardiac Dysfunction in Maladaptive Hypertrophy

RATIONALE

Abnormal SUMOylation has emerged as a characteristic of heart failure (HF) pathology. Previously, we found reduced SUMO1 (small ubiquitin-like modifier 1) expression and SERCA2a (sarcoplasmic reticulum Ca²⁺-ATPase) SUMOylation in human and animal HF models. SUMO1 gene delivery or small molecule activation of SUMOylation restored SERCA2a SUMOylation and cardiac function in HF models. Despite the critical role of SUMO1 in HF, the regulatory mechanisms underlying SUMO1 expression are largely unknown.

OBJECTIVE

To examine miR-146a-mediated SUMO1 regulation and its consequent effects on cardiac morphology and function.

METHODS AND RESULTS

In this study, miR-146a was identified as a SUMO1-targeting microRNA in the heart. A strong correlation was observed between miR-146a and SUMO1 expression in failing mouse and human hearts. miR-146a was manipulated in cardiomyocytes through AAV9 (adeno-associated virus serotype 9)-mediated gene delivery, and cardiac morphology and function were analyzed by echocardiography and hemodynamics. Overexpression of miR-146a reduced SUMO1 expression, SERCA2a SUMOylation, and cardiac contractility in vitro and in vivo. The effects of miR-146a inhibition on HF pathophysiology were examined by transducing a tough decoy of miR-146a into mice subjected to transverse aortic constriction. miR-146a inhibition improved cardiac contractile function and normalized SUMO1 expression. The regulatory mechanisms of miR-146a upregulation were elucidated by examining the major miR-146a-producing cell types and transfer mechanisms. Notably, transdifferentiation of fibroblasts triggered miR-146a overexpression and secretion through extracellular vesicles, and the extracellular vesicle-associated miR-146a transfer was identified as the causative mechanism of miR-146a upregulation in failing cardiomyocytes. Finally, extracellular vesicles isolated from failing hearts were shown to contain high levels of miR-146a and exerted negative effects on the SUMO1/SERCA2a signaling axis and hence cardiomyocyte contractility.

CONCLUSIONS

Taken together, our results show that miR-146a is a novel regulator of the SUMOylation machinery in the heart, which can be targeted for therapeutic intervention.

Human Cardiac Gene Therapy

In the past 10 years, there has been tremendous progress made in the field of gene therapy. Effective treatments of Leber congenital amaurosis, hemophilia, and spinal muscular atrophy have been largely based on the efficiency and safety of adeno-associated vectors. Myocardial gene therapy has been tested in patients with heart failure using adeno-associated vectors with no safety concerns but lacking clinical improvements. Cardiac gene therapy is adapting to the new developments in vectors, delivery systems, targets, and clinical end points and is poised for success in the near future.

Methods for the Preparation of an Excised, Cross-Circulated Rat Heart

The Emax-Pressure-Volume Area (PVA)-VO₂ framework proposed by Dr. Suga for canine hearts has dramatically advanced the field of cardiac mechanical work and energetics, i.e., mechanoenergetics. He and his collaborators investigated mechanoenergetics in the left ventricle (LV) of excised, cross-circulated canine heart preparations. We instituted the excised cross-circulated rat whole heart preparations and found a curvilinear end-systolic pressure-volume relation (ESPVR) in the rat LV, in contrast to the linear ESPVR in canine, rabbit, and human LVs. Although Emax, the slope of the linear ESPVR, could be used as an index of LV contractility, it was not applicable for evaluating LV contractility in the rat LV. Thus, we proposed a new index of contractility, equivalent Emax (eEmax) in the rat LV. We also found a linear VO₂-PVA relationship in the rat LV. Here, we introduce the methods for the preparation of excised, cross-circulated rat whole hearts and the eEmax-PVA-VO₂ framework in the rat LV. Using this method, we can obtain accurate LV volume and myocardial O₂ consumption in real time for estimating cardiac mechanoenergetics, which is very challenging in in vivo experiments.

Left ventricular mechanoenergetics in excised, cross-circulated rat hearts under hypo-, normo-, and hyperthermic conditions

We investigated the effects of altering cardiac temperature on left ventricular (LV) myocardial mechanical work and energetics using the excised, cross-circulated rat heart model. We analyzed the LV end-systolic pressure-volume relationship (ESPVR) and linear relationship between myocardial oxygen consumption per beat (VO2) and systolic pressure-volume area (PVA; total mechanical energy per beat) in isovolumically contracting rat hearts during hypo- (32 °C), normo- (37 °C), and hyperthermia (42 °C) under a 300-beats per minute pacing. LV ESPVR shifted downward with increasing cardiac temperature. The VO2-PVA relationship was superimposable in these different thermal conditions; however, each data point of VO2-PVA shifted left-downward during increasing cardiac temperature on the superimposable VO2-PVA relationship line. VO2 for Ca2+ handling in excitation-contraction coupling decreased, which was associated with increasing cardiac temperature, during which sarcoplasmic reticulum Ca2+-ATPase (SERCA) activity was suppressed, due to phospholamban phosphorylation inhibition, and instead, O2 consumption for basal metabolism was increased. The O2 cost of LV contractility for Ca2+ also increased with increasing cardiac temperature. Logistic time constants evaluating LV relaxation time were significantly shortened with increasing cardiac temperature related to the acceleration of the detachment in cross-bridge (CB) cycling, indicating increased myosin ATPase activity. The results suggested that increasing cardiac temperature induced a negative inotropic action related to SERCA activity suppression in Ca2+ handling and increased myosin ATPase activity in CB cycling. We concluded that thermal intervention could modulate cardiac inotropism by changing CB cycling, Ca2+ handling, and basal metabolism in rat hearts.

Correcting Calcium Dysregulation in Chronic Heart Failure Using SERCA2a Gene Therapy

Chronic heart failure (CHF) is a major contributor to cardiovascular disease and is the leading cause of hospitalization for those over the age of 65, which is estimated to account for close to seventy billion dollars in healthcare costs by 2030 in the US alone. The successful therapies for preventing and reversing CHF progression are urgently required. One strategy under active investigation is to restore dysregulated myocardial calcium (Ca²⁺), a hallmark of CHF. It is well established that intracellular Ca²⁺ concentrations are tightly regulated to control efficient myocardial systolic contraction and diastolic relaxation. Among the many cell surface proteins and intracellular organelles that act as the warp and woof of the regulatory network controlling intracellular Ca²⁺ signals in cardiomyocytes, sarco/endoplasmic reticulum Ca²⁺ ATPase type 2a (SERCA2a) undoubtedly plays a central role. SERCA2a is responsible for sequestrating cytosolic Ca²⁺ back into the sarcoplasmic reticulum during diastole, allowing for efficient uncoupling of actin-myosin and subsequent ventricular relaxation. Accumulating evidence has demonstrated that the expression of SERCA2a is downregulated in CHF, which subsequently contributes to severe systolic and diastolic dysfunction. Therefore, restoring SERCA2a expression and improving cardiomyocyte Ca²⁺ handling provides an excellent alternative to currently used transplantation and mechanical assist devices in the treatment of CHF. Indeed, advancements in safe and effective gene delivery techniques have led to the emergence of SERCA2a gene therapy as a potential therapeutic choice for CHF patients. This mini-review will succinctly detail the progression of SERCA2a gene therapy from its inception in plasmid and animal models, to its clinical trials in CHF patients, highlighting potential avenues for future work along the way.

MECHANISMS IN ENDOCRINOLOGY: Diabetic cardiomyopathy: pathophysiology and potential metabolic interventions state of the art review

Heart failure is a major cause of morbidity and mortality in type 2 diabetes. Type 2 diabetes contributes to the development of heart failure through a variety of mechanisms, including disease-specific myocardial structural, functional and metabolic changes. This review will focus on the contemporary contributions of state of the art non-invasive technologies to our understanding of diabetic cardiomyopathy, including data on cardiac disease phenotype, cardiac energy metabolism and energetic deficiency, ectopic and visceral adiposity, diabetic liver disease, metabolic modulation strategies and cardiovascular outcomes with new classes of glucose-lowering therapies.

Post-translational Modifications in Heart Failure: Small Changes, Big Impact

Heart failure is a complex disease process with various aetiologies and is a significant cause of morbidity and death world-wide. Post-translational modifications (PTMs) alter protein structure and provide functional diversity in terms of physiological functions of the heart. In addition, alterations in protein PTMs have been implicated in human disease pathogenesis. Small ubiquitin-like modifier mediated modification (SUMOylation) pathway was found to play essential roles in cardiac development and function. Abnormal SUMOylation has emerged as a new feature of heart failure pathology. In this review, we will highlight the importance of SUMOylation as a regulatory mechanism of SERCA2a function, and its therapeutic potential for the treatment of heart failure.

Small Molecular Allosteric Activator of the Sarco/Endoplasmic Reticulum Ca2+-ATPase (SERCA) Attenuates Diabetes and Metabolic Disorders

Dysregulation of endoplasmic reticulum (ER) Ca(2+) homeostasis triggers ER stress leading to the development of insulin resistance in obesity and diabetes. Impaired function of the sarco/endoplasmic reticulum Ca(2+)-ATPase (SERCA) has emerged as a major contributor to ER stress. We pharmacologically activated SERCA2b in a genetic model of insulin resistance and type 2 diabetes (ob/ob mice) with a novel allosteric activator, CDN1163, which markedly lowered fasting blood glucose, improved glucose tolerance, and ameliorated hepatosteatosis but did not alter glucose levels or body weight in lean controls. Importantly, CDN1163-treated ob/ob mice maintained euglycemia comparable with that of lean mice for >6 weeks after cessation of CDN1163 administration. CDN1163-treated ob/ob mice showed a significant reduction in adipose tissue weight with no change in lean mass, assessed by magnetic resonance imaging. They also showed an increase in energy expenditure using indirect calorimetry, which was accompanied by increased expression of uncoupling protein 1 (UCP1) and UCP3 in brown adipose tissue. CDN1163 treatment significantly reduced the hepatic expression of genes involved in gluconeogenesis and lipogenesis, attenuated ER stress response and ER stress-induced apoptosis, and improved mitochondrial biogenesis, possibly through SERCA2-mediated activation of AMP-activated protein kinase pathway. The findings suggest that SERCA2b activation may hold promise as an effective therapy for type-2 diabetes and metabolic dysfunction.

Small-molecule activation of SERCA2a SUMOylation for the treatment of heart failure

Decreased activity and expression of the cardiac sarcoplasmic reticulum calcium ATPase (SERCA2a), a critical pump regulating calcium cycling in cardiomyocyte, are hallmarks of heart failure. We have previously described a role for the small ubiquitin-like modifier type 1 (SUMO-1) as a regulator of SERCA2a and have shown that gene transfer of SUMO-1 in rodents and large animal models of heart failure restores cardiac function. Here, we identify and characterize a small molecule, N106, which increases SUMOylation of SERCA2a. This compound directly activates the SUMO-activating enzyme, E1 ligase, and triggers intrinsic SUMOylation of SERCA2a. We identify a pocket on SUMO E1 likely to be responsible for N106's effect. N106 treatment increases contractile properties of cultured rat cardiomyocytes and significantly improves ventricular function in mice with heart failure. This first-in-class small-molecule activator targeting SERCA2a SUMOylation may serve as a potential therapeutic strategy for treatment of heart failure.

SUMOylation of the cardiac calcium pump SERCA2a affects its activity and promotes cardiomyocyte contractility. Here the authors identify a small molecule N106 that increases SERCA2 SUMOylation and improves heart function in mice, and propose a promising therapeutic strategy for treatment of heart failure.

SERCA2a gene therapy in heart failure: an anti-arrhythmic positive inotrope

Therapeutic options that directly enhance cardiomyocyte contractility in chronic heart failure (HF) therapy are currently limited and do not improve prognosis. In fact, most positive inotropic agents, such as β-adrenoreceptor agonists and PDE inhibitors, which have been assessed in HF patients, cause increased mortality as a result of arrhythmia and sudden cardiac death. Cardiac sarcoplasmic reticulum Ca(2)(+) -ATPase2a (SERCA2a) is a key protein involved in sequestration of Ca(2)(+) into the sarcoplasmic reticulum (SR) during diastole. There is a reduction of SERCA2a protein level and function in HF, which has been successfully targeted via viral transfection of the SERCA2a gene into cardiac tissue in vivo. This has enhanced cardiac contractility and reduced mortality in several preclinical models of HF. Theoretical concerns have been raised regarding the possibility of arrhythmogenic adverse effects of SERCA2a gene therapy due to enhanced SR Ca(2)(+) load and induction of SR Ca(2)(+) leak as a result. Contrary to these concerns, SERCA2a gene therapy in a wide variety of preclinical models, including acute ischaemia/reperfusion, chronic pressure overload and chronic myocardial infarction, has resulted in a reduction in ventricular arrhythmias. The potential mechanisms for this unexpected beneficial effect, as well as mechanisms of enhancement of cardiac contractile function, are reviewed in this article.

Diabetic cardiomyopathy: pathophysiology and clinical features

Since diabetic cardiomyopathy was first reported four decades ago, substantial information on its pathogenesis and clinical features has accumulated. In the heart, diabetes enhances fatty acid metabolism, suppresses glucose oxidation, and modifies intracellular signaling, leading to impairments in multiple steps of excitation–contraction coupling, inefficient energy production, and increased susceptibility to ischemia/reperfusion injury. Loss of normal microvessels and remodeling of the extracellular matrix are also involved in contractile dysfunction of diabetic hearts. Use of sensitive echocardiographic techniques (tissue Doppler imaging and strain rate imaging) and magnetic resonance spectroscopy enables detection of diabetic cardiomyopathy at an early stage, and a combination of the modalities allows differentiation of this type of cardiomyopathy from other organic heart diseases. Circumstantial evidence to date indicates that diabetic cardiomyopathy is a common but frequently unrecognized pathological process in asymptomatic diabetic patients. However, a strategy for prevention or treatment of diabetic cardiomyopathy to improve its prognosis has not yet been established. Here, we review both basic and clinical studies on diabetic cardiomyopathy and summarize problems remaining to be solved for improving management of this type of cardiomyopathy.

Benefit of SERCA2a gene transfer to vascular endothelial and smooth muscle cells: a new aspect in therapy of cardiovascular diseases

Despite the great progress in cardiovascular health and clinical care along with marked decline in morbidity and mortality, cardiovascular diseases remain the leading causes of death and disability in the developed world. New therapeutic approaches, targeting not only systematic but also causal dysfunction, are ultimately needed to provide a valuable alternative for treatment of complex cardiovascular diseases. In heart failure, there are currently a number of trials that have been either completed or are ongoing targeting the sarcoplasmic reticulum calcium ATPase pump (SERCA2a) gene transfer in the context of heart failure. Recently, a phase 2 trial was completed, demonstrating safety and suggested benefit of adeno-associated virus type 1/SERCA2a gene transfer in advanced heart failure, supporting larger confirmatory trials. The experimental and clinical data suggest that, when administrated through perfusion, virus vector carrying SERCA2a can also transduce vascular endothelial and smooth muscle cells (EC and SMC) thereby improving the clinical benefit of gene therapy. Indeed, recent advances in understanding the molecular basis of vascular dysfunction point towards a reduction of sarcoplasmic reticulum Ca2+ uptake and an impairment of Ca2+ cycling in vascular EC and SMC from patients and preclinical models with cardiac diseases or with cardiovascular risk factors such as diabetes, hypercholesterolemia, coronary artery diseases, as well as other conditions such as pulmonary hypertension. In recent years, several studies have established that SERCA2a gene-based therapy could be an efficient option to treat vascular dysfunction. This review focuses on the recent finding showing the beneficial effects of SERCA2a gene transfer in vascular EC and SMC.

Impairment of calcium ATPases by high glucose and potential pharmacological protection

The review deals with impairment of Ca(2+)-ATPases by high glucose or its derivatives in vitro, as well as in human diabetes and experimental animal models. Acute increases in glucose level strongly correlate with oxidative stress. Dysfunction of Ca(2+)-ATPases in diabetic and in some cases even in nondiabetic conditions may result in nitration of and in irreversible modification of cysteine-674. Nonenyzmatic protein glycation might lead to alteration of Ca(2+)-ATPase structure and function contributing to Ca(2+) imbalance and thus may be involved in development of chronic complications of diabetes. The susceptibility to glycation is probably due to the relatively high percentage of lysine and arginine residues at the ATP binding and phosphorylation domains. Reversible glycation may develop into irreversible modifications (advanced glycation end products, AGEs). Sites of SERCA AGEs are depicted in this review. Finally, several mechanisms of prevention of Ca(2+)-pump glycation, and their advantages and disadvantages are discussed.

Gene therapy for heart failure: where do we stand?

Advances in understanding of the molecular basis of myocardial dysfunction, together with the development of increasingly efficient gene transfer technology, has placed heart failure within reach of gene-based therapy. Multiple components of cardiac contractility, including the Beta-adrenergic system, the calcium channel cycling pathway, and cytokine mediated cell proliferation, have been identified as appropriate targets for gene therapy. The development of efficient and safe vectors such as adeno-associated viruses and polymer nanoparticles has provided an opportunity for clinical application for gene therapy. The recent successful and safe completion of a phase 2 trial targeting the sarcoplasmic reticulum calcium ATPase pump (SERCA2a) has the potential to open a new era for gene therapy in the treatment of heart failure.

Potential of gene therapy as a treatment for heart failure

Advances in understanding the molecular basis of myocardial dysfunction, together with the evolution of increasingly efficient gene transfer technology, make gene-based therapy a promising treatment option for heart conditions. Cardiovascular gene therapy has benefitted from recent advancements in vector technology, design, and delivery modalities. There is a critical need to explore new therapeutic approaches in heart failure, and gene therapy has emerged as a viable alternative. Advances in understanding of the molecular basis of myocardial dysfunction, together with the development of increasingly efficient gene transfer technology, has placed heart failure within reach of gene-based therapy. The recent successful and safe completion of a phase 2 trial targeting the cardiac sarcoplasmic/endoplasmic reticulum Ca2+ ATPase pump (SERCA2a) has the potential to open a new era for gene therapy for heart failure.

Decoy peptides targeted to protein phosphatase 1 inhibit dephosphorylation of phospholamban in cardiomyocytes

Cardiac sarcoplasmic reticulum Ca(2+)-ATPase (SERCA2a) plays a crucial role in Ca(2+) handling in cardiomyocytes. Phospholamban (PLB) is an endogenous inhibitor of SERCA2a and its inhibitory activity is enhanced via dephosphorylation by protein phosphatase 1 (PP1). Therefore, the inhibition of PP1-mediated dephosphorylation of PLB might be an efficient strategy for the restoration of reduced SERCA2a activity in failing hearts. We sought to develop decoy peptides that would mimic phosphorylated PLB and thus competitively inhibit the PP1-mediated dephosphorylation of endogenous PLB. The phosphorylation sites Ser16 and Thr17 are located within the flexible loop region (amino acids 14-22) of PLB. We therefore synthesized a 9-mer peptide derived from this region (ΨPLB-wt) and two pseudo-phosphorylated peptides where Ser16 was replaced with Glu (ΨPLB-SE) or Thr17 was replaced with Glu (ΨPLB-TE). These peptides were coupled to the cell-permeable peptide TAT to facilitate cellular uptake. Treatment of adult rat cardiomyocytes with ΨPLB-SE or ΨPLB-TE, but not with ΨPLB-wt, significantly elevated the phosphorylation levels of PLB at Ser16 and Thr17. This increased phosphorylation of PLB correlated with an increase in contractile parameters in vitro. Furthermore, the perfusion of isolated rat hearts with ΨPLB-SE or ΨPLB-TE, but not with ΨPLB-wt, significantly improved left ventricular developed pressure that had been previously impaired by ischemia. These data indicate that ΨPLB-SE and ΨPLB-TE efficiently prevented dephosphorylation of PLB by serving as decoys for PP1. Therefore, these peptides may provide an effective modality to regulate SERCA2a activity in failing hearts.

Role of ER stress in ventricular contractile dysfunction in type 2 diabetes

Background

Diabetes mellitus (DM) is associated with an increased risk of ischemic heart disease and of adverse outcomes following myocardial infarction (MI). Here we assessed the role of endoplasmic reticulum (ER) stress in ventricular dysfunction and outcomes after MI in type 2 DM (T2DM).

Methodology and Principal Findings

In hearts of OLETF, a rat model of T2DM, at 25∼30 weeks of age, GRP78 and GRP94, markers of ER stress, were increased and sarcoplasmic reticulum calcium ATPase (SERCA)2a protein was reduced by 35% compared with those in LETO, a non-diabetic control. SERCA2a mRNA levels were similar, but SERCA2a protein was more ubiquitinated in OLETF than in LETO. Left ventricular (LV) end-diastolic elastance (Eed) was higher in OLETF than in LETO (53.9±5.2 vs. 20.2±5.6 mmHg/µl), whereas LV end-systolic elastance and positive inotropic responses to β-adrenergic stimulation were similar in OLETF and LETO. 4-Phenylbutyric acid (4-PBA), an ER stress modulator, suppressed both GRP up-regulation and SERCA2a ubiquitination and normalized SERCA2a protein level and Eed in OLETF. Sodium tauroursodeoxycholic acid, a structurally different ER stress modulator, also restored SERCA2a protein level in OLETF. Though LV dysfunction was modest, mortality within 48 h after coronary occlusion was markedly higher in OLETF than in LETO (61.3% vs. 7.7%). Telemetric recording showed that rapid progression of heart failure was responsible for the high mortality rate in OLETF. ER stress modulators failed to reduce the mortality rate after MI in OLETF.

Conclusions

ER stress reduces SERCA2a protein via its augmented ubiquitination and degradation, leading to LV diastolic dysfunction in T2DM. Even at a stage without systolic LV dysfunction, susceptibility to lethal heart failure after infarction is markedly increased, which cannot be explained by ER stress or change in myocardial response to sympathetic nerve activation.

Gene therapy for heart failure

Congestive heart failure accounts for half a million deaths per year in the United States. Despite its place among the leading causes of morbidity, pharmacological and mechanic remedies have only been able to slow the progression of the disease. Today's science has yet to provide a cure, and there are few therapeutic modalities available for patients with advanced heart failure. There is a critical need to explore new therapeutic approaches in heart failure, and gene therapy has emerged as a viable alternative. Recent advances in understanding of the molecular basis of myocardial dysfunction, together with the evolution of increasingly efficient gene transfer technology, have placed heart failure within reach of gene-based therapy. The recent successful and safe completion of a phase 2 trial targeting the sarcoplasmic reticulum calcium ATPase pump (SERCA2a), along with the start of more recent phase 1 trials, opens a new era for gene therapy for the treatment of heart failure.

Endogenous migration modulators as parent compounds for the development of novel cardiovascular and anti-inflammatory drugs

Development of novel cell migration modulators for anti-inflammatory and cardiovascular therapy is a complex task since any modulator will necessarily interfere with a balanced system of physiological regulators directing proper positioning of diverse immune cell types within the body. Whereas this shall serve efficient pathogen elimination, lack of proper control over these processes may result in counterproductive chronic inflammation and progressive tissue injury instead of healing. Prediction of the therapeutic potential or side effects of any migration modulator is not possible based on theoretical considerations alone but needs to be experimentally evaluated in preclinical disease models and by clinical studies. Here, we briefly summarize basic mechanism of cell migration, and groups of synthetic drugs currently in use for migration modulation. We then discuss one fundamental problem encountered with single-target approaches that arises from the complexity of any inflammation, with multiple interacting and often redundant factors being involved. This issue is likely to arise for any class of therapeutic agent (small molecules, peptides, antibodies, regulatory RNAs) addressing a single gene or protein. Against this background of studies on synthetic migration modulators addressing single targets, we then discuss the potential of endogenous proteins as therapeutic migration modulators, or as parent compounds for the development of mimetic drugs. Regulatory proteins of this type commonly address multiple receptors and signalling pathways and act upon the immune response in a phase-specific manner. Based on recent evidence, we suggest investigation of such endogenous migration modulators as novel starting points for anti-inflammatory and cardiovascular drug development.

Calcium cycling proteins and their association with heart failure

Heart failure (HF) has reached epidemic proportions in the United States and is one of the most important challenges to public health. Severe congestive HF is associated with substantial morbidity and mortality. HF afflicts approximately 5 million patients and contributes to 3 million hospitalizations and 300,000 deaths yearly. Late-stage HF has a poor prognosis, and therapeutic options are limited. Defective excitation–contraction (EC) coupling in HF may result from altered density or function of proteins relevant for Ca2+ homeostasis.

Calcium Upregulation by Percutaneous Administration of Gene Therapy in Cardiac Disease (CUPID): a phase 2 trial of intracoronary gene therapy of sarcoplasmic reticulum Ca2+-ATPase in patients with advanced heart failure

BACKGROUND

Adeno-associated virus type 1/sarcoplasmic reticulum Ca(2+)-ATPase was assessed in a randomized, double-blind, placebo-controlled, phase 2 study in patients with advanced heart failure.

METHODS AND RESULTS

Thirty-nine patients received intracoronary adeno-associated virus type 1/sarcoplasmic reticulum Ca(2+)-ATPase or placebo. Seven efficacy parameters were assessed in 4 domains: symptoms (New York Heart Association class, Minnesota Living With Heart Failure Questionnaire), functional status (6-minute walk test, peak maximum oxygen consumption), biomarker (N-terminal prohormone brain natriuretic peptide), and left ventricular function/remodeling (left ventricular ejection fraction, left ventricular end-systolic volume), plus clinical outcomes. The primary end point success criteria were prospectively defined as achieving efficacy at 6 months in the group-level (concordant improvement in 7 efficacy parameters and no clinically significant worsening in any parameter), individual-level (total score for predefined clinically meaningful changes in 7 efficacy parameters), or outcome end points (cardiovascular hospitalizations and time to terminal events). Efficacy in 1 analysis had to be associated with at least a positive trend in the other 2 analyses. This combination of requirements resulted in a probability of success by chance alone of 2.7%. The high-dose group versus placebo met the prespecified criteria for success at the group-level, individual-level, and outcome analyses (cardiovascular hospitalizations) at 6 months (confirmed at 12 months) and demonstrated improvement or stabilization in New York Heart Association class, Minnesota Living With Heart Failure Questionnaire, 6-minute walk test, peak maximum oxygen consumption, N-terminal prohormone brain natriuretic peptide levels, and left ventricular end-systolic volume. Significant increases in time to clinical events and decreased frequency of cardiovascular events were observed at 12 months (hazard ratio=0.12; P=0.003), and mean duration of cardiovascular hospitalizations over 12 months was substantially decreased (0.4 versus 4.5 days; P=0.05) on high-dose treatment versus placebo. There were no untoward safety findings.

CONCLUSIONS

The Calcium Upregulation by Percutaneous Administration of Gene Therapy in Cardiac Disease (CUPID) study demonstrated safety and suggested benefit of adeno-associated virus type 1/sarcoplasmic reticulum Ca(2+)-ATPase in advanced heart failure, supporting larger confirmatory trials.

CLINICAL TRIAL REGISTRATION

http://www.clinicaltrials.gov. Unique identifier: NCT00454818.

Endoplasmic-reticulum calcium depletion and disease

The endoplasmic reticulum (ER) as an intracellular Ca(2+) store not only sets up cytosolic Ca(2+) signals, but, among other functions, also assembles and folds newly synthesized proteins. Alterations in ER homeostasis, including severe Ca(2+) depletion, are an upstream event in the pathophysiology of many diseases. On the one hand, insufficient release of activator Ca(2+) may no longer sustain essential cell functions. On the other hand, loss of luminal Ca(2+) causes ER stress and activates an unfolded protein response, which, depending on the duration and severity of the stress, can reestablish normal ER function or lead to cell death. We will review these various diseases by mainly focusing on the mechanisms that cause ER Ca(2+) depletion.

Targeted gene therapy for the treatment of heart failure

Chronic heart failure is one of the leading causes of morbidity and mortality in Western countries and is a major financial burden to the health care system. Pharmacologic treatment and implanting devices are the predominant therapeutic approaches. They improve survival and have offered significant improvement in patient quality of life, but they fall short of producing an authentic remedy. Cardiac gene therapy, the introduction of genetic material to the heart, offers great promise in filling this void. In-depth knowledge of the underlying mechanisms of heart failure is, obviously, a prerequisite to achieve this aim. Extensive research in the past decades, supported by numerous methodological breakthroughs, such as transgenic animal model development, has led to a better understanding of the cardiovascular diseases and, inadvertently, to the identification of several candidate genes. Of the genes that can be targeted for gene transfer, calcium cycling proteins are prominent, as abnormalities in calcium handling are key determinants of heart failure. A major impediment, however, has been the development of a safe, yet efficient, delivery system. Nonviral vectors have been used extensively in clinical trials, but they fail to produce significant gene expression. Viral vectors, especially adenoviral, on the other hand, can produce high levels of expression, at the expense of safety. Adeno-associated viral vectors have emerged in recent years as promising myocardial gene delivery vehicles. They can sustain gene expression at a therapeutic level and maintain it over extended periods of time, even for years, and, most important, without a safety risk.

Cardiac gene therapy

Heart failure is a chronic progressive disorder in which frequent and recurrent hospitalizations are associated with high mortality and morbidity. The incidence and the prevalence of this disease will increase with the increase in the number of the aging population of the United States. Understanding the molecular pathology and pathophysiology of this disease will uncover novel targets and therapies that can restore the function or attenuate the damage of malfunctioning cardiomyocytes by gene therapy that becomes an interesting and a promising field for the treatment of heart failure as well as other diseases in the future. Of equal importance are developing vectors and delivery methods that can efficiently transduce most of the cardiomyocytes that can offer a long-term expression and that can escape the host immune response. Recombinant adeno-associated virus vectors have the potential to become a promising novel therapeutic vehicles for molecular medicine in the future.

Breviscapine ameliorates cardiac dysfunction and regulates the myocardial Ca(2+)-cycling proteins in streptozotocin-induced diabetic rats

To investigate the influence of breviscapine on the cardiac structure and function in diabetic cardiomyopathy rats as well as the expression of protein kinase C (PKC) and Ca(2+)-cycling proteins expression. Diabetes was induced in male Sprague-Dawley rats by a single intraperitoneal injection of streptozotocin and the control rats were injected with saline. After the induction of diabetes for 4 weeks, the animals were divided into different groups: (1) normal rats as control; (2) diabetic rats; (3) diabetic rats with administration of breviscapine (10 or 25 mg kg(-1) day(-2)). After treatment with breviscapine for 6 weeks, the invasive cardiac function and echocardiographic parameters were measured, and heart tissue was obtained for electron microscope study. The expression of protein kinase C (PKC) and calcium handling regulators, such as protein phosphatase inhibitor-1 (PPI-1), phospholamban (PLB) and Ca(2+)-ATPase (SERCA-2), ryanodine receptor (RyR) were detected by western blot or RT-PCR. The activity of SERCA-2 was measured using Ca(2+)-ATPase kit. Diabetic rats showed impaired cardiac structure and function compared with control rats. The expression of PKC, PLB increased significantly, while the PPI-1, SERCA-2 and RyR expression decreased. Treatment with breviscapine could reverse the cardiac dysfunction and structure changes in diabetic cardiomyopathy rats, and decrease the expression of PKC and PLB, as well as increase the expression of PPI-1, SERCA-2 and RyR. The protective effect of breviscapine was dose related. This study showed that breviscapine could regulate the expression of PKC, PPI-1, PLB and SERCA-2 and have protective effect on diabetic cardiomyopathy.

Gene delivery of sarcoplasmic reticulum calcium ATPase inhibits ventricular remodeling in ischemic mitral regurgitation

BACKGROUND

Mitral regurgitation (MR) doubles mortality after myocardial infarction (MI). We have demonstrated that MR worsens remodeling after MI and that early correction reverses remodeling. Sarcoplasmic reticulum Ca(+2)-ATPase (SERCA2a) is downregulated in this process. We hypothesized that upregulating SERCA2a might inhibit remodeling in a surgical model of apical MI (no intrinsic MR) with independent MR-type flow.

METHODS AND RESULTS

In 12 sheep, percutaneous gene delivery was performed by using a validated protocol to perfuse both the left anterior descending and circumflex coronary arteries with occlusion of venous drainage. We administered adeno-associated virus 6 (AAV6) carrying SERCA2a under a Cytomegalovirus promoter control in 6 sheep and a reporter gene in 6 controls. After 2 weeks, a standardized apical MI was created, and a shunt was implanted between the left ventricle and left atrium, producing regurgitant fractions of ≈30%. Animals were compared at baseline and 1 and 3 months by 3D echocardiography, Millar hemodynamics, and biopsies. The SERCA2a group had a well-maintained preload-recruitable stroke work at 3 months (decrease by 8±10% vs 42±12% with reporter gene controls; P<0.001). Left ventricular dP/dt followed the same pattern (no change vs 55% decrease; P<0.001). Left ventricular end-systolic volume was lower with SERCA2a (82.6±9.6 vs 99.4±9.7 mL; P=0.03); left ventricular end-diastolic volume, reflecting volume overload, was not significantly different (127.8±6.2 vs 134.3±9.4 mL). SERCA2a sheep showed a 15% rise in antiapoptotic pAkt versus a 30% reduction with the reporter gene (P<0.001). Prohypertrophic activated STAT3 was also 41% higher with SERCA2a than in controls (P<0.001). Proapoptotic activated caspase-3 rose >5-fold during 1 month in both SERCA2a and control animals (P=NS) and decreased by 19% at 3 months, remaining elevated in both groups.

CONCLUSIONS

In this controlled model, upregulating SERCA2a induced better function and lesser remodeling, with improved contractility, smaller volume, and activation of prohypertrophic/antiapoptotic pathways. Although caspase-3 remained activated in both groups, SERCA2a sheep had increased molecular antiremodeling "tone." We therefore conclude that upregulating SERCA2a inhibits MR-induced post-MI remodeling in this model and thus may constitute a useful approach to reduce the vicious circle of remodeling in ischemic MR.

SERCA2a gene transfer enhances eNOS expression and activity in endothelial cells

Congestive heart failure (HF) is associated with impaired endothelium-dependent nitric oxide-mediated vasodilatation. The aim of this study was to examine the effects of sarco/endoplasmic reticulum (ER) Ca(2+)-ATPase 2a (SERCA2a) gene transfer on endothelial function in a swine HF model. Two months after the creation of mitral regurgitation to induce HF, the animals underwent intracoronary injection of adeno-associated virus (AAV) carrying SERCA2a (n = 7) or saline (n = 6). At 4 months, coronary flow (CF) was measured in the mid-portion of the left anterior descending (LAD) artery. In the failing animals, CF was decreased significantly; SERCA2a gene transfer rescued CF to levels observed in sham-group [ml/min/g, 0.47 +/- 0.064 saline versus 0.89 +/- 0.116, SERCA2a; P < 0.05; 1.00 +/- 0. 185 sham P = NS (nonsignificant)]. In coronary arteries from HF animals, SERCA2a and endothelial isoform of nitric oxide synthase (eNOS) protein expression were decreased, but restored to normal levels by SERCA2a gene transfer. In human coronary artery endothelial cells (HCAECs), SERCA2a overexpression increased eNOS expression, phosphorylation, eNOS promoter activity, Ca(2+) storage capacity, and enhanced histamine-induced calcium oscillations, eNOS activity, and cyclic guanosine monophosphate (cGMP) production. Thus, SERCA2a gene transfer increases eNOS expression and activity by modulating calcium homeostasis to improve CF. These findings suggest that SERCA2a gene transfer improves vascular reactivity in the setting of HF.

Alpha1A-adrenergic receptor-directed autoimmunity induces left ventricular damage and diastolic dysfunction in rats

BACKGROUND

Agonistic autoantibodies to the alpha(1)-adrenergic receptor occur in nearly half of patients with refractory hypertension; however, their relevance is uncertain.

METHODS/PRINCIPAL FINDINGS

We immunized Lewis rats with the second extracellular-loop peptides of the human alpha(1A)-adrenergic receptor and maintained them for one year. Alpha(1A)-adrenergic antibodies (alpha(1A)-AR-AB) were monitored with a neonatal cardiomyocyte contraction assay by ELISA, and by ERK1/2 phosphorylation in human alpha(1A)-adrenergic receptor transfected Chinese hamster ovary cells. The rats were followed with radiotelemetric blood pressure measurements and echocardiography. At 12 months, the left ventricles of immunized rats had greater wall thickness than control rats. The fractional shortening and dp/dt(max) demonstrated preserved systolic function. A decreased E/A ratio in immunized rats indicated a diastolic dysfunction. Invasive hemodynamics revealed increased left ventricular end-diastolic pressures and decreased dp/dt(min). Mean diameter of cardiomyocytes showed hypertrophy in immunized rats. Long-term blood pressure values and heart rates were not different. Genes encoding sarcomeric proteins, collagens, extracellular matrix proteins, calcium regulating proteins, and proteins of energy metabolism in immunized rat hearts were upregulated, compared to controls. Furthermore, fibrosis was present in immunized hearts, but not in control hearts. A subset of immunized and control rats was infused with angiotensin (Ang) II. The stressor raised blood pressure to a greater degree and led to more cardiac fibrosis in immunized, than in control rats.

CONCLUSIONS/SIGNIFICANCE

We show that alpha(1A)-AR-AB cause diastolic dysfunction independent of hypertension, and can increase the sensitivity to Ang II. We suggest that alpha(1A)-AR-AB could contribute to cardiovascular endorgan damage.

Targeting the redox regulation of SERCA in vascular physiology and disease

The sarco/endoplasmic reticulum calcium ATPase (SERCA) is essential for the control of intracellular free Ca(2+) levels. Although the importance for this enzyme in cardiac myocytes is well recognized, it is only recently that SERCA has been identified as an important effector of nitric oxide (NO) action in vascular cells. NO can stimulate the uptake of cytosolic Ca(2+) via SERCA by adducting glutathione to the reactive cysteine-674. Mutation of this single amino acid prevents the stimulation of Ca(2+) uptake by NO, as well as its ability to inhibit smooth muscle cell functions including migration. NO function is impaired in a variety of cardiovascular diseases, including diabetes, hypercholesterolemia, and atherosclerosis, which are all associated with SERCA dysfunction caused by the increased oxidants in these diseases. Targeting the oxidant sources in vascular diseases to prevent SERCA from being oxidized and/or increasing the expression of SERCA may improve vascular disease development.

Modulation of vascular sarco/endoplasmic reticulum calcium ATPase in cardiovascular pathophysiology

Endothelial dysfunction associated with decreased nitric oxide (NO) bioactivity is a major feature of vascular diseases such as atherosclerosis or diabetes. Sodium nitroprusside (SNP)-induced relaxation is entirely dependent on cyclic guanosine monophosphate (cGMP) and preserved in atherosclerosis, suggesting that smooth muscle response to NO donor is intact. However, NO gas activates both cGMP-dependent and -independent signal pathways in vascular smooth muscle cells, and oxidative stress associated with vascular diseases selectively impairs cGMP-independent relaxation to NO. Sarco/endoplasmic reticulum Ca(2+) ATPase (SERCA), which regulates intracellular Ca(2+) levels by pumping Ca(2+) into store, is a major cGMP-independent target for NO. Physiological levels of reactive nitrogen species (RNS) S-glutathiolate SERCA at Cys674 to increase its activity, and the augmentation of RNS in vascular diseases irreversibly oxidizes Cys674 or nitrates tyrosine residues at Tyr296-Tyr297, which are associated with loss of function. S-glutathiolation of various proteins by NO can explain redox-sensitive cGMP-independent actions, and oxidative inactivation of target proteins for NO can be associated with the pathogenesis of cardiovascular diseases. Oxidative inactivation of SERCA is also implicated with dysregulation of smooth muscle migration, promotion of platelet aggregation, and impairment of cardiac function, which can be implicated with restenosis, pathological angiogenesis, thrombosis, as well as heart failure. Analysis of posttranslational oxidative modifications of SERCA and the preservation of SERCA function can be novel strategies against cardiovascular diseases associated with oxidative stress.

Sarcoplasmic reticulum Ca(2+) ATPase as a therapeutic target for heart failure

The cardiac isoform of the sarco/endoplasmic reticulum Ca(2+)ATPase (SERCA2a) plays a major role in controlling excitation/contraction coupling. In both experimental and clinical heart failure, SERCA2a expression is significantly reduced which leads to abnormal Ca(2+) handling and deficient contractility. A large number of studies in isolated cardiac myocytes and in small and large animal models of heart failure showed that restoring SERCA2a expression by gene transfer corrects the contractile abnormalities and improves energetics and electrical remodeling. Following a long line of investigation, a clinical trial is underway to restore SERCA2a expression in patients with heart failure using adeno-associated virus type 1. This review addresses the following issues regarding heart failure gene therapy: i) new insights on calcium regulation by SERCA2a; ii) SERCA2a as a gene therapy target in animal models of heart failure; iii) advances in the development of viral vectors and gene delivery; and iv) clinical trials on heart failure using SERCA2a. This review focuses on the new advances in SERCA2a- targeted gene therapy made in the last three years. In conclusion, SERCA2a is an important therapeutic target in various cardiovascular disorders. Ongoing clinical gene therapy trials will provide answers on its safety and applicability.

Gene remodeling in type 2 diabetic cardiomyopathy and its phenotypic rescue with SERCA2a

Background/Aim

Diabetes-associated myocardial dysfunction results in altered gene expression in the heart. We aimed to investigate the changes in gene expression profiles accompanying diabetes-induced cardiomyopathy and its phenotypic rescue by restoration of SERCA2a expression.

Methods/Results

Using the Otsuka Long-Evans Tokushima Fatty rat model of type 2 diabetes and the Agilent rat microarray chip, we analyzed gene expression by comparing differential transcriptional changes in age-matched control versus diabetic hearts and diabetic hearts that received gene transfer of SERCA2a. Microarray expression profiles of selected genes were verified with real-time qPCR and immunoblotting. Our analysis indicates that diabetic cardiomyopathy is associated with a downregulation of transcripts. Diabetic cardiomyopathic hearts have reduced levels of SERCA2a. SERCA2a gene transfer in these hearts reduced diabetes-associated hypertrophy, and differentially modulated the expression of 76 genes and reversed the transcriptional profile induced by diabetes. In isolated cardiomyocytes in vitro, SERCA2a overexpression significantly modified the expression of a number of transcripts known to be involved in insulin signaling, glucose metabolism and cardiac remodeling.

Conclusion

This investigation provided insight into the pathophysiology of cardiac remodeling and the potential role of SERCA2a normalization in multiple pathways in diabetic cardiomyopathy.

Long-term cardiac-targeted RNA interference for the treatment of heart failure restores cardiac function and reduces pathological hypertrophy

BACKGROUND

RNA interference (RNAi) has the potential to be a novel therapeutic strategy in diverse areas of medicine. Here, we report on targeted RNAi for the treatment of heart failure, an important disorder in humans that results from multiple causes. Successful treatment of heart failure is demonstrated in a rat model of transaortic banding by RNAi targeting of phospholamban, a key regulator of cardiac Ca(2+) homeostasis. Whereas gene therapy rests on recombinant protein expression as its basic principle, RNAi therapy uses regulatory RNAs to achieve its effect.

METHODS AND RESULTS

We describe structural requirements to obtain high RNAi activity from adenoviral and adeno-associated virus (AAV9) vectors and show that an adenoviral short hairpin RNA vector (AdV-shRNA) silenced phospholamban in cardiomyocytes (primary neonatal rat cardiomyocytes) and improved hemodynamics in heart-failure rats 1 month after aortic root injection. For simplified long-term therapy, we developed a dimeric cardiotropic adeno-associated virus vector (rAAV9-shPLB) to deliver RNAi activity to the heart via intravenous injection. Cardiac phospholamban protein was reduced to 25%, and suppression of sacroplasmic reticulum Ca(2+) ATPase in the HF groups was rescued. In contrast to traditional vectors, rAAV9 showed high affinity for myocardium but low affinity for liver and other organs. rAAV9-shPLB therapy restored diastolic (left ventricular end-diastolic pressure, dp/dt(min), and tau) and systolic (fractional shortening) functional parameters to normal ranges. The massive cardiac dilation was normalized, and cardiac hypertrophy, cardiomyocyte diameter, and cardiac fibrosis were reduced significantly. Importantly, no evidence was found of microRNA deregulation or hepatotoxicity during these RNAi therapies.

CONCLUSIONS

Our data show for the first time the high efficacy of an RNAi therapeutic strategy in a cardiac disease.

Interaction of diet and diabetes on cardiovascular function in rats

Genetic rodent models of type 2 diabetes are routinely utilized in studies of diabetes-related cardiovascular disease; however, these models frequently exhibit abnormalities that are not consistent with diabetic complications. The aim of this study was to develop a model of type 2 diabetes that exhibits evidence of cardiovascular dysfunction commonly seen in patients with diabetes with minimal nondiabetes-related pathologies. Young male rats received either control (Con), high-fat (HF; 60%), or Western (Wes; 40% fat, 45% carbohydrate) diets for 2 wk after which streptozotocin (2 x 35 mg/kg ip 24 h apart) was administered to induce diabetes (Dia). Blood glucose levels were higher in Con + Dia and Wes + Dia groups compared with the HF + Dia group (25 +/- 1, 25 +/- 2, and 15 +/- 1 mmol/l, respectively; P < 0.05) group. Liver, kidney, and pancreatic dysfunction and cardiomyocyte lipid accumulation were found in all diabetic animals. Despite lower heart rates in Con + Dia and HF + Dia groups, arterial and left ventricular pressures were not different between any of the experimental groups. All three diabetic groups had diastolic dysfunction, but only HF + Dia and Wes + Dia groups exhibited elevated diastolic wall stress, arterial stiffness (augmentation index), and systolic dysfunction (velocity of circumferential shortening, systolic wall stress). Surprisingly, we found that left ventricular dysfunction and arterial stiffness were more pronounced in the HF + Dia than the Con + Dia group and was similar to the Wes + Dia group despite significantly lower levels of hyperglycemia compared with either group. In conclusion, the HF + Dia group exhibited a stable, modest level of hyperglycemia, which was associated with cardiac dysfunction comparable with that seen in moderate to advanced stages of human type 2 diabetes.