Introduction: Chronic heart failure (HF) is characterized by enhanced circulating cardiotoxic hormones, among the most prominent of which is aldosterone, which contributes to the increased morbidity and mortality of the disease by... more
Introduction: Chronic heart failure (HF) is characterized by enhanced circulating cardiotoxic hormones, among the most prominent of which is aldosterone, which contributes to the increased morbidity and mortality of the disease by promoting cardiac adverse remodeling post-myocardial infarction (MI). Cardiac β-adrenergic receptor (ΑR) desensitization and downregulation are a hallmark abnormality in HF at the molecular level and are due to the concerted action of cardiac G protein-coupled receptor kinase-2 (GRK2), together with its co-factors in receptor desensitization, the βarrestins (βarrs). We have also recently established that βarr1 promotes angiotensin II-dependent aldosterone production in the adrenal cortex, and this leads to elevated circulating aldosterone levels in vivo, both under normal conditions and during post-MI HF progression. Hypothesis: Herein, we sought to investigate the effects of genetically deleting βarr1 on post-MI cardiac function and hyperaldosteronic status in mice progressing to HF. Methods: We uitilized the βarr1KO mouse model and studied these mice at 4 weeks after surgically induced MI, in parallel with C57/B6 wild type (WT) controls. Cardiac function was assessed by echocardiography and in vivo catheterization. Plasma aldosterone was measured by ELISA. Results: Cardiac function is markedly improved in βarr1KO`s at 4 weeks post-MI, as evidenced by increased ejection fraction compared to WT mice (41.5 + 2.8 % vs. 21.8 + 2.4 %, respectively, n=9, p<0.0001) and increased isoproterenol-induced contractility. Additionally, cardiac dimensions are significantly reduced compared to WT`s, indicating attenuation of adverse cardiac remodeling. Importantly, plasma circulating aldosterone levels are significantly lowered and cardiac βAR signaling and function appear elevated in post-MI βarr1KO`s compared to control WT`s. Conclusions: Genetic deletion of βarr1 substantially improves cardiac function, adverse remodeling, hyperaldosteronism, and cardiac βAR function during post-MI HF progression. The underlying mechanism is attenuation of both cardiac βAR desensitization/downregulation and adrenal aldosterone production, which is βarr1-dependent.
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ß 1 - and ß 2 -adrenergic receptors (ßARs) are G-protein coupled receptors (GPCRs) that play clearly distinct roles in cardiac physiology/pathology: cardiomyocyte contraction is readily stimulated by ß 1 AR but not ß 2 AR signaling, and ß... more
ß 1 - and ß 2 -adrenergic receptors (ßARs) are G-protein coupled receptors (GPCRs) that play clearly distinct roles in cardiac physiology/pathology: cardiomyocyte contraction is readily stimulated by ß 1 AR but not ß 2 AR signaling, and ß 1 AR signaling is largely pro-apoptotic in the heart, in contrast to the cardioprotective ß 2 AR signaling. These differences might be due to assembly of different macromolecular complexes containing phosphodiesterases (PDEs), which constrain pro-contractile 3'-5'-adenosine monophosphate (cAMP) signaling. Additionally, ß 2 AR is readily phosphorylated by GPCR kinase (GRK)-2, which then recruits ß-arrestin (ßarr), a universal GPCR adapter/scaffolding molecule, to the receptor. ßarrs reduce ß 2 AR pro-contractile signaling by desensitizing the receptor and can either increase or decrease apoptosis via interactions with several downstream effectors. Herein, we sought to investigate the effect of ßarr recruitment blockade on ß 2 AR-dependent contractility and survival in vivo. To this end, we crossed ß 1 AR knockout (B1KO) mice, lacking the ß 1 AR, with M27 mice, which overexpress, specifically in cardiac myocytes, the GRK2 inhibitor GRK2ct (or ßARKct). By blocking GRK2-mediated phosphorylation, ßarr binding to ß 2 AR is prevented. We studied the offspring both under normal conditions and after surgically induced myocardial infarction (MI). Contractility was significantly augmented in M27/B1KO mice compared to control B1KO's, both in healthy mice (ejection fraction (EF): 69+1.8% vs. 57+1.7%, respectively, p<0.05, n=8) and at 4 weeks post-MI (EF: 42.6+0.1% vs. 25+3.9%, respectively, p<0.05, n=8). In addition, M27/B1KO mice exhibited less cardiac dilatation, increased survival and decreased cardiac apoptosis and infarct size, compared to B1KO's, at 4 weeks post-MI. At the molecular level, M27/B1KO hearts displayed significantly less membrane recruitment of PDEs, upregulation of the anti-apoptotic Bcl-2 and a more favorable inflammatory cytokine profile vs. B1KO hearts. Thus, cardiac GRK2 inhibition by GRK2ct increases both ß 2 AR-dependent contractility and survival in post-MI heart failure and could be pursued in situations where ß 2 AR agonism is beneficial, e.g. in patients awaiting cardiac transplantation.
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Heart failure (HF) is the number one killer disease in the western world and new and innovative treatments are needed. Sarco(endo)plasmic reticulum Ca 2+ -ATPase (SERCA)-2a is a crucial, for contractile function, calcium-handling protein... more
Heart failure (HF) is the number one killer disease in the western world and new and innovative treatments are needed. Sarco(endo)plasmic reticulum Ca 2+ -ATPase (SERCA)-2a is a crucial, for contractile function, calcium-handling protein expressed in the mammalian myocardium and its downregulation is one of the molecular hallmarks of chronic HF. Its activation is part of the signaling mechanism by which the β 1 -adrenergic receptors (ARs) increase cardiac contractility. Agonist-bound β 1 ARs however, like most G protein-coupled receptors (GPCRs), undergo functional desensitization/internalization due to the actions of βarrestin1 or -2. These two arrestins are universal GPCR adapter proteins, mediating G protein-independent signaling via multi-protein scaffolding, and, among the cellular processes they can regulate, is protein SUMO (small ubiquitin-like modifier)-ylation, which generally increases protein stability/levels. In the heart, βarrestin1 appears detrimental, whereas βarrestin2 beneficial, for structure and function post-myocardial infarction (MI). Post-MI βarrestin1 knockout mice also display elevated SERCA2a activity and better contractility than post-MI wild type mice. In addition, reduced cardiac SERCA2a SUMOylation is known to underlie its downregulation in HF, decreasing cardiac contractility. Thus, in the present study, we sought to investigate a potential involvement of cardiac β 1 AR-activated βarrestins in regulation of SERCA2a SUMOylation and activity. By studying individual βarrestin knockout heart extracts, we found that βarrestin2, but not βarrestin1, interacts with SERCA2a in the mouse heart in vivo, promoting the latter`s SUMOylation and activity. This interaction is direct, as indicated by pull-down and FRET experiments. Finally, via in vitro studies in the cardiomyocyte-like cell line H9c2, we found that this interaction is both β 1 AR-, and beta-agonist-specific, and leads to increased Ubc9-dependent SERCA2a SUMOylation, which, in turn, acutely enhances SERCA2a activity in H9c2 cells. These results suggest that βarrestin2, presumed to also decrease cardiac function by desensitizing βARs, may actually (directly) enhance cardiac contractility, thereby opposing βarrestin1 in that regard.
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Rationale: β1 and β2-adrenergic receptors (βARs) play distinct roles in the heart, e.g. β1AR is pro-contractile and pro-apoptotic but β2AR anti-apoptotic and only weakly pro-contractile. G protein ...
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Aims Myocardial infarction (MI) is the most common cause of heart failure (HF) worldwide. G protein-coupled receptor kinase 5 (GRK5) is upregulated in failing human myocardium and promotes maladaptive cardiac hypertrophy in animal... more
Aims Myocardial infarction (MI) is the most common cause of heart failure (HF) worldwide. G protein-coupled receptor kinase 5 (GRK5) is upregulated in failing human myocardium and promotes maladaptive cardiac hypertrophy in animal models. However, the role of GRK5 in ischemic heart disease is still unknown. In this study, we evaluated whether myocardial GRK5 plays a critical role post-MI in mice and included the examination of specific cardiac immune and inflammatory responses. Methods and results Cardiomyocyte-specific GRK5 overexpressing transgenic mice (TgGRK5) and non-transgenic littermate control (NLC) mice as well as cardiomyocyte-specific GRK5 knockout mice (GRK5cKO) and wild type (WT) were subjected to MI and, functional as well as structural changes together with outcomes were studied. TgGRK5 post-MI mice showed decreased cardiac function, augmented left ventricular dimension and decreased survival rate compared to NLC post-MI mice. Cardiac hypertrophy and fibrosis as wel...
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β 1 - and β 2 -adrenergic receptors (βARs) are G-protein coupled receptors (GPCRs) that play clearly distinct roles in cardiac physiology/pathology. For instance, cardiomyocyte contraction is readily stimulated by β 1 AR but not β 2 AR... more
β 1 - and β 2 -adrenergic receptors (βARs) are G-protein coupled receptors (GPCRs) that play clearly distinct roles in cardiac physiology/pathology. For instance, cardiomyocyte contraction is readily stimulated by β 1 AR but not β 2 AR signaling. This might be explained by differences in assembly of macromolecular signaling complexes: β 1 AR forms a signaling complex with phosphodiesterase (PDE) type 4D8 directly, and agonist binding dissociates this complex. Conversely, GPCR kinase (GRK)2-induced β 2 AR phosphorylation leads to recruitment of a complex consisting of β-arrestin (βarr), a universal GPCR adapter/scaffolding molecule, and another PDE4D variant, PDE4D5. This PDE4D recruitment is postulated to constrain β 2 AR pro-contractile signaling by limiting compartmentalization of 3′-5′-adenosine monophosphate signaling. Thus, herein, we sought to investigate the effect of inhibition of this complex recruitment on β 2 AR pro-contractile signaling in vivo. In order to block β 2 AR-...
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Diabetes mellitus, a worldwide health threat, is considered an independent risk factor for cardiovascular diseases. The overall cardiovascular risk of diabetes is similar to the one having one myocardial infarction (MI) attack although... more
Diabetes mellitus, a worldwide health threat, is considered an independent risk factor for cardiovascular diseases. The overall cardiovascular risk of diabetes is similar to the one having one myocardial infarction (MI) attack although the precise impact of diabetes on MI-induced myocardial anomalies remains elusive. Given that mortality following MI is much greater in diabetic patients compared to nondiabetic patients, this study was designed to examine the effect of melatonin on MI injury-induced myocardial dysfunction in diabetes. Adult mice were made diabetic using high-fat feeding and streptozotocin (100 mg/kg body weight) prior to MI and were treated with melatonin (50 mg/kg/d, p.o.) for 4 weeks prior to assessment of cardiac geometry and function. The MI procedure in diabetes displayed overt changes in cardiac geometry (chamber dilation and interstitial fibrosis) and functional anomalies (reduced fractional shortening and cardiomyocyte contractile capacity) in association wit...
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Research Interests: Magnetic Resonance Spectroscopy, Medicine, Fourier Analysis, Cardioprotection, Temperature, and 10 moreMedical Biochemistry, Theranostics, Molecular Conformation, Reperfusion injury, NAD, Medicine and Health Sciences, Structure activity Relationship, Cardiomyocyte, Translational Medical Research, and nadp
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Cardiokines play an essential role in maintaining normal cardiac functions and responding to acute myocardial injury. Studies have demonstrated the heart itself is a significant source of C1q/TNF-related protein 9 (CTRP9). However, the... more
Cardiokines play an essential role in maintaining normal cardiac functions and responding to acute myocardial injury. Studies have demonstrated the heart itself is a significant source of C1q/TNF-related protein 9 (CTRP9). However, the biological role of cardiac-derived CTRP9 remains unclear. We hypothesize cardiac-derived CTRP9 responds to acute myocardial ischemia/reperfusion (MI/R) injury as a cardiokine. We explored the role of cardiac-derived CTRP9 in MI/R injury via genetic manipulation and a CTRP9-knockout (CTRP9-KO) animal model. Inhibition of cardiac CTRP9 exacerbated, whereas its overexpression ameliorated, left ventricular dysfunction and myocardial apoptosis. Endothelial CTRP9 expression was unchanged while cardiomyocyte CTRP9 levels decreased after simulated ischemia/`reperfusion (SI/R) in vitro. Cardiomyocyte CTRP9 overexpression inhibited SI/R-induced apoptosis, an effect abrogated by CTRP9 antibody. Mechanistically, cardiac-derived CTRP9 activated anti-apoptotic sign...
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Coronary heart disease patients with type 2 diabetes were subject to higher vulnerability for cardiac ischemia-reperfusion (I/R) injury. This study was designed to evaluate the impact of ZP2495 (a glucagon-GLP-1 dual-agonist) on cardiac... more
Coronary heart disease patients with type 2 diabetes were subject to higher vulnerability for cardiac ischemia-reperfusion (I/R) injury. This study was designed to evaluate the impact of ZP2495 (a glucagon-GLP-1 dual-agonist) on cardiac function and energy metabolism after myocardial I/R injury in db/db mice with a focus on mitochondrial function. C57BLKS/J-lepr/lepr(BKS) and db/db mice received 4-week treatment of glucagon, ZP131 (GLP-1 receptor agonist), or ZP2495, followed by cardiac I/R injury. The results showed that cardiac function, cardiac glucose metabolism, cardiomyocyte apoptosis, cardiac mitochondrial morphology, and energetic transition were improved or ameliorated by ZP2495 to a greater extent than that of glucagon and ZP131.study showed that ZP2495, rather than glucagon, alleviated mitochondrial depolarization, cytochrome C release, and mitochondria ROS generation in neonatal rat ventricular myocytes subjected to high-glucose and simulated I/R injury conditions, the e...
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Rationale: β1 and β2-adrenergic receptors (βARs) play distinct roles in the heart, e.g. β1AR is pro-contractile and pro-apoptotic but β2AR anti-apoptotic and only weakly pro-contractile. G protein ...
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The insulin-PI3K-mTOR pathway exhibits a variety of cardiovascular activities including protection against I/R injury. Lin28a enhanced glucose uptake and insulin-sensitivity via insulin-PI3K-mTOR signalling pathway. However, the role of... more
The insulin-PI3K-mTOR pathway exhibits a variety of cardiovascular activities including protection against I/R injury. Lin28a enhanced glucose uptake and insulin-sensitivity via insulin-PI3K-mTOR signalling pathway. However, the role of lin28a on experimental cardiac I/R injury in diabetic mice are not well understood. Diabetic mice underwent 30 min. of ischaemia followed by 3 hrs of reperfusion. Animals were randomized to be treated with lentivirus carrying lin28a siRNA (siLin28a) or lin28a cDNA (Lin28a) 72 hrs before coronary artery ligation. Myocardial infarct size (IS), cardiac function, cardiomyocyte apoptosis and mitochondria morphology in diabetic mice who underwent cardiac I/R injury were compared between groups. The target proteins of lin28a were examined by western blot analysis. Lin28a overexpression significantly reduced myocardial IS, improved LV ejection fraction (LVEF), decreased myocardial apoptotic index and alleviated mitochondria cristae destruction in diabetic mi...
Research Interests: Biology, Cytokines, Apoptosis, Medicine, Gene expression, and 15 moreWestern blotting, Signal Transduction, RNA interference, Insulin, Animals, Male, Heart, Phosphorylation, Clinical Sciences, microRNAs, Myocardium, Ejection Fraction, Sirolimus, Biochemistry and cell biology, and reverse transcriptase polymerase chain reaction
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S -nitrosothiols protect against ischemic injury in the heart by limiting signaling downstream of G protein–coupled receptors.
Research Interests: Biology, Medicine, Western blotting, Transgenic Mice, Signal Transduction, and 13 moreMice, G protein-coupled receptors, Nitric oxide, Animals, Heart, Rats, Myocardium, Knockout Mice, S-Nitrosylation, Biochemistry and cell biology, Nitric oxide donors, Isoproterenol, and reverse transcriptase polymerase chain reaction
Chronic heart failure (HF) is characterized by sympathetic overactivity reflected by enhanced circulating catecholamines (CAs), which contribute to increased morbidity and mortality. We recently reported that adrenal G-protein coupled... more
Chronic heart failure (HF) is characterized by sympathetic overactivity reflected by enhanced circulating catecholamines (CAs), which contribute to increased morbidity and mortality. We recently reported that adrenal G-protein coupled receptor kinase-2 (GRK2) is up-regulated in chronic HF, leading to enhanced CA release via desensitization/downregulation of the chromaffin cell a 2 -adrenergic receptors (a 2 ARs) that normally inhibit CA secretion. We also showed that adrenal GRK2 inhibition via adenoviral-mediated in vivo gene therapy acutely decreases circulating CAs and improves cardiac inotropic reserve and function ( Lymperopoulos, A. et al., Nat. Med.13 : 315–323, 2007). In the present study, we hypothesized that adrenal-targeted GRK2 gene deletion might be beneficial in chronic HF by means of normalizing sympathetic activity. Methods: To specifically delete GRK2 only in the chromaffin cells of the adrenal gland, we utilized the Cre/loxP technology, crossing PNMT-Cre mice, which express Cre recombinase under the gene promoter of phenylethanolamine N-methyl transferase (PNMT), a chromaffin cell-specific enzyme. We crossed these mice with floxGRK2 +/+ mice, which have the GRK2 gene flanked by loxP sites, thus targeted for deletion by Cre. At 2 months of age, offspring underwent surgical myocardial infarction (MI) to induce HF, and 4 weeks later, cardiac function, adrenal physiology and CA levels were assessed. Results: Genetic screening and western blotting in adrenal extracts confirmed a significant (54 ± 10 % vs. control, non-crossed floxGRK2 +/+ ) reduction of adrenal GRK2 protein levels in PNMTCre/floxGRK2 mice. Adrenal weight-to-body weight ratio was also significantly lower at 4 weeks post-MI, indicating prevention of post-MI adrenal hypertrophy. Additionally, plasma circulating CAs were reduced, and, importantly, cardiac ejection fraction of PNMTCre/floxGRK2 mice was markedly higher than that of floxGRK2 +/+ mice at 4-weeks post-MI (39.6 ± 1.0%, n = 9, vs. 30.9 ± 1.6%, n = 11, respectively, p = 0.0005). Moreover, contractile function and βAR signaling significantly improved. Conclusions: Adrenal-targeted GRK2 gene knockout decreases circulating CAs, leading to improved cardiac inotropic/adrenergic reserve in post-MI HF. This research has received full or partial funding support from the American Heart Association, AHA Great Rivers Affiliate (Delaware, Kentucky, Ohio, Pennsylvania & West Virginia).
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Research Interests: Endocrinology, Medical Genetics, Biology, Biological Chemistry, Medicine, and 15 moreBiological Sciences, Heart Failure, Humans, Internal Medicine, Epinephrine, Mice, Chronic Disease, Animals, CHEMICAL SCIENCES, Alpha, Catecholamines, Crosses, Genetic, Adrenal glands, and Medical and Health Sciences
β-Arrestin (βarr)-1 and β-arrestin-2 (βarrs) are universal G-protein–coupled receptor adapter proteins that negatively regulate cardiac β-adrenergic receptor (βAR) function via βAR desensitization and downregulation. In addition, they... more
β-Arrestin (βarr)-1 and β-arrestin-2 (βarrs) are universal G-protein–coupled receptor adapter proteins that negatively regulate cardiac β-adrenergic receptor (βAR) function via βAR desensitization and downregulation. In addition, they mediate G-protein–independent βAR signaling, which might be beneficial, for example, antiapoptotic, for the heart. However, the specific role(s) of each βarr isoform in cardiac βAR dysfunction, the molecular hallmark of chronic heart failure (HF), remains unknown. Furthermore, adrenal βarr1 exacerbates HF by chronically enhancing adrenal production and hence circulating levels of aldosterone and catecholamines. Herein, we sought to delineate specific roles of βarr1 in post–myocardial infarction (MI) HF by testing the effects of βarr1 genetic deletion on normal and post-MI cardiac function and morphology. We studied βarr1 knockout (βarr1KO) mice alongside wild-type controls under normal conditions and after surgical MI. Normal (sham-operated) βarr1KO mi...
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Rationale: G protein–coupled receptor kinase 2 (GRK2) is abundantly expressed in the heart, and its expression and activity are increased in injured or stressed myocardium. This upregulation has been shown to be pathological. GRK2 can... more
Rationale: G protein–coupled receptor kinase 2 (GRK2) is abundantly expressed in the heart, and its expression and activity are increased in injured or stressed myocardium. This upregulation has been shown to be pathological. GRK2 can promote cell death in ischemic myocytes, and its inhibition by a peptide comprising the last 194 amino acids of GRK2 (known as carboxyl-terminus of β-adrenergic receptor kinase [bARKct]) is cardioprotective. Objective: The aim of this study was to elucidate the signaling mechanism that accounts for the prodeath signaling seen in the presence of elevated GRK2 and the cardioprotection afforded by the carboxyl-terminus of β-adrenergic receptor kinase. Methods and Results: Using in vivo mouse models of ischemic injury and also cultured myocytes, we found that GRK2 localizes to mitochondria, providing novel insight into GRK2-dependent pathophysiological signaling mechanisms. Mitochondrial localization of GRK2 in cardiomyocytes was enhanced after ischemic an...
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Background— Recent evidence from cultured endothelial cell studies suggests that phosphorylation of endothelial nitric oxide synthase (eNOS) through the PI3-kinase– Akt pathway increases NO production. This study was designed to elucidate... more
Background— Recent evidence from cultured endothelial cell studies suggests that phosphorylation of endothelial nitric oxide synthase (eNOS) through the PI3-kinase– Akt pathway increases NO production. This study was designed to elucidate the signaling pathway involved in the antiapoptotic effect of insulin in vivo and to test the hypothesis that phosphorylation of eNOS by insulin may participate in the cardioprotective effect of insulin after myocardial ischemia and reperfusion. Methods and Results— Male Sprague-Dawley rats were subjected to 30 minutes of myocardial ischemia and 4 hours of reperfusion. Rats were randomized to receive vehicle, insulin, insulin plus wortmannin, or insulin plus L-NAME. Treatment with insulin resulted in 2.6-fold and 4.3-fold increases in Akt and eNOS phosphorylation and a significant increase in NO production in ischemic/reperfused myocardial tissue. Phosphorylation of Akt and eNOS and increase of NO production by insulin were completely blocked by wo...
Research Interests: Endocrinology, Enzyme Inhibitors, Apoptosis, Medicine, Internal Medicine, and 15 moreGlucose, Insulin, Nitric oxide, Animals, Male, Phosphorylation, Clinical Sciences, Nitric Oxide Synthase, Myocardium, Circulation, Insulin Receptor, Myocardial Ischemia, ENOS, Endothelial nitric oxide synthase, and Cardiovascular medicine and haematology
Background— A salient characteristic of dysfunctional myocardium progressing to heart failure is an upregulation of the adenylyl cyclase inhibitory guanine nucleotide (G) protein α subunit, Gα i2 . It has not been determined conclusively... more
Background— A salient characteristic of dysfunctional myocardium progressing to heart failure is an upregulation of the adenylyl cyclase inhibitory guanine nucleotide (G) protein α subunit, Gα i2 . It has not been determined conclusively whether increased Gi activity in the heart is beneficial or deleterious in vivo. Gi signaling has been implicated in the mechanism of cardioprotective agents; however, no in vivo evidence exists that any of the Gα subunits are cardioprotective. We have created a novel molecular tool to specifically address the role of Gi proteins in normal and dysfunctional myocardium. Methods and Results— We have developed a class-specific Gi inhibitor peptide, GiCT, composed of the region of Gα i2 that interacts specifically with G protein–coupled receptors. GiCT inhibits Gi signals specifically in vitro and in vivo, whereas Gs and Gq signals are not affected. In vivo expression of GiCT in transgenic mice effectively causes a “functional knockout” of cardiac Gα i2...
Research Interests: Apoptosis, Medicine, Heart Failure, Ischemia Reperfusion Injury, Humans, and 15 moreMice, Animals, Cell Death, Heart Disease, Clinical Sciences, In Vivo, Myocardial Infarction, Circulation, G protein, Infarct Size, Adenylyl Cyclase, Isoproterenol, Myocardial Ischemia, G Protein Coupled Receptors, and Cardiovascular medicine and haematology
Backgroundβ1- and β2–adrenergic receptors (ARs) play distinct roles in the heart, e.g. β1AR is pro-contractile and pro-apoptotic but β2AR anti-apoptotic and only weakly pro-contractile. G protein coupled receptor kinase (GRK)-2... more
Backgroundβ1- and β2–adrenergic receptors (ARs) play distinct roles in the heart, e.g. β1AR is pro-contractile and pro-apoptotic but β2AR anti-apoptotic and only weakly pro-contractile. G protein coupled receptor kinase (GRK)-2 desensitizes and opposes βAR pro-contractile signaling by phosphorylating the receptor and inducing beta-arrestin (βarr) binding. We posited herein that GRK2 blockade might enhance the pro-contractile signaling of the β2AR subtype in the heart. We tested the effects of cardiac-targeted GRK2 inhibition in vivo exclusively on β2AR signaling under normal conditions and in heart failure (HF).ResultsWe crossed β1AR knockout (B1KO) mice with cardiac-specific transgenic mice expressing the βARKct, a known GRK2 inhibitor, and studied the offspring under normal conditions and in post-myocardial infarction (MI). βARKct expression in vivo proved essential for β2AR-dependent contractile function, as β2AR stimulation with isoproterenol fails to increase contractility in e...
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Objective— Adiponectin (APN) system malfunction is causatively related to increased cardiovascular morbidity/mortality in diabetic patients. The aim of the current study was to investigate molecular mechanisms responsible for APN... more
Objective— Adiponectin (APN) system malfunction is causatively related to increased cardiovascular morbidity/mortality in diabetic patients. The aim of the current study was to investigate molecular mechanisms responsible for APN transmembrane signaling and cardioprotection. Methods and Results— Compared with wild-type mice, caveolin-3 knockout (Cav-3KO) mice exhibited modestly increased myocardial ischemia/reperfusion injury (increased infarct size, apoptosis, and poorer cardiac function recovery; P <0.05). Although the expression level of key APN signaling molecules was normal in Cav-3KO, the cardioprotective effects of APN observed in wild-type were either markedly reduced or completely lost in Cav-3KO. Molecular and cellular experiments revealed that APN receptor 1 (AdipoR1) colocalized with Cav-3, forming AdipoR1/Cav-3 complex via specific Cav-3 scaffolding domain binding motifs. AdipoR1/Cav-3 interaction was required for APN-initiated AMP-activated protein kinase (AMPK)–dep...
Research Interests: Endocrinology, Emergency Medicine, Cytokines, Apoptosis, Humans, and 15 moreDiabetes mellitus, Animal, cyclic AMP, Animals, Cardioprotection, AMPK, Clinical Sciences, Disease models, Adiponectin, Caveolae, Alternative and Complementary Medicine, Adaptor Proteins, Cadherins, Department of Emergency Medicine, and Cardiovascular medicine and haematology
Akt2 protein kinase has been shown to promote cell migration and actin polymerization in several cell types, including macrophages. Because migrating macrophages constitute an important inflammatory response after myocardial ischemia, we... more
Akt2 protein kinase has been shown to promote cell migration and actin polymerization in several cell types, including macrophages. Because migrating macrophages constitute an important inflammatory response after myocardial ischemia, we determined cardiac macrophage expression after ischemia-reperfusion (I/R) injury and cryo-injury in mice lacking Akt2 (Akt2-KO). At 7 days post-I/R, Akt2-KO cardiac tissues showed an increase in immunohistochemical staining for macrophage markers (Galectin 3 and F4/80) compared with wild-type (WT) mice, indicating macrophage density was increased in the injured Akt2-KO myocardium. This change was time dependent because macrophage density was similar between WT and Akt2-KO myocardium at 3 days post-I/R, but by 7 and 14 days post-I/R, macrophage density was significantly increased in Akt2-KO myocardium. Concomitantly, infarct size was larger and cardiac function was reduced in Akt2-KO mice subjected to I/R. However, when cryo-infarction produced simil...
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Recent studies from our lab and others have shown that the hematopoietic cytokine erythropoietin (EPO) can protect the heart from ischemic damage in a red blood cell-independent manner. Here we examined any protective effects of the... more
Recent studies from our lab and others have shown that the hematopoietic cytokine erythropoietin (EPO) can protect the heart from ischemic damage in a red blood cell-independent manner. Here we examined any protective effects of the long-acting EPO analog darbepoetin alfa (DA) in a rat model of ischemia-reperfusion (I/R) injury. Rats were subjected to 30-min ischemia followed by 72-h reperfusion. In a dose-response study, DA (2, 7, 11, and 30 μg/kg) or vehicle was administered as a single bolus at the start of ischemia. To determine the time window of potential cardioprotection, a single high dose of DA (30 μg/kg) was given at either the initiation or the end of ischemia or at 1 or 24 h after reperfusion. After 3 days, cardiac function and infarct size were assessed. Acute myocyte apoptosis was quantified by TUNEL staining on myocardial sections and by caspase-3 activity assays. DA significantly reduced infarct size from 32.8 ± 3.5% (vehicle) to 11.0 ± 3.3% in a dose-dependent manne...
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Rationale: Activation of prosurvival kinases and subsequent nitric oxide (NO) production by certain G protein–coupled receptors (GPCRs) protects myocardium in ischemia/reperfusion injury (I/R) models. GPCR signaling pathways are regulated... more
Rationale: Activation of prosurvival kinases and subsequent nitric oxide (NO) production by certain G protein–coupled receptors (GPCRs) protects myocardium in ischemia/reperfusion injury (I/R) models. GPCR signaling pathways are regulated by GPCR kinases (GRKs), and GRK2 has been shown to be a critical molecule in normal and pathological cardiac function. Objective: A loss of cardiac GRK2 activity is known to arrest progression of heart failure (HF), at least in part by normalization of cardiac β-adrenergic receptor (βAR) signaling. Chronic HF studies have been performed with GRK2 knockout mice, as well as expression of the βARKct, a peptide inhibitor of GRK2 activity. This study was conducted to examine the role of GRK2 and its activity during acute myocardial ischemic injury using an I/R model. Methods and Results: We demonstrate, using cardiac-specific GRK2 and βARKct-expressing transgenic mice, a deleterious effect of GRK2 on in vivo myocardial I/R injury with βARKct imparting c...