Therapeutic Targets for Treatment of Heart Failure: Focus on GRKs and β-Arrestins Affecting βAR Signaling

Heart failure (HF) is a heart disease that is classified into two main types: HF with reduced ejection fraction (HFrEF) and HF with preserved ejection fraction (HFpEF). Both types of HF lead to significant risk of mortality and morbidity. Pharmacological treatment with β-adrenergic receptor (βAR) antagonists (also called β-blockers) has been shown to reduce the overall hospitalization and mortality rates and improve the clinical outcomes in HF patients with HFrEF but not HFpEF. Although, the survival rate of patients suffering from HF continues to drop, the management of HF still faces several limitations and discrepancies highlighting the need to develop new treatment strategies. Overstimulation of the sympathetic nervous system is an adaptive neurohormonal response to acute myocardial injury and heart damage, whereas prolonged exposure to catecholamines causes defects in βAR regulation, including a reduction in the amount of βARs and an increase in βAR desensitization due to the upregulation of G protein-coupled receptor kinases (GRKs) in the heart, contributing in turn to the progression of HF. Several studies show that myocardial GRK2 activity and expression are raised in the failing heart. Furthermore, β-arrestins play a pivotal role in βAR desensitization and, interestingly, can mediate their own signal transduction without any G protein-dependent pathway involved. In this review, we provide new insight into the role of GRKs and β-arrestins on how they affect βAR signaling regarding the molecular and cellular pathophysiology of HF. Additionally, we discuss the therapeutic potential of targeting GRKs and β-arrestins for the treatment of HF

Thai Fruits Exhibit Antioxidant Activity and Induction of Antioxidant Enzymes in HEK-293 Cells

The cellular antioxidant enzymes play the important role of protecting the cells and organisms from the oxidative damage. Natural antioxidants contained in fruits have attracted considerable interest because of their presumed safety and potential nutritional value. Even though antioxidant activities of many fruits have been reported, the effects of phytochemicals contained in fruits on the induction of antioxidant enzymes in the cells have not been fully defined. In this study, we showed that extracts from Antidesma ghaesembilla, Averrhoa bilimbi, Malpighia glabra, Mangifera indica, Sandoricum koetjape, Syzygium malaccense, and Ziziphus jujuba inhibited H2O2-induced intracellular reactive oxygen species production in HEK-293 cells. Additionally, these Thai fruit extracts increased the mRNA and protein expressions of antioxidant enzymes, catalase, glutathione peroxidase-1, and manganese superoxide dismutase. The consumption of Thai fruits rich in phenolic compounds may reduce the risk of oxidative stress

TRPC3-Nox2 axis mediates nutritional deficiency-induced cardiomyocyte atrophy

Myocardial atrophy, characterized by the decreases in size and contractility of cardiomyocytes, is caused by severe malnutrition and/or mechanical unloading. Extracellular adenosine 5′-triphosphate (ATP), known as a danger signal, is recognized to negatively regulate cell volume. However, it is obscure whether extracellular ATP contributes to cardiomyocyte atrophy. Here, we report that ATP induces atrophy of neonatal rat cardiomyocytes (NRCMs) without cell death through P2Y2 receptors. ATP led to overproduction of reactive oxygen species (ROS) through increased amount of NADPH oxidase (Nox) 2 proteins, due to increased physical interaction between Nox2 and canonical transient receptor potential 3 (TRPC3). This ATP-mediated formation of TRPC3-Nox2 complex was also pathophysiologically involved in nutritional deficiency-induced NRCM atrophy. Strikingly, knockdown of either TRPC3 or Nox2 suppressed nutritional deficiency-induced ATP release, as well as ROS production and NRCM atrophy. Taken together, we propose that TRPC3-Nox2 axis, activated by extracellular ATP, is the key component that mediates nutritional deficiency-induced cardiomyocyte atrophy

β-Arrestin–dependent activation of Ca2+/calmodulin kinase II after β1–adrenergic receptor stimulation

β-Arrestin functions as a scaffold for CaMKII and the Rap guanine nucleotide exchange factor Epac to regulate signaling from β1-ARs

Gi/o Protein-Dependent and -Independent Actions of Pertussis Toxin (PTX)

Pertussis toxin (PTX) is a typical A-B toxin. The A-protomer (S1 subunit) exhibits ADP-ribosyltransferase activity. The B-oligomer consists of four subunits (S2 to S5) and binds extracellular molecules that allow the toxin to enter the cells. The A-protomer ADP-ribosylates the α subunits of heterotrimeric Gi/o proteins, resulting in the receptors being uncoupled from the Gi/o proteins. The B-oligomer binds proteins expressed on the cell surface, such as Toll-like receptor 4, and activates an intracellular signal transduction cascade. Thus, PTX modifies cellular responses by at least two different signaling pathways; ADP-ribosylation of the Gαi/o proteins by the A-protomer (Gi/o protein-dependent action) and the interaction of the B-oligomer with cell surface proteins (Gi/o protein-independent action)

Dual Blockade of TGF-β Receptor and Endothelin Receptor Synergistically Inhibits Angiotensin II-Induced Myofibroblast Differentiation: Role of AT₁R/G_αq-Mediated TGF-β1 and ET-1 Signaling

Angiotensin II (Ang II) upregulates transforming growth factor-beta1 (TGF-β1) and endothelin-1 (ET-1) in various types of cells, and all of them act as profibrotic mediators. However, the signal transduction of angiotensin II receptor (ATR) for upregulation of TGF-β1 and ET-1, and their effectors that play an essential role in myofibroblast differentiation, are not fully understood. Therefore, we investigated the ATR networking with TGF-β1 and ET-1 and identified the signal transduction of these mediators by measuring the mRNA expression of alpha-smooth muscle actin (α-SMA) and collagen I using qRT-PCR. Myofibroblast phenotypes were monitored by α-SMA and stress fiber formation with fluorescence microscopy. Our findings suggested that Ang II induced collagen I and α-SMA synthesis and stress fiber formation through the AT1R/Gαq axis in adult human cardiac fibroblasts (HCFs). Following AT1R stimulation, Gαq protein, not Gβγ subunit, was required for upregulation of TGF-β1 and ET-1. Moreover, dual inhibition of TGF-β and ET-1 signaling completely inhibited Ang II-induced myofibroblast differentiation. The AT1R/Gαq cascade transduced signals to TGF-β1, which in turn upregulated ET-1 via the Smad- and ERK1/2-dependent pathways. ET-1 consecutively bound to and activated endothelin receptor type A (ETAR), leading to increases in collagen I and α-SMA synthesis and stress fiber formation. Remarkably, dual blockade of TGF-β receptor and ETR exhibited the restorative effects to reverse the myofibroblast phenotype induced by Ang II. Collectively, TGF-β1 and ET-1 are major effectors of AT1R/Gαq cascade, and therefore, negative regulation of TGF-β and ET-1 signaling represents a targeted therapeutic strategy for the prevention and restoration of cardiac fibrosis

Multifaceted Roles of GLP-1 and Its Analogs: A Review on Molecular Mechanisms with a Cardiotherapeutic Perspective

Diabetes is one of the chronic metabolic disorders which poses a multitude of life-debilitating challenges, including cardiac muscle impairment, which eventually results in heart failure. The incretin hormone glucagon-like peptide-1 (GLP-1) has gained distinct recognition in reinstating glucose homeostasis in diabetes, while it is now largely accepted that it has an array of biological effects in the body. Several lines of evidence have revealed that GLP-1 and its analogs possess cardioprotective effects by various mechanisms related to cardiac contractility, myocardial glucose uptake, cardiac oxidative stress and ischemia/reperfusion injury, and mitochondrial homeostasis. Upon binding to GLP-1 receptor (GLP-1R), GLP-1 and its analogs exert their effects via adenylyl cyclase-mediated cAMP elevation and subsequent activation of cAMP-dependent protein kinase(s) which stimulates the insulin release in conjunction with enhanced Ca2+ and ATP levels. Recent findings have suggested additional downstream molecular pathways stirred by long-term exposure of GLP-1 analogs, which pave the way for the development of potential therapeutic molecules with longer lasting beneficial effects against diabetic cardiomyopathies. This review provides a comprehensive overview of the recent advances in the understanding of the GLP-1R-dependent and -independent actions of GLP-1 and its analogs in the protection against cardiomyopathies

New Therapeutics for Heart Failure: Focusing on cGMP Signaling

Current drugs for treating heart failure (HF), for example, angiotensin II receptor blockers and β-blockers, possess specific target molecules involved in the regulation of the cardiac circulatory system. However, most clinically approved drugs are effective in the treatment of HF with reduced ejection fraction (HFrEF). Novel drug classes, including angiotensin receptor blocker/neprilysin inhibitor (ARNI), sodium-glucose co-transporter-2 (SGLT2) inhibitor, hyperpolarization-activated cyclic nucleotide-gated (HCN) channel blocker, soluble guanylyl cyclase (sGC) stimulator/activator, and cardiac myosin activator, have recently been introduced for HF intervention based on their proposed novel mechanisms. SGLT2 inhibitors have been shown to be effective not only for HFrEF but also for HF with preserved ejection fraction (HFpEF). In the myocardium, excess cyclic adenosine monophosphate (cAMP) stimulation has detrimental effects on HFrEF, whereas cyclic guanosine monophosphate (cGMP) signaling inhibits cAMP-mediated responses. Thus, molecules participating in cGMP signaling are promising targets of novel drugs for HF. In this review, we summarize molecular pathways of cGMP signaling and clinical trials of emerging drug classes targeting cGMP signaling in the treatment of HF

Preparation of Readily-to-Use Stilbenoids Extract from Morus alba Callus Using a Natural Deep Eutectic Solvent

The consumer and cosmetic industries have recently placed a greater emphasis on ecofriendly solvents for botanical extraction, including natural deep eutectic solvents (NADES). In this study, NADES were prepared for Morus alba callus extraction. The efficiency of extraction from the NADES and methanol was investigated by comparison of the stilbenoids yield and anti-melanogenesis activity. Prior to testing the irritability of a suitable NADES on the reconstructed human epidermis (RhE), the effect of the selected NADES on stilbenoids stability was determined. The results showed that the highest yields of stilbenoids were obtained from choline chloride-glycerol mixtures (Ch1G2) and methanol extracts, with no significant difference in yields (5.06 ± 0.05 and 6.32 ± 0.40 mg/g callus dry weight, respectively). The NADES extracts of M. alba callus showed comparable anti-melanogenesis activity compared to methanol. In term of stability, stilbenoids in Ch1G2 remained stable after six months of storage at 4 °C except resveratrol. Furthermore, Ch1G2 had no irritation effect on RhE. Thus, based on the findings of this study, Ch1G2 is an intriguing green solvent alternative for the extraction of M. alba callus and may be advantageous for the preparation of skin-lightening cosmetics

Prolonged stimulation of β2-adrenergic receptor with β2-agonists impairs insulin actions in H9c2 cells

Insulin resistance is a condition in which there is a defect in insulin actions to induce glucose uptake into the cells. Overstimulation of β2-adrenergic receptors (β2ARs) is associated with the pathogenesis of insulin resistance in the heart. However, the mechanisms by which β2-agonists affect insulin resistance in the heart are incompletely understood. The β2-agonists are used for treatment of asthma due to bronchodilating effects. We also investigated the effects of β2-agonists in human bronchial smooth muscle (HBSM) cells. In this study, we demonstrate that chronic treatment with salbutamol, salmeterol, and formoterol inhibited insulin-induced glucose uptake and GLUT4 synthesis in H9c2 myoblast cells. Sustained β2AR stimulation also attenuated GLUT4 translocation to the plasma membrane, whereas short-term stimulation had no effect. In HBSM cells, prolonged treatment with β2-agonists had no effect on insulin-induced glucose uptake and did not alter insulin-induced expressions of GLUT1, GLUT4, and GLUT10. In addition, genetic polymorphisms at amino acid positions 16 and 27 of β2AR are linked to insulin resistance by significant suppression of GLUT4 translocation compared to wild-type. Thus, prolonged β2AR stimulation by β2-agonists impairs insulin actions through suppression of GLUT synthesis and translocation only in H9c2 cells. Keywords: β2AR polymorphism, β2-Agonist, GLUT translocation, Glucose uptake, Insulin resistanc