Myocardial oxidative stress contributes to transgenic β₂-adrenoceptor activation-induced cardiomyopathy and heart failure

Propranolol Alleviates Cardiac Injury After Acute Catecholamine Infusion Through p38-MAPK Pathways

ABSTRACT

Hypercatecholaminergic conditions are known to cause heart failure and cardiac fibrosis when severe. Although previous investigations have studied the effects of beta-blockade in experimental models of catecholaminergic states, the detailed benefits of beta-blockade in more realistic models of hyper-adrenergic states were less clear. In this study, we examined acute cardiac changes in rats with hyperacute catecholamine-induced heart failure with and without propranolol treatment. Male Sprague-Dawley rats (n = 12) underwent a 6-hour infusion of epinephrine and norepinephrine alone, with an additional propranolol bolus (1 mg/kg) at hour 1 (n = 6). Cardiac tissues were examined after 6 hours. Cardiac immunohistochemistry revealed significantly decreased expression of phosphorylated p-38 (left ventricle, P = 0.021; right ventricle, P = 0.021), with upregulation of reactive oxidative species and other profibrosis proteins, after catecholamine infusion alone. After 1 propranolol 1 mg/kg bolus, the levels of phosphorylated-p38 returned to levels comparable with sham (left ventricle, P = 0.021; right ventricle, P = 0.043), with additional findings including downregulation of the apoptotic pathway and profibrotic proteins. We conclude that catecholamine-induced heart failure exerts damage through the p-38 mitogen-activated protein kinase pathway and demonstrates profibrotic changes mediated by matrix metalloproteinase 9, alpha-smooth muscle actin, and fibroblast growth factor 23. Changes in these pathways attenuated acute catecholamine-induced heart failure after propranolol bolus 1 mg/kg. We conclude that propranolol bolus at 1 mg/kg is able to mediate the effects of catecholamine excess through the p-38 mitogen-activated protein kinase pathway, profibrosis, and extrinsic apoptosis pathway.

Molecular Imaging of Diffuse Cardiac Fibrosis with a Radiotracer That Targets Proteolyzed Collagen IV

Purpose To develop an approach for in vivo detection of interstitial cardiac fibrosis using PET with a peptide tracer targeting proteolyzed collagen IV (T-peptide). Materials and Methods T-peptide was conjugated to the copper chelator MeCOSar (chemical name, 5-(8-methyl-3,6,10,13,16,19-hexaaza-bicyclo[6.6.6]icosan-1-ylamino)-5-oxopentanoic acid) and radiolabeled with copper 64 (64Cu). PET/CT scans were acquired following intravenous delivery of 64Cu-T-peptide-MeCOSar (0.25 mg/kg; 18 MBq ± 2.7 [SD]) to male transgenic mice overexpressing β2-adrenergic receptors with intermediate (7 months of age; n = 4 per group) to severe (10 months of age; n = 11 per group) cardiac fibrosis and their wild-type controls. PET scans were also performed following coadministration of the radiolabeled probe with nonlabeled T-peptide in excess to confirm binding specificity. PET data were analyzed by t tests for static scans and analysis of variance tests (one- or two-way) for dynamic scans. Results PET/CT scans revealed significantly elevated (2.24-4.26-fold; P < .05) 64Cu-T-peptide-MeCOSar binding in the fibrotic hearts of aged transgenic β2-adrenergic receptor mice across the entire 45-minute acquisition period compared with healthy controls. The cardiac tracer accumulation and presence of diffuse cardiac fibrosis in older animals were confirmed by gamma counting (P < .05) and histologic evaluation, respectively. Coadministration of a nonradiolabeled probe in excess abolished the elevated radiotracer binding in the aged transgenic hearts. Importantly, PET tracer accumulation was also detected in younger (7 months of age) transgenic mice with intermediate cardiac fibrosis, although this was only apparent from 20 minutes following injection (1.6-2.2-fold binding increase; P < .05). Conclusion The T-peptide PET tracer targeting proteolyzed collagen IV provided a sensitive and specific approach of detecting diffuse cardiac fibrosis at varying degrees of severity in a transgenic mouse model. Keywords: Diffuse Cardiac Fibrosis, Molecular Peptide Probe, Molecular Imaging, PET/CT © RSNA, 2024.

Isoproterenol induces MD2 activation by β-AR-cAMP-PKA-ROS signalling axis in cardiomyocytes and macrophages drives inflammatory heart failure

Cardiac inflammation contributes to heart failure (HF) induced by isoproterenol (ISO) through activating β-adrenergic receptors (β-AR). Recent evidence shows that myeloid differentiation factor 2 (MD2), a key protein in endotoxin-induced inflammation, mediates inflammatory heart diseases. In this study, we investigated the role of MD2 in ISO-β-AR-induced heart injuries and HF. Mice were infused with ISO (30 mg·kg-1·d-1) via osmotic mini-pumps for 2 weeks. We showed that MD2 in cardiomyocytes and cardiac macrophages was significantly increased and activated in the heart tissues of ISO-challenged mice. Either MD2 knockout or administration of MD2 inhibitor L6H21 (10 mg/kg every 2 days, i.g.) could prevent mouse hearts from ISO-induced inflammation, remodelling and dysfunction. Bone marrow transplantation study revealed that both cardiomyocyte MD2 and bone marrow-derived macrophage MD2 contributed to ISO-induced cardiac inflammation and injuries. In ISO-treated H9c2 cardiomyocyte-like cells, neonatal rat primary cardiomyocytes and primary mouse peritoneal macrophages, MD2 knockout or pre-treatment with L6H21 (10 μM) alleviated ISO-induced inflammatory responses, and the conditioned medium from ISO-challenged macrophages promoted the hypertrophy and fibrosis in cardiomyocytes and fibroblasts. We demonstrated that ISO induced MD2 activation in cardiomyocytes via β1-AR-cAMP-PKA-ROS signalling axis, and induced inflammatory responses in macrophages via β2-AR-cAMP-PKA-ROS axis. This study identifies MD2 as a key inflammatory mediator and a promising therapeutic target for ISO-induced heart failure.

Redox differences between rat neonatal and adult cardiomyocytes under hypoxia

It is generally accepted that oxidative stress plays a key role in the development of ischemia-reperfusion injury in ischemic heart disease. However, the mechanisms how reactive oxygen species trigger cellular damage are not fully understood. Our study investigates redox state and highly reactive substances within neonatal and adult cardiomyocytes under hypoxia conditions. We have found that hypoxia induced an increase in H2O2 production in adult cardiomyocytes, while neonatal cardiomyocytes experienced a decrease in H2O2 levels. This finding correlates with our observation of the difference between the electron transport chain (ETC) properties and mitochondria amount in adult and neonatal cells. We demonstrated that in adult cardiomyocytes hypoxia caused the significant increase in the ETC loading with electrons compared to normoxia. On the contrary, in neonatal cardiomyocytes ETC loading with electrons was similar under both normoxic and hypoxic conditions that could be due to ETC non-functional state and the absence of the electrons transfer to O2 under normoxia. In addition to the variations in H2O2 production, we also noted consistent pH dynamics under hypoxic conditions. Notably, the pH levels exhibited a similar decrease in both cell types, thus, acidosis is a more universal cellular response to hypoxia. We also demonstrated that the amount of mitochondria and the levels of cardiac isoforms of troponin I, troponin T, myoglobin and GAPDH were significantly higher in adult cardiomyocytes compared to neonatal ones. Remarkably, we found out that under hypoxia, the levels of cardiac isoforms of troponin T, myoglobin, and GAPDH were elevated in adult cardiomyocytes, while their level in neonatal cells remained unchanged. Obtained data contribute to the understanding of the mechanisms of neonatal cardiomyocytes' resistance to hypoxia and the ability to maintain the metabolic homeostasis in contrast to adult ones.

The neurometabolic axis: A novel therapeutic target in heart failure

Abnormal cardiac metabolism or cardiac metabolic remodeling is reported before the onset of heart failure with reduced ejection fraction (HFrEF) and is known to trigger and maintain the mechanical dysfunction and electrical, and structural abnormalities of the ventricle. A dysregulated cardiac autonomic tone characterized by sympathetic overdrive with blunted parasympathetic activation is another pathophysiological hallmark of HF. Emerging evidence suggests a link between autonomic nervous system activity and cardiac metabolism. Chronic β-adrenergic activation promotes maladaptive metabolic remodeling whereas cholinergic activation attenuates the metabolic aberrations through favorable modulation of key metabolic regulatory molecules. Restoration of sympathovagal balance by neuromodulation strategies is emerging as a novel nonpharmacological treatment strategy in HF. The current review attempts to evaluate the 'neuro-metabolic axis' in HFrEF and whether neuromodulation can mitigate the adverse metabolic remodeling in HFrEF.

Evaluation of Coenzyme Q10 (CoQ10) Deficiency and Therapy in Mouse Models of Cardiomyopathy

ABSTRACT

Mitochondrial dysfunction plays a key role in the development of heart failure, but targeted therapeutic interventions remain elusive. Previous studies have shown coenzyme Q10 (CoQ10) insufficiency in patients with heart disease with undefined mechanism and modest effectiveness of CoQ10 supplement therapy. Using 2 transgenic mouse models of cardiomyopathy owing to cardiac overexpression of Mst1 (Mst1-TG) or β 2 -adrenoceptor (β 2 AR-TG), we studied changes in cardiac CoQ10 content and alterations in CoQ10 biosynthesis genes. We also studied in Mst1-TG mice effects of CoQ10, delivered by oral or injection regimens, on both cardiac CoQ10 content and cardiomyopathy phenotypes. High performance liquid chromatography and RNA sequencing revealed in both models significant reduction in cardiac content of CoQ10 and downregulation of most genes encoding CoQ10 biosynthesis enzymes. Mst1-TG mice with 70% reduction in cardiac CoQ10 were treated with CoQ10 either by oral gavage or i.p. injection for 4-8 weeks. Oral regimens failed in increasing cardiac CoQ10 content, whereas injection regimen effectively restored the cardiac CoQ10 level in a time-dependent manner. However, CoQ10 restoration in Mst1-TG mice did not correct mitochondrial dysfunction measured by energy metabolism, downregulated expression of marker proteins, and oxidative stress nor to preserve cardiac contractile function. In conclusion, mouse models of cardiomyopathy exhibited myocardial CoQ10 deficiency likely due to suppressed endogenous synthesis of CoQ10. In contrast to ineffectiveness of oral administration, CoQ10 administration by injection regimen in cardiomyopathy mice restored cardiac CoQ10 content, which, however, failed in achieving detectable efficacy at molecular and global functional levels.

Autonomic Nervous System and Cardiac Metabolism: Links Between Autonomic and Metabolic Remodeling in Atrial Fibrillation

Simultaneous activation of the sympathetic and parasympathetic nervous systems is crucial for the initiation of paroxysmal atrial fibrillation (AF). However, unbalanced activation of the sympathetic system is characteristic of autonomic remodeling in long-standing persistent AF. Moreover, the adrenergic activation-induced metabolic derangements provide a milieu for acute AF and promote the transition from the paroxysmal to the persistent phase of AF. On the other hand, cholinergic activation ameliorates the maladaptive metabolic remodeling in the face of metabolic challenges. Selective inhibition of the sympathetic system and restoration of the balance of the cholinergic system by neuromodulation is emerging as a novel nonpharmacologic strategy for managing AF. This review explores the link between cardiac autonomic and metabolic remodeling and the potential roles of different autonomic modulation strategies on atrial metabolic aberrations in AF.

Protocatechuic acid reverses myocardial infarction mediated by β-adrenergic agonist via regulation of Nrf2/HO-1 pathway, inflammatory, apoptotic, and fibrotic events

Myocardial infarction (MI) is an instant ischemic death of cardiomyocytes that remains a major global cause of mortalities. MI is accompanied by oxidative, inflammatory, apoptotic, and fibrotic insults. Protocatechuic acid (PCA) is a polyphenolic compound with various potent biological activities. In this study, we explored the possible cardioprotective role of PCA against isoproterenol (ISO)-mediated MI. Rats were either injected with ISO (85 mg/kg, subcutaneously) or pretreated with PCA (100 or 200 mg/kg, orally). PCA supplementation markedly normalized ISO-induced disturbed cardiac function markers (creatine kinase-MB, lactate dehydrogenase, and troponin T). Notably, PCA administration exerted remarkable increases in glutathione and its derived enzymes, superoxide dismutase, and catalase, as well as decreases in malondialdehyde and nitric oxide levels in the injured cardiac tissue. The molecular findings validated the augmented cellular antioxidative capacity by PCA via increasing the gene expressions of nuclear factor erythroid 2-related factor 2 and heme oxygenase-1. The cardioprotective efficacy of PCA extended to suppress cardiac inflammation as demonstrated by the decreased levels of tumor necrosis factor-alpha, interleukin-1 beta, and nuclear factor kappa B. Additionally, PCA prevented cardiomyocyte loss and fibrosis by decreasing Bax, caspase-3, transforming growth factor-β1 and matrix metalloproteinase-9, and enhancing B-cell lymphoma 2 and tissue inhibitors of metalloproteinase-3. The cardiac histological screening further confirmed the PCA's protective action. The obtained data recommend PCA as an alternative therapeutic agent to attenuate the molecular, biochemical, and histological alterations associated with MI development.

Changes in Cardiac Function During the Development of Uremic Cardiomyopathy and the Effect of Salvianolic Acid B Administration in a Rat Model

Background

Uremic cardiomyopathy (UC), the main cause of death in progressive chronic kidney disease (CKD), is characterized by diastolic dysfunction. Intraventricular pressure gradients (IVPG) derived from color m-mode echocardiography (CMME) and two-dimensional speckle tracking echocardiography (2DSTE) were established as novel echocardiographic approaches for non-invasive and repeatable assessment of cardiac function. Previously, salvianolic acid B (Sal B) showed the potential to alleviate concentric LV hypertrophy in the pressure overload model. The purpose of this study was to evaluate the changes in cardiac function in UC and assess the efficacy of Sal B therapy using IVPG and 2DSTE techniques.

Materials and Methods

Twenty-four rats underwent subtotal nephrectomy to produce progressive renal failure and were allocated equally into UC (n = 12) and Sal B-UC (n = 12) groups and monitored for 8 weeks. A sham-operated group was also included in this study (n = 12). Sal B was injected from weeks 4 to 8 in the Sal B-UC group. Conventional echocardiography, 2DSTE, and CMME were performed every 2 weeks post-operation, concomitantly with an evaluation of renal function. Histopathological and immunohistochemistry analyses were carried out to confirm the echocardiography findings.

Results

Renal failure and myocardial dysfunction were confirmed in the UC group from weeks 2 through 8. Eccentric and concentric hypertrophy was observed in the UC group, while the Sal B-UC group showed only eccentric hypertrophy. IVPG analysis did not reveal any significant differences between the groups. Edema, inflammation, fibrosis, and immunohistochemical expression of CD3 infiltration were higher in the UC group compared with sham and Sal B-UC groups.

Conclusion

2DSTE and IVPG explored the pathophysiology during the development of UC and indicated the incidence of myocardial dysfunction before ventricular morphological changes without intracardiac flow changes. This study confirmed increased ventricular stiffness and fibrosis in UC rats which was potentially treated by Sal B via decreasing edema, inflammation, and fibrosis.

A human relevant mixture of persistent organic pollutants induces reactive oxygen species formation in isolated human leucocytes: Involvement of the β2-adrenergic receptor

Exposure to chlorinated (Cl), brominated (Br) and perfluoroalkyl acid (PFAA) persistent organic pollutants (POPs) is associated with immunotoxicity and other adverse effects in humans and animals. Previous studies on POPs have mainly focused on single chemicals, while studies on complex mixtures are limited. Using DCF and luminol assays we examined effects on ROS generation in isolated human neutrophils, monocytes and lymphocytes, after in vitro exposure to a total mixture and sub-mixtures of 29 persistent compounds (Cl, Br, and PFAA). The mixtures were based on compounds prominent in blood, breast milk, and/or food. All mixture combinations induced ROS production in one or several of the cell models, and in some cases even at concentrations corresponding to human blood levels (compound range 1 pM - 16 nM). Whilst some interactions were detected (assessed using a mixed linear model), halogenated subgroups mainly acted additively. Mechanistic studies in neutrophils at 500× human levels (0.5 nM - 8 µM) indicated similar mechanisms of action for the Cl, PFAA, the combined PFAA + Cl and total (PFAA + Br + Cl) mixtures, and ROS responses appeared to involve β2-adrenergic receptor (β2AR) and Ca²⁺ signalling, as well as activation of NADPH oxidases. In line with this, the total mixture also increased cyclic AMP at levels comparable with the non-selective βAR agonist, isoproterenol. Although the detailed mechanisms involved in these responses remain to be elucidated, our data show that POP mixtures at concentrations found in human blood, may trigger stress responses in circulating immune cells. Mixtures of POPs, further seemed to interfere with adrenergic pathways, indicating a novel role of βARs in POP-induced effects.

Cardiac Metabolism in Sepsis

The mechanism of sepsis-induced cardiac dysfunction is believed to be different from that of myocardial ischemia. In sepsis, chemical mediators, such as endotoxins, cytokines, and nitric oxide, cause metabolic abnormalities, mitochondrial dysfunction, and downregulation of β-adrenergic receptors. These factors inhibit the production of ATP, essential for myocardial energy metabolism, resulting in cardiac dysfunction. This review focuses on the metabolic changes in sepsis, particularly in the heart. In addition to managing inflammation, interventions focusing on metabolism may be a new therapeutic strategy for cardiac dysfunction due to sepsis.

Insight into the Protective Effect of Salidroside against H2O2-Induced Injury in H9C2 Cells

Salidroside is the important active ingredient of Rhodiola species, which shows a wide range of pharmacological activities such as antioxidative stress, anti-inflammation, and antiliver fibrosis. In this paper, we aimed to study the protective effect and mechanism of salidroside against H2O2-induced oxidative damage in H9C2 cells by determining cell proliferation rate, intracellular reactive oxygen species (ROS) level, antioxidant enzyme activities, and the expression of apoptosis-related proteins. The results showed that salidroside significantly alleviated cell growth inhibition induced by H2O2 treatment in H9C2 cells, decreased the levels of intracellular ROS and malondialdehyde (MDA), and increased the activity of superoxide dismutase (SOD) and catalase (CAT); meanwhile, salidroside upregulated the expression of Bcl-2 while downregulated the expression of Bax, p53, and caspase-3 in H2O2-treated H9C2 cells. Furthermore, the antiapoptotic effect of salidroside was almost eliminated by the knockdown of Bcl-2. In the further exploration, the Bcl-2 expression was decreased by the p53 overexpression and increased by p53 knockdown in H2O2-treated H9C2 cells. Consequently, salidroside could protect H9C2 cells against H2O2-induced oxidative damage, and the underlying mechanism may be related to scavenging intracellular ROS, increasing the activities of intracellular antioxidant enzymes and inhibiting the expression of apoptosis-related proteins.

Ibogaine-Mediated ROS/Antioxidant Elevation in Isolated Rat Uterus Is β-Adrenergic Receptors and KATP Channels Mediated

Ibogaine effects are mediated by cellular receptors, ATP depletion followed by ROS production and antioxidant enzyme activity elevation in a dose and time dependent manner. Since the role of K_ATP channels and β-adrenoceptors in ROS cellular circuit was established here we explored their role in ibogaine pro-antioxidant effectiveness. Single dose of ibogaine (10 mg/L i.e., 28.8 μmol/L) was applied to isolated rat uterus (spontaneous and Ca²⁺-stimulated) and contractility and antioxidant enzymes activity were monitored during 4 h. Ibogaine increased amplitude and frequency of spontaneous active uteri immediately after addition that was prevented by propranolol (β₁ and β₂ adrenoceptors selective antagonists) and glibenclamide (K_ATP sensitive channels inhibitor; only frequency) pre-treatment. In Ca²⁺-stimulated uteri, ibogaine decreased both amplitude and frequency after 4 h. Pre-treatment with propranolol abolished ibogaine induced amplitude lowering, while glibenclamide had no effect. In both types of active uterus, ibogaine induced a decrease in SOD1 and an increase in CAT activity after 2 h. In Ca²⁺-stimulated uterus, there was also a decrease of SOD2 activity after 2 h. After 4 h, SOD1 activity returned to the baseline level, but GSH-Px activity increased. Pre-treatment with both propranolol and glibenclamide abolished observed changes of antioxidant enzymes activity suggesting that ibogaine pro-antioxidative effectiveness is β-adrenergic receptors and K_ATP channels mediated.

Sympatho-adrenergic mechanisms in heart failure: new insights into pathophysiology

The sympathetic nervous system is activated in the setting of heart failure (HF) to compensate for hemodynamic instability. However, acute sympathetic surge or sustained high neuronal firing rates activates β-adrenergic receptor (βAR) signaling contributing to myocardial remodeling, dysfunction and electrical instability. Thus, sympatho-βAR activation is regarded as a hallmark of HF and forms pathophysiological basis for β-blocking therapy. Building upon earlier research findings, studies conducted in the recent decades have significantly advanced our understanding on the sympatho-adrenergic mechanism in HF, which forms the focus of this article. This review notes recent research progress regarding the roles of cardiac β2AR or α1AR in the failing heart, significance of β1AR-autoantibodies, and βAR signaling through G-protein independent signaling pathways. Sympatho-βAR regulation of immune cells or fibroblasts is specifically discussed. On the neuronal aspects, knowledge is assembled on the remodeling of sympathetic nerves of the failing heart, regulation by presynaptic α2AR of NE release, and findings on device-based neuromodulation of the sympathetic nervous system. The review ends with highlighting areas where significant knowledge gaps exist but hold promise for new breakthroughs.

Collagen-Targeted Peptides for Molecular Imaging of Diffuse Cardiac Fibrosis

Background Cardiac fibrosis is the excessive deposition of extracellular matrix in the heart, triggered by a cardiac insult, aging, genetics, or environmental factors. Molecular imaging of the cardiac extracellular matrix with targeted probes could improve diagnosis and treatment of heart disease. However, although this technology has been used to demonstrate focal scarring arising from myocardial infarction, its capacity to demonstrate extracellular matrix expansion and diffuse cardiac fibrosis has not been assessed. Methods and Results Here, we report the use of collagen-targeted peptides labeled with near-infrared fluorophores for the detection of diffuse cardiac fibrosis in the β2-AR (β-2-adrenergic receptor) overexpressing mouse model and in ischemic human hearts. Two approaches were evaluated, the first based on a T peptide that binds matrix metalloproteinase-2-proteolyzed collagen IV, and the second on the cyclic peptide EP-3533, which targets collagen I. The systemic and cardiac uptakes of both peptides (intravenously administered) were quantified ex vivo by near-infrared imaging of whole organs, tissue sections, and heart lysates. The peptide accumulation profiles corresponded to an immunohistochemically-validated increase in collagen types I and IV in hearts of transgenic mice versus littermate controls. The T peptide could encouragingly demonstrate both the intermediate (7 months old) and severe (11 months old) cardiomyopathic phenotypes. Co-immunostainings of fluorescent peptides and collagens, as well as reduced collagen binding of a control peptide, confirmed the collagen specificity of the tracers. Qualitative analysis of heart samples from patients with ischemic cardiomyopathy compared with nondiseased donors supported the collagen-enhancement capabilities of these peptides also in the clinical settings. Conclusions Together, these observations demonstrate the feasibility and translation potential of molecular imaging with collagen-binding peptides for noninvasive imaging of diffuse cardiac fibrosis.

Apocynin attenuates diabetic cardiomyopathy by suppressing ASK1-p38/JNK signaling

Diabetic cardiomyopathy (DCM) significantly increased the morbidity of heart failure in diabetic patients. Long-time oxidative stress is an indisputable contributor for DCM development. Apocynin (APO) has been suggested to be a potential drug against oxidative stress. The study aims to find out the effects of APO on DCM and the related mechanisms. Mice were randomly divided into four groups: control (CON), APO, DCM and DCM + APO. Echocardiography analyses, histological analyses, Western blot and RT-PCR were used to explore the roles and mechanisms of APO in DCM. Isolated neonatal rat cardiomyocytes (NRCMs) and cardiac fibroblasts (CFs) were used for further confirming the APO treatment effects in vitro. Deteriorated cardiac function, enlarged cardiomyocytes, excess cardiac fibrosis and significant cardiac oxidative stress were observed in DCM group. However, APO treatment successfully improved cardiac function, decreased cardiac hypertrophy and fibrosis, and depressed oxidative stress. Mechanistically, APO treatment markedly suppressed apoptosis signal regulating kinase 1(ASK1)-p38/c-jun N-terminal kinase (JNK) signaling and reduced apoptosis. It also inhibited NRCM apoptosis and CF activation via depressing ASK1-p38/JNK signaling in vitro. Moreover, adenovirus-mediated ASK1 overexpression completely removed the protection of APO in vitro. In conclusion, APO treatment could effectively attenuate DCM-associated injuries in vivo and protect against high glucose-induced NRCM and CF injuries in vitro via suppressing ASK1-p38/JNK signaling. APO might be a potential ASK1 inhibitor for treating DCM.

Impact of Aldosterone on the Failing Myocardium: Insights from Mitochondria and Adrenergic Receptors Signaling and Function

The mineralocorticoid aldosterone regulates electrolyte and blood volume homeostasis, but it also adversely modulates the structure and function of the chronically failing heart, through its elevated production in chronic human post-myocardial infarction (MI) heart failure (HF). By activating the mineralocorticoid receptor (MR), a ligand-regulated transcription factor, aldosterone promotes inflammation and fibrosis of the heart, while increasing oxidative stress, ultimately induding mitochondrial dysfunction in the failing myocardium. To reduce morbidity and mortality in advanced stage HF, MR antagonist drugs, such as spironolactone and eplerenone, are used. In addition to the MR, aldosterone can bind and stimulate other receptors, such as the plasma membrane-residing G protein-coupled estrogen receptor (GPER), further complicating it signaling properties in the myocardium. Given the salient role that adrenergic receptor (ARs)—particularly βARs—play in cardiac physiology and pathology, unsurprisingly, that part of the impact of aldosterone on the failing heart is mediated by its effects on the signaling and function of these receptors. Aldosterone can significantly precipitate the well-documented derangement of cardiac AR signaling and impairment of AR function, critically underlying chronic human HF. One of the main consequences of HF in mammalian models at the cellular level is the presence of mitochondrial dysfunction. As such, preventing mitochondrial dysfunction could be a valid pharmacological target in this condition. This review summarizes the current experimental evidence for this aldosterone/AR crosstalk in both the healthy and failing heart, and the impact of mitochondrial dysfunction in HF. Recent findings from signaling studies focusing on MR and AR crosstalk via non-conventional signaling of molecules that normally terminate the signaling of ARs in the heart, i.e., the G protein-coupled receptor-kinases (GRKs), are also highlighted.

Nootkatone attenuates myocardial oxidative damage, inflammation, and apoptosis in isoproterenol-induced myocardial infarction in rats

BACKGROUND

Myocardial infarction (MI) is a lethal manifestation of cardiovascular diseases. Oxidative stress, inflammation, and subsequent cell death are known to play crucial roles in the pathogenesis of MI. Despite tremendous developments in interventional cardiology, there is need for novel drugs for the prevention and treatment of MI. For the development of novel drugs, usage of natural products has gained attention as a therapeutic approach for ischemic myocardial injury. Among many popular plant-derived compounds, Nootkatone (NKT), a natural bioactive sesquiterpene, abundantly found in grapefruit, has attracted attention for its plausible health benefits and pharmacological properties.

PURPOSE

The present study investigated the cardioprotective effects of NKT in rats against MI induced by isoproterenol (ISO), a synthetic catecholamine and β-adrenergic agonist that produces MI in a physiologically relevant manner.

METHODS

MI was induced in male Wistar albino rats by subcutaneous injection of ISO (85 mg/kg body weight) on 9^th and 10^th day. Rats were pre- and co-treated with NKT (10 mg/kg) through daily oral administration for eleven days.

RESULTS

ISO-induced MI was characterized by a significant decline in cardiac function, increased serum levels of cardiomyocyte injury markers, enhanced oxidative stress, and altered PI3K/Akt and NrF2/Keap1/HO-1 signaling pathways. ISO also elevated the levels of myocardial pro-inflammatory cytokines, promoted lysosomal dysfunction, altered TLR4-NFκB/MAPK signaling, and triggered intrinsic apoptotic pathway in heart tissues. However, NKT administration significantly restored or modulated majority of the altered biochemical and molecular parameters in ISO-treated rats. Furthermore, histopathological observations confirmed the myocardial restoring effect of NKT.

CONCLUSION

The present study concludes the cardioprotective effects and underlying mechanisms of NKT against ISO-induced MI in rats, and suggests that NKT or plants containing NKT could be an alternative to cardioprotective agents in ischemic heart diseases.

Pro-Resolving FPR2 Agonists Regulate NADPH Oxidase-Dependent Phosphorylation of HSP27, OSR1, and MARCKS and Activation of the Respective Upstream Kinases

Background: Formyl peptide receptor 2 (FPR2) is involved in the pathogenesis of chronic inflammatory diseases, being activated either by pro-resolving or proinflammatory ligands. FPR2-associated signal transduction pathways result in phosphorylation of several proteins and in NADPH oxidase activation. We, herein, investigated molecular mechanisms underlying phosphorylation of heat shock protein 27 (HSP27), oxidative stress responsive kinase 1 (OSR1), and myristolated alanine-rich C-kinase substrate (MARCKS) elicited by the pro-resolving FPR2 agonists WKYMVm and annexin A1 (ANXA1). Methods: CaLu-6 cells or p22phox^Crispr/Cas9 double nickase CaLu-6 cells were incubated for 5 min with WKYMVm or ANXA1, in the presence or absence of NADPH oxidase inhibitors. Phosphorylation at specific serine residues of HSP27, OSR1, and MARCKS, as well as the respective upstream kinases activated by FPR2 stimulation was analysed. Results: Blockade of NADPH oxidase functions prevents WKYMVm- and ANXA1-induced HSP-27(Ser82), OSR1(Ser339) and MARCKS(Ser170) phosphorylation. Moreover, NADPH oxidase inhibitors prevent WKYMVm- and ANXA1-dependent activation of p38MAPK, PI3K and PKCδ, the kinases upstream to HSP-27, OSR1 and MARCKS, respectively. The same results were obtained in p22phox^Crispr/Cas9 cells. Conclusions: FPR2 shows an immunomodulatory role by regulating proinflammatory and anti-inflammatory activities and NADPH oxidase is a key regulator of inflammatory pathways. The activation of NADPH oxidase-dependent pro-resolving downstream signals suggests that FPR2 signalling and NADPH oxidase could represent novel targets for inflammation therapeutic intervention.

Nootkatone, a Dietary Fragrant Bioactive Compound, Attenuates Dyslipidemia and Intramyocardial Lipid Accumulation and Favorably Alters Lipid Metabolism in a Rat Model of Myocardial Injury: An In Vivo and In Vitro Study

In the present study, we assessed whether nootkatone (NKT), a sesquiterpene in edible plants, can provide protection against dyslipidemia, intramyocardial lipid accumulation, and altered lipid metabolism in a rat model of myocardial infarction (MI) induced by subcutaneous injections of isoproterenol (ISO, 85 mg/kg) on days 9 and 10. The rats were pre- and co-treated with NKT (10 mg/kg, p.o.) administered daily for 11 days. A significant reduction in the activities of myocardial creatine kinase and lactate dehydrogenase, as well as non-enzymatic antioxidants, and alterations in lipids and lipoproteins, along with a rise in plasma lipid peroxidation and intramyocardial lipid accumulation, were observed in ISO-treated rats. ISO administration induced alterations in the activities of enzymes/expressions that played a significant role in altering lipid metabolism. However, NKT treatment favorably modulated all biochemical and molecular parameters altered by ISO and showed protective effects against oxidative stress, dyslipidemia, and altered lipid metabolism, attributed to its free-radical-scavenging and antihyperlipidemic activities in rats with ISO-induced MI. Additionally, NKT decreased the accumulation of lipids in the myocardium as evidenced from Oil red O staining. Furthermore, the in vitro observations demonstrate the potent antioxidant property of NKT. The present study findings are suggestive of the protective effects of NKT on dyslipidemia and the underlying mechanisms. Based on our findings, it can be suggested that NKT or plants rich in NKT can be promising for use as a phytopharmaceutical or nutraceutical in protecting the heart and correcting lipid abnormalities and dyslipidemia, which are risk factors for ischemic heart diseases.

Activation of β2 adrenergic receptor signaling modulates inflammation: a target limiting the progression of kidney diseases

Beta 2 adrenergic receptor (β₂-AR)-agonists, widely used as bronchodilators, have demonstrated wide-spectrum anti-inflammatory properties in both immune and non-immune cells in various tissues. Their anti-inflammatory properties are mediated primarily, but not exclusively, via activation of the canonical β₂-AR signaling pathway (β₂-AR/cAMP/PKA). As non-canonical β₂-AR signaling also occurs, several inconsistent findings on the anti-inflammatory effect of β₂-agonists are notably present. Increasing amounts of evidence have unveiled the alternative mechanisms of the β₂-AR agonists in protecting the tissues against injuries, i.e., by augmenting mitochondria biogenesis and SIRT1 activity, and by attenuating fibrotic signaling. This review mainly covers the basic mechanisms of the anti-inflammatory effects of β₂-AR activation along with its limitations. Specifically, we summarized the role of β₂-AR signaling in regulating kidney function and in mediating the progression of acute and chronic kidney diseases. Given their versatile protective effects, β₂-agonists can be a promising avenue in the treatment of kidney diseases.

Chrysophanol Protects Against Acute Heart Failure by Inhibiting JNK1/2 Pathway in Rats

BACKGROUND Acute heart failure (AHF) usually requires urgent therapy. Myocardial damage, oxidative stress, and inflammation are major components in the pathology of AHF. This study was designed to investigate the effects of chrysophanol on AHF. MATERIAL AND METHODS Sprague-Dawley rats were injected with isoprenaline hydrochloride to construct AHF rat models. AHF rats were treated with normal saline (negative control), chrysophanol, the combination of chrysophanol and SP600125, or benazepril (positive control) using sham rats as blank controls. Echocardiography, histological staining, and enzyme activity analysis were performed to assess the heart functions and myocardial damage. Effects on apoptosis, oxidative stress (OS), and inflammation were evaluated by biochemical analysis, TUNEL staining, and ELISA. RESULTS Chrysophanol improved the parameters of cardiac functions and alleviated the myocardial damage accompanied by the reduction of creatine kinase and lactate dehydrogenase activity. Meanwhile, chrysophanol inhibited the myocardial apoptosis along with the upregulation of Bcl-2 and downregulation of Bax and cleaved caspase-3. AHF-induced abnormal changes of OS parameters (MDA, GPx, CAT, SOD) and inflammatory markers (IL-6, IL-1ß, TNF-alpha, IFN-γ) were alleviated by chrysophanol. Benazepril treatment showed similar results with chrysophanol, while the addition of SP600125 enhanced the chrysophanol-mediated protection effects in AHF rats. Western blot analysis demonstrated that chrysophanol inhibited the phosphorylation of JNK1/2 and its upstream/downstream factors. CONCLUSIONS Chrysophanol improved cardiac functions and protected against myocardial damage, apoptosis, OS, and inflammation by inhibiting activation of the JNK1/2 pathway in AHF rat models. These finding indicate that chrysophanol may be a promising approach for treatment of AHF.

Association between heart rate variability indices and features of spontaneous ventricular tachyarrhythmias in mice

Direct evidence is limited for the association between heart rate variability (HRV) indices and ventricular tachyarrhythmias (VTAs). While galectin-3 (Gal-3) is regarded as a causal factor for cardiac remodelling and a biomarker for arrhythmias, its regulation on VTAs and HVR is unknown. Using aged transgenic (TG) mice with cardiac overexpression of β2 -adrenoceptors and spontaneous VTAs, we studied whether changes in HRV indices correlated with the severity of VTAs, and whether Gal-3 gene knockout (KO) in TG mice might limit VTA. Body-surface ECG was recorded (10-minute period) in 9- to 10-month-old mice of non-transgenic (nTG), TG and TG × Gal-3 knockout (TG/KO). Time-domain, frequency-domain and nonlinear-domain HRV indices were calculated using the R-R intervals extracted from ECG signals and compared with frequency of VTAs. TG and TG/KO mice developed frequent VTAs and showed significant changes in certain time-domain and nonlinear-domain HRV indices relative to nTG mice. The severity of VTAs in TG and TG/KO mice in combination, estimated by VTA counts and arrhythmia score, was significantly correlated with certain time-domain and nonlinear-domain HRV indices. In conclusion, significant changes in HRV indices were evident and correlated with the severity of spontaneous VTAs in TG mice. The frequency of VTA and HRV indices were largely comparable between TG and TG/KO mice. Deletion of Gal-3 in TG mice altered certain HRV indices implying influence by neuronally localized Gal-3 on autonomic nervous activity.

[6]-Gingerol Ameliorates ISO-Induced Myocardial Fibrosis by Reducing Oxidative Stress, Inflammation, and Apoptosis through Inhibition of TLR4/MAPKs/NF-κB Pathway

SCOPE

[6]-Gingerol is one of the primary pungent constituents of ginger. While [6]-gingerol has many pharmacological effects, its benefits for myocardial fibrosis, including its exact role and underlying mechanisms, remain largely unexplored. The present study is designed to characterize the cardio-protective effects of [6]-gingerol in myocardial fibrosis mice and possible underlying mechanisms.

METHODS AND RESULTS

Mice are subcutaneously injected with isoproterenol (ISO, 10 mg kg^-1 ) and gavaged with [6]-gingerol (10, 20 mg kg^-1 day^-1 ) for 14 days. Pathological alterations, fibrosis, oxidative stress, inflammation response, and apoptosis are examined. In ISO-induced myocardial fibrosis, [6]-gingerol treatment decreases the J-point, heart rate, cardiac weight index, left ventricle weight index, creatine kinase (CK), and lactate dehydrogenase serum levels, calcium concentration, reactive oxygen species, malondialdehyde, and glutathione disulfide (GSSG), and increases levels of superoxide dismutase, catalase, glutathione, and GSH/GSSG. Further, [6]-gingerol improved ISO-induced morphological pathologies, inhibited inflammation and apoptosis, and suppressed the toll-like receptor-4 (TLR4)/mitogen-activated protein kinases (MAPKs)/nuclear factor κB (NF-κB) signaling pathways.

CONCLUSION

The protective effect of [6]-gingerol in mice with ISO-induced myocardial fibrosis may be related to the inhibition of oxidative stress, inflammation, and apoptosis, potentially through the TLR4/MAPKs/NF-κB signaling pathway.

Involvement of Histamine 2 Receptor in Alpha 1 Adrenoceptor Mediated Cardiac Hypertrophy and Oxidative Stress in H9c2 Cardio Myoblasts

Despite the involvement of ɑ1adrenergic (ɑ1AR) and Histamine 2 receptors (H2R) in cardiac hypertrophy (CH), their relationship is yet to be studied. Our study investigated interrelationship between them using in vitro CH model. H9c2 cardiomyoblasts were exposed to phenylephrine (ɑ1AR agonist-50 μM) in the presence, the absence of famotidine (H2R antagonist-10 μM) and BAY 11-7082 (NF-kB inhibitor-10 μM). The impact of ɑ1AR stimulation on H2R expression and oxidative stress was assessed. Hypertrophic indices were assessed from activities of enzymatic mediators of cardiac hypertrophy, total protein content, BNP levels and cell volume. Additionally, the inverse agonistic property of famotidine and NFkB activity was also studied. ɑ1AR-induced H2R expression, oxidative stress and hypertrophic indices were significantly abolished by famotidine and pharmacological inhibitor of NFkB. Increase in constitutive activity of H2R was noticed correlating with increased receptor population. These results suggest involvement of NFkB-mediated upregulation of H2R in ɑ1AR-mediated CH.

Beneficial effects of benfotiamine, a NADPH oxidase inhibitor, in isoproterenol-induced myocardial infarction in rats

BACKGROUND

Acute myocardial infarction (AMI) remains the most common cause of morbidity and mortality worldwide. The present study was directed to investigate the beneficial effects of benfotiamine pre- and post-treatments in isoproterenol (ISO)-induced MI in rats.

METHODS

Myocardial heart damage was induced by subcutaneous injection of ISO (150 mg/kg) once daily for two consecutive days. Benfotiamine (100 mg/kg/day) was given orally for two weeks before or after ISO treatment.

RESULTS

ISO administration revealed significant changes in electrocardiographic recordings, elevation of levels of cardiac enzymes; creatinine kinase (CK-MB) and troponin-I (cTn-I), and perturbation of markers of oxidative stress; nicotinamide adenine dinucleotide phosphate (NADPH) oxidase, malondialdehyde (MDA), reduced glutathione (GSH), superoxide dismutase (SOD) and glutathione peroxidase (GPx) and markers of inflammation; protein kinase C (PKC), nuclear factor-kappa B (NF-κB) and metalloproteinase-9 (MMP-9). The apoptotic markers (caspase-8 and p53) were also significantly elevated in ISO groups in addition to histological alterations. Groups treated with benfotiamine pre- and post-ISO administration showed significantly decreased cardiac enzymes levels and improved oxidative stress, inflammatory and apoptotic markers compared to the ISO groups.

CONCLUSION

The current study highlights the potential role of benfotiamine as a promising agent for prophylactic and therapeutic interventions in myocardial damage in several cardiovascular disorders via NADPH oxidase inhibition.

Dissection of mechanisms of Chinese medicinal formula Si-Miao-Yong-an decoction protects against cardiac hypertrophy and fibrosis in isoprenaline-induced heart failure

ETHNOPHARMACOLOGICAL RELEVANCE

Si-Miao-Yong-An decoction (SMYAD) is a traditional Chinese herbal formulation. SMYAD first appeared in the Eastern Han Dynasty according to the "Shen Yi Mi Zhuan". Then the formula was recorded in the "Yan Fang Xin Bian" edited by medical scientist Bao Xiangao in the Qing Dynasty. This well-known prescription has been traditionally used for gangrene and vascular vasculitis. It is mainly used for cardiovascular and endocrine diseases in current clinical applications and research.

AIM OF STUDY

In this study, the potential mechanisms of SMYAD against cardiac fibrosis and hypertrophy in the β-adrenoceptor agonist isoprenaline induced heart failure model were investigated.

MATERIALS AND METHODS

The heart failure animal model was established via injected isoprenaline in rats. Echocardiography was used to detect the structure and function of the heart. HE staining and Masson's trichrome staining was performed to assess myocardial tissue morphology. The serum biochemical indexes were detected by dedicated biochemical kit. BNP was tested by ELISA kit. The levels of mRNA were detected by RT-qPCR. Cardiomyocyte morphology was assessed by immunofluorescence. Phosphorylated and total p38, Akt were analyzed by Western blot. The production of reactive oxygen species (ROS) was tested by CM-H2DCFDA probe. Formula identification of chemical constituents of SMYAD in plasma was disclosed through ultra-performance liquid chromatography coupled to quadrupole time-of-flight mass spectrometry (UPLC-Q/TOF-MS).

RESULTS

SMYAD was able to improve the heart function in ISO induced heart failure rat model via protecting rat from developing cardiac hypertrophy and fibrosis. SMYAD also decreased plasma expression of these biochemical indexes. It was found that SMYAD could regulate cardiac hypertrophy and fibrosis makers' mRNA levels in vitro and vivo. In addition, SMYAD inhibited the phosphorylation of p38 and Akt, which are key mediators in the pathological process of ISO-induced cardiac hypertrophy and myocardial fibrosis. It also showed that the components of SMYAD in rat plasma exerted myocardial cell protective activity.

CONCLUSION

In summary, SMYAD may comprise more than one active ingredient to the pursuit of combination therapies instead of specifically target a single disease-causing molecule. These experimental results suggest that SMYAD may be a potential drug candidate in diseases of cardiac hypertrophy and myocardial fibrosis caused by β-adrenoceptor abnormalities.

Gal-3 (Galectin-3) and KCa3.1 Mediate Heterogeneous Cell Coupling and Myocardial Fibrogenesis Driven by βAR (β-Adrenoceptor) Activation

Heart failure is associated with sympatho-βAR (β-adrenoceptor) activation and cardiac fibrosis. Gal-3 (galectin-3) and K_Ca3.1 channels that are upregulated in diverse cells of diseased heart are implicated in mediating myocardial inflammation and fibrosis. It remains unclear whether Gal-3 interacts with K_Ca3.1 leading to cardiac fibrosis in the setting of βAR activation. We tested the effect of K_Ca3.1 blocker TRAM-34 on cardiac fibrosis and inflammation in cardiac-restricted β₂-TG (β₂AR overexpressed transgenic) mice and determined K_Ca3.1 expression in β₂-TG×Gal-3^-/- mouse hearts. Mechanisms of K_Ca3.1 in mediating Gal-3 induced fibroblast activation were studied ex vivo. Expression of Gal-3 and K_Ca3.1 was elevated in β₂-TG hearts. Gal-3 gene deletion in β₂-TG mice decreased K_Ca3.1 expression in inflammatory cells but not in fibroblasts. Treatment of β₂-TG mice with TRAM-34 for 1 or 2 months significantly ameliorated cardiac inflammation and fibrosis and reduced Gal-3 level. In cultured fibroblasts, Gal-3 upregulated K_Ca3.1 expression and channel currents with enhanced membrane potential and Ca²⁺ entry through TRPV4 (transient receptor potential V4) and TRPC6 (transient receptor potential C6) channels leading to fibroblast activation. In conclusion, βAR stimulation promotes Gal-3 production that upregulates K_Ca3.1 channels in noncardiomyocyte cells and activates K_Ca3.1 channels in fibroblasts leading to hyperpolarization of membrane potential and Ca²⁺ entry via TRP channels. Gal-3-K_Ca3.1 signaling mobilizes diverse cells facilitating regional inflammation and fibroblast activation and hence myocardial fibrosis.

Evolving concepts in the pathogenesis of uraemic cardiomyopathy

The term uraemic cardiomyopathy refers to the cardiac abnormalities that are seen in patients with chronic kidney disease (CKD). Historically, this term was used to describe a severe cardiomyopathy that was associated with end-stage renal disease and characterized by severe functional abnormalities that could be reversed following renal transplantation. In a modern context, uraemic cardiomyopathy describes the clinical phenotype of cardiac disease that accompanies CKD and is perhaps best characterized as diastolic dysfunction seen in conjunction with left ventricular hypertrophy and fibrosis. A multitude of factors may contribute to the pathogenesis of uraemic cardiomyopathy, and current treatments only modestly improve outcomes. In this Review, we focus on evolving concepts regarding the roles of fibroblast growth factor 23 (FGF23), inflammation and systemic oxidant stress and their interactions with more established mechanisms such as pressure and volume overload resulting from hypertension and anaemia, respectively, activation of the renin-angiotensin and sympathetic nervous systems, activation of the transforming growth factor-β (TGFβ) pathway, abnormal mineral metabolism and increased levels of endogenous cardiotonic steroids.

Current advances in the study of diabetic cardiomyopathy: From clinicopathological features to molecular therapeutics (Review)

The incidence of diabetes mellitus has become a major public health concern due to lifestyle alterations. Moreover, the complications associated with diabetes mellitus deeply influence the quality of life of patients. Diabetic cardiomyopathy (DC) is a type of diabetes mellitus complication characterized by functional and structural damage in the myocardium but not accompanied by coronary arterial disease. Currently, diagnosing and preventing DC is still a challenge for physicians due to its atypical symptoms. For this reason, it is necessary to summarize the current knowledge on DC, especially in regards to the underlying molecular mechanisms toward the goal of developing useful diagnostic approaches and effective drugs based on these mechanisms. There exist several review articles which have focused on these points, but there still remains a lot to learn from published studies. In this review, the features, diagnosis and molecular mechanisms of DC are reviewed. Furthermore, potential therapeutic and prophylactic drugs are discussed.

β-Adrenoceptor activation affects galectin-3 as a biomarker and therapeutic target in heart disease

Myocardial fibrosis is a key histopathological component that drives the progression of heart disease leading to heart failure and constitutes a therapeutic target. Recent preclinical and clinical studies have implicated galectin-3 (Gal-3) as a pro-fibrotic molecule and a biomarker of heart disease and fibrosis. However, our knowledge is poor on the mechanism(s) that determine the blood level or regulate cardiac expression of Gal-3. Recent studies have demonstrated that enhanced β-adrenoceptor activity is a determinant of both circulating concentration and cardiac expression of Gal-3. Pharmacological or transgenic activation of β-adrenoceptors leads to increased blood levels of Gal-3 and up-regulated cardiac Gal-3 expression, effect that can be reversed with the use of β-adrenoceptor antagonists. Conversely, Gal-3 gene deletion confers protection against isoprenaline-induced cardiotoxicity and fibrogenesis. At the transcription level, β-adrenoceptor stimulation activates cardiac mammalian sterile-20-like kinase 1, a pivotal kinase of the Hippo signalling pathway, which is associated with Gal-3 up-regulation. Recent studies have suggested a role for the β-adrenoceptor-Hippo signalling pathway in the regulation of cardiac Gal-3 expression thereby contributing to the onset and progression of heart disease. This implies a therapeutic potential of the suppression of Gal-3 expression. In this review, we discuss the effects of β-adrenoceptor activity on Gal-3 as a biomarker and causative mediator in the setting of heart disease and point out pivotal knowledge gaps. LINKED ARTICLES: This article is part of a themed section on Adrenoceptors-New Roles for Old Players. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v176.14/issuetoc.

Stimulation of β-adrenoceptors up-regulates cardiac expression of galectin-3 and BIM through the Hippo signalling pathway

Background and Purpose

Expression of the pro‐fibrotic galectin‐3 and the pro‐apoptotic BIM is elevated in diseased heart or after β‐adrenoceptor stimulation, but the underlying mechanisms are unclear. This question was addressed in the present study.

Experimental Approach

Wild‐type mice and mice with cardiac transgenic expression of β₂‐adrenoceptors, mammalian sterile‐20 like kinase 1 (Mst1) or dominant‐negative Mst1, and non‐specific galectin‐3 knockout mice were used. Effects of the β‐adrenoceptor agonist isoprenaline or β‐adrenoceptor antagonists were studied. Rat cardiomyoblasts (H9c2) were used for mechanistic exploration. Biochemical assays were performed.

Key Results

Isoprenaline treatment up‐regulated expression of galectin‐3 and BIM, and this was inhibited by non‐selective or selective β‐adrenoceptor antagonists (by 60–70%). Cardiac expression of galectin‐3 and BIM was increased in β₂‐adrenoceptor transgenic mice. Isoprenaline‐induced up‐regulation of galectin‐3 and BIM was attenuated by Mst1 inactivation, but isoprenaline‐induced galectin‐3 expression was exaggerated by transgenic Mst1 activation. Pharmacological or genetic activation of β‐adrenoceptors induced Mst1 expression and yes‐associated protein (YAP) phosphorylation. YAP hyper‐phosphorylation was also evident in Mst1 transgenic hearts with up‐regulated expression of galectin‐3 (40‐fold) and BIM as well as up‐regulation of many YAP‐target genes by RNA sequencing. In H9c2 cells, isoprenaline induced YAP phosphorylation and expression of galectin‐3 and BIM, effects simulated by forskolin but abolished by PKA inhibitors, and YAP knockdown induced expression of galectin‐3 and BIM.

Conclusions and Implications

Stimulation of cardiac β‐adrenoceptors activated the Mst1/Hippo pathway leading to YAP hyper‐phosphorylation with enhanced expression of galectin‐3 and BIM. This signalling pathway would have therapeutic potential.

Linked Articles

This article is part of a themed section on Adrenoceptors—New Roles for Old Players. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v176.14/issuetoc

ADRB2 suppresses IL-13-induced allergic rhinitis inflammatory cytokine regulated by miR-15a-5p

Allergic rhinitis (AR) is a common hypersensitive disease that troubles patients a lot. Nasal epithelial cells (NECs), as the outmost protection of inhalation, play an important role in AR allergic response. Adrenoceptor beta 2 (ADRB2) is an important gene in inflammatory response, which has become the hot spot for AR development and treatment in recent years. MiR-15a-5p has been proved to be involved in AR immune response as the upstream regulator of ADRB2. Human primary NECs were isolated and stimulated by IL-13. qRT-PCR assay was used to detect the RNA level of target genes. ELISA and Western blotting were applied to detect target protein levels. Luciferase reporter assay and biotin pull-down assay were performed to test molecules interaction. ADRB2 was highly expressed in nasal mucosa of AR patients and was positively correlated with IL-13 stimulation, and knockdown of ADRB2 inhibited IL-13-induced expression of GM-CSF, eotaxin, and MUC5AC in NECs. ADRB2 was directly targeted by miR-15a-5p, and miR-15a-5p inhibited IL-13-induced expression of GM-CSF, eotaxin, and MUC5AC in NECs. ADRB2 mediated the effect of miR-15a-5p on the regulation of nasal epithelial immune responses. ADRB2 is negatively regulated by miR-15a-5p, which inhibits IL-13-induced nasal epithelial inflammatory responses.

The Role of Heat Shock Proteins in Regulating Receptor Signal Transduction

Heat shock proteins (Hsp) are a class of stress-inducible proteins that mainly act as molecular protein chaperones. This chaperone activity is diverse, including assisting in nascent protein folding and regulating client protein location and translocation within the cell. The main proteins within the Hsp family, particularly Hsp70 and Hsp90, also have a highly diverse and numerous set of protein clients, which when combined with the high expression levels of Hsp proteins (2%-6% of total protein content) establishes these molecules as "central regulators" of cell protein physiology. Among the client proteins, Hsps regulate numerous signal-transduction and receptor-regulatory kinases, and indeed directly regulate some receptors themselves. This also makes the Hsps, particularly Hsp90, central regulators of signal-transduction machinery, with important impacts on endogenous and drug ligand responses. Among these roles, Hsp90 in particular acts to maintain mature signaling kinases in a metastable conformation permissive for signaling activation. In this review, we will focus on the roles of the Hsps, with a special focus on Hsp90, in regulating receptor signaling and subsequent physiologic responses. We will also explore potential means to manipulate Hsp function to improve receptor-targeted therapies. Overall, Hsps are important regulators of receptor signaling that are receiving increasing interest and exploration, particularly as Hsp90 inhibitors progress toward clinical approval for the treatment of cancer. Understanding the complex interplay of Hsp regulation of receptor signaling may provide important avenues to improve patient treatment.

Review on Chamber-Specific Differences in Right and Left Heart Reactive Oxygen Species Handling

Reactive oxygen species (ROS) exert signaling character (redox signaling), or damaging character (oxidative stress) on cardiac tissue depending on their concentration and/or reactivity. The steady state of ROS concentration is determined by the interplay between its production (mitochondrial, cytosolic, and sarcolemmal enzymes) and ROS defense enzymes (mitochondria, cytosol). Recent studies suggest that ROS regulation is different in the left and right ventricle of the heart, specifically by a different activity of superoxide dismutase (SOD). Mitochondrial ROS defense seems to be lower in right ventricular tissue compared to left ventricular tissue. In this review we summarize the current evidence for heart chamber specific differences in ROS regulation that may play a major role in an observed inability of the right ventricle to compensate for cardiac stress such as pulmonary hypertension. Based on the current knowledge regimes to increase ROS defense in right ventricular tissue should be in the focus for the development of future therapies concerning right heart failure.

α-Bisabolol abrogates isoproterenol-induced myocardial infarction by inhibiting mitochondrial dysfunction and intrinsic pathway of apoptosis in rats

Mitochondrial dysfunction plays crucial role in the pathologenesis of myocardial infarction (MI). The present study evaluated the protective effect of α-bisabolol against isoproterenol (ISO)-induced mitochondrial dysfunction and apoptosis in rats. Male albino Wistar rats were pre- and co-treated with intraperitoneal injection of α-bisabolol (25 mg/kg body weight) daily for 10 days. To induce experimental MI, ISO (85 mg/kg body weight) was injected subcutaneously to the rats at an interval of 24 h for 2 days (9th and 10th day). ISO-induced MI was indicated by the decreased activities of heart creatine kinase and lactate dehydrogenase in rats. ISO administration also enhanced the concentrations of heart mitochondrial lipid peroxidation products and decreased the activities/concentrations of mitochondrial antioxidants, Kreb's cycle dehydrogenases and mitochondrial electron transport chain complexes I, II + III and IV in rats. Furthermore, ISO triggers calcium overload and ATP depletion in the rat's heart mitochondria followed by the mitochondrial cytochrome-C release and the activation of intrinsic pathway of apoptosis by upregulating the myocardial pro-apoptotic Bax, P⁵³, APAF-1, active caspase-3, active caspase-9 and down regulating the expressions of anti-apoptotic Bcl-2. α-Bisabolol pre and co-treatment showed considerable protective effects on all the biochemical and molecular parameters studied. Transmission electron microscopic study and mitochondrial swelling assay confirmed our biochemical and molecular findings. The in vitro study on hydroxyl radical also revealed the potent free radical scavenging activity of α-bisabolol. Thus, α-bisabolol attenuates mitochondrial dysfunction and intrinsic pathway of apoptosis in ISO-induced myocardial infarcted rats.

Cellular Stresses and Stress Responses in the Pathogenesis of Insulin Resistance

Insulin resistance (IR), a key component of the metabolic syndrome, precedes the development of diabetes, cardiovascular disease, and Alzheimer's disease. Its etiological pathways are not well defined, although many contributory mechanisms have been established. This article summarizes such mechanisms into the hypothesis that factors like nutrient overload, physical inactivity, hypoxia, psychological stress, and environmental pollutants induce a network of cellular stresses, stress responses, and stress response dysregulations that jointly inhibit insulin signaling in insulin target cells including endothelial cells, hepatocytes, myocytes, hypothalamic neurons, and adipocytes. The insulin resistance-inducing cellular stresses include oxidative, nitrosative, carbonyl/electrophilic, genotoxic, and endoplasmic reticulum stresses; the stress responses include the ubiquitin-proteasome pathway, the DNA damage response, the unfolded protein response, apoptosis, inflammasome activation, and pyroptosis, while the dysregulated responses include the heat shock response, autophagy, and nuclear factor erythroid-2-related factor 2 signaling. Insulin target cells also produce metabolites that exacerbate cellular stress generation both locally and systemically, partly through recruitment and activation of myeloid cells which sustain a state of chronic inflammation. Thus, insulin resistance may be prevented or attenuated by multiple approaches targeting the different cellular stresses and stress responses.

Upregulated galectin-3 is not a critical disease mediator of cardiomyopathy induced by β2-adrenoceptor overexpression

Preclinical studies have demonstrated that anti-galectin-3 (Gal-3) interventions are effective in attenuating cardiac remodeling, fibrosis, and dysfunction. We determined, in a transgenic (TG) mouse model of fibrotic cardiomyopathy, whether Gal-3 expression was elevated and whether Gal-3 played a critical role in disease development. We studied mice with fibrotic cardiomyopathy attributable to cardiac overexpression of human β2-adrenoceptors (β2-TG). Cardiac expression levels of Gal-3 and fibrotic or inflammatory genes were determined. The effect of Gal-3 inhibition in β2-TG mice was studied by treatment with Gal-3 inhibitors ( N-acetyllactosamine and modified citrus pectin) or by deletion of Gal-3 through crossing β2-TG and Gal-3 knockout mice. Changes in cardiomyopathy phenotypes were assessed by echocardiography and biochemical assays. In β2-TG mice at 3, 6, and 9 mo of age, upregulation of Gal-3 expression was observed at mRNA (~6- to 15-fold) and protein (~4- to 8-fold) levels. Treatment of β2-TG mice with N-acetyllactosamine (3 wk) or modified citrus pectin (3 mo) did not reverse cardiac fibrosis, inflammation, and cardiomyopathy. Similarly, Gal-3 gene deletion in β2-TG mice aged 3 and 9 mo did not rescue the cardiomyopathy phenotype. In conclusion, the β2-TG model of cardiomyopathy showed a robust upregulation of Gal-3 that correlated with disease severity, but Gal-3 inhibitors or Gal-3 gene deletion had no effect in halting myocardial fibrosis, remodeling, and dysfunction. Gal-3 may not be critical for cardiac fibrogenesis and remodeling in this cardiomyopathy model.

NEW & NOTEWORTHY We showed a robust upregulation of cardiac galectin-3 (Gal-3) expression in a mouse model of cardiomyopathy attributable to cardiomyocyte-restricted transgenic activation of β2-adrenoceptors. However, pharmacological and genetic inhibition of Gal-3 did not confer benefit in this model, implying that Gal-3 may not be a critical disease mediator of cardiac remodeling in this model.

Prevention of βeta-adrenergic-induced Adverse Cardiac Remodeling by Gonadectomy in Male but Not Female Spontaneously Hypertensive Rats

Chronic β-adrenergic stimulation induces left ventricular (LV) remodeling in male but not in female spontaneously hypertensive rats (SHRs). However, the role of sex steroids in mediating these effects has not been determined. The aim of the present study was to assess the impact of gonadectomy on isoproterenol (ISO)-induced LV remodeling in SHR. Gonadectomy was performed on 9-month-old male and female SHR. LV remodeling was induced by daily ISO injection (0.04 mg/kg) for 6 months. LV dimensions and functions were determined in vivo by echocardiography and ex vivo using isolated perfused heart preparations. In males, ISO increased LV end diastolic (LVED) diameter in sham-operated (in millimeter, ISO: 8.12 ± 0.26 vs. Con: 6.67 ± 0.20, P = 0.0002) but not in castrated SHR (ISO: 6.97 ± 0.31 vs. Con: 6.53 ± 0.15, P = 0.66). Similarly, ISO increased the volume intercept of the LVED pressure-volume relationship in sham-operated (in milliliters, ISO: 0.26 ± 0.02 vs. Con: 0.19 ± 0.01, P = 0.01) but not in castrated SHR (ISO: 0.17 ± 0.02 vs. Con: 0.17 ± 0.01, P = 0.99). In females, ISO only increased LVED diameter (ISO: 6.43 ± 0.13 vs. Con: 6.07 ± 0.09, P = 0.027). However, ovariectomy did not modify any LV dimensions measured in vivo and ex vivo. In conclusion, testosterone may be responsible for the chronic β-adrenergic-induced LV dilation and eccentric remodeling observed in male but not female SHR.

Hibiscus sabdariffa (roselle) polyphenol-rich extract averts cardiac functional and structural abnormalities in type 1 diabetic rats

Diabetes mellitus is often associated with cardiac functional and structural alteration, an initial event leading to cardiovascular complications. Roselle (Hibiscus sabdariffa) has been widely proven as an antioxidant and recently has incited research interest for its potential in treating cardiovascular disease. Therefore, this study aimed to determine the cardioprotective effects of H. sabdariffa (roselle) polyphenol-rich extract (HPE) in type-1-induced diabetic rats. Twenty-four male Sprague-Dawley rats were randomized into 4 groups (n = 6/group): nondiabetic, diabetic alone (DM), diabetic supplemented with HPE (DM+HPE), and diabetic supplemented with metformin. Type-1 diabetes was induced with streptozotocin (55 mg/kg intraperitoneally). Rats were forced-fed with HPE (100 mg/kg) and metformin (150 mg/kg) daily for 8 weeks. Results showed that HPE supplementation improved hyperglycemia and dyslipidemia significantly (p < 0.05) in the DM+HPE compared with the DM group. HPE supplementation attenuated cardiac oxidative damage in the DM group, indicated by low malondialdehyde and advanced oxidation protein product. As for the antioxidant status, HPE significantly (p < 0.05) increased glutathione level, as well as catalase and superoxide dismutase 1 and 2 activities. These findings correlate with cardiac function, whereby left ventricle developed pressure in DM+HPE (79.13 ± 3.08 mm Hg) was higher significantly compared with DM (45.84 ± 1.65 mm Hg). Coronary flow of DM+HPE (17.43 ± 0.62 mL/min) was also greater compared with DM (13.02 ± 0.6 mL/min), showing that HPE supplementation improved cardiac contractility and relaxation rate significantly (p < 0.05). Histological analysis showed a marked decrease in cardiomyocyte hypertrophy and fibrosis in DM+HPE compared with the DM group. Ultrastructural changes and impairment of mitochondria induced by diabetes were minimized by HPE supplementation. Collectively, these findings suggest that HPE is a potential cardioprotective agent in a diabetic setting through its hypoglycemic, anti-hyperlipidemia, and antioxidant properties.

A multidimensional sight on cardiac failure: uncovered from structural to molecular level

Heart failure is one of the leading causes of death, with high mortality rate within 5 years after diagnosis. Treatment and prognosis options for heart failure primarily targeted on hemodynamic and neurohumoral components that drive progressive deterioration of the heart. However, given the multifactorial background that eventually leads to the "phenotype" named heart failure, better insight into the various components may lead to personalized treatment opportunities. Indeed, currently used criteria to diagnose and/or classify heart failure are possibly too focused on phenotypic improvement rather than the molecular driver of the disease and could therefore be further refined by integrating the leap of molecular and cellular knowledge. The ambiguity of the ejection fraction-based classification criteria became evident with development of advanced molecular techniques and the dawn of omics disciplines which introduced the idea that disease is caused by a myriad of cellular and molecular processes rather than a single event or pathway. The fact that different signaling pathways may underlie similar clinical manifestations calls for a more holistic study of heart failure. In this context, the systems biology approach can offer a better understanding of how different components of a system are altered during disease and how they interact with each other, potentially leading to improved diagnosis and classification of this condition. This review is aimed at addressing heart failure through a multilayer approach that covers individually some of the anatomical, morphological, functional, and tissue aspects, with focus on cellular and subcellular features as an alternative insight into new therapeutic opportunities.

Role of the β3-adrenergic receptor subtype in catecholamine-induced myocardial remodeling

β₃-Adrenoceptors (AR) stimulate cardiac Na⁺/K⁺ pump in healthy hearts. β₃-ARs are upregulated by persistent sympathetic hyperactivity; however, their effect on Na⁺/K⁺ ATPase activity and ventricular function in this condition is still unknown. Here, we investigate preventive effects of additional β₃-AR activation (BRL) on Na⁺/K⁺ ATPase activity and in vivo hemodynamics in a model of noradrenaline-induced hypertrophy. Rats received NA or NA plus simultaneously administered BRL in vivo infusion for 14 days; their cardiac function was investigated by left ventricular pressure-volume analysis. Moreover, fibrosis and apoptosis were also assessed histologically. NA induced an hypertrophic pattern, as detected by morphological, histological, and biochemical markers. Additional BRL exposure reversed the hypertrophic pattern and restored Na⁺/K⁺ ATPase activity. NA treatment increased systolic function and depressed diastolic function (slowed relaxation). Additional BRL treatment reversed most NA-induced hemodynamic changes. NA decreased Na⁺/K⁺ pump α2 subunit expression selectively, a change also reversed by additional BRL treatment. Increasing β₃-AR stimulation may prevent the consequences of chronic NA exposure on Na⁺/K⁺ pump and in vivo hemodynamics. β₃-AR agonism may thus represent a new therapeutic strategy for pharmacological modulation of hypertrophy under conditions of chronically enhanced sympathetic activity.

The role of reactive oxygen species in myocardial redox signaling and regulation

Reactive oxygen species (ROS) are subcellular messengers in gene regulatory and signal transduction pathways. In pathological situations, ROS accumulate due to excessive production or insufficient degradation, leading to oxidative stress (OS). OS causes oxidation of DNA, membranes, cellular lipids, and proteins, impairing their normal function and leading ultimately to cell death. OS in the heart is increased in response to ischemia/reperfusion, hypertrophy, and heart failure. The concentration of ROS is determined by their rates of production and clearance by antioxidants. Increases in OS in heart failure are primarily a result of the functional uncoupling of the respiratory chain due to inactivation of complex I. However, increased ROS in the failing myocardium may also be caused by impaired antioxidant capacity, such as decreased activity of Cu/Zn superoxide dismutase (SOD) and catalase (CAT) or stimulation of enzymatic sources, including, cyclooxygenase, xanthine oxidase (XO), nitric oxide synthase, and nonphagocytic NAD(P)H oxidases (Noxs). Mitochondria are the main source of ROS during heart failure and aging. Increased production of ROS in the failing heart leads to mitochondrial permeability transition, which results in matrix swelling, outer membrane rupture, a release of apoptotic signaling molecules, and irreversible injury to the mitochondria. Alterations of "redox homeostasis" leads to major cellular consequences, and cellular survival requires an optimal regulation of the redox balance.

Different roles of β-arrestin and the PKA pathway in mitochondrial ROS production induced by acute β-adrenergic receptor stimulation in neonatal mouse cardiomyocytes

Reactive oxygen species (ROS) play a crucial role in various physiological and pathological processes mediated by β-adrenergic receptors (β-ARs) in cardiomyocytes. However, the sources and signaling pathways involved in ROS production induced by acute β-AR activation have not yet been fully defined. In primary neonatal mouse cardiomyocytes (NMCMs), the β-AR agonist isoproterenol (ISO) induced a rapid increase in mitochondrial ROS and total ROS production. Both the expression and activity of nicotinamide adenine dinucleotide phosphate (NADPH) oxidase 2/4 (NOX 2/4) remained unchanged after 2 h of ISO treatment, suggesting that acute ISO stimulation mainly induces mitochondrial ROS production in NMCMs. Knockdown of β-arrestin1, but not β-arrestin2, inhibited ISO-induced mitochondrial ROS production within 1-2 h after ISO treatment. Moreover, forskolin, an adenylyl cyclase (AC) activator, rapidly increased mitochondrial ROS as early as 15 min after ISO treatment. Inhibition of the cyclic adenosine monophosphate (cAMP)/protein kinase A (PKA) pathway abolished the mitochondrial ROS production within 15-60 min after ISO treatment. In conclusion, mitochondria are the major source of ROS production upon acute ISO stimulation. β-arrestin1, but not β-arrestin2, is involved in ISO-induced mitochondrial ROS production. Upon acute β-AR stimulation in NMCMs, the classical cAMP/PKA pathway is responsible for faster mitochondrial ROS production, whereas β-arrestin1 signaling is responsible for slower mitochondrial ROS production.

HDAC2 is required by the physiological concentration of glucocorticoid to inhibit inflammation in cardiac fibroblasts

We previously suggested that endogenous glucocorticoids (GCs) may inhibit myocardial inflammation induced by lipopolysaccharide (LPS) in vivo. However, the possible cellular and molecular mechanisms were poorly understood. In this study, we investigated the role of physiological concentration of GCs in inflammation induced by LPS in cardiac fibroblasts and explored the possible mechanisms. The results showed that hydrocortisone at the dose of 127 ng/mL (equivalent to endogenous basal level of GCs) inhibited LPS (100 ng/mL)-induced productions of TNF-α and IL-1β in cardiac fibroblasts. Xanthine oxidase/xanthine (XO/X) system impaired the anti-inflammatory action of GCs through downregulating HDAC2 activity and expression. Knockdown of HDAC2 restrained the anti-inflammatory effects of physiological level of hydrocortisone, and blunted the ability of XO/X system to downregulate the inhibitory action of physiological level of hydrocortisone on cytokines. These results suggested that HDAC2 was required by the physiological concentration of GC to inhibit inflammatory response. The dysfunction of HDAC2 induced by oxidative stress might be account for GC resistance and chronic inflammatory disorders during the cardiac diseases.