Leukocyte-Expressed β2-Adrenergic Receptors Are Essential for Survival After Acute Myocardial Injury

Effects of carvedilol on the prevention of cardiotoxicity induced by anthracyclines: Design and rationale of the CARDIOTOX trial

BACKGROUND

Patients with cancer undergoing chemotherapy with an anthracycline-based regimen are at increased risk of cardiotoxicity, predisposing to heart failure, arrhythmias and death. Whether carvedilol may confer benefit to prevent anthracycline-induced cardiotoxicity remains to be determined.

DESIGN

CARDIOTOX is a double-blind, placebo controlled randomized clinical trial that plan to enroll 1,018 patients across 25 study sites in Brazil. Patients with active cancer scheduled to undergo an anthracycline-based chemotherapy regimen are eligible. Patients with prior HF or cardiomyopathy are excluded. Patients are randomized in 1:1 ratio to carvedilol (starting dose 6.25mg BID up titrated to 25mg BID or maximum tolerated dose) or placebo, stratified by site and use of renin-angiotensin blockers at baseline. Study drug is administered through the duration of chemotherapy and up to 30 days after the last dose of anthracycline. Patients are scheduled to undergo echocardiographic evaluations at baseline and at 3, 6, and 12 months. The study primary endpoint is the composite of new left ventricle ejection fraction (LVEF) reduction by at least 10% leading to an LVEF <50%, cardiovascular death, myocardial infarction, urgent care visit or hospitalization for heart failure, or clinically significant arrhythmias at 12 months. Echocardiographic images will be analyzed by a central core lab, clinical outcomes will be adjudicated, and safety endpoints include serious adverse events and adverse events of special interest (symptomatic bradycardia, hypotension, syncope and bronchospasm).

SUMMARY

The CARDIOTOX trial is the largest trial to date analyzing the potential role of beta-blockers as prophylactic therapy to prevent cardiotoxicity induced by anthracyclines.

TRIAL REGISTRATION

Effects of Carvedilol on Cardiotoxicity in Cancer Patients Submitted to Anthracycline Therapy (CardioTox).

CLINICALTRIALS

gov ID NCT04939883. https://clinicaltrials.gov/study/NCT04939883.

Neuroimmune cross-talk in heart failure

Heart failure (HF) is characterized by autonomic nervous system (ANS) imbalance and low-grade chronic inflammation. The bidirectional relationship between the ANS and immune system (IS) is named 'neuroimmune cross-talk' (NICT) and is based on common signaling molecules, receptors, and pathways. NICT may be altered in HF, and neuroinflammation seems to be a main driver of HF progression. In HF, heightened sympathetic nerve activity triggers inflammatory cascades that lead to cardiomyocyte death and myocardial interstitial fibrosis. Concurrently, parasympathetic withdrawal may impair the cholinergic anti-inflammatory pathway, with a less effective immune response to infections or inflammatory events. Additionally, microglial activation and inflammatory molecules contribute to autonomic imbalance by acting on central nuclei and peripheral visceral feedbacks, which in turn promote adverse cardiac remodeling, HF decompensation, and potentially life-threatening arrhythmias. Therefore, neuroinflammation has been identified as a potential target for treatment. Pharmacological antagonism of the neurohormonal system remains the cornerstone of chronic HF therapy. While some drugs used in HF management may have additional benefits due to their anti-inflammatory properties, clinical trials targeting inflammation in patients with HF have so far produced inconclusive results. Nevertheless, considering the pathophysiological relevance of NICT, its modulation seems an appealing strategy to optimize HF management. Current research is therefore investigating novel pharmacological targets for anti-inflammatory drugs, and the immunomodulatory properties of denervation approaches and bioelectronic medicine devices targeting NICT and neuroinflammation in HF. A deeper understanding of the complex relationship between the ANS and IS, as outlined in this review, could therefore facilitate the design of future studies aimed at improving outcomes by targeting NICT in patients with HF.

Neuroimmune Interactions and Their Role in Immune Cell Trafficking in Cardiovascular Diseases and Cancer

Sympathetic nerves innervate bone marrow and various immune organs, where norepinephrine-the primary sympathetic neurotransmitter-directly interacts with immune cells that express adrenergic receptors. This article reviewed the key molecular pathways triggered by sympathetic activation and explored how sympathetic activity influences immune cell migration. Norepinephrine serves as a chemoattractant for monocytes, macrophages, and stem cells, promoting the migration of myeloid cells while inhibiting the migration of lymphocytes at physiological concentrations. We also examined the role of immune cell infiltration in cardiovascular diseases and cancer. Evidence suggests that sympathetic activation increases myeloid cell infiltration into target tissues across various cardiovascular diseases, including atherosclerosis, hypertension, cardiac fibrosis, cardiac hypertrophy, arrhythmia, myocardial infarction, heart failure, and stroke. Conversely, inhibiting sympathetic activity may serve as a potential therapeutic strategy to treat these conditions by reducing macrophage infiltration. Furthermore, sympathetic activation promotes macrophage accumulation in cancer tissues, mirroring its effects in cardiovascular diseases, while suppressing T lymphocyte infiltration into cancerous sites. These changes contribute to increased cancer growth and metastasis. Thus, inhibiting sympathetic activation could help to protect against cancer by enhancing T cell infiltration and reducing macrophage presence in tumors.

Role of macrophages in cardiac arrhythmias: Pathogenesis and therapeutic perspectives

The pathophysiology of arrhythmias is complex, involving changes in cardiac contractile and conduction systems, electrical conduction heterogeneity, and structural alterations. Recent studies indicate that cardiac macrophages can induce arrhythmias by interacting with cardiomyocytes or altering tissue composition. Due to the heterogeneity and diversity, macrophages develop different cellular functions during pathological processes. This review identifies various macrophage subpopulations and focuses on their pathological mechanisms in arrhythmogenesis. Furthermore, we explore the interactions of macrophages with other immune cells and summarize the promising approaches for targeting macrophages in arrhythmias treatment. Macrophages directly or indirectly influence arrhythmogenesis through multiple systemic effects. Preclinical studies suggest that modifying macrophages' phenotype or regulating their activity may directly affect cardiac conduction. This review provides a theoretical basis for developing immunotherapies for patients with cardiac arrhythmias.

Downregulation of CCR2 reduces ventricular remodeling after myocardial infarction by splenic nerve neuromodulation in acute and chronic rat models

OBJECTIVES

Pathological remodeling after myocardial infarction (MI) confers the development of heart failure. Our prior research has indicated that splenic nerve neuromodulation mitigates myocardial ischemia-reperfusion injury (IRI) by reducing levels of proinflammatory factors. This study aims to explore the potential therapeutic benefits of splenic nerve neuromodulation in MI and the underlying mechanism.

METHODS

Splenic nerve neuromodulation was performed through electrical splenic nerve stimulation (SpNS). In the acute myocardial IRI model, post-mortem analyses encompassed RNA sequencing and a range of molecular biology techniques, with the application of CCR2 antagonists (RS-504393) to inhibit the CCR2. In the chronic MI model, rats underwent echocardiographic assessment four weeks post-MI, after which tissues were harvested.

RESULTS

In the acute IRI model, the negative regulation of chemokines production pathway was enriched by RNA-seq, and SpNS reduced the levels of CCR2, CCL2, and CCL7. The administration of RS-504393 decreased cardiomyocyte apoptosis, reduced myocardial damage, and lowered proinflammatory cytokines levels following myocardial IRI. Additionally, SpNS was shown to inhibit oxidative stress, proinflammatory cytokine levels, and cardiac collagen deposition, as observed four weeks post-MI. SpNS also restrained sympathetic nerve remodeling and improved left ventricular function, in part by downregulating CCR2 in the chronic MI model.

CONCLUSIONS

SpNS demonstrated significant improvements in cardiac function, reductions of cardiac remodeling and inhibitions of excessive sympathetic activation in the chronic MI model by downregulation of CCR2. Our study provides novel evidence that splenic nerve neuromodulation may serve as a potential therapeutic intervention in MI patients.

The spleen in ischaemic heart disease

Ischaemic heart disease is a consequence of coronary atherosclerosis, and atherosclerosis is a systemic inflammatory disease. The spleen releases various immune cells in temporally distinct patterns. Neutrophils, monocytes, macrophages, B cells and T cells execute innate and adaptive immune processes in the coronary atherosclerotic plaque and in the ischaemic myocardium. Prolonged inflammation contributes to ischaemic heart failure. The spleen is also a target of neuromodulation through vagal, sympathetic and sensory nerve activation. Efferent vagal activation and subsequent activation of the noradrenergic splenic nerve activate β2-adrenergic receptors on splenic T cells, which release acetylcholine that ultimately results in attenuation of cytokine secretion from splenic macrophages. Coeliac vagal nerve activation increases splenic sympathetic nerve activity and drives the release of T cells, a process that depends on placental growth factor. Activation of the vagosplenic axis protects acutely from ischaemia-reperfusion injury during auricular tragus vagal stimulation and remote ischaemic conditioning. Splenectomy abrogates all these deleterious and beneficial actions on the cardiovascular system. The aggregate effect of splenectomy in humans is a long-term increase in mortality from ischaemic heart disease. The spleen has been appreciated as an important immune organ for inflammatory processes in atherosclerosis, myocardial infarction and heart failure, whereas its complex interaction with circulating blood factors and with the autonomic and somatic nervous systems, as well as its role in cardioprotection, have emerged only in the past decade. In this Review, we describe this newly identified cardioprotective function of the spleen and highlight the potential for translating the findings to patients with ischaemic heart disease.

Germline deletion of Rgs2 and/or Rgs5 in male mice does not exacerbate left ventricular remodeling induced by subchronic isoproterenol infusion

Sympathoexcitation is a hallmark of heart failure, with sustained β-adrenergic receptor (βAR)-G protein signaling activation. βAR signaling is modulated by regulator of G protein signaling (RGS) proteins. Previously, we reported that Gαi/o regulation by RGS2 or RGS5 is key to ventricular rhythm regulation, while the dual loss of both RGS proteins results in left ventricular (LV) dilatation and dysfunction. Here, we tested whether sustained βAR stimulation with isoproterenol (ISO, 30 mg/kg/day, 3 days) exacerbates LV remodeling in male mice with germline deletion of Rgs2 and/or Rgs5. Rgs2 KO and Rgs2/5 dbKO mice showed LV dilatation at baseline, which was unchanged by ISO. Rgs2 or Rgs5 deletion decreased Rgs1 expression, whereas Rgs5 deletion increased Rgs4 expression. ISO induced cardiac hypertrophy and interstitial fibrosis in Rgs2/5 dbKO mice without increasing cardiomyocyte size or LV dilation but increased expression of cardiac fetal gene Nppa, α-actinin, and Ca2+-/calmodulin-dependent kinase II. Single Rgs2 and Rgs5 KO mice had markedly increased CD45+ cells, whereas tissue from Rgs5 KO mice showed increased CD68+ cells, as revealed by immunohistochemistry. The results together indicate that ventricular remodeling due to Rgs2 and/or Rgs5 deletion is associated with augmented myocardial immune cell presence but is not exacerbated by sustained βAR stimulation.

Adrenergic orchestration of immune cell dynamics in response to cardiac stress

Immune cells contribute approximately 5-10 % of the heart's total cell population, including several myeloid cell and lymphocyte cell subsets, which, despite their relatively small percentages, play important roles in cardiac homeostasis and remodeling responses to various forms of injury and long-term stress. Pathological cardiac stress activates the sympathetic nervous system (SNS), resulting in the release of the catecholamines epinephrine and norepinephrine either systemically or from sympathetic nerve terminals within various lymphoid organs. Acting at α- or β-adrenergic receptors (αAR, βAR), catecholamines regulate immune cell hematopoiesis, egress and migration in response to stress. Classically, αAR stimulation tends to promote inflammatory responses while βAR stimulation has typically been shown to be immunosuppressive, though the effects can be nuanced depending on the immune cells subtype, the site of regulation and pathophysiological context. Herein, we will discuss several facets of SNS-mediated regulation of immune cells and their response to cardiac stress, including: catecholamine response to cardiovascular stress and action at their receptors, adrenergic regulation of hematopoiesis, immune cell retention and release from the bone marrow, adrenergic regulation of splenic immune cells and their retention, as well as adrenergic regulation of immune cell recruitment to the injured heart, including neutrophils, monocytes and macrophages. A particular focus will be given to βAR-mediated effects on myeloid cells in response to acute or chronic cardiac stress.

Neuro- and immuno-modulation mediated by the cardiac sympathetic nerve: a novel insight into the anti-ischemic efficacy of acupuncture

Communication between sympathetic nerves and the immune system is a crucial and active process during myocardial ischemia (MI), as myocardial damage and inflammatory stimuli concurrently occur. Sympathetic nerves undergo structural and functional changes after MI, leading to adverse left ventricular (LV) remodeling and heart failure (HF). The complex inflammatory response to MI, including local myocardial anti-inflammatory repair and systemic immune reactions, plays a key role in adverse LV remodeling. Here, we review the progressive structural and electrophysiological remodeling of the LV and the involvement of sympathetic tone in complex and dynamic processes that are susceptible to MI pathological conditions. Acupuncture has been reported to effectively improve cardiac function, eliminate arrhythmia, and mitigate adverse LV remodeling via somatosensory regulation after MI. Moreover, acupuncture has an anti-inflammatory effect on the pathological process of myocardial ischemia. In this Review, we aim to summarize the involvement of sympathetic nerve activation in the neuro-immune modulation of structural and functional cardiac changes after MI. As a noninvasive method for sympathetic regulation, acupuncture is an ideal option because of its anti-ischemic efficacy. A better understanding of the neural circuitry that regulates cardiac function and immune responses following MI could reveal novel targets for acupuncture treatment.

The role of β-adrenergic receptors in the regulation of cardiac tolerance to ischemia/reperfusion. Why do β-adrenergic receptor agonists and antagonists protect the heart?

BACKGROUND

Catecholamines and β-adrenergic receptors (β-ARs) play an important role in the regulation of cardiac tolerance to the impact of ischemia and reperfusion. This systematic review analyzed the molecular mechanisms of the cardioprotective activity of β-AR ligands.

METHODS

We performed an electronic search of topical articles using PubMed databases from 1966 to 2023. We cited original in vitro and in vivo studies and review articles that documented the cardioprotective properties of β-AR agonists and antagonists.

RESULTS

The infarct-reducing effect of β-AR antagonists did not depend on a decrease in the heart rate. The target for β-blockers is not only cardiomyocytes but also neutrophils. β1-blockers (metoprolol, propranolol, timolol) and the selective β2-AR agonist arformoterol have an infarct-reducing effect in coronary artery occlusion (CAO) in animals. Antagonists of β1- and β2-АR (metoprolol, propranolol, nadolol, carvedilol, bisoprolol, esmolol) are able to prevent reperfusion cardiac injury. All β-AR ligands that reduced infarct size are the selective or nonselective β1-blockers. It was hypothesized that β1-AR blocking promotes an increase in cardiac tolerance to I/R. The activation of β1-AR, β2-AR, and β3-AR can increase cardiac tolerance to I/R. The cardioprotective effect of β-AR agonists is mediated via the activation of kinases and reactive oxygen species production.

CONCLUSIONS

It is unclear why β-blockers with the similar receptor selectivity have the infarct-sparing effect while other β-blockers with the same selectivity do not affect infarct size. What is the molecular mechanism of the infarct-reducing effect of β-blockers in reperfusion? Why did in early studies β-blockers decrease the mortality rate in patients with acute myocardial infarction (AMI) and without reperfusion and in more recent studies β-blockers had no effect on the mortality rate in patients with AMI and reperfusion? The creation of more effective β-AR ligands depends on the answers to these questions.

Cardiac sympathetic overdrive, M2 macrophage activation and fibroblast heterogeneity are associated with cardiac remodeling in a chronic pressure overload rat model of HFpEF

Heart failure with preserved ejection fraction (HFpEF) is a multifaceted pathogenesis disease and the exact mechanisms driving HFpEF have not been completely elucidated. Pressure overload hypertrophy (POH) related fibroblasts and M2 macrophages in HFpEF myocardium have been recently identified and are now of great interest. Sympathetic overdrive has also been implicated in HFpEF. This study is designed to dynamically observe the potential roles of aforementioned mechanisms in pathological remodeling and cardiac dysfunction in chronic PO rats. Surgical constriction of the abdominal aorta was used for induction of HFpEF. Echocardiography, electrocardiogram, hemodynamic measurement, hematoxylin and eosin staining, Masson staining, immunohistochemistry and immunofluorescence were performed to assess the changes in heart dysfunction, cardiac remodeling and driving mechanisms at different time points (2, 18, 24 weeks). The PO induced HFpEF model was well established, which was confirmed by the persistent increase in carotid artery systolic and diastolic blood pressure, and left ventricle hypertrophy at the corresponding postoperative stage. Meanwhile, PO hypertrophy gradually developed into HFpEF, associated with QT and QTc intervals prolongation, normal systolic (EF was maintained at >50%) but impaired diastolic function (increasing LVEDP and LV -dP/dtmin, abnormal E/A ratio), increased myocytes size, and observed relatively slight inflammatory infiltration but robust reactive fibrosis. IHC staining further confirmed that macrophages (CD68) but not neutrophils (MPO) or T cells (CD3) accounted for a predominant proportion of infiltrating cells. Mechanistically, we found that the infiltrating macrophages in the heart expressed high levels of CD206 which was simultaneously adjacent to POH fibroblasts appeared to overexpression of α-SMA in PO rats at late stages. Interestingly, we distinguished two different POHF sub-populations during PO induced HFpEF development, according to non overlapping signals of α-SMA and PDGFRα/β proteins. Additionally, PO led to a pronounced exaggeration in sympathetic fibers at all time points. These findings suggest that the establishing model here begins with cardiac sympathetic overdrive, subsequently along with immune cells especially M2 macrophage accumulation and fibroblast heterogeneity at later stages is associated with the development of cardiac maladaptive remodeling and diastolic dysfunction thus further progression to HFpEF.

Immunomodulation and immunopharmacology in heart failure

The immune system is intimately involved in the pathophysiology of heart failure. However, it is currently underused as a therapeutic target in the clinical setting. Moreover, the development of novel immunomodulatory therapies and their investigation for the treatment of patients with heart failure are hampered by the fact that currently used, evidence-based treatments for heart failure exert multiple immunomodulatory effects. In this Review, we discuss current knowledge on how evidence-based treatments for heart failure affect the immune system in addition to their primary mechanism of action, both to inform practising physicians about these pleiotropic actions and to create a framework for the development and application of future immunomodulatory therapies. We also delineate which subpopulations of patients with heart failure might benefit from immunomodulatory treatments. Furthermore, we summarize completed and ongoing clinical trials that assess immunomodulatory treatments in heart failure and present several therapeutic targets that could be investigated in the future. Lastly, we provide future directions to leverage the immunomodulatory potential of existing treatments and to foster the investigation of novel immunomodulatory therapeutics.

Continuous short-term acclimation to moderate cold elicits cardioprotection in rats, and alters β-adrenergic signaling and immune status

Moderate cold acclimation (MCA) is a non-invasive intervention mitigating effects of various pathological conditions including myocardial infarction. We aim to determine the shortest cardioprotective regimen of MCA and the response of β1/2/3-adrenoceptors (β-AR), its downstream signaling, and inflammatory status, which play a role in cell-survival during myocardial infarction. Adult male Wistar rats were acclimated (9 °C, 1-3-10 days). Infarct size, echocardiography, western blotting, ELISA, mitochondrial respirometry, receptor binding assay, and quantitative immunofluorescence microscopy were carried out on left ventricular myocardium and brown adipose tissue (BAT). MultiPlex analysis of cytokines and chemokines in serum was accomplished. We found that short-term MCA reduced myocardial infarction, improved resistance of mitochondria to Ca2+-overload, and downregulated β1-ARs. The β2-ARs/protein kinase B/Akt were attenuated while β3-ARs translocated on the T-tubular system suggesting its activation. Protein kinase G (PKG) translocated to sarcoplasmic reticulum and phosphorylation of AMPKThr172 increased after 10 days. Principal component analysis revealed a significant shift in cytokine/chemokine serum levels on day 10 of acclimation, which corresponds to maturation of BAT. In conclusion, short-term MCA increases heart resilience to ischemia without any negative side effects such as hypertension or hypertrophy. Cold-elicited cardioprotection is accompanied by β1/2-AR desensitization, activation of the β3-AR/PKG/AMPK pathways, and an immunomodulatory effect.

Traumatic brain injury stimulates sympathetic tone-mediated bone marrow myelopoiesis to favor fracture healing

Traumatic brain injury (TBI) accelerates fracture healing, but the underlying mechanism remains largely unknown. Accumulating evidence indicates that the central nervous system (CNS) plays a pivotal role in regulating immune system and skeletal homeostasis. However, the impact of CNS injury on hematopoiesis commitment was overlooked. Here, we found that the dramatically elevated sympathetic tone accompanied with TBI-accelerated fracture healing; chemical sympathectomy blocks TBI-induced fracture healing. TBI-induced hypersensitivity of adrenergic signaling promotes the proliferation of bone marrow hematopoietic stem cells (HSCs) and swiftly skews HSCs toward anti-inflammation myeloid cells within 14 days, which favor fracture healing. Knockout of β3- or β2-adrenergic receptor (AR) eliminate TBI-mediated anti-inflammation macrophage expansion and TBI-accelerated fracture healing. RNA sequencing of bone marrow cells revealed that Adrb2 and Adrb3 maintain proliferation and commitment of immune cells. Importantly, flow cytometry confirmed that deletion of β2-AR inhibits M2 polarization of macrophages at 7th day and 14th day; and TBI-induced HSCs proliferation was impaired in β3-AR knockout mice. Moreover, β3- and β2-AR agonists synergistically promote infiltration of M2 macrophages in callus and accelerate bone healing process. Thus, we conclude that TBI accelerates bone formation during early stage of fracture healing process by shaping the anti-inflammation environment in the bone marrow. These results implicate that the adrenergic signals could serve as potential targets for fracture management.

Subthreshold splenic nerve stimulation prevents myocardial Ischemia-Reperfusion injury via neuroimmunomodulation of proinflammatory factor levels

OBJECTIVES

Clinical outcomes following myocardial ischemia-reperfusion (I/R) injury are strongly related to the intensity and duration of inflammation. The splenic nerve (SpN) is indispensable for the anti-inflammatory reflex. This study aimed to investigate whether splenic nerve stimulation (SpNS) plays a cardioprotective role in myocardial I/R injury and the potential underlying mechanism.

METHODS

Sprague-Dawley rats were randomly divided into four groups: sham group, I/R group, SpNS group, and I/R plus SpNS group. The highest SpNS intensity that did not influence heart rate was identified, and SpNS at this intensity was used as the subthreshold stimulus. Continuous subthreshold SpNS was applied for 1 h before ligation of the left coronary artery for 45 min. After 72 h of reperfusion, samples were collected for analysis.

RESULTS

SpN activity and splenic concentrations of cholinergic anti-inflammatory pathway (CAP)-related neurotransmitters were significantly increased by SpNS. The infarct size, oxidative stress, sympathetic tone, and the levels of proinflammatory cytokines, including TNF-α, IL-1β, and IL-6, were significantly reduced in rats subjected to subthreshold SpNS after myocardial I/R injury compared with those subjected to I/R injury alone.

CONCLUSIONS

Subthreshold SpNS ameliorates myocardial damage, the inflammatory response, and cardiac remodelling induced by myocardial I/R injury via neuroimmunomodulation of proinflammatory factor levels. SpNS is a potential therapeutic strategy for the treatment of myocardial I/R injury.

Quo Vadis? Immunodynamics of Myeloid Cells after Myocardial Infarction

Myocardial infarction (MI), a major contributor to worldwide morbidity and mortality, is caused by a lack of blood flow to the heart. Affected heart tissue becomes ischemic due to deficiency of blood perfusion and oxygen delivery. In case sufficient blood flow cannot be timely restored, cardiac injury with necrosis occurs. The ischemic/necrotic area induces a systemic inflammatory response and hundreds of thousands of leukocytes are recruited from the blood to the injured heart. The blood pool of leukocytes is rapidly depleted and urgent re-supply of these cells is needed. Myeloid cells are generated in the bone marrow (BM) and spleen, released into the blood, travel to sites of need, extravasate and accumulate inside tissues to accomplish various functions. In this review we focus on the "leukocyte supply chain" and will separately evaluate different myeloid cell compartments (BM, spleen, blood, heart) in steady state and after MI. Moreover, we highlight the local and systemic kinetics of extracellular factors, chemokines and danger signals involved in the regulation of production/generation, release, transportation, uptake, and activation of myeloid cells during the inflammatory phase of MI.

Modified DNA vaccine confers improved humoral immune response and effective virus protection against SARS-CoV-2 delta variant

Coronavirus disease 2019 (COVID-19), caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has led to a global pandemic. New technologies have been utilized to develop several types of vaccines to prevent the spread of SARS-CoV-2 infection, including mRNA vaccines. Our group previously developed an effective DNA-based vaccine. However, emerging SARS-CoV-2 variants of concern (VOCs), such as the delta variant, have escaped mutations against vaccine-induced neutralizing antibodies. This suggests that modified vaccines accommodating VOCs need to be developed promptly. Here, we first modified the current DNA vaccine to enhance antigenicity. Compared with the parental DNA vaccine, the modified version (GP∆-DNA vaccine) induced rapid antibody production. Next, we updated the GP∆-DNA vaccine to spike glycoprotein of the delta variant (GP∆-delta DNA vaccine) and compared the efficacy of different injection routes, namely intramuscular injection using a needle and syringe and intradermal injection using a pyro-drive jet injector (PJI). We found that the levels of neutralizing antibodies induced by the intradermal PJI injection were higher than intramuscular injection. Furthermore, the PJI-injected GP∆-delta DNA vaccine effectively protected human angiotensin-converting enzyme 2 (hACE2) knock-in mice from delta-variant infection. These results indicate that the improved DNA vaccine was effective against emerging VOCs and was a potential DNA vaccine platform for future VOCs or global pandemics.

Pepducin-mediated G Protein-Coupled Receptor Signaling in the Cardiovascular System

ABSTRACT

Pepducins are small-lipidated peptides designed from the intracellular loops of G protein-coupled receptors (GPCRs) that act in an allosteric manner to modulate the activity of GPCRs. Over the past 2 decades, pepducins have progressed initially from pharmacologic tools used to manipulate GPCR activity in an orthosteric site-independent manner to compounds with therapeutic potential that have even been used safely in phase 1 and 2 clinical trials in human subjects. The effect of pepducins at their cognate receptors has been shown to vary between antagonist, partial agonist, and biased agonist outcomes in various primary and clonal cell systems, with even small changes in amino acid sequence altering these properties and their receptor selectivity. To date, pepducins designed from numerous GPCRs have been studied for their impact on pathologic conditions, including cardiovascular diseases such as thrombosis, myocardial infarction, and atherosclerosis. This review will focus in particular on pepducins designed from protease-activated receptors, C-X-C motif chemokine receptors, formyl peptide receptors, and the β2-adrenergic receptor. We will discuss the historic context of pepducin development for each receptor, as well as the structural, signaling, pathophysiologic consequences, and therapeutic potential for each pepducin class.

Immune remodeling and atrial fibrillation

Atrial fibrillation (AF) is a highly prevalent arrhythmia that causes high morbidity and mortality. However, the underlying mechanism of AF has not been fully elucidated. Recent research has suggested that, during AF, the immune system changes considerably and interacts with the environment and cells involved in the initiation and maintenance of AF. This may provide a new direction for research and therapeutic strategies for AF. In this review, we elaborate the concept of immune remodeling based on available data in AF. Then, we highlight the complex relationships between immune remodeling and atrial electrical, structural and neural remodeling while also pointing out some research gaps in these field. Finally, we discuss several potential immunomodulatory treatments for AF. Although the heterogeneity of existing evidence makes it ambiguous to extrapolate immunomodulatory treatments for AF into the clinical practice, immune remodeling is still an evolving concept in AF pathophysiology and further studies within this field are likely to provide effective therapies for AF.

β2-Adrenoceptor Deficiency Results in Increased Calcified Cartilage Thickness and Subchondral Bone Remodeling in Murine Experimental Osteoarthritis

Purpose

Recent studies demonstrated a contribution of adrenoceptors (ARs) to osteoarthritis (OA) pathogenesis. Several AR subtypes are expressed in joint tissues and the β2-AR subtype seems to play a major role during OA progression. However, the importance of β2-AR has not yet been investigated in knee OA. Therefore, we examined the development of knee OA in β2-AR-deficient (Adrb2^-/-) mice after surgical OA induction.

Methods

OA was induced by destabilization of the medial meniscus (DMM) in male wildtype (WT) and Adrb2^-/- mice. Cartilage degeneration and synovial inflammation were evaluated by histological scoring. Subchondral bone remodeling was analyzed using micro-CT. Osteoblast (alkaline phosphatase - ALP) and osteoclast (cathepsin K - CatK) activity were analyzed by immunostainings. To evaluate β2-AR deficiency-associated effects, body weight, sympathetic tone (splenic norepinephrine (NE) via HPLC) and serum leptin levels (ELISA) were determined. Expression of the second major AR, the α2-AR, was analyzed in joint tissues by immunostaining.

Results

WT and Adrb2^-/- DMM mice developed comparable changes in cartilage degeneration and synovial inflammation. Adrb2^-/- DMM mice displayed elevated calcified cartilage and subchondral bone plate thickness as well as increased epiphyseal BV/TV compared to WTs, while there were no significant differences in Sham animals. In the subchondral bone of Adrb2^-/- mice, osteoblasts activity increased and osteoclast activity deceased. Adrb2^-/- mice had significantly higher body weight and fat mass compared to WT mice. Serum leptin levels increased in Adrb2^-/- DMM compared to WT DMM without any difference between the respective Shams. There was no difference in the development of meniscal ossicles and osteophytes or in the subarticular trabecular microstructure between Adrb2^-/- and WT DMM as well as Adrb2^-/- and WT Sham mice. Number of α2-AR-positive cells was lower in Adrb2^-/- than in WT mice in all analyzed tissues and decreased in both Adrb2^-/- and WT over time.

Conclusion

We propose that the increased bone mass in Adrb2^-/- DMM mice was not only due to β2-AR deficiency but to a synergistic effect of OA and elevated leptin concentrations. Taken together, β2-AR plays a major role in OA-related subchondral bone remodeling and is thus an attractive target for the exploration of novel therapeutic avenues.

Cardiac Resident Macrophages Prevent Fibrosis and Stimulate Angiogenesis

Supplemental Digital Content is available in the text.

The initial hypertrophy response to cardiac pressure overload is considered compensatory, but with sustained stress, it eventually leads to heart failure. Recently, a role for recruited macrophages in determining the transition from compensated to decompensated hypertrophy has been established. However, whether cardiac resident immune cells influence the early phase of hypertrophy development has not been established.

Immune cell β2-adrenergic receptors contribute to the development of heart failure

β-Adrenergic receptors (βARs) regulate normal and pathophysiological heart function through their impact on contractility. βARs are also regulators of immune function where they play a unique role depending on the disease condition and immune cell type. Emerging evidence suggests an important role for the β2AR subtype in regulating remodeling in the pathological heart; however, the importance of these responses has never been examined. In heart failure, catecholamines are elevated, leading to chronic βAR activation and contributing to the detrimental effects in the heart. We hypothesized that immune cell β2AR plays a critical role in the development of heart failure in response to chronic catecholamine elevations through their regulation of immune cell infiltration. To test this, chimeric mice were generated by performing bone marrow transplant (BMT) experiments using wild-type (WT) or β2AR knockout (KO) donors. WT and β2ARKO BMT mice were chronically administered the βAR agonist isoproterenol. Immune cell recruitment to the heart was examined by histology and flow cytometry. Numerous changes in immune cell recruitment were observed with isoproterenol administration in WT BMT mice including proinflammatory myeloid populations and lymphocytes with macrophages made up the majority of immune cells in the heart and which were absent in β2ARKO BMT animal. β2ARKO BMT mice had decreased cardiomyocyte death, hypertrophy, and interstitial fibrosis following isoproterenol treatment, culminating in improved function. These findings demonstrate an important role for immune cell β2AR expression in the heart's response to chronically elevated catecholamines.NEW & NOTEWORTHY Immune cell β2-adrenergic receptors (β2ARs) are important for proinflammatory macrophage infiltration to the heart in a chronic isoproterenol administration model of heart failure. Mice lacking immune cell β2AR have decreased immune cell infiltration to their heart, primarily proinflammatory macrophage populations. This decrease culminated to decreased cardiac injury with lessened cardiomyocyte death, decreased interstitial fibrosis and hypertrophy, and improved function demonstrating that β2AR regulation of immune responses plays an important role in the heart's response to persistent βAR stimulation.

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.

Role of β-Adrenergic Receptors and Estrogen in Cardiac Repair after Myocardial Infarction: An Overview

Acute myocardial infarction (MI) is associated with an intense inflammatory response that is critical for cardiac repair but is also involved in the pathogenesis of adverse cardiac remodeling, i.e., the set of size, geometry, and structure changes that represent the structural substrate for the development of post-MI heart failure. Deciphering the pathophysiological mechanisms underlying cardiac repair after MI is, therefore, critical to favorably regulate cardiac wound repair and to prevent development of heart failure. Catecholamines and estrogen play an active role in regulating the inflammatory response in the infarcted area. For example, stress-induced catecholamines alter recruitment and trafficking of leukocytes to the heart. Additionally, estrogen affects rate of cardiac rupture during the acute phase of MI, as well as infarct size and survival in animal models of MI. In this review, we will summarize the role of β-adrenergic receptors and estrogen in cardiac repair after infarction in preclinical studies.

Nerve-macrophage interactions in cardiovascular disease

The heart is highly innervated by autonomic neurons, and dynamic autonomic regulation of the heart and blood vessels is essential for animals to carry out the normal activities of life. Cardiovascular diseases, including heart failure and myocardial infarction, are often characterized in part by an imbalance in autonomic nervous system activation, with excess sympathetic and diminished parasympathetic activation. Notably, however, this is often accompanied by chronic inflammation within the cardiovascular tissues, which suggests there are interactions between autonomic dysregulation and inflammation. Recent studies have been unraveling the mechanistic links between autonomic nerves and immune cells within cardiovascular disease. The autonomic nervous system and immune system also act in concert to coordinate the actions of multiple organs that not only maintain homeostasis but also likely play key roles in disease-disease interactions, such as cardiorenal syndrome and multimorbidity. In this review, we summarize the physiological and pathological interactions between autonomic nerves and macrophages in the context of cardiovascular disease.

Norepinephrine promotes triglyceride storage in macrophages via beta2-adrenergic receptor activation

Tissue‐resident macrophages are required for homeostasis, but also contribute to tissue dysfunction in pathophysiological states. The sympathetic neurotransmitter norepinephrine (NE) induces an anti‐inflammatory and tissue‐reparative phenotype in macrophages. As NE has a well‐established role in promoting triglyceride lipolysis in adipocytes, and macrophages accumulate triglyceride droplets in various physiological and disease states, we investigated the effect of NE on primary mouse bone marrow‐derived macrophage triglyceride metabolism. Surprisingly, our data show that in contrast to the canonical role of NE in stimulating lipolysis, NE acting via beta2‐adrenergic receptors (B2ARs) in macrophages promotes extracellular fatty acid uptake and their storage as triglycerides and reduces free fatty acid release from triglyceride‐laden macrophages. We demonstrate that these responses are mediated by a B2AR activation‐dependent increase in Hilpda and Dgat1 gene expression and activity. We further show that B2AR activation favors the storage of extracellular polyunsaturated fatty acids. Finally, we present evidence that macrophages isolated from hearts after myocardial injury, for which survival critically depends on leukocyte B2ARs, have a transcriptional signature indicative of a transient triglyceride accumulation. Overall, we describe a novel and unexpected role of NE in promoting triglyceride storage in macrophages that could have potential implications in multiple diseases.

Macrophage beta2-adrenergic receptor is dispensable for the adipose tissue inflammation and function

OBJECTIVE

Neuroimmune interactions between the sympathetic nervous system (SNS) and macrophages are required for the homeostasis of multiple tissues, including the adipose tissue. It has been proposed that the SNS maintains adipose tissue macrophages (ATMs) in an anti-inflammatory state via direct norepinephrine (NE) signaling to macrophages. This study aimed to investigate the physiological importance of this paradigm by utilizing a mouse model in which the adrenergic signaling from the SNS to macrophages, but not to other adipose tissue cells, was disrupted.

METHODS

We generated a macrophage-specific B2AR knockout mouse (Adrb2ΔLyz2) by crossing Adrb2fl/fl and Lyz2Cre/+ mice. We have previously shown that macrophages isolated from Adrb2ΔLyz2 animals do not respond to NE stimulation in vitro. Herein we performed a metabolic phenotyping of Adrb2ΔLyz2 mice on either chow or high-fat diet (HFD). We also assessed the adipose tissue function of Adrb2ΔLyz2 animals during fasting and cold exposure. Finally, we transplanted Adrb2ΔLyz2 bone marrow to low-density lipoprotein receptor (LDLR) knockout mice and investigated the development of atherosclerosis during Western diet feeding.

RESULTS

We demonstrated that SNS-associated ATMs have a transcriptional profile indicative of activated beta-2 adrenergic receptor (B2AR), the main adrenergic receptor isoform in myeloid cells. However, Adrb2ΔLyz2 mice have unaltered energy balance on a chow or HFD. Furthermore, Adrb2ΔLyz2 mice show similar levels of adipose tissue inflammation and function during feeding, fasting, or cold exposure, and develop insulin resistance during HFD at the same rate as controls. Finally, macrophage-specific B2AR deletion does not affect the development of atherosclerosis on an LDL receptor-null genetic background.

CONCLUSIONS

Overall, our data suggest that the SNS does not directly modulate the phenotype of adipose tissue macrophages in either lean mice or mouse models of cardiometabolic disease. Instead, sympathetic nerve activity exerts an indirect effect on adipose tissue macrophages through the modulation of adipocyte function.

The gut microbial metabolite phenylacetylglycine protects against cardiac injury caused by ischemia/reperfusion through activating β2AR

BACKGROUND

Myocardial ischemia/reperfusion (I/R) injury is closely related to cardiomyocyte apoptosis. Stimulating β2 adrenergic receptor (β2AR) can effectively combat cardiomyocyte apoptosis. Previous studies demonstrate that the gut microbial metabolite phenylacetylglycine (PAGly) can stimulate β2AR. However, the effect of PAGly on myocardial I/R injury remains unknown.

METHODS

The hypoxia/reoxygenation (H/R) model was established using the neonatal mouse cardiomyocytes (NMCMs). Different doses of PAGly were used to treat NMCMs, and apoptosis was detected by terminal deoxynucleotidyl transferase-mediated nick end labeling (TUNEL) staining. Additionally, the level of cyclic adenosine monophosphate (cAMP) was examined by using a cAMP detection kit. Mouse model of myocardial I/R injury was established in C57BL/6 mice, and different doses of phenylacetic acid were administrated intraperitoneally. Apoptosis of myocardial cells was detected by TUNEL and α-actin staining. The area at risk and the infarct areas were identified by 2,3,5-triphenyltetrazolium chloride (TTC) and Evans blue staining. Western blotting was used to measure the protein expression levels of phosphorylated phosphatidylinositol 3-kinase (p-PI3K), total Akt (t-Akt), phosphorylated Akt (p-AKT), Bcl-2-associated X protein (Bax), B-cell lymphoma-2 (Bcl-2), cleaved caspase-3.

RESULTS

PAGly significantly suppressed H/R injury-induced apoptosis in NMCMs and inhibited apoptosis in myocardial I/R injured mice in vivo. We verified that PAGly activated the anti-apoptotic Gαi/PI3K/AKT signaling cascade in NMCMs via stimulating β2AR signaling. Continuous administration of PAGly at an appropriate dose could inhibit apoptosis and reduce the infarct size resulting from I/R injury in mice. However, high-dose PAGly treatment was associated with a higher mortality rate. Moreover, we demonstrated that Aspirin reduced the infarct size and the high mortality caused by high doses of PAGly in I/R injured mice.

CONCLUSIONS

These findings suggest that treatment with the gut microbial metabolite PAGly could suppress cardiomyocyte apoptosis caused by myocardial I/R injury and reduce the infarct size, which provides a novel therapeutic strategy for patients with myocardial infarction.

Recent Advances in GPCR-Regulated Leukocyte Responses during Acute Cardiac Injury

Following acute cardiac injury such as myocardial infarction (MI), the controlled activation and recruitment of various leukocytes to the site of tissue damage significantly impacts chronic changes to cardiac structure and function, and ultimately host survival. While recent research has focused primarily on how leukocytes respond to injury, understanding how to effectively modulate their responsiveness to dampen maladaptive inflammation and promote repair processes is not yet fully understood. The complex spatio-temporal migration and activation of leukocytes are largely controlled by various chemokines and their cognate receptors, belonging to the G protein-coupled receptor (GPCR) family. Beyond chemokine receptors, leukocytes express a host of additional GPCRs that have recently been shown to regulate their responsiveness to cardiac injury. In this minireview, we will briefly discuss the impact of chemokine receptors on leukocyte behaviour, with subsequent focus on the most recent advancements in understanding the impact and therapeutic potential of other GPCR classes on leukocyte responses after acute cardiac injury.

β2-Adrenergic Receptors Increase Cardiac Fibroblast Proliferation Through the Gαs/ERK1/2-Dependent Secretion of Interleukin-6

Fibroblasts are an important resident cell population in the heart involved in maintaining homeostasis and structure during normal conditions. They are also crucial in disease states for sensing signals and initiating the appropriate repair responses to maintain the structural integrity of the heart. This sentinel role of cardiac fibroblasts occurs, in part, through their ability to secrete cytokines. β-adrenergic receptors (βAR) are also critical regulators of cardiac function in the normal and diseased state and a major therapeutic target clinically. βAR are known to influence cytokine secretion in various cell types and they have been shown to be involved in cytokine production in the heart, but their role in regulating cytokine production in cardiac fibroblasts is not well understood. Thus, we hypothesized that βAR activation on cardiac fibroblasts modulates cytokine production to influence fibroblast function. Using primary fibroblast cultures from neonatal rats and adult mice, increased interleukin (IL)-6 expression and secretion occurred following β2AR activation. The use of pharmacological inhibitors and genetic manipulations showed that IL-6 elevations occurred through the Gαs-mediated activation of ERK1/2 and resulted in increased fibroblast proliferation. In vivo, a lack of β2AR resulted in increased infarct size following myocardial infarction and impaired wound closure in a murine dermal wound healing assay. These findings identify an important role for β2AR in regulating fibroblast proliferation through Gαs/ERK1/2-dependent alterations in IL-6 and may lead to the development of improved heart failure therapies through targeting fibrotic function of β2AR.

Translatome and Transcriptome Profiling of Hypoxic-Induced Rat Cardiomyocytes

Adult cardiac hypoxia as a crucial pathogenesis factor can induce detrimental effects on cardiac injury and dysfunction. The global transcriptome and translatome reflecting the cellular response to hypoxia have not yet been extensively studied in myocardium. In this study, we conducted RNA sequencing (RNA-seq) and ribosome profiling technique (polyribo-seq) in rat heart tissues and H9C2 cells exposed to different periods of hypoxia stress in vivo and in vitro. The temporal gene-expression profiling displayed the distinction of transcriptome and translatome, which were mainly concentrated in cell apoptosis, autophagy, DNA repair, angiogenesis, vascular process, and cardiac cell proliferation and differentiation. A large number of genes such as GNAI3, SEPT4, FANCL, BNIP3, TBX3, ESR2, PTGS2, KLF4, and ADRB2, whose transcript and translation levels are closely correlated, were identified to own a common RNA motif “5′-GAAGCUGCC-3′” in 5′ UTR. NCBP3 was further determined to recognize this RNA motif and facilitate translational process in myocardium under hypoxia stress. Taken together, our data show the close connection between alterations of transcriptome and translatome after hypoxia exposure, emphasizing the significance of translational regulation in related studies. The profiled molecular responses in current study may be valuable resources for advanced understanding of the mechanisms underlying hypoxia-induced effect on heart diseases.

Validation of diagnostic criteria and histopathological characterization of cardiac rupture in the mouse model of nonreperfused myocardial infarction

In patients with myocardial infarction (MI), cardiac rupture is an uncommon but catastrophic complication. In the mouse model of nonreperfused MI, reported rupture rates are highly variable and depend not only on the genetic background and sex of animals but also on the method used for documentation of rupture. In most studies, diagnosis of cardiac rupture is based on visual inspection during autopsy; however, criteria are poorly defined. We performed systematic histopathological analysis of whole hearts from C57BL/6J mice dying after nonreperfused MI and evaluated the reliability of autopsy-based criteria in identification of rupture. Moreover, we compared the cell biological environment of the infarct between rupture-related and rupture-independent deaths. Histopathological analysis documented rupture in 50% of mice dying during the first week post-MI. Identification of a gross rupture site was highly specific but had low sensitivity; in contrast, hemothorax had high sensitivity but low specificity. Mice with rupture had lower myofibroblast infiltration, accentuated macrophage influx, and a trend toward reduced collagen content in the infarct. Male mice had increased mortality and higher incidence of rupture. However, infarct myeloid cells harvested from male and female mice at the peak of the incidence of rupture had comparable inflammatory gene expression. In conclusion, the reliability of autopsy in documentation of rupture in infarcted mice is dependent on the specific criteria used. Macrophage-driven inflammation and reduced activation of collagen-secreting reparative myofibroblasts may be involved in the pathogenesis of post-MI cardiac rupture.NEW & NOTEWORTHY We show that cardiac rupture accounts for 50% of deaths in C57BL/6J mice undergoing nonreperfused myocardial infarction protocols. Overestimation of rupture events in published studies likely reflects the low specificity of hemothorax as a criterion for documentation of rupture. In contrast, identification of a gross rupture site has high specificity and low sensitivity. We also show that mice dying of rupture have increased macrophage influx and attenuated myofibroblast infiltration in the infarct. These findings are consistent with a role for perturbations in the balance between inflammatory and reparative responses in the pathogenesis of postinfarction cardiac rupture. We also report that the male predilection for rupture in infarcted mice is not associated with increased inflammatory activation of myeloid cells.

Leukocyte-Dependent Regulation of Cardiac Fibrosis

Cardiac fibrosis begins as an intrinsic response to injury or ageing that functions to preserve the tissue from further damage. Fibrosis results from activated cardiac myofibroblasts, which secrete extracellular matrix (ECM) proteins in an effort to replace damaged tissue; however, excessive ECM deposition leads to pathological fibrotic remodeling. At this extent, fibrosis gravely disturbs myocardial compliance, and ultimately leads to adverse outcomes like heart failure with heightened mortality. As such, understanding the complexity behind fibrotic remodeling has been a focal point of cardiac research in recent years. Resident cardiac fibroblasts and activated myofibroblasts have been proven integral to the fibrotic response; however, several findings point to additional cell types that may contribute to the development of pathological fibrosis. For one, leukocytes expand in number after injury and exhibit high plasticity, thus their distinct role(s) in cardiac fibrosis is an ongoing and controversial field of study. This review summarizes current findings, focusing on both direct and indirect leukocyte-mediated mechanisms of fibrosis, which may provide novel targeted strategies against fibrotic remodeling.

Immune cells as targets for cardioprotection: new players and novel therapeutic opportunities

New therapies are required to reduce myocardial infarct (MI) size and prevent the onset of heart failure in patients presenting with acute myocardial infarction (AMI), one of the leading causes of death and disability globally. In this regard, the immune cell response to AMI, which comprises an initial pro-inflammatory reaction followed by an anti-inflammatory phase, contributes to final MI size and post-AMI remodelling [changes in left ventricular (LV) size and function]. The transition between these two phases is critical in this regard, with a persistent and severe pro-inflammatory reaction leading to adverse LV remodelling and increased propensity for developing heart failure. In this review article, we provide an overview of the immune cells involved in orchestrating the complex and dynamic inflammatory response to AMI-these include neutrophils, monocytes/macrophages, and emerging players such as dendritic cells, lymphocytes, pericardial lymphoid cells, endothelial cells, and cardiac fibroblasts. We discuss potential reasons for past failures of anti-inflammatory cardioprotective therapies, and highlight new treatment targets for modulating the immune cell response to AMI, as a potential therapeutic strategy to improve clinical outcomes in AMI patients. This article is part of a Cardiovascular Research Spotlight Issue entitled 'Cardioprotection Beyond the Cardiomyocyte', and emerged as part of the discussions of the European Union (EU)-CARDIOPROTECTION Cooperation in Science and Technology (COST) Action, CA16225.

PKA/β2-AR-Gs/Gi signaling pathway is associated with anti-inflammatory and pro-apoptotic effects of Fuzi and Banxia combination on rats subjected to pressure overload

ETHNOPHARMACOLOGICAL RELEVANCE

Either Aconite Lateralis Radix Praeparata (Fuzi) or Pinelliae Rhizoma (Banxia) exerts anti-inflammatory activity and their combination has long been used in China for treating cardiovascular diseases. However, combination of two drugs is controversially prohibited in clinical prescriptions because it serves a representative incompatible pairs in "eighteen antagonisms". Up to date, whether the combination of Fuzi and Banxia could be used for treating heart failure with preserved ejection fraction (HFpEF) especially charactered by systemic inflammation and the potential mechanisms have not been elucidated.

AIM OF THE STUDY

The pros and cons of Fuzi in combination with Banxia were evaluated in pressure overload (PO) rat models of HF in vivo.

MATERIALS AND METHODS

Male Sprague Dawley rats were subjected to abdominal aorta constriction or sham-operated procedure. From week 12, rats were administered with low dose Fuzi (5.4 g kg^-1 d^-1), Banxia (5.4 g kg^-1 d^-1), combination (5.4 g kg^-1 d^-1 + 5.4 g kg^-1 d^-1), high dose Fuzi (10.8 g kg^-1 d^-1) or with vehicle (n = 15 per group) orally for additional 6 weeks.

RESULTS

Fuzi alone treatment led to exaggerated cardiac-renal response to PO, and occurred dramatically at high dose as manifested by markedly exacerbated cardiac-renal inflammation and myocardial fibrosis. Further studies revealed that cardiotoxicity of Fuzi may be associated with highly expression levels of β2-AR and PKA. In contrast, coadministration of Fuzi and Banxia restored cardiac function, as indicated by relieving inflammation and fibrosis as well as normalizing electrocardiogram parameters, which were accompanied by PKA down-regulation. More importantly, both high dose Fuzi and combination treatment enhanced induction of apoptosis, which could be partially associated with inhibition of β2-AR-Gi signaling.

CONCLUSION

Thus, combination of Fuzi and Banxia elicited concurrent protective and toxic effects in PO induced HF. The protective effect appeared to predominate and was associated with suppression of PKA/β2-AR-Gs signaling pathway. Unlike the eighteen antagonisms theory where Fuzi and Banxia combination was considered incompatible, in the present study, this herb pairs appeared to be benefit, and probably had potential therapeutic prospect in treating HFpEF and diseases associated with inflammation.

Prior β-blocker treatment decreases leukocyte responsiveness to injury

Following injury, leukocytes are released from hematopoietic organs and migrate to the site of damage to regulate tissue inflammation and repair, however leukocytes lacking β2-adrenergic receptor (β2AR) expression have marked impairments in these processes. β-blockade is a common strategy for the treatment of many cardiovascular etiologies, therefore the objective of our study was to assess the impact of prior β-blocker treatment on baseline leukocyte parameters and their responsiveness to acute injury. In a temporal and βAR isoform-dependent manner, chronic β-blocker infusion increased splenic vascular cell adhesion molecule-1 (VCAM-1) expression and leukocyte accumulation (monocytes/macrophages, mast cells and neutrophils) and decreased chemokine receptor 2 (CCR2) expression, migration of bone marrow cells (BMC) and peripheral blood leukocytes (PBL), as well as infiltration into the heart following acute cardiac injury. Further, CCR2 expression and migratory responsiveness was significantly reduced in the PBL of patients receiving β-blocker therapy compared to β-blocker-naïve patients. These results highlight the ability of chronic β-blocker treatment to alter baseline leukocyte characteristics that decrease their responsiveness to acute injury and suggest that prior β-blockade may act to reduce the severity of innate immune responses.

Prolonged elevated levels of c-kit+ progenitor cells after a myocardial infarction by beta 2 adrenergic receptor priming

Endogenous progenitor cells may participate in cardiac repair after a myocardial infarction (MI). The beta 2 adrenergic receptor (ß2-AR) pathway induces proliferation of c-kit+ cardiac progenitor cells (CPC) in vitro. We investigated if ß2-AR pharmacological stimulation could ameliorate endogenous CPC-mediated regeneration after a MI. C-kit+ CPC ß1-AR and ß2-AR expression was evaluated in vivo and in vitro. A significant increase in the percentage of CPCs expressing ß1-AR and ß2-AR was measured 7 days post-MI. Accordingly, 24 hrs of low serum and hypoxia in vitro significantly increased CPC ß2-AR expression. Cell viability and differentiation assays validated a functional role of CPC ß2-AR. The effect of pharmacological activation of ß2-AR was studied in C57 mice using fenoterol administered in the drinking water 1 week before MI or sham surgery or at the time of the surgery. MI induced a significant increase in the percentage of c-kit+ progenitor cells at 7 days, whereas pretreatment with fenoterol prolonged this response resulting in a significant elevated number of CPC up to 21 days post-MI. This increased number of CPC correlated with a decrease in infarct size. The immunofluorescence analysis of the heart tissue for proliferation, apoptosis, macrophage infiltration, cardiomyocytes surface area, and vessel density showed significant changes on the basis of surgery but no benefit due to fenoterol treatment. Cardiac function was not ameliorated by fenoterol administration when evaluated by echocardiography. Our results suggest that ß2-AR stimulation may improve the cardiac repair process by supporting an endogenous progenitor cell response but is not sufficient to improve the cardiac function.

Alpha2B-Adrenergic Receptor Regulates Neutrophil Recruitment in MSU-Induced Peritoneal Inflammation

Gout is one of the most common metabolic disorders in human. Previous studies have shown that the disease activity is closely associated with sympathetic nervous system (SNS). α2B-adrenergic receptor (α2BAR), a subtype of α2 adrenergic receptor, plays a critical role in many diseases. However, the role of α2BAR in the pathogenesis of gout remains unclear. Here, we assessed the role of α2BAR in the monosodium urate (MSU) crystals-induced peritonitis that mimics human gout by using the α2BAR-overexpressing mice (α2BAR-Tg). We found that the number of recruited neutrophils was significantly increased in the α2BAR-Tg mice after MSU treatment, when compared with wild type mice. In contrast, the number of macrophages was not changed. Importantly, there is no difference in the IL-1β levels and caspase-1 activity between wild type and α2BAR-Tg mice in the gout animal model. Notably, the enhanced neutrophil migration in α2BAR-Tg mice was dependent on the α2BAR overexpression in neutrophils, but not resulted from other tissues or cells with α2BAR overexpression. In conclusion, our data provide a direct evidence that α2BAR plays a critical role in neutrophil migration and MSU-induced inflammation.

Inflammation and fibrosis in murine models of heart failure

Heart failure is a consequence of various cardiovascular diseases and associated with poor prognosis. Despite progress in the treatment of heart failure in the past decades, prevalence and hospitalisation rates are still increasing. Heart failure is typically associated with cardiac remodelling. Here, inflammation and fibrosis are thought to play crucial roles. During cardiac inflammation, immune cells invade the cardiac tissue and modulate tissue-damaging responses. Cardiac fibrosis, however, is characterised by an increased amount and a disrupted composition of extracellular matrix proteins. As evidence exists that cardiac inflammation and fibrosis are potentially reversible in experimental and clinical set ups, they are interesting targets for innovative heart failure treatments. In this context, animal models are important as they mimic clinical conditions of heart failure patients. The advantages of mice in this respect are short generation times and genetic modifications. As numerous murine models of heart failure exist, the selection of a proper disease model for a distinct research question is demanding. To facilitate this selection, this review aims to provide an overview about the current understanding of the pathogenesis of cardiac inflammation and fibrosis in six frequently used murine models of heart failure. Hence, it compares the models of myocardial infarction with or without reperfusion, transverse aortic constriction, chronic subjection to angiotensin II or deoxycorticosterone acetate, and coxsackievirus B3-induced viral myocarditis in this context. It furthermore provides information about the clinical relevance and the limitations of each model, and, if applicable, about the recent advancements in their methodological proceedings.

β2-Adrenoceptors and GRK2 as Potential Biomarkers in Patients With Chronic Pulmonary Regurgitation

Pulmonary regurgitation (PR) is a frequent complication after repair of congenital heart disease. Three different GRK isoforms (GRK2, GRK5, and GRK3) and two β-adrenoceptors (β1-AR and β2-AR) are present in peripheral blood mononuclear cells (PBMC) and their expression changes as a consequence of the hemodynamic and neurohumoral alterations that occur in some cardiovascular diseases. Therefore, they could be useful as biomarkers in PR. A prospective study was conducted to describe the expression (TaqMan Gene Expression Assays) of β-ARs and GRKs in PBMC isolated (Ficoll^® gradient) from patients with severe PR before and after pulmonary valve replacement and establish if this expression correlates to clinical status. 23 patients with severe PR were included and compared with 22 healthy volunteers (controls). PR patients before the PVR had a significantly lower expression of β2-AR (513.8 ± 261.2 mRNA copies) vs. controls (812.5 ± 497.2 mRNA copies), so as GRK2 expression (503.4 ± 364.9 copies vs. 858.1 ± 380.3 mRNA copies). The expression of β2-AR and GRK2 significantly decreases in symptomatic and asymptomatic patients, as well as in patients under treatment with beta-blockers and non-treated patients. The expression of β2-AR and GRK2 in PR patients recovers the normal values after pulmonary valve replacement (754,8 ± 77,1 and 897,8 ± 87,4 copies, respectively). Therefore, changes in the expression of β2-AR and GRK2 in PBMC of PR patients, could be considered as potential biomarkers to determine clinical decisions.

Myofibroblast β2 adrenergic signaling amplifies cardiac hypertrophy in mice

Abnormal β-adrenergic signaling plays a central role in human heart failure. In mice, chronic β-adrenergic receptor (βAR) stimulation elicits cardiac hypertrophy. It has been reported that cultured cardiac fibroblasts express βAR; however, the functional in vivo requirement of βAR signaling in cardiac fibroblasts during the development of cardiac hypertrophy remains elusive. β2AR null mice exhibited attenuated hypertrophic responses to chronic βAR stimulation upon continuous infusion of an agonist, isoprenaline (ISO), compared to those in wildtype controls, suggesting that β2AR activation in the heart induces pro-hypertrophic effects in mice. Since β2AR signaling is protective in cardiomyocytes, we focused on β2AR signaling in cardiac myofibroblasts. To determine whether β2AR signaling in myofibroblasts affects cardiac hypertrophy, we generated myofibroblast-specific transgenic mice (TG) with the catalytic subunit of protein kinase A (PKAcα) using Cre-loxP system. Myofibroblast-specific PKAcα overexpression resulted in enhanced heart weight normalized to body weight ratio, associated with an enlargement of cardiomyocytes at 12 weeks of age, indicating that myofibroblast-specific activation of PKA mediates cardiac hypertrophy in mice. Neonatal rat cardiomyocytes stimulated with conditioned media from TG cardiac fibroblasts likewise exhibited significantly more growth than those from controls. Thus, β2AR signaling in myofibroblasts plays a substantial role in ISO-induced cardiac hypertrophy, possibly due to a paracrine effect. β2AR signaling in cardiac myofibroblasts may represent a promising target for development of novel therapies for cardiac hypertrophy.

Control of Leukocyte Trafficking by Stress-Associated Hormones

Leukocyte migration is a crucial process in both homeostatic and inflammatory conditions. The spatiotemporal distribution of immune cells is balanced between processes of cellular mobilization into the bloodstream, their adhesion to vascular beds and trafficking into tissues. Systemic regulation of leukocyte mobility is achieved by different signals including neuronal and hormonal cues, of which the catecholamines and glucocorticoids have been most extensively studied. These hormones are often associated with a stress response, however they regulate immune cell trafficking also in steady state, with effects dependent upon cell type, location, time-of-day, concentration, and duration of signal. Systemic administration of catecholamines, such as the sympathetic neurotransmitters adrenaline and noradrenaline, increases neutrophil numbers in the bloodstream but has different effects on other leukocyte populations. In contrast, local, endogenous sympathetic tone has been shown to be crucial for dynamic daily changes in adhesion molecule expression in the bone marrow and skeletal muscle, acting as a key signal to the endothelium and stromal cells to regulate immune cell trafficking. Conversely, glucocorticoids are often reported as anti-inflammatory, although recent data shows a more complex role, particularly under steady-state conditions. Endogenous changes in circulating glucocorticoid concentration induce redistribution of cells and potentiate inflammatory responses, and in many paradigms glucocorticoid action is strongly influenced by time of day. In this review, we discuss the current knowledge of catecholamine and glucocorticoid regulation of leukocyte migration under homeostatic and stimulated conditions.

Bidirectional Role of β2-Adrenergic Receptor in Autoimmune Diseases

Disorder of the sympathetic nervous system (SNS) is closely related to the pathogenesis of various autoimmune diseases (ADs). Catecholamine triggered beta2-adrenergic receptor (β2-AR) signaling is important in creating a bidirectional response in the progression of ADs due to factors including diverse expression patterns, single nucleotide polymorphisms (SNPs), biased signals, and desensitization of β2-AR, as well as different subtypes of Gα binding to β2-AR. In this review, we summarize the actions of β2-AR signaling in regulating the functions of immunocytes and in the pathogenesis of ADs, and the application of β2-AR agonists or antagonists in treating major types of ADs is also discussed. We suggest that restoring the immune balance via a soft regulation of the expression or activation of β2-AR is one of the promising therapeutic strategies for systematic ADs.

The Role of Leukocytes in Diabetic Cardiomyopathy

Diabetes is predominant risk factor for cardiovascular diseases such as myocardial infarction and heart failure. Recently, leukocytes, particularly neutrophils, macrophages, and lymphocytes, have become targets of investigation for their potential role in a number of chronic inflammatory diseases such as diabetes and heart failure. While leukocytes contribute significantly to the progression of diabetes and heart failure individually, understanding their participation in the pathogenesis of diabetic heart failure is much less understood. The present review summarizes the role of leukocytes in the complex interplay between diabetes and heart failure, which is critical to the discovery of new targeted therapies for diabetic cardiomyopathy.

Neutrophils as effectors of vascular inflammation

Vascular inflammation underlies most forms of cardiovascular disease, which remains a prevalent cause of death among the global population. Advances in the biology of neutrophils, as well as insights into their dynamics in tissues, have revealed that these cells are prominent drivers of vascular inflammation though derailed activation within blood vessels. The development of powerful imaging techniques, as well as identification of cells and molecules that regulate their activation within vessels, including platelets and catecholamines, has been instrumental to better understand the mechanisms through which neutrophils protect or damage the organism. Other advances in our understanding of how these leucocytes exert detrimental functions on neighbouring cells, including the formation of DNA-based extracellular traps, constitute milestones in defining neutrophil-driven inflammation. Here, we review emerging mechanisms that regulate intravascular activation and effector functions of neutrophils, and discuss specific pathologies in which these processes are relevant. We argue that identification of pathways and mechanisms specifically engaged within the vasculature may provide effective therapies to treat this prevalent group of pathologies.

The Role of Norepinephrine and α-Adrenergic Receptors in Acute Stress-Induced Changes in Granulocytes and Monocytes

OBJECTIVE

Acute stress induces redistribution of circulating leucocytes in humans. Although effects on lymphocytes as adaptive immune cells are well understood, the mechanisms underlying stress effects on granulocytes and monocytes as innate immune blood cells are still elusive. We investigated whether the stress hormone norepinephrine (NE) and α-adrenergic receptors (α-ADRs) may play a mediating role.

METHODS

In a stress study, we cross-sectionally tested 44 healthy men for associations between stress-induced NE increases and simultaneous granulocyte and monocyte cell count increases, as measured immediately before and several times after the Trier Social Stress Test. In a subsequent infusion study, 21 healthy men participated in three different experimental trials with sequential infusions of 1- and 15-minute duration with varying substances (saline as placebo, the nonspecific α-ADR blocker phentolamine [2.5 mg/min], and NE [5 μg/min]): trial 1 = saline+saline, trial 2 = saline+NE, trial 3 = phentolamine+NE. Granulocyte and monocyte cell numbers were assessed before, immediately after, 10 minutes, and 30 minutes after infusion procedures.

RESULTS

In the stress study, higher NE related to higher neutrophil stress changes (β = .31, p = .045, R change = .09), but not epinephrine stress changes. In the infusion study, saline+NE induced significant increases in neutrophil (F(3/60) = 43.50, p < .001, η = .69) and monocyte (F(3/60) = 18.56, p < .001, η = .48) numbers compared with saline+saline. With phentolamine+NE, neutrophil (F(3/60) = 14.41, p < .001, η = .42) and monocyte counts (F(2.23/44.6) = 4.32, p = .016, η = .18) remained increased compared with saline+saline but were lower compared with saline+NE (neutrophils: F(3/60) = 19.55, p < .001, η = .494, monocytes: F(3/60) = 2.54, p = .065, η = .11) indicating partial mediation by α-ADRs. Trials did not differ in eosinophil and basophil count reactivity.

CONCLUSIONS

Our findings suggest that NE-induced immediate increases in neutrophil and monocyte numbers resemble psychosocial stress effects and can be reduced by blockade of α-ADRs.

MicroRNA-532 protects the heart in acute myocardial infarction, and represses prss23, a positive regulator of endothelial-to-mesenchymal transition

Aims

Acute myocardial infarction (MI) leads to cardiac remodelling and development of heart failure. Insufficient myocardial capillary density after MI is considered a critical determinant of this process. MicroRNAs (miRs), negative regulators of gene expression, have emerged as important players in MI. We previously showed that miR-532-5p (miR-532) is up-regulated by the β-arrestin-biased β-adrenergic receptor antagonist (β-blocker) carvedilol, which activates protective pathways in the heart independent of G protein-mediated second messenger signalling. Here, we hypothesize that β2-adrenergic receptor/β-arrestin-responsive miR-532 confers cardioprotection against MI.

Methods and results

Using cultured cardiac endothelial cell (CEC) and in vivo approaches, we show that CECs lacking miR-532 exhibit increased transition to a fibroblast-like phenotype via endothelial-to-mesenchymal transition (EndMT), while CECs over-expressing miR-532 display decreased EndMT. We also demonstrate that knockdown of miR-532 in mice causes abnormalities in cardiac structure and function as well as reduces CEC proliferation and cardiac vascularization after MI. Mechanistically, cardioprotection elicited by miR-532 is in part attributed to direct repression of a positive regulator of maladaptive EndMT, prss23 (a protease serine 23) in CECs.

Conclusions

In conclusion, these findings reveal a pivotal role for miR-532-prss23 axis in regulating CEC function after MI, and this novel axis could be suitable for therapeutic intervention in ischemic heart disease.

β-arrestin-biased agonism of β-adrenergic receptor regulates Dicer-mediated microRNA maturation to promote cardioprotective signaling

RATIONALE

MicroRNAs (miRs) are small, non-coding RNAs that function to post-transcriptionally regulate target genes. First transcribed as primary miR transcripts (pri-miRs), they are enzymatically processed by Drosha into premature miRs (pre-miRs) and further cleaved by Dicer into mature miRs. Initially discovered to desensitize β-adrenergic receptor (βAR) signaling, β-arrestins are now well-appreciated to modulate multiple pathways independent of G protein signaling, a concept known as biased signaling. Using the β-arrestin-biased βAR ligand carvedilol, we previously showed that β-arrestin1 (not β-arrestin2)-biased β1AR (not β2AR) cardioprotective signaling stimulates Drosha-mediated processing of six miRs by forming a multi-protein nuclear complex, which includes β-arrestin1, the Drosha microprocessor complex and a single-stranded RNA binding protein hnRNPA1.

OBJECTIVE

Here, we investigate whether β-arrestin-mediated βAR signaling induced by carvedilol could regulate Dicer-mediated miR maturation in the cytoplasm and whether this novel mechanism promotes cardioprotective signaling.

METHODS AND RESULTS

In mouse hearts, carvedilol indeed upregulates three mature miRs, but not their pre-miRs and pri-miRs, in a β-arrestin 1- or 2-dependent manner. Interestingly, carvedilol-mediated activation of miR-466g or miR-532-5p, and miR-674 is dependent on β2ARs and β1ARs, respectively. Mechanistically, β-arrestin 1 or 2 regulates maturation of three newly identified βAR/β-arrestin-responsive miRs (β-miRs) by associating with the Dicer maturation RNase III enzyme on three pre-miRs of β-miRs. Myocardial cell approaches uncover that despite their distinct roles in different cell types, β-miRs act as gatekeepers of cardiac cell functions by repressing deleterious targets.

CONCLUSIONS

Our findings indicate a novel role for βAR-mediated β-arrestin signaling activated by carvedilol in Dicer-mediated miR maturation, which may be linked to its protective mechanisms.

The role of monocytosis and neutrophilia in atherosclerosis

Monocytosis and neutrophilia are frequent events in atherosclerosis. These phenomena arise from the increased proliferation of hematopoietic stem and multipotential progenitor cells (HSPCs) and HSPC mobilization from the bone marrow to other immune organs and circulation. High cholesterol and inflammatory signals promote HSPC proliferation and preferential differentiation to the myeloid precursors (i.e., myelopoiesis) that than give rise to pro-inflammatory immune cells. These cells accumulate in the plaques thereby enhancing vascular inflammation and contributing to further lesion progression. Studies in animal models of atherosclerosis showed that manipulation with HSPC proliferation and differentiation through the activation of LXR-dependent mechanisms and restoration of cholesterol efflux may have a significant therapeutic potential.