Pharmacological inhibition of GRK2 improves cardiac metabolism and function in experimental heart failure

Advances in Metabolic Remodeling and Intervention Strategies in Heart Failure

The heart is the most energy-demanding organ throughout the whole body. Perturbations or failure in energy metabolism contributes to heart failure (HF), which represents the advanced stage of various heart diseases. The poor prognosis and huge economic burden associated with HF underscore the high unmet need to explore novel therapies targeting metabolic modulators beyond conventional approaches focused on neurohormonal and hemodynamic regulators. Emerging evidence suggests that alterations in metabolic substrate reliance, metabolic pathways, metabolic by-products, and energy production collectively regulate the occurrence and progression of HF. In this review, we provide an overview of cardiac metabolic remodeling, encompassing the utilization of free fatty acids, glucose metabolism, ketone bodies, and branched-chain amino acids both in the physiological condition and heart failure. Most importantly, the latest advances in pharmacological interventions are discussed as a promising therapeutic approach to restore cardiac function, drawing insights from recent basic research, preclinical and clinical studies.

Acute heart failure: mechanisms and pre-clinical models-a Scientific Statement of the ESC Working Group on Myocardial Function

While chronic heart failure (CHF) treatment has considerably improved patient prognosis and survival, the therapeutic management of acute heart failure (AHF) has remained virtually unchanged in the last decades. This is partly due to the scarcity of pre-clinical models for the pathophysiological assessment and, consequently, the limited knowledge of molecular mechanisms involved in the different AHF phenotypes. This scientific statement outlines the different trajectories from acute to CHF originating from the interaction between aetiology, genetic and environmental factors, and comorbidities. Furthermore, we discuss the potential molecular targets capable of unveiling new therapeutic perspectives to improve the outcome of the acute phase and counteracting the evolution towards CHF.

A Kinase Interacting Protein 1 regulates mitochondrial protein levels in energy metabolism and promotes mitochondrial turnover after exercise

A Kinase Interacting Protein 1 (AKIP1) is a signalling adaptor that promotes mitochondrial respiration and attenuates mitochondrial oxidative stress in cultured cardiomyocytes. We sought to determine whether AKIP1 influences mitochondrial function and the mitochondrial adaptation in response to exercise in vivo. We assessed mitochondrial respiratory capacity, as well as electron microscopy and mitochondrial targeted-proteomics in hearts from mice with cardiomyocyte-specific overexpression of AKIP1 (AKIP1-TG) and their wild type (WT) littermates. These parameters were also assessed after four weeks of voluntary wheel running. In contrast to our previous in vitro study, respiratory capacity measured as state 3 respiration on palmitoyl carnitine was significantly lower in AKIP1-TG compared to WT mice, whereas state 3 respiration on pyruvate remained unaltered. Similar findings were observed for maximal respiration, after addition of FCCP. Mitochondrial DNA damage and oxidative stress markers were not elevated in AKIP1-TG mice and gross mitochondrial morphology was similar. Mitochondrial targeted-proteomics did reveal reductions in mitochondrial proteins involved in energy metabolism. Exercise performance was comparable between genotypes, whereas exercise-induced cardiac hypertrophy was significantly increased in AKIP1-TG mice. After exercise, mitochondrial state 3 respiration on pyruvate substrates was significantly lower in AKIP1-TG compared with WT mice, while respiration on palmitoyl carnitine was not further decreased. This was associated with increased mitochondrial fission on electron microscopy, and the activation of pathways associated with mitochondrial fission and mitophagy. This study suggests that AKIP1 regulates the mitochondrial proteome involved in energy metabolism and promotes mitochondrial turnover after exercise. Future studies are required to unravel the mechanistic underpinnings and whether the mitochondrial changes are required for the AKIP1-induced physiological cardiac growth.

GRK2 participation in cardiac hypertrophy induced by isoproterenol through the regulation of Nrf2 signaling and the promotion of NLRP3 inflammasome and oxidative stress

OBJECTIVE

In cases of heart failure, cardiac hypertrophy may be caused by the upregulation of G-protein-coupled receptor kinase 2 (GRK2). Both NLRP3 inflammasome and oxidative stress contribute to cardiovascular disease. In this study, we clarified the effect of GRK2 on cardiac hypertrophy in H9c2 cells induced by isoproterenol (ISO) and examined the underlying mechanisms.

METHODS

We randomly categorized H9c2 cells into five groups: an ISO group, a paroxetine plus ISO group, a GRK2 small-interfering RNA (siRNA) plus ISO group, a GRK2 siRNA combined with ML385 plus ISO group, and a control group. To determine the effect of GRK2 on cardiac hypertrophy induced by ISO, we carried out CCK8 assays, RT-PCR, TUNEL staining, ELISA assay, DCFH-DA staining, immunofluorescence staining, and western blotting.

RESULTS

By using paroxetine or siRNA to inhibit GRK2, we significantly decreased cell viability; reduced the mRNA levels of ANP, BNP, and β-MHC; and limited the apoptosis rate and protein levels of cleaved caspase-3 and cytochrome c in H9c2 cells treated with ISO. We also found that oxidative stress induced by ISO could be mitigated with paroxetine or GRK2 siRNA. This result was validated by decreased activities of the antioxidant enzymes CAT, GPX, and SOD and increased MDA levels and ROS production. We observed that the protein expression of NLRP3, ASC, and caspase-1 and the intensity of NLRP3 could be inhibited by paroxetine or GRK2 siRNA. Both paroxetine and GRK2 siRNA were able to abolish the increase in GRK2 expression induced by ISO. They also could increase protein levels of HO-1, nuclear Nrf2, and Nrf2 immunofluorescence intensity; however, they could not change the protein level of cytoplasmic Nrf2. By combining treatment with ML385, we were able to reverse GRK2 inhibition on H9c2 cells treated with ISO.

CONCLUSION

According to the results of this study, GRK2 participated in cardiac hypertrophy induced by ISO by mitigating NLRP3 inflammasome and oxidative stress through the signaling of Nrf2 in H9c2 cells.

Heart failure: an update from the last years and a look at the near future

In the last years, major progress occurred in heart failure (HF) management. Quadruple therapy is now mandatory for all the patients with HF with reduced ejection fraction. Whilst verciguat is becoming available across several countries, omecamtiv mecarbil is waiting to be released for clinical use. Concurrent use of potassium-lowering agents may counteract hyperkalaemia and facilitate renin-angiotensin-aldosterone system inhibitor implementations. The results of the EMPagliflozin outcomE tRial in Patients With chrOnic heaRt Failure With Preserved Ejection Fraction (EMPEROR-Preserved) trial were confirmed by the Dapagliflozin in Heart Failure with Mildly Reduced or Preserved Ejection Fraction (DELIVER) trial, and we now have, for the first time, evidence for treatment of also patients with HF with preserved ejection fraction. In a pre-specified meta-analysis of major randomized controlled trials, sodium-glucose co-transporter-2 inhibitors reduced all-cause mortality, cardiovascular (CV) mortality, and HF hospitalization in the patients with HF regardless of left ventricular ejection fraction. Other steps forward have occurred in the treatment of decompensated HF. Acetazolamide in Acute Decompensated Heart Failure with Volume Overload (ADVOR) trial showed that the addition of intravenous acetazolamide to loop diuretics leads to greater decongestion vs. placebo. The addition of hydrochlorothiazide to loop diuretics was evaluated in the CLOROTIC trial. Torasemide did not change outcomes, compared with furosemide, in TRANSFORM-HF. Ferric derisomaltose had an effect on the primary outcome of CV mortality or HF rehospitalizations in IRONMAN (rate ratio 0.82; 95% confidence interval 0.66-1.02; P = 0.070). Further options for the treatment of HF, including device therapies, cardiac contractility modulation, and percutaneous treatment of valvulopathies, are summarized in this article.

Adrenergic Receptor Regulation of Mitochondrial Function in Cardiomyocytes

ABSTRACT

Adrenergic receptors (ARs) are G protein-coupled receptors that are stimulated by catecholamines to induce a wide array of physiological effects across tissue types. Both α1- and β-ARs are found on cardiomyocytes and regulate cardiac contractility and hypertrophy through diverse molecular pathways. Acute activation of cardiomyocyte β-ARs increases heart rate and contractility as an adaptive stress response. However, chronic β-AR stimulation contributes to the pathobiology of heart failure. By contrast, mounting evidence suggests that α1-ARs serve protective functions that may mitigate the deleterious effects of chronic β-AR activation. Here, we will review recent studies demonstrating that α1- and β-ARs differentially regulate mitochondrial biogenesis and dynamics, mitochondrial calcium handling, and oxidative phosphorylation in cardiomyocytes. We will identify potential mechanisms of these actions and focus on the implications of these findings for the modulation of contractile function in the uninjured and failing heart. Collectively, we hope to elucidate important physiological processes through which these well-studied and clinically relevant receptors stimulate and fuel cardiac contraction to contribute to myocardial health and disease.

Role of GRK2 in Trophoblast Necroptosis and Spiral Artery Remodeling: Implications for Preeclampsia Pathogenesis

Impaired invasion of extravillous trophoblasts and severe oxidative stress manifest the poor placentation in preeclampsia, which is life-threatening and more than a hypertensive disease of pregnancy. Previous studies have reported that G protein-coupled receptor kinases (GRKs) play a key role in initiating hypertension and hypertensive renal damage, yet little evidence so far suggests a link between GRKs and preeclampsia-related hypertension. Here, we demonstrate GRK2 expression is significantly downregulated (P < 0.0001) in preeclamptic placentae compared to normotensive controls. Knockdown or inhibition of GRK2 in placentae caused insufficient arterial remodeling and elevated trophoblast necroptosis in vivo. These further induced preeclampsia-like phenotype in mice: hypertension, proteinuria, and elevated pro-angiogenic cytokines. By human extra-villous invasive trophoblast cell line (HTR8/SVneo cells), we revealed the knockdown or inhibition of GRK2 triggered excessive death with typical necroptotic characteristics: nuclear envelope rupture and the activation of RIPK1, RIPK3, and MLKL. Necrostatin-1, an inhibitor of RIPK1, is able to restore the survival of trophoblasts. Together, our findings demonstrated that insufficient GRK2 activity compromises spiral artery remodeling and initiates necrotic events in placentae, thereby leading to preeclampsia. These findings advance our understanding of GRK2 in the pathogenesis of preeclampsia and could shed light on a potential treatment for preeclampsia.

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.

New Targets in Heart Failure Drug Therapy

Despite recent advances in chronic heart failure management (either pharmacological or non-pharmacological), the prognosis of heart failure (HF) patients remains poor. This poor prognosis emphasizes the need for developing novel pathways for testing new HF drugs, beyond neurohumoral and hemodynamic modulation approaches. The development of new drugs for HF therapy must thus necessarily focus on novel approaches such as the direct effect on cardiomyocytes, coronary microcirculation, and myocardial interstitium. This review summarizes principal evidence on new possible pharmacological targets for the treatment of HF patients, mainly focusing on microcirculation, cardiomyocyte, and anti-inflammatory therapy.

Physical Exercise: A Novel Tool to Protect Mitochondrial Health

Mitochondrial dysfunction is a crucial contributor to heart diseases. Alterations in energetic metabolism affect crucial homeostatic processes, such asATP production, the generation of reactive oxygen species, and the release of pro-apoptotic factors, associated with metabolic abnormalities. In response to energetic deficiency, the cardiomyocytes activate the Mitochondrial Quality Control (MQC), a critical process in maintaining mitochondrial health. This process is compromised in cardiovascular diseases depending on the pathology's severity and represents, therefore, a potential therapeutic target. Several potential targeting molecules within this process have been identified in the last years, and therapeutic strategies have been proposed to ameliorate mitochondria monitoring and function. In this context, physical exercise is considered a non-pharmacological strategy to protect mitochondrial health. Physical exercise regulates MQC allowing the repair/elimination of damaged mitochondria and synthesizing new ones, thus recovering the metabolic state. In this review, we will deal with the effect of physical exercise on cardiac mitochondrial function tracing its ability to modulate specific steps in MQC both in physiologic and pathologic conditions.

Paroxetine-Overview of the Molecular Mechanisms of Action

In the 21st century and especially during a pandemic, the diagnosis and treatment of depression is an essential part of the daily practice of many family doctors. It mainly affects patients in the age category 15–44 years, regardless of gender. Anxiety disorders are often diagnosed in children and adolescents. Social phobias can account for up to 13% of these diagnoses. Social anxiety manifests itself in fear of negative social assessment and humiliation, which disrupts the quality of social functioning. Treatment of the above-mentioned disorders is based on psychotherapy and pharmacotherapy. Serious side effects or mortality from antidepressant drug overdose are currently rare. Recent studies indicate that paroxetine (ATC code: N06AB), belonging to the selective serotonin reuptake inhibitors, has promising therapeutic effects and is used off-label in children and adolescents. The purpose of this review is to describe the interaction of paroxetine with several molecular targets in various points of view including the basic chemical and pharmaceutical properties. The central point of the review is focused on the pharmacodynamic analysis based on the molecular mechanism of binding paroxetine to various therapeutic targets.

The Cardiovascular Phenotype in Fabry Disease: New Findings in the Research Field

Fabry disease (FD) is a lysosomal storage disorder, depending on defects in alpha-galactosidase A (GAL) activity. At the clinical level, FD shows a high phenotype variability. Among them, cardiovascular dysfunction is often recurrent or, in some cases, is the sole symptom (cardiac variant) representing the leading cause of death in Fabry patients. The existing therapies, besides specific symptomatic treatments, are mainly based on the restoration of GAL activity. Indeed, mutations of the galactosidase alpha gene (GLA) cause a reduction or lack of GAL activity leading to globotriaosylceramide (Gb3) accumulation in several organs. However, several other mechanisms are involved in FD’s development and progression that could become useful targets for therapeutics. This review discusses FD’s cardiovascular phenotype and the last findings on molecular mechanisms that accelerate cardiac cell damage.

GRK2 deletion improves the function of skin flap following ischemia-reperfusion injury by regulating Drp1

Skin flap ischemia-reperfusion (IR) injury is the key factor to the success rate of skin transplantation, the molecular mechanism of flap IR injury needs to be continuously explored to provide new ideas for its clinical treatment. G protein-coupled receptor kinase 2 (GRK2) was reported to be involved in regulating mitochondrial function, and mitochondria were essential in the process of flap IR. Thus, we aimed to investigate the function of GRK2 in flap ischemia-reperfusion injury and further explore the underlying mechanism. Sixty male C57BL/6 mice were randomly divided into four groups: sham, IR+sh-NC, IR+sh-GRK2 and IR+sh-GRK2+ dynamin-related GTPase 1 (Drp1). Flap function and mitochondrial function were determined after ischemia for 3 hours and reperfusion for 72 hours. Comparing with sham group, GRK2 was increased in flap after IR injury. Loss of GRK2 inhibited cell apoptosis and promoted cell proliferation of flap after IR injury. And deficiency of GRK2 promoted mitochondrial function in flap after IR injury. IR injury up-regulated Drp1 expression in flap, while sh-GRK2 down-regulated Drp1 expression. Furthermore, overexpression of Drp1 removed the protective effect of sh-GRK2. In conclusion, our study revealed that GRK2 deletion improved flap function and mitochondrial function by inhibiting Drp1 expression, which may provide a new insight for the clinical treatment of flap ischemia-reperfusion injury.

The Metabolic Role of GRK2 in Insulin Resistance and Associated Conditions

Insulin resistance (IRES) is a pathophysiological condition characterized by the reduced response to insulin of several tissues, including myocardial and skeletal muscle. IRES is associated with obesity, glucose intolerance, dyslipidemia, and hypertension, evolves toward type 2 diabetes, and increases the risk of developing cardiovascular diseases. Several studies designed to explore the mechanisms involved in IRES allowed the identification of a multitude of potential molecular targets. Among the most promising, G Protein Coupled Receptor Kinase type 2 (GRK2) appears to be a suitable one given its functional implications in many cellular processes. In this review, we will discuss the metabolic role of GRK2 in those conditions that are characterized by insulin resistance (diabetes, hypertension, heart failure), and the potentiality of its inhibition as a therapeutic strategy to revert both insulin resistance and its associated phenotypes.

Exploiting GRK2 Inhibition as a Therapeutic Option in Experimental Cancer Treatment: Role of p53-Induced Mitochondrial Apoptosis

Simple Summary

The involvement of GRK2 in cancer growth and an inverse correlation with p53 levels were suggested in breast cancer. Furthermore, increased GRK2 expression and activity were detected in thyroid cancer, but its effects and mechanisms of action were not investigated yet. This study aimed to explore the role of GRK2 in thyroid cancer both in vitro and in vivo and its crosstalk with p53. We demonstrated that thyroid cancer cells bearing a mutant form of p53 but not p53 null cells rely on GRK2 as a mechanism of proliferation by regulating p53 levels. Indeed, GRK2 indirectly induces p53 degradation through means of its catalytic activity. The pharmacological inhibition of the kinase effectively inhibits cancer growth by inducing p53-dependent mitochondrial pathways of apoptosis. Our results demonstrate a p53-dependent effect of GRK2 in cancer and suggest kinase inhibition as a potential therapeutic strategy for thyroid cancer.

Abstract

The involvement of GRK2 in cancer cell proliferation and its counter-regulation of p53 have been suggested in breast cancer even if the underlying mechanism has not yet been elucidated. Furthermore, the possibility to pharmacologically inhibit GRK2 to delay cancer cell proliferation has never been explored. We investigated this possibility by setting up a study that combined in vitro and in vivo models to underpin the crosstalk between GRK2 and p53. To reach this aim, we took advantage of the different expression of p53 in cell lines of thyroid cancer (BHT 101 expressing p53 and FRO cells, which are p53-null) in which we overexpressed or silenced GRK2. The pharmacological inhibition of GRK2 was achieved using the specific inhibitor KRX-C7. The in vivo study was performed in Balb/c nude mice, where we treated BHT-101 or FRO-derived tumors with KRX-C7. In our in vitro model, FRO cells were unaffected by GRK2 expression levels, whereas BHT-101 cells were sensitive, thus suggesting a role for p53. The regulation of p53 by GRK2 is due to phosphorylative events in Thr-55, which induce the degradation of p53. In BHT-101 cells, the pharmacologic inhibition of GRK2 by KRX-C7 increased p53 levels and activated apoptosis through the mitochondrial release of cytochrome c. These KRX-C7-mediated events were also confirmed in cancer allograft models in nude mice. In conclusion, our data showed that GRK2 counter-regulates p53 expression in cancer cells through a kinase-dependent activity. Our results further corroborate the anti-proliferative role of GRK2 inhibitors in p53-sensitive tumors and propose GRK2 as a therapeutic target in selected cancers.

Role of Endothelial G Protein-Coupled Receptor Kinase 2 in Angioedema

Excessive BK (bradykinin) stimulation is responsible for the exaggerated permeabilization of the endothelium in angioedema. However, the molecular mechanisms underlying these responses have not been investigated. BK receptors are Gq-protein-coupled receptors phosphorylated by GRK2 (G protein-coupled receptor kinase 2) with a hitherto unknown biological and pathophysiological significance. In the present study, we sought to identify the functional role of GRK2 in angioedema through the regulation of BK signaling. We found that the accumulation of cytosolic Ca²⁺ in endothelial cells induced by BK was sensitive to GRK2 activity, as it was significantly augmented by inhibiting the kinase. Accordingly, permeabilization and NO production induced by BK were enhanced, as well. In vivo, mice with reduced GRK2 levels in the endothelium (Tie2-CRE/GRK2^fl+/fl-) exhibited an increased response to BK in terms of vascular permeability and extravasation. Finally, patients with reduced GRK2 levels displayed a severe phenotype of angioedema. Taken together, these findings establish GRK2 as a novel pivotal regulator of BK signaling with an essential role in the pathophysiology of vascular permeability and angioedema.

Pharmacological inhibition of GRK2 improves cardiac metabolism and function in experimental heart failure

Aims

The effects of GRK2 inhibition on myocardial metabolism in heart failure (HF) are unchartered. In this work, we evaluated the impact of pharmacological inhibition of GRK2 by a cyclic peptide, C7, on metabolic, biochemical, and functional phenotypes in experimental HF.

Methods and results

C7 was initially tested on adult mice ventricular myocyte from wild type and GRK2 myocardial deficient mice (GRK2‐cKO), to assess the selectivity on GRK2 inhibition. Then, chronic infusion of 2 mg/kg/day of C7 was performed in HF mice with cryogenic myocardial infarction. Cardiac function in vivo was assessed by echocardiography and cardiac catheterization. Histological, biochemical, and metabolic studies were performed on heart samples at time points. C7 induces a significant increase of contractility in wild type but not in adult ventricle myocytes from GRK2‐cKO mice, thus confirming C7 selectivity for GRK2. In HF mice, 4 weeks of treatment with C7 improved metabolic features, including mitochondrial organization and function, and restored the biochemical and contractile responses.

Conclusions

GRK2 is a critical molecule in the physiological regulation of cardiac metabolism. Its alterations in the failing heart can be pharmacologically targeted, leading to the correction of metabolic and functional abnormalities observed in HF.