Does Cell-Type-Specific Silencing of Monoamine Oxidase B Interfere with the Development of Right Ventricle (RV) Hypertrophy or Right Ventricle Failure in Pulmonary Hypertension?

Increased mitochondrial reactive oxygen species (ROS) formation is important for the development of right ventricular (RV) hypertrophy (RVH) and failure (RVF) during pulmonary hypertension (PH). ROS molecules are produced in different compartments within the cell, with mitochondria known to produce the strongest ROS signal. Among ROS-forming mitochondrial proteins, outer-mitochondrial-membrane-located monoamine oxidases (MAOs, type A or B) are capable of degrading neurotransmitters, thereby producing large amounts of ROS. In mice, MAO-B is the dominant isoform, which is present in almost all cell types within the heart. We analyzed the effect of an inducible cardiomyocyte-specific knockout of MAO-B (cmMAO-B KO) for the development of RVH and RVF in mice. Right ventricular hypertrophy was induced by pulmonary artery banding (PAB). RV dimensions and function were measured through echocardiography. ROS production (dihydroethidium staining), protein kinase activity (PamStation device), and systemic hemodynamics (in vivo catheterization) were assessed. A significant decrease in ROS formation was measured in cmMAO-B KO mice during PAB compared to Cre-negative littermates, which was associated with reduced activity of protein kinases involved in hypertrophic growth. In contrast to littermates in which the RV was dilated and hypertrophied following PAB, RV dimensions were unaffected in response to PAB in cmMAO-B KO mice, and no decline in RV systolic function otherwise seen in littermates during PAB was measured in cmMAO-B KO mice. In conclusion, cmMAO-B KO mice are protected against RV dilatation, hypertrophy, and dysfunction following RV pressure overload compared to littermates. These results support the hypothesis that cmMAO-B is a key player in causing RV hypertrophy and failure during PH.

Comparison of the stage-dependent mitochondrial changes in response to pressure overload between the diseased right and left ventricle in the rat.

The right ventricle (RV) differs developmentally, anatomically and functionally from the left ventricle (LV). Therefore, characteristics of LV adaptation to chronic pressure overload cannot easily be extrapolated to the RV. Mitochondrial abnormalities are considered a crucial contributor in heart failure (HF), but have never been compared directly between RV and LV tissues and cardiomyocytes. To identify ventricle-specific mitochondrial molecular and functional signatures, we established rat models with two slowly developing disease stages (compensated and decompensated) in response to pulmonary artery banding (PAB) or ascending aortic banding (AOB). Genome-wide transcriptomic and proteomic analyses were used to identify differentially expressed mitochondrial genes and proteins and were accompanied by a detailed characterization of mitochondrial function and morphology. Two clearly distinguishable disease stages, which culminated in a comparable systolic impairment of the respective ventricle, were observed. Mitochondrial respiration was similarly impaired at the decompensated stage, while respiratory chain activity or mitochondrial biogenesis were more severely deteriorated in the failing LV. Bioinformatics analyses of the RNA-seq. and proteomic data sets identified specifically deregulated mitochondrial components and pathways. Although the top regulated mitochondrial genes and proteins differed between the RV and LV, the overall changes in tissue and cardiomyocyte gene expression were highly similar. In conclusion, mitochondrial dysfuntion contributes to disease progression in right and left heart failure. Ventricle-specific differences in mitochondrial gene and protein expression are mostly related to the extent of observed changes, suggesting that despite developmental, anatomical and functional differences mitochondrial adaptations to chronic pressure overload are comparable in both ventricles.

Novel drugs approved by the EMA, the FDA, and the MHRA in 2023: A year in review.

In 2023, seventy novel drugs received market authorization for the first time in either Europe (by the EMA and the MHRA) or in the United States (by the FDA). Confirming a steady recent trend, more than half of these drugs target rare diseases or intractable forms of cancer. Thirty drugs are categorized as "first-in-class" (FIC), illustrating the quality of research and innovation that drives new chemical entity discovery and development. We succinctly describe the mechanism of action of most of these FIC drugs and discuss the therapeutic areas covered, as well as the chemical category to which these drugs belong. The 2023 novel drug list also demonstrates an unabated emphasis on polypeptides (recombinant proteins and antibodies), Advanced Therapy Medicinal Products (gene and cell therapies) and RNA therapeutics, including the first-ever approval of a CRISPR-Cas9-based gene-editing cell therapy.

The Role of the Redox Enzyme p66Shc in Biological Aging of the Lung.

The mitochondrial adaptor protein p66Shc has been suggested to control life span in mice via the release of hydrogen peroxide. However, the role of p66Shc in lung aging remains unsolved. Thus, we investigated the effects of p66Shc-/- on the aging of the lung and pulmonary circulation. In vivo lung and cardiac characteristics were investigated in p66Shc-/- and wild type (WT) mice at 3, 12, and 24 months of age by lung function measurements, micro-computed tomography (µCT), and echocardiography. Alveolar number and muscularization of small pulmonary arteries were measured by stereology and vascular morphometry, respectively. Protein and mRNA levels of senescent markers were measured by western blot and PCR, respectively. Lung function declined similarly in WT and p66Shc-/- mice during aging. However, µCT analyses and stereology showed slightly enhanced signs of aging-related parameters in p66Shc-/- mice, such as a decline of alveolar density. Accordingly, p66Shc-/- mice showed higher protein expression of the senescence marker p21 in lung homogenate compared to WT mice of the corresponding age. Pulmonary vascular remodeling was increased during aging, but aged p66Shc-/- mice showed similar muscularization of pulmonary vessels and hemodynamics like WT mice. In the heart, p66Shc-/- prevented the deterioration of right ventricular (RV) function but promoted the decline of left ventricular (LV) function during aging. p66Shc-/- affects the aging process of the lung and the heart differently. While p66Shc-/- slightly accelerates lung aging and deteriorates LV function in aged mice, it seems to exert protective effects on RV function during aging.

Cardiac side effects of RNA-based SARS-CoV-2 vaccines: Hidden cardiotoxic effects of mRNA-1273 and BNT162b2 on ventricular myocyte function and structure.

BACKGROUND AND PURPOSE: To protect against SARS-CoV-2 infection, the first mRNA-based vaccines, Spikevax (mRNA-1273, Moderna) and Comirnaty (BNT162b2, Pfizer/Biontech), were approved in 2020. The structure and assembly of the immunogen-in both cases, the SARS-CoV-2 spike (S) glycoprotein-are determined by a messenger RNA sequence that is translated by endogenous ribosomes. Cardiac side-effects, which for the most part can be classified by their clinical symptoms as myo- and/or pericarditis, can be caused by both mRNA-1273 and BNT162b2. EXPERIMENTAL APPROACH: As persuasive theories for the underlying pathomechanisms have yet to be developed, this study investigated the effect of mRNA-1273 and BNT162b2 on the function, structure, and viability of isolated adult rat cardiomyocytes over a 72 h period. KEY RESULTS: In the first 24 h after application, both mRNA-1273 and BNT162b2 caused neither functional disturbances nor morphological abnormalities. After 48 h, expression of the encoded spike protein was detected in ventricular cardiomyocytes for both mRNAs. At this point in time, mRNA-1273 induced arrhythmic as well as completely irregular contractions associated with irregular as well as localized calcium transients, which provide indications of significant dysfunction of the cardiac ryanodine receptor (RyR2). In contrast, BNT162b2 increased cardiomyocyte contraction via significantly increased protein kinase A (PKA) activity at the cellular level. CONCLUSION AND IMPLICATIONS: Here, we demonstrated for the first time, that in isolated cardiomyocytes, both mRNA-1273 and BNT162b2 induce specific dysfunctions that correlate pathophysiologically to cardiomyopathy. Both RyR2 impairment and sustained PKA activation may significantly increase the risk of acute cardiac events.

Health position paper and redox perspectives - Disease burden by transportation noise.

Transportation noise is a ubiquitous urban exposure. In 2018, the World Health Organization concluded that chronic exposure to road traffic noise is a risk factor for ischemic heart disease. In contrast, they concluded that the quality of evidence for a link to other diseases was very low to moderate. Since then, several studies on the impact of noise on various diseases have been published. Also, studies investigating the mechanistic pathways underlying noise-induced health effects are emerging. We review the current evidence regarding effects of noise on health and the related disease-mechanisms. Several high-quality cohort studies consistently found road traffic noise to be associated with a higher risk of ischemic heart disease, heart failure, diabetes, and all-cause mortality. Furthermore, recent studies have indicated that road traffic and railway noise may increase the risk of diseases not commonly investigated in an environmental noise context, including breast cancer, dementia, and tinnitus. The harmful effects of noise are related to activation of a physiological stress response and nighttime sleep disturbance. Oxidative stress and inflammation downstream of stress hormone signaling and dysregulated circadian rhythms are identified as major disease-relevant pathomechanistic drivers. We discuss the role of reactive oxygen species and present results from antioxidant interventions. Lastly, we provide an overview of oxidative stress markers and adverse redox processes reported for noise-exposed animals and humans. This position paper summarizes all available epidemiological, clinical, and preclinical evidence of transportation noise as an important environmental risk factor for public health and discusses its implications on the population level.

Health position paper and redox perspectives on reactive oxygen species as signals and targets of cardioprotection.

The present review summarizes the beneficial and detrimental roles of reactive oxygen species in myocardial ischemia/reperfusion injury and cardioprotection. In the first part, the continued need for cardioprotection beyond that by rapid reperfusion of acute myocardial infarction is emphasized. Then, pathomechanisms of myocardial ischemia/reperfusion to the myocardium and the coronary circulation and the different modes of cell death in myocardial infarction are characterized. Different mechanical and pharmacological interventions to protect the ischemic/reperfused myocardium in elective percutaneous coronary interventions and coronary artery bypass grafting, in acute myocardial infarction and in cardiotoxicity from cancer therapy are detailed. The second part keeps the focus on ROS providing a comprehensive overview of molecular and cellular mechanisms involved in ischemia/reperfusion injury. Starting from mitochondria as the main sources and targets of ROS in ischemic/reperfused myocardium, a complex network of cellular and extracellular processes is discussed, including relationships with Ca2+ homeostasis, thiol group redox balance, hydrogen sulfide modulation, cross-talk with NAPDH oxidases, exosomes, cytokines and growth factors. While mechanistic insights are needed to improve our current therapeutic approaches, advancements in knowledge of ROS-mediated processes indicate that detrimental facets of oxidative stress are opposed by ROS requirement for physiological and protective reactions. This inevitable contrast is likely to underlie unsuccessful clinical trials and limits the development of novel cardioprotective interventions simply based upon ROS removal.

Teleworking and housing demand.

The COVID-19 pandemic accelerated the trend towards teleworking. Many predicted that this would shift housing demand to the suburbs and homes with the potential for high quality office space. We examine these predictions using a survey of the working age population who live in the private housing sector. The majority in the sector are happy with their current home, but new teleworkers who plan to continue to do so - accounting for one fifth of the population - are characterised by a higher intention to move. Consistent with predictions, these teleworkers value a high quality home office more than others and are prepared to live further away from the centre to find it.

Monoamine Oxidase A Contributes to Serotonin-But Not Norepinephrine-Dependent Damage of Rat Ventricular Myocytes.

Serotonin effects on cardiac hypertrophy, senescence, and failure are dependent either on activation of specific receptors or serotonin uptake and serotonin degradation by monoamine oxidases (MAOs). Receptor-dependent effects are specific for serotonin, but MAO-dependent effects are nonspecific as MAOs also metabolize other substrates such as catecholamines. Our study evaluates the role of MAO-A in serotonin- and norepinephrine-dependent cell damage. Experiments were performed in vivo to study the regulation of MAOA and MAOB expression and in vitro on isolated cultured adult rat ventricular cardiomyocytes (cultured for 24 h) to study the function of MAO-A. MAOA but not MAOB expression increased in maladaptive hypertrophic stages. Serotonin and norepinephrine induced morphologic cell damage (loss of rod-shaped cell structure). However, MAO-A inhibition suppressed serotonin-dependent but not norepinephrine-dependent damages. Serotonin but not norepinephrine caused a reduction in cell shortening in nondamaged cells. Serotonin induced mitochondria-dependent oxidative stress. In vivo, MAOA was induced during aging and hypertension but the expression of the corresponding serotonin uptake receptor (SLC6A4) was reduced and enzymes that reduce either oxidative stress (CAT) or accumulation of 5-hydroxyindolacetaldehyde (ALDH2) were induced. In summary, the data show that MAO-A potentially affects cardiomyocytes' function but that serotonin is not necessarily the native substrate.

Sex Difference in Cardioprotection against Acute Myocardial Infarction in MAO-B Knockout Mice In Vivo.

The cardiomyocyte-specific knockout (KO) of monoamine oxidase (MAO)-B, an enzyme involved in the formation of reactive oxygen species (ROS), reduced myocardial ischemia/reperfusion (I/R) injury in vitro. Because sex hormones have a strong impact on MAO metabolic pathways, we analyzed the myocardial infarct size (IS) following I/R in female and male MAO-B KO mice in vivo. METHOD AND RESULTS: To induce the deletion of MAO-B, MAO-B KO mice (Myh6 Cre+/MAO-Bfl/fl) and wild-type (WT, Cre-negative MAO-Bfl/fl littermates) were fed with tamoxifen for 2 weeks followed by 10 weeks of normal mice chow. Myocardial infarction (assessed by TTC staining and expressed as a percentage of the area at risk as determined by Evans blue staining)) was induced by 45 min coronary occlusion followed by 120 min of reperfusion. RESULTS: The mortality following I/R was higher in male compared to female mice, with the lowest mortality found in MAO-B KO female mice. IS was significantly higher in male WT mice compared to female WT mice. MAO-B KO reduced IS in male mice but had no further impact on IS in female MAO-B KO mice. Interestingly, there was no difference in the plasma estradiol levels among the groups. CONCLUSION: The cardiomyocyte-specific knockout of MAO-B protects male mice against acute myocardial infarction but had no effect on the infarct size in female mice.

Importance of Mitochondria in Cardiac Pathologies: Focus on Uncoupling Proteins and Monoamine Oxidases.

On the one hand, reactive oxygen species (ROS) are involved in the onset and progression of a wide array of diseases. On the other hand, these are a part of signaling pathways related to cell metabolism, growth and survival. While ROS are produced at various cellular sites, in cardiomyocytes the largest amount of ROS is generated by mitochondria. Apart from the electron transport chain and various other proteins, uncoupling protein (UCP) and monoamine oxidases (MAO) have been proposed to modify mitochondrial ROS formation. Here, we review the recent information on UCP and MAO in cardiac injuries induced by ischemia-reperfusion (I/R) as well as protection from I/R and heart failure secondary to I/R injury or pressure overload. The current data in the literature suggest that I/R will preferentially upregulate UCP2 in cardiac tissue but not UCP3. Studies addressing the consequences of such induction are currently inconclusive because the precise function of UCP2 in cardiac tissue is not well understood, and tissue- and species-specific aspects complicate the situation. In general, UCP2 may reduce oxidative stress by mild uncoupling and both UCP2 and UCP3 affect substrate utilization in cardiac tissue, thereby modifying post-ischemic remodeling. MAOs are important for the physiological regulation of substrate concentrations. Upon increased expression and or activity of MAOs, however, the increased production of ROS and reactive aldehydes contribute to cardiac alterations such as hypertrophy, inflammation, irreversible cardiomyocyte injury, and failure.

Interaction of Cardiovascular Nonmodifiable Risk Factors, Comorbidities and Comedications With Ischemia/Reperfusion Injury and Cardioprotection by Pharmacological Treatments and Ischemic Conditioning.

Preconditioning, postconditioning, and remote conditioning of the myocardium enhance the ability of the heart to withstand a prolonged ischemia/reperfusion insult and the potential to provide novel therapeutic paradigms for cardioprotection. While many signaling pathways leading to endogenous cardioprotection have been elucidated in experimental studies over the past 30 years, no cardioprotective drug is on the market yet for that indication. One likely major reason for this failure to translate cardioprotection into patient benefit is the lack of rigorous and systematic preclinical evaluation of promising cardioprotective therapies prior to their clinical evaluation, since ischemic heart disease in humans is a complex disorder caused by or associated with cardiovascular risk factors and comorbidities. These risk factors and comorbidities induce fundamental alterations in cellular signaling cascades that affect the development of ischemia/reperfusion injury and responses to cardioprotective interventions. Moreover, some of the medications used to treat these comorbidities may impact on cardioprotection by again modifying cellular signaling pathways. The aim of this article is to review the recent evidence that cardiovascular risk factors as well as comorbidities and their medications may modify the response to cardioprotective interventions. We emphasize the critical need for taking into account the presence of cardiovascular risk factors as well as comorbidities and their concomitant medications when designing preclinical studies for the identification and validation of cardioprotective drug targets and clinical studies. This will hopefully maximize the success rate of developing rational approaches to effective cardioprotective therapies for the majority of patients with multiple comorbidities. SIGNIFICANCE STATEMENT: Ischemic heart disease is a major cause of mortality; however, there are still no cardioprotective drugs on the market. Most studies on cardioprotection have been undertaken in animal models of ischemia/reperfusion in the absence of comorbidities; however, ischemic heart disease develops with other systemic disorders (e.g., hypertension, hyperlipidemia, diabetes, atherosclerosis). Here we focus on the preclinical and clinical evidence showing how these comorbidities and their routine medications affect ischemia/reperfusion injury and interfere with cardioprotective strategies.

Effects of Bempedoic Acid in Acute Myocardial Infarction in Rats: No Cardioprotection and No Hidden Cardiotoxicity.

Lipid-lowering drugs have been shown to have cardioprotective effects but may have hidden cardiotoxic properties. Therefore, here we aimed to investigate if chronic treatment with the novel lipid-lowering drug bempedoic acid (BA) exerts hidden cardiotoxic and/or cardioprotective effects in a rat model of acute myocardial infarction (AMI). Wistar rats were orally treated with BA or its vehicle for 28 days, anesthetized and randomized to three different groups (vehicle + ischemia/reperfusion (I/R), BA + I/R, and positive control vehicle + ischemic preconditioning (IPC)) and subjected to cardiac 30 min ischemia and 120 min reperfusion. IPC was performed by 3 × 5 min I/R cycles before ischemia. Myocardial function, area at risk, infarct size and arrhythmias were analyzed. Chronic BA pretreatment did not influence cardiac function or infarct size as compared to the vehicle group, while the positive control IPC significantly reduced the infarct size. The incidence of reperfusion-induced arrhythmias was significantly reduced by BA and IPC. This is the first demonstration that BA treatment does not show cardioprotective effect although moderately reduces the incidence of reperfusion-induced arrhythmias. Furthermore, BA does not show hidden cardiotoxic effect in rats with AMI, showing its safety in the ischemic/reperfused heart.

Cardioprotective efficacy of limb remote ischaemic preconditioning in rats: discrepancy between a meta-analysis and a three-centre in vivo study.

AIMS: Remote ischaemic preconditioning (RIPC) is a robust cardioprotective intervention in preclinical studies. To establish a working and efficacious RIPC protocol in our laboratories, we performed randomized, blinded in vivo studies in three study centres in rats, with various RIPC protocols. To verify that our experimental settings are in good alignment with in vivo rat studies showing cardioprotection by limb RIPC, we performed a systematic review and meta-analysis. In addition, we investigated the importance of different study parameters. METHODS AND RESULTS: Male Wistar rats were subjected to 20-45 min cardiac ischaemia followed by 120 min reperfusion with or without preceding RIPC by 3 or 4 × 5-5 min occlusion/reperfusion of one or two femoral vessels by clamping, tourniquet, or pressure cuff. RIPC did not reduce infarct size (IS), microvascular obstruction, or arrhythmias at any study centres. Systematic review and meta-analysis focusing on in vivo rat models of myocardial ischaemia/reperfusion injury with limb RIPC showed that RIPC reduces IS by 21.28% on average. In addition, the systematic review showed methodological heterogeneity and insufficient reporting of study parameters in a high proportion of studies. CONCLUSION: We report for the first time the lack of cardioprotection by RIPC in rats, assessed in individually randomized, blinded in vivo studies, involving three study centres, using different RIPC protocols. These results are in discrepancy with the meta-analysis of similar in vivo rat studies; however, no specific methodological reason could be identified by the systematic review, probably due to the overall insufficient reporting of several study parameters that did not improve over the past two decades. These results urge for publication of more well-designed and well-reported studies, irrespective of the outcome, which are required for preclinical reproducibility, and the development of clinically translatable cardioprotective interventions.

YB-1 Is a Novel Target for the Inhibition of α-Adrenergic-Induced Hypertrophy.

Cardiac hypertrophy resulting from sympathetic nervous system activation triggers the development of heart failure. The transcription factor Y-box binding protein 1 (YB-1) can interact with transcription factors involved in cardiac hypertrophy and may thereby interfere with the hypertrophy growth process. Therefore, the question arises as to whether YB-1 influences cardiomyocyte hypertrophy and might thereby influence the development of heart failure. YB-1 expression is downregulated in human heart biopsies of patients with ischemic cardiomyopathy (n = 8), leading to heart failure. To study the impact of reduced YB-1 in cardiac cells, we performed small interfering RNA (siRNA) experiments in H9C2 cells as well as in adult cardiomyocytes (CMs) of rats. The specificity of YB-1 siRNA was analyzed by a miRNA-like off-target prediction assay identifying potential genes. Testing three high-scoring genes by transfecting cardiac cells with YB-1 siRNA did not result in downregulation of these genes in contrast to YB-1, whose downregulation increased hypertrophic growth. Hypertrophic growth was mediated by PI3K under PE stimulation, as well by downregulation with YB-1 siRNA. On the other hand, overexpression of YB-1 in CMs, caused by infection with an adenovirus encoding YB-1 (AdYB-1), prevented hypertrophic growth under α-adrenergic stimulation with phenylephrine (PE), but not under stimulation with growth differentiation factor 15 (GDF15; n = 10-16). An adenovirus encoding the green fluorescent protein (AdGFP) served as the control. YB-1 overexpression enhanced the mRNA expression of the Gq inhibitor regulator of G-protein signaling 2 (RGS2) under PE stimulation (n = 6), potentially explaining its inhibitory effect on PE-induced hypertrophic growth. This study shows that YB-1 protects cardiomyocytes against PE-induced hypertrophic growth. Like in human end-stage heart failure, YB-1 downregulation may cause the heart to lose its protection against hypertrophic stimuli and progress to heart failure. Therefore, the transcription factor YB-1 is a pivotal signaling molecule, providing perspectives for therapeutic approaches.

Myocardial Protection and Current Cancer Therapy: Two Opposite Targets with Inevitable Cost.

Myocardial protection against ischemia/reperfusion injury (IRI) is mediated by various ligands, activating different cellular signaling cascades. These include classical cytosolic mediators such as cyclic-GMP (c-GMP), various kinases such as Phosphatydilinositol-3- (PI3K), Protein Kinase B (Akt), Mitogen-Activated-Protein- (MAPK) and AMP-activated (AMPK) kinases, transcription factors such as signal transducer and activator of transcription 3 (STAT3) and bioactive molecules such as vascular endothelial growth factor (VEGF). Most of the aforementioned signaling molecules constitute targets of anticancer therapy; as they are also involved in carcinogenesis, most of the current anti-neoplastic drugs lead to concomitant weakening or even complete abrogation of myocardial cell tolerance to ischemic or oxidative stress. Furthermore, many anti-neoplastic drugs may directly induce cardiotoxicity via their pharmacological effects, or indirectly via their cardiovascular side effects. The combination of direct drug cardiotoxicity, indirect cardiovascular side effects and neutralization of the cardioprotective defense mechanisms of the heart by prolonged cancer treatment may induce long-term ventricular dysfunction, or even clinically manifested heart failure. We present a narrative review of three therapeutic interventions, namely VEGF, proteasome and Immune Checkpoint inhibitors, having opposing effects on the same intracellular signal cascades thereby affecting the heart. Moreover, we herein comment on the current guidelines for managing cardiotoxicity in the clinical setting and on the role of cardiovascular confounders in cardiotoxicity.

Connexin 43 in Mitochondria: What Do We Really Know About Its Function?

Connexins are known for their ability to mediate cell-cell communication via gap junctions and also form hemichannels that pass ions and molecules over the plasma membrane when open. Connexins have also been detected within mitochondria, with mitochondrial connexin 43 (Cx43) being the best studied to date. In this review, we discuss evidence for Cx43 presence in mitochondria of cell lines, primary cells and organs and summarize data on its localization, import and phosphorylation status. We further highlight the influence of Cx43 on mitochondrial function in terms of respiration, opening of the mitochondrial permeability transition pore and formation of reactive oxygen species, and also address the presence of a truncated form of Cx43 termed Gja1-20k. Finally, the role of mitochondrial Cx43 in pathological conditions, particularly in the heart, is discussed.