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

Mechanisms of postischemic cardiac death and protection following myocardial injury

Acute myocardial infarction (MI) is a leading cause of death worldwide. Although with current treatment, acute mortality from MI is low, the damage and remodeling associated with MI are responsible for subsequent heart failure. Reducing cell death associated with acute MI would decrease the mortality associated with heart failure. Despite considerable study, the precise mechanism by which ischemia and reperfusion (I/R) trigger cell death is still not fully understood. In this Review, we summarize the changes that occur during I/R injury, with emphasis on those that might initiate cell death, such as calcium overload and oxidative stress. We review cell-death pathways and pathway crosstalk and discuss cardioprotective approaches in order to provide insight into mechanisms that could be targeted with therapeutic interventions. Finally, we review cardioprotective clinical trials, with a focus on possible reasons why they were not successful. Cardioprotection has largely focused on inhibiting a single cell-death pathway or one death-trigger mechanism (calcium or ROS). In treatment of other diseases, such as cancer, the benefit of targeting multiple pathways with a "drug cocktail" approach has been demonstrated. Given the crosstalk between cell-death pathways, targeting multiple cardiac death mechanisms should be considered.

Pharmacokinetics and cardioprotective efficacy of intravenous miR-125b* microRNA mimic in a mouse model of acute myocardial infarction

BACKGROUND AND PURPOSE

MicroRNA (miRNA) therapy is a promising approach to induce cardioprotection. We have previously identified cardiac microRNA-125b* (microRNA-125b-2-3p; miR-125b*) as a potential cardioprotective miRNA, termed ProtectomiR. We aimed to characterize the pharmacokinetics and pharmacodynamics, and the effect of miR-125b* mimic on infarct size using an in vivo mouse model.

EXPERIMENTAL APPROACH

To characterize the pharmacokinetics properties of miR-125b* mimic, a single injection of 10-μg miR-125b* mimic or its scramble miRNA control, or vehicle i.v. was given to C57BL/6 mice. MiR-125b* expression was measured from plasma, heart, kidney and liver samples. Effect of miR-125b* on area at risk and infarct size was assessed after 45-min coronary occlusion, followed by 24-h reperfusion; 10-μg miR-125b* mimic or 10-μg non-targeting miRNA mimic control or vehicle were administered via the right jugular vein at 10th mins of coronary occlusion. To assess molecular mechanism involved in cardioprotection, expression of mRNA targets of miR-125b* were measured from ventricular myocardium at 1, 2, 4, 8 or 24 h post-treatment using quantitative real time polymerase chain reaction.

KEY RESULTS

MiR-125b* expression was markedly increased in plasma and myocardium 1 h, and in the liver 2h after treatment. Infarct size was significantly reduced after miR-125b* mimic treatment when compared to the vehicle. The expression of Ccna2, Eef2k and Cacnb2 target mRNAs was significantly reduced 8 h after injection of miR-125b* mimic.

CONCLUSION AND IMPLICATIONS

This is the first demonstration of pharmacokinetic and molecular pharmacodynamic properties as well as the cardioprotective effect of miR-125b* mimic in vivo.

LINKED ARTICLES

This article is part of a themed issue Non-coding RNA Therapeutics. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v182.2/issuetoc.

Monoamine oxidases: A missing link between mitochondria and inflammation in chronic diseases ?

The role of mitochondria spans from the regulation of the oxidative phosphorylation, cell metabolism and survival/death pathways to a more recently identified function in chronic inflammation. In stress situations, mitochondria release some pro-inflammatory mediators such as ATP, cardiolipin, reactive oxygen species (ROS) or mitochondrial DNA, that are believed to participate in chronic diseases and aging. These mitochondrial Damage-Associated Molecular Patterns (mito-DAMPs) can modulate specific receptors among which TLR9, NLRP3 and cGAS-STING, triggering immune cells activation and sterile inflammation. In order to counter the development of chronic diseases, a better understanding of the underlying mechanisms of low grade inflammation induced by mito-DAMPs is needed. In this context, monoamine oxidases (MAO), the mitochondrial enzymes that degrade catecholamines and serotonin, have recently emerged as potent regulators of chronic inflammation in obesity-related disorders, cardiac diseases, cancer, rheumatoid arthritis and pulmonary diseases. The role of these enzymes in inflammation embraces their action in both immune and non-immune cells, where they regulate monoamines levels and generate toxic ROS and aldehydes, as by-products of enzymatic reaction. Here, we discuss the more recent advances on the role and mechanisms of action of MAOs in chronic inflammatory diseases.

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.

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.

Formononetin ameliorates isoproterenol induced cardiac fibrosis through improving mitochondrial dysfunction

Formononetin, an isoflavone compound, has been extensively researched due to its various biological activities, including a potent protective effect on the cardiovascular system. However, the impact of formononetin on cardiac fibrosis has not been investigated. In this study, C57BL/6 mice were used to establish cardiac fibrosis animal models by subcutaneous injecting of isoproterenol (ISO) and formononetin was orally administrated. The results showed that formononetin reversed ISO-induced heart stiffness revealed by early-to-atrial wave ratio (E/A ratio). Masson staining, western blot, immunohistochemistry and real-time PCR exhibited that the cardiac fibrosis and fibrosis-related proteins (collage III, fibronectin, TGF-β1, α-SMA, and vimentin) and genes (Col1a1, Col3a1, Acta2 and Tgfb1) induced by ISO were significantly suppressed by formononetin. Furthermore, by combining metabolomics and network pharmacology, we found three important targets (ALDH2, HADH, and MAOB), which are associated with mitochondrial function, were involved in the beneficial effect of formononetin. Further validation revealed that these three genes were more abundance in cardiomyocyte than in cardiac fibroblast. The mRNA expression of ALDH2 and HADH were decreased, while MOAB was increased in cardiomyocyte upon ISO treatment and these phenomena were reversed by formononetin. In addition, we investigated mitochondrial membrane potential and ROS production in cardiomyocytes, the results showed that formononetin effectively improved mitochondrial dysfunction induced by ISO. In summary, we demonstrated that formononetin via regulating the expressions of ALDH2, HADH, and MAOB in cardiomyocyte to improve mitochondrial dysfunction and alleviate β-adrenergic activation cardiac fibrosis.

Recent advances on the role of monoamine oxidases in cardiac pathophysiology

Numerous physiological and pathological roles have been attributed to the formation of mitochondrial reactive oxygen species (ROS). However, the individual contribution of different mitochondrial processes independently of bioenergetics remains elusive and clinical treatments unavailable. A notable exception to this complexity is found in the case of monoamine oxidases (MAOs). Unlike other ROS-producing enzymes, especially within mitochondria, MAOs possess a distinct combination of defined molecular structure, substrate specificity, and clinically accessible inhibitors. Another significant aspect of MAO activity is the simultaneous generation of hydrogen peroxide alongside highly reactive aldehydes and ammonia. These three products synergistically impair mitochondrial function at various levels, ultimately jeopardizing cellular metabolic integrity and viability. This pathological condition arises from exacerbated MAO activity, observed in many cardiovascular diseases, thus justifying the exploration of MAO inhibitors as effective cardioprotective strategy. In this context, we not only summarize the deleterious roles of MAOs in cardiac pathologies and the positive effects resulting from genetic or pharmacological MAO inhibition, but also discuss recent findings that expand our understanding on the role of MAO in gene expression and cardiac development.