Cardioprotective Mechanisms against Reperfusion Injury in Acute Myocardial Infarction: Targeting Angiotensin II Receptors

Clinical studies in Myxomatous Mitral Valve Disease dogs: most prescribed ACEI inhibits ACE2 enzyme activity and ARB increases AngII pool in plasma

The hypertension patient population has doubled since 1990, affecting 1.3 billion globally and >75% live in low-and middle-income countries. Angiotensin Converting Enzyme Inhibitors (ACEI) and Angiotensin Receptor Blockers (ARB) are the most prescribed drugs (>160 million times in the US), but mortality increased >30% since 1990s globally. Clinical relevance of Myxomatous Mitral Valve Disease (MMVD) is directly linked to WHO group 2 pulmonary hypertension, with no disease specific therapies. Therefore, MMVD pet dogs with elevated systolic blood pressure treated with ACEI/ARB, were supplemented with oral ACE2 enzyme and Angiotensin1-7 (Ang1-7) bioencapsulated in plant cells. The oral ACE2/Ang1-7 was well tolerated by healthy and MMVD dogs with no adverse events and increased sACE2 activity by 670-755% with ARB (Telmisartan) than with ACEI (Enalapril) background therapy. In vitro rhACE2 activity was inhibited >90% by ACEIs enalapril/benazeprilat at higher doses but lisinopril inhibited at much lower doses. Membrane ACE2 activity evaluated in exosomes was 43-fold higher than the sACE2 and this was also inhibited 211% by ACEI, when compared to ARB. Background ACEI treatment reduced the Ang-II pool by 11-20-fold and proportionately decreased the abundance of Ang1-7 + Ang1-5 peptides. In contrast, ARB treatment increased Ang-II pool 11-20-fold and Ang1-7 + Ang1-5 by 160-260%. Systolic blood pressure was regulated by ARB better than ACEI, despite very high Ang-II levels. This first report on evaluation of metabolic pools in the RAS pathway identifies surprising interactions between ACEI/ARB/ACE2 and significant changes in key molecular dynamics. Affordable biologics developed in plant cells may offer potential new treatment options for hypertension.

Preconditioning with acteoside ameliorates myocardial ischemia‑reperfusion injury by targeting HSP90AA1 and the PI3K/Akt signaling pathway

The present study aimed to investigate the cardioprotective effects of acteoside (AC) on myocardial ischemia‑reperfusion injury (MIRI). To meet this aim, a network pharmacological analysis was conducted to search for key genes and signaling pathways associated with AC and MIRI. The infarct size of the rat heart was evaluated using 2,3,5‑triphenyltetrazolium chloride staining, and the serum levels of creatine kinase MB isoenzyme, cardiac troponin I, malondialdehyde and superoxide dismutase were subsequently detected in an in vivo experiment. The inhibitory effect of AC on oxidative stress was further confirmed by assessing the intracellular accumulation of reactive oxygen species (ROS). Hematoxylin and eosin staining was subsequently carried out to observe cardiac histopathological damage. The anti‑apoptotic effects of AC were determined using terminal deoxynucleotidyl‑transferase‑mediated dUTP nick end labeling assay and Hoechst 33342 staining, and the expression levels of apoptosis‑associated proteins in the myocardial tissue were assessed using immunohistochemical analysis. In addition, cell viability was determined using a Cell Counting Kit‑8 assay, and the expression levels of key target proteins associated with AC and MIRI were detected by western blot analysis. The results suggested that pretreatment with AC could mitigate MIRI‑induced myocardial damage, oxidative stress and apoptosis. The anti‑apoptotic effects of AC were associated with elevated Bcl‑2 levels, and reduced caspase‑3 and Bax expression levels in myocardial tissue. In vitro, AC pretreatment both led to an increased rate of cell survival and alleviated oxidative stress, as demonstrated by a decreased level of intracellular ROS accumulation. Moreover, guided by the network pharmacological analysis, heat‑shock protein 90AA1 (HSP90AA1) and the phosphoinositide 3‑kinase (PI3K)/serine‑threonine protein kinase (Akt) signaling pathway emerged as key targets for the action of AC against MIRI. Furthermore, the western blot analysis results showed that pretreatment with AC led to a significant increase in the activity of the PI3K/Akt signaling pathway, in addition to increased expression levels of glycogen synthase kinase‑3β and HSP90AA1. Taken together, the findings of the present study revealed that AC may exert cardioprotective effects on MIRI through suppressing apoptosis and oxidative stress by regulating the expression and activity of key proteins.

Angiotensin 1-7 Attenuates the Development of Ischemia-Reperfusion-Induced Arrhythmia in Rats: Electrophysiology, Molecular, and Immunohistochemical Study

Arrhythmia is a common and serious global health problem, contributing to cardiovascular morbidity and mortality. The cardiac muscle is susceptible to ischemia-reperfusion (I/R) injury, which can lead to fatal arrhythmias during open-heart surgery. We investigated the potential prophylactic effect of angiotensin 1-7 (Ang 1-7) using an in vivo rat model of I/R injury and examined the underlying mechanisms. Rats were treated with Ang 1-7 (1 mg/kg, IP) 30 min before the surgical procedures. Twenty-four rats were equally divided into four groups: sham control, sham-treated with Ang 1-7, I/R injury group, and I/R injury group treated with Ang 1-7. In vivo I/R injury was induced by clamping the left coronary artery for 30 min, followed by 1 hour of reperfusion. The I/R group showed abnormal electrophysiological changes and arrhythmic episodes during electrocardiography (ECG) recording, increased oxidative stress, downregulation of peroxisome proliferator-activated receptor gamma (PPAR-γ), and upregulation of C-X-C motif chemokine ligand 16 (CXCL16) expression in cardiac tissue, which increased cardiac NF-kB expression and IL-17 levels. Moreover, I/R injury caused significant histological disruption and increased cyclooxygenase 2 (COX-2) and heat shock protein 90 (HSP90) immunoreactions, correlating with the extent of cardiac damage. However, preoperative Ang 1-7 administration significantly improved the electrophysiological, biochemical, and histopathological changes induced by I/R injury. This study demonstrated that Ang 1-7 exerted protective anti-arrhythmic, anti-inflammatory, and pro-healing effects by upregulating PPAR-γ and downregulating CXCL16, IL-17, and NF-kB pathways, suggesting it is a promising cardioprotective agent for preventing arrhythmias induced by I/R injury.

A perspective on small molecules targeting the renin-angiotensin-aldosterone system and their utility in cardiovascular diseases: exploring the structural insights for rational drug discovery and development

Renin-angiotensin-aldosterone system (RAAS) is crucial in cardiovascular homeostasis. Any disruption in this homeostasis often leads to numerous cardiovascular diseases (CVDs) and non-cardiovascular diseases. Small molecules that show ability toward mechanically modulating RAAS components have been developed to address this problem, thus providing opportunities for innovative drug discovery and development. This review is put forth to provide a comprehensive understanding not only on the signaling mechanisms of RAAS that lead to cardiovascular events but also on the use of small molecules targeting the modulation of RAAS components. Further, the detailed descriptions of the drugs affecting the RAAS and their pharmacodynamics, kinetics, and metabolism profiles are provided. This article also covers the limitations of the present therapeutic armory, followed by their mechanistic insights. A brief discussion is offered on the analysis of the chemical space parameters of the drugs affecting RAAS compared to other cardiovascular and renal categories of medications approved by the US FDA. This review provides structural insights and emphasizes the importance of integrating the current therapeutic regimen with pharmacological tactics to accelerate the development of new therapeutics targeting the RAAS components for improved and efficacious cardiovascular outcomes. Finally, chemical spacing parameters of RAAS modulators are provided, which will help in understanding their peculiarities in modulating the RAAS signaling through structural and functional analyses. Furthermore, this review will assist medicinal chemists working in this field in developing better drug regimens with improved selectivity and efficacy.

Assembly of ceria-Nrf2 nanoparticles as macrophage-targeting ROS scavengers protects against myocardial infarction

Myocardial infarction (MI) is a leading cause of morbidity and mortality worldwide, and mitigating oxidative stress is crucial in managing MI. Nuclear factor erythroid 2-related factor 2 (Nrf2) plays a critical role in combating oxidative stress and facilitating cardiac remodeling post-MI. Here, we engineered Cerium oxide (CeO2) nanoparticle-guided assemblies of ceria/Nrf2 nanocomposites to deliver Nrf2 plasmids. The CeO2/Nrf2 nanocomposites effectively activated the Nrf2/antioxidant response element (ARE) signaling pathway both in vivo and in vitro. In a mouse MI model induced by permanent ligation of the left anterior descending artery (LAD), CeO2/Nrf2 nanocomposites were administered via tail vein injection, predominantly targeting circulating monocytes and macrophages which will be recruited to the heart post MI due to the acute inflammatory response. We demonstrated that CeO2/Nrf2 nanocomposites alleviated cardiac systolic dysfunction and significantly reduced infarct size and scar fibrosis post-MI. Furthermore, CeO2/Nrf2 nanocomposites effectively mitigated MI-induced oxidative stress and downregulated Nrf2-regulated inflammatory genes (tumor necrosis factor-α, IL-6, and inducible nitric oxide synthase), thereby reducing cardiomyocyte apoptosis. These findings indicate that CeO2/Nrf2 nanocomposites significantly enhance Nrf2 signaling activation and confer protection against MI. This study identifies CeO2/Nrf2 nanocomposites as a promising strategy for post-MI therapy.

Ellagic acid protects against angiotensin II-induced hypertrophic responses through ROS-mediated MAPK pathway in H9c2 cells

The early myocardial response of hypertension is an elevation of angiotensin-II (Ang-II) concentration, leading to heart failure and cardiac hypertrophy. This hypertrophic event of the heart is mediated by the interaction of Ang type 1 receptors (AT-R1), thereby modulating NADPH oxidase activity in cardiomyocytes, which alters redox status in cardiomyocytes. Ellagic acid (EA) has anti-inflammatory and anti-oxidative capacities. Thus, EA has potential preventive effects on cardiovascular diseases and diabetes. In the last decades, because the protective effect of EA on Ang-II-induced hypertrophic responses is unclear, this study aims to investigate the protective effect of EA in cardiomyocytes. H9c2 cells were treated to Ang-II 1 μM for 24 h to induce cellular damage. We found that EA protected against Ang-II-increased cell surface area and pro-hypertrophic gene expression in H9c2. EA reduced Ang-II-caused AT-R1 upregulation, thereby inhibiting oxidative stress NADPH oxidase activation. EA mitigated Ang-II-enhanced p38 and extracellular-signal-regulated kinase (ERK) phosphorylation. Moreover, EA treatment under Ang-II stimulation also reversed NF-κB activity and iNOS expression. This study shows that EA protects against Ang-II-induced myocardial hypertrophy and attenuates oxidative stress through reactive oxygen species-mediated mitogen-activated protein kinase signaling pathways in H9c2 cells. Thus, EA may be an effective compound for preventing Ang-II-induced myocardial hypertrophy.

Chemical, Biological and Biomedical Aspects of Bioantioxidants

Bioantioxidants are biologically important antioxidants, a heterogeneous variety of molecules, which are difficult to classify using commonly shared structural features [...].