Remote Hind-Limb Ischemia Mechanism of Preserved Ejection Fraction During Heart Failure

Levosimendan Reverses Cardiac Malfunction and Cardiomyocyte Ferroptosis During Heart Failure with Preserved Ejection Fraction via Connexin 43 Signaling Activation

PURPOSE

In recent decades, the occurrence of heart failure with preserved ejection fraction (HFpEF) has outweighed that of heart failure with reduced ejection fraction by degrees, but few drugs have been demonstrated to improve long-term clinical outcomes in patients with HFpEF. Levosimendan, a calcium-sensitizing cardiotonic agent, improves decompensated heart failure clinically. However, the anti-HFpEF activities of levosimendan and underlying molecular mechanisms are unclear.

METHODS

In this study, a double-hit HFpEF C57BL/6N mouse model was established, and levosimendan (3 mg/kg/week) was administered to HFpEF mice aged 13 to 17 weeks. Different biological experimental techniques were used to verify the protective effects of levosimendan against HFpEF.

RESULTS

After four weeks of drug treatment, left ventricular diastolic dysfunction, cardiac hypertrophy, pulmonary congestion, and exercise exhaustion were significantly alleviated. Junction proteins in the endothelial barrier and between cardiomyocytes were also improved by levosimendan. Among the gap junction channel proteins, connexin 43, which was especially highly expressed in cardiomyocytes, mediated mitochondrial protection. Furthermore, levosimendan reversed mitochondrial malfunction in HFpEF mice, as evidenced by increased mitofilin and decreased ROS, superoxide anion, NOX4, and cytochrome C levels. Interestingly, after levosimendan administration, myocardial tissue from HFpEF mice showed restricted ferroptosis, indicated by an increased GSH/GSSG ratio; upregulated GPX4, xCT, and FSP-1 expression; and reduced intracellular ferrous ion, MDA, and 4-HNE levels.

CONCLUSION

Regular long-term levosimendan administration can benefit cardiac function in a mouse model of HFpEF with metabolic syndromes (namely, obesity and hypertension) by activating connexin 43-mediated mitochondrial protection and sequential ferroptosis inhibition in cardiomyocytes.

A systematic review of exosomes in remote ischemic conditioning

BACKGROUND

Remote ischemic conditioning (RIC) is considered a promising non-pharmacological therapeutic strategy to mitigate ischemic injury. Although the precise mechanisms of RIC's protective effects remain elusive, existing data suggest that exosomes contribute significantly to these processes through cell-to-cell communication OBJECTIVE: This review aims to elucidate the role of exosomes in RIC-mediated multi-organ protection.

METHODS

We systematically searched multiple databases through October 2023 for preclinical studies evaluating the effect of exosomes in ischemic models using RIC procedures. Key outcomes, such as improved organ function and reduced infarct size, were recorded. Articles were selected and data were extracted by independent pairs of reviewers.

FINDINGS

A total of 16 relevant studies were identified in this review, showing that circulating exosomes derived from the plasma of RIC-treated animals exhibited protective effects akin to those of the RIC procedure itself. Exosome concentrations were measured in eight studies, six of which reported significant increases in the RIC group. Additional findings indicated that RIC might primarily modulate the expression of miRNAs and bioactive molecules delivered by exosomes, rather than directly altering circulating exosome levels. Notably, the expression of 11 distinct exosomal miRNAs was altered after RIC intervention, potentially involving multiple pathways.

CONCLUSION

Exosomes appear to play a pivotal role in the protective effects induced by RIC. Clarifying their function in RIC under different pathological situations represents a grand challenge for future research.

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.

Renal Denervation Helps Preserve the Ejection Fraction by Preserving Endocardial-Endothelial Function during Heart Failure

Renal denervation (RDN) protects against hypertension, hypertrophy, and heart failure (HF); however, it is not clear whether RDN preserves ejection fraction (EF) during heart failure (HFpEF). To test this hypothesis, we simulated a chronic congestive cardiopulmonary heart failure (CHF) phenotype by creating an aorta-vena cava fistula (AVF) in the C57BL/6J wild type (WT) mice. Briefly, there are four ways to create an experimental CHF: (1) myocardial infarction (MI), which is basically ligating the coronary artery by instrumenting and injuring the heart; (2) trans-aortic constriction (TAC) method, which mimics the systematic hypertension, but again constricts the aorta on top of the heart and, in fact, exposes the heart; (3) acquired CHF condition, promoted by dietary factors, diabetes, salt, diet, etc., but is multifactorial in nature; and finally, (4) the AVF, which remains the only one wherein AVF is created ~1 cm below the kidneys in which the aorta and vena cava share the common middle-wall. By creating the AVF fistula, the red blood contents enter the vena cava without an injury to the cardiac tissue. This model mimics or simulates the CHF phenotype, for example, during aging wherein with advancing age, the preload volume keeps increasing beyond the level that the aging heart can pump out due to the weakened cardiac myocytes. Furthermore, this procedure also involves the right ventricle to lung to left ventricle flow, thus creating an ideal condition for congestion. The heart in AVF transitions from preserved to reduced EF (i.e., HFpEF to HFrEF). In fact, there are more models of volume overload, such as the pacing-induced and mitral valve regurgitation, but these are also injurious models in nature. Our laboratory is one of the first laboratories to create and study the AVF phenotype in the animals. The RDN was created by treating the cleaned bilateral renal artery. After 6 weeks, blood, heart, and renal samples were analyzed for exosome, cardiac regeneration markers, and the renal cortex proteinases. Cardiac function was analyzed by echocardiogram (ECHO) procedure. The fibrosis was analyzed with a trichrome staining method. The results suggested that there was a robust increase in the exosomes' level in AVF blood, suggesting a compensatory systemic response during AVF-CHF. During AVF, there was no change in the cardiac eNOS, Wnt1, or β-catenin; however, during RDN, there were robust increases in the levels of eNOS, Wnt1, and β-catenin compared to the sham group. As expected in HFpEF, there was perivascular fibrosis, hypertrophy, and pEF. Interestingly, increased levels of eNOS suggested that despite fibrosis, the NO generation was higher and that it most likely contributed to pEF during HF. The RDN intervention revealed an increase in renal cortical caspase 8 and a decrease in caspase 9. Since caspase 8 is protective and caspase 9 is apoptotic, we suggest that RDN protects against the renal stress and apoptosis. It should be noted that others have demonstrated a role of vascular endothelium in preserving the ejection by cell therapy intervention. In the light of foregoing evidence, our findings also suggest that RDN is cardioprotective during HFpEF via preservation of the eNOS and accompanied endocardial-endothelial function.

A review of remote ischemic conditioning as a potential strategy for neural repair poststroke

Ischemic stroke is one of the major disabling health-care problem and multiple different approaches are needed to enhance rehabilitation, in which neural repair is the structural basement. Remote ischemic conditioning (RIC) is a strategy to trigger endogenous protect. RIC has been reported to play neuroprotective role in acute stage of stroke, but the effect of RIC on repair process remaining unclear. Several studies have discovered some overlapped mechanisms RIC and neural repair performs. This review provides a hypothesis that RIC is a potential therapeutic strategy on stroke rehabilitation by evaluating the existing evidence and puts forward some remaining questions to clarify and future researches to be performed in the field.

Extracellular vesicle-mediated bidirectional communication between heart and other organs

In recent years, a wealth of studies has identified various molecular species released by cardiac muscle under physiological and pathological conditions that exert local paracrine and/or remote endocrine effects. Conversely, humoral factors, principally produced by organs such as skeletal muscle, kidney, or adipose tissue, may affect the function and metabolism of normal and diseased hearts. Although this cross communication within cardiac tissue and between the heart and other organs is supported by mounting evidence, research on the role of molecular mediators carried by exosomes, microvesicles, and apoptotic bodies, collectively defined as extracellular vesicles (EVs), is at an early stage of investigation. Once released in the circulation, EVs can potentially reach any organ where they transfer their cargo of proteins, lipids, and nucleic acids that exert potent biological effects on recipient cells. Although there are a few cases where such signaling was clearly demonstrated, the results from many other studies can only be tentatively inferred based on indirect evidence obtained by infusing exogenous EVs in experimental animals or by adding them to cell cultures. This area of research is in rapid expansion and most mechanistic interpretations may change in the near future; hence, the present review on the role played by EV-carried mediators in the two-way communication between heart and skeletal muscle, kidneys, bone marrow, lungs, liver, adipose tissue, and brain is necessarily limited. Nonetheless, the available data are already unveiling new, intriguing, and ample scenarios in cardiac physiology and pathophysiology.