Myocardial edema: A translational view

The impact of X-rays on cardiac hydrometabolism and the regulatory role of AS-IV

BACKGROUND

Radiation-induced cardiac injury has emerged as a significant pathological entity, with many studies focusing on the fibrotic changes in myocardial tissue. However, these do not offer solutions for the clinical prevention and treatment of radiation-induced heart disease. Regulating hydrometabolism presents a potential therapeutic target for the management of cardiovascular diseases. This research seeks to explore the impacts of irradiation on cardiac hydrometabolism and its regulatory mechanisms.

METHODS

The impact of X-ray radiation on cardiac and cardiomyocyte hydrometabolism was studied through in vivo and in vitro experiments, examining the pharmacological effects and mechanisms of PX-478 and AS-IV interventions in cardiomyocytes.

RESULTS

28 days after direct chest irradiation with 20 Gy X-rays, C57BL/6 mice exhibited an increased heart wet-to-dry weight ratio, significant enlargement of cardiomyocyte cross-sectional area, and elevated protein expression of HIF-1α, AQP1, AQP4, Cx43, Caspase3, and Bax, with decreased expression of Bcl-2. Irradiation with 6 Gy X-rays induced edema and damage in AC16 and HL-1 cardiomyocytes at 24, 48, and 72 h, with increased expression of HIF-1α, AQP1, AQP4, and Cx43 proteins post-radiation. Inhibition of HIF-1α ameliorated edema and apoptosis in AC16 and HL-1 cardiomyocytes, reducing the expression of HIF-1α, AQP1, AQP4, and Cx43 proteins. AS-IV demonstrated strong binding affinity with HIF-1α, and successfully attenuated the expression levels of HIF-1α, AQP1, AQP4, and Cx43 proteins, alleviating edema, mitochondrial swelling, and apoptosis in AC16 and HL-1 cardiomyocytes. Furthermore, AS-IV improved cardiomyocyte edema by restoring the activity of Na/K-ATPase.

CONCLUSION

Aberrant activation of the HIF-1α/AQPs/Cx43 axis is a key mechanism in X-ray-induced cardiomyocyte edema and damage. AS-IV can ameliorate X-ray induced cardiac damage by regulating hydrometabolism.

Cardioprotective effects of H3 receptor activation could be double-sided: insights from isoproterenol-induced cardiac injury

Histamine H3 receptors (H3Rs) are known to modulate neurotransmitter release in the nervous system, but their role in cardiac injury remains unclear. The present study aimed to investigate the cardioprotective role of H3Rs in a mouse model of myocardial injury. Forty BALB/c male mice were divided into four groups: Control (SF), Isoproterenol (ISO), Imetit (IMT), and IMT + ISO. The IMT and IMT + ISO groups were pretreated orally with 10 mg/kg imetit-dihydrobromide(imetit) for 7 days. In the last 2 days, the ISO and IMT + ISO groups received a subcutaneous injection of 85 mg/kg isoproterenol to induce myocardial ischemia. Electrocardiogram (ECG) recordings were obtained, and heart tissues were analyzed histopathologically. The results demonstrated that the administration of imetit resulted in the prolongation of the PR interval in the IMT group. QRS and QT intervals were prolonged in the ISO group. The J-wave area in the ISO group was significantly larger than in the other groups. Histopathological analyses revealed the presence of small vacuoles, inflammatory cell infiltration, and collagen aggregates in cardiomyocytes in the ISO group. No significant cellular changes were observed in the IMT group, in contrast. The IMT + ISO group exhibited fewer ischemic findings than the ISO group. Immunohistochemical analyses revealed positive H3R immunoreactivity in all groups. Imetit pretreatment increased the immunoreactivity of H3Rs in both the IMT and IMT + ISO groups. The findings of this study suggest that H3Rs may be present on the postsynaptic side in cardiac myocytes, in addition to adrenergic presynaptic nerve endings. Furthermore, imetit has been found to significantly reduce the effects of myocardial ischemia by activating H3Rs. The better characterization of the postsynaptic role of H3Rs offers potential for the development of new therapeutic strategies.

Cardiac Lymphatics and Therapeutic Prospects in Cardiovascular Disease: New Perspectives and Hopes

The lymphatic system is the same reticular fluid system as the circulatory system found throughout the body in vascularized tissues. Lymphatic vessels are low-pressure, blind-ended tubular structures that play a crucial role in maintaining tissue fluid homeostasis, immune cell transport, and lipid absorption. The heart also has an extensive lymphatic network, and as research on cardiac lymphatics has progressed in recent years, more and more studies have found that cardiac lymphangiogenesis may ameliorate certain cardiovascular diseases, and therefore stimulation of cardiac lymphangiogenesis may be an important tool in the future treatment of cardiovascular diseases. This article briefly reviews the development and function of cardiac lymphatic vessels, the interaction of cardiac lymphatic vessels with cardiovascular diseases (including atrial fibrillation, coronary atherosclerosis, and heart failure), and finally discusses the therapeutic potential of targeted cardiac lymphatic therapy for cardiovascular diseases.

Gasotransmitters and noble gases in cardioprotection: unraveling molecular pathways for future therapeutic strategies

Despite recent progress, ischemic heart disease poses a persistent global challenge, driving significant morbidity and mortality. The pursuit of therapeutic solutions has led to the emergence of strategies such as ischemic preconditioning, postconditioning, and remote conditioning to shield the heart from myocardial ischemia/reperfusion injury (MIRI). These ischemic conditioning approaches, applied before, after, or at a distance from the affected organ, inspire future therapeutic strategies, including pharmacological conditioning. Gasotransmitters, comprising nitric oxide, hydrogen sulfide, sulfur dioxide, and carbon monoxide, play pivotal roles in physiological and pathological processes, exhibiting shared features such as smooth muscle relaxation, antiapoptotic effects, and anti-inflammatory properties. Despite potential risks at high concentrations, physiological levels of gasotransmitters induce vasorelaxation and promote cardioprotective effects. Noble gases, notably argon, helium, and xenon, exhibit organ-protective properties by reducing cell death, minimizing infarct size, and enhancing functional recovery in post-ischemic organs. The protective role of noble gases appears to hinge on their modulation of molecular pathways governing cell survival, leading to both pro- and antiapoptotic effects. Among noble gases, helium and xenon emerge as particularly promising in the field of cardioprotection. This overview synthesizes our current understanding of the roles played by gasotransmitters and noble gases in the context of MIRI and cardioprotection. In addition, we underscore potential future developments involving the utilization of noble gases and gasotransmitter donor molecules in advancing cardioprotective strategies.

Acute Response of the Noninfarcted Myocardium and Surrounding Tissue Assessed by T2 Mapping After STEMI

BACKGROUND

ST-segment elevation myocardial infarction (STEMI) is associated with a systemic and local inflammatory response with edema. However, their role at the tissue level is poorly characterized.

OBJECTIVES

This study aims to characterize T2 values of the noninfarcted myocardium (NIM) and surrounding tissue and to investigate prognostic relevance of higher NIM T2 values after STEMI.

METHODS

A total of 171 consecutive patients with STEMI without prior cardiovascular events who underwent cardiac magnetic resonance after primary percutaneous coronary intervention were analyzed in terms of standard infarct characteristics. Edema of the NIM, liver, spleen, and pectoralis muscle was assessed based on T2 mapping. Follow-up was available for 130 patients. The primary endpoint was major adverse cardiac events (MACE), defined as cardiovascular death, myocardial infarction, unplanned coronary revascularization or rehospitalization for heart failure. The median time from primary percutaneous coronary intervention to cardiac magnetic resonance was 3 days (IQR: 2-5 days).

RESULTS

Higher (above the median value of 45 ms) T2 values in the NIM area were associated with larger infarct size, microvascular obstruction, and left ventricular dysfunction and did not correlate with C-reactive protein, white blood cells, or T2 values of the pectoralis muscle, liver, and spleen. At a median follow-up of 17 months, patients with higher (>45 ms) NIM T2 values had increased risk of MACE (P < 0.001) compared with subjects with NIM T2 values ≤45 ms, mainly caused by a higher rate of myocardial reinfarction (26.3% vs 1.4%; P < 0.001). At multivariable analysis, higher NIM T2 values independently predicted MACE (HR: 2.824 [95% CI: 1.254-6.361]; P = 0.012).

CONCLUSIONS

Higher NIM T2 values after STEMI are independently associated with worse cardiovascular outcomes, mainly because of higher risk of myocardial infarction.

The Role of T2 Mapping in Cardiac Amyloidosis

Cardiac amyloidosis (CA) is an infiltrative cardiomyopathy divided into two types: light-chain (LA) and transthyretin (ATTR) CA. Cardiac magnetic resonance (CMR) has emerged as an important diagnostic tool in CA. While late gadolinium enhancement (LGE), T1 mapping and extracellular volume (ECV) have a consolidate role in the assessment of CA, T2 mapping has been less often evaluated. We aimed to test the value of T2 mapping in the evaluation of CA. This study recruited 70 patients with CA (51 ATTR, 19 AL). All the subjects underwent 1.5 T CMR with T1 and T2 mapping and cine and LGE imaging. Their QALE scores were evaluated. The myocardial T2 values were significantly (p < 0.001) increased in both types of CA compared to the controls. In the AL-CA group, increased T2 values were associated with a higher QALE score. The myocardial native T1 values and ECV were significantly (p < 0.001) higher in the CA patients than in the healthy subjects. Left ventricular (LV) mass, QALE score and ECV were higher in ATTR amyloidosis compared with AL amyloidosis, while the LV ejection fraction was lower (p < 0.001). These results support the concept of the presence of myocardial edema in CA. Therefore, a CMR evaluation including not only myocardial T1 imaging but also myocardial T2 imaging allows for more comprehensive tissue characterization in CA.

Blood endothelium transition and phenotypic plasticity: A key regulator of integrity/permeability in response to ischemia

In the human body, the 1013 blood endothelial cells (ECs) which cover a surface of 500-700 m2 (Mai et al., 2013) are key players of tissue homeostasis, remodeling and regeneration. Blood vessel ECs play a major role in the regulation of metabolic and gaz exchanges, cell trafficking, blood coagulation, vascular tone, blood flow and fluid extravasation (also referred to as blood vascular permeability). ECs are heterogeneous in various capillary beds and have the exquisite capacity to cope with environmental changes by regulating their gene expression. Ischemia has major detrimental effects on the endothelium and ischemia-induced regulation of vascular integrity is of paramount importance for human health, as small amounts of fluid accumulation in the interstitium may be responsible for major effects on organ functions and patients outcome. In this review, we will here focus on the stimuli and the molecular mechanisms that control blood endothelium maintenance and phenotypic plasticity/transition involved in controlling blood capillary leakage that might open new avenues for therapeutic applications.

Mechanisms of Myocardial Edema Development in CVD Pathophysiology

Myocardial edema is the excess accumulation of fluid in the myocardial interstitium or cardiac cells that develops due to changes in capillary permeability, loss of glycocalyx charge, imbalance in lymphatic drainage, or a combination of these factors. Today it is believed that this condition is not only a complication of cardiovascular diseases, but in itself causes aggravation of the disease and increases the risks of adverse outcomes. The study of molecular, genetic, and mechanical changes in the myocardium during edema may contribute to the development of new approaches to the diagnosis and treatment of this condition. This review was conducted to describe the main mechanisms of myocardial edema development at the molecular and cellular levels and to identify promising targets for the regulation of this condition based on articles cited in Pubmed up to January 2024.

Pinacidil ameliorates cardiac microvascular ischemia-reperfusion injury by inhibiting chaperone-mediated autophagy of calreticulin

Calcium overload is the key trigger in cardiac microvascular ischemia-reperfusion (I/R) injury, and calreticulin (CRT) is a calcium buffering protein located in the endoplasmic reticulum (ER). Additionally, the role of pinacidil, an antihypertensive drug, in protecting cardiac microcirculation against I/R injury has not been investigated. Hence, this study aimed to explore the benefits of pinacidil on cardiac microvascular I/R injury with a focus on endothelial calcium homeostasis and CRT signaling. Cardiac vascular perfusion and no-reflow area were assessed using FITC-lectin perfusion assay and Thioflavin-S staining. Endothelial calcium homeostasis, CRT-IP3Rs-MCU signaling expression, and apoptosis were assessed by real-time calcium signal reporter GCaMP8, western blotting, and fluorescence staining. Drug affinity-responsive target stability (DARTS) assay was adopted to detect proteins that directly bind to pinacidil. The present study found pinacidil treatment improved capillary density and perfusion, reduced no-reflow and infraction areas, and improved cardiac function and hemodynamics after I/R injury. These benefits were attributed to the ability of pinacidil to alleviate calcium overload and mitochondria-dependent apoptosis in cardiac microvascular endothelial cells (CMECs). Moreover, the DARTS assay showed that pinacidil directly binds to HSP90, through which it inhibits chaperone-mediated autophagy (CMA) degradation of CRT. CRT overexpression inhibited IP3Rs and MCU expression, reduced mitochondrial calcium inflow and mitochondrial injury, and suppressed endothelial apoptosis. Importantly, endothelial-specific overexpression of CRT shared similar benefits with pinacidil on cardiovascular protection against I/R injury. In conclusion, our data indicate that pinacidil attenuated microvascular I/R injury potentially through improving CRT degradation and endothelial calcium overload.

Myocardial Oedema as a Consequence of Viral Infection and Persistence-A Narrative Review with Focus on COVID-19 and Post COVID Sequelae

Microvascular integrity is a critical factor in myocardial fluid homeostasis. The subtle equilibrium between capillary filtration and lymphatic fluid removal is disturbed during pathological processes leading to inflammation, but also in hypoxia or due to alterations in vascular perfusion and coagulability. The degradation of the glycocalyx as the main component of the endothelial filtration barrier as well as pericyte disintegration results in the accumulation of interstitial and intracellular water. Moreover, lymphatic dysfunction evokes an increase in metabolic waste products, cytokines and inflammatory cells in the interstitial space contributing to myocardial oedema formation. This leads to myocardial stiffness and impaired contractility, eventually resulting in cardiomyocyte apoptosis, myocardial remodelling and fibrosis. The following article reviews pathophysiological inflammatory processes leading to myocardial oedema including myocarditis, ischaemia-reperfusion injury and viral infections with a special focus on the pathomechanisms evoked by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. In addition, clinical implications including potential long-term effects due to viral persistence (long COVID), as well as treatment options, are discussed.

Exoskeleton Partial-Coated Stem Cells for Infarcted Myocardium Restoring

The integration of abiotic materials with live cells has emerged as an exciting strategy for the control of cellular functions. Exoskeletons consisting ofmetal-organic frameworks are generated to produce partial-coated bone marrow stem cells (BMSCs) to overcome low cell survival leading to disappointing effects for cell-based cardiac therapy. Partially coated exoskeletons can promote the survival of suspended BMSCs by integrating the support of exoskeletons and unimpaired cellular properties. In addition, partial exoskeletons exhibit protective effects against detrimental environmental conditions, including reactive oxygen species, pH changes, and osmotic pressure. The partial-coated cells exhibit increased intercellular adhesion forces to aggregate and adhere, promoting cell survival and preventing cell escape during cell therapy. The exoskeletons interact with cell surface receptors integrin α5β1, leading to augmented biological functions with profitable gene expression alteration, such as Vegfa, Cxcl12, and Adm. The partial-coated BMSCs display enhanced cell retention in infarcted myocardium through non-invasive intravenous injections. The repair of myocardial infarction has been achieved with improved cardiac function, myocardial angiogenesis, proliferation, and inhibition of cell apoptosis. This discovery advances the elucidation of potential molecular and cellular mechanisms for cell-exoskeleton interactions and benefits the rational design and manufacture of next-generation nanobiohybrids.

Effect of SGLT2 Inhibitor on Cardiomyopathy in a Rat Model of T2DM: Possible involvement of Cardiac Aquaporins

Diabetic cardiomyopathy (DCM) causes arrhythmia, heart failure, and sudden death. Empagliflozin, an SGLT-2 (Sodium glucose co-transporter) inhibitor, is an anti-diabetic medication that decreases blood glucose levels by stimulating urinary glucose excretion. Several aquaporins (AQPs) including AQP-1-3 and - 4 and their involvement in the pathogenesis in different cardiac diseases were detected. In the current study the effect of Empagliflozin on diabetic cardiomyopathy and the possible involvement of cardiac AQPs were investigated.

METHODS

56 adult male Sprague-Dawley rats were divided into 4 groups: Control, DCM: type 2 diabetic rats, low EMPA+DCM received empagliflozin (10 mg/kg/day) and high EMPA+DCM received empagliflozin (30 mg/kg/day) for 6 weeks.

RESULTS

Administration of both EMPA doses, especially in high dose group, led to significant improvement in ECG parameters. Also, a significant improvement in biochemical and cardiac oxidative stress markers (significant decrease in serum CK-MB, and malondialdehyde while increasing catalase) with decreased fibrosis and edema in histopathological examination and a significant attenuation in apoptosis (caspase-3) and edema (AQP-1& -4).

CONCLUSION

Both doses of Empagliflozin have a cardioprotective effect and reduced myocardial tissue edema with high dose having a greater effect. This might be due to attenuation of oxidative stress, fibrosis and edema mediated through AQP-1, - 3& - 4 expression.

Myocardial Recovery, Metabolism, and Structure after Cardiac Arrest with Cardioplexol

OBJECTIVES

 Clinical studies indicate encouraging cardioprotective potential for Cardioplexol. Its cardioprotective capacities during 45 minutes of ischemia compared with pure no-flow ischemia or during 90 minutes of ischemia compared with Calafiore cardioplegia were investigated experimentally.

METHODS

 Forty-four rat hearts were isolated and inserted into a blood-perfused pressure-controlled Langendorff apparatus. In a first step, cardiac arrest was induced by Cardioplexol or pure no-flow ischemia lasting 45 minutes. In a second step, cardiac arrest was induced by Cardioplexol or Calafiore cardioplegia lasting 90 minutes. For both experimental steps, cardiac function, metabolic parameters, and troponin I levels were evaluated during 90 minutes of reperfusion. At the end of reperfusion, hearts were fixed, and ultrastructural integrity was examined by electron microscopy.

RESULTS

 Step 1: after 90 minutes of reperfusion, hearts exposed to Cardioplexol had significantly higher left ventricular developed pressure (CP-45': 74%BL vs. no-flow-45': 45%BL; p = 0.046) and significantly better maximal left ventricular relaxation (CP-45': 84%BL vs. no-flow-45': 51%BL; p = 0.012). Oxygen consumption, lactate production, and troponin levels were similar in both groups. Step 2: left ventricular developed pressure was lower (22 vs. 48% of BL; p = 0.001) and coronary flow was lower (24 vs. 53% of BL; p = 0.002) when Cardioplexol was used compared with Calafiore cardioplegia. Troponin I levels were significantly higher under Cardioplexol (358.9 vs. 106.1 ng/mL; p = 0.016).

CONCLUSION

 Cardioplexol significantly improves functional recovery after 45 minutes of ischemia compared with pure ischemia. However, Cardioplexol protects the myocardium from ischemia/reperfusion-related damage after 90 minutes of ischemia worse than Calafiore cardioplegia.

Cardiac Magnetic Resonance-Detected Acute Myocardial Edema as Predictor of Favourable Prognosis: A Comprehensive Review

Acute myocardial edema (AME) is increased water content in the myocardium and represents the first and transient pathophysiological response to an acute myocardial injury. In-vivo and non-invasive evaluation is feasible with cardiac magnetic resonance (CMR), which is a powerful imaging technique capable of tissue characterization. In the clinical setting, early demonstration of AME has a recognized diagnostic value for acute coronary syndromes and acute myocarditis, although its prognostic value is not well established. This article provides a comprehensive narrative review on the clinical meaning of AME in heart diseases. In particular, the available evidence of a possible favourable prognostic value in several clinical scenarios is addressed.

Intravascularly infused extracellular matrix as a biomaterial for targeting and treating inflamed tissues

Decellularized extracellular matrix in the form of patches and locally injected hydrogels has long been used as therapies in animal models of disease. Here we report the safety and feasibility of an intravascularly infused extracellular matrix as a biomaterial for the repair of tissue in animal models of acute myocardial infarction, traumatic brain injury and pulmonary arterial hypertension. The biomaterial consists of decellularized, enzymatically digested and fractionated ventricular myocardium, localizes to injured tissues by binding to leaky microvasculature, and is largely degraded in about 3 d. In rats and pigs with induced acute myocardial infarction followed by intracoronary infusion of the biomaterial, we observed substantially reduced left ventricular volumes and improved wall-motion scores, as well as differential expression of genes associated with tissue repair and inflammation. Delivering pro-healing extracellular matrix by intravascular infusion post injury may provide translational advantages for the healing of inflamed tissues 'from the inside out'.

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.

Donor heart selection: Evidence-based guidelines for providers

The proposed donor heart selection guidelines provide evidence-based and expert-consensus recommendations for the selection of donor hearts following brain death. These recommendations were compiled by an international panel of experts based on an extensive literature review.

Hyperpolarized Metabolic and Parametric CMR Imaging of Longitudinal Metabolic-Structural Changes in Experimental Chronic Infarction

BACKGROUND

Prolonged ischemia and myocardial infarction are followed by a series of dynamic processes that determine the fate of the affected myocardium toward recovery or necrosis. Metabolic adaptions are considered to play a vital role in the recovery of salvageable myocardium in the context of stunned and hibernating myocardium.

OBJECTIVES

The potential of hyperpolarized pyruvate cardiac magnetic resonance (CMR) alongside functional and parametric CMR as a tool to study the complex metabolic-structural interplay in a longitudinal study of chronic myocardial infarction in an experimental pig model is investigated.

METHODS

Metabolic imaging using hyperpolarized [1-¹³C] pyruvate and proton-based CMR including cine, T₁/T₂ relaxometry, dynamic contrast-enhanced, and late gadolinium enhanced imaging were performed on clinical 3.0-T and 1.5-T MR systems before infarction and at 6 days and 5 and 9 weeks postinfarction in a longitudinal study design. Chronic myocardial infarction in pigs was induced using catheter-based occlusion and compared with healthy controls.

RESULTS

Metabolic image data revealed temporarily elevated lactate-to-bicarbonate ratios at day 6 in the infarcted relative to remote myocardium. The temporal changes of lactate-to-bicarbonate ratios were found to correlate with changes in T₂ and impaired local contractility. Assessment of pyruvate dehydrogenase flux via the hyperpolarized [¹³C] bicarbonate signal revealed recovery of aerobic cellular respiration in the hibernating myocardium, which correlated with recovery of local radial strain.

CONCLUSIONS

This study demonstrates the potential of hyperpolarized CMR to longitudinally detect metabolic changes after cardiac infarction over days to weeks. Viable myocardium in the area at risk was identified based on restored pyruvate dehydrogenase flux.

Platelets in Myocardial Ischemia/Reperfusion Injury

Coronary artery disease, including myocardial infarction (MI), remains a leading cause of global mortality. Rapid reperfusion therapy is key to the improvement of patient outcome but contributes substantially to the final cardiac damage. This phenomenon is called "ischemia/reperfusion injury (IRI)." The underlying mechanisms of IRI are complex and not fully understood. Contributing cellular and molecular mechanisms involve the formation of microthrombi, alterations in ion concentrations, pH shifts, dysregulation of osmolality, and, importantly, inflammation. Beyond their known action as drivers of the development of coronary plaques leading to MI, platelets have been identified as important mediators in myocardial IRI. Circulating platelets are activated by the IRI-provoked damages in the vascular endothelium. This leads to platelet adherence to the reperfused endothelium, aggregation, and the formation of microthrombi. Furthermore, activated platelets release vasoconstrictive substances, act via surface molecules, and enhance leukocyte infiltration into post-IR tissue, that is, via platelet-leukocyte complexes. A better understanding of platelet contributions to myocardial IRI, including their interaction with other lesion-associated cells, is necessary to develop effective treatment strategies to prevent IRI and further improve the condition of the reperfused myocardium. In this review, we briefly summarize platelet properties that modulate IRI. We also describe the beneficial impacts of antiplatelet agents as well as their mechanisms of action in IRI beyond classic effects.

Circadian dependence of microvascular obstruction during ST-segment elevation myocardial infarction

BACKGROUND

Microvascular obstruction (MVO) contributes significantly to adverse left-ventricular remodeling and mortality following ST-segment elevation myocardial infarction (STEMI). Because circadian processes contribute significantly to the timing and degree of ischemic injury in STEMI we hypothesized that the occurrence of MVO may also exhibit circadian behavior.

METHODS AND RESULTS

A single center cohort trial of 336 STEMI patients (273 M 63 F) with their first STEMI who were reperfused with primary percutaneous coronary intervention (PCI) and referred for cardiac MRI prior to discharge. The time of onset of chest pain was recorded from the patients chart and used to stratify patients with MVO over a 24-h cycle to analyze for circadian behavior. Subjects with MVO (n = 200) had greater infarct size by cMRI (45 vs. 20 g; p < 0.001), had reduced ejection fraction (LVEF = 50 vs 45%; p = 0.008) and significantly greater LV end-diastolic (LVEDVI) and end-systolic (LVESVI) volume index compared to subject without MVO (n = 136). The frequency of patients with MVO was compared against the frequency of patients without MVO at each 1-h and 3-h period over a 24-h cycle. A clear peak in patients with MVO (MVO + / MVO -) was seen at the 0700 h interval where 26 out of 27 patients had MVO (p = 0.0038) although MVO mass was not increased. This observation remained significant at the 06-09 time interval when 3-h segments were analyzed. Through 2021, mortality in patients with MVO was significantly greater compared to patients without MVO (n = 20 vs. 5, p < 0.03).

CONCLUSIONS

This analysis reveals for the first time a circadian dependence of the frequency of MVO in the setting of STEMI which could explain in part, the wide variation in MVO seen in STEMI patients with similar ischemic times and infarct size.

Characterization of early myocardial inflammation in ischemia-reperfusion injury

Background

Myocardial injury may be caused by myocardial ischemia-reperfusion (IR), and salvaging such an injury is still a great challenge in clinical practice. This study comprehensively characterized the physiopathologic changes of myocardial injury after IR to explore the underlying mechanism in the early reperfusion phase with particular emphasis on early myocardial inflammation.

Methods and Results

The experimental IR model was obtained by the left anterior descending artery's transient ligation of C57BL/6 mice. T2W signals of all mice showed increased signal at different IR stages. It was positively correlated with inflammatory cytokines and cells. T2W imaging by 7.0 T MRI surprisingly detected signal enhancement, but histopathology and flow cytometry did not reveal any inflammatory cells infiltration within 3 h after IR. Cardiomyocyte swelling and increased vascular permeability were observed by WGA staining and ultrastructural analysis, respectively. The 3 h IR group showed that the cardiomyocytes were severely affected with disintegrating myofilaments and mitochondria. Both VEGF and phosphorylated Src protein were markedly expressed in the 3 h IR group in comparison with the sham group, and TUNEL staining displayed little positive cells. Cleaved caspase-3 apoptin also has similar expression levels with that of the sham group. Resident macrophages had notably become M1 phenotype. The T2W signal was still elevated, and we observed that collagen deposition occurred from 1 to 7 days.

Conclusions

The inflammation response during the first week after reperfusion injury gradually increase 3 h later, but the main manifestation before that was edema. This study indicated that the first 3 h may be crucial to the early rescue process for reperfusion-induced myocardial injury due to inflammatory cell infiltration absence and apoptosis.

Xinshuitong Capsule extract attenuates doxorubicin-induced myocardial edema via regulation of cardiac aquaporins in the chronic heart failure rats

Doxorubicin (Dox), an effective antineoplastic drug, was limited use for cardiotoxicity. Xinshuitong Capsule (XST), a patented herbal formula, showed desirable beneficial effects in the treatment of chronic heart failure (CHF) patients. However, the drug on Dox-induced cardiotoxicity remains unclear. Ninety male Sprague-Dawley rats were randomized into two groups: 15 rats were selected as the normal group and 75 rats were injected intraperitoneally with Dox to establish CHF rat models, the success ones were randomly divided into five groups: low XST (LXST), medium XST (MXST) or high XST (HXST) (4.9, 9.8, or 19.6 g/kg d) administrated intragastrically twice a day for 4 weeks, with the captopril-treated group and the model group as comparison. The model group showed the cardiac functions generally impaired, and CHF mortality rate higher (47%) than those in the XST-treated groups (averaged 24%, P < 0.05). Compared with XST-treated groups, myocardial remodeling, inflammation and desarcomerization, and higher water content more severe in the cardiac tissue in the model group (P < 0.05), which was associated with higher expressions of mRNA or protein levels of AQP1, 4 and 7. Dox-impaired cardiac functions, cardiac remodeling and myocardial edema could be dose-dependently reverted by XST treatment. XST could inhibit AQP1, 4 and 7 at mRNA levels or at protein levels, which was associated with the attenuation of myocardial edema and cardiac remodeling, decreasing the ventricular stiffness and improving the cardiac functions and rats' survival. AQPs is involved in cardiac edema composed one of the mechanisms of Dox-induced cardiotoxicity, XSTvia inhibition of AQPs relieved the Dox-induced side effects.

Prognostic Role of Myocardial Edema as Evidenced by Early Cardiac Magnetic Resonance in Survivors of Out-of-Hospital Cardiac Arrest: A Multicenter Study

Background Sudden cardiac arrest (SCA) may be caused by an acute and reversible myocardial injury, a chronic and irreversible myocardial damage, or a primary ventricular arrhythmia. Cardiac magnetic resonance imaging may identify myocardial edema (ME), which denotes acute and reversible myocardial damage. We evaluated the arrhythmic outcome of SCA survivors during follow-up and tested the prognostic role of ME. Methods and Results We included a consecutive series of 101 (71% men, median age 47 years) SCA survivors from 9 collaborative centers who underwent early (<1 month) cardiac magnetic resonance imaging and received an implantable cardioverter-defibrillator (ICD). On T2-weighted sequences, ME was found in 18 of 101 (18%) patients. According to cardiac magnetic resonance imaging findings, the arrhythmic SCA was ascribed to acute myocardial injury (either ischemic [n=10] or inflammatory [n=8]), to chronic structural heart diseases (ischemic heart disease [n=11], cardiomyopathy [n=20], or other [n=23]), or to primarily arrhythmic syndrome (n=29). During a follow-up of 47 months (28 to 67 months), 24 of 101 (24%) patients received an appropriate ICD intervention. ME was associated with a significantly higher survival free from both any ICD interventions (log-rank=0.04) and ICD shocks (log-rank=0.03) and remained an independent predictor of better arrhythmic outcome after adjustment for left ventricular ejection fraction and late gadolinium enhancement. The risk of appropriate ICD intervention was unrelated to the type of underlying heart disease. Conclusions ME on early cardiac magnetic resonance imaging, which denotes an acute and transient arrhythmogenic substrate, predicted a favorable long-term arrhythmic outcome of SCA survivors. These findings may have a substantial impact on future guidelines on the management of SCA survivors.

The role of AQP3 and AQP4 channels in cisplatin-induced cardiovascular edema and the protective effect of melatonin

BACKGROUND

The present study evaluates the development of edema, the change in the AQP3, AQP4, p53 and Bax gene expressions, and the protective effects of melatonin in rat hearts administered with cisplatin.

METHODS AND RESULTS

A total of 28 Wistar albino rats were divided into four groups. The vehicle was administered intraperitoneally (i.p.) to the rats in the control group. The melatonin group (Mel) received melatonin at a dose of 10 mg/kg for 13 days. The cisplatin group (Cis) received cisplatin on days 1, 5, 9 and 13 at a dose of 4 mg/kg. The rats in the cisplatin + melatonin (Cis+Mel) group underwent the procedures both in the Mel and Cis groups. Blood and left ventricular samples were taken and analyzed on day 14 of the study. AQP3, p53 and Bax gene expressions were found to be significantly increased following cisplatin administration compared to the control, while melatonin administration significantly decreased the expression of these genes (p < 0.05). Melatonin administration also significantly decreased the level of AQP4 gene expression compared to the cis. On histological examination, congestion, hemorrhage, extracellular and intracellular edema, and degenerative changes were significantly more common in the Cis than in the control. Melatonin administration significantly decreased intracellular edema (p = 0.010) and degenerative changes (p = 0.010), and the improvement in extracellular edema was close to statistical significance (p = 0.051) in melatonin.

CONCLUSIONS

These results indicate that melatonin had an ameliorative effect on myocardial edema and AQP channels, and that it may be used as a protective molecule against myocardial edema secondary to cisplatin administration.

Ischemic heart disease and cardioprotection: Focus on estrogenic hormonal setting and microvascular health

Ischemic Heart Disease (IHD) is a clinical condition characterized by insufficient blood flow to the cardiac tissue, and the consequent inappropriate oxygen and nutrients supply and metabolic waste removal in the heart. In the last decade a broad scientific literature has underlined the distinct mechanism of onset and the peculiar progress of IHD between female and male patients, highlighting the estrogenic hormonal setting as a key factor of these sex-dependent divergences. In particular, estrogen-activated cardioprotective pathways exert a pivotal role for the microvascular health, and their impairment, both physiologically and pathologically driven, predispose to vascular dysfunctions. Aim of this review is to summarize the current knowledge on the estrogen receptors localization and function in the cardiovascular system, particularly focusing on sex-dependent differences in microvascular vs macrovascular dysfunction and on the experimental models that allowed the researchers to reach the current findings and sketching the leading estrogen-mediated cardioprotective mechanisms.

Reconditioning of circulatory death hearts by ex-vivo machine perfusion with a novel HTK-N preservation solution

BACKGROUND

Warm ischemia followed by blood reperfusion is associated with reduced myocardial contractility. Circulatory death (CD) hearts are maintained by machine perfusion (MP) with blood. However, the impact of MP with histidine-tryptophane-ketoglutarate (HTK) or novel HTK-N solution on reconditioning of CD-heart contractility is unknown.

METHODS

In a porcine model, native hearts were directly harvested (control), or CD was induced before harvesting, followed by left ventricular (LV) contractile assessment. In MP-groups, CD-hearts were maintained for 4 h by MP with blood (CD-B), cold oxygenated HTK (CD-HTK) or HTK-N (CD-HTK-N) before contractile evaluation (all groups n = 8). We performed immunohistochemistry of LV myocardial samples. We profiled myocardial expression of 84 oxidative stress-related genes and correlated the findings with myocardial contractility via a machine learning algorithm.

RESULTS

HTK-N improved end-systolic pressure (ESP=172±10 vs 132±5 mmHg, p = 0.02) and maximal slope of pressure increment (dp/dt_max=2161±214 vs 1240±167 mmHg/s, p = 0.005) compared to CD, whereas CD-B failed to improve contractility. Dp/dt_max (2161±214 vs 1177±156, p = 0.08) and maximal rate of pressure decrement (dp/dt_min=-1501±228 vs -637±79, p = 0.005) were also superior in CD-HTK-N compared to CD-B. In CD-HTK-N, myocardial 4-hydroxynonenal (marker for oxidative stress; p<0.001), nitrotyrosine (marker for nitrosative stress; p = 0.004), poly(adenosine diphosphate-ribose)polymerase (marker for necrosis; p = 0.028) immunoreactivity and cell swelling (p = 0.008) were decreased compared to CD-B. Strong correlation of gene expression with ESP was identified for oxidative stress defense genes in CD-HTK-N.

CONCLUSION

During harvesting procedure, MP with HTK-N reconditions CD-heart systolic and diastolic function by reducing oxidative and nitrosative stress and preventing cardiomyocytes from cell swelling and necrosis.

Targeting fibrosis in the failing heart with nanoparticles

Heart failure (HF) is a clinical syndrome characterized by typical symptoms and signs caused by a structural and/or functional cardiac abnormality, resulting in a reduced cardiac output and/or elevated intracardiac pressures at rest or during stress. Due to increasing incidence, prevalence and, most importantly mortality, HF is a healthcare burden worldwide, despite the improvement of treatment options and effectiveness. Acute and chronic cardiac injuries trigger the activation of neurohormonal, inflammatory, and mechanical pathways ultimately leading to fibrosis, which plays a key role in the development of cardiac dysfunction and HF. The use of nanoparticles for targeted drug delivery would greatly improve therapeutic options to identify, prevent and treat cardiac fibrosis. In this review we will highlight the mechanisms of cardiac fibrosis development to depict the pathophysiological features for passive and active targeting of acute and chronic cardiac fibrosis with nanoparticles. Then we will discuss how cardiomyocytes, immune and inflammatory cells, fibroblasts and extracellular matrix can be targeted with nanoparticles to prevent or restore cardiac dysfunction and to improve the molecular imaging of cardiac fibrosis.

The Rationale of Neprilysin Inhibition in Prevention of Myocardial Ischemia-Reperfusion Injury during ST-Elevation Myocardial Infarction

During the last three decades, timely myocardial reperfusion using either thrombolytic therapy or primary percutaneous intervention (pPCI) has allowed amazing improvements in outcomes with a more than halving in 1-year ST-elevation myocardial infarction (STEMI) mortality. However, mortality and left ventricle (LV) remodeling remain substantial in these patients. As such, novel therapeutic interventions are required to reduce myocardial infarction size, preserve LV systolic function, and improve survival in reperfused-STEMI patients. Myocardial ischemia-reperfusion injury (MIRI) prevention represents the main goal to reach in order to reduce STEMI mortality. There is currently no effective therapy for MIRI prevention in STEMI patients. A significant reason for the weak and inconsistent results obtained in this field may be the presence of multiple, partially redundant, mechanisms of cell death during ischemia-reperfusion, whose relative importance may depend on the conditions. Therefore, it is always more recognized that it is important to consider a "multi-targeted cardioprotective therapy", defined as an additive or synergistic cardioprotective agents or interventions directed to distinct targets with different timing of application (before, during, or after pPCI). Given that some neprilysin (NEP) substrates (natriuretic peptides, angiotensin II, bradykinin, apelins, substance P, and adrenomedullin) exert a cardioprotective effect against ischemia-reperfusion injury, it is conceivable that antagonism of proteolytic activity by this enzyme may be considered in a multi-targeted strategy for MIRI prevention. In this review, by starting from main pathophysiological mechanisms promoting MIRI, we discuss cardioprotective effects of NEP substrates and the potential benefit of NEP pharmacological inhibition in MIRI prevention.

The Relationship Between the Level of Serum ESM-1 and Lp-PLA2 in Patients With Acute ST-Segment Elevation Myocardial Infarction

Acute ST‐segment elevation myocardial infarction (STEMI) is the most lethal coronary heart disease with vascular endothelium dysfunction and inflammation in the disease development process. Endothelial cell‐specific molecule 1 (ESM‐1) and lipoprotein‐associated phospholipase A2 (Lp‐PLA2) are important for the diagnosis and characterization of STEMI. To date, no studies have reported the correlation between ESM‐1 and Lp‐PLA2 levels in patients with STEMI, which may be an important predictor of the fatal disease. To measure the level of serum ESM‐1 and Lp‐PLA2, and to evaluate the relationship and the clinical significance of these two biomarkers in patients with acute STEMI, 37 inpatients with acute STEMI were sequentially enrolled in the research group and 24 study objects with normal coronary artery function were included in the control group. The measurement of the relative parameters was done by enzyme‐linked immunosorbent assay using blood samples taken from the median cubital vein while the inpatients were enrolled. The levels of serum SEM‐1 and Lp‐PLA2 were significantly higher in patients with acute STEMI than in study objects with normal coronary artery function (P < 0.05). A significant correlation of serum SEM‐1 and Lp‐PLA2 was observed, leading to close linearity (r² = 0.8131, P < 0.0001). In conclusion, the endothelium dysfunction factor ESM‐1 and inflammatory factor Lp‐PLA2 are significantly higher and correlated in patients with acute STEMI. These two factors could be novel and effective biomarkers for acute STEMI diagnosis and evaluation.

Cardiovascular Magnetic Resonance Imaging: Identifying the Effects of Cancer Therapy

The era of modern oncology incorporates an ever-evolving personalized approach to hematological malignancies and solid tumors. As a result, patient survival rates have, in part, substantially improved, depending on the specific type of underlying malignancy. However, systemic therapies may come along with potential cardiotoxic effects resulting in heart failure with increased morbidity and mortality. Ultimately, patients may survive their malignancy but die as a result of cancer treatment. Cardiovascular magnetic resonance imaging has long been in use for the assessment of function and tissue characteristics in patients with various nonischemic cardiac diseases. Besides an introductory overview on the general definition of cardiotoxicity including potential underlying mechanisms, this review provides insight into the application of various cardiovascular magnetic resonance imaging techniques in the setting of cancer therapy-related cardiac and vascular toxicity. Early identification of cardiotoxic effects may allow for on-time therapy adjustment and/or cardioprotective measures to avoid subsequent long-term heart failure with increased mortality.

Myocardial ischaemia-reperfusion injury and cardioprotection in perspective

Despite the increasing use and success of interventional coronary reperfusion strategies, morbidity and mortality from acute myocardial infarction are still substantial. Myocardial infarct size is a major determinant of prognosis in these patients. Therefore, cardioprotective strategies aim to reduce infarct size. However, a perplexing gap exists between the many preclinical studies reporting infarct size reduction with mechanical and pharmacological interventions and the poor translation into better clinical outcomes in patients. This Review revisits the pathophysiology of myocardial ischaemia-reperfusion injury, including the role of autophagy and forms of cell death such as necrosis, apoptosis, necroptosis and pyroptosis. Other cellular compartments in addition to cardiomyocytes are addressed, notably the coronary microcirculation. Preclinical and clinical research developments in mechanical and pharmacological approaches to induce cardioprotection, and their signal transduction pathways, are discussed. Additive cardioprotective interventions are advocated. For clinical translation into treatments for patients with acute myocardial infarction, who typically are of advanced age, have comorbidities and are receiving several medications, not only infarct size reduction but also attenuation of coronary microvascular obstruction, as well as longer-term targets including infarct repair and reverse remodelling, must be considered to improve patient outcomes. Future clinical trials must focus on patients who really need adjunct cardioprotection, that is, those with severe haemodynamic alterations.

Hyperosmotic stress promotes endoplasmic reticulum stress-dependent apoptosis in adult rat cardiac myocytes

In different pathological situations, cardiac cells undergo hyperosmotic stress and cell shrinkage. This change in cellular volume has been associated with contractile dysfunction and cell death. However, the intracellular mechanisms involved in hyperosmotic stress-induced cell death have not been investigated in depth in adult cardiac myocytes. Given that osmotic stress has been shown to promote endoplasmic reticulum stress (ERS), a recognized trigger for apoptosis, we examined whether hyperosmotic stress triggers ERS in adult cardiac myocytes and if so whether this mechanism mediates hyperosmotic stress-induced cell death. Adult rat cardiomyocytes cultured overnight in a hypertonic solution (HS) containing mannitol as the osmolite, showed increased expression of ERS markers, GRP78, CHOP and cleaved-Caspase-12, compared with myocytes in isotonic solution (IS), suggesting that hyperosmotic stress induces ERS. In addition, HS significantly reduced cell viability and increased TUNEL staining and the expression of active Caspase-3, indicative of apoptosis. These effects were prevented with the addition of the ERS inhibitor, 4-PBA, indicating that hyperosmotic stress-induced apoptosis is mediated by ERS. Hyperosmotic stress-induced apoptosis was also prevented when cells were cultured in the presence of a Ca²⁺-chelating agent (EGTA) or the CaMKII inhibitor (KN93), suggesting that hyperosmotic stress-induced ERS is mediated by a Ca²⁺ and CaMKII-dependent mechanism. Similar results were observed when hyperosmotic stress was induced using glucose as the osmolite. We conclude that hyperosmotic stress promotes ERS by a CaMKII-dependent mechanism leading to apoptosis of adult cardiomyocytes. More importantly, we demonstrate that hyperosmotic stress-triggered ERS contributes to hyperglycemia-induced cell death.

Myocardial Fluid Balance and Pathophysiology of Myocardial Edema in Coronary Artery Bypass Grafting

Myocardial edema is one of the most common complications of coronary artery bypass grafting (CABG) that is linearly related to many coronary artery diseases. Myocardial edema can cause several consequences including systolic dysfunction, diastolic dysfunction, arrhythmia, and cardiac tissue fibrosis that can increase mortality in CABG. Understanding myocardial fluid balance and tissue and systemic fluid regulation is crucial in order to ultimately link how coronary artery bypass grafting can cause myocardial edema in such a setting. The identification of susceptible patients by using imaging modalities is still challenging. Future studies about the technique of imaging modalities, examination protocols, prevention, and treatment of myocardial edema should be carried out, in order to limit myocardial edema occurrence and prevent complications.

Transient Marked Myocardial Thickening after Reperfused Myocardial Infarction Causing Refractory Heart Failure

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Modest LV wall thickening is a common phenomenon after reperfusion therapy.

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Wall thickening may be due to myocardial interstitial edema and/or hemorrhage.

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Marked left ventricular wall thickening can reduce SV.

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MI is difficult to treat when SV is decreased during the acute phase.

Pathophysiology and diagnosis of coronary microvascular dysfunction in ST-elevation myocardial infarction

Early mechanical reperfusion of the epicardial coronary artery by primary percutaneous coronary intervention (PCI) is the guideline-recommended treatment for ST-elevation myocardial infarction (STEMI). Successful restoration of epicardial coronary blood flow can be achieved in over 95% of PCI procedures. However, despite angiographically complete epicardial coronary artery patency, in about half of the patients perfusion to the distal coronary microvasculature is not fully restored, which is associated with increased morbidity and mortality. The exact pathophysiological mechanism of post-ischaemic coronary microvascular dysfunction (CMD) is still debated. Therefore, the current review discusses invasive and non-invasive techniques for the diagnosis and quantification of CMD in STEMI in the clinical setting as well as results from experimental in vitro and in vivo models focusing on ischaemic-, reperfusion-, and inflammatory damage to the coronary microvascular endothelial cells. Finally, we discuss future opportunities to prevent or treat CMD in STEMI patients.

Functional Nanocomplexes with Vascular Endothelial Growth Factor A/C Isoforms Improve Collateral Circulation and Cardiac Function

Protein-based therapies are potential treatments for cancer, immunological, and cardiovascular diseases. However, effective delivery systems are needed because of their instability, immunogenicity, and so on. Crosslinked negatively charged heparin polysaccharide nanoparticle (HepNP) is proposed for protein delivery. HepNP can efficiently condense vascular endothelial growth factor (VEGF) because of the unique electronegative sulfonic acid and carboxyl domain of heparin. HepNP is then assembled with VEGF-C (Hep@VEGF-C) or VEGF-A (Hep@VEGF-A) protein for the therapy of myocardial infarction (MI) via intravenous (iv) injection. Hep@VEGF-A-mediated improvement of cardiac function by promoting angiogenesis is limited because of elevated vascular permeability, while Hep@VEGF-C effectively promotes lymphangiogenesis and reduces edema. On this basis, a graded delivery of VEGF-C (0.5-1 h post-MI) and VEGF-A (5 d post-MI) using HepNP is developed. At the dose ratio of 3:1 (Hep@VEGF-C vs Hep@VEGF-A), Hep@VEGF functional complexes substantially reduce the scar formation (≈-39%; p < 0.05) and improve cardiac function (≈+74%; p < 0.05). Such a HepNP delivery system provides a simple and effective therapeutic strategy for cardiovascular diseases by delivering functional proteins. Because of the unique binding ability of heparin with cytokines and growth factors, HepNP also has considerable application prospects in protein therapy for other serious diseases.

Ischemic Postconditioning Reduces Reperfusion Arrhythmias by Adenosine Receptors and Protein Kinase C Activation but Is Independent of KATP Channels or Connexin 43

Ischemic postconditioning (IPoC) reduces reperfusion arrhythmias but the antiarrhythmic mechanisms remain unknown. The aim of this study was to analyze IPoC electrophysiological effects and the role played by adenosine A1, A2A and A3 receptors, protein kinase C, ATP-dependent potassium (KATP) channels, and connexin 43. IPoC reduced reperfusion arrhythmias (mainly sustained ventricular fibrillation) in isolated rat hearts, an effect associated with a transient delay in epicardial electrical activation, and with action potential shortening. Electrical impedance measurements and Lucifer-Yellow diffusion assays agreed with such activation delay. However, this delay persisted during IPoC in isolated mouse hearts in which connexin 43 was replaced by connexin 32 and in mice with conditional deletion of connexin 43. Adenosine A1, A2A and A3 receptor blockade antagonized the antiarrhythmic effect of IPoC and the associated action potential shortening, whereas exogenous adenosine reduced reperfusion arrhythmias and shortened action potential duration. Protein kinase C inhibition by chelerythrine abolished the protective effect of IPoC but did not modify the effects on action potential duration. On the other hand, glibenclamide, a KATP inhibitor, antagonized the action potential shortening but did not interfere with the antiarrhythmic effect. The antiarrhythmic mechanisms of IPoC involve adenosine receptor activation and are associated with action potential shortening. However, this action potential shortening is not essential for protection, as it persisted during protein kinase C inhibition, a maneuver that abolished IPoC protection. Furthermore, glibenclamide induced the opposite effects. In addition, IPoC delays electrical activation and electrical impedance recovery during reperfusion, but these effects are independent of connexin 43.

Reappraisal of Ischemic Heart Disease

In recent years, it has become apparent that coronary microvascular dysfunction plays a pivotal pathogenic role in angina pectoris. Functional and structural mechanisms can affect the physiological function of the coronary microvasculature and lead to myocardial ischemia in people without coronary atheromatous disease and also in individuals with obstructive coronary artery disease. Abnormal dilatory responses of the coronary microvessels, coronary microvascular spasm, and extravascular compressive forces have been identified as pathogenic mechanisms in both chronic and acute forms of ischemic heart disease. The condition characterized by anginal symptoms and evidence of myocardial ischemia triggered by coronary microvascular dysfunction, in the absence of obstructive coronary disease, is known as microvascular angina. The concept of microvascular angina, however, may extend further to include patients with obstructive coronary artery disease and individuals with angina after coronary revascularization or heart transplantation because coronary microvascular dysfunction contributes to myocardial ischemia in many such patients. Patients with microvascular angina constitute a sizeable proportion of all cases of stable angina undergoing diagnostic coronary angiography and of those with persisting angina after successful coronary revascularization. Coronary microvascular dysfunction is also often responsible for angina in individuals with cardiomyopathy and heart valve disease as well as acute coronary syndrome cases such as Takotsubo syndrome and myocardial infarction with no obstructive coronary artery disease. Patients with stable microvascular angina present typically with effort or rest chest pain and a reduced coronary flow reserve or microvascular spasm. This condition, which affects women and men, can markedly impair quality of life and prognosis and represents a substantial cost burden to healthcare systems and individuals alike. In recent years, progress in the diagnosis of myocardial ischemia and the use of tests to investigate functional and structural causes for a reduced coronary flow reserve and microvascular spasm have allowed the identification of an increased number of cases of microvascular angina in everyday clinical practice. Although some of the available anti-anginal drugs may be helpful, treatment of coronary microvascular dysfunction remains a major challenge. The present article discusses the fundamental role that coronary microvascular dysfunction plays in the pathogenesis of ischemic heart disease, the clinical characteristics of patients presenting with microvascular angina, and possible diagnostic and therapeutic strategies.

Effects of Polyethylene Glycol-20k on Postresuscitation Myocardial and Cerebral Function in a Rat Model of Cardiopulmonary Resuscitation

OBJECTIVES

Polyethylene glycol-20k is a hybrid cell impermeant that reduces ischemia injury and improves microcirculatory flow during and following low flow states through nonenergy-dependent water transfer in the microcirculation. We investigated the effects of polyethylene glycol-20k on postresuscitation microcirculation, myocardial and cerebral function, and duration of survival in a rat model of cardiopulmonary resuscitation.

DESIGN

Ventricular fibrillation was induced in 20 male Sprague Dawley rats and untreated for 6 minutes. Animals were randomized into two groups (n = 10 for each group): polyethylene glycol-20k and control. Polyethylene glycol-20k (10% solution in saline, 10% estimated blood volume) and vehicle (saline) were administered at the beginning of cardiopulmonary resuscitation by continuous IV infusion. Resuscitation was attempted after 8 minutes of cardiopulmonary resuscitation.

SETTING

University-Affiliated Research Laboratory.

SUBJECTS

Sprague Dawley Rats.

INTERVENTIONS

Polyethylene glycol-20k.

MEASUREMENTS AND MAIN RESULTS

Buccal microcirculation was measured at baseline, 1, 3, and 6 hours after return of spontaneous circulation using a side-stream dark-field imaging device. Myocardial function was measured by echocardiography at baseline and every hour postresuscitation for 6 hours. The animals were then returned to their cage and observed for an additional 72 hours. Neurologic Deficit Scores were recorded at 24, 48, and 72 hours after resuscitation. Postresuscitation ejection fraction, cardiac output, and myocardial performance index were significantly improved in animals treated with polyethylene glycol-20k (p < 0.05). Perfused buccal vessel density and microcirculatory flow index values were significantly higher at all time points in the polyethylene glycol-20k group compared with the control group. Postresuscitation cerebral function and survival rate were also significantly improved in animals that received polyethylene glycol-20k.

CONCLUSIONS

Administration of polyethylene glycol-20k following cardiopulmonary resuscitation improves postresuscitation myocardial and cerebral function, buccal microcirculation, and survival in a rat model of cardiopulmonary resuscitation.

Myocardial Tissue Characterization and Fibrosis by Imaging

Myocardial fibrosis, either focal or diffuse, is a common feature of many cardiac diseases and is associated with a poor prognosis for major adverse cardiovascular events. Although histological analysis remains the gold standard for confirming the presence of myocardial fibrosis, endomyocardial biopsy is invasive, has sampling errors, and is not practical in the routine clinical setting. Cardiac imaging modalities offer noninvasive surrogate biomarkers not only for fibrosis but also for myocardial edema and infiltration to varying degrees, and have important roles in the diagnosis and management of cardiac diseases. This review summarizes important pathophysiological features in the development of commonly encountered cardiac diseases, and the principles, advantages, and disadvantages of various cardiac imaging modalities (echocardiography, single-photon emission computer tomography, positron emission tomography, multidetector computer tomography, and cardiac magnetic resonance) for myocardial tissue characterization, with an emphasis on imaging focal and diffuse myocardial fibrosis.

Cardiac MRI Endpoints in Myocardial Infarction Experimental and Clinical Trials: JACC Scientific Expert Panel

After a reperfused myocardial infarction (MI), dynamic tissue changes occur (edema, inflammation, microvascular obstruction, hemorrhage, cardiomyocyte necrosis, and ultimately replacement by fibrosis). The extension and magnitude of these changes contribute to long-term prognosis after MI. Cardiac magnetic resonance (CMR) is the gold-standard technique for noninvasive myocardial tissue characterization. CMR is also the preferred methodology for the identification of potential benefits associated with new cardioprotective strategies both in experimental and clinical trials. However, there is a wide heterogeneity in CMR methodologies used in experimental and clinical trials, including time of post-MI scan, acquisition protocols, and, more importantly, selection of endpoints. There is a need for standardization of these methodologies to improve the translation into a real clinical benefit. The main objective of this scientific expert panel consensus document is to provide recommendations for CMR endpoint selection in experimental and clinical trials based on pathophysiology and its association with hard outcomes.

Platelet Contributions to Myocardial Ischemia/Reperfusion Injury

Obstruction of a coronary artery causes ischemia of heart tissue leading to myocardial infarction. Prolonged oxygen deficiency provokes tissue necrosis, which can result in heart failure and death of the patient. Therefore, restoration of coronary blood flow (reperfusion of the ischemic area) by re-canalizing the affected vessel is essential for a better patient outcome. Paradoxically, sudden reperfusion also causes tissue injury, thereby increasing the initial ischemic damage despite restoration of blood flow (=ischemia/reperfusion injury, IRI). Myocardial IRI is a complex event that involves various harmful mechanisms (e.g., production of reactive oxygen species and local increase in calcium ions) as well as inflammatory cells and signals like chemokines and cytokines. An involvement of platelets in the inflammatory reaction associated with IRI was discovered several years ago, but the underlying mechanisms are not yet fully understood. This mini review focusses on platelet contributions to the intricate picture of myocardial IRI. We summarize how upregulation of platelet surface receptors and release of immunomodulatory mediators lead to aggravation of myocardial IRI and subsequent cardiac damage by different mechanisms such as recruitment and activation of immune cells or modification of the cardiac vascular endothelium. In addition, evidence for cardioprotective roles of distinct platelet factors during IRI will be discussed.

The coronary circulation in acute myocardial ischaemia/reperfusion injury: a target for cardioprotection

The coronary circulation is both culprit and victim of acute myocardial infarction. The rupture of an epicardial atherosclerotic plaque with superimposed thrombosis causes coronary occlusion, and this occlusion must be removed to induce reperfusion. However, ischaemia and reperfusion cause damage not only in cardiomyocytes but also in the coronary circulation, including microembolization of debris and release of soluble factors from the culprit lesion, impairment of endothelial integrity with subsequently increased permeability and oedema formation, platelet activation and leucocyte adherence, erythrocyte stasis, a shift from vasodilation to vasoconstriction, and ultimately structural damage to the capillaries with eventual no-reflow, microvascular obstruction (MVO), and intramyocardial haemorrhage (IMH). Therefore, the coronary circulation is a valid target for cardioprotection, beyond protection of the cardiomyocyte. Virtually all of the above deleterious endpoints have been demonstrated to be favourably influenced by one or the other mechanical or pharmacological cardioprotective intervention. However, no-reflow is still a serious complication of reperfused myocardial infarction and carries, independently from infarct size, an unfavourable prognosis. MVO and IMH can be diagnosed by modern imaging technologies, but still await an effective therapy. The current review provides an overview of strategies to protect the coronary circulation from acute myocardial ischaemia/reperfusion injury. This article is part of a Cardiovascular Research Spotlight Issue entitled 'Cardioprotection Beyond the Cardiomyocyte', and emerged as part of the discussions of the European Union (EU)-CARDIOPROTECTION Cooperation in Science and Technology (COST) Action, CA16225.

Aquaporin Channels in the Heart-Physiology and Pathophysiology

Mammalian aquaporins (AQPs) are transmembrane channels expressed in a large variety of cells and tissues throughout the body. They are known as water channels, but they also facilitate the transport of small solutes, gasses, and monovalent cations. To date, 13 different AQPs, encoded by the genes AQP0–AQP12, have been identified in mammals, which regulate various important biological functions in kidney, brain, lung, digestive system, eye, and skin. Consequently, dysfunction of AQPs is involved in a wide variety of disorders. AQPs are also present in the heart, even with a specific distribution pattern in cardiomyocytes, but whether their presence is essential for proper (electro)physiological cardiac function has not intensively been studied. This review summarizes recent findings and highlights the involvement of AQPs in normal and pathological cardiac function. We conclude that AQPs are at least implicated in proper cardiac water homeostasis and energy balance as well as heart failure and arsenic cardiotoxicity. However, this review also demonstrates that many effects of cardiac AQPs, especially on excitation-contraction coupling processes, are virtually unexplored.

Multitarget Strategies to Reduce Myocardial Ischemia/Reperfusion Injury: JACC Review Topic of the Week

Many treatments have been identified that confer robust cardioprotection in experimental animal models of acute ischemia and reperfusion injury. However, translation of these cardioprotective therapies into the clinical setting of acute myocardial infarction (AMI) for patient benefit has been disappointing. One important reason might be that AMI is multifactorial, causing cardiomyocyte death via multiple mechanisms, as well as affecting other cell types, including platelets, fibroblasts, endothelial and smooth muscle cells, and immune cells. Many cardioprotective strategies act through common end-effectors and may be suboptimal in patients with comorbidities. In this regard, emerging data suggest that optimal cardioprotection may require the combination of additive or synergistic multitarget therapies. This review will present an overview of the state of cardioprotection today and provide a roadmap for how we might progress towards successful clinical use of cardioprotective therapies following AMI, focusing on the rational combination of judiciously selected, multitarget therapies. This paper emerged as part of the discussions of the European Union (EU)-CARDIOPROTECTION Cooperation in Science and Technology (COST) Action, CA16225.

Pretreatment of carprofen impaired initiation of inflammatory- and overlapping resolution response and promoted cardiorenal syndrome in heart failure

Non-Steroidal Anti-Inflammatory Drugs (NSAIDs) are commonly used to control pain, inflammation, and limit the cardinal signs of injury in humans. However, prolonged use of NSAIDs increases the risk of heart attack (myocardial infarction; MI) and the subsequent risk of heart and renal failure. The molecular and cellular mechanism of action for this adverse effect, particularly along the cardiorenal network, is incomplete. To define the mechanism, carprofen (CAP), an NSAID was administered at the dose of 5 mg/kg to C57BL/6 male mice for two weeks. After last dose of CAP treatment mice were subjected to permanent occlusion of coronary artery that induces irreversible cardiac remodeling while maintaining naive and MI-controls. After MI, cardiac pathology and dysfunction were confirmed, along with additional measurements of kidney function, histology, and injury markers, such as plasma creatinine. CAP treatment increased plasma creatinine levels and subsequently, myocardial structural disorganization increased. Kidney neutrophil gelatinase associated lipocalin (NGAL) and protein expression were increased post-MI. After two weeks CAP treatment, the expression of pyrogenic pro-inflammatory cytokines TNF-α and IL-1β was increased compared to non-CAP treated mice, indicative of amplified inflammatory response. There was also evidence that renal injury of both the post-CAP treatment controls and post-CAP MI were much greater than the non-CAP treated naïve controls, as serum creatinine and NGAL levels were elevated along with obvious structural impairment of the glomerulus. Therefore, CAP treatment tampers with the acute inflammatory response that promotes cardiorenal syndrome and non-resolving inflammation post-MI in acute heart failure.