Loss of cardioprotection with ageing

Vasodilator reactive oxygen species ameliorate perturbed myocardial oxygen delivery in exercising swine with multiple comorbidities

Multiple common cardiovascular comorbidities produce coronary microvascular dysfunction. We previously observed in swine that a combination of diabetes mellitus (DM), high fat diet (HFD) and chronic kidney disease (CKD) induced systemic inflammation, increased oxidative stress and produced coronary endothelial dysfunction, altering control of coronary microvascular tone via loss of NO bioavailability, which was associated with an increase in circulating endothelin (ET). In the present study, we tested the hypotheses that (1) ROS scavenging and (2) ETA+B-receptor blockade improve myocardial oxygen delivery in the same female swine model. Healthy female swine on normal pig chow served as controls (Normal). Five months after induction of DM (streptozotocin, 3 × 50 mg kg-1 i.v.), hypercholesterolemia (HFD) and CKD (renal embolization), swine were chronically instrumented and studied at rest and during exercise. Sustained hyperglycemia, hypercholesterolemia and renal dysfunction were accompanied by systemic inflammation and oxidative stress. In vivo ROS scavenging (TEMPOL + MPG) reduced myocardial oxygen delivery in DM + HFD + CKD swine, suggestive of a vasodilator influence of endogenous ROS, while it had no effect in Normal swine. In vitro wire myography revealed a vasodilator role for hydrogen peroxide (H2O2) in isolated small coronary artery segments from DM + HFD + CKD, but not Normal swine. Increased catalase activity and ceramide production in left ventricular myocardial tissue of DM + HFD + CKD swine further suggest that increased H2O2 acts as vasodilator ROS in the coronary microvasculature. Despite elevated ET-1 plasma levels in DM + HFD + CKD swine, ETA+B blockade did not affect myocardial oxygen delivery in Normal or DM + HFD + CKD swine. In conclusion, loss of NO bioavailability due to 5 months exposure to multiple comorbidities is partially compensated by increased H2O2-mediated coronary vasodilation.

Mesenchymal stromal cells for improvement of cardiac function following acute myocardial infarction: a matter of timing

Acute myocardial infarction (AMI) is the leading cause of cardiovascular death and remains the most common cause of heart failure. Reopening of the occluded artery, i.e., reperfusion, is the only way to save the myocardium. However, the expected benefits of reducing infarct size are disappointing due to the reperfusion paradox, which also induces specific cell death. These ischemia-reperfusion (I/R) lesions can account for up to 50% of final infarct size, a major determinant for both mortality and the risk of heart failure (morbidity). In this review, we provide a detailed description of the cell death and inflammation mechanisms as features of I/R injury and cardioprotective strategies such as ischemic postconditioning as well as their underlying mechanisms. Due to their biological properties, the use of mesenchymal stromal/stem cells (MSCs) has been considered a potential therapeutic approach in AMI. Despite promising results and evidence of safety in preclinical studies using MSCs, the effects reported in clinical trials are not conclusive and even inconsistent. These discrepancies were attributed to many parameters such as donor age, in vitro culture, and storage time as well as injection time window after AMI, which alter MSC therapeutic properties. In the context of AMI, future directions will be to generate MSCs with enhanced properties to limit cell death in myocardial tissue and thereby reduce infarct size and improve the healing phase to increase postinfarct myocardial performance.

Aging-induced mitochondrial dysfunction: two distinct populations of mitochondria versus a combined population

Mitochondrial function in aged hearts is impaired, and studies of isolated mitochondria are commonly used to assess their function. The two populations of cardiac mitochondria, subsarcolemmal mitochondria (SSM) and interfibrillar mitochondria (IFM), are affected by aging. However, the yield of these mitochondria, particularly SSM, is limited in the mouse heart because of the smaller heart size. To address this issue, the authors developed a method to isolate a mixed population (MIX) of SSM and IFM mitochondria from a single mouse heart. The aim of the study was to compare the mitochondrial function between SSM, IFM, and the MIX population from young and aged mouse hearts. The MIX population had a higher yield of total protein and citrate synthase activity from both young and aged hearts compared with the individual yields of SSM or IFM. Oxidative phosphorylation (OXPHOS) decreased in aged SSM and IFM compared with young SSM and IFM, as well as in the MIX population isolated from aged hearts compared with young hearts, when using complex I or IV substrates. Furthermore, aging barely affected the sensitivity to mitochondrial permeability transition pore (MPTP) opening in SSM, whereas the sensitivity was increased in IFM isolated from aged hearts and in the MIX population from aged hearts compared with the corresponding populations isolated from young hearts. These results suggest that mitochondrial dysfunction exists in aged hearts and the isolation of a MIX population of mitochondria from the mouse heart is a potential approach to studying mitochondrial function in the mouse heart.NEW & NOTEWORTHY We developed two methods to isolate mitochondria from a single mouse heart. We compared mitochondrial function in young and aged mice using mitochondria isolated with different methods. Both methods can be successfully used to isolate cardiac mitochondria from single mouse hearts. Our results provide the flexibility to isolate mitochondria from a single mouse heart based on the purpose of the study.

Cardiomyocyte-specific deletion of endothelin receptor A (ETA) obliterates cardiac aging through regulation of mitophagy and ferroptosis

Advanced aging evokes unfavorable changes in the heart including cardiac remodeling and contractile dysfunction although the underlying mechanism remains elusive. This study was conducted to evaluate the role of endothelin-1 (ET-1) in the pathogenesis of cardiac aging and mechanism involved. Echocardiographic and cardiomyocyte mechanical properties were determined in young (5-6 mo) and aged (26-28 mo) wild-type (WT) and cardiomyocyte-specific ETA receptor knockout (ETAKO) mice. GSEA enrichment identified differentially expressed genes associated with mitochondrial respiration, mitochondrial protein processing and mitochondrial depolarization in cardiac aging. Aging elevated plasma levels of ET-1, Ang II and suppressed serum Fe2+, evoked cardiac remodeling (hypertrophy and interstitial fibrosis), contractile defects (fractional shortening, ejection fraction, cardiomyocyte peak shortening, maximal velocity of shortening/relengthening and prolonged relengthening) and intracellular Ca2+ mishandling (dampened intracellular Ca2+ release and prolonged decay), the effects with the exception of plasma AngII, ET-1 and Fe2+ were mitigated by ETAKO. Advanced age facilitated O2- production, carbonyl protein damage, cardiac hypertrophy (GATA4, ANP, NFATc3), ER stress, ferroptosis, compromised autophagy (LC3B, Beclin-1, Atg7, Atg5 and p62) and mitophagy (parkin and FUNDC1), and deranged intracellular Ca2+ proteins (SERCA2a and phospholamban), the effects of which were reversed by ETA ablation. ET-1 provoked ferroptosis in vitro, the response was nullified by the ETA receptor antagonist BQ123 and mitophagy inducer CsA. ETA but not ETB receptor antagonism reconciled cardiac aging, which was abrogated by inhibition of mitophagy and ferroptosis. These findings collectively denote promises of targeting ETA, mitophagy and ferroptosis in the management of aging-associated cardiac remodeling and contractile defect.

Targeting mitochondrial shape: at the heart of cardioprotection

There remains an unmet need to identify novel therapeutic strategies capable of protecting the myocardium against the detrimental effects of acute ischemia-reperfusion injury (IRI), to reduce myocardial infarct (MI) size and prevent the onset of heart failure (HF) following acute myocardial infarction (AMI). In this regard, perturbations in mitochondrial morphology with an imbalance in mitochondrial fusion and fission can disrupt mitochondrial metabolism, calcium homeostasis, and reactive oxygen species production, factors which are all known to be critical determinants of cardiomyocyte death following acute myocardial IRI. As such, therapeutic approaches directed at preserving the morphology and functionality of mitochondria may provide an important strategy for cardioprotection. In this article, we provide an overview of the alterations in mitochondrial morphology which occur in response to acute myocardial IRI, and highlight the emerging therapeutic strategies for targeting mitochondrial shape to preserve mitochondrial function which have the future therapeutic potential to improve health outcomes in patients presenting with AMI.

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.

Effects of resveratrol on tolerance to ischemia/reperfusion injury in aged male mice: Role of autophagy and apoptosis

Aged myocardium is more susceptible to ischemia/reperfusion (I/R) injury. Autophagy and apoptosis play important roles in cardiac I/R injury. However, whether resveratrol can reduce the I/R vulnerability of aged myocardium by regulating apoptosis and autophagy remains unclear. The present study aimed to investigate the effect of resveratrol on the tolerance to I/R injury in aged male mice and to determine the contribution of apoptosis and autophagy. We used aged C57 mice as our research subjects. The hearts of mice were isolated after 6 weeks of intragastric administration with resveratrol and subsequently perfused with Krebs-Henseleit buffer to produce the I/R model. We found that resveratrol alleviated cardiac I/R injury in aged mice, but not in SIRT1+/- mice. Aged mice exhibited decreased LC3 and Beclin1 expressions, which were significantly rescued by resveratrol treatment. In addition, resveratrol decreased the expression of Bax and the activity of Caspase-3, while increasing the expression of Bcl-2 and the activity of SIRT1 in aged mouse hearts. Coimmunoprecipitation assays revealed that resveratrol facilitated the binding of Bax to Bcl-2 and the dissociation of Bcl-2 from Beclin1 in aged mouse myocardium. Conversely, SIRT1 knockout enhanced the formation of the Beclin1/Bcl-2 complex and disrupted the interaction between Bcl-2 and Bax. The above results indicate that resveratrol can reduce the vulnerability of myocardial I/R injury in senile myocardium by inhibiting apoptosis and upregulating autophagy through the SIRT1 signaling pathway.

Post-acute sequelae of COVID-19 in older persons: multi-organ complications and mortality

INTRODUCTION

Evidence on long-term associations between coronavirus disease 2019 (COVID-19) and risks of multi-organ complications and mortality in older population is limited. This study evaluates these associations.

RESEARCH DESIGN AND METHODS

The cohorts included patients aged ≥60 year diagnosed with COVID-19 infection (cases), between 16 March 2020 and 31 May 2021 from the UK Biobank; and between 01 April 2020 and 31 May 2022 from the electronic health records in Hong Kong. Each patient was randomly matched with individuals without COVID-19 infection based on year of birth and sex and were followed for up to 18 months until 31 August 2021 for UKB, and up to 28 months until 15 August 2022 for HK cohort. Patients with COVID-19 infection over 6 months after the date of last dose of vaccination and their corresponding controls were excluded from our study. Characteristics between cohorts were further adjusted with Inverse Probability Treatment Weighting. For evaluating long-term association of COVID-19 with multi-organ disease complications and mortality after 21-days of diagnosis, Cox regression was employed.

RESULT

10,759 (UKB) and 165,259 (HK) older adults with COVID-19 infection with matched 291,077 (UKB) and 1,100,394 (HK) non-COVID-19-diagnosed older adults were recruited. Older adults with COVID-19 were associated with a significantly higher risk of cardiovascular outcomes [major cardiovascular disease (stroke, heart failure and coronary heart disease): hazard ratio(UKB): 1.4 (95% Confidence interval: 1.1,1.6), HK:1.2 (95% CI: 1.1,1.3)]; myocardial infarction: HR(UKB): 1.8 (95% CI: 1.3,2.4), HK:1.2 (95% CI: 1.0,1.4)]; respiratory outcomes [interstitial lung disease: HR(UKB: 3.4 (95% CI: 2.5,4.5), HK: 4.0 (95% CI: 1.3,12.8); chronic pulmonary disease: HR(UKB): 1.7 (95% CI: 1.3,2.2), HK:1.6 (95% CI: 1.3,2.1)]; neuropsychiatric outcomes [seizure: HR(UKB): 2.6 (95% CI: 1.7,4.1), HK: 1.6 (95% CI: 1.2,2.1)]; and renal outcomes [acute kidney disease: HR(UKB): 1.4 (95% CI: 1.1,1.6), HK:1.6 (95% CI: 1.3,2.1)]; and all-cause mortality [HR(UKB): 4.9 (95% CI: 4.4,5.4), HK:2.5 (95% CI: 2.5,2.6)].

CONCLUSION

COVID-19 is associated with long-term risks of multi-organ complications in older adults (aged ≥ 60). Infected patients in this age-group may benefit from appropriate monitoring of signs/symptoms for developing these complications.

No robust reduction of infarct size and no-reflow by metoprolol pretreatment in adult Göttingen minipigs

Whereas prior experiments in juvenile pigs had reported infarct size reduction by intravenous metoprolol early during myocardial ischaemia, two major clinical trials in patients with reperfused acute myocardial infarction were equivocal. We, therefore, went back and tested the translational robustness of infarct size reduction by metoprolol in minipigs. Using a power analysis-based prospective design, we pretreated 20 anaesthetised adult Göttingen minipigs with 1 mg kg-1 metoprolol or placebo and subjected them to 60-min coronary occlusion and 180-min reperfusion. Primary endpoint was infarct size (triphenyl tetrazolium chloride staining) as a fraction of area at risk; no-reflow area (thioflavin-S staining) was a secondary endpoint. There was no significant reduction in infarct size (46 ± 8% of area at risk with metoprolol vs. 42 ± 8% with placebo) or area of no-reflow (19 ± 21% of infarct size with metoprolol vs. 15 ± 23% with placebo). However, the inverse relationship between infarct size and ischaemic regional myocardial blood flow was modestly, but significantly shifted downwards with metoprolol, whereas ischaemic blood flow tended to be reduced by metoprolol. With an additional dose of 1 mg kg-1 metoprolol after 30-min ischaemia in 4 additional pigs, infarct size was also not reduced (54 ± 9% vs. 46 ± 8% in 3 contemporary placebo, n.s.), and area of no-reflow tended to be increased (59 ± 20% vs. 29 ± 12%, n.s.).Infarct size reduction by metoprolol in pigs is not robust, and this result reflects the equivocal clinical trials. The lack of infarct size reduction may be the result of opposite effects of reduced infarct size at any given blood flow and reduced blood flow, possibly through unopposed alpha-adrenergic coronary vasoconstriction.

Microvascular Leakage as Therapeutic Target for Ischemia and Reperfusion Injury

Reperfusion injury is a very common complication of various indicated therapies such as the re-opening of vessels in the myocardium or brain as well as reflow in hemodynamic shutdown (cardiac arrest, severe trauma, aortic cross-clamping). The treatment and prevention of reperfusion injury has therefore been a topic of immense interest in terms of mechanistic understanding, the exploration of interventions in animal models and in the clinical setting in major prospective studies. While a wealth of encouraging results has been obtained in the lab, the translation into clinical success has met with mixed outcomes at best. Considering the still very high medical need, progress continues to be urgently needed. Multi-target approaches rationally linking interference with pathophysiological pathways as well as a renewed focus on aspects of microvascular dysfunction, especially on the role of microvascular leakage, are likely to provide new insights.

Sexual dimorphism in bidirectional SR-mitochondria crosstalk in ventricular cardiomyocytes

Calcium transfer into the mitochondrial matrix during sarcoplasmic reticulum (SR) Ca2+ release is essential to boost energy production in ventricular cardiomyocytes (VCMs) and match increased metabolic demand. Mitochondria from female hearts exhibit lower mito-[Ca2+] and produce less reactive oxygen species (ROS) compared to males, without change in respiration capacity. We hypothesized that in female VCMs, more efficient electron transport chain (ETC) organization into supercomplexes offsets the deficit in mito-Ca2+ accumulation, thereby reducing ROS production and stress-induced intracellular Ca2+ mishandling. Experiments using mitochondria-targeted biosensors confirmed lower mito-ROS and mito-[Ca2+] in female rat VCMs challenged with β-adrenergic agonist isoproterenol compared to males. Biochemical studies revealed decreased mitochondria Ca2+ uniporter expression and increased supercomplex assembly in rat and human female ventricular tissues vs male. Importantly, western blot analysis showed higher expression levels of COX7RP, an estrogen-dependent supercomplex assembly factor in female heart tissues vs males. Furthermore, COX7RP was decreased in hearts from aged and ovariectomized female rats. COX7RP overexpression in male VCMs increased mitochondrial supercomplexes, reduced mito-ROS and spontaneous SR Ca2+ release in response to ISO. Conversely, shRNA-mediated knockdown of COX7RP in female VCMs reduced supercomplexes and increased mito-ROS, promoting intracellular Ca2+ mishandling. Compared to males, mitochondria in female VCMs exhibit higher ETC subunit incorporation into supercomplexes, supporting more efficient electron transport. Such organization coupled to lower levels of mito-[Ca2+] limits mito-ROS under stress conditions and lowers propensity to pro-arrhythmic spontaneous SR Ca2+ release. We conclude that sexual dimorphism in mito-Ca2+ handling and ETC organization may contribute to cardioprotection in healthy premenopausal females.

Remote ischemic preconditioning and clinical outcomes after pediatric cardiac surgery: a systematic review and meta-analysis

BACKGROUND

The benefit of remote ischemia preconditioning (RIPreC) in pediatric cardiac surgery is unclear. The objective of this systematic review and meta-analysis was to examine the effectiveness of RIPreC in reducing the duration of mechanical ventilation and intensive care unit (ICU) length of stay after pediatric cardiac surgery.

METHODS

We searched PubMed, EMBASE and the Cochrane Library from inception to December 31, 2022. Randomized controlled trials comparing RIPreC versus control in children undergoing cardiac surgery were included. The risk of bias of included studies was assessed using the Risk of Bias 2 (RoB 2) tool. The outcomes of interest were postoperative duration of mechanical ventilation and ICU length of stay. We conducted random-effects meta-analysis to calculate weighted mean difference (WMD) with 95% confidence interval (CI) for the outcomes of interest. We performed sensitivity analysis to examine the influence of intraoperative propofol use.

RESULTS

Thirteen trials enrolling 1,352 children were included. Meta-analyses of all trials showed that RIPreC did not reduce postoperative duration of mechanical ventilation (WMD -5.35 h, 95% CI -12.12-1.42) but reduced postoperative ICU length of stay (WMD -11.48 h, 95% CI -20.96- -2.01). When only trials using propofol-free anesthesia were included, both mechanical ventilation duration (WMD -2.16 h, 95% CI -3.87- -0.45) and ICU length of stay (WMD -7.41 h, 95% CI -14.77- -0.05) were reduced by RIPreC. The overall quality of evidence was moderate to low.

CONCLUSIONS

The effects of RIPreC on clinical outcomes after pediatric cardiac surgery were inconsistent, but both postoperative mechanical ventilation duration and ICU length of stay were reduced in the subgroup of children not exposed to propofol. These results suggested a possible interaction effect of propofol. More studies with adequate sample size and without intraoperative propofol use are needed to define the role of RIPreC in pediatric cardiac surgery.

Therapeutic or lifelong training effects on pancreatic morphological and functional parameters in an animal model of aging and obesity

AIMS

Obesity, aging, and physical training are factors influencing pancreatic functional and morphological parameters. Aiming to clarify the impact of the interaction of these factors, we analyzed the effect of therapeutic or lifelong physical training on body adiposity and pancreatic functional and morphological parameters of aged and obese rats.

METHODS

24 male Wistar rats were (initial age = 4 months and final age = 14 months) randomly divided into three aged and obese experimental groups (n = 8/group): untrained, therapeutic trained, and lifelong trained. Body adiposity, plasmatic concentration and pancreatic immunostaining of insulin, markers of tissue inflammation, lipid peroxidation, activity and immunostaining of antioxidant enzymes, and parameters of pancreatic morphology were evaluated.

RESULTS

Lifelong physical training improved the body adiposity, plasmatic insulin concentration, and macrophage immunostaining in the pancreas. The animals submitted to therapeutic and lifelong training showed an increase in the density of the pancreatic islets; lower insulin, Nuclear Factor Kappa B (NF-κB), and Transforming Growth Factor beta (TGF-β) immunostaining in the pancreatic parenchyma, as well as lower pancreatic tissue lipid peroxidation, lower fibrosis area, increased catalase and glutathione peroxidase (GPx) activity and increased heme oxygenase-1 (HO-1) immunostaining, with the greatest effect in the lifelong training group.

CONCLUSION

Lifelong training promoted greater beneficial effects on the pancreatic functional and morphological parameters of aged and obese animals compared to therapeutic exercise.

Mechanisms of MCL-1 Protein Stability Induced by MCL-1 Antagonists in B-Cell Malignancies

PURPOSE

Several MCL-1 inhibitors (MCL-1i), including AMG-176 and AZD5991, have shown promise in preclinical studies and are being tested for the treatment of hematologic malignancies. A unique feature of these agents is induction and stability of Mcl-1 protein; however, the precise mechanism is unknown. We aim to study the mechanism of MCL-1i-induced Mcl-1 protein stability.

EXPERIMENTAL DESIGN

Using several B-cell leukemia and lymphoma cell lines and primary chronic lymphocytic leukemia (CLL) lymphocytes, we evaluated molecular events associated with Mcl-1 protein stability including protein half-life, reverse-phase protein array, protein-protein interaction, phosphorylation, ubiquitination, and de-ubiquitination, followed by molecular simulation and modeling.

RESULTS

Using both in vivo and in vitro analysis, we demonstrate that MCL-1i-induced Mcl-1 protein stability is predominantly associated with defective Mcl-1 ubiquitination and concurrent apoptosis induction in both cell lines and primary CLL subjects. These MCL1i also induced ERK-mediated Mcl-1Thr163 phosphorylation, which partially contributed to Mcl-1 stability. Disruption of Mcl-1:Noxa interaction followed by Noxa degradation, enhanced Mcl-1 de-ubiquitination by USP9x, and Mule destabilization are the major effects of these inhibitors. However, unlike other BH3 proteins, Mule:Mcl-1 interaction was unaffected by MCL-1i. WP1130, a global deubiquitinase (DUB) inhibitor, abrogated Mcl-1 induction reaffirming a critical role of DUBs in the observed Mcl-1 protein stability. Further, in vitro ubiquitination studies of Mcl-1 showed distinct difference among these inhibitors.

CONCLUSIONS

We conclude that MCL-1i blocked Mcl-1 ubiquitination via enhanced de-ubiquitination and dissociation of Mcl-1 from Noxa, Bak and Bax, and Mule de-stabilization. These are critical events associated with increased Mcl-1 protein stability with AMG-176 and AZD5991.

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.

Review of Postoperative Care for Heart Transplant Recipients

The early postoperative management strategies after heart transplantation include optimizing the function of the denervated heart, correcting the causes of hemodynamic instability, and initiating and maintaining immunosuppressive therapy, allograft rejection surveillance, and prophylaxis against infections caused by immunosuppression. The course of postoperative support is influenced by the quality of allograft myocardial protection prior to implantation and reperfusion, donor-recipient heart size matching, surgical technique of orthotopic heart transplantation, and patient factors (eg, preoperative condition, immunologic compatibility, postoperative vasomotor tone, severity and reversibility of pulmonary vascular hypertension, pulmonary function, mediastinal blood loss, and end-organ perfusion). This review provides an overview of the early postoperative care of recipients and includes a brief description of the surgical techniques for orthotopic heart transplantation.

Protective effects of curcumin on ischemia/reperfusion injury

Ischemia/reperfusion (I/R) injury is a term used to describe phenomena connected to the dysfunction of various tissue damage due to reperfusion after ischemic injury. While I/R may result in systemic inflammatory response syndrome or multiple organ dysfunction syndrome, there is still a long way to improve therapeutic outcomes. A number of cellular metabolic and ultrastructural alterations occur by prolonged ischemia. Ischemia increases the expression of proinflammatory gene products and bioactive substances within the endothelium, such as cytokines, leukocytes, and adhesion molecules, even as suppressing the expression of other "protective" gene products and substances, such as thrombomodulin and constitutive nitric oxide synthase (e.g., prostacyclin, nitric oxide [NO]). Curcumin is the primary phenolic pigment derived from turmeric, the powdered rhizome of Curcuma longa. Numerous studies have shown that curcumin has strong antiinflammatory and antioxidant characteristics. It also prevents lipid peroxidation and scavenges free radicals like superoxide anion, singlet oxygen, NO, and hydroxyl. In our study, we highlight the mechanisms of protective effects of curcumin against I/R injury in various organs.

Preclinical multi-target strategies for myocardial ischemia-reperfusion injury

Despite promising breakthroughs in diagnosing and treating acute coronary syndromes, cardiovascular disease’s high global mortality rate remains indisputable. Nearly half of these patients died of ischemic heart disease. Primary percutaneous coronary intervention (PCI) and coronary artery bypass grafting can rapidly restore interrupted blood flow and become the most effective method for salvaging viable myocardium. However, restoring blood flow could increase the risk of other complications and myocardial cell death attributed to myocardial ischemia-reperfusion injury (IRI). How to reduce the damage of blood reperfusion to ischemic myocardium has become an urgent problem to be solved. In preclinical experiments, many treatments have substantial cardioprotective effects against myocardial IRI. However, the transition from these cardioprotective therapies to clinically beneficial therapies for patients with acute myocardial infarction remains elusive. The reasons for the failure of the clinical translation may be multi-faceted, and three points are summarized here: (1) Our understanding of the complex pathophysiological mechanisms of myocardial IRI is far from enough, and the classification of specific therapeutic targets is not rigorous, and not clear enough; (2) Most of the clinical patients have comorbidities, and single cardioprotective strategies including ischemia regulation strategies cannot exert their due cardioprotective effects under conditions of hyperglycemia, hypertension, hyperlipidemia, and aging; (3) Most preclinical experimental results are based on adult, healthy animal models. However, most clinical patients had comorbidities and received multiple drug treatments before reperfusion therapy. In 2019, COST Action proposed a multi-target drug combination initiative for prospective myocardial IRI; the optimal cardioprotective strategy may be a combination of additive or synergistic multi-target therapy, which we support. By establishing more reasonable preclinical models, screening multi-target drug combinations more in line with clinical practice will benefit the translation of clinical treatment strategies.

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

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

Primary Graft Dysfunction: The Role of Aging in Lung Ischemia-Reperfusion Injury

Transplant centers around the world have been using extended criteria donors to remedy the ongoing demand for lung transplantation. With a rapidly aging population, older donors are increasingly considered. Donor age, at the same time has been linked to higher rates of lung ischemia reperfusion injury (IRI). This process of acute, sterile inflammation occurring upon reperfusion is a key driver of primary graft dysfunction (PGD) leading to inferior short- and long-term survival. Understanding and improving the condition of older lungs is thus critical to optimize outcomes. Notably, ex vivo lung perfusion (EVLP) seems to have the potential of reconditioning ischemic lungs through ex-vivo perfusing and ventilation. Here, we aim to delineate mechanisms driving lung IRI and review both experimental and clinical data on the effects of aging in augmenting the consequences of IRI and PGD in lung transplantation.

Aging, sex and NLRP3 inflammasome in cardiac ischaemic disease

Experimentally, many strong cardioprotective treatments have been identified in different animal models of acute ischaemia/reperfusion injury (IRI) and coronary artery disease (CAD). However, the translation of these cardioprotective therapies for the benefit of the patients into the clinical scenario has been very disappointing. The reasons for this lack are certainly multiple. Indeed, many confounding factors we must deal in clinical reality, such as aging, sex and inflammatory processes are neglected in many experiments. Due to the pivotal role of aging, sex and inflammation in determining cardiac ischaemic disease, in this review, we take into account age as a modifier of tolerance to IRI in the two sexes, dissecting aging and myocardial reperfusion injury mechanisms and the sex differences in tolerance to IRI. Then we focus on the role of the gut microbiota and the NLRP3 inflammasome in myocardial IRI and on the possibility to consider NLRP3 inflammasome as a potential target in the treatment of CAD in relationship with age and sex. Finally, we consider the cardioprotective mechanisms and cardioprotective treatments during aging in the two sexes.

Nanocarrier-Based Targeted Therapies for Myocardial Infarction

Myocardial infarction is a major cause of morbidity and mortality worldwide. Due to poor inherent regeneration of the adult mammalian myocardium and challenges with effective drug delivery, there has been little progress in regenerative therapies. Nanocarriers, including liposomes, nanoparticles, and exosomes, offer many potential advantages for the therapy of myocardial infarction, including improved delivery, retention, and prolonged activity of therapeutics. However, there are many challenges that have prevented the widespread clinical use of these technologies. This review aims to summarize significant principles and developments in the field, with a focus on nanocarriers using ligand-based or cell mimicry-based targeting. Lastly, a discussion of limitations and potential future direction is provided.

No sex-related differences in infarct size, no-reflow and protection by ischaemic preconditioning in Göttingen minipigs

Aims

Female sex has been proposed to be cardioprotective per se. Studies with myocardial ischaemia/reperfusion and infarct size as endpoint have demonstrated cardioprotection in female, castrated male and male pigs. These studies are difficult to compare, given the different pig strains, models, durations of ischaemia and methods of infarct size quantification. The few studies using both female and male pigs reported no differences in infarct size and cardioprotection. We therefore prospectively compared infarct size in Göttingen minipigs undergoing ischaemia/reperfusion (I/R) without and with ischaemic preconditioning (IPC) between female, castrated male and male pigs.

Methods and Results

In a prospective, randomised approach, 28 Göttingen open-chest, anaesthetised minipigs underwent 60 min ischaemia by distal left anterior descending artery (LAD) occlusion and 180 min reperfusion without and with IPC by 3 cycles of 5 min LAD occlusion/10 min reperfusion. Infarct size with I/R was not different between female, castrated male and male pigs (45±8 vs. 45±13 vs. 41±9% area at risk), as was the reduction in infarct size with IPC (25±11 vs. 30±8 vs. 19±10% area at risk). Also, the area of no-reflow was not different between female, castrated male and male pigs with I/R (57±13 vs. 35±7 vs. 47±26% infarct size) or IPC (4±10 vs.12±20 vs. 0±0% infarct size). Phosphorylation of signal transducer and activator of transcription 3 was increased at 10 min reperfusion by IPC but not by I/R to the same extent in female, castrated male and male pigs (198±30 vs. 230±165 vs. 179±107% of baseline).

Conclusion

Our data do not support the notion of sex- or castration-related differences in infarct size, coronary microvascular injury and cardioprotection by ischaemic preconditioning.

Translational perspective

The translation of successful preclinical studies on cardioprotection to the benefit of patients with reperfused myocardial infarction has been difficult. The difficulties have been attributed to confounders such as co-morbidities and co-medications which patients typically have but animals don´t, but also to age and sex. Notably, female sex has been considered as protective per se. We have now, using our established and clinically relevant pig model of reperfused acute myocardial infarction and ischaemic preconditioning as the most robust cardioprotective intervention looked for sex-related differences of infarct size, no-reflow and cardioprotection by ischaemic preconditioning in a prospectively powered approach but found none such difference.

Network-Assisted Systems Biology Analysis of the Mitochondrial Proteome in a Pre-Clinical Model of Ischemia, Revascularization and Post-Conditioning

Infarct size is the major risk predictor for developing heart failure after an acute myocardial infarction (AMI). The discovery of the conditioning phenomena (i.e., repetitive brief cycles of ischemia applied either before or after a prolonged ischemic insult) has highlighted the existence of endogenous protective mechanisms of the heart potentially limiting infarct size after revascularization. However, most cardioprotective strategies, aiming at infarct size reduction, have failed in clinical studies. Thus, cardioprotection is an unmet clinical need. In the present study, we took a network-assisted systems biology approach to explore the mitochondrial proteomic signature of the myocardium after ischemia, ischemia with direct revascularization, and ischemia with re-establishment of blood flow by post-conditioning in a swine model of AMI. Furthermore, network extension with the ENCODE project human regulatory data allowed the prediction of potential transcription factors at play in the response to post-conditioning of the myocardium. Collectively, our results identify cardiac metabolism as a driver of cardioprotection, highlighting a dual role for post-conditioning promoting metabolic reprogramming of the myocardium, and a protective response mediated by VDAC2 and DJ-1 in the mitochondria.

Targeting IL-36 improves age-related coronary microcirculatory dysfunction and attenuates myocardial ischaemia-reperfusion injury in mice

Following myocardial infarction (MI), elderly patients have a poorer prognosis than younger patients, which may be linked to increased coronary microvessel susceptibility to injury. Interleukin-36 (IL-36), a newly discovered proinflammatory member of the IL-1 superfamily, may mediate this injury, but its role in the injured heart is currently not known. We first demonstrated the presence of IL-36(α/β) and its receptor (IL-36R) in ischemia/reperfusion-injured (IR-injured) mouse hearts and, interestingly, noted that expression of both increased with aging. An intravital model for imaging the adult and aged IR-injured beating heart in real time in vivo was used to demonstrate heightened basal and injury-induced neutrophil recruitment, and poorer blood flow, in the aged coronary microcirculation when compared with adult hearts. An IL-36R antagonist (IL-36Ra) decreased neutrophil recruitment, improved blood flow, and reduced infarct size in both adult and aged mice. This may be mechanistically explained by attenuated endothelial oxidative damage and VCAM-1 expression in IL-36Ra–treated mice. Our findings of an enhanced age-related coronary microcirculatory dysfunction in reperfused hearts may explain the poorer outcomes in elderly patients following MI. Since targeting the IL-36/IL-36R pathway was vasculoprotective in aged hearts, it may potentially be a therapy for treating MI in the elderly population.

Pretreatment with Nicotinamide Mononucleotide Increases the Effect of Ischemic-Postconditioning on Cardioprotection and Mitochondrial Function Following ex vivo Myocardial Reperfusion Injury in Aged Rats

The present study aims to evaluate the combined effect of ischemic-postconditioning (IPostC) and nicotinamide mononucleotide (NMN) on cardioprotection and mitochondrial function in aged rats subjected to myocardial ischemia-reperfusion (IR) injury. Sixty aged Wistar rats were randomly divided into 5 groups (n=12), including sham, control, NMN, IPostC, and NMN+IPostC. Regional ischemia was induced by 30-min occlusion of the left anterior descending coronary artery (LAD) followed by 60-min reperfusion. IPostC was applied at the onset of reperfusion, by 6 cycles of 10-s reperfusion/ischemia. NMN (100 mg/kg) was intraperitoneally injected every other day for 28 days before IR. Myocardial hemodynamics and infarct size (IS) were measured, and the left ventricles samples were harvested to assess cardiac mitochondrial function. The results showed that all treatments reduced lactate dehydrogenase release compared to those of the control group. IPostC alone failed to reduce IS and myocardial function. However, NMN and combined therapy could significantly improve myocardial function and decrease the IS compared to the control animals. Moreover, the effects of combined therapy on the decrease of IS, mitochondrial reactive oxygen species (ROS), and improvement of mitochondrial membrane potential (MMP) were greater than those of alone treatments. These results demonstrated that cardioprotection by combined therapy with NMN+IPostC was superior to individual treatments, and pretreatment of aged rats with NMN was able to correct the failure of IPostC in protecting the hearts of aged rats against IR injury.

Effects of ischaemic postconditioning in aortic valve replacement: a multicenter randomized controlled trial

OBJECTIVES

The effect of ischaemic postconditioning (IPost) on postcardioplegic cardiac function is not known. We hypothesized that IPost was cardioprotective in adult patients undergoing elective aortic valve replacement.

METHODS

In a multicentre, prospective, randomized trial, patients (n = 209) were randomized to either a standard operation (controls) or postconditioning. Immediately before the cross-clamp was released, patients in the postconditioning group underwent 3 cycles of flow/non-flow (2 min each) of normothermic blood via the antegrade cardioplegia line. The primary end point was cardiac index. Secondary end points included additional haemodynamic measurements, biomarkers of cardiomyocyte injury, renal function parameters, intra- and postoperative arrhythmias and use of inotropic agents.

RESULTS

There was no significant difference between the groups regarding cardiac index [mean between-group difference, 95% confidence interval (CI), 0.11 (-0.1 to 0.3), P = 0.27]. Postconditioning had no effect on other haemodynamic parametres. There was no between-group difference regarding troponin T or creatine kinase MB. Postconditioning reduced the relative risk for arrhythmias by 45% (P = 0.03) when postoperative atrial fibrillation and intraoperative ventricular fibrillation were combined. There were no differences in patients with/without diabetes, patients above/below 70 years of age or between the centres. However, after postconditioning, the cardiac index [95% CI, 0.46 (0.2-0.7), P = 0.001], cardiac output (P < 0.001), mean arterial pressure (P < 0.001) and left ventricular stroke work index (P < 0.001) were higher in males compared to females.

CONCLUSIONS

IPost had no overall cardioprotective effects in patients undergoing aortic valve replacement but improved postoperative cardiac performance in men compared to women.

Impact of Maturation on Myocardial Response to Ischemia and the Effectiveness of Remote Preconditioning in Male Rats

Aging attenuates cardiac tolerance to ischemia/reperfusion (I/R) associated with defects in protective cell signaling, however, the onset of this phenotype has not been completely investigated. This study aimed to compare changes in response to I/R and the effects of remote ischemic preconditioning (RIPC) in the hearts of younger adult (3 months) and mature adult (6 months) male Wistar rats, with changes in selected proteins of protective signaling. Langendorff-perfused hearts were exposed to 30 min I/120 min R without or with prior three cycles of RIPC (pressure cuff inflation/deflation on the hind limb). Infarct size (IS), incidence of ventricular arrhythmias and recovery of contractile function (LVDP) served as the end points. In both age groups, left ventricular tissue samples were collected prior to ischemia (baseline) and after I/R, in non-RIPC controls and in RIPC groups to detect selected pro-survival proteins (Western blot). Maturation did not affect post-ischemic recovery of heart function (Left Ventricular Developed Pressure, LVDP), however, it increased IS and arrhythmogenesis accompanied by decreased levels and activity of several pro-survival proteins and by higher levels of pro-apoptotic proteins in the hearts of elder animals. RIPC reduced the occurrence of reperfusion-induced ventricular arrhythmias, IS and contractile dysfunction in younger animals, and this was preserved in the mature adults. RIPC did not increase phosphorylated protein kinase B (p-Akt)/total Akt ratio, endothelial nitric oxide synthase (eNOS) and protein kinase Cε (PKCε) prior to ischemia but only after I/R, while phosphorylated glycogen synthase kinase-3β (GSK3β) was increased (inactivated) before and after ischemia in both age groups coupled with decreased levels of pro-apoptotic markers. We assume that resistance of rat heart to I/R injury starts to already decline during maturation, and that RIPC may represent a clinically relevant cardioprotective intervention in the elder population.

Hypoxia Inducible Factors as Central Players in the Pathogenesis and Pathophysiology of Cardiovascular Diseases

Cardiovascular (CV) diseases are the major cause of death in industrialized countries. The main function of the CV system is to deliver nutrients and oxygen to all tissues. During most CV pathologies, oxygen and nutrient delivery is decreased or completely halted. Several mechanisms, including increased oxygen transport and delivery, as well as increased blood flow are triggered to compensate for the hypoxic state. If the compensatory mechanisms fail to sufficiently correct the hypoxia, irreversible damage can occur. Thus, hypoxia plays a central role in the pathogenesis and pathophysiology of CV diseases. Hypoxia inducible factors (HIFs) orchestrate the gene transcription for hundreds of proteins involved in erythropoiesis, glucose transport, angiogenesis, glycolytic metabolism, reactive oxygen species (ROS) handling, cell proliferation and survival, among others. The overall regulation of the expression of HIF-dependent genes depends on the severity, duration, and location of hypoxia. In the present review, common CV diseases were selected to illustrate that HIFs, and proteins derived directly or indirectly from their stabilization and activation, are related to the development and perpetuation of hypoxia in these pathologies. We further classify CV diseases into acute and chronic hypoxic states to better understand the temporal relevance of HIFs in the pathogenesis, disease progression and clinical outcomes of these diseases. We conclude that HIFs and their derived factors are fundamental in the genesis and progression of CV diseases. Understanding these mechanisms will lead to more effective treatment strategies leading to reduced morbidity and mortality.

Effects of Aging on Cardiac Oxidative Stress and Transcriptional Changes in Pathways of Reactive Oxygen Species Generation and Clearance

Background Age-related heart diseases are significant contributors to increased morbidity and mortality. Emerging evidence indicates that mitochondria within cardiomyocytes contribute to age-related increased reactive oxygen species (ROS) generation that plays an essential role in aging-associated cardiac diseases. Methods and Results The present study investigated differences between ROS production in cardiomyocytes isolated from adult (6 months) and aged (24 months) Fischer 344 rats, and in cardiac tissue of adult (18-65 years) and elderly (>65 years) patients with preserved cardiac function. Superoxide dismutase inhibitable ferricytochrome c reduction assay (1.32±0.63 versus 0.76±0.31 nMol/mg per minute; P=0.001) superoxide and H2O2 production, measured as dichlorofluorescein diacetate fluorescence (1646±428 versus 699±329, P=0.04), were significantly higher in the aged versus adult cardiomyocytes. Similarity in age-related alteration between rats and humans was identified in mitochondrial-electron transport chain-complex-I-associated increased oxidative-stress by MitoSOX fluorescence (53.66±18.58 versus 22.81±12.60; P=0.03) and in 4-HNE adduct levels (187.54±54.8 versus 47.83±16.7 ng/mg protein, P=0.0063), indicative of increased peroxidation in the elderly. These differences correlated with changes in functional enrichment of genes regulating ROS homeostasis pathways in aged human and rat hearts. Functional merged collective network and pathway enrichment analysis revealed common genes prioritized in human and rat aging-associated networks that underlay enriched functional terms of mitochondrial complex I and common pathways in the aging human and rat heart. Conclusions Aging sensitizes mitochondrial and extramitochondrial mechanisms of ROS buildup within the heart. Network analysis of the transcriptome highlights the critical elements involved with aging-related ROS homeostasis pathways common in rat and human hearts as targets.

Preconditioning of mesenchymal stem cells with ghrelin exerts superior cardioprotection in aged heart through boosting mitochondrial function and autophagy flux

Application of mesenchymal stem cells (MSCs) is considered as a promising cell-based therapy to induce cardioprotection against ischemia-reperfusion (IR) injury. Preconditioning of MSCs is the key strategy to improve MSCs functions in vitro and their efficacy in vivo, especially in elderly subjects in whom cardioprotection is lost. This study investigated the effects of preconditioning of human umbilical cord-derived MSCs with ghrelin and their combination with nicotinamide-mononucleotide (NMN) on cardioprotection, and the role of autophagy flux and mitochondrial function in aged hearts subjected to IR injury. Aged Sprague Dawley rats (20-22 months old) were subjected to LAD occlusion-induced myocardial IR injury and treated with ghrelin-preconditioned or unconditioned-MSCs at early reperfusion. NMN (500 mg/kg, i.p) was also administered at early reperfusion and repeated 12 h later. Intra-myocardial injection of ghrelin-preconditioned MSCs reduced infarct size and cardiotroponin release of aged myocardium, and improved cardiac function following IR injury. MSCs preconditioning with ghrelin restored IR-induced mitochondrial reactive oxygen species and membrane potential depolarization and enhanced ATP production. To reveal possible mechanism, preconditioned-MSCs increased autophagy flux by downregulating the overexpression of Beclin-1 and P62 proteins and increasing the LC3-II expression and LC3-II/LC3-I ratio. Moreover, combining NMN to ghrelin-preconditioned MSCs synergistically augmented its protective effects on infarct size and mitochondrial function. All above effects were abolished by autophagy flux inhibitor, chloroquine. Thus, ghrelin may serve as a promising candidate to improve the cardioprotective efficacy of MSC-based therapy via autophagy/mitochondrial pathway and that NMN serves as a good booster in combination therapy in aged hearts.

Myocardial remote ischemic preconditioning: from cell biology to clinical application

Remote ischemic preconditioning (rIPC) is a cardioprotective phenomenon where brief periods of ischemia followed by reperfusion of one organ/tissue can confer subsequent protection against ischemia/reperfusion injury in other organs, such as the heart. It involves activation of humoral, neural or systemic communication pathways inducing different intracellular signals in the heart. The main purpose of this review is to summarize the possible mechanisms involved in the rIPC cardioprotection, and to describe recent clinical trials to establish the efficacy of these strategies in cardioprotection from lethal ischemia/reperfusion injury. In this sense, certain factors weaken the subcellular mechanisms of rIPC in patients, such as age, comorbidities, medication, and anesthetic protocol, which could explain the heterogeneity of results in some clinical trials. For these reasons, further studies, carefully designed, are necessary to develop a clearer understanding of the pathways and mechanism of early and late rIPC. An understanding of the pathways is important for translation to patients.

The Effect of Increasing Donor Age on Myocardial Ischemic Tolerance in a Rodent Model of Donation After Circulatory Death

Hearts from older donors or procured via donation after circulatory death (DCD) can alleviate transplant waitlist; however, these hearts are particularly vulnerable to injury caused by warm ischemic times (WITs) inherent to DCD. This study investigates how the combination of increasing donor age and pharmacologic supplementation affects the ischemic tolerance and functional recovery of DCD hearts and how age impacts cardiac mitochondrial respiratory capacity and oxidative phosphorylation.

Influence of strain, age, origin, and anesthesia on the cardioprotective efficacy by local and remote ischemic conditioning in an ex vivo rat model

Background

Local ischemic preconditioning (IPC) and remote ischemic conditioning (RIC) induced by brief periods of ischemia and reperfusion protect against ischemia‐reperfusion injury.

Methods

We studied the sensitivity to IR‐injury and the influence of strain, age, supplier, and anesthesia upon the efficacy of IPC and RIC in 7‐ and 16‐weeks‐old Sprague‐Dawley and Wistar rats from three different suppliers. The influence of sedation with a hypnorm and midazolam mixture (rodent mixture) and pentobarbiturate was compared.

Results

IPC attenuated infarct size in both 7‐weeks‐old Sprague–Dawley (48.4 ± 17.7% vs. 20.3 ± 6.9, p < 0.001) and 7‐weeks‐old Wistar (55.6 ± 10.9% vs. 26.8 ± 5.0%, p < 0.001) rats. Infarct size was larger in 16‐weeks‐old Sprague–Dawley rats, however, IPC still lowered infarct size (78.8 ± 9.2% vs. 58.3 ± 12.3%, p < 0.01). RIC reduced infarct sizes in 7‐weeks‐old Sprague–Dawley (75.3 ± 11.8% vs. 58.6 ± 8.9%, p < 0.05), but not in 7‐weeks‐old Wistar rats (31.7 ± 17.6% and 24.0 ± 12.6%, p = 0.2). In 16‐weeks‐old Sprague–Dawley rats, RIC did not induce protection (76.4 ± 5.5% and 73.2 ± 14.7%, p = 0.6). However, RIC induced protection in 16‐weeks‐old Wistar rats (45.2 ± 8.5% vs. 14.7 ± 10.8%, p < 0.001). RIC did not reduce infarct size in 7‐weeks‐old Sprague–Dawley rats from Charles River (62.0 ± 13.5% and 69.4 ± 10.4% p = 0.3) or 16‐weeks‐old Wistar rats from Janvier (50.7 ± 11.3 and 49.2 ± 16.2, p = 0.8). There was no difference between sedation with rodent mixture or pentobarbiturate.

Conclusion

The cardioprotective effect of IPC is consistent across rat strains independent of age, strain, and supplier. RIC seems to be less reproducible, but still yields protection across different rat strains. However, age, animal supplier, and anesthetics may modulate the sensitivity of IR‐injury and the response to RIC.

Decreasing myocardial estrogen receptors and antioxidant activity may be responsible for increasing ischemia- and reperfusion-induced ventricular arrhythmia in older female rats

AIMS

This study aimed to investigate the relationship between ischemia- and reperfusion-induced arrhythmia and blood serum estrogen levels, myocardial estrogen receptor levels, antioxidant enzyme activities, and the effects of the estrogen receptor blocker, fulvestrant (ICI 182 780).

MAIN METHODS

A total of 102 female Sprague-Dawley rats of different ages (2-3, 6-7, 14-15, and 20-21 months) were used in this study. Myocardial ischemia was produced by ligation of the descending branch of the left anterior descending coronary artery, and reperfusion was produced by releasing this artery. An electrocardiogram (ECG) and blood pressure were recorded for 6 min of ischemia and 6 min of reperfusion. The levels of superoxide dismutase (SOD), malondialdehyde (MDA), catalase (CAT), estrogen receptor α (ERα), and estrogen receptor β (ERβ) in myocardial tissue and 17 beta-estradiol (E2) in blood serum were measured via enzyme-linked immunosorbent assay (ELISA). The results were compared using a Mann-Whitney U test, one-way analysis of variance (ANOVA), and a student's t-test.

KEY FINDINGS

It is not the changes in serum estrogen levels but the decreasing myocardial estrogen receptors and antioxidant activities that could be responsible for the occurrence of more severe arrhythmia in response to reperfusion in older female rats.

SIGNIFICANCE

The death rate due to a heart attack in younger men is higher than in women. However, it equalizes after the menopausal stage in women. In this study, the reason for the increasing sudden post-menopausal death rate in women was investigated experimentally.

Targeting the Endothelium to Achieve Cardioprotection

Despite considerable improvements in the treatment of myocardial infarction, it is still a highly prevalent disease worldwide. Novel therapeutic strategies to limit infarct size are required to protect myocardial function and thus, avoid heart failure progression. Cardioprotection is a research topic with significant achievements in the context of basic science. However, translation of the beneficial effects of protective approaches from bench to bedside has proven difficult. Therefore, there is still an unmet need to study new avenues leading to protecting the myocardium against infarction. In line with this, the endothelium is an essential component of the cardiovascular system with multiple therapeutic targets with cardioprotective potential. Endothelial cells are the most abundant non-myocyte cell type in the heart and are key players in cardiovascular physiology and pathophysiology. These cells can regulate vascular tone, angiogenesis, hemostasis, and inflammation. Accordingly, endothelial dysfunction plays a fundamental role in cardiovascular diseases, which may ultimately lead to myocardial infarction. The endothelium is of paramount importance to protect the myocardium from ischemia/reperfusion injury via conditioning strategies or cardioprotective drugs. This review will provide updated information on the most promising therapeutic agents and protective approaches targeting endothelial cells in the context of myocardial infarction.

Secreted frizzled protein 3 is a novel cardioprotective mechanism unique to the clinically relevant fourth window of ischemic preconditioning

Most studies on ischemic preconditioning (IPC) use one or two ischemic stimuli before examining cardioprotection. To better simulate the clinical situation, we examined, in pigs, the effects of six episodes of 10 min coronary artery occlusion (CAO) 12 h apart, followed by 60 min CAO. We named this model the fourth window of IPC. To determine the novel mechanisms mediating cardioprotection in the fourth window, gene analysis was examined in fourth window IPC cardiac tissue 60 min after the last episode of 10 min CAO. Secreted frizzled-related protein 3 (sFRP3) was the most significantly upregulated gene that was unique to the fourth window, that is, not found in the first, second, or third window IPC. To study the effects of sFRP3 on cardioprotection, sFRP3 was injected in the hearts of wild-type (WT) mice. In the [CAO/coronary artery reperfusion (CAR)] model (30 min CAO followed by 24 h CAR), infarct size was less, P < 0.01, after sFRP3 injection (14% ± 1.7%) compared with vehicle injection (48% ± 1.6%). sFRP3 injection also protected the development of heart failure following permanent CAO for 2 wk. Left ventricular ejection fraction was significantly improved, P < 0.05, at 2 wk after CAO with sFRP3 (53% ± 5%) compared with vehicle (36% ± 2%) and was accompanied by significant, P < 0.01, reductions in myocardial fibrosis (53% ± 4%), myocyte size (17% ± 3%), apoptosis (100%), and mortality (56%). Thus, sFRP3, unique to the clinically relevant fourth window IPC model, is a novel mechanism mediating ischemic cardioprotection.NEW & NOTEWORTHY1) This investigation identifies the novel fourth window of ischemic preconditioning. 2) sFRP3 was identified as the most significantly upregulated gene in the fourth window and was shown to induce cardioprotection when administered to the hearts of wild-type mice.

Effect of ageing and hypertension on the expression and activity of PEPT2 in normal and hypertrophic hearts

Some dipeptides have been implicated in myocardial protection, but little is known about their membrane transporter PEPT2. The aim of this study was to determine whether the expression and activity of the cardiac-type PEPT2 cotransporter could be affected by ageing and/or hypertension. Sarcolemmal vesicles (SV) were isolated from the hearts of all rat groups using a standard procedure to investigate the transport activity and protein abundance by fluorescence spectroscopy and Western blot, respectively. SLC15A2 "PEPT2" gene expression was relatively quantified by RT-qPCR. In the Wistar rat groups, the protein and gene expression of PEPT2 were upregulated with ageing. These changes were accompanied by corresponding increases in the competitive inhibition and the transport rate (V_max) of β-Ala-Lys (AMCA) into SV isolated from middle-aged hearts. Although, the transport rate of β-Ala-Lys (AMCA) into SV isolated from old hearts was significantly the lowest compared to middle-aged and young adult hearts, the inhibition percentage of β-Ala-Lys (AMCA) transport by Gly-Gln was the highest. In the WKY and SHR rat groups, Y-SHR hypertrophied hearts showed an increase in PEPT2 gene expression accompanied by a significant decrease in protein expression and activity. With advanced age, however, M-SHR hypertrophied hearts revealed significantly lower gene expression, but higher protein expression and activity than Y-SHR hearts. These findings suggest that increased expression of PEPT2 cotransporter in all types of middle-aged hearts could be exploited to facilitate di-and tripeptide transport by PEPT2 in these hearts, which subsequently could result in improved myocardial protection in these populations.

Melatonin/Nrf2/NLRP3 Connection in Mouse Heart Mitochondria during Aging

Aging is a major risk for cardiovascular diseases (CVD). Age-related disorders include oxidative stress, mitochondria dysfunction, and exacerbation of the NF-κB/NLRP3 innate immune response pathways. Some of the molecular mechanisms underlying these processes, however, remain unclear. This study tested the hypothesis that NLRP3 inflammasome plays a role in cardiac aging and melatonin is able to counteract its effects. With the aim of investigating the impact of NLRP3 inflammasome and the actions and target of melatonin in aged myocardium, we analyzed the expression of proteins implied in mitochondria dynamics, autophagy, apoptosis, Nrf2-dependent antioxidant response and mitochondria ultrastructure in heart of wild-type and NLRP3-knockout mice of 3, 12, and 24 months-old, with and without melatonin treatment. Our results showed that the absence of NLRP3 prevented age-related mitochondrial dynamic alterations in cardiac muscle with minimal effects in cardiac autophagy during aging. The deficiency of the inflammasome affected Bax/Bcl2 ratio, but not p53 or caspase 9. The Nrf2-antioxidant pathway was also unaffected by the absence of NLRP3. Furthermore, NLRP3-deficiency prevented the drop in autophagy and mice showed less mitochondrial damage than wild-type animals. Interestingly, melatonin treatment recovered mitochondrial dynamics altered by aging and had few effects on cardiac autophagy. Melatonin supplementation also had an anti-apoptotic action in addition to restoring Nrf2-antioxidant capacity and improving mitochondria ultrastructure altered by aging.

Voluntary exercise training attenuated the middle-aged maturity-induced cardiac apoptosis

AIMS

Voluntary exercise training has cardioprotective effects in humans, but the underlying mechanism is unknown. This research was done to estimate the effect of voluntary exercise training to attenuate middle-aged maturity-induced cardiac apoptosis.

MATERIALS AND METHODS

The study was designed to divide 64 male mice randomly into four groups, consisting of a 9-month sedentary pre-middle-aged group (9M), 15-month sedentary middle-aged group (15M), and two exercise groups using a voluntary wheel running respectively (9M+EX, 15M+EX). After 3 months, the condition of cardiac apoptosis in different groups was measured by HE dying, TUNEL and DAPI staining, and Western Blot analysis.

KEY FINDINGS

TUNEL-positive cells were increased in 15M group compared with 9M group, while decreased in 9M+EX and 15M+EX groups compared with their control groups respectively. Protein levels of AIF, Endo G, TNF-α, TNFR1, TRAF2, TRADD, Fas, FasL, FADD, activated caspase 8, 3, 9, Bax/Bcl2, Bak/BclxL, and tBid were decreased in 9M+EX and 15M+EX groups compared with their control groups respectively. The protein levels of pBad/Bad, 14-3-3, IGF1, IGFR1, pPI3K/PI3K, and pAKT/AKT were more activated in the 9M+EX and 15M+EX groups than those in their control groups respectively. Significant differences were found between 9M group and 15M group for the protein levels of TRAF2, FADD, Bax/Bcl2, tBid and pAKT/AKT.

SIGNIFICANCE

Voluntary exercise training as an important lifestyle modification may prevent cardiac widely dispersed apoptosis and enhance cardiac survival at middle-aged maturity.

SIRT1/SIRT3 Modulates Redox Homeostasis during Ischemia/Reperfusion in the Aging Heart

Ischemia/reperfusion (I/R) injury is the central cause of global death in cardiovascular diseases, which is characterized by disorders such as angina, stroke, and peripheral vascular disease, finally causing severe debilitating diseases and death. The increased rates of morbidity and mortality caused by I/R are parallel with aging. Aging-associated cardiac physiological structural and functional deterioration were found to contribute to abnormal reactive oxygen species (ROS) production during I/R stress. Disturbed redox homeostasis could further trigger the related signaling pathways that lead to cardiac irreversible damages with mitochondria dysfunction and cell death. It is notable that sirtuin proteins are impaired in aged hearts and are critical to maintaining redox homeostasis via regulating substrate metabolism and inflammation and thus preserving cardiac function under stress. This review discussed the cellular and functional alterations upon I/R especially in aging hearts. We propose that mitochondria are the primary source of reactive oxygen species (ROS) that contribute to I/R injury in aged hearts. Then, we highlight the cardiomyocyte protection of the age-related proteins Sirtuin1 (SIRT1) and Sirtuin1 (SIRT3) in response to I/R injury, and we discuss their modulation of cardiac metabolism and the inflammatory reaction that is involved in ROS formation.

A review of myocardial ischaemia/reperfusion injury: Pathophysiology, experimental models, biomarkers, genetics and pharmacological treatment

Cardiovascular diseases are known to be the most fatal diseases worldwide. Ischaemia/reperfusion (I/R) injury is at the centre of the pathology of the most common cardiovascular diseases. According to the World Health Organization estimates, ischaemic heart disease is the leading global cause of death, causing more than 9 million deaths in 2016. After cardiovascular events, thrombolysis, percutaneous transluminal coronary angioplasty or coronary bypass surgery are applied as treatment. However, after restoring coronary blood flow, myocardial I/R injury may occur. It is known that this damage occurs due to many pathophysiological mechanisms, especially increasing reactive oxygen types. Besides causing cardiomyocyte death through multiple mechanisms, it may be an important reason for affecting other cell types such as platelets, fibroblasts, endothelial and smooth muscle cells and immune cells. Also, polymorphonuclear leukocytes are associated with myocardial I/R damage during reperfusion. This damage may be insufficient in patients with co-morbidity, as it is demonstrated that it can be prevented by various endogenous antioxidant systems. In this context, the resulting data suggest that optimal cardioprotection may require a combination of additional or synergistic multi-target treatments. In this review, we discussed the pathophysiology, experimental models, biomarkers, treatment and its relationship with genetics in myocardial I/R injury. SIGNIFICANCE OF THE STUDY: This review summarized current information on myocardial ischaemia/reperfusion injury (pathophysiology, experimental models, biomarkers, genetics and pharmacological therapy) for researchers and reveals guiding data for researchers, especially in the field of cardiovascular system and pharmacology.

ALKBH7 mediates necrosis via rewiring of glyoxal metabolism

Alkb homolog 7 (ALKBH7) is a mitochondrial α-ketoglutarate dioxygenase required for DNA alkylation-induced necrosis, but its function and substrates remain unclear. Herein, we show ALKBH7 regulates dialdehyde metabolism, which impacts the cardiac response to ischemia-reperfusion (IR) injury. Using a multi-omics approach, we find no evidence ALKBH7 functions as a prolyl-hydroxylase, but we do find Alkbh7^-/- mice have elevated glyoxalase I (GLO-1), a dialdehyde detoxifying enzyme. Metabolic pathways related to the glycolytic by-product methylglyoxal (MGO) are rewired in Alkbh7^-/- mice, along with elevated levels of MGO protein adducts. Despite greater glycative stress, hearts from Alkbh7^-/- mice are protected against IR injury, in a manner blocked by GLO-1 inhibition. Integrating these observations, we propose ALKBH7 regulates glyoxal metabolism, and that protection against necrosis and cardiac IR injury bought on by ALKBH7 deficiency originates from the signaling response to elevated MGO stress.

Role of hydrogen sulfide in cardiovascular ageing

Cardiovascular diseases are the main cause of morbidity and mortality in the Western society and ageing is a relevant non-modifiable risk factor. Morphological and functional alterations at endothelial level represent first events of ageing, inevitably followed by vascular dysfunction and consequent atherosclerosis that deeply influences cardiovascular health. Indeed, myocardial hypertrophy and fibrosis typically occur and contribute to compromise overall cardiac output. As regards the intracellular molecular mechanisms involved in the cardiovascular ageing, an intricate network is emerging, revealing a role for many mediators, including SIRT1/AMPK/PCG1α pathway, anti-oxidants factors (i.e. Nrf-2 and FOXOs) and pro-inflammatory cytokines. Thus, the search for pharmacological and non-pharmacological strategies that can promote a "healthy ageing", in order to slow down age-related machinery, are currently an exciting challenge for the biomedical research. Interestingly, hydrogen sulfide (H₂S) has been recently recognized as a new player capable to influence intracellular machinery involved in ageing and then it is view as a potential target for preventing cardiovascular diseases. Therefore, this review is focused on the role of H₂S in cardiovascular ageing, and on the evidence of the relationship between progressive decline in endogenous H₂S levels and the onset of various cardiovascular age-related diseases.

COVID-19-associated cardiovascular morbidity in older adults: a position paper from the Italian Society of Cardiovascular Researches

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infects host cells following binding with the cell surface ACE2 receptors, thereby leading to coronavirus disease 2019 (COVID-19). SARS-CoV-2 causes viral pneumonia with additional extrapulmonary manifestations and major complications, including acute myocardial injury, arrhythmia, and shock mainly in elderly patients. Furthermore, patients with existing cardiovascular comorbidities, such as hypertension and coronary heart disease, have a worse clinical outcome following contraction of the viral illness. A striking feature of COVID-19 pandemics is the high incidence of fatalities in advanced aged patients: this might be due to the prevalence of frailty and cardiovascular disease increase with age due to endothelial dysfunction and loss of endogenous cardioprotective mechanisms. Although experimental evidence on this topic is still at its infancy, the aim of this position paper is to hypothesize and discuss more suggestive cellular and molecular mechanisms whereby SARS-CoV-2 may lead to detrimental consequences to the cardiovascular system. We will focus on aging, cytokine storm, NLRP3/inflammasome, hypoxemia, and air pollution, which is an emerging cardiovascular risk factor associated with rapid urbanization and globalization. We will finally discuss the impact of clinically available CV drugs on the clinical course of COVID-19 patients. Understanding the role played by SARS-CoV2 on the CV system is indeed mandatory to get further insights into COVID-19 pathogenesis and to design a therapeutic strategy of cardio-protection for frail patients.

Plasma exosomes characterization reveals a perioperative protein signature in older patients undergoing different types of on-pump cardiac surgery

Although exosomes are extracellular nanovesicles mainly involved in cardioprotection, it is not known whether plasma exosomes of older patients undergoing different types of on-pump cardiac surgery protect cardiomyocytes from apoptosis. Since different exosomal proteins confer pro-survival effects, we have analyzed the protein cargo of exosomes circulating early after aortic unclamping. Plasma exosomes and serum cardiac troponin I levels were measured in older cardiac surgery patients (NYHA II-III) who underwent first-time on-pump coronary artery bypass graft (CABG; n = 15) or minimally invasive heart valve surgery (mitral valve repair, n = 15; aortic valve replacement, n = 15) at induction of anesthesia (T0, baseline), 3 h (T1) and 72 h (T2) after aortic unclamping. Anti-apoptotic role of exosomes was assessed in HL-1 cardiomyocytes exposed to hypoxia/re-oxygenation (H/R) by TUNEL assay. Protein exosomal cargo was characterized by mass spectrometry approach. Exosome levels increased at T1 (P < 0.01) in accord with troponin values in all groups. In CABG group, plasma exosomes further increased at T2 (P < 0.01) whereas troponin levels decreased. In vitro, all T1-exosomes prevented H/R-induced apoptosis. A total of 340 exosomal proteins were identified in all groups, yet 10% of those proteins were unique for each surgery type. In particular, 22 and 12 pro-survival proteins were detected in T1-exosomes of heart valve surgery and CABG patients, respectively. Our results suggest that endogenous intraoperative cardioprotection in older cardiac surgery patients is early mediated by distinct exosomal proteins regardless of surgery type.

Donor-recipient age interaction and the impact on clinical results after heart transplantation

To evaluate the impact of donor-recipient age matching on clinical outcomes after heart transplantation, a total of 509 patients (January 1990-December 2018, mean follow-up 111 ± 80 months) were stratified into 4 groups (young-R/young-D, young-R/old-D, old-R/young-D, old-R/old-D) according to the recipient (young-R < 60, old-R ≥ 60 years) and the donor (young-D < 50, old-D ≥ 50 years) age. No difference was found among 30-day mortality (P = .11) and postoperative complications between groups. Both unadjusted and adjusted survival was significantly higher for group young-R/young-D than that of other groups, in which survival was similar [adjusted HR for mortality of 2.0(1.2-3.4), 2.1(1.4-3.8) and 2.5(1.6-4.1) for groups old-R/young-D, young-R/old-D, old-R/old-D, respectively]. Compared to other groups, the incidence of grade ≥ 2 CAV was significantly lower in old-R/young-D group [adjusted HR 0.4(0.2-0.7)]. Among young recipients, the rate of acute grade ≥ 2 rejection episodes was higher in those receiving an old donor graft (P = .04). Old recipient groups were more affected by neoplasms and severe renal failure than young recipient groups (P < .01). Employment of hearts from donors ≥50 years of age adversely affects survival in recipients <60 years of age but does not influence outcomes in older recipients. Also, donor and recipient ages seem to have opposite effects on incidence of rejections and CAV of high grade.