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.

Conformationally adaptable macrocyclic receptors for ditopic anions: analysis of chelate cooperativity in aqueous containing media

The effect of chelate cooperativity on the binding of several ditopic anions to two tetrathiourea macrocycles has been analysed in competitive solvent mixtures (H2O : DMSO 1 : 9 v/v). The semi-flexible receptors bind dicarboxylates with high affinity dependent on the length and flexibility of the guest. Chemical double mutant cycle (DMC) analysis allowed the chelate cooperativity effects to be measured in detail and revealed both positive and negative cooperativity effects which were dependent on guest size, flexibility and spacer interactions between guest and macrocycle. 1H NMR and crystallographic studies confirmed the macrocycle hosts are adaptable, changing conformation to match their pore size to a selected guest.

Targeting succinate dehydrogenase with malonate ester prodrugs decreases renal ischemia reperfusion injury

Renal ischemia reperfusion (IR) injury leads to significant patient morbidity and mortality, and its amelioration is an urgent unmet clinical need. Succinate accumulates during ischemia and its oxidation by the mitochondrial enzyme succinate dehydrogenase (SDH) drives the ROS production that underlies IR injury. Consequently, compounds that inhibit SDH may have therapeutic potential against renal IR injury. Among these, the competitive SDH inhibitor malonate, administered as a cell-permeable malonate ester prodrug, has shown promise in models of cardiac IR injury, but the efficacy of malonate ester prodrugs against renal IR injury have not been investigated. Here we show that succinate accumulates during ischemia in mouse, pig and human models of renal IR injury, and that its rapid oxidation by SDH upon reperfusion drives IR injury. We then show that the malonate ester prodrug, dimethyl malonate (DMM), can ameliorate renal IR injury when administered at reperfusion but not prior to ischemia in the mouse. Finally, we show that another malonate ester prodrug, diacetoxymethyl malonate (MAM), is more potent than DMM because of its faster esterase hydrolysis. Our data show that the mitochondrial mechanisms of renal IR injury are conserved in the mouse, pig and human and that inhibition of SDH by ‘tuned’ malonate ester prodrugs, such as MAM, is a promising therapeutic strategy in the treatment of clinical renal IR injury.

•

Accumulation of succinate during renal ischemia is conserved across species.

•

Succinate dehydrogenase is a key therapeutic target in renal ischemia-reperfusion.

•

Malonate may inhibit succinate dehydrogenase during ischemia and on reperfusion.

•

Ester prodrugs enable delivery of malonate to succinate dehydrogenase in vivo.

•

Malonate ester prodrugs may be ‘fine-tuned’ to optimise their delivery and efficacy.

Comparative evaluation of itaconate and its derivatives reveals divergent inflammasome and type I interferon regulation in macrophages

Following activation, macrophages undergo extensive metabolic rewiring^1,2. Production of itaconate through the inducible enzyme IRG1 is a key hallmark of this process³. Itaconate inhibits succinate dehydrogenase^4,5, has electrophilic properties⁶ and is associated with a change in cytokine production⁴. Here, we compare the metabolic, electrophilic and immunologic profiles of macrophages treated with unmodified itaconate and a panel of commonly used itaconate derivatives to examine its role. Using wild-type and Irg1^-/- macrophages, we show that neither dimethyl itaconate, 4-octyl itaconate nor 4-monoethyl itaconate are converted to intracellular itaconate, while exogenous itaconic acid readily enters macrophages. We find that only dimethyl itaconate and 4-octyl itaconate induce a strong electrophilic stress response, in contrast to itaconate and 4-monoethyl itaconate. This correlates with their immunosuppressive phenotype: dimethyl itaconate and 4-octyl itaconate inhibited IκBζ and pro-interleukin (IL)-1β induction, as well as IL-6, IL-10 and interferon-β secretion, in an NRF2-independent manner. In contrast, itaconate treatment suppressed IL-1β secretion but not pro-IL-1β levels and, surprisingly, strongly enhanced lipopolysaccharide-induced interferon-β secretion. Consistently, Irg1^-/- macrophages produced lower levels of interferon and reduced transcriptional activation of this pathway. Our work establishes itaconate as an immunoregulatory, rather than strictly immunosuppressive, metabolite and highlights the importance of using unmodified itaconate in future studies.

Cardioprotective effect of succinate dehydrogenase inhibition in rat hearts and human myocardium with and without diabetes mellitus

Ischemia reperfusion (IR) injury may be attenuated through succinate dehydrogenase (SDH) inhibition by dimethyl malonate (DiMAL). Whether SDH inhibition yields protection in diabetic individuals and translates into human cardiac tissue remain unknown. In isolated perfused hearts from 24 weeks old male Zucker diabetic fatty (ZDF) and age matched non-diabetic control rats and atrial trabeculae from patients with and without diabetes, we compared infarct size, contractile force recovery and mitochondrial function. The cardioprotective effect of a 10 minutes DiMAL administration prior to global ischemia and ischemic preconditioning (IPC) was evaluated. In non-diabetic hearts exposed to IR, DiMAL 0.1 mM reduced infarct size compared to IR (55 ± 7% vs. 69 ± 6%, p < 0.05). Mitochondrial respiration was reduced by DiMAL 0.6 mM compared to sham and DiMAL 0.1 mM (p < 0.05). In diabetic hearts an increased concentration of DiMAL (0.6 mM) was required for protection compared to IR (64 ± 13% vs. 79 ± 8%, p < 0.05). Mitochondrial function remained unchanged. In trabeculae from humans without diabetes, IPC and DiMAL improved contractile force recovery compared to IR (43 ± 12% and 43 ± 13% vs. 23 ± 13%, p < 0.05) but in patients with diabetes only IPC provided protection compared to IR (51 ± 15% vs. 21 ± 8%, p < 0.05). Neither IPC nor DiMAL modulated mitochondrial respiration in patients. Cardioprotection by SDH inhibition is possible in human tissue, but depends on diabetes status. The narrow therapeutic range and discrepancy in respiration between experimental and human studies may limit clinical translation.

Novel Findings and Therapeutic Targets on Cardioprotection of Ischemia/ Reperfusion Injury in STEMI

Acute ST-segment elevation myocardial infarction (STEMI) remains a leading cause of morbidity and mortality around the world. A large number of STEMI patients after the infarction gradually develop heart failure due to the infarcted myocardium. Timely reperfusion is essential to salvage ischemic myocardium from the infarction, but the restoration of coronary blood flow in the infarct-related artery itself induces myocardial injury and cardiomyocyte death, known as ischemia/reperfusion injury (IRI). The factors contributing to IRI in STEMI are complex, and microvascular obstruction, inflammation, release of reactive oxygen species, myocardial stunning, and activation of myocardial cell death are involved. Therefore, additional cardioprotection is required to prevent the heart from IRI. Although many mechanical conditioning procedures and pharmacological agents have been identified as effective cardioprotective approaches in animal studies, their translation into the clinical practice has been relatively disappointing due to a variety of reasons. With new emerging data on cardioprotection in STEMI over the past few years, it is mandatory to reevaluate the effectiveness of "old" cardioprotective interventions and highlight the novel therapeutic targets and new treatment strategies of cardioprotection.

Cardiac metabolism as a driver and therapeutic target of myocardial infarction

Reducing infarct size during a cardiac ischaemic‐reperfusion episode is still of paramount importance, because the extension of myocardial necrosis is an important risk factor for developing heart failure. Cardiac ischaemia‐reperfusion injury (IRI) is in principle a metabolic pathology as it is caused by abruptly halted metabolism during the ischaemic episode and exacerbated by sudden restart of specific metabolic pathways at reperfusion. It should therefore not come as a surprise that therapy directed at metabolic pathways can modulate IRI. Here, we summarize the current knowledge of important metabolic pathways as therapeutic targets to combat cardiac IRI. Activating metabolic pathways such as glycolysis (eg AMPK activators), glucose oxidation (activating pyruvate dehydrogenase complex), ketone oxidation (increasing ketone plasma levels), hexosamine biosynthesis pathway (O‐GlcNAcylation; administration of glucosamine/glutamine) and deacetylation (activating sirtuins 1 or 3; administration of NAD⁺‐boosting compounds) all seem to hold promise to reduce acute IRI. In contrast, some metabolic pathways may offer protection through diminished activity. These pathways comprise the malate‐aspartate shuttle (in need of novel specific reversible inhibitors), mitochondrial oxygen consumption, fatty acid oxidation (CD36 inhibitors, malonyl‐CoA decarboxylase inhibitors) and mitochondrial succinate metabolism (malonate). Additionally, protecting the cristae structure of the mitochondria during IR, by maintaining the association of hexokinase II or creatine kinase with mitochondria, or inhibiting destabilization of F_OF₁‐ATPase dimers, prevents mitochondrial damage and thereby reduces cardiac IRI. Currently, the most promising and druggable metabolic therapy against cardiac IRI seems to be the singular or combined targeting of glycolysis, O‐GlcNAcylation and metabolism of ketones, fatty acids and succinate.

Glycyrrhizic acid exerts protective effects against hypoxia/reoxygenation-induced human coronary artery endothelial cell damage by regulating mitochondria

Hypoxia/reoxygenation (H/R) is one of the main causes of coronary artery disease (CAD), which is primarily induced by damage to coronary artery endothelial cells (CAECs). Glycyrrhizic acid (GA) is a natural and abundant pentacyclic triterpenoid glycoside of the licorice root extract, and it has been reported to elicit protective effects against hypoxia, inflammation and apoptosis in ischemic myocardium; therefore, GA may serve as a promising therapeutic agent for ischemia-associated CAD. In the present study, the protective effects of GA against H/R-induced injury in CAECs were investigated. Treatment with GA during H/R maintained cell viability and decreased H/R-induced cell apoptosis in human CAECs. In addition, H/R-mediated induction of intracellular and mitochondrial reactive oxygen species (ROS) was significantly decreased by GA exposure. Similar to ROS scavengers, GA treatment not only exhibited protective effects, but also maintained the mitochondrial membrane potential after H/R and inhibited H/R-induced mitochondrial dysfunction, including deficits in ATP synthesis, mitochondrial DNA copy number and mitochondrial transcriptional activity. Furthermore, GA decreased autophagy/mitophagy, and its protective effect against H/R was abolished by autophagy promotion. Collectively, the results suggested that GA exhibited protective effects against H/R-induced CAEC injury by decreasing ROS accumulation and maintaining mitochondrial homeostasis. Further investigation into the precise mechanisms underlying the decrease in ROS accumulation induced by GA is required.

Enhancing Glycolysis Protects against Ischemia-Reperfusion Injury by Reducing ROS Production

After myocardial ischemia-reperfusion, fatty acid oxidation shows fast recovery while glucose oxidation rates remain depressed. A metabolic shift aimed at increasing glucose oxidation has shown to be beneficial in models of myocardial ischemia-reperfusion. However, strategies aimed at increasing glucose consumption in the clinic have provided mixed results and have not yet reached routine clinical practice. A better understanding of the mechanisms underlying the protection afforded by increased glucose oxidation may facilitate the transfer to the clinic. The purpose of this study was to evaluate if the modulation of reactive oxygen species (ROS) was involved in the protection afforded by increased glucose oxidation. Firstly, we characterized an H9C2 cellular model in which the use of glucose or galactose as substrates can modulate glycolysis and oxidative phosphorylation pathways. In this model, there were no differences in morphology, cell number, or ATP and PCr levels. However, galactose-grown cells consumed more oxygen and had an increased Krebs cycle turnover, while cells grown in glucose had increased aerobic glycolysis rate as demonstrated by higher lactate and alanine production. Increased aerobic glycolysis was associated with reduced ROS levels and protected the cells against simulated ischemia-reperfusion injury. Furthermore, ROS scavenger N-acetyl cysteine (NAC) was able to reduce the amount of ROS and to prevent cell death. Lastly, cells grown in galactose showed higher activation of mTOR/Akt signaling pathways. In conclusion, our results provide evidence indicating that metabolic shift towards increased glycolysis reduces mitochondrial ROS production and prevents cell death during ischemia-reperfusion injury.

Xuan Bi Tong Yu Fang Promotes Angiogenesis via VEGF-Notch1/Dll4 Pathway in Myocardial Ischemic Rats

OBJECTIVE

To investigate the effect of Xuan Bi Tong Yu Fang (XBTYF) on angiogenesis via the vascular endothelial growth factor- (VEGF-) Notch1/delta-like 4 (Dll4) pathway. Materials and Methods. Sixty Sprague-Dawley rats were randomly divided into six groups: control, sham-operated, myocardial ischemia model, and XBTYF treatment at 3.2, 1.6, and 0.8 g/kg. Electrocardiography was performed to evaluate the successful establishment of the model. Hematoxylin-eosin staining and transmission electron microscopy were carried out to observe the morphology and mitochondrial structure in myocardial cells, respectively. TUNEL staining was performed to assess the degree of cell apoptosis. The expression of VEGF-A, Notch1, Dll4, Bcl2, Bax, caspase 3, caspase 9, and cytochrome-c (Cyt-c) was observed by western blot.

RESULTS

XBTYF inhibited changes to the morphology and mitochondrial structure in cardiomyocyte and reduced cell apoptosis. Compared with the model group, XBTYF at all doses (3.2, 1.6, and 0.8 g/kg) reduced the expression of Notch1, Dll4, Bax, caspase 3, caspase 9, and Cyt-c, whereas expression of VEGF-A and Bcl2 was increased.

CONCLUSION

XBTYF attenuated mitochondrial damage and cell apoptosis while promoting the angiogenesis of cardiomyocyte. The associated mechanism may be related to the VEGF-Notch1/Dll4 pathway.

Itaconate modulates tricarboxylic acid and redox metabolism to mitigate reperfusion injury

OBJECTIVES

Cerebral ischemia/reperfusion (IR) drives oxidative stress and injurious metabolic processes that lead to redox imbalance, inflammation, and tissue damage. However, the key mediators of reperfusion injury remain unclear, and therefore, there is considerable interest in therapeutically targeting metabolism and the cellular response to oxidative stress.

METHODS

The objective of this study was to investigate the molecular, metabolic, and physiological impact of itaconate treatment to mitigate reperfusion injuries in in vitro and in vivo model systems. We conducted metabolic flux and bioenergetic studies in response to exogenous itaconate treatment in cultures of primary rat cortical neurons and astrocytes. In addition, we administered itaconate to mouse models of cerebral reperfusion injury with ischemia or traumatic brain injury followed by hemorrhagic shock resuscitation. We quantitatively characterized the metabolite levels, neurological behavior, markers of redox stress, leukocyte adhesion, arterial blood flow, and arteriolar diameter in the brains of the treated/untreated mice.

RESULTS

We demonstrate that the "immunometabolite" itaconate slowed tricarboxylic acid (TCA) cycle metabolism and buffered redox imbalance via succinate dehydrogenase (SDH) inhibition and induction of anti-oxidative stress response in primary cultures of astrocytes and neurons. The addition of itaconate to reperfusion fluids after mouse cerebral IR injury increased glutathione levels and reduced reactive oxygen/nitrogen species (ROS/RNS) to improve neurological function. Plasma organic acids increased post-reperfusion injury, while administration of itaconate normalized these metabolites. In mouse cranial window models, itaconate significantly improved hemodynamics while reducing leukocyte adhesion. Further, itaconate supplementation increased survival in mice experiencing traumatic brain injury (TBI) and hemorrhagic shock.

CONCLUSIONS

We hypothesize that itaconate transiently inhibits SDH to gradually "awaken" mitochondrial function upon reperfusion that minimizes ROS and tissue damage. Collectively, our data indicate that itaconate acts as a mitochondrial regulator that controls redox metabolism to improve physiological outcomes associated with IR injury.

Ischemia and Reperfusion Injury in Kidney Transplantation: Relevant Mechanisms in Injury and Repair

Ischemia and reperfusion injury (IRI) is a complex pathophysiological phenomenon, inevitable in kidney transplantation and one of the most important mechanisms for non- or delayed function immediately after transplantation. Long term, it is associated with acute rejection and chronic graft dysfunction due to interstitial fibrosis and tubular atrophy. Recently, more insight has been gained in the underlying molecular pathways and signalling cascades involved, which opens the door to new therapeutic opportunities aiming to reduce IRI and improve graft survival. This review systemically discusses the specific molecular pathways involved in the pathophysiology of IRI and highlights new therapeutic strategies targeting these pathways.

Mitochondrial Quality Control: Role in Cardiac Models of Lethal Ischemia-Reperfusion Injury

The current standard of care for acute myocardial infarction or 'heart attack' is timely restoration of blood flow to the ischemic region of the heart. While reperfusion is essential for the salvage of ischemic myocardium, re-introduction of blood flow paradoxically kills (rather than rescues) a population of previously ischemic cardiomyocytes-a phenomenon referred to as 'lethal myocardial ischemia-reperfusion (IR) injury'. There is long-standing and exhaustive evidence that mitochondria are at the nexus of lethal IR injury. However, during the past decade, the paradigm of mitochondria as mediators of IR-induced cardiomyocyte death has been expanded to include the highly orchestrated process of mitochondrial quality control. Our aims in this review are to: (1) briefly summarize the current understanding of the pathogenesis of IR injury, and (2) incorporating landmark data from a broad spectrum of models (including immortalized cells, primary cardiomyocytes and intact hearts), provide a critical discussion of the emerging concept that mitochondrial dynamics and mitophagy (the components of mitochondrial quality control) may contribute to the pathogenesis of cardiomyocyte death in the setting of ischemia-reperfusion.

Evaluation of metal pollution-induced biological effects in Chinese shrimp Fenneropenaeus chinensis by NMR-based metabolomics

Metal pollution in Laizhou Bay along the Bohai Sea in China has been posing a risk on fishery species and hence may affect seafood quality. In this work, shrimps Fenneropenaeus chinensis were sampled from three sites, namely, a reference (site 6334) and two metal-polluted (sites 6262 and 7262) sites, located in Laizhou Bay. The metal concentrations in shrimp muscle tissues were tested using the ICP-MS technique. The Cr and Cu concentrations were the highest in the shrimp samples from site 7262, exceeding the national seafood safety standard Ⅱ, and the As concentration was much higher than the national seafood safety standard Ⅲ. NMR-based metabolomics indicated that metal pollution induced oxidative and immune stresses, damaged the muscular structure, and disrupted energy metabolism in shrimps at sites 6262 and 7262, in particular disturbed osmotic regulation in shrimps at site 7262. Glycine and serine could serve as biomarkers for Cd in F. chinensis.

Bioenergetics and translational metabolism: implications for genetics, physiology and precision medicine

It is now becoming clear that human metabolism is extremely plastic and varies substantially between healthy individuals. Understanding the biochemistry that underlies this physiology will enable personalized clinical interventions related to metabolism. Mitochondrial quality control and the detailed mechanisms of mitochondrial energy generation are central to understanding susceptibility to pathologies associated with aging including cancer, cardiac and neurodegenerative diseases. A precision medicine approach is also needed to evaluate the impact of exercise or caloric restriction on health. In this review, we discuss how technical advances in assessing mitochondrial genetics, cellular bioenergetics and metabolomics offer new insights into developing metabolism-based clinical tests and metabolotherapies. We discuss informatics approaches, which can define the bioenergetic-metabolite interactome and how this can help define healthy energetics. We propose that a personalized medicine approach that integrates metabolism and bioenergetics with physiologic parameters is central for understanding the pathophysiology of diseases with a metabolic etiology. New approaches that measure energetics and metabolomics from cells isolated from human blood or tissues can be of diagnostic and prognostic value to precision medicine. This is particularly significant with the development of new metabolotherapies, such as mitochondrial transplantation, which could help treat complex metabolic diseases.

Ischemia/Reperfusion Injury Revisited: An Overview of the Latest Pharmacological Strategies

Ischemia/reperfusion injury (IRI) permeates a variety of diseases and is a ubiquitous concern in every transplantation proceeding, from whole organs to modest grafts. Given its significance, efforts to evade the damaging effects of both ischemia and reperfusion are abundant in the literature and they consist of several strategies, such as applying pre-ischemic conditioning protocols, improving protection from preservation solutions, thus providing extended cold ischemia time and so on. In this review, we describe many of the latest pharmacological approaches that have been proven effective against IRI, while also revisiting well-established concepts and presenting recent pathophysiological findings in this ever-expanding field. A plethora of promising protocols has emerged in the last few years. They have been showing exciting results regarding protection against IRI by employing drugs that engage several strategies, such as modulating cell-surviving pathways, evading oxidative damage, physically protecting cell membrane integrity, and enhancing cell energetics.

Succinate accumulation drives ischaemia-reperfusion injury during organ transplantation

During heart transplantation, storage in cold preservation solution is thought to protect the organ by slowing metabolism; by providing osmotic support; and by minimising ischaemia-reperfusion (IR) injury upon transplantation into the recipient^1,2. Despite its widespread use our understanding of the metabolic changes prevented by cold storage and how warm ischaemia leads to damage is surprisingly poor. Here, we compare the metabolic changes during warm ischaemia (WI) and cold ischaemia (CI) in hearts from mouse, pig, and human. We identify common metabolic alterations during WI and those affected by CI, thereby elucidating mechanisms underlying the benefits of CI, and how WI causes damage. Succinate accumulation is a major feature within ischaemic hearts across species, and CI slows succinate generation, thereby reducing tissue damage upon reperfusion caused by the production of mitochondrial reactive oxygen species (ROS)^3,4. Importantly, the inevitable periods of WI during organ procurement lead to the accumulation of damaging levels of succinate during transplantation, despite cooling organs as rapidly as possible. This damage is ameliorated by metabolic inhibitors that prevent succinate accumulation and oxidation. Our findings suggest how WI and CI contribute to transplant outcome and indicate new therapies for improving the quality of transplanted organs.

Novel Molecular Targets Participating in Myocardial Ischemia-Reperfusion Injury and Cardioprotection

Worldwide morbidity and mortality from acute myocardial infarction (AMI) and related heart failure remain high. While effective early reperfusion of the criminal coronary artery after a confirmed AMI is the typical treatment at present, collateral myocardial ischemia-reperfusion injury (MIRI) and pertinent cardioprotection are still challenging to address and have inadequately understood mechanisms. Therefore, unveiling the related novel molecular targets and networks participating in triggering and resisting the pathobiology of MIRI is a promising and valuable frontier. The present study specifically focuses on the recent MIRI advances that are supported by sophisticated bio-methodology in order to bring the poorly understood interrelationship among pro- and anti-MIRI participant molecules up to date, as well as to identify findings that may facilitate the further investigation of novel targets.

Metabolomics and Heart Diseases: From Basic to Clinical Approach

BACKGROUND

The field of metabolomics has been steadily increasing in size for the last 15 years. Advances in analytical and statistical methods have allowed metabolomics to flourish in various areas of medicine. Cardiovascular diseases are some of the main research targets in metabolomics, due to their social and medical relevance, and also to the important role metabolic alterations play in their pathogenesis and evolution. Metabolomics has been applied to the full spectrum of cardiovascular diseases: from patient risk stratification to myocardial infarction and heart failure. However - despite the many proof-ofconcept studies describing the applicability of metabolomics in the diagnosis, prognosis and treatment evaluation in cardiovascular diseases - it is not yet used in routine clinical practice. Recently, large phenome centers have been established in clinical environments, and it is expected that they will provide definitive proof of the applicability of metabolomics in clinical practice. But there is also room for small and medium size centers to work on uncommon pathologies or to resolve specific but relevant clinical questions.

OBJECTIVES

In this review, we will introduce metabolomics, cover the metabolomic work done so far in the area of cardiovascular diseases.

CONCLUSION

The cardiovascular field has been at the forefront of metabolomics application and it should lead the transfer to the clinic in the not so distant future.

Protection against cardiac ischemia-reperfusion injury by hypothermia and by inhibition of succinate accumulation and oxidation is additive

Hypothermia induced at the onset of ischemia is a potent experimental cardioprotective strategy for myocardial infarction. The aim of our study was to determine whether the beneficial effects of hypothermia may be due to decreasing mitochondria-mediated mechanisms of damage that contribute to the pathophysiology of ischemia/reperfusion injury. New Zealand male rabbits were submitted to 30 min of myocardial ischemia with hypothermia (32 °C) induced by total liquid ventilation (TLV). Hypothermia was applied during ischemia alone (TLV group), during ischemia and reperfusion (TLV-IR group) and normothermia (Control group). In all the cases, ischemia was performed by surgical ligation of the left anterior descending coronary artery and was followed by 3 h of reperfusion before assessment of infarct size. In a parallel study, male C57BL6/J mice underwent 30 min myocardial ischemia followed by reperfusion under either normothermia (37 °C) or conventionally induced hypothermia (32 °C). In both the models, the levels of the citric acid cycle intermediate succinate, mitochondrial complex I activity were assessed at various times. The benefit of hypothermia during ischemia on infarct size was compared to inhibition of succinate accumulation and oxidation by the complex II inhibitor malonate, applied as the pro-drug dimethyl malonate under either normothermic or hypothermic conditions. Hypothermia during ischemia was cardioprotective, even when followed by normothermic reperfusion. Hypothermia during ischemia only, or during both, ischemia and reperfusion, significantly reduced infarct size (2.8 ± 0.6%, 24.2 ± 3.0% and 49.6 ± 2.6% of the area at risk, for TLV-IR, TLV and Control groups, respectively). The significant reduction of infarct size by hypothermia was neither associated with a decrease in ischemic myocardial succinate accumulation, nor with a change in its rate of oxidation at reperfusion. Similarly, dimethyl malonate infusion and hypothermia during ischemia additively reduced infarct size (4.8 ± 2.2% of risk zone) as compared to either strategy alone. Hypothermic cardioprotection is neither dependent on the inhibition of succinate accumulation during ischemia, nor of its rapid oxidation at reperfusion. The additive effect of hypothermia and dimethyl malonate on infarct size shows that they are protective by distinct mechanisms and also suggests that combining these different therapeutic approaches could further protect against ischemia/reperfusion injury during acute myocardial infarction.

Altered mitochondrial quality control in Atg7-deficient VSMCs promotes enhanced apoptosis and is linked to unstable atherosclerotic plaque phenotype

Vascular smooth muscle cells (VSMCs) are one of the main cellular determinants in arterial pathology. A large body of evidence indicates that death of VSMCs is associated with features of high-risk/vulnerable atherosclerotic plaques. Mitochondrial turnover is an essential aspect of the mitochondrial quality control in which dysfunctional mitochondria are selectively eliminated through autophagy and replaced through expansion of preexisting mitochondria. Even though successful autophagy promotes VSMC survival, it is unclear whether reduced autophagic flux affects mitochondrial quality control of VSMCs in atherosclerotic plaques. By using apolipoprotein E-deficient (ApoE^−/−) mice carrying a VSMC-specific deletion of the essential autophagy gene Atg7, we show in the present study that impaired VSMC autophagy promotes an unstable plaque phenotype, as well as the accumulation of fragmented mitochondria with reduced bioenergetic efficiency and more oxidative stress. Furthermore, we demonstrate that disrupted autophagic flux is linked to defective mitophagy and biogenesis of mitochondria, which exacerbate VSMC apoptosis and in turn plaque vulnerability. Overall, our data indicate that mitochondrial quality control is a promising therapeutic target to stabilize atherosclerotic plaques.

Coupling Krebs cycle metabolites to signalling in immunity and cancer

Metabolic reprogramming has become a key focus for both immunologists and cancer biologists, with exciting advances providing new insights into underlying mechanisms of disease. Metabolites traditionally associated with bioenergetics or biosynthesis have been implicated in immunity and malignancy in transformed cells, with a particular focus on intermediates of the mitochondrial pathway known as the Krebs cycle. Among these, the intermediates succinate, fumarate, itaconate, 2-hydroxyglutarate isomers (D-2-hydroxyglutarate and L-2-hydroxyglutarate) and acetyl-CoA now have extensive evidence for "non-metabolic" signalling functions in both physiological immune contexts and in disease contexts, such as the initiation of carcinogenesis. This review will describe how metabolic reprogramming, with emphasis placed on these metabolites, leads to altered immune cell and transformed cell function. The latest findings are informative for new therapeutic approaches which could be transformative for a range of diseases.

Mitochondrial mechanisms and therapeutics in ischaemia reperfusion injury

Acute kidney injury (AKI) remains a major problem in critically unwell children and young adults. Ischaemia reperfusion (IR) injury is a major contributor to the development of AKI in a significant proportion of these cases and mitochondria are increasingly recognised as being central to this process through generation of a burst of reactive oxygen species early in reperfusion. Mitochondria have additionally been shown to have key roles in downstream processes including activation of the immune response, immunomodulation, and apoptosis and necrosis. The recognition of the central role of mitochondria in IR injury and an increased understanding of the pathophysiology that undermines these processes has resulted in identification of novel therapeutic targets and potential biomarkers. This review summarises a variety of therapeutic approaches that are currently under exploration and may have potential in ameliorating AKI in children in the future.

Respiratory complex II in mitochondrial dysfunction-mediated cytotoxicity: Insight from cadmium

In the present work we studied action of several inhibitors of respiratory complex II (CII) of mitochondrial electron transport chain, namely malonate and thenoyltrifluoroacetone (TTFA) on Cd²⁺-induced toxicity and cell mortality, using two rat cell lines, pheochromocytoma PC12 and ascites hepatoma AS-30D and isolated rat liver mitochondria (RLM). It was shown that malonate, an endogenous competitive inhibitor of dicarboxylate-binding site of CII, restored in part RLM respiratory function disturbed by Cd²⁺. In particular, malonate increased both phosphorylating and maximally uncoupled respiration rates in KCl medium in the presence of CI substrates as well as palliated changes in basal and resting state respiration rates produced by the heavy metal on the mitochondria energized by CI or CII substrates. Notably, malonate enhanced Cd²⁺-induced swelling of the mitochondria energized by CI substrates in KCl and, in a much lesser extent and at higher [Cd²⁺], in sucrose media but did not influence on the Cd²⁺ effects in NaCl medium. Besides, malonate did not affect swelling in sucrose media of RLM energized by CIV substrates under using of Cd²⁺ or Ca²⁺ whereas it strongly increased the mitochondrial swelling produced by selenite. In addition, malonate produced some protection against Cd²⁺-promoted necrotic death of AS-30D and PC12 cells and reduced intracellular reactive oxygen species (ROS) formation evoked by Cd²⁺ in PC12 cells. Importantly, TTFA, an irreversible competitive inhibitor of Q-binding site of CII, per se induced apoptosis of AS-30D cells which was inhibited by co-treatment with Cd²⁺ as well as decreased the Cd²⁺-enhanced intracellular ROS formation. In turn, decylubiquinone (dUb) at low μM concentrations did not protect AS-30D cells against the Cd²⁺-induced necrosis and enhanced the Cd²⁺-induced apoptosis of the cells. High μM concentrations of dUb were highly toxic for the cells. As consequence, the findings give new evidence indicative of critical involvement of CII in mechanism(s) of Cd²⁺-produced cytotoxicity and support the notion on CII as a perspective pharmacological target in mitochondria dysfunction-mediated conditions and diseases.

Mitochondria as a therapeutic target for common pathologies

Although the development of mitochondrial therapies has largely focused on diseases caused by mutations in mitochondrial DNA or in nuclear genes encoding mitochondrial proteins, it has been found that mitochondrial dysfunction also contributes to the pathology of many common disorders, including neurodegeneration, metabolic disease, heart failure, ischaemia-reperfusion injury and protozoal infections. Mitochondria therefore represent an important drug target for these highly prevalent diseases. Several strategies aimed at therapeutically restoring mitochondrial function are emerging, and a small number of agents have entered clinical trials. This Review discusses the opportunities and challenges faced for the further development of mitochondrial pharmacology for common pathologies.

Human Tissue-Engineered Model of Myocardial Ischemia-Reperfusion Injury

IMPACT STATEMENT

Reducing ischemia-reperfusion injury would significantly improve patient survival. Current preclinical models are inadequate because they rely on animals, which do not emulate human physiology and the clinical setting. We developed a human tissue platform that allowed us to assess the human cardiac response, and demonstrated the platform's utility by measuring injury during ischemia-reperfusion and the effects of cardioprotective strategies. The model provides a foundation for future studies on how patient-specific backgrounds may affect response to therapeutic strategies. These steps will be necessary to help translate therapies into the clinical setting.

Detection of hydrogen peroxide production in the isolated rat lung using Amplex red

The objectives of this study were to develop a robust protocol to measure the rate of hydrogen peroxide (H₂O₂) production in isolated perfused rat lungs, as an index of oxidative stress, and to determine the cellular sources of the measured H₂O₂ using the extracellular probe Amplex red (AR). AR was added to the recirculating perfusate in an isolated perfused rat lung. AR's highly fluorescent oxidation product resorufin was measured in the perfusate. Experiments were carried out without and with rotenone (complex I inhibitor), thenoyltrifluoroacetone (complex II inhibitor), antimycin A (complex III inhibitor), potassium cyanide (complex IV inhibitor), or diohenylene iodonium (inhibitor of flavin-containing enzymes, e.g. NAD(P)H oxidase or NOX) added to the perfusate. We also evaluated the effect of acute changes in oxygen (O₂) concentration of ventilation gas on lung rate of H₂O₂ release into the perfusate. Baseline lung rate of H₂O₂ release was 8.45 ± 0.31 (SEM) nmol/min/g dry wt. Inhibiting mitochondrial complex II reduced this rate by 76%, and inhibiting flavin-containing enzymes reduced it by another 23%. Inhibiting complex I had a small (13%) effect on the rate, whereas inhibiting complex III had no effect. Inhibiting complex IV increased this rate by 310%. Increasing %O₂ in the ventilation gas mixture from 15 to 95% had a small (27%) effect on this rate, and this O₂-dependent increase was mostly nonmitochondrial. Results suggest complex II as a potentially important source and/or regulator of mitochondrial H₂O₂, and that most of acute hyperoxia-enhanced lung rate of H₂O₂ release is from nonmitochondrial rather than mitochondrial sources.

Extracellular vesicles derived from human umbilical cord mesenchymal stem cells alleviate rat hepatic ischemia-reperfusion injury by suppressing oxidative stress and neutrophil inflammatory response

Mesenchymal stem cells (MSCs) have been reported to exert therapeutic effects on immunoregulation, tissue repair, and regeneration from the bench to the bedside. Increasing evidence demonstrates that extracellular vesicles (EVs) derived from MSCs could contribute to these effects and are considered as a potential replacement for stem cell-based therapies. However, the efficacy and underlying mechanisms of EV-based treatment in hepatic ischemia-reperfusion injury (IRI) remain unclear. Here, we demonstrated that human umbilical cord MSC-EVs (huc-MSC-EVs) could protect against IRI-induced hepatic apoptosis by reducing the infiltration of neutrophils and alleviating oxidative stress in hepatic tissue in vivo. Meanwhile, huc-MSC-EVs reduced the respiratory burst of neutrophils and prevented hepatocytes from oxidative stress-induced cell death in vitro. Interestingly, we found that the mitochondria-located antioxidant enzyme, manganese superoxide dismutase (MnSOD), was encapsulated in huc-MSC-EVs and reduced oxidative stress in the hepatic IRI model. Knockdown of MnSOD in huc-MSCs decreased the level of MnSOD in huc-MSC-EVs and attenuated the antiapoptotic and antioxidant capacities of huc-MSC-EVs, which could be partially rescued by MnSOD mimetic manganese (III) 5,10,15,20-tetrakis (4-benzoic acid) porphyrin (MnTBAP). In summary, these findings provide new clues to reveal the therapeutic effects of huc-MSC-EVs on hepatic IRI and evaluate their preclinical application.-Yao, J., Zheng, J., Cai, J., Zeng, K., Zhou, C., Zhang, J., Li, S., Li, H., Chen, L., He, L., Chen, H., Fu, H., Zhang, Q., Chen, G., Yang, Y., Zhang, Y. Extracellular vesicles derived from human umbilical cord mesenchymal stem cells alleviate rat hepatic ischemia-reperfusion injury by suppressing oxidative stress and neutrophil inflammatory response.

Ischemic preconditioning protects against cardiac ischemia reperfusion injury without affecting succinate accumulation or oxidation

Ischemia-reperfusion (IR) injury occurs when blood supply to an organ is disrupted and then restored, and underlies many disorders, notably myocardial infarction and stroke. While reperfusion of ischemic tissue is essential for survival, it also initiates cell death through generation of mitochondrial reactive oxygen species (ROS). Recent work has revealed a novel pathway underlying ROS production at reperfusion in vivo in which the accumulation of succinate during ischemia and its subsequent rapid oxidation at reperfusion drives ROS production at complex I by reverse electron transport (RET). Pharmacologically inhibiting ischemic succinate accumulation, or slowing succinate metabolism at reperfusion, have been shown to be cardioprotective against IR injury. Here, we determined whether ischemic preconditioning (IPC) contributes to cardioprotection by altering kinetics of succinate accumulation and oxidation during IR. Mice were subjected to a 30-minute occlusion of the left anterior descending coronary artery followed by reperfusion, with or without a protective IPC protocol prior to sustained ischemia. We found that IPC had no effect on ischemic succinate accumulation with both control and IPC mice having profound increases in succinate compared to normoxia. Furthermore, after only 1-minute reperfusion succinate was rapidly metabolised returning to near pre-ischemic levels in both groups. We conclude that IPC does not affect ischemic succinate accumulation, or its oxidation at reperfusion.

Krebs Cycle Reimagined: The Emerging Roles of Succinate and Itaconate as Signal Transducers

Krebs cycle intermediates traditionally link to oxidative phosphorylation whilst also making key cell components. It is now clear that some of these metabolites also act as signals. Succinate plays an important role in inflammatory, hypoxic, and metabolic signaling, while itaconate (from another Krebs cycle intermediate, cis-aconitate) has an anti-inflammatory role.

Mitochondria "THE" target of myocardial conditioning

Several interventions, such as ischemic preconditioning, remote pre/perconditioning, or postconditioning, are known to decrease lethal myocardial ischemia-reperfusion injury. While several signal transduction pathways become activated by such maneuvers, they all have a common end point, namely, the mitochondria. These organelles represent an essential target of the cardioprotective strategies, and the preservation of mitochondrial function is central for the reduction of ischemia-reperfusion injury. In the present review, we address the role of mitochondria in the different conditioning strategies; in particular, we focus on alterations of mitochondrial function in terms of energy production, formation of reactive oxygen species, opening of the mitochondrial permeability transition pore, and mitochondrial dynamics induced by ischemia-reperfusion.

Accumulation of Succinate in Cardiac Ischemia Primarily Occurs via Canonical Krebs Cycle Activity

Succinate accumulates during ischemia, and its oxidation at reperfusion drives injury. The mechanism of ischemic succinate accumulation is controversial and is proposed to involve reversal of mitochondrial complex II. Herein, using stable-isotope-resolved metabolomics, we demonstrate that complex II reversal is possible in hypoxic mitochondria but is not the primary succinate source in hypoxic cardiomyocytes or ischemic hearts. Rather, in these intact systems succinate primarily originates from canonical Krebs cycle activity, partly supported by aminotransferase anaplerosis and glycolysis from glycogen. Augmentation of canonical Krebs cycle activity with dimethyl-α-ketoglutarate both increases ischemic succinate accumulation and drives substrate-level phosphorylation by succinyl-CoA synthetase, improving ischemic energetics. Although two-thirds of ischemic succinate accumulation is extracellular, the remaining one-third is metabolized during early reperfusion, wherein acute complex II inhibition is protective. These results highlight a bifunctional role for succinate: its complex-II-independent accumulation being beneficial in ischemia and its complex-II-dependent oxidation being detrimental at reperfusion.

IDH2 deficiency accelerates skin pigmentation in mice via enhancing melanogenesis

Melanogenesis is a complex biosynthetic pathway regulated by multiple agents, which are involved in the production, transport, and release of melanin. Melanin has diverse roles, including determination of visible skin color and photoprotection. Studies indicate that melanin synthesis is tightly linked to the interaction between melanocytes and keratinocytes. α-melanocyte-stimulating hormone (α-MSH) is known as a trigger that enhances melanin biosynthesis in melanocytes through paracrine effects. Accumulated reactive oxygen species (ROS) in skin affects both keratinocytes and melanocytes by causing DNA damage, which eventually leads to the stimulation of α-MSH production. Mitochondria are one of the main sources of ROS in the skin and play a central role in modulating redox-dependent cellular processes such as metabolism and apoptosis. Therefore, mitochondrial dysfunction may serve as a key for the pathogenesis of skin melanogenesis. Mitochondrial NADP⁺-dependent isocitrate dehydrogenase (IDH2) is a key enzyme that regulates mitochondrial redox balance and reduces oxidative stress-induced cell injury through the generation of NADPH. Downregulation of IDH2 expression resulted in an increase in oxidative DNA damage in mice skin through ROS-dependent ATM-mediated p53 signaling. IDH2 deficiency also promoted pigmentation on the dorsal skin of mice, as evident from the elevated levels of melanin synthesis markers. Furthermore, pretreatment with mitochondria-targeted antioxidant mito-TEMPO alleviated oxidative DNA damage and melanogenesis induced by IDH2 deficiency both in vitro and in vivo. Together, our findings highlight the role of IDH2 in skin melanogenesis in association with mitochondrial ROS and suggest unique therapeutic strategies for the prevention of skin pigmentation.

•

Melanogenesis is associated with the production of ROS.

•

IDH2 is an essential enzyme in the mitochondrial antioxidant system.

•

Downregulation of IDH2 induces ROS-dependent ATM-mediated p53 signaling.

•

IDH2 deficiency promotes skin pigmentation.

•

mito-TEMPO alleviates melanogenesis caused by IDH2 deficiency.

Zinc improves mitochondrial respiratory function and prevents mitochondrial ROS generation at reperfusion by phosphorylating STAT3 at Ser727

Serine 727 (Ser⁷²⁷) phosphorylation of STAT3 plays a role in the regulation of mitochondrial respiration. This study aimed to test if zinc could regulate mitochondrial respiration through phosphorylation of STAT3 at Ser⁷²⁷ in the setting of ischemia/reperfusion in the heart. Under normoxic conditions, treatment of isolated rat hearts with ZnCl₂ increased cytosolic STAT3 phosphorylation at Ser⁷²⁷ followed by phospho-STAT3 translocation to mitochondria. In isolated rat hearts subjected to 30 min regional ischemia followed by 20 min of reperfusion, ZnCl₂ given 5 min before the onset of reperfusion also increased mitochondrial phospho-STAT3. ZnCl₂ enhanced ERK phosphorylation and PD98059 reversed the effect of ZnCl₂ on STAT3 phosphorylation. ZnCl₂ improved the mitochondrial oxidative phosphorylation at reperfusion. This effect was abolished by STAT3S727A, a mutant in which Ser⁷²⁷ is replaced with alanine, in H9c2 cells subjected to hypoxia/reoxygenation. In addition, ZnCl₂ increased the mRNA level of the complex I subunit ND6, which was also reversed by STAT3S727A. Moreover, ZnCl₂ attenuated mitochondrial ROS generation and dissipation of mitochondrial membrane potential (ΔΨm) at reoxygenation through Ser⁷²⁷ phosphorylation. Finally, ZnCl₂ suppression of succinate dehydrogenase (SDH) activity upon the onset of reperfusion was nullified by the Ser⁷²⁷ mutation. In conclusion, zinc improves cardiac oxidative phosphorylation and inhibits mitochondrial ROS generation at reperfusion by increasing mitochondrial STAT3 phosphorylation at Ser⁷²⁷ via ERK. The preservation of ND6 mtDNA and the inhibition of SDH activity may account for the role of STAT3 in the beneficial action of zinc on the mitochondrial oxidative phosphorylation and ROS generation at reperfusion.

ROS and redox signaling in myocardial ischemia-reperfusion injury and cardioprotection

Ischemia-reperfusion (IR) injury is central to the pathology of major cardiovascular diseases, such as stroke and myocardial infarction. IR injury is mediated by several factors including the elevated production of reactive oxygen species (ROS), which occurs particularly at reperfusion. The mitochondrial respiratory chain and NADPH oxidases of the NOX family are major sources of ROS in cardiomyocytes. The first part of this review discusses recent findings and controversies on the mechanisms of superoxide production by the mitochondrial electron transport chain during IR injury, as well as the contribution of the NOX isoforms expressed in cardiomyocytes, NOX1, NOX2 and NOX4, to this damage. It then focuses on the effects of ROS on the opening of the mitochondrial permeability transition pore (mPTP), an inner membrane non-selective pore that causes irreversible damage to the heart. The second part analyzes the redox mechanisms of cardiomyocyte mitochondrial protection; specifically, the activation of the hypoxia-inducible factor (HIF) pathway and the antioxidant transcription factor Nrf2, which are both regulated by the cellular redox state. Redox mechanisms involved in ischemic preconditioning, one of the most effective ways of protecting the heart against IR injury, are also reviewed. Interestingly, several of these protective pathways converge on the inhibition of mPTP opening during reperfusion. Finally, the clinical and translational implications of these cardioprotective mechanisms are discussed.

Novel targets and future strategies for acute cardioprotection: Position Paper of the European Society of Cardiology Working Group on Cellular Biology of the Heart

Ischaemic heart disease and the heart failure that often results, remain the leading causes of death and disability in Europe and worldwide. As such, in order to prevent heart failure and improve clinical outcomes in patients presenting with an acute ST-segment elevation myocardial infarction and patients undergoing coronary artery bypass graft surgery, novel therapies are required to protect the heart against the detrimental effects of acute ischaemia/reperfusion injury (IRI). During the last three decades, a wide variety of ischaemic conditioning strategies and pharmacological treatments have been tested in the clinic-however, their translation from experimental to clinical studies for improving patient outcomes has been both challenging and disappointing. Therefore, in this Position Paper of the European Society of Cardiology Working Group on Cellular Biology of the Heart, we critically analyse the current state of ischaemic conditioning in both the experimental and clinical settings, provide recommendations for improving its translation into the clinical setting, and highlight novel therapeutic targets and new treatment strategies for reducing acute myocardial IRI.

Selective Inhibition of Succinate Dehydrogenase in Reperfused Myocardium with Intracoronary Malonate Reduces Infarct Size

Inhibition of succinate dehydrogenase (SDH) with malonate during reperfusion reduces infarct size in isolated mice hearts submitted to global ischemia. However, malonate has toxic effects that preclude its systemic administration in animals. Here we investigated the effect of intracoronary malonate on infarct size in pigs submitted to transient coronary occlusion. Under baseline conditions, 50 mmol/L of intracoronary disodium malonate, but not lower concentrations, transiently reduced systolic segment shortening in the region perfused by the left anterior descending coronary artery (LAD) in open-chest pigs. To assess the effects of SDH inhibition on reperfusion injury, saline or malonate 10 mmol/L were selectively infused into the area at risk in 38 animals submitted to ischemia-reperfusion. Malonate improved systolic shortening in the area at risk two hours after 15 min of ischemia (0.18 ± 0.07 vs 0.00 ± 0.01 a.u., p = 0.025, n = 3). In animals submitted to 40 min of ischemia, malonate reduced reactive oxygen species production (MitoSOX staining) during initial reperfusion and limited infarct size (36.46 ± 5.35 vs 59.62 ± 4.00%, p = 0.002, n = 11), without modifying reperfusion arrhythmias. In conclusion, inhibition of SDH with intracoronary malonate during early reperfusion limits reperfusion injury and infarct size in pigs submitted to transient coronary occlusion without modifying reperfusion arrhythmias or contractile function in distant myocardium.

New and revisited approaches to preserving the reperfused myocardium

Early coronary artery reperfusion improves outcomes for patients with ST-segment elevation myocardial infarction (STEMI), but morbidity and mortality after STEMI remain unacceptably high. The primary deficits seen in these patients include inadequate pump function, owing to rapid infarction of muscle in the first few hours of treatment, and adverse remodelling of the heart in the months that follow. Given that attempts to further reduce myocardial infarct size beyond early reperfusion in clinical trials have so far been disappointing, effective therapies are still needed to protect the reperfused myocardium. In this Review, we discuss several approaches to preserving the reperfused heart, such as therapies that target the mechanisms involved in mitochondrial bioenergetics, pyroptosis, and autophagy, as well as treatments that harness the cardioprotective properties of inhaled anaesthetic agents. We also discuss potential therapies focused on correcting the no-reflow phenomenon and its effect on healing and adverse left ventricular remodelling.

Remote ischemic conditioning provides humoural cross-species cardioprotection through glycine receptor activation

AIMS

Remote ischaemic conditioning (RIC) releases a humoural factor able to exert cross-species cardioprotection when plasma dialysate is applied to isolated hearts. However, the exact chemical nature of this factor is currently unknown.

METHODS AND RESULTS

RIC (4 × 5min femoral occlusion/5min reperfusion) was applied to 10 male pigs, and blood was taken before and after the manoeuvre. Discriminant analysis of ¹H-NMR spectra (n = 10-12) obtained from plasma dialysates (12-14 kDa cut-off) allowed to demonstrate a different metabolic profile between control and postRIC samples, with lactate (2.671 ± 0.294 vs. 3.666 ± 0.291 μmol/mL, P = 0.020), succinate (0.062 ± 0.005 vs. 0.082 ± 0.008 μmol/mL, P = 0.035) and glycine (0.055 ± 0.009 vs. 0.471 ± 0.151 μmol/mL, P = 0.015) being the main responsible for such differences. Plasma dialysates were then given to isolated mice hearts submitted to global ischaemia (35 min) and reperfusion (60 min), for 30 min before ischaemia or during the first 15 min of reflow. Infarct size was significantly reduced when postRIC dialysate was applied before ischaemia as compared with hearts pretreated with control dialysate (44.81 ± 3.22 vs. 55.55 ± 2.53%, P = 0.012, n = 12). Blockade of glycine receptors with strychnine 10 μM inhibited the protective effect caused by pretreatment with postRIC dialysate (52.76 ± 6.94 vs. 51.92 ± 5.78%, P-NS, n = 5), whereas pretreatment with glycine 3 mmol/L, but not succinate 100 μmol/L, mimicked RIC protection (41.90 ± 4.50% in glycine-treated vs. 61.51 ± 5.16 and 64.73 ± 4.47% in succinate-treated and control hearts, respectively, P < 0.05, n = 4-7).

CONCLUSIONS

RIC releases glycine and exerts cross-species cardioprotection against infarction through glycine receptor activation.

European contribution to the study of ROS: A summary of the findings and prospects for the future from the COST action BM1203 (EU-ROS)

The European Cooperation in Science and Technology (COST) provides an ideal framework to establish multi-disciplinary research networks. COST Action BM1203 (EU-ROS) represents a consortium of researchers from different disciplines who are dedicated to providing new insights and tools for better understanding redox biology and medicine and, in the long run, to finding new therapeutic strategies to target dysregulated redox processes in various diseases. This report highlights the major achievements of EU-ROS as well as research updates and new perspectives arising from its members. The EU-ROS consortium comprised more than 140 active members who worked together for four years on the topics briefly described below. The formation of reactive oxygen and nitrogen species (RONS) is an established hallmark of our aerobic environment and metabolism but RONS also act as messengers via redox regulation of essential cellular processes. The fact that many diseases have been found to be associated with oxidative stress established the theory of oxidative stress as a trigger of diseases that can be corrected by antioxidant therapy. However, while experimental studies support this thesis, clinical studies still generate controversial results, due to complex pathophysiology of oxidative stress in humans. For future improvement of antioxidant therapy and better understanding of redox-associated disease progression detailed knowledge on the sources and targets of RONS formation and discrimination of their detrimental or beneficial roles is required. In order to advance this important area of biology and medicine, highly synergistic approaches combining a variety of diverse and contrasting disciplines are needed.