Mitochondrial Bioenergetics During Ischemia and Reperfusion

Warm Cells, Hot Mitochondria: Achievements and Problems of Ultralocal Thermometry

Temperature is a crucial regulator of the rate and direction of biochemical reactions and cell processes. The recent data indicating the presence of local thermal gradients associated with the sites of high-rate thermogenesis, on the one hand, demonstrate the possibility for the existence of "thermal signaling" in a cell and, on the other, are criticized on the basis of thermodynamic calculations and models. Here, we review the main thermometric techniques and sensors developed for the determination of temperature inside living cells and diverse intracellular compartments. A comparative analysis is conducted of the results obtained using these methods for the cytosol, nucleus, endo-/sarcoplasmic reticulum, and mitochondria, as well as their biological consistency. Special attention is given to the limitations, possible sources of errors and ambiguities of the sensor's responses. The issue of biological temperature limits in cells and organelles is considered. It is concluded that the elaboration of experimental protocols for ultralocal temperature measurements that take into account both the characteristics of biological systems, as well as the properties and limitations of each type of sensor is of critical importance for the generation of reliable results and further progress in this field.

A bibliometric analysis of myocardial ischemia/reperfusion injury from 2000 to 2023

Background

Myocardial ischemia/reperfusion injury (MIRI) refers to the more severe damage that occurs in the previously ischemic myocardium after a short-term interruption of myocardial blood supply followed by restoration of blood flow within a certain period of time. MIRI has become a major challenge affecting the therapeutic efficacy of cardiovascular surgery.

Methods

A scientific literature search on MIRI-related papers published from 2000 to 2023 in the Web of Science Core Collection database was conducted. VOSviewer was used for bibliometric analysis to understand the scientific development and research hotspots in this field.

Results

A total of 5,595 papers from 81 countries/regions, 3,840 research institutions, and 26,202 authors were included. China published the most papers, but the United States had the most significant influence. Harvard University was the leading research institution, and influential authors included Lefer David J., Hausenloy Derek J., Yellon Derek M., and others. All keywords can be divided into four different directions: risk factors, poor prognosis, mechanisms and cardioprotection.

Conclusion

Research on MIRI is flourishing. It is necessary to conduct an in-depth investigation of the interaction between different mechanisms and multi-target therapy will be the focus and hotspot of MIRI research in the future.

A Systematic Review and Meta-Analysis of Phytoestrogen Protects Against Myocardial Ischemia/Reperfusion Injury: Pre-Clinical Evidence From Small Animal Studies

Background: Phytoestrogens are a class of natural compounds that have structural similarities to estrogens. They have been identified to confer potent cardioprotective effects in experimental myocardial ischemia-reperfusion injury (MIRI) animal models. We aimed to investigate the effect of PE on MIRI and its intrinsic mechanisms. Methods: A systematic search was conducted to identify PEs that have been validated in animal studies or clinical studies as effective against MIRI. Then, we collected studies that met inclusion and exclusion criteria from January 2016 to September 2021. The SYRCLE's RoB tool was used to evaluate the quality. Data were analyzed by STATA 16.0 software. Results: The search yielded 18 phytoestrogens effective against heart disease. They are genistein, quercetin, biochanin A, formononetin, daidzein, kaempferol, icariin, puerarin, rutin, notoginsenoside R1, tanshinone IIA, ginsenoside Rb1, ginsenoside Rb3, ginsenoside Rg1, ginsenoside Re, resveratrol, polydatin, and bakuchiol. Then, a total of 20 studies from 17 articles with a total of 355 animals were included in this meta-analysis. The results show that PE significantly reduced the myocardial infarct size in MIRI animals compared with the control group (p < 0.001). PE treatment significantly reduced the creatine kinase level (p < 0.001) and cTnI level (p < 0.001), increased left ventricular ejection fraction (p < 0.001) and left ventricular fractional shortening (p < 0.001) in MIRI animals. In addition, PE also exerts a significant heart rate lowering effect (p < 0.001). Conclusion: Preclinical evidence suggests that PE can be multi-targeted for cardioprotective effects in MIRI. More large animal studies and clinical research are still needed in the future to further confirm its role in MIRI.

Therapeutic Targets for Regulating Oxidative Damage Induced by Ischemia-Reperfusion Injury: A Study from a Pharmacological Perspective

Ischemia-reperfusion (I-R) injury is damage caused by restoring blood flow into ischemic tissues or organs. This complex and characteristic lesion accelerates cell death induced by signaling pathways such as apoptosis, necrosis, and even ferroptosis. In addition to the direct association between I-R and the release of reactive oxygen species and reactive nitrogen species, it is involved in developing mitochondrial oxidative damage. Thus, its mechanism plays a critical role via reactive species scavenging, calcium overload modulation, electron transport chain blocking, mitochondrial permeability transition pore activation, or noncoding RNA transcription. Other receptors and molecules reduce tissue and organ damage caused by this pathology and other related diseases. These molecular targets have been gradually discovered and have essential roles in I-R resolution. Therefore, the current study is aimed at highlighting the importance of these discoveries. In this review, we inquire about the oxidative damage receptors that are relevant to reducing the damage induced by oxidative stress associated with I-R. Several complications on surgical techniques and pathology interventions do not mitigate the damage caused by I-R. Nevertheless, these therapies developed using alternative targets could work as coadjuvants in tissue transplants or I-R-related pathologies

Lung injury after cardiopulmonary bypass: Alternative treatment prospects

Although the lung injury caused by cardiopulmonary bypass (CPB) has been extensively investigated, the incidence and mortality of lung injury after CPB remain a prominent clinical problem. The poor outcome has been attributed to multifactorial etiology, including the systemic inflammatory response and ischemia reperfusion (I/R) injury during CPB. Lung injury after CPB is a complex pathophysiological process and has many clinical manifestations of mild to severe disease. Which is associated with prognosis. To alleviate this lung injury, interventions that address the pathogenesis are particularly important. This review summarizes the pathogenesis, mechanism and treatment options of lung injury after CPB, such as lung protection with intralipid.

Endoplasmic Reticulum-Mitochondria Contacts: A Potential Therapy Target for Cardiovascular Remodeling-Associated Diseases

Cardiovascular remodeling occurs in cardiomyocytes, collagen meshes, and vascular beds in the progress of cardiac insufficiency caused by a variety of cardiac diseases such as chronic ischemic heart disease, chronic overload heart disease, myocarditis, and myocardial infarction. The morphological changes that occur as a result of remodeling are the critical pathological basis for the occurrence and development of serious diseases and also determine morbidity and mortality. Therefore, the inhibition of remodeling is an important approach to prevent and treat heart failure and other related diseases. The endoplasmic reticulum (ER) and mitochondria are tightly linked by ER-mitochondria contacts (ERMCs). ERMCs play a vital role in different signaling pathways and provide a satisfactory structural platform for the ER and mitochondria to interact and maintain the normal function of cells, mainly by involving various cellular life processes such as lipid metabolism, calcium homeostasis, mitochondrial function, ER stress, and autophagy. Studies have shown that abnormal ERMCs may promote the occurrence and development of remodeling and participate in the formation of a variety of cardiovascular remodeling-associated diseases. This review focuses on the structure and function of the ERMCs, and the potential mechanism of ERMCs involved in cardiovascular remodeling, indicating that ERMCs may be a potential target for new therapeutic strategies against cardiovascular remodeling-induced diseases.

Mitochondria-Induced Immune Response as a Trigger for Neurodegeneration: A Pathogen from Within

Symbiosis between the mitochondrion and the ancestor of the eukaryotic cell allowed cellular complexity and supported life. Mitochondria have specialized in many key functions ensuring cell homeostasis and survival. Thus, proper communication between mitochondria and cell nucleus is paramount for cellular health. However, due to their archaebacterial origin, mitochondria possess a high immunogenic potential. Indeed, mitochondria have been identified as an intracellular source of molecules that can elicit cellular responses to pathogens. Compromised mitochondrial integrity leads to release of mitochondrial content into the cytosol, which triggers an unwanted cellular immune response. Mitochondrial nucleic acids (mtDNA and mtRNA) can interact with the same cytoplasmic sensors that are specialized in recognizing genetic material from pathogens. High-energy demanding cells, such as neurons, are highly affected by deficits in mitochondrial function. Notably, mitochondrial dysfunction, neurodegeneration, and chronic inflammation are concurrent events in many severe debilitating disorders. Interestingly in this context of pathology, increasing number of studies have detected immune-activating mtDNA and mtRNA that induce an aberrant production of pro-inflammatory cytokines and interferon effectors. Thus, this review provides new insights on mitochondria-driven inflammation as a potential therapeutic target for neurodegenerative and primary mitochondrial diseases.

Inhibiting miR-205 Alleviates Cardiac Ischemia/Reperfusion Injury by Regulating Oxidative Stress, Mitochondrial Function, and Apoptosis

BACKGROUND

miR-205 is important for oxidative stress, mitochondrial dysfunction, and apoptosis. The roles of miR-205 in cardiac ischemia/reperfusion (I/R) injury remain unknown. The aim of this research is to reveal whether miR-205 could regulate cardiac I/R injury by focusing upon the oxidative stress, mitochondrial function, and apoptosis.

METHODS

Levels of miR-205 and Rnd3 were examined in the hearts with I/R injury. Myocardial infarct size, cardiac function, oxidative stress, mitochondria function, and cardiomyocyte apoptosis were detected in mice with myocardial ischemia/reperfusion (MI/R) injury. The primary neonatal cardiomyocytes underwent hypoxia/reoxygenation (H/R) to simulate MI/R injury.

RESULTS

miR-205 levels were significantly elevated in cardiac tissues from I/R in comparison with those from Sham. In comparison with controls, levels of Rnd3 were significantly decreased in the hearts from mice with MI/R injury. Furthermore, inhibiting miR-205 alleviated MI/R-induced apoptosis, reduced infarct size, prevented oxidative stress increase and mitochondrial fragmentation, and improved mitochondrial functional capacity and cardiac function. Consistently, overexpression of miR-205 increased infarct size and promoted apoptosis, oxidative stress, and mitochondrial dysfunction in mice with MI/R injury. In cultured mouse neonatal cardiomyocytes, downregulation of miR-205 reduced oxidative stress in H/R-treated cardiomyocytes. Finally, inhibiting Rnd3 ablated the cardioprotective effects of miR-205 inhibitor in MI/R injury.

CONCLUSIONS

We conclude that inhibiting miR-205 reduces infarct size, improves cardiac function, and suppresses oxidative stress, mitochondrial dysfunction, and apoptosis by promoting Rnd3 in MI/R injury. miR-205 inhibitor-induced Rnd3 activation is a valid target to treat MI/R injury.

Sex Hormone Regulation of Proteins Modulating Mitochondrial Metabolism, Dynamics and Inter-Organellar Cross Talk in Cardiovascular Disease

Cardiovascular disease (CVD) is the leading cause of death in the U.S. and worldwide. Sex-related disparities have been identified in the presentation and incidence rate of CVD. Mitochondrial dysfunction plays a role in both the etiology and pathology of CVD. Recent work has suggested that the sex hormones play a role in regulating mitochondrial dynamics, metabolism, and cross talk with other organelles. Specifically, the female sex hormone, estrogen, has both a direct and an indirect role in regulating mitochondrial biogenesis via PGC-1α, dynamics through Opa1, Mfn1, Mfn2, and Drp1, as well as metabolism and redox signaling through the antioxidant response element. Furthermore, data suggests that testosterone is cardioprotective in males and may regulate mitochondrial biogenesis through PGC-1α and dynamics via Mfn1 and Drp1. These cell-signaling hubs are essential in maintaining mitochondrial integrity and cell viability, ultimately impacting CVD survival. PGC-1α also plays a crucial role in inter-organellar cross talk between the mitochondria and other organelles such as the peroxisome. This inter-organellar signaling is an avenue for ameliorating rampant ROS produced by dysregulated mitochondria and for regulating intrinsic apoptosis by modulating intracellular Ca²⁺ levels through interactions with the endoplasmic reticulum. There is a need for future research on the regulatory role of the sex hormones, particularly testosterone, and their cardioprotective effects. This review hopes to highlight the regulatory role of sex hormones on mitochondrial signaling and their function in the underlying disparities between men and women in CVD.

In vitro P38MAPK inhibition in aged astrocytes decreases reactive astrocytes, inflammation and increases nutritive capacity after oxygen-glucose deprivation

Proper astroglial functioning is essential for the development and survival of neurons and oligodendroglia under physiologic and pathological circumstances. Indeed, malfunctioning of astrocytes represents an important factor contributing to brain injury. However, the molecular pathways of this astroglial dysfunction are poorly defined. In this work we show that aging itself can drastically perturb astrocyte viability with an increase of inflammation, cell death and astrogliosis. Moreover, we demonstrate that oxygen glucose deprivation (OGD) has a higher impact on nutritive loss in aged astrocytes compared to young ones, whereas aged astrocytes have a higher activity of the anti-oxidant systems. P38MAPK signaling has been identified to be upregulated in neurons, astrocytes and microglia after ischemic stroke. By using a pharmacological p38α specific inhibitor (PH-797804), we show that p38MAPK pathway has an important role in aged astrocytes for inflammatory and oxidative stress responses with the subsequent cell death that occurs after OGD.

Mitochondrial Biomarkers in Patients with ST-Elevation Myocardial Infarction and Their Potential Prognostic Implications: A Prospective Observational Study

Background: Mitochondrial biomarkers have been investigated in different critical settings, including ST-elevation myocardial infarction (STEMI). Whether they provide prognostic information in STEMI, complementary to troponins, has not been fully elucidated. We prospectively explored the in-hospital and long-term prognostic implications of cytochrome c and cell-free mitochondrial DNA (mtDNA) in STEMI patients undergoing primary percutaneous coronary intervention. Methods: We measured cytochrome c and mtDNA at admission in 466 patients. Patients were grouped according to mitochondrial biomarkers detection: group 1 (−/−; no biomarker detected; n = 28); group 2 (−/+; only one biomarker detected; n = 283); group 3 (+/+; both biomarkers detected; n = 155). A composite of in-hospital mortality, cardiogenic shock, and acute pulmonary edema was the primary endpoint. Four-year all-cause mortality was the secondary endpoint. Results: Progressively lower left ventricular ejection fractions (52 ± 8%, 49 ± 8%, 47 ± 9%; p = 0.006) and higher troponin I peaks (54 ± 44, 73 ± 66, 106 ± 81 ng/mL; p = 0.001) were found across the groups. An increase in primary (4%, 14%, 19%; p = 0.03) and secondary (10%, 15%, 23%; p = 0.02) endpoint rate was observed going from group 1 to group 3. The adjusted odds ratio increment of the primary endpoint from one group to the next was 1.65 (95% CI 1.04–2.61; p = 0.03), while the adjusted hazard ratio increment of the secondary endpoint was 1.55 (95% CI 1.12–2.52; p = 0.03). The addition of study group allocation to admission troponin I reclassified 12% and 22% of patients for the primary and secondary endpoint, respectively. Conclusions: Detection of mitochondrial biomarkers is common in STEMI and seems to be associated with in-hospital and long-term outcome independently of troponin.

Circular RNA ITCH mediates H2O2-induced myocardial cell apoptosis by targeting miR-17-5p via wnt/β-catenin signalling pathway

Cardiovascular disease is a severe threat health worldwide, and circRNAs have been shown to be correlated with the development of cardiovascular disease. Expression of circ-ITCH and miR-17a-5p was evaluated by RT-qPCR. Cell viability was measured using CCK-8. Flow cytometry was applied to measure apoptosis rate. Binding between miR-17-5p and circ-ITCH was detected via luciferase reporter assays. Levels of ATP in cells were examined with ATP testing. Western blot was used to evaluate apoptosis-related proteins and proteins in Wnt/β-catenin signalling pathway. H2O2 induced apoptosis of H9c2 cells and lowered cell viability as well as ATP levels and circ-ITCH expression. After overexpression, circ-ITCH enhanced cell viability and ATP concentration. Meanwhile, apoptosis was inhibited. MiR-17-5p was the target of circ-ITCH as evidenced by luciferase report assays, with higher expression in H2O2-induced H9c2 cells. Knockdown of miR-17-5p could promote cell viability and level of ATP and curb apoptosis and p53 and PARP expression. Moreover, overexpressed miR-17-5p could reverse the function of upregulated circ-ITCH. Wnt3a, Wnt5a and β-catenin in Wnt/β-catenin signalling pathway were increased after H2O2 induction. Suppression of Wnt/β-catenin signalling pathway could initiate the process of injury in H9c2 cells. Circ-ITCH could protect myocardial cells from injuries caused by H2O2 by suppressing apoptosis while miR-17-5p played a reverse role, which could upregulate apoptosis and inhibit cell viability via Wnt/β-catenin signalling pathway.

The mKATP Channels and protein-kinase C Are Involved in the Cardioprotective Effects of Genistein on Estrogen-Deficient Rat Hearts Exposed to Ischemia/Reperfusion: Energetic Study

Estrogenic deficiency is considered a risk of coronary disease in women. The phytoestrogen genistein could be a safe preventive strategy. The first aim of this work was to validate a model of cardiac stunning in which natural estrogenic deficiency rats, ie, adult young male (YM) and aged female (AgF), are compared with young female rats (YF). The second aim was to study whether the in vivo administration of genistein prevents the stunning in estrogenic deficiency rats. The third aim was to evaluate whether in our estrogenic deficiency model exists a synergy between genistein and estradiol. The fourth aim was to characterize the underlying mechanisms of genistein. Stunning was induced by ischemia/reperfusion (I/R) in isolated hearts inside a calorimeter. The left ventricular pressure (P) and total heat rate (Ht) were simultaneously measured, while diastolic contracture and muscle economy (P/Ht) were calculated. During R, P/Ht and P recovered less in AgF and YM than in YF rat hearts. Genistein through i.p. (GST-ip) improved P and P/Ht in AgF and YM, but not in YF. In YM, the cardioprotections of GST-ip and estradiol were synergistic. After ischemia, GST-ip increased SR Ca leak causing diastolic contracture. The GST-ip cardioprotection neither was affected by blockade of PI3K-Akt, NO synthases, or phosphatases, but it was sensitive to blockade of protein-kinase C and mKATP channels. Results suggest that (1) estrogenic deficiency worsens cardiac stunning, (2) GST-ip was more cardioprotective in estrogenic deficiency and synergistic with estradiol, and (3) cardioprotection of GST-ip depends on the protein-kinase C and mKATP channel pathway activation.

PLA2G6 guards placental trophoblasts against ferroptotic injury

The recently identified ferroptotic cell death is characterized by excessive accumulation of hydroperoxy-arachidonoyl (C20:4)- or adrenoyl (C22:4)- phosphatidylethanolamine (Hp-PE). The selenium-dependent glutathione peroxidase 4 (GPX4) inhibits ferroptosis, converting unstable ferroptotic lipid hydroperoxides to nontoxic lipid alcohols in a tissue-specific manner. While placental oxidative stress and lipotoxicity are hallmarks of placental dysfunction, the possible role of ferroptosis in placental dysfunction is largely unknown. We found that spontaneous preterm birth is associated with ferroptosis and that inhibition of GPX4 causes ferroptotic injury in primary human trophoblasts and during mouse pregnancy. Importantly, we uncovered a role for the phospholipase PLA2G6 (PNPLA9, iPLA2beta), known to metabolize Hp-PE to lyso-PE and oxidized fatty acid, in mitigating ferroptosis induced by GPX4 inhibition in vitro or by hypoxia/reoxygenation injury in vivo. Together, we identified ferroptosis signaling in the human and mouse placenta, established a role for PLA2G6 in attenuating trophoblastic ferroptosis, and provided mechanistic insights into the ill-defined placental lipotoxicity that may inspire PLA2G6-targeted therapeutic strategies.

Crosstalk between coronavirus disease 2019 and cardiovascular disease and its treatment

People with cardiovascular disease (CVD) often contract coronavirus disease 2019 (COVID-19). However, the interaction between COVID-19 and CVD is unclear. In this systematic review, the available evidence for the crosstalk between COVID-19 and CVD and its treatment was analysed. A search was performed in the electronic databases MEDLINE and EMBASE. Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infects human cells via angiotensin-converting enzyme 2. SARS-CoV-2 can cause CVD by inducing cytokine storms, creating an imbalance in the oxygen supply and demand and disrupting the renin-angiotensin-aldosterone system; SARS-CoV-2 infection can also lead to the development of CVD through the side effects of therapeutic drugs, psychological factors, and aggravation of underlying CVD. The most common CVDs caused by SARS-CoV-2 infection are acute myocardial injury, arrhythmia, and heart failure. Studies have found that there is an interaction between COVID-19 and CVD. Underlying CVD is associated with a high risk of mortality in patients with COVID-19. SARS-CoV-2 infection can also cause new-onset CVD. Clinicians need to pay close attention to cardiovascular complications during the diagnosis and treatment of patients with COVID-19 to reduce patient mortality.

Sodium-Glucose Cotransporter 2 Inhibitors Potentially Prevent Atrial Fibrillation by Ameliorating Ion Handling and Mitochondrial Dysfunction

Sodium-glucose cotransporter 2 inhibitors (SGLT2i) are a novel class of glucose-lowering agents that significantly improve the prognosis of patients with type 2 diabetes (T2D) and heart failure. SGLT2i has recently been implicated in the treatment of atrial fibrillation (AF) with clinical data demonstrating that these agents decrease the incidence of AF events in patients with T2D. Fundamental findings have suggested that SGLT2i may alleviate atrial electrical and structural remodeling. The underlying mechanisms of SGLT2i are likely associated with balancing the sodium and calcium handling disorders and mitigating the mitochondrial dysfunction in atrial myocytes. This review illustrates the advances in understanding the underlying mechanisms of SGLT2i as an evolving treatment modality for AF.

[Melatonin protects against myocardial ischemia-reperfusion injury by inhibiting contracture in isolated rat hearts]

OBJECTIVE

To investigate the protective effect of melatonin against myocardial ischemia reperfusion (IR) injury in isolated rat hearts and explore the underlying mechanisms.

METHODS

The isolated hearts from 40 male SD rats were randomly divided into 4 groups (n=10): the control group, where the hearts were perfused with KH solution for 175 min; IR group, where the hearts were subjected to global ischemia for 45 min followed by reperfusion for 120 min; IR+melatonin (Mel+IR) group, where melatonin (5 μmol/L) was administered to the hearts 1 min before ischemia and during the first 5 min of reperfusion, followed by 115 min of reperfusion; and IR+2, 3-butanedione monoxime (IR+BDM) group, where the hearts were treated with BDM (20 mmol/L) in the same manner as melatonin treatment. Myocardial injury in the isolated hearts was assessed based on myocardial injury area, caspase-3 activity, and expressions of cytochrome C and cleaved caspase-3 proteins. Cardiac contracture was assessed using HE staining and by detecting lactate dehydrogenase (LDH) activity and the content of cardiac troponin I (cTnI) in the coronary outflow, measurement of left ventricular end-diastolic pressure (LVEDP) and electron microscopy. The content of ATP in the cardiac tissue was also determined.

RESULTS

Compared with those in the control group, the isolated hearts in IR group showed significantly larger myocardial injury area and higher caspase-3 activity and the protein expressions of cytochrome C and cleaved caspase-3 with significantly increased LDH activity and cTnI content in the coronary outflow and elevated LVEDP at the end of reperfusion; HE staining showed obvious fractures of the myocardial fibers and the content of ATP was significantly decreased in the cardiac tissue; electron microscopy revealed the development of contraction bands. In the isolated hearts with IR, treatment with Mel or BDM significantly reduced the myocardial injury area, caspase-3 activity, and protein expressions of cytochrome C and cleaved caspase-3, obviously inhibited LDH activity, lowered the content of cTnI and LVEDP, reduced myocardial fiber fracture, and increased ATP content in the cardiac tissue. Both Mel and BDM inhibited the formation of contraction bands in the isolated hearts with IR injury.

CONCLUSIONS

Mel can alleviate myocardial IR injury in isolated rat hearts by inhibiting cardiac contracture, the mechanism of which may involve the upregulation of ATP in the cardiac myocytes to lessen the tear of membrane and reduce cell content leakage.

Endothelial cell dysfunction during anoxia-reoxygenation is associated with a decrease in adenosine triphosphate levels, rearrangement in lipid bilayer phosphatidylserine asymmetry, and an increase in endothelial cell permeability

BACKGROUND

Phosphatidylserine (PS) is normally confined in an energy-dependent manner to the inner leaflet of the lipid cell membrane. During cellular stress, PS is exteriorized to the outer layer, initiating a cascade of events. Because cellular stress is often accompanied by decreased energy levels and because maintaining PS asymmetry is an energy-dependent process, it would make sense that cellular stress associated with decreased energy levels is also associated with PS exteriorization that ultimately leads to endothelial cell dysfunction. Our hypothesis was that anoxia-reoxygenation (A-R) is associated with decreased adenosine triphosphate (ATP) levels, increased PS exteriorization on endothelial cell membranes, and increased endothelial cell membrane permeability.

METHODS

The effect on ATP levels during A-R was measured via colorimetric assay in cultured cells. To measure the effect of A-R on PS levels, cultured cells underwent A-R and exteriorized PS levels and also total cell PS were measured via biofluorescence assay. Finally, we measured endothelial cell monolayer permeability to albumin after A-R.

RESULTS

The ATP levels in cell culture decreased 27% from baseline after A-R (p < 0.02). There was over a twofold increase in exteriorized PS as compared with controls (p < 0.01). Interestingly, we found that during A-R, the total amount of cellular PS increased (p < 0.01). The finding that total PS changed twofold over normal cells suggested that not only is there a change in the distribution of PS across the cell membrane, but there may also be an increase in the amount of PS inside the cell. Finally, A-R increased endothelial cell monolayer permeability (p < 0.01).

CONCLUSION

We found that endothelial cell dysfunction during A-R is associated with decreased ATP levels, increased PS exteriorization, and increased in monolayer permeability. This supports the idea that PS exteriorization may a key event during clinical scenarios involving oxygen lack and may 1 day lead to novel therapies in these situations.

Exercise training protects the heart against ischemia-reperfusion injury: A central role for mitochondria?

Ischemic heart disease is one of the main causes of morbidity and mortality worldwide. Physical exercise is an effective lifestyle intervention to reduce the risk factors for cardiovascular disease and also to improve cardiac function and survival in patients with ischemic heart disease. Among the strategies that contribute to reduce heart damages during ischemia and reperfusion, regular physical exercise is efficient both in rodent experimental models and in humans. However, the cellular and molecular mechanisms of the cardioprotective effects of exercise remain unclear. During ischemia and reperfusion, mitochondria are crucial players in cell death, but also in cell survival. Although exercise training can influence mitochondrial function, the consequences on heart sensitivity to ischemic insults remain elusive. In this review, we describe the effects of physical activity on cardiac mitochondria and their potential key role in exercise-induced cardioprotection against ischemia-reperfusion damage. Based on recent scientific data, we discuss the role of different pathways that might help to explain why mitochondria are a key target of exercise-induced cardioprotection.

Measuring biological aging in humans: A quest

The global population of individuals over the age of 65 is growing at an unprecedented rate and is expected to reach 1.6 billion by 2050. Most older individuals are affected by multiple chronic diseases, leading to complex drug treatments and increased risk of physical and cognitive disability. Improving or preserving the health and quality of life of these individuals is challenging due to a lack of well-established clinical guidelines. Physicians are often forced to engage in cycles of "trial and error" that are centered on palliative treatment of symptoms rather than the root cause, often resulting in dubious outcomes. Recently, geroscience challenged this view, proposing that the underlying biological mechanisms of aging are central to the global increase in susceptibility to disease and disability that occurs with aging. In fact, strong correlations have recently been revealed between health dimensions and phenotypes that are typical of aging, especially with autophagy, mitochondrial function, cellular senescence, and DNA methylation. Current research focuses on measuring the pace of aging to identify individuals who are "aging faster" to test and develop interventions that could prevent or delay the progression of multimorbidity and disability with aging. Understanding how the underlying biological mechanisms of aging connect to and impact longitudinal changes in health trajectories offers a unique opportunity to identify resilience mechanisms, their dynamic changes, and their impact on stress responses. Harnessing how to evoke and control resilience mechanisms in individuals with successful aging could lead to writing a new chapter in human medicine.

Myocardial Adaptation in Pseudohypoxia: Signaling and Regulation of mPTP via Mitochondrial Connexin 43 and Cardiolipin

Therapies intended to mitigate cardiovascular complications cannot be applied in practice without detailed knowledge of molecular mechanisms. Mitochondria, as the end-effector of cardioprotection, represent one of the possible therapeutic approaches. The present review provides an overview of factors affecting the regulation processes of mitochondria at the level of mitochondrial permeability transition pores (mPTP) resulting in comprehensive myocardial protection. The regulation of mPTP seems to be an important part of the mechanisms for maintaining the energy equilibrium of the heart under pathological conditions. Mitochondrial connexin 43 is involved in the regulation process by inhibition of mPTP opening. These individual cardioprotective mechanisms can be interconnected in the process of mitochondrial oxidative phosphorylation resulting in the maintenance of adenosine triphosphate (ATP) production. In this context, the degree of mitochondrial membrane fluidity appears to be a key factor in the preservation of ATP synthase rotation required for ATP formation. Moreover, changes in the composition of the cardiolipin’s structure in the mitochondrial membrane can significantly affect the energy system under unfavorable conditions. This review aims to elucidate functional and structural changes of cardiac mitochondria subjected to preconditioning, with an emphasis on signaling pathways leading to mitochondrial energy maintenance during partial oxygen deprivation.

Intracardiac administration of ephrinA1-Fc preserves mitochondrial bioenergetics during acute ischemia/reperfusion injury

AIMS

Intracardiac injection of recombinant EphrinA1-Fc immediately following coronary artery ligation in mice reduces infarct size in both reperfused and non-reperfused myocardium, but the cellular alterations behind this phenomenon remain unknown.

MAIN METHODS

Herein, 10 wk-old B6129SF2/J male mice were exposed to acute ischemia/reperfusion (30minI/24hrsR) injury immediately followed by intracardiac injection of either EphrinA1-Fc or IgG-Fc. After 24 h of reperfusion, sections of the infarct margin in the left ventricle were imaged via transmission electron microscopy, and mitochondrial function was assessed in both permeabilized fibers and isolated mitochondria, to examine mitochondrial structure, function, and energetics in the early stages of repair.

KEY FINDINGS

At a structural level, EphrinA1-Fc administration prevented the I/R-induced loss of sarcomere alignment and mitochondrial organization along the Z disks, as well as disorganization of the cristae and loss of inter-mitochondrial junctions. With respect to bioenergetics, loss of respiratory function induced by I/R was prevented by EphrinA1-Fc. Preservation of cardiac bioenergetics was not due to changes in mitochondrial JH₂O₂ emitting potential, membrane potential, ADP affinity, efficiency of ATP production, or activity of the main dehydrogenase enzymes, suggesting that EphrinA1-Fc indirectly maintains respiratory function via preservation of the mitochondrial network. Moreover, these protective effects were lost in isolated mitochondria, further emphasizing the importance of the intact cardiomyocyte ultrastructure in mitochondrial energetics.

SIGNIFICANCE

Collectively, these data suggest that intracardiac injection of EphrinA1-Fc protects cardiac function by preserving cardiomyocyte structure and mitochondrial bioenergetics, thus emerging as a potential therapeutic strategy in I/R injury.

The Role of Mitochondria in the Mechanisms of Cardiac Ischemia-Reperfusion Injury

Mitochondria play a critical role in maintaining cellular function by ATP production. They are also a source of reactive oxygen species (ROS) and proapoptotic factors. The role of mitochondria has been established in many aspects of cell physiology/pathophysiology, including cell signaling. Mitochondria may deteriorate under various pathological conditions, including ischemia-reperfusion (IR) injury. Mitochondrial injury can be one of the main causes for cardiac and other tissue injuries by energy stress and overproduction of toxic reactive oxygen species, leading to oxidative stress, elevated calcium and apoptotic and necrotic cell death. However, the interplay among these processes in normal and pathological conditions is still poorly understood. Mitochondria play a critical role in cardiac IR injury, where they are directly involved in several pathophysiological mechanisms. We also discuss the role of mitochondria in the context of mitochondrial dynamics, specializations and heterogeneity. Also, we wanted to stress the existence of morphologically and functionally different mitochondrial subpopulations in the heart that may have different sensitivities to diseases and IR injury. Therefore, various cardioprotective interventions that modulate mitochondrial stability, dynamics and turnover, including various pharmacologic agents, specific mitochondrial antioxidants and uncouplers, and ischemic preconditioning can be considered as the main strategies to protect mitochondrial and cardiovascular function and thus enhance longevity.

Elevated Cardiac Troponin in Clinical Scenarios Beyond Obstructive Coronary Artery Disease

In this systematic review article, we aim to summarize the most up-to-date evidence regarding elevations of cardiac troponin, especially in clinical scenarios other than obstructive coronary artery disease. The accurate interpretation of raised cardiac troponin is challenging because it relies on unconfirmed postulations and dogmatic knowledge (e.g., the exclusive provenience of cardiac troponin from cardiac myocytes), based on which every troponin elevation is assumed to definitely indicate myocardial damage. Indeed, the investigation of the pathophysiologic mechanism leading to the release in the bloodstream of cardiac biomarkers should be the first step of the diagnostic process to fully understand the clinical significance of the elevated serum levels and identify the best management. A prominent effort should be put in place to identify the contribution of potential confounding factors, both cardiac and non-cardiac in etiology, with the ability to affect synthesis and clearance of cardiac biomarkers. Regardless of the underlying cause, it is well established that cardiovascular biomarkers are increasingly useful to further risk stratification and prognosticate patients. Accordingly, we sought to clarify the meaning and impact of elevated cardiac troponin in those frequently encountered real-world scenarios presenting clinicians with a diagnostic dilemma, with the final goal of facilitating the diagnosis and help optimize individually tailored treatment strategies.

Cardioprotective Mechanisms of Hypothyroidism on Ischemia/Reperfusion in Rats and Effects of Carvedilol: Energetic Study

Hypothyroidism is considered a cardiac risk factor, but there is controversial evidence about its effects on coronary disease. The aim of this work was to evaluate the influence of hypothyroidism in rat hearts exposed to 2 degrees of stunning due to ischemia and reperfusion (I/R) as well as the underlying mechanisms. Hypothyroid (HypoT) rats were obtained by drinking 0.02% methimazole during 15 days. Isolated hearts were perfused and introduced in a flow calorimeter to measure contractile performance (P), total heat rate (Ht), and muscle economy (P/Ht). Hearts were exposed to 2 models of I/R, moderate and severe (respectively 20 or 30 minutes I/45 minutes R). Moreover, free cytosolic and mitochondrial calcium changes were measured by confocal fluorometry on cardiomyocytes. Comparison to euthyroid (EuT) hearts was done. Hypothyroidism was cardioprotective, but HypoT hearts were more sensitive than EuT hearts to the preischemic blockade of mitochondrial transporters mNCX and mKATPchannels. Moreover, the postischemic recovery of P and P/Ht in HypoT hearts was strongly reduced by inhibition of the cellular pathways of PI3K/Akt and protein kinase C (PKC), and it was increased by nitric oxide synthase (NOS) inhibition. However, physiological concentrations of adrenaline reduced the cardioprotection of HypoT, but oral treatment with 20 mg/kg/day carvedilol prevented it. Results show that hypothyroidism reduces the mitochondrial Ca2+overload during I/R by mKATPchannel activation and Ca2+extrusion through mNCX, while the PI3K/Akt and PKC pathways are involved in that cardioprotection. Contrarily, NOS activation and adrenaline blunt such cardioprotection, but carvedilol prevented the adrenergic dysfunction. These results would explain why hypothyroidism is a clinical risk factor in angor patients under adrenergic exacerbation but reduced the incidence of acute episodes of coronary syndrome in hospitalized patients. Results suggest that a treatment with carvedilol could be a potential therapeutic agent to prevent cardiac postischemic dysfunction in hypothyroid patients.

Role of Cardiolipin in Mitochondrial Function and Dynamics in Health and Disease: Molecular and Pharmacological Aspects

In eukaryotic cells, mitochondria are involved in a large array of metabolic and bioenergetic processes that are vital for cell survival. Phospholipids are the main building blocks of mitochondrial membranes. Cardiolipin (CL) is a unique phospholipid which is localized and synthesized in the inner mitochondrial membrane (IMM). It is now widely accepted that CL plays a central role in many reactions and processes involved in mitochondrial function and dynamics. Cardiolipin interacts with and is required for optimal activity of several IMM proteins, including the enzyme complexes of the electron transport chain (ETC) and ATP production and for their organization into supercomplexes. Moreover, CL plays an important role in mitochondrial membrane morphology, stability and dynamics, in mitochondrial biogenesis and protein import, in mitophagy, and in different mitochondrial steps of the apoptotic process. It is conceivable that abnormalities in CL content, composition and level of oxidation may negatively impact mitochondrial function and dynamics, with important implications in a variety of pathophysiological situations and diseases. In this review, we focus on the role played by CL in mitochondrial function and dynamics in health and diseases and on the potential of pharmacological modulation of CL through several agents in attenuating mitochondrial dysfunction.

Trimetazidine attenuates high-altitude fatigue and cardiorespiratory fitness impairment: A randomized double-blinded placebo-controlled clinical trial

Trimetazidine (TMZ) has been shown to optimize myocardial energy metabolism and is a common anti-ischemic agent. Our trial (ChiCTR-TRC-13003298) aimed to explore whether TMZ has any preventive effect on high-altitude fatigue (HAF), cardiac function and cardiorespiratory fitness upon acute high-altitude exposure and how it works on HAF. Thirty-nine healthy young subjects were enrolled in a randomized double-blinded placebo-controlled trial and were randomized to take oral TMZ (n = 20) or placebo (n = 19), 20 mg tid, 14 days prior to departure until the end of study. The 2018 Lake Louise Score questionnaire, echocardiography, assessments of physical working capacity, circulating markers of myocardial energy metabolism and fatigue were performed both before departure and arrival at highland. At follow-up, TMZ significantly reduced the incidence of HAF (p = 0.038), reversed cardiorespiratory fitness impairment, decreased left ventricular end-systolic volume (LVESV, p = 0.032) and enhanced left ventricular ejection fraction (LVEF, p = 0.015) at highland. Relative to the placebo group, the TMZ group had significantly lower LDH (p = 0.025) and lactate levels before (p < 0.001) and after (p = 0.012) physical exercise after acute high-altitude exposure. Additionally, improved left ventricular systolic function might have contributed to ameliorating HAF during TMZ treatment (LVEF, OR = 0.859, 95% CI = 0.741-0.996, p = 0.044). In conclusion, our results demonstrated that TMZ could prevent HAF, cardiorespiratory fitness impairment and improves left ventricular systolic function during acute high-altitude exposure. This trial provides new insights into the effect of TMZ and novel evidence against HAF and cardiorespiratory fitness impairment at highland.

Non-genomic Effects of Estrogen on Cell Homeostasis and Remodeling With Special Focus on Cardiac Ischemia/Reperfusion Injury

This review takes into consideration the main mechanisms involved in cellular remodeling following an ischemic injury, with special focus on the possible role played by non-genomic estrogen effects. Sex differences have also been considered. In fact, cardiac ischemic events induce damage to different cellular components of the heart, such as cardiomyocytes, vascular cells, endothelial cells, and cardiac fibroblasts. The ability of the cardiovascular system to counteract an ischemic insult is orchestrated by these cell types and is carried out thanks to a number of complex molecular pathways, including genomic (slow) or non-genomic (fast) effects of estrogen. These pathways are probably responsible for differences observed between the two sexes. Literature suggests that male and female hearts, and, more in general, cardiovascular system cells, show significant differences in many parameters under both physiological and pathological conditions. In particular, many experimental studies dealing with sex differences in the cardiovascular system suggest a higher ability of females to respond to environmental insults in comparison with males. For instance, as cells from females are more effective in counteracting the ischemia/reperfusion injury if compared with males, a role for estrogen in this sex disparity has been hypothesized. However, the possible involvement of estrogen-dependent non-genomic effects on the cardiovascular system is still under debate. Further experimental studies, including sex-specific studies, are needed in order to shed further light on this matter.

Low-flow ischaemia and reperfusion in rat hearts: energetic of stunning and cardioprotection of genistein

Objectives

Low-flow ischemia (LFI) is consequent to coronary disease and produces cardiac stunning during reperfusion (R). Energetic performance and mechanisms of Ca2+ handling during LFI/R are not known. Moreover, cardioprotection of the phytoestrogen genistein (Gen) remains to be demonstrated in LFI/R. The aim was to study the mechanisms of the stunning consequent to LFI/R and the effects of Gen on both sexes.

Methods

Rat ventricles were perfused inside a calorimeter to measure maximal pressure development (P) and total heat rate (Ht) before and during exposition to LFI/R. The mechanisms of stunning were evaluated with selective drugs.

Key findings

Female hearts (FH) developed higher postischemic contractile recovery (PICR) and muscle economy (P/Ht) than males (MH). Cardioprotection was sensitive to blockade of mKATP channels, UCam and NOS. Perfusion of 20 μmol/l Gen reduced PICR and P/Ht during LFI/R in FH, and dysfunction was increased by mNCX blockade with mPTP opening. However, intraperitoneal 5 mg/kg Gen (Gen-ip) was cardioprotective in both sexes, and the beneficial effect of Gen-ip was blocked by 100 μmol/l 5-HD.

Conclusions

FH are more protected than MH against the LFI/R dysfunction, which involves mitochondrial Ca2+ loss; Gen-ip was more cardioprotective in MH than in FH, mainly by activation of the mKATP channels.

Role of the TRPM4 Channel in Cardiovascular Physiology and Pathophysiology

The transient receptor potential cation channel subfamily M member 4 (TRPM4) channel influences calcium homeostasis during many physiological activities such as insulin secretion, immune response, respiratory reaction, and cerebral vasoconstriction. This calcium-activated, monovalent, selective cation channel also plays a key role in cardiovascular pathophysiology; for example, a mutation in the TRPM4 channel leads to cardiac conduction disease. Recently, it has been suggested that the TRPM4 channel is also involved in the development of cardiac ischemia-reperfusion injury, which causes myocardial infarction. In the present review, we discuss the physiological function of the TRPM4 channel, and assess its role in cardiovascular pathophysiology.

Fisetin Confers Cardioprotection against Myocardial Ischemia Reperfusion Injury by Suppressing Mitochondrial Oxidative Stress and Mitochondrial Dysfunction and Inhibiting Glycogen Synthase Kinase 3β Activity

Acute myocardial infarction (AMI) is the leading cause of morbidity and mortality worldwide. Timely reperfusion is considered an optimal treatment for AMI. Paradoxically, the procedure of reperfusion can itself cause myocardial tissue injury. Therefore, a strategy to minimize the reperfusion-induced myocardial tissue injury is vital for salvaging the healthy myocardium. Herein, we investigated the cardioprotective effects of fisetin, a natural flavonoid, against ischemia/reperfusion (I/R) injury (IRI) using a Langendorff isolated heart perfusion system. I/R produced significant myocardial tissue injury, which was characterized by elevated levels of lactate dehydrogenase and creatine kinase in the perfusate and decreased indices of hemodynamic parameters. Furthermore, I/R resulted in elevated oxidative stress, uncoupling of the mitochondrial electron transport chain, increased mitochondrial swelling, a decrease of the mitochondrial membrane potential, and induction of apoptosis. Moreover, IRI was associated with a loss of the mitochondrial structure and decreased mitochondrial biogenesis. However, when the animals were pretreated with fisetin, it significantly attenuated the I/R-induced myocardial tissue injury, blunted the oxidative stress, and restored the structure and function of mitochondria. Mechanistically, the fisetin effects were found to be mediated via inhibition of glycogen synthase kinase 3β (GSK3β), which was confirmed by a biochemical assay and molecular docking studies.

Ginsenoside Rg1 Ameliorates Rat Myocardial Ischemia-Reperfusion Injury by Modulating Energy Metabolism Pathways

As a major ingredient of Radix ginseng, ginsenoside Rg1 (Rg1) has been increasingly recognized to benefit the heart condition, however, the rationale behind the role is not fully understood. In vitro study in H9c2 cardiomyocytes has shown the potential of Rg1 to increase ATP content in the cells. We thus speculated that the protective effect of Rg1 on heart ischemia and reperfusion (I/R) injury implicates energy metabolism regulation. The present study was designed to verify this speculation. Male Sprague-Dawley rats were subjected to 30 min of occlusion of left coronary anterior descending artery followed by reperfusion for 90 min. Rg1 (5 mg/kg/h) was continuously administrated intravenously 30 min before occlusion until the end of reperfusion. Myocradial blood flow and heart function were monitored over the period of I/R. Myocardial infarct size, structure and apoptosis, energy metabolism, and change in RhoA signaling pathway were evaluated 90 min after reperfusion. Binding of Rg1 to RhoA was assessed using Surface Plasmon Resonance (SPR). Rg1 prevented I/R-elicited insults in myocardium, including myocardial infarction and apoptosis, decreased myocardial blood flow (MBF) and heart function, and alteration in myocardium structure. Rg1 restored the production of ATP in myocardium after I/R. Rg1 was able to bind to RhoA and down-regulate the activity of RhoA signaling pathway. These results indicated that Rg1 had protective potential against I/R-induced myocardial injury, which may be related to inhibiting myocardial apoptosis and modulating energy metabolism through binding to RhoA.