Mitochondrial permeability transition pore opening as an endpoint to initiate cell death and as a putative target for cardioprotection

Myocardial protection in cardiac surgery: a comprehensive review of current therapies and future cardioprotective strategies

Cardiac surgery with cardiopulmonary bypass results in global myocardial ischemia-reperfusion injury, leading to significant postoperative morbidity and mortality. Although cardioplegia is the cornerstone of intraoperative cardioprotection, a number of additional strategies have been identified. The concept of preconditioning and postconditioning, despite its limited direct clinical application, provided an essential contribution to the understanding of myocardial injury and organ protection. Therefore, physicians can use different tools to limit perioperative myocardial injury. These include the choice of anesthetic agents, remote ischemic preconditioning, tight glycemic control, optimization of respiratory parameters during the aortic unclamping phase to limit reperfusion injury, appropriate choice of monitoring to optimize hemodynamic parameters and limit perioperative use of catecholamines, and early reintroduction of cardioprotective agents in the postoperative period. Appropriate management before, during, and after cardiopulmonary bypass will help to decrease myocardial damage. This review aimed to highlight the current advancements in cardioprotection and their potential applications during cardiac surgery.

Exogenous Oxidative Stress in Human Spermatozoa Induces Opening of the Mitochondrial Permeability Transition Pore: Effect on Mitochondrial Function, Sperm Motility and Induction of Cell Death

Oxidative stress (OS) and disrupted antioxidant defense mechanisms play a pivotal role in the etiology of male infertility. The alterations in reactive oxygen species (ROS) production and calcium (Ca2+) homeostasis are the main activators for the mitochondrial permeability transition pore (mPTP) opening. The mPTP opening is one of the main mechanisms involved in mitochondrial dysfunction in spermatozoa. This alteration in mitochondrial function adversely affects energy supply, sperm motility, and fertilizing capacity and contributes to the development of male infertility. In human spermatozoa, the mPTP opening has been associated with ionomycin-induced endogenous oxidative stress and peroxynitrite-induced nitrosative stress; however, the effect of exogenous oxidative stress on mPTP opening in sperm has not been evaluated. The aim of this study was to determine the effect of exogenous oxidative stress induced by hydrogen peroxide (H2O2) on mPTP opening, mitochondrial function, motility, and cell death markers in human spermatozoa. Human spermatozoa were incubated with 3 mmol/L of H2O2 for 60 min, and intracellular Ca2+ concentration, mPTP opening, mitochondrial membrane potential (ΔΨm), ATP levels, mitochondrial reactive oxygen species (mROS) production, phosphatidylserine (PS) externalization, DNA fragmentation, viability, and sperm motility were evaluated. H2O2-induced exogenous oxidative stress caused increased intracellular Ca2+, leading to subsequent mPTP opening and alteration of mitochondrial function, characterized by ΔΨm dissipation, decreased ATP levels, increased mROS production, and the subsequent alteration of sperm motility. Furthermore, H2O2-induced opening of mPTP was associated with the expression of apoptotic cell death markers including PS externalization and DNA fragmentation. These results highlight the role of exogenous oxidative stress in causing mitochondrial dysfunction, deterioration of sperm motility, and an increase in apoptotic cell death markers, including PS externalization and DNA fragmentation, through the mPTP opening. This study yielded new knowledge regarding the effects of this type of stress on mitochondrial function and specifically on mPTP opening, factors that can contribute to the development of male infertility, considering that the role of mPTP in mitochondrial dysfunction in human sperm is not completely elucidated. Therefore, these findings are relevant to understanding male infertility and may provide an in vitro model for further research aimed at improving human sperm quality.

Organophosphorus Flame Retardant TPP-Induced Human Corneal Epithelial Cell Apoptosis through Caspase-Dependent Mitochondrial Pathway

A widely used organophosphate flame retardant (OPFR), triphenyl phosphate (TPP), is frequently detected in various environmental media and humans. However, there is little known on the human corneal epithelium of health risk when exposed to TPP. In this study, human normal corneal epithelial cells (HCECs) were used to investigate the cell viability, morphology, apoptosis, and mitochondrial membrane potential after they were exposed to TPP, as well as their underlying molecular mechanisms. We found that TPP decreased cell viability in a concentration-dependent manner, with a half maximal inhibitory concentration (IC50) of 220 μM. Furthermore, TPP significantly induced HCEC apoptosis, decreased mitochondrial membrane potential in a dose-dependent manner, and changed the mRNA levels of the apoptosis biomarker genes (Cyt c, Caspase-9, Caspase-3, Bcl-2, and Bax). The results showed that TPP induced cytotoxicity in HCECs, eventually leading to apoptosis and changes in mitochondrial membrane potential. In addition, the caspase-dependent mitochondrial pathways may be involved in TPP-induced HCEC apoptosis. This study provides a reference for the human corneal toxicity of TPP, indicating that the risks of OPFR to human health cannot be ignored.

Pseudomonas aeruginosa quorum-sensing molecule N-(3-oxododecanoyl)-L-homoserine lactone mediates Ca+2 dysregulation, mitochondrial dysfunction, and apoptosis in human peripheral blood lymphocytes

N-(3-oxododecanoyl)-l-homoserine lactone is a Pseudomonas aeruginosa secreted quorum-sensing molecule that mediates the secretion of virulence factors, biofilm formation and plays a pivotal role in proliferation and persistence in the host. Apart from regulating quorum-sensing, the autoinducer signal molecule N-(3-oxododecanoyl)-l-homoserine lactone (3O-C12-HSL or C12) of a LasI-LasR circuit exhibits immunomodulatory effects and induces apoptosis in various host cells. However, the precise pathophysiological impact of C12 on human peripheral blood lymphocytes and its involvement in mitochondrial dysfunction remained largely elusive. In this study, the results suggest that C12 (100 μM) induces upregulation of cytosolic and mitochondrial Ca+2 levels and triggers mitochondrial dysfunction through the generation of mitochondrial ROS (mROS), disruption of mitochondrial transmembrane potential (ΔΨm), and opening of the mitochondrial permeability transition pore (mPTP). Additionally, it was observed that C12 induces phosphatidylserine (PS) exposure and promotes apoptosis in human peripheral blood lymphocytes. However, apoptosis plays a critical role in the homeostasis and development of lymphocytes, whereas enhanced apoptosis can cause immunodeficiency through cell loss. These findings suggest that C12 exerts a detrimental effect on lymphocytes by mediating mitochondrial dysfunction and enhancing apoptosis, which might further impair the effective mounting of immune responses during Pseudomonas aeruginosa-associated infections.

Heat Shock Protein 70 Is Involved in the Efficiency of Preconditioning with Cyclosporine A in Renal Ischemia Reperfusion Injury by Modulating Mitochondrial Functions

Cyclosporine A (CsA) preconditioning is known to target mitochondrial permeability transition pore and protect renal function after ischemia reperfusion (IR). The upregulation of heat-shock protein 70 (Hsp70) expression after CsA injection is thought to be associated with renal protection. The aim of this study was to test the effect of Hsp70 expression on kidney and mitochondria functions after IR. Mice underwent a right unilateral nephrectomy and 30 min of left renal artery clamping, performed after CsA injection and/or administration of the Hsp70 inhibitor. Histological score, plasma creatinine, mitochondrial calcium retention capacity, and oxidative phosphorylation were assessed after 24 h of reperfusion. In parallel, we used a model of hypoxia reoxygenation on HK2 cells to modulate Hsp70 expression using an SiRNA or a plasmid. We assessed cell death after 18 h of hypoxia and 4 h of reoxygenation. CsA significantly improved renal function, histological score, and mitochondrial functions compared to the ischemic group but the inhibition of Hsp70 repealed the protection afforded by CsA injection. In vitro, Hsp70 inhibition by SiRNA increased cell death. Conversely, Hsp70 overexpression protected cells from the hypoxic condition, as well as the CsA injection. We did not find a synergic association between Hsp70 expression and CsA use. We demonstrated Hsp70 could modulate mitochondrial functions to protect kidneys from IR. This pathway may be targeted by drugs to provide new therapeutics to improve renal function after IR.

Comprehensive transcriptional and metabolomic analysis reveals the neuroprotective mechanism of dietary gamma-aminobutyric acid response to hypoxic stress in the Chinese mitten crab (Eriocheir sinensis)

Hypoxia is one of the serious stress challenges that aquatic animals face throughout their life. Our previous study found that hypoxia stress could induce neural excitotoxicity and neuronal apoptosis in Eriocheir sinensis, and observed that gamma-aminobutyric acid (GABA) has a positive neuroprotective effect on juvenile crabs under hypoxia. To reveal the neuroprotective pathway and metabolic regulatory mechanism of GABA in E. sinensis exposed to hypoxia stress, an 8-week feeding trial and acute hypoxia challenge were performed. Subsequently, we performed a comprehensive transcriptomic and metabolomic analysis of the thoracic ganglia of juvenile crabs. Differential genes and differential metabolites were co-annotated to 11 KEGG pathways, and further significant analysis showed that only the sphingolipid signaling pathway and the arachidonic acid metabolism pathway were significantly enriched. In the sphingolipid signaling pathway, GABA treatment significantly increased long-chain ceramide content in thoracic ganglia, which exerted neuroprotective effects by activating downstream signals to inhibit hypoxia-induced apoptosis. Moreover, in the arachidonic acid metabolism pathway, GABA could increase the content of neuroprotective active substances and reduce the content of harmful metabolites by regulating the metabolism of arachidonic acid for inflammatory regulation and neuroprotection. Furthermore, the decrease of glucose and lactate levels in the hemolymph suggests the positive role of GABA in metabolic regulation. This study reveals the neuroprotective pathways and possible mechanisms of GABA in juvenile E. sinensis exposed to hypoxia stress and inspires the discovery of new targets for improving hypoxia tolerance in aquatic animals.

Mitochondrial protein dysfunction in pathogenesis of neurological diseases

Mitochondria are essential organelles for neuronal function and cell survival. Besides the well-known bioenergetics, additional mitochondrial roles in calcium signaling, lipid biogenesis, regulation of reactive oxygen species, and apoptosis are pivotal in diverse cellular processes. The mitochondrial proteome encompasses about 1,500 proteins encoded by both the nuclear DNA and the maternally inherited mitochondrial DNA. Mutations in the nuclear or mitochondrial genome, or combinations of both, can result in mitochondrial protein deficiencies and mitochondrial malfunction. Therefore, mitochondrial quality control by proteins involved in various surveillance mechanisms is critical for neuronal integrity and viability. Abnormal proteins involved in mitochondrial bioenergetics, dynamics, mitophagy, import machinery, ion channels, and mitochondrial DNA maintenance have been linked to the pathogenesis of a number of neurological diseases. The goal of this review is to give an overview of these pathways and to summarize the interconnections between mitochondrial protein dysfunction and neurological diseases.

Iron Overload via Heme Degradation in the Endoplasmic Reticulum Triggers Ferroptosis in Myocardial Ischemia-Reperfusion Injury

Ischemia-reperfusion (I/R) injury is a promising therapeutic target to improve clinical outcomes after acute myocardial infarction. Ferroptosis, triggered by iron overload and excessive lipid peroxides, is reportedly involved in I/R injury. However, its significance and mechanistic basis remain unclear. Here, we show that glutathione peroxidase 4 (GPx4), a key endogenous suppressor of ferroptosis, determines the susceptibility to myocardial I/R injury. Importantly, ferroptosis is a major mode of cell death in I/R injury, distinct from mitochondrial permeability transition (MPT)-driven necrosis. This suggests that the use of therapeutics targeting both modes is an effective strategy to further reduce the infarct size and thereby ameliorate cardiac remodeling after I/R injury. Furthermore, we demonstrate that heme oxygenase 1 up-regulation in response to hypoxia and hypoxia/reoxygenation degrades heme and thereby induces iron overload and ferroptosis in the endoplasmic reticulum (ER) of cardiomyocytes. Collectively, ferroptosis triggered by GPx4 reduction and iron overload in the ER is distinct from MPT-driven necrosis in both in vivo phenotype and in vitro mechanism for I/R injury. The use of therapeutics targeting ferroptosis in conjunction with cyclosporine A can be a promising strategy for I/R injury.

Paracrine Factors of Stressed Peripheral Blood Mononuclear Cells Activate Proangiogenic and Anti-Proteolytic Processes in Whole Blood Cells and Protect the Endothelial Barrier

Tissue-regenerative properties have been attributed to secreted paracrine factors derived from stem cells and other cell types. In particular, the secretome of γ-irradiated peripheral blood mononuclear cells (PBMCsec) has been shown to possess high tissue-regenerative and proangiogenic capacities in a variety of preclinical studies. In light of future therapeutic intravenous applications of PBMCsec, we investigated the possible effects of PBMCsec on white blood cells and endothelial cells lining the vasculature. To identify changes in the transcriptional profile, whole blood was drawn from healthy individuals and stimulated with PBMCsec for 8 h ex vivo before further processing for single-cell RNA sequencing. PBMCsec significantly altered the gene signature of granulocytes (17 genes), T-cells (45 genes), B-cells (72 genes), and, most prominently, monocytes (322 genes). We detected a strong upregulation of several tissue-regenerative and proangiogenic cyto- and chemokines in monocytes, including VEGFA, CXCL1, and CXCL5. Intriguingly, inhibitors of endopeptidase activity, such as SERPINB2, were also strongly induced. Measurement of the trans-endothelial electrical resistance of primary human microvascular endothelial cells revealed a strong barrier-protective effect of PBMCsec after barrier disruption. Together, we show that PBMCsec induces angiogenic and proteolytic processes in the blood and is able to attenuate endothelial barrier damage. These regenerative properties suggest that systemic application of PBMCsec might be a promising novel strategy to restore damaged organs.

[Imeglimin: features of the mechanism of action and potential benefits]

Imeglimin is the first drug in a new class of tetrahydrotriazine-containing oral hypoglycemic agents called «glimines». Its mechanism of action is aimed at achieving a double effect, firstly, to improve the function of beta cells of the pancreas, and secondly, to enhance the action of insulin in key tissues, including the liver and skeletal muscles. At the cellular level, imeglimin modulates mitochondrial function, which leads to an improvement in cellular energy metabolism, as well as to the protection of cells from death in conditions of excessive accumulation of reactive oxygen species. It is important to note that the mechanism of action of imeglimin differs from existing drugs used for the treatment of type 2 diabetes mellitus. Like glucagon-like peptide-1 receptor agonists, imeglimin enhances insulin secretion in an exclusively glucose-dependent manner, but their mechanism of action at the cellular level diverges. Sulfonylureas and glinides function by closing ATP-sensitive potassium channels to release insulin, which is also different from imeglimin. Compared with metformin, the effect of imeglimine is also significantly different. Other major classes of oral antihypertensive agents, such as sodium-glucose transporter-2 inhibitors, thiazolidinediones and α glucosidase inhibitors mediate their action through mechanisms that do not overlap with imeglimine. Given such differences in the mechanisms of action, imeglimin can be used as part of combination therapy, for example with sitagliptin and metformin. The imeglimine molecule is well absorbed (Tmax-4), and the half-life is 5-6 hours, is largely excreted through the kidneys, and also has no clinically significant interactions with either metformin or sitagliptin.

The Oxidative Balance Orchestrates the Main Keystones of the Functional Activity of Cardiomyocytes

This review is aimed at providing an overview of the key hallmarks of cardiomyocytes in physiological and pathological conditions. The main feature of cardiac tissue is the force generation through contraction. This process requires a conspicuous energy demand and therefore an active metabolism. The cardiac tissue is rich of mitochondria, the powerhouses in cells. These organelles, producing ATP, are also the main sources of ROS whose altered handling can cause their accumulation and therefore triggers detrimental effects on mitochondria themselves and other cell components thus leading to apoptosis and cardiac diseases. This review highlights the metabolic aspects of cardiomyocytes and wanders through the main systems of these cells: (a) the unique structural organization (such as different protein complexes represented by contractile, regulatory, and structural proteins); (b) the homeostasis of intracellular Ca²⁺ that represents a crucial ion for cardiac functions and E-C coupling; and (c) the balance of Zn²⁺, an ion with a crucial impact on the cardiovascular system. Although each system seems to be independent and finely controlled, the contractile proteins, intracellular Ca²⁺ homeostasis, and intracellular Zn²⁺ signals are strongly linked to each other by the intracellular ROS management in a fascinating way to form a "functional tetrad" which ensures the proper functioning of the myocardium. Nevertheless, if ROS balance is not properly handled, one or more of these components could be altered resulting in deleterious effects leading to an unbalance of this "tetrad" and promoting cardiovascular diseases. In conclusion, this "functional tetrad" is proposed as a complex network that communicates continuously in the cardiomyocytes and can drive the switch from physiological to pathological conditions in the heart.

Surgically Metabolic Resection of Pericardial Fat to Ameliorate Myocardial Mitochondrial Dysfunction in Acute Myocardial Infarction Obese Rats

BACKGROUND

Pericardial fat (PF) is highly associated with cardiovascular disease but the effectiveness of surgical resection of PF is still unknown for myocardial mitochondrial structure and function in acute myocardial infarction (AMI) with obesity. The aim of this study was to demonstrate the difference in myocardial mitochondrial structure and function between obese AMI with additionally resected PF and those without resected PF.

METHODS

Obese rats with 12-week high fat diet (45 kcal% fat, n = 21) were randomly assigned into 3 groups: obese control, obese AMI and obese AMI with additionally resected PF. One week after developing AMI and additional resection of PF, echocardiogram, myocardial mitochondrial histomorphology, oxidative phosphorylation system (OXPHOS), anti-oxidative enzyme and sarcoplasmic reticulum Ca²⁺ ATPase 2 (SERCA2) in the non-infarcted area were assessed between these groups.

RESULTS

There was significant improvement of systolic function in AMI with PF resection compared with the AMI group in the echocardiogram. Even though the electron microscopic morphology for the mitochondria seems to be similar between the AMI with PF resection and AMI groups, there was an improved expression of PGC-1α and responsive OXPHOS including NDUFB3, NDUFB5 and SDHB are associated with the ATP levels in the AMI with PF resection compared with those in the AMI group. In addition, the expression levels of antioxidant enzymes (MnSOD) and SERCA2 were improved in the AMI with PF resection compared with those in the AMI group.

CONCLUSION

Surgical resection of PF might ameliorate myocardial mitochondria dysfunction in obese AMI.

Dietary food additive monosodium glutamate with or without high-lipid diet induces spleen anomaly: A mechanistic approach on rat model

Globally, the trend of using food additives and eating ready-made fast food has led to a deleterious impact on immune organs. Monosodium glutamate (MSG), as a food additive in a high-lipid diet (HLD), acts as a silent killer of immune cells. Hence, the present study aimed to evaluate the role of MSG in HLD on spleen injury in rats. Results showed that a 2.52-fold and 1.91-fold increase in spleen index in MSG and MSG + HLD group indicates splenomegaly, whereas a 1.36-fold and 1.29-fold increase in pro-inflammatory cytokines in MSG and MSG + HLD-fed rats, respectively, promote the inflammatory response. Additionally, MSG and MSG + HLD induce oxidative stress by 1.81-fold and 1.1-fold increased generation of reactive oxygen species (ROS) in macrophage population, and 1.38-fold and 1.36-fold increased generation of ROS in lymphocytes population, respectively. Furthermore, mitochondrial membrane potential was significantly reduced by 1.43-fold and 1.18-fold in MSG and MSG + HLD groups. Therefore, the current study argues that MSG has more detrimental effects on the spleen than MSG + HLD due to the presence of antioxidants in HLD, which suppresses the deleterious impact of MSG. Hence, it can be inferred that MSG induces spleen injury via targeting redox-guided cellular signaling with inflammatory response, leading to severe immune system anomalies.

Quercetin and vitamin E ameliorate cardio-apoptotic risks in diabetic rats

Apoptosis is upregulated in all forms of diabetes, and the mitochondria act as target in diabetes pathophysiology. Quercetin and vitamin E have both shown usefulness in the delay of progression of diabetes-induced complications. However, their effect on the apoptotic process in diabetes mellitus is unknown. We hypothesize that quercetin treatment in diabetes may decrease the propensity for cardiomyocytic death via regulation of the mitochondria permeability transition (mPT) pore opening. Hearts from normal and streptozotocin-induced diabetic rats were used for the study. Low ionic strength heart mitochondria were used for swelling assay and mitochondrial lipid peroxidation (mLPO) activity was spectrophotometrically assessed. Levels of cytochrome c and caspase 3 and 9 were determined by immunohistochemistry, while lesions assessed by histology. Diabetic heart mPT pore showed larger amplitude swelling than control, while mLPO levels were increased in diabetic rats relative to control, this resulted in cytochrome c release. This initiated increased caspase 3 and 9 activity in diabetic rats (p < 0.05). Histology showed hemorrhagic lesions in diabetic rat hearts. Quercetin and vitamin E treatment reversed these effects, suggestive of their anti-apoptotic effect. Quercetin and vitamin E protection in diabetes is mediated by mPT pore inhibition and modulation of mitochondrial-mediated apoptosis.

Microplastics-Induced Eryptosis and Poikilocytosis in Early-Juvenile Nile Tilapia (Oreochromis niloticus)

This study aims to assess the impact of microplastics (MPs) on erythrocytes using eryptosis (apoptosis) and an erythron profile (poikilocytosis and nuclear abnormalities), considered to be novel biomarkers in Nile tilapia (Oreochromis niloticus). In this study, four groups of fish were used: The first was the control group. In the second group, 1 mg/L of MPs was introduced to the samples. The third group was exposed to 10 mg/L of MPs. Finally, the fourth group was exposed to 100 mg/L of MPs for 15 days, following 15 days of recovery. The fish treated with MPs experienced an immense rise in the eryptosis percentage, poikilocytosis, and nuclear abnormalities of red blood cells (RBCs) compared with the control group in a concentration-dependent manner. Poikilocytosis of MP-exposed groups included sickle cell shape, schistocyte, elliptocyte, acanthocyte, and other shapes. Nuclear abnormalities of the MPs-exposed groups included micronuclei, binucleated erythrocytes, notched, lobed, blebbed, and hemolyzed nuclei. After the recovery period, a greater percentage of eryptosis, poikilocytotic cells, and nuclear abnormalities in RBCs were still evident in the groups exposed to MPs when crosschecked with the control group. The results show concerning facts regarding the toxicity of MPs in tilapia.

Role of angiotensin II in the development of subcellular remodeling in heart failure

The development of heart failure under various pathological conditions such as myocardial infarction (MI), hypertension and diabetes are accompanied by adverse cardiac remodeling and cardiac dysfunction. Since heart function is mainly determined by coordinated activities of different subcellular organelles including sarcolemma, sarcoplasmic reticulum, mitochondria and myofibrils for regulating the intracellular concentration of Ca2+, it has been suggested that the occurrence of heart failure is a consequence of subcellular remodeling, metabolic alterations and Ca2+-handling abnormalities in cardiomyocytes. Because of the elevated plasma levels of angiotensin II (ANG II) due to activation of the renin-angiotensin system (RAS) in heart failure, we have evaluated the effectiveness of treatments with angiotensin converting enzyme (ACE) inhibitors and ANG II type 1 receptor (AT1R) antagonists in different experimental models of heart failure. Attenuation of marked alterations in subcellular activities, protein content and gene expression were associated with improvement in cardiac function in MI-induced heart failure by treatment with enalapril (an ACE inhibitor) or losartan (an AT1R antagonist). Similar beneficial effects of ANG II blockade on subcellular remodeling and cardiac performance were also observed in failing hearts due to pressure overload, volume overload or chronic diabetes. Treatments with enalapril and losartan were seen to reduce the degree of RAS activation as well as the level of oxidative stress in failing hearts. These observations provide evidence which further substantiate to support the view that activation of RAS and high level of plasma ANG II play a critical role in inducing subcellular defects and cardiac dys-function during the progression of heart failure.

Mitochondrial Modulations, Autophagy Pathways Shifts in Viral Infections: Consequences of COVID-19

Mitochondria are vital intracellular organelles that play an important role in regulating various intracellular events such as metabolism, bioenergetics, cell death (apoptosis), and innate immune signaling. Mitochondrial fission, fusion, and membrane potential play a central role in maintaining mitochondrial dynamics and the overall shape of mitochondria. Viruses change the dynamics of the mitochondria by altering the mitochondrial processes/functions, such as autophagy, mitophagy, and enzymes involved in metabolism. In addition, viruses decrease the supply of energy to the mitochondria in the form of ATP, causing viruses to create cellular stress by generating ROS in mitochondria to instigate viral proliferation, a process which causes both intra- and extra-mitochondrial damage. SARS-COV2 propagates through altering or changing various pathways, such as autophagy, UPR stress, MPTP and NLRP3 inflammasome. Thus, these pathways act as potential targets for viruses to facilitate their proliferation. Autophagy plays an essential role in SARS-COV2-mediated COVID-19 and modulates autophagy by using various drugs that act on potential targets of the virus to inhibit and treat viral infection. Modulated autophagy inhibits coronavirus replication; thus, it becomes a promising target for anti-coronaviral therapy. This review gives immense knowledge about the infections, mitochondrial modulations, and therapeutic targets of viruses.

Imeglimin preserves islet β-cell mass in Type 2 diabetic ZDF rats

Objectives

Type 2 diabetes (T2D) is driven by progressive dysfunction and loss of pancreatic β-cell mass. Imeglimin is a first-in-class novel drug candidate that improves glycaemia and glucose-stimulated insulin secretion in preclinical models and patients. Given evidence that imeglimin can attenuate β-cell dysfunction and protect β cells in vitro, we postulated that imeglimin could also exert longer term effects to prevent pancreatic β-cell death and preserve functional β-cell mass in vivo.

Methods

Zucker diabetic fatty (ZDF) male rats were treated by oral gavage with imeglimin at a standard dose of 150 mg/kg or vehicle, twice daily for five weeks. At treatment completion, oral glucose tolerance tests were performed in fasted animals before a thorough histomorphometry and immunohistochemical analysis was conducted on pancreas tissue slices to assess cellular composition and disease status.

Results

Imeglimin treatment significantly improved glucose-stimulated insulin secretion (augmentation of the insulinogenic index) and improved glycaemia. Both basal insulinaemia and pancreatic insulin content were also increased by imeglimin. In ZDF control rats, islet structure was disordered with few β-cells; after imeglimin treatment, islets appeared healthier with more normal morphology in association with a significant increase in insulin-positive β-cells. The increase in β-cell mass was associated with a greater degree of β-cell proliferation in the presence of reduced apoptosis. Unexpectedly, a decrease in as a α-cell mass was also documented due to an apparent antiproliferative effect of imeglimin on this cell type.

Conclusion

In male ZDF rats, chronic imeglimin treatment corrects a paramount component of type 2 diabetes progression: progressive loss of functional β-cell mass. In addition, imeglimin may also moderate a-cell turnover to further ameliorate hyperglycaemia. Cumulatively, these cellular effects suggest that imeglimin may provide for disease modifying effects to preserve functional β-cell mass.

Mechanism of action of Imeglimin: A novel therapeutic agent for type 2 diabetes

Imeglimin is an investigational first-in-class novel oral agent for the treatment of type 2 diabetes (T2D). Several pivotal phase III trials have been completed with evidence of statistically significant glucose lowering and a generally favourable safety and tolerability profile, including the lack of severe hypoglycaemia. Imeglimin's mechanism of action involves dual effects: (a) amplification of glucose-stimulated insulin secretion (GSIS) and preservation of β-cell mass; and (b) enhanced insulin action, including the potential for inhibition of hepatic glucose output and improvement in insulin signalling in both liver and skeletal muscle. At a cellular and molecular level, Imeglimin's underlying mechanism may involve correction of mitochondrial dysfunction, a common underlying element of T2D pathogenesis. It has been observed to rebalance respiratory chain activity (partial inhibition of Complex I and correction of deficient Complex III activity), resulting in reduced reactive oxygen species formation (decreasing oxidative stress) and prevention of mitochondrial permeability transition pore opening (implicated in preventing cell death). In islets derived from diseased rodents with T2D, Imeglimin also enhances glucose-stimulated ATP generation and induces the synthesis of nicotinamide adenine dinucleotide (NAD+ ) via the 'salvage pathway'. In addition to playing a key role as a mitochondrial co-factor, NAD+ metabolites may contribute to the increase in GSIS (via enhanced Ca++ mobilization). Imeglimin has also been shown to preserve β-cell mass in rodents with T2D. Overall, Imeglimin appears to target a key root cause of T2D: defective cellular energy metabolism. This potential mode of action is unique and has been shown to differ from that of other major therapeutic classes, including biguanides, sulphonylureas and glucagon-like peptide-1 receptor agonists.

Mitochondrial Dysfunction and Oxidative Stress Caused by Cryopreservation in Reproductive Cells

Mitochondria, fundamental organelles in cell metabolism, and ATP synthesis are responsible for generating reactive oxygen species (ROS), calcium homeostasis, and cell death. Mitochondria produce most ROS, and when levels exceed the antioxidant defenses, oxidative stress (OS) is generated. These changes may eventually impair the electron transport chain, resulting in decreased ATP synthesis, increased ROS production, altered mitochondrial membrane permeability, and disruption of calcium homeostasis. Mitochondria play a key role in the gamete competence to facilitate normal embryo development. However, iatrogenic factors in assisted reproductive technologies (ART) may affect their functional competence, leading to an abnormal reproductive outcome. Cryopreservation, a fundamental technology in ART, may compromise mitochondrial function leading to elevated intracellular OS that decreases sperm and oocytes' competence and the dynamics of fertilization and embryo development. This article aims to review the role played by mitochondria and ROS in sperm and oocyte function and the close, biunivocal relationships between mitochondrial damage and ROS generation during cryopreservation of gametes and gonadal tissues in different species. Based on current literature, we propose tentative hypothesis of mechanisms involved in cryopreservation-associated mitochondrial dysfunction in gametes, and discuss the role played by antioxidants and other agents to retain the competence of cryopreserved reproductive cells and tissues.

Myocardial Impact of NHE1 Regulation by Sildenafil

The cardiac Na⁺/H⁺ exchanger (NHE1) is a membrane glycoprotein fundamental for proper cell functioning due its multiple housekeeping tasks, including regulation of intracellular pH, Na⁺ concentration, and cell volume. In the heart, hyperactivation of NHE1 has been linked to the development of different pathologies. Several studies in animal models that reproduce the deleterious effects of ischemia/reperfusion injury or cardiac hypertrophy have conclusively demonstrated that NHE1 inhibition provides cardioprotection. Unfortunately, NHE1 inhibitors failed to reproduce these effects in the clinical arena. The reasons for those discrepancies are not apparent yet. However, a reasonable clue to consider would be that drugs that completely abolish the exchanger activity, including that its essential housekeeping function may not be the best therapeutic approach. Therefore, interventions tending to specifically reduce its hyperactive state without affecting its basal activity emerge as a novel potential gold standard. In this regard, a promising goal seems to be the modulation of the phosphorylation state of the cytosolic tail of the exchanger. Recent own experiments demonstrated that Sildenafil, a phosphodiesterase 5A inhibitor drug that has been widely used for the treatment of erectile dysfunction is able to decrease NHE1 phosphorylation, and hence reduce its hyperactivity. In connection, growing evidence demonstrates cardioprotective properties of Sildenafil against different cardiac pathologies, with the distinctive characteristic of directly affecting cardiac tissue without altering blood pressure. This mini-review was aimed to focus on the regulation of NHE1 activity by Sildenafil. For this purpose, experimental data reporting Sildenafil effects in different animal models of heart disease will be discussed.

Nitrite and myocardial ischaemia reperfusion injury. Where are we now?

Cardiovascular disease remains the leading cause of death worldwide despite major advances in technology and treatment, with coronary heart disease (CHD) being a key contributor. Following an acute myocardial infarction (AMI), it is imperative that blood flow is rapidly restored to the ischaemic myocardium. However, this restoration is associated with an increased risk of additional complications and further cardiomyocyte death, termed myocardial ischaemia reperfusion injury (IRI). Endogenously produced nitric oxide (NO) plays an important role in protecting the myocardium from IRI. It is well established that NO mediates many of its downstream functions through the 'canonical' NO-sGC-cGMP pathway, which is vital for cardiovascular homeostasis; however, this pathway can become impaired in the face of inadequate delivery of necessary substrates, in particular L-arginine, oxygen and reducing equivalents. Recently, it has been shown that during conditions of ischaemia an alternative pathway for NO generation exists, which has become known as the 'nitrate-nitrite-NO pathway'. This pathway has been reported to improve endothelial dysfunction, protect against myocardial IRI and attenuate infarct size in various experimental models. Furthermore, emerging evidence suggests that nitrite itself provides multi-faceted protection, in an NO-independent fashion, against a myriad of pathophysiologies attributed to IRI. In this review, we explore the existing pre-clinical and clinical evidence for the role of nitrate and nitrite in cardioprotection and discuss the lessons learnt from the clinical trials for nitrite as a perconditioning agent. We also discuss the potential future for nitrite as a pre-conditioning intervention in man.

Mitochondrial Function and Dysfunction in Dilated Cardiomyopathy

Cardiac tissue requires a persistent production of energy in order to exert its pumping function. Therefore, the maintenance of this function relies on mitochondria that represent the “powerhouse” of all cardiac activities. Mitochondria being one of the key players for the proper functioning of the mammalian heart suggests continual regulation and organization. Mitochondria adapt to cellular energy demands via fusion-fission events and, as a proof-reading ability, undergo mitophagy in cases of abnormalities. Ca²⁺ fluxes play a pivotal role in regulating all mitochondrial functions, including ATP production, metabolism, oxidative stress balance and apoptosis. Communication between mitochondria and others organelles, especially the sarcoplasmic reticulum is required for optimal function. Consequently, abnormal mitochondrial activity results in decreased energy production leading to pathological conditions. In this review, we will describe how mitochondrial function or dysfunction impacts cardiac activities and the development of dilated cardiomyopathy.

Monosodium Glutamate Induces Cytotoxicity in Rat Liver via Mitochondrial Permeability Transition Pore Opening

Monosodium glutamate (MSG) is a major food additive used as a flavor enhancer. A lot of controversies have been generated over the use of MSG. The present study therefore investigated whether MSG would induce cytotoxicity via the induction of mitochondrial permeability transition (mPT) pore opening. 36 male albino rats were used for this study. The rats were equally divided into six groups: group I is the control while group II, III, IV, V, and VI were orally treated with MSG (25, 50, 100, 200, and 400 mg/kg) daily for 28 days. The opening of the pore, cytochrome c release, mitochondrial ATPase activity, mitochondrial lipid peroxidation and hepatic DNA fragmentation were determined spectrophotometrically. Histological assessment of prostate and brain was carried out. The results show that MSG at concentrations ≤30 µg/ml did not induce mPT pore opening while higher concentrations caused significant induction of pore opening. Also, at lower doses (25 and 50 mg/kg), MSG did not cause any significant induction of mPT pore opening while at higher doses, there were significant induction of pore opening. Similar trend of results was recorded for cytochrome c release, mitochondrial ATPase activity and lipid peroxidation. The histological results show that at low doses (25 and 50 mg/kg), no significant lesion was observed while higher doses caused benign prostatic hyperplasia (BPH) in the prostate and necrotic damage in the brain. MSG administration at low dose is tolerable while high doses induce cytotoxicity via mPT pore opening.

Mitochondria-Targeted Drug Delivery in Cardiovascular Disease: A Long Road to Nano-Cardio Medicine

Cardiovascular disease (CVD) represents a major threat for human health. The available preventive and treatment interventions are insufficient to revert the underlying pathological processes, which underscores the urgency of alternative approaches. Mitochondria dysfunction plays a key role in the etiopathogenesis of CVD and is regarded as an intriguing target for the development of innovative therapies. Oxidative stress, mitochondrial permeability transition pore opening, and excessive fission are major noxious pathways amenable to drug therapy. Thanks to the advancements of nanotechnology research, several mitochondria-targeted drug delivery systems (DDS) have been optimized with improved pharmacokinetic and biocompatibility, and lower toxicity and antigenicity for application in the cardiovascular field. This review summarizes the recent progress and remaining obstacles in targeting mitochondria as a novel therapeutic option for CVD. The advantages of nanoparticle delivery over un-targeted strategies are also discussed.

Melatonin Can Modulate the Effect of Navitoclax (ABT-737) in HL-60 Cells

Melatonin (N-acetyl-5-methoxytryptamine MEL) is an indolamine that has antioxidant, anti-inflammatory and anti-tumor properties. Moreover, MEL is capable of exhibiting both anti-apoptotic and pro-apoptotic effects. In the normal cells, MEL possesses antioxidant property and has an anti-apoptotic effect, while in the cancer cells it has pro-apoptotic action. We investigated the combined effect of MEL and navitoclax (ABT-737), which promotes cell death, on the activation of proliferation in acute promyelocytic leukemia on a cell model HL-60. The combined effect of these compounds leads to a reduction of the index of mitotic activity. The alterations in the level of anti- and pro-apoptotic proteins such as BclxL, Bclw, Mcl-1, and BAX, membrane potential, Ca²⁺ retention capacity, and ROS production under the combined action of MEL and ABT-737 were performed. We obtained that MEL in combination with ABT-737 decreased Ca²⁺ capacity, dropped membrane potential, increased ROS production, suppressed the expression of anti-apoptotic proteins such as BclxL, Bclw, and Mcl-1, and enhanced the expression of pro-apoptotic BAX. Since, MEL modulates autophagy and endoplasmic reticulum (ER) stress in cancer cells, the combined effect of MEL and ABT-737 on the expression of ER stress and autophagy markers was checked. The combined effect of MEL and ABT-737 (0.2 μM) increased the expression of protein kinase R (PKR)-like endoplasmic reticulum kinase (PERK), leading to a decrease in the level of binding immunoglobulin protein (BIP) followed by an increase in the level of C/EBP homologous protein (CHOP). In this condition, the expression of ERO1 decreased, which could lead to a decrease in the level of protein disulfide isomerase (PDI). The obtained data suggested that melatonin has potential usefulness in the treatment of cancer, where it is able to modulate ER stress, autophagy and apoptosis.

Rosmarinic acid attenuates chromium-induced hepatic and renal oxidative damage and DNA damage in rats

Hexavelant chromium (Cr (V1)) is a widely distributed environmental pollutant inducing damage in different organs of human and animals. The current study was designed to investigate the mechanistic role of rosmarinic acid (RA) to diminish chromium-induced hepatorenal oxidative damage and preneoplastic lesions in rats. Plant material was collected, identified, and extracted. The isolated RA was elucidated relying on the nuclear magnetic resonance spectroscopic data. Twenty-eight male Wistar rats received the following materials daily via oral gavage for 60 days; (Gp1): normal saline, (Gp2) 25 mg/kg.bwt RA, (Gp3) 10 mg/kg.bwt potassium dichromate (K2 Cr2 O7 ), (Gp4) K2 Cr2 O7  + RA. All rats were euthanized at the end of the experiment by cervical dislocation and the liver and kidney were collected. Prolonged continuous exposure of rats to chromium-induced oxidant/antioxidant imbalance manifested by significant elevation of malondialdehyde with reduction in reduced glutathione levels. Remarkable histopathological alterations in the liver and kidney tissue sections were recorded and confirmed by overexpression of the immunohistochemical staining of caspase-3, placental glutathione-S transferase, proliferating cell nuclear antigen together with a significant downregulation of nuclear factor erythroid-2 related factor 2 (Nrf2) gene and upregulation of nibrin gene. Observable improvements in the entire toxicopathological parameters were recorded in group cotreated with RA. Our findings revealed that Cr-induced preneoplastic lesions on the liver and kidney tissues of rats when exposed daily for long period of time, as well as confirmed the ability of RA to alleviate this toxicity through upregulation of Nrf2 pathway and its powerful antioxidant effects.

Tongmai formula improves cardiac function via regulating mitochondrial quality control in the myocardium with ischemia/reperfusion injury

BACKGROUND

Mitochondrial quality control, regulated by mitochondrial dynamics and mitophagy, has been regarded as pivotal process to induce segregation of mitochondria during myocardial ischemia/reperfusion (I/R) injury. However, few works revealed the regulation of mitochondrial quality control by therapeutic agents. Tongmai formula (TM) is a clinically used botanical drug for treating cardiovascular diseases, which mechanism is unveiled. Thus, in this study, we investigated the pharmacological effects of TM on modulating mitochondrial quality control during cardiac injury.

METHODS

Rats subjected to myocardial I/R injury and neonatal rat ventricular myocytes (NRVMs) exposed to hypoxia/reoxygenation (H/R) were used to simulate cardiac injury during myocardial ischemia/reperfusion process. Morphological examination, histopathological examination, echocardiography, and immunohistochemistry were used to determine the cardiac injury after I/R injury. Biochemical indices in serum were estimated by the enzyme-linked immunosorbent assays (ELISA). 5,5',6,6'-tetrachloro-1,1',3,3'-tetraethylbenzimidazolcarbocyanine iodide (JC-1) was used for mitochondrial membrane potential (ΔΨm) evaluation. 2',7'-dichlorofluorescin diacetate (DCFH-DA) was used for intracellular reactive oxygen species (ROS) evaluation. Mitochondria in NRVMs were labeled by tetramethylrhodamine methyl ester (TMRM) for mitochondrial morphosis imaging and estimation. Western blotting was used for cytochrome c (CYCS), apoptosis inducing factor (AIF) and mitofusin 2 (Mfn2) contents evaluation. Immunochemistry fluorescence was used for dynamin related protein 1 (Drp1) expression measurement.

RESULTS

TM treatment markedly decreased myocardium infarct size. It also significantly improved left ventricular contractile function and alleviated cardiomyocytes apoptosis, as well as reduced the production of cardiac troponin T, creatine kinase, lactate dehydrogenase, malondialdehyde and elevated glutathione and superoxide dismutase. Intriguingly, we found that mitochondrial membrane potential loss and mitochondrial permeability transition pore (mPTP) opening were recovered after TM treatment. It also down-regulated cytochrome c and apoptosis inducing factor contents after myocardial I/R injury. In vitro study showed that TM treatment reduced intracellular ROS content and recovered ΔΨ_m in NRVMs after H/R injury. We also observed that TM could reduce the expression level of Drp1, while increased Mfn2 in NRVMs after H/R injury, which indicates that TM may regulate mitochondrial dynamics during H/R injury of NRVMs.

CONCLUSIONS

TM exhibited cardiac protective effect on ischemic myocardium of rats after reperfusion and improved mitochondrial quality control through mitochondrial dynamics in NRVMs after H/R injury.

Quercetin treatment increases H2O2 removal by restoration of endogenous antioxidant activity and blocks isoproterenol-induced cardiac hypertrophy

Oxidative stress, characterized by the accumulation of reactive oxygen species (ROS), is implicated in the pathogenesis of several diseases, including cardiac hypertrophy. The flavonoid quercetin is a potent ROS scavenger, with several beneficial effects for the cardiovascular system, including antihypertrophic effects. Oxidative imbalance has been implicated in cardiac hypertrophy and heart failure. In this work, we tested whether quercetin could attenuate cardiac hypertrophy by improving redox balance and mitochondrial homeostasis. To test this hypothesis, we treated a group of mice with isoproterenol (30 mg/kg/day) for 4 or 8 consecutive days. Another group received quercetin (10 mg/kg/day) from day 5th of isoproterenol treatment. We carried out the following assays in cardiac tissue: measurement of cardiac hypertrophy, protein sulfhydryl, catalase, Cu/Zn and Mn-superoxide dismutase (SOD) activity, detection of H₂O₂, and opening of the mitochondrial permeability transition pore. The animals treated with isoproterenol for the initial 4 days showed increased cardiac weight/tibia length ratio, decreased protein sulfhydryl content, compromised SOD and catalase activity, and high H₂O₂ levels. Quercetin was able to attenuate cardiac hypertrophy, restore protein sulfhydryl, and antioxidant activity, in addition to efficiently blocking the H₂O₂. We also observed that isoproterenol decreases mitochondrial SOD activity, while quercetin reverses it. Strikingly, quercetin also protects mitochondria against the opening of mitochondrial permeability transition pore. Taken together, these results suggest that quercetin is capable of reversing established isoproterenol-induced cardiac hypertrophy through the restoration of cellular redox balance and protecting mitochondria.

Pharmacological preconditioning with intralipid in patients undergoing off-pump coronary artery bypass surgery

Aims and Objectives:

The objective of the study was to determine the preconditioning myocardial protective effects of intralipid (IL) in off-pump coronary artery bypass (OPCAB) surgery by measuring highly sensitive troponin T (hsTnT) and cardiac-specific creatine kinase (CK-MB) as markers of myocardial injury.

Materials and Methods:

Thirty patients, scheduled to undergo elective OPCAB surgery, were randomly assigned to the IL group (n = 15) or control (C) group (n = 15); the IL group received an infusion of 20% IL 2 ml/kg, 30 min prior to revascularization and the control group received an equivalent volume of normal saline. Serum levels of hsTnT and CK-MB were measured before surgery and at 6 h, 24 h, 48 h, and 72 h postoperatively. Also, intraoperative hemodynamic parameters, inotrope use, ventilatory hours, ICU stay, postoperative left ventricular ejection fraction, postoperative lipid profile, renal and hepatic function tests were measured.

Results:

The hsTnT values at the 24 h, 48 h, and 72 h in IL group were significantly lower as compared with the control group. The decline in plasma levels of CK-MB mirrored the hsTnT levels post revascularization at 24 h and 48 h in the IL group compared with the control group; however, at 72 h, level was comparable in both the groups. None of the treated patients had abnormal lipid metabolism, deranged renal, and hepatic function.

Conclusion:

The study revealed Intralipid as a safe pharmacological preconditioning agent for OPCAB surgeries which can reduce the postischemic myocardial injury indicated by the reduction in postischemic cardiac enzymes hsTnT and CK-MB.

Taurine attenuates isoproterenol-induced H9c2 cardiomyocytes hypertrophy by improving antioxidative ability and inhibiting calpain-1-mediated apoptosis

Pathological cardiac hypertrophy is ultimately accompanied by cardiomyocyte apoptosis. Apoptosis mainly related to calpain-1-mediated apoptotic pathways. Studies had proved that taurine can maintain heart health through antioxidation and antiapoptotic functions, but the effect of taurine on cardiac hypertrophy is still unclear. This study aimed to determine whether taurine could inhibit calpain-1-mediated mitochondria-dependent apoptotic pathways in isoproterenol (ISO)-induced hypertrophic cardiomyocytes. We found that taurine could inhibit the increase in cell surface area and reduce the protein expression levels of the hypertrophic markers atrial natriuretic peptide, brain natriuretic polypeptide, and β-myosin heavy chain. Taurine also reduced ROS, intracellular Ca²⁺ overload and mitochondrial membrane potential. Moreover, taurine inhibited cardiomyocyte apoptosis by decreasing the protein expression of calpain-1, Bax, t-Bid, cytosolic cytochrome c, Apaf-1, cleaved caspase-9 and cleaved caspase-3 and by enhancing calpastatin and Bcl-2 protein expression. Calpain-1 small interfering RNA transfection results showed similar antiapoptotic effects as the taurine prevention group. However, compared with the two treatments, taurine inhibited the expression of cleaved caspase-9 more significantly. Therefore, we believe that taurine prevents ISO-induced H9c2 cardiomyocyte hypertrophy by inhibiting oxidative stress, intracellular Ca²⁺ overload, the calpain-1-mediated mitochondria-dependent apoptotic pathway and cleaved caspase-9 levels.

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.

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.

Shengmai Injection Suppresses Angiotensin II-Induced Cardiomyocyte Hypertrophy and Apoptosis via Activation of the AMPK Signaling Pathway Through Energy-Dependent Mechanisms

Shengmai injection (SMI), a traditional Chinese herbal medicine extracted from Panax ginseng C.A. Mey., Ophiopogon japonicus (Thunb.) Ker Gawl., and Schisandra chinensis (Turcz.) Baill., has been used to treat acute and chronic heart failure. This study aimed to further clarify the effects of SMI on energy metabolism. SMI could improve cell-survival rate and also reduce myocardial cell hypertrophy and apoptosis. Mitochondria are important sites of cellular energy metabolism, and SMI protects mitochondrial function which was evaluated by mitochondrial ultrastructure, mitochondrial respiratory control ratio (RCR), and mitochondrial membrane potential (ΔΨm) in this study. The expression levels of adenosine triphosphate (ATP), adenosine diphosphate (ADP), and phosphocreatine (PCr) increased. The expression levels of free fatty acid oxidation [carnitine palmitoyltransferase-1 (CPT-1)], glucose oxidation [glucose transporter-4 (GLUT-4)], and mitochondrial biogenesis-related genes (peroxisome proliferator-activated receptor-γ coactivator-1α [PGC-1α]) were upregulated after SMI treatment. AMP-activated protein kinase (AMPK) is an important signaling pathway regulating energy metabolism and also can regulate the above-mentioned indicators. In the present study, SMI was found to promote phosphorylation of AMPK. However, the effects of SMI on fatty acid, glucose oxidation, mitochondrial biogenesis, as well as inhibiting apoptosis of hypertrophic cardiomyocytes were partly blocked by AMPK inhibitor–compound C. Moreover, decreased myocardial hypertrophy and apoptosis treated by SMI were inhibited by AMPK knockdown with shAMPK to a certain degree and AMPK knockdown almost abolished the SMI-induced increase in the expression of GLUT-4, CPT-1, and PGC-1α. These data suggest that SMI suppressed Ang II–induced cardiomyocyte hypertrophy and apoptosis via activation of the AMPK signaling pathway through energy-dependent mechanisms.

Babao Dan induces gastric cancer cell apoptosis via regulating MAPK and NF-κB signaling pathways

Objective

The objective was to further investigate apoptosis induction by Babao Dan (BBD), which supports its anti-tumor mechanisms, using two human gastric cancer cell lines (AGS and MGC80-3).

Methods

After treatment with various BBD concentrations, cell viability and cytotoxic effects were investigated using methyl thiazolyl tetrazolium (MTT) and lactate dehydrogenase (LDH) assays, respectively. The following indicators of cell apoptosis were evaluated: Annexin V-APC staining, caspase-3/-8/-9 activation, and mitochondrial membrane potential loss. Apoptosis-related protein levels (including Bcl-2-associated X protein [Bax], B-cell CLL/lymphoma 2 [Bcl-2], factor associated suicide [Fas], and Fas ligand [FasL]) were determined by western blot. The following multi-pathway factors were also assessed: p-ERK1/2, p-JNK, p-p38, and p-NF-κB.

Results

The MTT and LDH assays both demonstrated increased BBD cytotoxicity. BBD induced cell apoptosis by stimulating caspase-3/-8/-9 activity and destroying the mitochondrial membrane potential. BBD also regulated key factor expression levels including Bcl-2, Bax, Fas, and FasL and down-regulated protein phosphorylation via the MAPK and NF-κB pathway.

Conclusions

The possible anti-tumor mechanism is that BBD induces apoptosis via the MAPK and NF-κB signaling pathways.

A New Approach for the Prevention and Treatment of Cardiovascular Disorders. Molecular Hydrogen Significantly Reduces the Effects of Oxidative Stress

Cardiovascular diseases are the most common causes of morbidity and mortality worldwide. Redox dysregulation and a dyshomeostasis of inflammation arise from, and result in, cellular aberrations and pathological conditions, which lead to cardiovascular diseases. Despite years of intensive research, there is still no safe and effective method for their prevention and treatment. Recently, molecular hydrogen has been investigated in preclinical and clinical studies on various diseases associated with oxidative and inflammatory stress such as radiation-induced heart disease, ischemia-reperfusion injury, myocardial and brain infarction, storage of the heart, heart transplantation, etc. Hydrogen is primarily administered via inhalation, drinking hydrogen-rich water, or injection of hydrogen-rich saline. It favorably modulates signal transduction and gene expression resulting in suppression of proinflammatory cytokines, excess ROS production, and in the activation of the Nrf2 antioxidant transcription factor. Although H2 appears to be an important biological molecule with anti-oxidant, anti-inflammatory, and anti-apoptotic effects, the exact mechanisms of action remain elusive. There is no reported clinical toxicity; however, some data suggests that H2 has a mild hormetic-like effect, which likely mediate some of its benefits. The mechanistic data, coupled with the pre-clinical and clinical studies, suggest that H2 may be useful for ROS/inflammation-induced cardiotoxicity and other conditions.

Acute Toxicity Assessment: Macroscopic and Ultrastructural Effects in Mice Treated with Oral Tetrodotoxin

Tetrodotoxin (TTX) is an extremely toxic marine compound produced by different genera of bacteria that can reach humans through ingestion mainly of pufferfish but also of other contaminated fish species, marine gastropods or bivalves. TTX blocks voltage-gated sodium channels inhibiting neurotransmission, which in severe cases triggers cardiorespiratory failure. Although TTX has been responsible for many human intoxications limited toxicological data are available. The recent expansion of TTX from Asian to European waters and diversification of TTX-bearing organisms entail an emerging risk of food poisoning. This study is focused on the acute toxicity assessment of TTX administered to mice by oral gavage following macroscopic and microscopic studies. Necropsy revealed that TTX induced stomach swelling 2 h after administration, even though no ultrastructural alterations were further detected. However, transmission electron microscopy images showed an increase of lipid droplets in hepatocytes, swollen mitochondria in spleens, and alterations of rough endoplasmic reticulum in intestines as hallmarks of the cellular damage. These findings suggested that gastrointestinal effects should be considered when evaluating human TTX poisoning.

Mechanisms by which hydrogen sulfide attenuates muscle function following ischemia-reperfusion injury: effects on Akt signaling, mitochondrial function, and apoptosis

Ischemia–reperfusion injury is caused by a period of ischemia followed by massive blood flow into a tissue that had experienced restricted blood flow. The severity of the injury is dependent on the time the tissue was restricted from blood flow, becoming more severe after longer ischemia times. This can lead to many complications such as tissue necrosis, cellular apoptosis, inflammation, metabolic and mitochondrial dysfunction, and even organ failure. One of the emerging therapies to combat ischemic reperfusion injury complications is hydrogen sulfide, which is a gasotransmitter that diffuses across cell membranes to exert effects on various signaling pathways regulating cell survival such as Akt, mitochondrial activity, and apoptosis. Although commonly thought of as a toxic gas, low concentrations of hydrogen sulfide have been shown to be beneficial in promoting tissue survival post-ischemia, and modulate a wide variety of cellular responses. This review will detail the mechanisms of hydrogen sulfide in affecting the Akt signaling pathway, mitochondrial function, and apoptosis, particularly in regards to ischemic reperfusion injury in muscle tissue. It will conclude with potential clinical applications of hydrogen sulfide, combinations with other therapies, and perspectives for future studies.

Pharmacological modulation of mitochondrial ion channels

The field of mitochondrial ion channels has undergone a rapid development during the last three decades, due to the molecular identification of some of the channels residing in the outer and inner membranes. Relevant information about the function of these channels in physiological and pathological settings was gained thanks to genetic models for a few, mitochondria-specific channels. However, many ion channels have multiple localizations within the cell, hampering a clear-cut determination of their function by pharmacological means. The present review summarizes our current knowledge about the ins and outs of mitochondrial ion channels, with special focus on the channels that have received much attention in recent years, namely, the voltage-dependent anion channels, the permeability transition pore (also called mitochondrial megachannel), the mitochondrial calcium uniporter and some of the inner membrane-located potassium channels. In addition, possible strategies to overcome the difficulties of specifically targeting mitochondrial channels versus their counterparts active in other membranes are discussed, as well as the possibilities of modulating channel function by small peptides that compete for binding with protein interacting partners. Altogether, these promising tools along with large-scale chemical screenings set up to identify new, specific channel modulators will hopefully allow us to pinpoint the actual function of most mitochondrial ion channels in the near future and to pharmacologically affect important pathologies in which they are involved, such as neurodegeneration, ischaemic damage and cancer. LINKED ARTICLES: This article is part of a themed section on Mitochondrial Pharmacology: Featured Mechanisms and Approaches for Therapy Translation. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v176.22/issuetoc.

Calcium phosphate buffer formed in the mitochondrial matrix during preconditioning supports ΔpH formation and ischemic ATP production and prolongs cell survival -A hypothesis

Ischemic preconditioning makes cells less sensitive to oxygen deprivation. A similar effect can be achieved by increasing the calcium concentration and applying potassium channel openers. A hypothetical mechanism of preconditioning is presented. In the mitochondrial matrix, there is a calcium hydroxide buffer consisting of a few insoluble calcium phosphate minerals. During ischemia, calcium ions stored in the matrix buffer start to leak out, forming an electric potential difference, while hydroxyl ions remain in the matrix, maintaining its pH and the matrix volume. Preconditioning factors increase the matrix buffer capacity. Production of ATP during ischemia might be the relic of a pre-endosymbiotic past.

Arsenic sulfide amplifies JQ1 toxicity via mitochondrial pathway in gastric and colon cancer cells

Purpose

Gastric and colon cancers have been the leading causes of cancer mortality in the world with limited therapy. Small molecules binding to bromodomains of bromodomain-containing protein 4 (BRD4) exert strong antitumor activities against hematological malignancies, while generally have limited efficacy in advanced solid tumors. Here, we found that the bromodomain and extra-terminal (BET)-bromodomain inhibitor JQ1, when combined with arsenic sulfide (As₄S₄, abbreviated as AS), synergistically decreased the expression of nuclear factor of activated T-cells (NFATs) as well as the downstream oncogene c-Myc and largely induced cell apoptosis via mitochondrial pathway in gastric and colon cancer cell lines.

Methods

The synergistic cytotoxicity of AS and JQ1 in gastric and colon cancer cells was determined by MTT assay and verified by FACS assay. Western blot analysis and quantitative real-time PCR (qPCR) assay were used to detect the expression of NFATs and downstream apoptotic proteins. The mitochondrial transmembrane potential was determined by FACS assay, and the metastasis of cancer cells was detected by the wound-healing assay.

Results

AS and JQ1 synergistically induced cell apoptosis in gastric and colon cancer cells by downregulating NFATs and upregulating apoptotic proteins. Combination of AS and JQ1 was associated with the decreased mitochondrial transmembrane potential, the cytochrome c release, and the subsequent caspase-3 activation.

Conclusion

Thus, our data indicate that AS can effectively enhance the cytotoxicity of BET inhibitors in gastric and colon cancer cells through mitochondrial-mediated apoptosis induction.

Leptin-induced cardiomyocyte hypertrophy is associated with enhanced mitochondrial fission

Cardiac pathology including hypertrophy has been associated with an imbalance between mitochondrial fission and fusion. Generally, well-balanced mitochondrial fission and fusion are essential for proper functions of mitochondria. Leptin is a 16-kDa appetite-suppressing protein which has been shown to induce cardiomyocyte hypertrophy. In the present study, we determined whether leptin can influence mitochondrial fission or fusion and whether this can be related to its hypertrophic effect. Cardiomyocytes treated for 24 h with 3.1 nM leptin (50 ng/ml), a concentration representing plasma levels in obese individuals, demonstrated an increase in surface area and a significant 1.6-fold increase in the expression of the β-myosin heavy chain. Mitochondrial staining with MitoTracker Green dye showed elongated structures in control cells with an average length of 4.5 µm. Leptin produced a time-dependent increase in mitochondrial fragmentation with decreasing mitochondrial length. The hypertrophic response to leptin was also associated with increased protein levels of the mitochondrial fission protein dynamin-related protein1 (Drp1) although gene expression of Drp1 was unaffected possibly suggesting post-translational modifications of Drp1. Indeed, leptin treatment was associated with decreased levels of phosphorylated Drp1 and increased translocation of Drp1 to the mitochondria thereby demonstrating a pro-fission effect of leptin. As calcineurin may dephosphorylate Drp1, we determined the effect of a calcineurin inhibitor, FK506, which prevented leptin-induced hypertrophy as well as mitochondrial fission and mitochondrial dysfunction. In conclusion, our data show that leptin-induced cardiomyocyte hypertrophy is associated with enhanced mitochondrial fission via a calcineurin-mediated pathway. The ability of leptin to stimulate mitochondrial fission may be important in understanding the role of this protein in cardiac pathology especially that related to mitochondrial dysfunction.

Pyridine nucleotides regulate the superoxide anion flash upon permeabilization of mitochondrial membranes: An MCLA-based study

The permeabilization of mitochondrial membranes via permeability transition pore opening or by the pore-forming peptide alamethicin causes a flash of superoxide anion (SA) and hydrogen peroxide production and the inhibition of matrix aconitase. It was shown using the SA probe 3,7-dihydro-2-methyl-6-(4-methoxyphenyl)imidazol[1,2-a]pyrazine-3-one (MCLA) that the substrates of NAD-dependent dehydrogenases, inhibitors of the respiratory chain, and NAD(P)H at millimolar concentrations suppressed or delayed SA flashes. In the presence of added NADH and NADPH, SA flashes were observed only after considerable oxidation of pyridine nucleotides. The production of SA was maximal at NADPH and NADH redox potentials from -315 to -295 mV and from -325 to -270 mV, respectively, depending on NAD(P)H concentration. SA generation supported by NADPH was severalfold greater than that supported by NADH. In intact mitochondria, NADPH- and NADH-dependent SA generation was negligible. Respiratory substrates at physiological or lower concentrations were incapable of suppressing the NADPH-supported SA flash. These data indicate that, in conditions close to pathophysiological, matrix NADPH oxidoreductase(s), presumably, an adrenodoxin reductase in complex with adrenodoxin, can essentially contribute to SA flashes associated with transient or irreversible permeability transition pore opening or membrane permeabilization by another mechanism.

Cardioprotection by ginseng: experimental and clinical evidence and underlying mechanisms

Protection of the ischemic and reperfused myocardium represents a major therapeutic challenge. Translating results from animal studies to the clinical setting has been disappointing, yet the need for effective intervention, particularly to limit heart damage following infarction or surgical procedures such as coronary artery bypass grafting, is substantial. Among the many compounds touted as cardioprotective agents is ginseng, a medicinal herb belonging to the genus Panax, which has been used as a medicinal agent for thousands of years, particularly in Asian societies. The biological actions of ginseng are very complex and reflect composition of many bioactive components, although many of the biological and therapeutic effects of ginseng have been attributed to the presence of steroid-like saponins termed ginsenosides. Both ginseng and many ginsenosides have been shown to exert cardioprotective properties in experimental models. There is also clinical evidence that traditional Chinese medications containing ginseng exert cardioprotective properties, although such clinical evidence is less robust primarily owing to the paucity of large-scale clinical trials. Here, we discuss the experimental and clinical evidence for ginseng, ginsenosides, and ginseng-containing formulations as cardioprotective agents against ischemic and reperfusion injury. We further discuss potential mechanisms, particularly as these relate to antioxidant properties.

Ex Vivo Cardiotoxicity of Antineoplastic Casiopeinas Is Mediated through Energetic Dysfunction and Triggered Mitochondrial-Dependent Apoptosis

Casiopeinas are a group of copper-based antineoplastic molecules designed as a less toxic and more therapeutic alternative to cisplatin or Doxorubicin; however, there is scarce evidence about their toxic effects on the whole heart and cardiomyocytes. Given this, rat hearts were perfused with Casiopeinas or Doxorubicin and the effects on mechanical performance, energetics, and mitochondrial function were measured. As well, the effects of Casiopeinas-triggered cell death were explored in isolated cardiomyocytes. Casiopeinas III-Ea, II-gly, and III-ia induced a progressive and sustained inhibition of heart contractile function that was dose- and time-dependent with an IC₅₀ of 1.3 ± 0.2, 5.5 ± 0.5, and 10 ± 0.7 μM, correspondingly. Myocardial oxygen consumption was not modified at their respective IC₅₀, although ATP levels were significantly reduced, indicating energy impairment. Isolated mitochondria from Casiopeinas-treated hearts showed a significant loss of membrane potential and reduction of mitochondrial Ca²⁺ retention capacity. Interestingly, Cyclosporine A inhibited Casiopeinas-induced mitochondrial Ca²⁺ release, which suggests the involvement of the mitochondrial permeability transition pore opening. In addition, Casiopeinas reduced the viability of cardiomyocytes and stimulated the activation of caspases 3, 7, and 9, demonstrating a cell death mitochondrial-dependent mechanism. Finally, the early perfusion of Cyclosporine A in isolated hearts decreased Casiopeinas-induced dysfunction with reduction of their toxic effect. Our results suggest that heart cardiotoxicity of Casiopeinas is similar to that of Doxorubicin, involving heart mitochondrial dysfunction, loss of membrane potential, changes in energetic metabolites, and apoptosis triggered by mitochondrial permeability.

Inhibition of Na+/H+ Exchanger With EMD 87580 does not Confer Greater Cardioprotection Beyond Preconditioning on Ischemia-Reperfusion Injury in Normal Dogs

Postischemic accumulation of intracellular Na⁺ promotes calcium overload and contributes to cellular necrosis. Cardioprotection afforded by pharmacologic blockade of the sodium-hydrogen exchanger subtype 1 (NHE1) is thought to be more remarkable than that obtained by ischemic conditioning (IC). The window of protection provided by IC pretreatment is maintained even when performed up to 48 hours before ischemia. In addition, the perception exists that combined NHE1 inhibition plus IC produces greater than additive protection against ischemic injury. The current study compared the efficacy of NHE1 blockade by N-[2-methyl-4,5-bis(methylsulfonyl)-benzoyl]-guanidine (EMD 87580 5 mg/kg) combined with first- or second-window IC on ischemic tolerance in dogs subject to 90-minute acute ischemia and 180-minute reperfusion. Infarct size (tetrazolium staining), vascular responses, and myocardial perfusion (microspheres) were assessed. EMD 87580 given before ischemia or before reperfusion did not reduce infarct size (compared to vehicle-treated group). Significant protection against tissue necrosis was obtained by both first- and second-window IC, but additive cardioprotection (ie, greater than that afforded by IC) was not observed by treatment with EMD 87580. Vascular reactivity in the infarct-related artery was not preserved after ischemia-reperfusion in any of the experimental groups. Likewise, either the pharmacologic or the nonpharmacologic interventions did not modify myocardial perfusion. These data demonstrate that EMD 87580 did not protect against ischemia-reperfusion injury regardless of the time of drug administration. Combined EMD 87580 and IC did not antagonize protection that was achieved by either first- or second-window IC alone; no additive protection beyond preconditioning was obtained. Further study is necessary to assess the value of NHE1 blockers as protective agents against myocardial injury.