Nicotinamide riboside promotes Mfn2-mediated mitochondrial fusion in diabetic hearts through the SIRT1-PGC1α-PPARα pathway.

Myocardial dysfunction is associated with an imbalance in mitochondrial fusion/fission dynamics in patients with diabetes. However, effective strategies to regulate mitochondrial dynamics in the diabetic heart are still lacking. Nicotinamide riboside (NR) supplementation ameliorated mitochondrial dysfunction and oxidative stress in both cardiovascular and aging-related diseases. This study investigated whether NR protects against diabetes-induced cardiac dysfunction by regulating mitochondrial fusion/fission and further explored the underlying mechanisms. Here, we showed an evident decrease in NAD+ (nicotinamide adenine dinucleotide) levels and mitochondrial fragmentation in the hearts of leptin receptor-deficient diabetic (db/db) mouse models. NR supplementation significantly increased NAD+ content in the diabetic hearts and promoted mitochondrial fusion by elevating Mfn2 level. Furthermore, NR-induced mitochondrial fusion suppressed mitochondrial H2O2 and O2•- production and reduced cardiomyocyte apoptosis in both db/db mice hearts and neonatal primary cardiomyocytes. Mechanistically, chromatin immunoprecipitation (ChIP) and luciferase reporter assay analyses revealed that PGC1α and PPARα interdependently regulated Mfn2 transcription by binding to its promoter region. NR treatment elevated NAD+ levels and activated SIRT1, resulting in the deacetylation of PGC1α and promoting the transcription of Mfn2. These findings suggested the promotion of mitochondrial fusion via oral supplementation of NR as a potential strategy for delaying cardiac complications in patients with diabetes.

Chronic magnesium deficiency causes reversible mitochondrial permeability transition pore opening and impairs hypoxia tolerance in the rat heart.

Chronic magnesium (Mg) deficiency induces and exacerbates various cardiovascular diseases. We previously investigated the mechanisms underlying decline in cardiac function caused by chronic Mg deficiency and the effectiveness of Mg supplementation on this decline using the Langendorff-perfused isolated mouse heart model. Herein, we used the Langendorff-perfused isolated rat heart model to demonstrate the chronic Mg-deficient rats (Mg-deficient group) had lower the heart rate (HR) and left ventricular pressure (LVDP) than rats with normal Mg levels (normal group). Furthermore, decline in cardiac function due to hypoxia/reoxygenation injury was significantly greater in the Mg-deficient group than in the normal group. Experiments on mitochondrial permeability transition pore (mPTP) using isolated mitochondria revealed that mitochondrial membrane was fragile in the Mg-deficient group, implying that cardiac function decline through hypoxia/reoxygenation injury is associated with mitochondrial function. Mg supplementation for chronic Mg-deficient rats not only improved hypomagnesemia but also almost completely restored cardiac and mitochondrial functions. Therefore, proactive Mg supplementation in pathological conditions induced by Mg deficiency or for those at risk of developing hypomagnesemia may suppress the development and exacerbation of certain disease states.

Allyl Methyl Sulfide Preserved Pressure Overload-Induced Heart Failure Via Modulation of Mitochondrial Function.

BACKGROUND: Cardiovascular diseases are the leading cause of death globally, and they are causing enormous socio-economic burden to the developed and developing countries. Allyl Methyl Sulfide (AMS) is a novel cardioprotective metabolite identified in the serum of rats after raw garlic administration. The present study explored the cardioprotective effect of AMS on thoracic aortic constriction (TAC)-induced cardiac hypertrophy and heart failure model in rats. METHODS: Thoracic aortic constriction (TAC) by titanium ligating clips resulted in the development of pressure overload-induced cardiac hypertrophy and heart failure model. Four weeks prior to TAC and for 8 weeks after TAC, Sprague Dawley (SD) rats were administered with AMS (25 and 50 mg/kg/day) or Enalapril (10 mg/kg/day). RESULTS: We have observed AMS (25 and 50 mg/kg/day) intervention significantly improved structural and functional parameters of the heart. mRNA expression of fetal genes i.e., atrial natriuretic peptide (ANP), alpha skeletal actin (α-SA) and beta myosin heavy chain (ß-MHC) were reduced in AMS treated TAC hearts along with decrease in perivascular and interstitial fibrosis. AMS attenuated lipid peroxidation and improved protein expression of endogenous antioxidant enzymes i.e., catalase and manganese superoxide dismutase (MnSOD) along with electron transport chain (ETC) complex activity. AMS increased mitochondrial fusion proteins i.e., mitofusin 1 (MFN1), mitofusin 2 (MFN2) and optic atrophy protein (OPA1), and reduced fission protein i.e., dynamin-related protein 1 (DRP1). Preliminary study suggests that AMS intervention upregulated genes involved in mitochondrial bioenergetics in normal rats. Further, in-vitro studies suggest that AMS reduced mitochondrial reactive oxygen species (ROS), preserved mitochondrial membrane potential and oxygen consumption rate (OCR) in isoproterenol-treated cardiomyoblast. CONCLUSION: This study demonstrated that AMS protected cardiac remodelling, LV dysfunction and fibrosis in pressure overload-induced cardiac hypertrophy and heart failure model by improving endogenous antioxidants and mitochondrial function.

Pathophysiological Basis for Nutraceutical Supplementation in Heart Failure: A Comprehensive Review.

There is evidence demonstrating that heart failure (HF) occurs in 1-2% of the global population and is often accompanied by comorbidities which contribute to increasing the prevalence of the disease, the rate of hospitalization and the mortality. Although recent advances in both pharmacological and non-pharmacological approaches have led to a significant improvement in clinical outcomes in patients affected by HF, residual unmet needs remain, mostly related to the occurrence of poorly defined strategies in the early stages of myocardial dysfunction. Nutritional support in patients developing HF and nutraceutical supplementation have recently been shown to possibly contribute to protection of the failing myocardium, although their place in the treatment of HF requires further assessment, in order to find better therapeutic solutions. In this context, the Optimal Nutraceutical Supplementation in Heart Failure (ONUS-HF) working group aimed to assess the optimal nutraceutical approach to HF in the early phases of the disease, in order to counteract selected pathways that are imbalanced in the failing myocardium. In particular, we reviewed several of the most relevant pathophysiological and molecular changes occurring during the early stages of myocardial dysfunction. These include mitochondrial and sarcoplasmic reticulum stress, insufficient nitric oxide (NO) release, impaired cardiac stem cell mobilization and an imbalanced regulation of metalloproteinases. Moreover, we reviewed the potential of the nutraceutical supplementation of several natural products, such as coenzyme Q10 (CoQ10), a grape seed extract, Olea Europea L.-related antioxidants, a sodium-glucose cotransporter (SGLT2) inhibitor-rich apple extract and a bergamot polyphenolic fraction, in addition to their support in cardiomyocyte protection, in HF. Such an approach should contribute to optimising the use of nutraceuticals in HF, and the effect needs to be confirmed by means of more targeted clinical trials exploring the efficacy and safety of these compounds.

Electroacupuncture pretreatment alleviates myocardial injury through regulating mitochondrial function.

BACKGROUND: Electroacupuncture is well known for its advantageous neuroanalgesic and therapeutic effects on myocardial ischemia-reperfusion injury. The purpose of the present research was to verify whether electroacupuncture can alleviate bupivacaine-induced myocardial injury. METHODS: Specific pathogen-free Wistar rats were used to establish the bupivacaine-induced myocardial injury model. Western blot, PCR, transmission electron microscope and enzyme-linked immunosorbent (ELISA) methods were used to evaluate bupivacaine-induced structure injury and dysfunction of the mitochondria as well as the alleviating effects of lipid emulsion, acupoint injection, and electroacupuncture pre-treatment of the oxidase stress response. RESULTS: Bupivacaine caused structural damage, degradation, and swelling of mitochondria. Furthermore, it reduced adenosine triphosphate (ATP) synthesis and impaired energy metabolism in the mitochondria. Structural and functional impairment of the mitochondria was alleviated via lipid emulsion injection, acupoint injection, and electroacupuncture pre-treatment. Electroacupuncture pre-treatment of PC6 yielded a greater alleviating effect than others approaches. Following electroacupuncture pre-treatment of PC6 point, the number of mitochondria increased; apoptosis was reduced, enzymatic activity of cytochrome C oxidase (COX) and superoxide dismutase and expression of uncoupling protein 2, voltage-dependent anion channel 1, and Bcl 2 were upregulated and SLC25A6, MDA levels were downregulated. Additionally, our findings indicated that electroacupuncture pre-treatment of PC6 point exerted an effect on the mitochondria via the mitochondrial-transcription-factor-A/nuclear-respiratory-factor-1/proliferator-activated-receptor-gamma-coactivator-1 pathway. CONCLUSION: The present study revealed that electroacupuncture pre-treatment of PC6 could effectively alleviate bupivacaine-induced myocardial mitochondrial damage, thereby providing a theoretical basis for clinical studies and applications of this treatment method.

Mitochondrial bioenergetics links inflammation and cardiac contractility in endotoxemia.

There is current awareness about the central role of mitochondrial dysfunction in the development of cardiac dysfunction in systemic inflammatory syndromes, especially in sepsis and endotoxemia. The aim of this work was to elucidate the mechanism that governs the link between the severity of the systemic inflammatory insult and mitochondrial function, analysing the consequences on heart function, particularly in cardiac contractile state. Female Sprague-Dawley rats were subjected to low-grade endotoxemia (i.p. injection LPS 0.5 mg kg-1 body weight) and severe endotoxemia (i.p. injection LPS 8 mg kg-1 body weight) for 6 h. Blood NO, as well as cardiac TNF-α and IL-1ß mRNA, were found increased as the severity of the endotoxemia increases. Cardiac relaxation was altered only in severe endotoxemia, although contractile and lusitropic reserves were found impaired in both treatments in response to work-overload. Cardiac ultrastructure showed disorientation of myofibrillar structure in both endotoxemia degrees, but mitochondrial swelling and cristae disruption were only observed in severe endotoxemia. Mitochondrial ATP production, O2 consumption and mitochondrial inner membrane potential decreases were related to blood NO levels and mitochondrial protein nitration, leading to diminished ATP availability and impairment of contractile state. Co-treatment with the NOS inhibitor L-NAME or the administration of the NO scavenger c-PTIO leads to the observation that mitochondrial bioenergetics status depends on the degree of the inflammatory insult mainly determined by blood NO levels. Unravelling the mechanisms involved in the onset of sepsis and endotoxemia improves the interpretation of the pathology, and provides new horizons for novel therapeutic targets.

Vagus Nerve Stimulation Attenuates Multiple Organ Dysfunction in Resuscitated Porcine Progressive Sepsis.

OBJECTIVES: To investigate the potential benefits of vagus nerve stimulation in a clinically-relevant large animal model of progressive sepsis. DESIGN: Prospective, controlled, randomized trial. SETTING: University animal research laboratory. SUBJECTS: Twenty-five domestic pigs were divided into three groups: 1) sepsis group (eight pigs), 2) sepsis + vagus nerve stimulation group (nine pigs), and 3) control sham group (eight pigs). INTERVENTIONS: Sepsis was induced by cultivated autologous feces inoculation in anesthetized, mechanically ventilated, and surgically instrumented pigs and followed for 24 hours. Electrical stimulation of the cervical vagus nerve was initiated 6 hours after the induction of peritonitis and maintained throughout the experiment. MEASUREMENTS AND MAIN RESULTS: Measurements of hemodynamics, electrocardiography, biochemistry, blood gases, cytokines, and blood cells were collected at baseline (just before peritonitis induction) and at the end of the in vivo experiment (24 hr after peritonitis induction). Subsequent in vitro analyses addressed cardiac contractility and calcium handling in isolated tissues and myocytes and analyzed mitochondrial function by ultrasensitive oxygraphy. Vagus nerve stimulation partially or completely prevented the development of hyperlactatemia, hyperdynamic circulation, cellular myocardial depression, shift in sympathovagal balance toward sympathetic dominance, and cardiac mitochondrial dysfunction, and reduced the number of activated monocytes. Sequential Organ Failure Assessment scores and vasopressor requirements significantly decreased after vagus nerve stimulation. CONCLUSIONS: In a clinically-relevant large animal model of progressive sepsis, vagus nerve stimulation was associated with a number of beneficial effects that resulted in significantly attenuated multiple organ dysfunction and reduced vasopressor and fluid resuscitation requirements. This suggests that vagus nerve stimulation might provide a significant therapeutic potential that warrants further thorough investigation.

Salvianolic Acid A Protects Neonatal Cardiomyocytes Against Hypoxia/Reoxygenation-Induced Injury by Preserving Mitochondrial Function and Activating Akt/GSK-3ß Signals.

OBJECTIVE: To investigate the effects of salvianolic acid A (SAA) on cardiomyocyte apoptosis and mitochondrial dysfunction in response to hypoxia/reoxygenation (H/R) injury and to determine whether the Akt signaling pathway might play a role. METHODS: An in vitro model of H/R injury was used to study outcomes on primary cultured neonatal rat cardiomyocytes. The cardiomyocytes were treated with 12.5, 25, 50 µg/mL SAA at the beginning of hypoxia and reoxygenation, respectively. Adenosine triphospate (ATP) and reactive oxygen species (ROS) levels were assayed. Cell apoptosis was evaluated by flow cytometry and the expression of cleaved-caspase 3, Bax and Bcl-2 were detected by Western blotting. The effects of SAA on mitochondrial dysfunction were examined by determining the mitochondrial membrane potential (△Ψm) and mitochondrial permeability transition pore (mPTP), followed by the phosphorylation of Akt (p-Akt) and GSK-3ß (p-GSK-3ß), which were measured by Western blotting. RESULTS: SAA significantly preserved ATP levels and reduced ROS production. Importantly, SAA markedly reduced the number of apoptotic cells and decreased cleaved-caspase 3 expression levels, while also reducing the ratio of Bax/Bcl-2. Furthermore, SAA prevented the loss of △Ψm and inhibited the activation of mPTP. Western blotting experiments further revealed that SAA significantly increased the expression of p-Akt and p-GSK-3ß, and the increase in p-GSK-3ß expression was attenuated after inhibition of the Akt signaling pathway with LY294002. CONCLUSION: SAA has a protective effect on cardiomyocyte H/R injury; the underlying mechanism may be related to the preservation of mitochondrial function and the activation of the Akt/GSK-3ß signaling pathway.

Modulation of age related protein expression changes by gelam honey in cardiac mitochondrial rats.

Aging is characterized by progressive decline in biochemical and physiological functions. According to the free radical theory of aging, aging results from oxidative damage due to the accumulation of excess reactive oxygen species (ROS). Mitochondria are the main source of ROS production and are also the main target for ROS. Therefore, a diet high in antioxidant such as honey is potentially able to protect the body from ROS and oxidative damage. Gelam honey is higher in flavonoid content and phenolic compounds compared to other local honey. This study was conducted to determine the effects of gelam honey on age related protein expression changes in cardiac mitochondrial rat. A total of 24 Sprague-Dawley male rats were divided into two groups: the young group (2 months old), and aged group (19 months old). Each group were then subdivided into two groups: control group (force-fed with distilled water), and treatment group (force-fed with gelam honey, 2.5 g/kg), and were treated for 8 months. Comparative proteomic analysis of mitochondria from cardiac tissue was then performed by high performance mass spectrometry (Q-TOF LCMS/MS) followed by validation of selected proteins by Western blotting. Proteins were identified using Spectrum Mill software and were subjected to stringent statistical analysis. A total of 286 proteins were identified in the young control group (YC) and 241 proteins were identified in the young gelam group (YG). In the aged group, a total of 243 proteins were identified in control group (OC), and 271 proteins in gelam group (OG). Comparative proteome profiling identified 69 proteins with different abundance (p < 0.05) in OC when compared to YC, and also in YG when compared to YC. On the other hand, 55 proteins were found to be different in abundance when comparing OG with OC. In the aged group, gelam honey supplementation affected the relative abundance of 52 proteins with most of these proteins showing a decrease in the control group. Bioinformatics analysis showed that the majority of the affected proteins were involved in the respiratory chain (OXPHOS) which play an important role in maintaining mitochondrial function.

Melatonin Efficacy in Obese Leptin-Deficient Mice Heart.

Cardiomyocytes are particularly sensitive to oxidative damage due to the link between mitochondria and sarcoplasmic reticulum necessary for calcium flux and contraction. Melatonin, important indoleamine secreted by the pineal gland during darkness, also has important cardioprotective properties. We designed the present study to define morphological and ultrastructural changes in cardiomyocytes and mainly in mitochondria of an animal model of obesity (ob/ob mice), when treated orally or not with melatonin at 100 mg/kg/day for 8 weeks (from 5 up to 13 week of life). We observed that ob/ob mice mitochondria in sub-sarcolemmal and inter-myofibrillar compartments are often devoid of cristae with an abnormally large size, which are called mega-mitochondria. Moreover, in ob/ob mice the hypertrophic cardiomyocytes expressed high level of 4hydroxy-2-nonenal (4HNE), a marker of lipid peroxidation but scarce degree of mitofusin2, indicative of mitochondrial sufferance. Melatonin oral supplementation in ob/ob mice restores mitochondrial cristae, enhances mitofusin2 expression and minimizes 4HNE and p62/SQSTM1, an index of aberrant autophagic flux. At pericardial fat level, adipose tissue depot strictly associated with myocardium infarction, melatonin reduces adipocyte hypertrophy and inversely regulates 4HNE and adiponectin expressions. In summary, melatonin might represent a safe dietary adjuvant to hamper cardiac mitochondria remodeling and the hypoxic status that occur in pre-diabetic obese mice at 13 weeks of life.

Iron-regulatory proteins secure iron availability in cardiomyocytes to prevent heart failure.

Aims: Iron deficiency (ID) is associated with adverse outcomes in heart failure (HF) but the underlying mechanisms are incompletely understood. Intracellular iron availability is secured by two mRNA-binding iron-regulatory proteins (IRPs), IRP1 and IRP2. We generated mice with a cardiomyocyte-targeted deletion of Irp1 and Irp2 to explore the functional implications of ID in the heart independent of systemic ID and anaemia. Methods and results: Iron content in cardiomyocytes was reduced in Irp-targeted mice. The animals were not anaemic and did not show a phenotype under baseline conditions. Irp-targeted mice, however, were unable to increase left ventricular (LV) systolic function in response to an acute dobutamine challenge. After myocardial infarction, Irp-targeted mice developed more severe LV dysfunction with increased HF mortality. Mechanistically, the activity of the iron-sulphur cluster-containing complex I of the mitochondrial electron transport chain was reduced in left ventricles from Irp-targeted mice. As demonstrated by extracellular flux analysis in vitro, mitochondrial respiration was preserved at baseline but failed to increase in response to dobutamine in Irp-targeted cardiomyocytes. As shown by 31P-magnetic resonance spectroscopy in vivo, LV phosphocreatine/ATP ratio declined during dobutamine stress in Irp-targeted mice but remained stable in control mice. Intravenous injection of ferric carboxymaltose replenished cardiac iron stores, restored mitochondrial respiratory capacity and inotropic reserve, and attenuated adverse remodelling after myocardial infarction in Irp-targeted mice but not in control mice. As shown by electrophoretic mobility shift assays, IRP activity was significantly reduced in LV tissue samples from patients with advanced HF and reduced LV tissue iron content. Conclusions: ID in cardiomyocytes impairs mitochondrial respiration and adaptation to acute and chronic increases in workload. Iron supplementation restores cardiac energy reserve and function in iron-deficient hearts.

Haloperidol aggravates transverse aortic constriction-induced heart failure via mitochondrial dysfunction.

Haloperidol is an antipsychotic drug that inhibits the dopamine D2 receptor among others. Haloperidol also binds the sigma-1 receptor (σ1R) and inhibits it irreversibly. A serious outcome of haloperidol treatment of schizophrenia patients is death due to sudden cardiac failure. Although the cause remains unclear, we hypothesized that these effects were mediated by chronic haloperidol inhibition of cardiac σ1R. To test this, we treated neonatal rat cardiomyocytes with haloperidol, exposed them to angiotensin II and assessed hypertrophy, σ1R expression, mitochondrial Ca(2+) transport and ATP levels. In this context, haloperidol treatment altered mitochondrial Ca(2+) transport resulting in decreased ATP content by inactivating cardiac σ1R and/or reducing its expression. We also performed transverse aortic constriction (TAC) and then treated mice with haloperidol. After two weeks, haloperidol-treated mice showed enhanced heart failure marked by deteriorated cardiac function, reduced ATP production and increasing mortality relative to TAC only mice. ATP supplementation via sodium pyruvate rescued phenotypes seen in haloperidol-treated TAC mice. We conclude that σ1R inactivation or downregulation in response to haloperidol treatment impairs mitochondrial Ca(2+) mobilization, depleting ATP depletion from cardiomyocytes. These findings suggest a novel approach to mitigate haloperidol-related adverse effects in schizophrenia patients by ATP supplementation.

Geniposide Prevents Hypoxia/Reoxygenation-Induced Apoptosis in H9c2 Cells: Improvement of Mitochondrial Dysfunction and Activation of GLP-1R and the PI3K/AKT Signaling Pathway.

BACKGROUND/AIMS: Myocardial ischemia/reperfusion injury is a major cause of morbidity and mortality associated with coronary heart disease. Many studies have demonstrated that natural products are promising chemotherapeutic drugs counteracting the loss of cardiomyocytes. Thus, the purpose of the present study was to investigate the effects of geniposide, a traditional Chinese herb extract from Gardenia jasminoides J. Ellis, on cardiomyocyte apoptosis induced by hypoxia/reoxygenation (H/R) in H9c2 cells, and their underlying mechanisms. METHODS: Cell viability and apoptosis ratio were assessed using the cell counting kit-8 assay and Annexin V/propidium iodide (PI) staining. The concentrations of lactate dehydrogenase (LDH), intracellular total superoxide dismutase (T-SOD), and malondialdehyde (MDA) were detected by microplate reader. The production of reactive oxygen species/reactive nitrogen species (ROS/RNS), the level of mitochondrial calcium, and mitochondrial membrane potential depolarization were measured by confocal laser scanning microscopy. Mitochondrial morphology was visualized using transmission electron microscopy. The expressions of Bcl-2 mRNA and Caspase-3 mRNA were measured by reverse transcription-polymerase chain reaction (RT-PCR). The protein levels of cleaved caspase-3, Bcl-2, Bax, AKT, p-AKTserine473, cytochrome-c were detected by western bloting. RESULTS: Geniposide pretreatment increased cell viability, decreased LDH levels in the supernatant, and inhibited cardiomyocyte apoptosis caused by H/R. Furthermore, geniposide reversed mitochondrial dysfunction by decreasing oxidative stress products (ROS/RNS and MDA), increasing anti-oxidative enzyme (T-SOD) level, improving mitochondrial morphology, attenuating mitochondrial calcium overload and blunting depolarization of mitochondrial membrane. Moreover, geniposide pretreatment increased Bcl-2 level and decreased Bax level, thus enhancing the Bcl-2/Bax ratio. Consistent with the above result, Bcl-2 mRNA expression was upregulated and caspase-3 mRNA expression was downregulated by geniposide. In addition, geniposide decreased the protein expression of cleaved caspase-3 and cytochrome-c and increased the level p-AKTserine473. The protective effects of geniposide were partially reversed by glucagon-like pepitide-1 receptor antagonist exendin-(9-39) and the phosphatidylinositol 3 kinase (PI3K) inhibitor LY294002. CONCLUSIONS: Our results suggest that geniposide pretreatment inhibits H/R-induced myocardial apoptosis by reversing mitochondrial dysfunction, an effect in part due to activation of GLP-1R and PI3K/AKT signaling pathway.

Screening SIRT1 Activators from Medicinal Plants as Bioactive Compounds against Oxidative Damage in Mitochondrial Function.

Sirtuin type 1 (SIRT1) belongs to the family of NAD(+) dependent histone deacetylases and plays a critical role in cellular metabolism and response to oxidative stress. Traditional Chinese medicines (TCMs), as an important part of natural products, have been reported to exert protective effect against oxidative stress in mitochondria. In this study, we screened SIRT1 activators from TCMs and investigated their activities against mitochondrial damage. 19 activators were found in total by in vitro SIRT1 activity assay. Among those active compounds, four compounds, ginsenoside Rb2, ginsenoside F1, ginsenoside Rc, and schisandrin A, were further studied to validate the SIRT1-activation effects by liquid chromatography-mass spectrometry and confirm their activities against oxidative damage in H9c2 cardiomyocytes exposed to tert-butyl hydroperoxide (t-BHP). The results showed that those compounds enhanced the deacetylated activity of SIRT1, increased ATP content, and inhibited intracellular ROS formation as well as regulating the activity of Mn-SOD. These SIRT1 activators also showed moderate protective effects on mitochondrial function in t-BHP cells by recovering oxygen consumption and increasing mitochondrial DNA content. Our results suggested that those compounds from TCMs attenuated oxidative stress-induced mitochondrial damage in cardiomyocytes through activation of SIRT1.

[Protective Effects of Cornus Officinalis Total Glycosides and Cornus Polysaccharides on Myocardial Mitochondria of Acute Myocardial Infarction Rats: an Experimental Study].

OBJECTIVE: To observe the effect of Cornus Officinalis total glycosides (COTG) and Cornus polysaccharides (CP) on myocardial mitochondria and expression levels of glycogen synthase kinase-3ß (GSK-3ß) of acute myocardial infarction (AMI) rats. METHODS: The AMI rat model was established by ligating the left anterior descending branch of coronary artery. Rats were divided into 5 groups according to random digit table, i.e., the sham-operation group, the model group, the COTG prevention group, the CP treatment group, the COTG treatment group, 12 in each group. Normal saline was administered to rats in the normal control group and the model group by gastrogavage. Corresponding medication was respectively administered to rats in the rest 3 groups by gastrogavage. The cardiac function was detected by echocardiography and hemodynamics. The infarct size was determined by Masson trichrome staining. The expression of mitochondrial biogenesis genes such as a subunit of peroxisome proliferators-activated receptor-γ coactivator-1 (PGC-1α), PGC-1ß, nuclear respiratory factor-1 (NRF-1), and GSK-3P mRNA were detected by Real-time PCR. RESULTS: Compared with the sham-operation group, the myocardial infarction size increased, cardiac function decreased, the expression of PGC-1α, PGC-1ß, and NRF-1 mRNA decreased, and the expression of GSK-3ß mRNA increased (all P <0. 05). Compared with the model group, myocardial infarction sizes were reduced, cardiac function was improved, the expression of NRF-1 mRNA was elevated in the COTG prevention group, the CP treatment group, the COTG treatment group; the expression of the PGC-1α and PGC-1ß mRNA was elevated in the COTG prevention group and the CP treatment group; the expression of GSK-3ß mRNA was reduced in the CP treatment group (all P <0. 05). Compared with the CP prevention group, fractional shortening (FS) and aortic systolic blood pressure (SBP) increased in the CP treatment group; ejection fraction (EF) decreased in the CP treatment group; the expression of PGC-1α, PGC-1ß, NRF-1 mRNA were reduced in the the CP treatment group and the COTG treatment group; the expression of GSK-3ß mRNA decreased in the CP treatment group (all P <0. 05). Compared with the COTG treatment group, FS, EF, left ventricular end systolic pressure (LVESP), SBP, and the expression of GSK-3ß mRNA were reduced in the CP treatment group (P <0. 05). CONCLUSIONS: COTG and CP could improve cardiac function, reduce the myocardial infarction area, and promote biogenesis of myocardial mitochondria. Their protective effects on the mitochondria of cadiocytes might be achieved by GSK-3ß signalina pathway.

Hydrogen sulfide alleviates cardiac contractile dysfunction in an Akt2-knockout murine model of insulin resistance: role of mitochondrial injury and apoptosis.

Hydrogen sulfide (H2S) is a toxic gas now being recognized as an endogenous signaling molecule in multiple organ systems, in particular, the cardiovascular system. H2S is known to regulate cardiac function and protect against ischemic injury. However, little information is available regarding the effect of H2S on cardiac function in insulin resistance. This study was designed to examine the impact of H2S supplementation on cardiac function using an Akt2 knockout model of insulin resistance. Wild-type and Akt2 knockout mice were treated with NaHS (50 µM·kg(-1)·day(-1) ip for 10 days) prior to evaluation of echocardiographic, cardiomyocyte contractile, and intracellular Ca(2+) properties, apoptosis, and mitochondrial damage. Our results revealed that Akt2 ablation led to overtly enlarged ventricular end-systolic diameter, reduced myocardial and cardiomyocyte contractile function, and disrupted intracellular Ca(2+) homeostasis and apoptosis, the effects of which were ameliorated by H2S. Furthermore, Akt2 knockout displayed upregulated apoptotic protein markers (Bax, caspase-3, caspase-9, and caspace-12) and mitochondrial damage (reduced aconitase activity and NAD(+), elevated cytochrome-c release from mitochondria) along with reduced phosphorylation of PTEN, Akt, and GSK3ß in the absence of changes in pan protein expression, the effects of which were abolished or significantly ameliorated by H2S treatment. In vitro data revealed that H2S-induced beneficial effect against Akt2 ablation was obliterated by mitochondrial uncoupling. Taken together, our findings suggest the H2S may reconcile Akt2 knockout-induced myocardial contractile defect and intracellular Ca(2+) mishandling, possibly via attenuation of mitochondrial injury and apoptosis.

Isoflurane modulates cardiac mitochondrial bioenergetics by selectively attenuating respiratory complexes.

Mitochondrial dysfunction contributes to cardiac ischemia-reperfusion (IR) injury but volatile anesthetics (VA) may alter mitochondrial function to trigger cardioprotection. We hypothesized that the VA isoflurane (ISO) mediates cardioprotection in part by altering the function of several respiratory and transport proteins involved in oxidative phosphorylation (OxPhos). To test this we used fluorescence spectrophotometry to measure the effects of ISO (0, 0.5, 1, 2mM) on the time-course of interlinked mitochondrial bioenergetic variables during states 2, 3 and 4 respiration in the presence of either complex I substrate K(+)-pyruvate/malate (PM) or complex II substrate K(+)-succinate (SUC) at physiological levels of extra-matrix free Ca(2+) (~200nM) and Na(+) (10mM). To mimic ISO effects on mitochondrial functions and to clearly delineate the possible ISO targets, the observed actions of ISO were interpreted by comparing effects of ISO to those elicited by low concentrations of inhibitors that act at each respiratory complex, e.g. rotenone (ROT) at complex I or antimycin A (AA) at complex III. Our conclusions are based primarily on the similar responses of ISO and titrated concentrations of ETC. inhibitors during state 3. We found that with the substrate PM, ISO and ROT similarly decreased the magnitude of state 3 NADH oxidation and increased the duration of state 3 NADH oxidation, ΔΨm depolarization, and respiration in a concentration-dependent manner, whereas with substrate SUC, ISO and ROT decreased the duration of state 3 NADH oxidation, ΔΨm depolarization and respiration. Unlike AA, ISO reduced the magnitude of state 3 NADH oxidation with PM or SUC as substrate. With substrate SUC, after complete block of complex I with ROT, ISO and AA similarly increased the duration of state 3 ΔΨm depolarization and respiration. This study provides a mechanistic understanding in how ISO alters mitochondrial function in a way that may lead to cardioprotection.

Doxorubicin-induced cardiotoxicity: from bioenergetic failure and cell death to cardiomyopathy.

Doxorubicin (DOX) is an anticancer anthracycline that presents a dose-dependent and cumulative cardiotoxicity as one of the most serious side effects. Several hypotheses have been advanced to explain DOX cardiac side effects, which culminate in the development of life-threatening cardiomyopathy. One of the most studied mechanisms involves the activation of DOX molecule into a more reactive semiquinone by mitochondrial Complex I, resulting in increased oxidative stress. The present review describes and critically discusses what is known about some of the potential mechanisms of DOX-induced cardiotoxicity including mitochondrial oxidative damage and loss of cardiomyocytes. We also discuss alterations of mitochondrial metabolism and the unique characteristics of DOX delayed toxicity, which can also interfere on how the cardiac muscle handles a "second-hit stress." We also present pharmaceutical and nonpharmaceutical approaches that may decrease DOX cardiac alterations in animal models and humans and discuss the limitations of each strategy.

Insulin receptor substrate signaling suppresses neonatal autophagy in the heart.

The induction of autophagy in the mammalian heart during the perinatal period is an essential adaptation required to survive early neonatal starvation; however, the mechanisms that mediate autophagy suppression once feeding is established are not known. Insulin signaling in the heart is transduced via insulin and IGF-1 receptors (IGF-1Rs). We disrupted insulin and IGF-1R signaling by generating mice with combined cardiomyocyte-specific deletion of Irs1 and Irs2. Here we show that loss of IRS signaling prevented the physiological suppression of autophagy that normally parallels the postnatal increase in circulating insulin. This resulted in unrestrained autophagy in cardiomyocytes, which contributed to myocyte loss, heart failure, and premature death. This process was ameliorated either by activation of mTOR with aa supplementation or by genetic suppression of autophagic activation. Loss of IRS1 and IRS2 signaling also increased apoptosis and precipitated mitochondrial dysfunction, which were not reduced when autophagic flux was normalized. Together, these data indicate that in addition to prosurvival signaling, insulin action in early life mediates the physiological postnatal suppression of autophagy, thereby linking nutrient sensing to postnatal cardiac development.

Docosahexaenoic acid supplementation alters key properties of cardiac mitochondria and modestly attenuates development of left ventricular dysfunction in pressure overload-induced heart failure.

PURPOSE: Supplementation with the n3 polyunsaturated fatty acid docosahexaenoic acid (DHA) is beneficial in heart failure patients, however the mechanisms are unclear. DHA is incorporated into membrane phospholipids, which may prevent mitochondrial dysfunction. Thus we assessed the effects of DHA supplementation on cardiac mitochondria and the development of heart failure caused by aortic pressure overload. METHODS: Pathological cardiac hypertrophy was generated in rats by thoracic aortic constriction. Animals were fed either a standard diet or were supplemented with DHA (2.3 % of energy intake). RESULTS: After 14 weeks, heart failure was evident by left ventricular hypertrophy and chamber enlargement compared to shams. Left ventricle fractional shortening was unaffected by DHA treatment in sham animals (44.1 ± 1.6 % vs. 43.5 ± 2.2 % for standard diet and DHA, respectively), and decreased with heart failure in both treatment groups, but to a lesser extent in DHA treated animals (34.9 ± 1.7 %) than with the standard diet (29.7 ± 1.5 %, P < 0.03). DHA supplementation increased DHA content in mitochondrial phospholipids and decreased membrane viscosity. Myocardial mitochondrial oxidative capacity was decreased by heart failure and unaffected by DHA. DHA treatment enhanced Ca(2+) uptake by subsarcolemmal mitochondria in both sham and heart failure groups. Further, DHA lessened Ca(2+)-induced mitochondria swelling, an index of permeability transition, in heart failure animals. Heart failure increased hydrogen peroxide-induced mitochondrial permeability transition compared to sham, which was partially attenuated in interfibrillar mitochondria by treatment with DHA. CONCLUSIONS: DHA decreased mitochondrial membrane viscosity and accelerated Ca(2+) uptake, and attenuated susceptibility to mitochondrial permeability transition and development of left ventricular dysfunction.