Alteration of mitochondrial function in a model of chronic ischemia in vivo in rat heart

Coronary Microvascular Dysfunction in Acute Cholestasis-Induced Liver Injury

BACKGROUND

Previous studies have shown cardiac abnormalities in acute liver injury, suggesting a potential role in the associated high mortality.

METHODS

We designed an experimental study exploring the short-term effects of acute cholestasis-induced liver injury on cardiac function and structure in a rodent bile duct ligation (BDL) model to elucidate the potential interplay. Thirty-seven male Sprague-Dawley rats were subjected to BDL surgery (n = 28) or served as sham-operated (n = 9) controls. Transthoracic echocardiography, Doppler evaluation of the left anterior descending coronary artery, and myocardial contrast echocardiography were performed at rest and during adenosine and dobutamine stress 5 days after BDL. Immunohistochemical staining of myocardial tissue samples for hypoxia and inflammation as well as serum analysis were performed.

RESULTS

BDL animals exhibited acute liver injury with elevated transaminases, bilirubin, and total circulating bile acids (TBA) 5 days after BDL (TBA control: 0.81 ± 2.54 µmol/L vs. BDL: 127.52 ± 57.03 µmol/L; p < 0.001). Concurrently, cardiac function was significantly impaired, characterized by reduced cardiac output (CO) and global longitudinal strain (GLS) in the echocardiography at rest and under pharmacological stress (CO rest control: 120.6 ± 24.3 mL/min vs. BDL 102.5 ± 16.6 mL/min, p = 0.041; GLS rest control: -24.05 ± 3.8% vs. BDL: -18.5 ± 5.1%, p = 0.01). Myocardial perfusion analysis revealed a reduced myocardial blood flow at rest and a decreased coronary flow velocity reserve (CFVR) under dobutamine stress in the BDL animals (CFVR control: 2.1 ± 0.6 vs. BDL: 1.7 ± 0.5 p = 0.047). Immunofluorescence staining indicated myocardial hypoxia and increased neutrophil infiltration.

CONCLUSIONS

In summary, acute cholestasis-induced liver injury can lead to impaired cardiac function mediated by coronary microvascular dysfunction, suggesting that major adverse cardiac events may contribute to the mortality of acute liver failure. This may be due to endothelial dysfunction and direct bile acid signaling.

Ontogeny of cardiomyocytes: ultrastructure optimization to meet the demand for tight communication in excitation-contraction coupling and energy transfer

The ontogeny of the heart describes its development from the fetal to the adult stage. In newborn mammals, blood pressure and thus cardiac performance are relatively low. The cardiomyocytes are thin, and with a central core of mitochondria surrounded by a ring of myofilaments, while the sarcoplasmic reticulum (SR) is sparse. During development, as blood pressure and performance increase, the cardiomyocytes become more packed with structures involved in excitation–contraction (e-c) coupling (SR and myofilaments) and the generation of ATP (mitochondria) to fuel the contraction. In parallel, the e-c coupling relies increasingly on calcium fluxes through the SR, while metabolism relies increasingly on fatty acid oxidation. The development of transverse tubules and SR brings channels and transporters interacting via calcium closer to each other and is crucial for e-c coupling. However, for energy transfer, it may seem counterintuitive that the increased structural density restricts the overall ATP/ADP diffusion. In this review, we discuss how this is because of the organization of all these structures forming modules. Although the overall diffusion across modules is more restricted, the energy transfer within modules is fast. A few studies suggest that in failing hearts this modular design is disrupted, and this may compromise intracellular energy transfer.

This article is part of the theme issue ‘The cardiomyocyte: new revelations on the interplay between architecture and function in growth, health, and disease’.

Cardiac expression and location of hexokinase changes in a mouse model of pure creatine deficiency

Creatine kinase (CK) is considered the main phosphotransfer system in the heart, important for overcoming diffusion restrictions and regulating mitochondrial respiration. It is substrate limited in creatine-deficient mice lacking l-arginine:glycine amidinotransferase (AGAT) or guanidinoacetate N-methyltranferase (GAMT). Our aim was to determine the expression, activity, and mitochondrial coupling of hexokinase (HK) and adenylate kinase (AK), as these represent alternative energy transfer systems. In permeabilized cardiomyocytes, we assessed how much endogenous ADP generated by HK, AK, or CK stimulated mitochondrial respiration and how much was channeled to mitochondria. In whole heart homogenates, and cytosolic and mitochondrial fractions, we measured the activities of AK, CK, and HK. Lastly, we assessed the expression of the major HK, AK, and CK isoforms. Overall, respiration stimulated by HK, AK, and CK was ∼25, 90, and 80%, respectively, of the maximal respiration rate, and ∼20, 0, and 25%, respectively, was channeled to the mitochondria. The activity, distribution, and expression of HK, AK, and CK did not change in GAMT knockout (KO) mice. In AGAT KO mice, we found no changes in AK, but we found a higher HK activity in the mitochondrial fraction, greater expression of HK I, but a lower stimulation of respiration by HK. Our findings suggest that mouse hearts depend less on phosphotransfer systems to facilitate ADP flux across the mitochondrial membrane. In AGAT KO mice, which are a model of pure creatine deficiency, the changes in HK may reflect changes in metabolism as well as influence mitochondrial regulation and reactive oxygen species production.NEW & NOTEWORTHY In creatine-deficient AGAT-/- and GAMT-/- mice, the myocardial creatine kinase system is substrate limited. It is unknown whether subcellular localization and mitochondrial ADP channeling by hexokinase and adenylate kinase may compensate as alternative phosphotransfer systems. Our results show no changes in adenylate kinase, which is the main alternative to creatine kinase in heart. However, we found increased expression and activity of hexokinase I in AGAT-/- cardiomyocytes. This could affect mitochondrial regulation and reactive oxygen species production.

Creatine in Health and Disease

Although creatine has been mostly studied as an ergogenic aid for exercise, training, and sport, several health and potential therapeutic benefits have been reported. This is because creatine plays a critical role in cellular metabolism, particularly during metabolically stressed states, and limitations in the ability to transport and/or store creatine can impair metabolism. Moreover, increasing availability of creatine in tissue may enhance cellular metabolism and thereby lessen the severity of injury and/or disease conditions, particularly when oxygen availability is compromised. This systematic review assesses the peer-reviewed scientific and medical evidence related to creatine's role in promoting general health as we age and how creatine supplementation has been used as a nutritional strategy to help individuals recover from injury and/or manage chronic disease. Additionally, it provides reasonable conclusions about the role of creatine on health and disease based on current scientific evidence. Based on this analysis, it can be concluded that creatine supplementation has several health and therapeutic benefits throughout the lifespan.

Cardiac hypoxic resistance and decreasing lactate during maximum apnea in elite breath hold divers

Breath-hold divers (BHD) enduring apnea for more than 4 min are characterized by resistance to release of reactive oxygen species, reduced sensitivity to hypoxia, and low mitochondrial oxygen consumption in their skeletal muscles similar to northern elephant seals. The muscles and myocardium of harbor seals also exhibit metabolic adaptations including increased cardiac lactate-dehydrogenase-activity, exceeding their hypoxic limit. We hypothesized that the myocardium of BHD possesses similar adaptive mechanisms. During maximum apnea ¹⁵O-H₂O-PET/CT (n = 6) revealed no myocardial perfusion deficits but increased myocardial blood flow (MBF). Cardiac MRI determined blood oxygen level dependence oxygenation (n = 8) after 4 min of apnea was unaltered compared to rest, whereas cine-MRI demonstrated increased left ventricular wall thickness (LVWT). Arterial blood gases were collected after warm-up and maximum apnea in a pool. At the end of the maximum pool apnea (5 min), arterial saturation decreased to 52%, and lactate decreased 20%. Our findings contrast with previous MR studies of BHD, that reported elevated cardiac troponins and decreased myocardial perfusion after 4 min of apnea. In conclusion, we demonstrated for the first time with ¹⁵O-H₂O-PET/CT and MRI in elite BHD during maximum apnea, that MBF and LVWT increases while lactate decreases, indicating anaerobic/fat-based cardiac-metabolism similar to diving mammals.

Fatty Acid Oxidation and Mitochondrial Morphology Changes as Key Modulators of the Affinity for ADP in Rat Heart Mitochondria

Fatty acids are the main respiratory substrates important for cardiac function, and their oxidation is altered during various chronic disorders. We investigated the mechanism of fatty acid-oxidation-induced changes and their relations with mitochondrial morphology and ADP/ATP carrier conformation on the kinetics of the regulation of mitochondrial respiration in rat skinned cardiac fibers. Saturated and unsaturated, activated and not activated, long and medium chain, fatty acids similarly decreased the apparent KmADP. Addition of 5% dextran T-70 to mimic the oncotic pressure of the cellular cytoplasm markedly increased the low apparent KmADP value of mitochondria in cardiac fibers respiring on palmitoyl-l-carnitine or octanoyl-l-carnitine, but did not affect the high apparent KmADP of mitochondria respiring on pyruvate and malate. Electron microscopy revealed that palmitoyl-l-carnitine oxidation-induced changes in the mitochondrial ultrastructure (preventable by dextran) are similar to those induced by carboxyatractyloside. Our data suggest that a fatty acid oxidation-induced conformational change of the adenosine diphosphate (ADP)/adenosine triphosphate (ATP) carrier (M-state to C-state, condensed to orthodox mitochondria) may affect the oxidative phosphorylation affinity for ADP.

Crosstalk between Mitochondria and Cytoskeleton in Cardiac Cells

Elucidation of the mitochondrial regulatory mechanisms for the understanding of muscle bioenergetics and the role of mitochondria is a fundamental problem in cellular physiology and pathophysiology. The cytoskeleton (microtubules, intermediate filaments, microfilaments) plays a central role in the maintenance of mitochondrial shape, location, and motility. In addition, numerous interactions between cytoskeletal proteins and mitochondria can actively participate in the regulation of mitochondrial respiration and oxidative phosphorylation. In cardiac and skeletal muscles, mitochondrial positions are tightly fixed, providing their regular arrangement and numerous interactions with other cellular structures such as sarcoplasmic reticulum and cytoskeleton. This can involve association of cytoskeletal proteins with voltage-dependent anion channel (VDAC), thereby, governing the permeability of the outer mitochondrial membrane (OMM) to metabolites, and regulating cell energy metabolism. Cardiomyocytes and myocardial fibers demonstrate regular arrangement of tubulin beta-II isoform entirely co-localized with mitochondria, in contrast to other isoforms of tubulin. This observation suggests the participation of tubulin beta-II in the regulation of OMM permeability through interaction with VDAC. The OMM permeability is also regulated by the specific isoform of cytolinker protein plectin. This review summarizes and discusses previous studies on the role of cytoskeletal proteins in the regulation of energy metabolism and mitochondrial function, adenosine triphosphate (ATP) production, and energy transfer.

Cardiomyocyte-specific loss of mitochondrial p32/C1qbp causes cardiomyopathy and activates stress responses

Aims

Mitochondria are important organelles, dedicated to energy production. Mitochondrial p32/C1qbp, which functions as an RNA and protein chaperone, interacts with mitochondrial mRNA and is indispensable for mitochondrial function through its regulation of mitochondrial translation in cultured cell lines. However, the precise role of p32/C1qbp in vivo is poorly understood because of embryonic lethality in the systemic p32-deficient mouse. The goal of this study was to examine the physiological function of mitochondrial p32/C1qbp in the heart.

Methods and results

We investigated the role of p32 in regulating cardiac function in mice using a Cre-loxP recombinase technology against p32 with tamoxifen-inducible knockdown or genetic ablation during postnatal periods. Cardiomyocyte-specific deletion of p32 resulted in contractile dysfunction, cardiac dilatation and cardiac fibrosis, compared with hearts of control mice. We also found decreased COX1 expression, decreased rates of oxygen consumption and increased oxidative stress, indicating that these mice had cardiac mitochondrial dysfunction provoked by p32-deficiency at early stage. Next, we investigated lifespan in cardiac-specific p32-deficient mice. The mice died beginning at 12 months and their median lifespan was ∼14 months. Cardiac mitochondria in the p32-deficient mice showed disordered alignment, enlargement and abnormalities in their internal structure by electron microscopy. We observed that, in p32-deficient compared with control myocytes, AMPKɑ was constitutively phosphorylated and 4EBP-1 and ribosomal S6K were less phosphorylated, suggesting impairment of mammalian target of rapamycin signalling. Finally, we found that expression levels of mitokines such as FGF21 and of integrated stress response genes were significantly increased. Metabolic analysis demonstrated that the urea cycle was impaired in the p32-deficient hearts.

Conclusion

These findings support a key role for mitochondrial p32 protein in cardiac myocytes modulating mitochondrial translation and function, and thereby survival.

International Society of Sports Nutrition position stand: safety and efficacy of creatine supplementation in exercise, sport, and medicine

Creatine is one of the most popular nutritional ergogenic aids for athletes. Studies have consistently shown that creatine supplementation increases intramuscular creatine concentrations which may help explain the observed improvements in high intensity exercise performance leading to greater training adaptations. In addition to athletic and exercise improvement, research has shown that creatine supplementation may enhance post-exercise recovery, injury prevention, thermoregulation, rehabilitation, and concussion and/or spinal cord neuroprotection. Additionally, a number of clinical applications of creatine supplementation have been studied involving neurodegenerative diseases (e.g., muscular dystrophy, Parkinson's, Huntington's disease), diabetes, osteoarthritis, fibromyalgia, aging, brain and heart ischemia, adolescent depression, and pregnancy. These studies provide a large body of evidence that creatine can not only improve exercise performance, but can play a role in preventing and/or reducing the severity of injury, enhancing rehabilitation from injuries, and helping athletes tolerate heavy training loads. Additionally, researchers have identified a number of potentially beneficial clinical uses of creatine supplementation. These studies show that short and long-term supplementation (up to 30 g/day for 5 years) is safe and well-tolerated in healthy individuals and in a number of patient populations ranging from infants to the elderly. Moreover, significant health benefits may be provided by ensuring habitual low dietary creatine ingestion (e.g., 3 g/day) throughout the lifespan. The purpose of this review is to provide an update to the current literature regarding the role and safety of creatine supplementation in exercise, sport, and medicine and to update the position stand of International Society of Sports Nutrition (ISSN).

Antioxidant Properties and Cardioprotective Mechanism of Malaysian Propolis in Rats

Propolis contains high concentrations of polyphenols, flavonoids, tannins, ascorbic acid, and reducing sugars and proteins. Malaysian Propolis (MP) has been reported to exhibit high 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical-scavenging activity and ferric reducing antioxidant power (FRAP) values. Herein, we report the antioxidant properties and cardioprotective properties of MP in isoproterenol- (ISO-) induced myocardial infarction in rats. Male Wistar rats (n = 32) were pretreated orally with an ethanol extract of MP (100 mg/kg/day) for 30 consecutive days. Subcutaneous injection of ISO (85 mg/kg in saline) for two consecutive days caused a significant increase in serum cardiac marker enzymes and cardiac troponin I levels and altered serum lipid profiles. In addition significantly increased lipid peroxides and decreased activities of cellular antioxidant defense enzymes were observed in the myocardium. However, pretreatment of ischemic rats with MP ameliorated the biochemical parameters, indicating the protective effect of MP against ISO-induced ischemia in rats. Histopathological findings obtained for the myocardium further confirmed the biochemical findings. It is concluded that MP exhibits cardioprotective activity against ISO-induced oxidative stress through its direct cytotoxic radical-scavenging activities. It is also plausible that MP contributed to endogenous antioxidant enzyme activity via inhibition of lipid peroxidation.

Metabolic compartmentation in rainbow trout cardiomyocytes: coupling of hexokinase but not creatine kinase to mitochondrial respiration

Rainbow trout (Oncorhynchus mykiss) cardiomyocytes have a simple morphology with fewer membrane structures such as sarcoplasmic reticulum and t-tubules penetrating the cytosol. Despite this, intracellular ADP diffusion is restricted. Intriguingly, although diffusion is restricted, trout cardiomyocytes seem to lack the coupling between mitochondrial creatine kinase (CK) and respiration. Our aim was to study the distribution of diffusion restrictions in permeabilized trout cardiomyocytes and verify the role of CK. We found a high activity of hexokinase (HK), which led us to reassess the situation in trout cardiomyocytes. We show that diffusion restrictions are more prominent than previously thought. In the presence of a competitive ADP-trapping system, ADP produced by HK, but not CK, was channeled to the mitochondria. In agreement with this, we found no positively charged mitochondrial CK in trout heart homogenate. The results were best fit by a simple mathematical model suggesting that trout cardiomyocytes lack a functional coupling between ATPases and pyruvate kinase. The model simulations show that diffusion is restricted to almost the same extent in the cytosol and by the outer mitochondrial membrane. Furthermore, they confirm that HK, but not CK, is functionally coupled to respiration. In perspective, our results suggest that across a range of species, cardiomyocyte morphology and metabolism go hand in hand with cardiac performance, which is adapted to the circumstances. Mitochondrial CK is coupled to respiration in adult mammalian hearts, which are specialized to high, sustained performance. HK associates with mitochondria in hearts of trout and neonatal mammals, which are more hypoxia-tolerant.

Restricted ADP movement in cardiomyocytes: Cytosolic diffusion obstacles are complemented with a small number of open mitochondrial voltage-dependent anion channels

Adequate intracellular energy transfer is crucial for proper cardiac function. In energy starved failing hearts, partial restoration of energy transfer can rescue mechanical performance. There are two types of diffusion obstacles that interfere with energy transfer from mitochondria to ATPases: mitochondrial outer membrane (MOM) with voltage-dependent anion channel (VDAC) permeable to small hydrophilic molecules and cytoplasmatic diffusion barriers grouping ATP-producers and -consumers. So far, there is no method developed to clearly distinguish the contributions of cytoplasmatic barriers and MOM to the overall diffusion restriction. Furthermore, the number of open VDACs in vivo remains unknown. The aim of this work was to establish the partitioning of intracellular diffusion obstacles in cardiomyocytes. We studied the response of mitochondrial oxidative phosphorylation of permeabilized rat cardiomyocytes to changes in extracellular ADP by recording 3D image stacks of NADH autofluorescence. Using cell-specific mathematical models, we determined the permeability of MOM and cytoplasmatic barriers. We found that only ~2% of VDACs are accessible to cytosolic ADP and cytoplasmatic diffusion barriers reduce the apparent diffusion coefficient by 6-10×. In cardiomyocytes, diffusion barriers in the cytoplasm and by the MOM restrict ADP/ATP diffusion to similar extents suggesting a major role of both barriers in energy transfer and other intracellular processes.

The impact of cardiac ischemia/reperfusion on the mitochondria-cytoskeleton interactions

Cardiac ischemia-reperfusion (IR) injury compromises mitochondrial oxidative phosphorylation (OxPhos) and compartmentalized intracellular energy transfer via the phosphocreatine/creatine kinase (CK) network. The restriction of ATP/ADP diffusion at the level of the mitochondrial outer membrane (MOM) is an essential element of compartmentalized energy transfer. In adult cardiomyocytes, the MOM permeability to ADP is regulated by the interaction of voltage-dependent anion channel with cytoskeletal proteins, particularly with β tubulin II. The IR-injury alters the expression and the intracellular arrangement of cytoskeletal proteins. The objective of the present study was to investigate the impact of IR on the intracellular arrangement of β tubulin II and its effect on the regulation of mitochondrial respiration. Perfused rat hearts were subjected to total ischemia (for 20min (I20) and 45min (I45)) or to ischemia followed by 30min of reperfusion (I20R and I45R groups). High resolution respirometry and fluorescent confocal microscopy were used to study respiration, β tubulin II and mitochondrial arrangements in cardiac fibers. The results of these experiments evidence a heterogeneous response of mitochondria to IR-induced damage. Moreover, the intracellular rearrangement of β tubulin II, which in the control group colocalized with mitochondria, was associated with increased apparent affinity of OxPhos for ADP, decreased regulation of respiration by creatine without altering mitochondrial CK activity and the ratio between octameric to dimeric isoenzymes. The results of this study allow us to highlight changes of mitochondrial interactions with cytoskeleton as one of the possible mechanisms underlying cardiac IR injury.

Post-Translational Modifications of Cardiac Mitochondrial Proteins in Cardiovascular Disease: Not Lost in Translation

Protein post-translational modifications (PTMs) are crucial in regulating cellular biology by playing key roles in processes such as the rapid on and off switching of signaling network and the regulation of enzymatic activities without affecting gene expressions. PTMs lead to conformational changes in the tertiary structure of protein and resultant regulation of protein function such as activation, inhibition, or signaling roles. PTMs such as phosphorylation, acetylation, and S-nitrosylation of specific sites in proteins have key roles in regulation of mitochondrial functions, thereby contributing to the progression to heart failure. Despite the extensive study of PTMs in mitochondrial proteins much remains unclear. Further research is yet to be undertaken to elucidate how changes in the proteins may lead to cardiovascular and metabolic disease progression in particular. We aimed to summarize the various types of PTMs that occur in mitochondrial proteins, which might be associated with heart failure. This study will increase the understanding of cardiovascular diseases through PTM.

Evaluation of cardioprotective effect of aqueous extract of Allium cepa Linn. bulb on isoprenaline-induced myocardial injury in Wistar albino rats

To investigate the cardioprotective potential of the aqueous extract of Allium cepa Linn. bulb in isoprenaline-induced myocardial injury in Wistar albino rats. In vitro total phenolic, total flavonoid content and 2, 2’-diphenyl-1-picrylhydrazyl hydrate radical scavenging activity was measured. Isoprenaline-induced myocardial injury model was used to evaluate in vivo effect of aqueous extract of A. cepa in Wistar albino rats. Seventy two rats were randomly divided in 6 groups. Rats were treated with A. cepa 400 mg/kg and 800 mg/kg doses for 30 days and myocardial injury was produced by subcutaneous injection of isoprenaline (ISO) 85 mg/kg on day 28 and 29. Carvedilol 1 mg/kg for 30 days served as active control. Electrocardiogram parameters, cardiac injury markers, oxidative stress markers and histopathological changes were evaluated in each group and compared using appropriate statistical tests. In vitro evaluation of aqueous extract of A. cepa showed significant antioxidant property. ISO produced significant myocardial injury as compared to normal control group (P < 0.05). Administration of A. cepa in the dose of 400 mg/kg significantly recovered the altered parameters (Troponin-I, Creatine kinase-MB, glutamate-pyruvate transaminase, HR, R-R interval, and oxidative stress markers) compared to disease control group (P < 0.05) while A. cepa in the dose 800 mg/kg recovered the altered parameters (HR, heart weight/body weight ratio, and superoxide dismutase level) compared to disease control group. Histopathological parameters did not recover in the doses of 400 and 800 mg/kg (P > 0.05). The aqueous extract of A. cepa 400 mg/kg was found to be cardioprotective against myocardial injury while A. cepa 800 mg/kg did not show significant cardioprotective activity. So, we presume that A. cepa might be effective within certain dose range only.

Amelioration of Isoproterenol-Induced Oxidative Damage in Rat Myocardium by Withania somnifera Leaf Extract

We investigated the protective role of Withania somnifera leaf extract (WSLEt) on isoproterenol- (ISO-) induced myocardial infarction (MI) in rats. Subcutaneous injection of ISO (85 mg/kg body weight (b.w.)) administered to rats for two consecutive days caused a significant increase in cardiac troponin I (cTnI) levels and serum lipid profiles, as well as the activities of some marker enzymes. In addition to these diagnostic markers, there were increased levels of lipid peroxidation (LPO) and decreased activities of enzymatic antioxidants (superoxide dismutase (SOD), glutathione peroxidase (GPx), glutathione reductase (GRx), and glutathione-S-transferase (GST)) in the myocardium. However, oral pretreatment (100 mg/kg b.w.) with WSLEt for 4 weeks elicited a significant cardioprotective activity by lowering the levels of cTnI, lipid profiles, and marker enzymes. The levels of LPO products were also significantly decreased. Elevated activities of antioxidant enzymes were also observed in rats pretreated with WSLEt. As further confirmed histopathologically, our findings strongly suggest that the cardioprotective effect of WSLEt on myocardium experiencing ISO-induced oxidative damage may be due to an augmentation of the endogenous antioxidant system and an inhibition of LPO in the myocardial membrane. We conclude that WSLEt confers some protection against oxidative damage in ISO-induced MI in rats.

Myocardial potency of Bio-tea against Isoproterenol induced myocardial damage in rats

Kombucha (Bio-tea) is a beverage produced by the fermentation of sugared black tea using a symbiotic association of bacteria and yeasts. Traditional claims about Kombucha report beneficial effects such as antibiotic properties, gastric regulation, relief from joint rheumatism and positive influence on the cholesterol level, arteriosclerosis, diabetes, and aging problems. The present investigation was carried out to understand the preventive effect of Kombucha on heart weight, blood glucose, total protein, lipid profile and cardiac markers in rats with myocardial damage induced using Isoproterenol. As Bio-tea is produced by fermenting tea, the parameters were compared in rats pre-treated with normal black tea and Bio-tea for 30 days followed by subcutaneous injection of Isoproterenol (85 mg/kg body weight). Normal rats as well as Isoproterenol induced myocardial infarcted rats were also used, which served as controls. Isoproterenol induced myocardial infarcted control rats showed a significant increase in heart weight, blood glucose and cardiac markers and a decrease in plasma protein. Increased levels of cholesterol, triglycerides, low density lipids (LDL) and very low density lipids (VLDL) were also observed, while the high density lipid (HDL) content decreased. Bio-tea showed a higher preventive effect against myocardial infarction when compared to tea, as was observed by the significant reduction in heart weight, and blood glucose and increase in plasma albumin levels. Bio-tea significantly decreased cholesterol, triglycerides, LDL and VLDL while simultaneously increasing the levels of HDL. Similarly a decrease in leakage of cardiac markers from the myocardium was also observed.

Cardioprotective Effects of Tualang Honey: Amelioration of Cholesterol and Cardiac Enzymes Levels

The present study was designed to investigate the cardioprotective effects of Malaysian Tualang honey against isoproterenol- (ISO-) induced myocardial infarction (MI) in rats by investigating changes in the levels of cardiac marker enzymes, cardiac troponin I (cTnI), triglycerides (TG), total cholesterol (TC), lipid peroxidation (LPO) products, and antioxidant defense system combined with histopathological examination. Male albino Wistar rats (n = 40) were pretreated orally with Tualang honey (3 g/kg/day) for 45 days. Subcutaneous injection of ISO (85 mg/kg in saline) for two consecutive days caused a significant increase in serum cardiac marker enzymes (creatine kinase-MB (CK-MB), lactate dehydrogenase (LDH), and aspartate transaminase (AST)), cTnI, serum TC, and TG levels. In addition, ISO-induced myocardial injury was confirmed by a significant increase in heart lipid peroxidation (LPO) products (TBARS) and a significant decrease in antioxidant enzymes (SOD, GPx, GRx, and GST). Pretreatment of ischemic rats with Tualang honey conferred significant protective effects on all of the investigated biochemical parameters. The biochemical findings were further confirmed by histopathological examination in both Tualang-honey-pretreated and ISO-treated hearts. The present study demonstrates that Tualang honey confers cardioprotective effects on ISO-induced oxidative stress by contributing to endogenous antioxidant enzyme activity via inhibition of lipid peroxidation.

Tight coupling of Na+/K+-ATPase with glycolysis demonstrated in permeabilized rat cardiomyocytes

The effective integrated organization of processes in cardiac cells is achieved, in part, by the functional compartmentation of energy transfer processes. Earlier, using permeabilized cardiomyocytes, we demonstrated the existence of tight coupling between some of cardiomyocyte ATPases and glycolysis in rat. In this work, we studied contribution of two membrane ATPases and whether they are coupled to glycolysis--sarcoplasmic reticulum Ca2+ ATPase (SERCA) and plasmalemma Na+/K+-ATPase (NKA). While SERCA activity was minor in this preparation in the absence of calcium, major role of NKA was revealed accounting to ∼30% of the total ATPase activity which demonstrates that permeabilized cell preparation can be used to study this pump. To elucidate the contribution of NKA in the pool of ATPases, a series of kinetic measurements was performed in cells where NKA had been inhibited by 2 mM ouabain. In these cells, we recorded: ADP- and ATP-kinetics of respiration, competition for ADP between mitochondria and pyruvate kinase (PK), ADP-kinetics of endogenous PK, and ATP-kinetics of total ATPases. The experimental data was analyzed using a series of mathematical models with varying compartmentation levels. The results show that NKA is tightly coupled to glycolysis with undetectable flux of ATP between mitochondria and NKA. Such tight coupling of NKA to PK is in line with its increased importance in the pathological states of the heart when the substrate preference shifts to glucose.

Cardiovascular Diseases and Panax ginseng: A Review on Molecular Mechanisms and Medical Applications

Ginseng is one of the most widely used herbal medicines and is reported to have a wide range of therapeutic and pharmacological applications. Ginseng may also be potentially valuable in treating cardiovascular diseases. Research concerning cardiovascular disease is focusing on purified individual ginsenoside constituents of ginseng to reveal specific mechanisms instead of using whole ginseng extracts. The most commonly studied ginsenosides are Rb1, Rg1, Rg3, Rh1, Re, and Rd. The molecular mechanisms and medical applications of ginsenosides in the treatment of cardiovascular disease have attracted much attention and been the subject of numerous publications. Here, we review the current literature on the myriad pharmacological functions and the potential benefits of ginseng in this area. In vitro investigations using cell cultures and in vivo animal models have indicated ginseng's potential cardiovascular benefits through diverse mechanisms that include antioxidation, modifying vasomotor function, reducing platelet adhesion, influencing ion channels, altering autonomic neurotransmitters release, and improving lipid profiles. Some 40 ginsenosides have been identified. Each may have different effects in pharmacology and mechanisms due to their different chemical structures. This review also summarizes results of relevant clinical trials regarding the cardiovascular effects of ginseng, particularly in the management of hypertension and improving cardiovascular function.

HS-1793, a recently developed resveratrol analogue protects rat heart against hypoxia/reoxygenation injury via attenuating mitochondrial damage

Resveratrol is known to exert a cardioprotective effect against hypoxia/reoxygenation (H/R) injury. HS-1793 is a novel, more stable resveratrol analog, but its cardioprotective effects were unknown. The present study aimed to test the cardioprotective effect of HS-1793 against H/R injury and investigate the role of mitochondria in Sprague Dawley rat heart damage using an ex vivo Langendorff system. HS-1793 ameliorated H/R-induced mitochondrial dysfunction by reducing mitochondrial reactive oxygen species production, improving mitochondrial oxygen consumption and suppressing mitochondrial calcium (Ca(2+)) overload during reperfusion. Moreover, HS-1793-treated rat heart showed reduced infarct size. Our data suggest that HS-1793 can protect cardiac against mitochondrial damage following H/R, thereby suppressing injury.

Impaired mitochondrial function in chronically ischemic human heart

Chronic ischemic heart disease is associated with myocardial hypoperfusion. The resulting hypoxia potentially inflicts damage upon the mitochondria, leading to a compromised energetic state. Furthermore, ischemic damage may cause excessive production of reactive oxygen species (ROS), producing mitochondrial damage, hereby reinforcing a vicious circle. Ischemic preconditioning has been proven protective in acute ischemia, but the subject of chronic ischemic preconditioning has not been explored in humans. We hypothesized that mitochondrial respiratory capacity would be diminished in chronic ischemic regions of human myocardium but that these mitochondria would be more resistant to ex vivo ischemia and, second, that ROS generation would be higher in ischemic myocardium. The aim of this study was to test mitochondrial respiratory capacity during hyperoxia and hypoxia, to investigate ROS production, and finally to assess myocardial antioxidant levels. Mitochondrial respiration in biopsies from ischemic and nonischemic regions from the left ventricle of the same heart was compared in nine human subjects. Maximal oxidative phosphorylation capacity in fresh muscle fibers was lower in ischemic compared with nonischemic myocardium (P < 0.05), but the degree of coupling (respiratory control ratio) did not differ (P > 0.05). The presence of ex vivo hypoxia did not reveal any chronic ischemic preconditioning of the ischemic myocardial regions (P > 0.05). ROS production was higher in ischemic myocardium (P < 0.05), and the levels of antioxidant protein expression was lower. Diminished mitochondrial respiration capacity and excessive ROS production demonstrate an impaired mitochondrial function in ischemic human heart muscle. No chronic ischemic preconditioning effect was found.

Analysis of molecular movement reveals latticelike obstructions to diffusion in heart muscle cells

Intracellular diffusion in muscle cells is known to be restricted. Although characteristics and localization of these restrictions is yet to be elucidated, it has been established that ischemia-reperfusion injury reduces the overall diffusion restriction. Here we apply an extended version of raster image correlation spectroscopy to determine directional anisotropy and coefficients of diffusion in rat cardiomyocytes. Our experimental results indicate that diffusion of a smaller molecule (1127 MW fluorescently labeled ATTO633-ATP) is restricted more than that of a larger one (10,000 MW Alexa647-dextran), when comparing diffusion in cardiomyocytes to that in solution. We attempt to provide a resolution to this counterintuitive result by applying a quantitative stochastic model of diffusion. Modeling results suggest the presence of periodic intracellular barriers situated ∼1 μm apart having very low permeabilities and a small effect of molecular crowding in volumes between the barriers. Such intracellular structuring could restrict diffusion of molecules of energy metabolism, reactive oxygen species, and apoptotic signals, enacting a significant role in normally functioning cardiomyocytes as well as in pathological conditions of the heart.

Mitochondrial proteome remodelling in pressure overload-induced heart failure: the role of mitochondrial oxidative stress

AIMS

We investigate the role of mitochondrial oxidative stress in mitochondrial proteome remodelling using mouse models of heart failure induced by pressure overload.

METHODS AND RESULTS

We demonstrate that mice overexpressing catalase targeted to mitochondria (mCAT) attenuate pressure overload-induced heart failure. An improved method of label-free unbiased analysis of the mitochondrial proteome was applied to the mouse model of heart failure induced by transverse aortic constriction (TAC). A total of 425 mitochondrial proteins were compared between wild-type and mCAT mice receiving TAC or sham surgery. The changes in the mitochondrial proteome in heart failure included decreased abundance of proteins involved in fatty acid metabolism, an increased abundance of proteins in glycolysis, apoptosis, mitochondrial unfolded protein response and proteolysis, transcription and translational control, and developmental processes as well as responses to stimuli. Overexpression of mCAT better preserved proteins involved in fatty acid metabolism and attenuated the increases in apoptotic and proteolytic enzymes. Interestingly, gene ontology analysis also showed that monosaccharide metabolic processes and protein folding/proteolysis were only overrepresented in mCAT but not in wild-type mice in response to TAC.

CONCLUSION

This is the first study to demonstrate that scavenging mitochondrial reactive oxygen species (ROS) by mCAT not only attenuates most of the mitochondrial proteome changes in heart failure, but also induces a subset of unique alterations. These changes represent processes that are adaptive to the increased work and metabolic requirements of pressure overload, but which are normally inhibited by overproduction of mitochondrial ROS.

Cardioprotective activity of Amaranthus viridis Linn: effect on serum marker enzymes, cardiac troponin and antioxidant system in experimental myocardial infarcted rats

BACKGROUND

Cardiovascular diseases (CVDs) have a high prevalence in developing and developed countries and myocardial infarction accounts for majority of deaths and disabilities. The current study dealt with the protective role of Amaranthus viridis Linn on isoproterenol (ISO)-induced myocardial infarction (MI) in rats.

METHODS

Subcutaneous injection of ISO (20 mg/kg body weight in 1 ml saline) to rats for two consecutive days offered significant alteration in cardiac marker enzymes (AST, ALT, LDH and CPK), cardiac troponin, lipid peroxidation products (TBARS and hydroperoxide) and antioxidant system (CAT, SOD, GPx, GST, GSH and GSSG). ISO-induced myocardial damage was indicated by increased activities of marker enzymes in serum and the levels of cardiac troponin in the serum. In addition to these diagnostic markers, the levels of lipid peroxidation products in the heart were significantly (p<0.05) increased and the activities of enzymic antioxidants and non-enzymic antioxidant such as glutathione in the heart was significantly (p<0.05) decreased and GSSG in the heart was increased in ISO-induced rats.

RESULTS

Effect of Amaranthus viridis oral treatment (100, 200 and 300 mg/kg body weight) for 45 days elicited a significant cardio protective activity by lowering the levels of serum marker enzymes, cardiac troponin, GSSG and lipid peroxidation and elevated the levels of antioxidant enzymes and GSH. The effect at a dose of 300 mg/kg of A. viridis was more pronounced than that of the dose 100 mg/kg and 200mg/kg and brought back all the parameters to near normal. The effect produced by A. viridis was compared with α-tocopherol.

CONCLUSIONS

The present findings have demonstrated that the cardioprotective effects of A. viridis in ISO-induced oxidative damage may be due to an augmentation of the endogenous antioxidants and inhibition of lipid peroxidation of membrane.

Cardiac proteomic responses to ischemia-reperfusion injury and ischemic preconditioning

Cardiac ischemia and ischemia-reperfusion (I/R) injury are major contributors to morbidity and mortality worldwide. Pathological mechanisms of I/R and the physiological mechanisms of ischemic preconditioning (IPC), which is an effective cardiac protective response, have been widely investigated in the last decade to search for means to prevent or treat this disease. Proteomics is a powerful analytical tool that has provided important information to identify target proteins and understand the underlying mechanisms of I/R and IPC. Here, we review the application of proteomics to I/R injury and IPC to discover target proteins. We analyze the functional meaning of the accumulated data on hundreds of proteins using various bioinformatics applications. In addition, we review exercise-induced proteomic alterations in the heart to understand the potential cardioprotective role of exercise against I/R injury. Further developments in the proteomic field that target specialized proteins will yield new insights for optimizing therapeutic targets and developing a wide range of therapeutic agents against ischemic heart disease.

An in vivo and in vitro study on the protective effects of N-acetylcysteine on mitochondrial dysfunction in isoproterenol treated myocardial infarcted rats

Altered mitochondrial function plays an important role in the pathology of myocardial infarction. We investigated the protective effects of N-acetylcysteine on mitochondrial dysfunction in isoproterenol induced myocardial infarcted rats. Rats were pretreated with N-acetylcysteine (10 mg/kg) orally daily for 14 days. After pretreatment, rats were induced myocardial infarction by isoproterenol (100 mg/kg) at an interval of 24 h for 2 days. Lipid peroxidation products, antioxidants, lipids, mitochondrial marker enzymes and calcium in the mitochondrial heart were determined. Transmission electron microscopic and in vitro studies were also done. Isoproterenol treatment caused significant increase in mitochondrial lipid peroxides and lipids except phospholipids with significant decrease in mitochondrial antioxidants. Significant decreased activities of marker enzymes and significant increased calcium were observed in mitochondria of myocardial infarcted rats. Pretreatment with N-acetylcysteine showed significant protective effects on all the biochemical parameters and preserved the integrity of heart tissue and restored normal mitochondrial function in myocardial infarcted rats. Transmission electron microscopic findings on the structure of the heart mitochondria confirmed the protective effects and in vitro study also confirmed the antioxidant potential of NAC. The possible mechanism for the improved cardiac mitochondrial function might be due to scavenging free radicals, improving the antioxidant and mitochondrial marker enzymes, maintaining GSH levels, lipids and Ca(2+) levels by its antioxidant effect. Thus, N-acetylcysteine protected the mitochondrial heart from ISO treated mitochondrial damage. A diet containing N-acetylcysteine may be beneficial to myocardial infarcted heart.

Iron overload and diabetes risk: a shift from glucose to Fatty Acid oxidation and increased hepatic glucose production in a mouse model of hereditary hemochromatosis

OBJECTIVE

Excess tissue iron levels are a risk factor for diabetes, but the mechanisms underlying the association are incompletely understood. We previously published that mice and humans with a form of hereditary iron overload, hemochromatosis, exhibit loss of β-cell mass. This effect by itself is not sufficient, however, to fully explain the diabetes risk phenotype associated with all forms of iron overload.

RESEARCH DESIGN AND METHODS

We therefore examined glucose and fatty acid metabolism and hepatic glucose production in vivo and in vitro in a mouse model of hemochromatosis in which the gene most often mutated in the human disease, HFE, has been deleted (Hfe⁻(/)⁻).

RESULTS

Although Hfe⁻(/)⁻ mice exhibit increased glucose uptake in skeletal muscle, glucose oxidation is decreased and the ratio of fatty acid to glucose oxidation is increased. On a high-fat diet, the Hfe⁻(/)⁻ mice exhibit increased fatty acid oxidation and are hypermetabolic. The decreased glucose oxidation in skeletal muscle is due to decreased pyruvate dehydrogenase (PDH) enzyme activity related, in turn, to increased expression of PDH kinase 4 (pdk4). Increased substrate recycling to liver contributes to elevated hepatic glucose production in the Hfe⁻(/)⁻ mice.

CONCLUSIONS

Increased hepatic glucose production and metabolic inflexibility, both of which are characteristics of type 2 diabetes, may contribute to the risk of diabetes with excessive tissue iron.

Dietary iron restriction or iron chelation protects from diabetes and loss of beta-cell function in the obese (ob/ob lep-/-) mouse

Iron overload can cause insulin deficiency, but in some cases this may be insufficient to result in diabetes. We hypothesized that the protective effects of decreased iron would be more significant with increased beta-cell demand and stress. Therefore, we treated the ob/ob mouse model of type 2 diabetes with an iron-restricted diet (35 mg/kg iron) or with an oral iron chelator. Control mice were fed normal chow containing 500 mg/kg iron. Neither treatment resulted in iron deficiency or anemia. The low-iron diet significantly ameliorated diabetes in the mice. The effect was long lasting and reversible. Ob/ob mice on the low-iron diet exhibited significant increases in insulin sensitivity and beta-cell function, consistent with the phenotype in mouse models of hereditary iron overload. The effects were not accounted for by changes in weight or feeding behavior. Treatment with iron chelation had a more dramatic effect, allowing the ob/ob mice to maintain normal glucose tolerance for at least 10.5 wk despite no effect on weight. Although dietary iron restriction preserved beta-cell function in ob/ob mice fed a high-fat diet, the effects on overall glucose levels were less apparent due to a loss of the beneficial effects of iron on insulin sensitivity. Beneficial effects of iron restriction were minimal in wild-type mice on normal chow but were apparent in mice on high-fat diets. We conclude that, even at "normal" levels, iron exerts detrimental effects on beta-cell function that are reversible with dietary restriction or pharmacotherapy.

Pretreatment with a traditional Chinese formula, guanxin II, reduces cardiac apoptosis via the Akt survival pathway in rats with myocardial ischemia

Guanxin II (GXII) is a traditional Chinese formula to treat coronary heart disease in China. Previous studies indicate cardioprotection of GXII are related to cardiomyocyte apoptosis. Akt is necessary and sufficient for inhibition of apoptosis in cardiomyocytes. Our aim was to examine whether or not the antiapoptotic mechanisms of GXII are related to the Akt pathway. Male Sprague-Dawley rats were randomly assigned to four groups: GXII administered at 2.5 or 0.5 g raw materials/kg, the vehicle control and sham-operated oral 0.9% NaCl. They were pretreated once a day for 15 consecutive days by gavage. Thirty min after the last administration, the left anterior descending coronary artery was occluded to induce myocardial ischemia except for the sham-operated rats. Compared with rats receiving vehicle, those rats pretreated with GXII at 2.5 g/kg significantly reduced infarct size and decrease apoptosis. Furthermore, GXII (2.5 g/kg) significantly activated Akt kinase, increased the Bcl-2/Bax ratio, inhibited cytochrome c release, reduced caspase-9 activation, and attenuated subsequent caspase-3 activation. GXII at 0.5 g/kg have no noticeable effect on these parameters. Meanwhile, GXII at 2.5 g/kg did not change myocardial blood flow of ischemic zone, indicating a direct action on cardiomyocytes. These results suggest GXII at 2.5 g/kg ensures the survival of myocardium by enhancing the Akt-mediated antiapoptosis pathway. The findings provide new evidence of the effective and safe therapy with GXII for patients with chronic coronary heart disease.

Glutathione peroxidase 1 protects mitochondria against hypoxia/reoxygenation damage in mouse hearts

Glutathione peroxidase 1 (GPx1) plays an important role in preventing cardiac dysfunction following ischemia-reperfusion injury. However, its role in protecting cardiac mitochondria against reoxygenation-induced reactive oxygen species (ROS) generation in vivo is unclear. We examined the role of GPx1 in protecting cardiac mitochondria against hypoxia-reoxygenation (HR) damage by testing for alterations in cardiac mitochondrial function. We used a two-dimensional gel electrophoresis proteomics analysis to examine the effects of reoxygenation on cardiac protein in wild-type (GPx1(+/+)) and GPx1 knockout (GPx1(-/-)) mouse hearts. We identified 42 protein spots showing differential expression in the two groups. Sixteen of the proteins identified were located in mitochondria and were involved in a number of key metabolic pathways. To verify our proteomics findings functionally, we performed NADH autofluorescence measurements and ATP production assays. The reduced expression of oxidative phosphorylation proteins in GPx1(-/-) mice following HR treatment resulted in loss of the mitochondrial membrane potential and decreased mitochondrial respiration. Mitochondrial ROS production and oxidative mtDNA damage were increased markedly during reoxygenation in GPx1(-/-) hearts. We also found morphological abnormalities in cardiac mitochondria and myocytes in HR-treated GPx1(-/-). This is the first report of the role of GPx1 in protecting cardiac mitochondria against reoxygenation damage in vivo. These findings will help clarify the mechanisms of HR injury and will aid in the development of antioxidant therapies to prevent cardiac mitochondrial dysfunction associated with reoxygenation.

Structure-function relationships in feedback regulation of energy fluxes in vivo in health and disease: mitochondrial interactosome

The aim of this review is to analyze the results of experimental research of mechanisms of regulation of mitochondrial respiration in cardiac and skeletal muscle cells in vivo obtained by using the permeabilized cell technique. Such an analysis in the framework of Molecular Systems Bioenergetics shows that the mechanisms of regulation of energy fluxes depend on the structural organization of the cells and interaction of mitochondria with cytoskeletal elements. Two types of cells of cardiac phenotype with very different structures were analyzed: adult cardiomyocytes and continuously dividing cancerous HL-1 cells. In cardiomyocytes mitochondria are arranged very regularly, and show rapid configuration changes of inner membrane but no fusion or fission, diffusion of ADP and ATP is restricted mostly at the level of mitochondrial outer membrane due to an interaction of heterodimeric tubulin with voltage dependent anion channel, VDAC. VDAC with associated tubulin forms a supercomplex, Mitochondrial Interactosome, with mitochondrial creatine kinase, MtCK, which is structurally and functionally coupled to ATP synthasome. Due to selectively limited permeability of VDAC for adenine nucleotides, mitochondrial respiration rate depends almost linearly upon the changes of cytoplasmic ADP concentration in their physiological range. Functional coupling of MtCK with ATP synthasome amplifies this signal by recycling adenine nucleotides in mitochondria coupled to effective phosphocreatine synthesis. In cancerous HL-1 cells this complex is significantly modified: tubulin is replaced by hexokinase and MtCK is lacking, resulting in direct utilization of mitochondrial ATP for glycolytic lactate production and in this way contributing in the mechanism of the Warburg effect. Systemic analysis of changes in the integrated system of energy metabolism is also helpful for better understanding of pathogenesis of many other diseases.

Diffusion restrictions surrounding mitochondria: a mathematical model of heart muscle fibers

Several experiments on permeabilized heart muscle fibers suggest the existence of diffusion restrictions grouping mitochondria and surrounding ATPases. The specific causes of these restrictions are not known, but intracellular structures are speculated to act as diffusion barriers. In this work, we assume that diffusion restrictions are induced by sarcoplasmic reticulum (SR), cytoskeleton proteins localized near SR, and crowding of cytosolic proteins. The aim of this work was to test whether such localization of diffusion restrictions would be consistent with the available experimental data and evaluate the extent of the restrictions. For that, a three-dimensional finite-element model was composed with the geometry based on mitochondrial and SR structural organization. Diffusion restrictions induced by SR and cytoskeleton proteins were varied with other model parameters to fit the set of experimental data obtained on permeabilized rat heart muscle fibers. There are many sets of model parameters that were able to reproduce all experiments considered in this work. However, in all the sets, <5–6% of the surface formed by SR and associated cytoskeleton proteins is permeable to metabolites. Such a low level of permeability indicates that the proteins should play a dominant part in formation of the diffusion restrictions.

Direct measurement of energy fluxes from mitochondria into cytoplasm in permeabilized cardiac cells in situ: some evidence for Mitochondrial Interactosome

The aim of this study was to measure energy fluxes from mitochondria in isolated permeabilized cardiomyocytes. Respiration of permeabilized cardiomyocytes and mitochondrial membrane potential were measured in presence of MgATP, pyruvate kinase - phosphoenolpyruvate and creatine. ATP and phosphocreatine concentrations in medium surrounding cardiomyocytes were determined. While ATP concentration did not change in time, mitochondria effectively produced phosphocreatine (PCr) with PCr/O(2) ratio equal to 5.68 +/- 0.14. Addition of heterodimeric tubulin to isolated mitochondria was found to increase apparent Km for exogenous ADP from 11 +/- 2 microM to 330 +/- 47 microM, but creatine again decreased it to 23 +/- 6 microM. These results show directly that under physiological conditions the major energy carrier from mitochondria into cytoplasm is PCr, produced by mitochondrial creatine kinase (MtCK), which functional coupling to adenine nucleotide translocase is enhanced by selective limitation of permeability of mitochondrial outer membrane within supercomplex ATP Synthasome-MtCK-VDAC-tubulin, Mitochondrial Interactosome.

Regulation of respiration controlled by mitochondrial creatine kinase in permeabilized cardiac cells in situ. Importance of system level properties

The main focus of this investigation is steady state kinetics of regulation of mitochondrial respiration in permeabilized cardiomyocytes in situ. Complete kinetic analysis of the regulation of respiration by mitochondrial creatine kinase was performed in the presence of pyruvate kinase and phosphoenolpyruvate to simulate interaction of mitochondria with glycolytic enzymes. Such a system analysis revealed striking differences in kinetic behaviour of the MtCK-activated mitochondrial respiration in situ and in vitro. Apparent dissociation constants of MgATP from its binary and ternary complexes with MtCK, Kia and Ka (1.94+/-0.86 mM and 2.04+/-0.14 mM, correspondingly) were increased by several orders of magnitude in situ in comparison with same constants in vitro (0.44+/-0.08 mM and 0.016+/-0.01 mM, respectively). Apparent dissociation constants of creatine, Kib and Kb (2.12+/-0.21 mM 2.17+/-0.40 Mm, correspondingly) were significantly decreased in situ in comparison with in vitro mitochondria (28+/-7 mM and 5+/-1.2 mM, respectively). Dissociation constant for phosphocreatine was not changed. These data may indicate selective restriction of metabolites' diffusion at the level of mitochondrial outer membrane. It is concluded that mechanisms of the regulation of respiration and energy fluxes in vivo are system level properties which depend on intracellular interactions of mitochondria with cytoskeleton, intracellular MgATPases and cytoplasmic glycolytic system.

Cardioprotection by Guanxin II in rats with acute myocardial infarction is related to its three compounds

AIM

We tested the hypothesis that cardioprotection afforded by traditional Chinese Guanxin II (GXII) formula is related to absorbed bioactive compounds (ABCs).

METHODS

Sprague-Dawley rats with acute myocardial infarction (AMI) were induced by coronary occlusion. ABCs including ferulic acid (F), hydroxyl safflor yellow A (A), tanshinol (T), protocatechualdehyde (P) and paeoniflorin (E) were measured in blood after oral GXII. The effects of GXII and FATPE, alone and in combination, and of some components of FATPE on infarct size, myocardial apoptosis and caspase-3 activity were determined. Myocardial blood flow (MBF) in AMI rat was detected 2h after oral GXII and FAT.

RESULTS

FATPE was found in rat blood. FAT was similar to FATPE and GXII in decreasing infarct size, myocardial apoptosis and caspase-3 activity of AMI. Both FAT and GXII were similar in increasing of MBF.

CONCLUSION

GXII and FAT protect the heart from ischemic injury by increasing MBF, and decrease infarct size by inhibiting myocardial apoptosis and caspase-3 activity. These findings provide a potential cardioprotective cocktail.

Cardioprotective activity of Ginkgo biloba Phytosomes in isoproterenol-induced myocardial necrosis in rats: a biochemical and histoarchitectural evaluation

The protective effects of Ginkgo biloba Phytosomes (GBP) in isoproterenol (ISO)-induced cardiotoxicity and the antioxidant activity involved in this protection were investigated in rats. Myocardial infarction was produced in rats with 65, 85, 120 and 200mg/kg of ISO administered subcutaneously (sc) twice at an interval of 24h. An ISO dose of 85mg/kg was selected for the present study as this dose offered significant alteration in biochemical parameters and moderate necrosis in heart. Effect of GBP oral treatment for 21 days at two doses (100mg and 200mg/kg body weight) was evaluated against ISO (85mg/kg, sc)-induced cardiac necrosis. Levels of marker enzymes (AST, LDH and CPK) were assessed in serum and heart, antioxidant parameters viz., reduced glutathione (GSH), superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx) and glutathione reductase (GR) and malondialdehde (MDA) were assayed in heart homogenate. Significant myocardial necrosis, depletion of endogenous antioxidants and increase in serum levels of marker enzymes were observed in ISO-treated animals when compared with the normal animals. GBP elicited a significant cardioprotective activity by lowering the levels of serum marker enzymes and lipid peroxidation and elevated the levels of GSH, SOD, CAT, GPx and GR. The present findings have demonstrated that the cardioprotective effects of GBP in ISO-induced oxidative damage may be due to an augmentation of the endogenous antioxidants and inhibition of lipid peroxidation of membrane.

MitoK(ATP)-dependent changes in mitochondrial volume and in complex II activity during ischemic and pharmacological preconditioning of Langendorff-perfused rat heart

It has been proposed that activation of the mitochondrial ATP-sensitive potassium channel (mitoK(ATP)) is part of signaling pathways triggering the cardioprotection afforded by ischemic preconditioning of the heart. This work was to analyze the mitochondrial function profile of Langendorff-perfused rat hearts during the different phases of various ischemia-reperfusion protocols. Specifically, skinned fibers of ischemic preconditioned hearts exhibit a decline in the succinate-supported respiration and complex II activity during ischemia, followed by a recovery during reperfusion. Meanwhile, the apparent affinity of respiration for ADP (which reflects the matrix volume expansion) is increased during preconditioning stimulus and, to a larger extent, during prolonged ischemia. This evolution pattern is mimicked by diazoxide and abolished by 5-hydroxydecanoate. It is concluded that opening the mitoK(ATP) channel mediates the preservation of mitochondrial structure-function via a mitochondrial matrix shrinkage and a reversible inactivation of complex II during prolonged ischemic insult.

Three-dimensional mitochondrial arrangement in ventricular myocytes: from chaos to order

We have developed a novel method to quantitatively analyze mitochondrial positioning in three dimensions. Using this method, we compared the relative positioning of mitochondria in adult rat and rainbow trout (Oncorhynchus mykiss) ventricular myocytes. Energetic data suggest that trout, in contrast to the rat, have two subpopulations of mitochondria in their cardiomyocytes. Therefore, we speculated whether trout cardiomyocytes exhibit two types of mitochondrial patterns. Stacks of confocal images of mitochondria were acquired in live cardiomyocytes. The images were processed and mitochondrial centers were detected automatically. The mitochondrial arrangement was analyzed by calculating the three-dimensional probability density and distribution functions describing the distances between neighboring mitochondrial centers. In the rat (8 cells with a total of 7,546 mitochondrial centers), intermyofibrillar mitochondria are highly ordered and arranged in parallel strands. These strands are separated by approximately 1.8 mum and can be found in any transversal direction relative to each other. Neighboring strands exhibit the same mitochondrial periodicity. In contrast to the rat, trout ventricular myocytes (22 cells; 5,528 mitochondrial centers) exhibit a relatively chaotic mitochondrial pattern. Neighboring mitochondria can be found in any direction relative to each other. Thus, two potential subpopulations of mitochondria in trout are not distinguishable by their pattern. The developed method required minor interaction in the filtering of the mitochondrial centers. It is therefore a practical approach to describe intracellular organization and may also be used for analysis of time-dependent organizational changes. The obtained quantitative description of mitochondrial organization is a requisite for accurate mathematical analysis of mitochondrial systems biology.

Cardiopulmonary resuscitation in a rat model of chronic myocardial ischemia

Our group has developed a rat model of cardiac arrest and cardiopulmonary resuscitation (CPR). However, the current rat model uses healthy adult animals. In an effort to more closely reproduce the event of cardiac arrest and CPR in humans with chronic coronary disease, a rat model of coronary artery constriction was investigated during cardiac arrest and CPR. Left coronary artery constriction was induced surgically in anesthetized, mechanically ventilated Sprague-Dawley rats. Echocardiography was used to measure global cardiac performance before surgery and 4 wk postsurgery. Coronary constriction provoked significant decreases in ejection fraction, increases in left ventricular end-diastolic volume, and increases left ventricular end-systolic volume at 4 wk postintervention, just before induction of ventricular fibrillation (VF). After 6 min of untreated VF, CPR was initiated on three groups: 1) coronary artery constriction group, 2) sham-operated group, and 3) control group (without preceding surgery). Defibrillation was attempted after 6 min of CPR. All the animals were resuscitated. Postresuscitation myocardial function as measured by rate of left ventricular pressure increase at 40 mmHg and the rate of left ventricular pressure decline was more significantly impaired and left ventricular end-diastolic pressure was greater in the coronary artery constriction group compared with the sham-operated group and the control group. There were no differences in the total shock energy required for successful resuscitation and duration of survival among the groups. In summary, this rat model of chronic myocardial ischemia was associated with ventricular remodeling and left ventricular myocardial dysfunction 4 wk postintervention and subsequently with severe postresuscitation myocardial dysfunction. This model would suggest further clinically relevant investigation on cardiac arrest and CPR.

Effect of mangiferin on mitochondrial energy production in experimentally induced myocardial infarcted rats

Mangiferin, from the leaves of Mangifera indica Linn., has been suggested as useful in the treatment of cardiovascular disorders. In the present study this drug was examined on the alteration of cardiac energy metabolism in isoproterenol (ISPH) administered myocardial infarcted rats. ISPH (20 mg/kg b.w.), which was administered s.c. twice at an interval of 24 h, caused a significant decrease in the activities of TCA cycle enzymes and antioxidant defense enzymes with a concomitant increase in the lipid peroxidation of heart mitochondria in rat model. The ATP production and the oxidation of succinate in State 3 and 4 decreased significantly in the cardiac mitochondria of ISPH administered rats. These functional alterations were supported by severe modifications in mitochondrial ultrastructure. Pretreatment with mangiferin (100 mg/kg b.w. i.p.) for 28 days prevented these mitochondrial alterations, oxidation with energy metabolism and restored the TCA cycle enzyme activities to near normal values following ISPH administration. The structural integrity of the heart was protected by mangiferin in ISPH administered rats when compared to the untreated controls. The present findings suggest that the protective effect of mangiferin can be attributed to its reducing effect on oxidative damage and activation of mitochondrial energy metabolism. These results could be useful to study and understand the cellular events involved in this cardioprotective mechanism of mangiferin. Our studies of mangiferin on heart failure may have important implication for future therapeutic approaches involving in the prevention of cardiovascular diseases.