Comparison of the stage-dependent mitochondrial changes in response to pressure overload between the diseased right and left ventricle in the rat.

The right ventricle (RV) differs developmentally, anatomically and functionally from the left ventricle (LV). Therefore, characteristics of LV adaptation to chronic pressure overload cannot easily be extrapolated to the RV. Mitochondrial abnormalities are considered a crucial contributor in heart failure (HF), but have never been compared directly between RV and LV tissues and cardiomyocytes. To identify ventricle-specific mitochondrial molecular and functional signatures, we established rat models with two slowly developing disease stages (compensated and decompensated) in response to pulmonary artery banding (PAB) or ascending aortic banding (AOB). Genome-wide transcriptomic and proteomic analyses were used to identify differentially expressed mitochondrial genes and proteins and were accompanied by a detailed characterization of mitochondrial function and morphology. Two clearly distinguishable disease stages, which culminated in a comparable systolic impairment of the respective ventricle, were observed. Mitochondrial respiration was similarly impaired at the decompensated stage, while respiratory chain activity or mitochondrial biogenesis were more severely deteriorated in the failing LV. Bioinformatics analyses of the RNA-seq. and proteomic data sets identified specifically deregulated mitochondrial components and pathways. Although the top regulated mitochondrial genes and proteins differed between the RV and LV, the overall changes in tissue and cardiomyocyte gene expression were highly similar. In conclusion, mitochondrial dysfuntion contributes to disease progression in right and left heart failure. Ventricle-specific differences in mitochondrial gene and protein expression are mostly related to the extent of observed changes, suggesting that despite developmental, anatomical and functional differences mitochondrial adaptations to chronic pressure overload are comparable in both ventricles.

Surgical Ablation of Permanent Atrial Fibrillation: Age, LV Dilatation, Obesity.

OBJECTIVES: Although concomitant surgical ablation can help to reach freedom from atrial fibrillation (FREEAF) even in patients with permanent atrial fibrillation (AF), some cardiac surgeons hesitate to perform concomitant ablation to avoid perioperative risk escalation. Here, we investigated outcome and predicators of therapeutic success of concomitant surgical ablation in an all-comers study. METHODS: Ablation-naïve patients with formerly accepted permanent AF (FAP, n = 41) or paroxysmal AF (parAF, n = 24) underwent concomitant epicardial bipolar radio frequency ablation and implantable loop recorder (ILR) at two surgical departments. Follow-up examination for 24 months included electrocardiogram, ILR readout, 24h Holter monitoring, echocardiography, and blood sampling. RESULTS: Eighty-six percent of parAF and 70% of FAP patients reached FREEAF (month 24). Mortality was low (parAF/FAP: 5.3 ± 0.2%/4.1 ± 0.3%; p < 0.05; EuroScoreII; 6.1 ± 0.7%/6.4 ± 0.4%, p = ns) and no strokes occurred. FREEAF induced atrial reverse remodeling (left atrial [LA] diameter: -6.7 ± 2.2 mm) and improved cardiac function (left ventricular ejection fraction [LVEF]: +7.3 ± 2.8%), while AF resulted in further atrial dilation (+8.0 ± 1.0 mm, p < 0.05) and LVEF reduction (-7.0 ± 1.3%, p < 0.05). Higher LV (odds ratio [OR]: 1.164) and LA diameter (OR: 1.218), age (OR: 1.180) and body mass index (BMI) (OR: 1.503) increased the risk factors of AF recurrence. Patients remaining in sinus rhythm (SR) demonstrated a decrease in BMI, while AF recurrence was associated with stable overweight. Further aging did not reduce FREEAF. CONCLUSIONS: Long-term SR is achievable by concomitant surgical ablation even in FAP patients. Therefore, it should be offered routinely. Obesity influences therapeutic long-term success but may also offer addressable therapeutic targets to reach higher FREEAF rates.

Calcium Handling Remodeling Underlies Impaired Sympathetic Stress Response in Ventricular Myocardium from Cacna1c Haploinsufficient Rats.

CACNA1C encodes the pore-forming α1C subunit of the L-type Ca2+ channel, Cav1.2. Mutations and polymorphisms of the gene are associated with neuropsychiatric and cardiac disease. Haploinsufficient Cacna1c+/- rats represent a recently developed model with a behavioral phenotype, but its cardiac phenotype is unknown. Here, we unraveled the cardiac phenotype of Cacna1c+/- rats with a main focus on cellular Ca2+ handling mechanisms. Under basal conditions, isolated ventricular Cacna1c+/- myocytes exhibited unaltered L-type Ca2+ current, Ca2+ transients (CaTs), sarcoplasmic reticulum (SR) Ca2+ load, fractional release, and sarcomere shortenings. However, immunoblotting of left ventricular (LV) tissue revealed reduced expression of Cav1.2, increased expression of SERCA2a and NCX, and augmented phosphorylation of RyR2 (at S2808) in Cacna1c+/- rats. The ß-adrenergic agonist isoprenaline increased amplitude and accelerated decay of CaTs and sarcomere shortenings in both Cacna1c+/- and WT myocytes. However, the isoprenaline effect on CaT amplitude and fractional shortening (but not CaT decay) was impaired in Cacna1c+/- myocytes exhibiting both reduced potency and efficacy. Moreover, sarcolemmal Ca2+ influx and fractional SR Ca2+ release after treatment with isoprenaline were smaller in Cacna1c+/- than in WT myocytes. In Langendorff-perfused hearts, the isoprenaline-induced increase in RyR2 phosphorylation at S2808 and S2814 was attenuated in Cacna1c+/- compared to WT hearts. Despite unaltered CaTs and sarcomere shortenings, Cacna1c+/- myocytes display remodeling of Ca2+ handling proteins under basal conditions. Mimicking sympathetic stress with isoprenaline unmasks an impaired ability to stimulate Ca2+ influx, SR Ca2+ release, and CaTs caused, in part, by reduced phosphorylation reserve of RyR2 in Cacna1c+/- cardiomyocytes.

Rationale and Initiative of the Impella in Cardiac Surgery (ImCarS) Register Platform.

OBJECTIVES: Cardiac support systems are being used increasingly more due to the growing prevalence of heart failure and cardiogenic shock. Reducing cardiac afterload, intracardiac pressure, and flow support are important factors. Extracorporeal membrane oxygenation (ECMO) and intracardiac microaxial pump systems (Impella) as non-permanent MCS (mechanical circulatory support) are being used increasingly. METHODS: We reviewed the recent literature and developed an international European registry for non-permanent MCS. RESULTS: Life-threatening conditions that are observed preoperatively often include reduced left ventricular function, systemic hypoperfusion, myocardial infarction, acute and chronic heart failure, myocarditis, and valve vitia. Postoperative complications that are commonly observed include severe systemic inflammatory response, ischemia-reperfusion injury, trauma-related disorders, which ultimately may lead to low cardiac output (CO) syndrome and organ dysfunctions, which necessitates a prolonged ICU stay. Choosing the appropriate device for support is critical. The management strategies and complications differ by system. The "heart-team" approach is inevitably needed.However despite previous efforts to elucidate these topics, it remains largely unclear which patients benefit from certain systems, when is the right time to initiate (MCS), which support system is appropriate, what is the optimal level and type of support, which therapeutic additive and supportive strategies should be considered and ultimately, what are the future prospects and therapeutic developments. CONCLUSION: The European cardiac surgical register ImCarS has been established as an IIT with the overall aim to evaluate data received from the daily clinical practice in cardiac surgery. Interested colleagues are cordially invited to join the register. CLINICAL REGISTRATION NUMBER: DRKS00024560. POSITIVE ETHICS VOTE: AZ 246/20 Faculty of Medicine, Justus-Liebig-University-Gießen.

The Same is Not the Same: Device Effect during Bipolar Radiofrequency Ablation of Atrial Fibrillation.

BACKGROUND: Different ablation devices deliver the same type of energy but use individual control mechanisms to estimate efficacy. We compared patient outcome after the application of radiofrequency ablation systems, using temperature- or resistance-control in paroxysmal and persistent atrial fibrillation (AF). METHODS: This is an unselected all-comers study. Patients underwent standardized left atrial (paroxysmal atrial fibrillation, [PAF] n = 31) or biatrial ablation (persistent atrial fibrillation [persAF] n = 61) with bipolar RF from October 2010 to June 2013. Patients with left atrial dilatation (up to 57 mm), reduced left ventricular (LV) function, and elderly were included. We used resistance-controlled (RC) or temperature-controlled (TC) devices. We amputated atrial appendices and checked intraoperatively for completeness of pulmonary vein exit block. All patients received implantable loop recorders. Follow-up interval was every 6 months. Antiarrhythmic medical treatment endured up to month 6. RESULTS: We reached 100% freedom from atrial fibrillation (FAF) in PAF. In perAF 19% of the RC but 82% of the TC patients reached FAF (12 months; p < 0.05). TC patients exhibited higher creatine kinase-muscle/brain (CK-MB) peak values. In persAF, CK-MB-levels correlated to FAF. No and no mortality (30 days) was evident. Twelve-month mortality did not correlate to AF type, AF duration, LV dimension, or function and age. Prolonged need of oral anticoagulants was 90.1% (RC) and 4.5% (TC). CONCLUSION: In patients with persAF undergoing RF ablation, TC reached higher FAF than RC. Medical devices are not "the same" regarding effectiveness even if used according to manufacturer's instructions. Thus, putative application of "the same" energy is not always "the same" efficacy.

Importance of Cx43 for Right Ventricular Function.

In the heart, connexins form gap junctions, hemichannels, and are also present within mitochondria, with connexin 43 (Cx43) being the most prominent connexin in the ventricles. Whereas the role of Cx43 is well established for the healthy and diseased left ventricle, less is known about the importance of Cx43 for the development of right ventricular (RV) dysfunction. The present article focusses on the importance of Cx43 for the developing heart. Furthermore, we discuss the expression and localization of Cx43 in the diseased RV, i.e., in the tetralogy of Fallot and in pulmonary hypertension, in which the RV is affected, and RV hypertrophy and failure occur. We will also introduce other Cx molecules that are expressed in RV and surrounding tissues and have been reported to be involved in RV pathophysiology. Finally, we highlight therapeutic strategies aiming to improve RV function in pulmonary hypertension that are associated with alterations of Cx43 expression and function.

Autocrine effects of PCSK9 on cardiomyocytes.

Proprotein convertase subtilisin kexin type 9 (PCSK9) is in the focus of cardiovascular research due to its role in hepatic low density lipoprotein (LDL) clearance. However, extrahepatic expression of PCSK9 such as in cardiomyocytes and its regulation by oxidized LDL (oxLDL) put notion on extrahepatic effects of PCSK9 as well. This study was aimed to reveal the role of PCSK9 in oxLDL-dependent regulation of cardiomyocyte function. Adult rat and mouse ventricular cardiomyocytes and isolated perfused hearts were used. OxLDL was applied to increase PCSK9 expression in cardiomyocytes. Cell function was analyzed by load-free cell shortening as well as left ventricular developed pressure of isolated hearts. OxLDL decreased shortening in wild-type-derived mouse cardiomyocytes but not in those isolated from PCSK9 knockout mice. Overexpression of human PCSK9 in rat cardiomyocytes reduced shortening in the absence of oxLDL. Addition of recombinant PCSK9 mimicked these effects. In cardiomyocytes, oxLDL induced PCSK9 release into the supernatant. Inhibition of PCSK9 by Pep 2-8 or alirocumab attenuated the oxLDL-induced loss of cardiomyocyte shortening. Cardiomyocytes express surfeit locus protein 4 (SURF-4), a protein required for PCSK9 secretion in human embryonic kidney cells (HEK 293 T), and silencing of SURF-4 reduced the oxLDL effects on cardiomyocytes. In isolated perfused rat hearts PCSK9 inhibition by alirocumab improved the function. In addition, left ventricular function of isolated hearts from PCSK9 knockout mice was increased under basal conditions as well as at 10 min and 120 min of reperfusion following 45 min of ischemia. Collectively, the data show that cardiomyocytes express and release PCSK9 that acts in an autocrine way on cardiomyocytes and impairs their function.

Effects of air pollution particles (ultrafine and fine particulate matter) on mitochondrial function and oxidative stress - Implications for cardiovascular and neurodegenerative diseases.

Environmental pollution is a major cause of global mortality and burden of disease. All chemical pollution forms together may be responsible for up to 12 million annual excess deaths as estimated by the Lancet Commission on pollution and health as well as the World Health Organization. Ambient air pollution by particulate matter (PM) and ozone was found to be associated with an all-cause mortality rate of up to 9 million in the year 2015, with the majority being of cerebro- and cardiovascular nature (e.g. stroke and ischemic heart disease). Recent evidence suggests that exposure to airborne particles and gases contributes to and accelerates neurodegenerative diseases. Especially, airborne toxic particles contribute to these adverse health effects. Whereas it is well established that air pollution in the form of PM may lead to dysregulation of neurohormonal stress pathways and may trigger inflammation as well as oxidative stress, leading to secondary damage of cardiovascular structures, the mechanistic impact of PM-induced mitochondrial damage and dysfunction is not well established. With the present review we will discuss similarities between mitochondrial damage and dysfunction observed in the development and progression of cardiovascular disease and neurodegeneration as well as those adverse mitochondrial pathomechanisms induced by airborne PM.

Phosphoinositide 3-Kinase Gamma Inhibition Protects From Anthracycline Cardiotoxicity and Reduces Tumor Growth.

BACKGROUND: Anthracyclines, such as doxorubicin (DOX), are potent anticancer agents for the treatment of solid tumors and hematologic malignancies. However, their clinical use is hampered by cardiotoxicity. This study sought to investigate the role of phosphoinositide 3-kinase γ (PI3Kγ) in DOX-induced cardiotoxicity and the potential cardioprotective and anticancer effects of PI3Kγ inhibition. METHODS: Mice expressing a kinase-inactive PI3Kγ or receiving PI3Kγ-selective inhibitors were subjected to chronic DOX treatment. Cardiac function was analyzed by echocardiography, and DOX-mediated signaling was assessed in whole hearts or isolated cardiomyocytes. The dual cardioprotective and antitumor action of PI3Kγ inhibition was assessed in mouse mammary tumor models. RESULTS: PI3Kγ kinase-dead mice showed preserved cardiac function after chronic low-dose DOX treatment and were protected against DOX-induced cardiotoxicity. The beneficial effects of PI3Kγ inhibition were causally linked to enhanced autophagic disposal of DOX-damaged mitochondria. Consistently, either pharmacological or genetic blockade of autophagy in vivo abrogated the resistance of PI3Kγ kinase-dead mice to DOX cardiotoxicity. Mechanistically, PI3Kγ was triggered in DOX-treated hearts, downstream of Toll-like receptor 9, by the mitochondrial DNA released by injured organelles and contained in autolysosomes. This autolysosomal PI3Kγ/Akt/mTOR/Ulk1 signaling provided maladaptive feedback inhibition of autophagy. PI3Kγ blockade in models of mammary gland tumors prevented DOX-induced cardiac dysfunction and concomitantly synergized with the antitumor action of DOX by unleashing anticancer immunity. CONCLUSIONS: Blockade of PI3Kγ may provide a dual therapeutic advantage in cancer therapy by simultaneously preventing anthracyclines cardiotoxicity and reducing tumor growth.

Inhibition of Protein Prenylation of GTPases Alters Endothelial Barrier Function.

The members of Rho family of GTPases, RhoA and Rac1 regulate endothelial cytoskeleton dynamics and hence barrier integrity. The spatial activities of these GTPases are regulated by post-translational prenylation. In the present study, we investigated the effect of prenylation inhibition on the endothelial cytoskeleton and barrier properties. The study was carried out in human umbilical vein endothelial cells (HUVEC) and protein prenylation is manipulated with various pharmacological inhibitors. Inhibition of either complete prenylation using statins or specifically geranylgeranylation but not farnesylation has a biphasic effect on HUVEC cytoskeleton and permeability. Short-term treatment inhibits the spatial activity of RhoA/Rho kinase (Rock) to actin cytoskeleton resulting in adherens junctions (AJ) stabilization and ameliorates thrombin-induced barrier disruption whereas long-term inhibition results in collapse of endothelial cytoskeleton leading to increased basal permeability. These effects are reversed by supplementing the cells with geranylgeranyl but not farnesyl pyrophosphate. Moreover, long-term inhibition of protein prenylation results in basal hyper activation of RhoA/Rock signaling that is antagonized by a specific Rock inhibitor or an activation of cAMP signaling. In conclusion, inhibition of geranylgeranylation in endothelial cells (ECs) exerts biphasic effect on endothelial barrier properties. Short-term inhibition stabilizes AJs and hence barrier function whereas long-term treatment results in disruption of barrier properties.

Heart and Mitochondria: Pathophysiology and Implications for Cardiac Surgeons.

Excluding the heart from systemic circulation during cardiac surgery renders the myocardium ischemic, resulting in cardiac damage. In addition, another hit to the myocardium will occur upon restoration of blood flow, in the reperfusion phase. Experimental data from animal models have revealed that loss of cardiac metabolic flexibility and mitochondrial dysfunctions contributes to contractile impairment in hypertrophied, failing, obese, and diabetic hearts. Such diseased hearts are prone to myocardial ischemia-reperfusion (I/R) injury. Although analyses in human cardiac samples are not as comprehensive as animal data, similar disease-associated metabolic and mitochondrial changes exist. Considering increasing age and comorbidities in patients nowadays, it is not surprising that I/R injuries remain a major cause of morbidity and mortality after cardiac surgery. Mitochondria have emerged as critical targets but also key regulators of myocardial I/R injury, and the extent of mitochondrial damage is a major determinant of myocardial I/R injury. Although cardioprotective mechanisms are diverse, many come together and involve steps at the point of mitochondria. We will, therefore, provide a description of mitochondrial alterations observed in various cardiac disease states and discuss the current experimental knowledge of the role of mitochondria in I/R and of potential protective mechanisms against myocardial I/R injury involving mitochondria. Within this review, we will focus on the protection against I/R injury conferred by caloric restriction (CR) and by ischemic conditioning. Further research is needed to establish whether strategies targeting mitochondria, which have been proposed from preclinical studies, could be translated into cardioprotective therapies against I/R injury in patients.

Mechanisms Involved in Premature Aging in the Heart-Is There an Implication for Cardiac Surgery?

During the past century, life expectancy has risen in Germany from 35.6 and 38.5 years in men and women (1871/1881) to 78.2 and 83.1 years (2013/2015). In recent years, the dominance of chronic diseases as major contributors to total global mortality has emerged. The incidence of cardiovascular diseases (CVD) increases in westernized societies and projected trends suggest that by 2030, CVD alone will also be responsible for more deaths in low-income countries than infectious diseases. The occurrence of CVD also seems to correlate to a further increase of biological age within westernized societies. Therefore, age-associated changes in the heart are an issue of high interest in cardiac surgery. The chronological age is a prognostic marker in some clinical scoring systems. However, it does not represent an adequate estimation of the biological age of patients or their perioperative risk. In fact, frailty might be a more powerful predictor for normal perioperative course or risk escalation. An unhealthy, sedentary lifestyle can induce premature aging of vessels and myocardium. Understanding the age-associated genetic, biochemical, and pathophysiological changes can help identify the therapeutic capability of aged myocardium. Future "therapeutic myocardial rejuvenation" may represent a powerful tool for the stabilization of the perioperative course in aged patients. In this review, we will focus on selected mediators or conditions with impact on age-associated myocardial changes with a major focus on obesity and discuss potential therapeutic strategies to utilize or modify these mediators.

Diastolic dysfunction in prediabetic male rats: Role of mitochondrial oxidative stress.

Although incidence and prevalence of prediabetes are increasing, little is known about its cardiac effects. Therefore, our aim was to investigate the effect of prediabetes on cardiac function and to characterize parameters and pathways associated with deteriorated cardiac performance. Long-Evans rats were fed with either control or high-fat chow for 21 wk and treated with a single low dose (20 mg/kg) of streptozotocin at week 4 High-fat and streptozotocin treatment induced prediabetes as characterized by slightly elevated fasting blood glucose, impaired glucose and insulin tolerance, increased visceral adipose tissue and plasma leptin levels, as well as sensory neuropathy. In prediabetic animals, a mild diastolic dysfunction was observed, the number of myocardial lipid droplets increased, and left ventricular mass and wall thickness were elevated; however, no molecular sign of fibrosis or cardiac hypertrophy was shown. In prediabetes, production of reactive oxygen species was elevated in subsarcolemmal mitochondria. Expression of mitofusin-2 was increased, while the phosphorylation of phospholamban and expression of Bcl-2/adenovirus E1B 19-kDa protein-interacting protein 3 (BNIP3, a marker of mitophagy) decreased. However, expression of other markers of cardiac auto- and mitophagy, mitochondrial dynamics, inflammation, heat shock proteins, Ca2+/calmodulin-dependent protein kinase II, mammalian target of rapamycin, or apoptotic pathways were unchanged in prediabetes. This is the first comprehensive analysis of cardiac effects of prediabetes indicating that mild diastolic dysfunction and cardiac hypertrophy are multifactorial phenomena that are associated with early changes in mitophagy, cardiac lipid accumulation, and elevated oxidative stress and that prediabetes-induced oxidative stress originates from the subsarcolemmal mitochondria.

Cardiac effects of echinocandins after central venous administration in adult rats.

Echinocandins have become the agents of choice for early and specific antifungal treatment in critically ill patients. In vitro studies and clinical case reports revealed a possible impact of echinocandin treatment on cardiac function. The aim of our study was to evaluate echinocandin-induced cardiac failure. Using an in vivo rat model, we assessed hemodynamic parameters and time to hemodynamic failure after central venous application (vena jugularis interna) of anidulafungin (low-dose group, 2.5 mg/kg body weight [BW]; high-dose group, 25 mg/kg BW), caspofungin (low-dose group, 0.875 mg/kg BW; high-dose group, 8.75 mg/kg BW), micafungin (low-dose group, 3 mg/kg BW; high-dose group, 30 mg/kg BW), and placebo (0.9% sodium chloride). Left ventricular heart tissue was collected to determine mitochondrial enzyme activity via spectrophotometric measurements. mRNA expression of transcriptional regulators and primary mitochondrial transcripts, mitochondrial DNA (mtDNA) content, and citrate synthase activity were also explored. Animals receiving high-dose anidulafungin or caspofungin showed an immediate decrease in hemodynamic function. All of the subjects in these groups died during the observation period. Every animal in the untreated control group survived (P < 0.001). Hemodynamic failure was not noticed in the anidulafungin and caspofungin low-dose groups. Micafungin had no impact on cardiac function. In analyzing mitochondrial enzyme activity and mitochondrial transcripts, we found no association between echinocandin administration and the risk for hemodynamic failure. Further experimental studies are needed to elucidate the underlying mechanisms involved in cardiotoxic echinocandin effects. In addition, randomized controlled clinical trials are needed to explore the clinical impact of echinocandin treatment in critically ill patients.

Ischemia and reperfusion related myocardial inflammation: A network of cells and mediators targeting the cardiomyocyte.

Occlusion of a coronary artery if maintained for longer period of time results in damage of the cardiac tissue. However, restoration of blood flow to previously ischemic tissue can itself induce further cardiac damage, a phenomenon known as myocardial reperfusion injury. Cardiac homoeostasis is supported by a network of direct and indirect interactions between cardiomyocytes and resident cell types such as fibroblasts, adipocytes, and endothelial cells or invading blood cells. This review will discuss the role of the cellular interplay in ischemia-reperfusion injury from a cardiomyocyte-centered view, although we are aware that other cellular interactions are equally important. We will try to work out currently unresolved questions and potential future directions in the field.

Is warm or cold Calafiore blood cardioplegia better? Hemodynamic, metabolic, and electron microscopic differences.

BACKGROUND: Controversy exists as to whether warm or cold Calafiore blood cardioplegia (BCP) is better for cardiac preservation. Therefore, we compared hemodynamic performance, myocardial metabolism, and ultrastructural preservation in rat hearts after application of cold or warm BCP. MATERIALS AND METHODS: The hearts of 24 male Wistar rats were excised and inserted into a blood perfused isolated heart apparatus, and after a stabilization period of 30 minutes, either cold (4°C) or warm (36°C) Calafiore BCP was administered during an aortic clamping time of 90 minutes (12 rats each). Hearts clamped without BCP and hearts immediately excised in anesthesia served as worst case and no damage controls, respectively (n=3 each). During reperfusion, functional hemodynamic parameters were recorded in BCP groups, and myocardial oxygen consumption and lactate production were calculated. After perfusion fixation, the hearts of three rats in each group were investigated for cellular edema and mitochondrial damage by morphometry using transmission electron microscopy. RESULTS: Cardiac function after BCP application during aortic clamping showed a slightly better recovery with warm than with cold Calafiore BCP as indicated by higher left ventricular developed pressure (warm 97% of baseline, cold 68% of baseline) after warm BCP. Other hemodynamic parameters and coronary flow were not different between warm and cold BCP. Myocardial oxygen consumption and lactate production were similar under warm and cold conditions. Electron microscopy showed typical signs of ischemia in the ischemia group without BCP. Mitochondrial ultrastructure was well preserved in both BCP groups, but cellular edema was more pronounced with cold than with warm BCP. The qualitative analysis was confirmed by the morphometric cellular edema index and the volume-to-surface ratio of the mitochondria. CONCLUSION: Only mild differences were observed between warm and cold BCP in rats with respect to cardiac function, metabolism, and tissue preservation after aortic clamping. However, a small tendency toward better postischemic recovery was observed with warm BCP.

The ratio of cytochrome c oxidase subunit 4 isoform 4I1 and 4I2 mRNA is changed in permanent atrial fibrillation.

AIMS: The conditions of hypoxia are suggested to induce permanent atrial fibrillation (AF). The regulation of COX4I2 and COX4I1 depends on oxygen availability in tissues. A role of COX4I2 in the myocardium of AF patients is supposed for pathogenesis of AF and subsequent alterations in the electron transfer chain (ETC) under hypoxia. METHODS AND RESULTS: In vitro, influence of hypoxia on HeLa 53 cells was studied and elevated parts of COX 4I2 were confirmed. Myocardial biopsies were taken ex vivo from the patients' Right Atria with SR (n = 31) and AF (n = 11), respectively. RT- PCR for mRNA expresson, mitochondrial respiration by polarography and the protein content of cytochrome c oxidase (CytOx) subunit 4I1 and CytOx subunit 4I2 by ELISA were studied. Clinical data were correlated to the findings of gene expressions in parallel. Patients with permanent AF had a change in isoform 4I2/4I1 expression along with a decrease of isoform COX 4I1 expression. The 4I2/4I1 ratio of mRNA expression was increased from 0.630 to 1.058 in comparison. However, the protein content of CytOx subunit 4 was much lower in the AF group, whereas the respiration/units enzyme activity in both groups remained the same. CONCLUSIONS: This study describes a possible molecular correlate for the development of AF. Due to the known functional significance of COX 4I2, mitochondrial dysfunction can be assumed as a part of the pathogenesis of AF.

Hypoxia-reoxygenation-induced endothelial barrier failure: role of RhoA, Rac1 and myosin light chain kinase.

Hypoxia-reoxygenation induces loss of endothelial barrier function and oedema formation, which presents a major impediment for recovery of the organ. The integrity of the endothelial barrier is highly dependent on its contractile machinery and actin dynamics, which are precisely regulated by Rho GTPases. Perturbed activities of these Rho-GTPases under hypoxia-reoxygenation lead to derangement of the actin cytoskeleton and therefore may affect the integrity of the endothelial barrier. The aim of the present study was to analyse the role of these GTPases in regulating endothelial barrier function during hypoxia-reoxygenation in cultured porcine aortic endothelial cells and isolated perfused rat hearts. Hypoxia-reoxygenation induced an increase in albumin permeability of endothelial monolayers accompanied by an activation of the endothelial contractile machinery, derangement of the actin cytoskeleton and loss of VE-cadherin from cellular junctions. Inhibition of contractile activation with ML-7 partially protected against hypoxia-reoxygenation-induced hyperpermeability. Likewise, reoxygenation caused an increase in RhoA and a reduction in Rac1 activity accompanied by enhanced stress fibre formation and loss of peripheral actin. Inhibition of RhoA/rho kinase (Rock) signalling with RhoA or Rock inhibitors led to a complete depolymerisation and derangement of the actin cytoskeleton and worsened hypoxia-reoxygenation-induced hyperpermeability. Activation of Rac1 using a cAMP analogue, 8-CPT-O-Me-cAMP, which specifically activates Epac/Rap1 signalling, restored peripheral localisation of actin and VE-cadherin at cellular junctions and abrogated reoxygenation-induced hyperpermeability. Similar results were reproduced in isolated saline-perfused rat hearts. These data show that activation of Rac1 but not the inhibition of RhoA preserves endothelial integrity against reoxygenation-induced loss of barrier function.

Age-dependent effects of high fat-diet on murine left ventricles: role of palmitate.

Obesity-associated heart disease results in myocardial lipid accumulation leading to lipotoxicity. However, recent studies are suggestive of protective effects of high-fat diets (HFD). To determine whether age results in differential changes in diet-induced obesity, we fed young and old (3 and 18 months) male C57Bl/6 mice control diet, low-fat diet (both 10 kcal% fat) or HFD (45 kcal% fat) for 16 weeks, after which we analyzed LV function, mitochondrial changes, and potential modifiers of myocardial structure. HFD or age did not change LV systolic function, although a mildly increased BNP was observed in all old mice. This was associated with increased myocardial collagen, triglyceride, diacylglycerol, and ceramide content as well as higher caspase 3 activation in old mice with highest levels in old HFD mice. Pyruvate-dependent respiration and mitochondrial biogenesis were reduced in all old mice and in young HFD mice. Activation of AMPK, a strong inducer of mitochondrial biogenesis, was reduced in both HFD groups and in old control or LFD mice. Cardiomyocytes from old rats demonstrated significantly reduced AMPK activation, impaired mitochondrial biogenesis, higher ceramide content, and reduced viability after palmitate (C16:0) in vitro, while no major deleterious effects were observed in young cardiomyocytes. Aged but not young cardiomyocytes were unable to respond to higher palmitate with increased fatty acid oxidation. Thus, HFD results in cardiac structural alterations and accumulation of lipid intermediates predominantly in old mice, possibly due to the inability of old cardiomyocytes to adapt to high-fatty acid load.