Akt mediated mitochondrial protection in the heart: metabolic and survival pathways to the rescue

Relief of pain in mice by an antibody with high affinity for cell adhesion molecule 1 on nerves

AIMS

Cell adhesion molecule 1 (CADM1) is a member of the immunoglobulin superfamily and is abundantly expressed on nerve fibers. Recently, the anti-CADM1 ectodomain antibody 3E1 has proven useful as a drug delivery vector for CADM1-expressing cells in vitro. When injected subcutaneously into mice, whether 3E1 accumulates on nerve fibers and serves as an analgesic was examined.

MAIN METHODS

Injected 3E1 was detected by immunohistochemistry and double immunofluorescence. Analgesic effects were verified by a formalin-induced chemical-inflammatory pain test and video-recorded behavior analysis that were performed 6, 12, and 24 h after antibody injection. Primary cultures of mouse dorsal root ganglion (DRG) cells were incubated with 3E1 and expressions of CADM1 and its key downstream molecules were examined by Western blot analyses and live cell imaging. DRG cells were loaded with a Ca2+ fluorescent indicator Fluo-8 and a femtosecond laser pulse was irradiated near the cell body to mechanically stimulate the nerves.

KEY FINDINGS

Subcutaneously injected 3E1 was widely localized almost exclusively on peripheral nerve fibers in the dermis. In formalin tests, 3E1-injected mice exhibited less pain-related behavior than control mice. When 3E1 was added to DRG cell cultures, it localized to neurites and resulted in decreased expression of CADM1, increased phosphorylation of Src and Akt, and CADM1-3E1 complex formation. Femtosecond laser-induced stimulation transmission along neurites was clearly visualized by Fluo-8 fluorescence in control cells, whereas it was markedly suppressed in 3E1-treated cells.

SIGNIFICANCE

3E1 was suggested to be a potential long-acting analgesic based on its high affinity for CADM1.

Xinshuaining preparation protects H9c2 cells from H2O2-induced oxidative damage through the PI3K/Akt/Nrf-2 signaling pathway

BACKGROUND

Cardiovascular disease (CVD) is the leading cause of death. Oxidative stress is an important pathological process of a variety of CVDs. Xinshuaining preparation has a therapeutic effect on the heart failure. However, the anti-oxidative stress role of Xinshuaining preparation in H9c2 cells is still unclear.

METHODS

The medicated serum of Xinshuaining preparation was acquired and utilized to hatch with H2O2-induced H9c2 cells. Main components in the Xinshuaining preparation were analyzed by liquid chromatography-mass spectrometry (LC/MS). The effect of medicated serum on the cell viability, apoptosis rate, the oxidative stress indicators (SOD, GSH-Px, and MDA), mitochondrial membrane potential (MMP), and ROS level was evaluated by CCK-8, flow cytometry, commercial biochemical detection kits, and JC-1 staining. Additionally, the associated mechanism was determined by the detection of the protein levels (PI3K, phosphorylated PI3K, Akt, phosphorylated Akt, and Nrf-2) through western blot assays, which was also further assessed with the application of LY294002.

RESULTS

The medicated serum of Xinshuaining preparation notably increased the H2O2-reduced, the cell viability, the concentration of SOD and GSH-Px, MMP level and the relative protein expression level of phosphorylated PI3K and Akt and Nrf-2, while dampened the H2O2-elevated the level of the cell apoptosis rate, MDA, and ROS. However, Xinshuaining preparation on the cell viability, apoptosis, and oxidative stress was notably antagonized by LY294002 pre-treatment.

CONCLUSIONS

The medicated serum of Xinshuaining preparation increased the cell viability and suppressed apoptosis and oxidative stress via the PI3K/Akt/Nrf-2 signaling pathway.

Resveratrol and beyond: The Effect of Natural Polyphenols on the Cardiovascular System: A Narrative Review

Cardiovascular diseases (CVDs) are among the leading causes of morbidity and mortality worldwide. Unhealthy dietary habits have clearly been shown to contribute to the development of CVDs. Beyond the primary nutrients, a healthy diet is also rich in plant-derived compounds. Natural polyphenols, found in fruits, vegetables, and red wine, have a clear role in improving cardiovascular health. In this review, we strive to summarize the results of the relevant pre-clinical and clinical trials that focused on some of the most important natural polyphenols, such as resveratrol and relevant flavonoids. In addition, we aim to identify their common sources, biosynthesis, and describe their mechanism of action including their regulatory effect on signal transduction pathways. Finally, we provide scientific evidence regarding the cardiovascular benefits of moderate, long-term red wine consumption.

Altered expression of proteins involved in metabolism in LGMDR1 muscle is lost in cell culture conditions

BACKGROUND

Limb-girdle muscular dystrophy R1 calpain 3-related (LGMDR1) is an autosomal recessive muscular dystrophy due to mutations in the CAPN3 gene. While the pathophysiology of this disease has not been clearly established yet, Wnt and mTOR signaling pathways impairment in LGMDR1 muscles has been reported.

RESULTS

A reduction in Akt phosphorylation ratio and upregulated expression of proteins implicated in glycolysis (HK-II) and in fructose and lactate transport (GLUT5 and MCT1) in LGMDR1 muscle was observed. In vitro analysis to establish mitochondrial and glycolytic functions of primary cultures were performed, however, no differences between control and patients were observed. Additionally, gene expression analysis showed a lack of correlation between primary myoblasts/myotubes and LGMDR1 muscle while skin fibroblasts and CD56- cells showed a slightly better correlation with muscle. FRZB gene was upregulated in all the analyzed cell types (except in myoblasts).

CONCLUSIONS

Proteins implicated in metabolism are deregulated in LGMDR1 patients' muscle. Obtained results evidence the limited usefulness of primary myoblasts/myotubes for LGMDR1 gene expression and metabolic studies. However, since FRZB is the only gene that showed upregulation in all the analyzed cell types it is suggested its role as a key regulator of the pathophysiology of the LGMDR1 muscle fiber. The Wnt signaling pathway inactivation, secondary to FRZB upregulation, and GLUT5 overexpression may participate in the impaired adipogenesis in LGMD1R patients.

CircAMOTL1 RNA and AMOTL1 Protein: Complex Functions of AMOTL1 Gene Products

The complexity of the cellular proteome facilitates the control of a wide range of cellular processes. Non-coding RNAs, including microRNAs and long non-coding RNAs, greatly contribute to the repertoire of tools used by cells to orchestrate various functions. Circular RNAs (circRNAs) constitute a specific class of non-coding RNAs that have recently emerged as a widely generated class of molecules produced from many eukaryotic genes that play essential roles in regulating cellular processes in health and disease. This review summarizes current knowledge about circRNAs and focuses on the functions of AMOTL1 circRNAs and AMOTL1 protein. Both products from the AMOTL1 gene have well-known functions in physiology, cancer, and other disorders. Using AMOTL1 as an example, we illustrate how focusing on both circRNAs and proteins produced from the same gene contributes to a better understanding of gene functions.

Effect of exercise training on cardiac mitochondrial respiration, biogenesis, dynamics, and mitophagy in ischemic heart disease

Objective

Cardiac mitochondrial dysfunction was found in ischemic heart disease (IHD). Hence, this study determined the effects of exercise training (ET) on cardiac mitochondrial respiration and cardiac mitochondrial quality control in IHD.

Methods

A narrative synthesis was conducted after searching animal studies written in English in three databases (PubMed, Web of Science, and EMBASE) until December 2020. Studies that used aerobic exercise as an intervention for at least 3 weeks and had at least normal, negative (sedentary IHD), and positive (exercise-trained IHD) groups were included. The CAMARADES checklist was used to check the quality of the included studies.

Results

The 10 included studies (CAMARADES score: 6–7/10) used swimming or treadmill exercise for 3–8 weeks. Seven studies showed that ET ameliorated cardiac mitochondrial respiratory function as manifested by decreased reactive oxygen species (ROS) production and increased complexes I-V activity, superoxide dismutase 2 (SOD2), respiratory control ratio (RCR), NADH dehydrogenase subunits 1 and 6 (ND1/6), Cytochrome B (CytB), and adenosine triphosphate (ATP) production. Ten studies showed that ET improved cardiac mitochondrial quality control in IHD as manifested by enhanced and/or controlled mitochondrial biogenesis, dynamics, and mitophagy. Four other studies showed that ET resulted in better cardiac mitochondrial physiological characteristics.

Conclusion

Exercise training could improve cardiac mitochondrial functions, including respiration, biogenesis, dynamics, and mitophagy in IHD.

Systematic review registration

https://www.crd.york.ac.uk/prospero/display_record.php?RecordID=226817, identifier: CRD42021226817.

Identifying the Effect of Nuanxin Capsules on Myocardial Injury Induced by Chronic Hypoxia via Network Pharmacology Analysis and Experimental Validation

Nuanxin capsule (NX), an in-hospital preparation of Guangdong Provincial Hospital of Chinese Medicine, has been used in heart failure (HF) treatment for 15 years, but its mechanism and protective effect have not been investigated. This study was aimed at exploring the mechanism and protective effect of NX on HF treatment via network pharmacology analysis and experimental validation. Network pharmacology analysis predicted that NX was involved in the regulation of response to apoptotic process and hypoxia via protecting cellular damage and mitochondrial dysfunction against chronic hypoxia. Its mechanism may be involved in the regulation of the PI3K-Akt signaling pathway, HIF-1 signaling pathway, AMPK signaling pathway, and MAPK signaling pathway. Experimental validation indicated that NX was capable of improving cellular viability, restoring cellular morphology, and suppressing cellular apoptosis cellular. NX also exerted cardioprotection by inhibiting mitochondrial membrane potential injury and protecting mitochondrial respiratory and energy metabolism in a chronic hypoxia cellular model, which was consistent with the results of network pharmacology prediction. In addition, the screened active compounds of NX did have a good binding with their key targets, indicating NX may exert protective effect through multicompounds and multitargets. In conclusion, NX had a protective effect on HF through cellular and mitochondrial protection against chronic hypoxia via multicompounds, multitargets, and multipathways, and its mechanism may be involved in modulating the PI3K-Akt signaling pathway, HIF-1 signaling pathway, AMPK signaling pathway, and MAPK signaling pathway.

Metabolic Inflexibility as a Pathogenic Basis for Atrial Fibrillation

Atrial fibrillation (AF), the most common sustained arrhythmia, is closely intertwined with metabolic abnormalities. Recently, a metabolic paradox in AF pathogenesis has been suggested: under different forms of pathogenesis, the metabolic balance shifts either towards (e.g., obesity and diabetes) or away from (e.g., aging, heart failure, and hypertension) fatty acid oxidation, yet they all increase the risk of AF. This has raised the urgent need for a general consensus regarding the metabolic changes that predispose patients to AF. “Metabolic flexibility” aptly describes switches between substrates (fatty acids, glucose, amino acids, and ketones) in response to various energy stresses depending on availability and requirements. AF, characterized by irregular high-frequency excitation and the contraction of the atria, is an energy challenge and triggers a metabolic switch from preferential fatty acid utilization to glucose metabolism to increase the efficiency of ATP produced in relation to oxygen consumed. Therefore, the heart needs metabolic flexibility. In this review, we will briefly discuss (1) the current understanding of cardiac metabolic flexibility with an emphasis on the specificity of atrial metabolic characteristics; (2) metabolic heterogeneity among AF pathogenesis and metabolic inflexibility as a common pathological basis for AF; and (3) the substrate-metabolism mechanism underlying metabolic inflexibility in AF pathogenesis.

The multifaceted role of cytochrome P450-Derived arachidonic acid metabolites in diabetes and diabetic cardiomyopathy

Understanding lipid metabolism is a critical key to understanding the pathogenesis of Diabetes Mellitus (DM). It is known that 60-90% of DM patients are obese or used to be obese. The incidence of obesity is rising owing to the modern sedentary lifestyle that leads to insulin resistance and increased levels of free fatty acids, predisposing tissues to utilize more lipids with less glucose uptake. However, the exact mechanism is not yet fully elucidated. Diabetic cardiomyopathy seems to be associated with these alterations in lipid metabolism. Arachidonic acid (AA) is an important fatty acid that is metabolized to several bioactive compounds by cyclooxygenases, lipoxygenases, and the more recently discovered, cytochrome P450 (P450) enzymes. P450 metabolizes AA to either epoxy-AA (EETs) or hydroxy-AA (HETEs). Studies showed that EETs could have cardioprotective effects and beneficial effects in reversing abnormalities in glucose and insulin homeostasis. Conversely, HETEs, most importantly 12-HETE and 20-HETE, were found to interfere with normal glucose and insulin homeostasis and thus, might be involved in diabetic cardiomyopathy. In this review, we highlight the role of P450-derived AA metabolites in the context of DM and diabetic cardiomyopathy and their potential use as a target for developing new treatments for DM and diabetic cardiomyopathy.

Ginsenoside-Rg1 attenuates sepsis-induced cardiac dysfunction by modulating mitochondrial damage via the P2X7 receptor-mediated Akt/GSK-3β signaling pathway

Ginsenoside-Rg1 (G-Rg1), a saponin that is a primary component of ginseng, is effective against inflammatory diseases. The P2X purinoceptor 7 (P2X7) receptor is an ATP-gated ion channel that is predominantly expressed in immune cells and plays a key role in inflammatory processes. We investigated the role of G-Rg1 in sepsis-related cardiac dysfunction and the underlying mechanism involving the regulation of the P2X7 receptor. We detected cell viability, cytotoxicity, cellular reactive oxygen species (ROS) levels, and mitochondrial membrane potential (MMP) with or without G-Rg1 in lipopolysaccharide (LPS)- or hypoxia/reoxygenation (H/R)-induced H9c2 cell models of ischemia/reperfusion injury. We applied cecal ligation and puncture (CLP) to induce a mouse model of sepsis and measured the survival duration and cardiac function of CLP mice. Next, we quantified the ROS level, MMP, respiratory chain complex I-IV enzymatic activity, and mitochondrial fusion in CLP mouse heart tissues. We then investigated the role of G-Rg1 in repairing LPS-induced cell mitochondrial damage, including mitochondrial superoxidation products. The results showed that G-Rg1 inhibited LPS- or H/R-induced cardiomyocyte apoptosis, cytotoxicity, ROS levels, and mitochondrial damage. In addition, G-Rg1 prolonged the survival time of CLP mice. G-Rg1 attenuated LPS-induced superoxide production in the mitochondria of cardiomyocytes and the excessive release of cytochrome c from mitochondria into the cytoplasm. Most importantly, G-Rg1 suppressed LPS-mediated induction of proapoptotic Bax, activated Akt, induced GSK-3β phosphorylation, and balanced mitochondrial calcium levels. Overall, G-Rg1 activates the Akt/GSK-3β pathway through P2X7 receptors to inhibit sepsis-induced cardiac dysfunction and mitochondrial dysfunction.

The Effect of Resveratrol on the Cardiovascular System from Molecular Mechanisms to Clinical Results

Cardiovascular diseases are the leading causes of death worldwide. The cardioprotective effects of natural polyphenols such as resveratrol (3,5,4-trihydroxystilbene) have been extensively investigated throughout recent decades. Many studies of RES have focused on its favorable effects on pathological conditions related to cardiovascular diseases and their risk factors. The aim of this review was to summarize the wide beneficial effects of resveratrol on the cardiovascular system, including signal transduction pathways of cell longevity, energy metabolism of cardiomyocytes or cardiac remodeling, and its anti-inflammatory and antioxidant properties. In addition, this paper discusses the significant preclinical and human clinical trials of recent years with resveratrol on cardiovascular system. Finally, we present a short overview of antiviral and anti-inflammatory properties and possible future perspectives on RES against COVID-19 in cardiovascular diseases.

An update of the molecular mechanisms underlying doxorubicin plus trastuzumab induced cardiotoxicity

Cardiotoxicity is a major side effect of the chemotherapeutic drug doxorubicin (Dox), which is further exacerbated when it is combined with trastuzumab, a standard care approach for Human Epidermal growth factor Receptor-type 2 (HER2) positive cancer patients. However, the molecular mechanisms of the underlying cardiotoxicity of this combination are still mostly elusive. Increased oxidative stress, impaired energetic substrate uses and topoisomerase IIB inhibition are among the biological processes proposed to explain Dox-induced cardiomyocyte dysfunction. Since cardiomyocytes express HER2, trastuzumab can also damage these cells by interfering with neuroregulin-1 signaling and mitogen-activated protein kinase (MAPK), phosphoinositide 3-kinase (PI3K)/Akt and focal adhesion kinase (FAK)-dependent pathways. Nevertheless, Dox and trastuzumab target other cardiac cell types, such as endothelial cells, fibroblasts, cardiac progenitor cells and leukocytes, which can contribute to the clinical cardiotoxicity observed. This review aims to summarize the current knowledge on the cardiac signaling pathways modulated by these two antineoplastic drugs highly used in the management of breast cancer, not only focusing on cardiomyocytes but also to broaden the knowledge of the potential impact on other cells found in the heart.

Mitochondrial protective effects of PARP-inhibition in hypertension-induced myocardial remodeling and in stressed cardiomyocytes

AIMS

During oxidative stress mitochondria become the main source of endogenous reactive oxygen species (ROS) production. In the present study, we aimed to clarify the effects of pharmacological PARP-1 inhibition on mitochondrial function and quality control processes.

MAIN METHODS

L-2286, a quinazoline-derivative PARP inhibitor, protects against cardiovascular remodeling and heart failure by favorable modulation of signaling routes. We examined the effects of PARP-1 inhibition on mitochondrial quality control processes and function in vivo and in vitro. Spontaneously hypertensive rats (SHRs) were treated with L-2286 or placebo. In the in vitro model, 150 μM H2O2 stress was applied on neonatal rat cardiomyocytes (NRCM).

KEY FINDINGS

PARP-inhibition prevented the development of left ventricular hypertrophy in SHRs. The interfibrillar mitochondrial network were less fragmented, the average mitochondrial size was bigger and showed higher cristae density compared to untreated SHRs. Dynamin related protein 1 (Drp1) translocation and therefore the fission of mitochondria was inhibited by L-2286 treatment. Moreover, L-2286 treatment increased the amount of fusion proteins (Opa1, Mfn2), thus preserving structural stability. PARP-inhibition also preserved the mitochondrial genome integrity. In addition, the mitochondrial biogenesis was also enhanced due to L-2286 treatment, leading to an overall increase in the ATP production and improvement in survival of stressed cells.

SIGNIFICANCE

Our results suggest that the modulation of mitochondrial dynamics and biogenesis can be a promising therapeutical target in hypertension-induced myocardial remodeling and heart failure.

Prospects for Radiopharmaceuticals as Effective and Safe Therapeutics in Oncology and Challenges of Tumor Resistance to Radiotherapy

The rapid advances in nuclear medicine have resulted in significant advantages for the field of oncology. The focus is on the application of radiopharmaceuticals as therapeuticals. In addition, the latest developments in cell biology (the understanding of the cell structure, function, metabolism, genetics, signaling, transformation) have given a strong scientific boost to radiation oncology. In this regard, the article discusses what is soon going to be a new jump in radiation oncology based on the already accumulated considerable knowledge at the cellular level about the mechanisms of cell transformation and tumor progression, cell response to radiation, cell resistance to apoptosis and radiation and cell radio-sensitivity. The mechanisms of resistance of tumor cells to radiation and the genetically determined individual sensitivity to radiation in patients (which creates the risk of radiation-induced acute and late side effects) are the 2 major challenges to overcome in modern nuclear medicine. The paper focuses on these problems and makes a detailed summary of the significance of the differences in the ionizing properties of radiopharmaceuticals and the principle of their application in radiation oncology that will shed additional light on how to make the anti-cancer radiotherapies more efficient and safe, giving some ideas for optimizations.

BGP-15 Protects against Heart Failure by Enhanced Mitochondrial Biogenesis and Decreased Fibrotic Remodelling in Spontaneously Hypertensive Rats

Heart failure (HF) is a complex clinical syndrome with poor clinical outcomes despite the growing number of therapeutic approaches. It is characterized by interstitial fibrosis, cardiomyocyte hypertrophy, activation of various intracellular signalling pathways, and damage of the mitochondrial network. Mitochondria are responsible for supplying the energy demand of cardiomyocytes; therefore, the damage of the mitochondrial network causes cellular dysfunction and finally leads to cell death. BGP-15, a hydroxylamine derivative, is an insulin-sensitizer molecule and has a wide range of cytoprotective effects in animal as well as in human studies. Our recent work was aimed at examining the effects of BGP-15 in a chronic hypertension-induced heart failure model. 15-month-old male SHRs were used in our experiment. The SHR-Baseline group represented the starting point (n = 7). Animals received BGP-15 (SHR-B, n = 7) or placebo (SHR-C, n = 7) for 18 weeks. WKY rats were used as age-matched normotensive controls (n = 7). The heart function was monitored by echocardiography. Histological preparations were made from cardiac tissue. The levels of signalling proteins were determined by Western blot. At the end of the study, systolic and diastolic cardiac function was preserved in the BGP-treated animals. BGP-15 decreased the interstitial collagen deposition via decreasing the activity of TGFβ/Smad signalling factors and prevented the cardiomyocyte hypertrophy in hypertensive animals. BGP-15 enhanced the prosurvival signalling pathways (Akt/Gsk3β). The treatment increased the activity of MKP1 and decreased the activity of p38 and JNK signalling routes. The mitochondrial mass of cardiomyocytes was also increased in BGP-15-treated SHR animals due to the activation of mitochondrial biogenesis. The mitigation of remodelling processes and the preserved systolic cardiac function in hypertension-induced heart failure can be a result-at least partly-of the enhanced mitochondrial biogenesis caused by BGP-15.

Pre- and Post-Conditioning of the Heart: An Overview of Cardioprotective Signaling Pathways

Since the discovery of ischemic pre- and post-conditioning, more than 30 years ago, the knowledge about the mechanisms and signaling pathways involved in these processes has significantly increased. In clinical practice, on the other hand, such advancement has yet to be seen. This article provides an overview of ischemic pre-, post-, remote, and pharmacological conditioning related to the heart. In addition, we reviewed the cardioprotective signaling pathways and therapeutic agents involved in the above-mentioned processes, aiming to provide a comprehensive evaluation of the advancements in the field. The advancements made over the last decades cannot be ignored and with the exponential growth in techniques and applications. The future of pre- and post-conditioning is promising.

Mitochondrial Protection by PARP Inhibition

Inhibitors of the nuclear DNA damage sensor and signalling enzyme poly(ADP-ribose) polymerase (PARP) have recently been introduced in the therapy of cancers deficient in double-strand DNA break repair systems, and ongoing clinical trials aim to extend their use from other forms of cancer non-responsive to conventional treatments. Additionally, PARP inhibitors were suggested to be repurposed for oxidative stress-associated non-oncological diseases resulting in a devastating outcome, or requiring acute treatment. Their well-documented mitochondria- and cytoprotective effects form the basis of PARP inhibitors’ therapeutic use for non-oncological diseases, yet can limit their efficacy in the treatment of cancers. A better understanding of the processes involved in their protective effects may improve the PARP inhibitors’ therapeutic potential in the non-oncological indications. To this end, we endeavoured to summarise the basic features regarding mitochondrial structure and function, review the major PARP activation-induced cellular processes leading to mitochondrial damage, and discuss the role of PARP inhibition-mediated mitochondrial protection in several oxidative stress-associated diseases.

Metabolic syndrome diminishes insulin-induced Akt activation and causes a redistribution of Akt-interacting proteins in cardiomyocytes

Metabolic syndrome (MetS) is a cluster of cardiometabolic risk factors, with insulin resistance as a critical component for its development. Insulin signaling in the heart leads to Akt (also known as PKB) activation, a serine/threonine protein kinase, which regulates cardiac glucose metabolism and growth. Cardiac metabolic inflexibility, characterized by impaired insulin-induced glucose uptake and oxidation, has been reported as an early and consistent change in the heart of different models of MetS and diabetes; however, the evaluation of Akt activation has yielded variable results. Here we report in cardiomyocytes of MetS rats, diminished insulin-induced glucose uptake and Akt activation, evaluated by its impaired mobilization towards the plasma membrane and phosphorylation, and reflected in a re-distribution of its interacting proteins, assessed by label-free mass spectrometry (data are available via ProteomeXchange with identifier PXD013260). We report 45 proteins with diminished abundance in Akt complex of MetS cardiomyocytes, mainly represented by energy metabolism-related proteins, and also, 31 Akt-interacting proteins with increased abundance, which were mainly related to contraction, endoplasmic reticulum stress, and Akt negative regulation. These results emphasize the relevance of Akt in the regulation of energy metabolism in the heart and highlight Akt-interacting proteins that could be involved in the detrimental effects of MetS in the heart.

Rosuvastatin protects isolated hearts against ischemia-reperfusion injury: role of Akt-GSK-3β, metabolic environment, and mitochondrial permeability transition pore

The cardioprotective activity of rosuvastatin (R) is yet to be known. The objective of this study was to research whether R perfusion before global ischemia can mitigate myocardial ischemia-reperfusion damage, considering the metabolic condition in which these effects occur, and to contemplate potential mitochondrial benefits. Protein kinase B (Akt)/glycogen synthase kinase-3β (GSK-3β) and mitochondrial permeability transition pore (MPTP) are key elements in myocardial injury produced by ischemia-reperfusion. Isolated rat hearts were subjected to 25-min ischemia and 1-h reperfusion in the presence or absence of R, with or without Wortmannin (W), a phosphatidylinositol 3-kinase (PI3K)/Akt inhibitor. Akt and GSK-3β were measured by Western blot analysis; lactate, glycogen, and G6PDH were determined; and Ca²⁺-induced MPTP opening was evaluated using a spectrophotometric method. Contractility was assessed by left ventricular developed pressure (LVDP), and rate-pressure product (RPP), peak rate of contraction and peak rate of relaxation (± dP/dt), and left ventricular end-diastolic pressure (LVEDP) were determined. Tissue samples were extracted to evaluate mitochondrial damage by electron microscopy and to assess infarct size. Statistical analysis employed ANOVA (n = 6/per group). Myocardial infarct size was significantly reduced by R, which also improved cardiac function. MPTP opening was delayed to 300 μM CaCl₂, while use of W resulted in MPTP opening at 200 μM CaCl₂. Electron microscopy showed better mitochondrial preservation with R, which reduced lactic acid production, increased glycogen consumption and G6PDH activity, as well as phosphorylation of Akt and GSK-3β. R before ischemia is cardioprotective against ischemic and reperfusion damage, activating Akt and regulating GSK-3β negatively and attenuating the MPTP opening.

Reciprocal Multifaceted Interaction Between HDL (High-Density Lipoprotein) and Myocardial Infarction

Despite decades of therapeutic advances, myocardial infarction remains a leading cause of death worldwide. Recent studies have identified HDLs (high-density lipoproteins) as a potential candidate for mitigating coronary ischemia/reperfusion injury via a broad spectrum of signaling pathways. HDL ligands, such as S1P (sphingosine-1-phosphate), Apo (apolipoprotein) A-I, clusterin, and miRNA, may influence the opening of the mitochondrial channel, insulin sensitivity, and production of vascular autacoids, such as NO, prostacyclin, and endothelin-1. In parallel, antioxidant activity and sequestration of oxidized molecules provided by HDL can attenuate the oxidative stress that triggers ischemia/reperfusion. Nevertheless, during myocardial infarction, oxidation and the capture of oxidized and proinflammatory molecules generate large phenotypic and functional changes in HDL, potentially limiting its beneficial properties. In this review, new findings from cellular and animal models, as well as from clinical studies, will be discussed to describe the cardioprotective benefits of HDL on myocardial infarction. Furthermore, mechanisms by which HDL modulates cardiac function and potential strategies to mitigate postmyocardial infarction risk damage by HDL will be detailed throughout the review.

Use of Multifactorial Treatments to Address the Challenge of Translating Experimental Myocardial Infarct Reduction Strategies

Myocardial tissue damage that occurs during an ischemic event leads to a spiraling deterioration of cardiac muscle structural and functional integrity. Reperfusion is the only known efficacious strategy and is the most commonly used treatment to reduce injury and prevent remodeling. However, timing is critical, and the procedure is not always feasible for a variety of reasons. The complex molecular basis for cardioprotection has been studied for decades but formulation of a viable therapeutic that can significantly attenuate myocardial injury remains elusive. In this review, we address barriers to the development of a fruitful approach that will substantially improve the prognosis of those suffering from this widespread and largely unmitigated disease. Furthermore, we proffer that ephrinA1, a candidate molecule that satisfies many of the important criteria discussed, possesses robust potential to overcome these hurdles and thus offers protection that surpasses the limitations currently observed.

Sitagliptin attenuates myocardial apoptosis via activating LKB-1/AMPK/Akt pathway and suppressing the activity of GSK-3β and p38α/MAPK in a rat model of diabetic cardiomyopathy

The present study aimed to investigate the protective effect of sitagliptin, a dipeptidyl peptidase-4 inhibitor, on diabetic cardiomyopathy (DCM)-associated apoptosis and if this effect is mediated via modulating the activity of the survival kinases; AMP-activated protein kinase (AMPK) and Akt & the apoptotic kinases; glycogen synthase kinase-3 β (GSK-3β) and p38 mitogen-activated protein kinase (p38MAPK). Diabetes was induced by a single intraperitoneal injection of streptozotocin (55 mg/kg). Diabetic rats were treated with sitagliptin (10 mg/kg/day, p.o.) and metformin (200 mg/kg/day, p.o. as positive control) for six weeks. Chronic hyperglycemia resulted in elevation of serum cardiac biomarkers reflecting cardiac damage which was supported by H&E stain. The mRNA levels of collagen types I and III were augmented reflecting cardiac fibrosis and hypertrophy which was supported by Masson trichome stain and enhanced phosphorylation of p38MAPK. Cardiac protein levels of cleaved casapse-3, BAX were elevated, whereas, the levels of Bcl-2 and p-BAD were reduced indicating cardiac apoptosis which could be attributed to the diabetes-induced reduced phosphorylation of Akt and AMPK with concomitant augmented activation of GSK-3β and p38MAPK. Protein levels of liver kinase B-1, the upstream kinase of AMPK were also supressed. Sitagliptin administration alleviated the decreased phosphorylation of AMPK and Akt, inactivated the GSK-3β and p38 AMPK, therefore, attenuating the apoptosis and hypertrophy induced by hyperglycemia in the diabetic heart. In conclusion, sitagliptin exhibits valuable therapeutic potential in the management of DCM by attenuating apoptosis. The underlying mechanism may involve the modulating activity of AMPK, Akt, GSK-3β and p38MAPK.

High-density lipoprotein protects cardiomyocytes against necrosis induced by oxygen and glucose deprivation through SR-B1, PI3K, and AKT1 and 2

The cardioprotective lipoprotein HDL (high-density lipoprotein) prevents myocardial infarction and cardiomyocyte death due to ischemia/reperfusion injury. The scavenger receptor class B, type 1 (SR-B1) is a high-affinity HDL receptor and has been shown to mediate HDL-dependent lipid transport as well as signaling in a variety of different cell types. The contribution of SR-B1 in cardiomyocytes to the protective effects of HDL on cardiomyocyte survival following ischemia has not yet been studied. Here, we use a model of simulated ischemia (oxygen and glucose deprivation, OGD) to assess the mechanistic involvement of SR-B1, PI3K (phosphatidylinositol-3-kinase), and AKT in HDL-mediated protection of cardiomyocytes from cell death. Neonatal mouse cardiomyocytes and immortalized human ventricular cardiomyocytes, subjected to OGD for 4 h, underwent substantial cell death due to necrosis but not necroptosis or apoptosis. Pretreatment of cells with HDL, but not low-density lipoprotein, protected them against OGD-induced necrosis. HDL-mediated protection was lost in cardiomyocytes from SR-B1^-/- mice or when SR-B1 was knocked down in human immortalized ventricular cardiomyocytes. HDL treatment induced the phosphorylation of AKT in cardiomyocytes in an SR-B1-dependent manner. Finally, chemical inhibition of PI3K or AKT or silencing of either AKT1 or AKT2 gene expression abolished HDL-mediated protection against OGD-induced necrosis of cardiomyocytes. These results are the first to identify a role of SR-B1 in mediating the protective effects of HDL against necrosis in cardiomyocytes, and to identify AKT activation downstream of SR-B1 in cardiomyocytes.

Dhcr24 activates the PI3K/Akt/HKII pathway and protects against dilated cardiomyopathy in mice

BACKGROUND

24-dehydrocholesterol reductase (Dhcr24) catalyzes the last step of cholesterol biosynthesis, which is required for normal development and anti-apoptotic activities of tissues. We found that Dhcr24 expression decreased in the cTnTR 141W dilated cardiomyopathy (DCM) transgenic mice. Therefore, we tested whether rescued expression of Dhcr24 could prevent the development of DCM and its possible mechanism.

METHODS

Heart tissue specific transgenic overexpression mice of Dhcr24 was generated, then was crossed to cTnTR 141W mouse to obtain the double transgenic mouse (DTG). The phenotypes were demonstrated by the survival, cardiac geometry and function analysis, as well as microstructural and ultrastructural observations based on echocardiography and histology examination. The pathway and apoptosis were analysed by western blotting and TUNEL assay in vivo and in vitro.

RESULTS

We find that Dhcr24 decreased in hearts tissues of cTnTR 141W and LMNAE 82K DCM mice. The transgenic overexpression of Dhcr24 significantly improves DCM phenotypes in cTnTR 141W mice, and activates PI3K/Akt/HKII pathway, followed by a reduction of the translocation of Bax and release of cytochrome c, caspase-9 and caspase-3 activation and myocyte apoptosis. Knockdown the expression of Dhcr24 reduces the activation of PI3K/Akt/HKII pathway and inhibition of the mitochondrial-dependent apoptosis. The anti-apoptotic effect of Dhcr24 could be completely removed by the inhibition of PI3K pathway and partly removed by the HKII inhibitor in H9c2 cell line.

CONCLUSION

Compensatory expression of Dhcr24 protect against DCM through activated PI3K/Akt/HKII pathway and reduce Bax translocation. This is the first investigation for the molecular mechanism of Dhcr24 participate in development of DCM.

CMX-2043 Mechanisms of Action In Vitro

α-Lipoic acid has been shown to provide cytoprotection in some tissues through antioxidant and antiapoptotic mechanisms. We have enhanced these properties by synthetic modification, resulting in a new chemical entity, CMX-2043, with proven efficacy in an animal model of cardiac ischemia-reperfusion injury. The present studies compare cytoprotective cellular pathways of R-α-lipoic acid and CMX-2043. Biochemical and cellular assays were used to compare antioxidant potency, tyrosine kinase activation, and protein kinase B (Akt) phosphorylation. CMX-2043 was more effective than lipoic acid in antioxidant effect, activation of insulin receptor kinase, soluble tyrosine kinase, and Akt phosphorylation. Activation of insulin-like growth factor 1 receptor was similar for both. CMX-2043 stimulation of Akt phosphorylation was abolished by the phosphatidylinositide 3-kinase inhibitor LY294002. Consistent with Akt activation, CMX-2043 reduced carbachol-induced calcium overload. The S-stereoisomer of CMX-2043 was less active in the biochemical assays than the R-isomer. These results are consistent with cytoprotection through activation of Akt and antioxidant action. CMX-2043 may thus provide a pharmacological approach to cytoprotection consistent with established anti-apoptotic mechanisms.

Cardioprotective Effect of Resveratrol in a Postinfarction Heart Failure Model

Despite great advances in therapies observed during the last decades, heart failure (HF) remained a major health problem in western countries. In order to further improve symptoms and survival in patients with heart failure, novel therapeutic strategies are needed. In some animal models of HF resveratrol (RES), it was able to prevent cardiac hypertrophy, contractile dysfunction, and remodeling. Several molecular mechanisms are thought to be involved in its protective effects, such as inhibition of prohypertrophic signaling molecules, improvement of myocardial Ca²⁺ handling, regulation of autophagy, and the reduction of oxidative stress and inflammation. In our present study, we wished to further examine the effects of RES on prosurvival (Akt-1, GSK-3β) and stress signaling (p38-MAPK, ERK 1/2, and MKP-1) pathways, on oxidative stress (iNOS, COX-2 activity, and ROS formation), and ultimately on left ventricular function, hypertrophy and fibrosis in a murine, and isoproterenol- (ISO-) induced postinfarction heart failure model. RES treatment improved left ventricle function, decreased interstitial fibrosis, cardiac hypertrophy, and the level of plasma BNP induced by ISO treatment. ISO also increased the activation of P38-MAPK, ERK1/2^{Thr183-Tyr185}, COX-2, iNOS, and ROS formation and decreased the phosphorylation of Akt-1, GSK-3β, and MKP-1, which were favorably influenced by RES. According to our results, regulation of these pathways may also contribute to the beneficial effects of RES in HF.

Cardioprotective effect of KR-33889, a novel PARP inhibitor, against oxidative stress-induced apoptosis in H9c2 cells and isolated rat hearts

Oxidative stress plays a critical role in cardiac injury during ischemia/reperfusion (I/R). Despite a potent cardioprotective activity of KR-33889, a novel poly (ADP-ribose) polymerase inhibitor, its underlying mechanism remains unresolved. This study was designed to investigate the protective effects of KR-33889 against oxidative stress-induced apoptosis in rat cardiomyocytes H9c2 cells and isolated rat hearts. H₂O₂ caused severe injury to H9c2 cells, mainly due to apoptosis, as revealed by TUNEL assay. However, KR-33889 pretreatment significantly attenuated H₂O₂-induced apoptosis of H9c2 cells, which was accompanied by decrease in expression of both cleaved caspase-3 and Bax and increase in Bcl-2 expression and the ratio of Bcl-2/Bax. KR-33889 also significantly enhanced the expression of anti-oxidant enzymes including heme oxygenase-1, Cu/Zn-superoxide dismutase (SOD), Mn-SOD, and catalase, thereby inhibiting production of intracellular ROS. Furthermore, KR-33889 reversed H₂O₂-induced decrease in phosphorylation of Akt, GSK-3β, ERK1/2, p38 MAPK, and SAPK/JNK during most H₂O₂ exposure time. In globally ischemic rat hearts, KR-33889 inhibited both I/R-induced decrease in cardiac contractility and apoptosis by increasing Bcl-2, decreasing both cleaved caspase-3 and Bax expression, and enhancing expression of anti-oxidant enzymes. Taken together, these results suggest that KR-33889 may have therapeutic potential to prevent I/R-induced heart injury in ischemic heart diseases mainly by reducing oxidative stress-mediated myocardial apoptosis.

Isoflurane reduces oxygen-glucose deprivation-induced oxidative, inflammatory, and apoptotic responses in H9c2 cardiomyocytes

Isoflurane (ISO) protects the heart from hypoxia-reperfusion injury. However, the molecular mechanisms of ISO in oxygen-glucose deprivation (OGD)-induced H9c2 cardiomyocyte injury is yet to be understood. Using H9c2 cells cultured in vitro, we examined the cytotoxicity of different doses of ISO (0.7%, 1.4%, and 2.1%) to H9c2 cells and found that 2.1% ISO had significant toxicity to the cell. Thus, 1.4% ISO was selected for the subsequent experiments. ISO notably ameliorated cell viability loss, lactate dehydrogenase release, and creatine kinase activity of H9c2 cells that were treated with OGD. ISO suppressed OGD-induced pro-inflammatory tumor necrosis factor-α, interleukin (IL)-1β, IL-6, IL-8 production, and nuclear factor (NF)-κB activation in H9c2 cells. ISO reduced the reactive oxygen species and malondialdehyde generation, but it enhanced the superoxide dismutase activity in OGD-stimulated H9c2 cells. In addition, diminished OGD-induced cell apoptosis and preserved mitochondrial membrane potential were observed in ISO-treated H9c2 cells. ISO markedly up-regulated the anti-apoptotic Bcl-2 expression but inhibited the pro-apoptotic expressions of Bax, procaspase-3, cleaved caspase-3, and caspase-3 activity. Mechanistically, the cardioprotective effects of ISO on OGD-induced H9c2 cell injury were mediated by the Akt signaling pathway. These findings suggest that ISO alleviates OGD-induced H9c2 cell injury and may therefore be used to prevent and treat ischemic heart diseases.

Lysophosphatidic Acid Receptor Is a Functional Marker of Adult Hippocampal Precursor Cells

Here, we show that the lysophosphatidic acid receptor 1 (LPA₁) is expressed by a defined population of type 1 stem cells and type 2a precursor cells in the adult mouse dentate gyrus. LPA₁, in contrast to Nestin, also marks the quiescent stem cell population. Combining LPA₁-GFP with EGFR and prominin-1 expression, we have enabled the prospective separation of both proliferative and non-proliferative precursor cell populations. Transcriptional profiling of the isolated proliferative precursor cells suggested immune mechanisms and cytokine signaling as molecular regulators of adult hippocampal precursor cell proliferation. In addition to LPA₁ being a marker of this important stem cell population, we also show that the corresponding ligand LPA is directly involved in the regulation of adult hippocampal precursor cell proliferation and neurogenesis, an effect that can be attributed to LPA signaling via the AKT and MAPK pathways.

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LPA₁-GFP⁺ allows the prospective isolation of hippocampal precursor cells

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Method for separation of proliferative from non-proliferative precursor cells

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Proliferative precursor cells have a unique immune-cell-like transcriptional profile

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LPA increases in vivo hippocampal neurogenesis via the LPA₁-AKT and MAPK pathways

The effect of 3-bromopyruvate on human colorectal cancer cells is dependent on glucose concentration but not hexokinase II expression

Cancer cells heavily rely on the glycolytic pathway regardless of oxygen tension. Hexokinase II (HKII) catalyses the first irreversible step of glycolysis and is often overexpressed in cancer cells. 3-Bromopyruvate (3BP) has been shown to primarily target HKII, and is a promising anti-cancer compound capable of altering critical metabolic pathways in cancer cells. Abnormal vasculature within tumours leads to heterogeneous microenvironments, including glucose availability, which may affect drug sensitivity. The aim of the present study was to elucidate the mechanisms by which 3BP acts on colorectal cancer (CRC) cells with focus on the HKII/Akt signalling axis. High HKII-expressing cell lines were more sensitive to 3BP than low HKII-expressing cells. 3BP-induced rapid Akt phosphorylation at site Thr-308 and cell death via both apoptotic and necrotic mechanisms. Cells grown under lower glucose concentrations showed greater resistance towards 3BP. Cells with HKII knockdown showed no changes in 3BP sensitivity, suggesting the effects of 3BP are independent of HKII expression. These results emphasize the importance of the tumour microenvironment and glucose availability when considering therapeutic approaches involving metabolic modulation.

Apelin-13 protects the heart against ischemia-reperfusion injury through the RISK-GSK-3β-mPTP pathway

INTRODUCTION

Apelin plays an important role in the protection against myocardial ischemia-reperfusion (I/R) injury, while the mechanism still remains unclear. In the current study, we aimed to evaluate the protective effect of apelin-13, and the main mechanism.

MATERIAL AND METHODS

The in vivo I/R injury model (Sprague-Dawley rat) was established, then infarct size, expression levels of phospho-protein kinase B (p-Akt), phospho-extracellular signal-regulated kinase (p-ERK) and phospho-glycogen synthase kinase-3β (p-GSK-3β) were measured. The fluorescence intensity of tetramethylrhodamine ethyl ester perchlorate (TMRE) of the isolated myocardial cells was determined to evaluate the opening of the mitochondrial permeability transition pore (mPTP) caused by oxidant stress and hypoxia/reoxygenation.

RESULTS

For the established I/R injury model, apelin-13 and SB216763 (GSK-3β inhibitor) significantly reduced the infarct size (p < 0.05), which could be abolished by LY294002 (PI3K inhibitor), PD98059 (MEK inhibitor) and atractyloside (mPTP accelerator). The enhanced expression levels of p-Akt, p-ERK and p-GSK-3β caused by apelin-13 (p < 0.05) could be counteracted by LY294002 and PD98059. The reduced fluorescence intensity of TMRE in the H2O2/apelin-13 and H2O2/SB216763 treated groups was significantly lower (p < 0.05), indicating that apelin-13 and SB216763 could reduce the decline in mitochondrial membrane potential caused by oxidant stress, and the fluorescence intensity in the hypoxia/reoxygenation + apelin-13 group was significantly lower (p < 0.05), which suggested that apelin-13 could inhibit the mitochondrial membrane potential changes induced by hypoxia/reoxygenation.

CONCLUSIONS

The protective mechanism of apelin-13 might be that inactivation of GSK-3β could inhibit the opening of mPTP by activating PI3K/Akt and ERK1/2 involved in the reperfusion injury salvage kinase (RISK) pathway.

Differences in Akt signaling and metabolism gene expression in the right heart, intraventricular septum and left heart of rodents

The right heart is functionally and structurally different from the left heart; however, potential differences in Akt signaling and the expression of metabolic genes between the right heart and left heart in different rodents are still unknown. Using Western blotting and real time quantification polymerase chain reaction, we measured the levels of total Akt, phosphorylated Akt and its downstream targets as well as metabolism genes including glucose transporter 1, glucose transporter 4 (GLUT4), peroxisome proliferator-activated receptor α, peroxisome proliferator-activated receptor γ, peroxisome proliferator-activated receptor δ, peroxisome proliferator-activated receptor gamma coactivator 1α (PGC-1α), and pyruvate dehydrogenase lipoamide kinase isozyme 4. We found that phosphorylated Akt and proline-rich Akt substrate 40 levels were significantly increased in the RV compared with the LV in rats but only had an increased trend in mice. Correspondingly, GLUT4 was significantly increased in the RV compared with the LV both in mice and rats. PGC-1α was significantly increased in the RV compared with the LV in mice but only had an increased trend in rats. Moreover, Akt signaling activity and metabolism genes' expression in the IVS were similar to the RV in mice but to the LV in rats. There were some differences in the activity of Akt signaling and in the levels of metabolism genes among the right ventricle, interventricular septum and left ventricle. Also, the diversity of activity of Akt and metabolism genes between the right ventricle and left ventricle are different between rats and mice. In conclusion, the activity of Akt signaling and the levels of metabolism genes are different among the right ventricle, interventricular septum and left ventricle providing some potential clues for exploring the roles of Akt signaling and cardiac metabolisms in different parts of the heart. Additionally, the differences in Akt activity and metabolism genes' levels between the right and left ventricles are different between mice and rats, to which we should pay attention when using different animal model in heart study.

Lean heart: Role of leptin in cardiac hypertrophy and metabolism

Leptin is an adipokine that has been linked with the cardiovascular complications resulting from obesity such as hypertension and heart disease. Obese patients have high levels of circulating leptin due to increased fat mass. Clinical and population studies have correlated high levels of circulating leptin with the development of cardiac hypertrophy in obesity. Leptin has also been demonstrated to increase the growth of cultured cardiomyocytes. However, several animal studies of obese leptin deficient mice have not supported a role for leptin in promoting cardiac hypertrophy so the role of leptin in this pathological process remains unclear. Leptin is also an important hormone in the regulation of cardiac metabolism where it supports oxidation of glucose and fatty acids. In addition, leptin plays a critical role in protecting the heart from excess lipid accumulation and the formation of toxic lipids in obesity a condition known as cardiac lipotoxicity. This paper focuses on the data supporting and refuting leptin’s role in promoting cardiac hypertrophy as well as its important role in the regulation of cardiac metabolism and protection against cardiac lipotoxicity.

Identical MicroRNAs Regulate Liver Protection during Anaesthetic and Ischemic Preconditioning in Rats: An animal study

Anaesthetic preconditioning (APC) and ischemic preconditioning (IPC) ameliorate liver ischemia-reperfusion (I/R) injury and are important for regulating hepatic I/R injury. MicroRNAs (miRNAs) are short, noncoding RNA molecules of 21-23 nucleotides in length, and are currently under intensive investigation regarding their ability to regulate gene expression in a wide range of species. miRNA activity is involved in controlling a wide range of biological functions and processes. We evaluated whether APC and IPC are mediated by the same miRNAs by performing comprehensive miRNA screening experiments in a rat model of hepatic I/R injury. Twenty-one rats were randomly divided into three groups (n = 7/group): control (mock preconditioning), APC, and IPC. Control rats were subjected to 60 min of hepatic ischemia followed by 4 h of reperfusion, whereas the APC and IPC groups were preconditioned with 2% sevoflurane and hepatic ischemia for 10 min prior to ischemia-reperfusion, respectively. Liver samples were collected to measure miRNA levels after 3 h of reperfusion, and gene networks and canonical pathways were identified using Ingenuity Pathway Analysis (IPA). Blood samples were collected to measure the levels of aspartate aminotransferase (AST) and alanine aminotransferase (ALT). Although haemodynamic parameters did not vary among the groups, AST and ALT levels were significantly higher in the control group than in the APC and IPC groups. Comprehensive miRNA screening experiments revealed that most miRNAs altered in the APC group were common to those in the IPC group. IPA identified five miRNAs related to the Akt-glycogen synthase kinase-3β (GSK-3β)-cyclin D1 pathway that were significantly affected by both preconditioning strategies. The application of either APC or IPC to ameliorate hepatic I/R injury results in expression of several common miRNAs that are related to the Akt-GSK-cyclin D1 pathway.

Endurance training or beta-blockade can partially block the energy metabolism remodeling taking place in experimental chronic left ventricle volume overload

Background

Patients with chronic aortic valve regurgitation (AR) causing left ventricular (LV) volume overload can remain asymptomatic for many years despite having a severely dilated heart. The sudden development of heart failure is not well understood but alterations of myocardial energy metabolism may be contributive. We studied the evolution of LV energy metabolism in experimental AR.

Methods

LV glucose utilization was evaluated in vivo by positron emission tomography (microPET) scanning of 6-month AR rats. Sham-operated or AR rats (n = 10-30 animals/group) were evaluated 3, 6 or 9 months post-surgery. We also tested treatment intervention in order to evaluate their impact on metabolism. AR rats (20 animals) were trained on a treadmill 5 times a week for 9 months and another group of rats received a beta-blockade treatment (carvedilol) for 6 months.

Results

MicroPET revealed an abnormal increase in glucose consumption in the LV free wall of AR rats at 6 months. On the other hand, fatty acid beta-oxidation was significantly reduced compared to sham control rats 6 months post AR induction. A significant decrease in citrate synthase and complex 1 activity suggested that mitochondrial oxidative phosphorylation was also affected maybe as soon as 3 months post-AR.

Moderate intensity endurance training starting 2 weeks post-AR was able to partially normalize the activity of various myocardial enzymes implicated in energy metabolism. The same was true for the AR rats treated with carvedilol (30 mg/kg/d). Responses to these interventions were different at the level of gene expression. We measured mRNA levels of a number of genes implicated in the transport of energy substrates and we observed that training did not reverse the general down-regulation of these genes in AR rats whereas carvedilol normalized the expression of most of them.

Conclusion

This study shows that myocardial energy metabolism remodeling taking place in the dilated left ventricle submitted to severe volume overload from AR can be partially avoided by exercise or beta-blockade in rats.

Electronic supplementary material

The online version of this article (doi:10.1186/1471-2261-14-190) contains supplementary material, which is available to authorized users.

Cordycepin, 3'-deoxyadenosine, prevents rat hearts from ischemia/reperfusion injury via activation of Akt/GSK-3β/p70S6K signaling pathway and HO-1 expression

Cordycepin (3'-deoxyadenosine) isolated from Cordyceps militaris, a species of the fungal genus Cordyceps, has been shown to exhibit many pharmacological functions, such as anticancer, anti-inflammatory, and antioxidant activities. In this study, we investigated the preventive role of cordycepin in ischemic/reperfusion (I/R) injury of isolated rat hearts and anesthetized rats. After Sprague-Dawley rats received cordycepin (3, 10, and 30 mg/kg) or control (0.5 % carboxyl methylcellulose) orally once a day for a week, hearts were isolated and mounted on Langendorff heart perfusion system. Isolated hearts were perfused with Krebs-Henseleit buffer for 15-min pre-ischemic stabilization period and subjected to 30-min global ischemia and 30-min reperfusion. Cordycepin administration (10 mg/kg, p.o.) significantly increased left ventricular developed pressure during the reperfusion period compared to that in the control group, but without any effect on coronary flow. Cordycepin (10 mg/kg, p.o.) significantly increased the phosphorylation of Akt/GSK-3β/p70S6K pathways, which are known to modulate multiple survival pathways. In addition, cordycepin decreased Bax and cleaved caspase-3 expression while increasing Bcl-2 expression, Bcl-2/Bax ratio, and heme oxygenase (HO-1) expression in isolated rat hearts. In anesthetized rats subjected to 30 min occlusion of left anterior descending coronary artery/2.5-h reperfusion, cordycepin (1, 3, and 10 mg/kg, i.v.) administered 15 min before the onset of ischemia dose-dependently decreased the infarct size in left ventricle. In conclusion, cordycepin could be an attractive therapeutic candidate with oral activity against I/R-associated heart diseases such as myocardial infarction.

Hexokinase II integrates energy metabolism and cellular protection: Akting on mitochondria and TORCing to autophagy

Accumulating evidence reveals that metabolic and cell survival pathways are closely related, sharing common signaling molecules. Hexokinase catalyzes the phosphorylation of glucose, the rate-limiting first step of glycolysis. Hexokinase II (HK-II) is a predominant isoform in insulin-sensitive tissues such as heart, skeletal muscle, and adipose tissues. It is also upregulated in many types of tumors associated with enhanced aerobic glycolysis in tumor cells, the Warburg effect. In addition to the fundamental role in glycolysis, HK-II is increasingly recognized as a component of a survival signaling nexus. This review summarizes recent advances in understanding the protective role of HK-II, controlling cellular growth, preventing mitochondrial death pathway and enhancing autophagy, with a particular focus on the interaction between HK-II and Akt/mTOR pathway to integrate metabolic status with the control of cell survival.

Remote ischemic preconditioning preserves mitochondrial function and activates pro-survival protein kinase Akt in the left ventricle during cardiac surgery: a randomized trial

BACKGROUND

Understanding the intracellular mechanisms induced by remote ischemic preconditioning (RIPC) in the human left ventricle opens new possibilities for development of pharmacological cardioprotection against ischemia and reperfusion injury. In this study we investigated the effects of RIPC on mitochondrial function, activation of pro-survival protein kinase Akt and microRNA expression in left ventricular biopsies from patients undergoing coronary artery bypass surgery (CABG).

METHODS

Sixty patients were randomized to control (n=30) or RIPC (n=30). A blood pressure cuff was applied to the arm of all patients preoperatively. The cuff remained deflated in control group, whereas RIPC was performed by 3 cycles of cuff inflation to 200 mm Hg for 5 min, separated by 5 min deflation intervals. Left ventricular biopsies were obtained before and 15 min after aortic declamping. The primary outcome was mitochondrial respiration measured in situ. Secondary outcomes were activation of protein kinase Akt, assessed by western immunoblotting, and expression of microRNAs assessed by array and real-time polymerase chain reaction.

RESULTS

Mitochondrial respiration was preserved during surgery in patients receiving RIPC (+0.2 μmol O2/min/g, p=0.69), and reduced by 15% in controls (-1.5 μmol O2/min/g, p=0.02). Furthermore, RIPC activated protein kinase Akt before aortic clamping (difference from control +43.3%, p=0.04), followed by increased phosphorylation of Akt substrates at reperfusion (+26.8%, p<0.01). No differences were observed in microRNA expression.

CONCLUSIONS

RIPC preserves mitochondrial function and activates pro-survival protein kinase Akt in left ventricle of patients undergoing CABG. Modulation of mitochondrial function and Akt activation should be further explored as cardioprotective drug targets.

CLINICAL TRIAL REGISTRATION

http://www.clinicaltrials.gov, unique identifier: NCT01308138.

A multi-parameter in vitro screen in human stem cell-derived cardiomyocytes identifies ponatinib-induced structural and functional cardiac toxicity

Ponatinib, a multi-targeted TKI and potent pan-ABL inhibitor, approved for the treatment of Ph + ALL and CML, was temporarily withdrawn from the U.S. market due to severe vascular adverse events. Cardiac-specific toxicities including myocardial infarction, severe congestive heart failure, and cardiac arrhythmias have also been shown with ponatinib. Targeted oncology agents such as ponatinib have transformed cancer treatment but often induce toxicity due to inhibition of survival pathways shared by both cancer and cardiac cells. These toxicities are often missed by the standard preclinical toxicity assessment methods, which include human Ether-à-go-go-related gene (hERG) and animal toxicity testing. In this study, we show that a multiparameter in vitro toxicity screening approach using human-induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CM) accurately predicted the cardiac toxicity potential of ponatinib. This in vitro model evaluated ponatinib's effect on the overall cell health, mitochondrial stress, and function of hiPSC-CM and also provided mechanistic insight into the signaling pathways and cellular structures altered with treatment. We show here that ponatinib rapidly inhibits prosurvival signaling pathways, induces structural cardiac toxicity (as shown by actin cytoskeleton damage, mitochondrial stress, cell death, and troponin secretion), and disrupts cardiac cell beating. Most of these effects occurred at doses between 10× and 50× ponatinib's Cmax, a dose range shown to be relevant for accurate prediction of in vivo toxicity. Together these studies show that a comprehensive in vitro screening tool in a more relevant human cardiac cell model can improve the detection of cardiac toxicity with targeted oncology agents such as ponatinib.

Ginsenoside Rd attenuates mitochondrial permeability transition and cytochrome C release in isolated spinal cord mitochondria: involvement of kinase-mediated pathways

Ginsenoside Rd (Rd), one of the main active ingredients in Panax ginseng, has multifunctional activity via different mechanisms and neuroprotective effects that are exerted probably via its antioxidant or free radical scavenger action. However, the effects of Rd on spinal cord mitochondrial dysfunction and underlying mechanisms are still obscure. In this study, we sought to investigate the in vitro effects of Rd on mitochondrial integrity and redox balance in isolated spinal cord mitochondria. We verified that Ca²⁺ dissipated the membrane potential, provoked mitochondrial swelling and decreased NAD(P)H matrix content, which were all attenuated by Rd pretreatment in a dose-dependent manner. In contrast, Rd was not able to inhibit Ca²⁺ induced mitochondrial hydrogen peroxide generation. The results of Western blot showed that Rd significantly increased the expression of p-Akt and p-ERK, but had no effects on phosphorylation of PKC and p38. In addition, Rd treatment significantly attenuated Ca²⁺ induced cytochrome c release, which was partly reversed by antagonists of Akt and ERK, but not p-38 inhibitor. The effects of bisindolylmaleimide, a PKC inhibitor, on Rd-induced inhibition of cytochrome c release seem to be at the level of its own detrimental activity on mitochondrial function. Furthermore, we also found that pretreatment with Rd in vivo (10 and 50 mg/kg) protected spinal cord mitochondria against Ca²⁺ induced mitochondrial membrane potential dissipation and cytochrome c release. It is concluded that Rd regulate mitochondrial permeability transition pore formation and cytochrome c release through protein kinases dependent mechanism involving activation of intramitochondrial Akt and ERK pathways.

Apelin-APJ effects of ginsenoside-Rb1 depending on hypoxia-induced factor 1α in hypoxia neonatal cardiomyocytes

OBJECTIVE

To investigate whether ginsenoside-Rb1 (Gs-Rb1) inhibits the apoptosis of hypoxia cardiomyocytes by up-regulating apelin-APJ system and whether the system is affected by hypoxia-induced factor 1α (Hif-1α).

METHODS

Neonatal rat cardiomyocytes were randomly divided into 6 groups: a control group, a simple CoCl group, a simple Gs-Rb1 group, a CoCl and Gs-Rb1 hypoxia group, a CoCl and 3-(5'-hydroxymethyl-2'-furyl)-1-benzylindazole (YC-1) group, a CoCl and YC-1 group and a Gs-Rb1 group, in which YC-1 inhibits the synthesis and accelerates the degradation of Hif-1a. The concentration of CoCl, Gs-Rb1 and YC-1 was 500 μmol/L, 200 μmol/L and 5 μmol/L, respectively; the apoptosis ratio was analyzed with a flow cytometer; and apelin, APJ and Hif-1α were assayed with immunocytochemistry, Western blot assays and reverse transcription polymerase chain reaction (RT-PCR).

RESULTS

(1) The anti-apoptosis effect of Gs-Rb1 on hypoxia cardiomyocytes was significantly inhibited by YC-1; (2) Hypoxia significantly up-graded the expression of mRNA and protein of apelin; this effect was further reinforced by Gs-Rb1 and significantly inhibited by YC-1; (3) Gs-Rb1 further strengthened the expression of APJ mRNA and APJ proteins once hypoxia occurred, which was significantly inhibited by YC-1; (4) Gs-Rb1 significantly increased the expression of Hif-1α, which was completely abolished by YC-1; (5) There was a negative relationship between AR and apelin (or APJ, including mRNA and protein), a positive correlation between apelin (or APJ) protein and Hif-1a protein, in hypoxia cardiomyocytes.

CONCLUSION

The apelin-APJ system plays an important role in the anti-apoptosis effect of Gs-Rb1 on hypoxia neonatal cardiomyocytes, which was partly adjusted by Hif-1α.

Phosphorylated AKT inhibits the apoptosis induced by DRAM-mediated mitophagy in hepatocellular carcinoma by preventing the translocation of DRAM to mitochondria

Increasing autophagy is beneficial for curing hepatocellular carcinoma (HCC). Damage-regulated autophagy modulator (DRAM) was recently reported to induce apoptosis by mediating autophagy. However, the effects of DRAM-mediated autophagy on apoptosis in HCC cells remain unclear. In this study, normal hepatocytes (7702) and HCC cell lines (HepG2, Hep3B and Huh7) were starved for 48 h. Starvation induced apoptosis and autophagy in all cell lines. We determined that starvation also induced DRAM expression and DRAM-mediated autophagy in both normal hepatocytes and HCC cells. However, DRAM-mediated autophagy was involved in apoptosis in normal hepatocytes but not in HCC cells, suggesting that DRAM-mediated autophagy fails to induce apoptosis in hepatoma in response to starvation. Immunoblot and immunofluorescence assays demonstrated that DRAM translocated to mitochondria and induced mitophagy, which led to apoptosis in 7702 cells. In HCC cells, starvation also activated the phosphatidylinositol 3-kinase (PI3K)/AKT pathway, which blocks the translocation of DRAM to mitochondria through the binding of p-AKT to DRAM in the cytoplasm. Inactivation of the PI3K/AKT pathway rescued DRAM translocation to mitochondria; subsequently, mitochondrial DRAM induced apoptosis in HCC cells by mediating mitophagy. Our findings open new avenues for the investigation of the mechanisms of DRAM-mediated autophagy and suggest that promoting DRAM-mediated autophagy together with PI3K/AKT inhibition might be more effective for autophagy-based therapy in hepatoma.

NecroX-5 suppresses sodium nitroprusside-induced cardiac cell death through inhibition of JNK and caspase-3 activation

Although sodium nitroprusside (SNP) is an effective hypotensive drug and is often used in pediatric intensive care units and to treat acute heart failure, clinical application of SNP is limited by its cardiotoxicity. NecroX-5 (NX-5) was recently developed and has the capacity to inhibit necrotic cell death. No current literature addresses whether NX-5 suppresses SNP-induced cell death or its mechanism of action. We have investigated the protective role of NX-5 against SNP-induced cell death in cardiomyocyte-like H9c2 cells. SNP treatment induced severe cell death, possibly through phosphorylation of stress-activated protein kinase/c-Jun NH₂-terminal kinase (JNK) and activation of the apoptotic signaling pathway, including downregulation of Bcl-2 and cleavage of caspase-3. However, NX-5 suppresses SNP-induced cell death through inhibition of JNK activation and suppression of both downregulation of Bcl-2 protein expression and caspase-3 cleavage. These findings will provide insights and facilitate development of antidotes to SNP toxicity in cardiac cells.

A new non-canonical pathway of Gα(q) protein regulating mitochondrial dynamics and bioenergetics

Contrary to previous assumptions, G proteins do not permanently reside on the plasma membrane, but are constantly monitoring the cytoplasmic surfaces of the plasma membrane and endomembranes. Here, we report that the Gαq and Gα11 proteins locate at the mitochondria and play a role in a complex signaling pathway that regulates mitochondrial dynamics. Our results provide evidence for the presence of the heteromeric G protein (Gαq/11βγ) at the outer mitochondrial membrane and for Gαq at the inner membrane. Both localizations are necessary to maintain the proper equilibrium between fusion and fission; which is achieved by altering the activity of mitofusin proteins, Drp1, OPA1 and the membrane potential at both the outer and inner mitochondrial membranes. As a result of the absence of Gαq/11, there is a decrease in mitochondrial fusion rates and a decrease in overall respiratory capacity, ATP production and OXPHOS-dependent growth. These findings demonstrate that the presence of Gαq proteins at the mitochondria serves as a physiological function: stabilizing elongated mitochondria and regulating energy production in Drp1 and Opa1 dependent mechanisms. This thereby links organelle dynamics and physiology.

Ginsenoside Rd attenuates myocardial ischemia/reperfusion injury via Akt/GSK-3β signaling and inhibition of the mitochondria-dependent apoptotic pathway

Evidence suggests Ginsenoside Rd (GSRd), a biologically active extract from the medical plant Panax Ginseng, exerts antioxidant effect, decreasing reactive oxygen species (ROS) formation. Current study determined the effect of GSRd on myocardial ischemia/reperfusion (MI/R) injury (a pathological condition where ROS production is significantly increased) and investigated the underlying mechanisms. The current study utilized an in vivo rat model of MI/R injury and an in vitro neonatal rat cardiomyocyte (NRC) model of simulated ischemia/reperfusion (SI/R) injury. Infarct size was measured by Evans blue/TTC double staining. NRC injury was determined by MTT and lactate dehydrogenase (LDH) leakage assay. ROS accumulation and apoptosis were assessed by flow cytometry. Mitochondrial membrane potential (MMP) was determined by 5, 5', 6, 6'-tetrachloro-1, 1', 3, 3'-tetrathylbenzimidazol carbocyanine iodide (JC-1). Cytosolic translocation of mitochondrial cytochrome c and expression of caspase-9, caspase-3, Bcl-2 family proteins, and phosphorylated Akt and GSK-3β were determined by western blot. Pretreatment with GSRd (50 mg/kg) significantly augmented rat cardiac function, as evidenced by increased left ventricular ejection fraction (LVEF) and ±dP/dt. GSRd reduced myocardial infarct size, apoptotic cell death, and blood creatine kinase/lactate dehydrogenase levels after MI/R. In NRCs, GSRd (10 µM) inhibited SI/R-induced ROS generation (P<0.01), decreased cellular apoptosis, stabilized the mitochondrial membrane potential (MMP), and attenuated cytosolic translocation of mitochondrial cytochrome c. GSRd inhibited activation of caspase-9 and caspase-3, increased the phosphorylated Akt and GSK-3β, and increased the Bcl-2/Bax ratio. Together, these data demonstrate GSRd mediated cardioprotective effect against MI/R-induced apoptosis via a mitochondrial-dependent apoptotic pathway.