Regulation of total LC3 levels by angiotensin II in vascular smooth muscle cells.

Hypertension is associated with high circulating angiotensin II (Ang II). We have reported that autophagy regulates Ang II-induced vascular smooth muscle cell (VSMC) hypertrophy, but the mechanism mediating this effect is still unknown. Therefore, we studied how Ang II regulates LC3 levels in VSMCs and whether Bag3, a co-chaperone known to regulate LC3 total levels, may be involved in the effects elicited by Ang II. A7r5 cell line or rat aortic smooth muscle cell (RASMC) primary culture were stimulated with Ang II 100 nM for 24 h and LC3 I, LC3 II and Bag3 protein levels were determined by Western blot. MAP1LC3B mRNA levels were assessed by RT-qPCR. Ang II increased MAP1LC3B mRNA levels and protein levels of LC3 I, LC3 II and total LC3 (LC3 I + LC3 II). Cycloheximide, but not actinomycin D, abolished LC3 II and total LC3 increase elicited by Ang II in RASMCs. In A7r5 cells, cycloheximide prevented the Ang II-mediated increase of LC3 I and total LC3, but not LC3 II. Moreover, Ang II increased Bag3 levels, but this increase was not observed upon co-administration with either losartan 1 µM (AT1R antagonist) or Y-27632 10 µM (ROCK inhibitor). These results suggest that Ang II may regulate total LC3 content through transcriptional and translational mechanisms. Moreover, Bag3 is increased in response to Ang II by a AT1R/ROCK signalling pathway. These data provide preliminary evidence suggesting that Ang II may stimulate autophagy in VSMCs by increasing total LC3 content and LC3 processing.

Mitochondrial E3 ubiquitin ligase 1 (MUL1) as a novel therapeutic target for diseases associated with mitochondrial dysfunction.

Mitochondrial E3 ubiquitin ligase 1 (MUL1) is a mitochondrial outer membrane-anchored protein-containing transmembrane domain in its N- and C-terminal regions, where both are exposed to the cytosol. Interestingly the C-terminal region has a RING finger domain responsible for its E3 ligase activity, as ubiquitin or in SUMOylation, interacting with proteins related to mitochondrial fusion and fission, cell survival, and tumor suppressor process, such as Akt. Therefore, MUL1 is involved in various cellular processes, such as mitochondrial dynamics, inter-organelle communication, proliferation, mitophagy, immune response, inflammation and cell apoptosis. MUL1 is expressed at a higher basal level in the heart, immune system organs, and blood. Here, we discuss the role of MUL1 in mitochondrial dynamics and its function in various pathological models, both in vitro and in vivo. In this context, we describe the role of MUL1 in: (1) the inflammatory response, by regulating NF-κB activity; (2) cancer, by promoting cell death and regulating exonuclear function of proteins, such as p53; (3) neurological diseases, by maintaining communication with other organelles and interacting with proteins to eliminate damaged organelles and; (4) cardiovascular diseases, by maintaining mitochondrial fusion/fission homeostasis. In this review, we summarize the latest advances in the physiological and pathological functions of MUL1. We also describe the different substrates of MUL1, acting as a positive or negative regulator in various pathologies associated with mitochondrial dysfunction. In conclusion, MUL1 could be a potential key target for the development of therapies that focus on ensuring the functionality of the mitochondrial network and, furthermore, the quality control of intracellular components by synchronously modulating the activity of different cellular mechanisms involved in the aforementioned pathologies. This, in turn, will guide the development of targeted therapies.

Polycystin-1 regulates cardiomyocyte mitophagy.

Polycystin-1 (PC1) is a transmembrane protein found in different cell types, including cardiomyocytes. Alterations in PC1 expression have been linked to mitochondrial damage in renal tubule cells and in patients with autosomal dominant polycystic kidney disease. However, to date, the regulatory role of PC1 in cardiomyocyte mitochondria is not well understood. The analysis of mitochondrial morphology from cardiomyocytes of heterozygous PC1 mice (PDK1+/- ) using transmission electron microscopy showed that cardiomyocyte mitochondria were smaller with increased mitochondria density and circularity. These parameters were consistent with mitochondrial fission. We knocked-down PC1 in cultured rat cardiomyocytes and human-induced pluripotent stem cells (iPSC)-derived cardiomyocytes to evaluate mitochondrial function and morphology. The results showed that downregulation of PC1 expression results in reduced protein levels of sub-units of the OXPHOS complexes and less functional mitochondria (reduction of mitochondrial membrane potential, mitochondrial respiration, and ATP production). This mitochondrial dysfunction activates the elimination of defective mitochondria by mitophagy, assessed by an increase of autophagosome adapter protein LC3B and the recruitment of the Parkin protein to the mitochondria. siRNA-mediated PC1 knockdown leads to a loss of the connectivity of the mitochondrial network and a greater number of mitochondria per cell, but of smaller sizes, which characterizes mitochondrial fission. PC1 silencing also deregulates the AKT-FoxO1 signaling pathway, which is involved in the regulation of mitochondrial metabolism, mitochondrial morphology, and processes that are part of cell quality control, such as mitophagy. Together, these data provide new insights about the controls that PC1 exerts on mitochondrial morphology and function in cultured cardiomyocytes dependent on the AKT-FoxO1 signaling pathway.

Impact of the Potential Antitumor Agent 2-(4-Hydroxyphenyl) Amino-1,4-Naphthoquinone (Q7) on Vasomotion Is Mediated by the Vascular Endothelium, But Not Vascular Smooth Muscle Cell Metabolism.

ABSTRACT: Vasomotion is defined as rhythmic oscillations in arterial diameter that regulate the blood flow and blood pressure. Because antitumor treatment may impair vascular functions and increase the blood pressure, we sought to evaluate whether a new naphthoquinone derivative, postulated as an antitumor agent, manifests adverse effects on vascular function. In this article, we evaluated the toxicity of 2-(4-hydroxyphenyl) amino-1,4-naphthoquinone (Q7) and its effects on vascular vasomotion in 3 models of vascular structure: endothelial cells, aortic ring, and smooth muscle cells. Although showing nontoxic effects, Q7 inhibited the formation of capillary-like structures of the EA.hy926 endothelial cell line grown on Matrigel. In exvivo experiments with aortic rings precontracted with phenylephrine (PE, 10-6 M), Q7 (10-5 M) significantly (P < 0.05) reduced vascular rhythmic contractions induced by the acetylcholine (ACh; 10-7-10-5 M), whereas sodium nitroprusside (a nitric oxide donor; 10-8 M) recovered the vasomotion. Furthermore, Q7 (10-5 M) did not decrease KCl-induced vascular rhythmic contractions in the aortic rings precontracted with BaCl2 (a nonselective K+ channel blocker; 10-3 M). Vascular smooth muscle cells (A7r5) preincubated with Q7 (10-5 M) for 3 hours also demonstrated a reduced glucose uptake. However, the Adenosine Triphosphate content was unaffected, suggesting that the rapid reduction in vasomotion observed in vascular reactivity experiments did not involve cellular metabolism but may be due to faster mechanisms involving endothelial nitric oxide and K+ channels leading to oscillations in intracellular Ca2+. In summary, the naphthoquinone derivative Q7 presents low cytotoxicity yet may alter the endothelial cell response and vasomotion in the absence of changes in smooth muscle cell metabolism.

Pro-fibrotic effect of oxidized LDL in cardiac myofibroblasts.

Inflammatory signals associated with cardiac diseases trigger trans-differentiation of cardiac fibroblasts to cardiac myofibroblasts. Cardiac myofibroblasts are the main cell type involved in the development of cardiac fibrosis, a diffuse and disproportionate accumulation of collagen in the myocardium. Although the role of the scavenger like-lectin receptor LOX-1 was previously investigated in cardiac fibroblasts and fibrosis, the involvement of the LOX-1 ligand -oxidized low-density lipoprotein (oxLDL)- on cardiac myofibroblast function still remains unexplored. In the present work, we investigated the effect of oxLDL/LOX-1 on fibrotic markers and cardiac myofibroblast function. Our in vitro results showed that oxLDL increased cardiac myofibroblast proliferation, triggered an increase in the synthesis of collagen type I and fibronectin containing extra domain A, and stimulated collagen type I secretion. oxLDL also decreased cardiac myofibroblast migration, collagen gel contraction and cell area, without modifying α-smooth muscle actin protein levels. These effects were dependent on LOX-1, because LOX-1 knockdown abolished oxLDL effects. Collectively these data showed that oxLDL has important modulatory effects on cardiac myofibroblast function.

Early left atrial dysfunction is associated with suboptimal cardiovascular health.

AIMS: Two-dimensional speckle-tracking echocardiography can assess left atrial (LA) function by measuring atrial volumes and deformation parameters (strain, strain rate). This cross-sectional analysis explores the association between ideal CV health (CVH), LA function, and systemic biomarkers in healthy individuals from the Chilean MAUCO Cohort. METHODS: We enrolled 95 MAUCO participants with different levels of CVH (mean age: 51 ± 8 years). We categorized participants into low or high CVH groups: A: 0-2, or B: 3-6 CVH risk factors. 2D echocardiography, glucose, insulin, total cholesterol, triglycerides, proBNP, hsCRP, insulin resistance index (HOMA), and right and left atrial strain (RASs and LASs, respectively) were determined. RESULTS: LASs was lower in Group A, while systolic and diastolic blood pressure (BP), body mass index (BMI), insulin, HOMA, total cholesterol, triglycerides, and LV and RV end-diastolic volume were significantly higher in Group A than Group B (P < .01). Change in LASs was inversely correlated with insulin (P = .040), HOMA (P = .013), total cholesterol (P = .039), glycemia (P = .018), and BMI (P = .0.037). CONCLUSION: LASs during the reservoir phase was diminished in subjects with a lower level of CVH. Higher insulin, HOMA, total cholesterol, glycemia, and BMI values were associated with decreased LA deformation during the reservoir phase. Morphofunctional alterations of the LA were also identified in the group with suboptimal CVH, as well as BP values in the range of hypertension. LA dysfunction in an asymptomatic population, along with metabolic syndrome, could be an early event in the continuum of CV damage.

Angiotensin-(1-7) Prevents Lipopolysaccharide-Induced Autophagy via the Mas Receptor in Skeletal Muscle.

Skeletal muscle atrophy, which occurs in lipopolysaccharide (LPS)-induced sepsis, causes a severe muscle function reduction. The increased autophagy contributes to sepsis-induced skeletal muscle atrophy in a model of LPS injection, increasing LC3II/LC3I ratio, autophagy flux, and autophagosomes. Angiotensin-(1-7) (Ang-(1-7)) has anti-atrophic effects via the Mas receptor in skeletal muscle. However, the impact of Ang-(1-7) on LPS-induced autophagy is unknown. In this study, we determined the effect of Ang-(1-7) on sepsis-induced muscle autophagy. C57BL6 wild-type (WT) mice and mice lacking the Mas receptor (KO Mas) were injected with LPS together with the systemic administration of Ang-(1-7) to determine autophagy in skeletal muscle. We also evaluated autophagy and p38 and c-Jun N-terminal kinase (JNK)activation. Our results show that Ang-(1-7) prevents LPS-induced autophagy in the diaphragm, tibialis anterior, and gastrocnemius of WT mice, which is demonstrated by a decrease in the LC3II/LC3I ratio and mRNA levels of lc3b and ctsl. This effect was lost in KO Mas mice, suggesting the role of the Mas receptor. The results in C2C12 cells show that Ang-(1-7) reduces several LPS-dependent effects, such as autophagy (LC3II/LC3I ratio, autophagic flux, and autophagosomes), activation of p38 and JNK, B-cell lymphoma-2 (BCL2) phosphorylation, and disassembly of the Beclin1/BCL2 complex. In conclusion, Ang-(1-7)/Mas receptor reduces LPS-induced autophagy in skeletal muscle. In vitro assays indicate that Ang-(1-7) prevents LPS-induced autophagy and modifies the MAPK signaling and the disassembly of a complex involved at the beginning of autophagy.

Moderate Aerobic Exercise Training Prevents the Augmented Hepatic Glucocorticoid Response Induced by High-Fat Diet in Mice.

Glucocorticoids (GCs) are critical regulators of energy balance. Their deregulation is associated with the development of obesity and metabolic syndrome. However, it is not understood if obesity alters the tissue glucocorticoid receptor (GR) response, and moreover whether a moderate aerobic exercise prevents the alteration in GR response induced by obesity. METHODS: To evaluate the GR response in obese mice, we fed C57BL6J mice with a high-fat diet (HFD) for 12 weeks. Before mice were sacrificed, we injected them with dexamethasone. To assess the exercise role in GR response, we fed mice an HFD and subjected them to moderate aerobic exercise three times a week. RESULTS: We found that mice fed a high-fat diet for 12 weeks developed hepatic GC hypersensitivity without changes in the gastrocnemius or epididymal fat GR response. Therefore, moderate aerobic exercise improved glucose tolerance, increased the corticosterone plasma levels, and prevented hepatic GR hypersensitivity with an increase in epididymal fat GR response. CONCLUSION: Collectively, our results suggest that mice with HFD-induced obesity develop hepatic GR sensitivity, which could enhance the metabolic effects of HFD in the liver. Moreover, exercise was found to be a feasible non-pharmacological strategy to prevent the deregulation of GR response in obesity.

Herpud1 impacts insulin-dependent glucose uptake in skeletal muscle cells by controlling the Ca2+-calcineurin-Akt axis.

Skeletal muscle plays a central role in insulin-controlled glucose homeostasis. The molecular mechanisms related to insulin resistance in this tissue are incompletely understood. Herpud1 is an endoplasmic reticulum membrane protein that maintains intracellular Ca2+ homeostasis under stress conditions. It has recently been reported that Herpud1-knockout mice display intolerance to a glucose load without showing altered insulin secretion. The functions of Herpud1 in skeletal muscle also remain unknown. Based on these findings, we propose that Herpud1 is necessary for insulin-dependent glucose disposal in skeletal muscle. Here we show that Herpud1 silencing decreased insulin-dependent glucose uptake, GLUT4 translocation to the plasma membrane, and Akt Ser473 phosphorylation in cultured L6 myotubes. A decrease in insulin-induced Akt Ser473 phosphorylation was observed in soleus but not in extensor digitorum longus muscle samples from Herpud1-knockout mice. Herpud1 knockdown increased the IP3R-dependent cytosolic Ca2+ response and the activity of Ca2+-dependent serine/threonine phosphatase calcineurin in L6 cells. Calcineurin decreased insulin-dependent Akt phosphorylation and glucose uptake. Moreover, calcineurin inhibition restored the insulin response in Herpud1-depleted L6 cells. Based on these findings, we conclude that Herpud1 is necessary for adequate insulin-induced glucose uptake due to its role in Ca2+/calcineurin regulation in L6 myotubes.

Increased active phase atrial contraction is related to marathon runner performance.

PURPOSE: Left atrial (LA) contraction is essential for left ventricular (LV) filling during exertion. We sought to evaluate the relationship of LA contraction and exercise capacity in trained athletes. METHODS: Sixteen male marathon runners were recruited and allocated into two groups according to their previous training status (≥ or < 100 km peer week). All subjects underwent a baseline cardiopulmonary test to evaluate maximal aerobic capacity and a transthoracic echocardiography previous and immediate post-marathon. LA contractile function evaluation was accomplished by measuring the negative deformation of the post P wave strain curve (LASa). LASa change was defined as LASa pre-marathon minus LASa immediate post-marathon. RESULTS: Mean age was 39 ± 6 years. LA volume index (39 ± 13 vs. 31 ± 5 mL/m2, p = 0.04), LV mass index (91 ± 21 vs. 73 ± 12 g/m2, p = 0.04), VO2 max (59 ± 3 vs. 50 ± 8 mL/kg/min, p = 0.036) were higher in more intensive trained group and marathon time was lower (185 ± 14 vs. 219 ± 24 min, p = 0.017). An increase in LASa after immediate post-marathon was observed in both groups, which was significantly greater in the highly trained group (18.9 ± 5.8 vs. 6.3 ± 3.5%, p < 0.003). Maximum VO2 measured previous to the marathon was inversely related to marathon time and directly correlated to LASa change (rho = 0.744, p = 0.001, rho = 0.546, p = 0.028, respectively). CONCLUSIONS: Athletes with more intensive training load have larger LV mass and LA size. An increase in LA contraction was seen post-marathon, which was significantly greater in the highly trained group. This increase in the LA contraction was related to the maximum VO2 measured previous to the marathon and to performance in a highly demanding test.

FoxO1 mediates TGF-beta1-dependent cardiac myofibroblast differentiation.

Cardiac fibroblast differentiation to myofibroblast is a crucial process in the development of cardiac fibrosis and is tightly dependent on transforming growth factor beta-1 (TGF-ß1). The transcription factor forkhead box O1 (FoxO1) regulates many cell functions, including cell death by apoptosis, proliferation, and differentiation. However, several aspects of this process remain unclear, including the role of FoxO1 in cardiac fibroblast differentiation and the regulation of FoxO1 by TGF-ß1. Here, we report that TGF-ß1 stimulates FoxO1 expression, promoting its dephosphorylation, nuclear localization and transcriptional activity in cultured cardiac fibroblasts. TGF-ß1 also increases differentiation markers such as α-smooth muscle actin, connective tissue growth factor, and pro-collagen I, whereas it decreases cardiac fibroblast proliferation triggered by fetal bovine serum. TGF-ß1 also increases levels of p21waf/cip-cycle inhibiting factor protein, a cytostatic factor promoting cell cycle arrest and cardiac fibroblast differentiation. In addition, TGF-ß1 increases cardiac fibroblast contractile capacity as assessed by collagen gel contraction assay. The effect of TGF-ß1 on cardiac fibroblast differentiation was prevented by FoxO1 down-regulation and enhanced by FoxO1 overexpression. Thus, our findings reveal that FoxO1 is regulated by TGF-ß1 and plays a critical role in cardiac fibroblast differentiation. We propose that FoxO1 is an attractive new target for anti-fibrotic therapy.

Inhibition of mitochondrial fission prevents hypoxia-induced metabolic shift and cellular proliferation of pulmonary arterial smooth muscle cells.

Chronic hypoxia exacerbates proliferation of pulmonary arterial smooth muscle cells (PASMC), thereby reducing the lumen of pulmonary arteries. This leads to poor blood oxygenation and cardiac work overload, which are the basis of diseases such as pulmonary artery hypertension (PAH). Recent studies revealed an emerging role of mitochondria in PAH pathogenesis, as key regulators of cell survival and metabolism. In this work, we assessed whether hypoxia-induced mitochondrial fragmentation contributes to the alterations of both PASMC death and proliferation. In previous work in cardiac myocytes, we showed that trimetazidine (TMZ), a partial inhibitor of lipid oxidation, stimulates mitochondrial fusion and preserves mitochondrial function. Thus, here we evaluated whether TMZ-induced mitochondrial fusion can prevent human PASMC proliferation in an in vitro hypoxic model. Using confocal fluorescence microscopy, we showed that prolonged hypoxia (48h) induces mitochondrial fragmentation along with higher levels of the mitochondrial fission protein DRP1. Concomitantly, both mitochondrial potential and respiratory rates decreased, indicative of mitochondrial dysfunction. In accordance with a metabolic shift towards non-mitochondrial ATP generation, mRNA levels of glycolytic markers HK2, PFKFB2 and GLUT1 increased during hypoxia. Incubation of PASMC with TMZ, prior to hypoxia, prevented all these changes and precluded the increase in PASMC proliferation. These findings were also observed using Mdivi-1 (a pharmacological DRP1 inhibitor) or a dominant negative DRP1 K38A as pre-treatments. Altogether, our data indicate that TMZ exerts a protective role against hypoxia-induced PASMC proliferation, by preserving mitochondrial function, thus highlighting DRP1-dependent morphology as a novel therapeutic approach for diseases such as PAH.

Molecular mechanisms of autophagy in the cardiovascular system.

Autophagy is a catabolic recycling pathway triggered by various intra- or extracellular stimuli that is conserved from yeast to mammals. During autophagy, diverse cytosolic constituents are enveloped by double-membrane vesicles, autophagosomes, which later fuse with lysosomes or the vacuole to degrade their cargo. Dysregulation in autophagy is associated with a diverse range of pathologies including cardiovascular disease, the leading cause of death in the world. As such, there is great interest in identifying novel mechanisms that govern the cardiovascular response to disease-related stress. First described in failing hearts, autophagy within the cardiovascular system has been characterized widely in cardiomyocytes, cardiac fibroblasts, endothelial cells, and vascular smooth muscle cells. In all cases, a window of optimal autophagic activity seems to be critical to the maintenance of cardiovascular homeostasis and function; excessive or insufficient levels of autophagic flux can each contribute to heart disease pathogenesis. Here, we review the molecular mechanisms that govern autophagosome formation and analyze the link between autophagy and cardiovascular disease.

Acute effect of iloprost inhalation on right atrial function and ventricular dyssynchrony in patients with pulmonary artery hypertension.

BACKGROUND: Right atrium function and ventricular function have significant prognostic value in pulmonary arterial hypertension patients. Acute changes in right ventricular synchrony and right atrium function postiloprost inhalation have not been evaluated. METHODS: Cross-sectional study. Consecutive pulmonary arterial hypertension patients (group I from Nice classification) were included. Echocardiographic right atrium and right ventricular function pre- and postiloprost inhalation, including a right ventricular dyssynchrony index and right atrium function using speckle tracking, were performed in all patients. RESULTS: Twenty pulmonary arterial hypertension patients, 44±7 years and 90% females, were included. After iloprost inhalation, we observed a significant increment in right ventricular fractional area change and a significant decrease in right ventricular dyssynchrony index (21.4±5.6% vs 26.1±4.0 %, P=.007 and 79±44 vs 32±22 mseconds, P<.01, respectively), also an improvement in right atrium reservoir function (8.6±3.1% vs 11.7±3.5 %, P=.002). CONCLUSIONS: Iloprost inhalation induces acute changes in right ventricular function, dyssynchrony, and right atrium performance that may add relevant clinical information in the management and risk stratification of pulmonary arterial hypertension patients.

Mitochondrial fission is required for cardiomyocyte hypertrophy mediated by a Ca2+-calcineurin signaling pathway.

Cardiomyocyte hypertrophy has been associated with diminished mitochondrial metabolism. Mitochondria are crucial organelles for the production of ATP, and their morphology and function are regulated by the dynamic processes of fusion and fission. The relationship between mitochondrial dynamics and cardiomyocyte hypertrophy is still poorly understood. Here, we show that treatment of cultured neonatal rat cardiomyocytes with the hypertrophic agonist norepinephrine promotes mitochondrial fission (characterized by a decrease in mitochondrial mean volume and an increase in the relative number of mitochondria per cell) and a decrease in mitochondrial function. We demonstrate that norepinephrine acts through α1-adrenergic receptors to increase cytoplasmic Ca(2+), activating calcineurin and promoting migration of the fission protein Drp1 (encoded by Dnml1) to mitochondria. Dominant-negative Drp1 (K38A) not only prevented mitochondrial fission, it also blocked hypertrophic growth of cardiomyocytes in response to norepinephrine. Remarkably, an antisense adenovirus against the fusion protein Mfn2 (AsMfn2) was sufficient to increase mitochondrial fission and stimulate a hypertrophic response without agonist treatment. Collectively, these results demonstrate the importance of mitochondrial dynamics in the development of cardiomyocyte hypertrophy and metabolic remodeling.

Atrial Function Assessed by Speckle Tracking Echocardiography Is a Good Predictor of Postoperative Atrial Fibrillation in Elderly Patients.

OBJECTIVE: Advanced age is an independent predictor of postoperative atrial fibrillation (POAF) in patients undergoing coronary artery bypass surgery. We evaluated whether left atrial (LA) dysfunction assessed by strain contributes to identifying elderly patients prone to POAF. METHODS: Case-control study of 70 subjects undergoing coronary artery bypass surgery. Clinical and laboratory characteristics were recorded at baseline and 72 hours after surgery. Echocardiography was performed during the preoperative period; LA dimensions and deformation by strain (systolic wave [LASs]) as well as strain rate (systolic wave [LASRs] and atrial contraction wave [LASRa]) were assessed. RESULTS: Postoperative atrial fibrillation occurred in 38.5% of patients within the first 72 hours after surgery (28.5% of the younger vs. 48.6% of the older group). Baseline and postoperative inflammatory markers as well as total surgical and aortic clamp time were similar between groups. LA function was markedly impaired in subjects with POAF. Age correlated with LASs, LASRs, and LASRa. These associations remained consistent when subjects 75 years or older were considered separately. Both LASs and LASRa for patients with or without POAF, respectively, were significantly impaired in elderly subjects with POAF. Multivariate analysis provided further evidence that both LASs and age are independent predictors for POAF. CONCLUSION: Age-related changes in atrial function preceding atrial dilation are evident only upon LA strain analysis. LA strain impairment is an independent predictor of POAF irrespective of age and may serve as a surrogate marker for biological processes involved in establishing the substrate for POAF.

Insulin/NFκB protects against ischemia-induced necrotic cardiomyocyte death.

In the heart, insulin controls key functions such as metabolism, muscle contraction and cell death. However, all studies have been focused on insulin action during reperfusion. Here we explore the cardioprotective action of this hormone during ischemia. Rat hearts were perfused ex vivo with an ischemia/reperfusion Langendorff model in absence or presence of insulin. Additionally, cultured rat cardiomyocytes were exposed to simulated ischemia in the absence or presence of insulin. Cytoprotective effects were measured by myocardial infarct size, trypan blue exclusion, released LDH and DNA fragmentation by flow cytometry. We found that insulin protected against cardiac ischemia ex vivo and in vitro. Moreover, insulin protected cardiomyocytes from simulated ischemia by reducing necrotic cell death. Protective effects of insulin were dependent of Akt and NFκB. These novel results show that insulin reduces ischemia-induced cardiomyocyte necrosis through an Akt/NF-κB dependent mechanism. These novel findings clarify the role of insulin during ischemia and further support its use in early GIK perfusion to treat myocardial infarction.

Local control of nuclear calcium signaling in cardiac myocytes by perinuclear microdomains of sarcolemmal insulin-like growth factor 1 receptors.

RATIONALE: The ability of a cell to independently regulate nuclear and cytosolic Ca(2+) signaling is currently attributed to the differential distribution of inositol 1,4,5-trisphosphate receptor channel isoforms in the nucleoplasmic versus the endoplasmic reticulum. In cardiac myocytes, T-tubules confer the necessary compartmentation of Ca(2+) signals, which allows sarcomere contraction in response to plasma membrane depolarization, but whether there is a similar structure tunneling extracellular stimulation to control nuclear Ca(2+) signals locally has not been explored. OBJECTIVE: To study the role of perinuclear sarcolemma in selective nuclear Ca(2+) signaling. METHODS AND RESULTS: We report here that insulin-like growth factor 1 triggers a fast and independent nuclear Ca(2+) signal in neonatal rat cardiac myocytes, human embryonic cardiac myocytes, and adult rat cardiac myocytes. This fast and localized response is achieved by activation of insulin-like growth factor 1 receptor signaling complexes present in perinuclear invaginations of the plasma membrane. The perinuclear insulin-like growth factor 1 receptor pool connects extracellular stimulation to local activation of nuclear Ca(2+) signaling and transcriptional upregulation through the perinuclear hydrolysis of phosphatidylinositol 4,5-biphosphate inositol 1,4,5-trisphosphate production, nuclear Ca(2+) release, and activation of the transcription factor myocyte-enhancing factor 2C. Genetically engineered Ca(2+) buffers--parvalbumin--with cytosolic or nuclear localization demonstrated that the nuclear Ca(2+) handling system is physically and functionally segregated from the cytosolic Ca(2+) signaling machinery. CONCLUSIONS: These data reveal the existence of an inositol 1,4,5-trisphosphate-dependent nuclear Ca(2+) toolkit located in direct apposition to the cell surface, which allows the local control of rapid and independent activation of nuclear Ca(2+) signaling in response to an extracellular ligand.

Novel players in cardioprotection: Insulin like growth factor-1, angiotensin-(1-7) and angiotensin-(1-9).

Insulin-like growth factor-1, angiotensin-(1-7) and angiotensin-(1-9) have been proposed to be important mediators in cardioprotection. A large body of evidence indicates that insulin like growth factor-1 has pleotropic actions in the heart (i.e., contractility, metabolism, hypertrophy, autophagy, senescence and cell death) and, conversely, its deficiency is associated with impaired cardiac function. Recently, we reported that insulin like growth factor-1 receptor is also located in plasma membrane invaginations with perinuclear localization, highlighting the role of nuclear Ca(2+) signaling in the heart. In parallel, angiotensin-(1-7) and angiotensin (1-9) acting through Mas receptor and angiotensin type 2 receptor have emerged as a novel anti-hypertensive molecules promoting vasodilatation and preventing heart hypertrophy. In this review we discuss the scientific evidence available regarding insulin-like growth factor-1, angiotensin-(1-7) and angiotensin-(1-9) in cardioprotection and its potential application as novel therapeutic targets for treating cardiac diseases.