Role of Perilipins in Oxidative Stress-Implications for Cardiovascular Disease

Oxidative stress is the imbalance between the production of reactive oxygen species (ROS) and antioxidants in a cell. In the heart, oxidative stress may deteriorate calcium handling, cause arrhythmia, and enhance maladaptive cardiac remodeling by the induction of hypertrophic and apoptotic signaling pathways. Consequently, dysregulated ROS production and oxidative stress have been implicated in numerous cardiac diseases, including heart failure, cardiac ischemia-reperfusion injury, cardiac hypertrophy, and diabetic cardiomyopathy. Lipid droplets (LDs) are conserved intracellular organelles that enable the safe and stable storage of neutral lipids within the cytosol. LDs are coated with proteins, perilipins (Plins) being one of the most abundant. In this review, we will discuss the interplay between oxidative stress and Plins. Indeed, LDs and Plins are increasingly being recognized for playing a critical role beyond energy metabolism and lipid handling. Numerous reports suggest that an essential purpose of LD biogenesis is to alleviate cellular stress, such as oxidative stress. Given the yet unmet suitability of ROS as targets for the intervention of cardiovascular disease, the endogenous antioxidant capacity of Plins may be beneficial.

Age-Related Shift in Cardiac and Metabolic Phenotyping Linked to Inflammatory Cytokines and Antioxidant Status in Mice

Age-related alterations in cardiac function, metabolic, inflammatory and antioxidant profiles are associated with an increased risk of cardiovascular mortality and morbidity. Here, we examined cardiac and metabolic phenotypes in relation to inflammatory status and antioxidant capacity in young, middle-aged and old mice. Real-time reverse transcription-polymerase chain reactions were performed on myocardium and immunoassays on plasma. Left ventricular (LV) structure and function were assessed by echocardiography using high-frequency ultrasound. Middle-aged mice exhibited an altered metabolic profile and antioxidant capacity compared to young mice, whereas myocardial expression of inflammatory factors (TNFα, IL1β, IL6 and IL10) remained unchanged. In contrast, old mice exhibited increased expression of inflammatory cytokines and plasma levels of resistin compared to young and middle-aged mice (p < 0.05). The pro-inflammatory signature of aged hearts was associated with alterations in glutathione redox homeostasis and elevated contents of 4-hydroxynonenal (4-HNE), a marker of lipid peroxidation and oxidative stress. Furthermore, echocardiographic parameters of LV systolic and diastolic functions were significantly altered in old mice compared to young mice. Taken together, these findings suggest age-related shifts in cardiac phenotype encompass the spectrum of metabo-inflammatory abnormalities and altered redox homeostasis.

Metabolic, Apoptotic and Fibro-Inflammatory Profiles of the Heart Exposed to Environmental Electromagnetic Fields

Environmental stress can disturb the integrative functioning of the cardiovascular system and trigger a number of adaptive and/or maladaptive cell responses. Concomitant with the expanding use of mobile communication systems, public exposure to electromagnetic fields (EMFs) raises the question of the impact of 900 MHz EMFs on cardiovascular health. Therefore, in this study, we experimentally investigated whether 915 MHz EMF exposure influenced cardiac metabolic, antioxidant, apoptotic, and fibro-inflammatory profiles in a mouse model. Healthy mice were sham-exposed or exposed to EMF for 14 days. Western blot analysis using whole cardiac tissue lysates demonstrated that there was no significant change in the expression of oxidative phosphorylation (OXPHOS) complexes between the control and EMF-exposed mice. In addition, the myocardial expression of fibro-inflammatory cytokines, antioxidant enzymes, and apoptosis-related markers remained unchanged in the EMF-challenged hearts. Finally, the structural integrity of the cardiac tissues was preserved among the groups. These findings suggest that the apoptotic, antioxidant, metabolic, and fibro-inflammatory profiles of the heart remained stable under conditions of EMF exposure in the analyzed mice.

Myocardial capacity of mitochondrial oxidative phosphorylation in response to prolonged electromagnetic stress

Introduction

Mitochondria are central energy generators for the heart, producing adenosine triphosphate (ATP) through the oxidative phosphorylation (OXPHOS) system. However, mitochondria also guide critical cell decisions and responses to the environmental stressors.

Methods

This study evaluated whether prolonged electromagnetic stress affects the mitochondrial OXPHOS system and structural modifications of the myocardium. To induce prolonged electromagnetic stress, mice were exposed to 915 MHz electromagnetic fields (EMFs) for 28 days.

Results

Analysis of mitochondrial OXPHOS capacity in EMF-exposed mice pointed to a significant increase in cardiac protein expression of the Complex I, II, III and IV subunits, while expression level of α-subunit of ATP synthase (Complex V) was stable among groups. Furthermore, measurement of respiratory function in isolated cardiac mitochondria using the Seahorse XF24 analyzer demonstrated that prolonged electromagnetic stress modifies the mitochondrial respiratory capacity. However, the plasma level of malondialdehyde, an indicator of oxidative stress, and myocardial expression of mitochondria-resident antioxidant enzyme superoxide dismutase 2 remained unchanged in EMF-exposed mice as compared to controls. At the structural and functional state of left ventricles, no abnormalities were identified in the heart of mice subjected to electromagnetic stress.

Discussion

Taken together, these data suggest that prolonged exposure to EMFs could affect mitochondrial oxidative metabolism through modulating cardiac OXPHOS system.

Galanin Regulates Myocardial Mitochondrial ROS Homeostasis and Hypertrophic Remodeling Through GalR2

The regulatory peptide galanin is broadly distributed in the central nervous systems and peripheral tissues where it modulates numerous physiological and pathological processes through binding to its three G-protein-coupled receptors, GalR1-3. However, the function and identity of the galaninergic system in the heart remain unclear. Therefore, we investigated the expression of the galanin receptors in cardiac cells and tissues and found that GalR2 is the dominant receptor subtype in adult mouse hearts, cardiomyocytes and H9C2 cardiomyoblasts. In vivo, genetic suppression of GalR2 promotes cardiac hypertrophy, fibrosis and mitochondrial oxidative stress in the heart. In vitro, GalR2 silencing by siRNA abolished the beneficial effects of galanin on cell hypertrophy and mitochondrial reactive oxygen species (ROS) production. These findings unravel new insights into the role of galaninergic system in the heart and suggest novel therapeutic strategies in heart disease.

Retrospective Study of 573 Patients with Heart Failure Evaluated for Coronary Artery Disease at Toulouse University Center, France

Background

Heart failure (HF) most commonly occurs due to ischemic heart disease from stenotic coronary artery disease (CAD). HF is classified into 3 groups based on the percentage of the ejection fraction (EF): reduced (HFrEF), mid-range (HFmrEF), and preserved (HFpEF). This retrospective study included 573 patients who presented with HF based on the evaluation of EF and were evaluated for CAD by coronary angiography before undergoing coronary angioplasty at a single center in Toulouse, France.

Material/Methods

This retrospective observational study included patients recently diagnosed with HF or acute decompensation of chronic HF and referred for coronary angiography at Toulouse University Hospital between January 2019 and May 2020.

Results

Significant CAD was found in 55.8%, 55%, and 55% of the whole population, HFpEF, and HFrEF groups, respectively. Older age, male sex, and diabetes mellitus were the main risk factors for ischemic HF. Except for age and sex, patients with ischemic HFpEF were comparable to those with non-ischemic HFpEF, unlike the ischemic HFrEF group, which had more common cardiovascular risk factors than the non-ischemic HFrEF group. The ischemic HFpEF group had an older age and higher rate of dyslipidemia than the ischemic HFrEF group.

Conclusions

At our center, CAD was diagnosed in more than half of patients who presented with heart failure with preserved or reduced EF. Older age and male sex were the common risk factors in patients with HFpEF and HFrEF.

Fibrosis Protein-Protein Interactions from Google Matrix Analysis of MetaCore Network

Protein-protein interactions is a longstanding challenge in cardiac remodeling processes and heart failure. Here, we use the MetaCore network and the Google matrix algorithms for prediction of protein-protein interactions dictating cardiac fibrosis, a primary cause of end-stage heart failure. The developed algorithms allow identification of interactions between key proteins and predict new actors orchestrating fibroblast activation linked to fibrosis in mouse and human tissues. These data hold great promise for uncovering new therapeutic targets to limit myocardial fibrosis.

Apilimod alters TGFβ signaling pathway and prevents cardiac fibrotic remodeling

Rationale: TGFβ signaling pathway controls tissue fibrotic remodeling, a hallmark in many diseases leading to organ injury and failure. In this study, we address the role of Apilimod, a pharmacological inhibitor of the lipid kinase PIKfyve, in the regulation of cardiac pathological fibrotic remodeling and TGFβ signaling pathway. Methods: The effects of Apilimod treatment on myocardial fibrosis, hypertrophy and cardiac function were assessed in vivo in a mouse model of pressure overload-induced heart failure. Primary cardiac fibroblasts and HeLa cells treated with Apilimod as well as genetic mutation of PIKfyve in mouse embryonic fibroblasts were used as cell models. Results: When administered in vivo, Apilimod reduced myocardial interstitial fibrosis development and prevented left ventricular dysfunction. In vitro, Apilimod controlled TGFβ-dependent activation of primary murine cardiac fibroblasts. Mechanistically, both Apilimod and genetic mutation of PIKfyve induced TGFβ receptor blockade in intracellular vesicles, negatively modulating its downstream signaling pathway and ultimately dampening TGFβ response. Conclusions: Altogether, our findings propose a novel function for PIKfyve in the control of myocardial fibrotic remodeling and the TGFβ signaling pathway, therefore opening the way to new therapeutic perspectives to prevent adverse fibrotic remodeling using Apilimod treatment.

Galanin promotes autophagy and alleviates apoptosis in the hypertrophied heart through FoxO1 pathway

Autophagy and apoptosis are powerful regulators of multiple facets of cellular metabolism and homeostasis. Here, we uncover that galanin, a pleiotropic peptide, regulates cardiac autophagy and deactivates apoptotic cell death through the Forkhead box protein O1 (FoxO1) pathway. In hypertrophied heart, galanin promotes autophagy and metabolic shift from fatty acid (FA) to glucose oxidation and preserves mitochondrial integrity. In cardiomyoblasts, galanin triggers autophagosome formation and alleviates hypertrophy, apoptotic cell death, and mitochondrial stress. Mechanistically, galanin dictates cell autophagic and anti-apoptotic phenotypes through FoxO1 pathway. Together, these findings uncover a previously unknown role for galanin in the regulation of cardiac autophagy and provide new insights into the molecular mechanisms supporting cell survival in the hypertrophic reprogramming of the heart.

Towards a large-scale assessment of the relationship between biological and chronological aging: The INSPIRE Mouse Cohort

Aging is the major risk factor for the development of chronic diseases. After decades of research focused on extending lifespan, current efforts seek primarily to promote healthy aging. Recent advances suggest that biological processes linked to aging are more reliable than chronological age to account for an individual’s functional status, i.e. frail or robust. It is becoming increasingly apparent that biological aging may be detectable as a progressive loss of resilience much earlier than the appearance of clinical signs of frailty. In this context, the INSPIRE program was built to identify the mechanisms of accelerated aging and the early biological signs predicting frailty and pathological aging. To address this issue, we designed a cohort of outbred Swiss mice (1576 male and female mice) in which we will continuously monitor spontaneous and voluntary physical activity from 6 to 24 months of age under either normal or high fat/high sucrose diet. At different age points (6, 12, 18, 24 months), multiorgan functional phenotyping will be carried out to identify early signs of organ dysfunction and generate a large biological fluids/feces/organs biobank (100,000 samples). A comprehensive correlation between functional and biological phenotypes will be assessed to determine: 1) the early signs of biological aging and their relationship with chronological age; 2) the role of dietary and exercise interventions on accelerating or decelerating the rate of biological aging; and 3) novel targets for the promotion of healthy aging. All the functional and omics data, as well as the biobank generated in the framework of the INSPIRE cohort will be available to the aging scientific community. The present article describes the scientific background and the strategies employed for the design of the INSPIRE Mouse cohort.

In vitro and in vivo cardioprotective and metabolic efficacy of vitamin E TPGS/Apelin

AIMS

Apelin and vitamin E have been proposed as signaling molecules, but their synergistic role is unknown. The aim of this work was to develop vitamin E TPGS/Apelin system to test their cardioprotective and metabolic efficacy in vitro and in vivo.

METHODS

FDA-approved surfactant D-α-tocopheryl polyethylene glycol 1000 succinate (TPGS-1000) and Apelin complex were characterized by physico-chemical methods (CMC determination, dynamic light scattering and circular dichroism). In vitro studies were carried out on H9C2 cardiomyoblasts and isolated murine cardiomyocytes. In vivo studies were performed in isoproterenol- and high-fat diet-induced cardiac remodeling models in mice.

RESULTS

We found that vitamin E TPGS/Apelin provide cardioprotective and metabolic efficacy in vitro and in vivo. In vitro studies revealed that vitamin E TPGS/Apelin reduces hypoxia-induced mitochondrial ROS production in cultured cardiomyocytes and H9C2 cardiomyoblasts. In addition, vitamin E TPGS/Apelin confers apoptotic response to hypoxic stress in cells. In a mouse model of isoproterenol-induced cardiac injury, TPGS is not able to affect cardiac remodeling, however combination of vitamin E TPGS and Apelin counteracts myocardial apoptosis, oxidative stress, hypertrophy and fibrosis. Furthermore, combination treatment attenuated obesity-induced cardiometabolic and fibrotic remodeling in mice.

CONCLUSION

Together, our data demonstrated the therapeutic benefits of vitamin E TPGS/Apelin complex to combat cardiovascular and metabolic disorders.

Metformin Protects the Heart Against Hypertrophic and Apoptotic Remodeling After Myocardial Infarction

Cardiovascular complications are the most prevalent cause of morbidity and mortality in diabetic patients. Metformin is currently the first-line blood glucose-lowering agent with potential relevance to cardiovascular diseases. However, the underpinning mechanisms of action remain elusive. Here, we report that metformin represses cardiac apoptosis at least in part through inhibition of Forkhead box O1 (FoxO1) pathway. In a mouse model of ischemia-reperfusion (I/R), treatment with metformin attenuated cardiac and hypertrophic remodeling after 14 days of post-reperfusion. Additionally, cardiac expression of brain-like natriuretic peptide (BNP) was significantly reduced in metformin-treated mice after 14 days of cardiac I/R. In cultured H9C2 cells, metformin counteracted hypertrophic and apoptotic responses to metabolic or hypoxic stress. FoxO1 silencing by siRNA abolished anti-apoptotic effect of metformin under hypoxic stress in H9C2 cells. Taken together, these results suggest that metformin protects the heart against hypertrophic and apoptotic remodeling after myocardial infarction.

Differential protein profiling as a potential multi-marker approach for obese patients with heart failure: A retrospective study

Identification of novel circulating biomarkers predicting death and major cardio-metabolic events in obese patients with heart failure (HF) remains a research priority. In this study, we compared multi-marker profile of non-obese (NOB) and obese (OB) HF patients in relation to mortality outcome. The new multiplex proximity extension assay technology was used to analyze the levels of 92 proteins in plasma samples from HF patients according to body mass index (BMI) categories. At 2-year follow-up, all-cause mortality rates were significantly greater in NOB patients (BMI < 30 kg/m²) compared to the OB patients (BMI > 30 kg/m²) with HF (odds ratio 26; 95% CI: 1.14–624, p < 0,04). Quantitative proteomic analysis revealed thirteen distinct proteins expression profiles of OB and NOB HF patients. Among these proteins, RAGE, CXCL6, CXCL1, CD40, NEMO, VEGF-A, KLK6, PECAM1, PAR1, MMP1, BNP and NTproBNP were down-regulated, whereas leptin was up-regulated in OB HF patients. In addition, an inverse correlation between plasma BNP levels and leptin in OB HF patients was observed (r = −0.58 p = 0.02). This study identifies specific plasma protein signature in OB and NOB patients with HF in relation to mortality outcome.

Inhibition of PIKfyve prevents myocardial apoptosis and hypertrophy through activation of SIRT3 in obese mice

PIKfyve is an evolutionarily conserved lipid kinase that regulates pleiotropic cellular functions. Here, we identify PIKfyve as a key regulator of cardiometabolic status and mitochondrial integrity in chronic diet‐induced obesity. In vitro, we show that PIKfyve is critical for the control of mitochondrial fragmentation and hypertrophic and apoptotic responses to stress. We also provide evidence that inactivation of PIKfyve by the selective inhibitor STA suppresses excessive mitochondrial ROS production and apoptosis through a SIRT3‐dependent pathway in cardiomyoblasts. In addition, we report that chronic STA treatment improves cardiometabolic profile in a mouse model of cardiomyopathy linked to obesity. We provide evidence that PIKfyve inhibition reverses obesity‐induced cardiac mitochondrial damage and apoptosis by activating SIRT3. Furthermore, treatment of obese mice with STA improves left ventricular function and attenuates cardiac hypertrophy. In contrast, STA is not able to reduce isoproterenol‐induced cardiac hypertrophy in SIRT3.KO mice. Altogether, these results unravel a novel role for PIKfyve in obesity‐associated cardiomyopathy and provide a promising therapeutic strategy to combat cardiometabolic complications in obesity.

Therapeutic Benefit and Gene Network Regulation by Combined Gene Transfer of Apelin, FGF2, and SERCA2a into Ischemic Heart

Despite considerable advances in cardiovascular disease treatment, heart failure remains a public health challenge. In this context, gene therapy appears as an attractive approach, but clinical trials using single therapeutic molecules result in moderate benefit. With the objective of improving ischemic heart failure therapy, we designed a combined treatment, aimed to simultaneously stimulate angiogenesis, prevent cardiac remodeling, and restore contractile function. We have previously validated IRES-based vectors as powerful tools to co-express genes of interest. Mono- and multicistronic lentivectors expressing fibroblast growth factor 2 (angiogenesis), apelin (cardioprotection), and/or SERCA2a (contractile function) were produced and administrated by intramyocardial injection into a mouse model of myocardial infarction. Data reveal that combined treatment simultaneously improves vessel number, heart function parameters, and fibrosis prevention, due to FGF2, SERCA2a, and apelin, respectively. Furthermore, addition of SERCA2a in the combination decreases cardiomyocyte hypertrophy. Large-scale transcriptome analysis reveals that the triple treatment is the most efficient in restoring angiogenic balance as well as expression of genes involved in cardiac function and remodeling. Our study validates the concept of combined treatment of ischemic heart disease with apelin, FGF2, and SERCA2a and shows that such therapeutic benefit is mediated by a more effective recovery of gene network regulation.

Myocardial protection from ischemia/reperfusion injury by exogenous galanin fragment

Background and purpose

Galanin is a multifunctional neuropeptide with pleiotropic roles. The present study was designed to evaluate the potential effects of galanin (2-11) (G1) on functional and metabolic abnormalities in response to myocardial ischemia-reperfusion (I/R) injury.

Experimental approach

Peptide G1 was synthesized by the 9-fluorenylmethoxycarbonyl (Fmoc)-based solid-phase method. The chemical structure was identified by ¹H-NMR spectroscopy and mass spectrometry. Experiments were conducted using a rat model of I/R injury in vivo, isolated perfused rat hearts ex vivo and cultured rat cardiomyoblast H9C2 cells in vitro. Cardiac function, infarct size, myocardial energy metabolism, hemodynamic parameters, plasma levels of creatine kinase-MB (CK-MB) and lactate dehydrogenase (LDH) were measured in order to evaluate the effects of G1 on myocardial I/R injury.

Key results

Treatment with G1 increased cell viability in a dose-dependent manner, inhibited cell apoptosis and excessive mitochondrial reactive oxygen species (ROS) production in response to oxidative stress in H9C2 cells. Pre- or postischemic infusion of G1 enhanced functional and metabolic recovery during reperfusion of the ischemic isolated rat heart. Administration of G1 at the onset of reperfusion significantly reduced infarct size and plasma levels of CK-MB and LDH in rats subjected to myocardial I/R injury.

Conclusions and implications

These data provide the first evidence for cardioprotective activity of galanin G1 against myocardial I/R injury. Therefore, peptide G1 may represent a promising treatment strategy for ischemic heart disease.

Cardioprotective properties of N-terminal galanin fragment (2-15) in experimental ischemia/reperfusion injury

Background and purpose

Galanin is an endogenous peptide involved in diverse physiological functions in the central nervous system including central cardiovascular regulation. The present study was designed to evaluate the potential effects of the short N-terminal galanin fragment 2-15 (G) on cardiac ischemia/reperfusion (I/R) injury.

Experimental Approach

Peptide G was synthesized by the automatic solid phase method and identified by 1H-NMR spectroscopy and mass spectrometry. Experiments were performed on cultured rat cardiomyoblast (H9C2) cells, isolated perfused working rat hearts and anaesthetized open-chest rats.

Key Results

Cell viability increased significantly after treatment with 10 and 50 nM of G peptide. In hypoxia and reoxygenation conditions, exposure of H9C2 cells to G peptide decreased cell apoptosis and mitochondrial reactive oxygen species (ROS) production. Postischemic infusion of G peptide reduced cell membrane damage and improved functional recovery in isolated hearts during reperfusion. These effects were accompanied by enhanced restoration of myocardial metabolic state. Treatment with G peptide at the onset of reperfusion induced minor changes in hemodynamic variables but significantly reduced infarct size and plasma levels of necrosis markers.

Conclusion and implications

These findings suggest that G peptide is effective in mitigating cardiac I/R injury, thereby providing a rationale for promising tool for the treatment of cardiovascular diseases.

Apelin-13 administration protects against ischaemia/reperfusion-mediated apoptosis through the FoxO1 pathway in high-fat diet-induced obesity

BACKGROUND AND PURPOSE

Apelin-13, an endogenous ligand for the apelin (APJ) receptor, behaves as a potent modulator of metabolic and cardiovascular disorders. Here, we examined the effects of apelin-13 on myocardial injury in a mouse model combining ischaemia/reperfusion (I/R) and obesity and explored their underlying mechanisms.

EXPERIMENTAL APPROACH

Adult male C57BL/6J mice were fed a normal diet (ND) or high-fat diet (HFD) for 6 months and then subjected to cardiac I/R. The effects of apelin-13 post-treatment on myocardial injury were evaluated in HFD-fed mice after 24 h I/R. Changes in protein abundance, phosphorylation, subcellular localization and mRNA expression were determined in cardiomyoblast cell line H9C2, primary cardiomyocytes and cardiac tissue from ND- and HFD-fed mice. Apoptosis was evaluated by TUNEL staining and caspase-3 activity. Mitochondrial ultrastructure was analysed by electron microscopy.

KEY RESULTS

In HFD-fed mice subjected to cardiac I/R, i.v. administration of apelin-13 significantly reduced infarct size, myocardial apoptosis and mitochondrial damage compared with vehicle-treated animals. In H9C2 cells and primary cardiomyocytes, apelin-13 induced FoxO1 phosphorylation and nuclear exclusion. FoxO1 silencing by siRNA abolished the protective effects of apelin-13 against hypoxia-induced apoptosis and mitochondrial ROS generation. Finally, apelin deficiency in mice fed a HFD resulted in reduced myocardial FoxO1 expression and impaired FoxO1 distribution.

CONCLUSIONS AND IMPLICATIONS

These data reveal apelin as a novel regulator of FoxO1 in cardiac cells and provide evidence for the potential of apelin-13 in prevention of apoptosis and mitochondrial damage in conditions combining I/R injury and obesity.

PI5P Triggers ICAM-1 Degradation in Shigella Infected Cells, Thus Dampening Immune Cell Recruitment

Shigella flexneri, the pathogen responsible for bacillary dysentery, has evolved multiple strategies to control the inflammatory response. Here, we show that Shigella subverts the subcellular trafficking of the intercellular adhesion molecule-1 (ICAM-1), a key molecule in immune cell recruitment, in a mechanism dependent on the injected bacterial enzyme IpgD and its product, the lipid mediator PI5P. Overexpression of IpgD, but not a phosphatase dead mutant, induced the internalization and the degradation of ICAM-1 in intestinal epithelial cells. Remarkably, addition of permeant PI5P reproduced IpgD effects and led to the inhibition of neutrophil recruitment. Finally, these results were confirmed in an in vivo model of Shigella infection where IpgD-dependent ICAM-1 internalization reduced neutrophil adhesion. In conclusion, we describe here an immune evasion mechanism used by the pathogen Shigella to divert the host cell trafficking machinery in order to reduce immune cell recruitment.

Structural apelin analogues: mitochondrial ROS inhibition and cardiometabolic protection in myocardial ischaemia reperfusion injury

BACKGROUND AND PURPOSE

Mitochondria-derived oxidative stress is believed to be crucially involved in cardiac ischaemia reperfusion (I/R) injury, although currently no therapies exist that specifically target mitochondrial reactive oxygen species (ROS) production. The present study was designed to evaluate the potential effects of the structural analogues of apelin-12, an adipocyte-derived peptide, on mitochondrial ROS generation, cardiomyocyte apoptosis, and metabolic and functional recovery to myocardial I/R injury.

EXPERIMENTAL APPROACH

In cultured H9C2 cardiomyoblasts and adult cardiomyocytes, oxidative stress was induced by hypoxia reoxygenation. Isolated rat hearts were subjected to 35 min of global ischaemia and 30 min of reperfusion. Apelin-12, apelin-13 and structural apelin-12 analogues, AI and AII, were infused during 5 min prior to ischaemia.

KEY RESULTS

In cardiac cells, mitochondrial ROS production was inhibited by the structural analogues of apelin, AI and AII, in comparison with the natural peptides, apelin-12 and apelin-13. Treatment of cardiomyocytes with AI and AII decreased cell apoptosis concentration-dependently. In a rat model of I/R injury, pre-ischaemic infusion of AI and AII markedly reduced ROS formation in the myocardial effluent and attenuated cell membrane damage. Prevention of oxidative damage by AI and AII was associated with the improvement of functional and metabolic recovery after I/R in the heart.

CONCLUSIONS AND IMPLICATIONS

These data provide the evidence for the potential of the structural apelin analogues in selective reduction of mitochondrial ROS generation and myocardial apoptosis and form the basis for a promising therapeutic strategy in the treatment of oxidative stress-related heart disease.

LEOPARD syndrome-associated SHP2 mutation confers leanness and protection from diet-induced obesity

LEOPARD syndrome (multiple Lentigines, Electrocardiographic conduction abnormalities, Ocular hypertelorism, Pulmonary stenosis, Abnormal genitalia, Retardation of growth, sensorineural Deafness; LS), also called Noonan syndrome with multiple lentigines (NSML), is a rare autosomal dominant disorder associating various developmental defects, notably cardiopathies, dysmorphism, and short stature. It is mainly caused by mutations of the PTPN11 gene that catalytically inactivate the tyrosine phosphatase SHP2 (Src-homology 2 domain-containing phosphatase 2). Besides its pleiotropic roles during development, SHP2 plays key functions in energetic metabolism regulation. However, the metabolic outcomes of LS mutations have never been examined. Therefore, we performed an extensive metabolic exploration of an original LS mouse model, expressing the T468M mutation of SHP2, frequently borne by LS patients. Our results reveal that, besides expected symptoms, LS animals display a strong reduction of adiposity and resistance to diet-induced obesity, associated with overall better metabolic profile. We provide evidence that LS mutant expression impairs adipogenesis, triggers energy expenditure, and enhances insulin signaling, three features that can contribute to the lean phenotype of LS mice. Interestingly, chronic treatment of LS mice with low doses of MEK inhibitor, but not rapamycin, resulted in weight and adiposity gains. Importantly, preliminary data in a French cohort of LS patients suggests that most of them have lower-than-average body mass index, associated, for tested patients, with reduced adiposity. Altogether, these findings unravel previously unidentified characteristics for LS, which could represent a metabolic benefit for patients, but may also participate to the development or worsening of some traits of the disease. Beyond LS, they also highlight a protective role of SHP2 global LS-mimicking modulation toward the development of obesity and associated disorders.

Transition from metabolic adaptation to maladaptation of the heart in obesity: role of apelin

Background/Objectives:

Impaired energy metabolism is the defining characteristic of obesity-related heart failure. The adipocyte-derived peptide apelin has a role in the regulation of cardiovascular and metabolic homeostasis and may contribute to the link between obesity, energy metabolism and cardiac function. Here we investigate the role of apelin in the transition from metabolic adaptation to maladaptation of the heart in obese state.

Methods:

Adult male C57BL/6J, apelin knock-out (KO) or wild-type mice were fed a high-fat diet (HFD) for 18 weeks. To induce heart failure, mice were subjected to pressure overload after 18 weeks of HFD. Long-term effects of apelin on fatty acid (FA) oxidation, glucose metabolism, cardiac function and mitochondrial changes were evaluated in HFD-fed mice after 4 weeks of pressure overload. Cardiomyocytes from HFD-fed mice were isolated for analysis of metabolic responses.

Results:

In HFD-fed mice, pressure overload-induced transition from hypertrophy to heart failure is associated with reduced FA utilization (P<0.05), accelerated glucose oxidation (P<0.05) and mitochondrial damage. Treatment of HFD-fed mice with apelin for 4 weeks prevented pressure overload-induced decline in FA metabolism (P<0.05) and mitochondrial defects. Furthermore, apelin treatment lowered fasting plasma glucose (P<0.01), improved glucose tolerance (P<0.05) and preserved cardiac function (P<0.05) in HFD-fed mice subjected to pressure overload. In apelin KO HFD-fed mice, spontaneous cardiac dysfunction is associated with reduced FA oxidation (P<0.001) and increased glucose oxidation (P<0.05). In isolated cardiomyocytes, apelin stimulated FA oxidation in a dose-dependent manner and this effect was prevented by small interfering RNA sirtuin 3 knockdown.

Conclusions:

These data suggest that obesity-related decline in cardiac function is associated with defective myocardial energy metabolism and mitochondrial abnormalities. Furthermore, our work points for therapeutic potential of apelin to prevent myocardial metabolic abnormalities in heart failure paired with obesity.

Apelin prevents cardiac fibroblast activation and collagen production through inhibition of sphingosine kinase 1

AIMS

Activation of cardiac fibroblasts and their differentiation into myofibroblasts is a key event in the progression of cardiac fibrosis that leads to end-stage heart failure. Apelin, an adipocyte-derived factor, exhibits a number of cardioprotective properties; however, whether apelin is involved in cardiac fibroblast activation and myofibroblast formation remains unknown. The aim of this study was to determine the effects of apelin in activated cardiac fibroblasts, the potential related mechanisms and impact on cardiac fibrotic remodelling process.

METHODS AND RESULTS

In vitro experiments were performed in mouse cardiac fibroblasts obtained from normal and pressure-overload hearts. Pretreatment of naive cardiac fibroblasts with apelin (1-100 nM) inhibited Transforming growth factor-β (TGF-β)-mediated expression of the myofibroblast marker α-smooth muscle actin (α-SMA) and collagen production. Furthermore, apelin decreased the spontaneous collagen production in cardiac fibroblasts isolated from hearts after aortic banding. Knockdown strategy and pharmacological inhibition revealed that prevention of collagen accumulation by apelin was mediated by a reduction in sphingosine kinase 1 (SphK1) activity. In vivo studies using the aortic banding model indicated that pretreatment with apelin attenuated the development of myocardial fibrotic remodelling and inhibited cardiac SphK1 activity and α-SMA expression. Moreover, administration of apelin 2 weeks after aortic banding prevented cardiac remodelling by inhibiting myocyte hypertrophy, cardiac fibrosis, and ventricular dysfunction.

CONCLUSION

Our data provide the first evidence that apelin inhibits TGF-β-stimulated activation of cardiac fibroblasts through a SphK1-dependent mechanism. We also demonstrated that the administration of apelin during the phase of reactive fibrosis prevents structural remodelling of the myocardium and ventricular dysfunction. These findings may have important implications for designing future therapies for myocardial performance during fibrotic remodelling, affecting the clinical management of patients with progressive heart failure.

New insights on receptor-dependent and monoamine oxidase-dependent effects of serotonin in the heart

Biogenic amines like serotonin (5-HT) and catecholamines usually act through stimulation of G-protein coupled receptors (GPCRs). We now have strong evidence that they can signal through receptor-independent mechanisms. One well described pathway is the degradation of biogenic amine by monoamine oxidases (MAOs) after transport into the cells by selective transporters. The oxidation of biogenic amines generates hydrogen peroxide, H(2)O(2), that can act as a signalling intermediate in the cell. This original mechanism of action of 5-HT is relevant in the heart since it is responsible for both cardiomyocyte hypertrophy and apoptosis. Moreover, in vivo experiments indicate a physiological significance for MAO in the damage during ischemia-reperfusion in the heart. Since functional 5-HT receptors are present in the heart and have also been demonstrated to contribute to cardiomyocyte growth and apoptosis, it is of major interest to evaluate respective contribution and cross-regulations between 5-HT receptors and MAO in cardiac function.

Dopamine D2-like receptor agonist bromocriptine protects against ischemia/reperfusion injury in rat kidney

BACKGROUND

Dopamine, via activation of D1-like and D2-like receptors, plays an important role in the regulation of renal sodium excretion. Recently, we demonstrated that dopamine D2-like receptor agonist (bromocriptine) stimulates p44/42 mitogen-activated protein kinases (MAPKs) and Na+,K(+)ATPase (NKA) activity in proximal tubular epithelial cells. Since both these parameters are compromised in ischemia/reperfusion (I/R) injury to the kidney, we investigated whether bromocriptine protects against the injury.

METHODS

In this study we used unilateral rat model of renal I/R injury. The Sprague-Dawley rats were divided into vehicle and bromocriptine groups. The vehicle and bromocriptine group was treated with vehicle and bromocriptine (500 microg/kg intravenously), respectively, 15 minutes before the induction of unilateral ischemia followed by 24- or 48-hour reperfusion. At the end of 24 or 48 hours the animals were sacrificed to collect control and ischemic kidney cortices, in which necrosis, apoptosis, NKA activity, NKA alpha1 subunit expression, and p44/42 MAPK phosphorylation were measured.

RESULTS

We found extensive necrosis, apoptosis, and decreased NKA activity (with no change in alpha1 subunit) in the ischemic kidney cortex compared to the nonischemic cortex from the vehicle-treated rats as early as 24 hours post-reperfusion. In contrast, I/R injury-induced necrotic, apoptotic, and decrease in NKA activity were absent in the outer cortex of bromocriptine-treated rats after 24 or 48 hours. Interestingly, we detected significantly higher phosphorylation of p44/42 MAPKs in control and ischemic kidneys of bromocriptine-treated rats compared to those of vehicle-treated rats.

CONCLUSION

Therefore, bromocriptine, a D1-like receptor agonist, may protect against I/R injury to proximal tubules of the kidney, via p44/42 MAPK activation.

Age-dependent increase in hydrogen peroxide production by cardiac monoamine oxidase A in rats

Oxidative stress is one of the factors involved in age-related impairment of cardiac function. In the present study, we investigated the role of the catecholamine-degrading enzyme monoamine oxidase (MAO) in H(2)O(2) production in the hearts of young, adult, and old rats. MAO-dependent H(2)O(2) production, measured by a chemiluminescence-based assay, increased with age, reaching the maximum in 24-mo-old rats (7.5-fold increase vs. 1-mo-old rats). The following observations indicate that the age-dependent increase in H(2)O(2) generation was fully related to the MAO-A isoform: 1) at all the ages tested, chemiluminescence production was inhibited by the MAO-A inhibitor clorgyline but not by the MAO-B inhibitor RO-19 6327; 2) enzyme assay, Western blot, and semiquantitative RT-PCR analysis showed an age-dependent increase in cardiac MAO-A activity, immunodetection, and mRNA expression, respectively; and 3) the MAO-B isoform was undetectable by enzyme assay and Western blot analysis. These results suggest that MAO-A could be a major source of H(2)O(2) in the aging heart.