PIKfyve-Dependent Phosphoinositide Dynamics in Megakaryocyte/Platelet Granule Integrity and Platelet Functions.

BACKGROUND: Secretory granules are key elements for platelet functions. Their biogenesis and integrity are regulated by fine-tuned mechanisms that need to be fully characterized. Here, we investigated the role of the phosphoinositide 5-kinase PIKfyve and its lipid products, PtdIns5P (phosphatidylinositol 5 monophosphate) and PtdIns(3,5)P2 (phosphatidylinositol (3,5) bisphosphate) in granule homeostasis in megakaryocytes and platelets. METHODS: For that, we invalidated PIKfyve by pharmacological inhibition or gene silencing in megakaryocytic cell models (human MEG-01 cell line, human imMKCLs, mouse primary megakaryocytes) and in human platelets. RESULTS: We unveiled that PIKfyve expression and its lipid product levels increased with megakaryocytic maturation. In megakaryocytes, PtdIns5P and PtdIns(3,5)P2 were found in alpha and dense granule membranes with higher levels in dense granules. Pharmacological inhibition or knock-down of PIKfyve in megakaryocytes decreased PtdIns5P and PtdIns(3,5)P2 synthesis and induced a vacuolar phenotype with a loss of alpha and dense granule identity. Permeant PtdIns5P and PtdIns(3,5)P2 and the cation channel TRPML (transient receptor potential mucolipin) 1 and TPC (two pore segment channel) 2 activation were able to accelerate alpha and dense granule integrity recovery following release of PIKfyve pharmacological inhibition. In platelets, PIKfyve inhibition specifically impaired the integrity of dense granules culminating in defects in their secretion, platelet aggregation, and thrombus formation. CONCLUSIONS: These data demonstrated that PIKfyve and its lipid products PtdIns5P and PtdIns(3,5)P2 control granule integrity both in megakaryocytes and platelets.

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.

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, IL1ß, 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.

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 AND 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.

Metformin Attenuates Postinfarction Myocardial Fibrosis and Inflammation in Mice.

Diabetes is a major risk factor for the development of cardiovascular disease with a higher incidence of myocardial infarction. This study explores the role of metformin, a first-line antihyperglycemic agent, in postinfarction fibrotic and inflammatory remodeling in mice. Three-month-old C57BI/6J mice were submitted to 30 min cardiac ischemia followed by reperfusion for 14 days. Intraperitoneal treatment with metformin (5 mg/kg) was initiated 15 min after the onset of reperfusion and maintained for 14 days. Real-time PCR was used to determine the levels of COL3A1, αSMA, CD68, TNF-α and IL-6. Increased collagen deposition and infiltration of macrophages in heart tissues are associated with upregulation of the inflammation-associated genes in mice after 14 days of reperfusion. Metformin treatment markedly reduced postinfarction fibrotic remodeling and CD68-positive cell population in mice. Moreover, metformin resulted in reduced expression of COL3A1, αSMA and CD68 after 14 days of reperfusion. Taken together, these results open new perspectives for the use of metformin as a drug that counteracts adverse myocardial fibroticand inflammatory remodeling after MI.

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.

TOM1 is a PI5P effector involved in the regulation of endosomal maturation.

Phosphoinositides represent a major class of lipids specifically involved in the organization of signaling cascades, maintenance of the identity of organelles and regulation of multiple intracellular trafficking steps. We previously reported that phosphatidylinositol 5-monophosphate (PI5P), produced by the Shigella flexneri phosphatase IpgD, is implicated in the endosomal sorting of the epidermal growth factor receptor (EGFR). Here, we show that the adaptor protein TOM1 is a new direct binding partner of PI5P. We identify the domain of TOM1 involved in this interaction and characterize the binding motif. Finally, we demonstrate that the recruitment of TOM1 by PI5P on signaling endosomes is responsible for the delay in EGFR degradation and fluid-phase bulk endocytosis. Taken together, our data strongly suggest that PI5P enrichment in signaling endosomes prevents endosomal maturation through the recruitment of TOM1, and point to a new function of PI5P in regulating discrete maturation steps in the endosomal system.

Phosphatidylinositol 5-phosphate: a nuclear stress lipid and a tuner of membranes and cytoskeleton dynamics.

Phosphatidylinositol 5-phosphate (PtdIns5P), the least characterized among the three phosphatidylinositol monophosphates, is emerging as a bioactive lipid involved in the control of several cellular functions. Similar to PtdIns3P, it is present in low amounts in mammalian cells, and can be detected at the plasma membrane and endomembranes as well as in the nucleus. Changes in PtdIns5P levels are observed in mammalian cells following specific stimuli or stresses, and in human diseases. Recently, the contribution of several enzymes such as PIKfyve, myotubularins, and type II PtdInsP-kinases to PtdIns5P metabolism has gained a strong experimental support. Here, we provide a picture emerging from recent studies showing how this lipid can be generated and act as a regulator of membrane and cytoskeleton dynamics, and as a modulator of gene expression. We briefly summarize the current methods and tools for studying PtdIns5P, and discuss how PtdIns5P can integrate and coordinate different functions in a spatiotemporal manner.

LG186: An inhibitor of GBF1 function that causes Golgi disassembly in human and canine cells.

Brefeldin A-mediated inhibition of ADP ribosylation factor (Arf) GTPases and their guanine nucleotide exchange factors, Arf-GEFs, has been a cornerstone of membrane trafficking research for many years. Brefeldin A (BFA) is relatively non-selective inhibiting at least three targets in human cells, Golgi brefeldin A resistance factor 1 (GBF1), brefeldin A inhibited guanine nucleotide exchange factor 1 (BIG1) and brefeldin A inhibited guanine nucleotide exchange factor 2 (BIG2). Here, we show that the previously described compound Exo2 acts through inhibition of Arf-GEF function, but causes other phenotypic changes that are not GBF1 related. We describe the engineering of Exo2 to produce LG186, a more selective, reversible inhibitor of Arf-GEF function. Using multiple-cell-based assays and GBF1 mutants, our data are most consistent with LG186 acting by selective inhibition of GBF1. Unlike other Arf-GEF and reported GBF1 inhibitors including BFA, Exo2 and Golgicide A, LG186 induces disassembly of the Golgi stack in both human and canine cells.

A charged prominence in the linker domain of the cysteine-string protein Cspα mediates its regulated interaction with the calcium sensor synaptotagmin 9 during exocytosis.

The cochaperone cysteine-string protein (Csp) is located on vesicles and participates in the control of neurotransmission and hormone exocytosis. Csp contains several domains, and our previous work demonstrated the requirement of the Csp linker domain in regulated exocytosis of insulin in rodent pancreatic ß cells. We now address the molecular details to gain insight into the sequence of events during exocytosis. According to pulldown experiments and in vitro binding assays, Cspα interacts indirectly with SNAP-25 and directly with the calcium sensor synaptotagmin 9 (Syt9), which could be an intermediate between the chaperone and the t-SNARE. The C(2)A calcium binding domain of Syt9 and the linker domain of Cspα constituted the minimal interacting module. FRET-FLIM experiments confirmed the interaction between Syt9 and Cspα. Moreover, the point mutation E93V in the linker domain of Cspα significantly reduced the interaction between the two proteins. Molecular modeling revealed that this point mutation abolished a charged prominence on the surface of Cspα required for interaction. Strikingly, free calcium in the physiological low micromolar range enhanced the interaction between Syt9 and the linker domain of Cspα in vitro. These data indicate that Cspα interacts with Syt9, and such a complex may be relevant in the calcium-mediated control of a late stage of exocytosis by triggering the specific recruitment of a folding catalyst at the fusion point.

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.

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.

Apilimod alters TGFß signaling pathway and prevents cardiac fibrotic remodeling.

Rationale: TGFß 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 TGFß 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 TGFß-dependent activation of primary murine cardiac fibroblasts. Mechanistically, both Apilimod and genetic mutation of PIKfyve induced TGFß receptor blockade in intracellular vesicles, negatively modulating its downstream signaling pathway and ultimately dampening TGFß response. Conclusions: Altogether, our findings propose a novel function for PIKfyve in the control of myocardial fibrotic remodeling and the TGFß signaling pathway, therefore opening the way to new therapeutic perspectives to prevent adverse fibrotic remodeling using Apilimod treatment.

The secretion inhibitor Exo2 perturbs trafficking of Shiga toxin between endosomes and the trans-Golgi network.

The small-molecule inhibitor Exo2 {4-hydroxy-3-methoxy-(5,6,7,8-tetrahydrol[1]benzothieno[2,3-d]pyrimidin-4-yl)hydraz-one benzaldehyde} has been reported to disrupt the Golgi apparatus completely and to stimulate Golgi-ER (endoplasmic reticulum) fusion in mammalian cells, akin to the well-characterized fungal toxin BFA (brefeldin A). It has also been reported that Exo2 does not affect the integrity of the TGN (trans-Golgi network), or the direct retrograde trafficking of the glycolipid-binding cholera toxin from the TGN to the ER lumen. We have examined the effects of BFA and Exo2, and found that both compounds are indistinguishable in their inhibition of anterograde transport and that both reagents significantly disrupt the morphology of the TGN in HeLa and in BS-C-1 cells. However, Exo2, unlike BFA, does not induce tubulation and merging of the TGN and endosomal compartments. Furthermore, and in contrast with its effects on cholera toxin, Exo2 significantly perturbs the delivery of Shiga toxin to the ER. Together, these results suggest that the likely target(s) of Exo2 operate at the level of the TGN, the Golgi and a subset of early endosomes, and thus Exo2 provides a more selective tool than BFA for examining membrane trafficking in mammalian cells.

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.

Cysteine-string protein isoform beta (Cspbeta) is targeted to the trans-Golgi network as a non-palmitoylated CSP in clonal beta-cells.

Cysteine string proteins (CSPs) belong to the DnaJ-like chaperone family and play an important role in regulated exocytosis in neurons and endocrine cells. The palmitoylation of several residues in a cysteine string domain may anchor CSPs to the exocytotic vesicle surface and in pancreatic beta-cells, Cspalpha is localized on insulin containing large dense core vesicles (LDCVs). An isoform closely related to Cspalpha, Cspbeta, has been obtained from testis cell cDNA libraries. To gain insights on this isoform and more generally on the properties of CSPs, we compared Cspalpha and Cspbeta. In pull-down experiments, Cspbeta was able to interact to the same extent with two of the known Cspalpha chaperone partners, Hsc70 and SGT. Upon transient overexpression in clonal beta-cells, Cspbeta but not Cspalpha was mainly produced as a non-palmitoylated protein and mutational analysis indicated that domains distinct from the cysteine string are responsible for this difference. As Cspbeta remained tightly bound to membranes, intrinsic properties of CSPs are sufficient for interactions with membranes. Indeed, recombinant Cspalpha and Cspbeta were capable to interact with membranes even in their non-palmitoylated forms. Furthermore, overexpressed Cspbeta was not associated with LDCVs, but was localized at the trans-Golgi network. Our results suggest a possible correlation between the specific membrane targeting and the palmitoylation level of CSPs.

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.

Synaptotagmin 8 is expressed both as a calcium-insensitive soluble and membrane protein in neurons, neuroendocrine and endocrine cells.

Synaptotagmins (syt) form a large family of transmembrane proteins and some of its isoforms are known to regulate calcium-induced membrane fusion during vesicular traffic. In view of the reported implication of the isoform syt8 in exocytosis we investigated the expression, localisation and calcium-sensitivity of syt8 in secretory cells. An immunopurified antipeptide antibody was generated which is directed against a C-terminal sequence and devoid of crossreactivity towards syt1 to 12. Subcellular fractionation and immunocytochemistry revealed two forms of synaptotagmin 8 (50 and 40 kDa). Whereas the 40-kDa was present in the cytosol in brain, in PC12 and in clonal beta-cells, the 50-kDa form was localised in very typical clusters and partially colocalised with the SNARE protein Vti1a. Moreover, in primary hippocampal neurons syt8 was only found within the soma. Amplification of syt8 by RT-PCR indicated that the observed protein variants were not generated by alternative splicing of the 6th exon and are most likely linked to variations in the N-terminal region. In contrast to the established calcium sensor syt2, endogenous cytosolic syt8 and transiently expressed syt8-C2AB-eGFP did not translocate upon a raise in cytosolic calcium in living cells. Syt8 is therefore not a calcium sensor in exocytotic membrane fusion in endocrine cells.

Liposome Flotation Assays for Phosphoinositide-protein Interaction.

Phosphoinositides are rare membrane lipids involved in the control of the major cellular functions and signaling pathways. They are able to recruit specific effector proteins to the cytosolic face of plasma membrane and organelles to coordinate a vast variety of signaling and trafficking processes, as well to maintain specific identity of the different subcellular compartments (Di Paolo and De Camilli, 2006; Lemmon, 2003). Therefore, analysis of these effectors' binding properties and specificity towards different phosphoinositides is crucial for the understanding of their cellular functions. This protocol describes a method to characterize the binding of proteins to different phosphoinositide-containing vesicles.

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.