Pharmacological Elevation of Circulating Bioactive Phosphosphingolipids Enhances Myocardial Recovery After Acute Infarction

Serum metabolism characteristics of patients with myocardial injury after noncardiac surgery explored by the untargeted metabolomics approach

BACKGROUND

Myocardial injury after noncardiac surgery (MINS) is one of the most common complications associated with postoperative adverse cardiovascular outcomes and mortality. However, MINS often fails to be timely diagnosed due to the absence of clinical symptoms and limited diagnostic methods. The metabolomic analysis might be an efficient way to discover new biomarkers of MINS. Characterizing the metabolomic features of MINS patients may provide new insight into the diagnosis of MINS.

METHODS

In this study, serum samples from 20 matched patients with or without MINS (n = 10 per group) were subjected to untargeted metabolomics analysis to investigate comprehensive metabolic information. Differential metabolites were identified, and the enriched metabolic pathway was determined based on the Kyoto Encyclopedia of Genes and Genomes (KEGG) database.

RESULTS

A comprehensive analysis revealed 124 distinct metabolites, predominantly encompassing lipids, amino acids and other compounds. The observed modifications in metabolic pathways in patients with or without MINS showed significant clustering in cholesterol metabolism, aldosterone synthesis and secretion, primary bile acid biosynthesis, as well as cysteine and methionine metabolism. Four specific metabolites (taurocholic acid, L-pyroglutamic acid, taurochenodeoxycholic acid, and pyridoxamine) exhibited promising potential as biomarkers for prognosticating MINS.

CONCLUSIONS

This study contributes valuable insights into the metabolomic features of MINS and the discovery of potential biomarkers which may help the early diagnosis of MINS. The identified metabolites and altered pathways offer valuable insights into the molecular underpinnings of MINS, paving the way for improved diagnostic approaches and potential intervention strategies.

Sphingosine-1-phosphate levels are inversely associated with left ventricular and atrial chamber volume and cardiac mass in men : The Study of Health in Pomerania (SHIP)

AIMS

Sphingosine-1-phosphate (S1P) is a signaling lipid, which is involved in several cellular processes including cell growth, proliferation, migration and apoptosis. The associations of serum S1P levels with cardiac geometry and function are still not clear. We investigated the associations of S1P with cardiac structure and systolic function in a population-based sample.

METHODS AND RESULTS

We performed cross-sectional analyses of 858 subjects (467 men; 54.4%), aged 22 to 81 years, from a sub-sample of the population-based Study of Health in Pomerania (SHIP-TREND-0). We analyzed the associations of serum S1P with structural and systolic function left ventricular (LV) and left atrial (LA) parameters as determined by magnetic resonance imaging (MRI) using sex-stratified multivariable-adjusted linear regression models. In men, MRI data showed that a 1 µmol/L lower S1P concentration was associated with an 18.1 mL (95% confidence interval [CI] 3.66-32.6; p = 0.014) larger LV end-diastolic volume (LVEDV), a 0.46 mm (95% CI 0.04-0.89; p = 0.034) greater LV wall thickness (LVWT) and a 16.3 g (95% CI 6.55-26.1; p = 0.001) higher LV mass (LVM). S1P was also associated with a 13.3 mL/beat (95% CI 4.49-22.1; p = 0.003) greater LV stroke volume (LVSV), an 18.7 cJ (95% CI 6.43-30.9; p = 0.003) greater LV stroke work (LVSW) and a 12.6 mL (95% CI 1.03-24.3; p = 0.033) larger LA end-diastolic volume (LAEDV). We did not find any significant associations in women.

CONCLUSIONS

In this population-based sample, lower levels of S1P were associated with higher LV wall thickness and mass, larger LV and LA chamber sizes and greater stroke volume and work of the LV in men, but not in women. Our results indicate that lower levels of S1P were associated with parameters related with cardiac geometry and systolic function in men, but not in women.

Phospholipids, the Masters in the Shadows during Healing after Acute Myocardial Infarction

Phospholipids are major components of cell membranes with complex structures, high heterogeneity and critical biological functions and have been used since ancient times to treat cardiovascular disease. Their importance and role were shadowed by the difficulty or incomplete available research methodology to study their biological presence and functionality. This review focuses on the current knowledge about the roles of phospholipids in the pathophysiology and therapy of cardiovascular diseases, which have been increasingly recognized. Used in singular formulation or in inclusive combinations with current drugs, phospholipids proved their positive and valuable effects not only in the protection of myocardial tissue, inflammation and fibrosis but also in angiogenesis, coagulation or cardiac regeneration more frequently in animal models as well as in human pathology. Thus, while mainly neglected by the scientific community, phospholipids present negligible side effects and could represent an ideal target for future therapeutic strategies in healing myocardial infarction. Acknowledging and understanding their mechanisms of action could offer a new perspective into novel therapeutic strategies for patients suffering an acute myocardial infarction, reducing the burden and improving the general social and economic outcome.

Recent Insight into the Role of Sphingosine-1-Phosphate Lyase in Neurodegeneration

Sphingosine-1-phosphate lyase (SPL) is a pyridoxal 5'-phosphate-dependent enzyme involved in the irreversible degradation of sphingosine-1-phosphate (S1P)-a bioactive sphingolipid that modulates a broad range of biological processes (cell proliferation, migration, differentiation and survival; mitochondrial functioning; and gene expression). Although SPL activity leads to a decrease in the available pool of S1P in the cell, at the same time, hexadecenal and phosphoethanolamine, compounds with potential biological activity, are generated. The increased expression and/or activity of SPL, and hence the imbalance between S1P and the end products of its cleavage, were demonstrated in several pathological states. On the other hand, loss-of-function mutations in the SPL encoding gene are a cause of severe developmental impairments. Recently, special attention has been paid to neurodegenerative diseases as the most common pathologies of the nervous system. This review summarizes the current findings concerning the role of SPL in the nervous system with an emphasis on neurodegeneration. Moreover, it briefly discusses pharmacological compounds directed to inhibit its activity.

Sphingolipid metabolism and signaling in cardiovascular diseases

Sphingolipids are a structural component of the cell membrane, derived from sphingosine, an amino alcohol. Its sphingoid base undergoes various types of enzymatic transformations that lead to the formation of biologically active compounds, which play a crucial role in the essential pathways of cellular signaling, proliferation, maturation, and death. The constantly growing number of experimental and clinical studies emphasizes the pivotal role of sphingolipids in the pathophysiology of cardiovascular diseases, including, in particular, ischemic heart disease, hypertension, heart failure, and stroke. It has also been proven that altering the sphingolipid metabolism has cardioprotective properties in cardiac pathologies, including myocardial infarction. Recent studies suggest that selected sphingolipids may serve as valuable biomarkers useful in the prognosis of cardiovascular disorders in clinical practice. This review aims to provide an overview of the current knowledge of sphingolipid metabolism and signaling in cardiovascular diseases.

Sex Differences in Cardiovascular Diseases: A Matter of Estrogens, Ceramides, and Sphingosine 1-Phosphate

The medical community recognizes sex-related differences in pathophysiology and cardiovascular disease outcomes (CVD), culminating with heart failure. In general, pre-menopausal women tend to have a better prognosis than men. Explaining why this occurs is not a simple matter. For decades, sex hormones like estrogens (Es) have been identified as one of the leading factors driving these sex differences. Indeed, Es seem protective in women as their decline, during and after menopause, coincides with an increased CV risk and HF development. However, clinical trials demonstrated that E replacement in post-menopause women results in adverse cardiac events and increased risk of breast cancer. Thus, a deeper understanding of E-related mechanisms is needed to provide a vital gateway toward better CVD prevention and treatment in women. Of note, sphingolipids (SLs) and their metabolism are strictly related to E activities. Among the SLs, ceramide and sphingosine 1-phosphate play essential roles in mammalian physiology, particularly in the CV system, and appear differently modulated in males and females. In keeping with this view, here we explore the most recent experimental and clinical observations about the role of E and SL metabolism, emphasizing how these factors impact the CV system.

Sphingosine-1-phosphate interactions in the spleen and heart reflect extent of cardiac repair in mice and failing human hearts

Sphingosine-1-phosphate (S1P) is a bioactive mediator in inflammation. Dysregulated S1P is demonstrated as a cause of heart failure (HF). However, the time-dependent and integrative role of S1P interaction with receptors in HF is unclear after myocardial infarction (MI). In this study, the sphingolipid mediators were quantified in ischemic human hearts. We also measured the time kinetics of these mediators post-MI in murine spleen and heart as an integrative approach to understand the interaction of S1P and respective S1P receptors in the transition of acute (AHF) to chronic HF (CHF). Risk-free 8-12 wk male C57BL/6 mice were subjected to MI surgery, and MI was confirmed by echocardiography and histology. Mass spectrometry was used to quantify sphingolipids in plasma, infarcted heart, spleen of mice, and ischemic and healthy human heart. The physiological cardiac repair was observed in mice with a notable increase of S1P quantity (pmol/g) in the heart and spleen significantly reduced in patients with ischemic HF. The circulating murine S1P levels were increased during AHF and CHF despite lowered substrate in CHF. The S1PR1 receptor expression was observed to coincide with the respective S1P quantity in mice and human hearts. Furthermore, selective S1P1 agonist limited inflammatory markers CCL2 and TNF-α and accelerated reparative markers ARG-1 and YM-1 in macrophages in the presence of Kdo2-Lipid A (KLA; potent inflammatory stimulant). This report demonstrated the importance of S1P/S1PR1 signaling in physiological inflammation during cardiac repair in mice. Alteration in these axes may serve as the signs of pathological remodeling in patients with ischemia.NEW & NOTEWORTHY Previous studies indicate that sphingosine-1-phosphate (S1P) has some role in cardiovascular disease. This study adds quantitative and integrative systems-based approaches that are necessary for discovery and bedside translation. Here, we quantitated sphinganine, sphingosine, sphingosine-1-phosphate (S1P) in mice and human cardiac pathobiology. Interorgan S1P quantity and respective systems-based receptor activation suggest cardiac repair after myocardial infarction. Thus, S1P serves as a therapeutic target for cardiac protection in clinical translation.

Isolation Methods for Human CD34 Subsets Using Fluorescent and Magnetic Activated Cell Sorting: an In Vivo Comparative Study

INTRODUCTION

Acute myocardial infarction (AMI) and resulting cardiac damage and heart failure are leading causes of morbidity and mortality worldwide. Multiple studies have examined the utility of CD34⁺ cells for the treatment of acute and ischemic heart disease. However, the optimal strategy to enrich CD34 cells from clinical sources is not known. We examined the efficacy of fluorescence activated cell sorting (FACS) and magnetic beads cell sorting (MACS) methods for CD34 cell isolation from mobilized human mononuclear peripheral blood cells (mhPBMNCs).

METHODS

mhPBCs were processed following acquisition using FACS or MACS according to clinically established protocols. Cell viability, CD34 cell purity and characterization of surface marker expression were assessed using a flow cytometer. For in vivo characterization of cardiac repair, we conducted LAD ligation surgery on 8-10 weeks female NOD/SCID mice followed by intramyocardial transplantation of unselected mhPBMNCs, FACS or MACS enriched CD34⁺ cells.

RESULTS

Both MACS and FACS isolation methods achieved high purity rates, viability, and enrichment of CD34⁺ cells. In vivo studies following myocardial infarction demonstrated retention of CD34⁺ in the peri-infarct region for up to 30 days after transplantation. Retained CD34⁺ cells were associated with enhanced angiogenesis and reduced inflammation compared to unselected mhPBMNCs or PBS treatment arms. Cardiac scar and fibrosis as assessed by immunohistochemistry were reduced in FACS and MACS CD34⁺ treatment groups. Finally, reduced scar and augmented angiogenesis resulted in improved cardiac functional recovery, both on the global and regional function and remodeling assessments by echocardiography.

CONCLUSION

Cell based therapy using enriched CD34⁺ cells sorted by FACS or MACS result in better cardiac recovery after ischemic injury compared to unselected mhPBMNCs. Both enrichment techniques offer excellent recovery and purity and can be equally used for clinical applications.

Polymer Cell Surface Coating Enhances Mesenchymal Stem Cell Retention and Cardiac Protection

Mesenchymal stem cell (MSC) therapy has been widely tested in clinical trials to promote healing post-myocardial infarction. However, low cell retention and the need for a large donor cell number in human studies remain a key challenge for clinical translation. Natural biomaterials such as gelatin are ideally suited as scaffolds to deliver and enhance cell engraftment after transplantation. A potential drawback of MSC encapsulation in the hydrogel is that the bulky matrix may limit their biological function and interaction with the surrounding tissue microenvironment that conveys important injury signals. To overcome this limitation, we adopted a gelatin methacrylate (gelMA) cell-coating technique that photocross-links gelatin on the individual cell surface at the nanoscale. The present study investigated the cardiac protection of gelMA coated, hypoxia preconditioned MSCs (gelMA-MSCs) in a murine myocardial infarction (MI) model. We demonstrate that the direct injection of gelMA-MSC results in significantly higher myocardial engraftment 7 days after MI compared to uncoated MSCs. GelMA-MSC further amplified MSC benefits resulting in enhanced cardioprotection as measured by cardiac function, scar size, and angiogenesis. Improved MSC cardiac retention also led to a greater cardiac immunomodulatory function after injury. Taken together, this study demonstrated the efficacy of gelMA-MSCs in treating cardiac injury with a promising potential to reduce the need for donor MSCs through enhanced myocardial engraftment.

Autotaxin inhibition reduces cardiac inflammation and mitigates adverse cardiac remodeling after myocardial infarction

OBJECTIVE

Acute myocardial infarction (AMI) initiates pathological inflammation which aggravates tissue damage and causes heart failure. Lysophosphatidic acid (LPA), produced by autotaxin (ATX), promotes inflammation and the development of atherosclerosis. The role of ATX/LPA signaling nexus in cardiac inflammation and resulting adverse cardiac remodeling is poorly understood.

APPROACH AND RESULTS

We assessed autotaxin activity and LPA levels in relation to cardiac and systemic inflammation in AMI patients and C57BL/6 (WT) mice. Human and murine peripheral blood and cardiac tissue samples showed elevated levels of ATX activity, LPA, and inflammatory cells following AMI and there was strong correlation between LPA levels and circulating inflammatory cells. In a gain of function model, lipid phosphate phosphatase-3 (LPP3) specific inducible knock out (Mx1-Plpp3^Δ) showed higher systemic and cardiac inflammation after AMI compared to littermate controls (Mx1-Plpp3^fl/fl); and a corresponding increase in bone marrow progenitor cell count and proliferation. Moreover, in Mx1- Plpp3^Δ mice, cardiac functional recovery was reduced with corresponding increases in adverse cardiac remodeling and scar size (as assessed by echocardiography and Masson's Trichrome staining). To examine the effect of ATX/LPA nexus inhibition, we treated WT mice with the specific pharmacological inhibitor, PF8380, twice a day for 7 days post AMI. Inhibition of the ATX/LPA signaling nexus resulted in significant reduction in post-AMI inflammatory response, leading to favorable cardiac functional recovery, reduced scar size and enhanced angiogenesis.

CONCLUSION

ATX/LPA signaling nexus plays an important role in modulating inflammation after AMI and targeting this mechanism represents a novel therapeutic target for patients presenting with acute myocardial injury.

The role of sphingosine 1-phosphate and its receptors in cardiovascular diseases

There are many different types of cardiovascular diseases, which impose a huge economic burden due to their extremely high mortality rates, so it is necessary to explore the underlying mechanisms to achieve better supportive and curative care outcomes. Sphingosine 1‐phosphate (S1P) is a bioactive lipid mediator with paracrine and autocrine activities that acts through its cell surface S1P receptors (S1PRs) and intracellular signals. In the circulatory system, S1P is indispensable for both normal and disease conditions; however, there are very different views on its diverse roles, and its specific relevance to cardiovascular pathogenesis remains elusive. Here, we review the synthesis, release and functions of S1P, specifically detail the roles of S1P and S1PRs in some common cardiovascular diseases, and then address several controversial points, finally, we focus on the development of S1P‐based therapeutic approaches in cardiovascular diseases, such as the selective S1PR1 modulator amiselimod (MT‐1303) and the non‐selective S1PR1 and S1PR3 agonist fingolimod, which may provide valuable insights into potential therapeutic strategies for cardiovascular diseases.

Gelatin Based Polymer Cell Coating Improves Bone Marrow-Derived Cell Retention in the Heart after Myocardial Infarction

BACKGROUND

Acute myocardial infarction (AMI) and the ensuing ischemic heart disease are approaching an epidemic state. Limited stem cell retention following intracoronary administration has reduced the clinical efficacy of this novel therapy. Polymer based cell coating is biocompatible and has been shown to be safe. Here, we assessed the therapeutic utility of gelatin-based biodegradable cell coatings on bone marrow derived cell retention in ischemic heart.

METHODS

Gelatin based cell coatings were formed from the surface-mediated photopolymerization of 3% gelatin methacrylamide and 1% PEG diacrylate. Cell coating was confirmed using a multimodality approach including flow cytometry, imaging flow cytometry (ImageStream System) and immunohistochemistry. Biocompatibility of cell coating, metabolic activity of coated cells, and the effect of cell coating on the susceptibility of cells for engulfment were assessed using in vitro models. Following myocardial infarction and GFP+ BM-derived mesenchymal stem cell transplantation, flow cytometric and immunohistochemical assessment of retained cells was performed.

RESULTS

Coated cells are viable and metabolically active with coating degrading within 72 h in vitro. Importantly, cell coating does not predispose bone marrow cells to aggregation or increase their susceptibility to phagocytosis. In vitro and in vivo studies demonstrated no evidence of heightened immune response or increased phagocytosis of coated cells. Cell transplantation studies following myocardial infarction proved the improved retention of coated bone marrow cells compared to uncoated cells.

CONCLUSION

Gelation based polymer cell coating is biologically safe and biodegradable. Therapies employing these strategies may represent an attractive target for improving outcomes of cardiac regenerative therapies in human studies.

Novel signaling aspects of ceramide 1-phosphate

The bioactive sphingolipid ceramide 1-phosphate (C1P) regulates key physiologic cell functions and is implicated in a number of metabolic alterations and pathological processes. Initial studies using different types of fibroblasts and monocytes/macrophages revealed that C1P was mitogenic and that it promoted cell survival through inhibition of apoptosis. Subsequent studies implicated C1P in inflammatory responses with a specific role as pro-inflammatory agent. Specifically, C1P potently stimulated cytosolic phospholipase A₂ (cPLA₂) resulting in elevation of arachidonic acid and pro-inflammatory eicosanoid levels. However, increasing experimental evidence suggests that C1P can also exert anti-inflammatory actions in some cell types and tissues. Specifically, it has been demonstrated that C1P inhibits the release of pro-inflammatory cytokines and blocks activation of the pro-inflammatory transcription factor NF-κB in some cell types. Moreover, C1P was shown to increase the release of anti-inflammatory interleukin-10 in macrophages, and to overcome airway inflammation and reduce lung emphysema in vivo. Noteworthy, C1P stimulated cell migration, an action that is associated with diverse physiological cell functions, as well as with inflammatory responses and tumor dissemination. More recently, ceramide kinase (CerK), the enzyme that produces C1P in mammalian cells, has been shown to be upregulated during differentiation of pre-adipocytes into mature adipocytes, and that exogenous C1P, acting through a putative Gi protein-coupled receptor, negatively regulates adipogenesis. Although the latter actions seem to be contradictory, it is plausible that exogenous C1P may balance the adipogenic effects of intracellularly generated (CerK-derived) C1P in adipose tissue. The present review highlights novel signaling aspects of C1P and its impact in the regulation of cell growth and survival, inflammation and tumor dissemination.

Ceramide 1-Phosphate Protects Endothelial Colony–Forming Cells From Apoptosis and Increases Vasculogenesis In Vitro and In Vivo

Objective:

Ceramide 1-phosphate (C1P) is a bioactive sphingolipid highly augmented in damaged tissues. Because of its abilities to stimulate migration of murine bone marrow–derived progenitor cells, it has been suggested that C1P might be involved in tissue regeneration. In the present study, we aimed to investigate whether C1P regulates survival and angiogenic activity of human progenitor cells with great therapeutic potential in regenerative medicine such as endothelial colony–orming cells (ECFCs).

Approach and Results:

C1P protected ECFC from TNFα (tumor necrosis factor-α)-induced and monosodium urate crystal–induced death and acted as a potent chemoattractant factor through the activation of ERK1/2 (extracellular signal-regulated kinases 1 and 2) and AKT pathways. C1P treatment enhanced ECFC adhesion to collagen type I, an effect that was prevented by β1 integrin blockade, and to mature endothelial cells, which was mediated by the E-selectin/CD44 axis. ECFC proliferation and cord-like structure formation were also increased by C1P, as well as vascularization of gel plug implants loaded or not with ECFC. In a murine model of hindlimb ischemia, local administration of C1P alone promoted blood perfusion and reduced necrosis in the ischemic muscle. Additionally, the beneficial effects of ECFC infusion after ischemia were amplified by C1P pretreatment, resulting in a further and significant enhancement of leg reperfusion and muscle repair.

Conclusions:

Our findings suggest that C1P may have therapeutic relevance in ischemic disorders, improving tissue repair by itself, or priming ECFC angiogenic responses such as chemotaxis, adhesion, proliferation, and tubule formation, which result in a better outcome of ECFC-based therapy.

Sphingosine 1-phosphate promotes mesenchymal stem cell-mediated cardioprotection against myocardial infarction via ERK1/2-MMP-9 and Akt signaling axis

AIMS

The sphingolipid metabolite sphingosine 1‑phosphate (S1P) has emerged as a potential cardioprotective molecule against ischemic heart disease. Moreover, S1P triggers mobilization and homing of bone marrow-derived stem/progenitor cells into the damaged heart. However, it remains elusive whether S1P promotes mesenchymal stem cells (MSCs)-mediated cardioprotection against ischemic heart diseases.

MAIN METHODS

Adipose tissue-derived MSCs (AT-MSCs) were obtained from GFP transgenic mice or C57BL/6J. Myocardial infarction (MI) was induced in C57BL/6J mice by ligation of the left anterior descending coronary artery (LAD). Subsequently, S1P-treated AT-MSCs or vehicle-treated AT-MSCs were intravenously administered for 24 h after induction of MI or sham procedure.

KEY FINDINGS

Pre-conditioning with S1P significantly enhanced the migratory and anti-apoptotic efficacies of AT-MSCs. In MI-induced mice, intravenous administration of S1P-treated AT-MSCs significantly augmented their homing and engraftment in ischemic area. Besides, AT-MSCs with S1P pre-treatment exhibited enhanced potencies to inhibit cardiomyocyte apoptosis and fibrosis, and stimulate angiogenesis and preserve cardiac function. Mechanistic studies revealed that S1P promoted AT-MSCs migration through activation of ERK1/2-MMP-9, and protected AT-MSCs against apoptosis via Akt activation. Further, S1P activated the ERK1/2 and Akt via S1P receptor 2 (S1PR2), but not through S1PR1. S1PR2 knockdown by siRNA, however, significantly attenuated S1P-mediated AT-MSCs migration and anti-apoptosis.

SIGNIFICANCE

The findings of the present study revealed the protective efficacies of S1P pretreatment on the survival/retention and cardioprotection of engrafted MSCs. Pre-conditioning of donor MSCs with S1P is an effective strategy to promote the therapeutic potential of MSCs for ischemic heart diseases.

Cathelicidin Related Antimicrobial Peptide (CRAMP) Enhances Bone Marrow Cell Retention and Attenuates Cardiac Dysfunction in a Mouse Model of Myocardial Infarction

BACKGROUND

Acute myocardial infarction (MI) and the ensuing ischemic heart disease are approaching epidemic state. Unfortunately, no definitive therapies are available and human regenerative therapies have conflicting results. Limited stem cell retention following intracoronary administration has reduced the clinical efficacy of this novel therapy. Cathelicidin related antimicrobial peptides (CRAMPs) enhance chemotactic responsiveness of BMSPCs to low SDF-1 gradients, suggesting a potential role in BMSPCs engraftment. Here, we assessed the therapeutic efficacy of CRAMPs in the context of BMSPCs recruitment and retention via intracardiac delivery of CRAMP-treated BMSPCs or CRAMP-releasing hydrogels (HG) post-AMI.

METHODS

For cell transplantation experiments, mice were randomized into 3 groups: MI followed by injection of PBS, BMMNCs alone, and BMMNCs pre-incubated with CRAMP. During the in vivo HG studies, BM GFP chimera mice were randomized into 4 groups: MI followed by injection of HG alone, HG + SDF-1, HG + CRAMP, HG + SDF-1 + CRAMP. Changes in cardiac function at 5 weeks after MI were assessed using echocardiography. Angiogenesis was assessed using isolectin staining for capillary density.

RESULTS

Mice treated with BMMNCs pre-incubated with CRAMP had smaller scars, enhanced cardiac recovery and less adverse remodeling. Histologically, this group had higher capillary density. Similarly, sustained CRAMP release from hydrogels enhanced the therapeutic effect of SDF-1, leading to enhanced functional recovery, smaller scar size and higher capillary density.

CONCLUSION

Cathelicidins enhance BMMNC retention and recruitment after intramyocardial administration post-AMI resulting in improvements in heart physiology and recovery. Therapies employing these strategies may represent an attractive method for improving outcomes of regenerative therapies in human studies.

Azithromycin therapy reduces cardiac inflammation and mitigates adverse cardiac remodeling after myocardial infarction: Potential therapeutic targets in ischemic heart disease

INTRODUCTION

Acute myocardial infarction (MI) is a primary cause of worldwide morbidity and mortality. Macrophages are fundamental components of post-MI inflammation. Pro-inflammatory macrophages can lead to adverse cardiac remodeling and heart failure while anti-inflammatory/reparative macrophages enhance tissue healing. Shifting the balance between pro-inflammatory and reparative macrophages post-MI is a novel therapeutic strategy. Azithromycin (AZM), a commonly used macrolide antibiotic, polarizes macrophages towards the anti-inflammatory phenotype, as shown in animal and human studies. We hypothesized that AZM modulates post-MI inflammation and improves cardiac recovery.

METHODS AND RESULTS

Male WT mice (C57BL/6, 6-8 weeks old) were treated with either oral AZM (160 mg/kg/day) or vehicle (control) starting 3 days prior to MI and continued to day 7 post-MI. We observed a significant reduction in mortality with AZM therapy. AZM-treated mice showed a significant decrease in pro-inflammatory (CD45+/Ly6G-/F4-80+/CD86+) and increase in anti-inflammatory (CD45+/Ly6G-/F4-80+/CD206+) macrophages, decreasing the pro-inflammatory/anti-inflammatory macrophage ratio in the heart and peripheral blood as assessed by flow cytometry and immunohistochemistry. Macrophage changes were associated with a significant decline in pro- and increase in anti-inflammatory cytokines. Mechanistic studies confirmed the ability of AZM to shift macrophage response towards an anti-inflammatory state under hypoxia/reperfusion stress. Additionally, AZM treatment was associated with a distinct decrease in neutrophil count due to apoptosis, a known signal for shifting macrophages towards the anti-inflammatory phenotype. Finally, AZM treatment improved cardiac recovery, scar size, and angiogenesis.

CONCLUSION

Azithromycin plays a cardioprotective role in the early phase post-MI through attenuating inflammation and enhancing cardiac recovery. Post-MI treatment and human translational studies are warranted to examine the therapeutic applications of AZM.

Mobilization studies in mice deficient in sphingosine kinase 2 support a crucial role of the plasma level of sphingosine-1-phosphate in the egress of hematopoietic stem progenitor cells

Sphingosine-1-phosphate (S1P) is a bioactive lipid involved in cell signaling and, if released from cells, also plays a crucial role in regulating the trafficking of lympho-hematopoietic cells, including primitive hematopoietic stem/progenitor cells (HSPCs). It has been demonstrated that S1P chemoattracts HSPCs, and its level in peripheral blood creates a gradient directing egress of these cells during mobilization. In this paper we analyzed hematopoiesis in mice deficient in sphingosine kinase 2 (Sphk2-KO mice) and studied the effect of this mutation on plasma S1P levels. We found that Sphk2-KO mice have normal hematopoiesis, and, in contrast to Sphk1-KO mice, the circulating S1P level is highly elevated in these animals and correlates with the fact that HSPCs in Sphk2-KO animals, also in contrast to Sphk1-KO animals, show enhanced mobilization. These results were recapitulated in wild type (WT) animals employing an Sphk2 inhibitor. We also administered an inhibitor of the S1P-degrading enzyme S1P lyase, known as tetrahydroxybutylimidazole (THI), to WT mice and observed that this resulted in an increase in S1P level in PB and enhanced mobilization of HSPCs. In sum, our results support a crucial role for S1P gradients in blood plasma in the mobilization process and indicate that small-molecule inhibitors of Sphk2 and Sgpl1 could be employed as mobilization-facilitating compounds. At the same time, further studies are needed to explain the unexpected effect of Sphk2 inhibition on increasing S1P levels in plasma.

Sphingolipid De Novo Biosynthesis: A Rheostat of Cardiovascular Homeostasis

Sphingolipids (SL) are both fundamental structural components of the eukaryotic membranes and signaling molecules that regulate a variety of biological functions. The highly-bioactive lipids, ceramide and sphingosine-1-phosphate, have emerged as important regulators of cardiovascular function in health and disease. In this review we discuss recent insights into the role of SLs, particularly ceramide and sphingosine-1-phosphate, in the pathophysiology of the cardiovascular system. We also highlight advances into the molecular mechanisms regulating serine palmitoyltransferase, the first and rate-limiting enzyme of de novo SL biosynthesis, with an emphasis on the recently discovered inhibitors of serine palmitoyltransferase, ORMDL and NOGO-B proteins. Understanding the molecular mechanisms regulating this biosynthetic pathway may lead to the development of novel therapeutic approaches for the treatment of cardiovascular diseases.

Bioactive Lipids and Circulating Progenitor Cells in Patients with Cardiovascular Disease

Bone marrow‐derived progenitor cells are mobilized into the peripheral blood after acute myocardial injury and in chronic ischemic heart disease. However, the mechanisms responsible for this mobilization are poorly understood. We examined the relationship between plasma levels of bioactive lipids and number of circulating progenitor cells (CPCs) in patients (N = 437) undergoing elective or emergent cardiac catheterization. Plasma levels of sphingosine‐1 phosphate (S1P) and ceramide‐1 phosphate (C1P) were quantified using mass spectrometry. CPCs were assessed using flow cytometry. S1P levels correlated with the numbers of CD34+, CD34+/CD133+, and CD34+/CXCR4+ CPCs even after adjustment for potential confounding factors. However, no significant correlation was observed between C1P levels and CPC count. Plasma levels of S1P correlated with the number of CPCs in patients with coronary artery disease, suggesting an important mechanistic role for S1P in stem cell mobilization. The therapeutic effects of adjunctive S1P therapy to mobilize endogenous stem cells need to be investigated. Stem Cells Translational Medicine2017;6:731–735

Implication of sphingosin-1-phosphate in cardiovascular regulation

Sphingosine-1-phosphate (S1P) is a bioactive sphingolipid metabolite generated by phosphorylation of sphingosine catalyzed by sphingosine kinase. S1P acts mainly through its high affinity G-protein-coupled receptors and participates in the regulation of multiple systems, including cardiovascular system. It has been shown that S1P signaling is involved in the regulation of cardiac chronotropy and inotropy and contributes to cardioprotection as well as cardiac remodeling; S1P signaling regulates vascular function, such as vascular tone and endothelial barrier, and possesses an anti-atherosclerotic effect; S1P signaling is also implicated in the regulation of blood pressure. Therefore, manipulation of S1P signaling may offer novel therapeutic approaches to cardiovascular diseases. As several S1P receptor modulators and sphingosine kinase inhibitors have been approved or under clinical trials for the treatment of other diseases, it may expedite the test and implementation of these S1P-based drugs in cardiovascular diseases.

Lysophospholipids in coronary artery and chronic ischemic heart disease

PURPOSE OF REVIEW

The bioactive lysophospholipids, lysophosphatidic acid (LPA) and sphingosine 1 phosphate (S1P), have potent effects on blood and vascular cells. This review focuses their potential contributions to the development of atherosclerosis, acute complications such as acute myocardial infarction, and chronic ischemic cardiac damage.

RECENT FINDINGS

Exciting recent developments have provided insight into the molecular underpinnings of LPA and S1P receptor signaling. New lines of evidence suggest roles for these pathways in the development of atherosclerosis. In experimental animal models, the production, signaling, and metabolism of LPA may be influenced by environmental factors in the diet that synergize to promote the progression of atherosclerotic vascular disease. This is supported by observations of human polymorphisms in the lysophospholipid-metabolizing enzyme PPAP2B, which are associated with risk of coronary artery disease and myocardial infarction. S1P signaling protects from myocardial damage that follows acute and chronic ischemia, both by direct effects on cardiomyocytes and through stem cell recruitment to ischemic tissue.

SUMMARY

This review will suggest novel strategies to prevent the complications of coronary artery disease by targeting LPA production and signaling. Additionally, ways in which S1P signaling pathways may be harnessed to attenuate ischemia-induced cardiac dysfunction will be explored.