Cardioprotective Effects of Sphingosine-1-Phosphate Receptor Immunomodulator FTY720 in a Clinically Relevant Model of Cardioplegic Arrest and Cardiopulmonary Bypass

Sphingosine 1 phosphate promotes hypertension specific memory T cell trafficking in response to repeated hypertensive challenges

We have previously shown that effector memory (TEM) cells accumulate in the bone marrow (BM) and the kidney in response to l-NAME/high salt challenge. It is not well understood if measures to block the exodus of that effector memory cells prevent redistribution of these cells and protect from hypertension-induced renal damage. We hypothesized that that effector memory cells that accumulate in the bone marrow respond to repeated salt challenges and can be reactivated and circulate to the kidney. Thus, to determine if mobilization of bone marrow that effector memory cells and secondary lymphoid organs contribute to the hypertensive response to delayed salt challenges, we employed fingolimod (FTY720), an S1PR1 functional antagonist by downregulating S1PR, which inhibits the egress of that effector memory cells used effectively in the treatment of multiple sclerosis and cardiovascular diseases. We exposed wild-type mice to the l-NAME for 2 weeks, followed by a wash-out period, a high salt diet feeding for 4 weeks, a wash-out period, and then a second high salt challenge with or without fingolimod. A striking finding is that that effector memory cell egress was dramatically attenuated from the bone marrow of mice treated with fingolimod with an associated reduction of renal that effector memory cells. Mice receiving fingolimod were protected from hypertension. We found that wild-type mice that received fingolimod during the second high salt challenge had a marked decrease in the renal damage markers. CD3⁺ T cell infiltration was significantly attenuated in the fingolimod-treated mice. To further examine the redistribution of bone marrow that effector memory cells in response to repeated hypertensive stimuli, we harvested the bone marrow from CD45.2 mice following the repeated high salt protocol with or without fingolimod; that effector memory cells were sorted and adoptively transferred (AT) to CD45.1 naïve recipients. Adoptively transferred that effector memory cells from mice treated with fingolimod failed to home to the bone marrow and traffic to the kidney in response to a high salt diet. We conclude that memory T cell mobilization contributes to the predisposition to hypertension and end-organ damage for prolonged periods following an initial episode of hypertension. Blocking the exodus of reactivated that effector memory cells from the bone marrow protects the kidney from hypertension-induced end-organ damage.

Cardioprotective effect of fingolimod against calcium paradox-induced myocardial injury in the isolated rat heart

Fingolimod (FTY720) inhibits Ca2+-permeable, Mg2+-sensitive channels called transient receptor potential melastatin 7 (TRPM7), but its effects on Ca2+ paradox (CP) - induced myocardial damage has not been evaluated. We studied the effect of FTY720 on CP-induced myocardial damage and used other TRPM7 channel inhibitors nordihydroguaiaretic acid (NDGA) and Mg2+ to test if any effect of FTY720 was via TRPM7 inhibition. Langendorff-perfused Wistar rat hearts were treated with FTY720 or NDGA and subjected to a CP protocol consisting of Ca2+ depletion followed by Ca2+ repletion. Hearts of rats pre-treated with MgSO4 were also subjected to CP. Hemodynamic parameters were measured using an intraventricular balloon, and myocardial infarct size was quantified using triphenyltetrazolium chloride stain. TRPM7 proteins in ventricular tissue were detected using immunoblot analysis. FTY720, but not NDGA, decreased CP-induced infarct size. Both FTY720 and NDGA minimized the CP-induced elevation of left ventricular end-diastolic pressure, but only FTY720 ultimately improved ventricular developed pressure. Mg2+ pre-treatment had no effect on CP-induced infarct size, nor hemodynamic parameters during CP, nor the level of TRPM7 protein expression in ventricular tissue. Overall, FTY720 attenuated CP-induced myocardial damage, with potential therapeutic implications on Ca2+-mediated cardiotoxicity; however, the cardioprotective mechanism of FTY720 seems to be unrelated to TRPM7 channel modulation.

Protein phosphatase 2A in the healthy and failing heart: New insights and therapeutic opportunities

Protein phosphatases have emerged as critical regulators of phosphoprotein homeostasis in settings of health and disease. Protein phosphatase 2A (PP2A) encompasses a large subfamily of enzymes that remove phosphate groups from serine/threonine residues within phosphoproteins. The heterogeneity in PP2A structure, which arises from the grouping of different catalytic, scaffolding and regulatory subunit isoforms, creates distinct populations of catalytically active enzymes (i.e. holoenzymes) that localise to different parts of the cell. This structural complexity, combined with other regulatory mechanisms, such as interaction of PP2A heterotrimers with accessory proteins and post-translational modification of the catalytic and/or regulatory subunits, enables PP2A holoenzymes to target phosphoprotein substrates in a highly specific manner. In this review, we summarise the roles of PP2A in cardiac physiology and disease. PP2A modulates numerous processes that are vital for heart function including calcium handling, contractility, β-adrenergic signalling, metabolism and transcription. Dysregulation of PP2A has been observed in human cardiac disease settings, including heart failure and atrial fibrillation. Efforts are underway, particularly in the cancer field, to develop therapeutics targeting PP2A activity. The development of small molecule activators of PP2A (SMAPs) and other compounds that selectively target specific PP2A holoenzymes (e.g. PP2A/B56α and PP2A/B56ε) will improve understanding of the function of different PP2A species in the heart, and may lead to the development of therapeutics for normalising aberrant protein phosphorylation in settings of cardiac remodelling and dysfunction.

Fingolimod (FTY720) Preserves High Energy Phosphates and Improves Cardiac Function in Heterotopic Heart Transplantation Model

During heart transplantation, donor heart leads to reduced oxygen supply resulting in low level of high energy phosphate (HEP) reserves in cardiomyocyte. Lower HEP is one of the underlying reasons of cell death due to ischemia. In this study we investigated the role of Fingolimod (FTY720) in heart transplantation ischemia. Eight groups of Sprague-Dawley rats (n = 5 for each subgroup) were made, A1 and C1 were given FTY720 1 mg/kg while B1 and D1 were given normal saline. The hearts were implanted into another set of similar rats after preservation period of 1 h at 4–8 °C. Significantly higher Left ventricular systolic pressure (LVSP), dP/dT maximum (p < 0.05), dP/dT minimum (p < 0.05) were recorded in the FTY720 treated group after 24 h of reperfusion while after 1 h of reperfusion, there were no significant differences in LVSP, maximum and negative dP/dT, and Left ventricular end diastolic pressure (LVEDP) between the control and the FTY720-treated transplant groups. Coronary blood flow (CBF) was enhanced (p < 0.05) in the FTY720 treated group after 1 and 24 h. ATP p < 0.001, p < 0.05 at 1 and 24 h, ADP p < 0.001, p > 0.05 at 1 and 24 h, and phosphocreatine p < 0.05, p > 0.05 at 1 and 24 h were better preserved by FTY720 treatment as compared to control group. The study concluded that pretreatment of grafted hearts with FTY720 improved hemodynamics, CBF, high energy phosphate reserves, reduces the peroxynitrite level and poly (ADP ribose) polymerase (PARP) inhibition that prevents ischemia-reperfusion injury.

Systemic and heart autonomous effects of sphingosine Δ4 desaturase deficiency in lipotoxic cardiac pathophysiology

Lipotoxic cardiomyopathy (LCM) is characterized by cardiac steatosis, including the accumulation of fatty acids, triglycerides and ceramides. Model systems have shown the inhibition of ceramide biosynthesis to antagonize obesity and improve insulin sensitivity. Sphingosine Δ4 desaturase (encoded by ifc in Drosophila melanogaster) enzymatically converts dihydroceramide into ceramide. Here, we examine ifc mutants to study the effects of desaturase deficiency on cardiac function in Drosophila Interestingly, ifc mutants exhibited classic hallmarks of LCM: cardiac chamber dilation, contractile defects and loss of fractional shortening. This outcome was phenocopied in global ifc RNAi-mediated knockdown flies. Surprisingly, cardiac-specific ifc knockdown flies exhibited cardiac chamber restriction with no contractile defects, suggesting heart autonomous and systemic roles for ifc activity in cardiac function. Next, we demonstrated that ifc mutants exhibit suppressed Sphingosine kinase 1 (Sk1) expression. Ectopic overexpression of Sk1 was sufficient to prevent cardiac chamber dilation and loss of fractional shortening in ifc mutants. Partial rescue was also observed with cardiac- and fat-body-specific Sk1 overexpression. Finally, we showed that cardiac-specific expression of Drosophila inhibitor of apoptosis (dIAP) also prevented cardiac dysfunction in ifc mutants, suggesting a role for caspase activity in the observed cardiac pathology. Collectively, we show that spatial regulation of sphingosine Δ4 desaturase activity differentially affects cardiac function in heart autonomous and systemic mechanisms through tissue interplay.

Bioactive Lipid Signaling in Cardiovascular Disease, Development, and Regeneration

Cardiovascular disease (CVD) remains a leading cause of death globally. Understanding and characterizing the biochemical context of the cardiovascular system in health and disease is a necessary preliminary step for developing novel therapeutic strategies aimed at restoring cardiovascular function. Bioactive lipids are a class of dietary-dependent, chemically heterogeneous lipids with potent biological signaling functions. They have been intensively studied for their roles in immunity, inflammation, and reproduction, among others. Recent advances in liquid chromatography-mass spectrometry techniques have revealed a staggering number of novel bioactive lipids, most of them unknown or very poorly characterized in a biological context. Some of these new bioactive lipids play important roles in cardiovascular biology, including development, inflammation, regeneration, stem cell differentiation, and regulation of cell proliferation. Identifying the lipid signaling pathways underlying these effects and uncovering their novel biological functions could pave the way for new therapeutic strategies aimed at CVD and cardiovascular regeneration.

Cocoa Flavonoids Reduce Inflammation and Oxidative Stress in a Myocardial Ischemia-Reperfusion Experimental Model

: Consumption of flavonoid-rich nutraceuticals has been associated with a reduction in coronary events. The present study analyzed the effects of cocoa flavonols on myocardial injury following acute coronary ischemia-reperfusion (I/R). A commercially available cocoa extract was identified by chromatographic mass spectrometry. Nineteen different phenolic compounds were identified and 250 mg of flavan-3-ols (procyanidin) were isolated in 1 g of extract. Oral administration of cocoa extract in incremental doses from 5 mg/kg up to 25 mg/kg daily for 15 days in Sprague Dawley rats (n = 30) produced a corresponding increase of blood serum polyphenols and become constant after 15 mg/kg. Consequently, the selected dose (15 mg/kg) of cocoa extract was administered orally daily for 15 days in a treated group (n = 10) and an untreated group served as control (n = 10). Both groups underwent surgical occlusion of the left anterior descending coronary artery and reperfusion. Cocoa extract treatment significantly reversed membrane peroxidation, nitro-oxidative stress, and decreased inflammatory markers (IL-6 and NF-kB) caused by myocardial I/R injury and enhanced activation of both p-Akt and p-Erk1/2. Daily administration of cocoa extract in rats is protective against myocardial I/R injury and attenuate nitro-oxidative stress, inflammation, and mitigates myocardial apoptosis.

Fingolimod Plays Role in Attenuation of Myocardial Injury Related to Experimental Model of Cardiac Arrest and Extracorporeal Life Support Resuscitation

Background: Sudden cardiac arrest is a major global health concern, and survival of patients with ischemia–reperfusion injury is a leading cause of myocardial dysfunction. The mechanism of this phenomenon is not well understood because of the complex pathophysiological nature of the disease. Aim of the study was to investigate the cardioprotective role of fingolimod in an in vivo model of cardiac arrest and resuscitation. Methods: In this study, an in vivo rat model of cardiac arrest using extracorporeal membrane oxygenation resuscitation monitored by invasive hemodynamic measurement was developed. At the beginning of extracorporeal life support (ECLS), animals were randomly treated with fingolimod (Group A, n = 30) or saline (Group B, n = 30). Half of the animals in each group (Group A1 and B1, n = 15 each) were sacrificed after 1 h, and the remaining animals (Group A2 and B2) after 24 h of reperfusion. Blood and myocardial tissues were collected for analysis of cardiac features, inflammatory biomarkers, and cell signaling pathways. Results: Treatment with fingolimod resulted in activation of survival pathways resulting into reduced inflammation, myocardial oxidative stress and apoptosis of cardiomyocytes. This led to significant improvement in systolic and diastolic functions of the left ventricle and improved contractility index. Conclusions: Sphingosine1phosphate receptor activation with fingolimod improved cardiac function after cardiac arrest supported with ECLS. Present study findings strongly support a cardioprotective role of fingolimod through sphingosine-1-phosphate receptor activation during reperfusion after circulatory arrest.