Activation of Pak1/Akt/eNOS signaling following sphingosine-1-phosphate release as part of a mechanism protecting cardiomyocytes against ischemic cell injury

Hull and York Medical School, Academic Cardiology, Kingston-upon-Hull, United Kingdom.
AJP Heart and Circulatory Physiology (Impact Factor: 3.84). 06/2011; 301(4):H1487-95. DOI: 10.1152/ajpheart.01003.2010
Source: PubMed


We investigated whether plasma long-chain sphingoid base (LCSB) concentrations are altered by transient cardiac ischemia during percutaneous coronary intervention (PCI) in humans and examined the signaling through the sphingosine-1-phosphate (S1P) cascade as a mechanism underlying the S1P cardioprotective effect in cardiac myocytes. Venous samples were collected from either the coronary sinus (n = 7) or femoral vein (n = 24) of 31 patients at 1 and 5 min and 12 h, following induction of transient myocardial ischemia during elective PCI. Coronary sinus levels of LCSB were increased by 1,072% at 1 min and 941% at 5 min (n = 7), while peripheral blood levels of LCSB were increased by 579% at 1 min, 617% at 5 min, and 436% at 12 h (n = 24). In cultured cardiac myocytes, S1P, sphingosine (SPH), and FTY720, a sphingolipid drug candidate, showed protective effects against CoCl induced hypoxia/ischemic cell injury by reducing lactate dehydrogenase activity. Twenty-five nanomolars of FTY720 significantly increased phospho-Pak1 and phospho-Akt levels by 56 and 65.6% in cells treated with this drug for 15 min. Further experiments demonstrated that FTY720 triggered nitric oxide release from cardiac myocytes is through pertussis toxin-sensitive phosphatidylinositol 3-kinase/Akt/endothelial nitric oxide synthase signaling. In ex vivo hearts, ischemic preconditioning was cardioprotective in wild-type control mice (Pak1(f/f)), but this protection appeared to be ineffective in cardiomyocyte-specific Pak1 knockout (Pak1(cko)) hearts. The present study provides the first direct evidence of the behavior of plasma sphingolipids following transient cardiac ischemia with dramatic and early increases in LCSB in humans. We also demonstrated that S1P, SPH, and FTY720 have protective effects against hypoxic/ischemic cell injury, likely a Pak1/Akt1 signaling cascade and nitric oxide release. Further study on a mouse model of cardiac specific deletion of Pak1 demonstrates a crucial role of Pak1 in cardiac protection against ischemia/reperfusion injury.

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Available from: Emmanuel E. Egom, Jul 12, 2015
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    • "Ischemia/reperfusion was previously found to markedly affect sphingolipid metabolism in the rodent myocardium [6]. In addition, it was recently reported that temporary coronary artery occlusion during elective percutaneous coronary intervention resulted in acute increase in total plasma long-chain sphingoid bases concentration [32]. This could explain our finding of sphingosine and sphinganine accumulation in erythrocytes isolated from the STEMI patients. "
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    ABSTRACT: Sphingosine-1-phosphate (S1P) is a cardioprotective sphingolipid present at high concentration in plasma and blood cells. However, effect of the myocardial infarction on S1P metabolism in blood is poorly recognized. Therefore, we aimed to examine the dynamics of changes in concentration of sphingolipids in blood of patients with acute ST-segment elevation myocardial infarction (STEMI). The study was performed on two groups of subjects: healthy controls (n=32) and patients with STEMI (n=32). In the latter group blood was taken upon admission to intensive heart care unit, and then on the second, fifth and thirtieth day, and approximately two years after admission. STEMI patients showed decreased plasma S1P concentration and accumulation of free sphingoid bases and their 1-phosphates in erythrocytes. This effect was already present upon admission, and was maintained for at least thirty days after the infarction. Interestingly, two years post-infarction plasma S1P level recovered only partially, whereas the content of erythrocyte sphingolipids decreased to the values observed in the control subjects. The most likely reason for the observed reduction in plasma S1P level was its decreased release or increased degradation by vascular endothelial cells, as we did not find any evidence for downregulation of S1P synthesis or release by blood cells. We conclude that patients with STEMI are characterized by marked alterations in sphingolipid metabolism in blood which could be a consequence of the infarction itself, the antiplatelet treatment given or both. Our data suggest that cardioprotective action of S1P may be diminished in patients with acute myocardial infarction.
    Full-text · Article · Oct 2013 · Prostaglandins & other lipid mediators
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    • "Multiple studies highlight the importance of Survivin-dependent replication of pre-existing β-cells.10-12 The p21-activated kinase 1 (PAK1) is a ubiquitously expressed serine/threonine kinase implicated in the promotion of cell survival in neuronal and cardiac cells.13-15 PAK1 has also been reported to play a critical role in cell proliferation.16,17 "
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    ABSTRACT: Functional β-cell mass deficiency in diabetes results from imbalanced β-cell death and replication, and decreased PAK1 protein levels in human islets from donors with type 2 diabetes implicates a possible role for PAK1 in maintaining β-cell mass. Here, we aim to address the linkage between PAK1 and Survivin, a protein essential for β-cell replication. PAK1 knockout (KO) mouse islets exhibited decreased expression of Survivin protein. MIN6 β-cells with siRNA-mediated suppression of PAK1 also had decreased Survivin protein and exhibited an increased level of ubiquitinated-Survivin. However, no significant changes in Survivin mRNA were found in islets from PAK1 KO mice and PAK1-depleted MIN6 β-cells. The decreased Survivin level in MIN6 cells subjected to hyperglycemic stress was prevented by expression of exogenous PAK1. Moreover, overexpressing Survivin restored proliferation of β-cells that was impaired by the loss of PAK1. These data implicate a role for PAK1 in regulating Survivin protein stability in the β-cell and suggest PAK1 as a potential molecular target for the restoration of β-cell mass.
    Full-text · Article · Apr 2013 · Islets
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    • "development and is essential for branching of the ureteric bud (Kirby et al. 2009). As shown in Figure 2, the downstream targets of S1P signalling include adenylate cyclase, Ras, mitogen-activated protein kinase (MAPK), phospholipase C, c-Src tyrosine kinase, hypoxia-inducible factor 1, the small GTPases Rac and Rho, phospholipase D, p125FAK, phosphatidylinositol 3-kinase/AKT, calcium, cAMP, eNOS and NF-jB signalling (Ishii et al. 2004, Hemmings 2006, Egom et al. 2011, Takuwa et al. 2012). "
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    ABSTRACT: Acute kidney injury (AKI) induced by ischaemia and reperfusion (I/R) injury is a common and severe clinical problem. Vascular dysfunction, immune system activation, and tubular epithelial cell injury contribute to functional and structural deterioration. The search for novel therapeutic interventions for I/R induced AKI is a dynamic area of experimental research. Pharmacologic targeting of injury mediators and corresponding intracellular signalling in endothelial cells, inflammatory cells and the injured tubular epithelium could provide new opportunities yet may also pose great translational challenge. Here, we focus on signalling mediators, their receptors and intracellular signalling pathways which bear potential to abrogate cellular processes involved in the pathogenesis of I/R induced AKI. Sphingosine 1 phosphate (S1P) and its respective receptors, cytochrome P450 (CYP450)-dependent vasoactive eicosanoids, NF-κB and protein kinase-C (PKC) related pathways are representatives of such "druggable" pleiotropic targets. For example pharmacologic agents targeting S1P and PKC isoforms are already in clinical use for treatment of autoimmune diseases and were previously subject of clinical trials in kidney transplantation where I/R induced AKI occurs as a common complication. We summarize recent in vitro and in vivo experimental studies using pharmacologic and genomic targeting and highlight some of the challenges to clinical application of these advances. Acta Physiologica © 2013 Scandinavian Physiological Society.
    Full-text · Article · Feb 2013 · Acta Physiologica
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