TY - JOUR A1 - Henry, Brian D. A1 - Neill, Daniel R. A1 - Becker, Katrin Anne A1 - Gore, Suzanna A1 - Bricio-Moreno, Laura A1 - Ziobro, Regan A1 - Edwards, Michael J. A1 - Muehlemann, Kathrin A1 - Steinmann, Joerg A1 - Kleuser, Burkhard A1 - Japtok, Lukasz A1 - Luginbuehl, Miriam A1 - Wolfmeier, Heidi A1 - Scherag, Andre A1 - Gulbins, Erich A1 - Kadioglu, Aras A1 - Draeger, Annette A1 - Babiychuk, Eduard B. T1 - Engineered liposomes sequester bacterial exotoxins and protect from severe invasive infections in mice JF - Nature biotechnology : the science and business of biotechnology N2 - Gram-positive bacterial pathogens that secrete cytotoxic pore-forming toxins, such as Staphylococcus aureus and Streptococcus pneumoniae, cause a substantial burden of disease. Inspired by the principles that govern natural toxin-host interactions, we have engineered artificial liposomes that are tailored to effectively compete with host cells for toxin binding. Liposome-bound toxins are unable to lyse mammalian cells in vitro. We use these artificial liposomes as decoy targets to sequester bacterial toxins that are produced during active infection in vivo. Administration of artificial liposomes within 10 h after infection rescues mice from septicemia caused by S. aureus and S. pneumoniae, whereas untreated mice die within 24-33 h. Furthermore, liposomes protect mice against invasive pneumococcal pneumonia. Composed exclusively of naturally occurring lipids, tailored liposomes are not bactericidal and could be used therapeutically either alone or in conjunction with antibiotics to combat bacterial infections and to minimize toxin-induced tissue damage that occurs during bacterial clearance. Y1 - 2015 U6 - https://doi.org/10.1038/nbt.3037 SN - 1087-0156 SN - 1546-1696 VL - 33 IS - 1 SP - 81 EP - U295 PB - Nature Publ. Group CY - New York ER - TY - JOUR A1 - Japtok, Lukasz A1 - Schmitz, Elisabeth I. A1 - Fayyaz, Susann A1 - Krämer, Stephanie A1 - Hsu, Leigh J. A1 - Kleuser, Burkhard T1 - Sphingosine 1-phosphate counteracts insulin signaling in pancreatic beta-cells via the sphingosine 1-phosphate receptor subtype 2 JF - The FASEB journal : the official journal of the Federation of American Societies for Experimental Biology N2 - Glucolipotoxic stress has been identified as a key player in the progression of pancreatic beta-cell dysfunction contributing to insulin resistance and the development of type 2 diabetes mellitus (T2D). It has been suggested that bioactive lipid intermediates, formed under lipotoxic conditions, are involved in these processes. Here, we show that sphingosine 1-phosphate (S1P) levels are not only increased in palmitate-stimulated pancreatic beta-cells but also regulate beta-cell homeostasis in a divergent manner. Although S1P possesses a prosurvival effect in beta-cells, an enhanced level of the sphingolipid antagonizes insulin-mediated cell growth and survival via the sphingosine 1-phosphate receptor subtype 2 (S1P(2)) followed by an inhibition of Akt-signaling. In an attempt to investigate the role of the S1P/S1P(2) axis in vivo, the New Zealand obese (NZO) diabetic mouse model, characterized by beta-cell loss under high-fat diet (HFD) conditions, was used. The occurrence of T2D was accompanied by an increase of plasma S1P levels. To examine whether S1P contributes to the morphologic changes of islets via S1P(2), the receptor antagonist JTE-013 was administered. Most interestingly, JTE-013 rescued beta-cell damage clearly indicating an important role of the S1P(2) in beta-cell homeostasis. Therefore, the present study provides a new therapeutic strategy to diminish beta-cell dysfunction and the development of T2D. KW - type 2 diabetes mellitus KW - sphingolipids KW - survival KW - proliferation KW - Akt signaling Y1 - 2015 U6 - https://doi.org/10.1096/fj.14-263194 SN - 0892-6638 SN - 1530-6860 VL - 29 IS - 8 SP - 3357 EP - 3369 PB - Federation of American Societies for Experimental Biology CY - Bethesda ER - TY - JOUR A1 - Michels, Meta A1 - Japtok, Lukasz A1 - Alisjahbana, Bachti A1 - Wisaksana, Rudi A1 - Sumardi, Uun A1 - Puspita, Mita A1 - Kleuser, Burkhard A1 - de Mast, Quirijn A1 - van der Ven, Andre J. A. M. T1 - Decreased plasma levels of the endothelial protective sphingosine-1-phosphate are associated with dengue-induced plasma leakage JF - Journal of infection N2 - Background: A transient endothelial hyperpermeability is a hallmark of severe dengue infections. Sphingosine-1-phosphate (S1P) maintains vascular integrity and protects against plasma leakage. We related plasma S1P levels to dengue-induced plasma leakage and studied mechanisms that may underlie the decrease in S1P levels in dengue. Methods: We determined circulating levels of S1P in 44 Indonesian adults with acute dengue and related levels to plasma leakage, as determined by daily ultrasonography, and to levels of its chaperone apolipoprotein M, other lipoproteins and platelets. Results: Plasma S1P levels were decreased during dengue and patients with plasma leakage had lower median levels compared to those without (638 vs. 745 nM; p < 0.01). ApoM and other lipoprotein levels were also decreased during dengue, but did not correlate to S1P levels. Platelet counts correlated positively with S1P levels, but S1P levels were not higher in frozen-thawed platelet rich plasma, arguing against platelets as an important cellular source of S1P in dengue. Conclusions: Decreased plasma S1P levels during dengue are associated with plasma leakage. We speculate that decreased levels of ApoM underlies the lower S1P levels. Modulation of S1P levels and its receptors may be a novel therapeutic intervention to prevent plasma leakage in dengue. (C) 2015 The British Infection Association. Published by Elsevier Ltd. All rights reserved. KW - Sphingosine 1phosphate KW - Dengue KW - APOM protein KW - Human KW - Blood platelets Y1 - 2015 U6 - https://doi.org/10.1016/j.jinf.2015.06.014 SN - 0163-4453 SN - 1532-2742 VL - 71 IS - 4 SP - 480 EP - 487 PB - Elsevier CY - London ER - TY - JOUR A1 - Carpinteiro, Alexander A1 - Becker, Katrin Anne A1 - Japtok, Lukasz A1 - Hessler, Gabriele A1 - Keitsch, Simone A1 - Pozgajova, Miroslava A1 - Schmid, Kurt W. A1 - Adams, Constantin A1 - Müller, Stefan A1 - Kleuser, Burkhard A1 - Edwards, Michael J. A1 - Grassme, Heike A1 - Helfrich, Iris A1 - Gulbins, Erich T1 - Regulation of hematogenous tumor metastasis by acid sphingomyelinase JF - EMBO molecular medicine N2 - Metastatic dissemination of cancer cells is the ultimate hallmark of malignancy and accounts for approximately 90% of human cancer deaths. We investigated the role of acid sphingomyelinase (Asm) in the hematogenous metastasis of melanoma cells. Intravenous injection of B16F10 melanoma cells into wild-type mice resulted in multiple lung metastases, while Asm-deficient mice (Smpd1(-/-) mice) were protected from pulmonary tumor spread. Transplanting wild-type platelets into Asm-deficient mice reinstated tumor metastasis. Likewise, Asm-deficient mice were protected from hematogenous MT/ret melanoma metastasis to the spleen in a mouse model of spontaneous tumor metastasis. Human and mouse melanoma cells triggered activation and release of platelet secretory Asm, in turn leading to ceramide formation, clustering, and activation of 51 integrins on melanoma cells finally leading to adhesion of the tumor cells. Clustering of integrins by applying purified Asm or C-16 ceramide to B16F10 melanoma cells before intravenous injection restored trapping of tumor cells in the lung in Asm-deficient mice. This effect was revertable by arginine-glycine-aspartic acid peptides, which are known inhibitors of integrins, and by antibodies neutralizing 1 integrins. These findings indicate that melanoma cells employ platelet-derived Asm for adhesion and metastasis. KW - acid sphingomyelinase KW - ceramide KW - integrins KW - platelets KW - tumor-metastasis Y1 - 2015 SN - 1757-4676 SN - 1757-4684 VL - 7 IS - 6 SP - 714 EP - 734 PB - Wiley-Blackwell CY - Hoboken ER - TY - JOUR A1 - Huston, Joseph P. A1 - Kornhuber, Johannes A1 - Muehle, Christiane A1 - Japtok, Lukasz A1 - Komorowski, Mara A1 - Mattern, Claudia A1 - Reichel, Martin A1 - Gulbins, Erich A1 - Kleuser, Burkhard A1 - Topic, Bianca A1 - Silva, Maria A. De Souza A1 - Mueller, Christian P. T1 - A sphingolipid mechanism for behavioral extinction JF - Journal of neurochemistry N2 - Reward-dependent instrumental behavior must continuously be re-adjusted according to environmental conditions. Failure to adapt to changes in reward contingencies may incur psychiatric disorders like anxiety and depression. When an expected reward is omitted, behavior undergoes extinction. While extinction involves active re-learning, it is also accompanied by emotional behaviors indicative of frustration, anxiety, and despair (extinction-induced depression). Here, we report evidence for a sphingolipid mechanism in the extinction of behavior. Rapid extinction, indicating efficient re-learning, coincided with a decrease in the activity of the enzyme acid sphingomyelinase (ASM), which catalyzes turnover of sphingomyelin to ceramide, in the dorsal hippocampus of rats. The stronger the decline in ASM activity, the more rapid was the extinction. Sphingolipid-focused lipidomic analysis showed that this results in a decline of local ceramide species in the dorsal hippocampus. Ceramides shape the fluidity of lipid rafts in synaptic membranes and by that way can control neural plasticity. We also found that aging modifies activity of enzymes and ceramide levels in selective brain regions. Aging also changed how the chronic treatment with corticosterone (stress) or intranasal dopamine modified regional enzyme activity and ceramide levels, coinciding with rate of extinction. These data provide first evidence for a functional ASM-ceramide pathway in the brain involved in the extinction of learned behavior. This finding extends the known cellular mechanisms underlying behavioral plasticity to a new class of membrane-located molecules, the sphingolipids, and their regulatory enzymes, and may offer new treatment targets for extinction- and learning-related psychopathological conditions. KW - acid sphingomyelinase KW - ceramide KW - extinction KW - hippocampus KW - operant behavior KW - sphingomyelin Y1 - 2016 U6 - https://doi.org/10.1111/jnc.13537 SN - 0022-3042 SN - 1471-4159 VL - 137 SP - 589 EP - 603 PB - Wiley-Blackwell CY - Hoboken ER - TY - JOUR A1 - Hollmann, Claudia A1 - Werner, Sandra A1 - Avota, Elita A1 - Reuter, Dajana A1 - Japtok, Lukasz A1 - Kleuser, Burkhard A1 - Gulbins, Erich A1 - Becker, Katrin Anne A1 - Schneider-Schaulies, Jürgen A1 - Beyersdorf, Niklas T1 - Inhibition of Acid Sphingomyelinase Allows for Selective Targeting of CD4(+) Conventional versus Foxp3(+) Regulatory T Cells JF - The journal of immunology N2 - CD4(+) Foxp3(+) regulatory T cells (Tregs) depend on CD28 signaling for their survival and function, a receptor that has been previously shown to activate the acid sphingomyelinase (Asm)/ceramide system. In this article, we show that the basal and CD28-induced Asm activity is higher in Tregs than in conventional CD4(+) T cells (Tconvs) of wild-type (wt) mice. In Asm-deficient (Smpd1(-/-); Asm(-/-)) mice, as compared with wt mice, the frequency of Tregs among CD4(+) T cells, turnover of the effector molecule CTLA-4, and their suppressive activity in vitro were increased. The biological significance of these findings was confirmed in our Treg-sensitive mouse model of measles virus (MV) CNS infection, in which we observed more infected neurons and less MV-specific CD8(+) T cells in brains of Asm(-/-) mice compared with wt mice. In addition to genetic deficiency, treatment of wt mice with the Asm inhibitor amitriptyline recapitulated the phenotype of Asm-deficient mice because it also increased the frequency of Tregs among CD4(+) T cells. Reduced absolute cell numbers of Tconvs after inhibitor treatment in vivo and extensive in vitro experiments revealed that Tregs are more resistant toward Asm inhibitor-induced cell death than Tconvs. Mechanistically, IL-2 was capable of providing crucial survival signals to the Tregs upon inhibitor treatment in vitro, shifting the Treg/Tconv ratio to the Treg side. Thus, our data indicate that Asm-inhibiting drugs should be further evaluated for the therapy of inflammatory and autoimmune disorders. Y1 - 2016 U6 - https://doi.org/10.4049/jimmunol.1600691 SN - 0022-1767 SN - 1550-6606 VL - 197 SP - 3130 EP - 3141 PB - American Assoc. of Immunologists CY - Bethesda ER - TY - JOUR A1 - Nojima, Hiroyuki A1 - Konishi, Takanori A1 - Freeman, Christopher M. A1 - Schuster, Rebecca M. A1 - Japtok, Lukasz A1 - Kleuser, Burkhard A1 - Edwards, Michael J. A1 - Gulbins, Erich A1 - Lentsch, Alex B. T1 - Chemokine Receptors, CXCR1 and CXCR2, Differentially Regulate Exosome Release in Hepatocytes JF - PLoS one N2 - Exosomes are small membrane vesicles released by different cell types, including hepatocytes, that play important roles in intercellular communication. We have previously demonstrated that hepatocyte-derived exosomes contain the synthetic machinery to form sphingosine-1-phosphate (S1P) in target hepatocytes resulting in proliferation and liver regeneration after ischemia/reperfusion (I/R) injury. We also demonstrated that the chemokine receptors, CXCR1 and CXCR2, regulate liver recovery and regeneration after I/R injury. In the current study, we sought to determine if the regulatory effects of CXCR1 and CXCR2 on liver recovery and regeneration might occur via altered release of hepatocyte exosomes. We found that hepatocyte release of exosomes was dependent upon CXCR1 and CXCR2. CXCR1-deficient hepatocytes produced fewer exosomes, whereas CXCR2-deficient hepatocytes produced more exosomes compared to their wild-type controls. In CXCR2-deficient hepatocytes, there was increased activity of neutral sphingomyelinase (Nsm) and intracellular ceramide. CXCR1-deficient hepatocytes had no alterations in Nsm activity or ceramide production. Interestingly, exosomes from CXCR1-deficient hepatocytes had no effect on hepatocyte proliferation, due to a lack of neutral ceramidase and sphingosine kinase. The data demonstrate that CXCR1 and CXCR2 regulate hepatocyte exosome release. The mechanism utilized by CXCR1 remains elusive, but CXCR2 appears to modulate Nsm activity and resultant production of ceramide to control exosome release. CXCR1 is required for packaging of enzymes into exosomes that mediate their hepatocyte proliferative effect. Y1 - 2016 U6 - https://doi.org/10.1371/journal.pone.0161443 SN - 1932-6203 VL - 11 SP - 6900 EP - + PB - PLoS CY - San Fransisco ER - TY - JOUR A1 - Reichel, Martin A1 - Rhein, Cosima A1 - Hofmann, Lena M. A1 - Monti, Juliana A1 - Japtok, Lukasz A1 - Langgartner, Dominik A1 - Füchsl, Andrea M. A1 - Kleuser, Burkhard A1 - Gulbins, Erich A1 - Hellerbrand, Claus A1 - Reber, Stefan O. A1 - Kornhuber, Johannes T1 - Chronic Psychosocial Stress in Mice Is Associated With Increased Acid Sphingomyelinase Activity in Liver and Serum and With Hepatic C16:0-Ceramide Accumulation JF - Frontiers in Psychiatry N2 - Chronic psychosocial stress adversely affects human morbidity and is a risk factor for inflammatory disorders, liver diseases, obesity, metabolic syndrome, and major depressive disorder (MDD). In recent studies, we found an association of MDD with an increase of acid sphingomyelinase (ASM) activity. Thus, we asked whether chronic psychosocial stress as a detrimental factor contributing to the emergence of MDD would also affect ASM activity and sphingolipid (SL) metabolism. To induce chronic psychosocial stress in male mice we employed the chronic subordinate colony housing (CSC) paradigm and compared them to non-stressed single housed control (SHC) mice. We determined Asm activity in liver and serum, hepatic SL concentrations as well as hepatic mRNA expression of genes involved in SL metabolism. We found that hepatic Asm activity was increased by 28% (P = 0.006) and secretory Asm activity by 47% (P = 0.002) in stressed mice. C16:0-Cer was increased by 40% (P = 0.008). Gene expression analysis further revealed an increased expression of tumor necrosis factor (TNF)-alpha (P = 0.009) and of several genes involved in SL metabolism (Cers5, P = 0.028; Cers6, P = 0.045; Gba, P = 0.049; Gba2, P = 0.030; Ormdl2, P = 0.034; Smpdl3B; P = 0.013). Our data thus provides first evidence that chronic psychosocial stress, at least in mice, induces alterations in SL metabolism, which in turn might be involved in mediating the adverse health effects of chronic psychosocial stress and peripheral changes occurring in mood disorders. KW - chronic psychosocial stress KW - acid sphingomyelinase KW - ceramide KW - sphingolipid metabolism KW - chronic subordinate colony housing (CSC) KW - liver metabolism Y1 - 2018 U6 - https://doi.org/10.3389/fpsyt.2018.00496 SN - 1664-0640 VL - 9 PB - Frontiers Research Foundation CY - Lausanne ER - TY - JOUR A1 - Nojima, Hiroyuki A1 - Freeman, Christopher M. A1 - Schuster, Rebecca M. A1 - Japtok, Lukasz A1 - Kleuser, Burkhard A1 - Edwards, Michael J. A1 - Gulbins, Erich A1 - Lentsch, Alex B. T1 - Hepatocyte exosomes mediate liver repair and regeneration via sphingosine-1-phosphate JF - Journal of hepatology N2 - Background & Aims: Exosomes are small membrane vesicles involved in intercellular communication. Hepatocytes are known to release exosomes, but little is known about their biological function. We sought to determine if exosomes derived from hepatocytes contribute to liver repair and regeneration after injury. Methods: Exosomes derived from primary murine hepatocytes were isolated and characterized biochemically and biophysically. Using cultures of primary hepatocytes, we tested whether hepatocyte exosomes induced proliferation of hepatocytes in vitro. Using models of ischemia/reperfusion injury and partial hepatectomy, we evaluated whether hepatocyte exosomes promote hepatocyte proliferation and liver regeneration in vivo. Results: Hepatocyte exosomes, but not exosomes from other liver cell types, induce dose-dependent hepatocyte proliferation in vitro and in vivo. Mechanistically, hepatocyte exosomes directly fuse with target hepatocytes and transfer neutral ceramidase and sphingosine kinase 2 (SK2) causing increased synthesis of sphingosine-1-phosphate (S1P) within target hepatocytes. Ablation of exosomal SK prevents the proliferative effect of exosomes. After ischemia/reperfusion injury, the number of circulating exosomes with proliferative effects increases. Conclusions: Our data shows that hepatocyte-derived exosomes deliver the synthetic machinery to form S1P in target hepatocytes resulting in cell proliferation and liver regeneration after ischemia/reperfusion injury or partial hepatectomy. These findings represent a potentially novel new contributing mechanism of liver regeneration and have important implications for new therapeutic approaches to acute and chronic liver disease. (C) 2015 European Association for the Study of the Liver. Published by Elsevier B.V. All rights reserved. KW - Liver injury KW - Sphingolipids KW - Sphingosine kinase KW - Ischemia/reperfusion KW - Transplantation Y1 - 2016 U6 - https://doi.org/10.1016/j.jhep.2015.07.030 SN - 0168-8278 SN - 1600-0641 VL - 64 SP - 60 EP - 68 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Al Fadel, Frdoos A1 - Fayyaz, Susann A1 - Japtok, Lukasz A1 - Kleuser, Burkhard T1 - Involvement of Sphingosine 1-Phosphate in Palmitate-Induced Non-Alcoholic Fatty Liver Disease JF - Cellular physiology and biochemistry : international journal of experimental cellular physiology, biochemistry and pharmacology N2 - Background/Aims: Ectopic lipid accumulation in hepatocytes has been identified as a risk factor for the progression of liver fibrosis and is strongly associated with obesity. In particular, the saturated fatty acid palmitate is involved in initiation of liver fibrosis via formation of secondary metabolites by hepatocytes that in turn activate hepatic stellate cells (HSCs) in a paracrine manner Methods: a-smooth muscle actin-expression (alpha-SMA) as a marker of liver fibrosis was investigated via western blot analysis and immunofluorescence microscopy in HSCs (LX-2). Sphingolipid metabolism and the generation of the bioactive secondary metabolite sphingosine I-phosphate (SIP) in response to palmitate were analyzed by LC-MS/MS in hepatocytes (HepG2). To identify the molecular mechanism involved in the progression of liver fibrosis real-time PCR analysis and pharmacological modulation of SIP receptors were performed. Results: Palmitate oversupply increased intra- and extracellular SIP-concentrations in hepatocytes. Conditioned medium from HepG2 cells initiated fibrosis by enhancing alpha-SMA-expression in LX-2 in a S1P-dependent manner In accordance, fibrotic response in the presence of SIP was also observed in HSCs. Pharmacological inhibition of SIP receptors demonstrated that S1P(3) is the crucial receptor subtype involved in this process. Conclusion: SIP is synthesized in hepatocytes in response to palmitate and released into the extracellular environment leading to an activation of HSCs via the S1P(3) receptor (C) 2016 The Author(s) Published by S. Karger AG, Basel KW - Palmitate KW - Liver fibrosis KW - Sphingosine 1-phosphate KW - Hepatic stellate cells KW - Hepatocytes KW - alpha-SMA Y1 - 2016 U6 - https://doi.org/10.1159/000453213 SN - 1015-8987 SN - 1421-9778 VL - 40 SP - 1637 EP - 1645 PB - Karger CY - Basel ER -