Ceramide

A cell-permeable ceramide analog. Induces apoptosis in a variety of cell types. Stimulates ceramide-activated protein phosphatases and activates ceramide-activated protein kinases.

Increased ceramide production sensitizes breast cancer cell response to chemotherapy.[Pubmed:28357533]

Cancer Chemother Pharmacol. 2017 May;79(5):933-941.

BACKGROUND: Advanced breast cancer remains clinically challenging due to its resistance to chemotherapy. To understand the underlying mechanisms of resistance and identify drugable target, the involvement of Ceramide metabolism is investigated. METHODS: Ceramide levels in breast cancer tissues derived from 30 patients with stage IV breast cancer before and after chemotherapy were analyzed using liquid chromatography mass spectrometry. mRNA and protein levels of Ceramide enzymes were examined using western blot and QRT-PCR. The effects of Ceramide analog were investigated using cellular assays and xenograft tumor model. RESULTS: The results demonstrated that pro-apoptotic Ceramide was significantly lower in all patients after chemotherapy, suggesting that downregulation of Ceramide is a common feature of breast cancer patients in response to chemotherapy. Molecular characteristics analysis of Ceramide indicated C16:0 as the predominant sphingolipid regulated by chemotherapy in breast cancer patients. Mechanistically, Ceramide levels were suppressed by chemotherapy via increasing mRNA and protein levels of UDP-glucose Ceramide glucosyltransferase (UGCG). Importantly, inhibition of UGCG using siRNA or upregulation of cellular Ceramide levels using C2 Ceramide alone inhibited proliferation and induced apoptosis of breast cancer cells, and enhanced the inhibitory effects of chemotherapeutic drugs in vitro and in vivo. CONCLUSIONS: This study clearly demonstrated that the decreased Ceramide production via up-regulating UGCG was involved in the resistance of breast cancer cells to chemotherapy. Stimulating Ceramide or decreasing UGCG can potentially be useful for breast cancer treatment.

A Cleanup Method for Mass Spectrometric Analysis of Sphingosine- and Ceramide-1-Phosphate in Blood and Solid Tissue Using a Phosphate Capture Molecule.[Pubmed:28361484]

Methods Mol Biol. 2018;1697:57-71.

Cleanup technology and mass spectrometric determination of sphingosine-1-phosphate (S1P) using a phosphate capture molecule are shown. The protocol is rapid, requires neither thin-layer chromatography nor liquid chromatography, and is applicable to both blood and solid tissue samples. The mass spectrometric method is also applicable to Ceramide-1-phosphate.

Synthesis and biological activities of C-glycosides of KRN 7000 with novel ceramide residues.[Pubmed:28365448]

Carbohydr Res. 2017 Apr 18;443-444:73-77.

The identification of immunoactive agents for clinical and mechanistic applications is a very active area of research. In this vein, analogues of the potent immunostimulant KRN 7000 with diverse cytokine profiles have attracted considerable attention. These compounds have been shown to activate iNKT cells via presentation by CD1d. Herein, we report on the synthesis and activity for four new C-glycosides of KRN 7000, 11-phenylundecanoyl and 11-p-fluorophenylundecanoyl derivatives of C-KRN 7000, 2,3-bis-epi-C-KRN 7000 and the reverse amide of C-KRN 7000. In mice, compared to C-KRN 7000, 2,3-bis-epi-C-KRN 7000 stimulated higher release of the anti-inflammatory cytokine IL-4 and lower release of the inflammatory cytokines IFN-gamma and IL-12. The phenyl terminated alkanoyl and reverse amide analogues were inactive. These data suggest that structure activity effects for KRN 7000 are not necessarily additive and their use in the design of new analogues will require an improved understanding of how subtle structural changes impact on cytokine activity.

Acid sphingomyelinase/ceramide regulates carotid intima-media thickness in simulated weightless rats.[Pubmed:28357491]

Pflugers Arch. 2017 Jun;469(5-6):751-765.

Structural adaptation of arteries to weightlessness might lower the working ability or even threaten the physical health of astronauts, but the underlying mechanism is unclear. Acid sphingomyelinase (ASM) catalyzes Ceramide (Cer) generation controlling arterial remodeling through multiple signaling pathways. In the present study, we aimed to investigate the contribution of ASM/Cer to the changes of common carotid artery intima-media thickness (CIMT) induced by simulated weightlessness. Hindlimb-unloaded tail-suspended (HU) rats were used to simulate the effect of weightlessness. Morphology of the carotid artery (CA) was examined by hematoxylin-eosin staining. Protein content of ASM or proliferating cell nuclear antigen (PCNA) was detected by Western blot. Cer level was measured by immunohistochemistry analysis. Apoptosis events were observed by transferase-mediated dUTP nick end labeling (TUNEL) staining. During 4 weeks of tail suspension, CIMT was increased gradually in HU but not in their synchronous control rats (P < 0.05). Correspondingly, the CA of HU rats had a lower apoptosis and higher proliferation of vascular smooth muscle cells (VSMCs). As compared to the control, both ASM protein expression and Cer content were reduced significantly in CA of HU rats (P < 0.05), incubation of which with permeable Cer reversed the changes in apoptosis and proliferation substantially. Furthermore, when the ASM protein content as well as Cer level in CA of control rats was diminished by using an ASM inhibitor, an increase of CIMT along with reduced apoptosis and enhanced proliferation of VSMCs was found. Our results suggest that by controlling the balance between apoptosis and proliferation, ASM/Cer plays an important role in the regulation of CIMT during simulated weightlessness.

Ceramide selectively decreases tau levels in differentiated PC12 cells through modulation of calpain I.[Pubmed:9282924]

J Neurochem. 1997 Sep;69(3):1020-30.

Ceramide has been recently proposed to be a signal mediator in several important physiological processes including apoptosis, cellular growth, and differentiation. Because the microtubule-associated protein tau plays an important role in the establishment and maintenance of neuronal morphology, the effects of Ceramide on tau were examined. Treatment of differentiated PC12 cells with the cell-permeable Ceramide derivative N-acetylsphingosine (C2) resulted in a significant reduction in tau levels. Significant decreases in tau levels were also observed when the cells were treated with another Ceramide derivative, N-hexanoylsphingosine (C6). In addition, C2 treatment increased the levels of a calpain-derived spectrin breakdown product but did not alter the levels of two cytoskeletal proteins, alpha-actin and alpha-tubulin. Because both tau and spectrin are proteolyzed in vitro by the calcium-activated cysteine protease calpain, the effects of Ceramide analogues on the activity of this protease were examined. Treatment of PC12 cells with C2 enhanced calcium-stimulated proteolytic activity significantly, as revealed by monitoring the hydrolysis of the membrane-permeable calpain-selective fluorescence probe N-succinyl-L-leucyl-L-leucyl-L-valyl-L-tyrosine-7-amido-4-methylcoumarin . This activity increase was not due to a direct effect of C2 on calpains, because C2 did not alter the activities of purified calpain I or II. In addition, C2 treatment of PC12 cells resulted in a significant increase in the levels of calpain I and, to a lesser extent, the levels of calpastatin (an endogenous calpain inhibitor protein), whereas the levels of calpain II were not changed. Moreover, treatment of the cells with the synthetic calpain-specific inhibitor N-carbobenzoxy-L-leucyl-L-leucyl-L-tyrosine diazomethyl ketone blocked the C2-induced decreases in tau levels. These results indicate that tau levels are regulated in response to a physiological factor and, thus, have implications for Ceramide-mediated changes in normal and pathological neuronal processes.

Ceramide mediates the apoptotic response of WEHI 231 cells to anti-immunoglobulin, corticosteroids and irradiation.[Pubmed:8048941]

Biochem Biophys Res Commun. 1994 Jul 29;202(2):710-4.

We demonstrate for the first time how immature B cells kill themselves. Ceramide is identified as the mediator of apoptosis in the murine B lymphoma line WEHI 231 commonly used as a model to study clonal deletion in B lymphocytes. We show that exogenous Ceramide induces apoptosis in WEHI 231 cells. To maintain self tolerance, immature lymphocytes readily undergo apoptotic death in response to the cross-linking of their antigen-specific receptors. We demonstrate that endogenously produced Ceramide accumulates in WEHI 231 cells exposed to anti-IgM, an antigen surrogate before the onset of apoptosis. We also show that two other inducers of apoptosis, irradiation and dexamethasone, cause intracellular accumulation of Ceramide.

Ceramide stimulates a cytosolic protein phosphatase.[Pubmed:1312082]

J Biol Chem. 1992 Mar 15;267(8):5048-51.

A sphingomyelin cycle has been identified whereby the action of certain extracellular agents results in reversible sphingomyelin hydrolysis and the concomitant generation of Ceramide. Moreover, a cell-permeable Ceramide, C2-Ceramide (N-acetylsphingosine), is a potent modulator of cell proliferation and differentiation. We report herein that C2-Ceramide, C6-Ceramide, and natural Ceramides activate a cytosolic serine/threonine protein phosphatase in a dose-dependent manner. Initial activation is observed at concentrations of Ceramide as low as 0.1 microM with peak response occurring at 5-10 microM. However, other closely related sphingolipids, sphingosine and sphingomyelin, were largely inactive. Ceramide-stimulated phosphatase was inhibited by okadaic acid, an inhibitor of protein phosphatases, with an IC50 of 0.1-1 nM, depending on the concentration of Ceramide. Ceramide-stimulated phosphatase was insensitive to Mg2+ and Mn2+ cations. Using sequential anion exchange chromatography, Ceramide-stimulated phosphatase activity could be resolved from Ceramide-nonresponsive phosphatases. The activity of partially purified enzyme was stimulated 3.5-fold by Ceramide. The identification of a phosphatase as a molecular target for the action of Ceramide defines a novel intracellular signaling pathway with potential roles in the regulation of cell proliferation and differentiation.

Identification of sphingomyelin turnover as an effector mechanism for the action of tumor necrosis factor alpha and gamma-interferon. Specific role in cell differentiation.[Pubmed:1845977]

J Biol Chem. 1991 Jan 5;266(1):484-9.

The biochemical signaling mechanisms involved in transducing the effects of tumor necrosis factor alpha (TNF alpha) and gamma-interferon (gamma-IFN) on leukemia cell differentiation are poorly defined. Recent studies established the existence of a sphingomyelin cycle that operates in response to the action of vitamin D3 on HL-60 cells and that may transduce the effects of vitamin D3 on cell differentiation (Okazaki, T., Bell, R., and Hannun, Y. (1989) J. Biol. Chem. 264, 19076-19080). The effects of TNF alpha and gamma-IFN on sphingomyelin turnover were determined, and the specificity and role of sphingomyelin hydrolysis in HL-60 human promyelocytic leukemia cells with 20% hydrolysis of sphingomyelin at 15 min, 40% hydrolysis at 30-60 min, and return to base line at 2 h. The hydrolyzed sphingomyelin (18 pmol/nmol total phospholipid) was accompanied by the concomitant generation of Ceramide (11.2 pmol/nmol total phospholipid). gamma-IFN also caused reversible hydrolysis of sphingomyelin with onset at 1 h and peak effect at 2 h. This sphingomyelin cycle appeared to be specific to the monocytic pathway of HL-60 differentiation, since it was not activated by retinoic acid or dibutyryl cAMP, inducers of granulocytic differentiation, nor with phorbol myristate acetate, an inducer of macrophage-like differentiation. Addition of synthetic Ceramide or bacterial sphingomyelinase induced monocytic differentiation of HL-60 cells. Cell-permeable Ceramide also caused prompt down-regulation of mRNA for the c-myc protooncogene. The time course of c-myc down-regulation was consistent with the action of Ceramide as the mediator of TNF alpha action. These results suggest that sphingomyelin turnover may be an important signaling mechanism transducing the actions of TNF alpha and gamma-IFN with specific function in cell differentiation.