Sulfatide-induced L-selectin activation generates intracellular oxygen radicals in human neutrophils: modulation by extracellular adenosine

Selective desorption/ionization of sulfatides by MALDI-MS facilitated using 9-aminoacridine as matrix

Recently, we used the favorable properties of 9-aminoacridine (9-AA) as matrix for the quantitative analysis of acidic metabolites and glycerophospholipids from extracts of biological materials [Sun, G., Yang, K., Zhao, Z., Guan, S., Han, X., and Gross, R.W. (2007) A shotgun metabolomics approach for rapid analysis of negatively-charged water-soluble cellular metabolites from mouse heart tissue. Anal. Chem. 79: 6629-6640; Sun, G., Yang, K., Zhao, Z., Guan, S., Han, X., and Gross, R.W. (2008) Matrix-assisted laser desorption/ionization-time of flight mass spectrometric analysis of cellular glycerophospholipids enabled by multiplexed solvent dependent analyte-matrix interactions. Anal. Chem. 80: 7576-7585.] by MALDI-MS. Herein, we extend this discovery and identified the selective desorption/ionization of sulfatides over other examined anionic lipids present in lipid extracts of biological samples by MALDI-MS using 9-AA as matrix. Through this approach, a high throughput method for the quantitative analysis of low to very low abundance sulfatide molecular species directly from crude lipid extracts has been developed. This method possessed a linear dynamic range of over 1,000-fold, a detection limit at the high attomole level, and a reproducibility of approximately 10% deviation. Many potential factors that might affect the quantitation of sulfatide species employing the method were examined and their effects were found to be negligible within experimental error. Collectively, these results demonstrate a powerful high throughput method for the measurement of sulfatides directly from extracts of biological samples, facilitating the study of sulfatide metabolism, trafficking, and homeostasis in health and disease.

Establishment of a quantitative, qualitative, and high-throughput analysis of sulfatides from small amounts of sera by matrix-assisted laser desorption ionization-time of flight mass spectrometry

Based on our previous measurements of sulfatides, we further developed a quantitative, qualitative, and high-throughput analytical method for serum sulfatides as forms of lysosulfatides by matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS). Using 0.1N NaOH in 90% MeOH for saponification instead of absolute MeOH, as previously used, we succeeded in eliminating the formation of lysosulfatide artifacts, facilitating much more sensitive detection. The use of MonoTip C18 allowed quantitation of serum sulfatides from 100 50-mul serum specimens within 1 working day. Purification of lysosulfatides with MonoTip C18 also gave rise to clear MALDI-TOF MS spectra, allowing overall analysis of sphingoid molecular species of sulfatides in serum. The composition was as follows: d18:1 (61.3+/-2.8%), d18:2 (13.3+/-1.7%), t18:0 (11.8+/-1.5%), d18:0 (7.6+/-0.8%), d20:0 (3.0+/-1.2%), t20:0 (2.3+/-0.8%), and d20:1 (1.6+/-0.5%). This is also the first detailed report on sphingoid molecular species of sulfatides in human serum. We believe that this method is suitable for daily clinical analysis of sulfatides in various clinical samples such as blood, urine, cerebrospinal fluid, and specimens from biopsies.

Adenosine 5'-triphosphate and adenosine as endogenous signaling molecules in immunity and inflammation

Human health is under constant threat of a wide variety of dangers, both self and nonself. The immune system is occupied with protecting the host against such dangers in order to preserve human health. For that purpose, the immune system is equipped with a diverse array of both cellular and non-cellular effectors that are in continuous communication with each other. The naturally occurring nucleotide adenosine 5'-triphosphate (ATP) and its metabolite adenosine (Ado) probably constitute an intrinsic part of this extensive immunological network through purinergic signaling by their cognate receptors, which are widely expressed throughout the body. This review provides a thorough overview of the effects of ATP and Ado on major immune cell types. The overwhelming evidence indicates that ATP and Ado are important endogenous signaling molecules in immunity and inflammation. Although the role of ATP and Ado during the course of inflammatory and immune responses in vivo appears to be extremely complex, we propose that their immunological role is both interdependent and multifaceted, meaning that the nature of their effects may shift from immunostimulatory to immunoregulatory or vice versa depending on extracellular concentrations as well as on expression patterns of purinergic receptors and ecto-enzymes. Purinergic signaling thus contributes to the fine-tuning of inflammatory and immune responses in such a way that the danger to the host is eliminated efficiently with minimal damage to healthy tissues.

Role of adenosine in immunomodulation: Review of the literature

OBJECTIVE

Advances in the understanding of sepsis have failed to deliver satisfactory new treatments aimed at attenuating inflammatory-mediated organ dysfunction. Phagocytic cells play a pivotal role in driving the inflammatory response and causing direct tissue injury. Adenoreceptor stimulation may attenuate such inflammatory-mediated damage by down-regulating phagocytic activity and preventing excessive respiratory burst activation.

DATA

A Medline database was used to perform a literature search for all articles relating to the use of adenosine as an immunomodulatory agent.

CONCLUSION

There is convincing evidence to suggest that adenoreceptor modulation can prevent tissue injury through a variety of pathways. The use of adenosine modulation in ischemia/reperfusion injury has been the subject of considerable investigation, although experience with its use in sepsis is limited.

Activation of NF-kappa B transcription factor in human neutrophils by sulphatides and L-selectin cross-linking

Sulphated galactocerebroside (sulphatide) has been established as a ligand for L-selectin and shown to trigger intracellular signals in human neutrophils. We have found that sulphatide activated transcription factor NF-kappa B in human neutrophils in a concentration-dependent manner whereas non-sulphated galactocerebroside did not demonstrate such an effect. The activation was inhibitable by pretreatment with primary monoclonal anti-L-selectin antibody (clone LAM1-116). Binding of the primary antibody to L-selectin was insufficient to induce NF-kappa B activation but cross-linking of L-selectin with a secondary antibody was effective. alpha-Chymotrypsin, the agent known to shed L-selectin, activated NF-kappa B by itself. The response to sulphatides was inhibited by jasplakinolide, an actin-polymerising agent known to downregulate surface expression of L-selectin, Fc gamma RIIIb, CD43 and CD44. Recently we have reported that sulphatide stimulated the attachment of human neutrophils to collagen via Mac1 (CD11b/CD18) integrin [Sud'ina et al., Biochem. J. 359 (2001) 621-629]. We now show signalling from sulphatide to NF-kappa B activation and discuss its involvement in neutrophil adhesion.

L-selectin in health and disease

This article reviews recent advances in the knowledge of the role of L-selectin, an adhesion molecule that is expressed on the surface of circulating leucocytes, in animal and human physiology and pathophysiology. After a brief discussion on nomenclature and structure, it progresses through the evidence for expression and regulation of L-selectin, cell collection and purification, physiological function and roles. The special role of knock out mice and monoclonal antibodies in determining a role for L-selectin in inflammatory states is described before proceeding to discuss the importance of L-selectin ligands and shed L-selectin. A second section describes a role for L-selectin in pathophysiological states in animals and man, with special reference to trauma, systemic inflammatory syndromes and sepsis. The review concludes with a summary of the potential role of anti-inflammatory medication and L-selectin blockers in the management of inflammation.

Sulphatides trigger polymorphonuclear granulocyte spreading on collagen-coated surfaces and inhibit subsequent activation of 5-lipoxygenase

Sulphatides are sulphate esters of galactocerebrosides that are present on the surfaces of many cell types and act as specific ligands to selectins. The present study was undertaken to investigate the effect of sulphatides on polymorphonuclear granulocyte (PMN) attachment, spreading and 5-lipoxygenase (5-LO) metabolism. Sulphatides, but not non-sulphated galactocerebrosides, dose-dependently enhanced attachment to collagen, as measured by the myeloperoxidase assay. Studies with blocking antibodies indicated that the increased attachment was mediated by CD11b/CD18 (Mac-1) beta 2 integrin. Scanning electron microscopy indicated that sulphatides also greatly enhanced the degree of cell spreading. In PMNs treated in suspension, sulphatides had no effect on the ionophore A23187-stimulated release of arachidonic acid and the synthesis of 5-LO metabolites. In contrast, in PMNs attached to collagen, the enzymic conversion of arachidonic acid by 5-LO was inhibited by sulphatides. Inhibition of 5-LO metabolism by sulphatides was observed even in the presence of exogenous substrate, suggesting that sulphatides directly inhibited 5-LO action. Consistent with this, sulphatides interfered with ionophore-induced translocation of the 5-LO to the nuclear envelope. Substances competing with sulphatide binding to cells, like dextran sulphate, or a strong inhibitor of cell spreading, like the actin-polymerizing agent jasplakinolide, prevented the effects of sulphatides on PMN attachment and spreading and leukotriene synthesis. We conclude that shape changes occurring in response to sulphatides specifically impair PMN leukotriene synthesis by inhibiting translocation of 5-LO.

Enhancement of Fc gamma R- and CR3-mediated neutrophil phagocytosis by cerebrosides

There is increasing evidence that the ligation of adhesion molecules such as L-selectin can activate phagocytes to their full inflammatory potential. Sulfatide has been established as ligand for L-selectin and shown to trigger intracellular signals in human neutrophils. However, it remains unclear whether the ligation of L-selectin with sulfatide affects neutrophil phagocytosis. We studied the effects of sulfatide upon Fc gamma R- and CR3-mediated human neutrophil phagocytosis. Adhesion of the cells to a sulfatide-coated surface resulted in a dose-dependent enhancement of phagocytosis mediated via Fc gamma R or CR3, or both receptors. Galactocerebroside, but not glucocerebroside, also enhanced phagocytosis by neutrophils; therefore, galactose residue is thought to be required on ceramide molecules for the activation. Chymotrypsin-treated neutrophils, from which most L-selectin had been removed, reacted with sulfatide and galactocerebroside to enhance phagocytosis. These results suggest that an unidentified receptor for these cerebrosides exists on neutrophils and participates in the enhancement of phagocytosis.

Inhibitory activity of sulphoglycolipid derivatives towards pancreatic trypsin

Amphipathic sulpholipids have been shown to inhibit pancreatic serine proteases due to their detergent-like properties. To evaluate the structural requirement for this inhibitory activity, we examined the effects of various derivatives of sulphoglycolipids, some of which were prepared by deacylation with sphingolipid ceramide N-deacylase, followed by acylation with acyl chloride, on the activity of pancreatic trypsin. Both deacylated sulphatides and seminolipids exhibited inhibitory activity towards trypsin without any requirement for solubilisation and preincubation. On the other hand, stronger inhibition was observed for acylated sulphatides than for deacylated ones, but increasing the chain length of the fatty acid moiety resulted in the need for a solubilisation agent and preincubation in order to achieve maximal inhibitory activity. The structural isomers of sulphoglycolipids, such as I(6)SO(3)-GalCer, and phytosphingosine- and diglyceride-containing sulphoglycolipids, showed similar inhibitory activity, indicating the involvement of sulphate and hydrophobic groups, irrespective of the fine structure, in the inhibition. Among the sulphoglycolipids examined, II(3)SO(3)-LacCer was found to exhibit the highest inhibitory activity.

Galactolipids in the formation and function of the myelin sheath

Among the most abundant components of myelin are the galactolipids galactocerebroside (GalC) and sulfatide. In spite of this abundance, the roles that these molecules play in the myelin sheath are not well understood. Until recently, our concept of GalC and sulfatide functions had been principally defined by immunological and chemical perturbation studies that implicate these lipids in oligodendrocyte differentiation, myelin formation, and myelin stability. Recently, however, genetic studies have allowed us to re-analyze the functions of these lipids. Two laboratories have independently generated mice that are incapable of synthesizing either GalC or sulfatide by inactivating the gene encoding the enzyme UDP-galactose:ceramide galactosyltransferase (CGT), which is required for myelin galactolipid synthesis. These galactolipid-deficient animals exhibit a severe tremor, hindlimb paralysis, and display electrophysiological deficits in both the central and peripheral nervous systems. In addition, ultrastructural studies have revealed hypomyelinated white matter tracts with unstable myelin sheaths and a variety of myelin abnormalities including altered node length, reversed lateral loops, and compromised axo-oligodendrocytic junctions. Collectively, these observations indicate that cell-cell interactions, which are essential in the formation and maintenance of a properly functioning myelin sheath, are compromised in these galactolipid-deficient mice.

A sulfatide receptor distinct from L-selectin is involved in lymphocyte activation

Sulfatide induces leukocyte activation, which is thought to be mediated via L-selectin. Here we demonstrate that lymphocytes express a receptor for sulfatide distinct from L-selectin and that this receptor is involved in sulfatide-induced cell activation. While cell surface L-selectin expression was abolished by phorbol 12-myristate 13-acetate (PMA), lymphocytes retained the ability to bind sulfatide in liquid phase as well as in immobilized solid phase. The novel sulfatide receptor obtained from PMA-treated lymphocytes showed a molecular size of 65 kDa. Stimulation through this receptor triggered cytosolic free Ca2+ elevation and intercellular aggregation.

Sulfated lipids as inhibitors of pancreatic trypsin and chymotrypsin in epithelium of the mammalian digestive tract

Cholesterol sulfate and I3SO3-GalCer, which were commonly contained in the epithelia of mammalian digestive tracts, were found to inhibit the activities of typical digestive enzymes, pancreatic trypsin and chymotrypsin, but steroid sulfates, gangliosides and the other membrane constituents did not show any inhibitory activity. The preincubation of trypsin with I3SO3-GalCer at 37 degrees C for 10min was necessary to inhibit the activity of trypsin, but cholesterol sulfate showed its inhibitory activity without preincubation. Sulfated lipid-treated enzyme gave the same Km as and lower Vmax than those of the original enzymes. Also, both sulfated lipids inhibited pronase from Streptomyces griseus, but not lysyl endopeptidase from Achromobacter lyticus. These findings indicate that cholesterol sulfate and I3SO3-GalCer in the digestive tract function as epithelial inhibitors to prevent tissue injury by endogenous and exogenous proteases.