Acid sphingomyelinase in macrophage apoptosis

Acid Sphingomyelinase Deficiency: A Clinical and Immunological Perspective

Acid sphingomyelinase deficiency (ASMD) is a lysosomal storage disease caused by deficient activity of acid sphingomyelinase (ASM) enzyme, leading to the accumulation of varying degrees of sphingomyelin. Lipid storage leads to foam cell infiltration in tissues, and clinical features including hepatosplenomegaly, pulmonary insufficiency and in some cases central nervous system involvement. ASM enzyme replacement therapy is currently in clinical trial being the first treatment addressing the underlying pathology of the disease. Therefore, presently, it is critical to better comprehend ASMD to improve its diagnose and monitoring. Lung disease, including recurrent pulmonary infections, are common in ASMD patients. Along with lung disease, several immune system alterations have been described both in patients and in ASMD animal models, thus highlighting the role of ASM enzyme in the immune system. In this review, we summarized the pivotal roles of ASM in several immune system cells namely on macrophages, Natural Killer (NK) cells, NKT cells, B cells and T cells. In addition, an overview of diagnose, monitoring and treatment of ASMD is provided highlighting the new enzyme replacement therapy available.

Acid Sphingomyelinase Mediates Oxidized-LDL Induced Apoptosis in Macrophage via Endoplasmic Reticulum Stress

Aim: Macrophage apoptosis is a vital event in advanced atherosclerosis, and oxidized low-density lipoprotein (ox-LDL) is a major contributor to this process. Acid sphingomyelinase (ASM) and ceramide are also involved in the induction of apoptosis, particularly in macrophages. Our current study focuses on ASM and investigates its role in ox-LDL-induced macrophage apoptosis.

Methods: Human THP-1 and mouse peritoneal macrophages were cultured in vitro and treated with ox-LDL. ASM activity and ceramide levels were quantified using ultra performance liquid chromatography. Protein and mRNA levels were analyzed using Western blot analysis and quantitative realtime PCR, respectively. Cell apoptosis was determined using Hoechst staining and flow cytometry.

Results: Ox-LDL-induced macrophage apoptosis was triggered by profound endoplasmic reticulum (ER) stress, leading to an upregulation of ASM activity and ceramide levels at an early stage. ASM was inhibited by siRNA or desipramine (DES), and/or ceramide was degraded by recombinant acid ceramidase (AC). These events attenuated the effect of ox-LDL on ER stress. In contrast, recombinant ASM upregulated ceramide and ER stress. ASM siRNA, DES, recombinant AC, and ER stress inhibitor 4-phenylbutyric acid were blocked by elevated levels of C/EBP homologous protein (CHOP); ox-LDL induced elevated levels of CHOP. These events attenuated macrophage apoptosis.

Conclusion: These results indicate that ASM/ceramide signaling pathway is involved in ox-LDL-induced macrophage apoptosis via ER stress pathway.

Control of inflammatory responses by ceramide, sphingosine 1-phosphate and ceramide 1-phosphate

Inflammation is a network of complex processes involving a variety of metabolic and signaling pathways aiming at healing and repairing damage tissue, or fighting infection. However, inflammation can be detrimental when it becomes out of control. Inflammatory mediators involve cytokines, bioactive lipids and lipid-derived metabolites. In particular, the simple sphingolipids ceramides, sphingosine 1-phosphate, and ceramide 1-phosphate have been widely implicated in inflammation. However, although ceramide 1-phosphate was first described as pro-inflammatory, recent studies show that it has anti-inflammatory properties when produced in specific cell types or tissues. The biological functions of ceramides and sphingosine 1-phosphate have been extensively studied. These sphingolipids have opposing effects with ceramides being potent inducers of cell cycle arrest and apoptosis, and sphingosine 1-phosphate promoting cell growth and survival. However, the biological actions of ceramide 1-phosphate have only been partially described. Ceramide 1-phosphate is mitogenic and anti-apoptotic, and more recently, it has been demonstrated to be key regulator of cell migration. Both sphingosine 1-phosphate and ceramide 1-phosphate are also implicated in tumor growth and dissemination. The present review highlights new aspects on the control of inflammation and cell migration by simple sphingolipids, with special emphasis to the role played by ceramide 1-phosphate in controlling these actions.

Surface hydrolysis of sphingomyelin by the outer membrane protein Rv0888 supports replication of Mycobacterium tuberculosis in macrophages

Sphingomyelinases secreted by pathogenic bacteria play important roles in host-pathogen interactions ranging from interfering with phagocytosis and oxidative burst to iron acquisition. This study shows that the Mtb protein Rv0888 possesses potent sphingomyelinase activity cleaving sphingomyelin, a major lipid in eukaryotic cells, into ceramide and phosphocholine, which are then utilized by Mtb as carbon, nitrogen and phosphorus sources, respectively. An Mtb rv0888 deletion mutant did not grow on sphingomyelin as a sole carbon source anymore and replicated poorly in macrophages indicating that Mtb utilizes sphingomyelin during infection. Rv0888 is an unusual membrane protein with a surface-exposed C-terminal sphingomyelinase domain and a putative N-terminal channel domain that mediated glucose and phosphocholine uptake across the outer membrane in an M. smegmatis porin mutant. Hence, we propose to name Rv0888 as SpmT (sphingomyelinase of Mycobacterium tuberculosis). Erythrocyte membranes contain up to 27% sphingomyelin. The finding that Rv0888 accounts for half of Mtb's hemolytic activity is consistent with its sphingomyelinase activity and the observation that Rv0888 levels are increased in the presence of erythrocytes and sphingomyelin by 5- and 100-fold, respectively. Thus, Rv0888 is a novel outer membrane protein that enables Mtb to utilize sphingomyelin as a source of several essential nutrients during intracellular growth.

Ex vivo and in vivo studies of CME-1, a novel polysaccharide purified from the mycelia of Cordyceps sinensis that inhibits human platelet activation by activating adenylate cyclase/cyclic AMP

INTRODUCTION

CME-1, a novel water-soluble polysaccharide, was purified from the mycelia of Cordyceps sinensis, and its chemical structure was characterized to contain mannose and galactose in a ratio of 4:6 (27.6 kDa). CME-1 was originally observed to exert a potent inhibitory effect on tumor migration and a cytoprotective effect against oxidative stress. Activation of platelets caused by arterial thrombosis is relevant to various cardiovascular diseases (CVDs). However, no data are available concerning the effects of CME-1 on platelet activation. Hence, the purpose of this study was to examine the ex vivo and in vivo antithrombotic effects of CME-1 and its possible mechanisms in platelet activation.

METHODS

The aggregometry, immunoblotting, flow cytometric analysis and platelet functional analysis were used in this study.

RESULTS

CME-1 (2.3-7.6 μM) exhibited highly potent activity in inhibiting human platelet aggregation when stimulated by collagen, thrombin, and arachidonic acid but not by U46619. CME-1 inhibited platelet activation accompanied by inhibiting Akt, mitogen-activated protein kinases (MAPKs), thromboxane B2 (TxB2) and hydroxyl radical (OH(●)) formation. However, CME-1 interrupted neither FITC-triflavin nor FITC-collagen binding to platelets. CME-1 markedly increased cyclic AMP levels, but not cyclic GMP levels, and stimulated vasodilator-stimulated phosphoprotein (VASP) phosphorylation. SQ22536, an inhibitor of adenylate cyclase, but not ODQ, an inhibitor of guanylate cyclase, obviously reversed the CME-1-mediated effects on platelet aggregation and vasodilator-stimulated phosphoprotein (VASP), Akt, p38 MAPK phosphorylation, and TxB2 formation. CME-1 substantially prolonged the closure time of whole blood and the occlusion time of platelet plug formation.

CONCLUSION

This study demonstrates for the first time that CME-1 exhibits highly potent antiplatelet activity that may initially activate adenylate cyclase/cyclic AMP and, subsequently, inhibit intracellular signals (such as Akt and MAPKs), ultimately inhibiting platelet activation. This novel role of CME-1 indicates that CME-1 exhibits high potential for application in treating and preventing CVDs.

CSF-1 receptor signaling in myeloid cells

The CSF-1 receptor (CSF-1R) is activated by the homodimeric growth factors colony-stimulating factor-1 (CSF-1) and interleukin-34 (IL-34). It plays important roles in development and in innate immunity by regulating the development of most tissue macrophages and osteoclasts, of Langerhans cells of the skin, of Paneth cells of the small intestine, and of brain microglia. It also regulates the differentiation of neural progenitor cells and controls functions of oocytes and trophoblastic cells in the female reproductive tract. Owing to this broad tissue expression pattern, it plays a central role in neoplastic, inflammatory, and neurological diseases. In this review we summarize the evolution, structure, and regulation of expression of the CSF-1R gene. We discuss the structures of CSF-1, IL-34, and the CSF-1R and the mechanism of ligand binding to and activation of the receptor. We further describe the pathways regulating macrophage survival, proliferation, differentiation, and chemotaxis downstream from the CSF-1R.

Platelet protease-activated receptor (PAR)4, but not PAR1, associated with neutral sphingomyelinase responsible for thrombin-stimulated ceramide-NF-κB signaling in human platelets

Thrombin activates platelets mainly through protease-activated receptor (PAR)1 and PAR4. However, downstream platelet signaling between PAR1 and PAR4 is not yet well understood. This study investigated the relationship between nSMase/ceramide and the NF-κB signaling pathway in PARs-mediated human platelet activation. The LC-MS/MS, aggregometry, flow cytometry, immunoprecipitation, and mesenteric microvessels of mice were used in this study. Human platelets stimulated by thrombin, 3-OMS (a neutral sphingomyelinase [nSMase] inhibitor) and Bay11-7082 (an NF-κB inhibitor) significantly inhibited platelet activation such as P-selectin expression. Thrombin also activated IκB kinase (IKK)β and IκBα phosphorylation; such phosphorylation was inhibited by 3-OMS and SB203580 (a p38 MAPK inhibitor). Moreover, 3-OMS abolished platelet aggregation, IKKβ, and p38 MAPK phosphorylation stimulated by PAR4-AP (a PAR4 agonist) but not by PAR1-AP (a PAR1 agonist). Immunoprecipitation revealed that nSMase was directly associated with PAR4 but not PAR1 in resting platelets. In human platelets, C24:0-ceramide is the predominant form of ceramides in the LC/MS-MS assay; C24:0-ceramide increases after stimulation by thrombin or PAR4-AP, but not after stimulation by PAR1-AP. We also found that C2-ceramide (a cell-permeable ceramide analog) activated p38 MAPK and IKKβ phosphorylation in platelets and markedly shortened the occlusion time of platelet plug formation in vivo. This study demonstrated that thrombin activated nSMase by binding to PAR4, but not to PAR1, to increase the C24:0-ceramide level, followed by the activation of p38 MAPK-NF-κB signaling. Our results showed a novel physiological significance of PAR4-nSMase/ceramide-p38 MAPK-NF-κB cascade in platelet activation.

Toxicity of oxidized phospholipids in cultured macrophages

Background

The interactions of oxidized low-density lipoprotein (LDL) and macrophages are hallmarks in the development of atherosclerosis. The biological activities of the modified particle in these cells are due to the content of lipid oxidation products and apolipoprotein modification by oxidized phospholipids.

Results

It was the aim of this study to determine the role of short-chain oxidized phospholipids as components of modified LDL in cultured macrophages. For this purpose we investigated the effects of the following oxidized phospholipids on cell viability and apoptosis: 1-palmitoyl-2-glutaroyl-sn-glycero-3-phosphocholine (PGPC), 1-palmitoyl-2-(5-oxovaleroyl)-sn-glycero-3-phosphocholine (POVPC) and oxidized alkylacyl phospholipids including 1-O-hexadecyl-2-glutaroyl-sn-glycero-3-phosphocholine (E-PGPC) and 1-O-hexadecyl-2-(5-oxovaleroyl)-sn-glycero-3-phosphocholine (E-POVPC). We found that these compounds induced apoptosis in RAW264.7 and bone marrow-derived macrophages. The sn-2 carboxyacyl lipid PGPC was more toxic than POVPC which carries a reactive aldehyde function in position sn-2 of glycerol. The alkylacyl phospholipids (E-PGPC and E-POVPC) and the respective diacyl analogs show similar activities. Apoptosis induced by POVPC and its alkylether derivative could be causally linked to the fast activation of an acid sphingomyelinase, generating the apoptotic second messenger ceramide. In contrast, PGPC and its ether analog only negligibly affected this enzyme pointing to an entirely different mechanism of lipid toxicity. The higher toxicity of PGPC is underscored by more efficient membrane blebbing from apoptotic cells. In addition, the protein pattern of PGPC-induced microparticles is different from the vesicles generated by POPVC.

Conclusions

In summary, our data reveal that oxidized phospholipids induce apoptosis in cultured macrophages. The mechanism of lipid toxicity, however, largely depends on the structural features of the oxidized sn-2 chain.

OxLDL-mediated survival of macrophages does not require LDL internalization or signalling by major pattern recognition receptors

Macrophages play a key role in the pathogenesis of atherosclerosis, in part by destabilizing plaques. We and others have shown that low concentrations of oxidized LDL (oxLDL) inhibit macrophage apoptosis. As oxLDL is present in lesions, this may be a mechanism by which macrophage populations in the intima are expanded. We have previously shown that oxLDL activates prosurvival signalling pathways such as the phosphoinositide 3-kinase (PI3K) pathway in bone marrow derived macrophages (BMDMs). However, little is known about more upstream signalling events especially at the receptor level. The endocytic pattern recognition receptors (PRRs), scavenger receptor A (SR-A) and CD36, are the main receptors on macrophages for uptake of oxLDL and are therefore important in foam cell formation. The signalling PRRs such as toll-like receptor (TLR) 2 and 4 also bind some types of oxLDL. This study was done to determine if any of the known PRRs are required for the anti-apoptotic effects of oxLDL in BMDMs. To do this, we tested the effect of oxLDL on viability of BMDMs lacking both SR-A and CD36 or lacking TLR2, TLR4, CD14, FcγRIIb, or RAGE. Our results indicate that none of these receptors are essential for activating the oxLDL prosurvival pathway. Furthermore, we show that the anti-apoptotic effect is not dependent on the uptake of oxLDL.

Impact of oxLDL on Cholesterol-Rich Membrane Rafts

Numerous studies have demonstrated that cholesterol-rich membrane rafts play critical roles in multiple cellular functions. However, the impact of the lipoproteins on the structure, integrity and cholesterol composition of these domains is not well understood. This paper focuses on oxidized low-density lipoproteins (oxLDLs) that are strongly implicated in the development of the cardiovascular disease and whose impact on membrane cholesterol and on membrane rafts has been highly controversial. More specifically, we discuss three major criteria for the impact of oxLDL on membrane rafts: distribution of different membrane raft markers, changes in membrane cholesterol composition, and changes in lipid packing of different membrane domains. We also propose a model to reconcile the controversy regarding the relationship between oxLDL, membrane cholesterol, and the integrity of cholesterol-rich membrane domains.

A potent sphingomyelinase inhibitor from Cordyceps mycelia contributes its cytoprotective effect against oxidative stress in macrophages

A novel water-soluble polysaccharide fraction, CME-1, with a molecular mass of 27.6 kDa and containing mannose and galactose in a respective ratio of 4:6, was prepared from Cordyceps sinensis mycelia and identified by NMR and GC-MS. In the current study, we examined whether CME-1 has anti-inflammatory effects in RAW264.7 cells. The ability of CME-1 to inhibit H(2)O(2)-induced cell death in RAW264.7 cells was assessed by using an MTT assay and annexin V/propidium iodide double staining; we found that CME-1 protected cells against H(2)O(2)-induced injury. H(2)O(2)-induced intracellular oxidative stress and mitochondrial membrane depolarization were also diminished with CME-1 treatment. We evaluated the hydroxyl radical scavenging ability of CME-1 by using the DMPO-electron spin resonance technique, which indicated that CME-1 acts as an intracellular antioxidant in a concentration-dependent manner through a mechanism other than its scavenging activity. Activities of both neutral and acid sphingomyelinases (SMases) were assessed in vitro, and results showed that the CME-1 inhibited activities of both neutral and acid SMases in a concentration-dependent manner. CME-1 reduced H(2)O(2) treatment-elevated C16- and C18-ceramide levels measured by LC/MS/MS in RAW264.7 cells. Results suggest that CME-1 protects RAW264.7 cells against oxidative stress through inhibition of SMase activity and reduction of C16- and C18-ceramide levels.

Control of metabolism and signaling of simple bioactive sphingolipids: Implications in disease

Simple bioactive sphingolipids include ceramide, sphingosine and their phosphorylated forms sphingosine 1-phosphate and ceramide 1-phosphate. These molecules are crucial regulators of cell functions. In particular, they play important roles in the regulation of angiogenesis, apoptosis, cell proliferation, differentiation, migration, and inflammation. Decoding the mechanisms by which these cellular functions are regulated requires detailed understanding of the signaling pathways that are implicated in these processes. Most importantly, the development of inhibitors of the enzymes involved in their metabolism may be crucial for establishing new therapeutic strategies for treatment of disease.

Ceramide and ceramide 1-phosphate in health and disease

Sphingolipids are essential components of cell membranes, and many of them regulate vital cell functions. In particular, ceramide plays crucial roles in cell signaling processes. Two major actions of ceramides are the promotion of cell cycle arrest and the induction of apoptosis. Phosphorylation of ceramide produces ceramide 1-phosphate (C1P), which has opposite effects to ceramide. C1P is mitogenic and has prosurvival properties. In addition, C1P is an important mediator of inflammatory responses, an action that takes place through stimulation of cytosolic phospholipase A2, and the subsequent release of arachidonic acid and prostaglandin formation. All of the former actions are thought to be mediated by intracellularly generated C1P. However, the recent observation that C1P stimulates macrophage chemotaxis implicates specific plasma membrane receptors that are coupled to Gi proteins. Hence, it can be concluded that C1P has dual actions in cells, as it can act as an intracellular second messenger to promote cell survival, or as an extracellular receptor agonist to stimulate cell migration.

Oxidative lipidomics of apoptosis: quantitative assessment of phospholipid hydroperoxides in cells and tissues

Oxidized phospholipids play essential roles in execution of mitochondrial stage of apoptosis and clearance of apoptotic cells. The identification and quantification of oxidized phospholipids generated during apoptosis can be successfully achieved by oxidative lipidomics. With this approach, diverse molecular species of phospholipids and their hydroperoxides are identified and characterized by soft-ionization mass-spectrometry techniques such as electrospray ionization (ESI). Quantitative assessment of lipid hydroperoxides is performed by fluorescence HPLC-based protocol. The protocol is based on separation of phospholipids using two-dimensional-high-performance thin-layer chromatography (2-D-HPTLC). Phospholipids are hydrolyzed using phospholipase A(2). The fatty acid hydroperoxides (FA-OOH) released is quantified by a fluorometric assay using Amplex red reagent and microperoxidase-11 (MP-11). Detection limit of this protocol is 1-2 pmol of lipid hydroperoxides. Lipid arrays vs. oxidized lipid arrays can be performed by comparing the abundance of phospholipids with the abundance of oxidized phospholipids. Using oxidative lipidomics approach we show that the pattern of phospholipid oxidation during apoptosis is nonrandom and does not follow their abundance in several types of cells undergoing apoptosis and a variety of disease states. This has important implications for evaluation of apoptosis in vivo. The anionic phospholipids, cardiolipin (CL) and phosphatidylserine (PS), are the preferred peroxidation substrates.

Doxorubicin induces ceramide and diacylglycerol accumulation in rat hepatocytes through independent routes

Doxorubicin (DOX) is a potent anticancer drug, whose clinical use is limited due to its toxicity. This toxicity has been associated with free radicals generated during the drug metabolism. We previously found that DOX increased the intracellular diacylglycerol (DAG) levels at 1h in isolated rat hepatocytes, probably by mobilizing choline-enriched phospholipids. In this work, we studied the effects of DOX on oxidative stress markers, and the possible contribution of ceramide metabolism to DAG accumulation. Other possible routes of DAG production, such as impairment of triacylglycerol (TAG) synthesis, and their connection with oxidative stress were also investigated. Time-course experiments revealed that DOX decreased intracellular GSH at 2h, but did not affect cell viability, ATP or malondialdehyde (MDA) levels at any time. DOX did not modify the intracellular levels of [(3)H]-ceramide during the first 90 min of exposure, but increased it significantly at 2h. [(3)H]-Sphingomyelin remained unchanged during the whole period. These results indicate that ceramide metabolism is not involved in the early DAG response to DOX. The drug markedly increased the incorporation of [(3)H]-oleate into intracellular DAG from 60 min. In contrast, DOX reduced the incorporation of [(3)H]-oleate into intracellular phospholipids and TAG. DOX inhibited TAG synthesis at the DAG acyltransferase step. These results suggest that DOX increases the intracellular levels of the lipid messengers, ceramide and DAG, by independent mechanisms. Activation of the de novo synthesis of ceramide is probably involved in the sphingolipid accumulation, while inhibition of TAG synthesis contributes to DAG accumulation, this response being independent of oxidative damage.

LOX-1 augments oxLDL uptake by lysoPC-stimulated murine macrophages but is not required for oxLDL clearance from plasma

Oxidized LDL (oxLDL) promotes lipid accumulation as well as growth and survival signaling in macrophages. OxLDL uptake is mainly due to scavenger receptors SR-AI/II and CD36. However, other scavenger receptors such as lectin-like oxLDL receptor-1 (LOX-1) may also play a role. We used mice with targeted inactivation of the LOX-1 gene to define the role of this receptor in the uptake of oxLDL and in activation of survival pathways. There was no difference in uptake or degradation of 125I-oxLDL in unstimulated macrophages from wild-type and LOX-1 knockout mice and no difference in the rate of clearance of oxLDL from plasma in vivo. However, when expression of LOX-1 was induced with lysophosphatidylcholine, oxLDL uptake and degradation increased 2-fold in wild-type macrophages but did not change in LOX-1 knockout macrophages. Macrophages lacking LOX-1 showed the same stimulation of PKB phosphorylation and enhancement of survival by oxLDL as wild-type cells. These data show that LOX-1 does not alter the uptake of oxLDL in unstimulated macrophages and is not essential for the pro-survival effect of oxLDL in these cells. However, LOX-1 expression is highly inducible by lysophosphatidylcholine and pro-inflammatory cytokines, and if that occurred in macrophages within atheromas, LOX-1 could substantially increase oxLDL uptake by lesion macrophages.

Acid sphingomyelinase is required for lipid Raft TLR4 complex formation

BACKGROUND

Lipid rafts, composed of sphingolipids, are critical to Toll-like receptor 4 (TLR4) assembly during lipopolysaccharide (LPS) exposure as a result of phosphokinase C (PKC)-zeta activation. However, the mechanism responsible for these events remains unknown.

PURPOSE

We determined whether LPS-induced TLR4 assembly and activation are dependent on the sphingolipid metabolite ceramide, produced by acid sphingomyelinase following the initial binding of LPS to CD14.

METHODS

Cultured THP-1 cells were stimulated with LPS, exogenous C(2) ceramide, or both. Selected cells were pretreated with the acid sphingomyelinase inhibitor imipramine or CD14 neutralizing antibody.

RESULTS

Exposure to LPS led to activation of acid sphingomyelinase, production of ceramide, phosphorylation of PKCzeta, and assembly of the TLR4 receptor within lipid rafts. This was followed by activation of the MAPK family of products and the liberation of tumor necrosis factor-alpha. Pretreatment with imipramine or CD14 blockade was associated with attenuation of all of these LPS-induced events. Simultaneous treatment with C(2) ceramide and LPS reversed all the inhibitory effects induced by imipramine, but not those associated with CD14 blockade.

CONCLUSION

Assembly and activation of the TLR4 receptor following LPS binding to CD14 requires the production of ceramide by acid sphingomyelinase.

Lipid rafts in membrane-cytoskeleton interactions and control of cellular biomechanics: actions of oxLDL

Membrane-cytoskeleton coupling is known to play major roles in a plethora of cellular responses, such as cell growth, differentiation, polarization, motility, and others. In this review, the authors discuss the growing amount of evidence indicating that membrane-cytoskeleton interactions are regulated by the lipid composition of the plasma membrane, suggesting that cholesterol-rich membrane domains (lipid rafts), including caveolae, are essential for membrane-cytoskeleton coupling. Several models for raft-cytoskeleton interactions are discussed. Also described is the evidence suggesting that raft-cytoskeleton interactions play key roles in several cytoskeleton-dependent processes, particularly in the regulation of cellular biomechanical properties. To address further the physiological significance of raft-cytoskeleton coupling, the authors focus on the impact of oxidized low density lipoproteins, one of the major cholesterol carriers and proatherogenic factors, on the integrity of lipid rafts/caveolae, and on the organization of the cytoskeleton. Finally, the authors review the recent studies showing that oxLDL and cholesterol depletion have similar impacts on the biomechanical properties of vascular endothelial cells, which in turn affect endothelial angiogenic potential.

Oxidative stress, lipid rafts, and macrophage reprogramming

Oxidant stress, induced under a variety of conditions, is known to lead to the molecular reprogramming of the tissue-fixed macrophage. This reprogramming is associated with an altered response to subsequent inflammatory stimuli, such as lipopolysaccharide (LPS), leading to enhanced liberation of proinflammatory chemokines and cytokines. Due to this altered response, dysregulated immunity ensues, leading to the development of clinical syndromes such as multiple organ dysfunction syndrome (MODS). Although the mechanisms responsible for this altered macrophage activity by oxidant stress remains complex and poorly elucidated, it appears, based on recent research, that early and direct alterations within lipid rafts are responsible. This early and direct interaction with lipid rafts by oxidants leads to the mobilization of annexin VI from lipid raft constructs, leading to the release of calcium. This increased cytosolic concentration of this secondary messenger, in turn, results in the activation of calcium-dependent kinases, leading to further alterations in lipid raft lipids and eventually lipid raft proteins. Due to these lipid raft compositional changes, preassembly of receptor complexes occur, leading to enhanced proinflammatory activation. Within this review, the complexity of oxidant-induced reprogramming within the tissue fixed macrophage as currently understood is explained.

Pathobiology of cigarette smoke-induced chronic obstructive pulmonary disease

Chronic obstructive pulmonary diseases (COPD), comprised of pulmonary emphysema, chronic bronchitis, and structural and inflammatory changes of small airways, is a leading cause of morbidity and mortality in the world. A better understanding of the pathobiology of COPD is critical for the developing of novel therapies, as the majority of patients with the disease have little therapeutic options at the present time. The pathobiology of COPD encompasses multiple injurious processes including inflammation (excessive or inappropriate innate and adaptive immunity), cellular apoptosis, altered cellular and molecular alveolar maintenance program, abnormal cell repair, extracellular matrix destruction (protease and anti-protease imbalance), and oxidative stress (oxidant and antioxidant imbalance). These processes are triggered by urban and rural air pollutants and active and/or passive cigarette smoke and modified by cellular senescence and infection. A series of receptor-mediated signal transduction pathways are activated by reactive oxygen species and tobacco components, resulting in impairment of a variety of cell signaling and cytokine networks, subsequently leading to chronic airway responses with mucus production, airway remodeling, and alveolar destruction. The authors provide an updated insight into the molecular and cellular pathobiology of COPD based on human and/or animal data.

Liquid chromatography with dual parallel mass spectrometry and 31P nuclear magnetic resonance spectroscopy for analysis of sphingomyelin and dihydrosphingomyelin

Liquid chromatography coupled to atmospheric pressure chemical ionization (APCI) and electrospray ionization (ESI) mass spectrometry (MS), in parallel, was used for simultaneous detection of bovine milk sphingolipids (BMS). APCI-MS mass spectra exhibited mostly ceramide-like fragment ions, [Cer-H(2)O+H](+) and [Cer-2H(2)O+H](+), which were used to identify individual molecular species of BMS according to fatty acyl chain length:degree of unsaturation and long-chain base (LCB). ESI-MS was used to confirm the molecular weights of BMS species. Both sphingomyelin (SM) and dihydrosphingomyelin (DSM) molecular species were identified, with DSM species constituting 20% of BMS. Approximately 56 to 58% of DSM species contained a d16:0 LCB, while 34 to 37% contained a d18:0 LCB. Approximately 26 to 30% of SM species contained a d16:1 LCB, while 57 to 60% contained a d18:1 LCB. BMS species contained both odd and even carbon chain lengths. The most abundant DSM species contained a d16:0 LCB with a 22:0, 23:0 or 24:0 fatty acyl chain, while the most abundant SM species contained a d18:1 LCB with a 16:0 or 23:0 fatty acyl chain. (31)P NMR spectroscopy was used to conclusively confirm that DSM is a dietary component in BMS.

Allograft inflammatory factor-1 (AIF-1) is crucial for the survival and pro-inflammatory activity of macrophages

Our previous studies revealed that macrophages played an important role in linking injury, inflammatory and immune response in small-for-size liver transplantation. However, the molecular basis that promoted macrophage activation was not clear. In the present study, we explored the potential role of allograft inflammatory factor-1 (AIF-1) in mediating the survival and pro-inflammatory activity of macrophages in a macrophage cell line. First, the expression of AIF-1 was investigated with the stimulation of pro-inflammatory cytokines and anti-inflammatory treatment. Second, the level of inducible nitric oxide synthase (iNOS) and the survival and migration activity of macrophages were determined with the alterations of AIF-1 expression. Finally, a potential molecule that regulated AIF-1 expression was identified by the proteomic approach. The macrophage cell line expressed a certain level of endogenous AIF-1, which could be enhanced by pro-inflammatory cytokines IL-1beta or tumor necrosis factor-alpha and suppressed by anti-inflammatory drug sodium salicylate. AIF-1 augmentation induced by AIF-1/PCDNA3.1(+) transfection enhanced the levels of iNOS and monocyte chemoattractant protein-1, and promoted the cell migration. On the other hand, suppression of AIF-1 expression by AIF-1/short interference RNA (siRNA) inhibited iNOS production, induced macrophage cell apoptosis and blocked the cell migration. Using two-dimensional electrophoresis, a disintegrin and metalloproteinase domain 3 (ADAM3) was identified after AIF-1/siRNA transfection. Transfection of ADAM3/PCDNA3.1(+) up-regulated the expression of AIF-1 and iNOS, whereas suppression of ADAM3 expression down-regulated AIF-1 and iNOS expression. In conclusion, AIF-1 played an important role in the survival and pro-inflammatory activity of macrophages, and ADAM3 might be an upstream molecule that regulated AIF-1 expression.