A bacterium lipopolysaccharide that elicits Guillain-Barré syndrome has a GM1 ganglioside-like structure

There is a strong association between Guillain-Barré syndrome (GBS) and Penner's serotype 19 (PEN 19) of Campylobacter jejuni. Sera from patients with GBS after C. jejuni infection have autoantibodies to GM1 ganglioside in the acute phase of the illness. Our previous work has suggested that GBS results from an immune response to cross-reactive antigen between lipopolysaccharide (LPS) of the Gram-negative bacterium and membrane components of peripheral nerves. To clarify the pathogenesis of GBS, we have investigated whether GM1-oligosaccharide structure is present in the LPS of C. jejuni (PEN 19) that was isolated from a GBS patient. After extraction of the LPS, the LPS showing the binding activity of cholera toxin, that specifically recognizes the GM1-oligosaccharide was purified by a silica bead column chromatography. Gas-liquid chromatography-mass spectrometric analysis has shown that the purified LPS contained Gal, GalNAc, and NeuAc, which are sugar components of GM1 ganglioside. 1H NMR methods [Carr-Purcell-Meiboom-Gill (CPMG), total correlation spectroscopy (TOCSY), and nuclear Overhauser effect spectroscopy (NOESY)] have revealed that the oligosaccharide structure [Gal beta 1-3 GalNAc beta 1-4(NeuAc alpha 2-3)Gal beta] protrude from the LPS core. This terminal structure [Gal beta 1-3GalNAc beta 1-4(NeuAc alpha 2-3)Gal beta] is identical to the terminal tetrasaccharide of the GM1 ganglioside. This is the first study to demonstrate the existence of molecular mimicry between nerve tissue and the infectious agent that elicits GBS.

Interleukin-10 expression and chemokine regulation during the evolution of murine type II collagen-induced arthritis

In the enclosed study we have examined the expression and contribution of specific chemokines, macrophage inflammatory protein 1 alpha (MIP-1 alpha) and macrophage inflammatory protein 2 (MIP-2), and interleukin 10 (IL-10) during the evolution of type II collagen-induced arthritis (CIA). Detectable levels of chemotactic cytokine protein for MIP-1 alpha and MIP-2 were first observed between days 32 and 36, after initial type II collagen challenge, while increases in IL-10 were found between days 36 and 44. CIA mice passively immunized with antibodies directed against either MIP-1 alpha or MIP-2 demonstrated a delay in the onset of arthritis and a reduction of the severity of arthritis. On the contrary, CIA mice receiving neutralizing anti-IL-10 antibodies demonstrated an acceleration of the onset and an increase in the severity of arthritis. Interestingly, anti-IL-10 treatment increased the expression of MIP-1 alpha and MIP-2, as well as increased myeloperoxidase (MPO) activity and leukocyte infiltration in the inflamed joints. These data suggest that MIP-1 alpha and MIP-2 play a crucial role in the initiation and maintenance, while IL-10 appears to play a regulatory role during the development of experimental arthritis.

Erythromycin modulates IL-8 expression in normal and inflamed human bronchial epithelial cells

Erythromycin (EM) and its 14-member macrolide analogues have attracted attention for its effectiveness in a variety of airway diseases, including diffuse panbronchiolitis (DPB), sinobronchial syndrome, and chronic sinusitis. However, its mechanisms of action remain unelucidated. We evaluated the effects of several antibiotics on IL-8 expression by normal and transformed human bronchial epithelial cells, an important source of this potent chemokine involved in cell recruitment into the airways. EM and clarithromycin (CAM) uniquely suppressed mRNA levels as well as the release of IL-8 at the therapeutic and noncytotoxic concentrations (% inhibition of IL-8 protein release: 25.0 +/- 5.67% and 37.5 +/- 8.99%, respectively, at 10(-6) M). The other antimicrobes, including a 16-member macrolide josamycin, showed no effect. Bronchial epithelial cells from very peripheral airways as well as from main bronchi were obtained from patients with chronic airway inflammatory diseases, and EM and CAM inhibited IL-8 release from these cells. Among five patients who underwent bronchoscopy before and after macrolide treatment, four showed decreased levels of IL-8 expression in airway epithelium as assessed by reverse transcription and polymerase chain reaction. Our findings showed these 14-member macrolides had inhibitory effect on IL-8 expression in human bronchial epithelial cells, and this new mode of action may have relevance to their clinical effectiveness in airway diseases.

Immunopathogenesis of delayed-type hypersensitivity

Cell-mediated immunity is defined as a beneficial host response characterized by an expanded population of specific T cells, which, in the presence of antigens, produce cytokines locally. The activation and recruitment of cells into an area of inflammation is a crucial step in the development of DTH responses. DTH is immunologically a process similar to cell-mediated immunity, involving T cells and cytokines. CD4 T helper (Th) 1 cells, differentiated from naive Th cells by IL-12 and IL-18 produced from macrophages, play a regulatory role in the expression of DTH and activation of macrophages via interferon gamma generated by Th1 and natural killer cells. Macrophages accumulate at the site of DTH and become activated through the CD4 Th1 cell-cytokine-macrophage axis. However, DTH leads to pathologic responses, such as granulomatous inflammation, calcification, caseation necrosis, and cavity formation. Granulomas usually form as a result of the persistence of a nondegradable product or as the result of DTH responses. DTH is also required for host defense against etiologic agents, such as Mycobacterium tuberculosis. The expression of cell-mediated immunity/DTH is a double-edged sword that may contribute to both clearance of the etiologic agent and tissue damage.

Neutrophil chemotaxis, phagocytosis and parameters of reactive oxygen species in human aging: cross-sectional and longitudinal studies

To assess the effect of aging on neutrophil (PMN) functions and the parameters related to reactive oxygen species (ROS), we measured the following in blood samples from 166 asymptomatic aged individuals: PMN activities including chemotaxis, phagocytosis and generation of ROS; the activity of superoxide dismutase (SOD) of blood cell; and serum lipid peroxide levels. Compared with non-aged adults, the older individuals showed markedly attenuated PMN chemotaxis, and slightly elevated serum lipid peroxide levels. Other parameters were not significantly different between the two aged groups. In contrast both to the elderly group as a whole and to the subgroup 65 to 79 years old, the subjects over greater than or equal to 80 years old showed normal PMN chemotaxis and serum lipid peroxide levels, as defined by the young adult control group. Thirty-two subjects who entered the study at ages 69 to 72 years were followed with serial assays for seven years; twenty-one of these subjects died during this observation period. There was a striking and significant difference between the survivors and nonsurvivors with regard to PMN chemotaxis and serum lipid peroxide levels; even when asymptomatic upon initial examination, the nonsurvivors showed diminished PMN chemotaxis and elevated lipid peroxide levels. It seems from both the cross-sectional and longitudinal parts of our study that PMN chemotaxis and serum lipid peroxide levels correlate with survival to advanced age.

Expression and regulation of human neutrophil-derived macrophage inflammatory protein 1 alpha

Neutrophil (polymorphonuclear leukocyte [PMN]) sequestration is one of the histologic hallmarks of an acute inflammatory response. During the natural evolution of an inflammatory response, PMNs are often replaced by mononuclear cells. This shift in the elicitation of specific leukocyte populations usually occurs as the inflammatory lesion enters either the repair/resolution stage or progresses to a chronic inflammation. To elucidate a potential mechanism for the temporal change from predominantly PMN recruitment to the presence of monocytes, we postulated that PMNs could be a rich source of monocyte chemotactic factors. In our studies, we have identified a dose-dependent induction of monocyte chemotactic activity by PMNs treated with lipopolysaccharide (LPS; 1-100 ng/ml). Interestingly, this monocyte chemotactic activity was significantly attenuated in the presence of neutralizing anti-human macrophage inflammatory protein 1 alpha (MIP-1 alpha) antibodies. Moreover, immunolocalization studies demonstrated the expression of MIP-1 alpha by stimulated PMNs. These findings showed that a significant amount of PMN-derived monocyte chemotactic activity was attributable to MIP-1 alpha. Subsequent characterization of MIP-1 alpha steady-state mRNA and antigen expression demonstrated both a dose- and time-dependent production by LPS-treated PMNs. Granulocyte/macrophage colony-stimulating factor (GM-CSF), a potent PMN activator, failed to induce the expression of MIP-1 alpha over a wide range of concentrations. However, PMNs stimulated in the presence of both LPS and GM-CSF resulted in a synergistic expression pattern for MIP-1 alpha. PMNs stimulated in the presence of both GM-CSF and LPS demonstrated an enhanced and prolonged expression for both MIP-1 alpha mRNA and antigen, as compared with LPS alone. Messenger RNA stabilization analyses demonstrated that MIP-1 alpha mRNA isolated from PMNs stimulated in the presence of GM-CSF and LPS had a prolonged mRNA t1/2, as compared with LPS alone. These findings support the notion that PMNs are capable of producing MIP-1 alpha in the presence of LPS, and that GM-CSF can influence this production through prolongation of MIP-1 alpha mRNA t1/2. The production of PMN-derived MIP-1 alpha, in association with the expression of appropriate adhesion molecules at a site of inflammation, may be one of the central events that contributes to the temporal shift from predominantly PMNs to monocytes during the evolution of inflammation.

Erythromycin suppresses nuclear factor-kappaB and activator protein-1 activation in human bronchial epithelial cells

Erythromycin (EM), and related 14-member macrolide antibiotics, has attracted attention for its effectiveness in airway diseases including diffuse panbronchiolitis and sinobronchial syndrome. However, its molecular mechanisms remain unknown. We evaluated the effects of EM on activation of several transcription factors, including nuclear factor-kappaB (NF-kappaB) and activator protein-1 (AP-1) in human bronchial epithelial cell line BET-1A, which are known to regulate the expression of many proinflammatory cytokines and chemokines such as interleukin-8 (IL-8). BET-1A cells were cultured with hormonally defined Ham's F12 medium, and were stimulated by phorbol myristate acetate (PMA). EM suppressed mRNA expression as well as the release of IL-8 at therapeutic and noncytotoxic concentrations (% inhibition of IL-8 protein release: 42.2 +/- 5.5%, at 10(-6) M). Furthermore, electrophoretic mobility shift assays revealed that EM inhibited the activations of NF-kappaB and AP-1 induced by PMA in BET-1A cells. These data indicate that EM has inhibitory effects not only on the mRNA expression and release of IL-8, but also on the activation of transcription factors NF-kappaB and AP-1. Our findings support the concept that the recruitment of neutrophils in airway diseases may be regulated by NF-kappaB and AP-1.

The role of chemokines in inflammatory joint disease

Rheumatoid arthritis (RA) is an autoimmune disease characterized by the elicitation and activation of a number of leukocyte populations within both the synovial space and joint tissue. The recruited leukocytes subsequently play an instrumental role in synovial cell proliferation, pannus formation, and bone erosion. Although it is know that leukocytes are important participants in the evolving joint pathology, the mechanism responsible for the successful elicitation of cells to the joint is not clear. A number of studies have identified an association of specific cytokines, including chemokines, with active arthritis, but longitudinal analyses of cytokine expression and the causal role of these mediators have not been defined. Animal models and cell culture systems have proved useful in identifying the expression of various cytokines during the maintenance of chronic joint inflammation. In addition, animal models have provided important information regarding the kinetic production and contribution of specific mediators to the development of experimental arthritis. These studies provide insights into the potential mechanisms for leukocyte involvement in inflammatory joint disease.

Vascular endothelial growth factor expression and regulation of murine collagen-induced arthritis

We have examined the expression and function of the angiogenic factor, vascular endothelial growth factor (VEGF) during the evolution of type II collagen-induced arthritis (CIA). Biologically active VEGF was expressed along a time course that paralleled the expression of two specific VEGF receptors, Flk-1 and Flt-1, and the progression of joint disease. Moreover, levels of VEGF expression correlated with the degree of neovascularization, as defined by vWF levels, and arthritis severity. Macrophage- and fibroblast-like cells, which infiltrated inflamed sites and were then activated by other inflammatory mediators, are probably important sources of VEGF and may thus regulate angiogenesis during the development of CIA. Administration of anti-VEGF antiserum to CIA mice before the onset of arthritis delayed the onset, reduced the severity, and diminished the vWF content of arthritic joints. By contrast, administration of anti-VEGF antiserum after the onset of the disease had no effect on the progression or ultimate severity of the arthritis. These data suggest that VEGF plays a crucial role during an early stage of arthritis development, affecting both neovascularization and the progression of experimentally induced synovitis.

Synthetic double-stranded RNA induces multiple genes related to inflammation through Toll-like receptor 3 depending on NF-kappaB and/or IRF-3 in airway epithelial cells

BACKGROUND

We hypothesized that synthetic double-stranded (ds)RNA may mimic viral infection and induce expression of genes related to inflammation in airway epithelial cells.

OBJECTIVE

We analysed what gene was up-regulated by synthetic dsRNA poly I : C and then focused this study on the role of Toll-like receptor 3 (TLR3), a receptor of dsRNA and its transcriptional pathway.

METHODS

Airway epithelial cell BEAS-2B and normal human bronchial epithelial cells were cultured in vitro. Expression of targets RNA and protein were analysed by PCR and ELISA. Localization of TLR3 expression in the cells was analysed with flow cytometry. To analyse the role of TLR3 and transcription factors, knockdown of these genes was performed with short interfering RNA (siRNA).

RESULTS

Real-time PCR revealed that poly I : C significantly increased the expression of mRNAs for chemokines IP-10, RANTES, LARC, MIP-1alpha, IL-8, GRO-alpha and ENA-78 and cytokines IL-1beta, GM-CSF, IL-6 and the cell adhesion molecule ICAM-1 in both cell types. Increases in protein levels were also observed. Expression of these genes was significantly inhibited in BEAS-2B cells in which TLR3 expression was knocked down. However, pre-treatment with anti-TLR3 mAb, which interferes with the function of TLR3 expressed on the cell surface, did not inhibit the genes expression and these data were concordant with the results that TLR3 was expressed inside airway epithelial cells. The study of siRNA for NF-kappaB and IRF3 showed that they transduce the signal of poly I : C, but their roles were different in each target gene.

CONCLUSION

TLR3 is expressed inside airway epithelial cells and transduces synthetic dsRNA signals. These signals may increase expression of inflammatory cytokines, chemokines and ICAM-1 through activation of transcription factors NF-kappaB and/or IRF3 in airway epithelial cells.

A novel allelic variant of serum amyloid A, SAA1 gamma: genomic evidence, evolution, frequency, and implication as a risk factor for reactive systemic AA-amyloidosis

Reactive systemic amyloidosis, also called AA-amyloidosis is a rare fatal complication of common chronic inflammatory diseases such as rheumatoid arthritis. It has been proposed that as yet undefined factors other than persistent elevation of serum level of the precursor protein, serum amyloid A (SAA), are also important for the development of AA-amyloidosis. In this work we show genomic evidence for a novel allelic variant of human SAA, SAA1 gamma, which we have recently identified at the protein level. The SAA1 gamma [Ala52(GCC), Ala57(GCG)] differed from SAA1 alpha [Val52(GTC), Ala57(GCG)] only at one base, indicating a single point mutation. On the other hand, SAA1 beta [Ala52(GCC), Val57(GTG)] had not only one, but additional differences in a nearby intron and this portion was identical to the SAA2 gene, suggesting a crossing-over between the SAA1 and SAA2 genes. Furthermore, we report that there was a significant difference in the observed numbers of SAA1 alleles between rheumatoid arthritis patients with AA-amyloidosis and the control population (chi 2(2) = 11.59, p = 0.003) with a higher frequency of gamma-allele in the AA-amyloid group (0.70 vs. 0.37). There was also a notable difference in the distribution of SAA1 genotypes (chi 5(2) = 14.63, p = 0.012) with an increased frequency of gamma/gamma-homozygotes in the AA-amyloid group (0.60 vs. 0.18). Thus our findings indicate that this novel allelic variant may be an important risk factor for the development of AA-amyloidosis.

Roxithromycin inhibits cytokine production by and neutrophil attachment to human bronchial epithelial cells in vitro

We evaluated the effect of roxithromycin on cytokine production and neutrophil attachment to human airway epithelial cells. Roxithromycin suppressed production of interleukin 8 (IL-8), IL-6, and granulocyte-macrophage colony-stimulating factor. It inhibited neutrophil adhesion to epithelial cells. Roxithromycin modulates local recruitment and activation of inflammatory cells, which may have relevance to its efficacy in airway diseases.

Benzene-extracted components are important for the major activity of diesel exhaust particles: effect on interleukin-8 gene expression in human bronchial epithelial cells

Epidemiologic and experimental studies suggest that diesel exhaust particles (DEPs) may be related to increasing respiratory mortality and morbidity. We have shown that DEPs augmented the production of inflammatory cytokines by human airway epithelial cells in vitro. To better understand the mechanisms of their proinflammatory activities, we studied the effects of several components extracted from DEPs on interleukin (IL)-8 expression in human bronchial epithelial cell line BEAS-2B and normal human airway epithelial cells obtained from very peripheral airways by an ultrathin bronchoscope. We used several agents active on signal transduction pathways in cytokine expression, such as the protein kinase C inhibitor staurosporin, antioxidant agents including N-acetyl cysteine (NAC) and pyrrolidine dithiocarbamate (PDTC), and p38 mitogen-activated protein kinase (MAPK) inhibitor SB203580. Benzene-extracted components showed effects mimicking DEPs on IL-8 gene expression, release of several cytokines (IL-8; granulocyte macrophage colony-stimulating factor; and regulated on activation, normal T cells expressed and secreted) and nuclear factor (NF)-kappa B activation. We also found that NAC, PDTC, and SB203580 suppressed the activities of DEPs and their benzene extracts, suggesting the roles of oxidants-mediated NF-kappa B activation and p38MAPK pathways. Finally, benzo[a]pyrene, one of the important compounds included in the benzene component, replicated the activities shown by DEPs.

A simple and quantitative purification of glycosphingolipids and phospholipids by thin-layer chromatography blotting

A new and simple method for purifying glycosphingolipids and phospholipids by using "TLC blotting" was established. Glycosphingolipids separated by two-dimensional thin-layer chromatography (TLC) were made visible with primuline reagent, and then bands were marked with a drawing colored pencil. The glycosphingolipids that separated on the HPTLC plate were transferred by TLC blotting to a polyvinylidene difluoride membrane together with the color marks. The marked areas were excised after which their glycosphingolipids were extracted and monitored by TLC. By this method, 20 glycosphingolipids showing homogeneous bands on a HPTLC plate were isolated from the neutral glycosphingolipid fraction of human meconium. Moreover, 10 kinds of acidic glycosphingolipids were purified as homogeneous bands from the bovine acidic glycosphingolipid fraction. The yields of glycosphingolipids (13 different ones) ranged from 68 to 92%, the mean value being 82.3%. The glycosphingolipids were confirmed to be purified as intact forms by mass spectrometric analysis and chromatographic mobilities on a HPTLC plate. The same procedure could also be used to purify phospholipids.

Cerebrotendinous xanthomatosis: clinical and biochemical evaluation of eight patients and review of the literature

We present the clinical and laboratory findings of 8 patients with cerebrotendinous xanthomatosis. The clinical features consisted of a combination of bilateral Achilles tendon xanthomas, cataracts, low intelligence, pyramidal signs, cerebellar signs, convulsions, peripheral neuropathy, foot deformity, cardiovascular disease or atherosclerosis, EEG abnormality, and increased CSF protein. Increased cholesterol was present in the serum, CSF and red cell membrane of all 8 patients. The bile of one patient with late age onset of the disease showed an attenuated production of bile acids and bile alcohols. Three of the 7 had obstruction and/or marked narrowing of the coronary arteries. Data on 136 patients reported throughout the world are reviewed.

The possible role of interleukin (IL)-12 and interferon-gamma-inducing factor/IL-18 in protection against experimental Mycobacterium leprae infection in mice

Cell-mediated immunity participates in host defense against mycobacterial infection. Both interleukin 12 (IL-12) and interferon-gamma-inducing factor (IGIF/IL-18), produced mainly by macrophages, play a critical role in expression of cell-mediated immunity. To investigate the role of IL-12 and IGIF/IL-18 in vivo, we examined cytokine profile, bacterial growth, and the potential benefit of cytokine therapy in susceptible and resistant mice infected with Mycobacterium leprae. The early expression of IL-12 p40 and IGIF/IL-18 at the site of inoculation was found in resistant mice 3-72 h after the infection, but not in susceptible mice. Both strains of mice did not show expression of IFN-gamma and IL-4. IL-12 administration resulted in a significant reduction of bacterial counts in mice with established M. leprae infection. The results imply that susceptible mice exhibit decreased expression of type 1 helper T (Th1) response without reciprocal increased Th2 response and show responsiveness to exogenous IL-12. IL-12 therapy may be a possible rationale for treatment of M. leprae infection.

Dipolar magnetism in ordered and disordered low-dimensional nanoparticle assemblies

Magnetostatic (dipolar) interactions between nanoparticles promise to open new ways to design nanocrystalline magnetic materials and devices if the collective magnetic properties can be controlled at the nanoparticle level. Magnetic dipolar interactions are sufficiently strong to sustain magnetic order at ambient temperature in assemblies of closely-spaced nanoparticles with magnetic moments of ≥ 100 μ_B. Here we use electron holography with sub-particle resolution to reveal the correlation between particle arrangement and magnetic order in self-assembled 1D and quasi-2D arrangements of 15 nm cobalt nanoparticles. In the initial states, we observe dipolar ferromagnetism, antiferromagnetism and local flux closure, depending on the particle arrangement. Surprisingly, after magnetic saturation, measurements and numerical simulations show that overall ferromagnetic order exists in the present nanoparticle assemblies even when their arrangement is completely disordered. Such direct quantification of the correlation between topological and magnetic order is essential for the technological exploitation of magnetic quasi-2D nanoparticle assemblies.

Expression of vascular endothelial growth factor by synovial fluid neutrophils in rheumatoid arthritis (RA)

Most of the leucocytes infiltrating rheumatoid synovial fluid (SF) are neutrophils capable of producing a variety of inflammatory mediators known to contribute significantly to the disease process during active RA. In the present study, we investigated the contribution made by SF neutrophils to the elevated levels of vascular endothelial growth factor (VEGF) seen in rheumatoid SF. Rheumatoid SF neutrophils were found to contain significantly larger amounts of both VEGF protein and its mRNA than peripheral blood neutrophils from either RA patients or healthy controls. Levels of cell-associated VEGF were well correlated with free VEGF in SF, which was significantly higher than in SF from osteoarthritis patients. Levels of SF neutrophil-associated VEGF also correlated with RA disease activity and cell surface integrin expression. Thus, SF neutrophil-associated VEGF may be considered an indicator of both local and systemic inflammation of RA, contributing to the neovascularization seen during RA synovitis.

Decreased synthesis of glycosphingolipids in cells lacking vimentin intermediate filaments

We are studying defects in glycosphingolipid synthesis in cells lacking vimentin intermediate filaments (vimentin-). Sugars can be incorporated into glycolipids whose ceramide is synthesized either de novo (pathway 1) or from sphingoid bases salvaged from hydrolysis of sphingolipids (pathway 2) and into glycolipids recycling from the endosomal pathway through the Golgi (pathway 3). Vimentin- embryonic fibroblasts, obtained from vimentin-knockout mice, incorporate less sugar into glycolipids than vimentin+ fibroblasts. Using two inhibitors of ceramide synthesis, beta-chloroalanine and fumonisin B1, we found the major defect in synthesis to be in pathway 2 and not in de novo synthesis. We used two additional approaches to analyze the functions of pathways 2 and 3. First, we used exogenous glucosylthioceramide ([14C]C8-Glc-S-Cer), a synthetic, nonhydrolyzable glycosphingolipid, as a precursor for synthesis of larger glycolipids. Vimentin- SW13 cells and embryonic fibroblasts glycosylated [14C]C8-Glc-S-Cer less extensively than their vimentin+ counterparts. Second, we used chloroquine to inhibit the hydrolysis of sphingolipids in endosomes and lysosomes. Chloroquine markedly decreased the incorporation of sugars into glycolipids larger than glucosylceramide. The defect in glycolipid synthesis in vimentin- cells probably results from impaired intracellular transport of glycolipids and sphingoid bases between the endosomal/lysosomal pathway and the Golgi apparatus and endoplasmic reticulum. Intermediate filaments may accomplish this function by contributing to the organization of subcellular organelles and/or by binding proteins that participate in transport processes.

Direct mass spectrometric analysis of glycosphingolipid transferred to a polyvinylidene difluoride membrane by thin-layer chromatography blotting

A simple, rapid method for the analysis of glycosphingolipid that combines "thin-layer chromatography (TLC) blotting" and mass spectrometry is reported. Glycosphingolipids developed by TLC were transferred to a polyvinylidene difluoride membrane by TLC blotting, after which the glycosphingolipid band on the membrane was excised and placed on a mass spectrometer probe tip, and a few microliters of triethanolamine was added as the matrix. The sample was analyzed by secondary ion mass spectrometry. About 1 microgram of glycosphingolipid subjected to TLC can be analyzed. The major advantage of this method is that glycosphingolipid can be analyzed structurally without purification by repeated column chromatography.

Vascular endothelial growth factor expression by activated synovial leukocytes in rheumatoid arthritis: critical involvement of the interaction with synovial fibroblasts

OBJECTIVE

To examine the expression and regulation of the angiogenic factor, vascular endothelial growth factor (VEGF), by fibroblast-like synoviocytes (FLS), monocytes, and polymorphonuclear neutrophils (PMNs) isolated from the synovial fluid (SF) of rheumatoid arthritis (RA) patients.

METHODS

Monocytes or PMNs obtained from RA SF were cocultured with unstimulated, semiconfluent RA FLS. Culture supernatants were assayed for the proliferation and in vitro tube formation of endothelial cells, and for the production of VEGF, by enzyme-linked immunosorbent assay. The expression of VEGF messenger RNA and protein was also determined by reverse transcription-polymerase chain reaction and immunohistochemistry, respectively.

RESULTS

We found that the interaction of inflammatory, activated leukocytes with FLS resulted in synergistic increases in VEGF expression and secretion, which contributed to the proliferation of endothelial cells and to in vitro endothelial tube formation. The induction of VEGF was mediated via specific adhesion molecules, as indicated by the finding that anti-integrin antibodies significantly inhibited VEGF. Furthermore, the levels of VEGF secretion correlated with the expression of cell surface integrin (CD11b and CD18) on both monocytes and PMNs in the SF.

CONCLUSION

VEGF expression within inflamed joints thus appears to be regulated not only by inflammatory cytokines, but also by the physical interaction of activated leukocytes and FLS. Once expressed, VEGF likely plays a crucial role in the neovascularization of the pannus and the progressive joint destruction associated with the synovial inflammation of RA.

Identification of glycosphingolipid receptors for pierisin-1, a guanine-specific ADP-ribosylating toxin from the cabbage butterfly

Pierisin-1, a cytotoxic protein found naturally in the cabbage butterfly, induces apoptosis of mammalian cells. Our recent studies suggest that pierisin-1 consists of an N-terminal ADP-ribosyltransferase domain, and a C-terminal region that binds to receptors on the surfaces of target cells and incorporates the protein into cells. The present study was undertaken to identify receptors for pierisin-1. The cross-linking and cloning experiments suggested that the proteins on cell membrane had no binding ability to pierisin-1. Inhibitory assays of fractionated lipids from human cervical carcinoma HeLa cells, which are highly sensitive to pierisin-1, indicated neutral glycosphingolipids on the cell surface to show receptor activity. Inhibitory assays and TLC immunostaining using anti-pierisin-1 antibodies demonstrated two neutral glycosphingolipids as active components. Analysis of their structures with glycosphingolipid-specific antibodies and negative secondary ion mass spectrometry identified them as globotriaosylceramide (Gb3) and globotetraosylceramide (Gb4). The receptor activities of Gb3 and Gb4 for pierisin-1 were also confirmed with these authentic compounds. Pierisin-1-insensitive mouse melanoma MEB4 cells were found to lack pierisin-1 receptors, including Gb3 and Gb4, but pretreatment of the cells with glycosphingolipid Gb3 or Gb4 enhanced their sensitivity to pierisin-1. Thus, Gb3 and Gb4 were proven to serve as pierisin-1 receptors. The C-terminal region of pierisin-1 consists of possible lectin domains of a ricin B-chain, containing QXW sequences, which are essential for its structural organization. Alteration of QXW by site-directed mutagenesis caused marked reduction of pierisin-1 cytotoxicity. Thus, our results suggest that pierisin-1 binds to Gb3 and Gb4 receptors at the C-terminal region, in a manner similar to ricin, and then exhibits cytotoxicity after incorporation into the cell.

Occurrence of an unusual phospholipid, phosphatidyl-L-threonine, in cultured hippocampal neurons. Exogenous L-serine is required for the synthesis of neuronal phosphatidyl-L-serine and sphingolipids

We have recently reported that L-serine released from astroglial cells supports the survival and neuritogenesis of hippocampal neurons under a serum- and glia-free culture condition (Mitoma, J., Furuya, S., and Hirabayashi, Y. (1998) Neurosci. Res. 30, 195-199). In this study, we show that exogenous L-serine is required for the synthesis of phosphatidyl-L-serine (PS) and sphingolipids in hippocampal neurons. When hippocampal neurons were maintained under an astroglial cell-free condition, the levels of sphingolipids and phosphatidyl-L-serine in the neurons were greatly reduced in the absence of external L-serine or glycine. Instead, a novel phospholipid appeared just ahead of PS on TLC. This novel lipid was determined to be phosphatidyl-L-threonine by TLC blotting/negative secondary ion mass spectrometry and amino acid analysis. Biochemical studies on rat brain microsomes have indicated that phosphatidyl-L-threonine is synthesized by the base exchange enzyme that is involved in PS synthesis with much lower affinity, that is, approximately (1)/(150) of L-serine. Addition of L-serine or glycine to the culture medium restored the synthesis of PS and sphingolipids in the neurons. These observations show that hippocampal neurons require exogenous L-serine for the synthesis of PS and sphingolipids in the absence of astroglial cells and suggested that astroglial cells contribute to neuronal lipid synthesis through the supply of L-serine.