Lipopolysaccharide induces physical proximity between CD14 and toll-like receptor 4 (TLR4) prior to nuclear translocation of NF-kappa B

CD14, a GPI-linked protein, plays a pivotal role in LPS-mediated signaling by potentiating leukocyte adherence, activation, and cytokine production. Recent studies have identified the Toll-like receptor 4 (TLR4) as a membrane cofactor in LPS-mediated transmembrane signaling in cytokine induction, although the mechanism responsible for this cooperation is unknown. Using fluorescence resonance energy transfer (RET) techniques, we demonstrate that LPS triggers a physical association between CD14 and TLR4. Because LPS stimulation upregulates CD14 and TLR4 expression, it was necessary to control for the possibility that these newly expressed molecules were associated with one another independent of LPS stimulation. Although the calcium ionophore A23187 increased the expression of CD14 and TLR4, they did not exhibit energy transfer. However, following A23187 treatment, LPS promoted physical proximity between CD14 and TLR4. Therefore, we suggest that a close interaction between CD14 and TLR4 participates in LPS signaling, leading to nuclear translocation of NF-kappaB.

Squid nerve sphingomyelin containing an unusual sphingoid base

A new methodology has been developed to determine sphingolipid structures by positive-ion fast atom bombardment tandem mass spectrometry (FAB-MS/MS). The method was verified by application to a structurally known glycosphingolipid, and then used in the structural study of an unusual sphingomyelin isolated from squid (Loligo pealei) nerve. Our previous study of this squid sphingomyelin indicated that the major base had a branched C(19) alkyl chain with three double bonds, two of which were conjugated. The positions of the branching as well as the double bonds of this base were unambiguously determined by directly comparing the product ion spectra of the long-chain base ion (LCB(+)) of two ceramides, one derived from squid nerve sphingomyelin and another, glucosylceramide, obtained from starfish spermatozoa. The latter served as the standard because the structure had already been determined by nuclear magnetic resonance (NMR). The precursor ion here was LCB(+), that is, [CH(2) - C(NH(2)) = CHR](+), rather than [M + H](+), where R represents the backbone hydrocarbon chain counting from C-4. The results clearly showed that the squid nerve base is identical to the base derived from starfish (Asterias amurensis), that is, 2-amino-9-methyl-4,8,10-octadecatriene-1,3-diol. This is the first report in which the detailed structure of a branched polyunsaturated sphingoid base was studied by tandem mass spectrometry without derivatization or the aid of NMR. The occurrence of such an unusual sphingoid base in various phyla and tissues suggests the conjugated polyunsaturated branched sphingoid base plays a significant role in animals.

Cephalometric comparisons of craniofacial and upper airway structures in young children with obstructive sleep apnea syndrome

We studied 15 children of preschool age who had obstructive sleep apnea syndrome to evaluate their dentofacial morphology in relation to the pharyngeal airway space. We found that (1) sleep apnea was often associated with mandibular retrognathia, (2) the lower incisors tended to exhibit a retrocline, (3) there were no significant differences in angular and linear measurements in the cranial base between patients with sleep apnea and a control group of 30 nonapneic children, and (4) the apneic children had a narrower epipharyngeal airway space than did the controls. These findings suggest that obstructive sleep apnea is probably caused by both adenoidal hypertrophy and abnormal development of the facial skeleton. We highly recommend cephalometric analysis as a valuable tool for conducting the presurgical evaluation of sleep apnea in children of preschool age.

Toll-like receptors confer responsiveness to lipopolysaccharide from Porphyromonas gingivalis in human gingival fibroblasts

Gingival fibroblasts produce proinflammatory cytokines in response to lipopolysaccharide (LPS) from periodontopathic bacteria. Recently it has become evident that the human homologue of Drosophila Toll can transduce intracellular signaling by LPS stimulation. Toll-like receptors (TLRs) have been identified in myeloid cells; however, their role in nonmyeloid cells such as gingival fibroblasts has not been fully elucidated. Here, we report that human gingival fibroblasts constitutively express TLR2 and TLR4 and that their levels of expression are increased by stimulation with LPS from Porphyromonas gingivalis. Upregulated expression of interleukin-6 gene and protein in fibroblasts stimulated with LPS is inhibited by anti-TLR4 antibody. These findings suggest that TLRs may confer responsiveness to LPS in gingival fibroblasts.

Cutting edge: cell surface expression and lipopolysaccharide signaling via the toll-like receptor 4-MD-2 complex on mouse peritoneal macrophages

The human MD-2 molecule is associated with the extracellular domain of human Toll-like receptor 4 (TLR4) and greatly enhances its LPS signaling. The human TLR4-MD-2 complex thus signals the presence of LPS. Little is known, however, about cell surface expression and LPS signaling of the TLR4-MD-2 complex in vivo. We cloned mouse MD-2 molecularly and established a unique mAb MTS510, which reacted selectively with mouse TLR4-MD-2 but not with TLR4 alone in flow cytometry. Mouse MD-2 expression in TLR4-expressing cells enhanced LPS-induced NF-kappaB activation, which was clearly inhibited by MTS510. Thioglycolate-elicited peritoneal macrophages expressed TLR4-MD-2, which was rapidly down-regulated in the presence of LPS. Moreover, LPS-induced TNF-alpha production by peritoneal macrophages was inhibited by MTS510. Collectively, the TLR4-MD-2 complex is expressed on macrophages in vivo and senses and signals the presence of LPS.

Cutting edge: endotoxin tolerance in mouse peritoneal macrophages correlates with down-regulation of surface toll-like receptor 4 expression

Monocytes/macrophages exposed to LPS show reduced responses to second stimulation with LPS, which is termed LPS tolerance. In this study, we investigated molecular mechanism of LPS tolerance in macrophages. Mouse peritoneal macrophages pre-exposed to LPS exhibited reduced production of inflammatory cytokines in a time- and dose-dependent manner. Activation of neither IL-1 receptor-associated kinase nor NF-kappaB was observed in macrophages that became tolerant by LPS pretreatment, indicating that the proximal event in Toll-like receptor 4 (TLR4)-MyD88-dependent signaling is affected in tolerant macrophages. Although TLR4 mRNA expression significantly decreased within a few hours of LPS pretreatment and returned to the original level at 24 h, the surface TLR4 expression began to decrease within 1 h, with a gradual decrease after that, and remained suppressed over 24 h. A decrease in inflammatory cytokine production in tolerant macrophages well correlates with down-regulation of the surface TLR4 expression, which may explain one of the mechanisms for LPS tolerance.

Regulatory roles for CD14 and phosphatidylinositol in the signaling via toll-like receptor 4-MD-2

The complex consisting of Toll-like receptor 4 (TLR4) and associated MD-2 signals the presence of lipopolysaccharide (LPS) when it is expressed in cell lines. We here show that normal human mononuclear cells express TLR4 and signal LPS via TLR4. CD14 is a molecule that binds to LPS and facilitates its signaling. Little is known, however, about the relationship of CD14 with TLR4-MD-2. We show that CD14 helps TLR4-MD-2 to sense and signal the presence of LPS. CD14 has also been implicated in recognition of apoptotic cells, which leads to phagocytosis without activation. Membrane phospholipids such as phosphatidylserine (PS) or phosphatidylinositol (PtdIns) are thought to serve as the ligands for CD14 in apoptotic cells. We find that PtdIns acts as an LPS antagonist in the signaling via TLR4-MD-2. TLR4-MD-2 seems to discriminate LPS from phospholipids. The signaling via TLR4-MD-2 is thus regulated by CD14 and phospholipid such as PtdIns.

Structural studies of the Maillard reaction products of a protein using ion trap mass spectrometry

The early stage products of the Maillard reaction of egg white lysozyme with D-glucose were studied. Incubation with D-glucose at 50 degrees C for 20 days caused reaction on the Lys and Arg residues of lysozyme as follows: all of the six Lys residues and 10 of the 11 Arg residues in lysozyme reacted with D-glucose; Arg 61 did not react with D-glucose. The Lys residues reacted with D-glucose with 1 mol of dehydration per mole of residue, and the Arg residues reacted with 2 mol of dehydration per mole of residue. The major constituent of the Amadori product with the epsilon-amino group of the Lys residue and the D-glucose was found to be the beta-pyranose form. The structure of the early stage product of the Maillard reaction of a protein with a sugar is the same as that of an amino acid with a sugar.

Mouse toll-like receptor 4.MD-2 complex mediates lipopolysaccharide-mimetic signal transduction by Taxol

Taxol, an antitumor agent derived from a plant, mimics the action of lipopolysaccharide (LPS) in mice but not in humans. Although Taxol is structurally unrelated to LPS, Taxol and LPS are presumed to share a receptor or signaling molecule. The LPS-mimetic activity of Taxol is not observed in LPS-hyporesponsive C3H/HeJ mice, which possess a point mutation in Toll-like receptor 4 (TLR4); therefore, TLR4 appears to be involved in both Taxol and LPS signaling. In addition, TLR4 was recently shown to physically associate with MD-2, a molecule that confers LPS responsiveness on TLR4. To determine whether TLR4.MD-2 complex mediates a Taxol-induced signal, we constructed transformants of the mouse pro-B cell line, Ba/F3, expressing mouse TLR4 alone, both mouse TLR4 and mouse MD-2, and both mouse MD-2 and mouse TLR4 lacking the cytoplasmic portion, and then examined whether Taxol induced NFkappaB activation in these transfectants. Noticeable NFkappaB activation by Taxol was detected in Ba/F3 expressing mouse TLR4 and mouse MD-2 but not in the other transfectants. Coexpression of human TLR4 and human MD-2 did not confer Taxol responsiveness on Ba/F3 cells, suggesting that the TLR4. MD-2 complex is responsible for the species specificity with respect to Taxol responsiveness. Furthermore, Taxol-induced NFkappaB activation via TLR4.MD-2 was blocked by an LPS antagonist that blocks LPS-induced NFkappaB activation via TLR4.MD-2. These results demonstrated that coexpression of mouse TLR4 and mouse MD-2 is required for Taxol responsiveness and that the TLR4.MD-2 complex is the shared molecule in Taxol and LPS signal transduction in mice.

Innate recognition of lipopolysaccharide by Toll-like receptor 4/MD-2 and RP105/MD-1

The Toll family of receptors has been implicated in innate recognition and subsequent activation of defense programs against pathogens such as bacteria and fungi. TLR4, for example, signals the presence of lipopolysaccharide (LPS), a membrane constituent of Gram-negative bacteria. LPS signaling via TLR4 is greatly enhanced by a molecule referred to as MD-2, which is associated with the extracellular domain of TLR4. The TLR4/MD-2 complex, therefore, recognizes LPS. RP105, another member of the Toll family, has a striking similarity to TLR4 in that it is associated with an MD-2-like molecule MD-1. B-cells lacking RP105 are severely impaired in LPS-induced proliferation and antibody production. Studies employing transfectants showed that RP105/MD-1, like MD-2, enhances the LPS signaling via TLR4. RP105/MD-1 thus constitutes an LPS-signaling complex on B-cells. These results suggest that a variety of cell surface molecules regulate LPS recognition/signaling by TLR4.

Observation of hydrogen-deuterium exchange of ubiquitin by direct analysis of electrospray capillary-skimmer dissociation with Fourier transform ion cyclotron resonance mass spectrometry

The structure of ubiquitin, a small cytoplasmic protein with an extended beta-sheet and an alpha-helix surrounding a hydrophobic core, has been characterized by hydrogen-deuterium (H/D) exchange labeling in conjunction with successive analysis by capillary-skimmer dissociation with electrospray ionization-Fourier transform ion cyclotron resonance mass spectrometry (ESI-FTICR MS). The deuterium content of each fragment ion was investigated at different times, and the results indicate that the deuterium incorporation rate into the backbone amides of ubiquitin varied depending on the environment of the amide hydrogens. Amide hydrogens of the N-terminal beta-strand showed quite slow exchange while those of the 35-39 loop were exchanged within a short exposure time to deuterium oxide. It was also possible to evaluate the difference in hydrogen-bond stability. The present data are consistent with the structural features obtained by X-Ray and NMR analyses. Although some of the labeling information might be lost by the scrambling of amide protons during capillary-skimmer dissociation, the results demonstrate that the present method provides useful higher-order structural information for proteins.

MD-2, a molecule that confers lipopolysaccharide responsiveness on Toll-like receptor 4

Toll-like receptor 4 (TLR4) is a mammalian homologue of Drosophila Toll, a leucine-rich repeat molecule that can trigger innate responses against pathogens. The TLR4 gene has recently been shown to be mutated in C3H/HeJ and C57BL/10ScCr mice, both of which are low responders to lipopolysaccharide (LPS). TLR4 may be a long-sought receptor for LPS. However, transfection of TLR4 does not confer LPS responsiveness on a recipient cell line, suggesting a requirement for an additional molecule. Here, we report that a novel molecule, MD-2, is requisite for LPS signaling of TLR4. MD-2 is physically associated with TLR4 on the cell surface and confers responsiveness to LPS. MD-2 is thus a link between TLR4 and LPS signaling. Identification of this new receptor complex has potential implications for understanding host defense, as well as pathophysiologic, mechanisms.

RP105 is associated with MD-1 and transmits an activation signal in human B cells

RP105 was originally discovered as a mouse B-cell surface molecule that transmits an activation signal. The signal leads to resistance against irradiation-induced apoptosis and massive B-cell proliferation. Recently, we found that mouse RP105 is associated with another molecule, MD-1. We have isolated here the human MD-1 cDNA. We show that human MD-1 is also associated with human RP105 and has an important role in cell surface expression of RP105. We also describe a monoclonal antibody (MoAb) that recognizes human RP105. Expression of RP105 is restricted to CD19(+) B cells. Histological studies showed that RP105 is expressed mainly on mature B cells in mantle zones. Germinal center cells are either dull or negative. RP105 is thus a novel human B-cell marker that is preferentially expressed on mature B cells. Moreover, the anti-RP105 MoAb activates B cells, leading to increases in cell size, expression of a costimulatory molecule CD80, and DNA synthesis. The B-cell activation pathway using RP105 is conserved in humans.

[Severe Legionella micdadei pneumonia effectively treated with hemofiltration therapy]

A 42-year-old man was admitted because of fever, productive cough, and progressive dyspnea. Chest x-ray films and computed tomographic scans disclosed dense consolidation in the left and right lung fields. No pathogenic agent was found despite extensive bacteriological examinations. Based on serological findings, the patient was given a diagnosis of acute pneumonia caused by Legionella micdadei. It has been reported that Legionnaire's disease is easily complicated by fatal systemic illnesses such as disseminated intravascular coagulation (DIC) and multiple organ failure. In fact, the patient suffered from severe hypotension and DIC on admission. Treatments against systemic complications were started together with intravenous administration of antibiotics including erythromycin. Continuous intravenous cathecolamin, however, failed to alleviate the patient's shock. We therefore applied endotoxin eliminating therapy using a polymyxin-B-column (PMX) and continuous hemofiltration (CHF). The patient recovered from critical shock immediately after the start of PMX, which together with CHF, alleviated his systemic complications. Although the factors responsible for fatal systemic complications in Legionnare's disease are not well-documented, our findings suggested that some substances removable by PMX and CHF play an important role in pathogenesis.

Collision-induced dissociation spectra obtained by Fourier transform ion cyclotron resonance mass spectrometry using a 13C,15N-doubly depleted protein

Fourier transform ion cyclotron resonance mass spectra of 13C,15N-doubly depleted cystatin A M65L, produced by Escherichia coli grown on 99.9% [12C]glucose and 99.99% [14N]ammonium sulfate, showed salient monoisotopic peaks composed of 12C and 14N. Collision-induced dissociation spectra were obtained by increasing the capillary-skimmer potential for the electrospray ionization and by extending the trapping time in a radio frequency-only hexapole ion guide. Fragment ions in the spectra could be readily assigned to the amino acid sequence, owing to their markedly improved resolution and sensitivity as compared to those with the natural isotopic composition. Detailed analyses of the fragmentation patterns, facilitated by the use of 13C,15N-doubly depleted proteins, enabled the assignment of approximately 180 fragment ions to the sequence, while natural isotopic cystatin A allowed the assignment of approximately 110 fragment ions. Interestingly, no fragmentation was detected between residues 50-61 and 62-67, which are stretches known to be involved in the antiparallel beta-sheet at the center of the protein.

An evaluation of infants' growth in the Kingdom of Nepal

BACKGROUND

The His Majesty's Government/Japan International Cooperation Agency Primary Health Care Project began in April 1993 in collaboration with the Saitama Prefectural Government, for the purpose of improving the health status of the people in model districts of the Kingdom of Nepal. Growth monitoring is one of the basic methods that defines the health and nutritional status of children.

METHODS

Anthropometric indices were measured in 759 children in the Bhaktapur district. We used the World Health Organization prototype growth chart and national growth standard for Japanese children (1990) to analyze the growth data.

RESULTS

We found that the average bodyweight growth curve of children up to 4 months of age followed the 50th percentile reference curve. For children of 5-12 months of age, there was a delay in bodyweight gain and the growth curve reached the 3rd percentile curve. For children more than 1 year old, the growth curve moved below the third percentile curve. Catch-up growth did not occur before the children reached 5 years of age. The main causes of catch-up growth being hampered were chronic undernutrition and inadequate nutritional balance.

CONCLUSIONS

As this was the first opportunity to evaluate infant growth in this district, the first important consequence of the results was to analyze the causes of growth faltering and failure-to-thrive in Nepalese children. Even more important, was the need to give appropriate counseling on improving feeding and other health-related practices, and the most important consequence of all was to instruct Nepalese health workers that utilizing the growth charts is an integral part of health care.

Mouse MD-1, a molecule that is physically associated with RP105 and positively regulates its expression

RP105 is a leucine-rich repeat molecule that is expressed on mouse B cells and transmits a growth-promoting signal. An anti-RP105 Ab precipitated additional molecules as well as RP105. These molecules were found to be a mouse homologue of chicken MD-1. Chicken MD-1 was previously isolated as a v-myb-regulated gene, since its transcription increases rapidly after v-myb induction. Mouse MD-1, when transiently expressed as an epitope-tagged protein, is secreted in culture fluid but tethered to the cell surface by coexpressed RP105. An association of these molecules was confirmed by immunoprecipitation with the anti-RP105 Ab and subsequent probing of the epitope tag on MD-1. Moreover, MD-1 has an effect on the expression of RP105. In transient transfection of RP105, the percentage of RP105-positive cells increased more than twice with the coexpression of MD-1. The stable expression of MD-1 conferred approximately a sevenfold increase in cell surface RP105 on a cell line that expresses RP105 alone. Thus, MD-1 is physically associated with RP105 and is important for efficient cell surface expression.

Structural characterization of mouse monoclonal antibody 13-1 against a porphyrin derivative: identification of a disulfide bond in CDR-H3 of Mab 13-1

The amino acid sequence of a mouse monoclonal antibody Mab13-1, a catalytic antibody against TCPP (meso-tetrakis(4-carboxyphenyl)porphyrin), was confirmed by mass spectrometric (MS) peptide mapping. The amino-terminal sequence of the heavy chain was established by MS/MS analysis of the isolated N-terminal peptide. The presence of a unique disulfide bond between Cys93H and Cys102H was identified by MS peptide mapping and sequence analysis of an S-S containing peptide. Positions of other disulfide bonds were identified to be conserved. The non-conserved disulfide bridge was found to be resistant as other intra-chain disulfide bonds against reduction under non-denaturing condition, and to be buried inside the molecule. This extra disulfide bond is expected to support antigen-binding by restricting the flexibility of CDR-H3 loop, and it might be favorable for the recognition of a plane antigen, a porphyrin derivative.

[Two cases of acetaminophen-induced pneumonitis]

This paper deals with two patients with acetaminophen-induced pneumonitis. A 64-year-old woman suffered from mastitis while being treated by corticosteroid therapy for phemphigoid. She was administered antibiotics and acetaminophen. However, her fever continued and she subsequently developed dyspnea and interstitial pneumonia. The other patient, a 70-year-old woman, was treated with corticosteroid for lower motor neuron disease. Anti-GM1-IgM antibodies were positive in her serum. She developed wet cough and mild fever. During treatment with antibiotics and acetaminophen, her illness was complicated by dyspnea and interstital pneumonia. As a result of histological findings of transbronchial lung biopsy specimens showing interstitial infiltration of mononuclear cells, as well as clinical courses in which cessation of acetaminophen directly lead to the improvement of interstitial pneumonia, both patients were diagnosed to have acetaminophen-induced pneumonitis. The peumonitis responded well to steroid therapy. In vitro culture of peripheral lymphocytes showed stimulated proliferation by acetaminophen in both patients. These findings suggest that allergic mechanism was involved in the pathogenesis of the pneumonitis. Underlying immunological disorders may have enhanced the occurrence. Although acetaminophen is one of the most popular drugs because of a very low incidence of side effects, this drug should be applied carefully, especially with patients who have such immunological disorders.

Characterization of the structural difference between active and inactive forms of the Ras protein by chemical modification followed by mass spectrometric peptide mapping

Ras is one of the guanosine triphosphate (GTP) binding proteins that plays a significant role in signaling events of cell growth and differentiation. It can exist in two states: guanosine diphosphate (GDP)-bound from (Ras.GDP; inactive) and GTP-bound form (Ras.GTP; active). This paper discusses the difference in tertiary structure between the active and inactive forms using the combination of chemical modification and mass spectrometry. This difference can be clearly recognized in the presence of a target protein. Raf-1 RBD (Raf-1 Ras-binding domain), as differing glycinamidation of carboxyl groups. It was possible to observe the difference between these two states using several hundred picomoles of sample. While it is true that it is difficult to obtain the whole picture of a protein by the combination of chemical modification and mass spectrometry, it is a promising approach for the characterization of surface structure using very small amounts of sample.

[Usefulness of enhanced computed tomography in the diagnosis of pulmonary thromboembolism]

Pulmonary thromboembolism (PTE) was diagnosed in 22 patients at Saga Medical School between 1981 and 1994. Enhanced computed tomography (CT) was done in 8 patients, and filling defects in the central pulmonary artery were identified in 6. Parenchymal shadows (wedge shaped shadows, subpleural consolidation, or nodular shadow's) were noted in 5. When enhanced CT was done during acute severe respiratory failure in 3 patients, pulmonary artery filling defects were found in all. These findings suggest that enhanced CT is useful as a diagnostic tool for acute PTE with respiratory failure. Electron beam CT may be a sensitive and specific means of diagnosing PTE because it can be done quickly and without breath-holding. We conclude that enhanced CT should be used as the first diagnostic procedure in patients with severe respiratory failure who may have PTE.

[A coagulation of fibrinolytic study in children with nephrotic syndrome: evaluation of hypercoagulability by measuring with plasmin- alpha 2 plasmin inhibitor complex and FDP D-dimer]

Increased plasma plasmin-alpha 2 plasmin inhibitor complex (PIC) and FDP D-dimer (D-dimer) reflect in vivo activation of the coagulation and fibrinolytic systems. We measured plasma PIC, D-dimer and other coagulation and fibrinolytic parameters in 42 children with nephrotic syndrome. Higher levels of both plasma PIC (0.67 +/- 0.48 micrograms/ml, P < 0.01) and D-dimer (154 +/- 105 ng/ml, P < 0.001) were observed at the active stage of nephrotic syndrome, compared to the remission stage (0.43 +/- 0.18 micrograms/ml, 72 +/- 48 ng/ml, respectively). In addition, plasma D-dimer correlated significantly with serum albumin, urinary protein, plasma fibrinogen, aPTT, and plasma antithrombin III activity. Although no thromboembolic complication was diagnosed clinically in the study period, increased plasma PIC or D-dimer may reflect a hypercoagulable state or subclinical thrombosis in nephrotic syndrome.

Characterization of mouse switch variant antibodies by matrix-assisted laser desorption ionization mass spectrometry and electrospray ionization mass spectrometry

The amino acid sequences of mouse monoclonal antibodies have been characterized completely by mass spectrometry. Antibodies used in the present study were derived from mouse switch variant cell lines that produce four kinds of immunoglobulin Gs (IgGs). The amino acid sequences of these antibodies had not been estimated from the corresponding DNA sequence, so the sequences of IgGs derived from other strains were used as references in this study. Intra- and interchain disulfide bonds of the IgGs were reduced and carboxymethylated and the products were subjected to proteolytic digestion. The existence of N-linked oligosaccharides also was taken into account. The capabilities and limitations of matrix-assisted laser desorption ionization-time-of-flight mass spectrometry and capillary liquid chromatography-electrospray ionization mass spectrometry are discussed in the structural characterization of the antibodies. Based on our results, allotypes of the antibodies examined are discussed. This study shows that amino acid sequences of proteins, such as IgG, can be investigated without information about the corresponding DNA sequence if appropriate reference sequences derived from other strains can be used.