Establishment of a human cell line (Mono Mac 6) with characteristics of mature monocytes

The 5-lipoxygenase promoter is regulated by DNA methylation

5-lipoxygenase (5-LO), the key enzyme in leukotriene biosynthesis, is expressed in a tissue- and cell differentiation-specific manner. The 5-LO core promoter required for basal promoter activity has a unique (G+C)-rich sequence that contains five tandem Sp1 consensus sequences. The mechanisms involved in the regulation of cell type-specific 5-LO expression are unknown. Here we show that 5-LO expression is regulated by DNA methylation. Treatment of the 5-LO-negative cell lines U937 and HL-60TB with the demethylating agent 5-aza-2'-deoxycytidine (AdC) up-regulated expression of 5-LO primary transcripts and mature mRNA in a similar fashion, indicating that AdC stimulates 5-LO gene transcription. Analysis of the methylation status of the 5-LO promoter revealed that the core promoter region was methylated in U937 and HL-60TB cells, whereas it was unmethylated in the 5-LO-positive parent HL-60 cell line. Reporter gene assays with 5-LO promoter constructs gave up to 68- and 655-fold repression of 5-LO promoter activity in HeLa and Mono Mac 6 cells by methylation. 1,25-dihydroxyvitamin D(3) and transforming growth factor-beta (TGFbeta), potent inducers of the 5-LO pathway in myeloid cell lines, increased 5-LO RNA expression in HL-60TB and U937 cells, but co-treatment with AdC was required to achieve 5-LO expression levels in HL-60TB cells that were comparable with wild-type HL-60 cells. In reporter gene assays, 1,25-dihydroxyvitamin D(3) and TGFbeta were unable to induce promoter activity when the 5-LO promoter constructs were methylated, which suggests that 5-LO promoter demethylation is a prerequisite for the high level induction of 5-LO gene expression by 1,25-dihydroxyvitamin D(3) and TGFbeta and that the effects of both agents on 5-LO mRNA expression are not related to DNA methylation.

Intramacrophage passage of Mycobacterium tuberculosis and M. avium complex alters the drug susceptibilities of the organisms as determined by intracellular susceptibility testing using macrophages and type II alveolar epithelial cells

Mycobacterium tuberculosis and M. avium complex strains given intramacrophage passage (I-type) were compared with those cultured in a liquid medium (E-type) for their drug susceptibilities when they were replicating in Mono-Mac-6 macrophages or A-549 cells. Their intracellular susceptibilities to rifalazil, clarithromycin, and levofloxacin were decreased more in I-type organisms than in E-type organisms, except that their rifalazil susceptibility inside A-549 cells was markedly increased in I-type organisms.

Expression of HIF-1alpha by human macrophages: implications for the use of macrophages in hypoxia-regulated cancer gene therapy

Large numbers of monocytes extravasate from the blood into human tumours, where they differentiate into macrophages. In both breast and prostate carcinomas, these cells accumulate in areas of low oxygen tension (hypoxia), where they respond to hypoxia with the up-regulation of one or more hypoxia-inducible factors (HIFs). These then accumulate in the nucleus and bind to short DNA sequences called hypoxia-response elements (HREs) near or in such oxygen-sensitive genes as that encoding the pro-angiogenic factor vascular endothelial growth factor (VEGF). This stimulates gene expression and could explain why, in part, macrophages express abundant VEGF only in avascular, hypoxic areas of breast carcinomas. It also suggests that macrophages could be used to deliver HRE-regulated therapeutic genes specifically to hypoxic tumour areas. A recent study suggested that hypoxic macrophages accumulate HIF-2 rather than HIF-1, prompting the search for HRE constructs that optimally bind HIF-2 for use in macrophage-based gene therapy protocols. However, the present study shows that human macrophages accumulate higher levels of HIF-1 than HIF-2 when exposed to tumour-specific levels of hypoxia in vitro; that macrophages in human tumours express abundant HIF-1; and that expression from HRE-driven reporter constructs in the human macrophage-like cell line MonoMac 6 correlates more closely with HIF-1 than with HIF-2 up-regulation under hypoxia. Taken together, these findings suggest that HIF-1 may be the major hypoxia-inducible transcription factor in macrophages and that HIF-1-regulated constructs are likely to be effective in macrophage delivery of hypoxia-regulated gene therapy to human tumours.

Detection of p53 gene mutations by single strand conformational polymorphism (SSCP) in human acute myeloid leukemia-derived cell lines

We have identified new mutations in the p53 gene in 3/11 growth factor-independent and in 2/8 growth factor-dependent human acute myeloid leukemia (AML)-derived cell lines by single-strand conformational polymorphism (SSCP) and sequencing analysis. MEG-01 had a triplet deletion at codon 304; F-36P, NB-4 and MV4-11 showed point mutations at codon 344. F-36P had a second point mutation at codon 270 and NB-4 additionally at codon 319. M-MOK had a nucleotide substitution at codon 191. The frequency of p53 mutations in the cytokine-independent cell lines was comparable to that in the cytokine-dependent lines. These results suggest that loss of Wild type (wt) p53 is not the decisive event causing tumor cells to proliferate in vitro without externally added growth factors.

Yersinia enterocolitica evasion of the host innate immune response by V antigen-induced IL-10 production of macrophages is abrogated in IL-10-deficient mice

The virulence-associated V Ag (LcrV) of pathogenic Yersinia species is part of the translocation apparatus, required to deliver antihost effector proteins (Yersinia outer proteins) into host cells. An orthologous protein (denoted as PcrV) has also been identified in the ExoS regulon of Pseudomonas aeruginosa. Additionally, it is known that LcrV is released by yersiniae into the environment and that LcrV causes an immunosuppressive effect when injected into mice. In this study, we demonstrate for the first time that rLcrV, but not PcrV, is capable of suppressing TNF-alpha production in zymosan A-stimulated mouse macrophages and the human monocytic Mono-Mac-6 cell line. The underlying mechanism of TNF-alpha suppression could be assigned to LcrV-mediated IL (IL)-10 production, because 1) LcrV induces IL-10 release in macrophages, 2) anti-IL-10 Ab treatment completely abrogated TNF-alpha suppression, and 3) TNF-alpha suppression was absent in LcrV-treated macrophages of IL-10-deficient (IL-10-/-) mice. The relevance of LcrV-mediated immunosuppression for the pathogenicity of yersiniae became evident by experimental infection of mice; in contrast to wild-type mice, IL-10-/- mice were highly resistant against Yersinia infection, as shown by lower bacterial load in spleen and liver, absent abscess formation in these organs, and survival.

Single chain antibodies specific for fatty acids derived from a semi-synthetic phage display library

The biological activities of many acylated molecules are lipid dependent. Lipids, however, are poorly immunogenic or non-immunogenic. We employed a phage display semi-synthetic human antibody library to isolate anti-lipid antibodies. Selection was done against methyl palmitate, a 16 carbon aliphatic chain, and a major component of bacterial glycolipids and lipoproteins in animal cells. The selected single chain variable fragment (scFv) bound specifically to a 16 carbon aliphatic chain and to a lesser extent to a 14 or 18 carbon aliphatic chain and poorly to either 12, 22 or 8 carbon aliphatic chains. Furthermore, the scFv prevented micelle formation of lipoteichoic acid from Gram-positive bacteria; inhibited lipopolysaccharide-induced tumor necrosis factor alpha release in mononuclear cells; bound to hydrophobic bacterial surfaces, especially those of Gram-positive bacteria, and bound to Lck, a mammalian palmitated lipoprotein. Our data suggest that the phage antibody library can be successfully employed to obtain human anti-aliphatic scFv human antibody fragment with potential therapeutic applications in neutralizing the deleterious effects of bacterial toxins as well as in structure--function analysis of lipoproteins in animal cells.

Alpha-lipoic acid modulates NF-kappaB activity in human monocytic cells by direct interaction with DNA

The constitutive activity of the redox-sensitive transcription factor, NF-kappaB, which regulates the production of many inflammatory cytokines and adhesion molecules, appears to be up-regulated in an age-associated manner and it is thought this might contribute to the increased incidence of chronic inflammatory conditions observed with increasing age. As some antioxidants have demonstrated protective effects against rheumatoid arthritis, we are investigating the effects of vitamin E, vitamin C and alpha-lipoic acid (ALA) on NF-kappaB activity and on the expression of intracellular adhesion molecule (ICAM)-1. MonoMac6 cells (a human monocytic cell line) stimulated with tumour necrosis factor-alpha (TNF-alpha) were treated with antioxidants at physiological achievable levels and ICAM-1 mRNA levels investigated. Both vitamin E and vitamin C had no effect on ICAM-1 expression at the doses used, but ALA reduced the TNF-alpha-stimulated ICAM-1 expression in a dose-dependent manner, to levels observed in unstimulated cells. Alpha-lipoic acid also reduced NF-kappaB activity in these cells in a dose-dependent manner. Addition of ALA to the binding reaction of nuclear extract with DNA prior to gel-shift analysis showed that it caused inhibition at this level. These initial results suggest that antioxidant modulation of monocyte activity might have potential benefits in inhibiting the dysregulated activity of redox-sensitive transcription factors that occurs with increasing age.

Combined modulation of the mesangial machinery for monocyte recruitment by inhibition of NF-kappaB

The activation of nuclear factor-kappaB (NF-kappaB) is required for the induction of many of the adhesion molecules and chemokines involved in the inflammatory leukocyte recruitment to the kidney. Here we studied the effects of NF-kappaB inhibition on the machinery crucial for monocyte infiltration of the glomerulus during inflammation. In mesangial cells (MC), the protease inhibitors MG-132 and N-alpha-tosyl-L-lysine chloromethyl ketone or adenoviral overexpression of IkappaB-alpha prevented the complete IkappaB-alpha degradation following tumor necrosis factor-alpha (TNF-alpha) stimulation. This resulted in a marked inhibition of TNF-alpha-induced expression of mRNA and protein for the immunoglobulin molecules intracellular adhesion molecule-1 and vascular cell adhesion molecule-1 and the chemokines growth-related oncogene-alpha, monocyte chemoattractant protein-1, interleukin-8, or fractalkine in MC. Finally, the inhibition of IkappaB-alpha degradation or IkappaB-alpha overexpression suppressed the chemokine-induced transendothelial monocyte chemotaxis toward MC and the chemokine-triggered firm adhesion of monocytic cells to MC. The inhibition of NF-kappaB by pharmacological intervention or gene transfer may present a multimodal approach to control the machinery propagating inflammatory recruitment of monocytes during glomerular disease.

Interaction of AP-1 with a cluster of NF-kappa B binding elements in the human TNF promoter region

Transcriptional activation of the human TNF gene involves multiple regulatory elements whose functional properties vary between stimuli and cell types. Here we have used a COS-7 expression system to dissect the transactivating potential of NF-kappa B binding sites in the human TNF promoter region from other regulatory influences. In this model, NF-kappa B acts largely through a dense cluster of three binding sites located 600 nt upstream of the transcription start site. We show that the transcriptional activity of this complex is highly sensitive to the p65:p50 ratio that is expressed. We demonstrate that the AP-1 complex c-Jun/Fra2 is capable of binding to this region and that this inhibits the transactivating effects of NF-kappa B. These results are suggestive of a complex regulatory element that mediates fine control rather than acting as a simple on-off switch for TNF gene expression.

A common single nucleotide polymorphism in the CD14 promoter decreases the affinity of Sp protein binding and enhances transcriptional activity

CD14 is a pattern recognition receptor that plays a central role in innate immunity through recognition of bacterial lipoglycans, primarily LPS. Recently, our group has identified a common single nucleotide polymorphism, -159C-->T, in the CD14 proximal promoter. Homozygous carriers of the T allele have a significant increase in soluble CD14, but a decreased total serum IgE. This epidemiologic evidence led us to investigate the molecular basis for the effects of CD14/-159C-->T on CD14 regulation in monocytes and hepatocytes, the two major cell types known to express this gene in vivo. EMSA analysis showed that the T allele results in decreased affinity of DNA/protein interactions at a GC box that contains a binding site for Sp1, Sp2, and Sp3 transcription factors. In reporter assays, the transcriptional activity of the T allele was increased in monocytic Mono Mac 6 cells, which express low levels of Sp3, a member of the Sp family with inhibitory potential relative to activating Sp1 and Sp2. By contrast, both alleles were transcribed equivalently in Sp3-rich hepatocytic HepG2 cells. Our data indicate that the interplay between CD14 promoter affinity and the [Sp3]:[Sp1 + Sp2] ratio plays a critical mechanistic role in regulating transcription of the two CD14 alleles. Variation in a key gene of innate immunity may be important for the pathogenesis of allergy and inflammatory disease through gene-by-gene and/or gene-by-environment interactions.

The chemokine KC, but not monocyte chemoattractant protein-1, triggers monocyte arrest on early atherosclerotic endothelium

In a reconstituted flow chamber system, preincubation with chemokines can trigger the arrest of rolling monocytes, suggesting that this interaction could help recruit these cells to early atherosclerotic lesions. To date, however, the contribution of endothelium-derived chemokines found in these lesion to monocyte arrests has not been investigated. The endothelium of lesion-prone carotid arteries from apolipoprotein E-deficient (ApoE(-/-)) mice, but not control mice, presents the chemokines KC (mouse GRO-alpha) and JE (mouse monocyte chemoattractant protein-1 [MCP-1]). Arrest of a monocytic cell line or mouse blood monocytes perfused through carotid arteries of ApoE(-/-) mice was reduced by treating with either pertussis toxin, an antagonist of CXCR2, or an antibody to KC, but this process was insensitive to agents that blocked CCR-2 or JE. Conversely, monocyte accumulation more than doubled upon pre-perfusion of the carotid artery with KC but not with mouse MCP-1. Blockade of alpha(4)beta(1) integrin (VLA-4) or vascular cell adhesion molecule-1, but not CD18 or intercellular adhesion molecule-1, almost completely inhibited the arrest of monocytes. We conclude that when presented by early atherosclerotic lesions, KC but not murine MCP-1 triggers VLA-4-dependent monocyte recruitment.

Survival of Chlamydia pneumoniae-infected Mono Mac 6 cells is dependent on NF-kappaB binding activity

The respiratory tract pathogen Chlamydia pneumoniae has been associated with atherosclerosis. Monocytes are supposed to serve as a vehicle for systemic dissemination of intracellular C. pneumoniae from the lung to the artery vessel wall. We were therefore interested in pathogen-induced cellular events associated with NF-kappaB, a crucial transcription factor for both inflammatory cytokines and antiapoptotic molecules. In this study we demonstrate by electrophoretic mobility shift assay that C. pneumoniae infection of the human monocytic cell line Mono Mac 6 induces activation of NF-kappaB over 48 h, with a maximum level at 1 h postinfection. As shown by supershift assay, the activated NF-kappaB complex consists of the subunits RelA (p65) and NF-kappaB1 (p50). Apoptotic host cells were not detected during the early stages of the infection when maximal activation of NF-kappaB was detected. Pretreatment of Mono Mac 6 with the antioxidant and NF-kappaB inhibitor PDTC (pyrrolidine dithiocarbamate) induced activation of caspase-3 and led to apoptotic cell death. The C. pneumoniae-induced activation of the NF-kappaB complex was reduced by PDTC, which in parallel resulted in an increased apoptosis, as quantified by annexin V labeling and terminal deoxynucleotidyltransferase-mediated dUTP-biotin nick end labeling reaction. In the complete absence of activated NF-kappaB, when Mono Mac 6 cells were pretreated with the more potent NF-kappaB inhibitors MG-132 and parthenolide a C. pneumoniae-mediated rescue of cells from induced apoptosis could not be achieved. Our results indicate that activation of NF-kappaB in C. pneumoniae-infected Mono Mac 6 cells is associated with protection of Mono Mac 6 cells against apoptosis and might thereby contribute to systemic spread of the pathogen.

The inhibitory effect of the autoantigen La on in vitro 3' processing of mammalian precursor tRNAs

Mammalian tRNA 3' processing endoribonuclease (3' tRNase) can remove a 3' trailer from various precursor (pre)-tRNAs. We investigated what effect the autoantigen La has on 3' processing, since the La protein is known to bind to a 3'-terminal uridine tract of pre-tRNAs. We tested sixteen different pre-tRNA(Arg) substrates containing various 3' trailers with or without a 5' leader sequence for in vitro processing by pig 3' tRNase, and for gel-retardation in the presence or absence of human La protein. The R-TUUU series consists of four pre-tRNAs containing 6, 8, 11 and 15 nt 3' trailers ending with UUU and no 5' leader, while the R-TAGC series consists of the same four pre-tRNAs as R-TUUU except that the terminal sequence is AGC. The R-6LTUUU and R-6LTAGC series are derived from R-TUUU and R-TAGC, respectively, by adding a 6 nt 5' leader. La differentially inhibited their processing and bound to the pre-tRNAs; the 50 % inhibitory concentrations for the R-TUUU, R-TAGC, R-6LTUUU, and R-6LTAGC series were 82 to >850, >850, 2 to 292 and 573 to 785 nM, respectively, and the dissociation constants were 10 to 840, >850, 3 to 203 and 155 to 520 nM, respectively. These results indicate that both the terminal sequence UUU and the 5' leader contribute to more severe inhibition of 3' processing via tighter interaction with La. With respect to the R-TUUU and R-6LTUUU series, on the whole, the La inhibition was enhanced as the 3' trailer lengths decreased. Taken together, our results suggest that the La protein sterically hinders 3' tRNase from binding a pre-tRNA molecule probably near the cleavage site.

Modification of lipid A biosynthesis in Neisseria meningitidis lpxL mutants: influence on lipopolysaccharide structure, toxicity, and adjuvant activity

Two genes homologous to lpxL and lpxM from Escherichia coli and other gram-negative bacteria, which are involved in lipid A acyloxyacylation, were identified in Neisseria meningitidis strain H44/76 and insertionally inactivated. Analysis by tandem mass spectrometry showed that one of the resulting mutants, termed lpxL1, makes lipopolysaccharide (LPS) with penta- instead of hexa-acylated lipid A, in which the secondary lauroyl chain is specifically missing from the nonreducing end of the GlcN disaccharide. Insertional inactivation of the other (lpxL2) gene was not possible in wild-type strain H44/76 expressing full-length immunotype L3 lipopolysaccharide (LPS) but could be readily achieved in a galE mutant expressing a truncated oligosaccharide chain. Structural analysis of lpxL2 mutant lipid A showed a major tetra-acylated species lacking both secondary lauroyl chains and a minor penta-acylated species. The lpxL1 mutant LPS has retained adjuvant activity similar to wild-type meningococcal LPS when used for immunization of mice in combination with LPS-deficient outer membrane complexes from N. meningitidis but has reduced toxicity as measured in a tumor necrosis factor alpha induction assay with whole bacteria. In contrast, both adjuvant activity and toxicity of the lpxL2 mutant LPS are strongly reduced. As the combination of reduced toxicity and retained adjuvant activity has not been reported before for either lpxL or lpxM mutants from other bacterial species, our results demonstrate that modification of meningococcal lipid A biosynthesis can lead to novel LPS species more suitable for inclusion in human vaccines.

Neuronal localization of the TNFalpha converting enzyme (TACE) in brain tissue and its correlation to amyloid plaques

The tumor necrosis factor (TNF)-alpha converting enzyme (TACE) can cleave the cell-surface ectodomain of the amyloid-beta precursor protein (APP), thus decreasing the generation of amyloid-beta (Abeta) by cultured non-neuronal cells. While the amyloidogenic processing of APP in neurons is linked to the pathogenesis of Alzheimer's disease (AD), the expression of TACE in neurons has not yet been examined. Thus, we assessed TACE expression in a series of neuronal and non-neuronal cell types by Western blots. We found that TACE was present in neurons and was only faintly detectable in lysates of astrocytes, oligodendrocytes, and microglial cells. Immunohistochemical analysis was used to determine the cellular localization of TACE in the human brain, and its expression was detected in distinct neuronal populations, including pyramidal neurons of the cerebral cortex and granular cell layer neurons in the hippocampus. Very low levels of TACE were seen in the cerebellum, with Purkinje cells at the granular-molecular boundary staining faintly. Because TACE was localized predominantly in areas of the brain that are affected by amyloid plaques in AD, we examined its expression in a series of AD brains. We found that AD and control brains showed similar levels of TACE staining, as well as similar patterns of TACE expression. By double labeling for Abeta plaques and TACE, we found that TACE-positive neurons often colocalized with amyloid plaques in AD brains. These observations support a neuronal role for TACE and suggest a mechanism for its involvement in AD pathogenesis as an antagonist of Abeta formation.

Characterisation of PAUSE-1, a powerful silencer in the human plasminogen activator inhibitor type 2 gene promoter

Plasminogen activator inhibitor type 2 (PAI-2) is a serine protease inhibitor traditionally regarded as a regulator of fibrinolysis and extracellular matrix degradation. More recently, PAI-2 has been implicated in diverse processes such as keratinocyte differentiation, cell death and viral pathogenesis. The PAI-2 promoter tightly regulates PAI-2 gene expression in a cell-specific manner and this control is mediated, in part, by the upstream silencer element, PAUSE-1. Here we have defined PAUSE-1 and investigated its activity as a silencer. A series of mutations were generated within the PAUSE-1 element and analysed for transcription factor binding and transcriptional silencing activity. These studies have defined the minimal functional PAUSE-1 element as TCTN(x)AGAN(3)T(4), where x = 0, 2 or 4. Examination of related elements present in other promoters, such as the human IFNbeta promoter, suggests that PAUSE-1 is a member of a family of universal silencers with the consensus sequence TCTN(x)AGA. UV crosslinking analyses determined that the PAUSE-1 binding protein was approximately 67 kDa. Insertion of PAUSE-1 into the heterologous (SV40) or the minimal PAI-2 promoters silenced transcription by 2.5-fold. These data show that PAUSE-1 acts as a powerful silencer of PAI-2 gene transcription and is likely to be important in the silencing of other genes as well.

Induction of iNOS in human monocytes infected with different Legionella species

The contribution of nitric oxide (NO) radicals to the suppression of intracellular replication of Legionella has been well established in rodents but remained questionable in humans. Considering the fact that human monocytes do not exhibit a high-output NO production, we used sensitive methods such as detection of inducible NO synthase (iNOS) mRNA by reverse transcription-PCR and demonstration of iNOS protein expression by means of flow cytometry and Western blot to compare the levels of iNOS induced by Legionella species which, in accordance to their human prevalence, show different multiplication rates within human monocytic cells. The expression of iNOS in Mono Mac 6 (MM6) cells showed an only moderate inverse correlation to the intracellular replication rate of a given Legionella species in the protein expression assays. However, stimulation of host cells with 1,25-dihydroxyvitamin D(3) to enhance NO production and inhibition of NO production by treatment of host cells with N(G)-methyl-L-arginine were not able to modify the intracellular multiplication of legionellae within MM6 cells. Therefore, NO production does not seem to play a crucial role for the restriction of intracellular replication of Legionella bacteria within human monocytic cells. Rodent models in investigations which are supposed to clarify the involvement of NO radicals in defense mechanisms against Legionella infections in humans are of doubtful significance.

Isolation, structural, and functional characterization of an apoptosis-inducing L-amino acid oxidase from leaf-nosed viper (Eristocophis macmahoni) snake venom

The enzyme L-amino acid oxidase (LAO) from the leaf-nosed viper (Eristocophis macmahoni) snake venom was purified to homogeneity in a single step using high performance liquid chromatography on a Nucleosil 7C18 reverse phase column. The molecular mass of the purified enzyme was 58734.0 Da, as determined by matrix-assisted laser desorption/ionization mass spectrometry. The N-terminal amino acid sequence (ADDKNPLEEAFREADYEVFLEIAKNGL) and the chemical composition of the purified LNV-LAO shows close structural homology with other L-amino acid oxidases isolated from different snake venoms. The secondary structural contents analysis of LAO, established by means of circular dichroism, revealed ca. 49% alpha-helix, 19% beta-sheet, 10% beta-turn, and 22% random coil structure. The purified LNV-LAO not only retained its specific enzymatic activity (73.46 U/mg), determined against L-leucine as a substrate, but also exhibited potent haemolytic (1-10 microg/ml), edema- (MED 4.8 microg/ml) and human platelet aggregation-inducing (ED50 33 microg/ml) properties. Unlike other haemorrhagic snake venom L-amino acid oxidases, the LNV-LAO does not produce haemorrhage. In addition to these local effects, the purified LNV-LAO showed apoptosis-inducing activity in the MM6 cell culture assay. After 18 h treatment with 25-100 microg/ml of LAO, the typical DNA fragmentation pattern of apoptotic cells was observed by means of fluorescent microscopy and agarose gel electrophoresis.

Phorbol ester up-regulates capacities for nuclear translocation and phosphorylation of 5-lipoxygenase in Mono Mac 6 cells and human polymorphonuclear leukocytes

The leukotrienes are inflammatory mediators derived from arachidonic acid. It was demonstrated that the priming of leukocytes with phorbol-12-myristate-13-acetate (PMA) leads to the increased formation of 5-lipoxygenase (5-LO) products in parallel with the increased association of 5-LO with the nucleus and the activation of kinases that can phosphorylate 5-LO in vitro. Stimulation of the monocytic cell line Mono Mac 6 with calcium ionophore gave low 5-LO product formation and no detectable redistribution of 5-LO. However, after priming of Mono Mac 6 cells with phorbol esters, ionophore led to the association of 45% to 75% of cellular 5-LO with the nuclear membrane, to 5-LO kinase activation, to enhanced release of arachidonate, and to substantial leukotriene synthesis. Similar results were obtained for human polymorphonuclear leukocytes stimulated with low-dose ionophore. In addition, for each cell type, PMA priming up-regulated leukotriene biosynthesis in the presence of exogenous arachidonic acid. A protein kinase inhibitor, calphostin C, reduced the association of 5-LO with the nucleus and 5-LO kinase activity, and the formation of 5-LO products was inhibited. These results suggest that PMA up-regulates leukotriene biosynthesis not only by increasing the release of endogenous arachidonate, but also by increasing the capacity for 5-LO phosphorylation and for the translocation of 5-LO to the nucleus in leukocytes.

Molecular and in silico characterization of a promoter module and C/EBP element that mediate LPS-induced RANTES/CCL5 expression in monocytic cells

The chemokine RANTES/CCL5 is a proinflammatory agent produced by a variety of tissues in response to specific stimuli. In human monocytes, RANTES/CCL5 transcription is up-regulated rapidly and transiently in response to LPS. We describe here two regions that help control LPS-driven transcription from the human RANTES/CCL5 promoter in monocytic cells. These sites were analyzed by using DNase I footprinting, transient transfection assays, site-directed mutagenesis, and EMSA. RANTES site E (R(E), -125/-99) constitutively binds C/EBP proteins in monocytic Mono Mac 6 cells. Mutation of region R(E) led to a significant (40%-50%) reduction in LPS-induced promoter reporter activity. Region R(AB) is composed of tandem kB-like elements R(A) and R(B) (-73/-34). These sites working in concert act as an LPS-responsive promoter module. R(A) constitutively binds Sp1, and Rel p50/p65 following LPS stimulation. Either factor can mediate transcriptional effects at R(A). Induced Rel p50/p50 binding to site R(B) is required for LPS regulation of RANTES/CCL5 transcription. A series of computer models based on the RANTES/CCL5 promoter were generated to represent the organization of these functional elements. The models could identify LPS-regulated promoters in human, other vertebrate, and viral sequences in various databases.

The Common vaccine adjuvant aluminum hydroxide up-regulates accessory properties of human monocytes via an interleukin-4-dependent mechanism

Aluminum adjuvants are widely used in human vaccines based on their ability to enhance antibody production. However, the mechanisms underlying these effects remain unknown. In the present study we assessed the direct in vitro effect of aluminum hydroxide on human peripheral blood monocytes, specifically with regard to its impact on the phenotype and functional properties of this cell population. Our results revealed significant changes in the accessory properties of monocytes following short-term exposure of cultured cells to aluminum hydroxide. Thus, flow cytometry analyses showed an increase in the expression of major histocompatibility complex (MHC) class II, CD40, CD54, CD58, CD83, and CD86 molecules on the monocytes. In addition, many cells in the cultures containing aluminum hydroxide acquired typical dendritic morphology. Increased synthesis of interleukin-4 (IL-4) mRNA, but not gamma interferon mRNA, was also noted after exposure to aluminum hydroxide. The increase in cell surface expression of MHC class II did not occur in the presence of neutralizing IL-4 antibody or in cultures of highly purified monocytes or CD4-depleted mononuclear cells. Our findings suggest that aluminum hydroxide directly stimulates monocytes to produce proinflammatory cytokines activating T cells. Activated Th2 cells release IL-4, which in turn can induce an increase in the expression of MHC class II molecules on monocytes. The increase in the expression of antigen-presenting and costimulatory molecules leads to enhanced accessory functions of monocytes. These properties of aluminum hydroxide observed in vitro may explain its potent in vivo adjuvant effect.

Signal transduction involved in MCP-1-mediated monocytic transendothelial migration

Monocyte chemoattractant protein-1 (MCP-1) is a major chemoattractant for monocytes and T lymphocytes. The MonoMac6 cell line was used to examine MCP-1 receptor-mediated signal transduction events in relation to MCP-1-mediated monocytic transendothelial migration. MCP-1 stimulates, with distinct time courses, extracellular signal-related kinases (ERK1 and ERK2) and stress-activated protein kinases (SAPK1/JNK1 and SAPK2/p38). SAPK1/JNK1 activation was blocked by piceatannol, indicating that it is regulated by Syk kinase, whereas SAPK2/p38 activation was inhibited by PP2, revealing an upstream regulation by Src-like kinases. In contrast, ERK activation was insensitive to PP2 and piceatannol. Pertussis toxin, a blocker of Go/Gi proteins, abrogated MCP-1-induced ERK activation, but was without any effect on SAPK1/JNK1 and SAPK2/p38 activation. These results underscore the major implication of Go/Gi proteins and nonreceptor tyrosine kinases in the early MCP-1 signaling. Furthermore, MCP-1-mediated chemotaxis and transendothelial migration were significantly diminished by a high concentration of SB202190, a broad SAPK inhibitor, or by SB203580, a specific inhibitor of SAPK2/p38, and abolished by pertussis toxin treatment. Altogether, these data suggest that coordinated action of distinct signal pathways is required to produce a full response to MCP-1 in terms of monocytic locomotion.

Characterization of IL-4 receptor components expressed on monocytes and monocyte-derived macrophages: variation associated with differential signaling by IL-4

The anti-inflammatory effects of IL-4 on activated monocytes differ from those on monocyte-derived macrophages (MDMac). While IL-4 suppresses LPS-induced IL-1beta , IL-12, IL-10 and TNFalpha production by monocytes, IL-4 suppresses only IL-1beta and IL-12 production by MDMac. The U937 and Mono Mac 6 cell lines have similar cytokine responses to IL-4 as monocytes and MDMac, respectively. The IL-4Ralpha and IL-2Rgamma (gammac) chains are well-characterized components of the IL-4 receptor. Cross-linking studies with 125I-IL-4 revealed that for monocytes and U937 cells, the binding of IL-4 to the receptor components was approximately 1:1 for IL-4Ralpha:gammac. In contrast, for MDMac and Mono Mac 6 cells that have a relative reduction in gammac surface expression, the binding of IL-4 to IL-4Ralpha:gammac was approximately 3:1. Furthermore, IL-4 induced IL-4Ralpha chain phosphorylation more rapidly in MDMac and Mono Mac 6 cells than in monocytes and U937 cells. This study identifies a correlation between altered 125I-IL-4 cross-linking to IL-4Ralpha:gammac, IL-4-induced signaling and regulation of pro-inflammatory cytokine production by IL-4.

A system establishment compatibility profiles for artificial oxygen carriers and other substances

Worldwide, great efforts are being made to develop a clinically useful artificial oxygen carrier. Toxicological and immunological compatibility is generally tested using animal experiments but inflammatory parameters in particular show large species-specific differences. Therefore, we developed an in vitro system using human components to establish a compatibility profile of unknown compounds. The test system comprises induction of hemolysis, activation of complement (C3a), induction/suppression of cytokine production, influence on cell proliferation, direct toxicity on peripheral leukocytes, and phagocytosis of the material under test and of microbes. The test system will be described, along with results of various perfluorocarbon emulsions. When testing lecithin-based perfluorodecalin (PFD) emulsions, and comparing them to Pluronic-based PFD emulsions, we could show that Pluronic-based emulsions were virtually untoxic to peripheral human leukocytes. They neither inhibited cell proliferation nor caused any hemolysis, but caused mild to moderate inhibition of endotoxin-induced cytokine production. At the same time, lecithin-based PFD emulsion caused substantial cytotoxicity in phagocytic cells like monocytes (60-100% after 24 h incubation) and granulocytes (10-20% after 24 h incubation). They also suppressed endotoxin-induced cytokine production in monocytes to more than 98% and inhibited cell proliferation of an endothelial (ECV 304) and a monocytic cell line (MonoMac6) to more than 95%.

Functional consequences of a polymorphism affecting NF-kappaB p50-p50 binding to the TNF promoter region

Stimulation of the NF-kappaB pathway often causes p65-p50 and p50-p50 dimers to be simultaneously present in the cell nucleus. A natural polymorphism at nucleotide -863 in the human TNF promoter (encoding tumor necrosis factor [TNF]) region provides an opportunity to dissect the functional interaction of p65-p50 and p50-p50 at a single NF-kappaB binding site. We found that this site normally binds both p65-p50 and p50-p50, but a single base change specifically inhibits p50-p50 binding. Reporter gene analysis in COS-7 cells expressing both p65-p50 and p50-p50 shows that the ability to bind p50-p50 reduces the enhancer effect of this NF-kappaB site. Using an adenoviral reporter assay, we found that the variant which binds p50-p50 results in a reduction of lipopolysaccharide-inducible gene expression in primary human monocytes. This finding adds to a growing body of experimental evidence that p50-p50 can inhibit the transactivating effects of p65-p50 and illustrates the potential for genetic modulation of inflammatory gene regulation in humans by subtle nucleotide changes that alter the relative binding affinities of different forms of the NF-kappaB complex.

Hepatocytes contribute to soluble CD14 production, and CD14 expression is differentially regulated in hepatocytes and monocytes

CD14 presents as a glycosylphosphatidylinositol-linked membrane protein on the surface of monocytes/macrophages and as a soluble protein in the serum. Our previous studies have shown that an 80-kilobase pair (kb) genomic DNA fragment containing the human CD14 gene is sufficient to direct CD14 expression in a monocyte-specific manner in transgenic mice. In addition, we discovered that human CD14 is highly expressed in hepatocytes. Here, we report the generation of transgenic mice with either a 24- or 33-kb human CD14 genomic DNA fragment. Data from multiple transgenic lines show that neither the 24- nor the 33-kb transgenic mice express human CD14 in monocytes/macrophages. However, human CD14 is highly expressed in the liver of the 33-kb transgenic mice. These results demonstrate that human CD14 expression is regulated differently in monocytes and hepatocytes. Furthermore, we identified an upstream regulatory element beyond the 24-kb region, but within the 33-kb region of the human CD14 gene, which is critical for CD14 expression in hepatocytes, but not in monocytes/macrophages. Most importantly, the data demonstrate that the liver is one of the major organs for the production of soluble CD14. These transgenic mice provide an excellent system to further explore the functions of soluble CD14.

Monocytic cells synthesize, adhere to, and migrate on laminin-8 (alpha 4 beta 1 gamma 1)

Laminins, a growing family of large heterotrimeric proteins with cell adhesive and signaling properties, are major components of vascular and other basement membranes. Expression, recognition, and use of laminin isoforms by leukocytes are poorly understood. In monoblastic THP-1 cells, transcripts for laminin gamma(1)-, beta(1)-, and alpha(4)-chains were detected by RT-PCR. Following immunoaffinity purification on a laminin beta(1) Ab-Sepharose column, laminin beta(1)- (220 kDa), gamma(1)- (200 kDa), and alpha(4)- (180/200 kDa) chains were detected by Western blotting in THP-1 cells and in two other monoblastic cell lines, U-937 and Mono Mac 6. After cell permeabilization, a mAb to laminin gamma(1)-chain reacted with practically all blood monocytes by immunofluorescence flow cytometry, and laminin-8 (alpha(4)beta(1)gamma(1)) could be isolated also from these cells. Monoblastic JOSK-I cells adhered constitutively to immobilized recombinant laminin-8, less than to laminin-10/11 (alpha(5)beta(1)gamma(1)/alpha(5)beta(2)gamma(1)) but to a higher level than to laminin-1 (alpha(1)beta(1)gamma(1)). Compared with the other laminin isoforms, adhesion to laminin-8 was preferentially mediated by alpha(6)beta(1) and beta(2) integrins. Laminin-8 and, to a lower extent, laminin-1 promoted spontaneous and chemokine-induced migration of blood monocytes, whereas laminin-10/11 was inhibitory. Altogether, the results indicate that leukocytes, as other cell types, are able to synthesize complete laminin molecules. Expression, recognition, and use of laminin-8 by leukocytes suggest a major role of this laminin isoform in leukocyte physiology.

Targeting cell-free HIV and virally-infected cells with anti-HLA-DR immunoliposomes containing amphotericin B

OBJECTIVE

To evaluate the ability of liposomes bearing anti-HLA-DR Fab' fragments (immunoliposomes) and containing amphotericin B (AmB) to target and neutralize cell-free HIV-1 particles and virally-infected cells.

METHODS

The effect of AmB on the attachment and fusion of HIV-1(NL4-3) to Jurkat E6.1 cells has been evaluated using a p24 enzymatic assay. The ability of AmB to inhibit HIV-1-based luciferase reporter viruses pseudotyped with HXB2, AML-V and VSV-G envelopes has been evaluated in Jurkat E6.1 cells. The efficacy of free and immunoliposomal AmB to inhibit cell-free HIV, that have incorporated or not HLA-DR molecules, has been evaluated in HLA-DR/negative (NEG) 1G5 T cells and HLA-DR/positive (POS) Mono Mac 1 cells.

RESULTS

AmB inhibited HIV infectivity independently of the nature of viral envelope proteins. Pretreatment of HIV with AmB had no major effect on viral attachment and fusion process to Jurkat E6.1 cells. Immunoliposomal AmB (0.5 microg/ml) led to a 77% inhibition of replication of HLA-DR/POS HIV-1 with no cell toxicity, whereas free AmB had no significant antiviral activity at this concentration. A complete inhibition of viral replication was observed following incubation of viruses with immunoliposomal AmB (2.5 microg/ml). Anti-HLA-DR immunoliposomes containing AmB had no effect on the infectivity of HLA-DR/NEG HIV-1 particles in HLA-DR/NEG T lymphoid cells but completely inhibited replication of viruses in an HLA-DR/POS monocytic cell line.

CONCLUSION

The incorporation of neutralizing agents in anti-HLA-DR immunoliposomes could represent a novel therapeutic strategy to specifically target cell-free HIV particles and virally-infected cells to treat HIV infection more efficiently.

Localization of Legionella bacteria within ribosome-studded phagosomes is not restricted to Legionella pneumophila

In this report, we investigate the intracellular fate of selected members of the genus Legionella within the monocytic cell line Mono Mac 6 cells. By means of electron microscopy and immunocytochemistry, we could show that Legionella pneumophila as well as Legionella longbeachae are able to induce ribosome-studded phagosomes which associate with the rough endoplasmic reticulum (RER), whereas Legionella micdadei remains to be located within smooth phagosomes but also shows signs of RER association. In addition, we could demonstrate a remarkable correlation between the phagosome type and the morphological phenotype of intracellular bacteria: within ribosome-studded phagosomes, bacteria generally lacked the outer coat of low electron density whereas bacteria within the smooth phagosomes still possessed this outer coat. The virulence factors responsible for inhibition of phagosome maturation and their distribution within the genus Legionella as well as the biological significance of the morphological difference of bacteria within smooth and ER-associated phagosomes remain to be investigated.

Inhibition of IL-6 and IL-10 signaling and Stat activation by inflammatory and stress pathways

The development and resolution of an inflammatory process are regulated by a complex interplay among cytokines that have pro- and anti-inflammatory effects. Effective and sustained action of a proinflammatory cytokine depends on synergy with other inflammatory cytokines and antagonism of opposing cytokines that are often highly expressed at inflammatory sites. We analyzed the effects of the inflammatory and stress agents, IL-1, TNF-alpha, LPS, sorbitol, and H(2)O(2), on signaling by IL-6 and IL-10, pleiotropic cytokines that activate the Jak-Stat signaling pathway and have both pro- and anti-inflammatory actions. IL-1, TNF-alpha, and LPS blocked the activation of Stat DNA binding and tyrosine phosphorylation by IL-6 and IL-10, but not by IFN-gamma, in primary macrophages. Inhibition of Stat activation correlated with inhibition of expression of IL-6-inducible genes. The inhibition was rapid and independent of de novo gene induction and occurred when the expression of suppressor of cytokine synthesis-3 was blocked. Inhibition of IL-6 signaling was mediated by the p38 subfamily of stress-activated protein kinases. Jak1 was inhibited at the level of tyrosine phosphorylation, indicating that inhibition occurred at least in part upstream of Stats in the Jak-Stat pathway. Experiments using Stat3 mutated at serine 727 and using truncated IL-6Rs suggested that the target of inhibition is contained within the membrane-proximal region of the cytoplasmic domain of the gp130 subunit of the IL-6 receptor and is different from the SH2 domain-containing protein-tyrosine phosphatase/suppressor of cytokine synthesis-3 docking site. These results identify a new level at which IL-1 and TNF-alpha modulate signaling by pleiotropic cytokines such as IL-6 and IL-10 and provide a molecular basis for the previously described antagonism of certain IL-6 actions by IL-1.

Antimycobacterial activities of 2,4-diamino-5-deazapteridine derivatives and effects on mycobacterial dihydrofolate reductase

Development of new antimycobacterial agents for Mycobacterium avium complex (MAC) infections is important particularly for persons coinfected with human immunodeficiency virus. The objectives of this study were to evaluate the in vitro activity of 2, 4-diamino-5-methyl-5-deazapteridines (DMDPs) against MAC and to assess their activities against MAC dihydrofolate reductase recombinant enzyme (rDHFR). Seventy-seven DMDP derivatives were evaluated initially for in vitro activity against one to three strains of MAC (NJ168, NJ211, and/or NJ3404). MICs were determined with 10-fold dilutions of drug and a colorimetric (Alamar Blue) microdilution broth assay. MAC rDHFR 50% inhibitory concentrations versus those of human rDHFR were also determined. Substitutions at position 5 of the pteridine moiety included -CH(3), -CH(2)CH(3), and -CH(2)OCH(3) groups. Additionally, different substituted and unsubstituted aryl groups were linked at position 6 through a two-atom bridge of either -CH(2)NH, -CH(2)N(CH(3)), -CH(2)CH(2), or -CH(2)S. All but 4 of the 77 derivatives were active against MAC NJ168 at concentrations of < or =13 microg/ml. Depending on the MAC strain used, 81 to 87% had MICs of < or =1.3 microg/ml. Twenty-one derivatives were >100-fold more active against MAC rDHFR than against human rDHFR. In general, selectivity was dependent on the composition of the two-atom bridge at position 6 and the attached aryl group with substitutions at the 2' and 5' positions on the phenyl ring. Using this assessment, a rational synthetic approach was implemented that resulted in a DMDP derivative that had significant intracellular activity against a MAC-infected Mono Mac 6 monocytic cell line. These results demonstrate that it is possible to synthesize pteridine derivatives that have selective activity against MAC.

Immunologic characterization of normal human pleural macrophages

Human pleural macrophages (PLM) have been studied in effusions, but little is known about normal human PLM. We therefore analyzed resting human PLM recovered by lavage before lobe resection from patients with a central bronchial tumor, not involving the pleura, and from patients with pulmonary chondroma, intrapulmonary hemorrhage, and pneumothorax. Analysis of surface antigens, phagocytosis capacity, and cytokine production was done in comparison to the regular CD14(++) blood monocytes and the recently described blood monocyte subset CD14(+)CD16(+) monocytes. When defining fluorescence intensity for the various markers on CD14(++) monocytes as 100%, the PLM gave the following pattern: CD14, 45%; CD32, 200%; CD64, 72%; CD11b, 128%; CD33, 74%; CD54, 299%; and HLA-DR, 1,906%. When CD16 on the CD14(+)CD16(+) monocytes was set as 100%, the level of CD16 expression on PLM was 7.7%. Taken together, when compared to blood monocytes, PLM appear to represent a cell-type intermediate of regular CD14(++) monocytes and the CD14(+)CD16(+) subset. In functional studies, we demonstrate that PLM can perform efficient Fc-receptor-mediated phagocytosis of antibody-coated sheep red blood cells. Compared with blood monocytes, the capacity of PLM to produce tumor necrosis factor is similar, but a striking finding in PLM was the constitutive interleukin-10 messenger RNA expression that could not be substantially increased by lipopolysaccharide stimulation. This first characterization of normal, noneffusion human PLM can form the basis for a better interpretation of findings in malignant and inflammatory exudates.

Antimicrobial activities of levofloxacin, clarithromycin, and KRM-1648 against Mycobacterium tuberculosis and Mycobacterium avium complex replicating within Mono Mac 6 human macrophage and A-549 type II alveolar cell lines

The antimicrobial activities of levofloxacin, clarithromycin and KRM-1648 against Mycobacterium tuberculosis (MTB) and Mycobacterium avium complex (MAC) residing in Mono Mac 6 human macrophage-like cells (MM6-Mphis) and A-549 human type II alveolar epithelial cells (A-549 cells) were studied. We measured the antimicrobial activity of test drugs in terms of effects on the behaviour of intracellular organisms during a 7-day cultivation of MTB- or MAC-infected cells in the medium containing the drugs at Cmax doses. Microbicidal action of levofloxacin against intracellular MTB within A-549 cells was markedly less than its activity against the same organisms in MM6-Mphis. The same effect was also noted for the action of KRM-1648 against MAC organisms but this did not occur with clarithromycin. The MIC of KRM-1648 for MAC multiplying within A-549 cells was 32 times larger than that for MAC residing in MM6-Mphis. These findings indicate that MTB and MAC organisms replicating in the type II lung epithelial cells resist the action of certain antimycobacterial agents such as quinolones and rifamycin derivatives but not when the organisms are contained in macrophages. It appears that the antimicrobial action of certain drugs against intracellular mycobacteria is differentially manifested depending on the types of host cells, i.e. professional phagocytes (MM6-Mphis) or non-professional phagocytes (A-549cells), in which the organisms are contained.

Role of Stat3 in lipopolysaccharide-induced IL-10 gene expression

IL-10 is a unique cytokine because it is anti-inflammatory and immunosuppressive. IL-10 is regulated at the level of transcription, but the critical motifs and the relevant transcription factors controlling this gene have remained elusive to date. We now report that a sequence at -120 bp in the human IL-10 promoter binds Stat3 but no other Stat proteins. Mutation of this motif abrogates LPS-induced trans-activation. Overexpression of dominant negative Stat3 suppresses promoter activity, while wild-type Stat3 leads to an enhancement of this activity. Our results show that Stat3, by binding to a single motif in the IL-10 promoter, is controlling expression of the human IL-10 gene.

Glutathione peroxidase-1 but not -4 is involved in the regulation of cellular 5-lipoxygenase activity in monocytic cells

In contrast to neutrophils or B-lymphocytes, cells of the monocytic lineage like rat macrophages, human peripheral blood monocytes and Mono Mac 6 cells contain a strong inhibitor of 5-lipoxygenase (5-LO) activity, which scavenges hydroperoxides and inhibits 5-LO activity in broken-cell preparations in the absence of exogenously added thiols. Chromatographic purification of the inhibitor from the human monocytic cell line Mono Mac 6 and amino acid sequence analysis revealed that the inhibitory factor is glutathione peroxidase-1 (GPx-1). In contrast to the peroxidase activity of GPx-1, 5-LO inhibition by GPx-1 was supported by beta-mercaptoethanol and there was no absolute requirement for millimolar concentrations of glutathione or dithiothreitol. These cofactor characteristics suggest that both activities address distinct catalytic properties of GPx-1. 5-LO inhibition by GPx-1 was not due to direct GPx-5-LO protein-protein interactions, since GPx-1 did not bind to immobilized 5-LO. Interestingly, 5-LO derived from granulocytes was significantly more resistant against GPx-1 inhibition than B-lymphocytic 5-LO, which correlates with the respective cellular 5-LO activities. In summary, the data suggest that, in addition to previously reported phospholipid hydroperoxide glutathione peroxidase (GPx-4), GPx-1 is an efficient inhibitor of 5-LO even at low thiol concentrations, and is involved in the regulation of cellular 5-LO activity in various cell types.

Ultrasonication of pyrogenic microorganisms improves the detection of pyrogens in the Mono Mac 6 assay

The monocytic cell line Mono Mac 6 is sensitive to pyrogens. When exposed to pyrogens secretion of interleukin-6 is induced. However, some eukaryotic pyrogenic microorganisms are not detectable. The aim of this study is to introduce a pretreatment of samples to expand the detection range of the assay. The interleukin-6 inducing capacity of a broad spectrum of UV-killed and ultrasonicated microorganisms is examined in Mono Mac 6 cells. The interleukin-6 secretion is determined in a sandwich immunoassay (DELFIA). The Mono Mac 6 assay is able to detect UV-killed Bacillus subtilis, Staphylococcus aureus and Salmonella typhimurium, but neither Candida albicans nor Aspergillus niger. After ultrasonication of the microorganisms it is possible to detect C. albicans and A. niger. The interleukin-6 inducing ability of the examined microorganisms is in no case reduced after ultrasonic treatment. However, ultrasonication of S. aureus results in a 100-fold increase in the interleukin-6 response. Even after ultrasonication Streptococcus faecalis can not be detected. Ultrasonication is an easy and simple method for expanding the detection range in the Mono Mac 6 assay.

Characterization of the Legionella pneumophila gene ligA

Legionella pneumophila is a bacterial pathogen that resides and multiplies in macrophages as well as in its natural aquatic hosts, the protozoa. Different bacterial factors contribute to pathogenicity and accompanying eukaryotic intracellular events. Sequencing of mip flanking regions revealed a gene of 2610 bp, ligA, that has no significant similarity to any of the genes identified previously. Epidemiological studies indicate that this gene is present in Legionella pneumophila, the species most often associated with cases of the Legionnaires' disease, but not in Legionella species other than L. pneumophila. The isogenic ligA deletion mutant was resistant to NaCl, and showed decreased cytotoxicity to human monocytes and decreased hemolytic activity to red blood cells. However, the most prominent effect of the L. pneumophila ligA mutant strain LEPF1 was the nearly completely reduced replication within the natural host Acanthamoeba castellanii. Since this gene is L. pneumophila specific and regulates numerous bacterial properties we designated this gene ligA for Legionella pneumophila infectivity gene A.

Localization, expression and genomic structure of the gene encoding the human serine protease testisin

Testisin is a recently identified human serine protease expressed by premeiotic testicular germ cells and is a candidate tumor suppressor for testicular cancer. Here, we report the characterization of the gene encoding testisin, designated PRSS21, and its localization on the short arm of human chromosome 16 (16p13.3) between the microsatellite marker D16S246 and the radiation hybrid breakpoint CY23HA. We have further refined the localization to cosmid 406D6 in this interval and have established that the gene is approximately 4. 5 kb in length, and contains six exons and five intervening introns. The structure of PRSS21 is very similar to the human prostasin gene (PRSS8) which maps nearby on 16p11.2, suggesting that these genes may have evolved through gene duplication. Sequence analysis showed that the two known isoforms of testisin are generated by alternative pre-mRNA splicing. A major transcription initiation site was identified 97 nucleotides upstream of the testisin translation start and conforms to a consensus initiator element. The region surrounding the transcription initiation site lacks a TATA consensus sequence, but contains a CCAAT sequence and includes a CpG island. The 5'-flanking region contains several consensus response elements including Sp1, AP1 and several testis-specific elements. Analysis of testisin gene expression in tumor cell lines shows that testisin is not expressed in testicular tumor cells but is aberrantly expressed in some tumor cell lines of non-testis origin. These data provide the basis for identifying potential genetic alterations of PRSS21 that may underlie both testicular abnormalities and tumorigenesis.

Topological localization of plasminogen activator inhibitor type 2

BACKGROUND

Plasminogen activator inhibitor type 2 (PAI-2) is a member of the serine protease inhibitor (SERPIN) superfamily and forms stable complexes with urokinase type plasminogen activator (uPA). uPA can be found on the cell surface attached to its specific receptor (uPAR), allowing for controlled degradation of the extracellular matrix by the activation of plasminogen into plasmin. The aim of this study was to evaluate if PAI-2 could also be detected on the cell surface, providing a means of regulating the activity of cell surface uPA.

METHODS

Intact or permeabilized cell lines or human peripheral blood leukocytes were assayed by flow cytometry for cell surface uPA or PAI-2. Plasma membrane-enriched preparations prepared from Jurkat, HaCaT, THP-1, U937, or MM6 cells were assayed by enzyme-linked immunosorbent assay (ELISA) or Western blotting for PAI-2 antigen.

RESULTS

By flow cytometry, cell surface PAI-2 was not detected on monocytes from human peripheral blood, MM6, or HaCaT cells. Cell surface PAI-2 was only detected very weakly on the surface of U937 cells. In contrast, PAI-2 could be detected in all of these cells when fixed and permeabilized. By ELISA, PAI-2 was very abundant in the cytosol-enriched preparations of U937, MM6, and HaCaT cells, but was present in lower amounts in the plasma membrane-enriched preparations. By Western blotting, monomeric nonglycosylated PAI-2, but not uPA/PAI-2 complexes, could be detected in the cytosol and plasma membrane-enriched preparations.

CONCLUSIONS

These results indicate that PAI-2 cannot be detected on the surface of PAI-2-expressing cells, and confirm that PAI-2 is predominantly a cytosolic protein.

Establishment and characterization of an arsenic-sensitive monoblastic leukaemia cell line (SigM5)

Few human monoblastic cell lines have been characterized to date. We have established the SigM5 cell line from a patient with acute monoblastic leukaemia (FAB M5a). Original leukaemic cells had a karyotype of 47,XY,+8, whereas the cell line showed a stemline clone of 81,XX,Y,Y,1,4,6,7,+8,+8,9,10,10,11,13,16,19[cp], with a minor sideline also present. Cytochemical staining was strongly positive with alpha-naphthylbutyrate acetate esterase, particulate positive with Sudan black and weakly positive for myeloperoxidase. Cells were positive for CD13, CD15, CD18, CD23, CD33, CD38, CD45, CD68 and myeloperoxidase. CD14 expression was 3-15%. SigM5 constitutively secreted interleukin (IL)-2, IL-8, IL-10, tumour necrosis factor (TNF)-alpha, ferritin, lysozyme, N-elastase and neopterin upon stimulation with interferon (IFN)-gamma. Cells expressed the proinflammatory mediator macrophage migration inhibitory factor (MIF). All NADPH oxidase subunits were constitutively present, but nitroblue tetrazolium reduction was only detectable upon activation with IFN-gamma. SigM5 monoblasts were sensitive to arsenic trioxide (As2O3) previously not described to induce apoptosis in monoblastic cells. Differing considerably in morphology, immunophenotype and sensitivity to arsenics from the widely used cell lines U937, HL-60 and THP-1, SigM5 is a new monoblastic cell line useful for studying leukaemogenesis, monocyte differentiation and tumour cell susceptibility to arsenic compounds.

Aminopeptidase N/CD13 is directly linked to signal transduction pathways in monocytes

In the present study, we characterized in monocytes the rise in [Ca(2+)](i) evoked by monoclonal antibodies (mAbs) to aminopeptidase N (APN)/CD13, showing a two-phase calcium increase with a small-belled [Ca(2+)](i) rise due to the release of calcium from intracellular stores and a more sustained plateau due to the influx of calcium from the extracellular environment. Tyrosine kinase inhibitors were able to inhibit the rise in [Ca(2+)](i) induced by ligation APN/CD13, as were inhibitors of the phosphatidylinositol 3-kinase. For the first time we can show that mAbs to APN/CD13 provoke phosphorylation of the mitogen-activated protein kinases ERK1/2, JNK, and p38. Furthermore, we show that mRNA of the chemotactic cytokine IL-8 is upregulated under the influence of APN/CD13 ligation. Although the in vivo ligand as well as possible cooperating membrane molecules remains to be identified, our results suggest that the membrane ectoenzyme APN/CD13 is a novel signal transduction molecule in monocytes.

Influence of Acanthamoeba castellanii on intracellular growth of different Legionella species in human monocytes

Previous studies using a murine model of coinhalation of Legionella pneumophila and Hartmannella vermiformis have shown a significantly enhanced intrapulmonary growth of L. pneumophila in comparison to inhalation of legionellae alone (J. Brieland, M. McClain, L. Heath, C. Chrisp, G. Huffnagle, M. LeGendre, M. Hurley, J. Fantone, and C. Engleberg, Infect. Immun. 64:2449-2456, 1996). In this study, we introduce an in vitro coculture model of legionellae, Mono Mac 6 cells (MM6) and Acanthamoeba castellanii, using a cell culture chamber system which separates both cell types by a microporous polycarbonate membrane impervious to bacteria, amoebae, and human cells. Whereas L. pneumophila has shown a maximal 4-log-unit multiplication within MM6, which could not be further increased by coculture with Acanthamoeba castellanii, significantly enhanced replication of L. gormanii, L. micdadei, L. steigerwaltii, L. longbeachae, and L. dumoffii was seen after coculture with amoebae. This effect was seen only with uninfected amoebae, not with Legionella-infected amoebae. The supporting effect for intracellular multiplication in MM6 could be reproduced in part by addition of a cell-free coculture supernatant obtained from a coincubation experiment with uninfected A. castellanii and Legionella-infected MM6, suggesting that amoeba-derived effector molecules are involved in this phenomenon. This coculture model allows investigations of molecular and biochemical mechanisms which are responsible for the enhancement of intracellular multiplication of legionellae in monocytic cells after interaction with amoebae.

Structural characterization of the inflammatory moiety of a variable major lipoprotein of Borrelia recurrentis

Louse-borne relapsing fever, caused by Borrelia recurrentis, provides one of the best documented examples of the causative role of tumor necrosis factor (TNF) in the pathology of severe infection in humans. We have identified the principal TNF-inducing factor of B. recurrentis as a variable major lipoprotein (Vmp). Here we report the complete gene sequence of Vmp, including its lipoprotein leader sequence. Using metabolically labeled forms of the native Vmp we confirm that the TNF inducing properties are associated with the lipid portion of the molecule. Quadrupole orthogonal time of flight mass spectrometry unequivocally locates the lipidic moiety at the NH(2)-terminal cysteine of the native polypeptide, and indicates the existence of three forms which are consistent with the structures C16:0, C16:0, C16:0 glyceryl cysteine; C18:1, C16:0, C16:0 glyceryl cysteine; and C18:0, C16:0, C16:0 glyceryl cysteine. These data provide the first direct evidence that the TNF inducing lipid modification of native Borrelia lipoproteins is a structural homologue of the murein lipoprotein of Escherichia coli.

Crosslinking of the Human Fc Receptor for IgA (FcαRI/CD89) Triggers FcR γ-Chain-Dependent Shedding of Soluble CD89

CD89/FcαRI is a 55- to 75-kDa type I receptor glycoprotein, expressed on myeloid cells, with important immune effector functions. At present, no information is available on the existence of soluble forms of this receptor. We developed an ELISA for the detection of soluble CD89 (sCD89) forms and investigated the regulation of sCD89 production. PMA/ionomycin stimulation of monocytic cell lines (U937, THP-1, and MM6), but not of neutrophils, resulted in release of sCD89. Crosslinking of CD89 either via its ligand IgA or with anti-CD89 mAbs similarly resulted in sCD89 release. Using CD89-transfected cells, we showed ligand-induced shedding to be dependent on coexpression of the FcR γ-chain subunit. Shedding of sCD89 was dependent on signaling via the γ-chain and prevented by addition of inhibitors of protein kinase C (staurosporine) or protein tyrosine kinases (genistein). Western blotting revealed sCD89 to have an apparent molecular mass of 30 kDa and to bind IgA in a dose-dependent fashion. In conclusion, the present data document a ligand-binding soluble form of CD89 that is released upon activation of CD89-expressing cells. Shedding of CD89 may play a role in fine-tuning CD89 immune effector functions.