Bacterial induction of beta interferon in mice is a function of the lipopolysaccharide component

We investigated the reason for the inability of lipopolysaccharide (LPS)-resistant (Lps-defective [Lps(d)]) C57BL/10ScCr mice to produce beta interferon (IFN-beta) when stimulated with bacteria. For this purpose, the IFN-beta and other macrophage cytokine responses induced by LPS and several killed gram-negative and gram-positive bacteria in LPS-sensitive (Lps-normal [Lps(n)]; C57BL/10ScSn and BALB/c) and Lps(d) (C57BL/10ScCr and BALB/c/l) mice in vitro and in vivo were investigated on the mRNA and protein levels. In addition, double-stranded RNA (dsRNA) was used as a nonbacterial stimulus. LPS and all gram-negative bacteria employed induced IFN-beta in the Lps(n) mice but not in the Lps(d) mice. All gram-positive bacteria tested failed to induce significant amounts of IFN-beta in all four of the mouse strains used. As expected, all other cytokines tested (tumor necrosis factor alpha, interleukin 1alpha [IL-1alpha], IL-6, and IL-10) were differentially induced by gram-negative and gram-positive bacteria. Stimulation with dsRNA induced IFN-beta and all other cytokines mentioned above in all mouse strains, regardless of their LPS sensitivities. The results suggest strongly that LPS is the only bacterial component capable of inducing IFN-beta in significant amounts that are readily detectable under the conditions used in this study. Consequently, in mice, IFN-beta is inducible only by gram-negative bacteria, but not in C57BL/10ScCr or other LPS-resistant mice.

In vitro differentiation and characterization of human peritoneal macrophages from CAPD-peritonitis patients

Studies on human macrophages are restricted due to difficulties in isolating significant numbers of human macrophages. High numbers of monocytes/macrophages can be obtained from peritonitis effluents of patients treated with peritoneal dialysis. To determine whether these cells might be useful for functional studies, we characterized peritoneal macrophages (PM) immediately after isolation from the dialysate effluents and their subsequent differentiation. During a 10 days culture period they differentiated morphologically and phenotypically (FACS-analysis) from monocyte-like cells to macrophages. Reflecting the intraperitoneal inflammation we found protein- and mRNA-synthesis of IL-8 and monocyte-chemoattractant-protein-1 (MCP-1) to be upregulated in PM after isolation from the effluents. In contrast, TNF-alpha was downregulated and could not be stimulated by LPS and/or IFN-gamma, reflecting the phenomenon of desensitization. After 10 days in culture, cytokine production normalized to a constitutive level and the TNF-alpha responsiveness to LPS was restored. These data suggest the recovery of PM from the inflammatory prestimulation. Therefore PM harvested from peritoneal dialysis effluents might provide a useful tool for further studies on the role of human macrophages in inflammation.

Distinct regulation of IL-8 and MCP-1 by LPS and interferon-gamma-treated human peritoneal macrophages

BACKGROUND

Interleukin-8 and monocyte chemotactic protein-1 (MCP-1) are major leukocyte chemoattractants during bacterial peritonitis by recruiting neutrophils and monocytes/macrophages respectively.

METHODS

Peritoneal macrophages (PM) from 12 different CAPD patients with peritonitis were stimulated with either 10 ng/ml LPS, 10 ng/ml IFN-gamma or LPS+IFN-gamma, and IL-8 and MCP-1 production was determined on protein and mRNA levels by using ELISA technique and Northern blot analysis. To obtain information from two different stages of activation, experiments were done with highly activated PM directly after isolation and with cells after 10 days in culture, each group being stimulated for 4 h. Unstimulated cells served as control.

RESULTS

Immediately after isolation IL-8 mRNA-expression and synthesis was high and could be further increased by LPS stimulation, whereas IFN-gamma treatment showed no significant influence. The levels of MCP-1 were also initially high but could not be further stimulated by LPS, whereas addition of IFN-gamma resulted in a significant rise in MCP-1 synthesis. After 10 days in culture LPS-stimulation of cells again revealed a significant increase in IL 8 protein synthesis, whereas IFN-gamma showed no effect. LPS anergy for MCP-1 was still seen in PM after 10 days in culture, and IFN-gamma treatment again induced a significant rise in MCP-1 synthesis. The overall production of both chemokines was far higher on day 1 compared to day 10.

CONCLUSION

Our data show differences in LPS/IFN-gamma regulation for IL-8 and MCP-1 in both highly activated and in resting, mature peritoneal macrophages, suggesting distinct pathways for these chemokines that may offer a means of control for the specific recruitment of neutrophils and monocytes/macrophages in bacterial peritonitis.

Downregulation of the proinflammatory cytokine response to endotoxin by pretreatment with the nontoxic lipid A analog SDZ MRL 953 in cancer patients

Interfering with the endotoxin-mediated cytokine cascade is thought to be a promising approach to prevent septic complications in gram-negative infections. The synthetic lipid A analog SDZ MRL 953 has been shown to be protective against endotoxic shock and bacterial infection in preclinical in vivo models. As part of a trial of unspecific immunostimulation in cancer patients, we conducted a double-blind, randomized, vehicle-controlled phase I trial of SDZ MRL 953 to investigate, first, its biologic effects and safety of administration in humans and, second, its influence on reactions to a subsequent challenge of endotoxin (Salmonella abortus equi). Twenty patients were treated intravenously with escalating doses of SDZ MRL 953 or vehicle control, followed by an intravenous application of endotoxin (2 ng/kg of body weight [BW]). Administration of SDZ MRL 953 was safe and well-tolerated. SDZ MRL 953 itself increased granulocyte counts and serum levels of granulocyte colony-stimulating factor (G-CSF) and interleukin-6 (IL-6), but not of the proinflammatory cytokines tumor necrosis factor-alpha (TNF-alpha), IL-1beta, and IL-8. Compared with vehicle control, pretreatment with SDZ MRL 953 markedly reduced the release of TNF-alpha, IL-1beta, IL-8, IL-6, and G-CSF, but augmented the increase in granulocyte counts to endotoxin. Induction of tolerance to the endotoxin-mediated cascade of proinflammatory cytokines by pretreatment with SDZ MRL 953 in patients at risk may help to prevent complications of gram-negative sepsis.

Induction of CD14 expression in Lpsn, Lpsd and tumor necrosis factor receptor-deficient mice

The involvement of CD14 in lipopolysaccharide (LPS) recognition and signaling has been demonstrated in several studies. For this reason, we investigated whether the resistance of Lpsd mice to LPS might be related to an impaired CD14 expression. We compared the in vivo and in vitro expression of CD14 in Lpsn (LPS sensitive) and Lpsd mice, and its modulation by LPS, killed gram-negative and gram-positive bacteria and double-stranded (ds)RNA. Untreated Lpsn and Lpsd cultured macrophages (M phi), expressed similar amounts of CD14 mRNA and membrane-bound (m)CD14. LPS enhanced CD14 expression only in Lpsn M phi, while all bacteria, or dsRNA, enhanced CD14 in Lpsn and Lpsd M phi. Similarly, in vivo administration of LPS induced or enhanced CD14 mRNA in different organs of Lpsn mice only, while bacteria or dsRNA in both types of mouse. Furthermore, exogenous recombinant tumor necrosis factor (TNF) induced in vivo and in vitro enhanced CD14 expression in Lpsn, Lpsd and also in TNF receptor 2-deficient (TNFR2-/-) mice, but failed to do so in TNFR1-/- mice, showing that TNFR1 mediates the effect of TNF on CD14. However, LPS, bacteria and dsRNA induced CD14 in both TNFR2-/- and TNFR1-/- mice to a similar extent, revealing that this induction does not require TNF signaling.

Human monocyte CD14 is upregulated by lipopolysaccharide

Membrane CD14 is involved in lipopolysaccharide (LPS)-induced monocyte activation; it binds LPS, and antibodies against CD14 block the effects of low-dose LPS. It is unknown how LPS regulates its own receptor CD14 in vitro. Therefore, we investigated the effects of LPS on CD14 mRNA and membrane and soluble CD14 (mCD14 and sCD14, respectively) in human monocytes and macrophages. No changes were observed during the first 3 h of LPS stimulation. After 6 to 15 h, LPS weakly reduced CD14 mRNA and mCD14 and transiently enhanced sCD14 release. A 2-day incubation with LPS caused increases in the levels of CD14 mRNA (2-fold), mCD14 (2-fold), sCD14 (1.5-fold), and LPS-fluorescein isothiocyanate binding (1.5-fold); a 5-h incubation with LPS was sufficient to induce the late effects on mCD14 and sCD14. The maximal effect on mCD14 and sCD14 was reached with > or = 1 ng of LPS per ml; the proportional distribution of the two sCD14 isoforms was not modified by LPS. Besides rough and smooth LPS, lipid A, heat-killed Escherichia coli, lipoteichoic acid, and Staphylococcus aureus cell wall extract (10 micrograms/ml) caused similar increases of mCD14. The LPS effect was blocked by polymyxin B but not by anti-tumor necrosis factor alpha, anti-interleukin-6, anti-gamma interferon, and anti-LPS-binding protein. LPS-induced tumor necrosis factor alpha production was abolished after a second 4-h challenge. In contrast, the LPS-induced increases CD14 mRNA, mCD14, and sCD14 were stronger and appeared earlier after a second LPS challenge. In conclusion, CD14 is transcriptionally upregulated by LPS and other bacterial cell wall constituents.

Synthesis and surface expression of ICAM-1 in polymorphonuclear neutrophilic leukocytes in normal subjects and during inflammatory disease

During bacterial peritonitis of patients on continuous ambulatory peritoneal dialysis (CAPD) leukocytes, particularly polymorphonuclear neutrophilic granulocytes (PMNs), migrate into the peritoneal cavity. However, at the site of inflammation PMNs are not sufficiently able to protect the host against micro-organisms. Adhesion molecules, such as ICAM-1 (CD54), are involved in the interaction between endothelial cells and PMNs leading to the accumulation of PMNs at the site of inflammation. As PMNs are the predominant cell type in the peritoneal cavity in peritonitis, the aim of this study was to find out whether PMNs from CAPD peritonitis patients were able to express ICAM-1. Flow cytometric analyses with the anti-CD54 monoclonal antibody demonstrated that normal PMNs constitutively express slight amounts of ICAM-1. In contrast to normal PMNs, peritoneal PMNs from patients with CAPD peritonitis expressed high amounts of ICAM-1 (p = 0.003). Furthermore, ICAM-1 expression on peripheral blood PMNs of these patients significantly differed from PMNs from healthy donor (p = 0.01). Furthermore, Northern blot analysis revealed a weak signal of ICAM-1 mRNA in normal PMNs. However, peritoneal PMNs from CAPD peritonitis patients expressed a strong signal for ICAM-1 mRNA, suggesting that ICAM-1 is newly synthesized when PMNs invade the peritoneal cavity. In summary, this study clearly demonstrates that peritoneal PMNs of CAPD peritonitis express high amounts of ICAM-1 receptor on the level of mRNA and on the surface. Therefore, it is tempting to speculate that peritoneal PMNs interact amongst each other between ICAM-1 and its counter receptors CD11a,b/CD18 receptor.(ABSTRACT TRUNCATED AT 250 WORDS)

Discordant adaptation of human peritoneal macrophages to stimulation by lipopolysaccharide and the synthetic lipid A analogue SDZ MRL 953. Down-regulation of TNF-alpha and IL-6 is paralleled by an up-regulation of IL-1 beta and granulocyte colony-stimulating factor expression

Human peritoneal macrophages were exposed to increasing doses of LPS or a synthetic lipid A analogue (SDZ MRL 953) and production of the cytokines IL-1 beta, IL-6, TNF-alpha, and G-CSF was assessed at the protein and mRNA level. Cells were also prestimulated with low doses of LPS and SDZ MRL 953 to study their adaptation to a secondary challenge with high doses of LPS. The ability of macrophages to produce high levels of TNF-alpha and IL-6 after stimulation with LPS could be relieved almost completely by preincubating cells with low doses of LPS. Decreases of TNF-alpha and IL-6 production resulted from inhibition of gene transcription and/or changes in mRNA stability, as transcript levels of these cytokines were down-modulated by the process of LPS adaptation. Surprisingly, however, adapted cells were able to synthesize even larger quantities of G-CSF and IL-1 beta when exposed to a secondary LPS challenge. mRNA levels of the adapted cells remained unaltered for IL-1 beta, but were slightly increased for G-CSF as assessed by Northern blot analysis. High doses of the synthetic lipid A analogue SDZ MRL 953 were also able to adapt macrophages to a secondary LPS challenge by down-regulating TNF-alpha and IL-6 production, whereas priming secretion of G-CSF and IL-1 beta as well. We describe here the discordant adaptation of human peritoneal macrophages to a secondary LPS stimulus in vitro. These findings appear to have ramifications for the in vivo endotoxin response during inflammation and also Gram-negative septicemia.

Discordant adaptation of human peritoneal macrophages to stimulation by lipopolysaccharide and the synthetic lipid A analogue SDZ MRL 953. Down-regulation of TNF-alpha and IL-6 is paralleled by an up-regulation of IL-1 beta and granulocyte colony-stimulating factor expression

Human peritoneal macrophages were exposed to increasing doses of LPS or a synthetic lipid A analogue (SDZ MRL 953) and production of the cytokines IL-1 beta, IL-6, TNF-alpha, and G-CSF was assessed at the protein and mRNA level. Cells were also prestimulated with low doses of LPS and SDZ MRL 953 to study their adaptation to a secondary challenge with high doses of LPS. The ability of macrophages to produce high levels of TNF-alpha and IL-6 after stimulation with LPS could be relieved almost completely by preincubating cells with low doses of LPS. Decreases of TNF-alpha and IL-6 production resulted from inhibition of gene transcription and/or changes in mRNA stability, as transcript levels of these cytokines were down-modulated by the process of LPS adaptation. Surprisingly, however, adapted cells were able to synthesize even larger quantities of G-CSF and IL-1 beta when exposed to a secondary LPS challenge. mRNA levels of the adapted cells remained unaltered for IL-1 beta, but were slightly increased for G-CSF as assessed by Northern blot analysis. High doses of the synthetic lipid A analogue SDZ MRL 953 were also able to adapt macrophages to a secondary LPS challenge by down-regulating TNF-alpha and IL-6 production, whereas priming secretion of G-CSF and IL-1 beta as well. We describe here the discordant adaptation of human peritoneal macrophages to a secondary LPS stimulus in vitro. These findings appear to have ramifications for the in vivo endotoxin response during inflammation and also Gram-negative septicemia.

N-RAS gene activation in acute myeloid leukemia: association with expression of interleukin-6

The 21 kDa proteins encoded by RAS genes are thought to be involved in intracellular signal transduction. Expression of RAS genes activated by point mutations after transfection into mammalian cells can modulate the response of these cells to exogenously added growth factors and their expression patterns of growth factors. We analyzed leukemic cells from 50 patients with acute myeloid leukemia (AML) for the presence of activating point mutations of the N-RAS gene using polymerase chain reaction (PCR) and differential oligonucleotide hybridization. This assay allows semiquantitative determination of the relative abundance of cells carrying N-RAS mutations. Clonal activation of N-RAS, noted in the large majority of leukemic cells of the six of these patients, was correlated significantly (p = 0.0003) with the ability of these cells to express interleukin 6 (IL-6), previously shown to be expressed at high levels in approximately 30% of primary AML cells. In 16 patients, the presence of N-RAS mutations was observed only in subpopulations of leukemic cells. The 'subclonal' involvement of some but not all leukemic cells was further demonstrated by PCR analysis of individual clones grown in soft agar culture. We investigated whether additional, complementary changes in oncogene structure occurred in cells exhibiting clonal activation of N-RAS. For instance, concomitant activation of N-RAS and amplification or rearrangement of c-MYC have been observed in various tumor tissues. Southern blot analysis did not, however, reveal gross alternations of MYC gene structure or copy number in these cells.

A time-resolved fluoroimmunoassay for recombinant human interleukin-3

We describe a time-resolved fluoroimmunoassay (TRFIA) for recombinant human interleukin-3 (IL-3). The assay design uses two different monoclonal anti-IL-3 antibodies, giving a two-site immunometric assay. The TRFIA for IL-3 is a direct adaptation from our existing ELISA for IL-3. By using the same assay configuration and exchanging a europium-streptavidin conjugate for alkaline phosphatase-streptavidin, we were able to minimize the time required to develop a TRFIA, but still increase the working range of the TRFIA over the ELISA by 20-fold. The limit of detection is 5 ng/L, with the limits of quantification set at 5 and 30,000 ng/L human plasma.

Preparation of europium-streptavidin in a time-resolved fluoroimmunoassay for interleukin-3

The preparation and immunoassay performance of europium-labeled streptavidin is described. The Eu-streptavidin conjugate can serve as a general detection reagent in time-resolved fluoroimmunoassays (TRFIA). The usefulness of such a strategy has previously been demonstrated with the Eu3+ chelate 4,7-bis(chlorosulfophenyl)-1,10-phenanthroline-2,9-dicarboxylic acid (Diamandis et al. 1988). In this report the conjugation of streptavidin was accomplished with the Eu3+ chelate of N1-(p-isothiocyanatobenzyl)diethylenetriamine-N1,N3,N3(+)-tetraace tic acid, using a 50 M excess of the label. The conjugation ratio of Eu3+/streptavidin was 16. The use of the Eu-streptavidin reagent in a two-site immunometric assay to measure human recombinant interleukin-3 in human plasma, showed that the useful range of the assay was 20-25,000 pg/ml.