Tumor necrosis factor triggers redistribution to a Triton X-100-insoluble, cytoskeletal fraction of beta 2 integrins, NADPH oxidase components, tyrosine phosphorylated proteins, and the protein tyrosine kinase p58fgr in human neutrophils adherent to fibrinogen

Tumor necrosis factor (TNF) triggers cell spreading, release of granule constituents, and production of toxic oxygen derivatives in human neutrophils adherent to fibrinogen. This response requires cytoskeleton reorganization and is dependent on expression of beta 2 integrins. We analyzed distribution of distinct proteins in Triton X-100-soluble and insoluble fractions in neutrophils adherent to fibrinogen. We found that stimulation of adherent neutrophils with TNF causes the redistribution to a Triton-insoluble fraction of alpha-actinin, beta 2 integrins, and the four components whose assembly constitutes an active NADPH oxidase: the gp91-phox, p22-phox, p47-phox, and p67-phox proteins. Redistribution of these different proteins to a Triton-insoluble fraction took relatively long times and was maximal after about 30 min of stimulation with TNF. Prevention of actin polymerization with cytochalasin B hampered the TNF-induced redistribution of these proteins from a Triton-soluble to an insoluble fraction. In addition, tyrosine phosphorylated proteins and the protein tyrosine kinase p58fgr were recovered in this Triton-insoluble fraction. These findings show that stimulated, beta 2 integrin-dependent adhesion of neutrophils to fibrinogen is accompanied by redistribution to cytoskeletal structures of (1) beta 2 integrins, that is, neutrophil receptors for fibrinogen; (2) proteins involved in neutrophil effector functions, that is, components of NADPH oxidase; and (3) tyrosine phosphorylated proteins and the protein tyrosine kinase p58fgr, molecules that are potentially involved in the formation of a submembranous signaling complex.

[Urinary albumin excretion increases during an acute myocardial infarct especially in patients who develop heart failure]

AIM OF THE STUDY

To evaluate the profile of albumin excretion rate (AER) in the first days of acute myocardial infarction (AMI), its relationship with serum enzymes and the presence of heart failure, and the effect of thrombolytic therapy.

METHODS

Two hundred and thirty-one consecutive patients admitted to coronary care unit for suspected AMI were examined. Patients with diabetes mellitus, urinary tract infections or proteinuric diseases were excluded. In 135 patients (95 males, 40 females) AMI diagnosis was confirmed. The remaining 96 (56 males, 40 females) were considered as controls. AER was measured by radioimmunoassay in 24-hour urine samples at the first, third and seventh day after admission and expressed as mg/24h. Statistical analysis was performed after AER logarithmic transformation using repeated measure ANOVA:

RESULTS

Mean age was 66.9 +/- 12.2 years (range = 35 -91) in the AMI group and 63.2 +/- 12.3 years (range = 33-91) in the controls (p = 0.023) Age-adjusted blood pressure was lower in the AMI group than in the controls (p < 0.0001 for both systolic and diastolic), while no difference was found in heart rate. Plasma cholesterol, triglycerides, creatinine and uric acid were similar in the 2 groups. Mean AER was 43.4 +/- 64.8, 26.9 +/- 51.2 and 23.9 +/- 52.7 mg/24h at 1st, 3rd and 7th day respectively in the AMI group and 24.9 +/- 58.2, 13.7 +/- 25.8 and 17.9 +/- 44.1 mg/24h respectively in the controls (p = 0.014). In the AMI group, first day AER significantly and positively correlated with CPK (r = 0.287, p = 0.001), CPK-MB (r = 0.239, p = 0.007) and GOT (r = 0.300, p = 0.001). Within the patients with AMI, those who developed heart failure (n = 57), had higher AER (48.6 +/- 68.4, 29.7 +/- 54.9 and 28.1 +/- 55.8 mg/24h at 1st, 3rd and 7th day in patients with mild heart failure -2nd Killip Class- and 100.0 +/- 141.7, 50.3 +/- 66.4 and 64.2 +/- 74.4 mg/24h in those with severe heart failure -3rd and 4th Killip Class-) than those who did not (31.0 +/- 41.7, 19.6 +/- 45.6 and 16.5 +/- 45.7 mg/24h respectively) (p = 0.004). In a multiple linear regression model AER was significantly related to peak values of GOT (1st day) and CPK (3rd day) and to presence of heart failure (3rd and 7th day). Thrombolytic therapy (n = 48) did not influence AER.

CONCLUSIONS

The results of the present study show that AER increases following AMI, chiefly in the subjects who develop heart failure. AER correlates with serum enzymes peak levels at 1st and 3rd day and with presence of heart failure at 3rd and 7th day after admission, and is not influenced by thrombolytic therapy. These data suggest that in AMI the initial increase in AER is due to the inflammatory process which accompanies cardiac necrosis, while in a later phase its rise is mainly due to the increased intraglomerular capillary pressure consequent to heart failure.

Sulfatides trigger cytokine gene expression and secretion in human monocytes

We investigated whether sulfatides are able to trigger transmembrane signals and activation of selective cell functions in human monocytes. Sulfatides stimulated an increase in cytosolic free-calcium in monocytes, and this depended on the release of calcium from intracellular stores. Non-sulfated galactocerebrosides had no effect on monocyte cytosolic free calcium. Sulfatides enhanced expression of tumor necrosis factor, interleukin-8, and interleukin-1 beta, but not interleukin-12/natural killer cell stimulating factor mRNAs. Sulfatides also triggered secretion of cytokines into the extracellular medium, although they were much less effective than lipopolysaccharide. Both enhanced expression of cytokine mRNAs and secretion by sulfatides required sulfation of the galactose ring of the glycolipid as non-sulfated galactocerebrosides had no effect. These findings suggest that sulfatides that are released at sites of inflammation can amplify the inflammatory reaction triggering cytokine expression in, and release by, monocytes.

Beta 2 integrin-dependent protein tyrosine phosphorylation and activation of the FGR protein tyrosine kinase in human neutrophils

Stimulation of adherent human neutrophils (PMN) with tumor necrosis factor (TNF) triggers protein tyrosine phosphorylation (Fuortes, M., W. W. Jin, and C. Nathan. 1993. J. Cell Biol. 120:777-784). We investigated the dependence of this response on beta 2 integrins by using PMN isolated from a leukocyte adhesion deficiency (LAD) patient, which do not express beta 2 integrins, and by plating PMN on surface bound anti-beta 2 (CD18) antibodies. Protein tyrosine phosphorylation increased in PMN plated on fibrinogen and this phosphorylation was enhanced by TNF. Triggering of protein tyrosine phosphorylation did not occur in LAD PMN plated on fibrinogen either in the absence or the presence of TNF. Surface bound anti-CD18, but not isotype-matched anti-Class I major histocompatibility complex (MHC) antigens, antibodies triggered tyrosine phosphorylation in normal, but not in LAD PMN. As the major tyrosine phosphorylated proteins we found in our assay conditions migrated with an apparent molecular mass of 56-60 kD, we investigated whether beta 2 integrins are implicated in activation of members of the src family of intracellular protein-tyrosine kinases. We found that the fgr protein-tyrosine kinase (p58fgr) activity, and its extent of phosphorylation in tyrosine, in PMN adherent to fibrinogen, was enhanced by TNF. Activation of p58fgr in response to TNF was evident within 10 min of treatment and increased with times up to 30 min. Also other activators of beta 2 integrins such as phorbol-12-myristate 13-acetate (PMA), and formyl methionyl-leucyl-phenylalanine (FMLP), induced activation of p58fgr kinase activity. Activation of p58fgr kinase activity, and phosphorylation in tyrosine, did not occur in PMN of a LAD patient in response to TNF. Soluble anti-CD18, but not anti-Class I MHC antigens, antibodies inhibited activation of p58fgr kinase activity in PMN adherent to fibrinogen in response to TNF, PMA, and FMLP. These findings demonstrate that, in PMN, beta 2 integrins are implicated in triggering of protein tyrosine phosphorylation, and establish a link between beta 2 integrin-dependent adhesion and the protein tyrosine kinase fgr in cell signaling.

Sulfatides trigger increase of cytosolic free calcium and enhanced expression of tumor necrosis factor-alpha and interleukin-8 mRNA in human neutrophils. Evidence for a role of L-selectin as a signaling molecule

Sulfatides have been established recently as ligands for L-selectin, and we investigated whether they trigger transmembrane signals through ligation of L-selectin. We found that sulfatides trigger the increase of cytosolic free calcium in neutrophils and that this effect was strictly dependent on sulfation of the galactose ring, as non-sulfated galactocerebrosides were not stimulatory. Chymotrypsin and phorbol 12-myristate 13-acetate treatment of neutrophils caused shedding of L-selectin, but not of class I major histocompatibility complex antigens or beta 2 integrins, and blunted the capability of neutrophils to respond to sulfatides with an increase of cytosolic free calcium. Four different anti-L-selectin antibodies (DREG-200, LAM1/3, LAM1/6, and LAM1/10), but not four control antibodies directed against different surface molecules of neutrophils, also triggered an increase of cytosolic free calcium. The anti-L-selectin antibodies were stimulatory both if used in a soluble form, after cross-linking with anti-mouse F(ab')2 fragments, and immobilized to protein A of Staphylococcus aureus through the Fc fragment. With immobilized antibodies, an increase of cytosolic free calcium was found also by plating neutrophils on antibodies bound to protein A-coated coverslips and monitoring the increase of cytosolic free calcium by fluorescence microscopy. Both sulfatides and anti-L-selectin antibody effects were not inhibited by pertussis toxin, thus indicating that a pertussis toxin-sensitive GTP-binding protein was not involved in signal transduction. Sulfatides also triggered an increase of tumor necrosis factor-alpha and interleukin-8 mRNAs in neutrophils. Also to act as stimuli of cytokine mRNA expression, sulfatides required sulfation of the galactose ring, as non-sulfated galactocerebrosides were not stimulatory, and depended on expression of L-selectin, as shedding of this molecules induced by chymotrypsin blunted their effects. These findings suggest that L-selectin can transduce signals activating selective cell function.

[Alcohol consumption, arterial pressure and metabolic parameters in a population of borderline hypertension subjects. The results of the HARVEST Multicenter Study. Hypertension and Ambulatory Recording Venetia Study]

In 544 borderline to mild hypertensive subjects (mean age 33.5 +/- 8.6 years) participating in the HARVEST trial the relationship between alcohol consumption, blood pressure levels and several clinical parameters was examined. Subjects were divided into 3 groups according to whether they did not drink (Group 1, n = 171) or their daily alcohol intake was < 50 g (Group 2, n = 184) or > 50 g (Group 3, n = 54). In the 409 men alcohol consumption was related to age (p < 0.0001), body weight (p < 0.05) and coffee consumption (p < 0.0001). Group 3 drinkers were also more sedentary than the 2 other groups (p < 0.05). Both office (p < 0.001) and 24-hour (p < 0.001) diastolic blood pressure were greater in the drinkers than in the non drinkers, while no difference was observed in systolic blood pressure. Twenty-four-hour heart rate was higher in Group 3, but urinary catecholamines were similar in the 3 groups of men. Blood glucose (p < 0.001), total cholesterol (p = 0.001) and triglyceride (p < 0.005) were related to alcohol consumption, while HDL-cholesterol was not different in the 3 groups. Albumin excretion rate and uricemia were also unrelated to alcohol intake. In the 135 women a similar alcohol-related trend was observed for office diastolic blood pressure and for the metabolic parameters. In conclusion, the results of the present study confirm the association between alcohol consumption and blood pressure levels, which was apparent also within a population of borderline to mild hypertensive subjects and stress the role of alcohol in determining an abnormality of the metabolic parameters.

Ligation of members of the beta 1 or the beta 2 subfamilies of integrins by antibodies triggers eosinophil respiratory burst and spreading

Eosinophils interact with extracellular matrix proteins and endothelial cells through adhesion proteins belonging to the beta 1 and beta 2 subfamilies of integrins. Extending previous observations, we found that tumour necrosis factor (TNF) and granulocyte-macrophage colony-stimulating factor stimulated generation of superoxide anion by eosinophils plated on fibronectin-coated surfaces. As studies with adherent neutrophils indicated that TNF might act as activating leucocyte integrins to deliver signals involved in activation of cell functions, we investigated the effects of monoclonal antibodies (mAb) directed against VLA-4 (CD49d/CD29), LFA-1 (CD11a/CD18), CR3 (CD11b/CD18) or the common beta 2 subunit (CD18) on generation of eosinophil toxic oxygen molecules and spreading. We show that cross-linking of members of both the beta 1 and the beta 2 integrin subfamilies triggers eosinophil respiratory burst and spreading. Evidence for the selectivity of anti-integrin mAb effects is derived from the findings that isotype-matched mAb of other specificities (anti-class I MHC Ag, anti-beta 2-microglobulin, anti-CD4) did not trigger eosinophil functions. The findings presented in this paper suggest that integrin-dependent, eosinophil adhesion in sites of allergic reaction may be accompanied by release of toxic oxygen molecules involved in tissue damage.

Alternative splicing of a previously unidentified CFTR exon introduces an in-frame stop codon 5' of the R region

The cystic fibrosis transmembrane conductance regulator (CFTR) has been extensively characterized as the carrier of the basic defect in cystic fibrosis. CFTR is part of a growing family of proteins encoded by a single gene, the variant isoforms of which are generated by alternative splicing or RNA editing. We have analyzed the CFTR mRNA in the region of exons 10-11 in T84 cells and detected an alternatively spliced exon (10b) accounting for about 5% of the CFTR mRNA. The exon 10b found in both the human and mice genomes, introduces an in-frame stop codon. The resulting mRNA is translated into a truncated CFTR protein, identified in T84 cells by immunoprecipitation with the CFTR-specific monoclonal antibody MATG 1061. The insertion of a differentially spliced exon carrying an in-frame stop codon is a novel cellular mechanism for the production of a protein sharing common sequences with another, but having different properties and functions.

Interferon-gamma and tumor necrosis factor-alpha enhance p60src expression in human macrophages and myelomonocytic cell lines

We investigated modulation of p60src expression in human mononuclear phagocytes. By analysis of [35S]methionine-labelled cells we found that synthesis of p60src is higher in human monocytes compared to macrophages derived from in vitro cultivation of monocytes. Western blot analysis showed that expression of p60src in monocyte-derived macrophages can be enhanced if monocytes are differentiated into macrophages in the presence of interferon-gamma (IFN-gamma), or tumor necrosis factor-alpha (TNF-alpha). Enhanced p60src expression caused by IFN-gamma or TNF-alpha correlated with an enhanced autophosphorylating kinase activity assayed in anti-p60src immune precipitates. In vivo phosphorylation of p60src and analysis of phosphopeptides by tryptic digestion showed that treatment with cytokines did not affect the pattern of phosphorylation of distinct phosphopeptides. The human monocytic cell lines, U937 and HL-60, induced to differentiate along the monocytic pathway by IFN-gamma, or a combination of IFN-gamma and TNF-alpha, expressed higher amounts of the p60src, but not of the p59fyn or p62yes, kinase activity. These findings show that p60src is modulated in the course of differentiation of human monocytes to macrophages, and that macrophage-activating cytokines increase p60src expression in human monocyte-derived macrophages.

Protein kinase C activates chloride conductance in C127 cells stably expressing the cystic fibrosis gene

The regulatory domain (R domain) of the cystic fibrosis transmembrane conductance regulator (CFTR) is phosphorylated by protein kinase A and protein kinase C (PKC) in vivo (Picciotto, M. R., Cohn, J. A., Bertuzzi, G., Greengard, P., and Nairn, A. C. (1992) J. Biol. Chem. 267, 12742-12752), but so far the functional effect of the PKC-dependent phosphorylation has not been clarified. We investigated the effect of PKC on the CFTR-mediated Cl- transport by treating with phorbol 12-myristate 13-acetate (PMA), the cell line C127i stably expressing CFTR wild type (C127 CFTRw/t), or CFTR bearing the most common mutation deltaF508 (C127 CFTRdF508). We show that PMA activates Cl- efflux in C127 CFTRw/t, but not in C127 CFTRdF508 and C127i. The PMA-dependent activation of CFTR is not mediated by increase of intracellular [cAMP] and is not the result of a primary activation of a K+ conductive pathway. These results strongly suggest that PKC activates directly CFTR-mediated Cl- transport.

The monosialoganglioside GM1 induces internalisation and degradation of the CD4 antigen in U937 cells: evidence for a novel mechanism of CD4 down-modulation in a p56lck-negative cell line, which is independent of protein kinase C activation

Sialated glycosphingolipids (gangliosides) were recently shown to induce internalisation of the CD4 Ag in lymphoid cells and dissociation of p56lck from CD4 (Repke et al. (1992) J. Immunol. 149, 2585-2591; Saggioro et al. (1993) J. Biol. Chem. 268, 1368-1375). The findings presented in this paper show that GM1 induces internalisation and the eventual degradation of the CD4 Ag also in the monocytic cell line U937. GM1 effects are independent of a possible activation of protein kinase C, as enzyme inhibitors which effectively blocked phorbol esters effects did not prevent GM1-induced CD4 internalisation and degradation. GM1 effects were also independent of a possible action on a CD4 associated kinase activity as we show that U937 cells lack any CD4-associated kinase activity.

Effect of inhibitors of distinct signalling pathways on neutrophil Q2- generation in response to tumor necrosis factor-alpha, and antibodies against CD18 and CD11a: evidence for a common and unique pattern of sensitivity to wortmannin and protein tyrosine kinase inhibitors

In these studies we show that stimulation of O2- generation by Tumor necrosis factor-alpha (TNF), or antibodies against the common beta 2 chain of leukocyte integrins (CD18), or LFA-1 (CD11a) displays a common and unique pattern of sensitivity or insensitivity to inhibitors of different signalling pathways. Both ways of stimulating neutrophil O2- generation were blocked by wortmannin, an inhibitor of myosin light chain kinase (Nakanishi, S., et al., 1992., J. Biol. Chem. 267, 2157-2163), and three different inhibitors of protein tyrosine kinases. Neither staurosporine, a protein kinase C inhibitor, nor Pertussis toxin, at concentrations which inhibited O2- generation in response to PMA, and FMLP, respectively, had any effect.

Mechanism of action of the monosialoganglioside GM1 as a modulator of CD4 expression. Evidence that GM1-CD4 interaction triggers dissociation of p56lck from CD4, and CD4 internalization and degradation

Analyzing the mechanisms underlying the capability of the monosialoganglioside GM1 to induce CD4 modulation we observed that GM1 has a dual effect on the CD4 molecule. GM1 treatment of the lymphoma cell line MOLT-3 and CD4-transfected HeLa cells for times shorter than 30 min prevented binding of monoclonal antibodies (mAbs) recognizing epitopes located within the first NH2-terminal domains of CD4, but not of the OKT4 mAb, which binds to the region of CD4 proximal to the transmembrane domain. However, no binding of the OKT4 mAb was observed after a few hours of treatment with GM1 in both MOLT-3 cells and HeLa cells transfected with an intact CD4 molecule, but not in HeLa cells transfected with a CD4 molecule lacking the bulk of the cytoplasmic domain, suggesting that modulation of CD4 by GM1 depends on the integrity of the cytoplasmic domain. GM1 treatment blocked binding of several mAbs which recognize epitopes located within the first two NH2-terminal domains of CD4 and did not induce CD4 down-modulation if MOLT-3 cells were preincubated with the OKT4A or the OKT4 mAbs. Immunoprecipitation studies with [35S]methionine-labeled MOLT-3 cells showed that GM1-induced CD4 down-modulation was accompanied by CD4 degradation, and this was preceded by dissociation of p56lck from CD4. GM1-induced CD4 down-modulation, dissociation of p56lck from CD4, and CD4 degradation were unaffected by staurosporine, which, on the contrary, blocked these events in response to phorbol 12-myristate 13-acetate. These observations demonstrate that the first action of GM1 is to mask epitopes located within the first two NH2-terminal domains; then, GM1 triggers protein kinase C-independent signals which cause p56lck dissociation from CD4 and the delivery of the molecule to an intracellular compartment where it is eventually degraded.

The CD4 molecule belongs to the phenotypic repertoire of most cases of acute myeloid leukemia

In the present study fresh leukemic cells obtained from 23 patients with acute myeloid leukemia (AML; FAB subtypes: three M1, five M2, two M3, five M4, eight M5) were investigated for the membrane expression of the CD4 molecule by cytofluorimetric analysis with an anti-CD4 monoclonal antibody (mAb). In 15 cases the presence of the CD4 mRNA was also investigated using Northern blot analysis. Membrane expression of the CD4 molecule was demonstrated in 19 out of 23 cases, and it was found to be weaker than in CD4+ lymphocytes and monocytes obtained from normal controls. Full-length CD4 mRNA was detected in 12 out of 15 (80%) cases, and AML cells positive for CD4 mRNA expression also expressed the CD4 antigen. Since the CD4 molecule expressed by T cells is associated with p56lck, a member of the src family of intracellular tyrosine kinases, we investigated whether the CD4 molecule expressed by myeloid blasts is also associated with a tyrosine kinase activity. In vitro kinase assays performed on anti-CD4 immunoprecipitates from lysates of myeloid leukemia cells from four CD4+ cases were negative for the presence of a tyrosine kinase activity. This finding was not due to the lack of expression of members of the src family since we were able to detect at least p60src and p59fyn in myeloid leukemia cells. According to our results, the CD4 molecule seems to belong to the phenotypic repertoire of most AML, irrespective of their FAB subtypes. However, in myeloid blasts this molecule is not associated with a tyrosine kinase activity as it occurs in T lymphocytes.

Effect of modulation of protein kinase C on the cAMP-dependent chloride conductance in T84 cells

The regulation of chloride conductance was investigated in the T84 human colon carcinoma cell line by the quenching of the fluorescent probe 6-methoxy-N-(3-sulfopropyl)quinolinium. The permeable cAMP analog 8-Br-cAMP (100 microM) and the calcium ionophore ionomycin (1 microM) activate a chloride conductance. A prolonged (4 h) preincubation of cells with phorbol 12-myristate 13-acetate (100 nM) or with the diacylglycerol analog 1-oleoyl-2-acetyl-glycerol (100 microM): (i) down-modulates to almost zero the protein kinase C activity in the membranes; (ii) inhibits the activation of the chloride conductance mediated by 8-Br-cAMP but not by calcium; (iii) reduces the mRNA without changing the expression of the protein product of the cystic fibrosis gene. The data suggest that PKC is essential for the activation of the cAMP-dependent chloride conductance in T84 cells.

IL-8 production by human polymorphonuclear leukocytes. The chemoattractant formyl-methionyl-leucyl-phenylalanine induces the gene expression and release of IL-8 through a pertussis toxin-sensitive pathway

IL-8 is a novel chemotactic cytokine, produced by a variety of blood and tissue cells, that has marked activating effects on polymorphonuclear leukocytes (PMN). We report that IL-8 is produced and released by human PMN after stimulation with the chemotactic agonist FMLP. Release of IL-8 in response to FMLP was transient and not influenced by PMN adherence or by the absence of serum in the medium. Maximum yields were usually obtained with 10 nM FMLP within 2 h of stimulation (0.5-3.5 ng/ml/7 x 10(6) cells, range of 17 different donors). IL-8 release was dependent on FMLP-induced de novo protein synthesis because it was inhibited by cycloheximide, was paralleled by enhanced expression of IL-8 mRNA and was potentiated from two- to sixfold after preincubation of PMN with cytochalasin B. The FMLP effect was direct and not dependent on LPS or on contaminating monocytes, which showed only low responsiveness to FMLP. Pretreatment of PMN with pertussis toxin prevented FMLP-dependent IL-8 production, the effect being evident both at the level of mRNA expression and protein secretion. In addition, two other chemoattractans, platelet-activating factor and C5a, were found capable to induce release of IL-8 by PMN. The results of this study suggest that chemotactically stimulated PMN may be able to amplify the recruitment process of PMN to the inflammatory site by releasing IL-8. As a long-lived cytokine, IL-8 could markedly prolong the attractant effect.

IL-8 production by human polymorphonuclear leukocytes. The chemoattractant formyl-methionyl-leucyl-phenylalanine induces the gene expression and release of IL-8 through a pertussis toxin-sensitive pathway

IL-8 is a novel chemotactic cytokine, produced by a variety of blood and tissue cells, that has marked activating effects on polymorphonuclear leukocytes (PMN). We report that IL-8 is produced and released by human PMN after stimulation with the chemotactic agonist FMLP. Release of IL-8 in response to FMLP was transient and not influenced by PMN adherence or by the absence of serum in the medium. Maximum yields were usually obtained with 10 nM FMLP within 2 h of stimulation (0.5-3.5 ng/ml/7 x 10(6) cells, range of 17 different donors). IL-8 release was dependent on FMLP-induced de novo protein synthesis because it was inhibited by cycloheximide, was paralleled by enhanced expression of IL-8 mRNA and was potentiated from two- to sixfold after preincubation of PMN with cytochalasin B. The FMLP effect was direct and not dependent on LPS or on contaminating monocytes, which showed only low responsiveness to FMLP. Pretreatment of PMN with pertussis toxin prevented FMLP-dependent IL-8 production, the effect being evident both at the level of mRNA expression and protein secretion. In addition, two other chemoattractans, platelet-activating factor and C5a, were found capable to induce release of IL-8 by PMN. The results of this study suggest that chemotactically stimulated PMN may be able to amplify the recruitment process of PMN to the inflammatory site by releasing IL-8. As a long-lived cytokine, IL-8 could markedly prolong the attractant effect.

Induction of differentiation of the human myeloid cell line, ML3, by tumour necrosis factor and interferon-gamma is accompanied by enhanced expression of the CD4 protein and messenger RNA

Tumour necrosis factor (TNF) and interferon-gamma (IFN-gamma) induce differentiation of human myeloid cell lines along the monocytic lineage. In this study we investigated the effects of TNF and IFN-gamma on the expression of the CD4 protein and messenger RNA (mRNA) in the two myeloid cell lines, ML3 and HL-60. We observed that CD4 antigen expression on ML3 cells is almost undetectable and that TNF and IFN-gamma induced CD4 antigen expression on these cells. HL-60 cells express surface CD4 antigen at high density and treatment with TNF and IFN-gamma caused a decrease of CD4 expression. We also investigated the expression of CD4 mRNA in ML3 and HL-60 cells. ML3 constitutively express, albeit at low levels, CD4 mRNA. TNF induced CD4 mRNA in ML3 cells and IFN-gamma synergistically potentiated the effect of TNF, thus indicating that the enhanced expression of the CD4 protein on ML3 cells is due, at least in part, to an enhanced accumulation of the CD4 mRNA. CD4 mRNA is constitutively expressed in HL-60 cells at high levels. TNF and IFN-gamma, alone or in combination, did not cause any significant change of CD4 mRNA expression in HL-60 cells, thus indicating that decrease of surface CD4, which accompanies differentiation with these cytokines, is likely due to alterations of the CD4 protein synthesis and/or transport to the plasma membrane. These results provide evidence that myeloid cell lines are heterogeneous in expression of CD4, and that in ML3 cells, which constitutively express low levels of CD4 mRNA and undetectable amounts of surface CD4, the predominant effect of the two cytokines is to induce both CD4 mRNA and protein.

Generation of signals activating neutrophil functions by leukocyte integrins: LFA-1 and gp150/95, but not CR3, are able to stimulate the respiratory burst of human neutrophils

To address the question whether leukocyte integrins are able to generate signals activating neutrophil functions, we investigated the capability of mAbs against the common beta chain (CD18), or the distinct alpha chains of CR3, LFA-1, or gp150/95, to activate neutrophil respiratory burst. These investigations were performed with mAbs bound to protein A immobilized to tissue culture polystyrene. Neutrophils plated in wells coated with the anti-CD18 mAbs IB4 and 60.3 released H2O2; H2O2 release did not occur when neutrophils were plated in wells coated with an irrelevant, isotype-matched mAb (OKDR), or with mAbs against other molecules (CD16, beta 2-microglobulin) expressed on the neutrophil surface at the same density of CD18. Four different mAbs, OKM1, OKM9, OKM10, 60.1, which recognize distinct epitopes of CR3 were unable to trigger H2O2 or O2- release from neutrophils. However, mAbs against LFA-1 or gp150/95 triggered both H2O2 and O2- release from neutrophils. Stimulation of neutrophils respiratory burst by both anti- CD18, and anti-LFA-1 or gp150/95 mAbs was totally inhibited by the microfilaments disrupting agent, cytochalasin B, and by a permeable cAMP analogue. While the capability to activate neutrophil respiratory burst was restricted to anti-LFA-1 and gp150/95 mAbs, we observed that mAbs against all members of leukocyte integrins, including CR3, were able to trigger neutrophil spreading. These findings indicate that, in neutrophils, all three leukocyte integrins can generate signals activating spreading, but only LFA-1 and gp150/95 can generate signals involved in activation of the respiratory burst. This observation can be relevant to understand the mechanisms responsible for the activation of neutrophil respiratory burst by tumor necrosis factor-alpha, which has been shown to be strictly dependent on expression of leukocyte integrins (Nathan, C., S. Srimal, C. Farber, E. Sanchez, L. Kabbash, A. Asch, J. Gailit, and S. Wright. 1989. J. Cell Biol. 109:13411349.

Protein myristoylation in human mononclear phagocytes: modulation by interferon-gamma and tumor necrosis factor-alpha

Labelling of cells with [3H]myristic acid and analysis of labelled proteins by SDS-PAGE and fluorography, enabled the identification of a limited number of myristoylated proteins in human monocytes and monocyte-derived macrophages. In human monocytes, cultivated for one to three days, major myristoylated proteins observed were of 18 kDa, 44 kDa, 60–62 kDa, 90 kDa, and a doublet of 38–40 kDa. Differentiation of monocytes to macrophages by in vitro cultivation was accompanied by a selective decrease in the 60–62 kDa protein. Cultivation of the cells in the presence of the macrophage-activating cytokines interferon-gamma (IFN-gamma) and tumor necrosis factor-alpha (TNF-alpha), prevented the decrease in the expression of the 60–62 kDa myristoylated protein. The effect of cytokines was observed when monocytes were treated with IFN-gamma or TNF-alpha for 24 or 48 h and protein myristoylation analyzed at day four of culture. Maintenance of monocytes in culture for up to nine days in the presence of cytokines prevented the decrease in the expression of the 60–62 kDa myristoylated protein. IFN-gamma had additional effects on myristoylation of macrophage proteins. Treatment of monocytes with IFN-gamma for a few hours caused the induction of a 66 kDa protein. Induction of this myristoylated protein by IFN-gamma was time-dependent and peaked at six hours. Analysis of the subcellular distribution of the 66 kDa protein induced by IFN-gamma showed that, analogously to other myristoylated proteins, most of it was associated with cell membranes.(ABSTRACT TRUNCATED AT 250 WORDS)

Activation of human monocyte-derived macrophages by interferon gamma is accompanied by increase of poly(ADP-ribose) polymerase activity

We have investigated poly(ADP-ribosyl)ation processes in human monocyte-derived macrophages and the effect of the activating cytokine, interferon gamma (IFN-gamma) on these processes. IFN-gamma was shown to increase the activity of poly(ADP-ribose) polymerase in human macrophages. A 2-3-fold enhancement of poly(ADP-ribose) polymerase activity was observed after 3-4 h of incubation with IFN-gamma, whose effects were dose-dependent and maximal at 20-50 U/ml. Staining with anti-poly(ADP-ribose) antibodies and purification of ADP-ribosylated nuclear proteins by affinity chromatography over boronate agarose showed that enhancement of poly(ADP-ribose) polymerase activity by IFN-gamma was accompanied by accumulation of poly(ADP-ribose) polymers in nuclear proteins. The effects of IFN-gamma on poly(ADP-ribose) polymerase activity were not due to an enhanced accumulation of the message for the enzyme, indicating that the activation of the enzyme activity was due to post-transcriptional modifications. IFN-gamma was shown to induce DNA strand breaks in human macrophages. This phenomenon followed the same time-course and was evident with the same doses of IFN-gamma that increased poly(ADP-ribose) polymerase activity. Since poly(ADP-ribose) polymerase is known to require DNA nicks for its activity, the capability of IFN-gamma to induce DNA strand breaks can explain its effects on poly(ADP-ribosyl)ation processes.

cAMP-dependent protein kinase inhibits the chloride conductance in apical membrane vesicles of human placenta

The role of adenosine 3',5'-monophosphate (cAMP) dependent protein kinase (PK-A) on the Cl- conductance has been studied in the apical membrane vesicles purified from the chorionic villi of human placenta. In order to phosphorylate the cytosolic side of the membranes, vesicles have been hypotonically lysed, loaded with 100 nM catalytic subunit of PK-A purified from human placenta and 1 mM of the phosphatase resistant adenosine 5'-thiotriphosphate (ATP-gamma-S) and resealed. Cl- conductance has been measured by the quenching of the fluorescent probe 6-methoxy-N-(3-sulfopropyl) quinolinium (SPQ) at 23 degrees C with membrane potential clamped at 0 mV. The actual volume of the resealed vesicles was measured in each experiment by trapping an impermeable radioactive molecule ([14C]-sucrose) and included in each Cl- flux calculation. In 19 independent experiments, the mean Cl- conductance in placental membranes in the absence of phosphorylation was 3.67 +/- 3.18 whereas with the addition of PK-A and ATP-gamma-S it was 1.97 +/- 1.75 nmol.sec-1. (mg protein)-1 (mean +/- SD). PK-A dependent phosphorylation reduced the Cl- conductance in 14/19 experiments. The same protocol applied to the apical membranes of bovine trachea, where PK-A is known to activate the Cl- channels, confirmed that the PK-A dependent phosphorylation increased in Cl- conductance in 11/13 experiments, from 1.01 +/- 0.61 to 1.85 +/- 0.99 nmol.sec-1.(mg protein)-1 (mean +/- SD). These studies indicate that the PK-A dependent phosphorylation inhibits one or more Cl- channel(s) of the apical membranes of human placenta.

Adenosine 3':5'-monophosphate-dependent protein kinase from human placenta: characterization of the catalytic subunit

The catalytic subunit of cAMP-dependent protein kinase (EC 2.7.1.37) was purified for the first time from human placenta by DEAE-cellulose and HTP chromatography. Sodium dodecyl sulfate/polyacrylamide gel electrophoresis showed a single band of average molecular weight of 42 kDa (SEM = 0.52). Kinetic experiments showed a Km for ATP of 12.6 +/- 1.2 mumol/l, for histone II-AS of 1.3 +/- 0.05 mg.ml-1, for kemptide of 11.4 +/- 4.4 mumol/l. The synthetic inhibitor IP20-amide showed a competitive mechanism of inhibition with a Ki of 5.0 nmol/l. The protein kinase inhibitors H7 and H9 showed an apparent Ki of 8.3 and 4.9 mumol/l respectively. Preparative isoelectric focusing revealed the presence of 5 different isoforms with an average pI of 6.17, 6.70, 7.15, 7.67, 8.9.