Interferons affect oxygen metabolism in human neutrophil granulocytes

Interferon-gamma activation of polymorphonuclear neutrophil function

As current research illuminates the dynamic interplay between the innate and acquired immune responses, the interaction and communication between these two arms has yet to be fully investigated. Polymorphonuclear neutrophils (PMNs) and interferon-gamma (IFN-gamma) are known critical components of innate and acquired immunity, respectively. However, recent studies have demonstrated that these two components are not entirely isolated. Treatment of PMNs with IFN-gamma elicits a variety of responses depending on stimuli and environmental conditions. These responses include increased oxidative burst, differential gene expression, and induction of antigen presentation. Many of these functions have been overlooked in PMNs, which have long been classified as terminal phagocytic cells incapable of protein synthesis. As this review reports, the old definition of the PMN is in need of an update, as these cells have demonstrated their ability to mediate the transition between the innate and acquired immune responses.

Modulation by interferons of human neutrophilic granulocyte migration

The effect of various interferons (IFN) on neutrophilic granulocyte (PMN) random and directed migration is incompletely understood. We, therefore, investigated PMN migration with a novel micropore membrane technique. No chemotactic effect of either 10-10000 U/ml IFN-alpha or IFN-beta, or 1-1000 U/ml IFN-gamma was observed on PMN isolated from normal human venous blood. However, when present on both sides of the micropore membrane, all the IFN (1000 U/ml IFN-alpha and IFN-beta, 100 U/ml IFN-gamma) inhibited both random and directed migration toward zymosan-activated serum (ZAS). IFN-gamma was the most potent inhibitory agent and produced an inhibition of about 30%. When the bacterial peptide fMLP was used as a chemoattractant, IFN-gamma also depressed chemotaxis. Taking the reduced random migration of IFN-gamma treated cells into account, however, chemotaxis per se-toward both ZAS and fMLP-was not significantly affected. Random migration and directed migration assessed simultaneously with PMN from the same donor were clearly correlated for both control and IFN-gamma treated cells, suggesting that a general antimotility effect of IFN-gamma might explain both reduced random migration and chemotaxis. The antimotility effect of IFN-gamma was not dependent on protein synthesis or on tyrosine kinase activity. In fact, inhibition of tyrosine kinase with herbimycin A increased the ZAS-stimulated motility of both control and IFN-gamma-inhibited PMN. In conclusion, our data indicate that IFN depress both random and directed PMN migration by mechanisms that do not involve protein synthesis or protein tyrosine kinase activity.

Interferon-gamma affects protein kinase C activity in human neutrophils

Interferon-gamma (IFN-gamma) is a priming agent of polymorphonuclear neutrophilic granulocyte (PMN) oxygen metabolism, and protein kinase C (PKC) is traditionally believed to play a central role in activation of this oxygen metabolism. In the present study, we have shown that the PKC activity in PMN is affected by IFN-gamma. After only 2 minutes exposure to IFN-gamma (100 U/ml), PKC activity was significantly increased in the noncytosolic fraction of the cells. This increase was transient, but toward the end of the priming period of 2 h, the membrane-associated PKC activity increased again to about 152% of control. In the cytosolic fraction, a small and hardly detectable decrease in PKC activity was observed. Treatment of PMN with granulocyte-macrophage colony-stimulating factor (GM-CSF), another PMN priming agent, showed no significant effects on the PKC activity. When the cells were stimulated with the bacterial peptide fMLP after a priming period with IFN-gamma or GM-CSF for 2 h, no significant difference between treated and control cells could be observed. PMN oxygen metabolism, measured by flow cytometry as an accumulation of the fluorescent compound dichlorofluorescein, was in these experiments significantly primed by IFN-gamma, both at baseline and when stimulated with fMLP. The protein kinase C inhibitors H7 and Ro31-8220 blocked the fMLP responses to some extent, but not completely. However, no significant difference between fMLP responses in control and IFN-gamma-treated cells could be detected after administration of inhibitors.(ABSTRACT TRUNCATED AT 250 WORDS)

Proteins induced by recombinant equine interferon-beta 1 within equine peripheral blood mononuclear cells and polymorphonuclear neutrophilic granulocytes

Peripheral blood mononuclear cells (PBMC) and polymorphonuclear neutrophilic granulocytes (PMN) as well as embryonic equine dermal fibroblasts and the equine fibroblast line E. Derm which were used as controls, were treated with recombinant equine interferon-beta 1 (rEqIFN-beta 1) in vitro which induced the expression of different proteins in these cells. A 74 kDa protein was induced in PBMC and an 82 kDa protein was additionally found in the equine fibroblast E. Derm cell line following treatment with rEqFN-beta 1. Both proteins reacted with anti-mouse and anti-human Mx protein antisera in immunoblot tests. The 74 kDa and perhaps the 82 kDa components may thus represent equine 'Mxanalogous proteins'. The 74 kDa protein was only detected in PBMC of ten out of 20 horses examined. The induction of Mx protein in the horse by Type 1 interferon may therefore resemble that in the mouse, where Mx protein is involved in selective resistance to influenza virus. The influence of rEqIFN-beta 1 on protein expression in equine PBMC and PMN was monitored by metabolic labeling and 2-D gel electrophoresis. Proteins of 82, 74, 58 and 40 kDa were induced in PBMC following exposure to rEqIFN-beta 1. A constitutively expressed 35 kDa protein, however, was no longer demonstrable upon treatment with interferon. None of the proteins induced within PBMC was found in highly purified PMN treated with interferon. PMN exposed to rEqIFN-beta 1 synthesized four proteins in the range of 25 to 27 kDa. These proteins have not been described in interferon-treated PMN of any other species.

Simultaneous assessment of migration and proliferation of murine fibrosarcoma cells, as affected by hydroxyurea, vinblastine, cytochalasin B, Razoxane and interferon

Using porous cell culture chambers, we have simultaneously assessed growth and locomotion of cancer cells to investigate whether certain agents affect cell motility in addition to cell division. First, cells from a murine fibrosarcoma cell line, 1.0/L1, were grown in ordinary flask cultures to determine appropriate cell inocula. Doses of agents were selected to reduce the final 4 day culture cellularity to about 50%, when present during the last two days of culturing. Secondly, the effects of these agents on cell numbers in the porous chambers and on cell migration out of the chambers ('emigration fraction') were recorded. We also examined, using a similar type of porous chamber, whether the agents could affect leucocyte chemotaxis. Hydroxyurea (an inhibitor of DNA synthesis) reduced cancer cell emigration as well as cell growth, without interfering with leucocyte chemotaxis. Cytochalasin B (a microfilament disrupting agent) inhibited cancer cell motility and growth, as well as leucocyte chemotaxis. Vinblastine (a microtubule disrupting agent), at the very low dose chosen, reduced cancer cell growth, but did not consistently affect the migration of either cell type. The experimental anti-metastasis agent Razoxane reduced growth, but had no detectable effects on motility. High doses of natural murine interferon-alpha/beta weakly inhibited both cancer cell growth and locomotion. This motivates for further studies of these and other cytokines, as treatment with agents inhibiting cancer cell locomotion might possibly prevent peri-operative spread of cancer in patients.

Effect of beta-adrenergic agents on human neutrophil granulocyte activation with N-formyl-methionyl-leucyl-phenylalanine and phorbol myristate acetate

Generation of reactive oxygen intermediates by activated polymorphonuclear neutrophil granulocytes plays an important role in development of microcirculatory injury. The effect of the beta 2-adrenergic receptor agonists (beta 2-agonists) isoprenaline and terbutaline on the chemiluminescence or oxygen consumption of human granulocytes in response to activation with n-formyl-methionyl-leucyl-phenylalanine (FMLP) and phorbol myristate acetate (PMA) was examined. The beta 2-agonist effect on activated cell aggregation and volume change was examined as well. As E. Coli lipopolysaccharide and FMLP may prime granulocytes for enhanced generation of reactive oxygen intermediates in response to other activators, the effect of beta 2-agonists on the priming effect of these agents was also investigated.

RESULTS

1) Optimal concentrations of beta 2-agonists decrease the human granulocyte generation of reactive oxygen intermediates in response to activation with FMLP by 40-60%, without affecting the response to PMA. 2) beta 2-Agonists modify the priming effect of FMLP on activation with PMA, but do not interfere with the priming effect of E. Coli lipopolysaccharide on activation with FMLP. 3) Isoprenaline have different effects on generation of reactive oxygen intermediates and cell aggregation in FMLP-activated granulocytes. 4) High concentrations of isoprenaline and terbutaline have contrasting non-specific effects on the chemiluminescence, but not on the oxygen consumption, of activated granulocytes.

Regulation of microglial function by interferons

Cultured neonatal rat microglia were pretreated with varying doses of either purified interferon (IFN) alpha/beta or recombinant IFN gamma for 24 or 48 h and the following functional parameters examined; superoxide anion production, interleukin-1 secretion and chemotaxis. IFN gamma produced a marked increase in superoxide anion levels when PMA was used to initiate superoxide anion production but had no effect in OPZ-stimulated microglia. Treatment with IFN alpha/beta potentiated superoxide anion production in both PMA and OPZ-stimulated cells. Interleukin-1 activity was decreased by treatment with IFN gamma for 24 h while IFN alpha/beta increased IL-1 activity at 48 h. Removal of serum from the treatment media prevented the action of IFN alpha/beta on IL-1 production. Treatment with IFN alpha/beta or gamma decreased chemotaxis of microglia in response to zymosan activated serum. The data indicate that IFN gamma and alpha/beta can regulate microglial function and that this regulation may differ from that seen for other monocytically derived macrophages.

The role of superoxide anions in the establishment of an interferon-alpha-mediated antiviral state

It has been suggested that CuZn-superoxide dismutase (CuZnSOD) is required for the establishment of an interferon (IFN)-mediated antiviral state. To investigate this possibility further, a panel of 6 stably transfected HeLa clones, expressing CuZnSOD activity from 1.6 to 7.3 times the normal level, were treated with different concentrations of recombinant human interferon alpha A (rHuIFN-alpha A) followed by challenge with vesicular stomatitis virus (VSV). A biphasic response curve was generated (r = 0.87, p less than 0.025). Clones with up to 3-fold basal level CuZnSOD activity exhibited an inverse relationship between their ability to generate an IFN-alpha-mediated antiviral state and CuZnSOD activity: the higher the CuZnSOD activity, the lower the sensitivity to IFN-alpha and the more IFN-alpha required for antiviral defense. Clones with between 4 to 7.3 times higher CuZnSOD activity than the non-transfected HeLa control showed a direct relationship between the CuZnSOD activity and the sensitivity to IFN-alpha. Furthermore, in agreement with the results obtained with the SOD1-transfected HeLa cells with up to 3 times the basal SOD activity, fetal fibroblasts derived from SOD1-transgenic mouse strains, TgHS-229 and TgHS-218, which also express 3 times the basal CuZnSOD activity, required higher IFN-alpha to achieve 50% protection. These results suggest a possible role for superoxide anion in the establishment of IFN-mediated antiviral effect, especially in the dose-response region in which the inverse relationship between the generation of the IFN-alpha-mediated antiviral state and CuZnSOD activity was observed. To assess this possibility, allopurinol was used as a xanthine oxidase inhibitor and hydroxyl radical scavenger in the IFN-alpha-mediated antiviral assay. Addition of 3 mM allopurinol diminished the IFN-mediated antiviral effect by between 40 and 50% (p less than 0.01), and there was a reduction in superoxide generation (p less than 0.05). The degree of reduction caused by allopurinol treatment was higher at an IFN-alpha concentration of 10 U/ml than at 100 U/ml, and there was no correlation between CuZnSOD activity and the degree of reduction. To establish further the role of superoxide as an antiviral agent, paraquat was used as a superoxide generator in the absence of IFN-alpha in the antiviral assay. Although paraquat at high concentrations is toxic to the cells, it actually showed a protective effect against VSV infection, and an inverse relationship (r = 0.79, r less than 0.025) between cell survival and CuZnSOD activity was observed with 150 mM paraquat treatment.(ABSTRACT TRUNCATED AT 400 WORDS)

Pulmonary, hepatic and splenic sequestration of technetium-99m labelled autologous rabbit granulocytes: scintigraphic cell distributions after intravenous and intraarterial injections, exsanguination and intraarterial injection of cells passed through an intermediary host

In man, about half the intravascular granulocytes are not freely circulating, but temporarily sequestered ('marginated'), so that they cannot be retrieved by bleeding. Where and how the sequestration occurs is not settled and is the subject of the present report. Isolated autologous rabbit granulocytes, labelled with two different 99mTc methods, were reinjected and followed with external scintigraphy. Intraarterial as well as intravenous injection led to rapid accumulation of radioactivity over the lungs. This finding was corroborated and extended by similar experiments, where the labelled cells had firstly been passed through an intermediary rabbit host to remove altered cells, i.e. cells damaged, 'primed' (pre-activated), or activated. In the final autologous host about two thirds of the label rapidly localized to the lungs and liver, and a few per cent to the spleen (which is very small in the rabbit). Even though more than half of the intermediary rabbit's calculated blood volume was removed, the blood sample contained only a few per cent of the rabbit's radioactivity; consequently, many of the labelled leucocytes had marginated during the bleeding. The proportional distribution of radioactivity over lungs, spleen, kidneys, and the rest of the intermediary animal was not markedly changed by this exsanguination, but there was a 4-20% decrease over the liver. Taken together, our findings indicate that normal granulocytes marginate in lungs, liver, and spleen--apparently explicable by the effects of cell size, vessel diameter, cell stiffness (visco-elastic properties) and size of the arterio-venous hydrostatic pressure difference. The liver and spleen seemed to play additional roles, since radioactivity over these organs decreased much slower than expected from reported blood half-times of intact and slightly damaged rabbit granulocytes. This led to a suggestion that macrophages exposed to blood normally phagocytose apoptotically dying granulocytes.

Compensatory growth in fibrotic lung injury

We induced severe left-sided lung fibrosis by the unilateral endobronchial instillation of paraquat (1.0 mg/kg) into the left lungs of adult Fischer 344 male rats. Growth of the contralateral lung as well as its proliferative activity were measured 6 or 14 days later. Whereas the left lung underwent severe fibrosis and shrinkage with more than 85% reduction in lung volume, the right lung more than doubled in size. In addition, there was a significant increase in total protein content, DNA content, and DNA synthesis. We conclude that unilateral lung injury resulting in ipsilateral fibrosis and loss of parenchyma is associated with compensatory growth of the contralateral lung.

Modulation of bovine mammary neutrophil function during the periparturient period following in vitro exposure to recombinant bovine interferon gamma

Effects of recombinant bovine interferon (rBoIFN) gamma on mammary gland neutrophil activity during the periparturient period were studied. Bovine mammary gland neutrophils were isolated and incubated in mammary gland secretions obtained from Holstein-Friesian cattle during the last 2 weeks of gestation. Cell functions were evaluated following treatment with 10 U, 100 U, and 1000 U of rBoIFN-gamma. Bacterial phagocytosis, bactericidal activity and chemiluminescence were significantly lower for neutrophils incubated in mammary gland secretions when compared with control neutrophils incubated in Hank's balanced salt solution. Treatment of mammary neutrophils with rBoIFN-gamma reversed the suppressive effects of mammary secretions resulting in higher chemiluminescent activity and significantly more bacterial phagocytosis and bactericidal activity when compared with untreated controls. Results from these preliminary in vitro data suggest that rBoIFN-gamma therapy may modulate mammary gland neutrophil functions in vivo and possibly facilitate the rapid clearance of mastitis-causing pathogens mammary glands during the periparturient period.

Granulocytes in the inflammatory process of BALB/c mice infected by Leishmania amazonensis. A quantitative approach

We used previously immunized (partially resistant) and naive (highly susceptible) BALB/c mice infected with Leishmania amazonensis for evaluating the role of granulocytes in the course of murine leishmaniasis. The animals were examined at different times post-infection and granulocytes counted in lesion tissues examined ultra-structurally. Polymorphonuclear granulocytes predominated during the early phase of infection and their number decreased with progression of infection; their number was similar in both groups during the early and intermediate phases of infection, though slightly higher in immunized animals during the late phase. Eosinophils represented approximately 10% of cells in the inflammatory infiltrate, being higher during the intermediate phase, and not differing between the groups. Another approach was the evaluation of granulocyte migration to the peritoneal cavity of susceptible BALB/c mice or resistant C57BL/6 mice under several stimuli. There was no statistically significant difference between resistant and susceptible animals in any of the treatments. Despite the influx of granulocytes to the lesion and its possible role in the initial destruction of injected Leishmania, this aspect does not seem to have an important effect on the outcome of the leishmanial infection.

Functional capacity of neutrophil granulocytes in deep-sea divers

Neutrophil granulocytes (PMN) are main defenders against invading microbes. We evaluated the adaptive response of PMN from divers exposed for weeks to high total and oxygen pressures. Under these conditions PMN could be primed to give a heightened respiratory burst upon stimulation with the bacterial peptide analogue, formyl-methionyl-leucyl-phenylalanine (FMLP): blood PMN sampled both shortly after operational saturation dives offshore and during an onshore test-dive gave larger responses than control pre- or post-dive PMN from the same subjects and PMN from laboratory personnel. The assays used measured oxygen consumption, intracellular H2O2 availability, and chemiluminescence. The submaximal responses provoked by the non-metabolizable diacylglycerol analogue phorbol myristate acetate (PMA) were less and less often increased. Such enhanced PMN responsiveness may possibly decrease resistance to skin and other infections that are encountered in divers, if PMN thereby failed to localize correctly to inflamed tissues.