Role of nitric oxide synthesis in macrophage antimicrobial activity.

Research over the past 5 years has demonstrated that immunologic activation of mouse macrophages induces the activity of nitric oxide synthase, which oxidizes a guanidino nitrogen of L-arginine, yielding citrulline and the reactive radical, nitric oxide. A review of the biochemistry and immunologic regulation of this pathway in macrophages provides a backdrop against which to evaluate its effector functions. Reports published in the past 2 years suggest that synthesis of NO mediates much of the antimicrobial activity of mouse macrophages against some fungal, helminthic, protozoal and bacterial pathogens.     

Suramin inhibits macrophage activation by human group IIA phospholipase A2, but does not affect bactericidal activity of the enzyme

Objective:  Suramin is a polysulphonated napthylurea antiprotozoal and anthelminitic drug, which also presents inhibitory activity against a broad range of enzymes. Here we evaluate the effect of suramin on the hydrolytic and biological activities of secreted human group IIA phospholipase A₂ (hsPLA₂GIIA). Materials and Methods:  The hsPLA₂GIIA was expressed in E. coli, and refolded from inclusion bodies. The hydrolytic activity of the recombinant enzyme was measured using mixed dioleoylphosphatidylcholine/dioleoylphosphatidylglycerol (DOPC/DOPG) liposomes. The activation of macrophage cell line RAW 264.7 by hsPLA₂ GIIA was monitored by NO release, and bactericidal activity against Micrococcus luteus was evaluated by colony counting and by flow cytometry using the fluorescent probe Sytox Green. Results:  The hydrolytic activity of the hsPLA₂ GIIA was inhibited by a concentration of 100 nM suramin and the activation of macrophages by hsPLA₂ GIIA was abolished at protein/suramin molar ratios where the hydrolytic activity of the enzyme was inhibited. In contrast, both the bactericidal activity of hsPLA₂ GIIA against Micrococcus luteus and permeabilization of the bacterial inner membrane were unaffected by suramin concentrations up to 50 μM. Conclusions:  These results demonstrate that suramin selectively inhibits the activity of the hsPLA₂ GIIA against macrophages, whilst leaving the anti-bacterial function unchanged. Received 26 June 2008; returned for revision 8 August 2008; received from final revision 11 September 2008; accepted by J.Skotnicki 8 October 2008     

The effects of thymulin on macrophage responsiveness to interferon-gamma.

The effect of in vivo and in vitro thymulin treatments on macrophage responsiveness to interferon-gamma was evaluated in chickens. Seven-week-old chickens were treated with 0, 1, 10, or 100ng thymulin per 100g body weight. Abdominal exudate cells (AEC), a source of macrophages, were harvested and cultured in the presence of graded levels of recombinant chicken interferon-gamma (ChIFN-gamma). Responsiveness to ChIFN-gamma was determined by measuring the induction of nitric oxide production. One and 2-day thymulin treatment at 10 and 100ng per 100g body weight doses significantly increased responsiveness to ChIFN-gamma while 1ng per 100g body weight had no effect. Other experiments compared the effect of thymulin treatments in Cornell K strain chickens, having normal serum thymulin levels with sex-linked dwarf (SLD) chickens which are deficient in serum thymulin. The dose of thymulin treatment required to significantly increase responsiveness to ChIFN-gamma differed between strains. Finally, the effect of direct in vitro thymulin treatments on macrophage responsiveness to ChIFN-gamma was evaluated. There were no significant increases in responsiveness to ChIFN-gamma between treatment groups within the macrophage cell line, HD-11, when cultured in the presence of 0-200pg thymulin/ml. These data suggest that the effect of thymulin on AEC responsiveness to ChIFN-gamma is indirectly mediated.     

ConA对巨噬细胞活性的影响

目的 探讨ConA对巨噬细胞（Mφ）活性的影响。方法 以不同剂量的ConA腹腔注射处理小鼠，48h后收集腹腔Mφ做体外培养。分别以扫描及透射电镜观察Mφ的形态变化。分别以MTT比色法和胸腺细胞增殖试验检测Mφ分泌TNF－α和IL－1β的水平，并用免疫细胞化学染色法检测这两种蛋白的表达强度。结果 ConA作用后的Mφ，表现为体积增大、指状突起增加和胞浆内线粒体等细胞器增加。ConA活化的腹腔Mφ分泌TNF－α和IL－1β的水平增加，其在Mφ胞浆内的表达增强。结论 ConA具有激活Mφ增强其产生TNF－α和IL-1β的作用。     

Effects of polynucleotides and levamisole on alveolar macrophage morphology and receptor activity.

Incubation of rabbit pulmonary alveolar macrophages in vitro with polyinosinic acid-polycytidylic acid [poly(I-C)] or levamisole results in enhanced immunoglobulin G receptor activity in comparison to untreated cells, Electron microscopy of cells treated with levamisole or poly(I-C) revealed mitochondrial swelling and cytoplasmic vacuolization. The modulation of receptor activity by these agents suggests that their immunopotentiating effects are due to direct simulation of the mononuclear phagocyte system. Lavaged alveolar macrophages have the capacity to change membrane function in vitro, and these cells provide a convenient system for studying agents with potential effects on macrophages.     

激活素A对RAW264.7巨噬细胞活性的调节作用

目的探讨激活素A对参与炎症反应的小鼠巨噬细胞活性调节作用。方法以LPS刺激活化的小鼠巨噬细胞系RAW264．7细胞作为阳性参照,ELISA法检测激活素A及LPS刺激的小鼠腹腔巨噬细胞系RAW264．7细胞IL-1β分泌水平,还原酶法分析NO分泌水平,RT-PCR检测IL-1β和iNOS mRNA的表达,瑞氏染色检测RAW264．7细胞吞噬活性。结果在激活素A刺激下RAW264．7细胞IL-1β和NO分泌水平均明显升高,IL-1β和iNOS mRNA表达亦增加,巨噬细胞吞噬活性增强;激活素A和LPS共刺激RAW264．7细胞时,激活素A明显抑制LPS刺激的RAW264．7细胞IL-1β和NO产生水平,以及IL-1β和iNOS mRNA表达,巨噬细胞吞噬活性也明显低于LPS单独刺激组。结论激活素对巨噬细胞的活性调节具有双重作用,这种作用与巨噬细胞的激活状态有关。     

Bimodal effects of MVE-2 on cytotoxic activity of natural killer cell and macrophage tumoricidal activities

Maleic anhydride divinyl ether of molecular weight 15,500 (MVE-2) increased tumoricidal activity of NK cells and M phi in a dose-dependent manner with the peak response of both effector cells occurring 3 days following treatment. Both effector cell responses were sustained for over 7 days following one injection. However, repeated injections with MVE-2 led to a hyporesponsiveness of NK cells whereas M phi activity remained high. Poly ICLC, but not C. parvum, reconstituted NK cell activity in mice hyporesponsive to MVE-2. Significant antitumor response was achieved when tumor cells were inoculated at the peak time of effector cell response, indicating the in vivo role of NK and/or M phi in exerting a tumoricidal effect.     

In vitro effects of interleukin-4 on interferon-gamma-induced macrophage activation.

Interferon-gamma (IFN-gamma) and interleukin-4 (IL-4) have been shown to be secreted by distinct T-helper cell subsets which have different roles in the determination of host resistance to infection. We studied the activity of these two cytokines on effector mechanisms of mouse macrophages. In vitro cultured bone marrow-derived macrophages from C57BL/6 mice were treated with IFN-gamma, IL-4, or a combination of both cytokines and the ability to secrete superoxide or nitrite or to restrict growth of Mycobacterium avium and Toxoplasma gondii was then evaluated. We found that IL-4 could inhibit the priming of macrophages for enhanced superoxide production induced by IFN-gamma although IL-4 when used alone did have some enhancing effect of its own. This effect of IL-4 on IFN-gamma-primed superoxide production was dose dependent and could be observed even if the treatment by IL-4 was done 24 hr after treatment by IFN-gamma. IL-4 did not, however, influence the enhanced production of nitrogen reactive intermediates, the induction of bacteriostatic activity against M. avium, or the restriction of T. gondii by IFN-gamma-treated macrophages, and did not have any effect of its own regarding these latter functions.     

Bioactivity studies of rainbow trout (Oncorhynchus mykiss) interleukin-6: effects on macrophage growth and antimicrobial peptide gene expression

Interleukin-6 (IL-6) is a pleiotropic cytokine that regulates hematopoiesis, inflammation, immune responses and bone homeostasis in mammals. Fish IL-6 has been cloned in recent years but to date no functional studies have been reported. Thus, in this paper we present for the first time in fish the functional characterisation of IL-6, using rainbow trout (Oncorhynchus mykiss) as the fish model and with a focus on macrophage effects. Trout IL-6 (tIL-6) expression in macrophages could be induced by proinflammatory agents (LPS, polyI:C, and IL-1β) and recombinant tIL-6 (rtIL-6) rapidly induced STAT3 phosphorylation and expression of SOCS-1 to -3, CISH and IRF-1, as seen in mammals. However, three findings in this study suggest a novel role of tIL-6 in fish. Firstly, macrophage growth was enhanced by rtIL-6 in vitro, suggesting that IL-6 produced during inflammatory events may promote macrophage proliferation locally. Secondly, rtIL-6 induced the expression of cathelicidin-2, an antimicrobial peptide with immune-modulatory function, but down-regulated the expression of IL-1β and TNF-α, indicating a role of IL-6 in host defence and also in limiting inflammation. Thirdly, rtIL-6 induced the expression of hepcidin in macrophages. In mammals hepcidin is antimicrobial but also regulates iron homeostasis by inhibiting iron absorption, and its expression is induced by IL-6 only in hepatocytes but not macrophages. Thus, in fish if IL-6 is induced in patrolling macrophages during sepsis this may act to reduce iron availability by induction of hepcidin expression and lead to iron deficiency, as a means to limit the spread of infection.     

The effects of bleomycin on alveolar macrophage growth factor secretion.

Previous work in this laboratory has demonstrated increased secretion of fibroblast growth factor (MDGF) activity by alveolar macrophages obtained from mice with bleomycin-induced pulmonary fibrosis. The mechanism by which bleomycin promotes this increase in MDGF secretion is not clear, however. The purpose of this study was to determine the direct effects of bleomycin on alveolar macrophages. Normal rat alveolar macrophages obtained by lavage were cultured in the presence or absence of bleomycin; conditioned media from these cultures were dialyzed to remove bleomycin and then assayed in vitro for MDGF activity. Alveolar macrophages incubated with 0.01 microgram to 1 microgram/ml bleomycin for 18 hours secreted significantly more MDGF than macrophages incubated without bleomycin. Viability of macrophages as determined by exclusion of trypan blue and release of LDH was unaffected by any dose tested. Maximal MDGF production was seen with bleomycin doses of greater than or equal to 0.1 microgram/ml. When alveolar macrophages were incubated with 0.1 microgram/ml bleomycin for 0.5-18 hours, MDGF activity was detected as early as 1 hour, with peak responses found at 4-8 hours. Macrophages stimulated with bleomycin continued to produce significant amounts of MDGF even after bleomycin was removed and replaced with fresh (bleomycin-free) media. MDGF secretion by bleomycin-stimulated alveolar macrophages was inhibited by cycloheximide, and the 5-lipoxygenase inhibitors NDGA (nordihydroguairetic acid) and BW755c, indicating not only a requirement for protein synthesis but also for metabolites of the 5-lipoxygenase pathway of arachidonic acid metabolism for full expression of activity(ABSTRACT TRUNCATED AT 250 WORDS)     

Antifungal activity of splenic, liver and pulmonary macrophages against Candida albicans and effects of macrophage colony-stimulating factor.

Disseminated infections due to Candida albicans are frequently encountered in immunocompromised patients. We compared the antifungal activities of macrophages residing in spleen, liver and lungs of rabbits against blastoconidia and pseudohyphae of C. albicans. Splenic adherent cells (SAC), Kupffer cells (KC) and pulmonary alveolar macrophages (PAM) all ingested blastoconidia efficiently. SAC caused significantly more damage to unopsonized pseudohyphae compared with KC (P < 0.01) or PAM (P < 0.001). Incubation of SAC with 15 ng ml(-1) of recombinant human macrophage colony-stimulating factor (M-CSF) at 37 degrees C for 2 days significantly enhanced phagocytosis (P = 0.02) and killing (P = 0.05) of blastoconidia. In contrast, M-CSF had no effect on phagocytic activities of KC or PAM against blastoconidia or on damage caused by any of the macrophages to pseudohyphae of C. albicans. Thus, although all three resident macrophage types ingest blastoconidia efficiently, they differ in their capacity to cause damage to pseudohyphae and in their responsiveness to M-CSF for antifungal activation. M-CSF augments the capacity of SAC to ingest and kill blastoconidia and may therefore have a role in the treatment and prevention of hematogenously disseminated candidiasis.     

Pam3Csk4 预处理增强巨噬细胞对耐甲氧西林金黄色葡萄球菌杀菌作用

目的:初步探讨TLR2激动剂Pam3Csk4预处理后,小鼠腹腔巨噬细胞对耐甲氧西林金葡菌(Methicillin-resistant S.aureus,MRSA)的免疫反应性。方法:1μg/ml Pam3Csk4作用于鼠腹腔巨噬细胞,12 h后以热灭活耐甲氧西林金葡菌刺激细胞,ELISA和荧光定量PCR(Q-PCR)法分别检测培养细胞中TNF-α、IL-6和IL-1及mRNA含量,流式检测小鼠腹腔巨噬细胞对热灭活金葡菌的吞噬能力,平板计数法检测Pam3Csk4预处理巨噬细胞对金葡菌杀菌能力;Q-PCR法检测Pam3Csk4预处理巨噬细胞6 h和12 h后吞噬相关受体与补体受体、一氧化氮诱导合成酶(i NOS)及抗菌肽LL37基因表达。结果:金葡菌刺激后,Pam3Csk4预处理组TNF-α、IL-6、IL-1蛋白和基因水平均显著低于未处理组(P0.05),但Pam3Csk4预处理组细胞对金葡菌吞噬和杀菌能力均显著增强(P0.05),对于MRSA菌株,增强的杀菌能力在补体和抗体参与。进一步Q-PCR结果显示Pam3Csk4预处理巨噬细胞6 h和12 h后调理吞噬相关受体FCγRⅠ/Ⅲ与补体受体CR1/3表达均显著增强,i NOS和LL37基因表达也显著增加。结论:Pam3Csk4预处理小鼠腹腔巨噬细胞能增强其对金黄色葡萄球菌甲氧西林敏感和耐药菌株杀菌或抑菌能力,并降低其相应炎症反应,该现象可能与Pam3Csk4激活巨噬细胞吞噬相关受体以及i NOS和抗菌肽表达有关。     

Different effects of phytohemagglutinin-activated lymphocytes and their culture supernatants on macrophage function.

When rabbit peritoneal exudate cells were incubated for 24 and 48 h with phytohemagglutinin-activated lymphocytes or their culture supernatants, two times as many cells remained adherent to culture slides as in the controls. More spreading cells were found among the adherent cells in the stimulated cultures. Eighty percent of spreading cells that were induced by supernatants were negative or faintly positive for beta-galactosidase. On the other hand, half of the spreading cells induced by activated lymphocytes were positive (1+ to 4+) for beta-lymphocytes and their supernatants. Under similar conditions, unstimulated peritoneal cells showed less marked activation. These findings show that macrophages can appear morphologically activated and yet not be enzymatically activated by lymphokines. Possible mechanisms of direct interaction of activated lymphocytes and macrophages are discussed.     

Antiendotoxin activity of cationic peptide antimicrobial agents.

The endotoxin from gram-negative bacteria consists of a molecule lipopolysaccharide (LPS) which can be shed by bacteria during antimicrobial therapy. A resulting syndrome, endotoxic shock, is a leading cause of death in the developed world. Thus, there is great interest in the development of antimicrobial agents which can reverse rather than promote sepsis, especially given the recent disappointing clinical performance of antiendotoxin therapies. We describe here two small cationic peptides, MBI-27 and MBI-28, which have both antiendotoxic and antibacterial activities in vitro and in vivo in animal models. We had previously demonstrated that these peptides bind to LPS with an affinity equivalent to that of polymyxin B. Consistent with this, the peptides blocked the ability of LPS and intact cells to induce the endotoxic shock mediator, tumor necrosis factor (TNF), upon incubation with the RAW 264.7 murine macrophage cell line. MBI-28 was equivalent to polymyxin B in its ability to block LPS induction of TNF by this cell line, even when added 60 min after the TNF stimulus. Furthermore, MBI-28 offered significant protection in a galactosamine-sensitized mouse model of lethal endotoxic shock. This protection correlated with the ability of MBI-28 to reduce LPS-induced circulating TNF by nearly 90% in this mouse model. Both MBI-27 and MBI-28 demonstrated antibacterial activity against gram-negative bacteria in vitro and in vivo against Pseudomonas aeruginosa infections in neutropenic mice.     

Chlamydia psittaci elementary body envelopes: ingestion and inhibition of phagolysosome fusion.

The cell surface of Chlamydia psittaci seems important for establishing infection since (i) UV-treated elementary bodies (EB) attach to and are ingested by L cells and (ii) heat or antibody treatment decreases attachment to L cells and promotes the fusion of chlamydiae-containing phagosomes with lysosomes in macrophages. In the studies reported here, [3H]uridine-labeled UV-treated EB also persisted in mouse resident peritoneal macrophages and L cells, suggesting that phagosome-lysosome fusion is inhibited. We therefore chose to investigate the ingestion and internal fate of isolated purified EB envelopes in both nonprofessional and professional phagocytic cells. EB envelopes are internalized by target host cells as efficiently as are whole EB. Transmission electron microscopy of macrophages whose lysosomes were marked with ferritin revealed the persistence of individual envelopes in phagosomes devoid of ferritin for the 3-h observation period. In contrast, EB envelopes heated to 56 degrees C for 15 min were consistently found in ferritin-labeled phagolysosomes as early as 30 min. As another index of persistence, isolated EB envelopes were radioisotopically labeled with a Bolton-Hunter analog, [3H]N-succinimidyl propionate, and their fate as trichloroacetic acid-precipitable material was followed. A third probe, employed to detect the persistence of non-biodegradable antigen, was indirect immunofluorescence. Fluorescein-positive antigens were brightly visible for 7 days in both macrophages and L cells when they were inoculated with untreated EB or EB maintained in penicillin. But L cells inoculated with EB envelopes or EB treated with UV or chloramphenicol, all of which prevent the conversion of infectious EB into the metabolically active reticulate bodies, displayed reduced internal fluorescence by 2 days and the appearance of fluorescent material on the cell surface. This release of EB envelope material occurred in the absence of phagolysosome fusion. The data add credence to the belief that the spontaneous breakdown or autolytic enzyme release of EB envelope components must occur preparatory to the conversion of EB to reticulate bodies.     

Effect of antilymphocyte serum on macrophage activity

Injection of anti-mouse lymphocyte serum has been demonstrated to alter phagocytic activity in mice. The effects on macrophage activity are of short duration and are probably due to the immunogenic properties of the serum and its toxic activity against other cell types rather than a direct effect on macrophages.     

Induction of macrophage procoagulant activity by Bacteroides fragilis.

Fibrin deposition in the peritoneal cavity during acute peritonitis appears to predispose the host to abscess formation by providing an environment for bacterial proliferation protected from host defenses. The purpose of the present study was to determine whether the potent abscess-inducing anaerobe Bacteroides fragilis could promote fibrin deposition by inducing mononuclear cells to express procoagulant activity (PCA). B. fragilis stimulated PCA in a dose-dependent fashion, achieving a maximum at 10(7) CFU/ml. Heat-killed B. fragilis induced comparable levels of PCA, while a nonspecific phagocytic stimulus, latex beads, was not stimulatory. B. fragilis was capable of inducing PCA even when phagocytosis was blocked by preexposure of cells to latex beads. The results suggested that phagocytosis was neither necessary nor sufficient for the generation of PCA. Cell separation studies showed that PCA was solely produced by macrophages and that lymphocytes did not augment its production. These studies suggest one potential mechanism by which B. fragilis might initiate abscess formation.     

Characterization of chemoselective surface attachment of the cationic peptide melimine and its effects on antimicrobial activity

Antimicrobial peptides (AMPs) are promising alternatives to current treatments for bacterial infections. However, our understanding of the structural–functional relationship of tethered AMPs still requires further investigation to establish a general approach for obtaining consistent antimicrobial surfaces. In this study, we have systematically examined the effects of surface orientation of a broad-spectrum synthetic cationic peptide, melimine, on its antibacterial activity against Gram-positive and Gram-negative bacteria. The attachment of melimine to maleimide-functionalized glass was facilitated by addition of a single cysteine amino acid into the peptide sequence at the N-terminus (CysN) or C-terminus (CysC), or at position 13 (Cys13, approximately central). The successful attachment of the modified melimine was monitored using X-ray photoelectron spectroscopy and time-of-flight secondary ion mass spectrometry (ToF-SIMS) with principle component analysis. The ToF-SIMS analysis clearly demonstrated structural difference between the three orientations. The peptide density for the modified surfaces was found to be between 3.5–4.0 × 10^?9 mol cm^?2 using a modified Bradford assay. The ability of the surfaces to resist Pseudomonas aeruginosa and Staphylococcus aureus colonization was compared using fluorescence confocal microscopy. Reductions in total P. aeruginosa and S. aureus adhesion of 70% (p < 0.001) and 83% (p < 0.001), respectively, after 48 h were observed for the melimine samples when compared to the blank control. We found that melimine attached via the N-terminus was the most effective in reducing total bacterial adhesion and bacterial viability with two- and four times (p < 0.001) more activity than melimine attached via the C-terminus for P. aeruginosa and S. aureus, respectively. Furthermore, for Cys13, despite having the highest measured peptide density of the three surfaces, the higher concentration did not confer the greatest antibacterial effect. This highlights the importance of orientation of the peptides on the surface to efficacy. Our results suggest that the optimal orientation of the cationic residues is essential for maximum surface activity, whereby the optimal activity is obtained when the cationic portion is more available to interact with colonizing bacteria.     

Serum amyloid P-component-induced enhancement of macrophage listericidal activity.

Purified serum amyloid P component (SAP), the major acute-phase reactant of mice, augmented the in vitro listericidal activity of inflammatory (elicited) macrophages, bone marrow-derived monocytes, and macrophages from a subcutaneous site of inflammation. Monocytes and macrophages from C57BL/B6 mice, which are relatively resistant to Listeria monocytogenes, exhibited a significantly greater enhanced killing capacity for listeria than macrophages from listeria-susceptible A/J mice. SAP did not alter the extent of phagocytosis by macrophages of opsonized L. monocytogenes, nor was SAP opsonic for listeria. Mannose-derived simple sugars inhibited the binding of SAP to macrophages and consequently prevented the enhanced SAP-dependent listericidal activity. Macrophages from lipopolysaccharide-hyporesponsive mice also had increased microbicidal activity following incubation with SAP. SAP activated macrophages independently of lymphokine. Therefore, SAP may serve as a mediator of the heightened nonspecific host defense response that is associated with the acute phase of the systemic inflammatory response.