Noninvasive assessment of localized inflammatory responses

Inflammatory diseases are associated with the accumulation of activated inflammatory cells, particularly polymorphonuclear neutrophils (PMNs), which release reactive oxygen species (ROS) to eradicate foreign bodies and microorganisms. To assess the location and extent of localized inflammatory responses, L-012, a highly sensitive chemiluminescent probe, was employed to noninvasively monitor the production of ROS. We found that L-012-associated chemiluminescence imaging can be used to identify and to quantify the extent of inflammatory responses. Furthermore, regardless of differences among animal models, there is a good linear relationship between chemiluminescence intensity and PMN numbers surrounding inflamed tissue. Depletion of PMNs substantially diminished L-012-associated chemiluminescence in vivo. Finally, L-012-associated chemiluminescence imaging was found to be a powerful tool for assessing implant-mediated inflammatory responses by measuring chemiluminescence intensity at the implantation sites. These results support the use of L-012 for monitoring the kinetics of inflammatory responses in vivo via the detection and quantification of ROS production.     

In vitro evaluation of the behaviour of human polymorphonuclear neutrophils in direct contact with chitosan-based membranes

Several novel biodegradable materials have been proposed for wound healing applications in the past few years. Taking into consideration the biocompatibility of chitosan-based biomaterials, and that they promote adequate cell adhesion, this work aims at investigating the effect of chitosan-based membranes, over the activation of human polymorphonuclear neutrophils (PMNs). The recruitment and activation of polymorphonuclear neutrophils (PMNs) reflects a primary reaction to foreign bodies. Activation of neutrophils results in the production of reactive oxygen species (ROS) such as O(2)(-) and HO(-) and the release of hydrolytic enzymes which are determinant factors in the inflammatory process, playing an essential role in the healing mechanisms. PMNs isolated from human peripheral blood of healthy volunteers were cultured in the presence of chitosan or chitosan/soy newly developed membranes. The effect of the biomaterials on the activation of PMNs was assessed by the quantification of lysozyme and ROS. The results showed that PMNs, in the presence of the chitosan-based membranes secrete similar lysozyme amounts, as compared to controls (PMNs without materials) and also showed that the materials do not stimulate the production of either O(2)(-) or HO(-). Moreover, PMNs incubated with the biomaterials when stimulated with phorbol 12-myristate 13-acetate (PMA) or formyl-methionyl-leucyl-phenylalanine (fMLP) showed a chemiluminescence profile with a slightly lower intensity, to that observed for positive controls (cells without materials and stimulated with PMA), which reflects the maintenance of their stimulation capacity. Our data suggests that the new biomaterials studied herein do not elicit activation of PMNs, as assessed by the low lysozyme activity and by the minor detection of ROS by chemiluminescence. These findings reinforce previous statements supporting the suitability of chitosan-based materials for wound healing applications.     

Functional Activity of Blood Polymorphonuclear Leukocytes as an Oxidative Stress Biomarker in Human Subjects

In the present work, we studied the role of polymorphonuclear leukocytes (PMN) in aged individuals and coronary heart disease (CHD)-bearing patients, two physiopathological processes associated with overproduction of reactive oxygen species (ROS). The effects of antioxidant supplementation on the functional activity of PMN from CHD patients were also determined. The function of PMNs was evaluated by measuring of phagocytosis, killing activity, and ROS production. Luminol amplified chemiluminescence (CL) was used to estimate ROS production by stimulated PMNs. Total cholesterol and the LDL-cholesterol fraction from CHD patients were found to be higher than those recommended, returning to normal levels after antioxidant therapy. PMN CL of CHD patients was found to be higher than the associated control groups. Antioxidant therapy administrated to CHD patients lead to an increase in the killing activity accompanied by a decrease in PMN CL of these subjects. The study also showed that killing activity of PMN from human subjects over 60 years was significantly lower than the activity measured in younger subjects. PMN CL produced after stimulation was found to be positively correlated with the increasing age of human subjects (r = .946, p < .01).     

Antioxidative activity of flavonoids in stimulated human neutrophils

The release and production of oxidative products generated by the respiratory burst under the influence of natural flavonoids: quercetin, kaempferol and isorhamnetin derivatives have been studied in the polymorphonuclear neutrophils (PMNs) from healthy human donors. Flavonoids were tested in vitro at concentration range 1-100 microM. The antioxidative potential of flavonoids was compared to the activity of a food preservative, butylated hydroxyanisole. Two methods were applied to the measurement of the PMNs respiratory burst: flow cytometry using dichlorofluorescein diacetate and luminol-dependent chemiluminescence. It was found that the studied products decreased the neutrophil hydrogen peroxide production in concentration-dependent manner. The highest degree of inhibition was registered for concentration of 100 microM, although in the chemiluminescence method the metabolic activity inhibition was more prominent. Antioxidative activity of flavonoids depended on the number of hydroxyl groups. These results provide useful data for establishing methods used to assess the respiratory burst in phagocytic cells.     

Surface protease of Treponema denticola hydrolyzes C3 and influences function of polymorphonuclear leukocytes

Treponema denticola is a dominant microorganism in human periodontal lesions. One of the major virulence factors of this microorganism is its chymotrypsin-like surface protease, dentilisin. The purpose of this study was to evaluate the effect of dentilisin on human polymorphonuclear leukocytes (PMNs). We used chemiluminescence to assess production of O(-)(2) by PMNs against T. denticola ATCC 35405 and dentilisin-deficient mutant K1. T. denticola ATCC 35405 induced production of O(-)(2), whereas dentilisin-deficient K1 did not. We found that chymostatin, a protease inhibitor, strongly reduced the ability of T. denticola ATCC 35405 to induce production of, O(-)(2), whereas K1 was relatively unaffected. We also used Immunoblot and ELISA to evaluate the activation of complement by this microorganism in relation to PMNs. T. denticola ATCC 35405 hydrolyzed the alpha-chain of C3, producing iC3b. Furthermore, strain ATCC 35405 induced a larger release of MMP-9 from PMNs than strain K1. Dentilisin activated PMNs via complement pathways and may play a role in establishing periodontal lesions.     

Effects of lysophospholipids on the generation of reactive oxygen species by fMLP‐ and PMA‐stimulated human neutrophils

In this study, the effects of exogenous lysophospholipids—lysophosphatidic acid, lysophosphatidylcholine, lysophosphatidylethanolamine and lysophosphatidylserine—on the kinetics of reactive oxygen species (ROS) production by human neutrophils are described. The ROS production by human neutrophils was monitored by luminol‐amplified chemiluminescence after cell stimulation with the chemotactic tripeptide, fMLP, or with the phorbol ester, PMA. The interaction of lysophospholipids with the membrane of human neutrophils was additionally tested by mass spectrometry. Lysophosphatidylcholine showed the most pronounced effect on the chemiluminescence pattern, as well as the intensity of the fMLP and PMA‐stimulated cells, whereas lysophosphatidic acid showed a slight priming effect when fMLP was used for stimulation. In the case of fMLP‐stimulated cells, lysophosphatidylcholine inhibited the first phase and enhanced the second phase of chemiluminescence, whereas the chemiluminescence of PMA‐stimulated neutrophils was inhibited in a concentration‐dependent manner. We conclude that lysophosphatidylcholine is able to interact with protein kinase C‐dependent signalling pathways leading to NADPH oxidase activation. Copyright © 2002 John Wiley & Sons, Ltd.     

Anti-inflammatory effects of Melaleuca alternifolia essential oil on human polymorphonuclear neutrophils and monocytes

OBJECTIVE AND DESIGN: The fungicidal and bactericidal actions of the essential oil (EO) of Melaleuca alternifolia seem well established, but their anti-inflammatory and anti-oxidative effects remain unclear. In this study, we investigated in vitro the possible role of whole M. alternifolia EO as a modulator of the oxidative response, i.e. reactive oxygen species (ROS) production, of leukocytes (monocytes and polymorphonuclear neutrophils (PMNs)) in humans. METHODS: Whole blood leukocytes from healthy human volunteers (n = 7), isolated from erythrocytes by haemolytic shock, were incubated for 30 min with M. alternifolia EO (0-0.1%) to determine their ROS production by flow cytometry with or without stimulation of cells. We compared the effects of 3 different stimulating agents acting differently on transductional pathways to stimulate the ROS production: a phorbol ester (PMA), formyl-methionyl-leucyl-phenylalanine (fMLP) and opsonised zymosan (OZ). RESULTS: As attested by the Krüskall-Wallis test, M. alternifolia EO at 0.1% directly stimulated ROS production by PMNs (x 8.7 vs. 0% EO, p < 0.05) and increased the intracellular ROS produced by monocytes. Whichever the stimulating agent used (PMA, fMLP or OZ), M. alternifolia EO decreased the intracellular ROS production at the dilution of 0.1% by PMNs and monocytes, more so with PMNs. CONCLUSION: M. alternifolia EO may be both a direct active mediator of the bactericidal action of the circulating leukocytes and may be efficient in protecting the organism from an excess of ROS, through an anti-oxidant and radical scavenging activity.     

Effect of methacrylic monomers on phagocytes reactive oxygen species: a possible BDDMA modulating action

In the last years the studies regarding the biocompatibility of dental materials investigate, in addition to the classic cytotoxic tests, the interactions between the materials and the host cells to better explain the causes of the adverse effects observed sometimes in the clinical practice. In the present study the ability of diurethane dimethacrylate (DUDMA) and 1,4‐butanediol dimethacrylate (BDDMA) methacrylic monomers present in dental composite resins to alter the functionality of peripheral blood monocytes (PBMs) and polymorphonucleate cells (PMNs) was examined. These cells are involve in the biological response to materials and in the host ability to respond to bacteria. The results obtained suggest that the examined methacrylates induce a relevant decrease of PBMs oxidative burst whereas the basal ROS production is only slightly decreased. In PMNs DUDMA induces a decrease of both basal and stimulated ROS production. BDDMA, on the contrary, it does not alter total oxidative burst in presence of stimulus while induces a statistically significant decrease of basal ROS production. Moreover this monomer alters the reaction kinetics of stimulated ROS production. The reported finding seems to indicate that this molecule could be able to stabilize PMNs in resting state and maximize their stimulated activity. Copyright © 2008 John Wiley & Sons, Ltd.     

Reactive oxygen species‐induced activation of ERK and p38 MAPK mediates PMA‐induced NETs release from human neutrophils

Neutrophils/polymorphonuclear leukocytes (PMNs), an important component of innate immune system, release extracellular traps (NETs) to eliminate invaded pathogens; however understanding of the role of signaling molecules/proteins need to be elucidated. In the present study role of p38 MAPK and extracellular signal regulated kinase (ERK) against phorbol 12‐myristate 13‐acetate (PMA) induced reactive oxygen species (ROS) generation and NETs formation has been investigated. Human neutrophils were treated with PMA to induce free radical generation and NETs release, which were monitored by NBT reduction and elastase/DNA release, respectively. PMA treatment led to the time dependent phosphorylation of p38 MAPK and ERK in PMNs. Pretreatment of PMNs with SB202190 or U0126 did not significantly reduce PMA induce free radical generation, but prevented NETs release. Pretreatment of PMNs with NADPH oxidase inhibitor (diphenyleneiodonium chloride) significantly reduced free radical generation, p38 MAPK and ERK phosphorylation as well as NETs release, suggesting that p38 MAPK and ERK activation was downstream to free radical generation. The present study thus demonstrates ROS dependent activation of ERK and p38 MAPK, which mediated PMA induced NETs release from human neutrophils. J. Cell. Biochem. 114: 532–540, 2013. © 2012 Wiley Periodicals, Inc.     

Pancreatic phospholipase A2--mediated enhancement of the respiratory burst response of human neutrophils

The aim of this study was to investigate the effects of exogenously added pancreatic phospholipase A2 (pPLA2) on the production of reactive oxygen species by human polymorphonuclear leukocytes (PMNs). Pancreatic PLA2 was used because PMNs do not possess a receptor for that enzyme and, therefore, the receptor-mediated effects could be excluded. Respiratory burst activity of PMNs was monitored by luminol-amplified chemiluminescence and the lipid composition of neutrophils after treatment with pPLA2 was determined by matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry. Our results show that the products of the pPLA2 digestion of the PMN membrane--lysophospholipids and the corresponding free fatty acids--significantly enhanced the respiratory burst response of human neutrophils.     

The plasminogen activator family from the salivary gland of the vampire bat Desmodus rotundus: cloning and expression

Complementary DNAs coding for four Desmodus rotundus salivary plasminogen activators (DSPAs) were isolated and characterized. The predicted amino acid sequences display structural features also found in tissue-type plasminogen activator. The largest forms (DSPA alpha 1 and -alpha 2) contain a signal peptide, a finger (F), an epidermal growth factor (EGF), a kringle, and a serine protease domain, whereas DSPA beta and -gamma lack the F and F-EGF domains, respectively. Additional differences between the four forms suggest that distinct genes code for the members of the DSPA family. Transfection of DSPA-encoding cDNAs, placed under the control of the simian virus 40 late promoter, into COS-1 cells resulted in the secretion of highly fibrin-dependent PAs.     

Proanthocyanidins suppress NLRP3 inflammasome and M1 macrophage polarization to alleviate severe acute pancreatitis in mice

The role of reactive oxygen species (ROS) is crucial for the pathogenesis of acute pancreatitis (AP). Proanthocyanidins (PAs) have been confirmed to exert antioxidant activity. Our study aimed to determine whether PAs alleviated SAP via reducing ROS, suppressing NLRP3 inflammasome, and inhibiting M1 macrophage polarization. Our study investigated the protective effects of PAs on pancreatic histopathological injury using SAP mice. The effects of PAs on macrophages were investigated in inflammatory RAW 264.7 cells or mouse bone marrow-derived macrophages (BMDMs) induced by lipopolysaccharide (LPS). Immunofluorescence staining and/or western blot assay were employed to evaluate NLRP3 inflammasome in macrophages and pancreatic tissue. Cell counting kit-8 (CCK-8) was used to access effects of PAs on cell viability and cytometry flow was used to determine the effects of the PAs on the ROS levels of the RAW 264.7 cells. Then, we evaluated M1 macrophage polarization using flow cytometry or real-time quantitative polymerase chain reaction (RT-qPCR). PAs administration alleviated pancreatic inflammation in SAP mice. The PAs depressed NLRP3 inflammasome and inhibited M1 macrophage polarization in pancreatic tissue. We also found that the PAs showed no cellular toxicity but decreased ROS levels in RAW 264.7 cells, downregulated the NLRP3 inflammasome in the macrophages, and inhibited cell M1 macrophage polarization. Our study indicates the anti-inflammatory properties of the PAs on SAP mice by decreasing ROS levels, suppressing NLRP3 inflammasome, and M1 macrophage polarization.     

Presence of the M-type sPLA(2) receptor on neutrophils and its role in elastase release and adhesion

Secretory phospholipase A(2) (sPLA(2)) produces lipids that stimulate polymorphonuclear neutrophils (PMNs). With the discovery of sPLA(2) receptors (sPLA(2)-R), we hypothesize that sPLA(2) stimulates PMNs through a receptor. Scatchard analysis was used to determine the presence of a sPLA(2) ligand. Lysates were probed with an antibody to the M-type sPLA(2)-R, and the immunoreactivity was localized. PMNs were treated with active and inactive (+EGTA) sPLA(2) (1-100 units of enzyme activity/ml, types IA, IB, and IIA), and elastase release and PMN adhesion were measured. PMNs incubated with inactive, FITC-linked sPLA(2)-IB, but not sPLA(2)-IA, demonstrated the presence of a sPLA(2)-R with saturation at 2.77 fM and a K(d) of 167 pM. sPLA(2)-R immunoreactivity was present at 185 kDa and localized to the membrane. Inactive sPLA(2)-IB activated p38 MAPK, and p38 MAPK inhibition attenuated elastase release. Active sPLA(2)-IA caused elastase release, but inactive type IA did not. sPLA(2)-IB stimulated elastase release independent of activity; inactive sPLA(2)-IIA partially stimulated PMNs. sPLA(2)-IB and sPLA(2)-IIA caused PMN adhesion. We conclude that PMNs contain a membrane M-type sPLA(2)-R that activates p38 MAPK.     

The mitogenic activities of phosphatidate are acyl-chain-length dependent and calcium independent in C3H/10T1/2 cells.

Phosphatidates (PA or phosphatidic acid) were shown to have mitogenic properties, including the stimulation of DNA synthesis and calcium mobilization in C3H/10T1/2 cells. Their continuous presence for a minimum of 7 h induced DNA synthesis with kinetics similar to that observed when 10% fetal bovine serum was used as a mitogen. PAs with long chain saturated fatty acid moieties were more mitogenic, in a dose-dependent fashion, than PAs with short saturated or unsaturated fatty acid moieties. When compared with lysostearoyl-PA (LSPA), distearoyl-PA (DSPA) was as potent with respect to the induction of DNA synthesis. Lysooleoyl-PA (LOPA) was slightly more potent than dioleoyl-PA (DOPA), but much weaker than DSPA and LSPA. Preincubation with dilauroyl-PA (DLPA) reduces the mitogenic effect of DSPA by 85%. The pattern of mitogenic inhibition suggests that a chain-length-independent, yet PA-specific, mechanism is involved. Both DSPA and DLPA are equally taken up by the cells after 30 min. LOPA, but not LSPA, produced a large calcium transient (1.3 microM), which we found to be derived from intracellular sources. DSPA, the most mitogenic PA tested, produced a weaker transient (0.6 microM). Interestingly, LSPA did not produce any detectable calcium transient. These results suggest that the chain-length-specific step in the signaling mechanism of PA occurs after the initial chain-length-independent partitioning and/or binding to the membrane and that the induction of DNA synthesis is not related to the observed calcium transients.     

Neutrophil effector functions triggered by Fc-gamma and/or complement receptors are dependent on B-ring hydroxylation pattern and physicochemical properties of flavonols

Tissue damage in autoimmune diseases involves excessive production of reactive oxygen species (ROS) triggered by immune complexes (IC) and neutrophil (PMN) interactions via receptors for the Fc portion of IgG (FcgammaR) and complement receptors (CR). Modulation of both the effector potential of these receptors and ROS generation may be relevant to the maintenance of body homeostasis. In the present study, the modulatory effect of four flavonols (myricetin, quercetin, kaempferol, galangin) on rabbit PMN oxidative metabolism, specifically stimulated via FcgammaR, CR or both classes of receptors, was evaluated by luminol- and lucigenin-dependent chemiluminescence assays. Results showed that flavonol inhibitory effect was not dependent on the cell membrane receptor class stimulated but related to the lipophilicity of the compounds (their apparent partition coefficient values were obtained by high-performance liquid chromatography), and was also inversely related to the number of hydroxyl groups in the flavonol B ring and the ROS-scavenger activity (assessed by the luminol--H2O2--horseradish peroxidase reaction). Under the experimental conditions the flavonols tested were not toxic to PMNs (evaluated by lactate dehydrogenase release and trypan blue exclusion) and did not interfere with IC-induced phagocytosis (evaluated by transmission electron microscopy). Our results suggested that inhibition of IC-stimulated PMNs effector functions by the flavonols tested herein was the result of cooperation of different cellular mechanisms.     

Effects of 60 Hz magnetic field exposure on polymorphonuclear leukocyte activation

We have investigated the effects of a sinusoidal 60 Hz magnetic field on free radical (superoxide anion) production, degranulation (beta-glucuronidase and lysozyme release) and viability in human neutrophils (PMNs). Experiments were performed blindly in very controlled conditions to examine the effects of a magnetic field in resting PMNs and in PMNs stimulated with a tumor promoter: phorbol 12-myristate 13-acetate (PMA). Exposure of unstimulated human PMNs to a 60 Hz magnetic field did not affect the functions examined. In contrast, exposure of PMNs to a 22 milliTesla (mT), 60 Hz magnetic field induced significant increases in superoxide anion (O2-) production (26.5%) and in beta-glucuronidase release (53%) when the cells were incubated with a suboptimal stimulating dose of PMA. Release of lysozyme and lactate dehydrogenase was unchanged by the magnetic field, whether the cells were stimulated or not. A 60 Hz magnetic field did not have any effect on O2- generation by a cell-free system xanthine/xanthine oxidase, suggesting that a magnetic field could upregulate common cellular events (signal transduction) leading to O2- generation and beta-glucuronidase release. In conclusion, exposure of PMNs to a 22 mT, 60 Hz magnetic field potentiates the effect of PMA on O2- generation and beta-glucuronidase release. This effect could be the result of an alteration in the intracellular signaling.     

Effects of COX-2 inhibitors on ROS produced by Chlamydia pneumoniae-primed human promonocytic cells (THP-1)

Chronic inflammation through foam cells and macrophages is important in atherosclerosis development, and can be considered as therapeutic targets. Cyclooxygenase and NADPH-oxidase were expressed within atherosclerotic lesions. Reactive oxygen species produced by NADPH oxidase were found to trigger the cyclooxygenase-2 expression. The effects of preferential COX-2 inhibitors on ROS produced by Chlamydia-primed human monocytes (THP-1 cells) were evaluated by fluorescence, chemiluminescence, oxymetry, and EPR spin trapping. Fluorescence assays showed an increased production of ROS with Chlamydia versus cells primed by 10(-8)M PMA. COX-2 inhibitors inhibited in a dose-dependent manner the luminol-enhanced CL while ibuprofen and diclofenac increased the chemiluminescence response. By EPR spin trapping, COX-2 inhibitors, ibuprofen, and diclofenac, exhibited a dose-dependent inhibiting effect (10 and 100muM) on the EPR signal appearance. Our cell model combining EPR, chemiluminescence, and oxymetry appeared relevant to study the modulating effects of preferential COX-2 inhibitors on the cell oxidant activity and chronic inflammatory diseases.     

Effect of 4-hydroxynonenal on superoxide anion production from primed human neutrophils

HNE (4-hydroxy-2,3-trans-nonenal), an aldehydic product of lipid peroxidation, has been reported to modulate different functional parameters of human and rat neutrophils (PMNs), such as chemiluminescence, migration and some enzymatic activities, thus exerting effects that varied according to the concentration tested. Experiments were done to evaluate the effects of HNE on superoxide anion (O₂^?.) production from human PMNs, isolated from healthy volunteers. After having tested that HNE by itself was not able to activate the cells, comparisons were made between its effects on PMNs, stimulated by either a single stimulus, N-formyl-methionyl-leucyl-phenylalanine (FMLP), or a combination of stimuli, such as FMLP and the neuropeptide substance P (SP; primed PMNs). In the concentration range tested (10^?12–10^?4 M ), HNE inhibited FMLP-evoked O₂^?. production with an IC₅₀ of 11·6 ± 1·5 × 10^?6 M ; at concentrations ≤10^?6 M , HNE enhanced O₂^?. production elicited by FMLP + SP, while higher concentrations were inhibitory. There was a bell-shaped dose–response curve to the enhancing effects of HNE, depending on the incubation time being recorded after only short periods (≤5 min) of the exposure of the cells to HNE; this was not shown by structurally-related aldehydes, such as 2-nonenal and nonanal. These results suggest that low concentrations of HNE may participate in the evolution of the inflammatory process, by contributing to the activation of PMNs. The effects of high concentrations of the aldehyde may represent a mechanism which contributes to the regulation of the extent of the inflammatory response.     

Polymorphonuclear leukocytes promote neurotoxicity through release of matrix metalloproteinases, reactive oxygen species, and TNF-alpha

As the first immune cells to infiltrate the nervous system after traumatic PNS and CNS injury, neutrophils (polymorphonuclear leukocytes, PMNs) may promote injury by releasing toxic soluble factors that may affect neuronal survival. Direct neurotoxicity of matrix metalloproteinases (MMPs), reactive oxygen species (ROS), and cytokines released by PMNs was investigated by culturing dorsal root ganglion (DRG) cells with PMN-conditioned media containing MMP inhibitor (GM6001), ROS scavengers, or tumor necrosis factor alphaR (TNF-alphaR) neutralizing antibody. Although DRGs exposed to PMN-conditioned media had 53% fewer surviving neurons than controls, neuronal cell loss was prevented by GM6001 (20 micromol/L), catalase (1000 U/mL), or TNF-alphaR neutralizing antibody (1.5 microg/mL), elevating survival to 77%, 94%, and 95%, respectively. In accordance with protection by GM6001, conditioned media collected from MMP-9 null PMNs was less neurotoxic than that collected from wild-type PMNs. Additionally, MMP inhibition reduced PMN-derived ROS; removal of ROS reduced PMN-derived MMP-9 activity; and TNF-alpha inhibition reduced both PMN-derived MMP-9 activity and ROS in PMN cultures. Our data provide the first direct evidence that PMN-driven neurotoxicity is dependent on MMPs, ROS, and TNF-alpha, and that these factors may regulate PMN release of these soluble factors or interact with one another to mediate PMN-driven neurotoxicity.     

Effect of Staphylococcus aureus serine proteinase on the respiratory burst in phagocytic cells in vitro

The in vitro effects of the Staphylococcus aureus serine proteinase (SASP) on the respiratory burst of human blood mononuclear phagocytes and rat lung macrophages were investigated. The generation of reactive oxygen species (ROS), determined by means of luminol-based chemiluminescence, was stimulated by treatment with SASP in both types of the defense cells. Cell activation depended on the concentration of the enzyme and the response of monocytes was an order of magnitude stronger relative to macrophages. The chemiluminescence emission kinetics were different for both cell types and the maximum signal was achieved in approximately 3 and 17 min, respectively. In experiments involving further cell activation by latex particles, macrophages pretreated with various SASP concentrations reacted with enhanced ROS generation whereas for monocytes, the latex-induced chemiluminescence was weakened by the enzyme. The results concerning the modification of the phagocytic host cell activity by SASP suggest that this enzyme might play an important role in pathomechanisms of staphylococcal infections in vivo.