Modulation of rat peripheral polymorphonuclear leukocyte response by nitric oxide and arginine

The effect of nitric oxide (NO) on the luminol-dependent chemiluminescence (LCL) response of rat polymorphonuclear leukocytes (PMNLs) was analyzed by using sodium nitroprusside (SNP), a NO donor, and L-arginine (L-arg), a NO precursor. A significant reduction in the LCL intensity was observed in presence of SNP (100 mumol/L) or L-arg (5 or 10 mmol/L) in arachidonic acid (AA) phorbol ester (PMA) and formyl- methionyl-leucyl-phenylalanine stimulated PMNLs. However, opsonized zymosan-induced LCL was not attenuated significantly. Reduction in hydroxyl radical and superoxide generation was also observed in SNP- or L-arg-pretreated cells. D-Arg (10 mmol/L) pretreatment did not inhibit PMNLs' LCL response. Furthermore, methylene blue (5 mumol/L) and L-NG- mono methyl-L-arginine (100 or 300 mumol/L) significantly attenuated the LCL response, as induced by various agonists. Cyclic GMP did not alter the reactive oxygen species generation from rat PMNLs. In addition, AA-induced release of myeloperoxidase, a marker of azurophilic granules, was found to be enhanced in L-arg- (10 mmol/L) pretreated PMNLs. The results suggest that NO inhibits free radical generation from rat PMNLs.     

中性粒细胞分泌功能与支气管哮喘

哮喘是由多种炎症细胞和炎症组分参与的气道慢性炎症。近年来发现中性粒细胞(PMN)在哮喘的发病机制中也起重要作用,尤其表现在重度哮喘和致命性哮喘中。激活的PMN能分泌多种酶、炎症介质和细胞因子等参与哮喘的发病过程。在此,对PMN分泌功能在哮喘中的作用作一综述。     

Modulation of polymorphonuclear leukocyte apoptosis in the critically ill by removal of cytokines with continuous hemodiafiltration

Delay of polymorphonuclear leukocyte (PMN) apoptosis caused by hypercytokinemia is considered to be a potential cause of tissue damage and resultant organ failure. We evaluated whether continuous hemodiafiltration using a polymethylmethacrylate membrane hemofilter (PMMA-CHDF), which can remove cytokines in the circulating blood, can modulate apoptosis in peripheral blood neutrophils and thereby reduce tissue damage and organ dysfunction in 25 critically ill patients. Following the completion of a 3-day PMMA-CHDF session, serum cytokine levels were significantly decreased and the percentage of apoptotic PMNs was significantly increased. A significant correlation was observed between the PMMA-CHDF-induced increase in the percentage of apoptotic PMNs and the degree of decrease in the serum interleukin-6 level. A significant correlation was also found between the increase in the percentage of apoptotic PMNs and improvement in sequential organ failure assessment score following PMMA-CHDF. These results suggest that PMMA-CHDF in critically ill patients with hypercytokinemia and concomitant delay in apoptosis of PMNs can alleviate the delay of PMN apoptosis through the removal of serum cytokines and thus may result in avoidance of organ dysfunction.     

Increased polymorphonuclear leukocyte respiratory burst function in type 2 diabetes

The predisposition to infection and chronic inflammation in diabetes may in part be related to the effects of hyperglycemia or other metabolic abnormality on polymorphonuclear leukocytes (PMN). We evaluated oxidative respiratory burst activity (superoxide production) in non-stimulated and stimulated PMN from 70 stable type 2 Hispanic diabetic patients, as compared to 70 healthy Hispanic individuals without diabetes. The influences of protein kinase C (PKC) inhibitors and certain antibiotics on superoxide production were examined. Both resting and stimulated (PMA, zymosan) PMN from diabetic individuals produced more superoxide than PMN from controls. Inhibitors of PKC, a possible mediator of the augmented respiratory burst activity, decreased superoxide production in all (resting and stimulated) diabetic and control PMN. Azithromycin, which is markedly concentrated by PMN, profoundly inhibited superoxide generation in all groups of diabetic and control cells. PMN from Hispanic diabetic patients produced greater quantities of superoxide than non-diabetic controls. This increased oxidative respiratory burst activity may predispose to infection and chronic inflammation in diabetes. PKC inhibitors and azithromycin inhibited this respiratory burst response. The possible role of PKC (especially PKC beta) as the mediator of this augmented respiratory burst response requires further evaluation, and may lead to therapeutic studies with appropriate inhibitors.     

Defective polymorphonuclear leukocyte metabolism and function in canine cyclic neutropenia.

Humans and grey collie dogs with cyclic neutropenia are known to suffer from an increased rate of bacterial infection. Because of the previously described microanatomic abnormalities of lysosome formation found in the polymorphonuclear leukocytes (PMNs) of dogs with canine cyclic neutropenia, studies of these cells were undertaken. PMNs from grey collie dogs were found to have significant metabolic and functional abnormalities when compared with normal collie PMNs. These included abnormally increased postphagocytic C1-glucose oxidation, decreased iodination of trichloroacetic acid-precipitable protein in the resting and phagocytizing state, decreased levels of intracellular myeloperoxidase,and a bactericidal defect against a variety of bacteria. Phagocytosis was normal. These abnormalities appear to differ from those previously described in the PMNs of patients with chronic granulomatous disease of childhood and the Chediak-Higashi syndrome and more closely resemble those seen in hereditary myeloperoxidase deficiency. Thus, the studies reported here demonstrate defective PMN function in a disease state previously believed to be a model only of periodic hematopoiesis.     

In vivo potentiation of polymorphonuclear leukocyte chemotaxis by clindamycin

Summary Polymorphonuclear leukocyte (PMNL) chemotaxis was evaluated in ten healthy volunteers who had received 600 mg of clindamycin intramuscularly. Serum obtained 3 hours after the administration of clindamycin significantly increased PMNL chemotaxis. Serum obtained at 12 and 24 hours after the administration of the drug did not induce significant increase in PMNL chemotaxis. The administration of clindamycin had no direct effect on the PMNLs in terms of their chemotactic activity. These results demonstrate serum-associated augmentation of PMNL chemotaxis by clindamycinin vivo which may be of potential clinical benefit in the outcome of infections.

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Potenzierung der Chemotaxis polymorphkerniger Leukozyten durch Clindamycin in Vivo

Zusammenfassung Die Chemotaxis polymorphkerniger Leukozyten (PMNL) wurde bei zehn freiwilligen Probanden nach intramuskulärer Applikation von 600 mg Clindamycin untersucht. Serum, das 3 h nach Gabe von Clindamycin gewonnen wurde, führte zu einer signifikanten Verstärkung der PMNL-Chemotaxis. Serum, das 12 bis 24 h nach Applikation von Clindamycin gewonnen wurde, induzierte hingegen keine signifikante Zunahme der PMNL-Chemotaxis. Clindamycin hatte auf PMNL keinen direkten Effekt hinsichtlich chemotaktischer Aktivität. Diese Ergebnisse weisen auf eine mit Serum assoziierte Verstärkung der PMNL-Chemotaxis durch Clindamycinin Vivo hin, die für die Bewältigung von Infektionen möglicherweise von Nutzen ist.

     

Platelet-dependent modulation of polymorphonuclear leukocyte chemiluminescence

Human blood platelets decreased luminol-enhanced chemiluminescence of human polymorphonuclear leukocytes (PMNL) stimulated with FMLP or Ca2+-ionophore A23187 by 56 or 47%, respectively. Horseradish peroxidase potentiated the decreasing effect of platelets on A23187-stimulated PMNL (92% inhibition) or reversed inhibition of FMLP-induced chemiluminescence to 94% potentiation, indicating dependence of platelet activity on availability of extracellular peroxidase. Moreover, platelet activity may depend also on the extent of platelet activation, as non-activated platelets (in the presence of FMLP) were found to potentiate PMNL-generated chemiluminescence, while platelets activated with A23187 displayed the opposite effect. Interference of platelets with formation and liberation of superoxide anion was indicated by platelet-modified isoluminol chemiluminescence. Superoxide dismutase with catalase and sodium azide were used, respectively, to differentiate the intracellular and the extracellular part of the chemiluminescence signal. Platelets were found to be capable of modifying both components of chemiluminescence, i.e., oxygen metabolites produced on the plasma membrane as well as on membranes of intracellular granules.     

Platelet-dependent modulation of polymorphonuclear leukocyte chemiluminescence

Human blood platelets decreased luminol-enhanced chemiluminescence of human polymorphonuclear leukocytes (PMNL) stimulated with FMLP or Ca2+-ionophore A23187 by 56 or 47%, respectively. Horseradish peroxidase potentiated the decreasing effect of platelets on A23187-stimulated PMNL (92% inhibition) or reversed inhibition of FMLP-induced chemiluminescence to 94% potentiation, indicating dependence of platelet activity on availability of extracellular peroxidase. Moreover, platelet activity may depend also on the extent of platelet activation, as non-activated platelets (in the presence of FMLP) were found to potentiate PMNL-generated chemiluminescence, while platelets activated with A23187 displayed the opposite effect. Interference of platelets with formation and liberation of superoxide anion was indicated by platelet-modified isoluminol chemiluminescence. Superoxide dismutase with catalase and sodium azide were used, respectively, to differentiate the intracellular and the extracellular part of the chemiluminescence signal. Platelets were found to be capable of modifying both components of chemiluminescence, i.e., oxygen metabolites produced on the plasma membrane as well as on membranes of intracellular granules.     

Prevention of degradation of human polymorphonuclear leukocyte proteins by diisopropylfluorophosphate

Proteases can complicate the characterization of proteins from cells, especially human polymorphonuclear leukocytes (PMN), which contain abundant neutral proteases. We tested the ability of agents to inhibit proteolysis, with special reference to the subunit polypeptides of the contractile proteins actin, myosin, and actin-binding protein (ABP). Phenylmethylsulfonyl fluoride (PMSF), O-phenanthroline, EGTA, EDTA, N- ethylmaleimide, alone or in combinations, failed to prevent extensive proteolysis of the PMN proteins during solubilization of cells with dodecyl sulfate. These inhibitors and also alpha-1-antitrypsin and soybean trypsin inhibitor similarly could not prevent proteolysis during homogenization of cells in cold isosomolar sucrose. Treatment of PMN with greater than or equal to mM diisopropylfluorophosphate (DFP) prior to solubilization or homogenization markedly inhibited proteolysis. PMSF and DFP were equally effective in inhibiting proteolysis in PMN extracts, suggesting that the efficacy of DFP may result from its permeation of intact cells and granules before barriers are disrupted by detergents or homogenization. Treatment of PMN with DFP under conditions inhibiting proteolysis did not affect their rate of phagocytosis. We recommend the use of DFP in future studies correlating functions and protein structure of PMN.     

Simvastatin treatment modifies polymorphonuclear leukocyte function in high-risk individuals: a longitudinal study

BACKGROUND: Although extensive experimental evidence supports a primary role of polymorphonuclear leukocytes (PMNs) in atherosclerosis, few data exist concerning the functional properties of these cells and their pharmacological modulation in high-risk individuals. OBJECTIVE: The production of the proinflammatory chemokine interleukin-8 (IL-8), migration and chemotaxis, and reactive oxygen species (ROS) generation were investigated in a longitudinal study in PMNs obtained from high-risk individuals during statin treatment. As a secondary endpoint we compared PMN function of high-risk patients with that of controls. METHODS AND RESULTS: PMNs were isolated from 21 high-risk individuals before treatment and 3 and 30 days after the beginning of simvastatin treatment, and from healthy controls. During treatment a significant reduction was observed both in resting (P = 0.009) and N-formyl-Met-Leu-Phe (fMLP)-stimulated (P = 0.008) IL-8 production, and in the chemotactic index (P = 0.038), whereas ROS generation did not significantly change. In comparison with cells from controls, PMNs obtained from patients before starting simvastatin treatment showed higher resting and fMLP-stimulated IL-8 release (P = 0.007 and P = 0.002, respectively) and ROS generation (resting, P = 0.009; and fMLP-stimulated, P = 0.046), whereas migration and the chemotactic index did not significantly differ. CONCLUSIONS: An activation of neutrophils is present in high-risk individuals, shown by the enhanced production of IL-8, and increased ROS generation. The 4-week statin treatment is able to reduce the cell capability to produce IL-8, and to decrease chemotaxis, thus affecting the proinflammatory properties of PMNs.     

Defective triggering of polymorphonuclear leukocyte oxidative metabolism by Legionella pneumophila toxin

Preincubation of human polymorphonuclear leukocytes (PMNLs) with Legionella pneumophila toxin impaired activation of the superoxide-generating complex induced by latex particles and by the Ca++ ionophore A23187. The toxin had no effect, however, on activation of the complex induced by phorbol myristate acetate (PMA), concanavalin A, valinomycin, or bromolasalocid. The toxin prevented PMNL plasma membrane depolarization induced by A23187 but failed to influence the membrane depolarization induced by PMA. These observations indicate that Legionella pneumophila toxin selectively impairs activation of the phagocyte superoxide-generating complex without affecting the functional integrity of components of the complex.     

Inhibition of human polymorphonuclear leukocyte chemotaxis by oxygenated sterol compounds.

When preincubated with certain oxygenated sterol compounds in lipoprotein-depleted serum [20% (vol/vol)], human polymorphonuclear leukocytes show inhibition of chemotaxis toward the synthetic dipeptide N-formylmethionylphenylalanine without alteration of random movement or loss of cell viability. These effects can occur at sterol concentrations as low as 6.25 microM and after as little as 5 min of preincubation, but they are increased at higher concentrations and longer preincubation times. The inhibition can be almost completely reversed by preincubation in lipoprotein-replete serum [human AB serum, 20% (vol/vol)] and may be partially corrected by addition of free cholesterol (0.125 mM) to the medium. These effects are unlikely to be due to inhibition of cellular sterol synthesis, competition for chemotaxin membrane binding sites, or deactivation of the leukocytes but they may be a consequence of insertion of the sterol molecule into the leukocyte plasma membranes.     

Enhancement of polymorphonuclear leukocyte function against gram-positive aerobic organisms grown in the presence of lincomycin

Summary The effect of pre-incubatingStaphylococcus aureus, Streptococcus pneumoniae andStreptococcus pyogenes with subinhibitory concentrations of lincomycin was studied with respect to polymorphonuclear leukocyte function against these organisms. Culturing the above organisms in the presence of lincomycin (1/4 MIC) resulted in a significant enhancement of polymorphonuclear leukocyte chemotaxis, phagocytosis and bactericidal activity against these organisms.

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Verstärkung der Funktion polymorphkerniger Leukozyten gegen in Anwesenheit von Lincomycin kultivierte grampositive aerobe Keime

Zusammenfassung Staphylococcus aureus, Streptococcus pneumoniae undStreptococcus pyogenes wurden mit subinhibitorischen Konzentrationen von Lincomycin präinkubiert, und es wurde untersucht, welche Veränderungen sich daraus für die Funktion polymorphkerniger Leukozyten gegenüber diesen Erregern ergeben. Wenn die genannten Keime in Gegenwart von Lincomycin (bei 1/4 MHK) kultiviert wurden, nahmen Chemotaxis, Phagozytose und bakterizide Aktivität polymorphkerniger Leukozyten gegen diese Keime signifikant zu.

     

Effect of high-dose methylprednisolone infusion on polymorphonuclear leukocyte function in patients with systemic lupus erythematosus

We have studied the effect of high-dose (1 gm) methylprednisolone infusion on polymorphonuclear leukocyte (PMN) function in 11 patients with active systemic lupus erythematosus (SLE). The only alteration of polymorphonuclear leukocyte function produced consistently by methylprednisolone was decreased adherence to plastic surfaces when tested 2 hours after infusion. This steroid-induced abnormality, however, was transient. Cells obtained from patients 24 hours after a single dose of drug exhibited normal adhesiveness. These results indicate that single, large doses of methylprednisolone do not produce long-lasting abnormalities of PMN function in patients with lupus.     

Platelet-derived growth factor promotes polymorphonuclear leukocyte activation

The platelet-derived growth factor (PDGF) has several well defined important biologic activities. Platelet-derived growth factor is the major mitogen in human serum for cells of mesenchymal origins; it is a potent chemoattractant protein for human monocytes, neutrophils, fibroblasts, and smooth muscle cells; and has been implicated in transformation by simian sarcoma virus and perhaps in transformation by other agents as well. In this article, PDGF has been shown to stimulate activation of human peripheral blood neutrophils defined by loss of membrane associated calcium as reflected by loss of chlortetracycline fluorescence, release of superoxide anion and specific granule enzymes, and enhanced neutrophil adherence and aggregation. These responses occurred in a dose-dependent fashion at concentrations of PDGF between 10 ng/mL (0.4 nmol/L) and 40 ng/mL (1.5 nmol/L) and were comparable to effects obtained with optimal concentrations of fMLP and C5a. Degranulation induced by PDGF was selective for secondary (specific) granules and not primary (azurophil) granules. Platelet-derived growth factor thus is ideally suited for a pivotal role in attracting inflammatory cells locally and initiating neutrophil activation at sites of blood vessel injury. Platelet-derived growth factor or a closely related protein also may play an important role in attracting and activating neutrophils in association with inflammatory tumors.     

Platelet modulation of polymorphonuclear leukocyte shear induced aggregation

A cone and plate viscometer and Coulter Counter were used to study platelet modulation of polymorphonuclear leukocyte (PMNL) aggregation caused by controlled shear stress. As an index of aggregation, the large-particle percentage (LPP) was calculated. This represents the ratio of aggregated cell count to total cell count. PMNL suspensions in buffer (1.0 X 10(7) cells per milliliter, final concentration) did not show any aggregate formation at shear stresses below 150 dynes/cm2 for one minute exposure time (LPP less than 3%). However, there was PMNL aggregation in mixed PMNL and platelet-rich plasma suspensions in this shear stress range. Supernatant plasma from sheared platelets initiated PMNL aggregation at moderate shear stress (150 dynes/cm2 for one minute; LPP, 20.3% +/- 2.5%). In contrast, platelet release factors, such as adenosine diphosphate (2 mumol/L) and serotonin (2 mumol/L) did not cause PMNL aggregation (LPP, 2.9% +/- 1.2% and 3.3% +/- 0.8%, respectively). The use of a cyclo-oxygenase inhibitor (acetylsalicylic acid, 50 mumol/L) did not suppress the aggregation of PMNLs after shear (LPP, 20.1% +/- 2.4%). However, preincubation with nordihydroguaiaretic acid (10 mumol/L), an inhibitor of C-5 and C-12 lipoxygenase, and 6,9- deepoxy-6,9-(phenylimino)-6,8-prostaglandin I1 (U-60257, 10 mumol/L), an inhibitor of C-5 lipoxygenase in human leukocytes, suppressed this aggregation (LPP, 9.1% +/- 2.5% and 10.4% +/- 3.2%, respectively). Also, the formation of lipoxygenase products (5-HETE, 12-HETE, 15-HETE, and LTB4) activated by shear stress was documented by reversed phase- high-performance liquid chromatography (RP-HPLC). These data support the possibility of a cooperation between platelets and leukocytes in shear-induced PMNL aggregation that is dependent on C-12 or C-5 lipoxygenase activity, or both.     

Amphotericin-B promotes leukocyte aggregation of nylon-wool-fiber-treated polymorphonuclear leukocytes

Severe pulmonary reactions have been reported in patients receiving leukocyte transfusion and amphotericin-B. To study the interaction of amphotericin-B with polymorphonuclear leukocytes (PMN), purified human PMN were incubated with 200 mg of nylon wool fiber for 60 min either in the absence or presence of 2 mM EDTA. PMN were recovered in acid citrate dextrose solution and were suspended in balanced salt solution for determination of their aggregation properties. The cells exposed to nylon wool fibers without EDTA aggregated in response to concentration as low as 1.25 micrograms/ml of amphotericin-B. Cells initially treated with EDTA, however, failed to aggregate. Serum from a patient treated with amphotericin-B aggregated PMN exposed to nylon wool fiber but not control cells, whereas serum taken before amphotericin was given without effect on the PMN treated with nylon wool fiber. Amphotericin-B at 5 micrograms/ml failed to potentiate the release of beta- glucocuronidase or lactic dehydrogenase by PMN treated by nylon wool beyond that seen with exposure to the fibers alone. Rabbit peripheral blood was similarly incubated with nylon wool fibers and the recovered PMN were infused into recipient rabbits that had received 1 mg/kg of amphotericin-B intravenously 1 hr prior to the infusion of the leukocytes. Rabbits were sacrificed 30 min after transfusion of PMN, and their lungs were excised for histologic sectioning. Those rabbits receiving a combination of amphotericin-B and 4 x 10(7) nylon-wool- fiber-treated PMN had evidence of pulmonary hemorrhage and accumulation of leukocytes in the pulmonary vasculature whereas those animals who received such cells alone had normal appearing lung tissue. In summary, amphotericin-B at concentrations achievable in vivo enhanced the aggregation of PMN damaged by incubation with nylon fiber with subsequent accumulation of the phagocytes in pulmonary tissue.     

Lactoferrin: a promoter of polymorphonuclear leukocyte adhesiveness

Polymorphonuclear leukocytes (PMN) degranulate, adhere to vascular endothelium, or aggregate to each other following exposure of the cells to high concentrations of chemotactic stimuli such as formyl-methionyl- leucyl phenylalanine (FMLP). PMN released the specific granule product lactoferrin more readily in response to chemotactic stimuli, which correlated with promotion of PMN aggregation as measured by light transmission and enhanced PMN adherence. Both concanavalin A (Con-A) and phorbol myristate acetate (PMA), agents that lead to specific granule discharge, induced and sustained human PMN aggregation. Similarly, supernatants, generated from Con-A-treated PMN, aggregated fresh PMN in the presence of alpha-methylmannoside, a competitive inhibitor of the lectin. Anti-human lactoferrin IgG but not normal goat IgG blunted the aggregation elicited by both PMA and FMLP. Both human milk lactoferrin and rabbit PMN lactoferrin aggregated human lactoferrin promoted PMN adherence to endothelial cells. The enhanced PMN stickiness was correlated with the early phase of degranulation. Thus, PMN lactoferrin serves an autoregulatory role to retain PMN at inflammatory sites to amplify the inflammatory response.