GM-CSF-deficient mice are susceptible to pulmonary group B streptococcal infection.
Granulocyte-macrophage colony-stimulating factor (GM-CSF) gene-targeted mice (GM-/-) cleared group B streptococcus (GBS) from the lungs more slowly than wild-type mice. Expression of GM-CSF in the respiratory epithelium of GM-/- mice improved bacterial clearance to levels greater than that in wild-type GM+/+ mice. Acute aerosolization of GM-CSF to GM+/+ mice significantly enhanced clearance of GBS at 24 hours. GBS infection was associated with increased neutrophilic infiltration in lungs of GM-/- mice, while macrophage infiltrates predominated in wild-type mice, suggesting an abnormality in macrophage clearance of bacteria in the absence of GM-CSF. While phagocytosis of GBS was unaltered, production of superoxide radicals and hydrogen peroxide was markedly deficient in macrophages from GM-/- mice. Lipid peroxidation, assessed by measuring the isoprostane 8-iso-PGF2alpha, was decreased in the lungs of GM-/- mice. GM-CSF plays an important role in GBS clearance in vivo, mediated in part by its role in enhancing superoxide and hydrogen peroxide production and bacterial killing by alveolar macrophages. (+info
Interaction of inflammatory cells and oral microorganisms. II. Modulation of rabbit polymorphonuclear leukocyte hydrolase release by polysaccharides in response to Streptococcus mutans and Streptococcus sanguis.
The release of lysosomal hydrolases from polymorphonuclear leukocytes (PMNs) has been postulated in the pathogenesis of tissue injury in periodontal disease. In the present study, lysosomal enzyme release was monitored from rabbit peritoneal exudate PMNs exposed to Streptocccus mutans or Streptococcus sanguis. S. mutans grown in brain heart infusion (BHI) broth failed to promote significant PMN enzyme release. S. sanguis grown in BHI broth, although more effective than S. mutants, was a weak stimulus for promotion of PMN hydrolase release. Preincubation of washed, viable S. mutans in sucrose or in different-molecular-weight dextrans resulted in the ability of the organisms to provoke PMN release reactions. This effect could bot be demonstrated with boiled or trypsinized S. mutans or with viable S. sanguis. However, when grown in BHI broth supplemented with sucrose, but not with glucose, both S. mutans and S. sanguis triggered discharge of PMN enzymes. The mechanism(s) whereby dextran or sucrose modulates PMN-bacterial interaction may in some manner be related to promotion of microbial adhesiveness or aggregation by dextran and by bacterial synthesis of glucans from sucrose. (+info
Interaction of inflammatory cells and oral microorganisms. III. Modulation of rabbit polymorphonuclear leukocyte hydrolase release response to Actinomyces viscosus and Streptococcus mutans by immunoglobulins and complement.
In the absence of antiserum, rabbit polymorphonuclear leukocytes (PMNs) released lysosomal enzymes in response to Actinomyces viscosus (19246) but not to Streptococcus mutans (6715). Antibodies had a marked modulating influence on these reactions. PMN hydrolase release was significantly enhanced to both organisms when specific rabbit antiserum and isolated immunoglobulin G (IgG) were included in the incubations. Immune complex F(ab')2 fragments of IgG directed against S. mutans agglutinated bacteria. Immune complexes consisting of S. mutans and F(ab')2 fragments of IgG directed against this organism were not effective as bacteria-IgG complexes in stimulating PMN release. The intensity of the release response to bacteria-IgG complexes was also diminished when PMNs were preincubated with isolated Fc fragments derived from IgG. Fresh serum as a source of complement components had no demonstrable effect on PMN release either alone or in conjuction with antiserum in these experiments. These data may be relevant to the mechanisms and consequences of the interaction of PMNs and plaque bacteria in the pathogenesis of periodontal disease. (+info
Lung weight parallels disease severity in experimental coccidioidomycosis.
Evidence provided by histopathological study of lesions is a valuable adjunct for evaluating chemotherapeutic efficacy in experimental animal models, In addition, this should be correlated with a measure of disease severity in the same animal. The latter could be obtained by homogenization of infected organs and quantitative enumeration of viable cells of the etiological agent, but this would preclude histopathological studies in the same animal. Progression of disease in pulmonary infection is associated with replacement of air space by fluid, cells, and cellular debris. Therefore, an increase in lung weight should reflect severity of disease. Results with the murine model of coccidioidomycosis demonstrate that increasing lung weight parallels the increasing census of fungus cells in the lungs of both treated and nontreated infected mice. This was supported with evidence obtained from microscopic studies of lesions indicating that specific chemotherapy limited spread of the infection and inhibited multiplication of the fungus in the lung. Therefore, lung weight can be used as a measure of disease severity in the murine model of coccidioidomycosis. (+info
Enhanced Th1 activity and development of chronic enterocolitis in mice devoid of Stat3 in macrophages and neutrophils.
We have generated mice with a cell type-specific disruption of the Stat3 gene in macrophages and neutrophils. The mutant mice are highly susceptible to endotoxin shock with increased production of inflammatory cytokines such as TNF alpha, IL-1, IFN gamma, and IL-6. Endotoxin-induced production of inflammatory cytokines is augmented because the suppressive effects of IL-10 on inflammatory cytokine production from macrophages and neutrophils are completely abolished. The mice show a polarized immune response toward the Th1 type and develop chronic enterocolitis with age. Taken together, Stat3 plays a critical role in deactivation of macrophages and neutrophils mainly exerted by IL-10. (+info
Characterization and partial purification of a novel neutrophil membrane-associated kinase capable of phosphorylating the respiratory burst component p47phox.
The phosphorylation of p47phox is widely viewed as an important step in the activation of the neutrophil respiratory burst oxidase system. The exact nature of the kinase(s) responsible remains to be elucidated. We show here that such a kinase was detected on neutrophil membranes activated by either PMA or formyl-methionyl-leucyl-phenylalanine. This enzyme is not intrinsic to the neutrophil membrane and could be eluted with 0.5 M NaCl. The kinase activity was partially purified and was found not to be due to the presence of previously suggested kinases, including protein kinase C isotypes, mitogen-activated protein kinase and protein kinase B. Gel filtration and renaturation in substrate gels suggest a molecular mass of between 45 and 51 kDa. The kinase activity was independent of calcium and lipids but was potently inhibited by staurosporine. Treatment with protein phosphatase 2Ac suggested that the kinase was activated by serine/threonine phosphorylation. Phosphopeptide maps indicated that the kinase phosphorylated p47phox on similar sites to those found in vivo. These results indicate that activation of neutrophils by PMA results in the activation of a membrane-associated kinase that may play a part in the regulation of neutrophil NADPH oxidase through its ability to phosphorylate p47phox. (+info
Non-serum-dependent chemotactic factors produced by Candida albicans stimulate chemotaxis by binding to the formyl peptide receptor on neutrophils and to an unknown receptor on macrophages.
Serum-free culture filtrates of six Candida species and Saccharomyces cerevisiae were found to contain chemoattractants for human polymorphonuclear leukocytes (PMNs) and a mouse macrophage-like cell line, J774. The chemotactic factors differed for the PMN and J774 cells, however, in terms of heat stability, kinetics of liberation by the yeast cells, and divalent cation requirements for production. The chemoattractant in Candida albicans culture filtrates appeared to act through the formyl peptide receptor (FPR) of PMNs, since it was found to induce chemotaxis of Chinese hamster ovary (CHO) cells that were expressing the human FPR but did not induce chemotaxis of wild-type CHO cells. The C. albicans culture filtrates also induced migration of PMNs across confluent monolayers of a human gastrointestinal epithelial cell line, T84; migration occurred in the basolateral-to-apical direction but not the reverse direction, unless the epithelial tight junctions were disrupted. J774 cells did not migrate toward the formylated peptide (fMet-Leu-Phe; fMLF), and chemotaxis toward the C. albicans culture filtrate was not inhibited by an FPR antagonist (t-butoxycarbonyl-Met-Leu-Phe), suggesting that a different receptor mediated J774 cell chemotaxis. In conclusion, we have identified a receptor by which a non-serum-dependent chemotactic factor (NSCF) produced by C. albicans induced chemotaxis of PMNs. Additionally, we have shown that NSCF was active across epithelial monolayers. These findings suggest that NSCFs produced by C. albicans and other yeast species may influence host-pathogen interactions at the gastrointestinal tract mucosal surface by inducing phagocytic-cell infiltration. (+info
Role of the extracellular signal-regulated protein kinase cascade in human neutrophil killing of Staphylococcus aureus and Candida albicans and in migration.
Killing of Staphylococcus aureus and Candida albicans by neutrophils involves adherence of the microorganisms, phagocytosis, and a collaborative action of oxygen reactive species and components of the granules. While a number of intracellular signalling pathways have been proposed to regulate neutrophil responses, the extent to which each pathway contributes to the killing of S. aureus and C. albicans has not been clearly defined. We have therefore examined the effect of blocking one such pathway, the extracellular signal-regulated protein kinase (ERK) cascade, using the specific inhibitor of the mitogen-activated protein kinase/ERK kinase, PD98059, on the ability of human neutrophils to kill S. aureus and C. albicans. Our data demonstrate the presence of ERK2 and a 43-kDa form of ERK but not ERK1 in human neutrophils. Upon stimulation with formyl methionyl leucyl phenylalanine (fMLP), the activities of both ERK2 and the 43-kDa form were stimulated. Despite abrogating the activity of both ERK forms, PD98059 only slightly reduced the ability of neutrophils to kill S. aureus or C. albicans. This is consistent with our finding that PD98059 had no effect on neutrophil adherence or degranulation, although pretreatment of neutrophils with PD98059 inhibited fMLP-stimulated superoxide production by 50%, suggesting that a change in superoxide production per se is not strictly correlated with microbicidal activity. However, fMLP-stimulated chemokinesis was markedly inhibited, while random migration and fMLP-stimulated chemotaxis were partially inhibited, by PD98059. These data demonstrate, for the first time, that the ERK cascade plays only a minor role in the microbicidal activity of neutrophils and that the ERK cascade is involved primarily in regulating neutrophil migration in response to fMLP. (+info