Increased monocyte oxidase activity in cystic fibrosis heterozygotes and homozygotes

Abnormalities in the pulmonary innate immune system in cystic fibrosis

Pulmonary infection is the dominant clinical feature of cystic fibrosis (CF), but the basis for this susceptibility remains incompletely understood. One hypothesis is that CF airway surface liquid (ASL) is abnormal and interferes with neutrophil function. To study this possibility, we developed an in vitro system in which we collected ASL from primary cultures of normal and CF airway epithelial cells. Microbial killing was less efficient when bacteria were incubated with neutrophils in the presence of ASL from CF epithelia compared with normal ASL. Antimicrobial functions of human neutrophils were assessed in ASL from CF and normal epithelia using a combination of quantitative bacterial culture, flow cytometry, and microfluorescence imaging. The results of these assays of neutrophil function were indistinguishable in CF and normal ASL. In contrast, the direct bactericidal activity of ASL to Escherichia coli and to clinical isolates of Staphylococcus aureus and Pseudomonas aeruginosa was substantially less in CF than in normal ASL, even when highly diluted in media of identical ionic strength. Together, these observations indicate that the antimicrobial properties of ASL in CF are compromised in a manner independent of ionic strength of the ASL, and that this effect is not mediated through a direct effect of the ASL on phagocyte function.

Altered intracellular pH regulation in neutrophils from patients with cystic fibrosis

Cystic fibrosis (CF) is a condition characterized by neutrophil-mediated lung damage and bacterial colonization. The physiological basis for reported functional alterations in CF neutrophils, including increased release of neutrophil elastase, myeloperoxidase, and oxidants, is unknown. These processes are, however, regulated by intracellular pH (pH(i)). We demonstrate here that pH(i) regulation is altered in neutrophils from CF patients. Although resting pH(i) is similar, pH(i) after acid loading and activation (N-formyl-methionyl-leucyl-phenylalanine and phorbol 12-myristate 13-acetate) is more acidic in CF cells than in normal cells. Furthermore, patients with non-CF-related bronchiectasis handle acid loading and activation in a fashion similar to subjects with normal neutrophils, suggesting that chronic pulmonary inflammation alone does not explain the difference in pH(i). This is further supported by data showing that normal neutrophils exposed to the CF pulmonary milieu respond by increasing pH(i) as opposed to decreasing pH(i) as seen in activated CF neutrophils. These pH(i) differences in activated or acid-loaded CF neutrophils are abrogated by ZnCl(2) but not by amiloride and bafilomycin A(1), suggesting that passive proton conductance is abnormal in CF. In addition, DIDS, which inhibits HCO(3)(-)/Cl(-) exchange, causes alkalinization of control but not of CF neutrophils, suggesting that anion transport is also abnormal in CF neutrophils. In summary, we have shown that pH(i) regulation in CF neutrophils is intrinsically abnormal, potentially contributing to the pulmonary manifestations of the condition.

Cytokine dysregulation in activated cystic fibrosis (CF) peripheral lymphocytes

Recent studies demonstrate in vivo and in vitro cytokine dysregulation in CF epithelial cells. To see if these abnormalities may be generalized to other cells expressing cystic fibrosis transmembrane conductance regulator (CFTR) but not directly exposed to local inflammation, we studied mRNA transcription, intracellular protein production and extracellular secretion of IL-2, IL-4, IL-5, IL-10 and interferon-gamma (IFN-gamma) from freshly isolated blood mononuclear and CD4+ T cells from CF patients and controls. Cells were activated by phorbol myristate acetate (PMA) and anti-CD3, PMA-ionomycin, or lipopolysaccharide (LPS) and assessed for cytokine mRNA transcription by semiquantitative reverse transcriptase-polymerase chain reaction, intracellular protein production by flow cytometry, and secretion by supernatant ELISA. Cytokine expression was highly stimulus-dependent. CF cells showed higher IL-10 transcription than control cells after maximal activation by LPS (P = 0.01); despite this, cytokine production and secretion were equivalent to controls. CF cells showed lower cellular IL-10 production after PMA-anti-CD3 activation (P = 0.002). CF cells secreted less IFN-gamma than control cells after maximal activation by PMA-anti-CD3 (1836 +/- 273 pg/ml versus 9635 +/- 3437 pg/ml, P = 0.04). IL-2, IL-4 and IL-5 regulation was similar to controls. We conclude that CF mononuclear cells show selective cytokine dysregulation after maximal activation, namely reduced IFN-gamma secretion and increased IL-10 mRNA without increased production or secretion. These findings extend defects described in respiratory epithelial cells to circulating immunoregulatory cells, suggesting a link between CF genotype and cytokine dysregulation.

Chemokine expression in CF epithelia: implications for the role of CFTR in RANTES expression

To delineate the mechanisms that facilitate leukocyte migration into the cystic fibrosis (CF) lung, expression of chemokines, including interleukin-8 (IL-8), monocyte chemoattractant protein-1 (MCP-1), and RANTES, was compared between CF and non-CF airway epithelia. The findings presented herein demonstrate that, under either basal conditions or tumor necrosis factor-alpha (TNF-alpha)- and/or interferon-gamma (IFN-gamma)-stimulated conditions, a consistent pattern of differences in the secretion of IL-8 and MCP-1 between CF and non-CF epithelial cells was not observed. In contrast, CF epithelial cells expressed no detectable RANTES protein or mRNA under basal conditions or when stimulated with TNF-alpha and/or IFN-gamma (P </= 0.05), unlike their non-CF counterparts. Correction of the CF transmembrane conductance regulator (CFTR) defect in CF airway epithelial cells restored the induction of RANTES protein and mRNA by TNF-alpha in combination with IFN-gamma (P </= 0.05) but had little effect on IL-8 or MCP-1 production compared with mock controls. Transfection studies utilizing RANTES promoter constructs suggested that CFTR activates the RANTES promoter via a nuclear factor-kappaB-mediated pathway. Together, these results suggest that 1) RANTES expression is altered in CF epithelia and 2) epithelial expression of RANTES, but not IL-8 or MCP-1, is dependent on CFTR.

Proteinase-free myeloperoxidase increases airway epithelial permeability in a whole trachea model

In cystic fibrosis the bronchiectatic conducting airways have large numbers of neutrophils in their walls and in their luminal contents. The neutrophil's primary granule enzyme activities of elastase and peroxidase are increased in the sputum of these patients. It has been postulated that these enzymes--together or individually--act to damage the airway epithelium. However, only peroxidase activity has consistently correlated with the degree of structural and functional airway disease in these patients with leakage of plasma protein into the airway lumen (Regelmann et al., Pediatr Pulmonol, 1995; 19:1-9). The present study was designed to test whether human neutrophil-derived myeloperoxidase can independently produce bronchial epithelial damage without the presence of proteases, as measured by increased permeability of the airway epithelium. Human peripheral blood neutrophils were purified, their primary granules isolated, and their peroxidase purified using affinity and ion exchange column chromatography. Activity of the proteinase-free peroxidase was measured using a chromogenic substrate. The effect of this peroxidase on the permeability of excised rat tracheas was measured using radioactive and fluorescent-labeled non-ionic molecules of varying molecular weight. Rat tracheas exposed to 15 minute treatments with either 130 U of peroxidase or hydrogen peroxide (10(-5) M) did not show a significant increase in the permeability of the epithelium to [3H]inulin, [14C]sucrose, and fluorescein isothiocyanate dextran 20 compared with control tracheas. However, those tracheas exposed to 130 U peroxidase followed by 10(-5) M hydrogen peroxide showed an increased permeability to each of the three test solutes. We conclude that proteinase-free myeloperoxidase, in the presence of non-toxic concentrations of its substrates, hydrogen peroxide and halide, produced increases in permeability to non-ionic molecules in the rat trachea within 15 minutes.

Sputum peroxidase activity correlates with the severity of lung disease in cystic fibrosis

Patients with cystic fibrosis (CF) of the same age differ significantly in their degree of pulmonary disease. Based on preliminary observations, we postulated that the activity of myeloperoxidase would be significantly increased in patients with greater structural lung damage than in those with less lung damage. Acid extracts of weighed sputum samples were assayed for lactoferrin concentrations by ELISA. Activities of peroxidase, cathespsin G, and elastase (with and without proteinase 3) were determined by kinetic analysis using chromogenic substrates. The patients were divided into quartiles based on their Brasfield chest-radiograph score. Patients in the first quartile (least amount of structural lung abnormality) were compared to those in the fourth quartile. The concentration of lactoferrin, a specific (secondary) granule protein of neutrophils, did not differ between the two patient groups. However, the activities of the neutrophil primary granule proteins, peroxidase, elastase, and elastase plus proteinase 3, were significantly elevated in the group with the most structural lung abnormality. Sputum albumin concentration was used to estimate leakages of plasma proteins into the airways. Peroxidase activity, but not the activity of cathepsin G, of elastase, or of elastase plus proteinase 3, correlated significantly with albumin/g sputum in both quartile groups. To confirm the association of sputum peroxidase activity with differences in lung structure and to test its correlation with lung function, spirometry was performed in a second group of patients during the week prior to the time of sputum sampling. In this second group, increased sputum peroxidase activity was associated with worse Brasfield scores and with decreased percent-predicted forced expiratory volume in 1 sec.(ABSTRACT TRUNCATED AT 250 WORDS)

Expression and regulation of tumor necrosis factor in macrophages from cystic fibrosis patients

Cachexia and anorexia commonly occur in patients with cystic fibrosis (CF), particularly those with severe pulmonary compromise and heavy tracheobronchial colonization with Pseudomonas aeruginosa. Current understanding of the pathophysiology of cachexia attributes much of the anorexia and weight loss to the effects of the cytokine tumor necrosis factor (TNF), which is secreted by endotoxin-stimulated macrophages. It has further been suggested that TNF may play a role in the pathobiochemistry of CF cachexia, secondary to the localized inflammatory response in the lung or wider systemic activation of cells of the monocyte-macrophage series in response to endotoxin. This study investigates TNF production and gene expression by peripheral blood monocyte-derived macrophages from CF patients, compared with normals (NL). The results indicate that although both cell populations responded dose-dependently to lipopolysaccharide (LPS); CF macrophages, upon stimulation with LPS at concentrations of 1 to 1,000 ng/ml, consistently produced substantially higher amounts of TNF than NL macrophages. At the molecular level, Northern blot analysis also revealed that both macrophage populations expressed TNF mRNA in response to LPS in a dose-dependent manner. However, at the same LPS concentrations, CF macrophage TNF mRNA expression was 2- to 4-fold greater than that of NL macrophages. LPS had no effect in either macrophage population on mRNA for CHO-B, a constitutive probe. To investigate differences between NL and CF macrophage TNF regulation, nuclear run-on/half-life studies as well as studies addressing potential differences in LPS membrane interactions and signal transduction were performed.(ABSTRACT TRUNCATED AT 250 WORDS)

Release of interleukin-8, interleukin-6, and colony-stimulating factors by upper airway epithelial cells: implications for cystic fibrosis

Cystic fibrosis (CF) is characterized by a dramatic neutrophil recruitment and repeated Pseudomonas infections in the lungs. To evaluate cytokine releasibility by airway epithelial cells in the context of CF, we studied primary nasal epithelial cells isolated from the upper airways and continuous epithelial cell lines from normal and CF subjects. Relatively low levels of interleukin (IL)-8, IL-6, and granulocyte/macrophage colony-stimulating factor (GM-CSF) were produced spontaneously by primary epithelial cells (< 50 pg/10(6) cells) and higher levels of colony-stimulating factor-1 (CSF-1) (1 to 2 ng/10(6) cells). Cells were stimulated with substances that are likely to be present in the inflamed lungs of CF patients-namely, the proinflammatory monokines IL-1 and tumor necrosis factor-alpha (TNF alpha) as well as neutrophil elastase and bacterial products from Pseudomonas (mucoid exopolysaccharide [MEP] and rhamnolipids). Both IL-1 and TNF alpha induced a dose-dependent release of IL-6 (5 to 10 ng/10(6) cells) and GM-CSF (2 to 3 ng/10(6) cells) by primary epithelial cells from eight normal volunteers. The TNF alpha/IL-1-stimulated GM-CSF release was blocked by the addition of 1 microM dexamethasone, whereas basal CSF-1 release was unaffected. Neutrophil elastase was a potent inducer of IL-8 and GM-CSF both in primary epithelial cells and in cell lines. Dexamethasone (1 microM) did not inhibit elastase-induced IL-8 release in either normal or CF epithelial cells. Rhamnolipids and MEP were found to stimulate the copious release of IL-8, GM-CSF, and IL-6 from epithelial cells, in a steroid-sensitive fashion.(ABSTRACT TRUNCATED AT 250 WORDS)