Human Neutrophil Lipocalin Research Articles

Late response to allergen is associated with increased concentrations of tumor necrosis factor-α and IL-5 in induced sputum

Bronchial antigen challenge of sensitized atopic patients with asthma results in an early fall in FEV 1, followed in a proportion of patients by a late (4 to 24 hours) fall. The late response is accompanied by an increase in bronchial reactivity, which is widely believed to reflect local influx and degranulation of inflammatory cells, particularly eosinophils, in association with elevated local secretion of cytokines. We hypothesized that the development of a late-phase bronchoconstrictor response and airway eosinophilia after allergen challenge of sensitized atopic patients with asthma is associated with elevated induced sputum concentrations of the eosinophil-active cytokines IL-5 and granulocyte-macrophage colony-stimulating factor and the proinflammatory cytokine tumor necrosis factor-α. We counted inflammatory leukocytes and measured cytokine concentrations in induced sputum at baseline and 24 hours after inhalational allergen challenge of 15 atopic patients with asthma who had previously demonstrated a late response. We observed significant increases in the numbers of eosinophils and the concentrations of their granule products, eosinophil cationic protein and eosinophil peroxidase. In contrast, the numbers of neutrophils and concentrations of two of their products, myeloperoxidase and human neutrophil lipocalin, did not significantly change. The numbers of sputum eosinophils correlated with the maximal late-phase fall in FEV 1. Concentrations of IL-5 and tumor necrosis factor-α, but not granulocyte-macrophage colony-stimulating factor, were significantly elevated after allergen challenge. We conclude that the relatively noninvasive technique of induced sputum production can be used to monitor the effect of bronchial provocation on cytokine concentrations in asthma. (J Allergy Clin Immunol 1997;99:693-8.)

The effect of granulocyte colony‐stimulating factor (G‐CSF) on the degranulation of secondary granule proteins from human neutrophils in vivo may be indirect

Granulocyte colony-stimulating factor (G-CSF) was administered at a dose of 7.5 or 10 micrograms/kg s.c. once daily for 6d (days 1-6) to two groups consisting of eight and six healthy volunteers. The administration of G-CSF resulted in a rapid decrease in neutrophil counts and serum levels of the secondary granule protein, human neutrophil lipocalin (HNL) after 30 min, followed by a recovery and gradual increase within 180 min. The number of circulating neutrophils and plasma and serum levels of neutrophil secondary granule proteins were dramatically elevated on day 2 (1 d after the administration of G-CSF) and stayed so until day 7. The plasma levels of HNL and lactoferrin (LF) showed a biphasic pattern with peaks at day 2 and days 5-7, and remained highly elevated at day 12. The serum levels of HNL and LF increased rapidly (about 8-fold and 6-fold, respectively) on day 2 and stayed elevated until day 7, subsequently returning to baseline levels. At day 5, neutrophil release induced in vitro by f-MLP was significantly enhanced. The cellular contents of HNL and LF were reduced to about 50% of levels before G-CSF administration at day 5. The release of lactoferrin and HNL, but not of myeloperoxidase (MPO), was slightly enhanced after preincubation of isolated normal neutrophils with G-CSF in vitro, but no obvious release of these proteins was observed with G-CSF alone. The administration of G-CSF resulted in a dramatic increase in the alkaline phosphatase (AP) activity in the plasma membrane, with maximal activity occurring at day 5. Furthermore, during administration of G-CSF, TNF-alpha in plasma increased about 25-fold. TNF-alpha started to rise at day 2 and peaked at day 6. After discontinuation of G-CSF the levels of TNF-alpha gradually decreased. The elevated levels of TNF-alpha (tumour necrosis factor-alpha) were temporally correlated to the other signs of neutrophil activation. GM-CSF and IL-8, however, were not detected in plasma. Our data suggest that G-CSF affects the neutrophils not only directly but also indirectly by the induction of the production of other cytokines such as TNF-alpha.

A sandwich enzyme immunoassay for the determination of neutrophil lipocalin in body fluids

Human neutrophil lipocalin was purified from human buffycoat. A polyclonal antibody was obtained by immunisation of rabbits. The antibody reacted with the free lipocalin as well as with the PMNL-gelatinase bound protein. This antibody was used to establish a sensitive sandwich-ELISA for the determination of the protein in body fluids using the biotin/streptavidin system. The mean intra-assay C.V. was 2.3% and the mean inter-assay C.V. 6.7%. The recovery in human plasma was determined to be 98.8%. The ELISA allowed the determination of the protein in the concentration range 0.2–25 μg/l. Measurement of the neutrophil lipocalin concentration showed that human plasma of healthy donors contained 97 ± 81 μg/l ( n = 122) and that the concentrations in serum were significantly higher ( P < 0,001) with 133 ± 90 μg/l ( n = 122). Neutrophil lipocalin was also found in the urine of healthy donors (8.1 μg/l; n = 9). Very high concentrations of this lipocalin were found in the synovial fluids of patients suffering from inflammatory rheumatoid arthritis (1.7 ± 1.4 mg/l; n = 37).

Cloning and expression of human neutrophil lipocalin cDNA derived from bone marrow and ovarian cancer cells

Human neutrophil lipocalin (HNL) cDNA was amplified by PCR technology in combination with deoxyinosine containing oligonucleotides for cloning, sequencing and production of the recombinant protein in E. coli. The primers were targeted to the corresponding DNA backtranslate of the mature protein resulting in a PCR amplified 534 bp cDNA from different reverse transcripts of ovarian cancer cell line and bone marrow cell mRNAs. Sequence analysis revealed that two different cDNAs from ovarian cancer and bone marrow cells could be obtained. Cloning and expression of HNL cDNAs were performed in E. coli strain HMS 174 [DE3] using the pET system yielding in two recombinant proteins with a molecular weight of 21 kDa which is consistent with an 178 amino acid residues containing sequence of the mature HNL protein. N-terminal amino acid sequence analysis of the expression products showed an identical polypeptide sequence missing the E. coli processed starting methionine.

Studies of the release and turnover of a human neutrophil lipocalin.

A 24-kDa protein was purified from human neutrophil extracts and shown to be the newly discovered neutrophil gelatinase-associated lipocalin (NGAL), based on structural and immunochemical data. A specific enzyme-linked immunosorbent assay (ELISA) was developed for the determination of NGAL in human plasma and tissue fluids. Normal human plasma contains 72 micrograms l-1 of NGAL (range 40-109 micrograms l-1) in two main forms, monomer and dimer. 35S-methionine metabolic studies of human neutrophils showed that granulocyte macrophagecolony-stimulating factor (GMCSF) stimulated significant synthesis and secretion of NGAL in a dose- and time-dependent fashion. NGAL was rapidly released as monomer and dimer on incubation of heparinized whole blood with opsonized yeast, reaching a plateau corresponding to about 35% of total cell content after 30 min. Following intravenous injection of 125-iodine labelled NGAL there was a more rapid initial clearance of the monomeric than of the dimeric form; t1/2 10 min vs. 20 min. During the second phase the two forms cleared at similar rates. Severe acute peritonitis was accompanied by a 10-fold increase in NGAL plasma levels and the NGAL level in peritoneal exudates, which reached about 40 mg l-1. There was a good linear correlation between the concentrations of NGAL, leucocyte elastase and NP4 (neutrophil proteinase 4 = P3).

The development of an assay for human neutrophil lipocalin (HNL) — to be used as a specific marker of neutrophil activity in vivo and vitro

Human neutrophil lipocalin (HNL) is a newly discovered protein from human neutrophil secretory granules. A double-antibody radioimmunoassay (RIA) was developed for the measurement of HNL in various body fluids and its high specificity was confirmed by the absence of cross-reaction with other granulocyte granule proteins. The RIA measures HNL within the range of 4–256 μg/l. The intra- and interassay coefficients of variation were less than 6% and 10%, respectively. When HNL was added to serum samples full recovery was obtained. Sera and plasma from 100 apparently healthy individuals revealed a mean level of 78.40 μg/l (range 37.95–190.87 μg/l) in serum and a mean level of 50.65 μg/l (range 30.51–105.8 μg/l) in EDTA-plasma. The distribution of HNL after gel filtration indicated that HNL exists mainly in two major forms, dimer and monomer. This, in addition to the excellent recovery, suggests that these major forms of HNL do not bind to compounds in serum or plasma that would interfere with the assay. The high specificity, sensitivity, reproducibility and accuracy of the present assay should facilitate the measurement of HNL in blood and other body fluids.

Purification and characterization of a human neutrophil lipocalin (HNL) from the secondary granules of human neutrophils.

A 45 kDa-protein was purified from the granules of human neutrophils. The protein consists of two apparently identical subunits. The isoelectric point was pH 8.40, and the molecular weight 45 kDa (unreduced) or 24 kDa (reduced). Treatment of the protein with Endoglucosidase F resulted in a reduction in the molecular weight to 20 kDa, indicating the presence of N-linked carbohydrate. The extinction coeffient was E1%,1cm = 13.76 at 280 nm. The 60 amino acid sequence revealed up to 65% sequence homology with rat alpha 2-microglobulin-related protein, which belongs to the lipocalin family. The protein co-sedimented with secondary (specific) granule marker proteins and correlated to the neutrophil content of Lactoferrin (r = 0.81, p < 0.001) and was estimated to be 0.59 microgram 10(-6) cells. Release studies showed that the neutrophils released 51.4 +/- 9.0% of the total cellular content of the protein when they were exposed to serum-opsonized particles, which was much higher than the release of Myeloperoxidase (12.7 +/- 3.5%) and Lactoferrin (22.9 +/- 4.7%). The N-terminal and four tryptic fragment amino acid sequence of the protein was identical with an N-formyl peptide binding 24 kDa protein and gelatinase associated protein of human neutrophils. In conclusion, we have purified and characterized a protein, human neutrophil lipocalin (HNL), from the secondary granules of human neutrophils and shown that it is readily mobilized from the neutrophils upon stimulation.

The monitoring of inflammation by specific cellular markers.

The use of specific assays for unique secretory components of various inflammatory cells in the clinical evaluation of inflammatory diseases is a new and fascinating possibility, since these assays seem to be more sensitive indicators of inflammatory activity than the conventionally used methods and since these unique cellular markers in addition provide us with useful pathophysiological information. So far the most widely used markers are eosinophil cationic protein (ECP) from the eosinophil and neutrophil markers such as myeloperoxidase and elastase. Serum measurements of the former are used quite extensively in the evaluation of the inflammatory process in the lung of asthmatics whereas the latter predominantly are used in relation to bacterial infections and as compatibility markers in relation to extracorporeal circulation. Recent developments have shown that the serum measurement of a new protein from the neutrophil, human neutrophil lipocalin (HNL), is a superior means to distinguish acute bacterial and viral infections. The future access to a panel of unique cellular markers of inflammatory cells will undoubtedly reveal new exciting possibilities in the diagnosis and therapeutic monitoring of patients with inflammatory diseases.