Relationship of plasma lactoferrin content to neutrophil regeneration and bone marrow infusion

Increased plasma lactoferrin levels in leucocytapheresis therapy in patients with rheumatoid arthritis

OBJECTIVE

The aim of this study was to clarify the mechanism of leucocytapheresis (LCAP) in patients with RA.

METHODS

Protein profiles of blood samples from two patients with RA obtained via LCAP column inlet and outlet lines were analysed by two-dimensional fluorescence difference gel electrophoresis and mass spectrometry. The lactoferrin (LTF) levels of peripheral and circulating blood samples from seven patients obtained via the LCAP column blood circuit were then determined by ELISA. Peripheral blood samples from 14 patients with RA were exposed to unwoven polyester fibre filters and the LTF level was determined. In addition, morphological changes in neutrophils after exposure to the filter were examined by optical microscopy, electronic microscopy and LTF immunostaining.

RESULTS

LTF levels were increased in both samples from the LCAP column outlet and peripheral blood at the end of LCAP treatment. Furthermore, peripheral blood samples exposed to the filter revealed a decreased number of neutrophils and an increased level of LTF. Morphological analysis of the exposed neutrophils showed vacuolization of the cytoplasm and degranulation of LTF-positive granules. These data suggest that LTF stored in the granules of neutrophils is released from the neutrophils caught in the LCAP column.

CONCLUSION

Because LTF has been reported to have multiple anti-inflammatory properties, increased levels of LTF may contribute to the clinical effect of LCAP in patients with RA.

Structural characterization of the interaction of human lactoferrin with calmodulin

Lactoferrin (Lf) is an 80 kDa, iron (Fe³⁺)-binding immunoregulatory glycoprotein secreted into most exocrine fluids, found in high concentrations in colostrum and milk, and released from neutrophil secondary granules at sites of infection and inflammation. In a number of cell types, Lf is internalized through receptor-mediated endocytosis and targeted to the nucleus where it has been demonstrated to act as a transcriptional trans-activator. Here we characterize human Lf’s interaction with calmodulin (CaM), a ubiquitous, 17 kDa regulatory calcium (Ca²⁺)-binding protein localized in the cytoplasm and nucleus of activated cells. Due to the size of this intermolecular complex (∼100 kDa), TROSY-based NMR techniques were employed to structurally characterize Ca²⁺-CaM when bound to intact apo-Lf. Both CaM’s backbone amides and the ε-methyl group of key methionine residues were used as probes in chemical shift perturbation and cross-saturation experiments to define the binding interface of apo-Lf on Ca²⁺-CaM. Unlike the collapsed conformation through which Ca²⁺-CaM binds the CaM-binding domains of its classical targets, Ca²⁺-CaM assumes an extended structure when bound to apo-Lf. Apo-Lf appears to interact predominantly with the C-terminal lobe of Ca²⁺-CaM, enabling the N-terminal lobe to potentially bind another target. Our use of intact apo-Lf has made possible the identification of a secondary interaction interface, removed from CaM’s primary binding domain. Secondary interfaces play a key role in the target’s response to CaM binding, highlighting the importance of studying intact complexes. This solution-based approach can be applied to study other regulatory calcium-binding EF-hand proteins in intact intermolecular complexes.

Low density lipoprotein receptor-related protein (LRP) is required for lactoferrin-enhanced collagen gel contractile activity of human fibroblasts

Fibroblasts plated on a type I collagen gel can reduce the size of the gel in a way that mimics the reorganization of the collagen matrix that accompanies the wound healing process. We demonstrated previously that lactoferrin (Lf) specifically binds to WI-38 human fibroblasts and enhances their collagen gel contractile activity. The effect of Lf correlated with the phosphorylation of myosin light chain (MLC), suggesting that Lf promotes fibroblast contractile activity by regulating MLC phosphorylation. We found here that the binding of Lf to WI-38 cells was inhibited by recombinant receptor-associated protein (RAP), a universal competitor for ligand binding to LRP (LDL receptor-related protein), and RAP can also promote the collagen gel contractile activity. These observations suggest that LRP is a receptor that mediates the Lf-induced enhancement of collagen gel contractile activity in WI-38 fibroblasts. To confirm the hypothesis, we utilized LRP antisense oligonucleotide, which was modified by morpholino linkage. Suppression of LRP expression abrogated the Lf-induced enhancement the contractile activity in fibroblasts. Treatment of fibroblasts with Lf enhanced the phosphorylation of ERK1/2 and the activation of MLC kinase (MLCK). These effects were attenuated by suppression of LRP expression. These findings suggest that LRP is involved in the Lf-enhanced collagen gel contractile activity of WI-38 fibroblasts by converting the Lf binding signal into the activation of ERK1/2 and MLCK.

Human neutrophil lactoferrin trans-activates the matrix metalloproteinase 1 gene through stress-activated MAPK signaling modules

It has been proposed that human neutrophil lactoferrin (Lf) could be involved in gene expression as a DNA-binding protein after its translocation into the nucleus. However, the molecular basis of Lf action has not been defined, and Lf-regulated target genes have not been identified. We report here that overexpressed Lf functions as a specific trans-activator of matrix metalloproteinase 1 (MMP1) gene, and that induction of this AP-1-responsive gene is mediated via the stress-activated MAPK signaling modules. Transactivation of the MMP1 promoter by overexpressed Lf requires the presence of an AP-1 binding site. In gel shift experiments, Lf did not interact directly with AP-1-containing fragments of the MMP1 promoter. However, nuclear extracts from Lf-expressing cells contained increased levels of proteins that bound to AP-1 elements. This Lf-induced AP-1 DNA binding activity was reduced by a p38 MAPK inhibitor. Inhibitors of the MEK kinases had little effect on Lf-induced AP-1. However, expression of dominant-negative MKK4 or JNK1 inhibited Lf-induced gene expression. The JNK activity stimulated by Lf correlates with the enhanced AP-1 binding ability. These findings demonstrate that the Lf-induced activation of AP-1 is mediated via JNK and p38 MAPK pathways.

Deficiency of the specific granule proteins, R-binder/transcobalamin I and lactoferrin, in plasma and saliva: a new disorder

The mechanisms of hereditary deficiency of R binder, which originates in neutrophils and exocrine gland epithelium, are unknown and may be multiple. This led us to examine if defective R binder synthesis also involves proteins that colocalize with it in neutrophil-specific granules and exocrine epithelial cells and may be under common regulatory control. Stored plasma and saliva samples from five unrelated R binder-deficient patients and control subjects were assayed for R binder, lactoferrin, cationic antimicrobial protein-18, neutrophil gelatinase-associated lipocalin, gelatinase, lysozyme, and myeloperoxidase. One patient, patient A, had lactoferrin levels below the limits of detection in both plasma and saliva in addition to his R binder deficiency. Although his deficiency involved lactoferrin as well, he had no history of predisposition to infection. PCR amplification of his R binder gene promoter region and the beginning of the first exon revealed no DNA abnormalities. His son and the son of his equally deficient brother, both presumptive heterozygotes, had mild deficiency of both R binder and lactoferrin. The results show that R binder deficiency exists in at least two forms. One, presumably the less common of the two forms, is the new hereditary entity described here, which is characterized by deficiency of more than one specific granule protein in both plasma and saliva. Despite this more widely distributed absence of the proteins than is found in congenital specific granule deficiency, infection posed no clinical problem in the affected patient.

Neutrophil function in pregnancy and rheumatoid arthritis

BACKGROUND

Pregnancy exerts suppressive effects on rheumatoid arthritis (RA). An attenuation in neutrophil function in late pregnancy which may explain this amelioration has previously been reported.

OBJECTIVE

A longitudinal investigation of neutrophil activity in healthy pregnant women (n=9) and pregnant patients with RA (n=9), compared with age matched non-pregnant patients with RA (n=12) and healthy controls (n=22).

METHODS

Neutrophil activation was measured in response to the physiological receptor agonists, n-formyl-methionyl-leucyl-phenylalanine (fMLP) and zymosan activated serum (ZAS). Superoxide anion production (respiratory burst) was determined by lucigenin enhanced chemiluminescence (LUCL); secondary granule lactoferrin release by enzyme linked immunosorbent assay (ELISA); and CD11b, CD18, and CD62L expression by flow cytometric analysis.

RESULTS

Stimulated neutrophil LUCL was significantly reduced in both pregnant women with RA and healthy pregnant women in the second (fMLP 43% and 69%, ZAS 43% and 59%, respectively) and third trimesters (fMLP 24% and 44%, ZAS 32% and 38%, respectively). Responses returned to normal within eight weeks of delivery and unstimulated levels remained unchanged throughout pregnancy. Basal and stimulated CD11b, CD18, and CD62L expression showed no variations throughout gestation for both pregnancy groups. Likewise, stimulated lactoferrin release and plasma lactoferrin remained unchanged. Certain morphological differences in RA neutrophils were highlighted by the flow cytometric analysis. Moreover, resting neutrophils and stimulated cells from patients with RA, including pregnant subjects, showed a marked increase in LUCL, but a reduction in CD11b, CD18, and CD62L. Low dose prednisolone and methylprednisolone had no effect on neutrophil parameters over the period of treatment with non-steroidal anti-inflammatory drugs.

CONCLUSION

The attenuation to neutrophil respiratory burst in both healthy and RA pregnancies may offer an explanation for the pregnancy induced remission of this inflammatory disorder.

Lactoferrin: a multifunctional glycoprotein

Lactoferrin is an iron-binding glycoprotein found in milk, exocrine secretions of mammals, and in secondary granules from polymorphonuclear neutrophils. This review describes the wide spectrum of functions ascribed to lactoferrin, with special emphasis on the antimicrobial properties of this protein, and its derived peptides.

Neutrophil function in women with pre-eclampsia

OBJECTIVE

To investigate the function of neutrophils in normal pregnancy and pre-eclampsia.

DESIGN

Baseline levels and activated responses of peripheral blood neutrophils were measured in response to the physiological agonists, n-formyl-met-leu-phe (fMLP) and zymosan activated serum.

SAMPLE

Neutrophils of 16 pre-eclamptic, 17 normal pregnant (third trimester) and 15 nonpregnant age-matched control women were calculated.

SETTING

Antenatal Clinic, City Hospital, Nottingham.

METHODS

Neutrophil superoxide anion production was determined by lucigenin-enhanced chemiluminescence; the release of secondary granule lactoferrin by ELISA; and the expression of cell surface adhesion molecules CD11b, CD18 and L-selectin (CD62L) by flow cytometric analysis.

RESULTS

Superoxide anion generation was reduced in the pregnant group compared with nonpregnant controls [fMLP by 51% (P = 0.03) and zymosan activated serum by 56% (P = 0.01)] but pre-eclamptic measurements did not show a similar reduction. There were no differences between the three study groups in the plasma levels of lactoferrin, or in the stimulated expression and release of CD11b and CD18, or lactoferrin and L-selectin. The base-line levels for the production of superoxide anions; the expression of CD11b or CD18 or L-selectin; and the release of lactoferrin showed no significant differences.

CONCLUSIONS

Circulating neutrophils in pregnancy and pre-eclampsia are neither activated nor primed in vivo, however the release of reactive oxygen species is diminished in normal pregnancy. In comparison, an elevation of reactive oxygen generation in pre-eclampsia may highlight a role for neutrophils in the oxidative stress and pathophysiology of this disease.

Effect of antibiotic treatment on inflammatory markers and lung function in cystic fibrosis patients with Pseudomonas cepacia

BACKGROUND

The acquisition of Pseudomonas cepacia in patients with cystic fibrosis is associated with increasing deterioration in lung function and more frequent hospital admissions. Pseudomonas cepacia is usually resistant to several antibiotics in vitro, but the response of patients colonised with the organism has not been extensively studied in vivo.

METHODS

A three month prospective study was performed to investigate the response of 14 Ps cepacia positive patients and 10 Ps cepacia negative patients to a two week course of intravenous antibiotics. All those who were Ps cepacia negative and six of the 14 Ps cepacia positive patients had Ps aeruginosa in their sputum which was sensitive to the prescribed therapy. The inflammatory markers C-reactive protein, white blood cell count, serum lactoferrin, neutrophil elastase/alpha 1-antitrypsin complex, and tumour necrosis factor alpha were measured at the start and end of each antibiotic course.

RESULTS

The median (range) % improvement in baseline FEV1 and FVC following treatment in the group as a whole was 15.2% (-23.5% to 156.3%) and 23.9% (-36.8% to 232.7%) respectively. There was no statistical difference in improvement in lung function, body weight, or inflammatory markers between individuals who were Ps cepacia positive and those who were Ps cepacia negative.

CONCLUSIONS

Patients who are Ps cepacia positive appear to respond as well to intravenous antibiotics as those who are Ps cepacia negative, despite having lower lung function and a bacterium in their sputum which is resistant in vitro to the antibiotics used.

The effect of rGM-CSF on neutrophil and eosinophil regeneration after ABMT as monitored by circulating levels of granule proteins

In order to further evaluate the effects of rGM-CSF on the reconstituting granulopoiesis, plasma and serum levels of myeloperoxidase (MPO) and lactoferrin (LF), as well as serum levels of eosinophil cationic protein (ECP), were monitored daily during a period of 3-4 weeks following ABMT in a group of 22 patients treated with either rGM-CSF (n = 11) or placebo (n = 11). Despite faster increase in the neutrophil counts in the rGM-CSF group, we did not observe any difference either in P-MPO or in P-LF during the period of early engraftment (days 11-19). This finding indicates that the proliferative effect of rGM-CSF on the neutropoiesis may be overestimated when neutrophil counts alone are taken into consideration, and suggests that other mechanisms may have contributed to the increase in the number of circulating neutrophils. The ratio of the serum to plasma level of LF, but not of MPO, was higher in the rGM-CSF group, probably reflecting a specific in vivo neutrophil priming effect. In the rGM-CSF group there was a clear increase of S-ECP during the second and third week post transplant, corresponding to an increase in eosinophil counts, which indicates that rGM-CSF stimulated eosinophil reconstitution without causing excessive activation of the mature eosinophils.

Lactoferrin and the inflammatory response

Polyclonal antibodies were prepared to purified breast milk lactoferrin and used in an ELISA to measure plasma concentrations in investigations of various aspects of the inflammatory response. They were also used, in situ, to evaluate granulocyte lactoferrin content in disease states. The first series of studies addressed the putative role of lactoferrin in the pathogenesis of the hypoferremic, hyperferritinemic response to acute inflammation. Dissociation between the lactoferrin response and the iron related changes in rheumatoid arthritis and after alpha-interferon administration suggested that the relationship observed in acute and chronic bacterial infection may reflect coincidental effects of inflammatory cytokines. That lactoferrin does not mediate the inflammatory hypoferremic response was established by the finding that bone marrow transplant recipients, post-myeloablation, developed a hypoferremic response during septic episodes despite virtually undetectable plasma lactoferrin concentrations. The second series of investigations employed the plasma lactoferrin concentration as an index of granulocyte activation and function in a number of inflammatory conditions. Markedly increased initial plasma concentrations in acute pneumonia reflecting profound intravascular granulocyte activation were documented to predict sepsis related mortality. Plasma and granulocyte lactoferrin studies established that viral infection is associated with an acquired granulocyte lactoferrin deficiency. Plasma measurements indicated that asthmatics, even when clinically asymptomatic, have evidence of persistent granulocyte activation.

Aspects of preanalytical variation of lactoferrin and elastase/alpha 1-protease inhibitor complexes

A number of interesting applications of plasma elastase/alpha 1-protease inhibitor complexes (ELA-PI) and lactoferrin (LAC) have recently been suggested. However, the clinical utility of these components often seems to be low. This might be improved by minimizing the preanalytical variation, if possible. Therefore, we have evaluated the influence of various aspects of sampling and handling conditions on the results obtained when measuring ELA-PI and LAC. Blood samples from both healthy persons as well as patients, who had undergone laparotomy the day before, were investigated. We confirmed the previous observations of higher concentrations of ELA-PI and LAC in serum compared to plasma. This was more pronounced in patients than in healthy adults. In EDTA-blood the most important change was seen in samples from patients when stored at room temperature. In this situation increases of LAC concentrations of 50% and 100% following 2 and 5 h, respectively were found. This in vitro release of LAC was abolished when samples were stored on ice until centrifugation within 5 h. In contrast, a statistically significant increase in ELA-PI of 10% was observed following storage on ice for 2 h of blood specimens drawn from healthy persons. EDTA-plasma obtained by venous puncture following minimal stasis contained 10% higher concentrations of LAC compared to samples drawn from intravenous catheters, while no difference was observed in the case of ELA-PI. However, in one individual prolonged venous stasis resulted in larger differences of both LAC and ELA-PI. Different centrifugation conditions (1500 vs. 3000 x g; room temperature vs. 4 degrees C) did not influence concentrations of LAC or ELA-PI measured, neither did eating a normal meal nor moderate physical activity (30 min walk). In conclusion, ELA-PI and LAC should be measured in EDTA-plasma. Blood must be drawn by venous puncture applying minimal stasis or from indwelling venous catheters. Samples for measuring LAC must be stored on ice until centrifugation. Separation of plasma from cells should be performed as fast as possible, but storage for up to 5 h can be accepted.

An enzyme-linked immunosorbent assay for plasma-lactoferrin. Concentrations in 362 healthy, adult blood donors

Very different concentrations of plasma-lactoferrin in healthy adults have been reported in the literature. We compared three commercially available lactoferrins and lactoferrin purified in our laboratory as calibrators in an ELISA. No statistical differences among these preparations of lactoferrin were detected. The concentration of purified lactoferrin was measured by dry weight, and efforts were made in order to minimize loss of purified lactoferrin by adhesion to tubes etc. and thus, secure accuracy of the method. Dilutions were made in PBS 0.01 mol l-1 with NaCl 0.436 mol l-1, (NH4)2SO4 0.5 mol l-1, BSA 5 gl-1 and normal rabbit IgG 10 mg l-1, which was shown to give parallel dilution curves of primary calibrator, secondary calibrator and plasma samples. No significant difference in the content of lactoferrin in neutrophils (median; range) among men (1.78; 0.83-4.48 micrograms 10(-6) neutrophils; n = 20) and women (2.12; 1.16-9.30 micrograms 10(-6) neutrophils; n = 14) was found. Lactoferrin was analysed in EDTA-plasma obtained from 135 female and 227 male blood donors. Median concentrations were 84.7 and 97.8 micrograms l-1 respectively, while 2.5% and 97.5% reference limits (with 90% confidence intervals) were estimated to 42.9 (38.7-47.4) micrograms l-1 and 166.9 (151.0-186.3) micrograms l-1 for women and 52.3 (49.1-55.6) micrograms l-1 and 189.9 (175.9-206.4) micrograms l-1 for men, respectively.

Myeloid regeneration after bone-marrow transplantation monitored by serum measurements of myeloperoxidase, lysozyme and lactoferrin

Bone-marrow regeneration after chemo- and radiotherapy-induced aplasia can be monitored by serum levels of myeloperoxidase (MPO), lysozyme (LYS) and lactoferrin (LF). In 10 patients with leukemia, serum measurements were performed before and after bone-marrow transplantation. Bone-marrow regeneration was suggested by increments in serum MPO and LYS 5 and 4 days prior to the increase in mononuclear cells (Mono) and 10 and 9 d before the increase in polymorphonuclear leukocytes (PMN) in the peripheral blood. LF started to rise 4.5 d before detectable circulating PMNs. 2 patients with early relapses of leukemia post transplantation are shown to display atypical patterns of serum MPO and LYS. We conclude that serum measurements of MPO, LYS and LF may be used as early and sensitive means to monitor bone-marrow activity during hematological regeneration. However, the findings also strongly support the earlier proposal that MPO alone may be used to reflect myeloid activity in the bone-marrow in general.

Lactoferrin and C-reactive protein in response to cytostatic drugs with emphasis on methotrexate

In this study plasma concentrations of lactoferrin (LF) and C-reactive protein (CRP) are examined in 9 children with different kinds of cancer but without any intercurrent infections. New, sensitive enzyme-linked immunosorbent assay for LF and CRP are described. The samples are drawn before, during, and after the cytotoxic drugs are given. The cytotoxic courses include cis-platinum, vincristine, adriamycin, cytarabine, and methotrexate (6 g/m2/24 h and 33.6 g/m2/24 h). During the infusion of methotrexate 33.6 g/m2 the concentrations of LF are increased, only a small increase of CRP is observed, and for the other groups there is no changes of both parameters.

Plasma lactoferrin content: differential effect of steroid administration and infective illnesses: lack of effect of ambient temperature at which specimens are collected

The effect of parenteral hydrocortisone on plasma lactoferrin concentration, neutrophil count and lactoferrin:neutrophil ratio was assessed in 10 volunteer subjects. Administration of a single dose of corticosteroid was followed by a significant rise in the circulating neutrophil count, a significant but proportionately smaller rise in the plasma lactoferrin concentration and a significant fall in the lactoferrin:neutrophil ratio. Acute viral infections were found to be associated with a disproportionately low plasma lactoferrin concentration relative to the circulating neutrophil count. The relatively low lactoferrin concentrations in both these situations could be of significance in regard to the propensity to bacterial infection and superinfection which these 2 groups of subjects display. Compared to patients with viral infection, those suffering from Plasmodium falciparum malaria showed a significantly elevated lactoferrin:neutrophil ratio, although this ratio was not significantly different when malarial patients were compared to normal individuals. These findings suggest that the pathogenesis of relative neutropenia in viral and protozoal illnesses is fundamentally different. Finally, it was found that the temperature at which specimen collection takes place does not appear to be a significant variable determining the plasma lactoferrin concentration.