Lactoferrin as an indicator of septicemia and endotoxemia in pigs

Acute phase responses induced in dwarf goats by r.BolL(-1beta), r.BolL(-2) and r.BolFN(-gamma)

The contribution of each of the pro-inflammatory cytokines to specific components of the host response to infection remains unclear. Therefore, the effects of single doses of cytokines were studied in dwarf goats. The present study was carried out to investigate the effects of r.BoIL(-1beta), r.BoIL(-2) and r.BoIFN(-gamma) on plasma zinc and iron concentrations, white blood cell counts, and body temperature. The i.v. injection of r.BolL(-1beta) (1 mug kg(-1)) resulted in an immediate fever which reached peak values 45 and 180 min after injection. Compared with fever induced by r.BoIL(-1beta), that caused by r.BoIFN(-gamma) (2 mug kg(-1)) was delayed in onset. Although the biphasic fever after r.BoIFN(-gamma) was more pronounced than after r.BoIL(-1beta), the reduction in plasma trace metal concentrations was less than after r.BoIL(-1beta), r.BoIL(-2) (1 mug kg(-1) i.v.) did not induce changes in these parameters. The haematologic changes observed revealed a cell type and cytokine specific pattern. The delayed onset of the effects induced by IFN(-gamma) suggests that they may be mediated through the induction of other mediators of inflammation.

Sepsis biomarkers: a review

INTRODUCTION

Biomarkers can be useful for identifying or ruling out sepsis, identifying patients who may benefit from specific therapies or assessing the response to therapy.

METHODS

We used an electronic search of the PubMed database using the key words "sepsis" and "biomarker" to identify clinical and experimental studies which evaluated a biomarker in sepsis.

RESULTS

The search retrieved 3370 references covering 178 different biomarkers.

CONCLUSIONS

Many biomarkers have been evaluated for use in sepsis. Most of the biomarkers had been tested clinically, primarily as prognostic markers in sepsis; relatively few have been used for diagnosis. None has sufficient specificity or sensitivity to be routinely employed in clinical practice. PCT and CRP have been most widely used, but even these have limited ability to distinguish sepsis from other inflammatory conditions or to predict outcome.

Human lactoferrin: a novel therapeutic with broad spectrum potential

Lactoferrin (Lf), a natural defence iron-binding protein, has been found to possess antibacterial, antimycotic, antiviral, antineoplastic and anti-inflammatory activity. The protein is present in exocrine secretions that are commonly exposed to normal flora: milk, tears, nasal exudate, saliva, bronchial mucus, gastrointestinal fluids, cervico-vaginal mucus and seminal fluid. Additionally, Lf is a major constituent of the secondary specific granules of circulating polymorphonuclear neutrophils (PMNs). The apoprotein is released on degranulation of the PMNs in septic areas. A principal function of Lf is that of scavenging free iron in fluids and inflamed areas so as to suppress free radical-mediated damage and decrease the availability of the metal to invading microbial and neoplastic cells. Mechanisms of action of Lf in addition to iron deprivation are also described. Administration of exogenous human or bovine Lf to hosts with various infected or inflamed sites has resulted in some prophylactic or therapeutic effects. However, an adverse response to the protein might occur if it were to stimulate antibody production or if it were to provide iron to the invading pathogen. The recombinant form of human Lf has become available and development of the product for use in a wide range of medical conditions can now be anticipated.

Lactoferrin and cyclic lactoferricin inhibit the entry of human cytomegalovirus into human fibroblasts

Lactoferrin is mainly produced by polymorphonuclear leukocytes and has been demonstrated in mammalian milk and external secretions. Lactoferrin is an iron-binding, multifunctional protein and may play an important role in immune regulation and in defense mechanisms against bacteria, fungi and viruses. Lactoferricin is a potent antimicrobial peptide generated from the N-terminal part of lactoferrin by pepsin cleavage. We demonstrate that lactoferrins from different species and its N-terminal peptide lactoferricin (particularly the cyclic form) inhibit expression of early and late antigens, as well as production of infectious viral progeny during human cytomegalovirus (HCMV) infection in vitro. Iron-saturated lactoferrin did not affect HCMV antigen expression. Heparin had the same effects as iron-depleted lactoferrin. Yet, mixtures of lactoferrin and heparin did not inhibit HCMV multiplication i.e. lactoferrin and heparin seemed to mutually block each other's antiviral activities. HCMV-infected cells exposed to lactoferrin and cyclic lactoferricin contained less intracellular virus than unexposed cells. The antiviral activity of cyclic lactoferricin was more than seven-fold weaker than that of the maternal molecule. Lactoferrin and cyclic lactoferricin prevented HCMV entrance into the host cell.

Characterization and functional analysis of the porcine lactoferrin gene promoter

Lactoferrin, a ferric binding glycoprotein found in milk, can possibly prevent microbial infection of the mammary gland and gastrointestinal tract. To define the regulation of the porcine lactoferrin gene (pLTF), we cloned its 5'-flanking region from a porcine liver genomic library and analyzed the 5' upstream region of approx. 4kb, two exons, and an intron. The transcription start site was localized by primer extension to residue G, which is 41 nucleotides upstream from the ATG start codon. The pLTF 5'-flanking region possesses several putative cis-acting regulatory elements found in both housekeeping and inducible genes; to define their function, they were inserted into a chloramphenicol acetyltransferase reporter construct. The region up to -156 sufficed for basic promoter activity, whereas the region up to -780 was required for maximal promoter activity in porcine testis cells (STcells), kidney cells (PK15 cells) and human mammary epithelial cells (HBL-100 cells). Detailed analysis of this proximal region by DNase I footprinting and electrophoretic mobility shift assays reveals that the ubiquitous factors SP1, AP2 and the mammary gland-specific factor (MGF) might play significant roles in regulating the transcription of the pLTF gene.

Iron: mammalian defense systems, mechanisms of disease, and chelation therapy approaches

During the past 6 decades, much attention has been devoted to understanding the uses, metabolism and hazards of iron in living systems. A great variety of heme and non-heme iron-containing enzymes have been characterized in nearly all forms of life. The existence of both ferrous and ferric ions in low- and high-spin configuration, as well as the ability of the metal to function over a wide range of redox potentials, contributes to its unique versatility. Not surprisingly, the singular attributes of iron that permit it to be so useful to life likewise render the metal dangerous to manipulate and to sequester. All vertebrate animals are prone to tissue damage from exposure to excess iron. In order to protect them from this threat, a complex system has evolved to contain and detoxify this metal. This is known as the iron withholding defense system, which mainly serves to scavenge toxic quantities of iron and also for depriving microbial and neoplastic invaders of iron essential for their growth. Since 1970, medical scientists have become increasingly aware of the problems involved in cellular iron homeostasis and of the disease states related to its malfunctioning. Scores of studies have reported that excessive iron in specific tissue sites is associated with development of infection, neoplasia, cardiomyopathy, arthropathy and a variety of endocrine and neurologic deficits. Accordingly, several research groups have attempted to develop chemical agents that might prevent and even eliminate deposits of excess iron. A few of these drugs now are in clinical use, e.g. deferiprone (L1). In the present review, we focus on recent developments in (i) selected aspects of the iron withholding defense system, and (ii) pharmacologic methods that can assist the iron-burdened patient.

The monocytic receptor for lactoferrin and its involvement in lactoferrin-mediated iron transport

Several studies suggest biological functions of the iron-binding neutrophilic glycoprotein lactoferrin that imply an initial interaction with cells from the monocyte/macrophage family. Among these, an important role of lactoferrin as responsible for the inflammatory-induced blood hyposideremia and accumulation of iron in the monocyte/macrophage system has been suggested mainly based on experiments in rodents. In a series of experiments we have examined the binding of human lactoferrin to human monocytes. We have demonstrated the presence of a receptor binding including a high-affinity component and a low-affinity component. The affinity of the binding is compatible with a biological significance of this receptor (KD is about 10(-8) M, and the number of receptors about 10(6) per cell). More than 90% of the lactoferrin will dissociate from the cell. The binding is not truly reversible since lactoferrin will lose its receptor-binding property after dissociation from the cell. The only observed change in the molecule is a small decrease in isoelectric point from 8.9 to 8.8. Lactoferrin is able to translocate at least 50% of its bound iron to intracellular ferritin in monocytes. These findings are compatible with the idea that lactoferrin might be involved in the pathogenesis of the disturbances in iron metabolism observed during inflammation.

Clinical detection of LPS and animal models of endotoxemia

The interest in the study of endotoxemia in the clinical area has increased recently as a result of a) improved and simplified endotoxin determination e.g. chromogenic-kinetic microplate methods (also an improved blood sampling tool is available), b) incidence of sepsis has increased due to improvement in early (e.g. posttraumatic) survival, c) interest in and good evidence for gut translocation as a source of endotoxemia, d) agents have developed, which can antagonize endotoxins. There is evidence that patients with positive endotoxin test in the ICU have a higher incidence of organ failure. To study the pathophysiological consequences of endotoxemia and possible ways of intervention animal models are necessary. The choice of the experimental setting depends on the aim of the study e.g. whether prolonged observation is necessary in survival studies or whether hemodynamic variables have to be measured or whether therapeutic agents only crossreact with primates. Since LPS levels are quite low in clinical studies, an important factor for selection of a relevant animal might be LPS sensitivity, or the use of additional sensitization techniques e.g. galactosamine. Another important aspect in this context is whether LPS is given as bolus or infused up to several days. In this review the dose, time, and route of LPS administration is also discussed. For screening purposes rodents are usually used, or sometimes rabbits due to their higher LPS sensitivity. Another very sensitive animal model is the sheep, which can be chronically instrumented and as a specialty allows lung lymph drainage and thus studies of LPS effects on pulmonary permeability. Pigs are used for hemodynamic studies and often in therapeutical studies if species-specificity of the drug tested is not important, in cases where a large animal is necessary. Finally the non-human primates offer a number of advantages due to human-like physiology, due to the cross-reactivity of human assay systems and accordingly also cross-reactivity of human therapeutic agents. While the chimpanzee also shares the LPS sensitivity of humans, baboons are insensitive like rodents. Thus each model serves to provide some useful purpose and the selection must be made to meet the requirements of the specific questions to be asked, with special emphasis of the chosen endotoxin model on relevance for the human sepsis state.

Interaction of calmodulin with lactoferrin

Calmodulin, as a major intracellular calcium-binding protein, regulates many Ca(2+)-dependent enzymes and plays an important role in a wide spectrum of cellular functions of the eukaryotes. Interaction between calmodulin and human lactoferrin, a 78 kDa protein with antibacterial properties, was found in the presence of Ca2+ using (i) a method for the detection of calmodulin binding proteins with biotinylated calmodulin, (ii) affinity chromatography on an agarose-calmodulin column with subsequent detection by an enzyme-linked immunosorbent assay (ELISA). The binding of calmodulin to lactoferrin blocked the ability of lactoferrin to agglutinate Micrococcus lysodeikticus.

Early response in neonatal septicemia. The effect of Escherichia coli, Streptococcus agalactiae and tumor necrosis factor on the generation of lactoferrin

Using an in vitro model, we report the early effect of Escherichia coli (E. coli), Streptococcus agalactiea (group B streptococci, GBS) and recombinant tumor necrosis factor alpha (TNF) on the release of lactoferrin (LF) and the generation of interleukin-1 (IL-1) due to E. coli, using heparinized whole blood from healthy full-term newborns. We wanted to find a dose response relationship between lactoferrin generation on the one hand and the amount of E. coli, GBS and TNF on the other hand. In a final concentration of 10(7) per ml both bacteria increased the release of LF significantly. The response to E. coli was immediate and mg/l +/- 0.29 mg/l, E. coli 1.83 mg/l +/- 0.76 mg/l, p less than 0.001). GBS was a less potent stimulant than E. coli and the response was only apparent after 20 minutes (mean +/- S.D.: 1.06 mg/l +/- 0.49 mg/l, p less than 0.01). TNF in a concentration of 10000 pg/ml as well as 1000 pg/ml increased the release of LF significantly (after 20 minutes mean +/- S.D.: 1.09 mg/l +/- 0.42 mg/l and 0.97 mg/l +/- 0.36 mg/l, respectively), whereas a concentration of 100 pg/ml had no effect. Whole blood incubated with different preparations of LF for 20 minutes did not increase the generation of LF significantly. No significant changes in IL-1 levels were observed. Lactoferrin had bacteriostatic but no bactericidal effect on GBS and Streptococcus mutans.

The production of tumour necrosis factor, tissue thromboplastin, lactoferrin and cathepsin C during lipopolysaccharide stimulation in whole blood

The release of tumour necrosis factor (TNF), lactoferrin (LF) and cathepsin C (CC) into plasma and production of thromboplastin (TPL) in monocytes were studied in lipopolysaccharide (LPS) stimulated heparinized whole blood from 10 healthy donors. The influence of dextran 70, haemaccel and methylprednisolone on levels of these parameters were examined. TNF concentration in plasma 5 min after the addition of LPS (0 h) was 250 pg/ml (median), 520 pg/ml after 1 h and 1300 pg/ml after 3 h. The addition of dextran 70 to the blood in addition to LPS at the same intervals gave significantly higher values of 740 pg/ml and 1800 pg/ml after 1 h and 3 h respectively. Unstimulated cells had no TPL but after 1 h with LPS, the TPL activity in incubated cells was 2.3 mU/10(6) monocytes and after 3 h, 2.7 mU/10(6) monocytes. LPS induced the secretion of LF from granulocytes (PMN) and the levels 5 min after the addition of LPS (0 h) were 2.1 mg/l (control 0.2 mg/l) and after 1 h, 5.3 mg/l (control 1.3 mg/l) in plasma after LPS stimulation. Haemaccel enhanced the LPS-induced generation of TPL in monocytes and production of CC. The LPS-induced secretion of LF was, to a small extent, influenced by the three reagents tested. Methylprednisolone (1 mmol/l) reduced the production and appearance of TNF in plasma and the generation of TPL activity in monocytes. This model for stimulating heparinized whole blood is suitable for examination of the production and appearance of cellular factors and the influence of drugs on this production.

Early fall of circulating iron and rapid rise of lactoferrin in septicemia and endotoxemia: an early defence mechanism

Total serum iron, plasma lactoferrin and circulating leukocytes were measured in piglets during the early phase of severe gram-negative septicemia and endotoxemia in 3 experimental settings: intravenous (i.v.) infusion of lipopolysaccharide (LPS) (n = 8), i.v. infusion of live Escherichia coli (n = 7) and intraperitoneal (i.p.) infusion of E. coli (n = 6). Iron dropped significantly during the first 30 min of LPS infusion from a median of 32 microM to 13.4 microM. A similar decrease in serum iron was demonstrated in the 2 other groups with minimum values at 120 min after the start of E. coli infusion. Plasma levels of lactoferrin increased significantly 120 min after the start of LPS infusion (median 6 mg/l) when compared to preinfusion values (0.25 mg/l). After i.v. infusion of E. coli a significant rise of plasma lactoferrin was demonstrated already 30 min after bacterial infusion (to 2.1 mg/l) compared to preseptic values (0.8 mg/l). This increase was accompanied with a significant drop of circulating leukocytes (to 7.3 x 10(9)/l) compared to before the infusion (17 x 10(9)/l) in the pigs given E. coli i.v. After i.p. E. coli infusion no significant change of plasma lactoferrin was observed. The rapid fall of total serum iron seen during endotoxemia and E. coli septicemia may in part be explained by the release of lactoferrin from granulocytes and the clearance of iron-bound lactoferrin in the blood or peritoneal cavity.