Effect of Aerosolized Escherichia coli and Staphylococcus aureus on Iron and Iron-Binding Proteins in Lung Lavage Fluid

Abstract

Iron-binding proteins have antibacterial activity; they have been identified in lung secretions, but their role in pulmonary antibacterial defenses is unclear. Murine lactoferrin and murine transferrin were used to generate polyclonal antiserum to lactoferrin and to transferrin, and the specificity of both antisera was shown by western blot. Mice were exposed to either aerosolized Escherichia coli or Staphylococcus aureus; they were killed 1, 4, 24, or 48 hr later; and their lungs were lavaged. We measured the levels of transferrin, lactoferrin, and albumin and did a cell count for the lavage fluid. The predominant iron-binding protein in resting animals was transferrin. Aerosolized E. coli caused a brisk PMNL response in the lungs that was associated with a major increase in the levels of lactoferrin. Challenge with S. aureus was associated with a moderate increase in the number of macrophages and a moderate decrease in the levels of transferrin and iron but no change in the levels of lactoferrin. The levels of iron-binding protein can vary according to the type of inflammatory response.

Lactoferrin inhibits or promotes Legionella pneumophila intracellular multiplication in nonactivated and interferon gamma-activated human monocytes depending upon its degree of iron saturation. Iron-lactoferrin and nonphysiologic iron chelates reverse monocyte activation against Legionella pneumophila.

“…Whereas the local concentrations oflactoferrin at sites of inflammation are not known, milligrams-per-milliliter concentrations seem likely given that concentrations of lactoferrin in human plasma during infection can exceed 0.2 mg/ml (38). PMN are prominent in acute bacterial infection of the lung, and in an experimental murine model of pneumonia, increased concentrations of lactoferrin were demonstrated in lung lavage fluid, primarily as a result of neutrophil degranulation (39,40). PMN are also prominent in L. pneumophila infection of the lung, which is characterized histologically by an initial influx of PMN followed by an influx of mononuclear phagocytes, such that most established cases of pneumonia demonstrate a mix of neutrophils and mononuclear phagocytes (41).…”

Antibody response to Pseudomonas aeruginosa surface protein antigens in a rat model of chronic lung infection

“…The method of inducing the infection was as reported previously (Lam et al, 1980). Late exponential phase cells of strain P A 0 579 grown in TSB + Fe were incorporated into agar beads and introduced into the left lobe of rats via a tracheotomy.…”

“…In the rat model of P. aeruginosa pulmonary infection developed by Cash et al (1979), chronic infection is achieved by incorporating bacteria in agar beads before intratracheal inoculation into the lung. Bacteria rapidly spread from these beads and form microcolonies which are widely distributed throughout the bronchioles (Lam et al, 1980). The histopathological changes which occur in the animal lungs resemble those seen in the lungs of CF patients infected with P. aeruginosa.…”

“…Most P. aeruginosa isolates from CF lung infection elaborate an extensive exopolysaccharide at their surface (Doggett et al, 1966) which often is not stable upon culture in vitro. Studies by electronmicroscopy of bronc hoscopy and postmortem lung specimens from CF patients infected with P. aeruginosa have revealed extensive formation of microcolonies embedded in exopolysaccharide (Lam et al, 1980). In the rat model of P. aeruginosa pulmonary infection developed by Cash et al (1979), chronic infection is achieved by incorporating bacteria in agar beads before intratracheal inoculation into the lung.…”

A method for bronchoalveolar lavage in live pigs

“…Pulmonary alveolar macrophages (PAM) play a central role in the clearance of bacteria and particles from the lungs (11,14). In addition, noncellular factors such as fatty acids, low molecular weight proteins, iron binding proteins, and immunoglobins, are believed essential in lung defense mechanisms against respiratory infections (6,13,16,20). Longitudinal studies have reported lung lavage methods for several animal species, including humans (2,3,15).…”