Effect of treatment with erythromycin on bronchoalveolar lavage fluid cell populations in foals.

The research investigates the effect of the antibiotic erythromycin on the inflammatory responses in the lungs of young horses, implied to have potential applications on pulmonary health.

Objective and Methodology

• The aim of the study was to determine the impact of orally administered erythromycin on the inflammatory response in the lungs of young horses, specifically in relation to bronchoalveolar lavage (BAL).
• Researchers used 12 healthy, unweaned, mixed-breed foals of either sex, between 2 and 4 months old.
• A standard process known as BAL was conducted on all foals. For this, liquid (a phosphate-buffered saline solution) was injected into the lungs and subsequently collected for analysis. The same procedure was repeated after four days.
• Half of the foals were treated with erythromycin, while the other half served as a control group. After 4 days, erythromycin and anhydroerythromycin A concentrations were measured in the blood plasma of the treated foals.

Results

• The study found a significant decrease in the percentage of neutrophils (immune cells indicating inflammation) in the BAL fluid of the erythromycin-treated group compared to the control group.
• This was associated with an apparent decrease in the ability of BAL fluid cells in the treated group to migrate towards a chemoattractant source, implying a mitigation of the inflammation process.
• Moreover, there was noticeably less adhesion of these cells to a cell culture substrate after erythromycin treatment.
• Erythromycin A, the active substance, was not detected in the plasma at the time of the second BAL, but a by-product or “degradation product” of erythromycin, anhydroerythromycin A, was detected in the plasma of most treated foals.

Conclusion

• The research implies that BAL induces neutrophilic inflammation that persists for a minimum of four days in the lungs of young horses.
• Erythromycin administered orally at a dosage of 25 mg/kg bi-daily reduces this inflammation, potentially by altering the function of BALF cells.
• The alterations in chemotaxis (cell migration) and adherence (cell sticking) of pulmonary lavage cells might be due to the presence of erythromycin degradation products or residues of the parent drug in the lungs.
• A notable non-antimicrobial finding was that erythromycin seemed to affect host cell metabolism and decrease inflammatory responses in the airways, which could have interesting implications for future research.