Effects of Nebulized Alpha-2 Macroglobulin in Horses with Lower Airway Inflammation.

Overview

• This study investigated whether nebulized alpha-2-macroglobulin (A2M), a natural anti-inflammatory protein, could improve clinical signs and reduce airway inflammation in horses with lower respiratory tract inflammation.
• The research tested the effects of A2M compared to saline placebo on respiratory symptoms, cellular inflammation in the lungs, and inflammatory cytokine levels in both lung fluid and blood.

Background and Rationale

• Equine asthma is a common chronic inflammatory disease affecting the lower airways of horses, leading to breathing difficulties and reduced performance.
• Current treatments often rely on corticosteroids, which can have safety concerns with long-term use.
• Alpha-2-macroglobulin (A2M) is a naturally occurring protease inhibitor with anti-inflammatory effects, suggesting potential as a non-steroidal therapeutic alternative.

Study Objectives

• To evaluate the impact of nebulized A2M treatment on horses with established lower airway inflammation.
• Parameters assessed included clinical respiratory scores, lung cytology from bronchoalveolar lavage fluid (BALF), and local (lung) plus systemic (blood) inflammatory cytokines, specifically TNF-α and IL-6.

Methods

• Subjects: 13 university-owned horses diagnosed with lower airway inflammation were enrolled and randomized into two groups.
• Treatment groups:
  • A2M group: Received nebulized alpha-2-macroglobulin suspension every 48 hours, for a total of 6 doses.
  • SALINE group: Received nebulized saline on the same schedule, serving as a placebo control.
• Assessment timeline:
  • Before each treatment and 24 hours after the 6th treatment, vital signs and clinical respiratory scores were recorded.
  • Rebreathing examination was conducted to assess respiratory function.
  • Bronchoalveolar lavage (BAL) was performed to collect fluid for cytologic analysis and inflammatory cytokine measurement by ELISA.
  • Blood samples were also collected to measure systemic cytokines.
• Data analysis used both descriptive (means, medians) and inferential statistics to detect any differences between groups and over time.

Results

• Clinical respiratory scores:
  • No significant improvement or change was seen in the A2M group over the treatment course.
  • The SALINE group showed an increase (worsening) in respiratory scores on days 2, 6, and 8, indicating progression of clinical signs in that group.
• Lung cytology:
  • Analysis of bronchoalveolar lavage fluid did not reveal significant differences between the A2M and SALINE groups at any time point.
  • This suggests that A2M did not reduce cellular inflammation markers in the lungs compared to placebo.
• Cytokine concentrations:
  • Levels of two key inflammatory cytokines, TNF-α and IL-6, measured in both BALF and plasma, showed no significant differences between the treatment groups throughout the study.
  • Indicates that nebulized A2M did not modulate local or systemic inflammation in these horses.

Conclusions

• Nebulizing alpha-2-macroglobulin did not significantly change clinical respiratory signs, lung inflammation, or inflammatory cytokine levels in horses with lower airway inflammation compared to saline placebo.
• While A2M has theoretical anti-inflammatory properties, this study suggests that, as administered, it is not effective as a non-steroidal treatment option for equine asthma or lower airway inflammation under the tested conditions.
• The findings highlight the continued need to explore new therapeutic strategies for managing chronic airway inflammation in horses.