The efficacy of N-acetylcysteine in decreasing airway inflammation and mucus accumulation in horses with 18 hours of head confinement

Abstract

Background: During transportation many horses develop post-transportation infection, which can be life-threatening and end their sport career. Preventing mucus accumulation and inflammation during transportation is vital, emphasizing the need for effective strategies to enhance overall horse health welfare.

Objectives: Assess the impact of N-acetylcysteine (NAC) on mucus accumulation and inflammation in horses subjected to 18 hours of head confinement.

Animals: Six healthy crossbred horses, 5.3 ± 2.1 years of age and weighing 387 ± 30 kg.

Methods: Prospective placebo-controlled cross-over design study. The horses' heads were restrained in their stalls for a period of 18 hours. They were studied under 4 conditions: Not confined (NC): before head confinement, placebo (P), and confined head (CH): 18 hours of head confinement without treatment, and N-Acetylcysteine (NAC): 18 hours of head confinement treated with NAC before confinement (15 mg/kg/day NAC PO for 3 days). Bronchoalveolar lavage (BAL) was performed in each condition. Mucus accumulation along the trachea was evaluated by endoscopy.

Results: Endoscopic scores were significantly different between CH and other conditions, whereas no significant differences were found among NC, P, and NAC. The BAL cell count (34 291 ± 2624 cells/μL), neutrophil and lymphocyte count (18 601 ± 3193 cells/μL and 3337.4 ± 593 cells/μL, respectively) in CH were significantly higher compared to NAC. Neutrophil percentage was significantly higher in CH (53.8 ± 8%) compared to horses that received NAC (20.08 ± 8%). Conversely, in comparison to NAC (66.33 ± 9%), the percentage of macrophages was significantly lower in CH (35.7 ± 10%).

Conclusions: N-acetylcysteine was found to significantly decrease mucus accumulation and inflammatory cell counts in horses with head confinement.

Keywords: N-acetylcysteine; head confinement; horse; inflammation; transportation.

FIGURE 1

Dot Plots illustrating the actual values (cells/μL in the final sediment) of total cell count (A), neutrophil count (B), lymphocyte count (C), and macrophage count (D) in BAL fluids after an 18‐hour period for four conditions: NC (Not‐confined head), P (Placebo), CH (18 hours of head confinement without treatment), and NAC (18 hours of head confinement treated with NAC) (n = 6). Means with standard deviations are represented by bars. The y‐axes are presented on an exponential scale to better visualize the range of cell counts. **P ≤ .001; *P ≤ .05.

FIGURE 2

Dot Plots illustrating the percentage (%) of total cell count (A), neutrophil count (B), lymphocyte count (C), and macrophage count (D) in BAL fluids after an 18‐hour period for four conditions: NC (Not‐confined head), P (Placebo), CH (18 hours of head confinement without treatment), and NAC (18 hours of head confinement treated with NAC) (n = 6). Means with standard deviations are represented by bars. **P ≤ .001; *P ≤ .05.

FIGURE 3

Photomicrographs of Giemsa‐stained BAL samples. (A) Control. A few normal ciliated epithelial cells (Green arrow) in a poorly cellular sample (×400 magnification). (B‐D) BAL samples taken from horse with head elevation for 12 hours. (B) A large number of degenerated PMNs in a high cellular sample (×400 magnification). (C) A cluster of degenerated PMNs (Black arrow) in a higher magnification (×1000 magnification). (D) Some bacteria as bacilli (Red arrow) arranged in a chain (×1000 magnification). (E and F) BAL samples taken from horse with head elevation for 12 hours and oral administration of N‐acetylcysteine. (E) Some inflammatory cells as vacuolated macrophages in a moderate cellular sample (×400 magnification). (F) Some vacuolated macrophages (Yellow arrow) and ciliated epithelial cells (Green arrow) in a sample higher magnification (×1000 magnification).