N-acetylcysteine and ambroxol inhibit endotoxin-induced phagocyte accumulation in rat lungs

We have investigated whether pretreatment with N-acetylcysteine (NAC) and/or ambroxol (Amb), drugs known as reactive oxygen species (ROS) scavengers, would minimize lipopolysaccharide (LPS)-induced leucocyte accumulation in rat lung microvasculature and protect lungs from damage and the effect of these drugs on chemotactic peptide (fMLP)-induced chemiluminescence of human polymorphonuclear leukocytes (PMNs). Animals were injected ip with NAC (27.6 mg/kg, n=8), ambroxol (70 mg/kg, n=8), combination NAC+ambroxol (n=8), or 1 ml buffer alone (n=8), once a day for 3 consecutive days. Then animals were injected with LPS (17 mg/kg), and killed 3 h later. In each of another four groups eight rats were used as a control, and received the same drug treatment but LPS was replaced with 0.9% NaCl. PMNs and macrophages (Ms) were counted in histologic slides of lung tissue. Using computer image analysis we measured the area of alveolar profiles. Luminol-enhanced chemiluminescence was measured in PMNs suspensions obtained from healthy volunteers. Chemiluminescence intensity was measured in resting and fMLP-stimulated cells, and compared between cells incubated with Amb, NAC or distilled water. We observed significant differences in the number of PMNs and Ms, alveolar profile area between control and LPS-treated animals (P<0.01). PMNs and Ms were numerous in lungs of LPS-administered animals (PMNs: Median (M)=137.5 per 6 high power fields range (r)=54.0; Ms: M=123.0 r=11.0), less numerous in ambroxol-treated group (PMNs: M=101.5 r=32.0 and Ms:53.5 r=36.0), not abundant in NAC (PMNs:M=56.0 r=28.0 and Ms:M=20.5 r=13.0) and in NAC+ambroxol treated rats (PMNs:M=53.5 r=21.0 and Ms:M=29.0 r=9.0), and rare in LPS+drugs-untreated control group (PMNs:M=40.5 r=19.0 and Ms:M=18.5 r=15.0). Chemiluminescence assay revealed that 100 micro;M ambroxol stimulated fMLP-induced PMNs chemiluminescence and NAC of the same concentration had no significant effect.

In our experiment we showed that pretreatment with NAC and ambroxol may inhibit phagocyte influx to rat lung and may protect it from damage. We also revealed that NAC at dose 27.6 mg/kg has stronger protective properties than ambroxol at dose 70 mg/kg and this may result from enhancing effect of ambroxol on fMLP-provoked PMNs chemiluminescence.