BACKGROUND: Endotoxins are pro-inflammatory substances present in the environment. In man, inhalation of its purified derivative lipopolysaccharide (LPS) induces inflammation related to macrophages and neutrophils. Corticosteroids and phosphodiesterase (PDE)-4 inhibitors have inhibiting effects on macrophages and neutrophils, respectively. This study investigated the effect of prednisolone and of the PDE-4 inhibitor cilomilast on the LPS-induced acute inflammation. METHODS: The study was a placebo-controlled, double-blind crossover design. On three occasions, at 2 weeks interval, 16 healthy subjects inhaled 50mug LPS after a 6-day treatment with cilomilast (15mgbd), prednisolone (10mgbd) or placebo. For the assessment of the inflammatory response, induced sputum was obtained before inclusion and 6h post-LPS while blood samples were collected before, 6 and 24h post-LPS. RESULTS: Inhaled LPS induced an increase in sputum neutrophils (p<0.0001), logMMP-9 (p<0.05), logMMP-9/TIMP-1 (p<0.01) and logTNF-alpha (p<0.02). At the blood level there were significant rise in neutrophilia (p<0.001), E-selectin (p<0.02), C-reactive protein (CRP) (p<0.001) and LPS-binding protein (p<0.001). There was both a slight, but not significant, increase in body temperature and decrease in forced expiratory volume in 1s (FEV(1)). Neither prednisolone nor cilomilast had protective effect on the LPS-induced airways' inflammation. The LPS-induced CRP acute-phase protein of inflammation (0.58+/-0.13 and 3.52+/-0.41mg/dL, before and after LPS, respectively) was significantly inhibited by a pre-treatment with prednisolone (1.39+/-0.32mg/dL, p<0.01) and attenuated (2.65+/-0.30mg/dL, p=0.09) with cilomilast. CONCLUSION: In healthy subjects, while the LPS-induced airways' inflammation was not modified either by oral prednisolone or by PDE-4 inhibitor cilomilast (at actual dosage), the LPS-induced acute phase of blood inflammation was reduced by prednisolone.