Effects of lipopolysaccharide binding protein on activation of p38 signaling pathway induced by LPS in macrophages

AIM:To investigate the regulatory effects of lipopolysaccharide binding protein(LBP)on activation of p38 signaling pathway induced by lipopolysaccharide(LPS)in alveolar macrophages.METHODS:The LBP from actue phase rat serum was purified by ammonium sulphate precipitation, Bio-Rex70 resin and the MonoQ column. Rat alveolar macrophages were exposed to LPS (0.01 mg/L or 1 mg/L) the various concentrations of LBP(0 mg/L, 0.01 mg/L, 0.1 mg/L, 1 mg/L and 10 mg/L).Western blotting were used to detect phospho-p38 in alveolar macrophages. RESULTS:SDS-PAGE analysis indicated that the purified preparation of rat LBP showed homogeneity and the molecu-lar weight was 60 kD.The binding of lipopolysaccharide to mononuclear cells were enhanced by purified rat LBP.Stimu-lation of rat alveolar macrophages with LPS at concentration of 0.01 mg/L was LBP dependent.LBP at concentrations up to 1 mg/L was able to increase the activation of p38.However, when LBP concentrations were further increased to 10mg/L, the phosphorylation levers of p38 were lower as compared with that in the presence of 1 mg/L.Stimulation of ratalveolar macrophages with LPS at concentrations of 1 mg/L was LBP-independent.CONCLUSION:The activation of p38 induced by LPS at lower concentration(0.01 mg/L) was LBP-dependent, meanwhile, LPS at higher concentration(1 mg/L) was LBP-independent.