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 molecular weight was 60 kD.The binding of lipopolysaccharide to mononuclear cells were enhanced by purified rat LBP. Stimulation 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 10 mg/L, the phosphorylation levers of p38 were lower as compared with that in the presence of 1 mg/L. Stimulation of rat alveolar 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.