Endotoxin-binding proteins in nasal lavage: evaluation as biomarkers to occupational endotoxin exposure

Exposure to endotoxin (LPS) can cause chronic respiratory disease, with symptoms that are more pronounced after exposure-free periods. The aim of this study was to evaluate LPS-response modulating proteins in nasal lavage and plasma as biomarkers for exposure to airborne endotoxin. We applied nasal lavage, lung function and exposure measurements in a small group (n = 11) of cotton workers during 6 weeks of observation (after 2 weeks free from exposure) and ten external controls. Lipopolysaccharide binding protein (LBP) and bactericidal/permeability increasing protein (BPI) were measured in nasal lavage fluid (NALF) along with classic markers such as differential cell counts, Interleukin-8 (IL-8) and albumin, to evaluate their use as markers in endotoxin exposure. In all control subjects and cotton workers LBP and BPI were readily detectable in NALF, although a high intra- and intervariability was noted. At the exposure levels in this study (cotton dust, geometric mean (GM) = 1.10 mg m(-3); endotoxin, GM = 2869 EU m(-3)), plasma BPI and BPI and LBP in NALF were significantly (P < 0.05) different from external controls. In addition, within the group of cotton workers, during the measurement period a significant increase was noted in BPI, albumin and BPI/LBP ratio in NALF (P < 0.05), while a significant decrease in total cell numbers was noted. However, none of the markers in NALF was correlated to the different exposure indices used, based on personal endotoxin or dust exposure measurements. The data show that LBP and BPI are present in nasal lavage fluid and that these markers as well as their ratio increase during airborne endotoxin exposure in cotton workers.