Chemiluminescence of non-differentiated THP-1 promonocytes: developing an assay for screening anti-inflammatory milk proteins and peptides.

Human leukemic THP-1 promonocytes are widely used as a model for peripheral blood monocytes. However, superoxide production during respiratory burst (RB) of non-differentiated THP-1 (nd-THP-1) cells is very low. Here we present a rapid and low-cost method for measuring the chemiluminescence (CL) of opsonized zymosan (OZ) induced RB which allows detection of Escherichia coli lipopolysaccharide (LPS) induced priming of nd-THP-1 cells on the basis of CL reaction kinetics. Maximum CL intensity obtained was 2.20 ± 0.25 and 1.30 ± 0.11 relative light units, while CL peak time was achieved at 18.1 ± 2.6 and 28.7 ± 1.3 min in primed and non-primed cells, respectively. The priming of nd-THP-1 cells with LPS evoked typical TNF-α and IL-6 production. We tested the effects of bovine lactoferrin and protein fractions from Lactobacillus helveticus BGRA43 fermented milk for potential anti-inflammatory effects on LPS primed nd-THP-1 cells. Four fractions were found to inhibit the OZ-induced CL in a dose-dependent manner (IC(50) 3-30 µg/mL), while lactoferrin inhibited CL to a lesser extent (IC(50) 270 µg/mL). These results suggest that measuring CL response of nd-THP-1 cells can serve as a method for screening anti-inflammatory compounds which could be used in reducing the risk of phagocyte-mediated inflammatory diseases.