Neutrophils activation can be diminished by apolipoprotein A-I

High density lipoprotein (HDL) has anti-inflammatory function. To investigate the effects of apolipoprotein A-I (ApoA-I), the major apolipoprotein of HDL, on activated neutrophils, we stimulated neutrophils in vitro with fMLP and PMA, as a receptor-binding and a nonreceptor-binding stimuli, respectively, and incubated ApoA-I with those neutrophils. Three conditions were utilized: 1) resting neutrophils + ApoA-I (0, 2.5,5, 10 microg/mL respectively), 2) fMLP(10(-7) mol/L)-activated neutrophils + ApoA-I (0, 2.5, 5, 10 microg/mL respectively), and 3) PMA(10(-7) mol/L)-activated neutrophils + ApoA-I (0, 2.5, 5, 10 microg/mL respectively). After incubation, we measured neutrophils adhesion to fibronectin, oxidative bust (O2- and H2O2 production), degranulation (release of MPO and elastase), and L929 cell mortality which were attacked by release-out of cytokines in activated neutrophils (using MTT). Our results showed that in vitro ApoA-I inhibits fMLP- and PMA- activated neutrophil adhesion, oxidative burst, degranulation and L929 cell mortality. These inhibition effects of ApoA-I on fMLP-activated neutrophils are more powerful than that on PMA-activated neutrophils. ApoA-I has no effect on resting neutrophils. We concluded that ApoA-I could diminish the function of activated neutrophils.