Inhibitory effects of α, β-unsaturated carbonyl-based compounds and their pyrazoline derivatives on the phagocytosis of human neutrophils

Abstract

A series of α, β-unsaturated carbonyl-based compounds (curcumin analogs and chalcone derivatives) and their pyrazoline derivatives were investigated for their in vitro inhibitory effects on the phagocytosis of human neutrophils. The effects of the compounds on the chemotactic migration, CD11a/18 expression, phagocytic activity, and reactive oxygen species (ROS) production by human whole blood cells (WBC) and isolated human polymorphonuclear neutrophils (PMNs) were assessed by using 24-well cell migration assay kit, flow cytometer, Phagotest assay kit, and luminol/lucigenin-based chemiluminescence assay, respectively. Compounds 4, 5, 6, 13, 23, 33, 39, and 41 showed strong inhibitory activity against PMNs chemotaxis with IC50 values, ranging from 0.22–1.68 µM which were much lower than those of ibuprofen and curcumin (IC50 values 11.02 and 5.0 µM, respectively). All compounds showed low or moderate inhibition of cell adhesion molecule expression except for compound 15, while compounds 4, 5, 8, and 21 at 100, 25, and 6.25 μg/mL showed strong inhibition of opsonized bacteria engulfment by neutrophils with the highest suppressive effects exhibited by compound 21 at 37.4%. Compounds 4, 11, 13, 14, 24, 25, 27, 33, and 34 significantly suppressed ROS generation by PMNs and WBC. Compounds with N-methyl 4-piperidone and 4-piperidone linkers (4, 13, 14, 23, 24) and 2-pyrazoline-1-carboxamide and 2-pyrazoline-1-carbothioamide derivatives showed strong inhibition on chemotactic and phagocytic activities, and ROS production. The results suggest that some of the α, β-unsaturated carbonyl-based compounds strongly modulated the innate immune responses of phagocytes at different steps, highlighting their potential as a source of new immunomodulatory agents.