Effects of gold-chloroquine complexes on respiratory burst of polymorphonuclear leukocytes

The effects of gold-chloroquine derivatives with the formula [Au(PR3)(CQ)]PF6 (where R = Ph (1), Et or Me) on the superoxide anion production by human neutrophils (PMNs, polymorphonuclear cells) were investigated. When these complexes (0.1-3 mumol/l) were added to PMNs prior to the activators formyl-methionyl-leucyl-phenylalanine (fMLP) or phorbol myristate acetate (PMA), they inhibited isoluminol-horseradish peroxidase-dependent chemiluminescence (CLisol). The inhibition was a direct result of effects on PMNs since chemiluminescence in the cell-free system (horseradish peroxidase-hydrogen peroxidase-isoluminol) was not affected. The above mentioned concentrations of the complexes did not show in vitro toxicity on the cells. On the other hand, when 1 mumol/l of complex 1 was added to cells after stimulation, the chemiluminescence of PMNs stimulated by PMA was inhibited, but not the chemiluminescence stimulated by fMLP. The gold-chloroquine binding was essential for the referred activity as chemiluminescence was not influenced by the precursors chloroquine (CAS 54-05-7) and AuCl(PPh3). Furthermore, the extent of inhibition of chemiluminescence in PMNs activated by PMA did not increase with the duration of preincubation in presence of 1 mumol/l of 1. Extensive washing of cells after preincubation with 1 mumol/l of 1 reversed the aforementioned inhibition. All these results show that the gold-chloroquine binding can lead to compounds with specific properties that could make them useful in the treatment of some inflammatory diseases.