Stimulation of human polymorphonuclear leukocytes potentiates the uptake of diclofenac and the inhibition of chemotaxis

Abstract

Diclofenac sodium, a non-steroidal anti-inflammatory drug, has been shown to impair the stimulation of human polymorphonuclear leukocytes (PMNs) by chemoattractants. To gain insight into the mechanism of action of this agent, we investigated the uptake of diclofenac by resting and activated PMNs and the effect of the drug on PMN locomotion. During incubation of resting PMNs at 37° in the presence of 78 μM (25 μg/mL) diclofenac, drug uptake reached a plateau in less than 2 min. The resulting cellular to extracellular diclofenac concentration ratio ( C E ) was 1.01 ± 0.13 (mean ± SD). Stimulation of PMNs at 37° but not at 4° with the chemoattractant formyl-methionyl-leucyl-phenylalanine (fMLP) or phorbol myristate acetate (PMA), induced a rise in diclofenac uptake, which was dependent on incubation lime and diclofenac and stimulus concentrations. Maximal C E was 1.83 ± 0.18 and 4.40 ± 0.60 (mean ± SD) for PMNs stimulated with 10 μM fMLP and 0.16 μM PMA, respectively. The diclofenac associated with PMNs was predominantly present in the soluble fraction of disrupted cells. Interestingly, PMNs which were pretreated with diclofenac and stimulated with fMLP, exhibited impaired random and directional locomotion induced by activated serum, as compared to controls, i.e. PMNs treated with diclofenac alone or fMLP alone. Thus, stimulation of PMNs enhances diclofenac uptake and potentiates the drug impairment of chemotactic activity. These findings could explain, in part, the observed anti-inflammatory properties of this compound.