NSAIDs cause the shedding of L-selectin proportionally to the reduction of intracellular ATP concentration.
(A) Effect of NSAIDs on intracellular concentration of ATP. Neutrophils were incubated with the different NSAIDs under the same conditions described in Figure 1. After centrifugation, cell pellets were lysed and the ATP concentration was tested by a commercial kit as described in “Materials and methods.” Values were obtained in duplicate determinations for each sample. The results represent the mean (M/106 cells) ± SE from 6 independent experiments. (B) Correlation between the reduction of ATP concentration and surface expression of L-selectin induced by NSAIDs in neutrophils. Neutrophils were incubated with the different NSAIDs under the same conditions described in Figure 1. After centrifugation, cell pellets were divided in 2 parts; one was used for ATP determination, which results are depicted in A, and the other part was used for the quantification of the L-selectin surface expression by flow cytometry as described in “Materials and methods.” There was a highly significant direct correlation between reduction of ATP and surface expression of L-selectin (r = 0. 8, P < .01; n = 6). (C) Correlation between the time-dependent variation of surface L-selectin expression (○) and intracellular ATP concentration (●) in neutrophils incubated with 20 μg/mL of flufenamic acid. Values are percentage of expression and concentration of L-selectin and ATP in respect to the basal conditions (medium alone) in each time. Data represent the mean ± SD of 3 independent experiments.
