Effect of anti-inflammatory drugs on splenocyte membrane fluidity

In this study, fluorescence anisotropy measurements were performed using the fluorescent probe 1,6-diphenyl-1,3,5-hexatriene to investigate the effects on membrane fluidity resulting from the interaction between nonsteroidal anti-inflammatory drugs (NSAIDs)-indomethacin, diclofenac, piroxicam, tenoxicam, indoprofen, clonixin, and etodolac-and mouse splenocyte membranes. This study was performed in splenocyte membranes because most of the fluidity studies have been performed in membrane models; thus, clear correlations of the pharmacological action of drugs with molecular effects at the cellular membrane level were lacking. Besides providing a basis for studying the molecular mechanism of pharmacological action of NSAIDs, this research provides a data analysis of steady-state anisotropy measurements, taking into account that the probe itself strongly influences the data given that this problem is usually overlooked. Results show that the anti-inflammatory drugs indomethacin, diclofenac, piroxicam, and tenoxicam increase the membrane fluidity in a concentration-dependent manner. Their order of effectiveness reflected in their respective IC50 values (concentration of each NSAID required to increase the fluidizing effect ratio by 50%) is as follows: tenoxicam > piroxicam > indomethacin > clonixin. For the other drugs, the perturbation in membrane fluidity is not evident under these circumstances.