Ameliorative Effect of Quercetin against Modification Induced by 5-Fluorouracil on Alpha-2-Macroglobulin

Abstract

Introduction: Alpha-2-macroglobulin (α2M) is large glycoprotein, found in the plasma of vertebrates and invertebrates, which plays a major role in regulation and transport. In this study, we report the interaction of 5-fluorouracil (5-FU) with α2M and the protective effect of quercetin against 5-FU induced modification of α2M.

Methods: Various biochemical and biophysical methods and techniques were employed to determine the binding interaction between α2M-5-FU and the preventive effect of quercetin on 5-FU induced modification of α2M. Fluorescence microscopy was performed to analyze the formation of free radicals by 5-FU and to examine the scavenging effect of quercetin.

Results: Our results of antiproteinase activity assay show that the 5-FU-α2M interaction causes functional inactivation of sheep α2M, while the 5-FU-α2M complex after exposure to quercetin regains its native conformation. Intrinsic fluorescence results suggest an increase of 5-FU quenching in the fluorescence intensity, and when the mixture was incubated with quercetin the α2M-FU-quercetin mixture showed the same intensity as that of native protein. The absorption spectra of 5-FU-α2M complex suggest the formation of a complex leading to increase in absorbance. CD and FTIR spectroscopy show 5-FU causes secondary structural alteration of α2M and quercetin provides a protective role against structural modification.

Conclusion: Our study suggests that 5-FU produces reactive oxygen species (ROS) in the presence of light and compromises the integrity of α2M. Quercetin quenches the ROS formed by 5-FU and helps the protein to maintain its native conformation. We have demonstrated the protective effect of quercetin for the first time against the toxicity induced by 5-FU on α2M.