Study On The Mechanism Of The Inhibition Of (+)-catechin On Nuclear Factor-κB Activation Induced By Glyoxal

Advanced glycation end products(AGEs) and its Receptor(RAGE) are closely related to inflammation. Nuclear factor-κB(NF-κB) is the core regulatory factor in the process of inflammation. Glyoxal(GO), a sugar metabolity, is a precursor of AGEs. Whether NF-κB can be directly activated by GO and its mechanism is not clear yet. Catechins are a kind of flavonoid polyphenols, which have properties of anti-AGEs, antioxidation and anti-inflammatory. However, whether(+)-catechin can influence NF-κB activation induced by GO has not been reported. In this study, the Schiff base and total AGEs formation, cell viability, the content of bovine serum albumin(BSA), the protein expression of Nε-(carboxymethyl)lysine(CML) and RAGE, and the levels of reactive oxygen species(ROS) generation and NF-κB phosphorylation were measured to study the mechanism of GO induced NF-κB activation. Results are as follows:The model of non-enzymatic glycosylation was successfully established by the incubation of GO and BSA. In this model, GO incubated with BSA which caused BSA reduction, and Schiff base, non-fluorescence CML and fluorescence AGEs formation. However, the GO induced BSA reduction and CML formation were significantly inhibited by(+)-catechin in a dose-dependent manner. At early stage(1h), the GO induced Schiff base formation was 9.9% to 29.0% inhibited by(+)-catechin. At 6 h and 12 h, the GO induced Schiff base formation was 3.0% to 67.0% inhibited by high concentration(1.6-4.0 mM) of(+)-catechin but not lower concentration of(+)-catechin. The GO induced fluorescence AGEs formation was not inhibited by lower concentration of(+)-catechin.0.1-1.6 mM GO induced the increased protein expression of CML and RAGE, ROS generation and NF-κB phosphorylation in BRL-3A cell in a dose- and time-dependent manner. The GO induced NF-κB phosphorylation could be inhibited by aminoguanidine(AG), RAGE inhibitors(anti-RAGE antibody and FPS-ZM1) and ROS scavenger(N-acetylcysteine, NAC). The GO induced ROS generation was not inhibited by FPS-ZM1. The protein expression of CML and RAGE, and the level of NF-κB phosphorylation induced by GO could be suppressed by(+)-catechin, but not did in the level of ROS generation.Conclusion: In the established model of non-enzymatic glycosylation, GO adducted with protein which caused Schiff base, non-fluorescence CML and fluorescence AGEs formation. However, the GO induced non-fluorescence CML formation could be suppressed by(+)-catechin. The GO induced fluorescence AGEs formation was not inhibited by(+)-catechin and the mechanism may be related to that the GO induced Schiff base formation was not effectively inhibited by(+)-catechin. In the BRL-3A cell, it was possible that GO activated NF-κB through the activation of CML/RAGE and ROS generation by itself.(+)-Catechin may suppress the activation of NF-κB induced by GO through CML/RAGE, but not via ROS.