Interaction between Ester-Type Tea Catechins and Neutrophil Gelatinase-Associated Lipocalin: Inhibitory Mechanism

Tea
is thought to alleviate neurotoxicity due to the antioxidative
effect of ester-type tea catechins (ETC). Neutrophil gelatinase-associated
lipocalin (NGAL) can sensitize β-amyloid (Aβ) induced
neurotoxicity, and inhibitors of NGAL may relieve associated symptoms.
As such, the interactions of ETC with NGAL were investigated by fluorescence
spectrometry and molecular simulation. NGAL fluorescence is quenched
regularly when being added with six processing types of tea infusion
(SPTT) and ETC. Thermodynamic analyses suggest that ETC with more
catechol moieties has a stronger binding capacity with NGAL especially
in the presence of Fe3+. (−)-Epicatechin 3-O-caffeoate (ECC), a natural product isolated from Zijuan
green tea, shows the strongest binding ability with NGAL (Kd = 15.21 ± 8.68 nM in the presence of
Fe3+). All ETC are effective in protecting nerve cells
against H2O2 or Aβ1–42 induced injury. The inhibitory mechanism of ETC against NGAL supports
its potential use in attenuation of neurotoxicity.