The present study investigated the effect of high-temperature-processed green tea extract (HTP_GTE) and its bioactive components on the reduction of reactive oxygen species (ROS) and amyloid-beta (Aβ) protein in human microvascular endothelial cells. Compared to Aβ1-42-only treatment, pretreatment of HTP_GTE was revealed to effectively inhibit ROS generation (P<0.05). HTP_GTE and catechins not only inhibit Aβ1-42 fibril formation but also destabilize preformed Aβ1-42 fibrils. The presence of HTP_GTE, Aβ1-42 fibril formation was significantly inhibited in a dose-dependent manner at 12.5-100 μg/ml of HTP_GTE, showing 86-56%, respectively. Treatment of various concentrations of HTP_GTE and catechins steadily destabilized the preformed Aβ1-42 fibrils for 24 h in a dose-dependent manner. It was observed that the gallated groups such as epigallocatechin gallate, epicatechin gallate, gallocatechin gallate, and catechin gallate more effectively disturbed Aβ1-42 fibril formation and destabilized the preformed Aβ1-42 fibrils than the non-gallated group. Taken together, these findings supported that sterilized green tea could be promising natural anti-amyloidogenic agents associated with therapeutic approaches in Alzheimer's disease by scavenging ROS generation and Aβ fibril in the brain tissue.
Keywords: Aβ1–42 fibrils; Blood-brain barrier; Catechins; High-temperature-processed green tea extract; Reactive oxygen species.