Xyloketal B Exhibits Its Antioxidant Activity through Induction of HO-1 in Vascular Endothelial Cells and Zebrafish

We previously reported that a novel marine compound, xyloketal B, has strong antioxidative actions in different models of cardiovascular diseases. Induction of heme oxygenase-1 (HO-1), an important endogenous antioxidant enzyme, has been considered as a potential therapeutic strategy for cardiovascular diseases. We here investigated whether xyloketal B exhibits its antioxidant activity through induction of HO-1. In human umbilical vein endothelial cells (HUVECs), xyloketal B significantly induced HO-1 gene expression and translocation of the nuclear factor-erythroid 2-related factor 2 (Nrf-2) in a concentration- and time-dependent manner. The protection of xyloketal B against angiotensin II-induced apoptosis and reactive oxygen species (ROS) production could be abrogated by the HO-1 specific inhibitor, tin protoporphyrin-IX (SnPP). Consistently, the suppressive effects of xyloketal B on NADPH oxidase activity could be reversed by SnPP in zebrafish embryos. In addition, xyloketal B induced Akt and Erk1/2 phosphorylation in a concentration- and time-dependent manner. Furthermore, PI3K inhibitor LY294002 and Erk1/2 inhibitor U0126 suppressed the induction of HO-1 and translocation of Nrf-2 by xyloketal B, whereas P38 inhibitor SB203580 did not. In conclusion, xyloketal B can induce HO-1 expression via PI3K/Akt/Nrf-2 pathways, and the induction of HO-1 is mainly responsible for the antioxidant and antiapoptotic actions of xyloketal B.