Psoralen and Isopsoralen Activate Nuclear Factor Erythroid 2-Related Factor 2 Through Interaction With Kelch-Like ECH-Associated Protein 1

As natural furocoumarins, psoralen and its isomer isopsoralen are widely distributed in various fruits including Ficus carica L., vegetables including celery, and medicinal herbs including Psoralea corylifolia L. Although psoralen and isopsoralen have been used as dietary supplements because of their bioactivities such as antibacterial and anti-inflammatory properties; however, the potential mechanisms underlying the antioxidant activities of these two furocoumarins still need to be explored. Hence, the aims of this work were to examine the activation of nuclear factor erythroid 2-related factor 2 (Nrf2) by psoralen and isopsoralen, as well as the binding interaction of Kelch-like ECH-associated protein 1 (Keap1) with these two furocoumarins. Interestingly, both psoralen and isopsoralen induced Nrf2 nuclear translocation in a dose-dependent manner in HEK293T cells. These two furanocoumarins also activated antioxidant response element (ARE)-driven luciferase activity. The mRNA expression of GCLM, HO-1, and NQO1 genes was significantly upregulated by treatment of HEK293T cells with psoralen and isopsoralen, respectively. Similarly, the expression of proteins can be promoted. Both psoralen and isopsoralen were located in the top of the central pocket of the Keap1 Kelch domain, suggesting that they were natural ligands of Keap1. In conclusion, both psoralen and isopsoralen activate Nrf2 through interaction with Keap1, thereby serving as natural antioxidants.