Nrf2 activation of the antioxidant response element (ARE) is central to cytoprotective gene expression against oxidative and/or electrophilic stress. Unless activated by inflammatory, environmental, or oxidative stressors, Nrf2 is sequestered in the cytoplasm by its repressor, Keap1. Because of its protective capabilities, small molecules that activate Nrf2 signaling are being examined as potential anti-cancer or anti-inflammatory agents. 2-HBA, a synthetic analog of curcumin, is an indirect inducer of enzymes that catalyze detoxification reactions through the Keap1-Nrf2-ARE pathway. As a double Michael reaction acceptor, 2-HBA can directly modify cysteine sulfhydryl groups in Keap1 and consequently suppress Nrf2 ubiquitination, which leads to enhanced expression of antioxidative and cytoprotective enzymes. 2-HBA doubles the specific activity of NAD(P)H:quinone acceptor oxidoreductase 1 (NQO1) in Hepa1c1c7 cells at 0.15 μM. In rapidly dividing mouse leukemia L1210 cells, 0.6 μM 2-HBA increases the activities of NQO1, glutathione reductase, and the levels of total glutathione. At 5-15 μM, 2-HBA causes G2/M cell cycle arrest and p53-independent, caspase 3-mediated apoptosis.
