Chrysin-induced apoptosis is mediated through caspase activation and Akt inactivation in U937 leukemia cells

Chrysin is a natural, biologically active compound extracted from many plants, honey, and propolis. It possesses potent anti-inflammation, anti-cancer, and anti-oxidation properties. The mechanism by which chrysin initiates apoptosis remains poorly understood. In the present report, we investigated the effect of chrysin on the apoptotic pathway in U937 human promonocytic cells. We show that chrysin induces apoptosis in association with the activation of caspase 3 and that Akt signal pathway plays a crucial role in chrysin-induced apoptosis in U937 cells. Furthermore, we have shown that inhibition of Akt phosphorylation in U937 cells by the specific PI3K inhibitor, LY294002 significantly, enhanced apoptosis. Overexpression of a constitutively active Akt (myr-Akt) in U937 cells inhibited the induction of apoptosis, activation of caspase 3, and PLC-gamma1 cleavage by chrysin. Together, these findings suggest that the Akt pathway plays a major role in regulating the apoptotic response of human leukemia cells to chrysin and raise the possibility that combined interruption of chrysin and PI3K/Akt-related pathways may represent a novel therapeutic strategy in hematological malignancies. (C) 2004 Elsevier Inc. All rights reserved.