ABSTRACT
The antiproliferative and proapoptotic effects of pomegranate extract (PE), as correlated with its prooxidant activity, were studied. PE exerted greater antiproliferative effects towards cancer, than to normal, cells, isolated from the human oral cavity. In cell-free systems, PE generated hydrogen peroxide (H(2)O(2)) in cell culture media and in phosphate buffered saline, with prooxidant activity increasing from acidic to alkaline pH, and oxidized glutathione (GSH) in an alkaline, phosphate buffer. Detection of PE-generated H(2)O(2) was greatly lessened in medium amended with N-acetyl-L-cysteine. Using HSC-2 carcinoma cells as the bioindicator, the cytotoxicity of PE was potentiated towards cells pretreated with the GSH depleter, 1-chloro-2,4-dinitrobenzene, and attenuated in cells co-treated with the H(2)O(2) scavengers, catalase, pyruvate, and divalent cobalt ion. Intracellular GSH was lessened in cells treated with PE; GSH depletion in PE-treated cells was confirmed visually with the fluorescent dye, Cell Tracker™ Green 5-chloromethylfluorescein diacetate. These studies demonstrated that the antiproliferative mechanism of PE was, in part, by induction of oxidative stress. The mode of cell death was by apoptosis, as shown by flow cytometry, activation of caspase-3, and cleavage of PARP. Lessening of caspase-3 activation and of PARP cleavage in cells co-treated with PE and either cobalt or pyruvate, respectively, as compared to PE alone, indicated that apoptosis was through the prooxidant nature of PE.
