Inducing the cell cycle arrest and apoptosis of oral KB carcinoma cells by hydroxychavicol: roles of glutathione and reactive oxygen species

Abstract

1 Hydroxychavicol (HC; 10 ± 50 mM), a betel leaf component, was found to suppress the 2% H 2 O 2 -induced lucigenin chemiluminescence for 53 ± 75%. HC (0.02 ± 2 mM) was also able to trap superoxide radicals generated by a xanthine/xanthine oxidase system with 38 ± 94% of inhibition. Hydroxyl radicals-induced PUC18 plasmid DNA breaks was prevented by HC (1.6 ± 16 mM). 2 A 24-h exposure of KB cells to HC (0.5, 1 mM) resulted in 54 ± 74% cell death as analysed by a 3-(4,5-dimethyl-thiazol-2-yl)-2,5-diphenyl-tetrazolium bromide (MTT) assay. HC (10, 50 mM) further suppressed the growth of KB cells (15 and 76%, respectively). Long-term colony formation of KB cells was inhibited by 51% with 10 mM HC. 3 Pretreatment of KB cells with 100 mM HC inhibited the attachment of KB cells to type I collagen and ®bronectin by 59 and 29%, respectively. 4 Exposure of KB cells to 0.1 mM HC for 24 h resulted in cell cycle arrest at late S and G2/M phase. Increasing the HC concentration to 0.25 and 0.5 mM led to apoptosis as revealed by detection of sub-G 0 /G 1 peaks with a concomitant decrease in the number of cells residing in late S and G 2 /M phase. 5 Inducing the apoptosis of KB cells by HC was accompanied by marked depletion in reduced form of GSH (40.2 mM) and the increasing of reactive oxygen species production (40.1 mM) as analysed by CMF-and DCF-single cell¯uorescence¯ow cytometry. 6 These results indicate that HC exerts antioxidant property at low concentration. HC also inhibits the growth, adhesion and cell cycle progression of KB cells, whereas its induction of KB cell apoptosis (HC40.1 mM) was accompanied by cellular redox changes.

Inhibitory action of eugenol compounds on the production of nitric oxide in RAW264.7 macrophages

“…Eugenol is widely used as a flavoring agent in cosmetic and food products (9), and is also utilized as an antiseptic drug in dentistry (2,21). Isoeugenol, an isomer of eugenol is found in monkey orange (19), and shows anti-oxidant properties (15,16).…”

Piper Betel Leaf: A Reservoir of Potential Xenohormetic Nutraceuticals with Cancer-Fighting Properties

“…For example, high hydroxychavicol concentrations provoke its pro-oxidant behavior as demonstrated by induction of oxidative damage in liver cancer cells (29). Interestingly, hydroxychavicol was found to be a potent antioxidant at lower doses in oral KB carcinoma, whereas high doses led to apoptosis induction by increasing ROS levels (22).…”

“…Hydroxychavicol has been shown to exploit this higher ROS level in cancer cells, and increases it even further to preferentially kill them while having no effect on the proliferation of normal cells (22,38). However, these phenolic compounds exhibit anti-and/or pro-oxidant behavior depending on their relative concentrations in vivo along with the redox potential of the surrounding areas.…”

“…Hydroxychavicol, a phenolic compound quantitatively present at approximately 26% in betel leaves, has been shown to exert antiproliferative activity in prostate cancer (20). Hydroxychavicol has also been shown to impede cell-cycle progression of prostate cancer and oral KB carcinoma cells (20)(21)(22). Several reports indicate hydroxychavicol as an antimutagenic agent (12,23) as well as an effective inhibitor of cyclooxygenase (COX), platelet calcium signaling, and thromboxane B2 production (21).…”

“…Cancer cells having moderate levels of ROS tend to adapt to the stress conditions and show enhanced expression of prosurvival molecules. When betel nutraceuticals interfere with this situation, causing the moderate ROS levels to increase over the threshold, the cancer cells can no longer withstand the oxidative stress and thus are killed via various possible mechanisms (12,22,27,29,37,38,45,47,62,(64)(65)(66).…”