With the availability of an ultraweak chemiluminescence analyzer, it is possible to monitor the production of a specific oxygen-derived reactive species, such as hydroxyl radical ((*)OH), whenever a suitable chemiluminescent probe is obtainable. Reported herein is the development of a rapid and specific method for detecting (*)OH production using a specific probe, indoxyl-beta-glucuronide (IBG), a low-level chemiluminescence emitter. Using the Fenton reagent as a source of (*)OH, it was shown that IBG could elicit a very strong intensity of chemiluminescence (CL) (16200 +/- 200 photon counts/s). Conversely, IBG was shown to be insensitive to either superoxide radical or hydrogen peroxide with their CL intensities nearly close to the background values (25 +/- 5 and 180 +/- 20 photon counts/s, respectively). Furthermore, it was also shown that this IBG-based CL production could be effectively quenched by the addition of (*)OH scavengers such as sodium salicylate, dimethyl sulfoxide, and penicillamine to the assay system. Taken together, these data indicate that IBG is a specific CL probe suitable for monitoring the production of (*)OH. This system demonstrated inhibitory activities of various aqueous extracts of food constituents on the CL of hydroxyl radicals generated by Fenton's reagents with the order of scavenging efficiencies being Prunus mume > Cordyceps sinensin > Lilium lancifolium > Astragalus membranceus.

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The anticancer effects of 6-dehydrogingerdione (6-DG), a compound isolated from the rhizomes of Zingiber officinale , and its mechanisms of sensitization to TRAIL-induced apoptosis were studied using human hepatoblastoma Hep G2 cells. This study demonstrates for the first time that 6-DG-induced apoptosis might be executed via mitochondrial- and Fas receptor-mediated pathways. Further studies also demonstrated that 6-DG could sensitize Hep G2 cells to TRAIL-induced apoptosis. 6-DG also up-regulated Ser-15 phosphorylation and evoked p53 nuclear translocation. Abrogation of p53 expression by p53 small interfering RNA significantly attenuated 6-DG-induced DR5 expression, thus rendering these cells resistant to TRAIL-induced apoptosis. DR5 expression after 6-DG treatment was accompanied by provoking intracellular reactive oxygen species (ROS) generation. Pretreatment with N-acetyl-l-cysteine (NAC) attenuated 6-DG-induced DR5 expression and inhibited TRAIL-induced apoptosis. In contrast to Hep G2 cells, DR5 up-regulation and sensitization to TRAIL-induced apoptosis instigated by 6-DG were not observed in normal MDCK cells. Taken together, these data suggested that in addition to the mitochondrial- and Fas receptor-mediated apoptotic pathways involved, ROS-dependent and p53-regulated DR5 expression was also demonstrated to play a pivotal role in the synergistic enhancement of TRAIL-induced apoptosis instigated by 6-DG in Hep G2 cells.

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We provide herein several lines of evidence to substantiate that folic acid (or folate) is a micronutrient capable of functioning as a novel redox regulator on hepatocellular carcinoma. First, we uncovered that folate deficiency could profoundly downregulate two prominent anti-apoptotic effectors including survivin and glucose-regulated protein-78. Silencing of either survivin or glucose-regulated protein-78 via small interfering RNA interfering technique established that both effectors could serve as reactive oxygen species sinker proteins. Second, folate deficiency-triggered oxidative-nitrosative stress could strongly induce endoplasmic reticulum stress that in turn could provoke cellular glutathione depletion through the modulation of the following two crucial events: (1) folate deficiency could strongly inhibit Bcl-2 expression leading to severe suppression of the mitochondrial glutathione pool and (2) folate deficiency could also profoundly inhibit two key enzymes that governing cellular glutathione redox regulation including γ-glutamylcysteinyl synthetase heavy chain, a catalytic enzyme for glutathione biosynthesis, and mitochondrial isocitrate dehydrogenase 2, an enzyme responsible for providing nicotinamide adenine dinucleotide phosphate necessary for regenerating oxidized glutathione disulfide back to glutathione via mitochondrial glutathione reductase. Collectively, we add to the literature new data to strengthen the notion that folate is an essential micronutrient that confers a novel role to combat reactive oxygen species insults and thus serves as a redox regulator via upregulating reactive oxygen species sinker proteins and averting mitochondrial glutathione depletion through proper maintenance of redox homeostasis via positively regulating glutathione biosynthesis, glutathione transporting system, and mitochondrial glutathione recycling process.