Biochimica et Biophysica Acta (BBA) - General Subjects
Flavonoids purified from Rhus verniciflua Stokes actively inhibit cell growth and induce apoptosis in human osteosarcoma cells
Introduction
Cell death can occur through several different mechanisms of which its most widely described forms are apoptosis and necrosis. A significant physiological consequence of cell death by apoptosis is that the apoptotic cells are immediately phagocytosed by macrophages. Therefore, the release of intracellular molecules that cause a secondary disturbance to the surrounding tissue is limited to a low level compared with necrosis, which causes further tissue destruction and inflammation [1], [2].
Recently, there has been a global trend toward the use of natural bioactive substances found in fruits, vegetables, and herbs, as antioxidants and functional foods [3], [4], [5], [6]. Some of these substances are believed to have potential as cancer chemopreventive or therapeutic agents [7], [8], [9]. Most of these substances exert their chemotherapeutic activity by blocking the cell cycle progression and triggering apoptotic cell death. Therefore, the induction of apoptosis in tumor cells has become an indicator of the tumor-treating ability of naturally-derived bioactive substances [10], [11]. Recent attention has also focused on the development of target organ-specific apoptosis inducers as novel cancer-preventive and therapeutic approaches [9].
Flavonoids are commonly found in most plants and are integral parts of the human diet [12]. Flavonoids exert a remarkable spectrum of biological activities affecting the basic cell functions, such as growth [13], differentiation [14], and apoptosis [15]. Flavonoids are known to have anticarcinogenic, anti-inflammatory, antibacterial, immune-stimulating, and antiviral activities [16], [17], [18], and the beneficial effects of flavonoids have been attributed to the inhibition of the enzymes involved in signal transduction and to their antioxidant properties. Indeed, many studies have shown that flavonoids inhibit PI3-kinase, protein kinase C, protein tyrosine kinase, and some transcriptional factors, and that such inhibition leads to cell growth arrest and tumor cell death [12], [19], [20]. However, the effects of flavonoids on inducing apoptosis in osteosarcoma cells have not been widely reported. In addition, the mechanism(s) by which flavonoids induce cell death in osteosarcoma cells are not clearly defined.
Previously, a flavonoid fraction, consisting mainly of protocatechuic acid, fustin, fisetin, sulfuretin, and butein, herein named RCMF (RVS chloroform-methanol fraction), was prepared from a crude acetone extract of Rhus verniciflua Stokes (RVS) which is traditionally used as a food additive and an herbal medicine [21]. In Korea, much attention has been paid to RVS because it is a well-known antioxidant and antitumor agent [22]. In addition, our previous findings indicated that RVS extract is protective against oxidative damage by scavenging radicals or by altering the oxidized forms of chemicals, and flavonoids are the active compounds responsible for the antioxidant property of RVS [23]. Preliminary experiments also found that RCMF had antitumor activity in lymphoma and hepatoma cell lines [21], [24]. This study evaluated the effects of RCMF on the proliferation and apoptosis using human osteosarcoma (HOS) cells. In addition, the mechanism of the growth inhibition of the HOS cells by the flavonoid fraction, RCMF, was assessed.
Section snippets
Chemicals and laboratory wares
Unless otherwise specified, all chemicals used in this study were obtained from the Sigma Chemical Co. (St. Louis, MO) and all the laboratory wares were purchased from Falcon Labware (Becton-Dickinson, Franklin Lakes, NJ). A purified flavonoid sample, RCMF, was prepared from a crude acetone extract of RVS wood, according to previously described procedures [21]. The RCMF was freshly dissolved in absolute ethanol and the final concentration of ethanol was not in excess of 0.1% (v/v) at any time
Effects of RCMF on proliferation of the HOS cells
The effect of RCMF treatment on cell proliferation was determined by tritium incorporation using HOS cells. As shown in Fig. 1, the addition of RCMF to the cultured HOS cells markedly inhibited the incorporation of tritium by the DNA in the cells, in a dose-dependent manner. For example, the level of tritium uptake by the cells treated with 20 μg/ml RCMF for 48 h was 10,745 ± 1000 cpm, which was a decrease of 64.6% from the 30,375 ± 3805 cpm of the untreated control cells. Treatment with 100 μg/ml
Discussion
Current studies involved in developing effective cancer-preventive approaches have focused mainly on the utilization of natural bioactive agents that can induce selective apoptosis in cancer cells [9]. Flavonoids exert various pharmacological properties and are believed to be beneficial compounds for cancer chemoprevention [14], [15], [26]. Previously, we prepared the purified flavonoid fraction, RCMF, and identified the active compounds contained in the RCMF [21]. In the present study, we
Acknowledgement
This work was supported by Korea Research Foundation Grant (KRF-2004-F00022).
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2015, Brain ResearchCitation Excerpt :Fisetin (3,3′,4′,7-tetrahydroxyxflavone) is a bioactive flavonol molecule with a defined chemical structure (Fig. 1), which can be found in fruits and vegetables such as strawberry, apple, persimmon, grape, onion and cucumber at concentrations in the range of 2–160 μg/g (Arai et al., 2000). Accumulating evidence indicates that fisetin has multiple biological activities, such as antioxidant, anticarcinogenic, anti-inflammatory, antibacterial, immune-stimulating, antiviral (Duarte et al., 1993; Jang et al., 2005; Rice-Evans et al., 1996), neuroprotective and neurotrophic (Maher et al., 2006; Zbarsky et al., 2005). However, there is no data available about its cytotoxic and genotoxic (Lapchak, 2013).
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Contributed equally to this work.