- Research Paper
- Open Access
Bosellia serrata-induced apoptosis is related with ER stress and calcium release
© Springer-Verlag 2007
- Published: 17 November 2007
It has been reported that the gum resin of Boswellia serrata (BS), which has been shown to have antiinflammatory properties, might also have anticancer effects. This study examined the potential of BS as an anticancer agent. The BS extract induces apoptosis in HeLa human cervical carcinoma cells, as confirmed by two apoptosis analyses, Hoechst staining and Annexin V/PI assay. Among the apoptosis pathways, the ER stress-associated mechanism was examined to determine its role in BS-induced apoptosis. The expression of GRP78 and CHOP, which are representatives of the ER stress proteins, and the calcium-binding protein-calpain were determined. The results showed significantly higher levels of both GRP78 and CHOP, and stronger calpain activity in the BS-treated cells than in the control cells. This shows that there is a correlation between ER stress signaling and apoptosis, which suggests the possibility of the BS–ER stress initiator as an anticancer therapeutic agent in human cervical carcinoma.
- Boswellia serrata
- ER stress
- Human cervical carcinoma
The successful eradication of cancer cells through apoptosis-programmed cell death is the ultimate aim of non-surgical treatments. Essentially, all cytotoxic drugs currently in clinical use induce the apoptosis of malignant cells when they do work. Microtubule binding drugs, DNA-damaging agents, nucleosides and other types of medicine including herbal medicines are important weapons in the treatment of cancer. Traditional herbal medications have been re-evaluated by clinicians on account of their fewer side effects and suitability for long-term use, compared with chemically synthesized medicines.
The gum resin of Boswellia serrata (BS), a type of deciduous tree grown in the drier parts of China, Korea and India, has been used in traditional medicine to treat inflammatory and arthritic diseases [1, 2]. Besides the anti-inflammatory effects, several studies on tumor cells have suggested that Boswellic acids, a component of BS, have anticancer effects [3, 4].
Cervical carcinoma is one of the most common cancers in females. It has been demonstrated that human cervical carcinoma cells appear to retain their functional apoptotic machinery because they respond to a wide spectrum of stimuli by undergoing apoptotic death [5, 6]. In this study, the apoptotic effect of BS was examined in human cervical carcinoma cells, HeLa cells. The signal transduction pathway underlying BS-induced apoptosis was investigated.
D-MEM, FBS, and tissue culture reagents were obtained from Life Technologies. The anti-GRP 78, CHOP and actin antibodies were supplied by Santacruz (Santa Cruz, Calif., USA). All other chemicals were purchased from Sigma. All reagents were at least of analytical grade.
Preparation of BS extracts
Hot water-extracted BS was prepared and concentrated to 1 g of medicine per ml of distilled water. After dissolution and mixing in PBS at 37°C for 30 min, the concentration was adjusted to 100 mg/ml. This solution was then centrifuged (1200 g, 30 min) to remove any insoluble ingredients. The supernatant was sequentially passed through 0.45 μm filters for sterilization. The extracts were used in all experiments.
The clonal human cervical carcinoma HeLa cells were obtained from ATCC. The cells were maintained in D-MEM supplemented with 10% FBS, penicillin G (100 U/ml), and streptomycin (100 μg/ml) in a humidified incubator.
Measurement of calpain activity
The calpain activity was measured in the cytosolic fraction using a calpain assay kit purchased from Calbiochem (San Diego, Calif., USA). The assay is based on the fluorometric detection of the cleavage of the calpain substrate, Suc-Leu-Tyr-7-amino-4-methylcoumarin (Suc-Leu-Tyr-AMC, 50 μM). The reaction buffer (145 mM NaCl, 100 mM Tris-HCl, pH 7.3) and substrate were then added to all samples. The reaction was carried out in a 96-well plate that was protected from light and incubated for 1 h at 37°C with constant shaking. The samples were read in a Gemini fluorescence microplate reader (Molecular Devices) using 360 nm excitation and 430 nm emission filters. All measurements were performed in triplicate, and repeated with heart extracts in two independent experiments.
Western blot analysis
Western blot analysis was performed as described previously . Briefly, whole-cell lysates were generated using a buffer consisting of 1% Nonidet P-40, 50 mM HEPES (pH 7.5), 100 mM NaCl, 2 mM EDTA, 1 mM pyrophosphate, 10 mM sodium orthovanadate, 1 mM phenylmethylsulfonyl fluoride and 100 mM sodium fluoride. Equal amounts of the lysates were subjected to sodium dodecyl sulfate-10% polyacrylamide gel electrophoresis and transferred to Immobilon-P membranes (Millipore) in a transfer buffer [25 mM Tris, 192 mM glycine, 20% (vol/vol) methanol]. The membranes were first rinsed in Tris-buffered saline (TBS: 10 mM Tris [pH 7.4], 150 mM NaCl) and then blocked overnight at room temperature in TBS-5% bovine serum albumin (BSA). Various antibodies including the anti-Bax antibody were each used at a dilution of 1:1,000 in TBS-5% BSA. The antibody–antigen complexes were detected using horseradish peroxidase-conjugated protein A or horseradish peroxidase-conjugated goat anti-rabbit immunoglobulin G (Bio-Rad) and a chemiluminescent substrate development kit (Kirkegaard and Perry Laboratories). An equal loading was determined by the presence of β-actin.
The data was analyzed by one-way analyses of variance using Microcal Origin software. The differences between the treated samples were analyzed using the individual contrast when the factor consisted of more than two levels. P values < 0.05 were considered significant.
Bosellia serrata extract induces apoptosis in Hela human cervical carcinoma cells
Bosellia serrata extract enhances the expression of the ER stress marker proteins in HeLa human cervical carcinoma cells
Although there is some controversy regarding the cell physiological association between the expression of the ER stress protein and apoptosis, prolonged ER stress was found to increase apoptosis with no adaptation. Considering that the expression of the ER stress proteins was consistently higher in the BS-treated cells, the expression may be directly related to the BS-induced apoptosis in human cervical carcinoma cells.
Bosellia serrata extract induces the activation of calpain in HeLa human cervical carcinoma cells
The study is supported by the Korean Research Foundation Grant funded by the Korean Government (KRF-2005-E00021) and by KOSEF for Biofood Research Program, Ministry of Science and Technology.
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