- Research Paper
- Open Access
Schisandra fructus extract ameliorates doxorubicin-induce cytotoxicity in cardiomyocytes: altered gene expression for detoxification enzymes
© Springer-Verlag 2007
- Published: 15 November 2007
The effect of Schisandra fructus extract (SFE) on doxorubicin (Dox)-induced cardiotoxicity was investigated in H9c2 cardiomyocytes. Dox, which is an antineoplastic drug known to induce cardiomyopathy possibly through production of reactive oxygen species, induced significant cytotoxicity, intracellular reactive oxygen species (ROS), and lipid peroxidation. SFE treatment significantly increased cell survival up to 25%, inhibited intracellular ROS production in a time- and dose-dependent manner, and inhibited lipid peroxidation induced by Dox. In addition, SFE treatment induced expression of cellular glutathione S-transferases (GSTs), which function in the detoxification of xenobiotics, and endogenous toxicants including lipid peoxides. Analyses of 31,100 genes using Affymetrix cDNA microarrays showed that SFE treatment up-regulated expression of genes involved in glutathione metabolism and detoxification [GST theta 1, mu 1, and alpha type 2, heme oxygenase 1 (HO-1), and microsomal epoxide hydrolase (mEH)] and energy metabolism [carnitine palmitoyltransferase-1 (CPT-1), transaldolase, and transketolase]. These data indicated that SFE might increase the resistance to cardiac cell injury by Dox, at least partly, together with altering gene expression, especially induction of phase II detoxification enzymes.
- Glutathione S-transferase
- Schisandra fructus
Schisandra fructus (SF), the fruit of the Schisandra chinensis Baillon, is a well-known traditional herbal medicine that is widely used as a stimulant, a sedative, an antitussive, and a tonic agent in China, Japan, and Korea . It has been reported that SF has various pharmacological activities, including antihepatotoxic [12, 27], anti-inflammatory , anticarcinogenic , antioxidant, and detoxificant effects [12, 16]. SF contains various active compounds, including essential oils, organic acids, tannins, anthocyanins and lignans .
Several in vitro and in vivo studies have shown that SF has potent antioxidative properties such as inhibition of lipid peroxidation, induction of the antioxidant system and scavenging of reactive oxygen species (ROS). Many studies also suggest that SF lignans protect hepatocytes and cortical cells against oxidative damage. These observed cytoprotective effects have been attributed to improvement of the glutathione (GSH) defense system and inhibition of cellular peroxide formation.
Doxorubicin (Dox) is an anthracycline antibiotic that is one of the most effective and widely used anticancer drugs. However, the clinical use of Dox has been limited as its use has been associated with the development of life-threatening cardiomyopathy and congestive heart failure [4, 20, 23]. Although Dox-induced myocardial dysfunction is multifactorial, the putative main mechanism for Dox-induced cardiotoxicity is the production of free radicals during its intracellular metabolism. Free radicals cause diverse oxidative damage to critical cellular components and membranes in heart tissues [6, 7, 17]. Moreover, the heart is very sensitive to oxidative stress owing to its highly oxidative metabolism, and it has a lower level of antioxidant defense systems than the liver .
Considerable efforts have been made to investigate the use of antioxidants to reduce the side effects of Dox administration. In our previous study, we found that anthocyanin, one of the antioxidant components of SF, reduced 5-fluorouracil-induced myelotoxicity , Dox-induced cytotoxicity, intracellular ROS production and lipid peroxidation in cardiomyocytes . SF lingans also have been reported to increase Hsp25/70 expression levels and inhibit nuclear factor-κB (NF-κB) activation.
Therefore, we investigated the protective effect of Shisandra fructus extract (SFE) on Dox-induced cytotoxicity and its antioxidative properties in H9c2 cardiomyocytes. The SFE-regulated gene expression in the Dox-induced cardiotoxicity system was further characterized using cDNA microarray techniques, which allowed us to systematically understand the cardioprotective mechanisms of SFE at the whole-genome level.
Extraction of Schizandra fructus
Dried fruits of Schizandra chinensis were extracted for 3 h with 80% ethanol by using a reflux apparatus to yield the extract after removal of the solvent in vacuo. The ethanol extract was then resolubilized in water and semi-purified by a solid-phase extraction (SPE) with a C18 cartridge (Waters Corp., Milford, MA). The final eluant (SFE) was freeze-dried and resolubilized in phosphate-buffered saline (PBS) for subsequent assays.
H9c2 myocardial cells, spontaneously immortalized ventricular myoblasts of rat embryo, were purchased from the American Type Culture Collection (Manassas, VA). Cells were cultured in Dulbecco’s modified Eagle’s medium (DMEM) supplemented with 10% fetal bovine serum (FBS) at 37°C in 5% CO2. Cell culture medium and supplements were purchased from GibcoBRL (Grand Island, NY). The medium was changed every 2–3 days.
Sub-confluent cells were trypsinized and seeded onto 96-well plates at a density of 1.5 × 105 cells/ml and incubated for 24 h before treatment. Thereafter, cells were exposed to 1 μM Dox for 24 h and then incubated in fresh medium with SFE at a concentration of 30–1,500 μg/ml as a gallic acid equivalent (GAE) for a further 24 h. The effects of SFE on Dox-induced cytotoxicity were assessed using the sulforhodamine B (SRB) assay, as previously described [2, 21]. In brief, after fixation of the cells by the addition of 50% trichloroacetic acid (TCA) solution, the plate was stained with 0.4% SRB solution, and excess dye was then washed out. The unwashed dye was eluted and quantified spectrophotometrically at 550 nm using a microplate reader (Molecular Devices, Sunnyvale, CA). Cell viability was determined as the percentage of surviving cells as compared with that of the Dox-treated control.
Intracellular ROS induced by Dox was measured using 2′7′-dichlorodihydrofluorescein diacetate (H2DCFDA, Molecular Probes, Eugene, OR) by the method of Wang and Joseph  with slight modifications. H9c2 cells were loaded with 20 μM H2DCFDA for 10 min, followed by two washes with HBSS. The dichlorodihydrofluorescein (DCF) fluorescence was detected using a fluorescence spectrophotometer (BMG LABTECH GmbH, Offenburg, Germany) with the excitation of 485 nm and emission of 520 nm, and fluorescence image was visualized by a fluorescence microscope.
The thiobarbituric acid reactive substances (TBARS) method was used to determine the effect of SFE on Dox-induced lipid peroxidation according to the method of Jo and Ahn  with slight modification. H9c2 cells were washed twice with PBS and lysed in sodium dodecyl sulfate (SDS) solution. The 200 μl of cell lysates were transferred to test tubes and 50 μl of butylated hydroxytoluene (BHT) was added to prevent sporadic lipid peroxidation during heating. Next, a solution of 1.5 ml of 0.5 M HCl, 1.5 ml of 20 mM TBA and distilled water was added. The reaction mixture was well mixed and then heated for 30 min in a boiling water bath. After cooling for 20 min, 2 ml of n-butanol was added. The mixture was mixed vigorously and centrifuged at 3,000 rpm for 15 min. The fluorescence of the organic layer was measured through a fluorescence spectrophotometer with an excitation of 515 nm and emission of 555 nm. TBARS levels were calculated from a standard curve using 1,1,3,3-tetramethoxypropane and normalized to the protein content.
Glutahione S-transferase activity
GST activity was assayed spectrophotometrically at 340 nm using the standard substrate 1-chloro-2, 3-dinitrobenzene (CDNB) and co-substrate GSH by the method of Habig et al. . The increase rate of absorbance at 340 nm is directly proportional to GST activity. The activity was calculated using an extinction coefficient of 9.6 mM−1 cm−1 and expressed as nmol of CDNB–GSH conjugate formed per min per mg protein.
Isolation of total RNA and microarray analysis
The total RNA from the H9c2 cells was isolated using TRIzol (Invitrogen, Carlsbad) and then cleaned using the RNeasy Mini Kit (Qiagen GmbH, Hilden, Germany) according to the manufacturer’s instructions. Probe synthesis from total RNA (5 μg), hybridization, detection and scanning was performed according to the standard protocols from Affymetrix (Affymetrix Inc., Santa Clara, CA). Briefly, cDNA was synthesized from total RNA using the one-cycle cDNA Synthesis Kit and T7-oligo (dT) primers. Double-stranded cDNA was used for in vitro transcription (IVT). cDNA was transcribed using the GeneChip IVT Labeling Kit (Affymetrix), and 10–15 μg of labeled cRNA was fragmented to form 35–200 bp fragments. After hybridization to the Rat 230 2.0 gene chips (Affymetrix), according to the Affymetrix standard protocol, the arrays were washed and stained with a streptavidin–phycoerythrin complex, and the intensities were determined using a GeneChip scanner 3000 (Affymetrix) and controlled by GCOS Affymetrix software 1.4 (Affymetrix). After data normalization, a DNA microarray data analysis was performed using GenPlex™ (Istech, Korea). The detectable expressed genes were defined using P-, M-, and A-calls according to the Affymetrix algorithm and intensity of the genes. We selected only those genes with at least four P-calls. Cross comparisons of the control versus treated data from each experiment were analyzed on the filtered probes. Only genes that were statistically significant and were up- or down-regulated by at least twofold compared with the control were judged as valid and identified as differentially expressed genes (DEGs).
All cytochemical data were given as mean ± SEM. Statistical analysis was carried out using the Student’s t test. Differences with p < 0.05 were accepted as statistically significant. For microarray data, signal intensities between two groups were analyzed by the Welch’s t test with a significance level of p < 0.05.
Modulation of Dox-induced cellular response in H9c2
Treatment of H9c2 cardiomyocytes with Dox and SFE affected cellular responses including cell viability, intracellular ROS production, lipid peroxidation and GST activity.
Altered gene expression by Dox and SFE treatment in H9c2
Classified target genes implicated in cytoprotective effects of SFE on Dox-induced toxicity
Glutathione metabolism and detoxification
Glutathione S-transferase theta 1
Glutathione S-transferase, mu 1
Glutathione S-transferase, alpha type2
Heme oxygenase (decycling) 1
Epoxide hydrolase 1, microsomal
Transmembrane 7 superfamily member 2
Carnitine palmitoyltransferase 1, liver
Leukotriene B4 12-hydroxydehydrogenase
Dehydrogenase/reductase (SDR family) member 3
Crystallin, lamda 1
Carboxylesterase 2 (intestine, liver)
Isocitrate dehydrogenase 1 (NADP+), soluble
Aldo-keto reductase family 7, member A2 (aflatoxin aldehyde reductase)
Aldehyde dehydrogenase family 3, member A1
Protein, amino acid metabolism
Branched chain ketoacid dehydrogenase E1, alpha polypeptide
Transmembrane and transport
gap junction membrane channel protein alpha 4
Potassium inwardly-rectifying channel, subfamily J, member 8
Similar to DNA segment, Chr 11, ERTO Doi 18, expressed
Potassium channel tetramerisation domain containing 13
Golgi associated, gamma adaptin ear containing, ARF binding protein 2
Solute carrier family 39 (iron-regulated transporter), member 1
Vacuolar protein sorting 33a (yeast)
Cytokine receptor-like factor 1 (predicted)
Chemokine-like factor 1
Immediate early response 3
Leukocyte cell derived chemotaxin 1
Integrin, beta 6
Electron transport, energy metabolism
Coenzyme Q6 homolog (yeast)
Similar to hypothetical protein MGC20446
Lactate dehydrogenase D
Germinal histone H4 gene
Histone 2, Hh2aa (predicted)
Cyclin-dependent kinase inhibitor 1A
Angiopoietin-like protein 4
Cell migration, cell motility, localization of cell
EPH receptor B1
Fc receptor, Igg, low affinity III
ABI gene family, member 3
Heme oxygenase (decycling) 1
hpaII tiny fragments locus 9C
Pregnancy-induced growth inhibitor
UDP-N-acteylglucosamine pyrophosphorylase 1-like 1 (predicted)
Ectonucleoside triphosphate diphosphohydrolase 5
Similar to RIKEN cDNA 0610039C21 (predicted)
Similar to Hist2h2aa1 protein
Hypothetical LOC300751 (predicted)
Similar to hypothetical protein
Similar to brain protein 17
Similar to RIKEN cDNA 4930570c03
Similar to 2310010G13Rik protein
Similar to cell surface receptor FDFACT, similar to paired immunoglobin-like type 2 receptor beta
Similar to RIKEN cDNA 2310011J03
Similar to RIKEN cDNA 6330406I15 (predicted)
Similar to hypothetical 55.1 kDa protein F09G8.5 in chromosome III
In the present study, Dox treatment significantly increased intracellular ROS production, lipid peroxidation and cytotoxicity in H9c2 cardiomyocytes. The addition of SFE–H9c2 cells provided significant cytoprotection against Dox-induced cytotoxicity and reduced in intracellular ROS and lipid peroxidation.
Aerobic organisms have a multi-tiered defense system to combat oxidative stress, which provides protection not only against ROS, but also against the toxic electrophilic compounds generated by the interaction of ROS with cellular constituents, particularly the lipid peroxidation products. Thus, ROS scavenging is the first line of defense and inactivation of lipid peroxides is the second line of defense. In this study, we found that SFE also directly scavenged the intracellular ROS as the fisrt line of defense and reduced lipid peroxidation as the second line of defense, thereby protecting against Dox-induced cytotoxicity.
The functional classification of target DEGs could provide some clues to the cytoprotective mechanisms of SFE against Dox-induced cytotoxicity. Glutathione metabolism and detoxification-related genes were considered as the primary target genes involved in the cytoprotective action of SFE. GSTs are a large and diverse group of phase II biotransformation enzymes that function in the detoxification of xenobiotics and endogenous toxicants. The compounds detoxified by GSTs include a broad range of carcinogens, anticancer drugs, metabolic byproducts, as well as environmental chemicals. Some GST isozymes, especially alpha class GSTs, can efficiently reduce fatty acid hydroperoxides as well as phospholipid hydroperoxides, and can disrupt the autocatalytic chain of lipid peroxidation by reducing these hydroperoxides that propagate lipid peroxidation chain reactions . Furthermore, GST alpha 1 and alpha 2 can use membrane phospholipid hydroperoxides as substrates in situ and can protect cell membranes at the sites of damage. The protective role of human GST alpha 2–2 (hGSTA 2–2) against oxidant toxicity has been demonstrated because transfection of K562 cells with hGSTA 2–2 protects these cells from H2O2 cytotoxicity .
Our microarray results showed that GST theta 1, mu 1, and alpha type 2 genes up-regulated by treatment with Dox and SFE compared with Dox treatment alone, as shown by the levels of cellular GST activity. Recently, it was reported that induction of cellular antioxidants and phase II enzymes, including GST alpha 1, mu 1, and pi 1, by 3H-1, 2-dithiole-3-thione (D3T) provided marked protection against H9c2 cell injury caused by various oxidants and simulated ischemia–reperfusion .
In addition, one of the phase II enzymes, heme oxygenase 1 (HO-1), which catalyzes the degradation of heme to release free iron, carbon monoxide and biliverdin, is up-regulated. Some reports have demonstrated the potent antioxidative and cytoprotective properties of heme-derived metabolites generated by HO-1 against various stress stimuli . Microsomal epoxide hydrolase (EHm), which is another phase II enzyme and catalyzes the addition of H2O across the epoxide to form the corresponding diol , was also up-regulated by Dox and SFE treatment. These up-regulated cellular detoxifying systems might increase resistance to cell injury caused by Dox.
Many of the target DEGs that are up-regulated with Dox and SFE treatment are involved in lipid, carbohydrate and energy metabolism. Carnitine palmitoyltransferase-1 (CPT-1), which is an integral outer mitochondrial membrane protein and the key regulatory enzyme of fatty acid oxidation, was up-regulated by SFE; long-chain fatty acids are the major substrates for energy production in the aerobic adult myocardium . Transaldolase and transketolase also were up-regulated with SFE treatment. These enzymes are involved in the pentose phosphate pathway (PPP), which produces NADPH as a reducing equivalent for biosynthetic reactions and ribose 5-phosphate for the synthesis of nucleotides, RNA and DNA. This up-regulation of lipid, carbohydrate and energy metabolism-related genes can be partially helpful to the cytoprotective action of SFE, because the heart has high energy demands for maintenance of cellular processes, and abnormalities in the metabolic pathway that reduce energy production, transfer and utilization is one cause of heart failure .
In conclusion, this study demonstrates that SFE reduced Dox-induced cytotoxicity and intracellular ROS and lipid peroxidation, and increased cellular GST activity in H9c2 cardiomyocytes. The cDNA microarray data showed that SFE treatment modulates the gene expression of phase II detoxification enzymes such as GSTs, HO-1 and EHm, indicating that SFE might increase the resistance to cardiac cell injury by Dox via induction of the cellular detoxifying system. Future work will be needed to confirm our array results and to determine the functional role of these genes in the reduction of Dox toxicity.
This work was supported by a research project on Functional Food Development from the Office for Government Policy Coordination, and by research grants from the Korea Institute of Science and Technology Evaluation and Planning (KISTEP) for functional food research and development, Ministry of Science and Technology, in the Republic of Korea.
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