Diallyl disulfide (DADS) induced apoptosis undergo caspase-3 activity in human bladder cancer T24 cells

The potential role of hydrogen sulfide in cancer cell apoptosis

For a long time, hydrogen sulfide (H2S) has been considered a toxic compound, but recent studies have found that H2S is the third gaseous signaling molecule which plays a vital role in physiological and pathological conditions. Currently, a large number of studies have shown that H2S mediates apoptosis through multiple signaling pathways to participate in cancer occurrence and development, for example, PI3K/Akt/mTOR and MAPK signaling pathways. Therefore, the regulation of the production and metabolism of H2S to mediate the apoptotic process of cancer cells may improve the effectiveness of cancer treatment. In this review, the role and mechanism of H2S in cancer cell apoptosis in mammals are summarized.

New Visions on Natural Products and Cancer Therapy: Autophagy and Related Regulatory Pathways

Macroautophagy (autophagy) has been a highly conserved process throughout evolution and allows cells to degrade aggregated/misfolded proteins, dysfunctional or superfluous organelles and damaged macromolecules, in order to recycle them for biosynthetic and/or energetic purposes to preserve cellular homeostasis and health. Changes in autophagy are indeed correlated with several pathological disorders such as neurodegenerative and cardiovascular diseases, infections, cancer and inflammatory diseases. Conversely, autophagy controls both apoptosis and the unfolded protein response (UPR) in the cells. Therefore, any changes in the autophagy pathway will affect both the UPR and apoptosis. Recent evidence has shown that several natural products can modulate (induce or inhibit) the autophagy pathway. Natural products may target different regulatory components of the autophagy pathway, including specific kinases or phosphatases. In this review, we evaluated ~100 natural compounds and plant species and their impact on different types of cancers via the autophagy pathway. We also discuss the impact of these compounds on the UPR and apoptosis via the autophagy pathway. A multitude of preclinical findings have shown the function of botanicals in regulating cell autophagy and its potential impact on cancer therapy; however, the number of related clinical trials to date remains low. In this regard, further pre-clinical and clinical studies are warranted to better clarify the utility of natural compounds and their modulatory effects on autophagy, as fine-tuning of autophagy could be translated into therapeutic applications for several cancers.

Improving the bioavailability and bioactivity of garlic bioactive compounds via nanotechnology

This review highlights main bioactive compounds and important biological functions especially anticancer effects of the garlic. In addition, we review current literature on the stability and bioavailability of garlic components. Finally, this review aims to provide a potential strategy for using nanotechnology to increase the stability and solubility of garlic components, providing guidelines for the qualities of garlic products to improve their absorption and prevent their early degradation, and extend their circulation time in the body. The application of nanotechnology to improve the bioavailability and targeting of garlic compounds are expected to provide a theoretical basis for the functional components of garlic to treat human health. We review the improvement of bioavailability and bioactivity of garlic bioactive compounds via nanotechnology, which could promisingly overcome the limitations of conventional garlic products, and would be used to prevent and treat cancer and other diseases in the near future.

Anticancer potential of garlic and its bioactive constituents: A systematic and comprehensive review

Vegetables of the Allium genus, such as garlic (Allium sativum L.), onions, shallots, leaks, and chives, have been used for many years for food consumption and for medicinal purposes. Historical medical texts have indicated the therapeutic applications of garlic as an antitumor, laxative, diuretic, antibacterial and antifungal agent. Specifically, garlic's antitumor abilities have been traced back 3500 years as a chemotherapeutic agent used in Egypt. Other beneficial effects of garlic consumption include lowering blood pressure, blood cholesterol, sugar and lipids. The processing and aging of garlic result in the production of non-toxic organosulfur by-products. These sulfur-containing compounds, such as allicin, diallyl sulfide, diallyl disulfide, diallyl trisulfide, alliin, S-allylcysteine, and S-allylmercaptocysteine, impact various stages of carcinogenesis. The anticancer mechanisms of action of these garlic-derived phytochemicals include altering mitochondrial permeability, inhibiting angiogenesis, enhancing antioxidative and proapoptotic properties, and regulating cell proliferation. All these effects of garlic's sulfur-compounds have been demonstrated in various human cancers. The intent of this literature research is to explore the potential of garlic-derived products and bioactive organosulfur compounds as cancer chemopreventive and chemotherapeutic agents. This investigation employs criteria for systematic review and critically analyzes published in vitro, in vivo and clinical studies. Concerns and limitations that have arisen in past studies regarding standards of measurement, bioavailability, and method of delivery are addressed. Overall, it is hoped that through this systematic and comprehensive review, future researchers can be acquainted with the updated data assembled on anticancer properties of garlic and its phytoconstituents.

Diallyl Disulfide Induces Apoptosis and Autophagy in Human Osteosarcoma MG-63 Cells through the PI3K/Akt/mTOR Pathway

Diallyl disulfide (DADs), a natural organic compound, is extracted from garlic and scallion and has anti-tumor effects against various tumors. This study investigated the anti-tumor activity of DADs in human osteosarcoma cells and the mechanisms. MG-63 cells were exposed to DADs (0, 20, 40, 60, 80, and 100 μM) for different lengths of time (24, 48, and 72 h). The CCK8 assay results showed that DADs inhibited osteosarcoma cell viability in a dose-and time-dependent manner. FITC-Annexin V/propidium iodide staining and flow cytometry demonstrated that the apoptotic ratio increased and the cell cycle was arrested at the G₂/M phase as the DADs concentration was increased. A Western blot analysis was employed to detect the levels of caspase-3, Bax, Bcl-2, LC3-II/LC3-I, and p62 as well as suppression of the mTOR pathway. High expression of LC3-II protein revealed that DADs induced formation of autophagosome. Furthermore, DADs-induced apoptosis was weakened after adding 3-methyladenine, demonstrating that the DADs treatment resulted in autophagy-mediated death of MG-63 cells. In addition, DADs depressed p-mTOR kinase activity, and the inhibited PI3K/Akt/mTOR pathway increased DADs-induced apoptosis and autophagy. In conclusion, our results reveal that DADs induced G₂/M arrest, apoptosis, and autophagic death of human osteosarcoma cells by inhibiting the PI3K/Akt/mTOR signaling pathway.

Nutraceutic Potential of Two Allium Species and Their Distinctive Organosulfur Compounds: A Multi-Assay Evaluation

This study aimed to evaluate the biological activities of two Allium species (garlic and onion) as well as diallyl disulphide (DADS) and dipropyl disulphide (DPDS) as their representative bioactive compounds in a multi-assay experimental design. The genotoxic, antigenotoxic, and lifespan effects of garlic, onion, DADS, and DPDS were checked in Drosophila melanogaster and their cytotoxic, pro-apoptotic, and DNA-clastogenic activities were analyzed using HL60 tumoral cells. All compounds were non-genotoxic and antigenotoxic against H₂O₂-induced DNA damage with a positive dose-response effect and different inhibition percentages (the highest value: 95% for DADS) at all tested concentrations. Daily intake of Allium vegetables, DADS, or DPDS had no positive effects on flies' lifespan and health span. Garlic and DADS exerted the highest cytotoxic effects in a positive dose-dependent manner. Garlic and DADS exerted a DNA-internucleosomal fragmentation as an index of induced proapoptotic activity on HL60 cells. Allium vegetables and DADS were able to induce clastogenic strand breaks in the DNA of HL60 cells. This study showed the genomic safety of the assayed substances and their protective genetic effects against the hydrogen peroxide genotoxine. Long-term treatments during the whole life of the Drosophila genetic model were beneficial only at low-median concentrations. The chemo-preventive activity of garlic could be associated with its distinctive organosulfur DADS. We suggest that supplementary studies are needed to clarify the cell death pathway against garlic and DADS.

Redox Reducible and Hydrolytically Degradable PEG-PLA Elastomers as Biomaterial for Temporary Drug-Eluting Medical Devices

With the aim to develop biomaterials for temporary medical devices, a series of novel reducible and/or degradable elastomers has been prepared from PLA-b-PEG-b-PLA copolymers photo-crosslinked with diallyl sulfide or pentaerythritol tetrakis(3-mercaptopropionate). Thermal and mechanical properties, including elastic limit and Young modulus, are assessed. Degradation is then evaluated under standard hydrolytic conditions. Reducibility of a selected elastomer is then illustrated using 2-mercaptoethanol or glutathione as reducing agents. The redox-sensitivity of the selected elastomer and the possibility to modulate the degradability are shown. Considering drug-eluting elastomeric devices applications, anti-inflammatory drug ibuprofen loading is illustrated with the two simplest elastomer formulations. A rapid or slow linear release is observed as a function of the low or high molecular weight of the triblock pre-polymers. Finally, the cytocompatibility of the degradable elastomers is assessed with regard to their potential to favor or inhibit L929 murine fibroblasts proliferation as a function of the hydrophilicity/hydrophobicity of the triblock copolymers.

Cytotoxicity and Apoptotic Effects of Polyphenols from Sugar Beet Molasses on Colon Carcinoma Cells in Vitro

Three polyphenols were isolated and purified from sugar beet molasses by ultrasonic-aid extraction and various chromatographic techniques, and their structures were elucidated by spectral analysis. Cytotoxicity and the molecular mechanism were measured by methyl thiazolyl tetrazolium (MTT) assay, flow cytometry, caspase-3 activity assay and Western blot assay. The results showed that gallic acid, cyanidin-3-O-glucoside chloride and epicatechin have cytotoxicity to the human colon, hepatocellular and breast cancer cells. Cyanidin-3-O-glucoside chloride showed its cytotoxicity against various tumor cell lines, particularly against colon cancer Caco-2 cells with half maximal inhibitory concentration (IC₅₀) value of 23.21 ± 0.14 μg/mL in vitro. Cyanidin-3-O-glucoside chloride may be a potential candidate for the treatment of colon cancer. In the mechanism study, cyanidin-3-O-glucoside chloride increased the ratio of cell cycle at G₀/G₁ phase and reduced cyclin D1 expression on Caco-2 cells. Cyanidin-3-O-glucoside chloride decreased mutant p21 expression, and increased the ratio of Bax/Bcl-2 and the activation of caspase-3 to induce apoptosis.

Diallyl disulfide induces apoptosis and autophagy via mTOR pathway in myeloid leukemic cell line

Leukemia is a hematological malignancy which is produced by uncontrolled proliferation of leukocyte precursors. Currently, alternative medicines, using herb extracts, have been developed for cancer treatment. In this study, the effect of diallyl disulfide (DADS) on the induction of apoptosis and autophagy was investigated in K562 and NB4 myeloid leukemia cells. Leukemia cells were treated with various concentrations of DADS for 24 and 48 h. The percentage of cell viability was measured using an MTT assay. The percentages of apoptosis and autophagy were analyzed by staining with annexin-FITC and anti-LC3 FITC-conjugated antibodies, respectively. Then, the stained cells were detected by flow cytometry. In addition, PP242, a mammalian target rapamycin (mTOR) inhibitor, was used to study the involvement of the mTOR pathway in DADS-induced apoptosis and autophagy. mTOR mRNA expression was measured by real-time PCR. The results showed that DADS decreased cell viability and increased the percentage of cell apoptosis in a dose- and time-dependent manner. mTOR expression was significantly decreased in DADS- and mTOR inhibitor-treated cells. The highest percentages of apoptosis and autophagy were shown in cells treated with 100 μg/ml DADS combined with 10 μM of the mTOR inhibitor. According to our results, DADS could induce apoptosis and autophagy via the mTOR pathway in both K562 and NB4 myeloid leukemia cell lines.

Oxidative Stress: A Promising Target for Chemoprevention

Cancer is a leading cause of death worldwide, and treating advanced stages of cancer remains clinically challenging. Epidemiological studies have shown that oxidants and free radicals induced DNA damage is one of the predominant causative factors for cancer pathogenesis. Hence, oxidants are attractive targets for chemoprevention as well as therapy. Dietary agents are known to exert an anti-oxidant property which is one of the most efficient preventive strategy in cancer progression. In this article, we highlight dietary agents can potentially target oxidative stress, in turn delaying, preventing, or treating cancer development. Some of these agents are currently in use in basic research, while some have been launched successfully into clinical trials.

Comparative effects of vitamin C on the effects of local anesthetics ropivacaine, bupivacaine, and lidocaine on human chondrocytes

BACKGROUND

Intra-articular injections of local anesthetics are commonly used to enhance post-operative analgesia following orthopedic surgery as arthroscopic surgeries. Nevertheless, recent reports of severe complications due to the use of intra-articular local anesthetic have raised concerns.

OBJECTIVES

The study aims to assess use of vitamin C in reducing adverse effects of the most commonly employed anesthetics - ropivacaine, bupivacaine and lidocaine - on human chondrocytes.

METHODS

The chondrocyte viability following exposure to 0.5% bupivacaine or 0.75% ropivacaine or 1.0% lidocaine and/or vitamin C at doses 125, 250 and 500 μM was determined by LIVE/DEAD assay and annexin V staining. Expression levels of caspases 3 and 9 were assessed using antibodies by Western blotting. Flow cytometry was performed to analyze the generation of reactive oxygen species.

RESULTS

On exposure to the local anesthetics, chondrotoxicity was found in the order ropivacaine<bupivacaine<lidocaine. Vitamin C effectively improved the reduced chondrocyte viability and decreased the raised apoptosis levels following exposure to anesthesia. At higher doses, vitamin C was found efficient in reducing the generation of reactive oxygen species and as well down-regulate the expressions of caspases 3 and 9.

CONCLUSIONS

Vitamin C was observed to effectively protect chondrocytes against the toxic insult of local anesthetics ropivacaine, bupivacaine and lidocaine.

Tetramethylpyrazine Protects Retinal Capillary Endothelial Cells (TR-iBRB2) against IL-1β-Induced Nitrative/Oxidative Stress

Blood-retinal barrier (BRB) breakdown is one of the primary causes of diabetic retinopathy (DR). The pro-inflammatory factor interleukin-1β (IL-1β) was reported to be involved in the induction of BRB breakdown during the pathogenesis of DR. In the present study, we investigated the protective effect of tetramethylpyrazine (TMP), a major active component of the traditional herb Ligusticum chuanxiong, on IL-1β-induced cell death of the rat retinal capillary endothelial TR-iBRB2 cells. Our results showed that IL-1β-induced cell dysfunction in TR-iBRB2 cells via inducing nitrative/oxidative stress; however, such effect was attenuated with the pre-treatment of TMP. The cellular protective effect of TMP was likely to be mediated through the inhibition of inducible nitric oxide synthase (iNOS) expression and leukostasis as well as suppression of reactive oxygen species (ROS) generation, mitochondrial dysfunction and MAPKs activation. These findings significantly contribute to a better understanding of the protective effect of TMP in DR and form the basis of the therapeutic development of TMP in treating such disease in the future.

Latex of Euphorbia antiquorum-induced S-phase arrest via active ATM kinase and MAPK pathways in human cervical cancer HeLa cells

Latex of Euphorbia antiquorum (EA) has demonstrated great chemotherapeutic potential for cancer. However, the mechanisms of anti-proliferation of EA on cancer cell remain to be further investigated. The purpose of this study was to explore the influence of EA in human cervical cancer cells. Here, the cell cycle distribution by flow cytometry was examined and the protein expression by the western blotting methods was analyzed. From the cytometric results it was shown that EA-induced S-phase arrest in a concentration manner both in human cervical cancer HeLa and CaSki cells. According the western blot results it was illustrated that EA could downregulate early cyclin E1-Cdk2; and cyclin A-Cdc2 provides a significant additional quantity of S-phase promotion, that in turn promoted the expression of p21(waf1/cip1) and p27(kip1) which were the inhibitors in the complex of cyclin A and Cdc2 that led to cell cycle arrest. Moreover, EA promoted the activation of ataxia telangiectasia mutated (ATM) and check-point kinase-2 (Chk2); however, it negatively regulated the expression of Topoisomerases I and II, Cdc25A, and Cdc25C signaling. Caffeine, an ATM/ATR inhibitor significantly reversed EA downregulation in the levels of Cdc25A. Furthermore, JNK inhibitor SP600125 and p38 MAPK inhibitor SB203580 both could reverse the EA upregulation of the protein of Chk2 level, significantly. This study, therefore, revealed that EA could downregulate topoisomerase, and activate ATM kinase, which then induce parallel Chk 1/2 and MAPK signaling pathways to promote the degradation of Cdc25A to induced S-phase arrest in human cervical cancer HeLa cells.

Amelioration of ferric nitrilotriacetate-induced hepatotoxicity in Wistar rats by diallylsulfide

Garlic contains diallylsulfide (DAS) and other structurally related compounds that are widely believed to be active agents in preventing cancer. This study shows the effect of DAS (a phenolic antioxidant used in foods, cosmetics, and pharmaceutical products) on ferric nitrilotriacetate (Fe-NTA)-induced hepatotoxicity in rats. Male albino rats of Wistar strain weighing 125-150 g were given a single dose of Fe-NTA (9 mg kg(-1) body weight, intraperitoneally) after 1 week of treatment with 100 and 200 mg kg(-1) DAS in corn oil respectively administered through the gavage. Fe-NTA administration led to 2.5-fold increase in the values of both alanine transaminase and aspartate aminotransferase, respectively, and 3.2-fold increase in the activity of lactate dehydrogenase, microsomal lipid peroxidation to approximately 2.0-fold compared to saline-treated control. The activities of glutathione (GSH) and other antioxidant enzymes decreased to a range of 2.2-2.5-fold. These changes were reversed significantly (p < 0.001) in animals receiving a pretreatment of DAS. DAS protected against hepatic lipid peroxidation, hydrogen peroxide generation, preserved GSH levels, and GSH metabolizing enzymes to 60-80% as compared to Fe-NTA alone-treated group. Present data suggest that DAS can ameliorate the toxic effects of Fe-NTA and suppress oxidant-induced tissue injury and hepatotoxicity in rats.

Evaluation of antitumor property of extracts and steroidal alkaloids from the cultivated Bulbus Fritillariae ussuriensis and preliminary investigation of its mechanism of action

BACKGROUND

Cancer is well known as a leading cause of death in the world. At present, it is the very active area to search for anticancer drugs from natural products. In this study, we evaluated the antitumor property of chloroform extract (CE), n-hexane extract (HE), water extract (WE) and steroidal alkaloids from the cultivated Bulbus Fritillariae ussuriensis (BFU) and its preliminary mechanism for its action was investigated.

METHODS

Firstly, cytotoxicity of the different extracts from BFU against Lewis lung carcinoma cell line (LLC), Human ovarian cancer cell line (A2780), human hepatocellular carcinoma cell line (HepG2), human lung carcinoma cell line (A549) was measured by MTT assay. Then, we identified the compounds from the active extract of BFU by bioassay guided isolation, determined their antitumor activity in vitro, and detected cell cycle distribution using flow cytometry. Moreover, the extract of BFU which showed remarked anti-proliferative activity in vitro was further evaluated using S180 and LLC tumor models. Additionally, a preliminary investigation of the mechanism of the action was carried out by using histological and immunohistochemical staining technique.

RESULTS

The results showed that CE and the purified total alkaloids of BFU (TAFU) exhibited stronger cytotoxic activity than the others (WE and HE). We further isolated the four main steroidal alkaloids from TAFU, and found all alkaloids showed significant cytotoxicity, and peimisine induced G0/G1 phase arrest and increased apoptosis. The results showed that TAFU had significant antitumor activity and low toxicity in vivo. Additionally, the immunohistochemical examinations signified that TAFU remarkably increased caspase-3 expression and reduced microvessel density (MVD) in tumor tissues of transplantable S180 and LLC tumor models.

CONCLUSIONS

These results achieved suggested that the steroidal alkaloids could hold a good potential for use as an antitumor drug. Notably, our finding is the first report on the antitumor activity of extracts and steroidal alkaloids from the cultivated BFU in vitro and in vivo and its mechanisms.

Chk1, but not Chk2, is responsible for G2/M phase arrest induced by diallyl disulfide in human gastric cancer BGC823 cells

Diallyl disulfide (DADS) has been shown to cause G2/M phase cell cycle arrest in several human cancers. Here we demonstrate a mechanism by which DADS induces G2/M phase arrest in BGC823 human gastric cancer cells via Chk1. From cell cycle gene array results, we next confirmed that cyclin B1 expression was decreased by DADS, while the expression of p21, GADD45α and p53 were increased. Despite the lack of change in Chk1 gene expression in response to DADS according to the array analysis, intriguingly overexpression of Chk1, but not Chk2, exhibited increased accumulation in G2/M phase. Moreover, overexpression of Chk1 promoted the effect of DADS-induced G2/M arrest. Augmented phosphorylation of Chk1 by DADS was observed in Chk1-transfected cells, followed by downregulation of Cdc25C and cyclin B1 proteins. In contrast, phosphorylated Chk2 showed no obvious change in Chk2-transfected cells after DADS treatment. Furthermore, knockdown of Chk1 by siRNA partially abrogated DADS-induced downregulation of Cdc25C and cyclin B1 proteins and G2/M arrest. In contrast, knockdown of Chk2 did not show these effects. Therefore, these data indicate that DADS may specifically modulate Chk1 phosphorylation, and DADS-induced G2/M phase arrest in BGC823 cells could result in part from Chk1-mediated inhibition of the Cdc25C/cyclin B1 pathway.

Ziyuglycoside II inhibits the growth of human breast carcinoma MDA-MB-435 cells via cell cycle arrest and induction of apoptosis through the mitochondria dependent pathway

Ziyuglycoside II is one of the major active compounds of Sanguisorba officinalis L., which has a wide range of clinical applications including hemostasis, antibiosis, anti-inflammation and anti-oxidation. This study investigated the effect of ziyuglycoside II on the growth of human breast carcinoma MDA-MB-435 cells for the first time. The results showed that ziyuglycoside II could significantly inhibit the growth of MDA-MB-435 cells through blocking cell cycle progression at G0/G1 and S phase as well as via inducing cell apoptosis. Accumulation of reactive oxygen species (ROS) was observed in the progression of cell cycle arrest, which was associated with the increased expression of cell cycle regulating factors, p53 and p21. Subsequent apoptosis induced by ziyuglycoside II was accompanied with the activation of mitochondrial pathway, in particular a decreased mitochondrial membrane potential (MMP) as well as increased Bax/Bcl-2 ratio, cytochrome c release and the activity of caspase-3 and caspase-9. In conclusion, our study was the first to report that ziyuglycoside II has inhibitory effect on the growth of MDA-MB-435 cells, which might become a potential therapeutic approach of breast cancer in the future.

Experimental study on inhibitory effects of diallyl sulfide on growth and invasion of human osteosarcoma MG-63 cells

The inhibitory effects of diallyl sulfide (DAS) derived from allicin on in vitro and in vivo proliferation of human osteosarcoma MG-63 cells and the action mechanism, and the influence of DAS on invasive capability of MG-63 cells were investigated in order to search for the novel medicines for osteosarcoma. In the in vitro experiment, MG-63 cells were treated with different concentrations of DSA, and the morphological changes of MG-63 cells were observed under an inverted phase microscope. MTT method was used to assay the proliferation of MG-63 cells. Semi-quantitative reverse transcription polymerase chain reaction (RT-PCR) was used to detect the VEGF mRNA expression level in MG-63 cells. By using Transwell invasion assay, the influence of DAS on invasive ability of MG-63 cells was tested. In the in vivo experiment, the nude mice MG-63 cells tumor-bearing model was established, and different concentrations of DAS were injected beside the tumor. Twenty-one days after treatment, the mice were killed, the tumor size and tumor inhibition rate were calculated. The microvessel density (MVD) was determined by using immunohistochemistry. In the in vitro experiment, different concentrations of DAS could obviously inhibit proliferation of MG-63 cells in a time- and concentration-dependent manner. RT-PCR revealed that the expression levels of VEGF mRNA in DSA groups (different concentrations) were significant reduced as compared with those in control group (all P<0.05). Transwell invasion assay indicated that in 20 and 40 μg/mL DAS groups, the number of migratory cells was 91.4±8.3 and 81.8±7.4 respectively, which was significantly declined as compared with that in control group (150.4±14.7, both P<0.05). In the in vivo experiment, DAS could significantly suppress the growth of MG-63 tumor-bearing tissue. Immunohistochemistry demonstrated that different concentrations (20 and 40 μg/mL) of DAS could significantly decrease MVD of MG-63 tumor-bearing tissue (all P<0.05). It was suggested that DAS could inhibit the growth of MG-63 cells probably by suppressing the expression of VEGF mRNA.

Experimental study on inhibitory effects of diallyl sulfide on growth and invasion of human osteosarcoma MG-63 cells. J Huazhong Univ Sci Technolog Med Sci. 2012;32:581-585. [PMID: 22886974 DOI: 10.1155/2014/378684]

Background. Allicin, the major component of freshly crushed garlic, is one of the most biologically active compounds of garlic; it has been reported to induce apoptosis in cancer cells; however, the mechanism by which allicin exerts its apoptotic effects is not fully understood. The aim of the present study was to further elucidate the apoptotic pathways induced by allicin in the human ovarian cancer cell line SKOV3. Methods. Cell proliferation and apoptosis were measured by cell-counting assay and flow cytometry analysis. Activation of the signaling pathway was screened by human phospho-kinase array analysis, and the activated pathway and its related proteins were further confirmed by western blot analysis. Results. Allicin induced SKOV3 cell apoptosis and JNK phosphorylation in a time- and dose-dependent manner, but these were significantly blocked by SP600125 (an inhibitor of JNK). The findings suggest that JNK phosphorylation is related to the action of allicin on SKOV3 cells. Furthermore, JNK activation induced Bcl-2 family activation, triggered mitochondria-mediated signaling pathways, and led to the translocation of a considerable amount of Bax and cytochrome c release. Conclusions. JNK activation and mitochondrial Bax translocation are involved in allicin-induced apoptosis in SKOV3 cells. Our data input new insights to the literature of allicin-induced apoptosis.

Reversion of p-glycoprotein-mediated multidrug resistance in human leukemic cell line by diallyl trisulfide

Multidrug resistance (MDR) is the major obstacle in chemotherapy, which involves multiple signaling pathways. Diallyl trisulfide (DATS) is the main sulfuric compound in garlic. In the present study, we aimed to explore whether DATS could overcome P-glycoprotein-(P-gp-)mediated MDR in K562/A02 cells, and to investigate whether NF-κB suppression is involved in DATS-induced reversal of MDR. MTT assay revealed that cotreatment with DATS increased the response of K562/A02 cells to adriamycin (the resistance reversal fold was 3.79) without toxic side effects. DATS could enhance the intracellular concentration of adriamycin by inhibiting the function and expression of P-gp, as shown by flow cytometry, RT-PCR, and western blot. In addition, DATS resulted in more K562/A02 cell apoptosis, accompanied by increased expression of caspase-3. The expression of NF-κB/p65 (downregulation) was significantly linked to the drug-resistance mechanism of DATS, whereas the expression of IκBα was not affected by DATS. Our findings demonstrated that DATS can serve as a novel, nontoxic modulator of MDR, and can reverse the MDR of K562/A02 cells in vitro by increasing intracellular adriamycin concentration and inducing apoptosis. More importantly, we proved for the first time that the suppression of NF-κB possibly involves the molecular mechanism in the course of reversion by DATS.

Gallic acid inhibits migration and invasion in human osteosarcoma U-2 OS cells through suppressing the matrix metalloproteinase-2/-9, protein kinase B (PKB) and PKC signaling pathways

Advanced cancer is a multifactorial disease which complicates treatment if the cancer cells have metastasized calling for the targeting of multiple cellular pathways. Gallic acid (GA) is known to possess multiple pharmacological activity including antitumor effects. This study investigated the mechanisms for the anticancer properties of GA on migration and invasion of human osteosarcoma U-2 OS cells. The migration and invasion in U-2 OS cells were determined by a Boyden chamber transwell assay. The expression levels and activities of MMP-2 and MMP-9 were measured by Western blotting, real-time PCR and gelatin zymography assays. All examined proteins levels from Western blotting indicated that GA decreased the protein levels of GRB2, PI3K, AKT/PKB, PKC, p38, ERK1/2, JNK, NF-κB p65 in U-2 OS cells. GA also inhibited the activities of AKT, IKK and PKC by in vitro kinase assay. GA suppressed the migration and invasive ability of U-2 OS cells, and it decreased MMP-2 and MMP-9 protein and mRNA levels and secreted enzyme activities in vitro. These results suggest that potential signaling pathways of GA-inhibited migration and invasion in U-2 OS cells may be due to down-regulation of PKC, inhibition of mitogen-activated protein kinase (MAPK) and PI3K/AKT, resulting in inhibition of MMP-2 and MMP-9 expressions.

Latex of Euphorbia antiquorum induces apoptosis in human cervical cancer cells via c-jun n-terminal kinase activation and reactive oxygen species production

Latex of Euphorbia antiquorum (EA) has inhibitory effects on several different cancer cell lines. However, the molecular mechanism of EA inhibitory effects on human cervical cancer HeLa cell growth has not been explored. EA induced apoptosis, which was characterized by morphological change, DNA fragmentation, increased sub-G1 population, and alterations in levels of apoptosis-associated proteins. Treatment with EA increased cell death and expression levels of caspase-8, -9, and -3. EA suppressed expression of Bcl-2, increased Bax, and reduced cleavage of Bid and the translocation of tBid to the mitochondria and the release of cytochrome c from mitochondria. EA caused a loss of mitochondrial membrane potential (ΔΨm) and an increase in cellular reactive oxygen species (ROS). EA-induced ROS formation was suppressed by cyclosporine A (an inhibitor of the ΔΨm) or allopurinol (an effective scavenger of ROS). EA also increased expression of Fas, FasL, and c-Jun N-terminal kinase (JNK), p38, and mitogen-activated protein kinase (MAPK) and decreased expression of extracellular signal-regulated kinase (ERK) 1/2-p. Co-treatment with the JNK inhibitor SP600125 inhibited EA-induced apoptosis and the activation of caspase-8, -9, and -3. Results of this study provide support for the hypothesis that EA causes cell death via apoptotic pathways in human cervical adenocarcinoma HeLa cells.

Dietary phytochemicals, HDAC inhibition, and DNA damage/repair defects in cancer cells

Genomic instability is a common feature of cancer etiology. This provides an avenue for therapeutic intervention, since cancer cells are more susceptible than normal cells to DNA damaging agents. However, there is growing evidence that the epigenetic mechanisms that impact DNA methylation and histone status also contribute to genomic instability. The DNA damage response, for example, is modulated by the acetylation status of histone and non-histone proteins, and by the opposing activities of histone acetyltransferase and histone deacetylase (HDAC) enzymes. Many HDACs overexpressed in cancer cells have been implicated in protecting such cells from genotoxic insults. Thus, HDAC inhibitors, in addition to unsilencing tumor suppressor genes, also can silence DNA repair pathways, inactivate non-histone proteins that are required for DNA stability, and induce reactive oxygen species and DNA double-strand breaks. This review summarizes how dietary phytochemicals that affect the epigenome also can trigger DNA damage and repair mechanisms. Where such data is available, examples are cited from studies in vitro and in vivo of polyphenols, organosulfur/organoselenium compounds, indoles, sesquiterpene lactones, and miscellaneous agents such as anacardic acid. Finally, by virtue of their genetic and epigenetic mechanisms, cancer chemopreventive agents are being redefined as chemo- or radio-sensitizers. A sustained DNA damage response coupled with insufficient repair may be a pivotal mechanism for apoptosis induction in cancer cells exposed to dietary phytochemicals. Future research, including appropriate clinical investigation, should clarify these emerging concepts in the context of both genetic and epigenetic mechanisms dysregulated in cancer, and the pros and cons of specific dietary intervention strategies.

Inhibition of matrix metalloproteinase activities and tightening of tight junctions by diallyl disulfide in AGS human gastric carcinoma cells

The effect of diallyl disulfide (DADS), a major component of an oil-soluble allyl sulfide garlic (Allium sativum) derivative, on the correlation between anti-invasive activity and tightening of tight junctions (TJs) was investigated in human gastric adenocarcinoma AGS cells. Our data indicated that the inhibitory effects of DADS on cell motility and invasiveness were found to be associated with increased tightness of the TJs, which was demonstrated by an increase in transepithelial electrical resistance. Activities of matrix metalloprotease (MMP)-2 and -9 in AGS cells were dose-dependently inhibited by treatment with DADS, and this was also correlated with a decrease in expression of their mRNA and proteins; however, tissue inhibitor of metalloproteinase (TIMP)-1 and -2 mRNA levels and proteins were increased. Additionally, immunoblotting results indicated that DADS repressed the levels of claudin proteins (claudin-2, -3, and -4), major components of TJs that play key roles in control and selectivity of paracellular transport. Although further studies are needed, these results suggest that DADS treatment may inhibit tumor cell motility and invasion and, therefore, act as a dietary source to decrease the risk of cancer metastasis.

Caspase-8 and p38MAPK in DATS-induced apoptosis of human CNE2 cells

Nasopharyngeal carcinoma is a common malignancy in Southern China of uncertain etiologic origin. Diallyl trisulfide (DATS), one of the major components of garlic (Allium sativum), is highly bactericidal and fungicidal. In this study, we investigated the function of p38 mitogen-activated protein kinase (MAPK) and caspase-8 in DATS-induced apoptosis of human CNE2 cells using MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide], flow cytometry assay, and Western blotting. After CNE2 cells were treated with DATS (50, 100, or 150 μM) for 24 h, cell viability rates were 75.9, 63.4 and 39.6%, and apoptosis rates were 24.5, 36.9, and 62.4%, respectively. The data showed that DATS induced CNE2 cell death in a dose-dependent manner. After human CNE2 cells were treated with 100 μM DATS and inhibitors (10 μM SB203580 and Z-LETD-FMK for p38MAPK and caspase-8, respectively), changes in cell viability and apoptosis and in p38MAPK and caspase-8 activity were detected. Cell viability rates were 66.5 and 68.1% and decreased 9.9 and 11.5% compared with inhibitor treatment alone. Apoptosis rates were 31.53 and 29.98% and increased 9.1 and 10% compared with inhibitor treatment alone. The results indicated that DATS activates p38MAPK and caspase-8, but both inhibitors have an effect on P38MAPK and caspase-8 activity. In conclusion, our data indicate that p38MAPK and caspase-8 are involved in the process of DATS-induced apoptosis in human CNE2 cells and interact with each other.

Anti-invasive activity of diallyl disulfide through tightening of tight junctions and inhibition of matrix metalloproteinase activities in LNCaP prostate cancer cells

Diallyl disulfide (DADS) is a major component of an oil-soluble allyl sulfide garlic (Allium sativum) derivative, which has been shown to exert a potential for anti-cancer activity. However, the biochemical mechanisms underlying DADS-induced anti-invasiveness and anti-metastasis have not been thoroughly studied. In this study, we investigated the effect of DADS on the correlation between tightening of tight junctions (TJs) and anti-invasive activity in human prostate carcinoma LNCaP cells. Inhibitory effects of DADS on cell motility and invasiveness were found to be associated with increased tightness of the TJ, which was demonstrated by an increase in transepithelial electrical resistance (TER). Additionally, immunoblotting results indicated that DADS repressed the levels of the claudin proteins, which are major components of TJs that play a key role in control and selectivity of paracellular transport. Furthermore, the activities of matrix metalloproteinase (MMP)-2 and -9 in LNCaP cells were dose-dependently inhibited by treatment with DADS, and this was also correlated with a decrease in expression of their mRNA and proteins. Although further studies are needed, the present study indicates that TJs and MMPs are critical targets of DADS-induced anti-invasiveness in human prostate cancer LNCaP cells.

The roles of p38MAPK and caspase-3 in DADS-induced apoptosis in human HepG2 cells

Objectives

To explore the function of p38MAPK and caspase-3 in DADS-induced apoptosis in human HepG2 cells, and discuss the signal transduetion mechanism of HepG2 cells in the apoptosis process induced by DADS by using the inhibitors of p38MAPK (SB203580) and caspase-3 (Z-DEVD-FMK).

Methods

After the human HepG2 cells had been treated with the DADS and inhibitors for 24 h, cell viability was determined by the MTT method, apoptosis was evaluated by flow cytometry (FCM) and the expressions of p38MAPK and caspase-3 were measured by western-blot.

Results

Our results indicated that DADS activities the p38MAPK and caspase-3, but the inhibitors, SB203580 and Z-DEVD-FMK (for p38MAPKand for caspase-3, respectively), both have the effect of inhibitory activity on P38MAPK and caspase-3. Furthermore, a combination treatment with both DADS and inhibitor (SB203580 or Z-DEVD-FMK) decreases the inhibitory and apoptotic activity of HepG2 cells increased compared with DADS-treated.

Conclusions

Our data indicate that p38MAPK and caspase-3 are involved in the process of DADS-induced apoptosis in human HepG2 cells and interact with each other.

The roles of p38mAPK and caspase-3 in dads-induced apoptosis in human HepG2 cells

The roles of p38MAPK and caspase-3 in DADS-induced apoptosis in human HepG2 cells were investigated. After the human HepG2 cells were treated with DADS, the cell viability, apoptosis and the activity changes of p38MAPK and caspase-3 were measured. The results indicated that DADS can activate p38MAPK and caspase-3. The results showed that p38MAPK and caspase-3 are involved in the process of DADS-induced apoptosis in human HepG2 cells and interact with each other.

Gallic acid induces apoptosis via caspase-3 and mitochondrion-dependent pathways in vitro and suppresses lung xenograft tumor growth in vivo

Several studies have shown that gallic acid (GA) induces apoptosis in different cancer cell lines, whereas the mechanism of action of GA-induced apoptosis at the molecular level in human non-small-cell lung cancer NCI-H460 cells is not well-known. Here, GA decreasing the percentage of viable NCI-H460 cells was investigated; GA-induced apoptosis involved G2/M phase arrest and intracellular Ca(2+) production, the loss of mitochondrial membrane potential (DeltaPsi(m)), and caspase-3 activation. The efficacious induction of apoptosis and DNA damage was observed at 50-500 microM for 24 and/or 48 h as examined by flow cytometry, DAPI staining, and Comet assay methods. Western blotting and flow cytometric analysis also demonstrated that GA increased protein levels of GADD153 and GRP78, activation of caspase-8, -9, and -3, loss of DeltaPsi(m) and cytochrome c, and AIF release from mitochondria. Moreover, apoptosome formation and activation of caspase cascade were associated with apoptotic cell death. GA increased Bax and Bad protein levels and decreased Bcl-2 and Bcl-xL levels. GA may also induce apoptosis through a caspase-independent AIF pathway. In nude mice bearing NCI-H460 xenograft tumors, GA inhibited tumor growth in vivo. The data suggest that GA induced apoptosis in NCI-H460 lung cancer cells via a caspase-3 and mitochondrion-dependent pathway and inhibited the in vivo tumor growth of NCI-H460 cells in xenograft models.

Garlic: nature's protection against physiological threats

Currently reliance on natural products is gaining popularity to combat various physiological threats including oxidative stress, cardiovascular complexities, cancer insurgence, and immune dysfunction. The use of traditional remedies may encounter more frequently due to an array of scientific evidence in their favor. Garlic (Allium sativum) holds a unique position in history and was recognized for its therapeutic potential. Recent advancements in the field of immunonutrition, physiology, and pharmacology further explored its importance as a functional food against various pathologies. Extensive research work has been carried out on the health promoting properties of garlic, often referred to its sulfur containing metabolites i.e. allicin and its derivatives. Garlic in its preparations are effective against health risks and even used as dietary supplements such as age garlic extract (AGE) and garlic oil etc. Its components/formulations can scavenge free radicals and protect membranes from damage and maintains cell integrity. It also provides cardiovascular protection mediated by lowering of cholesterol, blood pressure, anti-platelet activities, and thromboxane formation thus providing protection against atherosclerosis and associated disorders. Besides this, it possesses antimutagenic and antiproliferative properties that are interesting in chemopreventive interventions. Several mechanisms have been reviewed in this context like activation of detoxification phase-I and II enzymes, reactive oxygen species (ROS) generation, and reducing DNA damage etc. Garlic could be useful in preventing the suppression of immune response associated with increased risk of malignancy as it stimulates the proliferation of lymphocytes, macrophage phagocytosis, stimulates the release of interleukin-2, tumor necrosis factor-alpha and interferon-gamma, and enhances natural killer cells. In this paper much emphasis has been placed on garlic's ability to ameliorate oxidative stress, core role in cardiovascular cure, chemopreventive strategies, and indeed its prospective as immune booster.

Emodin has cytotoxic and protective effects in rat C6 glioma cells: roles of Mdr1a and nuclear factor kappaB in cell survival

1,3,8-Trihydroxy-6-methylanthaquinone (emodin) is recognized as an antiproliferative compound. In the present study, however, we show that emodin has both toxic and survival effects in glioma cells and that the survival effects involve Mdr1a. Emodin inhibited the proliferation and induced apoptosis of C6 cells in a 12-h treatment, but C6 cells survived a 72-h drug treatment, indicating resistance to emodin. Emodin-induced apoptosis was reduced by inhibition of the expression and activation of apoptosis-associated proteins including p53, Bax, Bcl-2, Fas, and caspase-3. C6 cells could express antioxidant proteins (superoxide dismutase and catalase) to decrease reactive oxygen species-induced cytotoxicity of emodin and overexpress multidrug resistance genes (Mdr1a, MRP2, MRP3, and MRP6) to decrease the intracellular accumulation of emodin. Electrophoretic mobility shift analysis showed that emodin decreased nuclear factor kappaB (NF-kappaB) expression in 24 h of treatment, but in 48 h, emodin increased NF-kappaB activity. A confocal microscope showed that emodin induced NF-kappaB translocation from cytoplasm to nuclei. C6 cells would activate the mitogen-activated protein kinase survival pathway and express the DNA repair gene (MGMT) and associated proteins (PARP and XRCC1) to recover the cell activity. C6 cells also expressed GRP78 to decrease emodin-induced endoplasmic reticulum (ER) stress that would cause apoptosis in C6 cells, and GRP78 inhibited the expression of GADD153 to enhance the expression of Bcl-2 that could balance the ER- and mitochondria-induced apoptosis of C6 cells.

Molecular targets of nutraceuticals derived from dietary spices: potential role in suppression of inflammation and tumorigenesis

Despite the fact cancer is primarily a preventable disease, recent statistics indicate cancer will become the number one killer worldwide in 2010. Since certain cancers are more prevalent in the people of some countries than others, suggests the role of lifestyle. For instance cancer incidence among people from the Indian subcontinent, where most spices are consumed, is much lower than that in the Western World. Spices have been consumed for centuries for a variety of purposes-as flavoring agents, colorants, and preservatives. However, there is increasing evidence for the importance of plant-based foods in regular diet to lowering the risk of most chronic diseases, so spices are now emerging as more than just flavor aids, but as agents that can not only prevent but may even treat disease. In this article, we discuss the role of 41 common dietary spices with over 182 spice-derived nutraceuticals for their effects against different stages of tumorigenesis. Besides suppressing inflammatory pathways, spice-derived nutraceuticals can suppress survival, proliferation, invasion, and angiogenesis of tumor cells. We discuss how spice-derived nutraceuticals mediate such diverse effects and what their molecular targets are. Overall our review suggests "adding spice to your life" may serve as a healthy and delicious way to ward off cancer and other chronic diseases.

Biological properties of garlic and garlic-derived organosulfur compounds

Medicinal properties of garlic (Allium sativum) have been widely known and used since ancient times till the present. Garlic enhances immune functions and has antibacterial, antifungal and antivirus activities. It is known to prevent platelet aggregation, and to have hypotensive and cholesterol- and triglyceride-lowering properties, although the latter features have been questioned. This review is focused on anticancer efficacy of Allium sativum, and attempts to explain the mechanisms of this action. Medicinal properties of garlic rely upon organosulfur compounds mostly derived from alliin. Organosulfur compounds originating from garlic inhibit carcinogen activation, boost phase 2 detoxifying processes, cause cell cycle arrest mostly in G2/M phase, stimulate the mitochondrial apoptotic pathway, increase acetylation of histones. Garlic-derived sulfur compounds influence also gap-junctional intercellular communication and participate in the development of multidrug resistance. This review presents also other little known aspects of molecular action of garlic-derived compounds, like modulation of cellular redox state, involvement in signal transduction and post-translational modification of proteins by sulfane sulfur or by formation of mixed disulfides (S-thiolation reactions).

Apoptosis induction by sulfur-containing compounds in malignant and nonmalignant human cells

Plants have traditionally represented a main source for the discovery of many biologically active substances with therapeutic values. Sulfur-containing compounds exhibit pleiotropic biological effects supporting their potential use in multitargeted cancer prevention and treatment. As potential anti-cancer agents, they have been shown to inhibit or retard the growth of various cancer cells in culture and implanted tumors in vivo. The compounds significantly inhibit experimental tumorigenesis in a wide range of animal models. A critical and well-elucidated cellular mechanism involved in the anticancer activities of sulfur-containing compounds is the induction of apoptosis through the fine-tuning of orchestrated intracellular signal transduction. This review summarizes the established proapoptotic activities of sulfur-containing compounds in malignant and nonmalignant cells with a special focus on their molecular mechanisms. The potential toxicological implications of proapoptotic effects on normal cells will also be discussed.

L-glutamate enhances methylmercury toxicity by synergistically increasing oxidative stress

Methylmercury (MeHg) is a well-known environmental toxicant. With its lipophilic nature and high reactivity to sulfhydryl groups, it is widely distributed and accumulated in the body to damage cells. Oxidative stress is proposed as a major mechanism underlying the cytotoxic action of MeHg. In the present study, we found that L-glutamate (L-Glu) concentration-dependently increased MeHg cytotoxicity in HeLa S3 cells. The enhancement of the toxicity was accompanied by enhanced apoptosis, increased production of reactive oxygen species, and decreased glutathione level. An anti-oxidant N-acetylcysteine largely alleviated the cytotoxicity, suggesting enhanced oxidative stress behind L-Glu-elicited increase of MeHg toxicity. The effect was specific to L-Glu and L-alpha-aminoadipate, whereas D-Glu, L-aspartate, and D-aspartate were not effective. In addition, the cystine uptake by the cells was mostly mediated by a L-Glu/L-alpha-aminoadipate-sensitive amino acid transport system x(-)(C). All these results suggest that the inhibition of system x(-)(C) by L-Glu underlies the enhancement of MeHg cytotoxicity. The enhancement was highly synergistic because MeHg and L-Glu alone had little toxic effect in the conditions used. This synergism was confirmed in neural cells (neuroblastoma cell lines). It is proposed that similar mechanisms may underlie the neural toxicity of MeHg, particularly in the locality of lesions characteristic of MeHg toxicity.

Diallyl disulfide induces apoptosis in human colon cancer cell line (COLO 205) through the induction of reactive oxygen species, endoplasmic reticulum stress, caspases casade and mitochondrial-dependent pathways

In this study, we investigated the effects of DADS on human colon cancer cell line COLO 205 on cell cycle arrest and apoptosis in vitro. After 24 h treatment of COLO 205 cells with DADS, the dose- and time-dependent decreases of viable cells were observed and the IC50 was 22.47 microM. The decreased percentages of viable cells are associated with the production of ROS. Treatment of COLO 205 cells with DADS resulted in G2/M phase arrest and apoptosis occurrence through the mitochondrial-pathway (Bcl-2, Bcl-xL down-regulation and Bak, Bax up-regulation). DADS increased cyclin B, cdc25c-ser-216-9 and Wee1 but did not affect CDK1 protein and gene expression within 24 h of treatment. DADS-induced apoptosis was examined and confirmed by DAPI staining and DNA fragmentation assay. DADS promoted caspase-3, -8 and -9 activity and induced apoptosis were accompanied by increasing the levels of Fas, phospho-Ask1 and -JNK, p53 and decreasing the mitochondrial membrane potential which then led to release the cytochrome c, cleavage of pro-caspase-9 and -3. The COLO 205 cells were pre-treated with JNK inhibitor before leading to decrease the percentage of apoptosis which was induced by DADS. Inhibition of caspase-3 activation blocked DADS-induced apoptosis on COLO 205 cells.

Effects of diallyl disulfide (DADS) on expression of apoptosis associated proteins in androgen independent human prostate cancer cells (PC-3)

Prostate cancer is a leading cause of death among the aging men. Surgical or radiotherapy is effective when the cancer is confined to the prostate gland but once the cancer spreads beyond the pelvis even chemotherapy and hormonal ablation therapy fails in curing this disease. Our previous studies have shown that diallyl disulfide (DADS) induces cell cycle arrest and also induces apoptosis in PC-3 cells. And now the present study is focused to see whether there is an activation of caspase cascade pathway. Hence, in the present study the apoptotic effect of DADS is studied by Western blot analysis of caspase-3, -9, -10 and Bcl-2, Bad, and Bax protein. The Apoptotic cells were assessed by Hoechst 33342 staining with 25 and 40 microM concentrations of DADS for 24 h. The results have shown that DADS at 25 and 40 microM concentrations has induced the activation of caspases. There is a significant increase in the expression of caspases (3, 9, and 10). The proapoptotic protein Bax has significantly increased at 40 microM of DADS treatment and there is significant increase of Bad protein at both the concentration. Bcl-2 protein has significantly decreased in DADS treated cells. Therefore, the present investigation serves as evidence that DADS may be a therapeutic drug in the treatment of prostate cancer.

Aloe-emodin suppressed NMDA-induced apoptosis of retinal ganglion cells through regulation of ERK phosphorylation

A high concentration of glutamate in the vitreous body and optic nerves of the eyes activates N-methyl-D-aspartate (NMDA) receptors and is toxic to retina ganglion cells (RGCs) in glaucomatous patients. Aloe-emodin sulfates/glucuronides (s/g), the major metabolites of aloe-emodin, was found to be effective in decreasing NMDA-induced apoptosis in RGCs. In order to elucidate the mechanisms, an in vitro optic neuropathy model adding NMDA to N18 RGCs was used in this study. The phosphorylation level of extra-cellular signal-regulated kinase1/2 (ERK1/2), c-Jun N-terminal kinase (JNK) and p38 kinase (cytokines-suppressive antiinflammatory drug binding protein kinase) were measured by western blotting and luciferase reporter assay. The results showed that aloe-emodin metabolites significantly decreased the activation of three major mitogen-activated protein (MAP) kinase pathways and the activation of downstream genes in nucleus induced by NMDA, which were verified by the addition of the respective inhibitors. Comparing the effect of the inhibitors of the three MAP kinase pathways, the ERK pathway was found to be the major route of aloe-emodin metabolites in decreasing the apoptosis of NMDA-treated RGCs. Besides, cfos rather then cjun was the target downstream gene. Aloe-emodin emodin metabolites could regulate the phosphorylation of ERK kinases and it was a promising candidate for NMDA-induced apoptosis of RGCs.

Erk is involved in the differentiation induced by diallyl disulfide in the human gastric cancer cell line MGC803

Diallyl disulfide (DADS) is a major constituent of garlic. Previously, we found that DADS both inhibited proliferation in human gastric cancer cells in vitro and in vivo, and induced G2/M arrest. In this study, we investigated whether this differentiation effect was induced by DADS in human gastric cancer MGC803 cells, and whether it was related to an alteration in ERK activity. The results showed that the growth of MGC803 cells was inhibited by DADS. Cells treated with DADS displayed a lower nucleocytoplasmic ratio and tended to form gland and intercellular conjunction structures. The ConA-mediated cell agglutination ratio and cells' ALP specific activity decreased. In MGC803 cells, dye transfer was limited to a few cells neighbouring the dye-injected cell and to a depth of 1-2 layers beneath the scrape site. However, after treatment with DADS, the LY (Lucifer Yellow) was transferred to several cells immediately neighbouring the microinjected cell and to a depth of 2-4 cell layers from the scrape site. This indicated that DADS induced differentiation in MGC803 cells. Western blot analysis revealed that although DADS did not influence the quantity of ERK1/2 protein expressed, it did decrease its phosphorylation in a concentration-dependent manner, compared with the controls. At 30 mg x L(-1), DADS inhibited the activation of ERK1/2 in 15-30 min. These results suggested that the DADS-induced differentiation of MGC803 cells involved an alteration of the ERK1/2 signaling pathway.

Transfection of hepatic stimulator substance gene desensitizes hepatoma cells to H2O2-induced cell apoptosis via preservation of mitochondria

Hepatic stimulator substance (HSS) protects liver cells from various toxins. However, the mechanism by which HSS protects hepatocytes remains unclear. In this study, we report that the HSS gene, after transfection into BEL-7402 hepatocma cells, is stably expressed in the mitochondria. Hydrogen peroxide (H(2)O(2))-induced cell apoptosis in the HSS-transfected cells is reduced, as shown by morphologic analysis. In the HSS-transfected cells, disruption of mitochondrial transmembrane potential (MTP) and cytochrome c leakage are reduced. The anti-apoptotic gene Bcl-2 is also highly expressed. In addition, ATP levels in the HSS-transfected cells are maintained. In conclusion, in hepatoma cells, HSS gene expression protects cells against H(2)O(2) injury, and this effect is likely to be associated with preservation of mitochondria.

Induction of apoptosis and histone hyperacetylation by diallyl disulfide in prostate cancer cell line PC-3

Prostate cancer is the most invasive and frequently occurred cancer in men. In the initial stages, it is androgen dependent and the androgen ablation therapy is effective at this stage. In the final stages, it becomes androgen-independent and is unresponsive to androgen ablation therapy. At this stage, induction of apoptosis is considered as a better strategy to control cancer. Histone acetylation and deacetylation are involved in transcriptional activation and transcriptional repression, respectively. Diallyl disulfide (DADS) induced histone hyperacetylation can be correlated with the expression of antiproliferative genes. Induction of apoptosis by DADS has been correlated with histone acetylation. In the present study, DADS, oil soluble organosulfur compound of garlic, has been studied for its effect on histone acetylation and induction of apoptosis in prostate cancer cells in vitro. The induction of apoptosis has been demonstrated by annexin V-FITC binding assay. Extent of apoptosis has been assessed measuring the activity of caspase-3. The results have shown that DADS induced apoptosis in prostate cancer cells in a dose dependent manner. At both 25 and 40 microM concentrations, DADS increased the number of both early and late apoptotic cells. Histone hyperacetylation was also observed in DADS treated cells. It is concluded that DADS, induces apoptosis by influencing histone acetylation in prostate cancer cells.

Sodium ascorbate inhibits growth via the induction of cell cycle arrest and apoptosis in human malignant melanoma A375.S2 cells

Vitamin C has been reported to be useful in the treatment and prevention of cancer. Inconsistent effects from growth stimulation to induction of apoptosis of malignant tumor cells, however, have been reported. Melanoma is an increasingly common and potentially lethal malignancy. It was reported that melanoma cells were more susceptible to ascorbate toxicity than any other tumor cells. The mechanisms accounting for ascorbate-induced apoptosis in human melanoma cells, however, have remained unclear. This study was undertaken to investigate the effect of sodium ascorbate on cytotoxicity and apoptosis in human malignant melanoma A375.S2 cells. A375.S2 cells were incubated with a certain range of concentrations of sodium ascorbate for various time periods. In order to examine the effects of sodium ascorbate on cell proliferation, cell cycle, apoptosis and necrosis, we performed 4,6-diamidino-2-phenylindole dihydrochloride assays and flow cytometry analysis. Polymerase chain reaction was used to examine the mRNA levels of p53, p21, p27, cyclin A, cyclin E, CDK2 and CDK4, which are associated with cell cycle S-phase arrest and apoptosis. Flow cytometric analysis showed that sodium ascorbate significantly induced cell cycle arrest and apoptosis in the A375.S2 cell line in a dose-dependent manner. The increased expressions of p53 and p21, and the decreased expressions of cyclin A, cyclin E, CDK2 and CDK4, indicated the cell cycle arrest at G1/S phase after the cells had been treated with sodium ascorbate. Induction of apoptosis involved an increase in the levels of p53, p21 and cellular Ca, and a decrease in mitochondrial membrane potential and activation of caspase 3 before culminating in apoptosis in sodium ascorbate-treated A375.S2 cells.