Role of Bim in diallyl trisulfide-induced cytotoxicity in human cancer 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.

The Anticancer Effects of the Garlic Organosulfide Diallyl Trisulfide through the Attenuation of B[a]P-Induced Oxidative Stress, AhR Expression, and DNA Damage in Human Premalignant Breast Epithelial (MCF-10AT1) Cells

Benzo[a]pyrene (B[a]P) is the most characterized polycyclic aromatic hydrocarbon associated with breast cancer. Our lab previously reported that the organosulfur compound (OSC), diallyl trisulfide (DATS), chemoprevention mechanism works through the induction of cell cycle arrest and a reduction in oxidative stress and DNA damage in normal breast epithelial cells. We hypothesize that DATS will inhibit B[a]P-induced cancer initiation in premalignant breast epithelial (MCF-10AT1) cells. In this study, we evaluated the ability of DATS to attenuate B[a]P-induced neoplastic transformation in MCF-10AT1 cells by measuring biological endpoints such as proliferation, clonogenicity, reactive oxygen species (ROS) formation, and 8-hydroxy-2-deoxyguanosine (8-OHdG) DNA damage levels, as well as DNA repair and antioxidant proteins. The results indicate that B[a]P induced proliferation, clonogenic formation, ROS formation, and 8-OHdG levels, as well as increasing AhR, ARNT/HIF-1β, and CYP1A1 protein expression compared with the control in MCF-10AT1 cells. B[a]P/DATS's co-treatment (CoTx) inhibited cell proliferation, clonogenic formation, ROS formation, AhR protein expression, and 8-OHdG levels compared with B[a]P alone and attenuated all the above-mentioned B[a]P-induced changes in protein expression, causing a chemopreventive effect. This study demonstrates, for the first time, that DATS prevents premalignant breast cells from undergoing B[a]P-induced neoplastic transformation, thus providing more evidence for its chemopreventive effects in breast cancer.

Antitumor and chemopreventive role of major phytochemicals against breast cancer development

Breast cancer continues to be one of the most commonly diagnosed cancers around the world. Despite the decrease in mortality, there has been a steady increase in its incidence. There is much evidence that naturally occurring phytochemicals could prove to be safer alternatives aimed at prevention and development of breast cancer. In the present review, we discuss important phytochemicals, namely capsaicin, alpha-santalol and diallyl trisulphide that are shown to have chemopreventive and anti-tumour properties against breast cancer development. We examined current knowledge of their bioavailability, safety and modulation of molecular mechanisms including their ability to induce apoptotic cell death, promote cell cycle arrest, and inhibit cellular proliferation in different breast cancer cell lines and in vivo models. This review emphasises the importance of these naturally occurring phytochemicals and their potential of becoming therapeutic options in the arsenal against breast cancer development provided further scientific and clinical validation.

Insight into drug sensitizing effect of diallyl disulfide and diallyl trisulfide from Allium sativum L. on paclitaxel-resistant triple-negative breast cancer cells

ETHNOPHARMACOLOGICAL RELEVANCE

Ayurvedic practitioners and herbal healers in India and China have extensively used garlic (Allium sativum L.) to treat cancers. Diallyl disulfide (DADS) and diallyl trisulfide (DATS) are major volatile organosulfur phytochemical constituents found in garlic.

AIM OF THE STUDY

To find new insight into the drug sensitizing effect of DADS and DATS on paclitaxel (PTX)-resistant triple-negative breast cancer cells (TNBC/PR).

MATERIALS AND METHODS

This study estimates the non-toxic concentration of DADS and DATS against normal healthy breast epithelial cell line (MCF-12A) by using a trypan blue viability assay. Also, it evaluates the effect of DADS and DATS on the sensitization of established stable TNBC/PR cell clones (MDA-MB 231 PR and MDA-MB 468 PR) by MTT, BrdU incorporation, intracellular ROS, cell cycle, and apoptosis assays.

RESULTS

The results show that DADS and DATS are non-cytotoxicity against MCF-12A cells. Nevertheless, DADS and DATS have shown significantly high cytotoxicity against MDA-MB 231 PR and MDA-MB 468 PR cells. They also inhibited PTX-resistant cell proliferation by blocking the cell cycle. Further, they induced apoptosis by activation of caspase 3 and 9. N-acetyl cysteine pre-treatment inhibited DADS and DATS-induced intracellular ROS release. In silico study shows that DADS and DATS interact with a large extracellular loop (LEL) of CD151 with a binding energy of -4.0 kcal/mol and transmembrane domain (TM) with a binding affinity of 11.7 and 13.6 kcal/mol, respectively. They also inhibited the surface expression of CD151 in TNBC/PR cells.

CONCLUSION

This study implies that DADS and DATS could be considered for sensitizing drug-resistant breast cancers.

In Vitro Toxicity Studies of Bioactive Organosulfur Compounds from Allium spp. with Potential Application in the Agri-Food Industry: A Review

Organosulfur compounds (OSCs) are secondary metabolites produced by different Allium species which present important biological activities such as antimicrobial, antioxidant, anti-inflammatory antidiabetic, anticarcinogenic, antispasmodic, etc. In recent years, their use has been promoted in the agri-food industry as a substitute for synthetic preservatives, increasing potential accumulative exposure to consumers. Before their application in the food industry, it is necessary to pass a safety assessment as specified by the European Food Safety Authority (EFSA). This work reviews the scientific literature on OSCs regarding their in vitro toxicity evaluation following PRISMA guidelines for systematic reviews. Four electronic research databases were searched (Web of Science, Scopus, Science Database and PubMed) and a total of 43 works were selected according to predeterminate inclusion and exclusion criteria. Different data items and the risk of bias for each study were included. Currently, there are very few in vitro studies focused on investigating the potential toxicity of OSCs. Most research studies aimed to evaluate the cytotoxicity of OSCs to elucidate their antiproliferative effects focusing on their therapeutic aspects using cancer cell lines as the main experimental model. The results showed that diallyl disulfide (DADS) is the compound most studied, followed by diallyl trisulfide (DATS), diallyl sulfide (DAS), Allicin and Ajoene. Only 4 studies have been performed specifically to explore the safety of OSCs for agri-food applications, and genotoxicity studies are limited. More toxicity studies of OSCs are necessary to ensure consumers safety and should mainly be focused on the evaluation of genotoxicity and long-term toxicity effects.

Monocarboxylate transporter 1 is a novel target for breast cancer stem like-cell inhibition by diallyl trisulfide

Diallyl trisulfide (DATS) is a promising small molecule phytochemical that exhibits in vitro and in vivo activity in multiple preclinical solid tumor models including breast cancer, but the underlying mechanism is not fully understood. We have shown previously that forkhead box Q1 (FoxQ1) transcription factor is a novel target for breast cancer stem-like cells (bCSC) inhibition by DATS. Analysis of the breast TCGA (The Cancer Genome Atlas) data revealed that FoxQ1 expression was positively associated with that of SLC16A1/monocarboxylate transporter 1 (MCT1). Western blot analysis confirmed increased expression of MCT1 protein in SUM159 (basal-like) and MCF-7 cells (luminal-type) stably transfected to overexpress FoxQ1. Furthermore, FoxQ1 was recruited to the promoter of SLC16A1/MCT1. Treatment of SUM159 and MCF-7 cell lines with DATS resulted in suppression of MCT1 protein level that was accompanied by a decrease in intracellular and secreted levels of lactate. Overexpression or knockdown of MCT1 protein failed to alter DATS-mediated inhibition of colony formation or cell migration when compared to corresponding control cells. On the other hand, overexpression of MCT1 protein conferred partial but statistically significant protection against DATS-mediated inhibition of bCSC fraction (CD49f^high /CD44^high and aldehyde dehydrogenase 1 activity). The size of the mammospheres was relatively smaller in the DATS-treated group compared to control group. Inhibition of bCSC upon DATS treatment was augmented by knockdown of the MCT1 protein. In conclusion, the present study reveals that MCT1 is a novel target for bCSC inhibition by DATS treatment.

Effect of Diallyl Trisulfide on TNF-α-induced CCL2/MCP-1 Release in Genetically Different Triple-negative Breast Cancer Cells

BACKGROUND/AIM

Diallyl trisulfide (DATS) has been shown to prevent and inhibit breast carcinogenesis. CCL2/MCP-1 has been shown to play a significant role in breast cancer. This study explored DATS efficacy on triple-negative breast cancer (TNBC) cells.

MATERIALS AND METHODS

DATS efficacy on TNF-α induced TNBC cells were examined via trypan blue exclusion test, wound-healing assay, human cytokine arrays, ELISA, and RT-PCR.

RESULTS

DATS significantly induced cell death and inhibited cell migration. Expression of CCL2/MCP-1, IL-6, PDGF-BB, NT-3, and GM-CSF in TNF-α-treated cells increased. However, DATS significantly decreased the expression of CCL2/MCP-1 in TNF-α-treated MDA-MB-231 but not in MDA-MB-468 cells. DATS significantly down-regulated mRNA expression of IKBKE and MAPK8 in both cell lines, indicating a possible effect in genes involved in the NF-κB and MAPK signaling.

CONCLUSION

DATS may have a role in TNBC therapy and prevention by targeting CCL2.

Diallyl Trisulfide Inhibits Leptin-induced Oncogenic Signaling in Human Breast Cancer Cells but Fails to Prevent Chemically-induced Luminal-type Cancer in Rats

Previous studies have demonstrated inhibitory effect of garlic component diallyl trisulfide (DATS) on growth of breast cancer cells in vitro and in vivo. This study investigated the effect of DATS on oncogenic signaling regulated by leptin, which plays an important role in breast carcinogenesis. Leptin-induced phosphorylation and nuclear translocation of STAT3 was inhibited significantly in the presence of DATS in MCF-7 (a luminal-type human breast cancer cell line) and MDA-MB-231 (a basal-like human breast cancer cell line). Leptin-stimulated cell proliferation, clonogenic cell survival, and migration and/or invasion ability in MCF-7 and/or MDA-MB-231 cells were also suppressed by DATS treatment. DATS exposure resulted in inhibition of leptin-stimulated expression of protein and/or mRNA levels of Bcl-2, Bcl-xL, Cyclin D1, vascular endothelial growth factor, and matrix metalloproteinase-2. Western blotting revealed a decrease in protein levels of phosphorylated STAT3 in breast cancer xenografts from DATS-treated mice when compared to controls in vivo. However, the incidence of N-methyl-N-nitrosourea-induced luminal-type breast cancer development in rats was not affected by oral administration of 5 mg/kg or 25 mg/kg DATS. The present study reveals that oncogenic signaling induced by leptin is inhibited in the presence of DATS but higher doses of this phytochemical may be required to achieve chemopreventive activity.

Diallyl Trisulfide Protects Motor Neurons from the Neurotoxic Protein TDP-43 via Activating Lysosomal Degradation and the Antioxidant Response

Amyotrophic lateral sclerosis (ALS) is a rapidly progressive motor neuron disease for which only limited effective therapeutics are available. Currently, TAR DNA-binding protein 43 (TDP-43) is recognized as a pathological and biochemical marker for ALS. Increases in the levels of aggregated or mislocalized forms of TDP-43 might result in ALS pathology. Therefore, clearance pathways for intracellular protein aggregates have been suggested as potential therapeutic targets for the treatment of ALS. Here we report that treatment of motor neuron-like NSC34 cells overexpressing TDP-43 with diallyl trisulfide (DATS) induced neuronal autophagy and lysosomal clearance of TDP-43 and C-terminal TDP-43 fragments. We also observed that the antioxidant transcription factor NF-E2-related factor 2 (Nrf2) was accumulated in the nucleus and the expression of the antioxidant enzymes heme oxygenase1 (HO-1) and NAD(P)H:quinone oxidoreductase (NQO1) was increased. Consequently, DATS suppressed the increase in the levels of reactive oxygen species induced by TDP-43 expression. This study extends the findings of prior reports indicating that lower doses of DATS mediate cell survival in part by inducing autophagy and activating the Nrf2/antioxidant response element pathway.

Redox Modulation at Work: Natural Phytoprotective Polysulfanes From Alliums Based on Redox-Active Sulfur

Purpose of review

This article provides a brief overview of natural phytoprotective products of allium with a special focus on the therapeutic potential of diallyl polysulfanes from garlic, their molecular targets and their fate in the living organisms. A comprehensive overview of antimicrobial and anticancer properties of published literature is presented for the reader to understand the effective concentrations of polysulfanes and their sensitivity towards different human pathogenic microbes, fungi, and cancer cell lines.

Recent findings

The article finds polysulfanes potentials as new generation novel antibiotics and chemo preventive agent. The effective dose rates of polysulfanes for antimicrobial properties are in the range of 0.5-40 mg/L and for anticancer 20-100 μM. The molecular targets for these redox modulators are mainly cellular thiols as well as inhibition and/or activation of certain cellular proteins in cancer cell lines.

Summary

Antimicrobial and anticancer activities of polysulfanes published in the literature indicate that with further development, they could be promising candidates for cancer prevention due to their selectivity towards abnormal cells.

Glutaredoxin 1 mediates the protective effect of steady laminar flow on endothelial cells against oxidative stress-induced apoptosis via inhibiting Bim

Endothelial cell apoptosis induced by oxidative stress is an early event in the development of atherosclerosis. Several antioxidant enzymes which can cope with oxidative stress are up-regulated by the anti-atherogenic laminar blood flow often seen in straight or unbranched regions of blood vessels. However, the molecular mechanism responsible for flow-induced beneficial effects is incompletely understood. Here we report the role of glutaredoxin 1 (Grx1), an antioxidant enzyme, in flow-mediated protective effect in endothelial cells. Specifically, we found that Grx1 is markedly up-regulated by the steady laminar flow. Increasing Grx1 reduces the pro-apoptotic protein Bim expression through regulating Akt-FoxO1 signaling and also attenuates H2O2-induced Bim activation via inhibiting JNK phosphorylation, subsequently preventing the apoptosis of endothelial cells. Grx1 knockdown abolishes the inhibitory effect of steady laminar flow on Bim. The inhibitory effect of Grx1 on Bim is dependent on Grx1's thioltransferase activity. These findings indicate that Grx1 induction plays a key role in mediating the protective effect of laminar blood flow and suggest that Grx1 may be a potential therapeutic target for atherosclerosis.

Dietary Bioactive Diallyl Trisulfide in Cancer Prevention and Treatment

Bioactive dietary agents have been shown to regulate multiple cancer hallmark pathways. Epidemiologic studies have linked consumption of Allium vegetables, such as garlic and onions, to decreased incidence of cancer. Diallyl trisulfide (DATS), a bioactive compound derived from Allium vegetables, has been investigated as an anti-cancer and chemopreventive agent. Preclinical studies provide ample evidence that DATS regulates multiple cancer hallmark pathways including cell cycle, apoptosis, angiogenesis, invasion, and metastasis. DATS has been shown to arrest cancer cells at multiple stages of the cell cycle with the G2/M arrest being the most widely reported. Additionally, increased pro-apoptotic capacity as a result of regulating intrinsic and extrinsic apoptotic pathway components has been widely reported following DATS treatment. Invasion, migration, and angiogenesis represent emerging targets of DATS and support its anti-cancer properties. This review summarizes DATS mechanisms of action as an anti-cancer and chemopreventive agent. These studies provide rationale for future investigation into its use as a cancer chemopreventive agent.

Epigenetic Upregulation of Metallothionein 2A by Diallyl Trisulfide Enhances Chemosensitivity of Human Gastric Cancer Cells to Docetaxel Through Attenuating NF-κB Activation

AIMS

Metallothionein 2A (MT2A) and nuclear factor-kappaB (NF-κB) are both involved in carcinogenesis and cancer chemosensitivity. We previously showed decreased expression of MT2A and IκB-α in human gastric cancer (GC) associated with poor prognosis of GC patients. The present study investigated the effect of diallyl trisulfide (DATS), a garlic-derived compound, and docetaxel (DOC) on regulation of MT2A in relation to NF-κB in GC cells.

RESULTS

DATS attenuated NF-κB signaling in GC cells, resulting in G2/M cell cycle arrest and apoptosis, culminating in the inhibition of cell proliferation and tumorigenesis in nude mice. The anti-GC effect of DATS was attributable to its capacity to epigenetically upregulate MT2A, which in turn enhanced transcription of IκB-α to suppress NF-κB activation in GC cells. The combination of DATS with DOC exhibited a synergistic anti-GC activity accompanied by MT2A upregulation and NF-κB inactivation. Histopathologic analysis of GC specimens from patients showed a significant increase in MT2A expression following DOC treatment. GC patients with high MT2A expression in tumor specimens showed significantly improved response to chemotherapy and prolonged survival compared with those with low MT2A expression in tumors.

INNOVATION AND CONCLUSION

We conclude that DATS exerts its anti-GC activity and enhances chemosensitivity of GC to DOC by epigenetic upregulation of MT2A to attenuate NF-κB signaling. Our findings delineate a mechanistic basis of MT2A/NF-κB signaling for DATS- and DOC-mediated anti-GC effects, suggesting that MT2A may be a chemosensitivity indicator in GC patients receiving DOC-based treatment and a promising target for more effective treatment of GC by combination of DATS and DOC. Antioxid. Redox Signal. 24, 839-854.

Diallyl trisulfide induces osteosarcoma cell apoptosis through reactive oxygen species-mediated downregulation of the PI3K/Akt pathway

Diallyl trisulfide (DATS) is a natural organosulfur compound isolated from garlic, and has been reported to possess anticancer activities. However, the cancer growth inhibitory effects and molecular mechanisms in human osteosarcoma cells have not been well studied. The present study demonstrated that DATS significantly reduced cell viability in a dose- and time-dependent manner in MG63 and MNNG/HOS cells. DATS-induced G0/G1 phase arrest was found to correlate with a decrease in cyclin D1 in concomitance with an increase in p21 and p27. DATS induced a marked increase in reactive oxygen species (ROS) levels and collapse of mitochondrial membrane potential (Δψm) in the osteosarcoma cells. DATS induced apoptosis in the MG63 and MNNG/HOS cells via inhibition of the PI3K/Akt signaling pathway and through the mitochondrial apoptotic pathway. The efficiency of DATS basically approached the efficacy of LY294002, a specific PI3K inhibitor. However, N-acetylcysteine (NAC), a general ROS scavenger, completely blocked the DATS-induced ROS increase, inhibition of the PI3K/Akt pathway and cell apoptosis. Overall, DATS has the potential to be developed as a new anticancer drug. The mechanisms of action involve the ROS-mediated downregulation of the PI3K/Akt pathway.

Activation of the apoptosis signal-regulating kinase 1/c-Jun N-terminal kinase pathway is involved in the casticin-induced apoptosis of colon cancer cells

Casticin is one of the main components of the fruits of Vitex rotundifolia L. Studies have shown that casticin inhibits the growth of various cancer cells, including colon cancer. In the present study, the anti-carcinogenic effects of casticin on human colon cancer and the underlying mechanisms were investigated. The results revealed that casticin significantly induced apoptosis of HT-29, HCT-116, SW480 and Caco-2 cells, induced the accumulation of reactive oxygen species (ROS) and increased the protein levels of apoptosis signal-regulating kinase 1 (ASK1), c-Jun N-terminal kinase (JNK) and B-cell lymphoma 2-interacting mediator of cell death (Bim) in HT-29 cells. Pretreatment with N-acetylcysteine, an antioxidant chemical compound, inhibited the activation of ASK1, JNK and Bim, as well as the apoptosis induced by casticin. Small interfering RNA targeting ASK1 significantly attenuated the induction of JNK and Bim activation and apoptotic cell death by casticin treatment. SP600125, a specific JNK inhibitor, attenuated Bim activation and apoptosis, but did not alter ASK1 phosphorylation levels. In addition, casticin treatment resulted in apoptosis by the same mechanism in HCT-116, SW480 and Caco-2 cells. These results suggest that casticin significantly induced apoptosis by the activation of the ASK1-JNK-Bim signaling cascade and the accumulation of ROS in colon cancer cells.

Effects of garlic oil on pancreatic cancer cells

BACKGROUND

To investigate the preventive and therapeutic potential of garlic oil on human pancreatic carcinoma cells.

METHODS

The 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-tetrazolium bromide (MTT) assay was performed to study the effects of garlic oil on three human pancreatic cancer cell lines, AsPC-1, Mia PaCa-2 and PANC-1. Cell cycle progression and apoptosis were detected by flow cytometry (FCM), staining with PI and annexin V-fluorescein isothiocyanate (FITC)/propidium iodide (PI), respectively. Morphologic changes of pancreatic cancer cells were observed under transmission electron microscopy (TEM) after treatment with garlic oil at low inhibitory concentrations (2.5 μM and 10 μM) for 24 hours.

RESULTS

Proliferation of the AsPC-1, PANC-1, and Mia PaCa-2 cells was obviously inhibited in the first 24 hours with the MTT assay. The inhibition effect was more significant after 48 hours. When cells were exposed to garlic oil at higher concentrations, an early change of the apoptotic tendency was detected by FCM and TEM.

CONCLUSION

Garlic oil could inhibit the proliferation of AsPC-1, PANC-1, and Mia PaCa-2 cells in this study. Moreover, due to programmed cell death, cell cycle arrest, or both, pro-apoptosis effects on AsPC-1 cells were induced by garlic oil in a dose and time dependent manner in vitro.

BIM upregulation and ROS-dependent necroptosis mediate the antitumor effects of the HDACi Givinostat and Sorafenib in Hodgkin lymphoma cell line xenografts

Relapsed/refractory Hodgkin's lymphoma (HL) is an unmet medical need requiring new therapeutic options. Interactions between the histone deacetylase inhibitor Givinostat and the RAF/MEK/ERK inhibitor Sorafenib were examined in HDLM-2 and L-540 HL cell lines. Exposure to Givinostat/Sorafenib induced a synergistic inhibition of cell growth (range, 70-80%) and a marked increase in cell death (up to 96%) due to increased H3 and H4 acetylation and strong mitochondrial injury. Gene expression profiling indicated that the synergistic effects of Givinostat/Sorafenib treatment are associated with the modulation of cell cycle and cell death pathways. Exposure to Givinostat/Sorafenib resulted in sustained production of reactive oxygen species (ROS) and activation of necroptotic cell death. The necroptosis inhibitor Necrostatin-1 prevented Givinostat/Sorafenib-induced ROS production, mitochondrial injury, activation of BH3-only protein BIM and cell death. Knockdown experiments identified BIM as a key signaling molecule that mediates Givinostat/Sorafenib-induced oxidative death of HL cells. Furthermore, in vivo xenograft studies demonstrated a 50% reduction in tumor burden (P<0.0001), a 5- to 15-fold increase in BIM expression (P < 0.0001) and a fourfold increase in tumor necrosis in Givinostat/Sorafenib-treated animals compared with mice that received single agents. These results provide a rationale for exploring Givinostat/Sorafenib combination in relapsed/refractory HL.

Diallyl trisulfide inhibits estrogen receptor-α activity in human breast cancer cells

Organosulfur compounds from garlic effectively inhibit growth of transplanted as well as spontaneous cancers in preclinical animal models without any adverse side effects. However, the mechanisms underlying anticancer effect of this class of compounds are not fully understood. This study reports, for the first time, that garlic organosulfide diallyl trisulfide (DATS) inhibits estrogen receptor-α (ER-α) activity in human breast cancer cells. Exposure of MCF-7 and T47D cells to DATS resulted in downregulation of ER-α protein, which peaked between 12- and 24-h post-treatment. DATS was relatively more effective in suppressing ER-α protein expression compared with its mono and disulfide analogs. The 17β-estradiol (E2)-induced expression of pS2 and cyclin D1, ER-α target gene products, was also decreased in the presence of DATS. Downregulation of ER-α protein expression resulting from DATS treatment was accompanied by a decrease in nuclear levels of ER-α protein, ER-α mRNA suppression, and inhibition of ERE2e1b-luciferase reporter activity. DATS-mediated inhibition of cell viability and apoptosis induction were not affected in the presence of E2. In agreement with these results, ectopic expression of ER-α in MDA-MB-231 cell line failed to confer any protection against cell proliferation inhibition or apoptosis induction resulting from DATS exposure. DATS treatment caused a decrease in protein levels of peptidyl-prolyl cis-trans isomerase (Pin1), and overexpression of Pin1 partially attenuated ER-α downregulation by DATS. DATS-induced apoptosis was modestly but significantly augmented by overexpression of Pin1. In conclusion, this study identifies ER-α as a novel target of DATS in mammary cancer cells.

A role for diallyl trisulfide in mitochondrial antioxidative stress contributes to its protective effects against vascular endothelial impairment

Persistent hyperglycemia increases a systemic oxidative stress, causing the onset of vascular endothelial dysfunction and atherosclerosis. Diallyl trisulfide (DAT), a natural organosulfur compound in garlic, has been reported to have actions of dilating blood vessels and antibacteria, etc. In this study, models of obese diabetic rat in vivo and high glucose concentration (HG)-induced endothelial cell injury in vitro were used to investigate the protective effects of DAT on vascular endothelial injury and its underlying mechanisms. In the in vivo model, the obese diabetic rats were injected venously with DAT (5.0 mg kg(-1)d(-1)) and Vitamin E (1.0 mg kg(-1)d(-1)) respectively, once daily for 7 consecutive days. In the in vitro model, HG-injured HUVEC were treated with or without DAT (25 µmol L(-1), 50 µmol L(-1), 100 µmol L(-1)) or Vitamin E (25 µmol L(-1)) respectively for 24h. The extents of vascular endothelial injury and protective effects of DAT were evaluated. The results both in vivo and in vitro displayed that DAT-treatment significantly attenuated the endothelial cell impairments. Besides, DAT-treatment markedly decreased the levels of malondialdehyde (MDA) and reactive oxygen species, whereas elevated the activities of superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) in mitochondrium. Moreover, DAT-treatment considerably improved mitochondrial respiration function. Taken together, our results suggest that DAT protects vascular endothelium from HG or hyperglycemia induced-injury by reducing mitochondrial oxidative stress. The findings provide a novel insight for DAT to potentially treat the oxidative stress diseases, i.e., atherosclerosis, diabetes, and neurodegenerative diseases.

BIMEL is a key effector molecule in oxidative stress-mediated apoptosis in acute myeloid leukemia cells when combined with arsenic trioxide and buthionine sulfoximine

BACKGROUND

Arsenic trioxide (ATO) is reported to be an effective therapeutic agent in acute promyelocytic leukemia (APL) through inducing apoptotic cell death. Buthionine sulfoximine (BSO), an oxidative stress pathway modulator, is suggested as a potential combination therapy for ATO-insensitive leukemia. However, the precise mechanism of BSO-mediated augmentation of ATO-induced apoptosis is not fully understood. In this study we compared the difference in cell death of HL60 leukemia cells treated with ATO/BSO and ATO alone, and investigated the detailed molecular mechanism of BSO-mediated augmentation of ATO-induced cell death.

METHODS

HL60 APL cells were used for the study. The activation and expression of a series of signal molecules were analyzed with immunoprecipitation and immunoblotting. Apoptotic cell death was detected with caspases and poly (ADP-ribose) polymerase activation. Generation of intracellular reactive oxygen species (ROS) was determined using a redox-sensitive dye. Mitochondrial outer membrane permeabilization was observed with a confocal microscopy using NIR dye and cytochrome c release was determined with immunoblotting. Small interfering (si) RNA was used for inhibition of gene expression.

RESULTS

HL60 cells became more susceptible to ATO in the presence of BSO. ATO/BSO-induced mitochondrial injury was accompanied by reduced mitochondrial outer membrane permeabilization, cytochrome c release and caspase activation. ATO/BSO-induced mitochondrial injury was inhibited by antioxidants. Addition of BSO induced phosphorylation of the pro-apoptotic BCL2 protein, BIMEL, and anti-apoptotic BCL2 protein, MCL1, in treated cells. Phosphorylated BIMEL was dissociated from MCL1 and interacted with BAX, followed by conformational change of BAX. Furthermore, the knockdown of BIMEL with small interfering RNA inhibited the augmentation of ATO-induced apoptosis by BSO.

CONCLUSIONS

The enhancing effect of BSO on ATO-induced cell death was characterized at the molecular level for clinical use. Addition of BSO induced mitochondrial injury-mediated apoptosis via the phosphorylation of BIMEL and MCL1, resulting in their dissociation and increased the interaction between BIMEL and BAX.

FoxO3a modulates hypoxia stress induced oxidative stress and apoptosis in cardiac microvascular endothelial cells

Cardiac microvascular endothelial cells (CMECs) dysfunction induced by hypoxia is an important pathophysiological event in myocardium ischemic injury, whereas, the underlying mechanism is not fully clarified. FoxO transcription factors regulate target genes involved in apoptosis and cellular reactive oxygen species (ROS) production. Therefore, the present study was designed to elucidate the potential role of FoxOs on the hypoxia-induced ROS formation and apoptosis in CMECs. Exposure to low oxygen tension stimulated ROS accumulation and increased apoptosis in CMECs within 6–24 h. Hypoxia also significantly increased the expressions of HIF-1α and FoxO3a. However, hypoxia decreased the phosphorylation of Akt and FoxO3a, correlated with increased nuclear accumulation. Conversely, the expression of FoxO1 was not significantly altered by hypoxia. After inhibition of HIF-1α by siRNA, we observed that hypoxia-induced ROS accumulation and apoptosis of CMECs were decreased. Meanwhile, knockdown of HIF-1α also inhibited hypoxia induced FoxO3a expression in CMECs, but did not affect FoxO1 expression. Furthermore, hypoxia-induced ROS formation and apoptosis in CMECs were correlated with the disturbance of Bcl-2 family proteins, which were abolished by FoxO3a silencing with siRNA. In conclusion, our data provide evidence that FoxO3a leads to ROS accumulation in CMECs, and in parallel, induces the disturbance of Bcl-2 family proteins which results in apoptosis.

Diallyl trisulfide sensitizes human melanoma cells to TRAIL-induced cell death by promoting endoplasmic reticulum-mediated apoptosis

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) is promising for cancer treatment because of its selective cytotoxicity toward tumor cells. However, some cancer cell types including malignant melanoma cells are resistant to TRAIL cytotoxicity. Here, we show that diallyl trisulfide (DATS), a garlic organosulfur compound, sensitizes melanoma cells to TRAIL-induced apoptosis while sparing normal cells. DATS also potentiates apoptosis induced by agonistic antibodies against death receptors (DR) 4 and DR5. The amplification of DR-mediated apoptosis was associated with increased mitochondrial membrane potential collapse and caspase-3/7 activation. However, these events were not sufficient for full sensitization. TRAIL also induced endoplasmic reticulum (ER) stress, as indicated by the activation of X-box-binding protein 1 and caspase-12 and DATS poten-tiated both events. Moreover, inhibition of caspase-12, but not caspase-4, abolished the amplification of apoptosis, indicating that ER stress plays a crucial role. On the other hand, DATS and/or TRAIL induced minimal apoptosis and caspase-12 activation in melanocytes despite their substantial expression of DR4 and DR5 on the cell surface. Our data suggest that DATS amplifies death ligand-induced melanoma cell death by disrupting their adaptation to ER-mediated death pathway. The present findings raise the possibility that DATS may be combined with death ligands to treat TRAIL-resistance melanoma cells without impairing its tumor selectivity.

Hyperthermia-enhanced TRAIL- and mapatumumab-induced apoptotic death is mediated through mitochondria in human colon cancer cells

Colorectal cancer is the third leading cause of cancer-related mortality in the world; death usually results from uncontrolled metastatic disease. Previously, we developed a novel strategy of TNF-related apoptosis-inducing ligand (Apo2L/TRAIL) in combination with hyperthermia to treat hepatic colorectal metastases. However, previous studies suggest a potential hepatocyte cytotoxicity with TRAIL. Unlike TRAIL, anti-human TRAIL receptor antibody induces apoptosis without hepatocyte toxicity. In this study, we evaluated the anti-tumor efficacy of humanized anti-death receptor 4 (DR4) antibody mapatumumab (Mapa) by comparing it with TRAIL in combination with hyperthermia. TRAIL, which binds to both DR4 and death receptor 5 (DR5), was approximately tenfold more effective than Mapa in inducing apoptosis. However, hyperthermia enhances apoptosis induced by either agent. We observed that the synergistic effect was mediated through elevation of reactive oxygen species, c-Jun N-terminal kinase activation, Bax oligomerization, and translocalization to the mitochondria, loss of mitochondrial membrane potential, release of cytochrome c to cytosol, activation of caspases, and increase in poly(ADP-ribose) polymerase cleavage. We believe that the successful outcome of this study will support the application of Mapa in combination with hyperthermia to colorectal hepatic metastases.

Effect of garlic-derived organosulfur compounds on mitochondrial function and integrity in isolated mouse liver mitochondria

The objectives of this work were to evaluate the direct effects of diallysulfide (DAS) and diallyldisulfide (DADS), two major organosulfur compounds of garlic oil, on mitochondrial function and integrity, by using isolated mouse liver mitochondria in a cell-free system. DADS produced concentration-dependent mitochondrial swelling over the range 125-1000μM, while DAS was ineffective. Swelling experiments performed with de-energized or energized mitochondria showed similar maximal swelling amplitudes. Cyclosporin A (1μM), or ethylene glycol-bis(2-aminoethylether)-N,N,N',N'-tetraacetic acid (EGTA, 1mM) were ineffective in inhibiting DADS-induced mitochondrial swelling. DADS produced a minor (12%) decrease in mitochondrial membrane protein thiols, but did not induce clustering of mitochondrial membrane proteins. Incubation of mitochondria with DADS (but not DAS) produced an increase in the oxidation rate of 2',7' dichlorofluorescein diacetate (DCFH-DA), together with depletion of reduced glutathione (GSH) and increased lipid peroxidation. DADS (but not DAS) produced a concentration-dependent dissipation of the mitochondrial membrane potential, but did not induce cytochrome c release. DADS-dependent effects, including mitochondrial swelling, DCFH-DA oxidation, lipid peroxidation and loss of mitochondrial membrane potential, were inhibited by antioxidants and iron chelators. These results suggest that DADS causes direct impairment of mitochondrial function as the result of oxidation of the membrane lipid phase initiated by the GSH- and iron-dependent generation of oxidants.

ROS-independent JNK activation and multisite phosphorylation of Bcl-2 link diallyl tetrasulfide-induced mitotic arrest to apoptosis

Garlic-derived organosulfur compounds including diallyl polysulfides are well known for various health-beneficial properties and recent reports even point to a potential role of diallyl polysulfides as chemopreventive and therapeutic agents in cancer treatment due to their selective antiproliferative effects. In this respect, diallyl tri- and tetrasulfide are reported as strong inducers of an early mitotic arrest and subsequent apoptosis, but the underlying molecular mechanisms and the link between these two events are not yet fully elucidated. Our data revealed that diallyl tetrasulfide acts independently of reactive oxygen species and tubulin represents one of its major cellular targets. Tubulin depolymerization prevents the formation of normal spindle microtubules, thereby leading to G2/M arrest. Here, we provide evidence that c-jun N-terminal kinase, which is activated early in response to diallyl tetrasulfide treatment, mediates multisite phosphorylation and subsequent proteolysis of the anti-apoptotic protein B-cell lymphoma 2. As the latter event occurs concomitantly with the onset of apoptosis and the chemical c-jun N-terminal kinase inhibitor SP600125 not only prevented B-cell lymphoma 2 phosphorylation and proteolysis but also apoptosis following diallyl tetrasulfide treatment, we suggest that these c-jun N-terminal kinase-mediated modulations of B-cell lymphoma 2 represent the missing link connecting early microtubule inactivation to the induction of apoptosis.

Hydrogen sulfide in biochemistry and medicine

SIGNIFICANCE

An abundance of experimental evidence suggests that hydrogen sulfide (H(2)S) plays a prominent role in physiology and pathophysiology. Many targets exist for H(2)S therapy. The molecular targets of H(2)S include proteins, enzymes, transcription factors, and membrane ion channels.

RECENT ADVANCES

Novel H(2)S precursors are being synthesized and discovered that are capable of releasing H(2)S in a slow and sustained manner. This presents a novel and advantageous approach to H(2)S therapy for treatment of chronic conditions associated with a decline in endogenous H(2)S, such as diabetes and cardiovascular disease.

CRITICAL ISSUES

While H(2)S is cytoprotective at physiological concentrations, it is not universally cytoprotective, as it appears to have pro-apoptotic actions in cancer cells and is well known to be toxic at supraphysiological concentrations. Many of the pleiotropic effects of H(2)S on health are associated with the inhibition of inflammation and upregulation of prosurvival pathways. The powerful anti-inflammatory, cytoprotective, immunomodulating, and trophic effects of H(2)S on the vast majority of normal cells seem to be mediated mainly by its actions as an extremely versatile direct and indirect antioxidant and free radical scavenger. While the overall effects of H(2)S on transformed (i.e., malignant) cells can be characterized as pro-oxidant and pro-apoptotic, they contrast sharply with the cytoprotective effects on most normal cells.

FUTURE DIRECTIONS

H(2)S has become a molecule of great interest, and several slow-releasing H(2)S prodrugs are currently under development. We believe that additional agents regulating H(2)S bioavailability will be developed during the next 10 years.

Apoptosis induction of U937 human leukemia cells by diallyl trisulfide induces through generation of reactive oxygen species

BACKGROUND

Diallyl trisulfide (DATS) is one of the major constituents in garlic oil and has demonstrated various pharmacological activities, including antimicrobial, antihyperlipidemic, antithrombotic, and anticancer effects. However, the mechanisms of antiproliferative activity in leukemia cells are not fully understood. In this study, the apoptotic effects of DATS were investigated in human leukemia cells.

RESULTS

Results of this study indicated that treatment with DATS resulted in significantly inhibited leukemia cell growth in a concentration- and time-dependent manner by induction of apoptosis. In U937 cells, DATS-induced apoptosis was correlated with down-regulation of Bcl-2, XIAP, and cIAP-1 protein levels, cleavage of Bid proteins, activation of caspases, and collapse of mitochondrial membrane potential. The data further demonstrated that DATS increased intracellular reactive oxygen species (ROS) generation, which was attenuated by pretreatment with antioxidant N-acetyl-l-cysteine (NAC), a scavenger of ROS. In addition, administration of NAC resulted in significant inhibition of DATS-induced apoptosis by inhibiting activation of caspases.

CONCLUSIONS

The present study reveals that the cytotoxicity caused by DATS is mediated by generation of ROS and subsequent activation of the ROS-dependent caspase pathway in U937 leukemia cells.

Molecular mechanisms and targets of cancer chemoprevention by garlic-derived bioactive compound diallyl trisulfide

Health benefits of garlic and other Allium vegetables (e.g., onions), such as lipid lowering and anticancer effects, are credited to metabolic byproducts, including diallyl trisulfide (DATS). Evidence for anticancer effects of garlic derives from both population-based case-control studies, and clinical and laboratory investigations using purified garlic constituents such as DATS. Studies have shown that DATS can offer protection against chemically-induced neoplasia as well as oncogene-driven spontaneous cancer development in experimental rodents. Mechanisms underlying cancer chemopreventive effects of DATS are not completely understood, but known pharmacological responses to this natural product include alteration in carcinogen-metabolizing enzymes, cell cycle arrest, induction of apoptotic cell death, suppression of oncogenic signal transduction pathways, and inhibition of neoangiogenesis. This article reviews mechanisms and targets of cancer chemoprevention by DATS.

Alteration in superoxide dismutase 1 causes oxidative stress and p38 MAPK activation following RVFV infection

Rift Valley fever (RVF) is a zoonotic disease caused by Rift Valley fever virus (RVFV). RVFV is a category A pathogen that belongs to the genus Phlebovirus, family Bunyaviridae. Understanding early host events to an infectious exposure to RVFV will be of significant use in the development of effective therapeutics that not only control pathogen multiplication, but also contribute to cell survival. In this study, we have carried out infections of human cells with a vaccine strain (MP12) and virulent strain (ZH501) of RVFV and determined host responses to viral infection. We demonstrate that the cellular antioxidant enzyme superoxide dismutase 1 (SOD1) displays altered abundances at early time points following exposure to the virus. We show that the enzyme is down regulated in cases of both a virulent (ZH501) and a vaccine strain (MP12) exposure. Our data demonstrates that the down regulation of SOD1 is likely to be due to post transcriptional processes and may be related to up regulation of TNFα following infection. We also provide evidence for extensive oxidative stress in the MP12 infected cells. Concomitantly, there is an increase in the activation of the p38 MAPK stress response, which our earlier published study demonstrated to be an essential cell survival strategy. Our data suggests that the viral anti-apoptotic protein NSm may play a role in the regulation of the cellular p38 MAPK response. Alterations in the host protein SOD1 following RVFV infection appears to be an early event that occurs in multiple cell types. Activation of the cellular stress response p38 MAPK pathway can be observed in all cell types tested. Our data implies that maintaining oxidative homeostasis in the infected cells may play an important role in improving survival of infected cells.