Apoptosis induction in human lung adenocarcinoma cells by oil-soluble allyl sulfides: triggers, pathways, and modulators

In Vitro Antitumor and Anti-Inflammatory Activities of Allium-Derived Compounds Propyl Propane Thiosulfonate (PTSO) and Propyl Propane Thiosulfinate (PTS)

Increasing rates of cancer incidence and the side-effects of current chemotherapeutic treatments have led to the research on novel anticancer products based on dietary compounds. The use of Allium metabolites and extracts has been proposed to reduce the proliferation of tumor cells by several mechanisms. In this study, we have shown the in vitro anti-proliferative and anti-inflammatory effect of two onion-derived metabolites propyl propane thiosulfinate (PTS) and propyl propane thiosulfonate (PTSO) on several human tumor lines (MCF-7, T-84, A-549, HT-29, Panc-1, Jurkat, PC-3, SW-837, and T1-73). We observed that this effect was related to their ability to induce apoptosis regulated by oxidative stress. In addition, both compounds were also able to reduce the levels of some pro-inflammatory cytokines, such as IL-8, IL-6, and IL-17. Therefore, PTS and PTSO may have a promising role in cancer prevention and/or treatment.

Dietary Phytochemicals as Potential Chemopreventive Agents against Tobacco-Induced Lung Carcinogenesis

Lung cancer is the second most common cancer in the world. Cigarette smoking is strongly connected with lung cancer. Benzo[a]pyrene (BaP) and 4-(N-methyl-N-nitrosamine)-1-(3-pyridyl)-butanone (NNK) are the main carcinogens in cigarette smoking. Evidence has supported the correlation between these two carcinogens and lung cancer. Epidemiology analysis suggests that lung cancer can be effectively prevented through daily diet adjustments. This review aims to summarize the studies published in the past 20 years exploring dietary phytochemicals using Google Scholar, PubMed, and Web of Science databases. Dietary phytochemicals mainly include medicinal plants, beverages, fruits, vegetables, spices, etc. Moreover, the perspectives on the challenges and future directions of dietary phytochemicals for lung cancer chemoprevention will be provided. Taken together, treatment based on the consumption of dietary phytochemicals for lung cancer chemoprevention will produce more positive outcomes in the future and offer the possibility of reducing cancer risk in society.

Diallyl trisulfide alleviates chemotherapy sensitivity of ovarian cancer via the AMPK/SIRT1/PGC1α pathway

Platinum-based chemotherapy promotes drug resistance in ovarian cancer. We investigated the antichemoresistance characteristics of diallyl trisulfide (DATS) in cisplatin-resistant ovarian cancer cells, in vitro and in vivo. Previous preclinical studies have revealed that DATS regulates distinct hallmark cancer-signaling pathways. The cell cycle pathway is the most investigated signaling pathway in DATS. Additionally, post-DATS treatment has been found to promote proapoptotic capacity through the regulation of intrinsic and extrinsic apoptotic pathway components. In the present study, we found that treating cisplatin-sensitive and cisplatin-resistant ovarian cell lines with DATS inhibited their proliferation and reduced their IC_50. It induced cell apoptosis and promoted oxidative phosphorylation through the regulation of the AMPK/SIRT1/PGC1α pathway, OXPHOS, and enhanced chemotherapy sensitivity. DATS treatment alleviated glutamine consumption in cisplatin-resistant cells. Our findings highlight the role of DATS in overcoming drug resistance in ovarian cancer in vitro and in vivo. In addition, we elucidated the role of the AMPK/SIRT1/PGC1α signaling pathway as a potential target for the treatment of drug-resistant ovarian cancer.

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 protects against concanavalin A-induced acute liver injury in mice by inhibiting inflammation, oxidative stress and apoptosis

AIMS

To investigate the protective effects and underlying mechanisms of diallyl trisulfide (DATS) against acute liver injury induced by concanavalin A (Con A).

MATERIALS AND METHODS

DATS (20, 40, 80 mg/kg) were gavaged to ICR mice 1 h before Con A (20 mg/kg) tail vein injection. The survival rate of mice, alterations of serum biochemical markers and liver histopathology were measured to evaluate the protective effects of DATS at 24 h after Con A exposure. The indexes of inflammation, oxidative stress and apoptosis were determined to explore the possible mechanisms.

KEY FINDINGS

DATS pretreatment increased survival rate of mice in a dose-dependent manner, inhibited the increase of liver-to-spleen ratio and serum liver injury markers, and attenuated liver pathological damage induced by Con A. Further study showed that DATS pretreatment inhibited the activation of Kupffer cells/macrophages, release of tumor necrosis factor-α (TNF-α) and Caspase-1-dependent inflammation induced by Con A. Moreover, DATS pretreatment alleviated the oxidative stress induced by Con A, which was evidenced by increased superoxide dismutase (SOD) and catalase (CAT) activities and decreased malondialdehyde (MDA) content in DATS and Con A co-treated mice compared with Con A alone group. Finally, DATS pretreatment reduced eosinophilic body formation, TUNEL positive staining and increased Bcl-2/Bax ratio in liver of Con A-injected mice, indicating attenuated apoptosis.

SIGNIFICANCE

Collectively, the results suggest that DATS displays potent protective effects against Con A-induced acute liver injury in mice possibly through inhibition of inflammation, oxidative stress and apoptosis.

Types of garlic and their anticancer and antioxidant activity: a review of the epidemiologic and experimental evidence

Garlic, an Allium vegetable, contains rich flavonoids organosulfur compounds (OSCs) that have potent anticancer properties. The aim of the review is to provide an overview of the different types of garlic, their active compounds, and the potential anticancer benefits with a focus on antioxidant activity. Animal and cell line studies have provided convincing evidence that garlic and its organosulfur compounds inhibit carcinogenesis through a number of events including induction of apoptosis, inhibiting cellular proliferation, scavenging radical oxygen species (ROS), increasing the activities of enzymes such as glutathione S-transferase, and reducing tumor size. Epidemiological studies showed compelling evidence that garlic consumption is associated with decreased risk of colorectal cancer, but inconsistent evidence for stomach, breast, and prostate cancers. Studies also suggest that the presence and potency of garlic OSCs varies with respect to the preparation and form of garlic. Further epidemiological studies with information on garlic form consumed or preparation methods and molecular studies regarding its antioxidant mechanisms, such as increasing enzymatic and nonenzymatic antioxidants levels, are warranted.

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.

Association of p38MAPK-p53-Fas aggregation in S-allyl cysteine mediated regulation of hepatocarcinoma

Bioactive components of dietary phytochemicals have been reported to possess antitumor activities. Evidences suggested key role of stress responsive p38MAPK in the induction of nutraceuticals mediated apoptosis in hepatocellular carcinoma (HCC). Current study demonstrated detailed molecular bagatelle associated with p38 MAPK mediated effective suppression of cell growth both in HepG2 and chemically induced liver carcinoma after S-allyl cysteine (SAC) treatment. SAC promoted p38MAPK activity responsible for p53 phosphorylation, its stabilization followed by nuclear translocation leading to induction in expression and oligomerization of Fas protein. Distinctive p38MAPK-p53 axis dependent Fas-FasL-FADD mediated caspase activities along with perturbed cell cycling became normalized with continuation of SAC treatment for another month to diethylnitrosamine induced liver carcinoma. Co-treatment with SB203580, the p38MAPK inhibitor, prevented pro-apoptotic effect of SAC by altering p53 phosphorylation and death inducing signaling complex conformation in HepG2 and induced HCC. Collectively study suggested significant contribution of p38MAPK-p53-DISC-Caspase pathway in the regulation of anti-neoplastic activity of SAC against HCC.

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.

Transcriptomic insights into the allelopathic effects of the garlic allelochemical diallyl disulfide on tomato roots

Garlic is an allelopathic crop that can alleviate the obstacles to continuous cropping of vegetable crops. Diallyl disulfide (DADS), one of the most important allelochemicals in garlic, promotes tomato root growth. Therefore, the global transcriptome profiles of DADS-treated tomato roots over time were investigated to reveal the potential growth-promoting mechanisms. We detected 1828, 1296 and 1190 differentially expressed genes (DEGs) in the 4, 24 and 48 h samples, respectively. Most DEGs involved in assimilatory sulfate reduction and glutathione metabolism were up-regulated after short-term (4 h) DADS treatment. In addition, increased activity of defensive enzymes and up-regulation of six peroxidase genes were observed, suggesting that DADS could induce tomato resistance. In plant-pathogen interactions, DEGs related to calcium signaling were primarily inhibited, while those encoding pathogenesis-related proteins were primarily up-regulated. Although plant hormone synthesis and signal transduction were both significantly affected by DADS, the expression trends of the genes in these two pathways were conflicting. This research provides comprehensive information concerning the changes in the tomato root transcriptome affected by DADS and may help direct further studies on DADS-responsive genes to enhance the current understanding of the mechanisms by which DADS alleviates the obstacles to continuous cropping.

Antimetastatic Therapies of the Polysulfide Diallyl Trisulfide against Triple-Negative Breast Cancer (TNBC) via Suppressing MMP2/9 by Blocking NF-κB and ERK/MAPK Signaling Pathways

BACKGROUND

Migration and invasion are two crucial steps of tumor metastasis. Blockage of these steps may be an effective strategy to reduce the risk. The objective of the present study was to investigate the effects of diallyl trisulfide (DATS), a natural organosulfuric compound with most sulfur atoms found in garlic, on migration and invasion in triple negative breast cancer (TNBC) cells. Molecular mechanisms underlying the anticancer effects of DATS were further investigated.

METHODS AND RESULTS

MDA-MB-231 cells and HS 578t breast cancer cells were treated with different concentrations of DATS. DATS obviously suppressed the migration and invasion of two cell lines and changed the morphological. Moreover, DATS inhibited the mRNA/protein/ enzymes activities of MMP2/9 via attenuating the NF-κB pathway. DATS also inhibited ERK/MAPK rather than p38 and JNK.

CONCLUSION

DATS inhibits MMP2/9 activity and the metastasis of TNBC cells, and emerges as a potential anti-cancer agent. The inhibitory effects are associated with down-regulation of the transcriptional activities of NF-κB and ERK/MAPK signaling pathways.

Diallyl disulfide inhibits growth and metastatic potential of human triple-negative breast cancer cells through inactivation of the β-catenin signaling pathway

SCOPE

Although diallyl disulfide (DADS), an important garlic (Allium sativum) derivative, has exhibited potential anticancer activity, the molecular mechanism of this activity remains unknown. In this study, we evaluated the antitumor activity of DADS in triple-negative breast cancer (TNBC) cell lines based in vitro and in vivo models.

METHODS AND RESULTS

We found that treatment with DADS resulted in decreased viability, increased apoptosis, and suppression of metastatic potential in TNBC cells. Furthermore, DADS induced dysregulation of B-cell lymphoma (Bcl)-2 family members, downregulation of matrix metalloproteinase (MMP)-9 and reversal of the epithelial-mesenchymal transition (EMT). Interestingly, DADS significantly inhibited activation of the β-catenin signaling pathway, which regulated Bcl-2 family members, MMP-9 and EMT in TNBC cells. Consistent with these in vitro findings, we also verified the anticancer potential of DADS in MDA-MB-231 xenograft mice. Treatment with DADS significantly reduced tumor volume and weight and increased apoptosis in these mice, while the expression of active β-catenin was decreased, and the downstream molecules were dysregulated.

CONCLUSION

Our results show that the antitumor effect of DADS on TNBC cells is mediated by the β-catenin pathway, suggesting that DADS could be used as a potential therapeutic agent for treating or preventing breast cancer.

Diallyl trisulfide inhibits migration, invasion and angiogenesis of human colon cancer HT-29 cells and umbilical vein endothelial cells, and suppresses murine xenograft tumour growth

Angiogenesis inhibitors are beneficial for the prevention and treatment of angiogenesis-dependent diseases including cancer. We examined the cytotoxic, anti-metastatic, anti-cancer and anti-angiogenic effects of diallyl trisulfide (DATS). In HT29 cells, DATS inhibited migration and invasion through the inhibition of focal adhesion kinase (FAK), extracellular signal-regulated kinase, c-Jun N-terminal kinase and p38 which was associated with inhibition of matrix metalloproteinases-2, -7 and -9 and VEGF. In human umbilical vein endothelial cells (HUVEC), DATS inhibited the migration and angiogenesis through FAK, Src and Ras. DATS also inhibited the secretion of VEGF. The capillary-like tube structure formation and migration by HUVEC was inhibited by DATS. The chicken egg chorioallantoic membrane (CAM) assay indicated that DATS treatment inhibited ex-vivo angiogenesis. We investigated the anti-tumour effects of DATS against human colon cancer xenografts in BALB/c^nu/nu mice and its anti-angiogenic activity in vivo. In this in-vivo study, DATS also inhibited the tumour growth, tumour weight and angiogenesis (decreased the levels of haemoglobin) in HT29 cells. In conclusion, the present results suggest that the inhibition of angiogenesis may be an important mechanism in colon cancer chemotherapy by DATS.

Reversion of P-glycoprotein-mediated multidrug resistance by diallyl trisulfide in a human osteosarcoma cell line

Diallyl trisulfide (DATS), the main sulfuric compound in garlic, has been shown to have antitumor effects. The present study aimed to ascertain whether DATS reverses the drug resistance of human osteosarcoma cells in vitro and to investigate its potential mechanisms. Human osteosarcoma U2-OS cells were treated with different concentrations of DATS. Cell proliferation was measured by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, while P-glycoprotein (P-gp) expression and the proportion of apoptotic cells were measured by flow cytometry. Morphological changes were observed under an optical microscope. Νuclear factor-κB (NF-κB) and inhibitor of NF-κB (IκB) activities were measured by PCR and western blot analysis. Results showed that the proliferation of U2-OS cells treated with different concentrations of DATS was significantly decreased in a concentration- and time-dependent manner. DATS increased the toxic effect of adriamycin on U2-OS cells. Moreover, P-gp expression was decreased and the apoptosis rate was increased in a concentration-dependent manner following treatment of DATS. Additionally, NF-κB activity was inhibited by DATS while expression of IκB was increased. Our data clearly suggest that DATS has significant anticancer effects on human osteosarcoma cells. The potential mechanisms include reducing the multidrug resistance and inducing apoptosis. NF-κB suppression may be involved in DATS-induced inhibition of cell proliferation.

Diallyl trisulfide-induced apoptosis of bladder cancer cells is caspase-dependent and regulated by PI3K/Akt and JNK pathways

Diallyl trisulfide (DATS) is one of the major organosulfur components of garlic (Allium sativum L.), which inhibits the proliferation of various cancer cells, but the exact mechanisms of this action in human bladder cancer cells still remain largely unresolved. In this study, we investigated how DATS induces apoptosis in T24 human bladder cancer cells in vitro. Treatment of T24 cells with DATS resulted in potent anti-proliferative activity. Additionally, some typical apoptotic characteristics, such as chromatin condensation and an increase in the population of sub-G1 hypodiploid cells, were observed. With respect to the mechanism underlying the induction of apoptosis, DATS reduced the expression of anti-apoptotic Bcl-2 and Bcl-xL, and inhibitor of apoptosis protein family proteins, but the expression of pro-apoptotic Bax and death receptor-related proteins was increased compared with the controls. DATS also activated caspase-8 and -9, the respective initiator caspases of the extrinsic and the intrinsic apoptotic pathways. The increase in mitochondrial membrane depolarization was correlated with activation of effector caspase-3 and cleavage of poly-ADP-ribose polymerase, a vital substrate of activated caspase-3. Blockage of caspase activation through treatment with a pan-caspase inhibitor consistently inhibited apoptosis and abrogated growth inhibition in DATS-treated T24 cells. The study further investigated the roles of the phosphatidylinositol 3-kinase (PI3K)/Akt and mitogen-activated protein kinases (MAPKs) pathways with respect to the apoptotic effect of DATS, and showed that DATS deactivates Akt. Additionally, DATS activates extracellular signal-regulated kinase (ERK) and c-Jun N-terminal protein kinase (JNK), but not p38 MAPK, in T24 cells. Unlike ERK, JNK inhibitors reversed DATS-induced apoptosis and growth inhibition; however, inhibition of PI3K/Akt notably enhanced the apoptotic action of DATS. The results suggest that the pro-apoptotic activity of DATS is probably regulated by a caspase-dependent cascade through the activation of both intrinsic and extrinsic signaling pathways, which is mediated through the blocking of PI3K/Akt and the activation of the JNK pathway.

Immunity: plants as effective mediators

In the domain of nutrition, exploring the diet-health linkages is major area of research. The outcomes of such interventions led to widespread acceptance of functional and nutraceutical foods; however, augmenting immunity is a major concern of dietary regimens. Indeed, the immune system is incredible arrangement of specific organs and cells that enabled humans to carry out defense against undesired responses. Its proper functionality is essential to maintain the body homeostasis. Array of plants and their components hold immunomodulating properties. Their possible inclusion in diets could explore new therapeutic avenues to enhanced immunity against diseases. The review intended to highlight the importance of garlic (Allium sativum), green tea (Camellia sinensis), ginger (Zingiber officinale), purple coneflower (Echinacea), black cumin (Nigella sativa), licorice (Glycyrrhiza glabra), Astragalus and St. John's wort (Hypericum perforatum) as natural immune boosters. These plants are bestowed with functional ingredients that may provide protection against various menaces. Modes of their actions include boosting and functioning of immune system, activation and suppression of immune specialized cells, interfering in several pathways that eventually led to improvement in immune responses and defense system. In addition, some of these plants carry free radical scavenging and anti-inflammatory activities that are helpful against cancer insurgence. Nevertheless, interaction between drugs and herbs/botanicals should be well investigated before recommended for their safe use, and such information must be disseminated to the allied stakeholders.

Isoalantolactone, a sesquiterpene lactone, induces apoptosis in SGC-7901 cells via mitochondrial and phosphatidylinositol 3-kinase/Akt signaling pathways

Isoalantolactone, a sesquiterpene lactone, possesses anti-fungal as well as cytotoxic properties. In this study, the effects of Isoalantolactone on cell viability, cell cycle, and apoptosis were investigated in human gastric adenocarcinoma SGC-7901 cells. The results demonstrated that Isoalantolactone induced morphological changes and decreased cell viability. Subsequently, we found that Isoalantolactone induced G2/M and S phase arrest, which was associated with a decrease in the expression level of cyclin B1. Apoptosis triggered by Isoalantolactone was visualized using propidium iodide (PI) and Annexin V-FITC/PI staining. Isoalantolactone-induced apoptosis of SGC-7901 cells was associated with the dissipation of mitochondrial membrane potential (ΔΨ m) that was due to the down-regulation of Bcl-2 and up-regulation of Bax that led to the cleavage of caspase-3. Additionally, it was found that Isoalantolactone was involved in the inhibition of phosphorylation of PI3K/Akt. Isoalantolactone-induced cytotoxicity and apoptosis of SGC-7901 cells involve mitochondria-caspase and PI3K/Akt dependent pathways, which gives the rationale for in vivo studies on the utilization of Isoalantolactone as a potential cancer therapeutic compound.

Multi-targeted DATS prevents tumor progression and promotes apoptosis in ectopic glioblastoma xenografts in SCID mice via HDAC inhibition

Glioblastoma, the most lethal brain tumor, remains incurable despite aggressive chemotherapy and surgical interventions. New chemotherapeutics for glioblastoma have been explored in preclinical models and some agents have reached the clinical setting. However, success rates are not significant. Previous investigations involving diallyl trisulfide (DATS), a garlic compound, indicated significant anti-cancer effects in glioblastoma in vitro. DATS has also been shown to inhibit histone deacetylase activity and impede glioblastoma tumor progression. We hypothesized that DATS would block ectopic U87MG tumor by multiple pro-apoptotic pathways via inhibiting histone deacetylase (HDAC). To prove this, we developed ectopic U87MG tumors in SCID mice and treated them daily with intraperitoneal injections of DATS for 7 days. Results indicated that DATS (10 μg/kg-10 mg/kg) dose-dependently reduced tumor mass and number of mitotic cells within tumors. Histological and biochemical assays demonstrated that DATS reduced mitosis in tumors, decreased HDAC activity, increased acetylation of H3 and H4, inhibited cell cycle progression, decreased pro-tumor markers (e.g., survivin, Bcl-2, c-Myc, mTOR, EGFR, VEGF), promoted apoptotic factors (e.g., bax, mcalpian, active caspase-3), and induced DNA fragmentation. Our data also demonstrated an increase in p21Waf1 expression, which correlated with increased p53 expression and MDM2 degradation following DATS treatment. Finally, histological assessment and enzyme assays showed that even the highest dose of DATS did not negatively impact hepatic function. Collectively, our results clearly demonstrated that DATS could be an effective therapeutic agent in preventing tumor progression and inducing apoptosis in human glioblastoma in vivo, without impairing hepatic function.

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.

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.

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.

Neuroprotective effects of diallyl sulfide against transient focal cerebral ischemia via anti-apoptosis in rats

OBJECTIVES

Diallyl sulfide (DAS) is the main organosulfur component of garlic and it is known for multiple pharmacological actions. Recent studies have demonstrated that DAS has neuroprotective effects against ischemia/reperfusion injury. While some of the possible mechanisms behind this protection have been explored, its ability to inhibit apoptosis has yet to be fully explained. In the present study, the effects of DAS on focal cerebral ischemia in rats were tested and its anti-apoptotic action was explored.

METHODS

To examine the protective effects of DAS, focal cerebral ischemia/reperfusion was induced in rats by transient middle cerebral artery occlusion for 2 hours followed by reperfusion for 24 hours. The animals received DAS in quantities of 100, 150, and 200 mg/kg (intraperitoneal; every day), for 7 days before transient middle cerebral artery occlusion. The neurological score and infarct volume were measured at 24 hours after the end of reperfusion. Apoptotic cells were counted by terminal dUTP nick end labeling staining and apoptotic mechanisms were studied by fluorescence immunohistochemistry staining and western blot analysis.

RESULTS

For animals with induced ischemia/reperfusion, those pretreated with 200 mg/kg DAS showed an infarct volume (22.36 ± 0.67%) significantly lower than that of the non-treated ischemia/reperfusion group (38.23 ± 0.72%), and the percentage of terminal dUTP nick-end labeling-positive cells (23.46 ± 1.02%) of the DAS-pretreated group was also significantly decreased compared to non-treated (36.41 ± 1.58%). Fluorescence immunohistochemistry staining and western blot analysis indicated that DAS reduced caspase-3 expression and increased Bcl-2 expression.

CONCLUSION

These results suggest that the mechanism by which DAS protects the brain from ischemia/reperfusion injury is related to its anti-apoptotic effects in part.

The Effect of Diallyl Polysulfanes on Cellular Signaling Cascades

Diallyl polysulfanes, such as diallyl trisulfide and diallyl tetrasulfide, are regarded as a group of potential chemopreventive compounds as they have been proven to be effective inhibitors of cancer cells. These agents have been implicated in signal transductions, including the generation of Reactive Oxygen Species (ROS), Endoplasmic Reticulum (ER) stress, mitogen-activated protein kinase (MAPK) signaling, regulation of cell cycle progression, and induction of apoptosis. Nonetheless, certain aspects of the diallyl polysulfane triggered inhibitory effects on cancer cells are still not clear. Understanding the targeted signaling pathways may help to develop new strategies to treat cancer and other diseases. This review is therefore aimed at addressing the targeting of specific intracellular signal transduction cascades by these diallyl polysulfanes in order to shed some light on possible mechanisms of action of these compounds.

In vitro efficacy of diallyl sulfides against the periodontopathogen Aggregatibacter actinomycetemcomitans

The in vitro antibacterial effects of diallyl sulfide (DAS) against the Gram-negative periodontopathogen Aggregatibacter actinomycetemcomitans, the key etiologic agent of the severe form of localized aggressive periodontitis and other nonoral infections, were studied. A. actinomycetemcomitans was treated with garlic extract, allicin, or DAS, and the anti-A. actinomycetemcomitans effects of the treatment were evaluated. Garlic extract, allicin, and DAS significantly inhibited the growth of A. actinomycetemcomitans (greater than 3 log; P < 0.01) compared to control cells. Heat inactivation of the garlic extracts significantly reduced the protein concentration; however, the antimicrobial effect was retained. Purified proteins from garlic extract did not exhibit antimicrobial activity. Allicin lost all its antimicrobial effect when it was subjected to heat treatment, whereas DAS demonstrated an antimicrobial effect similar to that of the garlic extract, suggesting that the antimicrobial activity of garlic extract is mainly due to DAS. An A. actinomycetemcomitans biofilm-killing assay performed with DAS showed a significant reduction in biofilm cell numbers, as evidenced by both confocal microscopy and culture. Scanning electron microscopy (SEM) analysis of DAS-treated A. actinomycetemcomitans biofilms showed alterations of colony architecture indicating severe stress. Flow cytometry analysis of OBA9 cells did not demonstrate apoptosis or cell cycle arrest at therapeutic concentrations of DAS (0.01 and 0.1 μg/ml). DAS-treated A. actinomycetemcomitans cells demonstrated complete inhibition of glutathione (GSH) S-transferase (GST) activity. However, OBA9 cells, when exposed to DAS at similar concentrations, showed no significant differences in GST activity, suggesting that DAS-induced GST inhibition might be involved in A. actinomycetemcomitans cell death. These findings demonstrate that DAS exhibits significant antibacterial activity against A. actinomycetemcomitans and that this property might be utilized for exploring its therapeutic potential in treatment of A. actinomycetemcomitans-associated oral and nonoral infections.

Effect of diallyl trisulfide derivatives on the induction of apoptosis in human prostate cancer PC-3 cells

The effects of five derivatives of diallyl trisulfide (DATS) were investigated on apoptosis in prostate cancer PC-3 cells, including dibutenyl trisulfide (DBTS), bis(2-methylallyl) trisulfide (2-M-DATS), dipentenyl trisulfide (DPTS), bis(3-methylbut-2-enyl) trisulfide (3-M-DBTS), and dihexenyl trisulfide (DHTS). Our present study demonstrated that DATS derivatives can suppress proliferation of PC-3 cells in a dose- and time-dependent manner, and that a change in the DATS structure could have an impact on its biological activity in the following order: 2-M-DATS > DBTS ≈ DPTS ≈ DATS > 3-M-DBTS ≈ DHTS. Typical apoptotic nuclei were shown by Hoechst 33342 staining with 80 μM concentrations of DATS derivatives for 24 h. And flow cytometric analysis and DNA fragmentation assay also demonstrated that DATS derivatives induced apoptosis in PC-3 cells. Meanwhile, experimental results showed that DBTS, 2-M-DATS, and DPTS cause G2-M phase cell cycle arrest. Furthermore, a series of apoptosis-associated features were observed, which include a notable decrease in the expression of procaspases-3, up-regulation of pro-apoptotic proteins Bax expression, and down-regulation of anti-apoptotic proteins Bcl-2 expression in PC-3 cells. All of the evidences above indicate that DATS derivatives suppressed proliferation of PC-3 cells which was associated with the induction of apoptosis regulated by Bax/Bcl-2.

The effects of garlic-derived sulfur compounds on cell proliferation, caspase 3 activity, thiol levels and anaerobic sulfur metabolism in human hepatoblastoma HepG2 cells

The aim of the present studies was to determine whether the mechanism of biological action of garlic-derived sulfur compounds in human hepatoma (HepG2) cells can be dependent on the presence of labile sulfane sulfur in their molecules. We investigated the effect of allyl sulfides from garlic: monosulfide, disulfide and trisulfide on cell proliferation and viability, caspase 3 activity and hydrogen peroxide (H(2)O(2)) production in HepG2 cells. In parallel, we also examined the influence of the previously mentioned compounds on the levels of thiols, glutathione, cysteine and cysteinyl-glycine, and on the level of sulfane sulfur and the activity of its metabolic enzymes: rhodanese, 3-mercaptopyruvate sulfurtransferase and cystathionase. Among the compounds under study, diallyl trisulfide (DATS), a sulfane sulfur-containing compound, showed the highest biological activity in HepG2 cells. This compound increased the H(2)O(2) formation, lowered the thiol level and produced the strongest inhibition of cell proliferation and the greatest induction of caspase 3 activity in HepG2 cells. DATS did not affect the activity of sulfurtransferases and lowered sulfane sulfur level in HepG2 cells. It appears that sulfane sulfur containing DATS can be bioreduced in cancer cells to hydroperthiol that leads to H(2)O(2) generation, thereby influencing transmission of signals regulating cell proliferation and apoptosis.

Harmful and beneficial effects of organic monosulfides, disulfides, and polysulfides in animals and humans

Many organic sulfides (mono-, di-, and polysulfides) are present in our environment. Simple derivatives are produced by some plants and animals, while complex sulfides are secondary metabolites of several genera of bacteria and fungi. Sulfides play an important role in the smell and taste of food, and many such compounds are used as food flavorings. Some sulfides are toxic, and there is evidence that such toxicity is caused by the ability of these substances to generate reactive oxygen species. Some sulfides, however, have been shown to protect against toxicants and carcinogens. These beneficial effects are believed to involve, at least in part, the ability of sulfides to inhibit the enzymatic activation of pro-toxicants and to increase tissue activities of enzymes that protect against electrophiles. Some sulfides also have potential as cancer chemotherapeutics. In this review, the toxic and beneficial effects of sulfides in animals are described, and the possible value of sulfides in cancer chemoprotection and cancer chemotherapy is discussed.

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

The aim of this study was to investigate the effect of garlic constituent diallyl trisulfide (DATS) on the cell-death signaling pathway in a human breast cell line (MDA-MB-231). We observed that DATS (10-100 µM) treatment resulted in dose- and time-dependent cytotoxicity. Treatment of MDA-MB-231 cells with a cytotoxicity inducing concentration of DATS (50-80 µM) resulted in an increase in the intracellular level of reactive oxygen species (ROS). Data from assay with MitoSOX(TM) Red reagent suggest that mitochondria are the main source of ROS generation during DATS treatment. DATS-induced oxidative stress was detected through glutaredoxin (GRX), a redox-sensing molecule, and subsequently GRX was dissociated from apoptosis signal-regulating kinase 1 (ASK1). Dissociation of GRX from ASK1 resulted in the activation of ASK1. ASK1 activated a downstream signal transduction JNK (c-Jun N-terminal kinase)-Bim pathway. SP600125, a JNK inhibitor, inhibited DATS-induced Bim phosphorylation and protected cells from DATS-induced cytotoxicity. Our results indicate that the cytotoxicity caused by DATS is mediated by the generation of ROS and subsequent activation of the ASK1-JNK-Bim signal transduction pathway in human breast carcinoma MDA-MB-231 cells.

Carcinoma infection and immune systems of Ehrlich ascites carcinoma-bearing mice treated with structurally similar sulfonium compounds

The effects of intraperitoneal administration of dimethylsulfonioacetate (DMSA), dimethlsulfoniopropionate (DMSP), and methylmethionine (MeMet) solutions (10 mM each) on the body weights and the hematological parameters (red and white blood cells) of Ehrlich ascites carcinoma (EAC)-bearing mice were examined for up to 10 d. Body weights significantly increased in the EAC-bearing mice treated with and without MeMet in contrast to those with DMSA and DMSP. This increase was attributed to the increased amounts of ascitic fluid. EAC-bearing mice with and without MeMet both showed abnormal values of hematological parameters, while those with DMSA and DMSP exhibited almost normal levels on the 10th day.

Role of Ras-related C3 botulinum toxin substrate 2 (Rac2), NADPH oxidase and reactive oxygen species in diallyl disulphide-induced apoptosis of human leukaemia HL-60 cells

1. Diallyl disulphide (DADS) has potential as a chemopreventive and therapeutic agent. Previous studies have reported that Ras-related C3 botulinum toxin substrate 2 (Rac2), a regulatory subunit of the NADPH oxidase complex, is upregulated in DADS-induced apoptosis in human leukaemia HL-60 cells. The aim of the present study was to investigate the role of Rac2, NADPH oxidase and reactive oxygen species (ROS) in DADS-induced apoptosis. 2. Expression of the Rac2 gene along with that of five other genes of NADPH oxidase subunits were in HL-60 cells measured by Sybergreen quantitative real-time polymerase chain reaction. RNA interference was used to test the effect of Rac2. Protein expression was evaluated using western blot analysis and ROS levels were measured by 2',7'-dichlorofluorescein diacetate (DCFH-DA) fluorescence. DNA fragmentation and flow cytometry analysis were used to detect apoptotic cells. 3. Levels of Rac2 gene and protein were significantly upregulated and NADPH oxidase was activated in DADS-induced apoptosis. Pretreatment of HL-60 cells with small interfering (si) RNAs to inhibit Rac2 blocked DADS-induced apoptosis. Diallyl disulphide-induced intracellular ROS production was increased in phorbol myristate acetate-stimulated cells, but decreased in Rac2 siRNA-treated cells. In Rac2 siRNA-treated cells, activator protein-1 and caspase 3 levels decreased, c-myc protein levels were increased and p38 protein levels were unchanged compared with Rac2-competent, DADS-treated cells. 4. These results demonstrate that NADPH oxidase is the main source of DADS-induced ROS. In addition, Rac2 selectively activates the c-Jun N-terminal kinase pathway, but not the p38 pathway, in DADS-induced apoptosis. So, Rac2, NADPH oxidase and ROS have a critical role in DADS-induced apoptosis in human leukaemia HL-60 cells.

Anticancer effects of a tertiary sulfonium compound, dimethylsulfoniopropionate, in green sea algae on Ehrlich ascites carcinoma-bearing mice

The saline and dimethylsulfoniopropionate (DMSP) solutions at 5, 10 and 20 mM were preliminarily injected intraperitoneally every other day into two control and three DMSP groups of mice (n=8) for 2 wk and thereafter Ehrlich ascites-carcinoma (EAC) cells were peritoneally injected to one control and three DMSP groups of mice, leaving one control group without the EAC injection. Then, the body weight and survival time of all mice were examined over a long rearing time up to 300 d. All EAC-bearing mice, especially the carcinoma control and 5 mM DMSP-carcinoma group mice, rapidly increased their body weights early and then died by day 50 and day 90, respectively. In contrast, the administration of 10 and 20 mM DMSP solutions prolonged the lives of EAC-bearing mice at the survival rate of 50 and 63% respectively up to 300 d without any side effects. Furthermore, the administration of 10 mM DMSP solution proved to activate the delayed-type hypersensitivity of EAC bearing-mice, and the DMSP solutions over the concentrations of 5 to 30 mM to slightly reduce the dead cells in EAC cells on the synthetic medium. Accordingly, the preliminary supplementation of 10 and 20 mM DMSP solutions to EAC-bearing mice was proven to maintain their lives at high survival rates without direct damage to EAC cells for a long time, probably due to the activation of the immune system without any side effects.