Concentrations Of Diallyl Disulfide Research Articles

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

Ethnopharmacological relevanceAyurvedic 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 studyTo 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 methodsThis 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. ResultsThe 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. ConclusionThis study implies that DADS and DATS could be considered for sensitizing drug-resistant breast cancers.

Headspace Characterization and Quantification of Aromatic Organosulfur Compounds in Garlic Extracts Using Surface-Enhanced Raman Scattering with a Mirror-in-a-Cap Substrate.

Surface-enhanced Raman scattering (SERS) has been deployed in the analysis of food at solid and aqueous states. However, its capability has not been fully explored in headspace profiling. To develop an innovative SERS method for analyzing headspace volatile compounds in foods. A volatile-capture device was developed by depositing a film of silver nanoparticles in a vial cap to capture the volatiles released from a model flavor compound (garlic). SERS peaks at 1632, 1400, 1291, 1191, 731, and 577 cm-1 were identified in the headspace of the garlic sample, which was representative of an organosulfur compound (diallyl disulfide), and its concentration was determined at 135 ppm, which was comparable to the value determined using GC. Preparation and analysis could be carried out in <10 min for the SERS method. The sensitivity of the SERS method (10 ppm), however, was slightly less than that of the GC method (5 pm). The SERS method was able to quantify the concentration of diallyl disulfide in the headspace of a raw garlic ethanolic extract. Compared to GC, the SERS method had a much shorter analysis time and simpler sample preparation procedure than GC when analyzing large numbers of samples. The innovative "mirror-in-a-cap" substrate was simpler and faster than other reported SERS substrates used for this purpose. Additionally, SERS has much better portability and the potential for real-time monitoring of changes in the garlic headspace concentration during manufacturing and processing.

Effects of Diallyl Disulfide on the Proliferation and Apoptosis of Epithelial Ovarian Cancer Cells by Inducing G2/M Arrest

Objective To explore the effects of diallyl disulfide(DADS)-induced G2/M phase arrest on proliferation and apoptosis of ovarian cancer cells and its possible molecular mechanism.Methods DADS was used to incubate SK-OV-3 and OVCAR-3 cells,respectively,in different concentrations. Cell proliferation was measured by MTT assay and cell apoptosis rate was detected by flow cytometry assay. Xenograft model assay were performed to analyze the antitumor effect in vivo. Cell cycle phase distribution was detected by flow cytometry. Expressions of cell cycle G2/M phase as well as proliferation- and apoptosis-related proteins were measured by Western blotting.Results MTT assay showed that,after treatment of SK-OV-3(F=247.86,P=0.000)and OVCAR-3 cells(F=302.54,P=0.000)with different concentrations of DADS,the cell proliferation inhibition rate was significantly elevated with the increase of DADS concentrations in a concentration-dependent manner. The inhibition rate of SK-OV-3(F=335.12,P=0.000)and OVCAR-3 cells(F=347.43,P=0.000)at 24 h was significantly higher than that at 12 h and 48 h,showing a significant time-dependence manner. Flow cytometry showed that,after SK-OV-3 and OVCAR-3 cells were treated with different concentrations of DADS,the apoptosis rates increased significantly with the increase of DADS concentration in a concentration-dependent manner(P<0.05). The apoptotic rates of SK-OV-3 and OVCAR-3 cells treated with DADS at 24 h was significantly higher than that at 12 h and 48 h in a significant time-dependence manner(P<0.05). Compared with the blank treatment group,intraperitoneal injection of DADS solution significantly inhibited the xenograft volume of ovarian cancer cells in nude mice(F=548.23,P=0.000;F=311.84,P=0.000). After 30 mg/L of DADS was applied to SK-OV-3 and OVCAR-3 cells for 24 h,the percentage of cells in G2 phase of SK-OV-3 and OVCAR-3 cells increased significantly(F=375.11,P=0.000;F=256.48,P=0.000),compared with the blank cells. After 30 mg/L DADS was applied to SK-OV-3 and OVCAR-3 cells for 24 h,the expressions of p-Chk1(ser345)(F=108.89,P=0.013;F=97.58,P=0.018),p-CDC25C(ser216)(F=87.25,P=0.025;F=114.25,P=0.009),p-P53(ser15)(F=112.41,P=0.011;F=255.87,P=0.000),P21WAF1(F=246.38,P=0.001;F=141.36,P=0.005)and p-CDK1(Thr14/Tyr15)protein(F=298.12,P=0.000;F=233.15,P=0.000)were significantly increased,whereas the expressions of CDK1(F=308.24,P=0.000;F=257.55,P=0.000)and CyclinB1 protein(F=223.15,P=0.001;F=241.28,P=0.000)were significantly reduced.The expressions of proliferation and apoptosis-related proteins PCNA(F=77.36,P=0.031;F=157.28,P=0.001),Ki-67(F=205.64,P=0.007;F=315.22,P=0.000)and Survivin(F=122.13,P=0.013;F=188.24,P=0.000)were significantly decreased and Cleaved-caspase3 protein was significantly increased(F=86.46,P=0.023;F=99.11,P=0.009).Conclusion DADS can inhibit the proliferation of ovarian cancer cells and induce their apoptosis,which may be related to the activation of Chk1-CDC25C and P53-P21WAF1 signaling pathways in G2/M checkpoint,decreased kinase activity of CDK1,down-regulated expressions of CDK1 and CyclinB1 proteins,and ultimately cell cycle arrest at G2/M phase.

The garlic allelochemical DADS influences cucumber root growth involved in regulating hormone levels and modulating cell cycling

Most allelochemicals are phytotoxic to the receiver plants and may influence the cell micro- and ultrastructure, cell division, phytohormone levels, and ultimately growth. In order to understand the allelopathic potential of garlic, the effects of its main bioactive allelochemical diallyl disulfide (DADS), experiments were carried out to observe the seed germination, root growth, and developmental responses in cucumber seedlings treated with various concentrations of DADS. The obtained data suggested active influence of DADS on cucumber root growth and development. Significant responses were observed in early root growth and elongation, mitotic cell division and elongation, and root architecture modulation. The effect, however, was dose dependent, and lower concentrations of DADS proved to be promotional whereas higher concentrations of DADS inhibited cucumber root growth and development. Relative root elongation (RRE) revealed that DADS could increase growth of cucumber roots in the early developmental days. Moreover, DADS application significantly influenced mitosis-related gene expression. Observed genes CYCA and CDKB were initially downregulated in the first 24 h but significantly upregulated after 48 h, while gene CDKA was upregulated in the first 24 h. Similarly, DADS application significantly altered primary plant hormones, such as IAA, ABA, GA3, and ZR, in the cucumber roots. Taken together, low concentrations of DADS treatment could promote cucumber root growth and induce main root elongation by upregulating CDKA and CDKB gene expression and regulating hormone balance in root. The current findings offer insight into the allelopathic potential of garlic allelochemical DADS and can be considered vital for establishing plant allelopathic studies.

Restoring the IL-1β/NF-κB-induced impaired chondrogenesis by diallyl disulfide in human adipose-derived mesenchymal stem cells via attenuation of reactive oxygen species and elevation of antioxidant enzymes

Strategies based on mesenchymal stem cell (MSC) therapy for restoring injured articular cartilage are not effective enough in osteoarthritis (OA). Due to the enhanced inflammation and oxidative stress in OA microenvironment, differentiation of MSCs into chondrocytes would be impaired. This study aims to explore the effects of diallyl disulfide (DADS) on IL-1β-mediated inflammation and oxidative stress in human adipose derived mesenchymal stem cells (hADSCs) during chondrogenesis. MTT assay was employed to examine the effects of various concentrations of DADS on the viability of hADSCs at different time scales to obtain non-cytotoxic concentration range of DADS. The effects of DADS on IL-1β-induced intracellular ROS generation and lipid peroxidation were evaluated in hADSCs. Western blotting was used to analyze the protein expression levels of IκBα (np), IκBα (p), NF-κB (np) and NF-κB (p). Furthermore, the gene expression levels of antioxidant enzymes in hADSCs and chondrogenic markers at days 7, 14 and 21 of differentiation were measured using qRT-PCR. The results showed that addition of DADS significantly enhanced the mRNA expression levels of antioxidant enzymes as well as reduced ROS elevation, lipid peroxidation, IκBα activation and NF-κB nuclear translocation in hADSCs treated with IL-1β. In addition, DADS could significantly increase the expression levels of IL-1β-induced impaired chondrogenic marker genes in differentiated hADSCs. Treatment with DADS may provide an effective approach to prevent the pro-inflammatory cytokines and oxidative stress as catabolic causes of chondrocyte cell death and enhance the protective anabolic effects by promoting chondrogenesis associated gene expressions in hADSCs exposed to OA condition.

Subcellular localization of DJ-1 in human HL-60 leukemia cells in response to diallyl disulfide treatment

Diallyl disulfide (DADS) has been demonstrated to exert potent anticancer effects in vitro and in vivo. Previous studies indicate that DADS may induce the differentiation and/or apoptosis of human leukemia cells in vitro. However, the mechanisms underlying these anticancer effects remain elusive. The aim of the present study was to investigate alterations in the subcellular localization of protein deglycase DJ-1 (also known as Parkinsonism associated deglycase-7, PARK-7) in the cytoplasm, nucleus and mitochondria of human leukemia HL-60 cells induced by DADS, in order to provide novel experimental evidence for the molecular mechanisms underlying the anticancer mechanisms of DADS in leukemia cells. HL-60 cells induced by DADS were collected at different time points, and proteins from the cytoplasm, nucleus and mitochondria of the cells were isolated using specific cellular component isolation kits. The protein expression levels of DJ-1 in these subcellular fractions of HL60 cells following exposure to DADS for varying lengths of time, were determined using western blotting, immunocytochemistry and immunofluorescence techniques. Following exposure of HL-60 cells to 1.25 mg/l DADS for 8 h, the protein expression levels of DJ-1 were significantly decreased in the cytoplasm, while nuclear fractions exhibited a significant increase in DJ-1 expression when compared with untreated controls. The protein expression levels of DJ-1 in mitochondria of HL-60 cells were significantly decreased following treatment with 5 and 10 mg/l DADS. These results demonstrate that exposure of HL-60 cells to low concentrations of DADS may promote DJ-1 protein translocation from the cytoplasm to the nucleus, which suggests that DJ-1 may function as a transcription factor or cofactor binding protein in the process of cell differentiation. The expression of DJ-1 in mitochondria may be associated with induction of apoptosis in HL-60 cells treated with moderate doses of DADS.

The Garlic Allelochemical Diallyl Disulfide Affects Tomato Root Growth by Influencing Cell Division, Phytohormone Balance and Expansin Gene Expression.

Diallyl disulfide (DADS) is a volatile organosulfur compound derived from garlic (Allium sativum L.), and it is known as an allelochemical responsible for the strong allelopathic potential of garlic. The anticancer properties of DADS have been studied in experimental animals and various types of cancer cells, but to date, little is known about its mode of action as an allelochemical at the cytological level. The current research presents further studies on the effects of DADS on tomato (Solanum lycopersicum L.) seed germination, root growth, mitotic index, and cell size in root meristem, as well as the phytohormone levels and expression profile of auxin biosynthesis genes (FZYs), auxin transport genes (SlPINs), and expansin genes (EXPs) in tomato root. The results showed a biphasic, dose-dependent effect on tomato seed germination and root growth under different DADS concentrations. Lower concentrations (0.01–0.62 mM) of DADS significantly promoted root growth, whereas higher levels (6.20–20.67 mM) showed inhibitory effects. Cytological observations showed that the cell length of root meristem was increased and that the mitotic activity of meristematic cells in seedling root tips was enhanced at lower concentrations of DADS. In contrast, DADS at higher concentrations inhibited root growth by affecting both the length and division activity of meristematic cells. However, the cell width of the root meristem was not affected. Additionally, DADS increased the IAA and ZR contents of seedling roots in a dose-dependent manner. The influence on IAA content may be mediated by the up-regulation of FZYs and PINs. Further investigation into the underlying mechanism revealed that the expression levels of tomato EXPs were significantly affected by DADS. The expression levels of EXPB2 and beta-expansin precursor were increased after 3 d, and those of EXP1, EXPB3 and EXLB1 were increased after 5 d of DADS treatment (0.41 mM). This result suggests that tomato root growth may be regulated by multiple expansin genes at different developmental stages. Therefore, we conclude that the effects of DADS on the root growth of tomato seedlings are likely caused by changes associated with cell division, phytohormones, and the expression levels of expansin genes.

Upregulation of miR-34a by diallyl disulfide suppresses invasion and induces apoptosis in SGC-7901 cells through inhibition of the PI3K/Akt signaling pathway.

Diallyl disulfide (DADS) exerts anticarcinogenic activity in various types of cancer. However, the mechanism underlying its anticarcinogenic activity remains to be elucidated. The aim of the present study was to explore the mechanism of the anticarcinogenic activity of DADS in gastric cancer (GC). The expression levels of microRNA (miR)-34a in GC and normal tissues were measured using reverse transcription-quantitative polymerase chain reaction (RT-qPCR). The expression of miR-34a was also measured using RT-qPCR in SGC-7901 cells following treatment with DADS. In addition, the effect of DADS on the invasion capability of SGC-7901 cells was observed in the presence of miR-34a or anti-miR-34a using a Matrigel invasion assay. Furthermore, in identical conditions, the apoptosis of SGC-7901 cells was observed using flow cytometry. Finally, the present study investigated the effects of DADS and miR-34a on the phosphoinositide 3-kinase (PI3K)/Akt signaling pathway in vitro. The level of miR-34a in GC tissues was reduced compared with that in adjacent normal tissues (P<0.05). Treatment with DADS upregulated miR-34a expression in SGC-7901 cells (P<0.05). In the Matrigel invasion assay, DADS inhibited the invasive capability of SGC-7901 cells (P<0.05 vs. control), which was improved by overexpression of miR-34a (P<0.01 vs. control) but reduced by downregulation of miR-34a (P<0.05 vs. DADS treatment group). Furthermore, DADS induced apoptosis of SGC-7901 cells (P<0.05 vs. control); and DADS and miR-34a synergistically enhanced apoptosis of SGC-7901 cells (P<0.01 vs. control). In addition, DADS and miR-34a inhibited the expression levels of phosphorylated (p)-PI3K and p-Akt (P<0.05 vs. control). By contrast, downregulation of miR-34a alleviated the decrease in p-PI3K and p-Akt expression induced by DADS (P<0.05 vs. DADS treatment group). Cell viability was reduced with increasing concentrations of DADS, however, DADS did not affect cell viability following inhibition of the PI3K/Akt signaling pathway. In conclusion, DADS suppresses invasion and induces apoptosis of SGC-7901 cells by upregulation of miR-34a, via inhibition of the PI3K-Akt signaling pathway.

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

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

Induction of apoptosis with diallyl disulfide in AGS gastric cancer cell line

PurposeDiallyl disulfide (DADS) is a major organosulfur compound derived from garlic. It has been reported that DADS is able to inhibit the proliferation of several tumor cells. In this study, the effect of DADS was investigated in terms of the proliferation of AGS, gastric adenocarcinoma cell line at various concentrations.MethodsThe viability of cultured cells was determined by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-tetrazolium bromide assay. To detect the induction of apoptosis, Annexin V-FITC/propodium iodide (PI) staining assay was performed. Analysis of reactive oxygen species (ROS) and the distribution of cells in the cell cycle were measured by a flow cytometer. And using the Western blot analysis, the change of Fas, caspase-3, Bax, Bcl-2 activity was measured.ResultsThe percentage of live AGS cells was decreased to 23% of that in the control group after 400 µM DADS treatment for 48 hours. The Annexin V positive/PI negative (apoptosis portion) area increased from low concentration of DADS to high concentration. When comparing among the DADS treatment groups, the amount of ROS production increased in a dose dependent manner. The percentage of sub-diploid DNA content increased from 8.71% at 50 µM to 25.74% at 400 µM DADS treatment group. The expressions of Fas, caspase-3, Bax were increased and that of Bcl-2 was decreased in a dose dependent manner.ConclusionDADS decreases the viability of AGS cell lines and induces apoptosis in a dose-dependent manner. But the relationship of the anti-proliferative effect of DADS and related molecular changes were not clearly proportional to the concentration of DADS.

Diallyl Disulfide Induces Caspase-Dependent Apoptosis via Mitochondria-Mediated Intrinsic Pathway in B16F-10 Melanoma Cells by Up-Regulating P53, Caspase-3 and Down-Regulating Pro-Inflammatory Cytokines and Nuclear Factor- κβ-Mediated Bcl-2 Activation

Diallyl disulfide (DADS) is a major organo-sulfur compound derived from garlic (Allium sativum), which inhibits the proliferation of various types of cancer cells. In this study we investigated the effect of DADS on the induction of apoptosis, as well as its regulatory effect on the activation of transcription factors in B16F-10 melanoma cells. Treatment of B16F-10 cells with nontoxic concentrations of DADS resulted in the presence of apoptotic bodies and induced DNA fragmentation in a dose-dependent manner. Cell-cycle analysis revealed that the occurrence of the sub-G1 peak was significantly elevated in DADS-treated cells. DADS treatment also down-reguated Bcl-2 expression and up-regulated p53, caspase-9, and caspase-3 expression in B16F-10 melanoma cells. The study also reveals that DADS inhibited the activation and nuclear translocation of p65, p50, and c-Rel subunits of nuclear factor (NF)-B and other transcription factors, such as c-fos, activated transcription factor-2, and cyclic adenosine monophosphate response element-binding protein, in B16F-10 melanoma cells The pro-inflammatory cytokine production and gene expression of tumor necrosis factor (TNF)-α, interleukin (IL)-1β, IL-6, and granulocyte-macrophage colony-stimulating factor (GM-CSF) were down-regulated in DADS-treated cells compared with control B16F-10 metastatic melanoma cells. DADS induces caspase-dependent apoptosis through a mitochondria-mediated intrinsic pathway in B16F-10 melanoma cells by activating p53 and caspase-3 gene expression and suppressing pro-inflammatory cytokines and NF-B-mediated Bcl-2 activation.

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

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

Antiproliferative effect of diallyl disulfide (DADS) on prostate cancer cell line LNCaP

Garlic has been used throughout the world to treat coughs, toothache, earache, dandruff, hypertension, hysteria, diarrhoea, dysentery, diptheria, vaginitis and many other conditions. Garlic contains a complex mixture of oil and water-soluble organosulfur compounds. Diallyl disulfide (DADS), an oil-soluble constituent of garlic seems to be effective in reducing tumour cells originating from colon, lung and skin. Hence our present study focuses on the dose-dependent effect of DADS on an androgen-dependent prostate cancer cell line. Various concentrations of DADS ranging from 25 to 100 microM were given to LNCaP cells and the activity of lactate dehydrogenase (LDH) prostatic acid phosphatase (PAcP) and the level of prostate specific antigen were studied. DADS reduced the secretory activity of LNCaP cells with the gradual increase in dosage. DADS was found to act as a good antiproliferative agent, which was confirmed by proliferation assay. DADS also induced apoptosis and nuclear segmentation in the higher doses.

Differential effects of diallyl disulfide on neuronal cells depend on its concentration

Diallyl disulfide (DADS) is one of the organosulfur compounds of garlic. The effects of DADS on neuronal cells have not clearly been established. We investigated its effects on the viability of neuronal cells (N18D3 cells), the levels of free radical and membrane lipid peroxidation, and the cell signals, such as phosphatidylinositol 3-kinase (PI3K)/Akt and glycogen synthase kinase-3 (GSK-3). When N18D3 cells were treated with several concentrations of DADS, the viability was not affected up to 25 μM, however, decreased at higher than 25 μM. The levels of free radicals and membrane lipid peroxidation were increased in a dose-dependent manner, especially at higher than 25 μM. The treatment of N18D3 cells with 25 μM DADS slightly increased the expressions of p85 a PI3K, phosphorylated Akt and phosphorylated GSK-3, but the treatment with 100 μM significantly reduced them. To evaluate whether low concentration of DADS, up to 25 μM, had protective effect on oxidative stress-injured N18D3 cells, the viability of N18D3 cells (pretreated with DADS for 2 h versus not pretreated) was evaluated 24 h after their exposure to 100 μM H 2O 2 for 30 min. Compared to the cells treated with only 100 μM H 2O 2, the pretreatment with 25 μM DADS increased the viability, and the expressions of p85 a PI3K, phosphorylated Akt and phosphorylated GSK-3. These results indicate that low concentration of DADS has protective effects on N18D3 cells, whereas high concentration is rather cytotoxic. Therefore, some specific optimum concentration of DADS may be a new potential therapeutic strategy for oxidative stress-injury in vitro model of neurodegenerative diseases.

Recycling natural rubber vulcanizates through mechanochemical devulcanization

Sulfur-cured gum natural rubber vulcanizates were devulcanized using two different concentrations of diallyl disulfide. The devulcanization process was performed at 110 °C for 10 min in an open two-roll cracker-cummixing mill. Natural rubber vulcanizates having various sulfur/accelerator ratios were used to study the cleavage of monosulfide, disulfide, and polysulfide bonds. The properties of devulcanized natural rubber increased upon increasing the disulfide concentration and the mechanical properties of the revulcanized natural rubber increased upon decreasing the sulfur content in the original rubber vulcanizates. The scorch time and the maximum state of cure both increased when the ground vulcanizates were treated with higher amounts of disulfide. TGA and DMA were conducted to study the effects of the devulcanization on the thermal stability and theTg behavior of the vulcanizates. SEM analysis was conducted to study how the failure mechanism was affected by the devulcanization process. It was possible to recover 70–80% of the original gum rubber properties by using this process. From IR spectroscopic analysis, we observed that the oxidation of the main chains did not occur during high-temperature milling.

Protective effect of diallyl disulfide on oxidative stress-injured neuronally differentiated PC12 cells

The effects of diallyl disulfide (DADS), a garlic-derived compound, on the viability of neuronal cells and cell signals, including phosphatidylinositol 3-kinase (PI3K)/Akt, glycogen synthase kinase-3 (GSK-3), cytochrome c, caspase-3, and poly(ADP-ribose) polymerase (PARP), were investigated in PC12 cells neuronally differentiated by nerve growth factor. To evaluate the toxicity of DADS itself, nPC12 cells were treated with several concentrations of DADS, and 3,(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay and trypan blue stain revealed that the viability was not affected by low concentration of DADS, up to 20 μM, but it was decreased at higher than this concentration. The levels of free radicals and membrane lipid peroxidation were significantly increased in nPC12 cells when treated with more than 50 μM DADS, and treatment of PC12 cells with 100 μM DADS killed the cells by inhibiting PI3K/Akt and by promoting activation of GSK-3 and caspase-3, release of cytochrome c, and cleavage of PARP. To evaluate the protective effects of low concentration of DADS on oxidative stress-injured nPC12 cells, the viability of the cells (pretreated with DADS for 2 h vs. not pretreated) was evaluated 24 h after exposure to 100 μM H 2O 2 for 30 min. Compared to the cells treated with 100 μM H 2O 2 only, pretreatment of the cells with 20 μM DADS before exposure to 100 μM H 2O 2 increased the viability and induced activation of PI3K and Akt, inactivation of GSK-3, and inhibition of cytochrome c release, caspase-3 activation, and PARP cleavage. These results indicate that low concentration of DADS has neuroprotective effects by activating PI3K/Akt and by inhibiting GSK-3 activation, cytochrome c release, caspase-3 activation, and PARP cleavage, whereas high concentration is rather cytotoxic. Therefore, some specific optimum concentration of DADS may be a new potential therapeutic strategy for oxidative stress injured in vitro model of neurodegenerative diseases.