Protective effect of three diallyl sulphides against glucose-induced erythrocyte and platelet oxidation, and ADP-induced platelet aggregation

Nutrition phytochemicals affecting platelet signaling and responsiveness: implications for thrombosis and hemostasis

Cardiovascular disease, in particular due to arterial thrombosis, is a leading cause of mortality and morbidity, with crucial roles of platelets in thrombus formation. For multiple plant-derived phytochemicals found in common dietary components, claims have been made regarding cardiovascular health and antiplatelet activities. Here we present a systematic overview of the published effects of common phytochemicals, applied in vitro or in nutritional intervention studies, on agonist-induced platelet activation properties and platelet signaling pathways. Comparing the phytochemical effects per structural class, we included general phenols: curcuminoids (e.g., curcumin), lignans (honokiol, silybin), phenolic acids (caffeic and chlorogenic acid), derivatives of these (shikimic acid) and stilbenoids (isorhapontigenin, resveratrol). Furthermore, we evaluated the flavonoid polyphenols, including anthocyanidins (delphinidin, malvidin), flavan-3-ols (catechins), flavanones (hesperidin), flavones (apigenin, nobiletin), flavonols (kaempferol, myricetin, quercetin), isoflavones (daidzein, genistein); and terpenoids including carotenes and limonene; and finally miscellaneous compounds like betalains, indoles, organosulfides (diallyl trisulfide) and phytosterols. We furthermore discuss the implications for selected phytochemicals to interfere in thrombosis and hemostasis, indicating their possible clinical relevance. Lastly, we provide guidance on which compounds are of interest for further platelet-related research.

A comprehensive understanding about the pharmacological effect of diallyl disulfide other than its anti-carcinogenic activities

Diallyl disulfide (DADS), an oil-soluble sulfur compound that is responsible for the biological effects of garlic, displays numerous biological activities, among which its anti-cancer activities are the most famous ones. In recent years, the pharmacological effects of DADS other than its anti-carcinogenic activities have attracted numerous attentions. For example, it has been reported that DADS can prevent the microglia-mediated neuroinflammatory response and depression-like behaviors in mice. In the cardiovascular system, DADS administration was found to ameliorate the isoproterenol- or streptozotocin-induced cardiac dysfunction via the activation of the nuclear factor E2-related factor 2 (Nrf2) and insulin-like growth factor (IGF)-phosphatidylinositol-3-kinase (PI3K)-protein kinase B (Akt) signaling. DADS administration can also produce neuroprotective effects in animal models of Alzheimer's disease and protect the heart, endothelium, liver, lung, and kidney against cellular or tissue damages induced by various toxic factors, such as the oxidized-low density lipoprotein (ox-LDL), carbon tetrachloride (CCl₄), ethanol, acetaminophen, Cis-Diammine Dichloroplatinum (CisPt), and gentamicin. The major mechanisms of action of DADS in disease prevention and/or treatment include inhibition of inflammation, oxidative stress, and cellular apoptosis. Mechanisms, including the activation of Akt, extracellular signal-regulated kinase 1/2 (ERK1/2), protein kinase A (PKA), and cyclic adenosine monophosphate-response element binding protein (CREB) and the inhibition of histone deacetylases (HDACs), can also mediate the cellular protective effects of DADS in different tissues and organs. In this review, we summarize and discuss the pharmacological effects of DADS other than its anti-carcinogenic activities, aiming to reveal more possibilities for DADS in disease prevention and/or treatment.

Synthesis of unsymmetrical disulfides via the cross-dehydrogenation of thiols

Organosulfur compounds with unsymmetrical S–S bonds are usually called unsymmetrical disulfides and are widely used in the biological, medicinal, and chemical fields. Their versatility has guided the development of various new methods for the synthesis of disulfides. In recent years, the synthesis of disulfides by cross-dehydrogenation of thiols has attracted much attention due to its high atomic economy. Herein, this review summarizes progress toward the synthesis of unsymmetrical disulfides under chemical oxidation, electrooxidation, or photocatalysis by cross-dehydrogenation of thiols.

Diallyl Trisulfide Inhibits Platelet Aggregation through the Modification of Sulfhydryl Groups

Diallyl trisulfide (DATS) is a secondary metabolite of allicin, a volatile organosulfur flavoring compound generated by the crushing of garlic. These compounds have various medicinal effects such as antiplatelet activity. In this study, we demonstrated for the first time the cellular mechanism involved in the inhibition of platelet aggregation by DATS and dipropyl trisulfide (DPTS), which is a saturated analogue of DATS. Washed murine platelets were incubated with these sulfides, and platelet aggregation was evaluated by light transmission aggregometry. The amount of reaction products produced by DATS, DPTS, and glutathione (GSH) was measured using liquid chromatography-mass spectrometry. Compared with DPTS, DATS potently inhibited platelet aggregation induced by thrombin, U46619, and collagen. N-Ethylmaleimide (NEM), which is commonly used to modify sulfhydryl groups, also suppressed platelet aggregation. The reactivity of DATS with GSH was higher than that of DPTS. These data suggested that DATS inhibited platelet aggregation through the reaction of sulfhydryl groups.

Effect of Diallyl Trisulfide on Ischemic Tissue Injury and Revascularization in a Diabetic Mouse Model

BACKGROUND AND OBJECTIVE

Allitridin [diallyl trisulfide (DATS)] is an extract from garlic (Allium sativum) that putatively improves endothelial function and is protective against cardiovascular diseases. Endothelial dysfunction after tissue ischemia in diabetic patients is partially due to poor angiogenic response. This study investigated whether DATS may improve angiogenesis in a diabetic mouse model with hind limb ischemia.

METHODS

Streptozotocin was administered by intraperitoneal injection to establish the model of diabetes in male C57BL/6 mice. After 14 days, nondiabetic and diabetic mice (n = 24, each) underwent unilateral hind limb ischemia by femoral artery ligation. The mice were apportioned to 4 groups: nondiabetic treated (or not) with DATS and diabetic treated (or not) with DATS. DATS treatment consisted of a single daily intraperitoneal injection of 500 μg·kg·d for 14 days, beginning on the day of induced ischemia. Ischemia was scored by standard criteria. Blood perfusion was determined using thermal infrared imaging. Tissue capillary density and oxidative stress levels were measured by immunohistochemistry and immunofluorescence, respectively. Serum lipids were measured by enzymatic colorimetric assay. Fasting serum insulin was detected using an insulin enzyme-linked immunosorbent assay kit. Nitric oxide (NO) metabolites and protein carbonyls in tissues were determined by enzyme-linked immunosorbent assay. Targeted protein concentrations were measured by western blotting.

RESULTS

At 14 days after ligation, the ischemic skeletal muscle of the streptozotocin-induced diabetic mice had lower levels of endothelial NO synthase, phosphorylated endothelial NO synthase, and vascular endothelial growth factor compared with nondiabetic group. In addition, the hind limb blood perfusion, capillary density, and NO bioactivity were lower in the diabetic group, whereas oxidative stress and protein carbonyl levels were higher. These changes were ameliorated by DATS treatment.

CONCLUSIONS

DATS treatment of diabetic mice promoted revascularization in ischemic tissue.

Electro-Oxidative S-H/S-H Cross-Coupling with Hydrogen Evolution: Facile Access to Unsymmetrical Disulfides

Sulfur is an essential element because it exists widely in proteins. The disulfide bond is an important moiety in many different types of significant organic molecules. A new approach for oxidant- and catalyst-free S-H/S-H cross-coupling, with hydrogen evolution, to construct unsymmetrical disulfides was developed. Under the conditions of an undivided cell at room temperature, a series of unsymmetrical disulfides were prepared with up to 87 % yield from the direct coupling of an aryl mercaptan and alkyl mercaptan. Gram-scale synthesis also highlights the synthetic utility of this electrochemical strategy.

Aged garlic extract suppresses platelet aggregation by changing the functional property of platelets

Aged garlic extract (AGE), a garlic preparation rich in water-soluble cysteinyl moieties, has been reported to have multiple beneficial effects on cardiovascular disease including inhibition of platelet aggregation. However, the mode of AGE action on platelets has not been clear. In this study, we examined the effect of AGE on the functional property of platelet by administering AGE to rats and evaluating the platelet aggregation in response to collagen in vitro. We found that AGE treatment significantly reduced the ability of platelet to aggregate and this effect of AGE was manifested on the 14 day, but not 7 day of treatment. In addition, AGE treatment produced platelets that responded to collagen by significantly increasing the amount of both the extracellular ATP and the extra- and intracellular TXB₂. AGE treatment also dose-dependently suppressed the phosphorylation of collagen-induced ERK, p38 and JNK. However, AGE administration did not affect the bleeding time. These findings suggest that AGE treatment results in suppression of platelet aggregation by changing the functional property of platelets to respond to collagen.

Diallyl disulfide induces MUC5B expression via ERK2 in human airway epithelial cells

Garlic has been shown to have antimicrobial, hypolipidemic, antithrombotic, antitumor and immunostimulatory properties. The medicinal effects of garlic are derived from the flavonoid and organosulfur components. Diallyl disulfide (DADS), an organosulfur, is the main component responsible for the diverse biological effects of garlic. However, the effects of DADS on mucin gene expression in airway epithelial cells have not been reported to date. Therefore, this study was performed to investigate the effects and brief signaling pathway of DADS associated with MUC5B expression in NCI-H292 epithelial cells using RT-PCR, ELISA, western blot, immunocytochemistry and cell transfection with siRNA. DADS induced MUC5B expression and activated the phosphorylation of ERK1/2 MAPK. In addition, U0126 inhibited DADS-induced MUC5B expression and DADS-activated phosphorylation of ERK1/2 MAPK. Moreover, the immunopositive cells for MUC5B protein did not appear after treatment of DADS with U0126, and the knockdown of ERK2 MAPK by ERK2 MAPK siRNA significantly blocked DADS-induced MUC5B mRNA expression. However, DADS did not activate the phosphorylation of p38 MAPK, and SB203580 did not inhibit DADS-induced MUC5B expression. This is the first study to show that DADS-induced MUC5B expression appears to be regulated by activation of the ERK2 MAPK signaling pathway in human NCI-H292 airway epithelial cells.

An oil-free microemulsion for intravenous delivery of diallyl trisulfide: formulation and evaluation

The aim of the present study was to develop an oil-free o/w microemulsion, Cremophor EL:ethanol-propylene glycol:saline, for diallyl trisulfide (DATS) for intravenous (i.v.) administration to modify the safety and pharmacokinetics of DATS. The ternary diagram was constructed to identify the regions of dilutable microemulsions, and the optimal composition of microemulsion was determined by evaluation of injection safety such as hemolysis, intravenous stimulation and injection anaphylaxis compared to commercial formulation Chentian(®). Promising microemulsion with modified injection safety was developed that could incorporate 100 mg/g of DATS. The droplet size of the microemulsion was about 26 nm in diameter with narrow distribution (polydispersity index: 0.14). Acute toxicity test showed that median lethal dose (LD(50)) of DATS microemulsion was 1.69-fold higher than that of Chentian(®). Pharmacokinetics was assessed by comparing with the commercial injection after intravenous administration to rats at a dose of 30 mg/kg. The developed microemulsion showed significant higher area under the drug concentration-time curve and lower clearance and distribution volume than those of Chentian(®) (p<0.05). This helped DATS to reach higher level in vessel, and circulate in the blood stream for a longer time resulting in better therapeutic effect. In conclusion, microemulsion would be a promising intravenous delivery system for DATS.

Garlic allyl derivatives interact with membrane lipids to modify the membrane fluidity

As a novel approach to the mode of medicinal action of garlic, its constituents were comparatively studied with respect to their interactions with membrane lipids to modify the membrane fluidity. Allyl derivatives rigidified tumor cell and platelet model membranes consisting of unsaturated phospholipids and cholesterol at 20-500 muM with the potency being diallyl trisulfide (DATS) > diallyl disulfide (DADS) by preferentially acting on the hydrocarbon cores of lipid bilayers. They were also effective in rigidifying candida cell model membranes prepared with ergosterol and phospholipids at 100-500 microM with the potency being DADS > DATS > diallyl sulfide (DAS), but not bacteria cell model membranes without ergosterol. Alliin, a precursor of these DASs, was not active on any membranes at 500 microM. Both relative intensity and selectivity in membrane effects correlated with those in antiproliferative, antiplatelet and antimicrobial effects. In cell culture experiments, membrane-active DASs inhibited the growth of tumor cells cultured for 24 and 48 h at 20-500 muM to show the potency being DATS > DADS, together with rigidifying cell membranes by acting on their deeper regions more intensively. However, membrane-inactive allyl derivatives were not growth-inhibitory on tumor cells. The membrane lipid interactions of DASs appear to be one of possible mechanisms underlying different effects of garlic.

Inhibitory effects of cardiotonic pills on platelet function in dogs fed a high-fat diet

Insulin resistance and the consequent metabolic disorders are associated with a state of platelet hyperactivity. Oxidative stress is responsible for the persistent platelet activation. We sought to study the inhibitory effect of cardiotonic pills, an oral herbal component, on platelet function in a dog model with insulin resistance induced by high-fat feeding. We fed 18 dogs with a high-fat diet and six dogs with normal chow as control for 6 months. Then, six dogs were fed with a high-fat diet and received additional aspirin (250 mg/day), and another six dogs received additional cardiotonic pills (1,000 mg/day) for 4 months. Time-course changes in metabolic parameters and platelet function were detected. After high-fat feeding for 6 months, 18 dogs developed a series of metabolic disorders including obesity, dyslipidemia, oxidative stress and insulin resistance. In addition, a platelet hyperactivity state, characterized by increased agonist (arachidonic acid, ADP and collagen) induced platelet aggregation, platelet expression of adhesion molecules (P-selectin and GP IIb/IIIa), and platelet intracellular calcium concentration, was indicated. Cardiotonic pills showed a significant antioxidative activity by presenting an increase in plasma superoxide dismutase and decrease in erythrocyte glutathione, as well as a lipid-lowering effect (decrease in both plasma cholesterol and triglyceride). Either aspirin or cardiotonic pills could significantly reverse the platelet hypersensitivity and hyperfunction. Compared with aspirin, cardiotonic pills showed a more exaggerated inhibitory effect on platelet function (a significantly decreased collagen-stimulated platelet aggregation, and expression of adhesion molecules). In conclusion, cardiotonic pills inhibited platelet hyperfunction in dogs with insulin resistance. This inhibitory effect may mainly be explained by antioxidative activity and metabolic control.

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 microM, however, decreased at higher than 25 microM. The levels of free radicals and membrane lipid peroxidation were increased in a dose-dependent manner, especially at higher than 25 microM. The treatment of N18D3 cells with 25 microM DADS slightly increased the expressions of p85a PI3K, phosphorylated Akt and phosphorylated GSK-3, but the treatment with 100 microM significantly reduced them. To evaluate whether low concentration of DADS, up to 25 microM, had protective effect on oxidative stress-injured N18D3 cells, the viability of N18D3 cells (pretreated with DADS for 2h versus not pretreated) was evaluated 24h after their exposure to 100 microM H(2)O(2) for 30 min. Compared to the cells treated with only 100 microM H(2)O(2), the pretreatment with 25 microM DADS increased the viability, and the expressions of p85a 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.

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 microM, 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 microM DADS, and treatment of PC12 cells with 100 microM 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 microM H2O2 for 30 min. Compared to the cells treated with 100 microM H2O2 only, pretreatment of the cells with 20 microM DADS before exposure to 100 microM H2O2 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.