Neurotrophic activity of organosulfur compounds having a thioallyl group on cultured rat hippocampal neurons

Antioxidant and Anti-Inflammatory Effects of Garlic in Ischemic Stroke: Proposal of a New Mechanism of Protection through Regulation of Neuroplasticity

Stroke represents one of the main causes of death and disability in the world; despite this, pharmacological therapies against stroke remain insufficient. Ischemic stroke is the leading etiology of stroke. Different molecular mechanisms, such as excitotoxicity, oxidative stress, and inflammation, participate in cell death and tissue damage. At a preclinical level, different garlic compounds have been evaluated against these mechanisms. Additionally, there is evidence supporting the participation of garlic compounds in other mechanisms that contribute to brain tissue recovery, such as neuroplasticity. After ischemia, neuroplasticity is activated to recover cognitive and motor function. Some garlic-derived compounds and preparations have shown the ability to promote neuroplasticity under physiological conditions and, more importantly, in cerebral damage models. This work describes damage/repair mechanisms and the importance of garlic as a source of antioxidant and anti-inflammatory agents against damage. Moreover, we examine the less-explored neurotrophic properties of garlic, culminating in proposals and observations based on our review of the available information. The aim of the present study is to propose that garlic compounds and preparations could contribute to the treatment of ischemic stroke through their neurotrophic effects.

Elephant Black Garlic's Beneficial Properties for Hippocampal Neuronal Network, Chemical Characterization and Biological Evaluation

Garlic has been used for decades as an important food and additionally for its beneficial properties in terms of nutrition and ancestral therapeutics. In this work, we compare the properties of fresh (WG) and aged (BG) extract obtained from elephant garlic, harvested on Chiloe Island, Chile. BG was prepared from WG with a 20-day aging process under controlled temperature and humidity conditions. We observed that in BG, compounds such as diallyl disulfide decrease, and compounds of interest such as 5-hydroxymethylfurfural (69%), diallyl sulfide (17%), 3H-1,2-Dithiole (22%) and 4-Methyl-1,2,3-trithiolane (16%) were shown to be increased. Using 2,2-diphenyl-1-picrylhydrazyl (DPPH, BG: 51 ± 5.7%, WG: 12 ± 2.6%) and 2,20-azino-bis-(3-ethylbenzothiazoline-6 sulfonate) diammonium salt (ABTS, BG: 69.4 ± 2.3%, WG: 21 ± 3.9%) assays, we observed that BG possesses significantly higher antioxidant activity than WG and increased cell viability in hippocampal slices (41 ± 9%). The effects of WG and BG were shown to improve the neuronal function through an increased in intracellular calcium transients (189 ± 4%). In parallel, BG induced an increase in synaptic vesicle protein 2 (SV-2; 75 ± 12%) and brain-derived neurotrophic factor (BDNF; 32 ± 12%) levels. Thus, our study provides the initial scientific bases to foster the use of BG from Chiloe Island as a functional food containing a mixture of bioactive compounds that may contribute to brain health and well-being.

Differential Effects of the Processed and Unprocessed Garlic (Allium sativum L.) Ethanol Extracts on Neuritogenesis and Synaptogenesis in Rat Primary Hippocampal Neurons

Garlic (Allium sativum L.) is an aromatic herb known for its culinary and medicinal uses for centuries. Both unprocessed (white) and processed (black) garlic are known to protect against the pathobiology of neurological disorders such as Alzheimer's disease (AD) and Parkinson's disease (PD), which has been attributed to their anti-inflammatory and antioxidant properties. The information on the effects of processed and unprocessed garlic on neuronal process outgrowth, maturation, and synaptic development is limited. This study aimed at investigating and comparing the effects of the ethanol extracts of unprocessed (white garlic extract, WGE) and processed (black garlic extract, BGE) garlic on the maturation of primary hippocampal neurons. Neurite outgrowth was stimulated in a dose-dependent manner by both WGE and BGE and the most effective doses were 15 μg/mL and 60 μg/mL, respectively, without showing cytotoxicity. At this optimal concentration, both extracts promoted axonal and dendritic growth and maturation. Furthermore, both extracts substantially increased the formation of functional synapses. However, the effect of WGE was more robust at every developmental stage of neurons. In addition, the gas chromatography and mass spectrometry (GC-MS) analysis revealed a chemical profile of various bioactives in both BGE and WGE. Linalool, a compound that was found in both extracts, has shown neurite outgrowth-promoting activity in neuronal cultures, suggesting that the neurotrophic activity of garlic extracts is attributed, at least in part, to this compound. By using network pharmacology, linalool's role in neuronal development can also be observed through its modulatory effect on the signaling molecules of neurotrophic signaling pathways such as glycogen synthase kinase 3 (GSK3β), extracellular signal-regulated protein kinase (Erk1/2), which was further verified by immunocytochemistry. Overall, these findings provide information on the molecular mechanism of processed and unprocessed garlic for neuronal growth, survival, and memory function which may have the potential for the prevention of several neurological disorders.

The Pharmacological Activity of Garlic (Allium sativum) in Parkinson's Disease: From Molecular Mechanisms to the Therapeutic Potential

Parkinson's disease (PD), one of the most common neurological diseases worldwide, is mainly characterized neuropathologically by the dopaminergic neurodegeneration in the substantia nigra pars compacta of the brainstem. Genetic and environmental factors contribute to PD pathophysiology through modulation of pleiotropic cellular mechanisms. The currently available treatment options focus only on replenishing dopamine and do not alter disease progression. Interestingly, garlic (Allium sativum), globally famed for its flavor and taste-enhancing properties, has shown protective activity in different PD models. Numerous chemical constituents of garlic, mainly the organosulfur compounds, have been shown to exhibit anti-Parkinsonian effects by targeting oxidative stress, mitochondrial impairment, and neuroinflammation-related signaling. However, despite its therapeutic potential against PD, the major bioactive components of garlic display some stability issues and some adverse effects. In the present review, we explore the therapeutic potential of garlic and its major constituents in PD, the molecular mechanisms responsible for its pharmaceutical activity, and the associated limitations that need to be overcome for its future potential use in clinical practice.

S-Allyl cysteine in garlic (Allium sativum): Formation, biofunction, and resistance to food processing for value-added product development

S-allyl cysteine (SAC), which is the most abundant bioactive compound in black garlic (BG; Allium sativum), has been shown to have antioxidant, anti-apoptotic, anti-inflammatory, anti-obesity, cardioprotective, neuroprotective, and hepatoprotective activities. Sulfur compounds are the most distinctive bioactive elements in garlic. Previous studies have provided evidence that the concentration of SAC in fresh garlic is in the range of 19.0-1736.3 μg/g. Meanwhile, for processed garlic, such as frozen and thawed garlic, pickled garlic, fermented garlic extract, and BG, the SAC content increased to up to 8021.2 μg/g. BG is an SAC-containing product, with heat treatment being used in nearly all methods of BG production. Therefore, strategies to increase the SAC level in garlic are of great interest; however, further knowledge is required about the effect of processing factors and mechanistic changes. This review explains the formation of SAC in garlic, introduces its biological effects, and summarizes the recent advances in processing methods that can affect SAC levels in garlic, including heat treatment, enzymatic treatment, freezing, fermentation, ultrasonic treatment, and high hydrostatic pressure. Thus, the aim of this review was to summarize the outcomes of treatment aimed at maintaining or increasing SAC levels in BG. Therefore, publications from scientific databases in this field of study were examined. The effects of processing methods on SAC compounds were evaluated on the basis of the SAC content. This review provides information on the processing approaches that can assist food manufacturers in the development of value-added garlic products.

Protective effects of functional foods against Parkinson's disease: A narrative review on pharmacology, phytochemistry, and molecular mechanisms

In Persian Medicine (PM), PD (brain-based tremor) is a known CNS disorder with several therapeutic and preventive options. In their medical textbooks and pharmacopeias, Persian great scientists such as Rhazes (854-925 AD), Avicenna (980-1037 AD), and Jorjani (1042-1136 AD), have discussed pharmacological and nutritional strategies for the prevention, slowing progression, and treatment of PD. In the present study, we surveyed plant- and animal-based foods recommended by PM for the prevention and treatment of CNS-related tremors. In vivo and in-vitro pharmacological evidence supporting the beneficial effects of PM-recommended foods in prevention and alleviating PD, major active phytochemicals along with the relevant mechanisms of action were studied. Several PM plants possess potent antioxidant, antiinflammatory, and PD preventing properties. Garlic and allicin, cabbage and isothiocyanates, chickpea seed and its O-methylated isoflavones biochanin A and formononetin, cinnamon, and cinnamaldehyde, saffron and its crocin, crocetin, and safranal, black cumin and its thymoquinone, black pepper and piperine, pistachio and genistein and daidzein, and resveratrol are among the most effective dietary itemsagainst PD. They act through attenuating neurotoxin-induced memory loss and behavioral impairment, oxidative stress, and dopaminergic cell death. PM-recommended foods can help alleviate PD progression and also discovering and developing new neuroprotective anti-PD pharmaceuticals.

In silicoinvestigation of Alliin as potential activator for AMPA receptor

Natural products from plants, such as flavonoids, arouse immense interest in medicine because of the therapeutic and many other bioactive properties. The molecular docking is a very useful method to screen the molecules based on their free binding energies and give important structural suggestions about how molecules might activate or inhibit the target receptor by comparing reference molecules. Alliin and Allicin differ from many other flavonoids because of containing no benzene rings and having nitrogen and sulfur atoms in their structure. In this study Alliin and Allicin affinity on AMPA, NMDA and GABA-A receptors were evaluated in the central nervous system by using the molecular docking method. Both Alliin and Allicin indicated no inhibitory effects. However Alliin showed significant selectivity to human AMPA receptor (3RN8) as an excitatory. The binding energy of glutamate to 3RN8 was -6.61 kcal mol^-1, while the binding energy of Allin was -8.08 kcal mol^-1. Furthermore Alliin's affinity to the other AMPA and NMDA receptors is quite satisfactory compared to the reference molecule glutamate. In conclusion based on the molecular docking study, Alliin can be useful for synaptic plasticity studies whereas might be enhance seizure activity because of the increased permeability to cations. It also can be beneficial to improve learning and memory and can be used as a supportive product to the hypofunction of NMDA associated problems.

Sulfur-containing Secondary Metabolites as Neuroprotective Agents

Sulfur-containing secondary metabolites are a relatively small group of substances of plant origin. The present review is focused on their neuroprotective properties. The results obtained in a series of in vitro and in vivo studies are reported. Among glucosinolates, the wide class of compounds in the sulfur-containing metabolites, glucoraphanin, sulforaphane and isothiocyanates proved to be the more studied in this context and showed interesting properties as modulators of several systems involved in the pathogenesis of neurologic diseases such as oxidative stress, inflammation and apoptosis. Allium sativum L. (garlic) is widely known for its sulfur-containing components endowed with health-promoting activities and its medicinal properties are known from ancient times. In recent studies, garlic components proved active in neuroprotection due to the direct and indirect antioxidant properties, modulation of apoptosis mediators and inhibiting the formation of amyloid protein. Dihydroasparagusic acid, the first dimercaptanic compound isolated from a natural source, effectively inhibited inflammatory and oxidative processes that are important factors for the etiopathogenesis of neurodegenerative diseases, not only for its antioxidant and radical scavenging properties but also because it may down-regulate the expression of several microglial-derived inflammatory mediators. Serofendic acid represents a rare case of sulfur-containing animal-derived secondary metabolite isolated from fetal calf serum extract. It proved effective in the suppression of ROS generation and in the expression of several inflammatory and apoptosis mediators and showed a cytotrophic property in astrocytes, promoting the stellation process. Lastly, the properties of hydrogen sulfide were also reported since in recent times it has been recognized as a signaling molecule and as a mediator in regulating neuron death or survival. It may be produced endogenously from cysteine but may also be released by sulfur-containing secondary metabolites, mainly from those present in garlic.

Improvement of Learning and Memory in Senescence-Accelerated Mice by S-Allylcysteine in Mature Garlic Extract

S-allylcysteine (SAC), a major thioallyl compound contained in mature garlic extract (MGE), is known to be a neuroactive compound. This study was designed to investigate the effects of SAC on primary cultured hippocampal neurons and cognitively impaired senescence-accelerated mice prone 10 (SAMP10). Treatment of these neurons with MGE or SAC significantly increased the total neurite length and number of dendrites. SAMP10 mice fed MGE or SAC showed a significant improvement in memory dysfunction in pharmacological behavioral analyses. The decrease of α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor, N-methyl-d-aspartate (NMDA) receptor, and phosphorylated α-calcium/calmodulin-dependent protein kinase II (CaMKII) in the hippocampal tissue of SAMP10 mice fed MGE or SAC was significantly suppressed, especially in the MGE-fed group. These findings suggest that SAC positively contributes to learning and memory formation, having a beneficial effect on brain function. In addition, multiple components (aside from SAC) contained in MGE could be useful for improving cognitive function by acting as neurotrophic factors.

Neuroprotective mechanisms of S-allyl-L-cysteine in neurological disease

S-allyl-L-cysteine (SAC) is a sulfur-containing amino acid present in garlic and exhibits a wide range of biological activities such as antioxidant, anti-inflammatory, and anticancer agent. An earlier study demonstrated that SAC ameliorates oxidative damage in a model of experimental stroke. However, the antioxidant property of SAC does not suffice to explain its beneficial effects in terms of the underlying mechanisms. Endoplasmic reticulum (ER) stress and ER stress-induced cell death have been shown to be involved in various neurological diseases such as brain ischemia, Alzheimer's disease, Parkinson's disease, amyotrophic lateral sclerosis and Huntington's disease. We have previously demonstrated that SAC exerts significant protective effects against ER stress-induced neurotoxicity in cultured rat hippocampal neurons and organotypic hippocampal slice cultures. Recently, we demonstrated that these results are due to the direct suppression of calpain activity via the binding of SAC to this enzyme's Ca²⁺-binding domain. We also found that the protective effects of the side-chain-modified SAC derivatives, S-ethyl-L-cysteine (SEC) and S-propyl-L-cysteine (SPC), against ER stress-induced neurotoxicity were more potent than those of SAC in cultured rat hippocampal neurons. In addition, SAC, SEC and SPC have been shown to decrease the production of amyloid-β peptide in the brains of mice with D-galactose-induced aging. These three hydrophilic cysteine-containing compounds have also been shown to exert neuroprotective effects against dopaminergic neuron injury in a murine model of Parkinson's disease induced by 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). In this review, we aim to provide a current overview of the protective actions of SAC and the SAC-related compounds, SEC and SPC, in neurodegenerative disease and discuss the promise of SAC as a prototype for developing novel therapeutic drugs for neurological diseases.

S-allyl-glutathione, a synthetic analogue of glutathione protected liver against carbon tetrachloride toxicity: Focus towards anti-oxidative efficiency

A simple analogue of well known natural antioxidant glutathione (GSH) called S-allyl-glutathione (SAG) was evaluated against carbon tetrachloride (CCl₄)-induced oxidative stress liver injury in rat. Pretreatment of SAG attenuated the CCl₄-toxicity induced elevation of liver injury markers such as enzymes (AST, ALT, GGT, ALP and LDH) and bilirubin in the blood circulation. Such protective effect of SAG resulted in preservation of liver function observed as normal level of total protein and albumin in plasma as well as inhibition of dyslipidemia in liver. In addition, in silico analysis has proved that SAG has strong affinity with the amino acids present in active site of the human cytochrome P450 2E1 and 3A4. Three important mechanisms provided by SAG such as scavenging of reactive oxidants, replenishing of endogenous antioxidants (SOD, catalase, GPx, GSH and vitamin C) and protection of mitochondrial function (oxidative phosphorylation complex activities) are involved in the optimal function of liver against CCl₄-toxicity.

Protective effect of Allium sativum (garlic) aqueous extract against lead-induced oxidative stress in the rat brain, liver, and kidney

The present investigation was undertaken to evaluate the ameliorative activity of Allium sativum against lead-induced oxidative stress in the brain, liver, and kidney of male rats. Four groups of male Wistar strain rats (100-120 g) were taken: group 1 received 1000 mg/L sodium acetate and group 2 was given 1000 mg/L lead acetate through drinking water for 2 weeks. Group 3 and 4 were treated with 250 mg/kg body weight/day of A. sativum and 500 mg/kg body weight/day of A. sativum, respectively, by oral intubation for a period of 2 weeks along with lead acetate. The rats were sacrificed after treatment and the brain, liver, and kidney were isolated on ice. In the brain, four important regions namely the hippocampus, cerebellum, cerebral cortex, and brain stem were separated and used for the present investigation. Blood was also drawn by cardiac puncture and preserved in heparinized vials at 4 °C for estimation of delta-aminolevulinic acid dehydratase (ALAD) activity. The results showed a significant (p < 0.05) increase in reactive oxygen species (ROS), lipid peroxidation products (LPP), total protein carbonyl content (TPCC), and lead in the selected brain regions, liver, and kidney of lead-exposed group compared with their respective controls. Blood delta-ALAD activity showed a significant (p < 0.05) decrease in the lead-exposed rats. However, the concomitant administration of A. sativum resulted in tissue-specific recovery of oxidative stress parameters namely ROS, LPP, and TPCC. A. sativum treatment also restored the blood delta-ALAD activity back to control. Overall, our results indicate that A. sativum administration could be an effective antioxidant treatment strategy for lead-induced oxidative insult.

Effects of S-Allylcysteine on Biomarkers of the Polyol Pathway in Rats with Type 2 Diabetes

OBJECTIVES

We evaluated the effects of S-allylcysteine (SAC) on biomarkers of the polyol pathway in streptozotocin-nicotinamide (STZ-NA)-induced diabetes in rats.

METHODS

Diabetes was induced in male albino Wistar rats by intraperitoneal administration of STZ (55 mg kg^-1 bw^-1) and NA (110 mg kg^-1 bw^-1). SAC (150 mg kg^-1 bw^-1) was orally administered to the rats with diabetes for 45 days to assess its effects on blood glucose, insulin, insulin resistance, glycated hemoglobin, aldose reductase (AR), sorbitol dehydrogenase (SDH), sorbitol, fructose, thiobarbituric acid-reactive substances (TBARS), hydroperoxide, hemoglobin and glutathione (GSH).

RESULTS

On SAC administration in the rats with diabetes, the levels of blood glucose, insulin resistance, glycated hemoglobin, AR, SDH, sorbitol, fructose, TBARS and hydroperoxide increased significantly (p<0.05), whereas those of insulin, hemoglobin and GSH decreased. SAC showed therapeutic effects similar to those of gliclazide in decreasing blood glucose, AR, SDH, sorbitol, fructose, glycosylated hemoglobin, TBARS and hydroperoxides levels and significant increases in insulin, hemoglobin and GSH activity in rats with diabetes. Moreover, histopathologic studies also revealed the protective effect of SAC on pancreatic beta cells.

CONCLUSIONS

The results indicate that SAC prevents complications of diabetes by reducing the influx of glucose in the polyol pathway, thereby elevating the GSH level and reducing the activities of AR and SDH. Therefore, SAC may have imperative implications for the deterrence and early treatment of type 2 diabetes.

Natural thioallyl compounds increase oxidative stress resistance and lifespan in Caenorhabditis elegans by modulating SKN-1/Nrf

Identification of biologically active natural compounds that promote health and longevity, and understanding how they act, will provide insights into aging and metabolism, and strategies for developing agents that prevent chronic disease. The garlic-derived thioallyl compounds S-allylcysteine (SAC) and S-allylmercaptocysteine (SAMC) have been shown to have multiple biological activities. Here we show that SAC and SAMC increase lifespan and stress resistance in Caenorhabditis elegans and reduce accumulation of reactive oxygen species (ROS). These compounds do not appear to activate DAF-16 (FOXO orthologue) or mimic dietary restriction (DR) effects, but selectively induce SKN-1 (Nrf1/2/3 orthologue) targets involved in oxidative stress defense. Interestingly, their treatments do not facilitate SKN-1 nuclear accumulation, but slightly increased intracellular SKN-1 levels. Our data also indicate that thioallyl structure and the number of sulfur atoms are important for SKN-1 target induction. Our results indicate that SAC and SAMC may serve as potential agents that slow aging.

Antioxidant and hypolipidemic potential of aged garlic extract and its constituent, s-allyl cysteine, in rats

Aged garlic extract (AGE) is one of the unique preparations standardized with 100% bioavailable active ingredients found in the bloodstream. The current research was aimed at exploring the role of AGE and its chief active constituent, s-allyl cysteine (SAC) as antioxidant and hypolipidemic agent in rats. At the end of treatment of AGE and SAC, separated serum and freshly prepared liver tissue homogenate were analyzed for biochemical enzymes and biomarkers to evaluate and compare potencies of investigational agents. Both AGE and SAC significantly declined elevated levels of triglyceride, total cholesterol, ALP, AST, ALT, malondialdehyde, glutathione peroxidase enzyme activity, total glutathione and oxidised glutathione in serum and inclined superoxide dismutase, catalase, ferric reducing/antioxidant power, and total sulfhydryl values in liver tissue with reduction in thiobarbituric acid reactive species. The protective effects were superior with AGE compared with SAC indicating potential implication of other active constituents apart from SAC in AGE for combating hyperlipidemic stress.

Protective effect of S-allyl-L-cysteine against endoplasmic reticulum stress-induced neuronal death is mediated by inhibition of calpain

Endoplasmic reticulum (ER) stress, implicated in various neurodegenerative processes, increases the level of intracellular Ca(2+) and leads to activation of calpain, a Ca(2+)-dependent cysteine protease. We have shown previously that S-allyl-L-cysteine (SAC) in aged garlic extracts significantly protects cultured rat hippocampal neurons (HPNs) against ER stress-induced neurotoxicity. The neuroprotective effect of SAC was compared with those of the related antioxidant compounds, L-cysteine (CYS) and N-acetylcysteine (NAC), on calpain activity in HPNs and also in vitro. SAC, but not CYS or NAC, reversibly restored the survival of HPNs and increased the degradation of α-spectrin, a substrate for calpain, induced by tunicamycin, a typical ER stress inducer. Activities of μ- and m-calpains in vitro were also concentration dependently suppressed by SAC, but not by CYS or NAC. At submaximal concentration, although ALLN (5 pM), which blocks the active site of calpain, and calpastatin (100 pM), an endogenous calpain-inhibitor protein, additively inhibited μ-calpain activity in vitro in combination with SAC, the effect of PD150606 (25 μM), which prevents interaction of Ca(2+) with the Ca(2+)-binding site of calpain, was unaffected by SAC. In contrast, SAC (1 mM) significantly reversed the effect of PD150606 at a concentration that elicited supramaximal inhibition (100 μM), but did not affect ALLN (1 nM)- and calpastatin (100 nM)-induced inhibition of μ-calpain activity. These results suggest that the protective effects of SAC against ER stress-induced neuronal cell death are not attributable to antioxidant activity, but to suppression of calpain through interaction with its Ca(2+)-binding site.

S-allylcysteine Improves Streptozotocin-Induced Alterations of Blood Glucose, Liver Cytochrome P450 2E1, Plasma Antioxidant System, and Adipocytes Hormones in Diabetic Rats

BACKGROUND

S-allylcysteine, a garlic derivative, could have a protective effect against pathogenesis of diabetes mellitus.

OBJECTIVES

Sustained free radical generation and oxidative damage to system leads to the final conclusion phase of diabetes and also it coexists with a constant diminution in the antioxidant status.The present study aims to evaluate the therapeutic effects of S-allylcysteine (SAC) against adipocytes hormones and antioxidant defense systems of plasma and erythrocytes of treptozotocin (STZ) induced diabetes in rats.

MATERIALS AND METHODS

Diabetic rats were administered SAC (150 mg/kg b.w) orally for 45 days. At 46(th) day, the rats were anesthetized, and blood and liver sample were collected for analyzing glucose, plasma insulin, CYP2E1 activity, Thiobarbituric acid reactive substances (TBARS), hydroperoxide, enzymatic and nonenzymatic antioxidants, reduced glutathione (GSH), ceruloplasmin, plasma leptin, and adiponectin.

RESULTS

The levels of glucose, CYP2E1 activity, Thiobarbituric acid reactive substances (TBARS), hydroperoxide, and ceruloplasmin were increased significantly; whereas, the levels of plasma insulin, reduced glutathione, enzymatic and nonenzymatic antioxidants, leptin and adiponectin were decreased in experimental diabetic rats. Administration of SAC to diabetic rats led to a decrease in the levels of glucose, CYP2E1 activity, TBARS, and ceruloplasmin. In addition, the levels of plasma insulin, enzymatic and nonenzymatic antioxidants leptin and adiponectin were increased in SAC treated diabetic rats. Gliclazide, a standard drug for diabetes, was used for the comparative purpose.

CONCLUSIONS

The results of the present investigation suggest that SAC could be used as a food supplement in the treatment of diabetes characterized by provoked antioxidant status, altered blood glucose, and hormones level.

RETRACTED: S-allyl cysteine protects against 6-hydroxydopamine-induced neurotoxicity in the rat striatum: involvement of Nrf2 transcription factor activation and modulation of signaling kinase cascades

Pharmacological activation at the basal ganglia of the transcription factor Nrf2, guardian of redox homeostasis, holds a strong promise for the slow progression of Parkinson's disease (PD). However, a potent Nrf2 activator in the brain still must be found. In this study, we have investigated the potential use of the antioxidant compound S-allyl cysteine (SAC) in the activation of Nrf2 in 6-hydoxydopamine (6-OHDA)-intoxicated rats. In the rat striatum, SAC by itself promoted the Nrf2 dissociation of Keap-1, its nuclear translocation, the subsequent association with small MafK protein, and further binding of the Nrf2/MafK complex to ARE sequence, as well as the up-regulation of Nrf2-dependent genes encoding the antioxidant enzymes HO-1, NQO-1, GR, and SOD-1. In vivo and in vitro experiments to identify signaling pathways activated by SAC pointed to Akt as the most likely kinase participating in Nrf2 activation by SAC. In PC12 cells, SAC stimulated the activation of Akt and ERK1/2 and inhibited JNK1/2/3 activation. In the rat striatum, the SAC-induced activation of Nrf2 is likely to contribute to inhibit the toxic effects of 6-OHDA evidenced by phase 2 antioxidant enzymes up-regulation, glutathione recovery, and attenuation of reactive oxygen species (ROS), nitric oxide (NO), and lipid peroxides formation. These early protective effects correlated with the long-term preservation of the cellular redox status, the striatal dopamine (DA) and tyrosine hydroxylase (TH) levels, and the improvement of motor skills. Therefore, this study indicates that, in addition to direct scavenging actions, the activation of Nrf2 by SAC might confer neuroprotective responses through the modulation of kinase signaling pathways in rodent models of PD, and suggests that this antioxidant molecule may have a therapeutic value in this human pathology.

The antioxidant mechanisms underlying the aged garlic extract- and S-allylcysteine-induced protection

Aged garlic extract (AGE) is an odorless garlic preparation containing S-allylcysteine (SAC) as its most abundant compound. A large number of studies have demonstrated the antioxidant activity of AGE and SAC in both in vivo--in diverse experimental animal models associated to oxidative stress--and in vitro conditions--using several methods to scavenge reactive oxygen species or to induce oxidative damage. Derived from these experiments, the protective effects of AGE and SAC have been associated with the prevention or amelioration of oxidative stress. In this work, we reviewed different antioxidant mechanisms (scavenging of free radicals and prooxidant species, induction of antioxidant enzymes, activation of Nrf2 factor, inhibition of prooxidant enzymes, and chelating effects) involved in the protective actions of AGE and SAC, thereby emphasizing their potential use as therapeutic agents. In addition, we highlight the ability of SAC to activate Nrf2 factor--a master regulator of the cellular redox state. Here, we include original data showing the ability of SAC to activate Nrf2 factor in cerebral cortex. Therefore, we conclude that the therapeutic properties of these molecules comprise cellular and molecular mechanisms at different levels.

Role of allyl group in the hydroxyl and peroxyl radical scavenging activity of S-allylcysteine

S-Allylcysteine (SAC) is the most abundant compound in aged garlic extracts, and its antioxidant properties have been demonstrated. It is known that SAC is able to scavenge different reactive species including hydroxyl radical (•OH), although its potential ability to scavenge peroxyl radical (ROO•) has not been explored. In this work the ability of SAC to scavenge ROO• was evaluated, as well as the role of the allyl group (-S-CH(2)-CH═CH(2)) in its free radical scavenging activity. Two derived compounds of SAC were prepared: S-benzylcysteine (SBC) and S-propylcysteine (SPC). Their abilities to scavenge •OH and ROO• were measured. A computational analysis was performed to elucidate the mechanism by which these compounds scavenge •OH and ROO•. SAC was able to scavenge •OH and ROO•, in a concentration-dependent way. Such activity was significantly ameliorated when the allyl group was replaced by benzyl or propyl groups. It was shown for the first time that SAC is able to scavenge ROO•.

S-allyl cysteine attenuates oxidative stress associated cognitive impairment and neurodegeneration in mouse model of streptozotocin-induced experimental dementia of Alzheimer's type

S-allyl cysteine (SAC), a sulfur containing amino acid derived from garlic, has been reported to have antioxidant, anti-cancer, antihepatotoxic and neurotrophic activity. This study was designed to examine the pre-treatment effects of SAC on cognitive deficits and oxidative damage in the hippocampus of intracerebroventricular streptozotocin (ICV-STZ)-infused mice. Mice pre-treated with SAC (30mg/kg) and vehicle (intraperitoneal; once daily for 15days) were bilaterally injected with ICV-STZ (2.57mg/kg body weight), whereas sham rats received the same volume of vehicle. The pre-treatment of this drug to Swiss albino mice has prevented the cognitive and neurobehavioral impairments. An increased latency and path length were observed in lesion, i.e. streptozotocin (STZ) group as compared to sham group and these were protected significantly in STZ group pre-treated with SAC. Levels of reduced glutathione (GSH) and its dependent enzymes (Glutathione peroxidase [GPx] and glutathione reductase [GR]) were decreased in STZ group as compared to sham group and pre-treatment of STZ group with SAC has protected their activities significantly. Conversely, the elevated level of thiobarbituric acid reactive substances (TBARS) in STZ group was attenuated significantly in SAC pre-treated group when compared with STZ lesioned group. Apoptotic parameters like DNA fragmentation, expression of Bcl2 and p53 were protected by the pre-treatment of SAC against STZ induced cognitive impairment. This study concludes that intervention of SAC could prevent free radicals associated deterioration of cognitive functions and neurobehavioral activities.

S-Allylcysteine, a garlic compound, protects against oxidative stress in 1-methyl-4-phenylpyridinium-induced parkinsonism in mice

S-Allylcysteine (SAC), the most abundant organosulfur compound in aged garlic extract, has multifunctional activity via different mechanisms and neuroprotective effects that are exerted probably via its antioxidant or free radical scavenger action. The 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine-treated mouse has been the most widely used model for assessing neuroprotective agents for Parkinson's disease. 1-Methyl-4-phenylpyridinium (MPP(+)) is the stable metabolite of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine, and it causes nigrostriatal dopaminergic neurotoxicity. Previous studies suggest that oxidative stress, via free radical production, is involved in MPP(+)-induced neurotoxicity. Here, we report on the neuroprotective effect of SAC against oxidative stress induced by MPP(+) in the striatum of C57BL/6J mice. Mice were pretreated with SAC (125 mg/kg ip) daily for 17 days, followed by administration of MPP(+) (0.72 mg/kg icv), and were sacrificed 24 h later to evaluate lipid peroxidation, different antioxidant enzyme activities, spontaneous locomotor activity and dopamine (DA) content. MPP(+) administration resulted in a significant decrease in DA levels in the striatum. Mice receiving SAC (125 mg/kg ip) had significantly attenuated MPP(+)-induced loss of striatal DA levels (32%). The neuroprotective effect of SAC against MPP(+) neurotoxicity was associated with blocked (100% of protection) of lipid peroxidation and reduction of superoxide radical production - indicated by an up-regulation of Cu-Zn-superoxide dismutase activity - both of which are indices of oxidative stress. Behavioral analyses showed that SAC improved MPP(+)-induced impairment of locomotion (35%). These findings suggest that in mice, SAC attenuates MPP(+)-induced neurotoxicity in the striatum and that an antioxidant effect against oxidative stress may be partly responsible for its observed neuroprotective effects.

S-allylcysteine reduces the MPTP-induced striatal cell damage via inhibition of pro-inflammatory cytokine tumor necrosis factor-α and inducible nitric oxide synthase expressions in mice

We have recently demonstrated that S-allylcysteine (SAC) induces protection on neurochemical, biochemical and behavioral markers of striatal damage in different neurotoxic animal models - including a murine model induced by 1-methyl-4-phenyl-1,2,3,6-tetrahydropiridinium (MPTP) injection to mice - indicating that pro-oxidant reactions underlie neurotoxicity in these models (García et al. 2008). In this work we investigated whether SAC can protect the striatum of mice from the morphological alterations in the MPTP toxic model, and if this response is correlated with a reduction in pro-inflammatory cytokine tumor necrosis factor-α (TNF-α) and inducible nitric oxide synthase (iNOS) expressions, and further reduction in astrocyte activation (glial fibrillary acidic protein (GFAP) expression). The striatal tissue from MPTP injected animals (30 mg/kg, i.p., ×5 days) showed a significant degree of cell damage and enhanced immunoreactivities to GFAP, TNF-α and iNOS, as well as an enhanced number of apoptotic nuclei. Treatment of mice with SAC (120 mg/kg, i.p., ×5 days) in parallel to MPTP significantly reduced or prevented all these markers. Our results suggest that MPTP-induced morphological alterations recruit a pro-inflammatory component triggered by cytokine TNF-α release and nitric oxide formation, which is sensitive to the antioxidant properties of SAC. This antioxidant is an effective experimental tool to reduce the brain lesions associated with oxidative damage and inflammatory responses.

Hypochlorous acid scavenging activities of thioallyl compounds from garlic

The hypochlorous acid (HOCl) scavenging capacities of 10 garlic compounds containing modifications in the thioallyl group (-S-CH2CH ═ CH2) were determined by a catalase protection assay, and the corresponding structure-activity relationships using molecular descriptors were calculated. This scavenging activity was enhanced by increasing the number of S atoms or by the alanyl group (-CH2CH-NH2-COOH) and decreased in the absence of the C ═ C bond or in the presence of a sulfoxide group in the thioallyl group. Interestingly, S-allylcysteine and its corresponding sulfoxide (alliin) showed the highest and lowest HOCl-scavenging capacities, respectively. Quantitative modeling by multiple regression analysis and partial least-squares projections showed that the topological descriptor polar surface area and two electronic properties, namely, highest occupied molecular orbital and total energy, contributed mainly to variations in the HOCl scavenging activity of thioallyl compounds. These observations provide new insights on the antioxidant mechanism of garlic derivatives in processes involving HOCl production.

Antioxidant strategy to rescue synaptosomes from oxidative damage and energy failure in neurotoxic models in rats: protective role of S-allylcysteine

The functional preservation of nerve endings since the early stages of toxicity in a given damaging insult-either acute or chronic-by means of antioxidant and neuroprotective agents is a primary need to design therapeutic strategies for neurodegenerative disorders, with particular emphasis on those diseases with excitotoxic and depleted energy metabolism components. S-allylcysteine (SAC), a well-known antioxidant agent, was tested as a post-treatment in different in vitro and in vivo neurotoxic models. Quinolinic acid (QUIN) was used as a typical excitotoxic/pro-oxidant inducer, 3-nitropropionic acid (3-NP) was employed as a mitochondrial function inhibitor, and their combination (QUIN + 3-NP) was also evaluated in in vitro studies. For in vitro purposes, increasing concentrations of SAC (10-100 microM) were added to isolated brain synaptosomes at different times (1, 3 and 6 h) after the incubation with toxins (100 microM QUIN, 1 mM 3-NP or the combination of QUIN (21 microM) + 3-NP (166 microM). Thirty minutes later, lipid peroxidation (LP) and mitochondrial dysfunction (MD) were evaluated. For in vivo studies, SAC (100 mg/kg, i.p.) was given to QUIN- or 3-NP-striatally lesioned rats for 7 consecutive days (starting 120 min post-lesion). LP and MD were evaluated 7 days post-lesion in isolated striatal synaptosomes. Circling behavior was also assessed. Our results describe a differential pattern of protection achieved by SAC, mostly expressed in the 3-NP toxic model, in which nerve ending protection was found within the first hours (1 and 3) after the toxic insult started, supporting the concept that the ongoing oxidative damage and energy depletion can be treated during the first stages of neurotoxic events.

S-allylcysteine attenuates renal injury by altering the expressions of iNOS and matrix metallo proteinase-2 during cyclosporine-induced nephrotoxicity in Wistar rats

Cyclosporine A (CsA) is the first choice immunosuppressant used for the prevention of allograft rejection in solid organ transplantation and immune-mediated diseases. Reactive oxygen species-induced oxidative stress and lipid peroxidation are implicated in the pathophysiology of CsA-induced renal injury. In this work, we have studied the effect of a garlic-derived compound, S-allylcysteine (SAC) on CsA-induced nephrotoxicity. CsA-induced nephrotoxicity was assessed in terms of increased activities of serum marker enzymes and levels of kidney markers. CsA administration induced significant elevation in lipid peroxidation along with abnormal levels of enzymic and non-enzymic antioxidants in the kidneys of the rats. SAC administration improved renal function by bringing about a significant decrease in peroxidative levels and increase in antioxidant status. Elevated expressions of inducible nitric oxide synthase (iNOS) and nuclear factor kappa B (NF-kappaB) due to CsA administration were reduced by SAC treatment. An increase in the expression of matrix metalloproteinase-2 (MMP-2) was evident in CsA-induced groups of rats, which was moderately reduced in SAC treated rats. An increase in the levels of serum constituent's urea, uric acid and creatinine was observed in the CsA-induced rats, which was reduced upon treatment with SAC. These results indicate that SAC has a protective action against CsA-induced nephrotoxicity which is also supported by histopathological studies. A comparative study of the antioxidant vitamin C and SAC is more valuable to assess the efficacy of the drug that can be used for the treatment of nephrotoxicity.

Lipid peroxidation, mitochondrial dysfunction and neurochemical and behavioural deficits in different neurotoxic models: protective role of S-allylcysteine

Experimental evidence on the protective properties of S-allylcysteine (SAC) was collected from three models exerting striatal toxicity. In the first model, SAC (120 mg kg(-1)x5) prevented lipoperoxidation (LP) and mitochondrial dysfunction (MD) in synaptosomal fractions from 1-methyl-4-phenyl-1,2,3,6-tetrahydropiridinium-treated mice (30 mg kg(-1)), but without complete restoration of dopamine levels. In the second model, SAC (300 mg kg(-1)x 3), prevented LP and MD in synaptosomes from rats infused with 6-hydroxydopamine (8 microg microl(-1)) into the substantia nigra pars compacta, but again, without total reversion of depleted dopamine levels. In the third model, SAC (100 mg kg(-1)x 1) prevented MD in synaptosomes from rats injected with 3-nitropropionic acid (10 mg kg(-1)), but in contrast to the other models, it failed to prevent LP. SAC also prevented the aberrant motor activity patterns evoked by the three toxins. Altogether, the results suggest that the antioxidant properties of SAC are responsible for partial or total preservation of neurochemical, biochemical and behavioural markers, indicating that pro-oxidant reactions underlie the neurotoxicity in these models.

Neuroprotective effects of several korean medicinal plants traditionally used for stroke remedy

The neuroprotective effect of six aqueous extracts and one alcoholic extract prepared from seven medicinal plants that have been recorded as having therapeutic effects for stroke in Korean traditional medicine were studied using both in vitro and in vivo cerebral ischemia models. Among the extracts tested, the aqueous extracts of Acorus gramineus, Chrysanthemum indicum, and Pinus densiflora and the alcoholic extract of Vitis vinifera significantly increased the cell viability of SK-N-SH human neuroblastoma cells exposed to oxygen-glucose deprivation (P < .05). Following two-vessel occlusion in gerbils, extracts of P. densiflora and V. vinifera significantly increased the number of surviving cells/mm(2) of the CA1 region by 2.1-2.2-fold (P < .01). Oral or intraperitoneal administration of S-allyl cysteine, as a positive control, also markedly increased cell survival up to about 3.3-fold at the dosage of 300 mg/kg of body weight (P < .01). These results indicate that P. densiflora and V. vinifera exert neuroprotective effects against ischemic insults in both the in vitro and in vivo cerebral ischemia models and prompted us to further characterize the detailed mechanism of action and elucidate the active principles.

Protective effect of S-allylcysteine against cyclophosphamide-induced bladder hemorrhagic cystitis in mice

S-Allylcysteine (SAC), an organosulfur compound of aged garlic extract (AGE) regulates the thiol status of the cell and scavenges free radicals. Depletion of thiols along with free radical generation has been implicated in cyclophosphamide (CP)-induced urotoxicity. We studied modulatory effect of SAC on CP-induced urotoxicity in mice focusing on hemorrhagic cystitis (HC). SAC (150 and 300 mg kg(-1)) was administered in CP treated animals (200 mg kg(-1)) and bladder was observed for histological and biochemical changes. CP treatment caused a marked increase in the lumen exudates, edema, vasodilation and HC in lamina propia in the bladder. These changes were accompanied by increase in lipid peroxidation (LPO), and decrease in reduced glutathione (GSH) and activities of antioxidant enzymes. SAC not only showed protection in tissue histology but also improved the decreased activities of antioxidant enzymes. SAC treatment also reduced LPO and increased GSH levels. Although SAC treatment did not ensure full recovery, the marked improvement in histology and antioxidants of bladder suggests that it has a significant modulatory effect on CP-induced urotoxicity. Since decrease in antioxidant level is the major cause of CP urotoxicity, the protective effect of SAC deserves its further exploration involving laboratory and clinical investigations.

Amelioration of early cognitive deficits by aged garlic extract in Alzheimer's transgenic mice

Subtle accumulation of beta-amyloid peptide (Abeta) oligomers of Abeta42 species in particular, is known to correlate with cognitive deficits independent of Abeta plaque deposition in the brain. Majority of the research showing behavioral improvement after cerebral Abeta reduction has been reported when the animals carried fewer/abundant amyloid plaques in the brain. Very few studies have addressed whether or not behavioral deficits exist even at the pre-plaque stage or in the absence of plaques that would parallel the mild cognitive impairment (MCI) stage of Alzheimer's disease (AD). Current study was undertaken to determine whether there exists any cognitive impairment during the pre-plaque stage which may parallel the MCI stage of AD, and to confirm whether the observed behavioral deficits correlate with Abeta42 predominance. In addition, the study determined whether anti-amyloidogenic effects of dietary aged garlic extract would prevent progressive behavioral impairment. For this purpose we used Tg2576 model showing slow plaque development with a predominance of Abeta40, and the TgCRND8 model showing accelerated plaque development with a predominance of Abeta42. The results show that at 2 months of age Tg2576 mice did not exhibit behavioral impairment in any of the tasks studied. While 2-month-old TgCRND8 mice displayed only a subtle behavioral deficit that matched the behavioral deficits observed in 7-month-old Tg2576 mice which may correlate with the MCI stage of AD. TgCRND8 mice at 7 months of age exhibited advanced deterioration in all behavioral tasks studied, suggesting that accelerated Abeta accumulation and the predominance of Abeta42 species may account for the pronounced cognitive deficits observed in TgCRND8. Feeding of aged garlic extract prevented deterioration of hippocampal based memory tasks in these mice, suggesting that aged garlic extract has a potential for preventing AD progression.

Amyloid beta-protein potentiates tunicamycin-induced neuronal death in organotypic hippocampal slice cultures

We have assessed amyloid beta protein (Abeta)-induced neurotoxicity, with and without added tunicamycin (TM), an inhibitor of N-glycosylation in the endoplasmic reticulum (ER), in rat organotypic hippocampal slice cultures (OHCs). In the rat OHCs cultured for 3 weeks, there was little neurotoxicity after treatment with Abeta(25-35) (25 microM) alone for 48 h. However, with TM alone, concentration-dependent neuronal death was observed at concentrations between 20 and 80 microg/mL. When amyloid-beta protein was combined with tunicamycin (Abeta+TM), cell death was more acute than with TM alone. Western blot analysis revealed that calpain activity and the active forms of caspase-12 and caspase-3 was increased after exposure to Abeta+TM as compared with exposure to TM alone. In contrast, the levels of glucose regulated protein (GRP)94, GRP78 and C/EBP homologous protein (CHOP) were not changed in the presence of Abeta. Abeta potentiation of TM neurotoxicity was reversibly blocked by S-allyl-L-cysteine (SAC), an organosulfur compound purified from aged garlic extract, and the L-type calcium channel blocker, nifedipine, in a restricted neuronal area of the OHCs. Simultaneously applied SAC also reversed the increases in calpain activity and the active forms of caspase-12 and caspase-3 by Abeta+TM with no change in the increased levels of GRP94, GRP78 and CHOP. These data indicate that Abeta facilitates the calpain-caspase-12-caspase-3 pathway, thus potentiating TM-induced neuronal death in the hippocampus.

Dietary S-allyl-L-cysteine reduces mortality with decreased incidence of stroke and behavioral changes in stroke-prone spontaneously hypertensive rats

S-Allyl-L-cysteine (SAC), an active organosulfur compound derived from garlic, was found to reduce mortality with lesser incidence of stroke and also to lower the overall stroke-related behavioral score in stroke-prone spontaneously hypertensive (SHRSP) rats by dietary administration. Consequently, the anti-stroke effect of dietary SAC was demonstrated in SHRSP rats.

Structure-activity relationship of neuroprotective and reactive oxygen species scavenging activities for allium organosulfur compounds

The neuroprotective and antioxidative activities of five organosulfur compounds with a thioallyl structure (-S-CH2CH=CH2) were characterized in terms of structure-activity relationships. Among five organosulfur compounds, only S-allyl-L-cysteine (SAC) having the alanyl group (-CH2CH-NH2-COOH) and lacking the oxo (O=) group with in between molecular properties, was effective in protecting cell death induced by both oxygen glucose deprivation and global cerebral ischemia. Conversely, lipophillic organosulfur compounds including diallyl sulfide, diallyl disulfide, and diallyl trisulfide were devoid of in vitro and in vivo neuroprotective activities. Furthermore, a significant correlation was only found between the in vivo neuroprotective activity and the OH- scavenging activity (gamma = 0.55 and p = 0.032) among reactive oxygen species scavenging activities. These results indicate that the presence of the alanyl group and the absence of the oxo group are essential for the manifestation of neuroprotective activity against ischemic insults and scavenging of OH radical, with SAC surfacing as a potent neuroprotectant.

S-Allylcysteine prevents the rat from 3-nitropropionic acid-induced hyperactivity, early markers of oxidative stress and mitochondrial dysfunction

We investigated the effects of S-allylcysteine (SAC) on early behavioral alterations, striatal changes in superoxide dismutase (SOD) activity, lipid peroxidation (LP) and mitochondrial dysfunction induced by the systemic infusion of 3-nitropropionic acid (3-NPA) to rats. SAC (300 mg/kg, i.p.), given to animals 30 min before 3-NPA (30 mg/kg, i.p.), prevented the hyperkinetic pattern evoked by the toxin. In addition, 3-NPA alone produced decreased activities of manganese- (Mn-SOD) and copper/zinc-dependent superoxide dismutase (Cu,Zn-SOD), increased LP (evaluated as the formation of lipid fluorescent products) and produced mitochondrial dysfunction in the striatum (measured as decreased 3-(3,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide reduction). In contrast, pretreatment of 3-NPA-injected rats with SAC resulted in a significant prevention of all these markers. Our findings suggest that the protective actions of SAC are related with its antioxidant properties, which in turn may be accounting for the preservation of SOD activity and primary mitochondrial tasks.

Preventive effect of S-allylcysteine on lipid peroxides and antioxidants in normal and isoproterenol-induced cardiotoxicity in rats: a histopathological study

The consumption of diets rich in plant foods are associated with a reduced risk of cardiovascular diseases. This study was aimed to evaluate the role of S-allylcysteine (SAC) in isoproterenol (ISO)-induced myocardial infarction (MI) in rats. Subcutaneous injection of ISO (150 mg/kg) to Wistar rats showed a significant decrease in the activities of marker enzymes such as creatine kinase, lactate dehydrogenase, aspartate and alanine transaminases in heart and a significant increase in the levels of thiobarbituric acid reactive substances and lipid hydroperoxides in plasma and heart. ISO-induced rats also showed a significant decrease in the activities of superoxide dismutase, catalase, glutathione peroxidase, glutathione reductase and glutathione S-transferase in heart and the levels of glutathione and ascorbic acid in plasma and heart. Oral administration of SAC (100 and 150 mg/kg) to ISO-treated rats daily for a period of 45 days caused a significant increase in the activities of marker enzymes and improved the antioxidant status by decreasing lipid peroxidative products and increasing the activities of antioxidant enzymes and the levels of nonenzyomic antioxidants. Administration of SAC to normal rats did not show any significant effect. Histopathological findings of the myocardial tissue showed a protective role of SAC in ISO-treated rats. The effect at a dose of 150 mg/kg of SAC was more pronounced than that of the dose 100mg/kg and brought back all the parameters to near normal. The effect exerted by 100 mg/kg of SAC was similar to that of alpha-tocopherol (60 mg/kg). The results of our study show that SAC possesses antioxidant activity in ISO-induced experimental MI.

Comparative study of endoplasmic reticulum stress-induced neuronal death in rat cultured hippocampal and cerebellar granule neurons

In this study, experiments were performed to characterize further the pathways responsible for neuronal death induced by endoplasmic reticulum (ER) stress in cultured hippocampal neurons (HPN) and cerebellar granule neurons (CGN) using tunicamycin (TM) and amyloid beta-peptide (Abeta). Exposure of HPN to Abeta or TM resulted in a time-dependent increase in the expression of 78-kDa glucose-regulated protein (GRP78) and caspase-12, an ER-resident caspase. In contrast, in CGN, although a drastic increase in the expression of GRP78 was found as was the case in HPN, no up-regulation of caspase-12 was detected. These results were consistent with immunohistochemical results that there were far lower number of caspase-12-positive cells in the cerebellum than in the cerebral cortex and hippocampus, and that caspase-12-positive cells were not identified in the external granule cell layer of the cerebellum of P7 rats. In CGN, a significant increase in the expression of C/EBP homologous protein (CHOP) protein was detected after exposure to Abeta or TM, whereas no such an increase in the protein expression was observed in HPN. In addition, S-allyl-L-cysteine (SAC), an organosulfur compound purified from aged garlic extract, protected neurons against TM-induced neurotoxicity in HPN but not in CGN, as in the case of Abeta-induced neurotoxicity. These results suggest that the pathway responsible for neuronal death induced by Abeta and TM in HPN differs from that in CGN, and that a caspase-12-dependent pathway is involved in HPN while a CHOP-dependent pathway is involved in CGN in ER stress-induced neuronal death.

Protective effect of S-allylcysteine on 3-nitropropionic acid-induced lipid peroxidation and mitochondrial dysfunction in rat brain synaptosomes

3-Nitropropionic acid is a neurotoxin that irreversibly inhibits succinate dehydrogenase, a relevant enzyme constituting the complex II of the respiratory chain during mitochondrial electron transport. 3-Nitropropionic acid is known to produce oxidative/nitrosative stress and evokes an experimental model of Huntington's disease. In this work we evaluated the effects of the antioxidant compound and major organosulfur garlic derivative, S-allylcysteine, on lipid peroxidation and mitochondrial dysfunction induced by 3-nitropropionic acid in synaptosomal fractions from rat brain. 3-Nitropropionic acid, at concentrations ranging 0.75-2.5 mM, produced enhanced levels of lipid peroxidation, while increasing concentrations of S-allylcysteine (0.1-2 mM) decreased the peroxidative action of 3-nitropropionic acid (1 mM) in synaptosomal fractions in a concentration-dependent manner. S-Allylcysteine (0.75 mM) also prevented the 3-nitropropionic acid (1mM)-induced mitochondrial dysfunction. These findings suggest that the protective actions that S-allylcysteine exert on the in vitro neurotoxicity induced by 3-nitropropionic acid are mediated by its antioxidant properties.