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

Ameliorative potential of metformin in LPS and glutamate-induced neurotoxicity in N2a cell-line

The study aims to explore the potential of metformin to counteract the lethal effects of glutamate and lipopolysaccharide (LPS)- induced neurotoxicity in Neuro2a (N2a) cells, resembling CNS-comorbidities generally associated with metabolic disorders. Glutamate and LPS-induced N2a cell models were used to conduct the in-vitro study to evaluate the beneficial effect of metformin. Cell viability assay, biochemical parameter viz. cytokines level, superoxide dismutase (SOD) was performed. Further, reactive oxygen species (ROS) were also staged using the Fluorescence-Activated Cell Sorting (FACS) technique to evaluate the beneficial effect of metformin on oxidative stress. Metformin treatments during the study revealed neuroprotective effects and abridged neurotoxicity by significantly reducing the levels of cytokines (viz. IL-1β, IL-6, and TNF-α), raising SOD enzyme activities and declining the ROS levels in LPS and glutamate-treated N2a cells. Based on experimental observation, in an in-vitro study, the effective dose of Met was 50 µM. The results showed that metformin had a neuroprotective effect by enhancing cell viability, diminishing the cytokine storm, and reducing various oxidative stressors. These findings imply that due to the anti-inflammatory, diminishing reactive oxidative species, and antioxidant properties of metformin, it can be considered a therapeutic drug candidate for treating and managing neurological disorders and CNS complications associated with metabolic abnormalities. Further, an in-vivo mechanistic study is warranted to validate the safety and efficacy of metformin for neurological disorders associated with metabolic abnormalities and neurodegenerative disorders.

Effect of Capsaicin on 3-NP-Induced Neurotoxicity: A Pre-Clinical Study

The study objectives are to investigate the ability of capsaicin to revert the toxic effects in glutamate and lipopolysaccharide (LPS)-induced neurotoxicity in Neuro2a (N2a) cells as well as thwarting cognitive impairments, mitochondrial deficits, and oxidative insults induced by 3-nitropropanoic acid (3-NP) in a rodent model of Huntington's disease. In-vitro study with N2a cells was performed through MTT and LDH assay and their biochemical examinations were also performed. 3-NP-administered mice (n = 6) were treated with capsaicin (5, 10, and 20 mg/kg) through the per-oral (p.o.) route for 7 consecutive days. Physiological and behavioral studies were performed in drug-treated mice. After behavioral studies, biochemical parameters were performed for cytokines levels, various oxidative stress parameters, and mitochondrial enzyme complex activities with mitochondrial permeability. N2a cells treated with capsaicin demonstrated neuroprotective effects and reduced neurotoxicity. Based on experimental observation, in an in-vitro study, the effective dose of CAP was 50 µM. Moreover, a 100 µM dose of capsaicin had toxic effects on neuronal cells (N2a cells). On the other hand, the effective dose of 3-NP was 20 mg/kg, (p.o.) in animals (in-vivo). All tested doses of capsaicin upturned the cognitive impairment and motor in-coordination effects induced by 3-NP. 3-NP-injected mice demonstrated substantially increased pro-inflammatory cytokine concentrations, defective mitochondrial complex activity, and augmented oxidative insult. However, capsaicin at different doses reduced oxidative damage and cytokines levels and improved mitochondrial complex activity along with mitochondrial permeability. Furthermore, capsaicin (10 and 20 mg/kg) improved the TNF-α concentration. These findings suggested because of the anti-inflammatory and antioxidant effect, capsaicin can be considered a novel treatment for the management of neurodegenerative disorders by reverting the antioxidant enzyme activity, pro-inflammatory cytokines concentration, and mitochondrial functions.

An Update of Kaempferol Protection against Brain Damage Induced by Ischemia-Reperfusion and by 3-Nitropropionic Acid

Kaempferol, a flavonoid present in many food products, has chemical and cellular antioxidant properties that are beneficial for protection against the oxidative stress caused by reactive oxygen and nitrogen species. Kaempferol administration to model experimental animals can provide extensive protection against brain damage of the striatum and proximal cortical areas induced by transient brain cerebral ischemic stroke and by 3-nitropropionic acid. This article is an updated review of the molecular and cellular mechanisms of protection by kaempferol administration against brain damage induced by these insults, integrated with an overview of the contributions of the work performed in our laboratories during the past years. Kaempferol administration at doses that prevent neurological dysfunctions inhibit the critical molecular events that underlie the initial and delayed brain damage induced by ischemic stroke and by 3-nitropropionic acid. It is highlighted that the protection afforded by kaempferol against the initial mitochondrial dysfunction can largely account for its protection against the reported delayed spreading of brain damage, which can develop from many hours to several days. This allows us to conclude that kaempferol administration can be beneficial not only in preventive treatments, but also in post-insult therapeutic treatments.

Evaluation of Expression of Cytochrome P450 Aromatase and Inflammatory, Oxidative, and Apoptotic Markers in Testicular Tissue of Obese Rats (Pre)Treated with Garlic Powder

Today, adolescent obesity is recognized as an epidemic and a cause of reproductive disorders. Decreased testosterone levels occur due to functional defects in the hypothalamus-pituitary axis, excessive activity of cytochrome P450 aromatase enzyme, and testicular dysfunction in these people. Oxidative damage, inflammation, and apoptosis are also the main mechanisms of testicular damage during obesity. The use of herbal products such as garlic can improve this disorder due to its anti-inflammatory and antioxidant properties. Therefore, the aim of this study is to investigate the effect of pretreatment and treatment of garlic powder on the expression of cytochrome P450 aromatase enzyme and the expression of genes involved in testosterone synthesis, inflammation, oxidative damage, apoptosis in testicular tissue, and metabolic function of liver tissue in young male obese rats. Eighty male Wistar rats were divided into the controlled and treated groups. Serum levels of lipid, glucose, and insulin as metabolic factors were measured along with the testicular antioxidant and inflammation markers. The expression of Bcl2, Bax, and caspase-3 along with NF-κB, SREBP-1c, CPT-1beta, Nrf-2, CD36, FAS, CYP19A1, P450scc, StAR, 17βHSD, PPARα, and aromatase (CYP19, P450arom) was also measured. Testicular histological evaluation and spermatogenic process was also performed. The results showed that oxidative, inflammatory, and metabolic factors significantly increased in obese rats. The testicular expression of aromatase, NF-κB, Bax, and caspase 3 increased and Nrf2 expression decreased in obese rats, while (pre) treatment with garlic powder significantly decreased the expression of these genes in obese rats. These results were also confirmed by the findings of the histological evaluation and sperm analysis. It can be concluded that garlic powder could improve reproductive dysfunction in obese rats.

Protective Effect of Fustin against Huntington's Disease in 3-Nitropropionic Treated Rats via Downregulation of Oxidative Stress and Alteration in Neurotransmitters and Brain-Derived Neurotrophic Factor Activity

Researchers have revealed that Rhus verniciflua heartwood, which contains fustin as an important component, possesses antioxidant-mediated, anti-mutagenic, and anti-rheumatoid arthritis characteristics. Additionally, out of the numerous plant-derived secondary metabolites, there are various research papers concentrating on flavonoids for potential advantages in neurological illnesses. The current study aims to assess the neuroprotective potential of fustin in rodents over 3-nitropropionic acid (3-NPA)-induced Huntington's disease (HD)-like consequences. The efficacy of fustin 50 and 100 mg/kg was studied with multiple-dose administrations of 3-NPA, which experimentally induced HD-like symptoms in rats for 22 days. At the end of the study, several behavioral tests were performed including a beam walk, rotarod, and grip strength tests. Similarly, some biochemical parameters were assessed to support oxidative stress (reduced glutathione-GSH, superoxide dismutase-SOD, catalase-CAT, and malondialdehyde-MDA), alteration in neurotransmitters (gamma-aminobutyric acid-GABA-and glutamate), alteration in brain-derived neurotrophic factor activity, and nitrite levels. Additionally, pro-inflammatory parameters were carried out to evaluate the neuroinflammatory responses associated with streptozotocin such as TNF-α, IL-1β, and COX in the perfused brain. The fustin-treated group exhibited a significant restoration of memory function via modulation in behavioral activities. Moreover, 3-NPA altered biochemical, neurotransmitters, brain protein levels, and neuroinflammatory measures, which fustin efficiently restored. This is the first report demonstrating the efficacy of novel phytoconstituent fustin as a potential future candidate for the treatment of HD via offering neuroprotection by subsiding the oxidative and enzymatic activity in the 3-NPA experimental animal paradigm.

Antitumor Effects of Natural Compounds Derived from Allium sativum on Neuroblastoma: An Overview

Garlic (Allium sativum) has been used in alternative medicine to treat several diseases, such as cardiovascular and neurodegenerative diseases, cancer, and hepatic diseases. Several publications have highlighted other features of garlic, including its antibacterial, antioxidative, antihypertensive, and antithrombotic properties. The properties of garlic result from the combination of natural compounds that act synergistically and cause different effects. Some garlic-derived compounds have been studied for the treatment of several types of cancer; however, reports on the effects of garlic on neuroblastoma are scarce. Neuroblastoma is a prevalent childhood tumor for which the search for therapeutic alternatives to improve treatment without affecting the patients’ quality of life continues. Garlic-derived compounds hold potential for the treatment of this type of cancer. A review of articles published to date on some garlic compounds and their effect on neuroblastoma was undertaken to comprehend the possible therapeutic role of these compounds. This review aimed to analyze the impact of some garlic compounds on cells derived from neuroblastoma.

Cytoprotective Potential of Aged Garlic Extract (AGE) and Its Active Constituent, S-allyl-l-cysteine, in Presence of Carvedilol during Isoproterenol-Induced Myocardial Disturbance and Metabolic Derangements in Rats

This study was conducted to determine the potential interaction of aged garlic extract (AGE) with carvedilol (CAR), as well as to investigate the role of S-allyl-l-cysteine (SAC), an active constituent of AGE, in rats with isoproterenol (ISO)-induced myocardial dysfunction. At the end of three weeks of treatment with AGE (2 and 5 mL/kg) or SAC (13.1 and 32.76 mg/kg), either alone or along with CAR (10 mg/kg) in the respective groups of animals, ISO was administered subcutaneously to induce myocardial damage. Myocardial infarction (MI) diagnostic predictor enzymes, lactate dehydrogenase (LDH) and creatinine kinase (CK-MB), were measured in both serum and heart tissue homogenates (HTH). Superoxide dismutase (SOD), catalase, and thiobarbituric acid reactive species (TBARS) were estimated in HTH. When compared with other groups, the combined therapy of high doses of AGE and SAC given alone or together with CAR caused a significant decrease in serum LDH and CK-MB activities. Further, significant rise in the LDH and CK-MB activities in HTH was noticed in the combined groups of AGE and SAC with CAR. It was also observed that both doses of AGE and SAC significantly increased endogenous antioxidants in HTH. Furthermore, histopathological observations corroborated the biochemical findings. The cytoprotective potential of SAC and AGE were dose-dependent, and SAC was more potent than AGE. The protection offered by aged garlic may be attributed to SAC. Overall, the results indicated that a high dose of AGE and its constituent SAC, when combined with carvedilol, has a synergistic effect in preventing morphological and physiological changes in the myocardium during ISO-induced myocardial damage.

Incorporation of a Biocompatible Nanozyme in Cellular Antioxidant Enzyme Cascade Reverses Huntington's Like Disorder in Preclinical Model

The potentiality of nano-enzymes in therapeutic use has directed contemporary research to develop a substitute for natural enzymes, which are suffering from several disadvantages including low stability, high cost, and difficulty in storage. However, inherent toxicity, inefficiency in the physiological milieu, and incompatibility to function in cellular enzyme networks limit the therapeutic use of nanozymes in living systems. Here, it is shown that citrate functionalized manganese-based biocompatible nanoscale material (C-Mn₃ O₄ NP) efficiently mimics glutathione peroxidase (GPx) enzyme in the physiological milieu and easily incorporates into the cellular multienzyme cascade for H₂ O₂ scavenging. A detailed computational study reveals the mechanism of the nanozyme action. The in vivo therapeutic efficacy of C-Mn₃ O₄ nanozyme is further established in a preclinical animal model of Huntington's disease (HD), a prevalent progressive neurodegenerative disorder, which has no effective medication to date. Management of HD in preclinical animal trial using a biocompatible (non-toxic) nanozyme as a part of the metabolic network may uncover a new paradigm in nanozyme based therapeutic strategy.

Trends in H2S-Donors Chemistry and Their Effects in Cardiovascular Diseases

Hydrogen sulfide (H₂S) is an endogenous gasotransmitter recently emerged as an important regulatory mediator of numerous human cell functions in health and in disease. In fact, much evidence has suggested that hydrogen sulfide plays a significant role in many physio-pathological processes, such as inflammation, oxidation, neurophysiology, ion channels regulation, cardiovascular protection, endocrine regulation, and tumor progression. Considering the plethora of physiological effects of this gasotransmitter, the protective role of H₂S donors in different disease models has been extensively studied. Based on the growing interest in H₂S-releasing compounds and their importance as tools for biological and pharmacological studies, this review is an exploration of currently available H₂S donors, classifying them by the H₂S-releasing-triggered mechanism and highlighting those potentially useful as promising drugs in the treatment of cardiovascular diseases.

Protective Effect of Natural Products against Huntington's Disease: An Overview of Scientific Evidence and Understanding Their Mechanism of Action

Huntington's disease (HD), a neurodegenerative disease, normally starts in the prime of adult life, followed by a gradual occurrence of characteristic psychiatric disturbances and cognitive and motor dysfunction. To the best of our knowledge, there is no treatment available to completely mitigate the progression of HD. Among various therapeutic approaches, exhaustive literature reports have confirmed the medicinal benefits of natural products in HD experimental models. Building on this information, this review presents a brief overview of the neuroprotective mechanism(s) of natural products against in vitro/in vivo models of HD. Relevant studies were identified from several scientific databases, including PubMed, ScienceDirect, Scopus, and Google Scholar. After screening through literature from 2005 to the present, a total of 14 medicinal plant species and 30 naturally isolated compounds investigated against HD based on either in vitro or in vivo models were included in the present review. Behavioral outcomes in the HD in vivo model showed that natural compounds significantly attenuated 3-nitropropionic acid (3-NP) induced memory loss and motor incoordination. The biochemical alteration has been markedly alleviated with reduced lipid peroxidation, increased endogenous enzymatic antioxidants, reduced acetylcholinesterase activity, and increased mitochondrial energy production. Interestingly, following treatment with certain natural products, 3-NP-induced damage in the striatum was ameliorated, as seen histologically. Overall, natural products afforded varying degrees of neuroprotection in preclinical studies of HD via antioxidant and anti-inflammatory properties, preservation of mitochondrial function, inhibition of apoptosis, and induction of autophagy.

Kynurenine Pathway as a New Target of Cognitive Impairment Induced by Lead Toxicity During the Lactation

The immature brain is especially vulnerable to lead (Pb²⁺) toxicity, which is considered an environmental neurotoxin. Pb²⁺ exposure during development compromises the cognitive and behavioral attributes which persist even later in adulthood, but the mechanisms involved in this effect are still unknown. On the other hand, the kynurenine pathway metabolites are modulators of different receptors and neurotransmitters related to cognition; specifically, high kynurenic acid levels has been involved with cognitive impairment, including deficits in spatial working memory and attention process. The aim of this study was to evaluate the relationship between the neurocognitive impairment induced by Pb²⁺ toxicity and the kynurenine pathway. The dams were divided in control group and Pb²⁺ group, which were given tap water or 500 ppm of lead acetate in drinking water ad libitum, respectively, from 0 to 23 postnatal day (PND). The poison was withdrawn, and tap water was given until 60 PND of the progeny. The locomotor activity in open field, redox environment, cellular function, kynurenic acid (KYNA) and 3-hydroxykynurenine (3-HK) levels as well as kynurenine aminotransferase (KAT) and kynurenine monooxygenase (KMO) activities were evaluated at both 23 and 60 PND. Additionally, learning and memory through buried food location test and expression of KAT and KMO, and cellular damage were evaluated at 60 PND. Pb²⁺ group showed redox environment alterations, cellular dysfunction and KYNA and 3-HK levels increased. No changes were observed in KAT activity. KMO activity increased at 23 PND and decreased at 60 PND. No changes in KAT and KMO expression in control and Pb²⁺ group were observed, however the number of positive cells expressing KMO and KAT increased in relation to control, which correlated with the loss of neuronal population. Cognitive impairment was observed in Pb²⁺ group which was correlated with KYNA levels. These results suggest that the increase in KYNA levels could be a mechanism by which Pb²⁺ induces cognitive impairment in adult mice, hence the modulation of kynurenine pathway represents a potential target to improve behavioural alterations produced by this environmental toxin.

3-Hydroxykynurenine and 3-Hydroxyanthranilic Acid Enhance the Toxicity Induced by Copper in Rat Astrocyte Culture

Copper is an integral component of various enzymes, necessary for mitochondrial respiration and other biological functions. Excess copper is related with neurodegenerative diseases as Alzheimer and is able to modify cellular redox environment, influencing its functions, signaling, and catabolic pathways. Tryptophan degradation through kynurenine pathway produces some metabolites with redox properties as 3-hydroxykynurenine (3-HK) and 3-hydroxyanthranilic acid (3-HANA). The imbalance in their production is related with some neuropathologies, where the common factors are oxidative stress, inflammation, and cell death. This study evaluated the effect of these kynurenines on the copper toxicity in astrocyte cultures. It assessed the CuSO₄ effect, alone and in combination with 3-HK or 3-HANA on MTT reduction, ROS production, mitochondrial membrane potential (MMP), GHS levels, and cell viability in primary cultured astrocytes. Also, the chelating copper effect of 3-HK and 3-HANA was evaluated. The results showed that CuSO4 decreased MTT reduction, MMP, and GSH levels while ROS production and cell death are increasing. Coincubation with 3-HK and 3-HANA enhances the toxic effect of copper in all the markers tested except in ROS production, which was abolished by these kynurenines. Data suggest that 3-HK and 3-HANA increased copper toxicity in an independent manner to ROS production.

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.

Glycyrrhizin ameliorates oxidative stress and inflammation in hippocampus and olfactory bulb in lithium/pilocarpine-induced status epilepticus in rats

Glycyrrhizin (GL) is a triterpene present in the roots and rhizomes of Glycyrrhiza glabra that has anti-inflammatory, hepatoprotective and neuroprotective effects. Recently, it was demonstrated that GL produced neuroprotective effects on the postischemic brain as well as on the kainic acid injury model in rats. In addition to this, GL also prevented excitotoxic effects on primary cultures. The aims of the present study were to evaluate GL scavenging properties and to investigate GL's effect on oxidative stress and inflammation in the lithium/pilocarpine-induced seizure model in two cerebral regions, hippocampus and olfactory bulb, at acute time intervals (3 or 24h) after status epilepticus (SE). Fluorometric methods showed that GL scavenged three reactive oxygen species: hydrogen peroxide, peroxyl radicals and superoxide anions. In contrast, GL was unable to scavenge peroxynitrite, hydroxyl radicals, singlet oxygen and 2,2-diphenil-1-picrylhydrazyl (DPPH) radicals suggesting that GL is a weak scavenger. Additionally, administration of GL (50mg/kg, i.p.) 30min before pilocarpine administration significantly suppressed oxidative stress. Moreover, malondialdehyde levels were diminished and glutathione levels were maintained at control values in both cerebral regions at 3 and 24 after SE. At 24h after SE, glutathione S-transferase and superoxide dismutase activity increased in the hippocampus, while both glutathione reductase and glutathione peroxidase activity were unchanged in the olfactory bulb at that time. In addition, GL suppressed the induction of the proinflammatory cytokines interleukin-1 beta (IL-1β) and tumor necrosis factor alpha (TNF-α) in both cerebral regions evaluated. These results suggest that GL confers protection against pilocarpine damage via antioxidant and anti-inflammatory effects.

Protective Effects of AGE and Its Components on Neuroinflammation and Neurodegeneration

Garlic (Allium sativum) is used for culinary and medicinal purposes in diverse cultures worldwide. When fresh garlic is soaked in aqueous ethanol under ambient environment over 4 months or longer, the majority of irritating taste and odor is eliminated and the antioxidant profile in the resulting aged garlic extract (AGE) changes significantly. Recently, AGE and its components have been demonstrated to exert neuroprotective effects in neurodegenerative diseases, including Alzheimer's disease, Parkinson's disease, Huntington's disease, and cerebral ischemia. Because of its health supporting potential, there is increasing interest in understanding the antioxidant and anti-inflammatory properties and the underlying mechanisms for its protective effects in heath and disease. There is evidence for AGE to exert its action on distinct signaling pathways associated with oxidative stress and neuroinflammation, although the primary molecular mechanisms remain unclear. By utilizing quantitative proteomic approaches, we demonstrated that AGE and two of its major ingredients, S-allyl-L-cysteine and N (α)-(1-deoxy-D-fructos-1-yl)-L-arginine, can attenuate neuroinflammatory responses in microglial cells through modulation of Nrf2-mediated signaling as well as other oxidative stress-related pathways. These experimental data provide information for the molecular targets of AGE and its components to mitigate neurodegeneration and neuroinflammation and show a promising potential of these compounds as dietary supplements for health maintenance.

Glutathione-garlic sulfur conjugates: slow hydrogen sulfide releasing agents for therapeutic applications

Natural organosulfur compounds (OSCs) from Allium sativum L. display antioxidant and chemo-sensitization properties, including the in vitro inhibition of tumor cell proliferation through the induction of apoptosis. Garlic water- and oil-soluble allyl sulfur compounds show distinct properties and the capability to inhibit the proliferation of tumor cells. In the present study, we optimized a new protocol for the extraction of water-soluble compounds from garlic at low temperatures and the production of glutathionyl-OSC conjugates during the extraction. Spontaneously, Cys/GSH-mixed-disulfide conjugates are produced by in vivo metabolism of OSCs and represent active molecules able to affect cellular metabolism. Water-soluble extracts, with (GSGaWS) or without (GaWS) glutathione conjugates, were here produced and tested for their ability to release hydrogen sulfide (H₂S), also in the presence of reductants and of thiosulfate:cyanide sulfurtransferase (TST) enzyme. Thus, the TST catalysis of the H₂S-release from garlic OSCs and their conjugates has been investigated by molecular in vitro experiments. The antiproliferative properties of these extracts on the human T-cell lymphoma cell line, HuT 78, were observed and related to histone hyperacetylation and downregulation of GAPDH expression. Altogether, the results presented here pave the way for the production of a GSGaWS as new, slowly-releasing hydrogen sulfide extract for potential therapeutic applications.

Medicinal Chemistry: Insights into the Development of Novel H2S Donors

Hydrogen sulfide (H2S) was traditionally considered as a toxic gas. However, recent studies have demonstrated H2S is an endogenously generated gaseous signaling molecule (gasotransmitter) with importance on par with that of two other well-known endogenous gasotransmitters, nitric oxide (NO) and carbon monoxide (CO). Although H2S's exact mechanisms of action are still under investigation, the production of endogenous H2S and the exogenous administration of H2S have been demonstrated to elicit a wide range of physiological responses including modulation of blood pressure and protection of ischemia reperfusion injury, exertion of anti-inflammatory effects, and reduction of metabolic rate. These results strongly suggest that modulation of H2S levels could have potential therapeutic values. In this regard, synthetic H2S-releasing agents (i.e., H2S donors) are not only important research tools, but also potential therapeutic agents. This chapter summarizes the knowledge of currently available H2S donors. Their preparation, H2S releasing mechanisms, and biological applications are discussed.

Effect of aged garlic extract and s-allyl cysteine and their interaction with atenolol during isoproterenol induced myocardial toxicity in rats

Objectives:

The study evaluates the cardioprotective effect of aged garlic extract (AGE) and its constituent; S-allylcysteine (SAC) and their interaction with atenolol during isoproterenol induced cardiac toxicity in rats.

Materials and Methods:

Rats were administered AGE at two different doses of 2 ml/kg or 5 ml/kg orally whereas SAC was administered either at a dose 13.1 mg/kg or 32.76 mg/kg. The AGE or SAC was given alone or in combination with atenolol (6 mg/kg, p.o), every alternate day for three weeks. At the end of treatment, two doses of isoproterenol (150 mg/kg, s.c) were administered to rats. The electrocardiogram (ECG) was recorded followed by withdrawal of blood to estimate serum lactate dehydrogenase (LDH) and creatinine kinase-MB (CK-MB) activities. The activities of LDH, CK-MB as well as superoxide dismutase (SOD), catalase and thiobarbituric acid reactive substances (TBARS) were also determined in the heart tissue homogenate (HTH).

Results:

The isoproterenol induced ECG changes were restored to normal in all treated groups. The AGE and SAC administration caused a decrease in serum LDH and CK-MB activities and an elevation of LDH and CK-MB activities in HTH. Atenolol alone or in combination with AGE and S-allylcsyteine demonstrated similar changes in biomarker activities.

Conclusion:

AGE showed dose-dependent cardioprotection. However, concurrent administration of SAC with atenolol (6 mg/kg, p.o) combated more effectively the myocardial dysfunction during isoproterenol induced cardiotoxicity in rats.

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.

Electromagnetic fields, oxidative stress, and neurodegeneration

Electromagnetic fields (EMFs) originating both from both natural and manmade sources permeate our environment. As people are continuously exposed to EMFs in everyday life, it is a matter of great debate whether they can be harmful to human health. On the basis of two decades of epidemiological studies, an increased risk for childhood leukemia associated with Extremely Low Frequency fields has been consistently assessed, inducing the International Agency for Research on Cancer to insert them in the 2B section of carcinogens in 2001. EMFs interaction with biological systems may cause oxidative stress under certain circumstances. Since free radicals are essential for brain physiological processes and pathological degeneration, research focusing on the possible influence of the EMFs-driven oxidative stress is still in progress, especially in the light of recent studies suggesting that EMFs may contribute to the etiology of neurodegenerative disorders. This review synthesizes the emerging evidences about this topic, highlighting the wide data uncertainty that still characterizes the EMFs effect on oxidative stress modulation, as both pro-oxidant and neuroprotective effects have been documented. Care should be taken to avoid methodological limitations and to determine the patho-physiological relevance of any alteration found in EMFs-exposed biological system.

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.

Prospects for cannabinoid therapies in basal ganglia disorders

Cannabinoids are promising medicines to slow down disease progression in neurodegenerative disorders including Parkinson's disease (PD) and Huntington's disease (HD), two of the most important disorders affecting the basal ganglia. Two pharmacological profiles have been proposed for cannabinoids being effective in these disorders. On the one hand, cannabinoids like Δ(9) -tetrahydrocannabinol or cannabidiol protect nigral or striatal neurons in experimental models of both disorders, in which oxidative injury is a prominent cytotoxic mechanism. This effect could be exerted, at least in part, through mechanisms independent of CB(1) and CB(2) receptors and involving the control of endogenous antioxidant defences. On the other hand, the activation of CB(2) receptors leads to a slower progression of neurodegeneration in both disorders. This effect would be exerted by limiting the toxicity of microglial cells for neurons and, in particular, by reducing the generation of proinflammatory factors. It is important to mention that CB(2) receptors have been identified in the healthy brain, mainly in glial elements and, to a lesser extent, in certain subpopulations of neurons, and that they are dramatically up-regulated in response to damaging stimuli, which supports the idea that the cannabinoid system behaves as an endogenous neuroprotective system. This CB(2) receptor up-regulation has been found in many neurodegenerative disorders including HD and PD, which supports the beneficial effects found for CB(2) receptor agonists in both disorders. In conclusion, the evidence reported so far supports that those cannabinoids having antioxidant properties and/or capability to activate CB(2) receptors may represent promising therapeutic agents in HD and PD, thus deserving a prompt clinical evaluation.

Neuroprotective effects of phytocannabinoid-based medicines in experimental models of Huntington's disease

We studied whether combinations of botanical extracts enriched in either Δ(9)-tetrahydrocannabinol (Δ(9)-THC) or cannabidiol (CBD), which are the main constituents of the cannabis-based medicine Sativex, provide neuroprotection in rat models of Huntington's disease (HD). We used rats intoxicated with 3-nitropropionate (3NP) that were given combinations of Δ(9)-THC- and CBD-enriched botanical extracts. The issue was also studied in malonate-lesioned rats. The administration of Δ(9)-THC- and CBD-enriched botanical extracts combined in a ratio of 1:1 as in Sativex attenuated 3NP-induced GABA deficiency, loss of Nissl-stained neurons, down-regulation of CB(1) receptor and IGF-1 expression, and up-regulation of calpain expression, whereas it completely reversed the reduction in superoxide dismutase-1 expression. Similar responses were generally found with other combinations of Δ(9)-THC- and CBD-enriched botanical extracts, suggesting that these effects are probably related to the antioxidant and CB(1) and CB(2) receptor-independent properties of both phytocannabinoids. In fact, selective antagonists for both receptor types, i.e., SR141716 and AM630, respectively, were unable to prevent the positive effects on calpain expression caused in 3NP-intoxicated rats by the 1:1 combination of Δ(9)-THC and CBD. Finally, this combination also reversed the up-regulation of proinflammatory markers such as inducible nitric oxide synthase observed in malonate-lesioned rats. In conclusion, this study provides preclinical evidence in support of a beneficial effect of the cannabis-based medicine Sativex as a neuroprotective agent capable of delaying disease progression in HD, a disorder that is currently poorly managed in the clinic, prompting an urgent need for clinical trials with agents showing positive results in preclinical studies.

Maturation increases superoxide radical production without increasing oxidative damage in the skeletal muscle of hooded seals (Cystophora cristata)

Diving vertebrates represent unique models for the study of the physiological responses to reactive oxygen species (ROS) production and oxidative stress because of their adaptability to cope with dive-derived ROS production. We hypothesized that in the skeletal muscle of a diving mammal, the hooded seal ( Cystophora cristata (Erxleben, 1777)), ROS production increases with maturation but the accumulation of oxidative damage does not. To test this, we analyzed the tissue capacity to produce ROS, the accumulation of oxidative damage, and the activity and protein content of the cooper, zinc, and manganese dependent superoxide dismutases (Cu,ZnSOD, MnSOD) in skeletal muscle from neonates, weaned pups, and adult hooded seals. Our results showed higher tissue capacity to produce ROS, higher Cu,ZnSOD and MnSOD activities, and higher MnSOD protein content in adult seals than in pups. No differences in oxidative damage to lipids, proteins, or DNA were detected among groups. Results suggest that increased SOD activity likely counters the oxidative damage commonly associated with increased ROS production. These findings highlight the unusual tolerance of skeletal muscle of seals to increased ROS production.

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.

Antidiabetic effect of S-allylcysteine: Effect on plasma and tissue glycoproteins in experimental diabetes

The present study was conducted to investigate the effect of S-allylcysteine (SAC) on dearrangement in glycoprotein levels in the streptozotocin induced diabetic model. SAC (150 mg/kg b.w./day) was administered orally for 45 days to normal and diabetic rats. STZ-induced diabetic rats showed significant increase in blood glucose and glycoprotein components such as hexose, hexosamine, fucose and sialic acid in plasma, liver and kidneys of diabetic rats. Oral administration of SAC to diabetic rats for a period of 45 days normalized all the above-mentioned biochemical parameters. The antihyperglycemic effect of SAC was compared with glyclazide, a well-known antihyperglycemic drug. The present study indicates that SAC possesses a significantly beneficial effect on the glycoprotein moiety in addition to its antidiabetic effect.

Beneficial effect of S-allylcysteine (SAC) on blood glucose and pancreatic antioxidant system in streptozotocin diabetic rats

The aim of the present study was to evaluate the possible protective effects of S-allyl cysteine (SAC) on the antioxidant defense system of pancreas in streptozotocin(STZ) induced diabetes in rats. The levels of blood glucose and TBARS in plasma and pancreas were estimated in control and experimental groups of rats. To assess the changes in the cellular antioxidant defense system, the level of reduced glutathione in plasma and pancreas and activities of superoxide dismutase and catalase were assayed in pancreatic tissue homogenate. The levels of glucose, TBARS and enzymatic antioxidants were altered in diabetic rats. These alterations were reverted back to near control levels after the treatment of SAC. The antidiabetic and antioxidant effect of SAC was compared with glyclazide, a well-known hypoglycemic drug. These findings suggest that SAC treatment exerts a therapeutic protective nature in diabetes by decreasing oxidative stress.

Potential of garlic and its active constituent, S-allyl cysteine, as antihypertensive and cardioprotective in presence of captopril

The purpose of the present study was to investigate the role of fresh garlic homogenate (FGH) and its bioactive sulphur compound S-allyl cysteine sulphoxide (SACS) in potentiating antihypertensive and cardioprotective activities of captopril in rats. SACS was extracted from the fresh garlic using ion exchange resins with yield of 890 mg/kg garlic. The dose of SACS was calculated based on the amount of SACS extracted from 125 to 250 mg of FGH. Albino rats weighing 150-200 g were fed with 10% fructose in fluid for 3 weeks for induction of hypertension and subsequently administered FGH (125 and 250 mg/kg, p.o.) or SACS (0.111 and 0.222 mg/kg/day, p.o.) for the next 3 weeks in their respective groups. In CAP alone and interactive groups (GH+CAP; SACS+CAP), captopril 30 mg/kg was given during sixth week of 10% fructose in fluid. At the end of drug treatment, animals were given isoproterenol 175 mg/kg subcutaneously for two consecutive days. Additionally, varying concentrations of SACS (4, 8, 16, 32 and 64 ng), CAP (1, 2, 4, 8 and 16 ng) and their combination (4:1) were checked for fall in blood pressure in hypertensive rats (10% fructose in fluid without pretreatment) as well as angiotensin-converting enzyme (ACE) inhibiting activity using guinea pig ileum. An isobolographic analysis was used to characterise the interaction between SACS and CAP for fall in blood pressure and ACE inhibiting evaluations. Administration of captopril, low and high doses of FGH (125, 250 mg/kg), either alone or together showed fall in fluid intake and body weight. The combined therapy of FGH 250 mg/kg and CAP was more effective in reducing systolic blood pressure, cholesterol, triglycerides and glucose. The SOD and catalase activities in heart tissue were significantly elevated in groups treated with FGH, SACS, CAP, FGH+CAP and SACS+CAP. Further, combined therapy of FGH 250 mg/kg and CAP caused significant fall in LDH and CK-MB activities in serum and elevation in heart tissue homogenate. SACS in low dose was less effective than low dose of FGH; similarly, high dose of FGH was more efficacious than high dose of SACS. Corroborating with this, combined therapy of garlic (250 mg/kg) with CAP demonstrated higher synergistic action than combination of SACS (0.222 mg/kg) with CAP suggesting the role of additional bioactive constituents apart from SACS, responsible for therapeutic efficacy of garlic. Moreover, combination of SACS and CAP exerted super-additive (synergistic) interaction with respect to fall in blood pressure and ACE inhibition. This study may represent an advertence on concomitant use of garlic or its bioactive constituent, SACS, with captopril.

3-Nitropropionic acid as a tool to study the mechanisms involved in Huntington's disease: past, present and future

Huntington's disease (HD) is an inheritable autosomal-dominant disorder whose causal mechanisms remain unknown. Experimental models have begun to uncover these pathways, thus helping to understand the mechanisms implicated and allowing for the characterization of potential targets for new therapeutic strategies. 3-Nitropropionic acid is known to produce in animals behavioural, biochemical and morphologic changes similar to those occurring in HD. For this reason, this phenotypic model is gaining attention as a valuable tool to mimick this disorder and further developing new therapies. In this review, we will focus on the past and present research of this molecule, to finally bring a perspective on what will be next in this promising field of study.

Possible neuroprotective effect of Withania somnifera root extract against 3-nitropropionic acid-induced behavioral, biochemical, and mitochondrial dysfunction in an animal model of Huntington's disease

Huntington's disease (HD) is a neurodegenerative disorder that results from the destruction of neurons in the basal ganglia, and oxidative stress has been implicated in its pathogenesis. 3-Nitropropionic acid (3-NP), a potent neurotoxin, has been reported to induce oxidative/nitrosative stress and causes neurobehavioral and biochemical changes that mimic HD in humans. It also inhibits complex II of the mitochondrial electron transport chain, thereby causing cellular energy deficit. In the present work, we evaluated the effects of a well-known antioxidant on behavioral, biochemical, and mitochondrial dysfunction induced by 3-NP. The study was designed to investigate the effects of Withania somnifera root extract against 3-NP-induced gait abnormalities, oxidative stress, and mitochondrial dysfunction in striatum and cortex of rat brain. Intraperitoneal administration of 3-NP (10 mg/kg for 14 days) caused a loss in body weight and a decline in motor function (locomotor activity and impaired rotarod activity). Chronic treatment with W. somnifera root extracts (100 and 200 mg/kg) for a period of 2 weeks dose-dependently improved 3-NP-induced behavioral, biochemical, and enzymatic changes (P < .05). Biochemical analysis revealed that systemic 3-NP administration significantly increased lipid peroxidation and nitrite and lactate dehydrogenase enzyme levels, depleted antioxidant enzyme (superoxide dismutase and catalase) levels, and blocked ATP synthesis by inhibiting the mitochondrial complex activity in the different regions (striatum and cortex) of the brain. Chronic administration of W. somnifera root extract (100 and 200 mg/kg) dose-dependently restored biochemical alterations induced by chronic 3-NP treatment (P < .05). These findings suggest that neuroprotective actions of W. somnifera are mediated via its antioxidant activity. However, further studies are required to elucidate the molecular mechanisms involved in order to support the clinical use of the plant extract as a therapeutic agent for the treatment of HD.

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.

Heterolytic reduction of fatty acid hydroperoxides by cytochrome c/cardiolipin complexes: antioxidant function in mitochondria

Cytochrome c (cyt c), a mitochondrial intermembrane electron shuttle between complexes III and IV, can, upon binding with an anionic phospholipid, cardiolipin (CL), act as a peroxidase that catalyzes cardiolipin oxidation. H(2)O(2) was considered as a source of oxidative equivalents for this reaction, which is essential for programmed cell death. Here we report that peroxidase cyt c/CL complexes can utilize free fatty acid hydroperoxides (FFA-OOH) at exceptionally high rates that are approximately 3 orders of magnitude higher than for H(2)O(2). Similarly, peroxidase activity of murine liver mitochondria was high with FFA-OOH. Using EPR spin trapping and LC-MS techniques, we have demonstrated that cyt c/CL complexes split FFA-OOH predominantly via a heterolytic mechanism, yielding hydroxy-fatty acids, whereas H(2)O(2) (and tert-butyl hydroperoxide, t-BuOOH) undergo homolytic cleavage. Computer simulations have revealed that Arg(38) and His(33) are important for the heterolytic mechanism at potential FFA-OOH binding sites of cyt c (but not for H(2)O(2) or t-BuOOH). Regulation of FFA-OOH metabolism may be an important function of cyt c that is associated with elimination of toxic FFA-OOH and synthesis of physiologically active hydroxy-fatty acids in mitochondria.

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.