s-Allyl cysteine, s-ethyl cysteine, and s-propyl cysteine alleviate β-amyloid, glycative, and oxidative injury in brain of mice treated by D-galactose

Untargeted metabolomics reveals intervention effects of wine-processed Schisandra chinensis polysaccharide on Alzheimer's disease mice

Schisandra chinensis (Turcz.) Baill (SC) is a traditional sedative in China, with wide applications for treating various neurological disorders. Its polysaccharide component has been gaining increased attention for its potential in nerve protection. While raw SC is the primary focus of current research, its processed products are primarily utilized as clinical medicines. Notably, limited research exists on the mechanisms underlying the effects of wine-processed Schisandra chinensis polysaccharide (WSCP) in Alzheimer's Disease (AD). Therefore, this study seeks to assess the therapeutic impact of WSCP on AD mice and investigate the underlying mechanisms through biochemical and metabolomics analyses. The results demonstrate that WSCP exerts significant therapeutic effects on AD mice by enhancing learning and memory abilities, mitigating hippocampal neuronal damage, reducing abnormal amyloid-beta (Aβ) deposition, and attenuating hyperphosphorylation of Tau. Biochemical analysis revealed that WSCP can increase SOD content and decrease MDA, IL-6, and TNF-α content in AD mice. Furthermore, serum metabolomic results showed that WSCP intervention can reverse metabolic disorders in AD mice. 43 endogenous metabolites were identified as potential biomarkers for WSCP treatment of AD, and the major metabolic pathways were Ala, Glu and Asp metabolism, TCA cycle. Overall, these findings will provide a basis for further development of WSCP.

Progress in the development of naturally derived active metabolites-based drugs: Potential therapeutics for Alzheimer's disease

Alzheimer's disease (AD) is an extensive age-associated neurodegenerative disorder. In spite of wide-ranging progress in understanding the AD pathology for the past 50 years, clinical trials based on the hypothesis of amyloid-beta (Aβ) have reserved worsening particularly at late-stage human trials. Consequently, very few old drugs are presently used for AD with inadequate clinical consequences and various side effects. We focus on widespread pharmacological and beneficial principles for existing as well as future drugs. Multitargeting approaches by means of general antioxidant and anti-inflammatory mechanisms allied with particular receptor and/or enzyme-mediated actions in neuroprotection and neurodegeneration. The plant kingdom comprises a vast range of species with an incredible diversity of bioactive metabolites with diverse chemical scaffolds. In recent times, an increasing body of facts recommended the use of phytochemicals to decelerate AD's onset and progression. The definitive goal of AD investigation is to avert the onset of neurodegeneration, thereby allowing successful aging devoid of cognitive decline. At this point, we discussed the neurological protective role of natural products and naturally derived therapeutic agents for AD from various natural polyphenolic compounds and medicinal plants. In conclusion, medicinal plants act as a chief source of different bioactive constituents.

Use of Steaming Process to Improve Biochemical Activity of Polygonatum sibiricum Polysaccharides against D-Galactose-Induced Memory Impairment in Mice

Polysaccharide from Polygonatum sibiricum (PSP) possesses antioxidant, antiaging, and neuroprotective activities. However, whether and how the steaming process influences the biological activities of PSP, especially against aging-related memory impairment, is not yet known. In this study, Polygonatum sibiricum rhizome was subjected to a “nine steaming and nine drying” process, then PSPs with different steaming times were abstracted. Thereafter, the physicochemical properties were qualified; the antioxidant activities of PSPs were evaluated in a D-gal-induced HT-22 cell model, and the effects of PSPs (PSP0, PSP5 and PSP9) on memory was evaluated using D-gal-injured mice. Our results showed that while the steamed PSPs had a low pH value and a large negative charge, they shared similar main chains and substituents. Cellular experiments showed that the antioxidant activity of steamed PSPs increased. PSP0, PSP5, and PSP9 could significantly ameliorate the memory impairment of D-gal-injured mice, with PSP5 showing the optimal effect. Meanwhile, PSP5 demonstrated the best effect in terms of preventing cell death and synaptic injury in D-gal-injured mice. Additionally, the steamed PSPs increased anti-oxidative stress-related protein expression and decreased inflammation-related protein expression in D-gal-injured mice. Collectively, the steaming process improves the effects of PSPs against D-gal-induced memory impairment in mice, likely by increasing the antioxidant activity of PSPs.

Therapeutic Potential of Allicin and Aged Garlic Extract in Alzheimer’s Disease

Garlic, Allium sativum, has long been utilized for a number of medicinal purposes around the world, and its medical benefits have been well documented. The health benefits of garlic likely arise from a wide variety of components, possibly working synergistically. Garlic and garlic extracts, especially aged garlic extracts (AGEs), are rich in bioactive compounds, with potent anti-inflammatory, antioxidant and neuroprotective activities. In light of these effects, garlic and its components have been examined in experimental models of Alzheimer’s disease (AD), the most common form of dementia without therapy, and a growing health concern in aging societies. With the aim of offering an updated overview, this paper reviews the chemical composition, metabolism and bioavailability of garlic bioactive compounds. In addition, it provides an overview of signaling mechanisms triggered by garlic derivatives, with a focus on allicin and AGE, to improve learning and memory.

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.

DL0410 Alleviates Memory Impairment in D-Galactose-Induced Aging Rats by Suppressing Neuroinflammation via the TLR4/MyD88/NF-κB Pathway

Oxidative stress and neuroinflammation have been demonstrated to be linked with Alzheimer's disease (AD). In this study, we examined the protective effects of DL0410 in aging rats and explored the underlying mechanism against oxidative damage and neuroinflammation, which was then validated in LPS-stimulated BV2 microglia. We firstly investigated the improvement effects of DL0410 on learning and memory abilities and explored the potential mechanisms in D-gal-induced aging rats. An 8-week treatment with DL0410 significantly improved the learning and cognitive function of D-gal-stimulated Alzheimer's-like rats in the Morris water maze test, step-down test, and novel object recognition test, and the therapeutic effect of DL0410 at 10 mg/kg was even better than that of donepezil. What is more, the results showed that DL0410 alleviated neuron injury, increased the number of synapses, and improved the level of postsynaptic density protein 95 (PSD95) in the hippocampus and cortex. Next, we examined the protective effects of DL0410 against oxidative damage and neuroinflammation. Our observations indicated that DL0410 reduced the production of harmful oxidation products and promoted the antioxidative system, decreased the levels of proinflammatory cytokines, including tumor necrosis factor α (TNF-α), interleukin 1β (IL-1β), and interleukin 6 (IL-6), and increased anti-inflammatory cytokines IL-10. Moreover, DL0410 inhibited the activation of astrocytes and microglia and suppressed the activation of the TLR4/MyD88/NF-κB signaling pathway. The anti-inflammation effect of DL0410 was further confirmed in LPS-stimulated BV2 cells, and the results showed that DL0410 reduced the level of inflammatory factors and inhibited the activation of the TLR4/MyD88/TRAF6/NF-κB signaling pathway in BV2 microglia. Molecular docking results indicated that DL0410 occupied the LPS recognition site in the TLR4/MD2 complex. Furthermore, the enhanced expression of claudin-1, claudin-5, occludin, CX43, and ZO-1 indicated that DL0410 protected the blood-brain barrier (BBB) integrity. Together, these results suggest that DL0410 exerts neuroprotective effects against hippocampus and cortex injury induced by D-galactose, and the possible mechanisms include antioxidative stress, antineuroinflammation, improving synaptic plasticity, and maintaining BBB integrity, which is mediated by the TLR4/MyD88/NF-κB signaling pathway inhibition. We suggest that DL0410 is a promising candidate for AD treatment.

Preventive electroacupuncture reduces cognitive deficits in a rat model of D-galactose-induced aging

Acupuncture can reduce cognitive deficits in Alzheimer’s disease. However, whether electroacupuncture can prevent or alleviate the cognitive deficits in animal models of aging remains poorly understood. Studies have shown that disordered epigenetic modifications play a critical role in age-related cognitive decline. Therefore, we hypothesized that preventive electroacupuncture might improve cognitive functions during aging by regulating epigenetic modifications. A rat model of aging was produced by intraperitoneal injection of 120 mg/kg D-galactose for 8 weeks. Baihui and Shenshu acupoints were stimulated by electroacupuncture for 8 weeks from the first day of D-galactose administration. Preventive electroacupuncture alleviated memory impairment, decreased tau hyperphosphorylation, and reduced glycogen synthase kinase-3β protein and mRNA expression levels in the brainstem dorsal raphe nucleus, where intracellular neurofibrillary tangle lesions first occur. In addition, the DNA methylation level in the promoter region of the glycogen synthase kinase-3β gene was increased. The effects of preventive electroacupuncture were stronger than those of preventive acupuncture. Intraperitoneal injection of 0.4 mg/kg 5-aza-2′-deoxycytidine, an inhibitor of DNA methyltransferase that blocks epigenetic modifications, antagonized the effects of preventive electroacupuncture. Our results suggest that preventive electroacupuncture treatment alleviates cognitive impairment in aging rats probably by affecting the epigenetic modification of the glycogen synthase kinase-3β gene in the dorsal raphe nucleus. This study was approved by the Animal Ethics Committee of Hubei University of Chinese Medicine, China (approval No. HUCMS201712001) on November 28, 2017.

Critical Review of the Alzheimer's Disease Non-Transgenic Models: Can They Contribute to Disease Treatment?

Alzheimer's disease (AD) is a growing neurodegenerative disease without effective treatments or therapies. Despite the use of different approaches and an extensive variety of genetic amyloid based models, therapeutic strategies remain elusive. AD is characterized by three main pathological hallmarks that include amyloid-β plaques, neurofibrillary tangles, and neuroinflammatory processes; however, many other pathological mechanisms have been described in the literature. Nonetheless, the study of the disease and the screening of potential therapies is heavily weighted toward the study of amyloid-β transgenic models. Non-transgenic models may aid in the study of complex pathological states and provide a suitable complementary alternative to evaluating therapeutic biomedical and intervention strategies. In this review, we evaluate the literature on non-transgenic alternatives, focusing on the use of these models for testing therapeutic strategies, and assess their contribution to understanding AD. This review aims to underscore the need for a shift in preclinical research on intervention strategies for AD from amyloid-based to alternative, complementary non-amyloid approaches.

Attenuation of Nrf2/Keap1/ARE in Alzheimer's Disease by Plant Secondary Metabolites: A Mechanistic Review

Alzheimer’s disease (AD) is a progressive neuronal/cognitional dysfunction, leading to disability and death. Despite advances in revealing the pathophysiological mechanisms behind AD, no effective treatment has yet been provided. It urges the need for finding novel multi-target agents in combating the complex dysregulated mechanisms in AD. Amongst the dysregulated pathophysiological pathways in AD, oxidative stress seems to play a critical role in the pathogenesis progression of AD, with a dominant role of nuclear factor erythroid 2-related factor 2 (Nrf2)/Kelch-like ECH-associated protein-1 (Keap1)/antioxidant responsive elements (ARE) pathway. In the present study, a comprehensive review was conducted using the existing electronic databases, including PubMed, Medline, Web of Science, and Scopus, as well as related articles in the field. Nrf2/Keap1/ARE has shown to be the upstream orchestrate of oxidative pathways, which also ameliorates various inflammatory and apoptotic pathways. So, developing multi-target agents with higher efficacy and lower side effects could pave the road in the prevention/management of AD. The plant kingdom is now a great source of natural secondary metabolites in targeting Nrf2/Keap1/ARE. Among natural entities, phenolic compounds, alkaloids, terpene/terpenoids, carotenoids, sulfur-compounds, as well as some other miscellaneous plant-derived compounds have shown promising future accordingly. Prevailing evidence has shown that activating Nrf2/ARE and downstream antioxidant enzymes, as well as inhibiting Keap1 could play hopeful roles in overcoming AD. The current review highlights the neuroprotective effects of plant secondary metabolites through targeting Nrf2/Keap1/ARE and downstream interconnected mediators in combating AD.

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.

s-Ethyl cysteine, an amino acid derivative, attenuated cisplatin induced nephrotoxicity

Renal protection from s-ethyl cysteine (SEC) against cisplatin (CP)-induced inflammatory and oxidative injury was examined. Mice were divided into five groups: normal group, 0.25% SEC group, CP group, 0.125% SEC + CP group, 0.25% SEC + CP group. After 2 weeks supplementation, mice of CP and SEC + CP groups received CP treatment. H&E stain showed that CP caused infiltration of inflammatory cells and necrosis of tubular cells. SEC pre-treatments attenuated CP-induced inflammatory injury and degeneration. SEC pre-treatments limited CP-stimulated release of interleukin (IL)-1beta, IL-6, tumor necrosis factor-alpha and prostaglandin E₂ in kidney. CP raised the renal activity and mRNA expression of cyclooxygenase-2 and nuclear factor kappa B. SEC pre-treatments reversed these alterations. CP increased the production of reactive oxygen species and nitric oxide, and lowered glutathione content, glutathione peroxidase and glutathione reductase activities in kidney. SEC pre-treatments reversed these changes. CP up-regulated renal inducible nitric oxide synthase (iNOS) mRNA expression, and down-regulated nuclear factor E2-related factor (Nrf)-2 and heme oxygenase (HO)-1 mRNA expression. SEC pre-treatments suppressed iNOS mRNA expression; and enhanced renal Nrf2 and HO-1 mRNA expression. These novel findings suggest that dietary SEC via exerting its multiple bio-functions could be considered as a protective agent for kidney against CP.

Neuroprotection: Targeting Multiple Pathways by Naturally Occurring Phytochemicals

With the increase in the expectancy of the life span of humans, neurodegenerative diseases (NDs) have imposed a considerable burden on the family, society, and nation. In defiance of the breakthroughs in the knowledge of the pathogenesis and underlying mechanisms of various NDs, very little success has been achieved in developing effective therapies. This review draws a bead on the availability of the nutraceuticals to date for various NDs (Alzheimer's disease, Parkinson's disease, Amyotrophic lateral sclerosis, Huntington's disease, vascular cognitive impairment, Prion disease, Spinocerebellar ataxia, Spinal muscular atrophy, Frontotemporal dementia, and Pick's disease) focusing on their various mechanisms of action in various in vivo and in vitro models of NDs. This review is distinctive in its compilation to critically review preclinical and clinical studies of the maximum phytochemicals in amelioration and prevention of almost all kinds of neurodegenerative diseases and address their possible mechanism of action. PubMed, Embase, and Cochrane Library searches were used for preclinical studies, while ClinicalTrials.gov and PubMed were searched for clinical updates. The results from preclinical studies demonstrate the efficacious effects of the phytochemicals in various NDs while clinical reports showing mixed results with promise for phytochemical use as an adjunct to the conventional treatment in various NDs. These studies together suggest that phytochemicals can significantly act upon different mechanisms of disease such as oxidative stress, inflammation, apoptotic pathways, and gene regulation. However, further clinical studies are needed that should include the appropriate biomarkers of NDs and the effect of phytochemicals on them as well as targeting the appropriate population.

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.

Aloin attenuates cognitive impairment and inflammation induced by d-galactose via down-regulating ERK, p38 and NF-κB signaling pathway

Oxidative stress is considered as major culprit for neurodegenerative diseases and triggers cognitive and memory impairments. The present study mainly aimed to study the protective effects and underlying mechanisms of aloin on d-galactose (d-gal) induced ageing mice. Our results demonstrated that chronic administration of d-gal (150 mg kg^-1) in mice caused spontaneous and cognitive impairments, as determined by open-field test and Morris water-maze test. Aloin treatment significantly ameliorated histopathological damage, attenuated the microglia activation and reduced levels of inflammatory mediators, such as tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β) and IL-6 in the hippocampus. Moreover, it effectively suppressed the level of reactive oxygen species (ROS) and increased antioxidant enzymes activities. Further data showed that these protective effects were accompanied by inhibition of the activation of nuclear factor kappa B and the phosphorylation of p38 and ERK. In conclusion, the present study suggests that aloin can ameliorate d-gal induced oxidative stress, cognitive impairment and inflammation, possibly via mediating the ERK, p38 and NF-κB signaling pathways.

Lycopene Supplementation Attenuates Oxidative Stress, Neuroinflammation, and Cognitive Impairment in Aged CD-1 Mice

The carotenoid pigment lycopene (LYC) possesses several properties, including antioxidative, anti-inflammatory, and neuroprotective properties. This study examined the effects of dietary supplementation with LYC on age-induced cognitive impairment, and the potential underlying mechanisms. Behavioral tests revealed that chronic LYC supplementation alleviated age-associated memory loss and cognitive defects. Histological and immunofluorescence-staining results indicated that LYC treatment reversed age-associated neuronal damage and synaptic dysfunctions in the brain. Additionally, LYC supplementation decreased age-associated oxidative stress via suppression of malondialdehyde levels, which increased glutathione, catalase, and superoxide dismutase activities and the levels of antioxidant-enzyme mRNAs, including those of heme oxygenase 1 and NAD-(P)-H-quinone oxidoreductase-1. Furthermore, LYC supplementation significantly reduced age-associated neuroinflammation by inhibiting microgliosis (Iba-1) and downregulating related inflammatory mediators. Moreover, LYC lowered the accumulation of Aβ_1-42 in the brains of aged CD-1 mice. Therefore, LYC has the potential for use in the treatment of several age-associated chronic diseases.

Supplementation of lycopene attenuates oxidative stress induced neuroinflammation and cognitive impairment via Nrf2/NF-κB transcriptional pathway

Oxidative stress, considered as a major culprit in brain aging, triggers cognitive and memory impairment. Lycopene (LYC), a carotenoid pigment, possesses potent antioxidative, anti-inflammatory, and neuroprotective properties. In the present study, the effects of LYC on oxidative stress-induced cognitive defects and the underlying mechanisms were determined. The behavioral tests, including Y-maze test, locomotor activity and Morris water maze test, revealed that chronic LYC supplementation (50 mg/kg bodyweight per day) alleviated d-galactose induced CD-1 male mice cognitive impairments. LYC ameliorated histopathological damage and restored brain derived neurotrophic factor (BDNF) levels in the hippocampus of mice. LYC also significantly elevated antioxidant enzymes activities and reduced levels of inflammatory cytokines in the d-galactose-treated mice serum. Moreover, LYC treatment activated the mRNA expressions of antioxidant enzymes HO-1 and NQO-1, and downregulated inflammatory cytokines IL-1β and TNF-α in mice hippocampus. Immunohistochemical results also demonstrated that LYC significantly restored the expression of glial cells inflammatory makers Iba-1 and GFAP. Furthermore, LYC attenuated neuronal oxidative damage through activation of Nrf2 signaling and inactivation of NF-κB translocation in a H₂O₂-induced SH-SY5Y cell model. Therefore, these results illustrated that LYC could ameliorate oxidative stress induced neuroinflammation and cognitive impairment possibly via mediating Nrf2/NF-κB transcriptional pathway.

Chronic Administration of S-Allylcysteine Activates Nrf2 Factor and Enhances the Activity of Antioxidant Enzymes in the Striatum, Frontal Cortex and Hippocampus

Oxidative stress plays an important role in neurodegenerative diseases and aging. The cellular defense mechanisms to deal with oxidative damage involve the activation of transcription factor related to NF-E2 (Nrf2), which enhances the transcription of antioxidant and phase II enzyme genes. S-allylcysteine (SAC) is an antioxidant with neuroprotective properties, and the main organosulfur compound in aged garlic extract. The ability of SAC to activate the Nrf2 factor has been previously reported in hepatic cells; however this effect has not been studied in normal brain. In order to determine if the chronic administration of SAC is able to activate Nrf2 factor and enhance antioxidant defense in the brain, male Wistar rats were administered with SAC (25, 50, 100 and 200 mg/kg-body weight each 24 h, i.g.) for 90 days. The activation of Nrf2, the levels of p65 and 8-hydroxy-2-deoxyguanosine (8-OHdG) as well as the activities of the enzymes glutathione peroxidase (GPx), glutathione reductase (GR), catalase (CAT), superoxide dismutase (SOD), and glutathione S-transferase (GST) were evaluated in the hippocampus, striatum and frontal cortex. Results showed that SAC activated Nrf2 factor in the hippocampus (25-200 mg/kg) and striatum (100 mg/kg) and significantly decreased p65 levels in the frontal cortex (25-200 mg/kg). On the other hand, SAC increased GPx, GR, CAT and SOD activities mainly in the hippocampus and striatum, but it did not change GST activity. Finally, no changes were observed in 8-OHdG levels mediated by SAC in any brain region, but the hippocampus showed a major level of 8-OHdG compared with the striatum and frontal cortex. All these results suggest that in the hippocampus, the observed increase in the activity of antioxidant enzymes could be associated with the ability of SAC to activate Nrf2 factor; however, a different mechanism could be involved in the striatum and frontal cortex, since no changes were found in Nrf2 activation and p65 levels.

S-allyl cysteine ameliorates cognitive deficits in streptozotocin-diabetic rats via suppression of oxidative stress, inflammation, and acetylcholinesterase

Diabetes mellitus (DM) is associated with learning, memory, and cognitive deficits. S-allyl cysteine (SAC) is the main organosulfur bioactive molecule in aged garlic extract with anti-diabetic, antioxidant, anti-inflammatory and nootropic property. This research was conducted to evaluate the efficacy of SAC on alleviation of learning and memory deficits in streptozotocin (STZ)-diabetic rats and to explore involvement of toll-like receptor 4 (TLR4), nuclear factor (erythroid-derived 2)-like 2 (Nrf2), nuclear factor-kappa B (NF-κB), and heme oxygenase 1 (HO-1) signaling cascade. Male Wistar rats were divided into control, diabetic, SAC-treated diabetic, and glibenclamide-treated diabetic (positive control) groups. SAC was administered at a dose of 150mg/kg for seven weeks. Treatment of diabetic rats with SAC lowered serum glucose, improved spatial recognition memory in Y maze, discrimination ratio in novel object recognition task, and restored step-through latency (STL) in passive avoidance paradigm. In addition, SAC reduced acetylcholinesterase activity, lipid peroxidation marker malondialdehyde (MDA) and augmented antioxidant defensive system including superoxide dismutase (SOD), catalase and reduced glutathione (GSH) in hippocampal lysate. Meanwhile, SAC lowered hippocampal NF-kB, TLR4, and TNFα and prevented reduction of Nrf2 and heme oxygenase-1 (HO-1) in diabetic rats. Taken together, chronic SAC treatment could ameliorate cognitive deficits in STZ-diabetic rats through modulation of Nrf2/NF-κB/TLR4/HO-1, and acetylcholinesterase and attenuation of associated oxidative stress and neuroinflammation.

The antioxidative properties of S-allyl cysteine not only influence somatic cells but also improve early embryo cleavage in pigs

In vitro cultivation systems for oocytes and embryos are characterised by increased levels of reactive oxygen species (ROS), which can be balanced by the addition of suitable antioxidants. S-allyl cysteine (SAC) is a sulfur compound naturally occurring in garlic (Allium sativum), which is responsible for its high antioxidant properties. In this study, we demonstrated the capacity of SAC (0.1, 0.5 and 1.0 mM) to reduce levels of ROS in maturing oocytes significantly after 24 (reduced by 90.33, 82.87 and 91.62%, respectively) and 48 h (reduced by 86.35, 94.42 and 99.05%, respectively) cultivation, without leading to a disturbance of the standard course of meiotic maturation. Oocytes matured in the presence of SAC furthermore maintained reduced levels of ROS even 22 h after parthenogenic activation (reduced by 66.33, 61.64 and 57.80%, respectively). In these oocytes we also demonstrated a growth of early embryo cleavage rate (increased by 33.34, 35.00 and 35.00%, respectively). SAC may be a valuable supplement to cultivation media.

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.

Lignans from Schisandra chinensis ameliorate cognition deficits and attenuate brain oxidative damage induced by D-galactose in rats

The aim of this study was to explore the neuroprotective effects of active compounds from Schisandra chinensis (Trucz.) Baill. (Magnoliaceae) against the D-galactose (D-gal)-induced neurotoxicity in rat. The Wistar rats were subcutaneously injected with D-gal (150 mg/(kg day)) for six weeks and orally administered with water extract or 95 % ethanol extract (partitioned with petroleum ether (PE), chloroform (CF), ethyl acetate (EA) and n-Butanol (NB), respectively) of the fruits of Schisandra chinensis simultaneously. The alteration of cognitive functions was assessed by using Morris water maze and Step-down type passive avoidance test. The results demonstrated that PE fraction was the most effective fraction to ameliorate cognitive deficits. Further biochemical examination indicated that PE could attenuate the activities decreasing of superoxide dismutase (SOD), catalase (CAT), the total antioxidant (T-AOC) induced by D-gal, and maintain the normal levels of glutathione (GSH), malondialdehyde (MDA) and nitric oxide (NO) in the serum, prefrontal cortex, striatum and hippocampus of the brain of related rat, selectively. Meanwhile, the compounds of PE fraction were also identified as mainly lignans, thus, these results suggest that lignans from the PE fraction of Schisandra chinensis represented a potential source of medicine for the treatment of the aging-associated neurodegenerative diseases.

S-allyl cysteine ameliorates the quality of sperm and provides protection from age-related sperm dysfunction and oxidative stress in rats

Reactive oxygen species play a central role in the pathophysiology of the age-related decrease in male fertility. It has been reported that the total protein of DJ-1 was decreased in a proteomic analysis of seminal plasma from asthenozoospermia patients and a DJ-1 protein acts as a sensor of cellular redox homeostasis. Therefore, we evaluated the age-related changes in the ratio of the oxidized/reduced forms of the DJ-1 protein in the epididymis. In addition, the protective effects of S-allyl cysteine (SAC), a potent antioxidant, were evaluated against sperm dysfunction. Male rats aged 15–75 weeks were used to assess age-associated sperm function and oxidative stress. Sperm count increased until 25 weeks, but then decreased at 50 and 75 weeks. The rate of sperm movement at 75 weeks was decreased to approximately 60% of the rate observed at 25 weeks. Expression of DJ-1 decreased, but oxidized-DJ-1 increased with age. In addition, 4-hydroxy-2-nonenal modified proteins in the epididymis increased until 50 weeks of age. The total number and DNA synthetic potential of the sperm increased until 25 weeks, and then decreased. In rats 75 weeks of age, SAC (0.45% diet) attenuated the decrease in the number, motility, and DNA synthesis of sperm and inhibited the oxidized proteins. These results suggest that SAC ameliorates the quality of sperm subjected to age-associated oxidative stress.

Astaxanthin alleviates brain aging in rats by attenuating oxidative stress and increasing BDNF levels

Astaxanthin (AST) is a carotenoid pigment which possesses potent antioxidative, anti-inflammatory, and neuroprotective properties. The aim of this study was to investigate whether administration of AST had protective effects on D-galactose-induced brain aging in rats, and further examined its protective mechanisms. The results showed that AST treatment significantly restored the activities of glutathione peroxidase (GSH-PX) and superoxide dismutase (SOD), and increased glutathione (GSH) contents and total antioxidant capacity (T-AOC), but decreased malondialdehyde (MDA), protein carbonylation and 8-hydroxy-2- deoxyguanosine (8-OHdG) levels in the brains of aging rats. Furthermore, AST increased the ratio of Bcl-2/Bax, but decreased the expression of Cyclooxygenase-2 (COX-2) in the brains of aging rats. Additionally, AST ameliorated histopathological changes in the hippocampus and restored brain derived neurotrophic factor (BDNF) levels in both the brains and hippocampus of aging rats. These results suggested that AST could alleviate brain aging, which may be due to attenuating oxidative stress, ameliorating hippocampus damage, and upregulating BDNF expression.

Inhibitory activities of acteoside, isoacteoside, and its structural constituents against protein glycation in vitro

BACKGROUND

Advanced glycation end products (AGE) are substances that can induce insulin resistance in adipocyte, hepatocyte and muscle cells. This resistance correlates highly with cardiovascular disease and diabetic complications. Acteoside (A), a phenylethanoid glycoside, is an active compound in several plants and traditional herbal medicines. Acteoside, its structural isomer, isoacteoside (I), and their constituents, caffeic acid (C) and 3,4-dihydroxyphenylethanol (D), were used in the study to investigate the inhibitory activity against AGE formations in vitro.

RESULTS

AGE formations were detected by anti-(N^ϵ-(carboxymethyl)lysine (anti-CML), using bovine serum albumin (BSA)/glucose (glc) and BSA/galactose (gal) as models, or by anti-argpyrimidine (anti-AP), using BSA/methylglyoxal (MGO) as models. It was found that A, I, C, or D, each at 5 mM, could attenuate the CML formations detected by ELISA in the BSA/gal model of a 3-day or 5-day reaction, and showed significant differences (P < 0.01 or P < 0.001) compared to the control. However, these compounds showed a minor effect after a 7-day incubation. It was also found that C or D could lower the CML formations in the BSA/glc model and showed significant differences (P < 0.05 or P < 0.01) compared to the control after a 3-day, 5-day and 7-day reaction. It was found that A, I, C, or D, each at 0.5 mM or 5 mM, could attenuate the AP formations in the BSA/MGO model of a 3-day reaction and showed significant differences (P < 0.001) compared to the control.

CONCLUSIONS

The results suggest the potential anti-glycation activities of A and I in vitro may apply to cell models at higher glucose concentrations or to diabetic animal models, and need further investigation.

Cerebrovascular protection of β-asarone in Alzheimer's disease rats: a behavioral, cerebral blood flow, biochemical and genic study

AIM OF THE STUDY

Recent studies have suggested that β-asarone have neuroprotective and cardiovascular protective effects in animal model. However, the influence of β-asarone on cerebrovascular system has not been explored so far. Therefore, present study was designed to determine whether repeated exposures to β-asarone resulted in positive effects on cerebrovascular function in AD rats.

MATERIALS AND METHODS

Alzheimer's disease induced rats was established by injecting both D-galactose (D-gal) and aluminum chloride (AlCl(3)) into abdominal cavity for 42 days. After injection of AlCl(3) and D-gal or saline for 28 days, the rats were treated with volume-matched vehicle or β-asarone (25mg/kg, 50mg/kg or 100mg/kg, i.h.) or Nimodipine (40mg/kg, i.g) once daily for consecutive 14 days, respectively. Behavioral responses of animals were assessed in a Morris water maze. CBF was measured by laser Doppler flowmetry. At the end of this period all rats were sacrificed, lactic acid, pyruvic acid content, Na+K+ATPase activity were determined in brain tissue homogenate to estimate the brain biochemical changes and mRNA expression of ET-1, eNOS and APP was measured with real-time RT-PCR method.

RESULTS

The spatial navigation task latencies, the times through platform zone and the time for the first through platform zone in the target quadrant in probe task, rCBF of right parietal lobe, the contents of lactic acid, pyruvic acid, and the activity of Na-K-ATP of cortex, and ET-1 and eNOS mRNA expression in hippocampus of AG rats were different from those of BG, P<0.05; The level of APP mRNA expression in model control group rats was higher than that in BG, though there was not a statistically significant difference, P>0.05; Compared with AG, HG rats spatial navigation task latencies were shorter, in probe task the times through platform zone in the target quadrant were bigger, rCBF and blood cell concentration of right parietal lobe were higher, the contents of pyruvic acid was lower, the activity of Na-K-ATP was higher, and ET-1 mRNA expression in hippocampus was lower, P<0.05; The level of eNOS and APP mRNA expression in HG rats was lower than that in AG, though there was not a statistically significant difference, P>0.05;

CONCLUSION

The present results suggested that β-asarone may be useful in memory impairment due to its cerebrovascular protection in AD rats and may develop as a therapeutic drug for treatment of AD patients.

Anti-glycative and anti-inflammatory effects of protocatechuic acid in brain of mice treated by D-galactose

Protocatechuic acid (PCA) at 0.5%, 1% or 2% was supplied to D-galactose (DG) treated mice for 8 week. PCA intake at 2% increased its deposit in brain. DG treatment increased brain level of reactive oxygen species, protein carbonyl, carboxymethyllysine, pentosidine, sorbitol, fructose and methylglyoxal (P<0.05). PCA intake, at 1% and 2%, lowered brain level of these parameters (P<0.05). DG treatments enhanced activity and protein expression of aldose reductase (AR) and sorbitol dehydrogenase, as well as declined glyoxalase I (GLI) activity and protein expression (P<0.05). PCA intake at 1% and 2% reduced activity and protein expression of AR (P<0.05), and at 2% restored GLI activity and expression (P<0.05). DG injection also elevated cyclooxygenase (COX)-2 activity and expression, and increased the release of interleukin (IL)-1beta, IL-6, tumor necrosis factor-alpha and prostaglandin E(2) in brain (P<0.05). PCA intake decreased these cytokines (P<0.05), and at 1% and 2% suppressed COX-2 activity and expression (P<0.05). PCA intake at 1% and 2% also lowered DG-induced elevation in activity, mRNA expression and protein production of nuclear factor kappa B p65 (P<0.05). These findings suggest that the supplement of protocatechuic acid might be helpful for the prevention or alleviation of aging.

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.

Nuclear factor κB-dependent anti-inflammatory effects of s-allyl cysteine and s-propyl cysteine in kidney of diabetic mice

Renal protection of s-allyl cysteine (SAC) and s-propyl cysteine (SPC) in diabetic mice against inflammatory injury was examined. Each agent at 0.5 and 1 g/L was added to the drinking water for 10 weeks. SAC or SPC intake significantly reduced the plasma blood urea nitrogen level and increased creatinine clearance (P < 0.05). These treatments significantly lowered the renal level of reactive oxygen species, nitric oxide, interleukin-6, tumor necrosis factor-α, and prostaglandin E(2) in diabetic mice (P < 0.05). Renal mRNA expression of inducible nitric oxide synthase, cyclooxygenase-2, protein kinase C (PKC)-α, PKC-β, and PKC-γ was enhanced in diabetic mice (P < 0.05); however, SAC or SPC treatments dose dependently declined mRNA expression of these factors (P < 0.05). Nuclear factor κB (NF-κB) activity, mRNA expression, and protein production in kidney of diabetic mice were significantly increased (P < 0.05). SAC or SPC intake dose dependently suppressed NF-κB activity, NF-κB p65 mRNA expression, and protein level (P < 0.05). Diabetes also enhanced renal protein expression of mitogen-activated protein kinase (P < 0.05). SAC and SPC, only at a high dose, significantly suppressed protein production of p-p38 and p-ERK1/2 (P < 0.05). Renal mRNA expression and protein generation of peroxisome proliferator-activated receptor (PPAR)-α and PPAR-γ were significantly down-regulated in diabetic mice (P < 0.05), but the intake of SAC or SPC at high dose up-regulated PPAR-α and PPAR-γ (P < 0.05). These findings support that SAC and SPC are potent anti-inflammatory agents against diabetic kidney diseases.