Therapeutic effect of organoselenium dietary supplementation in a sporadic dementia of Alzheimer's type model in rats

The Role of Gut Microbiota in the Neuroprotective Effects of Selenium in Alzheimer's Disease

The objective of the present review was to provide a timely update on the molecular mechanisms underlying the beneficial role of Se in Alzheimer's disease pathogenesis, and discuss the potential role of gut microbiota modulation in this neuroprotective effect. The existing data demonstrate that selenoproteins P, M, S, R, as well as glutathione peroxidases and thioredoxin reductases are involved in regulation of Aβ formation and aggregation, tau phosphorylation and neurofibrillary tangles formation, as well as mitigate the neurotoxic effects of Aβ and phospho-tau. Correspondingly, supplementation with various forms of Se in cellular and animal models of AD was shown to reduce Aβ formation, tau phosphorylation, reverse the decline in brain antioxidant levels, inhibit neuronal oxidative stress and proinflammatory cytokine production, improve synaptic plasticity and neurogenesis, altogether resulting in improved cognitive functions. In addition, most recent findings demonstrate that these neuroprotective effects are associated with Se-induced modulation of gut microbiota. In animal models of AD, Se supplementation was shown to improve gut microbiota biodiversity with a trend to increased relative abundance of Lactobacillus, Bifidobacterium, and Desulfivibrio, while reducing that of Lachnospiracea_NK4A136, Rikenella, and Helicobacter. Moreover, the relative abundance of Se-affected taxa was significantly associated with Aβ accumulation, tau phosphorylation, neuronal oxidative stress, and neuroinflammation, indicative of the potential role of gut microbiota to mediate the neuroprotective effects of Se in AD. Hypothetically, modulation of gut microbiota along with Se supplementation may improve the efficiency of the latter in AD, although further detailed laboratory and clinical studies are required.

Cholinergic neurotransmission in the brain of streptozotocin-induced rat model of sporadic Alzheimer's disease: long-term follow up

Rats treated intracerebroventricularly with streptozotocin (STZ-icv) develop pathologic features, which resemble those in Alzheimer's disease and have been proposed as a non-transgenic model for sporadic type of the disease (sAD). We aimed to characterize cholinergic transmission in the rat brain as a function of STZ-icv dose and time after the treatment. Acetylcholinesterase (AChE) activity and expression of muscarinic (M1, M4) and nicotinic (α7) receptors, cholin acetyltransferase (ChAT) and glial fibrillary acidic protein (GFAP) were measured in hippocampus (HPC) and parietotemporal cortex (CTX) of STZ-icv and age-matched control rats one week, and one, three, six and nine months after the icv administration of STZ (0.3, 1 and 3 mg/kg), respectively. Cholinergic and astroglial changes were found most pronounced with a highest STZ dose in time-dependent manner. The cortex and hippocampus exhibited specific alterations in cholinergic transmission following STZ-icv administration, with either similar or distinct patterns depending on the parameter observed: increased AChE activity in HPC and invariable in CTX; increased M4 and ChAT levels in both regions; substantial cortical M1 level increment and moderate hippocampal M1 decrement; and decreased α7 levels in both regions, with subsequent increase observed only in HPC. Alterations in cerebral cholinergic neurotransmission in STZ-icv rat model were mostly following a threephasic time pattern: acute response (Phase I), complete/partial compensation (Phase II), and reappearance/progression of changes (Phase III). Staging structure of cholinergic changes in STZ-icv rat model might be speculated to partly correlate with cholinergic pathology in clinical AD stages.

Selenium-containing compounds: a new hope for innovative treatments in Alzheimer's disease and Parkinson's disease

Neurodegenerative diseases are challenging to cure. To date, no cure has been found for Alzheimer's disease or Parkinson's disease, and current treatments are able only to slow the progression of the diseases and manage their symptoms. After an introduction to the complex biology of these diseases, we discuss the beneficial effect of selenium-containing agents, which show neuroprotective effects in vitro or in vivo. Indeed, selenium is an essential trace element that is being incorporated into innovative organoselenium compounds, which can improve outcomes in rodent or even primate models with neurological deficits. Herein, we critically discuss recent findings in the field of selenium-based applications in neurological disorders.

Oxidative damage in neurodegeneration: roles in the pathogenesis and progression of Alzheimer disease

Alzheimer disease (AD) is associated with multiple etiologies and pathological mechanisms, among which oxidative stress (OS) appears as a major determinant. Intriguingly, OS arises in various pathways regulating brain functions, and it seems to link different hypotheses and mechanisms of AD neuropathology with high fidelity. The brain is particularly vulnerable to oxidative damage, mainly because of its unique lipid composition, resulting in an amplified cascade of redox reactions that target several cellular components/functions ultimately leading to neurodegeneration. The present review highlights the "OS hypothesis of AD," including amyloid beta-peptide-associated mechanisms, the role of lipid and protein oxidation unraveled by redox proteomics, and the antioxidant strategies that have been investigated to modulate the progression of AD. Collected studies from our groups and others have contributed to unraveling the close relationships between perturbation of redox homeostasis in the brain and AD neuropathology by elucidating redox-regulated events potentially involved in both the pathogenesis and progression of AD. However, the complexity of AD pathological mechanisms requires an in-depth understanding of several major intracellular pathways affecting redox homeostasis and relevant for brain functions. This understanding is crucial to developing pharmacological strategies targeting OS-mediated toxicity that may potentially contribute to slow AD progression as well as improve the quality of life of persons with this severe dementing disorder.

Dietary Protection against Cognitive Impairment, Neuroinflammation and Oxidative Stress in Alzheimer's Disease Animal Models of Lipopolysaccharide-Induced Inflammation

Alzheimer's disease (AD) is a rapidly growing epidemic with a heavy social and economic burden. Evidence suggests that systemic inflammation, dysregulation of the immune response and the resulting neuroinflammation and neurodegeneration play a significant role in AD pathogenesis. Currently, given that there is no fully convincing cure for AD, the interest in lifestyle factors (such as diet), which potentially delay onset and reduce the severity of symptoms, is increasing. This review is aimed at summarizing the effects of dietary supplementation on cognitive decline, neuroinflammation and oxidative stress in AD-like animal models with a focus on neuroinflammation induced by lipopolysaccharide (LPS) injection, which mimics systemic inflammation in animals. The compounds reviewed include curcumin, krill oil, chicoric acid, plasmalogens, lycopene, tryptophan-related dipeptides, hesperetin and selenium peptides. Despite the heterogeneity of these compounds, there is a strong consensus on their counteracting action on LPS-induced cognitive deficits and neuroinflammatory responses in rodents by modulating cell-signaling processes, such as the NF-κB pathway. Overall, dietary interventions could represent an important resource to oppose AD due to their influence in neuroprotection and immune regulation.

Selenium-Derivative Compounds: A Review of New Perspectives in the Treatment of Alzheimer's Disease

BACKGROUND

Alzheimer's disease (AD) is one of the most prevalent types of dementia, affecting millions of older people worldwide. AD is stimulating efforts to develop novel molecules targeting its main features associated with a decrease in acetylcholine levels, an increase in oxidative stress and depositions of amyloid-β (Aβ) and tau protein. In this regard, selenium-containing compounds have been demonstrated as potential multi-targeted compounds in the treatment of AD. These compounds are known for their antioxidant and anticholinesterase properties, causing a decrease in Aβ aggregation.

OBJECTIVE

In this review, we approach structure-activity relationships of each compound, associating the decrease of ROS activity, an increase of tau-like activity and inhibition of AChE with a decrease in the self-aggregation of Aβ.

METHODS

We also verify that the molecular descriptors apol, nHBAcc and MlogP may be related to optimized pharmacokinetic properties for anti-AD drugs.

RESULTS

In our analysis, few selenium-derived compounds presented similar molecular features to FDA-approved drugs.

CONCLUSION

We suggest that unknown selenium-derived molecules with apol, nHBAcc and MlogP like FDA-approved drugs may be better successes with optimized pharmacokinetic properties in future studies in AD.

Delineation of Neuroprotective Effects and Possible Benefits of AntioxidantsTherapy for the Treatment of Alzheimer's Diseases by Targeting Mitochondrial-Derived Reactive Oxygen Species: Bench to Bedside

Alzheimer's disease (AD) is considered the sixth leading cause of death in elderly patients and is characterized by progressive neuronal degeneration and impairment in memory, language, etc. AD is characterized by the deposition of senile plaque, accumulation of fibrils, and neurofibrillary tangles (NFTs) which are responsible for neuronal degeneration. Amyloid-β (Aβ) plays a key role in the process of neuronal degeneration in the case of AD. It has been reported that Aβ is responsible for the production of reactive oxygen species (ROS), depletion of endogenous antioxidants, increase in intracellular Ca²⁺ which further increases mitochondria dysfunctions, oxidative stress, release of pro-apoptotic factors, neuronal apoptosis, etc. Thus, oxidative stress plays a key role in the pathogenesis of AD. Antioxidants are compounds that have the ability to counteract the oxidative damage conferred by ROS. Therefore, the antioxidant therapy may provide benefits and halt the progress of AD to advance stages by counteracting neuronal degeneration. However, despite the beneficial effects imposed by the antioxidants, the findings from the clinical studies suggested inconsistent results which might be due to poor study design, selection of the wrong antioxidant, inability of the molecule to cross the blood-brain barrier (BBB), treatment in the advanced state of disease, etc. The present review insights into the neuroprotective effects and limitations of the antioxidant therapy for the treatment of AD by targeting mitochondrial-derived ROS. This particular article will certainly help the researchers to search new avenues for the treatment of AD by utilizing mitochondrial-derived ROS-targeted antioxidant therapies.

Urea-functionalized organoselenium compounds as promising anti-HepG2 and apoptosis-inducing agents

Hepatocellular carcinoma is a highly aggressive and difficult-to-treat type of cancer. Incorporating urea functionality into the backbone of organoselenium compounds is expected to develop promising chemotherapeutic leads against liver cancer. Methods: Urea-functionalized organoselenium compounds were synthesized in good yields, and their cytotoxicity was evaluated against HepG2 cells. Results: 1,1'-(Diselanediylbis(4,1-phenylene))bis(3-phenylurea) (14) exhibited efficient anti-HepG2 activity in sub-micromolar concentrations, with no toxicity to normal human skin fibroblasts. The molecular mechanisms of the diselenide-based urea 14 were evaluated using colony formation, wound healing, 3D spheroid invasion assays, cell cycle analysis and apoptosis induction. Its redox properties were also assessed by using different bioassays. Conclusion: Our study revealed promising anticancer, antimigratory and anti-invasiveness properties of 1,1'-(diselanediylbis(4,1-phenylene))bis(3-phenylurea) (14) against HepG2.

Protective effects of selenium in tacrolimus-induced lung toxicity: potential role of heme oxygenase 1

The present study aimed to evaluate the protective effects of selenium (Sel) administration against tacrolimus (Tac) - induced lung toxicity and to assess the relation between heme oxygenase 1 (HO-1) and these effects. The study was conducted on 36 Wistar male albino rats equally divided into four groups: (i) normal control; (ii) Sel (0.1 mg/kg per day p.o. for four weeks); (iii) TAC 3 mg/mL as single oral dose on 27th day; and (iv) Tac + Sel. Lung tissues, lung homogenate, and bronchoalveolar lavage of the sacrificed animals were investigated biochemically and histopathologically, by immunohistochemistry or by PCR. The Tac group showed significantly lower expression of HO-1. Administration of Sel was associated with increased HO-1 expression. Oxidative (malondialdehyde, reduced glutathione, superoxide dismutase, myeloperoxidase, and glutathione peroxidase activity) and nitrosative stress (nitric oxide) markers and markers of inflammation (interleukin 1β (IL-1β), IL-6, and IL-10) showed changes corresponding to HO-1 levels in rat groups. Tac group showed the highest expression of caspase-3. Sel exerted a protective role against Tac-induced lung toxicity.

Toxicology and pharmacology of synthetic organoselenium compounds: an update

Here, we addressed the pharmacology and toxicology of synthetic organoselenium compounds and some naturally occurring organoselenium amino acids. The use of selenium as a tool in organic synthesis and as a pharmacological agent goes back to the middle of the nineteenth and the beginning of the twentieth centuries. The rediscovery of ebselen and its investigation in clinical trials have motivated the search for new organoselenium molecules with pharmacological properties. Although ebselen and diselenides have some overlapping pharmacological properties, their molecular targets are not identical. However, they have similar anti-inflammatory and antioxidant activities, possibly, via activation of transcription factors, regulating the expression of antioxidant genes. In short, our knowledge about the pharmacological properties of simple organoselenium compounds is still elusive. However, contrary to our early expectations that they could imitate selenoproteins, organoselenium compounds seem to have non-specific modulatory activation of antioxidant pathways and specific inhibitory effects in some thiol-containing proteins. The thiol-oxidizing properties of organoselenium compounds are considered the molecular basis of their chronic toxicity; however, the acute use of organoselenium compounds as inhibitors of specific thiol-containing enzymes can be of therapeutic significance. In summary, the outcomes of the clinical trials of ebselen as a mimetic of lithium or as an inhibitor of SARS-CoV-2 proteases will be important to the field of organoselenium synthesis. The development of computational techniques that could predict rational modifications in the structure of organoselenium compounds to increase their specificity is required to construct a library of thiol-modifying agents with selectivity toward specific target proteins.

Organoselenium Compounds as Acetylcholinesterase Inhibitors: Evidence and Mechanism of Mixed Inhibition

Acetylcholinesterase (AChE) inhibitors are actively used for the effective treatment of Alzheimer's disease. In recent years, the neuroprotective effects of organoselenium compounds such as ebselen and diselenides on the AChE activity have been investigated as potential therapeutic agents. In this work, we have carried out systematic kinetic and intrinsic fluorescence assays in combination with docking and molecular dynamics (MD) simulations to elucidate the molecular mechanism of the mixed inhibition of AChE by ebselen and diphenyl diselenide (DPDSe) molecules. Our MD simulations demonstrate significant heterogeneity in the binding modes and allosteric hotspots for DPDSe on AChE due to non-specific interactions. We have further identified that both ebselen and DPDSe can strongly bind around the peripheral anionic site (PAS), leading to non-competitive inhibition similar to other PAS-binding inhibitors. We also illustrate the entry of the DPDSe molecule into the gorge through a "side door", which offers an alternate entry point for AChE inhibitors as compared to the usual substrate entry point of the gorge. Together with results from experiments, these simulations provide mechanistic insights into the mixed type of inhibition for AChE using DPDSe as a promising inhibitor for AChE.

Co-nanoencapsulated meloxicam and curcumin improves cognitive impairment induced by amyloid-beta through modulation of cyclooxygenase-2 in mice

Alzheimer’s disease (AD) is a progressive brain disorder and complex mechanisms are involved in the physiopathology of AD. However, there is data suggesting that inflammation plays a role in its development and progression. Indeed, some non-steroidal anti-inflammatory drugs, such as meloxicam, which act by inhibiting cyclooxygenase-2 (COX-2) have been used as neuroprotective agents in different neurodegenerative disease models. The purpose of this study was to investigate the effects of co-nanoencapsulated curcumin and meloxicam in lipid core nanocapsules (LCN) on cognitive impairment induced by amyloid-beta peptide injection in mice. LCN were prepared by the nanoprecipitation method. Male Swiss mice received a single intracerebroventricular injection of amyloid-beta peptide aggregates (fragment 25–35, 3 nmol/3 μL) or vehicle and were subsequently treated with curcumin-loaded LCN (10 mg/kg) or meloxicam-loaded LCN (5 mg/kg) or meloxicam + curcumin-co-loaded LCN (5 and 10 mg/kg, respectively). Treatments were given on alternate days for 12 days (i.e., six doses, once every 48 hours, by intragastric gavage). Our data showed that amyloid-beta peptide infusion caused long-term memory deficits in the inhibitory avoidance and object recognition tests in mice. In the inhibitory avoidance test, both meloxicam and curcumin formulations (oil or co-loaded LCN) improved amyloid-beta-induced memory impairment in mice. However, only meloxicam and curcumin-co-loaded LCN attenuated non-aversive memory impairment in the object recognition test. Moreover, the beneficial effects of meloxicam and curcumin-co-loaded LCN could be explained by the anti-inflammatory properties of these drugs through cortical COX-2 downregulation. Our study suggests that the neuroprotective potential of meloxicam and curcumin co-nanoencapsulation is associated with cortical COX-2 modulation. This study was approved by the Committee on Care and Use of Experimental Animal Resources, the Federal University of Pampa, Brazil (approval No. 02-2015) on April 16, 2015.

Protection of cholinergic and antioxidant system contributes to the effect of Vitamin D3 ameliorating memory dysfunction in sporadic dementia of Alzheimer's type

OBJECTIVE

Investigate Vitamin D3 (VD3) effect on the Acetylcholinesterase (AChE), oxidative damage and behavioral tests in animals subjected to Intracerebroventicular injection of Streptozotocin (ICV-STZ) simulating a Sporadic Dementia of Alzheimer's Type (SDAT) and treated with VD3 (21 days).

METHODS

Animals were divided into eight groups: Vehicle, VD12.5 μg/kg, VD42 μg/kg, VD125 μg/kg, STZ, STZ+VD12.5 μg/kg, STZ+VD42 μg/kg, STZ+VD125 μg/kg.

RESULTS

VD3 prevented the increase in AChE in groups of VD42 µg/kg and VD125 µg/kg; in AChE of synaptossomes and TBARS levels prevented the increase in group VD125 µg/kg; in ROS levels there was not a significant difference; for the Carbonyl Content all doses prevented the increase. Total Thiols prevent the decrease in VD42 µg/kg and VD125 µg/kg, and Reduced Glutathione prevented the decrease in VD125 µg/kg, Oxidized Glutathione prevented the increase in VD125 µg/kg. In relation to behavioral tests, the VD3 prevented the increase in time to find (days 2 and 3), in the time to find the platform (day 3) and in time spent in the quadrant (day 2). However, in relation to crossings there was not difference in groups. These results indicated the therapeutic effect of the VD3 in model of STZ in rats.

Rosuvastatin alleviates high-salt and cholesterol diet-induced cognitive impairment in rats via Nrf2-ARE pathway

OBJECTIVE

The objectives of our study were to investigate the possible effect of rosuvastatin in ameliorating high salt and cholesterol diet (HSCD)-induced cognitive impairment and to also investigate its possible action via the Nrf2-ARE pathway.

METHODS

In silico studies were performed to check the theoretical binding of rosuvastatin to the Nrf2 target. HSCD was used to induce cognitive impairment in rats and neurobehavioral studies were performed to evaluate the efficacy of rosuvastatin in enhancing cognition. Biochemical analyses were used to estimate changes in oxidative markers. Western blot and immunohistochemical analyses were done to check Nrf2 translocation. TUNEL and caspase 3 tests were performed to evaluate reversal of apoptosis by rosuvastatin.

RESULTS

Rosuvastatin showed good theoretical affinity to Nrf2, significantly reversed changes in oxidative biomarkers which were induced by HSCD, and also improved the performance of rats in the neurobehavioral test. A rise in nuclear translocation of Nrf2 was revealed through immunohistochemical analysis and western blot. TUNEL staining and caspase 3 activity showed attenuation of apoptosis.

DISCUSSION

We have investigated a novel mechanism of action for rosuvastatin (via the Nrf2-ARE pathway) and demonstrated that it has the potential to be used in the treatment of cognitive impairment.

Cytoprotective and antioxidant properties of organic selenides for the myelin-forming cells, oligodendrocytes

Here a new series of twenty-one organoselenides, of potential protective activity, were synthesized and tested for their intrinsic cytotoxicity, anti-apoptotic and antioxidant capacities in oligodendrocytes. Most of the organoselenides were able to decrease the ROS levels, revealing antioxidant properties. Compounds 5b and 7b showed a high glutathione peroxidase (GPx)-like activities, which were 1.5 folds more active than ebselen. Remarkably, compound 5a diminished the formation of the oligodendrocytes SubG1 peak in a concentration-dependent manner, indicating its anti-apoptotic properties. Furthermore, based on the SwissADME web interface, we performed an in-silico structure-activity relationship to explore the drug-likeness of these organoselenides, predicting the pharmacokinetic parameters for compounds of interest that could cross the blood-brain barrier. Collectively, we present new organoselenide compounds with cytoprotective and antioxidant properties that can be considered as promising drug candidates for myelin diseases.

Selenoprotein S Reduces Endoplasmic Reticulum Stress-Induced Phosphorylation of Tau: Potential Role in Selenate Mitigation of Tau Pathology

Previous studies demonstrated that selenium in the form of sodium selenate reduces neurofibrillary tangle formation in Alzheimer's disease models. Hyperphosphorylation of tau, which leads to formation of neurofibrillary tangles in Alzheimer's disease, is increased by endoplasmic reticulum (ER) stress. Selenoprotein S (SelS) is part of an ER membrane complex that removes misfolded proteins from the ER as a means to reduce ER stress. Selenate, as with other forms of selenium, will increase selenoprotein expression. We therefore proposed that increased SelS expression by selenate would contribute to the beneficial actions of selenate in Alzheimer's disease. SelS expression increased with ER stress and decreased under conditions of elevated glucose concentrations in the SH-SY5Y neuronal cell line. Reducing expression of SelS with siRNA promoted cell death in response to ER stress. Selenate increased SelS expression, which significantly correlated with decreased tau phosphorylation. Restricting SelS expression during ER stress conditions increased tau phosphorylation, and also promoted aggregation of phosphorylated tau in neurites and soma. In human postmortem brain, SelS expression coincided with neurofibrillary tangles, but not with amyloid-β plaques. These results indicate that selenate can alter phosphorylation of tau by increasing expression of SelS in Alzheimer's disease and potentially other neurodegenerative disorders.

Design, Synthesis, and In Vitro Evaluation of a Novel Probucol Derivative: Protective Activity in Neuronal Cells Through GPx Upregulation

Recent studies have shown that probucol (PB), a hipocholesterolemic agent with antioxidant and anti-inflammatory properties, presents neuroprotective properties. On the other hand, adverse effects have limited PB's clinical application. Thus, the search for PB derivatives with no or less adverse effects has been a topic of research. In this study, we present a novel organoselenium PB derivative (RC513) and investigate its potential protective activity in an in vitro experimental model of oxidative toxicity induced by tert-butyl hydroperoxide (tBuOOH) in HT22 neuronal cells, as well as exploit potential protective mechanisms. tBuOOH exposure caused a significant decrease in the cell viability, which was preceded by (i) increased reactive species generation and (ii) decreased mitochondrial maximum oxygen consumption rate. RC513 pretreatment (48 h) significantly prevented the tBuOOH-induced decrease of cell viability, RS generation, and mitochondrial dysfunction. Of note, RC513 significantly increased glutathione peroxidase (GPx) activity and mRNA expression of GPx1, a key enzyme involved in peroxide detoxification. The use of mercaptosuccinic acid, an inhibitor of GPx, significantly decreased the protective activity of RC513 against tBuOOH-induced cytotoxicity in HT22 cells, highlighting the importance of GPx upregulation in the observed protection. In summary, the results showed a significant protective activity of a novel PB derivative against tBuOOH-induced oxidative stress and mitochondrial dysfunction, which was related to the upregulation of GPx. Our results point to RC513 as a promising neuroprotective molecule, even though studies concerning potential beneficial effects and safety aspects of RC513 under in vivo conditions are well warranted.

Selenofuranoside improves long-term memory deficits in rats after exposure to monosodium glutamate: Involvement of Na+, K+-ATPase activity

Monosodium glutamate (MSG) is the most widely used additive in the food industry; however, some adverse effects of this additive, including functional, learning, and behavioral alterations, have been observed in experimental animals and humans. Studies have shown learning and memory impairment in adult animals exposed to MSG. However, studies relating exposure to MSG to acetylcholinesterase (AChE) and Na⁺, K⁺-ATPase activities and memory damage are still scarce in the literature. The aim of the present study was to assess the possible protective effects of selenofuranoside, an organoselenium compound, against the impairment of long-term memory, Na⁺, K⁺-ATPase and AChE activities, and oxidative stress after MSG exposure in rats. MSG (2g/kg) and/or selenofuranoside (5mg/kg) were administered orally to 5-week-old male Wistar rats for 10days. On the 10th day, after the administration of last dose of the drug(s), the rats were subjected to behavioral tests: the open-field test and step-down passive avoidance task (SDPA). The blood, liver, kidney, cortex, and hippocampus were removed to determine the oxidative stress parameters, such as the levels of reactive species, lipid peroxidation, antioxidant enzyme activities, and endogenous nonenzymatic antioxidant content. Furthermore, the cortex and hippocampus were used to determine the Na⁺, K⁺-ATPase and AChE activities. The results demonstrate that the administration of MSG led to long-term memory impairment, as shown in the SDPA task, and also hippocampal and cortical Na⁺, K⁺-ATPase inhibition. There were no alterations in the AChE activity and oxidative stress parameters. Treatment with selenofuranoside attenuated memory impairment associated with MSG exposure by improving the hippocampal Na⁺, K⁺-ATPase activity.

N-acetylcysteine treatment attenuates the cognitive impairment and synaptic plasticity loss induced by streptozotocin

Alzheimer's disease (AD) is a neurodegenerative disorder pathologically characterized by severe neuronal and glial structural changes and progressive cognitive decline. N-acetylcysteine (NAC) is a well-known pharmacological agent with pro-neurogenic properties and neuroprotective effects. In this study, we evaluated NAC protective effects on cognitive impairment and associated pathological markers in a streptozotocin (STZ)-induced sporadic dementia of AD type mice model. Animals were divided into six groups: I) Sham, II) NAC, III) physostigmine (PHY), IV) STZ, V) NAC + STZ and VI) PHY + NAC. NAC (5 mg/kg) and PHY (0.25 mg/kg) were administrated orally for 30 consecutive days and STZ (2.5 mg/kg) intracerebroventricularly at the first and third days. Novel object recognition (NOR, days 26-27) and Morris water maze (MWM, days 26-30) tasks were assessed to evaluate learning and memory. On the thirty-first day animals were euthanized and brains collected for biochemical analysis. Interestingly, our results showed that STZ treatment induced cognitive impairment in mice in the NOR and MWM tasks. Both NAC and PHY treatments prevented from this impairment. The increase in AChE activity and decrease in pTrkB and MnSOD levels caused by STZ in the cerebral cortex and hippocampus, were prevented by the NAC and PHY treatments. The decrease in SYN, MAP2 and GFAP expressions were also prevented by NAC and PHY treatments. In conclusion, NAC treatment prevented the cognitive impairment induced by STZ, normalizing the AChE activity and rescuing the synaptic plasticity loss. Our results suggest that NAC is a promising therapeutic strategy for the treatment of AD.

p,p'-Methoxyl-diphenyl diselenide elicits an antidepressant-like effect in mice without discontinuation anxiety phenotype

Major depressive disorder is the most severe and debilitating disease among psychiatric illnesses. The abrupt interruption of antidepressant treatment may lead to a complex physiological and neuropsychiatric syndrome. The organoselenium compound (MeOPhSe)₂ has been reported to have neuroprotective properties in animal models. The study aimed to investigate the effects of single or repeated administration of (MeOPhSe)₂ on depressive-like behavior and if the compound administration, and its discontinuation, may affect the anxiolytic-like phenotype in Swiss mice. The results showed that repeated intragastric administration of (MeOPhSe)₂ (dose range: 0.1-5mg/kg), different from a single administration, reduced the immobility time in the mouse tail suspension test. A single administration of (MeOPhSe)₂ at a dose of 5mg/kg decreased the immobility time, increased the swimming time and did not alter the climbing behavior in the modified forced swimming test (mFST). Repeated administration of (MeOPhSe)₂ decreased the immobility time, did not alter the swimming time and increased the climbing behavior in the mouse mFST. Repeated administration of (MeOPhSe)₂ at a dose of 5mg/kg elicited a mouse anxiolytic-like phenotype in the elevated plus maze and light-dark tests. Markers of hepatic and renal function tests were not altered by repeated administration of (MeOPhSe)₂ to mice. The findings indicate that a single or repeated administration of (MeOPhSe)₂ elicited an antidepressant-like action in mice. Moreover, repeated treatment with (MeOPhSe)₂ produced an anxiolytic-like action in mice and its profile remained stable after discontinuation.

Selenium in the Therapy of Neurological Diseases. Where is it Going?

Selenium (₃₄Se), an antioxidant trace element, is an important regulator of brain function. These beneficial properties that Se possesses are attributed to its ability to be incorporated into selenoproteins as an amino acid. Several selenoproteins are expressed in the brain, in which some of them, e.g. glutathione peroxidases (GPxs), thioredoxin reductases (TrxRs) or selenoprotein P (SelP), are strongly involved in antioxidant defence and in maintaining intercellular reducing conditions. Since increased oxidative stress has been implicated in neurological disorders, including Parkinson’s disease, Alzheimer’s disease, stroke, epilepsy and others, a growing body of evidence suggests that Se depletion followed by decreased activity of Se-dependent enzymes may be important factors connected with those pathologies. Undoubtedly, the remarkable progress that has been made in understanding the biological function of Se in the brain has opened up new potential possibilities for the treatment of neurological diseases by using Se as a potential drug. However, further research in the search for optimal Se donors is necessary in order to achieve an effective and safe therapeutic income.

Synthesis and evaluation of 8-hydroxyquinolin derivatives substituted with (benzo[d][1,2]selenazol-3(2H)-one) as effective inhibitor of metal-induced Aβ aggregation and antioxidant

A series of 8-hydroxyquinolin derivatives substituted with (benzo[d][1,2]selenazol-3(2H)-one) at the 2-position were synthesized and evaluated for treatment of Alzheimer's disease. In vitro assays demonstrated that most of the target compounds exhibit significant inhibition of Cu(II)-induced Aβ1-42 aggregation, rapid H2O2 scavenging and glutathione peroxidise (GPx)-like catalytic activity. Among these molecules, compound 9a is the most potent peroxide scavenger that possesses the ability to scavenge most H2O2 within 200-220min and possesses GPx-like activity (v0=106.0μM·min(-1)), enabling modulation of metal-induced Aβ aggregation.

The hypolipidemic action of a diet supplemented with p,p'-methoxyl-diphenyl diselenide is not directly related to its antioxidant property

The present study investigated whether a p,p'-methoxyl-diphenyl diselenide (MeOPhSe)2-supplemented diet causes toxicity in rats. A second aim of this study was to determine whether a 10 ppm (MeOPhSe)2-supplemented diet has hypolipidemic effect on Triton WR-1339-induced hyperlipidemia in rats. To rule out the antioxidant property of (MeOPhSe)2 in its hypolipidemic action, parameters of oxidative stress were carried out. Wistar rats were fed with 3, 10, or 30 ppm of (MeOPhSe)2-supplemented diet for 30 days. None of (MeOPhSe)2-supplemented diets caused alteration in general parameters of toxicity and lipid profile of rats. The hypolipidemic effect of 10 ppm of (MeOPhSe)2-supplemented diet on rats treated with Triton WR-1339 (400 mg/kg, intraperitoneal) was investigated. The (MeOPhSe)2-supplemented diet partially protected against the levels of total cholesterol (TC) and non-HDL-C and reduced the atherogenic index (AI) increased by Triton WR-1339 in rats. A positive correlation between TC and triglyceride levels (r = 0.679) and non-HDL-C levels (r = 0.929) and AI (r = 0.889) was demonstrated. Triton WR-1339 altered parameters of oxidative stress in livers of rats but (MeOPhSe)2-supplemented diet did not protect against these alterations. The results demonstrated that the hypolipidemic action of (MeOPhSe)2-supplemented diet is not directly related to its antioxidant property and devoid of systemic toxicity in rats at the parameters analyzed.

Syntheses, structures and anti-tumor activity of four new organotin(iv) carboxylates based on 2-thienylselenoacetic acid

With the 2-thienylselenoacetic acid ligand, four new organotin complexes have been synthesized and characterized by X-ray crystallography, elemental analysis, FT-IR and NMR (¹H,¹³C, and¹¹⁹Sn) spectroscopy.

Experimental models of Alzheimer's disease for deciphering the pathogenesis and therapeutic screening (Review)

Despite decades of laboratory and clinical research, Alzheimer's disease (AD) is still the leading cause of dementia in adults and there are no curative therapies currently available for this disease. This may be due to the pathological features of AD, which include extensive extracellular amyloid plaques and intracellular neurofibrillary tangles, as well as subsequent neuronal and synaptic loss, which begin to appear several years prior to memory loss and the damge is already irreversible and extensive at the time of clinical diagnosis. The poor therapeutic effects of current treatments necessitate the introduction of experimental models able to replicate AD pathology, particularly in the pre-symptomatic stage, and then to explore preventive and therapeutic strategies. In response to this necessity, various experimental models reproducing human AD pathology have been developed, which are also useful tools for therapeutic screening. Although none of these models fully reproduce the key features of human AD, the experimental models do provide important insight into the pathological changes which occur in AD. This review summarizes the commonly used experimental models of AD and also discusses how the models may be used to decipher the pathogenesis underlying AD and to screen novel therapies for this disease.

Redox Status and Neuro Inflammation Indexes in Cerebellum and Motor Cortex of Wistar Rats Supplemented with Natural Sources of Omega-3 Fatty Acids and Astaxanthin: Fish Oil, Krill Oil, and Algal Biomass

Health authorities worldwide have consistently recommended the regular consumption of marine fishes and seafood to preserve memory, sustain cognitive functions, and prevent neurodegenerative processes in humans. Shrimp, crabs, lobster, and salmon are of particular interest in the human diet due to their substantial provision of omega-3 fatty acids (n-3/PUFAs) and the antioxidant carotenoid astaxanthin (ASTA). However, the optimal ratio between these nutraceuticals in natural sources is apparently the key factor for maximum protection against most neuro-motor disorders. Therefore, we aimed here to investigate the effects of a long-term supplementation with (n-3)/PUFAs-rich fish oil, ASTA-rich algal biomass, the combination of them, or krill oil (a natural combination of both nutrients) on baseline redox balance and neuro-inflammation indexes in cerebellum and motor cortex of Wistar rats. Significant changes in redox metabolism were only observed upon ASTA supplementation, which reinforce its antioxidant properties with a putative mitochondrial-centered action in rat brain. Krill oil imposed mild astrocyte activation in motor cortex of Wistar rats, although no redox or inflammatory index was concomitantly altered. In summary, there is no experimental evidence that krill oil, fish oil, oralgal biomass (minor variation), drastically change the baseline oxidative conditions or the neuro-inflammatory scenario in neuromotor-associated rat brain regions.

Oxidant/Antioxidant imbalance and the risk of Alzheimer's disease

Alzheimer's disease (AD) is the most common form of dementia characterized by progressive loss of memory and other cognitive functions among older people. Senile plaques and neurofibrillary tangles are the most hallmarks lesions in the brain of AD in addition to neurons loss. Accumulating evidence has shown that oxidative stress-induced damage may play an important role in the initiation and progression of AD pathogenesis. Redox impairment occurs when there is an imbalance between the production and quenching of free radicals from oxygen species. These reactive oxygen species augment the formation and aggregation of amyloid-β and tau protein hyperphosphorylation and vice versa. Currently, there is no available treatments can modify the disease. However, wide varieties of antioxidants show promise to delay or prevent the symptoms of AD and may help in treating the disease. In this review, the role of oxidative stress in AD pathogenesis and the common used antioxidant therapies for AD will summarize.

Selenium, selenoproteins and neurodegenerative diseases

A review of selenium's essential role in normal brain function and its potential involvement in neurodegenerative diseases.

Selenium partially prevents cisplatin-induced neurotoxicity: a preliminary study

Cisplatin is an anticancer drug and it has neurotoxic effects. On the other hand, the neuroprotective effect of selenium was observed in previous studies. However, the effect of selenium on cisplatin-induced neurotoxicity has not been studied yet. Therefore, we aimed to investigate whether selenium prevent cisplatin-induced neurotoxicity. Twenty-one male Wistar albino rats were divided into three groups: control (C), cisplatin (CS), cisplatin and selenium (CSE, n=7 in each group). Cisplatin (12 mg/kg/day, i.p.) was administered for 3 days to CS and CSE groups. Also, CSE group received via oral gavage 3 mg/kg/day (twice-a-day as 1.5 mg/kg) selenium 5 days before of cisplatin injection and continued for 11 consecutive days. The same volumes of saline were intraperitoneally and orally administered to C group at same time. At the end of experimental protocol, electrophysiological and histopathological examinations were performed. The nerve conduction velocity, amplitude of compound action potential and number of axon of CS group were significantly lower than the C group. However, the same parameters of CSE group were significantly higher than the CS group. Although, cisplatin has a peripheral neurotoxic effect in rats, this effect was partially prevented by selenium treatment. Thus, it appears that co-administration of selenium and cisplatin may be a useful approach to decrease severity of peripheral neurotoxicity.

Design, synthesis and evaluation of seleno-dihydropyrimidinones as potential multi-targeted therapeutics for Alzheimer's disease

We report the design, synthesis and evaluation of a series of seleno-dihydropyrimidinones as potential multi-targeted therapeutics for Alzheimer's disease.

Synthesis and evaluation of multi-target-directed ligands against Alzheimer's disease based on the fusion of donepezil and ebselen

A novel series of compounds obtained by fusing the cholinesterase inhibitor donepezil and the antioxidant ebselen were designed as multi-target-directed ligands against Alzheimer's disease. An in vitro assay showed that some of these molecules did not exhibit highly potent cholinesterase inhibitory activity but did have various other ebselen-related pharmacological effects. Among the molecules, compound 7d, one of the most potent acetylcholinesterase inhibitors (IC50 values of 0.042 μM for Electrophorus electricus acetylcholinesterase and 0.097 μM for human acetylcholinesterase), was found to be a strong butyrylcholinesterase inhibitor (IC50 = 1.586 μM), to possess rapid H2O2 and peroxynitrite scavenging activity and glutathione peroxidase-like activity (ν0 = 123.5 μM min(-1)), and to be a substrate of mammalian TrxR. A toxicity test in mice showed no acute toxicity at doses of up to 2000 mg/kg. According to an in vitro blood-brain barrier model, 7d is able to penetrate the central nervous system.