Neurotoxic Agent-Induced Injury in Neurodegenerative Disease Model: Focus on Involvement of Glutamate Receptors

Overview of a novel osmotin abolishes abnormal metabolic-associated adiponectin mechanism in Alzheimer's disease: Peripheral and CNS insights

Alzheimer's disease (AD) is a degenerative brain disease that affects millions of people worldwide. It is caused by abnormalities in cholinergic neurons, oxidative stress, and inflammatory cascades. The illness is accompanied by personality changes, memory issues, and dementia. Metabolic signaling pathways help with fundamental processes like DNA replication and RNA transcription. Being adaptable is essential for both surviving and treating illness. The body's metabolic signaling depends on adipokines, including adiponectin (APN) and other adipokines secreted by adipose tissues. Energy homeostasis is balanced by adipokines, and nutrients. Overconsumption of nutrients messes with irregular signaling of adipokines, such as APN in both peripheral and brain which leads to neurodegeneration, such as AD. Despite the failure of traditional treatments like memantine and cholinesterase inhibitors, natural plant bioactive substances like Osmotin (OSM) have been given a focus as potential therapeutics due to their antioxidant properties, better blood brain barrier (BBB) permeability, excellent cell viability, and especially nanoparticle approaches. The review highlights the published preclinical literature regarding the role of OSM in AD pathology while there is a need for more research to investigate the hidden therapeutic potential of OSM which may open a new gateway and further strengthen its healing role in the pathogenesis of neurodegeneration, especially AD.

Ovariectomy exacerbates the disturbance of excitation- inhibition balance in the brain of APP/PS-1/tau mice

Introduction

The prevalence of Alzheimer's disease (AD) is significantly gender-differentiated, with the number of female AD patients far exceeding that of males, accounting for two-thirds of the total prevalence. Although postmenopausal AD mice have been shown to have more prominent pathologic features and memory impairments than normal AD mice, the relevant molecular mechanisms leading to these outcomes have not been well elucidated. In the present study, we used the disturbance of excitation-inhibition balance in the postmenopausal brain as an entry point to explore the link between estrogen deficiency, disorders of the glutamatergic-GABAergic nervous system, and memory impairment.

Methods

Wild-type (WT) mice and APP/PS1/tau (3 × Tg-AD) mice (10 months old) were randomly divided into four groups: WT+Sham group, WT+OVX group, 3 × Tg-AD+Sham group and 3 × Tg-AD+OVX group. Ovariectomy (OVX) was performed in the WT+OVX group and the 3 × Tg-AD+OVX group, and sham surgery was performed in the WT+Sham group and the 3 × Tg-AD+Sham group. The learning and memory ability and the anxiety and depression-like behavior changes of mice were evaluated by behavioral experiments, and the association between estrogen-estrogen receptors pathway and glutamatergic/GABAergic nervous system and female AD was evaluated by neurochemical experiments.

Results

In WT and 3 × Tg-AD mice, OVX resulted in impaired learning and memory abilities and anxiety and depression-like behaviors; reduced estrogen levels and downregulated the expression of estrogen receptors; upregulated the expression of amyloid-β, amyloid precursor protein, presenilin 1, and p-tau; upregulated the expression of Bcl-2-associated X protein and downregulated the expression of B-cell lymphoma-2, promoting cell apoptosis; reduced the number of neuronal dendrites and downregulated the expression of postsynaptic density protein-95; more importantly, OVX increased brain glutamate levels but downregulated the expression of N-methyl-D-aspartate receptor-2B, excitatory amino acid transporter 1, excitatory amino acid transporter 2, γ-aminobutyric acid receptor-A and γ-aminobutyric acid receptor-B.

Conclusion

Our results suggested that OVX-induced estrogen-estrogen receptors pathway disruption caused learning and memory impairment and anxiety and depression-like behaviors, upregulated the expression of AD pathological markers, promoted apoptosis, destroyed neuronal structure, and most importantly, caused glutamatergic/GABAergic nervous system disorders.

A Capsicum annuum L. seed extract exerts anti-neuroexcitotoxicity in HT22 hippocampal neurons

The hippocampal memory deficit stands out as a primary symptom in neurodegenerative diseases, including Alzheimer's disease. While numerous therapeutic candidates have been proposed, they primarily serve to delay disease progression. Given the irreversible brain atrophy or injury associated with these conditions, current research efforts are concentrated on preventive medicine strategies. Herein, we investigated whether the extracts of Capsicum annuum L. seeds (CSE) and Capsicum annuum L. pulp (CPE) have preventive properties against glutamate-induced neuroexcitotoxicity (one of the main causes of Alzheimer's disease) in HT22 hippocampal neuronal cells. Pretreatment with CSE demonstrated significant anti-neuroexcitotoxic activity, whereas CPE did not exhibit such effects. Specifically, CSE pretreatment dose-dependently inhibited the elevation of excitotoxic elements (intracellular calcium influx and reactive oxygen species; ROS) and apoptotic elements (p53 and cleaved caspase-3). In addition, the glutamate-induced alterations of neuronal activity indicators (brain-derived neurotrophic factor; BDNF and cAMP response element-binding protein phosphorylation; CREB) were significantly attenuated by CSE treatment. We also found that luteolin is the main bioactive compound corresponding to the anti-neuroexcitotoxic effects of CSE. Our results strongly suggest that Capsicum annuum L. seeds (but not its pulp) could be candidates for neuro-protective resources especially under conditions of neuroexcitotoxicity. Its underlying mechanisms may involve the amelioration of ROS-mediated cell death and BDNF-related neuronal inactivity and luteolin would be an active compound.

Phenolic Compounds of Therapeutic Interest in Neuroprotection

The number of elderly people is projected to double in the next 50 years worldwide, resulting in an increased prevalence of neurodegenerative diseases. Aging causes changes in brain tissue homeostasis, thus contributing to the development of neurodegenerative disorders. Current treatments are not entirely effective, so alternative treatments or adjuvant agents are being actively sought. Antioxidant properties of phenolic compounds are of particular interest for neurodegenerative diseases whose psychopathological mechanisms strongly rely on oxidative stress at the brain level. Moreover, phenolic compounds display other advantages such as the permeability of the blood-brain barrier (BBB) and the interesting molecular mechanisms that we reviewed in this work. We began by briefly outlining the physiopathology of neurodegenerative diseases to understand the mechanisms that result in irreversible brain damage, then we provided an overall classification of the phenolic compounds that would be addressed later. We reviewed in vitro and in vivo studies, as well as some clinical trials in which neuroprotective mechanisms were demonstrated in models of different neurodegenerative diseases such as amyotrophic lateral sclerosis (ALS), Alzheimer's disease (AD), Parkinson's disease (PD), ischemia, and traumatic brain injury (TBI).

Neurotoxic stimulation alters prosaposin levels in the salivary systems of rats

Prosaposin (PSAP), a potent neurotrophic factor, is found in neuronal and non-neuronal tissues and various biological fluids. Neuropathological conditions often alter PSAP production in neural tissues. However, little is known about its alterations in non-neural tissues, particularly in the salivary glands, which are natural reservoirs of various neurotrophic factors. In this study, we explored whether neurotoxic stimulation by kainic acid (KA), a glutamate analog, altered PSAP levels in the salivary system of rats. The results revealed that KA injection did not alter total saliva production. However, KA-induced neurotoxic stimulation significantly increased the PSAP level in the secreted saliva but decreased it in the serum. In addition, KA-induced elevated immunoreactivities of PSAP and its receptors have been observed in the granular convoluted tubule (GCT) cells of the submandibular gland (SMG), a major salivary secretory organ. Indeed, a large number of PSAP-expressing immunogold particles were observed in the secretory granules of the SMG. Furthermore, KA-induced overexpression of PSAP was co-localized with secretogranin in secretory acini (mostly in GCT cells) and the ductal system of the SMG, suggesting the release of excess PSAP from the salivary glands into the oral cavity. In conclusion, the salivary system produces more PSAP during neurotoxic conditions, which may play a protective role in maintaining the secretory function of the salivary glands and may work in distant organs.

Pterosin sesquiterpenoids from Pteris laeta Wall. ex Ettingsh. protect cells from glutamate excitotoxicity by modulating mitochondrial signals

ETHNOPHARMACOLOGICAL RELEVANCE

The genus Pteris (Pteridaceae) has been used as a traditional herb for a long time. In particular, Pteris laeta Wall. ex Ettingsh. has been widely used in traditional Chinese medicine to treat nervous system diseases and some pterosin sesquiterpenes from Pteris show neuroprotective activity, but their underlying molecular mechanisms remain elusive. Therefore, to investigate the neuroprotective activity and working mechanism of pterosin sesquiterpenes from P. laeta Wall. ex Ettingsh. will provide a better understanding and guidance in using P. laeta Wall. ex Ettingsh. as a traditional Chinese medicine.

AIM OF THE STUDY

We aim to develop effective treatments for neurodegenerative diseases from pterosin sesquiterpenes by evaluating their neuroprotective activity and investigating their working mechanisms.

MATERIALS AND METHODS

Primary screening on the glutamate-induced excitotoxicity cell model was assessed by 3-(4,5-Dimethylthiazol-2-yl)-2,5-Diphenyltetrazolium Bromide (MTT) assay. Fluorescent-activated cell sorting (FACS) was used to analyze the activation level of glutamate receptors and mitochondria membrane potential after treatment. Transcriptomics and proteomics analysis was performed to identify possible targets of pterosin B. The key pathways were enriched by the Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis through the Database for Annotation, Visualization, and Integrated Discovery (DAVID). The core targets were visualized by a protein-protein interaction network using STRING. The mRNA and protein expressions were evaluated using real-time quantitative polymerase chain reaction (Q-PCR) and western blot, respectively. Immunocytochemistry was performed to monitor mitochondrial and apoptotic proteins. Cellular reactive oxygen species (ROS) were measured by ROS assay, and Ca²⁺ was stained with Fluo-4 AM to quantify intracellular Ca²⁺ levels.

RESULTS

We found pterosin B from Pteris laeta Wall. ex Ettingsh. showed significant neuroprotective activity against glutamate excitotoxicity, enhancing cell viability from 43.8% to 105% (p-value: <0.0001). We demonstrated that pterosin B worked on the downstream signaling pathways of glutamate excitotoxicity rather than directly blocking the activation of glutamate receptors. Pterosin B restored mitochondria membrane potentials, alleviated intracellular calcium overload from 107.4% to 95.47% (p-value: 0.0006), eliminated cellular ROS by 36.55% (p-value: 0.0143), and partially secured cells from LPS-induced inflammation by increasing cell survival from 46.75% to 58.5% (p-value: 0.0114). Notably, pterosin B enhanced the expression of nuclear factor-erythroid factor 2-related factor 2 (NRF2) and heme oxygenase-1 (HO-1) by 2.86-fold (p-value: 0.0006) and 4.24-fold (p-value: 0.0012), and down-regulated Kelch-like ECH-associated protein 1 (KEAP1) expression by 2.5-fold (p-value: 0.0107), indicating that it possibly promotes mitochondrial biogenesis and mitophagy to maintain mitochondria quality control and homeostasis, and ultimately inhibits apoptotic cell death.

CONCLUSIONS

Our work revealed that pterosin B protected cells from glutamate excitotoxicity by targeting the downstream mitochondrial signals, making it a valuable candidate for developing potential therapeutic agents in treating neurodegenerative diseases.

LincRNA-p21 Promotes Cellular Senescence by Down-regulating the Wnt/β-catenin Pathway in MPP+-treated SH-SY5Y Cells

AIM AND OBJECTIVE

Long intergenic non-coding RNA-p21 (lincRNA-p21) plays a critical role in various senescence-associated physiological and pathological conditions. We aimed to explore the senescence-associated effects of lincRNA-p21 in 1-methyl-4-phenylpyridinium (MPP+) treated neuroblastoma SH-SY5Y cell line as a therapeutic target.

MATERIALS AND METHODS

The RNA expression levels of lincRNA-p21, p53, p16, and telomere length were examined with reverse transcription-quantitative polymerase chain reaction (RTqPCR). The Telo TAGGG™ Telomerase PCR ELISA PLUS Kit was used to determine telomerase activity. Cellular viability was evaluated with the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay and lactate dehydrogenase (LDH) assay. Western blot was performed to analyze β-catenin protein expression. Besides, oxidative stress was evaluated by Jaggregate- forming delocalized lipophilic cation, 5,5',6,6'-tetrachloro-1,1',3,3'- tetraethylbenzimidazolocarbocyanine++ + iodide (JC‑1) stain, fluorescence spectrophotometry, colorimetric assay, and malondialdehyde (MDA) formation.

RESULTS

This research demonstrated that MPP+ caused a distinct increase in the expression of LincRNA- p21 in SH-SY5Y cells. MPP+ induced cellular senescence with decreasing cellular proliferation and viability, increasing expression levels of senescence-associated makers such as genes p53 and p16, accompanied by significantly decreasing telomere length and telomerase activity. At the same time, these effects were abolished by silencing lincRNA-p21 with small interfering RNA (siRNA). On the contrary, β-catenin silencing contributes to reversing anti-senescent effects caused by lincRNA-p21 silencing. Moreover, modifying lincRNA-p21 exerted an anti-senescent influence depending on decreasing oxidant stress.

CONCLUSION

Our study showed that in the treatment of MPP+, lincRNA-p21 might serve a role in the SH-SY5Y cell senescence by modulating the Wnt/β-catenin pathway, as well as increasing oxidant stress. Thus, trying to target lincRNA-p21 may have important therapeutic and practical implications for PD.

Mechanisms Underlying Cognitive Impairment Induced by Prenatal Alcohol Exposure

Alcohol is one of the most commonly used illicit substances among pregnant women. Clinical and experimental studies have revealed that prenatal alcohol exposure affects fetal brain development and ultimately results in the persistent impairment of the offspring's cognitive functions. Despite this, the rate of alcohol use among pregnant women has been progressively increasing. Various aspects of human and animal behavior, including learning and memory, are dependent on complex interactions between multiple mechanisms, such as receptor function, mitochondrial function, and protein kinase activation, which are especially vulnerable to alterations during the developmental period. Thus, the exploration of the mechanisms that are altered in response to prenatal alcohol exposure is necessary to develop an understanding of how homeostatic imbalance and various long-term neurobehavioral impairments manifest following alcohol abuse during pregnancy. There is evidence that prenatal alcohol exposure results in vast alterations in mechanisms such as long-term potentiation, mitochondrial function, and protein kinase activation in the brain of offspring. However, to the best of our knowledge, there are very few recent reviews that focus on the cognitive effects of prenatal alcohol exposure and the associated mechanisms. Therefore, in this review, we aim to provide a comprehensive summary of the recently reported alterations to various mechanisms following alcohol exposure during pregnancy, and to draw potential associations with behavioral changes in affected offspring.

Andrographis paniculata protects against brain hippocampus and cerebellum from mercury chloride induced damage by attenuating oxidative stress

Mercury chloride (HgCl2) is a neurotoxicant that remains a health hazard despite numerous efforts to reduce its levels in the environment. The use of medicinal plants in treating various diseases and other toxic agents has grown popular owing to their effectiveness and affordable rates. Andrographis paniculata (A. paniculata) is a plant with astringent and detoxifying characteristics and is widely used worldwide for its medicinal and antioxidant benefits. This study aimed to investigate the possible protective effects of A. paniculata aqueous extract against HgCl2-induced memory impairment, oxidative stress, and brain damage. Twenty-five adult Wistar rats were randomly divided into five groups: control, HgCl2 0.5 mg/kg, HgCl2+AP 250 mg/kg, HgCl2+AP 500 mg/kg, or HgCl2+Ascorbic acid 200 mg/kg. For 28 days, administrations were given through oral gavage once a day. HgCl2 injection resulted in memory impairment, increased glutamate concentrations in the brain, and the production of oxidative stress. Memory impairment was prevented in A. paniculata-treated groups by balancing the levels of AChE and dopamine activities, which then lowered glutamate concentration, avoided oxidative stress, and improved histopathological alterations in the brain. A. paniculata alleviated HgCl2-induced memory impairment in Wistar rats by increasing the memory index, regulating neurotransmitter levels, and reducing oxidative stress.

The autophagy inducer SMER28 attenuates microtubule dynamics mediating neuroprotection

SMER28 originated from a screen for small molecules that act as modulators of autophagy. SMER28 enhanced the clearance of autophagic substrates such as mutant huntingtin, which was additive to rapamycin-induced autophagy. Thus, SMER28 was established as a positive regulator of autophagy acting independently of the mTOR pathway, increasing autophagosome biosynthesis and attenuating mutant huntingtin-fragment toxicity in cellular- and fruit fly disease models, suggesting therapeutic potential. Despite many previous studies, molecular mechanisms mediating SMER28 activities and its direct targets have remained elusive. Here we analyzed the effects of SMER28 on cells and found that aside from autophagy induction, it significantly stabilizes microtubules and decelerates microtubule dynamics. Moreover, we report that SMER28 displays neurotrophic and neuroprotective effects at the cellular level by inducing neurite outgrowth and protecting from excitotoxin-induced axon degeneration. Finally, we compare the effects of SMER28 with other autophagy-inducing or microtubule-stabilizing drugs: whereas SMER28 and rapamycin both induce autophagy, the latter does not stabilize microtubules, and whereas both SMER28 and epothilone B stabilize microtubules, epothilone B does not stimulate autophagy. Thus, the effect of SMER28 on cells in general and neurons in particular is based on its unique spectrum of bioactivities distinct from other known microtubule-stabilizing or autophagy-inducing drugs.

A Preliminary Assessment of the Nutraceutical Potential of Acai Berry (Euterpe sp.) as a Potential Natural Treatment for Alzheimer's Disease

Alzheimer's disease (AD) is characterised by progressive neuronal atrophy and the loss of neuronal function as a consequence of multiple pathomechanisms. Current AD treatments primarily operate at a symptomatic level to treat a cholinergic deficiency and can cause side effects. Hence, there is an unmet need for healthier lifestyles to reduce the likelihood of AD as well as improved treatments with fewer adverse reactions. Diets rich in phytochemicals may reduce neurodegenerative risk and limit disease progression. The native South American palm acai berry (Euterpe oleraceae) is a potential source of dietary phytochemicals beneficial to health. This study aimed to screen the nutraceutical potential of the acai berry, in the form of aqueous and ethanolic extracts, for the ability to inhibit acetyl- and butyryl-cholinesterase (ChE) enzymes and scavenge free radicals via 2,2-diphenyl-1-picryl-hydrazyl-hydrate (DPPH) or 2,2'-azino-bis-3-ethylbenzthiazoline-6-sulphonic acid (ABTS) assays. In addition, this study aimed to quantify the acai berry's antioxidant potential via hydrogen peroxide or hydroxyl scavenging, nitric oxide scavenging, lipid peroxidation inhibition, and the ability to reduce ferric ions. Total polyphenol and flavonoid contents were also determined. Acai aqueous extract displayed a concentration-dependent inhibition of acetyl- and butyryl-cholinesterase enzymes. Both acai extracts displayed useful concentration-dependent free radical scavenging and antioxidant abilities, with the acai ethanolic extract being the most potent antioxidant and displaying the highest phenolic and flavonoid contents. In summary, extracts of the acai berry contain nutraceutical components with anti-cholinesterase and antioxidant capabilities and may therefore provide a beneficial dietary component that limits the pathological deficits evidenced in AD.

Dioscin-Mediated Autophagy Alleviates MPP+-Induced Neuronal Degeneration: An In Vitro Parkinson's Disease Model

Autophagy is a cellular homeostatic process by which cells degrade and recycle their malfunctioned contents, and impairment in this process could lead to Parkinson’s disease (PD) pathogenesis. Dioscin, a steroidal saponin, has induced autophagy in several cell lines and animal models. The role of dioscin-mediated autophagy in PD remains to be investigated. Therefore, this study aims to investigate the hypothesis that dioscin-regulated autophagy and autophagy-related (ATG) proteins could protect neuronal cells in PD via reducing apoptosis and enhancing neurogenesis. In this study, the 1-methyl-4-phenylpyridinium ion (MPP⁺) was used to induce neurotoxicity and impair autophagic flux in a human neuroblastoma cell line (SH-SY5Y). The result showed that dioscin pre-treatment counters MPP⁺-mediated autophagic flux impairment and alleviates MPP⁺-induced apoptosis by downregulating activated caspase-3 and BCL2 associated X, apoptosis regulator (Bax) expression while increasing B-cell lymphoma 2 (Bcl-2) expression. In addition, dioscin pre-treatment was found to increase neurotrophic factors and tyrosine hydroxylase expression, suggesting that dioscin could ameliorate MPP⁺-induced degeneration in dopaminergic neurons and benefit the PD model. To conclude, we showed dioscin’s neuroprotective activity in neuronal SH-SY5Y cells might be partly related to its autophagy induction and suppression of the mitochondrial apoptosis pathway.

Piperine Provides Neuroprotection against Kainic Acid-Induced Neurotoxicity via Maintaining NGF Signalling Pathway

The neuroprotective properties of piperine, the major alkaloid extracted from black pepper, have been under investigation, but its mechanism of action in excitotoxicity is still poorly understood. This study aimed to evaluate the protective effects of piperine with a focus on nerve growth factor (NGF) signalling in a kainic acid (KA) rat model of excitotoxicity. Rats were administered intraperitoneally (i.p.) piperine (10 or 50 mg/kg) before KA injection (15 mg/kg, i.p.). Our results show that KA exposure in rats caused seizure behaviour, intrinsic neuronal hyperactivity, glutamate elevation, hippocampal neuronal damage, and cognitive impairment. These KA-induced alterations could be restored to the normal state by piperine treatment. In addition, piperine decreased the expression of the NGF precursor proNGF and NGF-degrading protease matrix metalloproteinase 9, whereas it increased the expression of proNGF processing enzyme matrix metalloproteinase 7, NGF, and NGF-activated receptor TrkA in the hippocampus of KA-treated rats. Furthermore, KA decreased phosphorylation of the protein kinase B (Akt) and glycogen synthase kinase 3β (GSK3β) in the hippocampus, and piperine reversed these changes. Our data suggest that piperine protects hippocampal neurons against KA-induced excitotoxicity by upregulating the NGF/TrkA/Akt/GSK3β signalling pathways.

Group I mGluRs in Therapy and Diagnosis of Parkinson’s Disease: Focus on mGluR5 Subtype

Metabotropic glutamate receptors (mGluRs; members of class C G-protein-coupled receptors) have been shown to modulate excitatory neurotransmission, regulate presynaptic extracellular glutamate levels, and modulate postsynaptic ion channels on dendritic spines. mGluRs were found to activate myriad signalling pathways to regulate synapse formation, long-term potentiation, autophagy, apoptosis, necroptosis, and pro-inflammatory cytokines release. A notorious expression pattern of mGluRs has been evident in several neurodegenerative diseases, including Alzheimer’s disease, Parkinson’s disease, Huntington’s disease, and schizophrenia. Among the several mGluRs, mGluR5 is one of the most investigated types of considered prospective therapeutic targets and potential diagnostic tools in neurodegenerative diseases and neuropsychiatric disorders. Recent research showed mGluR5 radioligands could be a potential tool to assess neurodegenerative disease progression and trace respective drugs’ kinetic properties. This article provides insight into the group I mGluRs, specifically mGluR5, in the progression and possible therapy for PD.

Molecular Mechanisms and Therapeutic Potential of α- and β-Asarone in the Treatment of Neurological Disorders

Neurological disorders are important causes of morbidity and mortality around the world. The increasing prevalence of neurological disorders, associated with an aging population, has intensified the societal burden associated with these diseases, for which no effective treatment strategies currently exist. Therefore, the identification and development of novel therapeutic approaches, able to halt or reverse neuronal loss by targeting the underlying causal factors that lead to neurodegeneration and neuronal cell death, are urgently necessary. Plants and other natural products have been explored as sources of safe, naturally occurring secondary metabolites with potential neuroprotective properties. The secondary metabolites α- and β-asarone can be found in high levels in the rhizomes of the medicinal plant Acorus calamus (L.). α- and β-asarone exhibit multiple pharmacological properties including antioxidant, anti-inflammatory, antiapoptotic, anticancer, and neuroprotective effects. This paper aims to provide an overview of the current research on the therapeutic potential of α- and β-asarone in the treatment of neurological disorders, particularly neurodegenerative diseases such as Alzheimer’s disease (AD), Parkinson’s disease (PD), as well as cerebral ischemic disease, and epilepsy. Current research indicates that α- and β-asarone exert neuroprotective effects by mitigating oxidative stress, abnormal protein accumulation, neuroinflammation, neurotrophic factor deficit, and promoting neuronal cell survival, as well as activating various neuroprotective signalling pathways. Although the beneficial effects exerted by α- and β-asarone have been demonstrated through in vitro and in vivo animal studies, additional research is required to translate laboratory results into safe and effective therapies for patients with AD, PD, and other neurological and neurodegenerative diseases.

HDAC6 inhibition reverses long-term doxorubicin-induced cognitive dysfunction by restoring microglia homeostasis and synaptic integrity

Breast cancer is the most common female malignancy in both the developed and developing world. Doxorubicin is one of the most commonly used chemotherapies for breast cancer. Unfortunately, up to 60% of survivors report long-term chemotherapy-induced cognitive dysfunction (CICD) characterized by deficits in working memory, processing speed and executive function. Currently, no therapeutic standard for treating CICD exists. Here, we hypothesized that treatment with a blood-brain barrier permeable histone deacetylase 6 (HDAC6) inhibitor can successfully reverse long-term doxorubicin-induced cognitive dysfunction. Methods: The puzzle box test and novel object/place recognition test were used to assess cognitive function following a therapeutic doxorubicin dosing schedule in female mice. Mitochondrial function and morphology in neuronal synaptosomes were evaluated using the Seahorse XF24 extracellular flux analyzer and transmission electron microscopy, respectively. Hippocampal postsynaptic integrity was evaluated using immunofluorescence. Hippocampal microglia phenotype was determined using advanced imaging techniques and single-nucleus RNA sequencing. Results: A 14-day treatment with a blood-brain barrier permeable HDAC6 inhibitor successfully reversed long-term CICD in the domains of executive function, working and spatial memory. No significant changes in mitochondrial function or morphology in neuronal synaptosomes were detected. Long-term CICD was associated with a decreased expression of postsynaptic PSD95 in the hippocampus. These changes were associated with decreased microglial ramification and alterations in the microglia transcriptome that suggest a stage 1 disease-associated microglia (DAM) phenotype. HDAC6 inhibition completely reversed these doxorubicin-induced alterations, indicating a restoration of microglial homeostasis. Conclusion: Our results show that decreased postsynaptic integrity and a neurodegenerative microglia phenotype closely resembling stage 1 DAM microglia contribute to long-term CICD. Moreover, HDAC6 inhibition shows promise as an efficacious pharmaceutical intervention to alleviate CICD and improve quality of life of breast cancer survivors.

Metabotropic glutamate receptors and nitric oxide in dopaminergic neurotoxicity

Dopaminergic neurotoxicity is characterized by damage and death of dopaminergic neurons. Parkinson's disease (PD) is a neurodegenerative disorder that primarily involves the loss of dopaminergic neurons in the substantia nigra. Therefore, the study of the mechanisms, as well as the search for new targets for the prevention and treatment of neurodegenerative diseases, is an important focus of modern neuroscience. PD is primarily caused by dysfunction of dopaminergic neurons; however, other neurotransmitter systems are also involved. Research reports have indicated that the glutamatergic system is involved in different pathological conditions, including dopaminergic neurotoxicity. Over the last two decades, the important functional interplay between dopaminergic and glutamatergic systems has stimulated interest in the possible role of metabotropic glutamate receptors (mGluRs) in the development of extrapyramidal disorders. However, the specific mechanisms driving these processes are presently unclear. The participation of the universal neuronal messenger nitric oxide (NO) in the mechanisms of dopaminergic neurotoxicity has attracted increased attention. The current paper aims to review the involvement of mGluRs and the contribution of NO to dopaminergic neurotoxicity. More precisely, we focused on studies conducted on the rotenone-induced PD model. This review is also an outline of our own results obtained using the method of electron paramagnetic resonance, which allows quantitation of NO radicals in brain structures.

Diffusion tensor imaging of the hippocampus reflects the severity of hippocampal injury induced by global cerebral ischemia/reperfusion injury

At present, predicting the severity of brain injury caused by global cerebral ischemia/reperfusion injury (GCI/RI) is a clinical problem. After such an injury, clinical indicators that can directly reflect neurological dysfunction are lacking. The change in hippocampal microstructure is the key to memory formation and consolidation. Diffusion tensor imaging is a highly sensitive tool for visualizing injury to hippocampal microstructure. Although hippocampal microstructure, brain-derived neurotrophic factor (BDNF), and tropomyosin-related kinase B (TrkB) levels are closely related to nerve injury and the repair process after GCI/RI, whether these indicators can reflect the severity of such hippocampal injury remains unknown. To address this issue, we established rat models of GCI/RI using the four-vessel occlusion method. Diffusion tensor imaging parameters, BDNF, and TrkB levels were correlated with modified neurological severity scores. The results revealed that after GCI/RI, while neurological function was not related to BDNF and TrkB levels, it was related to hippocampal fractional anisotropy. These findings suggest that hippocampal fractional anisotropy can reflect the severity of hippocampal injury after global GCI/RI. The study was approved by the Institutional Animal Care and Use Committee of Capital Medical University, China (approval No. AEEI-2015-139) on November 9, 2015.

Ameliorating effect of melatonin on mercuric chloride-induced neurotoxicity in rats

Mercury is a highly toxic metal. It induces its toxicity via production of reactive oxygen species. Brain tissues are more susceptible to oxidative damage. Melatonin and its metabolites are free radical scavengers. The aim of this work is to elucidate the neuroprotective effect of melatonin on mercuric chloride-induced neurotoxicity in rats. Fifty male albino rats were used and divided into five groups. Group I acts as normal control. Group II (LD HgCl2) received mercuric chloride at a dose of 2 mg/kg. Group III (HD HgCl2) received HgCl2 at a dose of 4 mg/kg. Rats in group IV (LD HgCl2 +MLT) received HgCl2 2 mg/kg + Melatonin 5 mg/kg. Rats in group V (HD HgCl2+MLT) received HgCl2 4 mg/kg + Melatonin5 mg/kg. This study revealed that mercuric chloride decreased the activity of superoxide dismutase, catalase and glutathione peroxidase enzymes and increased malondialdehyde levels. Toxicity of mercuric chloride lead to upregulation of the gene expression level vascular endothelial growth factor. HgCl2 induced fragmentation of rough endoplasmic reticulum, ballooning of Golgi apparatus, nuclear and cytoplasmic degeneration of pyramidal neurones of rat cerebral cortex. This neuronal damage caused by HgCl2 was significantly improved by melatonin.

Impact of Curcumin on Traumatic Brain Injury and Involved Molecular Signaling Pathways

Traumatic Brain Injury (TBI) is one of the main causes of mortality and morbidity worldwide with no suitable treatment. The present study was designed to review the present literature about the protective effects of curcumin and the underlying mechanism against TBI. All published English language papers from beginning to 2019 were selected in this study. The findings indicate that curcumin may be effective against TBI outcomes by modulating the molecular signaling pathways involved in oxidative stress, inflammation, apoptosis, and autophagy. However, more experimental studies should be done to identify all mechanisms involved in the pathogenesis of TBI. Patents for Curcumin and chronic inflammation and traumatic brain injury management (WO2017097805A1 and US9101580B2) were published. In conclusion, the present study confirmed the potential therapeutic impact of curcumin for treating TBI.

Early Effects of the Soluble Amyloid β25-35 Peptide in Rat Cortical Neurons: Modulation of Signal Transduction Mediated by Adenosine and Group I Metabotropic Glutamate Receptors

The amyloid β peptide (Aβ) is a central player in the neuropathology of Alzheimer’s disease (AD). The alteration of Aβ homeostasis may impact the fine-tuning of cell signaling from the very beginning of the disease, when amyloid plaque is not deposited yet. For this reason, primary culture of rat cortical neurons was exposed to Aβ_25-35, a non-oligomerizable form of Aβ. Cell viability, metabotropic glutamate receptors (mGluR) and adenosine receptors (AR) expression and signalling were assessed. Aβ_25-35 increased mGluR density and affinity, mainly due to a higher gene expression and protein presence of Group I mGluR (mGluR₁ and mGluR₅) in the membrane of cortical neurons. Intriguingly, the main effector of group I mGluR, the phospholipase C β₁ isoform, was less responsive. Also, the inhibitory action of group II and group III mGluR on adenylate cyclase (AC) activity was unaltered or increased, respectively. Interestingly, pre-treatment of cortical neurons with an antagonist of group I mGluR reduced the Aβ_25-35-induced cell death. Besides, Aβ_25-35 increased the density of A₁R and A_2AR, along with an increase in their gene expression. However, while A₁R-mediated AC inhibition was increased, the A_2AR-mediated stimulation of AC remained unchanged. Therefore, one of the early events that takes place after Aβ_25-35 exposure is the up-regulation of adenosine A₁R, A_2AR, and group I mGluR, and the different impacts on their corresponding signaling pathways. These results emphasize the importance of deciphering the early events and the possible involvement of metabotropic glutamate and adenosine receptors in AD physiopathology.

The Concept of Folic Acid in Health and Disease

Folates have a pterine core structure and high metabolic activity due to their ability to accept electrons and react with O-, S-, N-, C-bounds. Folates play a role as cofactors in essential one-carbon pathways donating methyl-groups to choline phospholipids, creatine, epinephrine, DNA. Compounds similar to folates are ubiquitous and have been found in different animals, plants, and microorganisms. Folates enter the body from the diet and are also synthesized by intestinal bacteria with consequent adsorption from the colon. Three types of folate and antifolate cellular transporters have been found, differing in tissue localization, substrate affinity, type of transferring, and optimal pH for function. Laboratory criteria of folate deficiency are accepted by WHO. Severe folate deficiencies, manifesting in early life, are seen in hereditary folate malabsorption and cerebral folate deficiency. Acquired folate deficiency is quite common and is associated with poor diet and malabsorption, alcohol consumption, obesity, and kidney failure. Given the observational data that folates have a protective effect against neural tube defects, ischemic events, and cancer, food folic acid fortification was introduced in many countries. However, high physiological folate concentrations and folate overload may increase the risk of impaired brain development in embryogenesis and possess a growth advantage for precancerous altered cells.

TRAILR1 (rs20576) and GRIA3 (rs12557782) are not associated with interferon-β response in multiple sclerosis patients

Multiple sclerosis (MS) is an autoimmune-type inflammatory disorder in human central nervous system. Recombinant interferon beta (IFN-β) decreases the number of relapses and postpones disability progression in MS. However, up to 50% of patients treated with interferon beta continue experiencing relapses and/or worsening disability. Single nucleotide polymorphisms in different genes have been known to show significant associations with response to IFN-β in MS patients. In the present work, we examined the potential role of TRAILR1 and GRIA3 genes polymorphisms on response to IFN-β therapy in Iranian MS patients. The DNA was extracted from blood samples by standard procedures from 73 patients diagnosed with Multiple Sclerosis that were either responded to IFN-β or did not. We carried out RFLP -PCR and tetra-primer ARMS-PCR methods to study of rs20576 and rs12557782, respectively. All results were analyzed using the SPSS software. TRAILR1 rs20576 genotype frequencies in responders and non-responders were similar (χ² = 0.26, P = 0.87, Fisher^, s Exact test). Our results showed that response to IFN-β has not association with sex (p = 0.73). Also, genotypic frequencies of GRIA3 rs12557782 had no significant differences between two groups of female population (χ² = 3.75, p = 0.15). Furthermore, it had not been any statistical differences between responder and non-responder males (χ² = 0.7, p = 0.4) related to the SNP. Our results analysis revealed no significant association between the studied SNPs (TRAILR1 rs20576 and GRIA3rs 12,557,782) and response to IFN-β in Iranian MS patients.

Levodopa Improves Cognitive Function and the Deficits of Structural Synaptic Plasticity in Hippocampus Induced by Global Cerebral Ischemia/Reperfusion Injury in Rats

The cognitive impairment caused by cerebral ischemia/reperfusion is an unsolved problem in the field of international neural rehabilitation. Not only ameliorates the consciousness level of certain patients who suffered from ischemia-reperfusion injury and were comatose for a long time period after cerebral resuscitation treatment, but levodopa also improves the symptoms of neurological deficits in rats with global cerebral ischemia-reperfusion injury. However, Levodopa has not been widely used as a brain protection drug after cardiopulmonary resuscitation, because of its unclear repair mechanism. Levodopa was used to study the neuroplasticity in the hippocampus of global cerebral ischemia/reperfusion injury rat model, established by Pulsinelli's four-vessel occlusion method. Levodopa was injected intraperitoneally at 50 mg/kg/d for 7 consecutive days after 1st day of surgery. The modified neurological function score, Morris water maze, magnetic resonance imaging, Nissl and TH staining, electron microscopy and western blot were used in the present study. The results showed that levodopa improved the neurological function and learning and memory of rats after global cerebral ischemia/reperfusion injury, improved the integrity of white matter, and density of gray matter in the hippocampus, increased the number of synapses, reduced the delayed neuronal death, and increased the expression of synaptic plasticity-related proteins (BDNF, TrkB, PSD95, and Drebrin) in the hippocampus. In conclusion, levodopa can improve cognitive function after global cerebral ischemia/reperfusion injury by enhancing the synaptic plasticity in the hippocampus.

Environmental neurotoxic pollutants: review

Environmental pollutants are recognized as one of the major concerns for public health and responsible for various forms of neurological disorders. Some of the common sources of environmental pollutants related to neurotoxic manifestations are industrial waste, pesticides, automobile exhaust, laboratory waste, and burning of terrestrial waste. Among various environmental pollutants, particulate matter, ultrafine particulate matter, nanoparticles, and lipophilic vaporized toxicant (acrolein) easily cross the blood-brain barrier, activate innate immune responses in the astrocytes, microglia, and neurons, and exert neurotoxicity. Growing shreds of evidence from human epidemiological studies have correlated the environmental pollutants with neuroinflammation, oxidative stress, endoplasmic reticulum stress, mitochondrial dysfunction, myelin sheath disruption, and alterations in the blood-brain barrier anatomy leading to cognitive dysfunction and poor quality of life. These environmental pollutants also considerably cause developmental neurotoxicity, exhibit teratogenic effect and mental growth retardance, and reduce IQ level. Until now, the exact mechanism of pollutant-induced neurotoxicity is not known, but studies have shown interference of pollutants with the endogenous antioxidant defense system, inflammatory pathway (Nrf2/NF-kB, MAPKs/PI3K, and Akt/GSK3β), modulation of neurotransmitters, and reduction in long-term potentiation. In the current review, various sources of pollutants and exposure to the human population, developmental neurotoxicity, and molecular mechanism of different pollutants involved in the pathogenesis of different neurological disorders have been discussed.

Biological evidence of gintonin efficacy in memory disorders

Gintonin is a novel glycolipoprotein, which has been abundantly found in the root of Korean ginseng. It holds lysophosphatidic acids (LPAs), primarily identified LPA C18:2, and is an exogenous agonist of LPA receptors (LPARs). Gintonin maintains blood-brain barrier integrity, and it has recently been studied in several models of neurodegenerative diseases (NDDs) such as Alzheimer's disease (AD), Parkinson's disease, Huntington's disease and amyotrophic lateral sclerosis. Gintonin demonstrated neuroprotective activity by providing action against neuroinflammation-, apoptosis- and oxidative stress-mediated neurodegeneration. Gintonin showed an emerging role as a modulator of synaptic transmission and neurogenesis and also potentially regulated autophagy in primary cortical astrocytes. It also ameliorated the toxic agent-induced and genetic models of cognitive deficits in experimental NDDs. As a novel agonist of LPARs, gintonin regulated several G protein-coupled receptors (GPCRs) including GPR40 and GPR55. However, further study needs to be investigated to understand the underlying mechanism of action of gintonin in memory disorders.

Role of microRNAs in neurodegeneration induced by environmental neurotoxicants and aging

The progressive loss of neuronal structure and functions resulting in the death of neurons is considered as neurodegeneration. Environmental toxicants induced degeneration of neurons is accelerated with aging. In adult brains, most of the neurons are post-mitotic, and their loss results in the development of diseases like amyotrophic lateral sclerosis (ALS), Parkinson's disease (PD), Alzheimer's disease (AD), and Huntington's disease (HD). Neurodegenerative diseases have several similarities at the sub-cellular and molecular levels, such as synaptic degeneration, oxidative stress, inflammation, and cognitive decline, which are also known in brain aging. Identification of these similarities at the molecular level offers hope for the development of new therapeutics to ameliorate all neurodegenerative diseases simultaneously. Aging is known as the most strongly associated additive factor in the pathogenesis of neurodegenerative diseases. Studies carried out so far identified several genes, which are responsible for selective degeneration of neurons in different neurodegenerative diseases. Countless efforts have been made in identifying therapeutics for neurodegenerative diseases; however, the discovery of effective therapy remains elusive. Findings made in the last two decades identified microRNAs (miRNAs) as the most potent post-transcription regulatory RNA molecule, which can condition protein levels in the cell and tissue-specific manner. Identification of miRNAs, which regulate both neurotoxicant and aging-associated degeneration of brain cells, raises the possibility that roads leading to aging and neurotoxicant induced neurodegeneration cross at some point. Identification of miRNAs, which are common to aging and neurotoxicant induced neurodegeneration, will help in understanding the complex mechanism of neurodegenerative disease development. In the future, the use of natural miRNAs in vivo in therapy will be able to tackle several issues of aging and neurodegeneration. In the present review, we have provided a summary of findings made on the role of miRNAs in neurodegeneration and explored the common link made by miRNAs between aging and neurotoxicants induced neurodegeneration.

G-Protein-Coupled Receptors in CNS: A Potential Therapeutic Target for Intervention in Neurodegenerative Disorders and Associated Cognitive Deficits

Neurodegenerative diseases are a large group of neurological disorders with diverse etiological and pathological phenomena. However, current therapeutics rely mostly on symptomatic relief while failing to target the underlying disease pathobiology. G-protein-coupled receptors (GPCRs) are one of the most frequently targeted receptors for developing novel therapeutics for central nervous system (CNS) disorders. Many currently available antipsychotic therapeutics also act as either antagonists or agonists of different GPCRs. Therefore, GPCR-based drug development is spreading widely to regulate neurodegeneration and associated cognitive deficits through the modulation of canonical and noncanonical signals. Here, GPCRs’ role in the pathophysiology of different neurodegenerative disease progressions and cognitive deficits has been highlighted, and an emphasis has been placed on the current pharmacological developments with GPCRs to provide an insight into a potential therapeutic target in the treatment of neurodegeneration.

Antioxidants and Neuron-Astrocyte Interplay in Brain Physiology: Melatonin, a Neighbor to Rely on

This manuscript is a review focused onto the role of astrocytes in the protection of neurons against oxidative stress and how melatonin can contribute to the maintenance of brain homeostasis. The first part of the review is dedicated to the dependence of neurons on astrocytes by terms of survival under oxidative stress conditions. Additionally, the effects of melatonin against oxidative stress in the brain and its putative role in the protection against diseases affecting the brain are highlighted. The effects of melatonin on the physiology of neurons and astrocytes also are reviewed.

Neurotrophic and neuroprotective effects of a monomeric GLP-1/GIP/Gcg receptor triagonist in cellular and rodent models of mild traumatic brain injury

A synthetic monomeric peptide triple receptor agonist, termed "Triagonist" that incorporates glucagon-like peptide-1 (GLP-1), glucose-dependent insulinotropic polypeptide (GIP) and glucagon (Gcg) actions, was previously developed to improve upon metabolic and glucose regulatory benefits of single and dual receptor agonists in rodent models of diet-induced obesity and type 2 diabetes. In the current study, the neurotrophic and neuroprotective actions of this Triagonist were probed in cellular and mouse models of mild traumatic brain injury (mTBI), a prevalent cause of neurodegeneration in both the young and elderly. Triagonist dose- and time-dependently elevated cyclic AMP levels in cultured human SH-SY5Y neuronal cells, and induced neurotrophic and neuroprotective actions, mitigating oxidative stress and glutamate excitotoxicity. These actions were inhibited only by the co-administration of antagonists for all three receptor types, indicating the balanced co-involvement of GLP-1, GIP and Gcg receptors. To evaluate physiological relevance, a clinically translatable dose of Triagonist was administered subcutaneously, once daily for 7 days, to mice following a 30 g weight drop close head injury. Triagonist fully mitigated mTBI-induced visual and spatial memory deficits, evaluated at 7 and 30 days post injury. These results establish Triagonist as a novel neurotrophic/protective agent worthy of further evaluation as a TBI treatment strategy.

Potential Therapeutic Targets of Quercetin and Its Derivatives: Its Role in the Therapy of Cognitive Impairment

Quercetin (QC) is a flavonoid and crucial bioactive compound found in a variety of vegetables and fruits. In preclinical studies, QC has demonstrated broad activity against several diseases and disorders. According to recent investigations, QC is a potential therapeutic candidate for the treatment of nervous system illnesses because of its protective role against oxidative damage and neuroinflammation. QC acts on several molecular signals, including ion channels, neuroreceptors, and inflammatory receptor signaling, and it also regulates neurotrophic and anti-oxidative signaling molecules. While the study of QC in neurological disorders has focused on numerous target molecules, the role of QC on certain molecular targets such as G-protein coupled and nuclear receptors remains to be investigated. Our analysis presents several molecular targets of QC and its derivatives that demonstrate the pharmacological potential against cognitive impairment. Consequently, this article may guide future studies using QC and its analogs on specific signaling molecules. Finding new molecular targets of QC and its analogs may ultimately assist in the treatment of cognitive impairment.

The Methanol Extract of Allium cepa L. Protects Inflammatory Markers in LPS-Induced BV-2 Microglial Cells and Upregulates the Antiapoptotic Gene and Antioxidant Enzymes in N27-A Cells

Neuroinflammation, apoptosis, and oxidative stress are connected to the pathogenesis of neurodegenerative diseases (NDDs). Targeting these three factors, the intervention of neuroprotective agents may have great potential in the treatment of NDDs. In the current study, the anti-inflammatory effects of the methanol extract of Allium cepa (MEAC) in lipopolysaccharide (LPS)-induced BV-2 microglial cells were investigated. MEAC has been studied in regard to the regulation of the antiapoptotic gene (Bcl-2) and various antioxidant enzyme (HO-1, NQO-1, and catalase) expressions in N27-A cells. Additionally, the protective action of MEAC has also been studied against MPP⁺-induced death in N27-A cells. The results suggest that MEAC is significantly protected from NO release and increase iNOS expression at the mRNA and protein levels in LPS-stimulated BV-2 microglial cells. MEAC treatment also protects COX-2 expression at the mRNA and protein levels. Furthermore, MEAC treatment prevents LPS-stimulated increases of proinflammatory cytokines, including TNF-α, IL-6, and IL-1β. In N27-A cells, MEAC treatment significantly upregulates antiapoptotic gene (Bcl-2) and antioxidant enzyme (HO-1, NQO1, and catalase) expressions. Moreover, MEAC treatment protects against MPP⁺-induced death in N27-A cells. To conclude, A cepa extract takes protective action against LPS and MPP⁺, and upregulates the antioxidant enzymes that could potentially be used in the therapy of NDDs.

Inhibition and assessment of the biophysical gating properties of GluA2 and GluA2/A3 AMPA receptors using curcumin derivatives

The development of efficacious and safe drugs for the treatment of neurological diseases related to glutamate toxicity has been a focus in neuropharmacological research. Specifically, discovering antagonists to modulate the activity and kinetics of AMPA receptors, which are the fastest ligand-gated ion channels involved in excitatory neurotransmission in response to glutamate. Thus, the current study investigated novel curcumin derivatives on the biophysical properties of AMPA receptors, specifically on the homomeric GluA2 and the heteromeric GluA2/A3 subunits and assessed for inhibitory actions. The biophysical parameter (i.e., desensitization, deactivation, and peak currents) were measured by using whole-cell patch clamp electrophysiology with and without the administration of the derivatives onto HEK293 cells. CR-NN, CR-NNPh, CR-MeNH, and CR-NO of the tested derivatives showed inhibition on all AMPA receptors up to 6 folds. Moreover, the inhibitory derivatives also increased desensitization and deactivation, which further intensifies the compounds' neuroprotective effects. However, CR-PhCl, CR-PhF, and CR-PhBr did not show any significant changes on the peak current, deactivation or desensitization rates. By comparison to other discovered and widely used antagonist, the prepared curcumin derivatives are not selective to a specific AMPA subunit, instead implement its effect in the same way between all types of AMPA receptors. Additionally, the obtained results provide derivatives that not only noncompetitively inhibit AMPARs but also decrease its biophysical kinetics, specifically desensitization and deactivation rates. Hence, to potentially serve as a new AMPAR inhibitor with therapeutic potential, the current study provides compounds that are non-selective and non-competitive antagonist, which also effect the desensitization and deactivation rates of the receptor.

Taurine and its analogs in neurological disorders: Focus on therapeutic potential and molecular mechanisms

Taurine is a sulfur-containing amino acid and known as semi-essential in mammals and is produced chiefly by the liver and kidney. It presents in different organs, including retina, brain, heart and placenta and demonstrates extensive physiological activities within the body. In the several disease models, it attenuates inflammation- and oxidative stress-mediated injuries. Taurine also modulates ER stress, Ca2+ homeostasis and neuronal activity at the molecular level as part of its broader roles. Different cellular processes such as energy metabolism, gene expression, osmosis and quality control of protein are regulated by taurine. In addition, taurine displays potential ameliorating effects against different neurological disorders such as neurodegenerative diseases, stroke, epilepsy and diabetic neuropathy and protects against injuries and toxicities of the nervous system. Several findings demonstrate its therapeutic role against neurodevelopmental disorders, including Angelman syndrome, Fragile X syndrome, sleep-wake disorders, neural tube defects and attention-deficit hyperactivity disorder. Considering current biopharmaceutical limitations, developing novel delivery approaches and new derivatives and precursors of taurine may be an attractive option for treating neurological disorders. Herein, we present an overview on the therapeutic potential of taurine against neurological disorders and highlight clinical studies and its molecular mechanistic roles. This article also addresses the neuropharmacological potential of taurine analogs.

The Reactive Plasticity of Hippocampal Ionotropic Glutamate Receptors in Animal Epilepsies

Ionotropic glutamate receptors (iGluRs) mediate the synaptic and metabolic actions of glutamate. These iGluRs are classified within the α-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA)-type, kainate-type, and N-methyl-d-aspartate (NMDA)-type functional receptor families. The iGluR assemblies are regulated by transcription, alternative splicing, and cytoplasmic post-translational modifications. The iGluR subunit proteins are transported from the endoplasmic reticulum, inserted into the synaptic membranes, and anchored at their action site by different scaffolding and interacting proteins. The functional properties of iGluRs depend on their subunit composition, the amino acid sequence of the protein domains, and the scaffolding proteins in the synaptic membranes. The iGluRs are removed from the membranes by enzymatic action and endocytosis. Hippocampal iGluRs are rearranged through the upregulation and downregulation of the subunits following deafferentation and epileptic seizures. The rearrangement of iGluRs and the alteration of their subunit composition transform neurons into “pathological” cells, determining the further plasticity or pathology of the hippocampal formation. In the present review, we summarize the expression of AMPA, kainate, and NMDA receptor subunits following deafferentation, repeated mild seizures, and status epilepticus. We compare our results to literature descriptions, and draw conclusions as to the reactive plasticity of iGluRs in the hippocampus.

Toxicant-mediated redox control of proteostasis in neurodegeneration

Disruption in redox signaling and control of cellular processes has emerged as a key player in many pathologies including neurodegeneration. As protein aggregations are a common hallmark of several neuronal pathologies, a firm understanding of the interplay between redox signaling, oxidative and free radical stress, and proteinopathies is required to sort out the complex mechanisms in these diseases. Fortunately, models of toxicant-induced neurodegeneration can be utilized to evaluate and report mechanistic alterations in the proteostasis network (PN). The epidemiological links between environmental toxicants and neurological disease gives further credence into characterizing the toxicant-mediated PN disruptions observed in these conditions. Reviewed here are examples of mechanistic interaction between oxidative or free radical stress and PN alterations. Additionally, investigations into toxicant-mediated PN disruptions, specifically focusing on environmental metals and pesticides, are discussed. Finally, we emphasize the need to distinguish whether the presence of protein aggregations are contributory to phenotypes related to neurodegeneration, or if they are a byproduct of PN deficiencies.

Gastrointestinal non-motor dysfunction in Parkinson's disease model rats with 6-hydroxydopamine

Parkinson's disease (PD) is a neurodegenerative disease with a progressive loss of mesencephalic dopaminergic neurons of the substantia nigra (SN). To further evaluate its pathophysiology, accurate animal models are needed. The current study aims to verify the impact of a 6-hydroxydopamine (6-OHDA) bilateral microinjection into the SN on gastrointestinal symptoms in rats and confirm that the 6-OHDA rat model is an appropriate tool to investigate the mechanisms of Parkinsonian GI disorders. Immunohistochemistry, digital X-ray imaging, short-circuit current, FITC-dextran permeability and ultra-performance liquid chromatography tandem mass spectrometry were used in this study. The results indicated that the dopaminergic neurons in SN and fibres in the striatum were markedly reduced in 6-OHDA rats. The 6-OHDA rats manifested reductions in occupancy in a rotarod test and increases in daily food debris but no difference in body mass or daily consumption. Compared with control rats, faecal pellets and their contents were significantly decreased, whereas gastric emptying and intestinal transport were delayed in 6-OHDA rats. The increased in vivo FITC-dextran permeability and decreased intestinal transepithelial resistance in the model suggest attenuated barrier function in the digestive tract in the PD model. Moreover, inflammatory factors in the plasma showed that pro-inflammatory factors IL-1? and IL-8 were significantly increased in 6-OHDA rats. Collectively, these findings indicate that the model is an interesting experimental tool to investigate the mechanisms involved in the progression of gastrointestinal dysfunction in PD.

Attenuated glutamate induced ROS production by antioxidative compounds in neural cell lines

Glutamate is an excitatory neurotransmitter involved in neural function. Excess accumulation of intercellular glutamate leads to increasing concentration of reactive oxygen species (ROS) and reactive nitrogen species (RNS) in neuronal cells. In this study, we investigated the antioxidant activity of several typical superior compounds among four neuronal cells, and determined the scavenging activity of free radicals. The in vivo assay was also carried out to compare the protective effect of glutamate-induced cell damage. Hierarchical clustering analysis was used to identify the common properties. Glutamate induced neurotoxicity and ROS production, suggesting glutamate cytotoxicity was related to oxidative stress and widely exists in different cell lines. Those screening compounds exhibited strong antioxidant ability, but low cytotoxicity to neuronal cells, acting as agents against neurodegenerative diseases. Finally, a hierarchical clustering analysis assay indicated that hyperoside and rutin hydrate are the most effective compounds for attenuating intercellular ROS levels. The results suggested the activity more or less relies on structure, rather than residues. These data generate new supporting ideas to remove intracellular ROS and the identified compounds serve as potential therapeutic agents in multiple neurological diseases.

Glutamate is an excitatory neurotransmitter involved in neural function.