Recent Advance in the Relationship between Excitatory Amino Acid Transporters and Parkinson's Disease

Metabolic reprogramming of the inflammatory response in the nervous system: the crossover between inflammation and metabolism

Metabolism is a fundamental process by which biochemicals are broken down to produce energy (catabolism) or used to build macromolecules (anabolism). Metabolism has received renewed attention as a mechanism that generates molecules that modulate multiple cellular responses. This was first identified in cancer cells as the Warburg effect, but it is also present in immunocompetent cells. Studies have revealed a bidirectional influence of cellular metabolism and immune cell function, highlighting the significance of metabolic reprogramming in immune cell activation and effector functions. Metabolic processes such as glycolysis, oxidative phosphorylation, and fatty acid oxidation have been shown to undergo dynamic changes during immune cell response, facilitating the energetic and biosynthetic demands. This review aims to provide a better understanding of the metabolic reprogramming that occurs in different immune cells upon activation, with a special focus on central nervous system disorders. Understanding the metabolic changes of the immune response not only provides insights into the fundamental mechanisms that regulate immune cell function but also opens new approaches for therapeutic strategies aimed at manipulating the immune system.

Neuroprotective effects of L-Dopa-modified zinc oxide nanoparticles on the rat model of 6-OHDA-ınduced Parkinson's disease

Parkinson's disease (PD) is a chronic neurodegenerative case. As the disease progresses, the response time to doses of levodopa (L-Dopa) becomes shorter and the effects of the drug are severely limited by some undesirable side effects such as the 'on-off' phenomenon. In several diseases, including Parkinson's, nanoparticles can deliver antioxidant compounds that reduce oxidative stress. This study evaluates and compares the neuroprotective effects of L-Dopa-modified zinc nanoparticles (ZnNPs) in the 6-hydroxydopamine (6-OHDA)-induced PD rat model. For this purpose, the synthesis of NPs was carried out. Scanning electron microscopy, X-ray diffraction and Fourier transform infrared spectrophotometer were used for characterization. The rats were randomized into 9 experimental groups: control, lesion group (6-OHDA), 6-OHDA + 5 mg/kg L-Dopa, 6-OHDA + 10 mg/kg L-Dopa, 6-OHDA + 20 mg/kg L-Dopa, 6-OHDA + 20 mg/kg ZnNPs, 6-OHDA + 40 mg/kg ZnNPs, 6-OHDA + 30 mg/kg ZnNPs + L-Dopa, and 6-OHDA + 60 mg/kg ZnNPs + L-Dopa. Behavioral tests were performed on all groups 14 days after treatment. Phosphatase and tensin homolog, Excitatory amino acid transporter 1/2, and Glutamine synthetase gene analyses were performed on brain samples taken immediately after the tests. In addition, histological and immunohistochemical methods were used to determine the general structure and properties of the tissues. We obtained important findings that L-Dopa-modified ZnNPs increased the activity of glutamate transporters. Our experiment showed that glutamate increases neuronal cell vitality and improves behavioral performance. Therefore, L-Dopa-modified ZnNPs can be used to prevent neurotoxicity. According to what we found, results show that L-Dopa-modified ZnNPs will lend to the effective avoidance and therapy of PD.

Astroglial membrane camouflaged Ptbp1 siRNA delivery hinders glutamate homeostasis via SDH/Nrf2 pathway

Polypyrimidine tract-binding protein 1 (PTBP1) regulates numerous alternative splicing events during tumor progression and neurogenesis. Previously, PTBP1 downregulation was reported to convert astrocytes into functional neurons; however, how PTBP1 regulates astrocytic physiology remains unclear. In this study, we revealed that PTBP1 modulated glutamate uptake via ATP1a2, a member of Na+/K+-ATPases, and glutamate transporters in astrocytes. Ptbp1 knockdown altered mitochondrial function and energy metabolism, which involved PTBP1 regulating mitochondrial redox homeostasis via the succinate dehydrogenase (SDH)/Nrf2 pathway. The malfunction of glutamate transporters following Ptbp1 knockdown resulted in enhanced excitatory synaptic transmission in the cortex. Notably, we developed a biomimetic cationic triblock polypeptide system, i.e., polyethylene glycol44-polylysine30-polyleucine10 (PEG44-PLL30-PLLeu10) with astrocytic membrane coating to deliver Ptbp1 siRNA in vitro and in vivo, which approach allowed Ptbp1 siRNA to efficiently cross the blood-brain barrier and target astrocytes in the brain. Collectively, our findings suggest a framework whereby PTBP1 serves as a modulator in glutamate transport machinery, and indicate that biomimetic methodology is a promising route for in vivo siRNA delivery.

Activation and polarization of striatal microglia and astrocytes are involved in bradykinesia and allodynia in early-stage parkinsonian mice

In addition to the cardinal motor symptoms, pain is a major non-motor symptom of Parkinson's disease (PD). Neuroinflammation in the substantia nigra pars compacta and dorsal striatum is involved in neurodegeneration in PD. But the polarization of microglia and astrocytes in the dorsal striatum and their contribution to motor deficits and hyperalgesia in PD have not been characterized. In the present study, we observed that hemiparkinsonian mice established by unilateral 6-OHDA injection in the medial forebrain bundle exhibited motor deficits and mechanical allodynia. In these mice, both microglia and astrocytes in the dorsal striatum were activated and polarized to M1/M2 microglia and A1/A2 astrocytes as genes specific to these cells were upregulated. These effects peaked 7 days after 6-OHDA injection. Meanwhile, striatal astrocytes in parkinsonian mice also displayed hyperpolarized membrane potentials, enhanced voltage-gated potassium currents, and dysfunction in inwardly rectifying potassium channels and glutamate transporters. Systemic administration of minocycline, a microglia inhibitor, attenuated the expression of genes specific to M1 microglia and A1 astrocytes in the dorsal striatum (but not those specific to M2 microglia and A2 astrocytes), attenuated the damage in the nigrostriatal dopaminergic system, and alleviated the motor deficits and mechanical allodynia in parkinsonian mice. By contrast, local administration of minocycline into the dorsal striatum of parkinsonian mice mitigated only hyperalgesia. This study suggests that M1 microglia and A1 astrocytes in the dorsal striatum may play important roles in the development of pathophysiology underlying hyperalgesia in the early stages of PD.

Mechanistic study of the anti-excitatory amino acid toxicity of Bushen Zhichan decoction for Parkinson's disease based on the transcriptional regulation of EAAT1 by YY1

ETHNOPHARMACOLOGICAL RELEVANCE

Bushen Zhichan decoction (BSZCF) is derived from Liuwei Dihuang Pill, a famous Chinese herbal formula recorded in the book Key to Therapeutics of Children's Diseases. It has been widely used as a basic prescription for nourishing and tonifying the liver and kidneys to treat Parkinson's disease (PD), but its mechanism remains to be explored.

AIM OF THE STUDY

BSZCF, a Chinese herbal formula comprising five herbs: Rehmannia glutinosa (Gaertn.) DC., Dioscorea oppositifolia L., Cornus officinalis Siebold & Zucc., Fallopia multiflora (Thunb.) Haraldson and Cistanche tubulosa (Schenk) Wight, is used clinically to treat PD. In vivo and in vitro experiments were designed to elucidate the mechanism of BSZCF in the protection of dopamine (DA) neurons and the treatment of PD. The toxicity of excitatory amino acids (EAA) may be attenuated by inhibiting the transcription factor Yin Yang 1 (YY1) and up-regulating the expression of excitatory amino acid transporter 1 (EAAT1).

MATERIALS AND METHODS

IN VIVO: After 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) was intraperitoneally injected into specific pathogen free (SPF) C57BL/6J mice, model mice were intragastrically given adamantane hydrochloride tablets (AHT) or different doses of BSZCF for 14 days. Both open field and pole-climbing tests were conducted to assess behavioral changes. In vitro: 1-Methyl-4-phe-nylpyridiniumiodide (MPP+)-injured human neuroblastoma cells (SH-SY5Y) were utilized to construct PD cell models. Primary astrocytes were transfected with EAAT1 and YY1 lentiviruses for EAAT1 gene knockout and YY1 gene knockout astrocytes, respectively. The high performance liquid chromatography-mass spectrometry (HPLC-MS) analysis of BSZCF was performed to control the quality of blood drugs. The optimal concentration and time of PD cell models treated by BSZCF were determined by the use of Cell Counting Kit-8 (CCK8). Enzyme-linked immunosorbent assay (ELISA) was used for measuring glutamate (Glu) in the peripheral blood and cells of each group. Western blotting (WB) and real-time quantitative polymerase chain reaction (qPCR) were used to detect tyrosine hydroxylase (TH), dopamine transporters (DAT), EAAT1 and YY1 protein and mRNA. After the blockade of EAAT1, immunofluorescence (IF) assay was used to detect the TH protein in each group.

RESULTS

In vivo research showed that BSZCF improved the behavioral symptoms of PD mice, and reduced the death of DA neurons and the level of Glu. The mechanism may be related to the decrease of YY1 expression and the increase of EAAT1 levels. In vitro experiments showed that the anti-excitatory amino acid toxicity of BSZCF was achieved by inhibiting YY1 expression and regulating EAAT1.

CONCLUSIONS

By inhibiting YY1 to increase the expression of EAAT1 and attenuating the toxicity of Glu, BSZCF exerts the effect of protecting DA neurons and treating PD-like symptoms in mice.

Interhemispheric reactivity of the subthalamic nucleus sustains progressive dopamine neuron loss in asymmetrical parkinsonism

Parkinson's disease (PD) is characterized by the progressive and asymmetrical degeneration of the nigrostriatal dopamine neurons and the unilateral presentation of the motor symptoms at onset, contralateral to the most impaired hemisphere. We previously developed a rat PD model that mimics these typical features, based on unilateral injection of a substrate inhibitor of excitatory amino acid transporters, L-trans-pyrrolidine-2,4-dicarboxylate (PDC), in the substantia nigra (SN). Here, we used this progressive model in a multilevel study (behavioral testing, in vivo 1H-magnetic resonance spectroscopy, slice electrophysiology, immunocytochemistry and in situ hybridization) to characterize the functional changes occurring in the cortico-basal ganglia-cortical network in an evolving asymmetrical neurodegeneration context and their possible contribution to the cell death progression. We focused on the corticostriatal input and the subthalamic nucleus (STN), two glutamate components with major implications in PD pathophysiology. In the striatum, glutamate and glutamine levels increased from presymptomatic stages in the PDC-injected hemisphere only, which also showed enhanced glutamatergic transmission and loss of plasticity at corticostriatal synapses assessed at symptomatic stage. Surprisingly, the contralateral STN showed earlier and stronger reactivity than the ipsilateral side (increased intraneuronal cytochrome oxidase subunit I mRNA levels; enhanced glutamate and glutamine concentrations). Moreover, its lesion at early presymptomatic stage halted the ongoing neurodegeneration in the PDC-injected SN and prevented the expression of motor asymmetry. These findings reveal the existence of endogenous interhemispheric processes linking the primary injured SN and the contralateral STN that could sustain progressive dopamine neuron loss, opening new perspectives for disease-modifying treatment of PD.

Aquaporin-4 and Parkinson's Disease

The water-selective channel aquaporin-4 (AQP4) is implicated in water homeostasis and the functioning of the glymphatic system, which eliminates various metabolites from the brain tissue, including amyloidogenic proteins. Misfolding of the α-synuclein protein and its post-translational modifications play a crucial role in the development of Parkinson's disease (PD) and other synucleopathies, leading to the formation of cytotoxic oligomers and aggregates that cause neurodegeneration. Human and animal studies have shown an interconnection between AQP4 dysfunction and α-synuclein accumulation; however, the specific role of AQP4 in these mechanisms remains unclear. This review summarizes the current knowledge on the role of AQP4 dysfunction in the progression of α-synuclein pathology, considering the possible effects of AQP4 dysregulation on brain molecular mechanisms that can impact α-synuclein modification, accumulation and aggregation. It also highlights future directions that can help study the role of AQP4 in the functioning of the protective mechanisms of the brain during the development of PD and other neurodegenerative diseases.

The common denominators of Parkinson's disease pathogenesis and methamphetamine abuse

The pervasiveness and mortality associated with methamphetamine abuse has doubled during the past decade suggesting a possible worldwide substance use crisis. Epitomizing the pathophysiology and toxicology of methamphetamine abuse proclaims severe signs and symptoms of neurotoxic and neurobehavioral manifestations in both humans and animals. Most importantly, chronic use of this drug enhances the probability of developing neurodegenerative diseases manifolds. Parkinson's disease is one such neurological disorder, which significantly and evidently not only shares a number of toxic pathogenic mechanisms induced by methamphetamine exposure but is also interlinked both structurally andgenetically. Methamphetamine-induced neurodegeneration involves altered dopamine homeostasis that promotes the aggregation of α-synuclein protofibrils in the dopaminergic neurons and drives these neurons to make them more vulnerable to degeneration as recognized in Parkinson's disease. Moreover, the pathologic mechanisms such as mitochondrial dysfunction, oxidative stress, neuroinflammation and decreased neurogenesis detected in methamphetamine abusers dramatically resemble to what is observed in Parkinson's disease cases. Therefore, the present review comprehensively cumulates a holistic illustration of various genetic and molecular mechanisms putting across the notion of how methamphetamine administration and intoxication might lead to Parkinson's disease-like pathology and Parkinsonism.

Functional investigation of SLC1A2 variants associated with epilepsy

Epilepsy is a common neurological disorder and glutamate excitotoxicity plays a key role in epileptic pathogenesis. Astrocytic glutamate transporter GLT-1 is responsible for preventing excitotoxicity via clearing extracellular accumulated glutamate. Previously, three variants (G82R, L85P, and P289R) in SLC1A2 (encoding GLT-1) have been clinically reported to be associated with epilepsy. However, the functional validation and underlying mechanism of these GLT-1 variants in epilepsy remain undetermined. In this study, we reported that these disease-linked mutants significantly decrease glutamate uptake, cell membrane expression of the glutamate transporter, and glutamate-elicited current. Additionally, we found that these variants may disturbed stromal-interacting molecule 1 (STIM1)/Orai1-mediated store-operated Ca²⁺ entry (SOCE) machinery in the endoplasmic reticulum (ER), in which GLT-1 may be a new partner of SOCE. Furthermore, knock-in mice with disease-associated variants showed a hyperactive phenotype accompanied by reduced glutamate transporter expression. Therefore, GLT-1 is a promising and reliable therapeutic target for epilepsy interventions.

Impact of Calcium Influx on Endoplasmic Reticulum in Excitotoxic Neurons: Role of Chemical Chaperone 4-PBA

Excessive activation of α-amino-3-hydroxy-5-methyl-4-isoxazole propoinic acid (AMPA) receptors instigates excitotoxicity via enhanced calcium influx in the neurons thus inciting deleterious consequences. Additionally, Endoplasmic Reticulum (ER) is pivotal in maintaining the intracellular calcium balance. Considering this, studying the aftermath of enhanced calcium uptake by neurons and its effect on ER environment can assist in delineating the pathophysiological events incurred by excitotoxicty. The current study was premeditated to decipher the role of ER pertaining to calcium homeostasis in AMPA-induced excitotoxicity. The findings showed, increased intracellular calcium levels (measured by flowcytometry and spectroflourimeter using Fura 2AM) in AMPA excitotoxic animals (male Sprague dawely rats) (intra-hippocampal injection of 10 mM AMPA). Further, ER resident proteins like calnexin, PDI and ERp72 were found to be upregulated, which further modulated the functioning of ER membrane calcium channels viz. IP3R, RyR, and SERCA pump. Altered calcium homeostasis further led to ER stress and deranged the protein folding capacity of ER post AMPA toxicity, which was ascertained by unfolded protein response (UPR) pathway markers such as IRE1α, eIF2α, and ATF6α. Chemical chaperone, 4-phenybutric acid (4-PBA), ameliorated the protein folding capacity and subsequent UPR markers. In addition, modulation of calcium channels and calcium regulating machinery of ER post 4-PBA administration restored the calcium homeostasis. Therefore the study reinforces the significance of ER stress, a debilitating outcome of impaired calcium homeostasis, under AMPA-induced excitotoxicity. Also, employing chaperone-based therapeutic approach to curb ER stress can restore the calcium imbalance in the neuropathological diseases.

Is L-Glutamate Toxic to Neurons and Thereby Contributes to Neuronal Loss and Neurodegeneration? A Systematic Review

L-glutamate (L-Glu) is a nonessential amino acid, but an extensively utilised excitatory neurotransmitter with critical roles in normal brain function. Aberrant accumulation of L-Glu has been linked to neurotoxicity and neurodegeneration. To investigate this further, we systematically reviewed the literature to evaluate the effects of L-Glu on neuronal viability linked to the pathogenesis and/or progression of neurodegenerative diseases (NDDs). A search in PubMed, Medline, Embase, and Web of Science Core Collection was conducted to retrieve studies that investigated an association between L-Glu and pathology for five NDDs: Alzheimer's disease (AD), Parkinson's disease (PD), multiple sclerosis (MS), amyotrophic lateral sclerosis (ALS), and Huntington's disease (HD). Together, 4060 studies were identified, of which 71 met eligibility criteria. Despite several inadequacies, including small sample size, employment of supraphysiological concentrations, and a range of administration routes, it was concluded that exposure to L-Glu in vitro or in vivo has multiple pathogenic mechanisms that influence neuronal viability. These mechanisms include oxidative stress, reduced antioxidant defence, neuroinflammation, altered neurotransmitter levels, protein accumulations, excitotoxicity, mitochondrial dysfunction, intracellular calcium level changes, and effects on neuronal histology, cognitive function, and animal behaviour. This implies that clinical and epidemiological studies are required to assess the potential neuronal harm arising from excessive intake of exogenous L-Glu.

Roles of N-Methyl-D-Aspartate Receptors (NMDARs) in Epilepsy

Epilepsy is one of the most common neurological disorders characterized by recurrent seizures. The mechanism of epilepsy remains unclear and previous studies suggest that N-methyl-D-aspartate receptors (NMDARs) play an important role in abnormal discharges, nerve conduction, neuron injury and inflammation, thereby they may participate in epileptogenesis. NMDARs belong to a family of ionotropic glutamate receptors that play essential roles in excitatory neurotransmission and synaptic plasticity in the mammalian CNS. Despite numerous studies focusing on the role of NMDAR in epilepsy, the relationship appeared to be elusive. In this article, we reviewed the regulation of NMDAR and possible mechanisms of NMDAR in epilepsy and in respect of onset, development, and treatment, trying to provide more evidence for future studies.

Toxoplasmosis: Targeting neurotransmitter systems in psychiatric disorders

The most common form of the disease caused by Toxoplasma gondii (T. gondii) is latent toxoplasmosis due to the formation of tissue cysts in various organs, such as the brain. Latent toxoplasmosis is probably a risk factor in the development of some neuropsychiatric disorders. Behavioral changes after infection are caused by the host immune response, manipulation by the parasite, central nervous system (CNS) inflammation, as well as changes in hormonal and neuromodulator relationships. The present review focused on the exact mechanisms of T. gondii effect on the alteration of behavior and neurotransmitter levels, their catabolites and metabolites, as well as the interaction between immune responses and this parasite in the etiopathogenesis of psychiatric disorders. The dysfunction of neurotransmitters in the neural transmission is associated with several neuropsychiatric disorders. However, further intensive studies are required to determine the effect of this parasite on altering the level of neurotransmitters and the role of neurotransmitters in the etiology of host behavioral changes.

Misregulation of Wnt Signaling Pathways at the Plasma Membrane in Brain and Metabolic Diseases

Wnt signaling pathways constitute a group of signal transduction pathways that direct many physiological processes, such as development, growth, and differentiation. Dysregulation of these pathways is thus associated with many pathological processes, including neurodegenerative diseases, metabolic disorders, and cancer. At the same time, alterations are observed in plasma membrane compositions, lipid organizations, and ordered membrane domains in brain and metabolic diseases that are associated with Wnt signaling pathway activation. Here, we discuss the relationships between plasma membrane components-specifically ligands, (co) receptors, and extracellular or membrane-associated modulators-to activate Wnt pathways in several brain and metabolic diseases. Thus, the Wnt-receptor complex can be targeted based on the composition and organization of the plasma membrane, in order to develop effective targeted therapy drugs.

Effects of safinamide on pain in patients with fluctuating Parkinson's disease

BACKGROUND

Non-motor symptoms (NMS) are integral to Parkinson's Disease (PD) and management remains a challenge. Safinamide is a novel molecule in relation to addressing NMS due to its multifocal mechanism of action with both dopaminergic and non-dopaminergic properties.

OBJECTIVE

To investigate the efficacy of safinamide on NMS and its burden in PD patients with motor fluctuations after 6 months of treatment.

METHODS

This observational, multicenter, open-label, pilot study assessed a wide range of NMS using the following rating scales, NMSS (non-motor symptom scale), KPPS (King's PD pain scale), HADS (hospital anxiety and depression scale), PDQ-8 (Parkinson's disease quality of life questionnaire), and PDSS-2 (Parkinson's disease sleep scale), EuroQol-5D 3 level version (EQ-5D-3L), CGI-I (clinical global impression of improvement), and PGI-C (patient global impression of change). Motor examination using UPDRS part III (Unified Parkinson's disease rating scale, motor examination), UPDRS IV (complications of therapy) and Hoehn and Yahr staging were also obtained.

RESULTS

27 patients were included in the analysis and were evaluated at baseline and ≥ 6 months after safinamide treatment. 26 patients had a daily maintenance dose of 100 mg and 1 patient a daily dose of 50 mg. Significant improvements in UPDRS IV, KPPS item 5 (region-specific "off" dystonia), KPPS domain 3 (items 4-6, fluctuation related pain) and KPPS total score were observed after treatment with safinamide, while maintaining stable dopaminergic medication. No statistically significant differences were found in NMSS, HADS, PDSS-2, EQ-5D-3L, and PDQ-8 after treatment.

CONCLUSIONS

Our results suggest that safinamide may have a beneficial effect on pain, a key unmet need in fluctuating PD patients.

Exercise increases striatal Glu reuptake and improves motor dysfunction in 6-OHDA-induced Parkinson's disease rats

The purpose of this study is to clarify that exercise may improve the motor dysfunction of Parkinson's disease (PD) model rats by increasing the reuptake of glutamate (Glu) in the striatum. The neurotoxin 6-hydroxydopamine (6-OHDA) was injected into the medial forebrain bundle (MFB) of the rats' right brain to establish PD model rats with unilateral injury, and the sham operation group was given the same dose of normal saline at the same site as the control group. The reliability of the model was evaluated by apomorphine (APO)-induced rotation test combined with tyrosine hydroxylase (TH) immunohistochemical staining in the substantia nigra and striatum. The exercise group started treadmill training intervention (11 m/min, 30 min/day, 5d/week, and 4 weeks in total) 1 week after the operation. The balance bar test, suspension test, and the tail-lifting handstand test were used to evaluate exercise performance of rats; RT-PCR and western blotting were used to detect protein and mRNA expression of glutamate transporter-1 (GLT-1) and glutamine synthetase (GS) in the striatum; and isotope labeling was used to detect the ability of Glu reuptake in the striatum. (1) Compared with PD group, the number of TH immunoreactive cells in the substantia nigra and the content of TH immunoreactive fibers in the striatum did not change significantly in PD + Ex group. (2) Compared with PD group, the latency and total time of crossing the balance beam were significantly shorter (P < 0.01), the retention time of two forepaws on the metal wire was significantly longer (P < 0.01), the maximum lifting of head and trunk was significantly increased (P < 0.01) in PD + Ex group. (3) Compared with PD group, the ability of Glu reuptake in the striatum was significantly increased (P < 0.05), the expression levels of GLT-1 and GS mRNA in the striatum were significantly increased (P < 0.05), the protein expression of GLT-1 and GS in the striatum was significantly upregulated (P < 0.05) in PD + Ex group. Exercise intervention can significantly improve the motor dysfunction of PD model rats, increase the ability of striatal Glu reuptake significantly, and upregulate the expression levels of GLT-1 and GS protein and GS mRNA significantly. Exercise intervention may increase the protein expression level of GLT-1 and increase the reuptake ability of Glu in the striatum, thereby reducing the excitotoxic effect of excessive Glu on the postsynaptic membrane, and ultimately alleviate the motor dysfunction in PD model rats.

Characterizing the Expression Patterns of Parkinson's Disease Associated Genes

Background

The expression pattern represents a quantitative phenotype that provides an in-depth view of the molecular mechanism in Parkinson’s disease (PD); however, the expression patterns of PD-associated genes (PAGs) and their relation to age at onset (AAO) remain unclear.

Methods

The known PD-causing genes and PD-risk genes, which were collected from latest published authoritative meta-analysis, were integrated as PAGs. The expression data from Genotype-Tissue Expression database, Allen Brian Map database, and BrainSpan database, were extracted to characterize the tissue specificity, inhibitory-excitatory neuron expression profile, and spatio-temporal expression pattern of PAGs, respectively. The AAO information of PD-causing gene was download from Gene4PD and MDSgene database.

Results

We prioritized 107 PAGs and found that the PAGs were more likely to be expressed in brain-related tissues than non-brain tissues and that more PAGs had higher expression levels in excitatory neurons than inhibitory neurons. In addition, we identified two spatio-temporal expression modules of PAGs in human brain: the first module showed a higher expression level in the adult period than in the prenatal period, and the second module showed the opposite features. It showed that more PAGs belong to the first module that the second module. Furthermore, we found that the median AAO of patients with mutations in PD-causing genes of the first module was lower than that of the second module.

Conclusion

In conclusion, this study provided comprehensive landscape of expression patterns, AAO features and their relationship for the first time, improving the understanding of pathogenesis, and precision medicine in PD.

Molecular Mechanisms of Glutamate Toxicity in Parkinson's Disease

Parkinson’s disease (PD) is a common neurodegenerative disease, the pathological features of which include the presence of Lewy bodies and the neurodegeneration of dopaminergic neurons in the substantia nigra pars compacta. However, until recently, research on the pathogenesis and treatment of PD have progressed slowly. Glutamate and dopamine are both important central neurotransmitters in mammals. A lack of enzymatic decomposition of extracellular glutamate results in glutamate accumulating at synapses, which is mainly absorbed by excitatory amino acid transporters (EAATs). Glutamate exerts its physiological effects by binding to and activating ligand-gated ion channels [ionotropic glutamate receptors (iGluRs)] and a class of G-protein-coupled receptors [metabotropic glutamate receptors (mGluRs)]. Timely clearance of glutamate from the synaptic cleft is necessary because high levels of extracellular glutamate overactivate glutamate receptors, resulting in excitotoxic effects in the central nervous system. Additionally, increased concentrations of extracellular glutamate inhibit cystine uptake, leading to glutathione depletion and oxidative glutamate toxicity. Studies have shown that oxidative glutamate toxicity in neurons lacking functional N-methyl-D-aspartate (NMDA) receptors may represent a component of the cellular death pathway induced by excitotoxicity. The association between inflammation and excitotoxicity (i.e., immunoexcitotoxicity) has received increased attention in recent years. Glial activation induces neuroinflammation and can stimulate excessive release of glutamate, which can induce excitotoxicity and, additionally, further exacerbate neuroinflammation. Glutamate, as an important central neurotransmitter, is closely related to the occurrence and development of PD. In this review, we discuss recent progress on elucidating glutamate as a relevant neurotransmitter in PD. Additionally, we summarize the relationship and commonality among glutamate excitotoxicity, oxidative toxicity, and immunoexcitotoxicity in order to posit a holistic view and molecular mechanism of glutamate toxicity in PD.

Chinese Herbal Medicine Interventions in Neurological Disorder Therapeutics by Regulating Glutamate Signaling

Glutamate is the major excitatory neurotransmitter in the central nervous system, and its signaling is critical for excitatory synaptic transmission. The well-established glutamate system involves glutamate synthesis, presynaptic glutamate release, glutamate actions on the ionotropic glutamate receptors (NMDA, AMPA, and kainate receptors) and metabotropic glutamate receptors, and glutamate uptake by glutamate transporters. When the glutamate system becomes dysfunctional, it contributes to the pathogenesis of neurodegenerative and neuropsychiatric diseases such as Alzheimer's disease, Parkinson's disease, depression, epilepsy, and ischemic stroke. In this review, based on regulating glutamate signaling, we summarize the effects and underlying mechanisms of natural constituents from Chinese herbal medicines on neurological disorders. Natural constituents from Chinese herbal medicine can prevent the glutamate-mediated excitotoxicity via suppressing presynaptic glutamate release, decreasing ionotropic and metabotropic glutamate receptors expression in the excitatory synapse, and promoting astroglial glutamate transporter expression to increase glutamate clearance from the synaptic cleft. However, some natural constituents from Chinese herbal medicine have the ability to restore the collapse of excitatory synapses by promoting presynaptic glutamate release and increasing ionotropic and metabotropic glutamate receptors expression. These regulatory processes involve various signaling pathways, which lead to different mechanistic routes of protection against neurological disorders. Hence, our review addresses the underlying mechanisms of natural constituents from Chinese herbal medicines that regulate glutamate systems and serve as promising agents for the treatment of the above-mentioned neurological disorders.

Functional validation of a human GLUD2 variant in a murine model of Parkinson's disease

Parkinson's disease (PD) is a common neurodegenerative disease characterized by Lewy body formation and progressive dopaminergic neuron death in the substantia nigra (SN). Genetic susceptibility is a strong risk factor for PD. Previously, a rare gain-of-function variant of GLUD2 glutamate dehydrogenase (T1492G) was reported to be associated with early onset in male PD patients; however, the function and underlying mechanism of this variant remains elusive. In the present study, we generated adeno-associated virus expressing GLUD2 and its mutant under the control of the glial fibrillary acidic protein promotor and injected the virus into the SN pars compacta of either untreated mice or 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced PD model mice. Our results demonstrate that GLUD2 mutation in MPTP-induced PD mice exacerbates movement deficits and nigral dopaminergic neuron death and reduces glutamate transporters expression and function. Using GC-Q-TOF/MS-based metabolomics, we determined that GLUD2 mutation damages mitochondrial function by decreasing succinate dehydrogenase activity to impede the tricarboxylic acid cycle in the SN of MPTP-induced PD mice. Accordingly, GLUD2 mutant mice had reduced energy metabolism and increased apoptosis, possibly due to downregulation of brain-derived neurotrophic factor/nuclear factor E2-related factor 2 signaling in in vitro and in vivo PD models. Collectively, our findings verify the function of GLUD2 in PD and unravel a mechanism by which a genetic variant in human GLUD2 may contribute to disease onset.

Generation of a Novel Mouse Model of Parkinson's Disease via Targeted Knockdown of Glutamate Transporter GLT-1 in the Substantia Nigra

Parkinson's disease (PD) is a common neurodegenerative disease that is characterized by pathological dopaminergic (DA) neuronal death and α-synuclein aggregation. Glutamate excitotoxicity is a well-established pathogenesis of PD that involves dysfunctional expression of glutamate transporters. Glutamate transporter-1 (GLT-1) is mainly responsible for clearance of glutamate at synapses, including DA synapses. However, the role of GLT-1 in the aberrant synaptic transmission in PD remains elusive. In the present study, we generated small-interfering RNAs (siRNAs) to knockdown GLT-1 expression in primary astrocytes, and we report that siRNA knockdown of astrocytic GLT-1 decreased postsynaptic density-95 (PSD-95) expression in neuron-astrocyte cocultures in vitro. Using adeno-associated viruses (AAVs) targeting GLT-1 short-hairpin RNA (shRNA) sequences with a glial fibrillary acidic protein (GFAP) promoter, we abolished astrocytic GLT-1 expression in the substantia nigra pars compacta (SNpc) of mice. We found that GLT-1 deficiency in the SNpc induced parkinsonian phenotypes in terms of progressive motor deficits and nigral DA neuronal death in mice. We also found that there were reactive astrocytes and microglia in the SNpc upon GLT-1 knockdown. Furthermore, we used RNA sequencing to determine altered gene expression patterns upon GLT-1 knockdown in the SNpc, which revealed that disrupted calcium signaling pathways may be responsible for GLT-1 deficiency-mediated DA neuronal death in the SNpc. Taken together, our findings provide evidence for a novel role of GLT-1 in parkinsonian phenotypes in mice, which may contribute to further elucidation of the mechanisms of PD pathogenesis.

The Potential Role of Astrocytes in Parkinson's Disease (PD)

Astrocytes are multi-functional cells, now recognized as critical participants in many brain functions. They play a critical physiological role in the clearance of neurotransmitters, such as glutamate and gamma-aminobutyric acid (GABA), and in the regulation of K+ from the space of synaptic clefts. Astrocytes also express the excitatory amino acid transporters (EAATs) and aquaporin-4 (AQP4) water channel, which are involved in both physiological functions and neurodegenerative diseases (ND). Some of the ND are the Alzheimer's (AD), Huntington's (HD), Parkinson's diseases (PD), Cerebral edema, amyotrophic lateral sclerosis (ALS), and epilepsy pathological conditions in specific regions of the CNS. Parkinson's disease is the second most common age-related neurodegenerative disorder, characterized by degeneration of dopaminergic neurons of the substantia nigra pars compacta (SNpc). These project to the striatum, forming an important pathway within the basal ganglia. Mostly, PD has no clear etiology, and the mechanism of dopaminergic (DA) neuron loss is not well illustrated. The results of various studies suggest that astrocytes are involved in the pathophysiology of PD. Evidence has shown that the down-regulation of EAAT-2/GLT-1 and AQP4 expression is associated with PD pathogenesis. However, controversial results were reported in different experimental studies about the expression and function of EAAT-2/GLT-1 and AQP4, as well as their colocalization in different brain regions, and their involvement in PD development. Therefore, under neurological disorders, Parkinson's disease is related to the genetic and phenotypic change of astrocytes' biology. In this review, the authors summarized recent their research findings, which revealed the involvement of EAAT-2/GLT-1 and AQP4 expression, the physical interaction between EAAT-2/GLT-1 and AQP4 in astrocyte function, and their potential role in the development of PD in SNpc and Subthalamic nucleus (STN) of the basal ganglia nuclei.

The therapeutic role of cannabinoid receptors and its agonists or antagonists in Parkinson's disease

Parkinson's disease (PD) is a neurodegenerative disease and its characteristic is the progressive degeneration of dopaminergic neurons within the substantia nigra (SN) of the midbrain. There is hardly any clinically proven efficient therapeutics for its cure in several recent preclinical advances proposed to treat PD. Recent studies have found that the endocannabinoid signaling system in particular the comprised two receptors, CB1 and CB2 receptors, has a significant regulatory function in basal ganglia and is involved in the pathogenesis of PD. Therefore, adding new insights into the biochemical interactions between cannabinoids and other signaling pathways may help develop new pharmacological strategies. Factors of the endocannabinoid system (ECS) are abundantly expressed in the neural circuits of basal ganglia, where they interact interactively with glutamatergic, γ-aminobutyric acid-ergic (GABAergic), and dopaminergic signaling systems. Although preclinical studies on PD are promising, the use of cannabinoids at the clinical level has not been thoroughly studied. In this review, we evaluated the available evidence and reviewed the involvement of ECS in etiologies, symptoms and treatments related to PD. Since CB1 and CB2 receptors are the two main receptors of endocannabinoids, we primarily put the focus on the therapeutic role of CB1 and CB2 receptors in PD. We will try to determine future research clues that will help understand the potential therapeutic benefits of the ECS in the treatment of PD, aiming to open up new strategies and ideas for the treatment of PD.

Leptin-Mediated Sympathoexcitation in Obese Rats: Role for Neuron-Astrocyte Crosstalk in the Arcuate Nucleus

Introduction

Accumulated evidence indicates that obesity is associated with enhanced sympathetic activation. Hypothalamic leptin-mediated signaling may contribute to the exaggerated sympathoexcitation of obesity. The goal of this study was to investigate the "neuron-astrocyte" interaction affecting leptin-mediated sympathoexcitation within the arcuate nucleus (ARCN) of the hypothalamus in obese rats.

Methods and Results

Obesity was induced by high-fat diet (HFD, 42% of calories from fat) in Sprague Dawley rats. Twelve weeks of HFD produced hyperleptinemia, hyperlipidemia, and insulin resistance. In anesthetized rats, microinjections of leptin into the ARCN induced increases in heart rate (HR), renal sympathetic nerve activity (RSNA), and mean arterial pressure (MAP) in both control and HFD rats. However, microinjections of leptin in HFD rats elicited higher responses of RSNA and arterial pressure than control-fed rats. It also caused the inhibition of astrocytes within the ARCN using an astrocytic metabolic inhibitor, fluorocitrate, and reduced leptin-induced sympathetic activity and blood pressure responses. Moreover, the expression of the leptin receptor in the ARCN of HFD-fed rats was significantly increased compared to rats fed a control diet. Immunohistochemistry analysis revealed leptin receptor localization from both neurons and astrocytes of the ARCN. HFD rats exhibited increased protein expression of glial fibrillary acidic protein (GFAP) in the ARCN. We also found that the expression of astrocyte-specific glutamate transporters and excitatory amino acid transporter 1 (EAAT1) and 2 (EAAT2) were decreased within the ARCN of the HFD rats. In cultured astrocytic C6 cells, 24 h of leptin treatment increased the protein expression of GFAP and reduced the expression of EAAT1 and EAAT2.

Conclusion

The results suggest that central leptin signaling occurs via neuron-astrocyte interactions in the ARCN and contributing to the exaggerated sympathoexcitation observed in obese rats. The effects may be mediated by the action of leptin on regulating astrocytic glutamate transporters within the ARCN of the hypothalamus.

Review on Cross Talk between Neurotransmitters and Neuroinflammation in Striatum and Cerebellum in the Mediation of Motor Behaviour

Neurological diseases particularly Alzheimer's disease (AD), Parkinson's disease (PD), stroke, and epilepsy are on the rise all around the world causing morbidity and mortality globally with a common symptom of gradual loss or impairment of motor behaviour. Striatum, which is a component of the basal ganglia, is involved in facilitating voluntary movement while the cerebellum is involved in the maintenance of balance and coordination of voluntary movements. Dopamine, serotonin, gamma-aminobutyric acid (GABA), and glutamate, to name a few, interact in regulating the excitation and inhibition of motor neurons. In another hand, interestingly, the motor loss associated with neurological diseases is possibly resulted from neuroinflammation induced by the neuroimmune system. Toll-like receptors (TLRs) are present in the central nervous system (CNS), specifically and primarily expressed in microglia and are also found on neurons and astrocytes, functioning mainly in the regulation of proinflammatory cytokine production. TLRs are always found to be associated or involved in the induction of neuroinflammation in neurodegenerative diseases. Activation of toll-like receptor 4 (TLR4) through TLR4 agonist, lipopolysaccharide (LPS), stimulation initiate a signaling cascade whereby the TLR4-LPS interaction has been found to result in physiological and behavioural changes including retardation of motor activity in the mouse model. TLR4 inhibitor TAK-242 was reflected in the reduction of the spinal cord pathology along with the motor improvement in ALS mouse. There is cross talk with neuroinflammation and neurochemicals. For example, TLR4 activation by LPS is noted to release proinflammatory cytokines, IL-1β, from microglia that subsequently suppresses GABA receptor activities at the postsynaptic site and reduces GABA synthesis at the presynaptic site. Glial glutamate transporter activities are also found to be suppressed, showing the association between TLR4 activation and the related neurotransmitters and corresponding receptors and transporters in the event of neuroinflammation. This review is helpful to understand the connection between neurotransmitter and neuroinflammation in striatum- and cerebellum-mediated motor behaviour.

The 4b-4c loop of excitatory amino acid transporter 1 containing four critical residues essential for substrate transport

In the mammalians, the 4b-4c loop of excitatory amino acid transporters (EAATs) spans more than 50 amino-acid residues that are absent in glutamate transporter homologue of Pyrococcus horikoshii (Glt_Ph). This part of insertion is unique for metazoans and indispensable to the localization of EAATs. The excitatory amino acid transporter (EAAT) 1 is one of the two glial glutamate transporters, which are responsible for efficiently clearing glutamate from the synaptic cleft to prevent neurotoxicity and cell death. Although the crystal structure of EAAT1_cryst (a human thermostable EAAT1) was resolved in 2017, the structure-function relationship of the 4b-4c loop has not been elucidated in EAAT1_cryst. To investigate the role of the 4b-4c loop, we performed alanine-scanning mutagenesis in the mutants and observed dramatically decreased transport activities in T192A, Y194A, N242A, and G245A mutants. The surface expression of T192A and Y194A mutants even decreased by more than 80%, and most of them were detained in the cytoplasm. However, when T192 and Y194 were substituted with conservative residues, the transport activities and the surface expressions of T192S and Y194F were largely recovered, and their kinetic parameters (K_m values) were comparable to the wild-type EAAT1 as well. In contrast, N242 and G245 substituted with conservative residues could not rescue the uptake function, suggesting that N242 and G245 may play irreplaceable roles in the glutamate uptake process. These results indicate that the 4b-4c loop of EAAT1 may not only affect the glutamate uptake activity, but also influence the surface localization of EAAT1 by T192 and Y194.Communicated by Ramaswamy H. Sarma.

Wnt1 Promotes EAAT2 Expression and Mediates the Protective Effects of Astrocytes on Dopaminergic Cells in Parkinson's Disease

Background

Wnt/β-catenin signaling has been reported to exert cytoprotective effects in a cellular model of Parkinson's disease (PD). Glutamate excitotoxicity has been suggested to contribute to the pathogenesis of PD, and excitatory amino acid transporters (EAATs) play a predominant role in clearing excessive glutamate. EAAT2 is mainly expressed in astrocytes, which are an important source of Wnt signaling in the brain.

Methods

Wnt1-overexpressing U251 astrocytes were indirectly cocultured with dopaminergic SH-SY5Y cells treated with 6-hydroxydopamine (6-OHDA). Cell toxicity was determined by cell viability and flow cytometric detection. Glutamate level in the culture medium was determined by enzyme-linked immunosorbent assay (ELISA). Western blot analysis was used to detect the expression of Wnt1, β-catenin, and EAAT2. Immunofluorescence was used to display the expression and translocation of NF-κB p65.

Results

6-OHDA treatment significantly decreased cell viability in both U251 cells and SH-SY5Y cells, inhibited the expression of Wnt1, β-catenin, and EAAT2 in U251 cells, and increased the glutamate level in the culture medium. Coculture with Wnt1-overexpressing U251 cells attenuated 6-OHDA-induced apoptosis in SH-SY5Y cells. Overexpression of Wnt1 decreased the glutamate level in the culture media, upregulated β-catenin, EAAT2, and NF-κB levels, and promoted the translocation of NF-κB from the cytoplasm to the nucleus in U251 cells.

Conclusion

Wnt1 promoted EAAT2 expression and mediated the cytoprotective effects of astrocytes on dopaminergic cells. NF-κB might be involved in the regulation of EAAT2 by Wnt1.

Glutamate Transport and Preterm Brain Injury

Preterm birth complications are the leading cause of child death worldwide and a top global health priority. Among the survivors, the risk of life-long disabilities is high, including cerebral palsy and impairment of movement, cognition, and behavior. Understanding the molecular mechanisms of preterm brain injuries is at the core of future healthcare improvements. Glutamate excitotoxicity is a key mechanism in preterm brain injury, whereby the accumulation of extracellular glutamate damages the delicate immature oligodendrocytes and neurons, leading to the typical patterns of injury seen in the periventricular white matter. Glutamate excitotoxicity is thought to be induced by an interaction between environmental triggers of injury in the perinatal period, particularly cerebral hypoxia-ischemia and infection/inflammation, and developmental and genetic vulnerabilities. To avoid extracellular build-up of glutamate, the brain relies on rapid uptake by sodium-dependent glutamate transporters. Astrocytic excitatory amino acid transporter 2 (EAAT2) is responsible for up to 95% of glutamate clearance, and several lines of evidence suggest that it is essential for brain functioning. While in the adult EAAT2 is predominantly expressed by astrocytes, EAAT2 is transiently upregulated in the immature oligodendrocytes and selected neuronal populations during mid-late gestation, at the peak time for preterm brain injury. This developmental upregulation may interact with perinatal hypoxia-ischemia and infection/inflammation and contribute to the selective vulnerability of the immature oligodendrocytes and neurons in the preterm brain. Disruption of EAAT2 may involve not only altered expression but also impaired function with reversal of transport direction. Importantly, elevated EAAT2 levels have been found in the reactive astrocytes and macrophages of human infant post-mortem brains with severe white matter injury (cystic periventricular leukomalacia), potentially suggesting an adaptive mechanism against excitotoxicity. Interestingly, EAAT2 is suppressed in animal models of acute hypoxic-ischemic brain injury at term, pointing to an important and complex role in newborn brain injuries. Enhancement of EAAT2 expression and transport function is gathering attention as a potential therapeutic approach for a variety of adult disorders and awaits exploration in the context of the preterm brain injuries.

Glutamate, Glutamate Transporters, and Circadian Rhythm Sleep Disorders in Neurodegenerative Diseases

Glutamate, a primary excitatory neurotransmitter and an important intermediate in the cellular metabolism of the brain, has a widespread influence in the sleep-wake regulatory system. Glutamate transporters, including vesicular glutamate transporters and excitatory amino acid transporters, serve as the main force controlling the extracellular concentration of glutamate in the brain. These are likely to be critical tools needed for the brain to modulate the sleep-wake cycle and are likely innervated by the circadian rhythm system in a day-night variant pattern. Because in the initial stages, nearly all patients with neurodegenerative diseases have rhythmic sleep disorders that become aggravated with disease development and often exhibit glutamate uptake dysfunction, we examined whether the above glutamate transporters could be used as potential targets to help address circadian rhythm sleep disorders in patients with neurodegenerative diseases. Therefore, in this review, we sought to analyze the principles governing glutamate transmission and discuss whether the circadian rhythm regulatory properties of these processes endow glutamate transporters with unique functions in the sleep-wake shift of the brain. We attempt to provide a theoretical framework in this field for future studies, to help in the exploration of potential therapeutic targets to delay or prevent the development of neurodegenerative diseases.

Understanding multifactorial architecture of Parkinson's disease: pathophysiology to management

Parkinson's disease (PD) is the second most common multifactorial neurodegenerative disorder affecting 3% of population during elder age. The loss of substantia nigra, pars compacta (SNpc) neurons and deficiency of striatal dopaminergic neurons produces stables motor deficient. Further, increase alpha-synuclein accumulation, mitochondrial dysfunction, oxidative stress, excitotoxicity, and neuroinflammation plays a crucial role in the pathogenesis of PD. Alpha-synuclein protein encodes for SNCA gene and disturbs the normal physiological neuronal signaling via altering mitochondrial homeostasis. The level of α-synuclein is increased in both normal aging and PD brain to a greater extent and secondly reduced clearance results in accumulation of Lewy bodies (LB). Emerging evidences indicate that mitochondrial dysfunction might be a common cause but pathological insult through protein misfolding, aggregation, and accumulation leads to neuronal apoptosis. The observation supporting that expression of DJ-1, LLRK2, PARKIN, PINK1, and excessive excitotoxicity mediated by dysbalance between GABA and glutamate reduced mitochondrial functioning and increased neurotoxicity. Therefore, the present review summarizes the various pathological mechanisms and also explores the therapeutic strategies which could be useful to ameliorate movement disorder like Parkinsonism.

Toxicity, recovery, and resilience in a 3D dopaminergic neuronal in vitro model exposed to rotenone

To date, most in vitro toxicity testing has focused on acute effects of compounds at high concentrations. This testing strategy does not reflect real-life exposures, which might contribute to long-term disease outcome. We used a 3D-human dopaminergic in vitro LUHMES cell line model to determine whether effects of short-term rotenone exposure (100 nM, 24 h) are permanent or reversible. A decrease in complex I activity, ATP, mitochondrial diameter, and neurite outgrowth were observed acutely. After compound removal, complex I activity was still inhibited; however, ATP levels were increased, cells were electrically active and aggregates restored neurite outgrowth integrity and mitochondrial morphology. We identified significant transcriptomic changes after 24 h which were not present 7 days after wash-out. Our results suggest that testing short-term exposures in vitro may capture many acute effects which cells can overcome, missing adaptive processes, and long-term mechanisms. In addition, to study cellular resilience, cells were re-exposed to rotenone after wash-out and recovery period. Pre-exposed cells maintained higher metabolic activity than controls and presented a different expression pattern in genes previously shown to be altered by rotenone. NEF2L2, ATF4, and EAAC1 were downregulated upon single hit on day 14, but unchanged in pre-exposed aggregates. DAT and CASP3 were only altered after re-exposure to rotenone, while TYMS and MLF1IP were downregulated in both single-exposed and pre-exposed aggregates. In summary, our study shows that a human cell-based 3D model can be used to assess cellular adaptation, resilience, and long-term mechanisms relevant to neurodegenerative research.

Succinate dehydrogenase: Prospect for neurodegenerative diseases

Onset of Alzheimer's, Parkinson's and Huntington's diseases as neurodegenerative disorders is increased by age. Alleviation of clinical symptoms and protection of neurons against degeneration are the main aspects of researches to establish new therapeutic strategies. Many studies have shown that mitochondria play crucial roles in high energy demand tissues like brain. Impairments in mitochondrial activity and physiology can makes neurons vulnerable to stress and degeneration. Succinate dehydrogenase (SDH) connects tricarboxylic cycle to the electron transport chain. Therefore, dysfunction of the SDH could impair mitochondrial activity, ATP generation and energy hemostasis in the cell. Exceed lipid synthesis, induction of the excitotoxicity in neurodegenerative disorders could be controlled by SDH through direct and indirect mechanism. In addition, mutation in SDH correlates with the onset of neurodegenerative disorders. Therefore, SDH could behave as a key regulator in neuroprotection. This review will present recent findings which are about SDH activity and related pathways which could play important roles in neuronal survival. Additionally, we will discuss about all possibilities which candidate SDH as a neuroprotective agent.